A heat treatable solar control glass article comprising titanium nitride and niobium-based functional layers

Abstract

A material comprising a transparent substrate deposited with a stack of thin layers on at least one of its surface to act on the solar and / or infrared radiation likely to strike said surface is disclosed. The stack of thin layers successively comprises, starting from the substrate not more than two functional layers F1, F2 based on Nb / NbN and TiN, respectively and three dielectric coatings M1, M2, M3 comprising at least one dielectric layer such that each of the metallic functional layer is sandwiched between two dielectric coatings. The proposed material has desirably low solar heat gain coefficient (SHGC) or solar factor (SF); desirable visible transmission; thermal stability and color matchability upon heat treatment such as tempering and desirable selectivity value.

Description

A HEAT TREATABLE SOLAR CONTROL GLASS ARTICLE COMPRISING TITANIUM NITRIDE AND NIOBIUM-BASED FUNCTIONAL LAYERSTechnical FieldThe present invention relates, in general relates to a material comprising a transparent substrate, on the surface of which a stack of thin layers is deposited comprising two functional infrared (IR) reflecting and absorbing layers sandwiched between at least one dielectric layer making it possible to act on the solar and / or infrared radiation likely to strike said surface. More specifically, the present invention relates to a heat treatable solar control glass article that realizes one or more of: desirable glass side (RG) and / or coating side (RC) reflective color values; desirably low solar heat gain coefficient (SHGC) or solar factor (SF); desirable visible transmission; thermal stability and color matchability upon heat treatment such as tempering and desirable selectivity value. BackgroundSolar factor (SF or g-value) and selectivity values are desired in applications particularly, hot and humid 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 during hot ambient conditions.Selectivity relates to the ratio of the light transmission to the solar factor, (TL / g). High selectivity values are often desirable, because this combines high or desirable visible transmission with a low SF value which is indicative of good infra-red blockage. When good selectivity (TL / g) is achieved, there is provided a higher ratio of visible transmission to solar factor (SF), which will be appreciated by those skilled in the art. In other words, good selectivity values are desired in combination with rather low SF values. This permits coated articles and / or IG window units, for example, to realize desirable visible transmission while at the same time blocking significant undesirable radiation (e.g., IR) from reaching a building interior or the like.While low SF and high selectivity values, are 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.The absence of any substantial adverse effect upon heating the coating or its substrate, defines what is meant herein by the term "heat treatable". While in certain situations some characteristics may change somewhat during heat treatment, to be "heat treatable" as used herein means that the desired properties such as emissivity, sheet resistance, durability and corrosion resistance of the ultimate layer system and overall product must be achieved despite the fact that the coated glass has been subjected to one or more of the heat treatments (i.e. bending, tempering and / or heat strengthening). For most architectural purposes contemplated by this invention optimized heat treatability means that the glass and its layered coating remains substantially unchanged in at least its emissivity, sheet resistance, durability and with minimal color shift as between the pre-heat treated product and the final product after heat treatment.Solar control coatings are very well known in the art. For example, solar control coatings having a layer stack of glass / Si3N4 / TiN / Si3N4 / TiN / Si3N4 are known in the art. For example, U.S. Patent Document 2018 / 0186691 is incorporated herein by reference. Another example of solar control coatings having a layer stack of glass / Si3N4 / NiCrN / Si3N4 / TiN / Si3N4 are also known in the art. German patent document DE102014114330 is incorporated herein by reference. Yet another example of solar control coatings having a layer stack of glass / Si3N4 / NiCr or NiCrW / Si3N4 / TiN / Si3N4 is known from U.S. Patent Document 2017 / 0197874 and is herein incorporated by reference. Most of the known and above referenced coating system in the prior art either achieve a lower internal reflection or a lower external reflection, often at the cost of increasing the other. However, it would be desirable for a solar control coating to be designed so as to have a combination