EP4182278A1

EP4182278A1 - Low-emissivity material comprising a coating having a titanium oxide based oxidation gradient

Info

Publication number: EP4182278A1
Application number: EP21749241.2A
Authority: EP
Inventors: Denis Guimard; Anne Lelarge
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: 2020-07-16
Filing date: 2021-07-13
Publication date: 2023-05-24
Also published as: WO2022013496A1

Abstract

The invention relates to a material comprising a transparent substrate coated with a stack of layers including at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, so that each functional metal layer is placed between two dielectric coatings, the material being characterised in that the stack includes a coating having a titanium oxide-based oxidation gradient, located above and in contact with a silver-based functional metal layer, the portion of the coating having an oxidation gradient in contact with the functional layer is less oxidized than the portion of that coating further away from the functional layer.

Description

Title: Low-emissivity material comprising a coating comprising a titanium oxide-based oxidation gradient

The invention relates to a material comprising a transparent substrate coated with a stack of thin layers comprising a functional metallic layer based on silver. The invention also relates to glazing comprising these materials as well as the use of such materials for manufacturing thermal insulation and/or solar protection glazing.

The silver-based functional metal layers (or silver layers) have advantageous properties of electrical conduction and reflection of infrared radiation (IR), hence their use in so-called "solar control" glazing aimed at reducing the amount of incoming solar energy and/or in so-called “low-emission” glazing aimed at reducing the amount of energy dissipated outwards from a building or vehicle.

These silver layers are deposited between coatings based on dielectric materials generally comprising several dielectric layers (hereinafter “dielectric coatings”) making it possible to adjust the optical properties of the stack. These dielectric layers also make it possible to protect the silver layer from chemical or mechanical attack.

Frequently, such materials must undergo heat treatments, intended to improve the properties of the substrate and/or of the stack of thin layers. For example, in the case of glass substrates, it may involve thermal toughening treatment intended to mechanically reinforce the substrate by creating high compressive stresses on its surface.

The invention relates more particularly to materials comprising a substrate coated with a stack, intended to undergo a heat treatment at high temperature, having a low emissivity or a low square resistance. Emissivity and resistivity (or resistance) per square vary proportionately. Therefore, it is often possible to assess the emissivity of a material by evaluating its resistance per square.

The invention is also concerned with obtaining these materials having a low emissivity without significant modification of the absorption following the heat treatment.

Finally, it remains essential that the advantageous properties of emissivity and absorption are obtained without harming:

- mechanical resistance, in particular scratch and brush resistance, preferably before and after heat treatment,

- resistance to hot corrosion, and

- transparency resulting in the absence of blur after heat treatment. The optical and electrical properties such as the emissivity of the materials depend directly on the quality of the silver layers such as their crystalline state, their homogeneity as well as their environment. The term "environment" means the nature of the layers close to the silver layer and the surface roughness of the interfaces with these layers.

High temperature heat treatments such as annealing, bending and/or quenching cause changes within the silver layer.

In addition, heat treatments at high temperature generally make the stacks more sensitive to scratches. On the other hand, when scratches are created on a material before heat treatment, their visibility increases considerably after heat treatment.

To improve the quality of functional metal layers based on silver, it is known to use under the silver layers dielectric coatings comprising dielectric layers with stabilizing function intended to promote wetting and nucleation of the silver layer. . Dielectric layers based on crystallized zinc oxide are notably used for this purpose. Indeed, the zinc oxide deposited by the sputtering process crystallizes without requiring additional heat treatment. The layer based on zinc oxide can therefore serve as an epitaxial growth layer for the silver layer.

Another way to prevent the degradation of the silver layers lies in the choice of the layer located above and in contact with the silver layer. Among the known proposals is the use of so-called blocking layers or dielectric layers based on crystallized zinc oxide. The objective is to protect the functional layers from possible degradation during the deposition of the upper dielectric coating and/or during a heat treatment.

The blocking layers are generally based on a metal chosen from nickel, chromium, titanium, niobium, or an alloy of these various metals. The various metals or alloys mentioned can also be partially oxidized, in particular have an oxygen sub-stoichiometry (for example TiOx OR NiCrOx).

These blocking layers are very thin, normally less than 2 nm thick, and are susceptible at these thicknesses to being partially oxidized during heat treatment. In general, these blocking layers are sacrificial layers, capable of capturing oxygen coming from the atmosphere or from the substrate, thus avoiding the oxidation of the silver layer.

The use of these thin blocking layers does not make it possible to obtain sufficiently high-performance materials having in particular a sufficiently low resistivity.

Good results in terms of resistivity have been obtained hitherto with a material not comprising a blocking layer. The silver layer is located in contact with the two crystallized zinc oxide layers located respectively above and below the silver layer. Materials comprising the sequence ZnO/Ag/ZnO are qualified as reference material in the present application.

This solution consisting in using only layers based on crystallized zinc oxide below and below the silver makes it possible to obtain advantageous resistivity values. However, the following disadvantages remain:

- appearance of blur after heat treatment,

- appearance of corrosion spots after heat treatment.

The applicant has discovered that the use of a thick layer of titanium oxide located above and in contact with the silver-based functional layer, in a particular stack, makes it possible to overcome these drawbacks.

Surprisingly, this solution also makes it possible to further reduce the resistivity after heat treatment compared with a reference material.

This solution makes it possible to obtain advantageous resistivity values after heat treatment, without blurring or the appearance of corrosion points. A significant improvement in the mechanical properties of scratch resistance is also observed following the heat treatment, resulting in:

- less visible scratches and

- if present, the absence of hot corrosion of these existing scratches.

However, the mere presence of a thick layer of titanium oxide does not allow:

- to limit the increase in absorption before heat treatment,

- to obtain satisfactory mechanical resistance in the brush resistance test before and after heat treatment.

The applicant has therefore sought how to improve these properties. He surprisingly discovered that the use of a coating comprising an oxidation gradient based on titanium oxide not only makes it possible to overcome these drawbacks but also to provide other advantageous properties.

The invention therefore relates to a material comprising a transparent substrate coated with a stack of layers comprising at least one functional metallic layer based on silver and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, so as to that each functional metal layer is placed between two dielectric coatings, characterized in that the stack comprises a coating comprising an oxidation gradient based on titanium oxide located above and in contact with a functional metal layer at silver base, the part of the oxidation gradient coating in contact with the functional layer is less oxidized than the part of this coating further from the functional layer.

The stack comprises a coating comprising an oxidation gradient as deposited. This means that a coating having a gradient is directly deposited of oxidation. The gradient is present from the deposition. The gradient is not obtained following a possible heat treatment or a possible long storage.

The solution of the invention makes it possible to obtain, compared to the reference material:

- an improvement in the resistivity with the obtaining of a square resistance gain of at least 10%, or even 15%, for certain structures of the invention, both before and after heat treatment,

- an improvement in the mechanical properties of brush resistance before and after heat treatment.

In certain embodiments, the improvement in resistivity is obtained without an increase in absorption, before and after heat treatment.

The solution of the invention also makes it possible to obtain these advantageous properties, without blurring or the appearance of corrosion points. A significant improvement in the mechanical properties of scratch resistance is also observed following the heat treatment, resulting in:

- less visible scratches and

- if present, the absence of hot corrosion of these existing scratches.

