A film as claimed in claim 10, wherein the cycloolefin polymer COP1 is a cycloolefin copolymer and contains up to 99% by weight, based on the total weight of the cycloolefin copolymer, of polymerized units of an acyclic olefin of the formula VIII: ##STR9## where R9, R10, R11 and R12 are identical or different and are a hydrogen atom or C1 -C14 -hydrocarbon radical,.