<p>High optical uniformity is displayed by a thermoplastic resin film exhibiting no periodic thickness variation of sine waveform having a pitch of 50 mm or less and a thickness change of 0.5 mu m or more on continuous thickness measurement in the machine direction. An optical film having a retardation value of 1200 nm or less with a fluctuation of not more than 10% and a rate of change of not more than 1.3 %/cm, is obtained by stretching the thermoplastic resin film. The optical film is laminated to a polarizing sheet to serve as a phase retarder which finds particular application in liquid crystal displays.</p>
