Aqueous ballpoint pen ink

Abstract

To provide an aqueous ballpoint pen ink which can suppress deterioration in the metallic gloss of a written trace at the time of writing after storage and can also prevent aggregation from arising during storage.SOLUTION: An aqueous ballpoint pen ink comprising a silica-coated pigment, an alkali silicate, and a surfactant, wherein the content of the surfactant is 3 mass% to 10 mass% relative to 100 mass% of the silica-coated pigment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based ink for a ballpoint pen. [Background technology]

[0002] In recent years, water-based ballpoint pens capable of producing handwriting in a wide variety of colors have been developed. Among these, development is underway on water-based ballpoint pens capable of producing handwriting with a lustrous or metallic luster in order to enhance the design of the writing. Furthermore, from the viewpoint of user convenience and recent trends, development of retractable water-based ballpoint pens that do not require a cap is underway. In order to form handwriting with a lustrous or metallic luster, for example, a technique is known in which a lustrous pigment, particularly a plate-like metallic lustrous pigment, is contained in an aqueous ballpoint pen ink.

[0003] Patent Document 1 describes an aqueous ink composition for ballpoint pens that contains an aluminum pigment and 8 to 25 parts by mass of dense urethane particles of 3 to 10 μm, and the aluminum pigment used is a silica-coated aluminum powder pigment. However, previously known aqueous ballpoint pen inks containing a lustrous pigment such as an aluminum pigment have a risk of reducing the metallic gloss of handwriting when written after storage, and furthermore, have a risk of aggregation occurring during storage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-23615 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have discovered that by using an aqueous ballpoint pen ink that produces brilliant, metallic luster-like handwriting and that contains a silica-coated pigment, an alkali silicate, and a surfactant, and the surfactant content is within the range of 3% by mass to 10% by mass relative to 100% by mass of the silica-coated pigment, it is possible to prevent the metallic luster of the handwriting from decreasing when written after storage, and to prevent the occurrence of aggregation during storage.

[0006] The problem to be solved by the present invention is to provide an aqueous ballpoint pen ink that can suppress the decrease in metallic gloss of handwriting when writing after storage and can suppress the occurrence of aggregation during storage. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following water-based ballpoint pen ink, and have thus completed the present invention. [Section 1] silica-coated pigments, Alkali silicates, and surfactants, Contains The content of the surfactant is 3% by mass to 10% by mass relative to 100% by mass of the silica-coated pigment. Water-based ballpoint pen ink. [Effects of the Invention]

[0008] The present invention provides a water-based ballpoint pen ink that can suppress the decrease in metallic gloss of handwriting when written after storage and can suppress the occurrence of aggregation during storage.

[0009] The mechanism by which an aqueous ballpoint pen ink containing a silica-coated pigment, an alkali silicate, and a surfactant, in which the surfactant content is 3% to 10% by mass relative to 100% by mass of the silica-coated pigment, can suppress the decrease in metallic gloss of handwriting during writing after storage and can suppress the occurrence of aggregation during storage, is unknown, but the present inventors speculate as follows, although the present invention is not bound by this speculation.

[0010] In aqueous ballpoint pen inks containing a luster pigment such as an aluminum pigment, the pH decreases over time during storage, causing aggregation. Furthermore, the precipitation of aggregates on the surface of the luster pigment reduces the specularity of the surface of the luster pigment, resulting in a decrease in metallic gloss. The aqueous ballpoint pen ink of the present invention contains an alkali silicate, which prevents deterioration of the luster pigment and suppresses the decrease in pH over time that accompanies deterioration of the luster pigment during storage. Furthermore, since the ink contains a specific amount of surfactant, the surface of the luster pigment is sufficiently coated with the surfactant, and the specular properties of the luster pigment surface are not impaired. This is thought to prevent the metallic gloss of handwriting from decreasing when written after storage, and to prevent aggregation from occurring during storage. DETAILED DESCRIPTION OF THE INVENTION

[0011] The water-based ballpoint pen ink of the present invention will be described in detail below.

[0012] [Silica-coated pigment] The aqueous ballpoint pen ink of the present invention contains a silica-coated pigment. In the present invention, the silica-coated pigment is a pigment having a structure in which a silica layer is provided on the pigment surface. The silica-coated pigment may have other layers, such as a resin layer, a layer of an oxide other than silica, or a nitride layer, between the pigment surface and the silica layer, as necessary.

