Patent ID: 8728371

Claim:
A method of producing a stretched film comprising: melt-coextruding a thermoplastic resin A and a thermoplastic resin B to produce a composite film having both-end films of the thermoplastic resin B arranged in parallel at both end portions of the main film of the thermoplastic resin A in the direction of width thereof; stretching said composite film in the direction in which said both-end films of said main film are arranged; cutting portions of said composite film other than a portion of the main film having an allowable thickness; and removing the cut portions, which include the both-end films and a portion of the main film other than the portion of the main film having an allowable thickness; wherein a film stretch stress value of said both-end films is 1.5 to 6.9 times as great as a film stretch stress value of the main film at the same stretching ratio; and the width of said both-end films is not smaller than 5 mm on each side before being stretched.