It is required to adjust the three dimensional refractive index for an optical compensator film used in a liquid crystal display with wide visual angle. Although there have been various techniques proposed, such as biaxial stretching, doping a second component, and laminating, it is not easy to enhance the refractive index in the thickness direction of a film. Furthermore, the refractive index control has to be performed in the wide range of wavelength for color display. In this study, a cellulose triacetate film containing a specific additive having strong polarizability anisotropy is used to control the refractive index. Since the additive has an anisotropy also in its shape, it shows the orientation accompanying with the orientation of polymer chains. Consequently, the refractive index in three dimension is modified.