Oil-based ink composition and writing instrument

Abstract

Provided is an oil-based ink composition containing a pigment, an organic solvent, and a vinyl polymer or an acrylic polymer. The organic solvent contains glycol ether as a main solvent. The content of the polymer in the oil-based ink composition is 0.01 wt. % or more and 5.0 wt. % or less.

Description

Oil-based ink composition and writing instrument

[0001] The present disclosure relates to an oil-based ink composition and a writing instrument.

[0002] There are cases where writing is done on the surface of a metal (such as industrial parts) to which oil such as cutting oil adheres, using a writing instrument (such as an oil-based marker) that forms handwriting with an oil-based ink composition.

[0003] For example, in Patent Document 1, as an oil-based ink composition for a writing instrument capable of forming good handwriting without repulsion on writing surfaces of various materials, an ink composition containing a colorant, an organic solvent whose main solvent is ethanol, a resin, and an acrylic-silicone graft copolymer is described.

[0004] In Patent Document 2, as a marking ink composition capable of forming a clear image on a metal surface to which oil adheres, an ink composition containing a colorant, a resin, and one or more solvents selected from alcohols, glycol ethers, and esters is described.

[0005] In Patent Document 3, as an ink composition for an oil-based marking pen excellent in writing properties on an oil film, an ink composition containing a solvent component containing an alcohol having 2 to 4 carbon atoms, an alkali-soluble resin, and a basic dye is described.

[0006] Japanese Patent Application Laid-Open No. 2008-169321, Japanese Patent Application Laid-Open No. 2006-104364, Japanese Patent Application Laid-Open No. 2021-191847

[0007] In conventional oil-based ink compositions, when writing on a metal surface (writing surface) to which oil adheres, the ink may spread into the oil instead of reaching the writing surface, making the handwriting unreadable, or the pigments in the ink may aggregate on the writing surface, resulting in a lack of good handwriting.

[0008] In view of the above circumstances, at least one embodiment of the present invention aims to provide an oil-based ink composition and a writing instrument with good writing properties on a metal surface to which oil adheres.

[0009] An oil-based ink composition according to at least one embodiment of the present invention is an oil-based ink composition comprising a pigment, an organic solvent, and a polymer containing a vinyl polymer or an acrylic polymer, wherein the organic solvent contains glycol ether as the main solvent, and the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less.

[0010] Furthermore, a writing instrument according to at least one embodiment of the present invention comprises: an ink storage section in which the above-mentioned oil-based ink composition is contained; and a writing section configured to receive the oil-based ink composition from the ink storage section.

[0011] According to at least one embodiment of the present invention, an oil-based ink composition and a writing instrument are provided that exhibit good writing properties on oil-covered metal surfaces.

[0012] This is a schematic cross-sectional view of a marking pen, which is a writing instrument according to one embodiment.

[0013] Hereinafter, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0014] (Oil-based ink composition) An oil-based ink composition according to several embodiments comprises a pigment, an organic solvent, and a polymer containing a vinyl polymer or an acrylic polymer, wherein the organic solvent contains glycol ether as the main solvent, and the content of the polymer (vinyl polymer or acrylic polymer) in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less.

[0015] In this specification, the main solvent refers to the component that is present in the largest quantity among the organic solvents.

[0016] In the above-described embodiment, since the organic solvent in the oil-based ink composition contains glycol ether as the main solvent, when writing on a metal surface (writing surface) with oil on it, the ink repels the oil film on the metal surface and reaches the metal surface, thus forming a highly legible writing line.

[0017] Furthermore, in the above-described embodiment, since the content of vinyl polymer or acrylic polymer in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less, the surface tension of the oil-based ink composition is moderately low, allowing the ink to spread appropriately on the metal surface while suppressing pigment aggregation. That is, since the content of vinyl polymer or acrylic polymer is 0.01% by weight or more, the aggregation of pigment can be suppressed by lowering the surface tension of the oil-based ink composition, thus preventing the formation of shrunken writing. Also, since the content of vinyl polymer or acrylic polymer is 5.0% by weight or less, the surface tension of the oil-based ink composition is not excessive, so the aggregation of pigment due to the vinyl polymer or acrylic polymer spreading before the pigment can be suppressed, thus preventing the formation of shrunken writing. Therefore, when writing on an oil-covered metal surface, the ink can spread appropriately on the metal surface while suppressing the aggregation of pigment contained in the ink, resulting in the formation of good writing.

[0018] Therefore, according to the above embodiment, a writing instrument with good writing performance on oily metal surfaces can be obtained.

[0019] Furthermore, conventional oil-based ink compositions often have poor drying properties, which can cause some or all of the marking to be erased by rubbing, making it impossible to verify the marking. Alternatively, the pen tip can dry out easily, requiring the writing instrument to be capped each time a mark is made to prevent the tip from drying out, thus reducing work efficiency.

[0020] In this regard, in the above-described embodiment, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, the leveling properties of the ink composition can be improved. As a result, the ink film formed on the writing surface tends to be more uniform, and the solvent evaporates more easily, resulting in good drying properties of the ink.

[0021] Furthermore, in the above-described embodiment, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, a fragile film is formed on the pen tip surface. Additionally, since the oil-based ink composition contains glycol ether, the fusion between the vinyl polymer or acrylic polymer and the pen tip is promoted, resulting in a more uniform film thickness. As a result, the film formed on the pen tip surface prevents the pen tip from drying out, and even when writing again after the first writing, the film breaks easily, allowing for the formation of appropriate handwriting.

[0022] Therefore, according to the above-described embodiment, it is possible to achieve both quick drying of the writing and resistance to drying of the pen tip.

[0023] Some oil-based ink compositions according to certain embodiments include a pigment as a coloring agent.

[0024] Common pigments that can be used include inorganic pigments such as ochre, barium yellow, Prussian blue, cadmium red, barium sulfate, titanium dioxide, iron oxide, iron black, and carbon black; insoluble azo pigments; azo lake pigments; condensed azo pigments; diketopyrrolopyrrole pigments; phthalocyanine pigments; quinacridone pigments; isoindolinone pigments; isoindoline pigments; anthraquinone pigments; dioxazine pigments; indigo pigments; thioindigo pigments; quinophthalone pigments; benzoguanamine pigments; perinone; perylene pigments; and other organic pigments. These can be used individually or in combination of two or more pigments.

[0025] Specific examples of pigments include carbon black such as C.I. Pigment BLACK 6 and 7, C.I. Pigment Blue 2, 9, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17, 28, 29, 36, 60, 68, 76, 80, etc., and C.I. Pigment Red 2, 3, 5, 8, 14, 17, 22, 23, 31, 48:1, 48:2, 48:3, 48:4, 53:1, 53:2, 57:1, 112, 122, 144, 146, 149, 166, 170, 175, 176, 177, 179, 184, 185, 187, 188, 202, 207, 208, 209, 210, 211, 213, 214, 242, 253, 254, 255, 256, 257, 264, 266, 268, 270, 272, etc., C.I. Pigment Yellow 1, 3, 12, 13, 14, 16, 17, 55, 73, 74, 79, 81, 83, 93, 94, 95, 97, 109, 110, 111, 120, 128, 133, 136, 138, 139, 147, 151, 154, 155, 167, 173, 174, 175, 176, 180, 185, 191, 194, 213, etc., C. I. Pigment Orange 5, 13, 16, 34, 36, 38, 43, 62, 68, 72, 74, etc., C.I. Pigment Green 7, 36, 37, etc., C.I. Pigment Violet 19, 23, etc. can be used.

