OPTICAL FILM AND OPTICAL STACK

An optical film includes a plurality of alternating first and second polymeric layers, such that the first polymeric layers have a smaller average in-plane index of refraction than the second polymeric layers and the first polymeric layers have a glass transition temperature of at least 107 deg. C. The optical film may be a reflective polarizer. An optical stack includes a linear absorbing polarizer and the reflective polarizer disposed on, and bonded to, the absorbing polarizer. The reflective polarizer has an optical reflectance of at least 60% for a first polarization state and an optical transmittance of at least 60% for an orthogonal second polarization state. When heated at 105 deg. C. for 15 minutes, a difference in shrinkage of the reflective polarizer and the absorbing polarizer along the first and second polarization states is greater than about zero and 0.2%, respectively.