Transparent glass with heating coating

[0001] The invention relates to a transparent pane having an electric heating coating having the features of the preamble of claim 1.

[0002] There is a large demand on the market, especially for the vehicle windshields, for heating models in which the heating itself must be as noticeable as possible or visually burdensome. Therefore, there is an increasing need for a heating coating that is transparent to windows.

[0003] A general problem of heating coats with low light absorption is their relatively high surface resistivity which, in any case with large pane sizes for heating or for long current routes, requires a high operating voltage, which in any case is higher than the usual voltages on board vehicles. If one would like to lower the surface resistivity with currently known layered systems, the result would be a reduction in visible transmission , since the conductive layers would have to be thicker.

[0004] For technical reasons, it is now preferable to mount still glass panes heated by wires that can be easily supplied with the usually applied on-board voltage. These composite panes with heating fields with very thin wires built in are not accepted by all customers.

[0005] A method (WO 2006/024809 A1) is also known for equipping such panes heated by wires in a transparent thermally insulating coating in a composite form.

[0006] Another problem with the heating coatings is that sometimes they can not be applied homogeneously over the entire surface of the transparent pane, but one or more gaps, called "communication windows", must be provided, which deteriorate the heating current stream and possibly lead to to create "hot spots" on their edges. Such communication windows serve to ensure that a coating that inherently reflects short or infrared radiation is locally more permeable to certain information streams or signals.

[0007] For the introduction and removal of the heating current in such coatings, at least one pair of electrodes (in the form of tapes) or collecting cords (also "bus bars") are provided to introduce the current in a homogeneous manner as possible to the surface of the layer and unfold it with a wide front. In vehicle shafts, which are much wider than high, collective pipes are usually placed along the edges of long glazing (upper and lower edges in the assembly position), so that the heating current can circulate on the shortest route at the height of the glass. Similarly, said communication windows are most often located on the edge of the upper pane and extend there over a width of a few centimeters.

[0008] WO 00/72 635 A1 describes a transparent substrate equipped with an IR reflective coating and a communication window made by removing or omitting the coating from the surface.

[0009] Further, from DE 36 44 297 A1, there are numerous examples for splitting the car's windshield coatings. The divisions can be implemented by surface zones lacking layers and / or by cuts made mechanically or by laser radiation. They are used to regulate and deflect in a directed way the current stream inside the coated surface and must guarantee a homogeneous current density in the right surfaces as possible.

[0010] From WO 2004/032 569 A2, another configuration of a transparent pane with a heating liner is known, which also seeks to obtain homogenization of the heating power in the surface through the lines of partitions made in the shell.

[0011] Document DE 29 36 398 A1 relates to measures to prevent, in a transparent pane with a heating coating, up to the current peaks at the transition between collecting ducts and the coating. In general, the aim is to reduce the rapid difference in resistance between the coating and the collection lines, using materials or forms with the highest electrical resistance for the latter, or intermediate resistances. For a coating, surface resistances between 1 and 10 ohms are indicated by a square. In one of the numerous variants of the solutions described herein, the side of each collecting conduit facing the opposite collecting conduit is made in a corrugated form. In this case, the formation of peaks directed towards the heating coating should not take place. This approach tends to substantially extend the transition line between the collecting pipe and the coating and thus reduce the current density in this transition. All these measures, however, seem unable to feed the heating layer with relatively low voltage.

It is also known (DE 10 2004 050 158 B3), in the window pane using electric heating, shortening the current path through the coating, in the element zone, effectively extending the collecting conduits of the surface covered with a conductive layer with low ohmic resistance in the form of conductive tracks or conductive wires extending from the collecting cords up to the heating field. With such a solution, the heating power may, however, be too low in the zone of the layer directly adjacent to the collecting lines.

