Optical Design of a Normally-Black Twisted-Nematic Liquid Crystal Mode with Achromatic Dark State

Abstract

We propose an optical configuration to compensate dispersion characteristics in the dark state of a normally-black twisted-nematic (NB-TN) liquid crystal display (LCD). By optimization of parameters with a parameter space diagram (PSD), the high contrast-ratio (CR) over 500:1 could be obtained using two +A plates. Furthermore, excellent dispersion characteristics were also obtained in the bright state. We confirmed the performance of the proposed method and structure through both the numerical calculations and the experiments.

Keywords:

• liquid crystal display
• normally black mode
• twisted nematic

Acknowledgments

Work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea Government (MEST) (No. 2009-0078921).