Aqueous ink composition for ballpoint pens

Abstract

This aqueous ink composition for ballpoint pens contains at least: a colorant; a polyhydric alcohol and / or a glycol ether; and a starch decomposition product or a sugar alcohol obtained by reducing the starch decomposition product. The polyhydric alcohol and the glycol ether have 4 or more carbon atoms and a specific gravity at 25°C of less than 1.00, and the DE value of the starch decomposition product is 10 to 20.

Description

Water-based ink composition for ballpoint pens

[0001] The present invention relates to an aqueous ink composition for a ballpoint pen.

[0002] Generally, water-based ballpoint pens are characterized by a lighter writing feel than oil-based ballpoint pens and the ability to exude ink without rotating the ball. However, they are known to have a particular problem in that the lines they draw dry more slowly than oil-based ballpoint pens, and various studies have been conducted on them.

[0003] Patent Document 1 discloses an aqueous ink composition for a ballpoint pen, which is composed of at least a colorant and water, and further contains 0.5 to 45% by weight of a polyhydric alcohol and / or glycol ether that is soluble in water and has 4 or more carbon atoms and a specific gravity of less than 1.00 (at 25°C), and the total amount of ink constituents with a specific gravity of 1.00 or more is 50% by weight or more in the ink.

[0004] Patent Document 2 discloses an aqueous ink composition for a ballpoint pen, which contains at least dextrin having a DE value in the range of 2 to 5 and an average particle size in an aqueous medium in the range of 1 to 10 μm, a colorant, and water.

[0005] Patent Document 3 discloses an aqueous ink composition for a ballpoint pen, which is characterized by containing water, a pigment, a styrene-acrylic resin, and a polyethylene glycol surfactant.

[0006] JP 2006-193688 A JP 2015-40269 A JP 2023-20178 A

[0007] The present invention provides a novel aqueous ink composition for ballpoint pens that has good adhesion, good line drying properties, and good bleeding resistance, and that can also suppress smearing when starting to write and dripping of ink from the pen tip.

[0008] After extensive research, the present inventors have found that the above-mentioned problems can be solved by the following means, and have thus completed the present invention. Specifically, the present invention is as follows: <Aspect 1> An aqueous ink composition for a ballpoint pen, comprising at least a colorant, a polyhydric alcohol and / or glycol ethers, and a starch hydrolysate or a sugar alcohol obtained by reducing the starch hydrolysate, wherein the polyhydric alcohol and glycol ethers have 4 or more carbon atoms and a specific gravity at 25°C of less than 1.00, and the starch hydrolysate has a DE value of 10 or more and 20 or less. <Aspect 2> The aqueous ink composition for a ballpoint pen according to Aspect 1, wherein the polyhydric alcohol is at least one selected from the group consisting of hexylene glycol and 1,2-pentanediol. <Aspect 3> The aqueous ink composition for a ballpoint pen according to Aspect 1 or 2, further comprising an alkali-swelling associative thickener. <Aspect 4> A ballpoint pen comprising at least an ink reservoir, a writing portion having a ball, and a holder portion, wherein the ink reservoir stores the aqueous ink composition for ballpoint pens according to any one of Aspects 1 to 3. <Aspect 5> The ballpoint pen according to Aspect 4, wherein the ink reservoir is a hollow ink reservoir. <Aspect 6> The ballpoint pen according to Aspect 5, which is a knock-type ballpoint pen.

[0009] According to the present invention, it is possible to provide a novel aqueous ink composition for ballpoint pens that has good adhesion, good line drying properties, and good resistance to bleeding, and that can also suppress smearing when starting to write and dripping of ink from the pen tip.

