| abstract |
Provided are a polyester film excellent in productivity and a method for producing the same, which can maintain durability even under conditions of high temperature and high humidity, and can suppress the occurrence of defective thickness, breakage, film internal defects and the like in a film forming process. A film containing a polyester resin containing an alkali metal phosphate of 0.1 mol / t or more and 5.0 mol / t or less, wherein the intrinsic viscosity (IV) of the polyester resin constituting the film is 0.65 or more and 0 .80 or less, the terminal carboxyl group content is 20 equivalent / t or less, the diethylene glycol content is 0.9 mass% or more and 3.0 mass% or less, and the average ultrasonic conduction velocity of the film is 2.20 km / second or more. A biaxially oriented polyester film. |