Method for producing decorative panels with improved structure

Abstract

This invention relates to a method for producing a decorative panel, comprising the following steps: a) applying a decorative layer to a carrier; b) optionally applying an intermediate layer to the decorative layer; c) applying a cover layer to the decorative layer or the intermediate layer; and d) structuring at least one layer (28) to be structured, the layer (28) to be structured being selected from the decorative layer, the intermediate layer, and the cover layer, characterized in that step d) comprises the following steps: d1) generating a laser beam (12); d2) dividing the laser beam (12) into an array (16) of multiple sub-beams; d3) guiding the array (16) of the sub-beams to a modulation In the modulator (24), each sub-beam is selectively deactivated; d4) the sub-beam array (16) from the modulator (24) is directed into the optical scanner (26), the sub-beam array (16) following the modulator (24) comprising all sub-beams directed into the modulator (24) or a reduced number of sub-beams directed into the modulator (24); and d5) the sub-beam array (16) from the scanner (26) is directed onto the layer (28) to be structured; d6) the layer (28) to be structured is negatively structured under the action of the sub-beams to produce a three-dimensional structure (34).

Description

Technical Field

[0001] This invention relates to a method for producing decorative panels. In particular, this invention relates to a method by which highly precise structures can be introduced into panel layers in a simple and adaptable manner at high throughput using laser structuring. Background Technology

[0002] In the production of decorative panels, it may be desirable to provide layers with a structured, corresponding layered structure. This can typically be achieved, for example, by pressing a pressure plate onto the layers to be structured, particularly under the influence of temperature and pressure.

[0003] However, it is also known to introduce structures into the layers to be structured through laser processing.

[0004] DE102005046264A1 describes a method for producing a panel having a surface coating that is at least partially applied, comprising the following steps:

[0005] Apply an untreated porous layer;

[0006] Holes are introduced into the hole layer through laser processing.

[0007] The document also relates to a panel whose surface is at least partially provided with a perforated layer, into which holes are introduced by laser processing.

[0008] EP3685979A1 describes a method for producing floor panels, comprising the following steps:

[0009] Producing press plates with embossed designs;

[0010] Forming the aforementioned floor, wherein

[0011] The embossing plate is used at least to create an embossed portion on the upper surface of the plate, which is then used to form the floor. The embossing in the embossing plate is achieved by laser processing, and the laser processing is a material deposition process.

[0012] However, the aforementioned prior art can provide further improvement potential, particularly regarding the construction of decorative panels through laser processing. Summary of the Invention

[0013] Therefore, the object of the present invention is to at least partially overcome at least one of the disadvantages of the prior art. In particular, the object of the present invention is to provide a solution by which laser structuring can be performed at high resolution and high throughput as part of the production of decorative panels.

[0014] This objective is achieved by a method including the features of claim 1. Preferred embodiments of the invention are provided in the dependent claims or description, wherein further features described or shown in the dependent claims or description may constitute the object of the invention individually or in any combination unless the contrary result is clearly derived from the context.

[0015] A method for producing decorative panels is described, comprising the following steps:

[0016] a) Apply the decorative layer to the substrate;

[0017] b) Optionally, an intermediate layer can be applied to the decorative layer;

[0018] c) Applying a cover layer to the decorative or intermediate layer; and

[0019] d) Structure at least one layer to be structured, wherein the layer to be structured is selected from the group comprising a decorative layer, an intermediate layer, and a cover layer.

[0020] Method step d) includes the following method steps:

[0021] d1) Generate a laser beam;

[0022] d2) An array (matrix) that divides a laser beam into multiple sub-beams;

[0023] d3) The sub-beam array is introduced into the modulator to selectively deactivate the individual sub-beams;

[0024] d4) The sub-beam array from the modulator is introduced into the optical scanner, wherein the sub-beam array downstream of the modulator includes all or a reduced number of sub-beams introduced into the modulator; and

[0025] d5) Guide the sub-beam array from the scanner onto the layer to be structured, where

[0026] d6) The layer to be structured is negatively structured under the action of the sub-beam to produce a three-dimensional structure.

[0027] This method has significant advantages over existing technological solutions.

[0028] This method is used to produce decorative panels. In the context of this invention, the term "decorative panel" should be specifically understood as a wall, ceiling, door, or floor with decoration applied to a supporting panel. Decorative panels are used in a variety of ways in the interior architecture field and as decorative cladding for buildings, such as for exhibition booth construction. One of the most common applications of decorative panels is as floor coverings for ceilings, walls, or doors. For this purpose, decorative panels typically have decorative and surface structures designed to mimic natural materials. It is also advantageous if a tactile sensing structure is suitable for the decoration, i.e., the presence of so-called synchronous holes.

[0029] The method described in this article includes the following steps.

[0030] According to method step a), the decorative layer is applied to the substrate. Therefore, a suitable carrier can be provided first.

