Biaxially Oriented Polyester Film

June 7, 2005

A biaxially oriented polyester film prepared by biaxially drawing a polyester sheet was patented. The film has a glass transition temperature (Tg) of 60° C. or higher, in the longitudinal and transverse directions, wherein the biaxially oriented film has a specific gravity of 1.38 or less and a dead-fold retainability of at least 60% defined as below: Dead-fold retainability (%)=(180?ı)?100/180 wherein ı is an angle formed when a polyester film sheet is folded under a pressure of 30 psi for three seconds at room temperature and the folded sheet is kept at a vertical position for one hour.