[0026] Other examples of pigments include inorganic fluorescent pigments such as zinc sulfide, zinc silicate, zinc cadmium sulfate, calcium sulfide, strontium sulfide, and calcium tungstate, as well as other known organic fluorescent pigments. Examples of organic fluorescent pigments include FM-103 Red, FM-105 Lemon Yellow, FM-107 Pink, and FM-109 White (manufactured by Shinloihi Co., Ltd.).

[0027] As materials for the oil-based ink composition, the above pigments may be pre-mixed in a roll mill or the like using a nitrocellulose resin, a nitrocellulose plasticizer, and, if necessary, a dispersant to create color chips or an oil-based ink base dispersed in a solvent. Various conventionally known dispersants can be used for the pigments in the oil-based ink composition. Specific examples of color chips include NC896 BLACK, NC180 RED, NC588 BLUE, NC383 YELLOW, L1 / 8 Violet PRL (50), and NC783 WHITE (manufactured by Taihei Chemical Products Co., Ltd.).

[0028] Commercially available dispersed pigments may also be used. Specific examples include FUJI PGM WHITE 1078, prototype 6-12-2, FUJI PGM BLACK prototype 10-10-1, prototype 10-10-2, prototype 10-2-1, prototype 10-4-10, prototype 6-3-2, FUJI PGM RED prototype 4-25-6, FUJI PGM BLUE prototype 10-10-3, prototype 11-18-3, and prototype 11-21-1 (all manufactured by Fuji Pigment Co., Ltd.).

[0029] As glycol ethers, which are the main solvents in organic solvents, for example (the numbers in parentheses below are SP values), ethylene glycol monomethyl ether (12.11), ethylene glycol monoethyl ether (11.4), ethylene glycol monoisopropyl ether (10.6), ethylene glycol monobutyl ether (10.52), propylene glycol monomethyl ether (11.06), propylene glycol monoethyl ether (10.6), propylene glycol monopropyl ether (10.27), propylene glycol monobutyl ether (10), 3-methoxy-3-methyl-1-butanol (10.09), ethylene glycol monohexyl ether (10), ethylene glycol monophenyl ether (11.99), ethylene glycol diethyl ether (8.38), diethylene glycol monoethyl ether (10.87), diethylene glycol monophenyl ether (11.41), propylene glycol monophenyl ether (11.28), dipropylene glycol monoethyl ether (9.9), dipropylene glycol monophenyl ether (10.49), Tripropylene glycol monomethyl ether (9.68), Tripropylene glycol monoethyl ether (9.55), Tripropylene glycol monophenyl ether (10.33), Ethylene glycol monopropyl ether (10.9), Dipropylene glycol monomethyl ether (10.12), Diethylene glycol monomethyl ether (11.27), Diethylene glycol monopropyl ether (10.55), Diethylene glycol monobutyl ether (10.29), Ethylene glycol dimethyl ether (8.53), Ethylene glycol dibutyl ether (8.23), Ethylene glycol monomethoxymethyl ether (11.81), Diethylene glycol ethyl methyl ether (8.71), Diethylene glycol diethyl ether (8.64), Diethylene glycol dibutyl ether (8.44), Diethylene glycol dimethyl ether (8.8), Dipropylene glycol monobutyl ether (9.58), Dipropylene glycol monopropyl ether (9.73), Triethylene glycol dimethyl ether (8.95),Triethylene glycol monoethyl ether (10.57), triethylene glycol monomethyl ether (10.84), propylene glycol monomethyl ether acetate (8.84), etc. can be used.

[0030] The organic solvent may contain organic solvents other than glycol ether (the main solvent). Such organic solvents may include alkylene glycols such as ethylene glycol (19.16) or propylene glycol (16.05), aromatic hydrocarbons such as ethylbenzene (8.83) or xylene (8.69), cyclic hydrocarbons such as ethylcyclohexane (8.68), esters such as butyl acetate (8.64), alcohols such as ethanol (12.66), and the like.

[0031] The content of organic solvent in the oil-based ink composition may be 40% by weight or more and 80% by weight or less.

[0032] The SP value of the glycol ether contained as the main solvent in the oil-based ink composition may be 8.9 or more and 12.2 or less, 9.5 or more and 12.0 or less, or 9.5 or more and 11.1 or less.

[0033] If the SP value of the main solvent, glycol ether, is 8.9 or higher or 9.5 or higher, the organic solvent's affinity for oil is not excessive, thus suppressing the spread of the organic solvent onto the oil film adhering to the metal surface (writing surface). Furthermore, if the SP value of the main solvent, glycol ether, is 12.2 or lower, 12.0 or lower, or 11.1 or lower, the surface tension of the organic solvent does not tend to increase, thus suppressing the formation of droplets by repelling the ink composition containing the organic solvent on the metal surface or oil film. Therefore, the above-described oil-based ink composition makes it easy to form good writing marks on oil-adhered metal surfaces.

[0034] The content of glycol ether (main solvent) in the organic solvent may be 70% by weight or more and 100% by weight or less.

[0035] Glycol ethers have high drying properties. Therefore, as mentioned above, if the glycol ether content in the organic solvent is 70% by weight or more, the drying properties of the ink produced by the oil-based ink composition tend to be good.

[0036] Furthermore, glycol ether functions as a film-forming aid in oil-based ink compositions. Therefore, as mentioned above, if the glycol ether content in the organic solvent is 70% by weight or more, a fragile film of vinyl polymer or acrylic polymer is more likely to form on the pen tip surface. This tends to improve the pen tip's drying resistance.

[0037] As described above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less. In some embodiments, it may be 0.01% by weight or more and 1.0% by weight or less, 0.01% by weight or more and 0.60% by weight or less, greater than 0.60% by weight and 1.0% by weight or less, or greater than 1.0% by weight and 5.0% by weight or less.

[0038] If the content of the aforementioned vinyl polymer or acrylic polymer is 0.01% by weight or more, the aggregation of pigment can be suppressed by reducing the surface tension of the oil-based ink composition, thereby preventing the formation of shrunken handwriting. Furthermore, if the content of the aforementioned vinyl polymer or acrylic polymer is 5.0% by weight or less, or 1.0% by weight or less, the surface tension of the oil-based ink composition will not be excessive, so the aggregation of pigment due to the vinyl polymer or acrylic polymer spreading before the pigment can be suppressed, thereby preventing the formation of shrunken handwriting.

[0039] Furthermore, if the content of the vinyl polymer or acrylic polymer is 0.01% by weight or more and 0.60% by weight or less, it is possible to obtain handwriting on an oil-covered metal surface (writing surface) that is equivalent to that on a metal surface without oil. If the content of the vinyl polymer or acrylic polymer is greater than 0.60% by weight and 1.0% by weight or less, it is possible to obtain handwriting on an oil-covered metal surface (writing surface) that allows the handwriting and characters to be clearly visible. If the content of the vinyl polymer or acrylic polymer is greater than 1.0% by weight and 5.0% by weight or less, it is possible to obtain handwriting on an oil-covered metal surface (writing surface) that allows the markings such as dots and lines to be clearly visible.

