EP4100191A1

EP4100191A1 - Coated article comprising protective overcoat layers made from titanium zirconium hafnium nitride and carbon

Info

Publication number: EP4100191A1
Application number: EP21751338.1A
Authority: EP
Inventors: Priyesh DHANDHARIA; Yann COHIN; Soumyadeep MISRA
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-02-04
Filing date: 2021-02-03
Publication date: 2022-12-14
Also published as: PH12022551926A1; EP4100191A4; MX2022009556A; BR112022015397A2; CO2022012535A2; WO2021156889A1; ZA202208326B

Abstract

A coated solar control article including a stack of layers acting on solar radiation provided on the surface of the glass substrate comprising at least one functional layer and one or more protective overcoat layers deposited over at least a part of the functional layer is disclosed. The protective overcoat layers comprise TiZrHf or TiZrHfN with or without carbon and contribute to scratch resistivity of the coated article especially before heat treatment for up to 5N in Erichsen Scratch testing. The functional layers are free of silver and silver containing metal alloys. The coated solar control article exhibits enhanced durability in terms of scratch resistivity while retaining the original optical characteristics of the coated solar control article.

Description

COATED ARTICLE COMPRISING PROTECTIVE OVERCOAT LAYERS MADE FROM TITANIUM ZIRCONIUM HAFNIUM NITRIDE AND

CARBON

Technical Field The present disclosure relates, in general to a coated glass article including a stack of layers acting on solar radiation, and more specifically to a coated article provided with one or more protective overcoats comprising titanium zirconium hafnium or its nitride with or without carbon overlying the stack of layers acting on solar radiation. Background

Solar control glass has a large part to play in the future of construction, as external temperatures will continue to rise and so will the expectations of comfort. Solar control coatings provided with a layer stack of glass/ SEN^/NiCr/SENi and glass/SislNU/Nb/SislN are known in the art, where the metallic NiCr layer and Nb layer are the sole infrared (IR) absorbing layers, respectively in the coating stacks. These infrared (IR) absorbing layers can be nitrided. For example, see U.S. Patent No. 5,837,108; U.S. Publication No. 2002- 0192473; U.S. Patent No. 6,994,910 and PCT Publication No. W02005- 105687.

Unfortunately, while such layer stacks provide efficient solar control, they sometimes are lacking in terms of mechanical performance such as scratch resistance. Susceptibility to scratches are particularly troublesome in environments such as construction sites, where the layer stack on glazing’s once mounted face the interior of the buildings. But nevertheless are prone to deposition of construction debris which are often cleaned with sharp objects/ harsh chemicals that make the coated surface vulnerable to scratches. Another constraint is imposed progressively: when the glazing may have to undergo one or more heat treatments, such as bending if we want to shape them (window/ application in automotive industry), a tempering or annealing if they are to be stronger / less dangerous in case of shocks. Although the existing silicon nitride layer of such coated articles is hard, it has been found to have a tendency to scratch due to high surface friction and roughness, and such scratches can open other layer(s) to chemical attacks (i.e., corrosion). Thus, it can be seen that even though silicon nitride provides for good optical characteristics and is hard, it has chemical and/or mechanical durability issues.

There are existing prior art documents that teach providing protective overcoat layers over a solar control coating or the like in order to increase durability. However, in some instances, these overcoats may experience stress as-deposited, or may experience stress upon being heated, during heat treating, heat bending, thermal tempering, and the like. In certain cases, the stress from these overcoats may negatively affect the overall durability of the coating. Therefore, it may sometimes be desirable to provide a window unit or other coated glass articles with a more durable overcoat.

Despite the presence of these protective overcoat layers, scratches appear very frequently on the stack. Once these scratches are created on a substrate, their visibility increases considerably when the substrate is subjected to a heat treatment of the toughening type. Susceptibility to scratches is detrimental in terms of aesthetics and production yield. This can cause abnormally high rejection rate, most particularly in the case where these materials are curved windows/quenched.

It is known to use overcoat layers comprising zirconium oxide (ZrOx), titanium zirconium oxide (TiZrOx), titanium oxide (TiOx) or their nitrides. For example, see U.S. Publication No. 2017-355639; U.S. Patent No. 8,389,121 and U.S. Publication No. US2017-355639. Further, protective overcoat layers comprising other materials are provided in U.S. Publication No. US2018-208503; U.S. Patent No. 8,043,707 and U.S. Patent No. 8,389,121. Such overcoat layers are being used for both silver-based and non- silver-based layer stacks. However, as coated articles with silver-based layer stacks are generally used in double glazing configurations, the role of overcoat layers in these products are limited to preventing scratches during the handling process alone. Whereas coated articles comprising non- silver-based layer stacks are widely used in single glazed units and hence necessitate overcoat layers to resist scratches not only during handling but also during the life of the coated article (where they are generally used in window & facade applications) due to their exposure to external conditions and susceptibility to harsher mechanical and chemical interaction.

