Thermal inkjet printer ink composition

Abstract

To provide a thermal inkjet printer ink composition containing a colorant having excellent heat resistance, being free of heavy metals, adequately dissolving in a solvent, and presenting a good black color, with cogation being suppressed.SOLUTION: An ink composition comprises a colorant, a solvent, and a resin, the colorant including an azo iron complex represented by formula (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ink composition for thermal ink jet printers, which contains an azo iron complex as a colorant, a solvent, and a resin, and which can be suitably used as an ink in thermal ink jet printers. [Background technology]

[0002] Ink compositions are used to print or draw handwriting on recording media by means of inkjet printers, writing implements, recorders, etc. Among these, inkjet printers are printers that eject ink droplets from nozzles arranged in a row on a printer head and land them on a recording medium such as recording paper, thereby forming a large number of dots, thereby recording characters, images, etc. Compared to printers of other types, inkjet printers have the advantages of low cost, high quality, and ease of colorization.

[0003] Inkjet printers are classified into two types based on the method used to eject ink droplets: a piezoelectric type that uses a piezoelectric element to eject ink droplets, and a thermal type that uses a heat generating element.

[0004] Of these methods, the thermal method uses a heating element to locally heat the ink in the nozzle, generating bubbles that then push ink droplets out of the nozzle outlet and onto the recording medium. This thermal inkjet printer (hereinafter referred to as a thermal inkjet printer) is configured using a printer head equipped with a heating element that heats the ink and a drive circuit using a logic integrated circuit that drives the heating element.

[0005] An ink composition for a thermal ink jet printer used as ink in a thermal ink jet printer usually contains a colorant, a solvent, and a resin that is soluble in the solvent and serves as a fixing agent.

[0006] Examples of colorants contained in ink compositions include pigments and dyes. Among colorants, black colorants are in particularly high demand. Black colorants include black pigments and black dyes. Black pigments are less likely to discolor due to light or heat, but they have poor color development and may aggregate in the ink composition, resulting in poor storage stability. On the other hand, black dyes have high solubility in organic solvents and excellent color development and storage stability, but they deteriorate and discolor due to heat or light, resulting in poor heat resistance and light fastness. For this reason, metal complex dyes are used as black colorants, which maintain the high solubility in organic solvents inherent to black dyes while exhibiting high heat resistance and light fastness like black pigments and exhibiting a black color.

[0007] On the other hand, in addition to the ketone-based organic solvents such as acetone and methyl ethyl ketone that have been conventionally used as organic solvents contained in ink compositions, from the viewpoints of environmental conservation and ensuring safety for the human body, alcohol-based organic solvents such as ethanol and ethylene glycol, and ether-based organic solvents such as propylene glycol monoalkyl ethers are also used.

[0008] Known black dyes with excellent solubility in alcohol-based organic solvents include amine salts of azochrome complex dyes. 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.

[0009] However, since azochrome complex dyes contain chromium, a harmful heavy metal, their use is being avoided from the viewpoints of environmental conservation and ensuring safety for the human body. 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 studied.

[0010] As one example of such studies, Patent Document 2 proposes a complex mixed dye of three types of disazo compounds and iron as a specific complexing agent. Patent Document 3 also describes a polyazo iron complex dye. 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, but this monoazo iron complex salt compound is black-purple, which does not approach the blackness of azo chrome complex dyes.

[0011] Thermal inkjet printers use thermal energy to eject ink, forcing ink droplets out of ejection ports and onto a recording medium. When the heating elements are heated, the colorants and impurities in the ink decompose, and the decomposed materials deposit on the surface of the heating elements as foreign matter known as koga. This phenomenon, known as kogation, often becomes a problem. When kogation occurs in a thermal inkjet printer, the ink is not heated sufficiently, reducing the ejection speed of ink droplets and impeding their ejection.

[0012] As described above, due to the influence of kogation caused by heating of the heating element, many colorants that can be used in inks for non-thermal ink jet printers that do not involve heating, such as continuous ink jet printers in which ink is continuously extruded from a nozzle by a pump and ejected as fine droplets by an ultrasonic oscillator, cannot be used as colorants for inks for thermal ink jet printers due to their heat resistance, and there is a problem that excellent heat resistance is required.

[0013] Furthermore, cartridges used in thermal inkjet printers have many nozzles. If the colorant has low solubility in the solvent, it will precipitate near the nozzles, clogging the nozzles and causing ink ejection problems. Thus, colorants for inks used in thermal inkjet printers must also have high solubility in the solvent. [Prior art documents] [Patent documents]

[0014] [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]

[0015] The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an ink composition for thermal ink jet printers which does not contain harmful heavy metals, has sufficient solubility in organic solvents for practical use, exhibits a good black color, contains a colorant with excellent heat resistance, and suppresses kogation when heating elements of the thermal ink jet printer are heated. [Means for solving the problem]

[0016] In order to achieve the above object, an ink composition for a thermal ink jet printer is provided, which comprises a colorant, a solvent, and a resin, wherein the colorant is represented by the following chemical formula (1): [ka] (In formula (1), R 1 and R 2 may be the same or different and are linear or branched alkyl groups having 3 to 10 carbon atoms; R 3 is a cyano group, a nitro group, an acetyl group, or a sulfoamide group, and R 4 is a hydrogen atom, 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 halogen atom, or a sulfoamide group, and R 6is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a halogen atom, and R 7 is a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms, and A + is at least one cation selected from a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms and an ammonium ion of a guanidine derivative.

[0017] In the ink composition for a thermal ink jet printer, the colorant further contains a compound represented by the following chemical formula (2): [ka] (In formula (2), R 5 ~R 7 and A + is the same as the formula (1), and / or a monoazo-monoazo iron complex represented by the following chemical formula (3): [ka] (In formula (3), R 1 ~R 4 and A + is the same as the above formula (1).

