Surface-structured substrate with improved heat transfer

Abstract

The invention relates to a surface-structured substrate, having at least one first outer surface with a heat transfer region. Heat transfer properties of the substrate are advantageously increased within the heat transfer region. The invention additionally relates to a structured component which has such a surface-structured component, to a method for producing a surface-structured substrate, and to the use of a surface-structured substrate in an electronic circuit.

Description

[0001] SURFACE-STRUCTURED SUBSTRATE WITH IMPROVED HEAT TRANSFER

[0002] TECHNICAL FIELD

[0003] The present invention relates to a surface-structured substrate comprising at least one first outer surface with a heat transfer region. Within the heat transfer region, the heat transfer properties of the substrate are advantageously enhanced. Furthermore, the invention relates to a structured component comprising such a surface-structured component, a method for producing a surface-structured substrate, and the use of a surface-structured substrate in an electronic circuit.

[0004] STATE OF THE ART

[0005] A higher operating temperature of elements, such as semiconductor devices, leads to a reduction in their conductivity. Cooling such elements, especially semiconductor devices, is usually achieved with macroscopic heat sinks made of materials with high thermal conductivity properties. Typical heat sink designs use a series of fins or pins to maximize the surface area of ​​the heat sink, resulting in greater heat transfer to the surrounding medium. However, this approach encounters difficulties when the elements to be cooled are integrated components (devices) that are only a few millimeters or even smaller. The choice of heat sink material also plays an important role in ensuring high heat transfer. Among metals, copper and aluminum alloys are typically used for heat sinks.

[0006] As is well known, increasing the surface area improves the heat exchange properties of materials such as metals, which is the basis of the heat sink principle. In order to improve the cooling properties, i.e. the ability of a surface to dissipate heat, at the microscopic level, micro- or nanostructured thermally conductive materials have already been created. For example, Ayer (Study of the Influence of Surface Roughness on Heat Transfer; 2011) describes the role of surface roughness of aluminum surfaces on heat transfer. As a result, greater roughness increases the amount of heat transferred, which is in line with the general rule of increasing surface area. Furthermore, Jones et al.(The Influence of Surface Roughness on Nucleate Pool Boiling Heat Transfer; 2009) systematically investigated the changes in pool boiling of aluminum surfaces with different roughness and contact angles, finding that the heat transfer coefficient increases significantly at roughness values ​​greater than 1 pm. Roughness values ​​(R) were investigated. a ) in the range of 1.08 pm to 10.0 pm.

[0007] On the other hand, Ventola et al. (Rough surfaces with enhanced heat transfer for electronics cooling by direct metal laser sintering; 2014) investigated the thermal properties of laser-sintered heat sinks and found that roughened surfaces increased heat transfer to a peak value of 73% compared to flat surfaces. Furthermore, surface roughness also affects a body's emissivity, which in turn influences radiative heat transfer. As shown by Vorobyev et al. (Brighter light sources from black metal: Significant increase in emission efficiency of incandescent light sources; 2009), a significant increase in emissivity was observed when microstructures were fabricated on the filament of a tungsten lamp.

[0008] In addition, Alamri et al. (Increasing heat transfer of metals through periodical microstructures using Direct Laser Interference Patterning; 2019) also investigated the heat transfer properties of stainless steel plate surfaces featuring line-like microstructures with varying spatial spacing and depth. Periodic line structures in the micrometer and submicrometer range were created using so-called Direct Laser Interference Patterning (DLIP).

[0009] The fundamental problem with increasing surface roughness or enlarging the surface is that it is difficult to create defined structures. The disadvantage is that the energies introduced into the surface are usually so great that instead of a defined increase in the surface area compared to the non-structured surface, a polishing effect sometimes occurs. Due to the high heat diffusion lengths in the materials, the structures created become too large and, particularly with materials such as copper, the processing of which requires electromagnetic radiation in the UV range, very long heat diffusion lengths can occur. As a result, the known structures can only be applied to materials that have a short heat diffusion length. The disadvantage is that it is difficult to combine the advantageous properties of high thermal conductivity with high heat transfer at the surface of the layer.

[0010] TASK

[0011] The present invention is therefore based on the technical object of providing a substrate and a component with improved properties, in particular with improved heat transfer properties, which ensures improved thermal conductivity both inside the material and at the surface or interface.

[0012] Furthermore, it is an object of the present invention to provide a method with which such substrates and components can be produced in a targeted and reliably reproducible manner with predetermined properties.

[0013] SOLUTION

[0014] The object is achieved by a substrate having the features of claim 1, as well as a method and a component having the features of the subordinate claims. Further advantageous embodiments can be found in the subclaims, the description, and the exemplary embodiments.

[0015] The object is achieved in particular by a surface-structured substrate, preferably by a laser-surface-structured substrate. The surface-structured substrate, preferably the laser-surface-structured substrate, has at least a first outer surface with a heat transfer region. The heat transfer region is formed by a structured region and an unstructured region. According to the invention, the structured region has a first interference pixel, wherein the first interference pixel is formed from a first periodic structure of at least three, preferably seven, particularly preferably 19, surface irregularities deviating from a flat surface. Such surface irregularities are changes in the surface, which can be designed as either depressions or elevations.In particular, these can be linear structures, i.e., groove-like depressions or groove-like elevations. Furthermore, such surface irregularities can be formed as point-like structures, in particular as inverted pegs or as pegs. Different types of surface irregularities can also be present simultaneously on a surface or at an interface.

[0016] In this case, a groove-shaped depression or a groove-shaped elevation has an extension in a first dimension that is significantly larger, preferably at least 10 times larger, than the extension in the other two dimensions (structure depth and width dimension). The groove-shaped depression or the groove-shaped elevations run parallel to the surface having the structured region, in particular parallel to the first outer surface of the substrate or the cover layer.

[0017] The distance between two adjacent surface irregularities within an interference pixel, in particular within the first interference pixel, is a first interference period (pi). According to the invention, the first interference period, i.e., the period of the first periodic structure or the distance from a center point or center line of a depression to a depression arranged adjacent to it in a period direction, is in the range from 50 nm to 200 pm, preferably in the range from 1 pm to 45 pm.

[0018] The first interference period (pi) is in the range from 50 nm to 200 pm, preferably from 1 pm to 45 pm, preferably from 5 to 40 pm, particularly preferably from 10 to 35 pm, most preferably from 15 to 30 pm.

[0019] According to an advantageous embodiment, the interference period is at least 2.5 pm, preferably at least 4.0 pm. As a result, the surface in the heat transfer region is enlarged compared to the projected surface. This advantageously makes it possible to achieve improved heat transfer. The projected surface is the projection surface onto the first outer surface without surface irregularities. In the heat transfer region, the ratio of the actual surface with surface irregularities to the projected surface without surface irregularities according to the invention, in particular in the form of inverse pegs, pegs, groove-shaped depressions or groove-shaped elevations, has a value of at least 120%, preferably at least 150%, particularly preferably at least 200%, very particularly preferably at least 250%, in particular at least 300%, preferably even at least 350%.

[0020] The surface irregularities can, in particular, also occur superimposed. Of particular relevance here is an increase in the area of ​​the real surface compared to the projection surface. The projection surface can run along a plane, but it can also have curvatures. According to an advantageous embodiment, the substrate is flat, so that the projection surface is also flat. This allows for uncomplicated, improved heat transfer to a likewise flat surface of a further substrate or component. Alternatively, the substrate can also have a different shape, for example, it can be wire-shaped or spherical. The projection surface would then be the corresponding outer surface. With such shapes, improved heat dissipation can advantageously be achieved, particularly with respect to fluids, preferably with respect to air.

[0021] The structured region is formed by the various applied structures, in particular by the introduced surface irregularities. These can be a single line structure, a single dot structure, multiple superimposed line structures, multiple superimposed dot structures, or even superimposed dot and line structures. Even if the structured region consists of multiple, not necessarily interconnected, individual structured sub-regions, such as individual pegs or individual groove-shaped depressions, for the purposes of the invention, the entire portion of the surface that is structured, the surface of which has consequently changed due to treatment using a laser interference process, is regarded as a structured region. Thus, each surface can have only one structured region.

[0022] Any part of the surface that cannot be assigned to the structured area is then considered to belong to the unstructured area.

[0023] According to the invention, the material of the surface-structured substrate has a thermal conductivity, also referred to as a thermal conductivity coefficient or heat transfer coefficient, of at least 20 W / (m K), preferably 50 W / (m K), more preferably 100 W / (m K), and particularly preferably 200 W / (m K). The stated values ​​refer to a measurement at 20°C.

[0024] It is known to those skilled in the art that heat transfer and heat transfer, as well as all terms derived therefrom which are used in this disclosure, such as heat transfer and heat transfer coefficient, heat transfer and heat transfer range, heat transfer and heat transfer properties, can be used synonymously. The structures according to the invention could surprisingly also be produced reversibly on materials with high thermal conductivities. Since these materials lead to high heat diffusion lengths when energy is introduced, precise processing was difficult or not to be expected here. The long heat diffusion lengths disadvantageously lead to a leveling of the surface instead of to a desired increased surface roughness. By using particularly short laser pulse durations, preferably in the range of up to 1 ns, preferably up to 500 ps, ​​it was also possible to produce such materials with a structure orStructuring on the surface, particularly on the first outer surface.

[0025] With longer pulses starting from 1 ns, more heat, i.e. energy, is introduced into the material and a larger amount of material is melted, forming local wavefronts (at the maxima) that can overlap and thus lead to large structure heights.

[0026] With shorter pulses up to 1 ns, especially up to 500 ps, ​​the material is removed more quickly. Relevant effects here are cold ablation or material sputtering, so that pits are more likely to form and little to no melting occurs.

[0027] The period of the structure, i.e. the structure period, is called the interference period (p n). It generally depends on the structuring of a mask, the negative of the desired periodic dot or line structure on a mold, or the wavelength of the interfering laser beams, the angle of incidence of the interfering laser beams, and the number of interfering laser beams.

[0028] Further advantageous embodiments and developments emerge from the subclaims and from the description with reference to the figures.

[0029] GENERAL BENEFITS

[0030] The invention advantageously provides a substrate with a heat transfer region in which the heat transfer properties have been greatly improved. The substrate is advantageously highly environmentally friendly, as the use of chemicals during production is avoided. Furthermore, a substrate structured in this way exhibits greater durability of the resulting structure compared to conventional chemical coatings, as it is insensitive to abrasion and impact. Such a surface-structured substrate according to the invention, in particular also a structured component, can also be used in the field of automotive applications, where the dissipation of heat from the battery system into the cooling circuit is an important aspect. Efficient heat dissipation can improve the efficiency of such systems.

[0031] The surface-structured substrate has a wide range of applications in the automotive, aerospace, and especially in electronic circuits used in a variety of applications. The improved heat transfer is used either to improve heat dissipation, as in the electronics sector, or to prevent icing with less energy consumption, as is relevant in aviation, for example.

[0032] The present invention is based in particular on the finding that the properties, in particular the heat transfer properties, of a surface can be positively influenced by applying a structured area and that the thermal conductivity of a substrate, in particular of a surface of a substrate, can thereby be improved without the need to apply an additional layer.

[0033] Advantageously, a substrate with a heat transfer area can be produced in this way, wherein this heat transfer area has an enlarged surface compared to an unprocessed surface without such surface irregularities.

[0034] The inventive enlargement of the surface area at a microscopic level can advantageously improve the heat flow through the heat transfer area. This can advantageously facilitate heat dissipation.

[0035] By creating structures according to the invention in materials with high thermal conductivity, heat dissipation can be significantly improved, as heat is conducted both effectively through the substrate and via the heat transfer area from the substrate to the adjacent medium, such as air or a metal, and in particular also fluids with advantageous thermal conduction properties, also referred to as thermal fluids, such as special thermal pastes or cooling fluids. By increasing the actual surface area relative to the projected surface area, heat transfer through this surface can be further improved, in particular, the heat transfer coefficient can be increased.

[0036] DETAILED DESCRIPTION OF THE INVENTION

[0037] The surface-structured substrate according to the invention describes a substrate having a heat transfer region with at least one first periodic structure, in particular a dot structure, in the micrometer and / or submicrometer range, in particular with an enlarged surface and resulting increased heat transfer properties. The invention further comprises a component having such a surface-structured substrate, wherein the first outer surface of the substrate can then be an internal interface of the component. Furthermore, the invention also relates to a method for producing a structured substrate with such a heat transfer region.

[0038] Structured substrate

[0039] Substrat

[0040] For the purposes of the invention, the term “substrate” refers to a substrate (an object or a material) whose surface extends in multiple spatial directions. A substrate, preferably a flat substrate, can be a planar substrate or a curved substrate, for example a parabolic substrate. For the purposes of the invention, “flat” also means that the extension of a substrate, preferably a flat and / or transparent substrate, for example a planar substrate in the x and y directions, or the extension of a curved substrate along its radius of curvature, is greater than the extension of the region in which the at least three partial beams interfere with one another. In the case of a curved substrate with a curved first outer surface, the projected surface is then also curved.

[0041] In a preferred embodiment, the substrate is a substrate whose extent in the x and y directions, or whose extent along a radius of curvature is less than or equal to the extent of the region in which the at least three partial beams interfere with one another. Homogeneous structuring of the substrate is possible in one processing step (during one laser pulse). In a particularly preferred embodiment, the substrate is a flat substrate whose extent in the x and y directions, or whose extent along a radius of curvature is greater than the extent of the region in which the at least three partial beams interfere with one another. By moving the substrate in the x and y planes, flat, homogeneous structuring of the substrate is possible in several processing steps (with several laser pulses).The movement of the substrate can occur by rotation or translation or by a superposition of rotation and translation.

[0042] A structured substrate is characterized in particular by the fact that the substrate has a depth, also referred to as the substrate depth. The depth of the substrate is preferably greater, particularly preferably significantly greater, than the depth of the structures produced on the surface of the substrate, referred to herein as the structure depth. The structure depth is preferably less than 50% of the substrate depth, particularly preferably less than 25% of the substrate depth, very particularly preferably less than 10% of the substrate depth, further preferably less than 5% of the substrate depth, or less than 1% of the substrate depth, or less than 0.1% of the substrate depth. This preferably preserves the stability, i.e., the cohesion and fracture strength, of the structured substrate.

[0043] For the purposes of the invention, the term substrate encompasses a solid material with a preferably reflective surface, wherein the substrate is solid in particular at room temperature, so that any introduced surface irregularities remain on the surface. Examples of such substrates are, in particular, metals and semiconductors or compounds thereof, in particular copper and silicon. Other materials, in particular those with a good specific thermal conductivity of at least 20 W / (m K), particularly preferably of at least 50 W / (m K), very particularly preferably of at least 75 W / (m K), in particular of at least 100 W / (m K), even more preferably of at least 150 W / (m K), measured at 20 °C, are also suitable for such applications.Examples of suitable metals include copper (Cu, 240-401 W / (m K)), silver (Ag, 429 W / (m K)), gold (Au, 314 W / (m K)), tin (Sn, 67 W / (m K)), zinc (Zn, 110 W / (m K)), aluminum (Al, 236 W / (m K)), chromium (Cr, 86 W / (m K)), tungsten (W, 197 W / (m K)), nickel (Ni, 85 W / (m K)) or mixtures or alloys, such as brass (120 W / (m K)), copper alloys with tin, zinc, nickel and / or lead or aluminum alloys with manganese, magnesium, copper, silicon and / or zinc. Suitable semimetals or semiconductor materials are silicon (Si, 163 W / (m K)), indium (In, 81.6 W / (m K)), and semiconductors such as the binary III-V semiconductors GaAs, InAs, and AlAs and / or the ternary semiconductors InGaAs or InAlAs, and mixtures thereof. Furthermore, the person skilled in the art knows how to determine the specific thermal conductivity for a suitable material or can obtain it from familiar tables and reference works.Thermal conductivity is a property of a material and describes how quickly the material can conduct heat. The higher the thermal conductivity, the faster the material cools down. In the SI system, thermal conductivity is measured in W / (m K) (watts per meter and Kelvin).

[0044] According to an advantageous embodiment, the substrate comprises or consists of materials such as metals, semiconductors, or alloys. Suitable metals include copper or aluminum, but also gold, silver, platinum, palladium, rhodium, titanium, tantalum, and zirconium, as are preferably used in the manufacture of jewelry or medical devices. A suitable semiconductor material is, for example, silicon. Although these materials are often difficult to process due to their high thermal conductivity, they exhibit good heat dissipation capabilities. Other possible materials include composites.

[0045] Within the scope of the present invention, various semiconductor materials, including silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), silicon carbide (SiC), and gallium nitride (GaN), are also selected for the application of heat transfer regions. These materials are widely used in the semiconductor industry, from microchips and radio-frequency components to power electronics and optical components. The application of a heat transfer region as defined herein, in particular by generating the increase in the heat transfer coefficient as defined herein compared to the unstructured region, on these semiconductors therefore serves to improve heat dissipation, which is of great importance, particularly in miniaturized systems with high heat dissipation in a small space.

[0046] Due to the intrinsically high thermal conductivity of copper, coarse structures, preferably with structure depths of at least 2 pm, must be selected when structuring copper, since if the structures are too small, everything will melt again.

[0047] Other suitable materials include magnesium, titanium, and coatings or alloys based on them, as well as silicon carbide-based materials, ceramics, and preferably polymers and glass. An auxiliary layer is preferably applied to materials such as glass and polymers (as described herein), the material of which then forms the structure.

[0048] The material of the surface-structured substrate can also have a melting point of less than 1,400°C, preferably less than 1,200°C, particularly preferably less than 1,100°C. Those skilled in the art know how to determine the melting point or melting range for a suitable material, or they can obtain these values ​​from familiar tables and reference works. Structuring of such materials with a low melting point can also be advantageously achieved by using particularly short laser pulses, preferably of less than 500 ps (so-called ultrashort pulse lasers), particularly within ranges as defined herein. For other materials with higher melting points, such as stainless steel, pulse durations in the nanosecond (ns) range are sufficient and are significantly easier to implement.

[0049] The substrate can also be flexible, such as a metal foil. It is particularly important that the surface irregularities are retained after a cooling process.

[0050] Preferably, the surface-structured substrate, in particular the laser-surface-structured substrate, has a second outer surface on the side facing away from the first outer surface. The second outer surface is formed from a structured and an unstructured region, wherein the structured region has a periodic dot and / or line structure. Thus, the advantageous effects and properties, in particular the improved heat transfer, can also be effective on the further, second outer surface. Especially when used within a component and / or within an electronic circuit, this can increase the heat dissipation coefficient and thus improve heat dissipation.

[0051] The structured region (heat transfer region) preferably has a ratio of the real surface to the projected surface of at least 120%, preferably 150%, particularly preferably 200%, in particular 250%. The "projected surface" is the projection surface onto the first outer surface without surface irregularities and is defined as the projection of the virtual surface or plane of a substrate (in the case of essentially flat substrates) onto the real surface without taking into account any surface irregularities applied or introduced. The projection surface can run along a plane, but it can also have curvatures. According to an advantageous embodiment, the substrate is flat, so that the projection surface is also flat. Alternatively, the substrate can also have a different shape; for example, it can be wire-shaped or spherical.In this case, the projection surface is the corresponding lateral surface of the substrate and / or the molding base body, which comprises or consists of the substrate to be structured and / or structured. With such molds, improved heat dissipation can advantageously be achieved, particularly with respect to fluids, preferably with respect to air.

