Lighting device with flexible cover film and method of manufacture

Abstract

The invention relates to a lighting device for a vehicle, having a shell-shaped housing (1) in which a number of optical components are arranged for producing at least one light function having at least one predefined light distribution, wherein the housing (1) has a base and a wall (2) projecting from the base, which wall has an opening edge (4) defining an opening of the housing (1), and the lighting device has a cover panel fixedly connected to the housing (1) in the region of the opening edge (4), wherein the cover panel is configured as a printable cover film (3) which is force-locked to the opening edge (4) of the housing (1).

Description

Technical Field

[0001] The present invention relates to a lighting device for a vehicle having a shell-shaped housing in which a number of optical components are arranged for generating at least one light function having at least one predetermined light distribution, wherein the housing has a bottom and a wall protruding from the bottom, the wall having an opening edge defining an opening of the housing, and the lighting device having a cover plate fixedly connected to the housing in the region of the opening edge.

[0002] Furthermore, the present invention relates to a method for assembling lighting equipment according to claim 13 and a method for manufacturing a covering film according to claim 15. Background Technology

[0003] A lighting device for a vehicle is known from DE102023116226A1. The lighting device has a shell-shaped housing with a number of optical components. The opening of the housing is closed by a transparent cover plate. A flat light conductor is disposed inside the housing as an optical component, and light is coupled into the flat light conductor on its narrow side. At least one optical film with micro-optical elements and another optical lens are arranged between the flat light conductor and the cover plate, the at least one optical film with micro-optical elements and the other optical lens being planarly attached to each other. The planar attachment of the optical film and the optical lens on the flat light conductor is achieved by a housing frame mounted to the housing on the front side. The optical film serves as an optical component disposed inside the housing for deflecting the emitted light.

[0004] An operating area for a vehicle interior space is known from EP3690612B1, the operating area having a substrate and a flexible film applied to the substrate. The flexible film serves as an elastomeric layer of the operating area of ​​the vehicle interior space, the elastomeric layer being illuminated from behind by means of an integrated light source.

[0005] A lighting device for a vehicle is known from DE102016123203B4. This device has a shell-shaped housing in which multiple optical structural elements, such as light sources and optics, such as reflectors or light conductors, are arranged. The housing has a bottom and a wall projecting from the bottom, the wall forming an open edge with edge ridges at its free end. To cover the open edge, a cover plate is provided, which is connected to the open edge of the housing by laser welding. The cover plate has a light-transmitting main section and opaque, preferably black, blocking sections on the edge sides. Through the opaque blocking sections, the weld is not visible to an observer from the outside. When the cover plate is manufactured using a two-component injection molding method, the manufacturing cost for the cover plate is relatively high. A relatively large mold half is required. Furthermore, a relatively high material usage is required because the wall thickness of such a cover plate is in the range of 2 mm to 4 mm. Additionally, the recycling of pure species or pure materials is relatively costly. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a lighting device for a vehicle and a method for assembling the lighting device or manufacturing a cover plate, so as to provide an attractive appearance of the lighting device in a manner that is simple and cost-effective in manufacturing technology, wherein, in particular, the durability of the cover plate is ensured.

[0007] To address this task, the present invention, in conjunction with the preamble of claim 1, features that the cover plate is constructed as a printable cover film, the cover film being force-locked to the opening edge of the housing.

[0008] According to the present invention, the cover plate is constructed as a cover film, which is force-locked to the housing of the lighting device at its edge side. Since the cover film is constructed to be printable, it can have transparent or opaque graphics or color gradients, or edge-side shielding layers and / or decorations and / or optical microstructures, giving the lighting device a simple, independent appearance. The cover film is preferably constructed to be flexible, such that at least one edge of the cover film is deformable and force-locked to the opening edge of the housing in the assembly position. Because the cover film is force-locked to the housing only, the separation of the cover film from the housing after the end of the lighting device's service life is simplified. In particular, this also provides material recyclability.

[0009] According to an improvement of the invention, the cover film is configured to be at least partially reversibly deformable or bendable, such that after a force is applied to the cover film in its assembled state, the cover film automatically returns to its initial assembled state. This flexibility of the cover film enables pedestrian protection in the event of a vehicle-pedestrian collision, wherein damage to the cover film is avoided if the applied force does not exceed a predetermined threshold. Therefore, the cover film can advantageously absorb forces flexibly without being damaged. Advantageously, this avoids the need to replace headlights or lamps used as lighting devices. This results in savings in resources, materials, and costs.

