JP7790622B2 - Water-based pigment ink composition for writing instruments - Google Patents

Description

The present invention relates to an aqueous pigment ink composition for writing instruments, which uses a pigment as a coloring component to provide a coating liquid that is built into an applicator and provides a hiding effect for the base, a lustrous effect for the coating marks, and water resistance for the coating marks.

Conventionally, aqueous pigment ink compositions for writing instruments use pigments as coloring components to provide a hiding effect for the base, a shining effect on the coating marks, and water resistance to the coating marks. However, because pigments have a higher specific gravity than dyes and are dispersed and mixed rather than dissolved, the pigments gradually aggregate and settle over time as they are left to stand, forming a so-called hard cake that separates from the liquid, making it difficult to dispense from the application point of the writing instrument.
In ink compositions using such pigments, known means for delaying pigment aggregation and sedimentation include surface modification of the pigment with various surfactants and reducing the fluidity of the liquid by using thickeners or gelling agents.
For example, the invention described in Patent Document 1 discloses an aqueous ink composition for a writing instrument that uses water-soluble resins such as acrylic resins, vinyl resins, and various resin emulsions, water-soluble polysaccharides such as cellulose derivatives, and inorganic thickeners such as montmorillonite-based clay minerals to produce an ink with a specific viscosity relative to a specific shear rate, thereby achieving good redispersibility even when left to stand at 40°C for two weeks.Patent Document 2 discloses an aqueous pigment ink composition for use in a ballpoint pen that uses a combination of multiple specific water-soluble polysaccharides to maintain the ink dispersion stable and produce good handwriting even after storage for about two months at room temperature, as well as at temperatures as low as 0°C or as high as 60°C.

JP 2011-202086 A Japanese Patent Application Laid-Open No. 2006-45429

The invention described in the above-mentioned patent document had a problem where the pen would not write well after being left in a sub-zero temperature environment below -5°C for an extremely long period of time (3 months or more).

The objective of the present invention is to provide an aqueous pigment ink composition for writing instruments that can produce good application marks even when left standing in a sub-zero temperature environment of approximately -5°C for three months or more.

The first aspect of the present invention is an aqueous pigment ink composition for a writing instrument, which comprises at least a pigment, an amino acid anionic surfactant composed of an unsaturated fatty acid, an amino acid anionic surfactant composed of a saturated fatty acid, and water. The second aspect of the present invention is an aqueous pigment ink composition for a writing instrument, which further comprises a resin emulsion and a plate-like inorganic compound.

According to an embodiment of the present invention, it is possible to provide an aqueous pigment ink composition for writing instruments, such as marking pens, brush pens, ballpoint pens, and correction fluid applicators, which can be filled into writing instruments and can write well even when stored in a negative temperature environment for a long period of time and then used for writing in a similar low-temperature environment.

In other words, in the aqueous pigment ink composition for writing instruments of the present invention, an amino acid anionic surfactant composed of an unsaturated fatty acid and an amino acid anionic surfactant composed of a saturated fatty acid are bonded to the pigment surface, forming a composite in which the pigment surface is covered with the amino acid anionic surfactant composed of an unsaturated fatty acid and the amino acid anionic surfactant composed of a saturated fatty acid. This is thought to three-dimensionally moderate the interactions between the pigments and ensure the fluidity of the overall composition, even in low-temperature environments. Furthermore, when a resin emulsion or plate-like inorganic particles is added to this composition, the thickening effect of the solids is enhanced, and the gelling action of the plate-like inorganic particles such as bentonite forms a gentle gel structure that encases the pigment. In particular, the interaction between the amino acid anionic surfactant composed of an unsaturated fatty acid and the gel structure formed by the amino acid anionic surfactant composed of a saturated fatty acid and the plate-like inorganic particles forms a large gel structure composite, which is thought to prevent large plate-like pigments, such as shiny plate-like aluminum or aluminum flakes, from aligning and agglomerating as pigment particles.

FIG.

The pigment used in the aqueous pigment ink composition for writing instruments of the present invention is used as a coloring component to achieve a hiding effect for the base, a lustrous effect for the application marks, and water resistance for the application marks. Pigments that can be used are not particularly limited, and include organic pigments such as azo pigments, nitroso pigments, and nitro pigments used in conventional water-based and oil-based inks; inorganic pigments such as ochre, barium yellow, Prussian blue, cadmium red, barium sulfate, titanium oxide, red iron oxide, iron black, and carbon black; glitter pigments such as metal powders such as aluminum powder and bronze powder, metal-coated glass flakes, and metal-deposited films; and aqueous pigment bases in which pigments are dispersed in an aqueous medium. In particular, glitter pigments are used to create beautiful, lustrous handwriting.

