Patent Description:
A transparent roof assembly for a vehicle is generally known. For example, a glass panel is arranged over an opening in the roof of a vehicle to allow sunlight to enter an interior of the vehicle through the roof. In a known transparent roof assembly, the at least partly transparent panel is fixedly arranged over the opening, while in another known transparent roof assembly the panel is moveably arranged. In particular, the moveably arranged panel may be tiltable and/or slideable.

The document <CIT> discloses a known illuminated glazing for a vehicle.

Further, it is known to arrange a light source in a vicinity of an edge of the at least partly transparent panel such that light emitted by the light source is injected into the panel and the light propagates through the panel, wherein the panel functions as a light guide. In order to direct the light into the interior of the vehicle, light out-coupling structures are provided. For example, light reflecting dots may be arranged on a first surface of the panel. Light propagating in the panel and impinging on such reflective dots on the first surface is then redirected towards on opposite, second surface and leaves the panel at the second surface, thereby illuminating the interior of the vehicle.

In order to achieve light out-coupling as functional illumination, in the known transparent roof assembly, relatively large reflective dots are applied. The dots have a relatively large diameter. When illuminated, in particular with a dark background, e.g. in the night, the reflective dots light up clearly appearing separate light sources, thereby providing the functional illumination. However, e.g. during daytime with a light background, the dots are perceived as dark dots, obstructing the view.

In view of the above mentioned disadvantages of the known transparent roof assembly, it is an object of the present invention to provide for a transparent roof assembly configured to provide functional illumination without obstructing the view.

The object is achieved in a transparent roof assembly according to claim <NUM>. The open roof assembly according to claim <NUM> comprises a panel, a light source and an out-coupling pattern. The panel comprises a transparent area and is configured to be arranged over an opening in the vehicle roof to allow visible light to pass in a first direction through the transparent area. The first direction extends between an interior of the vehicle and an exterior of the vehicle and is substantially perpendicular to a surface of the panel. The light source is arranged to provide light in the panel in a second direction, wherein the second direction is substantially perpendicular to the first direction. The out-coupling pattern is arranged on the surface of the transparent area of the panel and comprises reflective dots of a light-redirecting material for out-coupling of light propagating in the panel. Each dot has a dot surface area and the dots each have a representative diameter of <NUM> microns or less. The representative diameter of a dot corresponds to a diameter of a circle having a same surface area as the dot surface area of said dot. A total dot surface area is smaller than <NUM>% of a total surface area of the transparent area, wherein the total dot surface area of the dots of the out-coupling pattern equals a sum of the dot surface area of all dots arranged on the surface of the transparent area.

According to the invention, small dots are applied in a pattern, wherein no more than <NUM>% of the surface area of the transparent area of the panel is covered with dots. The dots may take any kind of form or shape. At a normal viewing distance in a vehicle, these dots are preferably not individually distinguishable by the human vision due to their size. Therefore, the representative diameter may preferably be smaller than <NUM> microns. Moreover, as less than <NUM>% of the surface is covered, a view through the transparent area appears a clear view without obstructions. On the other hand, when illuminated by the light source, the small dots redirect the light into the interior, albeit that no clear and individual light source may be noticeable.

In a particular embodiment, however, the representative diameter may be larger than <NUM> microns. In such embodiment, the dots may be individually distinguishable, depending on the normal viewing distance which varies between vehicle types. Still, if the representative diameter of the dots remains smaller than about <NUM> microns, the dots remain invisible when the viewer focuses on the exterior viewings. In particular, due to the exterior light and the focus of the viewer being directed at a plane far away from the plane of the dots, the dots disappear in the viewed image.

In an embodiment, the representative diameter of the dots is within a range from about <NUM> microns to about <NUM> microns. Such dots are easily and cost-effectively manufacturable by screen printing. In another embodiment, the representative diameter is within a range from about <NUM> microns to about <NUM> microns. Dots with a size in this range may be provided by inkjet printing, for example. Due to their very small size, such dots are even more difficult to detect with the human eye.

Screen printing is a method that is very suitable to be used in combination with glass and other transparent materials used for a transparent roof system.

Inkjet printing is a manufacturing technique that allows for very small droplets of ink with relatively high accuracy in droplet size and droplet positioning, enabling to provide for a highly accurate and uniform distribution of the dots in the out-coupling pattern.

