WO2023202817A1

WO2023202817A1 - Glass pane with an anti-reflective surface and method for the production thereof

Info

Publication number: WO2023202817A1
Application number: PCT/EP2023/055718
Authority: WO
Inventors: Li-Ya Yeh; Jan Hagen; Roberto ZIMMERMANN
Original assignee: Saint-Gobain Glass France
Priority date: 2022-04-19
Filing date: 2023-03-07
Publication date: 2023-10-26
Also published as: CN117255772A

Abstract

The invention relates to a method for producing a glass pane with an anti-reflective surface, wherein (a) a substrate (1) made of glass is provided, (b) a surface of the substrate (1) is provided with a coating (2) based on silicon dioxide (SiO2), and (c) at least one region of the surface of the coating (2) facing away from the substrate (1) is structured, in that elevations (5) are generated by the beam (4) of a laser (3), wherein the beam (4) is circularly polarised and the laser (3) is operated in a pulsed manner with pulse lengths in the femtosecond- or nanosecond-range.

Description

Glass pane with a reflection-reduced surface and process for its production

The invention relates to a method for producing a glass pane with a reflection-reduced surface, the glass pane with the reflection-reduced surface and its use.

It is known to provide glass panes with anti-reflective coatings. This allows the reflection of light on the relevant surface of the glass pane to be significantly reduced. Various types of anti-reflective coatings are known. They are often formed from a plurality of thin layers, with alternating layers with high and low refractive index being arranged and the anti-reflective effect being caused by interference effects. Such anti-reflective coatings are for example from EP0490613A2, US6068914A and

WO2019179682A1 known. Such coatings are usually produced by physical vapor deposition, in particular magnetic field-assisted cathode sputtering (“magnetron sputtering”). Due to the large number of individual layers required, production is costly and time-consuming. In addition, sputtered coatings sometimes have limited stability against mechanical influences and aging.

Alternatively, anti-reflective coatings with a low refractive index are used, which are applied to the glass pane using wet chemicals. For example, coatings made of nanoporous silicon oxide are known, the antireflective effect being generated by avoiding an interface with an abrupt and strong change in the refractive index. Such a coating, which is produced using the sol-gel process, is known, for example, from WO2008059170A2. However, wet-chemically applied coatings often exhibit significant inhomogeneity, which is often insufficient for applications with high aesthetic demands. In addition, their stability against mechanical influences and aging is also limited.

From US2021138577A1 a method is known in which glass surfaces are functionalized using laser radiation. A structured surface is created with two-dimensionally distributed elevations, in particular so-called laser-induced ones periodic surface structures (LIPSS, Laser-Induced Periodic Surface Structures), which provide the surface with reflection-reduced properties. Applied to types of glass with high chemical purity, especially quartz glass made from pure silicon dioxide, the process produces good results. However, it has been shown that the process can only be transferred to other types of glass to a limited extent, in particular types of glass of lower chemical purity. On glass panes made of soda-lime glass, which is typically used as window glass, it was observed that the process leads to a less pronounced reflection-reducing effect and that the processed glass panes have significant inhomogeneities with regard to the aesthetic appearance. In particular, it was found that the glass panes became cloudy to a certain extent (“haze”), which affected their appearance to an unacceptable extent when viewed through the glass pane.

It is known from the scientific literature that an SiO2 coating on soda-lime glass means that the surface can be structured better and more homogeneously using plasma etching, in particular to create hydrophobic properties (E. Yu et al., Extreme wettability of nanostructured glass fabricated by non-lithographic, anisotropic etching, Scientific Reports 5 (2015), Article number: 9362).

From US6291797B1 a method is known in which a coating on a glass substrate, for example an SiO2 coating, is processed with pulsed laser radiation. This creates a surface structure made up of alternating convex and concave sections, particularly through evaporation or ablation. The glass substrate with the processed coating is intended, for example, as a diffraction grating. US6291797B1 does not address the polarization of the laser radiation used.

There is a need for improved processes for producing reflection-reduced surfaces that can be carried out cost-effectively, achieve a good anti-reflective effect, lead to aesthetically demanding results and can be used regardless of the type of glass, especially on glass panes made of soda-lime glass. The present invention is based on the object of providing such an improved glass pane with a reflection-reduced surface and an improved method for its production. The object is achieved according to the invention by a method according to claim 1. The object is also achieved by a glass pane according to the independent claim. Preferred versions and configurations emerge from the subclaims.

