POLYIMIDE FILM CONTAINING ULTRA-FINE PARTICLES

We have succeeded in fabricating a polyimide film with a molecular ali gnment superior to that obtainable by the conventional rubbing treatme nt. This phenomenon is realized by means of the dispersion of ultra-fi ne particles such as carbon and titanium dioxide in the polyimide prec ursor prior to the fabrication of the polyimide film and the rubbing t reatment. The molecular alignment was evaluated with birefringence and infrared dichroism measurements. Further experiments established that the adsorption of polyimide molecules on ultra-fine particles is a si gnificant factor in achieving a large orientational anisotropy. A mode l of the alignment is presented in which the rubbing treatment induces the particles to traverse the surface of the film, causing polyimide molecules adsorbed on them to be elongated in the rubbing direction. A potential application of oriented polyimide films is in the homogeneo us alignment of nematic and smectic liquid crystals.