Robust optical filter utilizing pairs of dielectric and metallic layers

• US 20090246552A1
• Filed: 03/26/2008
• Published: 10/01/2009
• Est. Priority Date: 03/26/2008
• Status: Active Grant

• Current Assignee: Southwall Technologies, Inc. (Eastman Chemical Company)
• Original Assignee: Southwall Technologies, Inc. (Eastman Chemical Company)
• Inventors: Wipfler, Richard T., Wahl, Andrew, Kozak, Julius, Boman, Lee, Stoessel, Chris H., Thielsch, Roland, Coda, Matthew
• Granted Patent: US 7,824,777 B2
• Time in Patent Office: Days
• US Class Current: 428/639
• CPC Class Codes: B32B 2255/10 on synthetic resin layer or on natural or synthetic rubber layer
• CPC Class Codes: B32B 2255/20 Inorganic coating
• CPC Class Codes: B32B 2255/28 Multiple coating on one surface
• CPC Class Codes: B32B 2307/204 Di-electric
• CPC Class Codes: B32B 2307/40 having particular optical properties light or UV resistant B32B2307/71
• CPC Class Codes: B32B 2307/412 Transparent
• CPC Class Codes: B32B 2307/416 Reflective
• CPC Class Codes: B32B 2307/418 Refractive
• CPC Class Codes: B32B 2307/714 Inert, i.e. inert to chemical degradation, corrosion
• CPC Class Codes: B32B 2419/00 Buildings or parts thereof walls, panels B32B2607/00
• CPC Class Codes: B32B 2551/00 Optical elements
• CPC Class Codes: B32B 2605/006 Transparent parts other than made from inorganic glass, e.g. polycarbonate glazings
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B32B 7/06 permitting easy separation
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: G02B 5/282 reflecting for infrared and transparent for visible light, e.g. heat reflectors, laser protection
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: Y10T 428/1266 O, S, or organic compound in metal component
• CPC Class Codes: Y10T 428/12792 Zn-base component
• CPC Class Codes: Y10T 428/12889 : Au-base component
• CPC Class Codes: Y10T 428/12896 : Ag-base component

Abstract

“Corrosion” performance of an optical filter is enhanced when a relatively thick zinc-based film functions as a seed layer for a subsequently formed silver-based film. At least two pairs of dielectric and metallic layers are included within the optical filter, where the zinc-based film is a second film of the dielectric layer and where the silver-based film is the metallic layer. The zinc-based film has a zinc content of at least 80 percent and has a thickness of at least 15 nm. In order to further improve the corrosion performance, gold may be incorporated into the silver-based film.

Claims

1. A method of providing an optical filter comprising:

forming a layer stack on a substrate to include pairs of dielectric and metallic layers, including defining each said pair by;

forming a transparent dielectric film as a first film of said dielectric layer, said transparent dielectric film having a refractive index of at least 1.1;

forming a zinc-based film as a second film of said dielectric layer, said zinc-based film having a zinc content of at least 80 percent and having a thickness of at least 15 nm; and

forming a silver-based film as said metallic layer, said silver-based film being in contact with said zinc-based film.

2. The method of claim 1 wherein forming said layer stack to include said pairs includes forming said zinc-based film of the pair adjacent to said substrate to be thinner than said zinc-based film of each said pair further from said substrate.

3. The method of claim 1 wherein forming said silver-based film includes depositing an alloy of silver and gold in which said gold is included to control corrosion of said layer stack.

4. The method of claim 3 wherein depositing said alloy includes intentionally incorporating different percentages of gold among said silver-based films on a basis of distance from said substrate.

5. The method of claim 4 wherein said silver-based film furthest from said substrate is formed to have a higher percentage of gold than said silver-based film nearest to said substrate.

6. The method of claim 1 further comprising selecting said thickness of said zinc-based film and selecting the percentage of said zinc content on a basis of promoting formation of said silver-based film.

7. The method of claim 1 wherein forming said transparent dielectric films of said pairs of dielectric and metallic layers includes using sputtering techniques to deposit indium-based films.

8. The method of claim 1 wherein forming said zinc-based provides a film thickness in the range of 15 nm to 40 nm.

9. The method of claim 1 further comprising attaching said layer stack to a window.

10. A filtering arrangement comprising:

a transparent substrate; and

a layer stack on said substrate, said layer stack including pairs of dielectric and metallic layers, each said pair being defined by;

a transparent dielectric film as a first film of said dielectric layer, said transparent dielectric layer having a refractive index of at least 1.1;

a zinc-based film as a second film of said dielectric layer, said zinc-based film having a zinc content of at least 80 percent and having a thickness in the range of 15 nm to 40 nm; and

a silver gold film as said metallic layer, said silver gold film being in contact with said zinc-based film.

11. The filtering arrangement of claim 10 wherein said zinc-based film in the pair of dielectric and metallic layers adjacent to said substrate is thinner than said zinc-based film of each of the other said pairs.

12. The filtering arrangement of claim 11 wherein each said zinc-based film is zinc tin or zinc aluminum and said zinc content is approximately 90 percent.

13. The filtering arrangement of claim 10 wherein each said transparent dielectric layer is indium oxide.

14. The filtering arrangement of claim 10 wherein said silver gold film in said pair of dielectric and metallic layers that is furthest from said substrate has a higher gold content than said silver gold film of each of the other said pairs.

15. The filtering arrangement of claim 10 wherein said substrate is attached to a window.

16. The filtering arrangement of claim 10 including three said pairs of dielectric and metallic layers.

17. The filtering arrangement of claim 10 wherein each said transparent dielectric film is In₂O₃.