CN219133858U

CN219133858U - Functional display, operating element and steering wheel for a motor vehicle

Info

Publication number: CN219133858U
Application number: CN202221246676.5U
Authority: CN
Inventors: A·克拉姆利克
Original assignee: Preh GmbH
Current assignee: Preh GmbH
Priority date: 2021-05-21
Filing date: 2022-05-20
Publication date: 2023-06-06
Anticipated expiration: 2032-05-20
Also published as: DE102021113316B3

Abstract

The utility model relates to a functional display, an operating element and a steering wheel for a motor vehicle, comprising: a planar light conductor made of at least one transparent or translucent first material having two opposite main faces, one of which faces the viewer as a display face and at least one end face, the other of which faces away from the viewer; at least one light source arranged such that light from the light source is coupled into the light conductor through an end face of the light conductor; wherein the main surface of the optical conductor is surface structured by a plurality of light refracting and/or light scattering microstructures introduced into the respective main surface to form a surface structured region of the respective main surface; wherein the surface structured region comprises at least one coherent uncoated surface structured symbol region or at least one coated surface structured region; a planar covert layer to minimize the discernability of the uncoated surface structured symbol region when the light source is turned off, particularly when the light source is exposed to extraneous light.

Description

Functional display, operating element and steering wheel for a motor vehicle

Technical Field

The utility model relates to a functional display for selectively displaying at least one symbol representing a switching function and/or a plurality of switching states.

Background

For example, in the case of a multifunctional operating element, such a functional display is required to visualize the switching function and/or the switching state connected to the operating element. Electronic pixel matrix displays are commonly used for this purpose, but they are relatively costly and limit creative designs and arrangements because of their rectangular main shape. In addition, electronic pixel matrix displays often suffer from "burn-in" when displaying static display content, that is, the display content remains undesirably continuously visible even when the display is turned off due to damage to the optically perceivable display imaging layer. In addition, such electronic pixel matrix displays have high power consumption. In some applications, conventional electronic pixel matrix displays are also disabled, as there may be a risk of injury, for example in the event of a head impact. As an alternative to pixel matrix displays, it is known to selectively couple out light coupled from a light source into the end face of a light guide by means of a surface structure on a main face serving as a display face, wherein only the area provided with the surface structure is provided locally and the symbol or the like is reproduced. A disadvantage is that the symbol is visible under incident light, for example when sunlight is shining into the vehicle interior, although the light source is off. This can lead to an observer, in particular a driver of the vehicle, for example, erroneously determining the actual switching state.

Disclosure of Invention

Against this background, it is an object of the utility model to provide a functional display in which the symbols are not recognized or at least less pronounced in the off-state of the light source, without at the same time affecting the creative room in the design of the functional display, which is inexpensive to produce, energy-efficient and reliable and/or reduces the risk of injury in particular in the event of a head impact.

The utility model relates to a functional display, in particular for a motor vehicle, for selectively displaying at least one symbol representing a switching function and/or a plurality of switching states. "selective display" is understood not only to mean that different symbols are selectively displayed from a number of predefined symbols, which is achieved in the solution according to the utility model by selectively selecting and energizing one or more light sources from a large number of light sources, but also by switching the light sources on and off, so that the symbols are either visually visible to the observer by activating the backlight or are almost vanished to the observer by switching the backlight off.

The functional display according to the utility model comprises at least one planar light conductor made of at least one transparent or translucent first material having two opposite main faces and at least one end face, one of the main faces being a display face facing a viewer, such as a vehicle driver, when the functional display is arranged as intended, and the other main face facing away from the viewer. The optical conductor has, for example, two opposite, preferably mutually parallel main faces which are connected via end faces which form a common edge with the main faces of the optical conductor, for example on the narrow side and on the longitudinal side of the optical conductor. For example, the end face is orthogonal to at least one or both major faces of the photoconductor.

For example, the first material is a plastic, preferably a thermoplastic such as Polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinylchloride (PVC), polyamide (PA), acrylonitrile Butadiene Styrene (ABS) or polymethyl methacrylate (PMMA), or a glass material. "principal face" is understood to mean, for example, those surfaces of the photoconductor which have the greatest surface area. Preferably, the main surface assumes a substantially planar design, except for the surface structuring described below. The light conductor may be provided with a transparent or translucent coating, such as a paint layer.

