Patent ID: 8496848

Claim:
A birefringent film which comprises: a first compound having a proton-accepting group and a first structure giving anisotropy in refractive index; and a second compound having a proton-donating group and a second structure giving anisotropy in refractive index, wherein said proton-accepting group of the first compound and said proton-donating group of the second compound are intermolecularly associated to form a monodomain, wherein the proton-accepting group is at least one group selected from the group consisting of carbonyl group and 6-metribered heterocyclic ring containing one nitrogen atom (the heterocyclic ring can be substituted with an alkyl group of 1 to 12 carbon atoms, an alkenyl group of 1 to 12 carbon atoms, an alkynyl group of 1 to 12 carbon atoms or a 5-membered or 6-membered ring and can he condensed with other ring), wherein the proton-donating group is a carboxyl group, wherein the first structure or the second structure is a rod-like structure or a disc-like structure; and wherein the film contains a liquid crystal phase.