Patent ID: 7229696

Claim:
A biaxially oriented, coextruded polyester film with a total thickness of from about 5 to about 200 μm which comprises a base layer disposed between two outer layers, said film comprising polyethylene terephthalate and from 8% to about 20% by weight—based on the weight of the entire film—of polyethylene naphthalate, wherein said film includes at least one functional outer layer, said films having a transmittance at 330 nm of less than 25%, said polyethylene naphthalate present within said base layer alone, said film having a melting peak between about 230 and about 270° C. and said coextruded layers providing an oxygen barrier of less than 100 {cm 3 /(m 2 d bar)}·{film thickness [μm]/12 [μm]}.