Heat transfer sheet

A heat transfer sheet comprising a substrate sheet, and a dye layer which is formed on one surface of the substrate sheet, the dye layer containing a sublimable dye represented by the following formula (I):

• ##STR126## wherein R.sub.1 and R.sub.2, which maya be the same or different and may form together a five- or six-membered ring which may contain an oxygen atom or a nitrogen atom, are a substituted or unsubstituted alkyl, cycloalkyl, aralkyl or aryl group;
• R.sub.3 is hydrogen, halogen, a cyano group, or a substituted or unsubstituted alkyl, cycloalkyl, alkoxyl, aralkyl, aryl, acyl, acylamino, sulfonylamino, ureido, carbamoyl, sulfamoyl or amino group;
• R.sub.4 is hydrogen, or a substituted or unsubstituted alkyl, cycloalkyl, aralkyl, aryl or heterocyclic group;
• R.sub.5 is hydrogen, halogen, a cyano group, a nitro group, or a substituted or unsubstituted alkyl, cycloalkyl, alkoxyl, aralkyl, aryl, heterocyclic, acyl, sulfonyl, acylamino, sulfonylamino, ureido, carbamoyl, sulfamoyl or amino group;
• X is hydrogen, or an atom or atomic group which forms a five- or six-membered ring together with R.sub.1 ;
• and
• n is an integer of 1 or 2.