RFI develops new FPD technology

Electronic News, Feb 6, 1995 by Walter Andrews

WOODBURY, N.Y.-- Research Frontiers, Inc. (RFI) has developed a new type of flat panel display (FPD) that is easier to build and read than conventional liquid crystal displays (LCDs) and is looking for manufacturers to license.

Developed in cooperation with London's Imperial College of Science, Technology and Medicine, the new FPDs use electrically-oriented colloidal particles dispersed in a liquid and are known as suspended particle displays, or SPDs.

Unlike LCDs, the SPDs do not require light-absorbing sheet polarizers and are thus simpler to construct and have reduced backlighting requirements, the company said. The SPDs offer high information content, good brightness and contrast as well as an excellent angle of view.

"We have now succeeded in making a high information content display work at under 20 volts and I'm sure the people who are manufacturing active-matrix displays will say that 'if a little company like Research Frontiers can do this well' they can do better and that's probably true," RFI president Robert L. Saxe told Electronic News.

He said RFI was a research company and was seeking FPD manufacturers to license the new SPD technology on a non-exclusive basis. The manufacturing companies with their resources and engineers should be able to lower the voltage much more. "I feel that if any of the people who are in the liquid crystal display business now were to license it from us and put some of their experts on the job they would in fairly short order be able to demonstrate some very good looking displays."

Mr. Saxe added: "The key number is the liquid crystal displays generally will be using under 20 volts. Under 20 volts they can use CMOS circuitry. The key number then would be under 20 volts. The lower you can go, the better."

The company president said, "Our displays should simplify the manufacturing process quite a bit and that could be quite important because every time you've got to add a component you've got a chance of failure and the manufacturing yields can be adversely affected."

He said the absence of sheet polarizers "is what makes ours so much more readable ... If you avoid those components, then you save a lot of light and that makes them much easier to read. The contrast and brightness are better and the angle of view is much better. .... The angle of view with most liquid crystal displays is not too good. .... With the same number of pixels, (the SPD) will look better."

Mr. Saxe said, "Numbers and letters displayed on an SPD are much easier to read than similar data shown on conventional liquid crystal displays used in laptop computers. Assuming manufacturers and consumers agree, a significant improvement in the quality of low-voltage panel displays could be forthcoming."

He said a first-generation prototype SPD uses 15 volts and has an overall size of 85 by 70 millimeters consisting of an active matrix of 340 columns and 280 rows. Each prototype display therefore comprises 95,200 pixels with a cadmium selenide thin-film transistor deposited on a glass substrate at each pixel to control light transmitted through the display.

RFI said it believes future SPD models will have many more pixels, require even less voltage and should be able to utilize amorphous or polyerystalline silicon thin-film transistors as well as cadmium selenide.

The RFI president said it is "very difficult" to quantify contrast and brightness at this point. "If you saw it you would just say qualitatively it looks better. We probably will be able to quantify it later this year ... in terms of brightness and contrast."