Method for concealing busbars in a laminated glazing body - Patent application

Abstract

The present invention relates to a method for concealing busbars in a heat-coated laminated glazing body formed by a first glass sheet (10) and a second glass sheet (20), each having an outer surface and an inner surface, the method comprising the steps of: - printing an enamel on the inner surface of the first glass sheet (10) and / or the second glass sheet (20), whereby the enamel forms a pattern (3), - firing the enamel, - covering at least a part of the pattern formed by the enamel with a coating (5), which coating extends to at least one area of ​​the enamel for applying busbars, - applying at least two silver paste busbars (40, 50) on the extended coating in this area, whereby at least one silver paste busbar (40) of the at least two silver paste busbars is concealed. has a first portion and a second portion, the first portion (42) being arranged to apply a voltage across a portion of the coating, thereby obtaining a stack including the at least two silver paste bus bars, the coating, and the enamel pattern; - firing the stack; - subjecting the first glass sheet and the second glass sheet to a heat treatment; - laminating the first glass sheet and the second glass sheet, thereby providing an interlayer sheet in contact with the inner surfaces of the first glass sheet and the second glass sheet, and providing the coating between the first glass sheet and the second glass sheet.

Description

[Technical Field]

[0001] The present invention relates generally to the field of laminated glazing bodies provided with an electrically conductive system comprising thin layers. [Background technology]

[0002] Laminated glazing bodies, comprising two (or more) glass panes laminated together by a thermoplastic interlayer, are known per se. Such interlayers are used for safety reasons. However, the interlayer may also be used to impart beneficial properties to the glazing body (e.g., solar control properties, electrical conductivity, thermal insulation). Laminated glass is, for example, the windshield of a vehicle.

[0003] Windshields containing conductive systems were first developed to provide infrared radiation filtering properties. Next, the windshields contain one or more metal layers, essentially based on silver, combined with a dielectric layer that protects the metal layers. Conductive systems of layers have also been proposed for heating windshields for the purpose of defogging or defrosting them. The heat generated by the Joule effect of the heating layer allows condensed water, ice, and snow to be removed in a short time. The advantage of using such windshields in automobiles is that the central field of vision has virtually no visual limitations.

[0004] The heating current is usually introduced into the heating layer via at least one pair of strip electrodes (so-called bus bars) that distribute the heating current as a collective conductor over a wide front. Generally, to obtain adequate heating power for practical applications, the heating voltage needs to be sufficiently high, while in internal combustion engine-driven vehicles, the currently standard effective on-board voltage is between 12 and 48 volts.

[0005] The need to have a sufficiently high area of power per unit surface area on the surface of the windshield has led to a variety of solutions.

[0006] Some solutions involve lines in the back of the structure that are free of a conductive layer, the lines themselves forming a heating network that extends from one busbar to another over the entire height of the windshield. The drawback of this solution is, of course, that the lines are visible, and although they only partially contribute to the heating, they remain visible. The lines therefore have a negative impact on the uniform appearance that is the desired heating layer.

[0007] The majority of automotive glazing bodies contain enamel patterns intended to hide unsightly elements, such as adhesive seals, electrical connections, and bus bars, among others. Conventionally, these patterns are obtained by applying compositions containing glass frit, pigments, and vectors that suspend the frit and pigment. The application of these enamel compositions is followed by a high-temperature firing that melts the frit and adheres the enamel to the substrate.

[0008] Unfortunately, when the enamel is fired, where the busbars, and more particularly the silver busbars, are provided, the busbars may remain partially visible, resulting in an unacceptable (unaesthetic) glazing body for the automobile manufacturer. Therefore, the choice of enamel type and enamel firing conditions are further driven by compatibility with the heatable coating provided on at least a portion of the surface of the glazing body.

[0009] Therefore, there is a need for an approach to accurately conceal busbars in laminated glazing bodies and the like (eg, windshields) that takes into account the above-mentioned constraints and requirements. Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of embodiments of the present invention to provide a method for concealing busbars in a heat-coated laminated glazing body.A further object of embodiments of the present invention is to provide a laminated glazing body with concealed busbars, which is obtained by applying the proposed method. [Means for solving the problem]

[0011] The above mentioned objectives are achieved by the solution according to the invention.

