Apparatus and method for laser interference structuring of a substrate with periodic dot structures having antireflection properties

Abstract

The present invention relates to the field of patterning substrates with a periodic dot pattern in the micrometer or sub-micrometer range, in particular to an apparatus and a method for patterning the surface and the interior of a transparent substrate by laser interference patterning. The patterned regions with a periodic dot pattern in the micrometer or sub-micrometer range produced in this way are distinguished by pronounced antireflection properties. The invention also relates to patterned substrates with antireflection properties comprising a periodic dot pattern.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of structuring substrates, in particular to an apparatus and a method for structuring the surface and the interior of a transparent substrate by means of laser interference. In addition, the invention relates to the structured substrate, here exemplarily a flat substrate, in particular a so-called anti-reflection glass, comprising a periodic point structure, with anti-reflection properties. BACKGROUND

[0002] Methods for treating surfaces are known from the prior art by means of which the surface of a transparent substrate, in particular glass, but also solid polymers, can be changed in such a way that the reflection of the substrate is reduced. Typical processes are the application of additional materials to the surface of the substrate in order to achieve anti-reflection (so-called structuring or building-up processes), in which the refractive indices of the various materials differ.

[0003] For example, in US 8,557,877 B2 a possible building-up process is described. In this process, a coating solution is first produced from at least two chemical starting materials, the pH value of the coating solution is then reduced and, before the coating solution is applied to the desired substrate, it is optionally diluted with another solution. This coating process uses various chemicals which usually have a negative environmental impact and are costly and time-consuming to handle and dispose of.

[0004] This process is based on the reduction of the reflection ratio by means of destructive interference. Here, the refractive index of the material used for the coating must match the substrate to be coated and the medium surrounding the substrate, which is usually air. Since not every coating material can be handled in the same way, such a process requires different processes for coating different substrate materials.

[0005] US 10,459,125 B2 therefore describes a process in which a so-called moth-eye structure is generated chemically on a substrate by applying a polymer film to the substrate. This structure is modelled on the moth-eye principle, there being a regular arrangement of nanostructures on its surface which are smaller than the wavelength of the light incident on it. This establishes a layer with a gradually changing refractive index at the transition between the medium surrounding the substrate and the substrate itself, which significantly reduces the reflection.

[0006] The film produced in this way can be used independently of the substrate to be coated, since the reduction of the reflection does not depend on the refractive index of the material used for the coating. However, this coating method is still based on chemicals, which have the above-mentioned disadvantages.

[0007] In addition, the coating produced in this way is susceptible to mechanical stress (abrasion, impact, etc.) and therefore ages quickly. As a result, over time the coating often falls off the substrate and / or loses its properties for reducing reflection.

[0008] WO 2019 / 166836 A1 describes a method for producing antireflective structures in which the surface of a substrate is processed using a laser to impart antireflective properties. The substrate material is modified using a focused laser beam, thereby establishing nanostructures through a self-assembly process of laser-induced periodic surface structures (LIPSS). By appropriately selecting the laser energy density and the superposition of the beam focus on the substrate surface, quasi-periodic repeating structures can be generated. This produces an antireflective surface. This method eliminates the need for chemicals and allows for the processing of a wide variety of substrate materials.

[0009] However, due to the self-assembly process underlying LIPSS, this method operates continuously and is time-consuming. Since LIPSS is formed by repeated processing only in nearby surface regions, large-area nanostructures cannot be built in a single step. Furthermore, the regularity of the structure depends on specific process and environmental conditions, meaning that variations in surface conditions (slightly different materials, micro-contamination) can lead to alterations in the results.

[0010] EP 2431120 A1 discloses a method for the direct structuring of thin films, wherein periodic structures can be generated in a metallic thin film by means of an interferometric laser beam. In this process, several pulsed laser beams are guided onto the thin film, thereby interfering in an interference region, causing the material of the thin film to vaporize in a high-intensity region. The process is characterized by the fact that the resulting structure can be altered by adjusting the intensity of the laser beams or by displacing the thin film in the Z-direction (i.e., in the direction of the incident laser beam, or away from it). Additional optical elements are used to establish a phase shift between the laser beams, which affects the interference pattern. The incident laser beam is focused onto the surface of the thin film by a focusing element, thereby reducing its size and creating a high-intensity region of vaporization of the thin film material.

[0011] This process requires altering the intensity of the incident laser beam. This can be done by specifying a particular laser source or by using a unit that controls the intensity of the laser beam. The intensity must be set according to the evaporation threshold of the thin film material. Therefore, different laser sources must be used for different materials, or additional intensity control elements may be required. Controlling the interference pattern generated by causing optical element displacement is also necessary. When processing materials with high evaporation thresholds, damage to optical elements in the laser beam's optical path can also be considered.

[0012] In US 2004 / 0227927 A1, a device for interferometric measurement is disclosed, which is designed to generate an interference pattern with a variable frequency on a focal point, wherein the device comprises a movable beam splitter element and a movable reflector, which split the incident laser beam into two laser sub-beams and deflect at least one of the laser sub-beams, wherein the frequency can be changed by moving the beam splitter element and the reflector. The beam splitter element and the reflector are moved by motorized stages.

[0013] The device has a complex and easily wear-prone structure, since the beam shaping affecting the frequency of the generated interference pattern can only be achieved by moving two optical elements, namely the beam splitter element and the reflector. In addition, the distance between the beam splitter element and the reflector is fixed, and their arrangement on the motorized stages is space-occupying.

[0014] Methods of direct laser interference patterning are known from scientific publications (“Microfabrication and Surface Functionalization of Soda Lime Glass through Direct Laser Interference Patterning”, Soldera et al., Nanomaterials, 2021). However, these methods require complex modifications and reconfigurations of more than one optical element in the optical path in order to control the generated structures. In high-volume industrial applications of substrates structured with different requirements for the width of the desired structures, this requires regular movement and adjustment of the optical elements in the optical path, which reduces the flexibility of the process and exposes the optical elements to a greater risk of wear and damage with each use due to the new adjustment of the respective optical elements.

[0015] Furthermore, the smallest structure size that can be manufactured by direct laser interference structuring is limited to the micrometer range. As found in the publications, the smallest size that can be generated is in the range of significantly larger than the wavelength of the radiation in the visible spectrum in some cases. Anti-reflection structures manufactured in this way can produce an undesirable diffraction pattern for light of particularly short wavelengths, and are not suitable for preventing reflections in these wavelength ranges or for ensuring the transmission of incident light rays from the entire visible spectrum.

[0016] Another publication (“Improving throughput and microstructure uniformity in Direct Laser Interference Patterning utilizing top-hat shaped beams”, El-Khoury et al., Research Square, 2021) discloses the use of laser beams with Gaussian and top-hat profiles in an optical setup for generating interference patterns on a substrate, wherein the optical setup comprises a laser beam source, a first deflection element, a beam shaping element, a beam splitter element, a further deflection element and a focusing element. The periodicity of the interference pattern can be adjusted by moving the optical elements relative to each other, in particular by moving the further deflection element in the optical path of the laser (sub) beam.

[0017] Here, a large number of optical elements is required to generate the interference pattern, making a complex and easily abradable setup necessary. Furthermore, the structure period that can be generated is limited to a minimum of 6.7 pm.

[0018] Furthermore, a method for establishing hierarchical microstructures using laser pattern stamping is known (“Hierarchical Microtextures Embossed on PET from Laser-Patterned Stamps”, Bouchard et al., Materials, 2021), wherein Direct Laser Writing (DLW) and Direct Laser Interference Patterning (DLIP) are used to establish the laser pattern stamp. A fixed optical setup is used, which results in a predetermined structure width of 3.1 pm for the interference pattern generation. The interference pattern generated in this way in the low micrometer range, which is superimposed on the laser pattern generated by the direct laser writing. Here, the laser beam is directed directly onto the material, thereby establishing structures, in particular cone structures, on the substrate in the region of maximum intensity. Here, the diameter of the structures is typically approximately 110 pm, which is a multiple of the structure period generated by the interference structuring. The structures established in the substrate by superimposing the two structures are referred to as hierarchical structures.

[0019] However, the presented method is not suitable for manufacturing antireflection coatings on large-area substrates, since the structuring process consists of several process steps (first DLW and then successive structuring using DLIP) and the smallest structure size that can be manufactured using the same apparatus is limited to a specified size (3.1 pm). Thus, the presented apparatus and the described method are not suitable for manufacturing uniform antireflection structures in one structuring step, but also not for manufacturing antireflection structures with variable structure width having antireflection properties for electromagnetic waves in the entire visible light spectrum.

[0020] US 2001 / 035991 A1 discloses an interference lithography system with which an incident laser beam can be divided into two or more parts ("sub-beams") and with which three-dimensional surface structures can be manufactured in a thin photoresist layer, whereby such surface structures can be formed as cylindrical or cup-shaped holes. However, the patent specification does not disclose that such structured substrates have antireflection properties or how such structures need to be designed in order to produce antireflection properties.

[0021] EP 2596899 B1 discloses an apparatus and a method for interference structuring of a large number of samples. The apparatus comprises a focusing device for focusing a laser beam into a sample volume. The laser beam can also be focused along another spatial direction which is not parallel to the first spatial direction. The apparatus contains a beam expansion and splitting device which is located in the optical path behind the focusing device and expands the laser beam. Only one such beam splitter which is only suitable for splitting the laser beam into two partial beams is part of the beam expansion and splitting device. SUMMARY

[0022] OBJECTS / TARGETS OF THE INVENTION

[0023] It is therefore an object of the present invention to provide an apparatus and a method with which a direct pattern of a surface (e.g. a transparent and / or large-area surface) can be manufactured without using environmentally harmful chemicals which give the material antireflection properties.

[0024] In addition, it is an object of the present invention to manufacture a pattern which is as robust as possible and which does not lose its effect by using transparent substances. In addition, a large number of samples should be able to be structured in a short time.

[0025] It is a further object of the present invention to provide a method of patterning by laser interference which is independent of the intensity of the laser radiation source. The method should be configured such that the optical elements are not damaged even at high intensities on the substrate to be patterned.

[0026] TECHNICAL SOLUTION

[0027] The invention provides a device which enables the patterning of substrates (e.g. large area and / or transparent substrates) by means of laser interference patterning. By means of the device, periodic point structures in the micrometer and sub-micrometer range can be generated on the surface or inside a transparent substrate, which gives the substrate anti-reflective properties (increased transmission).

[0028] According to the invention, this object is achieved by a laser interference patterning device according to claim 1 for the direct laser interference patterning of substrates (e.g. the large area and / or transparent substrates to be mentioned herein) comprising

[0029] - a laser radiation source (1) for emitting a laser beam,

[0030] - a beam splitter element (2) arranged in the light path (3) of the laser beam,

[0031] - a focusing element (4) arranged successively in the light path of the laser with the beam splitter element and configured in such a way that the sub-beams pass through in the interference region in a manner that the sub-beams can interfere inside the surface or volume of a substrate (5), preferably a large area and / or transparent substrate,

[0032] wherein the beam splitter (2) is freely movable along its optical axis in the light path (3) and wherein the beam splitter (2) is arranged to split the incident laser beam emitted by the laser radiation source (1) into at least 2, preferably at least 3, more preferably at least 4, in particular 4 to 8, i.e. 4, 5, 6, 7 or 8 sub-beams.

[0033] It is particularly preferred that the beam splitter (2) is configured in such a way that it splits the incident laser beam into an even number of sub-beams, i.e. 2, 4, 6 or 8, most preferably 4 sub-beams.

[0034] Alternatively or in addition, the beam splitter (2) can be configured in such a way that it comprises a first beam splitter and at least one further beam splitter arranged successively with the first beam splitter, wherein the first beam splitter splits the incident laser beam into at least two sub-beams and the further beam splitter is arranged in the light path of at least one of the sub-beams and splits it into at least two sub-beams when it passes through.

[0035] For the laser interference patterning of a substrate (5), preferably a large area and / or transparent substrate, the laser beam emitted by the laser radiation source is split by the beam splitter element (2) into at least 3, preferably at least 4 sub-beams. Only double-beam interference (i.e. patterning by interference of two sub-beams) is known from the prior art. However, such double-beam interference only produces linear patterns on the substrate.

[0036] Subsequently, in an interference region, also known as an interference pixel, the sub-beams are deflected by the focusing element (4) such that they interfere on the surface or inside a substrate (5), preferably a large-area and / or transparent substrate.

[0037] This allows the generation of two-dimensional periodic point structures in the micrometer and sub-micrometer range, the structure period of which can be freely adjusted by moving the beam splitter element (2) along its optical axis. Large-area processing of the substrate (5), preferably a large-area and / or transparent substrate, is possible.

[0038] Further advantageous embodiments can be found in the description and the dependent claims.

[0039] Main advantages

[0040] One advantage of the apparatus defined herein is that, when patterning a substrate, in particular when creating structures with anti-reflective properties, the apparatus and the method enabled by means of the apparatus can dispense with the use of chemicals and their expensive disposal. In addition, the substrate can also be dispensed with cleaning.

[0041] Furthermore, a variety of substrates, preferably large-area and / or transparent substrates, in particular transparent materials, can be processed with the apparatus. Since the process is independent of the refractive index or the adhesion of certain coating materials to the substrate, the process is more flexible than conventional chemical processes.

