| 摘要 |
PURPOSE:To reduce the angle dependency of an optical path difference by setting the main refractive index n3 of the phase difference plate in the thickness direction between the main refracting indexes n1 and n2 in direction parallel to the surfaces of the phase difference plate. CONSTITUTION:The phase difference plate is formed by placing an anisotropic sheet or film made of resin whose characteristic birefringent value is positive and an anisotropic film or sheet made of resin whose characteristic birefringent value is negative one over the other so that the directions wherein the degrees of orientation are large are substantially at right angles to each other. Then n1 < n3 < n2, where n1 and n2 are the main refractive indexes in the direction parallel to the surfaces of the phase difference plate and n3 is the main refrac tive index in the thickness direction. The angle dependency of the phase differ ence plate satisfying the relation n1<n3<n2 is improved remarkably and, spe cially, when n1-n3 = n3-n2, the incidence angle dependency of the optical path difference is specially small. |