[0010] <<Aqueous Ink Composition for Ballpoint Pens>> The aqueous ink composition for ballpoint pens of the present invention contains at least a colorant, a polyhydric alcohol and / or glycol ethers, and a starch hydrolysate or a sugar alcohol obtained by reducing the starch hydrolysate, wherein the polyhydric alcohol and the glycol ethers have 4 or more carbon atoms and a specific gravity at 25°C of less than 1.00, and the starch hydrolysate has a DE value of 10 or more and 20 or less.

[0011] The aqueous ballpoint pen ink composition of Patent Document 1 had relatively good bleeding resistance, line drying properties, and fixation properties due to the use of specific polyhydric alcohols and / or glycol ethers, but sometimes required a batting-like or comb-like collector in the ink reservoir of the ballpoint pen to prevent ink dripping from the pen tip. Also, the aqueous ballpoint pen ink composition of Patent Document 1 had room for improvement in terms of smearing when starting to write.

[0012] In response to this, the inventors have discovered that the above-described composition can suppress smearing at the start of writing and also suppress ink dripping from the pen tip while maintaining good bleed resistance, line drying properties, and adhesion. While not wishing to be bound by theory, the aqueous ink composition of the present invention is thought to be due to the fact that the specific polyhydric alcohol and / or glycol ether improves bleed resistance, line drying properties, and adhesion to a certain extent, while the starch hydrolysate having the above-described DE value or the sugar alcohol obtained by reducing this starch hydrolysate further improves these properties, allowing a smooth film to form on the pen tip at the start of writing and preventing spontaneous ink bleeding when the ink is left unused. This is thought to be due to the fact that the starch hydrolysate having the above-described DE value or the sugar alcohol obtained by reducing this starch hydrolysate has an appropriate bulkiness that is small enough to smoothly form a film on the pen tip at the start of writing and large enough to prevent spontaneous ink bleeding when the ink is left unused.

[0013] In the present invention, the term "aqueous ink composition" refers to an ink composition that contains an aqueous medium as a liquid component.

[0014] The aqueous ink composition for ballpoint pens of the present invention was －１The viscosity measured under these conditions can be, for example, 100 mPa·s or less, 90 mPa·s or less, 80 mPa·s or less, 70 mPa·s or less, 60 mPa·s or less, 50 mPa·s or less, 40 mPa·s or less, 30 mPa·s or less, 20 mPa·s or less, 19 mPa·s or less, 18 mPa·s or less, 17 mPa·s or less, 16 mPa·s or less, or 15 mPa·s or less, or 4 mPa·s or more, 5 mPa·s or more, 6 mPa·s or more, 7 mPa·s or more, 8 mPa·s or more, 9 mPa·s or more, or 10 mPa·s or more. This viscosity can be measured, for example, using an ELD viscometer.

[0015] The aqueous ink composition for ballpoint pens of the present invention may further contain an alkali-swelling associative thickener, which allows the aqueous ink composition for ballpoint pens to have a desired viscosity without impairing the above-mentioned effects.

[0016] Each component of the present invention will be described below.

[0017] <Aqueous Medium> Generally, the aqueous medium contains water and an optional water-soluble organic solvent. In particular, in the present invention, the aqueous medium contains at least water and the above-mentioned polyhydric alcohol.

[0018] The aqueous medium may further contain a water-soluble organic solvent other than the above polyhydric alcohol and the above glycol ether.

[0019] In the aqueous medium, among the liquid components, the water content is the highest, and in particular the water content may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 75% by mass or more, or 78% by mass or more, relative to the mass of the aqueous medium, and may be 100% by mass or less, 95% by mass or less, or 90% by mass or less.

[0020] Furthermore, the water content may be 50% by mass or more, 55% by mass or more, 60% by mass or more, or 63% by mass or more, and may be 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less, relative to the mass of the aqueous ink composition for ballpoint pens.

[0021] (Water) As the water, for example, tap water, purified water, distilled water, ion-exchanged water, pure water, etc. can be used.

