UV reflectors and UV-based light sources having reduced UV radiation leakage incorporating the same

• US 20020180351A1
• Filed: 04/30/2001
• Published: 12/05/2002
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: General Electric Company
• Inventors: Rose, James Wilson, McNulty, Thomas Francis, Doxsee, Daniel Darcy
• Granted Patent: US 6,686,676 B2
• Time in Patent Office: Days
• US Class Current: 313/512
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 5/206 comprising particles embedded in a solid matrix
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/19107 off-chip wires
• 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 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder

Abstract

UV reflectors incorporated in UV LED-based light sources reduce the amount of UV radiation emission into the surroundings and increase the efficiency of such light sources. UV reflectors are made of nanometer-sized particles having a mean particle diameter less than about one-tenth of the wavelength of the UV light emitted by the UV LED, dispersed in a molding or casting material surrounding the LED. Other UV reflectors are series of layers of materials having alternating high and low refractive indices; each layer has a physical thickness of one quarter of the wavelength divided by the refractive index of the material. Nanometer-sized textures formed on a surface of the multilayered reflector further reduce the emission of UV radiation into the surroundings. UV LED-based light sources include such a multilayered reflector disposed on an encapsulating structure of a transparent material around a UV LED, particles of a UV-excitable phosphor dispersed in the transparent material. Alternatively, the transparent material also includes nanometer-sized particles of a UV-radiation scattering material.

Claims

1. A UV reflector comprising particles of a UV-radiation scattering material dispersed in a substantially transparent material, said UV-radiation scattering material having a different refractive index than the refractive index of said substantially transparent material, said refractive indices being measured for light having wavelength of 555 nm.

2. The UV reflector according to claim 1, wherein said scattering material is selected from the group consisting of lead telluride, lead selenide, lead sulfide, germanium, gallium phosphide, silicon, indium arsenide, gallium arsenide, aluminum arsenide, rutile, boron phosphide, cadmium sulfide, cadmium telluride, zinc telluride, thallium bromoiodide, calcite, silicon carbide, cadmium lanthanum sulfide, strontium titanate, thallium chlorobromide, diamond, fabulite, zinc selenide, cadmium selenide, gallium nitride, aluminum nitride, lithium niobate, potassium niobate, germanium oxide, silver chloride, hafnium oxide, lithium iodate, zircon, yttrium oxide, silicon monoxide, sapphire, cesium iodide, lanthanum flint glass, cesium bromide, sodium iodide, magnesium iodide, dense flint glass, lanthanum trifluoride, silica, lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

3. The UV reflector according to claim 1, wherein said refractive index of said UV-radiation scattering material is less than the refractive index of said substantially transparent material.

4. The reflector according to claim 3, wherein said UV-radiation scattering material is selected from the group consisting of lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

5. The UV reflector according to claim 1, wherein said UV-radiation scattering material is a particulate dielectric material of which greater than 95% of the particle population has particle diameter less than about half of a maximum wavelength of UV radiation in said substantially transparent material and which has a mean particle diameter less than about one-tenth of said wavelength.

6. A UV reflector comprising a plurality of layers of materials having at least alternating first and second refractive indices, wherein said first refractive index is smaller than said second refractive index.

7. The UV reflector according to claim 6, wherein said first refractive index is less than the refractive index of a medium through which an incident light travels before impinging on said UV reflector, and said second refractive index is greater than the refractive index of said medium.

8. The UV reflector according to claim 6, wherein said first refractive index is less than about 2, preferably less than 1.5, more preferably less than about 1.4, and most preferably less than about 1.3.

9. The UV reflector according to claim 8, wherein said material having said first refractive index is selected from the group consisting of lithium iodate, zircon, sapphire, cesium iodide, lanthanum flint glass, sodium iodide, magnesium iodide, dense flint glass, silica, lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

10. The UV reflector according to claim 6, wherein said second refractive index is greater than about 1.5, preferably greater than about 1.7, more preferably greater than about 2, and most preferably greater than 2.3.

11. The UV reflector according claim 10, wherein said material having said second refractive index is selected from the group consisting of lead telluride, lead selenide, lead sulfide, germanium, gallium phosphide, silicon, indium arsenide, gallium arsenide, aluminum arsenide, rutile, boron phosphide, cadmium sulfide, cadmium telluride, zinc telluride, thallium bromoiodide, calcite, silicon carbide, cadmium lanthanum sulfide, strontium titanate, thallium chlorobromide, diamond, fabulite, zinc selenide, cadmium selenide, gallium nitride, aluminum nitride, lithium niobate, potassium niobate, germanium oxide, silver chloride, hafnium oxide, lithium iodate, zircon, yttrium oxide, silicon monoxide, sapphire, cesium iodide, lanthanum flint glass, cesium bromide, sodium iodide, magnesium iodide, dense flint glass, and mixture thereof.

