INCANDESCENT LAMP INCORPORATING INFRARED-REFLECTIVE COATING SYSTEM, AND LIGHTING FIXTURE INCORPORATING SUCH A LAMP

• US 20080049428A1
• Filed: 07/25/2007
• Published: 02/28/2008
• Est. Priority Date: 07/25/2006
• Status: Active Grant

• Current Assignee: David W. Cunningham
• Original Assignee: David W. Cunningham
• Inventors: Cunningham, David W.
• Granted Patent: US 8,436,519 B2
• Time in Patent Office: Days
• US Class Current: 362/293
• CPC Class Codes: G02B 5/0833 comprising inorganic materials only
• CPC Class Codes: H01K 1/325 Reflecting coating

Abstract

The present invention provides an improved lamp, and lighting fixture incorporating such a lamp, wherein the lamp'"'"'s envelope includes a special optical coating system configured to more effectively reflect infrared light back toward the lamp filament, thereby enhancing the lamp'"'"'s luminous efficacy. Multiple embodiments are disclosed, including coating systems deposited on one or both surfaces of the lamp envelope and including coating systems incorporating either a dielectric coating alone or specific combinations of a dielectric coating and a transparent conductive coating.

Claims

1. An incandescent lamp comprising:

a filament that, when heated, emits visible light and infrared light;

an envelope enclosing the filament and including an inner surface facing toward the filament and an outer surface facing away from the filament; and

a coating system deposited on the envelope and including

a dielectric coating configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament, and

a transparent conductive coating located on the side of the dielectric coating opposite the filament and configured to transmit a substantial portion of visible light emitted by the filament and transmitted through the dielectric coating, and further configured to reflect a substantial portion of infrared light emitted by the filament and transmitted through the dielectric coating.

2. The incandescent lamp as defined in claim 1, wherein the dielectric coating and the transparent conductive coating both are located on the inner surface of the envelope.

3. The incandescent lamp as defined in claim 2, wherein the coating system further includes a diffusion barrier located adjacent to the dielectric coating, on the side of the dielectric coating nearest the filament.

4. The incandescent lamp as defined in claim 3, wherein the diffusion barrier is configured to substantially reduce the diffusion of a halogen gas and halogen-containing compounds located within the envelope, wherein the halogen is selected from the group consisting of bromine, iodine, and fluorine.

5. The incandescent lamp as defined in claim 2, wherein the coating system further includes:

a first diffusion barrier located adjacent to the dielectric coating, on the side of the dielectric coating nearest the filament;

a second diffusion barrier located between the dielectric coating and the transparent conductive coating; and

a third diffusion barrier located between the transparent conductive coating and the envelope.

6. The incandescent lamp as defined in claim 5, wherein:

the first diffusion barrier is configured to substantially reduce the diffusion of a halogen gas and halogen-containing compounds located within the envelope, wherein the halogen is selected from the group consisting of bromine, iodine, and fluorine; and

the second and third diffusion barriers both are configured to substantially reduce the diffusion of a material selected from the group consisting of oxygen gas and doping elements present in the transparent conductive coating, including fluorine, tin, and aluminum.

7. The incandescent lamp as defined in claim 6, wherein the first, second, and third diffusion barriers comprise a material selected from the group consisting of silicon nitride, aluminum oxide, silicon dioxide, and mixtures thereof.

8. The incandescent lamp as defined in claim 2, wherein the envelope comprises a material selected from the group consisting of fused silica, alumino-silicate, and borosilicate glass.

9. The incandescent lamp as defined in claim 1, wherein the dielectric coating and the transparent conductive coating both are located on the outer surface of the envelope.

10. The incandescent lamp as defined in claim 9, wherein the coating system further includes an infrared-emissive coating located on the side of the transparent conductive coating opposite the dielectric coating, wherein the infrared-emissive coating has a weighted average emissivity greater than 0.3 in the wavelength range corresponding substantially to the spectral power distribution of a black body at the temperature of the envelope, and is configured to transmit a substantial portion of visible light transmitted through the transparent conductive coating.