[0042] Compared to WO 2019 / 166836 A1, the processing time according to the method is significantly shorter, since the periodicity of the structure is ensured by the interference of at least 3, preferably at least 4, incident sub-beams in the interference region, rather than being the result of a more time-consuming self-assembly process. Another advantage over conventional methods is that the shape of the generated micro / nanostructures can be controlled (structure design; geometry). The geometry of the structure can be controlled by the number, polarization of the interfering (sub) beams and by setting the process parameters, thereby influencing the anti-reflective properties in a targeted manner.

[0043] It is also worth mentioning that the stability of the periodic point structures established in this way is more durable than conventional coatings, since it cannot flake off the substrate to be coated over time and with the stresses arising in use.

[0044] If the patterning is carried out within the volume, i.e. inside the substrate, preferably a large-area and / or transparent substrate, in particular in a transparent material, the resulting structure, i.e. the periodic point structure of the patterned substrate, is less sensitive to impacts and abrasion than conventional coatings. The inventors have found that a structure inside the material, i.e. below the surface, also referred to as a texture herein, does not necessarily result in anti-reflective properties. However, a texture inside the material is advantageous for other applications such as product protection, optical data storage, decoration, etc.

[0045] It is particularly advantageous that the setup of the apparatus or the arrangement of the optical components disclosed herein allows for patterning a substrate at very high patterning rates, up to 0.9 m 2 / min, in particular in the range of 0.01 to 0.9 m 2 / min, preferably in the range of 0.05 to 0.9 m 2 / min, most preferably in the range of 0.1 to 0.9 m 2 / min. This is ensured by the fact that the preferred selection of the optical elements enables an enlargement of the area where the at least three sub-beams overlap, by which a large area can be irradiated in one process step. In contrast to methods known to the person skilled in the art, such as direct laser writing, no strong focusing is necessary to generate high-resolution features.

[0046] Such a setup advantageously allows for a fast scanning of the surface of the substrate, so that high patterning rates, up to 3 m 2 / min, in particular in the range of 0.05 to 2 m 2 / min, preferably in the range of 0.1 to 1 m 2 / min, most preferably in the range of 0.1 to 0.9 m 2 / min, can be achieved. The exact patterning rate depends, inter alia, on the available laser power. With future technologies having higher laser power, even higher patterning rates can thus be achieved.

[0047] Detailed description

[0048] The apparatus according to the present invention describes a structure for laser interference patterning of a substrate, e.g. for manufacturing a large-area and / or transparent substrate with a periodic point structure in the micrometer or sub-micrometer range, in particular for manufacturing so-called anti-reflective glass on or within the volume of the substrate, i.e. inside.

[0049] Substrate

[0050] For the purposes of this invention, the term "substrate" refers to a substrate whose surface extends in several spatial directions. The substrate, preferably a large-area and / or transparent substrate, can be a planar substrate or a curved substrate, such as a parabolic substrate. For the purposes of this invention, "large area" also means the extent of the substrate (preferably a large-area and / or transparent substrate, such as a planar substrate in the x and y directions), or the extent of a curved substrate along its radius of curvature that is greater than the area where at least three sub-beams interfere with each other.

[0051] In a preferred embodiment, the substrate is an extension in the x and y directions or along the radius of curvature that is less than or equal to the extension of the region where at least three sub-beams interfere with each other. Uniform patterning of the substrate is possible in a single process step (during a laser pulse).

[0052] In a particularly preferred embodiment, the substrate is a large-area substrate whose extent in the x and y directions, or along the radius of curvature, is greater than the area where at least three sub-beams interfere with each other. It is possible to perform large-area, uniform structuring of the substrate in several process steps (using several laser pulses) by moving the substrate in the x and y planes. The substrate can be moved by rotation or translation, or by a combination of rotation and translation.

[0053] For the purposes of this invention, the term substrate refers to a solid material having a reflective surface. Examples of such materials include metals, polymers, ceramics, and glass.

[0054] Regarding substrates having periodic point structures (especially those with anti-reflective properties) as defined herein that can be processed by applying the laser interference patterning method according to the invention, within the scope of the invention, there are various choices of transparent and translucent materials as well as non-transparent materials.

[0055] In a particularly preferred embodiment, the large-area substrate comprises a transparent material.

[0056] Transparent materials typically have high visible light transmittance, although this varies depending on the application. Under unbiased conditions within the visible light spectrum (wavelength 380 nm to 780 nm), the transmittance of a transparent material is not less than 70%, preferably not less than 80%, and more preferably not less than 90%.

[0057] The geometry of the substrate can be variable; therefore, large-area substrates and / or non-large-area substrates, such as tubes or fibers, can be used, for example, as planar, curved, or irregular surfaces.

[0058] Preferably, the substrate is a large-area and / or transparent material.

[0059] The substrate can be designed as a flexible and / or bendable substrate, such as flexible glass film, (artificial) leather, metal foil, sheet or plastic film, for example, for use in solar films or displays.

[0060] In a particularly preferred embodiment, the large-area substrate comprises a transparent material, preferably composed of a transparent material. For the purposes of this invention, a material or substrate is considered transparent if it has high transmittance for at least a subrange of the electromagnetic radiation spectrum between 1 nm and 1 m. For example, such a subrange includes electromagnetic radiation in the visible light range from 380 nm to 780 nm, or also includes electromagnetic radiation in the infrared range from 780 nm to 5000 nm, or electromagnetic radiation in the infrared (thermal radiation) range, or electromagnetic radiation in the microwave range, especially radar radiation in the wavelength range from 1 mm to 10 m, or other subranges adjusted according to the desired application, especially according to the wavelength of the laser source. Such a subrange preferably has a width of at least 10% or 50% of the wavelength, forming a lower limit of the subrange. For the purposes of this invention, for each wavelength within the subrange, i.e., for the entire spectrum within the subrange, the high transmittance within the subrange is at least 50%, preferably at least 70%, or particularly preferably at least 80% or at least 90%. However, transparent substrates can also be described as substrates that selectively exhibit high transmittance for certain wavelength ranges within the visible light range. For example, a substrate may have high transmittance for electromagnetic radiation with wavelengths ranging from 500 nm to 800 nm. The transmittance can vary with the range of transmitted wavelengths; for example, not less than 70% for wavelengths ranging from 380 nm to 500 nm, and not less than 90% for wavelengths ranging from 500 nm to 750 nm. For instance, the substrate transmits radiation with wavelengths from 380 nm to 780 nm. It exhibits particularly high transmittance, such as 90%, in the wavelength range from 450 nm to 690 nm; and transmittance, for example, is 70% for wavelengths below and above this range.

[0061] The translucency of transparent materials also provides the advantage of being able to perform laser interference processes in the plane / interior of the substrate volume.

[0062] For the purposes of this invention, transparent materials include a variety of transparent materials, especially glass (e.g., borosilicate glass, quartz glass, alkaline earth silicate glass (e.g., soda-lime glass), aluminosilicate glass, metallic glass), and also solid polymers (e.g., polycarbonate, such as...). and Polycarbonate blends, such as and Polymethyl methacrylate, such as polyesters; 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 are homopolycarbonates, copolycarbonates and thermoplastic polyester carbonates.

[0063] According to a particularly preferred embodiment, the transparent material comprises glass (as defined herein) or a solid polymer (as defined herein).

[0064] The silicate framework of the glass preferably provides a transmission window for wavelengths in the range between 170 nm and 5000 nm (i.e. a wavelength range including visible light in the range of 380 nm to 780 nm and including infrared radiation).

[0065] Alternatively, the substrate (preferably a large-area and / or transparent substrate) can also comprise a non-transparent material. By patterning the non-transparent material, a periodic point structure in the micrometer or sub-micrometer range as defined herein is established on the surface of the non-transparent material. Thus, a structure with anti-reflective properties can be generated on the non-transparent material, whereby the original roughness of the surface of the non-transparent substrate (i.e. before applying the patterning according to the present application) remains unchanged or almost unchanged in the macroscopic range, thereby effectively causing a reduction of reflection of other reflective surfaces (e.g. metallic surfaces) of the non-transparent material. Suitable non-transparent materials include metals (e.g. silicon, aluminum, copper, gold), metal alloys (e.g. steel, brass), ceramic materials (e.g. zirconium oxide, titanium dioxide, zirconium dioxide) as well as polymers (PEEK, polyether ether ketone; polyfluorocarbons such as Teflon) and combinations thereof. For example, such a patterned substrate is suitable as a negative mold for indirectly applying or generating structures on another substrate. For example, the patterned substrate can be used as a "stamp" to establish structures on an arbitrary number of other substrates which are inverted to the structures established on the substrate. In addition, such a patterned substrate exhibits an increased diffraction of electromagnetic radiation, whereby the patterning of the substrate leads to a reduction of the directed reflection of the substrate. Due to the structure size, a scattering process occurs on these structures which is introduced by the interference patterning at the level of the substrate (in particular one of its surfaces).

[0066] Point structure / interference pattern / anti-reflective glass

[0067] The invention also comprises a patterned substrate (5) having antireflective properties, wherein the patterned substrate comprises a periodic point structure in the micrometer or sub-micrometer range, wherein the periodic point structure is formed by inverted pyramids, and wherein the inverted pyramids are periodically spaced by a distance in the range from 50 nm to 50 pm, preferably in the range from 50 nm to 20 pm, more preferably in the range from 100 nm to 4 pm, more preferably in the range from 100 nm to 2 pm, even more preferably in the range from 200 nm to 1.5 pm, particularly extremely preferably in the range from 300 nm to 800 nm, with respect to their respective saddle points or height centers (circular base).

[0068] For the purposes of the present invention, the term inverted pyramid refers to a structure having a circular, elliptical, triangular or generally rectangular base, in particular a circular base, which is conically concentrated in the vertical direction onto the substrate and has a conical tip at its saddle point. The inverted pyramids are formed during the patterning process, i.e. when laser pulses, due to the high intensity of the regions of the substrate that are to be structured, impinge on the substrate, whereby the regions between the inverted pyramids on or in the substrate remain essentially unstructured due to the destructive interference of the intensity being zero. Thus, by focusing the laser (sub) beams on or in the substrate, the inverse of the intensity distribution is formed. The shape of the described inverted pyramids refers to the arrangement of the point structures on the surface of the substrate. The arrangement of the point structures on or along a plane within the volume results in a symmetrical shape. For the purposes of the present invention, the point structures generated within the volume by laser interference structuring are also referred to as inverted pyramids.

[0069] For example, by tilting the substrate with respect to the angle of incidence of the focused laser (sub) beams, by tilting the interference volume, i.e. the volume pixel, voxel; the angle at which the sub-beams are focused on the substrate surface or in the substrate volume so that they interfere in the interference region, to the substrate, for example by tilting the device to the substrate, or by a combination thereof, it is possible to produce pyramids having an elliptical base. According to a preferred embodiment, pyramids having an elliptical base are produced by tilting the substrate with respect to the angle of incidence of the focused laser (sub) beams.

[0070] For the purposes of the present invention, the period of the structure is referred to as Λ. It is generally dependent on the wavelength of the interfering laser (sub) beams, the angle of incidence of the interfering laser (sub) beams and the number of interfering laser (sub) beams.

[0071] For the purposes of the present invention, a patterned substrate with antireflection properties (referred to herein as antireflection glass) describes a substrate, preferably a large-area and / or transparent substrate, with a periodic point structure, the structure width of which is in the range of micrometers and submicrometers, i.e. in the range from 50 nm to 50 μm. These antireflection properties are achieved when the dimensions of the resulting structures, i.e. the structure period and the dimensions of the individual cones, are in the range of less than the wavelength of visible light.

[0072] In physics, reflection is the bouncing back of an electromagnetic wave at the interface of materials with different refractive indices. The angles of reflection and transmission of light in a transparent substrate can generally be calculated using Snell's law of refraction as follows

[0073] n1sin δ1 = n2sin δ2

[0074] where n1and n2indicate the refractive indices of air and the substrate, respectively, and δ1and δ2indicate the angles of the incident and reflected light beams, respectively.

[0075] Due to the periodic point structure on the surface or within the volume of the substrate, preferably a large-area and / or transparent substrate, the refractive index of the substrate changes in such a way that a graded refractive index is produced. As a result, light with a wavelength greater than the structure period Λ of the periodic point structure is increasingly transmitted. Light with a wavelength shorter than or equal to the periodic point structure is diffracted at the surface.

[0076] In the context of the present invention, antireflection properties mean that the periodic point structure, the dimensions of which are in the range of the incident electromagnetic waves, causes the incident waves to be diffracted away from the observer in such a way that there is no reflection to be understood as "disturbance". In addition, for the purposes of the present invention, antireflection properties also include that the refractive index at the boundary between the first medium, for example air, and the substrate, preferably a large-area and / or transparent substrate, is graded in such a way that there is no clear transition from one medium to the other for the incident electromagnetic waves, and the incident electromagnetic waves are increasingly transmitted.

[0077] For the purposes of the present invention, a patterned substrate with antireflection properties also describes a substrate comprising a periodic point structure, wherein the periodic point structure consists of superimposed structures, wherein at least one structure has dimensions in the submicrometer range, and wherein at least one structure is formed by an inverted cone, as defined herein, which can in particular be produced by means of an interference laser beam.

[0078] For example, when using an interference laser beam, the periodic point structure, in particular the periodic point structure consisting of superimposed structures, can be adapted optimally to the requirements of the respective application by correspondingly configuring the parameters (selection of the laser radiation source, arrangement of the optical elements, pulse duration and intensity, number of laser pulses impinging on the interference pixel).

