Black resin particle dispersion and aqueous ink composition for writing implements containing same

Abstract

Provided are: a black resin particle dispersion having excellent light resistance, blackness, and storage stability; and an aqueous ink composition for writing implements.　A black resin particle dispersion according to the present disclosure is characterized in that at least resin particles encapsulating an azo iron dye are dispersed in water.　The azo iron dye is preferably represented by formula (α). (In formula (α) the R1 groups are the same or different and represent a hydrogen atom or an alkyl group having 1-12 carbon atoms; the R2 groups and R3 groups are the same or different and represent an alkyl group having 3-10 carbon atoms; and A+ represents a monovalent ammonium ion that has an alkyl group having 3-18 carbon atoms or an ammonium ion of a guanidine derivative.)

Description

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

[0001] This specification 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.

[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 skeleton. Generally, these complexes have often used heavy metals that are harmful (such as Cr, Co, Cd, Pb, etc., as defined in the European standard: Toy Safety EN71-3:2019 and the International Toy Safety Standard (ISO 8124-3), Part 3 of the International Toy Safety Standard established by the International Organization for Standardization, ISO).

[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 good black color (see, for example, Patent Documents 1 and 2). On the other hand, as a higher quality oil-based black ink composition that suppresses the bleeding of dyes other than black from handwriting, a black ink composition is known that contains a black dye such as C.I. Solvent Black 7 as the main colorant, and is characterized by comprising an organic solvent consisting of a glycol ether-based solvent or an alcohol-based solvent, a black dye soluble in the organic solvent, a second dye which is a yellow dye such as C.I. 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 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. Furthermore, there is no disclosure regarding their application to aqueous solutions or their potential for use. Similarly, the black ink composition described in Patent Document 3 is suitable for oil-based writing instrument inks, but its storage stability may still be unstable, and its lightfastness may not be sufficient. Moreover, there is no disclosure regarding its application to aqueous solutions.

[0006] Japanese Patent Publication No. 2017-222751 (Claims, Examples, etc.), International Publication No. 2022 / 163736 (Claims, Examples, etc.), Japanese Patent Publication No. 2022-172778 (Claims, Examples, etc.)

[0007] This disclosure aims to address the problems of the prior art described above and to provide 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 (ISO 8124-3)), 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.

[0008] In light of the above-mentioned conventional problems, the Discloser has conducted diligent research and has 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 has completed this disclosure.

[0009] In other words, the black resin particle dispersion of this disclosure is characterized in that at least resin particles containing an azo iron dye are dispersed in water. Preferably, the azo iron dye is represented by the following formula (α) or the following formula (β). [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 ３is the same or different and is an alkyl group having 3 to 10 carbon atoms, A ＋ represents a monovalent ammonium ion having an alkyl group having 3 to 18 carbon atoms or an ammonium ion of a guanidine derivative.]] [In the above formula (β), R １ and R ２ are each independently an alkyl group having 3 to 10 carbon atoms, which is linear or branched, and R ３ is an electron-withdrawing group, R ４ is an alkyl group having 1 to 5 carbon atoms, which is linear or branched, or an alkoxy group having 1 to 5 carbon atoms, which is linear or branched, and R ５ is a nitro group, a sulfonamide group, or a halogen atom, and R ６ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, which is linear or branched, a nitro group, or a halogen atom, and R ７ is a hydrogen atom or an alkyl group having 3 to 12 carbon atoms, which is linear or branched, 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 disclosure is characterized by containing a black resin particle dispersion having the above configuration.

[0010] According to the present disclosure, there are provided a black resin particle dispersion and an aqueous ink composition for writing instruments, which are excellent in storage stability, do not contain harmful heavy metals, can raise the light resistance to the same level as that of a Cr complex dye, have a wide absorption spectrum wavelength range, and are excellent in blackness. The objects and effects of the present disclosure are recognized and obtained by using the components and combinations particularly 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 disclosure described in the claims.

[0011] Embodiments of this disclosure will be described in detail below. However, it should be noted that the technical scope of this disclosure is not limited to each embodiment described below, but extends to the inventions described in the claims and their equivalents. The black resin particle dispersion of this disclosure is characterized in that resin particles containing at least an azo iron dye are dispersed in water. In this disclosure, the azo iron dye that becomes the black dye is not particularly limited as long as it is a 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 each aromatic ring linked by an azo group (-N=N-) forms a complex salt with iron (Fe: metal). However, in terms of black performance, lightfastness, etc., an azo iron dye represented by the following formula (α) or the following formula (β) is preferred.

[0012] [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. [In the above formula (β), R １ and R ２ These are linear or branched alkyl groups having 3 to 10 carbon atoms, and R ３ R is an electron-withdrawing group, ４ R is a linear or branched alkyl group having 1 to 5 carbon atoms, or a linear or branched alkoxy group having 1 to 5 carbon atoms. ５ R is a nitro group, a sulfoamide group, or a halogen atom. ６ R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. ７ A is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms. ＋ This indicates a monovalent cation.

