Crystal Versatility

A big picture window that turns opaque at the flick of a switch, giving those inside instant shade and absolute privacy. A wall clock, no thicker than a pane of safety glass, that flashes the hour without any tick or hum. A small screen that records the face of a telephone caller even when no one is home to pick up the receiver. Such items may seem like excerpts from a catalogue of 21st century technology, but RCA scientists say that they are already within reach. And they are only a small sampling of the practical new uses that are promised by the chemical phenomenon known as liquid crystals.

These organic compounds made of carbon, nitrogen, hydrogen and oxygen resemble ordinary liquids. Yet their orderly molecular structure is similar to that of solid crystals such as diamonds, mica and quartz. The crystals themselves are not new, but it was only recently that scientists discovered that an electrical charge makes them light-reflecting; the higher the voltage, the greater the reflecting power. At first, this "electro-optical effect" could be shown only in the laboratory, since the crystals reacted to electricity only at certain temperatures. Now, after trying more than 100 compounds, RCA scientists have produced a crystal that responds to even small amounts of electricity throughout a temperature range from 20DEG F. to more than 200DEG F.

Animated Display. To demonstrate their compound's wide capability, RCA researchers sandwiched a thin film of the liquid crystals between two sheets of glass. The inner surface of each sheet was coated with a transparent electrical conducting material. When a small negative charge was applied to one sheet and a positive charge to the other, so much turbulence was caused inside the liquid crystals' molecular structure that the film turned instantly opaque. Next, in a more complicated display, the conducting surfaces were divided into a mosaic of squares, each separately linked to the external power source; this enabled the scientists to send the electrical current into selected areas of the liquid-crystal film. By directing the electrical charges into the proper combination of squares at just the right moment, the RCA men were able to form a rapid succession of numbers--in much the manner of an animated outdoor advertising sign.

Such uses of liquid crystals' electro-optical potential could be applied soon to a whole new generation of sports scoreboards, traffic-control signs, stock-market tickers, and instrument panels in cars and aircraft. Besides drawing very little power, the devices would work perfectly well in ordinary daylight, since liquid crystals reflect external light rather than produce their own. In the more distant future is a liquid-crystal TV screen. The entire television set, say the RCA researchers, not only would be as thin as a book, but could be watched even in the glaring light of a sun-drenched beach.

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