Liquid-ciystal displays, application

What do color-changing pens, bullet-resistant vests, and calculators have in common The chemicals that make each of them work are liquid ciystals. These chemicals find numerous applications you are probably most familiar with liquid ciystal displays (LCDs) and color-changing products, but these chemicals are also used to make superstrong synthetic fibers. 

In addition to depressing the liquid ciystal phase stability and often reducing melting points, a branched chain that introduces chirality increases viscosity. A high viscosity is not a problem in the non-display, thermochromic applications of chiral nematic materials. The steric effect of a chiral centre is well illustrated by difluoroterphenyl 5. 

Except these materials, ferroelectric liquid ciystals are another special class of ferroelectric polymer materials. They attracted ranch attention especially because of the application in the hquid ciystal display units. 

In linear optical processes the physical properties of the liquid ciystal, such as its molecular structure, individual or collective molecular orientation, temperature, density, population of electronic levels, and so forth, are not affected by the optical fields. The direction, amplitude, intensity, and phase of the optical fields are affected in a unidirectional way (i.e., by the physical parameters of the liquid ciystal). The optical properties of liquid crystals may, of course, be controlled by some externally applied dc or low-frequency fields this gives rise to a variety of electro-optieal effects which are widely used in mai eleetro-optieal display and image-processing applications as discussed in previous chapters. 

The commercial introductimi of Uquid ciystal polymers did not occur until 1984 since liquid crystal polymers could not be injection moulded till then (Tai-Shung 2001). Nowadays, liquid crystal polymers can be melt processed on conventional equipment at fast speeds with excellent replication of mould. Some of these LCPs, which constitute as simple conunon displays, are found in calculators or mobile phones. However, the numerous and increasingly sophisticated applications, relying uprm the use of liquid crystalline materials, require a complexity of superior properties to achieve improved devices performance. Currently, LCPs play a dominant role in a large part of the display technology. 

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