[0022] (Polyhydric Alcohol and Glycol Ether) The polyhydric alcohol and glycol ether in the aqueous ink composition for a ballpoint pen of the present invention are polyhydric alcohols having 4 or more carbon atoms and a specific gravity of less than 1.00 at 25° C. In this specification, the term "specific gravity" refers to the specific gravity of a substance at 25° C. when water at 25° C. is used as the standard substance, and refers to a value measured with a standard hydrometer.

[0023] Examples of such polyhydric alcohols that can be used include isoprene glycol (3-methyl-1,3 butanediol), 1,2-pentanediol, 1,5 pentanediol, 1,2-hexanediol, hexylene glycol, and octylene glycol.

[0024] Examples of glycol ethers that can be used include methyl glycol, isopropyl glycol, butyl glycol, butyl diglycol, butyl triglycol, isobutyl glycol, allyl glycol, methyl propylene glycol, methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, methyl propylene glycol acetate, dimethyl glycol, dimethyl diglycol, dimethyl triglycol, diethyl diglycol, and dimethyl propylene diglycol.

[0025] (Other Water-Soluble Organic Solvents) Examples of other water-soluble organic solvents that can be used include aromatics, alcohols, esters, second polyhydric alcohols other than the above-mentioned polyhydric alcohols, and ethers other than glycol ethers. These solvents may be used alone or in combination.

[0026] Examples of aromatic compounds that can be used include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, and alkylsulfonic acid phenyl esters.

[0027] Examples of alcohols that can be used include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, and 2-methylcyclohexanol.

[0028] As the second polyhydric alcohol, polyhydric alcohols having less than 4 carbon atoms or having a specific gravity of 1.00 or more at 25°C, such as ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1,3 propanediol, 1,3 butanediol, and octylene glycol, can be used.

[0029] Examples of ethers that can be used other than glycol ethers include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, and hexyl ether.

[0030] Examples of esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, Examples of usable surfactants include methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic acid triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0031] The content of the other water-soluble organic solvent may be 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, or 12% by mass or more, based on the total mass of the aqueous ink composition for ballpoint pens, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 17% by mass or less.

[0032] <Coloring Material> As the coloring material, various coloring materials that can be used in conventional inks can be used, such as dyes, pigments, or mixtures of dyes and pigments. These coloring materials can be used alone or in combination.

[0033] As the dye, any dye that dissolves or disperses in water can be used, and examples thereof include acid dyes such as eosin, foxin, water yellow #6-C, acid red, water blue #105, brilliant blue FCF, and nigrosine NB; direct dyes such as direct black 154, direct sky blue 5B, and violet BB; and basic dyes such as rhodamine and methyl violet.

[0034] As the pigment, any of conventionally known inorganic and organic pigments such as titanium oxide, resin particle pigments containing pigments or dyes, pseudo-pigments in which resin emulsions are colored with dyes or pigments, white plastic pigments, thermochromic pigments, photochromic particles, etc. can be used without limitation.

[0035] Examples of inorganic pigments that can be used include carbon black, titanium black, zinc white, red iron oxide, aluminum, chromium oxide, iron black, cobalt blue, iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, yellow lead, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, baryte powder, calcium carbonate, white lead, dark blue, iron blue, manganese violet, aluminum powder, and brass powder.

[0036] Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, nitroso pigments, etc. Examples of such organic pigments include C.I. Pigment Blue 17, C.I. Pigment Blue 15, C.I. Pigment Blue 17, C.I. Pigment Blue 27, C.I. Pigment Red 5, C.I. Pigment Red 22, C.I. Pigment Red 38, C.I. Pigment Red 48, C.I. Pigment Red 49, C.I. Pigment Red 53, C.I. Pigment Red 57, C.I. Pigment Red 81, C.I. Pigment Red 104, C.I. Pigment Red 146, C.I. Pigment Red 245, C.I. Pigment Yellow 1, C.I. Pigment Yellow 3, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 17, C.I. Pigment Yellow 34, C.I. Pigment Yellow 55, C.I. Pigment Yellow 74, C.I. Pigment Yellow 95, C.I. Pigment Yellow 166, C.I. Pigment Yellow 167, C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 16, C.I. Pigment Violet 1, C.I. Pigment Violet 3, C.I. Pigment Violet 19, C.I. Examples of suitable pigments include C.I. Pigment Violet 23, C.I. Pigment Violet 50, and C.I. Pigment Green 7.