[0013] In the silica-coated pigment, the proportion of silica coating on the pigment surface can be, for example, 10% or more, preferably 30% or more, more preferably 50% or more, and for example, 100% or less of the pigment surface area. The amount of silica coating can be, for example, 5 parts by mass or more, preferably 10 parts by mass or more, and for example, 30 parts by mass or less, preferably 25 parts by mass or less, per 100 parts by mass of the silica-coated pigment.

[0014] In silica-coated pigments, examples of pigments coated with silica include one or more selected from the group consisting of metals (aluminum, gold, silver, copper, zinc, iron, tin, nickel, chromium, stainless steel, brass, bronze, nickel alloys, aluminum alloys, magnesium, etc.), glass, metal oxides (titanium oxide, silicon oxide, aluminum oxide, iron oxide, natural mica, artificial mica, etc.), metal nitrides, etc. These may be formed into a plate shape by mechanical means such as shaving or rolling, or may be obtained by pulverizing a film product such as a cast film, a coated film, or a vapor-deposited film.

[0015] Since the surface of the silica-coated pigment is coated with silica, it is possible to suppress aggregation of pigments in the ink, stabilize the dispersion of the pigment, and suppress reaction between the pigment and water, thereby suppressing the generation of bubbles. Furthermore, since the surface of the silica-coated pigment is coated with silica, it is possible to suppress the elution of metal ions over time and to suppress the elution of metal ions due to deformation or damage of the pigment when shear force is applied from a stirrer or the like during ink production, thereby making it possible to improve the stability of the ink over time.

[0016] In silica-coated pigments, the shape of the pigment coated with silica is not particularly limited. Examples include spherical, plate-like (flake-like, thin plate-like, scale-like), fibrous, and irregular shapes. From the viewpoint of glitter during writing, a plate-like shape is preferred.

[0017] The volume average particle size of the silica-coated pigment is not particularly limited and can be, for example, 0.05 μm or more, preferably 0.1 μm or more, and more preferably 0.2 μm or more, and can be, for example, 100 μm or less, preferably 70 μm or less, and more preferably 50 μm or less. The aspect ratio can be, for example, 1.05 or more, preferably 1.1 or more, more preferably 1.3 or more, and can be, for example, 90 or less, preferably 80 or less, more preferably 70 or less. When the silica-coated pigment is plate-shaped, the thickness can be, for example, 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more, and can be, for example, 15 μm or less, preferably 12 μm or less, and more preferably 10 μm or less.

[0018] In the aqueous ballpoint ink of the present invention, the silica-coated pigment preferably contains a silica-coated aluminum pigment, and more preferably contains a silica-coated aluminum flake pigment (silica-coated plate-like aluminum pigment). In the water-based ink for a ballpoint pen of the present invention, the silica-coated pigment may be used alone or in combination of two or more.

[0019] The content of the silica-coated pigment in the aqueous ballpoint pen ink is not particularly limited and can be, for example, 0.5% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and can be, for example, 20% by mass or less, preferably 18% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink. If the content of silica-coated pigment exceeds 20% by mass, taking the total amount of the water-based ballpoint pen ink as 100% by mass, there is a risk of clogging at the pen tip, sedimentation during storage, thickening of the water-based ballpoint pen ink, and smearing during writing. If it is less than 0.5% by mass, there is a risk of reduced color development, brilliance, gloss, and hiding power.

[0020] [Alkali silicate] The aqueous ballpoint pen ink of the present invention contains an alkali silicate. Examples of alkali silicates include sodium silicate, potassium silicate, lithium silicate, sodium polysilicate, potassium polysilicate, and lithium polysilicate. Examples of alkali silicates include one or more selected from the group consisting of Na2SiO3, Na4SiO4, Na2Si2O5, Na2Si4O9, K2SiO3, KHSi2O5, K2Si4O9·H2O, Li2SiO3, Li2Si2O5, mK2O·nSiO2, and mNa2O·nSiO2 (where m and n are integers). In the aqueous ink for a ballpoint pen of the present invention, the alkali silicate can exhibit the functions of an inhibitor for deterioration of the glitter pigment, particularly the metallic pigment, in the ink, and an agent for stabilizing the pH of the ink.

