Method for depositing a thin layer and product thus obtained

CA 02674085 2014-09-25 1 THIN LAYER DEPOSIT PROCESS AND PRODUCT OBTAINED The invention relates to the field of inorganic thin films, in particular deposited on glass substrates.

It relates more particularly to a process for at least partial crystallization of said thin layers and to certain products obtained using this process.

Numerous thin layers are deposited on substrates, in particular in flat or slightly curved glass, in order to give the materials obtained particular properties: optical properties, for example of reflection or absorption of radiation from a range of wavelengths. data, specific electrical conduction properties, or properties related to ease of cleaning or the possibility for the material to self-clean.

These thin layers are most often based on inorganic compounds: oxides, nitrides, or even metals.

Their thickness generally varies from a few nanometers to a few hundred nanometers, hence their qualification of thin.

As examples, mention may be made of thin films based on mixed oxides of tin and indium (called ITO), based on mixed oxides of indium and zinc (called IZO), based on 'zinc oxide doped with gallium or aluminum, based on titanium oxide doped with niobium, based on cadmium or zinc stannate, based on tin oxide doped with fluorine and / or l 'antimony.

These different layers have the particularity of being transparent layers that are nevertheless conductive or semi-conductive, and are used in many systems where these two properties are necessary: ​​liquid crystal screens (LCD), solar or photovoltaic sensors, electrochromic devices or electroluminescent ...

Mention may also be made of thin films based on metallic silver, or even on metallic molybdenum or niobium, which have properties of electrical conduction and reflection of infrared radiation CA 02674085 2014-09-25 2, hence their use in solar control glazing, in particular anti-solar (aimed at reducing the amount of incoming solar energy) or low emissivity (aimed at reducing the amount of energy dissipated to the outside of a building or a vehicle).

Mention may also be made of thin layers based on titanium oxide, which have the particularity of being self-cleaning, by facilitating the degradation of organic compounds under the action of ultraviolet radiation and the elimination of mineral soiling (dust) under it. action of a water runoff.

The different layers have the particularity of seeing some of their properties improved when they are in an at least partially crystallized state.

We generally seek to increase as much as possible the rate of crystallization of these layers (the mass or volume proportion of crystallized material) and the size of the crystal grains (or the size of coherent diffraction domains measured by X-ray diffraction methods), or even in certain cases to favor a particular crystallographic form.

In the case of titanium oxide, it is known that titanium oxide crystallized in the anatase form is much more effective in terms of degradation of organic compounds than titanium oxide, amorphous or crystallized in the rutile or brookite form. .

It is also known that silver layers exhibiting a high crystallization rate and therefore a low residual amorphous silver content exhibit lower emissivity and resistivity than predominantly amorphous silver layers.

The electrical conductivity and the low emissivity properties of these layers are thus improved.

Likewise, the aforementioned transparent conductive layers, in particular those based on doped zinc oxide or the indium oxide layers doped with tin, exhibit an electrical conductivity that is all the higher as their degree of crystallization is high.

A process commonly used on an industrial scale for the deposition of thin films, in particular on a glass substrate, is the magnetic field assisted sputtering process, called the magnetron process CA 02674085 2014-09-25 3.

In this process, a plasma is created under a high vacuum in the vicinity of a target comprising the chemical elements to be deposited.

The active species of the plasma, by bombarding the target, tear off said elements, which are deposited on the substrate, forming the desired thin layer.

This process is said to be reactive when the layer consists of a material resulting from a chemical reaction between the elements torn from the target and the gas contained in the plasma.

It is thus known to deposit, by a magnetron process of the reactive type, layers of titanium oxide by using a target made of metallic titanium and an oxygen-based plasma gas. The major advantage of this process lies in the possibility of depositing on the same line a very complex stack of layers by successively scrolling the substrate under different targets, generally in one and the same device.

During the industrial implementation of the magnetron process, the substrate remains at room temperature or undergoes a moderate temperature rise (less than 80 ° C.), particularly when the travel speed of the substrate is high (which is generally desired for reasons economic).

What may appear to be an advantage, however, constitutes a disadvantage in the case of the aforementioned layers, since the low temperatures involved do not generally allow sufficient crystal growth. This is particularly the case for thin layers of low thickness and / or layers made up of materials with a very high melting point.

The layers obtained according to this process are therefore predominantly or even completely amorphous or nano-crystallized (the average size of the crystal grains being less than a few nanometers), and heat treatments are necessary to obtain the desired degree of crystallization or the desired grain size. .

Possible heat treatments consist in heating the substrate either during the deposition or at the end of the deposition, at the outlet of the magnetron line.

Most generally, temperatures of at least 200 C or 300 C are required.

Crystallization is in fact all the better and the size of the grains is all the greater as the temperature of the substrate is close to the melting point of the material constituting the thin film.

CA 02674085 2014-09-25 4 Heating the substrate in industrial magnetron lines (during deposition) has however proved difficult to implement, in particular because heat transfers under vacuum, necessarily of a radiative nature, are difficult to master and involve a high cost in the case of large substrates, several meters wide.

In the case of thin glass substrates, this type of treatment often involves high risks of breakage.

Heating the coated substrate after the deposition, for example by placing the substrate in an oven or an oven or by subjecting the substrate to infrared radiation from conventional heating devices such as infrared lamps, also has drawbacks because these various processes contribute to indiscriminately heating the substrate and the thin film.

Heating the substrate to temperatures above 150 ° C. is liable to generate breakage in the case of large substrates (several meters wide) because it is impossible to ensure an identical temperature over the entire width of the substrate.

Heating the substrates also slows down the entire process, as it is necessary to wait for their complete cooling before considering their cutting or storage, which usually takes place by stacking the substrates on top of each other.

Very controlled cooling is also essential to avoid the generation of stresses within the glass, and therefore the possibility of breakage.

Such very controlled cooling being very expensive, the annealing is generally not sufficiently controlled to eliminate the thermal stresses within the glass, which generates an increased number of in-line breaks.

Annealing also has the drawback of making it more difficult to cut the glass, the cracks having a less strong tendency to propagate linearly.

