| 摘要 |
PROBLEM TO BE SOLVED: To dispense with visual evaluation after the processing of a cellulose acetate film. SOLUTION: The cellulose acetate film is manufactured by a solution casting method so that the thickness change ratio in the width direction of the completed film after film formation becomes 0.04% or less (thickness change quantity at every 0.5 mm is not more than 0.0002 mm). For example, a dope 12 is prepared from cellulose acetate and a solvent such as dichloromethane or the like to be adjusted to a temperature of 30 deg.C and a viscosity of 500 poise. The dope 12 is cast on a belt 18 from a casting die 17 wherein the surface roughness (Ra value) of a die lip is set to 0.1 μm and a lip clearance (d) is set to 1.0 mm to form the film 19. If the thickness change ratio is not less than 0.04%, the film becomes a good product level of a streak-like flaw after product processing and visual evaluation is dispensed with. |
