Ink composition for writing instruments

Abstract

To provide an ink composition for writing instruments that exhibits excellent lightfastness and storage stability. [Solution] The ink composition contains at least an azo iron dye represented by formula (α). TIFF2026113016000037.tif62119 [In the formula, R 1 R is a hydrogen atom and an alkyl group having 1 to 12 carbon atoms. 2 , R 3 A is an alkyl group having 3 to 10 carbon atoms. + This represents a monovalent ammonium ion or a guanidine derivative ammonium ion having an alkyl group with 3 to 18 carbon atoms.

Description

[Technical Field]

[0001] This invention relates to an ink composition for writing instruments that has a high degree of blackness while also exhibiting excellent lightfastness and storage stability. [Background technology]

[0002] Traditionally, in order to create black ink compositions for writing instruments and other applications that provide fastness, primarily lightfastness, using black dyes, it has been necessary to use dyes with a heavy metal complex structure. Generally, these complexes often contain harmful heavy metals [heavy metals specified in the European standard: Toy Safety EN71-3:2019 and the International Toy Safety Standard (ISO8124-3), Part 3 of the International Toy Safety Standard (ISO8124-3) established by the International Organization for Standardization, such as Cr, Co, Cd, and Pb].

[0003] In current circumstances, it is necessary to address environmental impact and heavy metal regulations in various countries, and there is a demand for the use of dyes that do not contain heavy metals. However, simply dissolving heavy metal-free dyes directly in oily solvents or emulsifying them into inks results in poor lightfastness, insufficient blackness (bluish-black or reddish-black), and poor storage stability.

[0004] On the other hand, conventionally, oil-soluble black colorants such as azo iron dyes of a specific structure are known to be free of harmful heavy metals, have sufficient solubility in organic solvents for practical use, and exhibit a good black color (see, for example, Patent Documents 1 and 2). On the other hand, a higher quality oil-based black ink composition is known that suppresses the bleeding of dyes other than black from the handwriting, and is characterized by comprising a black dye such as CI Solvent Black 7 as the main colorant, an organic solvent consisting of a glycol ether-based solvent or an alcohol-based solvent, a black dye soluble in the organic solvent, a secondary dye which is a yellow dye such as CI Acid Yellow 42, which is soluble in the organic solvent and has a polarity index of 5.0 or higher represented by a specific formula, and a resin soluble in the organic solvent (see, for example, Patent Document 3).

[0005] However, the azo iron dyes of specific structures described in the above-mentioned Patent Documents 1 and 2 are oil-soluble black colorants, and still have issues such as unstable storage stability in oily environments and insufficient fastness, particularly in lightfastness. Furthermore, there is no disclosure regarding their application in aqueous solutions or their potential for use. Furthermore, while the black ink composition described in Patent Document 3 is suitable for oil-based writing instrument inks, its storage stability is still unstable, its lightfastness is not sufficient, and there is no disclosure regarding its application to aqueous solutions. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-222751 (Claims, Examples, etc.) [Patent Document 2] International Publication No. 2022 / 163736 (Claims, Examples, etc.) [Patent Document 3] Japanese Patent Publication No. 2022-172778 (Claims, Examples, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0007] In view of the problems of the above prior art, etc., the present invention aims to solve these problems. While using a dye that does not contain harmful heavy metals [heavy metals specified in European standard: Safety of toys EN71-3:2019 and international toy safety standard (ISO8124-3)], it responds to environmental loads and heavy metal regulations in various countries. In particular, it provides an ink composition for writing instruments that has excellent fastness centered on lightfastness, has storage stability, and exhibits blackness with a wide absorption spectrum.

Means for Solving the Problems

[0008] In view of the above conventional problems, etc., as a result of intensive research, the present inventor has found that, at least by containing a specific black dye, etc., an ink composition for writing instruments of the above object can be obtained, and has thus completed the present invention.

[0009] That is, the ink composition for writing instruments of the present invention is characterized by containing at least an azo iron dye represented by the following formula (α) or the following formula (β).

Chemical formula

Chemical formula

[0010] The present invention provides a writing instrument ink composition that is black in color while also having excellent drying properties, water resistance, light resistance, and storage stability, and a writing instrument equipped with this writing instrument ink composition. The object and effect of the present invention are recognized and obtained, in particular, by using the components and combinations indicated in the claims. Both the general description above and the detailed description below are illustrative and descriptive, and do not limit the present invention as described in the claims. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below. However, it should be noted that the technical scope of the present invention is not limited to each of the embodiments described below, but extends to the invention described in the claims and its equivalents. The ink composition for writing instruments of the present invention is characterized by containing at least an azo iron dye represented by the following formula (α) or formula (β).

[0012] [ka] [In the above formula (α), R 1 These are identical or different, hydrogen atoms, and alkyl groups having 1 to 12 carbon atoms, R 2 , R3 These are identical or different alkyl groups having 3 to 10 carbon atoms, and A + This indicates a residue obtained from a monovalent ammonium ion or a guanidine derivative ammonium ion having an alkyl group with 3 to 18 carbon atoms. [ka] [In the above formula (β), R 1 and R 2 These are linear or branched alkyl groups having 3 to 10 carbon atoms, and R 3 R is an electron-withdrawing group, 4 R 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. 5 R is a nitro group, a sulfoamide group, or a halogen atom. 6 R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. 7 A is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms. + This indicates a monovalent cation.

[0013] The azo iron dye used in the present invention is selected from at least one azo iron dye that is a black dye represented by the above formula (α) or (β), among dyes in which an azo dye having a complex-forming group such as a hydroxyl group (-OH) or a carboxyl group (-COOH) at the ortho position of each aromatic ring linked by an azo group (-N=N-) forms a complex salt with iron (Fe: metal).

[0014] <Azo iron dye that becomes a black dye represented by formula (α)> The azo iron dye shown in formula (α) above, which can be used, has a 2:1 complex structure in which a monoazo dye and trivalent iron form an anion that is bound to an ammonium ion. The azo iron dye represented by formula (α) is preferably the following formula (α-1) [ka] [In formula (α-1), R 2 , R 3 These are identical or different alkyl groups having 3 to 10 carbon atoms, and A + The formula is (α-2) [ka] (In formula (α-2), R 4 , R 6 These are identical or different, and represent a hydrogen atom and an alkyl group having 1 to 8 carbon atoms, R 5 represents an alkyl group having 1 to 18 carbon atoms. ) represents an ammonium ion or the following formula (α-3) [ka] (In formula (α-3), R 7 , R 8 It is an ammonium ion of a guanidine derivative represented by ), which is either the same or different and represents a hydrogen atom and an alkyl group having 1 to 8 carbon atoms. It is preferable that it is an azo iron dye represented by ].

[0015] A preferred embodiment of the azo iron dye of formula (α) of the present invention is the azo iron dye shown in formula (α-1) below. [ka] (In formula (α-1), R 2 , R 3 These are identical or different alkyl groups having 3 to 10 carbon atoms, and A + This is a residue obtained from a monovalent ammonium ion or a guanidine derivative ammonium ion having an alkyl group with 3 to 18 carbon atoms. The nitro group substituent in the azo iron dye shown in formula (α) above has a color-deepening effect, and when substituted at the p-position of the azo group shown in formula (5), the color-deepening effect is maximized, resulting in a jet-black color. Furthermore, it is preferable that the counterion of the azo iron dye shown in formula (α-1) is an ammonium ion represented by formula (α-2) or an ammonium ion of a guanidine derivative represented by formula (α-3). A mixture of ammonium ions represented by formula (α-2) or ammonium ions of guanidine derivatives represented by formula (α-3) may be used.