The invention also makes it possible to obtain an improvement in the solar factor. This improvement is partly related to the presence of a high-index layer in contact with the silver layer. The effect on the solar factor makes it possible to obtain:

- for a given thickness of agent, a higher solar factor, or

- for a given emissivity, a lower thickness for the silver layer.

The invention therefore allows the development of a material comprising a substrate coated with a stack comprising at least one functional layer based on silver having, following a heat treatment of the bending, quenching or annealing type, with respect to a reference material with the same silver layer thickness:

- low emissivity, in some cases without increased absorption, and higher solar factor and light transmission,

- low visibility of scratches (if present) following heat treatment,

- good resistance to the brush test, and

- significantly improved resistance to hot corrosion.

The invention therefore allows the development of a material comprising a substrate coated with a stack comprising at least one silver-based functional layer having, before or without heat treatment:

- low emissivity without increased absorption and

- good resistance to the brush test. According to a particularly advantageous embodiment, the coating comprising an oxidation gradient based on titanium oxide is associated with a layer based on particular zinc oxide and tin.

This embodiment combining a coating based on titanium oxide with an oxidation gradient and a layer based on zinc and tin oxide makes it possible to obtain the best performance.

The invention therefore also relates to a material comprising a transparent substrate coated with a stack of layers comprising at least one functional metallic layer based on silver and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, so that each functional metal layer is placed between two dielectric coatings, the stack comprises:

- a coating comprising an oxidation gradient based on titanium oxide located above and in contact with a functional metallic layer based on silver, the part of the coating with an oxidation gradient in contact with the functional layer is less oxidized than the part of this coating furthest from the functional layer,

- a layer based on zinc oxide and tin comprising at least 20% by mass of tin relative to the total mass of zinc and tin, located above and in contact with the layer based on titanium oxide.

The solution of the invention is particularly suitable in the case of stacks with several functional layers based on silver, in particular stacks with two or three functional layers which are particularly fragile from the point of view of scratches.

The present invention is also particularly suitable in the case of stacks with a single functional layer based on silver intended for applications where the stacks are highly subject to hot corrosion.

The invention also relates to:

- a glazing comprising a material according to the invention,

- glazing comprising a material according to the invention mounted on a vehicle or on a building, and

- the process for preparing a material or a glazing according to the invention,

- the use of a glazing according to the invention as solar control and/or low-emission glazing for the building or vehicles,

- a building, a vehicle or a device comprising a glazing according to the invention.

Throughout the description, the substrate according to the invention is considered laid horizontally. The stack of thin layers is deposited above the substrate. The meaning of the expressions “above” and “below” and “lower” and “higher” should be considered in relation to this orientation. In the absence of specific stipulation, the expressions "Above" and "below" do not necessarily mean that two layers and/or coatings are arranged in contact with one another. When it is specified that a layer is deposited "in contact" with another layer or a coating, this means that there cannot be one (or more) interposed layer(s) between these two layers (or layer and coating).

All the luminous characteristics described 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 the glazing used in glass for construction.

Sunlight entering a building is considered to flow from the exterior to the interior.

According to the invention, the luminous characteristics are measured according to the D65 illuminant at 2° perpendicular to the material mounted in a double glazing:

- TL corresponds to the light transmission in the visible in %,

- Rext corresponds to the external light reflection in the visible in %, observer outside space side,

- Rint corresponds to the interior light reflection in the visible in %, observer on the interior space side,

- a ^* T and b ^* T correspond to the colors in transmission a ^* and b ^* in the L ^* a ^* b ^{* system} ,

- a ^* Rext and b ^* Rext correspond to the colors in reflection a ^* and b ^* in the L ^* a ^* b ^{* system} , observer on the outer space side,

- a ^* Rint and b ^* Rint correspond to the colors in reflection a ^* and b ^* in the L ^* a ^* b ^{* system} , observer on the interior space side.

The preferred characteristics which appear in the remainder of the description are applicable both to the material according to the invention and, where applicable, to the glazing or to the process according to the invention.

The materials of the invention can be used both in untempered version and in tempered version.

The present invention relates to the unheat-treated coated substrate. The stack may not have undergone heat treatment at a temperature above 500°C, preferably 300°C.

The present invention relates to the heat-treated material. The heat treatments are chosen from:

- annealing, for example rapid annealing,

- quenching and/or bending.

The material, that is to say the transparent substrate coated with the stack, may have undergone a heat treatment at high temperature. Stacking and substrate may have been subjected to a heat treatment at a high temperature such as quenching, annealing or bending.

It is also possible to heat treat only the stack. In this case, the stack only may have undergone heat treatment.

In these two cases, the stack may have undergone a heat treatment at a temperature above 300°C, preferably 500°C. The heat treatment temperature (at the level of the stack) is greater than 300°C, preferably greater than 400°C, and better still greater than 500°C.

According to the invention, it is also possible to carry out rapid thermal annealing (“Rapid Thermal Process”) such as laser or flash lamp annealing. Rapid thermal annealing is for example described in applications WO2008/096089 and WO2015/185848. In these cases, only the stack is subjected to heat treatment. During this type of treatment, each point of the stack is brought to a temperature of at least 300 ^° C while maintaining a temperature less than or equal to 150 ^° C at any point on the side of the substrate opposite to that on which locate the stack. This method has the advantage of heating only the stack, without significant heating of the entire substrate.

In the case of laser treatment, the coated materials can be treated using a laser line formed from laser sources such as InGaAs diode lasers or Yb:YAG disc lasers. These continuous sources emit at a wavelength between 900 and 1100 nm. The laser line has a length on the order of 3.3 m, equal to the width 1 of the substrate, and an average FWHM half-width between 45 and 100 μm.

The materials are arranged on a roller conveyor so as to scroll along an X direction, parallel to its length. The laser line is fixed and positioned above the coated surface of the substrate with its longitudinal direction Y extending perpendicularly to the running direction X of the substrate, i.e. along the width of the substrate, in extending across that width.

The position of the focal plane of the laser line is adjusted to be within the thickness of the functional coating when the substrate is positioned on the conveyor. The surface power of the laser line at the focal plane is less than 100kW/cm2. The substrate was moved under the laser line at a speed of about 8 m/min.

The stack may therefore have been subjected to rapid thermal annealing in which each point of the stack is brought to a temperature of at least 300 ^° C while maintaining a temperature less than or equal to 150 ^° C at any point on the face. of the substrate opposite to that on which the stack is located.

It is also possible to combine heat treatments. For example, it is possible to carry out rapid thermal annealing followed by quenching. The stack and the substrate may have been subjected to a heat treatment at a high temperature above 500° C. such as quenching, annealing or bending.

The coated substrate of the stack can be bent or tempered glass.

The stack is deposited by cathode sputtering assisted by a magnetic field (magnetron process). According to this advantageous embodiment, all the layers of the stack are deposited by cathodic sputtering assisted by a magnetic field.

Unless otherwise stated, the thicknesses referred to in this document are physical thicknesses and the layers are thin layers. By thin layer is meant a layer having a thickness of between 0.1 nm and 100 micrometers.

The stack comprises a coating comprising a titanium oxide-based oxidation gradient located above and in contact with a silver-based functional metal layer, the part of the oxidation gradient coating in contact with the functional layer is less oxidized than the part of this coating furthest from the functional layer.

