WO2007077099A1

WO2007077099A1 - Vehicle glazing with light-guiding assembly

Info

Publication number: WO2007077099A1
Application number: PCT/EP2006/069561
Authority: WO
Inventors: Peter Paulus; Anke Neuhaus
Original assignee: Pilkington Automotive Deutschland Gmbh
Priority date: 2006-01-06
Filing date: 2006-12-11
Publication date: 2007-07-12
Also published as: EP1973762A1

Abstract

A vehicular glazing comprising two panes of glazing material spaced apart from one another, a functional layer extending between said panes, an optical coupler mounted with respect to the glazing and arranged to couple light into the glazing from an external light source, and an optical decoupling means (at least one light scattering centre) incorporated into the glazing and arranged to decouple light from within the glazing into the environment surrounding the glazing. The panes of glazing material may be glass panes, and the light scattering centre may be a micro-crack in the glass. The functional layer may provide a solar control function.

Description

VEHICLE GLAZING WITH LIGHT-GUIDING ASSEMBLY

The present invention relates to vehicular glazings, especially to vehicular glazings provided with a means of integrated lighting.

Vehicles, for example cars and buses, have a number of window openings in their bodywork into which glazings may be fitted; the glazings include windscreens, rear window glazings, side window glazings and roof glazings. In a typical car, the windscreen is a laminated glazing (i.e. having two plies of glazing material joined together by a ply of interlayer material extending between them) for safety reasons, and the remainder of the glazings are usually toughened glass (although laminated side window glazings are becoming increasingly popular in vehicles). In a typical bus, again the windscreen is a laminated glazing, the rear window glazing is usually toughened glass, and the side window and roof glazings may be double glazing units (i.e. having two plies of glazing material and a sealed airspace between them).

It is known to provide a vehicle glazing with a means of integrated lighting. WO 2005/054915 describes one example of such a glazing. It discloses a "light-guiding assembly" in the form of a laminated vehicle roof. The assembly comprises two sheets of glass joined together by a polymeric laminating interlayer material, and a means of integrated lighting in the form of light-coupling means for coupling light into the interlayer material. Light exits the assembly via "scattering centres" that are located across one or more of the surfaces of the interlayer material.

In addition to providing a vehicle glazing with a means of integrated lighting, it would be useful to be able to provide such a glazing with other functionality, but without compromising the lighting effect of the integrated lighting, and without significantly increasing the cost of producing such a glazing or the complexity of the production process.

Accordingly the present invention provides a vehicular glazing comprising: two panes of glazing material spaced apart from one another, a functional layer extending between said panes, an optical coupler mounted with respect to the glazing and arranged to couple light into the glazing from an external light source, and an optical decoupling means incorporated into the glazing and arranged to decouple light from within the glazing into the environment surrounding the glazing.

A vehicular glazing comprising a) a means of integrated lighting in the form of an optical coupler for coupling light into the glazing and its associated optical decoupling means and also b) a functional layer necessarily possesses multiple functionality that is able to provide additional advantage to the occupants of a vehicle into which such a glazing may be installed; thus in addition to benefiting from the lighting effect of light coupled into and subsequently decoupled and emitted by the glazing, the functional layer provides at least one further benefit as will be explained in more detail below.

The two panes of glazing material may be spaced apart from one another by a further ply of material which extends between the two panes, or they may be spaced apart such that there is a gaseous layer (for example a sealed airspace) between them, as will be described in more detail later.

The light to be coupled in to the glazing may be visible, infrared or ultraviolet light. The external light source may be a conventional halogen lamp, a gas discharge lamp, an incandescent light bulb, one or more high-energy light emitting diodes, etc.. Having a light source external of the glazing, rather than one which is provided within the glazing is advantageous for replacement of the source if and when it ceases to function, or when an alternative wavelength of light is desired (for example, a change in the colour of light to be emitted by the glazing). It is also advantageous if the glazing breaks because only the glazing itself and not the light source would need to be replace. The external light source may moreover be a composite element comprising two or more sources, to enable manual switching between each of them (for example, switching between a source emitting blue light and a source emitting green light). An automatically switching source, which cycles around the two or more light sources comprised in it so that the light emitted by the glazing continually changes, may also be employed.

The optical coupler is mounted with respect to an edge of one or more plies of material comprised in the glazing; either a pane of glazing material or some other ply of material (to be discussed in more detail later) may perform the function of a waveguide for the coupled-in light. There may be two or more optical couplers mounted with respect to the glazing. Each of these two or more optical couplers may be mounted with respect to different edges of the glazing and furthermore may be arranged to couple light into the glazing from independent external light sources.