of acceptable visible transmission (TL), desirable reflective coloration (e.g., desirable a* and b* reflective color values) and desirable visible light reflectance values in glass side (RG) and coating side (RC), low SF and high selectivity for a coated article in window applications.Most of the known solar control coatings disclose a layer stack comprising two TiN functional layers or a single TiN functional layer in combination with NiCr / NiCrN functional layer. There are no prior known solar control coatings that comprise a combination of TiN and Nb / NbN functional layers and as reasoned in US '691 niobium-based layers such as Nb, NbN, NbZr or NbZrN have in general high emissivity and solar heat gain coefficient (SHGC) values and low selectivity. Hence skilled artisans preferred to employ solar control coatings comprising either a double TiN functional layer or having a single TiN functional layer in combination with NiCr / NiCrN functional layer. However, the inventors of the present invention have surprisingly found that for layer stacks comprising a combination of TiN and Nb / NbN sandwiched between dielectric layers, the TiN functional layer contributes to the solar control performance of the layer stack and the Nb / NbN functional layer can be used to control the reflection color, reflection value and other optical characteristics of the solar control coating and thereby improve the aesthetics of the resulting solar control substrate. Further, it was found that the introduction of a niobium-based layer between the glass substrate and the TiN functional layer (i.e., the niobium-based layer in close proximity to the glass substrate) helped in controlling the optical characteristics of the glass side, particularly the glass side reflection value (Rg). Accordingly, the layer stack Glass / Dielectric / Nb-based layer / Dielectric / TiN / Dielectric is covered in the Indian patent application 202141057353 and is herein incorporated by reference.In furtherance to the above findings, the inventors of the present invention have now discovered that having the niobium-based layer distant from the glass substrate i.e., placing the niobium-based layer above the TiN functional layer helps in decreasing the internal coating side reflection value (Rc) significantly without drastically increasing the external glass side reflection value (Rg) and achieving a variable range of desirable visible light transmission. In other words, introducing the TiN functional layer between the glass substrate and the niobium-based layer contributes to controlling the optical characteristic of the solar control coated article particularly, optical characteristics of the coating side of the solar control coated article more particularly, the internal reflection value (RC) of the solar control coated article. Thus, embodiments of the present invention shall disclose how the inventors were able to achieve a relatively increased external reflection value (Rg) while maintaining a low internal reflection value (Rc) and having a wide range low and high visible light transmission. All the above in addition to low SF and high selectivity. It is thus a purpose of this disclosure to help achieve all the said characteristics, detail of which will become apparent to the skilled artisan once given the following disclosure.Summary of the DisclosureIn one aspect of the present disclosure, a solar control glass article comprising a transparent substrate having a first surface deposited with a stack of thin layers is disclosed. The stack of thin layers comprises, n functional layers and n+1 dielectric layers, wherein n=2 such that each functional layer is sandwiched between 2 dielectric layers and optionally an overcoat layer, wherein the overcoat layer forms the outermost layer of the thin multilayer coating is disclosed. The stack of thin layers is characterized in that the first functional layer (F1) comprises TiN having a thickness range between 1 nm to 90 nm and the second functional layer (F2) comprises niobium-based material having a thickness range of 1 nm to 60 nm. The solar control glass article is characterized in having an external reflection (RG) of less than 35% while maintaining the internal reflection (RC) at less than 15%.Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.Brief Description of the DrawingsEmbodiments are illustrated by way of example and are not limited to those shown in the accompanying figures.FIG. 1 illustrates a stack of thin layers deposited on a transparent glass substrate, according to one embodiment of the present disclosure; andFIG. 