Method for manufacturing aqueous ballpoint pen and ink composition for aqueous ballpoint pen

Abstract

To provide (i) a method for manufacturing an aqueous ballpoint pen, which can suppress the occurrence of the phenomenon of smearing of handwriting in the center when writing after long-term storage without providing a tip sealant at the tip of a ballpoint pen tip, and (ii) an ink composition for an aqueous ballpoint pen, which can suppress the occurrence of the phenomenon of smearing of handwriting in the center when writing after long-term storage without providing a tip sealant at the tip of the ballpoint pen tip.SOLUTION: There are provided (i) a method for manufacturing an aqueous ballpoint pen that is provided with a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, the method using an ink composition for an aqueous ballpoint pen that has a smaller contact angle to the tip ball than that to the stainless steel socket; and (ii) an ink composition for an aqueous ballpoint pen that is used for an aqueous ballpoint pen that is provided with a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, the ink composition for an aqueous ballpoint pen containing a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aqueous ballpoint pen and an ink composition for an aqueous ballpoint pen. [Background technology]

[0002] Water-based ballpoint pens are attracting attention due to their ability to produce handwriting in a wide variety of colors and thicknesses, and development is underway. A widely known water-based ballpoint pen has an ink reservoir tube formed by a ballpoint pen tip, which is composed of a tip ball and a socket that rotatably holds the tip ball, attached to the tip end either directly or via a connecting member, and an ink composition for the water-based ballpoint pen. With such a configuration, when writing, the ink composition for the water-based ballpoint pen flows out of the ink reservoir tube, adheres to the surface of the tip ball, and is transferred to the writing surface by the rotation of the tip ball. For example, Patent Document 1 discloses a ballpoint pen for writing on cloths, which has a ballpoint pen tip attached to one end, and which is directly filled with ink containing at least a resin emulsion with a minimum film-forming temperature of 25°C or less, a pigment, and water, and having a viscosity of 100 to 30,000 mPa·s (25°C), and an ink backflow preventer.

[0003] In aqueous ballpoint pen refills, a predetermined gap is provided between the tip ball and the socket that holds the tip ball. When aqueous ballpoint pens and aqueous ballpoint pen refills are shipped from the factory, a measure is taken to prevent ink from leaking out of the gap and evaporation of the ink solvent by forming a film of tip sealant on the tip of the ballpoint pen, as shown in Patent Document 2. However, there has been a problem in that this is not sufficient when storing the pen after it has been used once, or when storing the pen after the tip sealant has come off in a store or during transportation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-11575 [Patent Document 2] Japanese Patent Application Publication No. 57-178798 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors have conducted further research into water-based ballpoint pens and have found that when the diameter of the tip ball is large, at 0.7 mm or more, the gap between the tip ball and the socket that holds it becomes wider, and when the pen is stored without a tip sealant, air can enter through this gap and grow within the ink. In such cases, the handwriting begins normally, but after a while the handwriting becomes smudged and then returns to normal (a phenomenon known as smudged handwriting), and a solution was needed.

[0006] The first problem that the present invention aims to solve is to provide a method for manufacturing an aqueous ballpoint pen that can suppress the occurrence of hollow smearing of handwriting when writing after long-term storage without providing a tip sealant at the tip of the ballpoint pen tip. The second problem that the present invention aims to solve is to provide an aqueous ink composition for ballpoint pens that can suppress the occurrence of hollow smearing of handwriting when writing after long-term storage without providing a tip sealant at the tip end of the ballpoint pen tip. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following method for producing an aqueous ballpoint pen and the following ink composition for an aqueous ballpoint pen, and have thus completed the present invention. [Section 1] A method for manufacturing an aqueous ballpoint pen having a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, The method for manufacturing the water-based ballpoint pen uses an ink composition for a water-based ballpoint pen, the ink composition having a contact angle with the tip ball smaller than the contact angle with the stainless steel socket. [Section 2] Item 2. The method for producing an aqueous ballpoint pen according to Item 1, wherein the ink composition for an aqueous ballpoint pen contains an ethylene-vinyl acetate resin. [Section 3] Item 3. The method for producing an aqueous ballpoint pen according to Item 1 or 2, wherein the ink composition for an aqueous ballpoint pen contains a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin. [Section 4] An ink composition for an aqueous ballpoint pen, which is used in an aqueous ballpoint pen equipped with a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, comprising a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin. [Effects of the Invention]

[0008] The present invention provides a method for manufacturing an aqueous ballpoint pen that can suppress the occurrence of smeared handwriting when writing after long-term storage without providing a tip sealant at the tip end of the ballpoint pen tip. The present invention provides an aqueous ink composition for ballpoint pens that can suppress the occurrence of hollow smearing of handwriting when writing after long-term storage without providing a tip sealant at the tip end of the ballpoint pen tip. DETAILED DESCRIPTION OF THE INVENTION

[0009] A first aspect of the present invention relates to a method for producing a water-based ballpoint pen. A second aspect of the present invention relates to an ink composition for a water-based ballpoint pen. The method for producing an aqueous ballpoint pen according to the first aspect of the present invention and the ink composition for an aqueous ballpoint pen according to the second aspect of the present invention will be described in detail below.

[0010] [Water-based ballpoint pen manufacturing method] A first aspect of the present invention relates to a method for manufacturing an aqueous ballpoint pen that includes a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, wherein an ink composition for an aqueous ballpoint pen is used, the ink composition having a smaller contact angle with the tip ball than with the stainless steel socket. The water-based ink composition for a ballpoint pen may contain an ethylene-vinyl acetate resin. The water-based ink composition for a ballpoint pen may contain a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin.

[0011] <Chipboard> In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the tip ball of the aqueous ballpoint pen is a silicon carbide tip ball or a tungsten carbide tip ball. The diameter of the chipboard is not particularly limited and can be, for example, 0.1 mm or more, preferably 0.3 mm or more, more preferably 0.5 mm or more, even more preferably 0.7 mm or more, and particularly preferably 0.8 mm or more, and can be, for example, 3.0 mm or less, preferably 2.0 mm or less, and more preferably 1.5 mm or less. The Vickers hardness (HV) of the chipboard can be, for example, 700 or more, preferably 1000 or more, and can be, for example, 2000 or less.

