Writing utensil

Abstract

The present invention provides a writing utensil capable of suppressing discoloration of an aqueous ink caused by adsorption of a coloring material of the aqueous ink to a pen tip (a pen core or the like) in the writing utensil provided with the pen tip.　A writing utensil according to the present disclosure is equipped with an aqueous ink composition and is provided with a pen tip, the writing instrument being characterized in that the aqueous ink composition contains at least dye-containing colored resin particles which are each composed of a (meth)acrylic acid ester monomer and a dye, uncolored resin particles which are selected from the group Y described below, a phosphoric acid ester, and an alkali swellable emulsion.　Group Y: an acrylic resin, a styrene resin, a urethane resin, a vinyl acetate resin, and a nitrile resin

Description

writing implements

[0001] The present specification relates to a writing instrument loaded with an aqueous ink composition.

[0002] Conventionally, writing instruments equipped with aqueous ink compositions containing dye-based inks have had the problem that the dye gradually stains the pen tip over time, causing the drawn lines to differ from their initial hue and discolor when writing begins. In particular, in the case of inks that require YMCK color mixing and toning, when a pen tip, such as a pen body made of a resin material, is stored over time, only a specific dye stains the resin material, causing the drawn lines to not maintain their initial hue. For example, when green is produced by mixing yellow and blue, the yellow dye stains the resin of the pen tip over time, causing the drawn lines to turn blue. Similarly, in the case of red, the red dye stains the resin of the pen tip over time, causing the drawn lines to turn pale pink.

[0003] Specifically, conventional marking pens and brush pens use nibs made of various resins, such as nylon and polyester. Nylon nibs have good abrasion resistance and durability, allowing them to fully demonstrate the functions of a brush pen (stopping, flicking, strokes, etc.). However, they have the disadvantage of absorbing certain inks, which disrupts the color blend and causes the original color to be lost. The problem of ink absorption is determined by the structure of the colorant (dye), and Red No. 104 and Red No. 107 are typical examples of such dyes.

[0004] Known examples of nibs that are less likely to discolor when used with ink of a specific color, such as red, include a nylon nib for a brush pen that is made of a composite structure of nylon fibers with a single thread of 1 to 10 d and an elastomer resin, and that is characterized in that a dye-seat blocking element made of a halogenated diphenylurea derivative is attached to the nylon fibers (see, for example, Patent Document 1), and a nib for a brush pen that is made of a porous nib shape made of a bundled fiber body, and that is characterized in that the bundled fiber body is a composite structure of polytrimethylene terephthalate fibers and a polyurethane elastomer resin (see, for example, Patent Document 2).

[0005] However, even with the pen tips described in Patent Documents 1 and 2, discoloration of the ink can occur due to the coloring material of the writing instrument ink being adsorbed onto the pen core of the pen tip, and there are still issues with preventing discoloration, so the current situation is not satisfactory.

[0006] On the other hand, the applicant of the present application has disclosed: 1) a dispersion of colored resin microparticles for aqueous inks having excellent long-term stability and sufficient line drawing density, the dispersion comprising colored resin microparticles composed of at least a cyclohexyl (meth)acrylate monomer and a basic dye or an oil-soluble dye, the colored resin microparticles being dispersed in water, the content of the cyclohexyl (meth)acrylate monomer being 30% by mass or more, based on all polymer components constituting the colored resin microparticles, and the content of the basic dye or oil-soluble dye being 15% by mass or more, based on all polymer components; an aqueous ink composition for a writing instrument comprising this dispersion, a water-soluble organic solvent, and water; and a writing instrument incorporating this aqueous ink composition (see, for example, Patent Document 3); and 2) an aqueous ink composition for a writing instrument comprising at least colored resin particles (A) encapsulating a pigment (a) and uncolored resin particles (B) not containing any pigment (see, for example, Patent Document 4).

[0007] However, the aqueous ink composition for a writing instrument of Patent Document 3, which contains a dispersion in which colored resin microparticles encapsulating a dye are dispersed in water, and the writing instrument equipped with this aqueous ink composition, have excellent stability over time and a sufficient line density as an object and problem of the invention, and the aqueous ink composition for a writing instrument of Patent Document 4 contains colored resin particles encapsulating a pigment (a). Neither of these writing instruments nor aqueous ink compositions for writing instruments recognizes the problem that the coloring material of the aqueous ink for the writing instrument is adsorbed to the pen tip, and therefore differ in technical concept (configuration and its action and effect) from the present disclosure.

[0008] JP 09-315076 A (claims, examples, etc.) JP 2002-19368 A (claims, examples, etc.) JP 2019-112561 A (claims, examples, etc.) JP 2021-70715 A (claims, examples, etc.)

[0009] The present disclosure is made in view of the above-mentioned problems and current state of the prior art, and aims to solve these problems, and to provide a writing instrument that is equipped with an aqueous ink composition containing a dye-based ink and that can suppress discoloration of ink caused by the coloring material of the aqueous ink being adsorbed onto the nib (pen core, etc.) of the writing instrument.

[0010] In view of the above-mentioned conventional problems, the present inventors have conducted extensive research and have found that a writing instrument having a pen tip and an aqueous ink composition can be obtained by including colored resin particles containing a dye composed of at least a monomer having specific physical properties and a dye, specific uncolored resin particles, a phosphate ester, and an alkali association emulsion, thereby completing the present disclosure.

[0011] That is, the writing instrument of the present disclosure is a writing instrument equipped with a pen tip and equipped with an aqueous ink composition, wherein the aqueous ink composition contains at least colored resin particles encapsulating a dye composed of a (meth)acrylic acid ester monomer and a dye, uncolored resin particles selected from the following Group Y, a phosphate ester, and an alkali association emulsion. Group Y: acrylic resin, styrene resin, urethane resin, vinyl acetate resin, nitrile resin. The dye of the colored resin particles is preferably a dye selected from the following Group X. Group X: oil-soluble dyes, basic dyes, and acid dyes having an amine group and a heteroheterocycle. The pH of the aqueous ink composition is preferably 10.0 or less. The material of the pen tip is preferably selected from a polyester core, an acrylic core, a nylon core, a polybutylene terephthalate (PBT) core, a polyethylene core, a rubber core, a urethane core, a polyacetal (POM) core, a polypropylene (PP) core, a polyethylene naphthalate (PEN) core, and a polyethylene terephthalate (PET) core.

[0012] In accordance with the present disclosure, there is provided a writing instrument that can suppress discoloration of water-based ink caused by adsorption of a coloring material to the nib of the writing instrument. The objects and advantages of the present disclosure will be realized and attained by use of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the scope of the disclosure as defined by the claims.

[0013] 2A and 2B are drawings showing an example of an embodiment of a direct-flow writing instrument using the aqueous ink composition for a writing instrument of the present disclosure, where (a) is a front view, (b) is a front vertical cross-sectional view, and (c) is a vertical cross-sectional view of (b) viewed from a 90° expanded direction.

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[0023] Figures 5A and 5B show an example of an embodiment of a writing instrument using the aqueous ink composition for a writing instrument of the present disclosure with the filler-type cap removed, where (a) is a front view, (b) is a front view of (a) as viewed from a 90° expanded direction, (c) is a longitudinal cross-sectional view, and (d) is a longitudinal cross-sectional view of (c) as viewed from a 90° expanded direction.

[0024] Figures 5A and 5B show an example of another embodiment of a filler-type writing instrument using the aqueous ink composition for a writing instrument of the present disclosure, where (a) is a front view and (b) is a longitudinal cross-sectional view.

[0025] Figure 5B shows an enlarged longitudinal cross-sectional view of the portion indicated by the symbol X in Figure 5B.

[0014] Embodiments of the present disclosure are described in detail below. However, please note that the technical scope of the present disclosure is not limited to the respective embodiments detailed below, but extends to the inventions set forth in the claims and their equivalents. The writing instrument of the present disclosure is a writing instrument equipped with a pen tip and loaded with an aqueous ink composition, characterized in that the aqueous ink composition contains at least colored resin particles composed of a (meth)acrylic acid ester monomer and a dye, uncolored resin particles selected from the following Group Y, a phosphate ester, and an alkali association emulsion. Group Y: acrylic resin, styrene resin, urethane resin, vinyl acetate resin, nitrile resin

[0015] <Aqueous Ink Composition> In the aqueous ink composition of the present disclosure, the (meth)acrylic acid ester monomer used in the colored resin particles is used because it can produce the dye that can be encapsulated (described later) as long-lasting, stable particles, it does not have an adverse effect on other formulation components, etc., and it is available as a reaction substrate. The (meth)acrylic acid ester monomer used is not particularly limited, and it is preferable to use a (meth)acrylic acid ester monomer represented by the following general formula (I).