Inkjet printing may be a suitable manufacturing method for printing the dots on an flexible foil or web of material that is later used as an interlayer in a multi-layered panel. For example, the dots may be printed on a PVB or EVA foil. The printed PVB or EVA foil may then be arranged between two plies of glass. In particular, the printed surface of the foil may be arranged on a surface of the glass ply in which light is to be coupled in such that the printed dots are in contact with such glass ply for coupling out the light. In particular due to the small size and low surface coverage, the adherence strength between the glass ply and the EVA or PVB interlayer may remain sufficient.

An ink applied by either screen printing or inkjet printing or any other suitable technique, may be a white reflective ink to provide for the light-redirecting property. Further, a photoluminescent ink may be applied alternatively or additionally. Of course, the inkjet ink may be both reflective and photoluminescent. A photoluminescent ink may for example convert UV-light into visible light. Therefore, in a particular embodiment, at least two light sources may be provided: one light source outputting visible light that is reflected and one light source outputting UV light that is converted. Moreover, the light out-coupling pattern may be designed such that a certain light effect may be selectively obtained by suitable selecting one of the available light sources.

In an embodiment, the total dot surface area may be in a range from about <NUM>% to about <NUM>% and preferably in a range from about <NUM>% to about <NUM>% and more preferably in a range from about <NUM>% to <NUM>% of a total surface area of the transparent area. Using suitable light sources, in particular with respect to light output, it may suffice to further reduce the dot coverage of the transparent area. With a reduced coverage, the visibility of the dots is further reduced. It is noted that with sufficient intensity of light output by the light source, the coverage may be even further reduced in accordance with a desired light output of the out-coupling pattern.

In an embodiment, the dots are regularly arranged on the surface, wherein the dots are arranged at a spacing distance between adjacent dots. In particular, the spacing distance is more than <NUM> times the representative diameter, preferably more than <NUM> times the representative diameter and more preferably <NUM> times the representative diameter. Thus, low visibility of the pattern and correspondingly a high transparency is obtained.

In an embodiment, the light source comprises multiple LED's. For example, single LED's may be arranged regularly around a perimeter of the panel to provide a uniform light output over the transparent area. In another example, multiple LED's may be arranged at substantially the same position, wherein each LED may output a different colour of light, e.g. three LED's may output red, green and blue light, respectively. Thus, virtually any colour of light may be generated by controlling the light output per LED, as well known in the art. In general, using multiple LED's allows to provide for light effects.

In an embodiment, a dot coverage close to the light source is lower compared to the dot coverage farther away from the light source. As above indicated, a dot coverage is a ratio of a total dot surface area of all dots in a unit area over a total surface area of the unit area. With a higher dot coverage, more light is coupled out, while a lower dot coverage, less light is coupled out. Close to the light source, more light is available, while farther away from the light source, the amount of light is less. In order to achieve a uniform light output over the transparent area, the dot coverage close to the light source may be reduced and farther away from the light source, the dot coverage may be increased. Of course, it is noted that in another embodiment, another light effect may be desired and then a local dot coverage may be selected differently.

Further, in an embodiment, the panel may comprise an opaque area and a dot coverage in the opaque area may be higher than in the transparent area. In known transparent roof assemblies, the transparent area of the panel is surrounded by an opaque area, e.g. a black area provided by an enamel layer. Such an opaque area may, for example, be provided to cover functional elements of the open roof assembly or for any other reason. In such an opaque area, in view of the lack of transparency, the dot coverage may be relatively high and/or the dot surface area may be selected larger. Thus, in such an opaque area, the light output may be higher.

In a further embodiment, the panel may comprise an uncovered area wherein no dots are arranged. In particular, such an uncovered area may be provided adjacent to an edge of the panel where light is coupled into the panel by individual light sources, like LED light sources. In the uncovered area, very little or no light is coupled out, allowing the light from the individual light sources to mix and blend, preventing that the individual light sources are visible in the light image. For example, an array of individual LED's with three different colours, e.g. red, green and blue (RGB), may be provided and the uncovered area may be designed and arranged to allow the three colours to mix to white light before the light is out-coupled.