According to the utility model, the functional display comprises at least one light source which is arranged such that light from the light source is coupled into the light guide through the end face of the light guide so as not to blinding the viewer. In order to improve the light incoupling and/or to adapt the light emission characteristics of the light source to the end face of the light conductor, a lens and/or a diaphragm and/or a light channel is preferably arranged between the light conductor and the light source. The diaphragm or the light channel is also designed, for example, to prevent light from passing to the observer, other layers than the associated light guide or the light guide.

According to the utility model, at least one main surface of the optical conductor is surface structured by a plurality of microstructures which introduce the light refraction and/or light scattering effects of the respective main surface. A "microstructure" is understood to mean, for example, a single protrusion on a main face or a single depression on a main face. For example, each microstructure has a maximum dimension in the range of 1 μm to 50 μm. Preferably, the microstructure spacing is uniformly distributed over the entire surface structured region of the main face. The major face facing the viewer is preferably provided with microstructures. For example, the microstructures are shaped as pyramids or prisms. Preferably, the microstructures are in an equal configuration, more preferably, the microstructures have not only a uniform shape but also a uniform orientation. For example, in the case of a planar major face, a uniform orientation would result if each microstructure could be mapped to an adjacent microstructure by an imaginary displacement of a unique imaginary translation. More preferably, the microstructures are designed such that they produce a collimated light beam exiting the light guide from light originating from the light source and having previously entered the light guide through the end face. According to the utility model, the surface structured region corresponds precisely to at least one coherent uncoated surface structured symbol region, i.e. coincides with or contains this region, whereby the latter represents a sub-region.

When the light source is activated, refraction and/or scattering of light in the uncoated surface structured symbol region causes light coupled into the light conductor to act in a direction of the observer such that the observer can see the luminescent symbol produced by the uncoated surface structured symbol region. The surface structure enables, for example, enhanced light compared to the planar design of the relevant main surface to emerge in the direction of the observer by light refraction and/or light scattering. For example, the light is caused by the microstructure to impinge on the boundary surface of the microstructure setting at an angle that does not meet the total reflection condition, so that the light leaves the light conductor in the region of the microstructure.

According to the utility model, a planar concealing layer of at least one transparent or translucent second material is also provided, which concealing layer extends parallel to the light conductor such that one of the main faces of the concealing layer faces one of the main faces of the light conductor, which are separated by an air gap or a layer of a thinner optical material, and wherein a plurality of light-refracting and/or light-scattering concealing microstructures are introduced into at least one main face of the concealing layer and define, as a whole, a first surface-structured concealing region and a second surface-structured concealing region with the associated gaps of the associated main face, wherein, from the point of view of the observer, in particular, at least a part of the concealing microstructures are laterally misplaced and thus appear to be placed outside the symbol region, as seen perpendicularly to the main face of the light conductor which acts as a display face and faces the observer. The masking layer thus ensures that when the light source of the light conductor is switched off, in particular when extraneous light is incident, the symbol region is optically concealed with its microstructure in the background of the masking microstructure of the masking layer and is thus no longer optically represented, thereby excluding an incorrect determination by an observer of the switching state associated with the symbol reproduced in the symbol region. The functional display is simple and inexpensive to implement, giving the designer a large degree of freedom of design, which also includes the placement of the functional display. The functional display shows little signs of aging due to light radiation and is relatively energy efficient. The uncoated surface structured symbol region reproduces the symbol front as an image, its inverse representation or its outline, for example.

From the viewpoint of the viewer, the concealing layer is preferably arranged below the light conductor. The covert microstructures are preferably introduced on or into the surface of the covert layer facing the viewer.

For variants in which the surface structured region does not completely correspond to the uncoated surface structured symbol region but comprises it as a partial region, it is also preferred that the coating made of the transparent or translucent third material is applied only locally to the structured region of the main face. In this case, the coating is configured such that the microstructure provided in the surface structured region of the coating is filled with the coating. The coating preferably forms a continuous surface of the uncoated surface structured symbol region surrounding the major face. In this case, at least one coated surface structured region remains in the surface structured region in addition to at least one coherent uncoated surface structured symbol region of the main face. The at least one coated surface structured region preferably surrounds an uncoated surface structured symbol region. The coating thus "neutralizes" the light refracting and/or scattering effects of the microstructure.

