Method and apparatus for the production of flat glass

Abstract

The invention relates to the manufacture of flat glass and articles made of flat glass, as well as the corresponding glass articles. The invention also relates to a method and a device for processing the edges of continuous, endless, manufactured glass strips.

Description

[0001] The invention relates generally to the production of flat glass, or of articles made of flat glass, as well as corresponding glass articles. In particular, the invention relates to a method and a device for processing the edges of continuous, endless, manufactured glass strips. Background of the invention

[0002] Various methods for producing glass ribbons are known in the prior art. One possibility, particularly for the production of thin glass, is to manufacture the glass using a drawing process. In this process, molten glass is prepared and then drawn thin through a subsequent drawing process. The molten glass can be prepared using different methods.

[0003] For example, in the float process, molten glass is spread over a bath of liquid tin and drawn into a ribbon. A characteristic feature of glass ribbons produced using the float process is their thickened edges, also known as "border." These borders form primarily because the soft glass at the ribbon's edge contracts due to surface tension.

[0004] Another way to produce glass ribbons using a drawing process is through methods such as down-draw or up-draw. In these processes, the molten glass is supplied to a drawing tank with a nozzle. Even with these methods, edges can appear along the edges of the glass ribbon.

[0005] Cooling processes of the glass ribbon during the further manufacturing process lead to temporary stresses due to the thickness differences between the edge region (border) and the net area between the borders, as the border can be temporarily longer than the ribbon in the area between the borders. These temporary stresses can put strain on the glass ribbon and thus increase the risk of breakage. Additionally, permanent stresses can occur if the glass in the thicker border passes through the glass transformation temperature later during cooling than the thinner glass in the net area. These permanent stresses increase with further cooling and can also lead to an increased risk of breakage.Since the percentage difference in thickness between the thickened edge areas and the thinner working area is greater in thin glass ribbons than in thicker glass ribbons, the temperature difference between the edge areas and the working area is particularly pronounced. Consequently, the mechanical stresses in the glass ribbon increase with decreasing glass thickness. Therefore, the production of thin glass ribbons, especially those with thicknesses < 1.3 mm, is particularly susceptible to stress-induced fractures.

[0006] Besides glass thickness, glass properties can also affect stress build-up. In particular, the cooling of glasses with a comparatively large difference in their coefficient of thermal expansion above the glass transformation temperature α can lead to stress build-up. liq and the coefficient of thermal expansion in the temperature range of 20 to 300 °C α 20-300 leading to comparatively high stresses in the glass.

[0007] The stresses described above can, in principle, be minimized by a relatively slow cooling process. However, this is difficult or impossible to achieve, especially when dealing with rapidly crystallizing glasses. In such cases, slow cooling of the glass ribbon would lead to devitrification. Therefore, these glasses must be cooled as quickly as possible. However, a correspondingly rapid cooling process can result in the temperature profile varying in speed across different glass thicknesses, causing temporary stresses to affect different areas of the glass to varying degrees. These effects increase the risk of breakage and can thus increase the number of rejects during the manufacturing process.Furthermore, in rapidly crystallizing glasses, the slower cooling in the rim region can result in these areas exhibiting a higher degree of crystallization than the rest of the glass. Consequently, the individual glass regions can also differ in their linear coefficients of thermal expansion, which can lead to additional mechanical stresses in the glass ribbon during processing, or even increase existing mechanical stresses. Flat glasses with these properties are therefore not typically produced by drawing processes, or the resulting glasses have relatively high thicknesses. Thin glass ribbons made from glasses with a high tendency to crystallize or devitrify, on the other hand, are usually not produced, or not exclusively produced, by drawing processes, but rather by rolling processes, for example.In contrast to the production of glass strips in drawing processes, the maximum widths of the glass strips as well as their minimum thickness are limited when manufactured using rolling processes.

[0008] To reduce or avoid stresses resulting from temperature control, even during rapid cooling steps, it would be helpful to separate the thick edge areas (border) from the thin net strip, or from the usable area of ​​the glass ribbon, at an early stage. This would prevent stresses generated by the cooling process from overloading the glass material and potentially leading to breakage. Furthermore, physically separating the differently cooling glass areas would allow the glass ribbon to be cooled more quickly according to material-specific requirements, without generating excessive temporary stresses.

[0009] From WO 2015 / 172957 A1, a method and a device for producing a thin glass ribbon with a thickness of at most 300 micrometers are known, in which the edges are separated. The thin glass ribbon is drawn from a glass melt or a preform, the edges are separated from the thin glass ribbon by means of a separating device, and the resulting glass ribbon is cooled. The separation takes place at a location along the direction of movement of the thin glass ribbon, or at a time when, during the cooling of the thin glass ribbon, the viscosity of the glass is in the range of 10 7 dPas up to 10 11The dPas value is such that the edges of the thin glass ribbon, newly formed by separating the borders, become rounded. However, the process is limited to very thin glasses. Thus, usually only glasses with a thickness of less than 0.3 mm can be separated using the method described in WO 2015 / 172957 A1. The production of thin glass ribbons from easily crystallizable glasses is not disclosed in WO 2015 / 172957 A1. Furthermore, the method described in WO 2015 / 172957 A1 is limited to down-draw processes. Object of the invention

[0010] The invention is based on the objective of preventing or at least reducing the occurrence of mechanical stresses between edges and the thinner working area during the production of glass ribbons, particularly during the production of glass ribbons with a working thickness of 0.1 to 1.3 mm, during the manufacturing process and especially during the cooling process. Furthermore, a method is to be provided with which even thin glass ribbons made of easily crystallizable glasses and / or glasses with relatively large differences in their coefficients of thermal expansion α can be produced. liq and α 20-300 °C can be produced by drawing processes. A further objective is the provision of glass articles made from easily crystallizable glasses. This objective is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the respective dependent claims. Summary of the invention

[0011] The invention relates to a method for producing a glass ribbon. In this method, a glass ribbon is first provided. The glass ribbon is obtained through a drawing process. The molten glass can be provided for the drawing process in different ways. According to a first embodiment, the glass ribbon is formed by drawing or lifting molten glass onto a float bath. A second embodiment provides that molten glass is provided in a drawing tank with a nozzle, and the glass ribbon is drawn from the nozzle. This can be done, for example, by a down-draw or an up-draw process.

[0012] The glass ribbon has a usable area with a largely homogeneous thickness and thickened edge areas. These edge areas are thicker than the glass in the usable area and are also referred to as the edge area or edge. The edge areas extend along the edges of the glass ribbon in the direction of drawing. The drawing direction is the direction in which the glass ribbon is drawn or transported.

[0013] The glass ribbon drawn from the melt is deflected at most once. If the glass ribbon is provided by a float process, no deflection is necessary. Preferably, in this embodiment, the glass ribbon is transported lying down in all process steps.

[0014] During transport, the glass ribbon cools further. Preferably, the glass ribbon is drawn through a cooling oven. In these process steps, transport preferably takes place horizontally, i.e., perpendicular to gravity. In particular, the glass ribbon is not deflected again. This is especially advantageous when the glass is produced using the float process. One embodiment provides that the glass ribbon is lifted from a float bath without any deflection of the glass ribbon.

[0015] The peeled or lifted glass strip preferably has a thickness in the usable area of ​​at least 0.1 mm, more preferably at least 0.3 mm, particularly preferably at least 0.32 mm, and particularly preferably at least 0.33 mm. According to one embodiment, the glass strip has a thickness in the usable area of ​​at least 0.35 mm, more than 0.35 mm, or even at least 0.4 mm. In another embodiment, the usable area of ​​the glass strip has a thickness of at most 1.3 mm or even at most 0.8 mm.

[0016] The first embodiment of the invention provides that the glass ribbon is lifted from a float bath, i.e., it is a floated glass ribbon. According to one embodiment, the glass ribbon is lifted or drawn from a float bath and has a thickness of at least 0.1 mm or at least 0.15 mm in the usable area. Preferably, the glass ribbon has a thickness in the range of 0.1 to 1.3 mm in the usable area.