[0052] Here, structures that enable the creation of a heat transfer region on a substrate are applied directly to the substrate. No additional material or particles are applied to the substrate. Instead, structuring is performed using a subtractive process, i.e., regions of the substrate surface are removed (see inverse cones, interference patterns). This advantageously eliminates the need to apply films or coatings to create a heat transfer region, which, compared to the structuring according to the invention, are susceptible to abrasion and thus wear out quickly. A heat transfer region as disclosed herein is characterized by robustness against wear and stress.

[0053] A further significant advantage of the present invention is that, after structuring the substrate, no additional material removal is required to achieve the disclosed properties of the heat transfer region. This means that, in contrast to other methods such as masking and lithography methods, no subsequent processes such as grinding, polishing, or etching, for example, chemical dry and / or wet etching or plasma etching, are necessary. This is particularly advantageous because conventional methods often use cover or auxiliary structures that must be removed after structuring. Such processes are typically associated with the loss of additional substrate material, in particular material from the unstructured region or global unstructured region.The invention avoids this additional material loss and thus reduces the overall material expenditure and the complexity of the manufacturing process. Furthermore, this procedure can also contribute to improving process efficiency and cost-effectiveness, as fewer work steps and materials are required. For example, the method according to the invention enables direct and precise structuring without the need for subsequent processing, which can be of great benefit, particularly in the case of sensitive or expensive substrates or thin layers. A structured substrate, as disclosed herein, is further characterized in that the substrate surface has a high level of purity in the unstructured region, as there are no impurities on it. Impurities are, for example, residues of sacrificial layers which are present during an etching process in the form of a masking layer, e.g.Photoresist, were applied. Conventional structured substrates, which were produced by an etching process such as plasma dry etching and / or chemical wet etching, require the substrate to be coated with a photoresist layer to protect the areas that are to remain unstructured. After the etching process, this layer must be removed, which can result in residues forming on the substrate surface and, on the other hand, interaction between the substrate surface and the cleaning solution. This changes the properties of the substrate surface in an undesirable way compared to an unstructured substrate surface. A structured substrate as disclosed herein is characterized in that the material properties of the substrate are retained in the unstructured areas.

[0054] According to a particularly preferred embodiment, a structured substrate as defined herein is characterized in that it has a structured region, wherein the structured region is divided into at least two subregions, wherein the respective subregions, for example a first and a second subregion, are characterized in that the structural features contained therein (e.g. the shape of the surface irregularities, the structural depth and / or the spacing of the surface irregularities from one another) differ from one another. The variation in the structural depth, structural period and / or shape of the surface irregularities between the subregions makes it possible to specifically optimize the substrate for specific applications. For example, one region could be configured for better light absorption and another for improved light reflection.The ability to gradually and adjustably change the gloss contrast and the color contrast opens up new design options, e.g. for decorative purposes or for the incorporation / application of security features. The at least two partial regions can be arranged so as to overlap (lie one above the other), adjacent to (adjacent to) one another and / or at a distance from one another. Preferably, the at least two partial regions are arranged so as to overlap and / or adjacent to one another. In particular, the structure depth and / or the structure period of the respective structure features are different. This advantageously produces a structuring which is characterized by a gradual, adjustable change in the contrast, in particular the gloss contrast and / or the color contrast. Particularly preferably, the structure period and the shape of the structure features of the two partial regions are identical. Conventionally structured substrates, which e.g.are created by an etching process, are characterized by a homogeneous structure depth. Multiple etching processes to modify the structure depth in specific areas are difficult due to the requirement of a sacrificial layer. Due to the presence of pre-existing etched flanks, a homogeneous coating of a substrate that already has a structure with the sacrificial layer is difficult to achieve. This creates uncovered areas that are then attacked by a further etching process. Thus, homogeneous structuring is not guaranteed. A gradual, adjustable change in contrast, particularly in gloss contrast and / or color contrast, cannot be ensured.

[0055] Preferably, the at least two sub-regions are each formed independently of one another by a first periodic structure with a first interference period (pi) in the micro- or sub-micro range (e.g. the first sub-region) and by a second periodic structure with a second interference period (p2) in the micro- or sub-micro range (e.g. the second sub-region). The first and the second interference periods can be identical or different from one another. Preferably, the first periodic structure with a first interference period (pi) in the micro- or sub-micro range is produced by applying a first interference pixel once or multiple times, congruently and / or offset from one another, and the second periodic structure with a second interference period (p2) in the micro- or sub-micro range is produced by applying a second interference pixel once or multiple times, congruently and / or offset from one another.By applying an interference pixel multiple times in a congruent manner (multiple irradiation as defined herein), the structure depth can be adjusted in the corresponding partial area and / or a quasi-periodic line structure superimposed on the periodic structure, in particular a periodic dot structure, can be formed as a wave structure through self-organization processes.

[0056] For the purposes of the present invention, “adjacent subregions” refers to an arrangement in which at least two structured subregions of the surface-structured substrate are arranged in a stacked configuration. One subregion lies directly above another, with the two subregions occupying at least partially the same physical space and / or the same physical area (projected surface). This superimposed arrangement enables multidimensional structuring of the substrate, with each subregion being able to have different properties or structural features. For the purposes of the present invention, “adjacent subregions” refers to an arrangement in which two or more structured subregions of the substrate are arranged side by side with and / or without overlapping subregions.These sub-areas are directly adjacent to one another and occupy, entirely or at least partially, a different physical space and / or a different physical surface (projected surface), with their border forming a common boundary line or interface. This arrangement enables the creation of structures in which the transitions between the different sub-areas are clearly defined, thus allowing precise control of the contrast and structural properties at the boundaries.

[0057] The invention defines "spaced-apart partial regions" as an arrangement in which two or more structured partial regions of the substrate are arranged or applied at a significant spatial distance from one another on the surface of the surface-structured substrate. Between these partial regions there is either an unstructured region of the substrate or a gap. This arrangement is particularly advantageous for creating isolated structured regions, each with specific properties or functions, without direct interaction or influence from neighboring structured regions.

[0058] A structured region on the surface of a substrate is preferably characterized in that a regularly arranged structure (as defined herein) with a mean structure period is arranged within the structured region. A mean structure period refers in particular to the distance between two generated structural features, for example, dot structures and / or line or wave structures, with dimensions in the micrometer and / or submicrometer range. Within the meaning of the invention, a mean structure period also includes the distance between two structural features fluctuating around a statistical mean and / or the periodicity being broken by individual defects in the generated structural features.In this embodiment, the unstructured regions of the surface of the substrate which are located between two structural features arranged at a distance of a mean structural period, in particular dot structures and / or line or wave structures, are also regarded as being assigned to the structured region.

[0059] In this embodiment, the substrate has a global unstructured region. The global unstructured region is characterized by the fact that this region contains no structural features with dimensions in the micrometer and / or submicrometer range, which are arranged at a distance of an average structural period from one another. The effect of the increased heat transfer coefficient thus advantageously occurs only in the structured regions. As a result, regions with different heat transfer coefficients are arranged on the surface of the substrate, preferably a homogeneous material. These regions can be used, for example, in the context of microelectronics to specifically cool certain processor sections with increased heat generation. The targeted placement of the structured regions allows thermal management functions to be optimized, leading to improved performance and reliability of the electronic components.This is especially important in applications where precise temperature control is critical for the functionality and longevity of the components.

[0060] In a further embodiment of the invention, the surface of the substrate has a structured and a globally unstructured region. In this embodiment of the invention, a structured region borders a globally unstructured region, wherein the structured region is characterized in that the structural depths of the generated structural features vary within the structured region. In particular, within the structured region, at least one region of high structural depth borders at least one region of lower structural depth, wherein the gloss factor differs between the two regions. Preferably, a gradual transition between different gloss factors can be generated in this way.

[0061] Transparent substrate

[0062] According to one possible embodiment, the substrate consists of a transparent material. A material or substrate is transparent within the meaning of the present invention if it has a high transmittance for at least a partial range of the spectrum of electromagnetic radiation between 1 nm and 10 nm, preferably for light that is visible to the human eye or light in the infrared or ultraviolet radiation range. Such partial ranges are, for example, electromagnetic radiation in the range of ultraviolet (UV) light from 100 nm to 380 nm, in particular UV-A from 315 nm to 380 nm or UV-B from 280 nm to 315 nm or UV-C from 100 nm to 280 nm, visible light from 380 nm to 780 nm or in a range that also includes infrared light, from 780 nm to 5.000 nm or in a range of infrared light (heat radiation) or in a range of microwave radiation, in particular radar beams in the wavelength range from 1 mm to 10 m, or else another sub-range which is adapted according to the desired application, in particular to the wavelength of the laser source. Such a sub-range preferably has a width of at least 10% or 50% of the wavelength which forms the lower limit of the sub-range. A high permeability in a sub-range within the meaning of the invention is a transmittance of at least 50% or preferably at least 70% or particularly preferably at least 80% or at least 90% for each wavelength in the sub-range, i.e. for the entire spectrum in the sub-range.In contrast, a substrate is referred to as partially transparent if it has at least a certain degree of transmittance, preferably at least 20% for each wavelength in the sub-range, i.e., for the entire spectrum in a sub-range described herein. Those skilled in the art know how to determine the transparency and / or light transmittance for a suitable material or can obtain these values ​​from familiar tables and reference works.

[0063] Preferably, the substrate is transparent, i.e., in a sub-range of the electromagnetic spectrum, preferably in the range of visible light or near-infrared light or the UV range, in particular UV-A and / or UV-B and / or UV-C, it has a transmittance of at least 50%, preferably at least 70%, particularly preferably at least 80%, at least 90% for each wavelength in the sub-range.

[0064] A substrate can also be described as a transparent substrate if it has a high transmittance selectively for certain wavelength ranges in the visible light range, e.g. the substrate has a high transmittance for electromagnetic radiation with wavelengths in the range from 500 nm to 800 nm. The transmittance can vary across the wavelength range that is transmitted, e.g. for wavelengths in the range from 380 nm to 500 nm it can be no less than 70%, and in the range from 500 nm to 750 nm it can be no less than 90%. For example, the substrate transmits radiation with wavelengths from 380 nm to 780 nm. It has a particularly high transmittance, e.g. a transmittance of 90% at wavelengths from 450 nm to 690 nm; the transmittance at wavelengths below and above this is, for example, 70%.

[0065] A transparent material, in the sense of the present invention, includes transparent materials, in particular glass (e.g., borosilicate glasses, quartz glasses, alkali-alkaline earth silicate glasses (e.g., soda-lime glass), aluminosilicate glasses, metallic glasses), but also solid polymers (e.g., polycarbonates such as Makrolon® and Apec®; polycarbonate blends such as Makroblend® and Bayblen®; polymethyl methacrylate such as Plexiglas®; polyester; polyethylene terephthalate, polypropylene, polyethylene) as well as transparent ceramics (e.g., spinel ceramics such as Mg-Al spinel, ALON, aluminum oxide, yttrium aluminum garnet, yttrium oxide, or zirconium oxide) or mixtures thereof. Polycarbonates include homopolycarbonates, copolycarbonates, and thermoplastic polyestercarbonates.

[0066] A transparent material, in the sense of the present invention, includes transparent materials, in particular transparent ceramics (e.g., spinel ceramics such as Mg-Al spinel, ALON, aluminum oxide, yttrium aluminum garnet, yttrium oxide, or zirconium oxide) or mixtures thereof. Polycarbonates include homopolycarbonates, copolycarbonates, and thermoplastic polyestercarbonates.

[0067] To create a heat transfer area on a first outer surface of a transparent material, the structured area preferably consists of a different material, which rests on the transparent material as a cover layer. The surface irregularities on the surface of the transparent material are preferably studs or groove-like elevations formed from a different material. Advantageously, the transparency can also be at least partially retained in the heat transfer area.

[0068] Surface irregularities

[0069] Within the meaning of the invention, the surface irregularities can be formed as point-shaped surface irregularities or as linear surface irregularities. The point-shaped surface irregularities can be formed as studs or as inverse studs. The linear surface irregularities can be formed as groove-shaped depressions or as groove-shaped elevations. In particular, different interference pixels with different surface irregularities can also be arranged superimposed, so that different dimensions and / or different types of surface irregularities can be arranged on a surface-structured substrate, in particular within a heat transfer region. The dimensions of the surface irregularities can be adjusted by different process parameters when produced by laser interference structuring.In the sense of the invention, a superposition of different types of surface irregularities means a superposition of both point and line structures.

[0070] According to an advantageous embodiment, the side surfaces of the surface irregularities of the first periodic structure, preferably all surface irregularities, have a smooth surface. This distinguishes these structures significantly from surface irregularities produced by etching. Even when using masks, the side surfaces or lateral surfaces of the surface irregularities cannot be produced as smoothly as with laser interference structuring. This advantageously allows for the creation of defined structures and optimized properties.

[0071] A smooth lateral surface (lateral surface) of the surface irregularities, i.e., the studs or inverse studs or groove-shaped depressions or groove-shaped elevations, is preferably achieved by irradiating the individual surface irregularities no more than four times, in particular no more than three times, particularly preferably no more than twice, and most preferably only once during structuring using laser structuring methods, in particular direct laser interference structuring. Each interference pixel is preferably generated by a single irradiation.

[0072] For the purposes of the invention, a side surface of a structure, e.g. a tenon or inverse tenon or groove-shaped depressions or groove-shaped elevations, is considered smooth if the mean roughness value (R a) according to DIN EN ISO 4287:2010 is less than 200 nm, preferably less than 50 nm, particularly preferably less than 20 nm, most preferably less than 5 nm.

[0073] A smooth side surface, also known as the lateral surface, of the surface irregularity, i.e., the pegs and / or inverse pegs or groove-like depressions or groove-like elevations, has the advantage over a rough surface that, especially when electromagnetic radiation is irradiated, it is not diffusely scattered back from the surface. The side surface of the depressions thus serves, for example, in the adjustment of desired optical properties.

[0074] For example, a trapping effect occurring within the cones or inverse cones or groove-shaped depressions or groove-shaped elevations can be improved, thus increasing the light transmission through this interface. The side surface serves as a quasi-homogeneous mirror surface that reflects the portion of reflected incident electromagnetic radiation within the surface irregularities, particularly the inverse cones, up to the saddle point. At each additional reflection point within the lateral surface, a portion of the (remaining) electromagnetic radiation is coupled into the substrate, whose first outer surface is formed from such a structured and an unstructured area. This advantageously creates a matte surface with reduced glare effects. Point-like structure / interference pattern

[0075] According to an advantageous embodiment of the surface-structured substrate, the first interference pixel has a periodic lattice of at least three cones or inverse cones. This forms a first periodic dot structure. The surface irregularities, also referred to herein as structural features, are thus cones and / or inverse cones. The two-dimensional changes in the surface properties present here lead to an efficient enlargement of the surface and a resulting improved heat transfer. This allows a larger amount of heat to be conducted through the heat transfer area.

[0076] The term inverse cone in the sense of this invention refers to structures with a circular, elliptical, triangular or essentially rectangular base area, in particular with a circular base area, which taper conically into the substrate in the vertical direction and have a rounded cone tip at their saddle point. The inverse cones are formed during the structuring process, i.e. when a laser pulse strikes the substrate to be structured as a result of a region of high intensity impinging on it, whereby the regions between the inverse cones on or within the substrate ideally remain essentially unstructured due to destructive interference whose intensity is zero. Consequently, by focusing the (partial) laser beams on or within the substrate, the negative of what specifies the intensity distribution is formed.The described shape of the inverse cones refers to dot structures arranged on the surface of the substrate. An arrangement of the dot structures in or along a plane within the volume results in a more symmetrical shape. For the purposes of the invention, the dot structures generated within a volume by laser interference structuring are also referred to as inverse cones.

[0077] In a preferred embodiment, the inverse cones are preferably generated during the structuring process by means of laser structure application methods, in particular direct laser interference structuring, i.e. they are formed upon impact of a laser pulse as a result of the impact of a high-intensity region on the substrate to be structured, wherein the regions between the inverse cones on or within the substrate ideally remain essentially unstructured due to destructive interference whose intensity is zero, in particular below a material-dependent intensity threshold. Consequently, by focusing the (partial) laser beams on or within the substrate, the negative of what specifies the intensity distribution is formed. The described shape of the inverse cones refers to point structures arranged on the surface of the substrate.An arrangement of the dot structures in or along a plane within the volume results in a more symmetrical shape, i.e., more like an ellipsoid. For the purposes of the invention, the dot structures generated within a volume by laser interference structuring are also referred to as inverse cones.

[0078] Inverse cones with an elliptical base surface can be created in a structuring process using laser structure application methods, for example by inclining the substrate in relation to the angle of incidence of the focused laser beam(s).

[0079] For the purposes of this invention, "pins" refer to structures with a circular, elliptical, triangular, or substantially rectangular base, in particular with a circular base, which protrude conically from the substrate in the vertical direction and have a rounded cone tip or a truncated cone, in particular a rounded cone tip, at their saddle point. Pins can be applied to or embedded in a surface by applying a negative mold having inverse pins. Imprint lithography, e.g., nanoimprint lithography (as defined herein), is suitable for this purpose.

[0080] The periodic dot structures defined herein, which are preferably formed from studs and / or inverse studs (according to the orientation relative to an outer surface of a substrate or a cover layer, or in the direction of the stacking or coating direction), have the advantage over (periodic) line or wave structures that the individual depressions or elevations span a lateral surface that preferably extends radially across the stud cross-section (diameter of the base surface of the stud or inverse stud) to the saddle point. This enables the effects defined herein, such as improved heat transfer properties, to be adjusted independently of the spatial orientation of the respective surface or interface.

[0081] In optics, a pixel is generally understood to be an image point, defined as a finite unit created by the unification of light emanating from an object point by means of an optical system (https: / / de.wikipedia.org / wiki / Optische_Bildung). The term pixel is derived from the English word "picture element" and is an abbreviation that has been used with a fixed meaning in various US patents since 1911. The term pixel became established in technical literature in 1965 (https: / / de.wikipedia.org / wiki / Pixel) and is also used in the context of raster graphics, for example, in relation to image displays such as LCDs or OLEDs. It refers to a raster point within an image, where the pixels within a raster are arranged such that the distances between one pixel and the next are constant.A pixel is particularly characterized by the fact that it has a defined information content that varies or can be varied between individual pixels within a grid.