[0010] According to an improvement of the invention, the covering film has a wall thickness equal to or less than 1 mm. This provides the desired flexibility or flexibility, enabling it to absorb unwanted forces upon impact and simplifying the force-locking connection structure at the edges of the covering film. Since the covering film is bendable, it can be easily tensioned at its edges.

[0011] According to an improved embodiment of the invention, the covering film is connected to the housing via a threaded connection or a clamping member. Advantageously, this provides a simple, mechanical, and long-term stable connection structure.

[0012] According to an improved embodiment of the invention, the opening edge of the housing has a fixed flange extending from the side wall of the housing, and the edge of the covering film abuts against the fixed flange. An airtight connection can be established between the housing and the covering film through surface abutment.

[0013] According to an improved embodiment of the invention, the edge of the cover film is clamped and / or circumferentially sealed between the fixing flange of the housing and the front frame (Vorsatzrahmen) of the housing. Thus, the edge of the cover film is tensioned or clamped between the two fixing surfaces, wherein the tension force acts substantially perpendicular to the extension direction of the edge of the cover film. Advantageously, this provides a reliable and long-term stable fixing structure.

[0014] According to an improved embodiment of the invention, the edge of the covering film is clamped and / or circumferentially sealed between the fixed flange of the housing and the front frame. This ensures a planar and preferably sealed arrangement, such that the internal space of the housing is sealed off from the surrounding ambient air.

[0015] According to an improved embodiment of the invention, the fixing flange of the housing and / or the front frame has a raised portion and / or a recess on the side facing the edge of the cover film, such that the edge of the cover film is arranged in the assembly position in a manner that deforms transversely to its extending plane. Thus, when the cover film is assembled onto the housing, the edge of the cover film can be deformed and / or forcibly guided when connected to the housing or the front frame.

[0016] According to an improved embodiment of the invention, an additional clamping element is provided to ensure a force-locked assembly configuration of the edge of the cover film on the housing. The clamping element specifically surrounds the free edges of the cover film and the fixed flange, thereby preventing dust accumulation.

[0017] According to an improved embodiment of the invention, the clamping element is configured in a U-shape in cross-section such that the clamping element surrounds the free end of the fixed flange of the engagement housing, the edge of the covering membrane, and, if necessary, the outer edge of the front frame.

[0018] To solve the aforementioned task, the present invention provides an assembly method according to claim 13.

[0019] In the first step, the cover plate is advantageously positioned in an assembly position, where the edge of the cover film is placed flush against the housing's mounting flange and, if necessary, the front frame. In the second step, a force-locking connection is established between the housing's mounting flange and the edge of the cover film, ensuring a fixed and long-term stable connection. If the force-locking connection is a threaded connection, the cover film is preferably detachably connected to the housing, which simplifies recyclability.

[0020] To address the present invention, a manufacturing method according to claim 15 is provided.

[0021] Advantageously, the printing of colors and / or structures and / or decorations and / or optical microstructures on the masking film can be performed while the masking film is flat. Therefore, the printed masking film can be formed in a thermoforming mold under heat and / or pressure, wherein the main sections are substantially constructed to be flat. When the masking film is supplied to the forming mold on a roll rather than in sheet form, the individual masking films are finally separated from each other in sequence by a separating tool. Advantageously, this allows for the manufacture of masking films that, if necessary, have optical structures and / or graphic structures or masking sections. Attached Figure Description

[0022] The embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0023] In the attached diagram:

[0024] Figure 1 The image shows a front view of a lighting device having a covering film that obscures an opening in the device's housing.

[0025] Figure 2 The diagram shows a cross-section of the lighting fixture in the edge region, where the covering film is securely connected to the housing's mounting flange by means of clip-like clamping elements.

[0026] Figure 3 The diagram shows a cross-section of the lighting fixture in the edge region, wherein the masking film is fixedly connected to the housing's mounting flange by means of clip-like clamping elements, and wherein the edge of the masking film is clamped or tensioned between the housing's mounting flange and the front frame.

[0027] Figure 4 The diagram shows a cross-section of the lighting fixture in the edge region, wherein the edge of the shielding film is clamped or tensioned between the fixed flange of the housing and the front frame, and wherein the clamping element has raised portions arranged perpendicularly to its top on its opposing legs.