[0013] The collecting cords already mentioned several times may be formed either by printing (screen printing) before or after applying the coating on the glass, and by soldering thin metal strips, preferably copper (tinned). There are also combinations of printed cabling and metal bands (see for example DE 198 29 151 C1). Collector cables are of course mostly in the form of narrow bands, but they are opaque. optical, consequently placed nearby

That is why they are behind the edge due to each time the outer transparent panes considered. Most often, they can be covered with opaque edge coatings (usually also made with screen printing). Similarly, said communication windows may be covered by these edge coatings, provided that the latter are sufficiently transparent to transmit radiation.

[0014] In commonly used vehicle windshields, these opaque coatings are made in the form of frames, the other task of which is to protect the glued connection between the pane and the body against UV radiation. These frames surround the field of view of the windows. In the windshields, a further distinction is also made between the field of view A at the center of the viewing surface, in which there can be no obstacle to vision (e.g. colors, wires, or other damage), and a field of view B closer to the edge.

[0015] Finally, it is known to separately heat vehicle windows wiping the wipers in the wiping or parking zone of the wipers. EP 849 977 B1 describes heating with a wire loop covering only this parking zone. Document US 5 434 384 and document DE 101 60 806 A1, on the other hand, disclose shafts heated by heating layers, in which the heating field proper for the wipers parking area is separated from the heating layer and is equipped with its own collection pipes.

[0008] It is also known (DE 10 2004 054 161 A1) to create, in a limited area of ​​the surface of a vehicle window provided for transmitting infrared radiation for information, separate heating elements that are to prevent transmission of infrared in this zone by condensation, snow and / or frost.

It is also known from EP 0 524 537 an windshield, one glass pane of which is provided with an electrically conductive coating on its major part of the surface, the coating having a first part in the field of view and a second part in the wiper storage part at rest, the second part may be heated independently of the first part.

It is an object of the invention to provide another transparent glazing with a low-operating, and a heating surface which, however, can produce operating voltages, but produces a homogeneously distributed heat and reliable heating of the partial area of ​​the pane, e.g. a wiper zone, or other part zone (on an example of sensor windows or similar). For visual reasons, these zones will preferably be located on the edge of a corresponding window.

[0019] This object is achieved according to the invention by the features of claim 1. The features of the sub-claims represent preferred embodiments of the invention.

[0020] The fact of creating a heating by means of a separate heating element with resistance heating elements formed from printed in a particular zone in the zone of rest position of the wipers, instead of heating by means of a coating, allows to achieve several advantages, or prevent some of the inconveniences that characterized the previous windows.

[0021] In particular, when the layer heating zone is narrowed by said edge zone, the current path through the coating with high electrical resistance therefore becomes shorter, so that the relatively low supply voltage can be operated here. If desired, it is also possible, according to a preferred embodiment, to reduce in a well-known manner the distance between the collection conduits by means of additional conductive elements of low electrical resistance.

A separate heating element for the peripheral zone, which is arranged on the same side as the shell, further ensures that this edge zone can be heated separately or independently and therefore very quickly and effectively, and that no weakening of the heating power needs to be taken into account. when said additional conductive elements are provided on the collecting conduits for the heating coating.

Of course, this configuration is used in an absolutely beneficial manner for windscreens in which it is important that the visibility is good in the central field of vision for safe driving, however, the heated pits according to the invention can also be mounted in other places (e.g. rear window , side windows) in vehicles and other mobile machines and devices, as in buildings.

[0024] When it is used in vehicles, the embodiment according to the invention allows, in particular, direct heating of the windshield with a common on-board voltage from 12 to 14 V at constant voltage, which obviously corresponds very well to a coating with the lowest possible electrical resistance. The length of any additional conductive elements is dimensioned depending on the active surface resistance of the respective coating; the better the guide is the coating itself, the shorter the conductive elements may be.

[0025] Likewise, this configuration allows to preserve the coating over the entire surface of the transparent pane, with the exception of possible anticipated communication windows - so that no masking agent or layer removal is needed. In this way, the positive properties of the coating, i.e. in particular infrared reflection (thermal insulation) and a uniform color throughout the surface, are preserved.

[0026] Additional conductive elements as thin as possible limit the visibility of the window in a practically imperceptible manner.

