Oil-based ink composition for ballpoint pens, and oil-based ballpoint pens

Abstract

This invention provides an oil-based ink composition for ballpoint pens that excels in ink stability after long-term storage, suppresses skipping at the start of writing, and provides a soft and smooth writing feel, even when using dyes, and an oil-based ballpoint pen using the same. In particular, it provides a ballpoint pen that has good ink stability after long-term storage and good writing performance, even when nickel silver is used for the pen tip. [Solution] The oil-based ink composition for ballpoint pens of the present invention comprises at least a dye as the coloring agent, inorganic fine particles and / or resin, a glycol ether of the following formula (I), and a triazole represented by the molecular formula C2H3N3, and is tested at a temperature of 25°C and a shear rate of 300 s. -1 The viscosity measured under these conditions is 100-700 mPa·s. TIFF2026112064000010.tif25122 [R 1 , R 2 , R 3 [H or CH3 are independent.]

Description

[Technical Field]

[0001] This invention relates to an oil-based ink composition for ballpoint pens and an oil-based ballpoint pen. [Background technology]

[0002] A ballpoint pen typically consists of a metal tip made of brass, nickel silver, or stainless steel, and a transfer ball made of metal or ceramic that is held in the ball-receiving seat of the metal tip. In ballpoint pens with this configuration, metal leaching from the metal tip is a major cause of poor writing performance during long-term storage. In particular, when dyes are used as coloring agents and nickel silver is used for the metal tip components, metal leaching into the ink is significant, leading to problems such as the formation of precipitates and a drastic decrease in writing performance.

[0003] Conventionally, measures to prevent metal leaching from metal chips have included, for example, 1) An oil-based ink for ballpoint pens characterized by comprising a colorant, a resin, an organic solvent, and a benzotriazole derivative represented by a specific formula, and an oil-based ink for ballpoint pens in which the benzotriazole derivative comprises at least one of benzotriazole and toltriazole (see, for example, Patent Document 1). 2) An oil-based ink composition for ballpoint pens comprising a colorant, an organic solvent, and a benzotriazole derivative represented by a specific formula, and a ballpoint pen in which the tip of the ballpoint pen containing this oil-based ink composition is made of nickel silver (see, for example, Patent Document 2). 3) An oil-based ink for ballpoint pens characterized by comprising two or more cellulose derivatives with different molecular weights and one or more selected from benzotriazole and benzotriazole derivatives (see, for example, Patent Document 3). 4) A water-based ballpoint pen is known that comprises a water-based ballpoint pen ink containing carboxybenzotriazole, benzotriazole, a colorant, and water, a housing tube containing this ink, a tip holder made of at least one material selected from stainless steel, brass, and nickel silver, and a pen tip having a cemented carbide ball (see, for example, Patent Document 4).

[0004] While the oil-based ink compositions and water-based ballpoint pen inks described in the above-mentioned Patent Documents 1 to 4 have somewhat suppressed metal leaching from the metal tip, they have still not been sufficient to maintain good writing performance. In particular, in ballpoint pens that use an oil-based ink composition, employ dyes as colorants, and use nickel silver as the material constituting the metal tip, there is still metal leaching into the ink, and the resulting deposition of precipitates and other issues have led to a decline in writing performance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-64290 (Claims, Examples, etc.) [Patent Document 2] Japanese Patent Publication No. 2016-210828 (Claims, Examples, etc.) [Patent Document 3] Japanese Patent Publication No. 2024-106009 (Claims, Examples, etc.) [Patent Document 4] Japanese Patent Publication No. Hei 8-199107 (Claims, Examples, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0006] In view of the problems of the prior art described above, the present invention aims to solve these problems and to provide an oil-based ink composition for ballpoint pens, and an oil-based ballpoint pen, that exhibits good ink stability and writing performance after long-term storage, even when a dye is used as a coloring agent. [Means for solving the problem]

[0007] The inventors have conducted intensive research on the problems of the above-mentioned prior art and have found that the coloring agent consists of at least a dye, and comprises inorganic fine particles and / or a resin, a glycol ether represented by a specific formula, and a triazole represented by a specific molecular formula, and is used at a temperature of 25°C and a shear rate of 300 s. -1 By setting the viscosity measured under these conditions to a specific range, we discovered that the above-mentioned oil-based ink composition for ballpoint pens and an oil-based ballpoint pen can be obtained, thus completing the present invention.