[0021] In the water-based ballpoint ink of the present invention, the alkali silicate preferably contains sodium silicate. In the aqueous ballpoint ink of the present invention, the alkali silicates can be used alone or in combination of two or more.

[0022] The content of alkali silicate in the aqueous ballpoint pen ink 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 0.4% by mass or more, and can be, for example, 8% by mass or less, preferably 4% by mass or less, and more preferably 2% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink. If the content of alkali silicate is less than 0.05% by mass or more than 8% by mass, based on 100% by mass of the total amount of the water-based ballpoint pen ink, the stability over time of the water-based ballpoint pen ink may decrease.

[0023] [Surfactants] The aqueous ballpoint pen ink 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 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.

[0024] 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.

[0025] In the aqueous ballpoint ink of the present invention, the surfactant preferably contains a phosphate ester surfactant. In the aqueous ballpoint ink of the present invention, the surfactants can be used alone or in combination of two or more.

[0026] The phosphate ester surfactant is not particularly limited as long as it is suitable for use in aqueous ballpoint pen inks. 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.

[0027] 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.

[0028] Such phosphate ester surfactants may be commercially available, for example, at least one selected from the group consisting of 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 Plysurf series (A219B, etc.) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and salts thereof.

[0029] The content of the surfactant in the aqueous ballpoint pen ink is 3% by mass or more and 10% by mass or less, preferably 4% by mass or more, more preferably 5% by mass or more, and preferably 9% by mass or less, more preferably 8% by mass or less, relative to 100% by mass of the silica-coated pigment. If the content of the surfactant is less than 3% by mass or more than 10% by mass relative to 100% by mass of the silica-coated pigment, the stability over time of the aqueous ballpoint pen ink may decrease.

[0030] [water] The water-based ballpoint ink of the present invention contains water that functions as a dispersion medium and / or solvent to disperse and / or dissolve the constituent components.

[0031] 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.

[0032] The content of water in the aqueous ballpoint pen ink is not particularly limited. It can be adjusted appropriately depending on the content, viscosity, etc. of each component in the aqueous ballpoint pen ink. When the total amount of the aqueous ballpoint pen ink 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 water-based ballpoint pen ink to be 100% by mass, problems such as insufficient color development (light color) may occur, while if it is less than 15% by mass, problems such as smearing during writing and reduced shelf life may occur.

[0033] [Dispersing and fixing agent] The water-based ballpoint ink of the present invention may contain a dispersing and fixing agent. In the aqueous ballpoint pen ink of the present invention, the dispersing / fixing agent preferably has the effect of stabilizing the dispersion of the pigment and other components contained in the aqueous ballpoint pen ink, and by stabilizing the pigment and other components after dispersion, preventing the pigment and other components from settling, and at the same time also functions as a vehicle and fixing agent for forming an ink coating.

[0034] The dispersing and fixing agent is not particularly limited as long as it is one that can be used in water-based ballpoint pen inks, and can be, for example, one or more selected from the group consisting of styrene-(meth)acrylic acid resins, styrene-(meth)acrylic acid ester resins, styrene-maleic acid resins, styrene-maleic acid ester resins, (meth)acrylic resins, (meth)acrylic acid ester resins, vinyl acetate resins, vinyl chloride resins, polyurethane resins, cellulose resins, etc.

[0035] In the aqueous ballpoint pen ink of the present invention, the dispersing and fixing agent preferably contains 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, and cellulose resins.

[0036] The content of the dispersant / fixing agent in the aqueous ballpoint pen ink is not particularly limited and can be, for example, in the range of 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less, where the total amount of the aqueous ballpoint pen ink is taken as 100% by mass. If the content of dispersant / fixing agent exceeds 10% by mass, taking the total amount of water-based ballpoint pen ink as 100% by mass, the dispersant / fixing agent may act as a flocculating agent, causing aggregation of ingredients such as pigments.

[0037] [Water-soluble organic solvent] The water-based ballpoint ink of the present invention may contain a water-soluble organic solvent. In the aqueous ballpoint pen ink 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.

[0038] 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.

[0039] 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, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2,4-butanetriol, isopentanediol, and 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-hexa 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-hexanediol polyhydric alcohols such as decanediol, 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.

