Patent ID: 7198857

Claim:
A polyester film for forming which comprises a biaxially oriented polyester film comprising a copolyester component, wherein: (1) the stress at 100% elongation of the film in each of the machine direction and the transverse direction is 10 to 1000 MPa at 25° C. and is 1 to 100 MPa at 100° C.; (2) the storage viscoelasticity (E′) of the film in each of the machine direction and the transverse direction is 10 to 1000 MPa at 100° C. and is 5 to 40 MPa at 180° C.; and (3) the degree of heat distortion (initial load, 49 mN) of the film in the machine direction is −3% to +3% at 175° C.