Patent Publication Number: US-11027527-B2

Title: Silver colored coated article with low-E coating having absorber layer and low visible transmission

Description:
This application is the U.S. national phase of International Application No. PCT/US2016/057439 filed Oct. 18, 2016, the entire content of which is hereby incorporated by reference in this application. 
     This invention relates to a coated article including a low-emissivity (low-E) coating. In certain example embodiments, the low-E coating is provided on a substrate (e.g., glass substrate) and includes at least first and second infrared (IR) reflecting layers (e.g., silver based layers) that are spaced apart by contact layers (e.g., NiCr based layers), a layer comprising silicon nitride, and an absorber layer of or including a material such as niobium zirconium which may be oxided and/or nitrided. The absorber layer is designed to allow the coated article to realize glass side/exterior reflective silver color. In certain example embodiments, the coated article (monolithic form and/or in IG window unit form) has a low visible transmission (e.g., from 15-45%, more preferably from 22-39%, and most preferably from 24-35%). In certain example embodiments, the coated article may be heat treated (e.g., thermally tempered and/or heat bent). Coated articles according to certain example embodiments of this invention may be used in the context of insulating glass (IG) window units, vehicle windows, other types of windows, or in any other suitable application. 
     BACKGROUND OF THE INVENTION 
     Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, and/or the like. It is known that in certain instances, it is desirable to heat treat (e.g., thermally temper, heat bend and/or heat strengthen) such coated articles for purposes of tempering, bending, or the like. Heat treatment (HT) of coated articles typically requires use of temperature(s) of at least 580 degrees C., more preferably of at least about 600 degrees C. and still more preferably of at least 620 degrees C. Such high temperatures (e.g., for 5-10 minutes or more) often cause coatings to break down and/or deteriorate or change in an unpredictable manner. Thus, it is desirable for coatings to be able to withstand such heat treatments (e.g., thermal tempering), if desired, in a predictable manner that does not significantly damage the coating. 
     In certain situations, designers of coated articles strive for a combination of desirable visible transmission, desirable color, low emissivity (or emittance), and low sheet resistance (R s ). Low-emissivity (low-E) and low sheet resistance characteristics permit such coated articles to block significant amounts of IR radiation so as to reduce for example undesirable heating of vehicle or building interiors. 
     Silver coloration is sometimes desired in the context of monolithic windows, insulating glass (IG) window units, and/or other suitable applications. Desirable silver coloration (e.g., glass side reflective, or exterior), measured monolithically and/or in an IG window unit, may be characterized by: high glass side visible reflectance of from 23-43%, more preferably from 25-40%, and most preferably from 27-35%, glass side reflective a* color values of from −6.0 to +5.0, more preferably from −3.5 to +4.0, and most preferably −2.5 to +3.0; in combination with glass side reflective b* color values of from −11.0 to +3.0, more preferably from −9.0 to +1.0, and most preferably from −8.0 to −1.0; and a visible transmission (TY or T vis ) of from 15-45%, more preferably from 22-39%, and most preferably from 24-35%. Note that optical values (e.g., a*, b*, T vis , R GY , R FILM ) herein are measured in accordance with the Illuminant C, 2 degree, standard. 
     It has been difficult to achieve desirable silver glass side reflective coloration in combination with acceptable solar values such as low sheet resistance, SF, and/or SHGC. 
     Low solar factor (SF) and solar heat gain coefficient (SHGC) values are desired in some applications, particularly in warm weather climates. Solar factor (SF), calculated in accordance with EN standard 410, relates to a ratio between the total energy entering a room or the like through a glazing and the incident solar energy. Thus, it will be appreciated that lower SF values are indicative of good solar protection against undesirable heating of rooms or the like protected by windows/glazings. A low SF value is indicative of a coated article (e.g., IG window unit) that is capable of keeping a room fairly cool in summertime months during hot ambient conditions. Thus, low SF values are sometimes desirable in hot environments. While low SF values are sometimes desirable for coated articles such as IG window units, the achievement of lower SF values may come at the expense of sacrificing coloration. It is often desirable, but difficult, to achieve a combination of acceptable visible transmission, desirable glass side reflective coloration, and a low SF value for a coated article such as an IG window unit or the like. SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculated from the full spectrum (T, Rg and Rf) and are typically measured with a spectrophotometer such as a Perkin Elmer 1050. The SF measurements are done on monolithic coated glass, and the calculated values can be applied to monolithic, IG and laminated applications. 
     U.S. Patent Document 2012/0177899 discloses several different coatings. The Examples 1, 4 and 5 on page four of US &#39;899 in [0026] are glass/SiN/NiCrNx/SiN/NiCrNx/SiN. However, these examples have undesirably high sheet resistance values of from 40-75 ohms/square, and undesirable green or bronze glass side reflective coloration. Unfortunately, all Examples in US &#39;899 suffer from undesirably high sheet resistance values of from 40-75 ohms/square, and undesirably high SF and SHGC values. 