Whichever ply of the glazing acts as a waveguide, the principle under which light may be coupled into and propagated through the glazing is that of total internal reflection. To achieve total internal reflection, the refractive index (n₂) of the glazing ply (g) which acts as the waveguide must be greater than the refractive indices (ni; n₃) of the media (Hi₁; m₃) adjacent each side of it, according to the following construction: mi / g / m₃ -> ni < n₂ > n₃

Light must be introduced and coupled into the waveguide glazing ply (g) at an angle greater than the critical angle θc to the normal (i.e. the plane perpendicular to the surfaces of the glazing ply (g)). The value of the critical angle θc can be calculated from the following: sin θc ≥ (ni / n₂) and sin θc ≥ (n₃ / n₂)

Once coupled into the glazing ply (g), light undergoing total internal reflection will not exit the ply unless and until encouraged to do so; hence an optical decoupling means is provided to decouple the internally reflected light and enable it to be emitted over one or more surfaces of the glazing, in the direction(s) of choice. The optical decoupling means is thus necessarily incorporated into or onto the ply of glazing material which acts as the waveguide.

The optical decoupling means is preferably provided as at least one light scattering centre within the glazing. Further preferably there are at least twenty such scattering centres within the glazing to enable a sufficient amount of light to be emitted by the glazing. The scattering centres may be provided in a regular or irregular pattern which spans one or more surfaces of the glazing. The pattern may include a large number (i.e. hundreds) of scattering centres of a small size (up to 1 mm in width), or a smaller number (i.e. tens) of scattering centres of a larger size (ranging from 1 mm to 1 cm in width). Preferably, the spacing between adjacent scattering centres is such that a homogeneous scattering and decoupling of light may be achieved.

The optical decoupling means may also be provided as one or more areas of a thin film of material provided on one or more surfaces of the waveguide. The material may be any organic or inorganic material which has a refractive index greater than the refractive index (n₂) of the waveguide glazing ply (g), so that light coupled into the waveguide may be decoupled from it in the areas where the material is located because the condition for total internal reflection in these areas does not exist. The thin film of material may alternatively have a refractive index (1I₄) between the index (n₂) of the waveguide glazing ply (g) and the indices (ni;n₃) of the surrounding media (mi;m₃). In such a case, a fraction of the light may be decoupled from the waveguide ply (g), depending on the angle θ. In addition to its refractive index, the thin film material may have special, useful characteristics that may enable effective decoupling. It may have scattering centres (e.g. it may be hazy) or it may have fluorescent characteristics which may e.g. convert blue light from the light source into yellow light to be emitted from the thin film itself.

The one or more areas of material may be of similar number and dimension to the light scattering centres described above. However, the one or more areas may instead be of a larger dimension than said light scattering centres, forming discernible shapes (for example, letters of the alphabet or numbers) which would manifest as light exits the glazing upon its decoupling from it. The thin film material may be permanently provided on the waveguide glazing ply (g), or it may be applied temporarily by an occupant of the vehicle into which the glazing may be installed (the period of time for which the material remains on the glazing being determined by the vehicle occupant); thus the material itself may be a "wipe-clean" material, enabling it to be removed from the glazing when desired (noting that if the thin film material is the only optical decoupling means, removal of it would then prevent light from being decoupled and emitted by the glazing).

The optical coupler may be mounted with respect to the functional layer, in which case the optical decoupling means will be comprised in the functional layer. Alternatively or additionally, the optical coupler may be mounted with respect to one of the panes of glazing material, in which case the optical decoupling means will be comprised in that pane of glazing material. The pane of glazing material may be a pane of glass, and the optical decoupling means, in the form of at least one light scattering centre, may be at least one micro-crack having a pre-selected spatial configuration that has been deliberately introduced into the pane of glass. Preferably, the pane of glass is a pane of extra clear glass (glass having greater than 85 % visible light transmission (measured with Illuminant A) at thicknesses from 2 to 20 mm) to ensure that sufficient light is propagated through the glazing and subsequently decoupled and emitted. The at least one micro-crack may be located anywhere within the pane of glass (i.e. at one of the surfaces or somewhere within the body of the glass). Typically, a micro-crack is formed by application of a laser to the pane of glass; a laser can penetrate the glass to the desired depth to induce a micro-crack without damaging the surrounding body of glass or the surface(s) of the glass pane (as appropriate) through which the laser beam passes. At least one scattering centre in the form of at least one micro-crack may also be found in a glazing ply made from material other than glass (such other materials will be discussed later).