The heating of the substrates takes place in the case where the glazings are curved and / or toughened, because a reheating of the glass beyond its softening temperature (generally at more than 600 C, or even 700 C for a few minutes) is carried out.

Hardening or bending therefore makes it possible to obtain the desired result of crystallization of the thin layers.

However, it would be expensive to subject all glazing to such treatments for the sole purpose of CA 02674085 2014-09-25 to improve the crystallization of the layers.

In addition, toughened glazing can no longer be cut, and certain stacks of thin layers cannot withstand the high temperatures experienced during tempering of the glass.

The object of the invention is to propose a process which makes it possible to improve the crystallization properties of numerous thin layers but which does not have the aforementioned drawbacks.

To this end, the subject of the invention is a method for treating at least one continuous thin layer deposited on a first face of a substrate, characterized in that each point of said at least one thin layer 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 said substrate opposite to said first face, so as to increase the rate of crystallization of said thin layer while keeping it continuous and without a step of melting said thin layer.

For the purposes of the present invention, the term “continuous thin layer” is understood to mean that the layer covers substantially all of the substrate or, in the case of a stack, all of the underlying layer.

It is important that the continuous nature of the thin film (and therefore its advantageous properties) is preserved by the treatment according to the invention.

The term “point of the layer” is understood to mean an area of ​​the layer undergoing the treatment at a given time.

According to the invention, the entire layer (therefore each point) is brought to a temperature of at least 300 ° C., but each point of the layer is not necessarily treated simultaneously.

The layer can be treated at the same time as a whole, each point of the layer being simultaneously brought to a temperature of at least 300 C.

The layer can alternatively be treated so that the different points of the layer or sets of points are successively brought to a temperature of at least 300 ° C., this second mode being more often used in the case of a setting. continuous work on an industrial scale.

The method according to the invention makes it possible to provide sufficient energy to promote crystallization of the thin layer, by a physicochemical mechanism of crystal growth around seeds already present in the CA 02674085 2014-09-25 6 ​​layer, while remaining in solid phase.

The method according to the invention does not implement a mechanism of crystallization by cooling from a molten material, on the one hand because this would require bringing the thin layer to extremely high temperatures in order to obtain its fusion, and of on the other hand because this would be liable to modify the thicknesses and / or the refractive indices of the layers, and therefore their properties.

This would in particular modify their optical appearance by generating inhomogeneities detectable at The method according to the invention has the advantage of heating only the thin layer (or the thin layers in the case of a stack), without significant heating of the entire material. substrate.

It is thus no longer necessary to carry out a slow and controlled cooling of the substrate before cutting or storing the glass.

This method also makes it possible to integrate a heating device on existing continuous production lines, more particularly in the space located between the outlet of the vacuum deposition chamber of the magnetron line and the storage device of the magnetron line. stacked glass.

It is also possible in certain cases to carry out the treatment according to the invention within the vacuum deposition chamber itself.

In an industrial implementation integrated into a magnetron line, the process is generally continuous in the sense that the substrate is moving, and therefore undergoes a linear movement in an X direction.

Each point of the thin layer is then preferably treated according to one of the following methods: either the heating means are fixed and it is possible to simultaneously process a set of points forming a line in a direction Y perpendicular to the direction X, or the heating means are movable in the Y direction and each point is processed successively.

The method according to the invention can be implemented on a substrate placed both horizontally and vertically.

It can also be implemented on a substrate provided with thin layers on its two faces, at least one layer of one of the faces or of each face being treated according to the invention.

In the case where thin layers deposited on the two faces of the substrate are treated according to the invention, it is possible to treat said thin layers of each face either simultaneously or successively, by identical or distinct techniques, in particular according to CA 02674085 2014-09-25 7 that the nature of the treated layers is identical or distinct.

The case where the treatment according to the invention is carried out simultaneously on the two faces of the substrate is therefore well understood within the scope of the invention.

It is not physically possible to heat the layer without heating the substrate, because the temperature rise within the layer necessarily results, by thermal conduction mechanisms, in heating the area of ​​the substrate closest to the layer. , and therefore a high thermal gradient in the thickness of the substrate.

Such high thermal gradients, sometimes called thermal shocks, are known to systematically generate breakages in the case of soda-lime-silica glasses commonly used in the flat glass industry.

These breakages, which originate from the thermal expansion differential between the different areas of the glass subjected to different temperatures, occur more easily in the case of soda-lime-silica glasses because their coefficient of expansion is quite high.

They also occur more easily in the case of large substrates (at least 1 m, or even 2 or even 3 m wide) because it is more difficult to ensure high temperature homogeneity for large substrates.

The inventors have however demonstrated that a heat treatment only implementing moderate and controlled heating of a limited area of ​​the substrate made it possible to overcome this problem of breakage, which until then had been deemed inevitable.

It is therefore essential for the implementation of the present invention that the temperature of the face of the substrate opposite to the face bearing the treated thin layer is not greater than 150 ° C.

This characteristic is obtained by choosing a heating mode specially adapted to the heating of the thin film and not of the substrate and by controlling the heating time or intensity and / or other parameters according to the heating mode employed, as described. in more detail in the remainder of the text.

A characteristic common to all the heating modes which can be used according to the invention lies in the fact that they make it possible to generate an extremely high power per unit area, which cannot however be quantified absolutely because it depends on many factors among which the nature and thickness of the thin layer.

This high power by CA 02674085 2014-09-25 8 surface unit makes it possible to reach the desired temperature at the level of the layer extremely quickly (generally in a time less than or equal to 1 second) and consequently to limit as much the duration of the treatment, the heat generated then not having time to diffuse within the substrate.

Each point of the thin layer is subjected to the treatment according to the invention (that is to say brought to a temperature greater than or equal to 300 ° C.) for a period generally less than or equal to 1 second, or even 0.5 second. Conversely, the infrared lamps conventionally used do not make it possible to achieve these high powers per unit area, the treatment time must be longer to reach the desired temperatures (often several seconds), and the substrate is then necessarily worn. at high temperatures by heat diffusion, even if the wavelength of the radiation is adapted to be absorbed only by the thin film and not by the substrate.

