Pochi YEH

Electrical and Computer Engineering, University of California, Santa Barbara, CA 93016, U.S.A.

(Received July 10, 2008; Accepted December 15, 2008)

This paper elucidates the physical origin of leakage of light in the dark state of liquid crystal displays (LCDs) and describes birefringent thin film compensators to mitigate the problems. There are two fundamental sources of leakage of light in LCDs. They are the leakage of light through a pair of ideal crossed polarizers, and the leakage of light due to elliptical state of polarization after transmitting through the liquid crystal (LC) cell. The leakage of light in the dark state leads to poor contrast ratios and color instability, particularly at large viewing angles. The paper then describes the employment of sixth-wave (λ/6) plates as well as various wave plates that function as birefringent compensators for eliminating the leakage of light in LCDs.

Key words: birefringence, polarizers, uniaxial, biaxial, wave plates, thin films, liquid crystal displays