. . "(2) a triazine compound represented by the following general formula (II): ##STR3## wherein R3, R4 and R5 each independently represents an alkyl, aryl, alkenyl, alkoxy, aralkyl or alkylthio group which may be optionally substituted, provided that at least one of R3, R4 and R5 is a methyl group substituted with one, two or three halogen atoms; and" . . . .