CA2322307A1 - Noble metal interference filter for thermal pane - Google Patents

Abstract

A windowpanel assembly isdisclosed having an interference filter on one side,to control the transmittance of visible and infrared radiation therethrough. The panel assembly includesatransparent substrate having an interference filter deposited on one side. The interference filter includes at least one sequenceofmicro-fine laminations or layers including a base oxide layer, a metal alloy layer, and a protective layer. A
durability layer covers and protects the underlying oxides, alloys and protective layers.

Description

NOBLE METAL INTERFERENCE FILTER FOR THERMAL PANE
BACKGROUND OF THE INVENTION
Field of the Invention The instant inventionrelatesgenerallytoglassand ceramic coatings, and particularly to acoatingforatransparent panelwhich reducesthetransmission ofthermal radiation.
Discussion of the Related Art Coatings on transparent panels used in buildings, vehicles, and other structures have been used for a substantial number of years to control or reduce the transmittanceofsolar radiation. The principle goal'of such coatings hasbeentoreduce the transmission of the infrared portion ofthe spectrum yet permit transmission of the visible spectrum. At the same time, it was desired to keep the infrared spectrum from passingthroughthepanelintheoppositedirection.Inthisway,temperaturefluctuated less which in turn resulted in reduced heating and cooling costs.
Various processes have been employed to changethe optical properties of transparent panels, including the application of substrates to the panel using various tedmiquessuchaselec6rolysis, chemicalvapordeposition, and physical vapordeposition.
Thin metal films have been deposited on glass or plastic to increase the reflectance of solarradiation. Windowsdepositedwithmulti-layerdielectric-metal-dieleariccoetings have also beenformedwhich exhibit high visibletransmittance, and highreflectivityand lowemissivityofradiationintheinfraredrange.
Theindexofrefractionofthedielectric layer has typically been 2.0 or greater in order to minimize the visible reflectance and enhancethevisibletransrriittanceofthetransparentpanel.
Theopticalpropertiesofthe panels have also been modified by altering the composition ofthe substrate material.
Nevertheless, interference fi lter manufactured by one or more of the above described methods have been only partially successful in reflecting solar radiation to the degree required for significantenergy conservation. Anotherproblem predominantlyassociated with such interference filters or coatings is the structural integrity, particularly their inability to withstandcleaningandexposuretocleaningcompoundsandsolventswhich result in both chemical and mechanical degradation of the coatings.
SUMMARY OF THE INVENTION
In oneformoftheimrention, theinterferencepanel assembly isspecifically adapted to control the amount of infrared radiation transmitted through the panel and includesa sheet of transparent material such as glass or polymeric material havingone or more layer of an oxide material deposited on one side. A layer of metal alloy is deposited on top of the oxide layer to a thickness of about 200 Angstroms ( ~). In a preferred embodimentofthe invention, themetal alloy layer includes amixture ofsilver and goldwhereintheconcentrationofgoldisbetween0.2percentand0.5percent. The combinationofthegoldandsilveratomsarebelievedtoprovideauniquepackingpattern which produces unique filtering of the visible and thermal spectrum. The metal alloy layer is in turn covered by aprotective layerto prevent oxidation of the metal alloy. The sequence isthen repeated with another oxide layerthesamemetal alloy composition, and anotherprotective layer. Inthepreferred embodiment, the final sequence ofdeposition includesan oxide (aver, and an outerdurability layertowithstand abrasionand solvents, and protect the various layers on the panel.
The advantages ofthisunique deposition sequence and al loy composition isthe particularfilteringprovided bythe atomic structureafforded by the combination of thegoldandsilvermetals. The oxides, although primarily toimprovetheadhesionofthe metaialloytothepanelsurface,alsoimprovesthe~ransmissionofcertaincomponentsof the spectrum because of the difference in the index of refraction with that of the panel.
The atomic structure ofthe oxide and protective layersact in concertwith the metal alloy layers to reflectthethermal portion ofthespectrumwhiletransmittingthevisible portion of the spectrum, to reduce the amount of thermal radiation passed to the interior of the building. The same sequence keeps the thermal radiation within the building to help maintainaconstanttemperature. These andotherfeatures,advantagesandobjectsofthe present invention will befiutherunderstood and appreciated bythose skilled inthe artby reference to the following specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l isaschematicdiagramofatransparent panel and the reflectionand transmission of solar energy impinging upon the panel; and Fig. 2 is afragmentary section view of the transparent panel shown in Fig.
1'embodying the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
For purposes of the following description, the terms "upper," "lower,"
"left," "rear," "front," "vertical," "horizontal" and derivatives of such terms shall relate to the invention as oriented in Figs. 1 and 2. However, it is to be understood that the inventionmayass<anevariousalternativeorientations,exceptwhereexpresslyspecified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodimer~oftheinventiveconceptsdefined intheappended claims.
Specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
Referringtothedrawingfigures,Fig. l schematically illustratesawindow pane assembly 10 having a transparent panel 12 mounted in a frame 14. A beam of radiation 16 such as sunlight is shown impinging upon the transparent panel 12 at an anglesubstantiallydependentupontheinclinationofthesunandtheorientationofthe assembly 10. A portion 18 of beam 16 is reflected by the surface 20 while a second portion 22 passes and is transmitted through the panel 12. Preferably, a substantial portion of the infrared portion of the beam 16 is reflected as shown by numeral 18, and asubstantial portion ofthevisible spectrum ofthe beam 16 istransmitted as represented by numeral 22. The relative amounts of reflected and transmitted wavelengths of the spectrum can be controlled bytheangleofinclinationorangleofincidence of beam upon the surface 20 relative tothenormal shownb~ referencenumera123.
Forexample, it may be desirable to transmit greater amounts of the infrared spectrumwhenthe angle of incidence with respect to the normal 23 is less such as when the sun is lowrelativeto the horizon (winter months) than when the sun is high relative to the horizon (summer months). It is believed that the instant invention achieves these goals.