[0079] For example, the structure having anti-reflective properties produced in this way is a periodic point structure composed of inverted pyramids having an average size in the micrometer range, in particular an average distance of 1 pm to 50 pm with respect to their respective saddle points or height centers. Superimposed on this periodic point structure is a further structure, the average size of the superimposed structure preferably being in the range of the laser wavelength l or l / 2, in particular from 100 nm to 1000 nm, preferably from 100 nm to 800 nm, particularly preferably from 100 nm to 600 nm, in particular from 100 nm to 400 nm. For the purposes of the present invention, such a structure is also referred to as a layered structure.

[0080] In particular, the superimposed structure has a quasi-periodic wave structure, wherein the material on the surface of the substrate within the superimposed structure region has successive wave crests and troughs, the periodicity of which is in the sub-micrometer range, particularly preferably in the range from 100 nm to 1000 nm, preferably in the range from 100 nm to 800 nm, particularly preferably in the range from 100 nm to 600 nm, in particular in the range from 100 nm to 400 nm.

[0081] The wave structure is formed during the patterning process, i.e. the patterning is carried out by a self-assembly process, which is triggered by at least partial melting of the substrate material by the laser pulse in the high-intensity region, when the laser pulse hits the substrate to be structured as a result of the occurrence of the high-intensity region. In particular, the wave structure is produced using laser-induced periodic surface structures (LIPSS), the production of which is combined with the production of the periodic point structure by means of the interference laser beam.

[0082] Alternatively, according to the present application, the wave structure superimposed on the point structure of the inverted pyramids having an average size in the micrometer range can also be applied to the surface of the (prestructured) substrate by subsequently applying a further interference pixel, whereby the structure produced with the further interference pixel has a structure period with respect to the pyramids formed by the further interference pixel from the statistical average range (100 nm to 1000 nm, preferably in the range from 100 nm to 800 nm, particularly preferably from 100 nm to 600 nm, for example in the range from 200 nm to 500 nm, in particular in the range from 100 nm to 400 nm).

[0083] Advantageously, by means of the interference laser beam and the use of laser-induced periodic surface structures, it is thus possible to pattern a substrate, for example having anti-reflective properties, over a large area without having to accept long processing times or a large number of process steps that can be carried out successively. Thus, the present application enables the simultaneous generation of a layered structure, both in the field of substrates having anti-reflective properties and in the field of self-cleaning, hydrophobic or superhydrophobic and hydrophilic or superhydrophilic substrates having anti-icing and / or anti-fogging properties.

[0084] According to a preferred embodiment of the present application, the laser interference patterning is carried out by irradiating the substrate with several laser (sub-) beams at an angle of 45° to 90° (perpendicular) to the surface of the substrate, preferably at an angle of 60° to 90°, particularly preferably at an angle of 75° to 90°, for example in the angular range of 90° / to 90°, and applying interference pixels (or interference volumes generating interference pixels on or in the substrate) in the surface or volume of the substrate, for example first, second and / or third interference pixels. In each case, the angle is in the angular range of from / to 76°, 77°, 78°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, 90° with respect to the optical axis of the substrate. It is particularly preferred that the interference pixels are applied substantially perpendicularly, i.e. at an angle of 90° ± 1°, to the normal of the surface of the substrate.

[0085] Interference region or interference pixel

[0086] The device according to the present application is designed to produce periodic point structures in the micrometer or sub-micrometer range on a substrate, wherein the periodic point structures can be produced by laser beams that interfere in an interference region.

[0087] An interference region is characterized by alternating maxima and minima of the radiation intensity occurring in its spatial extent. These maxima and minima occur periodically, i.e. regularly repeated, and thus form an interference pattern that can be transferred to the substrate. The interference region from which the interference pattern can be identified is also referred to as interference pixel. The extent of the interference pixel is usually circular, but other geometric extents, for example elliptical or linear extents, are also conceivable. The interference region from which the interference pattern can be identified is physically limited by an intensity threshold of the substrate to be processed. The intensity threshold describes the energy at which the substrate material interacts with the incident laser beam such that a change in the material, for example melting or removal of the material, occurs within the material. In the case of a laser radiation source having a Gaussian radiation profile, the energy of the interference laser beam occurring at the maxima of the interference pattern decreases towards the edges of the interference region, so that the interference pixel applied to the substrate is smaller than the interference region, the exact dimensions being determined by the properties of the laser radiation source and the substrate.

[0088] Thus, in the context of the present application, the term interference pixel, for example first, second, third and / or further interference pixel, refers to a periodic pattern or grating of at least three inverted pyramids, preferably at least seven inverted pyramids, most preferably at least 19 inverted pyramids, formed on the surface of the substrate within the interference pixel (see Figure 6). Preferably, the periodic pattern or grid is generated by superimposing at least three, particularly preferably at least four, laser (sub) beams as a result of focusing (converging) the laser (sub) beams to the surface or the interior of the substrate, whereby the sub-beams constructively and destructively interfere at the surface or the interior of the substrate.

[0089] According to a preferred embodiment of the present application, the structured substrate comprises not only single interference pixels of one type, such as first interference pixels, second interference pixels and / or third interference pixels, but also a plurality of interference pixels of one type, such as a plurality of first interference pixels and / or a plurality of second interference pixels, which are arranged independently of one another in the plane next to one another in a repeatedly offset manner along at least one spatial direction (x and / or y direction), particularly preferably along both spatial directions (two-dimensionally). For example, it can be provided that in a first step at least a plurality of first interference pixels in the plane are applied to the plane or the volume of the surface of the substrate to be structured (see, for example, Fig. 2a), which are arranged repeatedly offset with respect to one another along at least one spatial direction, while in a second step a plurality of second interference pixels in the plane are applied repeatedly offset with respect to one another along at least the same spatial direction, superimposed on the plurality of first interference pixels. However, it can be provided that the plurality of first interference pixels and the plurality of second interference pixels are applied to the plane alternately, i.e. alternately first interference pixels, then second interference pixels, and then again from the beginning. Figure 6

[0090] By arranging the plurality of first interference pixels and the plurality of second interference pixels, it is possible to realize / apply specific properties, in particular anti-reflective properties, in a large-area range, in particular on the plane of the substrate spanned by the surface of the substrate, or in the volume of the substrate. For example, such a patterning with a plurality of first interference pixels and a plurality of second interference pixels can be realized by scanning the substrate using a polygon scanner.

[0091] Preferably, the periodic point structure within one interference pixel has a coefficient of variation of the cross-section of the pyramids (value resulting from the standard deviation divided by the mean value) of 15% or less, more preferably 10% or less, and even more preferably 5% or less. This allows for a better detectability of the substrate patterned according to the present application compared to conventional substrate patterning / coating substrate methods (e.g. etching, particle spraying, polymer coating), in which the deviation is larger due to the process and the resulting structure period mapping is less accurate.

[0092] Laser radiation source

[0093] ​The device according to the application has a laser radiation source (1) which emits a laser beam. The radiation profile of the emitted laser beam corresponds to a Gaussian profile or to a flat-top profile, particularly preferably to a flat-top profile. A flat-top profile contributes to a more uniform patterning or covering of the substrate surface to be structured, if necessary enabling an accelerated patterning rate.

[0094] In a particularly preferred embodiment, the laser radiation source (1) is a source which generates a pulsed laser beam. For example, the pulse width of the pulsed laser radiation source is in the range from 10 femtoseconds to 100 nanoseconds, in particular 50 femtoseconds to 10 nanoseconds, most preferably 50 femtoseconds to less than 100 picoseconds.

[0095] Unless explicitly stated otherwise, the term laser beam or sub-beam does not refer to an idealized beam of geometrical optics, but to a real beam, such as a laser beam which does not have an infinitesimally small beam cross-section, but an extended beam cross-section (Gaussian profile or intrinsic flat-top beam).

[0096] A flat-top profile or flat-top intensity distribution refers to an intensity distribution which can essentially be described by a rectangular function (rect(x)) with respect to at least one direction. The actual intensity distribution showing the deviation from the rectangular function in percent or in terms of the sloping edges is also referred to as flat-top distribution or flat-top profile. Methods and devices for generating flat-top profiles are known to the person skilled in the art and are described, for example, in EP 2 663 892. Optical elements for transforming the intensity distribution of a laser beam are also known. For example, diffractive and / or refractive optics can be used to transform a laser beam having a Gaussian-shaped intensity distribution into a laser beam having a flat-top-shaped intensity distribution in more than one defined plane, such as the Gaussian-flat-top focusing beam shaper from the company TOPAG Lasertechnik GmbH, see, for example, DE 102010005774 A1. Such laser beams having a flat-top-shaped intensity distribution are particularly attractive for laser material processing, in particular when using laser pulses shorter than 50 ps, since a substantially constant energy or power density enables particularly good and reproducible processing results.

[0097] The laser radiation source (1) comprised by the device according to the application can have an intensity of 0.01 to 5 J / cm 2 , particularly preferably 0.1 to 2 J / cm 2 , very particularly preferably 0.1 to 0.5 J / cm 2 . The device according to the application allows the intensity of the laser radiation source to be flexibly selected within a range. The beam diameter has no effect on the generation of interference patterns on a substrate, preferably a large-area and / or transparent substrate. Due to the preferred arrangement of the optical elements in the laser light path, no units are required to control the intensity of the laser beam.

[0098] The laser radiation source is preferably configured to emit wavelengths in the range from 200 nm to 15 μιη (e.g. CO2 laser in the range from 10.6 μιη), most preferably in the range from 266 nm to 1064 nm. Suitable laser radiation sources include ultraviolet laser beam sources, laser radiation sources emitting green light (532 nm) (155 to 355 nm), diode lasers (typically 800 to 1000 nm) or laser radiation sources emitting near-infrared radiation (typically 1064 nm), especially with wavelengths in the range from 200 to 650 nm. Lasers suitable for microprocessing are known to the person skilled in the art and include, for example, helium-neon lasers, helium-silver lasers (about 224 nanometers), neon-copper lasers (about 249 nanometers), Nd:YAG lasers (about 355 nanometers), YAG lasers (about 532 nanometers), InGaN lasers (about 532 nanometers).

[0099] According to a further embodiment, the device according to the application has at least one further laser radiation source which is designed such that it generates a laser beam which interferes with the laser beam of the first laser radiation source or the laser beam of the first laser radiation source split into sub-beams in the interference region. The additional laser radiation source has the same properties as described above, although these properties can be similar or different to the properties of the first laser radiation source.

[0100] Optical elements

[0101] The present application comprises a plurality of optical elements. These elements are mainly prisms and lenses.

[0102] These lenses can be refractive or diffractive lenses. Spherical, aspherical or cylindrical lenses can be used. In a preferred embodiment, cylindrical lenses are used. This makes it possible to compress the overlapping regions of the sub-beams (also referred to herein as interference pixels) in one spatial direction and to stretch them in the other spatial direction. If the lenses are not spherical / aspherical but cylindrical, this has the advantage that the beams can be deformed simultaneously. This allows the processing point, i.e. the interference pattern established on the substrate, to be deformed from a point to a line comprising the interference pattern. With sufficient energy from the laser, the length of this line can be in the range from 10 to 15 mm (and the thickness is about 100 μιη).

[0103] Furthermore, a spatial light modulator (SLM) can be used for beam shaping. The spatial modulation of the phase or the intensity or of the phase and the intensity of the incident beam using a SLM is known to the person skilled in the art. Beam splitting using a liquid crystal on silicon (LCoS) SLM is described in the literature and is also conceivable in the device according to the application. In addition, the SLM can also be used to focus the sub-beams on the substrate. Such a SLM can be controlled optically, electronically or acoustically.

[0104] All optical elements described in the following are arranged in the optical path (3) of the laser. For the purpose of the present invention, the optical path of the laser refers to both the path of the laser beam emitted by the laser radiation source and the path of the sub-beams split off by the beam splitter element. However, the optical axis of the optical path (3) is understood to be the optical axis of the laser beam emitted by the laser radiation source (1). Unless otherwise stated, all optical elements are arranged perpendicular to the optical axis of the optical path (3).

[0105] Beam splitter element (2)

[0106] The beam splitter element (2) is located in the optical path (3) of the laser behind the laser radiation source (1). The beam splitter element (2) can be a diffractive or a refractive beam splitter element. Diffractive beam splitter elements are also referred to as diffractive optical elements (DOE). For the purpose of the present invention, a diffractive beam splitter element refers to an optical element comprising micro- or nano-structures, preferably micro-structures, which split an incident light beam into different beams according to different diffraction orders. For the purpose of the present invention, a refractive beam splitter element refers to a beam splitter element which splits based on refractive index differences at a surface, typically a transparent optical element such as a prism or a bi-prism. Preferably, the beam splitter element (2) is a diffractive optical beam splitter element.

[0107] According to a preferred embodiment, the beam splitter element is a single optical element, in particular a diffractive or a refractive optical element, which constitutes in a way that subdivides the incident laser beam based on the optical properties of the beam splitter element. This advantageously ensures that a simpler optical structure can be achieved compared to a multi-component beam splitter element consisting of several optical elements, e.g. mirrors, prisms, etc. The required splitting can be achieved without the need to calibrate or adjust the arrangement of several optical elements relative to each other. Also, the movement of the beam splitter element in the optical path is easily achieved as only a single optical element needs to be moved. Additionally, the use of an integral beam splitter element results in fewer components which are prone to wear and can need to be replaced.

[0108] According to a possible embodiment, the beam splitter is designed as a polarizing beam splitter, wherein one of the generated light beams has a different polarization than the other generated light beam, or as a non-polarizing beam splitter, wherein the polarization does not play a role in the splitting.