Examples of brilliant pigments include LG neo R-GOLD #35, LG neo B-GOLD #35, LG neo S-GOLD #35, LG neo R-GOLD #100, LG neo B-GOLD #100, LG neo S-GOLD #100, LG neo RED #100, LG neo BLUE #100, LG neo GREEN #100, LG neo VIOLET #100, LG neo BLACK #100, LG neo COPPER #100, LG neo PINK #100, and LG neo YELLOW. #100, LZ neo R-GOLD #150, LZ neo B-GOLD #150, LZ neo S-GOLD #150, LZ neo RED #150, LZ neo BLUE #150, LZ neo GREEN #150, LZ neo VIOLET #150, LZ neo BLACK #150, LZ neo COPPER #150, LZ neo PINK #150, LZ neo YELLOW #150, LZ neo R-GOLD #200, LZ neo B-GOLD #200, LZ neo S-GOLD #200, LZ neo RED #200, LZ neo BLUE #200, LZ neo GREEN #200, LZ neo VIOLET #200, LZ neo BLACK #200, LZ neo COPPER #200, LZ neo PINK #200, LZ neo YELLOW #200, LZ neo R-GOLD #325, LZ neo B-GOLD #325, LZ neo S-GOLD #325, LZ neo RED #325, LZ neo BLUE #325, LZ neo GREEN #325, LZ neo VIOLET #325, LG neo BLACK #325, LG neo COPPER #325, LG neo PINK #325, LG neo YELLOW #325, LG neo SILVER #325, LG neo R-GOLD #500, LG neo B-GOLD #500, LG neo S-GOLD #500 (all manufactured by Oike Imaging Co., Ltd.), Diamond Piece LG Gold No. 55, Diamond Piece DG Gold No. 55, Diamond Piece Green No. 55, Diamond Piece Blue No. 55, Diamond Piece Red No. 55, Diamond Piece Maroon No. Diamond Piece Ocean Green No. 55, Diamond Piece Sky Blue No. 55, Diamond Piece Black No. 55, Diamond Piece Pink No. 55, Diamond Piece Violet No. 55, Diamond Piece Emerald No. 55, Diamond Piece Copper No. 55, Diamond Piece LG Gold H25, Diamond Piece DG Gold H25, Diamond Piece Green H25, Diamond Piece Blue H25, Diamond Piece Red H25, Diamond Piece Maroon H25, Diamond Piece Ocean Green H25, Diamond Piece Sky Blue H25, Diamond Piece Black H25, Diamond Piece Pink H25, Diamond Piece Violet H25, Diamond Piece Emerald H25, Diamond Piece Copper H25, Diamond Piece LG Gold H55, Diamond Piece DG Gold H55, Diamond Piece Green H55, Diamond Piece Blue H55, Diamond Piece Red H55, Diamond Piece Maroon H55, Diamond Piece Ocean Green H55, Diamond Piece Sky Blue H55, Diamond Piece Black H55, Diamond Piece Pink H55, Diamond Piece Violet H55, Diamond Piece Emerald H55, Diamond Piece Copper H55, Diamond Piece LG Gold CO-40UC, Diamond Piece DG Gold CO-40UC, Diamond Piece Green CO-40UC, Diamond Piece Blue CO-40UC, Diamond Piece Red CO-40UC, Diamond Piece Pink CO-40UC, Diamond Piece Lavender CO-40UC (all manufactured by Diamond Kogyo Co., Ltd.), Super Fine No. 22000, No. 22000WN, No. 1800WN, No. 18000, Fine No. 900, No. 800 (all manufactured by Yamato Metal Powder Co., Ltd.), AA12, AA8, No. 900, No. 1800, PaleGold E5, PaleGold 2L5, RichGold L7, RichGold 3L7, ECopper (all manufactured by Fukuda Metal Foil & Powder Co., Ltd.), Aluminum Powder 1000, Aluminum Powder 2700 (all manufactured by Nakatsuka Metal Foil & Powder Co., Ltd.), WB0230, WXM0630, Friend Color D452BL, Friend Color D462BL, Friend Color D851BL, Friend Color D451RE, Friend Color D462RE, Friend Color D111RE, Friend Color D452YE, Friend Color D462YE, Friend Color D85 1YE (all manufactured by Toyo Aluminum K.K.), stainless steel powder pigments, tin powder pigments, zinc powder pigments, nickel powder pigments, gold powder pigments, silver powder pigments, Metashine MT1030GP, Metashine MT2080GP, Metashine 2025PS, Metashine 1030PS, Metashine 2080PS, Metashine 5090PS, Metashine 5150PS, Metashine 5230PS, Metashine 5480PS (all manufactured by Nippon Sheet Glass Co., Ltd.), and the like.
When using a glitter pigment or the like, the average particle size is preferably 10 μm or more in order to form beautiful handwriting with a glittering feel, and an average particle size of 30 μm or more is particularly preferred because it provides an even stronger glittering feel.

Examples of inorganic pigments include aniline black (C.I. 50440), cyanine black, naphthol yellow S (C.I. 10316), Hansa yellow 10G (C.I. 11710), Hansa yellow 5G (C.I. 11660), Hansa yellow 3G (C.I. 11670), Hansa yellow G (C.I. 11680), Hansa yellow GR (C.I. 11730), Hansa yellow A (C.I. 11735), Hansa yellow RN (C.I. 1740), Hansa yellow R (C.I. 12710), and pigment yellow L (C.
CI 12720), Benzidine Yellow (CI 21090), Benzidine Yellow G (CI 21095), Benzidine Yellow GR (CI 21100), Permanent Yellow NCG (CI 20040), Balkan Fast Yellow 5G (CI 21220), Balkan Fast Yellow R (CI 21135), Tartrazine Lake (CI 19140), Quinoline Yellow Lake (CI 47005), Anthragen Yellow 6GL (CI 60520), Permanent Yellow FGL, Permanent Yellow H 10G, Permanent Yellow HR, Anthrapyrimidine Yellow (C.I. 68420), Sudan I (C.I. 12055), Permanent Orange (C.I. 12075), Lithol Fast Orange (C.I. 12125), Permanent Orange GTR (C.I. 12305), Hansa Yellow 3R (C.I. 11725), Balkan Fast Orange GG (C.I. 21165), Benzidine Orange G (C.I. 21110), Persian Orange (C.I. 15510), Indanthrene Brilliant Orange GK (C.I. . 59305), Indanthrene Brilliant Orange RK (C.I. 59105), Indanthrene Brilliant Orange GR (C.I. 71105), Permanent Brown FG (C.I. 12480), Para Brown (C.I. 12071), Permanent Red 4R (C.I. 12120), Para Red (C.I. 12070), Fire Red (C.I. 12085), Parachlor Orthoaniline Red (C.I. 12090), Lithol Fast Scarlet, Brilliant Fast Scarlet (C.I. 12315), Blue Lilliant Carmine BS, Permanent Red F2R (C.I. 12310), Permanent Red F4R (C.I. 12335), Permanent Red FRL (C.I. 12440), Permanent Red FRLL (C.I. 12460), Permanent Red F4RH (C.I. 12420), Fast Scarlet VD, Balkan Fast Rubin B (C.I. 12320), Balkan Fast Pink G (C.I. 12330), Light Fast Red Toner B (C.I. 12450), Light Fast Red Toner R (C.I. 12 455), Permanent Carmine FB (C.I. 12490), Pyrazolone Red (C.I. 12120), Lithol Red (C.I. 15630), Lake Red C (C.I. 15585), Lake Red D (C.I. 15500), Anthocine B (C.I. 18030), Brilliant Scarlet G (C.I. 15800), Lithol Rubin GK (C.I. 15825), Permanent Red F5R (C.I. 15865), Brilliant Carmine 6B (C.I. 15850), Pigment Scarlet 3B (C.I. 16105), Bordeaux 5B (C.I. 12170), Toluidine Maroon (C.I. 12350), Permanent Bordeaux F2R (C.I. 12385), Helio Bordeaux BL (C.I. 14830), Bordeaux 10B (C.I. 15880), Bon Maroon Light (C.I. 15825), Bon Maroon Medium (C.I. 15880), Eosin Lake (C.I. 45380), Rhodamine Lake B (C.I. 45170), Rhodamine Lake Y (C.I. 45160), Alizarin Lake (C.I. 58000), Thioindigo Red B (C.I. 7 3300), Thioindigo Maroon (C.I. 73385), Permanent Red FGR (C.I. 12370), PV Carmine HR, Watching Red, Monolight Fast Red YS (C.I. 59300), Permanent Red BL, Fast Violet B, Methyl Violet Lake (C.I. 42535), Dioxazine Violet, Alkali Blue Lake (C.I. 42750A, C.I. 42770A), Peacock Blue Lake (C.I. 42090), Peacock Blue Lake (C.I. 42025), Victoria Blue Examples of the pigments include Lu Lake (C.I. 44045), Phthalocyanine Blue (C.I. 74160), Fast Sky Blue (C.I. 74180), Indanthrene Blue RS (C.I. 69800), Indanthrene Blue BC (C.I. 69825), Indigo (C.I. 73000), Pigment Green B (C.I. 10006), Naphthol Green B (C.I. 10020), Green Gold (C.I. 12775), Acid Green Lake, Malachite Green Lake (C.I. 42000), and Phthalocyanine Green.