[0040] In some embodiments, the vinyl polymer or acrylic polymer may contain silicone. That is, a silicone chain may be included in the vinyl polymer or acrylic polymer.

[0041] According to the above embodiments, since the vinyl polymer or acrylic polymer contains silicone, the drying property of the handwriting is likely to be good, or the dryness resistance of the pen tip is likely to be good. Therefore, it becomes easier to achieve both good drying property of the handwriting and good dryness resistance of the pen tip.

[0042] Specific examples of the vinyl polymer include Disparon LHP-90 (active ingredient 50%) or Disparon LHP-91 (containing silicone, active ingredient 50%) (both manufactured by Nanben Kasei Co., Ltd.), etc. Here, the active ingredient refers to the content (weight) of the vinyl polymer or acrylic polymer in all components of the product including the dispersion medium, etc. (the same applies hereinafter).

[0043] The acrylic polymer may be an acrylic polymer, an acrylic copolymer, an acrylic polymer silicone, or an acrylic silicone polymer.

[0044] Specific examples of the acrylic polymer include Disparon LF-1980 (active ingredient 50%), Disparon LF-1982 (active ingredient 50%), Disparon LF-1983 (active ingredient 50%), Disparon LF-1984 (active ingredient 50%), Disparon LF-1985 (active ingredient 50%), Disparon UVX-35 (active ingredient 100%), Disparon UVX-36 (active ingredient 100%), Disparon LHP-95 (active ingredient 50%), Disparon SEI-1501 (active ingredient 100%), or Disparon SPL-85 (active ingredient 50%) (all manufactured by Nanben Kasei Co., Ltd.), etc.

[0045] Specific examples of acrylic copolymers include BYK-350 (active ingredient 100%), BYK-354 (active ingredient 51%), BYK-355 (active ingredient 52%), BYK-356 (active ingredient 98% or more), BYK-358N (active ingredient 52%), BYK-361N (active ingredient 98% or more), BYK-359 (active ingredient 100%), BYK-392 (active ingredient 52%), BYK-394 (active ingredient 80%), or BYK-3441 (active ingredient 52%) (manufactured by BYK Chemie Japan Co., Ltd., etc.).

[0046] Specific examples of acrylic polymer silicones include Disparon LHP-96 (silicone-containing, active ingredient 50%) (manufactured by Enomoto Kasei Co., Ltd., etc.).

[0047] Specific examples of acrylic silicone polymers include Disparon UVX-272 (silicone-containing, active ingredient 100%), Disparon UVX-2285 (silicone-containing, active ingredient 50%), Disparon LHP-810 (silicone-containing, active ingredient 10%), or Disparon NSH-8430HF (silicone-containing, active ingredient 10%) (manufactured by Enomoto Kasei Co., Ltd., etc.).

[0048] In some embodiments, the oily ink composition may further contain a rosin derivative.

[0049] In the above embodiments, since the oily ink composition contains a rosin derivative, the rosin derivative is oriented at the interface between the ink composition and the metal surface, so the affinity between the oily ink composition and the metal surface is improved. Also, since the rosin derivative is poorly soluble in oil, it has the effect of repelling oil at the interface between the oily ink composition and the metal surface. Therefore, the fixing property of the oily ink composition to the metal surface with oil attached can be improved.

[0050] Furthermore, when the oil-based ink composition contains a rosin derivative, the glycol ether, which functions as a film-forming aid, lowers the glass transition temperature of the rosin derivative. This promotes the fusion of the vinyl polymer or acrylic polymer with the pen tip, resulting in a more uniform film thickness of the vinyl polymer or acrylic polymer. Consequently, even when writing again after the initial writing, the aforementioned film breaks easily, making it easier to form a proper handwriting pattern. In other words, good pen tip drying resistance is easily achieved.

[0051] The content of the rosin derivative in the oil-based ink composition may be 1% by weight or more and 30% by weight or less. If the content of the rosin derivative is 1% by weight or more, the affinity between the oil-based ink composition and the metal surface can be appropriately improved, or the fusion between the vinyl polymer or acrylic polymer and the pen tip can be effectively promoted. If the content of the rosin derivative is 30% by weight or less, the affinity between the oil-based ink composition and the oil will not decrease too much, so the formation of shrunken lines can be suppressed.

[0052] The rosin derivative may include rosin-modified phenolic resin, disproportionated rosin ester, rosin, rosin ester, polymerized rosin, hydrogenated rosin ester, disproportionated rosin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, rosin-modified special synthetic resin, polymerized rosin ester, rosin metal soap, rosin alkali soap, maleated rosin, or rosin-modified alkyd resin.

[0053] Specific examples of rosin-modified phenolic resins include Tamanol 135, KG-837, Tamanol 386, Tamanol 901 (all manufactured by Arakawa Chemical Industries, Ltd.), Hariphenol P-160, or Hariphenol T3120 (all manufactured by Harima Chemicals, Ltd.).

[0054] A specific example of a disproportionated rosin ester is Pinecristel D-6011 (manufactured by Arakawa Chemical Industries, Ltd.).

[0055] Specific examples of rosin include Pinecristel KE-604, Pinecristel KR-85, or Pinecristel KR-120 (all manufactured by Arakawa Chemical Industries, Ltd.).

[0056] Specific examples of rosin esters include Pine Cristel KE-359, Pine Cristel KR-100, Pine Cristel KR-311, Super Ester A-75, Super Ester A-100, Super Ester A-115, Super Ester A-125, Ester Gum AA-L, Ester Gum AA-V, Ester Gum AA-G (all manufactured by Arakawa Chemical Industries, Ltd.), or Haritack ER95 (all manufactured by Harima Chemicals, Ltd.).

[0057] A specific example of polymerized rosin is Pinecristel KR-140 (manufactured by Arakawa Chemical Industries, Ltd.).

[0058] A specific example of maleated rosin is Marquid No. 3002 (manufactured by Arakawa Chemical Industries, Ltd.).

[0059] Specific examples of rosin-modified maleic acid resins include Marquid No. 1, Marquid No. 2, Marquid No. 5, Marquid No. 6, Marquid No. 8, Marquid No. 32 (all manufactured by Arakawa Chemical Industries, Ltd.), Harimac T-80, Harimac R-100, Harimac M-453, Harimac M-130A, or Harimac 145P (all manufactured by Harima Chemicals, Ltd.).

[0060] Specific examples of rosin-modified fumaric acid resins include Marquid No. 31 or Marquid No. 33 (both manufactured by Arakawa Chemical Industries, Ltd.).

[0061] Specific examples of rosin-modified special synthetic resins include Harimac R-80, Harimac AS-5, Hariester AD-130, Hariester MSR-4, Haritac F-75, or Haritac FG-90, Haritac AQ-90A (all manufactured by Harima Chemicals Co., Ltd.).

