Patent Application
20170251525
The invention is concerned with a glazing comprising a conductive coating and a data transmission window.
It is known in the field of automotive windscreens to provide a conductive coating suitable for electrical heating of a windscreen. A known problem is that such a conductive coating may block electromagnetic radiation in a frequency band needed by transmitters or receivers in a vehicle, i.e. the conductive coating is also a non-transmitting coating. A known solution is to provide a ‘data transmission window’ in the non-transmitting coating for a data signal. Data transmission windows are at least partly non-conductive, so that radiation of a desired frequency band may pass through. Multiple data transmission windows may be required in a windscreen of a vehicle having multiple transmitters or receivers. Examples of transmitters or receivers are cameras, rain sensors and automatic toll payment transponders.
Busbars are provided for supplying electrical power to an electrically heated region of the conductive coating. Perturbation of heating around a data transmission window, due to its position relative to a busbar or to another window, may result in “hotspots”. Hotspots may be defined as unacceptable due to exceeding a temperature threshold or temperature difference threshold.
EP1274597B1 (Glaverbel/Degand) discloses an automotive windscreen comprising an electrically heatable coating and at least two data transmission windows, at least partially in contact with the electrically heatable coating. In order to minimise hotspots, the two data transmission windows are separated by a portion which is also in contact with the electrically heatable coating.
EP1274597B1 further discloses that perturbation of heating is greatest when a data transmission window is substantially surrounded by the electrically heatable coating. To improve heating characteristics, it is believed that the two data transmission windows should be spaced from busbars by at least 150 mm and from each other by at least 40 mm. Thus an arrangement of data transmission windows to minimise hotspots according to EP1274597B1 may constrain a position of a receiver or a transmitter.
There remains a need for an alternative glazing comprising a conductive coating and at least one data transmission window, in order to reduce hotspots whilst permitting adequate freedom of position for transmitters or receivers.
According to the present invention from a first aspect, a glazing is provided comprising the features set out in claim 1 attached hereto.
The present invention provides at least one data transmission window separated from an electrically heated region of a conductive coating by a deletion line. Surprisingly, the inventors have found that unacceptable hotspots may be eliminated if a deletion line is arranged between a data transmission window and an electrically heated region of a conductive coating.
The inventors have found that forming a cut edge of a conductive coating and carrier film according to the prior art (in which a data transmission window is positioned at least partially in contact with the electrically heated region) using a blade causes cracks to propagate diagonally, at approximately 45 degrees to the cut edge. The cracks cause electrical discontinuities in the conductive coating, which result in unacceptable hotspots in the electrically heated region and in-service failure of a glazing. Surprisingly, the inventors have found that forming a deletion line in the conductive coating (leaving the carrier film intact) according to the invention causes fewer cracks in an electrically heated region than in the prior art.
In an advantageous embodiment, the deletion line is provided by laser ablation, which provides a smooth cut edge, so cracks are almost completely eliminated. Thus hotspots and in-service failures are significantly reduced compared with the prior art.
According to the present invention, at least two data transmission windows are separated by a deletion line from an electrically heated region of a conductive coating which substantially surrounds them, thus providing an unheated region of the conductive coating. The inventors have found that hotspots around at least two data transmission windows are reduced by positioning the data transmission windows in an unheated region of the conductive coating. By contrast, prior art discloses data transmission windows which are at least partially in contact with the electrically heated coating.
Preferably, the second region is electrically isolated from the second busbar.
The deletion line is preferably narrow, so as to be invisible to a driver. To the extent that the deletion line is visible to the driver, it serves the visual function of a picture frame around the data transmission windows, so is unobtrusive to the driver.
Preferably, the deletion line width is 100 um or less.
Preferably, the deletion line width is 10 um or less.
Preferably, the deletion line is a laser ablation line.
Preferably, each data transmission window is at least 40 mm wide and at least 20 mm in height.
Preferably, the first busbar extends substantially parallel with, and adjacent to, a portion of an upper edge of the glazing.
Preferably, the glazing further comprises an auxiliary busbar separated from the first busbar by the deletion line.
Preferably, the first busbar and the deletion line are arranged to contact each other, so that a corner of the electrically heated region is formed.
In an advantageous embodiment, the corner of the electrically heated region formed by the first busbar and the deletion line is substantially a right angle. The inventors have found that unacceptable hotspots can be eliminated when the first busbar and the deletion line are substantially perpendicular at a point of contact with each other.
Preferably, the conductive coating has sheet resistance in the range 2 ohms per square to 20 ohms per square.
Preferably, the glazing further comprises a carrier film for carrying the conductive coating. More preferably the carrier film material is polyethylene terephthalate (PET).