In order to limit the number of breaks as much as possible for the largest substrates (for example 6 m long and 3 m wide), a temperature of less than or equal to 100 ° C. is preferably maintained throughout the treatment, in particular 50 ° C. C, at any point on the face of the substrate opposite to the face on which the thin layer is deposited.

Another advantage of the invention lies in the fact that the process subjects the equivalent of a quenching to the thin film or to the stack of thin films.

It happens that certain stacks of thin films see their optical properties (colorimetric coordinates, light transmission or energy) modified when the glass is tempered.

The method according to the invention then makes it possible to obtain a non-tempered glass (therefore not having within it a stress profile specific to tempered glass, which makes it cuttable) but having substantially the same optical properties as if it had been soaked.

The degree of crystallization obtained using the process according to the invention is preferably greater than or equal to 20% or 50%, in particular 70% and even 90%.

This crystallization rate, defined as being the mass of material crystallized over the total mass of material, can be evaluated by X-ray diffraction in CA 02674085 2014-09-25 9 using the Rietveld method.

Due to a mechanism of crystallization by growth of crystal grains from seeds or nuclei, the increase in the rate of crystallization is generally accompanied by an increase in the size of the crystallized grains or in the coherent domains of diffraction measured by diffraction. X-rays.

The substrate is preferably transparent, made of glass, in particular soda-lime-silica.

It can also be made of plastic, such as polycarbonate or polymethyl methacrylate.

It 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, the method according to the invention being particularly advantageous for the thinnest substrates, the thickness of which is less than or equal to 4 mm, or even 2 mm.

The thin layer is preferably a layer of which at least one property is improved when the rate of crystallization of said layer increases.

For the reasons mentioned above, and related to the correlation between properties and crystallization rate, the thin layer is preferably based on a metal, oxide, nitride, or mixture of oxides chosen from silver, molybdenum, niobium, titanium oxide, mixed oxides of indium and zinc or tin, zinc oxide doped with aluminum or gallium, nitrides of titanium, aluminum or zirconium, titanium oxide doped with niobium, cadmium and / or tin stannate, tin oxide doped with fluorine and / or antimony.

It even preferably consists of such a metal, oxide, nitride or mixture of oxides. The thickness of the thin layer is preferably between 2 and 500 nm.

Most of the aforementioned thin layers have the particularity of being globally transparent to UV-visible radiation (the absorption being less than 50% in the visible range).

Their absorption spectrum being little different from that of the substrate (in particular in the case where the latter is made of glass), it is all the more difficult to specifically heat the layer and not the substrate. Other layers such as silicon exhibit strong absorption in the visible and near infrared, which facilitates their selective heating, for example CA 02674085 2014-09-25 in the case of the transformation of amorphous silicon into polysilicon.

The thin film treated according to the invention may be the only thin film deposited on the substrate.

It can also be included in a stack of thin layers comprising thin layers, generally chosen from oxides, nitrides or metals.

The thin layer can also be in itself a stack of thin layers.

In the case where the treated thin layer is included in a stack of thin layers, the method according to the invention can improve the crystallization properties of one or more thin layers of the stack.

When the thin layer is a silver or silver-based layer, it is preferably included in a stack of layers, in particular in order to avoid its oxidation.

In the case of solar control or low emissivity glazing, the thin silver-based layer is generally placed between two thin dielectric layers based on oxide or nitride.

A very thin layer intended to promote wetting and nucleation of the silver (for example in zinc oxide ZnO) and on the silver layer a second very thin layer (sacrificial, sacrificial, for example titanium) intended to protect the silver layer in the event that the deposition of the subsequent layer is carried out in an oxidizing atmosphere or in the event of heat treatments leading to oxygen migration within the stack.

The stacks can also comprise several layers of silver, each of these layers being generally affected by the implementation of the method according to the invention.

In the case where the stack comprises a layer of zinc oxide, the treatment of the silver layer is also generally accompanied by an increase in the rate of crystallization of the zinc oxide.

When the thin layer is a transparent conductive layer, for example based on zinc oxide doped with gallium and / or with aluminum, it can be included in a stack of layers comprising at least one sublayer acting as a barrier to migration of alkalis and / or at least one overlayer acting as an oxidation barrier.

This type of stack is by CA 02674085 2014-09-25 11 example described in application VVO 2007/018951.

The treatment according to the invention, however, makes it possible to advantageously dispense with this type of sublayer or overcoat, since the rapidity of the heating generates very little migration of alkalis or oxygen, compared with annealing or quenching.

This is all the more advantageous in the case where the conductive layer must serve as an electrode and must therefore be in direct electrical contact with other functional layers (for example in the case of photovoltaic or OLED applications): in the case of a quenching or annealing, the protective overcoat against oxidation is necessary during processing and must then be removed.

Thanks to the method according to the invention, it is possible to do without this overlayer.

The titanium oxide-based layer is preferably a titanium oxide layer (optionally doped). The entire surface of this layer is preferably in contact with the outside so that the titanium oxide can fully play its self-cleaning function.

In order to further improve the crystallization of these layers, it is possible to provide under the titanium oxide-based layer a sublayer having the effect of promoting the crystal growth of the titanium oxide, in particular in the anatase form.

It may in particular be a ZrO 2 sublayer, as described in application VVO 02/40417, or a sublayer promoting the heteroepitaxial growth of titanium oxide in anatase form, such as described for example in application WO2005 / 040058, in particular a layer of BaTiO3 or SrTiO3. .

The thin layer before treatment according to the invention can be obtained by any type of process, in particular processes generating predominantly amorphous or nano-crystallized layers, such as the magnetron process, the plasma-assisted chemical vapor deposition process ( PECVD), the vacuum evaporation process, or the sol-gel process.

However, it is preferably a dry layer, not containing an aqueous or organic solvent, as opposed to a wet layer, for example obtained by the sol-gel process.

It is even preferably obtained by cathodic sputtering, in particular assisted by a magnetic field (magnetron process).

CA 02674085 2014-09-25 12 In the case of a layer obtained by the sol-gel process, precursors in solution (sol) are deposited on the substrate, the layer obtained then having to be dried and annealed to remove all traces of solvent.