[0012] The chipboard may be a so-called matte ball, which has fine irregularities formed on the ball surface. By using a matte ball, it is possible to prevent smearing or skipping of lines when writing. In this case, the arithmetic mean roughness Ra (based on JIS B 0601) of the chipboard surface may be, for example, 5 nm or more, preferably 5.3 nm or more, more preferably 6 nm or more, and may be, for example, 25 nm or less, preferably 20 nm or less. The chip ball may be a ball having no minute irregularities formed on the surface thereof.

[0013] <socket> In the method for manufacturing an aqueous ballpoint pen according to the first aspect of the present invention, the socket that holds the tip ball of the aqueous ballpoint pen is a stainless steel socket from the viewpoints of abrasion resistance during writing, ink corrosion resistance, ease of socket formation, etc. Examples of stainless steel that forms the stainless steel socket include austenitic stainless steel (e.g., SUS304) and ferritic stainless steel (e.g., SUS430). From the viewpoints of workability and suppression of deformation at the tip of the ballpoint pen, it is preferable that the Vickers hardness (HV) is 150 or more and 300 or less. Furthermore, from the viewpoint of environmental impact, it is preferable that the socket does not contain lead. From the viewpoint of workability, etc., it is preferable that the socket contains bismuth (element symbol: Bi) as a lead substitute.

[0014] <Contact angle> In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the contact angle of the ink composition for an aqueous ballpoint pen with respect to the silicon carbide-based tip ball or the tungsten carbide-based tip ball is adjusted to be smaller than the contact angle of the ink composition for an aqueous ballpoint pen with respect to the stainless steel socket. The contact angle of the aqueous ballpoint pen ink composition with the silicon carbide chip ball or tungsten carbide chip ball can be, for example, 55° or more, preferably 65° or more, and more preferably 70° or more, and can be, for example, 95° or less, preferably 90° or less, and more preferably 85° or less. The contact angle of the aqueous ballpoint pen ink composition with the stainless steel socket can be, for example, 60° or more, preferably 65° or more, more preferably 70° or more, and can be, for example, 100° or less, preferably 95° or less, more preferably 90° or less.

[0015] Methods for adjusting the contact angle of an aqueous ballpoint pen ink composition with respect to a silicon carbide-based chip ball, a tungsten carbide-based chip ball, and a stainless steel-based socket include, for example, one or more of: (i) a method for adjusting the constituent components of an aqueous ballpoint pen ink composition and the amounts thereof blended, such as the type and amount of surfactant; (ii) a method for adjusting the constituent components and surface roughness of the silicon carbide-based chip ball and / or the tungsten carbide-based chip ball; and (iii) a method for adjusting the stainless steel material and surface roughness of the stainless steel socket. The present inventors have discovered that the contact angle of the aqueous ballpoint pen ink composition with a silicon carbide-based tip ball, a tungsten carbide-based tip ball, and a stainless steel socket can be easily adjusted by adjusting the content of the water-soluble organic solvent contained in the aqueous ballpoint pen ink composition, particularly the content of glycol ether. For example, when ethylene glycol monobutyl ether is used as the water-soluble organic solvent, increasing the content can reduce the contact angle of the aqueous ballpoint pen ink composition with a silicon carbide-based tip ball, a tungsten carbide-based tip ball, and a stainless steel socket, and can also increase the difference between the contact angle of the aqueous ballpoint pen ink composition with each tip ball and the contact angle of the aqueous ballpoint pen ink composition with a stainless steel socket. The present inventors have also found that the contact angle of an aqueous ballpoint pen ink composition with silicon carbide-based chipboard and tungsten carbide-based chipboard can be easily adjusted by adjusting the surface roughness Ra of the chipboard. For example, increasing the surface roughness Ra (nm) can reduce the contact angle of the aqueous ballpoint pen ink composition with the chipboard.

[0016] <Composition of water-based ballpoint pen> An example of the configuration of an aqueous ballpoint pen manufactured by the manufacturing method for an aqueous ballpoint pen of the first aspect of the present invention is a configuration in which an aqueous ballpoint pen refill is configured by filling an ink composition for an aqueous ballpoint pen in an ink reservoir tube formed by attaching a socket that rotatably holds a tip ball to the tip directly or via a connecting member, and the refill is disposed inside the barrel of the aqueous ballpoint pen. During writing, the ink composition for an aqueous ballpoint pen flows out of the ink reservoir tube, adheres to the surface of the tip ball, and is transferred to the writing surface by the rotation of the tip ball, thereby performing writing.

[0017] The structure and shape of the water-based ballpoint pen body are not particularly limited, and can be of any suitable type. The water-based ballpoint pen may be a retractable ballpoint pen that can store the pen tip inside the barrel, such as a knock type, a rotary type, or a slide type, and may be a single-color type, a multi-color type with two or more colors, or a multi-function type that is combined with a writing instrument other than a ballpoint pen. It may also be a cap-type ballpoint pen that has a cap that covers the pen tip. Known components can be used for the barrel and other components of the ballpoint pen. In the present invention, a retractable ballpoint pen is preferred.

[0018] <Ink storage tube> The material constituting the ink reservoir is not particularly limited. Examples include resins such as polypropylene, polyethylene, polyester, polyamide, polyurethane, and polyvinyl chloride, and metals such as nickel-chromium alloy steel (SUS304 stainless steel), chromium alloy steel (SUS430 stainless steel), austenitic stainless steel, free-cutting stainless steel, brass, aluminum, nickel silver, and phosphor bronze alloy. Preferably, polypropylene, polyethylene, polyester, polyamide, nickel-chromium alloy steel (SUS304 stainless steel), chromium alloy steel (SUS430 stainless steel), austenitic stainless steel, brass, and nickel silver are used.

