Technical Field The present disclosure relates, in general to a glazing comprising a transparent substrate, on the surface of which a stack of thin layers is deposited which comprises three functional layers, two based on silver and the other functional layer based on titanium nitride making the substrate possible to act on the solar and/or infrared radiation likely to strike said surface. More specifically the invention relates to a glazing comprising a bilayer silver stack that achieves high selectivity equivalent to that of triple layer silver stack. Background Functional metal layers based on silver have advantageous electrical conduction and reflection properties of infrared (IR) radiation, hence are widely used in "solar control" glazing aimed at reducing the amount of incoming solar energy and / or in so-called "low emissivity" glazing aimed at reducing the amount of energy dissipated to the outside of a building or a vehicle. These silver layers are deposited between coatings based on dielectric materials generally comprising several dielectric layers (hereinafter dielectric coatings) for adjusting the optical properties of the stack. These dielectric layers also make it possible to protect the silver layer from chemical or mechanical aggression. In countries where sunlight levels are high, low-emission glazing for so-called residential applications must also have the solar control effect, which cuts down the transmission of heat while keeping visual light transmission (VLT) reasonably high. The transmission of heat through a glass façade is quantified by the solar factor (g). Selectivity, defined as VLT/g, is a good and widely used metric to quantify solar control properties. A higher selectivity denotes better solar control. While a single silver-based functional metal layer improves the solar control, incorporating two or more silver layers in a coating can drastically enhance this property and improve selectivity due to their high IR reflectivity as well as low emissivity. A glass substrate (in absence of any coating) typically has a selectivity of about 1. A glass substrate provided with a single silver layer in the coating generally achieves selectivity between 1.2 and 1.4. A glass substrate provided with double and triple silver layers in the coating, generally achieve selectivity up to 1.8 and 2.2, respectively. Such solar control products are now commonly available in the market. It should be quite clear that increasing the amount of silver improves the selectivity of a coating. However, this results in an increase in light reflection to levels considered aesthetically undesirable. And further makes these coatings largely expensive owing to the increased cost associated with the increased silver content. Other highly conducting metals such as gold, copper, etc. can be used in place of silver in these coatings to achieve good selectivity, but their distinct colors are not always aesthetically appealing. Moreover, the cost of these materials can also be sufficiently high. In this context, finding a cheaper alternative material that can provide similar performance as silver is highly desirable. Titanium nitride (TiN), when deposited close to working point, shows excellent IR reflectivity while keeping visual light transmission reasonably high. This makes TiN a good candidate to substitute silver layers in a coating. Unfortunately, TiN has a much higher emissivity in comparison to silver. This means replacing all silver layers of a coating by TiN will not result in comparable performances. Hence the present invention proposes TiN as a material to be used alongside a bilayer of silver in a coating to achieve high selectivity (>1.8, or even >2.0). Several documents disclose the use of TiN material in a coating stack comprising silver based functional metal layer(s). CN102603209A, WO2019209202A2, CN102350833B and CN102825866A are referenced herein for disclosing coating stack comprising silver based functional metal layer(s) and TiN material as the dielectric layer. Several other documents disclose the use of TiN material in a coating stack as the IR reflecting layer that can be used in place of the silver based functional metal layer(s). US6416872, WO2008/060453, WO2016/107883 are referenced herein for coating stack disclosing TiN as one of the IR reflecting material. However, these references do not disclose performance of these coating stack neither in terms of solar factor (g) nor selectivity. JP2006143525A is particularly referenced for disclosing a thermal barrier film including a silver layer and a titanium nitride or oxynitride layer as the main components for achieving high visible light transmittance, low visible light reflectance, and high heat shielding performance. The invention proposes a glass plate having an antireflection film on the outdoor side and a thermal barrier film on the indoor side surface. However, positioning of the TiN layer over the silver functional layer in the stack configuration compromises the U-value. Still further documents WO2019/097192, WO2010072973, WO2010072974 and WO2014/044984 disclose thin film stacks comprising a single silver functional layer and one or more absorbent layers based on titanium or titanium nitride material to reduce light reflection. Solutions proposed in these prior art references show low selectivity (>1.4), high visible light transmission values (>55%) and do not particularly optimize achieving low emissivity, high selectivity alongside low internal and external reflection. The objective of the invention is to overcome the drawbacks of the prior art, by developing a new type of stack comprising two functional layers based on silver and a single functional layer based on titanium nitride such that the functional layer based on titanium nitride is positioned below at least one functional layer based on silver. This new type of stack achieves a low emissivity and high selectivity with visible light transmission values ranging between 20% to 65%. This proposed new type of stack having a combination of three functional layers: two based on silver and the another based on TiN exhibits improved performance (selectivity) as compared to coating stacks comprising double silver functional layer existing in the art. 