Abstract: To provide an aqueous ink composition for ballpoint pen having excellent ink discharge properties at the initial writing (initial touch) even after exposure of the pen tip for a long period of time. The aqueous ink composition for ballpoint pen contains at least 0.1 to 5% by mass of a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer composed of: (a) a polyoxyalkylene alkyl ether unit represented by Formula (I), (b) a maleic anhydride unit, and (c) a styrene unit, the allyl alcohol-maleic anhydride-styrene copolymer having the composition ratio (a):(b):(c) of 25 to 75:25 to 75:0 to 50% by mol and having a mass average molecular weight from 1000 to 50000, and polyoxyalkylene monoalkyl alcohol; 5 to 40% by mass of resin particles; and water; wherein in Formula (I), R represents an alkyl group having 1 to 5 carbons, and m is a positive number of 5 to 50.

Abstract: An ink composition for a water-based ballpoint pen and a water- based ballpoint pen, which have stable ink flowability even in a so-called fine ballpoint pen, have excellent luster of drawn lines, and do not cause a ball to fall off. The ink composition for a water-based ballpoint pen according to the present invention contains at least an aluminum pigment and 8 to 25 mass% of solid urethane particles with an average particle size of 0.3 to 10 ?m. In addition, a water-based ballpoint pen according to the present invention is provided with the ink composition for a water-based ballpoint pen that has the above composition.

Abstract: A water-based ballpoint pen contains an aqueous ink composition in which resin particles having an average particle diameter of at least 0.3 ?m are blended. The water-based ballpoint pen is provided with a ballpoint pen tip including a writing ball. The writing ball is formed from a mixture that includes a hard phase component comprising tungsten carbide, a binder phase component comprising cobalt and nickel, and chromium.

Abstract: Provided is an ink composition for water-based ballpoint pens, which can provide excellent low-viewing angle visibility on a dark-colored writing surface and drawing lines with good luster. The ink composition for water-based ballpoint pens according to the present invention includes at least an aluminum pigment and titanium oxide-enclosing resin particles having an average particle size from 0.5 to 3 ?m.

Abstract: Provided is an ink composition for an aqueous ballpoint pen, the composition having excellent ink discharging performance even if a pen point is exposed for a long period of time. The ink composition for an aqueous ballpoint pen according to the present invention is characterized by containing at least from 1 to 35 mass % of titanium oxide having an average particle size of greater than 0.1 ?m and smaller than or equal to 1 ?m, and from 1 to 35 mass % of non-tacky urethane particles having an average particle size from 0.1 to 6 ?m.

Abstract: Provided is an aqueous ink composition for writing instruments, having sufficient antibacterial and antifungal properties without hindering preservation stability and writing capability. The aqueous ink composition for writing instruments according to the present invention at least includes 0.001 mass % or greater and less than 0.1 mass % of a preservative, and 0.05 mass % or greater and less than 5 mass % of a straight-chain alkanediol selected from the group consisting of 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol.

Abstract: Provided is aqueous ink composition for a writing instrument, which contains water and microspheres having a water-insoluble dye and a matrix constituted from a polymer wherein the water-insoluble dye is higher densely present in the inner part of the matrix than at the surface of the matrix, and at least one of the following (a) and (b) is satisfied: (a) the circularity coefficient of the microspheres, as measured by image analysis, is 0.6-1.0, and (b) the 10% strength of the microspheres, as determined in a micro-compression test, is 5-30 MPa.

Abstract: Provided is an aqueous ink composition for a writing instrument with excellent stability of ink flow and the like, in which aggregation of a microcapsule pigment and clogging due to such aggregation are suppressed. The aqueous ink composition for a writing instrument includes a microcapsule pigment which includes inside, at least, a pigment and a medium of a fatty acid polyol ester. A melting point of the fatty acid polyol ester is preferably 40° C. or higher, and is preferably 70° C. or lower.

Abstract: Provided is an aqueous ink composition for writing instruments, which enables desired colorfulness to be obtained easily. The aqueous ink composition for writing instruments according to the present invention contains: pigmented microspheres each having a matrix comprising water and a polymer, and a water-insoluble dye; and unpigmented microspheres.