In the former variant, the coating layer thus sets the uncoated surface-structured symbol region, in particular its boundary (i.e. the boundary design between the uncoated surface-structured symbol region and the coated surface-structured region), its position and its size, which depend only on the choice of coating process and no longer on the choice of type and embodiment of the surface-structured process. This not only simplifies the manufacturing process, but also increases the freedom of creation of the representation symbol by using a surface coating as a means to achieve the symbol design specifications. This also creates the possibility of being able to pre-cast the optical conductors for a large number of symbols without forcing allocation to specific symbols.

Surface structuring may be introduced into the photoconductor by laser ablation. The surface structured areas (i.e. microstructures) in the photoconductor and the surface structured areas (i.e. covert microstructures) in the covert layer are preferably produced by embossing and/or moulding. The microstructure or covert microstructure is introduced into the relevant main face or surface by vacuum forming or injection molding, for example, by means of a tool, wherein the forming surface of the tool specifies the structure to be transferred to the light guide or covert layer.

In order to avoid internal reflection, the refractive indices of the first material and the third material are preferably different from each other by not more than 0.2, more preferably 0.1.

The third material is preferably a transparent hardening paint or a transparent hardening glue or a transparent hardening resin. The glue is preferably a heat curable glue which is introduced into the forming tool to produce a light conductor comprising the first material, e.g. by selecting the tool temperature to set the glue temperature e.g. above 280 ℃, whereby curing or hardening of the glue is achieved. "curing" is understood to mean, for example, chemical and/or physical hardening of the glue, such as the crosslinking enhancement of the glue.

According to a preferred embodiment, a second coating made of a transparent or translucent fourth material is applied to the concealing layer, whereby a portion of the concealing microstructure is filled by the second coating. For example, when viewed perpendicularly, a surface structured partial region of the relevant main face of the masking layer located below the uncoated surface structured symbol region is coated with a fourth material to form a second coating. The fourth material is preferably a transparent hardening paint or a transparent hardening glue or a transparent hardening resin.

According to a preferred embodiment, the surface structured region of the light conductor has a three-dimensional microstructure of equal configuration, and the first surface structured blind region and the second surface structured blind region have three-dimensional blind microstructures of equal configuration. In this case, the shape of the microstructure may be different from the shape of the hidden microstructure. But more preferably not only the microstructure and covert microstructure are equal in configuration to each other, but the shape of the microstructure and covert microstructure also correspond.

Still more preferably, they have a mean density in the range of 500 to 7000 per square millimeter, preferably in the range of 1000 to 4000 per square millimeter. Such intensity values have proved to produce a brightness distribution in the on state of the light source that is sufficient for optical recognition, while on the other hand, when the light source is switched off, it is optically inconspicuous that the surface structured areas are not recognized by the "naked eye" at the intended viewing distance, in particular the possible views of the functional display are clearly visible. More preferably, the mean densities of the microstructures and the covert microstructures are selected to be substantially the same, with the maximum deviation between the two referring to less than 100 per square millimeter.

Preferably, the maximum dimension of each of the microstructure and the covert microstructure is in the range of 1 μm to 25 μm.

Preferably, the area ratio of the total uncoated surface structured symbol region in the total surface structured region of the relevant main face of the light guide is less than 0.5, preferably less than 0.3.

The optical conductor need not be integrally formed and can be assembled from a plurality of components. In one embodiment, the light conductors each have at least one film, for example a multilayer film structure. For example, the light guide is made by back-molding a transparent film (e.g., a PC film or PE film) with a first material (especially a thermoplastic).

Preferably, the functional display is transparent to the viewer in areas of the display surface other than the uncoated surface structured symbol areas to allow viewing of areas behind the functional display, such as the route in the case of a vehicle or other display.

In order to prevent undesired propagation of light in the light guide and/or the concealing layer, in particular when exposed to extraneous light, according to a preferred embodiment the light guide and/or the concealing layer has an anti-reflection coating, also often referred to as anti-reflection coating or a protective layer, on at least one end face, preferably on the end face opposite to the end face facing the light source. The aim is to reduce the amount of light reflected into the optical conductor on the coated end face, for example by light absorption in the coating, i.e. compared to the uncoated end face. It may propagate circumferentially, for example in addition to a light entrance area provided for light from a light source. The optical refractive index of the anti-reflection coating is, for example, numerically between the refractive index of air and the refractive index of the material of the photoconductor or the concealing layer.

