GB2327839A

GB2327839A - Terminating electrical circuits on glazing panels

Info

Publication number: GB2327839A
Application number: GB9715903A
Authority: GB
Inventors: Etienne Degand
Original assignee: Glaverbel Belgium SA
Current assignee: AGC Glass Europe SA
Priority date: 1997-07-28
Filing date: 1997-07-28
Publication date: 1999-02-03
Anticipated expiration: 2017-07-28
Also published as: GB9715903D0; GB2327839B

Abstract

On a heated rear car window, the frit of an enamel layer 12 and the frit of a vitreous connection portion 13 of an electrical heating element which overlies the enamel layer are based on one or more of compounds of the same base element. Adherence of an electrical terminal 15 to the connection portion is improved. Other applications are disclosed, eg antennae alarm circuits.

Description

Attachment of electrical connectors This invention relates to attachment of an electrical conducting member and a conducting material. It is particularly, but not exclusively, directed to attachment between a metal strip and a thin conducting surface, for example attachment between an electrical terminal of a heated rear window of a car or other vehicle and an electrical heating network.

A common form of a heated vehicle window, for example a heated rear window for a car, comprises: a) a sheet of glass bearing a band of opaque colouring material, commonly an enamel, around the entire periphery of the inside surface of the window b) an electrical resistance heater comprising a grid or network of spaced, relatively thin electrically conducting paths passing across the window and terminating at a comparatively wide collector band at each side of the heater. The network is generally made of a ceramic based or vitreous based electrically conducting compound (commonly referred to as silver paste as it is often a silver containing compound) applied to the window by, for example, printing (particularly silk screen printing) and subsequently heated; and c) an electrical connector or terminal at each side of the heater grid, generally provided as a metal strip, soldered to the collector bands of the heater grid to provide a mechanical and electrical connection.

The collector bands of the heater grid and their associated connectors are at least partially hidden from the outside of the vehicle by the opaque border around the window.

Insufficient mechanical adherence between the electrical terminals and the heater network renders the terminals too easy to detach by, for example, pulling away with a force of less than two kilograms. This has been a recurrent problem in respect of a small but significant proportion of such attachments.

According to a first aspect, the present invention provides a glazing panel comprising an enamel layer and an overlaying vitreous connection portion of an electrical element in which the frit of the enamel layer and the frit of the connection portion are based on one or more compounds of the same base element.

The connection portion may be in direct contact with the enamel layer.

The enamel layer may be substantially opaque; it may be a decorative band.

The electrical element may be a heating element for a window.

The vitreous connection portion may comprise an enamel. It may comprise between 30% and 90% metal, preferably silver. The vitreous connection portion may take the form of a collector band; it preferably forms an integral part of the electrical element and is preferably made of the same material.

An electrical terminal, which may be a metallic strip, may be attached to the vitreous connection portion. The attachment may be made by fusing the electrical terminal to the vitreous connection portion, for example by soldering.

The frit of the enamel layer and the frit of the connection portion may be based on one or more compounds of bismuth. The frit of the enamel layer and the frit of the connection portion may comprise or may consist essentially of one or more compounds of bismuth.

The frit of the connection portion may consist essentially of bismuth borosilicate. The frit of the enamel layer may comprise one or more of the compounds selected from the group consisting of bismuth borosilicate, bismuth titanate, bismuth oxide. In addition to one or more compounds of bismuth, the frit of the enamel layer may comprise one or more alkali and/or alkaline earth metal oxides.

Alternatively, the frit of the enamel layer and the frit of the connection portion may be based on one or more compounds of zinc. The frit of the enamel layer and the frit of the connection portion may comprise or may consist essentially of one or more compounds of zinc.

The frit of the connection portion may consist essentially of zinc borosilicate; the frit of the enamel layer may comprise one or more of the compounds selected from the group consisting of zinc borosilicate, zinc titanate, zinc oxide. In addition to one or more compounds of zinc, the frit of the enamel layer may comprise one or more alkali and/or alkaline earth metal oxides.

A common practice in heated rear windows is to use a silver enamel having a lead based frit for the heating grid and to use an enamel having a bismuth based frit for the decorative opaque enamel band. A migration phenomenon between these two materials may be at least partially responsible for the recurrent intermittent problem of insufficient adherence of the electrical terminal attached to the heating grid. We have observed that there is diffusion of lead from the heater element frit into the opaque enamel band and, similarly that there is diffusion of bismuth from the frit of the opaque enamel band into the heating grid. Diffused bismuth in the silver containing heater grid can reach up to 10%. This may be responsible for impairing fusion and/or soldering leading to a weakened connection between the heating element and the electrical terminal.

According to a second aspect, the present invention provides for use on a glazing panel of a vitreous connection portion of an electrical element overlaying an enamel layer in which the frit of the connection portion and the frit of the enamel layer are based on one or more compounds of the same base element so as to facilitate adherence of an electrical terminal to the vitreous connection portion.

According to a third aspect, the present invention provides an electrical component comprising a vitreous, electrically conducting connection portion overlaying a non-electrically conducting vitreous layer in which the frit of the nonconducting layer and the frit of the connection portion are based on one or more compounds of the same base element.

An embodiment of the invention will now be described, by way of example only, with reference to Fig 1 which is a schematic cross section through a connection assembly of a heated rear car window.

