Patent ID: 7438957

Claim:
A negative birefringence film prepared from a poly(aryletherimide), wherein the poly(aryletherimide) is a reaction product of a dianhydride and a diamine, the dianhydide is a mixture of 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA) and 3,3′,4,4′-tetracarboxylicbiphenyl dianhydride, the molar ratio of the mixture is between 99 to 1 (99:1) and 40 to 60 (40:60), the diamine is selected from the group consisting of: 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether (6FODA), 4,4′-bis(4-amino-2-trifluoromethylphenoxy) benzene (6FOQDA), and 4,4′-bis(4-amino-trifluoromethylphenoxy)biphenyl (6FOBDA), and the film has a negative birefringence greater than 0.01, at a thickness of less than 15 μm, when the poly(aryletherimide) is solution cast or coated onto a substrate.