This invention relates to a coated article according to claim 1 and to a method according to claim 16.

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. High light-to-solar gain (LSG) values are also desirable. LSG is calculated as T_vis/SHGC. The higher the LSG value, the more visible light that is transmitted and the less amount of heat that is transmitted by the coated article. While low SF and SHGC values, and high LSG values, are sometimes desirable for coated articles such as IG window units and/or monolithic windows, the achievement of such values may come at the expense of sacrificing coloration and/or reflectivity values. In particular, conventional attempts to achieve low SHGC values have often resulted in undesirably low LSG values and/or undesirable visible coloration of the coating. It is often desirable, but difficult, to achieve a combination of acceptable visible transmission (TY or T_vis), desirable glass side reflective coloration (e.g., desirable a* and b* glass side reflective color values), low SHGC, desirably low film side visible reflectance, and high LSG for a coated article in window applications, especially if it desired to use a glass substrate that is not deeply tinted.

SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculated from the full spectrum (T_vis, 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.

Silver based low-E (low emissivity) coatings for windows are known in the art. However, the silver is not particularly durable, and can be easily corroded if exposed to moisture for instance. Thus, silver based low-E coatings are not desirable for monolithic applications such as monolithic windows, and are typically used in IG window units including multiple glass panes, because of the durability problems of silver based low-E coatings.

Solar control coatings are known in the art. For example, solar control coatings having a layer stack of glass/Si₃N₄/NiCr/Si₃N₄/NiCr/Si₃N₄ are known in the art, where the NiCr layer may be nitrided. For example, see U.S. Patent Document 2012/0177899. While layer stacks of U.S. Patent Document 2012/0177899 provide reasonable solar control and are overall good coatings, they are lacking in certain respects. The glass side reflective a* values (a* under R_GY) in Examples 1, 4 and 5 in paragraphs 0025-0026 of US '899 are -17.8, - 15.95, and +2.22, respectively, and the glass side visible reflectance values (R_GY) in Examples 1 and 4 are 36% and 36.87%, respectively. Examples 1 and 4 in US '899 are undesirable because the glass side visible reflectance (R_GY) values are too high at 36% and 36.87%, respectively, and because the glass side reflective a* values are too negative at -17.8 and -15.95, respectively. And when R_GY is reduced down to 15.82% in Example 5, this results in the glass side reflective a* color value in Example 5 becoming too red with a value of +2.22. Thus, the coatings described in US '899 were not able to achieve a combination of acceptable visible reflectivity values and glass side reflective a* coloration values.

Certain known solar control coatings use NbN, NbZr, or NbZrN as IR reflecting layers. For instance, see U.S. Patent Document 2012/0177899 and U.S. Patent No. 8,286,395. However, the instant inventors have surprisingly found that solar control coatings that use solely these materials NbN, NbZr, or NbZrN for IR reflecting layers are lacking in terms of normal emissivity (E_n) for a given IR reflecting layer(s) thickness. For a given IR reflecting layer(s) thickness, the instant inventors have found that such coatings have undesirably high normal emittance (E_n) values, undesirably high SHGC values; and/or undesirably low LSG values.
Document US 2016/002100 A1 discloses a pane with thermal radiation reflecting coating, comprising a substrate and at least one thermal radiation reflecting coating on at least one of the surfaces of the substrate, wherein the coating, proceeding from the substrate, comprises at least one lower dielectric layer, one functional layer that contains at least one transparent, electrically conductive oxide, and one upper dielectric layer, and wherein at least one darkening layer is arranged below the lower dielectric layer, between the lower dielectric layer and the functional layer, between the functional layer and the upper dielectric layer, and/or above the upper dielectric layer, and wherein the darkening layer contains at least one metal, one metal nitride, and/or one metal carbide with a melting point greater than 1900° C. and a specific electrical resistivity less than 500 µohm*cm.
Document WO 2015/197969 A1 discloses a glazing unit comprising a glass substrate provided on a first face, which is intended to form the face of said glazing unit in its use position, with a thin-film multilayer comprising, from said substrate, a transparent electrically conductive oxide film, a first dielectric film, a film based on niobium nitride, then a second dielectric film.
Document WO 2017/160326 A1 discloses coated articles that include two or more infrared (IR) reflecting layers (e.g., of or including NbZr, Nb, NiCr, NiCrMo, and/or a nitride thereof) sandwiched between at least dielectric layers, and/or a method of making the same. The coating may be designed so that the coated articles realize bronze glass side reflective coloration in combination with a low solar factor (SF) and/or a low solar heat gain coefficient (SFIGC). Such coated articles may be used in the context of monolithic windows, insulating glass (IG) window units, laminated windows, and/or other suitable applications, and may optionally be heat treated (e.g., thermally tempered) in certain instances.

