EP4031502A1

EP4031502A1 - Three-dimensionally formed thin sheet glass

Info

Publication number: EP4031502A1
Application number: EP20723054.1A
Authority: EP
Inventors: Michael Meister; Katharina Alt; Volker Seibert; Ulrich Lange; Stephan Corvers
Original assignee: Schott AG
Current assignee: Schott AG
Priority date: 2019-09-18
Filing date: 2020-04-27
Publication date: 2022-07-27
Also published as: US20220204382A1; WO2021052636A1; CN114423717A; JP2022548702A; DE102019125099A1

Abstract

The invention relates to thin sheet glass for an optical component, having a first side with a first surface, and a second side, opposite the first side, having a second surface. The thin sheet glass has a three-dimensional form with at least one desired curvature and a thickness of less than 700 µm. All surface structure components, on at least one first measuring surface of 3 x 3 mm² of the first surface, have an arithmetical mean height Sa of less than 30 nm in a wavelength range of 0.1 mm to 1mm.

Description

Three-dimensional formed thin glass

The present invention relates to a thin glass for an optical component which has a high surface quality and a high optical quality. Thin glass here denotes a glass substrate with a thickness of less than 700 μm, preferably less than 500 μm, in particular less than 300 μm. The invention further relates to an optical component comprising a thin glass, a product comprising a thin glass, a tool for producing a thin glass and a method for producing a thin glass.

Thin glass, in particular three-dimensionally formed thin glass, can be used in various applications. Possible fields of application are optics, ophthalmology, electronic devices and the automotive sector. In these and other fields, the thin glass according to the invention can be used, on the one hand, to achieve visually appealing, hard and scratch-resistant surfaces and, on the other hand, to enable a compact design and weight reduction. For example, thin glass can be laminated as a cover on plastic components in order to protect eyeglass lenses, display devices, displays, fittings and other sensitive components from negative mechanical, physical and / or chemical influences.

Background of the invention

The use of glass substrates with non-planar surfaces as a cover to protect sensitive components is known from various applications and is described, for example, in the introduction to document WO 2018/200454 A1.

When forming raw glass wafers into three-dimensional glass substrates by means of methods known from the prior art, however, defects often arise in the glass substrates, which negatively affect the optical quality of the end product. The resulting defects stand in the way of the use of the glass substrates in visually appealing applications and as a design element. In order to repair the defects that arise during the forming process, the three-dimensionally formed glass substrates are reworked in practice after the forming process. In particular, defects are repaired by subsequent polishing of the three-dimensional reshaped glass substrate. However, this makes the manufacturing process complex.

The document DE 102016 105004 A1 discloses an optical component with a surrounding formed glass substrate and an associated manufacturing process, whereby the optical component has a high surface quality even without post-treatment.

This from the prior art and other methods known from practice, which achieve three-dimensionally formed glass substrates with a relatively high surface quality with or without subsequent polishing, are, however, limited to the production of comparatively thick glass substrates. The comparatively great thickness of such glass substrates from the prior art, however, limits their usability, in particular with regard to compact and weight-critical components.

One object of the present invention is to provide a further improved glass substrate with high surface quality and high optical quality and a suitable manufacturing process for manufacturing such a glass substrate.

This object is achieved by a thin glass according to claim 1 and a method according to claim 18 and by means of a tool according to claim 15. Further developments and embodiments of the thin glass, the method and the tool are the subject of the dependent claims and the following description.

Description of the invention

One aspect of the invention relates to a thin glass for an optical component which comprises a first side with a first surface and a second side opposite the first side with a second surface. The thin glass has a three-dimensional shape with at least one desired curvature and a thickness of less than 700 μm. On at least one first measuring area of 3 x 3 mm ^{2 of} the first surface, all surface structure components in a wavelength range from 0.1 mm to 1 mm have an average arithmetic height Sa of less than 30 nm, preferably less than 20 nm, more preferably less than 10 nm , even more preferably below 8 nm. For example, on the first measuring surface, all surface structural components in a wavelength range from 0.1 mm to 1 mm can have a mean arithmetic height Sa between 1 nm and 30 nm, preferably between 3 nm and 20 nm, more preferably between 6 nm and 10 nm. The values for the mean arithmetic height relate to a measurement by means of white light interferometry, with a bandpass filtering of 0.1 mm to 1 mm, ie with a bandpass filtering for the observation of surface structure components in wavelength ranges from 0, 1 mm to 1 mm.

Surface structure components in a wavelength range from 0.1 mm to 1 mm can For the purposes of this invention, these are referred to as medium-scale surface structure components. They can be distinguished from short-scale surface structure components (here: smaller than 0.1 mm) and from long-scale surface structure components (here: larger than 1 mm). An entire surface structure of a surface of a thin glass can comprise short-scale, medium-scale and / or long-scale surface structure components. Here, the medium-scale surface structure components according to the invention relate to a waviness of a surface of the thin glass, while the short-scale surface structure components relate to a roughness of a surface of the thin glass and the long-scale surface structure components relate to a shape of the surface of the thin glass. The bandpass filtering of 0.1 mm to 1 mm can ensure that only selected surface structure components relating to the waviness of the thin glass are considered in a wavelength range of 0.1 mm and 1 mm. The inventors have recognized that the surface structure components in this wavelength range are particularly critical for the production of thin glasses with optically appealing and / or functional transmission and / or reflection, unlike in the production of thicker glasses. According to the invention, all of these medium-scale surface structure components of the first surface of the thin glass have the mean arithmetic height Sa specified above. The bandpass filtering thus enables a scale-adjusted observation or image of the surface, i.e. a so-called SL surface that has been adjusted for short-scale and long-scale components, which precisely highlights the area that is to be seen according to the invention as particularly relevant for thin glasses. The wavelength of a surface structure component can essentially correspond to a characteristic extent, in particular a lateral extent, of the surface structure component or at least map it. However, due to the filtering during surface detection, especially in the edge areas of surface structures, slight deviations can occur between the actual lateral extent of the surface structure component and its wavelength. It goes without saying that the term wavelengths can be used here to describe the surface structure components, since each surface structure can be represented by superimposing sine waves with different wavelengths and amplitudes.