In this case, the energy supplied by the heating then serves mainly to remove this solvent, without necessarily affecting the crystallization properties of the layer, and it is consequently more difficult to improve said properties in a sufficiently short time so as not to also heat the substrate.

For greater simplicity, the heating of the layer is preferably carried out in air and / or at atmospheric pressure.

However, certain heating modes are compatible with vacuum, and it may be advantageous to heat the layer itself within the vacuum deposition chamber, for example before a subsequent deposition.

Different heating means make it possible to implement the method according to the invention, allowing the generation of a very high power per unit area.

The heating parameters such as the power of the heating means or the heating time are to be adapted on a case-by-case basis by those skilled in the art according to various parameters such as the nature of the heating process, the thickness or the nature the layer, the size and the thickness of the substrates to be treated etc.

When the thin film is electrically conductive (in the case of silver for example), the heating of the thin film can be carried out by induction.

Induction heating of metal parts is a well-known process for reaching high temperatures in a rapid and controlled manner within solid conductive parts (reinforcement of steels, melting of silicon zones, etc.).

The main applications concern the fields of the food industry (heating of tanks, cooking of flat products on metal strips, cooking-extrusion) and metal fabrication (melting, reheating before forming, heat treatment in the mass, surface heat treatment, etc. coating treatment, welding, brazing).

An alternating current flowing through a coil (called a solenoid or turn) generates inside it a magnetic field oscillating at the same frequency.

If an electrically conductive part is placed inside the coil (or solenoid) CA 02674085 2014-09-25 13, currents induced by the magnetic field develop there and heat the part by the Joule effect.

Currents appear on the surface of the part to be heated.

A characteristic depth called skin thickness can be defined, giving as a first approach the thickness of the current layer. The skin thickness of the currents depends on the nature of the heated metal and decreases as the frequency of the current increases.

In the case of heating an insulating substrate covered with a conductive layer, it is preferable to use a high frequency bias in order to concentrate the influence of the inductor on the surface part of the material.

The frequency is preferably between 500 kHz and 5 MHz, in particular between 1 MHz and 3 MHz.

An inductor specially adapted for the treatment of flat surfaces is preferably employed.

Induction is not preferred when the thin film has a thickness of less than 20 nm, or even less than 10 nm.

For these particularly thin layers, a very high frequency is necessary, and the volume of the layer being very small, the effectiveness of the treatment is compromised.

When the thin film absorbs at least part of the infrared radiation, the heating of the thin film can be carried out using radiation the wavelength of which is included in said part of the infrared radiation absorbed by said layer.

In order to limit the heat input to the substrate as much as possible, the wavelength of the radiation chosen is preferably not included in the part of the infrared radiation absorbed by the substrate.

For the above reasons, the radiation must be characterized by a high power per unit area.

For this reason, the heating of the thin film is preferably carried out using a laser emitting infrared radiation.

Infrared lamp systems associated with a focusing device making it possible to achieve high powers per unit area can also be used.

In the case of a layer based on titanium oxide, it is preferable to use a laser emitting radiation with a wavelength of between 5 and 15 micrometers, for example a CO2 laser emitting a CA 02674085 2014-09-25 14 radiation with a wavelength of 10.6 micrometers.

In the case of a silver-based layer, it is preferable to use a laser emitting radiation whose wavelength is between 0.5 and 5 micrometers.

A YAG laser (aluminum and yttrium garnet Y2A11502) doped with neodymium, emitting, in continuous or pulsed mode, a radiation of about 1 micrometer in wavelength, has proved particularly well suited, in particular when the the substrate does not absorb in this wavelength range, which is the case for clear glasses, whose iron oxide content by weight is 0.1% or less.

The use of excimer lasers, emitting radiation in the ultraviolet range, is also possible for layers absorbing such radiation.

For increased simplicity of use, the lasers used in the context of the invention can be fiber-reinforced, which means that the laser radiation is injected into an optical fiber and then delivered near the surface to be treated by a focusing head.

The laser can also be fiber, in the sense that the amplification medium is itself an optical fiber.

As lasers can only irradiate a small area (typically of the order of a fraction of mm2 to a few hundred mm2), it is necessary, in order to treat the entire surface, to provide a system for moving the laser beam in the plane of the substrate or a system forming a laser beam in line simultaneously irradiating the entire width of the substrate, and under which the latter runs.

The heating of the thin layer can also be carried out by thermal spraying techniques, in particular by a plasma torch spraying technique (plasma spray).

A plasma is an ionized gas generally obtained by subjecting a so-called plasma gas to an excitation such as a strong direct or alternating electric field (for example an electric arc).

Under the action of this excitation, electrons are torn from the atoms of the gas and the charges thus created migrate towards the electrodes of opposite charge.

These charges then excite other atoms of the gas by collision, creating by avalanche effect a homogeneous or microfilament discharge CA 02674085 2014-09-25 or even an arc.

Plasmas can be hot (the gas is then fully ionized and the temperature of the plasma is of the order of 106 C), or thermal (the gas is almost entirely ionized and the temperature of the plasma is of the order of 104 C, case for example of electric arcs).

Plasmas contain many active species, that is to say, capable of interacting with matter, including ions, electrons or free radicals.

In the case of a plasma torch, a gas is blown through an electric arc, and the thermal plasma formed is blown towards the substrate to be treated.

The plasma torch is commonly used to deposit thin layers on various substrates by adding precursors in the form of powders to the plasma.

In the context of the invention, the plasma torch is preferably associated with an automatic displacement system located perpendicular to the direction of travel of the coated substrate and allowing the treatment of the entire surface by successive round trips from the torch to above the substrate.

The blown gas is preferably nitrogen, air or argon, advantageously comprising a hydrogen content by volume of between Set 50%, in particular between 15 and 30%.

Heating of the thin film can also be achieved by subjecting said thin film to the action of at least one flame.

This flame treatment is preferably carried out on a flame treatment bench located perpendicular to the direction of travel of the substrate.

The length of the flaming device is preferably at least equal to the width of the coated substrate, which easily allows the process to pass without requiring a displacement system.