[0037] Examples of thermochromic pigments include those produced by microencapsulating a thermochromic composition containing at least a leuco dye that functions as a color former, a color developer that is a component capable of causing the leuco dye to develop color, and a color change temperature regulator that can control the color change temperature during color development of the leuco dye and the color developer, so as to have a predetermined average particle size (e.g., 0.1 to 6 μm). This average particle size may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 0.9 μm or more, or may be 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0038] Examples of photochromic particles that can be used include photochromic particles composed of at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, and a resin such as a terpene phenol resin. Examples of photochromic particles include photochromic particles produced by microencapsulating a photochromic composition containing at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, so as to have a predetermined average particle size (e.g., 0.1 to 6 μm).

[0039] By suitably using the above-mentioned photochromic substance, the photochromic particles can be made to have the property of being colorless in an indoor lighting environment (indoor lighting equipment selected from incandescent lamps, fluorescent lamps, lamps, white LEDs, etc.) and becoming colored in an ultraviolet ray irradiation environment (irradiation with light having a wavelength of 200 to 400 nm, or irradiation with sunlight containing ultraviolet rays).

[0040] In the present invention (including the examples), the "average particle size" is appropriately selected depending on the size of the particles to be measured. For particles less than approximately 1 μm, it is the histogram mean particle size (D50) calculated on a volume basis in the scattering intensity distribution measured by dynamic light scattering, and for particles 1 μm or larger, it is the median diameter (D50) calculated on a volume basis by laser diffraction. The average particle size can be measured using a particle size analyzer [Microtrac HRA9320-X100 (Nikkiso Co., Ltd.)].

[0041] Examples of methods for microencapsulating the thermochromic pigment and the photochromic particles include interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid hardening coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and can be appropriately selected depending on the application.

[0042] For example, in the phase separation method from an aqueous solution, a thermochromic microcapsule pigment can be produced by a method comprising the following steps, particularly a method comprising carrying out the following steps in this order: (1) heating and melting a leuco dye, a color developer, and a color change temperature regulator; (2) adding the heated and melted leuco dye, color developer, and color change temperature regulator to an emulsifier solution, and heating and stirring to disperse them into oil droplets to produce a dispersion; (3) gradually adding, as a capsule film agent, a resin raw material capable of forming a wall film such as a urethane resin, an epoxy resin, or an amino resin, for example, an amino resin solution, specifically, an amino resin solution such as a methylolmelamine aqueous solution, a urea solution, or a benzoguanamine solution, to the above dispersion, and reacting this resin raw material to form a capsule film, thereby obtaining a thermochromic microcapsule pigment; and (4) filtering the dispersion containing the thermochromic microcapsule pigment.

[0043] In this thermochromic pigment, the color-developing temperature and decolorizing temperature of each color can be set to an appropriate temperature by appropriately combining the types and amounts of the leuco dye, color developer, and color-change temperature regulator.