12. The UV reflector according to claim 6, wherein a first layer of said plurality of layers comprises a material having said first refractive index, said first layer receiving an incident light having wavelengths in a UV-to-visible spectrum.

13. The UV reflector according to claim 12 further comprising an additional layer of a material having a third refractive index less than said first refractive index, said additional layer being attached to said first layer to receive said incident light.

14. The UV reflector according to claim 12, wherein each of said plurality of layers has a physical thickness in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer number selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said layer measured at light wavelength of 555 nm.

15. The UV reflector according to claim 14, wherein said plurality of layers comprises an odd number of layers.

16. The UV reflector according to claim 15, wherein said odd number of layers is greater than or equal to 5.

17. The UV reflector according to claim 15, wherein said odd number of layers is preferably greater than or equal to 11.

18. The UV reflector according to claim 12 further comprising a plurality of protrusions formed on a surface of said UV reflector on which an incident light impinges.

19. The UV reflector according to claim 18, wherein said protrusions are made of the same material as said first layer.

20. The UV reflector according to claim 19, wherein said protrusions have a shape selected from the group consisting of conical, pyramidal, and hemispherical shapes.

21. The UV reflector according to claim 18, wherein said protrusions have a largest dimension in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer number selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said protrusions measured at a light wavelength of 555 nm.

22. The UV reflector according to claim 21, wherein said largest dimension is a height of said protrusions.

23. The UV reflector according to claim 21, wherein said largest dimension is a largest cross-sectional dimension of a base of said protrusions.

24. The UV reflector according to claim 13 further comprising a plurality of protrusions formed on a surface of said additional layer on which said incident light impinges.

25. The UV reflector according to claim 24, wherein said protrusions are made of the same material as said additional layer.

26. The UV reflector according to claim 25, wherein said protrusions have a shape selected from the group consisting of conical, pyramidal, and hemispherical shapes.

27. The UV reflector according to claim 24, wherein said protrusions have a largest dimension in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said protrusion measured at a light wavelength of 555 nm.

28. The UV reflector according to claim 27, wherein said largest dimension is a height of said protrusions.

29. The UV reflector according to claim 27, wherein said largest dimension is a largest cross-sectional dimension of a base of said protrusions.

30. A light source based on at least one UV LED, said light source comprising:

a LED emitting UV radiation;

a shaped structure that comprises a substantially transparent molding or casting material, said shaped structure covering said LED;

particles of at least one phosphor that is excitable by said UV radiation, said phosphor disposed to receive said UV radiation and to convert said UV radiation to visible light; and

particles of at least one UV-radiation scattering material disposed among said particles of said phosphor;

wherein said particles of said phosphor and said particles of said scattering material are dispersed in at least a portion of said molding or casting material and wherein said particles are disposed in a vicinity of said LED.

31. The light source based on at least one UV LED according to claim 30, wherein said UV-radiation scattering material has a refractive index different from the refractive index of said molding or casting material, said refractive indices being measured for light having wavelength of 570 nm.

32. The light source based on at least one UV LED according to claim 31, wherein said scattering material is selected from the group consisting of lead telluride, lead selenide, lead sulfide, germanium, gallium phosphide, silicon, indium arsenide, gallium arsenide, aluminum arsenide, rutile, boron phosphide, cadmium sulfide, cadmium telluride, zinc telluride, thallium bromoiodide, calcite, silicon carbide, cadmium lanthanum sulfide, strontium titanate, thallium chlorobromide, diamond, fabulite, zinc selenide, cadmium selenide, gallium nitride, aluminum nitride, lithium niobate, potassium niobate, germanium oxide, silver chloride, hafnium oxide, lithium iodate, zircon, yttrium oxide, silicon monoxide, sapphire, cesium iodide, lanthanum flint glass, cesium bromide, sodium iodide, magnesium iodide, dense flint glass, lanthanum trifluoride, silica, lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

33. The light source based on at least one UV LED according to claim 31, wherein said refractive index of said UV-radiation scattering material is less than the refractive index of said substantially transparent molding or casting material.

34. The light source based on at least one UV LED according to claim 33, wherein said UV-radiation scattering material is selected from the group consisting of lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

35. The light source based on at least one UV LED according to claim 31, wherein said UV-radiation scattering material is a particulate dielectric material of which greater than 95% of the particle population has a particle diameter less than about half of a maximum wavelength of UV radiation in said substantially transparent molding or casting material and which has a mean particle diameter less than about one-tenth of said wavelength.

