liquid crystal


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liquid crystal,

liquid whose component particles, atoms or molecules, tend to arrange themselves with a degree of order far exceeding that found in ordinary liquids and approaching that of solid crystals. As a result, liquid crystals have many of the optical properties of solid crystals. Moreover, since the order is not as firmly fixed as that of a solid crystal, it can be easily modified with corresponding changes in the optical properties; typically, a small electrical impulse darkens the crystal so that it is clearly visible against the lighter background of neutral crystals. An array of seven lozenges, each of which can be darkened by a separate impulse, can yield any digit. Thus, liquid crystal displays (LCDs) have become the most common means of producing visual readouts on such devices as digital clocks and electronic calculators. Some liquid crystals vary the color of the light that they reflect as their temperature changes. Since the colors reflected at any given temperature are quite specific, temperature can be measured by this means to an accuracy of 0.1°C;.

Bibliography

See D. Dunmur and T. Sluckin, Soap, Science, and Flat-Screen TVs (2011).

liquid crystal

[′lik·wəd ′krist·əl]
(physical chemistry)
A liquid which is not isotropic; it is birefringent and exhibits interference patterns in polarized light; this behavior results from the orientation of molecules parallel to each other in large clusters.

liquid crystal

A liquid crystal is a state of matter between liquid and solid (a "mesophase"). They change shape like a fluid but have the molecular alignment characteristics of a solid crystal. Liquid crystals are composed of organic, rod-shaped molecules that align in parallel, and the common types used in electronic displays are nematic, cholesteric and smectic.

Nematic LCs
Randomly positioned in parallel, nematic LCs react quickly to electric fields, which is why they are used in the great majority of LCD screens. Meaning "thread" in Greek, nematic LCs are monostable and return to their original alignment when the electric field is removed. See LCD.

Cholesteric LCs (Chiral Nematic LCs)
Cholesteric LCs are lined up in separate layers that form a spiral (helix). The displays retain their image without power (bistable) but are slower to react to changes than nematic screens. See cholesteric LCD.

Smectic LCs
Positioned side-by-side in layers, smectic LCs are bistable with similar attributes as cholesteric LCs. They retain their image without power and are slower to react than nematics. Smectic means "soapy" in Greek.

Discovered in the 19th Century
In 1888, liquid crystals were identified by Austrian botanist Friedrich Reinitzer and German physicist Otto Lehmann. Studying the cholesterol in carrots using a temperature-controlled polarizing microscope, they noticed that the light passing through the carrot compound (later known as "cholesteryl benzoate") exhibited the refraction effect of a solid crystal when heat was applied. By 1907, Germany-based Merck was selling "liquid and flowing crystal" chemicals.
References in periodicals archive ?
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Displaytech's patented Ferroelectric Liquid Crystal on Silicon (FLCOS) technology enables super-fast light switching at speeds 100 times faster than other liquid crystals, making possible the creation of microdisplays that deliver unsurpassed image resolution, power efficiency and ease of manufacturability.
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John Erdmann has joined the company as a Liquid Crystal Display (LCD) Staff Scientist.

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