The physics and display applications of liquid crystals

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Abstract
After a short introduction, the general characteristics of liquid crystals are reviewed, the three main classes of thermotropic liquid crystals are described and the concept of order parameters introduced. The phase behaviour of thermotropic liquid crystals is considered in some detail and the continuum theory, describing the static behaviour of liquid crystals, is introduced. Electro-optical effects in liquid crystals and display construction methods are then covered and the operating principles and performance of dynamic scattering, twisted nematic and dyed phase-change displays are reviewed and compared. Threshold and realignment mechanisms in liquid crystal displays are then treated in some detail followed by a consideration of the physics of their dynamical behaviour and response times. The physical properties governing the design of liquid crystal materials and pleochroic dyes are discussed in relation to display performance. The applications of simple displays are then reviewed and the need to multiplex complex displays established. The problems of multiplexing liquid crystals are outlined with comparison to light-emitting displays. The state of the art relating to complex liquid crystal displays is described and two-frequency multiplexing methods are briefly reviewed. Alternatives to conventional multiplexing are then discussed and optical addressing techniques using photoconductors and lasers are outlined. The concept of an integrated electronics display, having a layer of non-linear elements adjacent to the liquid crystal, is introduced and the state of the art is reviewed. Finally, a tentative look is taken at some of the developments the next ten years may bring concerning the display applications and physics of liquid crystals.