Method for producing a coated glass pane having a non-fogging surface structure

Abstract

The invention relates to a method for producing a glass pane having an anti-fogging structure, comprising the following steps: • - providing a surface to be structured, the surface being at least a portion of a glass pane or a portion of a glass pane coated with a transparent oxide coating, • - introducing an anti-fogging structure into the portion of the surface of the glass pane by laser interference structuring with a pulsed laser in such a way that at least two laser beams are made to interfere with one another so that a pattern that is determined by the interference and has depressions with a depth of < 200 nm is created, any coating having a lower thickness than the depth of the structuring depressions. • - In the case of an uncoated glass pane, coating the structured portion with a transparent oxide coating, the coating having a lower thickness than the depth of the structuring depressions made in the surface. • The invention also relates to a glass pane produced in this way and having an anti-fogging structure and to the use thereof.

Description

[0001] Process for producing a coated glass pane with a non-fogging surface structure

[0002] The invention relates to a method for producing a coated glass pane with a non-fogging surface structure and a glass pane produced in this way, in particular for mirrors, refrigerator doors, shower partitions and vehicle parts.

[0003] Providing non-fogging glass objects has long been a technical challenge, and a variety of solutions have been proposed to impart anti-fog properties to the glass. The most widely used solution is anti-fog coatings, in which an additional coating imparts hydrophobic or superhydrophobic properties to a glass surface. Although this can achieve good results, such a coating can partially or completely lose its anti-fog properties over long periods of use due to loss of adhesion, mechanical stress, or exposure to the weather. Therefore, solutions have been sought that structure the glass surface itself in such a way that it does not exhibit the formation of water droplets, even due to physical effects. This is generally achieved by introducing a structure into the glass surface with a height and pitch in the micrometer range.

[0004] Structuring by etching the glass surface with hydrofluoric acid has been proposed. On the one hand, this solution has proven to be rather disadvantageous, as it only produces a very irregular and uneven structure, particularly in terms of height and spacing, resulting in a loss of transparency. Furthermore, the use of highly problematic hydrofluoric acid makes the process steps complex in terms of handling, safety equipment, and disposal.

[0005] Another approach to creating a pattern, for example, in a glass surface using ultrafast, femtosecond laser pulses, is described in US 2012 / 0328905 A1. Here, the surface is patterned by targeted laser exposure in such a way that it exhibits both micrometer-scale structures and nanometer-scale substructures. The goal of the patterning described here is to change the color or absorption capacity of the patterned material.

[0006] A similar approach is pursued by the solution proposed in WO 2022 / 258998 A1 for structuring a glass surface with the aim of preventing fogging while maintaining transparency as much as possible. The method involves the introduction of nanostructures by exposure to a focused, polarized, and pulsed laser beam. The structuring is applied over the entire surface to be structured and is introduced point by point by laser irradiation. This involves a high process complexity, since in addition to appropriate laser calibration, the points must be approached individually, preferably in overlap mode. Therefore, this laser structuring method is associated with a rather slow process speed.

[0007] A further development of this laser structuring is described in WO 2023 / 280793 A2. A method and a device for laser interference structuring of substrates with periodic dot structures for anti-reflection properties are presented. The structured substrate comprises a periodic dot structure in the micrometer or sub-micrometer range, wherein the periodic dot structure is formed from inverse pegs, and wherein the inverse pegs are periodically arranged at a distance from one another, based on their respective saddle point or center of height (circular base area), 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, in order to produce the desired anti-reflection property.Glass or a transparent polymer is described as a suitable substrate material. The resulting surfaces exhibit a durability that requires improvement. Due to various phenomena, particularly organic adsorption on the structured surface, it has been shown that durability decreases over time. Therefore, there is potential for improvement in this area with regard to long-lasting and / or weather-resistant products such as automotive parts or shower enclosures.

[0008] The object of the present invention is to provide a method for producing and providing a coated glass pane with an anti-fog structure in one of its surfaces, wherein the structured surface should furthermore have a very good transmission in the visible range of light as well as an improved durability in continuous use and wherein the method can be carried out at a high process speed.

[0009] These and other objects are achieved according to the invention by a method for producing a glass pane according to independent claim 1 and a glass pane with an anti-fog structure according to claim 9. Advantageous embodiments of the invention emerge from the subclaims.