[0013] In this disclosure, the resin particles containing at least one azo iron dye component selected from the azo iron dyes represented by formula (α) or formula (β) above are not particularly limited in function or resin type. Examples include homopolymers or copolymers of these monomers obtained from various resin monomers such as acrylic monomers, allyl monomers, isocyanate monomers, isothiocyanate monomers, epoxy monomers, diamine monomers, siol monomers, dicarboxylic acid chloride monomers, dicarboxylic acid monomers, disulfonyl chloride monomers, dithiol monomers, divinyl monomers, diallyl monomers, styrene monomers, tetracarboxylic anhydride monomers, nitrile monomers, bismaleimide monomers, lactone monomers, actide monomers, fluorine-containing monomers, and cyclic olefin monomers. Preferably, the resin particle dispersion of this disclosure is composed of a homopolymer or copolymer obtained from at least one monomer selected from the following group A, from the viewpoint of ease of encapsulation in resin particles, controllable reaction rate, post-reaction stability, and post-reaction dispersibility. <Group A> Acrylic monomers, styrene monomers, nitrile monomers, vinyl acetate monomers

[0014] To produce black resin particles containing at least one azo iron dye component selected from the azo iron dyes represented by formula (α) or formula (β) above, for example, each black resin particle dispersion can be obtained by polymerizing (homopolymerization or copolymerization) using at least one azo iron dye component selected from the azo iron dyes represented by formula (α) or formula (β) above, and at least one of the above-mentioned monomer components, using a suitable polymerization initiator depending on the monomer species. Furthermore, each black resin particle dispersion can be obtained by appropriately adjusting the manufacturing conditions such as temperature, stirring speed, and reaction time during polymerization. Examples of the copolymer resin particles of Group A mentioned above include: copolymer particles of acrylic monomer and styrene monomer; copolymer particles of acrylic monomer and nitrile monomer; copolymer particles of acrylic monomer and vinyl acetate monomer; copolymer particles of styrene monomer and nitrile monomer; copolymer particles of styrene monomer and vinyl acetate monomer; copolymer particles of nitrile monomer and vinyl acetate monomer; copolymer particles of acrylic monomer, styrene monomer and nitrile monomer; copolymer particles of acrylic monomer, styrene monomer and nitrile monomer; copolymer particles of acrylic monomer, styrene monomer and vinyl acetate monomer; copolymer particles of acrylic monomer, styrene monomer and vinyl acetate monomer; copolymer particles 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 its ability to produce particles with high blackness, strong fastness and durability of the encapsulable azo iron dye component described later, without adversely affecting other compounding components, and with high persistence of the predetermined effect of the azo iron dye component.

[0015] Furthermore, as the acrylic monomer that can be used, a (meth)acrylic acid ester monomer represented by the following general formula (X) is preferred. In the above formula (X), A is a hydrogen atom (H) or a methyl group (CH ３) where R represents a hydrogen atom (H), a C1-C22 alkyl group, or a substituent having a polyalkylene glycol chain with 2-18 carbon atoms in the alkylene chain, and the substituent having an alkyl group or polyalkylene glycol chain may have a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, a C1-C18 alkoxy group, a C1-C18 perfluoroalkyl group, or a trialkoxysilyl group as a substituent. Examples include a linear or branched alkyl group having 1-20 carbon atoms, a cycloalkyl group having 3-10 carbon atoms, an alkyl group having 1-18 carbon atoms which may have an epoxy group, a hydroxyl group, a dialkylamino group, or a C1-C4 alkoxy group as a substituent, and in particular examples include an alkyl group having 1-6 carbon atoms which may have an epoxy group, a hydroxyl group, or a C1-C2 alkoxy group as a substituent, and an alkyl group having 1-6 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 notation "(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-(phosphate)ethyl (meth)acrylate [2-(Methacryloyloxy)ethyl Examples include at least one of the following (each individually or in combination of two or more, hereinafter the same): phosphorate, trialkoxysilylpropyl methacrylate, dialkoxymethylsilylpropyl methacrylate, 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 easy industrial availability, ease of handling and safety during manufacturing, and their ability to further enhance the effects of this disclosure.

[0018] In this disclosure, in addition to the (meth)acrylic acid ester monomers described above, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers may be used, for the sake of obtaining sustained lightfastness and storage stability, and in the case of writing instrument inks, stable writing flow and quality of the written lines (writing performance, color development). As hydrophobic vinyl monomers, for example, at least one monomer other than the (meth)acrylic acid ester monomers described above, such as styrene and methylstyrene, may 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 this disclosure 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 used.

[0020] <Azo iron dye that becomes a black dye represented by formula (α)> The azo iron dye represented by formula (α) that can be used is a complex structure in which a monoazo dye and trivalent iron form a 2:1 type complex structure, which forms an anion and is bonded to an ammonium ion. The azo iron dye represented by formula (α) is preferably the following formula (α-1) [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) (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) (In formula (α-3), R ７ , R ８ It is an ammonium ion of a guanidine derivative represented by ), which is identical 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) in this disclosure is the azo iron dye shown in formula (α-1) below. (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 ammonium ion of a guanidine derivative having an alkyl group having 3 to 18 carbon atoms.) The nitro group of the substituent of 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 (α-1), 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) above 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 a guanidine derivative represented by formula (α-3) may also be used.