The gas used can be a mixture of an oxidizing gas, in particular chosen from air, oxygen or their mixtures, and a combustible gas, in particular chosen from natural gas, propane, butane, or even acetylene or hydrogen, or mixtures thereof. Oxygen is preferred as an oxidizing gas, in particular in combination with natural gas (methane) or propane, on the one hand because it makes it possible to reach higher temperatures and therefore to shorten the treatment and avoid the CA 02674085 2014-09-25 16 heater of the substrate, and on the other hand because it prevents the creation of NO nitrogen oxides.

In order to reach the desired temperatures at the level of the thin film, the coated substrate is generally positioned within the visible flame, in particular at the level of the hottest zone of the flame, a part of the visible flame then extending around the treated area.

Flaming is a technique commonly used for treating the surface of polymers in order to improve their wettability properties and facilitate their coating with paints.

In the use which is made of it, the principle is to subject the surface to be treated to the action of radicals created by combustion, without bringing said surface to a high temperature.

Application US 2006/128563 describes the use of this technique for activating the surfaces of titanium oxide layers in order to improve their hydrophilic properties. The treatments described, quite similar to those performed on polymeric substrates, consist in scrolling a substrate at or slightly below (a few centimeters) of the tip of the visible flame.

This type of treatment, which aims to create hydroxyl groups on the surface of the titanium oxide, is not, however, suitable for bringing the thin layer of titanium oxide to temperatures above 200 ° C. and increasing the rate. crystallization of titanium oxide, because the temperatures at the tip of the visible flame are insufficient.

Heating of the thin layer can also be carried out using radiation in the microwave range (wavelengths ranging from 1 millimeter to 30 centimeters, ie frequencies ranging from 1 to 300 GHz).

Heating of the thin layer can also be achieved by bringing said thin layer into contact with a solid or a hot liquid.

It may for example be a heated roller movable in rotation in contact with which the substrate coated with the thin layer to be heated scrolls.

The roll can be cylindrical or include a multiplicity of facets, thus making it possible to increase the contact surface between the roll and the substrate.

The hot solid, preferably in the form of a roll, is preferably made of a flexible material in order to be able to conform to any surface irregularities or deformations of the substrate.

It preferably has a high thermal conductivity in order to obtain good heat transfer to the surface of the substrate.

The solid is preferably brought to temperatures of at least 500 C, or even 600 C and even 700 C.

The induction and flame heating modes are preferred when it is not desired to use a mechanical device for moving above the substrate.

The heating modes by infrared radiation or induction can for their part be implemented within the vacuum deposition device of the magnetron line.

The latter are also advantageous when one does not wish to consume large quantities of gas.

When the thin layer is based on titanium oxide (or consists of titanium oxide), a preferred embodiment of the invention consists in bringing said thin layer to a temperature between 300 and 800 C, preferably between 400 and 600 C, so that said thin layer comprises titanium oxide in anatase form.

As indicated above, such crystallization makes it possible to considerably increase the photocatalytic activity of titanium oxide.

The heating of the layer is preferably carried out by one of the following techniques:

by contact with a hot solid at a temperature greater than or equal to 400 C, by heating using a plasma torch, using a CO2 laser emitting radiation with a wavelength of l 'of the order of 10 micrometers, by subjecting said thin layer to the action of at least one flame.

The process according to the invention is particularly advantageous in the case of titanium oxide, because when a substrate containing alkali metal ions (for example a glass of the silico-soda-lime type) is brought to a high temperature, said ions have a tendency to diffuse into the titanium oxide layer, very appreciably reducing, or even canceling, its photocatalytic properties.

For this reason, it is customary to interpose between the thin layer of titanium oxide and the substrate a barrier layer to the migration of alkalis, as taught in application EP-A-0 850 204, or to increase CA 02674085 2014-09-25 18 the thickness of the titanium oxide layer so that at least the extreme surface of the layer is not contaminated, as taught in application EP-A0 966 409.

In the case of the process according to the invention, the substrate is hardly heated and the migration of alkalis is consequently almost zero.

The method according to the invention therefore makes it possible to obtain substrates made of soda-lime glass coated directly with a thin layer of titanium oxide (for example of the order of 10 nanometers in thickness) and nevertheless exhibiting a very high photocatalytic activity.

When the thin layer is silver-based (or consists of silver), said thin layer is preferably brought to a temperature between 300 and 600 ° C., preferably between 350 and 550 ° C.

The preferred techniques are heating using a laser emitting infrared radiation, by induction, by plasma torch or by flame.

It has been observed in the case of silver-based layers that heating for too long or too high an intensity, in particular using a laser emitting in the infrared or by induction, could not only lead to a raising the temperature of the substrate, but also destroying the continuity of the layer by creating, from an initially continuous layer, a discontinuous layer comprising isolated silver nodules, producing a blur by direct observation or under strong illumination.

This embodiment is obviously not desirable and is not included within the scope of the invention.

The subject of the invention is also a process for obtaining a material comprising a substrate and at least one thin layer, characterized in that said at least one thin layer is deposited on said substrate by cathodic sputtering assisted by magnetic field. , and in that said at least one thin layer is subjected to a heat treatment according to the invention.

A further subject of the invention is the materials capable of being obtained by the process according to the invention.

The process according to the invention in fact makes it possible to obtain materials comprising a thin layer whose degree of crystallization could only be obtained by heat treatments of quenching, bending or annealing, CA 02674085 2014-09-25 19 either treatments affecting the entire substrate during deposition.

The materials obtained according to the invention therefore differ from the materials known from the prior art by a different structure, in particular by the fact that in their thickness they do not have a stress profile characteristic of that of a tempered glass and / or that they do not give rise to the same diffusion of elements (alkalis, oxygen, etc.) from the substrate or from the outside.

Such a material consists for example of a non-tempered glass substrate, coated with a stack of thin layers comprising at least one silver layer of thickness e (expressed in nm). The stack is characterized by a square resistance Rc (expressed in ohm) corresponding to the formula:

Rc x e2 ¨ 120 <25 x e.

The resistance per square of a thin conductive film depends on its thickness according to the Fuchs-Sondheimer law which is expressed as Rc x e2 = pxe + A.

