Functional display and related assembly method

Abstract

The invention relates to a functional display (1) for selectively displaying a plurality of symbols representing a switch function and / or representing at least two switch states, comprising: a stack of light pipes, which, given the intended attachment of the functional display (1), forms a display surface (8) facing an observer (B); wherein the stack of light pipes is composed of at least two transparent or semi-transparent planar light pipes (2, 3), which are arranged in an overlapping manner along the stacking direction, and the planar light pipes (2, 3) are arranged to be separated by a transparent or semi-transparent layer, which is composed of a material that is optically thinner than adjacent light pipes (2, 3), preferably an air gap (14), so that the light pipes (2, 3) each have a main surface (H) facing the observer (B) and a main surface (H') facing away from the observer (B), and in at least one light pipe (2), the main surface (H') facing away from the observer (B) faces the light pipe (3) that is most adjacent in the direction opposite to the stacking direction; each light pipe ( 2, 3) at least one light source (5, 5') configured such that: in each case, its light (L, L') is coupled into the respective light guide (2, 3) via the end face (11) of the associated light guide (2, 3) facing the light source (5, 5'); wherein, further, each light guide (2, 3) is provided with at least one microstructured symbol area (12a, 12b) provided in or on the light guide (2, 3), which is configured to illuminate an observer (2, 3) if the light source (5, 5') is activated respectively. B) visible, illuminated by light (L, L') coupled into the light guides (2, 3); a circuit board (7) on which a plurality of light sources (5, 5') are arranged and fixed; a panel (6) fixed to the stack of light guides by material-to-material and / or non-frontal and / or frontal connections, the circuit board (7) being fixed to the panel (6) while resting against a mounting surface (15), wherein the two light sources (5') of the circuit board serve as an alignment aid for connecting the circuit board (7) and the panel (6); and a related assembly method.

Description

Technical Field

[0001] The invention relates to a functional display, which is used for selectively displaying a plurality of symbols respectively representing switch functions and / or a plurality of switch states, and a related assembly method. Background Art

[0002] These functional displays are required in multifunctional control components to visualize the switch functions and / or switch states connected to the control components. Usually, electronic pixel matrix displays are used for this purpose. However, they are relatively expensive and, due to their mostly rectangular shape, restrict the design and placement. In addition, when depicting static display content, electronic pixel matrix displays often tend to "age", that is, due to visually perceptible damage to the imaging layer, the display content remains permanently and imperceptibly visible even when the display is turned off. In addition, the power consumption of such electronic pixel matrix displays is relatively high. In certain applications, the use of conventional electronic pixel matrix displays is prohibited due to the risk of injury (e.g. head collisions). As an alternative to pixel matrix displays, it is known to couple out light from a light source in a targeted manner, which is coupled to the end face of a planar light waveguide at the main surface used as a display surface via a surface structure, wherein the area with the surface structure is only provided in some parts and represents symbols, etc. In order to be able to display different symbols independently, several of these light guides are arranged in a stacked manner, overlapping each other, wherein the planar light guide is designed to be relatively thin and is configured, for example, as a plastic film to save construction space. Therefore, the exact alignment of the light-emitting diodes usually used as light sources, in particular their emission pattern relative to the end face, constitutes a problem, especially if for efficiency reasons the light sources cannot be mounted individually on each light guide but are arranged together on the circuit board. Thus, moving just one light source may result in a lower brightness of the associated symbol or even its complete failure. Summary of the invention

[0003] Against the above background, the object of the present invention is to provide a functional display which ensures reliable, precise and simultaneously reproducible light coupling between a light source associated with the functional display and a plurality of light guides also associated with the functional display, and which is inexpensive to produce, energy-saving, reliable and / or reduces the risk of injury, in particular in the event of a head impact. This object is achieved by the functional display of the present invention. Corresponding advantageous assembly methods are the subject matter of the independent claims. Advantageous embodiments are the subject matter of the respective dependent claims. It should be noted that the features cited individually in the patent claims can be combined in any technically meaningful way and present further embodiments of the invention. The description, in particular in conjunction with the drawings, provides additional description and provisions of the invention.

[0004] The invention relates to a functional display for selectively displaying a plurality of symbols, in particular for motor vehicles, each representing a switch function and / or at least two switch states. Selective display is not only understood to mean the selective display of different symbols from a plurality of predefined symbols, which in the present solution is achieved by selectively selecting one or more light sources from a plurality of light sources and energizing them, but also switching the light sources on and off in order to selectively make the symbols visible to an observer by means of an activated backlight or, if possible, to make the symbols virtually invisible to the observer by means of a switched-off backlight.

