ADHESION ENHANCEMENT AND LAMINATION OF POLYIMIDE FILMS

Fully imidized polyimide films were joined together in a lamination pr ocess to form a structure that is flexible and has superior thermal st ability. This profess was demonstrated using the commercially availabl e films Kapton(R) H and Upilex(R) S, as well as spuncast and thermally imidized pyromellitic dianhydride/4-amino phenyl ether (PMDA-ODA) fil ms. When any of these films without prior surface treatment, were plac ed together and laminated, the interface was very weak, always with a fracture energy G(c) < 10 J/m(2) as measured by a T-peel test, However , we were able to form a strong laminate structure by modifying the su rface of the base film, causing the region within 2000 Angstrom of the surface to convert to polyamic acid. We subsequently coated this surf ace modified base film with a thin layer of poly 4,4'-oxydiphenylene o xydiphthalimide (ODPA-ODA), a polyimide with T-g = 270 degrees C, and laminated two such surface clad films together at 350 degrees C, For t he case of the Kapton(R) H films, the interfacial fracture energy was too large to be measured with the T-peel test (G(c) greater than or eq ual to 1300 J/m(2).) The ODPA-ODA clad Upilex(R) S films had a G(c) = 440 +/- 80 J/m(2). The ODPA-ODA can also be used to bind sequentially spuncast layers together, In this case it is applied as a thin layer o nto a fully imidized PMDA-ODA layer before deposition and thermal imid ization of a second PMDA-ODA layer, This interlayer increased the frac ture energy by about an order of magnitude a with the exact amount of increase dependent upon the molecular weight of the interlayer and the annealing temperature.