阅读说明：本技术 水性的圆珠笔用墨组合物 (Water-based ink composition for ballpoint pen ) 是由 平山晓子 小椋孝介 三好花奈 于 2018-06-22 设计创作，主要内容包括：提供水性的圆珠笔用墨组合物,其即使长时间暴露笔尖后也具有优异的书写初期的墨排出性(初笔性)。水性的圆珠笔用墨组合物的特征在于：由(a)由式(I)表示的聚氧化烯烷基醚单元,(b)马来酸酐单元,和(c)苯乙烯单元构成；这些单元的组成比为(a):(b):(c)＝25～75:25～75:0～50,并且至少包含0.1-5质量％的质量平均分子量为1000～50000的烯丙醇-马来酸酐-苯乙烯共聚物与聚氧化烯单烷基醇的接枝化合物、5至40质量％的树脂颗粒、和水(在式(I)中,R表示C1-5烷基,和m为5-50的正数)。<Image he="183" wi="700" file="DDA0002345502370000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(Provided is a water-based ink composition for a ballpoint pen, which has excellent ink discharge properties (initial writing properties) at the initial stage of writing even after a pen tip is exposed for a long period of time. The aqueous ink composition for a ballpoint pen is characterized in that: composed of (a) a polyoxyalkylene alkyl ether unit represented by the formula (I), (b) a maleic anhydride unit, and (c) a styrene unit; the composition ratio of the units is (a) to (b) to (c) is 25 to 75:0 to 50, and at least 0.1 to 5 mass% of allyl alcohol having a mass average molecular weight of 1000 to 50000A graft compound of an alcohol-maleic anhydride-styrene copolymer with a polyoxyalkylene monoalkyl alcohol, 5 to 40 mass% of resin particles, and water (in formula (I), R represents a C1-5 alkyl group, and m is a positive number of 5 to 50).)

1. An aqueous ink composition for a ballpoint pen comprising at least:

0.1 to 5 mass% of a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer and a polyoxyalkylene monoalkyl alcohol; 5 to 40 mass% of resin particles; and water; the allyl alcohol-maleic anhydride-styrene copolymer is composed of (a) a polyoxyalkylene alkyl ether unit represented by the formula (I), (b) a maleic anhydride unit, and (c) a styrene unit, wherein the composition ratio of the allyl alcohol-maleic anhydride-styrene copolymer (a) to (b) is 25-75: 0-50 mol%, and the mass average molecular weight is 1000-50000,

wherein, in formula (I), R represents an alkyl group having 1 to 5 carbons, and m is a positive number of 5 to 50.

Technical Field

The present invention relates to an aqueous ink composition for a ballpoint pen, which has excellent initial ink discharge properties (initial writing properties) at the initial stage of writing even after a pen tip is exposed for a long period of time.

Background

In the prior art, a water-based ball-point pen using an ink having a high solid content concentration such as an ink containing a microcapsule pigment has a problem that, for example, ink discharge property at the initial stage of writing (initial writing property decrease) often occurs after a pen tip is exposed for a certain time.

As countermeasures against these problems, the following are known: 1) an aqueous ink composition for a ballpoint pen comprising at least a colorant, water, a thickener and a cationized dextran (for example, see patent document 1), 2) an aqueous ink composition for a ballpoint pen comprising at least water, a colorant, a water-soluble organic solvent, and one or more of the following derivatives: a pyridine derivative prepared by substituting 1 to 3 of carbons at positions 2, 4 and 6 of pyridine with the same hydrophilic electron-donating group, and a pyrimidine derivative prepared by substituting 1 to 3 of carbons at positions 2, 4 and 6 of pyrimidine with the same hydrophilic electron-donating group (for example, see patent document 2), 3) an aqueous ball-point pen ink composition comprising particles composed of a specific compound (for example, see patent document 3), and 4) an ink composition suitable for a writing instrument containing at least a compound selected from N, N-di (hydroxyethyl) glycine and tris (hydroxymethyl) methylglycine in a content of 0.1 to 10% by mass relative to the total amount of the ink composition (for example, patent document 4).

