Electroconductive glazing

Abstract

The invention relates to a method for obtaining glazing, comprising supplying a sheet of glass (1) coated on one of its faces with a stack of electroconductive thin films (2), then a step of depositing, on a portion of said stack of thin films (2), in a zone referred to as the connection zone (Z1, Z2), a washable solvent layer (4), then a heat treatment step, at the end of which the stack of thin films (2) located under the washable solvent layer (4) is dissolved by said washable solvent layer (4), then a step of removing the washable solvent layer (4), then a step of applying, on said connection zone (Z1, Z2) as well as on a portion of the stack of thin films (2) adjacent to the connection zone (Z1, Z2), at least one electroconductive strip (6). Figure 3

Description

Title of the invention: Electroconductive glazing

[0001] The invention relates to the field of glazing, more particularly that of electrically conductive glazing.

[0002] Electrically conductive glazings are glazings provided with a stack of thin layers conferring electrical conduction properties. Such glazings are used in various applications, for example as heating or anti-condensation glazings, both in the field of transport vehicles (anti-fog or anti-frost glazings) and in that of buildings (radiators) or even that of commercial refrigeration (anti-fog or anti-frost glazings).

[0003] In such glazing, the electrical current is generally supplied by screen printing silver paste, which is baked at high temperature during a heat treatment, generally tempering and / or bending of the glass. Silver paste is a paste comprising silver particles, a glass frit and an organic binder. After baking, collector strips (also called bus bars) are formed.

[0004] Such a process is however likely to create certain defects in the final glazing. In particular, it can lead to local deterioration of the stack of thin layers, in particular due to the creation of hot spots.

[0005] The invention aims to overcome these drawbacks by proposing a method creating fewer defects.

[0006] To this end, the invention relates to a method for obtaining glazing, comprising: - the supply of a glass sheet coated on one of its faces with a stack of thin electrically conductive layers, then - a step of depositing, on a part of said stack of thin layers, in a zone called the connection zone, a washable dissolving layer, then - a heat treatment step, at the end of which the stack of thin layers located under the washable dissolving layer is dissolved by said washable dissolving layer, then - a step of removing the washable dissolving layer, then - a step of applying, on said connection zone as well as on a part of the stack of thin layers adjacent to the connection zone, at least one electrically conductive strip.

[0007] Another subject of the invention is a glazing obtained (or capable of being obtained) by this method. This glazing comprises a glass sheet coated on one of its faces, with the exception of a zone called the connection zone, with a stack of thin layers electrically conductive, an electrically conductive strip being applied to said connection area as well as to a portion of the stack of thin layers adjacent to the connection area.

[0008] The inventors were able to demonstrate that such a process made it possible to create fewer defects in the final glazing.

[0009] The glass of the glass sheet is typically a soda-lime-silica glass, but other glasses, for example borosilicates or aluminosilicates, may also be used. The glass sheet is preferably obtained by floating, that is to say by a process consisting of pouring molten glass onto a bath of molten tin.

[0010] The glass sheet may be made of clear glass or tinted glass, for example green, gray or blue. To do this, the chemical composition of the glass sheet advantageously comprises iron oxide, in a weight content ranging from 0.5 to 2%. It may also comprise other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or even selenium. In the case of clear glass, however, the weight content of iron oxide will preferably be between 0.01 and 0.20%, in particular between 0.05 and 0.15%.

[0011] The glass sheet preferably has a thickness in a range from 0.7 to 19 mm, in particular from 1 to 10 mm, particularly from 2 to 6 mm, or even from 2 to 4 mm.

[0012] The lateral dimensions of the glass sheet are to be adapted according to the intended application. The glass sheet preferably has a surface area of ​​at least 1 m2.

[0013] Before depositing the washable dissolving layer, the glass sheet is preferably coated with the stack of thin layers over at least 90%, or even over the entire surface of the face of the glass sheet.

