1996 Volume 69 Issue 10 Pages 649-657
In order to develop a novel lightfast fluoran leuco dye for thermosensitive recording papers, the relationship between the structure of fluoran compounds and their lightfastness has been studied. The photostability of fluoran compounds depends strongly on the kind of 6-substituted amino group on the xanthene ring. Fluoran compounds having a phenylenediamine moiety exhibited prominently good lightfastness compared with the conventional dye (1). It was demonstrated that a thermosensitive recording paper using 2', 4'-dimethyl-6'- {[4- (N, N-dimethylamino) phenyl] amino} spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one (2) exhibited outstanding lightfastness. The image formed on this thermosensitive recording paper had a bluish-black colour and absorbed over a wide range from visible to the near infrared region.