The connection assembly 10 of Fig 1 is part of a heated rear car window. Only one edge portion of the window glass 11 is shown.

A layer or band of opaque enamel 12 extends around the entire periphery of the window on its inside surface. This peripheral enamel band is usually black in colour and, from the outside of the vehicle, hides the underlying attachment to the car's bodywork. It may also hide electrical connections and block UV radiation from deteriorating underlying glue or elastomers. An example of this enamel (composition prior to firing) is: a) about 60% by weight frit comprising bismuth borosilicate, bismuth titanate, bismuth oxide, alkali and/or alkaline earth metal oxides (e.g. sodium oxide and/or calcium oxide) b) about 15% by weight of colouring pigments comprising chrome oxide, copper oxide, cobalt c) a medium comprising pine oil, terpineol, cellulose ether resin.

An electrical resistance heating grid, of which only one of the connection portions 13 is shown, is positioned at the inside surface of the window.

The grid comprises silver in an enamel mixture and in this case is printed on to the window by a silk screen printing method. Examples of possible compositions for this silver enamel (prior to firing) include: 1. about 50% silver and about 6% by weight bismuth borosilicate frit in a medium comprising dibutyl phthalate (between about 1-5%), terpineol (between about 10-30%), cellulose ether resin, 2- (2-butoxyethoxy) ethyl acetate.

2. about 80% silver and about 6% by weight bismuth borosilicate frit in a medium comprising dibutyl phthalate (between about 1-5%), cellulose ether resin, 2- (2-butoxyethoxy) ethyl acetate.

3. about 65% to 75% silver and about 6% by weight bismuth borosilicate frit in a medium comprising dibutyl phthalate, terpineol, cellulose ether resin, 2- (2-butoxyethoxy) ethyl acetate.

As can be seen in Fig 1, the connection portion 13 of the heating grid overlays, and is in direct contact with the decorative enamel band 12.

An electrical terminal 15 in the form of a metal strip is attached to the connection portion 13 by means of solder 14. One possible composition for the solder is about 40% tin and about 60% lead. Altematively, the solder may contain about 70% lead, 20% tin and 2% silver. A composition of about 43% tin, 43% lead, 11% bismuth and 3% silver may also be used.

In this particular example, the frit of the enamel layer (12)and the frit of the connection portion (13) are based on one or more compounds of bismuth.

The heating grid of a heated vehicle window will generally have two electrical terminals; preferably, each of the terminals is attached as hereinbefore described.

Whilst the invention has been particularly described with reference to a heated rear window of a vehicle it will be appreciated that it is equally applicable to other articles having electrical connections, and particularly to articles where it is necessary to draw electricity from and/or supply electricity to an electrical circuit means provided on a substrate. One example is for incorporation of a radio antenna at or in a widow or vehicle window. Another example is for incorporation of part of a burglar alarm circuit across a window, for example a shop window or a window of a bank teller cage. A further example is for a heated window for a building. Yet another example is a heated vehicle window in which the heating element is provided by a substantially transparent conductive layer.

Claims

1. A glazing panel comprising an enamel layer and an overlaying vitreous connection portion of an electrical element in which the frit of the enamel layer and the frit of the connection portion are based on one or more compounds of the same base element.

2. A glazing panel in accordance with Claim 1, in which the vitreous connection portion is in direct contact with the enamel layer.

3. A glazing panel in accordance with Claim 1 or Claim 2, in which the frit of the enamel layer and the frit of the connection portion are based on one or more compounds of bismuth.

4. A glazing panel in accordance with any preceding claim, in which the frit of the vitreous layer and the frit of the connection portion comprise one or more compounds of bismuth.

5. A glazing panel in accordance with any preceding claim, in which the frit of the vitreous layer and the frit of the connection portion consist essentially of one or more compounds of bismuth.

6. A glazing panel in accordance with Claim 5, in which the frit of the connection portion consists essentially of bismuth borosilicate.

7. A glazing panel in accordance with any preceding claim, in which the frit of the vitreous layer comprises one of or more of the compounds selected from the group consisting of bismuth borosilicate, bismuth titanate, bismuth oxide.

8. A glazing panel in accordance with Claim 7, in which the frit of the vitreous layer comprises one or more alkali or alkaline earth metal oxides.

9. A glazing panel in accordance with any preceding claim, in which the frit of the connection portion is substantially free of lead compounds.

10. A glazing panel in accordance with any preceding claim, in which the electrical element is a heating element.

11. A glazing panel in accordance with any preceding claim, in which the glazing panel is a heated window for a vehicle.

12. A vehicle having a glazing panel in accordance with any preceding claim.

13. Use on a glazing panel of a vitreous connection portion of an electrical element overlaying an enamel layer in which the frit of the connection portion and the frit of the enamel layer are based on one or more compounds of the same base element so as to facilitate adherence of an electrical terminal to the vitreous connection portion.

14. An electrical component comprising a vitreous, electrically conducting connection portion in direct contact with a non-electrically conducting vitreous layer in which the frit of the non-conducting layer and the frit of the connection portion are based on one or more compounds of the same base element.

15. A glazing panel substantially as hereinbefore described.

16. An electrical connection substantially as hereinbefore described.