[0017] According to a second embodiment of the method, the glass ribbon is drawn from a drawing tank with a nozzle, preferably using a down-draw or up-draw process. The glass ribbon provided in this embodiment is drawn glass. In this embodiment, a glass ribbon with a thickness greater than 0.3 mm is obtained. Preferably, the glass has a thickness of at least 0.32 mm, and more preferably at least 0.33 mm. According to one embodiment, the thickness in the usable area is at least 0.35 mm or even more than 0.35 mm, preferably at least 0.4 mm. Preferably, the glass ribbons have a thickness of at most 1.3 mm in the usable area, more preferably at most 1.1 mm, and more preferably at most 1 mm.

[0018] During the cooling of the glass ribbon, a laser beam is directed onto it using at least one laser. The laser beam is irradiated at the point in the manufacturing process when the glass temperature is within a range of viscosity between 10 10 dPas and a viscosity of 10 15 dPas, preferably between a viscosity of 10 12 dPas and a viscosity of 10 13 dPas, lies. With respect to the cooling section or device, the point of impact on the glass occurs at a position where the temperature of the glass is in a range between the upper cooling point at a viscosity of 10 10 dPas and the lower cooling point at a viscosity of 10 15 dPas is located.

[0019] The laser beam strikes the glass ribbon perpendicularly to the glass surface, with the point(s) of impact being positioned in the area between the usable area and the edge of the glass ribbon. Due to the relative movement between the glass ribbon and the laser beam, particularly as the glass ribbon is advanced in the drawing direction, the laser beam sweeps a line in the drawing direction of the moving glass ribbon. This line forms the dividing line, spatially separating the usable area of ​​the glass ribbon from the edge area. According to one embodiment, the glass ribbon is moved horizontally while the laser beam sweeps across the glass. This is particularly advantageous for glass produced using float glass processes. Another embodiment provides for the glass ribbon to be transported vertically during laser irradiation.

[0020] The laser wavelength is preferably selected to have a shallow penetration depth into the glass of the glass ribbon. Preferably, the wavelength is chosen so that the glass ribbon is heated directly by the beam only in the near-surface regions, particularly to a depth of at most one-third of the glass thickness in the working area, measured from the glass surface. According to one embodiment, the glass ribbon is heated to a depth of 0.1 mm, measured from the glass surface. According to one embodiment, the laser beam is generated using a CO2 laser.

[0021] At the laser point of impact, the glass undergoes local photothermal processing. This photothermal process causes a significant local heating of the glass in the relevant area, potentially leading to a reduction in viscosity and / or ablation of the glass at the point of impact. For the purposes of this disclosure, the term "photothermal process" refers to a process that includes the melting of the glass and / or its laser ablation. The degree of melting and laser ablation can vary depending on the specific process parameters. Both processes in which the material is melted without ablation and processes in which laser ablation is the predominant activity fall under the term "photothermal process" as defined in this disclosure.

[0022] According to one embodiment, the photothermal process during laser beam application significantly reduces the viscosity of the glass at the point of impact. In this area, the glass melts across its entire thickness at the point of impact, forming a gap or a cluster of gaps along the dividing line. This at least partially separates the usable area of ​​the glass from the thickened edge. The usable area and the thickened edge are thus mechanically decoupled. New edges form along the line.

[0023] The glass ribbon processed in this way, i.e. the glass ribbon consisting of the usable area of ​​the glass ribbon, is further cooled after the separation process.

[0024] In the inventive method, the glass has a temperature at the time of laser irradiation that is close to the transformation point T. gIn the temperature range according to the invention between the second cooling point and the transformation point, the glass ribbon exhibits a viscosity that counteracts the formation of mechanical stresses.

[0025] Preferably, the laser irradiation takes place in a cooling oven, particularly in the hot zone of the oven. According to one embodiment, the temperature in the cooling oven is at least 580°C during laser irradiation. This places high demands on the control and adjustability of the process. It must be ensured that the laser's optical assembly is thermally highly stable and that the individual components are not exposed to temperatures above their decomposition temperatures. Therefore, according to one embodiment, the laser is purged with an inert or purge gas and / or individual components, such as deflection mirrors, are actively cooled.

[0026] Within this temperature range of the glass ribbon, it is possible to heat the glass locally at the laser's point of impact to such an extent that the local viscosity decreases so significantly that a gap forms. This gap extends across the entire thickness of the glass and is also referred to as a puncture. The formation of the gap or puncture can occur through either melting of the glass or partial ablation processes. In this process, the glass is not only melted or ablated in near-surface areas. The volume of the area where the gap forms is determined by the focal spot size of the incident laser beam, also referred to as the laser spot diameter, and the glass thickness. Thus, the glass is punctured at the point of impact of the laser beam.

[0027] The puncture can be achieved, in particular, with low viscosity and by utilizing the surface tension of the low-viscosity material. Surprisingly, once a puncture has formed, no further mechanical action on the glass ribbon is necessary to create the gap. Due to the surface tension of the glass, it contracts on both sides of the gap, forming new edges on either side. The contracting material also forms a new edge at the newly created edge in the working area. However, due to the comparatively small volume of molten glass, this new edge is small and therefore behaves similarly to the glass in the working area of ​​the glass ribbon in subsequent thermal processes.Unlike separation processes where the glass is broken, the inventive process creates a highly strong edge through melt rounding, which gives the glass ribbon high mechanical stability and strength in subsequent transport and handling processes. In particular, the edge has a fire-polished finish.

[0028] Despite the rounding of the enamel, the newly formed edge exhibits only a slight thickening of the enamel margin. This is achieved by keeping the enamel volume small.

[0029] Preferably, edge formation occurs along the entire irradiated area. However, isolated re-closures can also form at the edges.

[0030] Preferably, both thickened edge regions or border areas of the glass ribbon are separated using the method described above. Accordingly, the glass ribbon has two points of impact for two laser beams, and two new edges are formed on the usable area of ​​the glass ribbon. The glass ribbon thus formed preferably no longer has any border areas, and the usable area of ​​the glass ribbon is bounded by the two newly formed edges. The newly formed edges thus constitute the lateral edges of the glass ribbon, with the lateral edges running parallel or at least largely parallel to the transport direction of the glass ribbon.

[0031] According to one embodiment, the glass strip that can be produced using the described method has a rounded profile at the newly formed edge or edges.

[0032] In embodiments where the glass ribbon is transported horizontally and the laser beam strikes it perpendicularly, the gap is formed parallel to gravity. This causes the molten glass to be pulled out of the gap by gravity. Such embodiments are therefore particularly suitable for producing relatively thick glass ribbons without the need for additional mechanical cutting steps. In particular, glass ribbons with a thickness of at least 0.1 mm in the usable area, and especially those with a thickness greater than 0.3 mm up to 1.3 mm, can be produced. One embodiment provides for a glass thickness in the usable area of ​​the glass ribbon in the range of greater than 0.3 mm up to 1.3 mm, preferably in the range of 0.32 to 1.1 mm. In this way, glass ribbons with a thickness in the usable area of ​​0.35 to 1 mm can also be produced, which can be used, for example, as cover glass.

[0033] Preferably, the device is designed such that the focal spot diameter or laser spot diameter at the level of the glass ribbon is adjusted to the glass dimensions and viscosity behavior of the respective glass by changing the focus position via adaptive mirror optics. The gap width can be adjusted via the focal spot size of the laser beam. The focal spot size or laser spot diameter is selected such that the gap width is large enough to prevent or at least reduce the risk of the glass re-contacting at the edges due to surface tension and, if applicable, the effects of gravity on the molten glass when the glass is withdrawn. Simultaneously, the focal spot size limits the gap width and thus also the melt volume.This prevents excessive accumulation of molten glass volume and thus the re-formation of an increased border.