In an embodiment, the transparent roof assembly further comprises an image projector for projecting a light image, wherein the image projector is arranged to project the light image on the out-coupling pattern. Instead of switching on the light source, an image projector may be used to project an image or movie on the out-coupling pattern. Whereas the prior art patterns with relatively large dots were not suitable to provide for a sufficient image quality for viewing, the out-coupling pattern of the present invention provides for sufficient image resolution for showing a projected image or movie. The image projector may be position at any suitable location in a vehicle. For example, the projector may be arranged in a head rest of a driver seat or a passenger seat or, using suitable optics, even directly underneath the roof. Thus, compared to the course patterns of the prior art, the micro-dot pattern of the present invention is suitable for many more applications.

With the micro-dot pattern as a planar source of light, in an embodiment, the transparent roof assembly may be provided with a display layer and in particular with a liquid crystal display (LCD) layer. As a planar source of light, the micro-dot pattern is suitable as a source of backlight for the LCD display layer. Moreover, during daylight conditions, the LCD display layer may also be used as a means for filtering the light or for shielding against an excessive amount of light, thereby functioning as a sunshade.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description with reference to the appended schematical drawings, in which:.

It is noted that in <FIG>, the moveable panel 2a is in the open position.

The second roof opening 3b is arranged under the fixed panel 2b such that light may enter a vehicle interior space through the fixed panel 2b, presuming that the fixed panel 2b is a glass panel or a similarly transparent panel, for example made of a plastic material or any other suitable material. The second roof opening 3b with a transparent or translucent fixed panel 2b is optional and may be omitted in another embodiment of the open roof assembly.

<FIG> further illustrates a drive assembly having a first guide assembly 6a, a second guide assembly 6b, a first drive cable <NUM> and a second drive cable <NUM>. The first and second guide assemblies 6a, 6b are arranged on respective side ends SE of the moveable panel 2a and may each comprise a guide and a mechanism. The guide is coupled to the frame <NUM>, while the mechanism comprises moveable parts and is slideably moveable in the guide. The first and the second drive cables <NUM>, <NUM> are provided between the mechanisms of the respective guide assemblies 6a, 6b and a drive motor <NUM>.

The drive cables <NUM>, <NUM> couple the drive motor <NUM> to the mechanisms of the respective guide assemblies 6a, 6b such that upon operating the drive motor <NUM>, the mechanisms start to move. In particular, a core of the drive cable <NUM>, <NUM> is moved by the drive motor <NUM> such to push or pull on the mechanisms of the respective guides 6a, 6b. Such a drive assembly is well known in the art and is therefore not further elucidated herein.

In the illustrated embodiment, the drive motor <NUM> is mounted near or below the front end FE of the moveable panel 2a at a recess <NUM>. In another embodiment, the drive motor <NUM> may be positioned at any other suitable position or location. For example, the drive motor <NUM> may be arranged near or below the rear end RE of the moveable panel 2a or below the fixed panel 2b.

A control unit <NUM> is schematically illustrated and is operatively coupled to the drive motor <NUM>. The control unit <NUM> may be any kind of processing unit, either a software controlled processing unit or a dedicated processing unit, like an ASIC, as well known to those skilled in the art. The control unit <NUM> may be a stand-alone control unit or it may be operatively connected to another control unit, like a multipurpose, generic vehicle control unit. In yet another embodiment, the control unit <NUM> may be embedded in or be part of such a generic vehicle control unit. Essentially, the control unit <NUM> may be embodied by any control unit suitable for, capable of and configured for performing operation of the drive motor <NUM> and thus the moveable roof assembly.

The open roof assembly may further comprise an illumination system. <FIG> shows a prior art pattern of reflective dots that are arranged on a surface of the moveable panel 2a and/or the fixed panel 2b. In the prior art system, a light source <NUM>, e.g. an LED or an incandescent lamp or any other suitable light source, directs light into a light guide <NUM>, which may be cylindrical unit of transparent material. As known in the art, light may propagate through the light guide <NUM>. Due to total internal reflection at a boundary between the material of the light guide <NUM> and the surrounding air, the light is retained in the light guide <NUM>. Where the surface of the light guide <NUM> is not in contact with air, light may exit the light guide <NUM> or be reflected back into the light guide <NUM> at an angle such that the light may exit the light guide <NUM> at an opposite surface. With a known suitable configuration, the light originating from the light source <NUM> propagates through the light guide <NUM> and into a transparent panel on which the out-coupling pattern <NUM> is provided. For example, the out-coupling pattern <NUM> may be formed from a reflective paint or ink, e.g. a white paint or ink. As above mentioned, the dots of reflective paint or ink prevent total internal reflection of the light rays. Instead, the light rays impinging on the reflective dots reflect under another angle and are enabled to exit the transparent panel at the opposite surface. With a suitable configuration, it is thus enabled to direct the light from the light source <NUM> to the interior of a vehicle.