The glass pane according to the invention and the method according to the invention for producing it are presented together below, with explanations and preferred embodiments relating equally to the glass pane and the method. If preferred features are described in connection with the method, it follows that the glass pane is also preferably designed accordingly. Conversely, if preferred features are described in connection with the glass pane, it follows that the method is also preferably carried out accordingly.

According to the inventors' assumption, the poor results of surface structuring on glass panes made of soda-lime glass are related to their chemical composition. In contrast to quartz glass, which consists of pure silicon oxide, soda-lime glass and other utility glasses contain significant mineral admixtures, especially sodium and calcium oxide. The chemical composition is therefore significantly less homogeneous, which is particularly evident on a micro- and nanometer scale. The invention is based on the idea of providing the glass pane with a coating of silicon oxide (SiO2) and carrying out the laser structuring on this coating instead of on the glass substrate itself. The coating achieves a chemical homogenization of the substrate surface. In other words, the coating provides a chemically homogeneous material on which laser structuring can be carried out with high quality, while the chemically inhomogeneous glass substrate is not affected by laser processing. The SiO2 coating is easier and more cost-effective to apply than, for example, anti-reflective coatings made of several thin-film layers with different refractive indices. Due to the chemical similarity to the substrate, the SiO2 coating is also highly stable against mechanical influences. It acts as a kind of protective layer for the substrate. These are major advantages of the present invention.

The method according to the invention for producing a glass pane with a reflection-reduced surface comprises a sequence of process steps, wherein (a) a substrate made of glass is provided,

(b) a surface of the substrate is provided with a coating based on SiO2 and

(c) then at least a region of the surface of the coating facing away from the substrate is structured by producing elevations using the radiation of a laser.

According to the invention, the radiation from the laser is circularly polarized. The laser is operated in a pulsed manner with pulse lengths in the femtosecond or nanosecond range.

The glass pane according to the invention can be produced using the method according to the invention. The glass pane according to the invention with a reflection-reduced surface therefore comprises at least one substrate made of glass and a coating based on SiÜ2 on a surface of the substrate, with at least a region of the surface of the coating facing away from the substrate being structured by elevations. The elevations are introduced into the coating using the circularly polarized radiation of a pulsed laser with pulse lengths in the femtosecond or nanosecond range. The polarization of the laser radiation is expressed in the glass pane in particular in the shape of the elevations, the pulse length in the surface structure, and in particular the amount of melted material.

The reflection-reduced surface can also be referred to as an anti-reflective surface, and the coating processed according to the invention as an anti-reflection coating. The coating means that the reflection of the coated surface is reduced at least in part of the visible spectral range from 380 nm to 780 nm, in particular in the entire visible spectral range from 380 nm to 780 nm, compared to a surface of the same type Substrate with a similar coating based on SiÜ2, which is not structured using the method according to the invention.

In a preferred embodiment, the substrate is made of soda-lime glass or consists of soda-lime glass. Soda-lime glass is the most common type of glass (“normal glass”) and is particularly used as window glass. Therefore, glass substrates made from soda lime glass offer a large number of possible applications. Even if the invention was made in connection with soda-lime glass, it is not limited to such glass substrates. Rather, it can also be used on other types of glass, in particular other types of glass with mineral additions such as borosilicate glass or aluminosilicate glass. Applications are even conceivable using substrates made of pure quartz glass.

The substrate is preferably a plate-like object, such as is used as a window pane or cover pane in electrical and electronic applications. The substrate can be flat (for example in the case of window panes of buildings or vehicles such as trains, buses or agricultural vehicles) or curved (for example in the case of window panes of vehicles such as cars or trucks).

The thickness of the substrate can be chosen freely according to the requirements of the specific application. Thicknesses in the range from 0.5 mm to 10 mm, preferably from 1 mm to 5 mm, are common, particularly in the case of window panes and cover panes.