Inventions in the prior art such as patent documents 1 to 4 can achieve some effects, however, it is desirable that the effects can be maintained even after the pen tip is exposed for a longer time.

Disclosure of Invention

Problems to be solved by the invention

In view of the problems and the current situation of the conventional techniques, an object of the present invention is to provide an ink composition for a ball point pen, which is aqueous and has excellent ink discharge properties (initial writing properties) at the initial stage of writing even after a pen tip is exposed for a longer period of time.

Means for solving the problems

As a result of a special study in view of the state of the conventional art described above, the present inventors have found that a desired aqueous ink composition for a ballpoint pen can be obtained by making an aqueous ink composition for a writing instrument containing at least water, a specific compound and resin particles in a specific range, thereby completing the present invention.

Specifically, the water-based ink composition for a ballpoint pen according to the present invention comprises at least: 0.1 to 5 mass% of a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer and a polyoxyalkylene monoalkyl alcohol; 5 to 40 mass% of resin particles; and water; the allyl alcohol-maleic anhydride-styrene copolymer is composed of (a) polyoxyalkylene alkyl ether units represented by formula (I), (b) maleic anhydride units, and (c) styrene units, wherein the composition ratio of the allyl alcohol-maleic anhydride-styrene copolymer (a) to (b) is 25 to 75:0 to 50 mol%, and the mass average molecular weight is 1000 to 50000.

Wherein, in formula (I), R represents an alkyl group having 1 to 5 carbons, and m is a positive number of 5 to 50.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention provides an aqueous ink composition for a ballpoint pen, which has excellent ink discharge properties (initial writing properties) at the initial stage of writing even after a pen tip is exposed for a long period of time.

Detailed Description

The embodiments of the present invention are explained in detail below.

The water-based ink composition for a ballpoint pen of the embodiment of the present invention comprises at least: 0.1 to 5 mass% of a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer and a polyoxyalkylene monoalkyl alcohol; 5 to 40 mass% of resin particles; and water; the allyl alcohol-maleic anhydride-styrene copolymer is composed of (a) a polyoxyalkylene alkyl ether unit represented by the formula (I), (b) a maleic anhydride unit, and (c) a styrene unit, wherein the composition ratio of the allyl alcohol-maleic anhydride-styrene copolymer (a) to (b) is 25-75: 0-50 mol%, and the mass average molecular weight is 1000-50000.

Wherein, in formula (I), R represents an alkyl group having 1 to 5 carbons, and m is a positive number of 5 to 50.

The graft compound used in the present invention is a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer and a polyoxyalkylene monoalkyl alcohol, the allyl alcohol-maleic anhydride-styrene copolymer being composed of (a) a polyoxyalkylene alkyl ether unit represented by formula (I), (b) a maleic anhydride unit, and (c) a styrene unit, the composition ratio of the allyl alcohol-maleic anhydride-styrene copolymer (a) to (b) being 25 to 75:0 to 50 mol%, and the mass average molecular weight being 1000 to 50000.

The composition ratio of the units (a), (b) and (c) is 25 to 75:0 to 50 mol%.

When the styrene unit (c) is 0 mol%, styrene units are not included. In this case, the graft compound is a graft compound of an allyl alcohol-maleic anhydride copolymer composed of (a) polyoxyalkylene alkyl ether units represented by the formula (I) and (b) maleic anhydride units, wherein the composition ratio of (a) to (b) is 25 to 75:25 to 75 mol%, and the mass average molecular weight is 1000 to 50000, and a polyoxyalkylene monoalkyl alcohol.

In the case where the amount of (b) maleic anhydride units relative to (a) polyoxyalkylene monoalkylether units is outside the above range (less than or more than), the effect of the present invention cannot be achieved, which is not preferable. When the styrene unit is contained, in the case where the amount of styrene is more than the above range, the effect of the present invention cannot be achieved, which is not preferable.

When the styrene unit (c) is contained, the composition ratio of (a) to (c) is preferably 25 to 40:20 to 50 mol%.

The number of addition mols of the ethylene oxide unit of the component (b), specifically, m in the formula (I) is 5 to 50mol, and the effect of the present invention is achieved using this component in this range.

