Fundamental Limitations to the Viewing Angle of Liquid Crystal Displays with Birefringent Compensators

The limited viewing angle of twisted nematic (TN) active matrix liquid crystal displays is a major problem for applications in e.g. desk-top monitors. The range of viewing angles with acceptably displayed images can be extended by adding birefringent compensation layers to the display. Here it is shown that there are fundamental limitations to the viewing angle range that can be achieved in this way. It may turn out for a particular viewing angle that, (a) grey scale inversion cannot be remedied, and (b) increase of contrast leads to decrease of brightness. The existence of these limitations can be proven by analyzing the change in polarization of light propagating through the display. The vertical viewing angle range of the TN-effect suffers from both limitations. These limitations do leave significant room for improvement by using compensators. The horizontal viewing angle range is not fundamentally limited at all.