The substrate typically has two main surfaces intended to be seen through the substrate and a side edge surface extending therebetween. One of the main surfaces is provided with the coating according to the invention. According to the invention, the coating is based on SiÜ2. This means that the coating consists predominantly of silicon oxide, in particular essentially of silicon oxide in addition to any impurities or dopants. The proportion of silicon oxide is preferably more than 80% by weight, particularly preferably more than 90% by weight.

The silicon oxide can be deposited stoichiometrically, superstoichiometrically or substoichiometrically with respect to the oxygen content. Even if, for the sake of simplicity, silicon oxide is abbreviated with the stoichiometric molecular formula SiÜ2 in the context of the present invention, this does not provide any information about the stoichiometry. The silicon oxide can deviate from the stoichiometry of the empirical formula SiÜ2, which could therefore also be referred to as SiO _x , where x is preferably in the range from 1.5 to 2.5. However, stoichiometric deposition (x=2) is preferred.

The coating based on SiO2 (also called SiO2 coating) is in particular a single thin layer. This layer is preferably deposited directly on the substrate surface, so there are no further layers between the substrate and the SiO2 coating. However, additional layers can optionally be added to the SiO2 layer. Coating can be applied, for example to provide the glass pane with additional functions.

The SiC>2 coating should be sufficiently thick so that the structuring according to the invention can be formed in it. Good results are achieved in particular when the coating has a thickness of at least 30 nm, preferably at least 50 nm. On the other hand, the coating should not be made too thick, because then the production costs in particular increase significantly without a better reflection-reducing effect being achieved. In an advantageous embodiment, the coating has a thickness of at most 500 nm, preferably at most 200 nm, particularly preferably at most 150 nm. The thickness is, for example, in the range from 50 nm to 200 nm.

The SiO2 coating can have dopings, preferably boron, aluminum, titanium, zirconium or hafnium. Doping with nitrogen is also possible.

The refractive index of the coating is preferably less than or equal to 1.60, particularly preferably less than or equal to 1.55, most preferably less than or equal to 1.50, for example from 1.40 to 1.50 or from 1.45 to 1.50 . This achieves particularly good reflection-reducing properties. This is also due to the fact that the refractive index of the coating is then very similar to that of the glass substrate (for example soda lime glass: 1.47). The refractive index is measured at a wavelength of 550 nm. The refractive index is fundamentally independent of the measurement method and can be determined, for example, using ellipsometry. Ellipsometers are commercially available, for example from Sentech.

In an advantageous embodiment, the coating is deposited on the substrate by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Cathode sputtering (“sputtering”), in particular magnetic field-assisted cathode sputtering (“magnetron sputtering”), and plasma-assisted chemical vapor deposition (PECVD, plasma enhanced chemical vapor deposition) as well as chemical vapor deposition at atmospheric pressure (APCVD, atmospheric pressure chemical vapor deposition) are particularly preferred ). These processes are widely used industrially, are comparatively inexpensive and enable coatings with high mechanical and optical properties Quality. But other thin-film technologies can also be used in principle, such as vapor deposition or atomic layer deposition (ALD).

The coating is preferably applied over the entire surface of the substrate surface, so that the entire main surface of the substrate is provided with the coating. In principle, however, it is also possible to coat only one area of the surface, for example if only part of the glass pane is to be provided with the reflection-reduced properties.

According to the invention, at least one area of the coating is structured by laser processing. The entire coating is preferably structured. However, it is also possible to structure only a partial area of the coating, while another area of the coating is not treated with laser processing. This is conceivable, for example, if only part of the glass pane is to be provided with the reflection-reducing properties, but the substrate was still coated over the entire surface, for example because this was easier to carry out than just partial coating with complex masking techniques.

The structuring consists in providing the surface of the SiO2 coating with the elevations according to the invention. These elevations result in the reflection on the relevant surface of the glass pane being reduced. The reflection-reducing effect is caused in particular by the fact that the elevations cause a gradual spatial change in the refractive index. However, the material remains transparent. The spectral range in which the reflection-reducing effect occurs depends in particular on the dimensions of the elevations and the occupancy density of the surface with the elevations or the periodicity of the elevations. The glass pane can thus be specifically provided with the properties required for the specific application.

