WATER-BASED INK COMPOSITION FOR WRITING UTENSIL, INK CARTRIDGE BUILT IN THE SAME, AND DIRECT LIQUID TYPE WRITING INSTRUMENT

摘要

PROBLEM TO BE SOLVED: To provide: a water-based ink composition for writing utensil in which in a water-based ink applied to a writing utensil provided with a pen core, even if when being applied to a writing utensil of an ink cartridge type to say nothing of being able to prevent handwriting bleeding by maintaining pen core performance, ink supply to a pen point after exchange of a cartridge can be stably continued, and ink discharge stability at writing is excellent; an ink cartridge that builds in the same; and further a direct liquid type writing instrument.SOLUTION: A water-based ink composition for a writing utensil is a water-based ink composition built into a direct liquid type writing instrument that induces ink to a pen point through a pen core, wherein a dynamic surface tension measured by a maximum bubble pressure method is in a range of 30-55 mN/m in a lifetime of 20 ms, and a difference of a dynamic surface tension of a lifetime of 20 ms and a dynamic surface tension of a lifetime 5,000 ms is at most 10 mN/m. A direct liquid type writing instrument builds in the water-based ink composition.