One Diode, Three Colors

Taiwan’s AU Optronics Corp. (AUO) demonstrated a prototype 2-inch LCD that saves battery power by eliminating the color filter, which can absorb as much as 70 percent of a backlight’s output. It uses a technology known as Color Field Sequential Technology, or CFST, which a number of panel makers are also developing.

Rather than construct full color at each pixel by fitting three subpixels with red, green, and blue filters, AUO multiplexes a single light-emitting diode (LED) to alternate rapidly from red to green to blue. The LED spends the same amount of time on each color, but it varies the intensity. The end result is color mix like that of a standard LCD, but with 2.5 times as efficient use of light, according to AUO. Trial production is slated for the second quarter of 2007.

A More Refreshing Display

Where the LCD fails relative to the rival plasma display is in its tendency to blur fast action, such as that of a hockey player making a slap shot. To overcome this shortcoming, some manufacturers are trying various electronic tricks. The latest one involves pumping the picture refresh rate to 120 hertz, up from the standard 60 Hz.

South Korea’s Samsung Electronics Co. exhibited the industry’s first 70-inch full HDTV with a video refresh rate of 120 Hz, which the company claimed was good enough to compete with plasma head-on. It will become available in the first half of 2007.

To get around the various shortcomings of both LCD and plasma panels, Toshiba Corp. and Canon, both in Tokyo, have formed a joint venture to develop and produce a technology called Surface-conduction Electron-emitter Displays (SED).

Like the familiar cathode-ray tube, the SED fires electrons at a phosphor-coated screen to generate spots of light. But rather than firing a single electron gun inside a large tube and steering the resulting beam to each pixel, the SED furnishes each pixel with its own tiny electron emitter.

An emitter is composed of a two electrodes a few nanometers apart. When a voltage of some 10 volts is applied to the electrodes, electrons tunnel between them, and some of them are scattered. These then accelerate through a 10-kilovolt electric field and finally strike the target phosphor on the inside of the glass plate.

The result is a high-resolution flat panel measuring just a few centimeters thick that consumes less power than a cathode-ray tube. According to Canon and Toshiba, it also beats the LCD and plasma displays by delivering a more realistic image with more natural colors and a faster video response.

Certainly the 36-inch SED prototype, first exhibited in 2004, and the 55-inch prototype demonstrated this month both had impressive picture quality and brightness. But production has been put back a year, beginning in the second half of 2007, with mass production scheduled for 2008. The question then is, Will this impressive but untried technology be able to make inroads into what is fast becoming an entrenched market for LCD and plasma TVs? Time will tell.