The thin glass according to the invention can also be described as a three-dimensional, curved, hot-formed thin glass substrate with a high surface quality and a high optical quality, in particular in the visible range of light. The first and / or the second surface of the thin glass can form, at least in sections, a curved free-form surface, in particular an aspherically curved free-form surface. The thin glass can be curved around several bending axes. The multiple bending axes can be mutually exclusive to cut. The thin glass can have intersecting and non-intersecting bending axes. The first and / or the second surface of the thin glass can have at least one point (bending point) at which a first tangential direction is selected as the x-axis, at which a further tangential direction which is orthogonal to the x-axis , is selected as the y-axis, and on which a direction orthogonal to the x-axis and the y-axis is selected as the z-axis, the x-axis, the y-axis and the z-axis in the at least one Cut point. The thin glass can be bent at least at the at least one point. The associated surface of the thin glass can be bent at the at least one point in the X-axis direction, so that a first bending radius of the associated desired curvature lies in the XZ plane, which runs through the X-axis and the Z-axis. Additionally or alternatively, the associated surface of the thin glass can be bent at the at least one point in the Y-axis direction, so that a second bending radius of the associated desired curvature lies in the YZ-plane, which runs through the Y-axis and the Z-axis. The first and the second bending radius can be the same or different. In an embodiment with several points of the type described above, the bending radii in the individual points can be the same and / or different with regard to the number of bending radii and the size of the bending radii.

The thin glass according to the invention is preferably a thin glass that has not been reworked, that is, a thin glass that is left untreated or untreated after hot forming. This means that the thin glass according to the invention already has an optimal surface roughness and surface roughness without subsequent processing, for example without subsequent polishing. Well with at most minimal deviations from the arithmetic mean of the surface. In contrast to conventional three-dimensionally formed thin glasses, at least one work step can thus be saved in the production of the thin glass according to the invention.

A large number of different surface defects can occur in the production of intended-curved, three-dimensional thin glass. Reshaping thin glasses in particular is particularly difficult, as thin glasses tend to shape surface defects differently and sometimes more strongly than thicker glasses. The inventors of the present invention have recognized that among the possible surface defects, in particular the mean arithmetic height Sa and preferably the tangent error (ie the local slope deviation from the ideal target curvature) of surface structure components in certain wavelength ranges must be kept low, in order to achieve a sufficiently high surface quality and optical quality.

Furthermore, the inventors of the present invention have found a solution using a thin glass a three-dimensional shape and a very small thickness of less than 700 .mu.m, preferably less than 500 .mu.m, more preferably less than 300 .mu.m, even more preferably less than 250 .mu.m, even more preferably less than 150 .mu.m, to provide the high surface quality described and has optical quality and this without the need for post-processing. The thin glass according to the invention is therefore suitable for use as a hard, scratch-resistant surface with low weight in visually appealing applications (optics, ophthalmic technology, reflective surfaces with an appealing appearance, for example for the auto motive area or displays, etc.).

The provision of a three-dimensional thin glass with such a small thickness and the claimed high surface quality and quality is not possible with conventional methods of the state of the art. Known methods for producing three-dimensional, curved glass substrates with high surface quality are intended to relate to glass substrates with larger thicknesses. The parameters, process steps and tools used in known methods cannot be transferred to the production of thin glass with a thickness of less than 700 μm, preferably less than 500 μm, more preferably less than 300 μm. The reason for this lies in the glass thickness dependency of the deformation. The inventors of the present invention have recognized that when the glass substrate is reshaped by deep drawing and / or pressing in a transition area between a molded area and a viscosity-dominated area, a bending component acting on the glass also comes into play, which influences the molding behavior depending on the thickness. During the three-dimensional reshaping of comparatively thin glass substrates by means of known methods, larger defects would therefore form in the surface of the glass substrate, in particular in the range of defect widths between 0.1 and 1 mm. The inventors of the present invention have also recognized that in particular the tangent errors and height differences of medium-scale surface structure components in a certain wavelength range between 0.1 mm and 1 mm are negative for the use of thin glasses in visually appealing applications and have found a solution to use thin glasses with a thickness of less than 700 μm, preferably less than 500 μm, more preferably less than 300 μm, in which the occurrence of these errors is prevented to a sufficient extent. In other words, the inventors have recognized that defects with lateral dimensions in the area of the thickness of thin glasses in particular play a decisive role for the surface quality and quality of the thin glass, since defects in precisely this area are optically expressed by a distortion of a reflected or transmitted image can. In the case of conventional reshaping of thicker glasses, defects in the areas considered relevant according to the invention are of no importance, since thicker glasses essentially only mold long-scale defects. The first measuring surface can be a specific or any measuring surface on the first upper surface. In the embodiment in which the first measuring area is any measuring area on the first surface, the entire first surface has the surface quality and quality described. This means that any area of the claimed size at any point on the first surface can be selected as the first measuring area and always has the claimed surface quality and quality.

In one embodiment, the thin glass can have a thickness between 1 μm and 700 μm, preferably between 10 μm and 500 μm, more preferably between 20 μm and 300 μm.

The thin glass can comprise one or more desired curvatures. It goes without saying that the thin glass can have the at least one desired curvature in a region of the thin glass or over the entire surface of the thin glass. The thin glass can have different desired curvatures or the same desired curvature in different areas of the thin glass. The thin glass can also have no desired curvature in certain areas as long as it has at least one desired curvature in at least one area. The thin glass can have several desired curvatures in the same area.

The thin glass can, for example, have a bending radius belonging to the at least one desired curvature, which is greater than the thickness of the thin glass, preferably greater than or equal to twice the thickness. The following condition can therefore apply to the thin glass: R> D, preferably R> 2xD, where R is the bending radius and D is the thickness of the thin glass. In particular, a smallest bending radius of the thin glass can be greater than the thickness of the thin glass, preferably greater than or equal to twice the thickness. The thin glass can, for example, have a bending radius belonging to the at least one desired curvature of at least 1 mm, preferably of at least 2 mm, preferably of at least 5 mm. The thin glass can have a bending radius belonging to the at least one desired curvature of 10,000 mm or less, preferably of 5000 mm or less, preferably of 2500 mm or less, more preferably of 1500 mm or less. The thin glass can have a bending radius belonging to the at least one desired curvature between 1 mm and 10,000 mm, in particular between 1 mm and 5000 mm, preferably between 1 mm and 1500 mm. All desired curvatures of the thin glass can lie in the above ranges.

The thin glass can have a concave surface or a concave surface section, the surface or the surface section for this purpose being bent only in the X-axis direction or only in the Y-axis direction. The thin glass can have a convex surface or a concave surface section, the surface or the Surface section for this purpose is curved only in the X-axis direction or only in the Y-axis direction. The thin glass can have a concave surface or a concave surface section, the surface or the surface section for this purpose being curved in the X-axis direction and in the Y-axis direction. The thin glass can have a convex surface or a covex surface section, the surface or the upper surface section being curved for this purpose in the X-axis direction and in the Y-axis direction. The thin glass may have a surface or surface portion that has a convex shape in one direction (x-axis direction or y-axis direction) and a concave shape in another direction (y-axis direction or x-axis direction).