[0028] Figure 5 The diagram shows a cross-section of the lighting fixture in the edge region, wherein the edge of the shielding film is clamped or tensioned between the fixed flange of the housing and the front frame, wherein the clamping element has raised portions arranged perpendicularly to their tops on its opposing legs, and wherein a bulging sealing element is arranged on one side between the edge of the shielding film and the fixed flange of the housing and on the other side between the edge of the shielding film and the front frame, the sealing element being supported in recesses of the fixed flange and the front frame.

[0029] Figure 6 The diagram shows a cross-section of the lighting fixture in the edge region, wherein the edge of the shielding film is clamped or tensioned between the fixed flange of the housing and the front frame, wherein the clamping element has raised portions arranged perpendicularly to its top on its opposing legs, and wherein planar sealing elements are arranged perpendicularly to each other between the edge of the shielding film and the fixed flange of the housing, and on the other hand between the edge of the shielding film and the front frame, the sealing elements being supported in recesses of the fixed flange and the front frame.

[0030] Figure 7 The diagram shows a cross-section of the lighting device in the edge region, wherein the masking film is fixedly connected to the housing's fixed flange by means of a clip-like clamping element, wherein the edge of the masking film is clamped or tensioned between the housing's fixed flange and the front frame, wherein the fixed flange and the front frame are connected by means of a threaded connector. Detailed Implementation

[0031] Lighting devices for vehicles can be configured, for example, as headlights arranged in the front region of the vehicle to produce at least one light function having at least one light distribution. Alternatively, the lighting devices can also be arranged as taillights in the rear region of the vehicle.

[0032] The lighting device has a shell-shaped housing 1, which has a bottom (not shown) and a surrounding wall 2 extending from the bottom at an angle. The wall 2 has a height such that a light source (preferably not shown) and optical light-shaping devices (optical components), such as reflectors and / or light conductors and / or lenses, are located within the housing 1. The optical light-shaping devices are configured such that they deflect light generated by the light source according to a pre-defined light distribution, such as a near beam distribution and / or a far beam distribution, so that light energy is emitted by the lighting device along the main emission direction H.

[0033] To cover the opening of the housing 1, a cover film 3 is provided as a cover plate. This cover film is made of a light-transmitting plastic material, especially a transparent plastic material, such as PMMA. If the cover film is installed in a headlight, the cover film 3 is made of a glass-like transparent material. Alternatively, the cover film 3 can be colored; for example, if it is used, for example, as a taillight to produce a taillight or brake light distribution, the cover film can be red. The cover film 3 preferably has a constant wall thickness w of less than 1 mm. A The cover film 3 is configured to be flexible. The cover film is flexible such that when a normal force is applied to the cover film 3 while it is mounted on the housing 1, it deforms and automatically returns to its initial state after the force is released. Therefore, the cover film 3 is reversibly deformable. The cover film is elastically changeable in shape, wherein, as long as the force does not exceed a predetermined threshold force that would cause the cover film 3 to tear, the cover film returns to its initial state after the force is released.

[0034] Alternatively, the masking film 3 may be printed with colors and / or optical structures to produce its pre-defined appearance.

[0035] For example, the masking film 3 can be printed with black color around its edge areas, thus creating a masking frame on the masking film 3. Therefore, in particular, the opening edge 4 of the housing 1 can be covered from the outside for the observer.

[0036] The covering film 3 is force-locked to the opening edge 4 of the housing 1.

[0037] According to the present invention Figure 2In the first embodiment, the cover film 3 is clamped and / or latched to the fixing flange 5 extending laterally from the wall 2 of the housing 1. For this purpose, the edge 6 of the cover film 3 abuts against the front side of the fixing flange 5 along the main emission direction H of the lighting device. A clamping element 7 surrounds the fixing flange 5 of the housing 1, which engages the edge 6 of the cover film 3, wherein the opposing legs 8, 8' of the clamping element 7 generate a fixing force F relative to each other. Not only the legs 8 of the clamping element 7 abutting against the fixing flange 5, but also the second leg 8' abutting against the edge 6 of the cover film 3 has a raised portion 9 on the side facing the edge of the fixing flange 5 or the edge of the cover film 3, which enables additional form-locking. In particular, the fixing flange 5 has a recess 10 on the side facing the edge 6 of the cover film 3, a portion of the edge 6 of the cover film 3 being pressed into the recess by means of the raised portion 9 of the leg 8'. Advantageously, this allows for an increased contact surface, and especially for the non-flat contact surface between the edge 6 of the covering film 3 and the fixed flange 5, which improves the clamping force.

