Effect of working on the aligning capability of liquid crystals on the rubbed polymer surfaces

The washing effects on the liquid crystal (LC) alignment capability on the rubbed polyimide PI surface were investigated. The induced optical retardation from the nonwashing process on the rubbed PI surface is larger when compared with the washing processes; it is attributed to the removal of dust in the washing process. The generated pretilt angles in 4-n-pentyl-4′-cyanobiphenyl (5CB) from the nonwashing process on the rubbed PI surface are almost the same as that of the rubbed PI surface after washing process. The polar anchoring energy of the weakly rubbed PI surfaces is increased by the washing process; the washing effects are clearly observed. The surface order parameter S_S of 5CB for all washing processes is larger than that with the nonwashing process; it is attributed to the washing process. Consequently, we suggest that the LC aligning capability is largely attributed to the washing effects.