Further these overcoat layers need to be chosen also based on whether the resultant coated glass product is to be annealed or tempered. While it is true that the art describes certain overcoat layers for annealed and certain others for tempered products, a protective overcoat that is effective across both the variants of coated articles will be advantageous.

In view of the above, it will be appreciated that there exists a need in the art for a layer and/or overcoat that may be deposited over a solar control stack in order to increase the overall mechanical performance such as scratch resistance of the coated article, but which still is capable of acceptable solar control (e.g., blocking a reasonable amount of IR and/or UV radiation) and/or heat treatability with a fairly low DE* value (glass side and coating side reflectance and/or transmission). It is a purpose of this disclosure to eliminate disadvantages of the prior art discussed above and fulfill the needs of an ideal protective overcoat layers whose detail will become apparent to the skilled artisan once given the following disclosure.

Certain example embodiments of this invention relate to a coated article that is durable and has an increased thermal stability and mechanical performance while retaining the optical characteristics of the article. Certain example embodiments of this invention also relate to a method of making the same. The disclosure teaches the use of protective overcoat layers comprising titanium zirconium hafnium or its nitride with or without carbon. The protective overcoat, according to certain embodiments of the present disclosure is double-layered comprising a layer of titanium zirconium hafnium or titanium zirconium hafnium nitride provided directly under and in contact with another layer of carbon. The protective overcoat, according to certain other embodiments of the present disclosure is a single layer comprising titanium zirconium hafnium or titanium zirconium hafnium nitride optionally doped with carbon. Summary of the Disclosure

In one aspect of the present disclosure, a coated article including a stack of layers acting on solar radiation provided on the surface of the glass substrate comprising at least one functional layer and one or more protective overcoat layers deposited over at least a part of the functional layers is disclosed. The functional layers are free of silver and silver containing metal alloys and the protective overcoat layers comprise of TiZrHf or TiZrHfN with or without carbon. The protective overcoat layers contribute to scratch resistivity of the coated article before heat treatment for up to 5N in Erichsen scratch testing.

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 coated solar control glass article, according to one embodiment of the present disclosure;

FIG. 2 illustrates a coated solar control glass article sample A along with a comparative sample B, according to another embodiment of the present disclosure; and

FIG. 3 illustrates a coated solar control glass article sample C according to yet another embodiment of the present disclosure along with a comparative sample D.

Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.

Detailed 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 coated solar control glass article comprising protective overcoat layers made from titanium zirconium hafnium or its nitride with or without carbon.

A coated solar control glass article 100 according to one embodiment of the present disclosure is illustrated in FIG. 1. In this embodiment the coated solar control glass article 100 is provided with a layer stack 110 which includes a double-layered protective overcoat 120 comprising a layer of titanium zirconium hafnium (TiZrHf) or titanium zirconium hafnium nitride (TiZrHfN_x) overlaid with a layer comprising carbon. The double-layered protective overcoat 120 is provided over a plurality of underlying layers which include a functional layer i.e., an infrared (IR) absorbing layer 112 (e.g., Nb, Ta, Zr, Ni or their alloys or nitrides or the like) sandwiched between at least one overlayer 113 and one underlayer 111. In the double-layered protective overcoat 120 of TiZrHf/ TiZrHfN_x & carbon, the TiZrHf/ TiZrHfN_x provides mechanical and chemical durability (e.g., scratch resistance and resistance to corrosion from alkaline solutions and the like) and the overlying carbon layer helps in reducing the friction before tempering and burns off while tempering.