[0008] In other words, the oil-based ink composition for ballpoint pens of the present invention comprises at least a dye as the colorant, inorganic fine particles and / or resin, a glycol ether of the following chemical structural formula (I), and a triazole represented by the molecular formula C2H3N3, and is tested at a temperature of 25°C and a shear rate of 300 s. -1 It is characterized by having a viscosity of 100 to 700 mPa·s when measured under these conditions. [ka] [In the above formula (1), R 1 , R 2 , R 3 Each of these is independently either H (hydrogen atom) or CH3 (methyl group). It is preferable that the triazole represented by the molecular formula C2H3N3 is 1,2,4-triazole. It is preferable that the aforementioned dye is a salt-forming type oil-based dye. The oil-based ballpoint pen of the present invention is characterized by being equipped with the above-described oil-based ink composition for ballpoint pens, and the pen tip component is characterized by employing at least nickel silver in the components constituting the ballpoint pen tip. [Effects of the Invention]

[0009] According to the present invention, even when a dye is used, there is provided an oil-based ink composition for ballpoint pens that is excellent in suppressing ink stability after long-term storage and writing smudging during writing, and providing a soft and smooth writing feel, and an oil-based ballpoint pen using the same. In particular, even when an ivory white is adopted for the pen tip, it is possible to provide an oil-based ballpoint pen having good ink stability after long-term storage and good writing performance. The objects and effects of the present invention are recognized and obtained by using the components and combinations particularly pointed out in the claims. Both the above general description and the following detailed description are exemplary and explanatory, and do not limit the present invention described in the claims.

Brief Description of the Drawings

[0010] [Figure 1] It is a drawing showing an example of an embodiment of an oil-based ballpoint pen equipped with the oil-based ink composition for ballpoint pens of the present invention, where (a) is a front view and (b) is a longitudinal sectional view. [Figure 2] It is a drawing showing an example of a refill housed in the oil-based ballpoint pen of FIG. 1, where (a) is a front view and (b) is a longitudinal sectional view.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, note that the technical scope of the present invention is not limited to the embodiments described in detail below, and extends to the invention described in the claims and its equivalents. Also, the present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the art (including design matters and self-evident matters).

[0012] 《Oil-based Ink Composition for Ballpoint Pens》 The oil-based ink composition for ballpoint pens of the present invention is composed of at least a colorant consisting only of dyes, and contains inorganic fine particles and / or resins, a glycol ether represented by the following chemical structural formula (I), and a triazole represented by the molecular formula C2H3N3, and has a viscosity of 100 to 700 mPa·s measured under the conditions of a temperature of 25°C and a shear rate of 300 s -1 This is characterized by being. Here, in this specification, the "oil-based ink composition" means an ink composition for ballpoint pens 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.

[0013] [Chemical formula] [In the above formula (1), R 1 , R 2 , R 3 are each independently H (hydrogen atom) or CH3 (methyl group).]

