Coating method and silicon-containing coating

Abstract

The invention relates to a method for coating a substrate (2), comprising the following steps: - providing a transparent carrier foil (21) coated with silicon, - positioning the side of the carrier foil (21) coated with silicon on a surface of the substrate (2), - rastering the coated carrier foil (21) with laser radiation, whereby silicon is point-wise detached from the carrier foil (21) and deposited on the substrate (2) as a porous, rough, superhydrophilic layer (6).

Description

[0001] The invention relates to a coating method in which a material is transferred from a carrier foil to a substrate by means of laser radiation. The invention also relates to a porous silicon-containing coating.

[0002] DE 10 2018 109 337 A1 discloses a method for producing transparent conductive oxide coatings, particularly indium tin oxide coatings. In this method, a transparent carrier body coated with multiple layers, such as tin, is placed on a substrate, and the material is subsequently transferred from the carrier body to the substrate. The resulting indium tin oxide layer (ITO layer) on the substrate exhibits lyophobic properties, which remain even when the coating is subjected to mechanical stress.

[0003] The method for coating substrates described in WO 2016 / 055166 A2, which also operates with the aid of a laser, provides for coating a carrier foil made of polyethylene terephthalate (PET). In a method step prior to laser transfer, the coating material to be transferred to the substrate by laser guidance is deposited on the carrier foil by physical vapor deposition. The laser irradiation is performed in such a way that the coating material is only partially transferred from the carrier foil to the substrate.

[0004] In the method for laser-guided material transfer described in US 2002 / 0098614 A1, the laser is located outside the chamber in which the laser transfer occurs. The chamber may be a vacuum vessel or a vessel filled with an inert gas.

[0005] WO 03 / 080334 A1 describes in detail a multilayer laser transfer film for permanently inscribing components. In this case, in addition to an adhesive layer, at least two pigment layers are present on a carrier layer, one of which contains a glass flux pigment and the second contains a laser-sensitive pigment. Possible carrier materials include, in particular, PVC films and PET films.

[0006] EP 1 954 507 B1 deals with the laser transfer of security features. In this case, it proposes integrating non-reproducible security features into a layer system for marking products with anti-counterfeiting features and transferring them to the products using laser radiation. During the laser transmission, the laser energy is absorbed by laser-sensitive substances, such as carbon or metal oxides.

[0007] EP 1 942 961 B1 describes a method for producing an open-porous, biocompatible surface layer for implants. In this method, titanium particles are coated with a sintering aid, which may be silicon or cobalt.

[0008] The object of the present invention is to provide a further development of the prior art by providing a possibility for coating substrates with porous silicon-containing materials, which is characterized by high process reliability and product quality and a wide range of possible applications.

[0009] According to the invention, this object is achieved by the following method for substrate coating:

[0010] - providing a transparent carrier foil (21) coated with silicon,

[0011] - positioning the side of the carrier foil (21) coated with silicon on the surface of the substrate (2),

[0012] The coated carrier foil ( 21 ) is subjected to raster-like impact with laser radiation, whereby silicon is detached from the carrier foil ( 21 ) in a punctiform manner and deposited as a porous, rough, superhydrophilic layer ( 6 ) on the substrate ( 2 ).

[0013] This task is also accomplished by coatings that completely or partially cover the substrate as follows:

[0014] The coating is formed as a porous superhydrophilic layer (6) at least on a first sub-region (4) of the substrate (2), deposited on the substrate (2) by rastering laser radiation with a carrier of a silicon coating, and has lower roughness and thickness in regions (11) spaced apart from each other in a pattern corresponding to the grating of the laser radiation, wherein intermediate regions (12) located between these spaced-apart regions (11), which also belong to the superhydrophilic layer (6) and are also mainly formed by silicon deposited on the substrate (2), have relatively higher roughness and thickness.

[0015] The configurations and advantages explained below in relation to the device, ie the coating, of the present invention also apply mutatis mutandis to the coating method and vice versa.

[0016] The coating method comprises the following steps:

[0017] - providing a transparent carrier foil coated with silicon,

[0018] - positioning the side of the carrier foil coated with silicon on the surface of the substrate,

[0019] The coated carrier foil is subjected to raster-like impact with laser radiation, whereby the silicon is detached from the carrier foil in a spot-like manner and deposited as a porous, rough, superhydrophilic layer on the substrate.

[0020] The superhydrophilicity of this layer means that a drop of water applied to it immediately disperses and flows away, i.e., the contact angle is 0°. In particular, the contact angle can be an imaginary number. For example, when a drop of water is dropped onto a superhydrophilic layer, it produces a hypothetical contact angle of 6°. For background information on hypothetical contact angles produced on superhydrophilic surfaces, reference is made to WO 2013 / 087073 A2.

