A neutral-grey external reflection solar control glass article

Abstract

A neutral-grey external reflection solar glass article comprising a transparent substrate having a first surface provided with a thin multilayer coating comprising a first functional layer based on titanium nitride and a second functional layer based on niobium nitride, each functional layers sandwiched between two dielectric coatings The thin multilayer coating is characterized in that a ratio of thickness of the second functional layer to the first functional layer is less than 2 in combination with a ratio of the sum of the thicknesses of the dielectric coatings sandwiching each of the first and second functional layers to the thickness of the first dielectric coating is less than 6 provides for achieving the neutral-grey external reflection color desired by the present invention.

Description

[0001] A NEUTRAL-GREY EXTERNAL REFLECTION SOLAR CONTROL GLASS ARTICLE

[0002] TECHNICAL FIELD

[0003] The 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 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 achieves a neutral-grey external reflection without significantly compromising its solar performance.

[0004] BACKGROUND

[0005] Solar factor (SF or g-value) and selectivity values are desired in applications particularly, hot and humid weather climates. 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.

[0006] 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.

[0007] 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.

[0008] Yet another example of solar control coatings having a layer stack of glass / Si3N4 / NiCr orNiCrW / Si3N4 / TiN / Si3N4 is known from U.S. Patent Document 2017 / 0197874 and is herein incorporated by reference.

[0009] 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.

[0010] 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 andNb / 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.

[0011] Nonetheless an Indian patent application 202141057353 owned by the Applicant of the present invention is herein referenced as prior art wherein a layer stack comprising a combination of TiN and Nb / NbN sandwiched between dielectric layers was disclosed. The TiN functional layer was reported to contribute to the solar control performance of the layer stack and the Nb / NbN functional layer was reported to control the reflection color, reflection value and other optical characteristics of the solar control coating.

[0012] 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 i.e., the internal reflection value (RC) of the solar control coated article.

[0013] Thus, embodiments of the present invention shall disclose how the inventors were able to achieve a low external reflection value (Rg) without drastically increasing the internal reflection value (Rc), while simultaneously achieving an external reflection color of neutral-grey as popularly desired by the market for commercial buildings and residential communities. 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.

[0014] OBJECTS OF THE DISCLOSURE

[0015] An objective of the present invention disclosure is to provide a neutral-grey external reflection solar glass article with a transparent substrate with a thin multilayer coating.

[0016] Another objective of the present invention disclosure is to provide neutral -grey external reflection color by optimizing the thicknesses of the functional layers and the dielectric coatings that sandwich the functional layers.

[0017] Yet another objective of the present invention is to provide a first functional layer made of titanium nitride and a second functional layer made of niobium nitride to control the reflection level and / or its aesthetics of glass by the absorption of visible light and emission of infrared radiation.

[0018] Yet another objective of the present invention is to give flexibility to achieve low to high transmission levels without compromising on external aesthetics.

[0019] Yet another objective of the present invention disclosure is to provide a neutralgrey external reflection solar glass article with low external reflection value (Rg) without drastically increasing the internal reflection value (Rc),

[0020] SUMMARY OF THE DISCLOSURE

[0021] In one aspect of the present disclosure, a neutral-grey external reflection solar glass article comprising a transparent substrate having a first surface provided with a thin multilayer coating is disclosed. The thin multilayer coating comprises starting from the substrate: a first TiN functional layer and a second NbN functional layer, each functional layer sandwiched by a dielectric coating.

[0022] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments are illustrated by way of example and are not limited to those shown in the accompanying figures.

[0025] FIG. 1 illustrates a stack of thin layers deposited on a transparent glass substrate, according to one embodiment of the present disclosure; and

[0026] FIG. 2 illustrates a stack of thin layers deposited on a transparent glass substrate, according to one other embodiment of the present disclosure;

[0027] 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.

[0028] DETAILED DESCRIPTION

[0029] Wherever 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 glass article having a neutral-grey external reflection color, low external reflection values (RG) of less than or equal to 20% and a wide range of visible light transmittance. All the above optical characteristics are attained by the solar control glass of the present invention without drastically increasing the internal reflection (RC) value.

[0030] FIG. 1 illustrates a structure of a stack of thin layer having two functional layers Fl, F2 deposited on a transparent substrate 10. Each of the functional layers 50, 100 is positioned between dielectric coatings 20 (Ml), 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).

[0031] Achieving desired optical characteristics while maintaining the performance characteristics becomes challenging for a 5-layered solar control coating having a layer stack of glass / ShN NiCr / ShN NiCr / SiS^ 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 achieve a blue color external reflection color alongside low external reflection value without drastically increasing the internal reflection (RC) value and negatively impacting the solar control performance of the solar control coated glass article.