[0014] 〈Dye〉 The colorant used in the present invention is composed only of dyes from the viewpoints of color development property and the ability to reduce the cost during ink production. As the dyes that can be used, all dyes that can be dissolved or dispersed in a solvent can be used. Examples of organic solvent-soluble dyes (oil-soluble dyes) include monoazo, disazo, metal complex salt type monoazo, anthraquinone, phthalocyanine, triarylmethane, etc., which are generally commercially available. Furthermore, examples of salt-forming oil-soluble dyes in which functional groups such as acid and basic dyes are replaced with hydrophobic groups include, specifically, CI Solvent Yellow 114, 116 for the yellow series; CI Solvent Orange 67 for the orange series; CI Solvent Red 122, 146 for the red series; CI Solvent Blue 5, 36, 44, 63, 70, 83, 105, 111 for the blue series; CI Solvent Black 3, 7, 27, 29 for the black series; and Spiron Yellow C-2GH, Eisenspiron Yellow C-GNH, Eisenspiron Red C-GH, Eisenspiron Red C-BH, Eisenspiron Violet C-RH, Eisenspiron Blue C-RH, Eisen SBN Blue 701, Varifast Red 1360, Varifast Yellow 1110, etc., as salt-forming dyes of basic dyes and organic acids. Preferably, from the viewpoint of solubility over time, the use of the above-mentioned salt-forming type oil-soluble dye is desirable.

[0015] The dye content may be 0.1% by mass or more and 40% by mass or less, based on the total mass of the oil-based ink composition for ballpoint pens, from the standpoint of color development and writing performance after storage over time. 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 also 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.

[0016] <Inorganic particles> The inorganic fine particles used in this invention are included to prevent ink leakage from the pen tip and to improve writing performance. The inorganic fine particles that can be used have a primary particle size of 1 nm to 100 nm, and more preferably 5 nm to 50 nm, from the viewpoint of suppressing aggregation and sedimentation separation. Furthermore, the specific surface area of ​​the inorganic fine particles used is preferably 20 to 1000 m². 2 / g, and more preferably 20-500m 2 / g is preferable.

[0017] Specifically, suitable inorganic fine particles include silica, titanium dioxide, mica, calcium carbonate, aluminum oxide, etc., with the above-mentioned primary particle size and specific surface area. Commercially available inorganic fine particles having the above-mentioned primary particle size range and specific surface area range may also be used. Specifically, the silica products available from Nippon Aerosil Co., Ltd. are those represented by product names 50, 90G, 130, 200, 200V, 200CF, 200FAD, 300, 300CF, 380, R972, 972V, R972CF, R974, R202, R805, R812, R812S, OX50, TT600, RX200, RY200, and RY200. The silica and Al2O3 mixtures are represented by product names MOX80, MOX170, and COK84. Examples include those available from CABOT Corporation, represented by product names L90, LM-130, LM-5, M-5, M-5P, PTG, MS-55, MS-75, HS-5, EH-5, TS-530, TS-610, and TS-720, as well as those available from Mizusawa Chemical Industry Co., Ltd., represented by product names P-526, P-801, P-526N, P-801N, NP-8, P-802, P-527, P-832, P-73, P-75, P-78D, P-87, and P-363.

[0018] Titanium dioxide is available from Nippon Aerosil Co., Ltd., under the trade names T805 and P25. Aluminum oxide is also available from Nippon Aerosil Co., Ltd., under the trade name Aluminum Oxide C. Furthermore, mica and calcium carbonate can also be used without problems if they are in fine particulate form, although their effect is slightly less compared to the silica, titanium dioxide, and aluminum oxide mentioned above. Among these inorganic fine particles, the use of silica is preferable because it suppresses wear on the ball bearing seat within the tip and prevents ink leakage from the pen tip.

[0019] The content of these inorganic fine particles may be 0.01% by mass or more and 3.0% by mass or less, relative to the total mass of the oil-based ink composition for ballpoint pens, in order to prevent ink clogging of the pen tip and to prevent ink leakage from the pen tip. This content may be 0.02% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 2.5% by mass or less, 2.0% by mass or less, 1.5% by mass or less, or 1.0% by mass or less.

