Patent ID: 7327422

Claim:
A multilayer optical compensation film comprising one or more optically anisotropic layers X and one or more optically anisotropic layers Z wherein, said each layer X has its optic axis tilted with respect to the plane of said multilayer compensation film, and said each layer Z comprises amorphous polymer with glass transition temperature above 180C°, and satisfies the following two relations: | nx−ny|< 0.001 (1) Δ n th =nz −( nx+ny )/2<−0.005 (2) wherein: “nx” and “ny” are indices of refraction in the film plane parallel to the x and y directions which represent orthogonal directions in the plane of the film; “nz” is the index of refraction in the z-direction that corresponds to the film-thickness direction; and “Δn. th ”, is the out of-plane birefringence, wherein, one or more Z layers comprises a polymer selected from the group consisting of: poly(4,4′-hexafluoroisopropylidene-bisphenol)terephthalate-co-isophthalate; poly(4,4′-hexahydro-4,7-methanoinda n-5-ylidene bisphenol)terephthalate; poly(4,4′-isopropylidene-2,2′6,6′-tetrachlorobisphenol)terephthalate-co-isophthalate; poly(4,4′-hexafluoroisopropylidene)-bisphenol-co-(2-norbornylidene)-bis-phenol terephthalate; poly(4,4′-hexahydro-4,7-methanoindan-5-ylidene)-bi-sphenol-co-(4,4′-isopropylidene-2,2′,6,6′-tetrabromo)-bisphenol terephthalate; poly(4,4′-isopropylidene-bisphenol-co-4,4′-(2-norbornylidene)bisphenol)terephthalate-co-isophthalate; poly(4,4′-hexafluoroisopropylidene-bisphenol-co-4,4′-(2-norbornylidene)bisphenol) terephthalate-co-isophthalate and copolymers thereof.