Method for producing a structure in the volume of an at least partially transparent material using a laser beam

Abstract

The invention relates to a method for producing a structure in the volume of an at least partially transparent material using a laser beam that is moved relative to the material, such that the structure (3) in the material (1) comprises modification bubbles which are formed in a uniform periodic or random arrangement in at least one plane within the volume. The invention is characterized in that a device for emitting a focused laser beam is moved at least in phases relative to the material by means of a multi-axis robot in order to introduce predetermined structures into the inner volume of the material, wherein the device (13) for emitting the focused laser beam (S) comprises at least one laser source, a lens as focusing optics, and a laser scanner.

Description

[0001] The invention relates to a method for producing a structure in the volume of an at least partially transparent material using a laser beam that is moved relative to the material. It also relates to the use of the method for a vehicle.

[0002] For the state of the art, reference can be made to DE 10 2008 021 658 A1. This describes volume modulation using a laser in a emitting body surrounding a light-emitting diode. This allows a type of diffuser to be created in the transparent part of the LED housing, thereby increasing the LED's luminous efficacy. The structure is simply a diffuser, which does not require any graphic representation. To implement the volume modulation, the LED is moved relative to a stationary laser beam, which makes the setup very inflexible for manufacturing.

[0003] Other materials that are structured—for example, using laser beams—are also known from the prior art. WO 2015 / 044 168 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 / 044 168 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 lower 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.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 processing optics that direct a laser beam from a laser source to different points and / or along different paths using movable mirrors. The laser beam is typically focused using a lens. A similar method is also described in US 2015 / 0132541A1.

[0004] DE 10 2015 000 483 A1 describes a method for subsequently changing the color of previously introduced transparent colorants within a coating, such as a paint system, after completion using a laser beam.

[0005] From the two unpublished older German patent applications with file numbers 10 2024 138 585.5 and 10 2024 138 590.1, 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 within 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.

[0006] Further prior art includes devices for cutting material using laser beams. In this process, the material is removed from its surface by means of the laser beam. DE 10 2020 123 146 A1 describes a laser beam being moved by means of a handling device to make the cut. DE 20 2009 016 849 U1 describes an x / y carriage for moving solar modules under a laser beam for cutting. DE 10 2019 200 758 A1 describes the separation of laminated glass panes, whereby the polymeric interlayer is moved beneath a slit in the glass pane by means of a laser.

[0007] The object of the present invention is to provide an improved method for producing in-volume structuring, which can be implemented efficiently, especially for very large components.

[0008] 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 8.

[0009] The inventive method for producing a structure within the volume of an at least partially transparent material using a laser beam, similar to the prior art, involves relative movement between the laser and the material. According to the invention, a device for emitting a focused laser beam is moved at least in phases relative to the material by means of a multi-axis robot in order to introduce predetermined structures into the internal volume of the material.

[0010] 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.

[0011] The structures introduced by the process after material production alter the volume of the transparent material with respect to its optical properties compared to the unstructured volume. According to an advantageous embodiment of the process, the material can be designed as a surface coating, preferably in accordance with the aforementioned earlier German applications with file numbers 10 2024 138 585.5 and 10 2024 138 590.1, as well as the simultaneously filed application of the applicant entitled "Method for determining the layer thickness of an at least partially transparent surface coating" by the same inventors.

[0012] The material's structure comprises modification bubbles arranged in a uniform, periodic, or random pattern in at least one plane within the volume. This allows for the creation of white, gray, and black hues, as well as iridescent colors resembling a rainbow, in the surface coating. The resulting color effect can encompass the entire surface or only specific areas for displaying graphic elements such as logos. The optical effect is achieved by altering transmission and, in particular, reflection using an optical grating, resulting in different visual impressions depending on the viewing angle and the angle of incidence of light.

[0013] In the method according to the invention, a laser source, a lens as focusing optics, and a laser scanner are used as a device for emitting the focused laser beam. Such a laser scanner, as described above, can increase the process speed and further improve the accessibility of surface sections for processing due to the very fast and precise movement of the injected laser beam.

[0014] 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.

[0015] A highly advantageous further development of such a device for emitting the focused laser beam can also involve moving the material and the device into a working position relative to each other, after which the relative movement between the material and the focused laser beam is achieved exclusively 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. They remain there for the duration of the processing. Thus, the movement of the laser beam during the actual processing is solely controlled by the laser scanner. This allows for particularly high manufacturing precision, especially for very small structures with a spacing and / or structure size of less than one micrometer.In order to increase the production speed again, an advantageous embodiment may provide for the feeding of several laser beams into the laser scanner.

