Method for producing a structure in a volume of an at least partially transparent surface coating by means of a laser beam

Abstract

The invention relates to a method for producing a structure in a volume of an at least partially transparent surface coating by means of a laser beam that is moved relative to the surface coating. The invention is characterized in that the structuring is carried out by means of a focused laser beam in a processing volume which incorporates the surface coating as part of the processing volume, the entire processing volume being scanned by the focused laser beam.

Description

[0001] P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0002] 1

[0003] Method for producing a structure in a volume of at least partially transparent surface coating using a laser beam

[0004] The invention relates to a method for producing a structure in the volume of an at least partially transparent surface coating by means of a laser beam which is moved relative to the surface coating.

[0005] Materials that are structured—for example, using laser beams—are known from the prior art. WO 2015 / 044168 A1 describes transparent glass or glass-ceramic materials in its introductory section as prior art, in which microcracks are created within the volume using a laser beam. These microcracks scatter the light, so that, with a suitable arrangement of the microcracks within the material's volume, three-dimensional images can be generated. WO 2015 / 044168 A1 further develops this fundamentally known method by using a laser beam to non-destructively modify the optical properties of the material in order to reduce transmission or remission and increase absorption coefficients. This allows the material properties to be adjusted to achieve an image quality that goes beyond simply creating microcracks.

[0006] DE 10 2020 125 679 A1 discloses a device and a method for processing surfaces using a laser. In this process, a surface coating is processed both on the surface and within its interior using the laser in order to change the appearance of the surface or to refine the surface.

[0007] For further information on the state of the art, reference can also be made to DE 10 2015 000 483 A1, which describes the color changes in a coating by laser activation P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Promotion of Applied Research e. ​​V. / Device and method for the production of photonisophore crystals / ST / PM / 2024037859 / 08 December 2025

[0008] Reference is made to DE 10 2020 123 146 A1, which describes a laser-activatable dye, and DE 10 2019 200 758 A1, which describes the separation of a laminated glass pane by means of a laser to destroy the laminate layer.

[0009] The movement / focusing of the laser at different points in the material is achieved using a so-called laser scanner. In laser processing and laser welding, the term "laser scanner" typically refers to a processing optic that uses movable mirrors to direct a laser beam from a laser source to different points and / or along different paths.

[0010] From the two unpublished earlier German patent applications with file numbers 10 2024 138 585.5 and 10 2024 138 590.1, filed by the same applicants, it is known to provide materials, such as surface coatings or varnishes, with optical structures that enable graphic representation and color changes. For this purpose, modification bubbles are formed in the material in a uniform, periodic, or random arrangement in at least one plane within the volume. This allows, for example, the creation of iridescent colors in the case of periodic structures spaced on the order of the wavelength of visible light. The structures function in the manner of an optical grating.

[0011] From two further unpublished older German applications, file numbers 10 2024 138 957.5 and 10 2024 138 958.3, filed by one of the applicants, it is also known how such structures can be produced. It is crucial to position the structure precisely on the surface during production, which requires accurate knowledge of the layer thickness and / or the topography of the surface coating. Even though the method described in 10 2024 138 958.3 requires precise knowledge of the position of the P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for producing photonisoheric crystals / ST / PM / 2024037859 / 08 December 2025

[0012] 3

[0013] While surface coating in space is possible, precisely positioning the equipment and structures is very complex. This is especially true when processing surface coatings, such as paints, on large components, e.g., on vehicles.

[0014] The object of the present invention is therefore to provide an improved method for producing an in-volume structuring, which can do without knowledge of the exact position of the surface coating in space.

[0015] According to the invention, this problem is solved by a method with the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments of the method according to the invention are set forth in the dependent claims. Furthermore, the problem is solved by using the method according to claim 9.

