WO2010032067A1

WO2010032067A1 - Switchable glazings

Info

Publication number: WO2010032067A1
Application number: PCT/GB2009/051230
Authority: WO
Inventors: Joseph Jeremy Boote
Original assignee: Pilkington Group Ltd
Current assignee: Pilkington Group Ltd
Priority date: 2008-09-22
Filing date: 2009-09-22
Publication date: 2010-03-25
Anticipated expiration: 2011-03-22
Also published as: GB0817301D0

Abstract

A switchable film assembly is disclosed. The assembly comprises an active layer, the optical transmission of which changes with an applied voltage, laminated between first and second planar electrode layers. The planar electrode layers comprise a plastics substrate material having an electrically conductive coating disposed on the surface thereof remote from the active layer. At least one region of the plastics substrate material ofthe first planar electrode layer remains uncoated, forming an electrically isolated region, such that that a portion of the active layer remains unswitched when a voltage is applied.

Description

SWITCHABLE GLAZINGS

The present invention relates switchable to films and glazings containing such films, in particular, to the connection of such films to external power supplies.

In recent years, glazings having some form of additional functionality have become increasingly popular and sought-after. Typically, additional functionality is provided by using at least one ply of coated or tinted glass within a laminated glazing structure, to provide heat or UV-reflective properties. However, additional functionality can also be provided by including a functional device or film within a laminated glazing structure. Such devices or films may include lighting devices, such as LEDs (light emitting diodes), or switchable films, having an active layer whose optical transmittance can be altered, such as, LCDs (liquid crystal devices), or SPDs (suspended particle devices).

An SPD film, such as that described in WO2005/102688 and available under licence from Research Frontiers is a film comprising a plurality of particles suspended within a liquid suspension medium, which are held within a polymer medium. The film is switchable between a dark state (when no is voltage applied), and a highly transparent state (when voltage is applied). The degree of relative alignment between the particles is determined by the applied AC voltage, such that an SPD-based device exhibits a variable optical transmission when a variable voltage is applied.

The construction of a conventional SPD film is shown in Figure Ia. Figure Ia is a schematic cross-sectional view of a conventional SPD film assembly. The SPD film 1 has a laminated structure comprising an active layer of a suspended particle emulsion 2 arranged to lie between a first planar electrode 3a and a second planar electrode 3b. Each planar electrode comprises a ply of a plastics substrate material 4a, 4b, generally a ply of polyethylene terephthalate (PET), having an electrically conductive coating 5a, 5b, generally an indium tin oxide coating (ITO) disposed on at least a portion of one surface thereof. The electrically conductive coatings 5 a, 5b enable a direct electrical contact between the suspended particle emulsion 2 and an external power supply (not shown) to be provided via suitable electrical connectors. The optical transmission of the active layer 2 changes when a voltage is applied.

DE 100 43 141 discloses a glazing for use as a rooflight, which incorporates an SPD layer. Two plies of glass are formed into a double glazing structure having a partial vacuum in the gap between the plies, with an SPD layer deposited on the inner side of the lower glass ply. The SPD is switchable between a dark state and a light state.

It is preferable to be able to include a functional device, such as an SPD film within a laminated glazing structure, as the whole, or part of, the interlay er, as described in, for example, US2004/0257649, rather than using a partially evacuated double glazing structure. The interlayer used in typical laminated glazing constructions is a PVB (poly vinyl butyral) interlayer. In order to protect the SPD film within the interlayer, it is preferable that the edges of the film do not reach the edges of the glass. It is known to use a "picture frame" design, where three interlayers, rather than the usual one, are used to laminate a functional film within a glazing. A central layer, approximately the same thickness of the functional film, is cut such that the film can be placed within an interlayer frame. The film and interlayer frame are then placed between two further interlayers, and laminated between two plies of glass.

Figure Ib is a schematic drawing showing the construction of a glazing having an SPD film assembly laminated therein. The glazing 6 has an SPD film assembly 1 laminated within an interlayer structure 7, which is itself laminated between two plies of glass 8a, 8b. The laminated structure 7 comprises three layers of interlayer material, 9a, 9b, 9c. The first interlayer 9a has a region cut of the centre in which the SPD film assembly sits, such that the first interlayer 9a forms the "picture frame". Preferably the thickness of the SPD film assembly 1 is of the same order as the first interlayer 9a. The first interlayer 9a is laminated between second 9b and third 9c interlayers, which are co-extensive with the plies of glass 8a, 8b.