According to the invention, the titanium oxide coating is described as it is deposited, that is to say before any heat treatment or before any long storage. Indeed, a heat treatment at high temperature or a long storage can generate modifications within layers or coating. These modifications may in particular correspond to a rearrangement of the oxygen atoms within the coating, making it more difficult to observe the gradient.

The oxidation gradient coating has a thickness:

- greater than 3 nm, greater than 4 nm, greater than or equal to 5 nm,

- less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm, less than or equal to 15 nm, less than or equal to 10 nm, less than or equal to 8 nm.

The oxidation gradient coating may include:

- a layer of titanium oxide comprising an oxygen gradient,

- at least two layers of titanium oxide comprising different proportions of oxygen.

The layers based on titanium oxide comprise at least 50%, at least 60%, at least 70%, at least 80%, at least 95.0%, at least 96.5% and better still at least 98.0 % by mass of titanium relative to the mass of all the elements constituting the layer based on titanium oxide other than oxygen.

The layers based on titanium oxide can comprise or consist of elements other than titanium and oxygen. These elements can be chosen from silicon, chromium and zirconium. Preferably, the elements are chosen from zirconium. Preferably, the layer based on titanium oxide comprises at most 35%, at most 20% or at most 10% by mass of elements other than titanium relative to the mass of all the elements constituting the layer based on titanium oxide other than oxygen.

The layers based on titanium oxide can have a thickness:

- greater than or equal to 2 nm, greater than or equal to 3 nm, greater than or equal to 4 nm, greater than or equal to 5 nm, and/or

- less than or equal to 30 nm, less than or equal to 25 nm, less than or equal to 20 nm, less than or equal to 15 nm, less than or equal to 10 nm, less than or equal to 8 nm, less than or equal to 4 nm.

The layers based on titanium oxide can be obtained:

- by sputtering,

- from a metallic titanium target or a ceramic target based on titanium oxide, preferably sub-stoichiometric.

When the titanium oxide-based layer is obtained from a metal target, the deposition atmosphere includes significant proportions of oxygen.

The layers based on titanium oxide are preferably obtained from a ceramic target of titanium oxide, preferably under stoichiometric in oxygen, in an atmosphere comprising oxygen or without oxygen. The quantity of oxygen in the deposition atmosphere can be adapted according to the desired properties.

According to the preferred embodiment, a layer based on titanium oxide is deposited from a ceramic target, in particular sub-stoichiometric, in a controlled atmosphere comprising oxygen.

The layer based on titanium oxide can be deposited from a ceramic target of TiO _x with x between 1.5 and 2.

The layer based on titanium oxide can be deposited from a ceramic target of TiO _x under stoichiometric, where x is a number different from the stoichiometry of titanium oxide T1O2, i.e. different of 2 and preferably less than 2, in particular between 0.75 times and 0.99 times the normal stoichiometry of the oxide. TiOx may in particular be such that 1.5<x<1.98 or 1.5<x<1.7, or even 1.7<x<1.95.

The layer based on titanium oxide can be deposited in an atmosphere not containing oxygen or in a controlled atmosphere comprising oxygen.

According to the invention, the term “controlled atmosphere comprising oxygen” means an atmosphere comprising an optimized quantity of oxygen to obtain, after heat treatment, a gain in resistivity without harming the absorption on the one hand, and the brush resistance before and after annealing (EBT), on the other hand.

The deposition atmosphere comprises a mixture of noble gases (He, Ne, Xe, Ar, Kr) and oxygen. The noble gas is preferably argon. The following parameters are used to define the conditions for sputtering deposition:

- the deposition pressure,

- the composition of the gases in volume flow (unit sccm "standard cubic centimeter per minute").

The controlled atmosphere making it possible to obtain the advantageous effects of the invention was obtained in particular with the following parameters:

- the pressure in the deposition chamber is between 1 and 15 pbar, preferably 2 and 10 pbar or 2 and 8 pbar,

- the deposition atmosphere comprises a mixture of argon and oxygen.

The controlled atmosphere making it possible to obtain the advantageous effects of the invention was obtained with a percentage by volume flow of oxygen of between 0 and 10%, between 0.1 and 10%, between 0.1 and 5%, between 0.1 and 4%, between 0.5 and 3%, between 1 and 2.5% or between 1.5 and 2.0%.

The maximum oxygen threshold may vary to some extent depending on, for example:

- the nature of the TiOx target, in particular its oxygen sub-stoichiometry or

- power.

Indeed, if a low deposition power is used, the volume flow quantities of oxygen that can be used during the deposition will be lower because the TiOx is deposited more slowly and is therefore more likely to oxidize.

A person skilled in the art is able to define a satisfactory controlled atmosphere by varying these parameters to some extent. A person skilled in the art is in particular perfectly able to determine the power to be applied to the target and the volume flow rates of oxygen and noble gases.

For this, for a given deposition pressure, the person skilled in the art is able to make increasing additions of oxygen in order to determine the range of proportion of oxygen which makes it possible to lower the resistivity after heat treatment without harming the 'absorption.

The oxidation gradient coating may comprise at least one layer based on titanium oxide deposited from a ceramic target, in particular substoichiometric, in a controlled atmosphere comprising oxygen, preferably in a controlled atmosphere comprising oxygen. The layer based on titanium oxide can be deposited with a percentage of oxygen in volume flow representing between 0.1 and 10%.

The oxidation gradient coating can comprise at least two layers of titanium oxide each comprising different proportions of oxygen, that is to say different degrees of oxidation. In this case, the coating is obtained by depositing at least two consecutive layers based on titanium oxide. This deposition in several stages makes it possible to obtain mainly in the coating a layer of titanium oxide with a large quantity of oxygen, while protecting the functional layer based on silver from a first layer of titanium oxide weakly oxidized. The absorption of the stack before heat treatment is then greatly reduced.

The oxidation gradient coating can also comprise a first layer deposited from a ceramic target, in particular sub-stoichiometric, in an oxygen-free atmosphere.

The oxidation gradient coating may comprise a first layer based on titanium oxide deposited from a ceramic target, in particular sub-stoichiometric, in a non-oxidizing or oxidizing atmosphere whose percentage by volume flow rate of oxygen represents between 0 and 5%, between 0 and 4%, between 0.1 and 4%, between 0.5 and 4%, between 0 and 3%, between 0.1 and 3%, between 0.5 and 3%, between 0.1 and 2.5% or between 0.5 and 2%. This first layer based on titanium oxide is in contact with the functional layer based on silver.

The amount of oxygen in the first layer based on titanium oxide must be relatively low so as not to degrade the functional layer based on silver. For this, it is possible to use a first layer deposited from a ceramic target, in particular sub-stoichiometric, in an atmosphere without oxygen or with very little oxygen. However, using a little oxygen contributes to a better resistance to the brush test without inducing too great a penalty in absorption, especially before heat treatment.

The thickness of the first layer based on titanium oxide can be as thin as that of a standard blocking layer (<1nm), as long as the functional layer based on silver does not prove to be degraded by the oxygen present during the deposition of the next layer based on titanium oxide, deposited with more oxygen than the first.

The first layer has a thickness between 0.2 and 4 nm. The first layer can have a thickness of less than 3 nm, less than 2 nm, less than 1 nm or less than 0.5 nm.

The oxidation gradient coating comprises a second layer based on titanium oxide deposited from a ceramic target, in particular sub-stoichiometric, in an atmosphere comprising higher proportions of oxygen than that used for the first layer.