11. The incandescent lamp as defined in claim 10, wherein the coating system further includes a diffusion barrier located adjacent to the infrared-emissive coating, on the side of the infrared-emissive coating opposite the transparent conductive coating.

12. The incandescent lamp as defined in claim 10, wherein the coating system further includes:

a first diffusion barrier located between the dielectric coating and the transparent conductive coating;

a second diffusion barrier located between the transparent conductive coating and the infrared-emissive coating; and

a third diffusion barrier located adjacent to the infrared-emissive coating, on the side of the infrared-emissive coating opposite the transparent conductive coating.

13. The incandescent lamp as defined in claim 12, wherein the first, second, and third diffusion barriers comprise a material selected from the group consisting of silicon nitride, aluminum oxide, and silicon dioxide.

14. The incandescent lamp as defined in claim 10, wherein the infrared-emissive coating comprises a material selected from the group consisting of fluorine-doped tin oxide, fluorine-doped zinc oxide, tin-doped indium oxide, aluminum-doped zinc oxide, and mixtures thereof.

15. The incandescent lamp as defined in claim 1, wherein:

the dielectric coating is deposited on the inner surface of the envelope; and

the transparent conductive coating is deposited on the outer surface of the envelope.

16. The incandescent lamp as defined in claim 15, wherein the dielectric coating is deposited using a plasma-impulse chemical vapor deposition or atomic layer deposition process.

17. The incandescent lamp as defined in claim 15, wherein the coating system further includes:

a first diffusion barrier located adjacent to the dielectric coating, on the side of the dielectric coating nearest the filament;

a second diffusion barrier located between the envelope and the transparent conductive coating;

an infrared-emissive coating located on the side of the transparent conductive coating opposite the envelope, wherein the infrared-emissive coating has a weighted average emissivity greater than 0.3 in the wavelength range corresponding substantially to the spectral power distribution of a black body at the temperature of the envelope, and is configured to transmit a substantial portion of visible light transmitted through the transparent conductive coating;

a third diffusion barrier located between the transparent conductive coating and the infrared-emissive coating; and

a fourth diffusion barrier located on the infrared-emissive coating, on the side facing away from the filament.

18. The incandescent lamp as defined in claim 1, wherein:

the dielectric coating includes an inner dielectric coating located on the inner surface of the envelope and an outer dielectric coating located on the outer surface of the envelope; and

the transparent conductive coating is located adjacent to the outer dielectric coating, on the side of the outer dielectric coating facing away from the filament.

19. The incandescent lamp as defined in claim 18, wherein:

the inner dielectric coating and the outer dielectric coating each include a plurality of dielectric layers having prescribed refractive indices and prescribed thicknesses; and

the plurality of layers of the inner dielectric coating and the plurality of layers of the outer dielectric coating are identical to each other, relative to the envelope.

20. The incandescent lamp as defined in claim 19, wherein the inner and outer dielectric coating are deposited simultaneously using an atomic layer deposition process.

21. The incandescent lamp as defined in claim 19, wherein the coating system further includes:

a first diffusion barrier located adjacent to the inner dielectric coating, on the side of the inner dielectric coating facing the filament;

a second diffusion barrier located between the outer dielectric coating and the transparent conductive coating;

an infrared-emissive coating located on the side of the transparent conductive coating opposite the envelope, wherein the infrared-emissive coating has a weighted average emissivity greater than 0.3 in the wavelength range corresponding substantially to the spectral power distribution of a black body at the temperature of the envelope, and is configured to transmit a substantial portion of visible light transmitted through from the transparent conductive coating;

a third diffusion barrier located between the transparent conductive coating and the infrared-emissive coating; and

a fourth diffusion barrier located on the infrared-emissive coating, on the side facing away from the filament.