In order to connect the SPD film assembly 1 to a power supply, busbars are provided. Figure 2 is a schematic cross-section showing an SPD film assembly 1 with busbars attached. As before, the SPD film assembly 1 comprises a first (upper) planar electrode layer 3 a and a second (lower) planar electrode layer 3b having a layer of suspended particle emulsion 2 laminated therebetween. Each electrode 3 a, 3b comprises a polyethylene terephthalate substrate 4a, 4b each having a thin layer of electrically conductive indium tin oxide (ITO) 5a, 5b disposed on one surface. To form an electrical connection to the first (upper) planar electrode layer 3 a, an area of the second (lower) planar electrode layer 3b and the suspended particle laminate 2 are removed by cutting/scraping and or dissolution, exposing the ITO layer 5a. A region of electrically conductive silver tape 10 is adhered to the ITO layer 5a, to which a bus bar 11 comprising a tinned copper strip is soldered. To form an electrical connection to the second (lower) planar electrode layer 3b a region of the first (upper) planar electrode layer 3a and the suspended particle emulsion 2 are removed, and a region of electrically conductive silver tape 12 adhered to the ITO layer 5b. A further tinned copper strip busbar 13 is soldered to this region of electrically conductive silver tape 12.

Such methods are also used with other switchable films, such as LCD (liquid crystal device) incorporated into laminated glazings.

Unfortunately, there are several drawbacks to using such a method to provide busbars to a switchable film film:

• The method is both time-consuming and complicated;

• Film damage may occur during the cutting operation, introducing short circuits or problems with delamination, reducing the yield of the final product;

• The electrically conductive ITO layer may be damaged; • The regions where the busbars are applied are more susceptible to delamination, making edge sealing difficult; and

• As the ITO layers of the opposing electrodes are separated only by the suspended particle emulsion, it is possible to introduce short circuits if the layers come into contact after processing or laminating. In addition, the planar electrodes are provided across the entirety of the active layer of the switchable film, and cannot be broken down easily into smaller regions to give variable switching behaviour across the switchable film.

It is desirable therefore to be able to provide a switchable film that overcomes the above mentioned difficulties, and allows fully variable switching behaviour.

The present invention aims to address the above difficulties by providing a switchable film assembly comprising an active layer, the optical transmission of which changes with an applied voltage, laminated between first and second planar electrode layers, the planar electrode layers comprising a plastics substrate material having an electrically conductive coating disposed on the surface thereof remote from the active layer, wherein at least one region of the plastics substrate material of the first planar electrode layer remains uncoated, forming an electrically isolated region, such that that a portion of the active layer remains unswitched when a voltage is applied.

By providing an unswitched region, leading to independently controllable electrode regions, the entire switchable film is not switched at once when a voltage is applied. Where switched and unswitched regions are provided, the overall visual appearance of the film is one of variable switching behaviour.

The optical transmission of the active layer may be changed by changing the absorption properties or scattering properties of the active layer.

Preferably a plurality of regions of the plastic substrate of the first planar electrode layer remain uncoated.

Preferably the at least one region remaining uncoated separates two electrodes formed from the electrically conductive coating, such that the electrodes are in electrical isolation from each other. Desirably, the two electrodes are strip electrodes, which form part of a first parallel electrode array. Preferably, each electrode is adapted to be independently electrically controlled. Additionally, at least one region of the plastics substrate material of the second planar electrode layer may remain uncoated, forming an electrically isolated region. In this case, preferably a plurality of regions of the plastic substrate of the second planar electrode layer remain uncoated. The at least one region remaining uncoated preferably separates two electrodes formed from the electrically conductive coating, such that the electrodes are in electrical isolation from each other. Desirably, the two electrodes are strip electrodes, which form part of a second parallel electrode array.

Preferably, the second parallel electrode array is rotated by 90° with respect to the first electrode array. Preferably, each electrode is adapted to be independently electrically controlled.

The invention also provides a laminated glazing comprising such a switchable film laminated between two plies of glazing material by means of at least two plies of an inter layer material.

The laminated glazing may be used as a vehicle rooflight, a vehicle sidelight or a vehicle windscreen. The laminated glazing may be used as an interior window or exterior window in a building. In such cases, the switchable film preferably forms a blind for the glazing.

If used as a vehicle sidelight, preferably the uncoated portion of the plastics substrate of the first planar electrode obscures a sealed region around the periphery of the sidelight.

Preferably, the plies of glazing material are silicate float glass or a plastic material such as polycarbonate.

Preferably the interlayer material is PVB or EVA.

