Irreversible heat-sensitive composition

摘要

An irreversible heat-sensitive composition comprises a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution. A heat-sensitive ink comprises the irreversible heat-sensitive composition and an ink vehicle capable of diffusing the fused heat-fusible substance therein. A heat-sensitive ink according to another embodiment comprises microcapsules, which encapsulate the irreversible heat-sensitive composition. A heat-sensitive indicator comprises a substrate provided thereon with a printed heat-sensitive ink, the heat-sensitive ink being one of these heat-sensitive inks.