The thin glass can have a shell shape that is curved in only one direction. The thin glass can have a saddle shape curved in several directions. The thin glass can have bending points at several points and thus, for example, have a corrugated shape.

In a further development of the thin glass, all medium-scale surface structure components in a wavelength range of 0.1 mm to 1 mm can have a mean arithmetic height Sa of less than 30 nm, preferably less than 20 nm, on at least one second measuring area of 3 x 3 mm ^{2 of the second surface} , more preferably below 10 nm, even more preferably below 7 nm. For example, on the second measuring surface, all surface structural components in a wavelength range from 0.1 mm to 1 mm can have a mean arithmetic height Sa between 1 nm and 30 nm, preferably between 3 nm and 20 nm, more preferably between 6 nm and 10 nm. The values for the mean arithmetic height relate to a measurement by means of white light interferometry, with a bandpass filtering of 0.1 mm to 1 mm.

The second measuring area can be a specific measuring area or any measuring area on the second surface. In the embodiment in which the second measuring area is any measuring area on the second surface, the entire second surface has the surface quality and quality described. This means that any area of the claimed size at any point on the second surface can be selected as the second measuring area and always has the claimed surface quality and quality.

Based on the measuring areas of 3 x 3 mm ² , the mean arithmetic height Sa measured by means of white light interferometry of all medium-scale surface structure components in a wavelength range from 0.1 mm to 1 mm in the second measuring area on the second side can be increased by 1% to 20%, preferably 5% to 15%, more preferably 7% to 10%, less than in the first measuring area on the first page, based on the mean arithmetic Height Sa of the surface structure components of the first side. Such a ratio of the mean arithmetic heights Sa of the surface structure components mentioned on the first side and on the second side represents a very uniformly formed thin glass, the mean arithmetic height Sa being less than 30 nm on both sides. Such an embodiment accordingly has a particularly high surface quality and surface quality.

In one embodiment of the thin glass, on at least a third measuring area of 3 x 3 mm ^{2 of} the first surface, all medium-scale surface structure components in a wavelength range from 0.1 mm to 1 mm can have a slope error, i.e. a local slope deviation from the ideal target curvature, of on the arithmetic mean below 0.1 pm / mm, preferably below 0.07 pm / mm, more preferably below 0.05 pm / mm, even more preferably below 0.04 pm / mm. The third measuring area can preferably correspond to the first measuring area.

In one embodiment of the thin glass, on at least a fourth measuring area of at least 3 × 3 mm ^{2 of} the second surface, all medium-scale surface structure components in a wavelength range from 0.1 mm to 1 mm can have a tangent error of less than 0.1 pm / mm on the arithmetic mean , preferably below 0.06 pm / mm, more preferably below 0.04 pm / mm, even more preferably below 0.03 pm / mm. The fourth measuring area can preferably correspond to the second measuring area.

The measured values for the tangent error also relate to a measurement using white light interferometry, with a bandpass filtering of 0.1 mm to 1 mm.

In relation to the measuring areas of 3 x 3 mm ² , the tangent error of all medium-scale surface structure components measured by means of white light interferometry in a wavelength range of 0.1 mm to 1 mm in the fourth measuring area on the second side can be increased by 1% to 50%, preferably 10% up to 40%, more preferably 15% to 35%, less than in the third measurement area on the first side, based on the tangent error of the surface structure components on the first side in the arithmetic mean. This particular ratio of the tangent error on the first side and on the second side represents a very uniformly formed thin glass, the tangent error on both sides being below 0.1 pm / mm. Such an embodiment accordingly has a particularly high surface quality and surface finish.

The optional ratios of the surface qualities (based on the mean arithmetic height Sa and / or on the tangent error) of the first side and the second side can be achieved, for example, by a further development of the thin glass in which the first side may be a side facing the mold, which faces a mold during the manufacture of the thin glass. Accordingly, the second side of the thin glass can be a side facing away from the mold, which side faces away from the mold during the manufacture of the thin glass. The first side can preferably have a convex shape and the second side can have a concave shape.

In one embodiment of the thin glass, on at least a fifth measuring area of 0.33 × 0.33 mm ^{2 of} the first surface, all short-scale surface structure components in a wavelength range of up to 0.25 mm can have an average arithmetic height Sa of less than 5 nm, preferably below 3 nm, more preferably below 1 nm, even more preferably below 0.5 nm. These values for the mean arithmetic height relate to a measurement by means of white light interferometry with a high-pass filter of 0.25 mm. The fifth measuring area can preferably be in the area of the first measuring area and / or the third measuring area.

In one embodiment of the thin glass, on at least one sixth measuring area of 0.33 × 0.33 mm ^{2 of} the second surface, all short-scale surface structure components in a wavelength range of up to 0.25 mm can have an average arithmetic height Sa of less than 5 nm, preferably below 3 nm, more preferably below 1 nm, even more preferably below 0.5 nm. These values for the mean arithmetic height relate to a measurement by means of white light interferometry with a high-pass filter of 0.25 mm. The sixth measurement area can preferably lie in the region of the second measurement area and / or the fourth measurement area.

Based on the measuring areas of 0.33 x 0.33 mm ² , the mean arithmetic height Sa of all surface structure components in a wavelength range of a maximum of 0.25 mm in the sixth measuring area on the second side can be increased by a maximum of 20%, preferably a maximum of 15% preferably a maximum of 10%, from which deviate in the fifth measuring area on the first side, based on the mean arithmetic height Sa of the surface structure components on the first side. This ratio of the mean arithmetic heights Sa of the surface structure components mentioned on the first side and on the second side also represents a very uniformly formed thin glass, the mean arithmetic height Sa being less than 5 nm on both sides. Such an embodiment accordingly has a particularly high surface quality and surface quality.

According to a further development, the thin glass can have a glass transition temperature Tg between 400 ° C and 850 ° C, preferably between 500 ° C and 700 ° C. Another aspect of the invention relates to an optical component for use in optics, in ophthalmology, as a display, as a cover, etc., which comprises a material composite with a thin glass of the type described above and at least one further composite component made of plastic, metal, Glass, glass ceramic, ceramic, wood and / or fiber composite material includes. It goes without saying that this list is not exhaustive and that optical components can also be used in other applications and / or in conjunction with other materials.

The optical component can be post-processed. For example, the optical component can have one or more coatings of the following: anti-reflective coating, anti-glare coating or anti-glare coating, anti-fingerprint coating, anti-scratch coating or anti-scratch coating, UV protective coating and / or anti -Fog coating. The optical component can have an edge processing. The optical component can be perforated at least in sections. The optical component can be provided with holes, openings, cutouts and / or local surface structures by post-processing. The sequence of post-processing can be selected as desired, for example according to the intended use of the optical component.

