Methods for producing coated phosphor and host material particles using atomic layer deposition methods

Abstract

Layers of a passivating material and/or containing luminescent centers are deposited on phosphor particles or particles that contain a host material that is capable of capturing an excitation energy and transferring it to a luminescent center or layer. The layers are formed in an ALD process. The ALD process permits the formation of very thin layers. Coated phosphors have good resistance to ambient moisture and oxygen, and/or can be designed to emit a distribution of desired light wavelengths.

1 . A method comprising forming a layer of an inorganic material on the surface of a phosphor particle via an atomic layer deposition process. 
   
   
       2 . The method of  claim 1 , wherein the atomic layer deposition process is conducted at a temperature of no greater than 475°K. 
   
   
       3 . The method of  claim 2 , wherein the inorganic material has a thickness of about 5 to about 100 nm. 
   
   
       4 . The method of  claim 3 , wherein the inorganic material is a passivating layer. 
   
   
       5 . The method of  claim 3 , wherein the inorganic material is alumina or titania. 
   
   
       6 . The method of  claim 3 , wherein the phosphor includes a host material that contains luminescent centers. 
   
   
       7 . The method of  claim 6 , wherein the host material is at least one of ZnS, CaS, (ZnCd)S, CaS, (CaSrGa)S, CaGa 2 S 4 , ZnGa 2 O 4 , Zn 2 SiO 4 , Y 2 O 2 S, Y 2 SiO 5 , SrS, SrGa 2 S 4 , ZnO and Y 2 O 3 . 
   
   
       8 . The method of  claim 3 , further comprising depositing a layer of a hydrophobic material atop the layer of the inorganic material. 
   
   
       9 . A method comprising forming a luminescent layer on the surface of a particle of a host material, wherein the luminescent layer is formed via an atomic layer deposition process. 
   
   
       10 . The method of  claim 9 , wherein the luminescent layer is formed by intermittently and sequentially introducing into a reaction zone containing the host material particles, a first precursor mixture that includes a compound containing a metal that forms a luminescent center and a second compound that does not contain a metal that forms a luminescent center, and a second precursor material that reacts with the first precursor mixture at the surface of the host material particles. 
   
   
       11 . The method of  claim 9 , wherein the luminescent layer is formed in a series of reaction cycles by intermittently and sequentially introducing into a reaction zone containing the host material particles a metal precursor and a reducing agent for the metal precursor material, wherein the metal precursor is in some but not all reaction cycles a compound of a metal that forms a luminescent center. 
   
   
       12 . The method of  claim 11  wherein the host material is at least one of ZnS, CaS, (ZnCd)S, CaS, (CaSrGa)S, CaGa 2 S 4 , ZnGa 2 O 4 , Zn 2 SiO 4 , Y 2 O 2 S, Y 2 SiO 5 , SrS, SrGa 2 S 4 , ZnO and Y 2 O 3 . 
   
   
       13 . The method of  claim 11  wherein a passivating layer is deposited via an ALD process atop the luminescent layer. 
   
   
       14 . The method of  claim 13  wherein a hydrophobic layer is deposited atop the passivating layer. 
   
   
       15 . The method of  claim 10  or  11  wherein a hydrophobic layer is deposited atop the luminescent layer. 
   
   
       16 . A phosphor particle having a passivating film of 5-100 nm thickness which has been deposited by the method of  claim 1 . 
   
   
       17 . A host material having a luminescent layer of 5-100 nm in thickness. 
   
   
       18 . A host material of  claim 17  wherein the luminescent layer is deposited via an ALD process. 
   
   
       19 . The host material of  claim 18 , wherein the luminescent layer contains at least two different luminescent centers.