Sialon-based oxynitride phosphor and production method thereof

Abstract

The present invention relates to an oxynitride phosphor comprising an α-sialon as the main component, which is represented by the general formula: M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y (wherein 0.3≦x+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of the metal M is a and the atomic valence of the lanthanide metal Ln is b, m=ax+by) and in which the aggregation index, A 1 =D 50 /D BET ≦3.0 or the aggregation index A 2 =D 50 /D particle ≦3.0; and a production method and usage of the phosphor. The phosphor of the present invention has less aggregation and a narrow particle size distribution, and therefore is easy to uniformly mix with a resin or the like, and a high-brightness white LED can be easily obtained. D 50 [μm]: The median diameter in the grain size distribution curve. D BET [μm]: The equivalent-sphere diameter calculated on the basis of a BET specific surface area. D particle [μm]: The primary particle diameter measured by the image analysis of a scanning electron micrograph.

1 . An oxynitride phosphor comprising an α-sialon as the main component, which is represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y      
     (wherein 0.3≦x+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of the metal M is a and the atomic valence of the lanthanide metal Ln is b, m=ax+by), wherein an α-sialon with a part or all of the metal M (M is at least one metal selected from the group consisting of Li, Ca, Mg, Ba, Sr, Y and a lanthanide metal excluding La, Ce, Pr, Eu, Dy, Er, Th and Yb) solid-dissolved in the α-sialon being substituted by a lanthanide metal Ln (Ln is at least one lanthanide metal selected from the group consisting of Ce, Pr, Eu, Dy, Er, Th and Yb), which works as a luminescence center, is contained as the main component, and wherein the aggregation index, A 1 =D 50 /D BET , defined as the ratio between the median diameter D 50  [μm] in the particle size distribution curve and the equivalent-sphere diameter D BET  [μm] calculated on the basis of the BET specific surface area is 3.0 or less. 
   
   
       2 . An oxynitride phosphor comprising an α-sialon as the main component, which is represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y      
     (wherein 0.3≦x+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of the metal M is a and the atomic valence of the lanthanide metal Ln is b, m=ax+by), wherein an α-sialon with a part or all of the metal M (M is at least one metal selected from the group consisting of Li, Ca, Mg, Ba, Sr, Y and a lanthanide metal excluding La, Ce, Pr, Eu, Dy, Er, Th and Yb) solid-dissolved in the α-sialon being substituted by a lanthanide metal Ln (Ln is at least one lanthanide metal selected from the group consisting of Ce, Pr, Eu, Dy, Er, Th and Yb), which works as a luminescence center, is contained as the main component, and wherein the aggregation index, A 2 =D 50 /D particle , defined as the ratio between the median diameter D 50  [μm] in the particle size distribution curve and the primary particle diameter D particle  [μm] measured by the image analysis of a scanning electron micrograph is 3.0 or less. 
   
   
       3 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1  or  2 , wherein the median diameter D 50  in the particle size distribution curve is 8.0 μm or less. 
   
   
       4 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1  or  2 , wherein the equivalent-sphere diameter D BET  calculated on the basis of the BET specific surface area is 8.0 μm or less. 
   
   
       5 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1  or  2 , wherein the primary particle diameter D particle  measured by the image analysis of a scanning electron micrograph is 8.0 μm or less. 
   
   
       6 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1  or  2 , wherein the ratio D 90 /D 10  between the 90% diameter D 90  and the 10% diameter D 10  in the particle size distribution curve is 4.0 or less. 
   
   
       7 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1  or  2 , wherein in the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y , 1.0≦n≦1.25.   
   
   
       8 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 1 , wherein in the general formula: M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y , 0.5<n<1.0, and said aggregation index A 1 =D 50 /D BET  is 2.0 or less. 
   
   
       9 . The oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 2 , wherein in the general formula: M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y , 0.5<n<1.0, and said aggregation index A 2 =D 50 /D particle  is 2.0 or less. 
   
