Abstract: The application discloses a transparent, biaxially oriented polyester film having a base layer at least 80% by weight of which is composed of a thermoplastic polyester, and having at least one outer layer, wherein the outer layer is composed of a polymer, or of a mixture of polymers, which comprises at least 40% by weight of ethylene 2,6-naphthalate units and up to 40% by weight of ethylene terephthalate units and/or units from cycloaliphatic or aromatic diols and/or dicarboxylic acids, with the proviso that the Tg2 value of the polyester film is above the Tg2 value of the base layer but below the Tg2 value of the outer layer, and at least one film surface has a surface tension of from 35 to 65 mN/m and/or has been provided with a functional coating of thickness from 5 to 100 nm. The film has low atmospheric oxygen transmission. It is particularly suitable for packaging uses, specifically for packaging foods and other consumable items, and for laminating, metallizing and printing.