[0022] The substituent R of the azo iron dye shown in formula (α) or formula (α-1) above １The alkyl group is a linear or branched alkyl group having 1 to 12 carbon atoms, and 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, lauryl group, etc. Furthermore, i-butyl group, sec-butyl group, t-butyl group, i-pentyl group, and 2-ethylhexyl group are preferred. In addition, 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, and 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, n-octyl group, and 2-ethylhexyl group are preferred.

[0023] In the above formula (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, n-octyl group, and the like. Preferably, it is a methyl group. The alkyl group R5 in formula (α-2) 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] In the above formula (α-3), R 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, n-octyl group, and the like. 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, even in the azo iron complex, allowing it to exhibit a sufficiently black color for practical use. This 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 a black color, the color changes significantly upon fading because each colorant has different fastness, solubility, and hue. In contrast, the black azo iron dye represented by (α) above is a single colorant that exhibits a deep black color with minimal 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 using the method described above, or a commercially available product can be used if available.

[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.

[0028]

[0029]

[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, In the above formula (β), R １ and R ２ These are linear or branched alkyl groups having 3 to 10 carbon atoms, and R３ 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 azo group is bonded at the para position to the azo group on the same aromatic ring, and the electron-withdrawing group may be selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom. This azo iron dye is, for example, the following chemical formula (β-1) (In chemical formula (β-1), R ５ ~R ７ and A ＋ This is identical to chemical formula (β). Examples include those containing monoazo-monoazo iron complexes represented by the following chemical formula (β-2). Azo iron dyes that can be used are those with the following chemical formula (β-2) (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) (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 Examples include at least one selected from monovalent alkyl group-containing ammonium ions, where each is independently a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

[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: (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] (In chemical formula (β-5), R 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 The present invention provides a disazo-monoazo iron complex represented by the above chemical formula (β), comprising an iron complexization step of heating a monoazo dye represented by (where is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms) 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 the above formula (β). In the above formula (β), R １ and R ２These are linear or branched alkyl groups having 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 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, resulting in a sufficiently deep black color for practical use. ３ It is preferable in terms of deepening the color if the compound is bonded to the azo group on the same aromatic ring at the para position.

[0037] Such disazo-monoazo iron complexes are specifically represented by the following chemical formula (β-6) (In chemical formula (β-6), R １ ~R ７ and A ＋This is identical to the chemical formula (β). It is represented as ). 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) (In chemical formula (β-7), R １ ~R ７ and A ＋ This is identical to the chemical formula (β). It is represented as ). 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 azo group is bonded to 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 ６is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. Examples of this alkyl group include methyl group, ethyl group, 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 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 the halogen atom include fluorine, chlorine, bromine, and iodine.

[0040] Such a disazo-monoazo iron complex is specifically represented by the following chemical formula (β-8a) (In chemical formula (β-8a), R １ ~R ７ and A ＋ are the same as those in chemical formula (β).) and the following chemical formula (β-8b) (In chemical formula (β-8b), R １ ~R ７ and A ＋ are the same as those in chemical formula (β).)

[0041] In chemical formula (β), R ７is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms. Examples of such an alkyl group include n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, tert-octyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 2,2-dimethylhexyl group, 2,3-dimethylhexyl group, 2,4-dimethylhexyl group, 2,5-dimethylhexyl group, 3,3-dimethylhexyl group, 3,4-dimethylhexyl group, 2-ethylhexyl group, 3-ethylhexyl group, 2,2,3-trimethylpentyl group, 2,2,4-trimethylpentyl group, 2,3,3-trimethylpentyl group, 2,3,4-trimethylpentyl group, 2-methyl-3-ethylpentyl group, 3-methyl-3-ethylpentyl group, and 2,2,3,3-tetramethylbutyl group, n-nonyl group, n-decyl group, lauryl group, and dodecyl group, 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 diazo-monoazo iron complex is specifically represented by the following chemical formula ((β-9a) (In the chemical formula (β-9a), R １ to R ７ and A ＋ are the same as those in the chemical formula (β).), the following chemical formula (β-9b) (In the chemical formula (β-9b), R １ to R ７ and A ＋ are the same as those in the chemical formula (β).), the following chemical formula (β-9c), (In the chemical formula (β-9c), R １ to R ７and A ＋ This is identical to the chemical formula (β), and the following chemical formula (β-9d) (In chemical formula (β-9d), R １ ~R ７ and A ＋ This is identical to the chemical formula (β).

[0043] In the chemical formula (β) above, A ＋ This is a monovalent cation. Examples of this monovalent cation include hydrogen ions, alkali metal ions, and ammonium ions (NH₄). ４ ＋ Examples include ammonium ions containing monovalent alkyl groups. The disazo-monoazo iron complex may have only one or more of these monovalent cations. Among these, ammonium ions and monovalent alkyl group-containing ammonium ions are preferred. As alkali metal ions, lithium ions (Li ＋ ), sodium ions (Na ＋ ), and potassium ions (K ＋ Examples include the following. The alkali metal ions may originate from pH adjusters used in the synthesis process of the disazo-monoazo iron complex. Furthermore, the monovalent cation may be bonded to the iron complex anion by only one type, or by multiple types.

