BR112020021997A2 - pane comprising silver-based electroconductive tracks - Google Patents

Abstract

The invention relates to a pane (1) which has at least one transparent zone (3) and at least one opaque zone (4), said pane (1) comprising a glass sheet (2) coated on one of its surfaces of electroconductive tracks (5) based on silver in at least one transparent zone (3) and at least one opaque zone (4), said electroconductive tracks (5) located in at least one transparent zone (3) being covered in their upper surface (50) and on its lateral edges (51) by transparent protective tracks (6) based on an oxide.

Description

“GLASS THAT UNDERSTANDS ELECTRIC CONDUCTIVE TRACKS BASED ON SILVER”

[0001] The invention refers to the domain of glazing. It refers more especially to glazing, especially for motor vehicles, which comprise electroconductive tracks.

[0002] Electroconductive tracks, such as heating wires present in motor vehicle windows, are made from a conductive paste, such as a paste with silver screen-printed on a sheet of glass, and are connected to an electrical supply system by through connectors welded in the conductive paste. These tracks are often present on the rear windshields of motor vehicles.

[0003] It was revealed that the optical aspect of such silver-based tracks could degrade in certain environments. The polluted air in certain large cities, especially in Asia and South America, and notably due to high sulfur content, can lead to a fogging of the runways, which become progressively gray and then iridescent.

[0004] To solve this problem, the invention has as its object a glazing that has at least one transparent zone and at least one opaque zone, said glazing comprising a sheet of glass coated on one of its surfaces of electroconductive tracks based on silver in at least one transparent zone and at least one opaque zone, said electroconductive tracks located in at least one transparent zone being covered on its upper surface and on its lateral edges by transparent protective tracks based on an oxide.

[0005] The invention also has as its object a process of obtaining a glazing according to the invention. This process comprises the following successive steps: - a stage of placing electroconductive tracks by silkscreen with silver paste on the surface of a glass sheet, and then - a stage of placing transparent protective tracks based on an oxide by screen printing of a sol-gel solution, and then

- a cooking stage for said electroconductive and protective lanes.

[0006] The glass sheet is typically made of silica-soda-lime glass, but it can be made of other types of glass, for example borosilicate or aluminosilicate. It can be clear, or preferably tinted, for example in green, gray or blue. The light transmission (in the sense of the ISO 9050 standard) of the glass sheet is preferably between 15 and 80%, notably between 30 and 70%. The thickness of the glass sheet is preferably between 1 and 10 mm, notably between 2 and 6 mm. The glass sheet generally has a surface area of 1 to 3 m2.

[0007] In the pane according to the invention the glass sheet is preferably curved. However, it is preferably flat when placing the electroconductive and protective lanes. After placing these tracks, especially by screen printing, the glass sheet can be subjected to various treatments classically carried out in the field of automobile glazing, such as curving and / or tempering treatments, designed to give shape and shape. desired mechanical strength, and I simultaneously cook the electroconductive and protective lanes.

[0008] “Opaque zone” means a zone in which the light transmission factor (in the sense of the ISO 9050 standard) is a maximum of 5%, notably 2% and even 1%, and even is zero. The opaque areas preferably represent a maximum of 40%, notably 30%, and even 20%, of the pane's surface. They preferably comprise an opaque mineral layer, notably an enamel layer. In this case, the opaque zones make it possible to protect the polymeric joints against ultraviolet radiation, which are used for positioning and fixing the glass pane in a vehicle body compartment. They allow, on the other hand, to conceal said joints as well as other elements located in the window, such as the electrical connections or the collector strips, designed to collect electricity. An enamel is a mineral layer formed by cooking an enamel composition that comprises a glass frit, notably bismuth borosilicate glass, and pigments. The enamel is preferably a black enamel.