[0109] In a preferred embodiment, the beam splitter element (2) splits the emitted laser beam into at least 3, preferably at least 4, in particular 4 to 8, i.e. 4, 5, 6, 7 or 8 sub-beams.

[0110] In a further embodiment, the beam splitter element (2) splits the emitted laser beam into at least 2, preferably at least 3 to 4, in particular 4 to 10, i.e. 4, 5, 6, 7, 8, 9 or 10 sub-beams.

[0111] The beam splitter element (2) is freely movable along its optical axis. In other words, it is movable along its optical axis towards or away from the laser radiation source. The movement of the beam splitter element (2) changes the expansion of the at least three sub-beams so that they hit the focusing element at different distances from each other. Thus, the angle Θ at which the sub-beams hit the substrate (5), preferably a large-area and / or transparent substrate, can be changed. This leads to a seamless change of the structure period Λ from the superposition of the four sub-beams

[0112]

[0113] where λ is the wavelength of the emitted laser beam.

[0114] According to a preferred embodiment of the present application, the beam splitter element is designed as a rotating element. This advantageously allows changing the polarization of the sub-beams.

[0115] It is particularly preferred that the angle Θ at which the partial beams hit the substrate (5), preferably a large-area and / or transparent substrate, is in the range of 0.1° to 89.9°, preferably 5° to 85°, particularly preferably 10° to 60°, most preferably 15° to 45°.

[0116] The angle Θ also depends on the distance between the optical elements, in particular the distance between the optical elements and the beam splitter element, in particular the distance between the focusing element and the beam splitter element. Depending on the desired structure period to be produced on or in the large-area and / or transparent substrate, the position of the beam splitter element can be adjusted or calculated in such a way that the desired structure period can be set. It is taken into account that the position of the optical elements included in the device, in particular the position of the focusing element relative to the beam splitter element, is such that if the distance between the optical elements is large or small, the position of the beam splitter element can be adjusted accordingly.

[0117] In order to produce a patterned substrate with antireflection properties, it has been found that it is particularly advantageous if the distance between the beam splitter element (2) and the deflection element (7) is set to be in the range of 10 to 300 nm.

[0118] According to one embodiment, a dot-like structure with a small structure period, preferably a statistical mean value in the range of 100 nm to 1000 nm (or as further defined herein), can be generated directly by applying an interference pattern, wherein the distance between the beam splitter element (2) and the deflection element (7) is large, for example in the range of 40 mm to 200 mm, in particular 80 mm to 150 mm.

[0119] According to a further embodiment, dot-like structures with small structure periods, preferably with a statistical mean in the range of 100 nm to 1000 nm (or as further defined herein), can be produced by the self-organizing process of LIPSS, wherein the distance between the beam splitter element (2) and the deflection element (7) is small, e.g. in the range from 1 mm to 100 mm, in particular 50 mm to 75 mm, especially preferably 10 mm to 50 mm. In this way, by directly applying an interference pattern, an interference pattern with large structure periods can be produced, on which dot structures in the sub-micrometer range (as defined herein) are superimposed.

[0120] According to a preferred embodiment of the present application, the apparatus further comprises a measuring device, in particular a measuring device operated by a laser or an optical sensor, which is configured to measure the position of the beam splitter element and, if appropriate, the distance of the beam splitter element to other optical elements, in particular the position of the focusing element.

[0121] Furthermore, the apparatus according to the present application can comprise a control device, which is connected to the measuring device and, in particular, to the computing unit from the point of view of signal technology, so that the measured position of the beam splitter element can be compared to a first predetermined comparison value, the control device being configured from the point of view of programming, so that, if the distance of the beam splitter element to the position of other optical elements, in particular the focusing element and / or the deflection element (7), is greater or smaller than the first predetermined comparison value, a control signal is generated via the control device, by which at least one position of the optical elements, in particular the position of the beam splitter element (2) relative to the deflection element (7), is changed, so that the desired structure period is produced on the substrate.

[0122] In this context, the method for producing a substrate with dot structures in the micrometer or sub-micrometer range, in particular after step (a), can further comprise the following steps:

[0123] (i) measuring the position of the beam splitter element (2) and, if necessary, the distance of the beam splitter element to further optical elements or at least one further optical element, in particular to the position of the focusing element (4) and / or the deflection element (7),

[0124] (ii) comparing the measured position of the beam splitter element to a first predetermined reference value, and

[0125] (iii) if the measured distance of the beam splitter element to the other optical element or at least one other optical element, in particular the measured distance to the position of the focusing element (4) and / or the deflection element (7), is greater or smaller than a first predetermined reference value: changing the position of the optical element, in particular the position of the beam splitter element (2), in particular with respect to the position of the other optical element, in particular preferably the position of the beam splitter element (2) with respect to the deflection element (7), such that a desired structure period is generated on the substrate.

[0126] The splitting of the laser beam within the beam splitter element (2) can be performed by a partially reflective beam splitter element, for example a semi-transparent mirror, or by a transmissive beam splitter element, for example a dichroic prism.

[0127] In a preferred embodiment, further beam splitter elements are arranged in the optical path of the laser successively to the beam splitter element (2). These beam splitter elements are arranged in such a way that they split each of the at least three sub-beams into at least two further sub-beams. This allows to generate a larger number of sub-beams which are directed onto a substrate, preferably a large-area and / or transparent substrate, such that they interfere on the surface or inside the substrate. This allows to adjust the structure period of the interference pattern.

[0128] The focusing element (4)

[0129] Further, a focusing element (4) is arranged in the optical path (3) of the laser after the beam splitter element (2), the focusing element being configured in such a way that the sub-beams pass through the focusing element in a way that the sub-beams interfere on the surface or inside the substrate (5) to be structured in the interference region. The focusing element (4) focuses the at least three sub-beams in a spatial direction without focusing the at least three sub-beams in a spatial direction perpendicular thereto. For example, the focusing element (4) can be a focusing optical lens. In the context of the present invention, focusing means that the at least three sub-beams are brought together on the surface or inside the substrate, preferably a large-area and / or transparent substrate.

[0130] The focusing element (4) can be freely movable in the optical path (3). According to a preferred embodiment of the present invention, the focusing element (4) is fixed in the optical path or along the optical axis.

[0131] It is understood that the optical elements as defined herein can be arranged, for example, in a common housing for splitting and aligning the sub-beams in the direction of the substrate to be structured accordingly.

[0132] In a preferred embodiment, the focusing element (4) is a spherical lens. The spherical lens is configured in such a way that the incident at least three sub-beams pass through the spherical lens in a way that they interfere in an interference region on or in the surface of the substrate (5) to be structured, preferably a large-area and / or transparent substrate. The width of the interference region is preferably 1 to 600 pm, particularly preferably 10 to 400 pm, most preferably 20 to 200 pm. In this way, a high patterning rate, for example as defined herein, can be set at the same time.

[0133] In a particularly preferred embodiment, the focusing element (4) is a cylindrical lens. The cylindrical lens is configured in such a way that the region in which the at least three sub-beams overlap on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate, is stretched in the spatial direction. As a result, the region of the substrate in which the interference pattern can be generated is oval. The large semi-axis of this oval can reach a length of 20 pm to 15 mm. This increases the region that can be structured within one irradiation.

[0134] The first deflection element (7)

[0135] In a particularly preferred embodiment, the deflection element (7) is located before the focusing element (4) and is consecutive to the beam splitter element (2), which is preferably arranged in the optical path (3) of the laser. This deflection element (7) serves to enlarge the distance between the at least three sub-beams and thus also to change the angle at which the sub-beams hit the substrate (5), preferably a large-area and / or transparent substrate. It is configured in such a way that the difference of the at least three sub-beams is increased and thus the region in which the at least three sub-beams interfere along the optical axis of the optical path (3) is moved away from the laser radiation source (1).

[0136] In the context of the present application, enlarging the distance between the at least three sub-beams is understood to mean increasing the angle of the respective sub-beam to the optical axis of the laser beam emitted by the laser radiation source (1).

[0137] The enlargement of the sub-beams and the resulting deflection have the advantage that the sub-beams can be brought together more strongly by the focusing element (4). This leads to a higher intensity in the region in which the at least three sub-beams interfere on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate.

[0138] A suitable choice of the deflection elements means that a unit for controlling the intensity of the laser beam can be dispensed with. In a preferred embodiment of the device, a deflection element (7) is used which allows at least three sub-beams to be focused on the substrate (5) by the focusing element (4) by expanding the at least three sub-beams, whereby it is possible to achieve the intensity of the interference point on or in the surface of the substrate, preferably a large-area and / or transparent substrate, without additional adjustment of the intensity of the laser radiation source (1). This has the advantage that a laser radiation source with low intensity per area of power can also be used for patterning the substrate while producing a periodic point structure, whereby the optical elements are protected from wear.

[0139] Further deflection element (6)

[0140] Furthermore, it can be provided that a further deflection element (6) is arranged in the light path (3) of the laser radiation source (1) after the beam splitter element (3), which deflects the sub-beams in such a way that they are substantially parallel to each other after leaving the further deflection element (6). Thus, the device can be configured such that the processing point, i.e. the point at which the at least three sub-beams interfere on or in the surface of the substrate, preferably a large-area and / or transparent substrate, remains unchanged when the beam splitter element is moved along its optical axis in the light path of the laser. In the context of this document, the term "substantially parallel" is to be understood to mean an angular deviation between the two sub-beams of between +15° and -15°, in particular only between +10° and -10°, very preferably between +5° and -5°, but in particular, of course, also means a very small angular deviation, i.e. +1° to -1°. Ideally, the angular deviation is 0°, although slight deviations are possible due to manufacturing tolerances of the optical elements.

[0141] The further deflection element (6) can be a conventional refractive lens. Alternatively, however, the further deflection element (6) can also be designed as a diffractive lens (for example a Fresnel lens). Diffractive lenses have the advantage that they are significantly thinner and lighter, thus simplifying miniaturization of the device disclosed herein.

[0142] By suitable choice of the refractive indices of the optical elements (4), (6) and (7), it is possible to adjust the distance between the optical elements and the substrate as well as the structure period Λ. In addition to the beam splitter element (2), all optical elements can preferably be fixed within the light path (3) of the laser. This particularly preferred embodiment thus offers the advantage that only one element needs to be moved (i.e. only the beam splitter element (2) needs to be moved) to adjust the interference region or the interference angle. This saves handling steps when configuring the device, such as aligning the device to the desired structure period. Furthermore, the fixed arrangement, i.e. the preferred fixing of all optical elements within the light path (3) of the laser, prevents wear of the optical elements.

[0143] Polarization element (8)

[0144] In a further embodiment, a polarization element (8) is located behind the deflection element, particularly preferably behind the further deflection element (6) in a device having two deflection elements (6), (7), and in front of the focusing element (4) in at least one beam path of the at least three sub-beams, each sub-beam having one polarization element. The polarization element can change the polarization of the sub-beams relative to one another. This allows the interference pattern mapped out by the at least 3 sub-beams in the surface or volume of the substrate, preferably a large-area substrate and / or a transparent substrate, to be changed. By arranging a polarization element (8) in at least one beam path of the sub-beams, preferably not in each beam path of the sub-beams, preferably in up to (n-1) beam paths (where n is the number of sub-beams generated in the application process), it is possible to advantageously rotate the plane of polarization of at least one sub-beam in the beam path and thus to "interfere" with the pattern of interference pixels in the substrate plane.

[0145] In particular, the interference sub-beams can thus be unpolarized, linearly polarized, circularly polarized, elliptically polarized, radially polarized or azimuthally polarized.

[0146] Optical element for beam shaping

[0147] In a further embodiment, the laser radiation source (1) has a radiation profile corresponding to the Gaussian profile described above. In such an embodiment, a further optical element for beam shaping can be located behind the laser radiation source (1) and in front of the beam splitter element (2). This element serves to adjust the radiation profile of the laser radiation source to a flat-top profile.

[0148] For example, in the device according to the application, an optical element having a concave parabolic or planar reflective surface can also be provided, which optical element is designed to be rotatable about at least one axis or displaceable along the beam path (3). Thus, if necessary, an additional focusing element (4) or an additional deflection element (6) located in the beam path (3) can be dispensed with. For example, this optical element can be used to direct the laser beam or the laser sub-beams onto the surface of the focusing element (4) or a further focusing optical element before the beam reaches the substrate to be patterned to form the structural elements.

[0149] Alternatively, for example, at least one optical element having a concave parabolic or planar reflecting surface can also be provided, which is designed to be rotatable about at least one axis or displaceable along the light path (3), for example, which is positioned in the light path successively to the first deflection element (7) and the further deflection element (6). For example, the sub-beams can be deflected in the light path (deflection mirror) or focused in the light path in such a way that the substrate to be patterned can be located in a fixed position during the machining (so-called focusing mirror or galvanometer (laser scanner) (9).

[0150] Embodiments comprising a polygon scanner are also conceivable. In this embodiment, the at least one optical element comprises a periodic rotation prism, preferably a periodic rotation mirror prism, in particular a polygon mirror or polygon wheel, and a focusing element (4) arranged successively to the periodic rotation prism in the light path. The focusing element is configured in such a way that the sub-beams pass through the focusing element in such a way that the sub-beams interfere in the interference region on the surface or inside the substrate (5) to be patterned. In a preferred embodiment, the optical element further comprises at least one further deflection element, for example a reflective deflection element for deflecting the sub-beams in the light path. The at least one further deflection element can be arranged in front of and / or successively to the periodic rotation prism in the light path. In the light path, the at least one further deflection element is arranged before the focusing element.