[0010] The invention relates to a method for producing a glass pane with an anti-fog structure, comprising the steps: a1) providing a surface to be structured, wherein the surface is at least a section of a glass pane, b1) introducing an anti-fog structure into the section of a surface of the glass pane by laser interference structuring with a pulsed laser in such a way that at least two, preferably at least three laser beams are caused to interfere in order to introduce depressions into the surface, so that depressions with a depth of <200 nm, preferably <120 nm, are produced in a pattern determined by the interference, c1) coating the structured section with a transparent coating, wherein the coating has a smaller thickness than the depth of the structuring depressions introduced into the surface;or a2) providing a surface to be structured, wherein the surface is at least a section of a glass pane coated with a transparent coating, b2) introducing an anti-fog structure into the section of the coated surface of the glass pane by laser interference structuring with a pulsed laser such that at least two, preferably at least three laser beams are caused to interfere in order to introduce depressions into the surface, so that depressions with a depth of <200 nm, preferably <120 nm, are produced in a pattern determined by the interference, wherein the coating has a smaller thickness than the depth of the structuring depressions introduced into the surface.;

[0011] In other words, by using structuring with a pulsed laser, for example, Direct Laser Interference Patterning (DLIP), in conjunction with a transparent coating, it has been possible to introduce a plurality of structuring depressions into a glass surface in a single process step. These depressions are dimensioned on the micrometer or submicrometer scale in such a way that they impart long-lasting and permanently stable anti-fog properties to the glass surface. The combination of special laser structuring and transparent coating produced by the inventive method enhances the respective effect of the introduced interference pattern with uniform depressions on the one hand and the coating on the other to prevent fogging and adhesion.This makes it possible to impart superhydrophilic properties to a hydrophilic coating and superhydrophobic properties to a hydrophobic coating. Furthermore, it has been shown that the durability of the combined anti-fog effect can be significantly improved compared to glass panes with only the respective individual treatments, i.e., structured only by the DLIP process or provided with only a hydrophilic or hydrophobic coating. An anti-fog structure in a glass surface is generally known to those skilled in the art and encompasses structures in a specific micrometer range.These structures in the micrometer range, either elevations or depressions in the surface, result in the contact angle of water droplets on the structured surface changing in such a way that the condensation of water vapor prevents the formation of droplets on the surface that scatter the light and thus make the affected areas of the glass pane almost or completely opaque.

[0012] According to the present invention, it is provided that the anti-fog structure of the glass surface (step a1 / b1) or of the glass surface coated with a transparent coating (step a2 / b2) has a repeating interference pattern.

[0013] In physics, the term interference describes the superposition of two or more waves according to the superposition principle. This principle states that the amplitudes (not the intensities) of the waves are added together as they intersect. Interference occurs in all types of waves, regardless of whether they are sound waves, light waves, matter waves, or other types of physical waves. If waves cancel each other out, this is referred to in technical terms as complete destructive interference. If, on the other hand, the amplitudes amplify, this is referred to as constructive interference. A pattern composed of points of constructive interference and destructive interference is referred to as an interference pattern in the context of the present invention.In this case, characteristic interference minima and interference maxima alternate, which, within the scope of the present invention, result in depressions in the glass surface being arranged in a characteristic pattern. A common example of this is the stripe pattern or the dot pattern.

[0014] In other words, the interference pattern is composed of a plurality of depressions that are simultaneously generated by interference laser structuring. They are evenly spaced from one another and are formed together on the glass surface in the laser's impact area. The impact area of ​​the interfering laser radiation can be substantially round or square, so that the recurring interference pattern represents a sequence of such shaped areas. The unstructured spacing between these interference pattern areas is selected to further maintain the anti-fog function. Preferred values ​​for the size of the depressions formed by the laser interference, their individual spacing within the interference pattern, and the spacing of the repeating interference pattern areas are described below.

[0015] In other words, the repeating sequence of characteristic interference patterns eliminates the need for full-surface structuring, particularly by overlapping individual interference areas. This ensures high transparency and low scattering even in the area of ​​the anti-fog structure. For example, the reduction in transparency caused by the anti-fog structure in the green light wavelength range is only 0.2%.

[0016] Due to the characteristic arrangement of the depressions of the structuring by interference laser irradiation and due to the sequence of areas structured with the interference pattern and non-structured areas, the glass pane of the present invention provided with an anti-fog structure can be clearly distinguished from generic structured glass panes of the prior art.

