Method for attaching a functional layer to a plastic component of a lighting device

Abstract

Method for arranging a functional layer (10) on a plastic component (11) of a lighting device, in particular a frame, a cover frame, a support frame, an inner pane, a cover pane, a retaining element or the like, wherein the method comprises at least the following steps: - Providing a film-like layer composite (12) comprising the functional layer (10) with a thickness of 10 µm to 60 µm and a substrate (13) with a thickness of 50 µm to 400 µm, - Inserting the layered composite (12) into a receiving device (14) with a heating unit (22), - Switching on a vacuum in the receiving device (14) and suctioning the layered composite (12) via a suction surface (15) of the receiving device (14), wherein the suction surface (15) is provided with a porous metal body (17) via which a full-surface vacuum is generated on the layered composite (12), - Arranging the plastic component (11) on the layer assembly (12), and - partial welding of the layer composite (12) with the plastic component (11) by means of ultrasonic welding, wherein a circumferential weld seam is formed, so that the plastic component (11) forms a welding frame that receives the layer composite (12) around its circumference, and wherein the entire layer composite (12) within the circumferential welding area is heated uniformly via the heated receiving device, so that the welding is carried out at an increased temperature of the layer composite (12) compared to the plastic component (11).

Description

[0001] The present invention relates to a method for arranging a functional layer on a plastic component of a lighting device, in particular a bezel, a cover frame, a support frame, an inner pane, a cover pane, a retaining element or the like, wherein the functional layer in particular comprises a hologram. STATE OF THE ART

[0002] Today's headlights and taillights are both functional and stylistic elements that significantly contribute to a vehicle's overall appearance. The legally mandated functions are achieved through refractive optical systems such as reflectors, lenses, TIR bodies, or light guides, and are implemented as complex systems with numerous components. In the future, in addition to the familiar refractive optics, diffractive and holographic optics will be increasingly used, but their practical application will only become viable with the use and continuous development of LED and laser light sources. Holographic optics can be implemented as a surface structure on a component or as so-called volume holograms using a photopolymer layer as a carrier of the holographic information.

[0003] Furthermore, there are diffractive-optical films with different scattering behavior, which are used as optical scatterers or diffusers in optical systems and can be used to shape a defined light distribution, also in vehicle lighting systems, or decorative films serve for the stylistic design of components.

[0004] Plastic components with an applied functional layer incorporating a hologram will therefore also find application in vehicle lighting systems in the future, particularly to serve as optical elements and / or to fulfill additional design functions and improve the visual appearance of the lighting system. While vehicle lighting systems primarily have functional properties, stylistic requirements are now also emerging, for example, to personalize lighting systems as a vehicle signature.This requires providing lighting functions such as low beam, high beam, cornering light and turning light, or signal functions such as the tail light, brake light, direction indicator, reversing light and rear fog light, as well as being able to indicate the current vehicle status as a reflector, whereby lighting devices may also include design elements such as individually structured or printed surfaces, and holograms may also be used to signify headlights or taillights.

[0005] For example, DE 10 2007 053 399 A1 discloses a lighting device with a hologram that forms a movable beam-shaping element, which in turn serves as a means for adapting light guidance. Holograms are increasingly used for decorative purposes, for example, to fulfill design functions in addition to their technical ones. In particular, holograms embedded in functional layers can be used. The functional layers must be applied to a substrate, for example, a transparent plastic body. Advantageously, the plastic body can form a light lens of the lighting device, or it can form a frame, a bezel, a support frame, an internal illuminated component such as an additional light lens, a reflector, or an opaque viewing surface, or the like.The special feature is that the plastic body with the functional layer can be completely covered with the hologram from the side visible to an observer from the outside of the lighting device. It is also possible to stretch a functional layer within a frame-like plastic component and illuminate it either using a top-lighting method or with backlighting.

[0006] In the future, holographic technology will be used more extensively in lighting systems, particularly as optical and / or graphic elements. Holograms can be created analogously from a real object, written down, or as computer-generated holograms. Computer-generated holograms can therefore represent any illuminated surface, signature, object, or the like, since the holographic image, which is inscribed as illumination information in the holographic medium, can be designed in any way.