[0020] The resin used in this invention is included for the sake of the long-term stability of the ink and the abrasion resistance of the writing lines, and it has the same effects as the inorganic particles described above. It can be used in combination with the inorganic particles, or each can be used alone without being used in combination with the inorganic particles. The resins that can be used are those soluble in the solvents described later. Examples of such resins include ketone resins, styrene resins, styrene-acrylic resins, terpene phenol resins, rosin-modified maleic acid resins, rosin-phenol resins, alkylphenol resins, phenolic resins, styrene-maleic acid resins, rosin-based resins, acrylic resins, urea aldehyde-based resins, maleic acid-based resins, cyclohexanone-based resins, polyvinyl butyral, polyvinylpyrrolidone, and others. Among these resins, the use of ketone resins, polyvinyl butyral, styrene-acrylic resins, terpene phenol resins, and phenolic resins is preferable because they allow for relatively easy adjustment of the viscosity of the ink composition and provide good scratch resistance to the writing lines.

[0021] <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] [In the above formula, l, m, and n are positive numbers and are adjusted within the range of preferred mass-average molecular weight described later.]

[0022] The mass-average molecular weight of 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 also be 150,000 or less, 140,000 or less, 130,000 or less, 120,000 or less, or 115,000 or less. Here, the mass-average molecular weight is a standard polystyrene equivalent value based on measurements taken by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the solvent.

[0023] 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, and may also 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.

[0024] The above hydroxyl group content is the value expressed as a percentage (mol%) of the mole fraction obtained by dividing the amount of ethylene groups to which hydroxyl groups are attached by the total amount of ethylene groups in the main chain. The value expressed as a percentage (mol%) of the mole fraction obtained by dividing the amount of ethylene groups to which acetal groups are attached by the total amount of ethylene groups in the main chain.

[0025] 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 of the polyvinyl acetal resin are bonded, using a method compliant with JIS K6728 "Test Method for Polyvinyl Butyral".

[0026] Examples of commercially available ketone resins that can be used include Hi-Lac 111, Hi-Lac 110H (manufactured by Hitachi Chemical Co., Ltd.), and Ketone Resin K90 (manufactured by Arakawa Chemical Industries, Ltd.).

[0027] The content of these resins may be 0.1% by mass or more and 10% by mass or less, relative to the total mass of the oil-based ink composition for ballpoint pens, from the standpoint of adjusting the viscosity of the ink composition and the abrasion resistance of the writing lines. This content may be 0.2% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 3% by mass or more, and may also be 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, 5% by mass or less, or 4% by mass or less.

[0028] The glycol ether of the following structural formula (1) used in the present invention is used as an organic solvent, and is used in terms of the viscosity range and stability of the ballpoint pen oil ink composition, which will be described later. [ka] [In the above formula (1), R 1 , R 2 , R 3 Each of these is independently either H (hydrogen atom) or CH3 (methyl group).

[0029] As the glycol ether of the above structural formula (1), it is preferable to use at least one of the following: 1,3-butanediol, 3-methyl-1,3-butanediol, 3-methoxy-butanol, 3-methyl-3-methoxy-butanol, or hexylene glycol, from the viewpoint of the long-term stability of the ink.

[0030] The content of the glycol ether of the above structural formula (1) may be 20% by mass or more and 90% by mass or less, based on the total mass of the oil-based ink composition for ballpoint pens, from the standpoint of the long-term stability of the ink and the drying speed of the lines written on paper. This content may be 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, and may also be 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less.

[0031] Furthermore, in the present invention, in addition to the glycol ether of structural formula (1) above, an auxiliary solvent may be included. As the auxiliary solvent, for example, a solvent selected from alcohols, polyhydric alcohols, and glycol ethers other than those of structural formula (1) above can be used.

[0032] As for alcohols, aliphatic alcohols with two or more carbon atoms are preferred, and examples 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, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclohexanol, benzyl alcohol, and many other higher alcohols.

[0033] Furthermore, as polyhydric alcohols, those having two or more carbon atoms and two or more hydroxyl groups in the molecule are preferred. Examples include ethylene glycol, diethylene glycol, 3-methyl-1,3-puntanediol, triethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, and octylene glycol.

[0034] Examples of glycol ethers other than the above structural formula (1) include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl 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, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol phenyl 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.

