WO2020070393A1

WO2020070393A1 - Method for obtaining a sheet of glass coated with a functional layer

Info

Publication number: WO2020070393A1
Application number: PCT/FR2018/052440
Authority: WO
Inventors: Andriy Kharchenko
Original assignee: Saint-Gobain Glass France
Priority date: 2018-10-03
Filing date: 2018-10-03
Publication date: 2020-04-09

Abstract

The invention concerns a method for obtaining a material comprising a sheet of glass coated on at least one of its faces with at least one functional layer, the method comprising: - a heat treatment step, using radiation having at least one treatment wavelength of between 200 and 2500 nm, for treating a sheet of glass coated on at least one of its faces with the at least one functional layer and at least one sacrificial layer situated above the functional layer furthest away from the sheet of glass, then, - a step of eliminating the or each sacrificial layer by means of a solvent, the method being characterised in that at least one sacrificial layer is made from molybdenum or molybdenum oxide, and in that, if a sacrificial layer is made from molybdenum, said sacrificial layer is in contact with an atmosphere containing oxygen during the heat treatment step, and in that, if a sacrificial layer is made from molybdenum oxide, said sacrificial layer contains at least one absorbent element, which absorbs the radiation, or is surmounted by an absorbent layer, which absorbs the radiation.

Description

FUNCTIONAL LAYER

The invention relates to obtaining glass sheets coated with at least one functional layer.

Certain functional layers require heat treatments, either to improve their properties, or even to give them their functionality. By way of example, mention may be made of low-emissive functional layers based on silver or transparent conductive oxides (TCO), the emissivity and the electrical resistivity of which are lowered following heat treatments. Photocatalytic layers based on titanium oxide are also more active after heat treatment, because the latter promotes crystal growth. Heat treatments also make it possible to create porosity in silica-based layers to lower their light reflection factor.

WO 2010/139908 discloses a method of heat treatment by means of radiation, in particular laser radiation focused on the layer. Such a treatment makes it possible to heat the layer very quickly without significantly heating the glass sheet. Typically, the temperature at any point on the face of the glass sheet opposite to that carrying the layer does not exceed 150 ° C., or even 100 ° C. during the treatment. Other types of radiation, such as that from flash lamps can also be used for the same purpose. Some layers, however, absorb very little radiation, so that most of the radiation energy passes through the material without significantly heating it up. The known methods cannot then be used. Other layers absorb the radiation, but it may be desirable to improve the efficiency of the heat treatment by increasing the absorption of the stack deposited on the glass sheet. This allows for example to reduce the power of the radiation source and / or to speed up the treatment. However, the presence of absorbent layers is not always desirable in the final material.

Application WO 2012/022874 describes a process in which a soluble layer based on halides or sulphates is deposited on the layer to be treated, and surmounted by a layer absorbing infrared radiation. The latter can then be removed by washing. The high sensitivity to air humidity of this type of soluble layer, however, makes industrial implementation of this process difficult, in particular when the elimination of the soluble layer must be carried out in a place other than the heat treatment. . These also contain elements such as chlorine, sodium and / or sulfur, which can lead to corrosion of the functional stack, in particular when these elements are not completely eliminated during washing.

Application WO 2015/185848 describes the use of an organic absorbent sacrificial layer, such as an ink, or mineral, such as zinc. The zinc layers can be deposited by sputtering, which is an advantage when the functional layer is itself deposited by this process, and after oxidation can be removed using an acidic aqueous solution. This kind of solutions can however lead to degradation of the underlying layers.

The object of the present invention is to overcome these drawbacks by proposing a process for obtaining a material comprising a glass sheet coated on at least one of its faces with at least one functional layer, said process comprising:

a heat treatment step, by means of radiation having at least one treatment wavelength between 200 and 2500 nm, of a glass sheet coated on at least one of its faces with said at least one functional layer and at least one sacrificial layer situated above the functional layer furthest from the glass sheet, then,

a step of removing the or each sacrificial layer using a solvent,

said process being characterized in that at least one sacrificial layer is based on molybdenum or molybdenum oxide, and in that,

in the case where a sacrificial layer is based on molybdenum, said sacrificial layer is in contact with an oxygen-containing atmosphere during the heat treatment step, and in that,

in the case where a sacrificial layer is based on molybdenum oxide, said sacrificial layer contains at least one absorbent element, which absorbs said radiation, or is surmounted by an absorbent layer, which absorbs said radiation.