[0018] The ink composition for a thermal ink jet printer is a compound represented by the formula (1), preferably a compound represented by the formulas (1) to (3), + is represented by the following chemical formula (4) [ka] (In formula (4), R 8 is a linear or branched alkyl group having 1 to 18 carbon atoms, and R 9 and R 10 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms), and [ka] (In formula (5), R 11 and R 12 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms; R 13 is a linear or branched alkyl group having 1 to 18 carbon atoms), and the following chemical formula (6) [ka] (In formula (6), R 14 is a linear or branched alkyl group having 1 to 12 carbon atoms, and / or the following chemical formula (7): [ka] (In formula (7), R 15 is a linear or branched alkyl group having 1 to 18 carbon atoms; and a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms represented by the following chemical formula (8): [ka] (In formula (8), R 16 and R 17 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

[0019] In this ink composition for a thermal inkjet printer, the colorant may have a 5% weight loss temperature of 150° C. or higher.

[0020] In this ink composition for a thermal inkjet printer, the solvent may be a ketone-based solvent and / or an alcohol-based solvent.

[0021] This ink composition for a thermal ink jet printer is filled into a printer cartridge and subjected to 1,500 consecutive prints, and the number of clogged nozzles is NA and the total number of nozzles N0, the following formula (1) Nozzle clogging rate (%) = N A / N0×100 (1) The nozzle clogging rate obtained by the method may be 10% or less. [Effects of the Invention]

[0022] The ink composition for thermal ink jet printers of the present invention contains a non-toxic azo iron complex as a colorant instead of an azo chromium complex containing harmful heavy metals, and therefore is safer for the environment and humans. In addition, the ink composition has high heat resistance, so that kogation that occurs when the heating element of a thermal ink jet printer is heated can be effectively suppressed. Furthermore, the ink composition exhibits a good black color comparable to that of conventional ink compositions containing an azo chromium complex as a colorant.

[0023] This ink composition for thermal inkjet printers has an azo iron complex contained in a colorant that is sufficiently soluble in solvents such as ketone-based solvents and alcohol-based solvents and does not precipitate or deposit over time, so it has stability over time, can suppress nozzle clogging, and has excellent ejection stability. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a nozzle check pattern of an example in which ejection was normal, printed in a continuous printing test using an ink composition for a thermal ink jet printer to which the present invention is applied. [Figure 2] 1 is a nozzle check pattern of a comparative example in which ejection failure occurred when printed in a continuous printing test using an ink composition for a thermal ink jet printer to which the present invention is not applied. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments for carrying out the present invention will be described in detail, but the scope of the present invention is not limited to these embodiments.

[0026] The ink composition for a thermal ink jet printer of the present invention contains, as a colorant, a compound represented by the following chemical formula (1): [ka] (In formula (1), R 1 and R 2 may be the same or different and are linear or branched alkyl groups having 3 to 10 carbon atoms; R 3 is a cyano group, a nitro group, an acetyl group, or a sulfoamide group, and R 4 is a hydrogen atom, 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 halogen atom, or a sulfoamide group, and R 6 is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a halogen atom, and R 7 is a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms, and A + is at least one cation selected from a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms and an ammonium ion of a guanidine derivative.

[0027] If necessary, the colorant may further contain a compound represented by the following chemical formula (2): [ka] (In formula (2), R 5 ~R 7 and A + is the same as formula (1).) and / or a monoazo-monoazo iron complex represented by chemical formula (3) [ka] (In formula (3), R 1 ~R 4 and A + is the same as formula (1).

[0028] The disazo-monoazo iron complex, the monoazo-monoazo iron complex, and the disazo-disazo iron complex are, as shown in chemical formulas (1) to (3), trivalent iron is bonded to the following chemical formula (9): [ka] (In formula (9), R 1 ~R 4 is the same as the chemical formula (1). [ka] (In formula (10), R 5 ~R 7 is the same as chemical formula (1). The compound comprises an azo iron metal complex anion formed by the coordination of a monoazo dye represented by formula (1) with Fe(III), and at least one cation selected from the group consisting of a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms and an ammonium ion of a guanidine derivative.

[0029] In chemical formulas (1) and (3), 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 2-methyl-3-ethylpentyl, 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, and lauryl. Of these, n-butyl, isobutyl, sec-butyl, tert-butyl, isopentyl, and 2-ethylhexyl are preferred.

[0030] In chemical formulas (1) and (3), R 3 is a cyano group, a nitro group, an acetyl group, or a sulfoamide group.

[0031] In chemical formulas (1) and (3), R 4is a hydrogen atom, 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.

[0032] In chemical formulas (1) and (2), R 5 is a nitro group, a halogen atom, or a sulfoamide group. The halogen atoms include fluorine, chlorine, bromine, and iodine.

[0033] In chemical formulas (1) and (2), R 6is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, 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] In chemical formulas (1) and (2), R 7is a hydrogen atom or a straight-chain or branched-chain alkyl group having 1 to 12 carbon atoms. 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 group, a tert-octyl group, a 2-methylheptyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, an n-octyl group, a tert-octyl group, a 2-methylheptyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, a ... Examples of the alkyl group include a methyl group, a 3-methylheptyl group, a 4-methylheptyl group, a 2,2-dimethylhexyl group, a 2,3-dimethylhexyl group, a 2,4-dimethylhexyl group, a 2,5-dimethylhexyl group, a 3,3-dimethylhexyl group, a 3,4-dimethylhexyl group, a 2-ethylhexyl group, a 3-ethylhexyl group, a 2,2,3-trimethylpentyl group, a 2,2,4-trimethylpentyl group, a 2,3,3-trimethylpentyl group, a 2,3,4-trimethylpentyl group, a 2-methyl-3-ethylpentyl group, a 3-methyl-3-ethylpentyl group, and a 2,2,3,3-tetramethylbutyl group, an n-nonyl group, an n-decyl group, a lauryl group, and a dodecyl group. Of these, tert-butyl, isopentyl, hexyl, n-octyl, tert-octyl, 2-ethylhexyl, n-nonyl, n-decyl and dodecyl groups are preferred.

