Optical film stack including retardation layer
Optical film stacks are described. More particularly, optical film stacks including a half-wave retardation layer are described. Achromatic half-wave retardation layers, including achromatic half-wave layers formed from a quarter-wave and a three-quarters-wave retardation layer, are described. Film stacks including reflective polarizers tuned to reduce wavelength dispersion of the half-wave retardation layer are also described.
1. An optical film stack, comprising:
a tuned reflective polarizer having a top surface, a bottom surface, a transmission axis, and a reflection axis;
a half-wave retardation layer having a top surface, a bottom surface disposed on the top surface of the reflective polarizer, and a slow axis oriented substantially 45° with respect to the transmission axis of the reflective polarizer; and
an absorbing polarizer having a bottom surface disposed on the top surface of the half-wave retardation layer and a transmission axis oriented substantially 90° with respect to the transmission axis of the reflective polarizer;
wherein the tuned reflective polarizer is tuned to compensate for wavelength dispersion of the half-wave retardation layer.
2. The optical stack of claim 1 , wherein the tuned reflective polarizer comprises a multilayer reflective polarizer comprising a plurality of microlayers, wherein optical thicknesses of the microlayers are tuned to compensate for the wavelength dispersion of the half-wave retardation layer.