[0035] Among the glycol ether solvents listed above, glycol ethers with 2 to 7 carbon atoms are particularly preferred. Furthermore, from the standpoint of safety and oral toxicity, it is preferable to use organic solvents other than ethylene glycol derivatives.

[0036] In addition to the solvents listed above, auxiliary solvents listed below may also be added, provided they do not impair the solubility or volatility of the mixture of phosphate ester and amine compound. Examples of such solvents include polyhydric alcohol derivatives, such as sorbitan fatty acid derivatives, polyglycerol higher fatty acid derivatives, sucrose fatty acid derivatives, and propylene glycol fatty acid derivatives.

[0037] Examples of auxiliary solvents for 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 various esters 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 citrate, octyl oxystearate, propylene glycol monolicinolate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0038] Furthermore, diethers and diesters can be used as auxiliary solvents that do not contain hydroxyl groups in their molecules. Specifically, examples include ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0039] In addition to the glycol ether of structural formula (1) above, the content of the auxiliary solvent used can be within a range that does not impair the effects of the present invention, and may be 0.1% by mass or more and 15% by mass or less, 0.5% by mass or more, 1% by mass or more, or 13% by mass or less and 10% by mass or less, based on the total mass of the oil-based ink composition for ballpoint pens.

[0040] <Triazole> The triazole used in this invention is a triazole with the molecular formula C2H3N3. This triazole can be 1,2,4-triazole and / or 1,2,3-triazole. Among the triazoles, it is preferable to use 1,2,4-triazole having the following structure, from the viewpoint of suppressing the elution of metal (nickel silver). [ka]

[0041] The triazole content may be 0.001 to 7.00% by mass relative to the mass of the oil-based ink composition for ballpoint pens. This content 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, and may also be 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, a content of 0.01% by mass or more is preferable from the viewpoint of suppressing metal leaching, and a content of 5.50% by mass or less is preferable from the viewpoint of obtaining good writing performance.

[0042] <Other ingredients> Other components that do not impair the effects of the present invention include, for example, dispersants, leveling agents, preservatives, lubricants, pH adjusters, and surface modifiers. As leveling agents, for example, fluorine-based surfactants and silicone oils can be used. As lubricants, for example, phosphate esters can be used. As pH adjusters, for example, amines such as triethanolamine can be used. As surface modifiers, silicone-based surface modifiers can be used.

[0043] Other components include triazole compounds other than the triazoles mentioned above. Examples of such triazole compounds include benzotriazole and aminotriazole.

[0044] 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 these conditions, can be in the range of 100 to 700 mPa·s, from the viewpoint of obtaining a smooth writing feel and the long-term stability of the ink composition. This viscosity may be 100 mPa·s or more, 200 mPa·s or more, 300 mPa·s or more, 400 mPa·s or more, and 700 mPa·s or less, 600 mPa·s or less, or 500 mPa·s or less. If the viscosity range is less than 100 mPa·s, the long-term stability of the ink composition will decrease, while if it exceeds 700 mPa·s, the writing performance after long-term storage will decrease, which is undesirable.

[0045] The viscosity described above can be measured using a known viscosity measuring instrument, such as the TVE-20H (Toki Sangyo), with a regular cone corresponding to the R range. Furthermore, the viscosity range described above can be adjusted by selecting the appropriate type of component, such as the dye, inorganic fine particles and / or resin, and the glycol ether of the following chemical structural formula (I), determining the suitable content of each component, and determining the stirring method.

[0046] The oil-based ink composition for ballpoint pens configured in this way comprises at least a dye as the colorant, inorganic fine particles and / or resin, a glycol ether of the above chemical structural formula (I), and a triazole represented by the molecular formula C2H3N3, and is tested at a temperature of 25°C and a shear rate of 300 s. -1 By setting the viscosity measured under these conditions to 100-700 mPa·s, even when using dyes, it becomes possible to achieve excellent ink stability after long-term storage, suppress skipping at the start of writing, and create a soft and smooth writing feel.

