FILM

Abstract

A film contains an electrically actuated liquid having variable optical opacity under the influence of an electric field. The film comprises first and second spaced apart substrates defining a first cavity therebetween in which some or all of the liquid is contained. The film also comprises a liquid trap in fluid communication with the first cavity via a first opening. The liquid trap contains liquid that may flow from the first cavity through the first opening due to the volume of first cavity decreasing. The film may be included in a laminated glazing. A method of preparing a cell for a liquid is also described, and such a cell may be part of a film having variable optical opacity.

Claims

1. A film containing a liquid, the film comprising a first substrate joined to a second substrate, the first substrate being spaced apart from the second substrate to define a first cavity in which at least a portion of the liquid is contained, wherein upon applying a suitable electric field between the first and second substrates, the film changes from a first optical opacity to a second optical opacity, characterised in that the film comprises a liquid trap configured to be in fluid communication with the first cavity via at least a first opening, the liquid trap being arranged to contain liquid that flows from the first cavity through the first opening.

2. A film according to claim 1, wherein the liquid trap comprises a second cavity and liquid that passes through the first opening is containable in the second cavity.

3. A film according to claim 2, wherein the second cavity has an internal pressure less than atmospheric pressure and/or wherein the second cavity is configured as a channel having a length, a width and a height, the height of the channel being determined the spacing of the first and second substrates of the film.

4. A film according to claim 2, wherein the second cavity is configured as an expansion vessel to compensate for pressure changes inside the first cavity.

5. A film according to claim 4, wherein the expansion vessel has at least a first wall portion and wherein the first wall portion of the expansion vessel is movable and/or flexible and/or located inside the second cavity.

6. A film according to claim 1, wherein the liquid trap comprises a liquid absorber for containing liquid that passes through the first opening therein.

7. A film according to claim 1, wherein the first opening is configured such that for a predetermined pressure inside the first cavity, liquid is inhibited from flowing from the first cavity to the liquid traps.

8. (canceled)

9. A film according to claim 1, wherein the first and/or second substrate comprises a heat shrinkable material.

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. A laminated glazing comprising a film according to claim 1, the film being joined to a first sheet of glazing material by a first adhesive layer or a first sheet of adhesive interlayer material.

15. (canceled)

16. (canceled)

17. A method of preparing a cell for a liquid, the cell comprising a first substrate joined to a second substrate, the first and/or second substrate comprising a heat shrinkable material; the method comprising: (i) providing the first substrate; (ii) positioning the second substrate on the first substrate such that the first substrate is spaced apart from the second substrate; (iii) forming the cell by joining the second substrate to the first substrate to form a cavity having a first volume; and (iv) heating the cell formed at (iii) to cause the first volume of the cavity to decrease to a second volume.

18. (canceled)

19. (canceled)

20. A method according to claim 17, wherein the cell formed at (iii) has at least one hole therein in fluid communication with the cavity, and following (iv) liquid is introduced into the cavity via the hole, after which the hole is sealed thereby sealing liquid in the cavity of the cell.

21. (canceled)

22. A method according to claim 17, wherein after (i) a first amount of liquid is positioned on the first substrate, the first amount of liquid having a volume less than the first volume of the cavity.

23. (canceled)

24. (canceled)

25. (canceled)

26. A method according to claim 17, wherein the heating during (iv) is part of a lamination process whereby the cell is laminated to at least one sheet of glazing material by at least one sheet of adhesive interlayer material and/or wherein the heating during (iv) is part of a pre-processing step such that following (iv), the heat processed cell is used as a component of a laminated glazing comprising at least one sheet of glazing material and at least one sheet of adhesive interlayer material, the cell being joined to the at least one sheet of glazing material by the at least one sheet of adhesive interlayer material.

27. A laminated glazing comprising a film containing a liquid, a first sheet of glazing material and a first sheet of adhesive interlayer material; the film comprising a first substrate joined to a second substrate, the first substrate being spaced apart from the second substrate to define a first cavity in which at least a portion of the liquid is contained; the film being joined to the first sheet of glazing material by the first sheet of adhesive interlayer material; wherein the first sheet of adhesive interlayer material has at least a first void therein, the first void being arranged to accommodate at least a portion of the film into the first void.