[0040] In the aqueous ballpoint pen ink of the present invention, preferably, one or more solvents 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 mono-n-propyl ether are used.

[0041] The content of the water-soluble organic solvent in the aqueous ballpoint pen ink is not particularly limited and can be, for example, in the range of 10% by mass or less, preferably 8% by mass or less, and more preferably 6% by mass or less, where the total amount of the aqueous ballpoint pen ink is taken as 100% by mass.

[0042] [pH adjuster] The water-based ballpoint ink of the present invention may contain a pH adjuster. The pH adjuster is not particularly limited as long as it is one that is used in aqueous ballpoint pen inks. Examples thereof include one or more selected from the group consisting of alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; amines such as triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine, and triethylamine; ammonia (water); inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; and organic acids such as formic acid, acetic acid, propionic acid, benzenesulfonic acid, and toluenesulfonic acid.

[0043] The content of the pH adjuster in the aqueous ballpoint pen ink is not particularly limited and can be, for example, 0% by mass or more, preferably 0.01% by mass or more, and 2% by mass or less, preferably 1.5% by mass or less, based on the total mass of the aqueous ballpoint pen ink being 100% by mass.

[0044] [Coloring agent] The aqueous ballpoint pen ink of the present invention may contain a colorant other than the "silica-coated pigment" to provide beautiful handwriting with a desired color tone, provided that the effects of the present invention are not impaired. Such a colorant can be used without any particular restrictions, as long as it provides good writing properties without causing smearing or the like, and is excellent in drying properties, sedimentation stability, storage stability, etc.

[0045] The colorant is not particularly limited as long as it is one that can be used to color water-based ballpoint pen inks, and 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.

[0046] 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 that exhibit any desired color tone. Examples of resin materials that can be 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.

[0047] When the aqueous ballpoint pen ink of the present invention contains a colorant, it can be appropriately adjusted to achieve the desired color tone. When a colorant is contained, the content can be, for example, 0.01% by mass or more, preferably 0.07% 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. It can also be, for example, 20.0% by mass or less, preferably 10.0% by mass or less, and more preferably 6.0% 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. The colorant content is not limited to these ranges and can be appropriately selected depending on the type of colorant used.

[0048] [Preservative and fungicide] The water-based ink 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 is used in aqueous ballpoint pen inks, and examples thereof include one or more selected from the group consisting of isothiazolinone-based, pentachlorophenol-based, cresol-based, propylene glycol-based, and organic iodine-based antiseptic and antifungal 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 butylcarbamate, 1,2-benzisothiazolin-3(2H)-one, 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.

[0049] The content of the antiseptic and antifungal agent in the aqueous ballpoint pen ink is not particularly limited and can be, for example, 0% by mass or more, preferably 0.01% by mass or more, and 2.00% by mass or less, preferably 1.00% by mass or less, where the total amount of the aqueous ballpoint pen ink is taken as 100% by mass.

[0050] [Rust inhibitor] The water-based ink for a ballpoint pen of the present invention may contain a rust inhibitor to inhibit corrosion of metal components in the water-based ink for a ballpoint pen and / or metal materials in the refill. The rust inhibitor is not particularly limited as long as it is one that is used in water-based ballpoint pen inks, and examples thereof include one or more selected from the group consisting of benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponin, diisopropylammonium nitrite, sodium thiosulfate, ethylenediaminetetraacetate, octyl phosphate, imidazole, benzimidazole, dialkylthiourea, and derivatives thereof.

[0051] The content of the rust inhibitor in the aqueous ballpoint pen ink is not particularly limited and can be, for example, 0% by mass or more, preferably 0.01% by mass or more, and 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.2% by mass or less, based on 100% by mass of the total amount of the aqueous ballpoint pen ink.

[0052] [Viscosity adjuster] The aqueous ballpoint pen ink 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 inks. Examples of the viscosity modifier 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-based polymers, crosslinkable acrylic acid polymers, alkali-thickening acrylic resins, urethane association-type thickeners, N-vinylacetamide resins, and inorganic fine particles. The content of the viscosity modifier in the aqueous ballpoint pen ink is not particularly limited and can be, for example, 0% by mass or more, preferably 0.1% by mass or more, and can be, for example, 10% by mass or less, preferably 8% by mass or less, where the total amount of the aqueous ballpoint pen ink is taken as 100% by mass.

