Question:
Dr. Kido, we've heard a lot about organic EL displays recently, but what got you interested in this field?

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When I was a student 14 or 15 years ago I majored in polymer chemistry and worked with metal complexes. Metal complexes are hybrid materials in which organic substances are incorporated into metal ions. Especially certain rare earth metal complexes have very strong light emitting properties, and thinking it might be interesting to illuminate those substances electrically, I started doing some research. At that time I wasn't thinking about developing materials for displays, I just thought it was really interesting that you could light up organic matter with electricity. But since I began that research, I started to visualize the exciting new technologies that could emerge if we were able to illuminate organic material electrically. As an extreme example, imagine the possibilities if you could light up a piece of plastic with electricity. What's actually gaining a lot of attention around the world right now is the work of various companies who work in the field of displays, and who are using semiconductor technology to make amazing devices with high luminosity and lifespans of 100 to 1000 hours.

Question:
Can you tell us about the technical characteristics of organic EL displays? Also, explain how OEL fits in to the current market which is dominated by LCDs.

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B asically, organic EL elements are self-luminous bodies with simple structures that are thin and highly "light-efficient." They combine all characteristics of ideal light-emitting elements. In terms of color, while it's difficult to get blue out of inorganic EL, it's very easy with organic EL. Red, green, blue, white, yellow, or greenish-yellow: any of these colors are possible. Efficiencies can go down with certain colors, but all in all you have a lot of freedom in terms of the colors that can be emitted. Another characteristic of organic EL is that you don't need a device such as an inverter to generate a constant AC current to achieve the illumination, and this cuts down on external noise. Also, when compared to Braun tubes (CRT), OEL devices are incredibly thin and light. OEL has the same type of self-luminance as CRTs, so the image quality is far better than that of LCDs.

As for the market segmentation, the reflective liquid crystals in LCDs have extremely low power consumption, so organic EL will not replace LCDs at least in terms of reflectiveness. Light-emitters are especially unsuited for devices that can run for long periods on small batteries, such as watches, calculators, and other products. So I think the way this will play out is that only the reflex LCDs will survive, and transmissive LCDs with backlights will be replaced by OEL technology. I like to say that LCD begins with calculators and ends with calculators. You really need to have low power consumption in calculators, so self-luminance would be difficult to implement. Also, the market for these items is small and the prices are low, so I don't think that there are many people wanting to switch to organic EL.

In theory, backlights for LCDs are like fluorescent lights in that they are extremely efficient, but in practice only a certain percentage of that light can be used for the display so the efficiencies are actually quite low. Compared to 10 years ago the display functions on LCDs are much improved, but we still can't get satisfactory image quality at low cost so there's still a ways to go. From an efficiency standpoint they're quite good, but they have structural limits.
I think the potential for organic EL is way beyond that of LCDs. Already, the power consumption of the panels that Japanese makers have been demonstrating is lower than back-lit LCDs. The efficiency of organic EL is going to keep rising, so the power consumption could become many times less than present LCDs.