The OLED community got a shot of adrenaline yesterday when Universal Display Corporation (UDC) of Ewing, NJ (www.universaldisplay.com) announced that the company had been awarded a patent covering a structure and method for the ink-jet printing of small-molecule OLEDS - something that has not been possible to date.

Ken Werner
Senior Analyst and Editor
of HDTV Retailer

UDC says that its “broad patent capitalizes on ink-jet printing’s potential to become a low-cost manufacturing process, opening an additional avenue for the future mass production of large-area OLED displays.” An additional avenue? Additional to what?

Let’s back up for a moment. Nearly all of the small OLED (organic LED) displays that are currently used in portable media players and as the secondary display in clamshell-style cell phones use small-molecule (SM) organic electroluminescent materials. UDC’s proprietary PHOLED materials, which are on the verge of large-scale commercial application, are a kind of SMOLED material that is dramatically more efficient than traditional formulations. They are so efficient that they allowed Samsung SDI to make a prototype OLED cell-phone main display that was the first to be more efficient than an equivalent LCD in this application.

The problem was that the only practical way of applying SMOLED materials was to heat them in a vacuum until they evaporated, and then apply them through a shadow mask so they would become deposited on a substrate in the desired pattern. This vacuum thermal evaporation (VTE) technique is effective and reasonably economical for small displays, but cannot be scaled up effectively for large displays.

A technique that is suitable for large displays - and probably also cheaper for small displays - is ink-jet printing (IJP). The problem for UDC and SMOLED display makers is that SM materials have not been compatible with IJP. What is compatible with IJP are polymer (large-molecule) OLED materials, which can readily be prepared in solutions that can serve as inks for IJP. Developers of polymer materials, device structures, and process technologies, including Cambridge Display Technology (CDT), have been making this point energetically.

Now, UDC has patented a way of placing their PHOLED molecules in an ink-jettable carrier solution, thus permitting manufacturers to use IJP with SMOLED materials sets - materials with which the manufacturers have extensive experience. It also lets them migrate to PHOLED materials in a graceful way. That’s why the patent provides “an additional avenue for the future mass production of large-area OLED displays.”

The folks at UDC are understandably excited about this development, and the people at CDT must now deal with a competing technology. What is UDC’s commercial roadmap? Janice Mahon, UDC’s technology VP, told Insight Media that while the company is very pleased with ongoing technical developments, the roadmap also depends on the work being done by UDC’s display-making partners.

What is CDT’s reaction? Stay tuned - and read about it in the next issue of Display Watch.