The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which: Figure Ia (referred to above) is a schematic cross-sectional view of a conventional SPD film assembly;

Figure Ib (referred to above) is a schematic drawing showing the construction of a glazing having an SPD film assembly laminated therein; Figure 2 is a schematic cross-section showing an SPD film assembly with busbars attached;

Figure 3a is a schematic cross-section of a switchable film in accordance with a first embodiment of the present invention;

Figure 3b is a schematic plan view of the switchable film shown in Figure 3a; Figure 4a is a schematic cross-section of a switchable film in accordance with a second embodiment of the present invention;

Figure 4b is a schematic perspective view a sidelight comprising the switchable film shown in Figure 4a;

Figure 5a is a schematic cross-section of a switchable film in accordance with a third embodiment of the present invention; and

Figure 5b is a schematic plan view of the switchable film shown in Figure 5a in a laminated glazing.

In the present invention, it has been appreciated that the key to providing truly variable switching behaviour for a switchable film is in the design of the planar electrode layers and the manner in which electrical connections are made to the switchable film itself.

The present invention adopts a re-designed film structure that enables the utilisation of remote electrical connections. A remote electrical connection is one that is not in contact with the active layer of the switchable film to be driven by an external power supply. The remote electrical connector enables an electric field to be projected through the active layer, driving the switching process. Such remote electrical connections may be capacitive in nature, as discussed in more detail below. By using such remote electrical connectors, a direct, galvanic contact with the SPD emulsion within the SPD film is no longer necessary, and so can be removed. This provides relative freedom in designing the number and shape of electrically conductive regions provided as part of each planar electrode layer. Even more advantageous is the realisation that the electrically conductive portion of the planar electrode layer need not be in contact with the active layer of the switchable film, which can be driven remotely, either by creating a capacitor or by projecting an electric field

Although in each of the examples given, an SPD film is used as the switchable film, the invention is equally applicable to other switchable films incorporated into glazings or other laminated structures, where the optical transmission of an active layer changes when a voltage is applied. Such films include LCD films, other layered electronic devices, such as OLEDs (organic light emitting diodes) or electrochromic materials included in laminated glazings.

Figure 3a is a schematic cross-section of a switchable film in accordance with a first embodiment of the present invention. The switchable film 21 illustrated comprises an active layer 22 containing an emulsion of particles or crystals, such as in a suspended particle device or a liquid crystal device, laminated between a first 23 and a second 24 planar electrode layer. The optical transmission of the active layer changes when a voltage is applied i.e. when an electric field is projected through the active layer. The active layer may have overcoat layers on each major surface. Each planar electrode layer 23, 24 comprises a PET substrate 25, 26 provided with at least one region of an electrically conductive ITO coating 27, 28a. On the first planar electrode layer 23, the electrically conductive ITO coating 27 is provided across substantially all of one surface of the PET substrate 25 and in contact with the active layer 22. The second planar electrode layer 24 is provided with eight separate strip electrodes 28a - 298, which form a parallel electrode array 29. These strip electrodes 28a - 28h are provided on a surface of the PET substrate that is not in contact with the active layer 22, and so are positioned away from and in electrical isolation from the active layer 22. An uncoated region is provided between each strip electrodes, such that each of the strip electrodes 28a - 28h within the parallel electrode array 29 is electrically isolated from its neighbouring strip(s). Each electrode may also be independently electrically controlled. Therefore each strip electrode 28a - 28h in the parallel electrode array can be switched independently of any other strip electrode 28a - 28h anywhere in the parallel electrode array 29. This leads to a portion of the active layer remaining unswitched when a voltage is applied. Figure 3b is a schematic plan view of the switchable film shown in Figure 3 a. This plan view shows the arrangement of the strip electrodes 28a - 28h in the parallel electrode array 29 in more detail. The strip electrodes 28a - 28h are arranged in an equally spaced manner across the entire surface of the switchable film 21. The electrically isolated region separating each strip electrode 28a - 28h has been exaggerated for clarity, but in reality, it may be desirably for the separation distance to be a minimum, to give an effectively continuous appearance to the switched regions of the switchable film 21.

Figure 4a is a schematic cross-section of a switchable film in accordance with a second embodiment of the present invention. Figure 4a shows a switchable film 31, which comprises an active layer 32 containing an emulsion of particles or crystals, such as in a suspended particle device or a liquid crystal device, laminated between a first 33 and a second 34 planar electrode layer. The optical transmission of the active layer changes when a voltage is applied i.e. when an electric field is projected through the active layer. There may be an overcoat layer on one or both major surfaces of the active layer. Each planar electrode layer 33, 34 comprises a PET substrate 35, 36 provided with at least one region of an electrically conductive ITO coating 37, 38. On both the first 33 and the second 34 planar electrode layers, the electrically conductive ITO coatings 37, 38 are provided across the majority of the outer surfaces of the PET substrates 35, 36, but not at a peripheral region. This leaves a portion of the switchable film 31 that cannot be switched, such that the overall transmission of the switchable film 31 is non-uniform. Again, the electrically conductive ITO coatings 37, 38 are remote from the active layer 31 of the switchable film.

