Oil-based ink composition for ballpoint pens

Abstract

The present invention provides a novel ink composition for a ballpoint pen, which provides good writing properties after long-term storage.SOLUTION: The oil-based ink composition for a ballpoint pen of the present invention contains triazoles represented by C2H3N3's molecular formulae.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] An oil-based ink composition for a ballpoint pen is generally composed of a coloring material (colorant), an organic solvent, a resin, etc. Various proposals have been made for such an oil-based ink composition for a ballpoint pen.

[0003] Patent Document 1 discloses an oil-based ink composition characterized by containing a colorant consisting of a dye, a pigment, or a mixture of a dye and a pigment, an organic solvent, and one or more non-color-forming salt-forming compounds represented by a specific general formula.

[0004] It has also been noted that reactions, particularly corrosion reactions, between the constituent materials of the ballpoint pen tip, particularly the metals that make up the ball, holder, and spring that biases the ball and the components of the ink result in reduced writing performance, and various proposals have been made to suppress this.

[0005] Patent Document 2 discloses an ink composition for oil-based ballpoint pens, which contains 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, an organic solvent, a colorant, a resin, and a straight-chain fatty acid.

[0006] Patent Document 3 discloses an oil-based ink composition for ballpoint pens, which contains at least an organic solvent, a colorant, and a compound represented by a specific general formula.

[0007] Patent Document 4 discloses an oil-based ink composition for a writing instrument, which is characterized by comprising at least a colorant, an organic solvent, and kojic acid.

[0008] Patent Document 5 discloses an ink composition for oil-based ballpoint pens, which is characterized by containing a colorant, a resin, an organic solvent, and a specific aminotriazole derivative. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-285479 [Patent Document 2] Japanese Patent Application Publication No. 8-48928 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-10865 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-113545 [Patent Document 5] Japanese Patent Application Publication No. 6-271804 Summary of the Invention [Problem to be solved by the invention]

[0010] Although the above proposals have been able to somewhat suppress the reaction between the metal and the ink components, they are still not sufficient to maintain good writing properties.

[0011] The present invention provides a novel ink composition for ballpoint pens that provides good writing properties even after long-term storage. [Means for solving the problem]

[0012] The present inventors have conducted extensive research and found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows: <Aspect 1> An oil-based ink composition for a ballpoint pen, comprising a triazole represented by the molecular formula C2H3N3. Aspect 2: The oil-based ink composition for ballpoint pens according to Aspect 1, wherein the content of the triazole is 0.01 to 5.50% by mass relative to the mass of the oil-based ink composition for ballpoint pens. Aspect 3: The oil-based ink composition for ballpoint pens according to Aspect 1 or 2, wherein the triazole is a 1,2,4-triazole having the following structure: [ka] <Aspect 4> Temperature 25°C, shear rate 300 s -1 The viscosity measured under the conditions is in the range of 500 to 2000 mPa·s, and the temperature is 25°C, the shear rate is 1000 s -1 4. The oil-based ink composition for ballpoint pens according to any one of Aspects 1 to 3, wherein the viscosity measured under the above conditions is in the range of 500 to 2000 mPa·s. Aspect 5: The oil-based ink composition for ballpoint pens according to any one of Aspects 1 to 4, wherein the content of the organic solvent represented by the following formula (1) is 50% by mass or more relative to the mass of the oil-based ink composition for ballpoint pens: [ka] Aspect 6: The oil-based ink composition for ballpoint pens according to Aspect 5, wherein the organic solvent is at least one selected from the group consisting of 1,3-butanediol, 3-methyl-1,3-butanediol, 3-methoxy-1-butanol, and 3-methyl-3-methoxy-1-butanol. Aspect 7: The oil-based ink composition for ballpoint pens according to any one of Aspects 1 to 6, which contains a pigment and a dye as coloring materials. <Embodiment 8> An oil-based ballpoint pen having the oil-based ink composition for ballpoint pens according to any one of Embodiments 1 to 7. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a novel oil-based ink composition for ballpoint pens that provides good writing properties even after long-term storage. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Oil-based ink composition for ballpoint pens> The oil-based ink composition for ballpoint pens of the present invention contains a triazole represented by the molecular formula C2H3N3.

[0015] In this specification, the term "oil-based ink composition" refers to an ink composition for a ballpoint pen in which the content of water as a liquid component is less than 3% by mass, less than 2% by mass, less than 1% by mass, or particularly about 0% by mass. In particular, the oil-based ink composition for a ballpoint pen of the present invention may contain at least a colorant, an organic solvent, and a resin.