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 Disclosure In one aspect of the present disclosure, a glazing comprising a transparent substrate with a stack of thin layers is provided. Three functional layers are provided to have reflection properties in the infrared and/or solar radiation range. Dielectric coatings each comprising one or more dielectric layers are provided such as to sandwich each of the functional layers. Each dielectric layer independently comprises a dielectric material. The stack comprises n functional layer based on silver or silver-containing metal alloy, wherein n=2 and n’ functional layer based on titanium nitride, wherein n’=1. The functional layer based on titanium nitride has an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm and is positioned below at least one functional layer based on silver or silver- containing metal alloy. In one other aspect of the present disclosure, a glazing comprising a transparent substrate with a stack of thin layers comprising starting from the substrate: a first dielectric coating; a first functional layer based on titanium nitride having reflection properties in the infrared and/or solar radiation range, wherein the first functional layer has an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm; a second dielectric coating; a second functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; a third dielectric coating; a third functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; and a fourth dielectric coating is disclosed. The glazing is characterized in that when said transparent substrate is mounted in a double glazing with the stack of thin layers on face 2, the double glazing has visible light transmission ranging between 20% to 65%; and high selectivity greater than 1.8. In one other aspect of the present disclosure, a glazing comprising a transparent substrate with a stack of thin layers comprising starting from the substrate: a first dielectric coating; a first functional layer based on based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; a second dielectric coating; a second functional layer based on titanium nitride having reflection properties in the infrared and/or solar radiation range, wherein the first functional layer has an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm; a third dielectric coating; a third functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; and a fourth dielectric coating is disclosed. The glazing is characterized in that when said transparent substrate is mounted in a double glazing with the stack of thin layers on face 2, the double glazing has visible light transmission ranging between 20% to 65%; and high selectivity greater than 1.8. Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. Brief Description of the Drawings Embodiments 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; FIG.2A and FIG.2B illustrate stack of thin layers deposited on a transparent glass substrate, according to two different embodiments of the present disclosure; and FIG.3A and FIG.3B illustrates a stack of thin layers deposited on a transparent glass substrate, according to two exemplary embodiments 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. Detailed Description 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 a solar control glazing comprising two silver based functional layers, either one or both these layers positioned atop another functional layer based on TiN, having reflection properties in the infrared and/or solar radiation. The proposed glazing achieves higher selectivity (>1.8, even >2.0) as compared to conventional glazing comprising stacks having double silver based functional layers and conventional stacks mentioned in prior art that does not comprise any absorbing layers having selectivity close to 1.8 or even 1.85. The proposed glazing stack is a cost effective alternative to coating stack comprising triple layer silver functional layers as it provides for replacing one of the silver functional layers with a less expensive material such as TiN and yet achieves high selectivity as that of the triple layer silver functional layer stack. The selectivity "S" corresponds to the ratio of the light transmission TL in the visible of the glazing on the solar factor FS glazing (S = TL / FS). The solar factor "FS" corresponds to the ratio in% between the total energy entering the room through the glazing and the incident solar energy. All the luminous characteristics described herein are obtained according to the principles and methods of the European standard EN 410 relating to the determination of the luminous and solar characteristics of glazing used in glass for construction. Properties such as selectivity, outer or inner light reflection and color properties are calculated with: materials comprising a substrate coated with a stack of layers according to the present invention