[0038] According to an alternative embodiment of the invention (not shown), the clamping element 7 and / or the fixing flange 5 may also be without such a protrusion or recess, such that the edge 6 of the covering film 3 rests flat against the fixing flange 5 and is pressed against the fixing flange 5 by means of the clamping element 7.

[0039] The resulting clamping is preferably performed circumferentially along the edge 6 of the covering film 3. Figure 1 The outline of the lighting device or the cover film 3 or the opening edge 4 of the housing 1 is shown.

[0040] Alternatively, multiple clamping elements 7, preferably of the same construction, may be arranged spaced apart from each other in the circumferential direction of the opening edge 4.

[0041] Preferably, the free end or edge 11 of the covering film 3 and the edge 12 of the fixing flange 5 abut against the top 13 of the clamping element 7. The top 13 of the clamping element 7 connects the first leg 8 to the second leg 8'.

[0042] In this embodiment, the clamping element 7 is configured in a U-shape in cross-section. Preferably, the top 13 and the legs 8 and 8' are configured to be flat, wherein the legs 8 and 8' protrude from the top 13 at right angles.

[0043] The clamping element 7 can be made of metal or plastic. The legs 8 and 8' form locking elements that can only move apart from each other with a predetermined force, so that they apply a locking force F perpendicular to the extension direction of the edge 6 of the cover film 3 and the fixed flange 5 in the assembled position.

[0044] Depend on Figure 1As can be seen, the covering film 3 completely covers and seals the opening of the housing 1. The airtight sealing of the internal space 24 formed in this way in the housing 1 is achieved by the force-locking or clamping connection of the edge 6 of the covering film 3 on the fixed flange 5 of the housing 1.

[0045] According to Figure 3 Another embodiment of the present invention, and according to Figure 2 Unlike the first embodiment, an additional front frame 14 is provided, which is introduced as a separate component into the slot of the clamping element 7.

[0046] In the assembled position, the edge 6 of the cover film 3 extends between the front frame 14 and the fixing flange 5 of the housing 1.

[0047] The same components or component functions in different embodiments are given the same reference numerals.

[0048] This allows for a flat abutment between the edge 6 of the cover film 3 and the front frame 14 and the fixed flange 5, which are located forward along the main emission direction H. On the side facing the edge 6 of the cover film 3, the front frame 14 and the fixed flange 5 have flat abutment surfaces. In this embodiment, the front frame 14 and the fixed flange 5 are also constructed to be flat on the side opposite to the edge 6 of the cover film 3, such that there is no additional form-locking between the legs 8 and the fixed flange 5, and between the other legs 8' and the front frame 14. Instead, the protrusions 9 of the legs 8, 8' are constructed to be flat, so that they abut against the side or surface of the front frame 14 or the fixed flange 5 opposite to the cover film 3.

[0049] According to Figure 4 In another embodiment of the invention, the front frame 14 and the fixing flange 5 have a raised portion 15 or 16 on the side facing the edge 6 of the cover film 3, such that the cover film 3 undergoes deformation at the edge 6 during assembly and preferably undergoes forced guidance. In this embodiment, the raised portion 15 of the front frame 14 and the raised portion 16 of the fixing flange 5 are arranged vertically relative to the extending direction of the top 13 or in the extending direction E of the edge 6 or the fixing flange 5, such that the edge 6 of the cover film 3 is clamped and held in the assembled position in a wavy shape.

[0050] Depend on Figure 3 and Figure 4 It can be seen that the width b of the front frame 14 R The width b corresponding to the fixed flange 5 F The front frame 14 can be implemented as a shielding frame to shield the opening edge 4 of the housing 1.