[0082] The term interference pixel, or DLIP pixel, is established in the specialist literature from the field of surface structuring using direct laser interference structuring (e.g. “Development of a general model for direct laser interference patterning of polymers”, Alamri, Lasagni, Optics Express, Vol. 25, Issue 9; 2017; “How to Tailor Structural Colors for Extended Visibility and White Light Generation Employing Direct Laser Interference Patterning”, Storm et al., Macro-Molecular Chemistry and Physics, Vol. 220 Issue 13, 7.2019; “Scanner-Based Direct Laser Interference Patterning on Stainless Steel”, Madelung et al., Advanced Engineering Materials, VOL 23, Issue 6, 6.2021 ; “Direct laser interference patterning of stainless steel by ultrashort pulses for antibacterial surfaces”, Peter et al., Optics and Laser Technology 123, 2020) and refers to a spatial region, preferably on the surface of a substrate, preferably a flat and / or transparent substrate, in which laser (partial) beams directed onto the surface interfere constructively and destructively with each other, thus forming a pattern of periodically arranged intensity minima and intensity maxima. The region is preferably spatially limited in such a way that it encompasses an area that is significantly smaller than the surface of the substrate.

[0083] The term “interference pixel”, e.g. first, second, third and / or further interference pixel, in the sense of the present invention refers to a periodic pattern or grid of at least three cones or inverse cones, preferably of at least seven cones or inverse cones, very particularly preferably at least 19 cones or inverse cones on the surface of a substrate, which are formed within an interference pixel (cf. Fig. 15). An interference pixel which is formed from cones or inverse cones is preferably characterized in that the cones or inverse cones are repetitively aligned with one another in such a way that, when there are three cones or inverse cones, they are aligned with one another in such a way that their vertices (in the case of cones, their height centers or, in the case of inverse cones, their centers of the depressions) are at the same distance from one another (so-called interference period). When there are seven cones orIn the case of inverse cones, these are aligned with one another in such a way that one cone or inverse cone is arranged centrally in the grid, whereas the six remaining cones or inverse cones are arranged around the center in such a way that each of the vertices (in the case of cones, their height centers or, in the case of inverse cones, their centers of the depressions) of the six remaining cones or inverse cones is at the same distance from the cone or inverse cone in the center and from at least two other of its neighboring cones or inverse cones (so-called interference period).

[0084] Preferably, the periodic pattern or grating of the interference pixel, in particular comprising inverse cones, is produced by mechanical methods, laser structure application methods, and / or by chemical (post-)treatment, in particular by direct laser interference structuring. In the case of direct laser interference structuring, the periodic pattern or grating is preferably generated by superimposing at least two, preferably at least three, particularly preferably at least four laser (partial) beams by focusing (bundling) these laser (partial) beams onto the surface or into the interior of the substrate, whereby the partial beams interfere constructively and destructively on the surface or in the interior of the substrate.

[0085] The use of laser structure application methods, in particular direct laser interference structuring for the direct production or indirect production (e.g. in the case of imprint lithography, in particular nanoimprint lithography) for producing structured and unstructured regions on the surface of a substrate has the advantage that the cones or inverse cones of a periodic dot structure within a type of interference pixel have identical or almost identical dimensions. Preferably, the coefficient of variation, i.e. the value resulting from the quotient of the standard deviation and the average value, of the cone cross-section (diameter of the base area of ​​the cone or inverse cone) is max. 15.0% or less, more preferably max. 10.0% or less, even more preferably max. 5.0% or less, in particular max. 2.5% or less, even more preferably max. 1.0% or less.This allows for the production of studs or inverse studs that are virtually identical in shape. This also allows for better detection of the substrate structured according to the invention compared to conventional methods for structuring / coating substrates (e.g., etching, particle blasting, polymer coating). Particularly in the case of etching processes, deviations in the structural features can be detected in the edge regions of a substrate structured in this way. A coefficient of variation as specified here cannot be generated by an etching process.

[0086] Line structure or line-shaped structure

[0087] According to one possible embodiment, the first periodic structure is formed as a first periodic line structure, which is formed from at least three, preferably at least 5, more preferably at least 7, parallel groove-shaped depressions or groove-shaped elevations. The groove-shaped depressions or groove-shaped elevations are arranged such that the distance from a groove-shaped depression or a groove-shaped elevation to an adjacent groove-shaped depression or groove-shaped elevation within the periodic line structure is always identical. The individual groove-shaped depressions or groove-shaped elevations within the first periodic line structure are thus arranged equidistantly. This forms a first periodic line structure. The surface irregularities, also referred to herein as structural features, are therefore groove-shaped depressions and / or groove-shaped elevations.Such structures require only two superimposed laser beams. Therefore, they can be produced quickly and economically, thus improving cost-effectiveness.

[0088] The resulting period of the periodic line structure, i.e. the structure period, is referred to in the invention as the interference period (p n). The interference period is the shortest distance from a point on a grooved depression or a grooved elevation to an analogous point on the adjacent grooved depression or grooved elevation within the periodic line structure. For example, the interference period corresponds to the shortest path between two center lines or deepest lines on a grooved depression or highest lines on a grooved elevation. The deepest lines on a grooved depression are the center lines where the most material has been removed. Depth here applies relative to the corresponding surface, particularly relative to the unstructured area of ​​the surface.

[0089] The same applies analogously to groove-shaped elevations, with the deepest line then being the highest line. In the sense of the invention, groove-shaped elevations are structures that rise from the surface with the same shape as a groove or groove-shaped depression. One possibility for creating such groove-shaped elevations is to apply groove-shaped depressions to a negative mold and then transfer this structure to the cover layer. Analogous to the point structures, i.e. the pegs or inverse pegs, the groove-shaped depressions and the groove-shaped elevations can also be arranged within an interference pixel. An interference pixel has at least three, preferably at least five, more preferably at least seven parallel, equidistantly arranged groove-shaped depressions or groove-shaped elevations.

[0090] Repetitively arranged interference pixels can form either a periodic or a non-periodic global structure. The degrees of freedom are the selected interference period, the direction of the first dimension along which the groove-shaped depressions or groove-shaped elevations extend the most, the structure depth, and the spacing or offset of the individual interference pixels. The global structure forms the structured area.

[0091] The groove-shaped depressions are preferably produced by means of a mechanical process, a laser structure application process and / or by means of chemical (post-)treatment.

[0092] The structure, in particular its interference period, generally depends on the structuring of a mask, the negative of the desired periodic dot structure on a mold or the wavelength of the interfering laser beams, the angle of incidence of the interfering laser beams and the number of interfering laser beams.

[0093] In a preferred embodiment, the groove-shaped depressions are preferably created during the structuring process using laser structure application methods, in particular direct laser interference structuring, i.e., they are formed upon the impact of a laser pulse as a result of the impact of a high-intensity region on the substrate to be structured. The regions between the groove-shaped depressions on or within the substrate ideally remain substantially unstructured due to destructive interference whose intensity is below a material-dependent intensity threshold. Consequently, by focusing the laser (partial) beams on or within the substrate, the negative of what the intensity distribution specifies is formed.

[0094] In the case of producing the depressions, in particular the groove-shaped depressions, by direct laser interference structuring, the periodic structure is preferably produced by superimposing at least two, preferably exactly two, laser (partial) beams as a result of focusing (bundling) these laser (partial) beams onto the surface or into the interior of the substrate, whereby the partial beams interfere constructively and destructively on the surface or in the interior of the substrate.

[0095] The use of laser structure application methods, in particular direct laser interference structuring for the direct production or indirect production (e.g. in the case of imprint lithography, in particular nanoimprint lithography) for producing structured and unstructured regions on the surface of a substrate has the advantage that the depressions, in particular the groove-shaped depressions or the groove-shaped elevations, of a periodic dot structure within a type of periodic structure, in particular a periodic line structure, have identical or almost identical dimensions. Preferably, the coefficient of variation, i.e. the value resulting from the quotient of the standard deviation and the average value, of the groove width (width of the groove-shaped depression or width of the groove-shaped elevation, determined on the surface, i.e. preferably at the boundary to the unstructured region) is max.15.0% or less, more preferably max. 10.0% or less, even more preferably max. 5.0% or less, in particular max. 2.5% or less, even more preferably max. 1.0% or less. Thus, groove-shaped depressions or groove-shaped elevations can be produced that are almost identical to one another in shape. This also allows for better detectability of the substrate structured according to the invention compared to conventional methods for structuring / coating substrates (e.g., etching, particle blasting, polymer coating).

[0096] Rasterize

[0097] In a preferred embodiment, by moving the substrate, in particular the surface-structured substrate, in relation to the focusing point, which generates the interference pixel with a periodic point structure or a periodic line structure, in combination with pulsed laser (partial) beams, a planar, optionally homogeneous and periodic, point and / or line structure can be generated on the surface of a substrate.

[0098] As an alternative to moving the substrate in relation to the focusing point, the focusing point can also be guided over the sample or substrate (e.g. using scanner-based methods). Displacing the substrate to be structured, preferably a flat substrate, in the laser beam can be comparatively complex and slow due to the relatively large masses moved. It is therefore advantageous to keep the substrate, preferably a flat substrate, stationary during processing and to achieve the flat structuring of the substrate by focusing the partial beams onto the surface of the substrate by manipulating the partial laser beams with optical elements (focusing mirrors or galvo mirrors (laser scanners)) in the beam direction. Since the masses moved are relatively small, this can be achieved with far less effort and much more quickly. The substrate is preferably arranged in a stationary position during the process.It is also possible to switch between moving the substrate and guiding the focus point over the substrate, which allows large substrates, for example larger than 200 mm x 200 mm, to be structured efficiently yet in a defined and reproducible manner.

[0099] Global structure, especially global point structure

[0100] Advantageously, the individual pixels of a type of interference pixel, e.g., a first interference pixel, a second interference pixel, and / or a further interference pixel, which are arranged adjacently and repetitively offset from one another, can optionally form a periodic or a non-periodic global point and / or global line structure globally (i.e., over the extent of the plane to be structured). A fully periodic global point and / or global line structure is generated or exists when the preceding pixel and the following pixel of a type of interference pixel are each offset by a whole multiple (e.g., 2, 3, 4, 5) of the interference period (p n ) are shifted from each other in one spatial direction. This results in a fully periodic pattern over the extent of the plane to be structured, the period of which corresponds to the interference period (p n ) corresponds.

[0101] According to an advantageous embodiment of the surface-structured substrate, the structured region is formed from the first periodic dot structure or the first periodic line structure. The first periodic dot structure or the first periodic line structure consists of one or more offset interference pixels with the first interference period (pi). Thus, a fully periodic global dot or global line structure is preferably created, which forms the structured region.

[0102] A quasi-periodic global point and / or global line structure is created or exists when the preceding pixel and the following pixel of a type of interference pixel are each spaced apart by an equal multiple (e.g. 0.5; 1.3; 2.6) of the interference period (p n) are shifted relative to one another in a spatial direction. In contrast, a non-periodic global point and / or global line structure is created or exists when the interference period of the subsequent pixel is varied relative to the adjacent, preceding pixel and / or when adjacent, repetitively offset pixels are rotated, e.g., applied in a successively rotated manner.

[0103] For the purposes of the invention, a global structure describes a structure forming the structured region consisting of any surface irregularities, preferably inverse pegs and / or groove-shaped depressions, or according to a further preferred embodiment, pegs and / or groove-shaped elevations. Such a global structure can be fully periodic, whereby this preferably allows only one type of surface irregularity, or quasi-periodic or non-periodic. The type of periodicity has a major influence on the desired surface properties, particularly the optical properties.

[0104] According to an advantageous embodiment, deeper structural depths can be created by multiple irradiation of existing surface irregularities, such as groove-shaped depressions. In line structures, the structural depths become deeper, i.e., greater, the stronger the overlap, in particular the interference pixel-to-interference pixel overlap (herein also referred to simply as "pixel-to-pixel overlap" or "interference pixel overlap" or, when applied using laser structure application methods, in particular using laser interference structuring, as "pulse-to-pulse overlap"), in particular the pulse-to-pulse overlap, i.e., the overlap of the interference pixels, in the line direction. According to an advantageous embodiment, the overlap can be adjusted as desired to still create deep structures.

[0105] Preferably, an overlap occurs transverse to the line direction, which also leads to deeper structures.

[0106] In the case of point structures, the overlap is preferably adjusted such that the distance between the interference pixels corresponds exactly to a multiple of the interference period. In this way, very deep structures can be created here too. A pixel-to-pixel overlap, in the sense of the invention, is a superposition of interference pixels in which a first interference pixel can be arranged offset from a second and / or further interference pixel in such a way that, for example, at least 50% of the offset interference pixels have an overlap of at least 95%, preferably of at least 97%, particularly preferably of at least 99%, very particularly preferably of at least 99.5% with a neighboring interference pixel, preferably with several neighboring interference pixels.

[0107] A pixel-to-pixel overlap is also referred to as an "overlap of the interference pixels" and is understood as a spatial overlap of two interference pixels, i.e. the area that two overlapping interference pixels have in common compared to the area contained by a single one of the two interference pixels. Since each interference pixel is formed by a pulse during application using laser interference structuring, this overlap of the interference pixels is also referred to as a pulse-to-pulse overlap. An interference pixel has an area defined by a circle defined by the outer edges of the surface irregularities. This circle is the largest circle that just touches or is tangent to one of the contained surface irregularities. In case of doubt, the size of the overlap is related to the interference pixel with the smaller area.

[0108] The overlapping interference pixels can have the same periodic structures, each consisting of at least three surface irregularities, in particular in the form of inverse cones, cones, groove-shaped depressions, or groove-shaped elevations, or they can differ from one another in their periodic structures. Thus, in one embodiment, the structured region can have a plurality of first interference pixels arranged offset from one another, or first and second interference pixels, wherein the periodic structures of the second interference pixels differ from the periodic structures of the first interference pixels. Likewise, third or further interference pixels with likewise differing periodic structures can be arranged offset from the first and / or second interference pixels.

[0109] The repetitively arranged interference pixels are first generated along a first row. Then, a further row is generated that is offset therefrom. The pixel-to-pixel overlap, in particular the pulse-to-pulse overlap, is preferably very high within a row, i.e. preferably at least 90%, preferably at least 95%, while the overlap between the rows is low. In this way, defined structures can be generated quickly and effectively. However, a high pixel-to-pixel overlap can also be generated by generating a first row of interference pixels in such a way that there is a smaller overlap, for example in the range of 10% to 20%, or even no overlap at all, wherein the row is then generated again, the position of the newly generated row having a large overlap of at least 90%, preferably at least 95%, with the previously generated row.The overlap can therefore be created by rasterizing a row multiple times.

[0110] Structuring using pulse-to-pulse overlap has the advantage that at least individual structural elements within a first, second, and / or further interference pixel are irradiated multiple times. This allows self-organization processes to form a quasi-periodic line structure superimposed on the periodic dot structure as a wave structure, in particular a so-called LIPSS. Advantageously, hierarchical structures can be created quickly and effectively on the substrate surface, allowing the surface roughness of the wall of a periodic dot structure to be increased, particularly in the nanometer and / or submicrometer range, resulting in an increase in the surface area.

[0111] Since the structure depth strongly influences the ratio of the surface area to the projected surface area, a high structure depth can lead to an increased heat transfer coefficient, thus improving the heat transfer properties.

[0112] According to an advantageous embodiment of the surface-structured substrate, the heat transfer region, in particular the structured region, further comprises a second periodic structure with a second interference period (p2) in the micro- or submicro-range, which is formed as a periodic dot structure or as a periodic line structure.

[0113] Preferably, the structured region of the surface of the substrate further comprises a second periodic dot structure, wherein the second periodic structure is formed from at least one second interference pixel (11) with a second interference period (P2). To form a second periodic dot structure, the second interference pixel (11) comprises a periodic grid of at least three cones or inverse cones with a second interference period (P2). The structured region, i.e., the global structure, is thus formed from a superposition of a first periodic dot or line structure and at least one second periodic dot structure.

[0114] Optionally, the structured region has a second periodic line structure with a second interference period in the micrometer or submicrometer range. Preferably, the second periodic line structure is formed from at least one second interference pixel with a second interference period (P2). To form a second periodic line structure, the second interference pixel has at least three parallel groove-shaped depressions or groove-shaped elevations.

[0115] There is then a global structure which is a superposition of a first periodic point or line structure and a second periodic line structure.

[0116] According to an advantageous embodiment, the structured region has two superimposed line structures which differ in direction. Thus, a first interference pixel consisting of groove-shaped depressions and / or elevations and a second interference pixel consisting of groove-shaped depressions and / or elevations are superimposed. The first interference period and the second interference period can be identical or different. Preferably, a plurality of first and a plurality of second interference pixels with linear surface irregularities are superimposed in such a way that the linear surface irregularities of the first interference pixels all point in one direction and that the linear surface irregularities of the second interference pixels all point in one direction, i.e. enclose a maximum angle of 5°, preferably 1°.The repetitively arranged first interference pixels and also the second interference pixels are therefore not or hardly rotated relative to each other.

[0117] The linear surface irregularities of the first interference pixels and the linear surface irregularities of the second interference pixels are preferably arranged orthogonally to one another and preferably enclose an angle of 30° to 150°, preferably of 45° to 135°, particularly preferably of 60° to 120°, most particularly preferably of 80° to 100°, in particular of 85° to 95°. In this way, two-dimensional changes in the surface can be created. This can further improve heat transfer, in particular increase the heat transfer coefficient. Advantageously, line structures can be created more quickly and easily with only two partial laser beams, thus achieving an efficient improvement in heat transfer at the surface or interface. Two-dimensional changes in the surface, i.e. two-dimensional surface irregularities, are preferably present in the heat transfer region.This includes both the point structures, i.e., the cones or inverse cones, as well as the above-described superimposed line structures enclosing an angle in the range of 30° to 150°. The two-dimensional modification of the surface allows for a good surface roughness, i.e., a good ratio of the real surface to the projected surface of at least 120%, preferably more, in particular at least 150%, preferably at least 250%, particularly preferably at least 300%, and most preferably at least 350%, to be achieved.

[0118] In a preferred embodiment of the invention, the surface of the substrate is structured over its entire surface. In this embodiment, the structured region of the substrate extends over the entire substrate surface. In this case, a matting of the surface can be seen. The matting is characterized in that the gloss contrast between the surface of the original, unstructured substrate and the surface with a structured region, in particular at their boundary line (immediate transition between the two regions), is preferably greater than 0.85, preferably greater than 0.9, particularly preferably greater than 0.95, very particularly preferably greater than 0.99, and further preferably 1. Particularly preferably, the gloss contrast lies in a numerical range that is limited downwards by one of the following endpoint values: 0.85, 0.87, 0.88, 0.93, 0.94, 0.95, 0.97, 0.98, 0.99, 1.

[0119] In a further embodiment of the invention, the surface of the substrate has a structured region and a global unstructured region. In this embodiment of the invention, a structured region borders on a global unstructured region, wherein the global unstructured region has a lower heat transfer coefficient that is higher than the gloss factor of the structured region. Thus, a high gloss contrast can be generated between the structured region and the unstructured region, in particular at their boundary line (immediate transition between the two regions). The gloss contrast preferably lies in a numerical range that is limited downwards by one of the following endpoint values: 0.85, 0.87, 0.88, 0.93, 0.94, 0.95, 0.97, 0.98, 0.99, 1.

[0120] In a further embodiment of the invention, the surface of the substrate has a structured and a globally unstructured region. In this embodiment of the invention, a structured region borders a globally unstructured region, wherein the structured region is characterized in that the structural depths of the generated structural features vary within the structured region. In particular, within the structured region, at least one region of high structural depth borders at least one region of lower structural depth, wherein the gloss factor differs between the two regions. Preferably, a gradual transition between different gloss factors can be generated in this way.