Another object of the invention is a material comprising a glass sheet coated on at least one of its faces with at least one functional layer and at least one sacrificial layer based on molybdenum oxide situated above the functional layer furthest from the sheet of glass. This material corresponds to an intermediate material of the method according to the invention, before the step of removing the sacrificial layer.

All the characteristics or all the embodiments described below apply both to the process and to the material according to the invention.

The layers based on molybdenum or molybdenum oxide can be easily obtained by sputtering and, after oxidation in the case of molybdenum, are easily removed by washing with water without adding acid, and preferably without adding basic, while not exhibiting sensitivity to atmospheric humidity.

The step of eliminating the sacrificial layer implements the contact of the sacrificial layer with the solvent. This contact may or may not be accompanied by an automated or manual mechanical treatment of the sacrificial layer, for example by means of brushes, rags, etc. The step of eliminating the sacrificial layer may for example be carried out in a glass washing installation, in particular of the type commonly used in glass manufacturing or processing workshops. The step of removing the sacrificial layer can in particular be carried out in a glass washing machine.

The solvent is preferably aqueous. These include water. Its pH is preferably between 5 and 8. In this way, the water preferably contains no acid or base capable of degrading the other layers of the coating. According to an advantageous alternative, the pH of the aqueous solvent is between 7.5 and 10.5, in particular between 8.5 and 10.5. A small amount of base in fact facilitates the elimination of the sacrificial layer. The step of removing the sacrificial layer can be carried out just after the heat treatment step, near the heat treatment installation.

The elimination step can alternatively be carried out later or at a distance from the heat treatment installation. The sacrificial layer can indeed play a role of mechanical protection of the functional layer during its transport or its handling. For example, when the material is intended to be used in the manufacture of a glazing, the material can be delivered still coated with its sacrificial layer to a transformation workshop, and the sacrificial layer can be eliminated in this workshop, either before the transformation stage (cutting, insertion into insulating glass ...) or during or at the end of the transformation.

The glass sheet is preferably transparent, colorless (it is then a clear or extra-clear glass) or colored, for example in blue, gray, green or bronze. By extra-clear glass is meant a glass whose content by weight of iron oxide is at most 0.02% and whose light transmission factor is at least 90%. The glass is preferably of the silica-soda-lime type, but it can also be of borosilicate or alumino-borosilicate type glass, in particular for high temperature applications (oven doors, chimney inserts, fire-resistant glazing). The glass sheet advantageously has at least one dimension greater than or equal to 1 m, even 2 m and even 3 m. The thickness of the glass sheet generally varies between 0.1 mm and 19 mm, preferably between 0.7 and 12 mm, in particular between 1 and 8 mm, or even between 4 and 6 mm.

The glass sheet is preferably of the float type, that is to say capable of having been obtained by a process consisting in pouring the molten glass onto a bath of molten tin (“float” bath). In this case, the coating to be treated can be deposited on the “tin” side as well as on the “atmosphere” side of the glass sheet. The term “atmosphere” and “tin” faces is understood to mean the faces of the sheet having been respectively in contact with the atmosphere prevailing in the float bath and in contact with the molten tin. The tin face contains a small surface quantity of tin having diffused in the structure of the glass. The glass sheet can also be obtained by rolling between two rollers, a technique which makes it possible in particular to print patterns on the surface of the glass.

The functional and sacrificial layers, as well as possibly all of the layers deposited on or its layers, are typically thin layers, in the sense that their thickness is generally from 0.5 nm to 10 μm, more generally from 1 nm to 1 pm. By "thickness" is meant the physical thickness throughout this text.

The functional and sacrificial layers are preferably deposited on at least 90% of the surface of the glass sheet.

The expression "on" or "above" should be understood in that the sacrificial layer is further from the glass sheet than the functional layer farthest from the glass sheet. This expression does not however prejudge any direct contact between the two layers.

Throughout the text, the term “based on” means that a layer generally comprises at least 50% by weight of the element considered (metal, oxide, etc.), preferably at least 60% and even 70% or 80%, even 90%, 95% or 99% by weight of this element. In some cases, the layer consists of this element, except impurities.

The functional layer preferably provides the coated glass sheet with at least one functionality chosen from low emissivity, low electrical resistivity, anti-reflective effect, self-cleaning function or ease of cleaning.