[0051] According to Figure 5Another embodiment of the present invention, in accordance with Figure 4 In different implementations, the wavy assembly shape of the edge 6 of the covering film can be achieved by means of sealing elements 17 or 18. Sealing elements 17 are arranged not only on the side of the fixed flange 5 facing the edge 6 of the covering film 3, but also on the side of the front frame 14 facing the edge 6 of the covering film 3. These two sealing elements 17 and 18 are staggered along the extension direction of the fixed flange 5 or the covering film 3 and in a direction perpendicular to the top 13 of the clamping element 7. Sealing elements 17 and 18 can be made of elastic material, such as foam. They can be injection molded onto the corresponding surface of the fixed flange 5 or the front frame 14 or installed as separate components in the recess 19 of the fixed flange 5 or the recess 20 of the front frame 14. Sealing elements 17 and 18 are constructed as bulging, elliptical, or circular sealing elements in cross-section, and they preferably extend continuously in the circumferential direction of the covering film 3 as elongated sealing elements 17 and 18.

[0052] According to Figure 6 In an alternative implementation, plate-shaped sealing elements 21, 22 may be provided, thereby increasing the contact surface between the edge 6 of the cover film 3 and the corresponding sealing elements 21, 22.

[0053] According to Figure 7 In an alternative embodiment, the edge 6 of the cover film 3 is tensioned between the fixing flange 5 and the front frame 14 of the housing 1 by means of a threaded connection. For this purpose, a screw 23 is inserted perpendicularly to the fixing flange 5 from the side of the fixing flange 5 opposite to the cover film 3, the screw passing through the edge 6 of the cover film 3 and being threadedly engaged with the front frame 14. The embodiment of the fixing flange 5 and the front frame 14 can correspond to... Figure 4 The implementation method.

[0054] The masking film 3 is made of a thermoplastic material, for example, by extrusion. While the masking film 3 is flat, it is printed with color and / or optical patterns to create, for example, masking sections on the edge sides. In another step, the masking film 3 is formed by applying heat and / or pressure using a thermoforming mold, giving it a desired three-dimensional shape. The masking film 3 is preferably configured to be slightly arched to conform to the contours of a portion of the vehicle body.

[0055] Optional printing on the cover film 3 may include partial painting or the application of a diffuser structure or micro-optical devices on the inner side facing the housing 1. Such a diffuser structure or micro-optical devices can be applied to the cover film 3 using a roll-to-roll method. In the final step after printing and, if necessary, forming, the corresponding cover film 3 is cut or punched. If necessary, the forming may also provide relatively clear bends or curves with relatively small radii.

[0056] For assembling the lighting equipment, in the first step, the edge of the cover film 3 is brought into contact with the fixed flange 5 and, if necessary, the front frame 14. Then, in the second step, a force-locked connection is achieved by installing the clamping element 7 or a threaded connection. When the clamping element 7 is applied to the corresponding contact surfaces of the fixed flange 5, the cover film 3, and, if necessary, the front frame 14, the opposing legs 8, 8' move apart against the spring force until, in the assembled position, the legs press the edge 6 of the cover film 3 against the fixed flange 5 of the housing 1 under the applied fixing force F.

[0057] List of reference numerals

[0058] 1. Shell

[0059] 2 walls

[0060] 3 Cover plate

[0061] 4. Opening edge

[0062] 5 Fixed Flange

[0063] 6 edges

[0064] 7 clamping elements

[0065] 8, 8' outriggers

[0066] 9 raised parts

[0067] 10 recesses

[0068] 11 edge edges

[0069] 12 edge edges

[0070] 13 Top

[0071] 14 Front Frame

[0072] 15 raised sections

[0073] 16 raised sections

[0074] 17 Sealing elements

[0075] 18 sealing elements

[0076] 19 recesses

[0077] 20 recesses

[0078] 21 Sealing elements

[0079] 22 Sealing elements

[0080] 23 screws

[0081] E

[0082] H

[0083] F

[0084] w A

[0085] b R b F

Claims

1. A lighting device for a vehicle, the lighting device having a shell-shaped housing (1) in which a number of optical components are arranged for generating at least one light function having at least one pre-given light distribution, wherein, The housing (1) has a bottom and a wall (2) protruding from the bottom, the wall having an opening edge (4) defining an opening of the housing (1), and the lighting device having a cover plate fixedly connected to the housing (1) in the region of the opening edge (4), characterized in that the cover plate is constructed as a printable cover film (3), the cover film being force-locked to the opening edge (4) of the housing (1).

2. The lighting device according to claim 1, characterized in that, The covering film (3) is configured to be at least partially reversibly deformable.