Thus the carbon layer, in certain embodiments of the present disclosure enables the coated solar control glass article 100 to have a AE*_Rg; AE*_RC & DE*t value (glass side reflective and/or transmission) of no greater than 3.5, due to heat treatment and abrasion tests up to 2000 cycles. Thus it has surprisingly been found that the combination of TiZrHf/ TiZrHfN_x & carbon in a double-layered protective overcoat allows the coated solar control glass article 100 which is otherwise mechanically and chemically susceptible, to have desired optical characteristics such as transmission and/or reflectance, to be heat treatable and/or bendable in a commercially acceptable manner and have significantly improved mechanical and chemical resistivity. It has also been surprisingly found that the combination of TiZrHf/ TiZrHfN_x & carbon in a double-layered protective overcoat significantly improves the coated solar control glass article’s 100 resistance to damages, thereby improving its storage life. FIG. 1 illustrates a side cross-sectional view of the coated solar control glass article 100. The coated solar control glass article 100 includes a glass substrate 101 which can be clear, green, bronze, grey, blue or blue-green substrate measuring about 1.0 to 12.0 mm thick; at least one underlayer 112 comprising nitride or oxide or oxynitride or aluminum oxynitirde of silicon or aluminum or a mixture of at least two of these compounds provided above the glass substrate 101; at least one functional layer i.e., IR absorbing layer 112 comprising at least one metal or metal alloy or nitride of niobium, tantalum, zirconium or nickel arranged above the underlayer 111 and at least one over layer 113 comprising nitride or oxide or oxynitride or aluminum oxynitirde of silicon or aluminum or a mixture of at least two of these compounds arranged above the IR absorbing layer 112. The layer stack 110 of the coated solar control glass article 100 is overlaid and protected by the double-layered protective overcoat 120. In certain embodiments of the present disclosure, the double-layered protective overcoat 120 comprises of a layer containing TiZrHf or TiZrHfN_x 114 arranged above the IR absorbing layer 112 and another layer of carbon 115 overlaid and in direct contact with the layer containing TiZrHf or TiZrHfN_x. The carbon layer 115 is farthest and the outermost layer of the coated solar control glass article 100.

In one embodiment of the present disclosure, the underlayer 111 and over layer 113 are typically the dielectric layers of the layer stack 110 and comprise of either silicon nitride, silicon oxide, silicon oxynitride or silicon aluminum oxynitride or aluminum nitride, aluminum oxide, aluminum oxynitride or aluminum doped silicon nitride. In a preferred aspect of the present embodiment, the underlayer 111 and overlayer 113 dielectrics may essentially comprise of silicon nitride. It should be noted that the terms “oxide” and “nitirde” as used herein includes various stoichiometries.

Thus the overall coating of the coated solar control glass article 100 includes layers 111 - 115. Layers 111 - 115 may be deposited through magnetron sputtering or other types of sputtering or other suitable techniques. Other layers may be provided between illustrated layers in certain other embodiments of the present disclosure. In still other embodiments of the present disclosure, certain illustrated layers may be deleted. Thus, for example, the layer system and layers thereof shown in FIG. 1 are considered "on" the substrate 101 even when other layer(s) (not shown) are provided therebetween. Also, more than one IR absorbing layer may be provided in certain example embodiments of the present disclosure.

FIG. 2 illustrates two samples of coated solar control glass articles for the purpose of comparison. The sample (A) is made up of the following stack: glass/ Si₃N₄/NbN/Si₃N₄/TiZrHfN/C thereby including a double-layered protective overcoat according to the embodiment of the present disclosure illustrated in FIG. 1. For the purposes of comparison sample (B) is made up of the following stack: glass/ Si₃N₄/NbN/Si₃N₄, without the double-layered protective overcoat.

Sample (A) demonstrated a significant improvement in scratch resistance compared to the sample (B). Particularly, before the heat treatment of samples (A) and (B), sample (A) could not be significantly scratched with a Erichsen Scratch hardness tester. Post the heat treatment of sample (A), the sample’s resistance to scratchability was found to be slightly depleted, yet the scratch resistivity of sample (A) post heat treatment was found to be greater than that of sample (B). Sample (B) showed some level of scratches post heat treatment which were visible in reflection. Thus the presence of the protective overcoat layers in sample (A) has contributed to (i) the scratch resistivity of the sample (A) before heat treatment and (ii) enhanced scratch resistivity of the sample (A) post heat treatment. Sample (B) was not found to be resistant to scratches before or after the heat treatment. Therefore, the use of the protective overcoat layers of the present disclosure is advantageous for products which are not heat treated and also to products which undergo heat treatment.

In another embodiment of the present disclosure, the coated solar control glass article may comprise a single-layered protective overcoat 130 comprising TiZrHf or TiZrHfN. For example, the coated solar control glass article, according to this embodiment is made up of the following stack: glass/ Si₃N₄/NbN/Si₃N₄/TiZrF[fN. Similarly, a comparison of scratch resistance of a sample made of stack: Si₃N₄/NbN/Si₃N₄/TiZrHfN (sample (C)) with another sample made of stack: Si₃N₄/NbN/Si₃N₄ (Sample (D)) illustrated in FIG. 3, showed that the former sample (C) showed increased resistance to scratches when compared to sample (D) owing to the presence of the single-layered protective overcoat comprising TiZrHfN. However, it is to be noted that the scratch resistivity rendered to the sample C from the use of the single-layered protective overcoat is almost as equivalent (if not less) to the scratch resistivity rendered by the use of the double-layered protective overcoat to sample (A).

