摘要 |
PURPOSE:To contrive prevention of generation of creases on the surface of a film, by a method wherein the film is held at a temperature falling within a specific range and an inflation method wherein a temperature difference is provided between the central part and an end part is performed. CONSTITUTION:Polyarylate resin is melted and extruded through an annular die, flattened by a flattening device after formation of a bubble with pressurizing gas and introduced into a pair of pinch rolls in succession, in an inflation method. A blow-up ratio is made 0.8-2.5 times, a temperature of polyarylate film passage through the flattening device and a space between the pinch rolls is made so that the same falls within a range of 140 deg.C-190 deg.C, and the same at the central part of the film is made higher by 10 deg.C-30 deg.C as compared with the same at an end part. |