[0062] A specific example of a polymerized rosin ester is Haritack PCJ (manufactured by Harima Chemicals, Inc.).

[0063] Specific examples of modified rosin esters include Haritack 4821, Haritack 4740, or Haritack 28JA (all manufactured by Harima Chemicals Co., Ltd.).

[0064] Specific examples of hydrogenated rosin esters include ester gum H or ester gum HP (both manufactured by Arakawa Chemical Industries, Ltd.).

[0065] In some embodiments, the oil-based ink composition may contain a plasticizer. The inclusion of a plasticizer in the oil-based ink composition can provide appropriate flexibility and viscosity, resulting in good handwriting.

[0066] The plasticizer content in the oil-based ink composition may be 0.02% by weight or more and 3.0% by weight or less.

[0067] The plasticizer may include, for example, citrate compounds such as acetyl tributyl citrate, acetyl triethyl citrate, triethyl citrate, tributyl citrate, or tris acetylcitrate, or acetyl citrate compounds.

[0068] Furthermore, a thickening agent may be added to adjust the viscosity of the oil-based ink composition. Adding a thickening agent to the oil-based ink composition can suppress leakage and streaking, resulting in better handwriting. Any thickening agent with a thickening effect can be used. Specifically, examples include Aerosil R972, R974, and R974 (all manufactured by Nippon Aerosil Co., Ltd.), Esrec BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-S, BX-L, BM-1, BM-2, BM-5, BM-S, BH-3, BH-6, BH-S, BX-1, BX-5, KS-10, KS-1, KS-3, and KS-5 (all manufactured by Sekisui Chemical Co., Ltd.), RHEOBY K410, 430, and 431 (all manufactured by BIC Chemie Japan Co., Ltd.), and aluminum silicate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0069] Various conventional methods can be used to manufacture the writing instrument ink of the present invention. For example, the above components can be blended and mixed and dispersed using a high-speed agitator such as a homomixer or lab mixer, a disperser such as a ball mill, sand mill or bead mill, or a stirrer.

[0070] (Writing Instrument Configuration) Figure 1 is a schematic cross-sectional view of a marking pen 1, which is a writing instrument according to one embodiment. The marking pen 1 according to this embodiment includes a container 2 (ink storage section) that contains an application liquid (oil-based ink composition), and an applicator 5 (writing section) to which the oil-based ink composition is supplied from the container 2. The marking pen 1 also includes a front shaft 3. The front shaft 3 serves as a base for arranging various components such as a valve mechanism. The applicator 5 includes at least a liquid absorbent material. When the valve of the valve mechanism is opened by the user's operation, a supply passage opens for supplying the ink composition from the inside of the container 2 (the ink composition storage space) to the applicator 5, and the ink composition from the container 2 is supplied to the applicator 5 through the supply passage.

[0071] Container 2 in Figure 1 is a bottomed cylindrical container with an open front end. Container 2 may be made of a flexible thermoplastic resin material so that the coating liquid can be dispensed by pressing its sides. Examples of thermoplastic resin materials include nylon 6, low-density polyethylene, polypropylene, polyethylene terephthalate, and polyarylate, taking into consideration factors such as ease of pressing the container and reactivity with the coating liquid. Recycled materials of the aforementioned thermoplastic resin may also be used. Methods for molding the flexible container include direct blow molding, multilayer blow molding, injection blow molding, and injection molding.

[0072] The container 2 is not limited to this example; it may be made of a rigid material that does not have flexibility. Examples include high-density polyethylene, polyethylene naphthalate, polyacrylonitrile, and metals.

[0073] Furthermore, the inside of this container 2 serves as a coating liquid storage chamber. The coating liquid storage chamber contains a stirring member 9. The role of the stirring member 9 is to redisperse settled pigments when a coating liquid with settling properties, such as pigments, is filled into the container. Although two stirring members 9 are shown in the illustration, the number can be appropriately selected according to the type of ink used and the size of the container. The shape of the stirring member may also be spherical, cylindrical, cylindrical with chamfered ends, or hemispherical. The material of the stirring member may be a metal or high-density polymer with a higher specific gravity than the ink it contains, or a thermoplastic resin containing metal powder.

[0074] A roughly cylindrical front shaft 3 is attached to the opening of the container 2, extending through it from front to back so as to screw into the container 2. The front shaft 3 includes a single-tube front section at the front and a double-tube outer section and inner section at the rear. A flat plate-like section is provided from the tip of the inner section of the front shaft 3 toward the axis, and the axis of this flat plate-like section is open. A valve seat 3a is provided so as to widen to the rear in a funnel shape from the rear end of this opening.

[0075] A spring valve 8 is provided inside the inner cylinder portion of the front shaft 3. The spring valve 8 is composed of a spring portion 8a and a valve portion 8b. The spring portion 8a has an elastic function. The valve portion 8b is a component of the valve mechanism. The rear end of the spring valve 8 is coupled to the rear end of the inner cylinder portion of the front shaft 3 in an interlocking manner. The spring valve 8 has a front cylinder portion at its tip with a closed front end. A valve portion forming a spherical surface is provided behind the front cylinder portion. An enlarged middle cylinder portion is provided behind the valve portion. By pressing the valve portion 8b, which is biased by the spring portion 8a of the spring valve 8, against the valve seat portion 3a of the front shaft 3, an openable and closable valve mechanism is formed.

[0076] The synthetic resin constituting the spring valve 8 is either a thermoplastic resin or a thermosetting resin, with thermoplastic resins being particularly preferred due to their ease of injection molding. Examples of thermoplastic resins include polyolefin resins such as polypropylene and polyethylene, saturated polyester resins, polycarbonate resins, thermoplastic polyurethane resins, polyacetal resins, and polyamide resins. Examples of thermosetting resins include epoxy resins, phenolic resins, unsaturated polyester resins, and melamine resins. Note that for thermoplastic resins, the set load decreases due to the creep phenomenon of the resin, so it is necessary to select materials and dimensions that take this into consideration.

[0077] A coating material holding cylinder 4 is attached to the front opening of the front shaft 3. The coating material holding cylinder 4 is roughly cylindrical in shape, extending from front to back and protruding from the front end of the front shaft 3. A coating material 5 is inserted into the tip opening of this coating material holding cylinder 4. The coating material 5 is inserted so that its front portion protrudes. The role of the coating material 5 is to guide out the coating liquid. The coating material 5 can be appropriately selected from fiber bundles such as acrylic fibers, polyester fibers, nylon fibers, and rayon-based fibers, or molded products such as urethane-based resins, polyester-based resins, and nylon-based resins.

[0078] A cylindrical coating liquid absorber 6 is positioned on the rear inner surface of the coating body holding cylinder 4. The coating body 5 is inserted into the front of this coating liquid absorber 6. The role of the coating liquid absorber 6 is to prevent the coating liquid from dripping from the coating body 5 and to supply the coating liquid absorbed by the coating liquid absorber 6 to the coating body 5. The shape of the coating liquid absorber 6 is cylindrical. The material of the coating liquid absorber 6 is an elastic porous material. Examples of elastic porous materials include urethane sponge and wool.