Water-based pigment bases include Fuji SP Black 8031, Fuji SP Black 8119, Fuji SP Black 8167, Fuji SP Black 8276, Fuji SP Black 8381, Fuji SP Black 8406, Fuji SP Red 5096, Fuji SP Red 5111, Fuji SP Red 5193, Fuji SP Red 5220, Fuji SP Bordeaux 5500, Fuji SP Blue 6062, and Fuji SP Blue. 6133, Fuji SP Blue 6134, Fuji SP Blue 6401, Fuji SP Green 7051, Fuji SP Yellow 4060, Fuji SP Yellow 4178, Fuji SP Violet 9011, Fuji SP Pink 9524, Fuji SP Pink 9527, Fuji SP Orange 534, Fuji SP Brown 3074, Fuji SP RED 5543, FUJI SP RED 5544 (manufactured by Fuji Shiki Co., Ltd.), Emacol Black CN, Emacol Blue FBB, Emacol Blue FB, Emacol Blue KR, Emacol Green LXB, Emacol Violet BL, Emacol Brown 3101, Emacol Carmine FB, Emacol Red BS, Emacol Orange R, Emacol Yellow FD, Emacol Yellow IRN, Emacol Yellow 3601, Emacol Yellow FGN, Emacol Yellow GN, Emacol Yellow GG, Emacol Yellow F5G, Emacol Yellow F7G, Emacol Yellow 10GN, Emacol Yellow 10G, Sandy Super Black K, Sandy Super Black C, Sandy Super Gray B, Sandy Super Brown SB, Sandy Super Brown FRL, Sandy Super Brown RR, Sandy Super Green L5G, Sandy Super Green GXB, Sandy Super Navy Blue HRL, Sandy Super Navy Blue GLL, Sandy Super Navy Blue HB, Sandy Super Navy Blue FBLH, Sandy Super Navy Blue FBL-160, Sandy Super Navy Blue FBB, Sandye Super Violet BL H/C, Sandye Super Violet BL, Sandye Super Bordeaux FR, Sandye Super Pink FBL, Sandye Super Pink F5B, Sandy Super Rubine FR, Sandy super Carmmine FB, Sandye Super Red FFG, Sandye Super Red RR, Sandye Super Red BS, Sandye Super Orange FL, Sandye Super Orange R, Sandye Super Orange BO, Sandye Gold Yellow 5GR, Sandye Gold Yellow R, Sandye Gold Yellow 3R, Sandye Yellow GG, Sandye Yellow F3R, Sandy Yellow IRC, Sandy Yellow FGN, Sandye Yellow GN, Sandye Yellow GRS, Sandye Yellow GSR-130, Sandye Yellow GSN-130, Sandye Yellow GSN, Sandye Yellow 10GN (all manufactured by Sanyo Pigment Co., Ltd.), Rio Fast Black Fx 8012, Rio Fast Black Fx 8313, Rio Fast Black Fx 8169, Rio Fast Red Fx 8209, Rio Fast Red Fx 8172, Rio Fast Red S Fx 8315, Rio Fast Red S Fx 8316, Rio Fast Blue Fx 8170, Rio Fast Blue FX 8170, Rio Fast Blue S Fx 8312, Rio Fast Green S Fx 8314 (all manufactured by Toyo Ink Co., Ltd.), NKW-2101, NKW-2102, NKW-2103, NKW-2104, NKW-2105, NKW-2106, NKW-2107, NKW-2108, NKW-2117, NKW-2127, NKW-2137, NKW-2167, NKW-2101P, NK W-2102P, NKW-2103P, NKW-2104P, NKW-2105P, NKW-2106P, NKW-2107P, NKW-2108P, NK W-2117P, NKW-2127P, NKW-2137P, NKW-2167P, NKW-3002, NKW-3003, NKW-3004, NKW-3 005, NKW-3007, NKW-3077, NKW-3008, NKW-3402, NKW-3404, NKW-3405, NKW-3407, NK W-3408, NKW-3477, NKW-3602, NKW-3603, NKW-3604, NKW-3605, NKW-3607, NKW-3677, NKW-3608, NKW-3702, NKW-3703, NKW-3704, NKW-3705, NKW-3777, NKW-3708, NKW-6013, NKW-6038, NKW-6559 (all manufactured by Nippon Fluorescent Co., Ltd.), Cosmocolor S1000F series (manufactured by Toyo Soda Co., Ltd.), Victoria Yellow Examples include Victoria Orange G-16, G-21, Victoria Red G-19, G-22, Victoria Pink G-17, G-23, Victoria Green G-18, G-24, Victoria Blue G-15, G-25 (all manufactured by Mikuni Color Co., Ltd.), and the Pollux series, such as Pollux PC5T1020, Pollux Black PC8T135, and Pollux Red IT1030 (all manufactured by Sumika Color Co., Ltd.).

