Encapsulant with scatterer to tailor spatial emission pattern and color uniformity in light emitting diodes

• US 7,999,283 B2
• Filed: 06/14/2007
• Issued: 08/16/2011
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Keller, Bernd, Chakraborty, Arpan
• Primary Examiner(s): Sandvik; Benjamin P
• Assistant Examiner(s): KHAN, FARID H
• Application Number:
  US11/818,818
• Publication Number:
  US 20080308825A1
• Time in Patent Office: 1,524 Days
• Field of Search: 257/13, 257/79, 257/98, 257/100, 257/E51.02, 257/E51.002, 257/E33.001, 257/E33.059, 257/E33.074, 257/E25.028, 257/E25.032, 438/22, 438/25, 438/29, 438/35, 313/503, 313/512, 362/31, 359/599
• US Class Current: 257/100
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

A light emitting device having an encapsulant with scattering features to tailor the spatial emission pattern and color temperature uniformity of the output profile. The encapsulant is formed with materials having light scattering properties. The concentration of these light scatterers is varied spatially within the encapsulant and/or on the surface of the encapsulant. The regions having a high density of scatterers are arranged in the encapsulant to interact with light entering the encapsulant over a desired range of source emission angles. By increasing the probability that light from a particular range of emission angles will experience at least one scattering event, both the intensity and color temperature profiles of the output light beam can be tuned.

Claims

1. A light emitting device, comprising:

at least one light emitter; and

an encapsulant arranged such that light that is emitted from said at least one emitter passes through said encapsulant, said encapsulant having light scattering properties that vary spatially in relation to the emission angle of light propagating through said encapsulant,

wherein said encapsulant comprises multiple three-dimensional (3-D) regions containing light scattering particles, said 3-D regions arranged within said encapsulant to tune the intensity profile of the light emitted from said at least one light emitter as a function of the viewing angle.

2. The light emitting device of claim 1, wherein said light scattering particles comprise one or more material from the group of titanium dioxide (TiO₂), alumina (Al₂O₃), and fumed silica (SiO₂).

3. The light emitting device of claim 1, wherein at least one of said regions contains a higher concentration of said light scattering particles relative to the other of said regions.

4. The light emitting device of claim 3, wherein said encapsulant has a bisecting cross-section, said cross-section showing a tip area disposed distal to said at least one light emitter, said tip area defining one of said 3-D regions having a high concentration of light scattering particles relative to an adjacent region.

5. The light emitting device of claim 3, said encapsulant comprising multiple 3-D regions having a high concentration of light scattering particles relative to the other of said regions.

6. The light emitting device of claim 1, wherein one or more portions of the surface of said encapsulant are modified to scatter emitted light incident on said surface.

7. The light emitting device of claim 6, wherein a portion of the surface of said encapsulant is modified to scatter emitted light incident on said surface.

8. The light emitting device of claim 1, further comprising a layer of wavelength conversion material surrounding the exposed portions of said at least one light emitter.

9. The light emitting device of claim 1, further comprising a reflector element disposed on said substrate, said reflector having a substantially toroidal shape with said encapsulant and said at least one emitter arranged in the center, said reflector element comprising inner walls to redirect light from said at least one emitter toward said encapsulant.

10. The light emitting device of claim 9, wherein said reflector element inner walls are modified to scatter incident light.

11. The light emitting device of claim 1, wherein said at least one emitter comprises a plurality of emitters.

16. The light emitting device of claim 11, wherein said plurality of emitters emit at least two different colors of light.

12. A light emitting device, comprising:

at least one emitter disposed on a surface; and

an encapsulant disposed above said emitter such that light emitted from said device passes through said encapsulant, said encapsulant having multiple three-dimensional (3-D) regions with associated concentrations of light scattering particles, said 3-D regions arranged within said encapsulant to modify the output intensity and color temperature profiles of said light emitting device,

wherein said 3-D regions are arranged within said encapsulant to tune the intensity profile of the emitted light as a function of the viewing angles.

13. The light emitting device of claim 12, wherein said 3-D regions are arranged within said encapsulant to improve the color uniformity of the emitted light over a range of viewing angles.

14. The light emitting device of claim 12, wherein said encapsulant comprises a 3-D region having a high concentration of light scattering particles relative to an adjacent region, said 3-D region disposed at the tip of said encapsulant opposite said at least one emitter.

15. The light emitting device of claim 12, further comprising a plurality of emitters disposed on said surface.