Water-based ink composition for writing instruments

Abstract

Provided is an aqueous ink composition for writing instruments, which is suitable for writing instruments such as a signing pen, a marker pen, and a ballpoint pen, using colored resin particles having excellent color development. The aqueous ink composition for writing instruments of the present invention is characterized in that it contains colored resin particles, and the colored resin particles are colored with a salt-forming dye that is a salt-forming body of an acid dye and a basic dye.

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition for writing tools, which uses colored resin particles having excellent color development properties and is suitable for writing tools such as a signing pen, a marking pen, and a ballpoint pen. Background Art

[0002] It is known that a resin emulsion having a specific polymer composition is dyed with a dye and used as a coloring material, which is also called a pigment-like material.

[0003] For example, there is known an aqueous ink composition for writing instruments, characterized in that it contains at least a colored resin emulsion dyed with a dye capable of dyeing a resin emulsion, wherein the colored resin emulsion is dyed with polyoxyethylene styrenated phenyl ether (for example, see Patent Document 1 of the present application).

[0004] However, in producing the colored resin particles described in Patent Document 1, there is no disclosure or recognition of using a salt-forming dye having a structure of an acid dye and a basic dye.

[0005] Colored resin particles can be colored with various dyes, but there is a technical problem that the amount that can be mixed into the particles has an upper limit depending on the type of dye. The overall trend is that the upper limit of the amount of acid dyes is relatively low. Therefore, the current situation is that even acid dyes with excellent color development performance may not fully demonstrate their characteristics when used as colorants for colored resin particles, and colored resin particles with better color development properties are required.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-2121 (claims, examples, etc.) Summary of the invention

[0009] Problem that the invention aims to solve

[0010] The present invention is completed in view of the technical problems and current status of the above-mentioned prior art, and in order to overcome them. Its purpose is to provide an aqueous ink composition for writing instruments suitable for writing instruments such as signing pens, markers, and ballpoint pens using colored resin particles with excellent color development, and a writing instrument equipped with the aqueous ink composition for writing instruments.

[0011] Solutions for solving problems

[0012] The present inventors have conducted intensive research on the above-mentioned previous technical problems and found that the use of a salt-forming dye having a structure of an acid dye and a basic dye does not reduce the properties of the acid dye with good color development, and can obtain the above-mentioned target water-based ink composition for writing instruments, thereby completing the present invention.

[0013] That is, the aqueous ink composition for writing instruments of the present invention is characterized by containing colored resin particles colored with a salt-forming dye which is a salt-forming body of an acid dye and a basic dye.

[0014] The writing instrument of the present invention is characterized by being equipped with the above-mentioned aqueous ink composition for writing instruments.

[0015] Effects of the Invention

[0016] According to the present invention, there are provided an aqueous ink composition for writing instruments having excellent color development and suitable for writing instruments such as a signing pen, a marking pen, and a ballpoint pen, and a writing instrument equipped with the aqueous ink composition for writing instruments. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described in detail.

[0018] The aqueous ink composition for writing instruments of the present invention is characterized by containing colored resin particles colored with a salt-forming dye which is a salt-forming body of an acid dye and a basic dye.

[0019] <Salt-forming dyes>

[0020] The salt-forming dye used in the present invention as a salt-forming body (salt-forming compound) of an acid dye and a basic dye is a compound obtained by reacting an acid dye with a basic dye, and is a dye having excellent spectral characteristics and color purity of both acid dyes and basic dyes without reducing the characteristics of the acid dye with good color development as a raw material. In addition, it has the advantage that the spectral adjustment of the salt-forming body can be performed by combining the acid dye and the basic dye.

[0021] Furthermore, in the present invention, unlike inorganic salts of acid dyes having acidic groups such as sulfonate and carboxylate, salts of acid dyes and nitrogen-containing compounds, amide compounds such as sulfonamides of acid dyes which are derivatives of acid dyes, the salt-forming bodies of acid dyes and basic dyes are compounds obtained by a chemical (salt-forming) reaction between an acid dye whose dye ion is anionic and a basic dye whose dye ion is cationic, and therefore have an extremely rigid structure and are chemically stable.

[0022] Therefore, when a salt-forming dye comprising a salt-forming compound of an acid dye and a basic dye is used as a coloring material for colored resin particles, unlike the case of using a mixture of dyes, since it acts as a chemically stable compound, the excellent spectral characteristics and color purity of the acid dye and the basic dye respectively are not impaired, and colored resin particles with excellent color rendering and brightness can be obtained.

