Introduction to liquid crystals

Liquid crystals have been widely used for many years in electro-optic displays. We describe here selected, fundamental properties of liquid crystals which make them useful in electro-optic appli- cations. Our aim is to provide the background material needed for understanding the guest-host systems described in Chapter 10.2 and the polymer-dispersed liquid crystal films discussed in detail in Chapter 10.3. We also review the major liquid crystal (LC) electro-optic effects which have been used in display applications and comment on their potential advantages and disadvantages for large area transmittance control. For more information, we refer the reader to several excellent texts1-3 which discuss in detail the fundamentals of LC physics and chemistry and the basic electro- optic effects observed in these materials. Comprehensive reviews of the material characteristics and electro-optic effects most useful for LC displays have also been published.4,5