[0032] 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 article. Further, the first functional layer made of TiN provides m

[0033] While 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, none of these coating are able to achieve a neutral-grey external reflection color. Since the market has a high demand for glass articles that have a neutralgrey external reflection color, the inventors of the present invention have devised a means for achieving said neutral-grey external aesthetics without drastically impacting the performance properties of the solar control article. The teachings of the present invention demonstrate that by optimizing the thicknesses of the functional layers and the dielectric coatings that sandwich these functional layers the inventors of the present invention have demonstrated achieving neutral-grey external reflection color; low external reflection values (RG) of less than or equal to 20% and a wide range of visible light transmittance. This is made possible by the combination of the following conditions:

[0034] (i) ratio of thickness of the second functional layer to the first functional layer is less than 2; and

[0035] (ii) a ratio of the sum of the thicknesses of the dielectric coatings sandwiching each of the first and second functional layers to the thickness of the first dielectric coating is less than 6.

[0036] The combination of the two conditions contributes to achieving neutral-grey external reflection color which is characterized by a*G value & b*G value ranging between -5 to 2.

[0037] The first functional layer made of titanium nitride allows to give flexibility to achieve low to high transmission levels without compromising on external aesthetics. The second functional layer made of niobium nitride is used to control the reflection level and / or its aesthetics of glass by the absorption of visible light and emission of infrared radiation.

[0038] In few other embodiments of the present invention, the inventors of the present invention have demonstrated achieving neutral-grey external reflection color; low external reflection values (RG) of less than or equal to 20% and a wide range of visible light transmittance by the combination of the following conditions:

[0039] (i) ratio of thickness of the second functional layer to the first functional layer is less than 2;

[0040] (ii) a ratio of the sum of the thicknesses of the dielectric coatings sandwiching each of the first and second functional layers to the thickness of the first dielectric coating is less than 6; and

[0041] (iii) sum of the thicknesses of the first and second functional layers ranges between 15 nm and 75 nm.

[0042] In said embodiments, the combination of the three conditions contributes to achieving neutral-grey external reflection color which is characterized by a*G value & b*G value ranging between -5 to 2. 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. Tl, T2 and T3 according to the specific dielectric coating they refer to.

[0043] The inventors of the present invention have worked with two functional layer materials for Fl and F2: TiN and NbN. Thus, the thin multilayer coating proposed by the present invention comprise in multiple embodiments: Glass | Dielectric Coating (Ml) | TiN (Fl) | Dielectric coating (M2) | 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.

[0044] Teachings of the present invention in the following sections will demonstrate how the thicknesses of the dielectric coatings in combination with the thicknesses of the functional layers are designed to achieve the following properties of the solar control glass article:

[0045] (i) neutral-grey external reflection color characterized by a*G value ranging between -5 to 2 and b*G value ranging between -5 to 2; and

[0046] (ii) visible light transmission (TL) at any value less than or equal to 60%; and

[0047] (iii) external reflection value (Rg) less than or equal to 20%.

[0048] According to one embodiment of the present invention, thickness of Fl comprising TiN material is less than 60 nm and thickness of F2 comprising NbN material ranges between less than 40 nm. These thickness ranges for Fl and F2 are best suited for obtaining neutral-grey external reflection color. 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.

[0049] According to one other embodiment of the present invention, the functional layers Fl 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 SiAINx or Niobium. In specific embodiments where the Fl 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 Fl and / or F2 can be optionally oxidized either completely or partially. Accordingly, one or both functional layers may comprise oxygen not more than 5 wt%.

[0050] Sum of the thicknesses of the functional layers 50 (Fl) and 100 (F2) is preferred to be ranging between 15 nm and 75 nm. Total thickness of functional layers when exceeding 75 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.

[0051] According to multiple embodiments of the present invention, thickness of dielectric coating 20 (Ml) preferably is less than 55 nm; thickness of dielectric coating 40 (M2) preferably is less than 55 nm; and thickness of dielectric coating 80 (M3) preferably is less than 55 nm, inclusive of all said values mentioned for Ml, M2 and M3. The three dielectric coatings 20, 40, 80 comprise at least one dielectric layer based on a material selected from silicon nitride, silicon zirconium nitride, zirconium oxide, 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 (Ml), 40 (M2) and 80 (M3) is preferred to be ranging between 30 nm and 170 nm.

[0052] Dielectric coating 20 (Ml), 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.

[0053] 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 oxide 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 or zirconium oxide or titanium oxide.

[0054] 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 and colorless (it is then a clear or extra-clear glass). The glass is preferably of soda-lime-silica type, but it may also be made of glass of borosilicate or alumino-borosilicate type.

[0055] 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.

[0056] 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 AE* of less than 3.0 for external reflection and transmission, according to a preferred embodiment.

[0057] 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.

[0058] 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 Fl. 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Preferably, 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.

[0066] Examples

[0067] Example 1

[0068] Preparation of the Substrates: Stack of thin layers

[0069] Stack of thin layers, defined below, are deposited on substrates made of clear soda-lime glass with a thickness of 6 mm.