[0044] These colorants can be used alone or in combination of two or more. The average particle diameter of water-dispersible pigments, resin particle pigments, pseudopigments, white plastic pigments, multi-coated pigments, thermochromic pigments, photochromic particles, and the like among these colorants varies depending on the ball diameter, ink composition, viscosity, and other factors, but is preferably 0.02 to 6 μm. This average particle diameter may be, for example, 0.02 μm or more, 0.05 μm or more, 0.07 μm or more, 0.10 μm or more, 0.20 μm or more, 0.30 μm or more, 0.50 μm or more, 0.70 μm or more, or 0.90 μm or more, or may be 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0045] The content of these coloring materials can be increased or decreased as appropriate depending on the line density of the ink, but may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, or 1.0% by mass or more, relative to the total amount of the ink composition, and is preferably 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0046] <Starch hydrolysate or sugar alcohol> The starch hydrolysate (dextrin) or sugar alcohol is a starch hydrolysate having a DE value of 10 or more and 20 or less, or a sugar alcohol obtained by reducing the starch hydrolysate. This DE value may be 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, or 15 or more, and may be 20 or less, 19 or less, or 18 or less.

[0047] Here, in this specification, the "DE (Dextrose Equivalent) value," sometimes referred to as "dextrose equivalent," is an index showing the degree of decomposition when starch is decomposed with an acid or enzyme, and is known as a relative measure when the reducing power of dextrose (glucose) is set to 100. A DE value of 0 indicates starch, and the closer to 0 the value, the more similar the properties to starch. Conversely, the closer the DE value is to 100, the more advanced the starch hydrolysis is. The DE value of dextrin can be measured by the Somogyi-Nelson method. Furthermore, for example, the DE values ​​of commercially available starch hydrolysates can be found in the catalogs.

[0048] The starch hydrolysate may be a hydrolysate of cornstarch (dent cornstarch), waxy cornstarch, sweet potato starch, potato starch, tapioca (cassava starch), wheat starch, and / or rice starch (glutinous rice starch or non-glutinous rice starch), and among these, a hydrolysate of tapioca is preferred from the viewpoint of suppressing smearing when starting to write and suppressing ink dripping from the pen tip.

[0049] Such starch hydrolysates are commercially available and can be used if they have the above-mentioned DE value.

[0050] The sugar alcohol can be a sugar alcohol obtained by reducing the above-mentioned starch hydrolysate, i.e., a starch hydrolysate having the above-mentioned DE value. Such sugar alcohols can be commercially available and have the above-mentioned DE value before reduction. That is, the DE value can be referenced from the value listed in the catalog as the DE value before reduction.

[0051] <Alkali Swelling Associative Thickener> In the present invention, an "alkali swelling associative" thickener refers to an unneutralized acrylic polymer that contains acid groups, mainly carboxyl groups, in the three-dimensional structure of the polymer, which swells when neutralized with an alkali, and which ultimately dissolves when neutralized further; when the polymer swells, hydrophobic portions in the molecules associate with corresponding portions of other molecules, forming loose intermolecular bonds, thereby exhibiting thickening properties.

[0052] Alkali swelling associative thickeners are thought to have two main thickening actions. The first is that they dissolve only in the alkaline region of a mixture with water or a polar solvent, and hydrophilic groups such as carboxyl groups in the molecule hydrate and expand, causing steric hindrance in the solution and increasing viscosity. The second is that the hydrophobic and hydrophilic groups in the molecule each separately associate and adsorb with the hydrophobic and hydrophilic groups of components in the ink, such as pigments, solvents, and surfactants, to form network-like aggregates, increasing viscosity.

[0053] The alkali-swelling associative thickener of the present invention may be a polymer having a carboxyl group and a hydrophobic group. Examples of the hydrophobic group include a linear or cyclic hydrocarbon group, an aromatic hydrocarbon group, a halogenated alkyl group, and an organosilicon group (-SiR ３ ), a fluorocarbon group (—C ｎ F ２ｎ＋１ Specific examples of the polymer include polyacrylic acid, polymethacrylic acid, polyacrylic acid copolymers, and polymethacrylic acid copolymers.

[0054] The content of the alkali association type thickener may be 1% by mass or more, or 2% by mass or more, and may be 7% by mass or less, 6% by mass or less, 5% by mass or less, 4% by mass or less, or 3% by mass or less, relative to the mass of the aqueous ink composition for ballpoint pens.

