Method of preparing fluorescent material of small particle size

Claim 1

A method of preparing a fluorescent material of small particle size which comprises: synthesizing a fluorescent material consisting of Y 3 Al 5 O 12 :Tb, Y 2 O 2 S:Eu or Y 2 O 3 :Eu in a single phase; pulverizing the thus prepared fluorescent material whereby its luminescence is decreased, sieving the pulverized material so that particles of less than one micron particle size constitute less than 5% by volume of the sieved material, forming a mixture of the sieved fluorescent material and a flux, the mixture consisting of Y 3 Al 5 O 12 :Tb and BaF 2 flux, Y 2 O 2 lS:Eu and Na 2 CO 3 -(NH 4 ) 2 HPO 4 -S flux or Y 2 O 3 :Eu and BaCl 2 . 2H 2 O flux and heat treating said mixture at a temperature according to the following schedule: Y 3 Al 5 O 12 :Tb and BaF 2 flux at 1400° to 1700° C., Y 2 O 2 S:Eu and Na 2 CO 3 -(NH 4 ) 2 HPO 4 -S flux at 900° to 1000° C., and Y 2 O 3 :Eu and BaCl 2 ,2H 2 O flux at 1400° C. the heat treatment in each instance being sufficient so that the fluorescent material recovers substantially all the luminescence lost as a result of pulverizing.

Claim 2

A method of preparing a fluorescent material of small particle size which comprises: synthesizing a fluorescent material consisting of Y 3 Al 5 O 12 :Tb, Y 2 O 2 S:Eu or Y 2 O 3 :Eu in a single phase; pulverizing the thus prepared fluorescent material whereby its luminescence is decreased, sieving the pulverized material so that particles of less than one micron particle size constitute less than 5% by volume of the sieved material, forming a mixture of the sieved fluorescent material and a flux, the mixture consisting of Y 3 Al 5 O 12 :Tb and BaF 2 flux, Y 2 O 2 lS:Eu and Na 2 CO 3 -(NH 4 ) 2 HPO 4 -S flux or Y 2 O 3 :Eu and BaCl 2 . 2H 2 O flux and heat treating said mixture at a temperature according to the following schedule: Y 3 Al 5 O 12 :Tb and BaF 2 flux at 1400° to 1700° C., Y 2 O 2 S:Eu and Na 2 CO 3 -(NH 4 ) 2 HPO 4 -S flux at 900° to 1000° C., and Y 2 O 3 :Eu and BaCl 2 ,2H 2 O flux at 1400° C. the heat treatment in each instance being sufficient so that the fluorescent material recovers substantially all the luminescence lost as a result of pulverizing.