LASER ETCHED GRATINGS ON POLYMER LAYERS FOR ALIGNMENT OF LIQUID-CRYSTALS

Liquid crystal alignment layers are prepared using a noncontact method based on Inset ablation. Nonpolarized light from a KrF excimer laser at 248 nm is exposed through a phase mask to etch gratings of period 1 .1 mu m onto polyimide alignment layers. Twisted nematic cells were pr epared using one rubbed and one grating aligned surface, and azimuthal anchoring energies were found from measurements of the twist angles a s a function of grating depth. The measured anchoring energies agree w ith those predicted from the minimization of elastic strain energy whe n the liquid crystal directors at the surface are aligned parallel to the groove of the grating. This suggests that topographical rather tha n epitaxial alignment is achieved. (C) 1998 American Institute of Phys ics.