Cheaper, clearer. Ion treatment may yield better liquid crystal displays.

Rubbing Out the Rub

Staff Writer

The liquid crystal displays (LCDs) that light up laptop computers, cell phones, and other accessories of the digital age make up a $21-billion-a-year business. It could become even more profitable, now that researchers have eliminated a cumbersome step in the manufacturing process. The advance could simplify and speed display manufacture.

A typical LCD screen is made up of thousands of tiny cells. In each one, light enters through a polarizing filter at the back of the screen and is twisted 90 degrees by a spiral staircase of stacked liquid crystalline molecules. Then the light exits through a similar filter at the front of the screen that is oriented perpendicular to the first. When an electric voltage reorients the liquid crystal molecules, the light is no longer twisted and can't exit. The pixel goes dark.

To make the liquid crystal molecules in each cell stack up in the staircase-like fashion, displaymakers rub the two plastic layers that sandwich them in perpendicular directions with a velvet roller. This aligns the plastic molecules and causes the liquid crystals near them to line up in the same direction; with the liquid crystals on either side now stacked perpendicular to one another, the ones in between automatically form the staircase.

But this method can damage the transistors on the panel, introduce tiny contaminants onto the screen, and create streaks across it, says Mahesh Samant, a chemist at IBM's Almaden Research Center in San Jose, California. As a result, manufacturers frequently toss out hundreds of damaged screens.

Samant and his IBM colleagues in Yorktown Heights, New York, set out to develop a better method. They tried bombarding various thin surfaces with ions. The technique worked, they report in the 3 May issue of Nature: The ions created tracks in the films that oriented the liquid crystals. Together with colleagues at IBM's display and engineering business units in Japan, they used the new technique to make 15-inch and 22-inch LCD displays that team member James Lacey calls "sharper and crisper" than today's models.

Industry analysts are watching closely. LCD prices have plummeted recently as production soared, and the new process could help LCD makers drop prices even further, says Kimberly Allen of Stanford Resources, a company that analyzes display technology and markets.

Related sites

World of LCD's, from Sharp
How LCDs work, from howstuffworks.com
Stanford Resources
IBM Research

Posted in Technology