MULTILAYER CELLULOSE ESTER FILM HAVING REVERSED OPTICAL DISPERSION

摘要

The present invention relates to a multilayer cellulose ester film having a reversed optical dispersion. The film can have an A-B bi-layer or an A-B-A tri-layer configuration. The cellulose ester material for layer A has a hydroxyl degree of substitution (DSOH) from 0 to 0.5, while the cellulose ester material for layer B has a DSOH from 0.5 to 1.3. By manipulating the thickness of layers A and B, and the film stretching conditions, desirable optical retardation and optical dispersion properties can be obtained. The film can be used as an optical waveplate in liquid crystal displays to improve viewing angle, contrast ratio, and color shift.