R is a linear or branched alkyl group having 1 to 5 carbon atoms, and examples thereof include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, and n-pentyl, branched alkyl groups such as isopropyl, isobutyl, and isopentyl, and cyclic alkyl groups such as cyclopropyl and cyclopentyl.

Further, the graft compound has a mass average molecular weight of 1,000 to 50,000. In the case where the mass average molecular weight exceeds 50,000, the ink viscosity increases, while in the case where the mass average molecular weight is less than 1,000, the solubility decreases, and therefore both cases are not preferable.

Examples of the graft compound of the allyl alcohol-maleic anhydride-styrene copolymer and the polyoxyalkylene monoalkyl alcohol include compounds represented by formula (II), and the graft compound of the allyl alcohol-maleic anhydride copolymer and the polyoxyalkylene monoalkyl ether includes compounds represented by formula (III). The graft compound may be used alone or in combination of two or more thereof.

Specific examples include graft compounds represented by formula (II) in which m is 11 and n is 20, and the mass average molecular weight is 15000, such as commercially available MALIALIM AKM-0531 (manufactured by NOF Corporation); a graft compound represented by formula (II) wherein m is 13 and n is 18, and having a mass average molecular weight of 40000, such as commercially available MALIALIM AAB-0851 (manufactured by NOF Corporation); and a graft compound represented by formula (II) wherein m is 28 and n is 20, and the mass average molecular weight is 30000, such as commercially available MALIALIM AFB-1521 (manufactured by nof corporation). In formula (II), n is a positive number adjusted within the above-mentioned mass average molecular weight range (the same conditions are applied to formula (III) below).

Specific examples include graft compounds represented by formula (III) in which m ═ 11 and n ═ 14, and a mass average molecular weight of 10000[ a copolymer of methoxypolyethylene glycol (addition with 11mol of ethylene oxide) allyl ether and maleic anhydride ], such as commercially available MALIALIM SC-0505K (manufactured by NOF Corporation).

The total content of the graft compound is 0.1 to 5% by mass (hereinafter, "mass%" is referred to as "%"), preferably 0.2 to 4%, based on the total amount of the ink composition.

In the case where the content is less than 0.1%, the effect of the present invention cannot be exerted, while in the case where the content exceeds 5%, the stability of the ink with time is lowered, and therefore both of them are not preferable.

Examples of the resin particles used in the embodiment of the present invention include colored resin particles, hollow resin particles having voids inside the particles, and solid resin particles having no voids inside the particles. The colored resin particles that can be used herein are not particularly limited as long as they are constituted by the colored resin particles, and examples thereof include: 1) colored resin particles in which a colorant composed of an inorganic pigment such as carbon black and titanium oxide, an organic pigment such as a phthalocyanine-based pigment and an azo-based pigment, is dispersed in resin particles, 2) colored resin particles in which the surface of resin particles is covered with a colorant composed of a pigment as described above, 3) colored resin particles in which resin particles are colored with a colorant composed of a dye such as a direct dye, an acid dye, a basic dye, an edible dye or a fluorescent dye, 4) colored resin particles having a matrix composed of a polymer, a resin having an OH group and a water-insoluble dye, 5) colored resin particles having a thermochromic property based on a leuco dye, and 6) colored resin particles having a photochromic property based on a photochromic dye (compound) and a fluorescent dye.

Examples of the resin component of the above-mentioned colored resin particles 1) to 3) include at least one selected from polymers of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, styrene, acrylonitrile, and butadiene, or copolymers thereof, benzoguanamine, phenol resins, epoxy resins, and urethane resins. The polymer may be subjected to a treatment such as crosslinking, if necessary. These resins are colored by known methods such as suspension polymerization and dispersion polymerization.

The microspheres of 4) above have a matrix composed of a polymer, a resin having OH groups, and a water-insoluble dye.

Examples of the polymer constituting the matrix include an epoxy polymer, a melamine polymer, an acrylic polymer, a urethane polymer, or a urea polymer, or a combination thereof.

