Oil-based ink composition for writing instrument and writing instrument housing the same

Abstract

To provide an oil-based ink composition for writing instrument, which is excellent in adhesion on poorly wetted writing surfaces and makes it possible to form excellent calligraphy without blurring, with no precipitation of polyether-modified silicone in aqueous ink even in low-temperature environments by adding a dibasic acid ester, and a writing instrument housing the same.SOLUTION: An oil-based ink composition for a writing instrument at least contains a coloring agent, an organic solvent, a resin, a polyether-modified silicone, and a dibasic acid ester. The polyether-modified silicone is a side-chain type polyether-modified silicone, a both terminal type polyether-modified silicone, or an ABN type polyether-modified silicone.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an oil-based ink composition for writing instruments and a writing instrument containing the same. More specifically, the present invention relates to an oil-based ink composition for writing instruments that can be suitably used as ink for marking pens, felt pens, ballpoint pens, brush pens, etc., and a writing instrument containing the same.

Background Art

[0002] Conventionally, oil-based inks used in writing instruments such as marking pens are composed of a colorant, an organic solvent, a resin, and optionally a surfactant, and are written on writing surfaces made of various materials. Therefore, good adhesion is required for the formed handwriting. However, when writing on materials with poor wettability, such as synthetic resin films, paper with a resin-coated surface, metals, etc., the ink is repelled, resulting in insufficient adhesion and the inability to obtain good handwriting. In order to solve the above problems, by adding a polyether-modified silicone in which the side chain or both ends of dimethylpolysiloxane are substituted with polyether groups, when writing on non-absorbent surfaces such as metals and plastics, there is no ink repellency, and an oil-based marking pen with excellent adhesion and good handwriting can be obtained (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the oil-based inks of the cited documents, in a low-temperature environment, the polyether-modified silicone in the oil-based ink may precipitate, resulting in blurred handwriting or the inability to write.

[0005] The present invention solves the conventional problems, and even in a low-temperature environment, polyether-modified silicone does not precipitate in the oil-based ink, and it has excellent adhesion to a writing surface with poor wettability, has no repellency, and can form good handwriting. An object of the present invention is to provide an oil-based ink composition for writing instruments and a writing instrument containing the same.

Means for Solving the Problems

[0006] The present invention is an oil-based ink composition for writing instruments and a writing instrument containing the same, which at least contain a colorant, an organic solvent, a resin, a polyether-modified silicone, and a dibasic acid ester.

[0007] Further, it may be an oil-based ink composition for writing instruments in which the melting point of the polyether-modified silicone is 10°C or higher.

[0008] Further, the polyether-modified silicone may be a side-chain type polyether-modified silicone, a both-terminal type polyether-modified silicone, or an ABN type polyether-modified silicone, which is an oil-based ink composition for writing instruments.

[0009] Further, it may be an oil-based ink composition for writing instruments using glycol ethers having 5 or less carbon atoms and / or alcohols having 5 or less carbon atoms as the organic solvent.

[0010] Further, it may be an oil-based ink composition for writing instruments containing 0.1 to 20% by mass of the dibasic acid ester in the total amount of the ink composition.

[0011] Further, the dibasic acid ester may be an oil-based ink composition represented by the following general formula (1).

Chemical formula

[0012] Further, the dibasic acid ester may be an oil-based ink composition for writing instruments having a boiling point of 160°C or higher and 270°C or lower.

[0013] In addition, a writing instrument containing these oil-based ink compositions for writing instruments is provided.

Advantages of the Invention

[0014] According to the present invention, by adding a dibasic acid ester to an oil-based ink containing a polyether-modified silicone, it is possible to suppress the precipitation of the polyether-modified silicone even in a low-temperature environment, thereby eliminating writing defects such as faint handwriting. As a result, it is possible to provide an oil-based ink composition for writing instruments that can form good handwriting without repelling on a non-absorbent surface with poor wettability, and a writing instrument that contains the same, regardless of the temperature, climate, or region.

