20 October 2004 Overview: present status and future prospect of system and design in white LED lighting technologies
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“The light for the 21st century” METI national (Akari) project, which is based on the high-efficient white light-emitting diode (LED) lighting technologies using near ultraviolet (UV) LED and phosphor system, has started from 1998 and its first phase programme finished in 2004. The near UV white LED system linked with semiconductor technologies on GaN LED and compound phosphors for the general lighting applications has for the first time been proposed in the world. In particular, we have demonstrated high-efficient near UV LED having external quantum efficiencies more than 43% around an emission wavelength of 400 nm. Basic illumination properties, and applications of the high luminous efficacy (>40 lm/W) and the high general color rendering index (Ra>90) white LED sources are described. The near UV white LED technologies in conjunction with phosphor blends can offer superior color uniformity, high Ra and the excellent light quality, and the second phase programme has been performed in the MEXT national project “White LEDs for medical applications” from 2004 to 2009 for 5 years.
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Tsunemasa Taguchi, Tsunemasa Taguchi, "Overview: present status and future prospect of system and design in white LED lighting technologies", Proc. SPIE 5530, Fourth International Conference on Solid State Lighting, (20 October 2004); doi: 10.1117/12.567101; https://doi.org/10.1117/12.567101


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