Dye and heat sensitive transfer material comprising the same

An image forming dye represented by the following Formula (1):

• ##STR19## wherein R.sub.1 represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, a substituted or unsubstituted ureido group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted sulfonyl group or a substituted or unsubstituted sulfamoyl group;
• R.sub.2 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, a substituted or unsubstituted ureido group, a substituted or unsubstituted alkylthio group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted acyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkylsulfonyl group or a substituted or unsubstituted sulfamoyl group;
• X represents a hydroxy group or a N(R.sub.3 R.sub.4) group wherein R.sub.3 and R.sub.4 independently represent a substituted or unsubstituted alkyl, alkenyl, aryl, aralkyl group or cycloalkyl group, provided that R.sub.3 and R.sub.4 may combine with each other or with R.sub.1 to form a ring;
• Y.sub.1 and Y.sub.2 independently represent a carbon atom or a nitrogen atom, provided that one of Y.sub.1 and Y.sub.2 is a nitrogen atom;
• and Z represents an atomic group necessary to form a substituted or unsubstituted 5- or 6-membered nitrogen-containing heterocyclic ring which may be condensed with another ring, provided that one of R.sub.2 and a substituent on the ring represented by Z represents a group having a Hammett's value of not less than -0.05.