Patent ID: 7501165

Claim:
A retardation film consisting of a single-layer film in which a birefringent chain polymer is oriented, the polymer having as a side chain (a), a group represented by the following general formula (I), the retardation film having a smaller in-plane retardation at a shorter wavelength lying within a range of at least 450 to 650 nm, and having a larger in-plane retardation at a longer wavelength relative to the shorter wavelength lying within a range of at least 450 to 650 nm: wherein two oxygen atoms are bonded to atoms constituting a main chain, respectively; and R 1 and R 2 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aromatic group, and wherein at least either R 1 or R 2 is an aromatic group, and the aromatic group(s) represented by R 1 or/and R 2 is (are) arranged in a direction such that the planar structure thereof is substantially orthogonal to a virtual line obtained by connecting the two oxygen atoms.