2 illustrates a stack of thin layers deposited on a transparent glass substrate, according to one other embodiment of the present disclosure;Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.Detailed DescriptionWherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. Embodiments disclosed herein are related to material having a wide range of visible light transmittance, low SF, high selectivity while maintaining a low internal reflection (RC) value. All the above optical characteristics are attained by the solar control glass of the present invention without drastically increasing the external reflection (RG) value. FIG. 1illustrates a structure of a stack of thin layer having two functional layers F1, F2 deposited on a transparent substrate 10. Each of the functional layers 50, 100 is positioned between dielectric coatings 20 (M1), 40 (M2), 80 (M3) such that: the first functional layer 50, starting from the substrate, is positioned between the dielectric coatings 20, 40 and the second functional layer 100 is positioned between the dielectric coatings 40, 80. The dielectric coatings 20, 40 and 80 each comprise at least one dielectric layer. The stack of thin layers may further optionally comprise at least one overcoat layer 1000 (not represented) in contact with the dielectric coating 80 (M3). Achieving desired optical characteristics while maintaining the performance characteristics becomes challenging for a 5-layered solar control coating having a layer stack of glass / Si3N4 / NiCr / Si3N4 / NiCr / Si3N4 or glass / Si3N4 / TiN / Si3N4 / TiN / Si3N4. The inventors of the present invention have surprisingly found that the introduction of an NbN functional layer above the TiN functional layer provides the best opportunity to increase the glass side external reflection while keeping the coating side internal reflection decreased without negatively impacting the solar control performance of the solar control coated glass article. It was further found by the inventors of the present invention that the sum of thicknesses of the two functional layers significantly control the internal reflection (RC) and external reflection (RG) values of the solar control coated glass article. Furthermore, it is specifically elucidated by the inventors of the present invention that, the first functional layer made of TiN controls the solar control performance of the solar control coated glass article while the second functional layer made of Nb or NbN controls the reflection levels and the overall aesthetics of the solar control coated glass articleWhile most of the known solar control coating as highlighted in the earlier section optimize either the internal or external reflection of the coated glass article, the teachings of the present invention demonstrate that a slightly increased external reflection % can be achieved by the introduction of the intermediate TiN functional layer in between the glass substrate and the niobium-based functional layer. The presence of the absorbing niobium-based layer allows for achieving a variety of low visible light transmission values and high visible light transmission for the same internal and external reflective values obtained by the stack configuration of the present invention. Furthermore, the presence of niobium-based layer helps to control the reflective values of the coating side (Rc). This slightly increased external reflection % helps catering to specific want of the customer to have a product with visual comfort and privacy (internally) by having a marginally high reflective aesthetics (externally). Within the meaning of the present invention, the label “first”, “second” for the functional layers and “first”, “second”, “third” for the dielectric coatings are defined starting from the substrate bearing the stack and with reference to the layers or coatings having the same function. For example, the functional layer closest to the substrate is the first functional layer, the one farthest from the substrate is the second functional layer. Likewise, the dielectric coating closest to the substrate is the first dielectric coating, the next one moving away from the substrate is the second dielectric coating etc. Thicknesses stated in the present document with no other specifications are physical, real or geometric thicknesses referred to as T and are expressed in nanometers (and not optical thicknesses). The thickness of the dielectric coatings is represented as T. T1, T2 and T3 according to the specific dielectric coating they refer to.The inventors of the present invention have worked with two functional layer materials for F1 and F2: TiN and Nb or NbN. Thus, the thin multilayer coating proposed by the present invention comprise in multiple embodiments:Glass | Dielectric Coating (M1) | TiN (F1) | Dielectric coating (M2) | Nb or NbN (F2) | Dielectric coating (M3). FIG. 2 illustrates the stack of thin layers deposited on a transparent glass substrate as taught in the present invention. Teachings of the present invention