It would be desirable according to example embodiments of this invention for a coating to be designed so as to have a combination of acceptable visible transmission (TY or T_vis), desirable glass side reflective coloration (e.g., desirable a* and/or b* reflective color values), desirably low film side visible reflectance, low emittance/emissivity, low SHGC, and high LSG for a coated article in window applications.

In the example embodiments of this invention, the applications such as monolithic window applications desire glass side reflective coloration that is not significantly red. In other words, the applications such as monolithic window applications desire glass side reflective a* color values that are either negative or no greater than +1.6 or +1.0 (glass side reflective a* values higher than +1.6 are undesirably red). Such reflective a* values are especially desirable for example in the context of glass side reflective (R_{G[or outside, or exterior]}Y) a* values.

The embodiments of this invention relate to coated articles that include two or more functional infrared (IR) reflecting layers that may be sandwiched between at least transparent dielectric layers, and a method of making the same. The dielectric layers are of or include silicon nitride The first infrared (IR) reflecting layer is of or includes indium-tin-oxide (ITO) and the second infrared (IR) reflecting layer is of or includes titanium nitride (e.g., TiN). It has surprisingly and unexpectedly been found that the use of these different materials for the different IR reflecting layers (e.g., as opposed to using TiN for both IR reflecting layers) in a given solar control coating surprisingly results in improved optics such as improved glass side reflective a* values and/or high LSG values which are often desirable characteristics in window applications, and desirably low film side visible reflectance, and the provision of the first IR reflecting layer of or including ITO allows coated articles to be more easily tailored for desired visible transmission values while the second IR reflecting layer of or including TiN can keep the normal emissivity, SF and/or SHGC values reasonably low. Coating according to embodiments of this invention may be designed so that before and/or after any optional heat treatment such as thermal tempering the coated articles realize one or more of: desirable glass side reflective visible coloration that is not too red (e.g., reflective a* color value(s) from -8 to +1.6); a desirably low solar heat gain coefficient (SHGC); desirable visible transmission (TY or T_vis); desirably low film side visible reflectance; thermal stability upon optional heat treatment (HT) such as thermal tempering; desirably low normal emissivity/emittance (E_n); and/or desirably high light-to-solar gain ratio (LSG). Note that SHGC may be as high as 80% for uncoated glass. The higher the LSG value, the greater the energy saving. Such coated articles may be used in the context of monolithic windows, insulating glass (IG) window units, laminated windows, and/or other suitable applications.

In this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first infrared (IR) reflecting layer comprising ITO on the glass substrate; a first dielectric layer comprising silicon nitride on the glass substrate over at least the first IR reflecting layer comprising ITO; a second layer IR reflecting layer comprising a nitride of titanium on the glass substrate over at least the first dielectric layer comprising silicon nitride, so that the first dielectric layer comprising silicon nitride is located between at least the first IR reflecting layer comprising ITO and the second IR reflecting layer comprising the nitride of titanium; a second dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising the nitride of titanium; wherein the coating contains no IR reflecting layer based on silver; wherein the first IR reflecting layer comprising ITO is from 250-450 Angstroms thick; and wherein the coating has a normal emittance (E_n) value of no greater than 0.30; and wherein the coated article has: a visible transmission from about 15-80%, a film side visible reflectance no greater than 10%, a glass side visible reflectance no greater than about 30%, a glass side reflective a* value of from -10.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least 1.10.