[0031] There are no limitations on the carrier itself. In principle, it is preferred that the carrier be made of plastic. Particularly preferably, the carrier may comprise a material containing plastic. Plastics that can be used to produce the corresponding panel or carrier are, for example, thermoplastics such as polyvinyl chloride, polyolefins such as polyethylene (PE), polypropylene (PP), polyamide (PA), polyurethane (PU), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK), or mixtures or copolymers thereof. The plastic may contain common fillers such as calcium carbonate (chalk), alumina, silica gel, quartz powder, wood flour, and gypsum. They may also be colored in known ways. Preferably, the carrier may contain talc as a filler material, for example, the amount of talc is ≥30 wt.% to ≤70 wt.%, particularly ≥40 wt.% to ≤60 wt.%, based on the total material of the carrier. Furthermore, the carrier may be specified to be structurally multilayered, i.e., made of multiple films.

[0032] However, in the context of this invention, it is not excluded that the carrier is wood-based, for example, composed of wood, and thus, for example, an HDF or MDF carrier. Furthermore, the carrier can be, for example, a so-called WPC carrier, without departing from the scope of this invention.

[0033] Furthermore, the application of decorative layers is, in principle, unrestricted. However, in particular, decoration aims to imitate decorative templates. "Decorative template" can therefore be understood in the current sense, specifically as the original natural material, or at least the surface of such material, which will be decorated to imitate or simulate.

[0034] The application of decoration can be achieved, for example, by applying the decoration directly to the carrier, such as by means of a printing process, particularly digital printing. Furthermore, a suitable printed underside surface can be provided on the carrier. Alternatively, for the purposes of this invention, it is not excluded to apply the decoration in a manner such as by applying a pre-printed fiber layer (e.g., a paper layer) or a pre-printed film (e.g., polyethylene, polypropylene, or polyvinyl chloride) to the carrier.

[0035] In the context of this invention, the term "fiber material" refers to materials based on plant, animal, mineral, or even man-made fibers, such as paper and nonwoven fabrics, as well as cardboard.

[0036] In addition, for example, fiber layers or films can be printed onto a carrier to serve as the printing underside.

[0037] Furthermore, according to method step b), an intermediate layer, particularly a transparent layer, may optionally be applied to the decorative layer. Such an intermediate layer can also be selected in principle. For example, the intermediate layer can be used as a protective layer together with the subsequent cover layer. Another possibility is that the intermediate layer is a structural layer, i.e., it can be used, in particular, to introduce structures. As a non-limiting example, the intermediate layer can be, for example, a film, such as a plastic film, which is made of polypropylene, for example. Regarding films made of polypropylene, due to their physical and mechanical properties, it has been shown to be very suitable for laser-based structuring, even at high yields. Furthermore, there is another advantage, for example, that relatively fewer toxic vapors are generated during the evaporation process compared to PVC.

[0038] In principle, the intermediate layer can be made of, for example, elastomers, thermoplastics, amino plastics, or varnishes. Examples of thermoplastics include polyvinyl chloride (PVC), polyolefins such as polyethylene (PE) or polypropylene (PP), polyethylene terephthalate, polyester, thermoplastic polyurethane (TPU), styrene, or derivatives thereof (e.g., ASA, ABS). Examples of amino plastics include, for example, urea and melamine-formaldehyde resins, or mixtures thereof. Examples of varnishes include, for example, acrylic-based varnishes, such as acrylic-based UV-curable varnishes, and / or water-based paint systems.

[0039] Then, according to method step c), a particularly transparent overlay is applied to the intermediate or decorative layer. This layer, used to protect the applied decoration, can be applied in subsequent method steps as an abrasion layer or overlay above the decorative or intermediate layer, which in particular protects the decorative layer from abrasion or damage caused by dust, moisture, or mechanical impacts such as wear. For example, it is conceivable to apply the abrasion and / or overlay as a pre-formed overlay (e.g., based on melamine) to a printing carrier and bond it thereto by pressure and / or heat. Furthermore, it is preferable that a radiation-curable composition, such as a radiation-curable varnish, like an acrylic varnish, is applied to form the abrasion and / or overlay. In this case, the abrasion layer can be specified to include hard materials such as titanium nitride, titanium carbide, silicon nitride, silicon carbide, boron carbide, tungsten carbide, tantalum carbide, alumina (corundum), zirconium oxide, or mixtures thereof to increase the abrasion resistance of the layer. In this respect, the coating can be applied, for example, by a roller (such as a rubber roller) or by a pouring device.

[0040] In addition, the coating layer can be partially cured first, followed by a final coating and final curing with polyurethane acrylate, for example, with a gallium emitter.

[0041] Furthermore, the cover layer and / or abrasion layer may include means for reducing the static charge (electrostatic charge) of the final laminated material. For example, for this purpose, the cover layer and / or abrasion layer may be specified to include a compound such as choline chloride. In this case, the antistatic agent may be present in the cover and / or composition used to form the abrasion layer at a concentration, for example, ≥0.1 wt.-% and ≤40.0 wt.-% of the paper, preferably between a concentration of ≥1.0 wt.-% and ≤30.0 wt.-%.

[0042] Similarly, a transparent abrasion-resistant layer, such as that of a thermoplastic polymer, may be suitable, applied (e.g., laminated) to the decorative layer as a thin film, for example, as a film mesh. If necessary, an adhesion promoter / primer is required, which crosslinks with the decorative layer by radiation curing from above (“adhesive varnish”) or heat sealing (“hot melt”) to achieve sufficient adhesion. Thermoplastic abrasion-resistant layers also offer advantages for the recycling process of the entire structure. Surface structuring can be applied very easily by heating the structured sheet in a press or by heating the structured rolls in a calender (these can also be done concurrently with the decoration).

