Method and apparatus for stretching thin glass ribbons

Abstract

The present invention relates to a method for drawing a thin glass ribbon from a glass melt, the method comprising an apparatus for use in the method comprising a nozzle with a protrusion, which protrusion prevents necking of the glass ribbon. The apparatus comprises a drawing vessel for receiving a glass melt, the drawing vessel comprising a nozzle with an outlet opening through which the glass melt can flow downwards. The outlet opening is formed as a nozzle slit with two ends, the length of the nozzle slit being greater than the width of the nozzle slit. In a first lateral region and in a second lateral region, the nozzle slit is curved downwards, in particular consistently or continuously, towards these ends of the nozzle slit, so that these ends are lower than a central region of the nozzle slit arranged between these ends, and the width of the nozzle slit changes from the central part towards these ends.

Description

Technical Field

[0001] The present invention relates to an apparatus for stretching a glass ribbon from a glass melt, the apparatus comprising a stretching bath for containing the glass melt, the stretching bath comprising a nozzle having a discharge opening through which the glass melt can flow downward, the discharge opening being slit-shaped and forming a nozzle slit, and the nozzle slit being formed so as to be curved in at least one direction in at least one side region.

[0002] The large-scale production of very thin glass, for example glass having a thickness of less than 250 μm, is still particularly difficult, especially when high requirements are imposed with respect to surface quality, maximum thickness variation, and uniform width. As one of the manufacturing methods for very thin glass, for example, the production of a thin glass ribbon using the so-called down-draw method can be mentioned.

[0003] In the standard down-draw method, thin flat glass is produced using a slit nozzle. In this case, the glass melted in the melting bath is led to a conduit system and supplied to the stretching bath after passing through various process steps. At the lower end of the stretching bath, a nozzle having a slit is formed, and through this nozzle, the glass flows out of the stretching bath and is stretched downward by stretching rollers. Here, in order to adjust the final thickness of the produced thin glass ribbon, the stretching speed is used. The higher the speed at which the glass is stretched downward, the thinner the glass becomes. The glass thickness can also be affected by the width of the slit.

[0004] Furthermore, a temperature gradient can be set in the stretching chamber, ensuring that the temperature at the edges of the slits is lower than the temperature in the center of the slits. As a result, the downward-stretched glass ribbon always has higher viscosity on the outside than in the center, causing the glass to stretch between the edges of the ribbon. In this way, the width of the flat glass can be controlled and determined during manufacturing. If the viscosity is uniformly distributed across the width of the glass ribbon, necking will occur, leading to a disorderly narrowing of the glass ribbon's width.

[0005] However, because the viscosity is higher in the edge region of the glass ribbon, increasing the stretching speed to set a thinner glass thickness in the edge region than in the center of the ribbon increases the deformation force even more. As a result, the throughput is slightly improved in the edge region of the ribbon, and more glass is stretched from the slit compared to when it flows out without tensile force. This non-uniform increase in throughput changes the thickness distribution of the glass ribbon, where the edge region becomes thicker than the center, resulting in a concave thickness distribution. This non-flatness can then be compensated for by an edge roller placed below the nozzle. However, when manufacturing extremely thin glass ribbons of less than approximately 250 μm, such an edge roller can cause the glass ribbon to break.

[0006] To address this problem, U.S. Patent No. 1,626,382 presented a funnel-shaped nozzle slit configured such that the parallel slit shape narrows at the slit ends compared to the central region of the slit. On the one hand, because the funnel shape is less pronounced at the slit ends, more hot glass material is prepared at the slit ends, the glass does not cool as rapidly at the slit ends, and the temperature is maintained substantially uniformly throughout the entire length of the slit. On the other hand, narrowing the slit at the slit ends is intended to achieve an increase in tensile resistance. However, such a slit shape is not very practical. Firstly, the mechanically predetermined ratio of two different slit widths over the same length of slit is very specifically selected and can only be applied to very specific combinations of glass composition, given glass thickness, and corresponding tensile force. Secondly, the tensile properties and thickness ratio of the glass can change even with a slight change in tensile force. Therefore, the nozzle needs to be replaced every time the desired glass thickness changes, or if the tensile force fluctuates due to the process, and only very small tolerances are acceptable to obtain optimal results. Furthermore, since the gradient cannot be compensated for with a combination of two different slit widths, the uneven thickness distribution across the width of the glass ribbon caused by the temperature gradient cannot be reliably compensated for.