[0009] "Transparent zone" means a zone in which the light transmission factor (in the sense of ISO 9050) is at least 15%, notably 20% and even 30 or 40%, and even 50 or 60% or 70%, measured in locations without electroconductive leads. The light transmission factor is generally at most 90%, notably 80%. The transparent area is usually located in the central area of the window. It preferably represents at least 60%, notably at least 70% and even at least 80%, of the pane's surface.

[0010] By "lanes" is meant a plurality of portions of coverings that have an elongated shape, such as strips or threads.

[0011] The electroconductive tracks preferably occupy between 1 and 20%, notably between 2 and 10%, of the pane's surface.

[0012] The electroconductive tracks preferably comprise heating wires located at least in a transparent area of the window and collecting bands (also called "bus bars") located in an opaque area of the window. The collector strips are usually located parallel to the height of the window, on the side edges, and are electrically powered in order to circulate the electric current in the heating wires, to which they are connected. The heating wires generally extend in the direction of the width of the glass pane, between two collecting strips. The heating wires preferably have a width (in the plane of the glass) ranging from 0.1 to 1 mm, notably from 0.25 to 0.7 mm. The heating wires preferably present in the final pane, and therefore after cooking, a thickness (according to a normal pane) that ranges from 2 to 30 μm, notably from 2 to 20 μm.

[0013] The electroconductive tracks are preferably placed by silkscreen using a silver paste.

[0014] The silver paste preferably comprises, in the wet state, between 60 and 98% silver by weight. The weight content in silver is preferably at most 90%, notably 80% and even 75%. It is preferably comprised in a domain ranging from 66 to 75%, notably from 68 to 70%. Low levels of silver are specially adapted to lead-free welding alloys. The rest typically comprises glass frit as well as an organic medium, the latter being eliminated during cooking.

[0015] A screen printing process comprises placing, in particular with the aid of a scraper, a pasty liquid on a substrate through the meshes of a screen. The screen meshes are filled in the part that corresponds to the substrate zones that must remain bare, so that the paste can only pass through the screen in the areas to be printed, according to a predefined reason. The selective filling of the meshes is therefore done according to the negative of the pattern to be printed. This selective filling is usually carried out by applying a photoreticulable resin to the screen and then insolation, by means of ultraviolet radiation, of the parts of the screen to be filled. Selective insolation is achieved, for example, thanks to a slide comprising a transparent support, typically made of polyester, coated with an ultraviolet-opaque ink placed according to the pattern to be printed. The mesh of the screen is chosen according to the viscosity and the surface tension of the paste as well as according to the desired track thickness. The screens used for screen printing of electroconductive tracks preferably comprise 77 threads per cm for a thread diameter of 48 μm or 77 threads per cm for a thread diameter of 55 μm, or 90 threads per cm for a thread diameter of 48 μm.

[0016] Electroconductive tracks cover the upper surface and the lateral edges of the electroconductive tracks located in the transparent area. The visible electroconductive tracks are therefore completely protected from the environment: the inner surface of the tracks is in contact with the glass sheet and the parts that are likely to be in contact with the environment, namely the upper surface (parallel to the glass sheet) and the lateral edges (in the direction of the thickness of the tracks, substantially in accordance with a normal to the glass sheet) are covered by the protective tracks.

[0017] According to a preferred embodiment, only the electroconductive tracks located within a transparent area of the window are covered by the protective tracks. The electroconductive tracks located inside the opaque areas of the window are not really visible, so that the fogging of them is not uncomfortable from an aesthetic point of view. Alternatively, at least a part, and even the totality, of the electroconductive tracks (therefore even those located within an opaque zone) are covered by the protective tracks.

[0018] The thickness of the electroconductive tracks is preferably comprised within a range ranging from 0.1 to 5 μm, notably from 0.2 to 3 μm. Small thicknesses in fact proved to be sufficient to prevent the silver-based runways from fogging up. On the other hand, large thicknesses increase the visibility of the protective lanes, which is detrimental to the aesthetics of the glazing

[0019] The protective tracks preferably have a width, always in the plane of the window, (slightly) greater than that of the electroconductive tracks they protect. This width is typically 0.1 to 1.1 mm, notably 0.3 to 0.8 mm.

