Resin particle dispersion, and aqueous ink composition for writing instruments containing the same

Abstract

To provide a resin particle dispersion which is excellent in dispersion stability even after storage under low temperature environment, and efficiently exhibits a predetermined surface active agent action, and an aqueous ink composition for writing instruments containing the same, which has a sufficient wettability improving effect even under low temperature environment without destroying dispersion stability of aqueous ink, and highly achieves both a stable writing flow rate and a quality (writing property) of a written / drawn line.SOLUTION: There is provided a resin particle dispersion in which at least resin particles including at least one surface active agent component selected from the following group A are dispersed in water. [Group A] acetylene-based surface active agent, polyethylene glycol-based surface active agent, and silicone-based active agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin particle dispersion containing a surfactant, and an aqueous ink composition for a writing instrument containing the same. [Background technology]

[0002] BACKGROUND ART Conventionally, specific surfactants have been incorporated into aqueous ink compositions for writing implements and the like to improve the wettability of the ink. For example, 1) an ink composition for a water-based ballpoint pen, which contains at least water, carbon black, and a surfactant, wherein the carbon black has an oil absorption of 101 g or more ( / 100 g), and the surfactant is one or more selected from the group consisting of a silicone surfactant, an acetylene glycol surfactant, a fluorine-based surfactant, and a dialkyl sulfosuccinate, and an aqueous ballpoint pen using the same (see, for example, Patent Document 1); 2) A water-based ink composition for a brush pen, which contains a colorant, a surfactant having an acetylene bond, a defoaming agent, and water (see, for example, Patent Document 2); 3) A heat-erasable ink composition is known in which a colorant, which is produced by reacting a leuco dye with a color developer, and a desensitizer are dispersed in water, and a polyethylene glycol-type nonionic surfactant is used as the desensitizer (see, for example, Patent Document 3).

[0003] However, when these aqueous ink compositions directly contain an acetylene-based surfactant having an acetylene bond, a polyethylene glycol-based surfactant, a silicone-based surfactant, or the like, direct addition can frequently cause the dispersion system to become unstable or precipitates to form. Furthermore, depending on the liquid temperature of the ink, particularly in a low-temperature environment, the solubility decreases, making it difficult to obtain a sufficient surfactant effect after low-temperature storage, making it difficult to obtain a wettability improvement effect or a stable writing flow rate, and causing unevenness in the writing flow rate, which can also reduce the quality of the written lines (writing ability). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-28789 (claims, examples, etc.) [Patent Document 2] Japanese Patent Application Laid-Open No. 2021-123696 (claims, examples, etc.) [Patent Document 3] Japanese Patent Application Laid-Open No. 9-165537 (claims, examples, etc.) [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] In view of the problems of the above prior art and the like, the present invention aims to solve them. Even after storage in a low-temperature environment, a resin particle dispersion excellent in dispersion stability and capable of efficiently exhibiting a predetermined surfactant action is provided. In the aqueous ink composition for writing instruments containing this, the wettability is improved, and an aqueous ink composition for writing instruments that highly achieves both a stable writing flow rate and the quality (writing property) of the writing line is provided. [Means for Solving the Problems]

[0006] In view of the above conventional problems and the like, the present inventors conducted intensive research. As a result, they found that the resin particle dispersion of the above object can be obtained by, for example, resin particles containing at least a specific surfactant component being dispersed in water, and thus completed the present invention.

[0007] That is, the resin particle dispersion of the present invention is characterized in that resin particles containing at least one surfactant component selected from at least the following Group A are dispersed in water. <Group A> Acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants The resin particles encapsulating the surfactant component are composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group B. The resin particle dispersion according to claim 1. <Group B> Acrylic monomer, styrene monomer, nitrile monomer, vinyl acetate monomer The acetylene-based surfactant and the polyethylene glycol-based surfactant preferably have a water solubility of less than 10%. The acetylene-based surfactant preferably has an HLB value of 13.5 or less, the polyethylene glycol-based surfactant preferably has an HLB value of 10.0 or less, and the silicone-based surfactant preferably has an HLB value of 10.0 or less. The aqueous ink composition for writing instruments of the present invention is characterized by containing a resin particle dispersion having the above configuration.

Advantages of the Invention

[0008] According to the present invention, a resin particle dispersion is provided in which a predetermined surfactant action such as a sufficient wetting improvement effect can be efficiently exhibited even in a low-temperature environment without destroying the dispersion stability. In the aqueous ink composition for writing instruments containing this, without destroying the dispersion stability of the aqueous ink, it has a sufficient wetting improvement effect even in a low-temperature environment, and provides an aqueous ink composition for writing instruments that highly balances a stable writing flow rate and the quality (writing property) of the writing line. The objects and effects of the present invention are recognized and obtained by using the components and combinations particularly pointed out in the claims. Both the above general description and the following detailed description are exemplary and explanatory, and do not limit the present invention described in the claims.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail. However, note that the technical scope of the present invention is not limited to each of the embodiments described in detail below, and extends to the invention described in the claims and its equivalents. The resin particle dispersion of the present invention is characterized in that resin particles encapsulating at least one surfactant component selected from the following Group A are dispersed in water. <Group A> Acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants

[0010] In the present invention, the resin particles encapsulating at least one surfactant component selected from the above Group A are not particularly limited in terms of their function and resin type. For example, they can be composed of homopolymers obtained from various resin monomers such as acrylic monomers, allyl monomers, isocyanate monomers, isothiocyanate monomers, epoxy monomers, diamine monomers, thiol monomers, dicarboxylic acid chloride monomers, dicarboxylic acid monomers, disulfonyl chloride monomers, dithiol monomers, divinyl monomers, diallyl monomers, styrene monomers, tetracarboxylic acid anhydride monomers, nitrile monomers, bismaleimide monomers, lactone monomers, actide monomers, fluorine-containing monomers, cyclic olefin monomers, etc., or copolymers formed by combining these monomers. Preferably, the resin particle dispersion of the present invention is composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group B, from the viewpoints of ease of encapsulation into resin particles and stability under low-temperature environments. <Group B> Acrylic monomers, styrene monomers, nitrile monomers, vinyl acetate monomers

[0011] To produce resin particles encapsulating at least one surfactant component selected from the above Group A, for example, at least one surfactant component selected from the above Group A and at least one of the above monomer components are used, and polymerization (homopolymerization or copolymerization) is carried out using a suitable polymerization initiator, etc., according to each monomer type, to obtain each resin particle dispersion. Also, each resin particle dispersion can be obtained by appropriately adjusting production conditions such as the temperature, stirring speed, and reaction time during polymerization. Examples of resin particles of copolymers in Group B include particles of copolymers of acrylic monomers and styrene monomers, particles of copolymers of acrylic monomers and nitrile monomers, particles of copolymers of acrylic monomers and vinyl acetate monomers, particles of copolymers of styrene monomers and nitrile monomers, particles of copolymers of styrene monomers and vinyl acetate monomers, particles of copolymers of nitrile monomers and vinyl acetate monomers, particles of copolymers of acrylic monomers, styrene monomers and nitrile monomers, particles of copolymers of acrylic monomers, styrene monomers and vinyl acetate monomers, particles of copolymers of acrylic monomers, nitrile monomers and vinyl acetate monomers, particles of copolymers of styrene monomers, nitrile monomers and vinyl acetate monomers, and particles of copolymers of acrylic monomers, styrene monomers, nitrile monomers and vinyl acetate monomers. Particles composed of a homopolymer or copolymer obtained from at least one monomer selected from Group B are preferably used because they have the strength of the surfactant component that can be encapsulated, as described below, can produce long-lasting, stable particles, do not have an adverse effect on other blended components, and have a long-lasting effect of the surfactant component.