The second layer based on titanium oxide can be deposited from a metal target or a ceramic target.

The second layer based on titanium oxide can be deposited from a ceramic target, in particular sub-stoichiometric, in an oxidizing atmosphere whose percentage of oxygen in volume flow represents between 1 and 10%, between 1.5 and 8%, between 2 and 5%.

The second layer based on titanium oxide has a thickness between 0.2 and 30 nm, between 2 and 20 nm or between 5 and 15 nm.

The second layer based on titanium oxide can have a thickness:

- greater than 0.5 nm, greater than 1 nm, greater than 2 nm, greater than 3 nm, greater than 4 nm, greater than 5 nm,

- less than 30 nm, less than 20 nm, less than 15 nm or less than 10 nm.

The oxidation gradient coating can also comprise a single layer of titanium oxide comprising an oxygen gradient.

A coating based on titanium oxide comprising a single layer with an oxygen gradient can be obtained:

- by sputtering,

- in an atmosphere comprising a mixture of neutral gas and oxygen, by gradually increasing the flow rates of oxygen present in the atmosphere,

In this case, the volume flow rate of oxygen in the deposition atmosphere is gradually increased as the layer based on titanium oxide is deposited. The part of the oxidation gradient coating in contact with the functional layer is less oxidized than the part of this coating further from the functional layer.

Typically, when the target is a ceramic target under stoichiometric in oxygen, the proportions of oxygen in the deposition atmosphere can vary from 0% to 10%, preferably from 0 to 5%.

According to the invention, the stack comprises at least one functional metallic layer based on silver.

The silver-based functional metallic layer, before or after heat treatment, comprises at least 95.0%, preferably at least 96.5% and better still at least 98.0% by mass of silver with respect to the mass of the functional layer.

Preferably, the silver-based functional metal layer before heat treatment comprises less than 1.0% by mass of metals other than silver relative to the mass of the silver-based functional metal layer.

The thickness of the silver-based functional layer is between 5 to 25 nm, 8 to 20 nm or 8 to 15 nm.

The stack of thin layers comprises at least one functional layer and at least two dielectric coatings comprising at least one dielectric layer, so that each functional layer is placed between two dielectric coatings.

The stack of thin layers can comprise at least two metallic functional layers based on silver and at least three dielectric coatings comprising at least one dielectric layer, so that each functional layer is placed between two dielectric coatings.

The stack of thin layers can comprise at least three functional layers and at least four dielectric coatings comprising at least one dielectric layer, so that each functional layer is placed between two dielectric coatings.

The stack is located on at least one of the faces of the transparent substrate.

By "dielectric coating" within the meaning of the present invention, it should be understood that there may be a single layer or several layers of different materials inside the coating. A “dielectric coating” according to the invention mainly comprises dielectric layers. However, according to the invention, these coatings can also comprise layers of another nature, in particular absorbent layers or metallic layers other than functional layers based on silver. For example, the coating farthest from the substrate may comprise a protective layer deposited in metallic form.

It is considered that a "same" dielectric coating is located:

- between the substrate and the first functional layer,

- between each silver-based functional metal layer,

- above the last functional layer (furthest from the substrate).

By "dielectric layer" within the meaning 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. n designates the index of real refraction of the material at a given wavelength and k represents the imaginary part of the refractive index at a given wavelength; the ratio n/k being calculated at a given wavelength identical for n and for k.

The thickness of a dielectric coating corresponds to the sum of the thicknesses of the layers constituting it.

According to the invention, the layers based on titanium oxide form part of a dielectric coating. This means that when determining the thickness of a dielectric coating, the thickness of these layers is taken into consideration. Preferably, the dielectric coatings have a thickness greater than 10 nm, greater than 15 nm, between 15 and 200 nm, between 15 and 100 nm or between 15 and 70 nm.

The dielectric layers of the coatings have the following characteristics alone or in combination:

- they are deposited by cathodic sputtering assisted by a magnetic field,

- they are chosen from oxides or nitrides of one or more elements chosen from titanium, silicon, aluminium, zirconium, tin and zinc,

- they have a thickness greater than 2 nm, preferably between 2 and 100 nm, between 5 and 50 nm or between 5 and 30 nm.

Some dielectric layers have a barrier function. By dielectric layers with barrier function (hereinafter barrier layer) is meant a layer made of a material capable of forming a barrier to the diffusion of oxygen and water at high temperature, coming from the ambient atmosphere or from the substrate. transparent, towards the functional layer. Such dielectric layers are chosen from:

- the layers comprising silicon and/or aluminum and/or zirconium and are chosen for example from oxides such as Si02, nitrides such as silicon nitride Si3N4 and aluminum nitrides AlN, and oxynitrides SiOxNy, optionally doped with at least one other element,

- layers based on zinc and tin oxide,

- layers based on titanium oxide.

The material may comprise a layer based on zinc oxide and tin comprising at least 20% by mass of tin relative to the total mass of zinc and tin, located above and in contact with the layer based on titanium oxide.

The layer based on zinc oxide and tin comprises by mass of tin relative to the total mass of zinc and tin:

- at least 30%, at least 40%, at least 45%, at least 50% or at least 55%,

- at most 70%, at most 65% or at most 60% by mass of zinc.

The layer based on zinc oxide and tin has a thickness:

- greater than 5 nm, greater than 10 nm, greater than 15 nm, greater than 18 nm,

- less than 40 nm, less than 30 nm, less than 25 nm.

The stack may comprise at least one layer comprising silicon. Each dielectric coating may include at least one layer comprising silicon.

Layers comprising silicon are extremely stable to heat treatments. For example, no migrations of the constituent elements are observed. Therefore, these elements are not likely to alter the silver layer. Layers comprising silicon therefore also contribute to the non-alteration of the silver layers and therefore to obtaining a low emissivity after heat treatment.

The layers comprising silicon can be chosen from layers based on oxide, based on nitride or based on silicon oxynitride such as layers based on silicon oxide, layers based on silicon nitride and layers based on silicon oxynitride.

When each coating comprises a layer comprising silicon, these layers are not necessarily of the same nature.

The layers comprising silicon can comprise or consist of elements other than silicon, oxygen and nitrogen. These elements can be chosen from among aluminum, boron, titanium, and zirconium.

The layers comprising silicon can comprise at least 50%, at least 60%, at least 65%, at least 70% at least 75.0%, at least 80% or at least 90% by mass of silicon with respect to the mass of all the elements constituting the layer comprising silicon other than nitrogen and oxygen.

Preferably, the layer comprising silicon comprises at most 35%, at most 20% or at most 10% by mass of elements other than silicon relative to the mass of all the elements constituting the layer comprising silicon other than oxygen and nitrogen.

According to one embodiment, the layers comprising silicon comprise less than 35%, less than 30%, less than 20%, less than 10%, less than 5% or less than 1% by mass of zirconium with respect to the mass of all the elements constituting the layer based on silicon oxide other than oxygen and nitrogen.

The layer comprising silicon may comprise at least 2%, at least 5.0% or at least 8% by mass of aluminum relative to the mass of all the elements constituting the layer based on silicon oxide other than oxygen and nitrogen.

The amounts of oxygen and nitrogen in a layer are determined in atomic percentages relative to the total amounts of oxygen and nitrogen in the layer under consideration.