In the present disclosure, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first infrared (IR) reflecting layer comprising ITO on the glass substrate; a first dielectric layer comprising silicon nitride on the glass substrate over at least the first IR reflecting layer comprising ITO; a second layer IR reflecting layer comprising a nitride of titanium on the glass substrate over at least the first dielectric layer comprising silicon nitride, so that the first dielectric layer comprising silicon nitride is located between at least the first IR reflecting layer comprising ITO and the second IR reflecting layer comprising the nitride of titanium; a second dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising the nitride of titanium; wherein the coating contains no IR reflecting layer based on silver; wherein the coating has a normal emittance (E_n) value of no greater than 0.30; and wherein the coated article has: a visible transmission from about 15-80% and a light-to-solar gain ratio (LSG) of at least 1.15.

In the present disclosure, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first infrared (IR) reflecting layer comprising ITO on the glass substrate; a first dielectric layer on the glass substrate over and directly contacting the first IR reflecting layer comprising ITO; a second layer IR reflecting layer comprising a metal nitride on the glass substrate over and directly contacting the first dielectric layer, so that the first dielectric layer is located between and directly contacting the first IR reflecting layer comprising ITO and the second IR reflecting layer comprising the metal nitride; a second dielectric layer on the glass substrate over and directly contacting the second IR reflecting layer comprising the metal nitride; wherein the coating contains no IR reflecting layer based on silver; and wherein the coated article has a visible transmission from about 15-80%. In certain examples, the metal nitride may be a nitride of titanium, zirconium, niobium, or the like. In certain examples, one or more of the dielectric layers may be of or include silicon nitride.

Thus, this invention covers monolithic window units, IG window units, laminated window units, and any other article including a glass substrate having a coating thereon as claimed. Note that monolithic measurements may be taken by removing a coated substrate from an IG window unit and/or laminated window unit, and then performing monolithic measurements. It is also noted that for a given coating the SF and SHGC values will be significantly higher for a monolithic window unit than for an IG window unit with the same coated article.

Fig. 1 is a partial cross sectional view of a monolithic coated article (heat treated or not heat treated) according to an example embodiment of this invention.

Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views.

A coating 8 is designed so as to have a combination of acceptable visible transmission (TY or T_vis), desirable glass side reflective coloration (e.g., desirable a* and b* reflective color values), low film side visible reflectance, low SHGC, and high LSG for a coated article for use in window applications or the like. As visible transmission increases when the IR reflecting layer(s) become thinner, parameters such as SHGC will also increase, and E_n will decrease, with this being based on the desired transmission for instance of a given coated article for a given application. Example applications include architectural windows, residential windows, monolithic windows, automotive windows, and/or IG windows.