[0043] Furthermore, in the method described herein, according to method step d), at least one layer to be structured is structured, wherein the layer to be structured is selected from decorative layers, intermediate layers, and overlay layers. As explained above, structuring is specifically used to create tactilely perceptible structures on decorative panels, thereby giving an impression as realistic as possible relative to the original.

[0044] This structuring is essentially performed using lasers, hence the term laser structuring. Laser structuring is performed using the following methodological steps.

[0045] First, laser structuring is performed by generating a laser beam, according to method step d1). In principle, the type of laser beam generation can be chosen. However, specifically, the beam source and the generated laser beam, or its parameters, are selected based on the material of the layer to be structured. Ideally, the material should be evaporated by the laser beam, thus requiring specific parameters to be set accordingly.

[0046] Furthermore, according to method step d2), the laser beam is divided into an array of multiple sub-beams. This step allows the layer to be structured not only to be structured by a single laser beam, but also to be structured simultaneously at a large number of locations. This effectively increases the throughput, thereby improving the efficiency of the method. Each sub-beam can be used independently to generate structures that are separate from each other, or the laser beams can process the same structural locations continuously or simultaneously. Simultaneous processing of the same structural location is possible, especially when combining multiple scanners and corresponding overlaps of scanning fields.

[0047] In this regard, it should be noted that when the laser beam is split, the power data of each sub-beam is also reduced relative to the initial beam, or, assuming ideal conditions, the sum of the sub-beams has the same intensity as the initially generated laser beam. This suggests that multiple sub-beams may be advantageous for processing structures with desired depth, while fewer sub-beams or even just one sub-beam may be sufficient for structures with relatively shallow depth.

[0048] To achieve the aforementioned advantages particularly efficiently, it may be advantageous to perform method step d2) by splitting the laser beam into at least 250 sub-beams, for example, at least 500 sub-beams. This configuration achieves a particularly well-defined structure and also achieves particularly high efficiency. Furthermore, this division is possible using known means.

[0049] In this regard, a further preferred method step d2) involves splitting the laser beam into an array of sub-beams, performed using a diffractive optical element (DOE). Such an element can be, for example, a glass element in a manner known per se, having a microstructure, particularly a two-dimensional grating, which generates corresponding sub-beams from the initial beam through a diffraction pattern. Thus, the diffractive optical element is used as a beam splitter. As a further alternative, a so-called spatial light modulator (SLM) is applicable in principle to method step d2), wherein the invention is not limited in principle to the examples mentioned.

[0050] For example, using two so-called relay lenses, typically implemented as a so-called 4f setup, the sub-beams are separated and coupled into the modulator, as described below. Between the lenses, at the intermediate focal point, there is a mask used to filter out unwanted higher diffraction orders.

[0051] According to the described method, as mentioned above, the sub-beams generated in step d2) are then fed into a modulator for selectively deactivating individual sub-beams. By using such a modulator in the optical path of the laser beam, individual sub-beams can be deactivated, thus preventing them from reaching the layer to be structured or removing them from the optical path. As a result, the applicability of the method can be further improved, or the quality and adaptability of the structure to the template can be further improved. In particular, depending on the structure to be produced, not all sub-beams may be needed, allowing the method to be used for such structures without any problems.

[0052] Furthermore, acousto-optic modulators (AOMs) or electro-optic modulators (EOMs) may be particularly preferred as modulators. In particular, such modulators are capable of rapidly removing individual sub-beams from the beam path leading to the surface to be structured.

[0053] A modulator is understood as an optical element that influences or modulates the frequency and propagation direction or intensity of incident light. For this purpose, a grating is generated in an acousto-optic modulator using sound waves in a transparent solid. At this grating, the corresponding beam or sub-beam is diffracted, and its frequency is shifted. Light deflection in prior art acousto-optic modulators operates based on the principle of light diffraction at a grating. Correspondingly, in electro-optic modulators such as crystals, the optical thickness changes instantaneously as a function of the applied external electric field strength, thereby allowing the individual sub-beams to deflect. Thus, optical modulation based on electro-optic crystals occurs.

[0054] In particular, when combined with an acousto-optic modulator or electro-optic modulator as described above, it is perhaps even more preferable to use the beam trap in conjunction with the modulator. This makes it possible to reliably invalidate subbeams removed from the beam path, preventing them from impacting the surface to be structured, and furthermore, they do not have a negative impact on the environment or even pose a hazard.

[0055] In the method described above, step d4) further includes guiding a sub-beam array from the modulator into an optical scanner, wherein the sub-beam array downstream of the modulator comprises all or a reduced number of sub-beams introduced into the modulator. Thus, the sub-beam array exiting the modulator can be guided into the optical scanner, which therefore comprises a corresponding pattern of sub-beams suitable for the structure to be applied. The optical scanner can then guide the corresponding sub-beams to the desired locations of the layers to be produced, thereby causing the corresponding structuring. In this case, the optical scanner can guide all sub-beams onto the layer simultaneously, or, depending on the scanner, different sub-beams can be guided independently onto the layer to be structured.

