Oily ink composition for notebooks

Abstract

To provide an oily ink composition for a writing instrument which is excellent in dispersion stability of a pigment, and in writing on a non-absorption surface, suppresses "cissing", and is excellent in sticking property and scratch resistance of a coated film, and a writing instrument mounted with the oily ink composition.SOLUTION: An oily ink composition for a writing instrument contains at least a pigment, a resin, an organic solvent, polydimethylsiloxane and polytetrafluoroethylene particles, wherein the polydimethylsiloxane has polyether-modified groups at both terminals, and has a TI value (10 rpm / 100 rpm) of 1.15 to 2.00 in cone plate type viscosity measurement.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conventionally, examples of ink compositions for writing instruments containing silicones such as polydimethylsiloxane include: [1] A water-based marker ink characterized by comprising a silicone surfactant, a film-forming polymer, a pigment, and water is disclosed, in which the silicone surfactant is polydimethylsiloxane containing polyoxyethylene (see, for example, Patent Document 1). [2] An oil-based ink for a marking pen that is a low-toxicity non-aromatic hydrocarbon solvent-based ink and produces substantially smooth writing even on ink-impermeable surfaces without increasing the ink viscosity to an extent that it inhibits continuous flow of the ink from the nib of the marking pen, is an oil-based ink composition for a marking pen that contains, as essential components, a colorant, an organic solvent mainly composed of an aliphatic hydrocarbon and / or an alicyclic hydrocarbon, a resin soluble in the solvent, and at least one silicone oil selected from cyclic polydimethylsiloxane, alkyl-modified silicone, and terminal-modified polyether-modified silicone (see, for example, Patent Document 2);

[0003] [3] An oil-based ink composition for a writing instrument that has good writing properties on writing surfaces of various materials and has improved abrasion resistance that is resistant to repeated rubbing of handwriting after writing or to rubbing with stronger force, the oil-based ink composition for a writing instrument containing a colorant, a resin, an organic solvent, and polydimethylsiloxane, the polydimethylsiloxane having polyether-modified groups at both ends, and the total number of hydroxyl groups in the polyether-modified groups being 3 or more (see, for example, Patent Document 3); [4] An ink composition for an oil-based marking pen, which has high fixability on metals and plastics and removability on glass surfaces, includes a solvent, a colorant, a resin soluble in the solvent, and a modified silicone oil having a polyether structure in its side chain, the solvent containing propylene glycol monomethyl ether as a main component, and which has a surface tension of 24 mN / m or less at 20°C (see, for example, Patent Document 4). etc. are known.

[0004] However, the above Patent Document 1 is an aqueous ink, which differs from the present invention in terms of formulation properties, etc., and the above Patent Documents 2 to 4 disclose related technologies to the present invention, but the above Patent Document 2 is an oil-based ink that mainly uses dyes, which differs from the present invention in terms of formulation properties, etc. The above-mentioned Patent Document 3 is a prior application of the present applicant, and is partially similar to the present invention in that it uses a polydimethylsiloxane having polyether-modified groups at both ends, but the polyether-modified polydimethylsiloxane is used as a friction reducer, and its content is high at 1% by mass or more, and the formulation in the examples uses only a dye, so it differs from the present invention in terms of formulation properties, including the purpose of the invention. The above-mentioned Patent Document 4 uses a modified silicone oil having a polyether structure in the side chain, and differs from the present invention in terms of formulation properties, etc. Furthermore, each of Patent Documents 2 to 4 still has problems in that one or more of the following are insufficient: pigment dispersion stability, suppression of "repellency" when writing on non-absorbent surfaces, adhesion of the coating film, and abrasion resistance. At present, there is a strong demand for an oil-based ink composition for a writing instrument that is excellent in each of these properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 07-509271 A (claims, examples, etc.) [Patent Document 2] JP-A-09-111176 (claims, examples, etc.) [Patent Document 3] JP 2018-193523 A (claims, examples, etc.) [Patent Document 4] JP 2021-17463 A (claims, examples, etc.) Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned problems and current state of the prior art, and aims to solve these problems, and to provide an oil-based ink composition for a writing instrument that has excellent pigment dispersion stability, suppresses repellency when written on a non-absorbent surface, and provides excellent adhesion and abrasion resistance of the coating film, as well as a writing instrument equipped with this oil-based ink composition. [Means for solving the problem]

