Optical and electro-optic properties of polymer-stabilized blue phase liquid crystal cells with photoalignment layers

A comparative study of the optical and electro-optic properties of polymer-stabilized blue phase liquid crystal (PS-BPLC) cells with photoalignment layers and rubbing alignment layers is performed. The optical microscope (OM) images of the photoaligned and rubbing-aligned cells depict that they have uniform PS-BPLC textures, while the post-processed OM images of the two cells reveal that the former has a more uniform PS-BPLC texture than the latter. The relatively uniform PS-BPLC texture in the photoaligned cell is verified by the reflective spectra of the two cells. The voltage-dependent transmittance curves and time-dependent transmittance curves of another two photoaligned and rubbing-aligned cells with in-plane-switching (IPS) electrodes indicate that the contrast ratio of the former is 41% larger than that of the latter, and the operation voltage (response time) of the former is 11 (10) % smaller than that of the latter. This result arises from the fact that the photoaligned cell with the IPS electrodes exhibits a relatively uniform PS-BPLC texture and relatively weak voltage-shielding effect. Therefore, the photoalignment can improve the electro-optic properties of PS-BPLC cells with alignment layers. The photoaligned and rubbing-aligned cells have no thermal hysteresis in low voltage regions due to the uniform surface alignment layers, and exhibit very low voltage-induced hysteresis in high voltage regions owing to no thermal hysteresis. Briefly, uniform surface alignment layers can eliminate the thermal hysteresis of PS-BPLC cells, suppressing their voltage-induced hysteresis. In other words, the hysteresis of PS-BPLC cells with alignment layers is independent of alignment methods as long as the alignment layers have strong surface anchoring energy. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement