When biaxially oriented polyethylene terephthalate (PET-BO) film was laminated on tin free steel (TFS) at 260°C (melting point of PET) or slightly higher temperatures, it began to fuse in its interfacial layer, transforming to a non-oriented and amorphous film.
Amorphous PET layer contributed to the adhesion to TFT and the residual PET-BO layer influenced the formability and corrosion resistance. The more the residual PET-BO amount was, the better the PET film was in the water permeability resistance and the mechanical properties. On the other hand, as the residual PET-BO amount was less, the adhesion of PET film to TFS was better, being prominent when PET laminated TFS was deeply drawn into a cup.
Thus, the adhesion and the corrosion resistance after forming changed adversely each other. However, their properties were good when the residual PET-BO amount in PET film was kept within the range of 30 to 70%. As a rapid quenching after the lamination of PET-BO film to TFS could prevent the recrystallization of the formed amorphous PET layer, the excellent adhesion of PET film to TFS was obtained.