[0012] Furthermore, the acrylic monomer that can be used is preferably a (meth)acrylic acid ester monomer represented by the following general formula (X). [ka] In the above formula (X), A represents a hydrogen atom (H) or a methyl group (CH3), and 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. The alkyl group or the substituent having a polyalkylene glycol chain may have, as a substituent, 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. Examples of such alkyl groups include linear or branched alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 10 carbon atoms, and alkyl groups having 1 to 18 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, a dialkylamino group, or an alkoxy group having 1 to 4 carbon atoms. Particularly, alkyl groups having 1 to 6 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, or an alkoxy group having 1 to 2 carbon atoms, and alkyl groups having 1 to 6 carbon atoms which may have, as a substituent, an epoxy group. Preferably, R in the above general formula (X) 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, or the like. In this specification, the expression "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0013] Specific examples of the (meth)acrylic acid ester represented by the general formula (X) 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 perfluoroalkyl groups having 1 to 18 carbon atoms, 2-(methacryloyloxy)ethyl (meth)acrylate phosphate), trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, and the like (each may be used alone or in combination of two or more; the same applies hereinafter).

[0014] 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, as they are easily available industrially, are easy and safe to handle during production, and further improve the effects of the present invention.

[0015] In the present invention, in addition to the above-mentioned (meth)acrylic acid ester monomers, hydrophobic vinyl monomers and aqueous monomers other than the above-mentioned (meth)acrylic acid ester monomers can be preferably used in order to obtain a sustained wetting effect, dispersion stability, a stable writing flow rate, and quality of the written lines (writing properties). As the hydrophobic vinyl monomer, for example, at least one monomer other than the above (meth)acrylic acid ester monomers, such as styrene and methylstyrene, can be used. Examples of hydrophobic vinyl monomers that can be used include at least one of styrene, methylstyrene, chloromethylstyrene, alkylstyrenes having an alkyl group having 1 to 12 carbon atoms, methoxystyrene, chlorostyrene, bromostyrene, divinylbenzene, phenylstyrene, and vinylnaphthalene. 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, and propylene glycol-polybutylene glycol-monomethacrylate.

[0016] The surfactant component used in the present invention may be at least one selected from acetylene-based surfactants, polyethylene glycol-based surfactants, and silicone-based surfactants. In the case of acetylene-based surfactants and polyethylene glycol-based surfactants, those with a water solubility of less than 10%, and preferably 5% or less, are preferred in order to form more stable surfactant-encapsulated resin particles. The term "water solubility" as defined in the present invention means the solubility in water at 25°C (water solubility). Furthermore, the acetylene surfactants that can be used preferably have an HLB value of 13.5 or less, more preferably 10.0 or less, and particularly preferably 8.0 or less, in terms of dispersion stability, increasing the amount of encapsulation inside the particles, and achieving a sustained wettability effect. Furthermore, in the case of polyethylene glycol surfactants and silicone surfactants, it is preferable that the HLB value is 10.0 or less in terms of dispersion stability, increasing the amount of encapsulation inside the particles, and obtaining a sustained wettability effect.

[0017] The surfactant component used in the resin particle dispersion of the present invention is preferably a surfactant component having the above-described characteristics, and is composed of at least one surfactant component selected from an acetylene-based surfactant, a polyethylene glycol-based surfactant, and a silicone-based surfactant. Here, the HLB value is one of the scales that indicate the properties of a surfactant, and is a numerical representation of the balance between hydrophilic groups and lipophilic groups in the molecule. The HLB value has been proposed by several calculation methods, but in this specification, it is a value calculated by the Griffin method, and is calculated by the following formula (1): HLB value = 20 × (formula weight of hydrophilic part) / (molecular weight of surfactant) ... (1) The acetylene surfactant that can be used includes at least one selected from acetylene glycols, their alkylene oxide adducts, and acetylene alcohols, and specifically includes at least one selected from the following formulas (I) to (VI). [ka] [In the above formulas (I) to (III), R1 and R2 are each a linear or branched alkyl group having 1 to 8 carbon atoms, and m, n, x, and y are numbers from 1 to 100.]

[0018] [ka] [In the above formulas (IV) to (VI), R3, R4, and R5 represent a hydrogen atom or a straight or branched carbon chain having 0 to 10 carbon atoms, which may contain an unsaturated bond, R6 represents an alkylene group having 2 to 5 carbon atoms, and R7 represents an alkylene group having 1 to 5 carbon atoms.]

[0019] Examples of acetylene glycols and alkylene oxide adducts thereof that can be used include acetylene glycol represented by the above formula (I), a derivative (adduct) of acetylene glycol represented by the above formula (II) in which ethylene oxide (EO) is added, and a derivative (adduct) of acetylene glycol represented by the above formula (III) in which ethylene oxide (EO) or propylene oxide (PO) is added. Examples of the linear or branched alkyl group having 1 to 8 carbon atoms represented by R1 and R2 in the above formulas (I) to (III) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.

[0020] Examples of the acetylene glycol of the above formula (I) include 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, 5,8-dimethyl-6-dodecyne-5,8-diol, 2,4,7,9-tetramethyl-5-dodecyne-4,7-diol, 8-hexadecyne-7,10-diol, 7-tetradecyne-6,9-diol, 2,3,6,7-tetramethyl-4-octyne-3,6-diol, 3,6-diethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol. Examples of the alkylene oxide (EO, PO) adducts of the acetylene glycol of the above formula (II) and formula (III) include alkylene oxide derivatives of the above acetylene glycol.

[0021] The compounds represented by the general formulas (I) to (III) can be synthesized by various known methods, and commercially available compounds may also be used. Examples of acetylene glycols and their alkylene oxide adducts include commercially available Surfynol 104 (2,4,7,9-tetramethyl-5-dodecyne-4,7-diol, manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 4), which has a water solubility of less than 10%, Surfynol 104E (HLB value: 4), 104H, 104A (each HLB value: 4) obtained by diluting Surfynol 104 with various solvents, the Surfynol 104 series, such as 104S containing silica particles, and EO adducts of Surfynol 104, such as 420 (HLB value: 4), 440 (HLB value: 8), DF110D (HLB value: 3), DF37, DF58, DF75, and DF220.

[0022] The acetylene alcohols represented by (IV) to (VI) above have an acetylene group (-C≡C-) and a hydroxyl group (-OH) in their molecular structure. R3, R4, and R5 in the general formulas (IV) to (VI) above each represent a hydrogen atom, a linear or branched alkyl group, an alkenyl group, an aryl group, an aralkyl group, or the like. Here, the alkyl group and alkenyl group may be linear, branched, or cyclic, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, and a cyclohexenyl group. The aryl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. Furthermore, the aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a benzyl group, a phenethyl group, and a naphthylmethyl group. In the general formula (V), R6 represents an alkylene group having 2 to 5 carbon atoms, which may be linear, branched, or cyclic, with linear alkylene groups being particularly preferred. Examples of linear alkylene groups include ethylene, trimethylene, tetramethylene, and pentamethylene. Furthermore, R7 in the above general formula (VI) represents an alkylene group having 1 to 5 carbon atoms, and the alkylene group is a methylene group (having 1 carbon atom), and when the alkylene group has 2 or more carbon atoms, it is the same as R6 in the above general formula (V).

[0023] Specific examples of the acetylene alcohols of the general formula (IV) or derivatives thereof include 2-butyn-1-ol, 3-butyn-2-ol, 2-decyn-1-ol, 3,6-dimethyl-1-heptyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3,4-dimethyl-1-pentyn-3-ol, 1,1-diphenyl-2-propyn-1-ol, 3-ethyl-1-heptyn-3-ol, 4-ethyl-1-octyn-3-ol, 3-ethyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, 9-ethynyl-9-fluorenol, 1-heptyn- 3-ol, 2-heptyn-1-ol, 1-hexyn-3-ol, 2-hexyn-1-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-penten-4-yn-3-ol, 3-methyl-1-pentyn-3-ol, 2-methyl-4-phenyl-3-butyn-2-ol, 1-octyn-3-ol, 1-pentyn-3-ol, 2-pentyn-1-ol, 1-phenyl-2-propyn-1-ol, 3-phenyl-2-propyn-1-ol, 2-propyn-1-ol, 1,1,3-triphenyl-2-propyn-1-ol, and the like.

[0024] Specific examples of the acetylene alcohols of general formula (V) or derivatives thereof include at least one of 3-butyn-1-ol, 3-decyn-1-ol, 9-decyn-1-ol, 3-heptyn-1-ol, 3-hexyn-1-ol, 5-hexyn-1-ol, 3-nonyn-1-ol, 3-octyn-1-ol, 3-pentyn-1-ol, 4-pentyn-1-ol, 5-phenyl-4-pentyn-1-ol, and 10-undecyn-1-ol. Specific examples of the acetylene alcohols of the general formula (VI) or derivatives thereof include at least one of 4-heptyn-2-ol, 5-heptyn-3-ol, 5-hexyn-3-ol, and 4-pentyn-2-ol. Among the compounds specifically listed in the above general formulas (IV) to (VI), it is preferable to use 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol in terms of usability, cost, safety, and the ability to further exert the effects of the present invention.