[0007] German patent DE 10 2013 206 043 A1 discloses a manufacturing process for a component in which a tool die with a hologram negative acts on the component within a manufacturing tool, thus embossing the hologram during the manufacturing process through the action of the manufacturing tool on the component. The method is advantageous in that plagiarism protection can be ensured with holograms permanently integrated onto components. Furthermore, partial individualization of interior and exterior body components, such as vehicle parts, can be achieved. Disadvantages include the cost-intensive production of the tool and its inflexibility with regard to the production of the combination of a hologram and a plastic component. Additionally, the effects achievable with this method are less vivid and less three-dimensional compared to photopolymer holograms.Known applications of these manufacturing methods include foils with holograms for security features for, for example, banknotes, product labels or identity cards.

[0008] Functional layers containing holograms are extremely thin, for example, less than 100 µm. These thin layers are typically applied as a coating to the substrate, such as a carrier film or the plastic body used to manufacture the component. Because the photopolymer layer, being light-sensitive, must be protected from accidental light exposure through appropriate packaging and handling until it is used to record the holographic information, a film technology is more efficient and simpler to manufacture than a coated plastic body.

[0009] EP 2 923 819 A1 discloses a method for manufacturing a motor vehicle lamp, comprising the following steps: providing a receiving body bounded by a first circumferential profile; providing a lens-shaped body bounded by a second circumferential profile; and at least partially welding the lens-shaped body and the receiving body to the circumferential profiles. The method is characterized in that it provides at least one laser source emitting a beam of light with a characteristic emission spectrum, wherein the step of providing the lens-shaped body involves manufacturing the lens-shaped body using a casting technique and comprising at least a first and a second layer that at least partially overlap and are bonded together, the layers having different transmissivities with respect to the emission spectrum of the laser source.The welding of the lens-shaped body to the receiving body is carried out by means of laser welding, in which the light beam emitted by the laser source is directed in the direction of the circumferential profiles in order to reach the first circumferential profile of the receiving body, after transmission through at least one of the layers of the lens-shaped body, wherein the receiving body acts as an absorbing element and the lens-shaped body as a transmitting element with respect to the light beam.

[0010] DE 199 44 745 A1 discloses a method for infrared bonding a transparent plastic object with a first surface to an opaque plastic object with an opaque bonding surface, comprising the following steps: the transparent object is aligned with the opaque object; the transparent bonding surface is positioned opposite the opaque bonding surface; the IR beam passes through the transparent object; the IR beam is focused on the opaque bonding surface and heats and softens it; the transparent object contacts the opaque object; and the transparent and opaque bonding surfaces are assembled and fused together.

[0011] DE 10 2006 034 752 A1 discloses a lamp for vehicles, consisting of a housing, a lens and at least one lamp element in the lamp, which is permanently connected to the housing, wherein the lens and the housing are permanently connected to each other by means of a resistance welding process, which is carried out by energizing at least one resistance element.

[0012] DE 10 2004 037 517 A1 discloses a method for manufacturing a vehicle lamp comprising the following steps: forming an inclined contact surface of a lens along a circumferential section of the lens in such a way that it does not protrude beyond an outer surface of the lens; forming an inclined contact surface of a lamp body along a front opening of the lamp body corresponding to the inclined contact surface of the lens; and shining a laser beam from outside the lens for laser welding, wherein the laser beam is shining at a predetermined angle of incidence based on the refractive index of the outer surface of the lens, such that the angle of incidence of the laser beam shining onto the contact surfaces is in a direction substantially perpendicular to the inclined contact surfaces. REVELATION OF THE INVENTION

[0013] The object of the invention is to provide a method for attaching a functional layer to a plastic component of a lighting device, wherein the functional layer is to be attached to or combined with the plastic component in a simple and cost-effective manner. In particular, a composite is to be formed between the functional layer and the plastic component that is robust against damage overall and in which the very thin and sensitive functional layer is to be protected.

[0014] This problem is solved starting from a method according to claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0015] According to the invention, the method comprises at least the following steps: providing a layered composite comprising the functional layer with a thickness of 10 µm to 60 µm and a substrate with a thickness of 50 µm to 400 µm; placing the layered composite into a receiving device with a heating unit; applying a vacuum in the receiving device and drawing in the layered composite via a suction surface of the receiving device, wherein the suction surface is provided with a porous metal body, via which a full-surface vacuum is generated on the layered composite;Arranging the plastic component on the layered composite and at least partially joining the layered composite to the plastic component by means of ultrasonic welding, wherein a circumferential weld seam is formed so that the plastic component forms a welding frame that receives the layered composite around its circumference, and wherein the entire layered composite within the circumferential welding area is heated uniformly via the heated receiving device so that the welding is carried out at an increased temperature of the layered composite compared to the plastic component.

