EP4314636A1

EP4314636A1 - Decorative part with a planar light guide

Info

Publication number: EP4314636A1
Application number: EP22703909.6A
Authority: EP
Inventors: Hubert Bieder; Eva-Susanne Jaeger; Daniel Betz
Original assignee: Mercedes Benz Group AG
Current assignee: Mercedes Benz Group AG
Priority date: 2021-03-23
Filing date: 2022-01-27
Publication date: 2024-02-07
Also published as: CN116964378A; DE102021001512B4; WO2022199907A1; KR20230141831A; DE102021001512A1; JP2024511150A

Abstract

The invention relates to a planar light guide (1) comprising at least three layers (3, 4, 5, 7), wherein two layers embodied as films (4) have a lower refractive index than a light guiding layer (3) arranged therebetween, one of the films (4) having output coupling structures (6) for the light. The invention is characterized in that the layers (3, 4, 5, 7) form a film composite (2) with the light guiding layer formed therein as a film (3). In addition, the invention relates to a luminous element comprising such a planar light guide (1) and a coupled input coupling light guide (8). Furthermore, a decorative part (10) is specified in which a light source comprising illuminants (14, 16) and the input coupling light guide (8), said light source being coupled to the planar light guide (1), is arranged in such a way that a surface portion is actively illuminated and a surface portion that is not transmissive to light conceals the light source and the coupling, as seen from a viewing direction (B).

Description

Decorative part with a surface light guide

The invention relates to a decorative part with a flat light guide for actively illuminating a surface section according to the type defined in more detail in the preamble of claim 1.

Flat light guides are known in principle from the prior art. DE 102019001 333 A1 describes a lighting device with such a flat light guide. This is formed from two foils which are connected to the actual light guide by injecting the material from this light guide, for example polycarbonate, between the two foils with a lower refractive index than that of the light guide. The entire structure can thus be relatively flat with a component thickness of just a few millimeters, typically 3 or more millimeters. However, it does not allow any significant flexibility. Even structures thinner than the 3 mm mentioned are not realistic given the dimensions typically required for injection molding.

DE 102014 006490 B4 claims a planar lighting element with a light source and a planar light guide as well as a transparent film, with the film and the light guide being made of materials with different refractive indices and the light guide being produced by back-injection molding of the film, i.e. similar to the status mentioned above the technology is trained.

US 2007/0 133 935 A1 describes a flexible optical element with a waveguide. DE 102019202 804 A1 describes a light guide film that can be used in a film composite. DE 102013 021 600 A1 also describes a surface light which is made up of different layers. The core is in each case a transparent support structure, which is combined with a light guide made of foils, so that the support structure is formed with a lower refractive index than the foil of the actual light guide. This can also be closed off by a further film with a lower refractive index and decoupling structures in order to decouple light through the transparent carrier structure.

A similar structure with light coupling through a coupling element or a light guide made of optical fibers is described in WO 2007/077 099 A1,

DE 102019 112 889 A1 and DE 102013 010 163 A1 both describe light guide foils which can be arranged on vehicle windows.

These last-mentioned structures are not very flexible and are relatively bulky, particularly with regard to their thickness.

An illuminated decorative part is known from DE 102014 112 470 A1. In this case, light beams generated by a light source are coupled into a composite film with a light-guiding layer. A very similar decorative part is also known from US 2021/0 055 567 A1.

For further prior art, reference can also be made to US 2006/0 002 675 A1 and EP 2 157 366 A1. These come from the field of lighting or backlighting of screens and also show thin light-guiding layers.

The object of the present invention is therefore to specify an improved decorative part with a flat light guide for actively illuminating a surface section.

The decorative part according to the invention with a flat light guide for actively illuminating a surface section and with at least one light source arranged on the front side of the flat light guide now provides that the light source has at least one illuminant connected directly or indirectly to the flat light guide comprises, which is arranged concealed behind a non-translucent surface section in a direction of view of the decorative part and is connected to the flat light guide. In such a decorative part, the arrangement and coupling of the light source is thus arranged in particular in an area behind a section that is not transparent to light. This section, which is designed as an opaque surface section of the decorative part, thus covers the light coupling into the flat light guide as well as the light source itself Its actively illuminated surface enables an extraordinarily homogeneous and even coloring that is easy to design, which allows a great deal of design freedom with a high quality impression either directly or via a corresponding transparent decor placed in front of it.