[0025] The synthesis methods for each of the compounds listed in the general formulas (IV) to (VI) above are known and can be obtained by various production methods, or commercially available products may be used. For example, acetylene alcohols include commercially available products having a water solubility of less than 10%, such as Surfynol 61 (3,5-dimethyl-1-hexyn-3-ol), Olfine A (2,5-dimethylhexane-2,5-diol), Olfine B (3-methyl-1-butyn-3-ol), Olfine P (3-methyl-1-pentyn-3-ol), Olfine PD-002W, EXP.4200, WE-003, SPC, and other olefins manufactured by Nissin Chemical Industry Co., Ltd.

[0026] Usable polyethylene glycol surfactants include polyethylene glycol ethers and polyethylene glycol esters, and it is preferable to use the following general formula (VII). [ka] In the above formula (VII), R8 and R9 are hydrogen atoms or C n H 2n+1 , n is a number from 1 to 20, and m is a number from 5 to 40. Among the polyethylene glycol surfactants represented by the above formula (VII), the alkyl groups such as R8 and R9 preferably have 4 to 20 carbon atoms, more preferably 5 to 18 carbon atoms, and particularly preferably 8 to 15 carbon atoms. Furthermore, with respect to the ethylene oxide group -(CH2-CH2-O)m- in the above formula (VII), the number of moles of ethylene oxide added, m, is preferably 10-40, more preferably 20-40, and particularly preferably 30-40.

[0027] As with the acetylene-based surfactants described above, in order to produce more stable surfactant-encapsulated resin particles, it is preferable that this polyethylene glycol-based surfactant have a water solubility of less than 10%, and furthermore, that the HLB value be 10.0 or less, more preferably 8.0 or less, and particularly preferably 5.0 or less. Specific examples of polyethylene glycol surfactants that can be used include at least one of commercially available surfactants with a water solubility of less than 10%, such as EGMS-70V (manufactured by Nikko Chemicals, HLB value: 3.5), MYO-6V (manufactured by Nikko Chemicals, HLB value: 8.5), and Adeka Estol OEG-102 (manufactured by ADEKA, HLB value: 7.9).

[0028] In order to obtain more stable surfactant-encapsulated resin particles, silicone surfactants with an HLB value of 10.0 or less are desirable, more preferably 9.0 or less, and even more preferably 8.0 or less. Examples of silicone surfactants include dimethyl silicone, cyclic silicone, trimethylsiloxysilicate, methylphenyl silicone, and further preferred are polyether-modified silicone, methylstyryl-modified silicone, alkyl-modified silicone, higher fatty acid ester-modified silicone, higher alkoxy-modified silicone, fluorine-modified silicone, fluorine-based alkyl ester, polyether-modified silicone, polyglycerin-modified silicone, polyether-alkyl co-modified silicone, polyglycerin-alkyl co-modified silicone, and polyether-silicone-alkyl co-modified silicone. Any of linear, branched, and crosslinked types can be used, and emulsion types are also acceptable. These silicone surfactants can be used alone or in combination of two or more types.

[0029] Specific examples of silicone surfactants that can be used include at least one of commercially available surfactants with an HLB value of 8.0 or less, such as KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 4.5), KF-6004 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 9.0), KF-6038 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 3.0), and KF-6012 (manufactured by Shin-Etsu Chemical Co., Ltd., HLB value: 7.0).

[0030] The resin particle dispersion of the present invention is characterized in that resin particles encapsulating at least one surfactant component selected from Group A above are dispersed in water. The production method thereof can be, for example, by polymerizing (homopolymerizing or copolymerizing) at least one surfactant component selected from Group A above and at least one of the above-mentioned monomer components using a suitable polymerization initiator, etc., to obtain each resin particle dispersion. In addition, each resin particle dispersion can be obtained by appropriately adjusting production conditions such as temperature during polymerization, stirring speed, and reaction time.

[0031] In the case of a resin particle dispersion composed of a homopolymer or copolymer obtained from at least one monomer selected from the group B acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monomers, for example, a method is used in which at least one surfactant component selected from the acetylene-based surfactants and polyethylene glycol-based surfactants is dissolved in a styrene monomer, a nitrile monomer, a vinyl acetate monomer, a (meth)acrylic acid ester monomer, or the like (each alone or in combination of two or more thereof, the same applies hereinafter), or in a mixed monomer containing each of the above (meth)acrylic acid ester monomers and other hydrophobic vinyl monomers and / or aqueous monomers, and ammonium persulfate, potassium persulfate, hydrogen peroxide, or the like is used as a polymerization initiator, and a reducing agent is further used in combination with the polymerization initiator, and 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, ethoxylated polyglycerin methacrylate, or other crosslinking agents, 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 ester, polyoxyethylene styrenated phenyl ether phosphate ester, polyoxyethylene styrenated phenyl ether sulfate, polyoxyethylene alkyl ether sulfate,It can be produced by emulsion polymerization using a polymerizable surfactant (emulsifier) ​​such as polyoxyethylene sorbitan monolaurate (polysorbate 20), polyoxyethylene sorbitan palmitate (polysorbate 40), polyoxyethylene sorbitan monostearate (polysorbate 60), or polyoxyethylene sorbitan oleate (polysorbate 80), and after being produced as a dispersion of resin particles, it can be made into a resin particle dispersion by drying or the like. Use of a crosslinking agent such as triallyl isocyanurate is preferred because it can improve the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the resin particle dispersion.

[0032] During the emulsion polymerization, an appropriate amount of dicyclopenta(thenyl)(meth)acrylate monomer may be further mixed with the styrene monomer, nitrile monomer, vinyl acetate monomer, (meth)acrylic acid ester monomer, etc. The emulsion polymerization further mixed with dicyclopenta(thenyl)(meth)acrylate monomer is less likely to lose stability even if the water in the dispersion evaporates, and the above-mentioned surfactant-encapsulated resin particle dispersion having even better stability can be obtained. Dicyclopent(en)yl (meth)acrylate monomers that can be used include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate.

[0033] In the present invention, during the emulsion polymerization, in addition to the dicyclopenta(en)yl (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 styrene monomer, nitrile monomer, vinyl acetate monomer, acrylic acid monomer, or other hydrophobic vinyl monomer.

[0034] In the present invention, among the polymer components constituting the resin particle dispersion, the content of the monomers of Group B is preferably 30% by mass or more, more preferably 30 to 95% by mass, and particularly preferably 30 to 70% by mass, based on the total polymer components constituting the resin particle dispersion. In the present invention, the term "total polymer components" refers to the polymerizable components constituting the resin particle dispersion, specifically the total amount including all types of monomers that are raw materials for the final polymer and crosslinking agents, and in the case of Group B, refers to the total amount of the monomers of Group B used, other monomer components used, and the crosslinking agent described below. In the case of using this Group B monomer, the effects of the present invention can be further exerted by making the content of the Group B 30% by mass or more based on the total polymer components, while if this content is less than 30% by mass, the stability over time tends to be poor.

[0035] In addition, in the present invention, when Group B monomers such as the (meth)acrylic acid ester monomers are used among the polymer components constituting the resin particle dispersion, the content of other monomer components other than Group B monomers is the remainder of the total amount of the Group B monomers such as the (meth)acrylic acid ester monomers used and the crosslinking agent described below. Preferably, the content of other monomer components is 0.5 to 70% by mass based on the total polymer components, from the viewpoints of further exerting the effects of the present invention, dispersibility, and reactivity.

[0036] In the present invention, the total (solid content) content of the surfactants 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 surfactant performance, obtaining a sustained surfactant effect, and stability. By making the content of this surfactant component 1% by mass or more, sufficient surfactant performance and sustained surfactant effect can be exhibited, while if the content of the surfactant component is less than 1% by mass, the surfactant performance will be insufficient and the effects of the present invention will not be exhibited.