The matrix contains a resin having OH groups. Examples of the resin having an OH group include terpene phenol resin, rosin phenol resin, alkyl phenol resin, phenol resin, cresol phenol resin, butyral resin, polyvinyl alcohol resin, polyol-modified xylene resin, ethylene oxide-modified xylene resin, maleate resin, hydroxyl-modified acrylate resin, hydroxyl-modified styrene acrylate resin, carboxyl-modified acrylate resin, and carboxyl-modified styrene acrylate resin.

The water-insoluble dye is a dye insoluble in water at room temperature, and may be, for example, a halochromic dye (halochromic dye), a disperse dye or an oil-soluble dye such as a dye having a chemical structure of an azo series, a metal complex salt azo series, an anthraquinone series or a metal phthalocyanine series. From the viewpoint of color developability, a dye that develops color with an acid is preferably used.

The microspheres can be produced by, for example, the following production methods (emulsion polymerization method and phase separation method).

The preparation of microspheres by emulsion polymerization comprises the following steps: preparing an oil phase, preparing an aqueous phase, and mixing the oil phase and the aqueous phase to emulsify components of the oil phase, followed by polymerization.

The oil phase contains an organic solvent such as phenoxyethanol, benzyl alcohol, ethylene glycol monobenzyl ether, or ethyl acetate, a water-insoluble dye, a resin having OH groups, and a monomer or prepolymer. A variety of organic solvents may be included.

The oil phase is prepared by adding a water-insoluble dye and a resin having OH groups to an organic solvent under heating at a predetermined temperature, stirring the mixture, and then adding a monomer or prepolymer constituting a polymer, such as a melamine monomer or prepolymer, an epoxy monomer or prepolymer, an acrylic monomer or prepolymer, or an isocyanate monomer or prepolymer, and then further adding other optional organic solvents.

The aqueous phase may be prepared by mixing water and a dispersant. Examples of dispersants include, but are not limited to, polyvinyl alcohol.

The emulsification and polymerization steps may be performed by emulsifying the components of the oil phase, further polymerizing the oil phase by introducing the oil phase into the aqueous phase, and emulsifying and mixing the mixture under heating to a predetermined temperature using a homogenizer or the like.

The microsphere preparation step may include other steps, such as a step of fractionating the microspheres.

The microsphere preparation step by phase separation consists of preparing a dye-containing solution, preparing a solution comprising a protective colloid agent, and polymerizing a monomer or prepolymer.

The dye-containing solution may be prepared by dissolving a water-insoluble dye and a resin having OH groups in an organic solvent under heating. Examples of the water-insoluble dye, the resin having OH groups, and the organic solvent include those listed for the preparation step of microspheres using emulsion polymerization.

The solution containing the protective colloid agent can be prepared by dissolving the protective colloid agent in water. Examples of protective colloids include methyl vinyl ether-maleic anhydride copolymers.

The polymerization of the monomer or prepolymer can be carried out by dispersing the dye-containing solution in the form of oil droplets in a protective colloid agent-containing solution which has been heated to a predetermined temperature, and adding the above-mentioned monomer or prepolymer to the dispersion and stirring it while maintaining the temperature. As a result, the water-insoluble dye and the resin having OH groups are contained in the polymer obtained by polymerization of the monomer or prepolymer.

In the obtained microspheres, the content of the resin having OH groups is preferably 1% by mass or more and 40% by mass or less in the total amount of the microspheres, and the content of the water-insoluble dye is preferably 10% by mass or more and 45% by mass or less. The microspheres preferably have an average particle size of 0.3 μm to 3.0. mu.m. In embodiments of the present invention (including the examples described below), the term "average particle diameter" is a value of D50 calculated by laser diffraction method based on volume, and can be measured using, for example, a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso co.

5) Examples of the thermochromic colored resin particles of (a) include particles produced by microencapsulating a thermochromic composition containing at least a leuco dye which is an electron donating dye and serves as a colorant, a developer which is a component capable of developing the leuco dye, and a color change temperature regulating agent capable of controlling a color change temperature in coloring of the leuco dye and the developer, to have a predetermined average particle diameter (for example, 0.2 to 3 μm).