Another aspect of the invention relates to a product that comprises a thin lens of the type described above, the product, for example, a spectacle lens, protective goggles, a lens, (industrial or consumer) optics comprising plastic or glass (eg a lens Imaging system, a lens), a helmet visor, a smartphone display or a cover for a display device, a console, a fitting, a headlight, a watch glass, a window, a viewing window, an electronic component with a display function, a smart watch, a " Wearable electronics ”, a component with a light-conducting function, a piece of jewelery, a vehicle exterior paneling, a mirror, a decorative element (e.g. for the vehicle interior or a decorative element), protection for acoustic components (e.g. loudspeaker stiffener) or the like. In the automotive sector, the product can, for example, be a center console, a vehicle headlight, a taillight, a windshield, a plastic component outdoors or a vehicle exterior paneling, a display device, a part of the door indoors or outdoors, a baseboard, a mirror, a decorative element ( e.g. for the vehicle interior or a decorative element) etc. The product can also be a sensor component or an electronic component with an optical sensor function, the thin glass serving to protect sensors. Furthermore, the thin glass in a product from the electronics field can serve as a barrier layer, for example for oxygen, in order to protect electronic components, for example printed electronics, organic electronics and / or oxygen-sensitive and / or moisture- / water-vapor-sensitive electronics. The product can also AR (Augmented Reality) glasses, VR (Virtual Reality) glasses or an AR or VR component. In particular, the product can comprise an optical component with a material composite of the type described above.

Another aspect of the invention relates to a tool for producing a thin glass of the type described above. The tool comprises a mold for three-dimensional reshaping of the thin glass, the mold comprising a machine-polished molding surface with at least one desired curvature. The molding surface is provided in order to come into contact with the thin glass in the course of a deformation of the thin glass. The later at least one desired curvature of the formed thin glass is predetermined by the at least one desired curvature of the molding surface. In particular, the shaped surface can be an aspherically curved, essentially concave free-form surface. As a result of the machine polishing of the mold surface, the tool can have a high surface quality with few defects in the region of the mold or the mold surface. This can reduce the transfer of defects to the thin glass during the manufacturing process.

The features and parameters described in relation to the curvature of the thin glass can apply accordingly to the curvature of the shape of the tool.

In a further development of the tool, all medium-scale surface structure components in a wavelength range of 0.1 mm to 1 mm can have a mean arithmetic height Sa of less than 40 nm, preferably less than 35 nm, on at least one seventh measuring area of 3 x 3 mm ^{2 of the mold area,} more preferably below 30 nm, even more preferably below 20 nm. For example, on the seventh measuring surface, all surface structure components in a wavelength range from 0.1 mm to 1 mm can have a mean arithmetic height Sa between 1 nm and 40 nm, preferably between 3 nm and 30 nm, more preferably between 6 nm and 20 nm. The values for the mean arithmetic height relate to a measurement by means of white light interferometry, with a bandpass filtering of 0.1 mm to 1 mm.

In one embodiment of the tool to an eighth measuring surface of 0.33 can be at least x 0.33 mm ² of the mold surface every kurzskaligen surface structure components in egg nem wavelength range of up to 0.25 mm an arithmetic mean height Sa of having less than 500 nm, preferably below 300 nm, more preferably below 200 nm, even more preferably below 100 nm. These values for the mean arithmetic height relate to a measurement by means of white light interferometry with a high-pass filter of 0.25 mm. Furthermore, the parameters for surface quality and surface quality (tangent error, mean arithmetic height) described in relation to embodiments and developments of the thin glass can apply accordingly to the mold surface of the tool.

The surface qualities and surface finishes according to the invention do not have to be adhered to in the case of production methods known to tools, since the bending component recognized by the inventors of the present invention is of no relevance in the production of thicker glasses, which, however, significantly influences the molding behavior of thin glass and thus the achievable surface quality.

According to a further embodiment, the tool can comprise metal, a metal alloy, graphite, ceramic material, glass ceramic, such as Zerodur®, quartz, glass and / or carbides, for example silicon carbide and / or tungsten carbide, at least in the region of the mold surface. In particular, the tool can comprise isostatically pressed fine-grain graphite in the area of the mold surface or be made from it. A tool with isostatically pressed fine-grain graphite can be advantageous in order to produce thin glass with a high surface quality. The tool can be coated or uncoated in the area of the mold surface. In particular, when a porous tool is used in a vacuum process, the tool should be uncoated in the area of the mold surface. The tool can be at least partially permeable to pressures, in particular to vacuum, at least in the region of the mold surface, in order to at least partially transfer a (negative) pressure applied to the tool to the thin glass. For this purpose, the tool can be porous and / or have openings at least in the area of the mold surface.

Another aspect of the invention relates to a method for producing a thin glass, in particular a thin glass of the type described above. The method comprises the steps:

Providing a flat glass substrate, e.g., a glass wafer, with a thickness of less than 700 µm, preferably less than 500 µm, more preferably less than 300 µm;

Applying the glass substrate to a mold of a tool, the mold comprising a three-dimensionally curved mold surface, preferably an aspherically curved mold surface;

Heating the glass substrate to a target temperature above the glass transition temperature Tg and below the softening point temperature EW of the glass substrate with a temperature gradient of at least 35 K / min; When the target temperature is reached, the glass substrate is subjected to negative pressure by applying a vacuum to the mold of the tool and / or by applying it a pressing force on the glass substrate for a period of less than 120 s in order to three-dimensionally hot-form the glass substrate in the region of the mold;

Cooling the hot-formed glass substrate to a cooling temperature; and removing the hot-worked glass substrate from the mold.

The method according to the invention is carried out in particular in the order given above. The method can include further intermediate steps, preparation steps and / or post-processing steps.

In contrast to known methods, the method according to the invention enables the production of a thin glass with the properties according to the invention, i.e. with a very small thickness and high surface quality, in that the method is carried out very adapted as claimed and a structurally optimally designed tool is used.