[0021] As is generally known from the prior art, physical vapor deposition (PVD) is particularly suitable as a method for depositing silicon on a carrier foil. A pure silicon target or, in the case of sputtering, a target doped with a small amount of aluminum, for example, can be used as the starting material for sputtering or vapor deposition. Regardless of how the silicon-containing starting layer is deposited on the carrier foil, the laser transfer layer formed on the substrate is more adherent and porous than the starting layer.

[0022] PET films can be used, in particular, as carrier foils. Alternatively, carrier foils made of other plastics, such as PVC, PMMA, or PE, as well as glass carrier plates, are conceivable. The carrier object, particularly in the form of a carrier foil, is typically a few μm or tens to hundreds of μm thick. For example, the thickness of a transparent PET carrier foil ranges from 6 μm to 125 μm. The carrier foil can be in particular in the form of a roll, with the coating applied using a roll-to-roll coater, i.e., using roll-to-roll technology. For roll-to-roll coating methods, reference is made, for example, to EP 2 527 048 B1, DE 10 2010 048 984 A1, and DE 10 2015 109 809 A1.

[0023] A carrier plate made of glass typically has a thickness of one to several millimeters. Silicon on a rigid or flexible carrier material has, for example, a thickness in the range from 300 nm to 2 μm or 3 μm, in particular a thickness of approximately 700 nm.

[0024] The super-hydrophilic silicon-containing layer can have a microstructure that is not discernible to the naked eye. This is produced by directing laser radiation in the form of individual raster points at the carrier foil. In this case, each raster point of the laser radiation has a normalized diameter, which is defined as the diameter at which 68.27% of the incident power lies within a circle with the normalized diameter. The average distance between two adjacent raster points is preferably at least 125% and at most 250% of the normalized diameter.

[0025] The layer produced on the substrate by rasterized laser radiation has a non-uniform thickness, wherein low-thickness areas are unexpectedly found where the laser radiation is incident with maximum intensity. This means that the pattern described by the low-thickness areas corresponds to the pattern described by the laser radiation acting approximately in a point-like manner, i.e. the raster points. Between the low-thickness areas represented by the raster point pattern, intermediate areas of the coating are formed, in which silicon is also deposited on the substrate. In the intermediate areas, the coating is not only thicker than in the aforementioned areas, but also rougher, generally forming a regular dot pattern. In particular, the intermediate area can include a plurality of individual needles, which are located on the substrate in the form of individual tips. In extreme cases, the entire mesh-like intermediate area consists entirely of such needles. The needles can be explained as material splashes, which are completely or mainly attached to the substrate outside the relatively dense areas of low roughness and thickness produced by the more intense laser radiation.

[0026] The individual circular areas of low roughness and thickness, also referred to as laser spots, have a diameter of, for example, 22 to 25 μm. The distance between two laser spots, measured between their centers, is, for example, 33 to 43 μm. Accordingly, the minimum width of the intermediate area between two laser spots is approximately 10 to 20 μm. The layer thickness in the intermediate area is, for example, at least twice, in particular at least three times, the layer thickness in the raster-like arrangement of the areas of low roughness and thickness.

[0027] Regardless of which geometry describes the microscopically discernible grating within the superhydrophilic layer, the coating parameters can vary within the layer. Furthermore, a subregion of the substrate formed as a porous, superhydrophilic, microstructured layer can be adjacent to at least one other subregion of the substrate, wherein the adjacent subregion of the substrate, also when completely or predominantly coated with silicon, is less hydrophilic than the hydrophilically coated subregion. It is also possible that completely different coated or uncoated subregions are adjacent to superhydrophilically coated subregions. In all cases, the hydrophilic properties of the substrate surface can abruptly change at the boundaries between different subregions.

[0028] In a typical method, silicon is transferred to the substrate, primarily in liquid form, by rastering laser radiation onto a carrier foil. For this material transfer, laser radiation with a power of 1.0 to 6.0 W, a frequency of 10 to 200 kHz, a laser speed of 500 to 4,000 mm / s, and a laser line spacing of 0.02 to 0.3 mm is used, for example.

[0029] The porous, super-hydrophilic silicone coating formed as a laser transfer layer on a substrate can be designed in any pattern visible to the naked eye. For example, such a pattern can be formed as a striped pattern on the substrate. Alternatively, the laser transfer layer can be applied as text, graphics, or evenly over the entire surface, i.e., over a larger area. In all cases, the layer surface can be matte or rough. In many configurations, assuming a transparent substrate, the laser transfer layer appears as a brown layer on both the front and back sides. Depending on the thickness, structure, and precise composition of the layer, it can be completely opaque or slightly translucent.