in the following sections will demonstrate how the placement of the niobium-based function layer further away from the glass substrate is used for marginally increasing the reflective value of the glass side (external) and the intermediate TiN functional is used for optimizing the reflective value and reflective color of the coating side (internal). The above stated factors influence the internal reflection (RC), external reflection (RG), light transmission (TL), solar factor (SF) and selectivity.According to one embodiment of the present invention, thickness of F1 comprising TiN material ranges between 1 nm and 90 nm and thickness of F2 comprising Nb or NbN material ranges between 1 nm and 60 nm. More preferably, the thickness of F1 comprising TiN material is less than 50 nm and the thickness of F2 comprising Nb or NbN material is less than 40 nm. These thickness ranges for F1 and F2 are best suited for obtaining internal reflection (RC) of less than 15% and an external reflection (RG) greater than 10% and less than 35%. According to one other embodiment of the present invention, F2 comprising materials Nb or NbN is metallic or partially or fully nitride. In additional optional embodiments of the present invention, F2 further comprises materials such as zirconium or Molybdenum, wherein the materials comprised in F2 are one of NbZr, NbMo or NbZrMo.According to one other embodiment of the present invention, the functional layers F1 and / or F2 can be optionally sandwiched between barrier layers. In such embodiments, barrier layers are comprised of material selected from Titanium, NiCr, SiAl or absorbing SiAlNx or Niobium. In specific embodiments where the F1 is sandwiched by barrier layers, the barrier layer is made of Niobium. Thickness of such barrier layer range from 1 nm and 5 nm. According to optional embodiments, functional layers F1 and / or F2 can be optionally oxidized either completely or partially. Sum of the thicknesses of the functional layers 50 (F1) and 100 (F2) is preferred to be less than 90 nm. Total thickness of functional layers when exceeding 90 nm affects the visible light transmission of the solar control glass article leading to a product having very low visible light transmission. Said preferred thickness also has operational beneficial involving less thickness of material deposition. Further total thickness ranges outside the said preferred range lead to loss of one or more desired optical properties described. According to multiple embodiments of the present invention, thickness of dielectric coating 20 (M1) preferably ranges between 5 nm and 80 nm; thickness of dielectric coating 40 (M2) preferably ranges between 5 nm and 80 nm; and thickness of dielectric coating 80 (M3) preferably ranges between 5 nm and 80 nm, inclusive of all said values mentioned for M1, M2 and M3. The three dielectric coatings 20, 40, 80 comprise at least one dielectric layer based on a material selected from silicon nitride, aluminum nitride, oxynitrides of silicon and aluminum, silicon aluminium nitride, zinc oxide, tin and zinc oxide, tin oxide, titanium oxide, silicon oxide, aluminum oxide or titanium and tin oxide. According to a preferred embodiment of the present invention, the dielectric coatings 20, 40, 80 is made of silicon nitride. According to a most preferred embodiment of the present invention, the dielectric coatings 20, 40, 80 is made of silicon nitride doped with aluminum. According to an alternative preferred embodiment of the present invention, the dielectric coatings 20, 40, 80 is made of silicon zirconium nitride. Sum of the thicknesses of the dielectric coating 20 (M1), 40 (M2) and 80 (M3) is preferred to be ranging between 30 nm and 200 nm.Dielectric coating 20 (M1), 40 (M2) and 80 (M3) have a barrier function according to the present invention and should be understood layers made of a material capable of forming a barrier to the diffusion of sodium, oxygen and / or water at high temperature, originating from either the transparent substrate or the ambient atmosphere towards the functional layer. The constituent materials of the dielectric layer having a barrier function thus must not undergo chemical or structural modification at high temperature which would result in a modification to their optical properties. The layer or layers having a barrier function are preferably also selected from a material capable of forming a barrier to the constituent material of the functional layer. The dielectric layers having a barrier function thus allow the stack to be subjected, without excessively significant optical change, to heat treatments of the annealing, tempering or bending type.According to an optional embodiment, the stack of thin layers may further comprise at least one overcoat layer 1000 in contact with the dielectric