[0079] The cap 7 is a cap equipped with a clip function. The cap 7 can be easily attached to and detached from the front shaft 3. When not in use, the coating body 5 can be protected by attaching the cap 7. There is an airtight portion 10 at the contact point between the front shaft 3 and the cap 7. In the airtight portion 10, the entire circumference of the outer circumference of the opening tip of the front shaft 3 and the entire circumference rib inside the cap 7 are in contact. By bringing the entire circumference of the outer circumference of the opening tip of the front shaft 3 and the entire circumference rib inside the cap 7 into contact, airtight sealing is achieved. The role of the airtight portion 10 is to prevent the coating liquid held in the coating body 5, etc., from drying out.

[0080] The marking pen of the present invention is not limited to the structure of the marking pen 1 shown in the figure. The marking pen of the present invention may have various conventional structures, for example, a raw ink type marking pen. A raw ink type marking pen may be an applicator comprising, for example, a coating liquid storage chamber (ink storage section), an applicator body equipped with a temporary ink reservoir member and a fiber bundle (writing section), and a cap that can be attached to the applicator body. The temporary ink reservoir member has a comb-like cross-sectional shape that allows it to temporarily store ink. The role of the temporary ink reservoir member is to prevent ink leakage and to adjust the amount of ink dispensed. A raw ink type marking pen may also be an applicator comprising, for example, a barrel containing an ink absorbent, an applicator body formed by connecting a porous applicator to the ink absorbent, and a cap that can be attached to the applicator body.

[0081] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0082] As shown in Tables 1 to 14, oil-based ink compositions for Examples 1 to 130 and Comparative Examples 1 to 9 were prepared. The materials used are as follows. Tables 1 to 4 show the content (weight %) of each material in the ink composition.

[0083] <Colorants> Pigment (1): Color Chip NC896 BLACK (C.I. Pigment Black 7, 45% pigment content, manufactured by Taihei Chemical Products Co., Ltd.) Pigment (2): Color Chip NC180 RED (C.I. Pigment Red 170, 45% pigment content, manufactured by Taihei Chemical Products Co., Ltd.) Pigment (3): Color Chip NC588 BLUE (C.I. Pigment Blue 15:4, 45% pigment content, manufactured by Taihei Chemical Products Co., Ltd.) Pigment (4): Color Chip NC383 YELLOW (C.I. Pigment Yellow 83, 45% pigment content, manufactured by Taihei Chemical Products Co., Ltd.) Pigment (5): Color Chip NC783 WHITE (Titanium dioxide, 75% pigment content, manufactured by Taihei Chemical Products Co., Ltd.) Pigment (6): FM-107 Pink (benzoguanamine pigment, 99.9% pigment content, manufactured by Shinloihi Co., Ltd.) Pigment (7): FUJI PGM WHITE 1078 (titanium dioxide, 40% pigment content, 55% PGM, manufactured by Fuji Pigment Co., Ltd.) Pigment (8): FUJI PGM BLACK Prototype 10-4-10 (C.I. Pigment Black 7, 20% pigment content, 68% PGM, manufactured by Fuji Pigment Co., Ltd.) Pigment (9): FUJI PGM BLACK Prototype 6-3-2 (C.I. Pigment Black 7, titanium dioxide, 22.5% pigment content, 75% PGM, manufactured by Fuji Pigment Co., Ltd.) Pigment (10): FUJI PGM RED Prototype 4-25-6 (C.I. Pigment Red 254, Titanium Dioxide, Pigment Content 25%, PGM 72%, manufactured by Fuji Pigment Co., Ltd.) Pigment (11): FUJI PGM BLUE Prototype 11-18-3 (C.I. Pigment Blue 15:3, Titanium Dioxide, Pigment Content 30%, PGM 67%, manufactured by Fuji Pigment Co., Ltd.) Dye (1): NIGROSINE BASE EEF (manufactured by Orient Chemical Industry Co., Ltd.)

[0084] <Organic Solvents> Solvent (1): Propylene glycol monomethyl ether (SP value: 11.06) Solvent (2): Tripropylene glycol monoethyl ether (SP value: 9.55) Solvent (3): Ethylene glycol monophenyl ether (SP value: 11.99) Solvent (4): Triethylene glycol dimethyl ether (SP value: 8.95) Solvent (5): Ethylene glycol monomethyl ether (SP value: 12.11) Solvent (6): Ethanol (SP value: 12.66) Solvent (7): Xylene (SP value: 8.69)

[0085] <Activating Agents> Polymer (1): Disparon LHP-91 (Vinyl polymer, silicone-containing, active ingredient: 50%, manufactured by Kusumoto Chemical Co., Ltd.) Polymer (2): Disparon UVX-2285 (Acrylic silicone polymer, silicone-containing, active ingredient: 50%, manufactured by Kusumoto Chemical Co., Ltd.) Polymer (3): Disparon LHP-90 (Vinyl polymer, silicone-free, active ingredient: 50%, manufactured by Kusumoto Chemical Co., Ltd.) Polymer (4): Disparon LF-1985 (Acrylic polymer, silicone-free, active ingredient: >98%, manufactured by Kusumoto Chemical Co., Ltd.) Activating Agent (1): BYK-333 (Polyether-modified polydimethylsiloxane, silicone-containing, active ingredient: 50%, manufactured by Bic Chemie Japan Co., Ltd.)

[0086] <Resins> Rosin derivative (1): Marquid No. 8 (Rosin-modified maleic acid resin, manufactured by Arakawa Chemical Co., Ltd.) Rosin derivative (2): Marquid No. 32 (Rosin-modified maleic acid resin, manufactured by Arakawa Chemical Co., Ltd.) Rosin derivative (3): Harimac M-453 (Rosin-modified maleic acid resin, manufactured by Harima Chemicals Co., Ltd.) Rosin derivative (4): Harimac M-130A (Rosin-modified maleic acid resin, manufactured by Harima Chemicals Co., Ltd.) Rosin derivative (5): Pinecristel D-6011 (Disproportionated rosin ester, manufactured by Arakawa Chemical Co., Ltd.) Resin (1): YS Polystar K125 (Terpene phenol resin, manufactured by Yasuhara Chemical Co., Ltd.)

[0087] <Plasticizers> Plasticizer (1): ATBC (Acetyl tributyl citrate, manufactured by Taoka Chemical Industry Co., Ltd.) Plasticizer (2): ATEC (Acetyl triethyl citrate, manufactured by Hikawa Sangyo Co., Ltd.)

[0088] <Thickening Agent> Thickening agent (1): Esrec BL-1 (Polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd.)

[0089] (Preparation of oil-based ink compositions) The materials shown in Tables 1 to 14 were mixed and stirred overnight with a stirrer to obtain the oil-based ink compositions of Examples 1 to 130 and Comparative Examples 1 to 9.

[0090] (Preparation of test marking pens) The ink was removed from the container of a Pentel MMP20 medium-tip paint marker (direct-ink type marking pen) manufactured by Pentel Co., Ltd., and the prepared oil-based ink composition was filled into it. The ink was thoroughly permeated into the pen tip to obtain test marking pens.