[0030] Irradiating the carrier foil under atmospheric conditions is possible within a very wide range of possible laser parameters. Depending on the laser radiation parameters, the silicon can react with components of the air during transfer from the carrier foil to the substrate, resulting in a silicon-based layer on the substrate with an oxygen content of 1% to 10% by weight. Furthermore, the layer formed on the substrate by laser transfer can have a nitrogen content of 0.5% to 5% by weight.

[0031] Instead of using a carrier foil coated only with silicon, it is also possible to use a carrier foil with SiO x N y In this case, x is in particular in the range of 0.05 to 0.3 and y is in the range of 0.05 to 0.4. In addition to SiO x N y Outside the SiO layer x N y Adjacent layers may be present on the carrier foil with a thickness of several nanometers, for example, 1 nm to 20 nm, in particular 2 nm to 10 nm. This layer may be a titanium layer, for example. In any case, low silicon oxide, low silicon nitride, and low silicon oxynitride can be produced on the substrate in a targeted manner by varying the oxygen and nitrogen content of the coating initially present on the carrier foil. For transferring the material from the carrier foil to the substrate, including any chemical reaction (in particular with atmospheric oxygen), various conventional lasers with a wavelength in the range of 300 nm to 1400 nm can be used.

[0032] By adjusting the laser parameters during the coating process, the coating parameters can be varied in a targeted manner within the resulting layer. In particular, by adjusting the laser parameters (particularly the laser timing and power, as well as the laser pulse duration and the distance from the laser spot or line), hydrophilic and hydrophobic coating areas can be generated in a geometrically defined manner during the coating process. In particular, hydrophobic coating areas can be generated using laser speeds of less than 500 mm / s and laser line spacings greater than 0.3 mm.

[0033] Ultra-hydrophilic, silicone-based layers can be re-coated by repeatedly using the carrier foil in one and the same coating process. The layer thickness is increased by re-coating, wherein previously unused areas of the carrier foil are always used, i.e., even in the case of multiple re-coating, only previously unused areas of the carrier foil are used in each re-coating process.

[0034] In addition to or as an alternative to recoating, further supplementary, upstream or downstream process steps can be carried out, thereby making it possible to produce a wide variety of coating variants. For example, a porous, rough, superhydrophilic layer can be applied to the substrate in combination with a hydrophobic, known indium tin oxide layer, which is also deposited by laser transfer from the coating foil.

[0035] The combination of super-hydrophilic laser transfer layers and PVD layers, applied in a time-staggered manner, is also possible. Here, the layer to be generated by the PVD (physical vapor deposition) method can be applied to the workpiece to be coated under vacuum conditions in a method step downstream of the laser transfer.

[0036] An optional method variant provides that, in addition to the carrier foil on which the silicon layer is located, from which the superhydrophilic coating of the substrate is produced by laser transfer, a further carrier foil is provided. A layer deposited by a PVD method is present on this further carrier foil, the composition of which differs from that of the silicon layer located on the first carrier foil. This further carrier foil is used after the porous laser transfer layer has been produced on the substrate. Laser transfer methods, preferably under atmospheric conditions, can be used to transfer the PVD layer from the further carrier foil to the already at least partially porous coated workpiece.

[0037] Finally, it's also possible to apply a porous, rough, superhydrophilic layer only to a subregion of the substrate, while leaving areas of the substrate surface less hydrophilic than the porous layer uncoated. This superhydrophilic nature is clearly evident when the coating is applied in strips and loaded with water. If, for example, an 8-mm-wide coated area is loaded with water, the water can accumulate to a height of 4 mm without flowing into the adjacent uncoated areas. This water retention can be explained by the extremely high surface energy of the laser silicon layer.

[0038] There are essentially no restrictions on the geometry of the carrier foil. For example, if a superhydrophilic coating is to be applied to the inside of a transparent tube, a flexible tube-shaped carrier foil coated with silicon on the outside is used. The flexible tube-shaped carrier foil is introduced into the transparent tube, whose inside is to be superhydrophilicly coated, and the tube is inflated with air, causing the silicon layer to adhere to the tube's inner wall. Laser radiation applied to the flexible tube from the outside, penetrating the tube's wall, transfers the silicon to the tube's inner wall.

[0039] It is also possible to coat objects whose outer surfaces are described as non-rollable. In this case, a shrink tube coated with silicone on its inner side is suitable as a carrier foil, which is pulled over the workpiece with the non-rollable surface, the shrink tube being attached to the workpiece by heating before the laser transfer.