[0016] A in the above general formula (I) is a hydrogen atom (H) or a methyl group (CH ３) wherein R represents a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a substituent having a polyalkylene glycol chain in which the alkylene chain has 2 to 18 carbon atoms, and the alkyl group or the substituent having a polyalkylene glycol chain may have a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group as a substituent. Examples of R in the above general formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, and an alkyl group having 1 to 18 carbon atoms which may have an epoxy group, a hydroxyl group, a dialkylamino group, or an alkoxy group having 1 to 4 carbon atoms as a substituent, particularly an alkyl group having 1 to 6 carbon atoms which may have an epoxy group, a hydroxyl group, or an alkoxy group having 1 to 2 carbon atoms as a substituent, and an alkyl group having 1 to 6 carbon atoms which may have an epoxy group as a substituent. Preferably, R in the above general formula (I) is a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a hydroxyl group, a trifluoroethyl group, a dimethylaminoethyl group, a methoxyethyl group, a hydroxyethyl group, a hydroxypropyl group, an allyl group, a tetrahydrofurfuryl group, a phenyl group, a benzyl group, a butoxydiethylene glycol group, a methoxypolyethylene glycol group, a dimethylaminoethyl group, a diethylaminoethyl group, a dimethylaminoethyl group, a glycidyl group, ethyl phosphate, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, etc. In this specification, the expression "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0017] Specific examples of the (meth)acrylic acid ester represented by the general formula (I) used include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, Isobornyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate methyl chloride salt, diethylaminoethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-Hexanediol, trimethylolpropane tri(meth)acrylate, 2-(meth)acroyloxyethyl phthalate, 2-(meth)acroyloxyethyl hexahydrophthalate, trifluoroethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, diethylene glycol (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(dimethylamino)propyl, 2-(dimethylamino)butyl (meth)acrylate, 2-isocyanoethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, perfluoroethyl methacrylate having a perfluoroalkyl group having 1 to 18 carbon atoms, 2-(phosphate)ethyl (meth)acrylate [2-(methacryloyloxy)ethyl phosphate], trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, etc. (each may be used alone or in combination, the same applies hereinafter). Of these, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate are preferred, in terms of industrial availability, ease and safety in handling during production, and further improving the effects of the present disclosure.

[0018] In the present disclosure, in addition to the (meth)acrylic acid ester monomers described above, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers may preferably be used, for example, from the viewpoint of obtaining long-lasting and stable particles. Examples of hydrophobic vinyl monomers that can be used include at least one monomer other than the (meth)acrylic acid ester monomers described above, such as styrenes, methylstyrene, and other styrenes. Examples of hydrophobic vinyl monomers that can be used include at least one of styrene, methylstyrene, chloromethylstyrene, alkylstyrenes having an alkyl group containing 1 to 12 carbon atoms, methoxystyrene, chlorostyrene, bromostyrene, divinylbenzene, phenylstyrene, vinylnaphthalene, and the like. Examples of aqueous monomers that can be used include at least one of glycerin monomethacrylate, 2-sulfoethyl sodium methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-propylene glycol monomethacrylate, polyethylene glycol-tetramethylene glycol-monomethacrylate, propylene glycol-polybutylene glycol-monomethacrylate, and the like.

[0019] The dyes that can be used in the present disclosure include, without limitation, dyes that have been used in inks for conventional writing instruments. Usable dyes include, for example, oil-soluble dyes, basic dyes, acid dyes, metal complex dyes, salt-forming dyes, azine dyes, anthraquinone dyes, direct dyes, food dyes, and oxazine dyes. From the viewpoints of high coloring power and high compatibility with the particle skeleton resin, the dye of the colored resin particles is preferably a dye selected from the following Group X. Group X: oil-soluble dyes, basic dyes, and acid dyes having an amine group or heteroheterocycle.

[0020] As the oil-soluble dye to be used, can be mentioned the monoazo, disazo, metal complex type monoazo, anthraquinone, phthalocyanine, triarylmethane etc. that are generally commercially available, can also be used the salt-forming type oil-soluble dye that the functional group of acid or basic dye etc. is replaced with hydrophobic group, preferably, it is desirable to use the oil-soluble dye that has amine group or hetero heterocycle.As yellow, can be mentioned C.I. Solvent Yellow 114, 116;As orange, can be mentioned C.I. Solvent Orange 67;As red, can be mentioned C.I. Solvent Red 122, 146;As blue, can be mentioned C.I. Solvent Blue 5, 36, 44, 63, 70, 83, 105, 111;As black, can be mentioned C.I. Solvent Black 3, 7, 27, 29 etc. Specific examples of commercially available oil-soluble dyes include blue dye SBN Blue 701 (manufactured by Hodogaya Chemical Co., Ltd.), blue dye Oil Blue 650 (manufactured by Orient Chemical Industry Co., Ltd.), blue dye Saninyl Blue GLS (manufactured by Clariant), red dye SOC-1-0100 (manufactured by Orient Chemical Industry Co., Ltd.), Oil Black 860, Oil Pink 314, Oil Yellow 3G, Oil Yellow 129, Varifast Pink 2310N, Varifast Red 3312, Varifast Yellow CGHNnew, Varifast Yellow 1108, Varifast Black 3830, Varifast Blue 2680, and Optima Yellow 6101 (manufactured by Orient Chemical Industry Co., Ltd.). Preferred examples of oil-soluble dyes having an amine group or heteroheterocycle include Oil Pink 314, Varifast Pink 2310N, Varifast Red 3312, Varifast Yellow CGHNnew, Varifast Yellow 1108, and Varifast Blue 2680.

[0021] The acid dyes used are water-soluble dyes having an acidic group such as a sulfonic acid group or a carboxyl group in the dye molecule, or a salt structure thereof. Some acid dyes are classified as direct dyes, which have a large molecular weight and a planar structure among acid dyes, and the salt-forming compound of a direct dye and a basic dye has particularly excellent heat resistance. By suitably selecting the above-mentioned (meth)acrylic acid ester monomer of the resin particles used in the colored resin particles, the coloring properties and heat resistance can be further improved.

[0022] Usable direct dyes include, for example, azo dyes, thiazole dyes, anthraquinone dyes, oxazine dyes, and phthalocyanine dyes. Usable dyes are exemplified below by their Color Index (C.I.) numbers. Examples of azo dyes include C.I. Direct Yellow 2, 33, 34, 35, 39, 50, 69, 70, 71, 86, 93, 94, 95, 98, 102, 109, 129, 136, and 141; C.I. Direct Orange 41, 46, 56, 61, 64, 70, 96, 97, 106, and 107; and C.I. Direct Red 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 86, 93, 94, 95, 98, 102, 109, 129, 136, and 141; C.I. Direct Orange 41, 46, 56, 61, 64, 70, 96, 97, 106, and 107; and C.I. Direct Red 52, 53, 54, 55, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 C.I.Direct Violet 47, 52, 54, 60, 65, 66, 79, 80, 81, 82, 84, 89, 90, 93, 95, 96, 103, 104; C.I. Direct Blue 51, 57, 71, 81, 84, 85, 90, 93, 94, 95, 98, 100, 101, 113, 149, 150, 153, 160, 162, 163, 164, 166, 167, 170, 172, 188, 192, 193, 194, 196, 198, 2 C.I. Direct Green 27, 34, 37, 65, 67, 68, 69, 72, 77, 79, 82, etc. An example of a thiazole dye is C.I. Direct Yellow 54.

[0023] Examples of oxazine dyes include C.I. Direct Blue 97, 99, 106, 107, 108, 109, 190, and 293. Examples of anthraquinone dyes include C.I. Direct Blue 77. Examples of phthalocyanine dyes include C.I. Direct Blue 86, 87, 189, and 199. Other direct dyes include C.I. Direct Yellow 38, 43, 47, 58, 68, 108, 138; C.I. Direct Orange 34, 39, 50, 52, 57, 65, 68; C.I. Direct Red 91, 92, 96, 105, 184, 220, 234, 241; C.I. Direct Violet 59; C.I. Direct Blue 80, 114, 115, 117, 119, 137, 155, 156, 158, 159, 161, 171, 173; C.I. Direct Green 25, 31, 32, 63, 66, and the like.

[0024] Examples of acid dyes that can be used other than direct dyes include azo dyes, xanthene dyes, phthalocyanine dyes, anthraquinone dyes, quinoline dyes, azine dyes, and indigoid dyes. Examples of azo dyes include C.I. Acid Red 1, 3, 4, 6, 8, 11, 12, 14, 18, 26, 27, 33, 37, 53, 57, 88, 106, 108, 111, 114, 131, 137, 138, 151, 154, 158, 159, 173, 184, 186, 215, 257, 266, 296, and 337; C.I. Acid Orange 7, 10, 12, 19, 20, 22, 28, 30, 52, 56, 74, and 127; C.I. Acid Violet 11, 56, and 58; and C.I. Acid Yellow. C.I. Acid Brown 2, 4, 13, 248; C.I. Acid Blue 92, 102, 113, 117, and the like.