[0016] The substituent R of the azo iron dye shown in formula (α) or formula (α-1) above 1 The alkyl group is a linear or branched alkyl group having 1 to 12 carbon atoms. More specifically, examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neo-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-decyl group, and lauryl group. I-butyl group, sec-butyl group, t-butyl group, i-pentyl group, and 2-ethylhexyl group are even more preferred. Furthermore, substituent R of the azo iron dye shown in formula (α) or formula (α-1) above 2 , R 3 The alkyl group is a linear or branched alkyl group having 3 to 10 carbon atoms, more preferably a linear or branched alkyl group having 3 to 8 carbon atoms. More specifically, examples include n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neo-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, and 2-ethylhexyl group. Furthermore, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, i-pentyl group, n-hexyl group, n-octyl group, and 2-ethylhexyl group are preferred.

[0017] In the above equation (α-2), R 4 , R 6The alkyl groups are identical or different, linear or branched alkyl groups having 1 to 8 carbon atoms. Specifically, examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neo-pentyl group, n-hexyl group, n-heptyl group, and n-octyl group. Preferably, it is a methyl group. The alkyl group R5 in formula (3) is a linear or branched alkyl group having 1 to 18 carbon atoms. Specifically, examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neo-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-decyl group, todecyl group, lauryl group, stearyl group, and the like. Preferably, it is a linear or branched alkyl group having 7 to 16 carbon atoms, and particularly preferably, it is a branched alkyl group having 8 to 15 carbon atoms.

[0018] R in the above equation (α-3) 7 , R 8 The alkyl groups are identical or different, linear or branched alkyl groups having 1 to 8 carbon atoms. Specifically, examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neo-pentyl group, n-hexyl group, n-heptyl group, and n-octyl group. Preferably, it is a methyl group.

[0019] The black azo iron dye represented by (α) above has an amino group in its molecule, which is formed by bonding a nitro group to two alkyl groups with a specific range of carbon atoms. This causes the absorption wavelength in the visible light range to deepen in the azo iron complex, allowing it to exhibit a sufficiently black color for practical use. As a result, it avoids the use of certain transition metals that are avoided due to environmental concerns, such as chromium and cobalt, and also avoids the risks associated with hexavalent chromium. Furthermore, in colorants that use subtractive color mixing with the three primary colors to create black, the color changes significantly when fading because each colorant has different fastness, solubility, and hue. In contrast, the black azo iron dye described in (1) above is a single colorant that exhibits a deep black color and shows little discoloration after fading.

[0020] The method for producing the black azo iron dye represented by (α) above is known and includes at least the following steps: Step 1: obtaining a monoazo dye by a diazotization coupling reaction; Step 2: ironizing the monoazo dye to obtain an azo iron dye; Step 3: adjusting the counterions of the obtained azo iron dye; Step 4: filtering and washing the obtained azo iron dye with water; and Step 5: drying the filtered azo iron dye. By doing so, a high-purity black azo iron dye represented by (α) above can be obtained. The black azo iron dye represented by (α) above can be obtained by the above manufacturing method, or if a commercially available product is available, that can be used.

[0021] Examples of black azo iron dyes that can be specifically used, represented by (α) above, include compounds X1 to X17 and Y1 to Y9 shown in Tables 1 and 2 below, in the chemical formula shown by formula (α-4) below. [ka]

[0022] [Table 1]

[0023] [Table 2]

[0024] <Azo iron dye that becomes a black dye represented by formula (β)> Next, the black azo iron dye represented by the following formula (β) is: [ka] In the above formula (β), R 1 and R 2 These are linear or branched alkyl groups having 3 to 10 carbon atoms, and R 3 R is an electron-withdrawing group, 4 R 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. 5 R is a nitro group, a sulfoamide group, or a halogen atom. 6 R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. 7 A is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms. + This includes a disazo-monoazo iron complex represented by a monovalent cation.

[0025] The azo iron dye represented by the above formula (β) used is R 3 The electron-withdrawing group is bonded to the azo group on the same aromatic ring at the para position and may be selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom. This azo iron dye, for example, has the following chemical formula (β-1) [ka] (In chemical formula (β-1I), R 5 ~R 7 and A + This includes monoazo-monoazo iron complexes, which are identical to chemical formula (β). The azo iron dyes that can be used are those with the following chemical formula (β-2) [ka] (In chemical formula (β-2), R 1 ~R 4 and A + It may also contain a disazo-disazo iron complex represented by the chemical formula (β), which is identical to (β).

[0026] This azo iron dye, for example, has a monovalent cation that is an alkali metal ion, an ammonium ion, and the following chemical formula (β-3) [ka] (In chemical formula (β-3), R 8 R is a linear or branched alkyl group having 1 to 18 carbon atoms. 9 and R 10 The elements are, independently of each other, hydrogen atoms or linear or branched alkyl groups having 1 to 8 carbon atoms. The ammonium ions include at least one selected from monovalent alkyl groups represented by ().

[0027] The azo iron dyes that can be used may have peak area ratios of 20-70:5-80:0-50, respectively, of the chromatograms obtained by measuring the disazo-monoazo iron complex, the monoazo-monoazo iron complex, and the disazo-disazo iron complex at a wavelength of 254 nm in high-performance liquid chromatography.

[0028] The method for producing the azo iron dye used is as follows: [ka] (In chemical formula (β-4), R 1 and R 2 These are linear or branched alkyl groups having 3 to 10 carbon atoms, and R 3 R is an electron-withdrawing group, 4 (where 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.) Disazo dyes represented by the following chemical formula (β-5)

[0029] [ka] (In chemical formula (β-5), R 5 R is a nitro group, a sulfoamide group, or a halogen atom. 6R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. 7 The present invention provides a disazo-monoazo iron complex represented by the above chemical formula (I), comprising an iron complexization step of heating a monoazo dye represented by ( ) and an ironizing 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 agent to introduce a cation to be combined with the azo iron complex anion.

[0030] The disazo-monoazo iron complex contained in the azo iron dye used has a structure in which a monovalent cation is bonded to an azo iron complex anion containing trivalent iron and an azo ligand formed by combining the disazo dye and the monoazo dye in a 1:2 molar ratio, as can be seen from formula (β) above. In the above formula (β), R 1 and R 2These are linear or branched alkyl groups with 3 to 10 carbon atoms. Specifically, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, 2-methylheptyl group, 3-methylheptyl Examples of these groups include 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, and 2,2,3,3-tetramethylbutyl group, n-nonyl group, n-decyl group, and lauryl group. Among these, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, and 2-ethylhexyl group are preferred. In the above formula (β), R 3 R is an electron-withdrawing group, specifically including cyano groups, nitro groups, acetyl groups, sulfoamide groups, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. 3 When these are electron-withdrawing groups, the color-deepening effect of the azo iron dye is enhanced, and a sufficiently deep black color can be obtained for practical use. 3 It is preferable in terms of deepening the color if the compound is bonded to the azo group on the same aromatic ring at the para position.

[0031] Such disazo-monoazo iron complexes are specifically represented by the following chemical formula (β-6) [ka] (In chemical formula (β-6), R 1 ~R 7 and A + This is identical to the chemical formula (β). In the chemical formula (β), R 4 This group 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. Specifically, examples of this alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, and neopentyl groups, and examples of this alkoxy group include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy, and neopentyloxy groups.

[0032] Such disazo-monoazo iron complexes are specifically represented by the following chemical formula (β-7) [ka] (In chemical formula (β-7), R 1 ~R 7 and A + This is identical to the chemical formula (β). In the chemical formula (β), R 5 R is an electron-withdrawing substituent such as a nitro group, a sulfoamide group, or a halogen atom. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. 5 It is preferable that the compound is bonded at the 4th or 5th position relative to the azo group on the aromatic ring to which it is bonded, as this further improves the blackness of the disazo-monoazo iron complex and allows for a sufficiently deep black color to be obtained for practical use.

