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What is liquid crystal
A thermodynamic stable phase characterized by anisotropy of
properties without the existence of a three-dimensional crystal
lattice, generally lying in the temperature range between the
solid and isotropic liquid phase, hence the term mesophase. |
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| Classifications |
— According to structure
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• Nematic mesophase:
Liquid crystals are characterized by long-range orientational
order and the random disposition of the centers of gravity
in individual molecules. Nematics may be characterized
as the simplest spontaneously anisotropic liquids. Nematic
phases are composed of rod-shaped molecular aggregates
that are arranged with parallel but not lateral order.
• Cholesterics liquid crystal :
Also known as Chiral Nematic. Similar to the nematic phase,
however, in the cholesteric phase, molecules in the different
layers orient at a slight angle relative to each other
(rather than parallel as in the nematic). Each consecutive
molecule is rotated slightly relative to the one before
it. Therefore, instead of the constant director of the
nematic, the cholesteric director rotates helically throughout
the sample. Many cholesterol esters exhibit this phase,
hence the name cholesteric.
• Smectics:
The molecules organize themselves into layers. The smectic
phases form a one dimensional periodic lattice in which
the individual layers are two dimensional liquids. Now
12 different smectic phases have been identified.
— According to structure
material—
• Thermotropics:
Liquid crystal molecules which exhibit temperature dependent
liquid crystalline behavior.
• Lyotropics:
Materials in which liquid crystalline properties appear
induced by the presence of a solvent, with mesophases
depending on solvent concentration, as well as temperature.
It shows different liquid state in different consistency. |
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| Characteristics
of liquid crystal |
Liquid crystal has not only the directivity like
general crystal but also the flowability like liquid
and its direction can be controlled by electric field
or magnetic field. |
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| Liquid crystal
display (LCD) |
• Twisted Nematic Liquid crystal display
¡±TN type¡± for short
• Polymer dispersed liquid crystal liquid
crystal display: ¡°PDLC type¡± for short. |
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