Elemental semiconductor mirror for vehicles and method for making same

• US 6,286,965 B1
• Filed: 05/08/1998
• Issued: 09/11/2001
• Est. Priority Date: 05/15/1991
• Status: Expired due to Fees

• Current Assignee: Donnelly Corporation (Magna International Incorporated)
• Original Assignee: Donnelly Corporation (Magna International Incorporated)
• Inventors: Lynam, Niall R., Hichwa, Bryant P., Caskey, Gregory T.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US09/074,810
• Time in Patent Office: 1,222 Days
• Field of Search: 359/603, 359/608, 359/584, 359/585, 359/589, 359/883, 359/884, 437/81, 437/238, 437/240
• US Class Current: 359/603
• CPC Class Codes: B60R 1/082 using a single wide field mirror or an association of rigidly connected mirrors
• CPC Class Codes: B60R 1/083 Anti-glare mirrors, e.g. "day-night" mirrors
• CPC Class Codes: G02B 5/0833 comprising inorganic materials only
• CPC Class Codes: G02B 7/181 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A elemental mirror for vehicles having a luminous reflectance of at least about 30% includes a substrate coated with a thin layer of elemental semiconductor having an index of refraction of at least 3 and an optical thickness of at least about 275 angstroms. Preferably, the elemental semiconductor coating is sputter coated silicon or germanium and a light absorbing coating is included therebehind. The mirror is spectrally nonselective with elemental semiconductor optical thicknesses of about 275 to 2400 angstroms on the front substrate surface. Spectrally selective mirrors are provided by adding an interference coating to the elemental semiconductor layer coating, preferably of a dielectric such as silicon dioxide or silicon nitride, on either the front or rear substrate surface, or by using a thicker, single elemental semiconductor layer. Instead of an absorbing coating behind the mirror, additional elemental semiconductor and dielectric thin layers may be included to reduce secondary reflections. The method includes coating the thin elemental semiconductor layer on flat glass and heating to harden the layer and make it more scratch resistant, or heating and bending the glass without destroying the reflective properties of the mirror. The thin interference layer, secondary reflection reducing layers, and/or light absorbing coating may be coated before or after heating and bending.

Claims

1. A mirror for vehicles comprising:

a substrate having front and rear surfaces;

a thin layer of an elemental semiconductor on one surface of said substrate, said semiconductor coating layer having an index of refraction of at least 3 and an optical thickness of at least about 275 angstroms;

said thin layer providing said mirror with a luminous light reflectance of at least 30% of the light incident thereon from the direction of said front surface of said substrate, wherein said substrate is transparent and includes a light absorbing coating on said rear surface which absorbs light transmitted by said semiconductor thin layer and substrate.

2. The mirror of claim 1 wherein said elemental semiconductor is selected from the group including silicon and germanium.

3. The mirror of claim 2 wherein said mirror is a spectrally selective mirror and provides reflectance of a desired color/hue;

said elemental semiconductor thin layer being silicon, applied on said front surface of said substrate, and having an optical thickness of within the range of between about 2400 and 10,000 angstroms.

4. The mirror of claim 2 including additional thin film layers.

5. The mirror of claim 4 wherein said additional thin film layers include a second layer of an elemental semiconductor and a thin layer of dielectric material.

6. The mirror of claim 5 wherein said thin layer of elemental semiconductor is elemental silicon having an optical thickness of about 800 angstroms;

said additional thin film layers being disposed between said thin layer of elemental semiconductor and said substrate;

said additional thin film layers comprising a layer of silicon elemental semiconductor of optical thickness of at least about 4000 angstroms and a dielectric layer of silicon dioxide of an optical thickness of about 428 angstroms over said elemental silicon layer of said additional thin film layers.

7. The mirror of claim 5 wherein said thin layer of elemental semiconductor is elemental silicon having an optical thickness of about 800 angstroms coated on said rear surface of said substrate;

said additional thin film layers including a layer of silicon dioxide on the rear surface of said silicon thin layer and having an optical thickness of about 1500 angstroms, and a second thin layer of elemental silicon on the rear surface of said silicon dioxide and having an optical thickness of at least about 6800 angstroms.

8. The mirror of claim 1 wherein said light absorbing coating is selected from the group including black paint, and black lacquer.

9. The mirror of claim 1 wherein said light absorbing coating adheres to said rear surface and provides anti-scatter protection for pieces or fragments of said substrate should it be broken, said light absorbing coating being selected from the group including a) dark colored, flexible tape applied to said rear surface with an adhesive material, b) flexible tape applied to said rear surface with a dark colored adhesive material, c) a dark colored, UV-curable polymer applied to said rear surface, d) dark colored resinous plastic applied to said rear surface, and e) dark colored UV, thermally or catalytically cured epoxy material.

