LCDs (liquid crystal displays) are used in televisions, laptop computers, and many portable electronic devices. The properties of liquid crystals were first discovered in 1888 by Friedrich Reinitzer. He was measuring the melting point of a cholesterol-based substance and noticed that it had two melting points: it melted at 293°F (145°C) to give a cloudy, gluelike liquid, then again at 352°F (178°C) to give a clear liquid.
Otto Lehmann, an expert in crystal optics, studied these phases and found that the cloudy liquid had similar properties to the solid crystal. In the solid crystal, the molecules are lined up neatly and in parallel. In the cloudy liquid, the molecules can move around. However they tend to line up like in the solid crystal, reflecting light to appear cloudy. Lehmann named the liquid fliessende Kristalle, or liquid crystal.
In 1968 George Heilmeier (b. 1936) led a group at the Radio Corporation of America to develop the first LCD. They used the dynamic scattering method, in which an electrical charge is applied to a liquid crystal, causing the molecules to rearrange and scatter light.
The LCD was made up of a liquid crystal substance sandwiched between two polarized filters. When electricity is applied to the LCD, the electric field causes the molecules to twist. Light passes through the first filter, rotates around the liquid crystal, and passes through the second filter to produce a light spot on the reflecting screen. When no electric field is present, the molecules cannot twist, and light does not pass through, resulting in a dark spot on the screen. How much light can pass through depends on the degree to which the molecules are twisted.