[0034] Surprisingly, the use of a laser beam with a small focal spot size has proven particularly advantageous. This makes it possible to keep the gap width, and thus the melt volume, as small as possible to counteract edge thickening. Laser spot diameters of less than 4 mm, less than 2.5 mm, and preferably less than 1.5 mm have proven particularly advantageous. According to one embodiment, the laser spot has a diameter of less than 1 mm or even less than 0.8 mm. In an advantageous embodiment, the laser power is spatially and temporally synchronized.

[0035] The laser beam power is preferably at least 750 W or even at least 900 W. Surprisingly, in combination with the small focal spot sizes, sufficiently high power densities can be achieved even with these comparatively moderate laser powers, enabling the penetration of relatively thick glass. At the same time, the thermal influence zone, and thus the volume of molten glass, is kept small, thereby reducing edge thickening at the newly formed edges. A further development involves lateral and axial modulation of the laser focus. This is particularly advantageous for glass ribbons with a relatively large thickness in the working area, as the modulation allows the kerf to be kept open across the entire width of the material while simultaneously minimizing the overall energy input.In an advantageous embodiment, the laser power is spatially and temporally synchronized.

[0036] In the separation process, heat conduction into the thermally influenced zone behind the opened gap can cause the glass at the already formed separation edge to flow viscously. Due to surface tension, the glass can locally densify, leading to bridging across the gap. This results in a beaded arrangement of resealed gaps with a high material thickness. If the ratio of gap length to the length of the resealed areas (also known as glass plugs) is too small, the bonding material between the newly formed edges can cause locally increased stresses in the resealed areas, leading to the rejection of the corresponding glass ribbon. However, the inventors surprisingly discovered that lateral oscillation of the laser beam in the transverse direction and / or in the direction of the glass ribbon's feed, i.e.,In the longitudinal direction, this promotes uniform solidification of the molten glass, thus reducing the bridging described above through re-closure. Isolated re-closures of the edges, occurring locally, do not prevent separation of the borders. Therefore, edges exhibiting only isolated, particularly statistically distributed, re-closures are also subsumed under the term "separated edges."

[0037] A relative movement is performed between the laser point and the glass ribbon in the direction of the ribbon's pull. In one embodiment, the laser point is stationary, and the relative movement corresponds to the pull of the glass ribbon. Preferably, the feed rate is at least 1.5 m / min, more preferably at least 2.5 m / min, and most preferably at least 4 m / min. A correspondingly high feed rate results in a short exposure time of the glass at the laser point. Thus, the aforementioned high feed rates reduce heat conduction to adjacent glass areas and keep the heat-affected zone small. This, in turn, has a beneficial effect on the melt thickening. Furthermore, this prevents the formation of thickened, fused glass joints between the gaps.On the other hand, the feed rate must be sufficiently low to ensure complete penetration at the dividing line through the required heat conduction. According to one embodiment, the feed rate is therefore at most 16 m / min, preferably at most 10 m / min, or even at most 8 m / min. Another embodiment provides that the feed rate is at most 6 m / min, preferably 5.5 m / min. Alternatively or additionally, the feed rate is at least 1.5 m / min, preferably at least 4 m / min, and particularly preferably at least 4.5 m / min. According to one embodiment, the feed rate at the point of laser impact is in the range of 1.5 to 6 m / min, preferably in the range of 4 to 5.5 m / min.

[0038] According to one embodiment, the laser power is limited so that the ablation component in the photothermal process is largely reduced, and the glass separation occurs primarily through a reduction in glass viscosity. Such a process can also be referred to as soft cutting. It has proven advantageous to select an upper limit of less than 2 kW or even a maximum of 1.5 kW for the laser power. This has proven particularly advantageous for glass with a thickness of up to 0.6 mm and / or at glass ribbon transport speeds of up to 5 m / min.

[0039] The inventors discovered that even with glass ribbons of greater thickness, complete separation with barely thickened edges can be achieved during the cutting process if the laser spot diameter, feed rate, laser power, and glass thickness are optimally adjusted. A further development therefore stipulates that the following relationship between laser power, laser spot diameter, and feed rate applies: Laser power / (Laser spot diameter x Glass thickness x Feed rate) > 6 * 10 8 W*s / m 3 A ratio greater than 1*10 has proven particularly advantageous in this regard. 9 W*s / m 3 or even > 4*10 9 W*s / m 3 highlighted. According to one embodiment, the ratio is in the range of 6*10 9 up to 30* 10 9 W*s / m 3 .

[0040] The laser intensity profile can be Gaussian or similar continuous distributions, or top-hat, according to one embodiment. Particularly when cutting glass ribbons with a thickness in the millimeter range, or at least 1 mm, the use of a laser with a top-hat intensity profile has proven advantageous. Such glass thicknesses require high peak powers from the laser sources used. Surprisingly, it was found that the glass material does not tend to suffer edge damage (e.g., conchitis) or breakage due to the local, temporarily induced stresses, since the glass body already reaches a temperature close to its transformation temperature T. g The thermomechanical stresses are thus reduced more quickly than expected at a temperature adapted to the glass, and are therefore less critical than in typical processes at room temperature.

[0041] With lasers exhibiting a Gaussian intensity distribution, glass areas located at the edges of the beam profile are irradiated with an intensity insufficient for penetration. This intensity merely reduces the glass's viscosity to the point where it becomes locally fluid or temporarily relieves thermomechanical stresses, without contributing to the intended gap formation. Consequently, the thermally affected zone is significantly larger than the gap width, resulting in localized ridge buildup at the melt edge within the working area of ​​the glass ribbon. In contrast, a top-hat intensity profile, with its steeper slope, has a considerably larger area where the intensity exceeds the focal threshold for laser processing. Therefore, the heat-affected zone can be significantly reduced compared to a Gaussian intensity distribution.This allows for the reduction of undesirable effects such as an exaggerated melting edge. Furthermore, energy is used more efficiently in the top-hat-shaped intensity profile.

[0042] The above-described process steps for separating the edges enable rapid cooling rates of the glass ribbon to be achieved with the disclosed method, without excessive stress build-up in the glass and subsequent glass breakage. According to one embodiment, the glass ribbon is cooled after the edges have been removed at a cooling rate of more than 100 K / min, preferably more than 200 K / min or even more than 300 K / min. The early edge separation according to the invention and the resulting use of high cooling rates also allow thin glass ribbons to be produced from glasses with a high tendency to crystallize using the disclosed method.

[0043] According to a third variant of the procedure, a glass is therefore provided for which the following applies FB=αliq+α20−30030⋅10−6 / K⋅(4.6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1,preferred>1.1.

[0044] Here, αl iq the linear coefficient of thermal expansion above the glass transformation temperature of the glass, α 20-300 or linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η liq the liquid viscosity of the glass, dTdlog(η)(log(η)=13) the slope of the viscosity curve at the upper cooling point or at the temperature at which the glass has a viscosity η of 10 13 dPas exhibits and T 13 the temperature at which the glass has a viscosity η of 10 13 dPas. The slope of the viscosity curve at the upper cooling point is obtained from the Vogler-Tamman-Fulcher coefficient, also known as the VTF coefficient.

[0045] Glasses that meet the above-mentioned condition exhibit a high tendency towards devitrification or crystallization, so that during the drawing process, particularly in the production of thin glasses, preferably with a thickness in the usable range of no more than 1.3 mm, cooling at high cooling rates is necessary. According to one embodiment, glasses are provided for which the following applies: FB=αliq+α20−30030⋅10−6 / K⋅(4.6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1.2.

[0046] According to further training, the glass is a crystallizable glass used for the production of glass ceramics, hereinafter also referred to as green glass. Specifically, the glass is a green glass used for the production of LAS glass ceramics or AS glass ceramics.