10. The mirror of claim 1 wherein said light absorbing coating is a high temperature paint applied to said rear surface of said substrate prior to any heating and/or bending of said substrate.

11. The mirror of claim 1 wherein said substrate is heated to a temperature of at least about 200°

C. at one of prior to, during and subsequent to deposition of said elemental semiconductor thin layer.

12. A spectrally selective mirror for vehicles having a rearmost surface positioned farthest from a source of incident light to be reflected by said mirror comprising:

a substrate having front and rear surfaces;

a thin layer of an elemental semiconductor, and a single, thin, transparent interference coating on said semiconductor thin layer;

said elemental semiconductor thin layer coated with said interference coating providing said elemental semiconductor thin layer with an index of refraction of at least 3 and an optical thickness of at least 275 angstroms;

said interference coating having an index of refraction within the range of between about 1.3 and 2.7, an optical thickness of at least about 500 angstroms, and being positioned closest to the source of incident light to be reflected by said mirror;

said elemental semiconductor thin layer coated with said interference coating providing said mirror with a luminous reflectance of at least 30% of the light incident thereon from the direction of said front surface of said substrate and including a light absorbing coating on said rearmost surface of said mirror which absorbs light transmitted by said substrate and/or elemental semiconductor thin layer and interference coating.

13. The mirror of claim 12 wherein said elemental semiconductor thin layer is applied to said substrate front surface;

said interference coating being applied over and in front of said elemental semiconductor thin layer.

14. The mirror of claim 13 wherein said interference coating is a layer of dip-coated dielectric material;

said elemental semiconductor thin layer being selected from the group including silicon and germanium.

15. The mirror of claim 13 wherein said elemental semiconductor thin layer is elemental silicon having an optical thickness between about 345 and 2400 angstroms;

said interference coating being silicon dioxide having an optical thickness between about 1600 and 2800 angstroms;

said mirror providing a blue colored reflectance.

16. The mirror of claim 13 wherein said substrate is glass;

said light absorbing coating being a dark colored glass frit applied to at least one of said substrate front surface under said elemental semiconductor thin layer and said rear surface of said substrate.

17. The mirror of claim 12 wherein said light absorbing coating is selected from the group including black paint, and black lacquer.

18. The mirror of claim 12 wherein said light absorbing coating adheres to said rear surface and provides anti-scatter protection for pieces or fragments of said substrate should it be broken, said light absorbing coating being selected from the group including a) dark colored, flexible tape applied to said rear surface with an adhesive material, b) flexible tape applied to said rear surface with a dark colored adhesive material, c) a dark colored, UV-curable polymer applied to said rear surface, d) a dark colored resinous plastic applied to said rear surface, and e) a dark colored UV, thermally or catalytically cured epoxy material.

19. A high luminous reflectance mirrored substrate comprising:

a glass substrate having first and second surfaces;

a reflector coated upon said first surface thereof, said first surface adapted to face a source of light to be reflected;

said reflector comprising a multilayer thin film stack consisting of a first thin film layer of elemental silicon which is closest to said first surface of said glass substrate and has a refractive index of greater than 3.0, a second thin film layer which is farthest from said second surface of said glass substrate, and a third film layer disposed between said first thin film layer and said second thin film layer, said third thin film layer having a refractive index between about 1.3 and 2.7, said second thin film layer having a refractive index greater than said third thin film layer; and

said reflector having a light reflectance of at least about 60% of light incident thereon at the wavelength region of about 550 nanometers and being achromatic.

21. The mirrored substrate of claim 19 wherein said third thin film layer comprises a silicon compound.

22. The mirrored substrate of claim 21 wherein said silicon compound comprises silicon nitride.

23. The mirrored substrate of claim 21 wherein said silicon compound comprises silicon oxide.

24. The mirrored substrate of claim 19 wherein at least one of said first thin film layer and said second thin film layer comprises doped silicon.

25. The mirrored substrate of claim 24 wherein said doped silicon is doped with a material selected from the group consisting of phosphorous, aluminum, gallium, boron and arsenic.

26. The mirrored substrate of claim 19 where n at least one of said first thin film layer, said second thin film layer, and said third thin film layer is a non-vacuum coated layer.

27. The mirrored substrate of claim 26 wherein said non-vacuum coated layer is one of a dip-coated layer and a spin-coated layer.