[0005] The functional display according to the invention has a stack of light pipes, which, given the intended attachment of the functional display, form a display surface facing the observer. The stack of light pipes is composed of at least two transparent or translucent planar light pipes, which are arranged in an overlapping manner along the stacking direction, and the planar light pipes are arranged to be separated by a transparent or translucent layer, which is composed of a material that is optically thinner than that of the adjacent light pipes, preferably an air gap. In this case, the light pipes each have a main surface facing the observer and a main surface facing away from the observer. In at least one light pipe, the main surface facing away from the observer faces the light pipe that is most adjacent in the direction opposite to the stacking direction. For example, the spacing set by the layer or air gap between the light pipes is in the range of 1 mm to 3 mm, at least in the main part of the light pipe.

[0006] Optionally, the functional display according to the invention may have an outer transparent or translucent cover layer, which is arranged between the light guide stack and the observer, and through which the observer can see the display surface defined by the light guide stack given the intended functional unit arrangement. For example, the material of the cover layer and the light guide is a plastic, preferably a thermoplastic material, such as polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), acrylonitrile-butadiene-styrene (ABS) or polymethyl methacrylate (PMMA) or a glass material.

[0007] According to the invention, each light guide is provided with at least one light source, which is configured for coupling light into the respective light guide via the end face of the associated light guide. For example, the light guide has two opposing main surfaces, which preferably extend parallel to each other and are connected to each other by the end face, which forms a common edge with the main surfaces of the light guide, for example at the narrow side and the long side of the light guide. For example, the end face is orthogonal to at least one main surface or both main surfaces of the optical waveguide.

[0008] For example, the light source is a light emitting diode, preferably of SMD design. In order to improve the coupling of light and / or to adapt the emission properties of the light source to the end face of the light guide for introducing light, a lens is preferably arranged in each case between the light guide and the light source.

[0009] According to the invention, a microstructured symbol area per light guide is provided in or on the light guide, which comprises a plurality of light-refracting and / or light-scattering microstructures. The microstructured symbol area, acting alone or in combination with other microstructured symbol areas of the same light guide or of another light guide, forms a symbol which, if the light source is activated, will be visible to an observer, which is illuminated by the light coupled into the respective light guide due to the light refraction and / or light scattering caused by the plurality of microstructures at the respective microstructured surface. For example, the incident angle of the light on the relevant main surface is achieved by the microstructure, which does not satisfy the total reflection condition of the main surface of the light guide as an interface, so that the light coupled into the light guide leaves the light guide again.

[0010] According to the invention, a circuit board is provided, on which a plurality of light sources are arranged and fixed. Preferably, the fixing is achieved by soldering it to a metal contact pad of the circuit board. According to the invention, a panel is also provided, which is fixed to a stack of light pipes by means of a substance-to-substance and / or non-frontal and / or frontal connection. According to the invention, the panel forms a mounting surface to which the circuit board is fixed so as to be placed thereon, the panel preferably being formed of an opaque material. According to the invention, the panel has a plurality of optical axes open on both sides, accommodating respectively at least one light source of the circuit board, so that at least one light source is located end-to-face in order to couple light to the respective associated end face, preferably in order to ensure (if possible) an exclusive conversion of light from the light source to the associated light pipe (associated therewith due to the arrangement of its end face opposite to the respective light source). Therefore, the optical axes are preferably configured in such a way as to suppress unwanted conversion of light towards an observer, towards other layers or light pipes beside the associated light pipe.

[0011] According to the invention, a first gap between two optical axes located in the stacking direction and spaced laterally in the stacking direction and the associated light sources accommodated in the respective optical axes is smaller than a second gap between the remaining optical axes and the associated light sources accommodated in the respective optical axes located in the stacking direction. For example, the first gap is 0.05-0.20 mm, while the second gap is 0.5-5 mm. The first or second gap is understood to mean the net total distance between the light source and the optical axis in the stacking direction, the mobility of the individual light sources in the optical axis associated therewith being limited in the stacking direction. Thus, two light sources spaced laterally in the stacking direction cooperate with the optical axis respectively associated therewith for mechanical alignment between the panel and the circuit board, while the remaining light sources are not affected due to the larger gap. Due to the risk of damaging the light source or its electrical contact, such as loss of solder contacts or separation of contact pads of the circuit board due to shear forces, in particular in the case where the light source is configured as a light-emitting diode with an SMD design, such mechanical intervention is usually omitted in the known solutions, with the disadvantage that misalignment of the light source must be tolerated. The risk of damaging a maximum of two light sources can be tolerated, and the present embodiment uses them as a mechanical positioning aid or alignment aid for the connection between the circuit board and the panel, with the advantage that all light sources can be aligned sufficiently accurately with the relevant end faces, thereby ensuring optimal illumination of the relevant light guides, because, in particular, the light sources can be positioned on the circuit board with sufficient and fairly high positioning accuracy, for example in automatic mounting machines for SMD mounting.