[0055] <Other Components> The aqueous ink composition for ballpoint pens of the present invention may contain other optional components, such as a humectant, a dispersant, a lubricant, a pH adjuster, a rust inhibitor, a preservative, an antibacterial agent, and a fixing resin.

[0056] As the dispersant, a water-soluble resin is used, and preferably a water-soluble polymer is used.

[0057] As the lubricant, lubricants used in surface treatment agents for pigments can be used, and examples thereof include 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; anionic surfactants such as phosphate esters, alkyl sulfonates of higher fatty acid amides, and alkyl aryl sulfonates; derivatives of polyalkylene glycols; and polyether-modified silicones.

[0058] Examples of pH adjusters include ammonia, urea, amines such as monoethanolamine, diethanolamine, and triethanolamine, alkali metal salts of carbonate or phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and hydrates of alkali metal salts such as sodium hydroxide.

[0059] As the rust inhibitor, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponins, etc. can be used. As the antiseptic or antibacterial agent, phenol, sodium omadine, sodium benzoate, thiazoline compounds, benzimidazole compounds, etc. can be used.

[0060] The fixing resin is a resin used for adjusting viscosity and improving fixing strength as required. For example, a water-soluble resin and a resin emulsion can be used as the fixing resin.

[0061] Examples of the water-soluble resin that can be used include water-soluble resins having a hydrophobic moiety in the molecule, such as polyacrylic acid, water-soluble styrene-acrylic resin, water-soluble styrene-maleic acid resin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resin, water-soluble styrene resin, water-soluble ester-acrylic resin, ethylene-maleic acid copolymer, polyethylene oxide, and water-soluble urethane resin.

[0062] As the resin emulsion, for example, at least one selected from polyolefin emulsion, acrylic emulsion, vinyl acetate emulsion, urethane emulsion, styrene-butadiene emulsion, styrene-acrylonitrile emulsion, and the like can be used.

[0063] The fixing resins may be used alone or in combination. In particular, from the viewpoint of fixing property, it is preferable to use one or more types of the above-mentioned water-soluble resins and resin emulsions, i.e., a total of two or more types of fixing resins.

[0064] The above other components may be used alone or in combination of two or more. If commercially available, these may also be used.

[0065] <<Ballpoint Pen>> The ballpoint pen of the present invention comprises at least an ink reservoir, a writing part having a ball, and a holding part, and the above-described aqueous ink composition for ballpoint pens is stored in the ink reservoir.

[0066] The ink reservoir and writing portion may be integrated, i.e., the ballpoint pen of the present invention may have a refill having an ink reservoir and a writing portion.

[0067] The ballpoint pen of the present invention may be a knock-type ballpoint pen. A knock-type ballpoint pen is generally a ballpoint pen having a knock mechanism that allows the writing part to be extended outside the writing instrument and retracted inside the writing instrument. The location of the knock mechanism is not particularly limited, and may be at the rear end of the writing part, i.e., the end opposite the writing part, or may be located on the side of the holding part.

[0068] <Ink Storage Unit> The ink storage unit stores the above-described water-based ink composition for ballpoint pens.

[0069] Any ink reservoir can be used as long as it can store ink and supply ink to the writing part. The aqueous ink composition for ballpoint pens of the present invention is particularly useful in that it can prevent ink from dripping from the pen tip even when a hollow ink reservoir is used.

[0070] <Writing Part> The writing part can be a writing part having a ballpoint pen tip at the tip.

[0071] A ballpoint pen tip may be composed of a ball and a holder that rotatably holds the ball. The ball may be composed of any material used for ballpoint pen balls, such as stainless steel, cemented carbide, ceramics, etc. The shape of the ballpoint pen tip is not particularly limited, and may be, for example, bullet-shaped or needle-shaped.

[0072] Furthermore, from the viewpoint of writing feel, it is preferable that the surface roughness Ra of the ball be less than 10 nm, 8 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, or 3 nm or less. This surface roughness may be 1.0 nm or more, 1.5 nm or more, or 1.7 nm or more.

