LED LAMP WITH REMOTE PHOSPHOR COATING AND METHOD OF MAKING THE LAMP

• US 20110133222A1
• Filed: 06/24/2009
• Published: 06/09/2011
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Allen, Steven C., Speer, Richard S.
• Granted Patent: US 8,283,190 B2
• Time in Patent Office: Days
• US Class Current: 257/88
• CPC Class Codes: F21K 9/233 specially adapted for generating a spot light distribution, e.g. for substitution of reflector lamps
• 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 29/505 of reflectors
• CPC Class Codes: F21V 29/773 the planes containing the fins or blades having the direction of the light emitting axis
• CPC Class Codes: F21V 3/12 the coatings comprising photoluminescent substances
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body

Abstract

A light emitting diode (LED) lamp includes a base with one or more LED chips, an internal cover over the LED chips, where the cover is a translucent ceramic whose thermal conductivity is greater than glass, where the cover has an interior surface separated from the LED chips by a gap, and where an exterior surface of the cover is coated with a phosphor. The ceramic cover preferably has a bulk thermal conductivity of at least 5 W/(m·K), such as polycrystalline alumina. The LED chips preferably are blue LEDs and the phosphor is selected so that the lamp emits white light. In the method of making the lamp, the phosphor may be applied to the exterior surface of the cover as a preformed sheet or in a coating.

Claims

1. A light emitting diode (LED) lamp, comprising:

a base with one or more LED chips operably mounted thereon;

an internal cover on the base over the LED chips, the cover being an at least translucent ceramic whose thermal conductivity is greater than glass, an interior surface of the cover being separated from the LED chips by a gap; and

a phosphor coating an exterior surface of the cover, the phosphor converting light of a first wavelength range emitted by the LED chips to light of a different wavelength range.

2. The lamp of claim 1, wherein the ceramic has a bulk thermal conductivity of at least 5 W/(m·

K).

3. The lamp of claim 2, wherein the ceramic has a bulk thermal conductivity of at least 28 W/(m·

K).

4. The lamp of claim 2, wherein the ceramic is one of polycrystalline alumina, polycrystalline aluminum nitride, and polycrystalline aluminum oxynitride.

5. The lamp of claim 2, where the first wavelength range is 440-480 nm and the phosphor includes YAG:

Ce so that the lamp emits white light.

6. The lamp of claim 1, wherein the cover is a dome.

7. The lamp of claim 1, wherein the cover is a tube.

8. The lamp of claim 1, wherein the cover is a flat plate.

9. The lamp of claim 1, wherein the ceramic is one of single crystal alumina, aluminum nitride, and aluminum oxynitride.

10. The lamp of claim 1, further comprising a housing in which the base is mounted, the housing having an interior surface covered with a reflector that is arranged to redirect light emitted by the phosphor-coated cover and an exterior surface with heat dissipating fins.

11. The lamp of claim 1, further comprising a light reflective surface covering the base under the cover.

12. A method of making a light emitting diode (LED) lamp, comprising the steps of:

operably mounting one or more LED chips on a base;

covering the LED chips with an internal cover, the cover being an at least translucent ceramic whose thermal conductivity is greater than glass, an interior surface of the cover being separated from the LED chips by a gap; and

coating an exterior surface of the cover with a phosphor, the phosphor converting light of a first wavelength range emitted by the LED chips to light of a different wavelength range.

13. The method of claim 12, wherein the ceramic has a bulk thermal conductivity of at least 5 W/(m·

K).

14. The method of claim 13, wherein the ceramic is polycrystalline alumina.

15. The method of claim 13, where the first wavelength range is 440-480 nm and the phosphor includes YAG:

Ce so that the lamp emits white light.

16. The method of claim 12, further comprising mounting the base in a housing having an interior surface covered with a reflector that is arranged to redirect light emitted by the phosphor-coated cover and an exterior surface with heat dissipating fins.

17. The method of claim 12, further comprising covering the base under the cover with a light reflective surface.

18. The method of claim 12, wherein the coating step includes,

forming a sheet that includes the phosphor and a polymer matrix,

adhering the sheet to the exterior surface of the cover with an adhesive, and

removing the polymer matrix from the sheet by heating the sheet to at least 900°

F., leaving the phosphor on the exterior surface of the cover.

19. The method of claim 12, wherein the coating step includes,

coating the exterior surface of the cover with a suspension containing the phosphor and an organic binder, and

removing the organic binder by heating, leaving the phosphor on the exterior surface of the cover.

20. The method of claim 12, wherein the coating step includes,

coating the exterior surface of the cover with a suspension containing the phosphor and a silicone resin, and

curing the coated exterior surface, leaving the phosphor and silicone resin on the exterior surface of the cover.