According to the method according to the invention, the three-dimensional hot forming can be carried out exclusively by applying negative pressure (vacuum) to the glass substrate or exclusively by pressing the glass substrate with a pressing force or by a combination of these two applications. The pressing of the glass substrate can take place by applying a pressing force to the glass substrate by means of one or more press molds or one or more press punches of the tool. In the case of a combination (negative pressure and pressing), a first surface of a first side of the glass substrate can be subjected to negative pressure and an opposite second surface of a second side of the glass substrate can be pressed. Additionally or alternatively, the same surface on the same side of the glass substrate can be subjected to negative pressure and pressed by means of a tool. For example, the glass substrate can be pressed from above by means of a pressing tool, while at the same time a negative pressure can be applied to the pressing tool for sucking in the glass substrate. The application of negative pressure and the pressing can take place simultaneously or one after the other. The application of negative pressure and the pressing can be carried out with different tools or with different components of the same tool.

The flat glass substrate can be an essentially two-dimensional, planar raw glass sheet (for example glass wafer) with properties selected for the planned area of application. The glass transition temperature Tg and the softening point temperature EW are dependent on the material of the glass substrate used. Typical target temperatures can be between 450 ° C and 950 ° C, preferably between 550 ° C and 850 ° C, more preferably between 580 ° C and 750 ° C. Borosilicate glass, aluminosilicate glass or lithium aluminosilicate, for example, can be used as the glass substrate material. In particular, D263® or Xensation® can be used. During the manufacturing process, care must be taken to ensure that the glass substrate and the mold are extremely clean at the beginning and during the process in order to avoid defects caused by contamination.

The method according to the invention can in particular be carried out using a tool of the type described above. That is, the glass substrate can be applied to a mold of the above-described tool.

The application of negative pressure and / or pressing force to the glass substrate can preferably be carried out for a period of less than 100 s, more preferably less than 60 s. The specified duration of less than 120 s, preferably less than 100 s, more preferably less than 60 s is used to ensure the shortest possible mold contact, which in particular the formation of tangent errors and height differences in the range of error widths between 0.1 mm and 1 mm can be reduced. The duration and the amount of the negative pressure / the pressing force can be selected in accordance with the curvature to be achieved, with a greater curvature requiring a longer period of application.

The temperature gradient for heating the glass substrate to a target temperature above the glass transition temperature Tg and below the softening point temperature EW of the glass substrate can be at least 50 K / min. For example, the temperature gradient can be between 50 K / min and 300 K / min, in particular between 70 K / min and 280 K / min.

To heat the glass substrate to the target temperature above the glass transition temperature Tg and below the softening point temperature EW of the glass substrate, the glass substrate can be heated in several cycles, i.e. over several stations. The temperature gradient is selected depending on the time required for heating. The desired heating time depends on the number of cycles. A cycle can last, for example, 30 s, 60 s and / o of the 120 s. For example, at least three, preferably at least five, further preferably at least 6 cycles can be provided.

The negative pressure used in one embodiment of the method, which is applied to the shape of the tool, can be between 100 Pa and 90,000 Pa absolute, preferably between 50,000 Pa and 90,000 Pa.

The pressing force used in one embodiment of the method for pressing the glass substrate can be between 2 N and 4000 N absolute, preferably between 5 N and 2500 N. The pressing force can be applied to the glass substrate by means of at least one pressing ram. For example, at least two, preferably at least three Press plungers act one after the other on the glass substrate with the same or different pressing forces. For example, a ram can act several times in succession with the same or different pressing forces on the glass substrate. For example, three press rams can act on the glass substrate one after the other, with a first press ram with a pressing force of less than 2500 N, preferably between 5 N and 2000 N, acting on the glass substrate, with a second press ram with a pressing force of over 500 N, preferably between 800 N and 4000 N, acts on the glass substrate, and a third press punch with a pressing force of over 400 N, preferably between 500 N and 4000 N, acts on the glass substrate.

A further temperature gradient of at least 10 K / min, preferably of at least 30 K / min, can be provided for cooling the hot-formed glass substrate to the cooling temperature. A further temperature gradient of at most 140 K / min, preferably at most 100 K / min, can be provided for cooling. For example, a further temperature gradient between 10 K / min and 140 K / min, in particular between.

30 K / min and 100 K / min. The further temperature gradient for cooling should be selected as a function of the material used for the glass substrate in such a way that no harmful stresses arise in the glass substrate and, in particular, that the glass substrate does not break.

The cooling temperature to which the hot-formed glass substrate is cooled after shaping or after hot shaping can be between 250.degree. C. and 350.degree. C., preferably around 300.degree.

Another aspect of the invention relates to a thin glass produced by means of a method of the type described above.

Although some of the above features, effects, advantages, embodiments and further developments are only described with reference to the thin glass according to the invention, these apply accordingly to the method according to the invention and the tool according to the invention and vice versa.

Brief description of the figures

Embodiments of the present invention are explained in more detail below with reference to the accompanying schematic figures. They represent:

1 shows a diagram with measurement results for the mean arithmetic height of

Thin glasses according to the invention compared to thin glasses from the prior art of the technique.

2A shows a topographical image of a thin glass according to the invention from FIG. 1.

2B shows a topographical image of a thin glass from the prior art

Fig. 1.

Fig. 3 is a diagram with further measurement results on the tangent error of thin glasses according to the invention compared to thin glasses from the prior art.

4A shows a false color image of tangent defects of a thin glass according to the invention from FIG. 3.

FIG. 4B shows a false color image of tangent defects of a thin glass from the prior art from FIG. 3.

5 shows a diagram with further measurement results for the mean arithmetic

Height of thin glasses according to the invention compared to thin glasses from the prior art.

6 shows a glass wafer and a section of a tool according to the invention for

Carrying out a manufacturing method according to the invention or for producing a thin glass according to the invention.

Fiqurenbeschreibunq

1 shows measurement results of white light interferometry measurements of the mean arithmetic height Sa on a first measuring area of 3 x 3 mm ² on a first surface of a first side of thin glasses (right side of the diagram) and on a second measuring area of 3 x 3 mm ² a second surface of a second side of thin glasses (left side of the diagram), the second side being a side opposite to the first side for each thin glass. The first side here refers to the side facing the mold during the manufacturing process, which in the present example has a convex shape. The second side here denotes the side facing away from the mold during the manufacturing process, which in the present example has a concave shape. For each side, measurements on thin glasses according to the invention are compared with measurements on thin glasses of the prior art. In the thin glasses of the invention and the thin glasses of the prior art it concerns thin glasses that have not been reworked, that is, thin glasses that are left unfinished or untreated after hot forming.

In the example shown, measurement results of thin borosilicate glasses (here of the D263TEco type) with a thickness of 100 μm are shown, which have previously been three-dimensionally reshaped using a dome shape and each have a radius of curvature of 120 mm or 123.5 mm.

