PURPOSE: Composite films for covering package that are prepared by using rigid polyvinyl chloride, polystyrene, polycarbonate or polyester as layers other than the sealing one, thus reducing curl at the sealded part.

CONSTITUTION: Rigid polyvinyl chloride, polystyrene, polycarbonate, or polyester of 15W40 micron thickness is used for layers other than sealing one in composite films and the thickness of the sealing layer is made to less than 40 microns. Above rigid polyvinyl chloride, polystyrene, polycarbonate, and polester are superior in nerve among thermoplastic resins even when the films are relatively thin and resist curling at the part to be sealed in deep drawn package. Less than 15 microns in film thickness reduces the resistance to curling and exceeding 40 microns also does not develop the effect, thus 15W40 microns is suitalbe.