[0056] Therefore, optical scanners are used to guide sub-beams to the correct location of the layer to be structured, with positional accuracy depending on the structure to be produced.

[0057] It is particularly advantageous that at least one of the polygon scanner and the galvanometer scanner can be used as an optical scanner. For example, a polygon scanner or a galvanometer scanner or a galvanometer scanner and a polygon scanner can therefore be used, although of course multiple galvanometer scanners and / or polygon scanners can also be used.

[0058] This type of scanner is particularly well-suited for operation within a high dynamic range, and therefore ideal for achieving high throughput. Thus, in particular, the industrial production of decorative panels can be achieved through the use of this scanner, where efficient production can be combined with detailed construction. Specifically, the aforementioned scanner is advantageously used for applications involving very fine structures.

[0059] galvanometer scanners are particularly suitable for applications in which most of the processing plane is unprocessed, resulting in time gain due to the so-called "jump" between processing areas.

[0060] However, for constructing an entire surface, a polygon scanner is particularly suitable. By using a polygon scanner, a linear processing procedure can be selected, allowing scanning speeds >1 km / s. Therefore, in this application, the combination of a modulated switchable sub-beam and a polygon scanner as a deflection unit appears particularly advantageous for maximizing productivity. The sub-beams can be arranged in arrays of any shape, such as squares, rectangles, or lines.

[0061] Therefore, according to method step d5), the sub-beam array can optionally be guided from the scanner onto the layer to be structured using a suitable focusing optics.

[0062] Due to the influence of sub-beams, structuring is now performed according to step d6) of structuring the layer to be structured under the influence of sub-beams or sub-beam arrays, so as to generate a three-dimensional structure through negative structuring. Negative structuring is understood to refer to structuring in which a structure is introduced from the layer to be structured by selectively reducing the thickness of the corresponding layer, i.e., in the present case, material is removed from the layer according to the layer to be manufactured, particularly by evaporation.

[0063] It should also be noted that steps d2) to d6) above are preferably performed in numerical order, although the invention is not limited thereto. Furthermore, additional intermediate steps, or the beam passing through additional components between the components, may be inserted without departing from the scope of the invention. If this is thus described as radiation being guided or advanced from one component to another, this may include direct or direct guidance without other intermediate components, as well as indirect guidance with the insertion of other components. However, it is equally possible, however, to perform structuring using only method steps d1) to d6), such that the structuring consists of method steps d1) to d6).

[0064] The method described in this paper has significant advantages over known methods in the prior art.

[0065] In particular, the method described in this paper can use laser structuring to structure decorative panels, enabling high-volume and therefore efficient methods while achieving very precise structuring. This allows for the realization of exceptionally high-quality tactile sensory structures. This applies both to tactile sensation, creating a very realistic impression, and to the design reference templates for the structures. Due to the individual methodological steps, especially the laser structuring steps, the templates can be mimicked to the level of template identity, which further improves the structuring results.

[0066] Furthermore, this method is particularly effective because it enables high throughput. This is because structuring can be performed very quickly and with high quality due to the individual method steps, allowing for very high speeds of rolling the semi-finished products constructed for decorative panels. This also applies to continuous feeding as well as timed or sequential feeding. Therefore, the synergistic effect of the combination of the various method steps enables structuring that can be used on a large scale without any compromise in quality or flexibility. Therefore, the present invention particularly relates to a method by which high-precision structures can be introduced into panel layers in a simple and adaptable manner at high throughput via laser structuring.

[0067] Furthermore, structures can be introduced in a highly defined manner, allowing the layers to be structured, such as paint layers, to remain very thin. This is particularly advantageous in terms of cost and weight.

[0068] Furthermore, this method can improve the recyclability of the produced boards. In principle, it also offers a high degree of flexibility in construction, providing significant advantages, especially when combined with decorative applications utilizing digital printing.

[0069] Preferably, in method step d6), the layer to be structured can be negatively structured under the action of a sub-beam to produce a three-dimensional structure, such that material bulges are generated in the edge regions of the introduced structure by material discharge (e.g., material jetting of molten material).

[0070] This method can produce remarkably realistic structures. This is because sharp edges around the inserted structure are prevented in this way. More precisely, rounded edges can be created by material lifting, which introduces a structure that is tactilely very similar to the structure being replicated, such as a wooden structure.

[0071] Furthermore, the material height makes it easier to represent deep structures because the perceived depth of a structure is not just the actual depth of the introduced structure, but also the depth beyond the material height. This makes it possible to create deep or deep-working structures without the risk of damaging any decoration that might exist beneath the structure.

[0072] In detail, high-quality decorative panels typically strive to realistically reproduce the structure of wood or stone, for example, with a maximum possible structural depth in the range of 30–250 μm, particularly 80–140 μm. The material bulges created by the structuring process result in an increased tactile and visual perceived structural depth in the layer to be structured (e.g., the overlay of this product).