Certain embodiments of this invention relate to coated articles having a coating 8 on a glass substrate 1, where the coating includes two or more functional infrared (IR) reflecting layers 3 and 5 which may be sandwiched between at least transparent dielectric layers 2, 4, 6, 7, and/or a method of making the same. Some of the transparent dielectric layers, such as dielectric layer(s) 2 and/or 7, are optional and need not be provided in certain example embodiments. The dielectric layers 2, 4 and 6 are preferably amorphous, preferably have a k ≤ 0.1, and may be of or include silicon nitride, silicon oxynitride, zinc stannate, tin oxide, or the like. Transparent dielectric overcoat 7, of or including zirconium oxide or any other suitable material, is optional. In certain example embodiments, at least one of the IR reflecting layers is of or including titanium nitride (e.g., TiN) and at least another of the IR reflecting layers is of or including ITO. In the Fig. 1 embodiment, upper IR reflecting layer 5 is of or including titanium nitride (e.g., TiN) and lower IR reflecting layer 3 is of or including ITO. It has surprisingly and unexpectedly been found that the use of these different materials for the different IR reflecting layers 3 and 5 (e.g., as opposed to using TiN for both IR reflecting layers 3 and 5) in a given solar control coating surprisingly results in improved optics such as improved glass side reflective a* values and/or higher LSG values which are often desirable characteristics in window applications, and the provision of the IR reflecting 3 layer of or including ITO allows coated articles to be more easily tailored for desired visible transmission values and high LSG values while the IR reflecting layer of or including TiN 5 provides for desirably low normal emissivity and/or SHGC values for a given thickness of IR reflecting material. Coating 8 according to embodiments of this invention may be designed so that before and/or after any optional heat treatment such as thermal tempering the coated articles realize one or more of: desirable glass side reflective visible coloration that is not too red (e.g., reflective a* color value(s) from -8 to +1.6); a desirably low solar heat gain coefficient (SHGC); desirable visible transmission (TY or T_vis); low film side reflectance; thermal stability upon optional heat treatment (HT) such as thermal tempering; desirably low E_n; and/or a desirably high light-to-solar gain ratio (LSG). In example embodiments of this invention, the coating 8 contains no IR reflecting layer based on Ag or Au.

In the example embodiments of this invention, the applications such as monolithic window applications desire glass side reflective coloration that is not significantly red. In other words, the applications such as monolithic window applications desire glass side reflective a* color values that are either negative or no greater than +1.6 (glass side reflective a* values higher than +1.6 are undesirably red). Such glass side reflective a* values are not too red and are desirable in the context of glass side reflective (R_GY) a* values.

Coated articles may optionally be heat treated in certain example embodiments of this invention, and are preferably designed to be heat treatable. 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. Instead of HT at >600C (e.g., tempering), this coating can also achieve desired performance by activating HT at as low as 350 degrees C for example. After HT at 350 C for example, the glass is not tempered and may be cut to desired size.

Figure 1 is a cross sectional view of a coated article according to an example embodiment of this invention. In the Fig. 1 embodiment the solar control coating 8 includes two IR reflecting layers 3 and 5, and transparent dielectric layers 2, 4, 6 and 7. The coated article includes at least glass substrate 1 (e.g., clear, green, bronze, grey, blue, or blue-green glass substrate from about 1.0 to 12.0 mm thick, more preferably from 4-8 mm thick, with an example glass substrate thickness being 6 mm), transparent dielectric layers 2, 4, 6 (e.g., of or including silicon nitride [e.g., Si₃N₄], silicon oxynitride, silicon zirconium nitride, or some other suitable dielectric), and IR reflecting layers 3, 5. Upper IR reflecting layer 5 is of or including titanium nitride (e.g., TiN, preferably a stoichiometric or substantially stoichiometric type) and lower IR reflecting layer 3 is of or including conductive ITO. The upper IR reflecting layer 5 is of or includes TiN_x in certain example embodiments of this invention, where x is preferably from 0.8 to 1.2, more preferably from 0.9 to 1.1, with an example value being about 1.0. These "x" values provide for improved/lowered emittance values compared to if "x" is too low for instance. The titanium nitride has been found to be very durable compared to silver for example, and more resistant to moisture induced corrosion compared to silver for example. It has surprisingly and unexpectedly been found that the use of these different materials for the different IR reflecting layers 3 and 5 (e.g., as opposed to using TiN for both IR reflecting layers 3 and 5) in a given solar control coating provides for surprisingly results as explained herein. While the IR reflecting layer 5 may include some small amount of oxygen in certain instances, it is preferable that layer 5 is substantially free of oxygen such as no more than 8% oxygen, more preferably no more than about 5% oxygen, and most preferably no more than about 3% or 2% oxygen in certain embodiments (atomic %). While IR reflecting layer 5 is of or including titanium nitride in preferred embodiments of this invention, it is possible for upper IR reflecting layer 5 to be of another metal nitride such as zirconium nitride and/or niobium nitride in alternative embodiments of this invention. The coated article may optionally include transparent dielectric overcoat layer 7 of or including a protective material such as zirconium oxide (e.g., ZrO₂) or silicon oxynitride. Optionally, a dielectric layer of or including silicon oxynitride and/or zirconium silicon oxynitride of any suitable stoichiometry may be located between and contacting layers 6 and 7 in the upper part of the layer stack in certain example embodiments. In certain example embodiments of this invention, coating 8 does not include any metallic IR blocking or reflecting layer of or based on Ag or Au. In certain example embodiments of this invention, IR reflecting layers 3 and 5 reflect at least some IR radiation, and do not contact any other metal or metal based IR reflecting layer. In certain example embodiments, it is possible for each of the layers to include other materials such as dopants. It will be appreciated of course that other layers may also be provided, or certain layers may be omitted, and different materials may be used, in certain alternative embodiments of this invention. For example, another metal nitride layer 5 could be added above the ITO in certain alternative embodiments of this invention.