[0019] <Amount of ink flow> The amount of ink flowing out of the water-based ballpoint pen can be adjusted as needed, thereby preventing smearing of handwriting and allowing for the production of good handwriting. Furthermore, the amount of movement (clearance) of the ball in the ballpoint pen tip in the vertical axis direction can be adjusted appropriately depending on the amount of ink flowing out, and can be set to, for example, 20 μm to 50 μm.

[0020] <Water-based ballpoint pen refill> The water-based ballpoint pen refill contains an ink composition for a water-based ballpoint pen in an ink reservoir equipped with a ballpoint pen tip at the front end, and the rear end of the ink reservoir is filled with an ink follower to prevent backflow. The ink follower is a substance that is incompatible with the aqueous ballpoint pen ink composition filled in the ink reservoir and has a low specific gravity relative to the ink. For example, a base oil or a base oil containing a thickener can be used. The base oil used in the ink follower can be one or more water-insoluble or slightly soluble substances selected from polybutene, mineral oil, silicone oil, etc. Examples of thickeners that can be used in the ink follower include one or more selected from fine particle silica, calcium salts of phosphate esters, thermoplastic elastomers, etc. The ink follower may further contain one or more thickeners selected from the group consisting of thickening aids (clay thickeners, metal soaps, etc.), ink follower followability improvers (surfactants, etc.), antioxidants, etc., as needed. Examples of ink followers include polybutene, a mixture of mineral oil and metal soap, a mixture of silicone oil and silica, etc. The viscosity of the ink follower can be, for example, 1,000 mPa·s or more and 10,000 mPa·s or less.

[0021] <Water-based ballpoint pen ink composition> In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the ink composition for an aqueous ballpoint pen used is not particularly limited, as long as the contact angle of the ink composition with respect to the silicon carbide-based tip ball or tungsten carbide-based tip ball constituting the aqueous ballpoint pen is smaller than the contact angle with respect to the stainless steel socket constituting the aqueous ballpoint pen. In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the ink composition for an aqueous ballpoint pen used may contain an ethylene-vinyl acetate resin. In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the ink composition for an aqueous ballpoint pen used may contain a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin. In the method for producing an aqueous ballpoint pen according to the first aspect of the present invention, the ink composition for an aqueous ballpoint pen used may contain, in addition to the (meth)acrylic resin, colorant, and ethylene-vinyl acetate resin, water, a water-soluble organic solvent, a surfactant, a pH adjuster, an antiseptic and antifungal agent, a viscosity adjuster, and other additives.

[0022] The (meth)acrylic resin, colorant, and ethylene-vinyl acetate resin contained in the ink composition for an aqueous ballpoint pen used in the method for producing an aqueous ballpoint pen according to the first aspect of the present invention may be the same as the (meth)acrylic resin, colorant, and ethylene-vinyl acetate resin constituting the ink composition for an aqueous ballpoint pen according to the second aspect of the present invention. Furthermore, the water, water-soluble organic solvent, surfactant, pH adjuster, antiseptic and antifungal agent, viscosity adjuster, and other additives that may be contained in the ink composition for an aqueous ballpoint pen used in the manufacturing method for an aqueous ballpoint pen according to the first aspect of the present invention may be the same as the water, water-soluble organic solvent, surfactant, pH adjuster, antiseptic and antifungal agent, viscosity adjuster, and other additives that may be contained in the ink composition for an aqueous ballpoint pen according to the second aspect of the present invention. The viscosity, pH value, and production method of the ink composition for an aqueous ballpoint pen used in the method for producing an aqueous ballpoint pen according to the first aspect of the present invention may be the same as the viscosity, pH value, and production method of the ink composition for an aqueous ballpoint pen according to the second aspect of the present invention.

[0023] [Water-based ballpoint pen ink composition] A second aspect of the present invention relates to an ink composition for an aqueous ballpoint pen, which is used in an aqueous ballpoint pen equipped with a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel-based socket, and which contains a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin.

[0024] <(Meth)acrylic resin> The aqueous ballpoint pen ink composition of the present invention contains a (meth)acrylic resin. The (meth)acrylic resin preferably functions as a dispersant and fixative that stabilizes the dispersion of components such as pigments contained in the aqueous ballpoint pen ink composition, prevents the pigments and other components from settling after dispersion, and enables the formation of ink strokes.

[0025] The (meth)acrylic resin is not particularly limited as long as it is a resin having a repeating unit derived from a (meth)acrylic compound in the molecule. For example, one or more resins selected from the group consisting of styrene-(meth)acrylic acid resins, styrene-(meth)acrylic acid ester resins, (meth)acrylic acid ester resins, vinyl acetate-(meth)acrylic acid ester resins, and anion-modified resins obtained by modifying these resins by introducing an anionic functional group selected from a carboxylic acid (salt) group, a sulfonic acid (salt) group, and a phosphoric acid (salt) group can be used.

[0026] In the aqueous ballpoint pen ink composition of the present invention, the (meth)acrylic resin preferably contains at least one selected from the group consisting of styrene-(meth)acrylic acid resins, styrene-(meth)acrylic acid ester resins, (meth)acrylic acid ester resins, and anion-modified (meth)acrylic resins.

[0027] The content of the (meth)acrylic resin in the aqueous ballpoint pen ink composition is not particularly limited and can be, for example, 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more, and can be, for example, 10% by mass or less, preferably 8% by mass or less, and more preferably 5% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition. If the content of (meth)acrylic resin exceeds 10% by mass, taking the total amount of the aqueous ballpoint pen ink composition as 100% by mass, the dispersant / fixing agent may act as a flocculating agent, causing aggregation of ingredients such as pigments. If the content is less than 0.01% by mass, the coating film forming ability may be insufficient, and handwriting may not be formed.

