EP3549389A1

EP3549389A1 - Glazing comprising an array of heating wires and a method of producing the same

Info

Publication number: EP3549389A1
Application number: EP17807923.2A
Authority: EP
Inventors: Jonathan Barclay Dixon; Mark Andrew Chamberlain
Original assignee: Pilkington Group Ltd
Current assignee: Pilkington Group Ltd
Priority date: 2016-11-29
Filing date: 2017-11-28
Publication date: 2019-10-09
Anticipated expiration: 2037-11-28
Also published as: EP3549389B1; GB201620244D0; WO2018100348A1

Abstract

A laminated glazing (101) for a vehicle comprising an array of heating wires(160), a first busbar (121) and a second busbar (122) in electrical connection with the array of heating wires and arranged such that a voltage applied between the first busbar and the second busbar allows heating of the glazing, and a conductive track (130) electrically connected to the second busbar,further comprising a tape (150) comprising a polymer positioned between the conductive track and the array of heating wires for electrically insulating the conductive track from the array of heating wires.

Description

Glazing comprising an array of heating wires and a method of producing the same Field of the invention

[0001] The invention is concerned with a glazing comprising an array of heating wires.

[0002] In the field of automotive windscreens it is known to provide an array of closely spaced heating wires embedded in a ply of interlayer material between two outer plies of glass.

[0003] The heating wires extend between and are in electrical contact with two opposing busbars, typically positioned at or near the upper and lower edges of the glazing.

Background [0004] EP 1680945 Bl discloses a wired heated automotive glazing where heating wires are applied across a first busbar, second busbar and third busbar, and are severed to prevent electrical connection between the second and third busbars.

[0005] EP 1393593 Bl discloses a wired heated automotive glazing where the busbars extend laterally relative to heating resistors, and heating resistors are, starting from the first busbar, brought back by passing over the other busbar while isolated relative thereto.

Summary of the invention

[0006] There remains a need for an alternative glazing, comprising an array of heating wires, with electrical connections in close proximity to each other, in which a short circuit is prevented throughout the lifetime of the glazing. [0007] The present invention provides, in a first aspect, a laminated glazing for a vehicle comprising an array of heating wires, a first busbar and a second busbar in electrical connection with the array of heating wires and arranged such that a voltage applied between the first busbar and the second busbar allows heating of the glazing, and a conductive track electrically connected to the second busbar wherein a tape comprising a polymer is positioned between the conductive track and the array of heating wires for electrically insulating the conductive track from the array of heating wires.

[0008] In another embodiment of the first aspect of the present invention, the laminated glazing further comprises a connector for applying the voltage to the conductive track, wherein the first busbar is disposed between the second busbar and the connector.

[0009] In a further embodiment of the first aspect of the present invention, the tape comprises a polyester, a polyamide or a polyimide.

[0010] In a further embodiment of the first aspect of the present invention, the tape comprises an aromatic polyimide or poly(ethylene 2,6-napthalate) or plasticiser-free PVB. [0011] In a further embodiment of the first aspect of the present invention, shrinkage of the tape is less than 0.4% following oven heating at 200 °C for 2 hours.

[0012] In a further embodiment of the first aspect of the present invention, the tape is 1 pm to 200 pm thick, preferably 12 pm to 130 pm thick, more preferably 20 pm to 80 pm thick, most preferably 22 pm to 55 pm thick. [0013] In a further embodiment of the first aspect of the present invention, the tape is of a width not more than 2 cm wider than that of the conductive track section to which it is attached.

[0014] In a further embodiment of the first aspect of the present invention, the conductive track is between the first busbar and the lower edge of the glazing. [0015] According to a second aspect the present invention provides a process for manufacture of a glazing, comprising the steps: a. providing a first ply of interlayer material b. providing an array of heating wires on the ply of interlayer material c. providing a first busbar and a second busbar in electrical connection with the array of heating wires and arranged such that a voltage applied between the first busbar and the second busbar allows heating of the glazing d. providing a conductive track electrically connected to the second busbar e. arranging the ply of interlayer material between a first rigid ply and a second rigid ply, wherein the conductive track, the first and second busbars, and the array of heating wires are between the ply of interlayer material and the first rigid ply f. forming a laminated glazing, wherein, prior to forming the laminated glazing, the conductive track is provided with a tape comprising a polymer for insulating the conductive track from the array of heating wires. [0016] In another embodiment of the second aspect of the present invention, the tape comprises a polyester, a polyamide or a polyimide.