[0033] In the chemical formula (β), R 6The group consists of a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. Examples of alkyl groups include methyl, ethyl, 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, and n-octyl groups. Examples of halogen atoms include 2-methylheptyl group, 3-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, and 2,2,3,3-tetramethylbutyl group. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0034] Such disazo-monoazo iron complexes are specifically represented by the following chemical formula (β-8a): [ka] (In chemical formula (β-8a), R 1 ~R 7 and A + This is identical to the chemical formula (β). ) and the following chemical formula (β-8b) [ka] (In chemical formula (β-8b), R 1 ~R 7 and A + This is identical to the chemical formula (β).

[0035] In chemical formula (β), R 7 is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms. Examples of such an alkyl group include n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, tert-octyl group, 2-methylheptyl group, 3-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, and 2,2,3,3-tetramethylbutyl group, n-nonyl group, n-decyl group, lauryl group, and dodecyl group. Among them, tert-butyl group, isopentyl group, hexyl group, n-octyl group, tert-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, and dodecyl group are preferred.

[0036] Such a disazo-monoazo iron complex is specifically represented by the following chemical formula ((β-9a)

Chemical formula

[0037] In the above chemical formula (β), A + is a monovalent cation. Examples of this monovalent cation include hydrogen ion, alkali metal ion, ammonium ion (NH4 + ), and monovalent alkyl group-containing ammonium ion. <​​​​​​​​​​​​​​ In the above chemical formula (β-3), R 8 R is a linear or branched alkyl group having 1 to 18 carbon atoms. 9 and R 10 R is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, independently of each other. 7 The alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, 2-methylheptyl group, and 3-methylheptyl Examples of these groups include 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, and 2,2,3,3-tetramethylbutyl group, n-nonyl group, n-decyl group, undecyl group, lauryl group, and stearyl group. In particular, it is preferable that the alkyl group has 7 to 18 carbon atoms and is a straight or branched chain, more preferably that it has 8 to 15 carbon atoms and is a branched chain, and even more preferably that it has 11 to 14 carbon atoms and is a branched chain.

[0039] In the above chemical formula (β-3), R 9 and R 10Examples of alkyl groups 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. Among these, the methyl group is preferred. The disazo-monoazo iron complex, which is essential to the azo iron dye represented by (β) above in the present invention, is an amino group to which a dialkyl group having a specific range of carbon atoms is attached (-NR in chemical formula (β)). 1 R 2 ) and electron-withdrawing groups (same -R 3 A disazo ligand having a disazo ligand and an electron-withdrawing group (same -R 5 and / or -R 6 Due to its asymmetrical structure containing a monoazo ligand, the azo iron dye deepens in color, absorbing wavelengths in the visible light range and exhibiting a deep black color sufficient for practical use. Moreover, the aromatic ring of the disazo ligand is composed solely of arylene groups and does not contain a naphthalene ring, which is bulky and causes high molecular weight. Therefore, this azo iron dye has a lower molecular weight compared to azo iron dyes containing a naphthalene ring-containing disazo ligand, and thus exhibits high color development even in small amounts.

[0040] Furthermore, this disazo-monoazo iron complex has alkali metal ions, ammonium ions, and / or monovalent alkyl group-containing ammonium ions with an alkyl group having a specific range of carbon atoms as cations, thereby improving the solubility of the black azo iron complex anion. As a result, the azo iron dye represented by (β) above exhibits high solubility in alcohol-based organic solvents such as ethanol and ethylene glycol, and ketone-based organic solvents such as methyl ethyl ketone, making it practical as an ink composition, and also has high solubility stability, so it does not precipitate or precipitate in organic solvents. Moreover, since the azo iron dye does not contain chromium or cobalt, which are heavy metals harmful to the environment and human health, it can contribute to environmental protection and ensure safety for human health. In addition to the disazo-monoazo iron complex represented by the above chemical formula (β), it is preferable to further include a monoazo-monoazo iron complex having only the monoazo ligand, which is a ligand of the disazo-monoazo iron complex, and / or a disazo-disazo iron complex having only the disazo ligand.

[0041] This monoazo-monoazo iron complex has the chemical formula (β-1) (where R is located in the chemical formula (β-1)). 5 ~R 7 and A + The chemical formula (β) is the same as the chemical formula (β). The disazo-disazo iron complex is represented by the above chemical formula (β-2) (in the chemical formula (β-2), R 1 ~R 4 and A + This is identical to the chemical formula (β). When the azo iron dye represented by (β) above can be used includes disazo-monoazo iron complex (DM), monoazo-monoazo iron complex (MM), and disazo-disazo iron complex (DD), their molar ratios can be expressed as the peak area ratio in the chromatogram obtained when measured by high-performance liquid chromatography at a specific wavelength, for example, 254 nm. Specifically, a ratio of DM:MM:DD = 20-70:5-80:0-50 is preferred, 20-65:5-80:0-50 is more preferred, 20-60:20-80:0-30 is even more preferred, and 20-55:20-80:0-15 is even more preferred. The lower limit for the DD is 1 instead of 0. The above values ​​are obtained by calculating the peak area ratio to one decimal place and rounding it. For example, the notation 0, which is the lower limit for the DD field, includes values ​​greater than 0.0, specifically values ​​between 0.1 and 0.4.

[0042] The azo iron dye represented by (β) above, in addition to the asymmetric azo iron complex disazo-monoazo iron complex, further contains symmetric azo iron dyes such as monoazo-monoazo iron complexes having only monoazo ligands and / or disazo-disazo iron complexes having only disazo ligands, and by setting the ratio of each azo iron complex in the azo iron complex within an appropriate range, the blackness, solubility, and solubility stability of the azo iron dye can be further improved. Furthermore, the azo iron dye represented by (β) above preferably has an electrical conductivity K of 300 to 2200 μS / cm, and more preferably 600 to 2000 μS / cm. This 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 dye and immersing them in the solution. Furthermore, the alkali metal ion content of the azo iron dye is preferably 1000 ppm or less, and more preferably 500 ppm or less. Furthermore, additives such as leveling agents and anti-repellent agents contained in writing instrument ink compositions may contain silicone compounds or silicone-based surfactants. If the alkali metal ion content of the azo iron dye is within the above range, the formation of complexes between these silicone compounds and silicone-based surfactants and alkali metal ions can be suppressed, thereby preventing clogging in the ink reservoir and pen tip.

[0043] The production of azo iron dyes containing azo iron complexes represented by the above chemical formulas (β) to (β-2) is known, and can be carried out, for example, by employing a production method having the following steps 1 to 5. Step 1: Step to obtain a disazo dye using a diazo coupling reaction. Step 2: Step to obtain a monoazo dye using a diazo coupling reaction. Step 3: Process to obtain an azo iron dye by iron complexing a mixture of disazo dyes and monoazo dyes. Step 4: Process of modifying and preparing the cation of the azo iron dye. Step 5: The process of filtering, washing, drying, and grinding the azo iron dye. According to this manufacturing method, azo iron dyes containing azo iron complexes represented by the above chemical formulas (β) to (β-2) can be produced with high purity. The black azo iron dyes represented by (β) above can be those obtained by the above manufacturing method, or commercially available dyes can be used if available.

