Heat treatable coated article with low-E coating having zinc stannate based layer between IR reflecting layers and corresponding method

Abstract

A coated article is provided which may be heat treated (e.g., thermally tempered) in certain example instances. In certain example embodiments, the coated article includes a low-emissivity (low-E) coating having a zinc stannate based layer provided over a silver-based infrared (IR) reflecting layer, where the zinc stannate based layer is preferably located between first and second silver based IR reflecting layers. The zinc stannate based layer may be provided between and contacting (i) an upper contact layer of or including Ni and/or Cr (or Ti, or TiOx), and (ii) a layer of or including silicon nitride.

Claims

1. A coated article including a coating supported by a glass substrate, comprising: a first dielectric layer supported by the glass substrate; a second dielectric layer supported by the glass substrate and located over the first dielectric layer; a first infrared (IR) reflecting layer comprising silver supported by the glass substrate and located over at least the first and second dielectric layers; a first upper contact layer comprising an oxide of NiCr from 20-40 ? thick, the first upper contact layer located over and directly contacting the first IR reflecting layer comprising silver; a layer comprising zinc stannate from 350-600 ? thick located over and directly contacting the first upper contact layer comprising the oxide of Ni and Cr in order to improve color stability upon heat treatment; a first layer comprising silicon nitride located over and directly contacting the layer comprising zinc stannate; a layer comprising zinc oxide supported by the glass substrate and located over at least the first layer comprising silicon nitride; a second IR reflecting layer comprising silver located over at least the first layer comprising silicon nitride and the layer comprising zinc oxide, wherein the coating contains no more than two IR reflecting layers comprising silver; a second upper contact layer located over and directly contacting the second IR reflecting layer comprising silver; another dielectric layer located over at least the second IR reflecting layer and the second upper contact layer; and wherein layers of the coating are of materials and thicknesses configured so that the coated article will have a transmissive ?E* value of no greater than 5.0 upon heat treatment at about 650 degrees C. for all time periods between 0 and 30 minutes.

2. The coated article of claim 1, wherein the first dielectric layer comprises silicon nitride.

3. The coated article of claim 1, further comprising a layer comprising NiCr located between and directly contacting the first layer comprising silicon nitride and a further layer comprising silicon nitride.

4. The coated article of claim 1, wherein the layer comprising zinc stannate contains more Zn than Sn.

5. The coated article of claim 1, wherein the coating has a sheet resistance (R.sub.s) of no greater than 3.0 ohms/square.

6. The coated article of claim 1, wherein the coated article, measured monolithically, has a visible transmission of at least 40%.

7. The coated article of claim 1, wherein the layer comprising zinc stannate is the thickest layer in the coating.

8. A coated article including a coating supported by a glass substrate, comprising: a first dielectric layer supported by the glass substrate; a second dielectric layer supported by the glass substrate and located over the first dielectric layer; a first infrared (IR) reflecting layer comprising silver supported by the glass substrate and located over at least the first dielectric layer; an upper contact layer comprising an oxide of NiCr from 10-100 ? thick, the upper contact layer comprising an oxide of NiCr located over and directly contacting the first IR reflecting layer comprising silver; a layer comprising zinc stannate from 200-800 ? thick located over and directly contacting the upper contact layer comprising an oxide of NiCr; a first layer comprising silicon nitride from 80-200 ? thick located over and directly contacting the layer comprising zinc stannate; a layer comprising zinc oxide supported by the glass substrate and located over at least the first layer comprising silicon nitride; a second IR reflecting layer comprising silver located over at least the first layer comprising silicon nitride and located over and directly contacting the layer comprising zinc oxide, wherein the coating contains no more than two IR reflecting layers comprising silver; another dielectric layer located over at least the second IR reflecting layer; and wherein layers of the coating are of materials and thicknesses configured so that the coated article will have a transmissive ?E* value of no greater than 5.0 upon heat treatment at about 650 degrees C. for all time periods between 0 and 30 minutes.

9. The coated article of claim 8, wherein the layer comprising zinc oxide is located between and directly contacting the second layer comprising silicon nitride and the second IR reflecting layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross sectional view of a coated article according to an example embodiment of this invention.

(2) FIG. 2 is a cross sectional view of a coated article according to another example embodiment of this invention.

(3) FIG. 3 is a cross sectional view showing the coated article of FIG. 1 or FIG. 2 provided in an IG window unit according to example embodiments of this invention (on surface two of an IG window unit).

(4) FIG. 4 is a heat treatment (HT) time, in minutes, versus visible transmission (TY %) graph plotting Example 1 versus a Comparative Example (CE).

(5) FIG. 5 is a heat treatment (HT) time, in minutes, versus haze % graph plotting Example 1 versus a Comparative Example (CE).

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

(6) Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views/embodiments.

(7) Coated articles according to certain example embodiments of this invention may be used in the context of insulating glass (IG) window units, vehicle windows, or other types of windows. For example, coatings herein may be used on surface #2 of an IG window unit as shown in FIG. 3 for example. Coated articles according to example embodiments of this invention are characterized by one, two, three, four, five or all six of: (i) desirable visible transmission, (ii) good durability, (iii) desirable coloration, (iv) desirable emissivity, (v) low haze, and/or (vi) thermal stability upon HT.

(8) Example embodiments of this invention relate to a coated article including a low emissivity (low-E) coating 30 supported by a glass substrate 1. Coating 30 may be sputter-deposited. The coated article may be heat treated (e.g., thermally tempered, heat bent and/or heat strengthened). In certain example embodiments of this invention, the coated article includes a zinc stannate based layer 14 provided over a silver-based infrared (IR) reflecting layer 9, where the zinc stannate based layer 14 is preferably located between first and second silver based IR reflecting layers 9 and 19. In certain example embodiments, the zinc stannate based layer is 14 provided between and contacting (i) an upper contact layer 11 of or including Ni and/or Cr, and (ii) a layer 15 of or including silicon nitride, so that for example the layer stack between and/or including the IR reflecting layers moving away from the glass substrate 1 may include layers comprising the following materials: glass . . . Ag/NiCrOx/ZnSnO/SiN . . . Ag . . . (e.g., see layers 9, 11, 14 and 15 in FIGS. 1-2). Low-E coatings according to various embodiments of this invention may, for example, have two or three silver-based IR reflecting layers.

