Correlation between rub-induced grooves in a polyimide-treated substrate and microstructure of rubbing fiber: An atomic force microscopy study

Rubbed polyimide surfaces, which are used for liquid crystal alignment, generally exhibit microscopic grooves which lie parallel to the rubbing direction. Using atomic force microscopy we examined both the grooves and the fibers that create the grooves. We find that for a wide range of rubbing strengths, the microstructure of the grooves, as determined by their radii of curvature, correlates well with the microscopic topography of the fibers. This result indicates that the rubbing-induced topography depends on not only the characteristic rubbing strength, but on the structure of the rubbing fiber as well.