[0047] Another aspect of the invention relates to a glass ribbon, producible by the method described above, having two opposing surfaces and a homogeneous glass thickness extending between them. The glass ribbon with homogeneous thickness has a central region with a thickness d. Mitte as well as at least two boundary regions with thickness d Rand The edge regions form the edges of the glass ribbon. A glass ribbon with a homogeneous thickness is specifically defined as a glass ribbon with an edge region of a thickness d. Rand and a central region with a thickness of the central region d Mitte understood, where the maximum thickness of the boundary region d Rand,max is at most 150% greater than the thickness of the central region d MitteThe glass ribbon therefore has no thickened edge areas in the form of glass rims. The glass ribbon with a homogeneous thickness can also be referred to as a rim-free glass ribbon. Preferably, the thickness of the glass ribbon is at most 1.3 mm, particularly preferably at most 0.8 mm.

[0048] According to a first embodiment, the glass ribbon with homogeneous thickness is float glass and preferably has a higher tin concentration on one of its two surfaces compared to the composition of the bulk glass. The increased tin concentration is due to the floating of the molten glass onto a tin bath. In this embodiment, the glass ribbon is therefore produced using a float process. This glass ribbon with homogeneous thickness preferably has a thickness d in its central region. Mitte of at least 0.1 mm, preferably of more than 0.3 mm, particularly preferably in the range of at least 0.33 mm. Preferably the thickness d Mittein this embodiment in the range of 0.1 to 1.3 mm, particularly preferably in the range of 0.1 to 0.8 mm.

[0049] According to a second variant, the glass ribbon with homogeneous thickness is a drawn glass ribbon and / or has two fire-polished surfaces. In this embodiment, the glass ribbon with homogeneous thickness preferably has a thickness d in its central region. Mitte of more than 0.3 mm, preferably of at least 0.32 mm, particularly preferably of at least 0.33 mm, 0.35 mm or even at least 0.4 mm. Alternatively or additionally, in this embodiment, the thickness of the central region is at most 1.3 mm, preferably at most 1.1 mm, particularly preferably at most 1 mm. According to one embodiment, the thickness d Mitte in the range of 0.32 mm to 1.3 mm, preferably in the range of 0.33 mm to 1.1 mm, particularly preferably in the range of 0.4 mm to 1 mm.

[0050] Alternatively or in addition to the two variants mentioned above, the glass of the glass ribbon with homogeneous thickness satisfies the following equation according to a third variant: FB=αliq+α20−30030⋅10−6 / K⋅(4,6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1,preferred>1,1,especiallypreferred>1,2.

[0051] Here, αl iq the linear coefficient of thermal expansion above the glass transformation temperature of the glass, α 20-300 or linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η 1iq the liquid viscosity of the glass, dTdlog(η)(log(η)=13) the slope of the viscosity curve at the upper cooling point or at the temperature at which the glass has a viscosity η of 10 13 dPas exhibits and T 13 the temperature at which the glass has a viscosity η of 10 13The viscosity curve exhibits dPas. The slope of the viscosity curve at the upper cooling point is obtained from the Vogler-Tamman-Fulcher coefficient, also known as the VTF coefficient. In this embodiment, the glass preferably has a thickness of no more than 1.3 mm.

[0052] Further training stipulates that the edge area must have a thickness of d Rand exhibits, wherein the maximum thickness of the edge region d Rand,max preferably at most 120%, particularly preferably at most 100% greater than the thickness of the central region d MitteThus, due to the localized structure, there is little mass and therefore little material to cool in the newly formed edge region. If the glass ribbon with homogeneous thickness is passed through the cooling process again by Tg, the permanent material stresses can be minimized more quickly, since the volumes of the new edge pieces and the usable area of ​​the glass ribbon with homogeneous thickness, i.e., the edge-free glass ribbon, are relatively small. Accordingly, the differences in the cooling process of the two areas are minimized, so that, compared to the original glass ribbon with edge regions, significantly higher cooling rates can be achieved without stresses arising between the individual areas of the glass ribbon.

[0053] According to a further aspect, the invention relates to a plate-shaped or disc-shaped glass article, in particular a flat glass. A plate-shaped or disc-shaped glass article is understood to be, in particular, a glass article with two opposing surfaces having lateral extensions in the x and y directions and an intermediate edge surface. The extension of the edge surface in the z direction corresponds to the glass thickness d. Glas , where the lateral dimensions of the two surfaces in the x and y directions are greater than the glass thickness. The glass article is particularly suitable for use as cover glass, for example as cover glass in displays or for their manufacture.

[0054] Preferably, the glass article is manufactured or producible using the method described above or from the glass strip described above. According to one embodiment, the glass of the glass article is drawn glass, in particular drawn float glass. Since, during the manufacture of a drawn glass article, its surfaces do not come into contact with forming tools, such as the surface of rollers, in their malleable state, both surfaces of the glass article exhibit low roughness. One embodiment provides that at least one surface of the glass article has a fire polish. In contrast, for example, in glass articles obtained by rolling processes, at least one surface may be present whose minimum roughness is limited by the roughness and / or surface structure of the roller, provided that the corresponding surface is polished after the rolling process.

[0055] The following relationship applies to the properties of the glass in the glass article: FB=αliq+α20−30030⋅10−6 / K⋅(4,6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1,preferred>1,1,especiallypreferred>1,2.

[0056] Here, αl iq the linear coefficient of thermal expansion at temperatures above the glass transformation temperature of the glass, α 20-300 or linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η 1iq the liquid viscosity of the glass, dTdlog(η)(log(η)=13) the slope of the viscosity curve at the upper cooling point or at the temperature at which the glass has a viscosity η of 10 13 dPas has and T13 is the temperature at which the glass has a viscosity η of 10 13dPas. The slope of the viscosity curve at the upper cooling point is obtained from the Vogler-Tamman-Fulcher coefficient, also known as the VTF coefficient.

[0057] The glass article has a thickness of d Glas in the range of 0.1 to 1.3 mm, preferably in the range of 0.1 to 0.8 mm, and particularly preferably in the range of 0.3 to 0.8 mm. According to one embodiment, the smallest lateral dimension l min(x, y ) in the x and y directions of the glass article > 400 mm. Alternatively or additionally, according to a further embodiment, it is provided that the aspect ratio between the glass thickness d Glas and the smallest lateral dimension in the x and y directions l min(x, y) applies: 1min(x,y) / dGlas>500,preferred>1000,especiallypreferred>4000.

[0058] Preferably, the glass article has a maximum thickness deviation of the glass Δglass thickness = d Glas(max) - d Glas (min)< 0.1 mm. Alternatively or additionally, the glass thickness of the glass article varies by a maximum of 10%.

[0059] One embodiment provides that the glass of the glass ribbon or glass article is a borosilicate glass, in particular a borofloat glass with a thickness of at least 0.25 mm or a low-loss borosilicate glass with a thickness of at least 0.1 mm. A low-loss borosilicate glass is understood to be, in particular, a borosilicate glass that exhibits a very low dielectric loss at 10 GHz. For example, the dielectric loss at 10 GHz can be tan δ < 0.0023.

[0060] According to one embodiment, the glass of the glass article or glass strip is a borosilicate glass and contains the following components in wt.% SiO2 74 to 85 B2O3 8 to 25 Al2O3 0.5 to 4 Li2O 0 to 1 K2O 0.3 to 2 MgO 0 to 3 CaO 0 to 3

[0061] According to one embodiment, a glass of the glass article or glass ribbon comprises the following oxide-based components in wt.%: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit in each case may preferably be 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, wherein preferably the sum of the content of Al2O3 and SiO2, based on the value in wt.%, is between at least 75 and at most 92, preferably at most 90.

[0062] According to one embodiment, a glass of the glass article or glass ribbon comprises the following oxide-based components in wt.%: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit in each case may preferably be 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7 MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O5 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO2 0 to 3, preferably 0 to 2, which may still contain impurities and / or fining agents and / or coloring components in quantities of up to 2% by weight.