Preferably, the glazing further comprises first and second sheets of interlayer material, wherein the carrier film is laid over the first sheet of interlayer material and wherein the second sheet of interlayer material is laid over the carrier film. More preferably the interlayer material is polyvinylbutyral (PVB).
According to the present invention from a second aspect, an automotive vehicle is provided, comprising the features set out in claim 14 attached hereto.
Surprisingly, the inventors have found that an automotive vehicle comprising a glazing according to the invention and at least two data transmission windows has reduced hotspots compared with a glazing of the prior art.
According to the present invention from a third aspect, a process for manufacture of a glazing is provided, comprising the steps set out in claim 15 attached hereto.
Surprisingly, the inventors have found that a process for manufacture of a glazing according to the invention wherein a deletion line is made by laser ablation has reduced hotspots compared with a glazing of the prior art.
The invention will now be described by means of non-limiting examples with reference to the attached figures.
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.
A deletion line 20 is provided to define first and second regions 10a, 10b of the conductive coating 10. The deletion line 20 is typically narrow, so as to be invisible for a driver when the glazing 1 is installed in a vehicle. For a typical windscreen installation, a deletion line width should be 100 um or narrower.
First and second busbars 11, 12 are provided in the first region 10a for supplying electrical power to an electrically heated region 10c of the conductive coating 10. Typically the first busbar 11 is adjacent to an upper edge of the glazing 10 and the second busbar 12 is adjacent to a lower edge of the glazing 1.
A data transmission window 30 is provided in the second region 10b of the conductive coating 10 at a position suitable for one or more transmitters or receivers. Typically a data transmission window 30 is adjacent an upper edge of the glazing 1.
The data transmission window 30 is in a portion of the glazing 1 in which the conductive coating 10 is at least partly absent. The conductive coating may be removed by any deletion method, such as laser ablation or scratching.
The conductive coating 10 may be on a carrier film, such as a thin sheet of polyethylene terephthalate (PET). The carrier film is typically laid over a first sheet of interlayer material, such as polyvinylbutyral (PVB). First and second busbars 11, 12 are arranged in contact with the electrically heated region 10c of the conductive coating 10. The carrier film and the first sheet of interlayer material are arranged on a first sheet of glass. A second sheet of interlayer material is laid over the carrier film, so that the carrier film is arranged between the first and second sheets of interlayer material. A second sheet of glass is laid over the first and second busbars 11, 12.
In the embodiment of
First and second data transmission windows 30, 31 may be of any shape and size, for example circular, trapezoidal, rectangular with rounded corners or U-shaped.
The deletion line 20 may define the second region 10b to have any shape.
The deletion line 20 may circumscribe the second region 10b.
The second region 10b may extend between the deletion line 20 and an edge of the conductive coating 10.
A glazing was prepared according to the invention, in which a deletion line defined a second region of a conductive coating, and comprising a data transmission window in the second region. A comparative example was prepared having similar features but without a deletion line between the data transmission window and an electrically heated region.
In both the example and the comparative example, a conductive coating 10 was provided on a carrier film comprising a sheet of PET. Surface resistivity of the conductive coating 10 on the carrier film was between 2 and 20 ohms per square. The sheet of PET was laid over a first sheet of interlayer material (PVB) in a manner known in the art.
A first busbar 11 and an auxiliary busbar 13 were arranged on an electrically heated region 10c of the conductive coating 10 on the sheet of PET. The first sheet of PVB and the sheet of PET were laid over the first sheet of glass.
The sheet of PET was cut back from an edge of the first sheet of glass, in a manner known in the art to avoid corrosion at the edge of a laminated glazing. The cut-back edge of the sheet of PET and a ceramic print, known as an obscuration band, printed on surface 2 (inner surface) of the first sheet of glass, were arranged so that the cut-back edge was hidden by the obscuration band.
A second sheet of interlayer material (PVB) was laid over the carrier film so that the carrier film was between the two sheets of PVB. A second sheet of glass was laid on top of the second sheet of PVB to form an assembly. The assembly was pressed at its edges and degassed, then subjected to elevated temperature and elevated pressure in an autoclave according to a process known in the art to form a laminated glazing 1.
An electrical power supply was connected to the laminated glazing 1 by means of external wires, serving as electrodes. A positive electrode was connected to the first busbar 11, in parallel with the auxiliary busbar 13, and a negative electrode was connected to the second busbar 12. The laminated glazing 1 was thus electrically heated for a predetermined period. At the end of the predetermined period a temperature distribution was measured. The predetermined period was 12 minutes and a measurement apparatus was a thermal imaging camera.
In the comparative example, hotspots were observed exceeding 95 degrees C., which is defined as a threshold of unacceptable temperature. By contrast, in the example according to the invention no unacceptable hotspots were observed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1416175.6 | Sep 2014 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2015/052621 | 9/10/2015 | WO | 00 |
