Stretched film and manufacturing method thereof

A film having high rigidity and high heat resistance, surface oxidation, such as blackening copper foil surface was etched with an acid, releasability good from the copper foil surface roughening treatment of the surface, the multilayer to provide a film and a manufacturing method thereof suitable for printed circuit board (MLB) release film for the production. Film of the present invention, a layer comprising a copolymer obtained from other α- olefin of 4-methyl-1-pentene with 80 mol% or more of 4-methyl-1-pentene with ethylene or C3-20 a film that at least one of the outermost layer (a), the thermal shrinkage ratio in the stretching direction is 20% or more, or surface roughening treatment copper foil surface and the release area upon heat treatment more than 50% it is a stretched film.