[0016] The inventive method for producing a structure within a volume of an at least partially transparent surface coating using a laser beam provides that the structuring is carried out within a processing volume using a focused laser beam. Within this processing volume, the entire volume is scanned by the laser beam in order to make the corresponding modifications to the material. According to the invention, the surface coating is enclosed within the processing volume as part of it. The processing volume is therefore larger than the volume of the surface coating that is to be structured.

[0017] In this process, the laser beam source is first roughly positioned, and the laser beam parameters suitable for processing the surface coating are set. Then, not only is the surface coating itself structured, but also the P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for producing photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0018] The entire processing volume is covered in four steps, so that attempts are made to create structures above, below and, if necessary, to the sides of the surface coating.

[0019] Using a laser beam tuned to the material of the surface coating, the desired structure is created within the volume of the coating. If the laser beam strikes the substrate supporting the coating, no structuring occurs, or at least none that is optically effective. Conversely, if the laser beam strikes the air surrounding the surface coating on its opposite surface, no structuring is achieved.

[0020] The inventive method, which scans the entire processing volume with the laser beam, therefore eliminates the need for knowledge of the surface coating thickness and its exact position in space. This is achieved by selecting a processing volume large enough to encompass the entire surface coating to be structured. In this case, it is sufficient to process or scan the entire volume, and any unintentional focusing in the surrounding atmosphere or in the substrate layer for the surface coating has no adverse effect. Consequently, the method can be implemented very simply and efficiently without requiring high measurement accuracy with regard to the layer thickness and topography of the surface coating.

[0021] According to a preferred further development, the processing volume is cuboid in shape and defined by a starting point and a spatially diagonally opposite endpoint. It is then only necessary to ensure that the starting point lies, for example, below the lowest level of the surface coating and on the edge of the desired structuring area. Then structuring can be carried out across the entire area. [P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025]

[0022] 5

[0023] The desired effect can be achieved simply and efficiently by considering the volume between the starting point and the endpoint.

[0024] A suitable processing volume, which takes into account the expected position and thickness of the surface coating on the one hand, and incorporates typical manufacturing tolerances with a certain safety margin on the other, can be used to structure identical components with a surface coating in series production without requiring these components to have exactly the same dimensions and to measure them before structuring. This enables very fast and efficient series production, which is ideally suited, for example, for structuring at least partially transparent paint layers, especially clear coat layers, on or in vehicles or vehicle components.

[0025] As described in the aforementioned earlier writings, the structure can include modification bubbles, which are formed in a uniform, periodic, or random arrangement in at least one plane within the processing volume. This allows for the creation of white, gray, and black hues, or even iridescent colors resembling a rainbow, in the surface coating. The resulting color impression can encompass the entire surface or only specific areas for the representation of graphic elements such as logos. The generation of this optical effect through the alteration of transmission and, in particular, remission using an optical grating creates different optical impressions depending on the viewing angle and the angle of incidence of light.The entire processing volume is thus structured accordingly by focusing the laser in the area of ​​each potentially generated modification bubble. As mentioned above, in practice the modification bubbles are then only realized within the surface coating, since a P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e V / Device and method for the production of photonisoheric crystals / ST / PM / 2024037859 / 08 December 2025.

[0026] 6

[0027] Focusing in the ambient air or in the substrate does not lead to the desired optically effective structural changes.

[0028] The structures themselves are formed in several levels with point grids or line grids, whereby corresponding color effects can be achieved by different line or point spacings or by omitting individual points in an otherwise uniform grid.

[0029] Within the processing volume, the planes are designed parallel to each other according to the invention, in order to be able to scan the entire volume quickly and efficiently.

[0030] For structuring purposes, according to a highly advantageous embodiment of the inventive method, at least one device for emitting a focused laser beam is provided. According to a highly advantageous embodiment, this device can be moved in several axes in space by a robot or a handling device.

[0031] The use of a multi-axis robot or industrial robot offers the advantage that even complex and / or large components, such as entire vehicles, can be reliably textured with the desired structures at various points on their internal and external surfaces. This allows, for example, the subsequent application of these structures to painted surfaces. The structure itself is generated within the material's volume using a focused laser beam, such as an ultrashort pulse laser.