[0017] Direct Laser Interference Patterning is a holographic process that utilizes the phenomenon of interference between coherent electromagnetic waves to create very fine and specific intensity distributions of individual laser pulses. This approach allows a multitude of microstructures of varying characteristics, particularly individual depressions, to be introduced into the glass surface in parallel. In this way, intensity patterns are generated using superimposed coherent laser beams, which are then projected onto a component surface. Depending on the pulse length, the material is melted or even vaporized in areas of constructive interference, while it remains virtually unaffected in areas of destructive interference. The number and relative arrangement of the beams determines the type of applied pattern. This can be, for example, a line, cross, dot pattern, or almost any periodic surface pattern.The angle between the overlapping laser beams and the wavelength of the laser used determine the structure size of the applied, periodic intensity pattern. Unlike other processing methods, such as laser writing, the beam diameter does not need to be focused. This allows a significantly larger area to be processed per laser pulse. At the same time, microscopic structures, smaller than with beam focusing, which is subject to the diffraction limit, can be created quickly and without contact. DLIP, paired with a high-frequency laser, thus achieves processing speeds in the range of >1 m. 2 / min with the highest precision down to the nanometer range. In addition, the DLIP process offers a very high depth of field compared to laser writing, as DLIP does not rely on precise focusing of the laser beam, but rather creates an "interference volume" within which the surface is structured with the corresponding interference pattern.

[0018] No additional masks or chemicals are required, and DLIP transforms a multi-step process into a single-step process that is also contactless and therefore not only more sustainable but also faster.

[0019] The advantage of the process compared to other conventional laser processes is that the surface pattern to be applied is stored as an interference pattern across the entire laser beam diameter and that with just one laser pulse, hundreds to thousands of structures in micro- or nano-dimensions are applied to the surface in a few nano- to femtoseconds.

[0020] In contrast to other, equally fast processing methods, such as laser writing using a polygon scanner, the beam diameter does not have to be focused, but can even be widened depending on the required pulse energy in order to produce microscopically small structures with a significantly larger processing area per laser pulse. According to the invention, the depressions introduced into the surface by the laser pulses have a depth (measured from the surface vertically into the volume of the glass pane) in the range from 30 nm to <200 nm, preferably from 40 nm to <150 nm, particularly preferably from 50 nm to <100 nm. Their superficial extent (measured horizontally in the plane of the surface) is in the range from 0.5 pm to 20 pm, preferably from 2 pm to 10 pm.The spacing of the pits within an interference pattern generated by one or more laser pulses is determined by the wavelength of the laser and the associated regions of constructive and destructive interference.

[0021] DLIP, paired with a modern high-frequency laser, achieves processing speeds in the range of m 2 / min with the highest precision down to the micrometer range. The use of a polygon scanner is also possible with DLIP to achieve even faster processing speeds.

[0022] DLIP offers a de facto infinite variety of structuring possibilities through the use of nano-, pico- or femtosecond lasers, the number of interfering laser beams and their geometry relative to each other as well as the wavelength of the light used.

[0023] In one embodiment of the method, a picosecond laser with a fluence within an interference pixel of 20 - 50 J / cm 2 , preferably 30 - 40 J / cm 2 , used.

[0024] The laser fluence (or laser energy density), defined as the applied laser energy per unit area, is one of the most important parameters determining the morphology and quality of the periodic structures.

[0025] In one embodiment of the method according to the invention, the laser is operated in burst mode with N > 3. In burst mode, instead of a single pulse, a pulse series with N (sub-)pulses is generated in rapid succession. The energy density of the laser pulse, which occurs in a Gaussian distribution in a single pulse, is distributed much more efficiently through this division and used for ablating the surface material, thus achieving lower heat losses and improved ablation quality, as well as good edge qualities of the depressions of the introduced interference pattern. For example, by using burst mode, the ablation efficiency can be increased by 10% to 30% with the same (total) energy density.

[0026] To efficiently implement ablation laser processes, laser systems are required that, thanks to high repetition rates, allow for high average power with the ideal energy density for the respective material. This is achieved with the specified parameters for the intended glass processing.

[0027] In particular, the combination of selected wavelength, fluence and number N of (partial) pulses divided in burst mode leads to optimized structuring with high process speed and high-quality individual structures.

[0028] In one embodiment of the method according to the invention, the laser has a wavelength of 343 nm, 355 nm, 515 nm, 532 nm, 1030 nm or 1064 nm and is operated with a pulse duration of 200 fs - 15 ps, preferably with 10 ± 2 ps.

[0029] For the production of an anti-fogging structure according to the invention on float glass, for example, a picosecond laser with a wavelength of 532 nm and a pulse duration of approximately 10 ± 2 ps is used. To increase the interaction with the glass, a burst mode is used with N > 3, ie with N = 3, 4, 5, 6, 7 or 8. The peak power of the interference pulse is selected so that it is at a fluence of approximately 30 - 40 J / cm 2 within an interference pixel. This value is then independent of the number of interference maxima and their size.

[0030] However, when using a femtosecond laser, the values ​​can be lower. There are no restrictions on the type of glass pane. The preferred glass pane is float glass, quartz glass, tempered safety glass, or insulating glass.