[0023] In addition, due to the stable structure, the spectral characteristics of excellent heat resistance and light resistance are exhibited. In addition, the spectral characteristics and color purity of the acid dye and the basic dye are excellent, and the characteristics of the acid dye with good color development as the starting material of the salt-forming reaction are not reduced, so the spectral adjustment can be arbitrarily performed by changing the combination of the starting materials of the salt-forming reaction. Furthermore, water resistance is imparted by becoming a salt-forming compound, so the dispersibility in a water-containing solvent becomes excellent.

[0024] The acid dye used in the present invention is a water-soluble dye having a structure in which an acid group such as a sulfonic acid group, a carboxyl group, or a salt thereof is present in the dye molecule.

[0025] Among acid dyes, some are classified as direct dyes. Direct dyes are dyes with large molecular weight and planar structure among acid dyes. The salt compounds of direct dyes and basic dyes have particularly excellent heat resistance. By appropriately selecting the type of monomer of the resin particles used to color the resin particles, etc., the color development and heat resistance can be excellent.

[0026] As the direct dyes that can be used, for example, azo dyes, thiazole dyes, anthraquinone dyes, oxazine dyes, phthalocyanine dyes, etc. Usable dyes are listed below using color index (CI) numbers.

[0027] Examples of azo dyes include CIDirect Yellow 2, 33, 34, 35, 39, 50, 69, 70, 71, 86, 93, 94, 95, 98, 102, 109, 129, 136, and 141;

[0028] CIDirect Orange 41, 46, 56, 61, 64, 70, 96, 97, 106, 107;

[0029] CIDirect Red 79, 82, 83, 84, 97, 98, 99, 106, 107, 172, 173, 176, 177, 179, 181, 182, 204, 207, 211, 213, 218, 221, 222, 232, 233, 243, 246, 250;

[0030] CIDirect Violet 47, 52, 54, 60, 65, 66, 79, 80, 81, 82, 84, 89, 90, 93, 95, 96, 103, 104;

[0031] CIDirect 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 , 200, 207, 209, 210, 212, 213, 214, 222, 228, 229, 237, 238, 242, 243, 244, 245, 247, 248, 250, 251, 252, 256, 257, 259, 260, 268, 274, 275;

[0032] CIDirect Green 27, 34, 37, 65, 67, 68, 69, 72, 77, 79, 82, etc. As the thiazole dye, CIDirect Yellow 54 can be mentioned.

[0033] Examples of the oxazine dye include CIDirect Blue 97, 99, 106, 107, 108, 109, 190, and 293.

[0034] Examples of the anthraquinone-based dye include CIDirect Blue 77.

[0035] Examples of the phthalocyanine dye include CIDirect Blue 86, 87, 189, and 199.

[0036] CIDirect Yellow 38, 43, 47, 58, 68, 108, 138; CIDirect Orange 34, 39, 50, 52, 57, 65, 68; CIDirect Red 91, 92, 96, 105, 184, 220, 234, 241; CIDirect Violet 59; CIDirect Blue 80, 114, 115, 117, 119, 137, 155, 156, 158, 159, 161, 171, 173; CIDirect Green 25, 31, 32, 63, 66, etc. may be cited.

[0037] As acid dyes other than direct dyes, azo dyes, xanthene dyes, phthalocyanine dyes, anthraquinone dyes, quinoline dyes, azine dyes, indigo dyes and the like can be used.

[0038] Examples of the azo dye include CIAcid 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;

[0039] CIAcid Orange 7, 10, 12, 19, 20, 22, 28, 30, 52, 56, 74, 127;

[0040] CIAcid Violet 11, 56, 58;

[0041] CIAcid Yellow 1, 6, 6C, 17, 18, 23, 25, 36, 38, 42, 44, 54, 59, 72, 78, 151;

[0042] CIAcid Brown 2, 4, 13, 248;

[0043] CIAcid Blue 92, 102, 113, 117, etc.

[0044] Examples of the xanthene dye include CIAcid Red 50, 51, 52, and 87.

[0045] Examples of the phthalocyanine dye include CIAcid Blue 249.

[0046] Examples of the anthraquinone dye include CIAcid Red 82 and 92; CIAcid Violet 41, 42 and 43; CIAcid Blue 14, 22, 25, 40, 45, 78, 80, 127:1, 129, 145, 167 and 230; and CIAcid Green 25 and 27.

[0047] Examples of quinoline dyes include CIAcid Yellow 3.

[0048] Examples of the azine dye include CIAcid Blue 59 and 102.

[0049] As the indigo dye, CIAcid Blue 74 can be mentioned.

[0050] Examples of other dyes include CIAcid Violet 49, CIAcid Brown 19, CIAcid Blue 7, 9, 74, 112, 126, and 167, and CIAcid Green 9.