The overall coating 8 of Fig. 1 includes at least the illustrated layers in certain example embodiments, with layers 2 and 7 in particular being optional. It is noted that the terms "oxide" and "nitride" as used herein include various stoichiometries. For example, the term silicon nitride (for one or more of layers 2, 4, 6) includes stoichiometric Si₃N₄, as well as non-stoichiometric silicon nitride, and these layers may be doped with other material(s) such as Al and/or O. The illustrated layers may be deposited on glass substrate 1 via magnetron sputtering, any other type of sputtering, or via any other suitable technique in different embodiments of this invention. It is noted that other layer(s) may be provided in the stack shown in Fig. 1 such as between layers 2 and 3, or between layers 3 and 4, or between the substrate 1 and layer 2, or the like. Generally, other layer(s) may also be provided in other locations of the coating. Thus, while the coating 8 or layers thereof is/are "on" or "supported by" substrate 1 (directly or indirectly), other layer(s) may be provided therebetween. Thus, for example, the layer system 8 and layers thereof shown in Fig. 1 are considered "on" the substrate 1 even when other layer(s) may be provided therebetween (i.e., the terms "on" and "supported by" as used herein are not limited to directly contacting). However, there may be the direct contacts shown in Fig. 1 in preferred embodiments.

In certain example embodiments of this invention, dielectric layers 2, 4, and 6 may each have an index of refraction "n" of from 1.7 to 2.5 (at 550 nm), more preferably from 1.8 to 2.2 in certain embodiments, and most preferably from about 2.0 to 2.06 in preferred embodiments of this invention. One, two, three, or all of these layers 2, 4, 6 may be of or include silicon nitride and/or silicon oxynitride in certain example embodiments of this invention. In such embodiments of this invention where layers 2, 4, 6 comprise silicon nitride (e.g., Si₃N₄) or silicon oxynitride, sputtering targets including Si employed to form these layers may or may not be admixed with up to 1-20% (e.g., 8%) by weight aluminum or stainless steel (e.g. SS#316), with about this amount then appearing in the layers so formed. Even with this amount(s) of aluminum and/or stainless steel, such layers are still considered dielectric layers. In certain example embodiments, each of the IR reflecting layers 3 and 5 is provided between respective nitride layers (e.g., silicon nitride based layers 2, 4, 6) in order to reduce or prevent damage to the IR reflecting layers during possible heat treatment (e.g., thermal tempering, heat bending, and/or heat strengthening) thereby permitting predictable coloration to be achieved following the heat treatment at multiple viewing angles. While Fig. 1 illustrates a coated article according to an embodiment of this invention in monolithic form, coated articles according to other embodiments of this invention may comprise IG (insulating glass) window units or the like.

