Ion beam zaps molecules into line

17 Jun 2002

A contact-free technique that aligns molecules in liquid-crystal displays could make life easier for display manufacturers.

Researchers from IBM have developed a new method to align molecules in liquid-crystal displays that could revolutionize the way in which displays are made. Instead of using today's low-tech, messy procedure of rubbing a polymer film with a velvet cloth, P. Chaudhari and his colleagues at IBM's US and Japan-based laboratories have used an ion-beam technique to tease the molecules into place.

Liquid-crystal displays consist of two glass substrates, with the liquid crystal sandwiched in-between them. Typical displays have thin polymer films coated onto the side of the glass substrate that is in contact with the liquid crystal to influence molecular orientation prior to rubbing. In developing their contact-free alignment technique Chaudhari and colleagues decided to swap the polymer film for a diamond-like carbon film.

"We have replaced the polyimide film with a one-step evaporated or sputtered [diamond-like carbon] film, which is deposited at room temperature," the team reported in Nature 411 56-59. "This is not only cost-effective, but also more environmentally friendly."

By directing a low-energy ion beam at the film, the researchers were able to selectively rearrange atoms across the film before bringing the layer in contact with the liquid crystal to align the crystal molecules. They were also able to tilt the molecules by up to 10° to optimize the display's contrast.

The team believes that their technique will eventually outstrip conventional rubbing in terms of cost and quality of the display. "We have already produced a high-resolution 22-inch display in a manufacturing environment using this process," said Chaudhari. "We have found that more reliable and better-quality displays could be made at a lower cost than using the rubbing technique."