Light emitting device with phosphor wavelength conversion

• US 20090101930A1
• Filed: 10/17/2007
• Published: 04/23/2009
• Est. Priority Date: 10/17/2007
• Status: Active Grant

• Current Assignee: Intematix Corporation
• Original Assignee: Intematix Corporation
• Inventors: Li, Yi-Qun
• Granted Patent: US 7,915,627 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: F21K 9/232 specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: F21V 13/14 the elements being filters or photoluminescent elements, reflectors and refractors
• CPC Class Codes: F21V 3/062 the material being plastics
• CPC Class Codes: F21V 3/12 the coatings comprising photoluminescent substances
• CPC Class Codes: F21V 9/32 characterised by the arrangement of the photoluminescent material
• CPC Class Codes: F21V 9/38 Combination of two or more photoluminescent elements of different materials
• CPC Class Codes: F21Y 2103/10 comprising a linear array of point-like light-generating elements
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01L 33/50 Wavelength conversion elements

Abstract

A light emitting device comprises an excitation source (20), one or more light emitting diode(s) operable to generate excitation light of a first wavelength range (λ₁) and a light emitting surface (14) having a phosphor material (26) which absorbs at least a part of the excitation light and emits light of a second wavelength range (λ₂), wherein light (32) emitted by the device comprises combined light of the first and second wavelength ranges emitted by the light emitting surface. The device is characterized by the light emitting surface having one or more window areas (28) which does not include a phosphor material and which are substantially transparent to light of the first and second wavelengths. The light emitting surface can comprise a transparent substrate (14) having a pattern of phosphor material on a surface thereof with the one or more window areas evenly distributed over the light emitting surface.

Claims

1. A light emitting device comprising:

at least one excitation source operable to generate excitation light of a first wavelength range and a light emitting surface having at least one phosphor material which absorbs at least a part of the excitation light and emits light of a second wavelength range, wherein light emitted by the device comprises combined light of the first and second wavelength ranges emitted by the light emitting surface, characterized in that the light emitting surface has at least one window area which does not include the at least one phosphor material, said window area being substantially transparent to light of the first and second wavelengths.

2. The light emitting device according to claim 1, wherein the light emitting surface comprises a substrate which is substantially transparent to light of the first and second wavelengths and which has the at least one phosphor material on a surface thereof.

3. The light emitting device according to claim 2, wherein the at least one phosphor material comprises an array of phosphor regions in which the gaps between phosphor regions defines the at least one window area.

4. The light emitting device according to claim 3, wherein the phosphor regions are distributed over substantially the entire surface of the light emitting surface.

5. The light emitting device according to claim 4, wherein the phosphor regions are substantially uniformly distributed over the light emitting surface.

6. The light emitting device according to claim 3, wherein the shape of the phosphor regions is selected from the group consisting of being substantially:

polygonal, square;

circular;

elliptical;

triangular; and

rectangular.

7. The light emitting device according to claim 2, wherein the at least one phosphor material covers substantially the light emitting surface and includes an array of window areas.

8. The light emitting device according to claim 7, wherein the window areas are distributed over substantially the entire surface of the light emitting surface.

9. The light emitting device according to claim 8, wherein the window areas are substantially uniformly distributed over the light emitting surface.

10. The light emitting device according to claim 7, wherein the shape of the window areas is selected from the group consisting of being substantially:

polygonal, square;

circular;

elliptical;

triangular; and

rectangular.

11. The light emitting device according to claim 2, wherein the substrate comprises a waveguiding medium and wherein the excitation source is configured to couple the excitation light into the substrate.

12. The light emitting device according to claim 11, wherein the substrate is substantially planar in form and wherein the excitation light is coupled into at least a part of an edge of the substrate.

13. The light emitting device according to claim 12, and further comprising a reflector on at least a part of the surface of the substrate opposite to the light emitting surface.

14. The light emitting device according to claim 12, and further comprising the light emitting surface of the substrate having a surface topology to promote the emission of light from the light emitting surface substrate.

15. The light emitting device according to claim 2, and further comprising a pattern of at least two different phosphor materials.

16. The light emitting device according to claim 2, wherein the substrate is selected from the group consisting of:

an acrylic;

a polycarbonate;

a polythene; and

a glass.

17. The light emitting device according to claim 1, wherein the at least one excitation source comprises a blue light emitting diode.

18. The light emitting device according to claim 17, and further comprising at least one light emitting diode operable to generate light of a third wavelength range which contributes to light emitted by the device by the light emitting surface.

19. The light emitting device according to claim 18, wherein the at least one light emitting diode is operable to generate light of a third wavelength range which is selected from the group consisting of:

orange light;

red light; and

green light.

20. The light emitting device according to claim 1, wherein the at least one phosphor material is selected from the group consisting of:

a silicate-based phosphor;

an aluminate-based phosphor;

a nitride-based phosphor material;

a sulfate-based phosphor material;

an oxy-nitride-based phosphor;

an oxy-sulfate-based phosphor;

a garnet material;

a silicate-based phosphor of a general composition A₃Si(OD)₅ in which Si is silicon, O is oxygen, A comprises strontium (Sr), barium (Ba), magnesium (Mg) or calcium (Ca) and D comprises chlorine (Cl), fluorine (F), nitrogen (N) or sulfur (S);

a silicate-based phosphor of a general composition A₂Si(OD)₄ in which A comprises Sr, Ba, Mg or Ca and D comprises Cl, F, N or S; and

an aluminate-based phosphor of formula M<sub>1−

x</sub>Eu_xAl_yO_[1+3y/2] in which M is at least one of a divalent metal comprising Ba, Sr, Ca, Mg, Mn, Zn, Cu, Cd, Sm or thulium (Tm).

21. A light emitting device comprising:

an enclosure having a reflecting inner surface;

at least one excitation source housed within the enclosure and operable to generate excitation light of a first wavelength range; and

a light emitting surface covering the opening of the enclosure and having at least one phosphor material which absorbs at least a part of the excitation light and emits light of a second wavelength range, wherein light emitted by the device comprises combined light of the first and second wavelength ranges emitted by the light emitting surface, characterized in that the light emitting surface has at least one area which does not include the at least one phosphor material said area being substantially transparent to light of the first and second wavelengths thereby allowing a part of excitation light and reflected phosphor generated light to pass through the light emitting surface.