Turning back to the Fig. 1 embodiment, various thicknesses may be used consistent with one or more of the needs discussed herein. According to certain example embodiments of this invention, example thicknesses (in angstroms) and materials for the respective layers of the Fig. 1 embodiment on the glass substrate 1 are as follows in certain example embodiments for achieving desired transmission, glass side reflective coloration, and visible reflectance in combination with a desirably low SHGC value(s) and/or a desirably high LSG value (layers are listed in order moving away from the glass substrate 1): Layer Example Range (Å) Preferred (Å) Example (Å) silicon nitride (layer 2): 20-500 Ǻ 40-200 Ǻ 50 Ǻ IR reflector (e.g., ITO) (layer 3): 100-1,000 Ǻ 250-450 Ǻ 330 Ǻ silicon nitride (layer 4): 20-1100 Ǻ 25-400 Ǻ 300 Ǻ IR reflector (e.g., TiN) (layer 5): 50-450 Ǻ 130-300 Ǻ 200 Ǻ silicon nitride (layer 6): 20-800 Ǻ 300-550 Ǻ 450 Ǻ overcoat (e.g., ZrO₂) (layer 7): 10-150 Ǻ 20-40 Ǻ 30 Ǻ

Table 1 above relates to, for example, embodiments where coating 8 is designed so that before and/or after any optional heat treatment such as thermal tempering the coated articles realize one, two, three, four, five, six or all seven of: desirable glass side reflective visible coloration such as not too red reflective color (e.g., reflective a* color value(s) from -8 to +1.6); a desirably low SHGC; desirable visible transmission; low film side visible reflectance, thermal stability upon optional HT such as thermal tempering; desirably low E_n; and/or a desirably high LSG. In certain example embodiments, lower IR reflecting layer 3 may be physically thicker than upper IR reflecting layer 5 by at least 50 angstroms (Å), more preferably by at least 100 Å. In certain example embodiments of this invention, upper dielectric layer 6 is physically thicker than center dielectric layer 4 by at least 50 angstroms (Å), more preferably by at least 100 Å, and sometimes by at least 150 Å.

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 monolithically). 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. 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 in accordance with Illuminant C, 2 degree Observer, and are applicable to HT and non-HT coated articles herein. Glass side reflective coloration may be such that coated articles appear neutral colored, blue-green colored, or yellow-green colored in various example embodiments of this invention. General Preferred Most Preferred T_vis (TY): 15-80% 20-70% 30-60% (or 40-60%) a*_T -10 to +5 -8 to +2 -6 to 0 b*_T - -15 to +7 -10 to +3 -9 to 0 R_GY(glass side): ≤30% ≤25% ≤20% a*_G -10 to +1.6 -8 to +1.6 -6 to +1 b*_G -25 to +9 -9 to +4 -8 to +1 R_FY(film side): ≤10% ≤8% ≤5% a*_F -9 to +9 -6 to +7 -3 to +5 b*_F -14 to +9 -9 to +4 -8 to 0 E_n: ≤0.30 ≤ 0.25 ≤0.22 SHGC: ≤ 0.52 ≤ 0.45 ≤0.42 LSG: ≥ 1.10 ≥ 1.15 ≥ 1.22

For purposes of example only, Example 1 representing an example embodiments of this invention, as well we Comparative Examples (CE) 1-5, are set forth below.

Comparative Examples (CEs) 1-4 and Examples 1-2 were sputter-deposited (as all examples) layer stacks modeled on 4 mm thick clear glass substrates. And CE 5 was a layer stacks modeled on 4 mm thick green glass substrate. The optical measurements are monolithic measurements. Optical data for CEs 1-5 and Examples 1-2 is in accordance with Illuminant C, 2 degree Observer. The silicon nitride layers were doped with about 8% Al. The TiN layers were approximately stoichiometric. Layer thicknesses are in angstroms (Å). "L" in Table 4 below stand for Layer (e.g., L2 means layer 2 shown in Fig. 1, L3 means layer 3 shown in Fig. 1, and so forth). It will be shown below that the use of ITO for layer 3 in Examples 1-2 provided for unexpectedly improved optics compared to the use of TiN or NiCr for layer 3 in CEs 1-5. Example L2(Si₃N₄) L3(NiCr) or L3(TiN) L4(Si₃N₄) L5(TiN) L6(Si₃N₄) L7(ZrO₂) CE 1: 220 n/a 240 670 310 10 40 CE 2: 140 n/a 200 590 240 30 40 CE 3: 40 n/a 180 350 120 30 40 CE4: 50 68 n/a 723 268 171 30 CE5: 50 66 n/a 714 261 206 30

