Solution casting method
On a film transporting path in a film production equipment, there are a tension controlling device for controlling a tension to be applied to a TAC film. The tension cont v rolling device has a suction drum to which the TAC film is adsorbed and transported, and a dancer including a dancer roller. The film adsorption force of the suction drum is set in the range of 0.005N/cm 2 to 0.1N/cm 2 . If the surface temperature of the TAC film is at least 50° C., the loading applied to the dancer roller is determined such that the difference of the tension may be zero or at most 500N/m. Thus it is prevented that hole shape transfers, wrinkles, scratched wounds and the like occur.
1 . A solution casting method of producing a film from a dope containing a polymer and a solvent, comprising steps of:
casting said dope onto a support;
peeling said cast dope as said film from said support;
drying said film;
winding said film;
transporting said film with use of a dancer roller and a suction drum during the drying and/or the winding, said dancer roller being disposed in up- or downstream side from said suction drum, said suction drum feeding with adsorbing said film at an film adsorption force in the range of 0.005N/cm 2 to 0.1N/cm 2;
wherein when a temperature of said film is at least 50° C., a difference of tension between said up- and downstream sides from said suction drum is regulated to at most 100N/m, and when a temperature of said film is less than 50° C., said difference of tension is regulated to at most 500N/m.
2 . A solution casting method defined in claim 1 , wherein a difference of a surface temperature between said suction drum and said film at contacting to said suction drum is at most 20° C.
3 . A solution casting method defined in claim 1 , wherein a number of said suction drum is at least 2, and at least one of said suction drums contacts to a peeled surface of said film from said support.
4 . A solution casting method defined in claim 1 , wherein plural rollers rotating by supporting said film are used in the drying or the winding, and a bending deflection of a center to both edges in said roller is at most 1 mm.
5 . A solution casting method defined in claim 4 , wherein an anti-rotation torque per one roller is at most 0.025 Nm, and a number of said rollers in each interval between said two suction drums is at most 200.
6 . A solution casting method defined in claim 5 , wherein a dimple processing is made to a surface of at least one of said rollers, and said film is lapped on said at least one roller such that a film lapping angle may be at most 180°.
7 . A solution casting method defined in claim 1 , wherein said film is transported while a total electrostatic potential of the transported film is kept to at most 10 kV.
8 . A solution casting method defined in claim 7 , wherein when said surface temperature of said film is at least 70° C., a neutralization apparatus of a self-discharging type is used for keeping said total electrostatic potential to at most 10 kV, and when said surface temperature is less than 70° C., a neutralization apparatus of superimposed voltage type is used.