(9) It has surprisingly been found that the provision of the zinc stannate based layer 14 results in a coated article having improved thermal stability upon heat treatment (HT). Coated articles according to embodiments of this invention, if heat treated (e.g., thermally tempered), realize a low ?E* value (glass side reflective and/or transmissive), such as a ?E* value of no greater than 5.0, more preferably no greater than 4.0, within certain HT time periods such as one or more of 10 minutes, 16 minutes, and/or 24 minutes. It has surprisingly been found that the provision of the zinc stannate based layer 14 causes the product's glass side reflective and/or transmissive ?E* value to be surprisingly reduced in a desirable manner upon HT compared to if the zinc stannate based layer 14 was not present (e.g., compared to if the zinc stannate based layer 14 was instead a tin oxide layer).

(10) In example embodiments, the dielectric zinc stannate (e.g., ZnSnO, Zn.sub.2SnO.sub.4, or the like) based layer 14 may include more Zn than Sn by weight. For example, the metal content of zinc stannate based layer 14 may include from about 51-90% Zn and from about 10-49% Sn, more preferably from about 51-70% Zn and from about 30-49% Sn, with an example being about 52% Zn and about 48% Sn (weight %, in addition to the oxygen in the layer) in certain example embodiments of this invention. Thus, for example, the zinc stannate based layer may be sputter-deposited using a metal target comprising about 52% Zn and about 48% Sn in certain example embodiments of this invention. Optionally, the zinc stannate based layer 14 may be doped with other metals such as Al or the like.

(11) In certain example embodiments of this invention, the coating 30 includes a double-silver stack (e.g., see FIG. 1), although this invention is not so limited in all instances (e.g., three silver based layers can be used in certain instances, as shown for example in FIG. 2). It will be recognized that FIGS. 1-2 illustrated coated articles in monolithic form. For example, in certain example embodiments of this invention, heat treated and/or non-HT coated articles having multiple IR reflecting layers (e.g., two or three spaced apart silver based layers) are capable of realizing a sheet resistance (R.sub.s) of less than or equal to 3.0 ohms/square (more preferably less than or equal to 2.5, even more preferably less than or equal to 2.0, and most preferably less than or equal to 1.6 ohms/square). In certain example embodiments, in HT or non-HT form, as measured in monolithic form, coated articles herein are capable of realizing a visible transmission (Ill. C, 2 degree) of at least about 40%, more preferably of at least about 50%, more preferably at least about 55%, and most preferably of at least about 60%.

(12) The terms heat treatment and heat treating as used herein mean heating the article to a temperature sufficient to achieve thermal tempering, heat bending, and/or heat strengthening of the glass inclusive coated article. This definition includes, for example, heating a coated article in an oven or furnace at a temperature of least about 580 degrees C., more preferably at least about 600 degrees C., for a sufficient period to allow tempering, bending, and/or heat strengthening. In certain instances, the HT may be for at least about 4 or 5 minutes or more as discussed herein.

(13) FIG. 1 is a side cross sectional view of a coated article according to an example non-limiting embodiment of this invention, where the low-E coating 30 has two silver-based IR reflecting layers 9 and 19. The coated article includes substrate 1 (e.g., clear, green, bronze, or blue-green glass substrate from about 1.0 to 10.0 mm thick, more preferably from about 1.0 mm to 8.0 mm thick, e.g., about 6 mm thick), and coating (or layer system) 30 provided on the substrate 1 either directly or indirectly. The coating (or layer system) 30 includes: bottom silicon nitride inclusive transparent dielectric layer 3 which may be Si.sub.3N.sub.4, of the Si-rich type for haze reduction, or of any other suitable stoichiometry in different embodiments of this invention, first lower contact layer 7 (which contacts IR reflecting layer 9), first conductive and preferably metallic or substantially metallic infrared (IR) reflecting layer 9, first upper contact layer 11 (which contacts layer 9), transparent dielectric layer 14 of or including zinc stannate over and contacting the contact layer 11, transparent dielectric silicon nitride inclusive layers 15a and 15b which may or may not include some oxide, optional absorber and/or barrier layer 16 of or including NiCr, NiCrOx or the like, second lower contact layer 17 (which contacts IR reflecting layer 19), second conductive and preferably metallic or substantially metallic IR reflecting layer 19, second upper contact layer 21 (which contacts layer 19), transparent dielectric layer 23, and transparent silicon nitride inclusive dielectric layer 25. When barrier/absorber layer 16 is not present, the two silicon nitride based layers 15a and 15b can combine to form a single layer 15 of or including silicon nitride. The contact layers 7, 11, 17 and 21 each contact at least one IR reflecting layer (e.g., layer based on Ag). The aforesaid layers 3-25 make up sputter-deposited low-E (i.e., low emissivity) coating 30 which is provided on glass or plastic substrate 1.

(14) FIG. 2 is a side cross sectional view of a coated article according to another example embodiment of this invention. FIG. 2 illustrates a triple silver coating 30, whereas FIG. 1 illustrates a double silver coating 30. The FIG. 2 embodiment includes many of the layers illustrated in the FIG. 1 embodiment, as indicated by the reference numerals. The low-E coating 30 of the FIG. 2 embodiment, compared to the FIG. 1 embodiment, further includes transparent dielectric layer 5 of or including titanium oxide (e.g., TiO.sub.2), transparent dielectric lower contact layer 27 of or including zinc oxide, transparent third lower contact layer 28 of or including NiCr, NiCrOx or the like, third conductive and preferably metallic or substantially metallic IR reflecting layer 29, third upper contact layer 31 (which contacts layer 29), transparent dielectric layer 33, and transparent silicon nitride inclusive dielectric layer 35. NiCr or NiCrOx barrier layer 16 from the FIG. 1 embodiment need not be present in the FIG. 2 embodiment.

