The chromogenic azaphthalide compounds of the invention are of the formula: <IMAGE> (I) wherein A is a pyridine ring; R1 is hydrogen atom or alkyl radicals of from one to 4 carbon atoms; X is hydrogen atom, alkyl radicals of from one to 2 carbon atoms or alkoxy radicals of from one to 2 carbon atoms; R2 is alkyl radicals of from one to 2 carbon atoms or phenyl radical; R3 is hydrogen atom or alkyl radicals of from one to 8 carbon atoms. These compounds are particularly suitable for use in providing high quality pressure- or heat-sensitive copying sheets.