mounted in a double glazing unit, the double glazing having a configuration: 6-15 (Ar-90%) -6, that is to say a configuration consisting of a material comprising a substrate and another 6 mm glass substrate; two substrates are separated by a lamina of intermediate gas with 90% of argon and 10% of air with a thickness of 15 mm with the stack positioned in face 2. A coated solar control glass article 101 as illustrated in FIG.1, is disclosed in various embodiments of the invention. FIG. 1 illustrates a structure of a stack of thin layer having three functional layers 50, 100, 150 deposited on a transparent substrate 10. Each of the functional layers 50, 100, 150 are positioned between dielectric coatings 20 (first dielectric coating), 40 (second dielectric coating), 60 (third dielectric coating), 80 (fourth dielectric coating) such that: the first functional layer 50, starting from the substrate, is positioned between the dielectric coatings 20, 40; the second functional layer 100 is positioned between the dielectric coatings 40, 60; and the third functional layer 150 is positioned between the dielectric coatings 60, 80. The dielectric coatings 20, 40, 60, 80 each include at least one dielectric layer viz., 21; 41; 61; 81. Each dielectric layer includes a dielectric material. According to few embodiments of the present invention, the functional layer 50 is based on titanium nitride having reflection properties in the infrared and/or solar radiation range and has an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm. In few other embodiments, the functional layer 50 is based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range. Likewise, the functional layer 100 is based on silver or silver-containing metal alloy according to few embodiments of the present invention while in few other examples the functional layer 100 is based on titanium nitride. The functional layer 150 according to all embodiments of the present invention is based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range. The stack of thin layer comprises no more than two function layers based on silver or silver-containing metal alloy not more than one function layer based on titanium nitride. Thus in accordance to few embodiments, the invention relates to a material comprising a transparent substrate coated with a stack of thin layers comprising, starting from the substrate: - a first dielectric coating; - a first functional layer based on titanium nitride having reflection properties in the infrared and/or solar radiation range, - a second dielectric coating; - a second functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; - a third dielectric coating; - a third functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; and - a fourth dielectric coating. In accordance to few other embodiments, the invention relates to a material comprising a transparent substrate coated with a stack of thin layers comprising, starting from the substrate: - a first dielectric coating; - a first functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range, - a second dielectric coating; - a second functional layer based on titanium nitride having reflection properties in the infrared and/or solar radiation range; - a third dielectric coating; - a third functional layer based on silver or silver-containing metal alloy having reflection properties in the infrared and/or solar radiation range; and - a fourth dielectric coating. The functional layer based on titanium nitride is positioned below at least one functional layer based on silver or silver containing metal alloys to provide low emissivity and high selectivity. The sum of the optical thicknesses (nd, calculated at 480 nm wavelength) of the second and the third dielectric coatings 40, 60 ranges between 120 nm to 700 nm. The total optical thickness (nd, calculated at 480 nm wavelength) of the dielectric coating 20, 80 each range between 20 nm and 300 nm. The invention also relates to a multiple glazing comprising at least one material according to the invention and at least one second substrate, the material and the second substrate are separated by at least one interlayer of gas. Preferably, the stack is positioned in face 2. When the material is mounted in double glazing with the stack positioned in face 2, the double glazing presents: - a selectivity greater than 1.8 or greater than or equal to 2.0, - visible light transmission ranging between 20% to 65% - glass side reflection (Rg) less than 25%, - coating side reflection (Rc) less than 20%, The high selectivity of the stack of thin layers, attributable to the presence of titanium nitride in combination with silver, all functional layers reflecting infrared and/or solar radiation, depending on their position and thickness and also the titanium nitride layer having an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm that maximizes its reflection property. Titanium nitride, when deposited close to working point (herein ‘working point’ refers to the stack position of TiN layer that is optimally nitrided whose nitrogen content is optimal enough to nitride the layer as well as retain high deposition rate), shows excellent IR reflectivity while keeping visual light transmission reasonably high. However, titanium nitride has much higher emissivity as compared to silver. Hence if the titanium nitride layer is placed at a point where it is either sandwiched between the glass substrate and the silver layer or is sandwiched between two silver layers, one of the silver layers can then be used as a top functional layer to achieve