OLED Elements Can Now Be Applied to Film

Create flexible, light-emitting surfaces.

New technology developed by VTT Technical Research Centre of Finland Ltd. allows organic light-emitting diode (OLED) elements to be printed on plastics film to create patterned and flexible light-emitting surfaces on billboards, signage and lighting fixtures. The new method also enables transparent “smart surfaces” to be attached to window panels or packaging.

OLED technology is commonly used in mobile phone displays and television sets, though until now it has been limited in application to glass surfaces, using traditional microelectronics manufacturing methods. With VTT’s method, which relies on gravure and screen printing. OLED elements can now be printed on flexible plastic films, enabling significantly larger light surfaces.

OLED light surfaces are around 0.2 mm thick and include electrodes and polymer layers measuring up to a few hundred nanometers, in which the light emission occurs. This phenomenon is called electroluminescence, in which an organic semiconductor emits light in an electric field. The luminosity of OLED amounts up to around one third of an LED’s. But OLED emits light throughout its entire surface, whereas LED is a spotlight technology.

At this point, VTT’s plastic OLED film will only emit light for around a year, since light-emitting polymer materials are susceptible to oxygen and moisture. In the future, the film’s lifespan is expected to increase.

“The plastic film is optimally suited to advertising campaigns, in which large light-emitting surfaces can be used to draw significantly more attention than can be gained through mere printed graphics or e-ink-type black-and-white displays that do not emit light,” says Raimo Korhonen, who heads up research for VTT.

It is also possible to use OLED light as a transmitter in wireless data transfer, which opens up new possibilities for utilizing printed light surfaces in “Internet of Things” applications.

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