[0037] The polymerizable surfactant that can be used as needed is not particularly limited as long as it is a polymerizable surfactant that is commonly used in the emulsion polymerization. For example, the polymerizable surfactant may be an anionic or nonionic polymerizable surfactant, such as Adeka Reasoap NE-10, NE-20, NE-30, NE-40, SE-10N, SR-10, SR-20, ER-10, ER-20, ER-30, ER-40, or PP manufactured by ADEKA Corporation. α-70, LATEMURU S-180, S-180A, S-120A, PD-420, PD-430, and PD-450 manufactured by Kao Corporation, ELEMINOL JS-20, CLS-20, and RS-3000 manufactured by Sanyo Chemical Industries, Ltd., AQUALON AN-10, AN-20, AN-30, AN-5065, KH-05, KH-10, KH-1025, HS-10, AR-10, AR-1025, and AR-20 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and Spinomer NaSS manufactured by Tosoh Finechem Co., Ltd. The amount of these polymerizable surfactants used is 0 to 50% by mass, preferably 0.1 to 50% by mass, based on the total amount of the monomers. The content of the crosslinking agent such as triallyl isocyanurate is preferably 0 to 50% by mass, and more preferably 0.1 to 25% by mass, based on the total amount of the monomers.

[0038] In the present invention, the above-mentioned preferred embodiment, specifically, the above-mentioned polymerization, provides a resin particle dispersion (liquid dispersion) in which resin particles composed of a homopolymer obtained from each resin monomer or a copolymer combining these monomers, each having a surfactant component encapsulated therein, are dispersed in water. Alternatively, a resin particle dispersion (liquid dispersion) in which at least one surfactant component selected from the above-mentioned acetylene surfactants and polyethylene glycol surfactants is dissolved in a monomer selected from Group B acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monomers and emulsion-polymerized, or a mixed monomer containing at least one monomer selected from the above-mentioned acrylic monomers, styrene monomers, nitrile monomers, and vinyl acetate monomers and other monomer components is polymerized followed by dissolving the surfactant component and emulsion-polymerizing, can be obtained. The amount of resin particles in the resin particle dispersion obtained under these production conditions varies depending on the amount of the resin monomers (such as Group B monomers) and surfactant components used, the polymerization conditions, etc. From the standpoints of manufacturability, workability, and efficiency, it is preferable to produce the resin particle dispersion so that the solid content is 1 to 50% by mass. More preferably, the solid content is produced to be 10 to 40% by mass.

[0039] These resin particle dispersions (liquid dispersions) are more stable than those using the surfactant components alone when made into the resin particle dispersions of the present invention, since they have strong and long-lasting surfactant performance without adversely affecting other blended components, etc. In particular, they can be obtained as resin particle dispersions that can maintain or improve the surface activity effect of the surfactant components even after long-term storage. Furthermore, in the present invention, a surfactant component having a specific solubility or HLB is preferably used as the surfactant component. Therefore, in particular, in response to the issues of dispersion stability and allowing ink to penetrate without bleeding of drawn lines, the surfactant component is encapsulated in particles made of the resin monomer of the present invention, preferably a monomer of Group B, thereby improving the quality of written lines while suppressing bleeding, and providing the unique action and effect of being able to expect a sustained wetting effect.

[0040] In the present invention, the average particle size of the resin particles in the obtained resin particle dispersion varies depending on the type and content of the monomer and 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 diameter within the above preferred range, the resin particles can be used with excellent storage stability and have an average particle size within a range suitable for each application described below. When used in a water-based ink for a writing instrument, the resin particles do not clog the core of a writing instrument such as a felt-tip pen, a marking pen, or a ballpoint pen, and the resin particles can have excellent storage stability. The "average particle size" defined in the present invention is a histogram average particle size based on scattered light intensity distribution, and in the present invention (including the examples described below), it is the value D50 measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)].

[0041] In the resin particle dispersion of the present invention, the content of the resin particles contained in the dispersion is preferably 0.1 to 50 mass % in terms of solid content, and more preferably 1 to 30 mass %, depending on the intended use, etc., which will be described later. If the content of the resin particles is less than 0.1% by mass in terms of solid content, the effects of the present invention cannot be achieved, whereas if it exceeds 50% by mass, the long-term storage stability is likely to decrease.

[0042] The resin particle aqueous dispersion of the present invention thus constructed can efficiently exhibit the desired surfactant function, such as a sufficient wettability-improving effect, even at low temperatures without destroying dispersion stability. Therefore, the resin particle aqueous dispersion of the present invention can be used to impart surfactant properties, such as wettability, to a variety of products, including cosmetics, ink compositions for writing instruments, ink jet printers, and the like. The resin particle aqueous dispersion of the present invention can be used to impart surfactant properties, such as wettability, to a variety of products, including cosmetics, ink compositions for writing instruments, ink jet printers, and the like, in detergent applications where acetylene-based surfactants, polyethylene glycol-based surfactants, and the like have previously been directly blended, such as laundry detergents, fabric softeners, household detergents, dishwashing detergents, and hard surface cleaners; personal care applications such as shampoos, conditioners, lotions, emulsions, creams, sunscreens, foundations, eye makeup products, antiperspirants, and toothpastes; paints, adhesives, building materials, wood preservatives, cement admixtures, and ink compositions for writing instruments and ink jet printers. The resin particle dispersion of the present invention is highly stable and has excellent surface activity effects, such as the wettability of surfactant components, even at low temperatures and after long-term storage, while not affecting other compounded components. Therefore, as described above, it can be used to improve the wettability of a variety of products, and is particularly suitable for use in aqueous inks, inks for inkjet printers, detergent applications, personal care applications, paints for building materials, eyeliner inks, hair care applications, and inks for adhesives and pressure-sensitive adhesives. For example, the use of the resin particle dispersion in an aqueous ink composition for writing instruments will be described below.

[0043] (Water-based ink composition for writing instruments) The aqueous ink composition for a writing instrument of the present invention is characterized by containing at least the above-mentioned resin particle dispersion, and may contain a colorant and a water-soluble organic solvent in addition to this resin particle dispersion. From the viewpoints of exhibiting the effects of the present invention without impairing writing performance and of storage stability, the content of the resin particle dispersion in the ink composition is preferably 0.1 to 30.0 mass % in terms of solid content, and more preferably 1.0 to 15.0 mass %, relative to the total amount of the ink composition.

[0044] Usable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, and plastic pigments; hollow resin particles with voids inside the particles can be used as white pigments; colored resin particles (pseudo pigments) dyed with dyes that have excellent color development and dispersibility; and photochromic pigments such as thermochromic pigments, photochromic pigments, and aluminum pigments. As the water-soluble dye, any of direct dyes, acid dyes, food dyes and basic dyes can be used in an appropriate amount within a range that does not impair the effects of the present invention. The content of these colorants varies depending on the type of writing implement, but is generally 1 to 30% by mass based on the total amount of the ink composition.

[0045] 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-methylpentanediol. alkylene glycols such as 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.

[0046] 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, marking pen, or ballpoint pen, but is preferably 1 to 40% by mass relative to the total amount of the ink composition. In order to further improve the drying properties of drawn lines, it is particularly effective for ink compositions with a content of 10% by mass or less, and more preferably 3 to 8% by mass.

[0047] The aqueous ink composition for a writing instrument of the present invention may contain, in addition to the particles, colorant, and water-soluble solvent having the above-described properties, water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as the solvent as the remainder, as well as dispersants, lubricants, pH adjusters, rust inhibitors, thickeners, evaporation inhibitors, surfactants, and the like, as appropriate, within limits that do not impair the effects of the present invention.

[0048] Usable dispersants include nonionic and anionic surfactants other than the above-mentioned acetylene-based surfactants and polyethylene glycol-based surfactants, and water-soluble resins. Preferably, water-soluble polymers are used. Examples of lubricants include nonionic lubricants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic lubricants such as alkyl sulfonates and alkyl aryl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorine-based surfactants; and polyether-modified silicones.