     U.S. Pat. No. 5,557,462 discloses a low-E coating with a layer stack of SiN/NiCr/Ag/NiCr/SiN/NiCr/Ag/NiCr/SiN. However, the coated article of the &#39;462 patent has an undesirably high visible transmission of at least 63%, and a low glass side/exterior reflectance (R G Y) of less than about 10% which is too low to realize desirable silver coloration. The &#39;462 patent at column 3, lines 12-15, teaches that visible transmission below 70% (monolithic coated article) and below 63% (IG window unit) are undesirable. Thus, the &#39;462 patent teaches directly away from coated articles with visible transmission lower than 63%. Moreover, as largely explained in U.S. Pat. No. 8,173,263, coated articles of the &#39;462 patent are not reasonably heat treatable at least because upon heat treatment sheet resistance (R s ) goes way up such as from about 3-5 to well over 10. 
     U.S. Patent Document 2016/0185660 discloses a low-E coating with a layer stack of SiN/NiCr/Ag/NiCr/SiN/NiCr/Ag/NiCr/SiN/ZrO. However, it has been found here that durability of this layer stack can be improved upon. Moreover, the example coated articles described in the &#39;660 patent, namely Examples 1-3, have undesirably high visible transmissions of over 47%, and cannot realize desirable silver glass side/exterior coloration. For instance, the glass side/exterior visible reflectance values (R G Y) of Examples 1-3 in the &#39;660 patent document are from 8-12% which way too low to allow the coated articles to realize desirable silver glass side/exterior coloration. Thus, there is room for improvement regarding the &#39;660 patent document with respect to one or more of durability, visible transmission, coloration, and/or glass side visible reflectance. 
     Thus, it would be desirable if silver glass side reflective coloration could be achieved, measured monolithically and/or in an IG window unit, in combination with good durability, low sheet resistance, low visible transmission, and low SF and/or SHGC value(s). Note that a typical conventional IG window unit with two panes has an SHGC value around 0.70. 
     BRIEF SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION 
     Example embodiments of this invention relate to a coated article including a low-emissivity (low-E) coating. In certain example embodiments, the low-E coating is provided on a substrate (e.g., glass substrate) and includes at least first and second infrared (IR) reflecting layers (e.g., silver based layers) that are spaced apart by contact layers (e.g., NiCr based layers) and a dielectric layer of or including a material such as silicon nitride and an absorber layer of or including a material such as niobium zirconium which may be oxided (e.g., NbZrO x ) and/or nitrided (e.g., NbZrO x N y ). The addition of the absorber layer, which if oxided is preferably sub-oxided (partially oxided) and which if nitrided is preferably sub-nitrided (partially nitrided with fairly small amounts of nitrogen), has been found to increase durability and can be utilized to provide desirable silver glass side/exterior reflective coloration including high glass side visible reflectance, low visible transmission, desirable transmissive color and more desirable film side reflective b* values, and low SF and SHGC value(s). In certain example embodiments, the coated article (monolithic form and/or in IG window unit form) has silver glass side reflective visible coloration and a low visible transmission (e.g., from 15-45%, more preferably from 22-39%, and most preferably from 24-35%). In certain example embodiments, the coated article may be heat treated (e.g., thermally tempered and/or heat bent). Coated articles according to certain example embodiments of this invention may be used in the context of insulating glass (IG) window units, vehicle windows, other types of windows, or in any other suitable application. 
     In certain example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate and having silver glass side reflective color, the coating comprising: first and second infrared (IR) reflecting layers comprising silver, the first IR reflecting layer being located closer to the glass substrate than is the second IR reflecting layer; a first contact layer located over and directly contacting the first IR reflecting layer comprising silver; a dielectric layer comprising silicon nitride located over and directly contacting the first contact layer; wherein the dielectric layer comprising silicon nitride is split by a splitting absorber layer comprising Nb and Zr, so that the splitting absorber layer comprising Nb and Zr is located between and contacting a first portion of the dielectric layer comprising silicon nitride and a second portion of the dielectric layer comprising silicon nitride; a second contact layer located over the layer comprising silicon nitride; the second IR reflecting layer comprising silver located over and directly contacting the second contact layer; a third contact layer located over and directly contacting the second IR reflecting layer; another dielectric layer comprising silicon nitride located over the third contact layer; and wherein the coated article has a visible transmission of from 15-45%, a glass side visible reflectance of from 23-43%, a glass side reflective a* value from −6.0 to +5.0, and a glass side reflective b* value from −11.0 to +3.0. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of a coated article according to an example embodiment of this invention. 
         FIG. 2  is a cross sectional view showing the coated article of  FIG. 1  provided in an IG window unit according to an example embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION 
     Coated articles herein may be used in applications such as IG window units, laminated window units (e.g., for use in vehicle or building applications), vehicle windows, monolithic architectural windows, residential windows, and/or any other suitable application that includes single or multiple glass substrates. 