Preferably at least one functional layer is chosen from layers based on a metal, in particular silver, layers based on titanium oxide, layers based on silica or layers based on a transparent oxide. electrically conductive.

The functional layer may be the only layer deposited on the glass sheet (in addition to the sacrificial layer). Alternatively, the functional layer can be included in a stack of thin layers. In the following text, the assembly comprising the functional and sacrificial layers as well as any other layer deposited on the same face of the glass sheet is called a "coating".

The thickness of the or each functional layer is typically between 1 nm and 5 μm, in particular between 2 nm and 2 μm, more particularly between 10 nm and 1 μm.

According to a preferred embodiment, the at least one functional layer is based on a metal, typically silver, or even gold. The functional layer is preferably made of this metal. Such metals have properties of low emissivity and low electrical resistivity, so that the coated glass sheets can be used for the manufacture of glazing with reinforced thermal insulation, heated glazing or even electrodes. The thickness of the functional layer is then preferably within a range from 2 to 20 nm.

In this embodiment, the coating comprises at least one functional metallic layer, preferably two or three, each being generally disposed between at least two dielectric layers, typically layers of oxide, nitride or oxynitride, for example layers of silicon nitride, zinc oxide and / or tin oxide, titanium oxide etc ... This type of coating is preferably entirely deposited by sputtering, in particular assisted by magnetic field (magnetron process).

According to another preferred embodiment, the or at least one functional layer is a layer based on titanium oxide, in particular a layer made up or essentially made up of titanium oxide.

The thin layers based on titanium oxide have the particularity of being self-cleaning, facilitating the degradation of organic compounds under the action of ultraviolet radiation (photocatalysis phenomenon) and the elimination of mineral soiling (dust) under the action of water runoff. Titanium dioxide crystallized in the anatase form is much more effective in terms of degradation of organic compounds than titanium dioxide amorphous or crystallized in the rutile or brookite form. Titanium oxide can optionally be doped with a metal ion, for example an ion of a transition metal, or with nitrogen, carbon or fluorine atoms. Titanium oxide can also be sub-stoichiometric or super-stoichiometric in oxygen (TiCh or TiO.

The titanium oxide-based layer is preferably deposited by magnetron sputtering. However, this technique does not allow to obtain very active layers, because the titanium oxide which they contain is little or even not crystallized. Heat treatment is then necessary to confer appreciable self-cleaning properties. In order to improve these properties, it is preferable, in particular when the glass sheet is intended to undergo a prolonged heat treatment, for example a tempering treatment, to insert between the glass sheet and the titanium oxide layer at the at least one barrier layer to the migration of alkali metals, in particular chosen from layers based on silica, silicon oxycarbide, alumina, silicon nitride.

According to another preferred embodiment, the or at least one functional layer is a layer based on a transparent electrically conductive oxide, frequently called "TCO" in the art, acronym of the English expression "transparent conductive oxide". The transparent electrically conductive oxide is preferably chosen from the layers of tin and indium oxide (ITO), the zinc oxide layers doped with aluminum or gallium and the oxide layers d tin doped with fluorine or antimony.

This type of layer confers electrical conduction properties but also low emissivity, allowing the material to be used in the manufacture of insulating glazing, anti-condensation glazing, or electrodes, for example for photovoltaic cells, for display screens or for lighting devices.

According to yet another preferred embodiment, the or at least one functional layer is a layer based on silica. This type of layer absorbs little in the wavelength range considered, in particular in the near infrared, so that in the absence of a layer sacrificial absorbent heat treatment is ineffective.

The silica-based layer is preferably, after heat treatment, essentially made up or even made up of silica. The silica-based layer is advantageously anti-reflective, in the sense that the light reflection factor on the layer side is at most 6%, in particular 5% after heat treatment, when the layer is deposited on one side of the glass sheet ( the value therefore takes into account the reflection of the opposite uncoated face, which is approximately 4%).

According to a first variant, the silica-based layer comprises, before thermal treatment of silicon, oxygen, carbon and optionally hydrogen, these latter two elements being at least partially removed during the thermal treatment so as to obtain a porous layer essentially consisting of silica. This layer is preferably deposited by magnetron sputtering of a silicon or silica target or by chemical vapor deposition assisted by plasma using as an silicon precursor an organometallic compound such as for example hexamethyldisiloxane.