[0073] Depending on the process parameters, the material height can range, for example, from 1 to 100 μm. As a result, the thickness of the layer to be structured can be reduced while maintaining the structural depth. This offers the advantage of allowing for higher laser radiation transmittance during ablation to produce greater volumetric absorption without damaging the decorative layer (if present), or the use of a less favorable laser wavelength relative to the optimal wavelength for the coating material to be processed.

[0074] Furthermore, the method offers a high degree of variability. This is because the layer to be structured can be formed, for example, in the form of a thin film. In this case, the film can have a corresponding structure, for example, before lamination and printing. Additionally, the structured film can be applied to an already printed substrate to structure it on the substrate, and the film can also be printed from the back side. In principle, a so-called "roll-to-roll" process can also be used, where the film is unrolled from a roll, structured and stored on the roll until it is applied to the substrate. Alternatively, as mentioned above, the film can also be applied to the substrate immediately after structuring.

[0075] To control material emissions, it is advantageous to select at least one of the following based on the material of the layer to be structured: specific wavelength, pulse energy, pulse duration, spot diameter, repetition rate (i.e., the frequency of the pulsed laser), and pulse overlap (i.e., the percentage overlap of individual pulses in the scanning direction), and laser radiation impacts the layer to be structured.

[0076] In particular, these parameters can affect the incident intensity of radiation and the heat accumulation in the material to be structured, and thus directly determine the melt formation that occurs.

[0077] As a layer to be structured, the exemplary parameters used to create material bulges in transparent polypropylene are roughly as follows.

[0078] When using a UV UKP laser, the following parameters can be used:

[0079] Wavelength: 343nm

[0080] Spot diameter: 50μm

[0081] Repetition rate: 100kHz

[0082] Pulse energy: 36μJ

[0083] Pulse length: 300 fs

[0084] Pulse overlap: 80%

[0085] The height of the generated material: 1 μm

[0086] When using an infrared UKP laser, the following parameters can be used:

[0087] Wavelength: 1030nm

[0088] Spot diameter: 58μm

[0089] Repetition rate: 700kHz

[0090] Pulse energy: 70μJ

[0091] Pulse length: 800 fs

[0092] Pulse overlap: 80%

[0093] The height of the generated material: 2μm

[0094] When using a CO2 laser, the following parameters can be used:

[0095] Wavelength: 10.2μm

[0096] Spot diameter: 250μm

[0097] Repetition rate: 200kHz

[0098] Pulse energy: 500μJ

[0099] Pulse length: 2μs

[0100] Pulse overlap: 80%

[0101] The height of the generated material: 30 μm

[0102] For example, the material height can be in the range of >0 to ≤100m, preferably in the range of ≥5 to ≤30m.

[0103] Regarding the formation of material bulges, the following points should be noted.

[0104] Ablation during the structuring process is initiated by melting and evaporating the material of the layer to be structured. The recoil of the evaporated molecules causes partial ejection of molten material, which deposits as a material ridge at the edge of the structure. In other words, the resulting ablation morphology has a material height in the height profile, resulting from the ejection of molten material at the edge of the ablation pit. Therefore, the expression of this material height largely depends on the ratio of melt-based material ejection to evaporate-based material ejection.

[0105] The ratio between the laser radiation and the melting-based and evaporation-based interaction regions of the material can be optimally tuned in this process by adjusting the wavelength, pulse energy, and pulse duration of the laser radiation irradiating the layer to be structured, as well as the spot diameter, repetition rate, and pulse overlap. The decisive factor here is the radiation absorption behavior in the material of the layer to be structured. While surface absorption maximizes the proportion of evaporation-based ablation for the same energy input, the proportion of melting-based ablation increases with increasing volumetric absorption due to the lower proportion of energy transferred to the material.

[0106] Based on this principle, material-dependent laser radiation with specific wavelengths, pulse energies, and pulse durations can be selected to set the desired ratio of material ablation based on melting and evaporation. The aim here is, for example, to maximize material jetting in the edge regions of the introduced structure without damaging any decorative layers that may exist beneath the unstructured layers due to excessive transmission.

[0107] In principle, besides using only a single laser beam source with specific power, wavelength, beam profile, and spot diameter, it is also possible to combine multiple different beam sources with varying powers, wavelengths, beam profiles, and spot diameters. For example, it is possible to combine a 10 kW CO2 laser with a wavelength of 10.25 μm and a spot diameter of 250 μm with a 1 kW UKP laser with a wavelength of 343 nm and a spot diameter of 50 μm. This has several advantages in the structuring process. Most of the required material removal can be performed by the preceding CO2 laser spot, while the subsequent UKP laser spot performs fine finishing to achieve higher structural resolution. Therefore, the corresponding processing system can be designed to be more cost-effective due to the varying prices depending on the output power of each laser. It is also conceivable to preheat the material using only a CO2 laser and then remove it using a UKP laser. Different beam profiles can also be used, such as the classic Gaussian beam profile for material removal and the annular beam profile or so-called top hat beam profile with a uniform intensity distribution for preheating the material. The corresponding beam profile can be generated either in the beam source or through corresponding optical elements in the beam path, such as an axonometric pyramid, grating, or mirror.