[0025] Examples of xanthene dyes include C.I. Acid Red 50, 51, 52, and 87. Examples of phthalocyanine dyes include C.I. Acid Blue 249. Examples of anthraquinone dyes include C.I. Acid Red 82 and 92; C.I. Acid Violet 41, 42, and 43; C.I. Acid Blue 14, 22, 25, 40, 45, 78, 80, 127:1, 129, 145, 167, and 230; and C.I. Acid Green 25 and 27. Examples of quinoline dyes include C.I. Acid Yellow 3. Examples of the azine dyes include C.I. Acid Blue 59 and 102. Examples of the indigoid dyes include C.I. Acid Blue 74.

[0026] Other dyes include C.I. Acid Violet 49; C.I. Acid Brown 19; C.I. Acid Blue 7, 9, 74, 112, 126, 167; C.I. Acid Green 9, and the like.

[0027] The basic dye used in the present disclosure is a dye that has a basic group such as an amino group or an imino group in the molecule, or a salt structure thereof, and becomes a cation in an aqueous solution. Examples of usable basic dyes include di- and triarylmethane dyes; quinoneimine dyes such as azines (including nigrosine), oxazines, and thiazines; xanthene dyes; triazole azo dyes; thiazole azo dyes; benzothiazole azo dyes; azo dyes; methine dyes such as polymethines, azomethines, and azamethines; anthraquinone dyes; phthalocyanine dyes; acridine dyes, rhodamine dyes, and triarylmethane dyes, and preferably, water-soluble basic dyes are desirable. Specific examples of usable yellow basic dyes include C.I. Examples of the yellow basic dye include dyes listed in the COLOR INDEX, such as Basic Yellow 1, 2, 9, 11, 12, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 33, 34, 35, 36, 40, 41, 51, 63, 73, and 80. Examples of commercially available yellow basic dyes include AIZEN CATHILON YELLOW GPLH and Spillon Yellow C-GNH-new (trade names manufactured by Hodogaya Chemical Co., Ltd.).

[0028] Examples of orange basic dyes include dyes listed in the COLOR INDEX such as C.I. Basic Orange 1, 2, 7, 14, 15, 21, 22, 23, 24, 25, 30, 32, 33, and 34. Examples of red basic dyes include C.I. Examples of dyes include those described in the COLOR INDEX such as Basic Red-1, -2, -3, -4, -8, -9, -12, -13, -14, -15, -16, -17, -18, -22, -23, -24, -25, -26, -27, -29, -30, -32, -34, -35, -36, -37, -38, -39, -40, -41, -42, -43, -46, -49, -50, -51, -52, and -53. Commercially available red basic dyes include Aizen Cathilon Red BLH and Aizen Cathilon Red RH (trade names manufactured by Hodogaya Chemical Co., Ltd.), Diacryl Supra Brilliant Red 2G (trade name manufactured by Mitsubishi Chemical Corporation), and Sumiacryl Red B (trade name manufactured by Sumitomo Chemical Co., Ltd.).

[0029] Examples of purple basic dyes include dyes listed in the COLOR INDEX such as C.I. Basic Violet 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 11:1, 12, 13, 14, 15, 16, 18, 21, 23, 24, 25, 26, 27, 28, 29, 33, and 39. Examples of blue basic dyes include C.I. Examples of the dyes listed in the COLOR INDEX include Basic Blue 1, 2, 3, 5, 6, 7, 8, 9, 15, 18, 19, 20, 21, 22, 24, 25, 26, 28, 29, 33, 35, 37, 40, 41, 42, 44, 45, 46, 47, 49, 50, 53, 54, 58, 59, 60, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 75, 77, 78, 79, 82, 83, 87, and 88. Examples of commercially available blue basic dyes include AIZEN CATHILON TURQUOISE BLUE LH (trade name manufactured by Hodogaya Chemical Co., Ltd.). Examples of green basic dyes include C.I. Examples of the color index include dyes listed in the color index of C.I. Basic Green 1, 4, 6, 10, etc. In addition, commercially available green basic dyes include Diacryl Supra Brilliant Green 2GL (trade name of Mitsubishi Chemical Corporation). Examples of the brown basic dyes include dyes listed in the color index of C.I. Basic Brown 1, 2, 4, 5, 7, 11, 12, 13, 15. In addition, commercially available brown basic dyes include Janus Brown R (trade name of Nippon Chemical Industry Co., Ltd.) and AIZEN CATHILON BROWN GH (trade name of Hodogaya Chemical Co., Ltd.). Examples of the black basic dyes include C.I. Examples of the dyes include those listed in the Color Index such as Basic Black 1, 2, 3, 7, and 8, and Nigrosine-based basic dyes.

[0030] The colored resin particles of the present disclosure are composed of at least a (meth)acrylic acid ester monomer represented by the above general formula (I) or the like and a dye, and can be produced, for example, by dissolving the above-mentioned dyes, preferably at least one selected from oil-soluble dyes having an amine group and a heteroheterocycle, basic dyes, and acid dyes, in the above-mentioned (meth)acrylic acid ester monomer (either alone or in combination, the same applies hereinafter) or in a mixed monomer containing the above-mentioned (meth)acrylic acid ester monomer and other hydrophobic vinyl monomers and / or aqueous monomers, and then adding ammonium persulfate to the resulting mixture. The polymerization initiator may be sodium, potassium persulfate, hydrogen peroxide, or the like, or may be a polymerization initiator further combined with a reducing agent, and further, triallyl isocyanurate, triallyl isocyanurate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol acrylate, ditrimethylolpropane acrylate, dipentaerythritol acrylate, methoxylated bisphenol A methacrylate, pentaerythritol methacrylate, ditrimethylolpropane methacrylate, dipentaerythritol methacrylate, crosslinking agents such as ethoxylated polyglycerin methacrylate, and, if necessary, polyoxyethylene-1-(allyloxymethyl)-alkyl ether ammonium sulfate, ether sulfate, polyoxyethylene nonylpropenylphenyl ether ammonium sulfate, polyoxyethylene nonylpropenylphenyl ether, ammonium polyacrylate, styrene-maleic acid copolymer ammonium, polyoxyethylene alkyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene decyl ether, polyoxyethylene tridecyl ether, alkylbenzene sulfonate, dioctyl sulfosuccinate, sodium lauryl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene styrenated phenyl ether phosphate, polyoxyethylene styrenated phenyl ether sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene sorbitan monolaurate (polysorbate 20), polyoxyethylene sorbitan palmitate (polysorbate 40),The colored resin particles can be produced by emulsion polymerization using a polymerizable surfactant (emulsifier) ​​such as polyoxyethylene sorbitan monostearate (polysorbate 60) or polyoxyethylene sorbitan oleate (polysorbate 80), and can be formed into colored resin particles by producing a dispersion of resin particles and then drying the dispersion. The use of a crosslinking agent such as triallyl isocyanurate is preferred because it improves the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the colored resin particles.

[0031] In the present disclosure, the emulsion polymerization may be carried out by further mixing an appropriate amount of dicyclopenta(tenyl)(meth)acrylate monomer or the like with the (meth)acrylic acid ester monomer or the like. When this dicyclopenta(tenyl)(meth)acrylate monomer is further mixed and then emulsion polymerized, stability is less likely to be lost even if the water in the dispersion evaporates, and the dye-encapsulated colored resin particles described above have even better stability. Usable dicyclopenta(tenyl)(meth)acrylate monomers include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate. In the present disclosure, during the emulsion polymerization, in addition to the dicyclopenta(thenyl)(meth)acrylate monomer, an appropriate amount of a monomer having a reactive crosslinking group such as an epoxy group, a hydroxymethylamide group, or an isocyanate group, or a polyfunctional monomer having two or more vinyl groups may be blended to cause crosslinking, such as the (meth)acrylic acid ester monomer or other hydrophobic vinyl monomers.

[0032] In the present disclosure, the content of the (meth)acrylic acid ester monomer among the polymer components constituting the colored resin particles is preferably 30% by mass or more, more preferably 30 to 95% by mass, and particularly preferably 30 to 70% by mass, relative to the total polymer components constituting the colored resin particles. In the present disclosure, the term "total polymer components" refers to the polymerizable components constituting the colored resin particles, specifically the total amount of the (meth)acrylic acid ester monomer used, the other monomer components used, and the crosslinking agent described below. By ensuring that the content of the (meth)acrylic acid ester monomer is 30% by mass or more relative to the total polymer components, the effects of the present disclosure can be further exhibited. On the other hand, if this content is less than 30% by mass, the stability over time tends to be poor.

[0033] Furthermore, among the polymer components constituting the colored resin particles, the content of other monomer components other than the (meth)acrylic acid ester monomer is the remainder of the total amount of the (meth)acrylic acid ester monomer and the crosslinking agent described below. Preferably, the content of other monomer components is 0.5 to 70 mass% of the total polymer components from the viewpoints of further exhibiting the effects of the present disclosure, dispersibility, and reactivity.