[0017] In another embodiment of the second aspect of the present invention, the tape comprises an aromatic polyimide or poly(ethylene 2,6-napthalate) or plasticiser-free PVB.

[0018] In another embodiment of the second aspect of the present invention, the process further comprises a step of cutting the array of heating wires, preferably at a glazing edge.

[0019] The inventors have found that in a glazing with first and second busbars and with an array of heating wires extending over them, further comprising a conductive track in electrical connection with the second busbar and a connector, a polymer tape, bonded to the conductive track, eliminates a short circuit effect between the conductive track and the heating wires. Thus the said connector for the second busbar and a connector for the first busbar may be arranged adjacent to each other.

[0020] The inventors have additionally found that such a glazing eliminates short circuit effect throughout the lifetime of the glazing, allowing for heating and cooling cycles in use.

[0021] An additional advantage of the present invention is that it precludes the requirement to cut heating wires that connect the conductive track and a busbar of opposite polarity to the conductive track to prevent a short circuit effect. Cutting of such "shorting" heating wires may be difficult for the operator, reducing efficiency, or costly to perform in an automated manner. Where cutting of such "shorting" wires is carried out it is possible that, due to the aforementioned difficulties, a single or small number of such "shorting" wires remain. Such remaining "shorting" wires can be highly dangerous due to the concentration of current flow through a single wire or a small number of wires leading to a high

temperature and a risk of fire. Application of a polymer tape, as described by the invention, is a low cost solution to a problem of "shorting" wires, and may be used with or without a "shorting" wire cutting step.

[0022] A further additional advantage of the present invention is that, in the event that the heating wires extend beyond the edge of the glazing proximate to the conductive track, the conductive track is protected from moisture that may wick into the laminate. Such moisture is known to cause corrosion and may cause failure over the lifetime of the glazing.

[0023] A short circuit occurs when electrical current flows along a path of least resistance, essentially bypassing the intended functionality of the circuit. A short circuit may cause failure of the glazing unit by overheating, fire or explosion.

[0024] A laminated glazing comprises a ply of interlayer material arranged between two outer plies. The outer plies may be glass, polycarbonate or another suitable material. The interlayer may comprise polyvinyl butyral (PVB), polyethylene terephthalate {PET) or another suitable material. A laminated glazing for a vehicle will generally have a major face orientated to the inside of the vehicle, a major face orientated to the outside of the vehicle, an upper edge, a lower edge and two vertical edges when viewed in the vehicle aperture. The laminated glazing is preferably free of opaque objects that will obstruct the view of the vehicle operator within the vision area. The vision area is the substantially transparent central portion of the laminated glazing through which vehicle operator will view the vehicle surroundings. Many jurisdictions have regulations preventing obstruction of the vision area.

[0025] Laminated glazings according to the invention are suitable for use in a range of vehicles, including automobiles, railway rolling stock, aircraft and marine craft.

[0026] To prevent condensation of water on the glazing that may obstruct the view of the vehicle operator through the glazing, the laminated glazing is furnished with an array of heating wires. The array of heating wires provides resistive heating to the laminated glazing.

[0027] The array of heating wires is preferably configured to allow uniform heating of the glazing. The array of heating wires is preferably configured to extend across a major face of the glazing. The array of heating wires preferably comprises a series of parallel wires. Alternatively the array of heating wires comprises a series of wires at acute and obtuse angles to one another.

[0028] Preferably the array of heating wires comprises wires electrically connected in parallel. Alternatively the array of heating wires comprises wires electrically connected in series. An array of parallel wires may provide improved durability of the heating array, while an array of series wires may produce a system that has an alternative heating pattern. Preferably the array of heating wires comprises wires extending substantially between the lower edge of the glazing and the upper edge of the glazing. Alternatively the array of heating wires comprises wires extending substantially between the vertical edges of the glazing. The orientation of the array of heating wires will be selected depending on the particular requirements of the aperture and the user.

[0029] The array of heating wires preferably comprises a series of parallel vertical wires electrically connected in parallel. Alternatively the array of heating wires comprises a series of parallel horizontal wires electrically connected in parallel. Alternatively the array of heating wires comprises parallel vertical wires and parallel horizontal wires. Preferably the array of heating wires comprises wires of equal gauge. Alternatively the array of heating wires comprises wires of differing gauges. Preferably the array of heating wires comprises equally spaced wires. Alternatively the array of heating wires comprises differing spacing between wires. Wires of differing gauge and spacing may be used to preserve the uniform heating of the glazing. Preferably the array of heating wires comprises substantially straight wires. Alternatively the array of heating wires comprises wires with meandering, wavy or curved paths. Wires with meandering, wavy or curved paths may reduce influence of the heating array on the vision of the user, for example by controlling the diffraction of light by the array of heating wires.