(15) In each of the FIGS. 1 and 2 embodiments, it is also possible to replace tin oxide layer 33 with a zinc stannate layer similar to layer 14 so that the zinc stannate layer would be over and directly contacting contact layer 31. This could be advantageous for reasons similar to those explained above.

(16) In monolithic instances, the coated article includes only one glass substrate 1 as illustrated in FIGS. 1-2. However, monolithic coated articles herein may be used in devices such as laminated vehicle windshields, IG window units, and the like. As for IG window units, an IG window unit may include at least two spaced apart glass substrates. An example IG window unit is illustrated and described, for example, in U.S. Patent Document No. 2004/0005467, the disclosure of which is hereby incorporated herein by reference. FIG. 3 shows an example IG window unit including the coated glass substrate 1 shown in FIG. 1 or FIG. 2 coupled to another glass substrate 2 via spacer(s), sealant(s) 40 or the like, with a gap 50 being defined therebetween. This gap 50 between the substrates in IG window unit embodiments may in certain instances be filled with a gas such as argon (Ar), or a mixture of Ar gas and air. An example IG unit may comprise a pair of spaced apart clear glass substrates 1 and 2 each about 3-8 mm thick (e.g., about 6 mm thick), one of which is coated with a coating 30 herein in certain example instances, where the gap 50 between the substrates may be from about 5 to 30 mm, more preferably from about 10 to 20 mm, and most preferably about 16 mm. In certain example instances, the low-E coating 30 may be provided on the interior surface of either substrate facing the gap (the coating is shown on the interior major surface of substrate 1 in FIG. 3 facing the gap 50, but instead could be on the interior major surface of substrate 2 facing the gap 50). Either substrate 1 or substrate 2 may be the outermost substrate of the IG window unit at the building exterior (e.g., in FIG. 3 the substrate 1 is the substrate closest to the building exterior, and the low-E coating 30 is provided on surface #2 of the IG window unit). In preferred embodiments of this invention, the coating 30 is provided on surface #2 of the IG window unit as shown in FIG. 3. In certain example embodiments of this invention, the coating 30 of FIG. 1 or FIG. 2 could also be used in a triple glazed IG window unit, such as being located on surface #2 of such a triple glazed IG window unit or on any other suitable surface of such a unit.

(17) Dielectric layers 3, 15 (which includes 15a, 15b), 25 and 35 may be of or include silicon nitride in certain embodiments of this invention. Silicon nitride layers 3, 15, 25 and 35 may, among other things, improve heat-treatability of the coated articles, e.g., such as thermal tempering or the like, and may or may not include some oxygen. The silicon nitride of layers 3, 15, 25 and/or 35 may be of the stoichiometric type (i.e., Si.sub.3N.sub.4), or alternatively of the Si-rich type in different embodiments of this invention. For example, Si-rich silicon nitride 3 (and/or 15, and/or 25) combined with zinc stannate 14 may permit the silver to be deposited (e.g., via sputtering or the like) in a manner which causes its sheet resistance to be lessened compared to if certain other material(s) were under the silver. Moreover, the presence of free Si in a Si-rich silicon nitride layer(s) may allow certain atoms such as sodium (Na) which migrate outwardly from the glass 1 during heat treatment (HT) to be more efficiently stopped by the Si-rich silicon nitride inclusive layer before they can reach the silver and damage the same.

(18) In certain example embodiments, when Si-rich silicon nitride is used in one or more of layers 3, 15, 25, the Si-rich silicon nitride layer as deposited may be characterized by Si.sub.xN.sub.y layer(s), where x/y may be from 0.76 to 1.5, more preferably from 0.8 to 1.4, still more preferably from 0.85 to 1.2. Moreover, in certain example embodiments, before and/or after HT the Si-rich Si.sub.xN.sub.y layer(s) may have an index of refraction n of at least 2.05, more preferably of at least 2.07, and sometimes at least 2.10 (e.g., 632 nm) (note: stoichiometric Si.sub.3N.sub.4 which may also be used has an index n of 2.02-2.04). In certain example embodiments, it has surprisingly been found that improved thermal stability is especially realizable when the Si-rich Si.sub.xN.sub.y layer(s) as deposited has an index of refraction n of at least 2.10, more preferably of at least 2.20, and most preferably from 2.2 to 2.4. Also, the Si-rich Si.sub.xN.sub.y layer in certain example embodiments may have an extinction coefficient k of at least 0.001, more preferably of at least 0.003 (note: stoichiometric Si.sub.3N.sub.4 has an extinction coefficient k of effectively 0). Again, in certain example embodiments, it has surprisingly been found that improved thermal stability can be realized when k for the Si-rich Si.sub.xN.sub.y layer(s) is from 0.001 to 0.05 as deposited (550 nm). It is noted that n and k tend to drop due to heat treatment. Any and/or all of the silicon nitride layers 3, 15, 25, 35 discussed herein may be doped with other materials such as stainless steel or aluminum in certain example embodiments of this invention. For example, any and/or all silicon nitride layers discussed herein may optionally include from about 0-15% aluminum, more preferably from about 1 to 10% aluminum, in certain example embodiments of this invention. The silicon nitride may be deposited by sputtering a target of Si or SiAl in an atmosphere including at least nitrogen gas in certain embodiments of this invention.

(19) Infrared (IR) reflecting layers 9, 19 and 29 are preferably substantially or entirely metallic and/or conductive, and may comprise or consist essentially of silver (Ag), gold, or any other suitable IR reflecting material. IR reflecting layers 9, 19 and 29 help allow the coating to have low-E and/or good solar control characteristics. The IR reflecting layers may, however, be slightly oxidized in certain embodiments of this invention.