[0012] In a first aspect, the present invention relates to a method for concealing a busbar in a heat-coated laminated glazing body formed by a first pane and a second pane of glass, each pane having an outer surface and an inner surface, the method comprising: - carrying out enamel printing on the inner surface of the first glass sheet and / or the second glass sheet, whereby the enamel forms a pattern; - firing said enamel; - covering at least a part of the pattern formed by the enamel with a coating, the coating extending to at least one area of the enamel pattern for applying the busbar; - applying at least two silver paste bus bars onto the coating within the area, whereby at least one of the at least two silver paste bus bars has a first portion and a second portion, the first portion being arranged to apply a voltage and a current through a portion of the coating located below the first portion of at least one of the at least two silver paste bus bars, thereby obtaining a stack formed by the at least two silver paste bus bars, the coating and the enamel pattern, and the second portion of at least one of the at least two silver paste bus bars being configured not to generate a current through the portion of the coating, the coating acting as a barrier to migration of silver of the silver paste bus bars towards the enamel; - firing the stack; - subjecting the first glass sheet and the second glass sheet to a heat treatment; - laminating the first and second glass sheets with an interlayer sheet in contact with the inner surfaces of the first and second glass sheets, thereby providing a coating between the first and second glass sheets; Includes:

[0013] The proposed solution actually allows for the production of a coating-laminated glazing body with a silver paste busbar that is invisible when viewing the glazing body from the outside. The coating is applied so as to cover at least a portion of the pattern formed by the enamel and leave an area covered with the coating available for applying the busbar. One of at least two silver paste busbars, to which terminals can be connected for applying a voltage, is applied on top of the coating. Thus, no portion of the busbar is free of the coating. At least one of the silver paste busbars includes two portions (first and second), the first portion being used to apply this voltage through the coating or at least a portion of the coating. In some embodiments, the second portion of the at least one silver paste busbar is used solely to transfer the voltage to the busbar portion to which the voltage is applied. The second portion of at least one of the silver paste busbars is configured so as not to generate a current through a portion of the coating, and the coating acts as a barrier to the migration of silver from the silver paste busbar toward the enamel. The stack, including the silver paste busbar, coating, and enamel pattern, is then fired, a process step known per se. The first and second glass sheets then undergo a heat treatment. Finally, the treated first and second glass sheets are laminated together by establishing contact between the interlayer plate and the inner surfaces of the first and second glass sheets, i.e., with one or both sides of the glass sheets that have been treated as described above.

[0014] An advantage of the present invention is that by applying the busbars to a coating, it is ensured that there is always a coating that forms a barrier between the enamel and the silver paste.

[0015] The advantage of the present invention is that it avoids the migration of silver into the enamel, thus making the busbars invisible from the outside, and also avoids the occurrence of cracks in the enamel layer.

[0016] In an embodiment of the busbar concealment method according to the invention, the second portion is insulated from the coating by at least one insulating wire, and the step of providing the at least one insulating wire is preceded by masking or laser stripping or mechanically abrading part of the coating.

[0017] In some embodiments, two of the bus bars are substantially parallel and each bus bar is provided with a terminal for supplying power.

[0018] In certain embodiments, one of the bus bars is positioned along the periphery of substantially a portion of the enamel pattern on which the coating is applied.

[0019] Advantageously, the coating is a multi-layer conductive coating comprising at least one layer of conductive material (e.g., silver or gold). In a preferred embodiment, the coating is infrared reflective.

[0020] In an advantageous embodiment, the step of applying the heat treatment comprises bending the first and second glass sheets sheet by sheet, i.e., bending each sheet separately. When applying such a sheet by sheet approach, advantageously, firing the stack and heat treating the first and second glass sheets can be performed in a single operation. In another embodiment, the heat treatment is performed on the first and second glass sheets simultaneously, i.e., on the assembly of the two glass sheets.