[0035] In chemical formulas (1) to (3), A + When is a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms, it preferably has a structure represented by any one of the following chemical formulas (4) to (8).

[0036] [ka]

[0037] In chemical formula (4), R 8is a linear or branched alkyl group having 1 to 18 carbon atoms, and R 9 and R 10 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

[0038] In chemical formula (4), R 8 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.

[0039] 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.

[0040] [ka]

[0041] In chemical formula (5), R 11 and R 12 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms; R 13 is a straight or branched chain alkyl group having 1 to 18 carbon atoms.

[0042] In chemical formula (5), R 11 and R 12 Specific 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, and a tert-butyl group.

[0043] In chemical formula (5), R 13The 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.

[0044] [ka]

[0045] In chemical formula (6), R 14is a straight-chain or branched-chain alkyl group having 1 to 12 carbon atoms. Specifically, examples thereof 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, 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-methylhexyl group, a Examples of alkyl groups include arylheptyl, 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 undecyl groups.

[0046] [ka]

[0047] In chemical formula (7), R 15is a straight-chain or branched-chain alkyl group having 1 to 18 carbon atoms. Specific examples 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, 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 alkyl acrylates 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.

[0048] In chemical formulas (1) to (3), A + When is an ammonium ion of a guanidine derivative, it preferably has a structure represented by the following chemical formula (8).

[0049] [ka]

[0050] In chemical formula (8), R 16 and R 17 may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

[0051] In chemical formula (8), R 16 and R 17Specific 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, an n-heptyl group, and an n-octyl group.

[0052] A + may be any of the cations represented by chemical formulas (4) to (8), or may be a mixture of two or more types.

[0053] The disazo-monoazo iron complex is a dialkylamino group (-NR in chemical formula (1)) having a specific number 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 The asymmetric structure containing a monoazo dye having the formula (I) and a monoazo dye having the formula (II), results in deep color absorption in the visible light region. Therefore, ink compositions for thermal inkjet printers containing this azo iron complex as a colorant exhibit a deep black color sufficient for practical use.

[0054] Furthermore, when the colorant contains a monoazo-monoazo iron complex represented by chemical formula (2) and / or a disazo-disazo iron complex represented by chemical formula (3) in addition to the disazo-monoazo iron complex represented by chemical formula (1), the blackness, solubility, and dissolution stability of the colorant can be appropriately and arbitrarily adjusted by adjusting the molar ratios of the disazo-monoazo iron complex, the monoazo-monoazo iron complex, and the disazo-disazo iron complex in the colorant to fall within appropriate ranges.

[0055] These molar ratios can be expressed as the peak area ratio in a chromatogram obtained by high performance liquid chromatography at a specific wavelength, for example, 254 nm. Specifically, the disazo-monoazo iron complex:monoazo-monoazo iron complex:disazo-disazo iron complex ratio is preferably 20-70:5-80:0-50, more preferably 20-65:5-80:0-50, and even more preferably 20-55:20-80:0-15.

[0056] These azo iron complexes contain at least one cation selected from the group consisting of a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms and an ammonium ion of a guanidine derivative. This gives the azo iron complex anion excellent solubility in ketone-based and alcohol-based solvents, and they do not precipitate or settle in the solvent over time, making them ideal for inclusion in ink compositions for thermal inkjet printers. Furthermore, because these azo iron complexes do not contain heavy metals such as chromium, which are harmful to the environment and the human body, thermal inkjet printer inks contribute to environmental conservation and are safe for the human body.

[0057] The content of the disazo-monoazo iron complex, monoazo-monoazo iron complex, and / or disazo-disazo iron complex is preferably 0.1 to 30% by mass, more preferably 0.5 to 25% by mass, and even more preferably 1 to 20% by mass, of the total amount of the ink composition for thermal inkjet printers. If the content is less than 0.1% by mass, the coloring power and color development of the ink composition for thermal inkjet printers will be insufficient. If the content exceeds 30% by mass, blurring will occur during printing.

[0058] In the ink composition for thermal inkjet printers, the colorant containing the disazo-monoazo iron complex represented by chemical formula (1) or the colorant containing the disazo-monoazo iron complex and, optionally, the monoazo-monoazo iron complex represented by chemical formula (2) and / or the disazo-disazo iron complex represented by chemical formula (3) has excellent heat resistance, and its 5% weight loss temperature is preferably 150°C or higher, particularly 170°C or higher, and especially 180°C or higher. The 5% weight loss temperature is the temperature at which the weight of a sample to be measured has decreased by 5% from its initial weight (at the start of heating) when the sample is continuously heated from near room temperature to a specific high temperature at a constant heating rate, for example, 10°C / min, in thermogravimetric analysis. The higher the 5% weight loss temperature, the better the heat resistance. A colorant with a 5% weight loss temperature of 150°C or higher can effectively suppress thermal decomposition caused by heating the surface of a heating element in a thermal inkjet printer to a temperature as high as 300°C. Therefore, when this colorant is incorporated into an ink composition for a thermal inkjet printer, the colorant is less likely to thermally decompose even when locally heated by the heating element, effectively suppressing kogation caused by heating of the heating element. Therefore, the ink composition for a thermal inkjet printer containing this colorant can effectively prevent insufficient heating of the ink in the nozzle due to kogation, resulting in a reduction in the ink droplet ejection speed and obstruction of ink droplet ejection. There is no particular upper limit to the 5% weight loss temperature, but it is generally sufficient if it is 300°C or lower.

