| 摘要 |
A solvent in which dichloromethane is mixed with alcohol as a poor solvent is used for preparing a dope. Alcohol is supplied to the dope in a inline pipe to mix with a static mixer, such as a casting dope in which a composition of alcohol is increased. The temperature of the rotary drum is adjusted to -7° C. The casting dope is fed from a casting die to the rotary drum so as to form a casting film whose thickness is 40 mum. Since the content of alcohol is high and a storage modulus of the cooled casting film is at least 150 thousands Pa, the peeling defect does not occur, and the stretch is reduced as far as possible. A gel-like film is dried by a tenter type drying device, and stretched such that the stretch ratio is at most 110%. The produced film is thin and excellent in a surface condition and optical isotropy.
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