Oil-based ink composition for writing implement and writing implement with the same inside

Abstract

To provide an oil-based ink composition in which a defect such as precipitation of a coloring agent and deterioration of handwriting dryness does not occur and which therefore can effectively suppress a whitening phenomenon and enables formation of clear handwriting over a long period of time, and to provide a writing implement.SOLUTION: An oil-based ink composition for a writing implement is provided, which can include an organic solvent selected from aliphatic alcohol having 5 or less carbon atoms and / or glycol ether, a coloring agent, a resin and 1,3-dioxolane represented by a specific chemical formula. A writing implement with the oil-based ink composition inside is also provided.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an oil-based ink composition for a writing instrument, and more particularly to an oil-based ink composition for a writing instrument capable of forming clear handwriting by suppressing whitening that occurs when handwriting dries, and a writing instrument incorporating the same. [Background technology]

[0002] Conventionally, oil-based inks used in marking pens and the like have used volatile (low boiling point) organic solvents such as lower alcohols as the main solvent in order to make the handwriting dry quickly. Therefore, in high humidity conditions, the temperature drops as the organic solvent evaporates, causing the moisture in the air to condense, causing the handwriting coating to become white. This is a problem of whitening, where the resin in the handwriting coating partially precipitates, making the coating surface uneven rather than uniformly smooth, causing the handwriting to reflect light diffusely and appear white. In order to solve the above problems, the addition of various compounds has been considered, and for example, techniques for adding dipropylene glycol monomethyl ether or n-butyl lactate have been disclosed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-48926 [Patent Document 2] Japanese Patent Application Publication No. 63-135468 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology in the cited document involves adding the above-mentioned dipropylene glycol monomethyl ether or n-butyl lactate to an oil-based ink to delay the drying time of the handwriting and adjust the speed of coating film formation, thereby making the above-mentioned whitening less likely to occur. However, in the case of dipropylene glycol monomethyl ether, the types of colorants that can be used are limited due to their solubility, and in the case of n-butyl lactate, the strong odor causes the handwriting to dry more quickly when added in an amount that would achieve a whitening-inhibiting effect.

[0005] The present invention provides an oil-based ink composition for a writing instrument, which can effectively suppress the above-mentioned whitening phenomenon without causing problems such as precipitation of colorant or deterioration of drying properties of handwriting, and which can form clear handwriting for a long period of time, and a writing instrument. [Means for solving the problem]

[0006] The oil-based ink composition for writing instruments of the present invention comprises an organic solvent selected from an aliphatic alcohol and / or glycol ether having 5 or less carbon atoms, a colorant, a resin, and a 1,3-dioxolane represented by the following general formula (1) or (2): [ka] [In the formula, R1 and R2 are substituents selected from a hydroxyl group, a monovalent or divalent alcohol of a linear alkyl having 4 or less carbon atoms, and an aryl group, or an aromatic ring having 5 to 6 carbon atoms including the carbon atom of the base, R3 and R4 are substituents selected from a hydroxyl group, an alkyl group having 1 to 18 carbon atoms, an aryl group, and a halogenated alkyl group, and R5 and R6 are substituents selected from a halogen, a linear alcohol having 4 or less carbon atoms, and a polyoxyethylene adduct of a linear alcohol having 4 or less carbon atoms.] Further, it is required that the boiling point of the 1,3-dioxolanes is in the range of 170° C. to 230° C., and that the 1,3-dioxolanes are used in the range of 0.1% by mass to 20% by mass of the total amount of the ink composition. Further requirements are that the ink composition contains polyether-modified silicone, that the polyether-modified silicone is one or more selected from side-chain type polyether-modified silicone, both-end type polyether-modified silicone, and ABN type polyether-modified silicone, and that the polyether-modified silicone is used in an amount of 0.01% by mass to 5% by mass of the total amount of the ink composition. A further feature is a writing instrument incorporating the oil-based ink composition for writing instruments. Effect of the Invention

[0007] According to the present invention, it is possible to effectively suppress the whitening phenomenon caused by the condensation of moisture in the air and the partial precipitation of resin without causing problems such as precipitation of colorants and deterioration of the drying property of handwriting. Therefore, it is possible to provide an oil-based ink composition for a writing instrument and a writing instrument that can form clear handwriting for a long period of time. Furthermore, by using polyether-modified silicone, in addition to the above effect, it is possible to form good handwriting with excellent adhesion without causing repellency even on writing surfaces with poor wettability while maintaining a stable ink composition. By combining these, it is possible to obtain clearer handwriting regardless of the environmental temperature or writing surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The oil-based ink composition of the present invention, when an organic solvent selected from an aliphatic alcohol having 5 or less carbon atoms or a glycol ether is used as the main solvent, can suppress the whitening phenomenon of handwriting by using 1,3-dioxolanes represented by general formula (1) or (2), and can therefore form clear and good handwriting.