Section B of the out-coupling pattern <NUM> is shown in more detail in <FIG>. The out-coupling pattern <NUM> comprises the reflective dots <NUM> in a predetermined pattern. In particular, the reflective dots <NUM> are arranged at a lateral spacing distance 24a and a longitudinal spacing distance 24b, to either of which may be referred to as a spacing distance <NUM>. The spacing distance is the distance from a centre of a dot to the centre of an adjacent dot, commonly also referred to as the pitch.

In a particular embodiment, the lateral and longitudinal spacing distances 24a and 24b may be substantially equal. As used herein, the spacing distance <NUM> may refer to either of the longitudinal and lateral spacing distance 24a, 24b, as above mentioned, and, despite that only reference is made to the spacing distance <NUM> in general, the longitudinal and lateral spacing distances 24a, 24b may be equal or not. The person skilled in the art readily understands how to select and provide a suitable longitudinal spacing distance 24b and a suitable lateral spacing distance 24a in dependence of each other.

With reference to <FIG>, the spacing distance <NUM> may vary over the surface of the moveable panel 2a or fixed panel 2b. For example, in first area I, a relative small amount of relatively small dots may be present. In a second area II, more relatively small dots may be present, while in a third area III, the number of dots may be significantly larger and the size of the dots may be significantly larger. Of course, in an embodiment, the size of the dots in an area and the number of dots in such an area may be selected independently, albeit that an illumination effect will depend on, inter alia, both these aspects. So, in order to achieve a desired illumination effect, these aspects may be selected in dependence of each other.

As illustrated in more detail in <FIG>, in the first area I, the dots have a substantially square dot shape with a size of about <NUM> x <NUM>. A dot surface area of such dots is <NUM><NUM>. For ease of comparison herein, such dots are referred to as having a representative diameter of about <NUM> as a circular dot with a diameter of <NUM> has a same dot surface area of <NUM><NUM>. While the present invention is not limited to any kind of form or shape of the reflective dots, a representative diameter may be determined and assigned based on their dot surface area. With a spacing distance 24a, 24b of about <NUM>, there is one dot per area of about <NUM> x about <NUM>. Consequently, the dots locally cover about <NUM>/<NUM>,<NUM> = about <NUM> of the total surface area. Therefore, a total surface area coverage is about <NUM>%.

In the third area III, the reflective dots have an elongated rectangular shape of about <NUM> x <NUM> (<NUM><NUM>) with a spacing distance of <NUM>. Thus, the total surface area coverage is about <NUM>%. In the second area II, the total surface area coverage is about <NUM>%.

With an experimental setup, a luminance of the first, second and third area I, II and III have been measured:.

As apparent from Table <NUM>, the measured luminance is not proportional to the total surface area coverage (column: "Coverage"). Of course, in this prior art embodiment, the third area III with the highest total surface area coverage is arranged closest to the light guide <NUM>. Inevitably, the highest luminance may be expected in the third area III due to both the smallest distance to the light guide <NUM> and the highest total surface area coverage of the out-coupling pattern <NUM>.

It is noted that the size of the dots of the prior art embodiment of <FIG> is relatively large. This relatively large size provides for dots clearly lighting up, when the light source <NUM> is switched on. Further, the relatively small total surface area coverage in the first area I provides for a view to the outside. On the other hand, due to the size of the dots, the dots remain individually clearly visible, even in the first area I. Moreover, due to the number of the relatively large dots, a view to the outside is limited in the third area.

<FIG>shows a photograph of a glass panel <NUM> having four areas (a)-(d). Each area (a)-(d) is provided with an out-coupling pattern according to the present invention. The out-coupling patterns of areas (a)-(d) comprise dots having a representative diameter of about <NUM> micrometer and are formed from white screen print ink by screen printing on a surface of the glass panel <NUM>. The dots are arranged on a Cartesian grid, although the present invention is not limited with respect to the grid. The dots may be arranged uniformly on a regular grid, like a Cartesian grid, or may be arranged in accordance with any other regular or irregular grid. The areas (a)-(d) vary in the spacing distance between the dots as illustrated also in <FIG>:.

