Li-containing alpha-sialon-based phosphor, production process thereof, lighting device and image display device

Abstract

An Li-containing α-sialon-based phosphor represented by the formula (1): Li x Eu y Si 12-(m+n) Al (m+n) O n+δ N 16-n-δ (wherein assuming that average valence of Eu is a, x+ya+δ=m; 0.45≦x<1.2, 0.001≦y≦0.2, 0.9≦m≦2.5, 0.5≦n≦2.4, and δ>0).

1 . An Li-containing α-sialon-based phosphor represented by formula (I):
   Li x Eu y Si 12-(m+n) Al (m+n )O n+δ N 16-n-δ   (1)
 
 
       (wherein assuming that average valence of Eu is a, x+ya+δ=m; 0.45≦x<1.2, 0.001≦y≦0.2, 09≦m≦2.5, 0.5≦n≦2.4, and δ>0). 
     
     
         2 . The phosphor as claimed in  claim 1 , wherein said δ is from 0.05 to 1.2 and a ratio x/m between x and m is from 0.4 to 0.9. 
     
     
         3 . The phosphor as claimed in  claim 2 , wherein said x is 0.82≦x<1.2 and said x/m is from 0.5 to 0.9. 
     
     
         4 . The phosphor as claimed in  claim 1 , wherein fluorescence having a peak wavelength of 560 to 580 nm is emitted by injecting excitation light. 
     
     
         5 . The phosphor as claimed in  claim 1 , which is a powder wherein an average aspect ratio of primary particles as measured by image analysis of a scanning electron micrograph is 2 or less and average particle diameter D particle  is from 1 to 3.0 μm. 
     
     
         6 . The phosphor as claimed in  claim 5 , wherein in the particles measured by the image analysis of the scanning electron micrograph, a primary particle of 0.8 μm or more is present in an area ratio of 70% or more. 
     
     
         7 . The phosphor as claimed in  claim 5 , wherein a frequency distribution curve in a particle size distribution curve measured by a laser diffraction/scattering particle size distribution measuring apparatus is a single peak and median diameter is from 4 to 15 μm. 
     
     
         8 . The phosphor as claimed in  claim 5 , wherein the 10% diameter in the particle size distribution curve is 1.5 μm or more and the 90% diameter is 15 μm or less. 
     
     
         9 . The phosphor as claimed in  claim 1 , which is a powder wherein aspect ratio of a primary particle as measured by image analysis of a scanning electron micrograph is 3 or less and length of a short axis is more than 3 μm. 
     
     
         10 . A process for producing the Li-containing α-sialon-based phosphor claimed in  claim 1 , comprising weighing and mixing a silicon nitride powder and/or a nitrogen-containing silane compound, an AlN-containing substance working out to an aluminum source, a nitride, oxynitride or oxide of Li or a precursor substance capable of becoming an oxide of Li by pyrolysis, and a nitride, oxynitride or oxide of Eu or a precursor substance capable of becoming an oxide of Eu by pyrolysis, to give a composition containing lithium in excess over the composition of the Li-containing α-sialon-based phosphor represented by formula (I), and firing the mixture at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere under atmospheric pressure. 
     
     
         11 . The process of  claim 10 , wherein the Li-containing α-sialon-based phosphor after firing is subjected to acid washing. 
     
     
         12 . A process for producing the phosphor of  claim 5 , comprising weighing and mixing an amorphous silicon nitride powder and/or a nitrogen-containing silane compound, an AlN-containing substance working out to an aluminum source, a nitride, oxynitride or oxide of Li or a precursor substance capable of becoming an oxide of Li by pyrolysis, and a nitride, oxynitride or oxide of Eu or a precursor substance capable of becoming an oxide of Eu by pyrolysis, to give a composition containing lithium in excess over the composition of the Li-containing α-sialon-based phosphor represented by formula (1), and firing the mixture at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere under atmospheric pressure. 
     
     
         13 . A process for producing the phosphor of  claim 9 , comprising mixing an amorphous silicon nitride powder and/or a nitrogen-containing silane compound, an AlN-containing substance working out to an aluminum source, a nitride, oxynitride or oxide of Li or a precursor substance capable of becoming an oxide of Li by pyrolysis, a nitride, oxynitride or oxide of Eu or a precursor substance capable of becoming an oxide of Eu by pyrolysis, each in a theoretical amount giving the composition of formula (1), and an oxide of Li or a precursor substance capable of becoming an oxide of Li by pyrolysis, in an amount in excess over said theoretical amount, and firing the mixture at 1,500 to 1,800° C. in a nitrogen-containing inert gas atmosphere under atmospheric pressure. 
     
     
         14 . The process of  claim 13 , wherein the amount of metal lithium in the oxide of Li or the precursor substance capable of becoming an oxide of Li by pyrolysis, mixed in excess over said theoretical amount, is from 0.1 to 1.25 mol per mol of the Li-containing α-sialon-based phosphor as a product by a theoretical amount. 
     
     
         15 . A lighting device comprising a light emitting source and a phosphor containing the phosphor claimed in  claim 1 . 
     
     
         16 . The lighting device as claimed in  claim 15 , wherein said light emitting source is an LED capable of emitting light at a wavelength of 330 to 500 nm. 
     
     
         17 . The lighting device as claimed in  claim 16 , wherein said phosphor further contains a phosphor capable of emitting a red color at 600 to 650 nm. 
     
     
         18 . An image display device comprising an excitation source and a phosphor containing the Li-containing α-sialon-based phosphor claimed in  claim 1 . 
     
     
         19 . A lighting device comprising a light emitting source and a phosphor containing the phosphor claimed in  claim 5 . 
     
     
         20 . A lighting device comprising a light emitting source and a phosphor containing the phosphor claimed in  claim 9 .