Competitive effect of grooves and photoalignment on nematic liquid-crystal alignment using azobenzene polymer

Effect of an anisotropic photoalignment layer and microgrooves on nematic liquid-crystal (LC) alignment was quantitatively examined using azobenzene polymer thin film with surface relief grating (SRG) of about 1 µm pitch. The SRG with various modulation depths was treated with polarized light irradiation to align molecules at 45° from the groove. Nematic LC molecules, 4-n-pentyl-4-cyanobiphenyl, orient to the photoaligned direction on the SRG being shallower than 200 nm. The orientation rather sharply deviates from the photoaligned direction toward the groove direction with increasing grating depth into the deeper region than 200 nm and finally becomes parallel to the grooves on the SRG of 400 nm deep. This behavior is successfully simulated by the consideration of anisotropic surface interaction and an elastic energy of LCs.