US Patent 7713595 Optical compensation films produced by a carrier-web-casting process

A method of forming an optical compensation film includes coating one or more first layers and one or more second layers onto a carrier substrate, and stretching the first layers and second layers simultaneously. The one or more first layers include a polymer having an out-of-plane birefringence (Δnth) not more negative than −0.005 and not more positive than +0.005, and the one or more second layers include a polymer having an out-of-plane birefringence more negative than −0.005 or more positive than +0.005. The overall in-plane retardation (Rin) of the optical compensation film is greater than 20 nm and the out-of-plane retardation (Rth) of the optical compensation film is more negative than −20 nm or more positive than +20 nm.