Figure 4b is a schematic perspective view a sidelight comprising the switchable film shown in Figure 4a. In a sidelight, particularly a dropping sidelight (for example, the window contained in a driver or passenger door), it is desirable that the switchable film 31 does not extend to the very edge of the glazing. The reason for this is two-fold: firstly, it is necessary to include a waterproof sealant around the exposed edge of the laminated glazing; and secondly, when the switchable film 31 is switched, an edge fade-out region is seen around the periphery of the glazing, hiding any seal used to ensure that the assembly is watertight. Figure 5a is a schematic cross-section of a switchable film in accordance with a third embodiment of the present invention. The third embodiment of the invention has a more complex electrode arrangement, giving even greater flexibility in switching behaviour such that a variety of non-uniform or variable patterns can be created by switching the switchable film.

The switchable film 40 illustrated comprises an active layer 41 containing an emulsion of particles or crystals, such as in a suspended particle device or a liquid crystal device, laminated between a first 42 and a second 43 planar electrode layer. Each planar electrode layer 42, 43 comprises a PET substrate 44, 45 provided with at least one region of an electrically conductive ITO coating 46, 47. The first planar electrode layer 42 is provided with eight separate strip electrodes 48a - 48h, which form a first parallel electrode array 49. These strip electrodes 48a - 48h are provided on a surface of the PET substrate that is not in contact with the active layer 41, and so are positioned away from and in electrical isolation from the active layer 41. An uncoated region is provided between each strip electrode 48a - 48h, such that each of the strip electrodes 48a - 48h within the first parallel electrode array 49 is electrically isolated from its neighbouring strip(s). Each electrode may also be independently electrically controlled. Therefore each strip electrode 48a - 48h in the first parallel electrode array can be switched independently of any other strip electrode 48a - 48h anywhere in the parallel electrode array 49. This leads to non-uniform or variable switching behaviour of the switchable film 40. The second planar electrode layer 43 is also provided with four separate strip electrodes 50a - 5Od, which form a second parallel electrode array 51 (better shown in figure 5b). The second parallel electrode array 51 is rotated 90° with respect to the first parallel electrode array 49. The strip electrodes 50a - 5Od are provided on a surface of the PET substrate that is not in contact with the active layer 41, and so are positioned away from and in electrical isolation from the active layer 41. An uncoated region is provided between each strip electrode, such that each of the strip electrodes 50a - 5Od within the parallel electrode array 51 is electrically isolated from its neighbouring strip(s). Each electrode may also be independently electrically controlled. Therefore each strip electrode 50a - 5Od in the parallel electrode array can be switched independently of any other strip electrode 50a - 5Od anywhere in the parallel electrode array 51.

Figure 5b is a schematic isometric view of the switchable film shown in Figure 5 a, where two strip electrodes 48b, 48d in the first parallel electrode array 49 and two strip electrodes 50b, 5Od in the second parallel electrode array 51 are switched on. This view shows the arrangement of the strip electrodes both parallel electrode arrays 49, 51 in more detail. The strip electrodes 48a - 48h of the first parallel electrode array 49 are arranged in an equally spaced manner across the entire surface of the PET substrate 44 of the first planar electrode layer 42. The electrically isolated region separating each strip electrode 48a to 48h has been exaggerated for clarity, but in reality, it may be desirably for the separation distance to be a minimum (ensuring electrical isolation), to give an effectively continuous appearance to the switched regions of the switchable film 40. The strip electrodes 50a - 5Od of the second parallel electrode array 51 are also arranged in an equally spaced manner across the entire surface of the PET substrate 45 of the second planar electrode layer 43. The electrically isolated region separating each strip electrode 50a - 5Oh has been exaggerated for clarity, but in reality, it may be desirable for the separation distance to be a minimum (ensuring electrical isolation) to give an effectively continuous appearance to the switched regions of the switchable film 40.

By switching on four strip electrodes, two illuminated regions are observed. This leads to the creation of a grid pattern where at least one region of the active layer remains unswitched when a voltage is applied.

