| abstract |
Azulenesquaric acid dyes of the formula ##STR1## where L is substituted or unsubstituted C 1 -C 12 - alkylene, n R 1 is C 1 -C 20 - alkyl, C 5 -C 7 - cycloalkyl or substituted or unsubstituted phenyl and n R 2 , R 3 , and R 5 are each independently of the others hydrogen or substituted or unsubstituted C 1 -C 12 -alkyl, n with the proviso that when R 5 is hydrogen the positions of the substituents CH 2 --L--O--CO--NHR 1 and R 4 on an azulene ring may also be interchanged within a ring in either or both of the azulene rings, derived from azulene intermediates that contain urethane groups, are suitable for use in an optical recording medium. |