In the photograph, the glass panel <NUM> is arranged substantially vertically on a table. There is only ambient light; there is no light coupled into the glass panel <NUM>. A relatively large amount of light is incident on the front of the glass panel <NUM>, due to which the reflective dots reflect a significant amount of light resulting in a greyish appearance. Still, as apparent at least for areas (b), (c) and (d), the background is clearly visible through the glass panel <NUM>. For area (a) it is noted that the uniform dark background of the table top results in an appearance of a white surface. In practice, however, in a relatively dark interior of a vehicle and relatively light exterior, the white appearance diminishes.

<FIG> shows a photograph of two glass panels <NUM> with a total of eight areas (1a)-(1d) and (2a)-(2d). The areas (2a)-(2d) correspond to the areas (a)-(d), respectively, as shown in and described in relation to <FIG>and <FIG>. The areas (1a)-(1d) have an out-coupling pattern similar to the areas (a)-(d), respectively, as described in Table <NUM> hereinabove and shown in <FIG>. However, while the areas (2a)-(2d) have been formed with an opaque white ink, the areas (1a)-(1d) have been formed with a semi-transparent white ink. A part of light incident on the semi-transparent dots may pass through the semi-transparent ink, while another part of the incident light will be reflected. The ratio of passing light and reflected light depends, inter alia, on the specific properties of the ink and a thickness of the dots. While a semi-transparent ink reflects less light per unit area compared to an opaque white ink, it may provide a more transparent appearance during daytime, when looking through the transparent panel to the exterior surroundings.

In <FIG>, there is no ambient light, but light is provided through a light guide (cf. <FIG>) into the glass panel <NUM>. The areas (1a) - (1d) and (2a)-(2d) light up due to the out-coupling of the light by the out-coupling patterns. Referring to the first glass panel <NUM> with areas (1a)-(1d) with semi-transparent ink, one area (1a) reflects a significant amount of light, while the other three areas (1b)-(1d) reflect less light. The areas (2a)-(2d) on the second glass panel <NUM> are all clearly lit up. Even the least dense area (2d) with opaque white ink provides more light output than the densest area (1a) with semi-transparent ink. So, depending on application and desired appearance, a semi-transparent or an opaque ink may be used.

For comparison reasons, the actual luminance of the glass panel <NUM> with the semi-transparent ink has been measured for three sub-areas (cf. <FIG>: I, II, III) for the brightest area (1a):.

The luminance of the densest out-coupling pattern of semi-transparent ink is comparable to the luminance of the prior art out-coupling pattern despite the fact that the average total surface area coverage is significantly lower (<NUM>% vs. <NUM>%).

In <FIG>, a graph (solid line) of an average luminance of each of the four out-coupling patterns (1a) - (1d) of <FIG> is shown. For each out-coupling pattern (1a) - (1d) of <FIG>, a minimum local luminance, a maximum local luminance and an average luminance is determined. The luminance is determined for each out-coupling pattern (1a) - (1d) with each out-coupling pattern (1a) - (1d) arranged close to the light guide <NUM>. The corresponding measurement data are shown in Table <NUM>. <FIG> further shows a trend line (dashed line) based on the measured average luminance.

Based on the measurement data, it has appeared that the luminance of the different out-coupling patterns <NUM> of the panel <NUM> is not proportional to the total surface area coverage of the out-coupling pattern <NUM>. Instead, with a decreasing total surface area coverage, the luminance appears to decrease less than proportional. So, the luminance resulting from a less dense out-coupling pattern appears higher than what was expected. This enables to reduce the total surface area coverage more than would have been expected on an assumption of a proportional dependency of the luminance on the total surface area coverage.

It is noted that in the prior art embodiment of <FIG>, an opaque pattern is used, while in the embodiment used to obtain the data of Tables <NUM> and <NUM> a semi-transparent ink is used. Thus, in an embodiment of the present invention having semi-transparent ink dots, with outside day light, the view is not obstructed and a clear view is provided, while a same amount of light is output into the interior of the vehicle, when the light source is switched on, as compared to the prior art embodiment having relatively large dots. Further, with an opaque ink instead of a semi-transparent ink, the luminance is further increased (cf. <FIG>) allowing to further reduce the total surface area coverage without reducing the luminance.

