Patent ID: 8518551

Claim:
A biaxially oriented polyester film for automobile driving motors, composed primarily of polyethylene naphthalenedicarboxylate and characterized in that the plane orientation coefficient of the film is not less than 0.260 and not more than 0.280, the melting sub-peak temperature (Tsm) of the film is not less than 210° C. and not more than 230° C., the heat shrinkage percentages in the longitudinal direction and the transverse direction of the film after treatment at 150° C. for 30 minutes are each not less than 0% and not more than 1.0%, and the film thickness is not less than 100 μm and not more than 200 μm, wherein the Young's moduli in the longitudinal direction and the transverse direction of the film are each not less than 6000 MPa and less than 7000 MPa.