Modes for Carrying Out the Invention

[0015] Polyether-modified silicone is used to form good handwriting without repelling when writing on a non-absorbent surface such as metal or plastic.

[0016] The polyether-modified silicone in the present invention preferably has a melting point of 10°C or higher. When a polyether-modified silicone having a melting point of 10°C or higher is used in a low-temperature environment, it becomes difficult to dissolve in an organic solvent, so there is a risk that the polyether-modified silicone will precipitate as a solid in the ink. Therefore, by adding a dibasic acid ester to the ink, the polyether-modified silicone does not precipitate even in a low-temperature environment, and a desired handwriting effect can be obtained.

[0017] Examples of the polyether-modified silicone include side-chain type polyether-modified silicone, both-terminal modified type polyether-modified silicone, and ABN type polyether-modified silicone. Side-chain type polyether-modified silicone and both-terminal modified polyether-modified silicone are those in which a linear polyorganosiloxane is used as the main chain and the side chains or both ends of the main chain are substituted with polyether groups. ABN type polyether-modified silicone is a linear block copolymer of polyorganosiloxane and polyether. In addition, in the present invention, from the viewpoint of obtaining a good handwriting without bleeding, the polyorganosiloxane is preferably polydimethylsiloxane having a large molecular weight and higher hydrophobicity.

[0018] The polyether-modified silicone of the present invention can be appropriately selected without particular limitation. From the viewpoint of solubility, those having an HLB of 4 or more are preferred. Such polyether-modified silicones may be synthesized as appropriate or commercially available products may be used. Examples of commercially available products include those with the trade names "DOWSIL 501W Additive", "DOWSIL FZ-2104 Fluid", "DOWSIL FZ-2123", "DOWSIL FZ-2164", "DOWSIL FZ-2191", "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" manufactured by Dow Corning Toray Co., Ltd.; those with the trade names "KF-351A", "KF-353", "KF-354L", "KF-355A", "KF-615A", "KF-945", "KF-640", "KF-642", "KF-643", "KF-644", "KF-6204", "KF-6011", "KF-6012", "KF-6015", "KF-6017", "X-22-4952", "X-22-4272", "X-22-6266" manufactured by Shin-Etsu Chemical Co., Ltd.; those with the trade names "Silsurf 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", "Silsurf G8-I", etc. manufactured by SILTECH, Preferably, the product names include "DOWSIL FZ-2222" manufactured by The Dow Chemical Company and Toray Industries, Inc.; "KF-6004" manufactured by Shin-Etsu Chemical Co., Ltd.; "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", etc. manufactured by SILTECH.

[0019] From the viewpoints of excellent fixing property and formation of handwriting, the content of the polyether-modified silicone of the present invention is used in the range of 0.01 to 5% by mass, preferably 0.5 to 1.5% by mass, based on the total amount of the ink composition.

[0020] As the organic solvent of the present invention, it is preferable to use at least one selected from glycol ethers and alcohols having 5 or less carbon atoms as the main solvent. Specific 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, tripropylene glycol monophenyl ether, etc. Specific examples of the alcohol include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, s-butyl alcohol, t-butyl alcohol, pentyl alcohol, and the like. Further, known glycol ethers and alcohols can be used. Also, by using glycol ethers and alcohols having 5 or less carbon atoms, it is possible to excellently prevent whitening of handwriting and improve fastness.

[0021] In the present invention, by adding a dibasic acid ester to the oil-based ink, precipitation of the polyether-modified silicone can be suppressed even in a low-temperature environment. By suppressing precipitation in a low-temperature environment, it is possible to form a good handwriting without bleeding, which has excellent fixability to a writing surface with poor wettability regardless of temperature, region, and environment.