These pigments may be used alone or in combination of two or more.
The pigment content of the aqueous pigment ink composition is preferably 0.5% by weight or more and 20.0% by weight or less, and more preferably 1.0% by weight or more and 10.0% by weight or less, based on the total weight of the aqueous pigment ink composition. Within this range, the ink can be discharged stably without clogging the pen tip or brush tip with the pigment while maintaining its fluidity at low temperatures.

The amino acid anionic surfactant comprising an unsaturated fatty acid used in the present invention and the amino acid anionic surfactant comprising a saturated fatty acid are used in combination.
The amino acid anionic surfactant is preferably used in an amount of 0.1% by weight to 5.0% by weight based on the total weight of the aqueous pigment ink composition, which allows stable ink ejection while maintaining dispersion stability at low temperatures.

Examples of amino acid anionic surfactants made from unsaturated fatty acids include NIKKOL Sarcosinate OH (oleoyl sarcosine (condensation product of oleic acid and methylglycine)) and NIKKOL Sarcosinate OHV (oleoyl sarcosine (condensation product of oleic acid and methylglycine)) (both manufactured by Nikko Chemicals Co., Ltd.). Unsaturated fatty acids are fatty acids that have carbon-carbon double bonds, and it is preferable for the carbon-carbon double bonds to have more cis-type carbon-carbon double bonds than trans-type carbon-carbon double bonds, as this will provide better fluidity.

Examples of amino acid anionic surfactants consisting of saturated fatty acids include Amisoft CS-11 (N-coconut oil fatty acid acyl-L-glutamic acid sodium), Amisoft CA (N-coconut oil fatty acid acyl-L-glutamic acid), Amisoft LA-D (N-lauroyl-L-glutamic acid), Amisoft HA-P (N-stearoyl-L-glutamic acid), Amisoft LS-11 (N-lauroyl-L-glutamic acid sodium), Amisoft MK-11 (N-myristoyl-L-glutamic acid potassium), Amisoft MS-11 (N-myristoyl-L-glutamic acid sodium), Amisoft GS-11P (N-acyl-L-glutamic acid sodium), Amisoft HS-11P (N-stearoyl-L-glutamic acid sodium), and Amisoft CT-12 (N-coconut oil fatty acid acyl-L-glutamic acid). Amisoft LT-12 (aqueous solution of triethanolamine salt of lauroyl-L-glutamic acid), Amisoft CK-22 (aqueous solution of potassium salt of N-cocoyl-L-glutamic acid), Amisoft CS-22 (aqueous solution of sodium salt of N-cocoyl-L-glutamic acid) (all manufactured by Ajinomoto Healthy Supply Co., Ltd.), NIKKOL Alaninate LN-30 (30% aqueous solution of sodium lauroylmethylalanine), NIKKOL Sarcosinate CN-30 (30% aqueous solution of sodium cocoyl sarcosinate (sodium salt of condensation product of coconut oil fatty acid and methylglycine)), NIKKOL Sarcosinate CT-30 (30% aqueous solution of triethanolamine salt of cocoyl sarcosinate (condensation product of coconut oil fatty acid and methylglycine)), NIKKOL Examples of such surfactants include Sarcosinate LH (lauroyl sarcosine), NIKKOL Sarcosinate LN (sodium lauroyl sarcosine), NIKKOL Sarcosinate LN-30 (sodium lauroyl sarcosine, 30% aqueous solution), NIKKOL Sarcosinate LK-30 (potassium lauroyl sarcosine, 30% aqueous solution), NIKKOL Sarcosinate MN (sodium myristoyl sarcosine), and NIKKOL Sarcosinate PN (sodium palmitoyl sarcosine) (all manufactured by Nikko Chemicals Co., Ltd.). Amino acid anionic surfactants in which the amino acid moiety is glutamic acid are preferred because they have two carboxylic acids and therefore form a stable bond with the pigment. Furthermore, the amino acid anionic surfactant made from coconut oil fatty acid contains not only an amino acid anionic surfactant made from saturated fatty acid but also an amino acid anionic surfactant made from unsaturated fatty acid at a few weight percent as an impurity. However, when these are used alone, where the content of the amino acid anionic surfactant made from unsaturated fatty acid is less than 10 weight percent, no substantial effect of the combined use is achieved. It is essentially necessary that the content of each of the amino acid anionic surfactant made from unsaturated fatty acid and the amino acid anionic surfactant made from saturated fatty acid be 10 weight percent or more relative to the total content of amino acid anionic surfactants in the ink composition. It is preferable that the content of the amino acid anionic surfactant made from unsaturated fatty acid be 20 weight percent or more relative to the total content of amino acid anionic surfactants in the ink composition, and the content of the amino acid anionic surfactant made from saturated fatty acid be 20 weight percent or more relative to the total content of amino acid anionic surfactants in the ink composition, because this three-dimensionally gentles the interactions between the pigments, preventing the fluidity of the entire composition from being impaired even in low-temperature environments and enhancing the effect of enabling good writing.
Furthermore, it is particularly preferred that the content of the amino acid anionic surfactant consisting of an unsaturated fatty acid is 30% by weight or more relative to the total content of amino acid anionic surfactants in the ink composition, and the content of the amino acid anionic surfactant consisting of a saturated fatty acid is 30% by weight or more relative to the total content of amino acid anionic surfactants in the ink composition, since this makes the interactions between the pigments three-dimensionally gentle, does not impair the fluidity of the entire composition even in low-temperature environments, and further enhances the effect of enabling good writing.

