Patent ID: 8318072
Filing Date: 2012-11-27
Classification: B29C,B29K,C08J,G02B

Abstract:
1. A method for producing a stretched cellulose acylate film having an in-plane retardation, Re, of 100 nm or more and a relationship between a thickness direction retardation, Rth, and Re which satisfies Rth<(Re/2), by longitudinally stretching an unstretched cellulose acylate film in a longitudinal direction by pulling by means of a difference in circumferential velocity between a pair of stretching rollers, the method comprising: subjecting the cellulose acylate film to free-end uniaxial stretching to a longitudinal stretch ratio of 1 to 2; and while subjecting the film to said free-end uniaxial stretching, heating the film in a heating oven installed between the pair of stretching rollers at a stretching temperature in the range of Tc−10° C. to Tc+70° C., Tc being the crystallization temperature of the film, and with the temperature difference in the film width direction maintained within 10° C., wherein hot-air heating is carried out in the heating oven by blowing hot-air toward a film surface at a wind velocity of 0.5 to 20 m/sec from a heating nozzle, with the slit width of the blowout opening being 2 to 10 mm and the distance from the blowout opening to the cellulose acylate film surface being 20 to 500 mm.