In this formula p denotes the intrinsic resistivity of the material forming the thin film and A corresponds to the specular or diffuse reflection of the charge carriers at the interfaces. The invention makes it possible to obtain an improvement in the intrinsic resistivity p such that p is less than or equal to 25 and an improvement in the reflection of the carriers such that A is less than or equal to 120, preferably 110 and even 105.

The method according to the invention thus makes it possible to obtain layers exhibiting very low resistivities, which had hitherto only been possible with the aid of quenching.

The glass is not tempered, however does not present in its thickness the characteristic stress profile of a tempered glass (presence of extension stresses at the heart of the glass and of compression at the level of the two faces), and is not therefore cuttable.

The stack is preferably of the type previously described in the present text, or in applications W02007 / 110552, W02007 / 101964, W02007 / 101963, W02007 / 054656, W02007 / 054655, W02007 / 042688, W02007 / 042687, W02005 / 110939 , W02005 / 051858, W02005 / 019126, W004 / 043871, W000 / 24686, W000 / 29347, EP0995724, EP0995725 W099 / 45415, EP922681, EP894774, EP877006, EP745569, EP718250.

CA 02674085 2014-09-25 A material according to the invention also consists of a glass substrate of the silico-soda-lime type, coated with at least one thin layer comprising titanium oxide (and in particular consisting of (titanium oxide) at least partially crystallized in the anatase form, obtainable by the process according to the invention.

This material differs from substrates coated with a layer of titanium oxide deposited by the magnetron process on a hot substrate and / or annealed in an oven, in that the layer of titanium oxide (or possible sublayers) includes less sodium oxide from the substrate.

Since the process does not involve substantial heating of the substrate, the sodium ions have in fact very markedly less tendency to diffuse into the layer based on titanium oxide.

The titanium oxide-based layer is preferably deposited directly on the substrate, without an intermediate layer.

It can also be deposited on intermediate layers which do not have properties as a barrier to the diffusion of alkaline ions, but which have desirable properties (optical properties for example).

The glass substrate is preferably unhardened.

A material according to the invention also consists of a substrate coated with at least one transparent conductive thin layer based on mixed oxides of indium and zinc or of tin, of zinc oxide doped with aluminum. or gallium, based on titanium oxide doped with niobium, based on cadmium and / or zinc stannate, based on tin oxide doped with fluorine and / or antimony.

In particular, a particularly interesting material, which could not be obtained by techniques known until now, consists of a non-tempered glass substrate, coated with at least one layer based on zinc oxide doped with l. aluminum or gallium.

This material is characterized in that the roughness of the layer based on zinc oxide doped with aluminum or gallium has an RMS roughness less than or equal to 10 nm and a square resistance less than or equal to 15 ohms.

The RMS roughness is calculated from an AFM (atomic force microscopy) measurement carried out on a sample of one square micron.

The RMS roughness is even preferably less than or equal to 9 nm, or even 8 nm, and even 6 nm or 5 nm.

CA 02674085 2014-09-25 21 Such layers which are so little resistive (the thickness of which is quite high, sometimes greater than or equal to 500 nm) and yet so little rough have hitherto only been able to be obtained by a treatment of quenching. Conversely, such low resistive layers could be obtained on non-tempered glass by a magnetron-type deposition carried out on a heated substrate, but in this case the roughness obtained was much higher.

The layers of the different materials which have just been described can obviously exhibit any one of the characteristics described throughout the text, alone or in combination with other characteristics which are also described therein.

The substrates obtained according to the invention can be used in single, multiple or laminated glazing, mirrors, glass wall coverings.

In the case of multiple glazing comprising at least two glass sheets separated by a gas layer, it is preferable for the thin layer to be placed on the face in contact with said gas layer.

They can also be used in photovoltaic glazing or solar panels, the thin film treated according to the invention being for example an upper electrode based on ZnO: Al or Ga in stacks based on chalcopyrites (in particular of the CIS - CuInSe2 type. ) or based on amorphous and / or polycrystalline silicon, or else based on CdTe.

They can also be used in display screens of the LCD (Liquid Crystal Display), OLED (Organic Light Emitting Diodes) or FED (Field Emitting Display) type, the thin film treated according to the invention being for example an electrically conductive layer made of ITO. .

They can also be used in electrochromic glazing, the thin layer treated according to the invention being for example an upper transparent electroconductive layer, as taught in application FR-A-2 833 107.

The invention is illustrated with the aid of the non-limiting exemplary embodiments which follow.

CA 02674085 2014-09-25 22 EXAMPLE 1 A soda-lime-silica glass substrate obtained by the float process and then cut so that its size is 3 m in width and 6 m in length is coated in a known manner with the magnetron process of a thin layer of titanium oxide 10 nm thick.

In a first example, a 20 nm thick silica layer is interposed between the substrate and the titanium oxide layer (sample A).

In a second example, the titanium oxide layer is deposited directly on the substrate (sample B).

Between the output of the magnetron line and the storage device, a device is inserted comprising:

a CO2 laser emitting radiation at 10.6 micrometer wavelength focused on the Ti02 layer, the spot width being about 0.3 to 0.5 mm, and a rapid displacement system of the laser (from the order of 3 to 5 meters / second) in a direction perpendicular to the direction of travel of the substrate.

The temperature of the glass substrate during the treatment does not exceed 50 ° C., measured by pyrometry at the level of the face of the substrate opposite to the face bearing the coating of thin layers.

Table 1 below indicates the photocatalytic activity of the layer before treatment and after treatment.

The photocatalytic activity corresponds to a measurement of the rate of degradation of methylene blue in the presence of ultraviolet radiation.

An aqueous solution of methylene blue is placed in contact in a sealed cell with the coated substrate (the latter forming the bottom of the cell).

After exposure to ultraviolet radiation for 30 minutes , the concentration of methylene blue is evaluated by measuring light transmission.

The photocatalytic activity value (denoted Kb and expressed in g.1-1.min-1) corresponds to the decrease in the concentration of methylene blue per unit of exposure time.

CA 02674085 2014-09-25 23 Table 'I Sample Kb, before Kb, after treatment treatment A <7 25 B <7 23 The significant increase in photocatalytic activity after treatment according to the invention illustrates the improvement in crystallinity of the titanium oxide layer.