low emissivity and high selectivity. The applicant has thus demonstrated that, in a stack with a triple silver layer, the first or the second silver layer (considering the layers moving away from the glass substrate on which they are provided) can be replaced with a less expensive yet IR reflective material such as titanium nitride to achieve a product which is far less expensive but performs (selectivity) better than a double silver stack. While existing double silver stack have a selectivity of <1.8, the stack of thin layers of the present invention can achieve selectivity >1.8 or even >2.0 using a combination of three functional layers: one based on titanium nitride and two other functional layers based on silver or silver containing metal alloys. Surprisingly, by configuring the stack to: - provide low emissivity in spite of employing a TiN layer by placing at least one silver layer atop the TiN layer; - optimizing the thickness of the dielectric coatings (especially that of the second and the third dielectric coatings) to maximally reflect IR while at the same time allowing visible light as much as possible, we obtain a material that is satisfies: - high selectivity, - desirable visible light transmission between 20% to 65%, - less than 25% glass side reflection, - less than 20% coating side reflection, - low emissivity <0.05, - solar factor in order of increasing preference less than 36%, 30%, 25%. The preferred features which appear in the remainder of the description are applicable both to the material according to the invention and, where appropriate, to the glazing or to the process according to the invention. Unless otherwise stated, the thicknesses discussed herein are optical thicknesses (nd) at 480 nm wavelength, wherein ‘n’ denotes the actual refractive index of a dielectric layer at the given wavelength and ‘d’ is the physical thickness of the dielectric layer. The layers are thin layers. By thin film is meant a layer having a thickness of between 0.1 nm and 100 micrometers. For the purposes of the present invention, the phrase "reflection properties in the infrared and/or solar radiation" with particular reference to the material titanium nitride means a layer made of a material having an extinction coefficient k>3 in the wavelength ranging between 1000 nm to 2500 nm. Preferably, IR reflection, the reflection of infrared radiation in the solar spectrum between 1000 to 2500 nm, due to the reflecting layer, calculated by depositing only this reflecting layer (30 nm of TiN layer) on plain clear glass of 4 mm. The reflection, measured on the coating side, is greater than 50%. The stack comprises a single functional layer based on titanium nitride (TiN _x ), wherein x ranges between 0.7 and 1.3. Preferably, the titanium nitride based functional metal layer comprises less than 10.0% by weight of oxygen. The titanium nitride based functional metal layer may also include elements selected from, for example, Mo or Nb. Preferably, each of these elements represents less than 10%, less than 5%, less than 2%, less than 1%, less than 0.5% by weight of the functional titanium nitride layer. The maximum proportions of these element depend on the nature of these element. The physical thickness of the titanium nitride functional layer ranges between 3 nm and 50 nm. The stack comprises two functional layers based on silver. This type of stack is also called "functional bilayer stacking". This means that the stack does not include more than two silver-based functional layer. This further means in particular that the stack of thin layers of the present invention comprises no more than three functional layers. The silver-based functional layers comprise at least 85.0%, preferably at least 90%, and most preferably at least 95%, by weight of silver relative to the weight of the functional layer. Preferably, the silver-based functional metal layers comprise less than 1.0% by weight of non-silver metals relative to the weight of the silver functional metal layer. The silver-based functional metal layers may also include elements selected from, for example, copper, palladium, gold or aluminum or their combinations thereof. Preferably, each of these elements represents less than 15%, less than 10%, less than 5%, less than 1%, less than 0.5% by weight of the functional silver-based metal layer. The maximum proportions of these element depend on the nature of these element. The physical thickness of the silver-based functional layers range between 3 nm and 25 nm. The silver-based functional layers may be protected by a layer known as a protective layer. According to this embodiment, the stack of thin layers further comprises at least one protective layer 70, 71, 90, 91 located in direct contact below and/or above one or both the silver-based functional layers (as shown in FIG.2A and FIG.2B). FIG.2A illustrates embodiments of the present invention where the stack of thin layers comprises the TiN functional layer 50 as the closest functional layer to the substrate and hence the functional layers 100, 150 are provided with protective layer 70, 71, 90, 91. FIG. 2B illustrates embodiments of the present invention where the stack of thin layers comprises the TiN functional layer 50 as being sandwiched between the two silver functional layers 100, 150 that are provided with protective layer 70, 71, 90, 91. The protective layers are chosen from metal layers based on a metal or a metal alloy or metal nitride layers of one or more elements chosen from titanium, nickel, chromium, niobium, zirconium, silica and aluminum such