     Certain embodiments of this invention relate to a coated article including a low-emissivity (low-E) coating  30 . In certain example embodiments, the low-E coating  30  is provided on (directly or indirectly) a substrate (e.g., glass substrate)  1  and includes at least first and second infrared (IR) reflecting layers (e.g., silver based layers)  9 ,  19  that are spaced apart by contact layers (e.g., NiCr based layers)  11 ,  17  and a dielectric layer  14  of or including a material such as silicon nitride and an absorber layer  15  of or including a material such as niobium zirconium which may be oxided (e.g., NbZrO x ) and/or nitrided (e.g., NbZrO x N y ) in a substoichiometric manner. The addition of the absorber layer  15 , which if oxided is preferably sub-oxided (partially oxided) and which if nitrided is preferably sub-nitrided (partially nitrided with fairly small amounts of nitrogen), has been found to increase durability and can be utilized to provide desirable silver glass side/exterior reflective coloration including high glass side visible reflectance, low visible transmission, desirable transmissive color and more desirable film side reflective b* values, and low SF and SHGC value(s). Thus, the absorber layer  15  has been found to advantageously provide acceptable thermal performance in combination with desirable indoor and outdoor transmissive and/or reflective coloration. In certain example embodiments, the coated article (monolithic form and/or in IG window unit form) has a low visible transmission (e.g., from 15-45%, more preferably from 22-39%, and most preferably from 24-35%). In certain example embodiments, the coated article may be heat treated (e.g., thermally tempered and/or heat bent). In example embodiments of this invention, the coated article, if an insulating glass (IG) window unit having two glass substrates, has an SF value of no greater than 0.27 (more preferably no greater than 0.25, and most preferably no greater than 0.21) and/or an SHGC value of no greater than 0.27 (more preferably no greater than 0.25, and most preferably no greater than 0.23 or 0.20). Thus, such coatings provide for improved color control and/or ranges when desired, good durability and desirable visible transmission values, and desirable low SF and/or SHGC values indicating ability to keep rooms cool in warm environments. 
     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 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. The coated article may or may not be heat treated in different embodiments of this invention. 
     In certain example embodiments of this invention, the coating includes a double-silver stack. Referring to  FIG. 1  for example, in certain example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: first  9  and second  19  infrared (IR) reflecting layers comprising or consisting essentially of silver, the first IR reflecting layer  9  being located closer to the glass substrate  1  than is the second IR reflecting layer  19 ; a first contact layer comprising NiCr  7  located under and directly contacting the first IR reflecting layer comprising silver  9 , a second contact layer  11  located over and directly contacting the first IR reflecting layer comprising silver  9 ; a dielectric layer comprising silicon nitride  14  (the layer  14  is made up of lower layer portion  14   a  and upper layer portion  14   b ) located over and directly contacting the first contact layer comprising NiCr  11 ; wherein the dielectric layer comprising silicon nitride  14  is split by an absorbing layer  15  of or including niobium zirconium which may be sub-oxided and/or nitrided, so that the absorbing layer  15  is located between and contacting lower portion  14   a  of the dielectric layer comprising silicon nitride and upper portion  14   b  of the dielectric layer comprising silicon nitride; a third contact layer comprising NiCr  17  located over and directly contacting the upper portion  14   b  of the layer comprising silicon nitride  14 ; the second IR reflecting layer comprising silver  19  located over and directly contacting the second contact layer comprising NiCr  17 ; a fourth contact layer comprising NiCr  21  located over and directly contacting the second IR reflecting layer  19 . The lower IR reflecting layer  9  is at least 20 angstroms thicker, more preferably at least 40 angstroms thicker, than is the upper IR reflecting layer  19  in certain example embodiments, as this has been found to allow the glass side visible reflectance to be increased to help achieve silver glass side reflective coloration in combination with low visible transmission. The provision of the absorbing layer  15 , splitting the silicon nitride based layer  14  into two equal or unequal portions, has also been found to improve durability. The coating  30  may include three dielectric layers  3 ,  14  and  24  of or including silicon nitride, as shown in  FIG. 1 . Moreover, the coating  30  may include a layer (e.g., overcoat)  27  of or including zirconium oxide and/or zirconium oxynitride in certain example embodiments. In certain example embodiments, this overcoat layer of or including zirconium oxide and/or zirconium oxynitride  27  is thinner than one or both of the IR reflecting layers  9 ,  19  comprising silver in the coating. In certain example embodiments of this invention, each of the IR reflecting layers comprising silver  9  and  19  is at least twice as thick, and more preferably at least three times as thick, as the layer  27  or including zirconium oxide and/or zirconium oxynitride. In certain example embodiments of this invention, the coating includes only two IR reflecting layers  9 ,  19  of or including silver or the like. 
     In order to increase durability and to provide for desirable silver glass side/exterior coloration in combination with low sheet resistance and desirable optical/solar features, along with optics and thermal properties, coated articles according to certain example embodiments of this invention have a center dielectric layer  14  of or including silicon nitride split by the niobium zirconium inclusive absorber layer  15 , and lower contact layers  7 ,  17  may be based on NiCr (as opposed to ZnO). It has also been found that using metallic or substantially metallic NiCr (possibly partly nitrided) for layer(s)  7 ,  11 ,  17  and/or  21  improves chemical, mechanical and environmental durability (compared to using ZnO lower contact layers below silver and/or highly oxided NiCr upper contact layers above silver). However, ZnO may still be used in alternative embodiments. It has also been found that sputter-depositing silicon nitride inclusive layer  14  in an amorphous state, so that it is amorphous in both as-coated and HT states, helps with overall stability of the coating. For example, 5% HCl at 65 degrees C. for one hour will remove the coating of U.S. Pat. No. 7,521,096, whereas the coating shown in  FIG. 1  and the examples herein can survive this HCl test. And in high temperature and high humidity environment, there is less damage to the coating of  FIG. 1  and the examples herein after ten days of exposure, than to the coating of the &#39;096 patent after two days of exposure. And regarding high corrosive chemicals such as those used for “brick wash”, corrosion resistance is such that edge deletion need not be performed in certain example IG and laminated embodiments. Similarly, for mechanical abrasion tests, thermal cycling and salt fog tests, the coatings of the examples herein were found to be better than that of the &#39;096 patent. 