[0059] In the ink composition for thermal inkjet printers, the colorant containing the disazo-monoazo iron complex represented by chemical formula (1) or the colorant containing the disazo-monoazo iron complex, optionally further containing the monoazo-monoazo iron complex represented by chemical formula (2) and / or the disazo-disazo iron complex represented by chemical formula (3), exhibits excellent solubility in solvents, preferably at least 10%, particularly at least 15%, and especially at least 20% in methyl ethyl ketone. The solubility is measured by preparing a colorant solution by adding the colorant to methyl ethyl ketone at concentrations of 5%, 10%, 15%, and 20%, followed by ultrasonic dispersion for 10 minutes. The colorant solution is then filtered under reduced pressure through a membrane filter (1 μm pore size, PTFE). The concentration at which no undissolved material is visible on the membrane filter is considered the maximum concentration of the azo iron complex dye. A solubility of 10% or higher can prevent nozzle clogging. There is no particular upper limit to the solubility, but it is preferably 50% or less.

[0060] To obtain the colorant, a production method including the following first to fifth steps can be employed. Step 1: A step of obtaining a disazo dye represented by chemical formula (9) using a diazo coupling reaction. Step 2: A step of obtaining a monoazo dye represented by chemical formula (10) using a diazo coupling reaction. The third step is a step of forming an iron complex by subjecting the mixture of the disazo dye and the monoazo dye to iron complex formation to obtain an azo iron complex. Step 4: A step of exchanging and preparing the cation of the azo iron complex. Step 5: The azo iron complex is filtered, washed, dried, and pulverized. According to this manufacturing method, a colorant with high purity can be obtained. Each step will be described in detail below.

[0061] The first step is to obtain the disazo dye capable of becoming a disazo ligand in an azo iron complex.

[0062] (1-1: Synthesis of monoazo compounds) First, as shown in the following chemical reaction formula (11), an aniline derivative is diazotized by a known method, and then a diazo coupling reaction is carried out with a 3-aminophenol derivative by a conventional method to obtain a monoazo compound, which is an intermediate for a disazo dye. [ka] (In formula (11), R 3 and R 4 is the same as chemical formula (1).

[0063] In the reaction of chemical reaction formula (11), specifically, an aqueous solution of an aniline derivative having an electron-withdrawing 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 aniline derivative and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0064] Next, an unsubstituted or alkyl- or alkoxy-substituted 3-aminophenol derivative is dissolved or finely dispersed in an aqueous solution diluted with hydrochloric acid. 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 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, either after drying, or as a solution containing the monoazo compound.

[0065] (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 reaction formula (12), and then subjected to a diazo coupling reaction with a phenol derivative having a specific dialkylamino group by a conventional method to obtain a solution containing a disazo dye. [ka] (In formula (12), middle, R 1 ~R 4 is the same as chemical formula (1).

[0066] In the reaction of chemical reaction formula (12), specifically, an aqueous solution prepared by diluting the monoazo compound obtained in the synthesis of 1-1 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 monoazo compound and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0067] Next, the phenol derivative having a dialkylamino group is dissolved or finely dispersed in an alkaline aqueous solution, and the diazotization solution is added dropwise to the resulting solution. A diazo 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 disazo dye. The disazo dye is filtered and washed with water to obtain a disazo dye wet cake. This wet cake may be used in the subsequent iron complexation step after drying, or may be used as is, or the disazo dye-containing solution may be used as is.

[0068] The second step is a step of obtaining the monoazo dye capable of serving as a monoazo ligand in an azo iron complex.

[0069] First, a 2-aminophenol derivative is diazotized by a known method to obtain a diazotized solution. Specifically, an aqueous solution of a 2-aminophenol derivative having an electron-withdrawing substituent and a hydrogen atom or alkyl group, diluted with hydrochloric acid, and sodium nitrite (e.g., 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 2-aminophenol derivative and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0070] Next, as shown in the following chemical reaction formula (13), the diazo compound in the diazotized solution obtained as described above is subjected to a diazo coupling reaction with a 2-naphthol derivative having a hydrogen atom or an alkyl group by a conventional method to obtain a monoazo dye. [ka] (In formula (13), R 5 ~R 7 is the same as chemical formula (1).

[0071] The reaction of chemical reaction 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.

[0072] In the third step, the disazo dye and monoazo dye obtained in the previous step are reacted with an iron-forming agent to form an iron complex, thereby forming X of the azo-iron complex. + This is the iron complexation process to obtain the anionic form.

[0073] The disazo dye obtained in the first step and the monoazo dye obtained in the second step are charged in a predetermined molar ratio and mixed to obtain a mixed dye. This mixed dye is dispersed or dissolved in a solvent, and a predetermined equivalent amount of iron-containing agent is added to the mixed dye, followed by heating and stirring at 80 to 140°C for 1 to 5 hours. As a result, the X of the disazo-monoazo iron complex, monoazo-monoazo iron complex, and disazo-disazo iron complex is obtained, as shown in the following chemical reaction formula (14). + A mixture of anions is obtained. [ka] (In formula (14), R 1 ~R7 is the same as chemical formula (1), and X + is any cation such as a hydrogen ion derived from an acid or alkali, an alkali metal ion, or an alkaline earth metal ion.

[0074] 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 solvent contained in the ink composition for thermal inkjet printers.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 an azo-iron complex.

[0079] 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.