   
       10 . A production method of an oxynitride phosphor comprising an α-sialon as the main component, comprising:
 (A) a first step of firing a mixed powder obtained by adding at least one kind of a metal compound selected from the group consisting of:   (i) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of a metal M (M is at least one metal selected from the group consisting of Li, Ca, Mg, Ba, Sr, Y and a lanthanide metal excluding La, Ce, Pr, Eu, Dy, Er, Tb and Yb) solid-dissolved in an α-sialon represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y    
   (wherein 0.3≦x+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of the metal M is a and the atomic valence of the lanthanide metal Ln is b, m=ax+by), and   (ii) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of a lanthanide metal Ln (Ln is at least one lanthanide metal selected from the group consisting of Ce, Pr, Eu, Dy, Er, Th and Yb) substituting a part or all of the metal element M to work as a luminescence center,   to a silicon nitride powder, at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere to obtain a first raw material powder,   (B) a second step of adding at least one metal compound selected from the group consisting of:   (i) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of said metal M,   (ii) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of said lanthanide metal Ln substituting a part or all of said metal element M to work as a luminescence center, and   (iii) an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder or a precursor powder becoming aluminum oxide upon thermal decomposition,
 to said first raw material powder, and weighing and mixing these to give an α-sialon composition represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y    
 
   thereby obtaining a mixed powder, and   (C) a third step of firing the obtained mixed powder at 1,500 to 2,000° C. in a nitrogen-containing inert gas atmosphere.   
   
   
       11 . The production method of an oxynitride phosphor as claimed in  claim 10 , wherein said second step is a step of mixing at least one kind of a metal compound selected from the group consisting of:
 (i) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of the metal M solid-dissolved in the α-sialon represented by the general formula above, and   (ii) a nitride, an oxynitride, an oxide or a precursor substance becoming an oxide upon thermal decomposition, of the lanthanide metal Ln substituting a part or all of said metal element M to work as a luminescence center, together with   (iii) at least one kind of an aluminum compound powder selected from the group of an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder and a precursor powder becoming aluminum oxide upon thermal decomposition,   to obtain a second raw material powder, and weighing and mixing said first raw material powder and said second raw material powder to give an α-sialon composition represented by the general formula above, thereby obtaining a mixed powder.   
   
   
       12 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 10 , wherein said first step is a step of firing a mixed powder obtained by adding:
 (i) at least one kind of a metal M compound selected from the group consisting of a nitride, an oxynitride, an oxide and a precursor substance becoming an oxide upon thermal decomposition, of a metal M (M is at least one metal selected from the group consisting of Li, Ca, Mg, Ba, Sr, Y and a lanthanide metal excluding La, Ce, Pr, Eu, Dy, Er, Th and Yb) solid-dissolved in an α-sialon represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y    
   (wherein 0.3≦x+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of the metal M is a and the atomic valence of the lanthanide metal Ln is b, m=ax+by), and   (ii) at least one kind of a metal Ln compound selected from the group consisting of a nitride, an oxynitride, an oxide and a precursor substance becoming an oxide upon thermal decomposition, of a lanthanide metal Ln (Ln is at least one lanthanide metal selected from the group consisting of Ce, Pr, Eu, Dy, Er, Th and Yb) substituting a part or all of said metal element M to work as a luminescence center,
 to a silicon nitride powder, at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere to obtain a first raw material powder, 
   and said second step is a step of mixing two or more kinds of aluminum compound powders selected from the group consisting of (iii) an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder and a precursor powder becoming aluminum oxide upon thermal decomposition, to obtain a second raw-material powder, and weighing and mixing said first raw material powder and said second raw material powder to give said α-sialon composition, thereby obtaining a mixed powder.   
   
   
       13 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 10 , wherein:
 said first step is a step of firing a mixed powder comprising at least one kind of a europium compound powder selected from a europium nitride powder, a europium oxynitride powder, a europium oxide powder and a precursor powder becoming europium oxide upon thermal decomposition, and a silicon nitride powder at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere to obtain a first raw material powder, and   said second step is a step of adding:   at least one kind of an aluminum compound powder selected from the group consisting of an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder and a precursor powder becoming aluminum oxide upon thermal decomposition,   at least one kind of a calcium compound powder selected from a calcium nitride powder, a calcium oxynitride powder, a calcium oxide powder and a precursor powder becoming calcium oxide upon thermal decomposition, and   at least one kind of a lithium compound powder selected from a lithium oxide powder and a precursor powder becoming lithium oxide upon thermal decomposition,   to said first raw material powder, and weighing and mixing these to give an α-sialon composition represented by the general formula:
   Li x′ Ca x″ Si 12−(m+n) Al (m+n) O n N 16−n :Eu y    
   (wherein 0.3≦x′+x″+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of europium Eu is b, m=x′+2x″+by), thereby obtaining a mixed powder.   
   
