The lowly incandescent light bulb continues to come under increasing threat. First, came the fluorescent tube, then the compact fluorescent. More recently the LED (light emitting diode) seems to be gaining ground. Now LED technology takes another leap forward with printed LED “light sheets”.
[div class=attrib]From Technology Review:[end-div]
A company called Nth Degree Technologies hopes to replace light bulbs with what look like glowing sheets of paper (as shown in this video). The company’s first commercial product is a two-by-four-foot-square light, which it plans to start shipping to select customers for evaluation by the end of the year.
The technology could allow for novel lighting designs at costs comparable to the fluorescent light bulbs and fixtures used now, says Neil Shotton, Nth Degree’s president and CEO. Light could be emitted over large areas from curved surfaces of unusual shapes. The printing processes used to make the lights also make it easy to vary the color and brightness of the light emitted by a fixture. “It’s a new kind of lighting,” Shotton says.
Nth Degree makes its light sheets by first carving up a wafer of gallium nitride to produce millions of tiny LEDs—one four-inch wafer yields about eight million of them. The LEDs are then mixed with resin and binders, and a standard screen printer is used to deposit the resulting “ink” over a large surface.
In addition to the LED ink, there’s a layer of silver ink for the back electrical contact, a layer of phosphors to change the color of light emitted by the LEDs (from blue to various shades of white), and an insulating layer to prevent short circuits between the front and back. The front electrical contact, which needs to be transparent to let the light out, is made using an ink that contains invisibly small metal wires.
[div class=attrib]Read the entire article here.[end-div]
[div class=attrib]Image courtesy of Technology Review.[end-div]