Extrahigh color rendering white light-emitting diode lamps using oxynitride and nitride phosphors excited by blue light-emitting diode

The blue-light-excitation-type white light-emitting diode (LED) lamps are considered to be very suitable for lighting for art objects, shop window displays, and medical applications because they do not give infrared ray and ultraviolet ray. But their color rendering indices are needed to be improved for such applications. In this letter, the authors have fabricated white LED lamps with a broad range of color temperatures, and realized extrahigh color rendering index Ra values of 95–98 in them, using four oxynitride/nitride phosphors and a blue LED die. It means UV LED die is not always necessary for high color rendering white LED lamps. The luminous efficacies of white LED lamps are $28–35\mathrm{lm}∕\mathrm{W}$ , which are sufficiently high for extremely high color rendering white LED lamps.