<FIG> shows a cross-section of a multi-layered glass panel <NUM> for use in an open roof assembly according to the present invention, wherein an exterior glass panel <NUM> and an interior glass panel <NUM> are attached by an interlayer <NUM>. Such an interlayer is known in the art. For example, the interlayer <NUM> may be formed of EVA or PVB. Other materials are known and suitable as well.

At a side edge of the interior glass panel <NUM>, a light source <NUM> is provided. The light source <NUM> may be any light source suitable for coupling light <NUM> into the interior glass panel <NUM> through its side edge. For example, known light sources are LED's directing light directly into the side edge of the interior glass panel <NUM> or, alternatively or additionally, an elongated, side-emitting light guide arranged next to the side edge of the interior glass panel <NUM> (cf.

As hereinabove also described in relation to <FIG> but shown in more detail in <FIG>, an out-coupling pattern <NUM> is provided at a surface of the interior glass panel <NUM>. In particular, the out-coupling pattern <NUM> is arranged at an interface between the interior glass panel <NUM> and the interlayer <NUM>. As shown, a ray of light <NUM> propagates through the interior glass panel <NUM> and may impinge on a dot of the out-coupling pattern <NUM>. Upon impingement, the ray of light <NUM> is at least partly reflected and reflected light rays <NUM> are enabled to leave the interior glass panel <NUM> at an opposite surface of the interior glass panel <NUM> and is thus emitted into an interior passenger compartment <NUM> of a vehicle.

<FIG> show a first and a second embodiment, respectively, for manufacturing the multi-layered glass panel <NUM> of <FIG>. In the first embodiment of <FIG>, the out-coupling pattern <NUM> is provided on a surface of the interlayer <NUM>. The surface with the out-coupling pattern <NUM> thereon is then attached to a surface of the interior glass panel <NUM>, e.g. by application of heat and pressure in an autoclave. Due to the low area coverage and small dots of the pattern <NUM> there remains sufficient surface area of the interlayer <NUM> to be attached to the interior glass panel <NUM>.

The interlayer material may be a flexible foil and the out-coupling pattern <NUM> may be provided on the interlayer material by a simple processing technique, e.g. inkjet printing. Since the flexible foil may for example be stored on a roll, the flexible foil may be provided with the out-coupling pattern <NUM> using a common roll-to-roll inkjet printer.

For vehicle roofs, the multi-layered glass panel <NUM> usually is curved in two dimensions. When printing on the flat foil of interlayer material, the printed pattern may be adapted and prepared to the required stretching of the interlayer foil when the foil is provided on the curved interior glass panel <NUM>. For example, for achieving a pattern of dots aligned on a rectangular grid, as e.g. shown in <FIG>, the dots of the out-coupling pattern <NUM> as printed on the flat foil will need to be positioned on a different, non-rectangular grid. The non-rectangular grid is in such embodiment determined in accordance with the expected stretch and will, after stretch on the interior glass panel <NUM>, be substantially rectangular.

In another embodiment the out-coupling pattern <NUM> is applied directly on the interior glass panel <NUM>. A suitable technique is screen printing, although other techniques may be used as well. For example, inkjet printing may be applied.

Applying the out-coupling pattern <NUM> on the interior glass panel <NUM> may be performed prior to or after bending of the interior glass panel <NUM>. Prior to bending, the interior glass panel <NUM> is a flat glass plate, which eases the application of the out-coupling pattern <NUM> and many techniques can easily be used. Still, there may be a risk of damaging the printed out-coupling pattern <NUM> upon bending the interior glass panel <NUM>.

After bending, it may become more challenging to apply the out-coupling pattern <NUM>. For example, using inkjet printing, a robotic arm may follow the curved contours of the surface of the interior glass panel <NUM>, while applying the pattern <NUM>, or the curved interior glass panel <NUM> may be temporarily flattened on a table, e.g. a suction table, which is suitable for using screen printing.

<FIG> shows an embodiment of a multi-layered glass panel <NUM> for use in an open roof assembly according to the present invention, wherein further a first and a second functional layer 108a and 108b are introduced compared to the embodiment of <FIG>. In this embodiment, between the exterior glass panel <NUM> the interlayer <NUM>, the first functional layer 108a is provided. The first functional layer 108a may essentially be any functional layer. For example, a switchable sun-shading layer like an electrochromic layer, SPD layer or PDLC layer may be provided to control an amount of exterior light passing through the multi-layered panel <NUM>. The first functional layer 108a may, alternatively or additionally, comprise a passive layer such as an infrared-light filtering layer, as known in the art.