(20) The upper contact layers 11, 21 and 31 (and possibly lower contact layer 28) may be of or include nickel (Ni) oxide, chromium/chrome (Cr) oxide, or a nickel alloy oxide such as nickel chrome oxide (NiCrO.sub.x), or other suitable material(s) such as Ti or an oxide of Ti, in certain example embodiments of this invention. The use of, for example, NiCrO.sub.x in these layers allows durability to be improved. The NiCrO.sub.x of these layers may be fully oxidized in certain embodiments of this invention (i.e., fully stoichiometric), or alternatively may only be partially oxidized (i.e., sub-oxide). In certain instances, the NiCrOx layers may be at least about 50% oxidized. Contact layers 11, 21, 28, and/or 31 (e.g., of or including an oxide of Ni and/or Cr) may or may not be oxidation graded in different embodiments of this invention. Oxidation grading means that the degree of oxidation in the layer changes throughout the thickness of the layer. For example, a contact layer may be graded so as to be less oxidized at the contact interface with the immediately adjacent IR reflecting layer than at a portion of the contact layer(s) further or more/most distant from the immediately adjacent IR reflecting layer. Descriptions of various types of oxidation graded contact layers are set forth in U.S. Pat. No. 6,576,349, the disclosure of which is hereby incorporated herein by reference. Contact layers 11, 21, 28 and/or 29 (e.g., of or including an oxide of Ni and/or Cr) may or may not be continuous in different embodiments of this invention across the entire underlying or overlying IR reflecting layer.

(21) Transparent dielectric layers 23 and 33 may be of or include tin oxide in certain example embodiments of this invention. However, it may be doped with certain other materials in other example embodiments, such as with Al or Zn in certain example alternative embodiments.

(22) Lower contact or seed layers 7 and/or 17, and transparent dielectric layer 27, in certain embodiments of this invention are of or include zinc oxide (e.g., ZnO). The zinc oxide of these layers may contain other materials as well such as Al (e.g., to form ZnAlO.sub.x). For example, in certain example embodiments of this invention, one or more of zinc oxide layers 7, 17, 27 may be doped with from about 1 to 10% Al, more preferably from about 1 to 5% Al, and most preferably about 1 to 4% Al.

(23) Zinc stannate based layer 14 is provided over and contacting upper contact layer 11 comprising an oxide of Ni and/or Cr, and under and possibly contacting layer 15 (or 15a) of or including silicon nitride, in a central portion of the layer stack between first and second IR reflecting layers 9 and 19. As mentioned above, it has surprisingly been found that this layer stack significantly improves thermal stability upon HT and improves durability. In certain alternative embodiments, it is possible to dope the zinc stannate based layer 14 (e.g., ZnSnO) with other materials such as Al, Zn, N, or the like. The zinc stannate based layer 14 is substantially or substantially fully oxided in preferred embodiments of this invention. As explained above, the presence of the zinc stannate based layer 14 is the illustrated location has been found to surprisingly improve thermal stability of the coating, as will be more fully evidenced below with the examples vs. comparative examples herein.

(24) Other layer(s) below or above the illustrated coating may also be provided. Thus, while the layer system or coating is on or supported by substrate 1 (directly or indirectly), other layer(s) may be provided therebetween. Thus, for example, the coating of FIG. 1 or FIG. 2 may be considered on and supported by the substrate 1 even if other layer(s) are provided between layer 3 and substrate 1. Moreover, certain layers of the illustrated coating may be removed in certain embodiments, while others may be added between the various layers or the various layer(s) may be split with other layer(s) added between the split sections in other embodiments of this invention without departing from the overall spirit of certain embodiments of this invention.

(25) While various thicknesses and materials may be used in layers in different embodiments of this invention, example thicknesses and materials for the respective layers on the glass substrate 1 in the FIG. 1 embodiment are as follows, from the glass substrate outwardly:

Example Materials/Thicknesses; FIG. 1 Embodiment

(26) TABLE-US-00001 Layer Preferred Range More Preferred Glass (1-10 mm thick) ({acute over (?)}) ({acute over (?)}) Example (?) Si.sub.xN.sub.y (layer 3) 40-600 ? 200-500 ? 354 ? ZnAlO.sub.x (layer 7) 10-300 {acute over (?)} 60-140 {acute over (?)} 100 ? Ag (layer 9) 50-250 {acute over (?)} 80-120 {acute over (?)} 110 ? NiCrO.sub.x (layer 11) 10-100 {acute over (?)} 20-40 {acute over (?)} 30 ? ZnSnO (layer 14) 200-800 ? 350-600 ? 472 ? Si.sub.xN.sub.y (layer 15a) 50-350 {acute over (?)} 80-200 {acute over (?)} 120 ? NiCrO.sub.x (layer 16) 25-60 {acute over (?)} 30-60 {acute over (?)} 40 ? Si.sub.xN.sub.y (layer 15b) 50-350 {acute over (?)} 150-250 {acute over (?)} 204 ? ZnAlO.sub.x (layer 17) 10-300 {acute over (?)} 60-140 {acute over (?)} 100 ? Ag (layer 19) 120-260 {acute over (?)} 150-240 {acute over (?)} 207 ? NiCrO.sub.x (layer 21) 10-100 {acute over (?)} 20-40 {acute over (?)} 30 ? SnO.sub.2 (layer 23) 0-750 ? 70-180 ? 100 ? Si.sub.3N.sub.4 (layer 25) 10-750 {acute over (?)} 100-170 {acute over (?)} 120 ?

(27) It can be seen that in certain example embodiments of this invention, the zinc stannate inclusive layer 14 is the thickest layer in the coating 30, and thus may be thicker than all other layers in the coating 30. In certain example embodiments, the zinc stannate inclusive layer 14 is located between and directly contacting contact layer (e.g., oxide of Ni and/or Cr) 11 and silicon nitride inclusive layer 15a (or 15). In certain example embodiments, the zinc stannate inclusive layer 14 is at least two times thicker (more preferably at least five times thicker, and most preferably at least ten times thicker) than is the immediately adjacent contact layer (e.g., oxide of Ni and/or Cr) 11. In certain example embodiments, the zinc stannate inclusive layer 14 is at least two times thicker (more preferably at least three times thicker) than is the immediately adjacent silicon nitride based layer 15a (or 15). These apply to the FIG. 1 and/or FIG. 2 embodiments.