In order to improve the scratch resistance, the conventional solutions use "hard" layers that comprise of materials having a high hardness such as titanium oxide or the DLC (Diamond-like carbon) type amorphous carbon. The protective overcoat layer according to the present disclosure is clearly distinguished from these layers known as "hard". The mechanism behind obtaining a good protection to scratch lies not on the hardness of the layer but rather on lowering the coefficient of friction between the underlying layer and the protective overcoat layers. The protective overcoat layers, according to the present disclosure perform the function of antifriction layer. This effect is easily observed by rubbing with a cloth or paper slightly on the surface of the sample B provided with a stack of layers. In the absence of the protective overcoat layers according to the present disclosure, the upper surface of the stack was penetrated. Whereas, in sample A including the protective overcoat layers, the surface is "smooth". The use of metallic alloys along with a polymeric compound such as carbon is advantageous because this improves the friction phenomena that is crucial during the steps of transportation.

Indeed, the coated glass articles are in general, transported with the aid of glass harp carts. These harp carts comprise metallic strings coated with a polymeric sheath which are held against the coated glass articles. The contacts between these strings and the stack of layers, which may occur during insertion of the coated glass articles and/or during their transport, represent one of the principal causes of the generation of scratches. The tribological friction coefficient of the indenter metallic alloy/ layers of the stack is lowered when the stack includes protective overcoat layers according to the present disclosure. The improvement of the scratch resistance appears to be able to be connected to this reduction in the coefficient of friction.

The protective overcoat layer 115 is deposited by reactive sputtering from a target comprising at least 70% to 100% carbon. The protective overcoat layer 114 is deposited by reactive sputtering from a target comprising at least 60% to 90%, and more preferably 70% to 80% of Ti; at least 5% to 40% and more preferably 10% to 30% of Zr; at least 0.1% to 30% and more preferably 0.1% to 10% of Hf. In embodiments of the present disclosure that comprise a protective overcoat layer 114 comprising TiZrHfN, the atomic percentage of nitrogen present in the layer varies from 0.1 % to 50% .

In still another embodiment of the present disclosure, the overcoat layers may comprise alternating layers of TiZrHfN/Carbon. For example, in one example alternative embodiment of the present disclosure, the overcoat layers may comprise the following layers going away from the glass substrate: T iZrHfN/Carbon/ T iZrHfN/Carbon/ T iZrHfN/Carbon (where the T iZrHfN may be non-nitrided to be a metallic layer of TiZrHf).

While FIG. 1 illustrates a coated solar control glass article according to an embodiment of this invention in monolithic form, coated articles according to other embodiments of the present disclosure may comprise IG (insulating glass) window units provided as double and triple glazed units. In IG embodiments, coatings from FIG. 1 may be provided on the inner wall of the outer substrate of the IG unit, and/or on the inner wall of the inner substrate, or in any other suitable location.

Various thicknesses may be used consistent with one or more of the embodiments discussed. However, for purposes of example only, example thicknesses for the respective layers 111 - 115 on the glass substrate 101 are provided in the following table:

Table 1: Thickness Ranges of Coated Solar Control Glass Article 100 in FIG. 1

The thicknesses of the overcoat layers also vary depending on whether they as used as a single-layered protective overcoat or as double-layered protective overcoat. While being used as a single-layered protective overcoat, the thickness of the TiZrHf or TiZrHfN layer ranges between 0.5 to 5 nm. Likewise, the thickness of the TiZrHf or TiZrHfN layer ranges between 0.5 to 5 nm and that of carbon ranges between 0.1 to 5 nm while being used as a double-layered protective overcoat. Unless otherwise indicated, the thicknesses mentioned in the present disclosure are physical thicknesses and the layers are thin films. The term thin layer, a layer having a thickness of between 0.1 nm and 100 nm.

Throughout the description the glass substrate according to the present disclosure is considered to be placed horizontally. The stack of thin layers is deposited above the glass substrate. The direction of the expressions "above" "below" and "lower" and "upper" and should be considered with respect to this orientation. In the absence of specific stipulation, the expressions "above" and "below" does not necessarily mean that two layers and/or coatings are placed in contact with one another. When it is specified that a layer is deposited in "contact with" another layer or coating, this means that there cannot be one or more layers interposed between these two layers.