The flat light guide of the decorative part according to the invention comprises three layers comparable to the light guide described in the prior art mentioned at the outset, with two layers designed as foils having a lower refractive index than a light guide layer arranged between them. One of the foils also has decoupling structures for the light, similar to those described in the prior art mentioned at the outset. According to the invention, the layers form a composite film in which the light guide layer is also formed as a film. Such a structure, in which the hitherto always made of a solid material, for example a flat material made of polycarbonate or the like or made of such a material produced by injection or back injection, always has a relatively large thickness of typically at least 3 to 5 mm due to the principle and relatively low flexibility. The construction according to the invention from the three foils, which form a foil composite, with the two outer foils having a lower refractive index than the light guide foil in the middle, avoids all these disadvantages. The result is an extraordinarily compact structure, which is easy to implement in practice with a thickness of significantly less than one millimeter, in particular approximately 0.5 mm, of the film composite.

The films of the planar light guide are co-extruded, so that simple and efficient production is possible. The films themselves can, for example, consist of two Polymethyl methacrylate (PMMA) films are made, between which a film made of polycarbonate (PC) is inserted as a light-conducting layer. The entire structure can be produced simply and efficiently by coextrusion with a very small layer thickness and high mechanical strength in relation to the layer thickness.

The light source is formed in the decorative part according to the invention by a coupling light guide with at least one integrated light source. Of course, this is of particular advantage when the flat light guide consists of a composite film. In particular, the flat light guide and the coupling-in light guide can together form a lighting element.

According to an advantageous development of the decorative part according to the invention, it can also be provided that the composite film is provided with a protective layer on one or both sides. This protective layer can in turn be a film, for example a further polycarbonate film, but it can also be a lacquer or the like. In a structure in which the flat light guide or its composite film made up of the three layers is further processed directly, for example by spraying or injection-molding a decoration on one side and a transparent or, in particular, non-transparent carrier on the other side, the protective layers can of course also be dispensed with.

A lighting element of the decorative part according to the invention can comprise such a planar light guide as has just been described, as well as a light guide of greater thickness coupled to the composite film. The thickness relates to the comparison to the light-conducting film of the film composite. This light guide, which in particular is not formed from a film, is used to couple the light into the light-guiding layer of the planar light guide, which is designed as a film.

According to an advantageous development, it can therefore be provided that this light guide of greater thickness is coupled to at least one light source. The coupling can be implemented, for example, on a strip made of polycarbonate in such a way that one or more light sources, in particular LEDs, can be mechanically coupled to the structure. The bulbs, and possibly a Control electronics for these can, however, also be directly integrated into this light guide of greater thickness, for example injected.

This light guide of greater thickness, which could also be referred to as a coupling light guide, has the task of capturing the light emitted by the lamps and, especially if different colors are used, to homogenize this light within its overall length before it is introduced into the light-conducting film as Light guide layer takes place. This means that the light yield of the lamps can be used ideally, which would not be directly possible with the film due to its thinness. In addition, multicolored light always requires a certain running length of the light within a light guide until a homogeneous color mixture is created, so that this can also be achieved within the larger light guide before the then homogeneous light is coupled into the corresponding light guide layer of the flat light guide. The light guide with a greater thickness can be glued or welded to the composite film, or it can also be molded directly onto it. In this case, this light guide can be conventional, for example made of a single material such as polycarbonate, which is surrounded by an air gap in order to achieve the light-conducting properties, namely total reflection at the interfaces between the material of the light guide and the air. As an alternative to this, it can also be provided that this light guide of greater thickness is surrounded by a coating made of a material with a lower refractive index. This material can, for example, in turn be a film made of PMMA or the like, so that in principle a structure of the light guide of greater thickness can be provided in the form of DE 102019 001 333 A1 from the prior art mentioned at the outset. Alternative coatings, for example paints or the like, are of course also conceivable.

A further very advantageous embodiment of the decorative part according to the invention can now also provide that the flat light guide is connected to a carrier and a decoration by co-extrusion, calendering and/or back-injection molding. This structure made up of carrier, decoration and flat light guide can then be injection-molded onto the non-light-conducting surface section and the light source or, conversely, these can be injection-molded onto the structure. All in all, this results in an extraordinarily compact and efficient decorative part, particularly when the flat light guide is designed as the composite film described above. Inside the light guide are the components then very easily and efficiently connected to each other, so that even over a longer period of use, when the decorative part is used in a vehicle, for example, despite the vibrations that occur and the unavoidable movements of parts against one another in a vehicle, there is a stable structure that does not creak and in which individual Parts cannot hit each other.

The planar light guide according to the invention, the lighting element according to the invention and the decorative part according to the invention offer further advantages and configurations, which result in particular from the exemplary embodiments which are described in more detail below with reference to the figures.

show:

1 shows a basic representation of a possible embodiment of a flat light guide;

2 shows a basic section through a possible decorative part according to the invention with a first embodiment of a lighting element;

Fig. 3 shows a principle section through a possible decorative part according to the invention with a further embodiment of a lighting element; and

Fig. 4 different ways of connecting the light source to a light guide.

