"Examples of R1 to R4 in the above Formulas (I) to (IV), include halogen atoms such as a fluorine atom, chlorine atom, bromine atom and iodine atom; C1-20 alkyl groups such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, octyl group and 2-ethylhexyl group; C1-20 alkoxy groups such as a methoxy group, ethoxy group, propoxy group, butoxy group and phenoxy group; C6-20" . . . .