as Ti, Nb, NbN, NiCr, Zr, SiAl. When these protective layers are deposited in metallic or nitrided form, these layers may undergo partial or total oxidation according to their thickness and the nature of the layers which surround them, for example, at the time of deposition of the next layer or by oxidation in contact with the underlying layer. The protective layers are preferably chosen from metal layers, especially of a nickel-chromium (NiCr) alloy. Each protective layer has a physical thickness ranging between 0.1 nm and 3.0 nm. The protective layers, although deposited in metallic form and presented as being metal layers, are in practice oxidized layers because their primary function is to oxidize during the deposition of the stack in order to protect the functional layer. A protective layer is however sometimes interposed between one or each dielectric coating and the functional silver layer, the protective layer disposed under the functional layer towards the substrate protects it during a possible heat treatment at high temperature, the bending type and and/ or quenching and the protective layer disposed on the functional layer opposite the substrate protects this layer from possible degradation during the deposition of the upper dielectric coating and during a possible heat treatment at high temperature, such as bending and/ or quenching. According to the alternate optional embodiments of the present invention, a blocker layers are provided below and/or above the titanium nitride functional layer. In embodiments where the blocker layer is provided, the blocker layer comprises of a material selected from NiCr, Ti, Nb, NbN, Zr or SiAl. All the functional layers of the preset invention are each arranged between two dielectric coatings. The stack of thin layer of the invention is provided on at least one of the faces of the transparent substrate. By "coating" in the sense of the present invention, it should be understood that there may be a single layer or several layers of different materials inside the coating. Hence it should be understood that the thickness of the dielectric coating corresponds to the sum of the individual thicknesses of the layer(s) constituting the coating. The sum of the total optical thicknesses (nd, calculated @ 480nm) of the dielectric coatings 40, 60 ranges between 120 nm to 700 nm. The dielectric coatings 20 closest to the transparent substrate 10 and the dielectric coating 80 farthest from the transparent substrate each have a total optical thickness (nd, calculted @480nm) ranging between 20 nm and 300 nm. By "dielectric layer" in the sense of the present invention, it should be understood that from the point of view of its nature, the material is "non-metallic", that is to say is not a metal. In the context of the invention, this term designates a material having an n / k ratio over the entire visible wavelength range (from 380 nm to 780 nm) equal to or greater than 5. The dielectric layers of the coatings have the following characteristics alone or in combination: - they are deposited by magnetic field assisted sputtering, - they are chosen from oxides or nitrides or oxynitrides of one or more elements chosen from titanium, silicon, aluminum, zirconium, tin, niobium and zinc or their combinations thereof, - they have a physical thickness of up to 140 nm, preferably between 1 nm and 140 nm and most preferably between 10 nm and 140 nm. The dielectric layers may have a barrier function. The term barrier dielectric layers (hereinafter barrier layer) is understood to mean a layer made of a material capable of impeding the diffusion of oxygen and water at high temperature, originating from the ambient atmosphere or from the substrate. transparent, towards the functional layer. Such dielectric layers are chosen from the layers: - based on silicon and / or aluminum compounds chosen from oxides such as SiO ₂ , nitrides such as silicon nitride Si ₃ N ₄ and aluminum nitrides AIN, and oxynitrides SiOxNy, optionally doped with at least one other element, - based on zinc oxide and tin, - based on titanium oxide. The dielectric layers may also be so-called layers of wetting layers. By wetting layer is meant a layer of a material capable of stabilizing the interface with the functional layer. These wetting layers are generally based on zinc oxide or their derivatives. The zinc oxide layer may be optionally doped with at least one other element, such as aluminum or tin. The dielectric coating in few embodiments of the present invention comprise of at least one dielectric layer with barrier function and at least one dielectric layer as wetting layer. The dielectric layers can also be chosen according to their refractive index. One or more dielectric coatings, according to a few embodiments of the present invention further comprise a layer of absorber material. In such embodiments, the layer having the absorber material is in contact and in between two dielectric layers of one or more dielectric coatings. Such an absorber layer may comprise Nb, Zr, NbZr, NiCr, Ni, Cr, Si, Mn, Mo, Pd, Ta, W, In, Sn, InSn, Cu, Al, Zn, V, stainless steel, or their nitrides, oxides or oxynitrides. Thickness of such absorbent layer is in the range of 0.5 nm and 5 nm. The position of the absorber layer sandwiched between the dielectric layers of a dielectric coating provides for a better control over reflection values both in the external glass side and the internal coating side. Further this configuration of the absorber layer provides for achieving a wide range of reflection colors while maintaining the