April 27, 2007 – Ongoing work on materials for organic electroluminescent (OEL) flat-panel displays continues to improve the devices’ capabilities and reliability, and companies are flocking to the sector seeking profit opportunities, notes the Nikkei Business Daily.
The Japan Advanced Institute of Science and Technology (JAIST), working with instrument maker Kitano Seiki Co., has developed a manufacturing technique that improves working lifespan of OEL elements by a factor of five, by tweaking the vapor-deposition process used to create them.
To create the OEL elements, fluorescent organic molecules are vaporized by heating in a vacuum chamber and deposited on the glass substrate as thin films — a process that also leaves trace amounts of water, which can cause deterioration of the elements over time. So Kitano Seiki uses a special polishing technology to make the vacuum chamber’s walls extremely smooth so the water molecules won’t stick, and the chamber is baked with a heater to further evaporate the water and other contaminants prior to OEL fabrication.
The two tweaks, they claim, result in OEL elements that can operate for 29,000 hours before losing half their brightness — vs. just 6000 hours for conventional OEL elements. JAIST researchers also say the new method could also help improve yields and reduce costs.
Meanwhile, the Nikkei Business Daily notes that Nippon Steel Chemical Co., which already makes materials for OEL components, is positioning itself as the main supplier of new higher-efficiency film materials used in the two-layer structure that generates the light itself.
OEL displays incorporate a stack of organic materials between transparent electrodes, topped with glass or plastic substrates, the paper explained. Applying electricity to the electrodes causes the organic materials to emit light. The panels, which respond faster than LCDs and offer more forgiving viewing angles, are already used in cell phones and car navigation systems, though the real goal is to target bigger markets for flat-panel TVs and lighting applications.
US firm Universal Display Corp. holds many basic OEL patents and makes the dopants for coloring; many firms, however, including Nippon Steel Chemical (which already makes films for the electron transport layer) and other firms in Japan, see a market in supplying the “host” film material which delivers electric energy to the dopants, the paper notes. Most of these host films utilize inefficient fluorescent materials. Nippon Steel says its new materials have 4x greater efficiency (meaning lower power consumption).
Nippon Steel Chemical developed the red phosphorescent material in 2004, which Tohuko Pioneer Corp. is using it in car GPS systems. Late last year the company started selling a new green material, with plans for a blue material (the final one required for a full-colored display) to be ready later this year.
Nippon Steel Chemical says its background of refining coal tar gives it an edge in knowing how to maintain precise temperature control during the refining process, and do it in kilogram quantities, according to Yasuhiro Shimoura, executive officer and GM of the company’s OEL Department, quoted by the Nikkei Business Daily. Its facility in Kyushu currently has output capability of 70 kg/month of the red phosphorescent material.
The company believes availability of all three colored films by year’s end will address a significant pain point of display manufacturers, who have had to combine the newer more efficient red films with less-efficient conventional green and blue ones with different characteristics. Shimoura noted that the company hopes to “at least quintuple last year’s sales” to about 5 billion yen (~US $42 million) by fiscal 2010.
At the same time, Kyocera Corp. is planning to finally launch a business producing OEL displays for mobile phones, two years after announcing its intent, notes the daily Nikkei paper’s Friday morning edition. The company acquired rights from Taiwan’s Chi Mei Optoelectronics and readied a site in Japan, but had to overcome yield and other problems. New handsets featuring the OEL displays are expected to be available this fall, with supplies also due to industrial manufacturers, but the company hasn’t disclosed its sales or shipment targets, the paper notes.