[0063] According to one embodiment, a glass of the glass article or glass ribbon comprises the following oxide-based components in wt.%: SiO2 62-72, preferably 65-70 Al2O3 7-14, preferably 8-12 B2O3 0.1 - 8.5, preferably < 8.5 or ≤ 8, preferably 4 - 7, particularly preferably ≥ 5, most preferably > 5.5 Li2O 5-12, preferably 7-10 Na2O 0 - 2, preferably 0 - 1, particularly preferably ≥ 0.1 and / or < 1, most preferably ≥ 0.3 and / or < 0.8 K2O 0-2, preferably 0-1 with 0.8 < Li2O / (Li2O + K2O + Na2O) ≤ 1

[0064] According to one embodiment, a glass of the glass article or glass strip, in particular a ceramizable glass, comprises the following components in wt.% based on oxides: SiO2 55-75, preferably 62-72 Al2O3 18-27, preferably 18-23 Li2O 2.8-5, preferably 3-5 Na2O 0-4, preferably 0-2 K2O 0-4, preferably 0-2 MgO 0-8, preferably 0-4 CaO 0-4, preferably 0-2 SrO 0-4, preferably 0-2 BaO 0-4, preferably 0-2 ZnO 0-6, preferably 0-2 TiO2 0-4, preferably 0-3 ZrO2 0-5, preferably 1, 2-4 B2O3 0-2, preferably 0-0.1 SnO2 0-2, preferably 0.05-1.6 where preferably the following applies to the sum of the components TiO2 and ZrO2: 0<∑(TiO2+ZrO2)<9.5%, preferably 1.2<∑(TiO2+ZrO2)<9.5%, or preferably for the components SnO2, ZrO2 and TiO2: 0≤SnO2 / (ZrO2+TiO2)<0.8, preferably 0.01≤SnO2 / (ZrO2+TiO2)<0.7.

[0065] According to one embodiment, the glass of the glass article or glass ribbon is a crystallizable glass, in particular for the production of a lithium aluminum silicate glass ceramic (LAS ceramic) and comprises the following oxide-based components in wt.%: SiO2 65 to 71 Al2O3 10 to 15 B2O3 0 to 6 Li2O 0 to 11 Na2O 0.5 to 13 K2O 0.1 to 3 MgO 0 to 7 CaO 0 to 3 SrO 0 to 0.5

[0066] The invention further relates to a device for producing a glass ribbon of homogeneous thickness from a glass ribbon with a usable area and edge regions thickened compared to the usable area. The edge regions are separated. The device comprises a device for supplying a glass ribbon, preferably a float tray, a quenching oven, and transport devices for moving the glass ribbon from the device for supplying the glass ribbon through the quenching oven. According to one embodiment, the glass ribbon is transported horizontally by the transport devices. In particular, the transport of floated glass is horizontal. At least one laser beam is introduced into the quenching oven. One embodiment provides that the laser beam is introduced by means of an optical system designed as a cantilever arm, with this laser arm projecting laterally into the quenching oven.After exiting the laser, the laser beam is deflected orthogonally by a deflecting element so that it strikes the glass ribbon perpendicular or orthogonal to the transport or drawing direction. In an alternative embodiment, the laser beam is fed vertically through the furnace ceiling.

[0067] The point of impact of the laser beam relative to the glass ribbon is adjusted so that it lies on the boundary between the working area and the edge area. Within the annealing oven, the laser is positioned so that the point of impact strikes the glass ribbon at a location within the oven where the glass temperature is between the upper cooling point at a viscosity of 10 10 dPas and the lower cooling point at a viscosity of 10 15 dPas is located.

[0068] According to one embodiment, the deflecting element is an imaging mirror. It has proven particularly advantageous if the device includes a cooling system for actively cooling the deflecting element or the mirror.

[0069] In a further development, the laser arm is designed to be swiveling or sliding. This allows the laser arm to be removed from the cooling oven. This provides good accessibility, for example, for servicing the laser outside the hot zone of the cooling oven. Alternatively or additionally, the laser arm includes a device for purging with inert gas.

[0070] Rollers and / or belts have proven to be particularly advantageous as transport devices. Detailed description of the invention

[0071] The invention will now be described in more detail with reference to the Fig. 1 to 9 explained. They show: Fig.1 a schematic cross-sectional representation of an embodiment of the method in which the glass ribbon is provided by a float process, Fig. 2 a schematic representation of the process step of separation in overhead view according to an embodiment, Fig. 3 a schematic representation of the border separation of an exemplary embodiment in cross-section, Fig. 4 a photographic recording of the in Fig. 3 illustrated embodiment, Fig. 5 a schematic representation of the border separation of a further embodiment in cross-section, Fig. 6 a photographic image of a glass stopper Fig. 7 a schematic representation of the cooling furnace in cross-section, Fig. 8 a schematic representation of a glass article according to one embodiment and Fig. 9 a schematic cross-section through the in Fig. 8 embodiment shown.

[0072] Fig. Figure 1 shows a schematic representation of a first variant of the inventive method according to one embodiment. Here, the molten glass 17 flows from the tank onto a float bath 2. In this embodiment, the float bath 2 is a tin bath in the float tank 7. The glass ribbon 1 forms on the float bath 2, which has a thinner usable area and thickened edge areas at both edges (in Fig. (1 not shown). The glass ribbon 1 is lifted from the float bath 2 by the transport device 80 and transported in the transport or drawing direction 8 into the cooling oven 6. The glass ribbon 2, lifted from the float bath 2, is carried lying on the transport direction 80 at a speed v Vorschub transported. As from Fig.As is clearly shown in Figure 1, the glass ribbon 1 is transported in this embodiment lying down and perpendicular to gravity. In particular, the glass ribbon 1 is transported lying down throughout the entire process.

[0073] In the Fig. In the embodiment shown in Figure 1, a laser beam 90, 91 strikes the glass ribbon 1 inside the cooling oven 6. The points of impact 11, 110 are selected on the glass ribbon 1 such that they lie in the boundary region between the usable area and the thickened edge area or border area. Due to the perspective view, in Fig. 1 only a laser 90 and the corresponding point of impact 11 are shown.

[0074] The laser 9 is positioned so that the corresponding laser beam 90 hits the glass ribbon 1 at a position where the glass has a temperature in a range between the upper cooling point at a viscosity of 10 10 dPas and the lower cooling point at a viscosity of 10 15The laser 9 is thus positioned in the hot zone of the cooling oven. Depending on the specific design of the device, the laser 9 can also be positioned in front of the cooling oven 6, provided that the glass ribbon 1 has a temperature between a viscosity of 10 and a temperature of 10 at that point. 10 dPas and a lower viscosity of 10 15 exhibits dPas.

[0075] Thus, with the in Fig.In the process shown in Figure 1, the thickened edge regions or border areas are separated at an early stage of the process, so that the glass ribbon with homogeneous thickness 30 can subsequently be cooled quickly, i.e., at relatively high cooling rates. This enables the production of floated, thin glass ribbons from glasses with a high tendency to crystallize, which previously could not be produced using the float process. With the process according to the invention, however, even thin glasses, in particular glasses with a thickness of at most 1.3 mm, can be produced using the float process, for which the following applies: FB=αliq+α20−30030⋅10−6 / K⋅(4.6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1.