[0040] Regardless of the geometry of the object to be coated, the porosity of the super-hydrophilic layer is generally at least 5% and at most 40%. Porosity is defined as the proportion of hollow spaces in the material. In the case of the porosity limits of 5% and 40%, the density of the layer thus corresponds to 95% or 60% of the density of the raw material.

[0041] Superhydrophilic silicon layers can be deposited not only on smooth surfaces, particularly ceramics or metals, but also on fibrous materials. In particular, superhydrophilic layers can be deposited on paper or cardboard. Laser transfer can also be used to apply superhydrophilic silicon layers to plastics, textiles, stone, or wood. Particularly advantageously, the layer transfer can be achieved with low laser powers that only cause the silicon layer to melt, thus preventing damage to the substrate surface even with very temperature-sensitive materials (particularly organic materials or materials containing organic components).

[0042] Other applications for superhydrophilic layers are electrochemical products, catalysts, and solar cells. In each case, the large surface area available for the coating plays a role. This allows for particularly high power densities in fuel cells and redox flow batteries. In fuel cells in particular, superhydrophilic layers can be located on membrane electrode assemblies, electrodes, and / or bipolar plates.

[0043] In the case of batteries, the properties of the porous layer can be precisely adjusted during the coating process, making it possible to achieve variations in properties within very small spaces (in the submillimeter range if necessary). This opens up the possibility of creating regions with different space charges within the electrochemical product in question. In this way, the boundary region between p-material and n-material can be designed with a significantly different charge compared to conventional solutions. This significantly contributes to compact construction and high power density thanks to the resulting greater potential difference.

[0044] For the catalytically supported reactions that occur with the help of the superhydrophilic silicone base layer, the temperature stability of this layer also plays a role, depending on the reaction type. In a typical configuration, the porous, superhydrophilic layer is thermally stable up to over 600 degrees Celsius. Furthermore, the layer is abrasion-resistant, disinfectable, highly adhesive, and UV-stable. It can be cleaned with a cloth using common pH-neutral, acidic, or alkaline cleaners, particularly household cleaners, without damaging it.

[0045] The antimicrobial effect of the super-hydrophilic silicone-based layer created by laser transfer has proven particularly useful. Experimental testing of the test bacterium Staphylococcus epidermidis DSM 18857 was performed on a substrate surface coated with this coating. This test, conducted in accordance with ISO 22196-2007 (Determination of Antimicrobial Activity on Plastic Surfaces), demonstrated sufficient antimicrobial activity 24 hours after application, with over 99.99% of the bacteria being killed within the specified timeframe.

[0046] The catalytic properties of the porous layer, which is primarily made of silicon, can also be used, not necessarily photocatalytic properties. This is particularly important in solar cells. The catalytic properties can also be used to separate water into hydrogen and oxygen. Surprisingly, the catalytic properties of the layer can be observed even without UV irradiation. After loading the layer with distilled water, gas bubbles form rapidly. This is a significant difference from the known photocatalytic production of hydrogen, i.e. the splitting of water molecules under the influence of photons. Background information on this topic can be found in the following paper: Sarah Saborowski: - Photocatalytic hydrogen production on titanium dioxide layers, Friedrich-Schiller-Institute of Chemistry and Geosciences, University of Jena

[0047] der Friedrich-Schiller- Jena), 2010.

[0048] Furthermore, reference is made to EP 0 931 855 B1 which relates to the production of hydrogen from water using a hybrid photocatalytic electrolysis system.

[0049] To investigate the catalytic activity of the silicon-containing layer according to the present application, methylene blue was also tested. After applying methylene blue to the layer, it faded within minutes. Even after multiple reapplications, the effect remained consistent, and the fading did not diminish. The surface was cleaned with isopropyl alcohol after every ten test cycles.

[0050] The large surface area of ​​the layer produced by laser transfer is crucial for its strong catalytic activity, both in the decomposition of water molecules and in other cases. The layer is constructed in the form of a so-called solid powder, onto which water or other molecules are chemically adsorbed, thus reducing the activation energy for the decomposition of the molecules in question.

[0051] The optical properties of a super-hydrophilic silicone base layer depend on the precise layer composition. In many cases, it is a brown, translucent layer. When spectacle lenses are coated with this layer, in preferred embodiments, transmittance in the blue, green, and yellow wavelength ranges is reduced, and a blocking effect is achieved in the ultraviolet range. Because red and blue light have significantly different effects, lenses coated with a porous silicone layer can be of great benefit to those with red-green color blindness. Depending on the degree of amblyopia, the lens coating can enable a person to better distinguish red and green, or even to distinguish these colors at all.