[0007] The present inventors have conducted extensive research in light of the above-mentioned problems in the prior art, and as a result have found that an oil-based ink composition for a writing instrument and a writing instrument equipped with this oil-based ink composition can be obtained by containing at least a pigment, a resin, an organic solvent, a polydimethylsiloxane having specific physical properties, and polytetrafluoroethylene particles, and by setting the TI value (10 rpm / 100 rpm) within a specific range in a cone-and-plate viscosity measurement, and have thus completed the present invention.

[0008] That is, the oil-based ink composition for a writing instrument of the present invention contains at least a pigment, a resin, an organic solvent, a polydimethylsiloxane, and polytetrafluoroethylene particles, and is characterized in that the polydimethylsiloxane has polyether-modified groups at both ends and has a TI value (10 rpm / 100 rpm) of 1.15 to 2.00 in cone-plate viscosity measurement. The mass ratio of the pigment (A) to the polydimethylsiloxane (B) [(A) / (B)] is preferably 500 to 1,800. The ink composition preferably has a surface tension of 26 mN / m or less at 25°C. The writing implement of the present invention is characterized by being equipped with an oil-based writing ink composition having the above-described composition. [Effects of the Invention]

[0009] According to the present invention, there are provided an oil-based ink composition for a writing instrument that has excellent pigment dispersion stability, suppresses repellency when written on a non-absorbent surface, and provides excellent adhesion and abrasion resistance of the coating film, and a writing instrument equipped with this oil-based ink composition. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present invention. However, please note that the technical scope of the present invention is not limited to the embodiments described in detail below, but extends to the inventions set forth in the claims and their equivalents. Furthermore, the present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field (including design matters and obvious matters).

[0011] <Oil-based ink composition for writing instruments> The oil-based ink composition for a writing instrument of the present invention contains at least a pigment, a resin, an organic solvent, polydimethylsiloxane, and polytetrafluoroethylene particles, and is characterized in that the polydimethylsiloxane has polyether-modified groups at both ends and has a TI value (10 rpm / 100 rpm) of 1.15 to 2.00 in cone-plate viscosity measurement.

[0012] <Pigments> Examples of pigments that can be used in the present invention include inorganic pigments such as carbon black, graphite, and titanium dioxide, organic pigments such as talc, silica, alumina, mica, and alumina silicate, azo pigments, condensed azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, diketopyrrolopyrrole pigments, and various lake pigments, as well as fluorescent pigments, pearl pigments, and metallic pigments such as gold and silver. These pigments may be used alone or in combination. The average particle size of these pigments is not particularly limited, and pigments within a suitable range can be used depending on the pigment type, the application of the writing implement, the pen tip structure, dispersion stability, etc. Here, in the present invention, the average particle size refers to the average particle size value obtained by cumulant analysis of the scattering intensity distribution calculated using dynamic light scattering with a concentrated particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), or the D50 value calculated on a volume basis by laser diffraction, and this measurement is performed with, for example, a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd. In the present invention, dyes that can be used in oil-based ink compositions for writing instruments, such as oil-soluble dyes, direct dyes, acid dyes, basic dyes, mordant and acid mordant dyes, alcohol-soluble dyes, azoic dyes, sulfide and vat sulfide dyes, vat dyes, disperse dyes, food dyes, metal complex dyes, salt-forming dyes, and dyes obtained by dyeing a resin, can be used within a range that does not impair the effects of the present invention. The content of these pigments is preferably 15 to 25% by mass, more preferably 17 to 20% by mass, based on the total amount of the oil-based ink composition for writing instruments, in terms of obtaining the desired coloring effect and stability over time.