[0027] To separate the zone heated by the heating layer from the zone heated by the heating element, or the coating between the two heating zones, for example the cut-out line of the coating, is electrically separated or the coating at the level of the heating element is passive. In another variant, the area of ​​the surface heated by the heating element has no coating at all.

Given that the transparent pane, in practically any case, is a composite pane in which the eye coating itself is placed on the fl oor not inside the composite, the conductive elements could also, instead of printing, be made of thin wires that are fastened in a well-known manner on the adhesive foil of the composite and then applied with the foil onto the coating, which causes them to be electrically contacted with the coating. This contact is stable during the final gluing of the composite glass.

[0029] When they are made in the form of silk-screen structures, the conductive elements are applied to the substrate (glass or plastic pane or a plastic film) preferably before applying the coating. This can be done in one operation with the laying of proper busbars or busbars.

[0030] It is also possible to pass these conductive elements with low electrical resistance through the communication window made in the coating substantially on the edge of the pane, without fear of hot spots forming. Currents present in known problem zones at the side edges of these communication windows are very much reduced by conductive elements.

[0031] Other details and advantages of the object of the invention will emerge from the drawings of two embodiments of the vehicle windshield and from their detailed description below.

[0032] In these drawings, which are simplified illustrations without a particular scale,

Fig. 1 shows an electrically transparent one embodiment of a pane with a heated field of vision coating and with an additional heating element in a peripheral zone; and Fig. 2 shows a second embodiment with a variant of a separate heating element.

[0033] According to Figure 1, the electrically conductive and fully transparent coating 2 is incorporated in a well-known manner into a heated composite glass 1 in a substantially trapezoidal shape.

The dashed line, labeled 2T, indicates that the outer edge of the continuously coated surface is slightly retracted inwardly on all sides, relative to the outer edge 3 of the composite pane 1 or that the edge band is separated from the total coating. In this way, on the one hand, electrical insulation is obtained on the outside, and on the other hand, protection of the coating against corrosion attacks from the outer edge. The outer edge 2T can be removed by removing the coating along the edge of the pane, obstructing the substrate during application of the coating, or also delineating a perimeter separation line that passes through the coating along the outer edge of the pane, which can be sufficient for insulation and corrosion protection.

[0035] The coating itself preferably consists of and in a manner well known from a layer system capable of withstanding a high thermal load with at least one, and preferably several partial metallic layers (preferably silver) that it removes without injury, i.e. without impairing its optical properties, heat and electric reflection, temperatures above 650 ° C required for bending glass panes. In addition to metallic layers, the layer system further comprises other partial layers such as anti-reflective layers and possibly retention layers. The layer system used for the purpose set forth herein is disclosed, for example, in EP 1 412 300 A1.

In relation to the present invention, however, other electrically conductive layer systems with a minimum thermal capacity can also be used, and in particular also layer systems that are not directly applied to a rigid glass or plastic window, but to a plastic film. (preferably a PET film). All these layer systems are applied preferably by spraying (sputtering with a magnetron).

[0037] The surface resistance of common layer systems of the aforementioned type is between 1 and 5 Ω / □. The front windows of vehicles are equipped with such layer systems, in accordance with the applicable European standards, they must achieve a total light transmission of at least 75%. This means that the layer system itself must provide even higher optical transmittance. Unfortunately, the requirement for greater optical transparency is incompatible with the desire to achieve the lowest possible surface resistance for the coating. The thicker the partial conductive layers, the better they conduct electricity, but also their transparency decreases.

[0038] The composition and manufacture of the coating 2 are, however, of secondary importance here, so that there will no longer be any mention of them.