     In certain example embodiments of this invention such as  FIG. 1 , heat treated or non-heat-treated coated articles having multiple IR reflecting layers (e.g., two spaced apart silver based layers) are capable of realizing a sheet resistance (R s ) of less than or equal to 6.0 (more preferably less than or equal to 5.0, even more preferably less than or equal to 4.0). 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 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. The coated article may or may not be heat treated in different embodiments of this invention. 
       FIG. 1  is a side cross sectional view of a coated article according to an example non-limiting embodiment of this invention. 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 6.0 mm thick), and low-E coating (or layer system)  30  provided on the substrate  1  either directly or indirectly. The coating (or layer system)  30  includes, for example: bottom dielectric silicon nitride layer  3  which may be Si 3 N 4 , or of the Si-rich type silicon nitride for haze reduction, or of any other suitable stoichiometry silicon nitride in different embodiments of this invention, lower contact layer  7  (which contacts bottom IR reflecting layer  9 ), first conductive and preferably metallic or substantially metallic infrared (IR) reflecting layer  9 , upper contact layer  11  (which contacts IR reflecting layer  9 ), dielectric silicon nitride based and/or inclusive layer  14  split into two portions  14   a ,  14   b  by absorber layer  15 , lower contact layer  17  (which contacts IR reflecting layer  19 ), second conductive and preferably metallic or substantially metallic IR reflecting layer  19 , upper contact layer  21  (which contacts layer  19 ), dielectric silicon nitride layer  24  which may be Si 3 N 4 , of the Si-rich type for haze reduction, or of any other suitable stoichiometry silicon nitride in different embodiments of this invention, and overcoat layer  27  of or including a material such as zirconium oxide (e.g., ZrO 2 ) and/or zirconium oxynitride. The “contact” layers  7 ,  11 ,  17  and  21  each contact an IR reflecting layer (e.g., layer based on Ag). The aforesaid layers  3 - 27  make up low-E (i.e., low emissivity) coating  30  that is provided on glass or plastic substrate  1 . Layers  3 - 27  may be sputter-deposited on the substrate  1  in certain example embodiments of this invention, with each layer being sputter-deposited in vacuum using one or more targets as needed (the sputtering targets may be ceramic or metallic). Metallic or substantially metallic layers (e.g., layers  7 ,  9 ,  11 ,  17 ,  19  and  21 ) may be sputtered in an atmosphere containing argon gas, whereas nitrided layers (e.g., layers  3 ,  7 ,  11 ,  14 ,  17 ,  21  and/or  24 ) may be sputtered in an atmosphere containing a mixture of nitrogen and argon gas. Absorber layer  15  is preferably sputter-deposited from an NbZr target(s) in an atmosphere having a mixture of argon (Ar) and a small amount of oxygen (and possibly) nitrogen gas(es). As indicated above, the contact layers  7 ,  11 ,  17  and  21  may or may not be nitrided in different example embodiments of this invention. 
     In monolithic instances, the coated article includes only one glass substrate  1  as illustrated in  FIG. 1 . 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 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. 2  shows an example IG window unit including the coated glass substrate  1  shown in  FIG. 1  coupled to another glass substrate  2  via spacer(s), sealant(s)  40  or the like, with a gap being defined therebetween. This gap between the substrates in IG window unit embodiments may in certain instances be filled with a gas such as argon (Ar). An example IG unit may comprise a pair of spaced apart clear glass substrates, which may be matte glass substrates in certain example instances, each about 3-7 mm (e.g., 6 mm) thick, one of which is coated with a coating  30  herein in certain example instances, where the gap 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. 2  facing the gap, but instead could be on the interior major surface of substrate  2  facing the gap). Either substrate  1  or substrate  2  may be the outermost substrate of the IG window unit at the building exterior (e.g., in  FIG. 2  the substrate  1  is the substrate closest to the building exterior, and the coating  30  is provided on surface #2 of the IG window unit). While  FIG. 2  shows the coating  30  on surface #2 of the IG window unit (so that glass side reflective color is viewed from the exterior of the building), it is possible that the coating  30  may be provided on surface #3 of the IG window unit in alterative embodiments in which case glass side reflective color would be as viewed from the interior of the building. 