The utility model also relates to an operating element comprising a functional display according to any of the above embodiments. The operating element has, for example, a foot for fastening the operating element to a vehicle component, such as an instrument panel, a cabin panel or, in particular, a steering wheel of a motor vehicle. In this case, the main surface serving as the display surface is configured as or integrated in an operating surface of an operating portion of the operating element for touching or actuation. The operating part is configured, for example, as at least one cantilever lever arm. The cantilever lever arm is arranged on the foot, for example at one side, via a solid joint, in order to pivot the operating part about an imaginary pivot axis against a restoring force relative to the foot under the effect of an operating force acting perpendicularly to the operating surface. For example, a mechanism for detecting the degree of pivoting between the operating portion and the foot is also provided. Solid joints generally refer to regions of a component that allow pivoting between two rigid body regions by bending. By means of the solid joint, a play-free mounting of the operating part on the foot is achieved, so that no rattling occurs. For example, the legs and the handling portion are made of a thermoplastic such as Polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinylchloride (PVC), polyamide (PA), acrylonitrile Butadiene Styrene (ABS) or polymethyl methacrylate (PMMA). The operating element according to the utility model is particularly suitable for designs in which the maximum pivoting degree about an imaginary pivot axis from the non-actuated rest position to the maximally actuated pivot position is less than 10 °, preferably less than 5 °.

The utility model also relates to a steering wheel, for example having a steering wheel hub, at least one steering wheel spoke and a steering wheel rim carried by the steering wheel spoke. The steering wheel according to the utility model further comprises a functional display in any of the above embodiments. The functional display is preferably an integral part of the operating element attached to the steering wheel. For example, the legs of the operating element are fixed to the steering wheel rim in an anti-rotation manner. The display surface of the functional display is preferably arranged between the steering wheel rim and the steering wheel hub or a steering wheel buffer drum covering the steering wheel hub.

Drawings

The present utility model and its technical field are described in detail below with reference to the accompanying drawings. It should be noted that the drawings illustrate a particularly preferred embodiment variant of the utility model, but are not limited thereto. In the figure:

fig. 1 shows a schematic cross-section of a first embodiment of a functional display 1 according to the utility model;

fig. 2 shows a schematic cross-section of a second embodiment of a functional display 1 according to the utility model;

fig. 3 shows a schematic cross-section of a third embodiment of a functional display 1 according to the utility model.

Detailed Description

Fig. 1 schematically shows an embodiment of a functional display 1 according to the utility model for selectively displaying at least one symbol representing a switching function and/or a plurality of switching states, such as a hazard warning symbol or the like. By "selective display" is understood in particular that the light source is switched on and off, so that the symbol is optically apparent to the observer B or the symbol 7z is almost vanished to the observer B by switching off the backlight. In this case, the two light source states should be associated with different switching states and thus with the functional state of the vehicle component.

According to the utility model, the functional display 1 comprises a planar light conductor 2 made of at least one transparent or translucent first material having opposite first and second

main faces

8, 9 and at least one end face 12, wherein the first main face 8 is a display face facing a viewer B, such as a vehicle driver, when the functional display 1 is arranged as intended, and the second main face 9 is arranged facing away from the viewer B. The optical waveguide 2 has opposite first and second

main faces

8, 9 extending parallel to one another, which are connected by end faces, which form a common edge with the first and second

main faces

8, 9 of the optical waveguide 2 on the narrow and long sides of the optical waveguide 2. All end faces are here orthogonal to the first and second

main faces

8, 9 of the light guide body 2. For example, at least one transparent or translucent material is a plastic, preferably a thermoplastic, such as Polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinylchloride (PVC), polyamide (PA), acrylonitrile Butadiene Styrene (ABS) or polymethyl methacrylate (PMMA). The first and second

main faces

8, 9 are understood to be those surfaces of the photoconductor 2 which have the greatest surface area. The first and second

main faces

8, 9 take a substantially planar design except for the surface structures described below.