[0091] (Oil-coated surface writing performance test) Oil (Reliacut FM10, ENEOS) was applied to the lower half of one side of a steel plate (polished steel plate, ESCO, part number: EA441VG-62, material: steel (SPCC)) using a bar coater (Select-Roller L16, OSP-42, OSG System Products Co., Ltd.). The steel plate was then fixed in a vertical position and left to stand at 50°C for 30 minutes. The steel plate was then placed horizontally, and a test marking pen was used to draw a straight line three times in a single stroke from the uncoated part to the oiled part on one side of the steel plate. After the ink was dried, the width of each straight line was measured at five points using a microscope (digital microscope: VHX-7000, manufactured by Keyence), and the average value of the ratio (W1 / W2) between the ink width W1 in the coated area and the ink width W2 in the uncoated area was calculated. Tables 1 to 14 show the average values ​​of the ratio (W1 / W2) calculated for each example and comparative example.

[0092] (Adhesion Test) Oil (ReliaCut FM10, ENEOS) was applied to the surface of a steel plate (polished steel plate, ESCO, part number: EA441VG-62, material: steel (SPCC)) using a bar coater (Select-Roller L16, OSP-42, OSG System Products Co., Ltd.). Then, five times in a spiral pattern was written on the oiled steel plate using a test marking pen. After drying, the surface was wiped 10 times in one direction with tissue paper to check the degree of ink removal. The evaluation criteria are as follows. Tables 1 to 14 show the evaluation criteria for each example and comparative example. A: No peeling of the ink after wiping. B: Slight peeling of the ink after wiping, but the ink remains almost intact. C: After wiping, the ink peels off and is not visible as ink.

[0093] (Handwriting drying test) On the surface of a steel plate (polished steel plate, manufactured by ESCO, part number: EA441VG-62, material: steel (SPCC)) (without oil coating), five consecutive spiral handwriting strokes were made using a test marking pen. After a certain period of time, a sheet of fine paper was placed on top, and the writing was rubbed with a finger. The time it took for the transfer to the top sheet of fine paper to disappear was recorded. Tables 1 to 14 show the measured time (seconds) for each example and comparative example.

[0094] (Pen tip drying resistance test) Three circles (circular marks) were drawn in three rows (a total of nine circles) on the surface (without oil coating) of an iron plate (polished steel plate manufactured by ESCO, part number: EA441VG-62, material: iron (SPCC)) using a test marking pen. With the cap removed, the test marking pen was left horizontally at room temperature for 60 minutes. Multiple circles were then drawn on the aforementioned iron plate (without oil coating) using this test marking pen, and the number of circles drawn until the markings were equivalent to those before standing (markings without smudging) was counted. Tables 1 to 14 show the number of circles counted for each example and comparative example (the number of circles drawn until the markings were equivalent to those before standing). Note that a lower count indicates better pen tip drying resistance. In comparative examples 2 to 4, the notation ">50" means that even after writing circles 50 times, the handwriting did not become equivalent to that of the test marking pen before it was settled.

[0095]

[0096]

[0097]

[0098]

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[0109] The oil-based ink compositions of Examples 1 to 130 contain a pigment, an organic solvent, and a vinyl polymer or acrylic polymer, wherein the organic solvent mainly contains glycol ether, and the polymer content in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less.

[0110] The oil-based ink compositions of Examples 1 to 130 contain glycol ether as the main solvent. Therefore, when writing on an oil-covered metal surface (writing surface), the ink repels the oil film on the metal surface, allowing it to reach the metal surface and form highly legible handwriting (oil-covered surface writing performance). Furthermore, the oil-based ink compositions of Examples 1 to 130 contain a vinyl polymer or acrylic polymer content of 0.01% to 5.0% by weight, resulting in a moderately low surface tension. Consequently, when writing on an oil-covered metal surface, the ink can spread evenly on the metal surface while suppressing the aggregation of pigments, thus forming good handwriting (oil-covered surface writing performance).

[0111] Furthermore, since the oil-based ink compositions of Examples 1 to 130 contain vinyl polymers or acrylic polymers, the leveling properties of the ink compositions can be improved. As a result, the ink film formed on the writing surface tends to be more uniform, and the solvent evaporates more easily, which is thought to result in good drying properties of the ink (ink drying properties). In addition, since the oil-based ink compositions of Examples 1 to 130 contain vinyl polymers or acrylic polymers, a fragile film is formed on the pen tip surface, and since the oil-based ink compositions contain glycol ether, the fusion between the vinyl polymer or acrylic polymer and the pen tip is promoted, which makes it easier for the aforementioned film thickness to be uniform. As a result, the drying of the pen tip is suppressed by the film formed on the pen tip surface, and even when writing again after the first writing, the aforementioned film breaks easily, allowing for the formation of appropriate ink (pen tip drying resistance).

[0112] The oil-based ink compositions of Examples 1-13, 17-23, 27-33, 37-43, 47-51, 54-60, 64-68, 71-75, 78-82, 85-89, 92-96, 99-105, 109-110, 112-113, 115-116, 118-119, 121-122, 125-126, and 128-129 contain a vinyl polymer or acrylic polymer of 0.01% by weight or more and 1.0% by weight or less. Therefore, the surface tension of the oil-based ink composition is moderately low. As a result, when writing on an oil-adhered metal surface, it is possible to moderately wet and spread the ink on the metal surface while suppressing the aggregation of pigments contained in the ink, thereby forming a good writing line (writing performance on oil-adhered surfaces).

[0113] The oil-based ink compositions of Examples 1-9, 17-20, 27-30, 37-40, 47-49, 54-57, 64-66, 71-73, 78-80, 85-87, 92-94, 99-102, 109, 112, 115, 118, 121-122, 125, and 128 contain a vinyl polymer or acrylic polymer of 0.01% by weight or more and 0.60% by weight or less. Therefore, it is thought that the surface tension of the oil-based ink composition could be more effectively suppressed, making it easier to form better writing on oil-adhered metal surfaces (writing performance on oil-adhered surfaces).

[0114] The oil-based ink compositions of Examples 10-13, 21-23, 31-33, 41-43, 50-51, 58-60, 67-68, 74-75, 81-82, 88-89, 95-96, 103-105, 110, 113, 116, 119, 126, and 129 contain a vinyl polymer or acrylic polymer content greater than 0.60% by weight and 1.0% by weight or less. Therefore, it is thought that the surface tension of the oil-based ink composition was easily reduced, pigment aggregation was more effectively suppressed, and excessive surface tension of the oil-based ink composition was more effectively suppressed, resulting in good writing performance on oil-covered metal surfaces (writing performance on oil-covered surfaces).

[0115] The oil-based ink compositions of Examples 14-16, 24-26, 34-36, 44-46, 52-53, 61-63, 69-70, 76-77, 83-84, 90-91, 97-98, 106-108, 111, 114, 117, 120, 123-124, 127, and 130 contain a vinyl polymer or acrylic polymer content greater than 1.0% by weight and 5.0% by weight or less. Therefore, it is considered that the surface tension of the oil-based ink composition was easily reduced and pigment aggregation was effectively suppressed, resulting in good writing performance on oil-covered metal surfaces (writing performance on oil-covered surfaces).