[0080] The iron complexation step is preferably carried out under heating (including reflux stirring) at a temperature appropriate for the type of solvent used. Additives such as a reaction accelerator or pH adjuster may also be used.

[0081] The fourth step is a step for changing or adjusting the cation of the azo-iron complex. This is an ion exchange step in which an ammonium compound is used to exchange any cation of the azo-iron complex obtained in the third step with a monovalent ammonium ion having an alkyl group and / or an ammonium ion of a guanidine derivative.

[0082] By this cation exchange reaction, an azo iron complex having a monovalent ammonium ion introduced therein, for example, represented by chemical formula (4), is obtained, as shown in the following chemical reaction formula (15). [ka] (In 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.)

[0083] Examples of the ammonium compound include amine compounds having a linear alkyl group having 3 to 37 carbon atoms, such as propylamine, butylamine, pentylamine, hexylamine, octylamine, decylamine, dodecylamine, stearylamine, and N,N-dimethylstearylamine, or branched alkyl groups, such as 8,8-dimethylnonan-1-amine and 9,9-dimethyldecan-1-amine, and guanidine compounds, such as 1,3-diphenylguanidine and 1,3-di-O-tolylanidine. One type of ammonium compound may be used alone, or multiple types may be used in combination.

[0084] The cation exchange reaction in Step 4 can be carried out simultaneously or sequentially with the iron complexation reaction in Step 3. Step 4 may also be carried out by adding an ammonium compounding agent together with an organic solvent when preparing the ink composition.

[0085] The fifth step is carried out as necessary after the fourth step, and optionally includes a filtering step, a washing step, a drying step, and a grinding step.

[0086] A filtration step may be carried out. The filtration step is a step in which the reaction solution containing the azo-iron complex obtained in the fourth step is separated by filtration into a solid azo-iron complex and the solvent to obtain a wet cake of the azo-iron complex. 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, disk filters, drum filters, and Oliver filters; and pressure filtration methods such as filter presses, sealed leaf filters, and sealed multistage filters.

[0087] If necessary, a washing step may be carried out after the filtration step. The wet cake of the azo iron complex 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 as is.

[0088] If necessary, after the washing step, a drying step of drying the wet cake of the azo iron complex may be carried out. The dried azo iron complex in a lump form is crushed or pulverized using a known pulverizer to obtain a desired particle size.

[0089] The content of the solvent contained in the ink composition for thermal inkjet printers is set appropriately depending on the type of solvent and the type and content of the dye and pigment. In the case of ketone-based solvents and / or alcohol-based solvents, the content is preferably 20 to 97% by mass, and more preferably 30 to 95% by mass, of the total amount of the ink composition for thermal inkjet printers.

[0090] Examples of ketone 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 particularly suitable for ink compositions for co-thermal inkjet printers because of its excellent resin solubility, pigment dispersibility, and ink drying properties.

[0091] Alcohol-based solvents include lower alkyl alcohols such as methanol, ethanol, propanol, and isopropanol and butanol; glycols such as dioxane, ethylene glycol, diethylene glycol, and triethylene glycol.

[0092] Other organic solvents 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.

[0093] The organic solvents may be used alone or in combination of two or more.

[0094] The ink composition for thermal inkjet printers contains a resin soluble in the organic solvents described above to improve ink fixation, prevent show-through, improve the solubility and dispersibility of dyes and pigments, and adjust viscosity. Examples of such resins include cellulose-based resins, styrene-acrylic resins, terpene-phenolic 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.

[0095] Examples of cellulose-based resins include nitrocellulose; lower acyl group-substituted celluloses such as cellulose propionate, cellulose butyrate, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate; lower alkyl group-substituted celluloses such as methyl cellulose and ethyl cellulose; cellulose nitrate; and hydroxypropyl cellulose.

[0096] These cellulose resins come in a variety of types, varying in the degree of hydroxyl group substitution and molecular weight, and are selected appropriately depending on the viscosity required for the ink composition. Examples include cellulose esters in which the hydroxyl groups of the cellulose resin are completely 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. 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 have been substituted.

[0097] 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 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.

[0098] 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).

[0099] Terpene phenolic resins are copolymers of terpenes such as α-pinene, β-pinene, and dipentene with phenols such as phenol and bisphenol, and the monomers are selected based on the requirements of the ink composition, and the molar ratio of each monomer is set. Terpene phenolic resins are commercially available, for example, 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.).

[0100] The polyvinyl butyral resin is a copolymer of polyvinyl alcohol and butylaldehyde, and 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 a solvent, 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).

[0101] 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 hydrogenated and / or end-group modified. 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.).

[0102] 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.).

[0103] The ink composition for a thermal inkjet printer may contain a wetting agent. Examples of the wetting agent include surfactants, such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0104] Examples of anionic surfactants include fatty acid salts, alkyl sulfate ester 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 ester salts, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters.

[0105] Examples of cationic surfactants include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, and alkylimidazolium salts.

[0106] 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.

[0107] Examples of amphoteric surfactants include alkyl betaines, alkyl amine oxides, and phosphatidyl cholines.

[0108] In addition to or in place of the humectant, the ink composition for thermal ink jet printers may contain additives to improve print quality, ink fixation, and the solubility stability of the azo-iron complex dye, and to impart desired viscosity and surface tension. Such additives include antifoaming agents, chemical stabilizers, UV stabilizers, stabilizers that inhibit corrosion by salts, biocides such as bactericides and fungicides, and pH adjusters.

[0109] This ink composition for thermal inkjet printers has excellent ejection stability. For example, a method for evaluating this ejection stability can be to use a thermal inkjet printer cartridge with a 4×160 nozzle array, and measure the nozzle clogging rate by dividing the number of clogged nozzles by the total number of nozzles after 1,500 consecutive prints. This nozzle clogging rate is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. A nozzle clogging rate of 10% or less allows for printing without blurring.