[0028] <Coloring agent> The aqueous ballpoint pen ink composition of the present invention contains a colorant. The colorant is contained to impart a desired color tone, hiding power, etc. to handwriting. Any colorant can be used without particular limitations as long as it has good writing properties without causing smearing, and is excellent in drying properties, sedimentation stability, storage stability, etc. The colorant can be one or more selected from the group consisting of inorganic pigments, organic pigments, colored resin spheres, dyes, etc., which exhibit any desired color tone.

[0029] As the inorganic pigment, for example, one or more selected from the group consisting of carbon black, titanium oxide, zinc oxide, red iron oxide, yellow iron oxide, ultramarine, Prussian blue, metal powder such as aluminum powder or bronze powder, fluorescent pigment, glass flake, pearl pigment, luster pigment, etc. can be used. As the organic pigment, for example, one or more selected from the group consisting of known color pigments and fluorescent pigments such as phthalocyanine-based, azo-based, quinacridone-based, anthraquinone-based, dioxane-based, indigo-based, thioindigo-based, perinone-based, perylene-based, indolenone-based, and azomethine-based pigments can be used. Colored resin spheres are spherical, irregular, hollow, flattened, or other resin spheres colored with one or more inorganic pigments, organic pigments, or dyes of any desired color tone. Examples of resin materials used to form the colored resin spheres include polyethylene, polypropylene, vinyl chloride, polymethacrylate, benzoguanamine, melamine resin, and nylon. The dye is preferably water-soluble, and any of direct dyes, acid dyes, food dyes, and basic dyes can be used. For example, one or more dyes selected from the group consisting of coloring dyes and fluorescent dyes such as anthraquinone-based, methine-based, carbonium-based, and metal complex salt-based dyes can be used.

[0030] The content of the colorant in the aqueous ballpoint pen ink composition is not particularly limited, and can be adjusted appropriately to achieve the desired color tone. The content can be, for example, 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition. It can also be, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less. If the colorant content exceeds 20.0% by mass, the solid content increases, which can adversely affect fluidity, viscosity, handleability, sedimentation stability, blurring of handwriting, production costs, and the like. Furthermore, when producing a particularly dark-colored ink, the content of the colorant in the aqueous ballpoint pen ink composition can be 20% by mass or more, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition.

[0031] <Ethylene-vinyl acetate resin> The aqueous ballpoint pen ink composition of the present invention contains an ethylene-vinyl acetate resin. The ethylene-vinyl acetate resin preferably has a function of suppressing the occurrence of hollow smearing of handwriting during writing after storage when a ballpoint pen is produced using the aqueous ballpoint pen ink composition.

[0032] The ethylene-vinyl acetate resin is not particularly limited as long as it is a resin having a repeating unit derived from ethylene and a repeating unit derived from vinyl acetate in the molecule. In the present invention, the ethylene-vinyl acetate resin may be one or more selected from the group consisting of anion-modified resins modified by introducing an anionic functional group selected from a carboxylic acid (salt) group, a sulfonic acid (salt) group, and a phosphoric acid (salt) group into the molecule.

[0033] The vinyl acetate content in the ethylene-vinyl acetate resin is not particularly limited and can be, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 7% by mass or more, and can be, for example, 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less, based on 100% by mass of the ethylene-vinyl acetate resin.

[0034] The melting point of the ethylene-vinyl acetate resin is not particularly limited and can be, for example, 90°C or higher, preferably 95°C or higher, and more preferably 97°C or higher, and can be, for example, 125°C or lower, preferably 120°C or lower, and more preferably 115°C or lower.

[0035] The number average molecular weight of the ethylene-vinyl acetate resin is not particularly limited and is, for example, 1,000 or more, preferably 2,000 or more, and for example, 20,000 or less, preferably 10,000 or less.

[0036] In the present invention, the ethylene-vinyl acetate resin is preferably an ethylene-vinyl acetate wax emulsion. The volume average particle diameter of the ethylene-vinyl acetate wax in the ethylene-vinyl acetate wax emulsion is not particularly limited. For example, it can be 5 nm or more, preferably 10 nm or more, more preferably 15 nm or more, and can be 50 nm or less, preferably 45 nm or less, more preferably 30 nm or less.

[0037] The content of the ethylene-vinyl acetate resin in the aqueous ballpoint pen ink composition is not particularly limited and can be, for example, 0.05% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more, and can be, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition. If the content of the ethylene-vinyl acetate resin exceeds 20% by mass, taking the total amount of the aqueous ballpoint pen ink composition as 100% by mass, aggregation may occur during storage at low temperatures, causing problems in terms of storage stability. If the content is less than 0.1% by mass, problems may occur in terms of handwriting formation, such as smearing during writing.

[0038] <Water> The aqueous ballpoint pen ink composition of the present invention contains water that functions as a dispersion medium and / or solvent to disperse and / or dissolve the constituent components.

[0039] Examples of water that can be used include tap water, industrial water, purified water, distilled water, ion-exchanged water, ultrafiltered water, pure water, etc. Preferably, ion-exchanged water and / or distilled water is used.

[0040] The content of water in the aqueous ballpoint pen ink composition is not particularly limited. It can be adjusted appropriately depending on the content, viscosity, etc. of each component in the aqueous ballpoint pen ink composition. When the total amount of the aqueous ballpoint pen ink composition is taken as 100% by mass, the content of water can be, for example, 15% by mass or more, preferably 20% by mass or more, and more preferably 50% by mass or more, and can be, for example, 85% by mass or less, preferably 83% by mass or less, and more preferably 80% by mass or less. If the water content exceeds 85% by mass, assuming the total amount of the aqueous ballpoint pen ink composition to be 100% by mass, problems such as insufficient color development (light color) may occur, while if the water content is less than 15% by mass, problems such as smearing during writing and reduced storage stability may occur.

[0041] <Water-soluble organic solvent> The water-based ink composition for a ballpoint pen of the present invention may contain a water-soluble organic solvent. In the aqueous ballpoint pen ink composition of the present invention, the water-soluble organic solvent preferably functions as a dispersion medium and / or solvent for dispersing and / or dissolving the constituent components, as a wetting agent for adjusting drying properties, and as a viscosity adjuster for adjusting viscosity.

