Patent ID: 8552437

Claim:
A process for production of a fluorescent substance which emits luminescence having a peak in the wavelength range of 570 to 650 nm under excitation by light in the wavelength range of 250 to 500 nm, the process comprising: mixing a compound containing a metal element M 1 selected from the group consisting of tetravalent metal elements, a compound containing a metal element M 2 selected from the group consisting of trivalent metal elements other than In(III) and Ga(III), a compound containing a metal element M selected from the group consisting of metal elements, with the proviso that M is not M 1 , M 2 , In(III) and Ga(III), a compound containing an emission center element EC, with the proviso that EC is not M, M 1 , M 2 , In(III) and Ga(III), and a compound containing a metal element L selected from the group consisting of an oxide or nitride of In(III) and an oxide or nitride of Ga(III), to prepare a material mixture; and firing the material mixture to produce the fluorescent substance; wherein the fluorescent substance is of formula (I): (M 1-x EC x ) a M 1 b M 2 L c O d N e (I) wherein 0<x<0.4, 0.65<a<0.80, 2<b<3, 0<c<0.1, 0.3<d<0.6 and 4<e<5.