[0012] For example, to strengthen the mechanical connection of the two light sources used for mechanical alignment (hereinafter referred to as alignment light sources) to the circuit board, various measures may be taken, such as enlarged contact pads on the circuit board, more mechanically durable solder, different alignment of the alignment light sources, for example, compared to the remaining light sources of the circuit board. In another embodiment, another light source that is not used as an alignment light source may be designated as a redundant light source for the light guide associated with the alignment light source.

[0013] Preferably, two aiming light sources are assigned to one and the same light guide in order to ensure precise alignment with the respective light guide and thus uniform illumination thereof, since for the latter symbols are visually displayed which are essential for the function of the functional display, for example warning symbols which are indispensable during driving when the functional display is used in an automotive engineering environment.

[0014] The microstructured symbol area can be inserted three-dimensionally into the light guide by laser ablation (e.g. by laser inscription vitrography) or applied to one of its major surfaces. Preferably, the microstructured symbol area is formed by embossing one major surface on each light guide, thereby enabling a functional display to be realized in a cost-effective manner.

[0015] Preferably, the microstructure symbol area is formed by a plurality of microstructures configured with the same shape, which together form a continuous microstructure symbol area for each light guide. Preferably, a microstructure is understood to be a singular raised portion on the main surface or a singular recess on the main surface. In order to largely exclude the visibility of the naked eye, in this case, the maximum dimension of each microstructure is in the range of 1-50 μm, preferably in the range of 1μm to 25μm. Preferably, the microstructures are distributed in a uniformly spaced manner throughout the microstructure symbol area. For example, the microstructures form pyramids or prisms. Preferably, the microstructures are not only formed in the same shape (i.e. in a matching manner), but also have a matching alignment within the respective microstructure symbol area. For example, in the case of a planar main surface, a matching alignment occurs if each microstructure can be mapped to a neighboring microstructure of the same microstructure symbol area by a unique translational imaginary displacement. More preferably, the microstructures are configured so that they generate a collimated light beam leaving the light guide from light originating from a light source and having previously entered the light guide by an end face.

[0016] Preferably, the average number density of microstructures in each microstructure symbol region of the optical waveguide stack is 500-7000 / mm 2 In the range of 1000-4000 / mm 2 On the one hand, this ensures invisibility when the light source is switched off, while the impression of a seemingly uniformly illuminated symbol area can be simulated with the "naked eye". Preferably, the average number density of each light guide is selected to be substantially the same, wherein "substantially the same" means that the maximum deviation between the number densities of the light guides is less than 100 / mm 2 .

[0017] Preferably, all light guides outside the microstructured symbol area are transparent so that a large part of the functional display remains at least partially transparent and, for example, a possibility of viewing through the functional display is ensured in order to provide the observer with the possibility of following other displays, instruments or the route of the road through the functional display. For example, the functional display can be placed on the steering wheel, for example in the area between the steering wheel hub and the steering wheel rim, without obstructing the view on the instrument panel. Preferably, the surface proportion of all surface structured symbol areas is less than half of the display surface.

[0018] Preferably, at least one light guide, more preferably all light guides of the light guide stack, comprise a plastic film, such as a thermoplastic film, such as a PC film or a PE film. Each light guide is not absolutely required to be a one-piece configuration; it may consist of several components. In one configuration, at least one light guide has a multi-layer film layer structure. For example, at least one light guide is produced by back-molding a transparent film with another transparent or translucent material, in particular a thermoplastic material.

[0019] According to a preferred embodiment, it is provided that, given a vertical view on the display surface, in particular from a position above the geometrical centre of the display surface, for an observer the microstructured symbol areas of at least two light guides of the light guide stack do not overlap and are preferably spaced apart.

[0020] According to a preferred embodiment, it is provided that, given a vertical view on the display surface, in particular from a position above the geometric center of the display surface, for an observer, the microstructure symbol areas of at least two light guides of the light guide stack are adjacent, preferably overlapping, more preferably arranged identically.

[0021] According to a preferred embodiment, at least two light sources differ in the color of the light in order to provide an additional color effect.

[0022] Preferably, the panel has a plurality of grooves corresponding to the number of light pipes, which are respectively used to frontally accommodate the ends of the light pipes forming the end faces facing the light source, thereby achieving reliable positioning of the end faces. The web-like protrusions or ribs formed between the grooves are used for optical insulation between the light pipes.

[0023] According to a preferred embodiment, in order to fix the circuit board to the panel, the circuit board has a groove or a through hole, and the panel has a pin extending through the groove or through hole, the pin protruding from the mounting surface, and its free end is hot-melted. For example, the pin and the panel are integrally formed of thermoplastic material.

[0024] Preferably, in particular in order to avoid the risk of mutual optical crosstalk in adjacent light guides, at least the end of each outer light guide of the light guide stack has a curved portion, which forms an end face facing the light source. Preferably, the curved portion is formed to increase the distance between the light guides relative to the area of ​​the light guide provided with the microstructure symbol area, in order to improve the fixing of the light guides and to improve the mutual optical insulation due to the panel.