[0007] Chinese Patent Application Publication No. 110590132 describes a similar slit shape in which the nozzle slit is formed to be parallel in the central region and narrows non-linearly on the sides, thereby intended to achieve a more favorable thickness distribution. However, the problem remains that the nozzle must be replaced every time the glass thickness changes, and viscosity at the edges increases due to temperature gradients.

[0008] U.S. Patent No. 3,473,911 describes a funnel-shaped nozzle whose opening width can be changed. However, this is labor-intensive because the glass forming process must be interrupted to manually change the width. Furthermore, this method cannot compensate for existing viscosity gradients.

[0009] While a nozzle is also presented in U.S. Patent No. 2,422,466, this nozzle is funnel-shaped only in the central region. Similar to U.S. Patent No. 1,626,382, this nozzle slit is characterized by being narrower laterally than in the central region. Furthermore, because additional volume is similarly provided laterally, the glass does not cool as quickly at the ends of the slit. However, the nozzle is pocket-shaped rather than funnel-shaped laterally. As a result, while the glass does not cool as quickly, it cannot flow out of the slit and must be actively pulled. Therefore, if the tensile force is uniform, a certain amount of glass remains in the pocket, resulting in a problem of an uneven temperature distribution within the pocket. Also, if there are bends in the slit, the tensile force of the stretched glass ribbon will be partially unevenly distributed across the width of the nozzle slit. Thus, achieving a uniform width in the glass ribbon is difficult or even impossible.

[0010] Therefore, the object of the present invention is to provide a down-draw method and apparatus for stretching very thin glass ribbons that can produce different glass thicknesses without significantly changing the stretching chamber temperature, and thus can compensate for process-related tolerances, and guarantees not only a uniform thickness but also a uniform and controllable width of the glass ribbon. It is desirable that this enables more stable process operation. Furthermore, it is desirable to suppress necking of the glass ribbon, especially at high stretching speeds, as well as to suppress it as well as possible.

[0011] This problem is solved by the subject matter of the independent claim. Advantageous developmental forms are shown in their respective dependent claims.

[0012] Accordingly, the present invention relates to an apparatus for stretching a glass ribbon from a glass molten liquid. The apparatus comprises a stretching tank for containing the glass molten liquid, the stretching tank comprising a nozzle having a discharge opening through which the glass molten liquid can flow downward. The discharge opening is formed as a nozzle slit having two ends, the length of the nozzle slit being greater than the width of the nozzle slit. The nozzle slit is curved particularly consistently or continuously and therefore downward in the stretching direction toward these ends in a first lateral region and a second lateral region, so that these ends are lower than the central region of the nozzle slit which extends particularly linearly and is located between these ends, and the width of the nozzle slit changes from the central part toward these ends.

[0013] The nozzle slit extends particularly over length, width, and height, with the height extending parallel to the stretching direction of the glass ribbon. The width and length extend perpendicular to each other and also perpendicular to the height. Thus, the length of the nozzle slit can also be understood as the length in the lateral direction relative to the width and height. In this case, the length of the nozzle slit is greater than its width and height. When the height of the nozzle or nozzle slit is referred to below, it means the extension along the stretching direction, advantageously opposite to gravity. Thus, the height of the nozzle or nozzle slit extends from the top surface of the upper wall of the nozzle to the lower end. Thus, the width and length of the nozzle or nozzle slit extend horizontally, that is, particularly perpendicular to the stretching direction of the glass, in which case the length of the nozzle slit is advantageously given by the distance from the first end to the second end.