[0044] Examples of black azo iron dyes represented by the above formula (α) or (β) that can be specifically used are listed below. An example of a black azo iron dye represented by the above formula (α) is the azo iron dye shown in the following formula (α-5). The production of this azo iron dye shown in formula (α-5) is known and is briefly explained below. Note that the amount of each component used, the reaction time, the reaction temperature, etc. are predetermined amounts, predetermined times, predetermined temperatures, etc. [ka]

[0045] The azo iron dye represented by formula (α-5) was prepared by dissolving 5-nitro-2-aminophenol and 35 wt% concentrated hydrochloric acid in isopropanol as starting materials, and gradually adding a 36 wt% aqueous sodium nitrite solution while cooling in an ice bath to diazotize and obtain a diazonium salt. Meanwhile, a 20 wt% aqueous sodium hydroxide solution was added to water, and N,N-di-n-butyl-3-aminophenol was added and dispersed. The diazonium salt was then added dropwise to this dispersion and reacted. After adjusting the pH to 2.6, the precipitated monoazo compound was filtered off, washed with water, and a predetermined amount of wet cake was obtained. To the obtained wet cake of monoazo compound, a 20 wt% aqueous sodium hydroxide solution, water, and n-butanol were added and stirred at a predetermined temperature for a predetermined time, and then a 40 wt% aqueous ferric sulfate solution was gradually added and the reaction was carried out at a predetermined temperature for a predetermined time. After the reaction, the mixture was cooled to room temperature and adjusted to pH 2.5. The precipitated product was filtered and washed with water to obtain a wet cake. Water and methanol were added to the wet cake of the iron complex compound and heated to a predetermined temperature. An aqueous solution prepared in advance with water, 35 wt% concentrated hydrochloric acid, and 1,3-di-O-tolylguanidine was gradually added to this solution. After stirring at a predetermined temperature for an initial time, the mixture was filtered, washed with water, and dried to obtain the azo iron dye represented by the above formula (α-6).

[0046] Examples of black azo iron dyes represented by the above formula (β) include the disazo dye D-1 shown in the following formula (β-10a) and the monoazo dye M-1 shown in the following formula (β-10b), and the azo iron dyes shown in the following formulas (β-11a), (β-11b), and (β-11c). [ka] [ka] [ka] [ka] [ka]

[0047] The production of azo iron dyes represented by formulas (β-11a), (β-11b), and (β-11c) is known and is briefly explained below. The production of the azo iron dyes shown in these formulas was carried out by adding the disazo dye D-1 of formula (β-10a) and the monoazo dye M-1 of formula (β-10b) to an N,N-dimethylformamide solution and stirring at a predetermined temperature for a predetermined time (disazo dye:monoazo dye = 2:8 mol). A 41% aqueous ferric sulfate solution was then added dropwise, and after the addition was complete, the temperature was raised to a predetermined temperature and stirred for a predetermined time. After the reaction was complete, the mixture was allowed to cool to room temperature, and a 20% aqueous sodium hydroxide solution was added to adjust the pH to 10.0. A 5% aqueous tert-alkyl (C12~C14) primary amine solution was gradually added to the reaction mixture and heated and stirred at a predetermined temperature for a predetermined time. Subsequently, the precipitate was filtered, washed with water, and dried to obtain an azo iron complex dye containing the disazo-monoazo iron complex represented by the above chemical formula (β-11a) (DM form), the monoazo-monoazo iron complex represented by the above chemical formula (β-11b) (MM form), and the disazo-disazo iron complex represented by the above chemical formula (β-11c) (DD form).

[0048] <Ink composition for writing instruments> The ink composition for writing instruments of the present invention is characterized by containing at least one black dye selected from azo iron dyes that are black dyes represented by the following formula (α) or formula (β), and can be used as an ink composition for writing instruments such as ballpoint pens and marking pens. Preferably, the azo iron dye represented by (α) or formula (β) is dissolved in a solvent with a water solubility of 1% by mass or more, from the standpoint of color development, drying speed, water resistance, and not containing regulated heavy metals. In this invention, "water solubility" refers to the solubility in water at 25°C (water solubility). Examples of solvents with a water solubility of 1% by mass or more include methanol, ethanol, propylene glycol monomethyl ether, isopropanol, 1-propanol, butanol, 3-methoxy-3-methyl-1-butanol, tert-butanol, 2-ethylhexanol, benzyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, glycerin, diglycerin, methyl carbitol, cyclohexanol, ethyl carbitol, butyl carbitol, and methyl triglycol. More preferably, ethanol (water solubility 100%), isopropanol (water solubility 100%), 1-propanol (water solubility 10%), 3-methoxy-3-methyl-1-butanol (water solubility 10%), benzyl alcohol (water solubility 3.5%), and ethyl acetate (water solubility 8.7%) are used. As a method for preparing a solvent with a water solubility of 1% by mass or more, formula (α) or formula (β) can be easily prepared, for example, by stirring at room temperature for 2 hours.

[0049] In this invention, by using a solution in which an azo iron dye represented by formula (α) or formula (β) is dissolved in a solvent having a water solubility of 1% by mass or more, a writing instrument ink composition is obtained that has a predetermined degree of blackness in both oil-based and aqueous solutions, while also exhibiting excellent lightfastness and storage stability. The content of the azo iron dye, which is a black dye represented by formula (α) or formula (β) of the present invention, is preferably 0.01 to 40.0% by mass, more preferably 0.01 to 30.0% by mass, even more preferably 0.01 to 25.0% by mass, particularly preferably 0.1 to 20.0% by mass, and most preferably 1.0 to 15.0% by mass, based on the total amount of the aqueous or oil-based ink composition. If the azo iron dye content is less than 0.01% by mass, the coloring power and color development will be insufficient. On the other hand, if it exceeds 40.0% by mass, streaking is likely to occur, which is undesirable.

[0050] Furthermore, in the present invention, further improvement in blackness can be expected by using a material that absorbs at a specific wavelength in combination with the black dye represented by formula (α) or formula (β). Specifically, by using a solution prepared by dissolving the azo iron dye represented by formula (α) or formula (β) and a material that absorbs at a specific wavelength in a solvent with a water solubility of 1% by mass or more, it is possible to create a writing instrument ink composition that achieves an even higher level of balance between lightfastness and blackness in both oil-based and water-based inks, and has excellent storage stability.

[0051] Other materials besides the azo iron dye represented by formula (α) or formula (β), such as complementary dyes, may be used in combination, and further improvement in blackness can be expected. Examples of materials that may be used in combination include the following: Examples of oil-soluble dyes commonly available on the market include monoazo, disazo, metal complex salt type monoazo, anthraquinone, phthalocyanine, and triarylmethane. Salt-forming type oil-soluble dyes, in which functional groups such as acid and basic dyes are replaced with hydrophobic groups, can also be used. Examples of yellow shades include CI Solvent Yellow 14, 16, 29, 30, 33, 56, 62, 93, 98, 114, 116, 151, 157, 162, and Basic Yellow 40; examples of orange shades include CI Solvent Orange 22, 45, and 67; examples of red shades include CI Solvent Red 3, 18, 49, and 146, and Basic Red 1, 1:1; examples of blue shades include CI Solvent Blue 5, 35, 36, 44, 63, 70, 83, 105, and 111, and Basic Blue 1; examples of black shades include CI Solvent Black 3, 7, and 29; and examples of purple shades include CI Basic Violet 1, 11:1, etc. Specific examples of commercially available oil-soluble dyes include SBN Blue 701 (manufactured by Hodogaya Chemical Co., Ltd.), Oil Blue 650 (manufactured by Orient Chemical Industry Co., Ltd.), SAVIN BLOOKING LAS (manufactured by Clariant Co., Ltd.), SOC-1-0100 (manufactured by Orient Chemical Industry Co., Ltd.), Oil Black 860, Oil Pink 314, Oil Yellow 129, Oil Yellow 3G, Oil Yellow CGHNnew, Oil Yellow 1108 (manufactured by Orient Chemical Industry Co., Ltd.). The total content of these materials (complementary dyes, etc.) is preferably 0.01 to 40.0% by mass, and more preferably 0.2 to 25.0% by mass, relative to the total amount of the aqueous or oil-based ink composition, taking into consideration the range that can comply with heavy metal regulations, and from the viewpoint of further improving blackness and storage stability.