[0151] This arrangement advantageously allows a rapid scanning of the surface of the substrate, so that high patterning rates in the range of up to 3 m 2 / min, in particular in the range of 0.05 to 2 m 2 / min, particularly preferably in the range of 0.1 to 1 m 2 / min, most preferably in the range of 0.1 to 0.9 m 2 / min, can be achieved. The exact patterning rate is dependent, inter alia, on the available laser power. With future technologies having higher laser power, even higher patterning rates can thus be achieved.

[0152] Holding device for a substrate

[0153] In a further embodiment, the substrate (5), preferably a large area and / or transparent substrate, is movable in the xy-plane. By moving the substrate (5), preferably a large area and / or transparent substrate, in the xy-plane, a large area processing by laser interference patterning can be ensured. In each processing step (i.e. impinging a laser pulse on the substrate to be patterned), an interference pixel (as defined herein) is generated, the size D of which depends on the angle of incidence and intensity distribution of the laser beam, as well as the focusing properties of the optical element. The distance between different interference pixels, the pixel density Pd, is determined by the repetition rate of the laser radiation source (1) and the movement of the substrate relative to the focus point of the optical element (i.e. the point where the interference area is generated on the substrate surface or inside). If the pixel density Pd is smaller than the size D of the interference pixels, a uniform processing over a large area is feasible.

[0154] By moving the substrate relative to the focus point (where the interference pixels are generated) in combination with the pulsed laser (sub) beam, a large area, optionally uniform and periodic, point structure can be generated on the surface or inside of the substrate, preferably a large area and / or transparent substrate.

[0155] As an alternative to moving the substrate relative to the focus point, the focus point can also be moved on the sample or substrate (e.g. using a scanner-based approach).

[0156] Since the mass that is moved in the process is large, moving the substrate to be patterned, preferably a large area and / or transparent substrate, in the laser beam can be time-consuming and slow. Therefore, it is beneficial to provide the substrate, preferably a large area and / or transparent substrate, in a fixed position during processing and to achieve a large area patterning of the substrate by manipulating the sub-beam in the beam direction with an optical element (focusing mirror or galvanometer (laser scanner)) to focus the sub-beam on the surface or volume of the substrate. Since the mass that is moved in the process is small, this can be very labor-saving, i.e. faster. Preferably, the substrate is stationary during processing.

[0157] Method

[0158] The present invention also comprises a method of manufacturing a substrate, preferably a large area and / or transparent substrate, with a periodic point structure in the micrometer or sub-micrometer range by laser interference patterning.

[0159] According to the present invention, a method of manufacturing a patterned substrate, preferably a large area and / or transparent substrate, with a periodic point structure in the micrometer or sub-micrometer range by laser interference patterning, comprises the following steps:

[0160] A substrate (5), preferably a large-area and / or transparent substrate, is provided on a holding device. A laser beam is emitted from a laser radiation source (1). The laser beam is split into at least three, preferably four, sub-beams by a beam splitter element (2). The sub-beams impinge on a focusing element (4) which focuses the at least three, particularly preferably four, sub-beams on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate, such that the sub-beams constructively and destructively interfere on or in the surface of the substrate. As a result of the laser interference process, a periodic point structure in the micrometer or sub-micrometer range is produced on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate. The method is characterized in that the at least three sub-beams are superimposed in such a way that a two-dimensional pattern is created.

[0161] According to another embodiment of the present application, the laser beam is split into at least two sub-beams by a beam splitter element. The sub-beams impinge on a focusing element (4) which focuses the at least three, particularly preferably four, sub-beams on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate, such that the sub-beams constructively and destructively interfere on or in the surface of the substrate. As a result of the laser interference process, a periodic point structure in the micrometer or sub-micrometer range is produced on or in the surface of the substrate (5), preferably a large-area and / or transparent substrate. The method is characterized in that the at least three sub-beams are superimposed in such a way that a one-dimensional pattern, in particular a linear pattern, is created.

[0162] The point structures produced in this way are in the form of periodically arranged inverted pyramids, the statistical mean value of the distance between the apexes, i.e. the center of one elevation or the centers of multiple elevations, being in the range from 50 nm to 50 pm, preferably in the range from 50 nm to 20 pm, particularly preferably in the range from 100 nm to 4 pm, more preferably in the range from 100 nm to 2 pm, even more preferably in the range from 200 nm to 1.5 pm, very particularly preferably in the range from 300 nm to 800 nm.

[0163] The inventors of the present application have further found that, in addition to the periodicity, the structure depth, i.e. the depth of the inverted pyramids measured from the saddle point of the indentation to the apex, or the profile depth, has an influence on the anti-reflective properties, as defined herein. For example, the statistical mean value of the structure depth or profile depth of the inverted pyramids, i.e. of the elevations and depressions, is in the range from 5 nm to 500 nm, preferably in the range from 5 nm to 300 nm, most preferably in the range from 5 nm to 100 nm, even more preferably in the range from 5 nm to 75 nm. The structure depth of the inverted pyramids of the interference pixels is typically described by the average structure depth (d50) which defines that 50% of the pyramids within the interference pixel have a structure depth which is less than or greater than a specified value of the structure depth.

[0164] According to a preferred embodiment of the present application, the inverted cone has a structure depth in the range from 5 nm to 200 nm, particularly preferably in the range from 5 nm to 150 nm, most preferably 10 nm to 100 nm.

[0165] Preferably, the device is used for manufacturing a patterned substrate (5), preferably a large-area and / or transparent substrate, which comprises two deflection elements (6), (7). The deflection elements (6), (7) are arranged in the light path (3) of the laser between the beam splitter element (2) and the focusing element (4). The deflection elements (6), (7) serve to enlarge the diffraction angle of at least three, particularly preferably four, sub-beams, wherein they interfere on the surface or inside of the substrate (5), preferably a large-area and / or transparent substrate. By adjusting the distance between the optical elements, it can be ensured that only the beam splitter element (2) needs to be moved along its optical axis in order to change the structure period. This can make the adjustment process during the machining easier.

[0166] In a particularly preferred embodiment, a transparent material is provided as a large-area substrate. Due to the translucency of the transparent material, a laser interference process inside the substrate is possible, preferably with the above-described embodiments of the device.

[0167] In a preferred embodiment, the device using a pulsed laser radiation source (1) is used for producing a patterned substrate, preferably a large-area and / or transparent substrate. In a particularly preferred embodiment, the device for producing a patterned substrate, preferably a large-area and / or transparent substrate, is used, which has a holding device for the substrate, which is freely movable in the xy plane perpendicular to the light path (3) of the laser beam emitted by the laser radiation source (1).

[0168] The pixel density Pd, i.e. the distance at which an interference pixel having a width D can be applied to the substrate, preferably a large-area and / or transparent substrate, can be adjusted via the frequency f of the laser radiation source (1) and the movement speed v of the holding device:

[0169] Pd = v / f

[0170] If the width D of the interference pixel is greater than the pixel density Pd, then adjacent interference pixels overlap in an area. This area is known to those skilled in the art as the pulse overlap OV. It can be calculated as:

[0171] OV = (D - Pd) / D

[0172] In a preferred embodiment, Pd is smaller than D during the manufacturing of the patterned substrate, preferably a large-area and / or transparent substrate. The resulting pulse overlap OV leads to a multiple irradiation of the substrate, preferably a large-area and / or transparent substrate. Preferably, thus, a non-textured surface can be avoided.

[0173] In a particularly preferred embodiment, the same interference pixels are irradiated multiple times during the manufacturing of the patterned substrate, preferably a large-area and / or transparent substrate. This enables to increase the depth of the resulting microstructure.

[0174] An advantage of the patterned substrate, preferably a large-area and / or transparent substrate, manufactured by such a method is the high regularity of the resulting periodic point structure in the micrometer or sub-micrometer range. The periodic point structure in the micrometer or sub-micrometer range manufactured in this way preferably has a coefficient of variation of the cross-section of the pyramids (value resulting from the standard deviation divided by the average value) of 15% or less, more preferably 10% or less, even more preferably 5% or less.

[0175] The multiple irradiation of the substrate is particularly suitable for manufacturing a layered structure. The multiple irradiation of the same interference pixels leads to at least partial melting of the substrate material, whereby during the patterning process, i.e. when the laser pulses hit the substrate, a wavy structure is formed due to the occurrence of high intensity regions. The structure, in particular the wavy structure, is formed by a self-assembly process. In particular, the wavy structure is superimposed on the periodic point structure in the micrometer or sub-micrometer range that can be produced by laser interference patterning. Thus, a layered patterning in the substrate can be produced by one process step. According to a preferred embodiment of the present application, the same interference pixels are thus irradiated multiple times on the substrate, preferably 2-fold to 400-fold, in particular 20-fold to 300-fold, particularly preferably 50-fold to 200-fold, whereby a wavy structure (as defined herein), in particular a periodic point structure formed by superimposed structures, is formed, wherein at least one structure has dimensions in the sub-micrometer range, in particular a quasi-periodic wave structure, and wherein at least one structure is formed by an inverted pyramid. The time offset between the pulses is particularly preferably in the range of the pulse duration of the laser pulses, preferably in the range from 1 fs to 100 ns, particularly preferably in the range from 10 fs to 10 ns, very particularly preferably in the range from 10 fs to 15 ps.

[0176] Layered patterning refers to a pattern in which a first structure having dimensions in the micrometer or sub-micrometer range corresponding to the interference pattern is superimposed with a further structure having dimensions smaller than the dimensions of the first structure and formed by a self-assembly process. Preferably, the dimensions of the further structure formed by the self-assembly process are in the range from 1% to 30% of the dimensions of the first structure corresponding to the interference pattern.

[0177] There are many application technical fields in which layered patterns are of interest, for example in the production of substrates having hydrophobic or superhydrophobic as well as hydrophilic or superhydrophilic surfaces, and substrates having anti-icing or anti-fogging properties in addition to the anti-reflective properties mentioned at the outset. Advantageously, the method described herein for producing such layered patterns enables precise adjustment of the process parameters influencing the structure size by appropriate selection of the laser radiation source and corresponding displacement of the beam splitter element in the light path of the laser.

[0178] In addition, the method defined herein enables the provision of substrates having layered patterns by the same apparatus, and moreover, in the same process step, while the conventional processes, which are carried out sequentially, i.e. cannot simultaneously produce the first structures having dimensions in the micrometer or sub-micrometer range corresponding to the interference pattern and the further structures formed by the self-assembly process.

[0179] Moving the substrate to be patterned (preferably a large-area and / or transparent substrate) in the laser beam is relatively time-consuming and slow due to the greater mass that is moved in the process. It is therefore advantageous to provide the substrate (preferably a large-area and / or transparent substrate) in a fixed position during processing and to focus the sub-beams on the surface or volume of the substrate by manipulating the laser sub-beams in the beam direction using optical elements (focusing mirrors or galvanometer scanners (laser scanners)) so that large-area patterning of the substrate is achieved. This can be very labor-saving or faster since less mass is moved in the process. Preferably, the substrate is stationary during processing.

[0180] By moving the substrate in the laser beam, two-dimensional patterning of the substrate is of course also possible in principle.

[0181] Due to the micrometer and / or nanometer range periodic structures produced by the method and apparatus disclosed herein, the substrates patterned in this way have anti-reflective properties. This is ensured by the fact that light incident on the substrate is reflected less or at flat angles, so that there is no "disturbing" effect when the material surface is viewed normally.

[0182] Therefore, the present application also encompasses a patterned substrate having anti-glare properties, said substrate comprising a periodic point structure in the micrometer or sub-micrometer range, wherein the periodic point structure is formed by inverted pyramids, wherein the inverted pyramids have a periodically arranged spacing in the range from 50 nm to 50 pm, preferably in the range from 50 nm to 20 pm, particularly preferably in the range from 100 nm to 4 pm, more preferably in the range from 100 nm to 2 pm, even more preferably in the range from 200 nm to 1.5 pm, more preferably in the range from 100 nm to 1000 nm, particularly preferably in the range from 300 nm to 800 nm, with respect to the saddle point or center point.

[0183] According to a preferred embodiment of the present application, the patterned substrate is obtained by processing with the method as defined herein.

[0184] The present application also relates to a method for manufacturing a substrate having a periodic point structure in the micrometer or sub-micrometer range by laser interference patterning, in particular by the method as disclosed herein, comprising the following steps:

[0185] a) applying a first pulse on the surface of the substrate (5), preferably by the device as defined herein, which generates a first interference pixel on the surface of the substrate (5) or in the substrate (5),

[0186] b) applying a second pulse on the surface of the substrate (5), preferably by the device as defined herein, which generates a second interference pixel on the surface of the substrate (5) or in the substrate (5),

[0187] wherein the first and the second interference pixel each comprise a periodic point structure having dimensions in the micrometer or sub-micrometer range, respectively,

[0188] characterized in that the offset between the second interference pixel and the first interference pixel is in the range of 10% < x < 50% of the interference period.

[0189] This is particularly beneficial for establishing structures on substrates having anti-glare properties, in particular on transparent substrates.

[0190] In the context of the present application, glare refers to the reflection of light from a light source (e.g. the sun) on a transparent substrate (e.g. a window or a screen), which can make it difficult to see what is happening on the screen.

[0191] These glare effects can be reduced by an anti-glare treatment of the surface, which is usually made by a coating in the prior art. Anti-glare structures scatter the incident light on the surface, so that the glare can be significantly reduced.