[0016] The present inventors have found that the above-described composition provides good writing properties even after long-term storage. Without wishing to be bound by theory, this is believed to be due to the fact that the triazole is poorly soluble in organic solvents, and therefore preferentially adheres to the surface of a metal component, such as a ballpoint pen, thereby protecting the surface of the metal component from metal elution. Furthermore, the triazole has a smaller molecular weight than the conventionally used benzotriazole and aminotriazole, which is believed to promote the protection of the surface.

[0017] Temperature: 25°C and shear rate: 300 s -1 The viscosity of the oil-based ink composition for ballpoint pens of the present invention measured under the above conditions can be in the range of 500 to 2000 mPa·s. This viscosity may be 500 mPa·s or more, 600 mPa·s or more, 700 mPa·s or more, 800 mPa·s or more, 900 mPa·s or more, 950 mPa·s or more, or 980 mPa·s or more, and may be 2000 mPa·s or less, 1800 mPa·s or less, 1500 mPa·s or less, 1400 mPa·s or less, 1300 mPa·s or less, 1200 mPa·s or less, 1100 mPa·s or less, 1050 mPa·s or less, or 1000 mPa·s or less.

[0018] Temperature: 25°C and shear rate: 1000 s -1The viscosity of the oil-based ink composition for ballpoint pens of the present invention measured under the above conditions can be in the range of 500 to 2000 mPa·s. This viscosity may be 500 mPa·s or more, 600 mPa·s or more, 700 mPa·s or more, 800 mPa·s or more, or 850 mPa·s or more, and may be 2000 mPa·s or less, 1800 mPa·s or less, 1500 mPa·s or less, 1200 mPa·s or less, 1100 mPa·s or less, 1000 mPa·s or less, 950 mPa·s or less, 900 mPa·s or less, or 880 mPa·s or less.

[0019] The viscosity can be measured using a known viscosity measuring device, such as TVE-20H (Toki Sangyo), with a regular cone equivalent to the R range.

[0020] The oil-based ink composition for ballpoint pens of the present invention may contain other optional ingredients.

[0021] Each component of the present invention will be described below.

[0022] <Triazole> Triazole is a triazole represented by the molecular formula C2H3N3. As this triazole, 1,2,4-triazole and / or 1,2,3-triazole can be used.

[0023] As the triazole, it is particularly preferable to use 1,2,4-triazole having the following structure from the viewpoint of suppressing elution of metals. [ka]

[0024] The triazole content may be 0.001 to 7.00% by mass, relative to the mass of the ballpoint pen oil-based ink composition, and may be 0.001% by mass or more, 0.003% by mass or more, 0.005% by mass or more, 0.007% by mass or more, 0.010% by mass or more, 0.030% by mass or more, or 0.040% by mass or more, or 7.00% by mass or less, 6.50% by mass or less, 6.00% by mass or less, 5.50% by mass or less, 5.20% by mass or less, 5.00% by mass or less, 4.50% by mass or less, 4.00% by mass or less, 3.50% by mass or less, 3.00% by mass or less, 2.50% by mass or less, 2.00% by mass or less, 1.50% by mass or less, 1.00% by mass or less, or 0.70% by mass or less. In particular, the content is preferably 0.01% by mass or more from the viewpoint of suppressing metal elution, and is preferably 5.50% by mass or less from the viewpoint of obtaining good writing properties.

[0025] <Colorant> As the coloring material, various coloring materials that can be used in conventional inks can be used, such as pigments, dyes, or mixtures of pigments and dyes. These coloring materials can be used alone or in combination.

[0026] The colorant content can be increased or decreased as appropriate depending on the line density of the ink, and may be from 0.1% to 40% by mass, relative to the mass of the oil-based ink composition for ballpoint pens. This content may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 7.0% by mass or more, 10.0% by mass or more, 12.0% by mass or more, 13.0% by mass or more, or 14.0% by mass or more, and may be 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0027] (pigment) As the pigment, any of conventionally known inorganic and organic pigments such as titanium oxide, resin particle pigments containing pigments or dyes, pseudo-pigments in which resin emulsions are colored with dyes or pigments, white plastic pigments, thermochromic pigments, photochromic particles, etc. can be used without limitation.

