Biaxially oriented polyester film to be laminated onto metal plate and molded

Abstract

A biaxially oriented polyester film to be laminated onto a metal plate and molded, (A) which comprises a copolyester comprising (a) terephthalic acid in an amount of 82 to 100 mol % and 2,6-naphthalenedicarboxylic acid or a combination of 2,6-naphthalenedicarboxylic acid and other dicarboxylic acid in an amount of 0 to 18 mol % of the total of all dicarboxylic acid components and (b) ethylene glycol in an amount of 82 to 100 mol % and cyclohexanedimethanol or a combination of cyclohexanedimethanol and other diol in an amount of 0 to 18 mol % of the total of all diol components, having (c) a glass transition temperature of 78° C. or more and (d) a melting point of 210 to 250° C., and containing (e) porous silica particles with a pore volume of 0.5 to 2.0 ml/g which are agglomerates of primary particles having an average particle diameter of 0.001 to 0.1 &mgr;m; and (B) which has the following relationship between the highest peak temperature (Te, °C.) of loss elastic modulus and the glass transition temperature (Tg, °C.): Te−Tg≦30. This film has improved taste-and-flavor retainabilities, particularly taste and flavor retainabilities after a retort treatment, without losing the excellent moldability, heat resistance, impact resistance and retort resistance of a copolyester film.