[0039] At the edge of the composite glazing 1, a layer of opaque paint 4 is applied in the form of a frame, the inner edge 4R of which circumscribes the field of view of the transparent pane 1, or in other words its outer edge. It can also be located in a different plane (inside or outside the composite glass) of the composite pane than the coating 2. It serves as a UV protection layer for the adhesive band to which the glass is finished and glued to the body of the vehicle. In addition, it acts as an optical shield for connection elements of additional electrical functions of the glass

1. However, it has no effect on the conductivity of coating 2.

[0040] Thus, along the upper edge of the composite pane 1 in the surface area covered by the paint layer 4, the first collecting duct 5 and along the bottom edge of the second collection duct 6 can be seen. Both manifolds 5 and 6 are electrically connected to the coating 2, in a well known manner. way.

[0041] Numerous vehicle windshields are equipped with a colored band, but still a transparent ("filter band") along their upper edge, which especially diminishes the glare of the sun. The glass described herein may also include such a filter band; its lower bounding line is shown as an option with the dash line BF. Below this limit, the field of view of the pane is clear, above it is transparent and stained and / or stained more or less intensely.

[0042] It should be mentioned here that in real panes (windscreens), the height-width ratio can be practically square, which means that the current path in the shell can be very long when the collecting lines are arranged on the upper and lower edges.

[0043] The composite pane 1 generally consists of two rigid glass and / or plastic panes and an adhesive layer that connects them (for example, a thermoplastic polyvinyl butyral PVB adhesive film from EVA "EVA"). "or polyurethane" PU "). The coating 2 and the collection conduits 5 and 6 are applied to one of the surfaces inside the composite of one of the rigid panes and possibly hot-bent simultaneously with the glass before applying and gluing the adhesive layer to the rigid panes.

[0044] Bulk cables 5 and 6 may consist of thin and narrow metal foil strips (copper, aluminum) that are attached to the surface of the glazing panel and which electrically contact the coating 2 at the latest when the composite layers are assembled. The electrical contact can, however, also be provided by soldering or printing the collecting lines 5 and 6. During subsequent treatment in the autoclave, contact between the collection lines and the coating is ensured by the action of heat and pressure.

[0045] As already indicated, the collecting lines 5 and 6, in a variant or a supplementary manner, can be made by printing a conductive paste which is fired during the bending of the glazing. It is also definitely less expensive than applying sections of a metal tape. Nevertheless, the collective lines printed in each case, in the course of industrial production in a continuous manner, show a higher electrical resistance than the tapes of a metal foil. The selection of collective cables made of metal foil or by screen printing is then possible only depending on the unit type of glass and possibly on the total resistance of the heating system.

[0046] Compared with coating 2, the collection lines 5 and 6, however, still have small electrical resistances and practically do not heat up when heating is in operation.

In a well-known manner, two (or more than two) heating fields can be provided in the composite pane 1, which can be separately supplied with electricity (with vertical separation for example in the middle of the pane), which obviously must also be connected by separate external connections to the right voltage source. In this case, a common ground wire for both heating fields can be used so that only the collecting conduit 5 or the collection conduit 6 has to be divided into two sections while the other is continuous. In the first variant, four external connections are needed and only three in the second.

In the embodiment shown here, with only one heating field, the heating current circulates the wide front between the collection lines 5 and 6 in the direction of the shortest widening (i.e. vertical) of the window 1. The upper collection conduit 5 is guided from top to bottom towards the edge the lower pane, outside the surface of the electrically active coating 2 (i.e. between the outer edge of the pane and the separation line 2T, coinciding with the opaque paint layer 4), so that it can be electrically connected to the outside at a given point with the collecting duct 6. Of course, it is also possible to make such a local connection of connections at any other point on the perimeter of the glass, or alternatively also dispense with it, so that external connections that are further away from each other will result.

In the region of the bottom edge of the pane, the frame of opaque paint is definitely wider than along other edges of the pane. Similarly, the separation line 2T is preferably more retracted towards the center of the window in this edge region. In this way, a partial surface free of the heating layer or in any case not heated is formed in this lower edge zone. This partial surface can of course also be coated if it is applied over the entire surface prior to punching the glazing. However, it is not planned to heat this surface with a partial coating. Consequently, it can also be provided that the partial surface can not be coated at all, masking when the coating is applied only to the panes already cut, or to remove the coating applied to the partial surface again.

