As examples of the ???aromatic hydrocarbon group???, a monocyclic aromatic hydrocarbon group consisting of 6 to 18 carbon atoms and a fused polycyclic aromatic hydrocarbon group can be mentioned; specifically, an aryl group having 6 to 14 carbon atoms, such as phenyl, 1-naphthyl, 2-naphthyl, 2-indenyl, 2-anthryl and the like, can be mentioned.