[0021] In a preferred embodiment, the heat treatment includes bending the first glass sheet and the second glass sheet.

[0022] In another aspect, the present invention relates to a laminated glazing body including first and second glass sheets, each having an outer surface and an inner surface, and an interlayer sheet in contact with the inner surfaces of the first and second glass sheets. An enamel pattern is printed on the inner surface of at least one of the first and second glass sheets, and at least a portion of the pattern is covered with a coating. At least two silver paste bus bars are applied on top of the coating. At least one of the at least two silver paste bus bars has a first portion and a second portion, one of the portions being arranged to apply a voltage across at least a portion of the coating. The stack including the at least two silver paste bus bars, the coating, and the enamel pattern is fired, whereby a heat treatment is applied to the first and second glass sheets.

[0023] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above. It is to be understood, of course, that not all such objects or advantages can necessarily be achieved in accordance with any particular embodiment of the invention. Thus, for example, one skilled in the art will recognize that the invention can be embodied or practiced in a manner that achieves or optimizes one advantage or group of advantages as taught herein, without necessarily achieving other objects or advantages as taught or suggested herein.

[0024] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described below.

[0025] The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which like reference numerals refer to like elements in the various drawings, and in which: [Brief explanation of the drawings]

[0026] [Figure 1] 1 illustrates the nomenclature for the various surfaces of the outer and inner glass panes.

[0027] [Figure 2]Illustrates a glass plate on which an enamel pattern is printed.

[0028] [Figure 3] Illustrated is an embodiment in which the coating covers a portion of the enamel pattern and the glass pane.

[0029] [Figure 4] 1 illustrates an embodiment of a laminated glazing body to which the busbar concealment method according to the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited to those embodiments but only by the claims.

[0031] Moreover, the terms "first, second, etc." in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a sequence or order in time or space in any other way. Terms so used are interchangeable under appropriate circumstances, and embodiments of the invention described herein are capable of operating in sequences other than those described or illustrated herein.

[0032] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed below, and the term "comprising" does not exclude other elements or steps. Thus, "comprising" should be interpreted as specifying the presence of a given feature, integer, step or component as referenced, but does not exclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the term "a device comprising means A and B" should not be limited to a device consisting of only components A and B. The term "a device comprising means A and B" means, in the context of the present invention, that the only relevant components of the device are A and B.

[0033] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, appearances of the terms "in one embodiment" or "in an embodiment" in various places throughout this specification may, although do not necessarily, all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0034] Similarly, in describing exemplary embodiments of the invention, it will be appreciated that various features of the invention may be combined in a single embodiment, drawing, or specification of the invention for the purpose of streamlining the disclosure and aiding in understanding one or more of the various inventive aspects. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects comprise less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.

[0035] Furthermore, although some embodiments described herein may include some features (but not other features) included in other embodiments, combinations of features from different embodiments are intended to form different embodiments within the scope of the present invention, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments may be used in any combination.

[0036] It should be noted that the use of a particular term when describing a particular feature or aspect of the invention should not be taken to mean that the term has been redefined herein to be limited to include any particular characteristic of the feature or aspect of the invention with which the term is associated.

[0037] In the specification provided herein, numerous specific details are set forth. However, it is understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this specification.

[0038] The present invention proposes a method for obtaining concealed busbars in a laminated glazing body formed by joining a first glass sheet and a second glass sheet, thereby ensuring that the silver paste busbars applied to the first glass sheet and / or the second glass sheet cannot be seen from outside the glazing body. The first sheet may be the outer glass sheet and the second sheet may be the inner glass sheet, or vice versa.