The plate-like inorganic compound of the present invention can be, for example, a smectite or bentonite, which can form a gel structure when dispersed in water. Bentonite is an inorganic mineral composed primarily of montmorillonite, accompanied by secondary components such as quartz, cristobalite, feldspars, and carbonate minerals. The gelling action of plate-like inorganic particles such as bentonite forms a loose gel structure that envelops the pigment. In particular, the interaction between the amino acid activator composed of unsaturated fatty acid and the gel structure formed by the plate-like inorganic particles forms a large gel structure complex. This prevents large plate-like pigment particles, such as shiny plate-like aluminum or aluminum flakes, from aligning and agglomerating, thereby enabling the pigment to be stably ejected onto the writing surface. Specific examples of the plate-like inorganic compound include OPTIGEL-WX, OPTIGEL-CG, OPTIGEL-CK, OPTIGEL-CK XR, OPTIGEL-CL, OPTIGEL-CMO, OPTIGEL-LX, OPTIGEL-W 724, OPTIGEL-WA, OPTIGEL-WH, OPTIGEL-WM, and OPTIGEL-WX. XR, LAPONITE-RD, LAPONITE-EP, LAPONITE-RDS, LAPONITE-JS, LAPONITE-S482 (all manufactured by BYK Japan Co., Ltd.), Wenger, Wenger HV, Wenger FW, Wenger 15, Wenger 23, Wenger SH, Wenger A, Wenger W-100, Wenger W-100U, Wenger W-200U, Wenger W-300U, Wenger W-300H P, Esben NX, Esben NX80, Esben NZ, Esben NZ, 70 Esben NEZ, Esben NO12S, Esben NO12 (all manufactured by Hojun Co., Ltd.), Kunipia-F, Kunipia-G, Kunipia-G4, Moistonite-U, Moistonite-S, Sumecton-SA, Sumecton-ST, Sumecton-SWN, Sumecton-SWF, Sumecton-SEN (all manufactured by Kunimine Co., Ltd.), and the like.
These plate-like inorganic compounds may be used alone or in combination of two or more.
The content of the plate-like inorganic compound is preferably 0.05% by weight or more and 3.0% by weight or less based on the total amount of the aqueous pigment ink composition. Furthermore, 0.1% by weight or more and 2.0% by weight or less is even more preferable. Within the above numerical range, dispersion stability at low temperatures is maintained, the pigment does not clog the pen tip or tip, and stable ink ejection properties are obtained. If the content is more than 3.0% by weight, the viscosity of the ink increases dramatically, and the writing feel is likely to deteriorate.

In the resin emulsion of the present invention, the hydrophobic portion binds to the amino acid anionic surfactant, imparting flexibility to the composite of the amino acid surfactant consisting of unsaturated fatty acid and the amino acid surfactant consisting of saturated fatty acid that covers the pigment surface, thereby imparting fluidity even at ultra-low temperatures where diffusion is less likely.
Examples of resin emulsions include urethane resin emulsions, acrylic resin emulsions, acrylic-urethane resin emulsions, and vinyl acetate resin emulsions.
Specifically, urethane resin emulsions such as U-coat UWS-145 (solid content 35%), U-coat UX-300 (solid content 38%), U-coat UX-310 (solid content 40%), Permarin UA-150 (solid content 30%), Permarin UA-200 (solid content 30%), Permarin UA-368 (solid content 50%), and Permarin UA-4000 (solid content 38%) (all manufactured by Sanyo Chemical Industries, Ltd.), Acrit WBR-016U (solid content 30%) (manufactured by Taisei Fine Chemical Co., Ltd.), Neosticker 200 (solid content 35%), Neosticker 400 (solid content 37%), Neosticker 700 (solid content 37%), Neosticker 1200 (solid content 37%), Evaphanol HA-15 (solid content 30%), and Evaphanol HA-107C (solid content 40%), Evaphanol HA-50C (solid content 35%), Evaphanol HA-170 (solid content 37%), Evaphanol HA-560 (solid content 35%) (all manufactured by Nicca Chemical Co., Ltd.), acrylic resin emulsions such as Bonron XGS-001 (solid content 45%), Bonron XPL-100 (solid content 30%), Bonron XPL-200 (solid content 44%), Bonron PS-001 (solid content 50%), Bonron PS-002 (solid content 45%), Bonron XPS-004 (solid content 45%), Bonron XHS-20 (solid content 40%), Bonron XHS-21S (solid content 45%), Bonron XHS-50 (solid content 20%), and Bonron S-119H (50% solids), Bonron S-416BF (44.5% solids), Bonron S-415 (44% solids), Bonron S-403 (25% solids), Bonron S-476 (45% solids), Bonron S-1120 (45% solids), Bonron S-483TBF (45% solids), Bonron S-434 (45% solids), Bonron S-1360 (44.5% solids) (all manufactured by Mitsui Chemicals, Inc.), DM772 (46% solids), DM774 (46% solids) (all manufactured by Japan Coating Resins Co., Ltd.), Acrylate AKW-107 (30% solids), Acrylate ATW-008S (29.5% solids) (all manufactured by Taisei Fine Chemical Co., Ltd.), Joncryl 7100 (solid content 48.0%), Joncryl 711 (solid content 42.0%), Joncryl PDX-7370 (solid content 42.0%), Joncryl PDX-7323 (solid content 42.0%), Joncryl PDX-7611 (solid content 36.5%), Joncryl 352D (solid content 45.0%), Joncryl 538J (solid content 45.0%), Joncryl PDX-7700 (solid content 48.0%), Joncryl PDX-7177 (solid content 36.0%), Joncryl 7001 (solid content 87.0%) (all manufactured by BASF (Germany)), Aquabrid 46777 (solid content 30%), Aquabrid UX-100 (48% solids), Aquabrid UX-110 (48% solids), Aquabrid AST531 (56% solids), Aquabrid AST499 (40% solids), Cevian-A886 (42% solids) (all manufactured by Daicel FineChem Ltd.), Boncoat 40-418EF (55% solids), Boncoat 5400EF (55% solids), Boncoat 5495EF (55% solids), Boncoat CG-8400 (50% solids), Boncoat CG-8490 (50% solids), Boncoat CG-8520 (49% solids), Boncoat CG-8680 (50% solids), Boncoat CM-8430 (40% solids), Boncoat CP-6450 (40% solids), Boncoat DV-961 (solid content 40%), Boncoat EC-740EF (solid content 40%), Boncoat EC-905EF (solid content 50%), Boncoat SFC-55 (solid content 40%) (all manufactured by DIC Corporation), Acrylate WEM-202U (solid content 40%), Acrylate WEM-321U (solid content 38%), Acrylate WEM-3008 (solid content 32.5%) (all manufactured by Taisei Fine Chemical Co., Ltd.), which are made of acrylic urethane resin emulsions, Polysol S-5J (solid content 52%), Polysol AX-590 (solid content 49%), Polysol AX-751 (solid content 46%), Polysol AX-428J (solid content 46%), Polysol AX-510ZL (solid content 43%), Polysol AX-951 (solid content 41%), Polysol AX-1000 (solid content 39%), Polysol BX-8004 (solid content 48%), Polysol AX-747L (solid content 50%), Polysol P-503 (solid content 40%), Polysol PS-120 (solid content 50%), Polysol Examples of suitable acrylic resins include S-65 (solid content 50%) (manufactured by Showa Denko K.K.), Cevian-A210 (solid content 52%), Cevian-A215 (solid content 52.5%), Cevian-A217 (solid content 52.5%), Cevian-A218 (solid content 59%), Cevian-A220 (solid content 48%), Cevian-A240 (solid content 53.5%), Cevian-A415 (solid content 55%) and Cevian-A435 (solid content 57%) (manufactured by Daicel FineChem Ltd.).
These resin emulsions may be used alone or in combination of two or more.
The resin emulsion preferably has a solid content of 1.0% by weight to 10.0% by weight based on the total weight of the aqueous pigment ink composition, in order to obtain stable ink ejection properties while maintaining fluidity at low temperatures.