[0025] According to a preferred embodiment, a transparent electrode array arranged between the observer and the light guide stack and an associated electronic evaluation unit for capacitive, preferably spatially resolved capacitive touch detection are provided in order to change the functional state displayed by the symbol, for example by touch input.

[0026] According to a preferred embodiment, in order to save construction space, a circuit board surface of the circuit board carrying the light sources is provided which is arranged substantially parallel to the stacking direction determined by the position of the light guide.

[0027] Preferably, the functional display has a housing, wherein the circuit board is supported on the housing only in an elastic manner, or supported on the housing in an indirect manner. Preferably, only the elastic support is provided substantially in a direction perpendicular to the mounting surface to avoid mechanical damage to the light source.

[0028] The invention also relates to a method for assembling a functional display for selectively displaying symbols representing switch functions and / or switch states, in particular for motor vehicles, comprising the following steps. In a providing step, a stack of light guides is provided, which, given the intended attachment of the functional display, forms a display surface facing an observer. In this case, the light guide stack is formed by at least two transparent or translucent planar light guides arranged in an overlapping manner along the stacking direction, the two planar light guides being arranged to be separated by a transparent or translucent layer, the transparent or translucent layer consisting of a material that is optically thinner than the adjacent light guides, preferably an air gap, so that each light guide has a main surface facing the observer and a main surface facing away from the observer. In at least one light guide, the main surface facing away from the observer faces the light guide that is most adjacent in a direction opposite to the stacking direction. Further, each light guide is provided with at least one microstructured symbol area provided in or on the light guide, which comprises a plurality of light-refracting and / or light-scattering microstructures.

[0029] In a further providing step, a circuit board is provided carrying a plurality of light sources, the number of which corresponds at least to the number of light guides. Preferably, all light sources are arranged on one main surface of the circuit board, which main surface is referred to as the circuit board surface.

[0030] In a further provision step, a panel is provided which has a mounting surface for the circuit board to bear against and a plurality of optical axes open on both sides, wherein the optical axes are configured to accommodate in each case at least one light source of the circuit board, since one end thereof is preferably at the mounting surface.

[0031] For example, the steps provided provide for producing the light guide and the panel in a forming process, in particular a thermoforming process, such as an injection molding process. The respectively used forming processes may comprise, for example, structuring the main surface of the light guide with a number of microstructures by means of embossing.

[0032] In a subsequent step, the light guide is fixed to the panel by substance-to-substance and / or non-frontal and / or frontal connections.

[0033] In the alignment step, the circuit board is aligned by resting the circuit board against the mounting surface so that, in each case, at least one light source is located opposite one of the light guide end faces through the optical axis of the panel for coupling light, and each light source is accommodated in the associated optical axis. According to the invention, a first gap between two optical axes located in the stacking direction and spaced laterally in the stacking direction and the associated light sources accommodated in the respective optical axes is smaller than a second gap between the remaining optical axes located in the stacking direction and the associated light sources accommodated in the respective optical axes, so that the relative alignment of the panel and the circuit board is determined by the first gap.

[0034] In a subsequent step, the aligned circuit board is fixed to the panel in such a way that in each case the light of the light source is coupled into the respective light guide via the end face of the associated light guide facing the light source and, if the light source is activated respectively, the microstructured symbol area becomes visible to the observer, illuminated by the light coupled into the light guide, so that the symbol consisting of one or more microstructured symbol areas is displayed to the observer. A gap is understood to mean the clear total distance between the light source and the optical axis accommodating the light source in the stacking direction, so that the mobility of the individual light sources in the optical axis associated therewith is limited in the stacking direction. Thus, two light sources spaced laterally in the stacking direction cooperate with the optical axis associated therewith respectively for the mechanical alignment between the panel and the circuit board, while the remaining light sources remain unaffected due to the larger second gap. Due to the risk of damaging the light source or its electrical contact, such as loss of solder contacts or separation of contact pads of the circuit board due to shear forces, in particular in the case of light sources configured as light emitting diodes with an SMD design, such mechanical interventions are usually omitted in the known solutions, with the disadvantage that misalignment of the light sources must be tolerated. In order to tolerate the risk of damage to both light sources, the present embodiment uses them as a mechanical positioning aid for the connection between circuit board and panel, with the advantage that now all light sources are ensured to be aligned sufficiently accurately with the relevant end faces, thereby ensuring optimal illumination of the relevant light guides.

[0035] According to a preferred embodiment of the assembly method of the present invention, in order to fix the circuit board to the panel, a panel is provided with a pin, the pin extends through the groove or through hole of the circuit board, and the pin extends through the groove or through hole in a manner that there is a third gap greater than the first gap in the stacking direction. In this case, a fixing method including a final hot melt of the pin is adopted to fix the circuit board to the panel.

