Patent ID: 7586571

Claim:
A composite birefringent member comprising: a first birefringent layer; and a second birefringent layer, the second birefringent layer being formed on at least one surface of the first birefringent layer, wherein a value of Δnd x /Δnd 550 and a value of Rth x /Rth 550 of the composite birefringent member as a whole are different from each other in a wavelength range from 400 to 800 nm except 550 nm, and the composite birefringent member satisfies at least one of the following requirements (a) and (b): (a) the second birefringent layer is formed of at least one non-liquid crystal polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamide imide and polyesterimide; and (b) Δnd and Rth of the composite birefringent member satisfy formulae (I) and (II) below, Δnd 400 /Δnd 550 <1 (I) Rth 400 /Rth 550 >1 (II) and Δnd of the first birefringent layer>Δnd of the second birefringent layer, and Rth of the first birefringent layer<Rth of the second birefringent layer, In the above, Δnd x and Rth x respectively represent Δnd and Rth at a wavelength of x nm, Δnd 550 and Rth 550 respectively represent Δnd and Rth at a wavelength of 550 nm, Δnd is (nx−ny)×d, and Rth is (nx−nz)×d, where nx, ny and nz respectively represent refractive indices in an X-axis direction, a Y-axis direction, and a Z-axis direction in the composite birefringent member, the first birefringent layer and the second birefringent layer, with the X-axis direction being an axial direction exhibiting a maximum refractive index within a plane of the composite birefringent member, the Y-axis direction being an axial direction perpendicular to the X axis within the plane, and the Z-axis direction being a thickness direction perpendicular to the X axis and the Y axis, and d represents a thickness of the plane of the composite birefringent member.