[0028] Examples of inorganic pigments that can be used include carbon black, titanium black, zinc white, red iron oxide, aluminum, chromium oxide, iron black, cobalt blue, iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, yellow lead, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, baryte powder, calcium carbonate, white lead, dark blue, iron blue, manganese violet, aluminum powder, and brass powder.

[0029] Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, nitroso pigments, etc. Examples of such organic pigments include CI Pigment Blue 17, CI Pigment Blue 15, CI Pigment Blue 17, CI Pigment Blue 27, CI Pigment Red 5, CI Pigment Red 22, CI Pigment Red 38, CI Pigment Red 48, CI Pigment Red 49, CI Pigment Red 53, CI Pigment Red 57, CI Pigment Red 81, CI Pigment Red 104, CI Pigment Red 146, CI Pigment Red 245, CI Pigment Yellow 1, CI Pigment Yellow 3, CI Pigment Yellow 12 ... Examples of pigments that may be used include CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 17, CI Pigment Yellow 34, CI Pigment Yellow 55, CI Pigment Yellow 74, CI Pigment Yellow 95, CI Pigment Yellow 166, CI Pigment Yellow 167, CI Pigment Orange 5, CI Pigment Orange 13, CI Pigment Orange 16, CI Pigment Violet 1, CI Pigment Violet 3, CI Pigment Violet 19, CI Pigment Violet 23, CI Pigment Violet 50, and CI Pigment Green 7.

[0030] Examples of thermochromic pigments include those produced by microencapsulating a thermochromic composition containing at least a leuco dye that functions as a color former, a color developer that is a component capable of causing the leuco dye to develop color, and a color change temperature regulator that controls the color change temperature during color development of the leuco dye and the color developer, so as to have a predetermined average particle size (e.g., 0.1 to 6 μm). This average particle size may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 0.9 μm or more, or 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0031] Examples of photochromic particles that can be used include photochromic particles composed of at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, and a resin such as a terpene phenol resin. Examples of photochromic particles include photochromic particles produced by microencapsulating a photochromic composition containing at least one photochromic substance selected from photochromic dyes (compounds), fluorescent dyes, and other photochromic substances, an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, so as to have a predetermined average particle diameter (e.g., 0.1 to 6 μm).

[0032] By suitably using the above-mentioned photochromic substance, the photochromic particles can be made to have the property of being colorless in an indoor lighting environment (indoor lighting equipment selected from incandescent lamps, fluorescent lamps, lamps, white LEDs, etc.) and becoming colored in an ultraviolet irradiation environment (irradiation with wavelengths of 200 to 400 nm, or irradiation with sunlight containing ultraviolet rays).

[0033] In the present invention (including the examples), the "average particle size" is appropriately selected depending on the size of the particles to be measured. For particles less than approximately 1 μm, it is the histogram mean particle size (D50) calculated on a volume basis in the scattering intensity distribution measured by dynamic light scattering, and for particles 1 μm or larger, it is the median diameter (D50) calculated on a volume basis by laser diffraction. The average particle size can be measured using a particle size analyzer (Microtrac HRA9320-X100 (Nikkiso Co., Ltd.)).

[0034] Examples of methods for microencapsulating the thermochromic pigment and the photochromic particles include interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid hardening coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and can be appropriately selected depending on the application.

[0035] For example, in the phase separation method from an aqueous solution, a thermochromic microcapsule pigment can be produced by a method comprising the following steps, particularly a method comprising the following steps in this order: (1) Heating and melting the leuco dye, the color developer, and the color change temperature adjuster; (2) Adding the heated and melted leuco dye, developer, and discoloration temperature regulator to an emulsifier solution, and dispersing the mixture in the form of oil droplets by heating and stirring to prepare a dispersion; (3) A resin raw material capable of forming a wall film, such as a urethane resin, an epoxy resin, or an amino resin, is gradually added to the dispersion as a capsule film agent, specifically, an amino resin solution such as a methylolmelamine aqueous solution, a urea solution, or a benzoguanamine solution, and the resin raw material is reacted to form a capsule film, thereby obtaining a thermochromic microcapsule pigment; and (4) filtering the dispersion containing the thermochromic microencapsulated pigment;

[0036] In this thermochromic pigment, the color-developing temperature and decolorizing temperature of each color can be set to an appropriate temperature by appropriately combining the types and amounts of the leuco dye, color developer, and color-change temperature regulator.