The white light interferometry measurements to determine the mean arithmetic height Sa, i.e. the arithmetic mean of the deviations of the surfaces from the ideal topography, were carried out with bandpass filtering between 0.1 mm and 1 mm (Gaussian spline fixed with spline long period 1000 pm and spline short Period 100 pm) in order to consider medium-scale surface structure components in a wavelength range from 0.1 mm to 1 mm. The white light interference microscope (WLI), also called CSI (Coherence Scanning Interferometry), ZYGO® - NexView ™ (optical 3D profilometer with scanning and phase-shifting interferometry) with a 5.5X Mich NA 0.15 objective with an effective lateral resolution of 2.9 pm is used. The measurement type was "Surface" and the system reference was subtracted.

The ZYGO® - Mx ™ software (Instrument Control & Data Analysis Software for ZYGO 3D Optical Surface Profilers) was used to evaluate the measurement data. The data were filtered using "Form Remove" and a "Gaussian Spline Fixed" bandpass filter with a period of 100-1000 pm.

As can be seen in Fig. 1, the measured mean arithmetic height Sa of the thin glasses according to the invention is always well below 10 nm for both sides. More precisely, the best measurement result for the mean arithmetic height Sa is 3.0 nm for a thin glass according to the invention on the first, convex side and at 1.9 nm on the second, concave side. Furthermore, for a thin glass according to the invention, the worst measurement result of the mean arithmetic height Sa is 7.4 nm on the first, convex side and 6.8 nm on the second, concave side. In contrast, for a thin glass from the prior art, the best measurement result for the mean arithmetic height Sa is 11.1 nm on the first, convex side and 14.5 nm on the second, concave side. Furthermore, for a thin glass from the prior art, the worst measurement result of the mean arithmetic height Sa is 40.5 nm on the first, convex side and 35.9 nm on the second, concave side. The surface quality of the thin glass according to the invention is accordingly significantly improved compared to thin glasses from the prior art. 2A is a white light interferometric image of the topography of a borosilicate thin glass according to the invention after a bandpass filtering of 0.1 mm to 1 mm, while FIG. 2B shows a white light interferometric image of the topography of a borosilicate thin glass of the prior art after a bandpass filtering of 0.1 mm to 1 mm . The height deviation on the convex side of a dome with a radius of curvature of 120 mm is shown in FIGS. 2A and 2B with the same scaling on a measuring area of 3 × 3 mm ^2. In contrast to the topography of the thin glass of the prior art, which has a large number of defects 10 (for a better overview, only one defect was provided with a reference symbol), the thin glass according to the invention has a very uniform surface structure and thus a high surface quality .

3 shows measurement results of white light interferometry measurements of the averaged slope error on a third measuring area of 3 x 3 mm ² on the first surface of the first side of thin glasses (right side of the diagram) and on a fourth measuring area of 3 x 3 mm ² on the second surface of the second side of thin glasses (left side of the diagram), with the second side being a side opposite to the first side for each thin glass. The measurements on which the diagram from FIG. 3 is based were carried out on thin glasses on which the measurements on which the diagram from FIG. 1 is based were also carried out. Accordingly, thin borosilicate glasses (here of the D263TEco type) with a thickness of 100 μm were used, which had previously been shaped three-dimensionally by means of a dome shape and each had a radius of curvature of 120 mm or 123.5 mm. The thin glasses of the invention and the thin glasses of the prior art are thin glasses that have not been reworked, that is, thin glasses that are left untreated or untreated after hot forming.

In FIG. 3, measurements on thin glasses according to the invention are compared with measurements on thin glasses of the prior art for each of the two sides (facing and facing away from the shape). The y-axis of the diagram in FIG. 3 has a logarithmic scale.

The white light interferometry measurements to determine the averaged tangent error, i.e. the local slope deviation from the ideal target curvature, were carried out with a bandpass filtering between 0.1 mm and 1 mm (Gaussian spline fixed with spline long period 1000 pm and spline short period 100 pm), to consider medium-scale surface structure components in a wavelength range from 0.1 mm to 1 mm. Unless otherwise stated, the measurements for determining the tangent error were carried out with the same filtering, the same settings, the same measuring devices and the same measuring software as above in connection with FIG. see height Sa described. The slope magnitude was determined using the Zygo®-Mx ™ software. The iteration length corresponded to the lateral resolution.

As can be seen in FIG. 3, the measured tangent error in the arithmetic mean of the thin glasses according to the invention is always clearly below 0.05 μm / mm for both sides. More precisely, for a thin glass according to the invention, the measurement result of the tangent error in the arithmetic mean is always approx. 0.03 pm / mm on the first, convex side and approx. 0.02 pm / mm on the second, concave side. In contrast, for a thin glass from the prior art, the best measurement result of the tangent error in the arithmetic mean is 0.1 pm / mm on the first, convex side and 0.14 pm / mm on the second, concave side. Furthermore, for a thin glass from the prior art, the worst measurement result of the tangent error in the arithmetic mean is 0.77 pm / mm on the first, convex side and 0.44 pm / mm on the second, concave side. The surface quality of the thin glass according to the invention is accordingly significantly improved with regard to the tangent error compared to thin glasses from the prior art.

FIGS. 4A and 4B show the tangent errors of a borosilicate thin glass according to the invention (FIG. 4A) and a borosilicate thin glass of the prior art (FIG. 4B) in a false color image with the same scaling on a measuring area of 3 × 3 mm ² . Shown are recordings after a bandpass filtering of 0.1 mm to 1 mm on the convex side of a dome with a radius of curvature of 120 mm. In contrast to the topography of the thin glass of the prior art, which has a large number of tangent defects 20 (for a better overview, only one defect was provided with a reference symbol), the thin glass according to the invention has a very uniform surface structure and thus a high surface quality.

5 shows measurement results of white light interferometry measurements of the mean arithmetic height Sa on a fifth measuring area of 0.33 x 0.33 mm ² on the first surface of the first side of thin glasses (right side of the diagram) and on a sixth measuring area of 0, 33 x 0.33 mm ² on the second surface of the second side of thin glasses (left side of the diagram), with the second side being a side opposite to the first side for each thin glass. The measurements on which the diagram from FIG. 5 is based were carried out on thin glasses, on which the measurements on which the diagrams from FIGS. 1 and 3 are also based were carried out. Accordingly, thin borosilicate glasses (here of the D263TEco type) with a thickness of 100 μm were used, which had previously been formed three-dimensionally by means of a dome shape and each had a radius of curvature of 120 mm or 123.5 mm. With the thin glasses of the invention and the thin glasses of the stand According to the technology, thin glasses that have not been reworked are involved, that is, thin glasses that have not been left or treated after hot forming.

