Polymer film and production method thereof
A dope produced from cellulose acylate, solvent and additive, is cast on a belt and peeled as a film containing the solvent, with use of a peel roller. Then the film is dried to a film. After the peeling, the film is transported with use of plural rollers in an transfer section. Each roller is provided with a temperature controlling device for controlling the surface temperature of each roller. A surface temperature is controlled in the range of Tm (° C.) to Tm+50 (° C.), if the melting point of the additive for the dope is described as Tm (° C.). While the drying is made with support of the roller, the transporting becomes stable, and the roll-print defects and the scratch defects are reduced. Thus the produced film is excellent in smoothness and optical properties.
1 . A film production method with use of a polymer solution containing polymer, solvent and additive, comprising steps of:
casting said polymer solution onto a running support to form a casting film;
continuously peeling from said support said casting film as a film in a situation of containing said solvent; and
performing a first drying of said film by a plurality of rollers whose temperatures are independently controlled.
2 . A film production method according to claim 1 , wherein when melting point of said additive is described as Tm (° C.), a temperature of each of said rollers is in the range of Tm (° C.) to Tm+50 (° C.).
3 . A film production method according to claim 1 , further comprising steps of:
heating said film by a tenter dryer after the first drying so as to perform a second drying, said tenter dryer stretching and relaxing said film in a widthwise direction while transporting said film; and
controlling an ambient temperature of said film almost to a predetermined value while a width of said film is changed by stretching and relaxing.
4 . A film production method according to claim 1 , wherein said polymer is cellulose acylate.
5 . A polymer film produced by said film production method according to claim 1.