Patent attributes
The present invention relates to a retardation film obtained by subjecting a film formed from a cellulose derivative to an orientation treatment, wherein a hydroxyl group of cellulose is substituted by at least one kind of aliphatic acyl group having 5 to 20 carbon atoms, and a degree of substitution by said hydroxyl group is 1 to 3. According to the present invention, a retardation film having various wavelength dispersion characteristics, positiveness or negativeness in birefringence and viewing angle characteristics, in particular, an achromatic retardation film and a retardation film having a high birefringent property and the like can be obtained by preparing a retardation film using a properly selected said cellulose derivative as a raw material of the film.
