or an iodine atom examples of the alkyl group having 1 to 20 carbon atoms which is substituted with the halogen atom include a fluoromethyl group a difluoromethyl group a trifluoromethyl group a chloromethyl group a dichloromethyl group a trichloromethyl group a bromomethyl group a dibromomethyl group a tribomomethyl group an iodomethyl group a diiodomethyl group a triiodomethyl group a fluoroethyl group a difluoroethyl group a trifluoroethyl group a tetrafluoroethyl group a pentafluoroethyl group a chloroethyl group a dichloroethyl group a trichloroethyl group a tetrachloroethyl group pentachloroethyl group a bromoethyl group a dibromoethyl group a tribromoethyl group a tetrabromoethyl group pentabromoethyl group a perfluoropropyl group a perfluorobutyl group a perfluoropentyl group a perfluorohexyl group a perfluorooctyl group a perfluorododecyl group a perfluoropentadecyl group a perfluoroeicosyl group a perchloropropyl group a perchlorobutyl group a perchloropentyl group a perchlorohexyl group a perchlorooctyl group a perchlorododecyl group a perchloropentadecyl group a perchloroeicosyl group a perbromopropyl group a perbromobutyl group a perbromopentyl group a perbromohexyl group a perbromooctyl group a perbromododecyl group a perbromopentadecyl group a perbromoeicosyl group and the like further all of these alkyl groups may be partially substituted with an alkoxy group such as a methoxy group an ethoxy group or the like an aryloxy group such as a phenoxy group or the like or an aralkyloxy group such as a benzyloxy group or the like etc as the aralkyl group in the substituent x 1 r 1 r 2 r 3 r 4 r 5 or r 6 an aralkyl group having 7 to 20 carbon atoms is preferable and examples thereof.