     In certain example embodiments of this invention, one, two, three, or all four of contact layers  7 ,  11 ,  17 ,  21  may be of or include NiCr (any suitable ratio of Ni:Cr), and may or may not be nitrided (NiCrNx). In certain example embodiments, one, two, three or all four of these NiCr inclusive layers  7 ,  11 ,  17 ,  21  is substantially or entirely non-oxidized. In certain example embodiments, layers  7 ,  11 ,  17  and  21  may all be of metallic NiCr or substantially metallic NiCr (although trace amounts of other elements may be present). In certain example embodiments, one, two, three or all four of NiCr based layers  7 ,  11 ,  17 ,  21  may comprise from 0-10% oxygen, more preferably from 0-5% oxygen, and most preferably from 0-2% oxygen (atomic %). In certain example embodiments, one, two, three or all four of these layers  7 ,  11 ,  17 ,  21  may contain from 0-20% nitrogen, more preferably from 1-15% nitrogen, and most preferably from about 1-12% nitrogen (atomic %). NiCr based layers  7 ,  11 ,  17  and/or  21  may or may not be doped with other material(s) such as stainless steel, Mo, or the like. It has been found that the use of NiCr based contact layer(s)  7  and/or  17  under the silver-based IR reflecting layer(s)  9 ,  19  improves durability of the coated article (compared to if layers  7  and  17  were instead of ZnO). 
     Dielectric layers  3 ,  14  (including  14   a  and  14   b ), and  24  may be of or include silicon nitride in certain embodiments of this invention. Silicon nitride layers  3 ,  14  and  24  may, among other things, improve heat-treatability of the coated articles and protect the other layers during optional HT, e.g., such as thermal tempering or the like. One or more of the silicon nitride layers  3 ,  14 ,  24  may be of the stoichiometric type (i.e., Si 3 N 4 ), or alternatively of the Si-rich type of silicon nitride in different embodiments of this invention. The presence of free Si in a Si-rich silicon nitride inclusive layer  3  and/or  14  may, for example, allow certain atoms such as sodium (Na) which migrate outwardly from the glass  1  during HT to be more efficiently stopped by the Si-rich silicon nitride inclusive layer(s) before they can reach silver and damage the same. Thus, it is believed that the Si-rich Si x N y  can reduce the amount of damage done to the silver layer(s) during HT in certain example embodiments of this invention thereby allowing sheet resistance (R s ) to decrease or remain about the same in a satisfactory manner. Moreover, it is believed that the Si-rich Si x N y  in layers  3 ,  14  and/or  24  can reduce the amount of damage (e.g., oxidation) done to the silver and/or NiCr during HT in certain example optional embodiments of this invention. In certain example embodiments, when Si-rich silicon nitride is used, the Si-rich silicon nitride layer ( 3 ,  14  and/or  24 ) as deposited may be characterized by Si x N 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 0.82 to 1.2. Any and/or all of the silicon nitride layers 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  3 ,  14 ,  24  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 of layers  3 ,  14 ,  24  may be deposited by sputtering a target(s) of Si or SiAl, in an atmosphere having argon and nitrogen gas, in certain embodiments of this invention. Small amounts of oxygen may also be provided in certain instances in any or all of the silicon nitride layers  3 ,  14 ,  24 . 
     Absorber layer  15  is preferably of or including niobium zirconium, which may be sub-oxided and/or nitrided in certain example embodiments. It has been found that provision of the niobium zirconium based absorber layer  15  in a position to split the silicon nitride based layer  14  into two portions  14   a  and  14   b  results in improved durability, and allows desirable silver glass side/exterior coloration to be achieved in combination with other desirable optical/solar characteristics. For instance, when NbZr (or an oxide and/or nitride thereof) is used for absorber layer  15 , various ratios of Nb to Zr in the layer may be used including but not limited to a 50/50 ratio, an 85/15 ratio, or a 90/10 ratio. In certain example embodiments of this invention, the Nb/Zr ratio in absorber layer  15  may be from 1/1 to 9.5/1 (more preferably from 2/1 to 9/1) in various example embodiments of this invention, such that the layer  15  preferably contains more Nb than Zr. In certain example embodiments, the metal content of absorber layer is from 50-95% Nb, more preferably from 60-95% Nb, even more preferably from 70-95% Nb (e.g., with the remainder of the metal content being made up of Zr in certain example embodiments). While layer  15  consists of, or consists essentially of, NbZr, NbZrO x , or NbZrO x N y  in preferred embodiments of this invention, it is possible that other materials may be present in the layer. For instance, layer  15  may be doped with other materials in certain example instances. In certain example embodiments the absorber layer  15  may contain from about 0-10% nitrogen, more preferably from about 1-7% nitrogen. As mentioned herein, it is preferable that absorber layer  15  is not fully oxided, but is partially oxided (sub-oxided) in certain example embodiments of this invention. In certain example embodiments, absorber layer  15  contains from about 0-40% oxygen, more preferably from 1-35% oxygen, even more preferably from 3-30%, even more preferably from 5-20% oxygen (atomic %). The oxygen content of the layer  15  may be adjusted in order to adjust visible transmission in certain example instances. In certain example embodiments, there is more oxygen than nitrogen in absorber layer  15  (regarding atomic %). 
     While the absorber layer  15  is of NbZr, NbZrO x , or NbZrO x N y  in preferred embodiments of this invention, other materials are also possible in alternative embodiments. For example, it is possible that the absorber layer  15  may be of or include NiCr, NiCrO x , or NiCrO x N y  in other embodiments of this invention 
     Infrared (IR) reflecting layers  9  and  19  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  and  19  help allow the coating to have low-E and/or good solar control characteristics. 
     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  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. 
     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 (physical thicknesses recited): 
     Example Materials/Thicknesses; FIG.  1  Embodiment 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Layer 
                 Preferred 
                 More 
                   