[0052] By appropriately adjusting the reflectivity, the porous silicon layer can also be used in mirrors. In particular, high reflectivity can be achieved through repeated coating. Its superhydrophilic properties prevent water droplets from forming on the surface, offering general advantages for mirrors and eyeglass lenses, regardless of their optical properties.

[0053] The porosity of the superhydrophilic layer also allows for liquid transport via capillary action. This effect allows liquids to be transported from a low level to a higher level. Water, in particular, can be converted to the vapor phase at the higher level, for example, by exposure to light. The resulting drying of the layer in the upper region of the substrate allows for liquid transport via capillary action over an extended period of time.

[0054] Unlike known products, particularly those based on TiO2, the superhydrophilic properties of the layer according to the present application are permanently retained, without requiring activation by light, particularly UV light. This layer is particularly suitable for decorative items or other articles where the formation of water droplets or the visibility of fingerprints must be avoided. The capillary effect associated with the superhydrophilic properties can also be used to guide water in a targeted manner along the paths formed on the surface of the object by the superhydrophilic layer, acting as a kind of track for the water to flow along.

[0055] In principle, the evaporation of liquids from the surface of the layer can be used for any liquid, provided that the temperature of the coated substrate used is matched to the properties of the liquid. In particular, the coated substrate can be used to release fragrances contained in the liquid into the environment.

[0056] Another product, the gradiator tower, constructed from super-hydrophilic-coated components, also releases substances into the environment. Here, organic materials such as blackthorn bundles used in conventional gradiators are replaced with porous, super-hydrophilic-coated components that flow through salt water. Due to their high efficiency based on the area through which liquid (especially salt water) flows, this allows for the construction of miniaturized gradiators suitable for indoor installation, including in living rooms.

[0057] A general advantage of porous silicon-based layers is that their properties, particularly their superhydrophilicity, remain unchanged over long periods of time, under changing environmental conditions, and even with intermittent intense heating. In principle, the porous, superhydrophilic layer can be applied to the substrate in any desired form, covering the entire surface or only partially. In addition to geometric patterns in which the layer is applied, other examples include inscriptions, decorations, or logos formed by the layer.

[0058] Several exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings, in which:

[0059] Figure 1 A glass plate partially coated with a porous, super-hydrophilic silicon layer,

[0060] Figure 2 Schematic cross-sectional view of a workpiece with superhydrophilic coating,

[0061] Figure 3 Paper having a sub-region of a superhydrophilic coating,

[0062] Figure 4 Looking down at the structure of the surface with super hydrophilic coating,

[0063] Figure 5 according to Figure 4 Height distribution of the coating,

[0064] Figure 6 the arrangement of a transparent tube for coating on its inner side,

[0065] Figure 7 During the coating process, Figure 6 Details of the layout,

[0066] Figure 8 Semi-finished products for the production of ladder tower components,

[0067] Figure 9 Based on Figure 8 The semi-finished product forms the corrugated board,

[0068] Figure 10 Schematic side view with multiple basis Figure 9 The ladder tower of the plate,

[0069] Figure 11 a carrier foil coated with silicon and a metal substrate coated by laser transfer with the aid of this foil,

[0070] Figure 12 The surface of the workpiece with super hydrophilic coating in the electron micrograph,

[0071] Figure 13 and Figure 12The surfaces of the objects being compared in similar photos,

[0072] Figure 14 according to Figure 12 Cross-sectional view of the workpiece,

[0073] Figure 15 according to Figure 13 Cross-sectional view of the comparison item.

[0074] Unless otherwise stated, the following explanations relate to all exemplary embodiments. Essentially comparable components and geometrical structures are identified with the same reference numerals in all figures.

[0075] The workpiece, generally designated by reference numeral 1 , comprises a coating 3 on a substrate 2 , wherein different sub-regions 4 , 5 may be coated or uncoated in different ways. In each case, a superhydrophilic silicon-based layer 6 is at least partially present on the surface of the substrate 2 .

[0076] exist Figure 1 In this case, substrate 2 is a small piece of glass. In this case, superhydrophilic layer 6 is applied in strips on substrate 2. Between the individual strips formed by layer 6, the glass is uncoated. Water droplets 7 are visible on the glass surface in these uncoated areas. On the other hand, if water is dropped onto layer 6, it immediately disperses and flows away. No droplets form, meaning a contact angle of zero degrees.

[0077] This super-hydrophilic property of layer 6 is Figure 2 The layer is constructed of a solid 8 that is at least predominantly silicon in a porous form. Water 9 is absorbed by the pores of the solid 8. The thickness of the layer 6 is Figure 2 It is shown as constant for simplicity.