The functional layer 112 can be a metallic or a non-metallic layer completely free of silver and silver containing metal alloys. According to multiple embodiments of the present disclosure, the functional layer 112 is based on niobium, tantalum, zirconium, nickel. In specific embodiments, the functional layer 112 may be selected from the group consisting of niobium, niobium nitride, tantalum, zirconium, zirconium nitride or nickel chromium. The thickness of the functional layer ranges between 0.5 nm and 40 nm, preferably between lnm and 30 nm and more preferably between 1.5 nm and 25 nm. According to the embodiment described in, the functional layer 112 may comprise a single layer or more than one layer.

In all embodiments of the present disclosure, the functional layer 112 (one layer or more than one layer) are deposited between at least one overlayer and at least one underlayer. The overlayer and underlayer are generally the dielectric layers which make it possible to adjust the optical properties of the coated solar control glass article. These dielectric layers also make it possible to protect the functional layer from chemical and mechanical attacks. The overlayer and underlayer based on dielectric materials have a thickness greater than 10 nm, preferably between 10 and 80 nm and more preferably between 10 and 50 nm.

The overlayer and underlayer based on dielectric materials are deposited by sputtering assisted by a magnetic field. These layers’ act as barriers for the functional layer, protecting against the diffusion of oxygen and water at high temperatures and do a stabilizing function. The overlayer and underlayer are based on nitride or oxide or oxynitride or aluminum oxynitirde of silicon or aluminum or a mixture of at least two of these compounds.

The stack of layers acting on solar radiation therefore advantageously comprises at least one functional layer preferably free of silver, at least two coatings based on dielectric materials, each coating including at least one dielectric layer, so that each of the functional layer is disposed between two coatings based on dielectric materials. The dielectric layers may be located above and/or below of at least one functional layer or above and/or below of each of the functional layers and is either directly in contact with or is separated by additional underlayers and over layers.

According to one embodiment, the overlayer is below the protective overcoat layers, preferably, in contact with the protective overcoat layer 114. The protective overcoat layer 115 is preferably the last layer of the stack, i.e. the layer furthest away from the glass substrate coated with the stack of layers.

The additional underlayers and overlayers can comprise of the same material as that of the over layer 113 and underlayer 111 as described in the previous embodiment or can comprise of materials different from the layers 113 and 111. The purpose of additional underlayers and over layers is to protect the functional layer from possible degradation linked to the deposition of a coating based on dielectric materials and degradation as a result of heat treatment. According to one optional embodiment of the present disclosure, there can be at least one additional underlayer located underneath and in contact with the functional layer and at least one additional overlayer above and in direct contact with the functional layer. In a preferred embodiment the additional underlayer and additional overlayer can be metallic layers made of titanium. The thickness of each of the additional overlayer and additional underlayer directly sandwiching the functional layer can be at least 2 nm or at least 10 nm.

Therefore, the stack of layers acting on solar radiation according to one embodiment of the present disclosure comprises starting away from the glass substrate: a underlayer comprising a dielectric material optional additional underlayer at least one functional layer free of silver optional additional overlayer an overlayer comprising a dielectric material protective overcoat layer comprising TiZrHf or TiZrHfN protective overcoat layer comprising carbon

According to another embodiment of the present disclosure, the stack of layers acting on solar radiation comprises starting away from the glass substrate: a underlayer comprising a dielectric material at least one functional layer free of silver an overlayer comprising a dielectric material protective overcoat layer comprising TiZrHf or TiZrHfN protective overcoat layer comprising carbon

The coated solar control glass article according to the teachings of the present disclosure, can be annealed or can be intended to undergo thermal treatments at temperatures greater than 400 °C, preferably more than 500 °C or more preferably greater than 600 °C. The inclusion of a heat treatment or not depends entirely on the intended use of the coated solar control glass article. The properties of the coated solar control glass article demonstrated here, namely the scratch resistance, are independent of any thermal treatment. This means that the protective overcoat layers proposed by the present disclosure provide scratch resistance to coated solar control glass articles which are intended to be annealed, tempered, heat strengthened, toughened, hardened and / or curved or bent or laminated.

