liquid crystal

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, because its atomic or molecular order is not as firmly fixed as that of a solid crystal, a liquid can be easily modified by electromagnetic radiation, mechanical stress, or temperature, with corresponding changes in its optical properties. In typical early uses, a small electrical impulse darkened the crystal so that it was 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. Such liquid crystal displays (LCDs) have become the most common means of producing visual readouts on such devices as digital clocks and electronic calculators. Color LCD panels consisting of millions of pixels, or picture elements, each containing three subpixels (one each for red, blue, or green, with the color produced by a filter), are used as viewing screens in television sets, computer monitors, and other devices; the light source in LCD panels is now typically an LED backlight. LCDs have significantly lower energy requirements than the cathode-ray tubes formerly used in television sets and computer monitors. 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℃.

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

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