According to a second variant, the silica-based layer comprises, before heat treatment, a silica matrix and blowing agents, the latter being eliminated during the heat treatment so as to obtain a porous layer essentially consisting of silica. The blowing agents are preferably organic, in particular polymeric, for example made of polymethyl methacrylate, their average size preferably being within a range ranging from 20 to 200 nm. This layer is preferably deposited by a method of the sol-gel type. The or each functional layer can be obtained by any type of thin film deposition process. It can, for example, be processes of the sol-gel, pyrolysis (liquid or solid) type, chemical vapor deposition (CVD), in particular assisted by plasma (APCVD), optionally under atmospheric pressure (APPECVD), evaporation, spraying. cathodic, in particular assisted by a magnetic field (magnetron process). In the latter process, a plasma is created under a high vacuum in the vicinity of a target comprising the chemical elements to be deposited. The active plasma species, by bombarding the target, tear off said elements, which are deposited on the glass sheet, 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. The major advantage of this process lies in the possibility of depositing on a single line a very complex stack of layers by successively scrolling the glass sheet under different targets, this generally in a single device. It is thus possible to obtain in this way the complete stack, containing the or each sacrificial layer.

According to a first variant of the invention, the or at least one sacrificial layer is based on molybdenum, and is in contact with an atmosphere containing oxygen during the heat treatment step. The sacrificial layer is preferably essentially made up or even made up of molybdenum. The sacrificial layer is capable of oxidizing during the heat treatment step, thus giving a layer of soluble molybdenum oxide. Before oxidation, it is able to absorb at least part of the radiation. According to a second variant of the invention, the or at least one sacrificial layer is based on molybdenum oxide, in particular essentially constituted or even made of molybdenum oxide.

According to a first mode of this second variant, the sacrificial layer contains at least one absorbing element, capable of absorbing radiation having at least one wavelength between 200 and 2500 nm ("processing wavelength"). The or each absorbent element then allows the sacrificial layer to absorb the radiation during the heat treatment and consequently to improve the efficiency of the latter. At least one absorbent element is preferably a metallic element chosen from titanium, silver, tungsten, niobium, indium, tin, copper, molybdenum, zinc, zirconium, silicon, vanadium, aluminum, nickel, chromium, iron and gold. The at least one absorbent element is preferably present in the layer in the form of particles. The amount of absorbent element is preferably adapted so that the absorption of the sacrificial layer is at least 5% at at least one treatment wavelength. The sacrificial layer is preferably a composite containing molybdenum oxide and at least one metal. An example of this type of composite is called "cermet" in the art. The absorbent element can also be present in the sacrificial layer in the form of very thin layers, the sacrificial layer then being in the form of an assembly of superimposed layers, alternating layers of molybdenum oxide and layers of l absorbent element.

According to a second mode of the second variant, the sacrificial layer is surmounted by an absorbent layer, capable of absorbing radiation having at least a wavelength between 200 and 2500 nm ("processing wavelength"). In this second mode, the sacrificial layer is not (or only slightly) absorbent, and it is the presence of the absorbent layer which makes it possible to improve the efficiency of the heat treatment. The absorbent layer is preferably based on at least one metal chosen from molybdenum, titanium, zinc, zirconium, silver, indium, tin, nickel, chromium, niobium, vanadium, tungsten, copper, iron, silicon, gold. The absorbent layer may in particular be an alloy of one of these metals, for example an alloy of indium and tin. The absorbent layer is preferably porous or discontinuous or else itself soluble or made soluble by the heat treatment so as to be able to easily remove the underlying sacrificial layer.

The two modes described above can of course be combined with one another.

The absorption, in the first mode of the sacrificial layer and in the second mode of the absorbent layer, at at least one treatment wavelength, is preferably at least 5%, in particular 10% or 15%, even 20% and even 25 or 30%. The absorption can in a known manner be deduced from measurements carried out using a spectrophotometer.

Molybdenum oxide, whether it is obtained during the deposition of the sacrificial layer or during its heat treatment, is advantageously at least partly made up of molybdenum trioxide M0O3 which is the most soluble form.