[0022] The content of the dibasic acid ester in the present invention is used in the range of 0.1 to 20% by mass, preferably 0.5 to 15% by mass, based on the total amount of the ink composition, from the viewpoints of drying property, bleeding, and solubility of the handwriting.

[0023] The dibasic acid ester of the present invention is preferably a dibasic acid ester represented by the following general formula (1) from the viewpoint of the solubility of the polyether-modified silicone in the organic solvent.

Chemical formula

[0024] The dibasic acid ester of the present invention preferably has a boiling point of 160°C or higher and 270°C or lower. By having the boiling point within the above range, the solubility of the polyether-modified silicone in the organic solvent can be further increased, and the fixability and drying property of the handwriting are further excellent.

[0025] A dibasic acid ester is an ester of a dibasic acid and an alcohol. Specific examples of the dibasic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, fumaric acid, maleic acid, methylmalonic acid, ethylmalonic acid, dimethylmalonic acid, propylmethylmalonic acid, isopropylmalonic acid, ethylmethylmalonic acid, butylmalonic acid, isobutylmalonic acid, sec-butylmalonic acid, tert-butylmalonic acid, methylpropylmalonic acid, methylisopropylmalonic acid, diethylmalonic acid, pentylmalonic acid, neopentylmalonic acid, isopentylmalonic acid, sec-pentylmalonic acid, tert-pentylmalonic acid, ethylpropylmalonic acid, hexylmalonic acid, isohexylmalonic acid, dipropylmalonic acid, diisopropylmalonic acid, cyclopentylmalonic acid, cyclohexylmalonic acid, phenylmalonic acid, methylsuccinic acid, ethylsuccinic acid, propylsuccinic acid, isopropylsuccinic acid, ethylmethylsuccinic acid, butylsuccinic acid, isobutylsuccinic acid, sec-butylsuccinic acid, tert-butylsuccinic acid, pentylsuccinic acid, neopentylsuccinic acid, isopentylsuccinic acid, sec-pentylsuccinic acid, tert-pentylsuccinic acid, ethylpropylsuccinic acid, cyclopentylsuccinic acid, 2,3-dimethylsuccinic acid, 2,3-diethylsuccinic acid, 2-methyl-3-ethylsuccinic acid, 2-methyl-3-propylsuccinic acid, 2-methyl-3-isopropylsuccinic acid, 2-methyl-3-butylsuccinic acid, 2-methyl-3-isobutylsuccinic acid, 2-methyl-3-tert-butylsuccinic acid, 2-ethyl-3-propylsuccinic acid, 2-ethyl-3-isopropylsuccinic acid, cyclopentylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 2,2-dimethylglutaric acid, 3,3-dimethylglutaric acid, 2,4-dimethylglutaric acid, 2-propylglutaric acid, 3-isopropylglutaric acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and other dibasic acids in which the hydrocarbon group to which two carboxy groups of the dibasic acid are bonded has 2 to 7 carbon atoms and is an isomer. Specific examples of the alcohol include methanol, ethanol, propanol, isopropanol, and the like.However, without being particularly limited to these examples, known dibasic acid esters can be used.

