Disclosed is an optical multilayer comprising a polymeric substrate having
a non-zero out-of plane birefringence and an amorphous polymeric
overlayer that comprises an amorphous polymer having a Tg value above
160.degree. C. and having the sign of its out-of-plane birefringence
opposite to that of the polymeric substrate so as to provide a total
out-of-plane phase retardation of said optical multilayer of between -30
nm and 30 nm for wavelengths of light between 400 and 700 nm.