[0036] According to a preferred embodiment, the light sources are light emitting diodes configured with an SMD design and are soldered to the circuit board in a soldering step prior to providing the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention and technical content will be explained in more detail below with reference to the accompanying drawings. It must be noted that the accompanying drawings depict particularly preferred embodiments of the present invention, but the latter is not limited thereto. The figure schematically shows:

[0038] Figure 1 is a schematic cross-sectional view of a first embodiment of a functional display 1 according to the present invention;

[0039] Figure 2 yes Figure 1 A perspective view of the panel 6 of the first embodiment;

[0040] Figure 3 yes Figure 1 A perspective view of a circuit board 7 of the first embodiment;

[0041] Figure 4 yes Figure 1 A partial enlarged view of

[0042] Figure 5 is a schematic cross-sectional view of a second embodiment of a functional display 1 according to the invention. DETAILED DESCRIPTION

[0043] Figure 1 A first embodiment of a functional display 1 according to the invention is schematically shown. The functional display 1 comprises an outer transparent or translucent cover layer 18, which is not absolutely necessary, but is only optionally provided and, given the intended arrangement of the functional display 1, defines the surface facing the observer B. This is, for example, a layer consisting of plastic, preferably a thermoplastic material such as polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), acrylonitrile-butadiene-styrene (ABS) or polymethyl methacrylate (PMMA) or a glass material. The cover layer 18 can also be part of a layer structure consisting of multiple layers. A transparent conductive coating, which forms an electrode array and is used for spatially resolved touch detection and is connected in an electrically conductive manner to an evaluation unit, not shown, via a plurality of flexible conductors, is applied to the surface of the cover layer 18 facing away from the observer B.

[0044] The functional display 1 further comprises a light guide stack consisting of at least two transparent or translucent planar light guides 2, 3 arranged in an overlapping manner. The latter are also formed from a plastic, preferably a thermoplastic material, such as polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), acrylonitrile-butadiene-styrene (ABS) or polymethyl methacrylate (PMMA) or a glass material. Preferably, in each case this is a thermoplastic plastic layer or a thermoplastic plastic film. The light guides 2, 3 are separated from one another by a layer 14 arranged between the light guides 2, 3, in which case the air gap consists of a material (in this case air) having a lower refractive index than the refractive index of the adjacent light guides 2, 3. An air layer is also provided between the cover layer 18 and the uppermost adjacent light guide 2, which air layer is not defined in more detail in this context. The light pipes 2 and 3 each form at least one main surface H facing the observer B and a main surface H' facing away from the observer B, and the upper light pipe 2 closer to the observer B has a main surface H' facing away from the observer and toward the most adjacent light pipe 14 in the direction opposite to the stacking direction S.

[0045] At least one light source 5 or 5', i.e. a light emitting diode of SMD design in each case, is arranged so that the light it generates is coupled into a designated light guide 2, 3 via an end face 11 on the side facing the stacking direction S, assigned to the light guide 2, 3. In order to avoid unnecessary light scattering or emission of light into adjacent light guides 2, 3 in each case, a panel 6 consisting of an opaque material, in particular an opaque thermoplastic material, is provided. The panel 6 forms a protruding rib 13, which is received and fixed between the recesses receiving the light guides 2, 3, in particular at their ends, whose end faces 11 are used for coupling in light.

[0046] A frame-shaped housing 17 is provided on the opposite end faces. An anti-reflection coating, not shown, may be applied to the end faces of the light guides 2, 3 facing away from the light sources 5, 5', in order to minimize reflections back into the respective light guides 2, 3. A plurality of singular microstructures 4 are inserted by embossing or moulding into at least one main surface of the optical waveguide 2, in this case into the main surface H facing the observer B, ensuring that the light L' coupled into the light guide 2 is coupled out of the respective light guide 2 by light refraction and / or light scattering and defining a microstructure symbol area 12a containing the microstructures 4. If the associated light source 5' is activated accordingly, the latter can reproduce the shape of the symbol visible to the observer B in an illuminated manner, either by itself or by optical cooperation with other symbol areas.

[0047] The microstructures 4 are configured to be identical in shape to one another and have a maximum diameter in the range of 1-25 µm. The light guide 3 remote from the observer B, in its main surface H facing the observer B, also has microstructures 4 which are likewise configured singularly and identical in shape to one another. They are also inserted by embossing or moulding into the relevant main surface H of the light guide 3, which in this case faces the observer B. In this case, they also couple the light L coupled into the light guide 3 in the direction of the observer B, so as to reveal the symbol area 12b to the observer.

[0048] By selectively activating the light sources 5, 5', different switch states or switch functions can be visualized in a relatively simple manner. The functional display 1 is simple and cost-effective to implement and offers a great degree of design freedom to the designer, which is also related to the placement of the functional display 1. The functional display has almost no aging effects caused by light emission and is relatively energy-efficient. For example, the microstructured symbol area 12, 12b represents the symbol as an image, its reverse representation or its outline in a positive manner, either by itself or in combination with others. Among other factors, the distance between the light guides 2, 3 (e.g. the thickness of the air gap) produces a certain depth effect. For example, the distance is in the range of 1-3 mm.

