This work proposes a thermally rotatable grating that is based on hybrid-aligned cholesteric liquid crystals (HBA-cholesteric LCs). Experiments reveal that the HBA-cholesteric texture has a uniformly striped domain, which forms a grating, when the ratio of the cell gap to the helical pitch (d/p) is in the range of 2≤d/p≤3. The stripe direction of the HBA-cholesteric grating is predicted by the proposed vertically aligned LC layer model. The stripe direction of the HBA-cholesteric grating rotates continuously under thermal and electrical effects. Furthermore, the HBA-cholesteric grating has a larger rotational angle under the thermal effect (~101°) than under the electrical effect (~48°). Potential applications of the proposed thermally rotatable cholesteric grating for beam steering devices are emphasized.

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This work presents a simple compensation method for widening the viewing angle of transflective liquid-crystal displays (TR-LCDs). For an off-axis light, the slow axis of a biaxial film shifts linearly as the Nz factor is varied. By using this optical characteristic of a biaxial film, the broadband condition of broadband circular polarizers exactly holds over a full 80 degrees viewing cone, thus eliminating the off-axis light leakage to widen the viewing angle of TR-LCDs. Based on the proposed compensation method, the TR-LCDs theoretically have a wide spectral bandwidth and a viewing angle of 80 degrees for contrast-ratio (CR) >100:1 and >30:1 in transmissive and reflective modes, respectively. Experiments also show that the proposed TR-LCD has a viewing angle of over the entire 80 degrees and 65 degrees viewing cone in T-mode and R-mode, respectively, for CR>10:1. The proposed TR-LCD is highly promising for mobile display applications.

This work proposes a viewing angle switching (VAS) panel using twisted-nematic liquid-crystals (TN-LCs). Calculations reveal that, in a low voltage regime, a TN-LC behaves optically as a high twisted (∼90°) TN-LC in a vertical direction but as a low twisted (<25°) TN-LC in a horizontal direction. Additionally, a large difference in phase retardation of TN-LC from different viewing directions occurs at applied voltage 1.5Vth ⩽ V ⩽ 1.7Vth, where Vth is the threshold voltage of director reorientation. The large differences in the twisted angle and the phase retardation from different directions result in a large optically anisotropic behaviour of a TN-LC layer. The proposed VAS panel is developed using this large optically anisotropic behaviour of a TN-LC layer. Optical films are also used in the proposed VAS panel to enhance the optical anisotropy of a TN-LC layer. With the proposed panel, a display is only perceived clearly at a downward direction in a narrow viewing angle mode to ensure high privacy protection. Additionally, the proposed VAS panel achieves a high transmittance of 95%, making it highly promising for mobile device applications.