Traditionally used protective overcoat layer comprising titanium zirconium oxide when deposited above a layer stack comprising a functional layer free of silver or silver containing alloys provide scratch resistance to coated solar control glass articles if the glass articles are intended to be annealed. Whereas titanium zirconium oxide overcoat layer does not improve the scratch resistance of coated solar control glass articles which are intended to be thermally treated, for example, tempered. The above mentioned finding is true for protective overcoat layer comprising carbon, as the carbon layer is completely oxidized and burnt off during the thermal treatment of the glass article. Although the protective overcoat layer comprising titanium zirconium oxide and protective overcoat layer comprising carbon improve the scratch resistance of annealed glass articles, they do not improve the scratch resistance of thermally treated glass articles.

On the other hand, the protective overcoat layers proposed in the present disclosure improve the scratch resistance of coated solar control glass articles that are annealed or thermally treated.

The present disclosure also relates to a method of manufacturing a solar control coated glass articles provided with a stack of thin layers deposited by sputtering assisted by a magnetic field, the method comprising the steps of: depositing at least one underlayer based on dielectric material over the surface of the glass substrate; depositing at least one functional layer above the underlayer; depositing at least one overlayer based on dielectric material above the functional layer; depositing a protective overcoat layer comprising TiZrHf or TiZrHfN and optionally depositing a protective overcoat layer comprising carbon above the overlayer comprising TiZrHf or TiZrHfN. The method further includes the step of thermal treatment of the coated solar control glass article at temperatures greater than 400 °C, preferably greater than 500 °C and more preferably greater than 600 °C. The coated solar control coated glass article thus obtained can be used for the manufacture of a glazing for applications including but not limited to glass window or insulated glazing’s for buildings and laminated glazing for glass safety applications. In multiple embodiments, the coated solar control coated glass article can be tempered, annealed, enameled, laminated and/or bent. Examples Example 1

Different stack of thin layers according to the teachings of the present disclosure were sputtered over 4 mm glass substrates manufactured by Saint-Gobain India Private Limited. The specification of the multilayer coatings are as follows:

Table 1: Stack of Layers for Coated Solar Control Glass Articles Samples 2, 4 & 5 are prepared according to the teachings of the present disclosure with protective overcoat layer comprising TiZrHfN and samples 1 & 3 are comparative samples that do not include any protective overcoat layer. Optical and solar control properties of the above mentioned glass samples are summarized in Table 2.

Table 2: Optical & Solar Control Properties

R_ext=External reflection; a*G, b*G=a*, b* values measured on the external side, i.e., the glass side; Ri_nt=Internal reflection; a*C, b*C=a*, b* values measured on the internal side, i.e., the coating side

The light transmission of samples 1, 2, 3 & 4 are similar and comparable. The thickness of the protective overcoat layer TiZrHfN in samples 2, 4 & 5 have been engineered such that the optical properties of the samples 1 & 3 remain unchanged even after the inclusion of the protective overcoat layer TiZrHfN. Particularly the optical values of samples 1 & 2 and samples 3 & 4 can be seen to be similar.

Visible Scratch Resistance Testing

The visible scratch resistance is an important criterion for coated solar control glass articles. This visible scratch resistance provides mechanical resistance against scratches that can appear during cutting and edge grinding of glass that result in chipping off of edges and also against rough handling of samples. All the coated glass samples were observed for visible scratch in both annealed condition and post thermal treatment of the samples. Thus calculated scratch resistance of the samples are summarized in Table 3. Table 3: Scratch Resistance

Table 3 shows scratch force up to which scratches are not visible. For sample 4, in annealed form scratches are not visible till 5N force. Therefore, its scratch resistance is greater than 5N. In tempered form, scratches are visible after 2N, so its scratch resistance is less than 2N. Table 3 demonstrates that the protective overcoat layer when provided above a stack of layers comprising a functional layer that is free of silver (sample 4) provides much enhanced scratch resistance (both in annealed and tempered sample) than when provided above a stack of layers comprising a functional layer that comprises silver (sample 2). Further the above results also demonstrate that providing protective overcoat layer according to the teachings of the present disclosure above a functional layer that is free of silver is non-obvious from the prior art references that teach the use of TiZrHfN protective overcoat layer above the stack of layers comprising a silver functional layer.

This is because the scratch resistance shown by sample 5 is much less than that recorded by sample 4, when both the samples are provided with functional layer free of silver. Thus the deposition of TiZrHfN protective overcoat layer does not always improve the scratch resistance of the coated solar control glass articles. Since the thickness of the TiZrHfN layer is very less, the stress field generated during the scratch test will penetrate through the TiZrHfN layer and reach the functional layer and possibly the glass substrate as well. Therefore, the functional layer plays a key role in improving the scratch resistance of coated glass article. This is one of the reasons why the scratch resistance of sample 4 is more than the scratch resistance of sample 2.

