In the general formulae [4] and [6], the aryl group of the aryl group which may have a substituent, shown by R2 and R4 includes one having generally 6 to 16 carbon atoms, preferably 6 to 10 carbon atoms, which is specifically exemplified by the same as examples of the aryl group of the aryl group which may have a substituent, shown by R1 in the general formula [2], and among others, a preferable o