HEAT-SENSITIVE RECORDING MATERIAL AND NOVEL CRYSTAL OF BISPHENOL S DERIVATIVE

摘要

A thermal recording material having a thermal coloring layer provided on a substrate, the thermal coloring layer composed mainly of a color-developing compound which is usually colorless or has a light color and a developer compound capable of conducting color development of the color-developing compound upon exposure to heat, wherein the developer compound contains crystals of 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone having a DSC (Te) of 149 ~C or above and a crystal form characterized by an X-ray diffraction pattern having a peak at least at diffraction angles (2.theta.) ¢~! of 7.2 and 22.0 as measured by powder X-ray diffractometry using a Cu-K.alpha. line. The thermal recording material has high sensitivity, is less likely to cause fogging in unexposed areas upon exposure to moist heat, and provides images with excellent storage stability.