[0047] Oil-based ballpoint pen The oil-based ballpoint pen of the present invention is characterized by being equipped with an oil-based ink composition for ballpoint pens having the above configuration, and the pen tip component being made of at least nickel silver for the components constituting the ballpoint pen tip. As long as it has these configurations, other structures are not particularly limited. In this invention, "nickel silver" refers to an alloy composed of copper, zinc, and nickel, in which the proportions are adjusted in various ways according to the application, but in which the copper content exceeds 50%.

[0048] Examples of oil-based ballpoint pens that can be used include those equipped with an ink reservoir, a pen tip component comprising at least a writing portion and a holding portion having a ball as a component constituting the ballpoint pen tip, an oil-based ink composition for ballpoint pens having the above configuration mounted in the ink reservoir, and at least nickel silver being used for the components constituting the ballpoint pen tip (ball and / or holder). The ink storage section and the writing section may be integrated into a single unit. In other words, the ballpoint pen of the present invention may have a refill having an ink storage section and a writing section.

[0049] The oil-based ballpoint pen of the present invention may be a retractable ballpoint pen. A retractable ballpoint pen is generally a ballpoint pen having a retraction mechanism that allows the writing portion to be extended to the outside of the writing instrument and retracted into the writing instrument. The position of the retraction mechanism is not particularly limited and may be at the rear end of the writing portion, i.e., the end opposite to the writing portion, or it may be located on the side of the holder portion.

[0050] <Ink storage section> The ink storage section contains the above-mentioned oil-based ink composition for ballpoint pens. Any object can be used as the ink storage unit, as long as it can store ink and supply ink to the writing unit. In particular, the oil-based ink composition for ballpoint pens of the present invention is useful in that it can suppress ink dripping from the pen tip even when a hollow ink storage unit is used.

[0051] <Pen tip components> The pen tip component can be a writing section having a ballpoint pen tip at its end. The ballpoint pen tip may consist of a ball and a holder that rotatably holds the ball. The ball may be made of any material used for ballpoint pen balls, such as stainless steel, cemented carbide, nickel silver, or ceramics, and the ball diameter may be, for example, 0.18 to 2.0 mm. Furthermore, the shape of the ballpoint pen tip is not particularly limited and may be, for example, bullet-shaped or needle-shaped.

[0052] Furthermore, if the ballpoint pen tip has a spring to bias the ball toward the tip, the spring may be nickel (Ni) plated on its surface. In this case, the oil-based ink composition for ballpoint pens of the present invention can suppress the amount of Ni eluted, measured by CP-MS after storing the ballpoint pen in the ink storage compartment and then storing the ballpoint pen with the pen tip facing sideways for 30 days under conditions of 55°C and 90% humidity, to 40 ppm or less. This eluted amount can be 40 ppm or less, 35 ppm or less, 30 ppm or less, 25 ppm or less, or 20 ppm or less.

[0053] Furthermore, from the viewpoint of writing feel, the surface roughness Ra of the ball is preferably 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.

[0054] In this invention (including the embodiments described later), the "surface roughness Ra" was measured using a non-contact surface shape measuring instrument (NewView7200, Zygo) with a lens magnification of 50x, an evaluation length of 100 μm, and a Gaussian filter of 25 μm. All other measurements were performed in accordance with JIS B0601 (Geometrical Characteristics Specifications of Products - Surface Properties).

[0055] From the viewpoint of writing performance, the ball clearance, that is, the distance the ball can move in the longitudinal axis 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 measuring the distance between the state in which the ball is in contact with the seat of the ballpoint pen tip and the state in which the ball is in contact with the crimped part at the tip of the ballpoint pen tip using a measuring microscope.