desired levels of reflection. According to one embodiment of the present invention illustrated in FIG.1, the dielectric coating 20 comprising the dielectric layer 21 based on silicon nitride is located directly in contact with the transparent substrate below the functional layer 50 based on titanium nitride; the dielectric coating 40 comprising the dielectric layer 41 based on silicon nitride is located directly above and in contact with the functional layer 50 based on titanium nitride; the dielectric coating 60 comprising the dielectric layer 61 based on silicon nitride is located above the functional layer 100 based on silver or silver containing metal alloy; the dielectric coating 80 comprising dielectric layer 81 based on silicon nitride is located above functional layer 150 based on silver or silver containing metal alloy. According to another embodiment of the present invention illustrated in FIG. 2A, the dielectric coating 20 comprising the dielectric layer 21 based on silicon nitride is located directly in contact with the transparent substrate below the functional layer 50 based on titanium nitride; the dielectric coating 40 comprising the dielectric layer 41 based on zinc oxide and dielectric layer 42 based on silicon nitride is located directly above and in contact with the functional layer 50 based on titanium nitride; the dielectric coating 60 comprising the dielectric layer 61 based on silicon nitride and dielectric layer 62 based on zinc oxide is located above the functional layer 100 based on silver or silver containing metal alloy; the dielectric coating 80 comprising the dielectric layer 81 based on zinc oxide and dielectric layer 82 based on silicon nitride is located above functional layer 150 based on silver or silver containing metal alloy. According to yet another embodiment of the present invention illustrated in FIG. 2B, the dielectric coating 20 comprising the dielectric layer 21 based on silicon nitride and dielectric layer 22 based on zinc oxide is located directly in contact with the transparent substrate below the functional layer 100 based on silver or silver containing metal alloy; the dielectric coating 40 comprising the dielectric layer 41 based on zinc oxide and dielectric layer 42 based on silicon nitride is located above the functional layer 100 based on silver or silver containing metal alloy; the dielectric coating 60 comprising the dielectric layer 61 based on silicon nitride and dielectric layer 62 based on zinc oxide is located above the functional layer 50 based on titanium nitride; the dielectric coating 80 comprising the dielectric layer 81 based on zinc oxide and dielectric layer 82 based on silicon nitride is located above functional layer 150 based on silver or silver containing metal alloy. The stack of thin layers may optionally comprise an overcoat layer 200, as shown in FIG. 2A and FIG. 2B. The overcoat layer is preferably the last layer of the stack, that is to say the layer furthest from the substrate coated with the stack (before heat treatment). These layers generally have a thickness of between 0.5 and 10 nm, preferably 0.5 nm and 5 nm. This overcoat layer may be chosen from a layer comprising titanium or zirconium, or these metals being in metallic, oxidized or nitrided form (partially or wholly). According to one embodiment, the overcoat layer is based on titanium zirconium oxide and / or nitride, preferably based on titanium zirconium nitride. The transparent substrates according to the invention are preferably in a mineral rigid material, such as glass, or organic based on polymers (or polymer). The substrate is preferably glass or glass-ceramic sheet. The substrate is preferably transparent, colorless (it is then a clear or extra-clear glass) or colored, for example blue, gray or bronze. The glass is preferably of the silico-soda-lime type, but it may also be of borosilicate or alumino- borosilicate type glass. According to a preferred embodiment, the substrate is made of glass, in particular silico-soda-lime or polymeric organic material. 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, especially between 2 and 8 mm, or even between 4 and 6 mm. The substrate may be flat or curved, or even flexible. The invention relates to a method for preparing a material comprising a transparent substrate coated with a thin film stack deposited by cathodic sputtering possibly assisted by a magnetic field, the method comprises the following sequence of steps: first dielectric coating comprising at least one dielectric layer is deposited on the transparent substrate, a first functional layer based on titanium nitride is then deposited, a second dielectric coating comprising at least one dielectric layer is deposited on titanium nitride layer, a second functional layer based on silver or silver-containing metal alloy is then deposited followed by deposition of the third dielectric coating comprising at least one dielectric layer; a third functional layer based on silver or silver-containing metal alloy is then deposited over the third dielectric coating and a fourth dielectric coating comprising at least one dielectric layer is deposited atop the third functional layer, such a thin film stack according to one embodiment of the present invention is illustrated in FIG.3A. The invention also relates to a method for preparing a material comprising a transparent substrate coated with a thin film stack deposited by cathodic sputtering possibly assisted by a magnetic field, the method comprises the following sequence of steps: first dielectric coating