LCD Or Plasma - What's Your Pleasure? Understanding Modern Flat-Panel TV Technologies

Application Areas For Plasma

Plasma displays are found mostly in high-quality, large-format video systems. Their big size and video performance make them excellent for viewing DVDs, high definition or otherwise. Plasma is traditionally positioned at the high end sector of the market, where the issues of high cost, phosphor aging and high power consumption are secondary to performance and quality.

Looking a little farther into the future, it is clear that LCD will eat away at the plasma market by pushing it more and more into the very large sizes. The reason is simple: once the technology is under control, LCD fabrication is simpler and less costly.

Unless other innovations change the situation, plasma will remain limited to specific uses in the domestic area, essentially where a very large image is wanted without viewing from a close distance. The necessary viewing distance greatly limits its use.

The flickering problem associated with plasma panels also explains why the technology is of limited interest for computer use.

LCD Technology

A Promising Outsider

The term "liquid crystal" dates back not just to the last century, but the one before that - the phrase originated in 1889! And it comes to us not via electronics, but botany. However, it wasn't until 1968 that RCA became interested in the phenomenon and invented the first liquid-crystal display. In 1969, James Fergason discovered the twisted nematic (TN) effect. This was a fundamental discovery, since all the LCD displays we're familiar with are based on this principle of rotation of the plane of polarization. In 1973, George Gray invented the biphenyl liquid crystal, which made it possible to implement liquid-crystal solutions that were stable under normal pressure and temperature conditions. And as early as 1986, NEC produced the first portable computer with a Liquid Crystal Display (LCD). In 1995, LCD panels with large diagonal measurements - over 28" (71 cm) - began to be produced.

It's interesting to note that while plasma is associated with audiovisual applications, LCD came to maturity via computers and mobile devices. In that respect, it's an outsider where TV displays are concerned. But it has certain qualities that may well eventually make it the leader in that area too.

LCD, A Strange Operating Principle

The main difference between plasma and LCD technology is that LCD pixels don't emit any light. All the qualities but also all the faults of the technology stem from that key characteristic.

As with other technologies, an LCD pixel is made up of three sub-pixels in elementary colors. The operating principle is interesting though: the LCD doesn't emit light, but rather acts as a switch, which is why LCD displays need white backlighting. The light emitted by the backlighting passes through the liquid crystal and is then colored by a filter. Each sub-pixel has the same architecture - only the color of the filter changes depending on the pixel. The liquid crystal of each sub-pixel can be controlled electrically like a valve. More or less light is allowed to pass through the crystal to control how much red, green and blue is emitted for each pixel.