To further demonstrate this effect, stack of layers comprising with a very thick niobium functional layer was deposited with TiZrHfN overcoat layer (sample 5). Owing to the increased thickness of the niobium layer, the load bearing capability of this sample is better than sample 2 but yet is not as good as that of sample 4. This clearly implies that addition of protective overcoat alone will not necessarily improve the scratch resistance as much as desired.

5 Comparative Examples Comparative Example 1

Different stack of thin layers according to the teachings of the present disclosure were sputtered over 4 mm glass substrates manufactured by Saint-Gobain India Private Limited. The specification of the multilayer coatings 10 are as follows:

Table 4: Stack of Layers for Coated Solar Control Glass Articles

Sample 6, 7, 8 & 9 are prepared according to the teaching of the present disclosure comprising the various proposed protective overcoat layers 15 TiZrHf, TiZrHfN and carbon. Comparative samples 1 & 2 are prepared as per teachings of the prior art.

Erichsen Scratch Test (EST):

The samples in table 4 were rotated in a circular manner on the machine against a sharp indenter with increasing load. It was observed that no 20 scratch could be seen on the samples 6, 7 & 8 and comparative sample 2 up to 5N. In another testing method variant, the sample in table 4 were then heat treated at a temperature of 650 °C after the Erichsen scratch test (EST TT). This step reveals the presence of any minor scratches that occurred during the test procedure. It was found that the scratch resistance of the samples remains unchanged. Thus the heating process has not impacted the scratch resistance of the samples.

In another experiment, the samples were first heat treated at a temperature of 650 °C and then subjected to the Erichsen scratch test procedure (TT EST). The scratch resistance of these annealed (EST), tempered samples after EST (EST TT) and tempered samples before EST (TT EST) are summarized in Table 5. The values in the table represent the maximum load that was withstand by the samples.

Table 5: Erichsen Scratch Test Results

While comparative sample 2 increases the scratch resistance of annealed samples, it does not improve the scratch resistance of tempered samples. The same is true for sample 6 provided with a carbon comprising protective overcoat layer. Whereas samples 7, 8 & 9 that comprise of protective overcoat layer comprising TiZrHfN with or without carbon improve the scratch resistance of samples in the annealed state as well as in the tempered state. Color Change Post Heat Treatment:

The color change of the samples in table 4 post the heat treatment (DE*) was measured and are summarized in table 6.

Table 6: Color Change

Rc=Coating side reflection; Rc=Glass side reflection; T=Transmission

As can be seen in the table above, DE* of less than up to 2 can be achieved using the single-layered protective overcoat layer TiZrHfN. Whereas DE* of less than up to 3.4 can be achieved using the double-layered protective overcoat layer comprising one layer of TiZrHfN and another layer of carbon.

Example 2

Thickness vs Scratch Resistance

The scratch resistance of coated solar control glass articles also depends on the thickness of the protective overcoat layer used above the stack of layers. The impact of varying thicknesses of TiZrHfN overcoat layer provided above coated glass articles on their scratch resistance is illustrated in Table 7. Samples shown in Table 7 are all provided with the following stack: Glass/ Si3N4/NbN/Si3N4. Scratch resistance values for annealed samples and tempered samples are presented. The optical characteristics of all samples were seen to be similar.

Table 7: Thickness of Overcoat Layers Vs Scratch Resistance

Industrial Applicability

The coated solar control glass articles 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 a single glazing or a laminated glazing, but also optionally a multiple glazing. The glazing may also be enameled.

The coated solar control glass articles of the present disclosure can also be annealed, strengthened, toughened, tempered or curved and/or bent. The extensive durability in terms of scratch resistivity of the coated solar control glass article provides for an extended life of the product.

The tempered coated solar control glass article can also be used in building wall cladding panel of curtain walling for interior applications. Further the tempered coated solar control glass article can also be used as a side window, rear window or sunroof for an automobile or other vehicle.

Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.

The specification and illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all of the elements and features of apparatus and systems that use the structures or methods described herein. Certain features, that are for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in a sub combination. Further, reference to values stated in ranges includes each and every value within that range. Many other embodiments may be apparent to skilled artisans only after reading this specification. Other embodiments may be used and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Accordingly, the disclosure is to be regarded as illustrative rather than restrictive.

The description in combination with the figures is provided to assist in understanding the teachings disclosed herein, is provided to assist in describing the teachings, and should not be interpreted as a limitation on the scope or applicability of the teachings. However, other teachings can certainly be used in this application.

