| 摘要 |
PROBLEM TO BE SOLVED: To achieve a simultaneously biaxially stretched film that has uniform and stable quality stability by suppressing as far as possible an increase in thickness unevenness caused by stress relaxation being the problem in the simultaneous biaxial stretching method.SOLUTION: A film is stretched by a simultaneous biaxial stretching method, carried out by a tenter method, for simultaneously biaxially stretching an unstretched film vertically and laterally while holding both ends of the unstretched film by a plurality of clips. On that occasion, it is configured to set the following difference to ≤5% of the maximum stretch ratio, that is, the difference between a vertical stretch ratio locus when the clips are in a freely running state without holding a film and a vertical stretch ratio locus when in a stretching running state while holding a film at the arbitrary time point in a stretching process about the vertical draw ratio represented by the distance between the clips. |