One or more scattering centres in a glazing ply (either one of the panes of glazing material or the functional layer) may alternatively be made by one or more of the following techniques: grinding small discrete areas into the relevant glazing ply, stamping small holes into said ply, pasting onto the ply a transparent frit in the pattern desired, embossing the ply with a suitable embossing material to achieve the desired pattern, attaching members (for example, adhering plastic members) to the relevant ply. Each scattering centre may be configured to have a particular shape that is conducive for achievement of a particular distribution of decoupled, emitted light - a centre may be rounded or angled for example so that internally reflected light is intercepted and decoupled for emission in a particular, pre-selected direction.

The functional layer may comprise a visible light attenuation material for attenuating light transmitted though the glazing. Such functionality is especially useful when the optical decoupling means is provided as at least one light scattering centre, as described above, because light emitted by the glazing may be in the form of at least one discrete point source. Attenuated, diffuse light may be desired, for example, in courtesy or ambient lighting applications, in which case an attenuation material may be successfully included in a glazing and used both to reduce and to scatter the point source light before it exits the glazing.

Preferably the visible light attenuation material includes a liquid crystal film. A liquid crystal film may diffuse visible light passing through it as well as attenuating it. The liquid crystal may be electrically switchable between a clear state (resulting from a voltage being applied to the film) and an opaque state (having no voltage applied). The degree to which visible light passing though a liquid crystal film is attenuated and diffused may be controlled by regulation of the voltage applied to the film. Advantageously, the liquid crystal film may be divided into zones, and each zone may be independently switchable. Any known liquid crystal film material may be used, provided that it is suitable for inclusion in a vehicular glazing.

Combination of a functional interlayer which includes a liquid crystal film with a means of integrated lighting in the form of an optical coupler and associated decoupling means (especially when in the form of at least one light scattering centre) may be used to provide the following desirable scenarios for the occupants of a vehicle into which such a glazing may be installed: a) when the vehicle is driven during the night time, and: i) the liquid crystal film remains opaque and the glazing emits decoupled light, the vehicle occupants may experience a diffuse ambient lighting within the vehicle; ii) the liquid crystal film is electrically switched from opaque to clear and the glazing emits decoupled light, the vehicle occupants may experience "stellar" lighting, in that the emitted light may resemble the stars of the night sky; iii) the liquid crystal film remains opaque and light is not coupled into the glazing, the vehicle occupants may experience an opaque lighting, the intensity of which is determined by the amount of moonlight falling upon the glazing; (b) when the vehicle is driven during the daytime, and: i) the liquid crystal film remains opaque and light is not coupled into the glazing, the vehicle occupants may experience an opaque lighting in the form of diffuse, attenuated sunlight, the intensity of which is determined by the amount of sunlight falling upon the glazing.

It is of course also possible that light is neither coupled into the glazing nor the liquid crystal film electrically activated.

The visible light attenuation material may alternatively comprise a suspended particle device ("SPD"). An SPD may be electrically switchable between a darkened state (having no voltage applied to it) and a state of increased visible light transmittance (resulting from an AC voltage being applied to the device). Advantageously, the SPD may be divided into zones, and each zone may be independently switchable. Any known SPD may be used, provided that it is suitable for inclusion in a vehicular glazing.

The functional layer may comprise a ply of polymeric material which includes a visible light dispersant material for diffusing light transmitted through the glazing. Again such functionality may be especially useful when the optical decoupling means is provided as at least one scattering centre and light emitted by the glazing is in discrete quantities. Diffuse light may be achieved by including a dispersant material in the polymeric material to scatter the decoupled light within the polymeric material itself. This diffusive functionality may be in addition to, or an alternative to, the light attenuation function of the functional layer described earlier.

The functional layer may comprise a ply of polymeric material that is provided on one of its surfaces with a solar control coating. The nature of such coatings will be discussed in more detail below. The ply of polymeric material may be a ply of polyethylene terephthalate ("PET").

At least one of the panes of glazing material may be body-tinted glass, the composition of which includes one or more of the following colourants: iron oxide, cobalt oxide, selenium, chromium oxide, titanium oxide, manganese oxide, copper oxide, vanadium oxide, nickel oxide. The tint may be such that the glass absorbs an amount of infrared radiation; thus the solar control function of the glazing may be provided in this way in addition to, or as an alternative to, the presence of a solar control coating as part of the functional layer.

Both panes of glazing material may be panes of glass, and if only one pane is body-tinted, the other pane may be clear. It is also possible that both panes may be clear glass, or both panes may be body-tinted. One or both panes may be toughened glass. Rather than being a pane of glass, a pane of glazing material may instead be made from a plastics material, such as polycarbonate. The panes of glazing material may be flat or they may be curved. Each pane may be between 0.5 and 25 mm in thickness, preferably between 1 and 5 mm. The overall thickness of the glazing may therefore be between 1.5 and 100 mm, preferably between 2 and 50 mm, and further preferably between 2.5 and 20 mm. A solar control coating may be provided on a surface of at least one pane of glazing material.