[0009] It is presumed that the addition of 1,3-dioxolanes represented by the above general formula (1) or (2) to oil-based inks can suppress partial resin precipitation caused by moisture condensation in the air due to a temperature drop accompanying the evaporation of the organic solvent, without impairing the drying properties of the handwriting. In addition, when forming a handwritten coating film by writing, the resin film-forming speed can be kept uniform, making the coating surface uniformly smooth, so that the handwritten marks do not reflect light diffusely and become white, and a vivid hue can be seen.

[0010] In the 1,3-dioxolanes represented by the general formula (1), R1 and R2 in the formula are substituents selected from a hydroxyl group, a linear alkyl monohydric or dihydric alcohol having 4 or less carbon atoms, and benzene, or an aromatic ring having 5 to 6 carbon atoms including the carbon at the base (cyclopentadiene or benzene), and R3 and R4 are substituents selected from a hydroxyl group, an alkyl group having 1 to 18 carbon atoms, an aryl group, and a halogenated alkyl group. In addition, as the 1,3-dioxolanes represented by the general formula (2), R5 and R6 may be substituents selected from halogen, linear alcohols having 4 or less carbon atoms, and polyoxyethylene adducts of linear alcohols having 4 or less carbon atoms. Specific examples include 2-2-dimethyl-4-hydroxymethyl-1,3-dioxolane, 4-(2-hydroxyethyl)-2,2-dimethyl-1,3-dioxolane, 2,2-diisopropyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, 2-bromomethyl-1,3-dioxolane, 2-oxo-1,3-dioxolane, 4-fluoro-2-oxo-1,3-dioxolane, and 1,2-methylenedioxybenzene.

[0011] Among the 1,3-dioxolanes, those having a boiling point in the range of 230° C. or less are particularly excellent in handwriting drying properties, and those having a boiling point in the range of 170° C. or more are highly effective in suppressing whitening. Therefore, those having a boiling point in the range of 170° C. to 230° C. are more useful because they can efficiently improve the handwriting drying properties and the whitening suppression effects. Furthermore, in order to more effectively suppress whitening in low-temperature environments, 1,3-dioxolanes having a low melting point are used, which makes them less likely to precipitate in the ink, and therefore it is preferable that the melting point is 5° C. or lower.

[0012] The 1,3-dioxolanes are added to the ink in an amount of 0.1 to 20% by mass, preferably 1.0 to 10% by mass. If the content is less than 0.1% by mass, it is difficult to obtain the desired effect. Although it is possible to add a large amount, the desired effect can be obtained sufficiently at 20% by mass or less.

[0013] The organic solvent used in the oil-based ink of the present invention is at least one selected from aliphatic alcohols and glycol ethers having 5 or less carbon atoms as the main solvent. As the alcohol, a lower aliphatic alcohol having 1 to 5 carbon atoms is used, and specific examples thereof include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, s-butyl alcohol, t-butyl alcohol, and pentyl alcohol. Examples of the glycol ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monophenyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monophenyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and tripropylene glycol monophenyl ether. The organic solvents may be used alone or in combination in an amount of 30 to 85% by mass in the ink composition, and may be used in combination with a compatible general-purpose solvent.