[0042] Any water-soluble organic solvent can be used without particular limitation as long as it has excellent solubility in water. For example, a solvent having a solubility in water at 25°C of 20 g / L or more, preferably 50 g / L or more, can be used.

[0043] Examples of the water-soluble organic solvent include monoalcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tertiary butanol, pentanol, and hexanol; ethylene glycol, diethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2,4-butanetriol, and isopentylene. Tandiol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 3-methyl-1,3-butanediol, 2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1 ,3-Hexanediol, 2,4-diethyl-1,5-pentanediol, hexane-1,2,6-triol, 3-methyl-1,5-pentanediol, 2,5-hexanediol, 1,2-heptanediol, 1,3-heptanediol, 1,4-heptanediol, 1,5-heptanediol, 1,6-heptanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5- polyhydric alcohols such as hexanediol, 1,2-nonanediol, 1,9-nonanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-decanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin, triglycerin, and acetylene glycol;Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether Examples of the cyclic ester include glycol ethers such as tetrahydrofuran and dioxane, cyclic esters such as γ-butyrolactone, carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide, lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one, cyclic ureas such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimid-2-one, ketones such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate, ketoalcohols, carbonates, and the like.

[0044] Preferably, one or more selected from the group consisting of ethylene glycol, propylene glycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and dipropylene glycol monomethyl ether can be used.

[0045] The content of the water-soluble organic solvent in the aqueous ballpoint pen ink composition is not particularly limited and can be, for example, 0% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more, and can be, for example, 35% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less, where the total amount of the aqueous ballpoint pen ink composition is taken as 100% by mass.

[0046] <Surfactant> The aqueous ballpoint pen ink composition of the present invention contains a surfactant, which may be any of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. In the aqueous ballpoint pen ink composition of the present invention, the surfactant preferably functions as a dispersant for dispersing and / or dissolving the constituent components, as a lubricant for improving the lubricity between the tip ball and the socket that holds the tip ball, and as a rust inhibitor for the constituent components.

[0047] Examples of surfactants include one or more selected from the group consisting of phosphorus-based surfactants (e.g., alkyl phosphate esters, alkyl ether phosphate esters, alkylaryl phosphate esters, etc.), sulfonic acid-based surfactants (e.g., alkylarylsulfonic acid (salts), sulfosuccinate esters, sulfosuccinate diesters, etc.), ether-based surfactants (polyoxyalkylene alkyl ethers, etc.), acetylene glycol-based surfactants, ester-based surfactants (polyoxyalkylene fatty acid esters, polyoxyalkylene alkylaryl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, etc.), fluorine-based surfactants, and silicone-based surfactants.

[0048] In the aqueous ballpoint pen ink composition of the present invention, the surfactant preferably contains a phosphate ester surfactant. In the aqueous ink composition for a ballpoint pen of the present invention, the surfactants can be used alone or in combination of two or more.

[0049] The phosphate ester surfactant is not particularly limited as long as it is suitable for use in aqueous ballpoint pen ink compositions. The HLB value of the phosphate ester surfactant is not particularly limited, but is, for example, 9.0 or more, preferably 9.7 or more, and for example, 17.0 or less, preferably 15.0 or less. The HLB can be calculated by the Kawakami method [HLB=7+11.7 log(MW / MO), where MW is the sum of the formula weights of the hydrophilic moieties, and MO is the sum of the formula weights of the lipophilic moieties]. Alternatively, it may be determined experimentally.

[0050] Examples of the phosphate surfactant include one or more compounds represented by the following general formula (I). [ka] (wherein n is an integer of 0 to 20. R 1 is an alkyl group having 1 or more carbon atoms, an aryl group having 6 or more carbon atoms, an alkylaryl group having 6 or more carbon atoms, or an unsaturated hydrocarbon group having 4 or more carbon atoms. 2 is M or -(CH2CH2O) n -R 3 R 3 is either an alkyl group having 1 or more carbon atoms, an aryl group having 6 or more carbon atoms, an alkylaryl group having 6 or more carbon atoms, or an unsaturated hydrocarbon group having 4 or more carbon atoms. M is either a hydrogen atom, an alkali metal atom, an ammonium group, an organic ammonium group, or an organic amine group. When there are two M's, they may be different from each other. When there are two n's, they may be different from each other. Of these, it is preferable to use polyoxyethylene nonylphenyl ether phosphate and / or polyoxyethylene lauryl ether phosphate.

[0051] As such phosphate ester surfactants, commercially available products can be used. For example, the Phosphanol series (RS-710, RS-610, RS-410, RA-600, ML-200, ML-220, ML-240, PE-510, SM-172, ED-200, GF-339, etc.) manufactured by Toho Chemical Industry Co., Ltd., the Pricerf series (A219B, etc.) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and one or more selected from the group consisting of their salts can be used.

[0052] The content of the surfactant in the ink composition for aqueous ballpoint pens is not particularly limited. Assuming the total amount of the ink composition for aqueous ballpoint pens is 100% by mass, it can be, for example, 0% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and can be, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less.

[0053] <pH adjuster> The ink composition for aqueous ballpoint pens of the present invention may contain a pH adjuster. The pH adjuster is not particularly limited as long as it can be used in the ink composition for aqueous ballpoint pens. For example, hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; amines such as triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine, and triethylamine; ammonia (aqueous); inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; organic acids such as formic acid, acetic acid, propionic acid, benzenesulfonic acid, and toluenesulfonic acid; and one or more selected from the group consisting of these can be mentioned.

[0054] The content of the pH adjuster in the ink composition for aqueous ballpoint pens is not particularly limited. Assuming the total amount of the ink composition for aqueous ballpoint pens is 100% by mass, it can be, for example, 0% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and can be, for example, 3% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less.

