Liquid crystal display

A liquid crystal display (LCD) is a flat-panel display that forms images by controlling how much light passes through a layer of liquid crystals held between sheets of glass and polarizing filters. Liquid crystals are a state of matter between a solid and a liquid, whose molecules flow but stay partly ordered, so an electric field can change how they interact with light. LCDs became the dominant technology in computer monitors and television sets and are also used in calculators, watches and phones.

History of the liquid crystal display

Liquid crystals were discovered in 1888 by the Austrian botanist and chemist Friedrich Reinitzer, who was studying a cholesterol compound. He saw that it turned cloudy at one temperature and became a clear liquid only at a higher one. He wrote to the German physicist Otto Lehmann, who confirmed that this was a distinct state of matter and noted that light can travel through it in two different ways, a property known as birefringence.

The field then stayed quiet for decades. Display research took off in the early 1960s, helped by the French physicist and Nobel laureate Pierre-Gilles de Gennes, who showed that applying voltage to liquid crystals controls their orientation and therefore the passage of light.

At the RCA Laboratories, George Heilmeier and Richard Williams published a report in 1963 suggesting liquid crystal materials for displays. Heilmeier’s group first used a method called dynamic scattering, in which an electric charge rearranges the molecules so that they scatter light. The team judged that LCD television was many years away and concentrated on digital clock and watch displays instead. In 1968, RCA recognized Heilmeier with its David Sarnoff Award, and he is credited with setting in motion the use of LCDs in calculators, watches, computers and other instruments.

The twisted nematic effect, which became the basis of practical LCDs, has a shared history. The Lemelson-MIT Program credits James Fergason with inventing the improved twisted-nematic version in 1969. An EBSCO overview instead credits the Swiss physicist Martin Schadt at Hoffmann-La Roche with discovering it in the early 1970s, usually dated to 1971, while Fergason’s International Liquid Xtal Company patented it in the United States at the same time. Schadt himself wrote in Nature Electronics that the discovery allowed liquid crystal displays to become a practical and ubiquitous technology. Licensing the patents let manufacturers build the calculators and wristwatches that brought LCDs to consumers, and LCD televisions later overtook cathode ray tube sets.

How a liquid crystal display works

An LCD has a layer of liquid crystals between two glass plates, each coated with a transparent conductor. Polarizing films on the outside of the plates filter light, and they are turned 90 degrees to each other. With only the filters in place, light would be blocked, but the liquid crystals, which twist across the gap, can rotate the direction of polarized light so that it passes.

The voltage across each part of the layer controls how the crystals are oriented, and therefore how much light gets through. At intermediate voltages some light passes, which produces shades of gray. Color images are made from grids of tiny pixels, each combining red, green and blue light.

Simple displays such as those on calculators and watches have no light source of their own. Light enters the display, bounces off a reflective surface behind it and returns through the crystals. Larger color displays need a separate light behind the panel, and light-emitting diode backlighting is now a common choice, which is one reason the technology is closely tied to LED lighting.

Types of liquid crystals and displays

Liquid crystals can exist in several phases. In the smectic phase the molecules form layers, while in the nematic phase the layers disappear but the molecules remain aligned along a common direction. LCDs generally use rod-shaped, or calamitic, molecules in the nematic phase, which lighten or darken the screen as their alignment changes.

Displays can be sorted by how they get their light. Reflective, usually monochrome panels serve calculators and watches, while backlit color panels serve monitors and televisions. Researchers are also working on versions that respond faster and can be seen clearly from wider angles.

Applications of liquid crystal displays

LCDs appear in televisions, computer monitors, laptops, phones, calculators and watches. EBSCO also lists temperature monitoring among their uses. In 1981 the U.S. space agency NASA built a prototype stereoscopic head-mounted display from commercial Sony LCD television screens and special optics, an early step toward virtual reality headsets.

Advantages and disadvantages of liquid crystal displays

An EBSCO overview describes LCDs as energy-efficient, low-cost displays that can reach high resolution, which helps explain how they displaced older cathode ray tubes. They are thin, light and available in sizes from a wristwatch face to a wall-sized television.

The technical challenges are real. Because a liquid crystal exists only between its melting and clearing temperatures, designers must find materials that stay in that state across the temperatures where the device will be used. Improving one property, such as color or power use, can worsen another, so some displays blend several compounds. Response time and viewing angle are continuing areas of research. Discarded displays also add to electronic waste.

LCD vs. OLED

An organic light-emitting diode display works differently. The U.S. Department of Energy describes an OLED as a solid-state device with a thin carbon-based semiconductor layer that emits light when current passes through it. An LCD instead modulates light supplied by a backlight or by ambient light. The two technologies compete in televisions and phones, and each has its own balance of cost, brightness, lifetime and thickness.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 4, 2026Researched and drafted with AI assistanceReport an issue