Europium activated cesium bromide phosphor and radiation image storage sheet

Abstract

An europium activated cesium bromide phosphor having the formula of CsBr:xEu [0<x≦0.2], in which a relationship between an emission intensity (I E ) of Eu 2+ and a coloring intensity (I F ) at F (Br − ) center satisfies the condition of 0.2≦I E xI F , and/or in which a ratio of Eu 2+ to Eu 3+ contained in the phosphor in terms of emission intensity satisfies the condition of 5×10 −5 ≦Eu 3+ /Eu 2+ ≦0.1 gives an increased stimulated emission amount and is favorably employed for producing a radiation image storage sheet.

What is claimed is:  
     
         1 . An europium activated cesium bromide phosphor having the formula (I): 
       CsBr:xEu  (I) 
       in which x is a number satisfying the condition of 0<x≦0.2, wherein a relationship between an emission intensity of Eu 2+  and a coloring intensity at F(Br − ) center satisfies the following condition: 
       0.2≦I E xI F   
       in which I E  and I F  represent the emission intensity and the coloring intensity, respectively.  
     
     
         2 . The europium activated cesium bromide phosphor of  claim 1 , which is in the form of prismatic crystals.  
     
     
         3 . The europium activated cesium bromide phosphor of  claim 1 , wherein the relationship between the emission intensity of Eu 2+  and a coloring intensity at F(Br − ) center satisfies the following condition: 
       0.5≦I E xI F ≦30.0 
       in which I E  and I F  represent the emission intensity and the coloring intensity, respectively.  
     
     
         4 . The europium activated cesium bromide phosphor of  claim 1 , wherein a ratio of Eu 3+  to Eu 2+  contained in the phosphor in terms of emission intensity satisfies the following condition: 
       5×10 −5 ≦Eu 3+ /Eu 2+ ≦0.1. 
     
     
         5 . The europium activated cesium bromide phosphor of  claim 4 , wherein a ratio of Eu 3+  to Eu 2+  contained in the phosphor in terms of emission intensity satisfies the following condition: 
       1×10 −4 ≦Eu 3+ /Eu 2+ ≦1×10 −2 .  
     
     
         6 . A radiation image storage sheet comprising the europium activated cesium bromide phosphor of  claim 1 .  
     
     
         7 . The radiation image storage sheet of  claim 6 , wherein the europium activated cesium bromide phosphor in the form of prismatic crystals is provided according to a vapor-phase accumulation method to form a phosphor film.  
     
     
         8 . The radiation image storage sheet of  claim 6 , wherein the europium activated cesium bromide phosphor is dispersed a binder polymer to form a phosphor film.  
     
     
         9 . An europium activated cesium bromide phosphor having the formula (I): 
       CsBr:xEu  (I) 
       in which x is a number satisfying the condition of 0<x≦0.2, wherein a ratio of Eu 3+  to Eu 2+  contained in the phosphor in terms of emission intensity satisfies the following condition: 
       5×10 −5 ≦Eu 3+ /Eu 2+ ≦0.1. 
     
     
         10 . The europium activated cesium bromide phosphor of  claim 9 , which is in the form of prismatic crystals.  
     
     
         11 . The europium activated cesium bromide phosphor of  claim 9 , wherein a ratio of Eu 3+  to Eu 2+  contained in the phosphor in terms of emission intensity satisfies the following condition: 
       1×10 −4 ≦Eu 3+ /Eu 2+ ≦1×10 −2 . 
     
     
         12 . A radiation image storage sheet comprising the europium activated cesium bromide phosphor of  claim 9 .  
     
     
         13 . The radiation image storage sheet of  claim 12 , wherein the europium activated cesium bromide phosphor in the form of prismatic crystals is provided according to a vapor-phase accumulation method to form a phosphor film.  
     
     
         14 . The radiation image storage sheet of  claim 12 , wherein the europium activated cesium bromide phosphor is dispersed in a binder polymer to form a phosphor film.