[0053] [Other additives] The aqueous ballpoint pen ink of the present invention may contain, as necessary, components other than the silica-coated pigment, alkali silicate, surfactant, water, dispersant / fixer, water-soluble organic solvent, pH adjuster, colorant, antiseptic / fungal agent, and viscosity adjuster (hereinafter, sometimes referred to as "other additives"). The other additives are not particularly limited as long as they are used in aqueous ballpoint pen inks. Examples include one or more additives selected from the group consisting of ureas, antifoaming agents, leveling agents, anti-aggregating agents, ultraviolet absorbers, infrared absorbers, antioxidants, etc. These can be used in appropriate amounts to impart desired properties, etc.

[0054] [viscosity] The viscosity of the aqueous ballpoint pen ink 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 blotting, 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 water-based ballpoint pen ink is less than 1 mPa·s, problems may arise with ink flow from the tip of the writing instrument (the water-based ballpoint pen ink will flow out too much when writing, making it difficult to form accurate handwriting) and sedimentation stability, while if it exceeds 50,000 mPa·s, the viscosity will be too high and problems may arise with ink flow from the tip of the writing instrument (the ink will not flow out), ink handling, sedimentation stability, smearing of handwriting, and manufacturing costs. The viscosity of the water-based ballpoint pen ink of the present invention can be determined, for example, by measuring at 20°C using an E-type rotational viscometer (for example, a TVE-type viscometer manufactured by Toki Sangyo Co., Ltd., 3°R14 cone, 0.5 rpm).

[0055] [pH value] The pH value of the aqueous ballpoint pen ink of the present invention is not particularly limited. It can be set appropriately from the viewpoints of stability, color development, writing properties, prevention of component separation, etc. For example, the pH value can be 6.0 or higher, preferably 6.5 or higher, more preferably 7.0 or higher, and even more preferably more than 7.0, and can be, for example, 10.0 or lower, preferably 9.0 or lower. Regarding the pH value of water-based ballpoint pen ink, if the pH value approaches the acidic side, i.e., below 6.0, problems such as a decrease in the ink's stability over time and corrosion of metal parts that come into contact with the ink may occur. On the other hand, if the pH value approaches the strongly alkaline side, i.e., above 10.0, problems such as fading or discoloration of handwriting may occur. The pH value of the water-based ballpoint pen ink of the present invention can be determined, for example, by measurement at 20°C using a commercially available pH meter.

[0056] [Manufacturing method] The method for producing the water-based ballpoint pen ink of the present invention is not particularly limited, and any of the conventionally known methods for producing water-based ballpoint pen ink can be used. For example, all of the components can be placed in a container and mixed and stirred using a stirring device such as a ball mill, bead mill, roll mill, Henschel mixer, planetary mixer, homomixer, turbo mixer, propeller mixer, homogenizer, high-pressure homogenizer, kneader, or dissolver to disperse the components and produce a water-based ballpoint pen ink. For example, some of the components, such as water, carbon black, and alumina, are placed in a container and mixed and stirred using the device to disperse them to produce a dispersion, and then the remaining components are added and mixed and stirred to disperse each component, thereby producing an ink. When preparing the water-based ballpoint pen ink, procedures such as filtration, centrifugation, and degassing can be performed to remove coarse particles, gas, and bubbles. When preparing the water-based ballpoint pen ink, methods such as heating, cooling, pressurization, decompression, and inert gas substitution can be performed alone or in combination. Furthermore, an aging process may be performed after preparation of the water-based ballpoint pen ink.

[0057] [Application] The ink for a water-based ballpoint pen of the present invention is used in a water-based ballpoint pen equipped with a tip ball. Specifically, the ink for a water-based ballpoint pen of the present invention is filled into an ink reservoir formed by attaching a socket rotatably holding the tip ball to the tip end directly or via a connecting member, to form a water-based ballpoint pen refill, and the refill is disposed in the barrel of the water-based ballpoint pen to form the water-based ballpoint pen. When writing, the water-based ballpoint pen ink 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.

[0058] 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.