Measured monolithically after thermal tempering (HT), the CEs had the following characteristics. Parameter CE 1 CE 2 CE 3 CE4 CE5 T_vis (TY)(transmission ): 18.6% 24.2% 35.3% 23.1% 21.8% L*_T: 50.2 56.3 66.0 55.2 53.8 a*_T -7.2 -7.0 -5.5 -3.15 -5.86 b*_T -4.3 -1.5 -0.8 -8.27 -7.97 R_GY(glass side refl. %): 9.5% 9.2% 13.0% 12.0% 9.6% L*_G: 36.9 36.4 42.8 41.2 37.1 a*_G: -3.2 -2.8 -0.3 -0.8 -1.45 b*_G: -3.5 0.4 -5.7 -1.8 -2.1 R_FY(film side refl. %): 25.2% 19.1% 10.8% 14.1% 11.2% L*_F: 57.3 50.8 39.2 44.4 39.9 a*_F: 5.3 4.7 7.0 0.6 -0.3 b*_F: -8.3 -6.1 -5.4 -4.9 -4.1 E_n: 0.18 0.25 0.36 0.25 0.25 SHGC (NFRC-2001): 0.21 0.24 0.31 0.28 0.27 LSG: 0.80 1.01 1.14 0.83 0.81

Examples 1-2 according to examples of this invention had the following layer stack. Layer thicknesses are in angstroms (Å). Example L3(ITO) L4(Si₃N₄) L5(TiN) L6(Si₃N₄) L7(Si₃N₄) Ex. 1: 330 300 200 450 n/a Ex. 2: 330 20 180 350 40

Measured monolithically after HT, Examples 1-2 had the following characteristics. Parameter Example 1 Example 2 T_vis (TY)(transmission ): 51.97% 54.4% a*_T -3.14 -3.2 b*_T -2.81 -3.9 R_GY(glass side refl. %): 19.9% 16.0% a*_G: -4.0 -2.1 b*_G: -0.9 0.0 R_FY(film side refl. %): 2.2% 2.6% a*_F: +3.35 +5.6 b*_F: -4.71 +1.8 E_n: 0.20 0.22 SHGC (NFRC-2001): 0.41 0.42 LSG: 1.25 1.30

An advantage of using ITO and TiNx for the IR reflecting layers, instead of using TiNx for both IR reflecting layers, is improved thermal performance such as improved E_n and/or LSG value(s). This is shown in the tables above. It can be seen by comparing CEs 1-5 (Tables 3-4) with Examples 1-2 (Tables 5-6), that the use of ITO in Examples 1-2 (instead of TiN or NiCr in CEs 1-5) for layer 3 provided for unexpected results. For instance, the LSG values of CEs 1, 4 and 5 were all well less than 1.0, which is undesirable. And while the LSG values of CEs 2 and 3 were more acceptable, but still low, at 1.01 and 1.14, these CEs 2 and 3 along with the other CEs had undesirably high film side reflectance of 10.8% or higher. And CE3 had an undesirably high normal emittance/emissivity (E_n) of 0.36, which means that insufficient IR is blocked by the coating. Thus, for instance, all CEs had undesirably high film side reflectance values, and most had undesirably low LSG values. No comparative example (CE) has a sufficiently low normal emittance/emissivity (E_n) combined with desirably low film side visible reflectance and desirably high LSG.

