| 摘要 |
A method for producing a polyester film includes: an unstretched film formation step of forming an unstretched polyester film having a thickness of from 2.5 mm to 5.0 mm by melt-extruding a polyester resin using an extruder, and cooling the polyester resin; and a stretching step of stretching the formed unstretched polyester film in at least one direction after heating the formed unstretched polyester film so as to have a mean temperature T1 (° C.), a surface temperature, and a central temperature. The mean temperature T1 (° C.) satisfies a relationship represented by formula (1): Tg-20° C.<T1<Tg+25° C., wherein Tg represents a glass transition temperature (° C.) of the unstretched polyester film. The surface temperature is higher than the central temperature by from 0.3° C. to less than 15° C.
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