coating 80 (M3). The overcoat layer 1000 comprises titanium zirconium nitride or oxynitride, titanium zirconium hafnium nitride or oxynitride, zirconium oxide or titanium oxide or their combinations thereof. According to a preferred optional embodiment, the overcoat layer 1000 comprises titanium zirconium oxide. The configuration of the stack of thin layers is designed such that the external reflection (RG) is slightly higher, and the internal reflection (RC) is lower. This is because the slightly high external reflection (RG) provides privacy during the daytime and the low internal reflection (RC) provides a clear view of the external environment in addition to providing visual comfort. This marginal increase in external reflection (RG) achieved by the present invention will further allow visual comfort for people placed outside the building.According to a one embodiment of the present invention, a solar control glass constructed having the below configuration of the stack of thin layers:Glass | Dielectric Coating (M1) | TiN (F1) | Dielectric coating (M2) | Nb or NbN (F2) | Dielectric coating (M3), exhibits the following optical characteristics:internal reflection (RC) less than external reflection (RG);internal reflection (RC) less than 15%;external reflection (RG) less than 35%, more preferably ranging between 10% to 35%;visible light transmission (TL) ranging between 5% and 70%.The transparent substrates according to the present invention are preferably made of an inorganic rigid material, such as glass, or an organic material based on polymers (or made of polymer). The substrate is preferably a sheet of glass or of glass-ceramic. The substrate is preferably transparent, colorless (it is then a clear or extra-clear glass) or colored, for example colored blue, grey, green or bronze. The glass is preferably of soda-lime-silica type, but it may also be made of glass of borosilicate or alumino-borosilicate type.The substrate advantageously has at least one dimension greater than or equal to 1 m, or even 2 m and even 3 m. The thickness of the substrate generally varies between 0.5 mm and 19 mm, preferably between 0.7 and 9 mm, in particular between 2 and 12 mm, or even between 4 and 10 mm. The substrate may be flat or curved, or even flexible.The material, that is to say the substrate coated with the stack, may undergo a high-temperature heat treatment such as an annealing, for example a flash annealing such as a laser or flame annealing and / or a tempering. The temperature of the heat treatment is greater than 500° C, preferably greater than 550° C, and better still greater than 600° C. The substrate coated with the stack may therefore be tempered. The heat-treated solar control glass article has a superior color matchability with a ΔE* of less than 3.0 for external reflection and transmission, according to a preferred embodiment.The invention also relates to a glazing comprising a material according to the invention. Conventionally, the faces of a glazing are denoted starting from the outside of the building and by numbering the faces of the substrates from the outside towards the inside of the passenger compartment or room that it equips. This means that the incident solar light passes through the faces in the increasing order of their number.The stack is preferably positioned in the glazing so that the incident light coming from outside passes through the first dielectric coating before passing through the first functional layer F1. The stack is not deposited on the face of the substrate that defines the external wall of the glazing but on the inner face of this substrate. The stack is therefore advantageously positioned on face 2, face 1 of the glazing being the outermost face of the glazing, as is customary.The material may be intended for applications that require the substrate coated with the stack to have undergone a heat treatment at a high temperature such as a tempering or an annealing. The glazing of the invention may be in the form of monolithic, laminated or multiple glazing, in particular double glazing or triple glazing.In the case of a monolithic glazing, the stack is preferably deposited on face 2, that is to say that it is on the substrate that defines the external wall of the glazing and more specifically on the inner face of this substrate. A monolithic glazing comprises 2 faces; face 1 is on the outside of the building and therefore constitutes the external wall of the glazing, face 2 is on the inside of the building and therefore constitutes the internal wall of the glazing.A multiple glazing comprises at least two substrates kept at a distance so as to delimit a cavity filled by an insulating gas (e.g., dry air, Ar, Kr or their mixture). The materials according to the invention are very particularly suitable when