The similarity of the values ​​obtained depending on whether or not an underlayer is interposed between the substrate and the titanium oxide layer testifies to the fact that the low heating of the substrate does not generate significant diffusion of the alkali ions in the layer of titanium oxide.

The treatment according to the invention therefore makes it possible to make the sublayer barrier to the diffusion of alkali ions unnecessary.

EXAMPLE 2 A soda-lime-silica glass substrate obtained by the float process and then cut so that its size is 3 m in width for 6 m in length is coated in a known manner by the magnetron process with a stack of thin films comprising a layer of silver, said layer of silver imparting low emissivity properties to the glass.

This stack comprises in order (from the substrate to the outer surface) the following oxide, metallic or nitride layers, the geometric thicknesses being indicated in brackets:

Glass / Sn02 (20nm) / ZnO (15nm) / Ag (8.5nm) / Ni-Cr / ZnO (15nm) / Si3N4 (25nm).

Between the output of the magnetron line and the storage device, a device is inserted comprising:

- a YAG laser (garnet of aluminum and yttrium Y2A11502) doped with neodymium, emitting, in continuous or pulsed mode, a radiation at 1.09 CA 02674085 2014-09-25 24 micrometer of wavelength focused on the layer of silver, the width of the spot being about 0.3 to 0.5 mm, and a system of rapid displacement of the laser (of the order of 3 to 5 meters / second) in a direction perpendicular to the direction scrolling of the substrate.

The temperature of the glass substrate during the treatment does not exceed 50 ° C., measured by pyrometry at the level of the face of the substrate opposite to the face bearing the coating of thin layers.

Table 2 below indicates the variation following the treatment of the following properties:

the light transmission under illuminant D65, calculated from an experimental spectrum, taking as a reference the standard illuminant D65 and the CIE 1964 reference observer, for a double glazing whose glass sheets have a thickness of 4 mm and the gas layer (mixture of 90% argon and 10% air) has a thickness of 16 mm, transmission denoted TL and expressed in percent, the square resistance, denoted Rc and expressed in ohms, the normal emissivity at a temperature of 283 K calculated according to standard EN 12898 from a reflection spectrum in the spectral range 5 ¨ 50 micrometers, denoted En, and expressed in percent.

These last two properties (square resistance and ernissivity), which illustrate the performance of electrical conductivity and low-emissivity of the layer, reflect the rate of crystallization and the size of the crystals of the silver layer because silver layers better. crystallized products exhibit both higher electrical conductivity and better emissivity properties.

Table 2 TL (%) Rc (Q) In (%) before after before after before after 77.0 78.3 5.0 4.5 5.5 5.0 CA 02674085 2014-09-25 Variations due to treatment in terms of square resistance and normal emissivity are of the order of 10%.

These results show that the treatment of the stack (and in particular the treatment of the silver layer) using the infrared laser resulted in an improvement in the crystallization of the silver layer, characterized in particular by a stronger crystallization rate and larger crystal size.

A significant increase in the light transmission of the glazing obtained can also be noted.

EXAMPLE 3 A coated substrate identical to that of Example 2, therefore coated with a stack comprising a silver layer, is used in this example.

The heating process is induction, carried out using an inductor whose geometry is specifically adapted to the treatment of flat surfaces.

The frequency is 2 MHz, the power being able to vary around a few kW.

The temperature of the glass substrate during processing, which lasts only a few seconds, does not exceed 150 C.

The table below indicates the variation of the properties described in the case of Example 2.

Table 3 TL (%) Rc (0) sn (%) before after before after before after 76.9 77.5 5.0 4.6 5.5 5.1 Variations in square resistance and emissivity, fairly comparable with those induced by infrared laser treatment further demonstrate an increase in the rate of crystallization of the silver layer.

CA 02674085 2014-09-25 26 EXAMPLE 4 In this example, coated substrates identical to those of Example 1, and therefore coated with a stack comprising a layer of titanium oxide, are used.

The heating method employed is contact with a flat surface heated to 700 C for 1 second.

The temperature of the glass (side opposite to the layer) does not exceed 150 C during the treatment.

Table 4 below indicates the photocatalytic activity before and after treatment.

Table 4 Sample Kb, before Kb, after treatment treatment A <7 22 B <7 23 The values ​​obtained are similar to those obtained according to Example 1.

EXAMPLE 5 In the context of this example, a substrate identical to that treated according to Examples 2 and 3 is subjected to heating carried out using a plasma torch.

Plasma gas is a mixture of argon or nitrogen with hydrogen in a 4: 1 ratio.

The plasma torch, with a power of 25 to 40 kW, is mounted on a device for rapid displacement (of the order of 1 to 4 meters / second) in a direction perpendicular to the direction of travel of the substrate.

The width of the zone affected by the plasma torch is approximately 3 to 10 mm.

The temperature of the glass substrate during processing does not exceed 90 C.

CA 02674085 2014-09-25 27 Table 5 below shows the variations due to heating in terms of light transmission, square resistance and normal emissivity.

Table 5 TL (%) Rc (Q) Cri (%) before after before after before after 77.0 78.5 5.0 4.4 5.5 4.9 Table 6 below details the same properties, but for a stack in which the silver layer has a thickness of 15 nm.

Table 6 TL (%) Rc (1)) In (%) before after before after before after 71.0 72.0 2.2 2.0 2.4 2.2 As in the case of Examples 2 and 3, the heating induces an improvement in properties, a sign of better crystallization of the silver layer.

EXAMPLE 6:

In this example, coated substrates identical to those of Examples 1 and 4 are used, therefore coated with a stack comprising a layer of titanium oxide.

The plasma torch treatment device is identical to that described in the case of Example 5.

The temperature of the glass substrate during processing does not exceed 90 C.

Table 7 below indicates the photocatalytic activity of the titanium oxide layer before and after treatment.

CA 02674085 2014-09-25 28 Table 7 Sample Kb, before Kb, after treatment treatment A <7 25 B <7 22 EXAMPLE 7 The same coated substrate as that treated in Examples 2, 3 and 5 is subjected in the context of this example a heating using flames.

