Photochromic naphthacenequinones, process for their preparation and the use thereof

Abstract

Compounds of formula I or V, or mixtures thereof, ##STR1## wherein R is unsubstituted C.sub.6 -C.sub.14 aryl or C.sub.6 -C.sub.14 aryl which is substituted by C.sub.1 -C.sub.12 alkyl, C.sub.1 -C.sub.12 alkoxy, C.sub.1 -C.sub.12 alkylthiol, phenyl, benzyl, --CN,--CF.sub.3, halogen or --COOR.sub.5, and R.sub.5 is H, C.sub.1 -C.sub.18 alkyl, cyclohexyl, cyclopentyl, phenyl, C.sub.1 -C.sub.12 alkylphenyl, benzyl or C.sub.1 -C.sub.12 alkylbenzyl, and at least one of the substituents R.sub.1 to R.sub.4 is an organic thiol, sulfoxyl or sulfonyl group, and the other members R.sub.1 to R.sub.4 are H, F, Cl or Br, are reversible photochromic systems which can be used for contrast formation or light absorption.

Dependencies are inferred from the claim text.