T. Kyu Disclosure 214 U.S. Patent not yet issued This invention relates the development of birefringence-free optical adhesives and films using a birefringence compensation technique.
Most polymers are optically anisotropic because of the nature of the long macromolecular chains.
Depending on the chemical structure, a macromolecule could have a positive or negative birefringence. Polymers with aromatic compounds in the main chain generally have positive birefringence due to large polarizability along the chain axis compared with that in the transverse direction. This induced birefringence causes undesirable effects in many optical applications such as laser disks, electronic devices, etc. To minimize the birefringence of polymeric films and adhesives, it is customary to blend polymers with opposite anisotropy. However, the polymer pairs must be completely miscible, which is extremely difficult, if not impossible, to achieve.