Poly(ethyleneterephthalate) film: — of a thickness of not more than 20 μm, — coated on at least one side with a gas barrier layer consisting of: — a polymeric matrix in which silica has been dispersed and of a thickness of not more than 2 μm, or — a silica layer which is deposited through vapour deposition and of a thickness of not more than 1 μm