[0020] The protective tracks are transparent and based on an oxide. The protective lanes are preferably colorless. The light transmission factor, in the sense of ISO 9050, of the material that constitutes the protective lanes is preferably at least 90% for a thickness of 1 mm. It is understood by "based on" the fact that the material that constitutes the protective tracks preferably contains at least 50% by weight of an oxide. This content is preferably at least 60%, notably 70% and even 80% or 90%, and even 95 or 99%. The material can notably consist of an oxide.

[0021] The transparent lanes are preferably based on an oxide of at least one element chosen from silicon, titanium, zirconium, tin. Runways based on, and even made of silicon oxide are preferred. In fact, silicon oxide has several advantages, namely a great transparency, a little reflection and an absence of color that makes the protective tracks totally invisible to the user, as well as a great aptitude to resist the pollutions suffered.

[0022] The protective tracks are preferably placed by silkscreening a sol-gel solution.

[0023] By sol-gel solution, it is understood a solution, preferably aqueous, that contains precursors of the material that forms the protective lanes. Said precursors preferably comprise organometallic compounds of said material and / or nanoparticles of said material and / or chemical reaction products susceptible of being produced between said organometallic compounds and other constituents of the solution, for example water. Organometallic compounds are in fact susceptible to undergo hydrolysis and / or condensation reactions during the formation of the solution, and therefore before application.

[0024] The screen used for the screen printing stage of the protective tracks presents a motif close to that of the screen used for the screen printing stage of the electroconductive tracks. In the case where the protective tracks only cover the electroconductive tracks located within the transparent areas of the glass pane, however the meshes of the screen that correspond to the opaque zones are filled. On the other hand, in order to ensure a complete covering of the electroconductive tracks, including its lateral edges, the width of the motifs is slightly greater than that of the screen motifs of the electroconductive tracks. Generally, the protective lanes will have a thickness less than that of the electroconductive lanes. The screen of the screen of the protective tracks will therefore have a higher number of threads per centimeter, for example 120 threads / cm, and therefore a smaller mesh.

[0025] The glazing according to the invention is preferably a rear windshield for a motor vehicle.

[0026] The process according to the invention preferably comprises a drying step at the end of each step of laying tracks. The drying is carried out at a temperature between 100 and 200ºC.

[0027] The cooking step of the electroconductive and protective lanes is preferably carried out simultaneously with a curving of the glass sheet. The cooking temperature is preferably between 60 and 800ºC, especially between 620 and 750ºC.

[0028] The attached drawings illustrate the invention.

[0029] Figure 1 is a representation of a glazing according to the invention.

[0030] Figure 2 is a schematic sectional view of a window pane according to the invention, in a part of the transparent zone.

[0031] The pane 1 is a rear windshield of a motor vehicle It comprises a glass sheet 2 and has a central transparent zone 3 and a peripheral opaque zone 4, the opaque zone 4 comprising, placed on the glass sheet and a layer of black enamel. The glazing 1 also comprises electroconductive tracks located in the opaque zone 4, which are not visible, as well as electroconductive tracks 5, located in the transparent zone 3, in the form of heating wires. The heating wires 5 extend here across the width of the glass pane and are, for example, silkscreened with a silver paste. In the opaque part 4, the heating wires are electrically connected to other electroconductive tracks, in this case not visible collector bands, located on the side edges of the glass pane 1, which are also, for example, silkscreened with a silver paste. Transparent protective slopes 6 protect, in the transparent area 3 of the glass pane 1, the heating wires 5, covering both the upper surface 50 and its lateral edges 51 at the same time. The protective slopes 6 are for example made of silica and placed by silkscreen. a sol-gel solution.

[0032] The following examples illustrate the invention in a non-limiting manner.