[0030] The array of heating wires may comprise wires selected from the group comprising: printed wires, etched wires, extruded wires, or a combination thereof.

[0031] To supply electrical power to the array of heating wires the laminated glazing is preferably furnished with busbars. The busbars are in physical contact with the array of heating wires. Preferably the busbars are of metal, more preferably copper, of a thickness (i.e. height from the substrate to which they are applied) in a range of 25 μιτι to 200 pm, more preferably 40 pm to 60 pm. A thinner busbar will provide better lamination ability but reduced electrical conductivity, while a thicker busbar will provide improved electrical conductivity but reduced lamination ability. Preferably, the busbars are between 1 mm and 10 cm in width, more preferably between 9 mm and 3.5 cm in width. [0032] Alternatively the busbars are of a ceramic frit containing metal particles. Preferably the metal particles are silver. The ceramic frit busbars may be applied by screen printing, inkjet printing or the like. A ceramic frit busbar may be preferable to a metal busbar by its reduced thickness, but may be more susceptible to damage than a metal busbar. Preferably a first busbar and a second busbar are arranged to allow uniform heating of the glazing by the array of heating wires. More preferably the first busbar and the second busbar follow paths with sections that are substantially parallel to each other. Preferably the first busbar has a section proximate to the lower edge of the glazing and the second busbar has a section proximate to the upper edge of the glazing.

[0033] To supply electrical power to the busbars from an external circuit, the busbars may be in electrical communication with a connector. The busbars may be furnished with a connector. Alternatively a conductive track is electrically connected to a busbar and to a connector to supply electrical power to the busbar from an external circuit. Preferably the connectors are disposed proximate to a glazing edge. Even more preferably the connectors are disposed proximate to the lower edge of the glazing. Preferably the connectors are disposed between the lower edge of the glazing and the first busbar. Preferably the connectors are disposed in close proximity to each other. Preferably the connector is soldered to the conductive track. Alternatively the connector is soldered to the busbar. The solder is preferably of a lead-free type. Alternatively the connectors are attached to the busbar using a conductive adhesive. Alternatively the connectors are attached to the conductive track using a conductive adhesive. A conductive adhesive may provide a more easily formed connection than the soldered connection. A soldered connection may be of reduced resistance than a conductive adhesive connection.

[0034] To supply electrical power to the busbars the laminated glazing is preferably furnished with conductive tracks. Preferably, the conductive tracks are of metal, more preferably copper, of a thickness in a range of 25 pm to 200 pm, more preferably 40 pm to 60 pm. A thinner conductive track will provide better lamination ability but reduced electrical conductivity, while a thicker conductive track will provide improved electrical conductivity but reduced lamination ability. Preferably, the conductive tracks are between 0.1 cm and 10 cm in width, more preferably between 0.9 mm and 3.5 cm in width.

[0035] Alternatively the conductive tracks are of a ceramic frit containing metal particles. Preferably, the metal particles are silver. The ceramic frit conductive track may be applied by screen printing, inkjet printing or the like. A ceramic frit conductive track may be preferable to a metal conductive track by its reduced thickness, but may be more susceptible to damage than a metal conductive track.

[0036] Preferably a conductive track supplies electrical power to the second busbar.

Preferably the conductive track is in physical contact with the second busbar and a connector. Preferably a first section of the conductive track is in close proximity to the first busbar and the lower edge of the glazing and a second section of the conductive track extends between the first section and the second busbar. Preferably the first section is furnished with a tape for insulating the first section from the array of heating wires.