According to the invention:

- layers based on silicon oxide mainly contain oxygen and very little nitrogen,

- layers based on silicon nitride mainly contain nitrogen and very little oxygen,

- layers based on silicon oxynitride include a mixture of oxygen and nitrogen.

The silicon oxide layers include at least 90 atomic percent oxygen relative to the oxygen and nitrogen in the silicon oxide layer. The silicon nitride based layers include at least 90% atomic percent nitrogen relative to the oxygen and nitrogen in the silicon oxide based layer.

The layers based on silicon oxynitride include 10 to 90% (limits excluded) in atomic percentage of nitrogen relative to the oxygen and nitrogen in the layer based on silicon oxide.

Preferably, the layers based on silicon oxide are characterized by a refractive index at 550 nm, less than or equal to 1.55.

Preferably, the layers based on silicon nitride are characterized by a refractive index at 550 nm, greater than or equal to 1.95.

Preferably, the layers based on silicon oxynitride are characterized by a refractive index at 550 nm intermediate between a layer of non-nitrided oxide and a layer of non-oxidized nitride. The layers based on silicon oxynitride preferably have a refractive index at 550 nm greater than 1.55, 1.60 or 1.70 or between 1.55 and 1.95, 1.60 and 2.00 , 1.70 and 2.00 or 1.70 and 1.90.

These refractive indices may vary to some extent depending on the deposition conditions. Indeed, by playing on certain parameters such as the pressure or the presence of dopants, it is possible to obtain more or less dense layers and therefore a variation in refractive index.

The layers comprising silicon can be layers of silicon and aluminum nitride and optionally of zirconium. These layers of silicon nitride and aluminum and/or zirconium can also, by weight relative to the weight of silicon, aluminum and zirconium:

- 50 to 98%, 60 to 90%, 60 to 70% by weight of silicon,

- 2 to 10% by weight of aluminium,

- 0 to 30%, 10 to 30% or 15 to 27% by weight of zirconium.

The sum of the thicknesses of all the layers comprising silicon in each dielectric coating is greater than or equal to 5 nm, greater than or equal to 10 nm, or even greater than or equal to 15 nm.

These layers comprising silicon have, in increasing order of preference, a thickness:

- less than or equal to 40 nm and/or

- greater than or equal to 5 nm, greater than or equal to 10 nm or greater than or equal to 15 nm.

Preferably, at least one dielectric coating comprises a layer comprising silicon chosen from layers based on silicon nitride and/or aluminum.

Preferably, each dielectric coating comprises a layer comprising silicon chosen from layers based on silicon and/or aluminum nitride. The dielectric coatings may comprise layers other than these layers comprising silicon.

The sum of the thicknesses of all the layers comprising silicon in the dielectric coating located between the substrate and the first layer of silver can be greater than 30%, greater than 35%, greater than 50%, greater than 60% greater than 70 %, greater than 75% of the total thickness of the dielectric coating.

The sum of the thicknesses of all the layers comprising silicon based on silicon nitride in the dielectric coating located between the substrate and the first layer of silver can be greater than 30%, greater than 35%, greater than 50%, greater than at 60% greater than 70%, greater than 75% of the total thickness of the dielectric coating.

Preferably, the sum of the thicknesses of all the layers comprising silicon in each dielectric coating located above the first silver-based functional metal layer may be greater than 30%, greater than 35%, greater than 50%, greater than 60% greater than 70% greater than 75% of the total thickness of the dielectric coating.

Preferably, the sum of the thicknesses of all the layers comprising silicon based on silicon nitride in each dielectric coating located above the first functional metal layer based on silver can be greater than 30%, greater than 35% , greater than 50%, greater than 60% greater than 70%, greater than 75% of the total thickness of the dielectric coating.

The sum of the thicknesses of all the layers comprising silicon in each dielectric coating can be greater than 30%, greater than 35%, greater than 50%, greater than 60%, greater than 70%, greater than 75% of the total thickness dielectric coating.

Preferably, the stack does not include a metallic blocking layer or one based on titanium oxide below and in contact with the functional metallic layer based on silver. In this case, the silver-based functional metallic layer is located above and in contact with a dielectric layer of the dielectric coating. Preferably, this dielectric layer is a stabilizing or wetting layer made of a material capable of stabilizing the interface with the functional layer. These layers are generally based on zinc oxide.

The metallic functional layer can therefore be deposited above and in contact with a layer based on zinc oxide.

The layers based on zinc oxide, can comprise, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or 100% by mass of zinc by mass total of all the elements constituting the layer based on zinc oxide with the exclusion of oxygen and nitrogen.

To be correctly crystallized by sputtering deposition, the layers based on zinc oxide advantageously comprise at least 80%, even at least 90% by mass of zinc relative to the total mass of all the elements constituting the layer based zinc oxide excluding oxygen and nitrogen.

The layers based on zinc oxide can comprise one or more elements chosen from among aluminum, titanium, niobium, zirconium, magnesium, copper, silver, gold, silicon, molybdenum, nickel, chromium, platinum, indium, tin and hafnium, preferably aluminum.

Layers based on zinc oxide can optionally be doped with at least one other element, such as aluminum.

A priori, the layer based on zinc oxide is not nitrided, however traces may exist.

The layer based on zinc oxide comprises, in increasing order of preference, at least 80%, at least 90%, at least 95%, at least 98%, at least 100%, by mass of oxygen with respect to the total mass of oxygen and nitrogen.

Preferably, the dielectric coating located directly below the silver-based functional metal layer comprises at least one crystallized dielectric layer, in particular based on zinc oxide, optionally doped with at least one other element, such as aluminum. The metallic functional layer is deposited above and in contact with a layer based on zinc oxide.

The zinc oxide-based layer is deposited from a ceramic target, with or without oxygen or from a metal target.

The dielectric coating located between the substrate and the first silver layer can only consist of layers comprising silicon and layers based on zinc oxide.

Dielectric coatings can only consist of layers comprising silicon and layers based on zinc oxide.

In all stacks, the dielectric coating closest to the substrate is called the bottom coating and the dielectric coating furthest from the substrate is called the top coating. Stacks with more than one silver layer also include intermediate dielectric coatings located between the bottom and top coating.

Preferably, the lower or intermediate coatings comprise a crystallized dielectric layer based on zinc oxide located directly in contact with the metallic layer based on silver. The zinc oxide layers have a thickness:

- at least 1.0 nm, at least 2.0 nm, at least 3.0 nm, at least 4.0 nm, at least 5.0 nm, at least 6.0 nm and/or

- not more than 25 nm, not more than 10 nm, not more than 8.0 nm.

The sum of the thicknesses of all the oxide-based layers present in the dielectric coating located below the first functional metal layer may be less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 25% of the total thickness of the dielectric coating.

The sum of the thicknesses of all the oxide-based layers present in the dielectric coating(s) located above the first functional metallic layer may be less than 50%, less than 40%, less than 30%, less than 25% the total thickness of the dielectric coating.

The sum of the thicknesses of all the oxide-based layers present in each dielectric coating located above the first functional metal layer can be less than 70%, less than 60%, less than 50%, less than 40% at 30%, less than 25% of the total thickness of the dielectric coating.