[0031] In a preferred embodiment of the invention, the laser is guided further during laser interference structuring in such a way that the individual impact areas do not overlap.

[0032] This makes it possible to carry out the process very quickly and efficiently without reducing the function of the anti-fog structure.

[0033] In a preferred embodiment of the invention, the transparent coating of steps c1 / a2 is a hydrophilic coating, preferably a titanium oxide coating.

[0034] Of particular note are thin films based on titanium oxide, which possess self-cleaning properties by promoting the degradation of organic compounds under the influence of ultraviolet radiation and the removal of mineral contaminants (dust) under the influence of water runoff. Crystallized titanium oxide in anatase form is known to be more effective at degrading organic compounds than amorphous or crystallized titanium oxide in rutile or brookite form. A frequently used industrial-scale method for depositing thin films, particularly on glass substrates, is cathodic sputtering with magnetic field assistance, also known as the magnetron method. In this process, a plasma is generated under a high vacuum near a target containing the chemical elements to be deposited.The active plasma forms bombard the target and extract the elements, which are deposited on the substrate to form the desired thin film. This process is called reactive when the layer is formed from a material resulting from a chemical reaction between the elements extracted from the target and the gas contained in the plasma. A reactive magnetron process is used to deposit layers of titanium oxide using a metallic titanium target or a ceramic TiOx target (where x < 2) and an oxygen-based plasma-generating gas. In the industrial implementation of the magnetron process, the substrate remains at ambient temperature or is slightly heated (less than 80°C), especially when the substrate passage speed is high (which is generally desired for economic reasons).For example, a method for applying the oxide coating can also be chosen as described in detail in DE 20 2009 018 926 U1.

[0035] The combination of special laser structuring and transparent coating produced by the inventive method enhances the anti-fog effect of the applied interference pattern with uniform depressions and the coating. This makes it possible to impart superhydrophilic properties to a hydrophilic coating. Furthermore, it has been shown that the durability of the combined anti-fog effect can be significantly improved compared to glass panes with only the respective individual treatments, i.e., structured only by the DLIP process or provided only with a hydrophilic coating.

[0036] In a further preferred embodiment of the invention, the transparent coating of steps c1 / a2 is a hydrophobic coating, preferably a coating with fluoropolymers, in particular polytetrafluoroethylene, or a sol-gel coating, in particular a silane-based sol-gel coating. The hydrophobic coating can also be a coating comprising nanoparticles of oxides, for example, silica, fumed silica, titanium dioxide, or aluminum oxide, wherein the nanoparticles have been treated with a polydimethylsiloxane, a silanizing agent, or a combination thereof.

[0037] This makes it possible to impart superhydrophobic properties to a hydrophobic coating. Furthermore, it has been shown that the durability of the combined anti-fog effect can be significantly improved compared to glass panes with only the individual treatments, i.e., structured using the DLIP process or only coated with a hydrophobic coating.

[0038] The present invention further relates to a glass pane comprising a first surface and a second surface which is opposite the first surface, wherein at least one of the two surfaces has at least in sections an anti-fog structure comprising an oxide coating which is produced according to the method according to the invention described above, wherein the anti-fog structure of the surface has a plurality of separate regions, each having an interference pattern.

[0039] An anti-fog structure in a glass surface is generally known to those skilled in the art and comprises structures in a specific micrometer range. These micrometer-scale structures, either elevations or depressions in the surface, result in the contact angle of water droplets on the structured surface changing in such a way that, upon condensation of water vapor, droplets are prevented from forming on the surface, which scatter light and thus render the affected areas of the glass pane almost or completely opaque.

[0040] According to the present invention, the anti-fog structure of the glass surface has a repeating interference pattern in separate areas.

[0041] In physics, the word "interference" describes the superposition of two or more waves according to the superposition principle. This principle states that the amplitudes (not the intensities) of the waves are added together as they intersect. Interference occurs in all types of waves, regardless of whether they are sound waves, light waves, matter waves, or other types of physical waves. If waves cancel each other out, this is referred to in technical terms as complete destructive interference. If, on the other hand, the amplitudes are amplified, this is referred to as constructive interference. A pattern composed of points of constructive interference and destructive interference is referred to as an interference pattern in the context of the present invention.In this case, characteristic interference minima and interference maxima thus occur alternately, which in the context of the present invention lead to depressions in the glass surface being arranged in a characteristic pattern. A widespread example of this is the stripe pattern or the dot pattern. In other words, the interference pattern is composed of a plurality of depressions that are created simultaneously by interference laser structuring. They are evenly spaced from one another and are formed together on the glass surface in the area of ​​incidence of the laser. The area of ​​incidence of the interfering laser radiation can be essentially round or square, so that the recurring interference pattern represents a sequence of regions shaped in this way. Structured regions and unstructured regions without depressions alternate according to the invention.They are created by guiding the laser beam in such a way that the individual impact areas do not intersect or overlap. The unstructured spacing between these interference pattern areas is selected to maintain the anti-fog function. Preferred values ​​for the size of the depressions formed by the laser interference, their individual spacing within the interference pattern, and the spacing of the repeating interference pattern areas are described below.