[0026] As the colorant, dyes, pigments, etc. are not particularly limited and can be appropriately selected. Examples of the dye include organic solvent-soluble dyes classified as solvent dyes in the Color Index. Specific examples of the solvent dye include Valifast Black 3806 (C.I. Solvent Black 29), Valifast Black 3807 (trimethylbenzylammonium salt of the dye of C.I. Solvent Black 29), Valifast Black 3830 (azo compound chromium complex), Spirit Black SB (C.I. Solvent Black 5), Spiron Black GMH (C.I. Solvent Black 43), Valifast Red 1308 (salt formed from the dye of C.I. Basic Red 1 and the dye of C.I. Acid Yellow 23), Valifast Yellow AUM (salt formed from the dye of C.I. Basic Yellow 2 and the dye of C.I. Acid Yellow 42), Spiron Yellow C2GH (organic acid salt of the dye of C.I. Basic Yellow 2), Spiron Violet CRH (C.I. Solvent Violet 8-1), Valifast Violet 1701 (salt formed from the dye of C.I. Basic Violet 1 and the dye of C.I. Acid Yellow 42), Spiron Red CGH (organic acid salt of the dye of C.I. Basic Red 1), Spiron Pink BH (C.I. Solvent Red 82), Nigrosine Base EX (C.I. Solvent Black 7), Oil Blue 613 (C.I. Solvent Blue 5), Neozapon Blue 808 (C.I. Solvent Blue 70), etc. Examples of pigments include inorganic pigments such as carbon black, ultramarine, titanium dioxide pigments, etc., organic pigments such as azo pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, perylene pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, diketopyrrolopyrrole pigments, dioxazine pigments, perylene pigments, perinone pigments, isoindolinone pigments, etc., metal pigments such as aluminum powder and metal pigments obtained by treating the surface of aluminum powder with a coloring resin, metallic luster pigments obtained by forming a metal vapor deposition film such as aluminum on a transparent or colored transparent film, metal pigments with a thickness of 0.01 to 0.1 μm obtained by peeling off a metal vapor deposition film such as aluminum formed on a substrate such as a film, colloidal particles with an average particle diameter of 5 to 30 nm selected from gold, silver, platinum, and copper, fluorescent pigments, phosphorescent pigments, thermochromic pigments, pearl pigments obtained by coating the surface of natural mica, synthetic mica, glass flakes, alumina, and transparent film flakes as the core material with a metal oxide such as titanium dioxide, etc. The colorant may be used alone or in combination of two or more, and is used in the range of 1 to 25% by mass in the ink composition.

[0027] As the resin, any resin soluble in an organic solvent can be applied without particular limitation, and it can be added to the ink for the purpose of suppressing bleeding of handwriting, improving fixing properties, imparting fastness, etc. Specifically, 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, polyvinyl pyrrolidone, 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, etc. can be mentioned. 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 it is less than 0.5% by mass, it is difficult to obtain sufficient effects such as improving the fixing property of handwriting, imparting fastness, and suppressing bleeding to paper. If it is added in excess of 40% by mass, the solubility of the resin in the solvent may decrease, and the fluidity of the ink may decrease.

[0028] Furthermore, in the oil-based ink composition for writing instruments of the present invention, various additives such as antioxidants, ultraviolet absorbers, rust preventives, lubricants, viscosity modifiers, pigment dispersants, defoamers, shear-thinning property imparting agents, surfactants, etc. can be used in addition to the above components as necessary. The above additives are so-called conventional additives and can be appropriately used as necessary from known compounds.

[0029] As the rust preventive, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, etc. can be used. As the antioxidant, dibutylhydroxytoluene, nordihydroxytoluene, flavonoid, butylhydroxyanisole, ascorbic acid derivative, α-tocopherol, catechins, etc. can be used. As the ultraviolet absorber, 2-(2′-hydroxy-3′-t-butyl 5′-5′-methylphenyl)-5-chlorobenzotriazole, 2-(2′-hydroxy-5′-methylphenyl)benzotriazole, p-benzoic acid-2-hydroxybenzophenone, etc. can be used.

[0030] Also, when applying the oil-based ink composition of the present invention to a ballpoint pen, lubricants such as higher fatty acids such as oleic acid, nonionic surfactants having a long-chain alkyl group, and tri(alkoxycarbonylmethyl ester) thiophosphite or tri(alkoxycarbonylethyl ester) thiophosphite can be added as necessary. In particular, when using a phosphoric acid monoester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, a phosphoric acid diester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, or their metal salts, ammonium salts, amine salts, alkanolamine salts, etc., it has an excellent effect of preventing wear of the ball seat.