[0014] The stack of thin layers is preferably in contact with the glass sheet. During its deposition, the washable dissolving layer is preferably in contact with the stack of thin layers.

[0015] In the present text, the term "contact" means physical contact. The term "based on" preferably means that the layer in question comprises at least 50% by weight of the material in question, in particular 60%, or even 70%, and even 80% or 90%. The layer may even essentially consist of or consist of this material. By "essentially consist of", it should be understood that the layer may comprise impurities without any influence on its properties. The terms "oxide" or "nitride" do not necessarily mean that the oxides or nitrides are stoichiometric. They may in fact be substoichiometric, superstoichiometric or stoichiometric.

[0016] The stack preferably comprises at least one electrically conductive layer. The electrically conductive layer is preferably between two thin dielectric layers.

[0017] The at least one electrically conductive layer is advantageously chosen from - metallic layers, in particular silver or niobium, or even gold, and - layers of a transparent conductive oxide, in particular chosen from indium and tin oxide, doped tin oxides (for example with fluorine or antimony) and doped zinc oxides (for example with aluminum or gallium).

[0018] According to a preferred embodiment, the stack of thin layers comprises at least one silver layer, in particular one, two or three, or even four silver layers. The physical thickness of the silver layer or, where appropriate, the sum of the thicknesses of the silver layers is preferably between 2 and 40 nm, in particular between 3 and 20 nm.

[0019] According to another preferred embodiment, the stack of thin layers comprises at least one layer of indium and tin oxide. Its physical thickness is preferably between 30 and 200 nm, in particular between 40 and 150 nm.

[0020] In order to protect the or each electrically conductive thin layer (whether metallic or based on transparent conductive oxide), each of these layers is preferably framed by at least two dielectric layers. The dielectric layers are preferably based on oxide, nitride and / or oxynitride of at least one element chosen from silicon, aluminum, titanium, zinc, zirconium, tin.

[0021] At least part of the stack of thin layers can be deposited by various known techniques, for example by chemical vapor deposition (CVD), or by cathode sputtering, in particular assisted by a magnetic field (magnetron process).

[0022] The stack of thin layers is preferably deposited by cathode sputtering, in particular assisted by a magnetic field. 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 glass sheet, forming the desired thin layer. This process is called "reactive" when the layer is made of a material resulting from a chemical reaction between the elements torn off the target and the gas contained in the plasma. The major advantage of this process lies in the possibility of depositing on the same line a very complex stack of layers by successively moving the glass sheet under different targets, generally in a single device.

[0023] The stack is preferably coated with the washable dissolving layer at 1 to 25%, in particular 2 to 15%, or even 3 to 10% of its surface. Preferably, the connection zone comprises two disjointed strips arranged near two lateral edges of the glass sheet opposite each other.

[0024] The washable dissolving layer is preferably deposited from a fluid composition, in particular liquid or pasty. The washable dissolving layer is preferably deposited by screen printing. To do this, a screen printing screen is placed on the glass sheet, which comprises meshes, some of which are closed, then the fluid composition is deposited on the screen, then a doctor blade is applied in order to force the fluid composition to pass through the screen in the areas where the meshes of the screen are not closed, so as to form a washable dissolving layer. Alternatively, the washable dissolving layer can be deposited by digital printing, in particular by inkjet.

[0025] The thickness of the washable dissolving layer is preferably between 5 and 50 μm, in particular between 10 and 40 μm, or even between 15 and 30 μm.

[0026] The step of depositing the washable dissolving layer is preferably immediately followed by a drying step, intended to remove at least part of the solvent contained in the fluid composition. Such drying is typically carried out at a temperature between 120 and 180°C.

[0027] The washable dissolving layer is preferably a mineral layer comprising at least one phosphate. The phosphate is in particular an alkali phosphate, preferably a sodium phosphate. The term "phosphate" also means hydrogen phosphates and dihydrogen phosphates. The generic term sodium phosphate therefore also covers sodium hydrogen phosphate Na2HPO4, sodium dihydrogen phosphate NaH2PO4, and trisodium phosphate Na3PO4, as well as mixtures of these compounds.