Water is used as the main solvent of the ink. In the present invention, the main solvent means a solvent that accounts for 50% by weight or more of the total amount of solvents in the total amount of the ink composition. Ion-exchanged water or purified water is preferably used.
Furthermore, any organic solvent that has been conventionally known for the purposes of various qualities of ink, such as preventing ink from freezing at low temperatures and preventing ink from drying at the pen tip, can be used in combination without any particular limitation. Specific examples of organic solvents include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycerin, benzyl glycol, and benzyl diglycol; ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, sulfolane, dipropylene glycol monoethyl ether, ethylene glycol monobutyl ether, and ethylene glycol monohexyl ether. Examples of suitable organic solvents include glycol ethers such as ethylene glycol monophenyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, propylene glycol monobutyl ether, propylene glycol monophenyl ether, tripropylene glycol monobutyl ether, and tripropylene glycol monophenyl ether, alcoholic solvents such as isopropyl alcohol, 3-methyl-3-methoxy-1-butanol, benzyl alcohol, α-methylbenzyl alcohol, lauryl alcohol, tridecyl alcohol, isododecyl alcohol, and isotridecyl alcohol, as well as propylene glycol methyl ether acetate, propylene glycol diacetate, 2-pyrrolidone, N-methyl-2-pyrrolidone, sulfolane, and γ-butyrolactone. These organic solvents may be used alone or in combination of two or more.

The pH of the ink composition can be adjusted using pH adjusters such as basic substances such as sodium hydroxide, lithium hydroxide, triethanolamine, diethanolamine, monoethanolamine, and aminomethylpropanediol, or conventionally known acidic substances. Adjusting the pH to between 6.0 and 10.0 using these pH adjusters further improves the ink composition's fluidity maintenance effect. Furthermore, adjusting the pH to between 7.0 and 9.0 facilitates the formation of bonds between the amino acid anionic surfactant composed of unsaturated fatty acid and the amino acid anionic surfactant composed of saturated fatty acid and the pigment surface, which is expected to maintain the fluidity of the aqueous pigment ink composition for writing instruments for a long period of time. These pH adjusters may be used alone or in combination of two or more types.

In addition, various additives can also be used as needed.
For example, wax emulsions can be used to improve pigment adhesion. Specifically, RK-185 (solid content 45%) (manufactured by GOO Chemical Industry Co., Ltd.) and WE-65 (solid content 35%) (manufactured by Konishi Co., Ltd.) made of paraffin wax, and Chemipearl W100 (solid content 40%), Chemipearl W200 (solid content 40%), Chemipearl W300 (solid content 40%), Chemipearl W310 (solid content 40%), Chemipearl W400 (solid content 40%), Chemipearl W4005 (solid content 40%), Chemipearl W401 (solid content 40%), Chemipearl W410 (solid content 40%), Chemipearl W500 (solid content 40%), Chemipearl WF640 (solid content 40%), Chemipearl W700 (solid content 40%), Chemipearl W800 (solid content 40%), and Chemipearl are made of polyethylene wax. W900 (solid content 40%), Chemipearl W950 (solid content 40%) (all manufactured by Mitsui Chemicals, Inc.), HYTEC E-6500 (solid content 35%), HYTEC E-9015 (solid content 40%), HYTEC E-6400 (solid content 35%), HYTEC E-8237 (solid content 40%), HYTEC E-5403P (solid content 30%), HYTEC E-1000 (solid content 35%), HYTEC E-4A (solid content 35%) (all manufactured by Toho Chemical Industry Co., Ltd.), HYTEC P-9018 (solid content 35%), HYTEC P-5300 (solid content 30%), HYTEC P-5800 (solid content 30%), HYTEC P-5060P (solid content 40%) (manufactured by Toho Chemical Industry Co., Ltd.), Chemipearl A100 (solid content 40%) made of ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc.), Chemipearl V100 (solid content 40%), Chemipearl V200 (solid content 40%), Chemipearl V300 (solid content 40%) made of ethylene vinyl acetate copolymer resin (all manufactured by Mitsui Chemicals, Inc.), HYTEC S-3121 (solid content 25%), HYTEC S-3800 (solid content 25%), HYTEC S-9242 (solid content 20%), HYTEC S-9200 (solid content 20%), HYTEC S-8512 (solid content 25%), HYTEC S-3148K (solid content 25%) (all manufactured by Toho Chemical Industry Co., Ltd.) and the like.
These wax emulsions may be used alone or in combination of two or more.
Furthermore, as an antiseptic and antifungal agent for the aqueous pigment ink composition, sodium dehydroacetate, 1,2-benzisothiazalin-3-one, 2-pyridinethiol-1-oxide sodium salt, etc. can also be used. These antiseptic and antifungal agents have a synergistic effect when combined with 1,2-benzisothiazalin-3-one and 2-pyridinethiol-1-oxide sodium salt, and antiseptic and antifungal effects can be obtained with a smaller content.