[0059] <Chipboard> The arithmetic mean roughness Ra of the surface of the ballpoint pen is determined according to JIS B 0601. In the present invention, it can be, for example, 5 nm or more, preferably 5.3 nm or more, more preferably 6 nm or more, and can be, for example, 25 nm or less, preferably 20 nm or less. If the arithmetic mean roughness Ra of the ballpoint pen surface is less than 5 nm, there is a risk of smearing or skipping in handwriting. When using the aqueous ballpoint pen ink of the present invention, it is preferable to set the upper limit of the arithmetic mean roughness Ra of the ballpoint pen surface to 25 nm, as this prevents smearing or skipping in handwriting and provides a smooth writing feel. If the arithmetic mean roughness Ra of the ballpoint pen surface exceeds 25 nm, the writing performance on a writing surface contaminated with hand oils is improved, but the frictional resistance between the ballpoint pen and the socket increases, which may result in poor writing feel.

[0060] The material of the chip balls is not particularly limited. Examples include metals, cemented carbide, and ceramics, and preferably one or more selected from the group consisting of stainless steel, tungsten, tungsten carbide (WC), silicon carbide (SiC), titanium nitride (TiN), zirconia (ZrO2), and alumina (Al2O3). In the present invention, tungsten carbide-based chip balls or silicon carbide-based chip balls are preferred, and silicon carbide-based chip balls are more preferred.

[0061] 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. The diameter of the chip ball is not particularly limited and can be, for example, 0.05 mm or more, preferably 0.1 mm or more, and can be, for example, 3.0 mm or less, preferably 1.5 mm or less, more preferably 1.0 mm or less.

[0062] <socket> The material constituting the socket that holds the ballpoint pen is not particularly limited as long as it is wear-resistant and processable. Examples include metals (stainless steel, copper alloys such as brass and nickel silver, etc.) and resins (polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, nylon, polyphenylene ether, polyacrylate, etc.). Stainless steel is preferred from the standpoint of wear resistance during writing and corrosion resistance of ink, and austenitic stainless steel SUS304 and ferritic stainless steel SUS430 are generally used. From the standpoints of processability and suppression of deformation at the tip of the ballpoint pen, a Vickers hardness (HV) of 150 to 300 is preferred. Furthermore, lead-free materials are preferred from the standpoint of environmental impact. From the standpoint of processability, etc., bismuth (element symbol: Bi) is preferably used as a lead substitute.

[0063] <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.

[0064] <Amount of ink flow> The amount of ink flowing out of the water-based ballpoint pen refill 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.

[0065] <Water-based ballpoint pen refill> A water-based ballpoint pen refill contains water-based ballpoint ink 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 water-based ballpoint pen ink 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 substances selected from the group consisting of thickening aids (clay thickeners, metal soaps, etc.), ink follower followability improvers (surfactants, etc.), antioxidants, etc., as needed.

[0066] 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. [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] The following components were used for the water-based ballpoint pen ink: Silica-coated pigment: Silica-coated scaly aluminum paste (50% volume average particle size 7 μm, solid content 55% by mass, contains 45% by mass of propylene glycol monomethyl ether) Alkaline silicate: Sodium silicate-containing pigment anti-degradant Surfactant 1: Polyoxyethylene lauryl ether phosphate Surfactant 2: Polyoxyethylene alkyl (12-15) ether phosphate Dispersant / fixing agent 1: styrene acrylic resin (acid value 110 mg / g KOH, Tg 52°C) Dispersant / fixing agent 2: styrene acrylic resin (acid value 160 mg / g KOH, Tg 75°C) Dispersing and fixing agent 3: Carboxymethylcellulose sodium salt Water-soluble organic solvent 1: Butyl cellosolve Water-soluble organic solvent 2: Glycerin Water-soluble organic solvent 3: Ethylene glycol Water-soluble organic solvent 4: Propylene glycol pH adjuster 1: Triethanolamine pH adjuster 2: Sodium hydroxide Colorant 1: PIGMENT RED 268 Colorant 2: PIGMENT RED 122 Colorant 3: Carbon black Antiseptic and antifungal agent 1: 1,2-benzisothiazolin-3-one Antiseptic and antifungal agent 2: 3-iodo-2-propynyl-N-butylcarbamate Rust inhibitor: Benzotriazole-based rust inhibitor Viscosity adjuster: Welan gum

[0069] [Examples 1 to 5, Comparative Examples 1 to 3] <Preparation of water-based ballpoint pen ink> The components shown in Table 1 were placed in a container in the amounts (parts by mass) shown in Table 1, stirred and mixed using a stirrer, filtered through a mesh, and degassed to prepare each water-based ballpoint pen ink.