Examples of the microencapsulation process include an interfacial polymerization process, an interfacial polycondensation process, an in-situ polymerization process, a liquid internal curing coating process, a phase separation process from an aqueous solution, a phase separation process from an organic solvent, a melt dispersion cooling process, an air suspension coating process and a spray drying process. The method may be appropriately selected depending on the intended use. For example, in a phase separation method from an aqueous solution, a leuco dye, a developer, and a color-changing temperature adjuster are melted by heating, added to an emulsifier solution, and dispersed into oil droplets under heating and stirring. Subsequently, as a capsule film material, a resin material having a wall film of, for example, a polyurethane resin, an epoxy resin, an amino resin, or the like is used, and, for example, an amino resin solution, specifically, an aqueous methylolmelamine solution, a urea solution, a benzoguanamine solution, and other solutions are gradually added, and the mixture is continuously reacted to prepare a dispersion, and then the dispersion is filtered to obtain thermochromic colored resin particles containing a thermochromic microcapsule pigment. In the thermochromic colored resin particles, the coloring and decoloring temperatures of the respective colors can be set to appropriate temperatures by appropriately combining the kinds and amounts of the leuco dye, the developer, and the color-change temperature adjuster.

6) Examples of the photochromic colored resin particles of (a) include particles composed of at least one or more dyes selected from photochromic dyes (compounds) and fluorescent dyes, and a resin such as a terpene-phenolic resin, and particles produced by microencapsulating a photochromic composition comprising at least one or more dyes selected from photochromic dyes (compounds) and fluorescent dyes, an organic solvent and additives such as an antioxidant, a photostabilizer and a sensitizer to have a predetermined average particle diameter (for example, 0.2 to 3 μm). The microencapsulation process may be performed in the same manner as the preparation of the thermochromic resin particles described above.

By appropriately using dyes such as photochromic dyes (compounds) and fluorescent dyes, it is possible to make photochromic colored resin particles colorless in an indoor lighting environment (an indoor lighting device selected from incandescent lamps, fluorescent lamps, white LEDs) and develop color in an environment irradiated with UV (an environment irradiated with a wavelength of 200 to 400nm, or with sunlight including UV).

Further, in the present invention, in addition to the colored resin particles of 1) to 6) described above, hollow resin particles having voids inside the particles and solid resin particles having no voids inside the particles may also be used.

Examples of the material of the hollow resin particles and the solid resin particles include solid resin particles as follows: homopolymers of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polystyrene, polymethyl methacrylate, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyethylene terephthalate, and polyurethane; copolymers comprising two or more monomers, such as styrene-acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymers, and styrene-butadiene copolymers; and modified products thereof.

The resin particles used in the present invention may have various shapes such as a spherical shape (true spherical, nearly spherical, or nearly ellipsoidal), a polygonal shape, or a flat shape, but a spherical shape is preferable.

Among the above-mentioned resin particles, hollow resin particles having voids inside the particles can be used as a white pigment, and the colored resin particles of 1) to 6) can be used as a fluorescent pigment, a thermochromic pigment, and a photochromic pigment in the form of microencapsulated pigments and microspheres (colorants). Further, the resin particles of 1) to 6) described above may be resin particles produced by various methods, and may be commercially available products.

The content of these resin particles varies depending on the purpose, for example, in the case where the resin particles are used alone as a colorant, or in the case where non-colored resin particles and colored resin particles as a colorant are used in combination. The appropriate content depends on the case where the resin particles are used as, for example, a masking agent, a sealant or a colorant. Specifically, the decrease in the initial writing property and the content of the resin particles tend to be approximately proportional. The higher the content, the more likely the writing ability is decreased.

The total content of the resin particles (solid content) used is 5 to 40%, preferably 5 to 30%, relative to the total amount of the ink composition, from the viewpoint of high compatibility of writing performance, drawn line quality, and writing-initial property. If the content of the resin particles is less than 5%, the writing performance and the drawn line quality will be deteriorated, and in the case where the content exceeds 40%, a decrease in the initial writing property is observed. Both of these cases are not preferred.