[0034] In the present disclosure, the total (solids content) content of the dyes is desirably 1% by mass or more, preferably 5% by mass or more, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass, based on the total polymer components, from the viewpoints of obtaining sufficient line density, achieving sustained stabilizing effects, and suppressing precipitation. By setting the dye content to 1% by mass or more, sufficient line density and sustained stabilizing effects can be achieved, while a dye content of 50% by mass or less makes dye precipitation and dispersion collapse less likely to occur.

[0035] The polymerizable surfactant that can be used as needed is not particularly limited as long as it is a polymerizable surfactant that is normally used in the emulsion polymerization. For example, the polymerizable surfactant is an anionic or nonionic polymerizable surfactant, and examples thereof include at least one of ADEKA REASOAP NE-10, NE-20, NE-30, NE-40, and SE-10N manufactured by ADEKA CORPORATION, LATEMURU S-180, S-180A, and S-120A manufactured by Kao Corporation, ELEMINOL JS-20, CLS-20, RS-3000, and CARABO DA72 manufactured by Sanyo Chemical Industries, Ltd., AQUALON KH-05, 10, HS-10, AR-10, and RN-10 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and ANTOX MS-60 manufactured by Nippon Nyukazai Co., Ltd. The amount of the polymerizable surfactant used is preferably 0 to 50% by mass, and more preferably 0.1 to 50% by mass, based on the total amount of the monomers. The amount of the crosslinking agent such as triallyl isocyanurate used is preferably 0 to 50% by mass, and more preferably 0.1 to 25% by mass, based on the total amount of the monomers.

[0036] In the present disclosure, a preferred embodiment, specifically, at least one of the dyes described above, preferably oil-soluble dyes having an amine group or heteroheterocycle, basic dyes, and acid dyes, is dissolved in the (meth)acrylic acid ester monomer and emulsion-polymerized, or a mixed monomer containing the (meth)acrylic acid ester monomer and other monomer components is polymerized, followed by dissolving the dye and emulsion-polymerizing the resulting dye. The amount of resin particles in the colored resin particle dispersion obtained under these production conditions varies depending on the amount of the (meth)acrylic acid ester monomer and dye components used, the polymerization conditions, etc. From the perspectives of manufacturability, workability, efficiency, etc., it is preferable to produce the dispersion so that the solids content is 1 to 50% by mass. More preferably, it is preferable to produce the dispersion so that the solids content is 10 to 40% by mass.

[0037] In the present disclosure, the average particle size of the resulting colored resin particles varies depending on the (meth)acrylic acid ester monomer, the type and content of other monomers used, the polymerization conditions during polymerization, and the like, but is preferably 10 to 800 nm, more preferably 20 to 300 nm, and even more preferably 30 to 200 nm. By setting the average particle size within the above preferred range, the colored resin particles exhibit even better storage stability, and resin particles having an average particle size range suitable for each application described below can be used. When used in the aqueous ink composition of the writing instrument of the present disclosure, the ink does not clog the core of a writing instrument such as a felt-tip pen, a marking pen, or a ballpoint pen, and exhibits even better storage stability. The "average particle size" defined in the present disclosure is the histogram average particle size obtained by scattering light intensity distribution, and in the present disclosure (including the examples described below), it is the D50 value measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)].

[0038] The content of the colored resin particles of the present disclosure is preferably 0.1 to 50 mass % in terms of solid content relative to the total amount of the ink composition, and more preferably 1 to 30 mass %. If the content of these resin particles is less than 0.1 mass % in terms of solid content, the effects of the present disclosure cannot be exerted, while if it exceeds 50 mass %, the long-term storage stability is likely to decrease.

[0039] The uncolored resin particles used in the present disclosure are uncolored resin particles composed of a resin selected from Group Y: acrylic resin, styrene resin, urethane resin, vinyl acetate resin, and nitrile resin, and the manufacturing method, such as the polymerization method, is not particularly limited. Examples include crosslinked or cured resin particles, and uncrosslinked or uncured resin particles. Furthermore, commercially available products can be used. Urethane resins include urethane as well as urethane-based resins such as urea or ureaurethane. Examples of uncolored acrylic resin particles include polymethyl methacrylate, polymethyl acrylate, polybutyl methacrylate, polycyclohexyl methacrylate, polyisobornyl methacrylate, poly2-ethylhexyl acrylate, polyphthalic acid ester, polybutyl acrylate, lauryl acrylate, polyacrylic acid, polymethacrylic acid, polydiethylaminoethyl methacrylate, and composite acrylic polymers thereof, as well as copolymers of styrene, nitrile, vinyl acetate, and urethane. Examples of uncolored styrene resin particles include polystyrene, polymethylstyrene, polyisobutyl methacrylate ... Examples of uncolored resin particles of urethane resin include urethane (polyurethane resin), urea (polyurea resin), and ureaurethane (polyurea resin / polyurethane resin). Examples of uncolored resin particles of vinyl acetate resin include polyvinyl acetate. Examples of uncolored resin particles of nitrile resin include polyacrylonitrile, polymethacrylonitrile, ABS resin, and AS resin.

[0040] The average particle diameter of these uncolored resin particles is preferably 10 to 800 nm, more preferably 20 to 300 nm, and even more preferably 30 to 200 nm. By setting the average particle diameter of the uncolored resin particles within the preferred range, the storage stability and other properties can be further improved. Furthermore, the surface tension of the uncolored resin particles used is preferably higher than that of the colored resin particles described above, from the viewpoints of suppressing bleeding and improving dispersion stability. Specifically, it is preferably 5 mN / m or more higher than the surface tension of the colored resin particles, more preferably 10 mN / m to 30 mN / m. The surface tensions of these colored resin particles, uncolored resin particles, and the ink composition described below are measured at 25°C using a surface tension meter manufactured by Kyowa Interface Science Co., Ltd. and a platinum plate by the vertical plate method.

[0041] These uncolored resin particles are included for the purposes of preventing bleeding, adjusting wettability to components, adsorbing precipitates, improving dispersion stability, and adjusting viscosity. Their content is preferably 0.1 to 30% by mass, more preferably 1 to 25% by mass, in terms of solid content, relative to the total amount of the ink composition. If the content of these resin particles is less than 0.1% by mass in terms of solid content, the above-mentioned effects will not be fully achieved, and the effects of the present disclosure will not be exhibited. On the other hand, if the content exceeds 30% by mass, long-term storage stability will be reduced. Furthermore, when the solid content of the colored resin particles and the solid content of the uncolored resin particles in the total amount of the aqueous ink composition are (A) and (B), respectively, it is desirable from the perspectives of bleeding resistance and stability over time that the ratio A / B be 0.01 to 100, more preferably 0.5 to 10.

[0042] Examples of phosphate esters that can be used include alkyl phosphate esters, which are esters of aliphatic alcohols and phosphoric acid; alkyl ether phosphate esters, which are esters of alkylene oxide adducts of aliphatic alcohols and phosphoric acid; alkyl phenyl ether phosphate esters, which are esters of alkylene oxide adducts of aromatic alcohols and phosphoric acid; and derivatives thereof. These phosphate esters may be used alone or in combination of two or more. Preferred examples include polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoesters, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diesters and phosphate triesters, and derivatives thereof. In the present disclosure, particularly significant effects are achieved when using phosphate esters that are highly soluble in ink, specifically phosphate esters with an HLB value of 5 to 20. The "HLB value" in the present disclosure can be calculated using the Kawakami method (HLB value = 7 + 11.7 log (MW / MO), where MW is the molecular weight of the hydrophilic portion and MO is the molecular weight of the lipophilic portion).

[0043] Specific examples of phosphate esters that can be used include the Phosphanol series manufactured by Toho Chemical Industry Co., Ltd. and the Plysurf series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Examples of the Phosphanol series include Phosphanol ML-220, RB-410, RD-510Y, RD-720N, RL-210, RL-310, RS-410, RS-610, and RS-710 (all manufactured by Toho Chemical Industry Co., Ltd.), and products manufactured by Nikko Chemicals include NIKKOL DLP-10, DOP-8N, DDP-2, DDP-4, DDP-6, DDP-8, and DDP-10. Examples of the Plysurf series include Plysurf AL (polyoxyethylene styrenated phenyl ether phosphate, HLB value: 5.6), Plysurf A208B (polyoxyethylene (2) lauryl ether phosphate, HLB value: 6.6), Plysurf A208F (polyoxyethylene (3) alkyl (C8) ether phosphate, HLB value: 8.7), Plysurf A212C (polyoxyethylene (6) tridecyl ether phosphate, HLB value: 9.4), Plysurf A215C (polyoxyethylene (10) tridecyl ether phosphate, HLB value: 11.5), and Plysurf A219B (polyoxyethylene (20) lauryl ether phosphate, HLB value: 16.2). These can be used as is or as salts neutralized with alkali metals or organic bases. Two or more types may also be used in combination.