[0070] <Evaluation> (Evaluation of gloss reduction suppression) The resulting water-based ballpoint ink was applied to PHO Kent paper using a bar coater to a wet film thickness of 6.86 μm. After drying, the gloss of the dried coating film (gloss before storage) was measured using a Gloss Checker IG-310 manufactured by Horiba, Ltd. The resulting water-based ballpoint ink was left to stand in a thermostatic chamber at 50°C for one month, and then coated onto PHO Kent paper using a bar coater to a wet film thickness of 6.86µm. After drying, the gloss of the dried coating film (gloss after storage) was measured using a Gloss Checker IG-310 manufactured by Horiba, Ltd. The glossiness before and after storage was compared to confirm the change in glossiness before and after storage, and the glossiness reduction suppression was evaluated according to the following criteria: In the present invention, A is acceptable. A: There is no change in gloss value. C: The gloss value is reduced.

[0071] (Anti-agglomeration evaluation) 500 g of the resulting water-based ballpoint pen ink was allowed to stand for 3 months at room temperature (25°C ± 5°C). After storage, the water-based ballpoint pen ink was filtered through a 200 mesh filter, and aggregates on the mesh were visually observed. The aggregation prevention evaluation was performed according to the following criteria. In the present invention, A is acceptable. A: No agglomerates are observed on the mesh. C: Aggregates are observed on the mesh.

[0072] (Storage stability evaluation) The viscosity (viscosity before storage) of the obtained water-based ballpoint pen ink was measured using an E-type viscometer (rotation speed 0.5 rpm, R14 cone rotor 3°, measurement temperature 20°C) manufactured by Toki Sangyo Co., Ltd. In addition, the pH (pH before storage) at 20°C was measured using a pH meter manufactured by Horiba, Ltd. Separately, the obtained water-based ballpoint pen ink was left to stand in a thermostatic bath at 50°C for one month, and then the viscosity (viscosity after storage) was measured using an E-type viscometer manufactured by Toki Sangyo Co., Ltd. (rotation speed: 0.5 rpm, R14 cone rotor 3°, measurement temperature: 20°C). In addition, the pH at 20°C (pH after storage) was measured using a pH meter manufactured by Horiba, Ltd. The viscosity values before and after storage were compared, and the pH values before and after storage were compared, and the storage stability was evaluated according to the following criteria. In the present invention, A is acceptable. A: The viscosity after storage is within ±0.5 Pa·s of the viscosity before storage, or the pH after storage is within ±3 of the pH before storage. C: The viscosity after storage is outside the range of ±0.5 Pa·s of the viscosity before storage, or the pH after storage is outside the range of ±3 of the pH before storage.

[0073] [Table 1]

[0074] The results of Examples 1 to 5 show that water-based ballpoint pen inks containing a silica-coated pigment, an alkali silicate, and a surfactant, in which the surfactant content is 3% by mass to 10% by mass relative to 100% by mass of the silica-coated pigment, are excellent in suppressing gloss reduction, preventing aggregation, and storage stability. The results of Comparative Example 1 show that an aqueous ballpoint pen ink containing a silica-coated pigment, an alkali silicate, and a surfactant, but in which the surfactant content is less than 3% by mass relative to 100% by mass of the silica-coated pigment, has problems in terms of suppressing gloss reduction and preventing aggregation. The results of Comparative Example 2 show that an aqueous ballpoint pen ink containing a silica-coated pigment, an alkali silicate, and a surfactant, but in which the surfactant content exceeds 10% by mass relative to 100% by mass of the silica-coated pigment, has problems with storage stability. The results of Comparative Example 3 show that water-based ballpoint pen inks that do not contain alkali silicate have problems in terms of storage stability.

Claims

[Claim 1] silica-coated pigments, Alkali silicates, and surfactants, Contains The content of the surfactant is 3% by mass to 10% by mass relative to 100% by mass of the silica-coated pigment. Water-based ballpoint pen ink.

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