According to the invention, the laser radiation is circularly polarized, preferably essentially purely circularly polarized. This creates an elevation without a preferred direction within the irradiated area, in particular an elevation with a round, approximately circular base area. This has the advantage that the reflection-reducing properties generated are anisotropic, i.e. do not depend on the viewing angle. The laser radiation is directed onto the SiC>2 coating in order to structure it. The coating preferably hits the glass pane via the coated surface. The laser radiation therefore irradiates the coating without first passing through the substrate. The laser radiation is preferably focused on the SiO2 coating, in particular (at least approximately) on its surface facing away from the substrate. The laser radiation is focused using a focusing optical element, for example a lens or an objective. F-theta lenses or f-theta lenses are particularly suitable. These result in the foci of the laser radiation being arranged in one plane at different exit angles and enable a constant speed of movement of the laser radiation over the coating. The focal length of the focusing element determines the extent of the focus of the laser radiation and thus the extent of the elevations generated. The focal length of the focusing optical element is preferably from 50 cm to 450 cm, particularly preferably from 55 cm to 300 cm. In this area, in particular, expansions of the laser foci are achieved, which are advantageous for forming the structuring. The laser focus on the coating can have an (at least approximately) circular shape. However, the irradiated surface can also be designed differently, for example with an elliptical focus that is elongated perpendicular to the direction of movement. This means that a larger area can be irradiated in one pass of the laser radiation.

Between the laser and the focusing optical element, the radiation from the laser can be guided through at least one optical waveguide, for example a glass fiber. Additional optical elements can also be arranged in the beam path of the laser, for example collimators, diaphragms, filters or elements for frequency doubling.

The structuring of the SiO2 coating is created by moving the laser radiation relative to the coated substrate. In an advantageous embodiment, the substrate is stationary (for example arranged on a holder or a base) and the laser radiation is moved over the coating. The movement of the laser radiation is preferably carried out by at least one mirror which is connected to a movable component. The movable component allows the mirror to be tilted in two directions, preferably two mutually orthogonal directions, particularly preferably horizontally and vertically. The laser radiation can also be moved by several mirrors each connected to a movable component. For example, the movement of the laser radiation can take place through two mirrors, one mirror in the horizontal direction and the other mirror can be tilted vertically. Conventional laser scanning systems can be used to move the laser radiation, for example motorized xy(-z) scanners or galvanometer scanners. The laser radiation is moved over the coating in particular in a grid-like manner in the form of successive lines.

The relative movement of laser radiation and substrate can in principle also be realized in other ways. The movement of the laser radiation can alternatively take place by moving the focusing element and the laser or by moving the focusing element and an optical waveguide over the stationary substrate. Alternatively, the laser radiation can be stationary and the substrate can be moved.

The laser radiation is preferably moved several times over the coating. This has the advantage that the energy required to create the elevations is distributed successively at the appropriate points over several passes and not concentrated in a single pass. This reduces the risk of damaging the substrate and/or the coating. The irradiated areas are successively heated and melted, with the melted area of the coating solidifying again after each irradiation. The elevations are built up gradually, reaching a greater height with each pass of laser irradiation.

Alternatively, it is also possible to move the laser radiation over the coating only once. The speed of movement of the laser radiation should then be chosen to be lower than when moving the laser radiation multiple times over the coating in order to build up the elevations in a single pass. With slow processing, partial ablation of the coating can also occur, which further increases the surface structuring and may be desirable.

In an advantageous embodiment, the laser radiation is moved continuously over the coating. As a result of the continuous movement, successive laser pulses hit different points on the coating, the distance between which depends on the pulse repetition frequency (repetition frequency) of the laser and the speed of movement of the laser radiation. Pulse repetition frequency and movement speed can be coordinated with one another in such a way that the irradiated areas of successive pulses overlap or are completely separated from one another. Overlapping may be preferred to achieve greater local heating.

The laser radiation is preferably at a speed of 500 mm/s to 10,000 mm/s, particularly preferably 1,000 mm/s to 8,000 mm/s. This achieves particularly good results, especially with the preferred ranges for the repetition frequency of the pulses described below.