The fuel is propane, the oxidizer being air. Oxygen also makes it possible to obtain good results.

The coated substrate, after deposition within the magnetron deposition enclosure, is moved at constant speed under a fixed flaming bench whose width is greater than or equal to the width of the substrate, the latter moving at a speed between 2 and 10 meters / minute under the bench.

The layer to be treated is placed at the level of the hottest zone of the flame.

The temperature of the glass substrate during processing, however, does not exceed 100 C.

Table 8 below also shows a favorable evolution of the crystallization of the silver layer.

Table 8 TL (%) Rc (Q) En (%) before after before after before after 77.0 78.2 5.1 4.5 5.6 5.0 CA 02674085 2014-09-25 29 EXAMPLE 8:

In this example, coated substrates identical to those of Examples 1, 4 and 6 are used, therefore coated with a stack comprising a layer of titanium oxide.

The treatment is similar to that undergone in the case of Example 7 (treatment by flame treatment).

The temperature of the glass (side opposite to the layer) does not exceed 150 C.

Table 9 below shows the photocatalytic activity values ​​before and after treatment.

Table 9 Sample Kb, before Kb, after treatment treatment A <7 20 <7 18 EXAMPLE 9:

A layer of mixed indium and tin oxide (ITO) with a thickness of 500 nm is deposited on a glass substrate in a known manner by the magnetron process.

Its square resistance is 20 Q, which testifies to a very predominantly amorphous nature of the layer.

The treatment is similar to that undergone in the case of Example 7 (flame treatment), the temperature of the glass (side opposite the layer) not exceeding 150 C.

After treatment, the square resistance of the layer is 4,, a sign of a notable improvement in its rate of crystallization.

CA 02674085 2014-09-25 EXAMPLE 10:

A transparent conductive layer based on zinc oxide doped with aluminum 200 nm thick is deposited on a glass substrate by a magnetron process.

The treatment undergone is similar to that of Example 5 (plasma torch).

Table 10 below indicates the values ​​of square resistance, light absorption, electronic mobility and electron density (the latter two being measured by the Hall effect) before and after treatment.

Table 10 Absorption (%) Re (Q) Density Electronic mobility (cm2N. $) (X102. cm-3) before after before after before after before after 8.5 3.2 106 35 1.3 2.6 18 28 The method according to the invention therefore makes it possible to considerably improve the electronic conduction properties thanks to the improvement crystallization of the layer: the latter makes it possible not only to increase the mobility of electrons by reducing the grain boundaries, but also the density of carriers by reducing crystal defects.

The resistivity after treatment is thus divided by a factor ranging from 2 to 3.

The RMS roughness of the layer after treatment is 3 nm, calculated from an AFM measurement carried out on a sample of one square micron.

In the case of a treatment carried out on a stack comprising, in addition to the doped ZnO layer, a sublayer and a protective overlay, the improvement is less (approximately 35%).

EXAMPLE 11:

CA 02674085 2014-09-25 31 A transparent conductive layer based on zinc oxide doped with aluminum 180 nm thick is deposited on a glass substrate by a magnetron process.

The treatment undergone is similar to that of Example 7 (flame treatment).

Table 11 below shows the square resistance and light transmission values ​​before and after treatment.

Table 11 Transmission (%) Rc before after before after 72.5 75.0 120 60 The RMS roughness of the layer after treatment is 3 nm, calculated from an AFM measurement carried out on a sample of one square micron.

The same type of treatment was carried out on a layer of zinc oxide doped with aluminum 750 nm thick.

The square resistance went from 26 ohms (before treatment) to 9.7 ohms (after treatment), for an RMS roughness of between 3 and 5 nm.

EXAMPLE 12:

A transparent conductive layer based on zinc oxide doped with aluminum (thickness 190 nm) is deposited on a glass substrate by a magnetron process.

The treatment undergone is similar to that of Example 1 (CO2 laser treatment).

Table 12 below shows the square resistance and light transmission values ​​before and after treatment.

Table 12 Transmission (%) Rc (Q) CA 02674085 2014-09-25 32 before after before after 74.4 78.3 94.8 40.5 The RMS roughness of the layer after treatment is 3 nm, calculated from of an AFM measurement carried out on a sample of one square micron.

EXAMPLE 13 (comparative) A substrate coated with a stack comprising a silver layer already described in Examples 2, 3, 5 and 7, but in which the thickness of the silver layer is 9 nm, is moved after deposition under a series of lamps emitting infrared radiation and indiscriminately heating the layer as well as the substrate.

The power of the lamp was about 150 kW / m2 and the wavelength of the emitted radiation was between 1 and 3 micrometers.

Table 13 below shows that the heating with the aid of the lamps appreciably improves the crystallization of the silver layers.

The temperature of the substrate at the level of the face opposite to the face bearing the stack of layers, however, exceeded 300 ° C. during the treatment, causing breakage of the majority of the glass sheets treated.

Table 13 TL (/ 0) Rc (U) En (1) / 0) before after before after before after 77.2 78.5 4.6 3.8 5.1 4.3 EXAMPLE 14: (comparative) CA 02674085 2014-09-25 33 In this example, coated substrates identical to those of Example 1 are used, therefore coated with stacks comprising a layer of TiO 2.

The treatment is carried out by moving the substrate after deposition under a series of lamps emitting infrared radiation and indiscriminately heating the layer as well as the substrate.

The power of the lamp was about 150 kW / m2 and the wavelength of the emitted radiation was between 1 and 3 micrometers.

Only a small part of the radiation is absorbed by the substrate and the layer.

Table 14 below shows that the heating using the lamps makes it possible to improve the photocatalytic activity of the TiO 2 layers.

Table 14 Sample Kb, before Kb, after treatment treatment A <7 25 <7 <10 For heating times of 2 to 3 minutes, the temperature of the substrate at the level of the face opposite to the face bearing the stack of layer a however exceeded 300 C during the treatment, causing breakage of the majority of the glass sheets treated.

The significant heating of the substrate also causes the diffusion of sodium in the layer, considerably reducing the photocatalytic activity when no sublayer is used (case of example B).