[0049] Outside the microstructured symbol areas 12a, 12b, all light guides 2, 3 are transparent. Thus, a large part of the display surface 8 remains optically transmissive, thereby ensuring, for example, the possibility of viewing through the functional display 1, in order to provide the observer B with the possibility of following other displays or a road route through the functional display 1. For example, the functional display 1 can be placed on the steering wheel, for example in the area between the steering wheel hub and the steering wheel rim, without obstructing the view on the instrument panel. Looking perpendicularly at the display surface 8, the microstructured symbol areas 12a, 12b of the individual light guides 2, 3 do not overlap, so as not to affect the depiction quality of the symbol.

[0050] A circuit board 7 is provided on which a plurality of light sources 5, 5' are arranged and fixed. Here, they are fixed by soldering them to the metal contact pads of the circuit board 7. The above-mentioned panel 6 forms a mounting face 15 on its side facing away from the light pipes 2, 3 for contacting the face of the circuit board 7 equipped with the light sources 5, 5'. The direction of this face is parallel to the stacking direction S. The circuit board 7 has a through hole 9 through which a pin 10 formed by the panel 6 extends, and its free end is deformed by hot melting so as to reach the rear of the circuit board 7 and fix the circuit board 7. The panel 6 has a plurality of optical axes 8, 8', which are open on both sides and respectively accommodate at least one light source 5, 5' of the circuit board 7, so that in each case at least one light source 5, 5' is located opposite the end face 11, so as to couple light into the respectively associated end face 11 and ensure, where possible, a unique light conversion from the light source 5, 5' to the associated light pipe 2, 3, which is associated with it due to its end face 11 being arranged opposite to the corresponding light source 5, 5'. Thus, the optical axes 8, 8' are configured in such a way that unwanted conversion of light towards the observer B, towards other layers or light guides 2, 3 beside the relevant light guide 2, 3 is suppressed. Figure 2 A detailed view of a panel 6 is shown, wherein grooves 20 are formed between the ribs 13 for frontally accommodating and fixing the light guides 2, 3. Here, it is evident that the dimensions of the optical axes 8 and 8' in the stacking direction S are different.

[0051] Figure 4 A top view of a circuit board 7 on a surface 16 equipped with light sources 5, 5' is shown. In each case, the light sources 5, 5' are SMD light emitting diodes of identical shape soldered to contact pads of the circuit board 7. Due to the special dimensions assigned to their optical axes, the two light sources 5' are spaced apart in a direction transverse to the stacking direction, complying with the condition of so-called aligned light sources, as described below:

[0052] If the sizes of all light sources 5, 5' in the stacking direction S match, then Figure 3The scene shown. The first gap 21' between the two optical axes 8' located in the stacking direction S and spaced laterally in the stacking direction S and the associated light sources 5' accommodated in the respective optical axes 8' is smaller than the second gap 21 located in the stacking direction S between the remaining optical axes 8 and the associated light sources 5 accommodated in the respective optical axes 8. The first gap 21' or the second gap 21 is understood to represent the net total distance between the individual light sources 5, 5' and the optical axes 8, 8' in the stacking direction S, the mobility of the respective light sources 5, 5' in the optical axes 8, 8' associated therewith being limited in the stacking direction S. Therefore, the two light sources 5' spaced laterally in the stacking direction S and the light sources 5' accommodated almost frontally and the optical axes 8' respectively associated therewith cooperate for the mechanical alignment between the panel 6 and the circuit board 7, while the circuit board 7 rests on the mounting surface 15 of the panel 6. Due to the larger second gap 21, the remaining light sources 5 or the optical axes 8 are not affected thereby. Due to the risk of damage to the light sources 5, 5' or their electrical contacts, such as loss of soldered contacts or separation of contact pads of the circuit board 7 due to shear forces, in particular in the case where the light sources 5, 5' are configured as light-emitting diodes with an SMD design, such mechanical intervention is usually omitted in known solutions, with the disadvantage that misalignment of the light sources 5, 5' must be tolerated. In order to allow for the risk of damage to a maximum of two light sources 5', the present embodiment uses them as a mechanical positioning aid for the connection between the circuit board 7 and the panel 6, with the advantage that a sufficiently precise alignment of all light sources 5, 5' with the associated end face 11 is now ensured, thereby ensuring optimal illumination of the associated light guides 2, 3.

[0053] For example, in order to strengthen the mechanical connection of the two light sources 5' for mechanical alignment with the circuit board 7, formerly referred to as alignment light sources, various measures may be taken, such as enlarged contact pads on the circuit board 7, more mechanically durable solder, different alignment of the alignment light sources, for example compared to the remaining light sources 5 of the circuit board 7. In the embodiment shown, another light source 5 may be designated as a redundant light source of the light guide 2 associated with the alignment light source, which another light source 5 does not act as an alignment light source and therefore has a larger second gap 21 when arranged in the associated optical axis 8.