(28) It can be seen that in certain example embodiments of this invention (e.g., see FIG. 1), the upper silver based IR reflecting layer 19 is thicker than the lower silver based IR reflecting layer 9. In certain example embodiments, the upper silver based IR reflecting layer 19 is at least 20 angstroms thicker (more preferably at least 40 angstroms thicker, more preferably at least 60 angstroms thicker, and most preferably at least 70 angstroms thicker) than is the lower silver based IR reflecting layer 9. All thicknesses herein are physical thicknesses.

(29) In certain example embodiments of this invention, coated articles according to the FIG. 1 embodiment may have the following optical and solar characteristics when measured monolithically before and/or after optional HT. The sheet resistances (R.sub.s) herein take into account all IR reflecting layers (e.g., silver layers 9, 19).

Optical/Solar Characteristics (FIG. 1 Embodiment; Monolithic)

(30) TABLE-US-00002 Characteristic General More Preferred Most Preferred R.sub.s (ohms/sq.): <=3.0 <=2.5 <=2.0 or <=1.6 E.sub.n: <=0.07 <=0.04 <=0.03 T.sub.vis (Ill. C 2?): >=40% >=45% >=50%

(31) While various thicknesses and materials may be used in layers in different embodiments of this invention, example thicknesses and materials for the respective layers on the glass substrate 1 in the FIG. 2 embodiment are as follows, from the glass substrate outwardly:

Example Materials/Thicknesses; FIG. 2 Embodiment

(32) TABLE-US-00003 Layer Glass Preferred Range (1-10 mm thick) ({acute over (?)}) More Preferred ({acute over (?)}) Example (?) Si.sub.xN.sub.y (layer 3) 40-600 ? 100-300 ? 136 ? TiO.sub.x (layer 5) 7-150 ? 7-50 ? 10 ? ZnAlO.sub.x (layer 7) 10-300 {acute over (?)} 60-140 {acute over (?)} 90 ? Ag (layer 9) 50-250 {acute over (?)} 80-120 {acute over (?)} 109 ? NiCrO.sub.x (layer 11) 10-100 {acute over (?)} 20-40 {acute over (?)} 30 ? ZnSnO (layer 14) 200-800 ? 350-600 ? 435 ? Si.sub.xN.sub.y (layer 15) 50-350 {acute over (?)} 80-200 {acute over (?)} 130 ? ZnAlO.sub.x (layer 17) 80-300 {acute over (?)} 170-250 {acute over (?)} 220 ? Ag (layer 19) 60-160 {acute over (?)} 90-130 {acute over (?)} 110 ? NiCrO.sub.x (layer 21) 10-100 {acute over (?)} 20-40 {acute over (?)} 30 ? SnO.sub.2 (layer 23) 50-750 ? 150-300 ? 220 ? Si.sub.3N.sub.4 (layer 25) 10-750 {acute over (?)} 100-170 {acute over (?)} 130 ? ZnAlO.sub.x (layer 27) 50-300 {acute over (?)} 190-260 {acute over (?)} 238 ? NiCrO.sub.x (layer 28) 7-40 {acute over (?)} 7-20 {acute over (?)} 10 ? Ag (layer 29) 50-250 {acute over (?)} 120-135 {acute over (?)} 120 ? NiCrO.sub.x (layer 31) 10-100 {acute over (?)} 20-40 {acute over (?)} 30 ? SnO.sub.2 (layer 33) 0-750 ? 50-120 ? 75 ? Si.sub.3N.sub.4 (layer 35) 10-750 {acute over (?)} 100-250 {acute over (?)} 201 ?

(33) In certain example embodiments of this invention, coated articles according to the FIG. 2 embodiment may have the following optical and solar characteristics when measured monolithically before and/or after optional HT. The sheet resistances (R.sub.s) herein take into account all IR reflecting layers (e.g., silver layers 9, 19, 29).

Optical/Solar Characteristics (FIG. 2 Embodiment; Monolithic)

(34) TABLE-US-00004 Characteristic General More Preferred Most Preferred R.sub.s (ohms/sq.): <=3.0 <=2.5 <=2.0 or <=1.6 or <=1.4 E.sub.n: <=0.07 <=0.04 <=0.03 T.sub.vis (Ill. C 2?): >=40% >=50% >=60%

(35) The following examples are provided for purposes of example only, and are not intended to be limiting unless specifically claimed.

ExamplesFIG. 1 Embodiment

(36) The following examples were made via sputtering a coating as shown in FIG. 1 on a 6 mm thick clear glass substrate 1 so as to have the layer stacks set forth below. The thicknesses are in units of angstroms (?). It can be seen that the Comparative Example was the same as Example 1 of this invention except that the zinc stannate layer 14 in Example 1 of this invention was used instead of the tin oxide layer in the Comparative Example (n/a means that the applicable layer was not present in that example). In other words, Example 1 according to this invention was the same as the Comparative Example (CE) except that the tin oxide layer in the middle dielectric portion of the CE was replaced with the zinc stannate layer 14 in Example 1 according to this invention.

(37) TABLE-US-00005 Layer Glass Substrate Comparative Example Example 1 Si.sub.3N.sub.4 354 354 ZnAlO 100 100 Ag 110 110 NiCrO.sub.x 30 30 SnO.sub.2 472 n/a ZnSnO n/a 472 Si.sub.3N.sub.4 120 120 NiCrO.sub.x 40 40 Si.sub.3N.sub.4 204 204 ZnO 100 100 Ag 207 207 NiCrO.sub.x 30 30 SnO.sub.2 100 100 Si.sub.3N.sub.4 120 120