The sacrificial layer is preferably deposited by magnetron sputtering. The thickness of the sacrificial layer is preferably within a range from 0.5 to 100 nm, in particular from 1 to 50 nm, more preferably from 2 to 30 nm. When the sacrificial layer is based on molybdenum, its thickness is advantageously at most 10 nm, in particular between 2 and 10 nm, so that it can oxidize over its entire thickness during the heat treatment and thus be easily removed later. When the sacrificial layer is based on molybdenum oxide and the sacrificial layer is surmounted by an absorbent layer, the thickness of the latter is preferably within a range from 0.5 to 100 nm, in particular from 1 at 10 nm. When the sacrificial layer contains an absorbent element, the thickness of the sacrificial layer is to be adjusted according to the nature and the content of absorbent element, so as to obtain adequate absorption.

During the heat treatment, the radiation is preferably chosen from laser radiation or radiation from at least one flash lamp.

During the entire heat treatment step, the temperature at any point on the face of the glass sheet opposite to that carrying the functional layer is preferably at most 150 ° C., in particular 100 ° C. and even 50 ° C.

The maximum temperature undergone by each point of the functional layer during the heat treatment is preferably at least 300 ° C, in particular 350 ° C, even 400 ° C, and even 500 ° C or 600 ° C. During the heat treatment step, each point of the functional layer is subjected to this maximum temperature for a period generally not exceeding one second, preferably 0.5 seconds and even 0.05 seconds.

According to a first preferred embodiment, the radiation comes from at least one flash lamp. Such lamps are generally in the form of glass or quartz tubes sealed and filled with a rare gas, provided with electrodes at their ends. Under the effect of a short-lived electrical pulse, obtained by discharging a capacitor, the gas ionizes and produces a particularly intense incoherent light. The emission spectrum generally comprises at least two emission lines; it is preferably a continuous spectrum having a maximum emission in the near ultraviolet and extending to the near infrared. In this case, the heat treatment implements a continuum of treatment wavelengths.

The lamp is preferably a xenon lamp. It can also be an argon, helium or krypton lamp. The emission spectrum preferably comprises several lines, in particular at wavelengths ranging from 160 to 1000 nm.

The duration of the flash is preferably in a range from 0.05 to 20 milliseconds, in particular from 0.1 to 5 milliseconds. The repetition rate is preferably within a range from 0.1 to 5 Hz, in particular from 0.2 to 2 Hz.

The radiation can come from several lamps arranged side by side, for example 5 to 20 lamps, or even 8 to 15 lamps, so as to simultaneously treat a wider area. In this case, all the lamps can emit flashes simultaneously.

The or each lamp is preferably arranged transversely to the longest sides of the glass sheet. The or each lamp preferably has a length of at least 1 m, in particular 2 m and even 3 m, so that large sheets of glass can be processed. The capacitor is typically charged at a voltage of 500 V to 500 kV. The current density is preferably at least 4000 A / cm ² . The total energy density emitted by the flash lamps, relative to the surface of the coating, is preferably between 1 and 100 J / cm ² , especially between 1 and 30 J / cm ² , or even between 5 and 20 J / cm ² .

According to a second preferred embodiment, the radiation is laser radiation, in particular laser radiation focused on the functional layer in the form of at least one laser line.

The laser radiation is preferably generated by modules comprising one or more laser sources as well as shaping and redirection optics.

The laser sources are typically laser diodes or fiber lasers, in particular fiber, diode or even disc lasers. The laser diodes make it possible to economically achieve high power densities compared to the electrical power supply, for a small footprint. The size of the fiber lasers is even more reduced, and the linear power obtained can be even higher, at a cost however higher. Fiber lasers are understood to mean lasers in which the place of generation of the laser light is spatially offset from its place of delivery, the laser light being delivered by means of at least one optical fiber. In the case of a disc laser, the laser light is generated in a resonant cavity in which is located the emitting medium which is in the form of a disc, for example a thin disc (of about 0.1 mm thick) in Yb: YAG. The light thus generated is coupled in at least one optical fiber directed towards the place of treatment. Fiber or disc lasers are preferably optically pumped using laser diodes. The radiation from the laser sources is preferably continuous. Alternatively, it can be pulsed.

The wavelength of the laser radiation, therefore the processing wavelength, is preferably within a range from 800 to 1300 nm, in particular from 800 to 1100 nm. Power laser diodes emitting at one or more wavelengths chosen from 808 nm, 880 nm, 915 nm, 940 nm or 980 nm have been found to be particularly suitable. In the case of a disc laser, the processing wavelength is for example 1030 nm (emission wavelength for a Yb: YAG laser). For a fiber laser, the treatment wavelength is typically 1070 nm.