With reference to the aforementioned figures, the ITO conductive coatings on the outer surfaces of the planar electrode layers 23, 24, 33, 34, 42, 43 may be provided by printing, sputtering or other known coating methods. A series of electrodes may be deposited, or a single electrode, with sections of the coating removed to create electrical isolation regions. An important factor is that by being remote from the active layer itself, the design constraints on the electrodes themselves become almost limitless. Although linear geometric patterns are shown in the above examples, any type of pattern may be created. Glazings comprising such switchable films, in particular a film according to the first embodiment of the present invention are useful as windows in vehicles, an example of which is a vehicle rooflight. Such a construction with non-uniform or variable switching behaviour enables a blind effect to be created, thereby providing a means of controlling the amount of incident sunlight and heat entering the vehicle. The switchable film may be combined with a suitable switching mechanism, for example, a rotatable dashboard switch that switches on an increasing number of strip electrodes, individual switches for each strip electrode, or a capacitive touch switch on the actual glazing.

The switchable film is not limited to any particular switchable film design, construction or materials. For example, the planar electrode layers may comprise materials other than PET and ITO.

Typically, laminated vehicle glazings comprising switchable films having electrical connections in accordance with the present invention include rooflights, backlights, sidelights and privacy windows (fitted into the interior of a vehicle). However, the switchable film may be included within a windscreen to replace a sunshade or sun visor.

In such glazings, the switchable film assembly is laminated between two plies of glazing material by means of at least two plies of an interlay er material. Preferably the glazing material is a ply of silicate float glass having a thickness in the range of 1.2 to 3.0mm, giving an overall glazing thickness in the range of 3.0mm to 8.0mm. Alternatively, the glazing material may be a plastics material, such as polycarbonate. Although the adhesive interlayer films described above are preferably polyvinyl butyral, other suitable interlayer materials such as EVA (a co-polymer of ethylene vinyl acetate), ionomer and ionoplast materials may be used instead. Preferably the layer of adhesive interlayer material used has a thickness in the range of 0.3 to 0.8mm.

Claims

1. A switchable film assembly comprising an active layer, the optical transmission of which changes with an applied voltage, laminated between first and second planar electrode layers, the planar electrode layers comprising a plastics substrate material having an electrically conductive coating disposed on the surface thereof remote from the active layer, wherein at least one region of the plastics substrate material of the first planar electrode layer remains uncoated, forming an electrically isolated region, such that that a portion of the active layer remains unswitched when a voltage is applied.

2. Switchable film assembly according to claim 1, wherein a plurality of regions of the plastic substrate of the first planar electrode layer remain uncoated.

3. Switchable film assembly according to claim 1 or 2, wherein the at least one region remaining uncoated separates two electrodes formed from the electrically conductive coating, such that the electrodes are in electrical isolation from each other.

4. Switchable film according to claim 3, wherein the two electrodes are strip electrodes.

5. Switchable film according to claim 4, wherein the two electrodes form part of a first parallel electrode array.

6. Switchable film according to any of claims 3 to 5, wherein each electrode is adapted to be independently electrically controlled.

7. Switchable film according to any preceding claim, wherein at least one region of the plastics substrate material of the second planar electrode layer remains uncoated, forming an electrically isolated region.

8. Switchable film assembly according to claim 7, wherein a plurality of regions of the plastic substrate of the second planar electrode layer remain uncoated.

9. Switchable film assembly according to claim 7 or 8, wherein the at least one region remaining uncoated separates two electrodes formed from the electrically conductive coating, such that the electrodes are in electrical isolation from each other.

10. Switchable film according to claim 9, wherein the two electrodes are strip electrodes.

11. Switchable film according to claim 10, wherein the two electrodes form part of a second parallel electrode array.

12. Switchable film according to claim 11, wherein the second parallel electrode array is rotated by 90° with respect to the first electrode array.

13. Switchable film according to any of claims 9 to 11, wherein each electrode is adapted to be independently electrically controlled.

14. A laminated glazing comprising a switchable film according to any of claims 1 to 13 laminated between two plies of glazing material, preferably silicate float glass, by means of at least two plies of an interlay er material, preferably PVB or EVA.

15. Laminated glazing according to claim 14, used as a vehicle rooflight, a vehicle sidelight or a vehicle windscreen, or as an interior window or exterior window in a building.

16. Laminated glazing according to claim 15, wherein the switchable film forms a blind for the glazing.

17. Laminated glazing according to claim 15, wherein the uncoated portion of the plastics substrate of the first planar electrode obscures a sealed region around the periphery of the glazing.