[0121] According to an advantageous embodiment of the substrate, the heat transfer coefficient of the heat transfer region is increased by at least 10%, preferably by at least 17%, particularly preferably by at least 22%, and most particularly preferably by at least 29%, compared to the heat transfer coefficient of a surface without structuring, i.e., without surface irregularities, in particular, in subregions of the unstructured region. This allows for more efficient heat transfer. The heat conduction per unit time can be significantly increased in the heat transfer region compared to a non-structured region.

[0122] The structural depth of the first periodic structure, i.e. the depth or height of the surface irregularities relative to the unstructured surface on the first outer surface, is preferably in the range from 0.3 pm to 60 pm, preferably in the range from 0.5 pm to 40 pm, particularly preferably in the range from 1 pm to 35 pm, very particularly preferably in the range from 5 pm to 30 pm, in particular in the range from 10 pm to 20 pm. The range from 1 pm is particularly suitable.

[0123] In order to achieve such structure depths, there is preferably a large pixel-to-pixel overlap of the adjacent interference pixels of preferably at least 95% for at least 50% of the interference pixels.

[0124] Structured component

[0125] The invention also relates to a structured component, in particular a laser-structured component, which has at least one further layer adjacent to the substrate.

[0126] According to an advantageous embodiment, the first outer surface having the heat transfer region forms an interface between the substrate and the adjacent layer. This increases the interface in the heat transfer region between the layers, and advantageously allows for increased heat transfer between the two adjacent layers, in particular between the substrate and the additional layer.

[0127] The first outer surface of the substrate, which has the heat transfer region, can also form the seal against the environment. The heat transfer region is then arranged on an outer surface of the structured component. An enlarged surface in the outward-facing heat transfer region then leads to increased heat transfer from the component to the environment surrounding the component. In particular, heat dissipation away from the component, in particular to a fluid adjacent to the surrounding component, such as air or water, can be increased and thus advantageously improved.

[0128] Optionally, a heat flow density (also referred to as heat flux density) of more than 200 W / m 2 , preferably over 1000 W / m 2This allows for particularly good heat conduction between the layers. This can be particularly advantageous for heating, but also for heat dissipation for cooling.

[0129] Particularly preferred embodiments of the structured component (30) are those in which the heat transfer area between the surface-structured substrate (5) and the adjacent layer within the heat transfer area has a heat flux density of at least 200 W / m 2 , preferably over 1000 W / m 2 ,. The heat flux density is particularly preferably in a numerical range that is limited downwards by one of the following endpoint values: 200 W / m 2 , 225 W / m 2 , 250 W / m 2 , 275 W / m 2 , 300 W / m 2 , 325 W / m 2 , 350 W / m 2 , 375 W / m 2 , 400 W / m 2 , 425 W / m 2 , 450 W / m 2 , 475 W / m 2 , 500 W / m2 , 525 W / m 2 , 550 W / m 2 , 575 W / m 2 , 600 W / m 2 , 625 W / m 2 , 650 W / m 2 , 675 W / m 2 , 700 W / m 2 , 725 W / m 2 , 750 W / m 2 , 775 W / m 2 , 800 W / m 2 , 825 W / m 2 , 850 W / m 2 , 875 W / m 2 , 900 W / m 2 , 925 W / m 2 , 950 W / m 2 , 975 W / m 2 and 1000 W / m 2 The heat flux density q results from the heat transfer coefficient k and the temperature gradient VT of the material and is preferably determined using heat flow meters, also known as heat flow sensors. q = -kVT Such a high heat flux density in the heat transfer region of the component (30) enables more efficient and faster heat transfer compared to conventional components.

[0130] In an alternative embodiment of the invention, the heat flux density can also be located in a lower range, which is particularly preferred for materials with a naturally lower associated heat flux density. In this case, the heat flux density of the structured heat transfer region is configured to be at least 10%, preferably at least 20%, higher than that of a comparable unstructured region of the same material. The heat flux density is then preferably at least 20 W / m 2 , whereby a higher heat flux density of at least 40 W / m 2 is particularly advantageous. Even more preferably, the heat flux density is set in a range limited by one of the following endpoint values: 20 W / m 2 , 40 W / m 2 , 60 W / m 2 , 80 W / m 2 , 100 W / m 2 , 120 W / m 2 , 140 W / m 2 , 160 W / m 2 , 180 W / m 2, 200 W / m 2 This adjustment of the heat flux density allows even materials not typically used for heat transfer purposes to achieve increased heat flux density through appropriate structuring. This can be of great importance, for example, in the semiconductor sector, where the choice of materials for component substrates is often severely limited, thus enabling more efficient heat dissipation.

[0131] According to a preferred embodiment of the invention, for adjacent layers whose surfaces are formed from a structured and an unstructured region, the interface is structured such that one of the two adjacent layers has inverse pegs, whereas the adjacent layer has pegs. Preferably, the pegs of one layer are complementary to the inverse pegs of the adjacent layer, particularly preferably complementary to the inverse pegs of the adjacent layer such that each peg of one surface is arranged in an inverse peg of the other surface (the so-called "Lego principle").Such a complementarily arranged layer stack comprising at least two layers, in particular a substrate according to the invention and an adjacent layer, further has the advantage that the adjacent layers interlock, resulting in interlocking of the layers and thus in increased stability of the layer structure. Unlike with (periodically arranged) line or wave structures, this has the great advantage that the layers cannot be displaced relative to one another in a spatial direction and / or are not connected to one another over large distances, in particular across the width / length of a layer, via only a single web formed by the line or wave structure.

[0132] In addition, the interface where the two layers meet is significantly enlarged, as the studs and inverse studs have a significantly larger surface area compared to the projected interface, i.e., the interface without surface irregularities. This can generally be achieved by interlocking surface irregularities, i.e., by groove-like elevations of one layer engaging groove-like depressions of the adjacent layer. This can advantageously improve heat transfer, particularly by increasing the heat transfer coefficient.

[0133] Surface irregularities can also be introduced into a surface, in particular into a first outer surface, by first introducing structures into a type of stamp substrate. By structuring the stamp substrate, a periodic structure in the micrometer and / or submicrometer range, preferably a first periodic structure, is created on its surface, which can then function as a negative. In particular, such a structure can be used as a stamp to transfer the structural properties to a desired additional substrate. Suitable materials for such a stamp substrate are particularly metals (e.g. silicon, aluminum, copper, gold), metallic alloys (e.g. steel, brass), enamel-coated metals or glasses and ceramic materials (e.g. zirconium oxide, titanium dioxide, zirconium dioxide) and combinations thereof.For example, such a structured substrate is suitable as a negative mold for the indirect application or creation of structures on another substrate.

[0134] This process can be advantageously used in the production of components with multiple layers. To create or optimize a heat transfer area at an interface between two adjacent layers, a heat transfer area according to the invention with surface irregularities according to the invention can be introduced into one of the adjacent surfaces, and this is then transferred to the other adjacent surface by a force. This allows the heat transfer area to be created at an interface more quickly and thus more effectively and cost-effectively, since structuring of both adjacent surfaces is no longer necessary. Further effects to be achieved

[0135] Different properties can be created both within the heat transfer area and in other areas of the substrate's surface. To achieve this, the structuring is adjusted accordingly within and / or outside the heat transfer area, so that the corresponding properties are generated based on the introduced surface irregularities.

[0136] Optical effects:

[0137] Antireflection

[0138] The invention further comprises a surface-structured component which has anti-reflection effects, in particular within the heat transfer area.

[0139] For the purposes of the invention, anti-reflection properties herein relate in particular to the increased transmission or diffraction of incident electromagnetic radiation with wavelengths in the spectral range optically visible to humans, in particular 380 to 780 nm, or in the range of ultraviolet radiation (in particular 100 to 380 nm) or infrared radiation (in particular 780 to 10,000 nm), so that the electromagnetic radiation is not reflected but is preferably absorbed by the substrate.

[0140] To produce a surface having anti-reflection properties, the depressions, in particular the cones or inverse cones or the groove-shaped depressions or the groove-shaped elevations, of an interference pixel according to a preferred embodiment of the present invention have an average structural depth or profile depth on average d50 in the range from 5 nm to 10 pm, in particular in the range from 10 nm to 5 pm, particularly preferably in the range from 50 nm to 800 nm, very particularly preferably from 100 nm to 500 nm. The structural depth of the inverse cones of an interference pixel is generally described by the average structural depth (d50), which defines the proportions of cones within an interference pixel with a certain structural depth smaller or greater than the specified value for the structural depth.

[0141] Antireflection properties on a surface are preferably achieved by forming the structured region by a periodic structure, preferably by a periodic dot structure, in the nanoscale (submicrometer range) consisting of depressions, preferably inverse cones or cones, with average dimensions in the submicrometer range, or by at least having such a periodic dot structure in the nanoscale. The periodic dot structure of an interference pixel has, in particular, an interference period of 100 nm to 1,000 nm, particularly preferably 200 nm to 700 nm, and most preferably 200 nm to 450 nm.

[0142] The structural parameters defined herein for producing a surface having anti-reflection properties, such as the interference period and structure depth, in particular the interference period, advantageously allow the proportion of reflected radiation at an interface of a substrate, preferably within the heat transfer region, to be reduced by at least 50%, preferably at least 70%, particularly preferably at least 80%, very particularly preferably at least 90%, in particular at least 95%.

[0143] The anti-reflection properties for visible light are particularly achieved when the dimensions of the structure produced, i.e. the interference period and dimensions of the depressions, in particular of the individual cones or inverse cones, are in ranges smaller than the wavelength of visible light, i.e. preferably below 700 nm.

[0144] In physics, reflection is the rebound of an electromagnetic wave at an interface between materials with different refractive indices. The angle of reflection and the angle of transmission of light in transparent substrates can generally be calculated using Snell's law of refraction: n1 sinδ1 = n2 sinδ2, where m and n2 represent the refractive index of the surrounding medium, for example, air, and the material of the cover or base layer, and δ1 and δ2 represent the angles of the incident and reflected beams, respectively.

[0145] Due to the periodic structure, in particular the periodic dot structure, on the outer surface of the cover or base layer, the refractive index of the cover or base layer changes in the area of ​​the surface or interface, resulting in a gradual refractive index. This results in light with wavelengths longer than the interference period (p n) of the periodic dot structure is transmitted more intensively. Light with wavelengths less than or equal to the periodic structure, preferably the periodic dot structure, is diffracted at the surface. Antireflection properties, in the sense of the invention, refer to structures, preferably dot structures, but also line structures, whose dimensions lie in the range of the incident electromagnetic wave, so that the refractive index difference is "softened," resulting in the incident wave being coupled into the corresponding layer. In this case, a portion of the incident electromagnetic wave may also be slightly diffracted away from the observer.

[0146] In addition, the term "anti-reflection properties" within the meaning of the invention also encompasses the fact that the refractive index at the boundary between the first medium, for example, air, and the substrate is gradual, so that there is no clear transition from one medium to the other for the incident electromagnetic wave, and the incident electromagnetic wave is transmitted more strongly. An anti-reflection property is preferably understood to refer to visible light.

[0147] The refractive index of the structured substrate is gradual due to the created periodic dot structure. It decreases over the height of the structure, so that no clear medium-to-medium transition exists. This results in increased transmission of incoming electromagnetic waves with a wavelength longer than the interference period of the created structure, preferably a dot structure, and in the diffraction of incoming electromagnetic waves with a wavelength in the range of the interference period of the created structure into the cover or base layer.

[0148] For the purposes of the invention, a surface-structured substrate with anti-reflection properties describes such a substrate which has a structured region consisting of superimposed structures, i.e., wherein a further structure is superimposed on the first periodic structure, wherein at least one structure has dimensions in the micrometer or submicrometer range, and wherein at least one structure is formed from depressions, in particular from pegs or inverse pegs or groove-shaped depressions or groove-shaped elevations (as defined herein), which can be generated in particular by interfering laser beams. Preferably, the further structure is a line structure made up of groove-shaped depressions or groove-shaped elevations, or a further periodic dot structure made up of pegs or inverse pegs. In this way, several properties of the surface can advantageously be adjusted simultaneously.

[0149] For example, when using interfering laser beams, the structured area, in particular the structure of overlapping periodic structures, can be optimally adapted to the requirements of the respective application by appropriately designing the parameters, in particular the process parameters (selection of the laser radiation source, arrangement of the optical elements).

[0150] According to one possible embodiment, a surface-structured substrate with a first outer surface having anti-reflective properties has a periodic structure with a first interference period, which forms the structured region. This advantageously allows the anti-reflective properties to be adjusted very reliably and with good reproducibility.

[0151] In contrast to conventional methods for influencing surface or interface properties (e.g., etching, sandblasting, polymer coatings), when using laser structure application methods, in particular direct laser interference structuring, it is not necessary for the entire surface to be structured. The proportion of the structured surface (degree of coverage of depressions, in particular inverse cones, per unit area, which is determined by the number and diameter or width of the depressions, preferably the inverse cones), i.e., the proportion of the structured area of ​​the surface, is preferably 3% to 99%, particularly preferably 5% to 80%, very particularly preferably 7% to 70%, in particular 10% to 50%.This not only allows for better detectability compared to conventional methods for structuring / coating surfaces, but also has the advantage that fewer defects or more vulnerable structures are introduced into the plane of the surface and / or interface in order to achieve the properties defined herein.

[0152] Reduced reflection due to the trap effect

[0153] According to an advantageous embodiment, the surface irregularities are formed as inverted cones and / or groove-shaped depressions. Thus, a portion of the rays reflected from the surface again strikes a point within the same surface irregularity, and a portion of the electromagnetic radiation is again transmitted into the substrate. This advantageously increases the proportion of electromagnetic radiation transmitted into and absorbed by the substrate, thus reducing reflection. For the purposes of the invention, this phenomenon is referred to as reduced reflection due to the trapping effect.

[0154] The reduction of reflection due to the trap effect (as defined herein) by the formation of suitable structured and unstructured areas on the first outer surface of a substrate leads in particular to reduced glare effects and the optical impression can generally be improved by a matt impression.

[0155] Reducing reflection due to the trap effect (as defined herein) by forming suitable structured and unstructured regions on the outer surface and / or inner surface of a substrate is of great importance for reducing general reflection, especially also for reducing specular reflection. The surface irregularities are formed so deep that a light beam reflected within a surface irregularity re-impinges on a point within the surface irregularity, allowing a portion of it to penetrate the substrate, resulting in both transmission and absorption. In any case, such deep structures reduce reflection.

[0156] According to a preferred embodiment of the invention, the structured regions which reduce the reflection due to the trapping effect within the structured regions are arranged in such a way that, with respect to the direction of incidence of electromagnetic radiation, preferably light, inverse pegs and / or groove-shaped depressions are arranged at this interface into which the light enters, in such a way that they are formed into the substrate.

[0157] Such a structure for reducing reflection due to the trapping effect can also be created by forming a suitable structured and unstructured region, in particular a structured region, on the outer surface and / or inner surface of an optoelectronically active layer. Reducing reflection is particularly relevant at an interface to the optoelectronically active layer.

[0158] When utilizing the trap effect, the lateral surface of the cones or inverse cones serves as a mirror surface, preferably a quasi-homogeneous mirror surface, which reflects the portion of reflected incident electromagnetic radiation within the cones and / or inverse cones, in particular inverse cones, up to the saddle point. At each further reflection point within the lateral surface, a portion of the (remaining) electromagnetic radiation is coupled into the substrate, whose outer surface and / or inner surface is formed from such a structured and an unstructured region. According to a preferred embodiment of the invention, the lateral surface of the cones or inverse cones is smooth. Anti-glare

[0159] According to an advantageous embodiment, a structuring having anti-glare properties can be produced on the substrate, in particular in the heat transfer area.

[0160] Glare effects can be reduced with the help of a surface structuring described herein, in particular anti-glare structuring. An anti-glare structure scatters incident electromagnetic radiation, e.g., light, at a plane of the substrate, in particular the surface of the substrate, so that reflection of this electromagnetic radiation can be significantly reduced.

[0161] In the context of the invention, glare is understood to mean the reflection of light from a light source (e.g. the sun) on a substrate, e.g. a glass pane or a metal element.

[0162] With the help of an anti-glare surface treatment (typically achieved through coatings in the prior art), these glare effects can be reduced. An anti-glare structure scatters incident light on the surface, significantly reducing reflections. The surface then appears matte in this area.

[0163] According to a preferred embodiment of the invention, the interference periods of the dot structure of the first interference pixel and the period of the second interference pixel are identical.

[0164] According to a preferred embodiment of the present invention, the method according to step b) comprises applying at least one further type of interference pixel with a further interference period (p n), for example a third interference pixel (12) with a third interference period (p3) onto the surface of the substrate processed in step b), in particular by means of laser ablation, wherein the further, for example the third interference pixel (12) is arranged superimposed on the first interference pixel (10) and second interference pixel (11) according to the features defined herein. The ratio of the further interference period (p n ) to the other interference periods in the range of preferably 20:1 to 1:20, preferably in the range of 10:1 to 1:10, particularly preferably in the range of 5:1 to 1:5, in particular 3:1 to 1:3, whereby the properties defined herein, in particular the anti-glare properties or the reduction of reflection due to the trapping effect within the heat transfer range can be optimized.

[0165] The periodic structures thus generated within an interference pixel, preferably periodic dot structures, are designed as periodically arranged depressions, preferably pegs or inverse pegs. The interference period (i.e. the distance between the depressions, preferably the distance between the vertices of two adjacent inverse pegs - or the height centers relative to pegs or the center lines of the groove-shaped depressions or the center lines of the groove-shaped elevations) of a periodic structure, preferably a first periodic structure, in particular on a surface of the cover or base layer which has anti-glare properties, is on average in the range from 1 pm to 50 pm, preferably in the range from 5 pm to 50 pm, particularly preferably in the range from 10 pm to 30 pm.

[0166] Advantageously, the individual pixels of one type of interference pixel, i.e., with the same interference period and average structure depth, e.g., of a first interference pixel, a second interference pixel, and / or a further interference pixel, which are arranged adjacently and repetitively offset from one another, can globally (i.e., over the extent of the plane to be structured) optionally form a periodic or a non-periodic structure, preferably a periodic or non-periodic dot structure. A fully periodic dot structure is generated or exists when the preceding pixel and the following pixel of one type of interference pixel are each offset by a whole multiple (e.g., 2, 3, 4, 5) of the interference period (p n ) are shifted from each other in one spatial direction. This results in a fully periodic pattern over the extent of the plane to be structured, the period of which corresponds to the interference period (p n). A quasi-periodic dot structure is created or exists when the preceding pixel and the following pixel of a type of interference pixel are each spaced apart by an equal multiple (e.g. 0.5; 1.3; 2.6) of the interference period (p n ) are shifted from each other in one spatial direction.

[0167] In contrast, a non-periodic dot structure is created or exists when the interference period of the subsequent pixel is varied relative to the neighboring, preceding pixel and / or when adjacent pixels arranged repetitively offset from one another are rotated, e.g., applied successively rotated. Characteristic here is that the structured region is formed from a superposition of several periodic structures. In particular, several interference pixels are arranged repetitively adjacent to one another in such a way that the generated global structure, i.e., the structure that forms the structured region, is preferably non-periodic.