[0014] The variation in nozzle slit width can be understood as the nozzle slit being formed such that, in the first and / or second lateral regions, it is consistently nonlinear or, advantageously, curved along its length with respect to its width. The downward curve can be understood as the nozzle slit in the first and / or second lateral regions being formed such that, along its height, it is advantageously consistently nonlinear or, particularly, curved, so that the first and / or second ends are lower than those in the central region.

[0015] It should be noted that the discharge opening has an outlet surface through which the molten glass flows out. In particular, the nozzle slit opens to a nozzle opening that is preferably slit-shaped, corresponding to the outlet surface. In this case, the outlet surface is located at the lower end of the nozzle slit and is surrounded by the lower surface of the nozzle. Similar to the nozzle slit, its outlet surface extends in length, width, and height parallel to the direction of extension of the glass ribbon, in which case the outlet surface extends preferably in the central region, particularly parallel to the length and width of the nozzle slit. In the first and / or second lateral regions, the outlet surface extends, ideally, consistently nonlinear or particularly curved along the length of the outlet surface with respect to its height, and preferably also consistently nonlinear or particularly curved with respect to its height. Thus, when referring to the shape of the nozzle slit, it also means the configuration of the outlet surface defining the lower nozzle slit of the nozzle.

[0016] By changing the width of the nozzle slit, the local throughput of the glass melt can be affected. This reduces necking of the glass ribbon and allows the throughput to be adjusted along the length of the nozzle slit so that the effective width of the ribbon between the thickened edges is as large as possible. Advantageously, necking of the glass ribbon width is strongly suppressed by at least a partially curved nozzle slit or at least a partially curved outlet surface. In particular, a nozzle slit shape that curves downward in height improves the force distribution during stretching of the glass ribbon, so that the glass ribbon is also stretched in the width direction by forces acting horizontally.

[0017] Advantageously, the discharge opening, particularly the nozzle slit, tapers from the center to the end, so the width of the nozzle slit in the central region is larger than that of the ends. A tapered nozzle slit advantageously reduces the glass throughput through the slit, while the viscosity of the glass remains constant along the length of the slit. However, a frequently present temperature gradient results in an increase in the viscosity of the glass at the nozzle slit ends due to the lower temperature, thereby increasing the tensile force acting on the glass, which leads to an increase in throughput. Simultaneously, this also means that, in the presence of a temperature gradient, the throughput at the tapered nozzle slit ends can be matched to the throughput in the central region, thereby achieving the most uniform thickness possible in the glass ribbon.

[0018] It is also advantageous if the discharge opening, particularly the nozzle slit, is formed to continuously taper along its length from the center, preferably towards the side ends, or to increase monotonically along its length from the side ends toward the center. In this way, the throughput can be adjusted so that the glass throughput is uniform, and especially homogeneous, along the length of the nozzle slit when there is a temperature gradient and thus a viscosity gradient.

[0019] Therefore, the discharge opening, particularly the nozzle slit, may have an oval, elliptical, concave, or lenticular shape in the top view or in the extension direction, i.e., in terms of length and width. In this case, this shape can be understood as being wider in the center than at the ends, in particular, so that the nozzle slit forms a convex shape. In this shape, the nozzle slit tapers gently, linearly, or exponentially, and therefore can be adapted to a temperature gradient to a certain extent.

[0020] In one advantageous embodiment, the nozzle slit exhibits a continuous, or preferably gentle, curvature with respect to height in the first and second lateral regions, the height extending parallel to the stretching direction. The downward curvature of the nozzle slit in height improves the force distribution during stretching of the glass ribbon, so that the glass ribbon is also stretched in the width direction by the horizontally acting force. As the height of the nozzle slit is continuously varied, the exit surface toward the nozzle slit end also curves continuously, so that the horizontally acting portion of the force continuously increases toward the slit end. In other words, the stronger the necking of the glass ribbon, the stronger the force that prevents the necking, resulting in a uniform width of the glass ribbon. Ideally, the transition from the central region extending linearly and / or perpendicular to the height to the downwardly curved lateral region is also gradual or linear, so that no bends occur and a smooth transition or gradual change in the acting force is ensured. In this way, variations in the thickness and width of the glass ribbon can be avoided. Therefore, the central region may also be slightly curved downward, particularly in the direction of the lateral regions or towards the edges. Advantageously, in this case, the highest point lies in the central part of the central region.