[0028] The fluid composition preferably comprises a solvent, in particular organic, and a resin. The quantities of solvent and resin make it possible to regulate the viscosity of the composition, and are to be adapted according to the deposition process used.

[0029] The heat treatment step is preferably carried out at a temperature between 150 and 700°C, in particular between 550 and 700°C.

[0030] Such treatment makes it possible to eliminate the organic medium, or in general any organic component possibly present in the washable dissolving layer.

[0031] During the heat treatment, the stack of thin layers is dissolved by the washable dissolving layer. The dissolution of the stack can be observed by electron microscopy.

[0032] The heat treatment is preferably a thermal toughening and / or bending treatment of the glass sheet.

[0033] The step of removing the washable dissolving layer makes it possible to eliminate this last, notably thanks to a wash.

[0034] Washing is preferably carried out by spraying water under pressure or by means of a washing machine equipped with brushes. The brushes must be flexible so as not to damage the stack of thin layers.

[0035] After the removal step, in the connection zone, the surface of the glass is therefore bare, since it is no longer coated, either by the stack of thin layers or by the washable dissolving layer.

[0036] Preferably, the or each electrically conductive strip is an adhesive strip or a paint comprising an organic binder. Such materials may be cold applied to the glass sheet.

[0037] The adhesive strip preferably comprises a metal, in particular chosen from copper, aluminum and steel. Alternatively, the adhesive strip may be a textile (woven or non-woven) comprising conductive fillers. The adhesive used is preferably also electrically conductive.

[0038] The paint comprises an organic binder as well as electroconductive fillers, in particular metallic (silver, copper, etc.) or graphite.

[0039] In order to establish good electrical contact, the or each electrically conductive strip must be applied not only to the connection area (i.e. the bare glass area obtained by demarcation) but also to a portion of the stack of thin layers adjacent to this connection area. In other words, the electrically conductive strip must cover the interface areas between the connection area and the stack. It is in fact in this interface area that the electrically conductive strip will come into contact with the electrically conductive thin layer(s) of the stack. The or each electrically conductive strip preferably covers an area of ​​between 101 and 120% of the area of ​​the connection area.

[0040] The glazing obtained is preferably a heated glazing or an anti-condensation glazing for commercial refrigeration or transport vehicle.

[0041] In the case of glazing for commercial refrigeration, the glazing is preferably a multiple glazing, in particular double or triple glazing, comprising the glass sheet described above as well as at least one additional glass sheet, the glass sheets being secured by means of an intermediate frame providing a space filled with gas (air, argon, kypton, etc.). The glazing is preferably flat. Such glazing can be used to reduce or eliminate condensation (fog or frost) in the case of commercial refrigerators (positive cold) or freezers (negative cold). In such a multiple glazing, the stack is preferably located on face 2 of the glazing, that is to say on the face of the outer glass sheet which is turned towards the intermediate space. Low-emissivity stacks can also be arranged on face 3 in the case of double glazing, and on faces 3 and / or 5 in the case of triple glazing.

[0042] In the case of glazing for a vehicle, in particular a motor vehicle, the glazing is preferably a laminated glazing, in particular a windshield, comprising the glass sheet described above as well as an additional glass sheet, the glass sheets being joined by lamination by means of a polymeric interlayer, in particular polyvinyl butyral. Such glazing can be used to reduce or eliminate condensation (fog or frost).

[0043] The following figures schematically illustrate an embodiment of the invention. The various elements are of course not shown to scale. In particular, the thickness of the stack is greatly exaggerated, so as to allow its visualization.

[0044] [Fig.l] represents a glass sheet 1 coated on its surface with a stack of electrically conductive thin layers 2. In a connection zone, a washable dissolving layer 4 has been deposited on the stack 2. The connection zone here comprises two strips Zi and Z2 located near two opposite edges of the glass sheet.