[0168] This creates a large number of scattering centers on the surface, which, due to their irregularity, scatter the electromagnetic radiation, i.e., the light, in different directions. This advantageously prevents strong reflections in individual directions. Furthermore, effects such as a rainbow-like shimmer effect caused by refraction due to periodicity can be avoided or at least reduced.

[0169] To produce such a non-periodic structure, preferably at least 70%, more preferably at least 90%, and particularly preferably at least 98% of the neighboring interference pixels have different structural parameters, i.e. at least one different structural parameter or at least two different structural parameters selected from the interference period, the structural depth or average structural depth, and the arrangement of the cones or inverse cones within an interference pixel. For example, the position of the depressions, in particular of the cones or inverse cones, can be changed to obtain a non-periodic global structure. This advantageously makes it possible to obtain a suitable global structure with low periodicity at high process speeds, thereby advantageously avoiding the moiré effect and diffraction effects.Preferably, the change in the structural parameter(s) takes place according to a random distribution, in particular by means of a stochastic method.

[0170] According to a preferred embodiment of the present invention, the dot structure formed by adjacent, repetitively offset pixels of a type of interference pixel is a fully periodic dot structure or a quasi-periodic dot structure (each as defined above).

[0171] To produce a surface having anti-glare properties, the depressions, preferably the cones or inverse cones, of an interference pixel according to a preferred embodiment of the present invention have a mean structural depth or profile depth on average d50 in the range from 5 nm to 20 pm, particularly preferably in the range from 50 nm to 10 pm, very particularly preferably from 100 nm to 5 pm, even more preferably 200 nm to 2 pm. The structural depth of the inverse cones of an interference pixel is generally described by the mean structural depth (d50), which defines the proportions of cones within an interference pixel with a certain structural depth smaller or greater than the specified value for the structural depth.

[0172] It can be provided that first interference pixels and / or second interference pixels arranged adjacent to one another have, at least to a high extent of at least 70%, preferably at least 90%, preferably at least 98%, varying structural parameters, preferably selected from the group comprising the interference period of the interference pixel, the structural depth of the depressions, preferably of the inverse pegs, the diameter of the pegs or inverse pegs, the width of the groove-shaped depressions or the groove-shaped elevations, the shape of the pegs or inverse pegs and the size of the pegs or inverse pegs. Preferably, a further possible structural parameter is the arrangement or position of the depressions, preferably of the pegs or inverse pegs. This advantageously makes it possible to achieve a high degree of disorder, i.e.non-periodic structures are created, thereby minimizing or preventing unwanted or disturbing optical effects, such as moiré effects or color effects caused by diffraction on applied microstructures.

[0173] According to a preferred embodiment of the invention, the interference period of the dot structure of at least each further interference pixel of a type, for example each interference pixel of a first interference pixel, each interference pixel of a second interference pixel and / or each interference pixel of a third interference pixel, is substantially identical, i.e. differs by a maximum of 0% to 2.0%, particularly preferably by a maximum of 0 to 1.0%. Most preferably, the interference periods are identical. As a result, the parameters of the laser structuring device, in particular of the laser interference structuring device for applying the interference pixels to the plane of the substrate, can be kept constant, which minimizes the effort and the formation of defective structures.

[0174] According to a preferred embodiment of the present invention, the adjacent, repetitively offset interference pixels of one type, for example the first interference pixel, the second interference pixel and / or the third interference pixel, are rotated successively relative to the preceding interference pixel of this one type about an axis of rotation (i.e. a normal to the plane) arranged within the interference pixel (preferably about a central one), for example alternately or successively rotated relative to the one before it. Preferably, the subsequent interference pixel is rotated relative to the preceding interference pixel of the interference pixels of one type in the range around 51° to 90°, furthermore in the range around 3° to 85°, particularly preferably around 5° to 80°, 10° to 75°, very particularly preferably around 10° to 75°, in particular in the range around 15° to 60°.As a result, a high degree of disorder, i.e. non-periodic structures, is generated globally over a plane of the substrate that is spanned by a surface of the substrate or within the volume of the substrate, which also minimizes or prevents undesired or disturbing optical effects, such as moiré effects or color effects that arise from diffraction on applied microstructures.

[0175] In general, the aim of generating suitable anti-glare properties is to generate a dot structure with broken periodicity, i.e., without resulting periodicity, through the specific selection of the structural parameters of the first and second interference pixels and each additional type of interference pixel. The generated dot structures are therefore preferably arranged non-periodically, with the interference periods of the first and second interference pixels, or each additional type of interference pixel, preferably being different (not identical) from one another. Periodic effects that disrupt the resulting image can thus be advantageously avoided.

[0176] A superposition of first and second interference pixels, which have identical interference periods, can result in periodic dot structures in which the undesirable moiré effect occurs.

[0177] A high degree of disorder also prevents adverse changes in color behavior, which can occur due to diffraction effects on the introduced structures.

[0178] The existing dot structure leads to a scattering behavior of the incident light, which involves a multitude of minimal deflection processes of the photons at the introduced dot structures. The existing periodicity of the dot structures can thus lead to an increase in the deflection of the photons, i.e., the light, in certain directions, creating a glittering effect. While this effect is desirable for certain applications, it should be avoided for many others. The generation of non-periodic structures advantageously leads to a reduction or elimination of these glittering effects.

[0179] In the aforementioned case, the offset between the interference pixel of a first type and the interference pixel of a second type, for example the second interference pixel and the first interference pixel, is in the range of 5% < x < 50%, preferably in the range of 10% < x < 50%, in particular in the range of 20% < x < 50%, particularly preferably in the range of 25% < x < 45% of the interference period. If the periodic dot structure is designed such that an interference pixel of a further type is provided, at least a third interference pixel, this is arranged superimposed on the interference pixel of the previous type such that the offset between the interference pixel of the further type, for example the third interference pixel, and the second interference pixel is in the range of 5% < x < 50%, preferably in the range of 10% < x < 50%, in particular in the range of 20% < x < 50%, particularly preferably in the range of 25% < x < 45% of the interference period.An offset which lies below the interference period leads to an increase in the structure density or density of the point structure, which results in an increased scattering cross section and advantageously a greater scattering effect or a stronger reduction of the directed reflection.

[0180] According to a preferred embodiment of the present invention, the structured substrate, in particular the dot structure applied to the surface of the substrate, has at least one further type of interference pixel with a further interference period, for example a third interference pixel with a third interference period, wherein the further, for example the third interference pixel is arranged superimposed on the first interference pixel and the second interference pixel according to the aforementioned claims. As a result, further defects (i.e. dot structures in the micrometer and submicrometer range) can advantageously be created in the plane of the substrate to be structured. A higher number of inverse cones increases the number of scattering centers and reduces the directed reflection. Advantageously, the degree of disorder, i.e.non-periodic structures, thereby minimizing or preventing undesirable or disruptive optical effects, such as moiré effects or color effects caused by diffraction on applied microstructures. Furthermore, in displays, for example, this reduces or prevents the occurrence of a glitter effect, which occurs as a result of surface structures larger than or equal to the size of display pixels. With a glitter effect, a display pixel only illuminates a portion of the surface feature, creating scattering effects that are macroscopically perceived as a periodic pattern.

[0181] The structure defined herein for generating anti-glare properties, preferably a dot structure, is preferably a non-periodic dot structure composed of cones or inverse cones with average dimensions in the micrometer range, wherein the structure of an interference pixel in particular has an average distance, relative to the respective saddle point or height center of two adjacent cones of an interference pixel, of 1 pm to 50 pm, particularly preferably 5 pm to 50 pm, and most preferably 10 pm to 30 pm. A further structure in the nanometer range can be superimposed on this preferably anti-periodic dot structure in the micrometer range, wherein the average dimension of the superimposed structure preferably has dimensions in the range of the laser wavelength λ or λ / 2, in particular from 100 nm to 1,000 nm, particularly preferably from 200 nm to 500 nm. For the purposes of the invention, such a structure is also referred to as a hierarchical structure.

[0182] The invention also encompasses a surface-structured substrate with anti-glare properties, wherein a first outer surface has anti-glare properties. Preferably, such a surface further comprises a second periodic structure, preferably a second periodic dot structure, with a second interference period.

[0183] On the one hand, varying the interference period can reduce the periodicity of the structure, especially the global structure, thereby improving the anti-glare effect. Furthermore, a second periodic structure can also create additional properties.

[0184] Thus, the invention also encompasses a surface-structured substrate with anti-glare properties, wherein a first outer surface, particularly within the heat transfer region, has anti-glare properties and also other properties, such as an increased heat transfer coefficient at the surface and / or anti-icing properties. The superimposed structures are produced as described in the corresponding sections on the specific properties.

[0185] Anti-icing

[0186] The inventors have established a relationship between the surface properties of a substrate and the formation of ice on its surface. In particular, so-called anti-icing properties can be created, for example, on the outer surface of an external layer, if the feature size on the surface of a substrate is sufficiently small. The results have shown that a substrate with superhydrophobic properties (preferably as defined herein) can also exhibit anti-icing properties.

[0187] For the purposes of the invention, anti-icing properties mean that no or very little water freezes on the surface of a substrate, whereby this property is attributable to the surface properties, in particular the surface roughness. Such a substrate can be advantageously used in the aerospace sector, in wind turbines, in the field of automotive components or even telecommunications and antenna technology to protect exposed components from icing. This can advantageously improve de-icing efficiency. The combination of improved heat transfer at the surface and the anti-icing property of the surface leads to a synergistic effect that reduces the energy required for de-icing. This can result in enormous energy savings.It is precisely the synergy between the surface with anti-icing properties and the modified heat transfer properties of the structured surface of the substrate that can multiply the effective surface area, i.e. the surface area acting against icing, which leads to a change in the heat flux density of several tens of percent.

[0188] Hydrophobic properties depend on both the chemical and surface properties, particularly the surface roughness, of a substrate. The inventors have now surprisingly discovered that, by the method according to the invention, particularly hydrophobic substrates can be treated with superhydrophobic and self-cleaning properties by introducing structures in the micrometer and submicrometer range, particularly overlapping structures (as defined herein). Substrates with superhydrophobic properties are particularly preferably substrates with a hierarchical surface structure.Hierarchical surface structuring is defined here as a surface with regular structures with dimensions in the micrometer range, which in turn have a surface structure with dimensions in the submicrometer range. Such hierarchical structuring can lead to high surface roughness.

[0189] The inventors have also discovered that substrates structured primarily by a device or method disclosed herein are characterized by pronounced hydrophobic properties on the surface of a substrate. By means of the device and method disclosed herein for producing dot structures with dimensions in the micrometer and / or submicrometer range, structuring to produce a surface texture, in particular a surface roughness on the surface of a substrate, is also possible, which results in the substrate having hydrophobic or superhydrophobic properties. Hydrophobic material properties can be created by using direct laser interference structuring to create a structure with dimensions in the micrometer and / or submicrometer range. In a preferred embodiment, a structure with dimensions in the micrometer range is first created on the surface.Next, by moving the beam splitter element in the laser beam path, a structure with dimensions in the submicrometer range is generated on the surface of the first structure, preferably with multiple irradiation of the substrate. The hierarchical structure thus created has hydrophobic or superhydrophobic properties.

[0190] To create a substrate with hydrophobic properties, it is also conceivable to create only a dot structure with dimensions in the micrometer or submicrometer range, without moving the beam splitter element in an intermediate step. The dimensions mentioned refer to the interference periods or the size of the intermediate unstructured sections.

[0191] Advantageously, optoelectronic components with hydrophobic and / or superhydrophobic properties can be produced in a technically easily feasible manner using the same method and on the basis of the same device by creating a periodic dot structure in the micrometer or submicrometer range and / or a periodic dot structure with a hierarchical structure in the micrometer and submicrometer range. By moving the beam splitter element, at least two, but also any number of additional structurings can be realized on the surface of the substrate without further changes to the structure, e.g., without replacing optical elements or moving the substrate. This increases both the precision in the alignment of the structures and the speed of the process compared to conventional methods or devices.

[0192] To produce a surface which also has anti-icing properties in the heat transfer region, the surface irregularities preferably have an average structural depth or profile depth on average d50 in the range from 0.05 pm to 200 pm, preferably in the range from 0.5 pm to 50 pm, particularly preferably from 1.0 pm to 20 pm, very particularly preferably from 2.0 pm to 10.0 pm. The structural depth of the inverse cones of an interference pixel is generally described by the average structural depth (d50), which defines the proportions of cones within an interference pixel with a certain structural depth smaller or larger than the specified value for the structural depth.

[0193] Suitable interference periods are preferably in the range from 0.05 pm to 200 pm, preferably in the range from 0.5 pm to 50 pm, particularly preferably from 1.0 pm to 20 pm, very particularly preferably from 2.0 pm to 10.0 pm. In addition, these structure depths are characterized in that the lateral surface of the cones or inverse cones serves as a mirror surface, preferably a quasi-homogeneous mirror surface, as when utilizing the trap effect, which reflects the portion of reflected incident electromagnetic radiation within the cones and / or inverse cones, in particular inverse cones, up to the saddle point, wherein at each further reflection point within the lateral surface a portion of (remaining) electromagnetic radiation is coupled into the substrate, the outer surface and / or inner surface of which is formed from such a structured and an unstructured region.According to a preferred embodiment of the invention, the outer surface of the studs or inverse studs is smooth. This advantageously also allows for a reduction in reflection.

[0194] PROCEDURE

[0195] The present invention also encompasses a method for producing a surface-structured substrate, as defined herein, wherein the surface-structured substrate has at least one first outer surface with a heat transfer region, wherein the heat transfer region, the first outer surface, is formed by a structured region and an unstructured region. The method for producing a structured substrate (as defined herein), in particular a substrate with improved thermal conductivity, preferably comprises the following steps: a) providing a substrate to be structured, wherein the substrate to be structured has an interface, wherein the interface is formed as a direct contact surface between the surface of the substrate to be structured and an adjacent medium, for example a gas or an auxiliary layer,wherein the substrate to be structured or the medium adjacent thereto comprises or consists of a material with a thermal conductivity of at least 20 W / (m K), preferably at least 50 W / (m K), more preferably at least 100 W / (m K), particularly preferably at least 200 W / (m K), measured at 20 °C, b) applying a structured region to the surface to be structured, in particular to a first outer surface of the substrate to be structured, in particular by means of laser ablation (as defined herein), whereby a heat transfer region is created on the surface to be structured, wherein the structured region has at least one first interference pixel with a first interference period (pi), wherein the first interference pixel is formed from a first periodic structure of at least three surface irregularities, wherein the surface irregularities are in particular designed as a single line structure, a single dot structure,a plurality of superimposed line structures, a plurality of superimposed dot structures, or even superimposed dot and line structures can be formed, wherein the distance between two adjacent surface irregularities amounts to a first interference period (pi), wherein the first interference period (pi) lies in the range from 50 nm to 200 pm, preferably from 1 pm to 45 pm, wherein the heat transfer region has a ratio of the real surface to the projected surface of at least 120%, and wherein the heat transfer coefficient of the heat transfer region is preferably increased by at least 10% compared to the heat transfer coefficient of the unstructured region of the same material, preferably determined at 20°C.

[0196] Particularly advantageously, this allows a surface structuring to be created on the substrate which has improved thermal conductivity compared to the unstructured area of ​​a substrate.

[0197] Particularly preferably, the heat transfer coefficient of the heat transfer region has a value that is preferably at least 10% higher than the heat transfer coefficient of the unstructured region (29) of the same material, which has no surface irregularities, preferably determined at 20°C. This enables a higher thermal conductivity of the substrate produced according to the invention compared to an unstructured substrate, which enables the production of particularly thermally conductive surfaces with the advantages mentioned here.

[0198] The first interference period (p1) is in the range from 50 nm to 200 pm, preferably from 1 pm to 45 pm, more preferably from 5 to 40 pm, more preferably from 10 to 35 pm, most preferably from 15 to 30 pm. In a preferred embodiment, the structured region is formed directly on a surface to be structured of the substrate to be structured, in particular in the form of periodic structures, in particular as a periodic dot structure and / or periodic line structure, for example by adjacent, repetitively offset pixels of a type of interference pixel. In this case, the surface to be structured of the substrate to be structured has or consists of a material with a thermal conductivity of at least 20 W / (m K), preferably at least 50 W / (m K), more preferably at least 100 W / (m K), more preferably at least 200 W / (m K), measured at 20 °C.In a particularly preferred embodiment, the substrate to be structured is formed from the aforementioned material. The medium adjacent to the substrate to be structured is preferably a gas, e.g., air, nitrogen, a noble gas, or a mixture thereof.

[0199] According to a preferred embodiment, the structured region on a surface of the substrate is formed at least by superimposing a plurality of first interference pixels with a first interference period (pi) on the first outer surface of the substrate, thereby creating an interference pixel-to-interference pixel overlap (also referred to herein as "pixel-to-pixel overlap" or "overlap of the interference pixels" or, when applied by means of laser structure application methods, in particular by means of laser interference structuring, as "pulse-to-pulse overlap"). This means that a first interference pixel is superimposed on at least one further first interference pixel with the first interference period (pi) and / or a second interference pixel with a second interference period (P2) and / or a further interference pixel with a further interference period (p n) can be arranged offset from one another in such a way that, for example, at least 50% of the offset interference pixels have an overlap of at least 95%, preferably of at least 97%, particularly preferably of at least 99%, very particularly preferably of at least 99.5%, even more preferably of at least 99.8% with a neighboring interference pixel, preferably with a plurality of neighboring interference pixels. Advantageously, the very close arrangement of periodic structures arranged adjacent to one another, in particular periodic dot structures and / or line structures, e.g.by adjacent, repetitively offset pixels of a type of interference pixel, the surface in the structured region of the substrate is enlarged even more in relation to the projected surface, in particular to at least 200%, particularly preferably to at least 250%, thereby advantageously improving the heat transfer properties, in particular increasing the heat transfer coefficient. This allows better heat dissipation from a substrate or element, e.g. a component, to be achieved. The structuring of the surface of a substrate, ie the application of the structured regions, preferably takes place comprising a first, second, third and / or further.

[0200] Interference pixels by a mechanical process, by chemical (post-)treatment and / or by a laser structure application process, in particular by laser interference structuring.

[0201] To produce substrates whose outer surface is at least partially formed from a structured and an unstructured region, lithography, in particular photolithography or imprint lithography, such as nano-imprint lithography, can be used as a mechanical process. In lithography, a sacrificial layer is generally arranged on the surface of the substrate to be structured. The sacrificial layer serves to mask the surface to be structured and can be removed, in particular completely, after lithography. For example, the sacrificial layer can be applied to the surface to be structured and subsequently structured. The lateral structure of the sacrificial layer can then be transferred to the surface of the substrate, in particular by means of an etching process.

[0202] In photolithography, the sacrificial layer is usually a photosensitive resist layer whose chemical properties are locally modified by irradiation through a suitably structured mask, such as a metal mask, allowing the formation of structured regions in the sacrificial layer. This process can achieve structuring of surfaces with feature sizes of a few micrometers in the lateral direction. Both regular and irregular structures can be produced in this way.