[0037] These colorants can be used alone or in combination. The average particle diameter of water-dispersible pigments, resin particle pigments, pseudopigments, white plastic pigments, multi-coated pigments, thermochromic pigments, and photochromic particles varies depending on the ball diameter, ink composition, and viscosity, but is preferably 0.02 to 6 μm. This average particle diameter may be, for example, 0.02 μm or more, 0.05 μm or more, 0.07 μm or more, 0.10 μm or more, 0.20 μm or more, 0.30 μm or more, 0.50 μm or more, 0.70 μm or more, or 0.90 μm or more, or 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0038] The pigment content may be, for example, 0.1% by mass or more and 20% by mass or less, relative to the mass of the ballpoint pen oil-based ink composition. This content may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, and may be 20.0% by mass or less, 15.0% by mass or less, 10.0% by mass or less, 7.0% by mass or less, 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less.

[0039] (dye) As the dye, any dye that dissolves or disperses in water can be used, for example, acid dyes such as Eosin, Fuxin, Water Yellow #6-C, Acid Red, Water Blue #105, Brilliant Blue FCF, and Nigrosine NB; direct dyes such as Direct Black 154, Direct Sky Blue 5B, and Violet BB; basic dyes such as Rhodamine and Methyl Violet; and organic solvent-soluble dyes (oil-soluble dyes) such as commercially available monoazos, disazos, metal complex monoazos, anthraquinones, phthalocyanines, and triarylmethanes. Also included are salt-forming oil-soluble dyes in which the functional groups of acidic and basic dyes are replaced with hydrophobic groups, specifically, Examples of yellow pigments include CI Solvent Yellow 114 and 116; examples of orange pigments include CI Solvent Orange 67; examples of red pigments include CI Solvent Red 122 and 146; examples of blue pigments include CI Solvent Blue 5, 36, 44, 63, 70, 83, 105 and 111; and examples of black pigments include CI Solvent Black 3, 7, 27 and 29. Specific examples of commercially available oil-soluble dyes include blue dye SBN Blue 701 (manufactured by Hodogaya Chemical Co., Ltd.), blue dye Oil Blue 650 (manufactured by Orient Chemical Industry Co., Ltd.), blue dye Saninyl Blue GLS (manufactured by Clariant), red dye SOC-1-0100 (manufactured by Orient Chemical Industry Co., Ltd.), Oil Black 860, Oil Pink 314, Oil Yellow 3G, Varifast Pink 2310N, Varifast Red 3312, Varifast Yellow CGHNnew, Varifast Yellow 1108, and Varifast Black 3830 (manufactured by Orient Chemical Industry Co., Ltd.).

[0040] The dye content may be 0.1% by mass or more and 40% by mass or less, relative to the mass of the ballpoint pen oil-based ink composition. This content may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 7.0% by mass or more, 10.0% by mass or more, 12.0% by mass or more, 13.0% by mass or more, or 13.5% by mass or more, and may be 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0041] <Organic solvent> Examples of the organic solvent that can be used include alcohols, polyhydric alcohols, ethers, glycol ethers, aromatics, hydrocarbons, esters, etc. These solvents may be used alone or in combination.

[0042] Examples of alcohols that can be used include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methylamyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, nonanol, n-decanol, undecanol, n-decanol, tetradecanol, heptadecanol, cyclohexanol, and 2-methylcyclohexanol.

[0043] Examples of polyhydric alcohols that can be used include ethylene glycol, diethylene glycol, 3-methyl-1,3 butanediol, triethylene glycol, dipropylene glycol, 1,3 propanediol, 1,3 butanediol, 1,5 pentanediol, hexylene glycol, and octylene glycol.

[0044] Examples of ethers that can be used include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether.

[0045] Examples of glycol ethers that can be used include ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

[0046] Examples of aromatic compounds that can be used include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkylsulfonic acid phenyl ester, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, and dipropylene glycol dibenzoate.

[0047] As the hydrocarbons, for example, straight-chain hydrocarbons such as hexane, isohexane, heptane, octane, nonane, and decane, and cyclic hydrocarbons such as cyclohexane, methylcyclohexane, and ethylcyclohexane can be used.

[0048] Examples of esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, Examples of usable surfactants include methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic acid triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0049] Among these, it is preferable to use an organic solvent represented by the following formula (1) as the organic solvent from the viewpoints of viscosity and stability of the oil-based ink composition for ballpoint pens. [ka]

[0050] In particular, from the viewpoint of the stability of the ink over time, it is preferable to use 1,3-butanediol, 3-methyl-1,3-butanediol, 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, etc. as the organic solvent. These organic solvents may be used alone or in combination.