[0042] In other words, the repeating sequence of characteristic interference patterns eliminates the need for full-surface structuring. This ensures high transparency and low scattering even in the area of ​​the anti-fog structure. For example, the reduction in transparency caused by the anti-fog structure in the green light wavelength range is only 0.2%.

[0043] Due to the characteristic arrangement of the depressions of the structuring by interference laser irradiation, i.e., within the interference pattern, and due to the sequence of regions structured and unstructured with the interference pattern, which are created by structuring without overlapping the individual impact areas of the laser beams, the glass pane of the present invention provided with an anti-fog structure can be clearly distinguished from generic structured glass panes of the prior art. The type of glass pane is not limited. The glass pane is preferably a float glass pane, a quartz glass pane, a single-pane safety glass pane, or an insulating glass pane.

[0044] The type of coating is not limited. Advantageously, coatings are selected that impart either additional hydrophilic or hydrophobic properties to the glass pane. In a preferred embodiment of the invention, the transparent coating of steps c1 / a2 is a hydrophilic coating, preferably a titanium oxide coating. Further examples of hydrophilic coatings are nitride-based coatings, metallic layers, e.g., (NiCr), and DLC (diamond-like carbon)-based coatings.

[0045] Of particular note are thin films based on titanium oxide, which possess self-cleaning properties by promoting the degradation of organic compounds under the influence of ultraviolet radiation and the removal of mineral contaminants (dust) under the influence of water runoff. Crystallized titanium oxide in anatase form is known to be more effective at degrading organic compounds than amorphous or crystallized titanium oxide in rutile or brookite form. A frequently used industrial-scale method for depositing thin films, particularly on glass substrates, is cathodic sputtering with magnetic field assistance, also known as the magnetron method. In this process, a plasma is generated under a high vacuum near a target containing the chemical elements to be deposited.The active plasma forms bombard the target and extract the elements, which are deposited on the substrate to form the desired thin film. This process is called reactive when the layer is formed from a material resulting from a chemical reaction between the elements extracted from the target and the gas contained in the plasma. A reactive magnetron process is used to deposit layers of titanium oxide using a metallic titanium target or a ceramic TiOx target (where x < 2) and an oxygen-based plasma-generating gas. In the industrial implementation of the magnetron process, the substrate remains at ambient temperature or is slightly heated (less than 80°C), especially when the substrate passage speed is high (which is generally desired for economic reasons).For example, a method for applying the oxide coating can also be chosen as described in detail in DE 20 2009 018 926 U1.

[0046] With the combination of special laser structuring and coating produced by the inventive method, the respective anti-fog effect of the applied interference pattern with uniform depressions and the coating is enhanced. This makes it possible to impart superhydrophilic properties to a hydrophilic coating. Furthermore, it has been shown that the durability of the combined anti-fog effect can be significantly improved compared to glass panes with only the respective individual treatments, i.e., structured only by the DLIP process or provided only with a hydrophilic coating.

[0047] In a further preferred embodiment of the invention, the transparent coating of steps c1 / a2 is a hydrophobic coating, preferably a polytetrafluoroethylene coating, a silane-based sol-gel coating, or a coating comprising oxide nanoparticles, wherein the nanoparticles have been treated with a polydimethylsiloxane, a silanizing agent, or a combination thereof. Selected nanoparticles include, for example, silica, fumed silica, titanium dioxide, or aluminum oxide. Unmodified DLC (diamond-like carbon) coatings can also be mentioned in this context.

[0048] This makes it possible to impart superhydrophobic properties to a hydrophobic coating. Furthermore, it has been shown that the durability of the combined anti-fog effect can be significantly improved compared to glass panes with only the individual treatments, i.e., structured using the DLIP process or only coated with a hydrophobic coating.

[0049] In one embodiment of the invention, the repeating interference pattern has a line structure or a dot structure. The spacing of the individual depressions within the interference pattern is preferably between 2 and 50 pm, particularly preferably between 9 and 20 pm. This achieves very good anti-fogging properties. In one embodiment of the invention, the repeating interference pattern has a substantially round or square extension. The shape of the region that has the structuring created by interference laser processing can be determined, for example, by appropriate optical devices. Without further shaping devices, a substantially round shape is obtained.