[0014] As the colorant, general-purpose dyes and pigments that have been conventionally used in oil-based inks can be appropriately used. The dyes include, for example, organic solvent soluble dyes classified as solvent dyes in the Color Index. Specific examples of the solvent dye include Varifast Black 3806 (CI Solvent Black 29), Varifast Black 3807 (trimethylbenzylammonium salt of CI Solvent Black 29), Spirit Black SB (CI Solvent Black 5), Spiron Black GMH (CI Solvent Black 43), Varifast Red 1308 (a salt mixture of CI Basic Red 1 and CI Acid Yellow 23), Varifast Yellow AUM (a salt mixture of CI Basic Yellow 2 and CI Acid Yellow 42), and Spiron Yellow. -C2GH (organic acid salt of CI Basic Yellow 2 dye), Spiron Violet CRH (CI Solvent Violet 8-1), Varifast Violet 1701 (a salt formed from CI Basic Violet 1 and CI Acid Yellow 42 dyes), Spiron Red CGH (organic acid salt of CI Basic Red 1 dye), Spiron Pink BH (CI Solvent Red 82), Nigrosine Base EX (CI Solvent Black 7), Oil Blue 613 (CI Solvent Blue 5), Neozapon Blue 808 (CI Solvent Blue 70), etc. Examples of the pigment include inorganic pigments such as carbon black, ultramarine, and titanium dioxide pigments; organic pigments such as azo pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, threne pigments, quinacridone pigments, anthraquinone pigments, threne pigments, diketopyrrolopyrrole pigments, dioxazine pigments, perylene pigments, perinone pigments, and isoindolinone pigments; metal pigments obtained by treating aluminum powder or the surface of aluminum powder with a colored resin; metallic luster pigments obtained by forming a metal vapor deposition film of aluminum or the like on a transparent or colored transparent film; metal pigments having a thickness of 0.01 to 0.1 μm obtained by peeling off a metal vapor deposition film of aluminum or the like formed on a substrate such as a film; colloidal particles having an average particle size of 5 to 30 nm selected from gold, silver, platinum, and copper; fluorescent pigments, phosphorescent pigments, thermochromic pigments; and pearl pigments having a surface coated with a metal oxide such as titanium oxide, etc., of natural mica, synthetic mica, glass pieces, alumina, or transparent film pieces as a core material. The colorants may be used alone or in combination of two or more kinds, and are used in the range of 1 to 25% by mass in the ink composition.

[0015] The resin is not particularly limited as long as it is soluble in the organic solvent, and can be added to the ink for the purposes of inhibiting bleeding of handwriting, improving fixation, imparting fastness, and the like. Specific examples include ketone resins, amide resins, alkyd resins, rosin-modified resins, rosin-modified phenolic resins, phenolic resins, xylene resins, polyvinyl butyral resins, terpene resins, coumarone-indene resins, polyvinylpyrrolidone, polyethylene oxide, polymethacrylic acid esters, ketone-formaldehyde resins, α- and β-pinene-phenol polycondensation resins, polyvinyl butyral resins, acrylic resins, polyacrylic acid-polymethacrylic acid copolymers, and the like. These resins may be used alone or in combination of two or more, and are used in the range of 0.5 to 40% by mass, preferably 1 to 20% by mass, in the ink composition. If the amount is less than 0.5% by mass, sufficient effects such as suppression of bleeding of handwriting on paper, improvement of fixation, and imparting fastness cannot be exhibited, while if the amount is more than 40% by mass, the solubility of the resin in the solvent decreases, and the fluidity of the ink may decrease.

[0016] Furthermore, by using the ink composition of the present invention in combination with polyether-modified silicone, it is possible to maintain a stable ink composition and produce good handwriting without repelling, even when writing on non-ink-absorbing surfaces such as metals and plastics, or on paper that has been surface-treated with craft tape, etc., and by combining this with the inhibition of whitening by the 1,3-dioxolanes, it is possible to produce clearer handwriting in any environment, and on any surface. Among the materials used for the purpose of improving the fixation of handwriting on writing surfaces with poor fixation, polyether-modified silicones are particularly useful because they can achieve the desired effect while maintaining a stable ink composition without causing precipitation, even when used in combination with 1,3-dioxolanes of the general formula.

[0017] Examples of the polyether-modified silicone include side-chain type polyether-modified silicone, both-end-modified type polyether-modified silicone, and ABN type polyether-modified silicone. The side-chain type polyether-modified silicone and the both-end-modified type polyether-modified silicone are those in which a linear polyorganosiloxane serves as the main chain, and the side chain or both ends of the main chain are substituted with polyether groups. The ABN type polyether modified silicone is a linear block copolymer of polyorganosiloxane and polyether. In the present invention, the polyorganosiloxane is particularly preferably polydimethylsiloxane, which has a large molecular weight and is more hydrophobic, because it can effectively obtain good handwriting without bleeding.

