Black resin particle dispersion, and aqueous ink composition for writing instruments containing the same.

Abstract

The present invention provides a black resin particle dispersion and an aqueous ink composition for writing instruments that exhibit excellent lightfastness, blackness, and storage stability. [Solution] The black resin particle dispersion consists of resin particles containing at least an azo iron dye dispersed in water. The azo iron dye is preferably represented by the following formula (α). TIFF2026082096000038.tif62120 [A + This represents a monovalent ammonium ion having an alkyl group with 3 to 18 carbon atoms.

Description

[Technical Field]

[0001] The present invention relates to a dispersion of black resin particles containing a black azo iron dye, which is a black colorant, and to an aqueous ink composition for writing instruments containing the same. [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, azo iron dyes of a specific structure, which are oil-soluble black colorants, 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 their storage stability may still be unstable, and their fastness, particularly lightfastness, may not be sufficient. Moreover, there is no disclosure regarding their application in aqueous solutions or their potential for use in such solutions. 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 prior art described above, the present invention aims to resolve these issues and provides a black resin particle dispersion and an aqueous ink composition for writing instruments that do not contain harmful heavy metals (as defined in the European standard: Toy Safety EN71-3:2019 and the International Toy Safety Standard (ISO8124-3)), while complying with environmental impact and heavy metal regulations in various countries, and exhibiting excellent durability, particularly in lightfastness, as well as storage stability and exhibiting a blackness with a broad absorption spectrum. [Means for solving the problem]

[0008] In view of the above-mentioned conventional problems, the inventors conducted diligent research and found that, at the very least, a black resin particle dispersion for the above purpose can be obtained by dispersing resin particles containing a specific black dye in water, and thus completed the present invention.

[0009] In other words, the black resin particle dispersion of the present invention is characterized in that at least resin particles containing an azo iron dye are dispersed in water. The azo iron dye is preferably represented by the following formula (α) or formula (β). [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 , 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. [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, 4is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and R 5 is a nitro group, a sulfonamide group, or a halogen atom, and R 6 is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom, and 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. ]] The black resin particles encapsulating the azo iron dye are preferably composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group A. <Group A> Acrylic monomer, styrene monomer, nitrile monomer, vinyl acetate monomer The black resin particles encapsulating the azo iron dye preferably contain an ultraviolet absorber and / or a light stabilizer. The aqueous ink composition for writing instruments of the present invention is characterized by containing a dispersion of black resin particles having the above configuration.

Effects of the Invention

[0010] According to the present invention, there are provided a black resin particle dispersion and an aqueous ink composition for writing instruments, which have excellent storage stability, do not contain harmful heavy metals, can raise the light resistance to the same level as that of Cr complex dyes, have a wide absorption spectrum wavelength range, and are excellent in blackness. The objects and effects of the present invention are recognized and obtained by using the components and combinations specifically pointed out in the claims. Both the above general description and the following detailed description are exemplary and explanatory, and do not limit the present invention 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 black resin particle dispersion of the present invention is characterized in that at least resin particles containing an azo iron dye are dispersed in water. In the present invention, the azo iron dye that becomes a black dye is not particularly limited as long as it is a dye in which an azo pigment 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). However, from the viewpoint of black performance and lightfastness, azo iron dyes represented by the following formula (α) or the following formula (β) are preferred.

[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 , R 3 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. 7is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms, and A + represents a monovalent cation. ]

[0013] In the present invention, as the resin particles encapsulating at least one azo iron dye component selected from the azo iron dyes represented by the above formula (α) or formula (β), the function and resin type are not particularly limited. For example, acrylic monomer, allyl monomer, isocyanate monomer, isothiocyanate monomer, epoxy monomer, diamine monomer, thiol monomer, dicarboxylic acid chloride monomer, dicarboxylic acid monomer, disulfonyl chloride monomer, dithiol monomer, divinyl monomer, diallyl monomer, styrene monomer, tetracarboxylic acid anhydride monomer, nitrile monomer, bismaleimide monomer, lactone monomer, actide monomer, fluorine-containing monomer, cyclic olefin monomer, etc. Examples include those composed of a homopolymer obtained from each resin monomer or a copolymer obtained by combining these monomers. Preferably, the resin particle dispersion of the present invention is composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group A from the viewpoints of ease of encapsulation into resin particles, controllable reaction rate, stability after reaction, and dispersibility after reaction. <Group A> Acrylic monomer, styrene monomer, nitrile monomer, vinyl acetate monomer

[0014] In order to produce black resin particles encapsulating at least one azo iron dye component selected from the azo iron dyes represented by the above formula (α) or formula (β), for example, at least one azo iron dye component selected from the azo iron dyes represented by the above formula (α) or formula (β), and at least one of the above monomer components are used, and depending on each monomer type, polymerization (homopolymerization or copolymerization) is carried out using a suitable polymerization initiator, etc., to obtain each black resin particle dispersion. Also, each black resin particle dispersion can be obtained by appropriately adjusting production conditions such as temperature, stirring speed, and reaction time during polymerization. Examples of the copolymer resin particles of Group A mentioned above include: particles of a copolymer of acrylic monomer and styrene monomer; particles of a copolymer of acrylic monomer and nitrile monomer; particles of a copolymer of acrylic monomer and vinyl acetate monomer; particles of a copolymer of styrene monomer and nitrile monomer; particles of a copolymer of styrene monomer and vinyl acetate monomer; particles of a copolymer of nitrile monomer and vinyl acetate monomer; particles of a copolymer of acrylic monomer, styrene monomer and nitrile monomer; particles of a copolymer of acrylic monomer, styrene monomer and vinyl acetate monomer; particles of a copolymer of acrylic monomer, styrene monomer and vinyl acetate monomer; and particles of a copolymer of acrylic monomer, styrene monomer and nitrile monomer and vinyl acetate monomer. Each particle, composed of a homopolymer or copolymer obtained from at least one monomer selected from these Group A particles, is preferred for the following reasons: it can produce particles with high blackness, strong fastness, and lasting stability of the encapsulable azo iron dye component described later; it does not adversely affect other compounding components; and it provides high persistence of the predetermined effect of the azo iron dye component.