[0050] In one embodiment of the invention, the regions with interference patterns have a diameter of 10-100 pm, preferably 20-80 pm, and in particular approximately 60 pm. This achieves very good anti-fogging properties. At the same time, it is possible to structure a larger region in a single interference laser processing step, which represents a significant improvement in the process properties.

[0051] In one embodiment of the invention, the regions with interference patterns are spaced between 60 pm and 110 pm. The spacing between the regions with interference patterns is preferably not structured. They therefore remain untreated. In this way, the overall area to be structured can be significantly smaller than with generic glass panes of the prior art. This enables a significantly higher process speed, which leads to a reduction in the costs of producing the glass panes and makes these glass panes attractive for the first time, particularly for the consumer market and / or the automotive industry. The spacing between the regions with interference patterns depends in particular on the diameter or size of the regions. They must not be chosen to be too large, since otherwise the anti-fogging property is lost. A maximum spacing of approximately 110 pm has proven to be the approximate limit in this regard.The distances are preferably determined between the centers of two adjacent areas.

[0052] The glass panes designed or manufactured according to the invention are preferably used in a refrigerator door, a shower enclosure, a mirror, or on a vehicle. In this case, the entire component surface does not have to be provided with a non-fogging structure according to the invention; rather, only partial areas can be structured in this way. Such a partial area can, for example, provide a viewing window within the glass surface. It is conceivable to use such a structure in the camera area of ​​a windshield, enabling improved performance of the optical sensors for autonomous driving in the event of sudden fogging of the windshield in the interior.

[0053] In a laboratory test, the durability of an inventive design of the coated glass pane according to the present invention was investigated. For this purpose, a section of a glass pane was provided with a hydrophilic titanium oxide coating. The coating had a thickness in the range of between 10 nm and 20 nm. In a DILP structuring, a picosecond laser with a wavelength of 532 nm and a pulse duration of approximately 10 ± 2 ps was used. To increase the interaction with the glass, a burst mode is used with N > 3, i.e., with N = 3, 4, 5, 6, 7, or 8. The power of the interference pulse is selected so that it is at a fluence of approximately 30 - 40 J / cm 2lies within the interference pixel This value is independent of the number of interference maxima and their size. The laser beam was split into three (partial) beams and an interference was generated on the surface of the glass pane using the (partial) beams, creating depressions in a point-like interference pattern with an average (simple average of the numerical values) depth of 30 - 190 nm. The test pane produced in this way was stored in a climate chamber at 40 °C and 100% humidity for 24 days to simulate an aging process. For comparison, a glass pane without a coating and also structured with an interference laser was subjected to the same conditions. It was found that the anti-fog effect of the glass pane without a coating was still noticeable, but its extent was weakened, so that slight fogging was visible, particularly at the edges of the structured section.After 24 days of weathering, the anti-fog effect of the test pane, which features both laser interference structuring and a hydrophilic titanium oxide coating as described in the invention, was significantly improved and in no way diminished. Within the scope of the present invention, all embodiments mentioned for individual features can also be freely combined with one another, provided they do not contradict one another.

[0054] The invention is explained in more detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and not to scale. The drawings do not limit the invention in any way. They show:

[0055] Fig. 1 is a detailed view of a laser-structured glass sheet according to step b1) of the method of the present invention as a top view of a microscope image,

[0056] Fig. 2 shows a detailed view of a laser-structured glass pane according to step b1) of the method of the present invention as a top view of a microscope image in a different resolution,

[0057] Fig. 3 is a schematic, highly simplified representation of an embodiment of a laser-structured glass pane according to the invention according to step b1) of the method of the present invention,

[0058] Fig. 4 is a schematic, highly simplified representation of a further embodiment of a laser-structured glass pane according to the invention according to step b1) of the method of the present invention,

[0059] Fig. 5 is a schematic representation of steps a2) and b2) of a method of the present invention and

[0060] Fig. 6 is a schematic representation of steps a1), b1) and c1) of a method of the present invention in an alternative embodiment.

[0061] Figure 1 shows a greatly enlarged plan view of a section of a glass pane 110 laser-structured according to step b1) of the method in an embodiment according to the invention. A microscope image shows a first surface 2 in a region 6 having an anti-fog structure 4 in the form of a round, individual interference pattern 5. The interference pattern 5 is formed by point-shaped depressions 7 with sizes between 9 and 20 pm and a depth of <200 nm, preferably <120 nm. The areal extent, or in other words the diameter, of the interference pattern 5 is particularly preferably in the range of approximately 60 pm.