[0033] In a comparative example, a sheet of glass of 4.85 mm thick was coated by screen printing with electroconductive tracks made of silver. To do this, a silver paste containing 80% silver was screen-printed in a known way using a screen containing 77 threads / cm and then dried at 150ºC for 2 minutes. The silver paste was then cooked at 710 ° C for 3 minutes.

[0034] The example according to the invention is distinguished from the comparative example by the fact that protective tracks were placed on the electroconductive tracks based on silver. The protective tracks were placed by silkscreening a sol-gel solution containing silica precursors using a screen containing 120 threads / cm, and then dried at 150ºC for 2 minutes.

[0035] The resistance to fogging was measured as follows: a bowl containing 10 g of sulfur flower is placed in a desiccator containing 500 ml of demineralized water. The samples to be studied are inserted in an upright position inside the desiccator, the latter being then closed hermetically and then placed at a temperature of 70ºC for 2 days. The optical aspect of the samples is then assessed qualitatively.

[0036] In the case of the comparative example, the tracks had spots as well as an iridescent aspect characterized by an aspect in reflection that goes from orange to brown. In the case of the example according to the invention, on the other hand, the tracks have a homogeneous gray appearance.

Claims (14)

1. Glazing (1) characterized by the fact that it has at least one transparent zone (3) and at least one opaque zone (4), in which said glazing (1) comprises a glass sheet (2) coated in one of its surfaces of electroconductive tracks (5) based on silver in at least one transparent zone (3) and at least one opaque zone (4), said electroconductive tracks (5) located in at least one transparent zone (3) being covered in its upper surface (50) and its lateral edges (51) by transparent protective tracks (6) based on an oxide. Glazing (1) according to claim 1, characterized by the fact that the transparent zone (3) is located in the central zone of the glazing (1) and represents at least 60% of the glazing surface. 3. Glazing (1) according to any of the preceding claims, characterized by the fact that the electroconductive tracks (5) occupy between 1 and 20%, notably between 2 and 10%, of the surface of the glazing (1). 4. Glazing (1) according to any of the preceding claims, characterized by the fact that the electroconductive tracks comprise heating wires (5) located at least in a transparent area (3) of the glazing and collecting bands located in an opaque zone ( 4) the pane. 5. Glazing (1) according to claim 4, characterized by the fact that the heating wires have a width ranging from 0.1 to 1 mm, notably from 0.25 to 0.7 mm and a thickness ranging from 2 to 30 μm, notably 2 to 20 μm. 6. Glazing (1) according to any of the preceding claims, characterized by the fact that the electroconductive tracks (5) are placed by silkscreen using a paste with silver. 7. Glazing (1) according to any one of the preceding claims, characterized by the fact that the thickness of the protective tracks (6) is comprised in a range ranging from 0.1 to 5 μm, notably from 0.2 to 3 μm. 8. Glazing (1) according to any of the preceding claims, characterized by the fact that the protective tracks (6) are based on an oxide of at least one element chosen from silicon, titanium, zirconium, tin . 9. Glazing (1) according to claim 1, characterized by the fact that the protective tracks (6) are placed by serigraphy of a sol-gel solution. 10. Glazing (1) according to any of the preceding claims, characterized by the fact that the opaque zones (4) are located at least on the periphery of the glazing and comprise an opaque mineral layer, notably an enamel layer. 11. Glazing (1) according to any of the preceding claims, characterized by the fact that it is a rear windshield for a motor vehicle. 12. Process for obtaining a glass pane (1) as defined in any of the preceding claims, characterized by the fact that it comprises the following successive steps: - a step of placing electroconductive tracks (5) by silkscreen with silver paste on the surface of a sheet of glass (2), and then - a stage of placing transparent protective tracks (6) based on an oxide by silkscreening a sol-gel solution, and then - a cooking stage of the said electroconductive tracks (5) and protective (6). Process according to claim 12, characterized by the fact that it comprises a drying step at the end of each track laying step (5, 6). Process according to either of Claims 12 and 13, characterized in that the cooking step is carried out simultaneously with a curving of the glass sheet.