[0051] The basic dye used in the present invention is a dye having a basic group such as an amino group, an imino group or a structure of a salt thereof in the molecule and becoming a cation in an aqueous solution.

[0052] As basic dyes that can be used, for example, there can be listed: diarylmethane and triarylmethane dyes; quinoneimine dyes such as azine (including nigrosine), oxazine, and thiazine; xanthene dyes; triazole azo dyes; thiazole azo dyes; benzothiazole azo dyes; azo dyes; polymethine dyes such as polymethine, azomethine, and azamethine; anthraquinone dyes; phthalocyanine dyes; at least one of basic dyes such as acridine dyes, rhodamine dyes, and triarylmethane dyes, and water-soluble basic dyes are preferred.

[0053] Specific examples of yellow basic dyes that can be used include dyes described in COLOR INDEX such as CI 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. Commercially available yellow basic dyes include AIZEN CATHILON YELLOW GPLH and Spillon Yellow C-GNH-new (trade names manufactured by Hodogaya Chemical Industry Co., Ltd.).

[0054] Examples of the orange basic dye include dyes described in COLOR INDEX such as CI Basic Orange 1, 2, 7, 14, 15, 21, 22, 23, 24, 25, 30, 32, 33, and 34.

[0055] Examples of red basic dyes include dyes described in COLOR INDEX such as CI 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. Examples of commercially available red basic dyes include AIZEN CATHILON RED BLH and AIZEN CATHILON RED RH (trade names of Hodogaya Chemical Co., Ltd.), Diacryl Supra Brilliant Red 2G (trade names of Mitsubishi Chemical Corporation), and Sumiacryl Red B (trade name of Sumitomo Chemical Co., Ltd.).

[0056] Examples of violet basic dyes include dyes described in COLOR INDEX such as CI 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.

[0057] Examples of blue basic dyes include dyes described in COLOR INDEX such as CI 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, 88. In addition, commercially available blue basic dyes include AIZEN CATHILON TURQUOISE BLUE LH (trade name manufactured by Hodogaya Chemical Industry Co., Ltd.) and the like.

[0058] Examples of green basic dyes include dyes described in COLOR INDEX, such as CI Basic Green 1, 4, 6, and 10. Commercially available green basic dyes include Diacryl Supra Brilliant Green 2GL (trade name manufactured by Mitsubishi Chemical Corporation).

[0059] Examples of brown basic dyes include dyes described in COLOR INDEX: CI Basic Brown 1, 2, 4, 5, 7, 11, 12, 13, 15. Commercially available brown basic dyes include Janus Brown R (trade name manufactured by Nippon Chemical Co., Ltd.) and AIZEN CATHILON BROWN GH (trade name manufactured by Hodogaya Chemical Industry Co., Ltd.).

[0060] Examples of black basic dyes include dyes described in COLOR INDEX such as CI Basic Black 1, 2, 3, 7, and 8, and nigrosine-based basic dyes.

[0061] In the present invention, the method for producing the salt-forming dye as the salt-forming body of the acid dye and the basic dye can be applied by a known method. For example, an acid dye aqueous solution and a basic dye aqueous solution are prepared separately, and after mixing and stirring them, the salt-forming body is filtered, and the recovered precipitate is dried to obtain a predetermined salt-forming dye.

[0062] Furthermore, when producing colored resin particles, the preparation of the salt-forming body and the synthesis of colored resin particles may be performed continuously by mixing an acid dye and a basic dye.

[0063] In the present invention, the salt-forming dye composed of a salt-forming compound of a direct dye and a basic dye may be used alone, or a salt-forming dye composed of two or more salt-forming compounds may be used in combination.

[0064] In the present invention, a commercially available salt-formed dye which is a salt-formed product of an acid dye and a basic dye may be used, and a salt-formed dye synthesized from a commercially available acid dye and a basic dye may also be used.

[0065] Commercially available products include: VALIFAST RED 1308 (salt of CIAcid Yellow 23 and CIBasic Red 1), VALIFAST RED 1320 (salt of CIAcid Yellow 42 and CIBasic Red 1), VALIFAST RED 1355, VALIFAST RED 1388 (all salts of CIAcid Yellow 23 and CIBasic Red 1), VALIFAST GREEN 1501 (salt of CIAcid Yellow 42 and CIBasic Blue 1), VALIFAST VIOLET 1701 (salt of CIAcid Yellow 42 and CIBasic Violet 1), VALIFAST VIOLET 1704 (salt of CIAcid Yellow 36 and CIBasic Violet 1), and salt dyes synthesized from commercially available products (Water Yellow 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100 Salt-forming dyes of CIAcid Yellow 6C (manufactured by Orient Chemical Industries) and Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd., basic dye)], salt-forming dyes of CIAcid Blue 9 and Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd.), salt-forming dyes of CIAcid Blue 9 and CIBasic Violet 1, etc.

