WO2010032068A1

WO2010032068A1 - Switchable glazing

Info

Publication number: WO2010032068A1
Application number: PCT/GB2009/051232
Authority: WO
Inventors: Joseph Jeremy Boote
Original assignee: Pilkington Group Limited
Priority date: 2008-09-22
Filing date: 2009-09-22
Publication date: 2010-03-25
Also published as: GB0817299D0

Abstract

An edge sealed switchable film assembly is disclosed. The assembly comprises an active portion, 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 at least a portion of one surface thereof, and an edge seal adapted to prevent leakage or contamination of the active layer material provided around at least a portion of the periphery of the switchable film. At least the second planar electrode layer has the ply of plastics material in contact with the active portion.

Description

SWITCHABLE GLAZING

The present invention relates to switchable 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 3 a and a second planar electrode 3b. The optical transmission of the active layer changes with an applied voltage. The active layer may have an overcoat layer (not shown) on each surface thereof. 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.

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.

Generally, polyvinyl butyral-based interlayer materials are not suitable for use in laminating SPD films owing to their incompatibility. This is believed to be caused by migration of the plasticiser within the PVB material into the SPD film during lamination and subsequent exposure to heat. This results in a degradation in the switching properties of the switchable film over time. This problem is described, for example, in WO2005/102688 and WO2007/122428.

One solution to this problem is to provide a physical barrier layer around the periphery of the switchable film to prevent ingress of mobile plasticiser components during lamination or subsequently. In addition, such barrier seals prevent leakage of the active layer components when laminated in a glazing. Four such barrier seals are shown in Figures 2a, 2b, 2c and 2d.

Figure 2a is a schematic cross-section of a one-part edge seal around the exposed edge of an SPD film. A piece of tape 20 is adhered to an exposed surface of a first electrode 21 of the SPD film 22 and to the exposed surface of a second electrode 23 of the SPD film 22. The tape 20 stretches across the exposed edge of the SPD film 22. This creates a barrier along the exposed edge of the SPD film 22, all around its periphery.

Figure 2b is a schematic cross-section of a two-part edge seal around the exposed edge of an SPD film. In this case, a first piece of tape 24 is adhered to the exposed surface of the first electrode 21 and, and second piece of tape 25 is adhered to the exposed surface of the second electrode 23. The first 24 and second 25 pieces of tape are pressed together to form a joint 26. This forms a barrier all around its periphery.

Figure 2c is a schematic cross-section of a hot-melt barrier seal around the exposed edge of an SPD film. In this case, hot melt 27 is applied along the exposed edge of the SPD film 22, overlapping onto the exposed surfaces of both the first 21 and second 23 electrode. This forms a barrier all around the periphery of the SPD film 22.

Figure 2d is a schematic cross-section of a crimped seal around the exposed edge of an SPD film. In this case, the first 21 electrode and the second electrode 23 are pinched or melted together at their edges 28, effectively encapsulating the SPD emulsion within the SPD film 22. Again, this creates a barrier all around the periphery of the SPD film 22. However, each of these solutions may be disadvantageous, as the SPD film is soft and has a tendency to deform. In particular, around the edge region, the SPD emulsion is easily squashed during application of the barrier and/or subsequent processing. The main issue with this is that with the addition pressure applied to the periphery of the film during lamination, the SPD emulsion may be compressed enough that the electrically conductive surfaces of the two electrodes come into contact, leading to a short circuit.

Therefore it is desirable to be able to create a seal around the edge of the SPD or other switchable film that minimises the occurrences of short circuits whilst providing an effective barrier layer against chemical penetration.

The present invention aims to address these problems by providing an edge sealed switchable film assembly comprising an active portion, 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 at least a portion of one surface thereof, and an edge seal adapted to prevent leakage or contamination of the active layer material provided around at least a portion of the periphery of the switchable film, wherein at least the second planar electrode layer has the ply of plastics material in contact with the active portion.

By reversing one of the planar electrodes such that the electrically conductive coating is no longer in contact with the active portion of the switchable film, the possibility of shorting when the periphery of the film is compressed is removed.

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

Preferably, the first and second planar electrode layers have the ply of plastics material in contact with the active portion. Preferably the plastics substrate material of the first planar electrode layer is in between the active portion and the electrically conductive coating of the first planar electrode layer, and the electrically conductive coating of the second planar electrode layer is in between the active portion and the plastics substrate material of the second planar electrode layer.

Preferably the active portion comprises an active layer having at least one overcoat layer on one or both major surfaces thereof.

Preferably the active portion comprises a layer of a suspended particle emulsion or a layer of a liquid crystal.

Preferably, the switchable film is one of: a suspended particle device film or a liquid crystal device film.

Preferably the edge seal extends around the entire periphery of the switchable film.

