Abstract: A suction roller (65) is used as a drive roller for feeding a film in a solution casting method. The suction roller (65) has a surface (65a) on which a plurality of circular suction holes (91) is formed. The suction hole (91) has a diameter of 4 mm and a chamfered edge. The width of chamfer is 10% in ratio to the diameter of the hole. The surface (65a) is hardened by chrome plating so as to have a hardness of 900 in Vicars hardness. A roller temperature controller (100) is provided near the suction roller (65) to control the surface temperature of the roller by the air supply. The surface temperature of the suction roller (65) is about 10° C. higher than temperature of the film (61)immediately before contacting to the suction roller (65).

Abstract: A primary dope is obtained by mixing solvent and polymer, and an additive is added to the primary dope so as to prepare three sorts of dopes. The dopes are cast from a casting die onto a casting belt to form three-layer film. The thickness of the first layer t1 is the same as the thickness of the third layer t3 or less, and the thickness of the third layer t3 is the same as the thickness of the second layer t2 or less. After the film is peeled from the casting belt, both side edge portions of the film are clipped by clips. The film is stretched in a widthwise direction and dried. The film is excellent in smoothness and optical properties.

Abstract: In a solution casting system, a casting die causes dope containing polymer and solvent to flow. A casting support belt is disposed movably under the casting die, for forming cast film from the dope being cast. A stripping roller strips the cast film having a self-supporting property to form self-supporting cast film. A first dryer stretches the self-supporting cast film, and while the self-supporting cast film is stretched, applies first gas with temperature T2 to the self-supporting cast film containing the solvent, to evaporate the solvent therefrom. A second dryer, after the self-supporting cast film is stretched, applies second gas with temperature T3 to the self-supporting cast film containing the solvent, to evaporate the solvent therefrom for obtaining polymer film. The first and second dryers satisfy a condition of: 0<T2?T3<50. Also, a tentering machine contains the first and second dryers to stretch the self-supporting cast film.

Abstract: A suction roller (65) is used as a drive roller for feeding a film in a solution casting method. The suction roller (65) has a surface (65a) on which a plurality of circular suction holes (91) is formed. The suction hole (91) has a diameter of 4mm and a chamfered edge. The width of chamfer is 10% in ratio to the diameter of the hole. The surface (65a) is hardened by chrome plating so as to have a hardness of 900 in Vicars hardness. A roller temperature controller (100) is provided near the suction roller (65) to control the surface temperature of the roller by the air supply. The surface temperature of the suction roller (65) is about 10° C. higher than temperature of the film (61) immediately before contacting to the suction roller (65).