The stack of thin layers can optionally include a protective layer. The protective layer is preferably the last layer of the stack, that is to say the layer farthest from the coated substrate of the stack (before heat treatment). These layers generally have a thickness of between 0.5 and 10 nm, between 1 and 5 nm, between 1 and 3 nm or between 1 and 2.5 nm. This protective layer can be chosen from among a layer of titanium, zirconium, hafnium, silicon, zinc and/or tin, this or these metals being in metallic, oxidized or nitrided form.

According to one embodiment, the protective layer is based on zirconium oxide and/or titanium, preferably based on zirconium oxide, titanium oxide or titanium oxide and zirconium.

When determining the thickness of a dielectric coating, the thickness of the protective layer is taken into account.

The material of the invention may include:

- a layer comprising silicon, preferably based on silicon nitride,

- a layer based on zinc oxide,

- a silver-based layer,

- a coating comprising an oxidation gradient,

- a layer comprising silicon, preferably based on silicon nitride,

- possibly a protective layer.

The material of the invention may include:

- a layer comprising silicon, preferably based on silicon nitride, - a layer based on zinc oxide,

- a silver-based layer,

- a coating based on titanium oxide comprising an oxidation gradient,

- a layer based on zinc and tin oxide,

- a layer comprising silicon, preferably based on silicon nitride,

- possibly a protective layer.

The transparent substrates according to the invention are preferably made of a rigid mineral material, such as glass, or organic based on polymers (or polymer).

The organic transparent substrates according to the invention can also be made of polymer, rigid or flexible. Examples of polymers suitable according to the invention include, in particular:

- polyethylene,

- polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN);

- polyacrylates such as polymethyl methacrylate (PMMA);

- polycarbonates;

- polyurethanes;

- polyamides;

- polyimides;

- fluorinated polymers such as fluoroesters such as ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluorethylene (PCTFE), ethylene chlorotrifluorethylene (ECTFE), fluorinated ethylene-propylene copolymers (FEP);

- photocrosslinkable and/or photopolymerizable resins, such as thiolene, polyurethane, urethane-acrylate, polyester-acrylate and

- polythiourethanes.

The substrate is preferably a 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 soda-lime-silico type, but it can also be of borosilicate or alumino-borosilicate type glass.

According to a preferred embodiment, the substrate is made of glass, in particular silico-sodo-lime or of 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, in particular between 2 and 8 mm, or even between 4 and 6 mm. The substrate can be flat or curved, even flexible. The invention also relates to a glazing comprising at least one material according to the invention. The invention relates to glazing which may be in the form of monolithic, laminated and/or multiple glazing, in particular double glazing or triple glazing.

Monolithic glazing has 2 faces, face 1 is outside the building and therefore constitutes the outer wall of the glazing, face 2 is inside the building and therefore constitutes the inner wall of the glazing.

A multiple glazing unit comprises at least one material according to the invention and at least one additional substrate, the material and the additional substrate are separated by at least one spacer gas layer. The glazing creates a separation between an exterior space and an interior space.

Double glazing has 4 faces, face 1 is outside the building and therefore constitutes the outer wall of the glazing, face 4 is inside the building and therefore constitutes the inner wall of the glazing, faces 2 and 3 being inside the double glazing.

A laminated glazing comprises at least one structure of the first substrate/sheet(s)/second substrate type. The polymer sheet may in particular be based on polyvinyl butyral PVB, ethylene vinyl acetate EVA, polyethylene terephthalate PET, polyvinyl chloride PVC. The stack of thin layers is positioned on at least one of the faces of one of the substrates.

These glazings can be mounted on a building or a vehicle.

The following examples illustrate the invention.

Examples

I. Preparation of substrates: Stacks, deposition conditions

Stacks of thin layers defined below are deposited on clear soda-lime glass substrates with a thickness of 2 or 4 mm. In the examples of the invention:

- the functional layers are layers of silver (Ag),

- the dielectric layers are based on silicon nitride, doped with aluminum (S1 ₃ N ₄ : Al), zinc oxide and tin and zinc oxide (ZnO).

TiOx titanium oxide layers are deposited from a TiOx ceramic target with or without oxygen in the deposition atmosphere.

The deposition conditions of the layers, which were deposited by sputtering (so-called "magnetron cathodic" sputtering), are summarized in Table 1.

[Table 1]

%wt: % by weight

The tables below list the materials and the physical thicknesses in nanometers (unless otherwise indicated) of each layer or coating which constitutes the stacks according to their positions with respect to the carrier substrate of the stack.

[Table 2]

[Table 3]

[Table 4]

The stacks were made with titanium oxide-based coatings comprising different thickness ratios for a total thickness of 5 nm.

Titanium oxide based layers are deposited from a TiOx ceramic target with or without oxygen in the deposition atmosphere.

The stacks of the invention include a titanium oxide-based oxygen gradient coating above and in contact with the silver layer.

The oxygen-gradient titanium oxide-based coatings of stacks 1-1, 1-2 and 1-3 comprise a first layer based on titanium oxide deposited from an oxygen-free ceramic target in the deposit atmosphere.

The coatings based on titanium oxide with an oxygen gradient of stacks 2-1 and 2-2 comprise a first layer based on titanium oxide deposited from a ceramic target in an oxidizing atmosphere comprising 1.7 % oxygen.

The zinc oxide layers below and in contact with the silver layer are deposited from a ZnO ceramic target with 5% Ü2 in the deposition atmosphere.

The stacks 12-1, 12-2 and 12-3 comprise coatings based on titanium oxide (oxygen gradient coating) comprising at least two layers of titanium oxide comprising different proportions of oxygen. The first layer is deposited in contact with the silver layer and in an oxygen-free atmosphere with a thickness of 5 nanometers. This layer is therefore under-oxidized. The second layer based on titanium oxide is deposited in an atmosphere with 3.3% oxygen by volume flow and has a thickness varying from 0 to 15 nanometers. This layer is therefore more oxidized than the first.

Stacks 13 and 13-1 comprise an oxygen gradient coating comprising at least two layers of titanium oxide comprising different proportions of oxygen. Both layers are deposited from a ceramic target with oxygen. The second layer is more oxidized than the first.

II. Evolution of square resistance and absorption 1. Generality without SnZnO layer The square resistance Rsq, corresponding to the resistance referred to the surface, is measured by induction with a Nagy SMR-12.

The square resistance and absorption were measured before heat treatment (BT) and after heat treatments at a temperature of 650°C for 10 min (AT).

The square resistance variation was determined as follows:

ARsq(n-p)= (RsqRef-RsqEmp(n-p)) / RsqRef X 100.

The gain is positive when the resistance per sheet is improved and negative when the resistance per sheet is deteriorated following the heat treatment.

The tables below present the measurements of Rsq and absorption.

[Table 6]

BT: Before heat treatment, AT: After Gradient heat treatment with first layer of TiOx deposited without oxygen

Before and after heat treatment, the square resistance of the stacks of the invention Emp.1-1, 1-2 and 1-3 is lower than that of the reference stack. A gradient coating with a first layer of TiOx deposited without oxygen therefore makes it possible to obtain a gain in Rsq before and after heat treatment.

After heat treatment, the square resistance decreases compared to the reference stack when the thickness of the first layer comprising titanium oxide deposited without oxygen increases or when the thickness of the second layer comprising titanium oxide. titanium deposited with oxygen decreases (3.06 W/p > 3.00 W/D > 2.96 W/m).