The use of ITO for layer 3 in Example 1 (instead of TiN or NiCr in CEs 1-5) unexpectedly reduced the film side visible reflectance vales to more acceptable and aesthetically pleasing 2.2% and 2.6% and surprisingly increased the LSG value to 1.25 and 1.30 which means a significant energy saving. Moreover, the use of TiN for layer 5 and ITO for layer 3 allowed normal emittance (E_n) to remain in an acceptable range of no greater than 0.30, more preferably no greater than 0.25, and most preferably no greater than 0.22.

In this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first infrared (IR) reflecting layer comprising ITO on the glass substrate; a first dielectric layer comprising silicon nitride on the glass substrate over at least the first IR reflecting layer comprising ITO; a second layer IR reflecting layer comprising a nitride of titanium on the glass substrate over at least the first dielectric layer comprising silicon nitride, so that the first dielectric layer comprising silicon nitride is located between at least the first IR reflecting layer comprising ITO and the second IR reflecting layer comprising the nitride of titanium; a second dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising the nitride of titanium; wherein the coating contains no IR reflecting layer based on silver; wherein the first IR reflecting layer comprising ITO is from 250-450 Angstroms thick; and wherein the coating has a normal emittance (E_n) value of no greater than 0.30; and wherein the coated article has: a visible transmission from about 15-80%, a film side visible reflectance no greater than 10%, a glass side visible reflectance no greater than about 30%, a glass side reflective a* value of from -10.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least 1.10.

In the coated article of the immediately preceding paragraph, the coating in some instances contains only two IR reflecting layers.

In the coated article of any of the preceding two paragraphs, the first dielectric layer comprising silicon nitride may be located between and directly contacting the first and second IR reflecting layers.

In the coated article of any of the preceding three paragraphs, the second IR reflecting layer comprising the nitride of titanium may comprise TiN_x, where x is from 0.8 to 1.2, more preferably from 0.9 to 1.1.

In the coated article of any of the preceding four paragraphs, the second IR reflecting layer may contain from 0-8% oxygen (atomic %), more preferably from 0-5% oxygen (atomic %).

In the coated article of any of the preceding five paragraphs, the coating may further comprise another dielectric layer comprising silicon nitride or silicon oxynitride located between and contacting the glass substrate and the first IR reflecting layer.

In the coated article of any of the preceding six paragraphs, the second IR reflecting layer may consist essentially of the nitride of titanium.

In the coated article of any of the preceding seven paragraphs, the coating may further comprise an overcoat comprising an oxide of zirconium.

In the coated article of any of the preceding eight paragraphs, the coated article may have a visible transmission from about 20-70% and/or a light-to-solar gain ratio (LSG) of at least 1.15.

In the coated article of any of the preceding nine paragraphs, the coated article may have a light-to-solar gain ratio (LSG) of at least 1.22.

In the coated article of any of the preceding ten paragraphs, the coated article may have a film side visible reflectance no greater than 8%, more preferably no greater than 5%.

In the coated article of any of the preceding eleven paragraphs, the glass substrate may be a clear glass substrate.

In the coated article of any of the preceding twelve paragraphs, the coated article may have a glass side reflective a* value of from -8 to +1.0, and/or a film side reflective a* value of from -9 to +9.

In the coated article of any of the preceding thirteen paragraphs, one or more of the dielectric layers comprising silicon nitride may further comprise oxygen and/or may be doped with aluminum.

In the coated article of any of the preceding fourteen paragraphs, the coated article may be a monolithic window.

In the coated article of any of the preceding fifteen paragraphs, the coated article measured monolithically may have an SHGC value of no greater than 0.52, more preferably no greater than 0.45, and most preferably no greater than 0.42.

In the coated article of any of the preceding sixteen paragraphs, the first IR reflecting layer comprising ITO may be from 100-1,000 Å thick, and/or the second IR reflecting layer comprising the nitride of titanium may be from 50-450 Å thick.

In the coated article of any of the preceding seventeen paragraphs, the first IR reflecting layer comprising ITO is from 250-450 Å thick, and the second IR reflecting layer comprising the nitride of titanium may be from 130-300 Å thick.