[0203] Imprint lithography, e.g. nano-imprint lithography, is a microforming process or contact structuring process in which the surface of a substrate, e.g. the sacrificial layer, is structured using a suitably structured mold. This mold, such as a suitably structured stamp, is pressed into the surface of the substrate to be structured. The substrate to be structured can, for example, contain a thermoplastic polymer (Thermoplastic Nano Imprint Lithography, T-NIL) or a photosensitive material (Photo Nano Imprint Lithography, P-NIL). However, the substrate to be structured can also comprise or consist of an at least partially softened metal and / or an alloy. Metals with a low melting point or softening point, such as, for example,Copper (Cu), silver (Ag), gold (Au), tin (Sn), lead (Pb), zinc (Zn), aluminum (Al), or mixtures or alloys thereof, such as copper alloys with tin, zinc, nickel and / or lead. Nano-imprint lithography can be used to structure surfaces in a particularly simple manner. In particular, particularly small lateral structure sizes, i.e. structures below 1 pm down to the range below 10 nm, can be produced. Nano-imprint lithography is therefore particularly suitable for producing structure sizes that are on the order of the wavelength of radiation in the infrared, visible, or ultraviolet spectral range, for example for the production of structures for a photonic grating. Such a process is particularly suitable if the structured regions of the substrate surface are to have a periodic point structure (as defined herein) formed from cones and / or inverse cones.To produce the mold, it is advisable to apply the negative of the desired periodic dot structure to the surface of the substrate to be structured, in particular a negative with a correspondingly complementary periodic structure, which is formed from inverse pegs and / or pegs, for the indirect application or generation of structures on another substrate, for example by laser structure application methods, in particular the direct one.

[0204] Laser interference structuring, and transferring this negative onto the surface of the substrate to be structured.

[0205] In a preferred embodiment of the invention, the structuring of the substrate surface can be carried out using laser structuring methods, in particular direct laser interference structuring. A periodic intensity distribution is generated on the surface of the substrate or within its volume by interference of pulsed laser beams by splitting the original laser beam into several partial beams and subsequently superimposing these partial beams at any fixed point (focusing point) on the surface of the substrate or within the volume of the substrate.

[0206] A structured area on an outer surface of a substrate to be structured can be created as follows:

[0207] A substrate to be structured is provided, preferably a substrate that is flat on at least one side, which is located on a holding device. A laser beam is emitted from a laser radiation source. This laser beam is split into at least three, particularly preferably at least four partial beams by a beam splitter element, which can also be referred to as an optical beam splitter element. The partial beams thus generated impinge on a focusing element, which focuses (bundles) the at least three, particularly preferably four partial beams on the surface of the substrate, preferably a substrate that is flat on at least one side, so that the partial beams interfere constructively and destructively on the surface of the substrate.Thus, a periodic dot structure in the micrometer and / or submicrometer range is created on the surface of the substrate, preferably a flat and / or transparent substrate, by laser interference processing. The at least three partial beams are superimposed to create a 2D pattern.

[0208] According to one variant of the method, the periodic dot structure is created within an interference pixel on the outer surface of the substrate to be structured using a single laser pulse, referred to herein as single irradiation. Single irradiation means that the interference pixel is preferably exposed only once within a processing step using a single laser pulse. Thus, a dot structure with one interference period is created within an interference pixel by exposure to only one laser pulse. Adjacent interference pixels preferably do not overlap, so that a resulting inverse cone is not illuminated again. The maximum laser pulse energy depends on the pixel size and the material. The minimum pulse energy is preferably in the range from 50 pJ to 20 mJ, particularly preferably in the range from 300 pJ to 800 pJ.This advantageously allows for high processing speeds. Furthermore, the use of single irradiation can prevent the occurrence of quasi-periodic effects.

[0209] Wave structures, known as LIPSS, can be prevented by uncontrolled self-organization processes that alter the optical properties of the substrate surface. Consequently, the occurrence of LIPSS structures can be prevented by a single irradiation. This allows for significantly more precise process control and reliably achieves the desired properties of the heat transfer area.

[0210] The fact that the periodic dot structure within an interference pixel is generated by applying a single laser pulse using single irradiation also has the advantage that very small structure depths can be created, which is particularly advantageous for thin substrates.

[0211] Preferably, single irradiation produces shallow structural depths that can be adjusted according to the material or material composition of the substrate. For example, structural depths in the range from 0.05 pm to 2 pm, preferably from 0.1 pm to 1 pm, can be achieved in this way. For example, this can also be used to structure substrates that are additionally characterized by anti-reflection properties, with the structural depths being in the range from 5 nm to 200 nm, particularly preferably in the range from 5 nm to 150 nm, and most preferably 10 nm to 100 nm. Using a single laser pulse ensures that the structural depths of the periodic dot structure are shallow. This advantageously ensures that the optical properties of the substrate are not impaired compared to the unstructured substrate.

[0212] Notwithstanding this, structuring by means of single irradiation can also be provided for setting a pulse-to-pulse overlap. This means that a first interference pixel can be arranged offset from a second and / or further interference pixel in such a way that, for example, at least 50% of the offset interference pixels have an overlap of at least 95%, preferably of at least 97%, particularly preferably of at least 99%, and most preferably of at least 99.5% with a neighboring interference pixel, preferably with a plurality of neighboring interference pixels. Structuring by means of pulse-to-pulse overlap has the advantage that at least individual structural elements generated within a first, second, and / or further interference pixel are irradiated multiple times.This allows self-organization processes to form a quasi-periodic line structure superimposed on the periodic dot structure as a wave structure, particularly a so-called LIPSS. Advantageously, hierarchical structures can be created quickly and effectively on the substrate surface, allowing the surface roughness of the wall of a periodic dot structure to be increased, particularly in the nanometer and / or submicrometer range, resulting in an increase in the surface area.

[0213] In particular, achieving the desired interference periods of the LIPSS generated by the self-assembly processes depends on the material properties of the substrate to be patterned and the properties of the laser beam used for patterning, particularly the wavelength of the laser beam. A desired interference period can therefore be adjusted by selecting the appropriate laser radiation source.

[0214] According to a further embodiment of the invention, the same interference pixel is processed by means of a plurality of successive laser pulses through multiple irradiation. Multiple irradiation here means that the same region of the substrate to be structured is processed by a plurality of successive laser pulses, wherein the 2D pattern of a first pulse generated by the superposition of partial beams is congruent or essentially congruent (i.e., with a topological shift of less than 1.0%, preferably less than 0.5%) with a second and / or further pulse. Thus, a dot structure with an interference period within an interference pixel is exposed several times, wherein a resulting inverse cone is exposed again one or more times. The pulse length can be adjusted by the user.

[0215] In particular, in this method, the same interference pixel is processed by means of multiple irradiation. Thus, as a result of the successive multiple irradiation of an interference pixel, in particular at least three, particularly preferably at least four consecutive pulses with identical process parameters, a quasi-periodic line structure superimposed on the periodic structure, in particular a periodic dot structure, forms as a wave structure through self-organization processes. Process parameters within the meaning of the invention include, for example, the setting of the distance between the beam splitter element and the focusing element, the laser pulse duration, the laser pulse energy, the laser wavelength, and / or the position of the interference region on the substrate. Self-organization processes refer in particular to so-called LIPSS, as known from the prior art.LIPSS occur as a result of partial heating of the substrate surface and its subsequent solidification in the form of regular, quasi-periodic (as defined herein) wave structures. Advantageously, hierarchical structures can be created quickly and effectively on the surface of the substrate, thereby increasing the surface roughness of the wall of a periodic dot structure, resulting in an enlargement of the surface area. Readjustment of the laser interference device and / or realignment of the substrate is not necessary for this. In addition, the structural parameters of the periodic dot structure, in particular the structure depth, are thus also adjustable. A shallow structure depth is preferably achieved by adjusting the process parameters, in particular the laser pulse energy, such that the energy input due to the multiple irradiation per interference pixel remains as low as possible.

[0216] According to a further embodiment of the invention, a further periodic dot structure or periodic line structure with an interference period different from the interference period of the first periodic structure, the second periodic structure and / or a further periodic structure is applied to the substrate by multiple irradiation with mutually differing process parameters. The differing process parameters relate in particular to the distance of the beam splitter element from the focusing element, whereby the interference period of the further periodic dot structure or line structure is changed compared to the first periodic dot structure. However, an additional change in the laser pulse duration and / or energy is also possible. Thus, a flexible second structure with dimensions in the micrometer and / or submicrometer range can advantageously be applied to the substrate, which is independent of the first periodic dot structure.This ensures easy alignment of the interference pixels on the substrate. Furthermore, the proportion of structured area on the substrate surface is increased, allowing certain properties, such as the trapping effect to reduce reflection, to play a greater role.

[0217] The laser pulse duration is preferably in the range from 50 fs to 100 ns, preferably in the range from 500 fs to 50 ns, particularly preferably in the range from 800 fs to 20 ns, and most preferably in the range from 1 ps to 10 ns. This advantageously limits the energy so that defined structures can be created. This short laser pulse duration can prevent or at least minimize unwanted and / or uncontrolled melting of the substrate (e.g., in the form of a structural or chemical transformation), particularly as a result of local overheating, e.g., due to excessive energy input. This is particularly advantageous for the "sensitive" materials used herein which the substrates comprise or from which the substrates are made.

[0218] The laser radiation source is preferably configured to emit wavelengths in the range from 100 nm to 15 pm (e.g., CO2 lasers in the range from 10.6 pm), most preferably in the range from 266 nm to 1,064 nm. Suitable laser radiation sources include, for example, UV laser beam sources (155 nm to 355 nm), laser beam sources that emit green light (532 nm), diode lasers (typically 800 nm to 1,000 nm), or laser beam sources that emit radiation in the near infrared (typically 1,064 nm), in particular with a wavelength in the range from 200 nm to 650 nm. Lasers suitable for microprocessing are known to the person skilled in the art and include, for example, HeNe lasers, HeAg lasers (approx. 224 nm), NeCu lasers (approx. 249 nm), Nd:YAG lasers (approx. 355 nm), YAG lasers (approx. 532 nm), InGaN lasers (approx. 532 nm).

[0219] The laser pulse energy is preferably 50 pJ to 20 mJ, more preferably 300 pJ to 800 pJ, and particularly preferably 500 to 800 pJ. This low laser pulse energy per laser pulse can prevent or at least minimize unwanted and / or uncontrolled melting of the substrate (e.g., in the form of a structural or chemical transformation), particularly as a result of local overheating, e.g., due to excessive energy input. This is particularly advantageous for the "sensitive" materials used herein that the substrates comprise or are made of.

[0220] According to an advantageous embodiment of the method, pulses in the ps range are used. This allows for a reduction in energy input and thus also in the heat diffusion length. Since a reduced pulse duration leads to a shorter heat diffusion length, smaller structures can be advantageously created in a defined manner. This also enables the creation of defined structures even in materials with high thermal conductivities, with the heat diffusion length increasing with higher thermal conductivity.

[0221] According to a preferred embodiment of the invention, the interference periods of the periodic structure of the first interference pixel (pi) and the interference periods of the second interference pixel (p2) and / or each further interference pixel (p n ) are identical.

[0222] Method using an auxiliary layer

[0223] According to an advantageous embodiment of the method, the application of at least one structured region on a surface to be structured, in particular on a first outer surface, of the substrate to be structured takes place indirectly, in particular in the form of periodic structures, in particular as a periodic dot structure and / or periodic line structure, for example by adjacent pixels of a type of interference pixel arranged repetitively offset from one another, wherein an auxiliary layer is structured through a transparent base layer, wherein the transparent base layer is designed as the substrate to be structured and wherein the auxiliary layer is designed as a medium adjacent to the substrate to be structured.In this case, the medium adjacent to the substrate to be structured, at least in the region of the surface of the substrate to be structured, comprises or consists of a material with a thermal conductivity of at least 20 W / (m K), preferably at least 50 W / (m K), more preferably at least 75 W / (m K), preferably at least 100 W / (m K), furthermore at least 150 W / (m K), particularly preferably at least 200 W / (m K), measured at 20 °C. In a particularly preferred embodiment, the adjacent medium is formed from the aforementioned material. The laser beams, in particular the partial laser beams, are guided through the transparent base layer and focused onto the interface between the base layer and the auxiliary layer, which is preferably formed from a material as defined herein, in particular a metal, in particular onto the surface of the auxiliary layer.The material of the auxiliary layer is selected such that, in contrast to the base layer, it absorbs the laser light particularly well. This results in local overheating in the material of the auxiliary layer, preferably in the metal, as well as in partial melting of the auxiliary layer, in particular at the surface of the auxiliary layer, at the interface with the base layer. This allows a structure to be created on the base layer. The method according to the invention therefore also comprises the provision of an auxiliary layer before the step of applying at least one structured region to an interface, in particular on the surface of the substrate to be structured.

[0224] Preferably, the surface of the substrate to be structured and the adjacent surface of the auxiliary layer are complementary (i.e., congruent) to each other, preferably planar, in particular plane-parallel to each other, which allows the surface of the substrate to be structured to be brought into congruence with the adjacent surface of the auxiliary layer.

[0225] By applying at least one structured region at an interface between the transparent base layer and the auxiliary layer, a structured region is formed by surface irregularities made of the material of the auxiliary layer through a material transfer from the auxiliary layer to the transparent base layer to be structured. In one embodiment, the auxiliary layer remains on the transparent base layer following step (b), wherein the transparent base layer is formed, for example, as a cover layer on the auxiliary layer, which, for example, assumes a different function in a component. Following step (b), the auxiliary layer can be removed from the base layer, leaving a cover layer on the base layer. This advantageously allows good heat dissipation to be achieved even on transparent materials.

[0226] Preferably, the base layer comprises a transparent material (as defined herein with respect to partial transparency or translucency), preferably glass (e.g. borosilicate glasses, quartz glasses, alkali-alkaline earth silicate glasses (e.g. soda-lime glass), aluminosilicate glasses, metallic glasses), but also solid polymers (e.g. polycarbonates, such as Makrolon® and Apec®; polycarbonate blends, such as polycarbonate polyester (Makroblend®) and Bayblen®;

[0227] Polymethyl methacrylate, such as Plexiglas®; polyester; polyethylene terephthalate, polypropylene, polyethylene) as well as transparent ceramics (e.g. spinel ceramics, such as Mg-Al spinel, aluminum oxynitride (ALON), aluminum oxide, yttrium aluminum garnet, yttrium oxide or zirconium oxide) or mixtures thereof, or is formed from a transparent material, preferably glass. A suitable material for the transparent base layer is glass, which has a suitable transparency or translucency (each as defined herein), in particular in the visible light range. According to the invention, the material of the base layer has a thermal conductivity of at least 20 W / (m K).

[0228] A characteristic of the method according to the invention is that the structuring is always introduced into a layer made of a material with a thermal conductivity of at least 20 W / (m K), preferably at least 50 W / (m K), more preferably at least 75 W / (m K), preferably at least 100 W / (m K), particularly preferably at least 200 W / (m K), measured at 20 °C. Either the structuring is introduced directly onto the surface of a substrate made of such a material to be structured, or an auxiliary layer made of such a material is indirectly provided and processed in such a way that the structuring is produced on the surface of the substrate to be structured from the material of the auxiliary layer.

[0229] According to an advantageous embodiment of the invention, the transparent substrate, in particular the transparent base layer, and the surface thereof, in particular the heat transfer region thereof on the first outer surface, is formed from a structured and an unstructured region, after its structuring (ie after application of a first, second and / or further line and / or dot structure, as defined herein) continues to retain at least partially its transparency, so that it continues to be transparent or at least partially transparent.

[0230] Anti-glare

[0231] The invention also encompasses a method for producing a laser-surface-structured substrate having anti-glare properties, preferably by means of laser interference structuring, comprising the following steps: a) providing a substrate, b) applying at least one first interference pixel having a first interference period (pi) to a first outer surface of the substrate, wherein each of the first interference pixels has a periodic structure of at least three surface irregularities, preferably pegs or inverse pegs or groove-shaped depressions or groove-shaped elevations, with a first interference period (pi), wherein the structured region is formed by superimposed application of the first interference pixels to the first outer surface of the substrate.

[0232] A suitable method for generating anti-glare properties is the creation of hierarchical structures in which the interference period and / or average structure depth differ by at least a factor of 10. Hierarchical structures are particularly preferably created in such a way that self-organization processes effectively generate quasi-periodic structures, in particular quasi-periodic line structures, through multiple irradiation. This advantageously increases the surface roughness and easily increases the density of the depressions. This advantageously enables high processing speeds.

[0233] One possible embodiment of the method provides that a periodic structure is first created on a negative mold using a laser interference process and is then applied to the cover layer using the negative mold.

[0234] Alternatively, the process for creating the structures uses only a single irradiation, or at least a maximum of two or three irradiations, which can avoid LIPSS structures. This allows for highly reliable, reproducible structures to be created.

[0235] According to an advantageous variant for generating a non-periodic global structure, when generating neighboring interference pixels, at least one of the structure parameters differs to a high extent of at least 70%, preferably at least 90%, preferably at least 98%.

[0236] According to an advantageous embodiment of the invention, the adjacent, repetitively offset interference pixels of one type, for example the first interference pixel, the second interference pixel and / or the third interference pixel, are generated by means of a laser interference method and successively modified to the preceding interference pixel of this one type in that a phase shift in at least one of the at least two partial beams used for the laser interference method leads to a change in the position of the depressions within an interference pixel.

[0237] For this purpose, the polarization of a partial beam used for interference structuring is preferably varied. As a result, the phase shift can lead to a change in the structural parameters, in particular the position of the depressions. The inventors have further discovered that a modification of the structural parameters selected from the group comprising the interference period of the interference pixel, the structural depth of the inverse cones, the diameter of the inverse cones, the shape of the inverse cones and the size of the inverse cones contributes to a preferred asymmetry (non-periodicity) within the global dot structure and thus to a desired asymmetry of the roughened structure. Thus, it can be provided that the aforementioned structural parameters of individual, adjacent, repetitively offset pixels of a type of interference pixel, e.g. the pixels of the first interference pixel, are varied alternately or successively, e.g.be gradually modified. For example, it is possible to gradually increase the structure depth of each subsequent pixel to the adjacent, previous pixel and to gradually decrease it again starting at a different pixel. For this purpose, it is suitable in the method that each subsequent pixel is applied to the surface of the substrate or in the volume of the substrate with a varying, e.g. gradually increasing pulse energy (in the range as defined herein) and / or a gradually increasing pulse duration or pulse width (as defined herein). It can also be provided that an individual structure parameter is varied stochastically within a region when applying a pixel of a type of interference pixel. For example, in the method, the rotation of a subsequent pixel to the adjacent, previous pixel can not be successive (i.e., uniform), but alternately within the angular range defined herein, e.g.first in one direction and then in another or the same direction with the same or a different angular displacement.

[0238] A preferred embodiment of the method provides that one or more structural parameters are distributed randomly or according to a stochastic method among the different interference pixels, so that most neighboring interference pixels do not have identical structural parameters.