One also observes, before and after heat treatment, a gain in resistivity for a stack without gradient comprising only a layer of titanium oxide deposited without oxygen (Emp.0-1). On the other hand, the absorption of this stack is degraded (i.e., increased), and this, before or after heat treatment. This increase is expected due to the absence of oxygen during the deposition of the titanium oxide layer. Since titanium oxide is sub-stoichiometric, it is absorbent.

The absorption of gradient stacks is satisfactory. It is similar to that of a reference material and better than or equal to the non-gradient material.

For the stacks of the invention, the supply of oxygen in the second layer of titanium oxide makes it possible to lower the absorption of the stacks. The absorption, before and after heat treatment, of the stacks with a coating based on titanium oxide comprising a gradient is similar to that of a reference material and better than or equal to that of stacking with titanium oxide without gradient.

The lowest absorption, before and after heat treatment, is obtained for the Emp.1-1 stack comprising the thinnest layer of titanium oxide deposited without oxygen (2 nm) or the titanium oxide layer ratio produced with 0 ₂ / layer of titanium oxide produced without the most important 0 2 .

By further refining the thickness of the first layer of TiOx deposited without oxygen (e.g., 1 nm, or even less), we can hope to further reduce the absorption of the stack before and after heat treatment.

In order to use this type of structure for an “annealed” product (non-annealed layer), it is essential to be able to reduce the absorption as much as possible.

Gradient with first layer of TiOx deposited with oxygen (1.7%)

Before heat treatment, when the first layer of titanium oxide in contact with the silver is deposited in an atmosphere containing oxygen, the square resistance of the stacks is not improved, but identical or even degraded, compared to the reference structure. The supply of oxygen in the first layer of titanium oxide (1.7%) degrades the silver layer during deposition.

Before heat treatment, an absorption penalty is observed. This penalty remains more significant than that observed for the 1-1, 1-2 and 1-3 stacks.

After heat treatment, the gain in square resistance compared to the reference is at least 14%.

With regard to absorption, the positive impact of the two layers of TiOx with oxygen after heat treatment is visible: 5.9% (case emp.2-1) versus 6.5% for the reference.

The comparison of the stacks (1-1 and 2-1) and (1-3 and 2-2) differing only by the oxidation or not of the first layer of titanium oxide, shows that:

- after heat treatment, the best results in terms of absorption and square resistance are obtained with a first oxidized layer,

- before heat treatment, the best results in terms of absorption and square resistance are obtained with a non-oxidized first layer.

Between Emp.2-2 and 1-3 stacks, absorption drops from 7.9% to 5.9%. The impact of oxidation of the titanium oxide layer is decisive in controlling absorption after heat treatment.

2. With SnZnO layer

[Table 7]

In this stack, the layer based on zinc oxide and tin is directly in contact with the layer based on under-oxidized titanium oxide.

The presence of an over-oxidized layer of titanium oxide, regardless of its thickness, makes it possible to significantly lower the square resistance before heat treatment (3.47 vs. 4.01) and after heat treatment (2.85 vs. 3.44). This square resistance is improved regardless of the thickness of the superoxidized titanium oxide layer.

After heat treatment, the Rsq remains high for emp.12-0 comprising a layer of SnZnO in direct contact with a layer of under-oxidized TiOx with a gain between the square resistance obtained AT vs. Low BT.

When a layer of over-oxidized titanium oxide is inserted between the layer of under-oxidized titanium oxide and the layer of zinc and tin oxide, the square resistance remains low, with a gain between the square resistance obtained AT vs. BT up to 25%.

When an oxidized layer of titanium oxide is introduced between the SnZnO and TiOx (0%), the sheet resistance is therefore improved. The thicker the superoxidized titanium oxide layer, the greater this improvement. The gain of Rsq increases from 18 to 25% when the thickness of the overoxidized titanium oxide layer increases from 5 to 15 nm. The best results for square strength after heat treatment are obtained for the thickest layer of titanium oxide.

Increasing the thickness of the overoxidized titanium oxide layer from 5 nm to 15 nm, on the other hand, improves this absorption (10.3% vs. 11.7%) before annealing.

After heat treatment, the over-oxidized titanium oxide layer with a thickness of 15 nm associated with the layer based on zinc and tin oxide makes it possible to significantly reduce absorption: 5.4% vs. 7.7%.

Table 7 below presents the sheet resistance and absorption measurements in the case of material comprising an oxygen gradient coating with two layers of TiOx deposited with oxygen.

[Table 8]

Before heat treatment, the Rsq is neither improved nor degraded compared to the reference stack (4.50 W/p vs. 4.55 W/D). After heat treatment, the Rsq is lower in the case of the stack of the invention Emp.13-1 comprising the sequence Ag/TiOx_1.7%/TiOx_5%/SnZnO (3.20 W/p) compared to Emp.13 not comprising a layer of SnZnO (3.42 W/D).

The absorption is lower in the case of Ag/TiOx_1.7%/TiOx_5%/SnZnO stacking, before (7.8% vs. 8.5%) and after heat treatment (5.4% vs. 6.5%). The two layers of TiOx are deposited with oxygen and are therefore not very absorbent. This low absorption of the two TiOx layers is also visible in the Ag/TiOx_1.7%/TiOx_5% stack compared to the reference Ag/ZnO: 6.2% vs. 6.5%.

By further refining the thickness of the first layer of TiOx deposited with 02 (eg, 1 nm, or even less like the thickness of a TiOx blocker), one can hope to further reduce the absorption of the stack before thermal treatment. In order to use this type of structure for an “annealed” product (non-annealed layer), it is essential to be able to reduce the absorption as much as possible.

III. Microscopic Observations: Hot and Blur Corrosion

The morphology of the stacks is analyzed by optical microscopy (x50 magnification) after heat treatment. Figure 1 shows these images taken under an optical microscope. The images were taken after heat treatment.

[Table 9]

Observations under a microscope after heat treatment show no point of hot corrosion for the stacks according to the invention.

The stacks of the invention do not exhibit any blurring either. The presence of the titanium oxide layer on top of the layer in contact with the silver prevents the presence of blurring.

IV. Characterization of mechanical behavior

1. Brush resistance test after heat treatment

Brush resistance tests were carried out before and after heat treatment (“Erichsen brush test” before EBT heat treatment and after TT-EBT heat treatment).

Each sample is observed after a certain number of cycles: 50, 100, 200, 300.

The table below shows all the results, Rsq, Abs after heat treatment, and EBT and TT_TT_EBT tests.

The Ok boxes indicate good resistance to the EBT or TT-EBT test after 300 cycles. The figure beside corresponds to the number of cycles to which the sample was subjected. The Nok boxes indicate poor resistance to the EBT or TTEBT test after 300 cycles. The number indicated next corresponds to the number of cycles from which the test becomes bad (Nok).

[Table 10]

3T: Before heat treatment, AT: After heat treatment After heat treatment: TT EBT

The stacks according to the invention all make it possible to obtain good results in the brush test, whereas this is not the case either for the reference (Ref.) or for the stack without gradient. The presence of oxygen (overoxidation of the second layer of TiOx at 5%) is crucial for obtaining a good TT_EBT.

Before heat treatment: EBT

The EBT test is not good with examples 1-1, 1-2 and 1-3, i.e. with a first layer of TiOx deposited without 02.

The EBT test is drastically improved for 2-1 and 2-2 stacks comprising a first layer of weakly oxidized titanium oxide.