[0066] <Colored Resin Particles>

[0067] In the present invention, the colored resin particles are resin particles colored with a salt-forming dye which is a salt-forming body of the above-mentioned acid dye and basic dye. For example, acrylic resin particles, vinyl acetate resin particles, urethane resin particles, styrene-butadiene resin particles, and styrene acrylonitrile resin particles are resin particles colored with a salt-forming dye which is a salt-forming body of the above-mentioned acid dye and basic dye. They can be listed as various colored resin particles composed of at least one of each acrylic, vinyl acetate, urethane, styrene-butadiene, and styrene acrylonitrile raw material monomer and a salt-forming dye which is a salt-forming body of the above-mentioned acid dye and basic dye. Preferably, acrylic colored resin particles are desired from the perspective of further stabilizing the dyeing process, high concentration, stability over time, and excellent color development caused by the above-mentioned salt-forming dye.

[0068] Examples of such acrylic colored resin particles colored with a salt-forming dye include, for example, colored resin particles composed of a vinyl monomer having a carboxyl group as an acidic functional group and a solubility in water of 10% by mass or less, an ester monomer of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms, and a salt-forming dye which is a salt of the above-mentioned acidic dye and basic dye.

[0069] There are no particular restrictions on the vinyl monomers that can be used, which contain a carboxyl group as an acidic functional group and have a solubility in water of 10% by mass or less. As long as they are color-developing monomers, have a solubility in water of 10% by mass or less, and have an acidic functional group of a carboxyl group, for example, at least one of 2-methacryloyloxyethyl succinate [manufactured by Mitsubishi Rayon Co., Ltd., acrylate SA, solubility in water: 1.86% by mass], 2-methacryloyloxyethyl maleate [manufactured by Mitsubishi Rayon Co., Ltd., acrylate ML, solubility in water: 9.17% by mass], 2-methacryloyloxyethyl phthalate [manufactured by Mitsubishi Rayon Co., Ltd., acrylate PA, solubility in water: 0.08% by mass], and 2-methacryloyloxyethyl hexahydrophthalate [manufactured by Mitsubishi Rayon Co., Ltd., acrylate HH, solubility in water: 3.40% by mass] can be cited. In particular, 2-methacryloyloxyethyl hexahydrophthalate is preferably used from the viewpoint of providing compatibility with a salt-forming dye which is a salt-forming body of the above-mentioned acid dye and basic dye and more sufficient color development.

[0070] When the above-mentioned carboxyl-containing vinyl monomer having a solubility in water of less than 10% by mass is used, the ratio of the acidic monomer in the mixed monomer with the above-mentioned ester monomer can be increased, thereby allowing a very large amount of the salt-forming dye, which is a salt-forming body of the above-mentioned acidic dye and basic dye, to be mixed with the vinyl monomer. As a result, colored resin particles having a richer color and better color rendering properties caused by the salt-forming dye can be obtained.

[0071] The ester monomer of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms is a skeleton monomer, and is an ester of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms. Specifically, at least one of ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate can be suitably shown. It should be noted that the symbol of "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0072] In particular, it is preferable to use n-butyl (meth)acrylate, lauryl methacrylate, or cyclohexyl methacrylate, which further improves the drying property of the drawn line.

[0073] The acrylic colored resin particles colored with the salt-forming dye can be produced by dispersing colored resin particles composed of at least a vinyl monomer having a carboxyl group as an acidic functional group and having a solubility in water of 10% by mass or less, an ester monomer of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms, and a salt-forming dye which is a salt-forming body of an acidic dye and a basic dye in water to obtain an aqueous dispersion, and drying the aqueous dispersion. In addition, the aqueous dispersion of the colored resin particles can be used as the aqueous ink composition for writing instruments of the present invention.

[0074] As a specific manufacturing method, for example, the manufacturing method can be as follows: the salt-forming dye as a salt-forming body of the acid dye and the basic dye is dissolved in a mixed monomer containing the vinyl monomer containing a carboxyl group as an acidic functional group and having a solubility in water of 10% by mass or less, and the ester monomer of the acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms, and ammonium persulfate, potassium persulfate, hydrogen peroxide, etc. are used as a polymerization initiator, or a polymerization initiator of a reducing agent is further used, and emulsion polymerization is further performed using a polymerizable surfactant as needed. In addition, the dyeing and polymerization are performed simultaneously, but the salt-forming dye can also be dissolved after the polymerization and dyeing is performed.