[0055] <Antiseptic and antifungal agent> The water-based ink composition for a ballpoint pen of the present invention may contain an antiseptic and antifungal agent to inhibit putrefaction and mold growth. The antiseptic and antifungal agent is not particularly limited as long as it is one that can be used in an aqueous ballpoint pen ink composition, and examples thereof include one or more selected from the group consisting of antiseptic and antifungal agents such as isothiazolinone-based, benzotriazole-based, benzoic acid-based, pyridine-based, pentachlorophenol-based, cresol-based, propylene glycol-based, organic iodine-based, organic bromine-based, organic chlorine-based, dehydroacetic acid-based, sorbitan acid-based, phenoxy-based, and morpholine-based agents. For example, one or more selected from the group consisting of chloroacetamide, 2-pyridinethiol-1-oxide sodium salt, sodium dehydroacetate, sodium benzoate, sodium sorbate, potassium sorbate, 2-bromo-2-nitropropane-1,3-diol, 3-iodo-2-propynyl-N-butylcarbamate, 1,2-benzisothiazolin-3(2H)-one, 1,2,3-benzotriazole, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one thiabendazole, phenoxyethanol, sodium fluoride, 4-(2-nitrobutyl)morpholine, 1,3-dimorpholino-2-ethyl-2-nitropropane, etc. may be mentioned.

[0056] The content of the antiseptic and antifungal agent in the aqueous ballpoint pen ink composition is not particularly limited and can be, for example, 0% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, and can be, for example, 4% by mass or less, preferably 3% by mass or less, and more preferably 2.5% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition.

[0057] <Viscosity adjuster> The aqueous ballpoint pen ink composition of the present invention may contain a viscosity modifier to adjust the viscosity, etc. The viscosity modifier is not particularly limited as long as it is one that is used in aqueous ballpoint pen ink compositions. Examples include one or more selected from the group consisting of polysaccharides and derivatives thereof, such as xanthan gum, welan gum, succinoglycan (rheosan), diutan gum, guar gum, locust bean gum, and derivatives thereof, cellulose polymers, carboxyvinyl polymers, urethane associative thickeners, N-vinylacetamide resins, and inorganic fine particles.

[0058] The content of the viscosity modifier in the aqueous ballpoint pen ink composition is not particularly limited and can be, for example, 0% by mass or more, preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, and can be, for example, 3% by mass or less, preferably 2% by mass or less, and more preferably 1.5% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink composition.

[0059] <Other additives> The aqueous ballpoint pen ink composition of the present invention may contain components other than the (meth)acrylic resin, colorant, ethylene-vinyl acetate resin, water, water-soluble organic solvent, surfactant, pH adjuster, antiseptic / fungal agent, and viscosity adjuster (hereinafter, these may be referred to as "other additives"), as necessary.

[0060] Other additives are not particularly limited as long as they are used in aqueous ballpoint pen ink compositions. Examples include dispersing and fixing agents other than (meth)acrylic resins (such as styrene-maleic acid resins, styrene-maleic acid ester resins, vinyl acetate resins, vinyl chloride resins, polyurethane resins, and cellulose resins), rust inhibitors (such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponin, diisopropylammonium nitrite, sodium thiosulfate, ethylenediaminetetraacetate, octyl phosphate, imidazole, benzimidazole, dialkylthiourea, and derivatives thereof), ureas, antifoaming agents, leveling agents, anti-aggregating agents, ultraviolet absorbers, infrared absorbers, and antioxidants. These can be used in appropriate amounts to impart desired properties.

[0061] <Viscosity> The viscosity of the aqueous ballpoint pen ink composition of the present invention at 25°C is not particularly limited. It can be appropriately set from the viewpoints of writing performance, handwriting stability (prevention of dripping, smearing, bleeding, ink blobbing, strike-through, stable and uniform concentration, etc.), runoff, writing performance when dried, prevention of leakage, prevention of backflow, prevention of pigment sedimentation, prevention of component separation, production costs, etc. For example, the viscosity is 1 mPa·s or more, preferably 100 mPa·s or more, more preferably 1,000 mPa·s or more, and for example, 50,000 mPa·s or less, preferably 20,000 mPa·s or less, more preferably 10,000 mPa·s or less. If the viscosity of the aqueous ballpoint pen ink composition is less than 1 mPa·s, problems may arise with regard to ink outflow from the tip of the writing instrument (the aqueous ballpoint pen ink composition may flow out excessively when writing, making it impossible to form accurate handwriting), sedimentation stability, etc., whereas if the viscosity exceeds 50,000 mPa·s, the viscosity may be too high, which may result in problems with ink outflow from the tip of the writing instrument (the ink may not flow out), ink handling, sedimentation stability, smearing of handwriting, production costs, etc. The viscosity of the aqueous ballpoint pen ink composition of the present invention can be obtained, for example, by measuring at 25°C using an E-type rotational viscometer (for example, TVE-type viscometer manufactured by Toki Sangyo Co., Ltd., 3°R14 cone, 0.5 rpm).

[0062] <pH value> The pH value of the aqueous ballpoint pen ink composition of the present invention is not particularly limited. It can be appropriately set from the viewpoints of stability, color development property, writing property, prevention of component separation, etc. For example, the pH value can be 6.0 or more, preferably 6.5 or more, more preferably 7.0 or more, even more preferably more than 7.0, and for example, it can be 10.0 or less, preferably 9.0 or less. Regarding the pH value of the aqueous ballpoint pen ink composition, when the pH value approaches the acidic side of less than 6.0, there may be problems such as a decrease in the stability of the ink over time and corrosion of the metal members contacted by the ink. When the pH value exceeds 10.0 and approaches the strong alkaline side, there may be problems such as handwriting due to fading and discoloration. The pH value of the aqueous ballpoint pen ink composition of the present invention can be obtained, for example, by measuring at 20°C using a commercially available pH meter.