[0015] Furthermore, as the acrylic monomer that can be used, (meth)acrylic acid ester monomers represented by the following general formula (X) are preferred. [ka] In the above formula (X), A is a hydrogen atom (H) or a methyl group (CH3), and R represents a substituent having a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a polyalkylene glycol chain having 2 to 18 carbon atoms in the alkylene chain. The substituent having an alkyl group or a polyalkylene glycol chain may have a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group as a substituent. Examples include linear or branched alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 10 carbon atoms, and alkyl groups having 1 to 18 carbon atoms which may have an epoxy group, a hydroxyl group, a dialkylamino group, or an alkoxy group having 1 to 4 carbon atoms as a substituent. In particular, examples include alkyl groups having 1 to 6 carbon atoms which may have an epoxy group, a hydroxyl group, or an alkoxy group having 1 to 2 carbon atoms as a substituent, and alkyl groups having 1 to 6 carbon atoms which may have an epoxy group as a substituent. Preferably, R in the above general formula (X) is a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a hydroxyl group, a trifluoroethyl group, a dimethylaminoethyl group, a methoxyethyl group, a hydroxyethyl group, a hydroxypropyl group, an allyl group, a tetrahydrofurfuryl group, a phenyl group, a benzyl group, a butoxydiethylene glycol group, a methoxypolyethylene glycol group, a dimethylaminoethyl group, a diethylaminoethyl group, a dimethylaminoethyl group, a glycidyl group, ethyl phosphate, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, etc. In this specification, the term "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid."

[0016] Specific examples of (meth)acrylic acid esters represented by the above general formula (X) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, Isobornyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminoethyl methyl chloride (meth)acrylate, diethylaminoethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-Hexanediol, Trimethylolpropane tri(meth)acrylate, 2-(meth)acroyloxyethyl phthalate, 2-(meth)acroyloxyethyl hexahydrophthalate, Trifluoroethyl (meth)acrylate, Butoxyethyl (meth)acrylate, Methoxytetraethylene glycol (meth)acrylate, 2-Hydroxypropyl (meth)acrylate, 3-Chloro-2-Hydroxypropyl (meth)acrylate, 2-Hydroxy-3-Phenoxypropyl (meth)acrylate, Diethylene glycol (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(dimethylamino)propyl (meth)acrylate, 2-(dimethylamino)butyl (meth)acrylate, 2-Isocyanoethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, Perfluoroethyl methacrylate having perfluoroalkyl groups of 1 to 18 carbon atoms, 2-(meth)acrylate (phosphate)ethyl [2-(Methacryloyloxy)ethyl Examples include at least one of the following (each individually or in combination of two or more, hereinafter the same): phosphate, trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, etc.

[0017] Of these, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate are preferred, due to their ease of industrial availability, ease of handling and safety during manufacturing, and their ability to further enhance the effects of the present invention.

[0018] In the present invention, in addition to the (meth)acrylic acid ester monomers mentioned above, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers can be used, preferably, for reasons such as obtaining a sustained lightfastness effect and storage stability, and in the case of inks for writing instruments, a stable writing flow rate and quality of the written lines (writing performance, color development). As the hydrophobic vinyl monomer, for example, at least one monomer other than the (meth)acrylic acid ester monomers mentioned above, such as styrene and methylstyrene, can be used. Examples of hydrophobic vinyl monomers that can be used include at least one of styrene, methylstyrene, chloromethylstyrene, alkylstyrene having an alkyl group with 1 to 12 carbon atoms, methoxystyrene, chlorostyrene, bromostyrene, divinylbenzene, phenylstyrene, and vinylnaphthalene. Examples of aqueous monomers that can be used include at least one of glycerin monomethacrylate, sodium 2-sulfoethyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-propylene glycol monomethacrylate, polyethylene glycol-tetramethylene glycol-monomethacrylate, and propylene glycol-polybutylene glycol-monomethacrylate.

[0019] The black dye used in the present invention can be any dye 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 an aromatic ring linked by an azo group (-N=N-) forms a complex salt with iron (Fe: metal). Preferably, at least one selected from azo iron dyes that become black dyes represented by the above formula (α) or formula (β) is mentioned.

[0020] <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 ].

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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]

[0028] [Table 1]

[0029] [Table 2]

[0030] <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.

[0031] 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-1), 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).

[0032] 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 ().

[0033] 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.

[0034] 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)

[0035] [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.

[0036] 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 a cyano group, nitro group, acetyl group, sulfoamide group, and halogen atom. 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 for practical use can be obtained. 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] 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 this 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, etc. 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.

[0042] Such a disazo-monoazo iron complex is specifically represented by the following chemical formula ((β-9a)

Chemical formula

[0043] 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. The disazo-monoazo iron complex may have only one or a plurality of these monovalent cations. Among them, ammonium ion and monovalent alkyl group-containing ammonium ion are preferred. Examples of the alkali metal ion include lithium ion (Li + ), sodium ion (Na + ), and potassium ion (K + ). The alkali metal ion may be derived from the pH adjuster used in the synthesis process of the disazo-monoazo iron complex. Also, only one kind or a plurality of monovalent cations may be combined with the iron complex anion.

[0044] The monovalent alkyl group-containing ammonium ion is represented by the following chemical formula (β-3). [Chemistry] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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]

[0051] 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-5).

[0052] 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]

[0053] 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).