[0013] <Resin> Examples of resins that can be used in the present invention include ketone resins, sulfonamide resins, maleic acid resins, terpene resins, terpene phenol resins, rosin-modified resins, ester gums, xylene resins, alkyd resins, phenolic resins, butyral resins, rosin, polyvinylpyrrolidone, polyvinyl alcohol, acrylic resins, melamine resins, cellulose-based resins such as nitrocellulose, and derivatives thereof. These resins may be used alone or in combination. The content of these resins is preferably 10 to 20% by mass, more preferably 13 to 17% by mass, based on the total amount of the oil-based ink composition for writing instruments, from the viewpoints of ink ejection volume and stability over time.

[0014] <Organic solvent> Examples of organic solvents that can be used in the present invention include aromatics, alcohols, polyhydric alcohols, glycol ethers, hydrocarbons, esters, etc. These solvents may be used alone or in combination.

[0015] Examples of aromatic compounds that can be used include benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkylsulfonic acid phenyl ester, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, and dipropylene glycol dibenzoate.

[0016] Examples of alcohols that can be used include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methylamyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, and 2-methylcyclohexanol.

[0017] Examples of polyhydric alcohols that can be used include ethylene glycol, diethylene glycol, 3-methyl-1,3 butanediol, triethylene glycol, dipropylene glycol, 1,3 propanediol, 1,3 butanediol, 1,5 pentanediol, hexylene glycol, and octylene glycol.

[0018] Examples of glycol ethers include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, and ethylene glycol monohexyl ether. Examples of usable olefin copolymers include ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

[0019] Examples of hydrocarbons that can be used include straight-chain hydrocarbons such as hexane, isohexane, heptane, octane, nonane, and decane, and cyclic hydrocarbons such as cyclohexane, methylcyclohexane, and ethylcyclohexane.

[0020] Examples of esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, Examples of usable surfactants include methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic acid triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

[0021] The content of these organic solvents is determined in various mixing ratios taking into consideration the miscibility with the pigment, resin, polydimethylsiloxane, and other components to be blended, as well as the intended use of the writing instrument, and is generally about 20 to 80% by mass of the total amount of the oil-based ink composition for writing instruments.

[0022] <Polymethyldimethylsiloxane> The polymethyldimethylsiloxane used in the present invention is a compound represented by the following general formula, and has polyether modifying groups at both ends, i.e., R 1 and R 2 It is a polydimethylsiloxane having a [ka]

[0023] In the present invention, the polyether-modified group refers to, for example, a group having the following polyether structure at least in part: -R1(C2H4O)a(C3H6O)bR2 (In the formula, R1 represents an alkyl group having 1 to 10 carbon atoms, R2 represents hydrogen, an alkyl group having 1 to 50 carbon atoms, or an aryl group, a represents an integer of 1 to 50, and b represents an integer of 1 to 50). At least one of the polyether-modified groups preferably has a multi-branched molecular skeleton, and in particular, the polyether-modified group having a multi-branched molecular skeleton may have the above-mentioned polyether structure in at least one branch. Furthermore, such a polyether-modified group may have hydroxyl groups at all or some of the ends of the branches, so that the polyether-modified group as a whole may have multiple hydroxyl groups. By increasing the number of hydroxyl groups, preferably to three or more, the abrasion resistance of the coating film can be further improved. The atoms constituting the multi-branched molecular skeleton can be all or some of C, Si, O, and H. This multi-branched molecular skeleton can have a plurality of branches, for example, 2 or more, 3 or more, 5 or more, 7 or more, or 10 or more, and 100 or less, 80 or less, 50 or less, or 30 or less. By having this multi-branched molecular skeleton, the number of hydroxyl groups at the ends of the branches can be increased, which can further improve the scratch resistance of the coating film. As such hydroxyl group-containing polyether-modified polydimethylsiloxane, commercially available products such as BYK-Silclean 3720 (number of hydroxyl groups: 3 or more) manufactured by BYK and Protect 5000N (number of hydroxyl groups: 3 or more) manufactured by TEGO can be used.

