Negative dispersion retarder with a wide viewing angle made by stacking reactive mesogen on a polymethylmethacrylate film

We experimentally demonstrated a retarder with a wide field-of-view as well as a negative dispersion (ND) of birefringence. We stacked reactive mesogen, which has a positive birefringence, and polymethylmethacrylate which has a negative birefringence. The out-of-plane retardation (R_th) of the stacked film was 6 nm. This value is about a tenth of that of a general retarder and demonstrates a small change in the retardation (Re) at an oblique viewing angle. The stacked film showed an ND of the birefringence, where Re(450 nm)/Re(550 nm) = 0.818 and Re(650 nm)/Re(550 nm) = 1.110. The dispersion properties were close to the ideal dispersion of an achromatic retarder and showed a small Re-dependence on the wavelength of light.