28. A laminated glazing according to claim 27, wherein the first void is arranged to accommodate at least a portion of the film in the first void by expansion of the film into the first void

29. A laminated glazing according to claim 27, wherein a portion of the film is in the first void in the first sheet of adhesive interlayer material.

30. A laminated glazing according to claim 27, wherein a resilient material is contained in the first void, the resilient material being between the film and the first sheet of glazing material.

31. A laminated glazing according to claim 27, wherein the film comprises at least one weak zone, the weak zone being arranged to communicate with the first void such that upon an increase of pressure within the film the weak zone ruptures and liquid flows into the first void.

32. A laminated glazing according to claim 27, wherein a barrier delimits the first void such that adhesive interlayer material from the first sheet of adhesive interlayer material is prevented from flowing into the first void.

33. A laminated glazing according to claim 27, wherein the film changes from a first optical opacity to a second optical opacity upon applying an electric field between the first and second substrates, the film also comprising a liquid trap configured to be in flux communication with the first cavity via at feast a first opening, the liquid trap being arranged to contain liquid that flows from the first cavity through the first opening the liquid trap being at least partially in the first void.

Description

[0099] The present invention will now be described with reference to the following figures (not to scale) in which:

[0100] FIG. 1 is a plan view of a film according to the first aspect of the present invention;

[0101] FIG. 2 is a schematic cross-sectional view of the laminated glazing shown in FIG. 1 along the line A-A;

[0102] FIG. 3 is a plan view of another film according to the first aspect of the present invention;

[0103] FIG. 4 is a schematic cross-sectional view of the laminated glazing shown in FIG. 3 along the line B-B;

[0104] FIG. 5 is a schematic exploded side view of the component parts used to prepare a cell for a liquid in accordance with the second aspect of the present invention;

[0105] FIG. 6 is a schematic side view of the cell shown in FIG. 5; and

[0106] FIG. 7 is schematic cross-sectional view of a laminated glazing according to the third aspect of the present invention.

[0107] With reference to FIGS. 1 and 2, there is shown a film 1 comprising a first PET substrate 3 joined to a second PET substrate 5 by a first seal 7. The first seal 7 extends around the periphery of the first and second substrates 3, 5 to define a first cavity 9. Inside the first cavity 9 is a liquid 11. Also located in the first cavity 9 are spherical glass spacers (not shown) to maintain the spacing of the first and second substrates 3, 5.

[0108] In this example, the first and second substrates are each about 200 m thick that are spaced apart by about 50 m. The spacing may be about 20 m.

[0109] In this example the liquid 11 is a liquid crystal material, for example a guest host liquid crystal material, although the liquid 11 may be any liquid that has variable optical opacity under the action of an electric field. For example, under the influence of a first electric field E.sub.1 having a first magnitude M.sub.1 at a frequency F.sub.1, the optical opacity of the film 1 viewed through the film 1 at normal incidence to the first substrate 3 is O.sub.1, and under the influence of a second electric field E.sub.2 having a second magnitude M.sub.2 at the frequency F.sub.1, the optical opacity of the film 1 viewed through the film 1 at normal incidence to the first substrate 3 is O.sub.2 (the electrical field E.sub.1, E.sub.2 being applied between the first and second substrates 3, 5). Accordingly, the film 1 is a light control film. For example, under the influence of the electric field E.sub.1 the visible light transmission (Illuminant D65 10 Observer) may be greater than 50%, and under the influence of the electric field E.sub.2 the visible light transmission (Illuminant D65 10 Observer) may be less than 50%, for example less than 10%.

[0110] As just described, when an electric field is applied between the first and second PET substrates 3, 5, the optical opacity of the layer of liquid 11 in the first cavity changes. Optical wavelengths include at least one wavelength between 380 nm and 780 nm.

[0111] Films containing a layer of liquid crystal material are known in the art and may be operated with short switching times i.e. about a second, over a wide temperature range. An alternating voltage may be used to actuate the liquid crystal film to change the optical opacity thereof. In some such films it is known to use a switching voltage that may be 30 V or below and/or a frequency of 50-60 Hz. Liquid crystal films are also known having an operating voltage of 35-70 V AC with an operating frequency of 25-50 Hz square wave.