they are used in double glazings with enhanced thermal insulation (ETI). A double glazing comprises 4 faces; face 1 is outside of the building and therefore constitutes the external wall of the glazing, face 4 is inside the building and therefore constitutes the internal wall of the glazing, faces 2 and 3 being on the inside of the double glazing. The stack may be on face 2, 3 or 4 of the glazing.In the same way, a triple glazing comprises 6 faces; face 1 is outside of the building (external wall of the glazing), face 6 is inside the building (internal wall of the glazing) and faces 2 to 5 are on the inside of the triple glazing. A laminated glazing comprises at least one structure of first substrate / sheet(s) / second substrate type. The stack of thin layers is positioned on at least one of the faces of one of the substrates. The stack may be on the face of the second substrate not in contact with the, preferably polymer, sheet. This embodiment is advantageous when the laminated glazing is assembled as double glazing with a third substrate.This along with a slightly increased external reflection (RG) value of less than 35% and more than 10% aid in privacy for people placed inside the building and visual comfort for people placed in the exterior of the building.Furthermore, these visual appearance remains virtually unchanged irrespective of the angle of incidence with which the glazing is observed (normal incidence and under an angle). This means that an observer does not have the impression of a significant lack of uniformity in color or in appearance.According to advantageous embodiments, the glazing of the invention has, in particular, the following performances:a solar factor less than or equal to 0.85, preferably less than or equal to 0.70, and / ora high selectivity, in order of increasing preference, of at least 0.7, of at least 0.8Preferably, the stack is deposited by magnetron sputtering. According to this advantageous embodiment, all the layers of the stack are deposited by magnetron sputtering.The invention also relates to the process for obtaining a material according to the invention, wherein the layers of the stack are deposited by magnetron sputtering.ExamplesExample 1Preparation of the Substrates: Stack of thin layersStack of thin layers, defined below, are deposited on substrates made of clear soda-lime glass with a thickness of 6 mm.In the example of the invention:The first functional layer is TiN; the second functional layer is NbN; andthe dielectric layers are based on silicon nitride, doped with aluminum (Si3N4:Al).Table 1 lists the materials and thicknesses in nanometers for each layer or coating that forms the stacks as a function of their position with respect to the substrate bearing the stack (final line at the bottom of the table). The “Ref.” numbers correspond to the references from FIG. 1, for samples 1 and 2. The comparative samples are construed from known stack configurations comprising a single TiN based material. Table 1: Stack of thin layers (Inventive Samples)ElementRef No.Sample 1Thickness (nm)Sample 2Thickness (nm)Sample 3Thickness (nm)Sample 4Thickness (nm)Si3N4:Al8072.242.933.846NbN10049.54.221Si3N4:Al4050.447.930.478TiN5054.249.22Si3N4:Al205566.91030Glass106 mm6 mm6 mm6 mm Table 2: Stack of thin layers (Comparative Samples)ElementSample AThickness (nm)Sample BThickness (nm)Sample CThickness (nm)Sample DThickness (nm)Sample EThickness (nm)Si3N4:Al----100NbN----4Si3N4:Al108.390.864.273.250.4TiN1023.961.542.85Si3N4:Al62.866.91014.155Glass6 mm6 mm6 mm6 mm6 mm Solar Control and Optical PropertiesTable 2 lists the main optical characteristics measured when the glazings are part of a monolithic glazing of 6 mm glass. For these monolithic glazings:TL indicates: the light transmission in the visible region in %, measured according to the illuminant D65 Obs 2;a*T and b*T indicate the a* and b* colors in transmission in the L*a*b* system measured according to the illuminant D65 Obs 2 and measured perpendicularly to the glazing;RG indicates: the light reflection in the visible region in %, measured according to the illuminant D65 Obs 2 on the glass side of the glazing;a*RG and b*RG indicate the a* and b* colors in reflection in the L*a*b* system measured according to the illuminant D65 Obs 2 on the glass side of the glazing and thus measured at 8 deg from the glazing normal incidence;RC indicates: the light reflection in the visible region in %, measured according to the illuminant D65 Obs 2 on the coating side of the glazing;a*RC and b*RC indicate the a* and b* colors in reflection in the L*a*b* system measured according to the illuminant D65 Obs 2 on the coating side of the glazing and thus measured at 8 deg from the glazing normal incidence. Table 3: Optical & Solar Control Properties TransmissionExternal