[0116] Furthermore, since the oil-based ink compositions of Examples 1 to 130 have an SP value of 8.9 or higher for the glycol ether, which is the main solvent, the organic solvent's affinity for oil is not excessive, which is thought to have suppressed the spread of the organic solvent onto the oil film adhering to the metal surface (writing surface). Also, since the oil-based ink compositions of Examples 1 to 130 have an SP value of 12.2 or lower for the glycol ether, which is the main solvent, the surface tension of the organic solvent does not tend to become high, which is thought to have suppressed the formation of droplets by repelling the ink composition containing the organic solvent on the metal surface or oil film. Therefore, it is thought that the oil-based ink compositions of Examples 1 to 130 were able to easily form good writing marks on oil-adhered metal surfaces (writing performance on oil-adhered surfaces).

[0117] The oil-based ink compositions of Examples 1-120 and 125-130 contain silicone in the vinyl polymer or acrylic polymer, which is thought to have resulted in good drying properties for the ink or good drying resistance of the pen tip. Therefore, it is thought that it was easier to achieve both good ink drying properties and good drying resistance of the pen tip.

[0118] The oil-based ink compositions of Examples 1 to 127 contain rosin derivatives, and it is believed that the affinity between the oil-based ink composition and the metal surface is improved because the rosin derivatives are oriented at the interface between the ink composition and the metal surface. Furthermore, since rosin derivatives do not readily mix with oil, they have an oil-repellent effect at the interface between the oil-based ink composition and the metal surface. Therefore, it is considered that the oil-based ink compositions of Examples 1 to 127 exhibited good adhesion to oil-contaminated metal surfaces (adhesion).

[0119] Since the oil-based ink compositions of Examples 1 to 124 contain rosin-modified maleic acid resin as a rosin derivative, the affinity between the oil-based ink composition and the metal surface is easily improved, and it is thought that the oil-based ink composition adhered well to the oil-covered metal surface.

[0120] In contrast, the oil-based ink composition of Comparative Example 1 contained a dye as a coloring agent but no pigment. Therefore, it is believed that the interaction between the pigment and the glycol ether, vinyl polymer, or acrylic polymer was not obtained, resulting in poor writing performance on oily surfaces, drying time of ink, and pen tip drying resistance.

[0121] In Comparative Examples 2 and 3, the oil-based ink compositions use an organic solvent other than glycol ether as the main solvent. Therefore, compared to cases where the main solvent is glycol ether, when writing on an oil-covered metal surface (writing surface), the ink does not repel the oil film on the metal surface, making it difficult for the ink to reach the metal surface. As a result, it is thought that a highly legible line could not be formed (writing performance on oil-covered surfaces).

[0122] In Comparative Example 2, the main solvent was ethanol (SP value: 12.66). Since the SP value of the main solvent was greater than 12.2, the surface tension of the organic solvent increased, and it is possible that the ink composition containing the organic solvent was repelled from the metal surface or oil film, forming droplets (writing performance on oily surfaces).

[0123] In Comparative Example 3, the main solvent was xylene (SP value: 8.69), and since the SP value of the main solvent was less than 8.9, it is possible that the organic solvent's affinity for oil was excessive, and it was not possible to suppress the spread of the organic solvent onto the oil film attached to the metal surface (writing surface) (writing performance on oil-adhered surface).

[0124] In Comparative Examples 4 and 5, since the oil-based ink composition did not contain vinyl polymers or acrylic polymers, the surface tension of the oil-based ink composition was relatively high. Therefore, when writing on an oil-covered metal surface, the pigments contained in the ink aggregated on the writing surface, making it impossible to form a good writing line (writing performance on oil-covered surfaces).

[0125] In Comparative Examples 6 and 8, the content of vinyl polymers or acrylic polymers in the oil-based ink composition was less than 0.01% by weight. Therefore, the surface tension of the oil-based ink composition could not be sufficiently reduced, and pigment aggregation could not be suppressed. As a result, shrunken lines were formed, and it is possible that good handwriting could not be obtained (oil-adhering surface writing performance).

[0126] In Comparative Examples 7 and 9, the content of vinyl polymers or acrylic polymers in the oil-based ink composition was more than 5.0% by weight. As a result, the surface tension of the oil-based ink composition became excessive, and the aggregation of pigments due to the vinyl polymers or acrylic polymers spreading before the pigments could not be suppressed. This may have led to the formation of shrunken lines and the inability to obtain good handwriting (oil-adhering surface writing performance).

[0127] The contents described in each of the above embodiments can be understood, for example, as follows:

[0128] [1] An oil-based ink composition according to at least one embodiment of the present invention is an oil-based ink composition comprising: a pigment; an organic solvent; and a polymer containing a vinyl polymer or an acrylic polymer, wherein the organic solvent contains glycol ether as the main solvent, and the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less.

[0129] In the configuration described in [1] above, the organic solvent in the oil-based ink composition contains glycol ether as the main solvent. Therefore, when writing on an oil-covered metal surface (writing surface), the ink repels the oil film on the metal surface and reaches the metal surface, thus forming a highly legible writing line. Furthermore, in the configuration described in [1] above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less, so the surface tension of the oil-based ink composition is moderately low. As a result, when writing on an oil-covered metal surface, the aggregation of pigments contained in the ink is suppressed, and the ink can be spread appropriately on the metal surface, forming a good writing line. Thus, according to the configuration described in [1] above, a writing instrument with good writing performance on oil-covered metal surfaces can be obtained.

[0130] Furthermore, in the configuration described in [1] above, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, the leveling properties of the ink composition can be improved. As a result, the ink film formed on the writing surface tends to be uniform, and the solvent evaporates easily, resulting in good drying properties of the ink. In addition, in the configuration described in [1] above, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, a fragile film is formed on the pen tip surface, and since the oil-based ink composition contains glycol ether, the fusion between the vinyl polymer or acrylic polymer and the pen tip is promoted, making it easier for the aforementioned film thickness to be uniform. As a result, the film formed on the pen tip surface suppresses the drying of the pen tip, and even when writing again after the first writing, the aforementioned film breaks easily, allowing for the formation of appropriate ink. Thus, the configuration described in [1] above makes it possible to achieve both good ink drying properties and pen tip drying resistance.

[0131] [2] In some embodiments, in the configuration of [1] above, the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 1.0% by weight or less.

[0132] In the configuration described in [2] above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is 0.01% by weight or more and 1.0% by weight or less, so the surface tension of the oil-based ink composition becomes moderately low. Therefore, when writing on a metal surface to which oil has adhered, the ink can be spread moderately on the metal surface while suppressing the aggregation of pigments contained in the ink, thereby forming a good writing line. Thus, the configuration described in [2] above makes it easier to achieve good writing properties on metal surfaces to which oil has adhered.

[0133] [3] In some embodiments, in the configuration of [2] above, the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 0.60% by weight or less.

[0134] In the configuration described in [3] above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is 0.01% by weight or more and 0.6% by weight or less, so that the surface tension of the oil-based ink composition does not become excessively high, which can be suppressed more effectively. Therefore, it is easier to form good writing marks on metal surfaces to which oil is attached.

[0135] [4] In some embodiments, in the configuration of [1] or [2] above, the content of the polymer in the oil-based ink composition is greater than 0.60% by weight and 1.0% by weight or less.