28. The mirrors substrate of claim 19 wherein said glass substrate is a bent glass substrate having a curvature.

29. The mirrored substrate of claim 28 wherein said bent glass substrate has a generally convex surface and a generally concave surface.

30. The mirrored substrate of claim 29 wherein said reflector is coated on said convex surface.

31. The mirrored substrate of claim 29 wherein said reflector is coated on said concave surface.

32. The mirrored substrate of claim 28 wherein said bent glass substrate has a radius of curvature of at least about forty (40) inches.

33. The mirrored substrate of claim 28 wherein said bent glass substrate is heated to at least about 450°

C. following coating of said reflector and bent to said curvature after heating.

34. The mirrored substrate of claim 19 wherein said glass substrate is heated and bent following coating of said reflector on a surface thereof.

35. The mirrored substrate of claim 19 wherein said mirrored substrate bas a luminous transmission of about 10% or less.

36. The mirrored substrate of claim 35 wherein said mirrored substrate has a luminous transmission of about 4% or less.

37. The mirrored substrate of claim 19 wherein said mirrored substrate is a reflector suitable for use in a rearview mirror for a vehicle.

38. The mirrored substrate of claim 37 wherein said mirrored substrate is a reflector of an exterior rearview mirror on a vehicle.

39. The minored substrate of claim 38 wherein the vehicle is an automobile.

40. The mirrored substrate of claim 38 wherein the vehicle is a truck.

20. The mirrored substrate of clam 19 where said third thin film layer comprises one of an oxide, fluorides nitride, and sulfide.

41. A high luminous reflectance mirrored substrate comprising:

a glass substrate having first and second surfaces;

a reflector coated upon said second surface thereof, said second surface adapted to face away from a source of light to be reflected;

said reflector comprising a multilayer thin film stack consisting of a first thin film layer of elemental silicon which is farthest from said second surface of said glass substrate and has a refractive index of greater than 3.0, a second thin film layer which is closest to said second surface of said glass substrate, a third thin film layer disposed between said first thin film layer and said second thin film layer, said third thin film layer having a refractive index between about 1.3 and 2.7, said second thin film layer having a refractive index greater than said third thin film layer; and

said reflector having a light reflectance of at least about 60% of light incident thereon at the wavelength region of about 550 nanometers and being achromatic.

42. The mirrored substrate of claim 41 wherein said third thin film layer comprises one of an oxide, fluoride, nitride, and sulfide.

43. The mirrored substrate of claim 41 wherein said thin film layer comprises a silicon compound.

44. The mirrored substrate of claim 43 wherein said silicon compound comprises silicon nitride.

45. The mirrored substrate of claim 43 wherein said silicon compound comprises silicon oxide.

46. The mirrored substrate of claim 41 wherein at least one of said first in film layer and said second thin film layer comprises doped silicon.

47. The mirrored substrate of claim 46 wherein said doped silicon is doped with a material selected from the group consisting of phosphorous, aluminum, gallium, boron and arsenic.

48. The mirrored substrate of claim 41 wherein at least one of said first thin film layer, said second thin film layer, and said third thin film layer is a non-vacuum coated layer.

49. The mirrored substrate of claim 48 wherein said non-vacuum coated layer is one of a dip-coated layer and a spin-coated layer.

50. The mirrored substrate of claim 41 wherein said glass substrate is a bent glass substrate having a curvature.

51. The mirrored substrate of claim 50 wherein said bent glass substrate has a generally convex surface and a generally concave surface.

52. The mirrored substrate of claim 51 wherein said reflector is coated on said convex surface.

53. The mirrored substrate of claim 51 wherein said reflector is coated on said concave surface.

54. The mirrored substrate of claim 50 wherein said bent glass substrate has a radius of curvature of at least about forty (40) inches.

55. The mirrored substrate of claim 50 wherein said bent glass substrate is heated to at least about 450°

C. following coating of said reflector and bent to said curvature after heating.

56. The mirrored substrate of claim 41 wherein said glass substrate is heated and bent following coating of said reflector on a surface thereof.

57. The mirrored substrate of claim 41 wherein said mirrored substrate has a luminous transmission of about 10% or less.

58. The mirrored substrate of claim 57 wherein said mirrored substrate has a luminous transmission of about 4% or less.

59. The mirrored substrate of claim 41 wherein sad mirrored substrate is a reflector suitable for use in a rearview mirror for a vehicle.

60. The mirrored substrate of claim 59 wherein said mirrored substrate is a reflector of an exterior rearview mirror on a vehicle.

61. The mirrored substrate of claim 60 wherein the vehicle is an automobile.

62. The mirrored substrate of claim 60 wherein the vehicle is a truck.