[0108] In this embodiment, painting, which can be performed after structuring, is particularly advantageous by preventing sharp edges. This is because the radius generated by the material height allows for improved surface wettability during the coating process, as described below.

[0109] Regarding the coatability of the structured layer as described above, this can therefore be affected as follows. Due to the proportion of melting-based ablation, the ablation morphology produced in the structured layer can lead to improved coatability of the structured surface. If the material is mainly absorbed by the surface through radiation and thus removed by evaporation, sharp-edge structures with small radii are produced in the upper and lower edge regions of the ablation pit.

[0110] Due to the surface tension of the paint system, wetting of the coating layer becomes more difficult, especially in the lower region of the ablation pit. If the material is also discharged through volumetric absorption, and is therefore melt-based, the melt discharge described earlier results in a structure with less sharp edges and a larger radius in the upper and lower regions of the ablation pit. This is advantageous for wetting during the coating of structured surfaces compared to structuring primarily based on evaporation.

[0111] Regarding laser structuring, it is further advantageous that step d) is performed using a laser selected from ultrashort pulse lasers, CO2 lasers, and excimer lasers. In particular, by using the aforementioned laser sources, the method, especially the laser structuring sub-step, can be performed efficiently, making convincing structuring results possible.

[0112] If an ultrashort pulse laser, also known as a UKP laser, is used in laser structuring, it is preferable that step d) is performed in such a manner that the wavelength of the generated laser beam is in the range of ≥150 nm to ≤1070 nm, the laser operates at a power of ≥500 W to ≤100,000 W, and the beam diameter of the laser beam is in the range of ≥10 μm to ≤500 μm. Using these parameters, the material of the layer to be structured can preferably be evaporated, and thus negative structuring can be reliably performed. Furthermore, very fine structures with high contrast can be generated, making the structuring results appear particularly realistic.

[0113] It should be noted that, in principle, the wavelength and beam diameter apply equally to both the initial beam and the generated sub-beams for all lasers used. On the other hand, the power decreases from the initial beam's power to the sub-beam's power as a function of the number of generated sub-beams.

[0114] Particularly preferably, in method step d), the laser beam can be generated in a pulsed manner, using a pulse frequency in the range of ≤100 MHz and a pulse duration in the range of ≤1000 ns, approximately from ≥2100 fs to ≤1000 ns. This embodiment is particularly possible by using an ultrashort pulse laser. This pulsed application of the laser beam is particularly capable of generating the lowest possible thermal stress on the layer to be structured or the material of the layer to be structured. Therefore, particularly high surface quality of the structured layer can be achieved.

[0115] Furthermore, the combination of the ultrashort pulse laser in step d1) and the polygon scanner as an optical scanner in step d5) offers particular advantages. This is because, in order to remove material with the lowest possible melt and thermal stress on the workpiece, the required laser power of the UKP laser is typically in the range of a maximum of 50 W. The polygon scanner, in particular, offers a promising opportunity to increase productivity by utilizing the increased average laser power of the UKP laser. This allows for scanning on the workpiece at high scanning speeds and high repetition rates greater than 1 km / s. Splitting the laser beam into an array of sub-beams that move across the workpiece using a galvanometer scanner also helps reduce thermal stress on the workpiece, even at high power densities.

[0116] Further preferred, and particularly as an alternative to using a UKP laser, step d) can be performed using a CO2 laser, wherein the wavelength of the generated laser beam is in the range of ≥9.8μm to ≤10.6μm, wherein the laser operates in the power range of ≥500W to ≤100000W, and wherein the beam diameter of the laser beam is in the range of ≥150μm to ≤1000μm.

[0117] This type of laser is also advantageously suited to the methods described herein, and is readily available in large quantities and in various forms on the market. Therefore, particularly when using a CO2 laser, good adaptability to specific applications or desired results can be achieved.

[0118] As an alternative, step d) can be performed using an excimer laser, wherein the wavelength of the generated laser beam is in the range of ≥100 nm to ≤380 nm, wherein the laser operates at a power in the range of ≥1000 W to ≤100000 W, and wherein the beam diameter of the laser beam is in the range of ≥150 μm to ≤1000 μm, for example up to ≤500 μm. Such a laser can also advantageously operate in pulsed mode, which can maintain very low thermal stress on the layer to be structured.

[0119] Preferably, prior to method step d5), the method includes additional method steps:

[0120] d7) Guiding the laser beam through a scanning objective, particularly an f-θ objective. Using a scanning objective, especially an f-θ objective, allows the laser beam or laser to be positioned on a planar image field, i.e., on the planar surface of the layer to be structured. In this case, the focal size can remain almost constant. Therefore, by using a scanning objective, particularly defined structuring can be performed, in which particularly fine structures can be represented with exceptionally high quality.

[0121] For example, in step c), a film-like interlayer can be applied to the decoration, and this interlayer can be structured in step d). The interlayer, such as the film-like interlayer, can in particular be formed of plastic, such as polypropylene.