Preferably the first section is between the second busbar and the lower edge of the glazing. Preferably the second section of the conductive track extends substantially parallel to a vertical glazing edge. Preferably the second section extends within 30 cm of a vertical glazing edge. More preferably the second section extends within 15 cm of a vertical glazing edge. Yet more preferably the second section extends within 12 cm of a vertical glazing edge. Preferably the second section does not impinge on the vision area of the laminated glazing. Preferably the second section extends no closer than 0.5 cm from a glazing edge. Yet more preferably the second section extends no closer than 3 cm from a glazing edge. A second section closer to a glazing edge may be at risk of corrosion or other negative effects from the ingress of water or damage to the edge of the glazing. A further conductive track may supply electrical connector to the first busbar. [0037] The tape comprises polymer, preferably a polyester, polyamide or polyimide, more preferably an aromatic polyimide or poly(ethylene 2,6-napthalate) (PEN). The tape may comprise PVB, preferably a plasticiser-free PVB. As defined herein, a plasticiser-free PVB contains less 5% plasticiser, preferably less than 1% plasticiser. A suitable plasticiser-free PVB is Mowital® or Trosifol® Thin Film, available from Kuraray Europe GmbH, Hattersheim, Germany. Plasticiser-free PVB may be a preferred tape composition due strong bonding to other components following lamination. Preferably the tape is of a thickness in a range of 1 pm to 200 pm, preferably 12 pm to 130 pm, more preferably 20 pm to 80 pm, most preferably 22 pm to 55 μιτι. A thicker tape will provide improved insulating properties and handling ability with reduced lamination ability, while a thinner tape will provide improved lamination ability with reduced insulating properties and handling ability. Preferably, the tape is of a width a least as great as that of the conductive track section to which it is attached. Preferably, the tape is of a width not more than 2 cm wider than that of the conductive track section to which it is attached. A tape not more than 2 cm wider than the conductive track avoids lamination faults associated with the tape, and reduces cost.

Preferably the tape is arranged within the laminate such that it is completely overlapped with an area of the laminate outside the vision area of the laminate. [0038] Preferably, shrinkage of the tape is less than 0.4% following oven heating at 200 °C for 2 hours, more preferably less than 0.15%. A tape with a high shrinkage property may have reduced lamination ability, and may not sufficiently insulate the conductive track from the array of heating wires. Preferably, dielectric strength of the tape is greater than 80 kV/mm. Preferably, peel strength of the tape from copper is greater than 1.2 N/cm. The tape is preferably applied as a single piece. Alternatively the tape is applied in multiple sections. The tape may be applied from a roll or applied as a pre-shaped layer. The tape is preferably transparent. Alternatively the tape is opaque. The tape may be tinted, coloured or dyed.

[0039] Relating to the second aspect of the present invention, preferably the process further comprises the steps of providing a first ply of interlayer material, positioning a conductive track alongside the ply of interlayer material, configuring an arrangement such that the ply of interlayer material is interleaved between a first rigid ply and a second rigid ply, and the conductive track and the array of heating wires are between the ply of interlayer material and the first rigid ply, and forming a laminated glazing. [0040] Preferably prior to configuring the arrangement such that the ply of interlayer material is interleaved between the first rigid ply and the second rigid ply, and the conductive track and the heating means are between the ply of interlayer material and the first rigid ply, the conductive track is provided with a tape for insulating the conductive track from the array of heating wires. Preferably the conductive track is laid over the first ply of interlayer material and adhered to the ply of interlayer material using a soldering iron, either in discrete places along a length of the conductive track or by running the soldering iron along a length of the conductive track. Alternatively the conductive track is adhered to the ply of interlayer material using heated air, vibrations or other common means. A further ply of interlayer material may be configured in the arrangement such that it is interleaved between the ply of interlayer material and the first rigid ply.

[0041] Preferably, the process further comprises a step of cutting the array of heating wires. The array of heating wires may be cut at a glazing edge, to ensure that the array of heating wires does not extend beyond the glazing. Cutting the array of heating wires at a glazing edge is an efficient method of cutting. Alternatively, the array of heating wires may be cut between the conductive track and the glazing edge. Cutting the array of heating wires between the conductive track and the glazing edge may reduce the amount of moisture wicked in to the glazing by the array of heating wires compared to cutting the array of heating wires at a glazing edge. The array of heating of heating wires may be cut between the conductive track and the first busbar. Cutting the array of heating wires between the conductive track and the first busbar may reduce the incidence of "shorting" wires.

[0042] The tape is of polymer, preferably a polyester, polyamide or polyimide, more preferably an aromatic polyimide or poly(ethylene 2,6-napthalate) (PEN). The tape may comprise PVB, preferably a plasticiser-free PVB. As defined herein, a plasticiser-free PVB contains less 5% plasticiser, preferably less than 1% plasticiser. A suitable plasticiser-free PVB is Mowital® or Trosifol® Thin Film, available from Kuraray Europe GmbH, Hattersheim, Germany. Plasticiser-free PVB may be a preferred tape composition due to strong bonding to other components following lamination. Preferably the tape is of a thickness in a range of 1 pm to 200 pm, preferably 12 pm to 130 pm, more preferably 20 pm to 80 pm, most preferably 22 pm to 55 pm. A thicker tape will provide improved insulating properties and handling ability with reduced lamination ability, while a thinner tape will provide improved lamination ability with reduced insulating properties and handling ability. Preferably, the tape is of a width a least as great as that of the conductive track section to which it is attached. Preferably, the tape is of a width not more than 2 cm wider than that of the conductive track section to which it is attached. A tape not more than 2 cm wider than the conductive track avoids lamination faults associated with the tape, and reduces cost.