[0110] Examples of print media onto which the ink composition for thermal inkjet printers can be ejected from a thermal inkjet printer include slips, cardboard boxes, product packaging, plastic bottles, etc. Examples of plastic materials for plastic bottles include polyolefins such as polyethylene and polypropylene; polyvinyl chloride; polyamide; polyesters such as PET; polycarbonate; polyacetal; polyacrylate; polyurethane; polyether; polystyrene; polyimide, etc.

[0111] Furthermore, this ink composition for thermal inkjet printers can be ejected from a thermal inkjet printer and used for printing 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 to roughen it or pickling it with an acid. [Example]

[0112] Examples to which the present invention is applied and comparative examples to which the present invention is not applied will be described in detail below. In the examples, "%" means "% by mass".

[0113] Synthesis Example 1 (Synthesis Example 1-1: 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.

[0114] 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 solution, 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 (16) was obtained.

[0115] [ka]

[0116] 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.

[0117] In a separate beaker, 88 g (0.40 mol) of N,N-dibutylaminophenol and 133 g of 48% potassium hydroxide aqueous solution were added to 1332 g of methanol and stirred under ice cooling until dissolved. 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 (17).

[0118] [ka]

[0119] (Synthesis Example 1-2: 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.

[0120] 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 (18):

[0121] [ka]

[0122] (Synthesis Example 1-3: Synthesis of azo complex dye 1) 5.3 g (0.011 mol) of the dried wet cake of disazo dye D-1 obtained in Synthesis Example 1-1, 22.1 g (water content 40%, 0.043 mol) of wet cake of monoazo dye M-1 obtained in Synthesis Example 1-2, and 3.6 g (0.060 mol) of urea were added to 120 g of N,N-dimethylformamide solution and stirred for 1 hour at 55°C (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 completion of the dropwise addition, the temperature was raised to 120°C and the mixture was stirred for 3 hours. After the reaction was complete, the mixture 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 10.0. 103.6 g of a 5% aqueous solution of tert-alkyl (C12-C14) primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added to the reaction mixture, which was then 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 complex dye 1, which includes a disazo-monoazo iron complex represented by the following chemical formula (19), a monoazo-monoazo iron complex represented by the following chemical formula (20), and a disazo-disazo iron complex represented by the following chemical formula (21).

[0123] [ka]

[0124] [ka]

[0125] [ka]

[0126] (Confirmation of the composition of azo complex dyes) Azo complex dye 1 obtained in Synthesis Example 1-3 was analyzed by high-performance liquid chromatography under the measurement conditions shown below using a solution prepared by dissolving 1 mg of azo complex dye 1 in 10 ml of dimethylformamide as a measurement sample, and the relative abundance ratios (molar ratios) of the disazo-monoazo iron complex represented by chemical formula (19), the monoazo-monoazo iron complex represented by chemical formula (20), and the disazo-disazo azo iron complex represented by chemical formula (21) contained in azo complex dye 1 were determined from the peak area ratios in the resulting chromatogram. As a result, the molar ratio of disazo-monoazo iron complex represented by chemical formula (19):monoazo-monoazo iron complex represented by chemical formula (20):disazo-disazo azo iron complex represented by chemical formula (21) was 40:59:1. [Measurement conditions] High-performance liquid chromatography analyzer: Prominence (Shimadzu Corporation) Column: L-Column 2 ODS (length 250 mm × inner diameter 4.6 mm, particle size 5 μm; Chemicals Evaluation and Research Institute, Japan) 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 (volume / volume) Solution B: ultrapure water / 10 mM tetraethylammonium aqueous solution (manufactured by Waters) = 500 / 7.5 (volume / volume) Gradient: Solution A / Solution B 50:50 → 70:30 (vol / vol) Detector: PDA (Photo Diode Array) Measurement wavelength: 254nm (ultraviolet)

[0127] (Measurement of 5% weight loss temperature) Using the azo complex dye 1 obtained in Synthesis Example 1-3 as a sample, 2.00 mg of the sample was weighed and subjected to thermogravimetric analysis using a simultaneous differential thermal analyzer (TG-DTA6200EXSTAR6000, Hitachi High-Tech Science Corporation) at a heating rate of 10°C / min from 30°C to 550°C. The temperature at which the sample weight had decreased by 5% from the initial weight (at the start of heating) was read from the chart as the 5% weight loss temperature. The results are shown in Table 1 below.

[0128] Synthesis Example 2 (Synthesis Example 2-1: Synthesis of disazo dye D-2) 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.

[0129] 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.

[0130] [ka]

[0131] 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.

[0132] In a separate beaker, 193.2 g (0.88 mol) of N,N-dibutylaminophenol 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. The pH was adjusted to 4.0 using 35% hydrochloric acid, and the mixture was then 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-2, represented by the following chemical formula (23):

[0133] [ka]

[0134] (Synthesis Example 2-2: Synthesis of monoazo dye M-2) 188.2 g (1.00 mol) of p-aminophenol-4-sulfonamide and 312.5 g of 35% hydrochloric acid were dissolved in 1000 g of ion-exchanged water, and 175.9 g of a 40% aqueous solution of sodium nitrite was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0135] In another beaker, 1000 g of water was placed, 600 g of 20% aqueous sodium hydroxide solution was added, and 144.2 g of 2-naphthol was then added and dispersed. The previously prepared diazonium salt was added dropwise to this dispersion and allowed to react for 3 hours. The pH was then adjusted to 4-5, and the precipitated monoazo compound was filtered and washed with water to obtain a wet cake. This was then dried at 80°C to obtain 308 g of monoazo dye M-2, represented by the following chemical formula (24):

[0136] [ka]