The number of laser lines and their arrangement are advantageously chosen so that the entire width of the glass sheet is treated.

Several disjoint lines can be used, for example be staggered or as the crow flies.

It is however more advantageous, in order to ensure a more homogeneous treatment, to use a single laser line. In the case of narrow width substrates, this laser line can be generated by a single laser module. For glass sheets of large width, on the other hand, for example greater than 1 m, even 2 m and even 3 m, the laser line advantageously results from the combination of a plurality of elementary laser lines each generated by independent laser modules. The length of these elementary laser lines typically ranges from 10 to 100 cm, in particular from 30 to 75 cm, or even from 30 to 60 cm. The elementary lines are preferably arranged so as to overlap partially in the lengthwise direction and preferably have an offset in the widthwise direction, said offset being less than half the sum of the widths of two adjacent elementary lines. The term "length" of the line means the largest dimension of the line, measured on the surface of the covering in a first direction, and "width" the dimension in the second direction, perpendicular to the first direction. As is customary in the field of lasers, the width w of the line corresponds to the distance (in this second direction) between the axis of the beam (where the intensity of the radiation is maximum) and the point where the radiation intensity is equal to l / e ² times the maximum intensity. If the longitudinal axis of the laser line is named x, we can define a width distribution along this axis, called w (x).

The average width of the or each laser line is preferably at least 35 micrometers, in particular lying in a range from 40 to 100 micrometers or from 40 to 70 micrometers. Throughout this text, "average" means the arithmetic average. Over the entire length of the line, the width distribution is narrow in order to limit as far as possible any heterogeneity of treatment. Thus, the difference between the largest width and the smallest width is preferably at most 10% of the value of the average width. This figure is preferably at most 5% and even 3%.

The linear power of the laser line is preferably at least 300 W / cm, advantageously 350 or 400 W / cm, in particular 450 W / cm, even 500 W / cm and even 550 W / cm. It is even advantageously at least 600 W / cm, in particular 800 W / cm, or even 1000 W / cm. The linear power is measured at the point where the or each laser line is focused on the coating. It can be measured by placing a power detector along the line, for example a calorimetric power meter, such as in particular the Beam Finder S / N 2000716 power meter from Cohérent Inc. The power is advantageously distributed homogeneously over the entire length of the or each line. Preferably, the difference between the highest power and the lowest power is less than 10% of the average power.

In order to treat the entire surface of the glass sheet, a relative displacement between the radiation source and said glass sheet is preferably created. Preferably, in particular for large glass sheets, the or each radiation source (in particular laser line or flash lamp) is fixed, and the glass sheet is in motion, so that the relative displacement speeds will correspond to the running speed of the glass sheet. Preferably, the or each laser line is substantially perpendicular to the direction of movement.

The energy density supplied to the coating by the radiation is preferably at least 20 J / cm ² , or even 30 J / cm ² .

The high powers and energy densities allow the coating to be heated very quickly, without significantly heating the glass sheet.

As mentioned previously, the maximum temperature undergone by each point of the coating during the heat treatment is preferably at least 300 ° C, in particular 350 ° C, even 400 ° C, and even 500 ° C or 600 ° C. The maximum temperature is notably undergone at the moment when the point of the coating considered passes under the laser line or is irradiated by the flash lamp flash. At a given instant, only the points on the surface of the coating located under the laser line or under the flash lamp and in its immediate surroundings (for example less than a millimeter) are normally at a temperature of at least 300 ° C. . For distances to the laser line (measured according to direction scrolling) greater than 2 mm, in particular 5 mm, including downstream of the laser line, the coating temperature is normally at most 50 ° C, and even 40 ° C or 30 ° C.

Each point of the coating undergoes heat treatment (or is brought to the maximum temperature) for a period advantageously included in a range ranging from 0.05 to 10 ms, in particular from 0.1 to 5 ms, or from 0.1 to 2 ms. In the case of a treatment by means of a laser line, this duration is fixed both by the width of the laser line and by the speed of relative movement between the glass sheet and the laser line. In the case of treatment with a flash lamp, this duration corresponds to the duration of the flash.

