Patent ID: 6383412
Filing Date: 2002-05-07
Classification: C09K,G21K

Abstract:
A process for preparing a rare earth element-activated, alkaline earth metal fluorohalide based stimulable phosphor which is represented by the basic compositional formula (I):Ba1âˆ’xMIIxFX:yMI,zLnâ€ƒâ€ƒ(I) wherein MII represents at least one alkaline earth metal selected from the group consisting of Sr and Ca; MI represents at least one alkaline metal selected from the group consisting of Li, Na, K, Rb, and Cs; X represents at least one halogen selected from the group consisting of Cl, Br, and I; Ln represents at least one rare earth element selected from the group consisting of Ce, Pr, Sm, Eu, Gd, Tb, Tm, and Yb; and x, y, and z represent, respectively, numerals within the ranges of 0&lE;x&lE;0.5, 0&lE;y&lE;0.05, and 0a mother liquor preparing step for preparing a reactant mother liquor which is an aqueous solution containing BaX2, a water-soluble compound of Ln, a halide, nitrate, nitrite, or acetate of MII in addition if x in the basic compositional formula (I) is not 0, and a halide, nitrate, nitrite, or acetate of MI in addition if y in the basic compositional formula (I) is not 0, wherein the solution has a BaX2 concentration of 2.5 mol/L or less if X is Cl or Br, or alternatively, a BaX2 concentration of 5.0 mol/L or less if X is I after the foregoing components are dissolved; a precipitate forming step for preparing the precipitate of crystals of a phosphor precursor by adding an aqueous solution of an inorganic fluoride salt to the reactant mother liquor kept at 20 to 100Â° C. while adjusting the adding rate in such a manner that the amount of the precipitate of crystals of a phosphor precursor to be formed during the addition is within the range of from 0.001 to 10 N/minute, where N is the amount of the precipitate of crystals of a phosphor precursor to be finally obtained; a separating step for separating the precipitate of crystals of a phosphor precursor from the aqueous solution; and a firing step for firing the separated precipitate of crystals of a phosphor precursor while avoiding sintering thereof.