[0054] The black resin particle dispersion of the present invention is characterized in that resin particles containing at least one black dye component selected from azo iron dyes that are black dyes represented by formula (α) or formula (β) above are dispersed in water. As for the manufacturing method, for example, each black resin particle dispersion can be obtained by polymerization (homopolymerization or copolymerization) using an azo iron dye represented by chemical formula (α), at least one black dye component selected from azo iron dyes containing azo iron complexes represented by chemical formulas (β) to (β-2), and at least one of the above monomer components, using a suitable polymerization initiator. Furthermore, each resin particle dispersion can be obtained by appropriately adjusting the manufacturing conditions such as the temperature, stirring speed, and reaction time during polymerization.

[0055] In a resin particle dispersion composed of a homopolymer or copolymer obtained from at least one monomer selected from the acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monopolymers of group A, for example, at least one black dye component selected from azo iron dyes that become black dyes represented by formula (α) or formula (β) is dissolved in styrene monomer, nitrile monomer, vinyl acetate monomer, (meth)acrylic acid ester monomer, etc. (each individually or in pairs or more, the same applies hereinafter), or in a mixed monomer containing each of the above monomers such as (meth)acrylic acid ester monomer and other hydrophobic vinyl monomers and / or aqueous monomers, and ammonium persulfate, potassium persulfate, hydrogen peroxide, etc. are used as polymerization initiators, and reducing agents are further used as polymerization initiators, and further triallyl isocyanurate, triallyl isocyanurate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol acrylate, ditrimethylolpropane acrylate, dipentaerythritol acrylate, methoxylated bisphenol A methacrylate, Crosslinking agents such as pentaerythritol methacrylate, ditrimethylolpropane methacrylate, dipentaerythritol methacrylate, and ethoxylated polyglycerin methacrylate, and, if necessary, polyoxyethylene-1-(allyloxymethyl)-alkyl ether sulfate ammonium, ether sulfate, polyoxyethylene nonylpropenylphenyl ether sulfate ammonium, polyoxyethylene nonylpropenylphenyl ether, ammonium polyacrylate, styrene-maleate copolymer ammonium, polyoxyethylene alkyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene decyl ether, polyoxyethylene tridecyl ether, alkylbenzene sulfonate, dioctyl sulfosuccinate, sodium lauryl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene styrene phenyl ether phosphate, polyoxyethylene styrene phenyl ether sulfate, polyoxyethylene alkyl ether sulfate,It can be manufactured by emulsion polymerization using polymerizable surfactants (emulsifiers) such as polyoxyethylene sorbitan monolaurate (polysorbate 20), polyoxyethylene sorbitan palmitate (polysorbate 40), polyoxyethylene sorbitan monostearate (polysorbate 60), and polyoxyethylene sorbitan oleate (polysorbate 80). After being produced as a dispersion of black lipid particles, it can be dried to form black resin particles. Using a crosslinking agent such as triallyl isocyanurate as described above is preferable because it improves the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the resin particle dispersion.

[0056] In the emulsion polymerization described above, the styrene monomer, nitrile monomer, vinyl acetate monomer, (meth)acrylic acid ester monomer, etc. may be further mixed in an appropriate amount with dicyclopenta(thenyl(meth)acrylate monomer before emulsion polymerization. When dicyclopenta(thenyl(meth)acrylate monomer is further mixed in and emulsion polymerization is carried out, the stability is less likely to be impaired even if the water in the dispersion evaporates, and a resin particle dispersion containing the aforementioned surfactant with even greater stability can be obtained. The dicyclopentanyl(meth)acrylate monomers that can be used include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate.

[0057] Furthermore, in the present invention, when performing the emulsion polymerization described above, in addition to the dicyclopenta(thenyl(meth)acrylate monomer, monomers having reactive crosslinking groups such as epoxy groups, hydroxymethylamide groups, and isocyanate groups, or polyfunctional monomers having two or more vinyl groups may be appropriately blended and crosslinked.

[0058] In the present invention, the amount of monomer used among the polymer components constituting the resin particle dispersion is preferably 30% by mass or more, more preferably 30 to 95% by mass, and particularly preferably 30 to 70% by mass, relative to the total polymer components constituting the resin particle dispersion. In this invention, "total polymer components" refers to the polymerizable components that constitute the resin particle dispersion, specifically the total amount of all types of monomers that serve as raw materials for the final polymer, and the crosslinking agent. In the case of Group A, it refers to the total amount of Group A monomers used, other monomer components used, and the crosslinking agent described later. In products using monomers of group A, the effects of the present invention can be further enhanced by setting the content of group A to 30% by mass or more relative to the total polymer components. On the other hand, if the content is less than 30% by mass, the stability over time tends to be poor.

[0059] Furthermore, in the present invention, when using group A polymer components such as the (meth)acrylic acid ester monomers mentioned above among the polymer components constituting the black resin particle dispersion, the content of other monomer components other than group A will be the remainder of the total amount of group A components such as the (meth)acrylic acid ester monomers used and the crosslinking agent described later. Preferably, the content of other monomer components is 0.5 to 70% by mass relative to the total polymer components, from the viewpoint of further exhibiting the effects of the present invention, dispersibility, and reactivity.

[0060] In the present invention, the total (solid content) of the azo iron dye that becomes the black dye represented by formula (α) or formula (β) above is preferably 0.1% by mass or more, more preferably 1% by mass or more, relative to the total polymer components in the particles, from the viewpoint of black color development and storage stability.

[0061] The polymerizable surfactant that can be used as needed as described above is not particularly limited as long as it is a polymerizable surfactant that is normally used in emulsion polymerization. For example, the polymerizable surfactant can be anionic or nonionic polymerizable surfactant, such as Adekaria Soap NE-10, NE-20, NE-30, NE-40, SE-10N, SR-10, SR-20, ER-10, ER-20, ER-30, ER-40, or PP manufactured by ADEKA Corporation. Examples include at least one of the following polymerizable surfactants: -70, Latemul S-180, S-180A, S-120A, PD-420, PD-430, PD-450 manufactured by Kao Corporation, Eleminol JS-20, CLS-20, RS-3000 manufactured by Sanyo Chemical Industries, Ltd., Aqualon AN-10, AN-20, AN-30, AN-5065, KH-05, KH-10, KH-1025, HS-10, AR-10, AR-1025, AR-20 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and Spinomer NaSS manufactured by Tosoh Finechem. The amount of these polymerizable surfactants used is preferably 0.1 to 50% by mass, relative to the total amount of the above monomers. Furthermore, the content of the crosslinking agent, such as triallyl isocyanurate, is preferably 0 to 50% by mass, more preferably 0.1 to 25% by mass, relative to the total amount of monomer.

