Viewing Direction-Tunable Light Control Using Liquid Crystal Film for Simultaneous Implementation of Automotive Display Visibility and Safety

Automotive displays provide driving or traffic information and mutual communication with the external environment. With the expansion of technology, there are multiple demands for the expansion of functions, such as providing simple driving and traffic information in addition to entertainment such as movies and games. However, the technology implementation in this regard is limited due to the challenges in ensuring safety and conformance to legal regulations. Therefore, technologies that are capable of providing convenience to occupants while ensuring safety by preventing driver distractions are required. This paper presents a method for controlling the viewing angle using twisted nematic liquid crystal (TN-LC) materials for automotive display applications. A TN-LC film with a polarizer was laminated on a display panel, where the absorption axes of the added and existing top polarizers were mutually perpendicular. In normal mode, in the absence of an applied electric field, the light emitted from the display panel was transmitted over the entire viewing cone, such that wide viewing angle characteristics could be achieved. In the privacy mode, with a low applied electric field, the light emitted toward the driver side could be blocked while the light emitted toward the passenger side. We achieved switching between the normal and privacy modes with a change in viewing-angle-dependent retardation through the reorientation of the TN-LC molecules under crossed polarizers by applying a vertical electric field. Moreover, light leakage at high polar angles in the privacy mode was eliminated by employing a specialized optical compensation film. This device can serve as a potential candidate for providing convenience, e.g., information and safety, in automotive display applications.