Polarization analysis of a twisted nematic liquid crystal display using a Poincare sphere

Twisted nematic liquid crystal displays (TN-LCD) are being widely adopted for personal computers. Figure 1 shows the transmittance -voltage (T-V) characteristics for the normally - white mode of a first minimum TN display. Here the polarizer transmission axis is parallel to the liquid crystal (LC) alignment direction on the adjacent substrates (e-mode TN-LCD). Figure 2 shows the viewing angles. In the lower azimuth view, the T-V curve oscillates, causing gray scale image inversion. In the upper azimuth view, the transmittance at an intermediate voltage is high and the gray scale image washes out. In the right and left azimuth view, the T-V curve is almost the same as a normal view, giving a clear gray scale image. The symmetry of viewing characteristics has been investigated 1), and light propagation in the normal direction has been calculated using a Poincare sphere2. Light propagation for oblique viewing had not yet been examined. We investigated this using a Poincare sphere.