[0054] like Figure 4 As shown, pins 10 for fixing the circuit board 7 are provided on the panel 6 (at least before hot melting), which extend through the through holes 9 on the circuit board 7 to define a third gap 22 in the stacking direction S, which is at least larger than the first gap 21', so as not to hinder the alignment of the circuit board 7. During the placement of the circuit board 7 on the mounting surface 15 and the insertion of the light sources 5, 5' into the relevant optical axes before hot melting, the displacement or twisting of the circuit board 7 relative to the panel 6 or the mounting surface 15 can be achieved, at least within a limited range.

[0055] Figure 5A second embodiment of a functional display 1 according to the invention is shown. The latter differs greatly from the first embodiment due to the shaping of the light pipes 2, 3. In order to avoid the risk of mutual optical crosstalk in adjacent light pipes 2, 3, at least the outer light pipes 2, 3 of the light pipe stack have at the end a curved portion 23 forming an end face 11 facing the light source 5, 5'. Here, the curved portion 23 is formed to increase the distance between the light pipes 2, 3 in the direction of the panel 6 relative to the area of ​​the light pipes 2, 3 where the microstructure symbol areas 12a, 12b are arranged, so as to improve the fixing of the light pipes 2, 3 and improve the mutual optical insulation due to the panel 6. Furthermore, in contrast to the first embodiment, the housing 17 is configured in a frame shape, wherein direct contact between the housing 17 and the circuit board 7 is excluded.

Claims

1. A function display (1), the function display (1) being used to selectively display a plurality of symbols respectively representing a switch function and / or respectively representing at least two switch states, the function display comprising: A stack of light pipes, the stack of light pipes forming a display surface facing an observer (B) given the intended attachment of a functional display (1); wherein the stack of light pipes is composed of at least two transparent or translucent planar light pipes (2, 3), the planar light pipes (2, 3) being arranged in an overlapping manner along the stacking direction, the planar light pipes (2, 3) being arranged to be separated by a transparent or translucent layer, the transparent or translucent layer being composed of a material that is optically thinner than adjacent light pipes (2, 3), so that the light pipes (2, 3) each have a main surface (H) facing the observer (B) and a main surface (H') facing away from the observer (B), and in at least one light pipe (2), the main surface (H') facing away from the observer (B) faces the light pipe (3) that is most adjacent in the direction opposite to the stacking direction; Each light guide (2, 3) has at least one light source (5, 5') which is configured such that its light (L, L') is coupled into the respective light guide (2, 3) in each case via the end face (11) of the associated light guide (2, 3) facing the light source (5, 5'); wherein further, each light guide (2, 3) is provided with at least one microstructure symbol area (12a, 12b) provided in or on the light guide (2, 3), which includes a plurality of light-refracting and / or light-scattering microstructures (4) and is configured to be visible to an observer (B) and illuminated by light (L, L') coupled into the light guide (2, 3) if the light sources (5, 5') are respectively activated, so as to display a symbol consisting of one or more microstructure symbol areas (12a, 12b) to the observer (B); A circuit board (7) on which a plurality of light sources (5, 5') are arranged and fixed; A panel (6) is fixed to the stack of light pipes by material-to-material and / or non-frontal and / or frontal connections, the circuit board (7) is fixed to the panel (6) and abuts against a mounting surface (15), wherein the panel (6) has a plurality of optical axes (8, 8'), the optical axes are open on both sides and respectively accommodate at least one light source (5, 5') of the circuit board (7), so that at least one light source (5, 5') is located opposite to a related end face (11) to couple light (L, L') to the related end face (11), wherein a first gap (21') between two optical axes (8') located in the stacking direction (S) and laterally spaced from the stacking direction (S) and the related light sources (5') accommodated in the corresponding optical axes (8') is smaller than a second gap (21) between the remaining optical axes (8) and the related light sources (5) accommodated in the corresponding optical axes (8) in the stacking direction (S).

2. The functional display (1) according to claim 1, characterized in that The function display (1) is used to selectively display a plurality of symbols of the motor vehicle, each representing a switch function and / or each representing at least two switch states.

3. The functional display (1) according to claim 1, characterized in that The transparent or semi-transparent layer consists of air gaps (14).

4. The functional display (1) according to claim 1, characterized in that The light source (5, 5') is a light emitting diode configured with an SMD design.

5. The functional display (1) according to claim 1, characterized in that The microstructured symbol regions (12a, 12b) have in each case a plurality of microstructures (4) arranged in the same shape.

6. The functional display (1) according to claim 5, characterized in that The number of the microstructures (4) is odd.

7. The functional display (1) according to claim 1, characterized in that The panel (6) has a plurality of grooves (20) corresponding to the number of the light pipes (2, 3), respectively used to frontally accommodate the ends of the light pipes (2, 3) forming end surfaces (11) facing the light sources (5, 5').