(38) After being sputter deposited onto the glass substrates 1, the samples of the CE and Example 1 were heat treated (HT) for various times between 12 and 30 minutes in a box furnace at 650 degrees C. The Table immediately below illustrates the results for the Comparative Example (CE) and shows various color values (a*, b*), visible transmission % (TY), L* values, visible glass side reflectance (RgY), visible film side reflectance (RfY), sheet resistance (R.sub.s in units of ohms/square), and haze % after various times of heat treatment [Ill. C 2 deg. Observer]. In order to obtain the data below, multiple identical CEs were made and a respective one was removed and measurements taken therefrom after each of the HT times in the table immediately below. The table below for the CE also illustrates the transmissive, glass side reflective, and film side reflective ?E* values due to the HT period of from 0-16 minutes (?E* 0/16). In particular, for a 16 minute heat treatment at 650 degrees C., the CE realized a transmissive ?E* value of 3.27, a glass side reflective ?E* value of 1.29, and a film side reflective ?E* value of 2.16. The row ?E* 16/30 in the table below indicates the change in ?E* between the CE sample that was heat treated for 16 minutes and the CE sample that was heat treated for 30 minutes. Thus, regarding glass side reflective ?E* values for example, ?E* changed 1.29 during the first 16 minutes of HT, but then changed an additional 2.87 for the further HT period from the 16 minute mark to the 30 minutes mark. Therefore, it will be appreciated that the glass side reflective color values did not stabilize and continued to significantly change during the HT period from the 16 minute mark to the 30 minute mark.

(39) TABLE-US-00006 Table for Comparative Example (CE) for Various HT Times HT time Rs Haze (min.) TY TL* Ta* Tb* Rg Y Rg L Rg a* Rg b* RfY Rf L Rf a* Rf b* (?/squ.) (%) 0 51.65 77.07 ?7.57 1.82 11.01 39.59 ?1.36 ?10.46 20.19 52.05 8.88 11.89 1.66 0.00 12 53.35 78.08 ?6.69 ?1.01 11.05 39.67 0.58 ?10.29 20.56 52.46 9.03 12.88 1.59 0.34 14 53.59 78.22 ?6.52 ?0.99 11.44 40.31 ?0.17 ?10.31 21.21 53.18 8.30 12.00 1.50 0.50 16 53.72 78.30 ?6.50 ?1.01 11.73 40.78 ?0.91 ?10.68 21.69 53.70 7.68 11.18 1.40 0.36 18 53.71 78.29 ?6.76 ?1.14 11.25 40.00 ?0.60 ?11.49 21.10 53.06 8.03 10.51 1.48 0.37 22 53.03 77.89 ?6.92 ?1.48 11.76 40.83 ?2.18 ?11.55 21.76 53.77 7.95 10.14 1.37 0.48 24 52.40 77.52 ?7.45 ?1.64 11.75 40.81 ?2.43 ?12.15 21.78 53.79 8.72 9.33 1.37 0.91 30 51.05 76.71 ?8.12 ?2.15 12.53 42.05 ?3.16 ?11.94 22.32 54.37 9.60 8.68 1.38 1.03 ?E* 0/16 3.27 1.29 2.16 ?E* 16/30 2.54 2.87 3.22

(40) The Table immediately below illustrates the results for Example 1 according to this invention, and shows various color values (a*, b*), visible transmission % (TY), L* values, visible glass side reflectance (RgY), visible film side reflectance (RfY), sheet resistance (R.sub.s in units of ohms/square), and haze % after various times of heat treatment [Ill. C 2 deg. Observer]. In order to obtain the data below, multiple identical samples of Example 1 were made and a respective one was removed and measurements taken therefrom after each of the HT times in the table immediately below. The table below for Example 1 also illustrates the transmissive, glass side reflective, and film side reflective ?E* values due to the HT period of from 0-16 minutes (?E* 0/16). In particular, for a 16 minute heat treatment at 650 degrees C., Example 1 realized a transmissive ?E* value of 2.50, a glass side reflective ?E* value of 2.70, and a film side reflective ?E* value of 3.74. The row ?E* 16/30 in the table below indicates the change in ?E* between the Example 1 sample that was heat treated for 16 minutes and the Example 1 sample that was heat treated for 30 minutes. Thus, regarding glass side reflective ?E* values for example, ?E* changed 2.70 during the first 16 minutes of HT, but then changed only an additional 1.25 for the further HT period from the 16 minute mark to the 30 minutes mark. And regarding transmissive ?E* values for Example 1, ?E* changed 2.50 during the first 16 minutes of HT, but then changed only an additional 0.93 for the further HT period from the 16 minute mark to the 30 minutes mark.

(41) TABLE-US-00007 Table for Example 1 for Various HT Times HT time Rs Haze (min.) TY TL* Ta* Tb* Rg Y Rg L Rh a* Rg b* RfY RF L Rf a* Rf b* (?/squ.) (%) 0 50.30 76.25 ?7.63 0.95 11.77 40.85 ?2.32 ?12.23 21.73 53.74 8.72 12.16 1.55 0.00 12 53.89 78.40 ?7.35 ?0.38 11.52 40.44 ?0.9 ?13.38 22.55 54.61 7.06 10.37 1.23 0.34 14 53.86 78.38 ?7.34 ?0.49 11.57 40.53 ?0.95 ?13.27 22.70 54.76 8.98 10.51 1.22 0.36 16 53.89 78.40 ?7.08 ?0.20 11.52 40.44 ?0.64 ?14.30 22.71 54.77 7.18 8.91 1.20 0.31 18 54.01 78.47 ?7.12 ?0.03 11.67 40.69 ?0.83 ?14.50 22.81 54.88 7.16 8.45 1.21 0.30 22 53.64 78.25 ?6.92 ?0.39 11.72 40.77 ?1.51 ?13.90 23.05 55.12 6.78 9.59 1.25 0.41 24 53.71 78.29 ?6.98 ?0.44 11.65 40.65 ?1.30 ?13.82 22.98 55.05 6.96 9.15 1.23 0.47 30 53.01 77.88 ?7.24 ?0.96 11.29 42.06 ?1.75 ?14.74 22.36 54.41 8.08 8.20 1.31 0.54 ?E* 0/16 2.50 2.70 3.74 ?E* 16/30 0.93 1.25 1.20

