l, m, o and p are the same or different, integers from 0 to 2, and at least one group selected from the following groups: ##STR3## may form a condensed ring with benzene ring which may have a lower alkyl group, lower alkoxy group or halogen atom as a substituent. ##STR4## wherein R10 is a hydrogen atom or alkyl group. ##STR5## wherein R11, R12, R13 and R14 are the same or different, hydrogen atom