[0024] The content (solid content) of polyether-modified polydimethylsiloxane having these characteristics is preferably 0.001 to 0.25% by mass, more preferably 0.02 to 0.05% by mass, of the total amount of the oil-based ink composition for writing instruments, from the viewpoints of surface tension and the strength of the ink coating.

[0025] In the present invention, the mass ratio of the pigment (A) to the polydimethylsiloxane (B) [(A) / (B)] is preferably 500 to 1800, more preferably 600 to 1000, from the viewpoints of coating film smoothness and ink repellency on non-absorbent surfaces.

[0026] Furthermore, the oil-based ink composition for a writing instrument of the present invention must further contain polytetrafluoroethylene (PTFE) particles in addition to the above-mentioned pigment, resin, organic solvent, and polydimethylsiloxane, from the viewpoints of abrasion resistance of the coating film and peeling of the coating film. The PTFE particles that can be used preferably have an average particle size of 0.1 μm or more and 0.5 μm or less when measured by dynamic light scattering, from the viewpoints of dispersion stability and coexistence with pigments. The content (solid content) of PTFE particles having these characteristics is preferably 1.0 to 10.0% by mass, more preferably 3.0 to 6.0% by mass, of the total amount of the oil-based ink composition for writing instruments, from the viewpoints of abrasion resistance of the coating film and peeling of the coating film.

[0027] In addition to the above-mentioned components, the oil-based ink composition for a writing instrument of the present invention may contain, for example, a leveling agent such as a phosphate ester surfactant, a rust inhibitor, a preservative, a lubricant, an anti-wear agent, and the like, within a range that does not impair the effects of the present invention.

[0028] The oil-based ink composition for a writing instrument of the present invention must have a TI (Thixotropic index) value (10 rpm / 100 rpm) of 1.15 to 2.00 in cone-plate viscosity measurement, and preferably 1.30 to 1.50. By setting this TI value in the above range of 1.15 to 2.00, it is possible to prevent pigment sedimentation within the pen core and redisperse any pigment that has settled. If this TI value is less than 1.15, sedimentation within the pen core occurs, and new ink must be expelled wastefully when writing again. On the other hand, if the TI value exceeds 2.00, the ink tends to be hard to eject and a high shear force is required to redisperse the pigment, which is undesirable.

[0029] In addition, in the present invention, the surface tension of the oil-based ink composition for a writing instrument at 25°C is preferably 26 mN / m or less, more preferably 22 to 25 mN / m, from the standpoint of coating film smoothness and ink repellency on non-absorbent surfaces. The TI value and surface tension of the oil-based ink composition for writing instruments of the present invention can be adjusted by appropriately combining the types of ingredients used, such as the pigment, resin, organic solvent, and polydimethylsiloxane, as well as the amounts of each ingredient, and by using a suitable kneading machine or the like.

[0030] The oil-based ink composition for a writing instrument of the present invention is prepared by appropriately combining at least the pigment, resin, organic solvent, polydimethylsiloxane, PTFE particles, and other components according to the intended use of the ink for the writing instrument (for a ballpoint pen, a marking pen, etc.), stirring and mixing the resulting mixture with a stirrer such as a homomixer, homogenizer, or disper, and then, if necessary, removing coarse particles from the ink composition by filtration or centrifugation, thereby obtaining the desired oil-based ink composition for a writing instrument.

[0031] The oil-based ink composition for a writing instrument of the present invention thus constructed contains at least a pigment, a resin, an organic solvent, a polydimethylsiloxane, and PTFE particles, and the polydimethylsiloxane has polyether-modified groups at both ends and a TI value (10 rpm / 100 rpm) of 1.15 to 2.00 in cone-and-plate viscosity measurement, thereby providing excellent pigment dispersion stability, suppressing repellency when written on non-absorbent surfaces, and providing excellent adhesion and abrasion resistance of the coating film.