[0049] 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 alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of thickeners include carboxymethylcellulose (CMC) or its salts, cellulose derivatives such as fermented cellulose and crystalline cellulose, and polysaccharides. Usable polysaccharides include, for example, xanthan gum, guar gum, hydroxypropylated guar gum, casein, gum arabic, gelatin, amylose, agarose, agaropectin, arabinan, curdlan, callose, carboxymethyl starch, chitin, chitosan, quince seed, glucomannan, gellan gum, tamarind seed gum, dextran, nigeran, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkaloid gum, succinoglycan, locust bean gum, and tara gum. These may be used alone or in combination. Furthermore, commercially available products of these may be used. Examples of the evaporation inhibitor include pentaerythritol, p-xylene glycol, trimethylolpropane, triethylolpropane, and dextrin. Examples of surfactants include fluorine-based, silicone-based, and acetylene glycol-based surfactants. Furthermore, in the present invention, the use of olefin-based resin particles is preferred to improve the quality of the written lines. The content of these olefin-based resin particles is 0.01 to 20% by mass, preferably 1 to 5% by mass, of the total amount of the ink composition. The olefin-based resin particles that can be used are not particularly limited in terms of shape or structure, as long as they have a needle penetration hardness of 1 or greater and an average particle diameter measured by the Coulter Counter method of 15 μm or less. Commercially available examples include Chemipearl W100, W200, W400, and W500 manufactured by Mitsui Chemicals, Inc., and similar olefin-based resin particles (Chemipearl products) such as Chemipearl W300, W308, W310, W700, and W900. A needle penetration hardness of 1 or greater is expected to improve ink outflow and provide a stable writing flow rate.

[0050] The aqueous ink composition for a writing instrument of the present invention can be prepared by appropriately combining the resin particle dispersion having the above-described properties, the water-soluble solvent, and other components depending on the intended use of the ink for the writing instrument (for a ballpoint pen, a marking pen, etc.), stirring and mixing them using a stirrer such as a homomixer, a homogenizer, or a disper, and then, if necessary, removing coarse particles from the ink composition by filtration or centrifugation.

[0051] Furthermore, the pH (25°C) of the aqueous ink composition for a writing instrument of the present invention is preferably adjusted to 5 to 10 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 more preferably 6 to 9.5.

[0052] The aqueous ink composition for writing implements of the present invention is loaded onto ballpoint pens, marking pens, etc. equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, and plastic tips. As a ballpoint pen, the aqueous ink composition for a writing instrument having the above composition is applied to a ballpoint pen having a diameter of 0.18 to 2.0 mm. The ink is contained in an ink container (refill) for a ballpoint pen equipped with a 100-mm ball, and a substance that is incompatible with the aqueous ink composition contained in the ink container and has a low specific gravity relative to the aqueous ink composition, such as polybutene, silicone oil, or mineral oil, is contained as an ink follower. Note that the amount of movement (distance) of the writing ball in the axial direction (vertical direction) in the ballpoint pen is preferably 15 to 80 μm from the viewpoints of appropriately ejecting resin particles and stabilizing the writing flow rate. The structure of the ballpoint pen or marking pen is not particularly limited, and may be, for example, a direct ink ballpoint pen or marking pen having a collector structure (ink retention mechanism) in which the barrel itself serves as an ink container and is filled with the aqueous ink composition for a writing instrument having the above-described structure.

[0053] In the aqueous ink composition for writing instruments of the present invention, which is configured in this manner, the resin particle dispersion having the above-described properties is blended into the aqueous ink composition for writing instruments. Therefore, the aqueous ink composition for writing instruments does not cause the instability of the dispersion system or the formation of precipitates that frequently occurs when an acetylene-based surfactant or the like is directly added, and has a sufficient wettability-improving effect, making it stable when blended into a variety of aqueous inks. In particular, depending on the liquid temperature of the ink, particularly in a low-temperature environment, direct addition can reduce solubility, making it difficult to obtain a sufficient activator effect after low-temperature storage, making it difficult to obtain a stable writing flow rate, and causing unevenness in the writing flow rate, which in turn reduces the quality of the written lines. However, in the present invention, by preparing the present resin particle dispersion that encapsulates an acetylene-based surfactant and / or a polyethylene glycol-based surfactant component, it is possible to obtain an aqueous ink composition for writing instruments that has a sufficient wettability-improving effect even in a low-temperature environment, without destroying the dispersion stability of the original aqueous ink, and that achieves a high level of both a stable writing flow rate and quality (writing ability) of the written lines.

[0054] (Water-based inkjet ink composition) The aqueous inkjet ink composition of the present invention is characterized by containing at least the resin particle dispersion having the above-described configuration, and may contain, in addition to this resin particle dispersion, a colorant and a solvent such as a water-soluble organic solvent.

[0055] Usable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, and plastic pigments; hollow resin particles with voids inside the particles can be used as white pigments; colored resin particles (pseudo pigments) dyed with dyes that have excellent color development and dispersibility; and luster pigments such as aluminum pigments. As the water-soluble dye, any of direct dyes, acid dyes, food dyes and basic dyes can be used in an appropriate amount within a range that does not impair the effects of the present invention. The content of these colorants varies depending on the inkjet device and method, but is generally 1 to 30% by mass based on the total amount of the ink composition.

[0049] When the resin particle dispersion is used in an aqueous inkjet ink composition, the colored resin particles may contain a preservative, a reducing agent, a fragrance, an oil or fat, an ultraviolet absorber, a light stabilizer, and the like, in addition to the surfactant component of Group A, in order to further enhance the stability over time, antiseptic properties, color development properties, fragrance, and light resistance.

[0056] The aqueous inkjet ink composition can be prepared by adding a colorant and a solvent to the inkjet colored resin particle dispersion having the above-described configuration, followed by stirring. If necessary, a resin, a dispersant, etc. may also be added. The solvent used in the inkjet ink is not particularly limited, but specifically, water (purified water, ion-exchanged water, distilled water, pure water, etc., hereinafter simply referred to as "water") and a water-soluble organic solvent can be used as a mixed solvent. The content of water is the remainder of the contents of each component, and is approximately 1.0 to 70.0 mass %.

[0057] Examples of water-soluble organic solvents that can be used include alkyl alcohols having 1 to 4 carbon atoms, such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; amides, such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols, such as acetone and diacetone alcohol; ethers, such as tetrahydrofuran and dioxane; polyalkylene glycols, such as polyethylene glycol and polypropylene glycol; alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; glycerin; lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred. The content of the water-soluble organic solvent is preferably in the range of 3 to 50% by mass, and more preferably in the range of 3 to 30% by mass, based on the total amount of the ink composition.

[0058] The resin used in inkjet inks is not particularly limited as long as it dissolves or disperses in the solvents used in the ink. Specific examples include acrylic resins, polyester resins, phenolic resins, polyamides, polyvinyl butyral, cellulose acetate butyrate, nitrocellulose resins, urethane resins, and vinyl chloride-vinyl acetate copolymers. These resins can be used alone or in combination. The type of resin can be selected depending on the type of medium. Preferred resins include urethane resin emulsions, acrylic resin emulsions, styrene resin emulsions, styrene-acrylic resin emulsions, and olefin resin emulsions, which have excellent functionality as fixing resins. The content of these resins is preferably 0.1 to 50.0% by mass, more preferably 3.0 to 30.0% by mass, of the total ink composition.

[0059] In the aqueous inkjet ink composition of the present invention, the above-mentioned resin particle dispersion can be used as is, or the above-mentioned colorant, solvent, and, if necessary, resin and dispersant can be blended. Furthermore, various additives commonly used in the relevant field can be added within a range that does not impair the object of the present invention. For example, a nozzle clogging inhibitor, an antioxidant, a conductivity modifier, a viscosity modifier, a surfactant, an oxygen absorber, etc. can be added as appropriate. The types of these additives are not particularly limited, and those commonly used in the relevant field can be used. The resin particle dispersion can also be diluted with a non-aqueous solvent.

[0060] The content of the colored resin particles varies depending on the printing method, etc., but is preferably 1 to 30% by mass in terms of solid content relative to the total amount of the aqueous inkjet ink composition. The viscosity of the aqueous inkjet ink composition varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, and other factors, but is generally preferably 1 to 20 mPa·s at 25°C.

