We propose a switchable privacy display with liquid crystals for co-driver displays (CDDs) in vehicles. The display minimizes driver distraction while allowing the co-driver to enjoy infotainment content. By combining electrically controllable birefringence (ECB) and hybrid-aligned nematic (HAN) cells, we control the viewing angle of the display. Our device achieves an operating angle of 30°, effectively blocking the driver’s view while providing a wide viewing angle for the co-driver. It maintains excellent transmittance properties in privacy and public modes, with symmetric luminance characteristics. The versatility of the proposed display extends to various technologies like LCDs, OLEDs, and micro-LEDs. This switchable privacy display has the potential to enhance driver safety and infotainment experiences in vehicles.

We evaluated hexadecyltrimethylammonium bromide (HTAB) for liquid crystals (LCs) in layered ITO cells with various cell gap conditions. HTAB is a surfactant that can self-align vertically on the surface of indium tin oxide (ITO) substrates and induce homeotropic alignment of the LC molecules. For implementing RF devices with HTAB and LCs, we should consider limitations caused by the design conditions which are different from conventional liquid crystal displays such as cell gap. We quantified the concentration of HTAB ([HTAB]) that is necessary to form and maintain a sufficiently dense vertical alignment of 5CB (4-Cyano-4′-pentylbiphenyl). The required [HTAB] for full-homeotropic alignment was increased to the cell gap until it was too large to support the transfer of the surface alignment to the LC molecules, due to the weak anchoring nature of HTAB. We also showed the phase-change characteristic of the LC mixture related to [HTAB] for the design of RF devices driven by light or heat. This study may help to guide the development of new approaches to designing efficient RF devices that use LCs.

We evaluated hexadecyltrimethylammonium bromide (HTAB) for use in radio frequency (RF) applications in which liquid crystals (LCs) are used in layered structures that have various cell gap conditions. HTAB is a surfactant that can self-align vertically on the surface of indium tin oxide (ITO) substrates, and can induce homeotropic alignment of the LCs. For implementing RF devices with HTAB and LCs, we should consider limitations caused by the design conditions which are different from conventional liquid crystal displays such as cell gap. We quantified the concentration of HTAB ([HTAB]) that is necessary to form and maintain a sufficiently dense vertical alignment of 5CB (4-Cyano-4'-pentylbiphenyl). The required [HTAB] for full-homeotropic alignment was proportional to the cell gap until it was too large to support the transfer of the surface alignment to the LC, due to the weak anchoring nature of HTAB. We also showed the phase-change characteristic of the LC mixture depended on [HTAB] for the design of RF devices driven by light or heat. This work may help to guide the development of new approaches to designing efficient RF devices that use LCs.