To provide an alkali saponification method of a polymer film, by which method a cellulose ester film can be suitably subjected to an alkali saponification treatment in order to easily produce an optical film having a large area free from display defects in a liquid crystal display device; a cellulose acylate film produced by the above method; and an optical film, a polarizing plate, and a liquid crystal display device produced by using the cellulose acylate film.
The alkali saponification method of a polymer film has a process for washing an alkali solution present on a polymer film by using water or an alkali washing liquid containing water and an organic solvent, the process for washing being conducted by using a roll coater or a rod coater. A cellulose acylate film produced by the method is provided, and an optical film, a polarizing plate, and a liquid crystal display device prepared by using the cellulose acylate film are also provided.
Hironori Honda
Toshimitsu Ichikawa
Takeshi Takamatsu
Kiyozumi Yazawa