[0122] In principle, as already noted above, relay lens assemblies can be provided, for example, having two lenses at different points in the optical path. This allows sub-beams to be spatially separated. This can provide opportunities to insert more components (such as masking devices). Furthermore, relay lens assemblies can advantageously achieve or improve coupling to optical components (such as modulators or scanners). For example, the lens assembly can be implemented as a so-called 4f setup, where 4f refers to the arrangement of the modules and the spacing between them, and f represents the focal length of the lens. Attached Figure Description

[0123] The invention will now be explained in more detail with reference to the accompanying drawings.

[0124] Figure 1 An illustration of an implementation of the method according to the invention is shown. Detailed Implementation

[0125] exist Figure 1 The embodiment of the method according to the present invention is shown in the figure.

[0126] In detail, Figure 1 First, the beam source 10 that generates the laser beam 12 is shown.

[0127] according to Figure 1 The beam source 10 in the configuration is an ultrashort pulse laser, wherein the wavelength of the generated laser radiation is in the range of ≥150 nm to ≤1070 nm. Furthermore, the beam source 10 operates at a power in the range of ≥500 W to ≤100000 W, and the laser beam 12 has a beam diameter in the range of ≥10 μm to ≤500 μm. Moreover, the laser beam 12 is generated in a pulsed manner by using a pulse frequency in the range of ≤100 MHz and a pulse duration in the range of ≥100 fs to ≤1000 ns.

[0128] The resulting laser beam 12 now illuminates a diffractive optical element 14, in which the laser beam 12 is divided into an array 16 of multiple sub-beams. For example, the laser beam can be divided into more than 250 or more sub-beams. Depending on the design of the diffractive optical element 14, the incident laser beam 12 can therefore be divided into a desired number of principal diffraction orders, thereby splitting into sub-beams.

[0129] Subbeams can be coupled to a deflection unit and spatially separated by a relay lens assembly, for example using two lenses 18 and 20, typically implemented as a so-called 4f setup. Furthermore, at the intermediate focal point, a mask 22 is provided between lenses 18 and 20, which filters out unwanted higher diffraction orders. Additionally, behind mask 22 and in front of the second lens 20, a so-called acousto-optic multichannel modulator (AOMC) is provided, as an example of an acousto-optic modulator (AOM) or modulator 24. In the AOM, the conversion of acoustic waves in a transparent solid produces a grating that diffracts and deflects the subbeam, typically into a beam trap. This is used to selectively shut off individual subbeams.

[0130] In this configuration, multiple individual AOMs can be used in principle to fully process the array 16 of sub-beams via modulator 24, and to individually modulate or switch sub-beams. In contrast, a multi-channel AOM allows for the modulation of multiple individual sub-beams. In principle, multiple modulators 24 or one or more multi-channel modulators 24 can be used.

[0131] Figure 1 The diagram schematically illustrates the presence of a reduced number of sub-beams in array 16 after modulator 24, which are now guided into optical scanner 26, which serves as a deflection unit. With the aid of scanner 26, the sub-beams can be guided at high speed onto the surface or layer 28 of the semi-finished product 30 for decorative panels, where they are to be structured. Optical scanner 26 is specifically a polygon scanner.

[0132] More precisely, after exiting the scanner 26, the sub-beam can be focused onto the workpiece or the layer 28 to be structured by the f-θ objective lens 32. The f-θ objective lens is used in particular because, on the one hand, it keeps the laser point focused as the radiation deflects on the workpiece, and on the other hand, it can partially compensate for the scan field distortion that occurs in mirror-based 2D scanning systems, thereby enabling a constant scanning speed on the workpiece.

[0133] In principle, regardless of the specific design, the following should be mentioned. Besides the distortions caused by the deflection system and focusing optics, the diffractive optical element 14 can already induce distortion in the working plane, and this distortion increases due to the increased distance between sub-beams and the increased number of beams in array 16. This problem can be addressed, in addition to optical compensation methods such as the f-θ objective 32, by creating software-based, scanner-based scan vector corrections for each individual sub-beam. However, as an alternative or supplement, additional compensation for distortion is still possible through any optical component, such as the f-θ objective 32.

[0134] Figure 1 The diagram also schematically illustrates how layer 28 to be structured is negatively structured under the influence of matrix 16 at the sub-beam to produce a three-dimensional structure 34. In this case, layer 28 to be structured can be, for example, a thin film made of polypropylene, which is applied to the decorative layer. Furthermore, it is possible to generate material bulges caused by material discharge 20 in the edge regions of the introduced structure 34.

[0135] After the structuring shown, optionally, a cover layer can still be applied to the structuring layer to produce the finished decorative panel.

[0136] In addition, circumferential interlocking devices can be introduced, which can allow panels to interlock with other panels, for example, in the production of floor coverings.

[0137] An exemplary embodiment for structuring may be as follows.

[0138] For processing panels measuring 1300×1280mm, the following setup might be an example. A total of 9 polygon scanners can be used, with a scanning field size of 450mm. 2 ×450mm 2 The sub-beam spot size is 50 μm. Furthermore, 50% pulse overlap of the corresponding pulses generated by the scanner can be achieved. Additionally, 160 ablation layers can be used, resulting in 0.5 μm ablation per layer or per processing step for a structure depth of 80 μm.

[0139] The processing time for each panel can be 2.229 seconds, for example, the panel feed speed is 35 m / min.