In the representation of FIG. 1, a possible structure of a flat light guide 1 made of a film composite 2 is shown in principle. The film composite 2 consists of at least three films. A central light-guiding layer is designed as a light-guiding film 3 . It is implemented, for example, as a polycarbonate film. This light guide foil 3 is enclosed by two foils 4, 5 with a lower refractive index than that of the light guide foil 3. The two foils 4, 5 can be made of PMMA (polymethyl methacrylate), for example. One of these two foils, foil 5 here in the illustration in FIG. These decoupling structures 6 can, for example, by a ground surface, by a Structures introduced by laser processing can be realized via structures printed by screen printing or the like. In particular, they can be adapted to a later curvature or the like of the planar light guide 1 in order to achieve a uniform and homogeneous light output independently of the three-dimensional geometric design of the later structure. The direction in which the light is coupled out is at the top in the illustration in FIG.

The structure described here, consisting of the three films 3, 4, 5, is completely sufficient for the actual film composite 2 of the planar light guide 1. Depending on the further processing, this structure can be realized with injection-moulded decorative layers, injection-moulded support layers or the like. In particular, the structure can also be placed in a corresponding injection molding tool and shaped three-dimensionally before it is completed by back-injection molding with a carrier layer and/or the application of a decorative layer on the upper surface from viewing direction B and is cured in the shape specified by the tool.

Irrespective of this, it is possible, in addition to the three layers 3, 4, 5 mentioned, to also integrate two protective layers 7, for example in the form of thin polycarbonate films, into the film composite 3. This optional configuration can be seen in the illustration in FIG. 1, in which case, as mentioned, the two protective films 7 could also be omitted. Depending on the structure, only one of the two protective films 7 can be provided, for example only on the visible side if a carrier is molded on the opposite side.

In contrast to a structure that can be produced purely by injection molding of the light guide, for example the structure mentioned in the prior art mentioned at the outset, in which the light guide is injected between two PMMA films, it is possible here to produce the entire composite film 3 by coextrusion and this with it to be made much thinner. In practice, the film composite 3 shown as an example in FIG. 1 has a thickness of less than 1 mm. By dispensing with one or both protective layers 7, the thickness of the structure can be further reduced, so that, for example, a functional, flat light guide can be made from the three Foils 3, 4, 5 can be realized with a layer thickness of about 0.5 mm. The enclosed light-guiding layer of the light-guiding foil 3 is somewhat thicker than the respective layer thickness of the adjacent PMMA foils 4, 5, as is also indicated approximately to scale in the illustration in FIG.

In principle, it is conceivable for light to be coupled into such a film composite 2 from the front side. In practice, however, this is very difficult because even small light sources such as micro-LEDs have a certain size and width and because they emit their light in particular at an angle of typically around 120°. With a direct connection to the end face of the film composite 2, a not inconsiderable part of the light would therefore be lost.

The film composite 2 of the planar light guide 1 can therefore preferably be combined with a coupling-in light guide 8 with greater thickness. This is shown in principle in the following representation of FIG. The structure shown there includes a decorative part 10 which has a flat light guide 1 . This is made up of the film composite 2, in particular with the three films 3, 4, 5, whereby in the illustration in Figure 2 of this film composite 2 only the decoupling structures designated 6 are shown again, in order to show the alignment of the film composite 2 of the planar light guide 1 to make recognizable in the representation of Figure 2. The direction of light is directed upwards here, the line of sight B accordingly from top to bottom onto the decorative part 10. This consists of a plastic carrier 11 and a decorative panel, for example made of polycarbonate, wood, aluminum or the like. This is backlit by the light coupled out by the planar light guide 1 against the viewing direction B. The surface section 12 that is transparent to the light is also adjoined by an opaque surface section, which is designated here by 13 and is shown with correspondingly changed hatching. This section 13 is impermeable to light and therefore, viewed from the viewing direction B, hides the components lying behind it in the viewing direction B. In the exemplary embodiment illustrated here, these are the in-coupling light guide 8 with the greater thickness, which is designed as a conventional light guide and has corresponding out-coupling structures 9 in a manner known per se. This decoupling light guide can be realized, for example, molded onto the film composite 2 of the planar light guide 1, so as light, which in the Light guide 8 is coupled via lamps shown later, pass on in the flat light guide. From viewing direction B, the structure of the light guide 8 and its connection to the film composite 2 is below the non-translucent surface area, so that the coupling of the light and its transmission are not visible through the translucent section 12 of the decorative panel. The decorative part 10 can therefore be realized with a homogeneous illumination of its actively illuminated surface section 12 through the composite film 2 of the planar light guide 1 without the typically inhomogeneously illuminated area of the light coupling point becoming visible.