[0112] Also located around the periphery of the first and second substrates 3, 5 is a second seal 13. Inboard of the second seal 13 is a second cavity 15.

[0113] To help with clarity, a portion of FIG. 1 is shown in close-up. The first cavity 9 is in fluid communication with the second cavity 15 via an opening 17. The opening 17 is an opening in the first and second seals 7, 13 and provides a path for liquid 11 to flow (in the direction of arrow 19) from the first cavity 9 into the second cavity 15.

[0114] In the event of shrinkage of the first and/or second PET substrates 3, 5, the volume of the first cavity 9 is caused to decrease. The pressure inside the first cavity 9 is increased such that liquid 11 may flow into the second cavity 15 via the opening 17.

[0115] In this example, the second cavity 15 functions as a liquid trap to contain any liquid that may be caused to flow therein due to the decrease in volume of the first cavity 9 by shrinkage of the first and/or second substrates 3, 5.

[0116] In the embodiment shown, the opening 17 is sized such that surface tension is able to prevent the liquid 11 from flowing into the second cavity 15 until a predetermined pressure is created in the first cavity 9.

[0117] Liquid may also flow from the first cavity 9 to the second cavity 15 upon applying pressure to the exposed major surface of at least one of the first and second substrates 3, 5.

[0118] In an alternative to the embodiment shown in FIGS. 1 and 2, the opening 17 has a barrier to cause the opening to be closed until a sufficient pressure is created in the first cavity 9 to cause the barrier to rupture and liquid 11 to flow through the opening 17 into the second cavity 15. The barrier may be a thin sheet of PET, or may be part of the seal 7, 13 having a suitable thickness.

[0119] In another alternative to the embodiment shown in FIGS. 1 and 2, the second cavity has a flexible wall portion, which may be a portion of the second seal 13. The flexible wall portion is able to adjust the volume of second cavity 15 to compensate for pressure differences in the first cavity 9. In such an embodiment the second cavity 15 functions as an expansion vessel or a bladder.

[0120] In a similar embodiment to just described, in addition to the walls defining the second cavity 15, a movable wall is included inside the second cavity 15. The movable wall, which may be flexible, functions as a diaphragm in the second cavity to allow the second cavity to compensate for pressure variations in the first cavity.

[0121] The film 1 may be included as an interlayer in a laminated glazing. The first substrate 3 may be bonded to a first sheet of glazing material via a first interlayer structure comprising at least one sheet of adhesive interlayer material such as PVB, EVA or PU. The second substrate 5 may be bonded to a second sheet of glazing material via a second interlayer structure comprising at least one sheet of adhesive interlayer material such as PVB, EVA or PU. Such a laminated glazing may be made using conventional lamination techniques.

[0122] As the temperature of the film 1 is increased for lamination, the substrates 3, 5 shrink and some of the liquid 11 flows from the first cavity 9 into the second cavity 15 via the opening 17.

[0123] The film 1 may be made as follows. Firstly, a first sheet of PET is provided as the first substrate 3. The first sheet of PET may have an electrically conductive, optically transparent coating such as ITO on a major surface thereof.

[0124] Next, a first layer of adhesive is provided around the perimeter of one of the major surfaces of the first substrate 3 to produce a receptacle for containing liquid 11. A second layer of adhesive is provided to divide the receptacle into a first region and a second region. Opening 17 is then made in the second layer of adhesive using a blade. Alternatively, the opening 17 may be provided by interrupting the flow of the second layer of adhesive when the receptacle is divided into the first and second regions.

[0125] Next, liquid 11 is deposited into the first region, preferably using a one drop filing process.

[0126] Next, a second sheet of PET (to provide the second substrate 5) is positioned on the first and second layers of adhesive and caused to become joined thereto. For example, the adhesive may suitably cure by exposure to UV radiation. With the second sheet of PET joined to the first sheet of PET, the liquid in the first region becomes enclosed in a first cavity 9 and the first cavity 9 is in fluid communication with a second cavity 15 via the opening 17. The first cavity includes the first region of the receptacle and the second cavity 15 includes the second region of the receptacle.