[0076] Table 1 shows the coefficients of thermal expansion, the viscosity above the glass transformation temperature, the slope of the temperature-viscosity curve at the upper cooling point, and the characteristic value that can be obtained using equation (1) for three exemplary embodiments. Glasses 1 to 3 are thin glasses with a thickness of at most 1.3 mm. Glasses 1 to 3 are ceramizable glasses for the production of LAS glass-ceramics. These green glasses therefore exhibit high crystallizability, but should be in their glass state during the production of the thin glasses. Devitrification during the drawing process must therefore be avoided. Table 1 a 1iq [10 -6 m*K] a 20-300 [10 -6 m*K] η liq [dPas] T 13 [°C] dTdlog(n)(log(n)=13) FB Glass 1 30,00 3,9 3,23 662,9 0,9805 2,106 Glass 2 17,00 3,96 3,56 724,6 1,0803 1,679 Glass 3 17,00 4,1 3,96 708,4 1,0562 1,3019

[0077] Glass 1 is a crystallizable green glass which can be transformed into a LAS glass-ceramic by subsequent ceramicization processes. Glass 1 preferably has the following composition in wt.%: SiO2 55-75, preferably 62-72 Al2O3 18-27, preferably 18-23 Li2O 2.8-5, preferably 3-5 Na2O 0-4, preferably 0-2 K2O 0-4, preferably 0-2 MgO 0-8, preferably 0-4 CaO 0-4, preferably 0-2 SrO 0-4, preferably 0-2 BaO 0-4, preferably 0-2 ZnO 0-6, preferably 0-2 TiO2 0-4, preferably 0-3 ZrO2 0-5, preferably 1, 2-4 B2O3 0-2, preferably 0-0.1 SnO2 0-2, preferably 0.05-1.6 where preferably the following applies to the sum of the components TiO2 and ZrO2: 0<∑(TiO2+ZrO2)<9.5%, preferably 1.2<∑(TiO2+ZrO2)<9.5% or preferably for the components SnO2, ZrO2 and TiO2: 0≤SnO2 / (ZrO2+TiO2)<0.8, preferably 0.01 <SnO2 / (ZrO2+TiO2)<0,7.

[0078] Glass 2 is also a green glass used for the production of LAS glass-ceramic. The crystallizability of this green glass, required for the production of glass-ceramics, is accompanied by a correspondingly high tendency for the glasses to crystallize. This tendency to crystallize, and the associated relatively high tendency for devitrification, has hitherto been an obstacle to the production of thin glasses of glasses 1 and 2 in the float process. However, by separating the thickened edge regions or border regions according to the invention, and the resulting rapid cooling, a devitrification process or premature crystallization during the production of the thin glasses can be counteracted in the process according to the invention.

[0079] Glass 3 is also a green glass used for the production of LAS glass ceramics and could previously only be produced with glass thicknesses of approximately 4 mm using float processes. At glass thicknesses of approximately 4 mm, the cooling rates necessary to suppress crystallization are still low enough to avoid introducing excessive mechanical stresses, even without removing the edges. However, thinner glasses require higher cooling rates, so the production of floated thin glasses with reduced thicknesses was previously not possible with Glass 3. By removing the edges and the resulting higher cooling rates, however, crystallization during the drawing process can be prevented even with thin glasses of Glass 3. Thus, with the method according to the invention, floated thin glasses with very small thicknesses, in particular with thicknesses in the range of 0.1 to 1.3 mm, can also be obtained for Glass 3.

[0080] Fig.2 shows a schematic representation of the in Fig. The process shown in Figure 1 is carried out after the glass ribbon 1 has been lifted from the float bath 2, in a top view. The glass ribbon 1 has a central working area 3 and two thickened edge areas 5. After the glass ribbon is transported into the cooling oven 6, a laser beam 90, 91 from lasers 9, 10 each strikes the glass ribbon 1 at the boundary areas between the working width 3 and the edge areas 5. At the point of impact, the glass ribbon 1 has a temperature below the upper cooling point and above the lower cooling point of the glass. At the point of impact, the laser beam penetrates the glass ribbon 1. Since the glass ribbon 1 simultaneously expands with the feed rate v VorschubAs the glass strips are moved in the transport direction 8, a gap is formed between the working area 3 and the edge areas 5. New edges are formed on both the working area 3 and the edge areas 5. This process yields the thickened glass strips 50, 51, as well as a new glass strip 30 with a new edge area 32. The edge area 32 is only slightly thicker than the central area of ​​the glass strip 30. The glass strip 30 with a homogeneous thickness is then conveyed further through the annealing furnace. The glass strips 50 and 51 represent waste and can, for example, be remelted. Several options are available for the further treatment of the glass strips 50, 51. According to one embodiment, the glass strips 50, 51, like the glass strip 30 with a homogeneous thickness, can be continuously conveyed further through the annealing furnace 6. Since the glass strips are connected to each other and the glass is heated to temperatures below T gAlthough the glass is rigid, there is a risk of breakage when handling the separated glass strips 50, 51, which can affect the entire glass ribbon 1 and the separation zone. Therefore, another embodiment provides for the glass strips 50, 51 to be cut into short, manageable sections directly after separation from the glass ribbon with a homogeneous thickness 30. Thermal blasting of the individual sections of the glass strips 50, 51 has proven particularly advantageous in this regard. This process exerts only very minor mechanical influences on the entire glass ribbon 1. Furthermore, the thermal blasting process is particularly easy to perform on the glass strips 50, 51, since the glass has relatively high temperatures, i.e., just below Tg. Accordingly, a thermal shock is easy to achieve. A further development provides for an initial defect to be introduced into the glass strips 50, 51 before the thermal shock.Mechanical scoring of the glass has proven particularly advantageous in this process. Due to the high glass temperatures, a thermally stable material, such as a high-temperature-resistant metal, must be used.

[0081] In Fig. Figure 3 schematically shows the separation of the thickened edge region 5 from the glass ribbon 1 in cross-section. The point of impact 11 of the laser beam 90 lies in the boundary region between the usable area 3 and the thickened edge region 5. The hatched area 12 represents the volume of glass that is melted by the laser beam 90. In the Fig. In the embodiment shown in Figure 3, the glass ribbon has a thickness d of 0.6 mm in the usable area. A CO2 laser is used as the laser source, the incident power is 1000 W, and the focal spot size is 1 mm. 2Thus, a relatively high power is irradiated onto a small area, resulting in a correspondingly high power density. This allows penetration through the glass to form a gap 13. The glass ribbon 1 is therefore separated into the glass ribbon with homogeneous thickness 30 and the glass strip 50, forming edges 33 and 34. The small focal spot size and the feed rate of 4.3 m / min, which the glass ribbon experiences during the process perpendicular to the laser irradiation, keep the gap width small. Furthermore, the small focal spot size and relatively fast feed rate result in a relatively small heat-affected zone. In particular, essentially only the glass areas in which the gap 13 forms are melted.

[0082] At the in Fig.In the embodiment shown in Figure 3, the ratio of laser power, spot size, and feed rate is set such that the two glass areas 3 and 5 of the glass ribbon 1 are completely separated from each other by the gap 13. At the same time, the newly formed edges 33, 34 have only a slightly raised fusion edge.

[0083] This is also evident from Fig. 4 clearly shows a photographic image of the two separate glass bands 30 and 50.

[0084] The ratio of laser power / (laser spot diameter x glass thickness x feed rate) is 23 * 10 in this embodiment. 9 W*s / m 3 .

[0085] Fig. 5 shows, as well as Fig. 3, the separation of the thickened edge region 5 from the glass ribbon 1 in cross-section according to a further embodiment. Here, a larger focal spot size of 7 mm was used. 2The melting volume 120 is correspondingly larger. The glass ribbon 1 was moved orthogonally to the laser beam direction at a feed rate of 35 mm / s. As in the first embodiment, a gap 130 is formed first, whereby the glass ribbon with homogeneous thickness 30 and the glass strip 50 with edges 330 and 340 are formed. Since the melting volume is larger here and, moreover, does not solidify as quickly due to the slower feed rate as in the Fig.In the embodiment shown in Figure 4, isolated areas can form between edges 330 and 340, which contain a glass plug 14. This can lead to a local resealing of the gap 130 in isolated cases. Since the formation of the glass plug 14 occurs only sporadically, the separability of the edges 50 is not affected, or not significantly so. Edges 330, 340 that contain isolated glass plugs 14 are therefore also referred to as separated edges within the meaning of the disclosure. Thus, the isolated glass plugs can spontaneously break during the process, for example, due to vibrations or movements of the glass edges 330, 340, and thereby release both glass edges 330, 340 without requiring a further process step.