[0192] According to a preferred embodiment of the present application, the period of the point structure of the first interference pixel is the same as the period of the second interference pixel.

[0193] Further, it can be provided that after step b) a third pulse is applied on the surface of the substrate (5), preferably by means of the apparatus as defined herein, wherein the third interference pixels comprise a periodic point structure having a size in the micrometer and sub-micrometer range, wherein the third pulse generates third interference pixels on the surface of the substrate (5) or within the substrate (5), wherein the third interference pixels have an offset in the range of 10% < x < 50% of the interference period with respect to the second interference pixels.

[0194] Patterned substrate

[0195] The inventors have found that a substrate patterned mainly by means of the apparatus or method disclosed herein is characterized by pronounced anti-reflective properties. Thus, the present invention also relates to a patterned substrate having anti-reflective properties as defined herein, comprising a periodic point structure in the micrometer or sub-micrometer range, wherein the periodic point structure is formed by inverted pyramidal structures (also referred to as inverted pyramids herein), wherein the inverted pyramids have a periodically spaced arrangement in the range of from 50 nm to 50 pm, preferably in the range of from 50 nm to 20 pm, particularly preferably in the range of from 100 nm to 4 pm, more preferably in the range of from 100 nm to 2 pm, even more preferably in the range of from 200 nm to 1.5 pm, more preferably in the range of from 100 nm to 1000 nm, particularly preferably in the range of from 300 nm to 800 nm, with respect to their saddle points or center points.

[0196] The periodic point structure generated in this way has the property that incident electromagnetic radiation having a wavelength in the range of from 10 nm to 1 mm can be increasingly transmitted or diffracted by the periodic structure depending on its structure size, resulting in a reduced reflection at the surface of the substrate. If the period of the generated periodic point structure is in the wavelength range of the incident electromagnetic waves, diffraction occurs at the surface of the substrate. If the period of the generated periodic point structure is smaller than the wavelength of the incident electromagnetic waves, transmission occurs.

[0197] The periodic point structure is preferably formed such that the structured substrate transmits electromagnetic radiation having a wavelength of more than 550 nm at periodic point structures of less than 1000 nm, preferably more than 550 nm at periodic point structures of less than 750 nm, most preferably more than 450 nm at periodic point structures of less than 600 nm. Depending on the structure depth of the inverted pyramids, wavelengths in the red and / or yellow spectrum, the green spectrum and even the blue spectrum can be transmitted into the substrate.

[0198] Due to the established periodic point structure, the refractive index of the patterned substrate is gradually varying. The refractive index decreases gradually with the height of the structure, so that there is no distinct air-medium transition. This leads to an increased transmission of incident electromagnetic waves having a wavelength larger than the period of the generated point structure, and a diffraction of incident electromagnetic waves having a wavelength in the range of the period of the generated point structure.

[0199] Due to the very small structure size that can be manufactured, the apparatus and method for manufacturing an antireflective pattern disclosed herein are also suitable for manufacturing a surface having hydrophobic and / or superhydrophobic as well as hydrophilic and / or superhydrophilic properties.

[0200] The hydrophobic properties depend on the chemical properties and the surface properties of the substrate, in particular the surface roughness. The inventors have now surprisingly found that by the method according to the present application, in particular a hydrophobic substrate is obtainable by introducing structures in the micrometer and sub-micrometer range, in particular a substrate surface having a superhydrophobic and self-cleaning property (as defined herein) superimposed structure. A substrate having superhydrophobic properties is in particular preferably a substrate having a hierarchical surface pattern. A hierarchical surface pattern herein means that there is a surface having regular structures in the micrometer range (which in turn has a pattern on the surface having dimensions in the sub-micrometer range). Such a hierarchical pattern can lead to a high surface roughness.

[0201] The inventors have also found that a substrate patterned mainly by the apparatus or method disclosed herein is characterized by distinct hydrophobic properties on the surface of the substrate. By the apparatus and method for generating an antireflective pattern having dimensions in the micrometer and sub-micrometer range disclosed herein, it is also possible to generate a pattern of surface patterns, in particular a surface roughness on the surface of the substrate, which leads to a substrate having hydrophobic or superhydrophobic properties. The hydrophobic material properties can be generated by using direct laser interference patterning, thereby establishing structures having dimensions in the micrometer and / or sub-micrometer range. In a preferred embodiment, first structures having dimensions in the micrometer range are established on the surface. Subsequently, structures having dimensions in the sub-micrometer range are generated on the surface of the first structures by moving the beam splitter element in the light path of the laser, preferably by multiple irradiation of the substrate. The hierarchical pattern generated in this way has hydrophobic or superhydrophobic properties.

[0202] For manufacturing a substrate having hydrophobic properties, it is also conceivable to only manufacture structures having dimensions in the micrometer or sub-micrometer range without moving the beam splitter element in an intermediate step.

[0203] Beneficially, by the same method and based on the same apparatus, in a technically easy to implement manner, by manufacturing periodic point structures in the micrometer or sub-micrometer range and / or periodic point structures with a layered pattern in the micrometer and sub-micrometer range, it is thus possible to manufacture substrates with hydrophobic and / or superhydrophobic properties. By moving the beam splitter element, it is possible to implement at least two, but any number of additional structures on the surface of the substrate without additional changes to the setup, for example without exchanging optical elements or moving the substrate. This both increases the precision of the alignment of the structures and the process speed compared to conventional methods or apparatuses.

[0204] The inventors have established a correlation between the surface properties of a substrate and the icing on its surface. In particular, if the structure size on the surface of a substrate is small enough, a so-called anti-icing property can be generated. The results of the investigations have shown that a substrate with superhydrophobic properties can also exhibit anti-icing properties.

[0205] For the purposes of the present invention, anti-icing properties are understood to mean that no or only very little water ices on the surface of the substrate, which properties can be attributed to the surface properties, in particular the surface roughness.

[0206] Such a substrate can beneficially be used in the field of aerospace, wind turbines, automotive components, and in the field of telecommunications and antenna technology, to protect exposed components from icing.

[0207] The inventors have also found that a substrate patterned mainly by the apparatus or method disclosed herein is characterized by a distinct hydrophilic property on the surface of the substrate. By the apparatus and method disclosed herein for generating an anti-reflective pattern with dimensions in the micrometer and sub-micrometer range, the patterning can be used to generate a surface texture, in particular a surface roughness, on the surface of the substrate, which leads to a substrate with hydrophilic or superhydrophilic properties.

[0208] The hydrophilic material properties can be generated by establishing a pattern with dimensions in the micrometer and / or sub-micrometer range using direct laser interference patterning. In a preferred embodiment, a pattern with dimensions in the micrometer range is first established on the surface. Subsequently, by moving the beam splitter element in the laser light path, preferably by multiple irradiation of the substrate, a pattern with dimensions in the sub-micrometer range is generated on the surface of the first pattern. The layered structure generated in this way has hydrophilic or superhydrophilic properties.

[0209] For the manufacture of a substrate with hydrophilic properties, it is also conceivable to only manufacture a pattern with dimensions in the micrometer or sub-micrometer range without moving the beam splitter element in an intermediate step.

[0210] Beneficially, in a technically easy to implement manner, by the same process and based on the same apparatus, by manufacturing periodic point structures in the micrometer or sub-micrometer range and / or periodic point structures with a layered structure in the micrometer and sub-micrometer range, it is thus possible to manufacture substrates with hydrophobic and / or superhydrophobic properties. By moving the beam splitter element, it is possible to implement at least two, but any number of additional patterns on the surface of the substrate without additional changes to the structure, for example without exchanging optical elements or moving the substrate. This both increases the precision of the structure alignment and the process speed compared to conventional methods or apparatuses.

[0211] The inventors have established a correlation between the surface properties of a substrate and the formation of condensation, in particular in the form of fog or frost, on its surface. In particular, if the structure size on the surface of the substrate is small enough, a so-called anti-fogging property can be produced. The results of the investigations have shown that substrates with superhydrophilic properties can also exhibit anti-fogging properties.

[0212] In the context of the present invention, the anti-fogging property is understood to mean that no or only very little water condenses in the form of water droplets on the surface of the substrate, which property can be attributed to the surface properties, in particular the surface roughness.

[0213] Such a substrate can beneficially be used in the field of aerospace, in the field of automotive components or in the field of telecommunications and antenna technology, to protect exposed components from fogging.

[0214] In one embodiment of the present application, the methods and devices disclosed herein are suitable for the manufacture of a substrate comprising micrometer- or sub-micrometer-range periodic point structures which have been manufactured by laser interference patterning and which are characterized by antireflection properties. In the context of the present application, antireflection properties refer herein to an increased transmission or diffraction of incident electromagnetic radiation having a wavelength in the range of visible light, in particular having a wavelength in the range from 400 nm to 700 nm. The substrate is characterized by the fact that the periodic point structures comprised by it preferably have dimensions in the sub-micrometer range, in particular preferably in the nanometer range. It is particularly preferred that the dimensions of the periodic point structures are in the range of the wavelengths of electromagnetic radiation in the range of visible light. Thus, for the transmission or diffraction of red light, the dimensions of the periodic point structures are preferably in the range from 630 nm to 700 nm; for the transmission or diffraction of red and orange light, the dimensions of the periodic point structures are preferably in the range from 590 nm to 630 nm; for the transmission or diffraction of red, orange and yellow light, the dimensions of the periodic point structures are preferably in the range from 560 nm to 590 nm; for the transmission or diffraction of red, orange, yellow and green light, the dimensions of the periodic point structures are preferably in the range from 500 nm to 560 nm; for the transmission or diffraction of red, orange, yellow, green and blue-green light, the dimensions of the periodic point structures are preferably in the range from 475 nm to 500 nm; for the transmission or diffraction of red, orange, yellow, green, blue-green and blue light, the dimensions of the periodic point structures are preferably in the range from 450 nm to 475 nm; for the transmission or diffraction of orange, yellow, green, blue-green, blue and indigo light, the dimensions of the periodic point structures are preferably in the range from 425 nm to 450 nm; for the transmission or diffraction of red, orange, yellow, green, blue-green, blue, indigo and ultraviolet light, the dimensions of the periodic point structures are preferably in the range from 400 nm to 425 nm. Thus, the antireflection properties of the substrate can be controlled by varying the dimensions of the periodic point structures.

[0215] In one embodiment of the present application, the methods and devices disclosed herein are suitable for the manufacture of a substrate comprising micrometer- or sub-micrometer-range periodic point structures which have been manufactured by laser interference patterning and which are characterized by antireflection properties. In the context of the present application, antireflection properties refer herein to an increased transmission or diffraction of incident electromagnetic radiation having a wavelength in the range of non-visible light, in particular in the range of infrared or thermal radiation, in particular having a wavelength in the range from 780 nm to 1 mm. The substrate is characterized by the fact that the periodic point structures comprised by it preferably have dimensions in the micrometer range. Advantageously, the heat transfer of the substrate can be adjusted by varying the dimensions of the periodic point structures.

[0216] In one embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a periodic point structure in the micrometer or sub-micrometer range which has been manufactured by laser interference patterning and which is characterized by antireflection properties. In the context of the present application, antireflection properties refer herein to an increased transmission or diffraction of incident electromagnetic radiation having a wavelength in the range of non-visible light, in particular in the range of ultraviolet radiation (IV radiation), in particular having a wavelength in the range of 100 nm to 380 nm. The substrate is characterized by the fact that it comprises a periodic point structure which preferably has dimensions in the nanometer range. Advantageously, a substrate patterned in this way can be used in fields which require protection against UV radiation.

[0217] In a further embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a hierarchical pattern which has been generated by laser interference patterning of multiple irradiations of the same interference pixel and which is characterized by hydrophobic or superhydrophobic properties. Hydrophobic or superhydrophobic properties are due to the fact that structures having dimensions in the micrometer or sub-micrometer range, in particular hierarchical patterns having dimensions in the micrometer and sub-micrometer range, change the wetting angle of a liquid on the substrate in a way that it becomes larger. A larger wetting angle means that a liquid hitting the surface cannot wet it well but rather rolls off from it. A substrate treated in this way has self-cleaning and water-repellent properties. Materials which are particularly suitable for such a patterned substrate are materials which already have hydrophobic properties, such as metal or polymer surfaces.

[0218] In a further embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a hierarchical pattern which has been generated by laser interference patterning of multiple irradiations of the same interference pixel and which is characterized by anti-icing properties, i.e. properties which prevent the formation of an ice layer. Anti-icing properties are based on the fact that structures having dimensions in the micrometer or sub-micrometer range, in particular hierarchical patterns having dimensions in the micrometer or sub-micrometer range, change the wetting angle of a liquid on the substrate in a way that it becomes larger. Thus, the patterned substrate exhibits hydrophobic or superhydrophobic properties. A larger wetting angle means that a liquid hitting the surface cannot wet it well but rather rolls off from it. This also makes it more difficult for an ice layer to deposit on the surface. Materials which are particularly suitable for such a patterned substrate are materials which already have hydrophobic properties, such as metal or polymer surfaces.

[0219] In a further embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a hierarchical pattern which has been produced by laser interference patterning with multiple irradiations of the same interference pixel and which is characterized by hydrophilic or superhydrophilic properties. Hydrophilic or superhydrophilic properties are due to the fact that structures with dimensions in the micrometer or sub-micrometer range, in particular hierarchical patterns with dimensions in the micrometer and sub-micrometer range, change the wetting angle of a liquid on the substrate in such a way that it becomes smaller. The smaller wetting angle means that the liquid which hits the surface wets it very well and no water droplets are formed. In contrast, a uniform wetting is achieved which does not impair the transparency of the substrate. Materials which are particularly suitable for such a patterned substrate are materials which already have hydrophilic properties, such as glass surfaces.