[0061] The inkjet recording method using the aqueous inkjet ink composition of the present invention is not particularly limited, and examples thereof include known methods, such as a charge control method in which the ink composition is ejected by utilizing electrostatic attraction, a drop-on-demand method (pressure pulse method) in which the vibration pressure of a piezoelectric element is utilized, an acoustic inkjet method in which an electric signal is converted into an acoustic beam and the ink composition is irradiated with the acoustic beam, thereby ejecting the ink composition by utilizing radiation pressure, and a thermal inkjet (Bubble Jet (registered trademark)) method in which the ink composition is heated to form bubbles and the resulting pressure is utilized. The recording medium is not particularly limited, and may be plain paper, glossy paper, copy paper, special paper, cloth, film, OHP sheet, or the like.

[0062] The aqueous inkjet ink composition of the present invention, which is configured in this manner, is highly stable and has excellent surface activity effects, such as the wettability of the surfactant component, even at low temperatures and after long-term storage. Furthermore, since it contains a resin particle dispersion that does not affect other blended components, it is suitable for aqueous inkjet ink compositions with improved wettability. Furthermore, these particles do not impair storage stability or inkjet performance, can be made small in particle size, and are free from problems such as clogging of nozzles, etc. Therefore, it has outstanding functionality as an inkjet ink that exhibits excellent performance. Therefore, an aqueous inkjet ink composition can be obtained that is suitable for any printing method, such as piezo, electrostatic, or thermal, and for printing on plain paper, glossy paper, special paper, fabric (clothing such as T-shirts), film, OHP sheets, etc. [Example]

[0063] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0064] [Production Examples 1 to 22: Production of Resin Particle Dispersions (Particles 1 to 22)] Each resin particle dispersion was produced according to the following Production Examples 1 to 22. In the following, "parts" refers to parts by mass, and the surfactant component is the solid content.

[0065] (Production Example 1) A 2-liter flask was fitted with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000-ml separatory funnel for introducing monomers, and placed in a warm water bath. 354.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blenmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 20 parts of a polymerizable surfactant (ADEKA Corporation, Adeka Reasoap SR-10, 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.

[0066] Separately, a liquid was prepared by mixing a mixed monomer consisting of 55 parts of cyclohexyl methacrylate monomer and 20 parts of n-butyl methacrylate with 20 parts of an acetylene-based surfactant 1 (Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component and 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC). This prepared solution was added from the separatory funnel to the flask maintained at about 90°C over a period of 3 hours with stirring to carry out emulsion polymerization. The mixture was further aged for 5 hours to complete the polymerization, yielding a resin particle dispersion (dispersion) (particles 1). The content of the methacrylic acid ester monomer was 58.6% by mass, and the content of the surfactant component was 20.7% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 62 nm.

[0067] (Production Example 2) A resin particle dispersion (dispersion liquid) (particles 2) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 50 parts, and 30 parts of an acetylene-based surfactant 2 [Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4] was used as the surfactant component. The content of the methacrylic acid ester monomer was 60.0 mass % of the total polymer components constituting the resin particles, and the content of the surfactant component was 20.0 mass % of the total polymer components. The average particle size of the resin particles was 68 nm.

[0068] (Production Example 3) A resin particle dispersion (dispersion liquid) (particles 3) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 45 parts, the amount of n-butyl methacrylate was 35 parts, and 30 parts of acetylene-based surfactant 3 [Surfynol 440; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 8] was used as the surfactant component. The content of the methacrylic acid ester monomer was 60.0 mass % of the total polymer components constituting the resin particles, and the content of the surfactant component was 20.0 mass % of the total polymer components. The average particle size of the resin particles was 112 nm.

[0069] (Production Example 4) A resin particle dispersion (dispersion liquid) (particles 4) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 337.5 parts, the amount of cyclohexyl methacrylate monomer was 28 parts, the amount of n-butyl methacrylate was 44 parts, and 30 parts of acetylene-based surfactant 4 [Olfine EXP. 4200; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.1 to 1.0%, HLB value: 10 to 13] was used as the surfactant component. The content of the methacrylic acid ester monomer was 50.6% by mass, and the content of the surfactant component was 18.5% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 71 nm.

[0070] (Production Example 5) A resin particle dispersion (dispersion liquid) (particles 5) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 349.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 15 parts of acetylene-based surfactant 5 (Olfine PD-002W; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.3 to 0.5%, HLB value: 9 to 10) was used as the surfactant component. The content of the methacrylic acid ester monomer was 56.7% by mass, and the content of the surfactant component was 10.0% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 51 nm.

[0071] (Production Example 6) A resin particle dispersion (dispersion liquid) (particles 6) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, 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 45 parts, and 30 parts of acetylene-based surfactant 6 (Dynol 604; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 8) was used as the surfactant component. The content of the methacrylic acid ester monomer was 51.5% by mass, and the content of the surfactant component was 18.2% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 60 nm.

[0072] (Production Example 7) A resin particle dispersion (dispersion liquid) (particles 7) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 339.0 parts, the amount of cyclohexyl methacrylate monomer was 30.5 parts, the amount of n-butyl methacrylate was 45 parts, and 25 parts of acetylene-based surfactant 7 (Surfynol SE-F; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 6) was used as the surfactant component. The content of the methacrylic acid ester monomer was 53.3% by mass, and the content of the surfactant component was 15.6% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 43 nm.

[0073] (Production Example 8) A resin particle dispersion (dispersion liquid) (particles 8) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 339.5 parts, the amount of cyclohexyl methacrylate monomer was 30.0 parts, the amount of n-butyl methacrylate was 45.0 parts, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the methacrylic acid ester monomer was 53.1% by mass of the total polymer components constituting the resin particles, and the content of the surfactant component was 15.6% by mass of the total polymer components. The average particle size of the resin particles was 82 nm.

[0074] (Production Example 9) A resin particle dispersion (dispersion liquid) (particles 8) was obtained in the same manner as in Production Example 1 above, except that in Production Example 1, the amount of distilled water was 334.5 parts, the amount of cyclohexyl methacrylate monomer was 45.0 parts, the amount of n-butyl methacrylate was 30.0 parts, and 9.0 parts of a silicone surfactant [KF-6004; PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the methacrylic acid ester monomer was 51.5% by mass, and the content of the surfactant component was 18.2% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 104 nm.

[0075] (Production Example 10) A liquid was prepared by mixing 369.5 parts of distilled water, 50 parts of methacrylonitrile monomer, 40 parts of an acetylene-based surfactant 1 (surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component, 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC), and 30 parts of an acetylene-based surfactant 2 (surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as a surfactant component. This prepared liquid was added from the separatory funnel to the flask maintained at a temperature of about 90°C over a period of 3 hours with stirring to carry out emulsion polymerization. The mixture was further aged for 5 hours to terminate the polymerization, and the resin particle dispersion (dispersion) was recovered to obtain a resin particle dispersion (dispersion) (particles 10). The content of the nitrile monomer was 38.5% by mass, and the content of the surfactant component was 23.1% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 87 nm.

[0076] (Production Example 11) A resin particle dispersion (dispersion liquid) (particles 11) was obtained in the same manner as in Production Example 10, except that 370.5 parts of distilled water was used, 54 parts of methacrylonitrile monomer was used, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the nitrile monomer was 41.9% by mass, and the content of the surfactant component was 19.4% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 91 nm.

[0077] (Manufacturing Example 12) A resin particle dispersion (dispersion liquid) (particles 12) was obtained in the same manner as in Production Example 10, except that the amount of distilled water was 374.5 parts, the amount of methacrylonitrile monomer was 45 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the nitrile monomer was 36.0% by mass, and the content of the surfactant component was 24.0% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 101 nm.

[0078] (Manufacturing Example 13) A liquid was prepared by mixing 364.5 parts of distilled water, 75 parts of styrene monomer, 40 parts of an acetylene-based surfactant 1 (surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as a surfactant component, 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC), and 30 parts of an acetylene-based surfactant 2 (surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as a surfactant component. This prepared liquid was added from the separatory funnel to the flask maintained at a temperature of about 90°C over a period of 3 hours with stirring to carry out emulsion polymerization. The mixture was further aged for 5 hours to terminate the polymerization, and the resin particle dispersion (dispersion) was recovered to obtain a resin particle dispersion (dispersion) (particles 13). The content of the styrene monomer was 48.4% by mass, and the content of the surfactant component was 19.4% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 58 nm.

[0079] (Manufacturing Example 14) A resin particle dispersion (dispersion liquid) (particles 14) was obtained in the same manner as in Production Example 13, except that in Production Example 13, 354.5 parts of distilled water was used, 70 parts of styrene monomer was used, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) was used as the surfactant component. The content of the styrene monomer was 48.3% by mass, and the content of the surfactant component was 17.2% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 77 nm.

