Question:
What are the technological issues that have to be resolved for organic EL displays?

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Definitely lifespan and efficiency. If we could achieve lifespans that support today's portable devices I think the state of the art as it stands now would be sufficient for practical applications. But for television we will have to go up to the next level. With regard to efficiency, we're still not getting 100% of OEL's potential, and there's room to grow, so I think there's a lot more research that must be done. Of course, if the efficiency increases so will the lifespan. I believe that by 2004-2005, lifespans will increase tenfold thus making the technology feasible for television applications.

Also, there is a lot of competition between the low molecular weight and high molecular weight researchers, but I think rather than competing we should focus on the low molecular designs first, and then move naturally into the high molecular work. At this point we don't have all the materials necessary to manufacture products using high molecular weight technology, so it's not practical to go in that direction.

As a manufacturing process inkjet coating is the ultimate, so I definitely want to use it. If high molecular designs lose out to low molecular ones, the high molecular work will be abandoned. Instead of competing, I wish the people doing high molecular weight research would take more time and get it right.

If we achieve the lifespans of 10,000 hours needed for television, the need for developing new materials will go away, and research at universities along with it. Besides displays, there are other applications such as fluorescent-style lighting. There are several methods for outputting white but they're rather complicated so I think there's a lot of work that can be done at universities. Still, after 5 or maybe 10 years at the latest, much of the university work will be gone.

Question:
What research topics will be left after that?

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When we're talking about organic EL, we're really talking about applied technologies in organic semiconductors. In addition to OEL, organic semiconductors includes organic transistors and organic solar cells, and researchers are starting to look into those. Organic transistors are different from silicon transistors in that you can make the transistors by inkjet-coating them onto a polymer semiconductor; you can even create a transistor on a plastic sheet. Also, you can coat a large surface area at once, so it's inexpensive and allows for a wide variety of uses. Also, Europe and America have what are called polymer solar cells. Current silicon solar cells, including those for home-use, cost about 20,000 dollars US even after subsidies are included, so if we can bring down the price of organic solar cells I think they would be widely accepted.
There's still a lot of work to be done in the field of organic semiconductors, and it's similar to OEL technology so I'm sure I will want to get involved in the future. Actually, instead of amorphous silicon, I've already begun research utilizing low molecular or high molecular organic thin-film transistors (organic TFT) to activate liquid crystals.

The "ultimate" device that we are in the running for is a flexible 100-inch or larger active display in which a film of organic TFT is formed on a plastic film plate, and is then laminated with an OEL layer.

That goal should take about 20 years, giving me lots to do in the meantime.
Our current 5-year goal is a 60 inch display, which no one has yet to achieve.

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At Yokogawa, we are looking forward to watching developments in organic EL and the next generation of electronic displays. We will strive to offer measuring instruments that contribute to the development and manufacturing of OEL displays and related technology.
(Interviewer: Yokogawa T&M Measurement PMK Product Group 3 Leader, Mr. Keiji Tsuneoka )