Nematic Phase LCD

The greatest advantage of a nematic phase liquid crystal substance is that it can bring about predictable controlled changes according to the electric current passed through them. All the liquid crystals are according to their reaction on temperature difference and also the nature of the substance.

Twisted Nematics, a particular nematic substance is twisted naturally. When a known voltage is applied to the substance, it gets untwisted in varying degrees according to our requirement. This in turn is useful in controlling the passage of light. A nematic phase liquid crystal can be again classified on the basis in which the molecules orient themselves in respect to each other. This change in   orientation mainly depends on the director, which can be anything ranging from a magnetic field to a surface with microscopic grooves. Classification includes Smectic and also cholesteric. Smectic can be again classified as smectic C, in which the molecules in each layer tilt at an angle from the previous layer. Cholesteric, on the other hand has molecules that twist slightly from one layer to the next, causing a spiral like design. There are also combinations of these two called Ferro-electric liquid crystals (FLC), which include cholesteric molecules in a smectic C type molecule so that the spiral nature of these molecules allows the microsecond switching response time. This makes FLCs to be of good use in advanced displays.

Liquid crystal molecules are further classified into thermotropic and lyotropic crystals. The former changes proportionally with respect to changes in pressure and temperature. They are further divided into nematic and isotropic. Nematic liquid crystals have a fixed order of pattern while isotropic liquid crystals are distributed randomly.  The lyotropic crystal depends on the type of solvent they are mixed with. They are therefore useful in making detergents and soaps.