Typically, a solar control coating (as referred to above) may include either a) at least one silver-based layer or b) at least one tin-based layer. Accordingly the solar control coating may comprise one or more layers of zinc oxide, titanium dioxide and/or silver. Alternatively the solar control coating may comprise fluorine-doped tin oxide. The coating may also include one or more layers of silicon nitride, aluminium nitride and/or nichrome (NiCr). The solar control coating may include a single layer of a metal or metal oxide (the latter preferably being a transparent conductive oxide). Oxides of metals such as tin, zinc, indium, tungsten and molybdenum may be comprised in the single layer of metal oxide. The coating may further comprise a dopant, for example fluorine, chlorine, antimony, tin, aluminium, tantalum, niobium, indium or gallium, so that a coating such as fluorine- doped tin oxide or tin-doped indium oxide may result. A solar control coating may be provided with an underlayer, for example comprising silicon oxide or silicon oxynitride, which serves as a barrier to control migration of alkali metal ions from the glass and/or as a colour suppressing layer to suppress iridescent reflection colours resulting from variations in thickness of the solar control layer. A number of solar control coatings are known in the art, any of which may be used in accordance with the invention.

Alternatively, the solar control coating may comprise a multilayer coating stack which normally includes at least one metal layer or metal oxide layer and at least one dielectric layer. The multilayer stack structure may be repeated to further enhance the solar control function of the coating. Amongst other similar metals, silver, gold, copper, nickel and chromium may be used as the metal layer in a multilayer stack; indium oxide, antimony oxide or the like may be used as the metal oxide layer. Coatings comprising one or two layers of silver interleaved between layers of a dielectric such as an oxide of silicon, aluminium, titanium, vanadium, tin or zinc are typical multilayer stacks. Generally the one or more layers from which the coating is formed are of the order of tens of nanometres in thickness.

Preferably, the glazing has a visible light transmission (measured with CIE Illuminant A) of greater than 70 % and further preferably greater than 75 % when the panes of glazing material are substantially clear. If the glazing overall has a tint (because either at least one pane of glazing material is body- tinted or the interlayer material is tinted), it preferably has a visible light transmission (measured with CIE Illuminant A) of less than 40 %, further preferably less than 30 % and most preferably less than 25 %, and a total energy transmission (Parry Moon; Air Mass 1.5) of less than 30 %, further preferably less than 25 % and most preferably less than 20 %. The glazing may have these properties regardless of its laminar composition.

The optical coupler comprised in the glazing may include an optical fibre, which may extend into the glazing between any two of the plies comprised in the glazing. Thus an optical fibre may be arranged to couple light into the glazing and also to propagate light via total internal reflection within the glazing. With an optical fibre, the optical decoupling means is typically provided as the end of the fibre, which is located within the glazing. If not an optical fibre, the optical coupler may be a plastics member that has been shaped and configured such that when it is mounted with respect to the glazing, light from an external light source may be introduced into it and subsequently coupled into the glazing at an angle to the normal of the waveguide material that is greater that the required critical angle θc.

The vehicular glazing of the invention may be in the form of a laminate, having a ply of laminating interlayer material joining the panes of the glazing together. Thus the two panes of glazing material may be joined together by the ply of laminating interlayer material. The functional layer may be provided as the ply of laminating interlayer material or it may additionally be laminated into the glazing. In the latter case, the functional layer may be interleaved between two plies of laminating interlayer material to form a composite interlayer. The laminating interlayer material may be any material known in the art that is suitable for forming a laminate. It may be polyvinylbutyral ("PVB"), polyvinyl chloride ("PVC"), polyurethane ("PU") or an ethyl vinyl acetate ("EVA"). It is typically provided in a thickness of between 0.38 and 1.1 mm, but most commonly 0.76 mm. The interlayer material may be clear, body-tinted or it may be infrared absorbing or reflecting (thereby providing, or at least contributing to, the solar control function of the glazing). The interlayer material may perform the function of a waveguide, i.e. the optical couple may be mounted with respect to the interlayer ply. In this case, the interlayer material is preferably clear. The ply of laminating interlayer material may be a composite ply comprising a core ply of material interleaved between two laminating plies. The core ply of material may act as waveguide, provided its refractive index is greater than the refractive indices of each of the laminating interlayer plies adjacent to it.

Alternatively, the glazing of the invention may be in the form of a double glazing unit, having a sealed airspace between the two panes of glazing material. The two panes may be spaced apart from one another by spacer elements located along at least two opposing edges of the panes. If the glazing includes a functional layer, this may be located adjacent to a surface of one of the panes of glazing material that faces into the airspace, or on the surface of the glazing that will face into the vehicle into which the glazing may be installed.

