Price could drop for HDTVs thanks to carbon nanotubes

The price of big-screen TVs may come down to a point where most people can afford one. This is thanks to carbon-nanotube technology now in the works at Nano-Proprietary Inc., Austin, Tex. (www.appliednanotech.com). The carbon tubes act like electron guns: when subjected to an electric field, they emit electrons. So grouping the tubes around red, green, and blue phosphors creates pixels on a screen allowing large flat panels only 2-mm thick.
"The tubes can be made from single or multiple layers of carbon," says Zvi Yaniv, president of Nano-Proprietary. "They are about 5 to 6 nanometers in diameter, but relatively long, about 10 to 30 micrometers. Best of all, they are rich in pi electrons, those that strip off easily in an electric field," he adds.

Yaniv says he has built a gray-scale prototype screen based on nanotubes and that a color version is in the works. Carbon-nanotube raw material for the screens comes from Carbon Nanotubes Inc., Houston, and other companies.

A problem in the display world, explains Yaniv, is that there are many technologies but developers are trying to push each to its limits - even to a point of making a square peg fit in a round hole. For example, the largest liquid-crystals displays are not economical in large sizes - 60-in. diagonals and up. Nevertheless, screen manufacturers are trying to push the technology to larger diagonals because they know HDTV will be the next big market. Plasma, another flat-panel technology, is not good for small displays, as on laptop computers but has benefits for larger formats. "So already plasmas are in the 50 to 60-in. sizes," says Yaniv. "But plasma is costly and energy hungry," he says. CRTs are out because they are too bulky.

The beauty of carbon nanotubes is that each pixel has its own electron gun that is basically the thickness of the glass substrate. Yaniv says his company won't manufacture sets based on the prototype they've devised. "We control the intellectual property. We will conceptualize the manufacturing and prove it works."

Several Japanese manufacturers have also shown prototypes based on carbon nanotubes, understandable because the market for large monitors could exceed $100 billion. Yaniv suggests a commercial version could be out by second quarter of next year.

An artist's model of a carbon nanotube shows a one-layer version. Tubes can be several layers thick. Their great advantage is that in an electric field, carbon atoms easily give up electrons, so they act as little electron guns.

A prototype carbon-nanotube panel is about
2-mm thick. This proof-of-concept version has a 13.6-in. diagonal, holds 96 3 96 pixels, and can produce 64 levels of gray. A color HDTV version 60 in. or larger could have a switching voltage of less than 100 V.

The display screen Yaniv proposes is made in four simple layers starting with low-cost glass. First to go on are metal electrodes, overlaid with a black layer to support following layers. The black layer is patterned to leave the pixel area exposed. Carbon nanotubes then get deposited on the pixels with a proprietary technology. A metal grid over the black sustaining material finishes the cathode.