Phosphor surface treatment method
A red phosphor in the form of a Mn-activated complex fluoride having the formula: A 2 MF 6 :Mn wherein M is one or more tetravalent elements selected from Si, Ti, Zr, Hf, Ge, and Sn, and A is one or more alkali metals selected from Li, Na, K, Rb, and Cs, and contains at least Na and/or K, is surface treated with a treating solution containing a surface treating agent selected from an organic amine, quaternary ammonium salt, alkyl betaine or fluorochemical surfactant, alkoxysilane, and fluorinated polymer.
1. A phosphor surface treatment method, comprising treating the surface of a red phosphor with a treating solution comprising a surface treating agent, wherein
said red phosphor is a Mn-activated complex fluoride of formula (1):
A 2 MF 6 :Mn (1)
wherein M is Si, and A is one or more alkali metals selected from the group consisting of Li, Na, K, Rb, and Cs, and contains at least Na and/or K; and
said surface treating agent is selected from the group consisting of:
(A) an organic amine of formula (2):
NR 1 R 2 R 3 (2)
wherein at least one of R 1 , R 2 and R 3 is a substituted or unsubstituted monovalent hydrocarbon group, and the remainder is hydrogen, and
(B) a quaternary ammonium salt of formula (2-1):
R 4 R 5 R 6 R 7 N + X − (2-1)
wherein R 4 , R 5 , R 6 and R 7 each are a substituted or unsubstituted monovalent hydrocarbon group, and X is a halogen atom.
2. The phosphor surface treatment method of claim 1 , wherein the treating solution is an aqueous solution of the surface treating agent containing hydrofluoric acid or an organic solvent solution of the surface treating agent.
3. The phosphor surface treatment method of claim 1 , wherein the treating solution further contains a complex fluoride of formula (3):
A 2 MF 6 (3)
wherein M is one or more tetravalent elements selected from the group consisting of Si, Ti, Zr, Hf, Ge, and Sn, and A is one or more alkali metals selected from the group consisting of Li, Na, K, Rb, and Cs, and contains at least Na and/or K.
4. The phosphor surface treatment method of claim 1 , wherein said red phosphor is a Mn-activated complex fluoride having the formula (1), which is obtained through the steps of:
adding a manganese compound of formula: Na 2 MnF 6 or K 2 MnF 6 to at least one of a first solution containing a fluoride of a tetravalent element M wherein M is Si, and a second solution containing a compound selected from the group consisting of a fluoride, hydrogenfluoride, nitrate, sulfate, hydrogensulfate, carbonate, hydrogencarbonate, and hydroxide of an alkali metal A wherein A is one or more metals selected from the group consisting of Li, Na, K, Rb, and Cs, and/or a solid compound of the alkali metal A, and
mixing the first solution with the second solution and/or the solid compound for thereby reacting the fluoride of tetravalent element M, the compound of alkali metal A, and the manganese compound.
5. The phosphor surface treatment method of claim 1 , wherein said red phosphor prior to the treating step is in particulate form of particle size distribution having a 50% by volume cumulative particle diameter D50 of at least 2 μm and a 90% by volume cumulative particle diameter D90 of up to 60 μm.
6. The phosphor surface treatment method of claim 1 , wherein the treating step includes immersing the red phosphor in the treating solution.
7. The phosphor surface treatment method of claim 1 , wherein the treating solution further contains a complex fluoride of formula (3):
A 2 MF 6 (3)
wherein M is Si, and A is one or more alkali metals selected from the group consisting of Li, Na, K, Rb, and Cs, and contains at least Na and/or K.