tfe copolymers of tfe and hexafluoropropylene copolymers of tfe and a perfluoroalkoxyethylene polychlorotrifluoroethylene polyvinylidene fluoride and polyvinyl fluoride fig1 shows a conventional vacuum evaporation apparatus which can be employed for a coating method according to the invention the apparatus comprises a bell jar type vessel 10 which provides therein a vacuum chamber 12 as the evaporating source a low molecular weight fluororesin 14 preferably in powder form as mentioned hereinbefore is placed at a usual position in the vacuum chamber there is a resistance heater 16 to heat the evaporating source 14 a substrate 18 on which the fluororesin 14 is to deposit is placed above and at a suitably adjusted distance from the evaporating source 14 and a resistance heater 20 is provided to heat the substrate 18 a freely openable shutter 22 is disposed between the evaporating source 14 and the substrate 18 the magnitude of vacuum in the vacuum chamber 12 is regulated to a desired level within the range from 10 1 to 10 6 torr and then the low molecular weight fluororesin 14 is heated if the pressure in the chamber 12 is higher than 10 1 torr the molecules of the residual gas constitute a serious obstruction to free movement of the molecules of the evaporated fluororesin therefore the molecules of the evaporated fluororesin remain short in their mean free path and before arriving at the substrate 18 repeatedly collide against each other with resultant growth to large particles and loss of kinetic energy and soon fall down although a very high vacuum is favorable for vacuum evaporation operations it is difficult in industrial practice to keep the pressure in the chamber 12 below 10 6 torr in practice a vacuum of 10 4 torr suffices for accomplishment of.