METHODS OF STRETCHING FILMS AND SUCH FILMS

摘要

A method of biaxially stretching a polymeric film according to an overstretc h stretch profile to a final first direction stretch parameter and a final second direction stretch parameter. The method comprising the steps of: a) imparting a sufficiently high temperature to the film to allow a significant amount of biaxal stretch; b) biaxial tenter stretching the film to a peak first direction stretch parameter (48) that is at least 1.2 times the final first direction stretch parameter (14), wherein the final first direction stretch parameter is no larger than the final second direction stretch parameter; and c) subsequent to step (b), retracting the film in the first direction to the final first direction stretch parameter.