[0062] In the present invention, a resin particle dispersion (dispersion) is obtained in which resin particles containing an azo iron dye component is dispersed in water, specifically in the above preferred embodiment, which is a homopolymer obtained from each resin monomer containing an azo iron dye component that becomes a black dye represented by formula (α) or formula (β) by the above polymerization, or a copolymer of these monomers. Alternatively, a resin particle dispersion (dispersion) is obtained in which resin particles containing an azo iron dye component are dispersed in water, by dissolving at least one azo iron dye component selected from the above black dyes represented by formula (α) or formula (β) in a monomer selected from acrylic monomer, styrene monomer, nitrile monomer, and vinyl acetate monomer of group A, and performing emulsion polymerization, or by dissolving an azo iron dye component that becomes a black dye represented by formula (α) or formula (β) after polymerization of a mixed monomer containing at least the above acrylic monomer, styrene monomer, nitrile monomer, and vinyl acetate monomer and other monomer components, and performing emulsion polymerization. The amount of resin particles in the black resin particle dispersion obtained under these manufacturing conditions varies depending on the amount of resin monomer used (such as monomers from group A), the amount of azo iron dye component that becomes a black dye represented by formula (α) or formula (β), the polymerization conditions, etc. From the viewpoint of manufacturability, workability, and efficiency, it is preferable to manufacture it so that the solid content is 1 to 50% by mass. More preferably, it is preferable to manufacture it so that the solid content is 10 to 40% by mass.

[0063] In the present invention, it is preferable that the black resin particles contain an ultraviolet absorber and / or a light stabilizer in order to further enhance the light resistance and light stability effect. 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Examples of commercially available UV absorbers include "Tinuvin900," "Tinuvin928," "Tinuvin348-2," "Tinuvin479," "Tinuvin405," and "Tinuvin400" (all manufactured by BASF, trade names, Tinuvin®), and "RUVA-93" (both manufactured by Otsuka Chemical Co., Ltd., trade names). The UV absorber content in these black resin particles can be 1 to 50% by mass, and preferably 10 to 40% by mass, relative to the total amount of particles excluding the solvent, from the viewpoints of color development, lightfastness, and stability.

[0068] 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. A more preferred embodiment of the light stabilizer is a polymerizable (reactive) light stabilizer having the above-mentioned methacrylic group, etc. A polymerizable (reactive) light stabilizer that readily polymerizes with the above-mentioned (meth)acrylic acid ester, styrene, nitrile, vinyl acetate, etc., and can incorporate the light-stabilizing functional group into the polymer chain can be suitably used, and black resin particles with high safety and long-term stable light stability can be obtained without volatilization or elution of the light stabilizer. In addition, even non-polymerizable light stabilizers can be included in the black resin particles to impart the desired light stability.

[0069] 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.

[0070] Furthermore, commercially available hindered amine-based light stabilizers include, for example, "Tinuvin765," "Tinuvin770DF," "Tinuvin144," "Tinuvin622SF," and "Tinuvin152" (all manufactured by BASF, trade names, Tinuvin®), "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). The content of the light stabilizer in these black resin particles can be 1 to 50% by mass, and preferably 10 to 40% by mass, relative to the total amount of particles excluding the solvent, from the viewpoints of color development, lightfastness, and stability.

[0071] In the present invention, in order to further enhance long-term stability, preservative properties, color development, and fragrance, the black resin particles may contain, along with the azo iron dye which is a black dye represented by formula (α) or formula (β) above, a preservative, a reducing agent, a coloring agent containing a dye or pigment other than the black dye, a coloring agent containing a thermochromic, a fragrance, etc.

[0072] The production of black resin particles containing an azo iron dye that becomes a black dye represented by formula (α) or formula (β) above, along with preferred components such as an ultraviolet absorber and a light stabilizer, can be carried out in accordance with the production of black resin particles containing an azo iron dye that becomes a black dye represented by formula (α) or formula (β) above. At a minimum, a black resin particle dispersion (dispersion) in which black resin particles are dispersed in water can be obtained by dissolving the azo iron dye that becomes a black dye represented by formula (α) or formula (β), an ultraviolet absorber, and a light stabilizer in each of the above monomers, such as the above (meth)acrylic acid ester monomer, and then emulsion polymerization, or by dissolving the azo iron dye that becomes a black dye represented by formula (α) or formula (β), an ultraviolet absorber, and a light stabilizer after homopolymerization or copolymerization of a mixed monomer containing the above (meth)acrylic acid ester monomer and other monomer components, or a monomer selected from group A above, and then emulsion polymerization. The amount of black resin particles in the black resin particle dispersion obtained under these manufacturing conditions varies depending on the amount of the above-mentioned Group A materials used, monomers such as (meth)acrylic acid esters, azo iron dyes that become black dyes represented by formula (α) or formula (β), ultraviolet absorbers, light stabilizers, etc., as well as polymerization conditions. From the viewpoint of manufacturability, workability, and efficiency, it is preferable to manufacture the dispersion so that the solid content is 1 to 50% by mass. More preferably, it is preferable to manufacture the dispersion so that the solid content is 10 to 40% by mass.

[0073] Furthermore, in this invention, further improvements in blackness can be expected by using materials that have absorption at specific wavelengths in combination, etc. 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 30.00% by mass, and particularly preferably 0.1 to 15.0% by mass, relative to the total polymer components in the particles, from the viewpoint of further improving blackness and improving particle stability.