[0073] The "surface roughness Ra" in the present invention (including the examples described later) was measured using a non-contact surface profiler (NewView 7200, Zygo Corporation) under the following conditions: lens magnification: 50x, evaluation length: 100 μm, Gaussian filter: 25 μm; and other conditions were measured in accordance with JIS B0601 (geometric characteristics specifications of products - surface properties).

[0074] From the viewpoint of writing performance, the ball clearance, i.e., the distance that the ball can move in the longitudinal direction of the ballpoint pen tip body, is preferably 30 μm or more, 40 μm or more, 50 μm or more, or 60 μm or more, and 120 μm or less, 110 μm or less, 100 μm or less, or 90 μm or less. This clearance can be measured by using a measuring microscope to measure the distance between the state where the ball is in contact with the ballpoint pen tip seat and the state where the ball is in contact with the crimped portion at the tip of the ballpoint pen tip.

[0075] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0076] The substances shown in Table 1 were mixed in the parts by mass shown in Table 1 to obtain 100 parts by mass of an aqueous ink composition for a ballpoint pen.

[0077] Details of the substances shown in Table 1 are as follows. Note that the DE values ​​of the sugar alcohols indicate the values ​​before reduction. Starch A: starch hydrolysate derived from tapioca (Pine Index #4, Matsutani Chemical Industry Co., Ltd., DE value: 19) Sugar Al A: sugar alcohol obtained by reducing starch hydrolysate derived from tapioca (H-PDX, Matsutani Chemical Industry Co., Ltd., DE value before reduction: 18) Sugar Al B: sugar alcohol obtained by reducing starch hydrolysate derived from tapioca (BDH-1, Matsutani Chemical Industry Co., Ltd., DE value before reduction: 11) Starch B: starch hydrolysate derived from tapioca (Pine Index #2, Matsutani Chemical Industry Co., Ltd., DE value: 11) Starch C: starch hydrolysate derived from tapioca (Pine Index #3, Matsutani Chemical Industry Co., Ltd., DE value: 25) Starch D: starch hydrolysate derived from tapioca (Max 1000, Matsutani Chemical Industry Co., Ltd., DE value: 9) Starch E: tapioca-derived starch hydrolysate (Pinex #100, Matsutani Chemical Industry Co., Ltd., DE value: 4) Phosphate ester: Phosphanol RD-510Y (Toho Chemical Industry Co., Ltd.) pH adjuster: triethanolamine Colorant: black pigment (carbon black MCF-88, Mitsubishi Chemical Corporation) Dispersant: Joncryl 60J, BASF Resin: styrene acrylic resin (Joncryl PDX-7741, BASF) Polyoxyethylene (POE) surfactant: Newpol PE-108, Sanyo Chemical Industry Co., Ltd. Acetylene glycol (AG) surfactant: Surfynol 104H, Nissin Chemical Industry Co., Ltd.

[0078] The viscosity of the prepared ink was measured using an ELD viscometer at a temperature of 25°C and a shear rate of 38.3 sec. －１ The measurement was carried out under the following conditions.

[0079] <Evaluation> Each of the prepared aqueous ink compositions for ballpoint pens was filled into a ballpoint pen to prepare an aqueous ballpoint pen. Specifically, a refill was prepared using the barrel of a ballpoint pen (Signo UM-100, Mitsubishi Pencil Co., Ltd.), which consisted of a hollow polypropylene ink reservoir tube with an outer diameter of 6.0 mm, an inner diameter of 3.8 mm, and a length of 113 mm, a stainless steel tip (carbide alloy ball, ball diameter 0.38 mm, surface roughness less than 10 nm), and a joint connecting the reservoir tube and the tip, and the ink composition and an ink follower were loaded into the rear end of the ink.