[0220] In a further embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a hierarchical pattern which has been produced by laser interference patterning with multiple irradiations of the same interference pixel and which is characterized by anti-fogging properties (i.e. no-fogging properties). Anti-fogging properties are based on the fact that structures with dimensions in the micrometer or sub-micrometer range, in particular hierarchical patterns with dimensions in the micrometer or sub-micrometer range, change the wetting angle of a liquid on the substrate in such a way that it becomes smaller. The structured substrate thus exhibits hydrophilic or superhydrophilic properties. The smaller wetting angle means that the liquid which hits the surface wets it very well and no water droplets are formed. In contrast, a uniform wetting is achieved which does not impair the transparency of the substrate. Materials which are particularly suitable for such a patterned substrate are materials which already have hydrophilic properties, such as glass surfaces. Substrates patterned in this way can be used advantageously in the automotive and aerospace industries, but also generally in the field of glazing in the building technology.

[0221] In one embodiment of the present application, the methods and devices disclosed herein are suitable for manufacturing a substrate comprising a micrometer or sub-micrometer periodic point structure which has been produced by laser interference patterning. The micrometer or sub-micrometer periodic point structure is based on the fact that the surface texture is changed in the micrometer or sub-micrometer range by the periodic point structure introduced into the substrate, in particular on the fact that the surface of the substrate has elevations and depressions due to the introduced periodic point structure. In particular, an increased surface roughness can be achieved by patterning the substrate with the methods and devices described herein with a hierarchical pattern with dimensions in the micrometer and sub-micrometer range by laser interference patterning with multiple irradiations of the same interference pixel. Substrates processed in this way can be used advantageously in the manufacturing sector, for example to increase the static and / or sliding friction between technical components, or in the medical technology sector to increase the adhesion of cells on the outer surface.

[0222] In one embodiment of the present application, the methods and apparatuses disclosed herein are suitable for producing a substrate comprising a periodic point structure in the micrometer or sub-micrometer range produced by laser interference patterning, which has an increased surface area compared to an unpatterned substrate having the same outer dimensions. The periodic point structure in the micrometer or sub-micrometer range contributes to the fact that the surface area of the substrate increases proportionally to the density of the interference area per interference pixel. In particular, by patterning a substrate by means of the methods and apparatuses described herein, an increased surface area compared to an unpatterned substrate having the same outer dimensions can be achieved by means of laser interference patterning with a layered pattern having dimensions in the micrometer and sub-micrometer range by means of multiple irradiation of the same interference pixel. A substrate processed in this way can be advantageously used in the technical field of high heat conduction, since the increased surface area provides greater heat exchange capacity compared to an unpatterned substrate having the same outer dimensions. Furthermore, a substrate processed in this way can be used in the technical field of electrical connection technology in order to reduce the contact resistance, since the increased surface area means that more contact points between the materials to be contacted can be produced compared to an unpatterned substrate having the same outer dimensions. In addition, a substrate patterned in this way can be used in the technical field of battery technology, in particular for patterning anodes and cathodes, since the increased surface area means that there is more ability for exchange of charge carriers between the metals of the electrodes compared to an unpatterned substrate having the same outer dimensions.

[0223] Furthermore, the methods and apparatuses disclosed herein are suitable for manufacturing a substrate comprising a periodic point structure having dimensions in the micrometer or sub-micrometer range, which has antibacterial (antiseptic) properties. In a preferred embodiment, the periodic point structure has a much larger (at least 10 to 30 percent larger) size than the bacteria deposited thereon. This isolates the bacteria deposited on the surface and thus renders them harmless. In a particularly preferred embodiment, the periodic point structure has a much smaller (at least 10 to 30 percent smaller) size than the bacteria deposited thereon. This prevents the bacteria from adhering to the surface and keeps the surface sterile.

[0224] The patterned substrate manufactured by the methods and apparatuses disclosed herein is also suitable for further processing by a further coating process, in which the substrate can receive a physical and / or chemical coating. Such a coating can enhance the properties of the patterned substrate, such as antireflection properties and / or hydrophilic and / or hydrophobic properties. It is conceivable to apply a chemical spray coating and / or to apply a coating by chemical vapor deposition and / or sputtering and / or a sol-gel process.

[0225] According to a preferred embodiment of the present application, the patterned substrate comprises a dot structure formed by first and second interference pixels, wherein the first and second interference pixels each independently comprise a periodic dot structure having dimensions in the micrometer and sub-micrometer range, wherein the first interference pixels and the second interference pixels are arranged on top of each other such that the offset between the second interference pixels and the first interference pixels is in the range of 10% < x < 50% of the interference period, especially in the range of 20% < x < 50% of the interference period, particularly preferably in the range of 25% < x < 45% of the interference period. This is particularly beneficial, as by the dimensions of the dot structure defined herein (regardless of its application area) on the substrate, especially on a transparent substrate, a pattern with anti-glare properties can be manufactured.

[0226] According to a preferred embodiment of the present application, the periodic dot structure is designed such that at least a third interference pixel is superimposed on the first and second interference pixels such that the offset between the third interference pixel and the second interference pixel is in the range of 10% < x < 50% of the interference period, especially in the range of 20% < x < 50% of the interference period, particularly preferably in the range of 25% < x < 45% of the interference period.

[0227] Use of the patterned substrate

[0228] For example, the patterned substrate with anti-reflective properties defined herein is used in photovoltaic systems, whereby by introducing anti-reflective properties the efficiency of these photovoltaic systems can be significantly increased. A major challenge in the field of photovoltaic systems is the huge loss caused by reflection of the sun rays. On average, reflection causes a 40% energy / power loss per system. Therefore, the efficiency of photovoltaic systems has to be constantly increased. One of the most promising approaches is to reduce reflection by means of anti-reflective coatings and / or surface texturing. The use of the process disclosed herein simplifies, accelerates and improves the surface treatment.

[0229] It is also known that monitors and screens are usually placed in fixed positions and are therefore susceptible to the effects of adverse light incidence, which leads to visual problems for the viewer. Although ways exist to minimize this effect, these methods are not widely used, as they tend to just alleviate the symptoms rather than actually solve the problem. For example, the patterned substrate with anti-reflective properties defined herein is very suitable for application or integration into the field of displays, for example, in the form of anti-reflective glass for monitors, screens and display screens.

[0230] Another application area opens up possibilities for achieving anti-reflection within optical fibers, ensuring higher transmission rates and minimizing back reflections. Therefore, the process disclosed herein is well-suited for patterning glass fibers, providing further application examples of the patterned substrates with anti-reflection properties defined herein. Consequently, the invention also includes using the patterned substrates defined herein as components of glass fibers.

[0231] Furthermore, the inventors have discovered that the method defined herein is applicable to patterning window glass (as another example of anti-reflective glass). For example, the patterned substrate disclosed herein can be used in the form of anti-reflective glass, or as a thin film coating on the exterior walls of buildings, preferably a large-area and / or transparent substrate, as, for example, insulating glass that can be used to prevent concentrated solar radiation from curved exterior walls of buildings and improve the thermal insulation performance of buildings.

[0232] Furthermore, reducing reflections in microscopes and telescopes can improve the contrast of images recorded by them, thereby improving the efficiency and usability of these optical devices. Therefore, the present invention also includes the use of the patterned substrate defined herein as an optical element having a periodic dot structure in the micrometer or submicrometer range in optical devices such as microscopes and telescopes, for which beam guiding, beam shaping, beam focusing, and / or beam focusing are necessary.

[0233] Using the patterned substrates defined herein as molds (so-called master molds) is also useful, for example, in applying or creating structures on another substrate midway through an embossing process. For instance, it is suitable in roll-to-roll processes where structures are continuously transferred from a master mold (typically a metal such as nickel) to a polymer film (e.g., PET) using hot embossing or UV embossing processes. This allows for the high-throughput fabrication of inverted structures as periodic point structures in the micron or submicron range on other substrates.

[0234] The apparatus and method according to the invention also provide the possibility of manufacturing large-area substrates with hydrophobic or superhydrophobic properties without significant technical effort. Substrates patterned in this manner have wide applications in fields requiring self-cleaning properties of hydrophobic and / or superhydrophobic substrates, such as in automotive parts, displays, or glass, and in the aerospace or antenna technology fields.

[0235] The device according to the invention and the method according to the invention also provide the possibility of manufacturing large-area substrates with hydrophilic or superhydrophilic properties without a great deal of technical effort. In the field of substrates that require uniform wetting properties of the hydrophilic and / or superhydrophilic substrates, for example in the field of automotive components, displays or glass, and in the field of aviation or antenna technology, the substrates patterned in this way have a wide range of applications.

[0236] Furthermore, the method and the device according to the invention also provide the possibility of manufacturing patterned substrates that are suitable for further processing, for example chemical and / or physical treatment, in particular by means of chemical spray coating and / or in order to increase and / or change the antireflection properties and / or the hydrophobic or superhydrophobic and / or the hydrophilic or superhydrophilic properties of the resulting substrates.

[0237] According to a preferred embodiment of the invention, the method disclosed herein is suitable for patterning a substrate surface such that it has anti-glare properties. Particularly suitable for this purpose is a patterned substrate having a dot structure, as defined herein, which dot structure is formed by a first and a second interference pixel, wherein the first and the second interference pixel each independently comprise a periodic dot structure having a size in the micrometer and sub-micrometer range, wherein the first interference pixel and the second interference pixel are arranged on top of each other such that the offset between the second interference pixel and the first interference pixel is in the range of 10% < x < 50% of the interference period, in particular in the range of 20% < x < 50% of the interference period, particularly preferably in the range of 25% < x < 45% of the interference period.

[0238] List of reference signs

[0239] 1 laser radiation source

[0240] 2 beam splitter element

[0241] 3 optical path

[0242] 4 focusing element

[0243] 5 substrate

[0244] 6 further deflection element

[0245] 7 deflection element

[0246] 8 polarization element

[0247] 9 focusing mirror or galvanometer mirror

[0248] 31 optical axis

[0249] 91 polygon wheel BRIEF DESCRIPTION OF DRAWINGS

[0250] The application is explained in further detail using the following figures and examples without limiting the application to these. In particular, features shown in the figures and described for the respective examples are not limited to the respective examples.

[0251] Herein

[0252] Figure 1 : Schematic perspective view of a device according to the application.

[0253] Figure 2 : Schematic perspective view of a device according to the application, comprising a deflection element (6) for parallelizing the sub-beams.

[0254] Figure 3 : Schematic perspective view of a device according to the application, comprising a deflection element (7) for widening the angle of the sub-beams relative to the optical axis of the light path (3).

[0255] Figure 4A : Schematic perspective view of a device according to the application, comprising an optical element (6) having a plane reflective surface deflecting the partial beams onto the focusing element (4).

[0256] Figure 4B : Schematic perspective view of a device according to the application, comprising a galvanometer (9) as an optical element for beam shaping, which allows for a fixed positioning of the substrate to be patterned during the patterning process.

[0257] Figure 5: Schematic perspective view of a device according to the application, wherein the device comprises a polarization element (8) which shifts the phase trajectories of the sub-beams relative to each other, wherein

[0258] a) The beam splitter element (2) is located in the light path (3) close to the laser radiation source (1).

[0259] b) The beam splitter element (2) is located in the light path (3) close to the deflection element (7).

[0260] Figure 6 : Schematic view of the interference pixels generated on or in the surface of a substrate having a width D and the distribution of the interference pixels on or in the surface of the substrate, the interference pixels being shifted relative to each other by a pixel density Pd.

[0261] Figure 7 : Schematic perspective view of a patterned substrate (5) having generated periodic point structures consisting of inverted pyramids on the patterned substrate, the dimensions being in the micrometer and sub-micrometer range and symbolizing the transmission of incident electromagnetic waves having a wavelength greater than the period of the generated structures and the diffraction of incident electromagnetic waves having a wavelength in the range of the generated structures or smaller than the generated structures.

[0262] Figure 8 A schematic perspective view of the device according to the invention includes a galvanometer (9) and a polygonal wheel (91) as optical elements, the galvanometer having a planar reflective surface that reflects a sub-beam onto a focusing element (4).

[0263] Figure 9 Graphical representation of the diffraction angle and wavelength of incident light for patterned substrates with three different structural widths.

[0264] Figure 10 : A schematic three-dimensional view of a patterned substrate (5), wherein the patterned substrate has a generated periodic point structure composed of inverted cones with a size in the micrometer range, and a periodic wave structure in the submicrometer range superimposed thereon. Detailed Implementation

[0265] Figure 1 The first embodiment shows an apparatus according to the invention, which includes a laser radiation source (1) for emitting a laser beam. A beam splitter element (2) is movably arranged in the optical path (3) of the laser beam following the laser radiation source (1). A focusing element (4) is located in the optical path (3) of the laser beam following the beam splitter element (2). A holding device is arranged in the optical path (3) of the laser beam following the focusing element (4), on which a substrate (5), preferably a large-area and / or transparent substrate, is mounted.

[0266] In this embodiment, the laser radiation source (1) emits a pulsed laser beam. In this case, the laser radiation source is an ultraviolet laser with a wavelength of 355 nm and a pulse duration of 12 ps. In this embodiment, the radiation profile of the laser radiation source corresponds to a flat-top profile.

