Switchable Privacy Mode for Symmetrically Viewed Automotive Displays: Dependence on the Optical Parameters of the Retarder

A display featuring switchable privacy mode (SPM) is achieved by stacking a vertical-alignment (VA) liquid-crystal display (LCD) and an in-plane-switching (IPS) LCD. The SPM display is designed for a center information display (CID) of an automobile that is seen at symmetric viewing angles by the driver and passenger. A retarder is located between the VA and the IPS LCD to achieve SPM. The orientation, in-plane retardation, retardation dispersion, and biaxiality of the retarder are varied, and their effects on the optical quality in privacy and shared modes were investigated. The light to the driver's position could be blocked better after optimization of the retarder's parameters, minimizing the transmittance decrease in the passenger's viewing direction.