[0075] In the emulsion polymerization, dicyclopentyl (meth)acrylate monomer may be further mixed with the carboxyl group-containing vinyl monomer component and the ester of acrylic acid or methacrylic acid and a linear or cyclic alcohol having 2 to 18 carbon atoms and emulsion polymerization may be performed. This is because the polymer obtained by further mixing the dicyclopentyl (meth)acrylate monomer and emulsion polymerization is less likely to lose stability even if the water in the dispersion evaporates, and a dispersion of colored resin particles and a water-based ink composition for writing instruments with better stability can be obtained.

[0076] It should be noted that the dicyclopentyl (meth)acrylate monomer includes dicyclopentyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentyl methacrylate monomer, and dicyclopentenyl methacrylate monomer.

[0077] In addition, during the above-mentioned emulsion polymerization, in addition to the above-mentioned components, other hydrophobic vinyl monomers can also be mixed and emulsion polymerization can be carried out. There is no particular restriction on the hydrophobic vinyl monomers that can be used, for example, styrenes such as styrene and methyl styrene can be listed. In addition, in this emulsion polymerization, monomers with reactive crosslinking groups such as epoxy, methylol amide, isocyanate groups, and polyfunctional monomers with two or more vinyl groups can be mixed and crosslinked.

[0078] In the present invention, the total content of the carboxyl group-containing vinyl monomer and the ester monomer in the polymer component constituting the colored resin particles is preferably 60% by mass or more, more preferably 70% by mass or more to 100% by mass, in the polymer composition from the viewpoint of improving the drying property of the drawn line, based on the functions as the coloring material such as color development, weather resistance, and stability. It is particularly preferred that the content of the carboxyl group-containing vinyl monomer is 40% by mass or more and the content of the ester monomer is 20% by mass or more.

[0079] When the dicyclopentenyl (meth)acrylate monomer is further used in the polymer component constituting the colored resin particles, the content thereof is 1 to 25% by mass, more preferably 5 to 15% by mass, from the viewpoint of stability and further improvement of ink performance.

[0080] In the present invention, the content of the salt-forming dye is preferably 0.2 to 50% by mass, more preferably 0.5 to 10% by mass, based on the total amount of monomers, from the viewpoint of color development, weather resistance, stability and other functions as a coloring material.

[0081] As the polymerizable surfactant that can be used according to the above needs, there is no particular limitation as long as it is a polymerizable surfactant commonly used in the above emulsion polymerization. For example, as the polymerizable surfactant, an anionic or nonionic polymerizable surfactant, at least one of ADEKA REASOAP NE-10, ADEKA REASOAP NE-20, ADEKA REASOAP NE-30, ADEKA REASOAP NE-40, ADEKA REASOAP SE-10N manufactured by ADEKA Corporation, LATEMUL S-180, LATEMUL S-180A, LATEMUL S-120A manufactured by Kao Corporation, and Eleminol JS-20 manufactured by Sanyo Chemical Industries, Ltd. can be listed. The amount of these polymerizable surfactants used is 0 to 50% by mass, preferably 0.1 to 50% by mass, relative to the total amount of the above monomers.

[0082] In the above preferred embodiment, specifically, at least the above-mentioned salt-forming dye is dissolved in a mixed monomer containing 40% by mass or more of the above-mentioned carboxyl group-containing vinyl monomer and 20% by mass or more of the above-mentioned ester monomer, and then emulsion polymerization is performed; or at least the above-mentioned salt-forming dye is dissolved after the above-mentioned polymerization and dyeing is performed, thereby dispersing 20 to 50% by mass of colored resin particles in water based on the resin solid content to obtain a dispersion of colored resin particles, and the dispersion is dried to obtain colored resin particles. It should be noted that when used in an aqueous ink composition for writing instruments, the dispersion of colored resin particles obtained above can be used directly.

[0083] It should be noted that, although acrylic colored resin particles are described in detail above, even vinyl acetate colored resin particles, urethane colored resin particles, styrene-butadiene colored resin particles, and styrene acrylonitrile colored resin particles can also be used to produce colored resin particles composed of each monomer raw material and the above-mentioned salt-forming dye which is a salt-forming body of the acid dye and the basic dye.

[0084] The obtained colored resin particles have an unprecedentedly excellent color development property and can be used as a coloring material for aqueous ink compositions for writing instruments such as roller pens, marker pens, and ballpoint pens.