When the glass sheet is in movement, in particular in translation, it can be set in motion using any mechanical conveying means, for example using strips, rollers, trays in translation. The conveyor system makes it possible to control and regulate the speed of movement. The conveying means preferably comprises a rigid frame and a plurality of rollers. The pitch of the rollers is advantageously included in a range from 50 to 300 mm. The rollers preferably comprise metal rings, typically of steel, covered with plastic bandages. The rollers are preferably mounted on bearings with reduced clearance, typically at the rate of three rollers per bearing. In order to ensure perfect flatness of the conveying plane, the positioning of each of the rollers is advantageously adjustable. The rollers are preferably moved using sprockets or chains, preferably tangential chains, driven by at least one motor. The speed of the relative movement of movement between the glass sheet and the or each source of radiation (in particular the or each laser line) is advantageously at least 2 m / min, in particular 5 m / min and even 6 m / min or 7 m / min, or even 8 m / min and even 9 m / min or 10 m / min. According to certain embodiments, in particular when the absorption of radiation by the coating is high or when the coating can be deposited with high deposition rates, the speed of the movement of relative movement between the glass sheet and the radiation source (in particular the or each laser line or flash lamp) is at least 12 m / min or 15 m / min, in particular 20 m / min and even 25 or 30 m / min. In order to ensure treatment that is as homogeneous as possible, the speed of the relative movement of movement between the glass sheet and the or each source of radiation (in particular the or each laser line or flash lamp) varies during the treatment of plus 10% relative, especially 2% and even 1% compared to its nominal value.

The heat treatment device can be integrated into a layer deposition line, for example a sputtering deposition line assisted by magnetic field (magnetron process), or a chemical vapor deposition line (CVD), in particular assisted by plasma (PECVD), under vacuum or at atmospheric pressure (APPECVD). The line generally includes devices for handling glass sheets, a deposition installation, optical control devices, stacking devices. The glass sheets pass, for example on conveyor rollers, successively in front of each device or each installation.

The heat treatment device is preferably located just after the installation for depositing the coating, for example at the outlet of the installation for deposit. The coated glass sheet can thus be processed online after the coating has been deposited, at the outlet of the deposition installation and before the optical control devices, or after the optical control devices and before the sheet stacking devices. of glass .

The heat treatment device can also be integrated into the deposition installation. For example, the laser or the flash lamp can be introduced into one of the rooms of a sputtering deposition installation, in particular in a room where the atmosphere is rarefied, in particular under a pressure between 1CT ⁶ mbar and 1CT ² mbar . The heat treatment device can also be placed outside the deposition installation, but so as to treat a glass sheet located inside said installation. It suffices to provide for this purpose a window transparent to the wavelength of the radiation used, through which the radiation would come to treat the layer. It is thus possible to treat a layer (for example a layer of silver) before the subsequent deposition of another layer in the same installation.

Whether the heat treatment device is outside or integrated into the deposition installation, these “on-line” processes are preferable to a recovery process in which it would be necessary to stack the glass sheets between the deposition step and heat treatment.

The processes in recovery can however have an interest in the cases where the implementation of the heat treatment according to the invention is made in a place different from that where the deposit is carried out, for example in a place where the transformation of the glass is carried out . The heat treatment device can therefore be integrated into other lines than the layer deposition line. It can for example be integrated into a production line for multiple glazing (double or triple glazing in particular), to a production line for laminated glazing, or even to a production line for curved and / or toughened glazing. Laminated or curved or toughened glazing can be used as well as building or automotive glazing. In these different cases, the heat treatment according to the invention is preferably carried out before the production of multiple or laminated glazing. However, the heat treatment can be carried out after double glazing or laminated glazing has been produced.

The heat treatment device is preferably placed in a closed enclosure making it possible to secure people by avoiding any contact with the radiation and avoiding any pollution, in particular of the glass sheet, the optics or the treatment area.

The material obtained by the process according to the invention can form or be integrated into a glazing, in particular for building or transport. It can be, for example, multiple glazing (double, triple, etc.), monolithic glazing, curved glazing, laminated glazing. In the case of self-cleaning titanium oxide layers, the material can in particular constitute the first sheet of multiple glazing, the functional layer being positioned opposite 1 of said glazing. In the case of silver-based layers, the functional layer is preferably positioned inside the multiple glazing.