[0032] In an advantageous embodiment of the method according to the invention, at least one laser scanner as defined above is used as the device for emitting the laser beam. Such a laser scanner can increase the process speed and improve the accessibility of surface sections due to the very fast and precise movement of the emitted laser beam. P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for producing photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0033] 7. Further improvements to the processing. To provide the required focused laser beam or to focus it on the point to be processed, this laser scanner is combined with a downstream optical lens.

[0034] In particular, but not exclusively, such a laser scanner allows processing to be carried out during the setup process using the multi-axis robot. This "on-the-fly" processing is very fast and can be implemented in very short cycle times.

[0035] A highly advantageous further development of the use of a laser scanner involves moving the material and the device for emitting the focused laser beam into a working position relative to each other. The relative movement between the material and the focused laser beam is then solely controlled by the laser scanner. The multi-axis robot, and possibly also the carriage or handling device, moves the device and the material into this working position, where they remain for the duration of the processing. Thus, the movement of the laser beam during the actual processing is controlled exclusively by the laser scanner. This allows for particularly high manufacturing precision, especially for very small structures with distances and / or structure sizes of less than one micrometer.In order to increase the manufacturing speed, an advantageous embodiment may provide for the introduction of several laser beams into the at least one laser scanner.

[0036] As mentioned above, a surface coating that is at least partially transparent can be used as the material; preferably, this is designed as a lacquer layer, in particular a clear lacquer. P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0037] 8

[0038] It can particularly preferably be formed on a vehicle or on a component for a vehicle, for which the manufacturing process according to the invention is then used to form an in-volume structuring of the surface coating, e.g. in the manner described in the above-mentioned earlier applications 10 2024 138 585.5 and 10 2024 138 590.1.

[0039] Further advantageous embodiments will also become clear from the following exemplary embodiments, which are described with reference to the figures.

[0040] This shows:

[0041] Fig. 1 shows a schematic view of a system for producing a structure in the volume of an at least partially transparent surface coating, here the clear coat of a vehicle;

[0042] Fig. 2 shows a three-dimensional section of a substrate with a transparent lacquer layer and a structure inside the lacquer layer;

[0043] Fig. 3 shows a top view of the representation according to Fig. 2 in a first embodiment a) and a second embodiment b);

[0044] Fig. 4 possible forms of modification bubbles; and

[0045] Fig. 5 is a photographic illustration of a surface coating according to the invention on a section of a rim.

[0046] Figure 1 shows a three-dimensionally curved

[0047] Surface coating 1 in the form of a clear lacquer 1 shown schematically. P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0048] 9

[0049] The clear coat layer 1 is curved and lies in space in Figure 1, without the supporting substrate 2, which is visible in Figure 2. The section of clear coat 1 shown is the section to be provided with an optically effective structure 3, as further illustrated and described in Figures 2 ff. To avoid needing precise knowledge of the position and thickness of the clear coat 1, the process of introducing the structures 3 into the volume of the clear coat 1 is carried out within a processing volume 10, outlined by a dashed line in Figure 1. Within this processing volume 10, a laser beam S, which can be focused with pinpoint accuracy, is used to create a modification bubble 5 (Figs. 2 ff) in the clear coat 1 at each of the scanned positions, as described later.The laser beam S is guided through the processing volume in individual planes, which are stacked according to the arrow, starting from a starting point 11 at the front bottom of Figure 1 and ending at an endpoint 12 at the rear top of Figure 1. The laser beam S thus scans the entire processing volume 10 and attempts to generate the aforementioned modification bubble 5 at each point where this is intended. At least one laser beam S can be generated and focused with pinpoint accuracy by a device 13. This device 13 can, for example, include a laser scanner, which can position the laser with high precision within small areas, such as rectangles with sides of a few hundred meters. The device 13 also includes an optical lens, which is configured to provide the necessary high-intensity focusing of the laser beam for generating the modification bubbles 5.This device 13, comprising the laser scanner and a lens, is then supplied with the laser via a free beam or a fiber laser. It can preferably be positioned on a suggested robot arm 14, allowing it to move along several axes within space. P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for producing photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025.