[0086] Fig. Figure 6 shows a photographic image of a section of the in Fig.Example 5 shown. Between the glass edges 330, 340, a glass plug 14 has formed in the gap 13 at the point shown. The one in Fig. The section shown in Figure 6 is not representative of edges 330 and 340, but rather shows a single point where a glass plug 14 was formed. For the most part, however, edges 330 and 340 are separated from each other by the gap 13.

[0087] Fig.Figure 7 shows a schematic cross-sectional representation of the cooling oven 6 according to one embodiment. In this embodiment, the glass ribbon is transported in the horizontal plane. The glass ribbon 1, with its thickened edge regions 5 and usable area 3, is transported horizontally through the cooling oven 6 by the transport device 80. The transport direction lies in the plane of the illustration. The laser arms 15, 150 of the lasers 9, 10 project laterally into the cooling oven 6 through the lateral openings in the cooling oven 61, 62. The laser arms 15, 150 each also contain an imaging mirror 16, 160. The laser beam 90, 91 emitted by the lasers 9, 10 initially exits parallel to the glass ribbon 1 and is deflected downwards by the mirrors 16, 160. At the points of impact 11, 110, the laser beam 90, 91 hits the glass orthogonally to the feed direction of the glass ribbon.The point of impact 11, 110 lies in the boundary region between the thickened edge region 5 and the usable area 3 of the glass ribbon 1. The laser arms 15, 150 can be extended or pivoted out of the cooling oven 6 through the lateral openings 61, 62 of the cooling oven 6. According to one embodiment, the mirrors 16, 160 are actively cooled. In addition, the laser arms 15, 150 can carry a device for purging with a purge gas (in ). Fig. 7 not shown), so that the laser arms 15, 150 are closed off from the atmosphere in the cooling oven 6.

[0088] Fig. Figure 8 shows a schematic representation of a glass article according to the invention in an exemplary embodiment, in top view, in Fig. Figure 9 shows a schematic cross-section through this glass article. The information contained in the Fig. 8 and Fig.The illustrations shown in Figure 9 are not to scale, particularly with regard to the individual dimensions of the glass article. The glass article has two opposing side surfaces 24, 26 and a circumferential edge surface 24. The side surfaces 24, 26 have lateral dimensions l x , l y in the x and y directions. The lateral dimension of the edge surface 25 in the z direction corresponds to the glass thickness d. Glas . That in the Fig. 8 and Fig. The embodiment shown in figure 9 has a minimum lateral dimension l x , l y the side surfaces 24, 26 in x and y directions of > 400 mm and a glass thickness d Glas< 0.8 mm. The glass article of this embodiment was produced using the method according to the invention and is a floated glass. In this process, the glass was lifted from a tin bath, with the side surface 26 remaining in contact with the tin bath. The near-surface areas of the side surface 26 therefore exhibit a higher tin concentration compared to the bulk glass.

[0089] The glass of the glass article corresponds to glass 3 from Table 1. The glass article has a fire polish on the side surface 24. Reference symbol list 1 glass strip 2 Float bath 3 Usable area of ​​the glass ribbon 1 4 Tank 5 thickened edge area or border of the glass band 1 6 Cooling oven 7 Float tub 8. Transport or pulling direction 9, 10 Laser 11, 110 Point of impact 12, 120 melting volume 13, 130 gap 14, 140, 141 Glass stopper 15, 150 laser arm 16, 160 mirrors 17 molten glass 24, 26 side faces of 27 25 edge area of ​​27 27 glass items 30 glass ribbons with homogeneous thickness 31 middle range of 30 32 Edge area of ​​30 33, 34, 330, 340 Fire polished edge 50, 51 glass strips 61, 62 side opening in the cooling oven 80 Transport device 90, 91 laser beam QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2015 / 172957 A1

[0009]