[0085] In the present invention, the average particle size of the obtained colored resin particles varies depending on the type and content of each monomer, the polymerization conditions during polymerization, etc., but is 1 μm or less, and does not cause clogging in the refills of writing tools such as signature pens, marker pens, and ballpoint pens. It should be noted that in the present invention, the "average particle size" refers to the value of the particle size (D50) at the volume accumulation of 50% of the particle size distribution calculated on a volume basis measured by a laser diffraction method. Here, the average particle size can be measured by a laser diffraction method, for example, using a particle size distribution analyzer HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0086] <Aqueous ink composition for writing instruments>

[0087] The aqueous ink composition for writing instruments of the present invention contains the colored resin particles colored with the salt-forming dye which is a salt-forming body of an acid dye and a basic dye, and preferably further contains a water-soluble organic solvent and water.

[0088] The content of the colored resin particles varies depending on the type of writing instrument such as a signing pen, a marker pen, or a ballpoint pen, but is preferably 0.1 to 30.0% by mass, more preferably 0.5 to 20.0% by mass, based on the total amount of the ink composition in terms of resin solid content.

[0089] Examples of usable water-soluble organic solvents include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol, 2-methylpentane-2,4-diol, 3-methyl- ...1,5-pentanediol, 2,5-hexanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5-pentanediol, 1,5- At least one of alkylene glycols such as pentane-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 ethylene glycol 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-imidazolidinone.

[0090] In addition, water-soluble solvents such as alcohols such as methanol, ethanol, isopropanol, n-butanol, tert-butanol, isobutanol, hexanol, octanol, nonanol, decanol, and benzyl alcohol, amines such as dimethylformamide and diethylacetamide, and ketones such as acetone may be mixed.

[0091] The content of these water-soluble organic solvents varies depending on the type of writing instruments such as signing pens, marker pens, and ballpoint pens, and is 1 to 40% by mass relative to the total amount of the ink composition. From the perspective of further improving the drying properties of the drawn lines, it is particularly effective to set the ink composition to 10% by mass or less, and more preferably 3 to 8% by mass.

[0092] The content of water (tap water, purified water, ion-exchanged water, distilled water, pure water, etc.) is preferably 30 to 90% by mass, more preferably 40 to 60% by mass, based on the total amount of the ink composition.

[0093] In the aqueous writing ink composition of the present invention, an antiseptic or mildew-proofing agent, a pH adjuster, a defoaming agent, a dispersant, etc. may be appropriately selected and used according to the type of the writing instrument and as needed, within a range not impairing the effects of the present invention.

[0094] Examples of the pH adjuster include at least one of ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, aminomethyl propanol, sodium tripolyphosphate, alkali metal salts of carbonic acid such as sodium carbonate, alkali metal salts of phosphoric acid, and alkali metal hydroxides such as sodium hydroxide.

[0095] Examples of the preservative or antifungal agent include at least one of phenol, sodium omadine, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, alkali metal salts of benzoic acid, sorbic acid or dehydroacetic acid, and benzimidazole compounds.

[0096] Examples of the lubricant include at least one of phosphate esters, polyalkylene glycol derivatives such as polyoxyethylene lauryl ether, fatty acid alkali salts, nonionic surfactants, fluorine-based surfactants such as perfluoroalkyl phosphate esters, and polyether-modified silicones such as polyethylene glycol adducts of dimethylpolysiloxane.

[0097] The aqueous ink composition for writing instruments of the present invention constructed as described above contains colored resin particles or their dispersion liquid colored with a salt-forming dye which is a salt-forming body of an acid dye and a basic dye and has excellent color development, so that an aqueous ink composition for writing instruments suitable for writing instruments such as signing pens, marker pens, and ballpoint pens can be obtained.

[0098] <Writing tools>

[0099] The writing instrument of the present invention is characterized by being equipped with the aqueous ink composition of the writing instrument having the above-mentioned structure.

[0100] Specifically, the aqueous ink composition for writing instruments having the above configuration is placed on a ballpoint pen, a marking pen, or the like having a pen tip such as a ballpoint pen tip, a fiber tip, a felt tip, or a plastic tip.

[0101] Examples of ballpoint pens include: a pen in which the aqueous ink composition for a writing instrument of the above composition is contained in an ink container (refill) for a ballpoint pen having a ball with a diameter of 0.18 to 2.0 mm, and a substance that is incompatible with the aqueous ink composition contained in the ink container and has a small specific gravity relative to the aqueous ink composition, such as polybutene, silicone oil, mineral oil, etc., is contained as an ink follower.

[0102] It should be noted that there is no particular restriction on the structure of a ballpoint pen or a marker. For example, it may be a straight liquid ballpoint pen or a marker having the following structure: the pen barrel itself is used as an ink storage body, and a collector structure (ink retaining mechanism) formed by filling the pen barrel with the aqueous ink composition of the writing tool constructed as described above.

