Brightness enhancement for bistable cholesteric displays

Abstract

The present invention is directed to a cholesteric liquid crystal display that includes a homogeneous alignment surface effective to provide increased brightness, low focal conic reflectance and/or reflected light that is to a significant degree circularly polarized. The homogeneous alignment surface substantially homogeneously aligns the liquid crystal director adjacent thereto. The homogeneous alignment surface may be disposed on one or both sides of a cell of the display. In the case of a cell in which the homogeneous alignment surface is disposed on only one side, the substrate with the inhomogeneous alignment surface may be upstream or downstream of the substrate with the homogeneous alignment surface relative to a direction of incident light. Also included especially in the case of a cell that has the homogeneous alignment surface on both sides is the use of a polarizer to provide very good brightness and low focal conic reflectance. Such a cell may employ an alignment layer material with a high pretilt angle. A stacked display may be produced including at least one cell with at least one homogeneous alignment surface. In particular, a stacked cell display may include a lower cell with two homogeneous alignment surfaces and an upper cell in which the top side has an inhomogeneous alignment surface and the bottom side has a homogeneous alignment surface. The present invention achieves any one or combinations of the above features through the use of the homogeneous alignment surface produced with a predetermined alignment layer material and predetermined alignment conditions. The invention also includes a method of making the inventive display and the stacked inventive display.