A double glazing unit is the most basic form of a multiple glazing unit; the glazing of the invention may comprise three or more panes of glazing material, each spaced apart from one another by a sealed airspace. A multiple pane glazing unit may have one or more of its panes in the form of a laminated glazing. In such a glazing unit, the laminate ply preferably forms the inner ply (the ply in contact with the environment inside the vehicle).

The inner surface of the glazing is preferably provided with a low emissivity coating. By "the inner surface of the glazing" is meant that surface which would face into and contact the environment inside a vehicle into which the glazing may be installed (such surface could be touched by the occupants of the vehicle). The emissivity of a particular coating refers to the tendency of that coating to radiate energy. Thus a low emissivity coating is a poor thermal radiator (compared to a blackbody entity, which is a perfect radiator and is defined as having an emissivity of unity).

The low emissivity coating provided on the inner surface of the glazing will normally be such that, when applied to 3 mm clear float glass, the coated glass has an emissivity in the range from 0.05 to 0.45; the actual value being measured according to EN 12898 (a published standard of the European Association of Flat Glass Manufacturers). Coatings (when used on 3 mm clear float glass) resulting in an emissivity less than 0.3 are preferred. A hard coating (which when on a pane of glass is typically formed "on-line" by pyrolytically depositing the coating onto a surface of the glass during its formation, in known manner, for example by use of a chemical vapour deposition process) may generally have an emissivity greater than 0.15 (and preferably less than 0.2), whilst an off-line coating (which when on a pane of glass is typically deposited onto the surface of the pane subsequent to complete manufacture of the glass, and is normally a sputtered coating) may generally have an emissivity greater than 0.05 (and preferably less than 0.1). In both cases, the emissivity may be compared with the assumed normal emissivity of clear uncoated glass, which has a value of around 0.89.

The composition of the low emissivity coating may be the same as that described earlier for the solar control coating: essentially either a single layer of an optionally doped metal or metal oxide, or a multilayer stack including at least one metal or metal oxide layer and at least one dielectric layer.

A vehicular glazing according to the invention may be fitted into any window in the bodywork of a vehicle. It may be especially used as a roof window.

For a better understanding the present invention will now be more particularly described by way of non-limiting example with reference to, and as shown in, the accompanying schematic drawings wherein:

Figure 1 is a perspective view of a vehicular glazing according to the invention; Figure 2 is a cross section viewed along line A-A of Figure 1;

Figure 3 is a cross section viewed along line A-A of an alternative construction of the glazing in Figure 1 ;

Figure 4 is a cross section viewed along line A-A of a second alternative construction of the glazing in Figure 1 ; and

Figure 5 is a cross section viewed along line A-A of a third alternative construction of the glazing in Figure 1.

Figure 1 shows a vehicular glazing, in the form of a roof window 10, comprising an optical coupler 11, mounted with respect to one of the short edges of the glazing (although it could be mounted with respect to one of the long edges), and optical decoupling means in the form of a plurality of light scattering centres 13 within the glazing. Optical coupler 11 is linked to external light source 12 via an optical fibre which provides the light that is to be coupled into roof window 10. External light source 12 is in this example a conventional halogen lamp, but could alternatively be a gas discharge lamp, an incandescent light bulb, one or more high-energy light emitting diodes, etc.. In some cases however, external light source 12 may be attached directly to roof window 10 (omitting optical coupler 11), for example when light source 12 is in the form of one or more light emitting diodes. The light scattering centres 13 are located so as to form a regular pattern, although any pattern, regular or irregular, and any number of scattering centres could be provided. Around the periphery of roof window 10 there is an obscuration band 14, which is there to disguise and protect the sealant (not shown) that is used to fix the window into a vehicle (not shown). Obscuration band 14 is made from opaque ink that has been screen printed onto the glazing and subsequently fired. However, it may be composed of and applied using any other known means. For the avoidance of doubt, obscuration band 14 is merely an optional addition to roof window 10.

Figure 2 provides more detail about the construction of roof window 10 in that it is a laminate which comprises outer pane of glazing material, in the form of a pane of soda lime silica glass 21, inner pane of glazing material, also in the form of a pane of soda lime silica glass 22, functional layer 23, waveguide 24, adhesive 25 for attaching optical coupler 11 to the edge of the glazing and interlayer plies 26 which are interleaved between each ply of the laminate and join them all together.