[0127] As will be readily apparent with reference to FIGS. 1 and 2, the first layer of adhesive gives rise to the second seal 13 and parts of the first seal 7. The second layer of adhesive completes the first seal 7. The layers of adhesive may be applied differently to provide the configuration shown in FIGS. 1 and 2.

[0128] The second sheet of PET may have an electrically conductive, optically transparent coating such as ITO on a major surface thereof.

[0129] If either or both of the first and second sheets of PET have an electrically conductive, optically transparent coating on a major surface thereof, it is preferred that said coating does not face the first and/or second cavity 9, 15.

With reference to FIGS. 3 and 4, there is shown another film 21 in accordance with the first aspect of the present invention.

[0130] The film 21 is similar to the film 1 described above and comprises a first PET substrate 23 joined to a second PET substrate 25 by a first seal 27. The first seal 27 extends around the periphery of the first and second substrates 23, 25 to define a first cavity 29. Inside the first cavity 29 is a liquid 31. Also located in the first cavity 29 are spherical glass spacers (not shown) to maintain the spacing of the first and second substrates 23, 25.

[0131] In this example, the first and second substrates are each about 100 m thick that are spaced apart by about 25 m.

[0132] Located between the first and second substrates 23, 25 is a liquid absorber in the form of a sponge 33.

[0133] To help with clarity, a portion of FIG. 3 is shown in close-up.

[0134] The sponge 33 is adjacent a portion of the seal 27. In the portion of the seal 27 that is adjacent the sponge 33 is an opening 37. The opening 37 provides a path for liquid 31 to flow (in the direction of arrow 39) from the first cavity 29 into the sponge 33.

[0135] In the event of shrinkage of the first and/or second PET substrates 23, 25, the volume of the first cavity 29 is caused to decrease. The pressure inside the first cavity 29 is increased such that liquid 31 may flow through the opening 37 to be absorbed by the sponge 33.

[0136] In this example, the sponge function as a liquid trap to contain any liquid that may be caused to flow therein due to the decrease in volume of the first cavity 29 by shrinkage of the first and/or second substrates 23, 25. Although in this example the sponge is shown along one edge of the first cavity 29, the sponge may be along two or more edges of the first cavity 29. In some embodiments, the sponge surrounds the first cavity 29 with openings being provided at one or more side to help improve the flow of liquid to the sponge.

[0137] In the embodiment shown, the opening 37 is sized such that surface tension is able to prevent the liquid 31 from flowing into the sponge 33 until a predetermined pressure is created in the first cavity 29.

[0138] The sponge 33 may be contained in a second cavity of the type described above with reference to FIGS. 1 and 2.

[0139] With reference to FIGS. 5 and 6, a method of preparing a cell 41 for a liquid such as a liquid crystal material is described. The cell 51 comprises a first substrate 53 joined to a second substrate 55. In this example the first and second substrates 53, 55 are sheets of PET that are each about 100 m thick.

[0140] To prepare the cell 51 for a liquid, the first substrate 51 is laid out horizontally. In this example, a plurality of spacers (only three are shown and labelled 57a, 57b, 57c) are then laid onto the upper facing major surface of the first substrate. The spacers 57a, 57b, 57c are glass spheres having a diameter that determines the spacing of the cell 51.

[0141] Next a layer of adhesive 59 is deposited on the upper facing major surface of the first substrate 53. The layer of adhesive 59 surrounds the plurality of spacers and is used to define the wall of a first cavity 61.

[0142] Next the second substrate 55 is positioned on the first substrate 53 to contact the layer adhesive 59 and the spacers 57a, 57b, 57c.

[0143] In this example the second substrate 55 has a hole 60 extending between opposing major surfaces thereof.

[0144] The layer of adhesive 59 is then allowed to cure such to form the cell 51 having a first cavity 61 having a first volume. The cured layer of adhesive 59 joins the first substrate 53 to the second substrate 55 and acts as a seal between the cavity and the outside environment.

[0145] The cell 51 is then heated at a temperature of about 150 C. for about one hour to cause the first and second substrates 53, 55 to shrink. The shrinkage of the substrates causes the volume of the cavity 61 to decrease from the first volume to a second volume. Other times and temperatures may be determined by experiment.

[0146] The cell 51 has then been prepared and may be used to contain a liquid in the cavity 61. Liquid may be introduced into the cavity 61 via the hole 60. The hole 60 may be sealed thereafter.