The present invention also provides a laminated glazing comprising such an the edge- sealed switchable film assembly, the edge-sealed switchable film assembly being located within a frame formed from a ply of an interlay er material, the frame being laminated between first and second plies of an interlay er material, the first and second plies of interlayer material, the frame and the edge sealed switchable frame assembly being laminated between two plies of a glazing material.

Preferably, the edge seal is further adapted to prevent the ingress of mobile plasticiser components within the plies of interlayer materials into the active portion.

Preferably, the plies of interlayer material are one of: polyvinyl butyral (PVB); ethylene vinyl acetate co-polymer (EVA); polyurethane (PU) or poly vinyl chloride (PVC) interlayer materials. Preferably, the edge seal is formed by one of: a plastics material; a hot melt material or crimping.

Preferably, the glazing material is silicate float glass. The silicate float glass may be toughened, semi-toughened or annealed. Desirably, at least one of the glazing material and the interlayer materials are tinted.

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 2a (referred to above) is a schematic cross-section of a two-part edge seal around the exposed edge of an SPD film;

Figure 2b (referred to above) is a schematic cross-section of a one-part edge seal around the exposed edge of an SPD film;

Figure 2c (referred to above) is a schematic cross-section of a hot-melt barrier seal around the exposed edge of an SPD film; Figure 2d is a schematic cross-section of a crimped seal around the exposed edge of an

SPD film;

Figure 3 is a schematic cross-section showing an SPD film assembly that may be edge sealed in accordance with the present invention;

Figure 4 shows the edge sealed film assembly of figure 3; Figure 5 is a schematic cross-section showing another edge sealed SPD film assembly in accordance with the present invention; and

Figure 6 is a schematic cross-section of a laminated glazing comprising an edge-sealed switchable of the type shown in figure 5.

In the present invention, it has been realised that it is possible to prevent contact of the electrically conductive surfaces of the planar electrode layers of an SPD film whilst maintaining the ability to drive the switching behaviour using an external power supply. 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. Removing the planar electrode layers that are normally in contact with the SPD emulsion ensures that there is no shorting of the film, even if the layers around the periphery are crimped or sealed tightly together. Whilst there may be electrically insulating overcoat layers on the surfaces of the SPD emulsion, such overcoat layers are typically of insufficient thickness to prevent electrical shorting of an edge sealed SPD film of the type shown in figure 1.

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 3 is a schematic cross-section showing an SPD film assembly that may be edge sealed in accordance with a first embodiment of the present invention.

The SPD film assembly 30 comprises an active layer 31, (containing the suspended particle emulsion), laminated between first 32 and second 33 planar electrode layers. Each planar electrode layer 32, 33 comprises a PET substrate 34, 35 having an electrically conductive ITO coating 36, 37 disposed thereon. In this embodiment, the orientation of the first planar electrode layer 32 is reversed, such that the PET substrate 34 contacts the active layer 31, and the ITO coating 36 is exposed. Thus the ITO coating 36 is contactable with a layer of an adhesive interlayer material, such as polyvinyl butyral (not shown) when the film assembly is included in a laminated glazing. The ITO coating 37 of the second planar electrode layer 33 remains in contact with the active layer 31.

The optical transmission of the active layer may be switched by projecting an electric field therethrough. The SPD film assembly may be connected to a suitable power supply by direct galvanic connections to each ITO coating 36, 37. A direct galvanic connection may be made to the ITO coating 37 by first removing a portion of the PET substrate 34.

Alternatively, an electrically conductive region may be positioned on the uncoated surface of the PET substrate 35 such that a capactive connection may be made to the ITO coating 37. Suitable electrical connectors are tinned copper strips, attached to the surface of the ITO coatings 36, 37 by means of electrically conductive silver paint and electrically conductive tape.

By reversing the orientation of the electrode layer 32, the PET substrate 34 provides sufficient electrical insulation to prevent the ITO coatings 36, 37 from electrically shorting when the SPD film assembly 30 is edge sealed at the periphery of the film.

Figure 4 shows the SPD film assembly 30 having an edge seal produced by crimping (see figure 2d). Since the orientation of the electrode layer 32 has been reversed relative to the orientation of the electrode layer 33, the PET substrate 34 forms an electrically insulating barrier between the ITO coatings 36, 37 thereby preventing electrical shorting.

Figure 5 is a schematic cross-section showing an SPD film assembly 40 that may be edge sealed in accordance with a second embodiment of the present invention.

The SPD film assembly 40 comprises an active layer 41, (containing the suspended particle emulsion), laminated between first 42 and second 43 planar electrode layers. Each planar electrode layer 42, 43 comprises a PET substrate 44, 45 having an electrically conductive ITO coating 46, 47 disposed thereon. In this embodiment, the orientation of the first planar electrode layer 42 is reversed, such that the PET substrate 44 contacts the active layer 41, and the ITO coating 46 is exposed. Thus the ITO coating 46 is contactable with a layer of an adhesive interlayer material, such as polyvinyl butyral (not shown) when the film assembly is included in a laminated glazing. The orientation of the second planar electrode layer 43 is also reversed, such that the PET substrate 45 contacts the active layer 41, and the ITO coating 47 is exposed. Thus the ITO coating 47 is contactable with a layer of an adhesive interlayer material, such as polyvinyl butyral (not shown) when the film assembly 40 is included in a laminated glazing.