[0018] The polyether-modified silicone can be appropriately selected from general-purpose silicones without any particular limitations, but from the viewpoint of solubility, those having an HLB value of 4 or more are particularly preferred. The polyether-modified silicone may be appropriately synthesized or a commercially available product may be used. Examples of commercially available products include those sold under the trade names "DOWSIL 501W Additive", "DOWSIL FZ-2104 Fluid", "DOWSIL FZ-2123", "DOWSIL FZ-2164", "DOWSIL FZ-2191", "DOWSIL FZ-2208", "DOWSIL FZ-2215", "DOWSIL L-7001", "DOWSIL L-7604", "DOWSIL OFX-0309 Fluid", "DOWSIL OFX-5221 Fluid", "DOWSIL SF-8410 Fluid", "DOWSIL OFX-0193 Fluid", "DOWSIL SH-3746 Fluid", "DOWSIL SH-8400 Fluid", "DOWSIL SH-8700 Fluid", "BY11-030", "SILSTYLE104", and "OP-8496 Conditioning Fluid" manufactured by Dow Toray Co., Ltd. Product name: "KF-351A", "KF-353", "KF-354L", "KF-355A", "KF-615A", "KF-945", "KF-640", "KF-642", "KF-643", "KF-644", manufactured by Shin-Etsu Chemical Co., Ltd. "KF-6204", "KF-6011", "KF-6012", "KF-6015", "KF-6017", "KP-541", "X-22-4952", "X-22-4272", "X-22-6266"; Product name "Silsurf" manufactured by SILTECH A004”, “Silsurf A004-UP”, “Silsurf A008”, “Silsurf A008-UP”, “Silsurf A010-D-UP”, “Silsurf CR1115”, “Silsurf Di-2012", "Silsurf G8-I", "Siltech OP-8", "Siltech OP-11", "Siltech OP-12", "Siltech OP-15", "Siltech OP-20", "Siltech C-241", "Siltech C-442", and "Silsurf G8-I". In particular, materials useful in combination with the 1,3-dioxolanes include products manufactured by Dow Toray Industries, Inc. under the trade names "DOWSIL FZ-2208" and "DOWSIL FZ-2222"; products manufactured by Shin-Etsu Chemical Co., Ltd. under the trade names "KF-6004" and "KP-541"; products manufactured by SILTECH under the trade names "Silsurf B608", "Silsurf C208", "Silsurf C410", "Silsurf D208", "Silsurf D208-30", "Silsurf D212-CG", "Silsurf Di-1510", "Silsurf Di-15-I", "Silsurf E608", "Silsurf J1015-O", "Silsurf J1015-O-AC", "Silsurf J208", "Silsurf J208-6", "Siltech C-241", and "Siltech C-442", "BY11-030", "SILSTYLE104", and "OP-8496 Conditioning Agent".

[0019] The content of the polyether-modified silicone is in the range of 0.01 to 5 mass %, preferably 0.5 to 1.5 mass %, based on the total amount of the ink composition, from the viewpoints of excellent fixation and formation of clear handwriting.

[0020] Furthermore, in addition to the above-mentioned components, various additives such as antioxidants, ultraviolet absorbers, rust inhibitors, lubricants, viscosity modifiers, release agents, pigment dispersants, defoamers, shear thinning agents, and surfactants may be used in the oil-based ink composition for writing instruments of the present invention, if necessary. The additives are so-called conventional additives, and may be selected from known compounds and used as necessary.

[0021] As the rust inhibitor, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, etc. can be used. As the antioxidant, dibutylhydroxytoluene, nordihydroxytoluene, flavonoids, butylhydroxyanisole, ascorbic acid derivatives, α-tocopherol, catechins, etc. can be used. Examples of ultraviolet absorbents that can be used include 2-(2'-hydroxy-3'-t-butyl-5'-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and p-benzoic acid-2-hydroxybenzophenone. As the defoaming agent, dimethylpolysiloxane or the like can be used.