By "outer pane" of glazing material is meant the pane which contacts the environment external to a vehicle into which roof window 10 may be fitted; similarly, by "inner pane" is meant the pane which contacts the interior environment of said vehicle. A pane of soda lime silica glass may be clear glass having a composition in the range (by weight): SiO₂ 68 - 75 %; Al₂O₃ 0 - 5 %; Na₂O 10 - 18 %; K₂O 0 - 5 %; MgO 0 - 10 %; CaO 5 - 15 %; SO₃ 0 - 2 %. The glass may also contain other additives, for example, refining aids, which would normally be present in an amount of up to 2 %.

One or more of the panes may alternatively be tinted glass (thereby providing roof window 10 with a solar control function) having, for example, one of the following compositions: Composition 1

Base glass (by weight): 72.1 % SiO₂, 1.1 % Al₂O₃, 13.5 % Na₂O, 0.6 % K₂O, 8.5 % CaO, 3.9% MgO and 0.2 % SO₃; colourant portion (by weight): 1.45 % total iron (calculated as Fe₂O₃), 0.30 % ferrous oxide (calculated as FeO), 230 ppm Co₃O₄, 210 ppm NiO and 19 ppm Se. Such a glass is currently available as GALAXSEE™ from Pilkington pic in the United Kingdom; Composition 2

Same base glass as composition 1 described above; colourant portion (by weight): 1.57 % total iron (calculated as Fe₂O₃), 0.31 % ferrous oxide (calculated as FeO), 115 ppm Co₃O₄, 0 ppm NiO and 5 ppm Se. Such a glass is currently available as SUND YM™, again from Pilkington pic in the United Kingdom.

Functional layer 23 is provided between waveguide 24 and the inner surface of inner pane 22 (surface 3 of the glazing), and is in the form of a ply of polymeric material on which is provided a solar control coating; in this example, the coating is a silver-based coating containing one or more of the following layers (in addition to at least one silver layer): TiO₂, In₂O₃, Si₃N₄, NiCr, AlN, ZnO, SnO₂, Zn_xSnOy. Functional layer 23 could instead be provided between waveguide 24 and the inner surface of outer pane 21 (surface 2 of the glazing). Surface 4 of roof window 10 could be provided with a low emissivity coating (not shown) to further increase the solar control function of the glazing.

The example glazing shown in Figures 1 and 2 has functional layer 23 in the form of a ply of polymeric material, for example PET, bearing a solar control coating on one of its surfaces. The solar control coating may be comprised of multiple alternate layer of silver and indium oxide. Plies of coated PET suitable for inclusion in a vehicle glazing are currently available from, for example, Southwall Technologies Inc., 3975 East Bayshore Road, Palo Alto, California 94303, US (www.southwall.com). Alternatively, functional layer 23 may be in the form of a liquid crystal layer. Further alternatively functional layer 23 may be in the form of a ply of polymeric material, for example PVB or PET, which includes a visible light dispersant material. It is also possible that functional layer 23 may incorporate two or more of these three alternatives.

Waveguide 24 is in the form of a layer of polycarbonate (which is interleaved between two plies of interlayer material 26, typically PVB). Optical coupler 11 is attached to waveguide 24 using adhesive 25, and is in the form of a plastics element that is specifically shaped to ensure that light coupled into roof window 10 by it enters waveguide 24 at an angle greater than the appropriate critical angle θc. The refractive index (n₂) of polycarbonate is 1.58, while the refractive index (ni) of PVB is 1.52, making the critical angle θc for the PVB interlayer 26 / polycarbonate waveguide 24 / PVB interlayer 26 combination of layers 74.2 °. Arrow B shows the path of light coupled into the polycarbonate core layer via optical coupler 11.

From Figure 2 it can be seen that light scattering centres 13 are provided as small discrete areas that have been ground into polycarbonate waveguide 24. Each scattering centre 13 is dome-shaped. There is a plurality of scattering centres 13 in the glazing shown and the distance between adjacent centres 13 is such that homogeneity in scattering of the light may be achieved, giving a uniform appearance to the glazing when emission occurs. Arrows C indicate the directions in which light scattered by scattering centres 13 would travel as it is decoupled from, and is emitted by, roof window 10. Decoupled light passes sequentially through one ply of interlayer material 26, functional layer 23, a further ply of interlayer material 26 and finally inner pane of glass 22 before exiting the glazing.

