Method for producing coated alkaline earth metal silicate phosphor particles
A method for producing film-coated alkaline-earth metal silicate phosphor particles that can have improved light-emitting characteristics may include a coating film having high moisture resistance. Strontium-containing alkaline-earth metal silicate phosphor particles are pretreated with an alkaline-earth metal compound solution whose strontium compound concentration is 1 to 15% by mass with respect to the phosphor particles and whose pH is 6 or higher but 10 or lower. Then, a base layer of an aluminum organic metal compound is formed on the surface of the pretreated phosphor particles. Then, the phosphor particles are coated with a coating material composed of a partially-hydrolyzed condensate of a silane organic metal compound, and are then dried and heat-treated to form, on their surface, a coating film made of an amorphous inorganic compound mainly containing Si and O.
1. A method for producing film-coated alkaline-earth metal silicate phosphor particles, the method comprising the steps of:
forming a first coating layer on a plurality of starter particles by treating the starter particles with an alkaline-earth metal compound solution;
forming a second coating layer on the starter particles which have been coated with the first coating layer;
forming a third coating layer on the starter particles which have been coated with the second coating layer; and
after forming the third coating layer, drying and heat-treating the coated starter particles;
wherein the starter particles are strontium-containing alkaline-earth metal silicate phosphor particles,
wherein the second coating layer contains an aluminum organic metal compound,
wherein the third coating layer contains a partially-hydrolyzed condensate of a silane organic metal compound,
wherein the alkaline-earth metal compound solution contains at least 1 to 15% by mass of a strontium compound with respect to the starter particles and having a pH inclusively between 6 and 10.
2. The method for producing film-coated alkaline-earth metal silicate phosphor particles according to claim 1 , wherein the strontium compound contained in the alkaline-earth metal compound solution is at least one selected from strontium acetate and strontium chloride.
3. The method for producing film-coated alkaline-earth metal silicate phosphor particles according to claim 1 , wherein the alkaline-earth metal compound solution contains 2 to 100% by mass of an aluminum organic metal compound with respect to the starter particles.
4. The method for producing film-coated alkaline-earth metal silicate phosphor particles according to claim 1 , wherein the first coating layer is formed by adding and mixing the starter particles to and with the alkaline-earth metal compound solution with stirring at a temperature of 18 to 60° C. for 1 to 24 hours.
5. The method for producing film-coated alkaline-earth metal silicate phosphor particles according to claim 1 , wherein each of the starter particles further comprises at least one metal selected from barium and calcium.
6. The method for producing film-coated alkaline-earth metal silicate phosphor particles according to claim 1 ,
wherein the alkaline-earth metal silicate phosphor in the starter particles is one selected from the group consisting of Sr 3 SiO 5 :Eu, (Sr a Ba b Ca c ) 3 SiO 5 :Eu, (Sr w Ba x Ca y Mg z ) 2 SiO 4 :Eu, and
wherein 0.9≦a≦1.0, 0≦b≦0.05, 0≦c≦0.05, 0<w≦0.7, 0≦x≦0.7, 0≦y≦0.7, and 0≦z≦0.5.