Preferably, the shrinkage of the tape is less than 0.4% following oven heating at 200 °C for 2 hours, more preferably less than 0.15%. A tape with a high shrinkage property may have reduced lamination ability, and may not sufficiently insulate the conductive track from the array of heating wires. Preferably, the dielectric strength of the tape is greater than 80 kV/mm. Preferably a peel strength of the tape from copper is greater than 1.2 N/cm. The tape is preferably applied as a single piece. Alternatively the tape is applied in multiple sections. The tape may be applied from a roll or applied as a pre-shaped layer. The tape is preferably transparent. Alternatively the tape is opaque. The tape may be tinted, coloured or dyed. [0043] The laminated glazing may be formed by a lamination process using elevated temperature and, usually, high pressure e.g. in an autoclave.

[0044] The laminated glazing may be formed by methods involving a first step using a vacuum bag around the laid-up laminate, and wherein a vacuum is applied at approximately room temperature to de-gas the interlayer ply or plies. In a second step, still under vacuum, the first and second glass plies are heated to a temperature in the range 80 °C to 110 °C, such that the interlayer ply softens sufficiently to bond with the first and second glass plies. In a third step, the first and second glass plies are laminated together in an autoclave in the pressure range 6 bar to 14 bar and in the temperature range 120 °C to 150 °C.

[0045] As used herein, the terms in electrical connection and electrically connected describe the facile flow of electrons between discrete physical elements.

[0046] As used herein, the term electrically insulating describes the retarded or prevented flow of electrons between discrete physical elements.

Description of the drawings

[0047] The invention will now be described by means of non-limiting examples with reference to the attached figures.

[0048] Fig. 1 shows a glazing according to the invention in a plane containing heating wires.

[0049] Fig. 2 shows a glazing according to the invention in cross section, viewed on line A-A of Fig. 1.

[0050] Fig. 3 shows a further glazing according to the invention. [0051] Although the invention is described herein with particular reference to an automotive windscreen, it will be understood that it has applications to other vehicle glazing, for example a rear window or a side window. [0052] Fig. 1 and Fig. 2 depict a first embodiment of the invention as applied to a glazing with an array of wires suitable for heating the glazing.

[0053] Fig. 1 shows a glazing 101 comprising a lower edge 111, an upper edge 112 and a side edge 113 wherein a first busbar 121 is proximate and substantially parallel to the lower edge 111 of the glazing 101. A second busbar 122 is disposed in a position proximate to the upper edge 112 and is substantially parallel to the first busbar 121. A first connector 141 and a second connector 142 are disposed at the lower edge 111 of the glazing 101. The first busbar 121 is in electrical communication with the first electrical connector 141, and the second busbar 122 is in electrical communication with the second electrical connector 142. A conductive track 130 serves to provide electrical power to the second busbar 122 from the second connector 142. The conductive track 130 comprises a first section 131 between and substantially parallel to the first busbar 121 and the lower edge 111, and a second section 132 in a position proximate and substantially parallel to the side edge 113. An array 160 of heating wires is laid over the glazing 101. The array 160 extends vertically over the first section 131 and the second busbar 122. The first section 131 is furnished with a tape 150. The tape 150 extends across the width of, and along the length of, the first section 131 sufficiently that the first section 131 is not in electrical communication with the array 160.