[0039] When two glass sheets (an outer sheet and an inner sheet) are connected via an interlayer sheet, the inner and outer surfaces of the two glass sheets are usually referred to as follows (see Figure 1). The P1 and P2 surfaces correspond to the outer and inner surfaces of the outer glass sheet, respectively. When the laminated glazing body is a vehicle windshield, the P1 surface corresponds to the side that is attached to the vehicle and that is the outer side of the windshield when viewed from the outside of the vehicle, while the P2 surface is the other side of the outer sheet. The P3 and P4 surfaces belong to the inner glass sheet. The P4 surface represents the outer surface of the inner glass sheet as viewed from the inside of the vehicle. Finally, the P3 surface corresponds to the inner side of the inner glass sheet. This is the nomenclature commonly used in the field of laminated glazing bodies.

[0040] The busbar concealment method of the present invention can be applied to any glass sheet, i.e., the outer sheet, the inner sheet, or both the outer sheet and the inner sheet. At the end of the processing of the outer glass sheet, the inner glass sheet, or both sheets, the sheet is joined to another sheet to form a laminated glazing body. For example, in an advantageous embodiment, the laminated glazing body may be an automobile windshield, and "automobile" may mean a car, a train, an airplane, etc.

[0041] In the proposed approach, one starts with glass panes obtained by cutting and polishing a raw glass pane, one of which is the outer pane of the laminated glazing body, and the other glass pane is the inner pane if the laminated glazing body is to be installed, for example, in a vehicle.

[0042] The inner surface of the outer and / or inner sheet (thus, surface P2 or P3 in FIG. 1) is printed with enamel, which forms some pattern (e.g., a square or rectangular pattern with a specific width). Typically, the enamel is applied up to the edge of the glass sheet. In some cases, a small margin can be maintained between the sheet edge and the enamel. FIG. 2 illustrates the inner surface (14) of a glass sheet on which enamel has been printed in a rectangular pattern (3).

[0043] The enamel is then typically fired: it is gradually heated from ambient temperature to a higher temperature in order to achieve sufficient fusion of the glass frit within the enamel.

[0044] In an embodiment of the present invention, a conductive coating is then applied to at least a portion of the pattern formed by enamel printing. The heatable coating is applied using a known method, for example, by magnetic field enhanced cathode sputtering, which allows for a simple, rapid, economical and uniform coating.

[0045] Preferably, the heatable coating is transparent. In the context of this invention, a "transparent coating" means a coating having a transmittance of at least 50%, preferably at least 70%, in the visible spectral range, which allows the glazing body to be used as a windshield for automobiles.

[0046] The conductive coating has at least one conductive layer. Furthermore, the coating can have a dielectric layer, which, for example, serves to adjust the plate resistance, prevent corrosion, or reduce reflection. Preferably, the conductive layer contains silver (e.g., at least 99% silver) or a conductive oxide (transparent conductive oxide (TCO)) (e.g., indium tin oxide (ITO)). The conductive coating may contain one silver layer, two silver layers, three silver layers, or even more silver layers. One preferred coating contains two (Ag2) or three (Ag3) conductive layers containing silver. Preferably, the conductive layers have a thickness of 5 nm to 200 nm, particularly preferably 10 nm to 50 nm. In this way, an excellent compromise between the transparency and conductivity of the layer is achieved. To simultaneously improve conductivity with high transparency, the coating can have multiple conductive layers separated from each other by at least one dielectric layer. The conductive coating can contain, for example, two, three, or four conductive layers. Typical dielectric layers comprise oxides or nitrides (e.g. silicon nitride, silicon oxide, aluminum nitride, aluminum oxide, zinc oxide, or titanium oxide). Such coatings are particularly advantageous in terms of the transparency of the glazing body on the one hand and the electrical conductivity of the glazing body on the other hand.

[0047] In a preferred embodiment, the coating is an infrared-reflective coating (e.g., comprising two or three silver layers (Ag2 or Ag3)). Having a laminated glazing body provided with such a coating in a vehicle is advantageous for keeping the temperature inside the vehicle under control.

[0048] The sheet resistance of the conductive coating is preferably between 0.3 and 7 ohms / sq. Thus, advantageous heating powers are obtained at voltages typically used, for example, in the automotive industry, with the result that a lower sheet resistance results in a higher heating power at the same applied voltage.