The conventional light guide 8 serves to collect the light from the individual light sources and, due to its greater thickness, can collect the light from these light sources very well, so that a large part of the light reaches the conventional light guide 8 and, via this, the planar light guide 1. In addition, different colored light sources or light sources that are able to generate different colors, for example RGB LEDs, can be used. Due to the size of the conventional light guide 8, there is a sufficient path for the light to travel so that the colors mix sufficiently and a homogeneous light color reaches the area of the flat light guide 1.

In the exemplary embodiment shown here, the conventional light guide 8 is surrounded by air, so that if it is made of a material such as polycarbonate, it is sufficient. The air surrounding it then forms the environment with a lower refractive index than that of the polycarbonate, so that the light-guiding effect is achieved accordingly and the light can be coupled largely completely into the composite film 2 of the flat light guide 1 .

An alternative configuration can be seen in the illustration in FIG. This largely corresponds to the representation shown in FIG. However, it is the case here that the conventional light guide 8 is molded onto the structure of the film composite 2 on the one hand and onto the structure of the decorative part 10 on the other hand. Here the structure is formed, for example, with the surface section 13 that is impermeable to light being sprayed. To the property of a light guide in such a molded or in particular fully injected structure, in which the plastic carrier 11 still surrounds the conventional light guide 8, which would also be conceivable here, the conventional light guide 8 must be provided with a corresponding coating made of a material with a low refractive index. It can, for example, be surrounded by a film made of PMMA or coated with a corresponding paint with low-index properties.

Otherwise, what has already been described in connection with FIG. 2 applies analogously to the structure shown in FIG.

Finally, in the illustration in FIG. 4, three different possibilities for coupling light into the conventional light guide 8 are shown. In the illustration in Figure 4a, several light sources 14, here RGB LEDs, are mechanically coupled to the structure of the light guide in order to supply it with light over a corresponding area and to pass on the light according to the arrow marked 15, in particular to the molded film composite 2 .

An alternative structure is shown in the illustration in FIG. 4b. Instead of several small lamps 14, as shown in FIG. 4a, two larger lamps 16 are each arranged on the end faces of the conventional light guide 8 and couple the light. The light can then be coupled out of the conventional light guide 8 upwards or downwards or towards or away from the viewer, for example, via outcoupling structures not shown here.

A further variant of the conventional light guide 8 can also be seen in the illustration in FIG. 4c. The lighting means 14 are again designed as smaller LEDs than in the illustration in FIG. 4b. Unlike in the previous figures, they are injected directly into the material of the light guide 8, for example into the polycarbonate. Of course, this structure would also be conceivable with larger lamps in the area of the end faces as a supplement or as an alternative to the structure shown here. Likewise, the light coupling of FIGS. 4a and 4b could be combined with one another. In addition, it would also be conceivable to couple light accordingly to the conventional light guide 8 on the one hand via injected lighting means 14, 16 and on the other hand additionally via further lighting means 14, 16 that are merely coupled.

Claims

patent claims

1. Decorative part (10) with a flat light guide (1) for actively illuminating a surface section (12) and with at least one light source arranged on the end face of the flat light guide (1), the flat light guide (1) having at least three layers (3, 4 , 5, 7), wherein two layers designed as foils (4) have a lower refractive index than a light-conducting layer (3) arranged between them, wherein one of the foils (4) has decoupling structures (6) for the light, and wherein the layers

(3, 4, 5, 7) form a composite film (2), in which the light-guiding layer (3) is designed as a film (3), the light source having at least one illuminant (14, 16 ), wherein the light source is arranged concealed behind a non-translucent surface section (13) in a viewing direction (B) onto the decorative part (10) and is connected to the flat light guide (1), characterized in that the foils (3, 4 , 5, 7) are coextruded, and that the light source is formed by a coupling light guide (8) with at least one integrated light source (14, 16).

2. Decorative part (10) according to claim 1, characterized in that the film composite (2) has a thickness of less than 1 mm.

3. decorative part (10) according to claim 1 or 2, characterized in that the composite film (2) is provided with a protective layer, in particular a protective film (7), on one or both surfaces.

4. Decorative part (10) according to one of Claims 1 to 3, characterized in that the flat light guide (1) and the coupling light guide (8) have a lighting element made of the flat light guide (1) and a light guide coupled to the film composite (2). (8) greater thickness.

5. Decorative part (10) according to claim 4, characterized in that the light guide (8) of greater thickness is glued, welded or molded onto the film composite (2).

6. Decorative part (10) according to one of Claims 1 to 6, characterized in that the flat light guide (1) is connected to a carrier (11) and a decoration (12) by coextrusion, calendering and/or back-injection molding, with this structure with a flat light guide (1), the carrier (11) and the translucent decoration (12) is sprayed onto the non-translucent surface section (13) and the light source or these are sprayed onto the structure.