[0032] The writing instrument of the present invention is characterized by being equipped with the oil-based ink composition for a writing instrument having the above-mentioned configuration. The writing instrument of this embodiment includes, for example, at least an ink reservoir, a writing portion, and a holding portion. The ink reservoir stores the oil-based ink composition for a writing instrument. In the present invention, the writing instrument may be a marking pen or a ballpoint pen. Here, in this specification, "marking pen" means a pen that has a mechanism that supplies ink stored in an ink reservoir to a resin writing part (pen tip, etc.) by capillary action, and also includes pens that are referred to by those skilled in the art as "sign pens." Also, in this specification, "ballpoint pen" means a pen that has a mechanism that causes ink stored in an ink reservoir to seep out by the rotation of a ball provided in the writing part. The ink reservoir stores the oil-based ink composition for a writing instrument described above. Any ink reservoir can be used as the ink reservoir as long as it can store ink and supply ink to the writing part. The writing instrument of the present invention, configured in this manner, is equipped with an oil-based ink composition for a writing instrument having the above-described characteristics, and therefore has excellent pigment dispersion stability, suppresses "repellency" when writing on non-absorbent surfaces, and provides excellent adhesion and abrasion resistance of the coating film. Furthermore, in the present invention, as described above, various pigments can be used as the pigment. In particular, when a pigment with a high specific gravity such as titanium oxide is used, there has conventionally been a problem of the pigment settling within the pen tip. However, in a writing instrument equipped with the oil-based ink composition for a writing instrument of the present invention, settling within the pen tip is suppressed, and there is no change in density from the start of writing, allowing for the production of good drawn lines. [Example]

[0033] Next, the present invention will be explained in more detail with reference to Examples 1 to 5 and Comparative Examples 1 to 6 of oil-based ink compositions for writing instruments and writing instruments equipped with the same, but the present invention is not limited to the following examples.

[0034] [Examples 1 to 6 and Comparative Examples 1 to 5 〕 Each oil-based ink composition for a writing instrument was prepared by a conventional method according to the formulation of each pigment, resin, organic solvent, polydimethylsiloxane, polytetrafluoroethylene (PTFE particle) dispersion, and other oil-based ink components for a writing instrument shown in Table 1 below. The resulting oil-based ink compositions for writing instruments were evaluated for surface tension at 25°C, TI value (10 rpm / 100 rpm), stirring ball movement, sedimentation in the pen core, adhesion, and line repellency using the methods described below. The results are shown in Table 1.

[0035] [Method for measuring surface tension] The surface tension (25°C) of each of the resulting oil-based ink compositions for writing instruments was measured using a surface tension measuring device DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0036] (Ink viscosity, TI value calculation method) For each of the oil-based ink compositions for writing instruments obtained, the ink viscosity at 10 rpm (25°C, mPa·s) and at 100 rpm (25°C, mPa·s) were measured using a cone-plate viscometer (TVE-35L, manufactured by Toki Sangyo Co., Ltd., and the ratio of the viscosity at 10 rpm to the viscosity at 100 rpm (TI value) was calculated using these viscosity values. A 3°×R14 cone-plate was used.

[0037] (Method for evaluating dispersion stability) Each of the oil-based ink compositions for writing instruments thus obtained was used to prepare a felt-tip pen having the following components: Product name and model number: PC-5M, manufactured by Mitsubishi Pencil Co., Ltd. Shaft material: Polypropylene (PP) resin Pen core: Nylon, Shape: Double-edged, Porosity: 70-75% Valve mechanism and stirring ball (φ6.4mm, stainless steel) built into the barrel

[0038] A felt-tip pen filled with each oil-based ink composition was left standing with the cap facing upward in an environment at 50°C for 12 weeks (3M), and then the felt-tip pen was shaken. The number of times it was shaken until the stirring ball began to move in the oil-based ink composition (dispersion stability) was evaluated according to the following evaluation criteria. Evaluation criteria: A: 1 to 10 times B: 11~50 times C: 51~100 times or more