[0016] A preferred embodiment of the method according to the invention provides that the material is moved along a slide in two axes. This further increases the flexibility of the processing. In the aforementioned example of vehicles, the slide could be a moving carriage, which also moves the vehicle from station to station through a flow production process. Alternatively, movement of the material via a handling device in more than two axes, particularly in three axes, would also be conceivable. Ultimately, both the material and the device for emitting a focused laser beam could be arranged on independently designed and independently movable multi-axis robots or industrial robots. This embodiment guarantees maximum flexibility in the execution of the relative movement and thus maximum accessibility to even hidden areas on the material.a component provided with the material.

[0017] 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 coating.

[0018] Particularly in the case of such a relatively thin surface coating, it can also be provided that the device for emitting the focused laser beam has a measuring device for detecting the thickness and / or topography of the surface coating. This allows the thickness and / or topography of the layer to be measured in order to precisely apply the structures. The measured values ​​can be used directly for creating the structure or recorded in advance and stored for later use. The measuring device can preferably be designed to operate according to the method described in the simultaneously filed application of the applicant entitled "Method for Determining the Layer Thickness of an At Least Partially Transparent Surface Coating" and by the same inventors.

[0019] 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 German applications with file numbers 10 2024 138 585.5 and 10 2024 138 590.1.

[0020] Further advantageous embodiments will also become clear from the following exemplary embodiment, which is described with reference to the figures.

[0021] This shows: Fig. 1 a schematic view of a system for producing a structure in the volume of a material that is at least partially transparent, here the clear coat of a vehicle; Fig. 2 a cross-section through a substrate with a transparent lacquer layer and a structure inside the lacquer layer; Fig. 3 a top view of the representation according to Fig. 2 in a first embodiment a) and a second embodiment b); Fig. 4 a cross-section through a substrate with a transparent lacquer layer and an alternative design of the structure inside the lacquer layer; and Fig. 5 a photographic illustration of a surface coating according to the invention on a section of a rim.

[0022] In the presentation of the Fig. Figure 1 shows a system 10 for producing an optical structure 3 on a vehicle 11. The structure 3 is to be introduced, in particular, into the inner volume of a surface coating 1 of the vehicle 11, specifically its clear coat. For this purpose, a device 13 is used to emit at least one focused laser beam S. The device 13 can include a laser scanner and a lens to move and focus the laser beam S generated by a laser source in a targeted manner within the clear coat 1, thereby forming the specified structure 3 from modification bubbles, which will be described in more detail later.

[0023] The device 13 is moved relative to the vehicle 11 by an industrial robot 14 with up to 6 axes. Additionally, the vehicle 11 can be moved on an assembly frame or slide 15, for example, in a flow production line. Typically, however, it will remain stationary during the production of the structure 3, and only the industrial robot 14 moves the device 13 to the various required positions relative to the vehicle 11. This allows the desired structures to be incorporated into the clear coat 1, preferably using an ultrashort pulse laser. In the illustration of the Fig. 1. Through the structures 3, for example, a logo 12 is realized, which is indicated here as an example circle.

[0024] Since the clear coat 1 is typically very thin and the structures 3 must therefore be significantly smaller in their dimensions than the clear coat thickness itself, high precision is required. Optionally, a measuring device 16 can be provided in the apparatus 13. This device can be used to measure the thickness and / or topography of the clear coat 1. The measured values ​​can be used directly for the production of the structure 3, or they can be recorded in advance during a simple measuring movement of the apparatus 13 and temporarily stored for the subsequent production of the structure 3. The measuring device 16 can preferably operate according to the method described in the simultaneously filed application of the applicant entitled "Method for Determining the Layer Thickness of an At Least Partially Transparent Surface Coating" and by the same inventors. Fig. 1 The measuring beam designated M can preferably originate from the same laser source as the laser beam S for structuring the volume of the clear coat 1.

[0025] In the presentation of the Fig. Figure 2 shows a section of logo 12 in a schematic and highly magnified cross-section. The clear coat 1 is applied to a substrate designated 2, in this case, for example, the body panel or a base coating thereof. Within the thickness of the clear coat 1, the structures 3 are arranged in three planes, one behind the other, starting from a visible surface 4 of the clear coat 1. Each of these planes can contain a dot matrix.

