Metal-coated multilayer mirror

• US 5,699,188 A
• Filed: 06/26/1995
• Issued: 12/16/1997
• Est. Priority Date: 06/26/1995
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Ouderkirk, Andrew J., Gilbert, Laurence R.
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US08/494,418
• Time in Patent Office: 904 Days
• Field of Search: 359/580, 359/583, 359/584, 359/585, 359/586, 359/588, 359/589, 359/494, 359/495, 359/500, 359/884, 359/359, 359/352, 359/360
• US Class Current: 359/584
• CPC Class Codes: B32B 15/08 of synthetic resin
• CPC Class Codes: B32B 2307/416 Reflective
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2551/08 Mirrors
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/0866 incorporating one or more organic, e.g. polymeric layers
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

A metal-coated multilayer mirror having high reflectivity and high specularity. The mirror comprises a multilayered polymer film and a reflective metal layer. The multilayered polymer film preferably comprises layers of a crystalline, semi-crystalline, or liquid crystalline material, such as a naphthalene dicarboxylic acid polyester, having an average thickness of not more than 0.5 microns and layers of a second polymer having an average thickness of not more than 0.5 microns. Preferably, the layers of semi-crystalline naphthalene dicarboxylic acid polyester have a positive stress optical coefficient. The reflective metal layer comprises a metal selected from the group consisting of silver, gold, aluminum, nickel, copper, and titanium, with silver and aluminum being particularly preferred. The metal-coated multilayer mirrors are useful in applications requiring broad bandwidth reflection, high specularity, low manufacturing costs, and high reflectivity.

Claims

1. A metal-coated multilayer mirror comprising a multilayered polymer film and a metal layer;

the multilayered-polymer film comprising;

(A) layers of a birefringent semi-crystalline having an average thickness of not more than 0.5 microns; and

(B) layers of a selected second polymer having an average thickness of not more than 0.5 microns;

and the metal layer comprising a reflective metal.

2. The mirror of claim 1 wherein the birefringent polymer is semi-crystalline naphthalene dicarboxylic acid polyester.

3. The mirror of claim 2 wherein the reflective metal is selected from the group consisting of aluminum, silver, gold, copper, nickel, and titanium.

4. The mirror of claim 2 wherein the metal is silver.

5. The mirror of claim 4 wherein the silver layer has a thickness of at least about 75 nm to about 100 nm.

6. The mirror of claim 2 wherein the metal is aluminum.

7. The mirror of claim 6 wherein the aluminum layer has a thickness of at least about 20 nm to about 100 nm.

8. The mirror of claim 2 wherein the reflective metal is coated on the multilayered polymer film by vapor deposition or cathode sputtering.

9. The mirror of claim 2 wherein the reflective metal comprises a metalized polymer or glass sheet that is laminated to the multilayered polymer film.

10. The mirror of claim 2 wherein the reflective metal comprises a metal sheet laminated to the multilayered polymer film.

11. The mirror of claim 2 wherein its reflectivity of visible light is greater than 90%.

12. The mirror of claim 2 wherein its reflectivity of visible light is greater than 95%.

13. The mirror of claim 2 wherein the naphthalene dicarboxylic acid polyester is more positively birefringent than the second polymer.

14. The mirror of claim 2 wherein the layers of the naphthalene dicarboxylic acid polyester and the layers of the second polymer are immediately adjacent alternating layers.

15. The mirror of claim 2 wherein there are at least 50 of each of the layers of the naphthalene dicarboxylic acid polyester and the layers of the second polymer.

16. The mirror of claim 2 wherein the film has been stretched in at least one direction.

17. The mirror of claim 16 wherein the film has been stretched in at least one direction to at least twice that direction'"'"'s unstretched dimension.

18. The mirror of claim 17 wherein the layers of the naphthalene dicarboxylic acid polyester having a higher index of refraction associated with at least one in-plane axis than the layers of the second polymer.

19. The mirror of claim 18 wherein the higher index of refraction is at least 0.05 higher.

20. The mirror of claim 18 wherein the higher index of refraction is at least 0.10 higher.

21. The mirror of claim 18 wherein the higher index of refraction is at least 0.20 higher.

22. The mirror of claim 2 wherein the film has been stretched in at least two directions.

23. The mirror of claim 2 wherein the naphthalene dicarboxylic acid polyester is a poly(ethylene naphthalate).

24. The mirror of claim 2 wherein the naphthalene dicarboxylic acid polyester is a copolyester comprising naphthalate units and terephthalate units.

25. The mirror of claim 2 wherein the second polymer is a polyester.

26. The mirror of claim 25 wherein the second polymer includes naphthalene units.

27. The mirror of claim 2 wherein the second polymer is a copolyester comprising naphthalate units and terephthalate units.

28. The mirror of claim 2 wherein the second polymer is selected from the group consisting of a polystyrene, fluoropolymer, polyacrylate, polymethacrylate, and polyolefin.

44. The mirror of claim 24 wherein the film has been stretched in least two directions.

29. A metal-coated multilayer mirror comprising a multilayered polymer film and a metal layer;

the multilayered polymer film comprising;

(A) layers of a birefringent semi-crystalline polymer having an average thickness of not more than 0.5 microns; and

(B) layers of a selected second polymer having an average thickness of not more than 0.5 microns;

wherein the film has been stretched in at least one direction to at least twice that direction'"'"'s unstretched dimension;

and the metal layer comprising a reflective metal.

30. The mirror of claim 29 wherein the reflective metal is selected from the group consisting of aluminum, silver, gold, copper, nickel, and titanium.

31. The mirror of claim 29 wherein the metal is silver.

32. The mirror of claim 31 wherein the silver layer has a thickness of at least about 75 nm to about 100 nm.

33. The mirror of claim 29 wherein the metal is aluminum.

34. The mirror of claim 33 wherein the aluminum layer has a thickness of at least about 20 nm to about 30 nm.

35. The mirror of claim 29 wherein the reflective metal is coated on the multilayered polymer film by vapor deposition or cathode sputtering.

36. The mirror of claim 29 wherein the reflective metal comprises a metalized polymer or glass sheet that is laminated to the multilayered polymer film.

37. The mirror of claim 29 wherein the reflective metal comprises a metal sheet laminated to the multilayered polymer film.

38. The mirror of claim 29 wherein its reflectivity of visible light is greater than 90%.

39. The mirror of claim 29 wherein its reflectivity of visible light is greater than 95%.

40. The mirror of claim 29 wherein the polyester is a poly(alkylene terephthalate).

41. The mirror of claim 29 wherein the second polymer is a polyester.

42. The mirror of claim 29 wherein the layers of a polyester and the layers of a second polymer are immediately adjacent alternating layers.

43. The mirror of claim 29 wherein there are at least 50 of each of the layers of a polyester and the layers of a second polymer.