[0239] LASER INTERFERENCE STRUCTURING DEVICE

[0240] As an example of a laser interference structuring device for producing a structured substrate, in particular a substrate with a heat transfer region, the present invention also relates to a laser interference structuring device for the direct laser interference structuring of a substrate, for example, flat and / or transparent substrates, comprising a laser radiation source (1) for emitting a laser beam, a beam splitter element (2) arranged in the beam path (3) of the laser beam, in particular in the beam path (3) of the laser beam emitted by the laser radiation source (1), a focusing element (4) configured such that the partial beams pass through it in such a way that the partial beams can be interfered with on the surface or in the volume of a substrate, preferably a flat and / or transparent substrate (5) in an interference region,wherein the beam splitter (2) is freely movable along its optical axis in the beam path (3), and wherein the beam splitter (2) is designed to split the incident laser beam emitted by the laser radiation source (1) into at least 3, preferably at least 4 partial beams, in particular 4 to 8, i.e. 4, 5, 6, 7, or 8 partial beams.

[0241] Particularly preferably, the beam splitter (2) is designed such that it divides the incident laser beam into an even multiple, ie 4, 6 or 8 partial beams, very particularly preferably 4 partial beams.

[0242] Alternatively or additionally, a beam splitter element (2) can be provided such that it comprises a first beam splitter and at least one further beam splitter arranged downstream of the first beam splitter, wherein the first beam splitter splits the incident laser beam into at least two partial beams and the further beam splitter is arranged in at least one beam path of a partial beam and splits this partial beam into at least two partial beams as it passes through.

[0243] For laser interference structuring of the substrate (5), preferably a flat and / or transparent substrate, the laser beam emitted by the laser radiation source is split into at least three, preferably at least four, partial beams by the beam splitter element (2). Only two-beam interference (i.e., structuring by interference of two partial beams) is known from the prior art. However, such two-beam interference only produces line structures on the substrate.

[0244] The partial beams are then deflected by the focusing element (4) in such a way that they interfere in an interference region on the surface or inside a substrate (5), preferably a flat and / or transparent substrate.

[0245] This allows the creation of a two-dimensional, periodic dot structure with dimensions in the micrometer and submicrometer range, the structure period of which can be freely adjusted by displacing the beam splitter element (2) along its optical axis. Surface processing of a substrate (5), preferably a flat and / or transparent substrate, is possible.

[0246] According to a preferred embodiment, the beam splitter element is a single optical element, in particular a diffractive or refractive optical element, which is constructed such that the division of the incident laser beam is based on the optical properties of the beam splitter element. This advantageously ensures that a simple optical structure can be implemented compared to a multi-part beam splitter element consisting of several optical elements (e.g., mirrors, prisms, etc.). The desired beam splitting can be achieved without the need to calibrate or adjust the arrangement of several optical elements to one another. The mobility of the beam splitter element within the beam is also very easy to implement, since only a single optical element needs to be moved.In addition, the use of a one-piece beam splitter element results in fewer components that are susceptible to wear and tear and may need to be replaced.

[0247] One advantage of the device defined herein is that this device and the method that can be implemented with its aid eliminate the use of chemicals and their costly disposal when structuring substrates, particularly when creating a structure with improved heat transfer properties, especially with an increased heat transfer coefficient. Furthermore, substrate purification is also eliminated.

[0248] Furthermore, a wide range of substrates, preferably flat and / or transparent substrates, especially transparent materials, can be processed with the device. Since the process is not dependent on the refractive index or the adhesion of specific coating materials to the substrate, this method is more flexible than conventional chemical processes.

[0249] Compared to conventional methods, such as WO 2019 / 166836 A1, the processing time using this method is significantly shorter, as the periodicity of the structures is ensured by the interference of the incident at least three, preferably at least four partial beams in an interference region, rather than resulting from more time-consuming self-organization processes. Another advantage over conventional methods is that the shape (structural design; geometry) of the generated micro / nanostructures can be controlled. By adjusting the number of interfering (partial) beams, their polarization, and the setting of the process parameters, the geometry of the structures can be controlled, thereby specifically influencing the heat transfer properties, in particular the heat transfer coefficient.

[0250] Furthermore, the stability of the dot structure created in this way should be mentioned, which is more durable than conventional coatings, since it cannot detach from the substrate to be coated over time and due to the material stresses caused by use.

[0251] If the structuring is performed in the volume, i.e., inside the substrate, preferably a flat and / or transparent substrate, especially in the transparent material, the resulting structuring (i.e., the dot structure of the structured substrate) is less sensitive to impact and abrasion than conventional coatings. The inventors have discovered that structuring (also referred to herein as texturing) inside the material (i.e., below the surface) does not necessarily produce anti-reflective properties. However, texturing inside the material is interesting for other applications, such as product protection, optical data storage, decoration, etc.

[0252] It is particularly advantageous that the structure of the device or the arrangement of the optical component disclosed herein enables substrates with very high structuring rates of up to 4.0 m 2 / min, especially in the range from 0.01 to 4.0 m 2 / min, particularly preferably in the range of 0.05 to 3.5 m 2 / min, most preferably in the range of 0.1 to 3.0 m 2 This is ensured by the fact that the area in which the at least three partial beams are superimposed can be expanded through a preferred selection of optical elements, allowing a large area to be irradiated in a single processing step. In contrast to methods known to those skilled in the art, such as direct laser writing, no strong focusing is necessary to create high-resolution features.

[0253] USE

[0254] The invention also encompasses the use of a surface-structured substrate and a component structured according to the invention in an electronic circuit and also generally in the field of microelectronics, in particular in or on a semiconductor component, for heat dissipation. This advantageously allows the operating temperature to be reduced and adjusted even at high computing power levels. The use of a surface-structured substrate according to the invention advantageously allows the required component sizes to be reduced.

[0255] Furthermore, such surface-structured substrates can also be used in de-icing applications, where heat must be transferred to specific surfaces. This process can also be carried out quickly and efficiently, with a reduction in the required energy being achieved, particularly when combined with anti-icing properties of the surface. This can advantageously improve de-icing efficiency. The combination of improved heat transfer at the surface and the anti-icing properties of the surface leads to a synergistic effect that reduces the energy required for de-icing.

[0256] EXAMPLES OF IMPLEMENTATION

[0257] The present invention is explained in more detail with reference to the following figures and exemplary embodiments, without limiting the invention to these.

[0258] This shows

[0259] Fig. 1 : a section through a surface-structured substrate with a periodic dot structure

[0260] Fig. 2: A section through a surface-structured, preferably surface-structured component with a periodic dot structure

[0261] Fig. 3: a surface-structured component with a periodic structure, which is designed as a periodic line structure.

[0262] Fig. 4: A surface-structured substrate with line structures running in two directions to create two-dimensional surface irregularities

[0263] Fig. 5: The generation of cones using an auxiliary layer.

[0264] Fig. 6: a groove-shaped depression.

[0265] Fig. 7A: a schematic representation of an inverse cone.

[0266] Fig. 7B: a schematic representation of a cone-like depression with a circular base.

[0267] Fig. 7C: a schematic representation of a cone-like depression with an irregular base.

[0268] Fig. 8: a cumulative structure of the dot structure from a superposition of several interference pixels,

[0269] Fig. 9: a dot structure formed from the superposition of several first and second interference pixels,

[0270] Fig. 10: a schematic perspective view of a device according to the invention.

[0271] Fig. 11: a schematic perspective view of a device according to the invention, which contains a deflection element (6) for parallelizing the partial beams.

[0272] Fig. 12: a schematic perspective view of a device according to the invention, which contains a deflection element (7) for widening the angle of the partial beams to the optical axis of the beam path (3).

[0273] Fig. 13A: a schematic perspective view of a device according to the invention, which includes optical elements (6) with a planar, reflective surface that deflect the partial beams onto the focusing element (4). Fig. 13B: a schematic perspective view of a device according to the invention, which includes a galvo mirror (9) as an optical element for beam shaping, which allows for stationary positioning of the substrate to be structured during the structuring process.

[0274] Fig. 14: a schematic perspective view of a device according to the invention, wherein the device contains a polarization element (8) which shifts the phase profile of the partial beams relative to each other, wherein

[0275] A) the beam splitter element (2) is positioned in the beam path (3) close to the laser radiation source (1).

[0276] B) the beam splitter element (2) is positioned in the beam path (3) close to the deflection element (7).

[0277] Fig. 15: a schematic view of the interference pixels with width D resulting on the surface or inside the substrate, and the distribution of the individual interference pixels on the surface or inside the substrate, wherein the interference pixels are shifted relative to each other with the pixel density Pd.

[0278] Fig. 16: a schematic perspective view of the structured substrate (5) with the generated periodic dot structures, consisting of inverse cones, with dimensions in the micro- and submicrometer range, and symbolically the transmission of incident electromagnetic waves with wavelengths greater than the interference period of the generated structures, as well as the diffraction of incident electromagnetic waves with wavelengths in the range or smaller of the generated structures.

[0279] Fig. 17: a schematic perspective view of a device according to the invention, which contains as optical element a galvo mirror (9) with a planar, reflective surface, which deflects the partial beams onto the focusing element (4), and a polygon wheel (91).

[0280] Fig. 18: a graphical representation of the diffraction angle of incident light versus the wavelength of the incident light for structured substrates with three different feature sizes.

[0281] Fig. 19: a schematic perspective view of the structured substrate (5) with the generated periodic dot structures consisting of inverse cones with dimensions in the micrometer range, on which a periodic wave structure in the submicrometer range is superimposed.

[0282] Fig. 20: a schematic

[0283] A) Top view and B) a cross-sectional view of a quasi-periodic wave structure in the submicrometer range.

[0284] Fig. 21 a schematic representation of a structured component for visualizing the trapping effect.

[0285] Fig. 22 is a schematic view of the interference pixels with width D resulting on the surface or inside the substrate, and the distribution of the individual interference pixels on the surface or inside the substrate, wherein the interference pixels are shifted relative to each other with the pixel density Pd, wherein a global unstructured area results between the individual interference pixels.

[0286] Fig. 1 shows a perspective view of a section of a substrate 5. The substrate 5 has a first outer surface 32. The first outer surface 32 generally faces the environment, i.e., in particular, the air, water, or another fluid. When incorporated into a component, the first outer surface can also be formed as an interface within the component.

[0287] The first outer surface 32 is formed from a structured region 28 and an unstructured region 29. The structured region 28 shown here is formed from a periodic structure of surface irregularities 34. According to an alternative embodiment, the structured region 28 can also be formed from a superposition of several periodic structures, so that the superimposed structure, also referred to as a global structure, or in the case of point structures, as a global point structure, does not have to be periodic, in particular not fully periodic. The surface irregularities 34 are formed here as inverse pegs 14, wherein the periodic structure is a periodic point structure.

[0288] A section of a surface-structured component 30 comprising a further layer 35 adjacent to the substrate and a substrate 5 arranged thereabove is shown in a perspective view in Fig. 2.

[0289] Here, too, the first outer surface 32 of the substrate 5 is formed from a structured region 28 and an unstructured region 29. In the variant illustrated here, the entirety of the inverse pegs 14 forms the structured region 28. Fig. 3 shows a surface-structured component 30 with a periodic structure, which is designed as a periodic line structure. Here, the surface irregularities 34 arranged on the first outer surface 32 of the substrate 5, from which the structured region 28 is formed, are designed as groove-shaped depressions 36 with a large extent in a first dimension Dim1. The extent of the groove-shaped depressions 36 in a second dimension Dim2 and in a third dimension Dim3 is significantly smaller.

[0290] The periodicity of the structure results from the repetition of the groove-shaped depressions 36 with equal spacing, so that the interference period p, in particular the first interference period p1, extends from a certain point of the groove-shaped depression 36, for example the deepest point, to the point corresponding to this point of the groove-shaped depression 36 arranged next to it.

[0291] Fig. 4 shows a substrate 5 in which first and second groove-shaped (linear) depressions 36A, 36B are represented as surface irregularities 34, the first dimensions Dim1A and Dim1B of which extend in different directions. As a result, the remaining unstructured regions 29 form two-dimensional changes in the surface. The structured region is formed here by the groove-shaped depressions 36A, 36B. The different directions Dim1A and Dim1B enclose an orthogonal angle.

[0292] In Fig. 5, cones 43 are created on a substrate 5 by depositing an auxiliary layer 31 on a transparent base layer 37. A laser beam 3 is guided through the base layer 37, which is transparent to the wavelength of the laser light, to the auxiliary layer 31. The surface of the base layer 37 facing the auxiliary layer 31 is scanned, creating cones 43. The auxiliary layer 31 is then removed, leaving only the cones 43 made of the material of the auxiliary layer 31.

[0293] Fig. 6 schematically shows a surface irregularity 34 formed as a groove-shaped depression 36. The deepest line in such a symmetrical structure is the center line 39.

[0294] The area where the groove-shaped depression 36 intersects the corresponding surface is referred to as the base area 40 of the surface irregularity. The base area 40 then forms the section of the structured area of ​​the surface that can be assigned to this surface irregularity. The side surfaces 41 are smooth here. However, a groove-shaped depression can also be overlaid with a quasi-periodic line structure. In this embodiment, the width b of the groove-shaped depression 36 is smaller than the structure depth x.

[0295] Fig. 7A shows a schematic representation of an inverted stud 14 produced by a laser interference method, which has a structure depth x. The base surface 40 of the inverted stud 14 is circular in shape with a diameter d. The side surfaces 41 are smooth.

[0296] A schematic representation of a peg-like depression 42, such as can be generated, for example, by means of an etching process using a mask with circular openings (not shown here), is shown in Fig. 7B. Although the illustrated base surface 40 is circular, the side surfaces 41 are irregularly shaped.

[0297] Fig. 7C shows a schematic representation of a peg-like depression 42 with an irregular base surface 40 and an irregular, completely variable side surface 41. Such a depression is generated, for example, during etching without a mask.

[0298] Fig. 8 visualizes the cumulative structure of the dot structure from a superposition of several interference pixels (10, 11, 12, 13). Each interference pixel (10, 11, 12, 13) consists of several inverse cones (14) introduced into the substrate by laser interference structuring.

[0299] Partial image (A) shows the first interference pixel (10), which has several inverse cones (14, 14.1). Partial image (B) visualizes an overlay of the first interference pixel (10) and the second interference pixel (11), with this overlay consisting of inverse cones (14.1) of the first interference pixel (10) and inverse cones (14.2) of the second interference pixel (11).

[0300] There is an offset (15) between the first interference pixel (10) and the second interference pixel (11), whereby the inverse cones (14.2) of the second interference pixel (11) are shifted by this offset (15) relative to the inverse cones (14.1) of the first interference pixel (10).

[0301] Partial figure (C) visualizes an overlay in which a third interference pixel (12) is additionally superimposed on the first two interference pixels (10, 11). The superimposed structure in partial image (C) thus has inverse cones (14.1) of the first interference pixel (10), inverse cones (14.2) of the second interference pixel (11), and inverse cones (14.3) of the third interference pixel (12). In this exemplary embodiment, the third interference pixel (12) is shifted relative to the second interference pixel (11) in the same spatial direction along the x-axis as the second interference pixel (11) is shifted relative to the first interference pixel (10).

[0302] Partial image (D) shows an overlay in which a fourth interference pixel (13) is also superimposed, which is shifted in a different spatial direction along the y-axis compared to the third interference pixel (12). Thus, the section in partial image (D) exhibits a dot structure consisting of a superposition of four interference pixels (10, 11, 12, 13). The graphs arranged below the interference pixels (10, 11, 12, 13) serve to visualize the periodic structures within an interference pixel (10, 11, 12, 13). Due to the formation of the interference pixels (10, 11, 12, 13) via the process of laser interference structuring, i.e. according to the interference pattern of the laser (partial beams), each individual interference pixel (10, 11, 12, 13), which was formed within an illumination or irradiation process within a selected pulse duration, has a periodic arrangement of the inverse cones (14).The distance between the inverse cones (14.1) of the first interference pixel (10), which results from the distance between the intensity maxima of the interference image generating the first interference pixel (10), represents the interference period (p1). The intensity corresponds to the intensity required to generate the inverse cones (14.1) in the interference pattern of the laser (partial) beams. Thus, the distance between the intensity maxima of the interference image corresponds to the interference period (p1). The second interference pixel (11) has a second interference period (p2).

[0303] Fig. 9 shows a dot structure (16) formed from the superposition of several first interference pixels (10) with a first interference period (p1) and several second interference pixels (11) with a second interference period (p2). The first interference pixels (10) have inverse cones (14.1), which are shown here with a vertical pattern fill. The second interference pixels (11) have inverse cones (14.2), which are shown with a horizontal pattern fill. The interference period (p1) of the first interference pixel (10) is smaller than the second interference period (p2) of the second interference pixel (11).

[0304] In an optional setting of the interference pixels (10, 11) such that the number of inverse cones (14.1, 14.2) within the interference pixels (10, 11) is identical, the area of ​​the interference pixels (10, 11) varies, which is visualized here by the circles. One of the first interference pixels (10) is schematically represented here by all inverse cones (14.1) with vertical pattern filling within the smaller circle. One of the second interference pixels is, in turn, visualized by the inverse cones (14.2), which are represented with a horizontal pattern structuring, within the larger circle.

[0305] The plurality of first interference pixels (10) are arranged adjacently and repetitively offset from one another, and the plurality of first interference pixels (10) thereby form a pattern with the interference period (p1). Furthermore, the plurality of second interference pixels (11) are arranged adjacently and repetitively offset from one another, and the plurality of second interference pixels (11) thus form a pattern with the second interference period (p2) different from the first interference period (p1). The graph arranged below the dot structure (16) visualizes the arrangement of the inverse cones (14.1, 14.2) along a line through the dot structure (16). The intensity maxima correspond to the center of the inverse cones (14.1, 14.2). As in Fig. 8, this graph serves to illustrate the principle. The intensity corresponds to the intensity required to generate the inverse cones (14.1, 14.2) in the interference pattern of the laser (partial) beams.

[0306] Fig. 10 visualizes, in a first embodiment, the device according to the invention, comprising a laser radiation source (1) for emitting a laser beam. Arranged in the beam path (3) of the laser beam behind the laser radiation source (1) is a beam splitter element (2), which is movably arranged in the beam path (3). Arranged in the beam path (3) of the laser beam behind the beam splitter element (2) is a focusing element (4). Arranged in the beam path (3) of the laser beam behind the focusing element (4) is a holding device on which a substrate (5), preferably a flat and / or transparent substrate, is mounted.

[0307] In this embodiment, the laser radiation source (1) emits a pulsed laser beam. The laser radiation source is a UV laser with a wavelength of 355 nm and a pulse duration of 12 ps. The radiation profile of the laser radiation source in this embodiment corresponds to a top-hat profile.

[0308] In this embodiment, the beam splitter element (2) corresponds to a diffractive beam splitter element. A diffractive beam splitter element here is a beam splitter element that contains micro- or nanostructures. The beam splitter element (2) divides the laser beam into four partial beams.