The light conductor 2 may be provided with a transparent or translucent coating, such as a lacquer layer, or the light conductor 2 may be in a film structure, such as by back-moulding.

The functional display 1 has at least one light source 14, which light source 14 is arranged such that light L from the light source 14 is coupled into the light conductor 2 through the end face 12 of the light conductor 2. In order to improve the light incoupling and/or to adapt the light emission characteristics of the light source 14 to the end face 12 of the light conductor 2, lenses and/or light channels 19 and/or diaphragms may be arranged between the light conductor and the light source. In the exemplary embodiment of fig. 1 to 3, the frame-shaped carrier 13 forms the light channel 19, while the light sources 14 are arranged on a common printed circuit board 15. Light channels 19 are provided to prevent light from passing into the hidden layer 3 belonging to the functional display 1, which hidden layer 3 extends parallel to the light conductors 2. The concealing layer 3 is made of a transparent or translucent second material, such as a plastic, preferably a thermoplastic, for example Polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinylchloride (PVC), polyamide (PA), acrylonitrile Butadiene Styrene (ABS) or polymethyl methacrylate (PMMA).

According to the utility model, at least one of the first and second

main faces

8, 9 of the light conductor 2 (here the first main face 8 facing the observer B) is surface structured by a plurality of microstructures 4 which introduce light-refracting and/or light-scattering effects of the first main face 8. In the illustrated embodiment, the microstructure 4 is understood to be a single depression in the first main face 8, the largest dimension of which ranges from 1 μm to 999 μm, preferably ranging from 1 μm to 25 μm. In the embodiment shown in fig. 1, the microstructures 4 are uniformly spaced, but are distributed only over the surface structured symbol areas 6a of the first main face 8. All microstructures 4 are equal and have a uniform orientation, the microstructures 4 being configured such that they produce a collimated light beam exiting the light guide 2 from light L originating from the light source 14 and having previously entered the light guide 2 through the end face 12.

When the light source 14 is activated, refraction and/or scattering of light in the uncoated surface structured symbol region 6a causes the light L coupled into the light guide 2 to act in the direction of the observer B, so that the observer B can see the luminescent symbol produced by the uncoated surface structured symbol region 6 a. The surface structuring allows, for example, by light refraction and/or light scattering, an enhanced light emission in the direction of the observer B compared to the planar, rather than surface structured design of the first main surface 8 concerned, which can thus be explained by: the light L is made to impinge by the microstructure 4 at an angle which does not meet the total reflection conditions on the boundary surface set by the microstructure 4, so that the light L leaves the light conductor 2 in the region of the microstructure 4. The uncoated surface-structured symbol region 6a reproduces the symbol front as an image, its inverse representation or its contour, for example.

In order to render the symbol unrecognizable and to avoid doubt or perceived errors of the actual switching state when the light source 14 is switched off, in particular when extraneous light is incident, a planar masking layer 3 is provided which extends parallel to the light conductor 2 and is made of a transparent or translucent second material, such that a third main face 10 of the third and fourth main faces 10, 11 of the masking layer 3 faces a second main face 9 of the first and second

main faces

8, 9 of the light conductor 2, which are separated by an air gap 18.

In order to prevent undesired propagation of light in the light guide and/or the concealing layer, especially when exposed to extraneous light, the light guide 2 and the concealing layer 3 have an anti-reflection coating 20, also often referred to as an anti-reflection coating or a protective layer, on at least one end face, preferably on the end face opposite to the end face 12 facing the light source 14. The aim is, for example, to reduce the amount of light reflected into the light guide body 2 on the coated end face compared to the uncoated end face by light absorption in the coating. It may propagate circumferentially, for example in addition to the light entry area provided for the light from the light source 14. The optical refractive index of the anti-reflection coating is, for example, numerically between the refractive index of air and the refractive index of the material of the light conductor 2 or the concealing layer 3.