[0026] In the two in Fig. In the top views shown in 3 a) and b), these dot matrices can be seen in two possible embodiments. Fig. 3 a) shows that individual lines 6, each formed from a series of modification bubbles, create a regular rectangular grid. This acts as an optical grid and can very precisely and homogeneously alter the optical properties across its entire extent, particularly the transmission and remission behavior within the clear coat 1.

[0027] The modification bubbles themselves are droplet-shaped. Their diameter ranges from 0.1 to 10 µm, typically from approximately 2 to 8 µm. These modification bubbles alter the refractive index of the clear lacquer 1 used. According to current understanding, 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.

[0028] Lines 6 are formed by a series of modification bubbles, indicated here by the dotted representation of lines 6. With a spacing x of the lines 6 ranging from a few nanometers to a few tens of micrometers, e.g., approximately 30 micrometers, black, white, and shades of gray can be generated. This allows for a high degree of design flexibility. The somewhat more complex optical gratings enable the achievement of very homogeneous colors or gradients. If this is not strictly necessary, alternatives can be used. Fig. 3 b) Good results can also be achieved. Instead of the periodically repeating lines 6, individual modification bubbles are used, which are distributed in a random pattern. The color nuances then result solely from the average area density of the modification bubbles. However, the resulting gray tone may appear somewhat less homogeneous than in the implementation according to Fig. 3 a).

[0029] It is particularly interesting when in an optical grating, as in Fig. 3a) shows that the distance x between the individual lines 6 is on the order of 400 to 780 nm, i.e., in the visible light range. This allows, as detailed in the earlier German application with file number 10 2024 138 585.5, an iridescent color effect, i.e., a shimmering in rainbow colors, to be achieved.

[0030] With both variants, structures 3 can be subsequently introduced into an already applied layer of clear lacquer 1 via the device 13, e.g. in the form of the brand logo 12.

[0031] If different layers are provided with different grids, different distances x between the modification bubbles in line 6, for the distance x between lines 6 or modification bubbles, and for the distance between the layers can also be selected, further increasing the design possibilities. In addition, the angles of the individual layers to each other and to the visible surface 4 can now also be changed. This is shown in the illustration of the Fig. 4 to recognize which are otherwise analogous to Fig. 2 is to be understood.

[0032] In conclusion, in Fig.Figure 5 shows a photograph of a section of a rim 7 for the vehicle 11. The rim 7 is sealed with clear coat 1. Structures 3 are introduced into this clear coat 1 in at least one plane, particularly parallel to the visible surface 4 of the clear coat 1. These structures represent a logo designated 12, in the image the brand logo "Maybach" (corresponding to a protected trademark of one of the co-applicants). The entire optical effect that makes the brand logo 12 visible as a structure 3 within the clear coat 1 is based on modification bubbles formed in a lattice structure.

Claims

[1] Method for producing a structure (3) in the volume of an at least partially transparent material (1) by means of a laser beam (S) which is moved relative to the material (1) such that the structure (3) in the material (1) comprises modification bubbles which are formed in a uniform periodic or random arrangement in at least one plane in the volume, characterized by , that a device (13) for emitting a focused laser beam (S) is moved at least in phases relative to the material (1) by means of a multi-axis robot (14) in order to introduce predetermined structures (3) into the inner volume of the material (1), wherein the device (13) for emitting the focused laser beam (S) comprises at least a laser source, a lens as focusing optics and a laser scanner. [2] Method according to claim 1, characterized by , that the material (1) is moved in two axes via a slide (15). [3] Method according to claim 1, characterized by , that the material (1) is moved via a handling device in more than two axes, in particular in three axes. [4] Method according to any one of claims 1 to 3, characterized by , that the material (1) and the device (13) for emitting the focused laser beam (S) are moved into a working position relative to each other, after which the relative movement between the material (1) and the focused laser beam (S) is realized exclusively by the laser scanner. [5] Method according to any one of claims 1 to 4, characterized by that several laser beams (S) are fed into the laser scanner. [6] Method according to any one of claims 1 to 5, characterized by , that as at least partially transparent material (1) an at least partially transparent surface coating (1), preferably an at least partially transparent lacquer layer (1), particularly preferably a clear lacquer layer (1), is used. [7] Method according to claim 6, characterized by , that the device (13) for emitting the focused laser beam (S) has a measuring device (16) for detecting the thickness and / or topography of the surface coating (1), the measured values ​​of which are used directly for the production of the structure (3) or are pre-detected and stored for later production of the structure (3). [8] Use of the method according to claim 6 or 7 for in-volume structuring of an at least partially transparent surface coating (1) in or on a vehicle (11) or on a component (7) for a vehicle (11).

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