Claims

[1] Method for producing a glass ribbon with homogeneous glass thickness (30) in which a glass ribbon (1) is obtained from the melt by a drawing process, wherein - the glass strip (1) has a usable area (3) and edge areas (5) that are thickened compared to the usable area and extend along the edges of the glass strip (1) in the drawing direction (8), wherein - the glass ribbon (1) is cooled, whereby - during cooling, a laser beam (90, 91) is directed onto the glass ribbon (1) by means of at least one laser (9, 10), such that, due to the movement of the glass ribbon (1), it sweeps out a line in the direction of travel of the horizontally moving glass ribbon (1), wherein - the point of impact (11) of the laser beam (90, 91) is chosen such that the line (13) forms a designated dividing line between the usable area (3) and the thickened edge area (5), and that - the point of impact on the glass occurs at a position where the temperature of the glass is in a range between an upper viscosity of 10 10 dPas and a lower viscosity of 10 15 dPas is located, and where - the laser beam (90, 91) photothermally processes the glass ribbon (1) in the irradiated area (12, 120), such that a gap (13, 130) forms between the usable area (3) and the thickened edge area (5) along the line, and a glass ribbon with a homogeneous glass thickness (30) and a new edge (33) parallel to the drawing direction (8) and a separated, thickened edge area (50) are obtained, and wherein the cooling of the glass ribbon with homogeneous thickness (30) is continued after separation, wherein - the usable area of ​​the glass ribbon (1) has a thickness of more than 0.3 mm, or wherein - the usable area of ​​the glass ribbon (1) has a thickness of more than 0.1 mm and the drawing process includes a float process and the glass ribbon (1) is lifted from a float bath, or wherein - the following applies to the glass of the glass ribbon: FB=αliq+α20−30030⋅10−6 / K⋅(4.6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1. with α 1iq = linear coefficient of thermal expansion above the glass transformation temperature of the glass, α 20-300 o = linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η 1iq = Liquid viscosity of the glass, dTdiag(η)(log(η)=13)=slope of the viscosity curve at the upper cooling point, or at the temperature at which the glass has a viscosity η of 10 13 dPas exhibits, T 13 = Temperature at which the glass has a viscosity η of 10 13dPas has, and the glass ribbon (1) in the usable area preferably has a thickness of no more than 1.3 mm. [2] Method according to the preceding claim, characterized by at least one of the characteristics: - the laser beam (90, 91) has a wavelength at which the glass of the glass ribbon (1) is heated by the beam only in the near-surface region, preferably to a depth of at most 0.1 mm, - the laser beam (90, 91) is generated using a CO2 laser - the glass ribbon (1) is transported lying down during cooling and / or during laser irradiation. [3] Method according to one of the preceding claims, wherein the laser beam (90, 91) has a laser spot diameter of less than 4 mm 2 , preferably less than 3 mm 2 and preferably of no more than 1.5 mm 2 exhibits. [4] Method according to one of the preceding claims, wherein a relative movement in the drawing direction (8) of the glass ribbon (1) is carried out between the glass ribbon (1) and the point of impact of the laser (11, 110) and wherein this relative movement has a feed rate of at least 1.5 m / min, preferably at least 2.5 m / min and particularly preferably at least 4 m / min and / or the feed rate has a maximum of 6 m / min, preferably a maximum of 5.5 m / min. [5] Method according to one of the preceding claims, wherein the laser beam (90, 91) has a power of at least 750 W, preferably at least 900 W. [6] Method according to one of the preceding claims, wherein the following applies to the ratio of laser power, laser spot diameter, glass thickness and feed rate: Laser power / (laser spot diameter × glass thickness × feed rate) > 7 * 10⁸ W*s / m³, preferred > 1 * 10⁹ W*s / m³, especially > 4 * 10⁹ W*s / m³. [7] Method according to one of the preceding claims, wherein the glass ribbon (1) is provided by drawing on a float bath (2) by means of floating. [8] Method according to one of the preceding claims, wherein the glass ribbon (1) in the usable area (3) has a thickness of at least 0.32 mm, preferably at least 0.33 mm, particularly preferably at least 0.35 mm and most preferably at least 0.4 mm and / or has a thickness in the range of 0.33 to 1.3 mm, preferably in the range of 0.35 to 1.1 mm, particularly preferably in the range of 0.4 to 1 mm. [9] Method according to one of the preceding claims, wherein the method is carried out in a cooling oven (6). [10] Method according to one of the preceding claims, wherein the newly formed edge (33) is fire-polished. [11] Glass strip with homogeneous thickness (30), producible by a method according to one of the preceding claims, wherein the glass strip with homogeneous thickness (30) has a central region (31) and at least one edge region (32), wherein the edge region (32) forms the edge (33) of the glass strip with homogeneous thickness (30), wherein the glass strip with homogeneous thickness (30) has a thickness d in the central region (31). Mitte of more than 0.3 mm and wherein the edge region (32) has a thickness d Rand exhibits, wherein d Rand a maximum thickness d Rand,max exhibits a thickness that is at most 120% greater than the thickness d Mitte in the central area (31) of the glass ribbon with homogeneous thickness (30). [12] Glass strip with homogeneous thickness (30) according to the preceding claim, wherein the edge region (32) is rounded so that the edge (33) has a rounded profile, and / or the edge (33) is fire-polished. [13] Glass ribbon with homogeneous thickness (30) according to one of the two preceding claims, wherein the glass ribbon with homogeneous thickness (30) has a tin concentration in the near-surface areas of a side surface which is greater than the tin concentration of the glass in the bulk material. [14] Glass strip with homogeneous thickness (30) according to any one of the preceding claims 11 to 13, wherein the glass of the glass strip with homogeneous thickness (30) is characterized as follows: FB=αliq+α20−30030⋅10−6 / K⋅(4,6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1, preferably>1,1, especially preferred>1,2. with α 1iq = linear coefficient of thermal expansion above the glass transformation temperature of the glass, α 20-300 o = linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η 1iq = Liquid viscosity of the glass, dTdlog(η)(log(η)=13)=slope of the viscosity curve at the upper cooling point, or at the temperature at which the glass has a viscosity η of 10 13 dPas exhibits, T 13 = Temperature at which the glass has a viscosity η of 10 13 exhibits dPas. [15] Glass articles (27), in particular in the form of a flat glass with two opposite side faces (24, 26) and a glass thickness d Glas , where the glass thickness d Glas at most 1.3 mm, preferably at most 0.8 mm, and wherein the following applies to the glass of the glass article: FB=αliq+α20−30030⋅10−6 / K⋅(4,6log(ηliq / dPas))2⋅dTdlog(η)(log(η / dPas)=13)−28°C⋅T13650°C>1, preferably>1,1, especially preferred>1,2. with α 1iq = linear coefficient of thermal expansion above the glass transformation temperature of the glass, α 20-300 = linear coefficient of thermal expansion of the glass at temperatures between 20°C and 300°C, η 1iq = Liquid viscosity of the glass, dTdlog(η)(log(η)=13)=slope of the viscosity curve at the upper cooling point, or at the temperature at which the glass has a viscosity η of 10 13 dPas exhibits, T 13 = Temperature at which the glass has a viscosity η of 10 13 exhibits dPas. [16] Glass article (27) according to the preceding claim, wherein the glass article (27) is drawn glass and preferably both side surfaces are fire-polished. [17] Glass article (27) according to claim 15, wherein the glass article (27) is float glass. [18] Glass articles (27) according to any one of the preceding claims 15 to 17, wherein the lateral dimensions of the side surfaces (24, 26) l x , l y > 400 mm and / or for the ratio between the smallest lateral dimension of the side surfaces l min(x,y) and the glass thickness is also affected: lmin(x,y) / dGlas>500, preferably>1000, particularly preferred>4000. [19] Glass ribbon of homogeneous thickness (30) according to any one of claims 11 to 14 above or glass article (27) according to any one of claims 15 to 18 above, wherein the glass comprises the following oxide-based components in wt.%: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can preferably be 67 in each case, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, wherein preferably the sum of the content of Al2O3 and SiO2, based on the value in wt.%, is between at least 75 and at most 92, preferably at most 90. [20] Glass ribbon with homogeneous thickness (30) according to any one of the preceding claims 11 to 14 or glass article (27) according to any one of the preceding claims 15 to 18, wherein the glass comprises the following oxide-based components in wt.%: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit may preferably be 67 in each case, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7 MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O5 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO2 0 to 3, preferably 0 to 2, which may still contain impurities and / or fining agents and / or coloring components in quantities of up to 2% by weight. [21] Glass ribbon with homogeneous thickness (30) according to any one of the preceding claims 11 to 14 or glass article (27) according to any one of the preceding claims 15 to 18, wherein the glass comprises the following oxide-based components in wt.%: SiO2 62-72, preferably 65-70 Al2O3 7-14, preferably 8-12 B2O3 0.1 - 8.5, preferably < 8.5 or ≤ 8, preferably 4 - 7, particularly preferably ≥ 5, most particularly preferably > 5.5 Li2O 5-12, preferably 7-10 Na2O 0 - 2, preferably 0 - 1, particularly preferably ≥ 0.1 and / or < 1, most preferably ≥ 0.3 and / or < 0.8 K2O 0-2, preferably 0-1 with 0.8 < Li2O / (Li2O + K2O + Na2O) ≤ 1 [22] Glass ribbon of homogeneous thickness (30) according to any one of claims 11 to 14 above or glass article (27) according to any one of claims 15 to 18 above, wherein the glass comprises the following oxide-based components in wt.%: SiO2 55-75, preferably 62-72 Al2O3 18-27, preferably 18-23 Li2O 2.8-5, preferably 3-5 Na2O 0-4, preferably 0-2 K2O 0-4, preferably 0-2 MgO 0-8, preferably 0-4 CaO 0-4, preferably 0-2 SrO 0-4, preferably 0-2 BaO 0-4, preferably 0-2 ZnO 0-6, preferably 0-2 TiO2 0-4, preferably 0-3 ZrO2 0-5, preferably 1, 2-4 B2O3 0-2, preferably 0-0.1 SnO2 0-2, preferably 0.05-1.6 where preferably the following applies to the sum of the components TiO2 and ZrO2: 0<∑(TiO2+ZrO2)<9.5% preferred 1.2<∑(TiO2+ZrO2)<9.5%, or preferably for the components SnO2, ZrO2 and TiO2: 0≤SnO2 / (ZrO2+TiO2)<0.8, preferably 0.01 <sno2 (zro2+tio2)<0,7.[23] Device for producing a glass ribbon with homogeneous thickness (30) from a glass ribbon (1), wherein the glass ribbon (1) has a usable area (3) and edge areas (5) thickened compared to the usable area (3), by separating the edge areas (5), wherein the device comprises a drawing device for producing a glass ribbon (1) from a glass melt (17), a cooling oven (6) and transport devices (80) for transporting the glass ribbon (1) from the drawing device into the cooling oven (6), wherein a laser (9, 10) is arranged in the cooling oven (6) such that the laser beam (90, 91) strikes the glass ribbon (1) perpendicular to the transport direction (8), wherein the point of impact (11, 110) of the laser is set such that it lies on the glass ribbon (1) in the boundary region between the usable area (3) and the edge area (5). [24] Device according to the preceding claim, wherein the laser (9, 10) has at least one laser arm (17) which is arranged laterally in the cooling oven (6), wherein the laser beam (90, 91) is deflected perpendicularly after exiting the laser (9, 10) by a deflecting element (16). [25] Device according to claim 24, wherein the device has at least one of the following features: - the device has an imaging mirror as a deflecting element (16), - the device has a cooling device for actively cooling the deflecting element (16), - the device includes at least one device for purging the laser arm (17) with purge gas - the laser arm (17) is movable and designed so that it can be removed from the cooling oven (6). - the device has a float tray (7) as a drawing device, - Rollers are used as a transport device (8).

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