| 摘要 |
A casting film (24) is formed by casting a cellulose acylate solution (16) onto a cold drum (22) continuously running. The cellulose acylate solution (16) contains at most 0.01% of a compound which is extracted to a liquid incompatible with the water in a mixture of the water and the liquid. That is, at most 50 mg of the compound is contained in 100 g of cellulose acylate. In the cellulose acylate solution (16), a concentration C1 of Ca is at most 100 ppm, a proportion of the C1 to a concentration C2 of sulfuric acid satisfies the following formula: 0.5<=C1/C2<=1.5, and a concentration of Mg is in the range of 5 ppm to 50 ppm. Thereby, contamination of the surface of the cold drum (22) is prevented.
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