Optimization of retarder parameters for switchable privacy mode automotive displays under asymmetric viewing conditions

A switchable privacy mode (SPM) display should not be seen by a driver during driving (privacy mode), but it needs to be seen by the driver and a co-driver when a car is stopped (share mode). In this work, a SPM display was designed using a bottom twisted-nematic (TN) liquid crystal display (LCD) and a top in-plane switching (IPS) LCD where a half-wave plate (HWP) is located between the two LCD panels. The SPM display in front of the co-driver was considered, which is seen under asymmetric viewing conditions. The orientation of the slow axis, retardation dispersion, and biaxiality of the retarder were varied to maximize the SPM’s optical performance in the driver’s and co-driver’s viewing directions. Transmittance at the driver’s viewing direction can be reduced from 4.22 to 0.03% in privacy mode by replacing the positive dispersion retarder with a negative dispersion retarder.