[0062] Figure 2 also shows a greatly enlarged plan view of a larger section of a glass pane 110 laser-structured according to step b1) in a comparable embodiment compared to the illustration in Figure 1. The microscope image shown here shows a first surface 2 in an area provided with an anti-fog structure 4, which has a repeating interference pattern 5. The interference pattern 5 is formed by point-shaped depressions 7 with sizes in the areal extent (horizontally in the plane of the surface) of between 9 and 20 pm and a depth of <200 nm, preferably <120 nm. The extent (diameter) of an individual interference pattern 5 is in the range of 10 - 100 pm, preferably 20 - 80 pm, and in particular approximately 60 pm.In this embodiment, the sequence of separate regions 6 of interference patterns 5 is arranged regularly in rows, and the distances between the regions with interference pattern structuring are a maximum of approximately 110 pm, with structured regions 6 and unstructured regions alternating. In other words, the structured regions 6 are separated from one another by unstructured regions and do not overlap. Advantageously, this significantly reduces the process time and manufacturing effort. Glass panes 100 produced in this way with anti-fog structure 4 can be easily distinguished from other glass panes with overlapping laser structuring due to this characteristic structuring.

[0063] Figure 3 shows a schematic, highly simplified representation of a further embodiment of a laser-structured glass pane 100 according to the invention according to step b1) of the method. Compared to the embodiment of Figure 2, the repeating interference pattern 5 now has an approximately square extent. Here, too, the interference pattern 5 is formed by point-shaped depressions 7 with sizes between 9 and 20 pm and a depth t of <200 nm, preferably <120 nm. In this embodiment, the sequence of regions 6 with interference patterns 5 is also arranged regularly in rows, and the distances between the regions 6 with interference pattern structuring amount to a maximum of approximately 110 pm, so that structured regions 6 and unstructured regions alternate, and there is no overlap of the structured regions.

[0064] Figure 4 shows a schematic, highly simplified representation of a further embodiment of a glass pane 100 according to the invention, structured according to step b1) of the method. Compared to the embodiment of Figure 3, the repeating interference pattern 5 also has an approximately square extent. Here, too, the interference pattern 5 is formed by point-shaped depressions 7 with sizes between 9 and 20 pm and a depth t of <200 nm, preferably <120 nm. In this embodiment, the sequence of interference patterns 5 is not arranged in regular rows, but irregularly. The distances between the regions 6 with interference pattern structuring continue to be a maximum of approximately 110 pm, with structured regions 6 and unstructured regions alternating, i.e., the interference patterns 5 are spatially separated from one another by the unstructured regions, and there is no overlap of the structured regions 6.

[0065] Figure 5 shows a schematic representation of steps a2) and b2) of a method of the present invention. In method step a2), a glass pane 110 is provided with a transparent oxide coating 3, which in a preferred embodiment is a hydrophobic coating, preferably a zirconium oxide coating. In an alternative, preferred embodiment, the transparent coating 3 is a hydrophilic coating, preferably a titanium oxide coating. The transparent coating 3 is applied to the glass pane 110 in a thickness of approximately in the range between 5 nm and 50 nm, preferably between 10 nm and 30 nm, particularly preferably between 15 nm and 20 nm.In step b2), the anti-fog structure 4 is then subsequently formed in the section of the coated surface of the glass pane 110 by laser interference structuring with a pulsed laser 8, specifically in such a way that at least two, preferably at least three laser beams are caused to interfere to introduce depressions 7 into the surface of the section, so that depressions 7 with a depth of <200 nm, preferably <120 nm, are produced in a pattern 5 determined by the interference (analogous to Figs. 1-4). According to the invention, the transparent coating 3 always has a smaller thickness than the depth of the depressions 7 of the structuring introduced into the surface.

[0066] Figure 6 shows a schematic representation of steps a1), b1), and c1) of a method of the present invention in an alternative embodiment. In step a1), a glass pane 110 is provided and, in step b1), structured by laser interference structuring with a pulsed laser 8, in such a way that at least two, preferably at least three, laser beams of the laser 8 are caused to interfere to introduce depressions 7 into the surface, so that depressions 7 with a depth of <200 nm, preferably <120 nm, are produced in a pattern 5 determined by the interference (see Figures 1-4). For example, picosecond lasers with a fluence within an interference pixel of 20-50 J / cm 2 , preferably 30 - 40 J / cm 2, are used for structuring. The pulse length is preferably 10 ps. In the subsequent step c1), the structured section of the glass pane 110 is coated with a transparent coating 3. The coating 3 has a smaller thickness than the depth of the structuring recesses 7 introduced into the surface.

