Patent ID: 7285322

Claim:
An at least two-layered polyester film with a total thickness of from about 5 to about 200 μm which comprises a base layer and at least one polyethylene naphthahtte (PEN)-free outer layer, said film comprising, alongside polyethylene terephthalate, from anout 2 to about 20% by weight—based of on the weight of the entire film—of PEN, wherein (i) said base layer comprises PEN and (ii) at least one PEN-free outer layer comprises less than 0.1% by weight of PEN (based on the weight of this outer layer), and the polyethylene naphthalate content in each layer does not exceed 25% by weight, said films having a transmittance at 330 nm of less than 25%, said PEN-free outer layer reducing the blue fluorescence exhibited by said film in ultraviolet light in comparison to a comparable flim that lacks said PEN-free outer layer, wherein said film exhibits an oxygen barrier of less than 110 {cm 3 /(m 2 d bar)}·{film thickness [μm]/12 [μm ]}in the absence of an additional barrier layer and said film contains no additional UV absorber.