Method for manufacturing polyimide-based film and polyimide-based film manufacture

A polyimide-based film manufactured by a roll-to-roll manner, the roll-to-roll manner comprising:

• conducting first heat treatment (S1) on a polyimide-based film obtained as a gel state formed by being cast on a support while elongating the polyimide-based film at an elongation percentage of more than 100% and less than 135% in a machine direction (MD) and shrinking the polyimide-based film at a shrinkage percentage of more than 75% and less than 100% in a transverse direction (TD);
• and
• conducting second heat treatment (S2) on the first heat-treated polyimide-based film while further elongating the polyimide-based film in the machine direction (MD) at a tension not less than 30 N/mm2 and less than 160 N/mm2,
• wherein a maximum heating temperature during the first heat treatment is 250° C. to 330° C., and
• the second heat treatment is performed for 200 seconds or longer at a temperature within −10° C. to +30° C. of the maximum heating temperature reached during the first heat treatment,
• wherein the polyimide-based film has a yield strain in a uniaxial direction of 3% or more and less than 8%.