[0078] A coating 3 consisting entirely or partially of a porous layer 6 is suitable not only for workpieces 1 with smooth surfaces, but also for rough, in particular fibrous, surfaces. Figure 3 , the layer 6 is located, for example, on a commercially available paper 10. In this case, individual water droplets 7 can also be seen outside the coating 3. Figure 1 As in the case of the coating 6, no water droplets will form on the coating 6. Instead, the water will be absorbed by the coating 3 and distributed in the coating 3.

[0079] and Figures 1 to 3 In contrast to what can be seen in FIG, the porous layer 6 is by no means constructed as a homogeneous surface when observed under a microscope. Figure 4 and 5, which show the microstructure of layer 6. Individual, approximately point-shaped areas, arranged in a uniform rectangular pattern and referred to as laser spots 11, are easily recognizable. The position of each laser spot 11 corresponds to the location where a laser pulse impinges on the silicon-coated foil used for coating substrate 2, which is placed on substrate 2 during the coating process. The pattern of laser spots 11 thus reflects the raster of the laser pulses during the coating process.

[0080] Surprisingly, layer 6 is thinnest in the region of laser spot 11. Figure 4 The layer thickness in these areas shown in light colors is determined by h L A generally mesh-shaped intermediate region 12 is formed outside the laser spot 11, which has a layer thickness h z , at least the layer thickness h L The average diameter of the laser spot 11 is given by D L The distance between the centers of the two laser points 11 is represented by d L Indicates. Figure 4 In the embodiment, the average diameter D L is about 22 μm, and the average distance d L It is approximately in the range from 33μm to 43μm. Figure 4 In a top view of the laser beam, intermediate region 12 appears as a structure of individual dot-like regions, referred to as nanodots 13, that are significantly smaller than laser spot 11. Each of these nanodots 13 can be interpreted as spatter generated during the coating process due to the energy introduced by the laser and deposited on substrate 2. In this case, individual nanodots 13 can have an elongated or needle-like shape, with nanodots 13 positioned perpendicular to substrate 2, i.e., aligned with the surface normal. The ability of layer 3 to absorb and distribute water is primarily due to this structure of intermediate region 12.

[0081] Figure 6 and 7 The diagram shows a special case of laser-guided transfer of layer 6 onto substrate 2, wherein substrate 2 is a transparent tube 14. First, a hose 15 with the silicon layer 6 on its outside is introduced into tube 14. In this exceptional case, the base material of hose 15 does not necessarily have to be transparent. The hose 15 located in tube 14 is inflated until layer 6 adheres to the inner wall of tube 14. Figure 7 The gap between the hose 15 and the tube 14, visible in the drawing, is only drawn to clarify the process. After the hose 15 has been correctly positioned, the laser radiation LS, in this case guided by means of a mirror 16, is directed onto the layer 6 located on the hose 15. As a result, the essentially liquid material 17, i.e. silicon droplets, detach from the surface of the hose 15 and are deposited on the inner wall of the tube 14. The resulting coating 3 of the tube 14, i.e. the inner coating, has a characteristic of the coating already obtained according to Figures 1 to 5Structures of the type described, in which any desired structuring, for example strip-shaped structuring, can be produced.

[0082] Figures 8 to 10 The figure shows another example of the application of the coating 3, namely in a stair tower. First, a flat, plate-like substrate 2 made of metal, i.e. a metal sheet, is coated with a porous, super-hydrophilic layer 6. The coated workpiece 1 is then reshaped and given a wave shape, similar to commercially available roof panels, such as Figure 9 A plurality of such corrugated plates 18, each provided with a coating 3 on its upper side, are used for a ladder tower, which comprises a support structure 19 on which the plates 18 are suspended, and a collecting trough 20. Instead of plates 18 already coated as semi-finished products, it is also possible to use rougher workpieces or workpieces structured in any manner, such as metal fabrics or knitted metal fabrics, onto which the porous, superhydrophilic silicon layer 6 is deposited.

[0083] Before the portion of brine that is not distributed into the environment reaches the collection tank 20 and is pumped back, the brine dripping onto the coating plate 18 and / or other coated workpieces will come into contact with a very large surface due to the microstructure of the porous layer 6. In this case, the capillary action of the porous layer 6 can also be used to transport the brine.

[0084] exist Figure 11 In addition to the coated substrate 2, which in this case is made of metal, a carrier foil 21 can be seen for applying the coating 3. This carrier foil, a PET foil, has a thickness of 72 μm in the present case. Figure 11 It can be seen that the carrier foil 21, from which the layer transfer took place, is significantly bent. This is due to internal layer stresses that were generated during vacuum deposition (i.e., during the silicon coating of the carrier foil 21). Such internal stresses are not present in the porous silicon coating 3 deposited on the substrate 2.