[0044] The content of these phosphate esters is desirably 0.05 to 2.0%, preferably 0.1 to 1.0%, of the total amount of the ink composition from the viewpoints of suppressing dye adsorption to the pen core and preventing the drawn lines from bleeding. Furthermore, as surfactants other than the above phosphate esters, nonionic surfactants, anionic surfactants, and cationic surfactants can be used as appropriate, with nonionic surfactants or anionic surfactants being preferred. Of these, fluorine-based, acetylene-based, or silicone-based nonionic or anionic surfactants are preferred.

[0045] The alkali association emulsion used is thickened by adding alkali to neutralize it.Specific examples of the alkali association emulsion include poly(meth)acrylic acid emulsion polymer, polymer emulsions having a copolymer of acrylic acid and alkyl acrylate ester as the polymer fraction, polymer emulsions having a copolymer of acrylic acid and alkyl methacrylate ester as the polymer fraction, polymer emulsions having a copolymer of acrylic acid, alkyl acrylate ester and alkyl methacrylate ester as the polymer fraction, polymer emulsions having a copolymer of acrylic acid, alkyl acrylate ester and alkyl methacrylate ester as the polymer fraction, polymer emulsions having a copolymer of acrylic acid, alkyl acrylate ester and polyethylene glycol acrylate as the polymer fraction, Examples of suitable emulsions include polymer emulsions containing a copolymer of acrylic acid, an alkyl methacrylate, and an acrylic acid (polyoxyethylene monoalkyl ether) ester as the polymer content, polymer emulsions containing a copolymer of acrylic acid, an alkyl methacrylate, and an acrylic acid (polyoxyethylene monoalkyl ether) ester as the polymer content, polymer emulsions containing a copolymer of acrylic acid, an alkyl methacrylate, and an acrylic acid (polyoxyethylene monoalkyl ether) ester as the polymer content, polymer emulsions containing a copolymer of acrylic acid, an alkyl acrylate, and an itaconic acid (polyoxyethylene monoalkyl ether) ester as the polymer content, and the like. The alkyl groups of the alkyl acrylates and alkyl methacrylates may be one type having 1 to 12 carbon atoms, or two or more types. Natural polysaccharide thickeners may also be used as appropriate in combination with the above-mentioned alkali association emulsions.

[0046] As described above, the alkali association emulsion used is an alkali-thickening type, and therefore preferably contains acrylic acid or methacrylic acid as an essential monomer constituting the polymer. When acrylic acid or methacrylic acid is contained in the constituent monomers of the polymer, the carboxyl group is neutralized by the alkali, causing the structure of the polymer in water to change and the viscosity to increase. Specifically, (meth)acrylic acid emulsion polymers, polymer emulsions containing a copolymer of acrylic acid and an alkyl acrylate ester as the polymer component, and polymer emulsions containing a copolymer of acrylic acid and an alkyl methacrylate ester as the polymer component are preferably used.

[0047] Commercially available alkali association emulsions include "Primal TT-615" (solid content: 30%, alkali association acrylic resin emulsion, manufactured by Rohm & Haas), "Rheotec 3800" (solid content: 30%, manufactured by Arkema), and "SN Thickener 630" (solid content: 30%, manufactured by SAN NOPCO). These may be used singly or in appropriate combination of two or more types, as required.

[0048] These alkali association emulsions are contained in order to enhance the effect of inhibiting dyeing of the pen core and to inhibit bleeding onto the paper surface, and their content is preferably 0.1 to 30 mass % in terms of solid content relative to the total amount of the ink composition, and more preferably 1 to 25 mass %. If the content of this alkali association emulsion is less than 0.1 mass % in terms of solid content, the active ingredient will be insufficient and the effects of the present disclosure will not be exerted, whereas if it exceeds 30 mass %, the ink viscosity will increase, resulting in poor ink tracking during writing and poor stability over time.

[0049] The aqueous ink composition to be incorporated into the writing instrument of the present disclosure is characterized by containing at least colored resin particles composed of a (meth)acrylic acid ester monomer and a dye, uncolored resin particles selected from the above-mentioned Group Y, a phosphate ester, and an alkali association emulsion, and may contain, in addition to these components, a water-soluble organic solvent, a pH adjuster, a preservative, etc.

[0050] Examples of usable water-soluble organic solvents include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol, and 2-methylpentane. alkylene glycols such as 1,2,4-diol, 3-methylpentane-1,3,5-triol, and 1,2,3-hexanetriol; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; glycerols such as glycerol, diglycerol, and triglycerol; lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol mono-n-butyl ether; N-methyl-2-pyrrolidone; and 1,3-dimethyl-2-imidalidinone.

[0051] Other water-soluble solvents that can be mixed include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol, amides such as dimethylformamide and diethylacetamide, and ketones such as acetone. The content of these water-soluble organic solvents varies depending on the type of writing implement, such as a felt-tip pen or marking pen, and the type of pen tip component, but is particularly effective in an ink composition with a content of 1 to 40% by mass of the total ink composition, and 10% by mass or less from the viewpoint of further improving the drying properties of drawn lines, and more preferably 3 to 8% by mass.

[0052] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonate or phosphate such as sodium tripolyphosphate and sodium carbonate, and hydrates of alkali metals such as sodium hydroxide.

[0053] Examples of preservatives include at least one of phenol, sodium omadine, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylphonyl)pyridine, alkali metal salts of benzoic acid, sorbic acid, and dehydroacetic acid, and benzimidazole compounds. If commercially available products of these are available, they can be used in the prescribed amounts.

[0054] Furthermore, the pH (25°C) of the aqueous ink composition to be used in the writing instrument of the present disclosure is preferably adjusted to a pH of 10 or less using a pH adjuster or the like from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, and is desirably set to 2.0 to 10.0, more preferably 2.5 to 7.5, from the viewpoints of dispersion stability of the emulsion particles and the stability of the ink over time.

[0055] The aqueous ink composition to be used in the writing instrument of the present disclosure contains, in addition to the above-mentioned components, water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as the solvent as the remainder, and the aqueous ink composition to be used in the writing instrument can be prepared by appropriately combining these components in predetermined amounts, stirring and mixing them using a stirrer such as a homomixer, homogenizer, or disper, and then, if necessary, removing coarse particles from the ink composition by filtration or centrifugation. The aqueous ink composition to be used in the writing instrument of the present disclosure preferably has a surface tension of 28 mN / m to 65 mN / m, and more preferably 30 mN / m to 55 mN / m, from the viewpoints of suppressing bleeding and improving dispersion stability.

[0056] [Writing Instrument] The writing instrument of the present disclosure is not particularly limited in structure as long as it is equipped with the aqueous ink composition of the above configuration and a pen tip, and other than this, there are no particular limitations on the structure of the writing instrument, the ink mounting structure (ink occluder impregnation, direct liquid method), the ink supply method, etc. Preferably, in order to further demonstrate the effects of the present disclosure and in terms of writing performance, the pen tip is composed of a core selected from a polyester core, an acrylic core, a nylon core, a polybutylene terephthalate (PBT) core, a polyethylene core, a rubber core, a urethane core, a polyacetal (POM) core, a polypropylene (PP) core, a polyethylene naphthalate (PEN) core, and a polyethylene terephthalate (PET) core.

[0057] The shape, size, hardness, etc. of the pen tip, other than the above-mentioned material, vary depending on the use of the writing instrument, the ink supply method, the line width, etc., and are not particularly limited. The shape can be, for example, a sloping shape (knife-cut shape), a bullet shape, a brush shape (brush body), etc., so that the inclination is easy to write with, and the size, hardness, etc. can each be within a predetermined range.

[0058] 1 to 6 illustrate embodiments of writing instruments having various structures according to the present disclosure. Writing instrument A in FIGS. 1 to 3 shows an example of an embodiment of a direct-flow writing instrument in which the aqueous ink composition for a writing instrument having the above-described configuration is directly loaded into an ink tank in the barrel. FIGS. 1(a) to 1(c) show the writing instrument with the cap attached, FIGS. 2(a) to 2(d) show the writing instrument with the cap removed, and FIGS. 3(a) and 3(b) show the writing instrument in use. Writing instrument A of this embodiment is loaded with the aqueous ink for a writing instrument having the above-described characteristics, and as shown in FIGS. 1(a) to 1(c), has an ink tank 11 in a barrel 10 and an ink reservoir (collector) 12 in the barrel 10 that temporarily stores overflowing ink in response to pressure changes in the ink tank 11.

[0059] That is, this writing instrument A has an ink reservoir member 12 provided in front of an ink tank 11. The ink reservoir member 12 is formed watertight by a disk-shaped plate portion 13 extending vertically from the rear end of a generally cylindrical central portion, which is fitted to the inner periphery of the barrel 10 body. A plurality of thinner disk-shaped thin plate portions 14 are arranged in front of the rear end plate portion 13, and the gaps between these thin plate portions 14, 14, 14, ... form an ink reservoir portion with ink reservoir grooves (horizontal grooves) formed by capillary force. The barrel 10 is molded into a cylindrical shape using a resin such as polypropylene, and functions as the main body (barrel) of the writing instrument. The barrel 10 is molded opaque or transparent (and translucent), but either may be adopted from the standpoint of appearance and practicality.