8. The functional display (1) according to claim 1, characterized in that The panel (6) is provided with a pin (10) which extends through a groove or a through hole (9) of the circuit board (7) and whose free end is hot-melted to fix the circuit board (7) to the panel (6).

9. The functional display (1) according to claim 1, characterized in that At least the outer light guides (2, 3) of the light guide stack have a curved portion (23) at the end forming the end surface (11) facing the light source (5, 5').

10. The functional display (1) according to claim 1, characterized in that It further comprises a cover layer (18) composed of a transparent material, the cover layer being arranged between the light pipe stack and the observer (B).

11. The functional display (1) according to claim 1, characterized in that It further comprises a transparent electrode array (19) arranged between an observer (B) and the light guide stack, and an associated electronic evaluation unit for capacitive touch detection.

12. The functional display (1) according to claim 11, characterized in that The capacitive property is a spatially resolved capacitive property.

13. The functional display (1) according to claim 1, characterized in that The circuit board (7) has a circuit board surface (16) that carries the light source (5, 5'), and the stacking direction is parallel to the circuit board surface (16).

14. Functional display (1) according to any one of the preceding claims, characterized in that It further comprises a housing (17), wherein the circuit board (7) is supported on the housing (17) in an indirect manner or only in an elastic manner.

15. A method for assembling a function display (1), the function display (1) being used to selectively display symbols representing switch functions and / or switch states, the method comprising the following steps: A stack of light pipes is provided, wherein the stack of light pipes forms a display surface facing an observer (B) given the intended attachment of a functional display (1); wherein the stack of light pipes is composed of at least two transparent or translucent planar light pipes (2, 3), the planar light pipes (2, 3) being arranged in an overlapping manner along the stacking direction, the planar light pipes (2, 3) being arranged to be separated by a transparent or translucent layer, the transparent or translucent layer being composed of a material that is optically thinner than adjacent light pipes (2, 3), so that the light pipes (2, 3) each have a main surface (H) facing the observer (B) and a main surface (H') facing away from the observer (B), and in at least one light pipe (2), the main surface (H') facing away from the observer (B) faces the light pipe (3) that is most adjacent in a direction opposite to the stacking direction; wherein further, each light pipe (2, 3) is provided with at least one microstructure symbol area (12a, 12b) provided in or on the light pipe (2, 3), which includes a plurality of light refractive and / or light scattering microstructures (4); Providing a circuit board (7) on which a plurality of light sources (5, 5') corresponding to at least a plurality of light guides (2, 3) are arranged; Providing a panel (6) having a mounting surface (15) for the circuit board (7) to bear against, and a plurality of optical axes (8, 8') open on both sides, wherein the optical axes (8, 8') are configured to accommodate in each case at least one light source (5, 5') of the circuit board (7); securing the light guide stack to the panel (6) by material-to-material and / or non-frontal and / or frontal connections; The circuit board (7) is aligned when the circuit board (7) abuts against the mounting surface (15) so that in each case at least one light source (5, 5') is located opposite the end face (11) of one of the light guides (2, 3) so as to couple light via one of the optical axes (8, 8') and the light sources (5, 5') are each accommodated in one of the optical axes (8, 8'); wherein a first gap (21') between two optical axes (8') located in the stacking direction (S) and spaced laterally in the stacking direction (S) and the associated light source (5') accommodated in the respective optical axis (8') is smaller than a second gap (21) between the remaining optical axes (8) and the associated light source (5) accommodated in the respective optical axis (8); The circuit board is fixed to the panel so that in each case the light of the light source is coupled into the respective light guide (13, 14, 15) via the end face (S) of the associated light guide (13, 14, 15) facing the light source and if the light source (12, 12') is activated respectively, the microstructured symbol area becomes visible to an observer (B) and is illuminated by the light coupled into the light guide (13, 14, 15) to display a symbol (18) consisting of one or more microstructured symbol areas to the observer (B).

16. The assembly method according to claim 15, characterized in that: The function display (1) is used to selectively display symbols representing switch functions and / or switch states of the motor vehicle.

17. The assembly method according to claim 15, characterized in that: The transparent or semi-transparent layer consists of air gaps (14).

18. The assembly method according to claim 15, characterized in that: The panel (6) is provided with a pin (10) which extends through a groove or a through hole (9) of the circuit board (7), and a third gap (22) which is at least larger than the first gap (21') exists in the stacking direction (S); a fixing method including a final hot melt of the pin (10) is adopted to fix the circuit board (7) to the panel (6).

19. Assembly method according to any one of the preceding claims, characterized in that The light sources (5, 5') are light emitting diodes configured with an SMD design and are soldered to the circuit board (7) in a soldering step before providing the circuit board (7).

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