On the second day of the successful IDTechEx conference Printed Electronics Asia the subjects were OLED Display technology, E-Paper Display, Printing Technology, Material Advances and Future Possibilities. By popular request, there was considerable technical content - too much to even summarise in a short article but here are some highlights.
OLEDs
A number of players no longer see entirely organic devices as the end game, though some do. For example, in its OLED displays, Samsung is testing inorganic passivation, transistor gates, barrier layers and electrodes as well as organic alternatives. Materials include Cu, SiO2 and SiNx. One ink jet layer has replaced six earlier layers in a display.
However, the challenges have increased because, "Our concept has changed to flexible displays," said Dr Bonwon Koo of Samsung Display Laboratory in Korea. There are no longer any illusions about selling OLEDs at a premium against LCDs given the tremendous progress with LCD viewing angles and other features. "We need to be cost competitive with LCD" said Dr Reid Chesterfield of DuPont Displays, adding that, "The holy grail of OLED development is life."
At least the OLED developers are open about life and it was interesting to hear that, although blue is traditionally the color with least life, in actual devices, other colors can be limiting. DuPont is unfazed by the rush to inkjet: it uses slot coating and nozzle printing as appropriate.
Others mentioned flexographic printing. Dr Kiyoshi Yoneda of Kodak Japan presented its white OLED approach to displays and lighting where 40% reduction in power consumption comes with a few problems that can probably be solved in due course, working with Dainippon Screen of Japan.
Displays were neatly categorised into those for watching - where OLEDs are seen as the most important future product - and those for reading - where E-Ink front planes are dominant and the reading A4 and A3 formats are of particular interest, not least because existing printed text does not need to be reformatted. Bridgestone of Japan is the potential competition now Xerox has got out of the business and its electrophoretic product, which uses air instead of water, will be launched in 2009.
Advantages seem to be faster response, tolerance of low temperatures and no need for a polarizer or reflective layer. However, the operating voltage at 70-80V is about double that of E-Ink. E-Ink of the USA will launch color versions of its front planes in 2010.
Materials
As for materials, there was much discussion of how to optimise inkjet systems for various tasks, the PixDro tools and modules and a novel flexographic printing process from Asahi Kasei Chemicals in Japan.
Competitors Merck Chemicals and BASF, both of Germany, were in agreement as to what has to be achieved in further developing the various OLED and transistor inks and they described their progress. Of course, mobilities and thus operating frequencies of organic transistors need to improve but Dr Peter Eckerle of BASF counselled that, "The main challenge in RFID is high yield in production." HC Starck has improved its PEDOT-PSS conducting printing ink to give a wider range of compromises in properties as needed for different printing technologies and applications. For example, the acidity is quenched in a version that surrenders a modest amount of conductivity to achieve this. Sadly, there is still no widely used replacement for indium tin oxide ITO despite indium prices rising and these films emitting oxygen and having limited rollability. However, Hitachi Chemical of Japan announced its copper inks that cure at low temperature to maintain solderability. That may reduce worries about recent trends in the silver price, though another approach is to use truly nanosilver that requires much less material. Frontier Carbon Corporation of Japan described its huge repertoire of fullerene formulations.
Professor Takao Someya of Tokyo University discussed his stretchable electronics and his transistors, memories and circuits made using sub femtoliter inkjets.
If you missed this event then attend Printed Electronics USA 2008 or Printed Electronics Europe 2009.