[0044] A monovalent alkyl group-containing ammonium ion is represented by the following chemical formula (β-3). 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. ７The 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 methylhexyl 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 linear or branched, more preferably that it has 8 to 15 carbon atoms and is branched, and even more preferably that it has 11 to 14 carbon atoms and is branched.

[0045] In the above chemical formula (β-3), R ９ and R １０ Examples 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 this disclosure, is an amino group to which a dialkyl group having a specific range of carbon atoms is bonded (the -NR in chemical formula (β)). １ R ２ ) and electron-withdrawing groups (same -R３ 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 having an alkyl group with 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 that is practical as an ink composition in alcohol-based organic solvents such as ethanol and ethylene glycol, and ketone-based organic solvents such as methyl ethyl ketone, and also has high solubility stability, so it does not precipitate or precipitate in organic solvents. Moreover, the azo iron dye does not contain chromium or cobalt, which are heavy metals harmful to the environment and human body, so it can contribute to environmental protection and ensure safety for the human body. In addition to the disazo-monoazo iron complex represented by the chemical formula (β) above, it is preferable to further include a monoazo-monoazo iron complex having only the monoazo ligand, which is a ligand of this disazo-monoazo iron complex, and / or a disazo-disazo iron complex having only the disazo ligand.

[0047] This monoazo-monoazo iron complex is the same as 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 ＋The chemical formula (β) is the same as (β). When the azo iron dye represented by (β) that 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, it is preferable that DM:MM:DD = 20-70:5-80:0-50, more preferably 20-65:5-80:0-50, even more preferably 20-60:20-80:0-30, and still more preferably 20-55:20-80:0-15. The lower limit for the DD is 1 instead of 0. Note that 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 ​​from 0.1 to 0.4.

[0048] The azo iron dye represented by (β) above contains, in addition to the asymmetric azo iron complex, the disazo-monoazo iron complex, as well as symmetric azo iron dyes such as a monoazo-monoazo iron complex having only a monoazo ligand and / or a disazo-disazo iron complex having only a disazo ligand. 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 electrical conductivity K of the azo iron dye represented by (β) above is preferably 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. 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 produced, for example, by employing a production method having the following first to fifth steps: First step: A step to obtain a disazo dye using a diazo coupling reaction. Second step: A step to obtain a monoazo dye using a diazo coupling reaction. Third step: A step to obtain an azo iron dye by iron-complexizing a mixture of disazo dye and monoazo dye. Fourth step: A step to change and prepare the cation of the azo iron dye. Fifth step: A step to filter, wash, dry, and pulverize the azo iron dye. According to this production method, azo iron dyes containing azo iron complexes represented by the above chemical formulas (β) to (β-2), etc., can be produced in high purity. The black azo iron dye represented by (β), etc., can be obtained by the above production method, or if a commercially available product is available, that can be used.

[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 described below. The amount of each component used, the reaction time, the reaction temperature, etc. are predetermined amounts, predetermined time, predetermined temperature, etc.

[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 that, the pH was adjusted to 2.6, the precipitated monoazo compound was filtered off and washed with water to obtain a predetermined amount of wet cake. 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).

[0053] The production of azo iron dyes represented by formulas (β-11a), (β-11b), and (β-11c) is known and is briefly described below. The production of azo iron dyes represented by each of these formulas is as follows: Disazo dye D-1 of formula (β-10a) and monoazo dye M-1 of formula (β-10b) are added to an N,N-dimethylformamide solution and stirred at a predetermined temperature for a predetermined time (disazo dye:monoazo dye = 2:8 mol). A 41% ferric sulfate aqueous solution is added dropwise, and after the addition is complete, the temperature is raised to a predetermined temperature and stirred for a predetermined time. After the reaction is complete, the mixture is allowed to cool to room temperature, a 20% sodium hydroxide aqueous solution is added to adjust the pH to 10.0, and a 5% tert-alkyl (C12-C14) primary amine aqueous solution is gradually added to the reaction solution 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 this disclosure 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 polymerizing (homopolymerization or copolymerization) using a suitable polymerization initiator, etc., with an azo iron dye represented by chemical formula (α) above, at least one black dye component selected from azo iron dyes containing azo iron complexes represented by chemical formulas (β) to (β-2) above, and at least one of the above monomer components. Furthermore, each resin particle dispersion can be obtained by appropriately adjusting the manufacturing conditions such as 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 manufactured as a dispersion of black resin particles, it can be dried to form black resin particles. Using a crosslinking agent such as triallyl isocyanurate 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 performed, 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 dicyclopenta(thenyl)(meth)acrylate monomers that can be used include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate.

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

[0058] In this disclosure, the content of the 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 disclosure, "total polymer components" refers to the polymerizable components constituting the resin particle dispersion, specifically the total amount of all types of monomers that become 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. When using Group A monomers, the effects of this disclosure 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 this disclosure, 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 is the remainder of the total amount of Group A polymer 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 of the total polymer components, from the viewpoint of further exhibiting the effects of the present invention, dispersibility, and reactivity.