36. The light source based on at least one UV LED according to claim 30 further comprising a additional layer that comprises a particulate UV-radiation scattering material dispersed in a substantially transparent molding or casting material, said additional layer being disposed on said shaped structure in a direction of a viewer.

39. The light source based on at least one UV LED according to claim 38, wherein said first refractive index is smaller than the refractive index of said molding or casting material, and said second refractive index is greater than the refractive index of said molding or casting material.

40. The light source based on at least one UV LED according to claim 38, wherein said first refractive index is preferably less than about 1.5, more preferably less than about 1.4, and most preferably less than about 1.3;

and said second refractive index is preferably greater than about 1.7, more preferably greater than about 2, and most preferably greater than about 2.3.

41. The light source based on at least one UV LED according to claim 38, wherein said material having said first refractive index is selected from the group consisting of lithium iodate, zircon, sapphire, cesium iodide, lanthanum flint glass, sodium iodide, magnesium iodide, dense flint glass, silica, lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof.

42. The light source based on at least one UV LED according to claim 38, wherein said material having said second refractive index is selected from the group consisting of lead telluride, lead selenide, lead sulfide, germanium, gallium phosphide, silicon, indium arsenide, gallium arsenide, aluminum arsenide, rutile, boron phosphide, cadmium sulfide, cadmium telluride, zinc telluride, thallium bromoiodide, calcite, silicon carbide, cadmium lanthanum sulfide, strontium titanate, thallium chlorobromide, diamond, fabulite, zinc selenide, cadmium selenide, gallium nitride, aluminum nitride, lithium niobate, potassium niobate, germanium oxide, silver chloride, hafnium oxide, lithium iodate, zircon, yttrium oxide, silicon monoxide, sapphire, cesium iodide, lanthanum flint glass, cesium bromide, sodium iodide, magnesium iodide, dense flint glass, and mixture thereof.

43. The light source based on at least one UV LED according to claim 38, wherein said first layer of said plurality of layers comprises a material having said first refractive index, said first layer receiving an incident light traversing said shaped structure.

44. The light source based on at least one UV LED according to claim 38, wherein said UV reflector further comprises an additional layer of a material having a third refractive index less than said first refractive index, said additional layer being attached to said first layer to receive said incident light.

45. The light source based on at least one UV LED according to claim 43, wherein each of said plurality of layers has a physical thickness in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said layer measured at light wavelength of 555 nm.

46. The light source based on at least one UV LED according to claim 43, wherein said plurality of layers comprises an odd number of layers.

47. The light source based on at least one UV LED according to claim 43, wherein said odd number of layers is greater than or equal to 5.

48. The light source based on at least one UV LED according to claim 43, wherein said odd number of layers is preferably greater than or equal to 11.

49. The light source based on at least one UV LED according to claim 43, wherein said UV reflector further comprises a plurality of protrusions formed on a surface of said UV reflector on which an incident light traversing said shaped structure impinges.

50. The light source based on at least one UV LED according to claim 43, wherein said protrusions are made of the same material as said first layer.

51. The light source based on at least one UV LED according to claim 50, wherein said protrusions have a shape selected from the group consisting of conical, pyramidal, and hemispherical shapes.

52. The light source based on at least one UV LED according to claim 49, wherein said protrusions have a largest dimension in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer number selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said protrusions measured at a light wavelength of 555 nm.

53. The light source based on at least one UV LED according to claim 52, wherein said largest dimension is a height of said protrusions.

54. The light source based on at least one UV LED according to claim 52, wherein said largest dimension is a largest cross-sectional dimension of a base of said protrusions.

55. The light source based on at least one UV LED according to claim 44 further comprising a plurality of protrusions formed on a surface of said additional layer on which said incident light impinges.

56. The light source based on at least one UV LED according to claim 55, wherein said protrusions are made of the same material as said additional layer.

57. The light source based on at least one UV LED according to claim 56, wherein said protrusions have a shape selected from the group consisting of conical, pyramidal, and hemispherical shapes.

58. The light source based on at least one UV LED according to claim 55, wherein said protrusions have a largest dimension in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said protrusion measured at a light wavelength of 555 nm.

59. The light source based on at least one UV LED according to claim 58, wherein said largest dimension is a height of said protrusions.

60. The light source based on at least one UV LED according to claim 58, wherein said largest dimension is a largest cross-sectional dimension of a base of said protrusions.