To connect the SPD film assembly to a power supply, direct galvanic connections made be made to the exposed ITO coatings 46, 47. Suitable electrical connectors are formed from tinned copper strips, attached to the surface of the ITO coatings 46, 47 by means of electrically conductive silver paint and electrically conductive tape.

The SPD film assembly has been edge sealed by crimping ( see figure 2a). Shorting of the electrode layers 42, 43at the periphery of the SPD film 40 when sealed together is prevented because of the electrically insulating effect of the PET substrates 44, 45.

Figure 6 is a schematic cross-section of a laminated glazing comprising an edge-sealed switchable film in accordance with the present invention. The glazing 50 comprises a switchable film, such as an SPD film 51 laminated within a picture-frame construction 52 comprising three plies of interlayer material 53a, 53b, 53c. The switchable film 51 is held within a frame of interlayer material 53a, which in turn is laminated between first 53b and second 53c plies of interlayer material. These first 53b and second 53c layers of interlayer material serve to bond the switchable film 51 to two plies of glazing material 54a, 54b, such as silicate float glass. The switchable film 51 itself comprises an active layer 55 containing an emulsion of switchable film particles, and two planar electrode layers 56a, 56b. Each planar electrode layer 56a, 56b comprises a substrate of a plastics material 57a, 57b supporting an electrically conductive ITO coating 58a, 58b. Each substrate of plastics material 57a, 57b is in contact with the active layer 55, and each electrically conductive ITO coating 58a, 58b is in contact with a ply of interlayer material 53b, 53c. A barrier material 59 is provided around the periphery of the switchable film 51, to avoid any leakage of the switchable film emulsion in the active layer 55 into the laminated glazing 50 structure, and to prevent contact with the picture frame layer 53a. In order to drive the switchable film 51 , busbars 60a, 60b are attached to the electrically conductive ITO coatings 58a, 58b of the planar electrode layers 56a, 56b. The busbars 60a, 60b are formed from tinned copper strips, attached to the surface of the ITO coatings 58a, 58b by means of electrically conductive silver paint and electrically conductive tape. Applying a voltage creates an electric field through the SPD film 51, driving the switching behaviour of the active layer 55.

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, 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 any of these situations, 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. An edge sealed switchable film assembly comprising an active portion, 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 at least a portion of one surface thereof, and an edge seal adapted to prevent leakage or contamination of the active portion material provided around at least a portion of the periphery of the switchable film, wherein at least the second planar electrode layer has the ply of plastics material in contact with the active portion.

2. The edge sealed switchable film assembly of claim 1, wherein the first and second planar electrode layers have the ply of plastics material in contact with the active portion.

3. The edge sealed switchable film assembly of claim 1, wherein the plastics substrate material of the first planar electrode layer is in between the active portion and the electrically conductive coating of the first planar electrode layer, and wherein the electrically conductive coating of the second planar electrode layer is in between the active portion and the plastics substrate material of the second planar electrode layer.

4. The edge sealed switchable film assembly of any preceding claim, wherein the active portion comprises a layer of a suspended particle emulsion or a layer of a liquid crystal.

5. The edge sealed switchable film assembly of any preceding claim, wherein the switchable film is one of: a suspended particle device film or a liquid crystal device film.

6. The edge sealed switchable film assembly of any of the preceding claims, wherein the edge seal extends around the entire periphery of the switchable film.

7. A laminated glazing comprising the edge-sealed switchable film assembly of any of the claims 1 to 6, the edge-sealed switchable film assembly being located within a frame formed from a ply of an interlayer material, the frame being laminated between first and second plies of an interlayer material, the first and second plies of interlayer material, the frame and the edge sealed switchable frame assembly being laminated between two plies of a glazing material.

8. The laminated glazing of claim 7, wherein the edge seal is further adapted to prevent the ingress of mobile plasticiser components within the plies of interlayer materials into the active portion.

9. The laminated glazing of claim 7 or 8, wherein the plies of interlayer material are one of: polyvinyl butyral (PVB); ethylene vinyl acetate co-polymer (EVA); polyurethane (PU) or poly vinyl chloride (PVC) interlayer materials.

10. The laminated glazing of claim 7, 8 or 9, wherein the edge seal formed by one of: a plastics material; a hot melt material or crimping.

11. The laminated glazing of any of claims 7 to 10, wherein the glazing material is silicate float glass.

12. The laminated glazing of claim 11, wherein the silicate float glass is toughened, semi-toughened or annealed.

13. The laminated glazing of any of claims 7 to 12, wherein at least one of the glazing material and the interlayer materials are tinted.