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 μm. 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.
二氯甲烷与作为劣质溶剂的
酒精混合的溶剂用于制备涂料。
酒精通过内联管道供应到涂料中,与静态混合器混合,如增加
酒精成分的铸造涂料。将浇注料从浇注模具送入旋转滚筒,以形成厚度为 40 μm 的浇注膜。由于
酒精含量高,冷却后的浇注膜的储存模量至少为 15 万帕,因此不会出现剥离缺陷,拉伸也尽可能减小。凝胶状薄膜由拉幅机干燥,拉伸率不超过 110%。生产出的薄膜很薄,表面状态和光学各向同性都很好。