[0021] In a further embodiment, the nozzle slit has the following features: - The nozzle slit is always curved to the end, and is especially always curved from the central region to the end, and advantageously extends linearly in the central region or curves only slightly. - The nozzle slit curves towards the end, and this curve has an inflection point. It has at least one of the following.

[0022] It is obvious that the nozzle slit may be formed to taper with respect to its width and height, and preferably in a funnel or trough shape. In this case, the taper in width of the nozzle slit may extend linearly or nonlinearly, in particular curved, thereby assisting the drawing or outflow of glass through the nozzle slit and, correspondingly, reducing the tensile force that must be applied for this purpose.

[0023] The nozzle may have one projection in each of the first and second lateral regions for accommodating an additional volume of molten glass, the projection extending along the extension direction, i.e., projecting downward, and the internal space of the projection may be provided to determine the size of the additional volume of molten glass. Alternatively, the projection may be considered as a depth at the nozzle slit end, particularly at the first and second nozzle slit ends. This depth or projection can also provide a downwardly curved path in the nozzle slit and, advantageously, an internal space of the projection. In this case, the internal space is preferably defined by the wall surrounding the nozzle slit, i.e., the nozzle wall, particularly the wall in the lateral region of the projection. The internal space is advantageously formed to provide an additional volume for accommodating molten glass, and the wall of the internal space, or the wall of the nozzle slit, provides a higher surface area, and therefore can accelerate the cooling of the molten glass. In this case, the molten glass can release heat with the increased surface area. As a result, the temperature of the glass as it flows out of the nozzle slits is lower than it would be in the absence of these protrusions / deep sections. The lower temperature leads to higher viscosity, which suppresses necking of the glass ribbon. Therefore, by selecting the appropriate additional volume or internal space, the temperature gradient and, consequently, the viscosity of the glass melt can be controlled as desired.

[0024] Furthermore, it is also provided that the ratio of the height of the internal space of the protrusion to the width of the internal space of the protrusion is greater than 0.2, preferably greater than 0.5, preferably greater than 0.8 and / or less than 2, preferably less than 1.6, preferably less than 1.2. This relationship is important because the smaller the width, the greater the pressure loss that the incoming glass must clear. On the other hand, if the internal space is too wide, the cooling of this glass volume will be poor because the path of heat conduction through the glass to the nozzle slit or to the cooling wall of the internal space becomes longer. Therefore, such a ratio of height to width of the internal space is the optimal ratio between pressure loss and cooling of the glass melt.

[0025] In an advantageous embodiment, the radius of curvature of the nozzle slit, particularly the minimum radius, is determined by the height of the protrusion and the length of the protrusion such that the nozzle slit, particularly the exit surface, curves downward.

[0026] It is also conceivable that the radius of curvature of the nozzle slit is greater than 100 mm, preferably greater than 130 mm, preferably greater than 160 mm and / or less than 260 mm, preferably less than 230 mm, preferably less than 200 mm. Thereby, an optimal force transfer of the force having a horizontal component increasing towards the end can be achieved. Advantageously, the average radius is between 100 mm and 260 mm. According to one embodiment, in order to ensure a continuous increase of the horizontal force component with respect to the vertical force component, the radius decreases, particularly linearly or exponentially, with the increase in the length of the nozzle slit or towards its end. In this way, excessive necking of the glass ribbon can be prevented, particularly at a particularly high drawing speed such as that used for a glass ribbon having a thickness of less than 100 μm, and the glass ribbon can be drawn particularly greatly, especially at the ends.