22. The incandescent lamp as defined in claim 1, wherein the transparent conductive coating comprises a material selected from the group consisting of indium-doped tin oxide, aluminum-doped zinc oxide, titanium-doped indium oxide, fluorine-doped tin oxide, fluorine-doped zinc oxide, cadmium stannate, gold, silver, and mixtures thereof.

23. The incandescent lamp as defined in claim 1, wherein the dielectric coating comprises a plurality of dielectric layers having prescribed refractive indices and prescribed thicknesses.

24. The incandescent lamp as defined in claim 23, wherein:

the plurality of dielectric layers comprise alternating layers of a first material having a relatively low refractive index and of a second material having a relatively high refractive index; and

the envelope has a coefficient of thermal expansion that is equal to or greater than that of the second material.

25. The incandescent lamp as defined in claim 24, wherein:

the second material is selected from the group consisting of niobia, titania, tantala, and mixtures thereof; and

the envelope comprises a material selected from the group consisting of alumino-silicate and borosilicate glass.

26. The incandescent lamp as defined in claim 24, wherein the second material of the dielectric coating is deposited at a temperature intermediate 25°

C. and the temperature of envelope when the lamp is operated at full power.

27. The incandescent lamp as defined in claim 26, wherein the second material of the dielectric coating is deposited at a temperature in the range of 350 to 450°

C.

28. The incandescent lamp as defined in claim 1, and further comprising a concave reflector integral with the envelope, for reflecting light emitted by the filament.

29. A lighting fixture comprising:

a housing;

a concave reflector mounted on the housing;

an electrical socket mounted in a prescribed position relative to the concave reflector;

an incandescent lamp including

a base configured to releasably seat in the electrical socket and to receive electrical power therefrom,

a filament that, when heated, emits visible light and infrared light,

an envelope secured to the base and cooperating with the base to enclose the filament, wherein the envelope includes an inner surface facing toward the filament and an outer surface facing away from the filament, and

a coating system deposited onto the envelope and including

a dielectric coating configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament, and

a transparent conductive coating located on the side of the dielectric coating opposite the filament and configured to transmit a substantial portion of visible light emitted by the filament and transmitted through the dielectric coating, and further configured to reflect a substantial portion of infrared light emitted by the filament and transmitted through the dielectric coating.

30. The lighting fixture as defined in claim 29, wherein the dielectric coating and the transparent conductive coating of the coating system both are located on the inner surface of the envelope.

31. The lighting fixture as defined in claim 29, wherein:

the dielectric coating and the transparent conductive coating of the coating system both are located on the outer surface of the envelope; and

the coating system further includes an infrared-emissive coating located on the side of the transparent conductive coating opposite the dielectric coating, wherein the infrared-emissive coating has a weighted average emissivity greater than 0.3 in the wavelength range corresponding substantially to the spectral power distribution of a black body at the temperature of the envelope, and is configured to transmit a substantial portion of visible light transmitted through the transparent conductive coating.

32. The lighting fixture as defined in claim 29, wherein.

the dielectric coating of the coating system is deposited on the inner surface of the envelope;

and

the transparent conductive coating of the coating system is deposited on the outer surface of the envelope.

33. The lighting fixture as defined in claim 29, wherein the dielectric coating includes an inner dielectric coating located on the inner surface of the envelope and an outer dielectric coating located on the outer surface of the envelope.

34. The lighting fixture as defined in claim 29, wherein the transparent conductive coating comprises a material selected from the group consisting of indium-doped tin oxide, aluminum-doped zinc oxide, titanium-doped indium oxide, fluorine-doped tin oxide, fluorine-doped zinc oxide, cadmium stannate, gold, silver, and mixtures thereof.

35. The lighting fixture as defined in claim 29, wherein the dielectric coating comprises a plurality of dielectric layers having prescribed refractive indices and prescribed thicknesses.