[0016] Ultrasonic welding processes can be advantageously adapted with respect to many parameters, making it possible to weld the very sensitive and thin functional layer without damaging it in the intended optical application area. The core concept of the invention lies particularly in the fact that the functional layer is first bonded to a substrate to form a layered composite, making the composite more durable overall, especially when the substrate has a significantly greater thickness than the functional layer with an inscribed hologram. The handling of the composite and the welding of the composite to the plastic component can be carried out using parameters that are also employed in a substantially conventional ultrasonic welding process.For welding, the larger, more robust plastic component is held in a sonotrode and pressed against the composite layer, which is already in contact with the suction surface of the holding device under vacuum. Particularly at the edges, the weld joint can be created using ultrasonic welding. The sonotrode generates ultrasonic vibrations against the holding device, causing the device to act as an anvil. The vacuum applied to the suction surface draws the composite layer so tightly onto the holding device that handling the composite layer is entirely in conjunction with handling the robust holding device. Once the weld is complete, the plastic component is released from the sonotrode, and the vacuum is released, allowing the finished composite, consisting of the plastic component and the welded composite layer, to be removed.

[0017] In particular, the layer assembly can be inserted into the holding device with the substrate facing the suction surface, thus ensuring the functional layer borders the welding area of ​​the plastic component. Alternatively, the layer assembly can be inserted with the functional layer facing the suction surface and the substrate bordering the plastic component. The functional layer has a thickness of 10 µm to 60 µm, and the substrate has a thickness of 50 µm to 400 µm. Therefore, regardless of the orientation of the layer assembly on the suction surface of the holding device, the entire layers can be welded together, so that even if the functional layer is in contact with the plastic component, the substrate is also welded.The reason for this lies particularly in the extremely thin functional layer.

[0018] According to the invention, the partial welding of the layered composite is carried out at an elevated temperature relative to the plastic component. For this purpose, at least the suction surface of the receiving device is heated before and / or during the partial welding of the layered composite to the plastic component by means of the heating unit integrated into the receiving device. After the welding process and removal of the composite from the plastic component, the layered composite cools down, creating mechanical stress on the plastic component as it contracts due to the cooling. This results in a smooth, wave-free surface of the welded layered composite, enabling high-quality implementation of a holographic function.

[0019] A particularly good result is achieved by forming a continuous weld seam, so that the plastic component creates a continuous weld frame that accommodates the films. As the layered composite cools after welding, and especially after the vacuum is released and the composite is removed, tension is created within the composite layer on the plastic component. This results in a wrinkle-free arrangement of the composite layer and thus of the functional layer on the plastic component, producing a reproducible and aesthetically pleasing hologram appearance.

[0020] According to the invention, the suction surface of the receiving device is provided by a porous metal body, via which a surface-wide negative pressure can be generated on the layered composite. A porous metal body, in particular a porous aluminum, preferably an aluminum foam known under the brand name Metapor®, enables the generation of a full-surface negative pressure for suctioning the layers.

[0021] For example, a solid-surface plastic component, such as a lens, can be used to mount the layered composite. The layered composite is clamped and welded to the plastic component via a web, creating a gap between the solid-surface plastic component and the layered composite. The web can, for example, be incorporated around the perimeter of the plastic component and extend along the surrounding weld frame, so that the web overlaps the surrounding weld frame of the mounting device when the layered composite is positioned between the surrounding weld frame and the web. When the plastic component is pressed onto the mounting device, the web is also pressed onto the surrounding weld frame of the suction device, and the layers of the composite seal the suction surface of the mounting device.After the welding process is carried out using the ultrasonic method and the composite is removed from the plastic component and the layer composite, the layer composite can cool down, and the planar stress is formed in the layer composite, whereby as a result the layer composite is stretched over the web at a distance from the surface of the plastic component.