               
               
                 Glass (1-10 mm thick) 
                 Range (Å) 
                 Preferred (Å) 
                 Example (Å) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Si x N y  (layer 3) 
                 100-1100 
                 Å 
                 400-1000 
                 Å 
                 674 
                 Å 
               
               
                 NiCr or NiCrN (layer 7) 
                 5-70 
                 Å 
                 7-30 
                 Å 
                 8 
                 Å 
               
               
                 Ag (layer 9) 
                 60-170 
                 {acute over (Å)} 
                 80-120 
                 Å 
                 151 
                 Å 
               
               
                 NiCr or NiCrN (layer 11) 
                 5-70 
                 Å 
                 10-35 
                 Å 
                 14 
                 Å 
               
               
                 Si x N y  (layer 14a) 
                 100-700 
                 Å 
                 200-550 
                 Å 
                 430 
                 Å 
               
               
                 NbZrO x  (layer 15) 
                 15-100 
                 Å 
                 20-60 
                 Å 
                 32 
                 Å 
               
               
                 Si x N y  (layer 14b) 
                 100-800 
                 Å 
                 250-650 
                 Å 
                 519 
                 Å 
               
               
                 NiCr or NiCrN (layer 17) 
                 5-70 
                 Å 
                 10-35 
                 Å 
                 15 
                 Å 
               
               
                 Ag (layer 19) 
                 50-140 
                 {acute over (Å)} 
                 70-110 
                 Å 
                 90 
                 Å 
               
               
                 NiCr or NiCrN (layer 21) 
                 5-70 
                 Å 
                 7-30 
                 Å 
                 8 
                 Å 
               
               
                 Si 3 N 4  (layer 24) 
                 100-500 
                 Å 
                 200-450 
                 Å 
                 329 
                 Å 
               
               
                 ZrO 2  (layer 27) 
                 20-85 
                 Å 
                 25-55 
                 Å 
                 37 
                 Å 
               
               
                   
               
            
           
         
       
     
     The upper portion  14   b  of the silicon nitride based layer  14  is at least 20 angstroms (more preferably at least 50 angstroms) than is the lower portion  14   a  in certain example embodiments of this invention, although they need not be in alternative embodiments of this invention. Moreover, in certain example embodiments of this invention the absorber layer  15  is thinner than both the silver layers  9 ,  19  (e.g., by at least 20 angstroms), and is also thinner than both of the silicon nitride layers  14   a ,  14   b  in certain example embodiments of this invention. In certain example embodiments of this invention, the absorber layer  15  is at least 20 angstroms (Å) thinner than both the silver layers  9 ,  19 , and/or is at least angstroms 100 angstroms (more preferably at least 200 angstroms, and most preferably at least 250 angstroms) thinner than both of the silicon nitride layers  14   a ,  14   b  in certain example embodiments of this invention. 
     In certain example embodiments, the overcoat layer of or including zirconium oxide and/or zirconium oxynitride  27  is thinner than each of the IR reflecting layers  9 ,  19  comprising silver in the coating  30 . In certain example embodiments of this invention, each of the IR reflecting layers comprising silver  9  and  19  is at least twice as thick as the overcoat layer  27  or including zirconium oxide and/or zirconium oxynitride. 
     In certain example embodiments, the center silicon nitride based layer  14  total thickness ( 14   a + 14   b ) is thicker than the silicon nitride layer  24  thickness, preferably by at least 100 angstroms, more preferably by at least 300 angstroms, and most preferably by at least 400 angstroms. In certain example embodiments, silicon nitride layer  3  is at least 50 angstroms thicker (more preferably at least 100 angstroms thicker) than each of silicon nitride based layers  14   a  and  14   b . Moreover, in certain example embodiments, each of the silicon nitride based layers  3 ,  14  and  24  is at least two times as thick as the zirconim oxide inclusive layer  27 , more preferably at least three times as thick, and most preferably at least four or five times as thick. 
     Before and/or after any optional heat treatment (HT) such as thermal tempering, in certain example embodiments of this invention coated articles according to the  FIG. 1  embodiment have color/optical characteristics as follows in Table 2 (measured monolithic and/or in an IG unit). It is noted that subscript “G” stands for glass side reflective, subscript “T” stands for transmissive, and subscript “F” stands for film side reflective. As is known in the art, glass side (G) means when viewed from the glass side (as opposed to the layer/film side) of the coated article, i.e., same as when viewed from the exterior side of a window when viewed from a building exterior when the coating is on the inner side of the outer glass substrate  1  as shown in  FIG. 2  for instance. Film side (F) means when viewed from the side of the coated article on which the coating is provided. The characteristics below in Table 2 are applicable to HT and/or non-HT coated articles herein. However, HT will cause certain parameters to change such as increasing visible transmission and lowering sheet resistance (color values will also change due to HT). 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Color/Optical Characteristics (FIG. 
               
