Stretched film and method for producing the same

A method for producing a stretched film, the method comprising stretching a long film in a desired direction by moving both side edges in a width direction of the long film along respective constant trajectories with the film held at the both side edges in the width direction, the both side edges consisting of a pair of one side edge and the other side edge,

• wherein the method performs at least once each a first step of stretching the long film by increasing a holding distance in the width direction of the film and a second step of shrinking by heating the long film having been stretched at the first step by decreasing the holding distance,
• the one side edge of the long film having a traveling direction with at least three bending travels,
• the other side edge thereof having a traveling direction with at least two bending travels,
• both the first step and the second step including a bending travel at either one or both of the side edges,
• at least one of the first step and the second step including such a traveling trajectory that the both side edges of the long film travel as bending to either the right or the left of the traveling direction, and
• wherein the long film has a center line formed by connecting centers in the width direction of the long film,
• the center line of the long film in the firstly-performed first step bending with respect to the center line of the immediately preceding long film,
• the stretched film having undergone all the first steps and the second steps having a width larger than a width of the long film before the firstly-performed first step,
• the traveling direction of the long film immediately before the firstly-performed first step of all the first steps being a direction angle difference of 0±3 degrees as that of the long film immediately after performing all the first steps and the second steps, and
• wherein the center line of the long film in the at least one first step and the center line of the long film in the at least one second stets form an angle of 160° to 174°.