[0060] In this disclosure, the total (solid content) of the azo iron dye that becomes the black dye represented by formula (α) or formula (β) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and more preferably 3 to 30% by mass, and particularly preferably 4 to 20% by mass, 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 is an anionic or nonionic polymerizable surfactant, such as Adeka Soap NE-10, NE-20, NE-30, NE-40, SE-10N, SR-10, SR-20, ER-10, ER-20, ER-30, ER-40, PP-70 manufactured by ADEKA Corporation, and Latte Examples of polymerizable surfactants include at least one of the following: MUR S-180, S-180A, S-120A, PD-420, PD-430, PD-450, Eleminol JS-20, CLS-20, RS-3000 from 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 from Daiichi Kogyo Seiyaku Co., Ltd., and Spinomer NaSS from 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 the monomer.

[0062] In this disclosure, a resin particle dispersion (dispersion) is obtained in which resin particles containing an azo iron dye component are dispersed in water, specifically, a resin particle dispersion (dispersion liquid) is obtained in which resin particles containing an azo iron dye component that becomes a black dye represented by formula (α) or formula (β) by the polymerization described above are dispersed in water. Alternatively, a resin particle dispersion (dispersion liquid) 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 black dyes represented by formula (α) or formula (β) described above 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) described above after polymerization of a mixed monomer containing at least one monomer selected from the 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 this disclosure, it is preferable that the black resin particles contain an ultraviolet absorber and / or a light stabilizer in order to further enhance the lightstability effect and improve light resistance. Conventional ultraviolet absorbers can be used, such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, benzophenone absorbers, etc., and it is preferable that the above ultraviolet absorbers have polymerizable unsaturated groups.

[0064] Specific examples of benzotriazole 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 lium-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 "Tinuvin 900", "Tinuvin 928", "Tinuvin 348-2", "Tinuvin 479", "Tinuvin 405", "Tinuvin 400" (all manufactured by BASF, trade name, Tinuvin®), and "RUVA-93" (all manufactured by Otsuka Chemical Co., Ltd., trade name). 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, light resistance, and stability.

[0068] Suitable light stabilizers include, for example, hindered amine light stabilizers, hindered phenol antioxidants, phenol radical scavengers, sulfur antioxidants, phosphorus antioxidants, triazine compounds, benzotriazole compounds, phenol ultraviolet absorbers, malonic acid ester ultraviolet absorbers, oxanilide ultraviolet absorbers, and benzophenone compounds. A more preferred embodiment of the light stabilizer is a polymerizable (reactive) light stabilizer having the above-mentioned methacrylic group. A polymerizable (reactive) light stabilizer that readily polymerizes with the above-mentioned (meth)acrylic acid esters, styrene, nitrile, vinyl acetate, etc., and incorporates the light-stabilizing functional group into the polymer chain can be suitably used, resulting in black resin particles with high safety and long-term stable light stability without volatilization or elution of the light stabilizer. Even non-polymerizable light stabilizers can impart the desired light stability when included in the black resin particles.

[0069] Conventionally known hindered amine light stabilizers such as hindered piperidine compounds can be used. Furthermore, the above-mentioned hindered amine light stabilizers may have particularly polymerizable unsaturated groups. Specific examples of hindered amine 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-bonded 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, "Tinuvin 765," "Tinuvin 770DF," "Tinuvin 144," "Tinuvin 622SF," and "Tinuvin 152" (all manufactured by BASF, trade names, Tinuvin®), "Adekastab LA-52," "Adekastab LA-57," "Adekastab LA-63P," "Adekastab LA-72," "Adekastab LA-77Y," "Adekastab LA-81," "Adekastab LA-82," and "Adekastab LA-87" (all manufactured by ADEKA Corporation, trade names, Adekastab, ADKSTAB, and Adekastab®). 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, light resistance, and stability.

[0071] In this disclosure, in order to further enhance long-term stability, preservative properties, color development, and fragrance, the black resin particles may also contain, along with the azo iron dye which is a black dye represented by formula (α) or formula (β), preservatives, reducing agents, colorants containing dyes or pigments other than the black dye, colorants containing thermochromic agents, fragrances, etc.

