Patent ID: 8178601

Claim:
A polymer film, comprising: a wavelength dispersion regulator represented by formula (I): wherein R 1 and R 2 each independently represents a hydrogen atom, an alkyl group or an aryl group, provided that both R 1 and R 2 are not hydrogen atoms at the same time; and R 3 and R 4 each independently represents an electron-withdrawing substituent, and R 1 and R 2 , or R 3 and R 4 may be bonded together to form a ring, and wherein the polymer film has a retardation value that satisfies the following formulae (1) and (2): 70 nm≦R th (548)≦300 nm Formula (1) R th (628)<R th (548)<R th (446) Formula (2) wherein Rth(λ) represents a retardation value expressed in nm in a film thickness direction measured at a wavelength of λ nm, and wherein the polymer film further comprises a light-fastness improving agent represented by formula (II): wherein X 1 represents —NR 4 —, —O— or —S—; X 2 represents —NR 5 —, —O— or —S—; X 3 represents —NR 6 —, —O— or —S—; R 1 , R 2 and R 3 each independently represents an alkyl group, an alkenyl group, an aryl group or a heterocyclic group; and R 4 , R 5 and R 6 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group.