[0049] FIG. 3 illustrates a portion of the enamel pattern (3) and the coating (5) applied to the glass. The coating extends to at least one area of the enamel that is wide enough to allow the application of a busbar. In a preferred embodiment, the coating is applied so that the frame-like edge of the glazing body, which has the enamel printed on it, remains uncovered with the heatable coating. This edge is sometimes called an edge removal or cutback. In this way, the heatable coating is not in contact with the ambient atmosphere, thus ensuring protection against corrosion; the coating is, so to speak, encapsulated by an interlayer. The width of the uncoated edge is typically in the range of 0.5 mm to 20 mm, in particular 1 mm to 10 mm. The glazing body may further comprise other uncoated areas, obtained by, for example, masking such areas (before the coating is applied) or by laser removal or mechanical abrasion (after the coating is applied). Such areas can be used, for example, as data transmission or communication windows. In another embodiment, for example as shown in Figure 3, the part of the glass pane that was not printed with enamel may be completely covered with a coating, in which case the coating is placed directly on the glass.

[0050] Next, at least two silver paste bus bars are added on top of the coating. Various techniques are available to those skilled in the art for performing this step, such as using screen printing, digital printing, or spraying. This ensures that the bus bars are applied only on top of the coating and not on the enamel. Each bus bar includes a terminal for supplying power to heat the coating or at least a portion of the coating. At least one of the silver paste bus bars includes two (first and second) portions, with the first portion positioned to apply a voltage through the coating or at least a portion of the coating. In some embodiments, the at least one second portion of the silver paste bus bar is used only to transfer voltage to the bus bar portion to which the voltage is applied. The at least one second portion of the silver paste bus bar is configured not to generate current through the portion of the coating, and the coating acts as a barrier to the migration of silver from the silver paste bus bar toward the enamel pattern. Next, a stack including two or more bus bars, the coating to which the bus bars are applied, and the portion of the enamel pattern to which the coating is applied is fired. Thereby, the stack is gradually heated from ambient temperature to a higher temperature in order to achieve sufficient melting of the glass frit within the silver paste to form a solid band of silver that adheres / sticks to the substrate.

[0051] FIG. 4 provides an example. In the illustrated embodiment, one busbar (40) is placed on the coating, essentially following the periphery of the portion of the pattern formed by the enamel printing that remains uncovered by the heatable coating. A second busbar (50) is then placed parallel to one of the sides of the enamel pattern. This arrangement offers the advantage of being able to place the electrical terminals close to each other. The first busbar (40) comprises two parts (a first part and a second part). The first part (42) is intended to apply a voltage through the coating or at least a portion of the coating. In this embodiment, the second part (44) of the busbar serves to transfer the voltage to itself. This second part is positioned around the coating area, and therefore near the edge of the enamel printed on the glazing body. Advantageously, this busbar, and in particular the second part (44) of the busbar, uses the extended area where the enamel is provided. The second portion (44) is configured to not generate current through a portion of the coating, and the coating acts as a barrier to migration of silver from the silver paste busbar towards the enamel.

[0052] To transfer voltage and avoid current flow in the coating (by a short-circuit effect), in a preferred embodiment, the coating is provided with at least one insulating line (46), positioned between the busbars (40, 50) and extending along the outer edge of the glazing body, as shown in FIG. 3 . In some embodiments, there are multiple insulating lines. Such insulating lines can be obtained, for example, by locally masking the coating or by laser removal of portions of the coating. In this disclosure, "insulating line" refers to a linear area in the conductive coating that is not electrically conductive. The width of the insulating line depends on the technique used to obtain it. Preferably, the width is 500 μm or less, particularly preferably 10 μm to 250 μm, and most particularly preferably 20 μm to 150 μm. However, if the insulating line is obtained by applying masking, a minimum width of 500 μm is required. Preferably, the insulating line extends beyond the entire thickness of the conductive coating, but at least beyond the entire thickness of the conductive layer of the coating. Thus, the insulating line creates different zones that are electrically isolated from each other. In this way, a short circuit between the two busbars is avoided.