[0072] The production of black resin particles containing an azo iron dye that becomes a black dye represented by the above formula (α) or formula (β), 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 the above formula (α) or formula (β). 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 the above 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 the above 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, 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, this disclosure suggests that further improvements in blackness can be expected by using materials that have absorption at specific wavelengths in combination. Materials other than azo iron dyes represented by formula (α) or formula (β), such as complementary dyes, may also be used in combination, which can further improve blackness. Examples of materials that may be used in combination include: As oil-soluble dyes, commercially available monoazo, disazo, metal complex type monoazo, anthraquinone, phthalocyanine, triarylmethane, etc. Salt-forming type oil-soluble dyes in which functional groups such as acidic and basic dyes are replaced with hydrophobic groups can also be used. Examples of yellow dyes include C.I. Solvent Yellow 14, 16, 29, 30, 33, 56, 62, 93, 98, 114, 116, 151, 157, 162, and Basic Yellow 40; as orange dyes, C.I. Solvent Orange 22, 45, 67; and as red dyes, C.I. Examples of color combinations include Solvent Red 3, 18, 49, 146 and Basic Red 1, 1:1; for blues, C.I. Solvent Blue 5, 35, 36, 44, 63, 70, 83, 105, 111 and Basic Blue 1; for blacks, C.I. Solvent Black 3, 7, 29; and for purples, C.I. Basic Violet 1, 11:1, etc. Specific examples of commercially available oil-soluble dyes include the blue dye SBN Blue 701 (manufactured by Hodogaya Chemical Co., Ltd.), the blue dye Oil Blue 650 (manufactured by Orient Chemical Industry Co., Ltd.), the blue dye Savinyl Blue GLS (manufactured by Clariant Co., Ltd.), the red dye 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 include silicone-based, mineral oil-based, polymer-based, and fatty acid ester-based agents. Preferably, as a silicone-based defoaming agent, an emulsion-type defoaming agent, for example, a silicone oil compound emulsified with a nonionic surfactant, is easy to handle, highly safe, and comes 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. Furthermore, if a self-emulsifying type is used, examples include KS-530 from Shin-Etsu Chemical Co., Ltd.

[0075] Furthermore, in this disclosure, the average particle size of the obtained black resin particles (containing an azo iron dye that becomes a black dye represented by formula (α) or formula (β), or containing an azo iron dye that becomes a black dye represented by formula (α) or 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 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 is adjusted by suitably combining the above-mentioned monomer species and their amounts, polymerization conditions (temperature, pressure, etc.). In this disclosure, "average particle size" refers to the histogram average particle size (D50) based on the scattered light intensity distribution measured with a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)]. By setting the average particle size within the above preferred range, it can be suitably used for various applications and has excellent storage stability. Furthermore, in this disclosure, it is more preferable to use polymerizable ultraviolet absorbers and / or light stabilizers.

[0076] The black resin particle dispersion of this disclosure contains an azo iron dye, which is a black dye represented by formula (α) or formula (β) above. The particles have excellent storage stability, do not contain harmful heavy metals, can raise the lightfastness to the same level as Cr complex dyes, have a wide absorption spectral wavelength range, and exhibit excellent blackness and lightfastness, while maintaining their durability without adversely affecting other components, and also have excellent dispersion stability. As a result, the above-mentioned excellent performance can be exhibited, and the sustained effect of these performances is long-lasting. Furthermore, the black resin particles containing the above-mentioned azo iron dye, ultraviolet absorber, and light stabilizer can be used to obtain an unprecedented black resin particle dispersion that is even more lightfast and weather-resistant without impairing storage stability, blackness, or lightfastness. Moreover, the black resin particle dispersion of this disclosure has the unique effect of improving blackness by encapsulating the dye in resin particles rather than directly blending it into a solution medium.

[0077] As described above, the black resin particle dispersion (dispersion) of this disclosure 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) when used in aqueous ink compositions for writing instruments such as felt-tip pens, marking pens, and ballpoint pens will be described in detail below.

[0078] (Aqueous Ink Composition for Writing Instruments) The aqueous ink composition for writing instruments of this disclosure 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. 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, in terms of solid content, relative to the total amount of the ink composition, from the standpoint of exhibiting the effects of this disclosure 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 like methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol, amides like dimethylformamide and diethylacetamide, and ketones like acetone 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 where the content is 1 to 40% by mass relative to the total amount of the ink composition, and 10% by mass or less is desirable to further improve the drying properties of the lines drawn. More preferably, it is desirable to have a content of 3 to 8% by mass.

[0081] The aqueous ink composition for writing instruments disclosed herein contains, in addition to the black resin particle dispersion having the above-mentioned properties and a water-soluble solvent, the remainder may include, as appropriate, 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 disclosure herein.

[0082] Suitable dispersants include nonionic and anionic surfactants other than the acetylene-based surfactants and polyethylene glycol-based surfactants mentioned above, as well as water-soluble resins. Water-soluble polymers are preferred. Suitable lubricants include nonionic surfactants 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 surfactants such as alkyl sulfonates and alkyl allyl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorine-based 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 thickeners 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 disclosure, it is preferable to use olefin-based resin particles in order to improve the quality of the writing lines, and the content of these olefin-based resin particles is preferably 0.01 to 20% by mass, more preferably 1 to 5% by mass, based on the total amount of the ink composition. The olefin resin particles that can be used are those with a hardness of 1 or higher by the penetrometry method and an average particle diameter of 15 μm or less as measured by the Coulter counter method. Their shape and structure are not particularly limited. For example, commercially available products include ChemiPearl W100, W200, W400, and W500 manufactured by Mitsui Chemicals, and other similar olefin resin particles (ChemiPearl products) such as ChemiPearl W300, W308, W310, W700, and W900. If the hardness by the penetrometry method is 1 or higher, improved ink flow can be expected, and a stable writing flow rate can be obtained.

