Dichroic color sensitive polarizer

In this technique one standard polarizer is replaced by a dichroic color sensitive polarizer. For the yellow mode this results in a compensation of the off state and only slight influence on the on state. This mode of operation is called the neutral STN-mode (NSTN). For the complementary blue mode a compensation of the on state is achieved. A disadvantage of this technique is the low polarization efficiency of only (50-75)%. This limits its use to low-multiplexed displays with moderate requirements of contrast and viewing angle. 

A color difference ratio allows us not only to evaluate the usual luminance contrast (4.59), but also to evaluate a color purity and the color hue that makes the human eye very sensitive to the variation of CDR. Reference [170] demonstrates the increase by a factor of three of the number of distinguished rows of the display when evaluating by the colorimetry methods. This effect may be understood by the fact that the human eye is more sensitive to the color contrast than to the luminance one, as the hue and the chroma both contribute to the former. Color differences between on and off display states could be optimized by a special choice of polarizers [170-172], concentration of a dichroic dye (guest) in a liquid crystal matrix (host) [166, 173], using the reflective screens [173], etc. Colorimetric evaluations are very useful in the quality control of both the guest host and twist displays [172, 174]. 

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