comprising at least one dielectric layer is deposited on the transparent substrate, a first functional layer based on silver or silver-containing metal alloy is then deposited, a second dielectric coating comprising at least one dielectric layer is deposited on silver layer, a second functional layer based on titanium nitride is then deposited followed by deposition of the third dielectric coating comprising at least one dielectric layer; a third functional layer based on silver or silver-containing metal alloy is then deposited over the third dielectric coating and a fourth dielectric coating comprising at least one dielectric layer is deposited atop the third functional layer, such a thin film stack according to one embodiment of the present invention is illustrated in FIG.3B. Within the meaning of the present invention, the label “first”, “second”, “third” for the functional layers and/ or 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 next one moving away 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. In a still further alternative embodiment, the solar control glass article 101 is provided with a temporary protective coating conventionally known in the art in order as the furthest layer from the substrate to protect the underlying stack of thin layers during heat treatment. As is known from the conventional processes this temporary protective layer is burned off during the heat treatment. The invention also relates to a glazing unit comprising at least one material according to the invention. The glazing may be in the form of monolithic glazing or single glazing, laminated glazing or multiple glazing. A monolithic glazing has 2 faces, the face 1 is outside the building and therefore constitutes the outer wall of the glazing, the face 2 is inside the building and therefore constitutes the inner wall of the glazing. A double glazing has 4 faces, the face 1 is outside the building and therefore constitutes the outer wall of the glazing, the face 4 is inside the building and therefore constitutes the inner wall of the glazing, the faces 2 and 3 being inside the double glazing. 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 metallic layer. 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 3 of the glazing being the outermost face of the glazing, as is customary. The glazing is preferably chosen from multiple glazings, in particular a double- glazing unit or a triple-glazing unit, comprising at least one material according to the invention and at least one second substrate, the material and the second substrate being separated by at least one intermediate gas, said glazing providing a separation between an outer space and an interior space. These double glazings advantageously have: - visible light transmission ranging between 20% to 65%, and / or - high selectivity greater than 1.8, more preferably greater than 2.0, and / or - glass side reflection (Rg) less than 25%, and / or - coating side reflection (Rc) less than 20%. These windows are mounted on a building or a vehicle. 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, a tempering and/or a bending. 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 curved and/or tempered. In the case of a multiple 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. 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. The glazing according to the invention, used in a multiple glazing e.g., a double glazing unit, has internal and external reflection colors that is not too dull at the same time is not too reflective. These two features aid in visual comfort for people facing the interior and exterior of the glazing. According to a particular exemplary embodiment of the present invention, a coated solar control glass article 101 having the stack of thin layers comprises starting from the glass substrate 10, as illustrated in FIG.3A: a first dielectric layer 21 made of silicon nitride; a functional layer 50 based on TiN _x ; a second dielectric coating 40 comprising a dielectric layer 41 made of silicon nitride and dielectric layer 42 zinc oxide; a protective layer 70 made of Ni and Cr; a functional layer 100 based on silver; a protective layer 71 made of Ni and Cr; a third dielectric coating 60 comprising a dielectric layer 61 made of zinc oxide, a dielectric layer 62 made of silicon nitride, a dielectric layer 63 made of tin zinc oxide and a dielectric layer 64 made of zinc oxide; a protective layer 90 made of Ni and Cr; a functional layer 150 based on silver; a protective layer 91 made of Ni and Cr; a fourth dielectric coating 80 comprising a dielectric layer 81 made of zinc oxide and dielectric layer 82 made of silicon nitride; and optionally one overcoat layer 200 made of TiZrN _x . According to another particular exemplary embodiment of the present invention, a coated solar control glass article 101 having the stack of thin layers comprises starting from the glass substrate 10, as illustrated in FIG.3B: a first dielectric coating 20 comprising dielectric layer 21 made of silicon nitride and dielectric layer 22 made of zinc oxide; a protective layer 70 made of Ni and Cr; a functional layer 100 based on silver; a protective layer 71 made of Ni and Cr; a second dielectric coating 40 comprising a dielectric layer 41 made of zinc oxide and dielectric layer 42 made of silicon nitride; a functional layer 50 based on TiN _x ; a third dielectric coating 60 comprising a dielectric layer 61 made of silicon nitride, a dielectric layer 62 made of tin zinc oxide and a dielectric layer 63 made of zinc oxide; a protective layer 90 made of Ni