[0050] 10

[0051] The inventive method works such that the laser beam S is focused accordingly at each point where a modification bubble 5 might be required. If the ambient air is located within the processing volume 10 at this point, nothing happens. If the clear coat 1, on whose material the processing parameters of the laser beam S are set, is located at this point, the desired modification bubble 5 is formed here. If the laser beam S penetrates the substrate 2 located below the clear coat 1, nothing happens here either.

[0052] By applying the appropriate structuring 3 over a large area within the processing volume 10, ensuring that the clear coat layer 1 is completely enclosed, it is guaranteed that the entire clear coat layer 1 is structured in its desired area, for example, to display a logo. Nothing happens to the surrounding areas, allowing them to be processed without any problems. Depending on the size of the processing volume 10, this is significantly faster and more cost-effective than prior measurement of the position and thickness of the clear coat 1 followed by a very complex adjustment of the system. Such an adjustment would be particularly time-consuming because it would require a very high accuracy of less than 10 m.

[0053] Figure 2 shows a three-dimensional section of a portion of the clear lacquer 1 on the comparatively thin substrate 2. The scale is for illustrative purposes only and does not correspond to reality. Within the clear lacquer 1, the structures 3 are arranged in different levels 3.1, 3.2, ... 3.n. Starting from the substrate 2, a lower level 3.1 is shown, consisting of modification bubbles 5, indicated here as stars. In the lower level 3.1, these stars are not filled in. In the next level above, 3.2, the stars symbolizing the modification bubbles 5 are filled in to improve their distinguishability. These levels 3.1 and 3.2 can P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Promotion of Applied Research e V / Device and method for the production of photonisoheric crystals / ST / PM / 2024037859 / 08 December 2025.

[0054] 1. Many more levels follow, as indicated here by the dots. In the illustration of Figure 2, an upper level 3.n is shown below the visible surface 4 of the clear coat 1.

[0055] For example, in level 3.2 and in level 3.n individual defects 8 can be seen, via which specific optical properties can be achieved.

[0056] The modification bubbles 5 already mentioned, as well as the structures 3 generated by the laser beam S, can be designed and arranged in various ways. In the two top views shown in Figure 3 a) and b), these point matrices can be seen in two possible embodiments. In Figure 3 a), it can be seen that individual lines 6, each formed from a series of modification bubbles 5 (described in more detail in Figures 4 and 5), create a regular rectangular grid. This grid acts as an optical grating and can very precisely and homogeneously alter the optical properties, particularly the transmission and remission within the clear coat 1, across its entire extent.

[0057] The lines 6 are formed by a series of modification bubbles 5, which is indicated here by the dotted representation of the lines 6. With a spacing x of the lines 6 of a few tens of pm, e.g., approximately 30 pm, but in any case above the order of magnitude of visible light, black, white, and shades of gray can be produced. This allows for a high degree of design flexibility. The somewhat more complex optical gratings enable the achievement of very homogeneous colors or color gradients. If this is not strictly necessary, good results can also be achieved with the alternative shown in Figure 3 b). Here, instead of the periodically repeating lines 6, individual modification bubbles 5 are used, distributed in a random pattern. The color nuances then arise solely from the average area density of the modification bubbles 5.The generated grey tone can be P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Promotion of Applied Research e V / Device and method for the production of photonisoheric crystals / ST / PM / 2024037859 / 08 December 2025.

[0058] 12, however, appear somewhat less homogeneous than in the implementation according to Figure 3 a).

