Electro Optical Characteristics of High-Pretilt Twisted Liquid Crystal pi-Cells

Abstract

We studied the transformation between the twist state and bend state of a twist-stabilized optical compensated bend (TOCB) nematic liquid crystal cell. The theoretical calculation results show that when driving the TOCB cell, the bend-to-twist transition results in an optical bounce in the optical transmittance. To eliminate the optical bounce, the substrate pretilt angle should be larger than a critical value (26°). The TOCB cell with a critical pretilt angle of about 26° does not require a warm-up voltage, but achieves high transmittance, fast response, and a wide viewing angle.

Equilibrium configurations in a nematic pi-cell under an electric field

“…In 1984 (Bos and Koehler/Beran, 1984), demonstrated that the pi-cell can be used for fast optical-switching devices in the V-state, also known as optically compensated bend (OCB) mode. Since then, many liquid crystal display devices with fast response time, large viewing angles, and high transmittance have been proposed based on the pi-cell (Yu and Kwok, 2004;Jhun et al, 2006;Wu et al, 2012;Lin et al, 2015;Zhou et al, 2017).…”