[0054] Fig. 2 is a cross-section of the glazing 101 on line A-A of Fig. 1 proximate to the glazing lower edge 111, comprising a first ply of glass 171 and a second ply of glass 172, with first interlayer ply 181 and second interlayer ply 182 between them. Between the interlayer plies 181 and 182 is the heating wire array 160. The first section 131 of the conductive track 130 and the first busbar 121 are embedded in the first interlayer ply 181. The first section 131 is furnished with the tape 150 such that the first section 131 is not in electrical communication with the heating wire array 160. [0055] Fig. 2 depicts a heating wire array 160 that terminates inside the glazing 101. This may be advantageous, in order to reduce the likelihood of moisture wicking into the glazing 101. Alternatively the heating wire array 160 may terminate outside the glazing 101. In this case the tape 150 protects the conductive track 130 from moisture that may wick into the glazing 101. [0056] During manufacture, for example during application of the heating wire array 160 to the first interlayer ply 181 or during the lamination process, heating of the first interlayer ply 181 may cause the first interlayer ply 181 to flow around the heating wire array 160. The flow of the first interlayer ply 181 embeds the heating wire array 160 within first interlayer ply 181 and forms a second interlayer ply 182. This process may reduce the cost of the glazing unit. [0057] Fig. 3 shows a glazing 301 comprising a lower edge 311, an upper edge 312 and a side edge 313 wherein a first busbar 321 is proximate and substantially parallel to the lower edge 311 of the glazing 301. A second busbar 322 is disposed in a position proximate to the upper edge 312 and is substantially parallel to the first busbar 321. A first connector 341 and a second connector 342 are disposed at the lower edge 311 of the glazing 301. The first busbar 321 is in electrical communication with the first electrical connector 341, and the second busbar 322 is in electrical communication with the second electrical connector 342. A first conductive track 330 serves to provide electrical power to the second busbar 322 from the second connector 342. A first section 331 of the first conductive track 330 is positioned at an angle to the lower edge 311 of the glazing 301. A second conductive track 332 serves to provide electrical power to the first busbar from the first connector 341. An array 360 of heating wires is laid over the glazing 301. The array 360 extends over the first busbar 321, the second busbar 322, the first section 331 of the first conductive track 330, and the second conductive track 332. The first section 331 of the conductive track 330 is furnished with a first section of tape 351. The first section of tape 351 extends across the width of, and along the length of, the first section 331 sufficiently that the first section 331 is not in electrical communication with the array 360. The second conductive track 332 is furnished with a second section of tape 352. The second section of tape 352 extends across the width of, and along the length of, the second conductive track 332 sufficiently that the second conductive track 332 is not in electrical communication with the array 360.

Claims

1. A laminated glazing for a vehicle comprising an array of heating wires, a first busbar and a second busbar in electrical connection with the array of heating wires and arranged such that a voltage applied between the first busbar and the second busbar allows heating of the glazing, and a conductive track electrically connected to the second busbar characterised by a tape comprising a polymer positioned between the conductive track and the array of heating wires for electrically insulating the conductive track from the array of heating wires.

2. The laminated glazing of claim 1 further comprising a connector for applying the voltage to the conductive track, wherein the first busbar is disposed between the second busbar and the connector.

3. The laminated glazing of any preceding claim wherein the tape comprises a

polyester, a polyamide or a polyimide.

4. The laminated glazing of any preceding claim wherein the tape comprises an

aromatic polyimide or poly(ethylene 2,6-napthalate) or plasticiser-free PVB.

5. The laminated glazing of any preceding claim wherein shrinkage of the tape is less than 0.4% following oven heating at 200 °C for 2 hours.

6. The laminated glazing of any preceding claim wherein the tape is 1 pm to 200 pm thick, preferably 12 pm to 130 pm thick, more preferably 20 pm to 80 pm thick, most preferably 22 pm to 55 pm thick.

7. The glazing of any preceding claim wherein the tape is of a width not more than 2 cm wider than that of the conductive track section to which it is attached.

8. The glazing of any preceding claim wherein the conductive track is between the first busbar and the lower edge of the glazing.

9. A process for manufacture of a glazing, comprising the steps: a. providing a first ply of interlayer material b. providing an array of heating wires on the ply of interlayer material c. providing a first busbar and a second busbar in electrical connection with the array of heating wires and arranged such that a voltage applied between the first busbar and the second busbar allows heating of the glazing d. providing a conductive track electrically connected to the second busbar e. arranging the ply of interlayer material between a first rigid ply and a second rigid ply, wherein the conductive track, the first and second busbars, and the array of heating wires are between the ply of interlayer material and the first rigid ply f. forming a laminated glazing, characterised in that prior to forming the laminated glazing, the conductive track is provided with a tape comprising a polymer for insulating the conductive track from the array of heating wires.

10. The process of claim 9 wherein the tape comprises a polyester, a polyamide or a polyimide.

11. The process of claim 9 wherein the tape comprises an aromatic polyimide or

poly(ethylene 2,6-napthalate) or plasticiser-free PVB.

12. The process of claim 9 further comprising a step of cutting the array of heating

wires, preferably at a glazing edge.