[0022] It is also possible to use a frame-like plastic component, so that the layered composite is freely suspended within the frame after welding. Particularly when the plastic component forms a support frame, a cover frame, or the like with a corresponding recess, it creates the possibility of fully displaying the hologram in the functional layer using transmitted light imaging. This design is advantageously suited to reducing the weight of the assembly. PREFERRED EXAMPLE OF THE INVENTION

[0023] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show: Fig. 1 a cross-sectional view through a receiving device with a layered composite arranged on the top and a plastic component arranged above it, Fig. 2 a detailed view X according to Fig. 1, Fig. 3 a perspective view of the recording device, Fig. 4 a first embodiment of a composite consisting of a plastic component with a layer composite, wherein the plastic component is formed over the entire surface, Fig. 5 Another embodiment of the composite with a layer composite and a plastic component, wherein the plastic component is frame-like and has a recess, Fig. 6. A perspective view of the plastic component with a recess for arranging a layered composite comprising a functional layer and Fig. 7 a composite 1 made of the plastic component 11 according to Fig. 6 and a layered composite comprising the functional layer, wherein the layered composite is only partially shown arranged in the recess.

[0024] Fig. Figure 1 shows a receiving device 14 in cross-section. On the upper side of the receiving device 14 is a porous metal body 17, the upward-facing free surface of the porous metal body 17 forming a suction surface 15. A composite layer 12 is applied to the suction surface 15, bearing flat against it. Above the composite layer 12 is a plastic component 11 comprising a frame cross-section 20.

[0025] The receiving device 14 has a vacuum port 23 with which a vacuum can be generated in the porous metal body 17. The vacuum draws the layered composite 12 to the suction surface 15 of the porous metal body 17, so that the layered composite 12 adheres firmly to the suction surface 15.

[0026] The plastic component 11 can be held in a sonotrode in a manner not shown in detail. By applying a vertically oriented normal force to the suction surface 15, the plastic component 11 is set into a preferably lateral oscillating motion with the sonotrode. This oscillating motion results in ultrasonic welding between the layered composite 12 and the plastic component 11.

[0027] To heat the layered composite 12 before and / or during welding, the holding device 14 has a heating unit 22, which is schematically represented as heating wires. The entire layered composite 12 within the circumferential welding area is heated uniformly via the heated holding device. In particular, the area in which the weld seam between the layered composite 12 and the plastic component 11 is produced is heated. Detail X is shown in the following Fig. 2 shown in more detail.

[0028] Detail X shows a section of the arrangement of the plastic component 11 with the frame cross-section 20 on the receiving device 14. The receiving device 14 comprises the porous metal body 17, which forms the suction surface 15 on its upper side. The composite layer 12, comprising a functional layer 10 and a substrate 13, lies flat on the suction surface 15 of the porous metal body 17. A web 16 is formed on the plastic component 11, which preferably forms a continuous, closed contour. The web 16 seals against a solid support edge 18 with the intervening composite layer, the support edge 18 simultaneously enclosing a portion of the porous metal body 17, which can thus generate a vacuum that draws the composite layer 12 against the suction surface 15.

[0029] When the plastic component 11 is vibrated by a sonotrode, the end face of the web 16 welds to the composite layer 12. The web 16 is designed as an extension of the frame cross-section 20, the frame cross-section 20 enclosing a recess 21. After welding, when the composite consisting of the plastic component 11 and the composite layer 12 is removed from the suction surface 15 by switching off the vacuum, the composite layer 12 within the web 16 contracts due to thermally induced changes in length during cooling and consequently becomes stressed, so that the stressed area of ​​the composite layer 12, together with the functional layer 10, closes part of the recess 21 of the plastic component 11. If a hologram is inscribed in the functional layer 10, it can be viewed in particular through the recess 21 of the plastic component 11, or the hologram is illuminated from behind in particular through the recess 21.

[0030] The weld point 19 is formed only between the web 16 and the layer composite 12, with the functional layer 10, for example, pointing towards the web 16. It is also possible for the layer composite 12 to rest on the suction surface 15 in the opposite direction, so that the substrate 13 points towards the web 16. In both positions, the layer composite 12 can be welded to the web 16 of the plastic component 11, whereby both film-like layers of the layer composite 12, i.e., the functional layer 10 and the substrate 13, can be locally melted and welded during the welding process.

[0031] Fig. Figure 3 shows a perspective view of the receiving device 14 with the porous metal body 17 and a surrounding welded frame 24. The suction surface 15 is formed on the upper side of the porous metal body 17 and enclosed by the surrounding welded frame 24 beneath the overlying plastic component 11. A suction effect can be generated on the suction surface 15 by means of the vacuum connection 23. Although the porous metal body 17 essentially forms a flat surface, its porous properties allow for a full-surface suction effect on the suction surface 15. For this purpose, the vacuum connection 23 is connected to the porous metal body 17 by a vacuum connection (not shown in detail).The circumferential weld frame 24 is brought into overlap with the web 16 of the plastic component 11, wherein, when the plastic component 11 is arranged on the weld frame 24, the layer composite 12 is arranged between web 16 and weld frame 24, as shown in . Fig. 2 shown in cross-section.