[0074] It is preferable to use an appropriate amount of defoaming agent during the above manufacturing process. Examples of defoaming agents that can be used include silicone-based, mineral oil-based, polymer-based, and fatty acid ester-based agents. Preferably, as a silicone-based defoamer, an emulsion-type defoamer, such as a silicone oil compound emulsified with a nonionic surfactant, is easy to handle, highly safe, and available in a wide variety of types, making it suitable for use in various aqueous liquids. Specifically, examples include KM-90 and KM-7752 from Shin-Etsu Chemical Co., Ltd., and Surfinol 104A, 104E, 104H, 104PA, 104PG-50, AD01, DF110D, and MD-20 from Nisshin Chemical Industry Co., Ltd., as well as KS-530 from Shin-Etsu Chemical Co., Ltd. if it is a self-emulsifying type.

[0075] Furthermore, in the present invention, the average particle size of the black resin particles obtained (containing an azo iron dye that becomes a black dye represented by formula (α) or the above formula (β), or containing an azo iron dye that becomes a black dye represented by formula (α) or the above formula (β) and an ultraviolet absorber and / or light stabilizer, the same applies hereinafter) varies depending on the monomer, its content, polymerization conditions during polymerization, etc. However, a particle size of 30 to 200 nm is desirable in terms of storage stability, clogging of pen nibs in the case of writing instruments, and clogging of nozzles in the case of inkjet inks. The average particle size of the black resin particles can be adjusted by suitably combining the above monomer species and their amounts, polymerization conditions (temperature, pressure, etc.). In this invention, the "average particle diameter" refers to the histogram average particle diameter (D50) obtained from the scattered light intensity distribution measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)]. By setting the average particle diameter within the preferred range described above, it can be suitably used for various applications and will also have excellent storage stability. Furthermore, in the present invention, it is more desirable to use polymerizable ultraviolet absorbers and / or light stabilizers.

[0076] The black resin particle dispersion of the present invention contains azo iron dyes that are black dyes represented by the above formula (α) or (β). These particles exhibit excellent storage stability, do not contain harmful heavy metals, have lightfastness at the same level as Cr complex dyes, have a wide absorption spectral wavelength range, exhibit excellent blackness and lightfastness, and maintain their properties without adversely affecting other components, and have excellent dispersion stability. As a result, the dispersion exhibits the above-mentioned excellent properties, and the sustained effect of these properties lasts for a long period of time. Furthermore, the black resin particles containing the aforementioned azo iron dye, UV absorber, and light stabilizer will yield a unique black resin particle dispersion that is even more lightfast and weather-resistant without compromising storage stability, blackness, or lightfastness. Furthermore, the black resin particle dispersion of the present invention has the unique effect of improving the blackness by encapsulating the dye within the resin particles, rather than directly incorporating the dye into the solution medium.

[0077] As described above, the black resin particle dispersion (dispersion) of the present invention exhibits excellent effects and can therefore be used, for example, in aqueous ink compositions for writing instruments. Furthermore, the form of the black resin particle dispersion (dispersion) of the present invention when used in an aqueous ink composition for writing instruments such as felt-tip pens, marking pens, and ballpoint pens will be described in detail below.

[0078] (Water-based ink composition for writing instruments) The aqueous ink composition for writing instruments of the present invention is characterized by containing at least a dispersion of black resin particles having the above-described structure, and may also contain a water-soluble organic solvent in addition to this dispersion of black resin particles. The amount of black resin particles in the ink composition is preferably 0.1 to 30.0% by mass, and more preferably 1.0 to 15.0% by mass, based on the solid content of the total ink composition, in order to exhibit the effects of the present invention without impairing writing performance and from the standpoint of storage stability.

[0079] Examples of water-soluble organic solvents that can be used include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol, and 2-methylpentanediol. Examples include alkylene glycols such as -2,4-diol, 3-methylpentane-1,3,5-triol, and 1,2,3-hexanetriol; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; glycerols such as glycerol, diglycerol, and triglycerol; lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol mono-n-butyl ether; and at least one of the following: N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidalidinone.

[0080] In addition, water-soluble solvents such as alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, benzyl alcohol, etc.), amides (dimethylformamide, diethylacetamide, etc.), and ketones (acetone, etc.) can also be mixed. The content of these water-soluble organic solvents varies depending on the type of writing instrument, such as felt-tip pens, marking pens, and ballpoint pens. It is particularly effective for ink compositions in which the content is 1 to 40% by mass relative to the total amount of ink composition, and 10% by mass or less is used to further improve line drying properties. More preferably, it is desirable to use 3 to 8% by mass.

[0081] The aqueous ink composition for writing instruments of the present invention contains, in addition to the black resin particle dispersion and water-soluble solvent having the above-mentioned properties, the remainder may include water as a solvent (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), as well as other complementary colorants, dispersants, lubricants, pH adjusters, rust inhibitors, thickeners, evaporation inhibitors, surfactants, etc., to the extent that they do not impair the effects of the present invention.

[0082] Other dispersants that can be used include nonionic and anionic surfactants and water-soluble resins, in addition to the acetylene-based surfactants and polyethylene glycol-based surfactants mentioned above. Water-soluble polymers are preferably used. 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.

[0083] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonic acid and phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitride, and saponins. Examples of thickening agents include cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, fermented cellulose, and crystalline cellulose, as well as polysaccharides. Examples of polysaccharides that can be used include xanthan gum, guar gum, hydroxypropylated guar gum, casein, gum arabic, gelatin, amylose, agarose, agaropectin, arabinan, curdlan, callose, carboxymethyl starch, chitin, chitosan, quince seed, glucomannan, gellan gum, tamarind seed gum, dextran, nigellan, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkasi gum, succinoglycan, locust bean gum, and tara gum. These may be used individually or in combination of two or more. Commercially available products of these may also be used.

