Present Status of White LED Lighting Technologies in Japan

“The light for the 21st century” Japanese 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 been started at 1998. The near UV white LED system linked with semiconductor technologies on GaN LED and ZnS phosphors for general lighting applications has for the first time been proposed in the project. The outline and purpose of this project are briefly introduced. In particular, we have demonstrated high-efficient nUV LED having external quantum efficiencies more than 43 % around an emission wavelength of 400 nm. Basic illumination properties 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 for many lighting applications.