(42) Therefore, unlike the CE, it can be seen from the above tables that in Example 1 when the zinc stannate layer 14 was present at least the glass side reflective color values and the transmissive color values did indeed stabilize and did not significantly change during the HT from the 16 minute mark to the 30 minute mark. In particular, the ?E* 16/30 values for Example 1 were significantly and surprisingly lower than those for the CE, thereby demonstrating the unexpected advantages associated with using the zinc stannate based layer 14 (the zinc stannate layer 14 was present in Example 1, but not in the CE). Unlike the CE, Example 1 was able to substantially realize substantially its final desired color values (e.g., a*, b* and L* in one or both of transmissive or glass side reflective) within the first 16 minutes or so of the HT process, so that Example 1 remained substantially stable with respect to a*, b* and L* values (glass side reflective and/or transmissive) over the heat treating time period of from 16 to 30 minutes. Therefore, for example, a pair of thermally tempered products of Example 1 would substantially match each other with respect to transmissive and glass side reflective values when one was heat treated for 16 minutes and the other for 30 minutes. This would not be the case for the CE, noting the undesirably high transmissive ?E* value over 5 for the CE for the heat treating period of from 0 to 30 minutes which value is obtained by adding transmissive ?E* 0/16 (3.27) and transmissive ?E* 16/30 (2.54) for the CE. Moreover, Example 1 advantageously had glass side reflective, film side reflective, and transmissive ?E* 16/30 values that were lower than the corresponding glass side reflective, film side reflective, and transmissive ?E* 0/16 values which indicates that the appearance of the samples in Example 1 substantially stabilized prior to potential lengthy heat treatment processingwhereas the CE could not achieve this for glass side reflective or film side reflective ?E* values, again indicating that the use of the zinc stannate based layer 14 surprisingly improved the thermal stability of the coating. Furthermore, it can be seen that all transmissive ?E* values were significantly better (lower) for Example 1 than for the corresponding ?E* values for the CE.

(43) FIGS. 4-5 also illustrate the improved thermal stability achieved by use of the zinc stannate based layer 14 as shown in FIG. 1. FIG. 4 is a heat treatment (HT) time, in minutes, versus visible transmission (TY %) graph plotting Example 1 versus the Comparative Example (CE); and FIG. 5 is a heat treatment (HT) time, in minutes, versus haze % graph plotting Example 1 versus the CE. The Example 1 plot (ZnSn) in FIGS. 4-5 has a plurality of circles, whereas the CE plot (Sn) in FIGS. 4-5 has a plurality of Xs. FIG. 4 illustrates that the visible transmission of Example 1 substantially plateaus (e.g., does not change by more than 1.5%, more preferably does not change by more than 1.0%) between HT times of from about 12-24 minutes, whereas the visible transmission for the CE substantially plateaus for a much shorter HT time period, thereby demonstrating that Example 1 is more thermally stable with respect to visible transmission than is the CE. This is advantageous because in real world applications the coating will likely be heat treated for different periods of time based on the thickness of the supporting glass 1 to which the coating is applied and the type of furnace used by the heat treater, and the improved thermal stability over a longer HT range is advantageous because it allows a greater percentage of the manufactured coatings to realized the appearance ultimately desired. Likewise, FIG. 5 illustrates that Example 1 was fairly stable with respect to haze % from the 22-30 minute marks of HT, whereas the CE spiked significantly upward in an undesirable manner after the 22 minute mark of HT. Again, this demonstrates that Example 1 with respect to haze was thermally stable over a longer range of potential HT times than was the CE. Coated articles in example embodiments of this invention realize a haze % of no greater than 0.60% over the entire HT period of from 0-30 minutes. Again, the thermal stability over a longer period of potential HT time with respect to haze, color, and/or visible transmission is advantageous because in real world applications the coating will likely be heat treated for different periods of time based on the thickness of the supporting glass 1 to which the coating is applied and the type of furnace used by the fabricator heat treater, and the improved thermal stability over a longer HT range is advantageous because it allows a greater percentage of the manufactured coatings to realized the appearance ultimately desired.

ExamplesFIG. 2 Embodiment

(44) The following examples were made via sputtering a coating as shown in FIG. 2 on a 6 mm thick clear glass substrate 1 so as to have the layer stacks set forth below. The thicknesses are in units of angstroms (?). It can be seen that the Comparative Example (CE) was the same as Example 2 of this invention except that the tin oxide layer adjacent the zinc stannate layer 14 in the CE was not present in Example 2 of this invention (n/a means that the applicable layer was not present in that example). In other words, Example 2 according to this invention was essentially the same as the Comparative Example (CE) except for the zinc stannate thickness and that the zinc stannate layer 14 in Example 2 was in direct contact with the NiCrOx contact layer 11 (as opposed to having a tin oxide layer therebetween in the CE). The zinc stannate layers were sputtered via ZnSn targets with a Zn/Sn wt. % ratio of 52/48.

(45) TABLE-US-00008 Layer Glass Substrate Comparative Example Example 2 Si.sub.3N.sub.4 136 136 TiO.sub.x 10 10 ZnAlO 90 90 Ag 109 109 NiCrO.sub.x 30 30 SnO.sub.2 267 n/a ZnSnO 167 435 Si.sub.3N.sub.4 130 130 ZnO 220 220 Ag 110 110 NiCrO.sub.x 30 30 SnO.sub.2 220 220 Si.sub.3N.sub.4 130 130 ZnO 238 238 NiCrO.sub.x 10 10 Ag 120 120 NiCrO.sub.x 30 30 SnO.sub.2 75 75 Si.sub.3N.sub.4 201 201

(46) After being sputter deposited onto the glass substrates 1, the samples of the CE and Example 2 were then heat treated (HT) for various times from 10-24 minutes in a box furnace at 650 degrees C. The Table immediately below illustrates certain results for both the Comparative Example (CE) and Example 2 [Ill. C 2 deg. Observer]. See the discussion regarding the data above regarding Example 1 for an understanding of the data.