[0067] List of reference symbols

[0068] 100 coated glass pane with anti-fog structure

[0069] 110 glass pane

[0070] 2 first surface of the glass pane 3 oxide coating

[0071] 4 Anti-fog structure

[0072] 5 interference patterns

[0073] 6 Area with interference pattern

[0074] 7 Deepening 8 Laser

Claims

Patent claims 1. A method for producing a glass pane (100) with an anti-fog structure (4), comprising the steps of: a1) providing a surface to be structured, wherein the surface is at least a portion (1) of a glass pane (110), b1) introducing an anti-fog structure (4) into the portion of a surface of the glass pane (100) by laser interference structuring with a pulsed laser (8) such that at least two, preferably at least three laser beams are caused to interfere in order to introduce depressions into the surface, so that depressions (7) with a depth of <200 nm, preferably <120 nm, are produced in a pattern (5) determined by the interference, c1) coating the structured portion with a transparent coating (3), wherein the coating (3) has a smaller thickness than the depth of the depressions (7) of the structuring introduced into the surface;or a2) providing a surface to be structured, wherein the surface is at least a section of a glass pane (100) coated with a transparent coating (3), b2) introducing an anti-fog structure (4) into the section of the coated surface of the glass pane (110) by laser interference structuring with a pulsed laser (8) in such a way that at least two, preferably at least three laser beams are caused to interfere in order to introduce depressions into the surface, so that depressions (7) with a depth t of <200 nm, preferably <120 nm, are produced in a pattern (5) determined by the interference, wherein the coating (3) has a smaller thickness than the depth of the depressions (7) of the structuring introduced into the surface.; 2. Method according to claim 1, characterized in that the laser is guided further during laser interference structuring in such a way that the individual impact areas do not overlap.

3. Method according to claim 1 or 2, characterized in that the transparent coating (3) is a hydrophilic coating, preferably a titanium oxide coating.

4. The method according to claim 1 or 2, characterized in that the transparent coating (3) is a hydrophobic coating, preferably a polytetrafluoroethylene coating, a silane-based sol-gel coating, or a coating comprising nanoparticles of oxides, wherein the nanoparticles have been treated with a polydimethylsiloxane, a silanizing agent or a combination thereof.

5. Method according to one of claims 1 to 3, characterized in that the thickness d of the coating is in the range between 5 nm and 50 nm, preferably between 10 nm and 30 nm, particularly preferably between 15 nm and 20 nm.

6. Method according to one of claims 1 to 4, characterized in that the laser has a wavelength of 343 nm, 355 nm, 515 nm, 532 nm, 1030 nm or 1064 nm and is operated with a pulse duration of 200 fs - 15 ps, preferably with a pulse duration of 10 ± 2 ps.

7. Method according to one of claims 1 to 5, characterized in that a picosecond laser with a fluence within an interference pixel of 20 - 50 J / cm 2 , preferably 30 - 40 J / cm 2 is used.

8. Method according to one of claims 1 to 6, characterized in that the laser is operated in a burst mode with N > 3.

9. Method according to one of claims 1 to 7, characterized in that step b1) or b2) is carried out in such a way that separate regions (6) with interference structuring are obtained, which do not overlap each other.

10. Glass pane (100) comprising a first surface (2) and a second surface (3) which is opposite the first surface, wherein at least one of the two surfaces (2, 3) has at least in sections an anti-fog structure (4) comprising a transparent coating (3) which is produced according to the method according to one of claims 1 to 8, characterized in that that the anti-fog structure (4) of the surface (2, 3) has a plurality of separate areas (6), each with an interference pattern (5).

11. Glass pane (100) according to claim 9, characterized in that the glass pane (110) is a float glass pane, a quartz glass pane, a single-pane safety glass or an insulating glass pane.

12. Glass pane (100) according to claim 9 or 10, characterized in that the repeating interference pattern (5) has a line structure or preferably a point structure.

13. Glass pane (100) according to one of claims 9 to 11, characterized in that the depressions of the repeating interference pattern (5) each have a substantially round or square extension.

14. Glass pane (100) according to claim 12, characterized in that the regions (6) with interference patterns (5) each have a diameter of 10 - 100 pm, preferably of 20 - 80 pm, and in particular of approximately 60 pm.

15. Glass pane (100) according to claim 12 or 13, characterized in that the regions (6) with interference pattern (5) have a non-structured distance from one another between 60 pm and 110 pm.

16. Use of a glass pane (100) according to one of claims 9 to 14 or a glass pane (100) manufactured according to one of claims 1 to 8 in a refrigerator door, a shower partition, a mirror or on a vehicle.

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