[0053] In a preferred embodiment, there are two bus bars. An example is given in Figure 4. However, in other embodiments, there may be more than two bus bars. In some embodiments, the bus bars may be arranged in the laminated glazing body in a left-right direction, e.g., covering substantially the full width of the screen. Alternatively, the bus bars may be arranged in a top-to-bottom direction, e.g., covering substantially the full height of the screen.

[0054] The length of the busbar depends on the design of the laminated glazing body, in particular on the length of the edge on which the busbar is arranged, and can be appropriately selected by a person skilled in the art in each case. The "length" of a typical band-shaped collective busbar means the longer dimension that normally brings the busbar into contact with the different heating zone parts.

[0055] In an embodiment, the busbar is realized as a printed and fired conductive structure. The printed busbar comprises silver and optionally at least one other metal. Preferably, the electrical conductivity is realized by metal particles contained in the assembly conductor, particularly preferably by silver particles. The metal particles can be contained in an organic and / or inorganic matrix (e.g., paste or ink), preferably as a fired screen printing paste with glass frit. The layer thickness of the printed assembly busbar is preferably 5 μm to 40 μm, particularly preferably 8 μm to 20 μm, and most particularly preferably 10 μm to 18 μm. Printed busbars with these thicknesses are technically easy to realize and have advantageous current-carrying capacities.

[0056] Once the silver paste printing has been performed on the inner layer of (one of) the glass sheets, the following further processing steps may be performed: A heat treatment is applied to the first and second glass sheets to pre-form them. In a preferred embodiment, this heat treatment may be bending, optionally followed by a tempering operation. In a preferred embodiment, the heat treatment (e.g., bending) is performed sheet by sheet, i.e., separately for the first and second glass sheets. In this case, firing of the stack and heat treatment of the first and second glass sheets can be performed in a single operation. In another embodiment, the first and second glass sheets are first brought together and the assembly of the two glass sheets is heat-treated.

[0057] The interlayer plate is formed by at least one thermoplastic bonding film, which comprises at least one thermoplastic polymer, preferably ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), or polyurethane (PU), or a mixture, copolymer, or derivative thereof, particularly preferably PVB. The thickness of the thermoplastic bonding film is preferably in the range of 0.2 mm to 2 mm, particularly preferably 0.3 mm to 1 mm (e.g., 0.38 mm or 0.76 mm).

[0058] The proposed method leaves open the possibility of carrying out a step of enamel printing on the outer surface of one of the glass sheets. In certain embodiments of the method, for example, adding such a second enamel layer on the P4 surface can avoid the adhesion problems encountered when directly gluing the glass surfaces.

[0059] In another aspect, the present invention relates to a laminated glazing body to which the busbar concealment method described above has been applied during manufacture. More specifically, such a laminated glazing body includes a first glass sheet (10) and a second glass sheet (20), each having an outer surface and an inner surface, and an interlayer sheet in contact with the inner surfaces of the first and second glass sheets. Enamel is printed on the inner surfaces of the first and second glass sheets, or both, to form a pattern. At least a portion of the pattern is covered with a coating, as described above. At least two silver paste bus bars (40, 50) are applied on top of the coating. In other words, all of the busbar ground surfaces are in contact with the coating. At least one of the two or more silver paste bus bars has a first portion and a second portion, and the first portion is arranged to apply a voltage across at least a portion of the coating. The second portion of at least one of the two or more silver paste bus bars is configured to prevent current from flowing through the portion of the coating, and the coating acts as a barrier to the migration of silver from the silver paste bus bar into the enamel. The stack formed by the various bus bars, the coating under each bus bar, and the portion of the enamel pattern to which the coating is applied is then subjected to a firing process. The two glass panes are then heat-treated. This heat treatment can be performed on each pane or together.

[0060] To establish a connection with an external voltage supply, a supply line is provided in electrical contact with at least one busbar. Preferably, each busbar has such a supply line. The supply line can terminate already within the laminated glazing body, i.e., it can contact the flat conductor before reaching the edge of the glazing body. Alternatively, the supply line can extend beyond the edge of the glazing body to contact an external connection cable on the outside of the laminated glazing body.