The presence of a weakly oxidized first layer is necessary to obtain a correct EBT.

The insertion of SnZnO as an overlayer thus makes it possible to have a good TT-EBT. This example highlights the role of the combination of TiOx/SnZnO layers in the EBT mechanical test. Good behavior of the stack of the invention Emp.13-1 TiOx gradient /SnZnO at IΈBT and at TT_EBT is observed. By comparing the two stacks 13 and 13-1 differing in the presence of the SnZnO layer, it can be seen that this layer indeed allows the improvement of the EBT test.

V. Characterization of scratch behavior after heat treatment 1. Visibility of scratches: EST-TT test

Images of the scratches after EST at different forces followed by heat treatment at 650°C (EST-TT) were taken. This illustrates the scratch behavior of the stack after heat treatment.

The graphs of FIGS. 2 and 3 explained by table 11 and table 10 below illustrate the visibility of the scratches (in arbitrary units) as a function of the force applied (in newtons) to carry out the EST-TT test.

[Table 12]

[Table 13]

A clear improvement in the case of the 13-1 stack of the invention is observed compared to the reference stack Ref.O.

The scratches made between 0.3 and 5 N on the reference stack are much more visible than the scratches made at the same force on the stacks of the invention.

2. Observation of the hot corrosion of the scratches

Figures 3 explained by table 12 represent images taken under a microscope (x50 magnification) of the scratches made at 5N. This highlights the corrosion of the scratches after heat treatment for the reference stack and the absence of corrosion for the stack of the invention Emp.13-1.

[Table 12]

VI. Laser type heat treatment

The coated materials were processed using a laser line formed from a disc laser. The following conditions were used: - disc laser source: Yb:YAG,

- wavelength: 1030nm,

- width: 60pm,

- power density: 70kW/cm ² .

The laser treatment was carried out on the following stacks: Emp.0-1, EmpO-2, Emp.1-1, Emp.1-2, Emp.1-3, Emp.2-1, Emp. 2-2, Emp.12-1, Emp.12-2, Emp.12-3, Emp.13, Emp.13-1.

VI.1. Evolution of square resistance and absorption

The sheet resistance and the absorption were determined as before.

Although the absorption and resistivity results are slightly different from those obtained by a quenching type treatment, the same trends are observed in particular:

- the beneficial effect of using a layer of TiOx deposited from a ceramic target in a controlled atmosphere comprising oxygen,

- the beneficial effect of using an oxidation gradient coating,

- the beneficial effect of a layer of zinc and tin oxide in contact with the titanium oxide-based layer or the oxidation gradient coating.

Microscopic observations were also made

VI.2. Microscopic Observations: Hot and Blur Corrosion

Observations under the microscope after laser heat treatment show no point of corrosion for the stacks according to the invention. Furthermore, the stacks of the invention do not exhibit any blurring either.

VII. Conclusion

The examples of the invention show that an oxidation gradient coating based on titanium oxide makes it possible to obtain after heat treatment:

- a marked improvement in blurring: absence of blurring,

- square resistance: decrease in square resistance,

- scratch resistance:

- less visible scratches and

- if present, absence of hot corrosion of existing scratches,

- for a given Rsq to lower the thickness of the silver layer and allow an increase in light transmission and solar factor,

The oxidation gradient also allows:

- control absorption, before and after heat treatment,

- to obtain mechanical resistance to the brush after satisfactory heat treatment. Finally, the use of a first weakly oxidized layer also makes it possible to obtain after thermal treatment :

- a gain in Rsq of 10-15%,

- similar absorption, or even less than that of a reference stack,

- an improvement of the EBT and TT-EBT test.

Claims

1. Material comprising a transparent substrate coated with a stack of layers comprising at least one silver-based functional metal layer and at least two dielectric coatings, each dielectric coating comprising at least one dielectric layer, so that each layer functional metallic layer is placed between two dielectric coatings, characterized in that the stack comprises a coating comprising, as deposited, an oxidation gradient based on titanium oxide located above and in contact with a functional metallic layer based on silver, the part of the oxidation gradient coating in contact with the functional layer is less oxidized than the part of this coating further from the functional layer.

2. Material according to any one of the preceding claims, characterized in that the oxidation gradient coating comprises at least one layer based on titanium oxide deposited from a ceramic target, in particular under stoichiometric, in an atmosphere including oxygen.

3. Material according to the preceding claim, characterized in that the layer based on titanium oxide is deposited with a percentage of oxygen in volume flow representing between 0.1 and 10%.

4. Material according to any one of the preceding claims, characterized in that the oxidation gradient coating comprises at least two layers of titanium oxide each comprising different proportions of oxygen.

5. Material according to the preceding claim, characterized in that the oxidation gradient coating comprises a first layer deposited from a ceramic target, in particular substoichiometric, in an atmosphere whose percentage by volume flow rate of oxygen represents between 0 and 4%.

6. Material according to the preceding claim, characterized in that the oxidation gradient coating comprises a first layer deposited from a ceramic target, in particular substoichiometric, in an oxidizing atmosphere whose percentage by volume flow of oxygen represents between 0.5 and 3%.

7. Material according to any one of claims 4 to 6 characterized in that the first layer has a thickness of between 0.2 and 4 nm.

8. Material according to any one of claims 6 to 7, characterized in that the oxidation gradient coating comprises a second layer based on titanium oxide deposited from a ceramic target, in particular substoichiometric, in a atmosphere comprising higher proportions of oxygen than that used for the first layer.

9. Material according to claim 8 characterized in that the second layer has a thickness of between 0.2 and 30 nm.

10. Material according to any one of the preceding claims, characterized in that the stack comprises at least one layer comprising silicon.

11. Material according to claim 10 characterized in that the sum of the thicknesses of all the layers comprising silicon in the dielectric coating located above the first functional metal layer based on silver is greater than 50% of the thickness total dielectric coating.

12. Material according to any one of claims 10 to 11 characterized in that the sum of the thicknesses of all the layers comprising silicon in each dielectric coating is greater than 50%.

13. Material according to any one of the preceding claims, characterized in that the stack also comprises a layer based on zinc oxide and tin comprising at least 20% by mass of tin relative to the total mass. of zinc and tin, located above and in contact with the layer based on titanium oxide.

14. Material according to the preceding claim, characterized in that the layer based on zinc oxide and tin has a thickness:

- greater than 5 nm,

- less than 40 nm.

15. Material according to claim 13 or 14 characterized in that the stack further comprises a layer comprising silicon, located above and in contact with the layer based on zinc oxide and tin, preferably a layer based on silicon nitride.

16. Material according to any one of the preceding claims, characterized in that the metallic functional layer is deposited above and in contact with a layer based on zinc oxide.

17. Material according to any one of the preceding claims, characterized in that the sum of the thicknesses of all the oxide-based layers present in the dielectric coating located above the first functional metal layer is less than 50% of the total thickness of the dielectric coating.

18. Material according to any one of the preceding claims, characterized in that the stack has been subjected to rapid thermal annealing.

19. Material according to any one of the preceding claims, characterized in that the stack and the substrate have been subjected to a heat treatment at a high temperature above 500° C. such as quenching, annealing or bending.

20. Glazing comprising a material according to any one of claims 1 to 19 characterized in that it is in the form of monolithic, laminated and/or multiple glazing.