Patent ID: 6805924
Filing Date: 2004-10-19
Classification: C09K,G02F

Abstract:
An optical compensation film for Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display comprising, a first and a second optically anisotropic layers containing positively birefringent material disposed on a substrate, wherein the optic axis of said first optically anisotropic layer tilts in a first plane with an average tilt angle between 10Â° and 60Â°, and the optic axis of said second optically anisotropic layer tilts in a second plane with an average tilt angle between 0Â° and 30Â°, the difference between said average tilt angle of said first optically anisotropic layer and said average tilt angle of said second optically anisotropic layer is larger than 10Â°;said first and said second planes are perpendicular to the plane of said optical compensation film with the angle between said first and said second planes being 90Â±10Â°, and the retardation defined by (ne1âˆ’no1)d1 of said first optically anisotropic layer is between 60 nm and 220 nm and the retardation defined by (ne2âˆ’no2)d2 of the said second optically anisotropic layers is between 85 nm and 210 nm, where ne1 and no1 are extraordinary and ordinary indices of refraction of said positively birefringent material of said first optically anisotropic layer, respectively, and ne2 and no2 are extraordinary and ordinary indices of refraction of said positively birefringent material of said second optically anisotropic layer, respectively, and d1 and d2 are thickness of the said first and said second optically anisotropic layer, respectively, wherein said substrate is a negative C-plate and the out-of-plane retardation defined by (nesâˆ’nos)ds of said substrate is between âˆ’200 nm and âˆ’60 nm, where nes and nos are extra ordinary and ordinary indices of refraction of said substrate, respectively, and ds is the thickness of said substrate, or a biaxial plate satisfying both relations (1) and (2): Relation (1) nxs>nys>nzs Relation (2) (nxsâˆ’nys)/(nxs+nys)&lE;005, where nxs is the maximum index of refraction and nys is the minimum index of refraction both in the plane of said substrate, and nzs is the index of refraction in the thickness direction of said substrate, and the out-of-plane retardation defined by {nzsâˆ’(nxs+nys)/2} is between âˆ’200 nm and âˆ’60 nm.