reflectionInternal reflectionSolar FactorSelectivity TL %a*Tb*TRG %a*Gb*GRC%a*Cb*CSFSample 155.11.41.116.2-9.77.414-10.53.555.40.99Sample 243.30.81.019.0-10.4-5.27.2-0.7-1.748.80.89Sample 319.7-3.72.518.97.829.48.2-3.7-17.926.00.76 Sample 428.57-0.70.2928.42-9.99-5.796.3113.6336.8836.480.78 Com. sample A56.821.415.2-7.112.527.3-9.81.258.10.98 Com. sample B43.92.36.717.4-5.916.829.5-10.3-3.049.10.89 Com. sample C20-3.34.919.49.231.617.8-4.4-14.825.60.78 Com. sample D26-3.671.6427.694.1940.6125.03-2.96-7.4129.30.89 Com. sample E52.00.4-1.012.8-4.323.519.2-3.813.458.10.89 From the results of the inventive samples depicted in Table 3, it can be understood that the invention described herein can be visualized for low TL products such as sample 3 and high TL products such as samples 1 & 2. While Samples 1, 2 and 3 exhibit low internal and external reflection values, sample 4 is a good example to demonstrate the invention also results in products having high internal reflection value of 28% while still maintaining an internal reflection values of just 6%. Such products find increasing applications in commercial and residential markets in different parts of India.As described previously, RG of all inventive samples are increased as compared to the RC values. Sample 4 is especially advantageous having 28% RG and a meager 6% RC. Thanks to the presence of the absorbing NbN layer further from the glass substrate that the external reflection is increased. Selectivity of all inventive samples are notable at least 0.7 or 0.9. A wide range of external reflection colors are possible to be obtained by the present invention. Sample 1 exhibits a greenish yellow in external reflection while samples 2 and 4 exhibit a green external reflection. Sample 3 exhibits a golden external reflection. Mentioned external reflection colors are exemplary and not limiting to the possible external reflection colors that are obtainable from the present invention.As to the comparative samples not comprised of the absorbing layer of NbN as shown in Table 2 and Table 3 (Samples A - D), although the desired visible light transmission is achieved by these samples, their internal reflection values (RC) are high compromising the visual comfort of the people situated inside the building. This increased RC caused by such layer stack is controlled by the addition of the absorbing layer of NbN material atop the TiN functional layer in the inventive samples and as outlines in the present invention. On the other hand, sample E which is comprised of a NbN layer atop the TiN functional layer still does not provide internal reflection less than 15% owing to the thickness of the dielectric layers not satisfying the desired total thickness. The inventive samples and comparative samples were heat treated (tempered) at 630°C for about 6 minutes and the color matchability post tempering were assessed. The results demonstrate that the optical properties of samples do not influence the tempering shift in the sample and the results are similar. The color shift of sample 1 in the glass side is very low. Example 2More inventive examples are provided in Table 4. Table 4: Stack of thin layers (Inventive Samples)ElementRef No.Sample 6Thickness (nm)Sample 7Thickness (nm)Sample 8Thickness (nm)Sample 9Thickness (nm)Si3N4:Al8059.5761.5124.240.38NbN10049.4213.7215.226.35Si3N4:Al4079.0475.1747.758.22TiN503.3250.726.256.63Si3N4:Al2050.1224.578.36.09Glass106 mm6 mm6 mm6 mm Solar Control and Optical PropertiesTable 5 lists the main optical characteristics measured when the glazings are part of a monolithic glazing of 6 mm glass.Table 5: Optical & Solar Control Properties TransmissionExternal reflectionInternal reflectionRG Color TL %a*Tb*TRG %a*Gb*GRC%a*Cb*CSample 69.10-3.16-5.9225.16-0.6326.658.950.69-35.57GoldenSample 716.18-0.991.5514.070.733.986.5640.50-33.96BronzeSample 829-361081128-116BronzeSample 95.10-2.576.4420.4014.360.6916.851.8536.40Rose Inventive samples 6 – 9 demonstrate that a further wide range of external reflection colors are possible to be obtained by the present invention.Industrial ApplicabilityThe solar control glass article described in the present disclosure finds application as a glazed element in building. In this application case, the glazing may form a monolithic glazing with the coating side of the glass arranged facing the closed space inside the building. The glazing may also form a laminated glazing whose stack of layers may be in contact with the thermoplastic adhesive material connecting the substrates, in general PVB. The glazing may also be part of an insulation glazing window. The glazing of the present disclosure can also be annealed, strengthened, toughened and / or tempered. The tempered glazing can also be used in building wall cladding panel of curtain walling for interior applications. Further can also be used as a side window, rear window or sunroof for an automobile or other vehicle.Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Certain features, that are for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in a sub combination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.The description in combination with the figures is provided to assist in understanding the teachings disclosed herein, is provided to assist in describing the teachings, and should not be interpreted as a limitation on the scope or applicability of the teachings. However, other teachings can certainly be used in this application.As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).Also, the use of "a" or "an" is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item.Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent that certain details regarding specific materials and processing acts are not described, such details may include conventional approaches, which may be found in reference books and other sources within the manufacturing arts.While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.       List of Elements TITLE: A HEAT TREATABLE SOLAR CONTROL GLASS ARTICLE COMPRISING TITANIUM NITRIDE AND NIOBIUM-BASED FUNCTIONAL LAYERS 10 Glass Substrate20 First Dielectric Layer M140 Second Dielectric Layer M250 First Functional Layer F180 Third Dielectric Layer M3100 Second Functional Layer F21000 Overcoat Layer 

Claims

AMENDED CLAIMS received by the International Bureau on 5 May 2025 (05.05.2025)ClaimsWe claim,1) A solar control glass article comprising a transparent substrate having a first surface provided with a thin multilayer coating comprising: n functional layers and n+1 dielectric layers, wherein n=2 such that each functional layer is sandwiched between 2 dielectric layers and optionally an overcoat layer, wherein the overcoat layer forms the outermost layer of the thin multilayer coating, characterized in that: the first functional layer comprises TiN having a thickness range between 1 nm to 90 nm; and the second functional layer comprises niobium having a thickness range between 1 nm to 60 nm, wherein said solar control glass article has an external reflection (RG) less than 35% while maintaining the internal reflection (RC) at less than 15%.2) The solar control glass article as claimed in claim 1, wherein the second functional layer comprising niobium has a thickness less than 40 nm.3) The solar control glass article as claimed in claim 1, wherein the first functional layer comprising TiN has a thickness of less than 50 nm.4) The solar control glass article as claimed in claim 1, wherein the sum of thicknesses of the first and second functional layers does not exceed 90 nm.5) The solar control glass article as claimed in claim 1, wherein the second functional layer comprises metallic niobium or partially or fully nitrided niobium.6) The solar control glass article as claimed in claim 1, wherein the dielectric layer comprises a material selected from the group consisting of silicon nitride, aluminum nitride, silicon aluminium nitride, oxynitrides of silicon and aluminum, zinc oxide, tin and zinc oxide, tin oxide, titanium oxide, silicon oxide, aluminum oxide or titanium and tin oxide.7) The solar control glass article as claimed in claim 1, wherein the dielectric layer comprises silicon nitride.8) The solar control glass article as claimed in claim 6, wherein the dielectric layer comprising silicon nitride is doped with aluminum.9) The solar control glass article as claimed in claim 1, wherein the sum of thicknesses of the dielectric layers ranges between 30 nm and 200 nm.10) The solar control glass article as claimed in claim 1 has a visible light transmission (TL) ranging between 5% and 70%.11) The solar control glass article as claimed in claim 1 has external reflection (RG) higher than 10% and less than 35%.12) The solar control glass article as claimed in claim 1, wherein one or both functional layers are partially or completely oxidized.13) The solar control glass article as claimed in claim 12, wherein one or both functional layers comprise oxygen not more than 5 wt%.14) The solar control glass article as claimed in claim 1, wherein the overcoat comprises titanium zirconium nitride or oxynitride, titanium zirconium hafnium nitride or oxynitride, zirconium oxide or titanium oxide or their combinations thereof.15) The solar control glass article as claimed in any of the preceding claims is a monolithic window or is a part of an insulation glazing window.16) The solar control glass article as claimed in any of the preceding claims is heat treatable from the glass side with a AE*G of less than or equal to 3 and a has selectivity of more than 0.7.

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