Aqueous ink composition for reversibly thermochromic writing instrument, and refill and aqueous ballpoint pen incorporating aqueous ink composition for reversibly thermochromic writing instrument

Abstract

A reversibly thermochromic aqueous ink composition having excellent writability and few problems such as aggregation of a colorant, an increase in viscosity of the composition, or a decrease in handwriting density, and a refill or an aqueous ballpoint pen using the reversibly thermochromic aqueous ink composition. The reversibly thermochromic composition is a reversibly thermochromic aqueous ink composition containing a reversibly thermochromic microcapsule pigment encapsulated in a microcapsule formed from an organic resin, an N-vinyl-2-pyrrolidone polymer, glycerin, and water, in which when contents (% by mass) of the reversibly thermochromic microcapsule pigment, the N-vinyl-2-pyrrolidone polymer, and the glycerin with respect to a total mass of the ink composition are PMC, PPVP, and PG, respectively, 0.3≤PMC/(PPVP+PG)≤4, and 0.2≤PPVP/PG≤5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

Dependencies are inferred from the claim text.