[0039] (Evaluation of the degree of settling inside the pen core) After the ink was sufficiently absorbed into the pen tip, the felt-tip pens filled with each oil-based ink composition were stored with the pen tip facing upward in an environment of 25°C for one week. Writing was performed in a spiral manner on an iron plate wiped with ethanol, and the degree of sedimentation within the pen tip was evaluated based on the density of the drawn line according to the following evaluation criteria. Evaluation criteria: A: There was no change in density from the beginning of writing, and the lines were drawn well. B: A decrease in density was observed at the beginning of writing, but the density returned to normal as writing continued. C: The density decreases from the beginning of writing, and does not return to normal even when writing continues.

[0040] (Evaluation of adhesion) Each oil-based ink composition was filled with a felt-tip pen and written on the surface of a polypropylene (PP) film, glass, or polyethylene terephthalate (PET), and the written lines were allowed to dry. The lines were then rubbed with a Kimwipe carrying a 500 g weight and moved five times to evaluate adhesion according to the following criteria. Evaluation criteria: A: After rubbing, the drawn lines did not peel at all. B: After rubbing, the drawn lines peeled off slightly, but most of the drawn lines remained. C: After rubbing, peeling occurred to the extent that no drawn lines remained.

[0041] (Method for evaluating line repellency) Using the above-mentioned felt-tip pen filled with the ink composition obtained above, a PET film that is particularly ink-repellent was selected, and writing was performed on the PET film, and the repelling properties of the written lines were evaluated according to the following evaluation criteria. Evaluation criteria: A: The ink is not repelled at all, and clear written lines are obtained. B: Some repelling is observed. C: Ink is repelled significantly, causing chips in the written lines.

[0042] [Table 1]

[0043] As is clear from the results in Table 1 above, Examples 1 to 3, which fall within the scope of the present invention, 6 The oil-based ink composition for a writing instrument and the writing instrument equipped with the same are Comparative Examples 1 to 3, which are outside the scope of the present invention. 5 It has been confirmed that, compared to the conventional oil-based ink composition, it has excellent dispersion stability, no pigment sedimentation in the pen core, excellent adhesion, and moreover, it produces clear written lines without any repulsion, and that the writing instrument equipped with this ink composition can also be used. Considering the comparative examples individually, Comparative Example 1 does not contain polydimethylsiloxane having polyether-modified groups at both ends, Comparative Example 2 contains polydimethylsiloxane with carbinol-modified groups at both ends, and Comparative Example 3 does not contain PTFE particles. Comparative Examples 4 and 5 It was confirmed that the TI values ​​were outside the range of the present invention, and in these cases the effects of the present invention could not be achieved. [Industrial Applicability]

[0044] An oil-based ink composition for writing instruments suitable for felt-tip pens, marking pens, etc., and writing instruments such as felt-tip pens and marking pens loaded with this ink composition can be obtained.

Claims

1. An oil-based ink composition for a writing instrument, comprising at least a pigment, a resin, an organic solvent, polydimethylsiloxane, and polytetrafluoroethylene particles, wherein the polydimethylsiloxane has polyether-modified groups at both ends, and the TI value (10 rpm / 100 rpm) of the oil-based ink composition for a writing instrument is 1.15 to 2.00 in a cone-plate viscosity measurement.

2. 2. The oil-based ink composition for a writing instrument according to claim 1, wherein the mass ratio of the pigment (A) to the polydimethylsiloxane (B) [(A) / (B)] is 500 to 2,200.

3. 3. The oil-based ink composition for a writing instrument according to claim 1, wherein the ink composition has a surface tension of 26 mN / m or less at 25[deg.] C.

4. A writing instrument equipped with the oil-based ink composition for writing instruments according to any one of claims 1 to 3.

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