NOVELTY - A back film has a layer structure comprising a layer of hot-melt resin or adhesive resin (1), a bi-axial stretching polyester layer (3), a polyesterurethane type adhesive layer (a) (5), a layer of aluminum foil or polychlorotrifluoroethylene resin (7), a polyesterurethane type adhesive layer (b) (9), a (meth)acrylic-type resin layer and a fluorine resin layer (13). The layer of hot-melt resin or adhesive resin is a photovoltaic element, and is a layer to adhere during manufacture of solar cell.    USE - Back film is used for solar cells.    ADVANTAGE - The back film has excellent water resistance. The curl and interfacial removal of layer containing aluminum foil in the back film is suppressed.    DETAILED DESCRIPTION - A back film has a layer structure comprising a layer of hot-melt resin or adhesive resin, a bi-axial stretching polyester layer, a polyesterurethane type adhesive layer (a), a layer of aluminum foil or polychlorotrifluoroethylene resin, a polyesterurethane type adhesive layer (b), a (meth)acrylic-type resin layer and a fluorine resin layer. The layer of hot-melt resin or adhesive resin is a photovoltaic element, and is a layer to adhere during manufacture of solar cell. The back cell is adhered on a non-light-receiving surface side of photovoltaic element on which an electrode layer (e1), a semiconductor light-active layer and an electrode layer (e2) are laminated sequentially. The layer of hot-melt resin or adhesive resin is layer of ethylene-based copolymer resin or layer of ethylene and vinyl acetate copolymer. The fluorine resin layer contains polyvinylidene fluoride, tetrafluoroethylene perfluoroalkoxy ethylenic copolymer, tetrafluoroethylene and hexafluoropropylene copolymer, tetrafluoroethylene ethylenic copolymer, polychlorotrifluoroethylene resin and/or polyvinyl fluoride, preferably polyvinylidene fluoride. The (meth)acrylic-type resin layer is a layer of resin composition containing polyvinylidene fluoride and polymethyl methacrylate or layer of polymethyl methacrylate. The (meth)acrylic-type resin layer contains dispersed ultraviolet absorber in the layer.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of the back film.    Layer of hot-melt resin or adhesive resin (1)    Bi-axial stretching polyester layer (3)    Polyesterurethane type adhesive layers (5,9)    Layer of aluminum foil or polychlorotrifluoroethylene resin (7)    Fluorine resin layer (13)