Reversible thermal discoloration aqueous ink composition and writing instrument using the same, the writing instrument set

摘要

To provide a reversible thermal discoloration aqueous ink composition which is capable of suppressing the lightening and deepening of handwriting at the time when a writing implement containing the reversible thermal discoloration aqueous ink composition in the barrel, and particularly, which does not lighten the color of handwriting with time in an erecting state or does not lighten the color of handwriting by the application of vibration at transportation or at the time when it is carried on in an erecting state, as well as a writing implement using the same and a writing implement set. A reversible thermal discoloration aqueous ink composition comprising water, a reversible thermal discoloration microcapsule pigment including a reversible thermal discoloration composition composed of (A) an electron donative coloring organic compound, (B) an electron accepting compound and (C) a reaction medium which determines a temperature at which color reactions of the both compounds occur, a polymer flocculant, a comb-type polymer dispersant having a carboxyl group at the side chain, an organic nitrogen sulfur compound, and a water-soluble resin; a writing implement 1 using the ink composition; and a writing implement set comprising the writing implement and a frictional body.