[0056] Figures 1 and 2 are diagrams showing an example of an embodiment of an oil-based ballpoint pen equipped with the oil-based ink composition for ballpoint pens of the present invention. Figure 1(a) is a front view of the oil-based ballpoint pen, and (b) is a longitudinal cross-sectional view thereof. Figure 2 is a diagram showing an example of a refill housed in the oil-based ballpoint pen of Figure 1, where (a) is a front view and (b) is a longitudinal cross-sectional view.

[0057] As shown in Figures 1 and 2, this oil-based ballpoint pen A comprises a cap 10 that detachably covers the tip for protection, and a barrel 20 that houses a refill 30. A ballpoint pen tip 35 is provided at the tip of the refill 30. The cap 10 is made of resin and is formed in a cylindrical shape. Inside the cap 10, there is an inner cap 11 to cover the tip of the ballpoint pen tip 35. A clip 12 is also provided on the cap 10.

[0058] The shaft 20 is made of resin and consists of a shaft body 21 and an outer cylinder 22, forming a cylindrical body with a closed rear end. The cap 10 described above can be attached to and detached from the tip of this shaft 20. A roughly frustoconical tip member 25 made of resin or stainless steel is fixed to the end of the barrel 20. The tip of a ballpoint pen tip 35, which will serve as the pen nib, protrudes from this tip member 25. As shown in Figures 2(a) and 2(b), the refill 30 housed inside the barrel 20 has a metal ballpoint pen tip 35 made of nickel silver or the like fixed to the tip of a cylindrical ink storage tube 31 made of a resin such as polypropylene resin. An oil-based ink composition 40 having the above-described composition is loaded inside this ink storage tube 31, and an ink follower 41 is provided on the rear end side of the oil-based ink composition 40. The holder 36 of this ballpoint pen tip 35 does not contain a spring, and the ink reservoir tube 31 and the ballpoint pen tip 35 are directly connected. The holder 36 has a writing ball 37 made of superhard alloy that is rotatably mounted inside its tip, and a crimping part (not shown) is provided at the tip of the holder 36 to hold the writing ball 37 in place so that it does not fall out of the holder 36. The writing ball 37 may be made of the superhard alloy mentioned above, or it may contain nickel silver, and its diameter can be one of the conventionally known types, between 0.1 mm and 2.1 mm. The oil-based ballpoint pen of the present invention is equipped with the oil-based ink composition for ballpoint pens having the above configuration, and the pen tip component is made of at least nickel silver, but is not limited to the above embodiment and may also be a retractable or direct-ink type oil-based ballpoint pen.

[0059] The oil-based ballpoint pen of the present invention, configured in this way, is equipped with the above-described oil-based ink composition for ballpoint pens, and even if the pen tip component uses at least nickel silver for the components constituting the tip, it is possible to obtain an oil-based ballpoint pen that excels in ink stability after long-term storage, suppresses skipping at the start of writing, and provides a soft and smooth writing feel. [Examples]

[0060] The present invention will be specifically described by examples and comparative examples, but the present invention is not limited thereto.

[0061] Examples 1-12 and Comparative Examples 1-5: Preparation of Oil-Based Ink Compositions for Ballpoint Pens Oil-based ink compositions for writing instruments (100% by mass) were prepared by mixing according to the formulations shown in Table 1 below (each dye, each resin, each inorganic particle, each rust inhibitor, each solvent). Furthermore, the viscosity of each oil-based ink composition for writing instruments obtained was measured using the evaluation method described below, and the compositions were also mounted on writing instruments with the configuration described below. Using each of the obtained writing instruments, the ink's long-term stability and its writeability after long-term storage (inhibition of metal leaching) were evaluated using the evaluation methods described below. These results are shown in Table 1 below.

[0062] Furthermore, the triazole used as a rust inhibitor was the 1,2,3-triazole of the above formula, and the benzotriazole was the one of the formula shown below. [ka]

[0063] The viscosity of the obtained oil-based ink composition for ballpoint pens was measured using a viscometer (TVE-20H, Toki Sangyo) with a regular cone equivalent to the R range. Viscosity was measured at a temperature of 25°C and a shear rate of 300 s. -1 The measurements were taken under the following conditions.