[0022] Furthermore, a release agent can be added for the purpose of imparting scratch-erasability when writing on a non-permeable surface.As the release agent, any compound that can impart release property contained in the ink composition used for writing boards (whiteboards) made of materials such as enamel, glass, metal, or thermoplastic or thermosetting plastics can be used, and examples thereof include carboxylic acid esters, silicone surfactants, and nonionic surfactants, but the release agent that is preferably used is a compound selected from polyoxyalkylene alkyl ether sulfate esters, polyoxyalkylene alkyl aryl ether sulfate esters, polyoxyethylene alkyl ether phosphate esters or salts thereof, aliphatic dibasic acid esters, aliphatic monobasic acid esters, and polyalkylene glycol esters, and one or more of them can be used in combination.

[0023] Furthermore, when the oil-based ink composition of the present invention is applied to a ballpoint pen, a lubricant such as a higher fatty acid such as oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, or a thiophosphite triester such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester) can be added as necessary, but the use of a polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphoric acid monoester, a polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphoric acid diester, or a metal salt, ammonium salt, amine salt or alkanolamine salt thereof, in particular, provides an excellent effect in preventing wear of the ball seat.

[0024] Furthermore, by adding a shear thinning agent, it is possible to prevent ink from leaking from the gap between the ball and the tip when not in use, and to prevent ink from flowing back when the writing tip is left facing upwards (upright position). As the shear thinning agent, a conventionally known compound can be used, and examples thereof include crosslinked acrylic resins, emulsion-type crosslinked acrylic resins, crosslinked N-vinyl carboxylic acid amide polymers or copolymers, non-crosslinked N-vinyl carboxylic acid amide polymers or copolymers, aqueous solutions of non-crosslinked N-vinyl carboxylic acid amide polymers or copolymers, hydrogenated castor oil, waxes such as fatty acid amide wax and oxidized polyethylene wax, fatty acid metal salts such as aluminum stearate, aluminum palmitate, aluminum octylate, and aluminum laurate, dibenzylidene sorbitol, dextrin fatty acid esters, N-acyl amino acid compounds, smectite inorganic compounds, montmorillonite inorganic compounds, bentonite inorganic compounds, hectorite inorganic compounds, and silica.

[0025] The ink composition is used in practice by being filled into a ballpoint pen or a marking pen having a tip attached to the writing end. When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited, and examples include a structure in which ink is impregnated into an ink absorbing body made of a fiber bundle contained inside the barrel and ink is supplied to the writing tip, a structure in which ink is directly contained inside the barrel and an ink flow rate regulator in the shape of a comb groove or made of a fiber bundle is interposed, and a ballpoint pen having an ink reservoir tube filled with the ink composition inside the barrel, which ink reservoir tube communicates with a tip having a ball attached to its tip, and further having an ink follower such as a liquid stopper or solid stopper in close contact with the end face of the ink to prevent backflow. When loading ink into a marking pen, the structure and shape of the marking pen itself are not particularly limited, and examples of such marking pens include a structure in which a fiber tip, felt tip, or plastic tip is attached to the writing tip and ink is impregnated into an ink absorbing body made of a fiber bundle contained inside the barrel to supply ink to the writing tip; a structure in which ink is directly contained inside the barrel and an ink flow rate adjustment member in the form of a comb groove or made of a fiber bundle is interposed; and a structure in which ink is directly contained inside the barrel and a valve mechanism supplies a predetermined amount of ink to the writing tip. In particular, when a polyester tip, which is a resin-processed polyester fiber bundle, is used as the tip applied to the marking pen, the writing feel is soft and the ink tracking is good, but it is disadvantageous in terms of dry-up resistance, so the effects of the ink of the present invention are easily manifested and are effective. EXAMPLES

[0026] The ink compositions of the examples and comparative examples are shown in the table below. The composition values ​​in the table are in parts by weight.