[0050] It should be emphasized that the partial surface on which the wipers rest when the window is mounted on the vehicle will be relatively narrow relative to the total surface area of ​​the pane. In the case of a sensor vision window, the partial surface will also not be as wide as the one shown here. Here, an additional heating element 7 of a generally conventional type can be seen, i.e. a bundle of parallel wires or conductors 8 of a material with low electrical resistance to the coating that extend parallel to the edge of the lower pane and which can be connected to the electrical voltage by two Bulk ducts 9 and 10. While the collection duct 9 may be quite short at the left end of the heating element 7, since it is in any case in the external contact area of ​​the header lines 5 and 6, the right collector pipe 10 is bent over the heater element 7 and is extended until the end of the left heating element 7 so that it can also be connected externally in the contact area . This has the advantage that only one external connection element must extend beyond the finished window.

[0051] The heating element 7, in a well-known manner, can be prefabricated as a separate element on the film and be fully embedded in the composite pane. It can also be placed - also in a well-known manner - on an adhesive film that is provided for folding by gluing the surface of the rigid panes of the composite. Finally, it can also be produced by printing on the surface of rigid panes - especially preferably on a surface that is also provided with a coating 2.

[0052] The heating element 7 can function independently of surface heating by the coating 2, but of course also simultaneously with it if the electric vehicle (the power of two electrical protection devices has sufficient generator resources). In this way, these heating can also be independent of one another.

[0053] For example, the heating element 7 can be automatically activated once the wipers are freezed. This automatic functioning depending on the outside temperature and air humidity level can for example be reasonably used when - which is not uncommon in practice - the vehicle is stopped with still wipers and start, wipers activated next when, if possible frozen they want to start but are blocked . With automatic defrost, which takes into account the current position of the wiper switch, at least serious damage to the wiper drive system could be avoided.

[0054] These external connections will not be described in detail here because they have been described many times in the prior art. Preferably, flat cable elements (an insulating film with several parallel conductor tracks, of the type described, for example, in DE 195 36 131 C1) are used, which can be used without problems in the composite pane and go out of it.

In a well-known manner, as indicated here on the upper collecting line 5, a bundle of conductive elements 5E can be stretched in the field of view of the composite pane 1 starting from the edge zone covered by the paint layer 3 up to the field of view on the edge side of the pane. These conductive elements 5E are electrically connected to the collecting conduit 5 and to the envelope 2, and from their side with low electrical resistance compared to the latter. On the one hand, they are hidden from view by a layer of paint, other masking, as already mentioned, may optionally be formed by a color-stained band (filter band) not shown here.

[0056] Such conductive elements (not shown here) may also, if desired, extend in the field of view of the composite pane 1 starting from the lower collector duct 6.

[0057] Whereas, in conventional shafts with heating through this type of layer, the heating current should only circulate in the sheath over the entire distance between the collection lines, this distance can be reduced to values ​​of 50 to 80% of the conductive elements of the present invention, part of the current overcomes the remaining distance in the conductive elements.

[0058] As before, the current flow is reduced over the entire surface of the coating, since the collection lines are not separated from the shell in the sections between the conductive elements.

[0059] In order to achieve the above-discussed object of the present invention, these additional conductive elements 5E must also have direct contact with the coating 2, in addition to their good conductivity. Of course, you can basically make them in the form of wire sections. Preferably, however, they are printed, before applying the coating, on the surface of the pane, which is then to be coated.

[0060] It is also possible to print them simultaneously with collecting conduits on a finite coating, without the risk of damaging the coating - which must also be very mechanically robust in its last compositions. This has the advantage that a coating can be applied over the entire surface of the glass strips, punch out the glass strokes, then print and finally send them to a heat treatment such as bending and / or pre-tensioning.

[0061] From a functional point of view, the heating current circulates in the envelope 2 in the same direction as in the conductive elements 5E, i.e. perpendicular to the main extension of the elongated manifolds.

[0062] Preferably, the conductive elements and collecting cords are printed from a screen printing paste containing at least 80%, and preferably more than 85% silver.