[0060] In addition, slit-shaped ink guide grooves (vertical grooves) 15 are formed in the multiple thin plate portions 14 along the length of the ink reservoir member 12, excluding the central tube portion. The width of these ink guide grooves 15 is smaller than the width of any of the ink storage grooves 16, allowing them to be constantly filled with ink and immediately guide excess ink into the ink storage grooves 16 when pressure builds up in the ink tank 11. The ink guide grooves 15 are formed between the thin plate portions 14 and are continuous with the opening grooves 20 in the plate-like portion 13 that lead to the ink tank 11. In the ink reservoir member 12, the thin plate portions 14 are integrally molded into a structure connected and supported by the hollow central tube portion 12a. A relay core 25, such as a fiber core, is housed within the hollow portion around the inner periphery of the central tube portion 12a. This relay core 25 supplies the aqueous ink composition for a writing instrument of the present disclosure from the ink tank 11 to a pen tip 30, which is disposed at the tip of the barrel 10 and is integral with the relay core 25.

[0061] The pen tip 30, which is integral with the intermediate core 25, is composed of a material selected from the group consisting of polyester, acrylic, nylon, polybutylene terephthalate (PBT), polyethylene, rubber, urethane, polyacetal (POM), polypropylene (PP), polyethylene naphthalate (PEN), and polyethylene terephthalate (PET). In this embodiment, the pen tip 30 is composed of a polyester core. The pen tip 30 has semicircular arc-shaped notches 31, 31 on both sides, and its tip has a writing section 32 that is inclined (knife-cut) to facilitate writing. The inclination of the writing section 32 is appropriately set according to the ease of use, such as writing. Furthermore, the writing section 32 preferably draws lines with a width of 1 mm or more, and more preferably 2 mm or more. The intermediate core 25 and pen tip 30 do not have to be integrally constructed, but may be composed of two parts. Furthermore, the porosity, size, hardness, etc. of the pen tip 30 used vary depending on the type of writing implement (direct ink type, padded type, etc.), and for example, a porosity of 30 to 70% is preferable. In the present disclosure, "porosity" is calculated as follows. First, a writing lead with a known mass and apparent volume is immersed in water, and after sufficient water has been absorbed, the mass is measured when it is removed from the water. From the measured mass, the volume of water absorbed into the writing lead is derived. The volume of this water is considered to be the same as the pore volume of the writing lead, and the porosity is calculated from the following formula: Porosity (unit: %) = (volume of water) / (apparent volume of pen tip 30) x 100

[0062] The outer periphery of the thin plate portion 14 of the ink reservoir member 12 is formed with a series of notches 17 serving as air passages in the longitudinal direction of the ink reservoir member 12. The pen tip 30 is attached to the large-diameter cylindrical portion 12b extending to the tip of the ink reservoir member 12. A cylindrical holder 35 is fitted between the outer periphery of the front of the ink reservoir member 12, including this large-diameter cylindrical portion 12b, and the inner periphery of the front of the barrel 10, preventing the ink reservoir member 12 from coming off the barrel 10. An air passage is formed between a groove 12c on the outer periphery of the large-diameter cylindrical portion 12b and the inner periphery of the holder 35, and this air passage communicates with the open groove 20 via the air passage of the notches 17, allowing smooth gas-liquid replacement in the ink tank 11.

[0063] The cap 40, a cylindrical cap with a bottom that covers the nib 30 when the writing instrument is not in use, is removably attached to the barrel 10 so that it partially covers the portion where the ink reservoir 12 is installed. The cap 40 has a structure in which a lid-like member 41 at the top is fitted into a side tubular member 42, and although not shown, the lid-like member 41 has an air vent hole formed from the tip to the interior. Inside the cap 40, a cup-shaped inner cap 45 that covers the nib 30 and fits onto the tip of the holder 35 is provided so that it can move back and forth with the help of a spring 46. When the cap 40 is removably attached to the barrel 10, the inner cap 45 first fits onto the tip of the holder 35, but in this state the cap 40 is not completely fitted onto the barrel 10. As the cap 40 is further pushed in, the spring 46 presses the inner cap 45, and a locking mechanism inside the open end of the cap 40 fits and secures it to the barrel 10.

[0064] As shown in Figure 1, the barrel 10 is provided with a partition wall 18 at a position closer to the center from the end (rear end) opposite the side where the ink reservoir member 12 is disposed, and the space within the barrel 10 between the partition wall 18 and a plate-like portion 19 at the rear end of the ink reservoir member 12 serves as the ink tank 11. The cylindrical rear end opening 10a of the barrel 10 behind the partition wall 18 is sealed with a tail plug 50. The tail plug 50 has a generally cylindrical shape that is open at the front, a closed rear end, and a flange 51 that protrudes to the side. The side of the tail plug 50 has multiple protruding ribs 52, 52 to improve adhesion to the rear end of the barrel.

[0065] At the rear end of the barrel 10, where the breech plug 50 fits and seals, an arbitrary number of vertical grooves 53 are formed on the inner peripheral surface as a structure for venting air. When trying to fit the breech plug 50 by pushing it into the open rear end of the barrel, if the vertical grooves 53 were not present, the internal pressure behind the partition wall 18 within the barrel 10 would increase depending on the distance the breech plug 50 is pushed in, preventing the breech plug from moving forward. However, because air escapes through the vertical grooves 53, the internal pressure does not increase, and the breech plug 50 can move forward smoothly and fit snugly.

[0066] In the direct ink type writing instrument A, which is the embodiment shown in Figures 1 and 2 and is configured as described above, an aqueous ink composition containing colored resin particles composed of at least the above-mentioned (meth)acrylic acid ester monomer and dye, uncolored resin particles selected from the above-mentioned Group Y, and an alkali association emulsion is directly loaded into the ink tank 11.As shown in Figures 3(a) and (b), the nib 30 made of the above material allows writing (marking) to be performed as a marking pen, and discoloration of the ink, which occurs when the colorant of the aqueous ink in a writing instrument equipped with a nib is adsorbed to the nib, can be suppressed, and a writing instrument with excellent writing performance suitable for a marking pen, etc. can be obtained.

[0067] FIG. 4 shows an example of an embodiment of a padded writing instrument, with (a) to (d) showing the pen with the cap removed, which has a structure similar to that of cap 40 in FIG. 1 . Note that components similar to those of writing instrument A in FIGS. 1 and 2 are designated by the same reference numerals and will not be described again. Writing instrument B of this embodiment houses an ink occlusion body 60 occluding the aqueous ink composition for a writing instrument, as described above, within the barrel (writing instrument body) 10 on the front side (toward the nib 30) of the partition wall 18. It has a structure similar to the integrated intermediate core 25 and nib 30 used in writing instrument A, i.e., ink is supplied to the nib 30 by capillary force via the intermediate core 25 attached to the insertion hole 61 of the ink occlusion body 60. The nib 30 is fitted to the front opening of the barrel 10 via a coupling member 65, which is fixed by fitting. The ink occlusion body 60 is impregnated with an aqueous ink composition for a writing instrument having the above-described characteristics, and includes, for example, fiber bundles made of one or a combination of two or more types of natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, polyphenylene resins, etc., processed fiber bundles such as felt, and porous bodies such as sponges, resin particles, and sintered bodies.

[0068] Even in the padded writing instrument B of the embodiment shown in Figure 4, as shown in Figures 3(a) and (b), the pen tip 30 allows writing (marking) as a marking pen, and discoloration of the ink caused by the coloring material of the water-based ink in a writing instrument equipped with a pen tip being adsorbed to the pen tip can be suppressed, and a writing instrument suitable for use as a marking pen with excellent writing performance can be obtained.

[0069] Figures 5 and 6 show an example of another embodiment of a padded writing instrument according to the present disclosure. Figure 5(a) is a front view, Figure 5(b) is a longitudinal cross-sectional view thereof, and Figure 6 is an enlarged longitudinal cross-sectional view of the portion indicated by the reference symbol X in Figure 5(b). As shown in Figures 5 and 6, the writing instrument C of this embodiment includes a shaft 70, which serves as the main body of the writing instrument, an ink occlusion body 80, a nib (pen core) 90, and a cap 95. The shaft 70 is formed of, for example, a thermoplastic resin or a thermosetting resin. As shown in Figures 5(b) and 6, the shaft 70 houses the ink occlusion body 80 impregnated with the water-based ink for the writing instrument. The shaft 70 integrally includes a tapered front end 71 into which the nib 90 is fitted, and a tail plug 75 is fixed to the rear end of the shaft 70, which holds and closes the rear end of the ink occlusion body 80. A cylindrical mounting member 76 is fixed to a stepped portion 72 on the front outer periphery of the shaft 70. The cross section of the shaft 70 is rounded square, with no sharp edges, making it easy to grip. The ink occlusion body 80 is impregnated with the aqueous ink composition for a writing instrument having the above-described configuration, and may be made of, for example, a fiber bundle made of one or a combination of two or more of natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, polyphenylene resins, etc.; a processed fiber bundle such as felt; or a porous body such as a sponge or resin particles. The ink occlusion body 80 is contained and held within the shaft 70.