(47) TABLE-US-00009 Comparative Example Example 2 ?E* 0/16 2.46 1.81 Glass side reflective ?E* 16/24 2.11 1.21 Glass side reflective ?E* 0/16 2.32 2.73 Transmissive ?E* 16/24 2.14 0.69 Transmissive R.sub.s (ohms/square) 1.64 1.63 No HT R.sub.s (ohms/square) 1.49 1.36 14 min. HT R.sub.s (ohms/square) 1.38 1.36 16 min. HT R.sub.s (ohms/square) 1.34 1.35 24 min. HT

(48) For example, for a 16 minute heat treatment at 650 degrees C., the CE realized a glass side reflective ?E* value of 2.46. The row ?E* 16/24 in the table above indicates the change in ?E* between the sample that was heat treated for 16 minutes and the sample that was heat treated for 24 minutes. Thus, regarding glass side reflective ?E* values for example, for the CE ?E* changed 2.46 during the first 16 minutes of HT, but then changed an additional 2.11 for the further HT period from the 16 minute mark to the 24 minutes mark. However, for Example 2, regarding glass side reflective ?E* values for example, ?E* changed 1.81 during the first 16 minutes of HT, but then changed only an additional 1.21 for the further HT period from the 16 minute mark to the 24 minutes mark. The transmissive ?E* 16/24 value of Ex. 2 (0.69) is also significantly better (lower) than that of the CE, which again is advantageous as explained above. Therefore, it will be appreciated that the glass side reflective color values stabilized more for Example 2 than for the CE. This improvement of thermal stability widens the process window of the tempering process as explained above, and makes it easier to achieve the final product or essentially the final product color even though in real world applications the heat treating may occur for different periods of time as explained above based on different glass thicknesses and/or different types of tempering furnaces.

(49) In certain embodiments of this invention there is provided a coated article including a coating supported by a glass substrate, comprising: a first dielectric layer supported by the glass substrate; a first infrared (IR) reflecting layer comprising silver supported by the glass substrate and located over at least the first dielectric layer; an upper contact layer (e.g., comprising an oxide of Ni and/or Cr, or Ti, or an oxide of Ti), the upper contact layer located over and directly contacting the first IR reflecting layer comprising silver; a layer comprising zinc stannate located over and directly contacting the upper contact layer; a first layer comprising silicon nitride located over and directly contacting the layer comprising zinc stannate; a second IR reflecting layer comprising silver located over at least the first layer comprising silicon nitride; and another dielectric layer located over at least the second IR reflecting layer.

(50) The coated article of the immediately preceding paragraph may further comprise a layer comprising zinc oxide located under and directly contacting the second IR reflecting layer comprising silver.

(51) In the coated article of any of the preceding two paragraphs, the upper contact layer may comprise an oxide of NiCr.

(52) In the coated article of any of the preceding three paragraphs, the first dielectric layer may comprise silicon nitride.

(53) In the coated article of any of the preceding four paragraphs, there may be another dielectric layer that comprises tin oxide.

(54) In the coated article of any of the preceding five paragraphs, there may be a layer comprising NiCr that is located between and directly contacting the first layer comprising silicon nitride and a further layer comprising silicon nitride.

(55) The coated article of any of the preceding six paragraphs may further comprise a layer comprising zinc oxide located under and directly contacting the first IR reflecting layer comprising silver.

(56) It is possible that the coated article of any of the preceding seven paragraphs may have no more than two IR reflecting layers comprising silver.

(57) In the coated article of any of the preceding eight paragraphs, the layer comprising zinc stannate may contain more Zn than Sn.

(58) In the coated article of any of the preceding nine paragraphs, the layer comprising zinc stannate, with respect to metal content, may contain from 51-90% Zn and from 10-49% Sn (wt. %).

(59) In the coated article of any of the preceding ten paragraphs, the layer comprising zinc stannate may be substantially fully oxided.

(60) In the coated article of any of the preceding eleven paragraphs, the layer comprising zinc stannate may consist of or consist essentially of zinc stannate.

(61) In the coated article of any of the preceding twelve paragraphs, the coating may have a sheet resistance (R.sub.s) of no greater than 3.0 ohms/square.

(62) In the coated article of any of the preceding thirteen paragraphs, the coated article, measured monolithically, may have a visible transmission of at least about 40%.

(63) In the coated article of any of the preceding fourteen paragraphs, the coated article may be heat treated.

(64) In the coated article of any of the preceding fifteen paragraphs, the layer comprising zinc stannate may be the thickest layer in the coating.

(65) In the coated article of any of the preceding sixteen paragraphs, the layer comprising zinc stannate may be at least five times thicker than is the upper contact layer.

(66) In the coated article of any of the preceding seventeen paragraphs, the layer comprising zinc stannate may be at least twice as thick as the layer comprising silicon nitride that is located over and directly contacting the layer comprising zinc stannate.

(67) In the coated article of any of the preceding eighteen paragraphs, the second IR reflecting layer comprising silver may be at least 40 angstroms thicker than is the first IR reflecting layer comprising silver.

(68) In the coated article of any of the preceding nineteen paragraphs, the layer comprising zinc stannate may be from 350-600 angstroms thick.

(69) The coated article of any of the preceding twenty paragraphs may further comprise a third IR reflecting layer comprising silver that is located over at least the another dielectric layer.

(70) In the coated article of any of the preceding twenty-one paragraphs, layers of the coating may be of materials and thicknesses so that the coated article will have a transmissive and/or glass side reflective ?E* value(s) of no greater than 5.0 upon heat treatment at about 650 degrees C. for all time periods between 0 and 30 minutes.

(71) In the coated article of any of the preceding twenty-two paragraphs, layers of the coating may be of materials and thicknesses so that the coated article will have a glass side reflective and/or transmissive ?E* value of no greater than 4.0 upon heat treatment at about 650 degrees C. for all time periods between 0 and 24 minutes.

(72) In the coated article of any of the preceding twenty-three paragraphs, layers of the coating may be of materials and thicknesses so that the coated article will have a haze % of no greater than 0.60% upon heat treatment at about 650 degrees C. for all time periods between 0 and 30 minutes.

(73) In the coated article of any of the preceding twenty-four paragraphs, the layers of the coating may be of materials and thicknesses so that visible transmission of the coated article substantially plateaus and thus does not change by more than 1.0% between heat treating times of from 12-24 minutes at a heat treating temperature of about 650 degrees C.

(74) While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.