Coatings for Photoluminescent Materials

Abstract

The teachings are generally directed to phosphors having combination coatings with multifunctional characteristics that increase the performance and/or reliability of the phosphor. The teachings include highly reliable phosphors having coatings that contain more than one inorganic component, more than one layer, more than one thicknesses, more than one combination of layers or thicknesses, a gradient-interface between components, a primer thickness or layer to inhibit or prevent leaching of phosphor components into the coatings, a sealant layer to inhibit or prevent entry of moisture or oxygen from the environment, a mixed composition layer as a sealant and multifunctional combination coatings.

What is claimed is: 
     
         1 . A coated photoluminescent material, said coating being a multifunctional coating comprising:
 a photoluminescent material having a surface; and   at least two oxides, the two oxides including:
 a primer material having a primer thickness on the surface of said photoluminescent material, said primer thickness functioning to at least inhibit a leaching of a component of said photoluminescent material into said coating; and 
 an outermost, sealant material having a sealant thickness that functions to inhibit or prevent oxygen and moisture from diffusing through said coating and into said photoluminescent material; 
 wherein said at least two oxides are selected from the group consisting of metal oxides and semiconductor oxides. 
   
     
     
         2 . The coated photoluminescent material of  claim 1 , wherein said primer thickness is a discrete layer, and said sealant thickness is a discrete layer. 
     
     
         3 . The coated photoluminescent material of  claim 2 , wherein said primer thickness is titanium oxide and said outermost, sealant thickness is silicon oxide. 
     
     
         4 . The coated photoluminescent material of  claim 1 , wherein the coating further comprises a gradient-interface thickness between said primer thickness and said outermost, sealant thickness. 
     
     
         5 . The coated photoluminescent material of  claim 4 , wherein the gradient-interface thickness has a mixture of titanium oxide and silicon oxide. 
     
     
         6 . The coated photoluminescent material of  claim 1 , wherein said coating has a mixed oxide composition throughout the thickness of said coating. 
     
     
         7 . The coated photoluminescent material of  claim 6 , wherein said mixed oxide composition comprises aluminium oxide and silicon oxide. 
     
     
         8 . The coated photoluminescent material of  claim 6 , wherein said mixed oxide composition varies throughout the thickness of said coating. 
     
     
         9 . The coated photoluminescent material of  claim 1 , wherein said photoluminescent material comprises a silicate phosphor, an aluminate phosphor, a nitride phosphor, an oxynitride phosphor, a sulfide phosphor or an oxysulfide phosphor. 
     
     
         10 . The coated photoluminescent material of  claim 1 , wherein said photoluminescent material has the formula Ca 1-x AlSiN 3 Eu x :D; wherein, x ranges from about 0.0001 to about 0.500 and D comprises fluorine, chlorine, bromine, or iodine. 
     
     
         11 . A method of synthesizing a photoluminescent material having a multifunctional coating, the method comprising:
 adding a photoluminescent material to a solvent to form a first mixture;   adding precursors of coating layer oxides to the first mixture to form a second mixture;   mixing the second mixture for a period of time while maintaining said second mixture at an elevated temperature sufficient to allow for a deposition of said coating layer oxides on a surface of the photoluminescent material;   washing the coated photoluminescent material;   purifying the coated photoluminescent material;   drying the coated photoluminescent material; and,   calcining the coated photoluminescent material.   
     
     
         12 . The method of  claim 11 , wherein said solvent is an alcohol or water solution. 
     
     
         13 . The method of  claim 11 , further comprising adjusting the pH of the first mixture to prepare for a hydrolysis of said precursors of said coating layer oxides. 
     
     
         14 . The method of  claim 11 , wherein said coating layer oxides include titanium oxide. 
     
     
         15 . The method of  claim 11 , wherein said coating layer oxides include silicon oxide. 
     
     
         16 . The method of  claim 11 , wherein said coating layer oxides include aluminum oxide. 
     
     
         17 . The method of  claim 11 , wherein said precursors are organometallic compounds or inorganic salts. 
     
     
         18 . The method of  claim 11 , wherein said photoluminescent material comprises a silicate phosphor, an aluminate phosphor, a nitride phosphor, an oxynitride phosphor, a sulfide phosphor or an oxysulfide phosphor. 
     
     
         19 . A method of synthesizing a photoluminescent material having a multifunctional coating, the method comprising:
 adding a photoluminescent material to water to form a first mixture;   adding a first precursor for a metal oxide to said first mixture to form a second mixture;   adding a second precursor for a semiconductor oxide to said second mixture to form a third mixture;   adding urea as an ammonia releasing agent to control pH change slowly during aluminum and silicon precursor hydrolysis in water;   adjusting the pH of said third mixture;   heating the pH adjusted third mixture to a set temperature;   mixing the heated pH adjusted third mixture while maintaining said set temperature for a period of time to allow for a deposition of the coating layer oxide on a surface of the photoluminescent material;   washing the coated photoluminescent material;   drying the coated photoluminescent material; and   calcining the coated photoluminescent material.   
     
     
         20 . The method of  claim 18 , wherein said first precursor is for aluminum oxide. 
     
     
         21 . The method of  claim 18 , wherein said second precursor is for silicon oxide. 
     
     
         22 . The method of  claim 18 , wherein the precursors are organometallic compounds or inorganic salts. 
     
     
         23 . The method of  claim 18 , wherein the addition sequence of the precursors can be varied. 
     
     
         24 . The method of  claim 18 , wherein said photoluminescent material comprises a silicate phosphor, an aluminate phosphor, a nitride phosphor, an oxynitride phosphor, a sulfide phosphor or an oxysulfide phosphor. 
     
     
         25 . A light emitting device, comprising:
 a solid state light emitter; and   the coated photoluminescent material of  claim 1 .