当代显示技术 第一章(15)

当代显示技术 第一章

Common LCDs are made with nematic, thermotropic and

calamitic (rod shape) liquid crystals.

Examples of common LC materials:

MBBA (p-methyoxybenzylidene-p’-butylaniline)

CH3

O -

- CH = N -- C4H9

However, most nematic LCDs are doped to have a twiststructure. TN, STN.

For any LC, we can describe the orientation of the moleculesby the director n. For the simplest case

n = n(z)

where z is distance perpendicular to the LC cell. The directorn is fully defined by the polar angle φ and the azimuthal angleθ. For a LC cell, the tilt angle is defined as 90-θ. It is the anglebetween the director and the x-y plane.For nematic LC, we can define an order parameter S todescribe the degree of ordering:S = 13cos2θ 12