Transparent coating systems for improving the environmental durability of transparency substrates

• US 5,939,188 A
• Filed: 11/06/1997
• Issued: 08/17/1999
• Est. Priority Date: 07/15/1991
• Status: Expired due to Term

• Current Assignee: GKN Aerospace Transparency Systems, Inc. (Melrose Industries Plc)
• Original Assignee: Pilkington Aerospace, Inc. (Melrose Industries Plc)
• Inventors: Moncur, Marlowe Vern, Jeungst, Clifford David
• Primary Examiner(s): Nakarani, D. S.
• Application Number:
  US08/968,892
• Time in Patent Office: 649 Days
• Field of Search: 428/328, 428/331, 428/332, 428/336, 428/423.1, 428/423.3, 428/425.5, 428/425.6, 428/428, 428/429, 428/432, 428/433, 428/434, 428/448
• US Class Current: 428/332
• CPC Class Codes: C03C 17/42 at least one coating of an organic material and at least one non-metal coating
• CPC Class Codes: C08J 7/0423 with at least one layer of inorganic material and at least one layer of a composition containing a polymer binder
• CPC Class Codes: C08J 7/043 Improving the adhesiveness of the coatings per se, e.g. forming primers adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50
• CPC Class Codes: C08J 7/044 Forming conductive coatings; Forming coatings having anti-static properties
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/31554 Next to second layer of polyamidoester
• CPC Class Codes: Y10T 428/31598 Next to silicon-containing [silicone, cement, etc.] layer
• CPC Class Codes: Y10T 428/31601 Quartz or glass
• CPC Class Codes: Y10T 428/31612 As silicone, silane or siloxane

Abstract

Transparent substrates having at least one surface coated with a transparent coating system to improve their environmental durability are described. The transparent coating system consists of a combination of components having different properties applied as separate layers to the transparent substrate. A thin layer of a silica-based adhesion promoter is applied directly to at least one surface of the substrate, followed by an organosilane primer layer, then a low modulus polyurethane layer, and, lastly, a thermoset aliphatic polyurethane layer. Alternatively, the low modulus polyurethane may also contain silanol groups or functional groups that can be hydrolyzed to silanol, thereby making a separate primer layer unnecessary.

Claims

1. A transparent substrate having at least one surface coated with a transparent coating system to improve its environmental durability when the coated surface is exposed to the environment, comprising:

a transparent glass or plastic substrate having a transparent thin film coating on at least one surface, wherein the thin film coating comprises one or more layers of a first dielectric or semiconductive metal oxide material; and

a transparent coating system on the transparent thin film coating, wherein said transparent coating system comprises;

a silica-based adhesion promoter layer which is applied to the exposed surface of the thin film coating, wherein the silica-based adhesion promoter layer consists essentially of silica or a mixture of silica and a second metal oxide material,

an organosilane primer layer which is applied over the silica-based adhesion promoter layer, wherein the organosilane includes silanol groups or functional groups that can be hydrolyzed to silanol, and at least one additional reactive organic fimctional group,

a low modulus thermoset polyurethane layer which is applied over the organosilane primer layer, wherein the fully cured low modulus thermoset polyurethane has a tensile modulus at 100% elongation of less than about 500 psi at room temperature and a glass transition temperature of about -20°

C. or less, and

a protective thermoset aliphatic polyurethane layer which is applied over the low modulus thermoset polyurethane layer, wherein the fully-cured protective thermoset polyurethane has a tensile modulus at 100% elongation of more than about 500 psi but less than about 10,000 psi, and a tensile elongation of at least 100%.

2. The coated transparent substrate of claim 1 wherein the silica-based adhesion promoter layer is applied by physical vapor deposition or by chemical vapor deposition.

3. The coated transparent substrate of claim 2 wherein the silica-based adhesion promoter layer is applied by sputtering.

4. The coated transparent substrate of claim 2 wherein the silica-based adhesion promoter layer is applied by evaporation.

5. The coated transparent substrate of claim 2 wherein the thickness of the silica-based adhesion promoter layer is from about 0.001 to about 0.5 microns.

6. The coated transparent substrate of claim 1 wherein the functional groups in the organosilane that can be hydrolyzed to silanol include chlorosilyl, acetoxysilyl, and alkoxysilyl.

7. The coated transparent substrate of claim 1 wherein the additional reactive organic functional group in the organosilane is selected from the group consisting of amino, hydroxy, carboxy, epoxy, isocyanato, and mercapto functional groups.

8. The coated transparent substrate of claim 7 wherein the organosilane is an amino-functional organosilane.

9. The coated transparent substrate of claim 7 wherein the organosilane is selected from the group consisting of 3-glycidoxypropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane, N-(2-aminoethyl)aminopropyl trimethoxysilane, 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, N'"'"'-(2-aminoethyl)-N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane.

