Biaxially oriented laminated film

Abstract

A biaxially oriented laminated polyester film which has dimensional stability against environmental changes such as temperature and humidity variations and rarely elongates when a load is applied thereto at a high temperature. The biaxially oriented laminated film comprises a film layer (A) made of an aromatic polyester (A) and a film layer (B) made of an aromatic polyester (B), wherein the content of a 6,6′-(alkylenedioxy)di-2-naphthoic acid component represented by the following formula (I) based on the total of all the acid components is less than 5 mol % in the aromatic polyester (A) and not less than 5 mol % and less than 80 mol % in the aromatic polyester (B); and the peak temperature of tan δ on a high temperature side is 135° C. or higher when viscoelasticity is measured in the machine direction. (in the formula (I), R is an alkylene group having 1 to 10 carbon atoms.)

Dependencies are inferred from the claim text.