[0031] Furthermore, by adding a shear-thinning viscosity-imparting agent, it is possible to prevent ink from leaking out of the gap between the ball and the tip when not in use, or to prevent the backflow of ink when the writing tip is left facing upward (in the upright state). As the shear-thinning viscosity-imparting agent, conventionally known compounds can be used. For example, crosslinked acrylic resins, emulsion types of crosslinked acrylic resins, crosslinked N-vinylcarboxylic acid amide polymers or copolymers, non-crosslinked N-vinylcarboxylic acid amide polymers or copolymers, aqueous solutions of non-crosslinked N-vinylcarboxylic acid amide polymers or copolymers, hydrogenated castor oil, fatty acid amide waxes, waxes such as oxidized polyethylene waxes, fatty acid metal salts such as aluminum stearate, aluminum palmitate, aluminum octylate, aluminum laurate, dibenzylidene sorbitol, dextrin fatty acid esters, N-acyl amino acid-based compounds, smectite-based inorganic compounds, montmorillonite-based inorganic compounds, bentonite-based inorganic compounds, hectorite-based inorganic compounds, silica, etc. can be exemplified.

[0032] The ink composition of the present invention is not limited to those used in writing instruments such as marking pens and ballpoint pens, and can also be accommodated in an ink storage body (ink cartridge) that is detachable and replaceable from the writing instrument body.

[0033] When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited. For example, a structure in which an ink reservoir made of a fiber bundle accommodated inside the shaft tube is impregnated with ink and the ink is supplied to the writing tip, a structure in which ink is directly accommodated inside the shaft tube and a comb-shaped ink flow regulating member or an ink flow regulating member made of a fiber bundle is interposed, an ink storage tube filled with the ink composition in the shaft tube, the ink storage tube communicates with a tip having a ball attached to the tip, and an ink follower such as a liquid plug or a solid plug is in close contact with the end face of the ink to prevent backflow. Examples of ballpoint pens with such a structure can be given.

[0034] When filling a marking pen, the structure and shape of the marking pen itself are not particularly limited. For example, a fiber tip, a felt tip, a plastic tip, a brush, etc. are attached to the writing tip, and an ink storage body composed of a fiber bundle accommodated inside the shaft cylinder is impregnated with ink, and a structure for supplying ink to the writing tip, ink is directly accommodated inside the shaft cylinder, and a structure in which an ink flow rate adjusting member in the form of a comb-shaped groove or an ink flow rate adjusting member composed of a fiber bundle is interposed, and a structure in which ink is directly accommodated inside the shaft cylinder and a predetermined amount of ink is supplied to the writing tip by a valve mechanism. Examples of marking pens include those having such structures. In particular, when a fiber aggregate made of acrylic fiber, polyester fiber, or nylon fiber is used as the tip applied to the marking pen, although the ink followability is good, the tip gap is clogged due to the precipitation of polyether-modified silicone, and writing defects are likely to occur. Therefore, the effect of the ink of the present invention is remarkable.

Examples

[0035] The ink compositions of the examples and comparative examples are shown in the following table. Note that the numerical values of the compositions in the table indicate parts by mass.

[0036]

Table 1

[0037] The contents of the raw materials in the table will be described according to the reference numbers. (1) Manufactured by Orient Chemical Industry Co., Ltd., product name: VALIFAST BLACK 3830 (2) 3-Methoxy-3-methyl-1-butanol, manufactured by Kuraray Co., Ltd., product name: Solfit (3) Manufactured by Yasuhara Chemical Co., Ltd., product name: YS Polyster T-160 (4) Manufactured by Yasuhara Chemical Co., Ltd., product name: YS Polyster G-150 (5) Manufactured by Arakawa Chemical Industries, Ltd., product name: Hyper B CH-B (6) Manufactured by Honshu Chemical Industry Co., Ltd., product name: TrisP-HAP (7) Side-chain type polyether modified silicone, manufactured by SILTECH, product name: Siltech C-241 (8) Both-end type polyether modified silicone, manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-6004 (HLB: 9) (9) ABN type polyether modified silicone, manufactured by Dow Corning Toray Co., Ltd., product name: DOWSIL FZ-2222 (HLB: 6) (10) Dimethyl 2-methylglutarate, manufactured by Solvay, product name: Rhodiasolv IRIS (boiling point 235°C) (11) Three-component mixed solvent (dimethyl succinate, dimethyl glutarate, dimethyl adipate), manufactured by Sojitz Corporation, product name: DBE (boiling point 196°C - 225°C) (12) Dimethyl adipate (boiling point 251°C) (13) Dibutyl adipate (boiling point 305°C) (14) Diethyl sebacate (boiling point 309°C) (15) Di(2-ethylhexyl) maleate (boiling point 150°C) (16) Benzotriazole, manufactured by Kawaguchi Chemical Industry Co., Ltd., product name: BT

