[Printable Electronics] Panasonic Employs Printing Method to Make OLED Lighting Panel

Feb 26, 2009 19:34 Tetsuo Nozawa, Nikkei Electronics

Panasonic Electric Works Co Ltd prototyped an organic EL lighting panel, part of whose organic semiconductors were made by printing processes.

The panel has high luminance efficiency and color rendering properties, according to the company. It was introduced in a speech delivered by the company at Printable Electronics 2009, which took place from Feb 18 to 20, 2009.

This organic EL lighting panel features a luminance efficiency of 40lm/W and a CRI (color rendering index) value of 95. The external quantum efficiency is 36.1%, and the half-life of the luminance exceeds 20,000 hours when the initial luminance is 1,000cd/m², according to Panasonic.

Among the manufacturing processes used, the semiconductor called hole-injecting layer was manufactured by the "slit coating method," a kind of printing methods. This method was employed because "a good material for the hole-injecting layer happened to be suitable for use with a coating method," the company said.

The slit coating method is a technology to manufacture color filters of LCD panels. Panasonic modified equipment provided by Tazmo Co Ltd, the company's partner in the development of organic EL lighting technologies, to use it for organic ELs.

"The film produced by the slit coating method is 40 to 50nm thick with a uniformity of ±5% and a coating speed of 100mm/s," the company said.

Panasonic said the 40lm/W luminance efficiency is "almost equivalent to actual luminance efficiencies of fluorescent lights." Luminance efficiencies of fluorescent lights vary from 80 to 100lm/W. But their actual efficiencies drop to less than 50% when they are used with a hood for diffusing light and a low-reflectance reflector, according to the company.

In respect to luminance efficiency, some manufacturers have achieved higher values. For example, Universal Display Corp (UDC) of the US attained a value as high as 102lm/W. However, the CRI value of the panel manufactured by UDC is low at only 70.

Panasonic places priority on the color rendering properties of organic EL lighting because "on a panel with low rendering properties, a strawberry looks as if it's rotten," the company said.

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