[0084] Examples of evaporation inhibitors include pentaerythritol, p-xylene glycol, trimethylolpropane, triethylolpropane, and dextrin. Examples of surfactants include fluorine-based, silicone-based, and acetylene glycol-based surfactants. Furthermore, in this invention, it is preferable to use olefin resin particles in order to improve the quality of the writing lines, and the content of these olefin resin particles is preferably 0.01 to 20% by mass, more preferably 1 to 5% by mass, relative to the total amount of ink composition. The olefin resin particles that can be used are not particularly limited in shape and structure, as long as they have a hardness of 1 or more by the penetration test and an average particle diameter of 15 μm or less as measured by the Coulter counter method. For example, commercially available products include Chemipearl W100, W200, W400, and W500 manufactured by Mitsui Chemicals, and even among the same type of olefin resin particles (Chemipearl products), Chemipearl W300, W308, W310, W700, and W900 can be mentioned. If the hardness by the penetration test is 1 or more, improved ink flow can be expected, and a stable writing flow rate can be obtained.

[0085] The aqueous ink composition for writing instruments of the present invention can be prepared by appropriately combining the above-described black resin particle dispersion, water-soluble solvent, and other components according to the application of the ink for writing instruments (ballpoint pens, marking pens, etc.), and stirring and mixing them with a stirrer such as a homomixer, homogenizer, or disper, and further removing coarse particles from the ink composition by filtration or centrifugation as necessary.

[0086] Furthermore, the pH (at 25°C) of the aqueous ink composition for writing instruments of the present invention is preferably adjusted to 5 to 10 using a pH adjuster or the like, and more preferably to 6 to 9.5, from the viewpoint of usability, safety, stability of the ink itself, and compatibility with the ink container.

[0087] The aqueous ink composition for writing instruments of the present invention is used in ballpoint pens, marking pens, and the like, which are equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, and plastic tips. 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 containing a ball measuring mm in diameter, and an ink follower containing a substance that is incompatible with the aqueous ink composition contained within the ink refill and has a lower specific gravity than the aqueous ink composition, such as polybutene, silicone oil, or mineral oil. In a ballpoint pen, the axial movement (vertical direction) (distance) of the writing ball is preferably 15 to 80 μm, from the standpoint of appropriately dispensing resin particles and stabilizing the writing flow rate. The structure of the ballpoint pen and marking pen is not particularly limited. For example, it may be a direct-ink type ballpoint pen or marking pen equipped with a collector structure (ink holding mechanism) in which the barrel itself serves as the ink reservoir and the above-described aqueous ink composition for writing instruments is filled into the barrel.

[0088] In the aqueous ink composition for writing instruments of the present invention configured in this way, since the black resin particle 09 dispersion with the above-mentioned properties is incorporated into the aqueous ink composition for writing instruments, conventionally, oil-based azo iron dyes that become black dyes represented by formula (1) or formula (I) have been used, but even in aqueous solutions, it exhibits excellent dispersion stability and can be stably incorporated into various water-based inks. In the present invention, by producing this black resin particle dispersion containing the azo iron dye component that becomes black dye represented by formula (1) or formula (I), an aqueous ink composition for writing instruments can be obtained that has excellent storage stability, a wide absorption spectral wavelength range, and excellent blackness and lightfastness. [Examples]

[0089] 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.

[0090] [Manufacturing Examples 1-20: Manufacturing of resin particle dispersions (particles 1-20)] Each resin particle dispersion was manufactured according to the following manufacturing examples 1 to 20. Note that "parts" below refers to parts by mass. The amount of surfactant components is the solid content.

[0091] (Manufacturing Example 1) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 309.5 parts distilled water, 5 parts glycerin monomethacrylate [Bremmer GLM, NOF Corporation], 5 parts sodium 2-sulfoethyl methacrylate [Acrylates SEM-Na, Mitsubishi Chemical Corporation], 40 parts polymerizable surfactant [ADEKA Corporation, Adekarya Soap SR-10, ether sulfate], and 0.5 parts ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas.

[0092] On the other hand, a solution was prepared by mixing a mixed monomer consisting of 55 parts of cyclohexyl methacrylate monomer and 20 parts of n-butyl methacrylate with 35 parts of a substance represented by formula (α) as an azo iron dye component and 10 parts of a crosslinking agent [trialyl isocyanurate, manufactured by Nippon Chemical Corporation, TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 90°C, under stirring for 1 hour to carry out emulsion polymerization. After further aging for 6 hours, polymerization was completed to obtain a black resin particle dispersion (dispersion) (particle 1). The methacrylic acid ester monomer content was 44.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 18.4% by mass relative to the total polymer components. The average particle size of the black resin particles was 108 nm.

[0093] (Manufacturing example 2) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 2) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 304.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and as an azo iron dye component, the substance represented by formula (α) was used: 35 parts, and as a complementary dye, Oil Yellow 129 manufactured by Orient Chemical Industry Co., Ltd. was used: 10 parts. The methacrylate ester monomer content was 46.2% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 17.9% by mass relative to the total polymer components. The average particle size of the resin particles was 82 nm.

[0094] (Manufacturing Example 3) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 3) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 304.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and the azo iron dye component was 35 parts of a substance represented by formula (β) manufactured by Orient Chemical Industry Co., Ltd. The methacrylate ester monomer content was 46.2% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 17.9% by mass relative to the total polymer components. The average particle size of the resin particles was 98 nm.

[0095] (Manufacturing example 4) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particles 4) was obtained in the same manner as in Production Example 1, except that 309.5 parts of distilled water were used and 10 parts of Optima Yellow 6101, manufactured by Orient Chemical Industry Co., Ltd., were used as the complementary dye. The methacrylic acid ester monomer content was 47.2% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 87 nm.