3. The lighting device according to claim 1 or 2, characterized in that, The covering film (3) has a wall thickness equal to or less than 1 mm (w A ).

4. The lighting device according to any one of claims 1 to 3, characterized in that, The covering film (3) is connected to the housing (1) by a threaded connector (23) or by a clamping member (7).

5. The lighting device according to any one of claims 1 to 4, characterized in that, The opening edge (4) of the housing (1) has a fixed flange (5) extending laterally from the wall (2) of the housing (1), and the surrounding edge (6) of the covering film (3) abuts against the fixed flange.

6. The lighting device according to any one of claims 1 to 5, characterized in that, The edge (6) of the covering film (3) is clamped and / or circumferentially sealed between the fixed flange (5) of the housing (1) and the front frame (14).

7. The lighting device according to any one of claims 1 to 6, characterized in that, The width (b) of the front frame (14) R The width (b) of the fixed flange (5) of the housing (1) and the housing (1) F )same.

8. The lighting device according to any one of claims 1 to 7, characterized in that, The fixed flange (5) of the housing (1) and / or the front frame (14) have a raised portion (9) and / or a recess (10) on the side facing the edge (6) of the cover film (3), such that the edge (6) of the cover film (3) is arranged in the assembly position in a manner that is deformed laterally to its extending plane (E).

9. The lighting device according to any one of claims 1 to 8, characterized in that, An additional clamping element (7) is provided, wherein the edge (6) of the covering film (3) can be clamped to the fixed flange (5) of the housing (1) by means of the clamping element, or the edge (6) of the covering film (3) arranged between the fixed flange (5) of the housing (1) and the front frame (14) is clamped to the fixed flange and the front frame by means of the clamping element.

10. The lighting device according to any one of claims 1 to 9, characterized in that, The clamping element (7) is configured in a U-shape in cross-section and has sealing elements (17, 18; 21, 22) arranged between the edge (6) of the covering film (3) and the fixing flange (5) on the one hand and / or between the edge (6) of the covering film (3) and the front frame (14) on the other hand.

11. The lighting device according to any one of claims 1 to 10, characterized in that, The edge (6) of the covering film (3) is arranged between the fixed flange (5) of the housing (1) and the front frame (14) in a planar and flat abutment, the fixed flange (5) and the front frame (14) are pressed together by means of the clamping element (7), and a plurality of clamping elements (7) are arranged spaced apart from each other in the circumferential direction of the housing (1).

12. The lighting device according to any one of claims 1 to 11, characterized in that, The raised portion (9) and / or recess (10) of the fixed flange (5) and the front frame (14) and / or the sealing elements (17, 18) abutting the fixed flange (5) and the additional sealing elements (21, 22) abutting the front frame are staggered in the extending direction (E) of the edge (6) of the covering film (3), such that the edge (6) of the covering film (3) is wavy in the assembled position.

13. A method for assembling lighting equipment, wherein, A shell-shaped housing (1) having a bottom and a wall (2) extending from the bottom and a cover plate (3) closing the opening of the housing are fixedly connected to each other. The feature is that, in a first step, the cover plate (3) is placed in an assembly position while covering the opening of the housing (1), in which the edge (6) of the cover plate (3) is flatly abutted against a fixing flange (5) extending laterally from the wall (2) of the housing (1), and in a second step, the edge (6) of the cover plate (3) and the fixing flange (5) are tensioned to each other by means of a clamping element (7) that can be fitted from the free side of the edge (6) or by means of a threaded connection.

14. The method according to claim 13, characterized in that, In the first step, the front frame (14) is additionally mounted on the edge (6) of the cover film (3) such that the edge (6) of the cover film (3) is arranged between the fixing flange (5) and the front frame (14), and the fixing flange (5) and the front frame (14) have at least one recess or one protrusion such that after the edge (6) of the cover film (3) is tensioned between the fixing flange (5) and the front frame (14), the edge (6) of the cover film (3) has a wavy shape.

15. A method for manufacturing a covering film (3) according to any one of claims 1 to 12, characterized in that, The masking film (3) is made of thermoplastic material, printed with color and / or optical structure in a flat state, and then shaped by heat and / or pressure, such that the masking film has an arched shape covering the opening of the housing, and the inherent stiffness of the masking film is small enough that the masking film can reversibly elastically deform when a load is applied with a normal force not exceeding a predetermined threshold force.

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