Heat treatable four layer anti-reflection coating

• US 9,163,150 B2
• Filed: 01/31/2014
• Issued: 10/20/2015
• Est. Priority Date: 01/27/2011
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Broadway, David M., Krasnov, Alexey, Den Boer, Willem
• Primary Examiner(s): SAMPLE, DAVID R
• Application Number:
  US14/169,163
• Publication Number:
  US 20140147582A1
• Time in Patent Office: 627 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3423 at least one of the coatings comprising a suboxide
• CPC Class Codes: C03C 17/3435 comprising a nitride, oxynitride, boronitride or carbonitride
• CPC Class Codes: C03C 2217/73 Anti-reflective coatings with specific characteristics
• CPC Class Codes: C09D 5/006 Anti-reflective coatings
• CPC Class Codes: G02B 1/115 Multilayers

Abstract

A coated article includes a heat treatable (e.g., temperable) antireflection (AR) coating having four layers. The AR coating includes a layer adjacent the glass substrate having an index of refraction substantially matching that of the glass substrate, and having a compressive residual stress. In certain example embodiments, the coating may include the following layers from the glass substrate outwardly: stress-reducing layer/medium index layer/high index layer/low index layer. In certain example embodiments, depending on the chemical and optical properties of the high index layer and the substrate, the stress-reducing layer of the AR coating is selected to cause a net compressive residual stress and thus improve the overall performance of the antireflection coating when the coated article is heat treated.

Claims

1. A method of making a heat treatable coated article comprising an anti-reflection coating, the method comprising:

disposing a stress-reducing layer over and contacting a glass substrate, the stress-reducing layer having an index of refraction that substantially matches an index of refraction of the glass substrate;

disposing a layer having a medium index of refraction over the stress-reducing layer;

disposing a layer having a high index of refraction over the medium index layer; and

disposing a layer having a low index of refraction over the high index layer,

wherein the index of refraction of the high index layer is greater than those of the medium and low index layers, and the index of refraction of the low index layer is less than that of the medium index layer; and

wherein a net residual stress of the anti-reflection coating is compressive.

2. The method of claim 1, further comprising heat treating the coated article with the stress-reducing layer, as well as the medium, high, and low index layers disposed thereon.

3. The method of claim 1, wherein the stress-reducing layer comprises silicon oxynitride.

4. The method of claim 1, wherein the stress-reducing layer comprises silicon oxide.

5. The method of claim 1, wherein the high index layer comprises an oxide of niobium.

6. The method of claim 1, wherein the high index layer comprises an oxide of titanium.

7. The method of claim 1, wherein the high index layer comprises a thickness of from about 80 to 120 nm.

8. The method of claim 1, wherein a net stress value is approximated by the equation:

9. The method of claim 8, wherein the predicted net residual stress σ

_Net of the anti-reflection coating differs from a measured net residual stress value by no more than about 15%.

10. The method of claim 8, wherein the predicted net residual stress σ

_Net of the anti-reflection coating differs from the measured net residual stress value by no more than about 13%.

11. The method of claim 1, wherein the stress reducing layer, medium index layer, and low index layer each comprise an oxide of silicon.

21. The method of claim 2, further comprising:

disposing a second stress-reducing layer over and contacting a second major surface of a glass substrate, the second stress-reducing layer comprising silicon, and having an index of refraction that differs from an index of refraction of the glass substrate differ by no more than about 0.2;

disposing a second layer comprising silicon oxynitride over the second stress-reducing layer;

disposing a second layer comprising an oxide of niobium over the second layer comprising silicon oxynitride; and

disposing a second layer comprising an oxide of silicon over the second layer comprising an oxide of niobium,

wherein the index of refraction of the second high index layer is greater than the indices of refraction of the second medium and second low index layers, and the index of refraction of the second low index layer is less than that of the second medium index layer, and

wherein a net residual stress of the coating disposed on the second major surface of the glass substrate is compressive.

12. A method of making a heat treatable coated article comprising an anti-reflection coating, the method comprising:

disposing a stress-reducing layer over and contacting a first major surface of a glass substrate, the stress-reducing layer comprising silicon, and having an index of refraction that differs from an index of refraction of the glass substrate differ by no more than about 0.2;

disposing a layer comprising silicon oxynitride over the stress-reducing layer;

disposing a layer comprising an oxide of niobium over the layer comprising silicon oxynitride; and

disposing a layer comprising an oxide of silicon over the layer comprising an oxide of niobium,

wherein the index of refraction of the high index layer is greater than the indices of refraction of the medium and low index layers, and the index of refraction of the low index layer is less than that of the medium index layer, and

wherein a net residual stress of the coating is compressive.

13. The method of claim 12, further comprising heat treating the coated article after the layer comprising the oxide of silicon has been disposed over the layer comprising an oxide of niobium.

14. The method of claim 12, wherein the stress-reducing layer comprises silicon oxynitride.

15. The method of claim 12, wherein the stress-reducing layer consists essentially of silicon oxide.

16. The method of claim 12, wherein the stress-reducing layer and the layer comprising an oxide of silicon comprise approximately the same thickness.

17. The method of claim 12, wherein the layer comprising an oxide of niobium comprises a thickness of from about 80 to 120 nm.

18. The method of claim 12, wherein a net stress value is determined by the equation:

19. The method of claim 18, wherein the predicted net residual stress σ

_Net of the anti-reflection coating differs from a measured net residual stress value by no more than about 15%.

20. The method of claim 18, wherein the predicted net residual stress σ

_Net of the anti-reflection coating differs from the measured net residual stress value by no more than about 13%.