               
                 1 embodiment monolithic or IG) 
               
            
           
           
               
               
               
               
            
               
                   
                 General 
                 Preferred 
                 Most Preferred 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 T vis  (TY): 
                 15-45% 
                 22-39% 
                 24-35% 
               
               
                 a* T   
                 −10 to +2  
                 −8 to −1 
                 −6.5 to −3.0 
               
               
                 b* T   
                 −12 to +4  
                 −8 to +1 
                 −6 to 0  
               
               
                 R G Y(glass side): 
                 23-43% 
                 25-40% 
                 27-35% 
               
               
                 a* G   
                 −6 to +5 
                 −3.5 to +4.0 
                 −2.5 to +3.0 
               
               
                 b* G   
                  −11 to +3.0 
                     −9 to +1.0 
                 −8.0 to −1.0 
               
               
                 R F Y(film side): 
                 &lt;=19% 
                 &lt;=17% 
                 &lt;=15% 
               
               
                 a* F   
                 −22 to +10 
                 −16 to 0  
                 −14 to −3  
               
               
                 b* F   
                 −20 to +10 
                 −12 to +5  
                 −9 to 0  
               
               
                 R s  (Ω/sq): 
                 ≤6.0 
                 ≤5.0 
                 ≤4.0 
               
               
                 SF [IG]: 
                 &lt;=0.27 
                 &lt;=0.25 
                 &lt;=0.21 
               
               
                 SHGC [IG]: 
                 &lt;=0.27 
                 &lt;=0.25 
                 &lt;=0.23 (or .20) 
               
               
                   
               
            
           
         
       
     
     For purposes of example only, Examples 1-2 below represent different example embodiments of this invention. 
     EXAMPLES 
     Examples 1 and 2 has the below-listed layer stack on a 5.9 mm thick, 75 mm×75 mm, clear matte glass substrate  1  as shown in  FIG. 1 . The examples were measured monolithically, heat treated and measured again after the HT. They were also put into IG window units after HT as shown in  FIG. 2 , and measured. The silicon nitride layers  3 ,  14 ,  24  in each example were deposited by sputtering a silicon target (doped with about 8% Al) in an atmosphere including argon and nitrogen gas. In the IG window unit, the matte glass substrates  1  and  2  were clear and 5.9 mm thick, and the air gap between the substrates in the IG window unit was 13 mm thick. The NbZr based absorber layer in each example was deposited by sputtering approximately 90/10 Nb/Zr magnetron sputtering targets in an atmosphere including argon and a small amount of nitrogen and oxygen gas (1.2 ml/kW of oxygen gas was used). Thus, the absorber layer  15  was of NbZrO x N y  in these examples. Layer thicknesses for Examples 1-2 were in angstroms (Å) and are as follows, moving from the glass substrate  1  outwardly. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Layer Stacks of Examples 1-2 
               
            
           
           
               
               
               
            
               
                   
                 Layer 
                   
               
               
                   
                 Glass (5.9 mm thick) 
                 Examples 1-2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Si 3 N 4  (layer 3) 
                 674 
                 Å 
               
               
                   
                 NiCr (layer 7) 
                 8 
                 Å 
               
               
                   
                 Ag (layer 9) 
                 151 
                 Å 
               
               
                   
                 NiCr (layer 11) 
                 14 
                 Å 
               
               
                   
                 Si x N y  (layer 14a) 
                 430 
                 Å 
               
               
                   
                 NbZrO x N y  (layer 15) 
                 32 
                 Å 
               
               
                   
                 Si x N y  (layer 14b) 
                 519 
                 Å 
               
               
                   
                 NiCr (layer 17) 
                 15 
                 Å 
               
               
                   
                 Ag (layer 19) 
                 90 
                 Å 
               
               
                   
                 NiCr (layer 21) 
                 8 
                 Å 
               
               
                   
                 Si 3 N 4  (layer 24) 
                 329 
                 Å 
               
               
                   
                 ZrO 2  (layer 27) 
                 37 
                 Å 
               
               
                   
                   
               
            
           
         
       