[0045] [Fig.2] represents the glass sheet 1 after heat treatment leading to the dissolution of the stack 2 in the connection zone Zb Z2, then elimination of the washable dissolving layer. In the connection zone Zb Z2, the glass is bare.

[0046] [Fig.3] represents the glass sheet 1 after application of an electrically conductive strip 6 on each connection zone Zi and Z2. As shown in the figure, the strip 6 is wider than the connection zone, so that it also covers the parts of the stack 2 which are adjacent to the connection zones Zi and Z2.

[0047] In an exemplary embodiment, a 4 mm thick clear soda-lime-silica glass sheet was coated by cathodic sputtering with a stack of thin layers comprising a silver layer (7 nm thick), surrounded by silicon nitride layers as well as by NiCr blockers, the assembly being topped with a thin layer of titanium oxide. A washable dissolving layer based on sodium phosphate (Vibrantz, TDF9283) was then deposited by screen printing on the stack so as to create two strips 5 mm wide and 55 mm long, as shown in [Fig.l]. After drying (160°C for 180 seconds), the glass sheet was heat treated for 180 seconds in a furnace heated to 710°C. Washing with water removed the washable solvent layer and left bare glass in the connection area, as shown in [Fig.2].Two conductive copper adhesive strips were then deposited as shown in [Fig. 3]. A resistance of about 350 to 400 Ω was measured. For comparison, an infinite resistance was measured by applying the adhesive strips directly onto the stack.

Claims

Claims

1. Method for obtaining glazing, comprising: - providing a glass sheet (1) coated on one of its faces with a stack of electrically conductive thin layers (2), then - a step of depositing, on a part of said stack of thin layers (2), in a zone called the connection zone (Zb Z2), a washable dissolving layer (4), then - a heat treatment step, at the end of which the stack of thin layers (2) located under the washable dissolving layer (4) is dissolved by said washable dissolving layer (4), then - a step of removing the washable dissolving layer (4), then - a step of applying, on said connection zone (Zb Z2) as well as on a part of the stack of thin layers (2) adjacent to the connection zone (Zb Z2), at least one electrically conductive strip (6).

2. Method according to claim 1, in which the stack of thin layers (2) comprises at least one electrically conductive layer, in particular chosen from metallic layers, in particular silver or niobium, and layers of a transparent conductive oxide, in particular chosen from indium and tin oxide, doped tin oxides and doped zinc oxides.

3. Method according to one of the preceding claims, in which the washable dissolving layer (4) is a mineral layer comprising at least one phosphate, in particular an alkaline phosphate.

4. Method according to one of the preceding claims, in which the washable dissolving layer (4) is deposited by screen printing or by digital printing.

5. Method according to one of the preceding claims, in which the thickness of the washable dissolving layer (4) is between 5 and 50 μm, in particular between 10 and 40 μm.

6. Method according to one of the preceding claims, in which the connection zone (Zb Z2) comprises two disjointed strips arranged near two lateral edges of the glass sheet opposite each other.

7. A method according to any preceding claim, wherein the or each electrically conductive strip (6) is an adhesive strip or a paint comprising an organic binder.

8. Method according to the preceding claim, in which the adhesive strip (6) comprises a metal, in particular chosen from copper, aluminum and steel.

9. Glazing obtained by the method of one of the preceding claims, comprising a glass sheet (1) coated on one of its faces, with the exception of a zone called the connection zone (Zb Z2), with a stack of electrically conductive thin layers (2), an electrically conductive strip (6) being applied to said connection zone (Zb Z2) as well as to a part of the stack of thin layers (2) adjacent to the connection zone (Zb Z2).

10. Glazing according to the preceding claim, which is a heating glazing or an anti-condensation glazing for commercial refrigeration or transport vehicle.

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