[0070] The pen tip 90 is composed of a porous material, such as a porous material having air holes. Specific examples include molded bodies such as foams and sintered bodies. In the present disclosure, the pen tip 90 is preferably composed of a material selected from the group consisting of polyester, acrylic, nylon, polybutylene terephthalate (PBT), polyethylene, rubber, urethane, polyacetal (POM), polypropylene (PP), polyethylene naphthalate (PEN), and polyethylene terephthalate (PET) cores, in order to further enhance the effects of the present disclosure and to ensure writing performance. The shape, size, hardness, and other factors of the pen tip, other than the above-mentioned materials, vary depending on the application of the writing instrument, ink supply method, line width, and the like, and are not particularly limited. The shape may be, for example, a slanted shape (knife-cut shape), a bullet shape, a brush shape (brush body), a pen-shaped shape, or the like, to provide an inclination that facilitates writing. The size, hardness, and other factors can be within predetermined ranges. In this embodiment, the pen-shaped shape is used.

[0071] In the writing instrument C configured in this manner, the writing instrument C can be easily produced by inserting and retaining the ink occlusion body 80 occluding the aqueous ink composition having the above-described characteristics into the barrel 70, which constitutes the main body of the writing instrument, and then fastening the pen tip 90, tail plug 75, and mounting member 76 in that order by fitting or the like, and the aqueous ink composition having the above-described characteristics occluded in the ink occlusion body 80 is efficiently supplied to the pen tip 90 by capillary force and is then used for writing. The structure of the pen is not particularly limited, and may be, for example, a direct ink marking pen equipped with a collector structure (ink retention mechanism) in which the barrel itself serves as an ink reservoir and is filled with the aqueous ink composition having the above-described characteristics, or even a valve-type writing instrument.

[0072] In the writing instrument C of this embodiment, as shown in Figures 5(a) and (b) and 6, the pen tip 90 allows writing etc. to be performed as a marking pen, and discoloration of the ink that occurs when the coloring material of the water-based ink in a writing instrument equipped with a pen tip is adsorbed to the pen tip can be suppressed, and a writing instrument suitable for use as a marking pen etc. with excellent writing performance can be obtained.

[0073] The writing instrument of the present disclosure, configured as described above, is a writing instrument that is loaded with an aqueous ink composition and is equipped with a pen tip, and the aqueous ink composition contains colored resin particles encapsulating a dye composed of at least a (meth)acrylic acid ester monomer and a dye, uncolored resin particles selected from acrylic resins, styrene resins, vinyl acetate resins, and acrylonitrile resins of Group Y, a phosphate ester, and an alkali association emulsion.The reason why this results in a writing instrument that does not stain the pen tip and that suppresses discoloration of the ink is speculated to be as follows. In other words, the mechanism by which the hue of the drawn line changes due to the transfer of dye to the pen tip or batting is thought to be that the dye becomes more likely to migrate from the colored resin particles to the outside of the particles via the free surfactant remaining in the ink, resulting in the dye transferring and adsorbing to the pen tip or batting, causing a change in the hue of the drawn line.However, in the present disclosure, the free surfactant in the ink that contributes to dye transfer is incorporated (adsorbed) into the colorless resin particles as the micelles seek to stabilize particles with excess adsorption sites, thereby suppressing the transfer of dye from the colored resin particles and suppressing changes in the hue of the drawn line, resulting in a writing instrument that does not stain the pen tip and suppresses discoloration of the ink. In particular, a writing instrument whose nib material is selected from polyester core, acrylic core, nylon core, polybutylene terephthalate (PBT) core, polyethylene core, rubber core, urethane core, polyacetal (POM) core, polypropylene (PP) core, polyethylene naphthalate (PEN) core, and polyethylene terephthalate (PET) core will result in further suppressed discoloration of ink.

[0074] Next, the present disclosure will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present disclosure is not limited to the following Examples, etc.

[0075] [Production Examples 1 to 4: Production of Colored Resin Particles (Colored Particles 1 to 4)] Each colored resin particle was produced according to the following Production Examples 1 to 4. Note that the "parts" below represent parts by mass. The surfactant component is the solid content.

[0076] Production Example 1 A 2-liter flask was equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000 ml separatory funnel for introducing monomers, and set in a warm water bath. 344.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blemmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 40 parts of a polymerizable surfactant (ADEKA Corporation, Adeka Reasoap SE-10N, ether sulfite), and 0.5 parts of ammonium persulfate were then charged, and the internal temperature was raised to 50° C. while introducing nitrogen gas.

[0077] Separately, a solution was prepared by mixing a monomer mixture consisting of 55 parts cyclohexyl methacrylate monomer and 20 parts n-butyl methacrylate with 20 parts of an oil-soluble dye having an amine group and a heteroheterocycle (Oil Pink 314, manufactured by Orient Chemical Industry Co., Ltd.) as the dye component and 10 parts of a crosslinker (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Co., Ltd., TAIC). This prepared solution was added from the separatory funnel to the flask maintained at a temperature of approximately 50°C over 3 hours with stirring, and emulsion polymerization was carried out. The mixture was then aged for another 5 hours to terminate the polymerization, yielding a colored resin particle dispersion (dispersion) (particle 1). The content of the methacrylic acid ester monomer relative to the total polymer components constituting the colored resin particles was 54.8% by mass, and the content of the dye component relative to the total polymer components was 12.9% by mass. The average particle diameter of the colored resin particles was 98 nm, and the surface tension of the colored resin particles was 36.0 mN / m.

[0078] (Production Example 2) A colored resin particle dispersion (dispersion) (particles 2) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 334.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and 30 parts of a basic dye (Valifast Yellow 1120, manufactured by Orient Chemical Industry Co., Ltd.) was used as the dye component. The content of the methacrylic acid ester monomer was 52.9% by mass, based on the total polymer components constituting the colored resin particles, and the content of the dye component was 17.6% by mass, based on the total polymer components. The average particle diameter of the colored resin particles was 69 nm, and the surface tension of the colored resin particles was 35.1 mN / m.

[0079] (Production Example 3) A colored resin particle dispersion (dispersion) (particles 3) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 329.5 parts, the amount of cyclohexyl methacrylate monomer was 40 parts, the amount of n-butyl methacrylate was 35 parts, and 30 parts of an acid dye (Water Yellow 6C, manufactured by Orient Chemical Industry Co., Ltd.) was used as the dye component. The content of the methacrylic acid ester monomer was 52.9% by mass, based on the total polymer components constituting the colored resin particles, and the content of the dye component was 17.6% by mass, based on the total polymer components. The average particle diameter of the colored resin particles was 61 nm, and the surface tension of the colored resin particles was 30.8 mN / m.

[0080] (Production Example 4) A colored resin particle dispersion (dispersion) (particles 4) was obtained in the same manner as in Production Example 1, except that the amount of distilled water was 327.5 parts, the amount of cyclohexyl methacrylate monomer was 28 parts, the amount of n-butyl methacrylate was 44 parts, and 40 parts of a salt-forming dye (Spilon Violet C-RH, manufactured by Hodogaya Chemical Co., Ltd.) was used as the dye component. The content of the methacrylic acid ester monomer was 47.7% by mass, based on the total polymer components constituting the colored resin particles, and the content of the dye component was 23.3% by mass, based on the total polymer components. The average particle diameter of the colored resin particles was 117 nm, and the surface tension of the colored resin particles was 32.1 mN / m.

[0081] [Uncolored Resin Particles (Uncolored Particles) 1 to 8] Uncolored resin particles (uncolored particles) 1 to 8 were used with the following configuration. (1) For acrylic resin A, uncolored resin particles 1 made of polymethyl methacrylate and having an average particle diameter of 65 nm were used. The surface tension of this acrylic resin A was 56.1 mN / m. (2) For acrylic resin B, uncolored resin particles 2 made of polyn-butyl methacrylate and having an average particle diameter of 49 nm were used. The surface tension of this acrylic resin B was 61.2 mN / m. (3) For acrylic resin C, uncolored resin particles 3 made of polycyclohexyl methacrylate and having an average particle diameter of 71 nm were used. The surface tension of this acrylic resin C was 52.1 mN / m. (4) Acrylic resin D was composed of poly(n-butyl methacrylate):poly(cyclohexyl methacrylate)=1:1 (weight ratio) and was composed of uncolored resin particles 4 having an average particle size of 60 nm. The surface tension of this acrylic resin D was 58.8 mN / m.

