Examples of the aromatic-aliphatic hydrocarbon group include a phenylalkyl having 7 to 9 carbon atoms such as benzyl, phenethyl, 1-phenylethyl, 3-phenylpropyl, 2-phenylpropyl, 1-phenylpropyl and the like; naphthylalkyl having 11 to 13 carbon atoms such as ??-naphthylmethyl, ??-naphthylethyl, ??-naphthylmethyl, ??-naphthylethyl and the like. [0063] The aromatic hydrocarbon group is preferably an ar