Patent attributes
A negative birefringence film prepared from a poly(aryletherimide) which is the reaction product of a dianhydride and a diamine, where the dianhydride is 4,4′-[4,4′-(p-phenyleneoxy)isopropylidene]bis(phthalic anhydride) (BisADA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), 4,4′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride (BPEDA), 1,4-bis(3,4-dicarboxyphenyloxy)phenyl dianhydride (BPQDA), 3,3′,4,4′-tetracarboxylicbiphenyl dianhydride (BPDA), or 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA), alone or a mixture with one or more of:3,3′,4,4′-tetracarboxylicbiphenyl dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA); and where the diamine is 1,4-bis(2-trifluoromethyl-4-aminophenoxy)-2,5-di(t-butyl)benzene (BTBDA), 3,3′-dimethyl-4,4′-diamino biphenyl (OTOL), or mixtures thereof and wherein when a mixture of dianhydrides is present, they are present in a molar amount of between 99 to 1 (99:1) and 1 to 99 (1:99), 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.