[0082] (5) For the styrene resin, uncolored resin particles 5 were used, which were composed of polystyrene:polycyclohexyl methacrylate = 2:1 (weight ratio) and had an average particle size of 82 nm. The surface tension of this styrene resin was 61.1 mN / m. (6) For the urethane resin, uncolored resin particles 6 were used, which were composed of polyurethane and had an average particle size of 110 nm. The surface tension of this polyurethane resin was 49.7 mN / m. (7) For the vinyl acetate resin, uncolored resin particles 7 were used, which were composed of polyvinyl acetate and had an average particle size of 103 nm. The surface tension of this vinyl acetate resin was 39.7 mN / m. (8) For the nitrile resin, uncolored resin particles 8 were used, which were composed of polymethacrylonitrile:polycyclohexyl methacrylate = 2:1 (weight ratio) and had an average particle size of 91 nm. The surface tension of this nitrile resin was 46.5 mN / m.

[0083] [Preparation of Aqueous Ink Compositions for Writing Instruments] Using the colored resin particle dispersions (particles) 1 to 4 and the uncolored resin particle dispersions (uncolored particles) 1 to 8 obtained in Production Examples 1 to 4, aqueous ink compositions for writing instruments were prepared by conventional methods according to the formulations shown in Tables 1 and 2 below. The solid content of each of the colored resin particle dispersions (particles) 1 to 4 and the uncolored resin particle dispersions (uncolored particles) 1 to 8 was 30%, and the formulation amounts in Tables 1 and 2 are expressed as the volume of each dispersion. The pH of each aqueous ink composition (at 25°C) was measured using a pH meter (F-72S, manufactured by Horiba, Ltd.). The surface tension of each aqueous ink composition was measured at 25°C using a surface tension meter manufactured by Kyowa Interface Science Co., Ltd., using a platinum plate by the vertical plate method. The measurement results are shown in Tables 1 and 2 below.

[0084] [Examples 1 to 19 and Comparative Examples 1 to 16] Each of the obtained aqueous ink compositions for writing instruments (total amount 100% by mass) was loaded into writing instruments having the following pen tip (pen core) materials and shapes, and evaluated for pen core discoloration, line discoloration, bleeding resistance (bleeding onto paper), and stability over time (rubbing) using the evaluation methods described below. The results of these evaluations are shown in Tables 1 and 2 below.

[0085] (Preparation of Writing Instruments) Marking pens conforming to Figures 5 and 6 (manufactured by Mitsubishi Pencil Co., Ltd., product name: PEM-SY, nib: various nibs with the following configurations) were filled with the ink compositions for each writing instrument to prepare marking pens. The nibs of Examples 1 to 19 were made of the materials shown below. Examples 1 to 8 (acrylic) were made of acrylic resin, bullet-shaped, φ2.0 x 30 mm. Example 9 (PET) was made of polyethylene terephthalate resin, bullet-shaped, φ2.0 x 30 mm. Example 10 (PE) was made of a sintered core (porous body of polyethylene powder, porosity 60%), inclined (knife-cut) shape, φ3.2 x 32 mm. Example 11 (POM) was made of polyacetal (POM) resin, bullet-shaped, φ2.0 x 30 mm. Examples 12 and 19 (PBT) were constructed from polybutylene terephthalate (PBT) resin, bullet-shaped (φ2.0 x 30 mm). Example 13 (Nylon) was constructed from nylon resin, brush-shaped (brush body) (φ2.0 x 30 mm). Example 14 (Rubber) was constructed from styrene butadiene (SBR) rubber, brush-shaped (brush body) (φ2.0 x 30 mm). Example 15 (Urethane) was constructed from polyurethane resin, brush-shaped (brush body) (φ2.0 x 30 mm). Example 16 (PP) was constructed from polypropylene (PP) resin, brush-shaped (brush body) (φ2.0 x 30 mm). Example 17 (PEN) was constructed from polyethylene naphthalate (PEN) resin, bullet-shaped (φ2.0 x 30 mm). Example 18 (acrylic) was constructed from acrylic resin, with a sloped shape (knife-cut shape) of φ3.2 × 32 mm. Comparative Examples 1 to 16 had a bullet-shaped pen tip (pen core) of φ2.0 × 30 mm, and were made of acrylic, PET, PE, POM, PBT, nylon, rubber, urethane, PP, or PEN, and were evaluated in the same manner as in Examples 1 to 18. The bullet-shaped pen tips of Examples 1 to 9, 11 to 12, 17, and 19, and Comparative Examples 1 to 16, and the sloped shape (knife-cut shape) of Example 18 each had a porosity in the range of 30 to 75%.

[0086] [Method for evaluating pen tip discoloration] Using the writing instrument having the above configuration, after 3 months at 50°C, pen tip discoloration was evaluated visually and sensorily according to the following evaluation criteria to see if the color of the pen tip had changed due to dyeing. The color change of the entire pen tip was compared with the initial color and evaluated. <Evaluation criteria> A+: No change from the initial color A: Slight change was observed in part of the pen tip B: Change was observed throughout the pen tip, but the degree was slight C: Significant discoloration was observed throughout the pen tip

[0087] [Method for evaluating discoloration of drawn lines] Using the writing implement having the above configuration, writing was performed on PPC paper after 3 months at 50°C, and the discoloration of the drawn lines was evaluated visually and sensorily according to the following evaluation criteria to see whether the hue of the written lines was different from the initial hue (immediately after production). <Evaluation criteria> A: No change from the initial state B: Slight discoloration observed C: Significant discoloration observed

[0088] [Method for evaluating bleeding resistance] Using the writing implement having the above configuration, spiral writing was performed on PPC paper after 3 months at 50°C, and the bleeding of the written lines onto the paper was visually evaluated according to the following evaluation criteria. <Evaluation criteria> A: Clear handwriting without bleeding B: Slight bleeding C: Blurring and unclear handwriting

[0089] [Method for evaluating stability over time (rubbing)] Using the writing instrument having the above configuration, after storing at 50°C for 3 months with the pen tip facing downward, a straight line was written on PPC paper, and the rubbing of the written line onto the paper was visually evaluated by a sensory evaluation according to the following evaluation criteria to evaluate stability over time. <Evaluation criteria> A: Writing possible without problems from the start B: Blurring of more than 0 mm but less than 5 mm was observed from the start C: Blurring of 5 mm or more was observed from the start

[0090]

[0091]

[0092] *1 to *9 in Tables 1 and 2 above are as follows: *1: Oil Pink 314, manufactured by Orient Chemical Industry Co., Ltd. *2: SWT Yellow-2, manufactured by Hodogaya Chemical Co., Ltd. *3: Water Red 1, manufactured by Orient Chemical Industry Co., Ltd. *4: Phosphanol RD-510 (HLB 9.9), manufactured by Toho Chemical Industry Co., Ltd. *5: Phosphanol RS-710 (HLB 13.3), manufactured by Toho Chemical Industry Co., Ltd. *6: Primal TT-615 (solid content: 30%), manufactured by DOW *7: Rheotec 3800 (solid content: 30%), manufactured by ARKEMA *8: Emal 2FG, manufactured by Kao Corporation *9: Bioden S, manufactured by Yamato Chemical Industry Co., Ltd.

[0093] Considering Tables 1 and 2 above, it was confirmed that Examples 1 to 19, which fall within the scope of the present disclosure, are superior in pen core discoloration, line discoloration, bleeding resistance (bleeding onto paper), and stability over time (rubbing) without adversely affecting other ink formulation components, compared to Comparative Examples 1 to 16, which fall outside the scope of the present disclosure.

[0094] The writing instrument of the present disclosure can be suitably used in felt-tip pens and marking pens that have nib members with ink supply systems of batting type, valve type, or direct ink type.

Claims

1. A writing instrument equipped with a pen tip and loaded with an aqueous ink composition, characterized in that the aqueous ink composition contains at least colored resin particles encapsulating a dye composed of a (meth)acrylic acid ester monomer and a dye, uncolored resin particles selected from the following Group Y, a phosphate ester, and an alkali association emulsion: Group Y: acrylic resin, styrene resin, urethane resin, vinyl acetate resin, nitrile resin.

2. The writing implement according to claim 1, wherein the dye of the colored resin particles is a dye selected from the following Group X: Group X: oil-soluble dyes having an amine group or heteroheterocycle, basic dyes, and acid dyes.

3. The writing implement according to claim 1 or 2, wherein the pH of the aqueous ink composition is 10.0 or less.

4. A writing instrument according to claim 1 or 2, characterized in that the material of the nib is selected from the group consisting of polyester core, acrylic core, nylon core, polybutylene terephthalate (PBT) core, polyethylene core, rubber core, urethane core, polyacetal (POM) core, polypropylene (PP) core, polyethylene naphthalate (PEN) core, and polyethylene terephthalate (PET) core.

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