[0085] Also like Figure 11 As shown, the two flat rectangular and square areas (from which the silicon was detached from the carrier foil 21 by laser irradiation in order to transfer it to the substrate 2 with the corresponding geometry) do not completely release the material deposited on the carrier foil, so that the corresponding areas are not completely transparent. The material remaining on the carrier foil film 21, namely the silicon, is the result of rasterization of the carrier foil 21, which is also made of PET in this case, rather than full-surface laser irradiation.

[0086] In electron micrographs, Figures 12 to 15 Coating 3 ( Figure 12 and 14 ) and the comparative article 22 ( Figure 13 and 15). The comparative article 22 is coated with silicon by vacuum sputtering. For this reason, the comparative article 22 has a layered structure, which is also seen in the case of the coated carrier foil 21. On the one hand Figure 12 and 14 On the other hand Figure 13 and 15 The comparison clearly shows that the roughness of the laser coating 3 caused by laser transfer is much greater than that of the comparative article 22. The structure of the coating 3 with its very large specific surface area can be understood as a powder that can solidify.

[0087] References

[0088] 1 Workpiece

[0089] 2 base

[0090] 3 Coating

[0091] 4 First sub-area

[0092] 5 Second sub-area

[0093] 6. Porous, super-hydrophilic layer

[0094] 7 Water Drops

[0095] 8 solid

[0096] 9 Water absorbed in the porous layer

[0097] 10 Paper

[0098] 11 Laser points, raster points, areas

[0099] 12 Central Area

[0100] 13 nanodots

[0101] 14 Transparent tube

[0102] 15 hose

[0103] 16 Mirror

[0104] 17 Liquid Materials

[0105] 18 corrugated panels

[0106] 19 Support structure

[0107] 20 Collection Tanks

[0108] 21 Carrier foil

[0109] 22 Comparison items

[0110] d L The distance between the two laser points

[0111] D L Laser spot diameter

[0112] h L Laser point height

[0113] h z Mid-range height

[0114] LS laser radiation

Claims

1. A method for coating a substrate (2), comprising the following steps: - providing a transparent carrier foil (21) coated with silicon, - positioning the side of the carrier foil (21) coated with silicon on the surface of the substrate (2), The coated carrier foil ( 21 ) is subjected to raster-like impact with laser radiation, whereby silicon is detached from the carrier foil ( 21 ) in a punctiform manner and deposited as a porous, rough, superhydrophilic layer ( 6 ) on the substrate ( 2 ).

2. The method according to claim 1, characterized in that The laser radiation is directed towards the carrier foil (21) in the form of individual raster points, wherein each raster point has a normalized diameter (D L ), which is defined as follows: 68.27% of the incident power is located at a point with a normalized diameter (D L ) and the average distance between two adjacent grating points (d L ) is at least the normalized diameter (D L ) of 125% and at most 250%.

3. The method according to claim 1, characterized in that Silicon, predominantly in liquid form, is transferred to the substrate (2) by laser radiation acting in a raster pattern on a carrier foil (21).

4. The method according to claim 1, wherein In order to transfer the material forming the superhydrophilic layer from the carrier foil (21) to the substrate (2), laser radiation with a power of 1.0 to 6.0 W, a frequency of 10 to 150 kHz, a laser speed of 500 to 4000 mm / s and a laser line spacing of 0.02 to 0.3 mm is used.

5. The method according to claim 1, wherein The carrier foil (21) is irradiated with laser radiation under atmospheric conditions.

6. The method according to claim 5, characterized in that During the transfer process from the carrier foil (21) to the substrate (2), the silicon reacts with components of the air so that a layer (6) having an oxygen content of 1% to 10% on a silicon basis, expressed in % by weight, is formed on the substrate (2).

7. The method according to claim 1, characterized in that For transferring a laser-guided material onto a substrate (2), a coating on a carrier foil (21), namely a metal layer a few nanometers thick, and then a SiO x N y layer is heated by a laser, wherein, based on the number of silicon atoms, the SiO x N y layer contains oxygen and nitrogen atom contents in the ranges of 0.05 < x < 0.3 and 0.05 < y < 0.

4.

8. The method according to claim 7, characterized in that The metal layer having a thickness of several nanometers is a titanium layer having a thickness of at most 10 nm.

9. The method according to claim 1, characterized in that The carrier foil (21) is irradiated with laser radiation having a wavelength of at least 300 nm and at most 1,400 nm.

10. The method according to claim 1, wherein The parameters of the layer transferred from the carrier foil (21) are varied by adjusting the laser parameters during the coating process.

11. The method according to claim 10, characterized in that By adjusting the laser parameters, hydrophilic and hydrophobic coating areas are generated in a defined geometric manner during the coating process.

