Patent attributes
A cellulose acylate film producing method of producing cellulose acylate film by casting dope containing cellulose acylate and solvent is provided. The cellulose acylate film producing method includes adding a magnesium salt to the dope to satisfy a condition of a value of M2/M1 being equal to or more than 1×10−6 and equal to or less than 1×10−3, where M1 is a weight of the cellulose acylate, and M2 is a weight of magnesium in the magnesium salt. If the dope contains a calcium ion, the magnesium salt suppresses creation of insoluble precipitate of a calcium salt of a fatty acid from a fatty acid ion in the dope. Preferably, the magnesium salt is magnesium sulfate. A value of M3/M2 is equal to or more than 1×10−3 and equal to or less than 10, where M3 is a weight of calcium contained in the dope.