The material obtained by the process according to the invention can also be integrated into a photovoltaic cell. In the case of anti-reflective silica-based layers such as mentioned above, the material which is coated with it can form the front face of a photovoltaic cell.

The material obtained by the method according to the invention can also be integrated into a display screen or a lighting device or a photovoltaic cell, as a substrate provided with an electrode.

The invention is illustrated with the aid of the following nonlimiting exemplary embodiments.

A sheet of glass has been coated in known manner, by magnetron sputtering, with a stack of thin layers with low emissivity comprising a silver layer placed between dielectric stacks. In a comparative example, the stack deposited on the glass sheet did not contain any other layer.

In an example according to the invention, the stack was coated with a sacrificial layer of molybdenum oxide with a thickness of 30 nm, itself coated with a non-continuous absorbent layer of an alloy of indium and tin, a few nanometers thick.

The sacrificial layer was deposited using a molybdenum target of 21 * 9 cm ² , supplied with a power of 700 W. A plasma mixture containing argon (flow rate of 30 sccm) and oxygen ( flow rate of 20 sccm) was introduced into the deposition chamber during the deposition of the sacrificial layer.

The glass sheets thus coated (comparative example and example according to the invention) were then heat treated by passing under a laser line emitting radiation with a wavelength of 980 nm.

After heat treatment, the glass sheet coated with the sacrificial layer was immersed in water not added with an acid, a base, or more generally of any additive, for a period ranging from 10 to 15 seconds, then dried. The sacrificial layer and the absorbent layer were completely removed by this washing. In another test, water with a small amount of base added so as to obtain a pH of 9 was used, the elimination of the sacrificial layer then being much faster, obtained after only 1 to 2 seconds.

In both cases, a relative improvement in the square resistance of 18 to 19% was obtained, but for a running speed of 4.5 m / min in the case of the comparative example, and of 10 m / min in the case of the example according to the invention.

Claims

1. A method for obtaining a material comprising a glass sheet coated on at least one of its faces with at least one functional layer, said method comprising: a heat treatment step, by means of radiation having at least a treatment wavelength between 200 and 2500 nm, of a glass sheet coated on at least one of its faces with said at least one functional layer and at least one sacrificial layer located above the layer farthest from the glass sheet, then,

a step of removing the or each sacrificial layer using a solvent,

2. Method according to claim 1, such that the solvent is aqueous, its pH preferably being between 5 and 8, or between 7.5 and 10.5.

3. Method according to one of the preceding claims, such that the radiation is chosen from laser radiation or radiation from at least one flash lamp.

4. Method according to the preceding claim, such that the laser radiation is focused on the functional layer in the form of at least one laser line.

5. Method according to one of the preceding claims, such that during the heat treatment step, each point of the functional layer is subjected to a maximum temperature of at least 300 ° C for a period not exceeding one second.

6. Method according to one of the preceding claims, such that at least one functional layer is chosen from layers based on a metal, in particular silver, layers based on titanium oxide, layers based silica or layers based on a transparent electrically conductive oxide.

7. Method according to one of the preceding claims, such that at least one absorbent element is a metallic element chosen from titanium, silver, tungsten, niobium, indium, tin, copper, molybdenum, zinc, zirconium, silicon, vanadium, aluminum, nickel, chromium, iron and gold, or the absorbent layer is based on at least one metal chosen from molybdenum, titanium, zinc, zirconium, silver, indium, tin, nickel, chromium, niobium, vanadium, tungsten, copper, iron, silicon, gold.

8. Material comprising a glass sheet coated on at least one of its faces with at least one functional layer and at least one sacrificial layer based molybdenum oxide located above the functional layer furthest from the glass sheet.

9. Material according to the preceding claim, such that at least one sacrificial layer contains an absorbent element, capable of absorbing radiation having at least a wavelength between 200 and 2500 nm or is surmounted by an absorbent layer, capable of absorbing radiation having at least one wavelength between 200 and 2500 nm.

10. Material according to the preceding claim, such that the absorbent element is a metallic element chosen from titanium, silver, tungsten, niobium, indium, tin, copper, molybdenum, zinc, zirconium, silicon, vanadium, aluminum, nickel, chromium, iron and gold, or the absorbent layer is based on at least one metal chosen from molybdenum, titanium, zinc, zirconium, silver, indium, tin, nickel, chromium, niobium, vanadium, tungsten, copper, iron, silicon, gold.