[0051] The content of the organic solvent, particularly the organic solvent represented by formula (1), may be 50% by mass or more and 90% by mass or less, based on the mass of the ballpoint pen oil-based ink composition. This content may be 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, or 75% by mass or more, and may be 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0052] <resin> The resin is contained in the oil-based ink composition for ballpoint pens of the present invention.

[0053] The resin may be any resin that can be used to fix the coating film, such as sulfonamide resin, maleic acid resin, terpene resin, terpene phenol resin, ester gum, xylene resin, alkyd resin, phenol resin, rosin, polyvinyl acetal such as polyvinyl pyrrolidone and polyvinyl butyral, polyvinyl alcohol, acrylic resin, melamine resin, nitrocellulose resin, urea resin, and derivatives thereof. These resins may be used alone or in combination.

[0054] The resins may be used alone or in combination. In particular, from the viewpoint of adhesion, it is preferable to use one or more types of the above-mentioned water-soluble resins and resin emulsions, i.e., a total of two or more types of fixing resins.

[0055] The resin content may be 1% by mass or more and 30% by mass or less, relative to the mass of the ballpoint pen oil-based ink composition. This content may be 1% by mass or more, 3% by mass or more, 5% by mass or more, 6% by mass or more, or 7% by mass or more, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, or 9% by mass or less.

[0056] <Resin: Polyvinyl butyral> Polyvinyl butyral is a (co)polymer produced by reacting polyvinyl alcohol with butyraldehyde. Specifically, this resin is a copolymer represented by the following formula: [ka]

[0057] The weight average molecular weight of the polyvinyl butyral may be 10,000 or more, 20,000 or more, 30,000 or more, 40,000 or more, 50,000 or more, 60,000 or more, 70,000 or more, 80,000 or more, 90,000 or more, 100,000 or more, or 105,000 or more, and may be 150,000 or less, 140,000 or less, 130,000 or less, 120,000 or less, or 115,000 or less.

[0058] Here, the mass average molecular weight is a value converted into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0059] The hydroxyl group content of polyvinyl butyral may be 20 mol% or more and 37 mol% or less. This content may be 37 mol% or less, or 35 mol% or less, or may be 20 mol% or more, 22 mol% or more, 25 mol% or more, 28 mol% or more, 30 mol% or more, or 32 mol% or more.

[0060] The hydroxyl group content is a molar fraction calculated by dividing the amount of ethylene groups having hydroxyl groups bonded thereto by the total amount of ethylene groups in the main chain, expressed as a percentage (mol%). It is also a molar fraction calculated by dividing the amount of ethylene groups having acetal groups bonded thereto by the total amount of ethylene groups in the main chain, expressed as a percentage (mol%).

[0061] The amount of ethylene groups to which the hydroxyl groups are bonded can be determined, for example, by measuring the amount of ethylene groups to which the hydroxyl groups are bonded in the polyvinyl acetal resin by a method in accordance with JIS K6728 "Testing methods for polyvinyl butyral."

[0062] <Other ingredients> Examples of other components include dispersants, leveling agents, preservatives, lubricants, pH adjusters, and surface conditioners. Examples of leveling agents that can be used include fluorine-based surfactants and silicone oils. Examples of lubricants that can be used include phosphate esters. Examples of pH adjusters that can be used include amines such as triethanolamine. Examples of surface conditioners that can be used include silicon-based surface conditioners.

[0063] Other components include triazole compounds other than the above-mentioned triazoles, such as benzotriazole and aminotriazole.

[0064] Oil-based ballpoint pen The ballpoint pen of the present invention comprises at least an ink reservoir, a writing part having a ball, and a holding part, The oil-based ink composition for ballpoint pens is stored in the ink storage section. It's a ballpoint pen.

[0065] The ink reservoir and writing portion may be integrated, i.e., the ballpoint pen of the present invention may have a refill having an ink reservoir and a writing portion.

[0066] The ballpoint pen of the present invention may be a knock-type ballpoint pen. A knock-type ballpoint pen is generally a ballpoint pen having a knock mechanism that allows the writing part to be extended outside the writing instrument and retracted inside the writing instrument. The location of the knock mechanism is not particularly limited, and may be at the rear end of the writing part, i.e., the end opposite the writing part, or may be located on the side of the holding part.

