Disclosed is a method for manufacturing a film. 50 wt % to 85 wt % of a first polyester and 50 wt % to 15 wt % of a second polyester are dried and mixed to form a mixture. The first polyester is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or combinations thereof. The second polyester is copolymerized of 1 part by mole of terephthalic acid, m parts by mole of 1,4-cyclohexanedimethanol (1,4-CHDM), n parts by mole of 1,3-cyclohexanedimethanol (1,3-CHDM), and o parts by mole of ethylene glycol (EG). m+n+o=1, 0≤o≤0.4, 0.6≤m+n≤1, and 0.06≤n/m≤1.31. The mixture is melted and blended to form a polyester composition, which is extruded to form a sheet. The sheet is then biaxially stretched to obtain a film. The biaxially stretched film is then treated with a thermal setting.