12. The method according to claim 11, characterized in that The laser parameters are the timing and power of the laser as well as the duration of the laser pulses and the spacing of the laser spots or lines.

13. The method according to claim 11, characterized in that At least one of the hydrophobic coating regions is produced using a laser speed of less than 500 mm / s and a laser line spacing of greater than 0.3 mm.

14. The method according to claim 1, wherein The porous, rough, superhydrophilic layer (6) is repeatedly coated by repeatedly using the same carrier foil (21) in the same coating process.

15. The method according to claim 14, characterized in that Previously unused areas of the carrier foil (21) are used for re-coating the superhydrophilic layer (6), which means increasing its layer thickness, wherein in the case of multiple re-coating, only previously unused areas of the carrier foil (21) are used in each re-coating process.

16. The method according to claim 1, wherein The porous, rough, superhydrophilic layer (6) is produced in combination with a hydrophobic indium tin oxide layer which is also deposited by laser transfer from the coated foil.

17. The method according to claim 1, wherein The porous, rough, superhydrophilic layer (6) is applied in conjunction with a PVD layer produced in a vacuum in a subsequent method step.

18. The method according to claim 1, wherein The porous, rough, superhydrophilic layer (6) is applied in conjunction with a PVD layer which is transferred by means of laser in a subsequent method step.

19. The method according to claim 1, wherein The porous, rough, superhydrophilic layer (6) is deposited only on a first subregion (4) of the substrate (2), while a second subregion (5) of the substrate (2) which is less hydrophilic than the superhydrophilic layer (6) remains uncoated.

20. The method according to any one of claims 1 to 19, characterized in that The carrier foil (21) is designed as a hose (15) coated with silicon on its outer side, wherein the hose is introduced into a transparent tube (14) to be coated on its inner side with a superhydrophilic coating and is inflated in the transparent tube (14), so that the silicon layer adheres to the inner wall of the transparent tube (14), and wherein the silicon is transferred to the inner wall of the transparent tube (14) by laser radiation acting on the hose (15) from the outside, penetrating the wall of the transparent tube (14).

21. The method according to any one of claims 1 to 19, characterized in that The carrier foil (21) is designed as a shrink tube coated with silicone on its inner side, which is pulled onto the workpiece to be coated and adhered to the workpiece by heating before laser transfer.

22. The method according to claim 21, characterized in that The workpiece has a non-rollable surface.

23. A coating, which is formed as a porous superhydrophilic layer (6) on at least a first sub-area (4) of a substrate (2), deposited on the substrate (2) by rastering laser radiation with a carrier coated with silicon, and has low roughness and thickness in areas (11) spaced apart from each other in a pattern corresponding to the grating of the laser radiation, wherein intermediate areas (12) located between the areas (11) that are spaced apart from each other and also belong to the superhydrophilic layer (6) and are also mainly formed by silicon deposited on the substrate (2) have relatively high roughness and thickness.

24. The coating according to claim 23, characterized in that The layer thickness (h z ) is at least the layer thickness (h) given in the mutually spaced regions (11) in the form of a raster pattern L ) three times.

25. The coating according to claim 23, characterized in that The second subregion (5) of the substrate (2), which is also coated at least predominantly with silicon, has a lower hydrophilicity than the superhydrophilically coated first subregion (4).

26. The coating according to claim 25, characterized in that Regardless of the degree of variation of the coating parameters within the same super-hydrophilic layer (6), a boundary is formed between the super-hydrophilic layer (6) and the second sub-region (5), at which the maximum gradient of at least one parameter is given.

27. The coating according to claim 26, characterized in that The parameter is hydrophilicity.

28. The coating according to claim 23, characterized in that The super hydrophilic layer (6) has a porosity of at least 5% and at most 40%.

29. The coating according to claim 23, characterized in that The super-hydrophilic layer (6) is formed in a regular pattern on the substrate (2).

30. The coating according to claim 29, characterized in that The regular pattern is in the form of stripes.

31. The coating according to claim 23, wherein When the super hydrophilic layer (6) is wetted by water, there is an imaginary contact angle.

32. The coating according to claim 23, wherein The super hydrophilic layer (6) is on paper (10) as a substrate.

33. The coating according to claim 23, wherein The super hydrophilic layer (6) is located on at least one of a membrane electrode unit, an electrode and a bipolar plate assembly of a fuel cell.

34. Use of a coating according to any one of claims 23 to 33 in a ladder tower.

35. Use of a coating according to any one of claims 23 to 33 for the catalytic production of hydrogen.

36. The use according to claim 35, characterized in that The catalytic production of hydrogen occurs in the absence of UV radiation.

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