[0063] <Manufacturing method> The manufacturing method of the aqueous ballpoint pen ink composition of the present invention is not particularly limited. Any of the conventionally known manufacturing methods of aqueous ballpoint pen ink compositions can be used. For example, all the components are put into a container and mixed and stirred by a stirring device such as a ball mill, bead mill, roll mill, Henschel mixer, planetary mixer, homomixer, turbo mixer, propeller stirrer, homogenizer, high-pressure homogenizer, kneader, dissolver, etc. to disperse each constituent component, and an aqueous ballpoint pen ink composition can be prepared. For example, after manufacturing a dispersion liquid by putting some of the components such as water, carbon black, alumina, etc. into a container and mixing and stirring them by the above device to disperse them, the remaining components are put in and mixed and stirred to disperse each constituent component, and ink can be prepared. When preparing an aqueous ballpoint pen ink composition, coarse particles, gas, and bubbles can be removed by filtration, centrifugation, degassing, and the like. When preparing an aqueous ballpoint pen ink composition, heating, cooling, pressurization, decompression, inert gas substitution, and the like can be performed alone or in combination. Furthermore, an aging step may be performed after preparation of the aqueous ballpoint pen ink composition.

[0064] <Application> The ink composition for an aqueous ballpoint pen according to the second aspect of the present invention is used in an aqueous ballpoint pen comprising a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel-based socket. Specifically, an aqueous ballpoint pen refill is prepared by filling an ink reservoir formed by attaching a socket rotatably holding the tip ball to the tip end directly or via a connecting member with the ink composition for an aqueous ballpoint pen of the present invention, and then disposing the refill in the barrel of the aqueous ballpoint pen. During writing, the water-based ink composition for the ballpoint pen flows out of the ink reservoir tube, adheres to the surface of the tip ball, and is transferred to the writing surface by the rotation of the tip ball, thereby performing writing.

[0065] The structure and shape of the water-based ballpoint pen body are not particularly limited, and can be of any suitable type. The water-based ballpoint pen may be a retractable ballpoint pen that can store the pen tip inside the barrel, such as a knock type, a rotary type, or a slide type, and may be a single-color type, a multi-color type with two or more colors, or a multi-function type that is combined with a writing instrument other than a ballpoint pen. It may also be a cap-type ballpoint pen that has a cap that covers the pen tip. Known components can be used for the barrel and other components of the ballpoint pen. In the present invention, a retractable ballpoint pen is preferred.

[0066] The silicon carbide-based tip ball, tungsten carbide-based tip ball, stainless steel socket, ink reservoir, water-based ballpoint pen refill, and ink follower in an aqueous ballpoint pen in which the ink composition for an aqueous ballpoint pen according to the second aspect of the present invention is used may be the same as the silicon carbide-based tip ball, tungsten carbide-based tip ball, stainless steel socket, ink reservoir, water-based ballpoint pen refill, and ink follower described in the method for producing an aqueous ballpoint pen according to the first aspect of the present invention. Furthermore, the ink flow rate in the aqueous ballpoint pen refill and the amount of movement of the ball in the ballpoint pen tip in the vertical direction (clearance) can also be made similar to the ink flow rate in the aqueous ballpoint pen refill and the amount of movement of the ball in the ballpoint pen tip in the vertical direction (clearance) described in the method for manufacturing an aqueous ballpoint pen according to the first embodiment of the present invention. [Example]

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0068] [Components of water-based ballpoint pen ink composition] The following components were used as constituents of the aqueous ballpoint pen ink composition. Acrylic resin 1: Anion-modified acrylic resin Acrylic resin 2: Styrene acrylic resin Colorant 1: Carbon black Colorant 2: Pigment Red 268 Colorant 3: Pigment Blue 15:3 EVA: Anion-modified ethylene-vinyl acetate resin wax emulsion (volume average particle size 30 nm, melting point 105°C) Water-soluble organic solvent 1: Ethylene glycol monobutyl ether Water-soluble organic solvent 2: Glycerin Water-soluble organic solvent 3: Ethylene glycol Water-soluble organic solvent 4: Propylene glycol Water-soluble organic solvent 5: Dipropylene glycol methyl ether Surfactant 1: Polyoxyethylene nonylphenyl ether phosphate Surfactant 2: Polyoxyethylene lauryl ether phosphate pH adjuster: sodium hydroxide Antiseptic and antifungal agent 1: Sodium benzoate Antiseptic and antifungal agent 2: 1,2-benzisothiazolin-3-one Antiseptic and antifungal agent 3: 1,2,3-benzotriazole Antiseptic and antifungal agent 4: 3-iodo-2-propynyl-N-butylcarbamate Viscosity adjuster 1: Carboxyvinyl polymer (average molecular weight approximately 3 million) Viscosity adjuster 2: Carboxyvinyl polymer (average molecular weight approximately 4 million) Viscosity modifier 3: Xanthan gum

[0069] [evaluation] <Writability after storage> Using the manufactured ballpoint pen, 10 circles each about 3 cm in diameter were drawn consecutively on a test paper. After writing, the ballpoint pens were left uncapped and no hot melt adhesive was attached to the tip of the pen, and the ballpoint pens were stored in a thermostatic chamber at 50°C for 4 weeks, either horizontally or upright with the pen tip facing up. After storage, each ballpoint pen was removed from the thermostatic chamber and returned to room temperature (25°C ± 5°C). Ten circles approximately 1.5 cm in diameter were written consecutively on a test piece of paper, and the writing performance after storage was evaluated according to the following criteria. In this invention, S is a pass.

[0070] (Evaluation criteria) S: Over 90% of writing is normal (less than one full ballpoint pen stroke) A: 80% to less than 90% normal writing (smearing occurs between one and two ballpoint pens) B: 60% to less than 80% normal writing (smearing occurs between 2 and 4 ballpoint pen rounds) C: Less than 60% normal writing possible (more than 4 ballpoint pen rounds)

[0071] <Contact angle> Using an automatic extremely small contact angle meter ("MCA-3" manufactured by Kyowa Interface Science Co., Ltd.), the contact angles of each ink composition for ballpoint pen, the silicon carbide-based tip ball used in the ballpoint pen refill, or the tungsten carbide-based tip ball used in the ballpoint pen refill, and the stainless steel socket were measured.