The viscosity of the aqueous pigment ink composition for writing instruments of the present invention is not particularly limited and can be adjusted appropriately to suit the embodiment, such as a free-fill marker, ballpoint pen, brush, calligraphy pen, or correction fluid. Adjusting the viscosity appropriately to suit the embodiment is preferable because it ensures writing performance and storage stability, such as writing feel, uniformity of handwriting, handwriting density, suppression of bleeding, ink discharge stability, control of handwriting bleed-through to the paper, suppression of handwriting smearing, suppression of drying of the pen tip and nib, writing performance when dry, and pigment dispersion stability.

The aqueous pigment ink composition for writing instruments of the present invention can be produced by a variety of conventional methods. For example, water and bentonite are mixed and dispersed in a high-shear mixer such as a Henschel mixer, propeller mixer, homogenizer, turbo mixer, high-pressure homogenizer, or fine flow mill, followed by further mixing and stirring. The ink composition can be easily obtained by adding the pigment and other remaining ingredients dispersed in a disperser such as a Henschel mixer, propeller mixer, homogenizer, turbo mixer, high-pressure homogenizer, ball mill, bead mill, or roll mill, and further mixing and stirring. Furthermore, during these preparation processes, the generated heat of dispersion can be used for stirring, or the mixture can be heated or cooled for stirring. Removal of bubbles using a defoamer or filtration of coarse particles using a filter may also be performed as needed. These various mixing, dispersing, filtering, heating, and cooling processes may each be performed independently, or two or more of these processes may be performed in parallel.

The aqueous pigment ink composition for writing instruments of the present invention can be suitably used by filling it into a writing instrument, but it is not limited to writing instruments and may also be used in applicators for cosmetics such as eyeliner and eyebrow pencils.
Alternatively, the coating liquid storage chamber may be provided with a temporary ink reservoir member having a comb-like cross section that stores ink directly without using an ink absorbing material such as a fiber bundle, or may be provided with a valve mechanism that opens and closes automatically in response to operation or changes in internal pressure.
When the aqueous pigment ink composition used uses titanium oxide or a large-diameter plate-shaped luster pigment, it is preferable to store the ink composition directly in the coating liquid storage chamber without absorbing it in a fiber bundle called a batting so that the ink stored in the chamber is used up, and the ink supply mechanism to the coating tip is preferably one that uses a valve mechanism that can ensure a relatively large ink passage rather than one that passes through fine holes in a fiber bundle or a temporary ink reservoir member with a comb-like cross section, or one that is a ballpoint pen that controls ink discharge with a valve formed in the pen tip or has a tip valve mechanism. Furthermore, by using a brush-type coating tip that can freely form wide application marks as desired, wide application marks that demonstrate the luster of the ink can be formed.

FIG. 1 shows an example of the structure of a writing implement.
This is a brush pen type applicator with a so-called rear end knock type valve mechanism, in which a relatively soft object such as a brush tip is used as the application tip, a valve mechanism is arranged at the connection between the application tip and the application liquid storage chamber, and the valve mechanism is opened and closed by a rear end knock operation to control the ink supply to the application tip.
The barrel 1 has an application tip 2 at its tip and a push-in type operating part 3 at its rear end, and a cap 4 that protects the application tip 2 can be fitted to the tip of the barrel 1. The cap 4 has a roll prevention rib 4a on its side wall that prevents the applicator from rolling when attached.
The barrel 1 has a front barrel 1a having an opening through which the application tip 2 projects, and a rear barrel 1b to which the operating part 3 is connected.

The front section of the front barrel 1a, closest to the tip of the nib, has a small diameter that matches the diameter of the nib, while the rear section has a large diameter where it connects to the rear barrel 1b. Vertical ribs 5 that support the nib are evenly spaced around the inside wall of the small diameter section. Grooves 6 formed between these vertical ribs 5 also serve as vents for drawing in air equivalent to the volume of ink composition expelled during writing. The large-diameter rear section of the front barrel 1a houses a valve seat member 7 of the valve mechanism that controls the flow of ink. The valve seat member 7 has a central hole 7a at its center that serves as an ink passage, and its peripheral edge serves as a valve seat that can come into circumferential contact with the valve rod (described below). A coil spring 9 is fixed to the rear end of the valve seat member 7, which biases the valve rod 8 backward, keeping it in tight contact with the valve seat when not in use.

The rear barrel 1b has a rear hole 10 at its rear end, in which the operating element 3 is located. A connecting rod 11 protrudes from the rear hole 10, transmitting the pushing operation of the operating element 3 to the valve rod 8, and is liquid-tight sealed by a packing member 12 made of a rubber-elastic material and having a soft hinge portion 12a. When the operating element 3 is pushed toward the inside of the barrel, it abuts against the rear end of the packing member 12, and the packing member 12 receives a pushing force, causing the hinge portion 12a to deform and transmit the pushing force to the connecting rod 11. As the connecting rod 11 advances, the valve rod 8 advances against the elastic force of the coil spring 9, releasing the valve mechanism and allowing the ink composition to flow. The coil spring 9 abuts against the tip surface of the connecting rod 11, which forms the connecting step between the connecting rod 11 and the valve rod 8, and urges the connecting rod 11 and the valve rod 8 rearward. When the pressing operation is released, the connecting rod 11 and the valve rod 8 move rearward, closing the valve mechanism.