[0067] <Ink storage section> The ink reservoir stores the above-mentioned oil-based ink composition for ballpoint pens.

[0068] Any ink reservoir can be used as long as it is capable of storing ink and supplying ink to the writing part. The oil-based ink composition for ballpoint pens of the present invention is particularly useful in that it can prevent ink from dripping from the pen tip even when a hollow ink reservoir is used.

[0069] <Writing Department> The writing part can be a writing part having a ballpoint pen tip at its tip.

[0070] A ballpoint pen tip may be composed of a ball and a holder that rotatably holds the ball. The ball may be composed of any material used for ballpoint pen balls, such as stainless steel, cemented carbide, ceramics, etc. The shape of the ballpoint pen tip is not particularly limited, and may be, for example, bullet-shaped or needle-shaped.

[0071] In particular, when the ball is made of a cemented carbide containing cobalt (Co), the oil-based ink composition for ballpoint pens of the present invention can suppress the amount of Co elution to 10 ppm or less after storing the ballpoint pen in an ink reservoir with the pen tip facing sideways at a temperature of 55°C and a humidity of 90%, as measured by CP-MS (inductively coupled plasma mass spectrometry). This elution amount can be 10 ppm or less, 8 ppm or less, 7 ppm or less, 5 ppm or less, or 3 ppm or less.

[0072] Furthermore, when the holder is made of stainless steel containing iron (Fe), the oil-based ink composition for ballpoint pens of the present invention can suppress the amount of eluted Fe to 30 ppm or less after storing the ballpoint pen in the ink reservoir with the pen tip facing sideways at a temperature of 55°C and a humidity of 90%, as measured by CP-MS. This eluted amount can be 30 ppm or less, 25 ppm or less, 20 ppm or less, 15 ppm or less, 11 ppm or less, or 10 ppm or less.

[0073] The ballpoint pen tip may also have a spring for biasing the ball toward the tip. The surface of the spring may be nickel (Ni) plated. In this case, the amount of Ni elution measured by CP-MS after storing the ballpoint pen in an ink reservoir with the pen tip positioned horizontally at a temperature of 55°C and a humidity of 90% for 30 days can be suppressed to 40 ppm or less. This elution amount can be 40 ppm or less, 35 ppm or less, 30 ppm or less, 25 ppm or less, or 20 ppm or less.

[0074] Furthermore, from the viewpoint of writing feel, it is preferable that the surface roughness Ra of the ball is less than 10 nm, 8 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, or 3 nm or less. This surface roughness may be 1.0 nm or more, 1.5 nm or more, or 1.7 nm or more.

[0075] The "surface roughness Ra" in the present invention (including the examples described later) was measured using a non-contact surface profiler (NewView7200, Zygo) under the following conditions: lens magnification: 50x, evaluation length: 100 μm, Gaussian filter: 25 μm; and all other conditions were measured in accordance with JIS B0601 (geometric characteristics specifications of products - surface properties).

[0076] From the viewpoint of writing performance, the ball clearance, i.e., the distance the ball can move in the longitudinal direction of the ballpoint pen tip body, is preferably 30 μm or more, 40 μm or more, 50 μm or more, or 60 μm or more, and 120 μm or less, 110 μm or less, 100 μm or less, or 90 μm or less. This clearance can be measured by using a measuring microscope to measure the distance between the state where the ball is in contact with the ballpoint pen tip seat and the state where the ball is in contact with the crimped portion at the tip of the ballpoint pen tip. [Example]

[0077] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0078] <<Preparation of Oil-Based Ink Composition for Ballpoint Pens>> The substances shown in Table 1 were mixed in the parts by mass shown in Table 1 to obtain 100 parts by mass of an aqueous ink composition for a ballpoint pen.

[0079] The details of the substances shown in Table 1 are as follows: Blue pigment: Copper phthalocyanine blue Blue dye: Spilon Blue C-RH, Hodogaya Chemical Industry Co., Ltd. White fluorescent dye: MPI-609, Nippon Fluorescent Co., Ltd. PVB: S-LEC B BH-3, Sekisui Chemical Co., Ltd., hydroxyl group approx. 34 mol%, molecular weight approx. 110,000

[0080] The structure of the benzotriazole used in the comparative examples is as follows: [ka]

[0081] The structures of the triazole-like structural substances used in the comparative examples are as follows: [ka]

[0082] The viscosity of the obtained oil-based ink composition for ballpoint pens was measured using a viscosity measuring instrument (TVE-20H, Toki Sangyo) with a regular cone equivalent to the R range. The viscosity was measured at a temperature of 25°C and a shear rate of 300 s -1 The conditions were a temperature of 25°C and a shear rate of 1000 s -1 The measurements were carried out under the following conditions.

