Kabushiki Kaisha Pilot Corporation

Itsuka Ohno

Naoto Masushige

Mamiko Ogura

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 P, P, and P, respectively, 0.3≤P/(P+P)≤4, and 0.2≤P/P≤5, and a refill or an aqueous ballpoint pen incorporating the reversibly thermochromic aqueous ink composition.

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

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Tokyo-to, Japan

Itsuka Ohno