[0052] <Water-based ink composition for writing instruments> In the writing instrument ink composition of the present invention, in the aqueous form, in addition to the azo iron dye of formula (α) or formula (β) described above, the remainder may contain water as a solvent (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), and depending on the application for each writing instrument (for ballpoint pens, marking pens, etc.), water-soluble organic solvents, thickeners, lubricants, rust inhibitors, humectants, preservatives, or antibacterial agents may be appropriately included, to the extent that the effects of the present invention are not impaired.

[0053] Examples of water-soluble organic solvents that can be used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 3-butylene glycol, thiodiethylene glycol, and glycerin, as well as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether, which can be used alone or in combination.

[0054] The thickening agents that can be used are preferably at least one selected from the group consisting of synthetic polymers, cellulose, and polysaccharides. Specifically, examples include gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, gelan gum, succinoglycan, dieutan gum, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch glycolic acid and its salts, propylene glycol alginate, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylic acid and its salts, carboxyvinyl polymer, polyethylene hydroxide, copolymer of vinyl acetate and polyvinylpyrrolidone, crosslinked acrylic acid polymer and its salts, non-crosslinked acrylic acid polymer and its salts, styrene acrylic acid copolymer and its salts, and the like.

[0055] Examples of lubricants include nonionic compounds such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, higher polyoxyalkylene fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic compounds such as alkyl sulfonates and alkyl allyl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorinated surfactants; and polyether-modified silicones. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitride, and saponins, while examples of preservatives or antibacterial agents include phenol, sodium omazine, sodium benzoate, and benzimidazole compounds.

[0056] In the present invention, preferably, in order to further improve the non-drying properties of the pen tip, the storage stability of the ink, and to obtain stability over time at high temperatures, sugar alcohol and / or glycine betaine [also known as trimethylglycine, (CH3)2N] is used as a humectant. + (CH3)CH2COO -It is desirable that the product contains glycine betaine and a sugar alcohol of disaccharide or higher, with pentasaccharide or higher sugar alcohols making up 50% by mass or more of the total amount of disaccharide or higher sugar alcohols. Examples of sugar alcohols that can be used include monosaccharide alcohols such as sorbitol, xylitol, mannitol, and erythritol; disaccharide alcohols such as isomaltitol, maltitol, and lactitol; trisaccharide alcohols such as maltotriitol, isomalttriitol, and panitol; tetrasaccharide or higher sugar alcohols such as oligosaccharide alcohols; and reduced starch hydrolysates and reduced starch hydrolysates made from disaccharide or higher sugar alcohols. Preferably, the product contains maltitol, isomalttriitol, and reduced starch hydrolysates and reduced starch hydrolysates made from disaccharide or higher sugar alcohols. In particular, to more effectively exhibit the effects of the present invention, it is desirable that the product contains glycine betaine and a sugar alcohol of disaccharide or higher, with pentasaccharide or higher sugar alcohols making up 50% by mass or more of the total amount of disaccharide or higher sugar alcohols. Commercially available products include SE-20 (manufactured by Bussan Food Science Co., Ltd., containing approximately 5-20% by mass of sugar alcohols with five or more saccharides) and A-600 (manufactured by Bussan Food Science Co., Ltd., containing approximately 1-5% by mass of sugar alcohols with five or more saccharides). Furthermore, sugar alcohols in which 50% or more by mass consist of sugar alcohols with an average degree of polymerization of 5 or higher relative to the total amount of sugar alcohols with two or more saccharides include, for example, H-PDX [containing approximately 75% by mass of sugar alcohols with five or more saccharides (pentasaccharide: 6.4% by mass, hexasaccharide: 10% by mass, heptasaccharide: 58.5% by mass), manufactured by Matsutani Chemical Industry Co., Ltd.] and SE-100 (manufactured by Bussan Food Science Co., Ltd., containing approximately 64-82% by mass of sugar alcohols with five or more saccharides).

[0057] The content of these sugar alcohols and / or humectants such as glycine betaine is preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass, relative to the total amount of the aqueous ink composition for writing instruments, from the viewpoint of ink discharge performance and ink storage stability. If the content is less than 0.5% by mass, it will not be possible to further improve the non-drying properties of the pen tip, while if it exceeds 10% by mass, the ink viscosity will increase, impairing the quality of the lines, such as causing smudging during writing.

[0058] This aqueous ink composition for writing instruments can be manufactured using conventionally known methods. For example, it can be obtained by mixing a predetermined amount of the above-mentioned aqueous components with an azo iron dye represented by formula (α) or formula (β) or a solution obtained by dissolving the azo iron dye in a solvent with a water solubility of 1% or more, and stirring and mixing them with a stirrer such as a homomixer or disperser. Furthermore, if necessary, coarse particles in the ink composition may be removed by filtration or centrifugation. Furthermore, the aqueous ink composition for writing instruments may be prepared as an emulsion ink. Emulsified inks can be divided into O / W type inks, which are contained in the form of an oil-in-water emulsion, and W / O type inks, which are contained in the form of a water-in-oil emulsion. In O / W type inks, high HLB emulsifiers can be used, for example, by mixing an aqueous solution of sodium dodecyl sulfate in the range of 5 to 20% by mass. In W / O type inks, low HLB emulsifiers can be used, for example, by using polyoxyethylene (9) nonylphenyl ether (Igepal CO-630), POE isodecyl ether (Nonion ID-209, manufactured by NOF Corporation), or phenol ethoxylate (ADEKA Corporation Adecatol SP-12). In the case of O / W type inks, the average particle size of the oil droplets in the oil-in-water emulsion is preferably 20 to 800 nm in terms of dispersion stability of the emulsion droplets and overall ink uniformity. The oil phase is preferable in terms of the uniformity of the emulsified ink if its viscosity at 25°C and a shear rate of 38 / second is 5 to 500,000 mPa·s. Furthermore, the aqueous ink composition for writing instruments of the present invention may be used in combination with other pigments, such as microcapsule pigments that change color with heat or light, colored resin particles in which a dye is applied to a resin, and white resin particles, to the extent that the effects of the invention are not impaired.

[0059] <Oil-based ink composition for writing instruments> In the writing instrument ink composition of the present invention, in the oil-based version, it is preferable to contain an azo iron dye represented by formula (α) or formula (β) with the above configuration, or a solution obtained by dissolving the azo iron dye in a solvent with a water solubility of 1% by mass or more, and to contain at least one selected from polypropylene glycol, polybutylene glycol, polyoxypropylene diglyceryl ether, and glycol ethers as the main solvent. By selecting and using these solvents as the main solvent, it is possible to prevent the azo iron dye represented by formula (1) or formula (I) from agglomerating over time.

[0060] While polypropylene glycol and polybutylene glycol of various degrees of polymerization can be used, to further enhance the effects of the present invention, it is preferable to use polypropylene glycol with a degree of polymerization (weight average) in the range of 400 to 700, and polybutylene glycol with a degree of polymerization (weight average) in the range of 500 to 700. Furthermore, the polyoxypropylene diglyceryl ether [POP(n) diglyceryl ether] used in the present invention is obtained by addition polymerization of polyoxypropylene to the hydroxyl group of diglycerin. In the present invention, the number of moles (n) of oxypropylene added to the polyoxypropylene diglyceryl ether [POP(n) diglyceryl ether] is preferably 4 to 25, and more preferably 4 to 14, in order to further exhibit the effects of the present invention. Among glycol ethers, those having 2 to 7 carbon atoms are particularly preferred, specifically 1,3-butanediol, 3-methyl-1,3-butanediol, 3-methoxy-butanol, 3-methyl-3-methoxy-butanol, and hexylene glycol.

