A spontaneously colour changing type thermal sensitive recording medium

摘要

A spontaneously colour changing type thermal sensitive recording medium, the colour of recorded pattern on said medium gradually changing and the pattern just after having been developed can easily be distinguished from that of one day passed comprising a thermally sensitive recording medium which comprises, on a substrate, a thermally sensitive recording layer comprising (a) a colorless or pale color dye precursor which is a triphenylmethane-based leuco dye; (b) a reddish colored developing leuco dye having a maximum absorption wavelength from 450 to 560nm; and (c) an organic color developer which is a 4-hydroxybenzoic ester of the formula (I) wherein R is an unsubstituted or substituted C1-C7 alkyl group or a benzyl group is described.