In the illustrated embodiment, from the perspective of the viewer B, the concealing layer 3 extends under the light guide 2 such that they overlap. In this case, a plurality of light-refracting and/or light-scattering-acting covert microstructures 5 are introduced into the third main face 10 of the third and fourth main faces 10, 11 of the covert layer 3 facing the observer B, thereby defining first and second surface-structured covert regions 7a, 7B. In this case, from the point of view of the observer B, in particular perpendicular to the first main face 8 of the light conductor 2 which acts as a display face and faces the observer B and to the masking microstructures 5 located in the second surface-structured masking region 7B, at least a part of the masking microstructures 5 are laterally displaced and thus appear to lie outside the symbol region 6a alongside the symbol region 6 a. The concealing layer 3 ensures that when the light source 14 of the light conductor 2 is turned off, in particular when extraneous light is incident, the symbol region 6a is optically concealed with its microstructure 4 in the background of the concealing microstructure 5 of the concealing layer 3 and is thus not optically presented anymore, thereby excluding the erroneous judgment of the observer B about the on-off state associated with the symbol reproduced by the symbol region 6 a. The functional display is simple and inexpensive to implement, giving the designer a large degree of freedom of design, which also includes the placement of the functional display.

Fig. 2 shows a second embodiment in which the surface structured areas of the optical conductor 2 are not limited to the uncoated surface structured symbol areas 6a only, but are included as sub-areas. In addition, a coating 16 of a transparent or translucent third material is provided, which coating 16 is applied only locally to the surface structured areas of the first main face 8 of the light conductor 2. The third material is, for example, a transparent hardening paint or a transparent hardening glue or a transparent hardening resin.

The coating 16 is configured such that the coating 16 not only fills the microstructures 4 provided in the coated surface structured region 6b, but the coating 16 also constitutes a continuous surface surrounding the uncoated surface structured symbol region 6a of the first major face 8. In addition to the at least one coherent uncoated surface structured symbol region 6a of the first main face 8, at least one coated surface structured region 6b remains in the surface structured region, while the coated surface structured region 6b loses its refractive properties due to filling of the microstructure 4.

In the second example, the coating 16 therefore sets the uncoated surface-structured symbol region 6a, in particular its boundaries (i.e. the boundary design between the uncoated surface-structured symbol region 6a and the coated surface-structured region 6 b), its position and its dimensions, which depend only on the choice of coating process and no longer on the choice of type and implementation of the surface-structured process. This not only simplifies the manufacturing process, but also increases the freedom of creation of the representation symbol by using a surface coating as a means to achieve the symbol design specifications. This also creates the possibility of being able to pre-cast the optical conductors for a large number of symbols without forcing allocation to specific symbols.

Also in this embodiment, in order to prevent undesired propagation of light in the light guide and/or the concealing layer, especially when exposed to extraneous light, the light guide 2 and the concealing layer 3 are provided with an anti-reflection coating 20, also often referred to as anti-reflection coating or sheath, on at least one end face, preferably on the end face opposite to the end face 12 facing the light source 14. The aim is, for example, to reduce the amount of light reflected into the light guide body 2 on the coated end face compared to the uncoated end face by light absorption in the coating. It may propagate circumferentially, for example in addition to the light entry area provided for the light from the light source 14. The optical refractive index of the anti-reflection coating is, for example, numerically between the refractive index of air and the refractive index of the material of the light conductor 2 or the concealing layer 3.

In a third embodiment of the functional display 1 shown in fig. 3, a second coating 17 made of a transparent or translucent fourth material is applied to the third main face 10 of the concealing layer 3 facing the viewer B, whereby a portion of the concealing microstructure 5 is filled by the second coating 17. Here, the surface structured partial region of the associated third main face 10 of the masking layer 3, which is located below the uncoated surface structured symbol region 6a, is coated with a fourth material when viewed perpendicularly, in order to form a second coating 17. The fourth material is, for example, a transparent hardening paint or a transparent hardening glue or a transparent hardening resin. This embodiment also includes the above-described anti-reflection coating on the light conductor 2 and the concealing layer 3.

