Patent ID: 8097200

Claim:
A method for producing a stretched film comprising: supplying a film composed of a thermoplastic resin along a direction that is different from a taking-up direction of a post-stretch film, and obliquely stretching the film while transferring the film with the edges thereof being gripped by gripping devices, to produce the stretched film having an orientation angle θ being within 45±1° with respect to the taking-up direction, wherein the stretching is performed so that an angle θL (°) and a stretching speed V (mm/min) satisfy the following formulae (1) and (2): θ−20°≦θ L≦θ− 5° (1) 1000 mm/min< V≦ 2500 mm/min (2) wherein the angle θL is an angle between two directions, one of which is along a straight line connecting a pair of the gripping devices when they are at a stretching completion point, the pair of the gripping devices having been opposed to each other along a direction that is approximately perpendicular to a film supplying direction when the pair has been at a point of film gripping commencement by the gripping devices, and the other of which is a direction perpendicular to the taking-up direction.