Also in FIG. 5, measurements on thin glasses according to the invention are compared with measurements on thin glasses of the prior art for each of the two sides (facing the shape and facing away from the shape). The y-axis of the diagram in FIG. 5 has a logarithmic scale.

The white light interferometry measurements to determine the mean arithmetic height Sa were carried out with a high-pass filtering with a cut-off frequency of 0.25 mm (Gaussian spline fixed with spline long period 250 pm) in order to detect short-scale surface structure components in a wavelength range of up to 0.25 mm consider. Here, too, the white light interference microscope (WLI), also called CSI (Coherence Scanning Interferometry), ZYGO® - NexView ™ (optical 3D profilometer with scanning and phase-shifting interferometry) was used. A 50X Mirau NA 0.55 with an effective lateral resolution of 0.6 pm was used as the objective for these measurements. The measurement type was "Surface" and the system reference was subtracted.

The ZYGO® - Mx ™ software (Instrument Control & Data Analysis Software for ZYGO 3D Optical Surface Profilers) was also used to evaluate the measurement data. The data were filtered using “Form Remove” and a “Gaussian Spline Fixed” high pass filter with a long period of 250 pm.

As can be seen in FIG. 5, the measured mean arithmetic height Sa of the thin glasses according to the invention is always below 0.4 nm for both sides , 1 nm on the first, convex side and at approx. 0.1 nm on the second, concave side. Furthermore, for a thin glass according to the invention, the worst measurement result of the mean arithmetic height Sa is approximately 0.3 nm on the first, convex side and approximately 0.3 nm on the second, concave side. In contrast, for a thin glass from the prior art, the best measurement result for the mean arithmetic height Sa is 0.9 nm on the first, convex side and 0.4 nm on the second, concave side. Furthermore, for a thin glass from the prior art, the worst measurement result of the mean arithmetic height Sa is 21.9 nm on the first, convex side and 5.4 nm on the second, concave side. The surface quality of the thin glass according to the invention is accordingly significantly improved compared to thin glasses from the prior art.

Further white light interferometry measurements were made on a borosilicate thin glass according to the invention (of the D263TEco type) with a thickness of 210 μm and a bending radius of 120 mm carried out. On the one hand, the mean arithmetic height Sa was also determined on a measuring area of 3 x 3 mm ² on a first surface of a first side and on a measuring area of 3 x 3 mm ² on a second surface of a second opposite side of the thin glass. On the other hand, the mean arithmetic height Sa was measured on a measuring area of 0.33 x 0.33 mm ² on the first surface of the first side and on a measuring area of 0.33 x 0.33 mm ² on the second surface of the second opposite Side of the thin glass determined. The first side here also refers to the side facing the mold during the manufacturing process, which in the present example has a convex shape. The second side here refers to the side facing away from the mold during the manufacturing process, which in the present example has a concave shape. The thin glasses according to the invention for this measurement are likewise non-post-processed thin glasses, that is to say thin glasses that are left unfinished or untreated after hot forming.

The white light interferometry measurements to determine the mean arithmetic height Sa on the measuring areas of 3 x 3 mm ² were carried out with a bandpass filtering between 0.1 mm and 1 mm (Gaussian spline fixed with spline long period 1000 pm and spline short period 100 pm). The white light interferometry measurements to determine the mean arithmetic height Sa on the measuring areas of 0.33 x 0.33 mm ² were carried out with high-pass filtering with a cut-off frequency of 0.25 mm (Gaussian spline fixed with spline long period 250 pm) To consider short-scale surface structure components in a wavelength range of up to 0.25 mm, analogous to the measurements described above on borosilicate thin glasses with a thickness of 100 μm.

The measurement results of these further measurements show that the mean arithmetic height Sa for the measurements on the measurement areas of 3 × 3 mm ^{2 is} always well below 15 nm for both sides. More specifically, the mean arithmetic height Sa is 13.1 nm on the first, convex side and 5.9 nm on the second, concave side. Furthermore, the measurement results of the other measurements show that the mean arithmetic height Sa for the measurements on the measurement areas of 0.33 × 0.33 mm ^{2 is} always well below 5 nm for both sides. More specifically, the mean arithmetic height Sa is 2.6 nm on the first, convex side and 0.2 nm on the second, concave side.

A thin glass with the properties according to the invention can be provided by means of an adapted method and in particular using a tool according to the invention.

In one exemplary embodiment of the method, a flat glass wafer 100 made of borosilicate glass with a thickness d of less than 300 μm is provided. For example, the glass wafer have a thickness of 100 pm or 210 pm. The glass wafer 100 is applied to a mold 110 of a tool 120, the mold 110 comprising an aspherically curved mold surface 130 for three-dimensional reshaping of the thin glass 100.

The molding surface 130 is provided in order to come into contact with the thin glass 100 in the course of a deformation of the thin glass. The desired curvature of the thin glass 100 to be reshaped is predetermined by the desired curvature of the shaping surface 130. The mold surface is machined, so that the tool 120 in the region of the mold surface 130 has a high surface quality with few defects. In this way, the transfer of defects to the thin glass 100 during the manufacturing process can be avoided. In the exemplary embodiment shown, the tool 120 is made in the region of the mold surface 130 from isostatically pressed fine-grain graphite.

After being applied to the tool 120, the glass wafer 100 is heated to a setpoint temperature above the glass transition temperature Tg and below the softening point temperature EW of the glass wafer 100. Here the target temperature is 600 ° C. The heating is carried out with a temperature gradient of approx. 60 K / min.

When the target temperature of 600 ° C. is reached, a vacuum of 10000 Pa absolute is applied to the glass wafer 100 by applying a vacuum to the mold 110 of the tool 120 for a period of about 30 seconds. Here, the glass wafer 100 is hot-formed three-dimensionally in the area of the mold 110. As a result of the comparatively short exposure, the shortest possible mold contact is ensured, so that molding of defects in the mold 110 onto the glass wafer or thin glass 100 is further avoided.

After the reshaping, the hot-reshaped glass wafer 100 is cooled to a cooling temperature of approximately 300 ° C. with a further tempera ture gradient of approximately 10 K / min.

The hot-formed glass wafer 100 is then removed from the tool 120 or the mold 110.

In contrast to known methods, the method according to the invention enables the manufacture of thin glass with a very small thickness and at the same time very high surface quality. List of reference symbols

10 defect (mean arithmetic height Sa)

20 defect (tangent error)

100 glass wafer 110 form 120 tool

130 mold surface

Claims

Expectations

1. Thin glass for an optical component, comprising a first side with a first surface, a second side opposite the first side with a second surface, the thin glass having a three-dimensional shape with at least one desired curvature and a thickness of less than 700 μm, and wherein on at least one first measuring area of 3 × 3 mm ^{2 of} the first surface all surface structure components in a wavelength range from 0.1 mm to 1 mm have an average arithmetic height Sa of less than 30 nm.

