Grey-scale OLED patterns reach 12,700 dpi resolution
The electron beam process is performed after finalizing the OLED panels, including the encapsulation, hence leveraging the volume production of un-patterned OLEDs before individually modifying the emission characteristics of the active layers, at a pixel pitch down to 2µm.
The energy of the electrons determines their penetration depth in the layer stack. With a suitable choice of process parameters, the encapsulation can also be penetrated by the electron beam and the luminous characteristics of the organic layers beneath will change without destroying or compromising the encapsulation itself, the researchers report. Depending on the application, it is even possible to modify individual layers directly.
“This fixed image writing achieves resolutions way beyond what could be achieved through OLED layer deposition, achieving continuous grey-scale rather than a binary on-off OLED state”, told eeNews Europe, Elisabeth Bodenstein from the development team at Fraunhofer FEP.
Compared to overlay dimming alternatives, often consisting of a sticker or a screen-printed mask on top of the fully lit OLED, the new process allows very fine and permanent watermarking of any production OLED, while reducing the power consumption of the OLED. “This is because the dimmed pixels consume less as their resistance is increased by the e-beam process”, clarified Bodenstein.
The longer the e-beam exposure, the darker the OLED will appear on a given spot. The researchers patterned an image of the Dresden Semperoper opera house, structured with the electron beam in under a hundred seconds, at a resolution of 12,700 dpi corresponding to a 2µm dot pitch.
Such fine resolutions and permanent markings may find applications to secure branding, to write unalterable safety messages (think exit panels) or even to create unforgeable lit items.
The process can be adapted to any OLED, regardless of its substrate, its colour or its encapsulation characteristics, say the researchers who plan to work on full-colour patterning by applying their technique to individual colour layers.The technology was developed within a project funded by the Fraunhofer Gesellschaft.
Bodenstein will be presenting these findings at SID Display Week 2016 in San Francisco / USA from May 24 – 26, with the poster “Electron Beam Induced High-Resolution Modification of OLED Emission”
Visit Fraunhofer FEP at www.fep.fraunhofer.de
Related articles:
OLED startup attracts $13.5m from global OLED panel makers
LG slashes 4K OLED TV prices to pressure LCD rivals
Japan’s TSNC invests in Chinese OLED material developer
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
