Patent ID: 7132133

Claim:
A process for manufacturing an optical negative birefringent layer consisting of a monomer material or a prepolymer material and having an optical axis perpendicular to a surface thereof, said process comprising (1) pouring the monomer material or the prepolymer material (a) over a rigid substrate surface, (b) between two rigid substrate surfaces separated by deformable spacers, or (c) between two rigid substrate surfaces separated by non-deformable spacers, to form a material layer; (2) polymerizing said material layer at an elevated temperature which is lower than a glass phase transition temperature of the polymerized monomer material or the prepolymer material, such that for (a) or (b) said material layer is fully cured, and for (c) said material layer polymerizes at room temperature to a first level at which viscosity of the monomer material or the prepolymer material is increased to a point that the monomer material or the prepolymer material does not leak out from between the substrate surfaces, followed by removal of the non-deformable spacers, and completion of the polymerizing at said elevated temperature, so that for (a), (b) and (c) the material layer unrestrainably shrinks in a direction perpendicular to the substrate surface or the substrate surfaces, wherein said polymerizing of said material layer is conducted in such a manner to provide a spontaneous deformation of molecules forming the monomer material or the prepolymer material, which is induced by an anisotropic mechanical strain due to shrinking the material layer in contact with and parallel to the substrate surface or the substrate surfaces, which is permanently frozen-in by cross-linking polymerization and results in strain-induced negative birefringent properties in the material layer; and (3) cooling said material layer following said polymerizing to room temperature.