NARROW-BAND RED PHOSPHORS FOR LED LAMPS
A light emitting device (LED-Filament) comprises: a light-transmissive substrate; at least one blue LED chip mounted on a face of the light-transmissive substrate; and a photoluminescence material at least partially covering the at least one blue LED chip. The photoluminescence material comprises phosphor particles of at least one Group IIA/IIB selenide sulfide-based phosphor material that generates red light with a peak emission wavelength in a range of 600 nm to 640 nm and a full width at half maximum emission intensity of 50 nm to 55 nm. The LED-filament can be incorporated in a lamp, with a yellow to green-emitting phosphor that generates yellow to green light with a peak emission wavelength in a range of 520 nm to 570 nm, to provide light with a color temperature in a range of 1500 K to 4000 K and a General Color Rendering Index (CRI Ra) of greater than or equal to 90 and a CRI R9 greater than or equal to 50.
1 . A light emitting device comprising:
a light-transmissive substrate;
at least one blue LED chip mounted on a face of said light-transmissive substrate; and
a photoluminescence material at least partially covering said at least one blue LED chip, said photoluminescence material comprising phosphor particles of at least one Group IIA/IIB selenide sulfide-based phosphor material;
wherein said phosphor particles generate red light with a peak emission wavelength in a range of 600 nm to 640 nm and a full width at half maximum emission intensity of 50 nm to 55 nm.
2 . The light emitting device of claim 1 , wherein said Group IIA/IIB selenide sulfide-based phosphor material has a composition MSe 1-x S x : Eu, wherein M is at least one of Mg, Ca, Sr, Ba and Zn and 0<x<1.0.
3 . The light emitting device of claim 1 , wherein said phosphor particles generate red light with a peak emission wavelength in a range of 624 nm to 628 nm.
4 . The light emitting device of claim 1 , wherein said phosphor particles generate red light with a peak emission wavelength of about 626 nm.
5 . The light emitting device of claim 1 , wherein individual ones of said phosphor particles comprise an impermeable coating.
6 . The light emitting device of claim 5 , wherein said impermeable coating comprises one or more materials chosen from the group consisting of: amorphous alumina, aluminum oxide, silicon oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, boron oxide, chromium oxide, calcium fluoride, magnesium fluoride, zinc fluoride, aluminum fluoride and titanium fluoride.
7 . The light emitting device of claim 1 , wherein said light emitting device is characterized by CRI Ra of greater than or equal to 90.
8 . The light emitting device of claim 7 , wherein said light emitting device is further characterized by a CRI R9 of greater than or equal to 50.
9 . The light emitting device of claim 1 , wherein said phosphor particles comprise first particles with a first peak emission wavelength in a range of 624 nm to 628 nm and second particles with a second peak emission wavelength in a range of 630 nm to 638 nm.
10 . The light emitting device of claim 9 , wherein said light emitting device is characterized by a CRI Ra of greater than or equal to 90 and a CRI R9 of greater than or equal to 50.
11 . The light emitting device of claim 10 , wherein said first peak emission wavelength is about 626 nm and said second peak emission wavelength is about 634 nm.
12 . The light emitting device of claim 11 , wherein said photoluminescence material further comprises particles of a yellow to green-emitting phosphor that generates yellow to green light with a peak emission wavelength in a range of 520 nm to 570 nm.
13 . The light emitting device of claim 12 , wherein said yellow to green-emitting phosphor generates green light with a peak emission wavelength in a range of 520 nm to 540 nm.
14 . The light emitting device of claim 1 , wherein at least a part of said light-transmissive substrate comprises a material selected from the group consisting of magnesium oxide, sapphire, aluminum oxide, quartz glass, aluminum nitride and diamond.
15 . The light emitting device of claim 1 , wherein said light-transmissive substrate is elongate in form.
16 . A lamp comprising:
a light-transmissive envelope; and
at least one light emitting device located within said light-transmissive envelope, said light emitting device comprising:
a light-transmissive substrate;
at least one blue LED chip mounted on a face of said light-transmissive substrate; and
a photoluminescence material at least partially covering said at least one blue LED chip, said photoluminescence material comprising:
phosphor particles of at least one Group IIA/IIB selenide sulfide-based phosphor material that generates red light with a peak emission wavelength in a range of 600 nm to 640 nm and a full width at half maximum emission intensity of 50 nm to 55 nm; and
phosphor particles of a yellow to green-emitting phosphor that generates yellow to green light with a peak emission wavelength in a range of 520 nm to 570 nm;
wherein said lamp is operable to generate light with a color temperature in a range of 1500 K to 4000 K and a CRI Ra of greater than or equal to 90.
17 . The lamp of claim 16 , further characterized by generating light with a CRI R9 of greater than or equal to 50.
18 . The lamp of claim 16 , wherein said light-transmissive envelope is filled with an inert gas.
19 . The lamp of claim 18 , wherein said inert gas comprises helium.
20 . The lamp of claim 16 , wherein said Group IIA/IIB selenide sulfide-based phosphor material has a composition MSe 1-x S x :Eu, wherein M is at least one of Mg, Ca, Sr, Ba and Zn and 0<x<1.0.
21 . The lamp of claim 16 , wherein said phosphor particles generate red light with a peak emission wavelength in a range of 624 nm to 628 nm.
22 . The lamp of claim 16 , wherein said phosphor particles generate red light with a peak emission wavelength of about 626 nm.
23 . The lamp of claim 16 , wherein individual ones of said phosphor particles comprise an impermeable coating.
24 . The lamp of claim 23 , wherein said impermeable coating comprises one or more materials chosen from the group consisting of amorphous alumina, aluminum oxide, silicon oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, boron oxide, chromium oxide, calcium fluoride, magnesium fluoride, zinc fluoride, aluminum fluoride, and titanium fluoride.
26 . The lamp of claim 16 , wherein said phosphor particles comprise first particles with a first peak emission wavelength in a range of 624 nm to 628 nm and second particles with a second peak emission wavelength in a range of 630 nm to 638 nm.
27 . The lamp of claim 26 , wherein said first peak emission wavelength is about 626 nm and said second peak emission wavelength is about 634 nm.
28 . The lamp of claim 16 , wherein said yellow to green-emitting phosphor generates green light with a peak emission wavelength in a range of 520 nm to 540 nm.
29 . The lamp of claim 16 , wherein at least a part of said light-transmissive substrate comprises a material selected from the group consisting of magnesium oxide, sapphire, aluminum oxide, quartz glass, aluminum nitride, and diamond.
30 . The lamp of claim 16 , wherein said light-transmissive substrate is elongate in form.