[0061] In an advantageous embodiment, the laminated glazing body may be a windshield that can be installed in a car, train, aircraft or other means of transport.

[0062] Such a windshield is arranged to be defrosted or defogged when at least a portion of the windshield is heated by applying a voltage to a busbar provided on the windshield. In the proposed solution, where the busbar is completely within the coating area of the windshield, the heating is primarily concentrated in the coating portion of the windshield. It should be noted that, according to the present invention, the busbar further comprises a second portion that is not used for the heating function. In that portion of the busbar, the coating is essentially used to form a barrier between the busbar and the enamel.

[0063] Because the silver paste busbars are above the paint film, the busbars are not visible when looking at the windshield from outside the vehicle in which it is installed, or when looking at the windshield from inside the vehicle.

[0064] While the invention has been illustrated and described in detail in the drawings and foregoing specification, such illustration and description are to be considered illustrative or exemplary and not restrictive. The foregoing specification details particular embodiments of the invention. However, no matter how detailed the above appears in text, it will be understood that the invention can be practiced in many ways. The invention is not limited to the disclosed embodiments.

[0065] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in a claim. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. A computer program may be stored / distributed on a suitable medium (e.g., an optical storage medium or a solid-state medium supplied together with or as part of other hardware pieces), but may also be distributed in other forms (e.g., via the Internet or other wired or wireless telecommunication systems). Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 1. A method for concealing busbars in a heat-coated laminated glazing body formed by a first glass sheet (10) and a second glass sheet (20), each having an outer surface and an inner surface, comprising: - carrying out enamel printing on the inner surface (14) of said first glass sheet (10) and / or said second glass sheet (20), whereby said enamel forms a pattern (3); - firing the enamel; - covering at least a part of the pattern formed by the enamel with a coating (5), said coating extending up to at least one area of the enamel pattern for applying busbars; - applying at least two silver paste bus bars (40, 50) on top of the coating in said area, whereby at least one silver paste bus bar (40) of said at least two silver paste bus bars has a first portion (42) and a second portion (44), said first portion (42) being arranged to apply a voltage and a current through at least a portion of said coating located below said first portion (42) of said at least one silver paste bus bar of said at least two silver paste bus bars, thereby obtaining a stack comprising said at least two silver paste bus bars, said coating and said enamel, said second portion (44) being arranged not to generate a current through said portion of the coating, said coating acting as a barrier to migration of silver of said silver paste bus bars towards said enamel pattern; - firing the stack; - subjecting the first glass sheet and the second glass sheet to a heat treatment to cause bending; - laminating the first and second glass sheets with an interlayer sheet in contact with the inner surfaces of the first and second glass sheets, thereby providing the coating between the first and second glass sheets; A method for concealing a bus bar, comprising:

2. 2. The method for concealing a busbar of claim 1, wherein said second portion (44) is insulated from said coating by at least one insulating wire.

3. 3. The method for concealing a busbar according to claim 2, wherein masking or laser removing or mechanically polishing a portion of the coating precedes the at least one insulating wire.

4. A method for concealing busbars according to any one of claims 1 to 3, wherein two of the busbars are parallel and each busbar is provided with a terminal for supplying power.

5. A method for concealing busbars according to any one of claims 1 to 4, wherein one of the busbars is positioned along the periphery of the pattern.

6. A method for concealing busbars according to any one of claims 1 to 5, wherein the coating is infrared reflective.

7. A method for concealing busbars according to any one of claims 1 to 6, wherein the coating is a multi-layer conductive coating comprising at least one layer of conductive material.

8. 8. The method for concealing busbars according to claim 1, wherein the step of subjecting the first glass sheet and the second glass sheet to the heat treatment is carried out sheet by sheet.

9. The method for concealing busbars according to any one of claims 1 to 7, wherein the heat treatment is carried out simultaneously on the first glass sheet and the second glass sheet.

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