[0027] [Table 1]

[0028] The ingredients in the table are explained according to the note numbers. (1) CISolvent Black 7 (2) Salt complex of CI Acid Yellow 42 and CI Basic Red 1 (3) CI Pigment Black 7 20%, polyvinyl butyral 20%, ethanol 60% dispersion (4) 2-2-Dimethyl-4-hydroxymethyl-1,3-dioxolane (boiling point 191°C) (5) 4-(2-hydroxyethyl)-2,2-dimethyl-1,3-dioxolane (boiling point 200°C) (6) 2,2-diisopropyl-1,3-dioxolane (boiling point 172°C) (7) 2-phenyl-1,3-dioxolane (boiling point 225°C) (8) 4-Fluoro-2-oxo-1,3-dioxolane (boiling point 210°C) (9) 2-Oxo-1,3-dioxolane (boiling point 244°C) (10) Side-chain type polyether modified silicone, manufactured by SILTECH, product name: Siltech C-241 (11) Double-ended polyether-modified silicone, manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-6004 (HLB: 9) (12) ABN type polyether modified silicone, manufactured by Dow Toray Co., Ltd., product name: DOWSIL FZ-2222 (HLB: 6)

[0029] Ink Preparation The raw materials of the above-mentioned Examples and Comparative Examples were mixed and stirred in a disperser at 40° C. for 2 hours to obtain an oil-based ink composition for writing instruments.

[0030] Making a marking pen 1.5 g of the obtained ink composition was filled into a commercially available marking pen exterior (manufactured by Pilot Corporation; SC-EU, equipped with an acrylic tip) to obtain an oil-based marking pen.

[0031] Written exam Using each marking pen, five consecutive circles were written on a transparent PET film in the following environments: 20°C and 65% humidity, 30°C and 90% humidity, 20°C and 90% humidity, and 10°C and 90% humidity. The condition of the marks after drying was visually confirmed. Drying test Using each marking pen, a 15 cm straight line was written on a transparent PET film in an environment of 20°C and 65% humidity in 1 second, and the mark was then rubbed in one direction with a thumb. The time until the mark no longer peeled off was measured. Handwriting Retention Test Writing was done on the surface of a craft tape (manufactured by Nichiban Co., Ltd., product name: craft adhesive tape No. 313), and the presence or absence of repelling of the writing was visually observed. The test results are shown in the table below.

[0032] [Table 2]

[0033] The symbols in the table are explained below. Written exam ○: Clear handwriting is obtained. ×: Whitening is observed in the handwriting, resulting in a matte handwriting. Drying test ○: Dries within 20 seconds. △: Dries within 40 seconds. ×: The writing does not dry even after 40 seconds. Handwriting Retention Test ○: No repelling of handwriting was observed, and clear handwriting was obtained. ×: The handwriting was blurred and had some smudges.

Claims

1. The oil-based ink composition for a writing instrument comprises an organic solvent selected from an aliphatic alcohol and / or a glycol ether having 5 or less carbon atoms, a colorant, a resin, and a 1,3-dioxolane represented by the following general formula (1) or (2): 【Chemistry 1】 [In the formula, R1 and R2 are substituents selected from a hydroxyl group, a monovalent or divalent alcohol of a linear alkyl having 4 or less carbon atoms, and an aryl group, or an aromatic ring having 5 to 6 carbon atoms including the carbon atom of the base, R3 and R4 are substituents selected from a hydroxyl group, an alkyl group having 1 to 18 carbon atoms, an aryl group, and a halogenated alkyl group, and R5 and R6 are substituents selected from a halogen, a linear alcohol having 4 or less carbon atoms, and a polyoxyethylene adduct of a linear alcohol having 4 or less carbon atoms.]

2. 2. The oil-based ink composition for writing instruments according to claim 1, wherein the boiling point of the 1,3-dioxolanes is in the range of 170°C to 230°C.

3. 3. The oil-based ink composition for writing instruments according to claim 1, wherein the 1,3-dioxolanes are used in an amount of from 0.1% by mass to 20% by mass based on the total amount of the ink composition.

4. 2. The oil-based ink composition for writing instruments according to claim 1, which comprises a polyether-modified silicone.

5. 5. The oil-based ink composition for writing instruments according to claim 4, wherein the polyether-modified silicone is at least one member selected from the group consisting of side-chain type polyether-modified silicone, both-end type polyether-modified silicone and ABN type polyether-modified silicone.

6. 6. The oil-based ink composition for writing instruments according to claim 4, wherein the polyether-modified silicone is used in an amount of 0.01% by mass to 5% by mass based on the total amount of the ink composition.

7. A writing instrument incorporating the oil-based ink composition for writing instruments according to any one of claims 1 to 6.

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