and Cr; a functional layer 150 based on silver; a protective layer 91 made of Ni and Cr; a fourth dielectric coating 80 comprising a dielectric layer 81 made of zinc oxide and dielectric layer 82 made of silicon nitride; and optionally one overcoat layer 200 made of TiZrN _x . Examples: Example 1: The following example illustrate the present invention. Preparation of the Substrates: Stack of thin layers and Heat Treatments Stack 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: two functional layers are layers of silver (Ag), another functional layer is a layer of titanium nitride (TiN _x ), the protective layers are metallic layers made of nickel-chromium alloy (NiCr), the dielectric barrier layers are based on silicon nitride (Si ₃ N ₄ ), the dielectric wetting layers are based on zinc oxide (ZnO) and/or tin zinc oxide (SNZnO) the overcoat layer is made of titanium zirconium oxide (TiZrNx). 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), according to one embodiment of the present invention. The “Ref.” numbers correspond to the references from FIG.3A. Table 2 lists 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), according to another embodiment of the present invention. The “Ref.” numbers correspond to the references from FIG.3B. Table 1: Stack of thin layers – Inventive Samples TiZrNx 200 5 5 5 5 Si ₃ N ₄ 82 34.1 33.4 34.5 25.9 ZnO _x 81 6 6 6 6 NiCr 91 0.2 0.2 0.2 0.2 Ag 150 23.1 21.7 20.2 21.8 NiCr 90 0.2 0.2 0.2 0.2 ZnO _x 64 6 6 6 6 SnZnO 63 20 13.3 20.0 20.0 Si ₃ N ₄ 62 43.2 48.2 42.6 49.2 ZnO _x 61 6 6 6 6 NiCr 71 0.2 0.2 0.2 0.2 Ag 100 18.5 17.8 15.3 12.8 NiCr 70 0.2 0.2 0.2 0.2 ZnO _x 42 6 6 6 6 Si ₃ N ₄ 41 62.1 69.3 62.4 35.3 TiN _x 50 35.5 22.8 17.0 4.2 Si ₃ N ₄ 21 Glass 10 Table 2: Stack of thin layers – Inventive Samples Example 2 Comparative samples 1, 2 & 3 were also prepared using solar control product available in the market place comprising double silver layers that exhibit a selectivity of <1.85. Solar Control and Optical Properties Table 3 lists the main optical characteristics measured when the glazings are part of double glazing having a 6/15/6 structure: 6 mm glass/15 mm interlayer space filled with 90% argon and 10% air/6 mm glass, the stack being positioned on face 2 (face 1 of the glazing being the outermost face of the glazing, as is customary). For these double glazings: T _L 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; R _ext indicates: the light reflection in the visible region in %, measured according to the illuminant D65 Obs 2 on the side of the outermost face, face 1; a*R _ext and b*R _ext indicate the a* and b* colors in reflection in the L*a*b* system measured according to the illuminant D65 Obs 2 on the side of the outermost face and thus measured perpendicularly to the glazing; R _int indicates: the light reflection in the visible region in %, measured according to the illuminant D65 Obs 2 on the side of the internal face, face 4; a*R _int and b*R _int indicate the a* and b* colors in reflection in the L*a*b* system measured according to the illuminant D65 Obs 2 on the side of the internal face and thus measured perpendicularly to the glazing. The colorimetric values at an angle a*g60° and b*g60° are measured on single glazing under an incidence of 60° is shown in Table 4. This takes into account the stability of the colors at an angle. Table 3: Optical & Solar Control Properties Table 4: Calorimetric Values The samples according to the present invention all achieve high selectivity values >2.0. The inventive samples are particularly advantageous since they have, in addition to a high selectivity, low external reflection, particularly less than 20%, low internal reflection, particularly less than 20%. Although, comparative example 2 exhibited a selectivity of 1.82, the internal reflection of the glazing is undesirable being >20%. The proposed invention therefore makes it possible to achieve combined desired solar performance, optical and aesthetic properties. Comparative samples 1, 2 & 3 are particularly useful to demonstrate how the inventive samples prepared according to the teachings of the present invention have improved performance (selectivity) as compared to the comparative samples. Thus the inventive sample is able to achieve a high selectivity without any additional silver layers. Industrial Applicability The glazing described in the present disclosure finds application as a glazed element in building. In this application case, the glazing may form a double or triple glazing with the coating side of the glass arranged facing the closed space inside the multiple glazing. 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 according to the invention is, however, particularly useful when the multilayer stack is facing the outer environment, whether it is an insulated glazing or laminated glazing, but also optionally a multiple glazing. The glazing may also be enameled. The glazing of the present disclosure can also be annealed, strengthened, toughened, tempered or curved and/or bent. The tempered glazing can also be used in building wall cladding panel of curtain walling for interior applications. Further an 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: GLAZING COMPRISING A STACK OF THIN LAYERS HAVING TWO FUNCTIONAL LAYERS BASED ON SILVER AND TITANIUM NITRIDE Glass Substrate 20 First Dielectric Coating 21 Dielectric Layers 50, 100, 150 Functional Layers 40 Second Dielectric Coating 41 Dielectric Layers 70, 71 Protective Layers 91, 92 Protective Layers 60 Second Dielectric Coating 61 Dielectric Layers 80 Overcoat Layer