[0080] (Manufacturing Example 15) A resin particle dispersion (dispersion liquid) (particles 15) was obtained in the same manner as in Production Example 13, except that the amount of distilled water was 339.5 parts, the amount of styrene monomer was 80 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the styrene monomer was 50.0 mass % of the total polymer components constituting the resin particles, the content of the surfactant component was 18.8 mass % of the total polymer components, and the average particle size of the resin particles was 91 nm.

[0081] (Manufacturing Example 16) A mixture of 354.5 parts distilled water, 65 parts vinyl acetate monomer, 40 parts acetylene surfactant 1 (Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3) as surfactant component, 10 parts crosslinker (triallyl isocyanurate, manufactured by Nippon Kasei Chemical Industry Co., Ltd., TAIC), and 30 parts acetylene surfactant 2 (Surfynol 104E; manufactured by Nissin Chemical Industry Co., Ltd., water solubility 1% or less, HLB value: 4) as surfactant component was prepared. This mixture was added from the separatory funnel to the flask maintained at approximately 90°C over a period of 3 hours with stirring to carry out emulsion polymerization. The mixture was then aged for another 5 hours to terminate the polymerization, and the resin particle dispersion (dispersion) was recovered to obtain resin particle dispersion (dispersion) (particles 16). The content of the vinyl acetate monomer was 44.8% by mass, and the content of the surfactant component was 20.7% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 115 nm.

[0082] (Manufacturing Example 17) A resin particle dispersion (dispersion liquid) (particles 17) was obtained in the same manner as in Production Example 16, except that 364.5 parts of distilled water, 60 parts of vinyl acetate monomer, and 25 parts of a polyethylene glycol surfactant (ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9) were used as the surfactant component. The content of the vinyl acetate monomer was 44.4% by mass, and the content of the surfactant component was 18.5% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 121 nm.

[0083] (Manufacturing Example 18) A resin particle dispersion (dispersion liquid) (particles 18) was obtained in the same manner as in Production Example 16, except that the amount of distilled water was 349.5 parts, the amount of vinyl acetate monomer was 70 parts, and 9.0 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0] was used as the surfactant component. The content of the vinyl acetate monomer was 46.7% by mass, and the content of the surfactant component was 20.0% by mass, based on the total polymer components constituting the resin particles. The average particle size of the resin particles was 119 nm.

[0084] (Manufacturing Example 19) A resin particle dispersion (dispersion) (particles 19) was prepared using 349.5 parts of distilled water, 35 parts of cyclohexyl methacrylate monomer, and 35 parts of methacrylonitrile monomer, as surfactant components: 10 parts of an acetylene-based surfactant 1 [Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3], 10 parts of a polyethylene glycol-based surfactant [ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. The content of the monomer was 50.3% by mass of the total polymer components constituting the resin particles, and the content of the surfactant component was 18.9% by mass of the total polymer components. The average particle size of the resin particles was 102 nm.

[0085] (Manufacturing Example 20) A resin particle dispersion (dispersion liquid) (particles 20) was obtained using 349.5 parts of distilled water, 35 parts of cyclohexyl methacrylate monomer, and 35 parts of styrene monomer, as surfactant components: 15 parts of a polyethylene glycol surfactant [ADEKA Estol OEG-102; polyethylene glycol oleate, manufactured by ADEKA Corporation, water solubility 1% or less, HLB value: 7.9], 5.0 parts of a silicone surfactant [KF-6004 PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. The content of the monomer was 48.2% by mass of the total polymer components constituting the resin particles, and the content of the surfactant component was 33.1% by mass of the total polymer components. The average particle size of the resin particles was 75 nm.

[0086] (Manufacturing Example 21) A resin particle dispersion (dispersion liquid) (particles 21) was prepared using 349.5 parts of distilled water, 30 parts of cyclohexyl methacrylate monomer, and 20 parts of vinyl acetate monomer. The surfactant components included 10 parts of a silicone surfactant [KF-6004PEG-32 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., water solubility 1% or less, HLB value: 9.0], 10 parts of an acetylene surfactant 5 [Olfine PD-002W, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.3 to 0.5%, HLB value: 9 to 10], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. The content of the monomer was 45.2% by mass of the total polymer components constituting the resin particles, the content of the surfactant component was 30.1% by mass of the total polymer components, and the average particle size of the resin particles was 89 nm.

[0087] (Manufacturing Example 22) A resin particle dispersion (dispersion liquid) (particles 22) was obtained using 349.5 parts of distilled water, 20 parts of methacrylonitrile monomer, 20 parts of styrene monomer, and 20 parts of vinyl acetate monomer, as well as 20 parts of an acetylene-based surfactant 1 [Surfynol DF110D; 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, manufactured by Nissin Chemical Industry Co., Ltd., water solubility 0.03%, HLB value: 3] as surfactant components, and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. The content of the monomer was 50.5% by mass of the total polymer components constituting the resin particles, and the content of the surfactant component was 21.6% by mass of the total polymer components. The average particle size of the resin particles was 109 nm.

[0088] The obtained resin particle dispersions of Production Examples 1 to 22 were evaluated for wettability and dispersion stability after low-temperature storage by the following evaluation methods. The solid content of the resin particles in each of the resin particle dispersions (dispersions) obtained in Production Examples 1 to 22 was 35 to 40% by mass.These results are shown in Table 1 below.

[0089] [Method for evaluating wettability after low-temperature storage] Each of the resin particle dispersions (dispersions) obtained in Production Examples 1 to 22 was filled into a glass vial, capped, and stored in an environment at -10°C for one month, and the wettability after low-temperature storage was evaluated according to the following evaluation criteria. The wettability was evaluated by dropping 0.5 ml of each resin particle dispersion (dispersion) onto a glass plate with a dropper, spreading it with a cotton swab, and visually inspecting the state of the coating film, and then performing a sensory evaluation according to the following evaluation criteria. Evaluation Criteria A: The coating is in good condition with no visible bleeds or pinholes. B: There are some bleeds and pinholes in the coating. C: Repelling and pinholes are observed throughout the coating film.

[0090] <Method for evaluating dispersion stability after low-temperature storage> Each resin particle dispersion (dispersion liquid) obtained in Production Examples 1 to 22 above was filled into a glass vial, capped, and stored in a -10°C environment for 3 months. After leaving it in a 25°C environment for 3 hours to return to room temperature, the top and bottom of the dispersion liquid (ink) in the vial were checked for the presence of sediment or floating matter. The top and bottom of the dispersion liquid were sampled with a dropper, spread on a glass slide, and visually inspected using an optical microscope to check for the presence of sediment or floating matter. Evaluation was performed according to the following criteria. Evaluation criteria: A: No sediment or floating matter is observed. B: A small amount of sediment or floating matter can be seen. C: Multiple sediments and floating objects are observed.

[0091] [Table 1]

[0092] Considering Table 1 above, it was found that Production Examples 1 to 22, which fall within the scope of the present invention, have a high degree of wettability and dispersion stability after low-temperature storage, and in particular, acetylene-based surfactants and polyethylene glycol-based surfactants with surfactant components having a water solubility of less than 10% have excellent wettability and dispersion stability after low-temperature storage. These results are shown in Table 1 below. For reference, dispersions were prepared by mixing various surfactants to obtain solid contents similar to those of the above-mentioned Production Examples 1 to 22. However, it was confirmed that the wettability and dispersion stability after low-temperature storage were inferior to those of the resin particle dispersions of Production Examples 1 to 22 of the present invention.

