PROCESS FOR MAKING AN OPTICAL FILM AND ROLLS OF OPTICAL FILM

摘要

Exemplary methods include includes providing a film comprising at least one polymeric material; widening the film under a first set of processing conditions in a first draw step along the crossweb direction such that in-plane birefringence, if any, created in the film is low; and drawing the film in a second draw step along a downweb direction under a second set of processing conditions, wherein the second set of processing conditions creates in-plane birefringence in at least one polymeric material. Exemplary roll of film includes an oriented optical film characterized by an effective orientation axis. The oriented optical film comprises only one birefringent polymeric material, at least one birefringent material and at least one isotropic material, or a first birefringent material and a second birefringent material, the birefringent materials characterized by effective orientation axes along the MD. The optical film has a width of greater than 0.3 m and a length a length greater than 10 m.