[0072] [Examples A-1 to A-3] Each ink composition for a ballpoint pen was prepared by using the components shown in Table 1 in the amounts (parts by mass) shown in Table 1, stirring and mixing them using a stirrer, filtering through a mesh, and degassing. A tip formed by rotatably holding a silicon carbide-based tip ball (0.8 mm in diameter) or a tungsten carbide-based tip ball (0.8 mm in diameter) in a stainless steel socket was attached to the front end of an ink reservoir tube, and each of the prepared ballpoint pen ink compositions was filled in. After that, an ink follower was filled into the rear end of the ink reservoir tube to prevent backflow, and the tube was centrifuged to prepare a ballpoint pen refill. The prepared ballpoint pen refill was placed in the barrel of a ballpoint pen to prepare the ballpoint pen. The writing properties of the prepared ballpoint pens were evaluated after storage. The results are shown in Table 1. In addition, the contact angles of each of the prepared ink compositions for ballpoint pens were measured against the silicon carbide-based tip balls used in the ballpoint pen refills, the tungsten carbide-based tip balls used in the ballpoint pen refills, and the stainless steel sockets. The results are also shown in Table 1.

[0073] [Comparative examples A-1 to A-3] For commercially available water-based ballpoint pens, the contact angle of the ink composition for water-based ballpoint pens to the tip ball and the contact angle of the ink composition for water-based ballpoint pens to the stainless steel socket were measured. In Comparative Example A-1 (Pentel Co., Ltd. "Energel" (black)), the contact angle of the aqueous ballpoint pen ink composition to the chipboard was 77.8°, and the contact angle of the aqueous ballpoint pen ink composition to the stainless steel socket was 68.0°. In Comparative Example A-2 (PILOT "G-2" (black)), the contact angle of the aqueous ballpoint pen ink composition to the chipboard was 76.3°, and the contact angle of the aqueous ballpoint pen ink composition to the stainless steel socket was 69.3°. In Comparative Example A-3 (SHARPIE "S-GEL" (black)), the contact angle of the aqueous ballpoint pen ink composition to the chipboard was 87.6°, and the contact angle of the aqueous ballpoint pen ink composition to the stainless steel socket was 73.9°.

[0074] [Table 1]

[0075] [Examples B-1 to B-3, Comparative Examples B-1 to B-3] The components shown in Table 2 were used in the amounts (parts by mass) shown in Table 2, respectively, and these were stirred and mixed using a stirrer, filtered through a mesh, and degassed to prepare each ink composition for a ballpoint pen. A tip formed by rotatably holding a 0.8 mm diameter tungsten carbide-based tip ball (Examples B-1 to B-3, Comparative Example B-1) or a 0.8 mm diameter silicon carbide-based tip ball (Comparative Example B-2, Comparative Example B-3) in a stainless steel socket was attached to the front end of an ink reservoir tube, and each of the prepared ballpoint pen ink compositions was filled in. After that, an ink follower was filled into the rear end of the ink reservoir tube to prevent backflow, and the tube was centrifuged to prepare a ballpoint pen refill. The prepared ballpoint pen refill was placed in the barrel of a ballpoint pen to prepare the ballpoint pen. The writing properties of the prepared ballpoint pens were evaluated after storage. The results are shown in Table 2.

[0076] [Table 2]

[0077] From the results of Examples A-1 to A-3, in a method for manufacturing an aqueous ballpoint pen equipped with a large-diameter silicon carbide-based tip ball or a large-diameter tungsten carbide-based tip ball and a stainless steel socket, by using an ink composition for an aqueous ballpoint pen whose contact angle with the tip ball is smaller than the contact angle with the stainless steel socket, all of the writing performance evaluations after storage were rated S. This shows that even after long-term storage (4 weeks) at high temperature (50°C), which is a harsher condition than actually expected storage conditions, the occurrence of hollow and smeared handwriting during writing can be suppressed.

[0078] The results of Examples A-1 to A-3 and B-1 to B-3 show that when the ink composition for an aqueous ballpoint pen containing a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin was used in an aqueous ballpoint pen equipped with a large-diameter silicon carbide tip ball or a large-diameter tungsten carbide tip ball and a stainless steel socket, the writing performance after storage was all rated S. This shows that even after long-term storage (4 weeks) at high temperature (50°C), which is harsher than the storage conditions actually expected, the ink composition can suppress the occurrence of hollow smearing in handwriting during writing, making it suitable as an ink composition for an aqueous ballpoint pen.

[0079] On the other hand, the results of Comparative Examples B-1 to B-3 show that when an ink composition for an aqueous ballpoint pen that does not contain an ethylene-vinyl acetate resin is used in an aqueous ballpoint pen equipped with a large-diameter silicon carbide tip ball and a stainless steel socket, the writing performance after storage is rated B or C, and the occurrence of hollow and smeared handwriting during writing after long-term storage (4 weeks) at high temperature (50°C) cannot be suppressed, indicating that the ink composition is problematic as an aqueous ballpoint pen ink composition.

Claims

1. A method for manufacturing an aqueous ballpoint pen having a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, The method for manufacturing the water-based ballpoint pen uses an ink composition for a water-based ballpoint pen, the ink composition having a contact angle with the tip ball smaller than the contact angle with the stainless steel socket.

2. 2. The method for producing an aqueous ballpoint pen according to claim 1, wherein the ink composition for an aqueous ballpoint pen contains an ethylene-vinyl acetate resin.

3. 3. The method for producing an aqueous ballpoint pen according to claim 1, wherein the ink composition for an aqueous ballpoint pen contains a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin.

4. The ink composition for an aqueous ballpoint pen is used for an aqueous ballpoint pen equipped with a silicon carbide-based tip ball or a tungsten carbide-based tip ball and a stainless steel socket, and contains a (meth)acrylic resin, a colorant, and an ethylene-vinyl acetate resin.

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