[0309] In this embodiment, the focusing element (4) corresponds to a refractive, spherical lens that directs the essentially parallel partial beams onto the substrate (5), preferably a flat and / or transparent substrate, such that they interfere there in an interference region. The interference angle in this embodiment corresponds to 27.2°, resulting in an interference period of 550 nm for the periodic dot structure with the same polarization state.

[0310] According to this embodiment, the planar substrate is irradiated once, resulting in a processing time per structural unit, ie per interference pixel, of 12 ps.

[0311] The substrate (5), preferably a flat and / or transparent substrate, is a glass, very specifically a quartz glass, which is mounted on a holding device so that it is movable in the xy plane, perpendicular to the beam path of the laser beam emitted by the laser radiation source (1).

[0312] Fig. 11 visualizes in a further embodiment the device as described in Fig. 10, additionally comprising a deflection element (6) which is located in the beam path (3) of the laser after the beam splitter element (2) and the focusing element (4).

[0313] In this embodiment, the deflection element is a conventional, refractive, convex lens. The partial beams impinge on the deflection element (6) in such a way that, after passing through the deflection element, they run essentially parallel to each other. This allows the point at which the partial beams interfere on the surface or inside the substrate to be adjusted.

[0314] Fig. 12 illustrates a further embodiment of a device based on the structure shown in Fig. 10 and Fig. 11. This structure additionally comprises a further deflection element (7), which is arranged in the beam path (3) of the laser between the beam splitter element (2) and the deflection element (6).

[0315] In this embodiment, the additional deflection element (7) is a conventional, refractive, concave lens. The partial beams impinge on the additional deflection element in such a way that their angle to the optical axis of the beam path is widened. This allows the interference angle at which the partial beams interfere on the surface or inside the substrate, preferably a flat and / or transparent substrate, to be changed.

[0316] In this embodiment, all optical elements except for the beam splitter element (2) are fixed along the optical axis of the beam path (3). The interference angle of the partial beams on the substrate is adjusted by moving the beam splitter element (2) along the optical axis of the beam path.

[0317] Fig. 13A shows a further embodiment of a device as in Fig. 12, comprising the optical elements (6) with a planar, reflective surface, which are configured to deflect the partial beams onto the focusing element (4). In this embodiment, the at least three partial beams are deflected onto the substrate by shifting the optical elements (6) at a preferred angle. This eliminates the need for a deflection element in the form of a lens (reference numeral (6) in Fig. 12).

[0318] Fig. 13 B shows a schematic perspective view of an inventive

[0319] Device comprising a galvo mirror (9) as an optical element for beam shaping, which allows a fixed positioning of the substrate 5 to be structured during the structuring process.

[0320] Fig. 14 visualizes in a further embodiment a device as in Fig. 10, additionally comprising one polarization element (8) per partial beam, which are arranged in the beam path (3) of the laser beam between the deflection element (6) and the focusing element (4).

[0321] The polarization element is arranged in such a way that it changes the polarization of the individual partial beams relative to one another in such a way that a change in the interference pattern results.

[0322] This embodiment is shown in two different configurations. In Fig. 14A, the beam splitter element (2) is positioned in the beam path (3) close to the laser radiation source (1). In Fig. 14B, the beam splitter element (2) is positioned in the beam path (3) close to the deflection element (7). In this way, the interference pattern of the interfering partial beams on the surface of the substrate (5) can be continuously adjusted without having to move the other optical elements in the structure or the substrate. In addition, it would also be conceivable for the arrangement to contain an additional optical element for beam shaping, which is arranged downstream of the laser radiation source (1) in the beam path (3). In this embodiment, the radiation profile of the laser radiation source corresponds to a Gaussian profile. The optical element for beam shaping converts this profile into a top-hat profile.

[0323] Fig. 15 contains a schematic view of the interference pixels with the width D resulting on the surface or inside the substrate, and the distribution of the individual interference pixels on the surface or inside the substrate, wherein the interference pixels are shifted from each other with the pixel density Pd.

[0324] In this embodiment, the pixel density Pd is smaller than the width of an interference pixel, D. As a result, by moving the substrate (5) using a pulsed laser beam, a planar, homogeneous, periodic dot structure can be generated on the surface or inside a substrate, preferably a planar and / or transparent substrate. The successively applied interference pixels are preferably arranged next to one another. In this embodiment, there is an overlap between two adjacent interference pixels. Due to the multiple irradiation, self-organization processes are preferably stimulated within the structured region, i.e., within the inverse cones 14. This allows a hierarchical structure to be efficiently generated. Fig.Figure 16 visualizes the structured substrate (5) produced by the method according to the invention, with the generated periodic dot structures consisting of inverse cones with dimensions in the micrometer and submicrometer range. It also symbolically illustrates the transmission of incident electromagnetic waves with wavelengths greater than the interference period of the generated structures, as well as the diffraction of incident electromagnetic waves with wavelengths in the range of or smaller than the generated structures.

[0325] Fig. 17 shows, in a further embodiment, a device as in Fig. 13B, comprising the optical element (91) with a planar, reflective surface, which is a polygon wheel configured to rotate about a marked axis. The incident partial beams are deflected such that they impinge on a galvo mirror (9), which directs the beams onto the substrate via a focusing element (4). The rotation of the polygon wheel causes the point at which the beams are focused on the substrate to move along a line during the exposure process. The partial beams thus scan the substrate, which leads to an increased process speed.

[0326] Fig. 18 graphically illustrates the transmission and diffraction capabilities of a structured substrate as a function of the structure size. The diffraction angle of light is shown as a function of its wavelength for structures with three different structure sizes. If the wavelength of the incident light is longer than the structure size, the light is completely transmitted. At wavelengths in the range of the structure size or smaller, diffraction occurs. The diffraction angles can be seen in the graph.

[0327] Fig. 19 visualizes the structured substrate (5) produced by the inventive method with the generated periodic dot structures consisting of inverse cones with dimensions in the micrometer range. Superimposed on this periodic dot structure in the micrometer range is a periodic wave structure in the submicrometer range, which can also be produced in a single production step by the inventive method described herein.

[0328] Fig. 20A visualizes a quasi-periodic wave structure (19) in a plan view and Fig. 20B in a sectional view, as it has a structured substrate which can be produced by a method disclosed herein, in particular by multiple irradiation or by single irradiation with high intensity. The sectional view of Fig. 20B represents a cross-section through the structure shown in Fig. 20A approximately along the section line AA. Self-organization processes occurring in the materials lead to the formation of wave-like structures with wave crests (20) and wave troughs (21) within such an irradiated area. The resulting structures generally exhibit a certain periodicity, although defects (22), i.e., irregularities, also occur.Thus, in contrast to a truly periodic structure, such a structure exhibits both deviations in the structural dimensions, particularly in the distances between the wave crests and the wave troughs, as well as defects, so that the generated wave structure is not homogeneous.

[0329] A schematic cross-sectional view of a structured component is shown in Fig. 21 to visualize the reduction in reflection due to the trapping effect. A substrate 5 is shown facing upwards. A further layer is shown below the substrate.

[0330] Inverse cones 14 are arranged on the substrate, with the sectional view lying straight in a row of inverse cones 14. Light 44 incident on the inverse cones 14 also partially strikes an interface point 45 arranged within an inverse cone 14. A portion of the light 44 is transmitted at this interface point 45 through the interface into the interior of the substrate 5. However, a further portion of the light 44 is reflected and strikes another interface point 45 arranged within an inverse cone 14. There, too, a portion of the light 44 is transmitted through the interface between air and substrate, and a smaller portion is reflected. In this illustration, this reflected portion also reaches another interface point 45, where again a portion of the light 44 is transmitted. As a result, the total amount of light 44 transmitted through the interface can be determined.1 can be significantly increased compared to a surface without inverse cones 14.

[0331] Fig. 22A contains a schematic view of the interference pixels with the width D resulting on the surface or inside the substrate, and the distribution of the individual interference pixels on the surface or inside the substrate, wherein the interference pixels are shifted from each other with the pixel density Pd.

[0332] In this embodiment, the pixel density Pd is greater than the width of an interference pixel, D. This allows for a planar structuring of the substrate surface by moving the substrate (5) using a pulsed laser beam, which omits certain areas of the substrate surface. This results in a globally unstructured area in which the properties of the substrate remain unchanged compared to the unstructured substrate.

[0333] Fig. 22B contains a schematic view of the interference pixels resulting on the surface or inside the substrate with the width D, and the distribution of the individual interference pixels on the surface or inside the substrate, wherein the interference pixels are shifted from each other with the pixel density Pd, and wherein a first and a second interference pixel have been applied on the surface.

[0334] In this embodiment, the first and second interference pixels are arranged with an offset from each other that is smaller than the diameter of the interference pixels. This results in an overlap of the two interference pixels in one region. In this embodiment, the first interference pixel and the second interference pixel are identical.

[0335] In this embodiment, the pixel density Pd is greater than the width of an interference pixel, D. This allows for a planar structuring of the substrate surface by moving the substrate (5) using a pulsed laser beam, which omits certain areas of the substrate surface. This results in a globally unstructured area in which the properties of the substrate remain unchanged compared to the unstructured substrate.

[0336] Fig. 22C shows, in a further embodiment, a structured substrate consisting of a structured, an unstructured, and a global unstructured region. The structuring on the surface of the substrate is carried out in such a way that targeted recesses are created, which allow the formation of a pattern.

[0337] QR codes or logos, for example, can preferably be applied in this way.

[0338] LIST OF REFERENCE SYMBOLS

[0339] 1 laser radiation source

[0340] 2 beam splitter element

[0341] 3 Beam path, laser beam

[0342] 4 Focusing element

[0343] 5 Substrat

[0344] 6 additional deflection element

[0345] 7 Deflection element

[0346] 8 Polarization element

[0347] 9 Focusing mirror or galvo mirror

[0348] 91 Polygon wheel

[0349] 10 first interference pixel

[0350] 11 second interference pixel

[0351] 12 third interference pixel

[0352] 13 fourth interference pixel

[0353] 14 inverse cones

[0354] 14.1 Inverse cones of the first interference pixel

[0355] 14.2 Inverse cones of the second interference pixel

[0356] 14.3 Inverse cones of the third interference pixel

[0357] 14.4 inverse cones of the fourth interference pixel

[0358] 15 Offset

[0359] 16 point structure

[0360] Pi first interference period

[0361] P2 second interference period

[0362] 19 quasi-periodic wave structure

[0363] 20 Wave Mountain

[0364] 21 wave trough

[0365] 22 Defect

[0366] 23 Water contact angle

[0367] AA cutting line

[0368] 28 structured area

[0369] 29 unstructured area

[0370] 29.1 global unstructured area

[0371] 30 Surface-structured component

[0372] 31 auxiliary shift

[0373] 32 First outer surface 33 Second outer surface

[0374] 34 Surface unevenness

[0375] 35 Additional layer adjacent to the substrate

[0376] 36 groove-shaped depressions

[0377] 36A First groove-shaped depressions

[0378] 36B Second groove-shaped depressions

[0379] 37 Base layer

[0380] 39 Center line

[0381] 40 floor space

[0382] 41 side surface

[0383] 42 Cone-like depression

[0384] 43 cones

[0385] 44 Incident light

[0386] 44.1 Transmitted light

[0387] 45 interface point

[0388] Dim1 first dimension

[0389] Dim2 second dimension

[0390] Dim3 third dimension

[0391] Dim1A first dimension of a first groove-shaped depression

[0392] Dim1B first dimension of a second groove-shaped depression

[0393] D Width of the interference pixel

[0394] Pd pixel density d diameter of an inverse cone b width x structure depth

Claims

PATENT CLAIMS 1. A surface-structured substrate (5), wherein the surface-structured substrate (5) has at least one first outer surface (32) with a heat transfer region, wherein the heat transfer region is formed by a structured region (28) and an unstructured region (29), wherein the structured region (28) has a first interference pixel (10), wherein the first interference pixel (10) is formed from a first periodic structure of at least three surface irregularities (34), wherein the distance between two adjacent surface irregularities (34) is a first interference period (p1), wherein the first interference period (p1) is in the range from 50 nm to 200 pm, preferably from 1 pm to 45 pm, wherein the heat transfer region has a ratio of the real surface to the projected surface of at least 120%,wherein the material of the surface-structured substrate (5) has a thermal conductivity of at least 20 W / (m K)., 2. Surface-structured substrate (5) according to claim 1, wherein the heat transfer coefficient of the heat transfer region, wherein the heat transfer region has a ratio of the real surface to the projected surface of at least 120%, has a value at least 10% higher than the heat transfer coefficient of the unstructured region (29) which has no surface irregularities.

3. Surface-structured substrate (5) according to claim 1 or 2, wherein the material of the surface-structured substrate (5) comprises, preferably consists of, at least one metal, preferably copper and / or aluminum, an alloy and / or a semiconductor, preferably silicon.

4. Surface-structured substrate (5) according to one of claims 1 to 3, wherein the material of the surface-structured substrate (5) has a melting point of less than 1,400°C.

5. Surface-structured substrate (5) according to one of claims 1 to 4, wherein the first interference pixel (10) has a periodic grating of at least three cones (43) or inverse cones (14).

6. Surface-structured substrate (5) according to one of claims 1 to 5, wherein the first interference pixel (10) is formed of a first periodic line structure made up of at least three groove-shaped depressions (36) or groove-shaped elevations arranged next to one another, running parallel to one another and arranged equidistantly.

7. Surface-structured substrate (5) according to one of claims 5 or 6, wherein the structured region (28) is formed from the first periodic dot structure or from the first periodic line structure, wherein the first periodic dot structure or the first periodic line structure consists of one or more interference pixels arranged offset from one another and having the first interference period (pi).

8. Surface-structured substrate (5) according to one of claims 1 to 7, wherein the structured region (28) further comprises a second periodic structure with a second interference period (P2) in the micro- or submicro-range, which is formed as a periodic dot structure or as a periodic line structure.

9. Surface-structured substrate (5) according to one of claims 1 to 8, wherein the surface-structured substrate (5) has, on the side facing away from the first outer surface (32), a second outer surface (33), wherein the second outer surface (33) is formed from a structured region (28) and an unstructured region (29), wherein the structured region (28) has a periodic dot and / or line structure.

10. Surface-structured substrate (5) according to one of claims 1 to 9, wherein the structure depth (x) of the first periodic structure on the first outer surface is in the range from 0.3 pm to 60 pm, preferably in the range from 0.5 pm to 40 pm.

11. Surface-structured substrate (5) according to one of claims 1 to 10, wherein the side surfaces (41) of the surface irregularities (34) of the first periodic structure have a smooth surface.

12. Surface-structured substrate (5) according to one of claims 1 to 11, wherein the substrate (5) has a base layer (37) and an auxiliary layer (31) formed adjacent to the base layer (37), wherein the base layer (37) is formed from a transparent material, wherein the surface irregularities (34) are formed from the material of the auxiliary layer (31).

13. A method for producing a laser-surface-structured substrate (5) according to one of claims 1 to 12, preferably by means of laser interference structuring, comprising the following steps: a) providing a substrate (5) to be structured, wherein the substrate (5) to be structured has an interface, wherein the interface is designed as a direct contact surface between the surface of the substrate (5) to be structured and a medium adjacent thereto, wherein the substrate (5) to be structured or the medium adjacent thereto comprises a material with a thermal conductivity of at least 20 W / (m K), b) applying a structured region (28) to the surface of the substrate (5) to be structured, whereby a heat transfer region is generated on the surface to be structured,wherein the structured region (28) has at least one first interference pixel (10) with a first interference period (pi), wherein the first interference pixel (10) is formed from a first periodic structure of at least three surface irregularities (34), wherein the distance between two adjacent surface irregularities (34) is a first interference period (pi), wherein the first interference period (pi) is in the range from 50 nm to 200 pm, wherein the heat transfer region has a ratio of the real surface to the projected surface of at least 120%, and wherein the heat transfer coefficient of the heat transfer region has a value that is preferably at least 10% higher than the heat transfer coefficient of the unstructured region (29) of the same material that does not have any surface irregularities, preferably determined at 20°C.

14. The method according to claim 13, wherein the structured region (28) is formed by superimposed application of the first interference pixels (10) on the first outer surface (32) of the substrate (5).

15. The method according to claim 13 or 14, wherein the substrate (5) to be structured is designed as a base layer and the medium adjacent to the substrate (5) to be structured is designed as an auxiliary layer (31) with a material having a thermal conductivity of at least 20 W / (m K).

16. The method according to claim 15, wherein the auxiliary layer (31) is removed from the base layer following step (b), leaving a cover layer adjacent to the base layer.

17. The method according to claim 15 or 16, wherein the base layer comprises a transparent material, preferably glass, or is formed from a transparent material, preferably glass.

18. Method according to one of claims 13 to 17, wherein material having a thermal conductivity of at least 20 W / (m K) comprises or is formed from at least one metal, preferably copper and / or aluminum, at least one alloy or at least one semiconductor, preferably silicon.

19. The method according to any one of claims 13 to 18, wherein the first interference period (pi) is formed in the range from 50 nm to 200 pm, preferably from 1 pm to 45 pm.

20. The method according to any one of claims 13 to 19, wherein the application according to step (b) is carried out by means of a laser interference method, wherein partial beams are preferably generated in the laser interference method by means of a beam splitter element (2) and the interference period (p) of an interference pixel, preferably the first interference period (pi) of the first interference pixel (10), is continuously adjusted by means of a displacement of the beam splitter element (2), wherein the further optical elements are preferably fixed in their spatial arrangement.

21. Method according to one of claims 13 to 20, wherein the periodic structure is first produced on a negative mold by means of a laser interference method and is applied to the surface of the substrate (5) to be structured by means of the negative mold.

22. The method according to any one of claims 13 to 21, wherein the periodic structure within an interference pixel is generated by applying a single laser pulse by means of single irradiation.

23. Method according to one of claims 13 to 22, wherein a hierarchical structure with a dot and / or line structure arranged in the depressions is produced by means of multiple irradiation of an interference pixel with identical process parameters.

24. Method according to one of claims 13 to 23, wherein a periodic line and / or dot structure superimposed on the first periodic structure is generated with varied method parameters.

25. The method according to any one of claims 20 to 24, wherein the laser pulse duration is in the range of 50 fs to 100 ns, preferably in the range of 500 fs to 50 ns, preferably in the range of 800 fs - 20 ns, particularly preferably in the range of 1 ps to 10 ns.

26. Structured component (30), comprising at least one surface-structured substrate (5) according to one of claims 1 to 12 and at least one further layer (35) adjacent to the substrate.

27. Structured component (30) according to claim 26, wherein the first outer surface (32) having the heat transfer region forms an interface between the surface-structured substrate (5) and the adjacent layer (35).

28. Structured component (30) according to claim 26 or 27, wherein the first outer surface (32) having the heat transfer region forms a seal against the environment.

29. Structured component (30) according to one of claims 26 to 28, wherein the heat transfer area, which has a ratio of the real surface to the projected surface of at least 120%, has a heat flux density of at least 200 W / m between the surface-structured substrate (5) and the adjacent layer within the heat transfer area. 2 has.

30. Use of a surface-structured substrate (5) according to one of the claims 1 to 12 or a structured component (30) according to one of claims 26 to 29 for heat dissipation in an electronic circuit.

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