| 摘要 |
A retardation film having biaxial or achromatic properties, which is produced by uniaxially stretching a film made of either a cellulose derivative wherein hydroxyl groups are replaced by acyl having 5 to 20 carbon atoms, preferably 7 to 20 carbon atoms, still preferably 8 to 20 carbon atoms or a product of crosslinking of the cellulose derivative. The retardation film exhibits negative birefringence and excellent optical characteristics, can be easily produced by uniaxial stretching, and is improved in heat resistance or tear strength which conventional cellulose ester films are problematic in.
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