[0137] (Synthesis Example 2-3: Synthesis of azo complex dye 2) 8.4 g (0.016 mol) of the disazo dye D-2 obtained in Synthesis Example 2-1 and 32.6 g (40% water content, 0.038 mol) of the wet cake of the monoazo dye M-2 obtained in Synthesis Example 2-2 were added to 100 g of water and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 3:7 mol). 12.4 g (0.013 mol) of a 41% aqueous solution of ferric sulfate was added dropwise, and after the addition, the temperature was raised to 90°C and stirred for 3 hours. After the reaction was completed, the mixture was allowed to cool to room temperature. 9.0 g of a 20% aqueous solution of sodium hydroxide was added to adjust the pH to 10.0. 103.6 g of a 5% aqueous solution of tert-alkyl (C12-C14) primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added to the reaction mixture, and the mixture was heated and stirred at 40°C for 1 hour. Thereafter, the precipitate was filtered, washed with water, and dried to obtain 23.1 g of azo complex dye 2 containing a disazo-monoazo iron complex represented by the following chemical formula (25), a monoazo-monoazo iron complex represented by the following chemical formula (26), and a disazo-disazo iron complex represented by the following chemical formula (27).

[0138] [ka]

[0139] [ka]

[0140] [ka]

[0141] For the azo complex dye 2 obtained in Synthesis Example 2-3, the relative abundance ratios (molar ratios) of the disazo-monoazo iron complex represented by the above chemical formula (25), the monoazo-monoazo iron complex represented by the above chemical formula (26), and the disazo-disazo iron complex represented by the above chemical formula (27) contained in the azo complex dye 2 were determined in the same manner as in Synthesis Example 1-3. As a result, the molar ratio of the disazo-monoazo iron complex represented by the above chemical formula (25): the monoazo-monoazo iron complex represented by the above chemical formula (26): the disazo-disazo iron complex represented by the above chemical formula (27) was 54:39:7.

[0142] The 5% weight loss temperature of the obtained azo complex salt dye 2 was measured in the same manner as in Synthesis Example 1-3. The results are shown in Table 1 below.

[0143] Synthesis Example 3 (Synthesis Example 3-1: Synthesis of azo complex dye 3) 8.2 g (0.015 mol) of disazo dye D-1 obtained in Synthesis Example 1-1, 11.8 g (0.035 mol) of monoazo dye M-2 obtained in Synthesis Example 2-2, and 3.6 g (0.060) of urea were added to 50 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 3:7 mol). 11.8 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 reaction solution was allowed to cool to 90°C and poured into a beaker containing 200 g of water. To this was gradually added 100.0 g of a 5% aqueous solution of tert-alkyl (C12-C14) primary amine (manufactured by The Dow Chemical Company; trade name PRIMENE 81-R), followed by heating and stirring for 1 hour at 35° C. The precipitate was then filtered, washed with water, and dried to obtain 23.3 g of azo complex dye 3 containing a disazo-monoazo iron complex represented by the following chemical formula (28), a monoazo-monoazo iron complex represented by the following chemical formula (26), and a disazo-disazo iron complex represented by the following chemical formula (21).

[0144] [ka]

[0145] [ka]

[0146] [ka]

[0147] For the azo complex dye 3 obtained in Synthesis Example 3-1, the relative abundance ratios (molar ratios) of the disazo-monoazo iron complex represented by the above chemical formula (28), the monoazo-monoazo iron complex represented by the above chemical formula (26), and the disazo-disazo iron complex represented by the above chemical formula (21) contained in the azo complex dye 3 were determined in the same manner as in Synthesis Example 1-3. As a result, the molar ratio of the disazo-monoazo iron complex represented by the above chemical formula (28): the monoazo-monoazo iron complex represented by the above chemical formula (26): the disazo-disazo iron complex represented by the above chemical formula (21) was 31:67:2.

[0148] The 5% weight loss temperature of the obtained azo complex salt dye 3 was measured in the same manner as in Synthesis Example 1-3. The results are shown in Table 1 below.

[0149] (Comparative Example) The 5% weight loss temperature of an azochrome metal-containing dye (Orasol Black X45, manufactured by BASF) was measured in the same manner as in Synthesis Example 1-3. The results are shown in Table 1 below.

[0150] Table 1 shows the results of measuring the 5% weight loss temperatures of the azo complex salt dyes 1 to 3 obtained in Synthesis Examples 1 to 3 and the azo chrome metal-containing dye of the comparative example.

[0151] [Table 1]

[0152] As shown in Table 1, the azo complex dyes 1 to 3 obtained in Synthesis Examples 1 to 3 all have a high 5% weight loss temperature exceeding 180°C, second only to the azo chrome metal-containing dyes, and have excellent heat resistance. Therefore, when they are blended as colorants in ink compositions for thermal inkjet printers and used in thermal inkjet printers, kogation can be effectively prevented.

[0153] Azo-iron complex dyes 1-3 obtained in Synthesis Examples 1-3 and the azo chrome complex of the comparative example were added to methyl ethyl ketone to prepare azo metal complex dye solutions at concentrations of 5%, 10%, 15%, and 20%, and ultrasonically dispersed for 10 minutes. The azo metal 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 results are shown in Table 2.

[0154] [Table 2]

[0155] The azo iron complex dyes 1 to 3 obtained in Synthesis Examples 1 to 3 exhibited high solubilities of 10% or more in methyl ethyl ketone. On the other hand, the azo chromium complex dye of the comparative example generated a large amount of residue when added at 5%, and its solubility was low.

