NEUTRAL COLOURING PHOTOCHROMIC 2H-NAPHTHO(1,2-B)PYRANS AND HETEROCYCLIC PYRANS

摘要

Compositions comprising a naphtho [1,2-b]pyran of formula (I):wherein R7 and/or R9 is hydrogen or an amino group provided that R7 and R9 are not both hydrogen, and the other substituents are as defined in the specifcation.