2. Thin glass according to claim 1, which has a thickness of less than 500 pm, preferably we niger than 300 pm.

3. Thin glass according to claim 1 or 2, which has a bending radius belonging to the at least one desired curvature, which is greater than the thickness of the thin glass, preferably greater than or equal to twice the thickness, the thin glass in particular one belonging to the at least one desired curvature Has a bending radius between 1 mm and 10,000 mm, in particular between 1 mm and 5000 mm, preferably between 1 mm and 1500 mm.

4. Thin glass according to one of the preceding claims, wherein on at least one second measuring area of 3 x 3 mm ^{2 of} the second surface all surface structure components in a wavelength range from 0.1 mm to 1 mm have an average arithmetic height Sa of less than 30 nm, preferably less than 20 nm, more preferably below 10 nm, even more preferably below 7 nm.

5. Thin glass according to one of the preceding claims, wherein the mean arithmetic height Sa of all surface structure components in a wavelength range from 0.1 mm to 1 mm on the second side by 1% to 20%, preferably 5% to 15%, more preferably 7 % to 10%, is less than on the first page, based on the mean arithmetic height Sa of the surface structure components of the first page.

6. Thin glass according to one of the preceding claims, wherein on at least a third measuring area of 3 x 3 mm ^{2 of} the first surface all surface structure components in a wavelength range from 0.1 mm to 1 mm have a tangent error of below 0.1 pm / mm on the arithmetic mean preferably below 0.07 pm / mm, more preferably below 0.05 pm / mm, even more preferably below 0.04 pm / mm.

7. Thin glass according to one of the preceding claims, wherein on a fourth measuring area of at least 3 x 3 mm ^{2 of} the second surface, all surface structure components in a wavelength range have a tangent error of below 0.1 pm / mm on the arithmetic mean, preferably below 0.06 pm / mm, more preferably below 0.04 pm / mm, even more preferably below 0.03 pm / mm.

8. Thin glass according to one of the preceding claims, wherein the tangent error of all surface structure components in a wavelength range from 0.1 mm to 1 mm on the second side by 1% to 50%, preferably 10% to 40%, more preferably 15% to 35 %, is lower than on the first page, based on the tangent error of the surface structure components on the first page in the arithmetic mean.

9. Thin glass according to one of the preceding claims, wherein the first side is a side facing away from the shape, which faces a mold during the production of the thin glass, and / or the wherein the second side is a side facing away from the shape, which is during the production of the thin glass is turned away from the shape.

10. Thin glass according to one of the preceding claims, wherein on at least one fifth measuring area of 0.33 x 0.33 mm ^{2 of} the first surface all surface structure components in a wavelength range of up to 0.25 mm have an average arithmetic height Sa of less than 5 nm preferably below 3 nm, more preferably below 1 nm, even more preferably below 0.5 nm.

11. Thin glass according to one of the preceding claims, wherein on at least one sixth measuring area of 0.33 x 0.33 mm ^{2 of} the second surface all surface structure components in a wavelength range of up to 0.25 mm have an average arithmetic height Sa of less than 5 nm preferably below 3 nm, more preferably below 1 nm, even more preferably below 0.5 nm.

12. Thin glass according to one of the preceding claims, wherein the thin glass has a glass transition temperature Tg between 400 ° C and 850 ° C, preferably between 500 ° C and 700 ° C.

13. An optical component comprising a material composite with a thin glass according to one of claims 1 to 12 and at least one further composite component made of plastic, metal, glass, glass ceramic, ceramic, wood and / or fiber composite material.

14. Product comprising a thin glass according to one of claims 1 to 12, wherein the product is a helmet visor, a smartphone display, a cover for a display device, a Console, a dashboard, a vehicle headlight, a taillight, industrial optics, consumer optics, spectacle lenses, protective goggles, AR glasses, VR glasses, a windshield, a watch glass, a window, a Electronic component with a display function, a smart watch, an electronic component with an optical sensor function, a component with a light-conducting function, a lighting element, a piece of jewelery, a vehicle exterior paneling, a vehicle interior paneling, a mirror, a decorative element, a protective element for acoustic components and / or Something similar is.

15. Tool (120) for producing a thin glass according to one of claims 1 to 12, with a mold (110) for three-dimensional reshaping of the thin glass, the mold (110) comprising a machine-polished molding surface (130) with at least one desired curvature.

16. Tool (120) according to claim 15, wherein on at least one seventh measuring area of 3 x 3 mm ^{2 of} the mold surface (130) all surface structure components in a wavelength range from 0.1 mm to 1 mm have a mean arithmetic height Sa of less than 40 nm aufwei sen, and / or wherein on at least an eighth measuring area of 0.33 x 0.33 mm ^{2 of} the form area (130) all surface structure components in a wavelength range of up to 0.25 mm have an average arithmetic height Sa of less than 500 nm .

17. Tool (120) according to claim 15 or 16, wherein the tool (120) at least in the loading area of the mold surface (130) metal, a metal alloy, graphite, in particular isostatically ge pressed fine-grain graphite, ceramic material, glass ceramic, quartz, and glass / or carbide, for example silicon carbide and / or tungsten carbide.

18. A method for producing a thin glass, in particular a thin glass according to one of claims 1 to 12, wherein the method comprises the steps:

Providing a flat glass substrate (100) with a thickness (d) of less than 700 µm;

- Application of the glass substrate (100) to a mold (110) of a tool (120), in particular a special tool (120) according to one of claims 15 to 17;

Heating the glass substrate (100) to a target temperature above the glass transition temperature Tg and below the softening point temperature EW of the glass substrate (100) with a temperature gradient of at least 35 K / min; when the target temperature is reached, the glass substrate (100) is subjected to negative pressure by applying a vacuum to the mold (110) of the tool (120) and / or by applying a pressing force to the glass substrate for a period of less than 120 s in order to keep the glass substrate ( 100) three-dimensional hot forming;

- cooling the hot-formed glass substrate (100) to a cooling temperature; and Removing the thermoformed glass substrate (100) from the mold (110).

19. The method according to claim 18, wherein the temperature gradient for heating the glass substrate to the target temperature is between 50 K / min and 300 K / min, in particular between 70 K / min and 280 K / min.

20. The method according to claim 18 or 19, wherein the glass substrate with a further Tempe raturgradienten of at least 10 K / min, preferably of at least 30 K / min, and / or of at most 140 K / min, preferably of at most 100 K / min the cooling temperature is cooled down.