[0096] (Manufacturing example 5) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 5) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 309.5 parts, the amount of cyclohexyl monomer methacrylate was 30 parts, and the amount of n-butyl methacrylate was 45 parts. The content of the methacrylic acid ester monomer was 44.7% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 18.4% by mass relative to the total polymer components. The average particle size of the resin particles was 79 nm.

[0097] (Manufacturing example 6) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 6) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 319.5 parts and the crosslinking agent [trialyl isocyanurate, manufactured by Nippon Chemical Corporation, TAIC] was excluded. The methacrylate ester monomer content was 47.2% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 105 nm.

[0098] (Manufacturing example 7) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 7) was obtained in the same manner as in Production Example 1, except that 309.5 parts of distilled water were used and 10 parts of Valifast Yellow 1108, manufactured by Orient Chemical Industry Co., Ltd., were used as the complementary color dye component. The methacrylic acid ester monomer content was 44.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 18.4% by mass relative to the total polymer components. The average particle size of the black resin particles was 101 nm.

[0099] (Manufacturing example 8) In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particle 7) was obtained in the same manner as in Production Example 1, except that 309.5 parts of distilled water were used and 10 parts of Oil Yellow 105M, manufactured by Orient Chemical Industry Co., Ltd., were used as the complementary color dye component. The methacrylic acid ester monomer content was 44.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 18.4% by mass relative to the total polymer components. The average particle size of the black resin particles was 83 nm.

[0100] (Manufacturing example 9) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 309.5 parts of distilled water, 40 parts of polymerizable surfactant [ADEKA Corporation, Adekaria Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas. A solution was prepared by mixing 75 parts of the aforementioned methacrylonitrile monomer with 20 parts of the substance represented by formula (α) and 15 parts of the substance represented by formula (β) as azo iron dye components, 10 parts of Oil Yellow 129 manufactured by Orient Chemical Industry Co., Ltd. as a complementary dye, and 10 parts of a crosslinking agent [trialyl isocyanurate, manufactured by Nippon Chemical Industries, Ltd., TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 90°C, under stirring for 3 hours to carry out emulsion polymerization. After further aging for 5 hours, polymerization was completed, and the resin particle dispersion (dispersion) was collected to obtain a black resin particle dispersion (dispersion) (particle 9). The nitrile monomer content was 41.7 parts by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4 parts by mass relative to the total polymer components. The average particle size of the black resin particles was 94 nm.

[0101] (Manufacturing example 10) A black resin particle dispersion (dispersion) (particles 10) was obtained in the same manner as in Production Example 9 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (α) were used as the azo iron dye component. The nitrile monomer content was 41.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 89 nm.

[0102] (Manufacturing Example 11) A black resin particle dispersion (dispersion) (particles 11) was obtained in the same manner as in Production Example 9 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (β) were used as the azo iron dye component. The nitrile monomer content was 41.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 88 nm.

[0103] (Manufacturing Example 12) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 309.5 parts of distilled water, 40 parts of polymerizable surfactant [ADEKA Corporation, Adekaria Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas. A solution was prepared by mixing 75 parts of the aforementioned styrene monomer with 15 parts of the substance represented by formula (α) and 20 parts of the substance represented by formula (β) as azo iron dye components, 10 parts of Oil Yellow 129 manufactured by Orient Chemical Industry Co., Ltd. as a complementary dye, and 10 parts of a crosslinking agent [trialyl isocyanurate, manufactured by Nippon Chemical Industries, Ltd., TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 90°C, under stirring for 3 hours to carry out emulsion polymerization. After further aging for 5 hours, polymerization was completed, and the resin particle dispersion (dispersion) was collected to obtain a black resin particle dispersion (dispersion) (particle 12). The styrene monomer content was 41.7 parts by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4 parts by mass relative to the total polymer components. The average particle size of the black resin particles was 61 nm.

[0104] (Manufacturing Example 13) A black resin particle dispersion (dispersion) (particles 13) was obtained in the same manner as in Production Example 12 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (α) was used as the azo iron dye component. The styrene monomer content was 41.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 69 nm.

[0105] (Manufacturing Example 14) A black resin particle dispersion (dispersion) (particle 14) was obtained in the same manner as in Production Example 12 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (β) were used as the azo iron dye component. The styrene monomer content was 41.7% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 88 nm.

[0106] (Manufacturing example 15) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 309.5 parts of distilled water, 40 parts of polymerizable surfactant [ADEKA Corporation, Adekaria Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas. A solution was prepared by mixing 75 parts of the aforementioned vinyl acetate monomer with 15 parts of the substance represented by formula (α) and 20 parts of the substance represented by formula (β) as azo iron dye components, 10 parts of Oil Yellow 129 manufactured by Orient Chemical Industry Co., Ltd. as a complementary dye, and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Chemical Industries, Ltd., TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 90°C, under stirring for 3 hours to carry out emulsion polymerization. After further aging for 5 hours, polymerization was completed, and the resin particle dispersion (dispersion) was collected to obtain a black resin particle dispersion (dispersion) (particle 15). The content of the vinyl acetate monomer was 41.7 parts by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 19.4 parts by mass relative to the total polymer components. The average particle size of the black resin particles was 91 nm.

[0107] (Manufacturing example 16) A black resin particle dispersion (dispersion) (particles 16) was obtained in the same manner as in Production Example 15 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (α) was used as the azo iron dye component. The content of vinyl acetate monomer was 41.7% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 123 nm.

[0108] (Manufacturing example 17) A black resin particle dispersion (dispersion) (particle 17) was obtained in the same manner as in Production Example 15 above, except that 309.5 parts of distilled water were used and 35 parts of the substance represented by formula (β) were used as the azo iron dye component. The content of vinyl acetate monomer was 41.7% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 107 nm.

[0109] [Manufacturing Example 18 (Comparative Example 1)] In the above-mentioned Production Example 1, a black resin particle dispersion (dispersion) (particles 18) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 304.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and as the azo chromium dye component, Valifast Black 3830, manufactured by Orient Chemical Industry Co., Ltd., a mixture of azo compound chromium complex dye and amine, was used in 35 parts. The content of the methacrylic acid ester monomer was 44.7% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 18.4% by mass relative to the total polymer components. The average particle size of the resin particles was 108 nm.