[0064] "evaluation" The oil-based ink compositions prepared for ballpoint pens were each filled into ballpoint pens to create oil-based ballpoint pens. Specifically, the ballpoint pens used in the tests had a polyethylene tube with an inner diameter of 1.6 mm and a ball tip with a diameter of 1.0 mm (the holder part contained nickel silver, and the ball was made of cemented carbide). After filling with ink, an ink-following element was installed to prevent ink leakage.

[0065] This ballpoint pen was stored with the tip facing downwards under conditions of 55°C and 90% humidity for three months, after which the following evaluation was performed.

[0066] <Method for evaluating the long-term stability of ink> After storage, oil-based ballpoint pens were disassembled, and the oil-based ink composition contained in the tip was collected and uniformly coated onto a glass plate. This coated film was then observed under an optical microscope. The presence or absence of precipitates in the ink was visually inspected, and the long-term stability of the ink was evaluated according to the following criteria. Evaluation criteria: A: No precipitates are observed. B: Slight precipitates are visible. C: Significant precipitates are visible.

[0067] <Method for evaluating writability (inhibition of metal leaching) after storage over time> Using an oil-based ballpoint pen after storage, the words "Mitsubishi Pencil" were written, and the degree of ink bleeding and fading was visually inspected to evaluate the ink's long-term stability according to the following criteria. Evaluation criteria: A: In good condition with no blurring or smudging of the text. B: Some letters are blurred or smudged. C: The entire text is very smudged and blurred.

[0068] [Table 1]

[0069] Details of the substances shown in Table 1 above (*1 to *6) are as follows: *1: Eisenspiron Yellow C-GNH (Hodogaya Chemical Co., Ltd.) *2: Savvy Blue GLS (Heubach) *3: Eisenspiron Black GMH (Hodogaya Chemical Co., Ltd.) *4: PVB (Seslec B BH-3, Sekisui Chemical Co., Ltd., approximately 34 mol% hydroxyl groups, mass-average molecular weight 110,000) *5: K-90 (Arakawa Chemical Industries, Ltd.) *6:AEROSIL R972 (EVONIK, primary particle diameter approximately 16nm, specific surface area 110±20m) 2 / g)

[0070] As is clear from the results in Table 1 above, the ballpoint pen oil-based ink compositions for Examples 1 to 12, which fall within the scope of the present invention and contain triazole represented by the molecular formula C2H3N3, were found to be superior to the ballpoint pen oil-based ink compositions for Comparative Examples 1 to 5, which fall outside the scope of the present invention. This superiority was observed in the use of dyes, resulting in superior ink stability after long-term storage, suppression of skipping at the start of writing, and a soft and smooth writing feel. This confirmed the production of both the ballpoint pen oil-based ink compositions for ballpoint pens and the ballpoint pens using them.

Claims

1. The coloring agent consists of at least a dye, inorganic fine particles and / or resin, a glycol ether of the following chemical structural formula (I), and C ２ H ３ N ３ It contains a triazole represented by the molecular formula, and is tested at a temperature of 25°C and a shear rate of 300 s. －１ An oil-based ink composition for ballpoint pens, characterized in that its viscosity, measured under the specified conditions, is 100 to 700 mPa·s. 【Chemistry 1】 [In the above formula (1), R １ , R ２ , R ３ Each of these is independently either H (hydrogen atom) or CH ３ (It is a methyl group.)

2. The above-mentioned C ２ H ３ N ３ The ballpoint pen oil-based ink composition according to claim 1, wherein the triazole represented by the molecular formula is 1,2,4-triazole.

3. The ballpoint pen oil-based ink composition according to claim 1 or 2, characterized in that the dye is a salt-forming type oil-based dye.

4. An oil-based ballpoint pen characterized by being equipped with the oil-based ink composition for ballpoint pens described in claim 1 or 2, and the pen tip member being made of at least nickel silver in the components constituting the ballpoint pen tip.

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