When the laser radiation hits the coating, the elevations according to the invention are generated. The laser structuring according to the invention can be understood as a type of laser-induced periodic surface structures (LIPSS, laser-induced periodic surface structures), without the invention being tied to a scientific theory. The formation of LIPSS is probably related to an inhomogeneous energy absorption of a rough surface and the hydrodynamic behavior of the resulting melted material during and immediately after irradiation. It is conceivable that the laser irradiation initially leads to the roughening of the SiO2 surface, from which the elevations then form as LIPSS.

The irradiated surface is heated by the laser radiation, whereby the SiO2 coating is locally melted or melted and a plurality of local elevations are formed. By moving the laser radiation multiple times over the coating, the individual areas are successively heated and melted, with the melted area of the coating solidifying again after each irradiation. The elevations are built up step by step, reaching a greater height with each pass of laser irradiation. The surface structuring using LIPSS leads in particular to elevations whose dimensions (extent of the base area) are significantly smaller than the extent of the laser focus on the coating. Therefore, when the laser focus hits an area, a plurality of bumps are created simultaneously in this area. In addition to LIPSS, partial ablation processes can occur, especially when the procedure is carried out slowly, which also contributes to surface structuring.

In an alternative embodiment, the laser radiation is not moved continuously, but stepwise over the coating, with the laser focus at each irradiation position remains for a while before it is moved to the next irradiation position. The laser radiation is moved step by step from one irradiation position to the next. Each irradiation position is irradiated with several laser pulses. The irradiation positions can be selected depending on the extent of the laser focus on the coating in such a way that the irradiated surface of adjacent irradiation positions overlaps. In this embodiment, too, the laser radiation is preferably moved several times over the coating, so that a comparatively small number of laser pulses (for example two to five laser pulses) hit each irradiation position with each pass. In this way, the individual areas of the coating can be successively heated and melted, with the melted area of the coating solidifying again after each irradiation. The elevations are built up gradually, reaching a greater height with each pass of laser irradiation. This reduces the risk that the substrate and/or the coating will be damaged as a result of excessive radiation.

The elevations are distributed two-dimensionally over the structured area of the SiC>2 coating (or over the entire SiC>2 coating if the entire coating is structured with the laser radiation). The surveys can be distributed regularly or approximately regularly. In this way, particularly homogeneous reflection-reducing properties can be achieved. With regularly distributed surveys, the distance between neighboring surveys is essentially constant and the area occupancy is independent of location. However, an irregular distribution of surveys is also possible.

Due to the circular polarization of the laser radiation, the base area is typically rounded, in particular (at least approximately) circular or elliptical. The elevations taper upwards, i.e. in the direction away from the substrate. The elevations can in particular be described at least approximately as a spherical segment or segment of an ellipsoid of revolution.

The elevations in particular have an extent in the nanometer range, being greater than or equal to 1 nm and less than 1 pm. By extension we mean the height and the longest dimension of the base area. The extent of the elevations is particularly preferably from 1 nm to 1000 nm, very particularly preferably from 20 nm to 500 nm, in particular from 50 nm to 200 nm. The extent of the elevations is determined in particular by the size of the laser focus on the coating. Also the distances neighboring elevations are preferably in the nanometer range, particularly preferably in the above-mentioned ranges for expansion.

Such a structure consisting of elevations in the nanometer range is produced by the method according to the invention using laser processing. The glass pane according to the invention can therefore also be characterized as a glass pane with a reflection-reduced surface, comprising at least: a substrate made of glass and a coating based on silicon oxide (SiO2) on a surface of the substrate, at least a region of the surface of the coating facing away from the substrate is structured by elevations which are distributed two-dimensionally over the said area and have an extent and mutual distances in the nanometer range.

According to the invention, the pulse length of the laser is in the femtosecond or nanosecond range. The pulse length is preferably at most 15 ps, particularly preferably from 400 fs to 15 ps, very particularly preferably from 800 fs to 10 ps. This achieves particularly good results, especially with regard to efficient heating and melting of the SiO2 coating and efficient formation of the elevations. The repetition frequency of the laser pulses is preferably from 1 kHz to 1 MHz, preferably from 400 kHz to 1 MHz.