   
       14 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 11 , wherein:
 said first step is a step of firing a mixed powder comprising:
 at least one kind of a europium compound powder selected from a europium nitride powder, a europium oxynitride powder, a europium oxide powder and a precursor powder becoming europium oxide upon thermal decomposition, 
 at least one kind of a lithium compound powder selected from a lithium oxide powder and a precursor powder becoming lithium oxide upon thermal de-composition, and 
 a silicon nitride powder, 
 at 1,400 to 1,800-C in a nitrogen-containing inert gas atmosphere to obtain a first raw material powder, and 
   said second step is a step of mixing:
 at least one kind of an aluminum compound powder selected from the group consisting of an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder and a precursor powder becoming aluminum oxide upon thermal decomposition, and 
 at least one kind of a calcium compound powder selected from the group consisting of a calcium nitride powder, a calcium oxynitride powder, a calcium oxide powder and a precursor powder becoming calcium oxide upon thermal decomposition, 
 to obtain a second raw material powder, and weighting and mixing said first raw material powder and said second raw material powder to give an α-sialon composition represented by the general formula:
   Li x′ Ca x″ Si 12−(m+n) Al (m+n) O n N 16−n :Eu y    
 
   (wherein 0.3≦x′+x″+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of europium Eu is b, m=x′+2x″+by), thereby obtaining a mixed powder.   
   
   
       15 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 12 , wherein:
 said first step is a step of firing a mixed powder comprising:
 at least one kind of a europium compound powder selected from the group of a europium nitride powder, a europium oxynitride powder, a europium oxide powder and a precursor powder becoming europium oxide upon thermal decomposition, 
 at least one kind of a calcium compound powder selected from the group of a calcium nitride powder, a calcium oxynitride powder, a calcium oxide powder and a precursor powder becoming calcium oxide upon thermal decomposition, 
 a lithium oxide powder or a precursor powder becoming lithium oxide upon thermal decomposition, and 
 a silicon nitride powder, 
 at 1,400 to 1,800-C in a nitrogen-containing inert gas atmosphere to obtain a first raw material powder, and 
   said second step is a step of:
 mixing at least two kinds of aluminum compound powders selected from an aluminum nitride powder, an aluminum oxynitride powder, an aluminum oxide powder and a precursor powder becoming aluminum oxide upon thermal decomposition to obtain a second raw material powder, and 
 weighting and mixing said first raw material powder and said second raw material powder to give an α-sialon composition represented by the general formula:
   Li x′ Ca x″ Si 12−(m+n) Al (m+n) O n N 16−n :Eu y    
 
   (wherein 0.3≦x′+x″+y<1.5, 0<y<0.7, 0.3≦m<4.5, 0<n<2.25, and assuming that the atomic valence of europium Eu is b, m=x′+2x″+by), thereby obtaining a mixed powder.   
   
   
       16 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in any one of  claims 10  to  14 , wherein said silicon nitride powder is at least one kind of a silicon nitride powder selected from the group consisting of a nitrogen-containing silane compound, an amorphous silicon nitride and a crystalline silicon nitride. 
   
   
       17 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 15 , wherein said silicon nitride powder is a mixture of two or more kinds of silicon nitride powders selected from the group consisting of a nitrogen-containing silane compound, an amorphous silicon nitride and a crystalline silicon nitride. 
   
   
       18 . The production method of an oxynitride phosphor comprising an α-sialon as the main component as claimed in any one of  claims 10  to  12 , wherein the oxynitride phosphor comprising an α-sialon as the main component obtained by firing is acid-washed to remove the excessive glass phase. 
   
   
       19 . A lighting device comprising an emission light source and the oxynitride phosphor comprising an α-sialon as the main component claimed in  claim 1  or  2 , the phosphor being represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y .   
   
   
       20 . The lighting device comprising an emission light source and an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 18 , wherein the emission light source is. LED of emitting light at a wavelength of 330 to 500 nm. 
   
   
       21 . An image display device comprising an excitation source and the oxynitride phosphor comprising an α-sialon as the main component claimed in  claim 1  or  2 , the phosphor being represented by the general formula:
   M x Si 12−(m+n) Al (m+n) O n N 16−n :Ln y .   
   
   
       22 . The image display device comprising an excitation source and an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 20 , wherein the excitation source is selected from the group consisting of an electron beam, an electric field, a vacuum ultraviolet ray and an ultraviolet ray. 
   
   
       23 . The image display device comprising an excitation source and an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 20 , wherein the image display device is one of a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP) and a cathode ray tube (CRT). 
   
   
       24 . The image display device comprising an excitation source and an oxynitride phosphor comprising an α-sialon as the main component as claimed in  claim 21 , wherein the image display device is one of a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP) and a cathode ray tube (CRT).