In addition, the average particle diameter of the resin particles tends to be approximately proportional to the decrease in the initial writing property. When the average particle diameter of the resin particles is 0.4 μm or more, a decrease in the initial impact is slightly observed, and when the average particle diameter is 1.0 μm or more, the initial impact tends to be further decreased. The upper limit of the average particle diameter is preferably 20 μm or less in view of writing performance and drawn line quality.

The aqueous ink composition for a ballpoint pen according to the present invention may include, in addition to the graft compound and the resin particles, water (such as tap water, purified water, distilled water, ion-exchanged water, or pure water) as a solvent for the rest, other colorants, common components such as a water-soluble organic solvent, a thickener, a lubricant, a rust preventive, a preservative, a bactericide, or a pH adjuster, in an appropriate amount within a range not to impair the effects of the present invention.

Examples of other colorants that may be used include pigments and/or water-soluble dyes that are commonly used in aqueous ink compositions for writing instruments. The pigment may optionally be selected from inorganic and organic pigments.

Examples of the inorganic pigment include carbon black, titanium oxide, and metal powder. Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, lake dyes, nitro pigments, and nitroso pigments.

The water-soluble dye may be a direct dye, an acid dye, a food dye or a basic dye.

These colorants may be used alone in an appropriate amount, or two or more colorants may be used in combination.

Examples of the water-soluble organic solvent which can be used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 3-butanediol, thiodiethylene glycol, and glycerin; ethylene glycol monomethyl ether and diethylene glycol monomethyl ether. The solvents may be used alone or as a mixture.

The content of the water-soluble organic solvent varies depending on the purpose. For example, the content is preferably more than 10% for the purpose of improving the writing feeling and preventing the drying of the nib.

On the other hand, in a writing instrument using an ink containing resin particles having a large average particle diameter, the ink flow rate is often increased. As a result, a problem of deterioration in the drying property of the drawn line occurs. Therefore, it is desirable to reduce the content within a range that does not impair the overall performance of the writing instrument. From the above viewpoint, the content thereof is preferably 10% or less, and more preferably 5 to 10%, based on the total amount of the ink composition.

The thickener that can be used herein is preferably at least one selected from the group consisting of synthetic polymers, celluloses, and polysaccharides, for example. Specific examples include gum arabic, gum tragacanth, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, welan gum, succinoglycan, diutan gum, dextran, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, starch glycolic acid and its salts, propylene glycol alginate, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide, vinyl acetate-polyvinyl pyrrolidone copolymers, crosslinked acrylic acid polymers and their salts, uncrosslinked acrylic acid polymers and their salts, and styrene-acrylic acid copolymers and their salts.

Examples of the lubricant include, but are not limited to, nonionic surfactants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments, anionic surfactants such as alkyl sulfonates and alkylaryl sulfonates of higher fatty acid amides, and derivatives of polyalkylene glycols, fluorine-containing surfactants, and polyether-modified silicones.

Examples of the rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of preservatives or bactericides include phenol, sodium pyrithione (sodium omadine), sodium benzoate, benzisothiazoline, and benzimidazole compounds.

Examples of the pH adjuster include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; amine compounds such as triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine and triethylamine; and ammonia.

The production of the aqueous ink composition for a ballpoint pen of the present invention can use a known method, and the composition can be used, for example, by stirring and mixing the graft compound represented by the formula (I), the resin particles, the other colorant and the above aqueous component in a prescribed amount using a mixer such as a homomixer or a disperser. Further optionally, coarse particles in the ink composition may be removed by filtration or centrifugation.

The water-based ink composition for a ballpoint pen obtained in the embodiment of the present invention is used for ink refills (ink refills) equipped with a ballpoint pen tip such as a metal tip or a resin tip, and a ballpoint pen.

The aqueous ink composition for a ballpoint pen of the present invention comprises at least 0.1 to 5% by mass of a graft compound, 5 to 40% by mass of resin particles, and water, and thus achieves excellent ink discharge properties (initial writing properties) even after a pen tip is exposed for a long time.