Abstract: Provided is aqueous ink composition for a writing instrument, which contains water and microspheres having a water-insoluble dye and a matrix constituted from a polymer wherein the water-insoluble dye is higher densely present in the inner part of the matrix than at the surface of the matrix, and at least one of the following (a) and (b) is satisfied: (a) the circularity coefficient of the microspheres, as measured by image analysis, is 0.6-1.0, and (b) the 10% strength of the microspheres, as determined in a micro-compression test, is 5-30 MPa.

Abstract: To provide an aqueous ink composition for ballpoint pen having excellent ink discharge properties at the initial writing (initial touch) even after exposure of the pen tip for a long period of time. The aqueous ink composition for ballpoint pen contains at least 0.1 to 5% by mass of a graft compound of an allyl alcohol-maleic anhydride-styrene copolymer composed of: (a) a polyoxyalkylene alkyl ether unit represented by Formula (I), (b) a maleic anhydride unit, and (c) a styrene unit, the allyl alcohol-maleic anhydride-styrene copolymer having the composition ratio (a):(b):(c) of 25 to 75:25 to 75:0 to 50% by mol and having a mass average molecular weight from 1000 to 50000, and polyoxyalkylene monoalkyl alcohol; 5 to 40% by mass of resin particles; and water; wherein in Formula (I), R represents an alkyl group having 1 to 5 carbons, and m is a positive number of 5 to 50.

Abstract: Provided is an aqueous ink composition for writing instruments, which enables desired colorfulness to be obtained easily. The aqueous ink composition for writing instruments according to the present invention contains: pigmented microspheres each having a matrix comprising water and a polymer, and a water-insoluble dye; and unpigmented microspheres.

Abstract: Provided are a microcapsule pigment, though it is a microcapsule pigment obtained by microcapsulating a pigment having a large specific gravity such as titanium oxide and carbon black having a little difficulty in dispersibility, which makes it easier to be improved in dispersibility and which makes it possible to control a specific gravity and a particle diameter as desired, and an aqueous ink composition for writing instruments prepared by using the same. The microcapsule pigment described above is characterized by comprising at least a pigment and a poorly water-soluble medium having a specific gravity of less than 1 at 20° C., and the aqueous ink composition for writing instruments described above is characterized by containing the microcapsule pigment described above.

Abstract: To provide an ink composition for a water-based ballpoint pen, having properties such as excellent writing stability in which writing failure such as starving does not occur. Disclosed is an ink composition for a water-based ballpoint pen, including an aqueous phase, and an oil phase contained in the aqueous phase in a state of an oil-in-water type emulsion, wherein the oil phase, or the oil phase and the aqueous phase contains a colorant, and the oil phase contains, in components composing the oil phase, a fatty acid having 6 to 22 carbon atoms.

Abstract: An object of the present invention is to provide an oil-in-water type emulsion ink composition for a water-based ballpoint pen, having improved storage stability, which does not cause phase separation even when stored at high or low temperature over the long period. Disclosed is an ink composition for a water-based ballpoint pen, comprising an aqueous phase, and an oil phase contained in the aqueous phase in a state of an oil-in-water type emulsion, wherein at least one of the oil phase and the aqueous phase comprises a colorant, and the oil phase comprises, in components composing the oil phase, an estolide which is a fatty acid oligomer in which fatty acids having a hydroxyl group are mutually condensed or a fatty acid having a hydroxyl group is condensed with a fatty acid having no hydroxyl group, or comprises an ester of the estolide and an alcohol.

Abstract: An object of the present invention is to provide an oil-in-water type emulsion ink composition for a water-based ballpoint pen, having improved storage stability, which does not cause phase separation even when stored at high or low temperature over the long period. Disclosed is an ink composition for a water-based ballpoint pen, comprising an aqueous phase, and an oil phase contained in the aqueous phase in a state of an oil-in-water type emulsion, wherein at least one of the oil phase and the aqueous phase comprises a colorant, and the oil phase comprises, in components composing the oil phase, an estolide which is a fatty acid oligomer in which fatty acids having a hydroxyl group are mutually condensed or a fatty acid having a hydroxyl group is condensed with a fatty acid having no hydroxyl group, or comprises an ester of the estolide and an alcohol.