Patent ID: 7462300

Claim:
A method of producing a doped-type zinc sulfide phosphor nanoparticle whose surface is modified with a surface modifier, comprising the steps of: carrying out a reaction of a doping metal ion and a matrix zinc ion, with a sulfide ion, in water and/or a hydrophilic solvent by a coprecipitation method, in which a solution comprising the doping metal ion and the matrix zinc ion and a solution comprising the sulfide ion are mixed under high speed stirring by a single-jet method or a double-jet method, wherein the total number of moles of the doping metal ion and the matrix zinc ion is greater than the number of moles of the sulfide ion by 2 to 40%; and adding thereto a surface modifier comprising a compound represented by formula [I]: HS-L-W Formula [I] wherein L represents a divalent linking group; and W represents COOM or NH 2 , in which M represents a hydrogen atom, an alkali metal atom, or NX 4 , in which X represents a hydrogen atom or an alkyl group, wherein the number average particle diameter of the zinc sulfide phosphor nanoparticle is from 1 to 10 nm and the particle size distribution of the zinc sulfide phosphor nanoparticle is from 0 to 20% in terms of coefficient of variation.