In principle, laser radiation in the UV range, in the visible range or in the IR range of the electromagnetic spectrum can be used. The wavelength of the laser radiation is preferably from 200 nm to 1100 nm, particularly preferably from 300 nm to 1100 nm. Particularly good results are achieved in this way. Solid-state lasers can preferably be used (for example Nd:YAG laser or Yb:YAG laser), which can be frequency-doubled, frequency-tripled or frequency-doubled twice if necessary. Such lasers are widely used industrially, relatively inexpensive and efficient. Alternatively, diode lasers, excimer lasers, gas lasers or dye lasers can also be used.

The irradiation of the laser radiation on the coating is preferably from 1 J/cm ² to 5 J/cm ² , particularly preferably from 1.47 J/cm ² to 3.8 J/cm ² . The radiation can also be referred to as irradiation. It is the time-integrated irradiance and gives the incident radiation energy of the laser radiation per area. It can be advantageous to choose the irradiation smaller than, but close to, the ablation limit at which laser ablation of the SiC>2 coating begins. A large amount of energy is then advantageously introduced to heat the coating and the formation of the elevations is efficient without the coating being damaged by the laser radiation.

The output power of the laser is preferably from 20 W to 50 W.

The size and periodicity or occupancy density of the surveys can be influenced by the parameters of the laser radiation. The wavelength in particular plays a crucial role.

In an advantageous development of the invention, after laser structuring of the SiC>2 coating, a further coating is applied or deposited on the SiC>2 coating. Additional coating allows the glass pane to be given additional functions. In a preferred embodiment, the further coating is a hydrophilic or hydrophobic coating in order to additionally provide the glass pane with hydrophilic or hydrophobic properties. Such coatings can be formed, for example, from fluoropolymer or silicone polymer layers.

The invention also includes the use of a glass pane according to the invention as a window pane of vehicles, buildings or interiors (or as a component thereof, for example as a component of a composite pane or insulating glazing), as a cover pane for electrical or electronic devices (for example as a cover pane for solar cells), or as Part of furniture and furnishings. The invention is explained in more detail using a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way. Show it:

1 shows a cross section through an embodiment of a glass pane according to the invention with a surface with reduced reflection,

2 is an enlarged view of section Z from FIG. 1,

Fig. 3 Cross section through the glass pane from Figure 1 at different times of its production using the method according to the invention.

Figure 1 and Figure 2 each show a detail of a glass pane according to the invention. The glass pane comprises a substrate 1 made of soda-lime glass with a thickness of, for example, approximately 3 mm. A coating 2 made of SiO2, which can be doped with aluminum, for example, is applied over the entire surface of the substrate 1.

The surface of the coating 2 facing away from the substrate 1 is not flat, but has a structure. The structure is formed by a large number of elevations 5, which have been introduced into the coating 2 by laser radiation. The surface of the coating 2, which is flat in the initial state, has been structured by the laser radiation.

The elevations 5 are distributed essentially regularly and two-dimensionally over the surface of the coating 2. They have an approximately circular base area on which they are dome-shaped. The elevations 5 approximately have the shape of a segment of a prolate ellisoid of revolution, in particular a half-ellipsoid of revolution. Between the elevations 5 in the cutting line (hatched), the elevations 5 of the row behind them can be seen in FIG. 2 (not hatched).

The elevations have, for example, a diameter of approximately 125 nm (based on the base area) and a height of approximately 100 nm. The distance between adjacent elevations 5 is, for example, approximately 125 nm. The structuring in the form of the elevations 5 provides the surface of the glass pane with reflection-reducing properties. In principle, such a structuring can also be formed directly in the substrate surface, as taught in US2021138577A1. In the case of substrates 1 made of types of glass with mineral additives, such as soda-lime glass, this does not lead to satisfactory results. The inventors attribute the observation to the chemical inhomogeneity of the glass. The coating 2 ensures a chemical homogenization of the surface, which now essentially consists of SiO2, apart from impurities and any dopants. The chemically comparatively homogeneous coating 2 can be provided with the elevations 5 in a higher optical quality.

Figure 3 shows cross sections through the glass pane during its production according to the invention. First, the substrate 1 is provided (Figure 3a). A surface of the substrate 1 is then provided with the coating 2 (FIG. 3b), for example by magnetic field-assisted cathode sputtering (“magnetron sputtering”). The coating 2 is then deposited flat on the surface.