[0093] Examples 1 to 23 and Comparative Examples 1 to 9: Preparation of aqueous ink compositions for writing instruments (Examples 1 to 22) Using each of the resin particle dispersions (particles 1 to 22) produced in the above Production Examples, each of the aqueous ink compositions for writing instruments was prepared by a conventional method according to the formulation shown below (total amount 100% by mass). Ink composition: (total 100% by mass) Each resin particle dispersion (particles 1 to 22: each solid content 50% by mass) 15.0% by mass Colorant (carbon black MA100, manufactured by Mitsubishi Chemical Corporation) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water Remaining

[0094] Example 23 Using the resin particle dispersion (particles 1) produced in the above Production Example and colored resin particles having the following composition as a colorant, aqueous ink compositions for writing instruments were prepared by a conventional method according to the formulation shown below (total amount 100% by mass). Ink composition: (total 100% by mass) Resin particle dispersion (particle 1: solid content 50% by mass) 15.0% by mass Colorant (colored resin particles with the following composition) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water Remaining

[0095] (Production example of colored resin particles) 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 placed in a warm water bath. 329.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blenmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 20 parts of a polymerizable surfactant (ADEKA Corporation, Adeka Reasoap SE-10N, ether sulfate), and 0.5 parts of ammonium persulfate were then charged, and the internal temperature was raised to 50°C while introducing nitrogen gas. Separately, a liquid was prepared by mixing a mixed monomer consisting of 55 parts of cyclohexyl methacrylate monomer and 35 parts of n-butyl methacrylate as another monomer with 40 parts of an oil-soluble dye (Savinyl Blue GLS, manufactured by Clariant) and 10 parts of a crosslinking agent (triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., "TAIC"). This prepared solution was added from the separatory funnel to the flask maintained at a temperature of about 50°C over a period of 3 hours with stirring to carry out emulsion polymerization. The mixture was then aged for a further 5 hours to complete the polymerization, yielding a dispersion of colored resin microparticles for aqueous ink (particles 1). The content of the cyclohexyl methacrylate monomer was 50.0% by mass, and the content of the oil-soluble dye was 36.4% by mass, based on the total polymer components constituting the colored resin microparticles. The average particle size of the colored resin microparticles was 40 nm.

[0096] As Comparative Examples 1 to 9, ink compositions for writing instruments were prepared by mixing the acetylene-based surfactants 1 to 7, polyethylene glycol-based surfactants, and silicone-based surfactants described in the above manufacturing examples to achieve solid contents similar to those of Examples 1 to 23.

[0097] The resulting aqueous ink compositions for writing instruments (total amount 100% by mass) were evaluated for wettability and writability (rubbing) after low-temperature storage, and dispersion stability after low-temperature storage, using the writing instruments having the following configurations and the evaluation methods described below. The evaluation results of Examples 1 to 23 are shown in Table 2 below, and the evaluation results of Comparative Examples 1 to 9 are shown in Table 3 below.

[0098] (Writing implement: Marking pen production) Each of the above aqueous ink compositions was loaded into a marking pen (manufactured by Mitsubishi Pencil Co., Ltd., trade name: Propass Window PUS-102T, pen tip, thick: PE resin sintered core, thin: PET fiber core) to prepare a marking pen.

[0099] [Method for evaluating wettability (glass surface) after low-temperature storage] Using the writing instruments having the above-described configuration, each aqueous ink composition for a writing instrument was filled, and writing was performed in a spiral on a glass plate. The degree of repellency of the written lines was visually confirmed, and the wettability (glass surface) after low-temperature storage was evaluated according to the following evaluation criteria. Evaluation criteria: A: The ink is not repelled at all, and clear written lines are obtained. B: Some repelling is observed. C: Ink is repelled significantly, causing chips in the written lines.

[0100] [Method for evaluating writing performance (smearing, bleeding) after low-temperature storage] The writing implement having the above structure was used to write in a spiral on PPC paper, and the initial writing properties were evaluated according to the following evaluation criteria. Evaluation criteria: A: You can write without any problems from the start. B: Blurring or bleeding of more than 0mm but less than 10mm is observed from the start of writing. C: Blurring or bleeding of 10mm or more is observed from the beginning of writing.

[0101] [Method for evaluating dispersion stability after low-temperature storage] Each aqueous ink composition for writing instruments was filled into a glass vial, the lid was closed, and stored in an environment at -10°C for 3 months. After leaving it in an environment at 25°C for 3 hours to return to room temperature, the top and bottom of the dispersion in the vial were checked for the presence of sediment or floating matter. The top and bottom of the dispersion were sampled with a dropper and spread on a glass slide, and the presence or absence of sediment or floating matter was visually confirmed using an optical microscope and evaluated according to the following evaluation criteria. Evaluation criteria: A: No sediment or floating matter is observed. B: A small amount of sediment or floating matter can be seen. C: Multiple sediments and floating objects are observed.

[0102] [Table 2]

[0103] [Table 3]

[0104] Considering the results in Tables 2 and 3, it was confirmed that Examples 1 to 23, which fall within the scope of the present invention, do not adversely affect other ink formulation components and do not adversely affect excellent wettability and writability after low-temperature storage, compared to Comparative Examples 1 to 9, which fall outside the scope of the present invention. Furthermore, it was confirmed that, with regard to dispersion stability after low-temperature storage, no sediment or floating matter was observed, compared to the Comparative Examples. It was also confirmed that the writing implement produced above was free from smearing or bleeding, had sufficient line density, and produced clear lines.

[0105] Example 24: Preparation of aqueous inkjet ink composition Using the resin particle dispersion (particles 1) produced in Production Example 1 above, an aqueous inkjet ink composition was prepared by a conventional method with the following formulation (total amount 100% by mass). Each of the obtained aqueous inkjet ink compositions was evaluated for dispersion stability after low-temperature storage in accordance with the evaluation method described above, and was also filled into a cartridge of an inkjet device [inkjet printer (PM-3000C, manufactured by Epson Corporation)] and printed on a support (printing paper) made of copy paper, and the color development and storage stability were evaluated using the evaluation methods described below. These results are shown below.

[0106] Ink composition: (total 100% by mass) Resin particle dispersion (particle 1, solid content 50% by mass) 50.0% by mass Colorant (colored resin particles of Example 23) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water Remaining

[0107] (Method for evaluating color development) The printed portion printed by the inkjet device was visually evaluated according to the following criteria. Evaluation criteria: A: The printed area is vivid and has excellent color development. B: The printed area is slightly dull and the color development is slightly inferior. C: The printed area is noticeably dull, and the overall color development is poor.

[0108] (Method for evaluating storage stability) The above aqueous inkjet ink composition was filled into a glass vial, the lid was closed, and the vial was stored in an environment at -10°C for 3 months. After leaving it in an environment at 25°C for 3 hours to return to room temperature, inkjet printing was performed using the ink after storage using the method described above to obtain printed paper. The color development of the obtained printed paper was confirmed. The storage stability of the ink was evaluated according to the following evaluation criteria. The storage stability was judged visually by comparing the color development with that of printed paper printed with the aqueous inkjet ink composition before storage (initial). Evaluation criteria: A: The printed area is vivid and has excellent color development. B: The printed area is slightly dull and the color development is slightly inferior. C: The printed area is noticeably dull, and the overall color development is poor.

[0109] It was confirmed that the aqueous inkjet ink composition of Example 24 obtained above does not adversely affect other ink components, has excellent storage stability after low-temperature storage, and has excellent color development properties. [Industrial Applicability]

[0110] The resin particle dispersion of the present invention can be suitably used in writing instrument inks (low-viscosity ballpoint pens, swath-type writing instruments and direct-fill writing instruments, gel ballpoint pens, swath-type felt-tip pens, valve-type felt-tip pens, and direct-fill felt-tip pens), as well as inkjet inks, cosmetics such as eyeliners, and hair dyes.

Claims

1. A resin particle dispersion comprising resin particles encapsulating at least one surfactant component selected from Group A below dispersed in water. <Group A> Acetylene-based surfactants, polyethylene glycol-based surfactants, silicone-based surfactants

2. 2. The resin particle dispersion according to claim 1, wherein the resin particles encapsulating the surfactant component are composed of a homopolymer or copolymer obtained from at least one monomer selected from the following Group B: <Group B> Acrylic monomers, styrene monomers, nitrile monomers, vinyl acetate monomers

3. 3. The resin particle dispersion according to claim 1, wherein the acetylene-based surfactant and the polyethylene glycol-based surfactant have a water solubility of less than 10%.

4. 3. The resin particle dispersion according to claim 1, wherein the acetylene-based surfactant has an HLB value of 13.5 or less, the polyethylene glycol-based surfactant has an HLB value of 10.0 or less, and the silicone-based surfactant has an HLB value of 10.0 or less.

5. An aqueous ink composition for a writing instrument, comprising the resin particle dispersion according to claim 1 or 2.

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