US Patent 7438957 Poly(aryletherimides) for negative birefringent films for LCDs

A class of soluble poly(aryletherimides) (PAEIs) having flexible backbones, useful in the manufacture of polymeric optical films are disclosed. The poly(aryletherimides) are dissolved in organic solvents, such as ketones and ketone solvent mixtures and coated on variety of substrates such as triacetyl cellulose (TAC), to form clear thin-layer films which display negative birefringence. The thin films can serve as compensation layers in liquid crystal displays (LCDs), and can be combined with other types of optical films, such as polarizers, brightness enhancement films, or other compensation films, to from multi-layered films that are especially useful in the manufacture of LCDs.