36. An incandescent lamp comprising:

a filament that, when heated, emits visible light and infrared light;

an envelope enclosing the filament and including an inner surface facing toward the filament and an outer surface facing away from the filament; and

a coating system deposited onto the envelope and including a dielectric coating configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament, wherein the dielectric coating comprises a plurality of alternating layers of a first material having a relatively low refractive index and of a second material having a relatively high refractive index;

wherein the envelope has a coefficient of thermal expansion that is equal to or greater than that of the second material of the dielectric coating.

37. The incandescent lamp as defined in claim 36, wherein:

the second material of the dielectric coating is selected from the group consisting of niobia, titania, tantala, and mixtures thereof; and

the envelope comprises a material selected from the group consisting of alumino-silicate and borosilicate glass.

38. The incandescent lamp as defined in claim 36, wherein the second material of the dielectric coating is deposited at a temperature intermediate 25°

C. and the temperature of the envelope when the lamp is operated at full power.

39. The incandescent lamp as defined in claim 38, wherein the second material of the dielectric coating is deposited at a temperature in the range of 350 to 450°

C.

40. The incandescent lamp as defined in claim 36, wherein the coating system further includes a transparent conductive coating located on the side of the dielectric coating opposite the filament and configured to transmit a substantial portion of visible light emitted by the filament and transmitted through the dielectric coating, and further configured to reflect a substantial portion of infrared light emitted by the filament and transmitted through the dielectric coating.

41. A lighting fixture comprising:

a housing;

a concave reflector mounted on the housing;

an electrical socket mounted in a prescribed position relative to the concave reflector;

an incandescent lamp including

a base configured to releasably seat in the electrical socket and to receive electrical power therefrom,

a filament that, when heated, emits visible light and infrared light;

an envelope enclosing the filament and including an inner surface facing toward the filament and an outer surface facing away from the filament; and

a coating system deposited onto the envelope and including a dielectric coating configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament, wherein the dielectric coating comprises a plurality of alternating layers of a first material having a relatively low refractive index and of a second material having a relatively high refractive index;

wherein the envelope has a coefficient of thermal expansion that is equal to or greater than that of the second material of the dielectric coating.

42. An incandescent lamp comprising:

a filament that, when heated, emits visible light and infrared light;

an envelope enclosing the filament and including an inner surface facing toward the filament and an outer surface facing away from the filament; and

a coating system deposited on the envelope and including an inner dielectric coating deposited on the inner surface of the envelope and an outer dielectric coating deposited on the outer surface of the envelope, wherein the coating system is configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament.

43. The incandescent lamp as defined in claim 42, wherein the inner and outer dielectric coatings each include a plurality of dielectric layers having prescribed refractive indices and prescribed thicknesses.

44. The incandescent lamp as defined in claim 43, wherein the plurality of layers of the inner dielectric coating and the plurality of layers of outer dielectric coating are identical to each other, relative to the envelope.

45. The incandescent lamp as defined in claim 44, wherein the inner and outer dielectric coating are deposited simultaneously using an atomic layer deposition process.

46. The incandescent lamp as defined in claim 42, wherein:

the coating system further includes a transparent conductive coating deposited on the outer surface of the envelope, on the side of the outer dielectric coating opposite the filament; and

the transparent conductive coating is configured to transmit a substantial portion of visible light emitted by the filament and transmitted through the inner and outer dielectric coatings and is further configured to reflect a substantial portion of infrared light emitted by the filament and transmitted through the inner and outer dielectric coatings.

47. A lighting fixture comprising:

a housing;

a concave reflector mounted on the housing;

an electrical socket mounted in a prescribed position relative to the concave reflector;

an incandescent lamp including

a base configured to releasably seat in the electrical socket and to receive electrical power therefrom,

a filament that, when heated, emits visible light and infrared light;

an envelope enclosing the filament and including an inner surface facing toward the filament and an outer surface facing away from the filament; and

a coating system deposited on the envelope and including an inner dielectric coating deposited on the inner surface of the envelope and an outer dielectric coating deposited on the outer surface of the envelope, wherein the coating system is configured to transmit a substantial portion of visible light emitted by the filament and to reflect a substantial portion of infrared light emitted by the filament.