Traditional printing techniques combine in OLED display manufacture

Researchers have developed large-surface, light-emitting plastic film based on OLED technology that can be fabricated using gravure and screen-printing methods.

Developed by VTT Technical Research Centre of Finland, this method is claimed to provide manufacturers with the opportunity to create patterned and flexible light-emitting surfaces on advertising displays, signs or lighting fixtures.

VTT add that the method also enables transparent smart surfaces to be attached to window panels or packaging.

OLED technology (Organic Light-Emitting Diode) is commonly used in mobile phone displays and television sets, but until now has only been found in glass surfaces, implemented using traditional microelectronics manufacturing methods.

Using VTT’s method, OLED elements can now be printed not only onto glass or steel surfaces but also onto flexible plastic films, enabling significantly larger light surfaces and expanding the usage possibilities of the technology.

It is claimed that this type of light-emitting plastic film and processing in ambient atmosphere has not been created on this scale before.

Manufactured using the gravure and screen printing methods, OLED light surfaces are around 0.2 mm thick, and include electrodes and polymer layers measuring up to a few hundred nanometres, in which the light emission occurs. This phenomenon – electroluminescence – entails an organic semiconductor emitting light in an electric field.

The luminosity of OLED (lm/W) amounts up to around one third of an LED’s luminosity. It has one advantage in that OLED emits light throughout its entire surface, whereas LED is a spotlight technology.

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 will increase as the development of screen protectors continues and the film’s application possibilities grow.

In a statement, VTT’s Raimo Korhonen, head of research area, printed functionality said: ‘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.’

It further claimed that it is also possible to use OLED light as a transmitter in wireless data transfer, which opens up new possibilities for utilising printed light surfaces in Internet of Things applications.