APPARATUS FOR HEAT-TREATING FILM

摘要

PURPOSE:To optically give an isotropy by heating at least one end of a film in a specified range of temperature and under the condition of cooling speed at the time when a thermoplastic film is heated preliminarily to Tg or higher and cooled thereafter. CONSTITUTION:A thermoplastic film is preliminarily heated to Tg or higher and then at least one end of the film is heat-treated under the condition wherein the temperature of the film is in the range of (Tg+10) deg.C to (Tg-15) deg.C and the cooling speed is controlled to 1-0.01 deg.C/sec. The afore-mentioned preliminary heating temperature is preferred to preliminarily heat the film to (Tg+35) deg.C or higher. The film cooling atmospheric temperature in a pre-cooling process is preferred to be in the range of (Tg+35) deg.C-(Tg-100) deg.C and the film auxiliary heating temperature is preferred to be higher than the atmospheric temperature by 2-100 deg.C.