Further, another preferred compound is a compound in which the ring formed with Z is adamantylidene and the ring formed with Y is a heterocyclic, in particular, thiophene group, which may be substituted with aryl having 6 to 10 carbon atoms or alkoxyaryl having 7 to 14 carbon atoms (i.e., aryl having 6 to 10 carbon atoms substituted with alkoxyl having 1 to 4 carbon atoms).