10. The coated transparent substrate of claim 1 wherein the organosilane has the formula (Y-R)_n Si(X)_m, where m and n are integers from 1-3, and m+n=4;

Y is a reactive functional group selected from the group consisting of amino, hydroxy, carboxy, epoxy, isocyanato, and mercapto functional groups;

R is a linear or branched saturated aliphatic bivalent hydrocarbon radical; and

X is hydroxy or a group that yields hydroxy upon hydrolysis.

11. The coated transparent substrate of claim 1 wherein the thickness of the organosilane primer layer is from about 0.1 to about 50 microns.

12. The coated transparent substrate of claim 1 wherein the low modulus thermoset polyurethane is prepared from a branched, isocyanate-functional, moisture-curable prepolymer made from methylene diphenyl diisocyanate and polytetramethylene oxide polyols which include at least one polyol with hydroxyl functionality greater than two and having an equivalent weight of about 3,900.

13. The coated transparent substrate of claim 1 wherein the low modulus thermoset polyurethane is prepared from bis(4-isocyanatocyclohexyl)methane including isomeric mixtures and polytetramethylene oxide diol having a molecular weight of at least 1,000.

14. The coated transparent substrate of claim 1 wherein the thickness of the low modulus thermoset polyurethane layer is from about 5 to about 250 microns.

15. The coated transparent substrate of claim 1 wherein the protective thermoset polyurethane has a tensile modulus at 100% elongation between about 1,000 psi and about 4,000 psi.

16. The coated transparent substrate of claim 1 wherein the protective thermoset polyurethane has a tensile elongation of at least 150%.

17. The coated transparent substrate of claim 1 wherein the protective thermoset polyurethane is an aliphatic polyester urethane.

18. The coated transparent substrate of claim 1 wherein the thickness of the protective thermoset polyurethane is from about 25 to about 1,250 microns.

19. The coated transparent substrate of claim 1 wherein the protective thermoset polyurethane contains at least one additive selected from the group consisting of UV absorbers, antioxidants, and antistatic agents.

20. The coated transparent substrate of claim 1, wherein the thin film coating further comprises a metal layer sandwiched between layers of the oxide material.

21. The coated transparent substrate of claim 20, wherein said metal is gold and said first oxide material is indium tin oxide.

22. The coated transparent substrate of claim 20, wherein said metal is silver and said first oxide material is indium tin oxide.

23. The coated transparent substrate of claim 20, wherein said metal is gold and said first oxide material is titanium oxide.

24. The coated transparent substrate of claim 20, wherein said metal is silver and said first oxide material is titanium oxide.

25. The coated transparent substrate of claim 20, wherein said metal layer comprises silver.

26. The coated transparent substrate of claim 25, wherein said oxide material is indium tin oxide.

27. The coated transparent substrate of claim 25, wherein said oxide material is titanium oxide.

28. The coated transparent substrate of claim 20, wherein said metal layer comprises gold.

29. The coated transparent substrate of claim 1, wherein said first oxide material is selected from the group consisting of indium tin oxide, titanium oxide, bismuth oxide, and germanium oxide.

30. The coated transparent substrate of claim 1, wherein said transparent, thin film coating is electrically conductive.

33. The coated transparent substrate of claim 21 wherein the functional groups in the low modulus thermoset polyurethane that can be hydrolyzed to silanol include chlorosilyl, acetoxysilyl, and alkoxysilyl.

31. A transparent substrate having at least one surface coated with a transparent coating system to improve its environmental durability when the coated surface is exposed to the environment, comprising:

a transparent glass or plastic substrate having a transparent thin film coating on at least one surface, wherein the thin film coating comprises one or more layers of a first dielectric or semiconductive metal oxide material;

a transparent coating system on the transparent thin film coating, wherein said transparent coating system comprises

a silica-based adhesion promoter layer which is applied to the exposed surface of the thin film coating, wherein the silica-based adhesion promoter layer consists essentially of silica or a mixture of silica and a second metal oxide material,

a low modulus thermoset polyurethane layer which is applied over the silica-based adhesion promoter layer, wherein low modulus thermoset polyurethane includes silanol groups or functional groups that can be hydrolyzed to silanol, and the fully-cured low modulus thermoset polyurethane has a tensile modulus at 100% elongation of less than about 500 psi at room temperature, and a glass transition temperature of -20°

C. or less, and

a protective thermoset aliphatic polyurethane layer which is applied over the low modulus thermoset polyurethane layer, wherein the fully-cured protective thermoset polyurethane has a tensile modulus at 100% elongation of more than about 500 psi but less than about 10,000 psi, and a tensile elongation of at least 100%.