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the use of "a" or "an" is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise. For example, when a single item is described herein, more than one item may be used in place of a single item. Similarly, where more than one item is described herein, a single item may be substituted for that more than one item.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, methods, and examples are illustrative only and not intended to be limiting. To the extent that certain details regarding specific materials and processing acts are not described, such details may include conventional approaches, which may be found in reference books and other sources within the manufacturing arts. While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

List of Elements

TITLE: COATED ARTICLE COMPRISING PROTECTIVE OVERCOAT LAYERS MADE FROM TITANIUM ZIRCONIUM HAFNIUM NITRIDE AND CARBON

100 Coated Solar Control Glass Article

101 Glass Substrate

110 Layer Stack

111 Underlayer

112 Functional Layer

113 Over layer

114 Layer Containing TiZrHf or TiZrHfN_x

115 Layer Containing Carbon

120 Double-layered Protective Overcoat 130 Single-layered Protective Overcoat

Claims

We claim,

1) A coated article including a stack of layers provided on the surface of the glass substrate, the stack of layers acting on solar radiation comprising: at least one functional layer and one or more protective overcoat layers deposited over at least a part of the functional layer, wherein the functional layers are free of silver and silver containing metal alloys; wherein the protective overcoat layers comprise TiZrHf or TiZrHfN with or without carbon and contribute to scratch resistivity of the coated article before heat treatment for up to 5N in Erichsen Scratch Testing.

2) The coated article as claimed in claim 1, wherein the protective overcoat layers comprise a layer of TiZrHf or TiZrHfN provided directly under and in contact with another layer of carbon.

3) The coated article as claimed in claim 1, wherein the protective overcoat layers comprise of TiZrHf or TiZrHfN possibly doped with carbon.

4) The coated article as claimed in claim 1, wherein the protective overcoat layers are deposited by reactive sputtering from a target comprising 70% to 80% of Ti, 10% to 30% of Zr and 0.1 to 10% of Hf, in the presence of Argon and nitrogen.

5) The coated article as claimed in claim 1, the protective overcoat layers may comprise nitrogen, whose atomic percentage varies from 0.1% to 50%.

6) The coated article as claimed in claim 1, characterized in that the coated article is intended to undergo a heat treatment. 7) The coated article as claimed in claim 1, characterized in that the coated article is tempered or annealed.

8) The coated article as claimed in claim 1, characterized in that the coated article is tempered, enameled, laminated and / or bent.

9) The coated article as claimed in claim 1, wherein the at least one functional layer predominantly comprising at least one metal or metal alloy belonging to the group consisting of niobium, tantalum, zirconium, nickel.

10) The coated article as claimed in claim 1, wherein the at least one functional layer characterized in that the layer is based on a partially or entirely nitrided metal belonging to the group consisting of niobium, tantalum, zirconium, nickel.

11) The coated article as claimed in claim 1, wherein the at least one functional layer characterized in that the layer is positioned between at least one overlayer based on nitride or oxide or oxynitride or aluminum oxynitirde of silicon or aluminum or a mixture of at least two of these compounds and at least one underlayer based on nitride or oxide or oxynitride or aluminum oxynitirde of silicon or aluminum or a mixture of at least two of these compounds.

12) The coated article as claimed in claim 1, characterized in that the stack of layers comprises a plurality of underlayers between the glass substrate and the functional layer and / or a plurality of overlayers between the functional layer and the protective overcoat layers.

13) The coated article as claimed in claim 1, characterized in that the stack of layers comprises of one or more functional layers made of Nb or NbN or Ta or Zr or ZrN or NiCr, an overlayer made of silicon nitride and a underlayer made of silicon nitride.

14) The coated article as claimed in claim 1, characterized in that the stack of layers comprises of one or more functional layers made of Nb or NbN or Ta or Zr or ZrN or NiCr, an overlayer made of silicon nitride, a underlayer made of silicon nitride, an additional overlayer between the functional layers and the protective overcoat layers and an additional underlayer between the glass substrate and the functional layers.

15) The coated article as claimed in claim 1, characterized in that the thickness of the protective overcoat layers comprising TiZrHf or TiZrHfN ranges between 0.5 nm to 5 nm.

16) The coated article as claimed in claim 1, characterized in that the thickness of the protective overcoat layers comprising carbon ranges between 0.1 nm to 5 nm.

17) The coated article as claimed in claim 1, characterized in that the coated article has a colorimetric variation in glass side-reflection and coating side- reflection, AE*_Rg & AE*_RC of less than 3.5 when said coated article is subjected to a temperature of at least 630° C and not more than 670° C.