[0147] The cell 51 that has been prepared according to the second aspect of the present invention has already undergone shrinkage so that when the cell 51 having liquid in the cavity thereof is used in a subsequent process involving increasing the temperature of the cell 51, there is little, if any shrinkage of the first and second substrates 53, 55.

[0148] A subsequent process is a lamination process where the cell 51 may be laminated between two sheets of glass using sheets of PVB either side of the cell 51.

[0149] Also shown in FIGS. 5 and 6 is the option provision of a second layer of adhesive 63 used to define a second cavity 65. Such a cell is useful in making a film in accordance with the first aspect of the present invention. In embodiments having a second cavity in fluid communication with a first cavity, the method may not include a heating step to pre-shrink the cell.

[0150] In an alternative to the method described above, a second substrate is provided without a hole 60 therein. In such an embodiment, the liquid to be contained in the cavity is introduced before the second substrate is positioned on the first substrate. The amount of liquid introduced is less than the volume of the cavity 61 produced. However, when the cavity 61 decreases in volume due to the shrinkage of the first and second substrates 53, 55, the amount of liquid is sufficient to completely fill the cavity having the second volume.

[0151] In such an embodiment, the heating step to cause the cavity 61 to decrease in volume may be part of another processing step, for example a lamination step.

[0152] FIG. 7 shows a laminated glazing 80 in accordance with the third aspect of the present invention.

[0153] The laminated glazing 80 comprises a first sheet of glass 82 and a second sheet of glass 84. Between the first and second sheets of glass 82, 84 are a first sheet of PVB 86, a second sheet of PVB 88 and a film 91. The film 91 is between the first and second sheets of PVB 86, 88. The first sheet of PVB 86 is between the film 91 and the first sheet of glass 82. The second sheet of PVB 88 is between the film 91 and the second sheet of glass 84. The sheets of PVB 86, 88 are about 0.8 mm thick i.e. between about and about 0.8 mm thick.

[0154] The film 91 comprises a first PET substrate 93 spaced apart from a second PET substrate 95. The first PET substrate 93 is joined to the second PET substrate 95 by a seal 97. The seal 97 extends around the periphery of the inner facing major surfaces of the first and second PET substrates 93, 95. A suitable seal 97 is a cured epoxy.

[0155] A first cavity is defined by the inner facing major surfaces of the first and second PET substrates 93, 95 and the seal 97. A liquid 99 is contained in the first cavity just described.

[0156] The first sheet of PVB 86 has a void 87 therein. The void 87 may be made by stamping out a portion of the first sheet of PVB 86. A barrier material (not shown) may be used to delimit the void 87. A suitable barrier material is PET tape which may be used to cover the edges of the PVB facing into the void 87 and prevents PVB flow into the void during lamination.

[0157] The laminated glazing 80 is made using a conventional lamination process, using a suitably high pressure and a suitably high temperature, for example between 80 C. and 150 C.

[0158] The high temperature during lamination may cause the first and second substrates 93, 95 of the film 91 to shrink. In order to accommodate the increased pressure that is caused in the cavity of the film 91, the film 91 may expand into the void 87 in the first sheet of PVB 86.

[0159] In an alternative example to that shown in FIG. 7, the first substrate 93 of the film 91 has weak zones in the vicinity of the void 87, for example localised thickness variations in the first substrate 93. Upon increasing pressure in the cavity of the film 91, the weak zones cause the first substrate 93 to rupture thereby allowing some liquid 99 to flow into the void 87.

[0160] In another alternative example to that shown in FIG. 7, an elastomeric material is positioned in the void 87 to provide resistance to the film 91 from expanding into the void. Expansion of the film into the void 87 is only possible once a predetermined pressure in the first cavity of the film 91 has been exceeded.

[0161] In the previous examples, the liquid may be a liquid crystal containing material. In such embodiments, the first and second substrates of the film and/or cell may also include suitable electrodes (i.e. ITO coating layers or other suitable electrically conductive coating that is preferably optically transparent), a polarisation layer and alignment layers as known in the art.

[0162] The present invention is particularly useful for films that undergo shrinkage when heated. The heating may be part of a process to incorporate the film into another product such as a laminated glazing.