NOVELTY - Modified fluorinated resin slice, comprises a fluorinated resin, a plasticizer, a stabilizer, a coupling agent, an antioxidant and a filler. The plasticizer is e.g. dibutyl phthalate, glycerol triacetate or propylene carbonate. The stabilizer is e.g. 2-(2'-hydroxy-3',5'-di-tert-butyl phenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methyl phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butyl phenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-(1,1-dimethylpropyl)phenyl)-2H-benzotriazole, di(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate or 2-hydrdoxy-4-(octyloxy)benzophenone.    USE - The modified fluorinated resin slices is useful for preparing a solar photovoltaic back film e.g. extrusion film and blow film.    DETAILED DESCRIPTION - Modified fluorinated resin slices, comprises (in wt.%) a fluorinated resin (25-90), a plasticizer (0.1-25), a stabilizer (0.1-10), a coupling agent (0.2-10), an antioxidant (0.2-10) and a filler (2-50). The plasticizer is dibutyl phthalate, glycerol triacetate, sulfolane or propylene carbonate. The stabilizer is 2-(2'-hydroxy-3',5'-di-tert-butyl phenyl)benzotriazole, UV-325, 2-(2'-hydroxy-3'-tert-butyl-5'-methyl phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butyl phenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-(1,1-dimethylpropyl)phenyl)-2H-benzotriazole, di(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, sebacic acid di-2,2,6,6-tetramethyl piperidine ester or 2-hydroxy-4-(octyloxy)benzophenone. The coupling agent is silane coupling agent or titanate coupling agent. The filler is silica powder, quartz powder, calcium carbonate powder, calcium silicate powder, talc, mica powder or titanium white powder. The melting flow rate (MFR) of the modified fluorine-containing resin slices measured at 230 degrees C is 2-30 g/10 minutes for a measured load of 2.16 kg, based on the American Society for Testing and Materials (ASTM) D1238. The melting point is 150-170 degrees C and the degree of crystallinity is 29-40%. An INDEPENDENT CLAIM is also included for preparing the modified fluorinated resin slices comprising weighing the materials in their prescribed amount, mixing uniformly, transferring the mixture into a double-screw or single-screw extrusion pelletizer, melting, plasticizing and extruding at the set temperature and screw rotating speed, and processing the extruded material by cutting and granulating to obtain the product.