Effects of the surface relief profile on liquid crystal aligning capabilities of laser-induced periodic surface structures

Abstract

The effect of the surface-relief profile on the liquid crystal (LC) alignment was studied using surface-relief gratings (SRGs) that were created on photo-resist (PR) films by holographic lithography. By measuring the anchoring energies of the LC molecules for various surface-relief profiles, we found that the LC molecules on the SRG-patterned PR (SRG-PPR) substrate had a large anchoring energy for a short SRG period and/or a large SRG depth. The anchoring energy of LC molecules on the SRG-PPR substrate was obtained from the analyzer-angle-dependent transmittance of the [Rubbed PI/LC/SRG-PPR] type, 90 degrees-twisted nematic liquid crystal (TNLC) cell prepared using a rubbed polyimide substrate and an SRG-PPR substrate with one of four different SRG periods (or an SRG-PPR substrate with one of three different SRG depths) as the front and the back alignment layers.