Regularity and Narrowness of the Intervals of the Microgrooves on the Rubbed Polymer Surfaces for Liquid Crystal Alignment

It has been proved that genuine microgrooves on the rubbed polymer surfaces for liquid crystal alignment have very regular and narrow intervals. The minimum mean interval, 0.03 μm, is observed by field-emission scanning electron microscope (FE-SEM) after staining the polyimide alignment layer with ruthenium tetroxide (RuO4) at room temperature. Its coefficient of variance is 14.7%. Results on Atomic Force Microscope (AFM) measurements essentially coincide with that of FE-SEM. On the other hand, microgrooves of the poly(amic acid) which has poor ability to let the liquid crystals align, have less regular and wider intervals than polyimide. Five other polymers were also observed in the same manner. Non-destructive staining at room temperature and the existence of heavy metal compound on and just beneath the surface may make possible observation of the real topography of the rubbed polyimide surface. It is also emphasized from dichroic ratio measurements that observation without any distortion of the samples is very important.