[0085] The aqueous ink composition for writing instruments of this disclosure 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 (for 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 this disclosure is preferably adjusted to 5 to 10 by 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 disclosed herein is used in ballpoint pens, marking pens, etc., equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, and plastic tips. An example of a ballpoint pen is one in which the aqueous ink composition of the above composition is contained in a ballpoint pen ink container (refill) equipped with a ball with a diameter of 0.18 to 2.0 mm, and a substance that is incompatible with the aqueous ink composition contained within the ink container and has a lower specific gravity than the aqueous ink composition, such as polybutene, silicone oil, or mineral oil, is contained as an ink follower. In a ballpoint pen, the axial movement (distance traveled) of the writing ball is preferably 15 to 80 μm, from the viewpoint 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 this disclosure, the black resin particle dispersion having the above-mentioned properties is incorporated into the aqueous ink composition for writing instruments. Conventionally, the azo iron dye that becomes the black dye represented by formula (α) or formula (β) has been oil-based, but even in aqueous solutions, it exhibits excellent dispersion stability and can be stably incorporated into various water-based inks. In this disclosure, by preparing the black resin particle dispersion containing the azo iron dye component that becomes the black dye represented by formula (α) or formula (β), 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.

[0089] Next, the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure 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 Manufacturing Examples 1-20 below. Note that "parts" below refers to parts by mass. The amount of surfactant components is the solid content.

[0091] (Manufacturing Example 1) A stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input were attached to a 2-liter flask and placed in a hot water bath. 309.5 parts of distilled water, 5 parts of glycerin monomethacrylate [Bremmer GLM, manufactured by NOF Corporation], 5 parts of sodium 2-sulfoethyl methacrylate [Acrylates SEM-Na, manufactured by Mitsubishi Chemical Corporation], 40 parts of polymerizable surfactant [ADEKA Corporation, Adekarya 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.

[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 above separatory funnel to the above flask, which was kept at a temperature of around 90°C, under stirring for 1 hour, and emulsion polymerization was carried out. After further aging for 6 hours, polymerization was completed to obtain a black resin particle dispersion (dispersion) (particle 1). The content of the methacrylate 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 black resin particles was 108 nm.

[0093] (Production Example 2) A black resin particle dispersion (dispersion) (particles 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 the azo iron dye component, the substance represented by formula (α) was used: 35 parts, and as the complementary dye, Oil Yellow 129 manufactured by Orient Chemical Industry Co., Ltd. was used: 10 parts. The content of the methacrylate ester monomer was 46.2% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 17.9% by mass relative to the total polymer components. The average particle size of the resin particles was 82 nm.

[0094] (Production Example 3) A black resin particle dispersion (dispersion) (particles 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 as the azo iron dye component, 35 parts of a substance represented by formula (β) manufactured by Orient Chemical Industry Co., Ltd. was used. The content of the methacrylate ester monomer was 46.2% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 17.9% by mass relative to the total polymer components. The average particle size of the resin particles was 98 nm.

[0095] (Production Example 4) 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 content of the methacrylate 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 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 87 nm.

[0096] (Production Example 5) A black resin particle dispersion (dispersion) (particles 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 methacrylate monomer was 30 parts, and the amount of n-butyl methacrylate was 45 parts. The content of the methacrylate 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] (Production Example 6) A black resin particle dispersion (dispersion) (particles 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 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 19.4% by mass relative to the total polymer components. The average particle size of the resin particles was 105 nm.

[0098] (Production Example 7) A black resin particle dispersion (dispersion) (particles 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., was used as the complementary color dye component. The content of the methacrylate 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 black resin particles was 101 nm.

[0099] (Production Example 8) A black resin particle dispersion (dispersion) (particles 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 content of the methacrylate 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 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, Adekarya Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged, and the internal temperature was raised to 50°C while introducing nitrogen gas. The amount of methacrylonitrile monomer was set to 75 parts, and a solution was prepared by mixing 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., and 10 parts of the crosslinking agent [triallyl isocyanurate, manufactured by Nippon Chemical Corporation, TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at 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] (Production Example 10) A black resin particle dispersion (dispersion) (particles 10) was obtained in the same manner as in Production Example 9, except that 309.5 parts of distilled water were used and 35 parts of a substance represented by formula (α) were used as the azo iron dye component. The content of the nitrile 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 89 nm.

[0102] (Production Example 11) A black resin particle dispersion (dispersion) (particles 11) was obtained in the same manner as in Production Example 9, except that 309.5 parts of distilled water were used and 35 parts of a substance represented by formula (β) were used as the azo iron dye component. The content of the nitrile 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 88 nm.

[0103] (Manufacturing Example 12) A stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input were attached to a 2-liter flask and placed in a hot water bath. 309.5 parts of distilled water, 40 parts of polymerizable surfactant [ADEKA Corporation, Adekarya Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged, and the internal temperature was raised to 50°C while introducing nitrogen gas. The amount of styrene monomer was set to 75 parts, and a solution was prepared by mixing the substance represented by formula (α) as an azo iron dye component: 15 parts, the substance represented by formula (β) as an azo iron dye component: 10 parts of Oil Yellow 129, manufactured by Orient Chemical Industry Co., Ltd., and 10 parts of a crosslinking agent [triallyl isocyanurate, Nippon Chemical Corporation, TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at 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) (particles 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] (Production Example 13) A black resin particle dispersion (dispersion) (particles 13) was obtained in the same manner as in Production Example 12, except that 309.5 parts of distilled water were used and 35 parts of a substance represented by formula (α) 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 69 nm.