[0156] Thermal inkjet printer inks were prepared using the azo-based iron complex dyes 1-3 obtained in Synthesis Examples 1-3 and the comparative azochromium complex dyes according to the following procedure. 1.80 g of YS POLYSTER U115 (manufactured by Yasuhara Chemical Co., Ltd.) and 1.80 g of PGMEA were added to a 300 mL reaction vessel, and then mixed with 79.20 g of MEK, 73.80 g of 1,3-dioxolane, 1.80 g of 1-propanol, and 0.18 g of BYK®-3550 (manufactured by BYK-Chemie) to dissolve the mixture. After stirring for 45 minutes, 1.80 g of PGME was added and stirred for an additional 25 minutes. Next, 18.0 g of dye was added, and the mixture was stirred for 1 hour. After filtration using No. 3100 filter paper, thermal inkjet printer inks were obtained.

[0157] The resulting inks were filled into ink cartridges (640 nozzles: N0), and the nozzle check pattern shown in Figure 1 was printed 1,500 times continuously using a thermal inkjet printer (Funai Electric Co., Ltd.). A straight line was printed from a normal nozzle, and either nothing was printed (missing lines) or a distorted line (distortion) was printed from a nozzle with an ejection error. The total number of missing lines and distortions (N A The blockage rate was calculated using the following formula (1) and the results are shown in Table 3. Nozzle clogging rate (%) = N A / N0×100 (1)

[0158] [Table 3]

[0159] As shown in Table 3, the thermal inkjet printer inks containing the azo iron complex salt dyes 1 to 3 obtained in Synthesis Examples 1 to 3 showed only 0 to 40 nozzles with ejection defects even after 1,500 consecutive print runs, and the clogging rate was low at 0 to 6.3%. In particular, the thermal inkjet printer inks containing the azo iron complex salt dyes 1 and 2 obtained in Synthesis Examples 1 and 2 showed almost no ejection defects even after 1,500 consecutive print runs, and printed a nozzle check pattern as shown in Figure 1. On the other hand, the thermal inkjet printer ink containing the comparative azo chrome complex dye showed many nozzles with ejection defects, and printed a nozzle check pattern with many chips and distortions, as shown in Figure 2. Furthermore, the resulting nozzle check pattern was strongly bluish and could not be described as black.

[0160] As shown in Tables 1 to 3, the azo iron complex dyes 1 to 3 obtained in Synthesis Examples 1 to 3 have both heat resistance and solubility in solvents, and are therefore suitable for use in inks for thermal inkjet printers. On the other hand, the azo chromium complexes of the comparative examples have high heat resistance, but their low solubility in solvents causes ejection defects and makes them unsuitable for use in inks for thermal inkjet printers.

[0161] Furthermore, the ink compositions for thermal inkjet printers containing the above-mentioned azo complex salt dyes 1 to 3 as colorants contain azo complex salt dyes that are relatively safe, but do not contain metals such as chromium used in the comparative examples, and therefore are excellent in safety and environmental friendliness. [Industrial Applicability]

[0162] The ink composition for thermal ink jet printers of the present invention can be suitably used in thermal ink jet printers.

Claims

1. An ink composition for a thermal ink jet printer, comprising a colorant, a solvent, and a resin, wherein the colorant is represented by the following chemical formula (1): 【Chemistry 1】 (In formula (1), R １ and R ２ may be the same or different and are linear or branched alkyl groups having 3 to 10 carbon atoms; R ３ is a cyano group, a nitro group, an acetyl group, or a sulfoamide group, and R ４ is a hydrogen atom, 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 halogen atom or a sulfoamide group, and R ６ is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a halogen atom; R ７ is a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms, ＋ is at least one cation selected from the group consisting of a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms and an ammonium ion of a guanidine derivative.

2. The colorant further comprises a compound represented by the following chemical formula (2): 【Chemistry 2】 (In formula (2), R ５ ~R ７ and A ＋ is the same as the formula (1), and / or a monoazo-monoazo iron complex represented by the following chemical formula (3): 【Transformation 3】 (In formula (3), R １ ~R ４ and A ＋ is the same as the formula (1).

2. The ink composition for a thermal ink-jet printer according to claim 1, comprising a disazo-disazo iron complex represented by the formula (1).

3. In the chemical formula (1), A ＋ is represented by the following chemical formula (4) 【Chemistry 4】 (In formula (4), R ８ is a linear or branched alkyl group having 1 to 18 carbon atoms, and R ９ and R １０ may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, and 【Transformation 5】 (In formula (5), R １１ and R １２ may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms; R １３ is a linear or branched alkyl group having 1 to 18 carbon atoms, and the following chemical formula (6) 【Transformation 6】 (In formula (6), R １４ is a linear or branched alkyl group having 1 to 12 carbon atoms, and / or the following chemical formula (7): 【Transformation 7】 (In formula (7), R １５ is a linear or branched alkyl group having 1 to 18 carbon atoms; and a monovalent ammonium ion having a linear and / or branched alkyl group having 3 to 37 carbon atoms represented by the following chemical formula (8): 【Transformation 8】 (In formula (8), R １６ and R １７ and n may be the same or different and are a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

4. 2. The ink composition for a thermal ink jet printer according to claim 1, wherein the colorant has a 5% weight loss temperature of 150[deg.] C. or higher.

5. 2. The ink composition for a thermal ink jet printer according to claim 1, wherein the solvent is a ketone-based solvent and / or an alcohol-based solvent.

6. The ink composition for a thermal ink jet printer was filled into a printer cartridge, and when 1,500 consecutive prints were performed, the number of clogged nozzles N Ａ and the total number of nozzles N ０ From the following formula (1): Nozzle clogging rate (%) = N Ａ / N ０ × 100 ... (1) 2. The ink composition for a thermal ink jet printer according to claim 1, wherein the nozzle clogging rate obtained by the method of claim 1 is 10% or less.

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