The glazing shown in Figure 3 is similar to that shown in Figure 2 in that it is a laminate comprising outer pane of glazing material, in the form of a pane of clear soda lime silica glass 31, inner pane of glazing material, also in the form of a pane of clear soda lime silica glass 32, functional layer 33, composite interlayer 34, adhesive 35 for attaching optical coupler 11 to the edge of the glazing and interlayer ply 36 which helps to join the plies of the laminate together. The description of the glazing shown in Figure 2 applies to that shown in Figure 3 except: functional layer 33 is provided between composite interlayer 34 and surface 2 of the glazing. Again, functional layer 33 may additionally include a liquid crystal layer and/or a light dispersant material in the ply of polymeric material; optical coupler 11 is attached to inner pane of glazing material 32 using adhesive

35. Inner pane of glazing material 32 is a pane of low- iron, extra clear glass, for example a pane of OPTIWHITE™ glass available from Pilkington pic in the UK, having a visible light transmission of greater than 85 % at thicknesses in the range of 2 to 20 mm, which may be important if a particular intensity of decoupled light is to be maintained. Outer pane of glazing material 31 may alternatively be a pane of extra clear glass and have optical coupler 11 attached to it; composite interlayer 34 comprises an upper layer of polymeric material such as

PVB, PU, etc, and a lower layer of a material having a refractive index (ni) which is less than the refractive index (n₂) of inner pane of extra clear glass 32. Such a low refractive index layer may be obtained from, for example, 3M United

Kingdom pic, 3M Centre, Cain Road, Bracknell, RG12 8HT, UK in the form of an

Optically Clear Laminating Adhesive (8141, 8142, 8161 or 9483); arrow B shows the path of light coupled into the inner pane of extra clear glass 32 via optical coupler 11 ; light scattering centres 13 are provided as micro-cracks in inner pane of extra clear glass 32. Typically the separation between such micro-cracks is in the 1 to 10 cm range. Alternatively light scattering centres 13 may be provided as areas of a thin film material (having a refractive index (n₃) higher than the refractive index (n₂) of inner pane of glazing material 32) on the outer surface of inner pane 32 to decouple light coupled into the glazing. The thin film material may be applied by the occupant of the vehicle into which the glazing may be installed using, for example, an ink-dispensing pen such as a Neon Board Marker currently available from Edding (UK) Limited, Merlin Centre, Acrewood Way, St. Albans, AL4 OJY, UK (www.edding.com); decoupled light passes directly from inner pane of extra clear glass 32 into the interior compartment of a vehicle into which roof window 10 may be installed.

The construction of roof window 10 shown in Figure 4 is that of a double glazing unit which comprises outer pane of glazing material, in the form of a pane of soda lime silica glass 41, inner pane of glazing material, also in the form of a pane of soda lime silica glass 42, functional layer 43, interlayer ply 47 and spacers 44 which maintain the panes of glass 41,42 spaced apart from one another. Spacers 44 are used to seal the airspace 45 between panes 41,42. Although airspace 45 may be filled with air, it may alternatively be filled with any other gas, preferably an inert gas, that provides the glazing with good thermal insulation properties.

The composition of each pane of glass 41,42 is as described above for Figure 2. Functional layer 43 is provided on surface 2 of the glazing via interlayer ply 47, and is in the form of a solar control silver based coating, as described earlier. Functional layer 43 could instead be provided on surface 3 of the glazing.

The example glazing shown in Figures 1 and 4 has functional layer 43 in the form of a ply of polymeric material, for example PET, bearing a solar control coating. Alternatively, functional layer 43 may be in the form of a liquid crystal layer, interleaved between two plies of polymeric material. Further alternatively functional layer 43 may be in the form of a ply of polymeric material, for example PVB or PET, which includes a visible light dispersant material. It is also possible that functional layer 43 may incorporate two or more of these three alternatives.

Optical coupler 11 is attached to inner pane of glass 42 using adhesive 46, and is in the form of a plastics element that is specifically shaped to ensure that light coupled into roof window 10 by it enters inner pane of glass 42 at an angle greater than the appropriate critical angle θc. Arrow B shows the path of light coupled into inner pane of glass 42 (which is a pane of extra clear glass as described earlier) via optical coupler 11. From Figure 4 it can be seen that light scattering centres 13 are provided as micro- cracks that have been lasered into the glass. Each scattering centre 13 is approximately hemispherical in its configuration. The shape of each scattering centre 13 determines the manner in which light within the glazing is decoupled, so that light can be emitted from the glazing in a particular direction, as shown by arrows C.

The construction of roof window 10 shown in Figure 5 is that of a laminate comprising outer pane of glazing material, in the form of a pane of clear soda lime silica glass 51 , inner pane of glazing material, also in the form of a pane of clear soda lime silica glass 52, functional layer 53 and interlayers 54 which join the plies of the laminate together.

The composition of each pane of glass 51,52 is as described above for Figure 2. Functional layer 53 is provided on surface 3 of the glazing, and is in the form of a liquid crystal layer, interleaved between two plies of interlayer material 54. Alternatively, functional layer 53 may be in the form of a ply of polymeric material bearing a solar control coating, as described earlier. Further alternatively functional layer 53 may be in the form of a ply of polymeric material which includes a visible light dispersant material, again as described earlier. It is also possible that functional layer 53 may incorporate two or more of these three alternatives.