[0059] It is particularly interesting when, in an optical grating as shown in Figure 3a), the distance between the modification bubbles 5 of each individual line 6 is on the order of 400 to 780 nm. The distance x between the individual lines 6 is, for example, more than 30 pm. This allows an iridescent color effect, i.e., a shimmering in rainbow colors, to be achieved, as is explained in detail in the aforementioned 10 2024 138 585.5.

[0060] With both variants, structures 3 can be selectively introduced into an already applied layer of clear lacquer 1 via the device 13, according to a predetermined optical design, e.g. in the form of a brand logo.

[0061] The modification bubbles 5 themselves are droplet-shaped. Their diameter ranges from 0.1 to 10 pm, typically from approximately 2 to 8 pm. The modification bubbles 5 alter the refractive index of the clear lacquer 1 used. According to current findings, this is likely due to a reorganization / rapid solidification of the molten clear lacquer 1, as well as a local change in chemical composition caused by irradiation.

[0062] Figure 4 illustrates various conceivable alternative shapes for the individual modification bubbles 5. Spherical, cylindrical, octahedral, torus-shaped, and other possible shapes of the modification bubbles 5 are shown in principle. Similar to the modification bubbles 5 described above, they can be achieved using a focused laser, whereby the corresponding settings of the laser beam S are adjusted to achieve the desired shape of the modification bubble 5. P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025

[0063] 13

[0064] Finally, Figure 5 shows a photograph of a section of a rim 7 for a vehicle 11, which is not shown in its entirety. The rim 7 is sealed with clear lacquer 1. Structures 3 are incorporated into this clear lacquer 1 in at least one plane, in particular parallel to the visible surface 4 of the clear lacquer 1. These structures represent a brand logo, in this case, the logo of the "Maybach" brand (corresponding to a registered trademark of one of the co-applicants). The entire optical effect that makes the brand logo visible as a structure 3 within the clear lacquer 1 is based on modification bubbles 5, which are formed in a lattice structure.

Claims

P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025 14 Patent claims 1. Method for producing a structure (3) in a volume of at least partially transparent surface coating (1) by means of a laser beam (S) which is moved relative to the surface coating (1), characterized in that the structuring is carried out by means of a focused laser beam (S) in a processing volume (10) which includes the surface coating (1) as part of the processing volume (10), wherein the entire processing volume (10) is scanned by the focused laser beam (S).

2. Method according to claim 1, characterized in that the processing volume (10) is cuboid in shape and is defined by a starting point (11) and a spatially diagonally opposite endpoint (12).

3. Method according to claim 1 or 2, characterized in that the structure (3) comprises modification bubbles (5) which are formed in at least one plane (3.1 , 3.2, ... 3.n) in the processing volume (10).

4. Method according to claim 3, characterized in that the structure (3) comprises several levels (3.1 , 3.2, ... 3.n) with point grids or P 2023-03322WO / 2023PF03322 / ILT - 2021 F66500 / Mercedes-Benz Group AG, Fraunhofer Society for the Advancement of Applied Research e. ​​V. / Device and method for the production of photonisophoric crystals / ST / PM / 2024037859 / 08 December 2025 15 Line grids made up of modification bubbles (5) are included.

5. Method according to claim 4, characterized in that the planes (3.1 , 3.2, ... 3.n) are formed parallel to each other in the processing volume (10).

6. Method according to one of claims 1 to 5, characterized in that at least one device (13) for emitting the focused laser beam (S) is used for structuring, which is moved in several axes in space via a multi-axis robot (14) or a handling device.

7. Method according to claim 6, characterized in that a laser source and at least one laser scanner with a downstream optical lens are used as the device (13) for emitting the focused laser beam (S).

8. Method according to one of claims 1 to 7, characterized in that an at least partially transparent lacquer layer (1), preferably a clear lacquer layer (1), is used as the at least partially transparent surface coating (1).

9. Use of the method according to any one of claims 1 to 8 for in-volume structuring of an at least partially transparent surface coating (1) in or on a vehicle or on a component (7) for a vehicle.

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