Liquid Crystal Displays
Joel E. Goldmacher and Joseph A. Castellano filed a patent application in 1966 for the first room-temperature liquid crystal display. Their work paved the way for today's 100 billion dollar industry in low-power LCDs, found in popular consumer goods such as laptop computers, televisions and cell phones.
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Liquid crystals are everywhere; they are in cell phones, laptop computers, games, MP3 players, and all manner of electronic devices. They are thin and lightweight and are run on little power. But what is it about liquid crystals that make all this possible?
The name liquid crystal sounds like an impossible contradiction. Liquids can flow and crystals are solid. How can there be a liquid crystal? In a normal crystal, the molecules have an orderly arrangement. In a liquid, the molecules are jumbled and disordered. Liquid crystals, on the other hand, have molecules that can flow, but that also have an orderly arrangement.
There are several types of liquid crystals, but all of them contain molecules that are linear and polar. Linear molecules have atoms arranged generally along a line, so they are considerably longer than they are wide. A polar molecule is one in which the electrons are distributed unevenly, leaving certain regions with a slight positive electrical charge and other regions with a negative charge. The charges make the ends of the molecules behave somewhat like the poles of a magnet, and the molecules are attracted to each other. If the molecules have a suitable shape, they will line up. No permanent attachments are formed between molecules, so the material does not solidify.
Liquid crystals are typically long, thin organic molecules that change orientation in an electric field. The most common type of liquid crystal is the nematic liquid crystal.
More than 50,000 different liquid crystals are known.
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Excerpted with permission, ChemMatters
Copyright © 2005American Chemical Society