[0032] Fig. Figure 4 shows an embodiment of a plastic component 11 with a full-surface design. The layered composite 12, comprising the functional layer, is held at a distance from the surface of the plastic component 11 by means of the web 16. This forms a composite 1, which can, for example, form a light pane or an inner pane as a plastic component 11.

[0033] Fig. 5 shows a variation of Fig. 4. The composite 1 consists of the layer composite 12 with the functional layer, wherein the layer composite 12 is spaced apart from the plastic component 11 by means of the web 16. The plastic component 11 has a recess 21 so that the layer composite 12 with the photopolymer and comprising the hologram can be used within a frame.

[0034] Fig. Figure 6 shows an embodiment of a plastic component 11 in the form of a bezel of a rear light with a recess 21.

[0035] Fig.Figure 7 shows the plastic component 11, in which a layered composite 12 is welded into the recess 21 by a weld seam 25, the weld seam 25 running along the web 16. The layered composite 12 is partially shown to better illustrate its arrangement in the recess 21. This illustrates an example of a composite 1 that includes a plastic component 11 in the form of a bezel, the bezel serving as a support frame for a layered composite 12 with a functional layer comprising a hologram that can be viewed from the outside of a vehicle's taillight.

[0036] The invention is not limited in its implementation to the preferred embodiment described above. Reference symbol list 1 network 10 functional layer 11 Plastic component 12-layer composite 13 Substrat 14 Recording device 15 Intake area 16 Bridge 17 porous metal bodies 18 Support edge 19 welding point 20 frame cross-section 21 recess 22 heating units 23 Vacuum connection 24 surrounding welded frames 25 weld seam

Claims

[1] Method for arranging a functional layer (10) on a plastic component (11) of a lighting device, in particular a frame, a cover frame, a support frame, an inner pane, a cover pane, a retaining element or the like, wherein the method comprises at least the following steps: - Providing a film-like layer composite (12) comprising the functional layer (10) with a thickness of 10 µm to 60 µm and a substrate (13) with a thickness of 50 µm to 400 µm, - Inserting the layered composite (12) into a receiving device (14) with a heating unit (22), - Switching on a vacuum in the receiving device (14) and suctioning the layered composite (12) via a suction surface (15) of the receiving device (14), wherein the suction surface (15) is provided with a porous metal body (17) via which a full-surface vacuum is generated on the layered composite (12), - Arranging the plastic component (11) on the layer assembly (12), and - partial welding of the layer composite (12) with the plastic component (11) by means of ultrasonic welding, wherein a circumferential weld seam is formed, so that the plastic component (11) forms a welding frame that receives the layer composite (12) around its circumference, and wherein the entire layer composite (12) within the circumferential welding area is heated uniformly via the heated receiving device, so that the welding is carried out at an increased temperature of the layer composite (12) compared to the plastic component (11). [2] Method according to claim 1, characterized by , that as a functional layer (10) a photopolymer layer comprising at least a hologram or a decorative film or a diffractive optical film is provided. [3] Method according to claim 1 or 2, characterized by, that the layer assembly (12) is inserted into the receiving device (14) with an orientation in which the substrate (13) points towards the suction surface (15). [4] Method according to claim 1 or 2, characterized by , that the layer composite (12) is inserted into the receiving device (14) with an orientation in which the functional layer (10) points towards the suction surface (15). [5] Method according to any of the aforementioned claims, characterized by , that a full-surface plastic component (11) is used for arrangement on the layer assembly (12), wherein the layer assembly (12) is clamped and welded to the plastic component (11) via a web (16), so that a gap is created between the full-surface plastic component (11) and the layer assembly (12). [6] Method according to any one of claims 1 to 4, characterized by, that a frame-like plastic component (11) is used, so that the layer composite (12) is freely suspended in the frame-like plastic component (11) after welding. [7] Method according to any of the aforementioned claims, characterized by , that by cooling the layer composite (12) after welding a stress is generated in the layer composite (12) in arrangement on the plastic component (11).

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