Defect-free twisted-nematic cells with low pretilt using chiral polyimide surfaces

The authors have demonstrated a technique for rodlike liquid crystal alignment using polyimide films with chiral carbons in the side chains. The authors succeeded in lifting degeneracy of two twisted configurations in the 90°twisted-nematic cells, even though the pretilt angle in the cell with rubbed polyimide (PI) surfaces is low (≤1°). This phenomenon is due to chirality of molecular level on the PI surfaces, which is transferred to the bulk and acts as a kind of symmetry breaking powers.