[0061] The content of these main solvents is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass, relative to the total amount of solvent in the oil-based ink composition. By having a main solvent content of 50% by mass or more, the occurrence of aggregation over time can be suppressed as much as possible. In addition to the main solvents mentioned above, solvents that are compatible with the main solvents, such as glycerin, diglycerin, and propylene glycol, can be appropriately included as long as they do not impair the effects of the present invention.

[0062] This oil-based ink composition for writing instruments may contain, in addition to the azo iron dye represented by (α) or formula (β) above, or a solution obtained by dissolving the azo iron dye in a solvent with a water solubility of 1% by mass or more, and a main solvent, resins, dispersants, rust inhibitors, preservatives, lubricants, ink drip inhibitors, etc., that are compatible with each writing instrument (for ballpoint pens, marking pens, etc.) and may be included as needed, without adversely affecting the oil-based ink. Examples of resins that can be used include ketone resins, styrene resins, styrene-acrylic resins, terpene phenol resins, rosin-modified maleic acid resins, rosin-phenol resins, alkylphenol resins, phenolic resins, styrene-maleic acid resins, rosin-based resins, acrylic resins, urea aldehyde-based resins, maleic acid-based resins, cyclohexanone-based resins, polyvinyl butyral, and polyvinylpyrrolidone. Polyvinyl butyral can be used to adjust the viscosity of oil-based ink compositions for writing instruments. In this case, the mass-average molecular weight of the polyvinyl butyral may be 10,000 or more, 20,000 or more, 30,000 or more, 40,000 or more, 50,000 or more, 60,000 or more, 70,000 or more, 80,000 or more, 90,000 or more, 100,000 or more, or 105,000 or more, and can also be 150,000 or less, 140,000 or less, 130,000 or less, 120,000 or less, or 115,000 or less. The resin content is preferably 0.1 to 10% by mass, and more preferably in the range of 0.2 to 8% by mass or 0.3 to 7% by mass, relative to the total mass of the oil-based ink composition for writing instruments.

[0063] In the oil-based ink composition for writing instruments of the present invention, pigments may be used in combination, to the extent that they do not impair the effects of the invention. As the pigment dispersant, resins such as those listed above can be appropriately selected and used. Surfactants and oligomers can also be included, as long as they are suitable for the purpose. Specific examples of dispersants include polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, polyvinyl ether, styrene-maleic acid copolymer, ketone resin, synthetic resins such as hydroxyethylcellulose and its derivatives, and styrene-acrylic acid copolymer, as well as PO·EO adducts and polyester amine oligomers. Furthermore, the various water-based rust inhibitors, preservatives, and lubricants mentioned above can be used as rust inhibitors, preservatives, and lubricants.

[0064] As an ink drip prevention agent, fine silica particles can be used, with a specific surface area of ​​50 m². 2 It is preferable to use fine particle silica with a specific surface area of ​​50 m² or more, and is particularly suitable when used as an ink composition for oil-based ballpoint pens. The fine particle silica used in this invention has a specific surface area of ​​50 m². 2 It is 1 / g or more, preferably 80m 2 / g, more preferably 100m 2 It is 1 / g or more. The specific surface area is 50 m². 2 If the value is smaller than / g, the primary particle size is large and the above effects are difficult to obtain. Fine particle silica can be commercially available, for example, hydrophobic grades such as R972, R972V, R972CF, R974, R202, R805, R812, and R812S from the AEROSOL series manufactured by Nippon Aerosil Co., Ltd., or hydrophilic grades such as 50, 130, 200, 300, 380, and TT600 from the AEROSOL series manufactured by Nippon Aerosil Co., Ltd. The fine silica particles used in this invention are preferably those whose silica surface has been hydrophobized. If many hydrophilic groups remain on the silica surface, these hydrophilic groups tend to interact with other silica particles and dispersants, making it difficult to obtain an oil-based ink composition for writing instruments that is stable over time and does not have the properties to prevent ink dripping. In the present invention, from the viewpoint of preventing ink dripping from the pen tip and ensuring storage stability, it is desirable that the oil-based ink composition for writing instruments contains 0.01 to 5% by mass of fine particles of silica, more preferably 0.1 to 4.0% by mass, and particularly preferably 0.5 to 3.0% by mass.

[0065] This oil-based ink composition for writing instruments can be manufactured using conventionally known methods. For example, it can be obtained by mixing a predetermined amount of the oil-based components with an azo iron dye represented by formula (1) or formula (I) above, or a solution obtained by dissolving the azo iron dye in a solvent with a water solubility of 1% by mass or more, and stirring and mixing them with a stirrer such as a homomixer or disper. Furthermore, if necessary, coarse particles in the ink composition may be removed by filtration or centrifugation. Furthermore, oil-based ink compositions for writing instruments may be prepared using the above-mentioned solvents, resins, dispersants, etc., in appropriate ranges: low viscosity range (ink viscosity at a shear rate of 38.3 / s (25°C) in the range of 1 to 30 mPa·s) or high viscosity range (ink viscosity at a shear rate of 38.3 / s (25°C) in the range of 100 to 10,000 mPa·s). Each viscosity range can be measured using an E-type viscometer (manufactured by Toki Sangyo). The oil-based ink compositions for writing instruments may also be used as W / O type inks, containing the ink in the form of a water-in-oil emulsion. These writing instrument ink compositions can be appropriately selected in form, such as for felt-tip pens or ballpoint pens, depending on the viscosity range.

[0066] In the present invention, in the aqueous ink composition for writing instruments and the oil-based ink composition for writing instruments, it is desirable to use anionic or nonionic surfactants together with the black dye represented by formula (α) or formula (β) above, from the viewpoint of quick drying of the lines and resistance to bleeding. The effect can be fully exhibited when the surfactant is included in an amount of 0.01 to 5.0% by mass, preferably 0.05 to 3.0% by mass, and particularly preferably 0.1 to 2.0% by mass, based on the total amount of the aqueous or oil-based ink composition. Furthermore, at least one anionic surfactant can be mentioned, such as phosphate esters, polyalkylene glycol derivatives such as polyoxyethylene lauryl ether, fatty acid alkali salts, nonionic surfactants, fluorine-based surfactants such as perfluoroalkyl phosphate esters, polyether-modified silicones such as polyethylene glycol adducts of dimethylpolysiloxane, acetylene glycols, and acetylene derivatives selected from their ethylene oxide adducts. Specifically, this includes Aqualon AN-10, AN-20, AN-30, AN-5065 (all polyoxyethylene styrene-propenylphenyl ether: EO addition moles 10, 20, 30, 40, 50) and Aqualon RN-10, RN-20, RN-30, RN-50 (all polyoxyethylene propenylphenyl ether (nonylphenyl type): EO addition moles 10, 20, 30, 50) from Daiichi Kogyo Seiyaku Co., Ltd., Latemul PD-420, PD-430, PD-450 (all polyoxyalkylene alkenyl ether) from Kao Corporation, Bremmer PE-90, PE-200, PE-350 (all PEG monomethacrylate: EO addition moles 2, 4.5, 8) and Bremmer AE-200, AE-400 (all PEG monoacrylate: EO addition moles) from NOF Corporation. Numbers 4.5, 10), Bremmer PP-1000, PP-500, PP-800 (all PPG monomethacrylate: PO addition moles 4-6, 9, 13), Bremmer AP-200, AP-400, AP-550, AP-800 (all PPG monoacrylate: PO addition moles: 3.5, 6, 9, 13), NOF Corporation's Uniox PKA-5001, PKA-5002, PKA-5 Examples include 003, PKA-5004, Unisafe PKA-5014F, Adeka's Adeka Soap ER-10, ER-20, ER-30, ER-40 (all alkyl type: EO addition moles: 10, 20, 30, 40), and Adeka Soap NE-10, NE-20, NE-30 (all alkylphenol type: (nonylphenyl type) EO addition moles: 10, 20, 30).