Optical coupler 11 is in the form of a plurality of optical fibres which are laminated into the glazing. One end of each of the fibres is attached to external light source 12 (shown in Figure 1) allowing light to be coupled into each fibre, whilst the other end of each fibre terminates within the glazing (at differing locations forming scattering centres 13) allowing the light to be decoupled from the fibres and subsequently emitted by the glazing. Arrow B shows the path of light coupled into a single fibre, arrows C show the direction of decoupled light emitted by the fibre and arrows D show the light emitted by the glazing after it has passed through the liquid crystal film 53 (which in this example remains opaque). It is also possible that at least one of the optical fibres could be modified along its length within the laminate so that its outer surface also acts as an optical decoupling means, for example, by embossing the outer surface.

As a further alternative to being in the form of a plurality of optical fibres, optical coupler 11 could be a thin ply of material (such as polycarbonate) that extends into the glazing (in a similar manner to the fibres shown in Figure 5). Light would be decoupled from the terminating edge of optical coupler 11 within the glazing and subsequently emitted by the glazing.

Claims

Claims :

1. A vehicular glazing comprising two panes of glazing material spaced apart from one another, a functional layer extending between said panes, an optical coupler mounted with respect to the glazing and arranged to couple light into the glazing from an external light source, and an optical decoupling means incorporated into the glazing and arranged to decouple light from within the glazing into the environment surrounding the glazing.

2. A vehicular glazing as claimed in claim 1 wherein the optical decoupling means is at least one light scattering centre provided within the glazing.

3. A vehicular glazing as claimed in claim 2 wherein the optical coupler is mounted with respect to the functional layer and the at least one light scattering centre is comprised in the functional layer.

4. A vehicular glazing as claimed in claim 2 wherein the optical coupler is mounted with respect to a pane of glazing material and the at least one light scattering centre is comprised in that pane of glazing material.

5. A vehicular glazing as claimed in claim 4 wherein the pane of glazing material is a pane of glass and the at least one light scattering centre is a micro-crack in the pane of glass.

6. A vehicular glazing as claimed in claim 5 wherein the micro- crack is formed by application of a laser to the pane of glass.

7. A vehicular glazing as claimed in claim 5 or claim 6 wherein the pane of glass is a pane of extra clear glass.

8. A vehicular glazing as claimed in any preceding claim wherein the functional layer comprises a visible light attenuation material.

9. A vehicular glazing as claimed in claim 8 wherein the visible light attenuation material includes a liquid crystal.

10. A vehicular glazing as claimed in claim 9 wherein the liquid crystal is electrically switchable between a clear state and an opaque state.

11. A vehicular glazing as claimed in claim 10 wherein the liquid crystal is divided into zones, each zone being independently switchable.

12. A vehicular glazing as claim in claim 8 wherein the visible light attenuation material comprises a suspended particle device.

13. A vehicular glazing as claimed in any preceding claim wherein the functional layer comprises a ply of polymeric material which includes a visible light dispersant material.

14. A vehicular glazing as claimed in any preceding claim wherein the functional layer comprises a ply of polymeric material that is provided on one of its surfaces with a solar control coating.

15. A vehicular glazing as claimed in any preceding claim wherein at least one pane of glazing material is body-tinted glass, the composition of which includes one or more of the following colourants: iron oxide, cobalt oxide, selenium, chromium oxide, titanium oxide, manganese oxide, copper oxide, vanadium oxide, nickel oxide.

16. A vehicular glazing as claimed in any preceding claim wherein a solar control coating is provided on a surface of at least one pane of glazing material.

17. A vehicular glazing as claimed in claim 14 or claim 16 wherein the solar control coating includes either a) at least one silver-based layer or b) at least one tin-based layer.

18. A vehicular glazing as claimed in any preceding claim having a visible light transmission (Illuminant A) of less than 40 % and a total energy transmission (Parry Moon; Air Mass 1.5) of less than 30 %.

19. A vehicular glazing as claimed in any preceding claim wherein the optical coupler includes an optical fibre.

20. A vehicular glazing as claimed in claim 19 wherein the optical fibre extends into the glazing.

21. A vehicular glazing as claimed in any preceding claim in the form of a laminate having a ply of laminating interlay er material joining the plies of the glazing together.

22. A vehicular glazing as claimed in claim 21 wherein the ply of laminating interlay er material either absorbs or reflects infrared radiation.

23. A vehicular glazing as claimed in any of claims 1 to 20 in the form of a double glazing unit having a sealed airspace between the two panes of glazing material.

24. Use of a vehicular glazing as claimed in any preceding claim as a roof window.