Claims

1. A functional display (1) for selectively displaying at least one symbol representing a switching function and/or a plurality of switching states, comprising:

a planar light guide (2) made of at least one transparent or translucent first material, having opposite first and second main faces (8, 9) and at least one end face (12), wherein the first main face (8) faces a viewer (B) as a display face and the second main face (9) faces away from the viewer (B);

at least one light source (14) arranged such that light (L) from the light source (14) is coupled into the light guide (2) through an end face (12) of the light guide (2);

wherein a first main face (8) of the first and second main faces (8, 9) of the light guide body (2) is surface structured by introducing a plurality of light refracting and/or light scattering microstructures (4) of the respective first main face (8) to form surface structured areas of the respective first main face (8); wherein the surface structured areas comprise at least one coherent uncoated surface structured symbol area (6 a) or at least one coated surface structured area (6 b);

wherein, when the light source (14) is activated, refraction and/or scattering of light in the uncoated surface structured symbol region (6 a) results in light (L) coupled into the light guide (2) acting in a direction of the observer (B) such that the observer (B) can see the luminescent symbol produced by the uncoated surface structured symbol region (6 a);

a planar covert layer (3) made of at least one transparent or translucent second material, the covert layer (3) extending parallel to the light guide (2) such that a third main face (10) of the third and fourth main faces (10, 11) of the covert layer (3) faces a second main face (9) of the first and second main faces (8, 9) of the light guide (2), both of which are separated by an air gap (18) or a layer of thinner optical material, and wherein a plurality of light refracting and/or light scattering acting covert microstructures (5) are introduced in at least one third main face (10) of the third and fourth main faces (10, 11) of the covert layer (3) and define first and second surface structured covert regions (7 a, 7B), wherein the symbol (6 a) is misplaced from the viewer (B) by at least a portion of the first and second surface structured covert regions (7 a, 7B) of the covert microstructures (5).

2. Functional display (1) according to claim 1, characterized in that the functional display (1) is a functional display of a motor vehicle.

3. Functional display (1) according to claim 1, characterized in that a coating (16) made of a transparent or translucent third material is provided which is applied only locally to the surface structured region of the first main face (8) of the light guide (2) in order to present at least one coated surface structured region (6 b) of the respective first main face (8) of the light guide (2) and to fill the microstructures (4) provided in the coated surface structured region (6 b) by means of the coating (16), and to retain at least a coherent uncoated surface structured symbol region (6 a) of the respective first main face (8).

4. A functional display (1) according to claim 3, characterized in that the first material and the third material each have an optical refractive index, wherein these refractive indices differ from each other by no more than 0.2.

5. Functional display (1) according to claim 4, characterized in that the refractive indices differ from each other by 0.1.

6. Functional display (1) according to any of claims 3 or 4, wherein the third material is a transparent hardening lacquer or a transparent hardening glue or a transparent hardening resin.

7. Functional display (1) according to claim 1, characterized in that a second coating (17) made of a transparent or translucent fourth material is applied onto the hidden layer (3), whereby a portion of the hidden microstructure (5) is filled by the second coating (17).

8. Functional display (1) according to claim 1, characterized in that the microstructures (4) and the hidden microstructures (5) are embossed and/or molded.

9. Functional display (1) according to claim 1, characterized in that the surface structured areas of the light conductor (2) have three-dimensional microstructures (4) of equal configuration, the first and second surface structured hidden areas (7 a, 7 b) having three-dimensional hidden microstructures (5) of equal configuration with a mean density in the range of 500 to 7000 per square millimeter.

10. Functional display (1) according to claim 9, characterized in that the mean density ranges from 1000 to 4000 per square millimeter.

11. Functional display (1) according to claim 1, characterized in that the maximum dimensions of the microstructures (4) and the hidden microstructures (5) range from 1 μm to 25 μm.

12. Functional display (1) according to claim 1, characterized in that the area ratio of all uncoated surface structured symbol areas (6 a) on the respective first main face (8) of the light guide body (2) is less than 0.5.

13. Functional display (1) according to claim 12, characterized in that the area ratio of all uncoated surface structured symbol areas (6 a) on the respective first main face (8) of the light guide body (2) is less than 0.3.

14. Functional display (1) according to claim 1, characterized in that the light guide (2) and the concealing layer (3) are accommodated in a common frame-shaped carrier (13).

15. Functional display (1) according to claim 1, characterized in that the functional display (1) is transparent to the viewer (B) in a display area outside the uncoated surface structured symbol area (6 a).

16. Operating element comprising a functional display (1) according to any one of claims 1-15 and an operating portion, characterized in that the first main face (8) serving as a display face is configured as or integrated in an operating face for touching or actuating the operating portion of the operating element.

17. Steering wheel for a motor vehicle, characterized by comprising an operating element according to claim 16.