[0103] Since the writing implement thus constructed is equipped with the above-mentioned aqueous ink composition for writing implements with excellent color development, writing implements such as signing pens, marker pens, and ballpoint pens with excellent color development and desired bright colors (yellow, red, blue, black, etc.) can be obtained.

[0104] Example

[0105] Next, the present invention will be described in more detail by using production examples of salt-forming dyes and colored resin particles, examples of aqueous ink compositions for writing instruments, and comparative examples, but the present invention is not limited to the following examples and the like.

[0106] (Production Example 1)

[0107] When producing the colored resin particles described below, the preparation of a salt former (salt-forming dye) and the synthesis of colored resin particles are continuously performed by mixing an acid dye and a basic dye, thereby obtaining colored resin particles 1 .

[0108] A 2-liter flask was equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet, and a 1000-ml separating funnel for adding monomers. The flask was placed in a warm water tank, and 500 g of distilled water, 50 g of a polymerizable surfactant [manufactured by ADEKA Corporation, "ADEKA REASOAP SE-10N"], and 3 g of ammonium persulfate were added. The internal temperature was raised to 50° C. while introducing nitrogen.

[0109] On the other hand, 20 g of Water Yellow 6C (Orient Chemical Industries: Acid yellow 6C) as an acid dye and 25 g of Spillon Yellow C-GNH-new (Hodogaya Chemical Co., Ltd.) as a basic dye were mixed with 500 g of a mixed monomer consisting of 300 g of 2-methacryloyloxyethyl phthalate [manufactured by Mitsubishi Rayon Co., Ltd., acrylate PA, solubility in water: 0.08 mass %] and 200 g of n-butyl methacrylate to prepare a liquid.

[0110] The prepared liquid was added from the separating funnel to the flask maintained at a temperature of approximately 50° C. over 3 hours under stirring to carry out emulsion polymerization. The polymerization was completed by further aging for 5 hours to obtain a dispersion of colored resin particles.

[0111] (Production Example 2)

[0112] Colored resin particles 2 were obtained in the same manner as in Production Example 1 except that the acid dye was replaced with 20 g of CIAcid Blue 9 and the basic dye was replaced with 25 g of Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd.).

[0113] (Production Example 3)

[0114] In the above-mentioned Production Example 1, the acid dye was replaced with CIAcid Yellow 42: 18 g, and the basic dye was replaced with CIBasic Violet 1: 22 g. The colored resin particles 3 were obtained in the same manner as in the above-mentioned Production Example 1.

[0115] (Production Example 4)

[0116] In the above-mentioned Production Example 1, instead of 20 g of the acid dye [Water Yellow 6C (manufactured by Orient Chemical Industries: Acid yellow 6C) and 25 g of the basic dye [Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd.)], 45 g of VALIFAST RED1308 (a salt of CI Acid Yellow 23 and CI Basic Red 1) manufactured by Orient Chemical Industries was used as the salt-forming dye, and colored resin particles 4 were obtained in the same manner as in the above-mentioned Production Example 1.

[0117] (Production Example 5)

[0118] Colored resin particles 5 were obtained in the same manner as in Production Example 4 except that 45 g of VALIFAST RED 1320 (a salt of CI Acid Yellow 42 and CI Basic Red 1) manufactured by Orient Chemical Industries was used instead of the salt-forming dye.

[0119] (Production Example 6)

[0120] Colored resin particles 6 were obtained in the same manner as in Production Example 4 except that 45 g of VALIFAST GREEN 1501 (salt of CI Acid Yellow 42 and CI Basic Blue 1) manufactured by Orient Chemical Industries was used as the salt-forming dye.

[0121] (Production Example 7)

[0122] Colored resin particles 7 were obtained in the same manner as in Production Example 4 except that 45 g of VALIFAST VIOLET 1701 (a salt of CI Acid Yellow 42 and CI Basic Violet 1) manufactured by Orient Chemical Industries was used instead of the salt-forming dye.

[0123] (Production Example 8)

[0124] Colored resin particles 8 were obtained in the same manner as in Production Example 4 except that 45 g of VALIFAST VIOLET 1704 (a salt of CI Acid Yellow 36 and CI Basic Violet 1) manufactured by Orient Chemical Industries was used instead of the salt-forming dye.

[0125] (Comparative Manufacturing Example 1)

[0126] In the above-mentioned Production Example 1, instead of using 25 g of the basic dye [Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd.)], 40 g of the acid dye (Water Yellow 6C (manufactured by Orient Chemical Industries: Acidyellow 6C)) was used to obtain colored resin particles 9 in the same manner as in the above-mentioned Production Example 1.