[0080] <Smearing at the start of writing> Using the prepared ballpoint pen, a line approximately 25 cm long was handwritten on writing paper conforming to ISO standards, and the writing feel was evaluated sensorily. The evaluation criteria are as follows: A: No smearing occurred. B: Smearing occurred, but the drawn line was fully recognizable. C: Smearing occurred to the extent that it significantly affected the recognition of the drawn line.

[0081] <Bleeding Resistance> Using the prepared ballpoint pen, a line approximately 25 cm long was handwritten on writing paper conforming to ISO standards, and the presence or absence of bleeding of the drawn line was visually confirmed. The evaluation criteria are as follows: A: No bleeding. B: Bleeding occurred at the end of the stroke. C: Bleeding occurred over the entire drawn line.

[0082] <Line Drying Property> Using the prepared ballpoint pen, a spiral was written freehand on writing paper conforming to ISO standards, and after a certain time had passed, the line drawn was rubbed with the thumb to check whether or not there was a transfer mark of ink on the finger, and the result was evaluated according to the following criteria: A+: No transfer mark remained even when rubbed 1 second after writing. A: No transfer mark remained even when rubbed 2 to 3 seconds after writing. B: No transfer mark remained between 4 and 5 seconds after writing. C: No transfer mark remained until writing for more than 5 seconds.

[0083] <Adhesion> Using the prepared ballpoint pen, a line approximately 25 cm long was handwritten on writing paper conforming to ISO standards. After drying, the drawn line was lightly rubbed perpendicularly to the drawn line with a finger wearing a finger cot (Office Finger Cot Meku-2, Kokuyo Co., Ltd.), and the presence or absence of peeling of the drawn line was visually confirmed. The evaluation criteria are as follows: A+: No change A: The color was slightly lighter, but no peeling was observed B: Partial peeling was observed C: Most of the line was peeled.

[0084] <Ink Dripping from the Pen Tip> The prepared ballpoint pen was left facing down in an environment of 25°C and 60% RH for 24 hours, and the phenomenon of direct ink flow from the pen tip was evaluated according to the following criteria. A: No leakage at all, or slight wetting was observed. B: Ink pools with a diameter of 0.5 mm or more were observed. C: Ink dripped.

[0085] Table 1 shows the configurations and evaluation results of the examples and comparative examples.

[0086]

[0087] From Table 1, it can be seen that the aqueous ink compositions for ballpoint pens of the examples, which contain a polyhydric alcohol having 4 or more carbon atoms and a specific gravity of less than 1.00 at 25°C, and a starch hydrolysate or a sugar alcohol obtained by reducing the starch hydrolysate, with a DE value of 10 to 20, have good adhesion, line drying properties, and bleeding resistance, and can also suppress smearing when starting to write and dripping of ink from the pen tip.

Claims

1. An aqueous ink composition for a ballpoint pen, comprising at least a colorant, a polyhydric alcohol and / or glycol ethers, and a starch hydrolysate or a sugar alcohol obtained by reducing the starch hydrolysate, wherein the polyhydric alcohol and glycol ethers have 4 or more carbon atoms and a specific gravity at 25°C of less than 1.00, and the starch hydrolysate has a DE value of 10 or more and 20 or less.

2. The aqueous ink composition for a ballpoint pen according to claim 1, wherein the polyhydric alcohol is at least one selected from the group consisting of hexylene glycol and 1,2-pentanediol.

3. The aqueous ink composition for ballpoint pens according to claim 1 or 2, further comprising an alkali-swelling associative thickener.

4. A ballpoint pen comprising at least an ink reservoir, a writing part having a ball, and a holding part, wherein the aqueous ink composition for ballpoint pens according to any one of claims 1 to 3 is stored in the ink reservoir.

5. The ballpoint pen of claim 4, wherein said ink reservoir is a hollow ink reservoir.

6. The ballpoint pen according to claim 5, which is a knock type.

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