An application tip connection tube 13 is attached to the front end of the valve rod 8, and a brush-shaped application tip 2 is connected to the front end of the application tip connection tube 13. Therefore, the application tip 2 moves forward in conjunction with the pressing of the operating part 3, and when the pressing operation is released, the application tip 2 also moves backward due to the elastic force of the coil spring 9. In this way, an external force is applied to the ink composition present in the space around the application tip 2 with each operation, preventing it from drying and solidifying, and also assists in ejecting the ink composition. This mechanism is particularly effective when using a liquid with a relatively high solids content.

The interior of the rear barrel 1b primarily serves as the coating liquid storage chamber. A cylindrical polypropylene volume adjuster 14, which adjusts the volume of the coating liquid storage chamber, is positioned around the connecting rod 11 as an internal component. While the volume adjuster 14 may be fixed to the rear barrel 1b, it is preferable to leave it unfixed and free to move back and forth relative to the moving connecting rod 11. Reducing the volume of the coating liquid storage chamber in this way prevents the ink composition from being blown out by the expanded gas when the valve mechanism is opened, which would otherwise be generated by the vaporization of air or ink composition solvents due to temperature or pressure changes. Furthermore, using a transparent or translucent material for the rear barrel makes it possible to narrow at least a portion of the gap to facilitate the visibility of the color of the ink composition contained within, especially when using a luminous pigment or white titanium oxide as a colorant. Furthermore, the color of the ink composition can be further enhanced by selecting a color for the volume adjuster 14, such as black, white, or milky white.

When the rear barrel 1b is pressed to eject the ink composition, the rear barrel 1b can be made of a flexible material such as polyolefin resins such as low-density polyethylene, high-density polyethylene, and polypropylene, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamide, polyacrylonitrile, polycarbonate, polyvinyl chloride, polystyrene, polyoxymethylene, and various elastomers.

The above describes embodiments of the present invention, but the present invention is not limited to the above-described embodiments and also includes modifications to the above-described embodiments and appropriate combinations of these embodiments.

In this specification, expressions such as "identical,""equal," and "homogeneous" that indicate that things are in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
Furthermore, in this specification, the expressions "comprise,""include," or "have" a component are not exclusive expressions that exclude the presence of other components.

REFERENCE SIGNS LIST 1 barrel 1a front barrel 1b rear barrel 2 application point 3 operation part 4 cap 4a anti-roll rib 5 vertical rib 6 groove 7 valve seat member 7a central hole 8 valve rod 9 coil spring 10 rear hole part 11 connecting rod 12 packing member 12a hinge part 13 application point connection pipe 14 volume adjustment body

Claims (13)

An aqueous pigment ink composition for a writing instrument comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, and containing no dye, wherein the content of each of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid is 20% by weight or more of the total amino acid anionic surfactant content of the ink composition. An aqueous pigment ink composition for a writing instrument comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, and containing no dye, wherein the content of each of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid is 30% by weight or more of the total amino acid anionic surfactant content of the ink composition. An aqueous pigment ink composition for writing instruments comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, wherein the pigment content is 0.5% by weight or more and 20% by weight or less based on the total weight of the ink composition; the composition does not contain any dye; and the contents of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid are each 10% by weight or more based on the total amino acid anionic surfactant content of the ink composition. The aqueous pigment ink composition for writing instruments according to claim 3, wherein the content of the pigment is 1.0% by weight or more and 10.0% by weight or less based on the total weight of the ink composition. An aqueous pigment ink composition for a writing instrument, comprising at least two or more pigments, an amino acid anionic surfactant composed of an unsaturated fatty acid, an amino acid anionic surfactant composed of a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, containing no dye, wherein the content of each of the amino acid anionic surfactant composed of an unsaturated fatty acid and the amino acid anionic surfactant composed of a saturated fatty acid is 10% by weight or more of the total amino acid anionic surfactant content of the ink composition. An aqueous pigment ink composition for a writing instrument comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, and containing no dye; the total content of the amino acid anionic surfactants in the ink composition is 0.1% by weight or more and 5.0% by weight or less based on the total weight of the ink composition; and the content of each of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid is 10% by weight or more based on the total content of the amino acid anionic surfactants in the ink composition. An aqueous pigment ink composition for a writing instrument comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, and containing no dye, wherein the content of the resin emulsion is 1.0% by weight or more and 10.0% by weight or less based on the total weight of the ink composition, and the content of each of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid is 10% by weight or more based on the total amino acid anionic surfactant content of the ink composition. An aqueous pigment ink composition for a writing instrument comprising at least a pigment, an amino acid anionic surfactant comprising an unsaturated fatty acid, an amino acid anionic surfactant comprising a saturated fatty acid, a resin emulsion, a plate-like inorganic compound, and water, and containing no dye, wherein the content of the plate-like inorganic compound is 0.05% by weight or more and 3.0% by weight or less based on the total weight of the ink composition, and the content of each of the amino acid anionic surfactant comprising an unsaturated fatty acid and the amino acid anionic surfactant comprising a saturated fatty acid is 10% by weight or more based on the total amino acid anionic surfactant content of the ink composition. The aqueous pigment ink composition for writing instruments according to claim 8, wherein the content of the plate-like inorganic compound is 0.1% by weight or more and 2.0% by weight or less based on the total amount of the ink composition. The aqueous pigment ink composition for a writing instrument according to claim 8 or claim 9, wherein the plate-like inorganic compound is bentonite. A writing instrument or applicator that contains an aqueous pigment ink composition for a writing instrument in a coating liquid storage chamber, the coating liquid comprising at least a pigment, an amino acid anionic surfactant made from unsaturated fatty acids, an amino acid anionic surfactant made from saturated fatty acids, a resin emulsion, a plate-like inorganic compound, and water, and that does not contain a dye, and in which the content of each of the amino acid anionic surfactant made from unsaturated fatty acids and the amino acid anionic surfactant made from saturated fatty acids is 10% by weight or more relative to the total amino acid anionic surfactant content of the ink composition, and that can be discharged from the coating tip. The writing instrument or applicator according to claim 11, wherein the writing instrument is a marking pen, a brush pen, a ballpoint pen, or a correction fluid applicator. The writing instrument or applicator according to claim 11, wherein the applicator is either an eyeliner or an eyebrow pencil.