Heat sensitive recording sheets containing sulfone derivatives

In a heat sensitive recording sheet which comprises a base support and a heat sensitive recording layer formed over the base support and which contains a colorless or pale colored basis chromogenic material and an electron accepting color developing material capable of forming a color when contacted with the chromogenic material, the recording layer contains as the color developing material at least a compound selected from the group consisting of 3,4-dihydroxydiphenyl sulfone derivatives being represented by the structural formula:

• ##STR5## wherein X is hydrogen atom, halogen atom, alkyl group or alkoxy group, and R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are respectively hydrogen atom, halogen atom, hydroxyl group, alkyl group, cycloalkyl group, aralkyl group, aryl group, alkoxy group, aralkyloxy group, aryloxy group, alkylthio group, aralkylthio group or arylthio group, or, both R.sub.1 and R.sub.2 or both R.sub.2 and R.sub.3 may form a naphthalene ring, a tetrahydronaphthalene ring or an indane ring together with their adjacent benzene ring.