The coating 2 is then structured using laser processing (FIG. 3c), with the elevations 5 being formed. The radiation 4 from a laser 3 is focused onto the coating 2 using, for example, an f-theta lens as a focusing element 6. The radiation 4 is purely circularly polarized and has a wavelength of, for example, 355 nm. Laser 3 is a “frequency-tripled” Nd:YAG laser (sum frequency mixing of the fundamental radiation with the frequency-doubled radiation; third harmonic). The laser 3 is operated in pulsed mode with a pulse length of 10 ps and a repetition frequency of 400 kHz. The radiation 1 can be moved over the coating 2 by means of a movable mirror 7. For the sake of simplicity, only one mirror 7 is shown to clarify the principle. In reality, conventional laser scanning systems are typically used that have a larger number of movable mirrors. The radiation 4 is now moved repeatedly over the coating 2 in a grid-like manner and continuously. The coating 2 is thereby successively heated and melted in areas and solidifies again until the next pass. As a result, the elevations 5 are gradually formed, in particular as laser-induced periodic surface structures (LIPSS). The elevations 5 grow with each pass. List of reference symbols:

(1) Glass substrate

(2) Coating based on SiC>2 (3) Laser

(4) Radiation from laser 4

(5) Survey

(6) focusing element

(7) tiltable mirror

Z enlarged area

Claims

Claims Method for producing a glass pane with a reflection-reduced surface, wherein

(a) a substrate (1) made of glass is provided,

(b) a surface of the substrate (1) is provided with a coating (2) based on silicon oxide (SiÜ2) and

(c) at least a region of the surface of the coating (2) facing away from the substrate (1) is structured by generating elevations (5) using the radiation (4) of a laser (3), the radiation (4) being circularly polarized and the laser (3) is operated in a pulsed manner with pulse lengths in the femtosecond or nanosecond range. Method according to claim 1, wherein the elevations (5) are distributed two-dimensionally over said area and have an extent and mutual distances in the nanometer range, preferably from 20 nm to 500 nm, particularly preferably from 50 nm to 200 nm. Method according to claim 1 or 2, wherein the substrate (1) is made of soda-lime glass. Method according to one of claims 1 to 3, wherein the coating (2) has a thickness of 30 nm to 500 nm, preferably 50 nm to 200 nm. Method according to one of claims 1 to 4, wherein the coating (2) has a refractive index of less than or equal to 1.60, preferably less than or equal to 1.55, particularly preferably less than or equal to 1.50. Method according to one of claims 1 to 5, wherein the coating (2) is deposited on the substrate (1) by magnetic field-assisted cathode sputtering, by plasma-assisted chemical vapor deposition or by chemical vapor deposition at atmospheric pressure. Method according to one of claims 1 to 6, wherein the radiation (4) is moved over the coating (2) in method step (c), preferably several times. Method according to claim 7, wherein the radiation (4) is moved continuously over the coating (2). Method according to one of claims 1 to 8, wherein the pulse length of the laser (3) is at most 15 ps, preferably from 400 fs to 15 ps, particularly preferably from 800 fs to 10 ps. Method according to one of claims 1 to 9, wherein the wavelength of the radiation (4) is from 200 nm to 1100 nm. Method according to one of claims 1 to 10, wherein the laser (3) is operated in a pulsed manner with a repetition frequency of 1 kHz to 1 MHz. Method according to one of claims 1 to 11, wherein the irradiation of the radiation (4) on the coating (2) is from 1 J/cm ² to 5 J/cm ² . Method according to one of claims 1 to 12, wherein after method step (c) a hydrophilic or hydrophobic coating is deposited on the coating (2). Glass pane with a reflection-reduced surface, in particular produced using the method according to one of claims 1 to 13, at least comprising:

- a substrate (1) made of glass and

- a coating (2) based on silicon oxide (SiÜ2) on a surface of the substrate (1), at least a region of the surface of the coating (2) facing away from the substrate (1) being structured by elevations (5) which are two-dimensional are distributed over the said area and have an extent and mutual distances in the nanometer range. Use of a glass pane according to claim 14 as a window pane of vehicles, buildings or interiors, as a cover pane for electrical or electronic devices or as a component of furniture and furnishings.