当代显示技术 第一章(16)

当代显示技术 第一章

where we have defined the direction of the LC as the z-axis.Note that this is different from a LC cell. The averaging over φis zero. S is a measure of randomness of n. n is distributedabout the z-axis in a cone. Thereforeπ1π2S = ∫(3cosθ 1)f(θ)sinθdθ/∫f(θ)sinθdθ200

where f(θ) is the distribution function of θ.

Check: if f=constant, i.e. the director is randomly distributed,

S = 0

If f(θ) = δ(0), i.e. the director is perfectly pointing in the samedirection,

S = 1.

Maier-Saupe Theory shows that in general yTS = 1 T cl β