A coextrusion film has a core layer made of thermoplastic elastomer, and first and second outer layers sandwiching the core layer. The outer layers are each formed from a polymer having a lower elasticity than the thermoplastic elastomer of the core, each have a layer thickness of less than 15 μm, each have a density of less than 0.800 g/cm3, and each have more than 500 gas-filled cells per 1 cubic millimeter of volume.