Fig. 2 illustrates a fragmentary cross-section of the transparent panel assembly l0embodyingtheinventionandincludesthetransparentsubstratesuchaspanel 12 having an outer or exterior surface 20 and an inner or interior surface 24.
Substrate 12 may be made from many types of materials capable of transmitting a substantial portionofthespectrumrangingfromtheultra-violettotheinfrared. Conventional glass has been usedtoformpanei 12 and isthepreferable material for this invention although awiderangeofpolymericmaterialsmayalsobeusedincludingplasticsandresins. The dimensions of panel 12 may also vary ranging from as much as more than one-half inch thicktoaslittleasone-sixteenthofaninch,dependinguponthedesiredapplication.The dimensions in theheight andwidthwill depend greatly uponthemanufacturing ability of the glass producer.
In one form of the invention, an interference filter assembly (IFA) 26 is deposited on one surface 24 ofthe panel 12. Tlie interferencefilter assembly 26 includes atleastone,andpreferablymultiplesequences26ofmicrofinelaminations.Ingeneral, each sequence includes abase oxide layer30 underlyingametallic alloy layer32 which, inturn, is overlain by aprotection layer 34. It is contemplated thatafinal durability layer 36 would be deposited ontopto protecttheunderlying oxide Iayer30,thealloy layer32 and the protection layer 34. In a preferred embodiment such as shown in Fig.
2, two micro fine lamination sequences 28 and 28A are provided wherein the first or base sequence 28 includes oxide layer 30 adjacent surface 24 ofpanel 12. Base oxide layer 30 is overlaid by the metallic alloy layer 32 which, in turn, is covered by a protection layer 34. Deposited on top of protection layer 34 is a second base oxide layer 30A, followed by a second metal alloy layer 32A which, in turn, is covered by a second protectionlayer34A. Terminatingthesequenceandprovidingabondingsurfaceforthe durability layer 36 is an oxide layer 38.
Ingeneral, oxide layers 30, 30A and 38 provide abondingsurfaceforthe adjacent components. Inotherwords,theoxidelayersprovidemolecular bonding sites for the adjacent material. In addition, the oxide layers provide an index of refraction complementarytothemetalalloylayerssuchtha2certainportionsofthespectrumimpact the alloy layeratashallowangle, andthevisibleportion ofthespec~um impactthealloy layer at a steeper angle to be transmitted there through. Suitable oxides include those selectedfromthegroup oftitanium dioxide(T,OZ); niobiumpentoxide(Nb205);
stannous oxide (SI~10.~~; indium oxide; bismuth oxide andzirconium oxideand othersdescribed in U. S. Patent Nos. 4,462,833 and 5,563,734, the contents ofwhich are incorporated herein by reference. In substitution ofthe oxides describedabove, compositefilmsmay beused such as those selected from the group ofzirconium rlitrideand silicon nitrideformed by contemporaneousdeposition. Othernitrideswhichmaybesuitableincludecomposites oftitanium nitride and silicon nitride, hafnium nitride and silicon nitride, oramixture of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride and/ or hafnium nitride. Themethod ofdepositing the different combinations or composites of nitrides isdisclosed inU.S. Patent No. 5,563,734, the substance of which isincorporated herein by reference.
Generally, the thickness of the first base oxide layer 30 ranges from approximately 50 to 300 Angstroms (~), preferably from about 75 to 200 (~), and most preferably from approximately 100 to 150 (~). Regarding the second and third oxide layers 30A and 30B, respectively, thicknesses may be ofthe same order. In the event a composite film is used such one or more of the nitrides mentioned above, the layer correspondingto numeral 30 may haveathicknessrangingpreferably from about 1 OOto 200 (~), and most preferably from approximately 125 to 200 ( fit). Subsequent nitride layers such as those corresponding to layers 30A and 30B may be within the same thickness range.
Deposited ontop of, and bound to base oxide layer 30 is metal layer 32.
Metal layer 32 may be deposited or applied to base layer 30 in various ways including sputterdepositiontoathicknessrangingfromabout200 to300(A),sufficienttoprovide atint orcolorto panel 12 asviewed from side20, but insufficientto blockmorethan 20%
of the visible spectrum. In one embodiment, meal layer 32 comprises an alloy of the noble metals gold and silver wherein silver forms the dominant component. In a preferred embodiment, goldformsmorethan0.2 percent, but less than 0.5 percentofthe al loy, and in the most preferred embodiment, about two to three percent. For example, in aprototypeofthe invention,themetal alloy layer32 includedgold and silverwherein gold comprised about two percent of the alloy.
Deposited on top of the metal alloy layer 32, and preventing oxidation thereof is a protective layer 34. Protective layer 34 may be any one of a number of transparentmaterialswhichalsohavealowpermeabilitysuchasapolymer. Theprimary purpose oftheprotective layer isto preventoxidation ofthemetal alloy layers.
Although inapreferredformoftheinvention,theprotectivelayerisdepositedoverthemetal alloy layers, polymeric materials may also be used, including a sheet adhered to metal alloy layer32 by anadhesive(notshown) orbonded byapplication ofheatsufficientto render polymer34tackyandadheretometal alloy layer32. Thicknessesforsuchlayersoffilm _g_ 34 may range from about 50 ~ to 100 ~1, or if made from a polymer, from about one-quarter to about on-half mill, and most preferably no greater than 1 to about 2 mill.
In the preferred form of the invention, the lamination sequence 28 just described is repeated at least once to form sequence 28A. However, it is contemplated there may be situations where one sequence 28 is desirable. However, in the case of multiple sequences such as 28 and 28Ashown, each subsequentoxidelayer, such as 30A, is deposited ontop of and bondedtothe underly~ngprotective layersuch asrepresented by layer 34 using the same deposition technique described above. The deposition methods and sequences for the metal alloy layer 32A and protective layer 34A
are repeated. Inthepreferred embodiment,thicknesses ofthe layers in the subsequent layer sequences are not substantially changed from that of the initial layer sequence.
Inthe preferred embodimentoftlie invention, the upper surface afthelayer sequencestack(28, 28A) isprotected by durability layer36 deposited ontop ofthefinal oxidelayer38. Thedurabilitylayer36mayalsobeformedusingadepositiontechnique such as one of those mentioned above, or may be a polymer sheet on top of oxide layer 38. Polymer layer 36 is preferably much more resilient to solvents and abrasions than either one or both of layers 34 or 34A as layer 36 forms the primary barrier against cleansers and applicators. Thicknessesfor durability layer36 may also vary depending upon the type of material being used.