[0127] (Comparative Manufacturing Example 2)

[0128] In the above-mentioned Production Example 2, colored resin particles 10 were obtained in the same manner as in the above-mentioned Production Example 2 except that 25 g of the basic dye [Spillon Yellow C-GNH-new (manufactured by Hodogaya Chemical Co., Ltd.)] was not used and 45 g of the acid dye CIAcid Blue 9 was used.

[0129] (Comparative Manufacturing Example 3)

[0130] In the above-mentioned Production Example 3, instead of using 22 g of the basic dye [CI Basic Violet 1], 45 g of the acid dye CIAcid Yellow 42 were used, and colored resin particles 11 were obtained in the same manner as in the above-mentioned Production Example 3.

[0131] (Comparative Production Example 4)

[0132] In the above-mentioned Production Example 4, the colored resin particles 12 were obtained in the same manner as in the above-mentioned Production Example 4 except that the salt-forming dye (VALIFAST RED 1308) was replaced with the acid dye CIAcidYellow 23:45 g.

[0133] (Comparative Production Example 5)

[0134] In the above-mentioned Production Example 8, the colored resin particles 13 were obtained in the same manner as in the above-mentioned Production Example 8 except that the salt-forming dye (VALIFAST VIOLET 1704) was replaced with the acid dye CIAcid Yellow 36: 45 g.

[0135] (Examples 1 to 8 and Comparative Examples 1 to 5: Preparation of aqueous ink compositions for writing instruments)

[0136] Using the dispersions of the colored resin particles obtained in the above-mentioned Production Examples 1 to 8 and Comparative Production Examples 1 to 5, aqueous ink compositions for writing instruments were prepared by a conventional method according to the formulations shown below.

[0137] The average particle diameter of each dispersion of the colored resin particles for aqueous ink was in the range of 30 to 500 nm, and the resin solid content was 30% by mass.

[0138] (Compound composition)

[0139]

[0140] For each of the obtained aqueous ink compositions for writing instruments (total amount 100% by mass), a marking pen as a writing instrument was prepared by the following method, and the color development property was evaluated by the following evaluation method.

[0141] The evaluation results of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1 below.

[0142] (Writing tools: Preparation of marker pens)

[0143] Each ink composition prepared in Examples 1 to 8 and Comparative Examples 1 to 5 was loaded into a marker pen [manufactured by Mitsubishi Pencil Co., Ltd., trade name: PROPUS WINDOW PUS-102T, pen tip, thick: PE resin, thin: PET fiber] to prepare a marker pen.

[0144] (Evaluation method of color rendering)

[0145] Using the marker pen obtained above and filled with each of the ink compositions prepared in Examples 1 to 8 and Comparative Examples 1 to 5, writing was performed on PPC paper, and evaluation was performed according to the following evaluation criteria.

[0146] Evaluation criteria:

[0147] A: High concentration color development

[0148] B: Color development at a slightly lower concentration

[0149] C: Light concentration or incomplete coloring

[0150] [Table 1]

[0151]

[0152] As can be seen from Table 1, Examples 1 to 8 within the scope of the present invention provide aqueous ink compositions for writing instruments having excellent color development properties, compared with Comparative Examples 1 to 5 outside the scope of the present invention.

[0153] Industrial Applicability

[0154] The aqueous ink composition suitable for use in writing instruments such as a signing pen, a marking pen, and a ballpoint pen can be obtained.

Claims

1. A water-based ink composition for writing tools, characterized in that: The invention contains colored resin particles, the colored resin particles include acrylic resin particles and are colored with a salt-forming dye which is a salt-forming body of an acid dye and a basic dye, The acrylic resin particles include a polymer of at least an ester monomer and a carboxyl group-containing vinyl monomer. The carboxyl group-containing vinyl monomer is a carboxyl group-containing vinyl monomer having a solubility in water of 10% by mass or less, The ester monomer is an ester monomer of acrylic acid or methacrylic acid and a linear alcohol or a cyclic alcohol having 2 to 18 carbon atoms.

2. The aqueous ink composition for writing instruments according to claim 1, wherein In the monomer components constituting the polymer of the acrylic resin particles, the total content of the carboxyl group-containing vinyl monomer and the ester monomer is 60% by mass or more.

3. The aqueous ink composition for writing instruments according to claim 1, wherein In the monomer components constituting the polymer of the acrylic resin particles, the content of the carboxyl group-containing vinyl monomer is 40% by mass or more, and the content of the ester monomer is 20% by mass or more.

4. The aqueous ink composition for writing instruments according to claim 1, wherein The monomer components of the polymer constituting the acrylic resin particles further include 1 to 25% by mass of a dicyclopentenyl (meth)acrylate monomer.

5. A writing tool, characterized in that: A writing instrument equipped with the aqueous ink composition according to any one of claims 1 to 4.

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