The second functional layer 108b is provided on an interior side of the interior glass panel <NUM>. Thus, light coming from the light source <NUM> and redirected by the out-coupling pattern <NUM> into the vehicle interior passes through the second functional layer 108b. This second functional layer 108b may therefore be a functional layer that uses this light. For example, the second functional layer 108b may be a display layer and in particular a liquid crystal display (LCD) layer. As a planar source of light, the micro-dot out-coupling pattern <NUM> is suitable as a source of backlight for such a LCD display layer. Moreover, during daylight conditions, the LCD display layer may also be used as a means for filtering the light or for shielding against an excessive amount of light, thereby functioning as a sunshade, in addition to or as an alternative for the first functional layer 108a.

As apparent to those skilled in the art, the first and the second functional layers 108a, 108b may provide for any other function as well, wherein each functional layer may be an active layer or a passive layer.

It is noted that in this embodiment of <FIG>, two additional functional layers 108a, 108b have been shown and described. As apparent to those skilled in the art, more functional layers may be added or either one of the shown functional layers 108a, 108b may be omitted, depending on the desired functionality of the multi-layered glass panel <NUM>.

<FIG> illustrate a further embodiment, wherein an uncovered area <NUM> is provided between an array <NUM> of individual light sources 111A - 111D, such as e.g. LED's, and an out-coupling pattern <NUM>. As shown in <FIG>, the individual light sources 111A - 111D each emit a respective bundle of light 112A - 112D having a bundle angle α. Only after a predetermined distance d, adjacent individual bundles overlap. Hence, over the distance d, individual bundles can be visible. To reduce the visibility thereof, no out-coupling dots are provided in the uncovered area.

The distance d is dependent on a distance between the individual light sources 111A - 111D and the bundle angle α, for example. Moreover, a distance for the light to become uniform may be larger than the distance d. Therefore, as apparent to those skilled in the art, a width of the uncovered area, i.e. a distance between the individual light sources 111A - 111D and the out-coupling pattern <NUM> may be suitably selected dependent on the requirements, wherein also other aspects may be considered such as the distance between the individual light sources 111A - 111D.

In a particular embodiment, the individual light sources 111A - 111D may have different colours. For example, the light sources 111A - 111D may have three colours like red, green and blue (RGB). Mixing the colours RGB leads to white light. The uncovered area may be designed and arranged such that the out-coupling pattern <NUM> is arranged at a distance where the three colours are mixed to white light. Then, depending on which light sources 111A - 111D are switched on, the colour of light out-coupled may be varied without the separate different colours of the light sources 111A - 111D being locally visible close to the individual light sources 111A - 111D.

<FIG> shows a first embodiment of the present invention, wherein a moveable or fixed panel <NUM> of an open roof assembly is provided with a transparent area <NUM> and a first light guide 22a and a second light guide 22b. In the transparent area <NUM>, a uniform out-coupling pattern, e.g. cf. <FIG>, is provided in accordance with the present invention, i.e. with relatively small dots and a low total surface area coverage. When both light guides 22a, 22b are lit up by a suitable light source (not shown), a light spread as shown in <FIG> is obtained (see also Table <NUM> above). Close to the light guides 22a, 22b a relatively large amount of light is coupled out, while in a centre part of the transparent area <NUM> significantly less light is coupled out.

<FIG> illustrate a second embodiment of the present invention, wherein the light is provided by light sources <NUM>, e.g. LED's, directly into the panel <NUM>. Individually addressable light sources <NUM> and/or providing light sources <NUM> along each edge of the panel <NUM> allow to provide for a light pattern in the transparent area <NUM>. For example, with more intense light output (indicated by larger blocks) from the light sources 21a directed at a centre of the transparent area <NUM> and less intense light output (indicated by smaller blocks) from the light sources 21b arranged near a corner of the panel <NUM>, a star-like light pattern is obtainable as shown in <FIG>. Many other patterns may be obtained as apparent to those skilled in the art.