In an alternate form ofthe invention, metal al toy protection layers 34 and 34A may be formed from dielectric materials having indices of refraction greater than about 1.5, and preferably between about 2.1 and 2.9. Suitable dielectric layers would includethenitridesorcompositefilmsmentionedabove. Eachdiel~ctriclayermayhave S athicknessrangingfromabout200 Auptoabout600 ~l,preferablybetweenabout250 A
and about S50 ~, and most preferably between about 250 ~t and S00 ~l.
Thicknesses may vary as certain film compositions transmit less:visible light than others. For these materials, thicknesses may be reduced to improve transmittance or emissivity.
The above description is considered that of the preferred embodiments only. Modificationsoftheinventionwilloccurtothoseskilledintheartandtothosewho makeorusetheinvention. Therefore,itisunderstoodthattheembodimentsshowninthe drawings and described above are merely for illustrative purposes and not intended to limitthescopeofthe invention, which is defined by thefollowingclaimsasinterpreted according to the principles of patent law, including the doctrine of equivalents.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
I Claim:

Claims (20)

1. A low emissivity panel assembly, comprising:
a transparent substrate having a first and second surface;
a first filter sequence on at least one surface of said transparent substrate including a first base layer, a first metal alloy layer, and a first metal alloy protective layer;
a second filter sequence on said first filter sequence, including a second base layer, a second metal alloy layer, and a second metal alloy protective layer; and a third deposition sequence overlaying said second filter sequence, including a third base layer, and a durability layer.

2. The low emissivity panel assembly as defined in claim 1, wherein said first, second and third base layers include a substantially transparent dielectric material.

3. The low emissivity panel assembly as defined in claim 1, wherein said first and second metal alloy layers include a combination of about 0.2 percent to about 0.5 percent gold and about 99.5 percent to about 99.8 percent silver.

