| abstract |
The present invention provides a kind of polyester film and its manufacture method, even if described polyester film also can maintain durability under the conditions of hot and humid, and can suppress the generation of thickness undesirable cracking in film making process, film internal flaw etc., productivity ratio is excellent.The double axial orientated polyester film of the present invention contains polyester resin, described polyester resin contains the alkali metal phosphate of 5.0 moles/below t of 0.1 mole/more than t, the intrinsic viscosity (IV) constituting the polyester resin of film is less than more than 0.65 0.80, terminal carboxyl group amount is 20 equivalents/below t, diethylene glycol content is below more than 0.9 mass % 3.0 mass %, and the mean ultrasonic conduction velocity of film is 2.20km/ more than the second. |