*6.4.1 OFF-state transmittance (scattering) (*T*OFF)*

In the absence of field, i.e. OFF state, the directors of LC droplet are randomly aligned. In this situation, most of the light incident normal to the film surface gets scattered giving opaque appearance to the film. The reason behind this is the mismatch of RI (a) between two adjacent droplets, (b) between a LC droplet and polymer and (c) within a LC droplet [135]. The OFF-state transmittance of a PDLC film depends on the birefringence of the LC. To minimize the value of OFF-state transmittance, the difference between LC extraordinary and ordinary refractive indices *Δn* ¼ *ne* � *no* must be as large as possible.

*An Overview of Polymer-Dispersed Liquid Crystal Composite Films and Their Applications DOI: http://dx.doi.org/10.5772/intechopen.91889*