[0140] In addition, each scanner 26 can process 740 45-watt (energy flow 0.08J / cm²) units. 2 The system comprises switchable sub-beams, which are divided and arranged in rows via DOE 14 and can be switched via corresponding AOMs. The distance between each sub-beam striking the panel can be approximately 600 μm.

[0141] Using this embodiment, the processing speed of the polygon scanner can be 717 m / s, the required laser power can be 300 kW, and the required repetition rate or frequency of the UKP laser can be 28.68 MHz. The pulse length can be <10 ps, ​​preferably <1 ps.

[0142] Using the above values, namely the panel size and the panel processing parameters, the vector length of each panel, 10,649,600m, can be obtained. This is the total length of the laser processing line caused by all processing operations, which is calculated by multiplying the line length of each panel by the number of processing layers.

[0143] Reference Symbol List

[0144] 10 beam sources

[0145] 12 laser beams

[0146] 14 Diffractive optical elements

[0147] 16 array

[0148] 18 lenses

[0149] 20 Lenses

[0150] 22 Mask

[0151] 24 Modulator

[0152] 26 Scanners

[0153] 28th floor

[0154] 30 Semi-finished products

[0155] 32f-θ objective lens

[0156] 34 structure

Claims

1. A method for producing decorative panels, comprising the following steps: a) Apply the decorative layer to the substrate; c) Apply a cover layer to the decorative layer; as well as d) Structure at least one layer (28) to be structured, wherein the layer (28) to be structured is selected from the group consisting of: the decorative layer, and the cover layer. Its features are: Method step d) includes the following method steps: d1) Generate a laser beam using a laser (12); d2) Divide the laser beam (12) into an array (16) of multiple sub-beams; d3) The array (16) of the sub-beams is guided into the modulator (24) for selective deactivation of the individual sub-beams; d4) Introducing an array (16) of the sub-beams from the modulator (24) into an optical scanner (26), wherein the array (16) of the sub-beams following the modulator (24) comprises all the sub-beams introduced into the modulator (24) or a reduced number of sub-beams introduced into the modulator (24); and d5) The array (16) of the sub-beams from the optical scanner (26) is directed onto the layer (28) to be structured; wherein d6) The layer to be structured (28) is negatively structured under the action of the sub-beam to produce a three-dimensional structure (34).

2. The method according to claim 1, characterized in that, In method step d6), the layer (28) to be structured is negatively structured under the action of the sub-beam used to generate the three-dimensional structure (34), such that material bulges caused by material expulsion are generated in the edge region of the introduced structure (34).

3. The method according to claim 2, characterized in that, In order to control the material discharge, at least one of the following is selected based on the material of the layer to be structured (28): specific wavelength, pulse energy, pulse duration, spot diameter, repetition rate, and pulse overlap of the laser radiation irradiating the layer to be structured.

4. The method according to claim 1 or 2, characterized in that, The modulator (24) is used in conjunction with at least one beam trap.

5. The method according to claim 1 or 2, characterized in that, Method step d2) is performed by splitting the laser beam (12) into at least 250 sub-beams.

6. The method according to claim 1 or 2, characterized in that, Use at least one of a polygon scanner and a galvanometer scanner as an optical scanner (26).

7. The method according to claim 1 or 2, characterized in that, Method step d) is performed by using an ultrashort pulse laser, wherein the wavelength of the generated laser beam (12) is in the range of ≥150nm to ≤1070nm, wherein the ultrashort pulse laser operates in the power range of ≥500W to ≤100000W, and wherein the laser beam (12) has a beam diameter in the range of ≥10µm to ≤500µm.

8. The method according to claim 7, characterized in that, In method step d1), the ultrashort pulse laser is used as a beam source (10), and in method step d5), the polygon scanner is used as an optical scanner (26).

9. The method according to claim 1 or 2, characterized in that, Method step d) is performed by using a CO2 laser, wherein the wavelength of the generated laser beam (12) is in the range of ≥9.8μm to ≤10.6μm, wherein the CO2 laser operates in the power range of ≥500W to ≤100000W, and wherein the laser beam (12) has a beam diameter in the range of ≥150μm to ≤1000μm.

10. The method according to claim 1 or 2, characterized in that, Method step d) is performed by using an excimer laser, wherein the wavelength of the generated laser beam (12) is in the range of ≥100nm to ≤380nm, wherein the excimer laser operates in the power range of ≥1000W to ≤100000W, and wherein the laser beam (12) has a beam diameter in the range of ≥10μm to ≤1000μm.

11. The method according to claim 1 or 2, characterized in that, The method includes an additional method step prior to method step d5): d7) The array (16) of the sub-beams is guided through the scanning objective.

12. The method according to claim 1 or 2, characterized in that, The laser beam is split into multiple sub-beams by the diffractive optical element (14) in method step d2).

13. The method according to claim 1 or 2, characterized in that, In method step c), a film-like intermediate layer is applied to the decorative layer, and in method step d), the intermediate layer is structured, wherein the cover layer is applied to the intermediate layer.

14. The method according to claim 13, characterized in that, The intermediate layer is formed of thermoplastic, amino plastic or paint.

15. The method according to claim 11, characterized in that, The scanning objective is an f-θ objective (32).

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