4. The lowemissivity panel assembly as defined in claim 1, wherein said first and secondmetal alloy protective layers include at least one of a substantially transparent polymer and a substantially transparent dielectric material.

5. A low emissivity panel for a window assembly, comprising in combination:
a substantially transparent substrate having at least one surface;
afirstsubstantially transparent micro-fine laminate filter sequence on said at least one surface of said substantially transparent substrate;
a second substantially transparent micro-fine laminate filter sequence overlying said first substantially transparent micro-fine laminate filter sequence; and a substantially transparent durability sequence overlying said second substantially transparent micro-fine laminate filter sequence.

6. The low emissivity panel for a window assembly as defined in claim 5, wherein said first substantially transparent micro-fine laminate filter sequence includes:
a first substantially transparent dielectric layer;
a first substantially transparent metal alloy layer overlying said first dielectric layer and made from acombination of noble metals, including about 0.2 percent to about 0.5 percent gold, and about 99.5 percent to about 99.8 percent silver; and a first substantially transparent metal alloy protective layer on said first metal alloy layer.

7. The low emissivity panel for a window assembly as defined in claim 5, wherein said second substantially transparent micro-fine laminate filter sequence includes:
a second substantially transparent dielectric layer on said first metal alloy protective layer;
a second substantially transparent metal alloy layer on said second dielectric layer and made from a combination of noble metals including about 0.2percent to about 0.5 percent gold, and about 99.5 percent to about 99.8 percent silver; and a second substantially transparent metal alloy protective layer on said second metal alloy layer.

8. The low emissivity panel for a window assembly as defined in claim 5, wherein said substantially transparent durability sequence includes:
a third substantially transparent dielectric layer on said second metal alloy protective layer; and a durability layer on said third dielectric layer.

9. The low emissivity panel for a window assembly as defined in claim 6, wherein said first metal alloy protective layer includes at least one of a substantially transparent polymer and a substantially transparent dielectric material.

10. The low emissivity panel for a window assembly as defined in claim 6, wherein said first substantially transparent dielectric layer includes at least one of an oxide and a nitride.

11. An interference filter assembly far a window panel, comprising:
a transparent substrate having a generally uniform thickness defined by two opposing surfaces;
at least one filter sequence deposited of one of said two opposing surfaces, said at least one filter sequence including an initial oxide base layer deposited on said one of said towopposing surfaces, a metal alloy layer overlying said initial oxide layer, and a protective layer overlying said metal alloy layer; and wherein said initial oxide layer, metal alloy layer, and said protective layer are arranged to reduce an amount of radiation passing therethrough because of a stacked molecular sequence of said layers.

12. The interference filter assembly is defined by claim 11, wherein said intima oxide base layer includes an oxide formed from one of the following: titanium dioxide, niobium pentoxide, stannous oxide, indium oxide, bismuth oxide, zirconium oxide.

13. The interference filter assembly as defined by claim 11 wherein said metal alloy layer includes less than three percent by volume of gold.

14. The interference filter assembly as defined by claim 11, wherein each of said layers are deposited on said one of said two opposing surfaces.

15. The interference assembly as defined in claim 11, wherein each of said layers is sputtered onto said one of said two opposing surfaces.

16. The interference filter assembly as defined in claim 11 wherein said transparent substrate includes at least one glass panel.

17. A transparent panel assembly, comprising in combination:
a transparent substrate having an index of refraction less than about 3.0 and greater than about 1.0, said transparent substrate having at least one planar surface;

at least one dielectric base layer deposited on said at least one planar surface to a thickness less than 200 .ANG., said base dielectric layer selected from the group titanium dioxide, niobium pentoxide, stannous oxide, indium oxide, bismuth oxide zirconium oxide, zirconium nitride, silicon nitride, hafnium nitride, aluminum nitride and titanium nitride;
at least one metal alloy layer deposited on said dielectric base layer, said metal alloy layer including zinc oxide, titanium oxide, silicon intrometal, silver and gold;
and at least one protective layer deposited on said at least one metal alloy layer, said protective layer reducing the chance said at least one metal alloy layer and aid dielectric base layer may be removed from said transparent substrate.

18. The transparent panel assembly as defined in claim 17, further including a second dielectric base layer, a second metal alloy layer, and a second protection layer, respectively, deposited on the first sequence of layers.

19. The transparent panel assembly as defined in claim 17, further including a final durability layer overlying said dielectric layer, metal alloy layer and said protective layer.

20. The transparent panel assembly as defined in claim 17, wherein said metal alloy layer is formed from a mixture of zinc oxide, titanium oxide, silicon nitro metal, more than 10%, but less that 25% silver, and less than .5% gold.