61. The light source based on at least one UV LED according to claim 38 further comprising particles of a UV-radiation scattering material dispersed among said particles of said phosphor, said particles of said UV-radiation scattering material and said phosphor being dispersed in a portion of said molding or casting material.

37. A light source based on at least one UV LED, said light source comprising:

a LED emitting UV radiation;

a shaped structure that comprises a substantially transparent molding or casting material, said shaped structure covering said LED;

particles of at least one phosphor that is excitable by said UV radiation, said phosphor disposed to receive said UV radiation and to convert said UV radiation to visible light; and

a plurality of air bubbles having nanometer sizes, said air bubbles being formed among said particles of said phosphor in said substantially transparent molding or casting material;

wherein said particles of said phosphor and said air bubbles are dispersed in at least a portion of said molding or casting material and are disposed in a vicinity of said LED.

38. A light source based on at least one UV LED, said light source comprising:

a LED emitting UV radiation;

a shaped structure that comprises a substantially transparent molding or casting material, said shaped structure covering said LED;

particles of at least one phosphor that is excitable by said UV radiation, said phosphor disposed in a vicinity of said LED to receive said UV radiation and to convert said UV radiation to visible light, said particles of said phosphor dispersed in a portion of said molding or casting material; and

a UV reflector comprising a plurality of layers of materials having at least alternating first and second refractive indices, said first refractive index being smaller than said second refractive index, said UV reflector being disposed on said shaped structure in a direction of a viewer, wherein a first layer of said plurality of layers is disposed adjacent to said shaped structure.

62. A light source based on at least one UV LED, said light source comprising:

a LED emitting UV radiation;

a shaped structure that comprises a substantially transparent molding or casting material, said shaped structure covering said LED;

particles of at least one phosphor that is excitable by said UV radiation, said phosphor disposed in a vicinity of said LED to receive said UV radiation and to convert said UV radiation to visible light;

particles of at least one UV-radiation scattering material disposed among said particles of said phosphor, said particles of said phosphor and said particles of said UV-radiation scattering material being dispersed in a portion of said molding or casting material; and

a UV reflector comprising;

a plurality of layers of materials having at least alternating first and second refractive indices, said first refractive index being smaller than said second refractive index; and

a plurality of protrusions formed on a surface of said UV reflector adjacent to said shaped structure;

said UV reflector being disposed on said shaped structure in a direction of a viewer.

63. The light source based on at least one UV LED according to claim 62, wherein:

said UV-radiation scattering material has a different refractive index than the refractive index of said molding or casting material;

said UV-radiation scattering material is selected from the group consisting of lead telluride, lead selenide, lead sulfide, germanium, gallium phosphide, silicon, indium arsenide, gallium arsenide, aluminum arsenide, rutile, boron phosphide, cadmium sulfide, cadmium telluride, zinc telluride, thallium bromoiodide, calcite, silicon carbide, cadmium lanthanum sulfide, strontium titanate, thallium chlorobromide, diamond, fabulite, zinc selenide, cadmium selenide, gallium nitride, aluminum nitride, lithium niobate, potassium niobate, germanium oxide, silver chloride, hafnium oxide, lithium iodate, zircon, yttrium oxide, silicon monoxide, sapphire, cesium iodide, lanthanum flint glass, cesium bromide, sodium iodide, magnesium iodide, dense flint glass, lanthanum trifluoride, silica, lithium fluoride, magnesium fluoride, potassium fluoride, sodium fluoride, and mixtures thereof;

greater than ninety-five percent of said UV-radiation scattering particles has particle diameters less than about half of a maximum wavelength of UV radiation traversing said substantially transparent material and said UV-radiation scattering particles have a mean particle diameter less than about one-tenth of said wavelength;

said first refractive index of said UV reflector is less than about 1.5 and said second refractive index of said UV reflector is greater than about 1.7;

said plurality of layers comprising an odd number of layers, each of said layers having a physical thickness in a range from about 540 k/(4 n) to about 580 k/(4 n), wherein k is a positive integer selected from the group consisting of 1 and positive even integer numbers and where n is a refractive index of a material of said layer measured at a light wavelength of 555 nm;

a first layer of said plurality of layers disposed adjacent to said shaped structure has said first refractive index; and

said plurality of protrusions have a shape selected from the group consisting of conical, pyramidal, and hemispherical shapes, and said protrusions have a largest dimension in a range from about 540 k/(4 n) to about 580 k/(4 n),

wherein k is a positive integer number selected from the group consisting of 1 and positive even integer numbers and wherein n is a refractive index of a material of said protrusions, said largest dimensions being selected from the group consisting of a height and a largest cross-sectional dimension of a base of said protrusions.