Other light effects may be obtained by adapting the local total surface area coverage of reflective dots. For example, as shown in <FIG>, the panel <NUM> may comprise a transparent area <NUM> and an opaque area <NUM>. In the already opaque area <NUM>, a total surface area coverage may be relatively high such to obtain a significantly higher luminance as shown in <FIG>. Moreover, as shown in e.g. <CIT> (see e.g. Fig. <NUM>), a light source <NUM> may be provided in a recess in a transparent panel. Arranging a light source <NUM> at a boundary between the transparent area <NUM> and the opaque area <NUM> may provide a suitable configuration. In a particular embodiment, at least two light sources <NUM> may be provided in such a recess at said boundary such that it may be selected which of the transparent and opaque areas <NUM>, <NUM> is lit up. Of course, the light source may be provided in such a recess in any other embodiment as well and is thus not limited to an embodiment having a transparent area and an opaque area.

In an embodiment, the local total surface area coverage may be adapted to obtain a more uniform light image. In such embodiment, the total surface area coverage near the light source may be kept low, while farther away the local total surface area coverage may be increased.

<FIG> illustrates a further application of the out-coupling pattern according to the present invention. <FIG> shows the glass panel <NUM> of <FIG>, wherein in day light conditions an image is projected on the out-coupling pattern by a common beamer device. A difference in the amount of reflected light per area due to the differences in total surface area coverage is clearly visible in a difference in contrast in the image. A projecting device may be arranged in a vehicle for projecting images or movies on the transparent area <NUM> of the opaque area <NUM>, if any. These may be projected as entertainment, but may as well be used in a more functional way. For example, warning signals may be projected.

In general, either by use of a projector or by suitable light sources such as individually addressable LED's, e.g. red, green and blue LED's, the open roof assembly according to the present invention may be used to generate a certain ambiance in the interior of the vehicle. For example, on a hot day, blue light may be created which results in a cool feeling, while on a cold day, more reddish light may be provided. Colours of the light may also be used for keeping the driver awake (blue light) or warn the driver for upcoming traffic, when coupled to a navigation system, by creating an alerting ambiance (red/yellow), for example.

More effects and/or light output increase without affecting a transparency of the panel <NUM> may be achieved by e.g. using not only reflective dots. For example, the dots may be formed of a photoluminescent ink. In particular, a fluorescent white ink may be applied and a suitable light source, e.g. an UV light source, may be used additionally or alternatively.

Further, it is noted that the actual luminance is dependent on the light output of the light source. Using multiple LED's along the panel <NUM> may be expected to provide for more light output compared to an embodiment with only a single light source and light guide. It is however noted that in an embodiment with a light guide, multiple light sources may be used as well, e.g. with aid of a branched/forked light guide with multiple light sources directing light into the light guide. Further, the light source may have a selectable light output (dimmable) in order to provide for the possibility to adapt the light output. It has been shown that with high intensity light sources such as suitable LED's, the total surface area coverage of the dots may be further reduced, while maintaining sufficient light output. In particular, a total surface area coverage of dots of opaque white ink may be reduced to about <NUM>% or even less.

Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in expectedly any appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any advantageous combination of such claims are herewith disclosed.

Claim 1:
A transparent roof assembly for a vehicle roof (<NUM>), the roof assembly comprising
• a panel (<NUM>) having a transparent area (<NUM>), the panel being configured to be arranged over an opening (3a, 3b) in the vehicle roof to allow visible light to pass in a first direction through the transparent area, the first direction extending between an interior of the vehicle and an exterior of the vehicle and substantially perpendicular to a surface of the panel;
• a light source (<NUM>) arranged to provide light in the panel in a second direction, wherein the second direction is substantially perpendicular to the first direction;
• an out-coupling pattern (<NUM>) arranged on the surface of the transparent area of the panel, the out-coupling pattern comprising reflective dots (<NUM>) of a light-redirecting material, such as a reflective paint or ink, for example an opaque or semi-transparent white ink, for out-coupling of light propagating in the panel, each reflective dot having a dot surface area;
wherein a total dot surface area of the reflective dots of the out-coupling pattern equals a sum of the dot surface area of all reflective dots arranged on the surface of the transparent area and wherein the total dot surface area is smaller than <NUM>% of a total surface area of the transparent area;
characterized in that the reflective dots each have a representative diameter of <NUM> microns or less, wherein the representative diameter of a reflective dot corresponds to a diameter of a circle having a same surface area as the dot surface area of said reflective dot.