[0038] Preparation of Ink The raw materials of the above Examples and Comparative Examples were mixed and stirred at 40°C for 2 hours with a disperser to obtain an oily ink composition for writing instruments.

[0039] Manufacture of Marking Pen 1.5 g of the obtained ink composition was filled into a commercially available marking pen exterior (manufactured by Pilot Corporation; MEF-12EU, equipped with an acrylic tip) to obtain an oily marking pen.

[0040] Using each of the prepared marking pens, writing was done on kraft tape, and after drying for 1 day, rubbing with a tissue paper under a load of 500 g was performed 10 times back and forth. As a result, none of the handwriting was peeled off and it was in good condition.

[0041] Using the oily marking pen prepared as described above, the following tests were conducted. Writing test The surface of kraft tape (manufactured by Nichiban Co., Ltd., product name: Kraft Adhesive Tape No. 313) was written on, and the presence or absence of ink repellency of the handwriting was visually observed.

[0042] Using the oil-based ink composition adjusted as described above, the following tests were conducted. Low-temperature solubility test 10 mL of the oil-based ink compositions of the examples and comparative examples were sealed in each glass bottle, stored in an environment at 10°C for 1 day, and the presence or absence of deposits at the bottom of the glass bottle was visually observed.

[0043] The results of the writing test and the low-temperature solubility test are shown in the following table.

Table 2

[0044] Note that the evaluation symbols in the table are as follows. Writing test ○: No ink repellency of the handwriting was confirmed. ×: Ink repellency of the handwriting was confirmed. Low-temperature solubility test ○: No deposits were confirmed. ×: Deposits were confirmed.

Claims

1. An oil-based ink composition for writing instruments comprising at least a colorant, an organic solvent, a resin, a polyether-modified silicone, and a dibasic acid ester.

2. The oil-based ink composition for writing instruments according to claim 1, wherein the melting point of the polyether-modified silicone is 10°C or higher.

3. The oil-based ink composition for writing instruments according to claim 1, wherein the polyether-modified silicone is a side-chain type polyether-modified silicone, a double-ended type polyether-modified silicone, or an ABN type polyether-modified silicone.

4. The oil-based ink composition for writing instruments according to claim 1, comprising glycol ethers having 5 or fewer carbon atoms and / or alcohols having 5 or fewer carbon atoms as the main solvent.

5. The oil-based ink composition for writing instruments according to claim 1, comprising 0.1 to 20% by mass of the dibasic acid ester in the total amount of the ink composition.

6. The oil-based ink composition for writing instruments according to claim 1, wherein the dibasic acid ester is represented by the following general formula (1). 【Chemistry 1】 (In formula (1), R1 and R2 represent hydrocarbon groups having 1 to 3 carbon atoms, and R3 represents a hydrocarbon group having 0 to 7 carbon atoms.)

7. The oil-based ink composition for writing instruments according to claim 1, wherein the dibasic acid ester has a boiling point of 160°C or higher and 270°C or lower.

8. A writing instrument containing an oil-based ink composition according to any one of claims 1 to 7.

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