If printed bands 5 and 6 are used, the optionally provided conductive elements 5E can be made in one operation and from the same printing paste. Then, no separate operation is no longer needed to electrically connect the conductive elements to the collection lines.

[0064] If the heating element 7 is also to be formed by printing, it is advisable to perform it during one screen printing operation simultaneously with the collection lines 5 and 6 and optionally with optional conductive elements. However, it is also possible to assume printing the heating element 7 on a separate transfer foil, which is then inserted into the composite, the heating conductors being laid on the surface of the window that also carries the coating 2.

[0065] The lengths, arrangements and mutual distances of the conductive elements 5E, their number and dimensions of the collection lines can here be presented only in a schematic manner. However, you can see relative dimensions. Whilst the proper collecting ducts 5 and 6 are made with a width of a few millimeters in the form of a conventional tape, the conductive elements 5E are as narrow and as little visible as possible, but definitely longer than the width of the collection lines.

[0066] The individual configuration in a particular composite pane can of course be predetermined in a wide range by simulations, but it depends to a large extent on the size or dimensions of a particular pane, the type of manifolds and the electrical properties of the actual coating. For more detailed details and in particular illustrations in cross-section of these glazing units, reference has been made to document DE 10 2004 050 158 B3, already mentioned in the introduction, the disclosure of which is incorporated herein.

At the front windscreens of the vehicles, care must in particular be taken that the conductive elements do not extend in any case in the normalized field of view A of the window in which the visibility can not be disturbed by any clearly visible obstacle due to the permissive provisions. In the field of view B surrounding the field of view A, however, there may be small obstacles to visibility.

[0068] Figure 2 shows a variant of the pane 1 in which the heating element 7 is printed as a single winding conductor 8 ', also in a manner well known. This meander covers the entire zone on which the wipers resist in their rest position. At the same time, the collecting duct 16 (as a functional unit consisting of a collecting duct 6 and a collecting duct 10 from Figure 1) also serves as a common ground for the coating 2 and for the heating element 7. For this purpose it has been marked with the mass symbol at its end after connection page. The power connections of the shell 2 and heating element 7 are, however, marked with arrows pointing outwards (which represent the direction of the current). This arrangement represents, in relation to Figure 1, the advantage that only three conductors or conductors of the cable are needed as external connections. Optionally, electrical separations of the coating and the heating zone are possible without problems on the outside of the pane 1, possibly also inside the composite (thin-film resistors, diodes, etc.).

[0069] In this embodiment according to Figure 2, it is recommended to remove the coating 2 in the peripheral zone (lower) of the pane 1 or even not to apply it at all. Considering that the electrical separation between the conductive track 8 'and the coating is difficult to represent, the purpose of the meander (i.e. the virtual widening of the conductor 8') could be thwarted by a partial shorting through the envelope 2.

[0070] In the embodiment according to Figure 1, with the bond of parallel conductors, the coating 2 may instead remain continuous, since here no short-circuit phenomenon need be considered here.

[0071] According to yet another variant of the heating element 7, which is not shown here, it could also be presented in the form of a closed conductive loop without distinction of conductive tracks and collecting lines or multiple conductor loops nested one after another with common starting and ending points.

[0072] The final choice among these possible solutions depends on the electrical power produced, the input voltage applied and, first of all, the dimensions of the heating element 7.

[0073] Finally, it should be emphasized that the mounting position of the heating element 7 on the edge side can also be modified. Whereas, especially in most vehicles, the wipers are retained along the edge of the lower pane in the mounting position, there are also vehicles in which the rest position of the wipers is vertical and thus parallel to one or several vertical edges of the mounted windshield. Of course, heating elements of the type described can also be provided in such panes; it will then be necessary to optionally provide two side heating elements, when it is necessary to heat two wipers. Of course, this also applies to the rear windows of vehicles that are equipped with wipers.

Saint-Gobain Glass France

Proxy:

41P38624PL00

EP 2 127 475 B1