     
     Measured monolithically before tempering (HT), Examples 1-2 according to embodiments of this invention had the following characteristics with the measurements being taken from the center of the coated glass article (annealed and non-HT, monolithic) (Ill. C, 2 degree observer). 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Measured Monolithic, annealed (as coated: before tempering) 
               
            
           
           
               
               
               
               
            
               
                   
                 Parameter 
                 Ex. 1 
                 Ex. 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 T vis  (TY)(transmission ): 
                 28.6% 
                 28.9% 
               
               
                   
                 a* T   
                 −4.2 
                 −4.5 
               
               
                   
                 b* T   
                 −0.9 
                 −0.3 
               
               
                   
                 R G Y(glass side refl. %): 
                 28.9% 
                 29.1% 
               
               
                   
                 a* G : 
                 2.6 
                 2.8 
               
               
                   
                 b* G : 
                 −5.9 
                 −6.6 
               
               
                   
                 Glass side refl. color: 
                 silver 
                 silver 
               
               
                   
                 R F Y(film side refl. %): 
                 8.7% 
                 9.2% 
               
               
                   
                 a* F : 
                 −9.6 
                 −8.7 
               
               
                   
                 b* F : 
                 −2.0 
                 −2.6 
               
               
                   
                 Sheet Resistance (Ω/sq): 
                 3.0 
                 3.0 
               
               
                   
                   
               
            
           
         
       
     
     It can be seen from Table 4 above that measured monolithically prior to any optional thermal tempering Examples 1-2 were able to realize a combination of (i) desirable silver glass side reflective visible color including high glass side visible reflectance (R G Y), (ii) a low sheet resistance, and (iii) desirable visible transmission. 
     Measured monolithically after tempering (HT), Examples 1-2 according to embodiments of this invention had the following characteristics (HT, monolithic) (Ill. C, 2 degree observer). 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Measured Monolithic, HT (after tempering) 
               
            
           
           
               
               
               
               
            
               
                   
                 Parameter 
                 Ex. 1 
                 Ex. 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 T vis  (TY)(transmission ): 
                 31.6% 
                 31.8% 
               
               
                   
                 a* T   
                 −3.8 
                 −4.0 
               
               
                   
                 b* T   
                 −3.9 
                 −3.4 
               
               
                   
                 R G Y(glass side refl. %): 
                 32.3% 
                 32.6% 
               
               
                   
                 a* G : 
                 −1.3 
                 −0.9 
               
               
                   
                 b* G : 
                 −0.4 
                 −0.8 
               
               
                   
                 Glass side refl. color: 
                 silver 
                 silver 
               
               
                   
                 R F Y(film side refl. %): 
                 7.4% 
                 7.7% 
               
               
                   
                 a* F : 
                 −11.9 
                 −10.0 
               
               
                   
                 b* F : 
                 −6.6 
                 −7.9 
               
               
                   
                 Sheet Resistance (Ω/sq): 
                 2.6 
                 2.6 
               
               
                   
                   
               
            
           
         
       
     
     It can be seen from Table 5 above that following thermal tempering (HT) Examples 1-2 had a combination of (i) desirable silver glass side reflective visible color including high glass side visible reflectance, (ii) low sheet resistance, and (iii) desirable visible transmission values. 
     Measured in an IG window unit as shown in  FIG. 2  (with the coating  30  on surface two) after HT, Examples 1-2 had the following characteristics (tempered, IG unit) (Ill. C, 2 degree observer). 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 IG Unit, HT (after tempering) 
               
            
           
           
               
               
               
               
            
               
                   
                 Parameter 
                 Ex. 1 
                 Ex. 2 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 T vis  (TY)(transmission ): 
                 28.4% 
                 28.5% 
               
               
                   
                 a* T   
                 −4.8 
                 −4.9 
               
               
                   
                 b* T   
                 −3.6 
                 −3.1 
               
               
                   
                 R G Y(glass side refl. %): 
                 33.1% 
                 33.4% 
               
               
                   
                 a* G : 
                 −1.4 
                 −1.2 
               
               
                   
                 b* G : 
                 −0.6 
                 −1.0 
               
               
                   
                 Glass side refl. color: 
                 silver 
                 silver 
               
               
                   
                 R F Y(film side refl. %): 
                 14.1% 
                 14.3% 
               
               
                   
                 a* F : 
                 −7.0 
                 −6.2 
               
               
                   
                 b* F : 
                 −3.6 
                 −4.4 
               
               
                   
                 Sheet Resistance (Ω/sq): 
                 2.6 
                 2.6 
               
               
                   
                 SF (EN410-673 2011): 
                 0.20 
                 0.20 
               
               
                   
                 SHGC (NFRC-2001): 
                 0.19 
                 0.19 
               
               
                   
                   
               
            
           
         
       
     
     It can again be seen from the table above, following thermal tempering (HT), IG window units including Examples 1 and 2, respectively, had a combination of: (i) desirable silver glass side/exterior reflective visible color including high glass side (exterior) reflectance, (ii) low sheet resistance, and (iii) desirable visible transmission values, and (v) desirably low SF and SHGC values. 
     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.