[0267] In this embodiment, the beam splitter element (2) corresponds to the diffraction beam splitter element. Here, the diffraction beam splitter element is a beam splitter element containing microstructures or nanostructures. The beam splitter element (2) divides the laser beam into 4 sub-beams.

[0268] In this embodiment, the focusing element (4) corresponds to a refracting spherical lens, which directs sub-beams extending substantially parallel to each other onto a substrate (5) in such a way that they interfere in the interference region, preferably a large-area and / or transparent substrate. In this embodiment, the interference angle corresponds to 27.2°, resulting in a structural period of 550 nm for the periodic point structures in the same polarization state.

[0269] According to this example, a large-area substrate is irradiated once, resulting in a processing time of 12 ps per structural unit (i.e., per interference pixel).

[0270] A substrate (5), preferably a large-area and / or transparent substrate, is a glass, in particular quartz glass, which is mounted on a holding device in such a way that it can be moved in the xy plane, perpendicular to the optical path of the laser beam emitted by the laser radiation source (1).

[0271] Figure 2 The device as described in the foregoing is embodied in a further embodiment as Figure 1 The device as described in the foregoing is embodied in a further embodiment as

[0272] In this embodiment, the deflection element is a conventional refractive convex lens. The sub-beams hit the deflection element (6) in such a way that they are substantially parallel to each other after passing through the deflection element. This allows the point at which the sub-beams interfere on the surface of the substrate or inside the substrate to be adjusted.

[0273] Figure 3 The device as described in the foregoing is embodied in a further embodiment as Figure 1 and Figure 2 The device as described in the foregoing is embodied in a further embodiment as

[0274] In this embodiment, the further deflection element (7) is a conventional refractive concave lens. The sub-beams hit the further deflection element in such a way that their angle to the optical axis of the optical path widens. This allows the angle of interference at which the sub-beams interfere on the surface of the substrate, preferably a large-area and / or transparent substrate, or inside the substrate to be changed.

[0275] In this embodiment, all optical elements except the beam splitter element (2) are fixed along the optical axis of the optical path (3). The angle of interference of the sub-beams on the substrate is set by moving the beam splitter element (2) along the optical axis of the optical path.

[0276] Figure 4A The device as described in the foregoing is embodied in a further embodiment as Figure 3 The device as described in the foregoing is embodied in a further embodiment as

[0277] In this embodiment, at least three sub-beams are deflected onto the substrate at a preferred angle by displacing the optical element (6). This means that a deflection element in the form of a lens (6) can be dispensed with. Figure 3

[0278] Figure 5 shows in a further embodiment the device as described in the foregoing as Figure 3 ​The device according to the application comprises a polarization element (8) arranged in the light path (3) of the laser beam between the deflection element (6) and the focusing element (4) for each sub-beam.

[0279] The polarization element is arranged in such a way that the polarization of the sub-beams relative to each other is changed in a way that leads to a change of the interference pattern.

[0280] The present embodiment is shown in two different configurations. In Fig. 5a) the beam splitter element (2) is located close to the laser radiation source (1) in the light path (3). In Fig. 5b) the beam splitter element (2) is located close to the deflection element (7) in the light path (3). In this way the interference pattern of the sub-beams interfering on the surface of the substrate (5) can be adjusted indefinitely without the need to move other optical elements in the device or the substrate.

[0281] It is also conceivable that the device comprises an additional optical element for beam shaping arranged consecutively to the laser radiation source (1) in the light path (3) of the laser beam. In the present 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 flat-top profile.

[0282] Figure 6 Schematic representation of the interference pixels generated on or in the surface of a substrate having a width D and the distribution of the interference pixels on or in the surface of the substrate, whereby the interference pixels are displaced relative to each other with a pixel density Pd.

[0283] In this embodiment the pixel density Pd is smaller than the width D of the interference pixels. Thus, by moving the substrate (5) with the help of the pulsed laser beam a large area of uniform periodic point structures can be generated on or in the surface of the substrate, preferably a large area and / or transparent substrate.

[0284] Figure 7 A patterned substrate (5) manufactured by the method according to the application is shown, which has a generated periodic point structure consisting of inverted pyramids, the dimensions of which are in the micrometer and sub-micrometer range. The transmission of incident electromagnetic waves with a wavelength larger than the structure period of the generated structure and the diffraction of incident electromagnetic waves with a wavelength in the range of the generated structure or smaller than the generated structure are also illustrated symbolically in the figure.

[0285] Figure 8 In another embodiment it is shown that the device according to the application comprises a polarization element (8) arranged in the light path (3) of the laser beam between the deflection element (6) and the focusing element (4) for each sub-beam. Figure 4BApparatus comprising an optical element (91) with a planar reflective surface, the optical element being a polygonal wheel configured such that it rotates about an axis of the mark. Incident sub-beams are deflected in such a way that they hit the galvanometer (9), which directs the light beam onto the substrate via the focusing element (4). During the exposure process, the rotation of the polygonal wheel moves the point at which the light beam is focused on the substrate along a straight line. As a result, the sub-beams scan the substrate, which leads to an increased processing speed.

[0286] Figure 9 A graphical representation showing the transmission and diffraction capabilities of a patterned substrate as a function of the structure width. The diffraction angle of light is shown as a function of the wavelength for structures with three different structure widths. If the wavelength of the incident light is larger than the structure width, the light is transmitted completely. When the wavelength is in the range of the structure width or smaller, diffraction occurs. The diffraction angle can be derived from the graph.

[0287] Figure 10 A patterned substrate (5) manufactured by the method according to the invention is visualized, which has a resulting periodic point structure consisting of inverted pyramids, the size being in the micrometer range. Superimposed on this periodic point structure in the micrometer range is a periodic wave structure in the sub-micrometer range, which can also be manufactured in one manufacturing step by the method according to the invention described herein.

Claims

1. A patterned substrate with anti-reflective properties, comprising a periodic dot structure in the micrometer or submicrometer range, in, The periodic point structure is formed by an inverted cone. The inverted cones are arranged periodically, with a spacing between them ranging from 50 nm to 50 µm. The other structures are superimposed on the periodic point structure. The superimposed structure has a quasi-periodic wave structure, wherein the material on the surface of the substrate in the region of the superimposed structure has continuous peaks and troughs with a period in the range of 100nm to 1000nm.

2. The patterned substrate according to claim 1, wherein, The periodic dot structure is formed such that the structured substrate transmits electromagnetic radiation with a wavelength greater than 550 nm at the periodic dot structure with a wavelength less than 1000 nm.

3. The patterned substrate according to claim 2, wherein, The periodic dot structure is formed such that the structured substrate transmits electromagnetic radiation with a wavelength greater than 500 nm at the periodic dot structure with a wavelength less than 750 nm.

4. The patterned substrate according to claim 3, wherein, The periodic dot structure is formed such that the structured substrate transmits electromagnetic radiation with a wavelength greater than 450 nm at the periodic dot structure with a wavelength less than 600 nm.

5. The patterned substrate according to claim 1, comprising a periodic dot structure in the micrometer or submicrometer range, wherein, The periodic wave structure is superimposed on the periodic point structure.

6. The patterned substrate according to claim 1, wherein, The patterned substrate includes a dot structure formed by first and second interference pixels, wherein the first and second interference pixels each independently include a periodic dot structure having dimensions in the micrometer and / or submicrometer range, wherein the first interference pixel and the second interference pixel are arranged overlapping each other such that the offset between the second interference pixel and the first interference pixel is in the range of 10% ≤ x ≤ 50% of the interference period.

7. The patterned substrate according to claim 6, wherein, The periodic point structure is formed such that at least a third interference pixel is arranged overlapping the first and second interference pixels, such that the offset between the third interference pixel and the second interference pixel is within the range of 10% ≤ x ≤ 50% of the interference period.

8. The patterned substrate according to claim 1, wherein, The substrate includes physical and / or chemical coatings.

9. The patterned substrate according to claim 1, wherein, The patterned substrate includes a transparent material, wherein the transparent material is selected from the group consisting of glass, solid polymers, transparent ceramics, or mixtures thereof.

10. The patterned substrate according to claim 1, wherein, The refractive index of the patterned substrate is gradually varying.

11. The patterned substrate according to claim 1, wherein, The substrate has hydrophobic or superhydrophobic properties.

12. The patterned substrate according to claim 1, wherein, The substrate has anti-icing properties.

13. The patterned substrate according to claim 1, wherein, The substrate has hydrophilic or superhydrophilic properties.

14. The patterned substrate according to claim 1, wherein, The substrate has anti-fogging properties.

15. A laser interference patterning apparatus for direct laser interference patterning of a substrate to manufacture the patterned substrate according to claim 1, comprising: - Laser radiation source (1), which is used to emit a laser beam, - Beam splitter element (2), which is arranged in the optical path (3) of the laser beam, - A focusing element (4), which is arranged in the optical path of the laser after the beam splitter element, and configured such that the sub-beam passes through the focusing element in such a way that the sub-beam can interfere in the interference region on the surface or in the volume of the substrate (5). Its features The beam splitter element (2) is able to move freely along its optical axis in the optical path (3). The beam splitter element (2) is configured to split the incident laser beam emitted by the laser radiation source (1) into at least three sub-beams. In the optical path (3) of the laser radiation source (1), a first deflection element (7) is arranged after the beam splitter element (2), and the first deflection element is configured such that at least three sub-beams are widened when passing through the first deflection element (7).

16. The device according to claim 15, wherein, In the optical path (3), following the laser radiation source (1) and the beam splitter element (2), there is an additional deflection element (6) configured to deflect the sub-beams in such a way that they extend substantially parallel to each other after the sub-beams have detached from the additional deflection element (6).

17. The device according to claim 15, wherein, The beam splitter element (2) is a diffraction type beam splitter element or a refractive type beam splitter element.

18. The device according to claim 15, wherein, The first deflection element (7) is a concave lens.

19. The device according to claim 16, wherein, The other deflection element (6) is a convex lens.

20. The device according to claim 15, wherein, The focusing element (4) is a convex lens.

21. The device according to claim 16, wherein, The device includes at least one polarizing element (8) arranged in the optical path between the first deflecting element and the other deflecting element and the focusing element.

22. The device according to claim 15, wherein, The laser radiation source is a pulsed laser radiation source with a pulse width ranging from 10 nanoseconds to 10 femtoseconds.

23. The device according to claim 15, wherein, The radiation profile of the laser beam emitted by the laser radiation source corresponds to a Gaussian profile or a flat-top profile.

24. The device according to claim 15, wherein, Additional optical elements capable of beam shaping are located in front of the beam splitter elements.

25. The device according to claim 15, wherein, The device includes a holding device, the substrate is mounted on the holding device, and the holding device is movable in the xy plane perpendicular to the optical path (3) of the laser beam (1) emitted by the laser radiation source.

26. The device according to claim 15, wherein, The substrate comprises a transparent material.

27. A method for fabricating a substrate with periodic point structures in the micrometer or submicrometer range by laser interference patterning, comprising the following steps: a) Provide a base (5), b) A laser beam is emitted from the laser radiation source (1). c) The laser beam is split into at least three sub-beams by a beam splitter element (2). d) Focus the sub-beam onto the surface or volume of the substrate (5) such that the sub-beam constructively and destructively interferes with the surface or volume of the substrate. The characteristic feature is that the at least three sub-beams are superimposed on the substrate by focusing, thereby generating a periodic point structure in the micrometer or submicrometer range on the surface or within the volume of the substrate. The periodic point structure is formed by an inverted cone. The inverted cones are arranged periodically, with a spacing between them ranging from 50 nm to 50 µm. The other structures are superimposed on the periodic point structure. The superimposed structure has a quasi-periodic wave structure, wherein the material on the surface of the substrate in the region of the superimposed structure has continuous peaks and troughs with a period in the range of 100nm to 1000nm.

28. The method according to claim 27, wherein, By moving the beam splitter element (2) along its optical axis in the optical path (3), the structural period of the periodic point structure generated on the substrate (5) can be continuously adjusted in the micrometer or submicrometer range.

29. The method according to claim 27, wherein, The substrate (5) comprises a transparent material, and the sub-beam interferes within the transparent material.

30. The method of claim 27, further comprising the following steps: I) A first pulse is applied to the surface of the substrate (5), which generates a first interference pixel on the surface of the substrate (5) or within the substrate (5). II) A second pulse is applied to the surface of the substrate (5), which generates a second interference pixel on or within the surface of the substrate (5). The first and second interference pixels each independently comprise periodic point structures with dimensions in the micrometer and submicrometer range, respectively. The offset between the second interference pixel and the first interference pixel is within the range of 10% ≤ x ≤ 50% of the interference period.

31. The method according to claim 30, wherein, The point structures of the first interference pixel and the second interference pixel have the same period.

32. The method according to claim 30, wherein, Following step b), a third pulse is applied to the surface of the substrate (5), wherein the third interference pixel comprises a periodic dot structure having dimensions in the micrometer and submicrometer range. The third pulse generates a third interference pixel on the surface of the substrate (5) or in the substrate (5), wherein the third interference pixel has an offset relative to the second interference pixel within the range of 10% ≤ x ≤ 50% of the interference period.

33. The method according to claim 30, wherein, The offset of the interference period is consistent in at least one spatial direction.

34. The application of the patterned substrate according to claim 1 in a photovoltaic system.

35. The application of the patterned substrate according to claim 1 as anti-reflective glass for monitors, screens and displays.

36. The application of the patterned substrate according to claim 1 in glass fiber.

37. The patterned substrate according to claim 1 as an application of a negative mold for indirectly applying or creating a pattern on another substrate.

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