[0067] In the present invention, it is preferable that the above-mentioned aqueous ink composition for writing instruments and oil-based ink composition for writing instruments further contain an ultraviolet absorber and / or a light stabilizer in order to further enhance lightfastness and storage stability against light. The ultraviolet absorbers that can be used are those that are conventionally known, such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers, and it is preferable that the above ultraviolet absorbers have polymerizable unsaturated groups.

[0068] Specific examples of benzotriazole-based absorbents include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, and 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chloro Examples include lobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2-{2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl}benzotriazole, and 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole.

[0069] Specific examples of triazine-based absorbents include 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-isooctyloxyphenyl)-1,3,5-triazine, 2-[4((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.

[0070] Specific examples of salicylic acid derivative-based absorbents include phenyl salicylate, p-octylphenyl salicylate, and 4-tert-butylphenyl salicylate. Specific examples of benzophenone-based absorbents include 4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, and sodium Examples include 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 5-chloro-2-hydroxybenzophenone, resorcinol monobenzoate, 2,4-dibenzoylresorcinol, 4,6-dibenzoylresorcinol, hydroxydodecylbenzophenone, and 2,2'-dihydroxy-4(3-methacrylateoxy-2-hydroxypropoxy)benzophenone.

[0071] Examples of commercially available UV absorbers include "Tinuvin900," "Tinuvin928," "Tinuvin348-2," "Tinuvin479," "Tinuvin405," and "Tinuvin400" (all manufactured by BASF, trade names; Tinuvin is a registered trademark), and "RUVA-93" (both manufactured by Otsuka Chemical Co., Ltd., trade name). The amount of this UV absorber can be 0.1 to 20.0% by mass, and preferably 1.0 to 10.0% by mass, relative to the total amount of the aqueous or oil-based ink composition, from the viewpoint of further lightfastness and storage stability.

[0072] Suitable light stabilizers include, for example, hindered amine light stabilizers, hindered phenol antioxidants, phenolic radical scavengers, sulfur antioxidants, phosphorus antioxidants, triazine compounds, benzotriazole compounds, phenolic ultraviolet absorbers, malonic acid ester ultraviolet absorbers, oxanilide ultraviolet absorbers, benzophenone compounds, and the like.

[0073] Conventionally known hindered amine light stabilizers, such as hindered piperidine compounds, can be used. Furthermore, the above-mentioned hindered amine light stabilizers may particularly have polymerizable unsaturated groups. Specific examples of hindered amine-based light stabilizers include monomer types such as bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 4-benzoyloxy-2,2',6,6'-tetramethylpiperidine, and bis(1,2,2,6,6-pentamethyl-4-piperidyl){[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}butylmalonate; and poly{[6-(1,1,3,3-tetramethyl]. Known examples include oligomeric types such as [(methylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)iminol]}; polyester-linked types such as polyesters of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and succinic acid; and those having polymerizable unsaturated groups such as 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate.

[0074] Furthermore, commercially available hindered amine-based light stabilizers include, for example, "Tinuvin765," "Tinuvin770DF," "Tinuvin144," "Tinuvin622SF," and "Tinuvin152" (all manufactured by BASF, trade names; Tinuvin is a registered trademark), "ADEKA LA-52," "ADEKA LA-57," "ADEKA LA-63P," "ADEKA LA-72," "ADEKA LA-77Y," "ADEKA LA-81," "ADEKA LA-82," and "ADEKA LA-87" (all manufactured by ADEKA Corporation, trade names; ADKSTAB and ADEKA LA-87 are registered trademarks). The content of this light stabilizer can be 0.1 to 20.0% by mass, and preferably 1.0 to 10.0% by mass, relative to the total amount of the aqueous or oil-based ink composition, from the viewpoint of further light resistance and storage stability.

[0075] The ink composition for writing instruments of the present invention, configured in this manner, can be suitably applied as either water-based or oil-based inks, and can be used as a writing instrument by being mounted on marking pen bodies, sign pen bodies equipped with fiber tips, felt tips, or plastic tips at the writing tip, or on ballpoint pen bodies equipped with ballpoint pen tips at the writing tip. As a ballpoint pen, the water-based ink composition for writing instruments having the above composition is used with a diameter of 0.18 to 2.0 Examples include a ballpoint pen ink refill equipped with a ball of mm in diameter, in which an ink follower is contained, which is incompatible with the writing instrument ink composition contained within the ink refill and has a lower specific gravity than the writing instrument ink composition, such as polybutene, silicone oil, or mineral oil. In a ballpoint pen, the axial (vertical) movement (distance) of the writing ball may be 10 to 120 μm, more preferably 15 to 100 μm, and particularly preferably 20 to 80 μm, from the standpoint of properly ejecting the ink composition and stabilizing the writing flow rate. This axial movement of the ball can be measured by measuring the distance between the state in which the ball is in contact with the seat of the ballpoint pen tip and the state in which the ball is in contact with the crimped part at the tip of the ballpoint pen tip, using a measuring microscope. Furthermore, the surface roughness Ra of the ball may be less than 10 nm, more preferably 1.0 to 8.0 nm. This "surface roughness Ra" can be measured using a non-contact surface shape measuring instrument (NewView7200, Zygo) under the conditions of a lens magnification of 50x, an evaluation length of 100 μm, and a Gaussian filter of 25 μm, with other conditions conforming to JIS B0601 (Geometric specifications of products - surface properties).

[0076] Furthermore, if the ballpoint pen tip has a spring to bias the ball toward the tip, the spring may be nickel (Ni) plated on its surface. A bullet-shaped tip is more preferable for the ballpoint pen tip because it provides good writing performance. The structure of ballpoint pens, marking pens, etc., is not particularly limited. For example, a direct-ink type ballpoint pen or marking pen may have a collector structure (ink holding mechanism) in which the barrel itself serves as the ink reservoir and the above-described writing instrument ink composition is filled into the barrel.

[0077] The present invention provides an ink composition and writing instrument for writing instruments that contain an azo iron dye represented by formula (α) or formula (β) above, or a solution obtained by dissolving the azo iron dye in a solvent with a water solubility of 1% by mass or more, and further a solution obtained by dissolving a material having absorption at the above-mentioned specific wavelength. By formulating an aqueous or oil-based ink, when writing on paper or the like with a ballpoint pen body, marking pen body, or other writing instrument equipped with this ink, the present invention provides an ink composition and writing instrument that exhibits blackness while also having excellent lightfastness and storage stability. [Examples]

[0078] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. [Examples 1-6, Comparative Examples 1-2: Aqueous Ink Compositions for Writing Instruments] A water-based ink composition for writing instruments was prepared according to the formulation shown in Table 3 below. The azo iron dye solutions 1-5 and chromium-containing gold dye solution 1 used in this water-based ink composition for writing instruments were as follows. Additionally, the colorants listed in Table 1 (product names, etc.) were used as colorants in Comparative Examples 1-2.

[0079] (Azo iron dye solution 1) Azo iron dye solution 1 was prepared by dissolving 15 parts of the substance represented by formula (α) as the azo iron dye component in 85 parts of ethanol, which is a solvent with a water solubility of 1% by mass or more. (Azo iron dye solution 2) Azo iron dye solution 2 was prepared by dissolving 15 parts of the substance represented by formula (α) as the azo iron dye component and 5 parts of Oil Yellow 129, manufactured by Orient Chemical Industry Co., Ltd., as a complementary dye, in 80 parts of ethanol, a solvent with a water solubility of 1% by mass or more. (Azo iron dye solution 3) Azo iron dye solution 3 was prepared by dissolving 10 parts of the substance represented by formula (β) as the azo iron dye component in 90 parts of ethanol, a solvent with a water solubility of 1% by mass or more.

