Illumination System Comprising a Radiation Source and a Luminescent Material

Abstract

Illumination system comprising a radiation source and a luminescent material comprising a first phosphor capable of absorbing part of the light emitted by the radiation source and emitting light of a wavelength different from that of the absorbed light; wherein said first phosphor comprises europium(III) as an activator in a host lattice selected from the compounds of an anionic oxygen-containing species with a cationic metal species, comprising yttrium(III) and gadolinium(III). A light-emitting diode as a radiation source is especially contemplated. The invention also relates to a red to amber yellow emitting europium(III)-activated phosphor comprises europium(III) as an activator in a host lattice selected from the compounds of an anionic oxygen-containing species with a cationic metal species, comprising yttrium(III) and gadolinium(III). Furthermore the invention relates to the use of the phosphor for general illumination, traffic and signage lighting, automotive and for backlighting of liquid crystal displays.

Description

FIG. 1 is a schematic view of a dichromatic white LED lamp comprising a phosphor of the present invention positioned in a pathway of light emitted by an LED structure.

FIG. 2 shows the emission spectrum of a white light emitting LED with Tc=2500 K (CRI=76) comprising a blue (460 nm) emitting LED chip, (Y,Gd)₂O₃:Eu(III) as a red-emitting phosphor, and a broad-band green phosphor.

FIG. 3 shows luminous efficacy and CRI of a white light emitting LED with Tc=2500 K (CRI=76) comprising a blue (460 nm) emitting LED die, (Y,Gd)₂O₃:Eu(III) as a red-emitting phosphor and a broad-band green phosphor.

FIG. 4 shows the emission spectrum of a white light emitting LED with Tc=2500 K (CRI=76) comprising a blue (460 nm) emitting LED die, (Y,Gd)₂O₃:Eu(III) as a red-emitting phosphor, and (Ce,Tb)MgAl₁₁O₁₉ as a green phosphor.

FIG. 5 shows the luminous efficacy and CRI of a white light emitting LED with Tc=2500 K (CRI=76) comprising a blue (460 nm) emitting LED die, (Y,Gd)₂O₃:Eu(III) as a red-emitting phosphor, and (Ce,Tb)MgAl₁₁O₁₉ as a green phosphor.

Claims

1. Illumination system, comprising a radiation source and a luminescent material comprising a first phosphor capable of absorbing part of the light emitted by the radiation source and emitting light of a wavelength different from that of the absorbed light; wherein said first phosphor comprises europium(III) as an activator in a host lattice selected from the compounds of an anionic oxygen-containing species with a cationic metal species, comprising yttrium(III) and gadolinium(III).

2. Illumination system according to claim 1, wherein the radiation source is a light-emitting diode having an emission with a peak emission wavelength in the range of 325 to 495 nm.

3. Illumination system according to claim 1, wherein the luminescent material in addition comprises a second phosphor.

4. Illumination system according to claim 3, wherein the second phosphor is a green phosphor selected from the group of terbium(III)-activated compounds.

5. Illumination system according to claim 4, wherein the second phosphor is selected from the group of YxGd1-x)BO3:Tb (0<x<1),LaPO4:Tb; LaPO4:Ce,Th; (YxGd1-x)3Al5O12:Tb (0<x<1); CeMgAl11O19:Tb; GdMgB5O10:Ce,Th; (YxGd1-x)BO3:Tb(0<x<1); (YxGd1-x)2SiO5:Tb (0<x<1), Gd2O2S:Tb; LaOBr:Tb, and LaOCl:Tb.

6. Illumination system according to claim 1, wherein the luminescent material comprises a first phosphor combined with a photonic bandgap material.

7. Illumination system according to claim 1, wherein the luminescent material comprises a first phosphor having a medium (median?) grain size dm1>500 nanometers.

8. Illumination system according to claim 1, wherein the luminescent material comprises the first phosphor exhibiting a transparent monolithic ceramic microstructure.

9. Illumination system according to claim 1, wherein the luminescent material comprises a first phosphor having a grain size dm1 and a second phosphor having a grain size dm2<dm1.

10. Phosphor capable of absorbing part of the light emitted by the radiation source and emitting light of a wavelength different from that of the absorbed light; wherein said phosphor comprises europium(III) as an activator in a host lattice selected from the compounds of an anionic oxygen-containing species with a cationic metal species, comprising yttrium(III) and gadolinium(III).

11. Phosphor according to claim 10, wherein the molar proportion of the amount of gadolinium in the host lattice is less than 50 mole percent.

12. Phosphor according to claim 12, comprising in addition a co-activator selected from bismuth(III) and praseodymium(III).

13. Phosphor according to claim 12, wherein the anionic oxygen-containing species is selected from the group of oxide, oxysulfide, oxyhalides, borates, aluminates, gallates, silicates, germanates, phosphates, arsenate, vanadate, niobate, tantalate, and mixtures thereof.

14. Phosphor as claimed in claim 12, which phosphor comprises the activator in a molar proportion of 0.001 to 20 mole % relative to the cation in the host lattice.

15. Phosphor as claimed in claim 12, which phosphor comprises the co-activator in a molar proportion of 0.001 to 2 mole % relative to the cation in the host lattice.

16. Phosphor as claimed in claim 12, selected from the group of: (Y1-x-yGdx)2O2S:Euy, (Y1-x-yGdx)VO4:Euy, (Y1-x-y-zGdx)OCl:EuyBiz, (Y1-x-yGdx)(V,P,B)O4:Euy, (Y1-x-yGdx)NbO4:Euy, (Y1-x-yGdx)TaO4:Euy, and (Y1-x-y-zGdx)2O3:EuyBiz, wherein 0<x<1; 0<y<0.2 and 0<z<0.02.

17. Phosphor according to claim 12, wherein the phosphor is provided with a coating selected from the group of fluorides and orthophosphates of the elements aluminum, scandium, yttrium, lanthanum, gadolinium, and lutetium, the oxides of aluminum, yttrium, and lanthanum, and the nitride of aluminum.

18. Use of a phosphor according to claim 10 for general illumination, traffic and signage lighting, automotive and for backlighting of liquid crystal displays.