[0136] According to the configuration described in [4] above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is greater than 0.60% by weight and 1.0% by weight or less. This makes it easier to lower the surface tension of the oil-based ink composition and more effectively suppress pigment aggregation, as well as more effectively suppress excessive surface tension in the oil-based ink composition. Therefore, it is easier to improve the writing performance on oil-covered metal surfaces.

[0137] [5] In some embodiments, in the configuration of [1] above, the content of the polymer in the oil-based ink composition is greater than 1.0% by weight and 5.0% by weight or less.

[0138] In the configuration described in [5] above, the content of vinyl polymer or acrylic polymer in the oil-based ink composition is greater than 1.0% by weight and 5.0% by weight or less. Therefore, the surface tension of the oil-based ink composition is easily reduced, and pigment aggregation is effectively suppressed. Thus, a writing instrument with good writing performance on oil-covered metal surfaces can be obtained.

[0139] [6] In some embodiments, in any of the configurations [1] to [5] above, the SP value of the glycol ether is 8.9 or more and 12.2 or less.

[0140] In the configuration described in [6] above, since the SP value of the glycol ether, which is the main solvent, is 8.9 or higher, the organic solvent does not readily blend with oil, thus suppressing the spread of the organic solvent onto the oil film attached to the metal surface (writing surface). Furthermore, in the configuration described in [6] above, since the SP value of the glycol ether, which is the main solvent, is 12.2 or lower, the surface tension of the organic solvent does not easily become high, thus suppressing the formation of droplets by repelling the ink composition containing the organic solvent on the metal surface or oil film. Therefore, according to the configuration described in [6] above, it is easy to form good writing marks on an oil-covered metal surface.

[0141] [7] In some embodiments, in any of the configurations of [1] to [6] above, the vinyl polymer or acrylic polymer contains silicone.

[0142] According to the configuration of [7] above, since the vinyl polymer or acrylic polymer contains silicone, the surface tension of the ink composition can be moderately reduced. This makes it easier to obtain a writing instrument with good writing properties on oily metal surfaces. Furthermore, in the configuration of [7] above, as described above, the surface tension of the ink composition is moderately reduced, so the leveling properties of the ink composition tend to be good. As a result, the ink film of the writing tends to be more uniform, and the solvent evaporates more easily, so the drying properties of the writing tend to be good. Therefore, it becomes easier to achieve both good drying properties of the writing and good drying resistance of the pen tip.

[0143] [8] In some embodiments, in any configuration of [1] to [7] above, the oil-based ink composition further comprises a rosin derivative.

[0144] According to the configuration of [8] above, since the oil-based ink composition contains a rosin derivative, the rosin derivative is oriented at the interface between the ink composition and the metal surface, thereby improving the affinity between the oil-based ink composition and the metal surface. Furthermore, since the rosin derivative does not readily mix with oil, it has an oil-repellent effect at the interface between the oil-based ink composition and the metal surface. Therefore, according to the configuration of [8] above, the adhesion of the oil-based ink composition to an oil-contaminated metal surface can be improved.

[0145] [9] In some embodiments, in the configuration of [8] above, the rosin derivative includes a rosin-modified maleic acid resin.

[0146] According to the configuration of [9] above, since the oil-based ink composition contains a rosin-modified maleic acid resin as a rosin derivative, the affinity between the oil-based ink composition and the metal surface is easily improved. Therefore, according to the configuration of [9] above, the adhesion of the oil-based ink composition to a metal surface to which oil is attached is easily improved.

[0147]

[10] A writing instrument (1) according to at least one embodiment of the present invention comprises: an ink storage section (for example, the container 2 described above) that contains the oil-based ink composition described in any one of [1] to [9] above; and a writing section (for example, the applicator 5 described above) configured to receive the oil-based ink composition from the ink storage section.

[0148] In the configuration of

[10] above, the organic solvent in the oil-based ink composition contains glycol ether as the main solvent. Therefore, when writing on an oil-covered metal surface (writing surface), the ink repels the oil film on the metal surface and reaches the metal surface, thus forming a highly legible writing line. Furthermore, in the configuration of

[10] above, the content of vinyl polymers or acrylic polymers in the oil-based ink composition is 0.01% by weight or more and 1.0% by weight or less, so the surface tension of the oil-based ink composition is moderately low. Therefore, when writing on an oil-covered metal surface, the aggregation of pigments contained in the ink is suppressed, and the ink can be moderately wetted and spread on the metal surface, thus forming a good writing line. Thus, according to the configuration of

[10] above, a writing instrument with good writing performance on oil-covered metal surfaces can be obtained.

[0149] Furthermore, in the configuration of

[10] above, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, the leveling properties of the ink composition can be improved. As a result, the ink film formed on the writing surface tends to be uniform, and the solvent evaporates easily, resulting in good drying properties of the ink. In addition, in the configuration of

[10] above, since the oil-based ink composition contains a vinyl polymer or an acrylic polymer, a fragile film is formed on the pen tip surface, and since the oil-based ink composition contains glycol ether, the fusion between the vinyl polymer or acrylic polymer and the pen tip is promoted, so the aforementioned film thickness tends to be uniform. As a result, the film formed on the pen tip surface suppresses the drying of the pen tip, and even when writing again after the first writing, the aforementioned film breaks easily, allowing for the formation of appropriate ink. Thus, the configuration of

[10] above makes it possible to achieve both good ink drying properties and pen tip drying resistance.

[0150] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0151] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0152] 1 Marking pen 2 Container 3 Front shaft 3a Valve seat 4 Applicator holding cylinder 5 Applicator 6 Applicator absorber 7 Cap 8 Spring valve 8a Spring part 8b Valve part 9 Stirring member 10 Airtight part

Claims

1. An oil-based ink composition comprising a pigment, an organic solvent, and a polymer containing a vinyl polymer or an acrylic polymer, wherein the organic solvent contains glycol ether as the main solvent, and the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 5.0% by weight or less.

2. The oil-based ink composition according to claim 1, wherein the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 1.0% by weight or less.

3. The oil-based ink composition according to claim 2, wherein the content of the polymer in the oil-based ink composition is 0.01% by weight or more and 0.60% by weight or less.

4. The oil-based ink composition according to claim 1 or 2, wherein the content of the polymer in the oil-based ink composition is greater than 0.60% by weight and 1.0% by weight or less.

5. The oil-based ink composition according to claim 1, wherein the content of the polymer in the oil-based ink composition is greater than 1.0% by weight and 5.0% by weight or less.

6. The oil-based ink composition according to any one of claims 1 to 5, wherein the SP value of the glycol ether is 8.9 or more and 12.2 or less.

7. The oil-based ink composition according to any one of claims 1 to 6, wherein the vinyl polymer or acrylic polymer contains silicone.

8. An oil-based ink composition according to any one of claims 1 to 7, further comprising a rosin derivative.

9. The oil-based ink composition according to claim 8, wherein the rosin derivative comprises a rosin-modified maleic acid resin.

10. A writing instrument comprising: an ink storage section containing an oil-based ink composition according to any one of claims 1 to 9; and a writing section configured to receive the oil-based ink composition from the ink storage section.

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