[0083] "evaluation" Each of the prepared oil-based ink compositions for ballpoint pens was filled into a ballpoint pen to prepare an aqueous ballpoint pen. Specifically, a ballpoint pen (Signo UM-100, Mitsubishi Pencil Co., Ltd.) barrel was used, and the ink composition and an ink follower were loaded into a refill consisting of a hollow polypropylene ink reservoir tube with an outer diameter of 6.0 mm, an inner diameter of 3.8 mm, and a length of 113 mm, a ballpoint pen tip, and a joint connecting the reservoir tube and the tip. The ballpoint pen tip had a stainless steel holder, a Ni-plated spring, and a cemented carbide ball (ball diameter 0.38 mm, surface roughness less than 10 nm).

[0084] This ballpoint pen was stored with the pen tip facing sideways under conditions of a temperature of 55°C and a humidity of 90% for 30 days, and then the following evaluations were carried out.

[0085] <Writability after storage> The ballpoint pens thus prepared were stored at 50°C for 3 months, and then the writing properties were checked. The evaluation criteria were as follows: A: No smearing occurred at all. B: There was some smearing. C: Significant blurring occurred.

[0086] <Amount of metal elution> After storage, the oil-based ink composition for ballpoint pens was collected from the oil-based ballpoint pens and incinerated at 500°C. 5 ml of nitric acid was added to the incinerated ink composition, which was then dried at 120°C for 1 hour. The incinerated ink composition was then washed and filtered using No. 5C quantitative filter paper and purified water, and the volume was adjusted to 50 ml. The amounts of Co, Fe, and Ni eluted (ppm) were calculated using inductively coupled plasma mass spectrometry (CP-MS).

[0087] Table 1 shows the configurations and evaluation results of the examples and comparative examples. [Table 1]

[0088] From Table 1, it can be seen that the oil-based ink composition for ballpoint pens of the present invention, which contains a triazole represented by the molecular formula C2H3N3, suppresses the amount of metal elution after long-term storage and provides good writing properties.

[0089] In contrast, it can be seen that the comparative oil-based ink composition for ballpoint pens, which does not contain triazole represented by the molecular formula C2H3N3, does not sufficiently suppress the amount of metal leaching and does not have good writing properties, even though it contains benzotriazole represented by the molecular formula C6H5N3, or pyrrole (molecular formula C4H5N), pyrrolidine (molecular formula C4H9N), or imidazole (molecular formula C3H4N2), which have a structure similar to triazole.

Claims

1. C ２ H ３ N ３ An oil-based ink composition for a ballpoint pen, comprising a triazole represented by the molecular formula:

2. 2. The oil-based ink composition for ballpoint pens according to claim 1, wherein the content of said triazole is 0.01 to 5.50% by mass relative to the mass of said oil-based ink composition for ballpoint pens.

3. 3. The oil-based ink composition for ballpoint pens according to claim 1, wherein the triazole is a 1,2,4-triazole having the following structure: 【Chemistry 1】

4. Temperature 25℃, shear rate 300s －１ The viscosity measured under the conditions is in the range of 500 to 2000 mPa·s, and the temperature is 25°C, the shear rate is 1000 s －１ 3. The oil-based ink composition for ballpoint pens according to claim 1, wherein the viscosity measured under the conditions of (a) is in the range of 500 to 2000 mPa·s.

5. 3. The oil-based ink composition for ballpoint pens according to claim 1, wherein the content of the organic solvent represented by the following formula (1) is 50% by mass or more relative to the mass of the oil-based ink composition for ballpoint pens: 【Chemistry 2】

6. 6. The oil-based ink composition for ballpoint pens according to claim 5, wherein the organic solvent is at least one selected from the group consisting of 1,3-butanediol, 3-methyl-1,3-butanediol, 3-methoxy-1-butanol, and 3-methyl-3-methoxy-1-butanol.

7. 3. The oil-based ink composition for ballpoint pens according to claim 1, wherein the coloring materials are a pigment and a dye.

8. An oil-based ballpoint pen comprising the oil-based ink composition for ballpoint pens according to claim 1 or 2.

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