32. The coated transparent substrate of claim 31 wherein the silica-based adhesion promoter layer is applied by physical vapor deposition or by chemical vapor deposition.

34. The coated transparent substrate of claim 31 wherein the protective thermoset polyurethane has a tensile modulus at 100% elongation between about 1,000 psi and about 4,000 psi.

35. The coated transparent substrate of claim 31 wherein the protective thermoset polyurethane has a tensile elongation of at least 150%.

36. The coated transparent substrate of claim 31 wherein the protective thermoset polyurethane is an aliphatic polyester urethane.

37. The coated transparent substrate of claim 31 wherein the protective thermoset polyurethane contains at least one additive selected from the group consisting of UV absorbers, antioxidants, and antistatic agents.

38. The coated transparent substrate of claim 31, wherein the thin film coating further comprises a metal layer sandwiched between layers of the first oxide material.

39. The coated transparent substrate of claim 38, wherein said metal is gold and said first oxide material is indium tin oxide.

40. The coated transparent substrate of claim 38, wherein said metal is silver and said first oxide material is indium tin oxide.

41. The coated transparent substrate of claim 38, wherein said metal is gold and said first oxide material is titanium oxide.

42. The coated transparent substrate of claim 38, wherein said metal is silver and said first oxide material is titanium oxide.

43. The coated transparent substrate of claim 38, wherein said metal layer comprises silver.

44. The coated transparent substrate of claim 43 wherein said first oxide material is indium tin oxide.

45. The coated transparent substrate of claim 43, wherein said first oxide material is titanium oxide.

46. The coated transparent substrate of claim 38, wherein said metal layer comprises gold.

47. The coated transparent substrate of claim 31, wherein said first oxide material is selected from the group consisting of indium tin oxide, titanium oxide, bismuth oxide, and germanium oxide.

48. The coated transparent substrate of claim 31, wherein said transparent, thin film coating is electrically conductive.

49. A transparent substrate having at least one surface coated with a transparent coating system to improve its environmental durability when the coated surface is exposed to the environment, comprising:

a transparent glass or plastic substrate having a transparent thin film coating on at least one surface, wherein the thin film coating comprises one or more layers of a first dielectric or semiconductive metal oxide material; and

a transparent coating system on the transparent thin film coating, wherein said transparent coating system comprises;

a silica-based adhesion promoter layer which is applied to the surface of the thin film coating, wherein the silica-based adhesion promoter layer consists essentially of silica or a mixture of silica and a second metal oxide material,

an organosilane primer layer which is applied over the silica-based adhesion promoter layer, wherein the organosilane includes silanol groups or functional groups that can be hydrolyzed to silanol, and at least one additional reactive organic functional group selected from the group consisting of amino, hydroxy, carboxy, epoxy, isocyanato, and mercapto functional groups,

a low modulus thermoset polyurethane layer which is applied over the organosilane primer layer, wherein the fully cured low modulus thermoset polyurethane has a tensile modulus at 100% elongation of less than about 500 psi at room temperature, and a glass transition temperature of about -20°

C. or less, and

a protective thermoset aliphatic polyurethane which is applied over the low-modulus thermoset polyurethane layer, wherein the fully-cured protective thermoset polyurethane has a tensile modulus at 100% elongation of between about 1,000 psi and about 4,000 psi, a tensile elongation of at least 150%, and contains at least one additive selected from the group consisting of UV absorbers, antioxidants, and antistatic agents.

50. The coated transparent substrate of claim 49, wherein the thin film coating further comprises a metal layer sandwiched between layers of the first oxide material.

51. The coated transparent substrate of claim 50, wherein said metal is gold and said first oxide material is indium tin oxide.

52. The coated transparent substrate of claim 50, wherein said metal is silver and said first oxide material is indium tin oxide.

53. The coated transparent substrate of claim 50, wherein said metal is gold and said first oxide material is titanium oxide.

54. The coated transparent substrate of claim 50, wherein said metal is silver and said first oxide material is titanium oxide.

55. The coated transparent substrate of claim 50, wherein said metal layer comprises silver.

56. The coated transparent substrate of claim 55, wherein said first oxide material is indium tin oxide.

57. The coated transparent substrate of claim 55, wherein said first oxide material is titanium oxide.

58. The coated transparent substrate of claim 50, wherein said metal layer comprises gold.

59. The coated transparent substrate of claim 49, wherein said first oxide material is selected from the group consisting of indium tin oxide, titanium oxide, bismuth oxide, and germanium oxide.

60. The coated transparent substrate of claim 49, wherein said transparent, thin film coating is electrically conductive.