[0070] In the example of the invention:

[0071] The first functional layer is TiN; the second functional layer is NbN; and the dielectric layers are based on silicon nitride, doped with aluminum (SisN^Al).

[0072] 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.

[0073] Table 1 : Stack of thin layers (Inventive Samples)

[0074] Table 2: Stack of thin layers (Comparative Samples)

[0075] I Si3N4:Al j 18.61 [ 87.12 | 95 r'SEN4:A ''T 74'55 f'' '87'28 J .35" j Glass j 6 mm j 6 mm j 6 mm j

[0076] Solar Control and Optical Properties:

[0077] Table 2 lists the main optical characteristics measured when the glazings are part of a monolithic glazing of 6 mm glass. For these monolithic glazings:

[0078] 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;

[0079] 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;

[0080] 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.

[0081] Table 3: Optical & Solar Control Properties

[0082] 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 2 and high TL products such as sample 3. All inventive samples can be seen to have low external reflection value (RG) as desired below 20% and even better with RG less than 15%. Sample 3 is especially useful in that the low internal reflection value does not drastically increase the internal reflection value (RC) wherein the sample showed only 11% Internal reflection.

[0083] Nonetheless all inventive samples achieve neutral-grey external reflection color. a*T, b*T values for transmission color are also seen to be within the desired color coordinate values of -5 to 2. Such products find increasing applications in commercial and residential markets in different parts of India.

[0084] As to the comparative samples, none of then achieve a neutral-grey transmission color which is evident from the a*G, b*G values. Additionally, a*T, b*T values can also seen to be largely deviated from the desired range of -5 to 2. Counter Sample C does not achieve a neutral-grey external reflection color owing to a thick dielectric coating above the second functional layer. As for the counter samples A and B, although the stack thicknesses of these products are well within the desired thickness ranges of the individual layers, these products do not satisfy the necessary conditions viz., ratio of thickness of the second functional layer to the first functional layer greater than 2 and the sum of the thicknesses of the two functional layers greater than 75nm. 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.

[0085] Industrial Applicability

[0086] The 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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.

[0095] 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.

[0096] List of Elements

[0097] 10 Glass Substrate

[0098] 20 First Dielectric Layer Ml

[0099] 40 Second Dielectric Layer M2

[0100] 50 First Functional Layer F 1

[0101] 80 Third Dielectric Layer M3

[0102] 100 Second Functional Layer F2

[0103] 1000 Overcoat Layer

Claims

We Claim:1) A neutral-grey external reflection solar glass article comprising a transparent substrate (10) having a first surface provided with a thin multilayer coating comprising: a first TiN functional layer (50) and a second NbN functional layer (100), each functional layer sandwiched by a dielectric coating (20, 40 and 80), characterized in that: a ratio of thickness of the second functional layer to the first functional layer is less than 2; and a ratio of the sum of the thicknesses of the dielectric coatings sandwiching each of the first and second functional layers to the thickness of the first dielectric coating is less than 6.2) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the sum of the thicknesses of the first and second functional layers ranges between 15 nm and 75 nm.3) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the first TiN functional layer has a thickness of less than 60 nm.4) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the second NbN functional layer has a thickness ranging less than 40 nm.5) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the dielectric coating comprises one or more dielectric layers made of a material selected from the group consisting of silicon nitride, silicon zirconium nitride, aluminum nitride, silicon aluminium nitride, oxynitrides ofsilicon and aluminum, zinc oxide, tin and zinc oxide, tin oxide, titanium oxide, zirconium oxide, silicon oxide, aluminum oxide or titanium and tin oxide.6) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the dielectric coating comprises one or more dielectric layers made of silicon nitride, silicon zirconium nitride or silicon nitride doped with aluminum.7) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the dielectric coating positioned below the first TiN functional layer has a thickness of less than 55 nm.8) The neutral-grey external reflection solar glass article as claimed in claim 1, wherein the dielectric coating positioned above the first TiN functional layer and above the second NbN functional layer, each have a thickness of less than 90 nm.9) The neutral-grey external reflection solar glass article as claimed in claim 1 has a visible light transmission (TL) ranging between 5% and 60% and an external reflection (RG) value of less than 20%.10) The neutral-grey external reflection solar glass article as claimed in claim 1 has an a*G value ranging between -5 to 2 and a b*G value ranging between -5 to 2.11) The neutral-grey external reflection solar glass article as claimed in claim 1 further comprises an overcoat layer forming the outermost layer of the thin multilayer coating comprising titanium zirconium nitride or oxynitride, titanium zirconium hafnium nitride or oxynitride, zirconium oxide or titanium oxide or their combinations thereof.2) The neutral-grey external reflection solar glass article as claimed in claim 11, wherein the overcoat is titanium oxide or titanium zirconium oxide or zirconium oxide.

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