Polarization Analysis of a Black and White Supertwisted Nematic Liquid Crystal Display with Two Laminated Birefringent Films of Different Optical Axes

概要

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Film supertwisted nematic liquid crystal displays (F-STN-LCDs) with a single birefringent plastic film can be used for monochromatic black-and-white (B/W) LCDs, but their contrast ratio is inferior to that of Double layered (D-)STN-LCDs. By measuring the wavelength dependence of the ellipticity and azimuth in STN-LCDs, the F-STN cell conditions which increase the contrast ratio are obtained. The incident linearly polarized light needs to pass through the STN-LCDs without changing the state of its polarized light in all wavelength regions. Accordingly an optical compensating layer which has the same wavelength dependence for the ellipticity and azimuth as the driving STN cell, must be positioned between the polarizer and the driving STN cell. By laminating two birefringent films with different optical axes, the optical activity caused by the liquid crystal's twist structure is canceled, and the contrast ratio of the F-STN-LCDs increases from 10:1 to 20:1.
社団法人応用物理学会の論文
1993-02-15