[0110] [Manufacturing Example 19 (Comparative Example 2)] In the above-mentioned production example 18, a black resin particle dispersion (dispersion) (particles 19) was obtained in the same manner as in production example 18, except that 314.5 parts of distilled water were used and 30 parts of Valifast Black 3804, a mixture of azo compound chromium complex dye and amine, manufactured by Orient Chemical Industry Co., Ltd., was used as the azo chromium dye component. The methacrylic acid ester monomer content was 45.9% by mass relative to the total polymer components constituting the resin particles, and the azo iron dye component content was 16.2% by mass relative to the total polymer components. The average particle size of the resin particles was 120 nm.

[0111] [Manufacturing Example 20 (Comparative Example 3)] In the above production example 18, a black resin particle dispersion (dispersion) (particles 20) was obtained in the same manner as in production example 18, except that 319.5 parts of distilled water were used and 25 parts of Oil Black 860: azo compound dye, manufactured by Orient Chemical Industry Co., Ltd., were used as the azo dye component. The content of the methacrylic acid ester monomer was 47.2% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 13.9% by mass relative to the total polymer components. The average particle size of the resin particles was 148 nm.

[0112] Each of the resin particle dispersions obtained from the above production examples 1 to 20 was evaluated for specified heavy metal content, black color development, lightfastness, and storage stability using the evaluation method described below. The solid content of resin particles in each resin particle dispersion (dispersion) obtained in the above manufacturing examples 1 to 20 was 35 to 40% by mass. These results are shown in Table 3 below.

[0113] (Evaluation of specified heavy metal content) The presence or absence of heavy metals in each of the above black resin particle dispersions was evaluated according to the following evaluation criteria. The presence or absence of heavy metals was evaluated for the chromium compounds contained in each black resin particle dispersion 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, an 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.

[0114] (Method for evaluating the color development of black) The black resin particle dispersion (dispersion) obtained above was used to visually evaluate the black color development. For the evaluation of black color, a comparative example was used in which the same amount of azo iron dye as the black resin particle dispersion (dispersion) was directly dissolved, and the coating films applied to Catherine paper with a bar coater were compared relatively. The black color development of the coating film with the same amount of azo iron dye as the black resin particle dispersion (dispersion) was judged as "C", and a relative evaluation was performed according to the following criteria. Evaluation criteria: A: Has a much higher black color rendering than C. B: Slightly better black color rendering than C. C: Using a directly dissolved azo iron dye.

[0115] (Method for evaluating lightfastness) Using the black resin particle dispersion (dispersion) obtained above, the light resistance was tested using a Suga Test Instruments X25 xenon weather meter under xenon arc light according to JIS L 0843 at 50 W / 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. D: Not visible.

[0116] (Method for evaluating storage stability) Using the black resin particle dispersion (dispersion) obtained above, the temporal stability was evaluated by visually inspecting the presence or absence of precipitates after placing the black resin particle dispersion (dispersion) in a glass mayonnaise bottle (manufactured by AS ONE Corporation) at a temperature of 60°C for a period of 2 weeks, according to the evaluation criteria below. Evaluation criteria: A: No precipitates B: Some precipitation is visible. C: Precipitation is visible throughout. D: Precipitates have accumulated.

[0117] Furthermore, using black resin particle dispersions (Production Examples 1, 9-12, 18-20), aqueous ink compositions for writing instruments with the compositions shown in Table 2 below were prepared. These compositions were then loaded into writing instruments (sign pens) with the following configurations, and their specified heavy metal content, black color development, lightfastness, and storage stability were evaluated in the same manner as described above. The results are shown in Table 4 below.

[0118] (Writing instrument: Making a felt-tip pen) A felt-tip pen was prepared by filling the storage chamber with the obtained water-based ink for writing instruments using a felt-tip pen [manufactured by Mitsubishi Pencil Co., Ltd., product name: PUS-138, pen tip: PET sintered core].

[0119] [Table 3]

[0120] [Table 4]

[0121] As is clear from the results in Tables 3 and 4 above, the black resin particle dispersions (acrylic, styrene, nitrile, vinyl acetate, urethane) of Production Examples 1 to 17, which fall within the scope of the present invention, and the aqueous ink compositions for writing instruments of Examples 1 to 5, which contain the same and also fall within the scope of the present invention, were found to be superior in terms of blackness, lightfastness, and storage stability compared to Comparative Examples 1 to 3, which fall outside the scope of the present invention and do not use azo iron dyes. [Industrial applicability]

[0122] The black resin particle dispersion of the present invention can be suitably used in writing instrument inks (low viscosity ballpoint pens, cotton-filled writing instruments & direct-ink writing instruments, gel ballpoint pens, cotton-filled felt-tip pens, valve-type felt-tip pens, direct-ink felt-tip pens), as well as for inkjet applications, cosmetics: eyeliner, hair dye, etc.

Claims

1. A black resin particle dispersion characterized in that at least resin particles containing an azo iron dye are dispersed in water.

2. The black resin particle dispersion according to claim 1, characterized in that the azo iron dye is represented by the following formula (α) or the following 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.)

3. The black resin particle dispersion according to claim 1 or 2, characterized in that the resin particles containing the azo iron dye are composed of a homopolymer or copolymer obtained from at least one monomer selected from group A below. <Group A> Acrylic monomer, styrene monomer, nitrile monomer, vinyl acetate monomer

4. The black resin particle dispersion according to any one of claims 1 to 3, characterized in that the resin particles containing the azo iron dye contain an ultraviolet absorber and / or a light stabilizer.

5. An aqueous ink composition for writing instruments, characterized by comprising a resin particle dispersion according to any one of claims 1 to 4.

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