Long-lasting phosphor ceramics and manufacturing method thereof

Abstract

A method for manufacturing MAl 2 O 4 :Eu,RE type long-lasting phosphor ceramics that is capable of producing the ceramics at a reduced raw material cost. In addition, a sintered product of a long-lasting phosphor having no yellow body color. More specifically, the method for manufacturing MAl 2 O 4 :Eu,RE type long-lasting phosphor ceramics in which M is an alkaline earth element and RE is a rare earth element other than europium, involving mixing a BAM (alkaline earth aluminate) phosphor, an alkaline earth compound, an aluminum compound and a rare earth compound to form a mixture, and then firing the mixture; and a white MAl 2 O 4 :Eu,RE type long-lasting phosphor resulting from the method.

What is claimed is: 
     
         1 . Long-lasting phosphor ceramics obtained by the method according  claim 1 ,
 comprising the steps of:   mixing an alkaline earth aluminate phosphor, an alkaline earth compound, an aluminum compound, and a rare earth compound to form a mixture; and   firing the mixture, and   being represented by the compositional formula (1):
   M (1-r-t) Al 2 O 4 :Eu r ,RE s ,Mn t   (1)
 
   wherein M is at least one element selected from the group consisting of Ba, Sr, Mg and Ca; RE is at least one rare earth element other than Eu; r is a number from 0.005 to 0.05; s is a number from 0.005 to 0.05; and t is a number from 0 to 0.08.   
     
     
         2 . The long-lasting phosphor ceramics according to  claim 1 , having a whiteness of L*≧80, −10≦a*≦10 and −10≦b*≦10, as evaluated in an L*a*b* color system. 
     
     
         3 . The long-lasting phosphor ceramics according to  claim 1 , being represented by the compositional formula (2):
   M (1-r-t) Al 2 O 4 :Eu r ,Dy s ,Mn t   (2)
   wherein M is at least one element selected from the group consisting of Ba, Sr, Mg, and Ca; r is a number from 0.005 to 0.05; s is a number from 0.005 to 0.05; and t is a number from 0 to 0.08; and   having a whiteness of L*≧80, −10≦a*≦10 and −10≦b*≦10, as evaluated in an L*a*b* color system.