[0080] (Azo iron dye solution 4) Azo iron dye solution 2 was prepared by dissolving 10 parts of the substance represented by formula (β) as the azo iron dye component and 11085 parts of OValifast Yellow, manufactured by Orient Chemical Industry Co., Ltd., as a complementary dye, in 85 parts of ethanol, a solvent with a water solubility of 1% by mass or more. (Azo iron dye solution 5) Azo iron dye solution 5 was prepared by dissolving 10 parts of the substance denoted by (α) as an azo iron dye component, 10 parts of the substance denoted by formula (β) as an azo iron dye component, and 80 parts of ethanol, a solvent with a water solubility of 1% by mass or more. (Chromium complex dye solution 1) As a chromium complex dye component, 15 parts of VALIFASTBLACK 3830 (manufactured by Orient Chemical Industry Co., Ltd.), a mixture of an azo compound chromium complex dye and an amine, were dissolved in 85 parts of ethanol, a solvent with a water solubility of 1% by mass or more, to prepare chromium-containing dye solution 1.

[0081] Using the obtained azo iron dye solutions 1-5 and chromium-containing dye solution 1, aqueous ink compositions for writing instruments, Examples 1-6 and Comparative Examples 1-2, were prepared by conventional methods according to the formulations shown in Table 1 below. These compositions were then applied to writing instruments (sign pens, ballpoint pens) with the following configurations, and evaluated for black color development, lightfastness, storage stability, and specified heavy metal content using the evaluation methods described below. The results are shown in Table 3 below.

[0082] (Writing instrument: Making a felt-tip pen) A felt-tip pen was prepared by filling the storage chamber with the obtained aqueous ink composition for writing instruments using a felt-tip pen [manufactured by Mitsubishi Pencil Co., Ltd., product name: Pin, pen tip: POM resin core, cap type].

[0083] (Method for evaluating the color development of black) Using the writing instruments obtained above, the color development of the black ink was visually evaluated. For the evaluation of black ink, VALIFAST BLACK 3810 (manufactured by Orient Chemical Industry Co., Ltd.), a chromium complex dye, was used as a comparative example. A 2cm x 2cm square was uniformly filled into Catherine paper (white, manufactured by HEIWA PAPER Co., Ltd.) by machine writing. The blackness of the ink-coated area was compared relatively. The color development of the black ink prepared using only the chromium complex dye was judged as "C," and a relative evaluation was performed according to the following criteria. Evaluation criteria: A: It has a much higher blackness than chromium-complex dyes. B: Slightly blacker than chromium complex dyes. C: Blackness of chromium complex dyes

[0084] (Method for evaluating lightfastness) Using the writing instruments described above, a 2cm x 2cm square of Catherine paper (white, manufactured by HEIWA PAPER) was filled in. The lightfastness was then tested using a Suga Test Instruments X25 xenon weather meter under JIS L 0843 xenon arc light at 50W / m². 2 After 6 hours of irradiation with (300-400nm) light, the visibility when a 365nm UV lamp was applied was evaluated visually and by the rate of change in fluorescence intensity (365nm) according to the following evaluation criteria. Evaluation criteria: A: The blackness remains unchanged from the initial version, so there are no visibility issues. B: Visible, but a slight change in blackness is noticeable. C: Difficult to see, but still visible. Significant changes in blackness are observed.

[0085] (Method for evaluating storage stability) The aqueous ink composition for writing instruments obtained above was used to assess its stability over time. The aqueous ink composition was placed in a glass mayonnaise bottle (manufactured by AS ONE Corporation) and stored at 60°C for two weeks. After that, the aqueous ink composition was dropped onto filter paper (circular quantitative filter paper, No. 5C, manufactured by ADVANTEC Corporation), and the presence or absence of precipitates on the filter paper was visually evaluated according to the evaluation criteria below. Evaluation criteria: A: No precipitates B: Some precipitates are visible. C: A considerable amount of deposits can be seen.

[0086] (Evaluation of specified heavy metal content) The presence or absence of heavy metals in each of the above azo iron dye solutions was evaluated according to the following evaluation criteria. The presence or absence of heavy metals was evaluated for the chromium compounds contained in each azo iron dye solution using high-performance liquid chromatography-intensity spectrometry (LC-ICP / MS). The evaluation criteria were based on the heavy metal leaching test, "European standard EN71 Part 3 Migration of specific elements," by measuring the amount of leached material. If chromium (trivalent chromium / hexavalent chromium) exceeding the standard was detected, a leaching test was conducted, and a judgment was made based on the standard value (standard value after May 20, 2021, based on EN 71-3:2019+A1:2021). Evaluation criteria: ○: Meets the standard value. ×: Does not meet the standard value.

[0087] [Examples 7-12, Comparative Examples 3-4: Oil-based ink compositions for writing instruments] Using the azo iron dye solutions 1 to 5 and chromium-containing dye solution 1 obtained above, oil-based ink compositions for writing instruments were prepared by conventional methods according to the formulations shown in Table 4 below for Examples 7 to 12 and Comparative Examples 3 to 4.

[0088] The oil-based ink compositions for writing instruments obtained in Examples 7-12 and Comparative Examples 3-4 were used in writing instruments (ballpoint pens) with the following configurations, and their black color development, lightfastness, and storage stability were evaluated according to the evaluation methods described above. The results are shown in Table 2 below. Regarding the specified heavy metal content, the oil-based ink compositions for writing instruments used the azo iron dye solutions 1-5 described above, so the evaluation is the same as for the aqueous ink compositions for writing instruments.

[0089] (Writing instrument: Ballpoint pen manufacturing) Using the obtained oil-based ink composition for writing instruments, an oil-based ballpoint pen was prepared by filling the storage chamber with each of the above-mentioned aqueous ink compositions using a ballpoint pen [Mitsubishi Pencil Co., Ltd., product name: Uni-ball i UB-150, pen tip: metal, cap type, ball diameter: 0.5 mm].

[0090] [Table 3]

[0091] [Table 4]

[0092] As is clear from the results in Tables 3 and 4 above, the aqueous ink compositions for writing instruments of Examples 1 to 6, which are within the scope of the present invention, and the oil-based ink compositions for writing instruments of Examples 7 to 12, were found to be superior to Comparative Examples 1 to 4, which are outside the scope of the present invention, in terms of lightfastness and storage stability, while maintaining blackness, even when containing black azo iron dye in the ink, regardless of whether they are aqueous or oil-based. [Industrial applicability]

[0093] The ink composition for writing instruments of the present invention can be suitably used as an aqueous ink composition for writing instruments such as low viscosity ballpoint pens, cotton-filled writing instruments and direct-ink writing instruments, gel ink ballpoint pens, cotton-filled felt-tip pens, valve-type felt-tip pens, and direct-ink felt-tip pens, as well as an oil-based ink composition for writing instruments.

Claims

1. A writing instrument ink composition characterized by containing at least an azo iron dye represented by the following formula (α) or formula (β). 【Chemistry 1】 [In the above formula (α), R １ These are identical or different, hydrogen atoms, and alkyl groups having 1 to 12 carbon atoms, R ２ , R ３ These are identical or different alkyl groups having 3 to 10 carbon atoms, and A ＋ This represents a monovalent ammonium ion or a guanidine derivative ammonium ion having an alkyl group with 3 to 18 carbon atoms. 【Chemistry 2】 (In the above formula (β), R １ and R ２ are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, R ３ 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, R ５ is a nitro group, a sulfonamide group, or a halogen atom, 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 ＋ represents a monovalent cation.)

2. The writing instrument ink composition according to claim 1, comprising dissolving an azo iron dye represented by formula (α) or formula (β) in a solvent with a water solubility of 1% by mass or more.

3. A writing instrument characterized by incorporating the writing instrument ink composition described in claim 1 or 2.

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