High CRI electroluminescent lamp
An electroluminescent lamp having a high color rendering index (CRI) can be made using a phosphor blend comprising a mixture of an electroluminescent phosphor and an europium-activated alkaline earth silicon nitride phosphor, wherein the electroluminescent phosphor is selected from a blue-emitting electroluminescent phosphor, a blue-green-emitting electroluminescent phosphor, or a combination thereof. Preferably, the lamp exhibits a CRI of at least about 75, and, more preferably, at least about 80. A preferred blend contains from about 10% to about 20% by weight of the europium-activated alkaline earth silicon nitride phosphor.
1. An electroluminescent lamp including a phosphor blend comprised of a mixture of an electroluminescent phosphor and an europium-activated alkaline earth silicon nitride phosphor, the electroluminescent phosphor selected from a blue-emitting electroluminescent phosphor, a blue-green-emitting electroluminescent phosphor, or a combination thereof.
2. The lamp of claim 1 wherein the europium-activated alkaline earth silicon nitride phosphor is represented by the formula, M x Si y N z :Eu, wherein M is selected from Ca, Sr, and Ba and wherein z=2x/3+4y/3.
3. The lamp of claim 1 wherein the europium-activated alkaline earth silicon nitride phosphor is represented by the formula, M 2 Si 5 N 8 :Eu wherein M is selected from Ca, Sr, and Ba.
4. The lamp of claim 1 wherein the europium-activated alkaline earth silicon nitride phosphor is represented by the formula, MSi 7 N 10 :Eu wherein M is selected from Ca, Sr, and Ba.
5. The lamp of claim 1 wherein the europium-activated alkaline earth silicon nitride phosphor is Ca 2 Si 5 N 8 :Eu.
6. The lamp of claim 1 wherein the blend contains from about 10% to about 20% by weight of the europium-activated alkaline earth silicon nitride phosphor.
7. The lamp of claim 1 wherein the blue-emitting electroluminescent phosphor is ZnS:Cu and the blue-green-emitting electroluminescent phosphor is ZnS:Cu,Cl.
8. The lamp of claim 1 wherein the blue-emitting electroluminescent phosphor emits at a wavelength from about 400 nm to about 470 nm and the blue-green-emitting electroluminescent phosphor emits at a wavelength from about 470 nm to about 550 nm.
9. The lamp of claim 8 wherein the europium-activated alkaline earth silicon nitride phosphor is excited at a wavelength from about 200 nm to about 500 nm and exhibits an emission maximum at a wavelength from about 600 nm to about 680 nm.
10. The lamp of claim 1 wherein the lamp exhibits a CRI of at least about 75.
11. The lamp of claim 1 wherein the lamp exhibits a CRI of at least about 80.
12. The lamp of claim 5 wherein the lamp exhibits a CRI of about 85.
13. The lamp of claim 1 wherein the lamp exhibits an x color coordinate from about 0.29 to about 0.39 and a y color coordinate from about 0.35 to about 0.39.
14. The lamp of claim 13 wherein the blend contains from about 10% to about 20% by weight of the europium-activated alkaline earth silicon nitride phosphor.
15. The lamp of claim 14 wherein the europium-activated alkaline earth silicon nitride phosphor is Ca 2 Si 5 N 8 :Eu.
16. The lamp of claim 2 wherein the europium concentration is from 1 to 10 atomic % compared to the alkaline earth ion.