[0105] (Production Example 14) A black resin particle dispersion (dispersion) (particles 14) was obtained in the same manner as in Production Example 12, except that 309.5 parts of distilled water were used and 35 parts of a 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 stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input were attached to a 2-liter flask and placed in a hot water bath. 309.5 parts of distilled water, 40 parts of polymerizable surfactant [ADEKA Corporation, Adekarya Soap SR-10, ether sulfate] and 0.5 parts of ammonium persulfate were charged, and the internal temperature was raised to 50°C while introducing nitrogen gas. The amount of vinyl acetate monomer was set to 75 parts, and a solution was prepared by mixing the substance represented by formula (α) as an azo iron dye component: 15 parts, the substance represented by formula (β) as an azo iron dye component: 10 parts of Oil Yellow 129, manufactured by Orient Chemical Industry Co., Ltd., and 10 parts of a crosslinking agent [triallyl isocyanurate, Nippon Chemical Corporation, TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at 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) (particles 15). The content of 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] (Production Example 16) A black resin particle dispersion (dispersion) (particles 16) was obtained in the same manner as in Production Example 15, except that 309.5 parts of distilled water were used and 35 parts of a substance represented by formula (α) 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 123 nm.

[0108] (Production Example 17) A black resin particle dispersion (dispersion) (particles 17) was obtained in the same manner as in Production Example 15, except that 309.5 parts of distilled water were used and 35 parts of a 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] [Production Example 18 (Comparative 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, a mixture of azo compound chromium complex dye and amine, manufactured by Orient Chemical Industry Co., Ltd., was used in 35 parts. The content of the methacrylate 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] [Production Example 19 (Comparative Example 2)] 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 content of the methacrylic acid ester monomer was 45.9% by mass relative to the total polymer components constituting the resin particles, and the content of the azo iron dye component was 16.2% by mass relative to the total polymer components. The average particle size of the resin particles was 120 nm.

[0111] [Production Example 20 (Comparative Example 3)] 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] The resin particle dispersions obtained in Production Examples 1 to 20 were 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 Production Examples 1 to 20 was 35 to 40% by mass. These results are shown in Table 3 below.

[0113] (Evaluation of 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 elution test, "European Standard EN71 Part 3 Migration of Specific Elements," and the amount of eluted material was measured. If chromium (trivalent chromium / hexavalent chromium) exceeding the standard was detected, an elution 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 Black Color Development) The black resin particle dispersion (dispersion) obtained above was used to visually evaluate the black color development. For the evaluation of black, a comparative example was used in which the same amount of azo iron dye was directly dissolved as the black resin particle dispersion (dispersion), 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 dissolved as the black resin particle dispersion (dispersion) was judged as "C", and relative evaluation was performed according to the following criteria. Evaluation criteria: A: Black color development is much higher than C B: Black color development is slightly higher than C C: A solution of azo iron dye directly dissolved was used

[0115] (Method for evaluating lightfastness) Using the black resin particle dispersion (dispersion) obtained above, the lightfastness was evaluated using a Suga Test Instruments X25 xenon weather meter under xenon arc light in accordance with JIS L 0843 at 50 W / m². ２ After 6 hours of irradiation with (300-400 nm) light, the visibility when exposed to a 365 nm UV lamp was evaluated based on visual inspection and the rate of change in fluorescence intensity (365 nm) according to the following evaluation criteria. Evaluation criteria: A: No change in blackness from the initial state, no problem with visibility. B: Visible, but a slight change in blackness is observed. C: Difficult to see, but still visible. A significant change in blackness is observed. D: Not visible.

[0116] (Method for evaluating storage stability) Using the black resin particle dispersion (dispersion) obtained above, the time-dependent stability was evaluated by placing the black resin particle dispersion (dispersion) in a glass mayonnaise bottle (manufactured by AS ONE Corporation), and visually inspecting for the presence or absence of precipitates after 2 weeks at a temperature of 60°C according to the following evaluation criteria. Evaluation criteria: A: No precipitates B: Slight precipitates observed C: Precipitations observed 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 4 below were prepared. These compositions were then loaded into writing instruments (sign pens) with the following configurations, and evaluated for specified heavy metal content, black color development, lightfastness, and storage stability in the same manner as described above. The results are shown in Table 4 below.

[0118] (Writing instrument: Preparation of felt-tip pen) A felt-tip pen was prepared by filling the container chamber with the water-based ink composition described above using a felt-tip pen [manufactured by Mitsubishi Pencil Co., Ltd., product name: PUS-138, pen tip: PET sintered core] and the water-based ink composition described above.

[0119]

[0120]

[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 this disclosure, and the aqueous ink compositions for writing instruments of Examples 1 to 5, which also fall within the scope of this disclosure and contain the same, 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 this disclosure and do not use azo iron dyes.

[0122] The black resin particle dispersion of this disclosure 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 and cosmetics: eyeliner, hair dye, etc.

Claims

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