Patent ID: 7052747
Filing Date: 2006-05-30
Classification: C09K,G02B,G02F

Abstract:
1. A birefringent optical film comprising at least two kinds of polymer materials, and comprising a laminate of at least two polymer layers, each of which are formed of at least one of the two kinds of polymer materials, wherein Σ(Cn×Wn) is a summation of the products of Cn and Wn, and satisfies a numerical formula (1): where Cn and Wn denote respectively a photoelastic coefficient and a volume fraction of each polymer material, and the birefringent optical film comprises a first polymer material having a photoelastic coefficient value of at least 60×10 −8 cm 2 /N and a second polymer material having a negative value of photoelastic coefficient, wherein at least one of the polymer layers comprises the first polymer material having a photoelastic coefficient value of at least 60×10 −8 cm 2 /N and at least another of the polymer layers comprises the second polymer material having a negative value of photoelastic coefficient, and wherein nx, ny and nz of at least one of the polymer layers comprising the first polymer material having a photoelastic coefficient value of atleast 60×10 −8 cm 2 /N, satisfy numerical formulae (3) and (4): where nx and ny denote main refractive indices in two directions in the plane of the polymer layer and nz denotes a refractive index in the thickness direction of the polymer layer.