SURFACE ANISOTROPY OF POLYIMIDE FILM IRRADIATED WITH LINEARLY POLARIZED ULTRAVIOLET-LIGHT

Using polarized infrared (TR) absorption, we have investigated the sur face anisotropy of a poly [4, 4'-oxydiphenylene-pyromellitimide] (PMDA -ODA) film that arises from anisotropic decomposition of the polyimide chain during irradiation with linearly polarized ultraviolet (LPUV) l ight. To monitor the surface anisotropy, we designed the sample struct ure so that the polyimide films decomposed uniformly over the entire f ilm thickness. The: surface anisotropy has a maximum at an irradiation energy of 105 J/cm(2). For PMDA-ODA, the maximum surface anisotropy i s significantly smaller than the surface anisotropy generated by rubbi ng. By analyzing the irradiation energy dependence of an LR absorption band, we: found that the decomposition rate of the polyimide chain or iented parallel to the polarization direction of the LPUV light is gre ater only by similar to 23% than that oriented perpendicular to it. Th is is the reason for the small surface anisotropy induced by the LPUV light irradiation. (C) 1998 American Institute of Physics.