[0027] It is also advantageous if the ratio of the length of the protrusion to the height of the protrusion is less than 2.8, preferably less than 2.6, preferably less than 2.4. This is the optimal ratio for achieving an appropriate force distribution. When the horizontal component is of the same magnitude as or even greater than the vertical component, i.e., when the ratio of the length to the height of the protrusion is less than 2.4, and the vertical direction with respect to the nozzle slit is ≧45° with respect to the drawing direction, this has an adverse effect on the width of the glass ribbon because if the proportion of the horizontal component is too high, it may cause necking.

[0028] It is also conceivable that the curved portion of the protrusion in the first lateral region faces the curved portion of the protrusion in the second lateral region. In particular, the nozzle slit having a protrusion or a deep part is formed to be mirror-symmetric at least in one direction, but preferably in terms of length and / or width. By doing so, a uniform thickness and width can be created over the entire width of the glass ribbon.

[0029] It may be provided that the height of the internal space of the protrusion is greater than 10 mm, preferably greater than 15 mm, preferably greater than 20 mm and / or less than 80 mm, preferably less than 60 mm, preferably less than 40 mm.

[0030] In an advantageous embodiment, the width of the protrusion is given by the product of the width of the nozzle slit, in particular the width of the cross-section of the discharge opening, and a value greater than 1 mm, preferably greater than 1.5 mm, preferably greater than 2 mm and / or less than 15 mm, preferably less than 10 mm, preferably less than 5 mm. The height and width of the protrusion or the internal space of the protrusion define an additional volume available for accommodating the glass melt, and thus determine the possibility of adjusting the temperature and viscosity of the glass. Therefore, with the values shown above, an optimal temperature or viscosity gradient of the glass melt can be achieved over the width of the nozzle slit, thereby ensuring a uniform width and thickness of the glass ribbon with a uniform tensile force.

[0031] It may also be provided that the protrusion has a lower wall that closes the internal space of the protrusion in the extending direction, and a discharge opening or an exit surface is arranged on this lower wall. Advantageously, the nozzle includes, in addition to the lower wall, an upper wall facing the lower wall and side walls particularly in the first and second lateral regions, and the internal space of the protrusion is defined by these side walls. Ideally, the lower wall of the protrusion is formed to be curved in the extending direction, particularly consistently or continuously, so as to provide an internal space between the lower wall and the upper wall. Due to the curvature of the lower wall, the internal space tapers towards the central region of the nozzle.

[0032] This problem is also solved by a method for stretching a thin glass ribbon from a glass molten state, wherein the glass is melted, and the glass flows out of a stretching tank through which the glass molten state passes, which has an discharge opening, and the glass is pulled out so that it moves downward in the stretching direction, thereby obtaining a thin glass ribbon. After the thin glass ribbon flows out from the discharge opening, the glass transition temperature T g The thin glass ribbon can be cooled by at least one cooling unit until it falls below the glass transition temperature T. The thin glass ribbon is drawn in the stretching direction by contact with a stretching roller that transmits tensile force to the thin glass ribbon. The stretching roller is cooled when the temperature is below the glass transition temperature T. g Contact with the glass occurs at a position below a certain temperature. Passive cooling of the glass can also be considered here. The apparatus described above is used in this method, and this apparatus is equipped with a nozzle having a projection that prevents necking of the glass ribbon. This nozzle with a projection is characterized by two mechanisms of action. On the one hand, the projection is configured so that the molten glass flows out towards the end at a lower temperature, thereby creating a viscosity gradient, which increases the viscosity of the molten glass at the nozzle end and consequently increases the tensile force of the glass ribbon. As a result, the glass ribbon is stretched more strongly in its width direction. Therefore, a temperature gradient is created across the width of the nozzle, and the temperature of the molten glass decreases towards the end.

[0033] Furthermore, the glass flowing out from the center of the nozzle slit travels a distance determined by the height of the protrusion, reaching the same height as the end or endpoint of the nozzle slit. Therefore, the glass coming from the center has already cooled slightly by the time it flows out from the end of the nozzle slit at the same height. As a result, the thin glass in the center has achieved high viscosity at this point, which also prevents necking of the glass ribbon.

[0034] On the other hand, the nozzle is formed such that the tensile force on the glass ribbon generated below the discharge opening is divided into a vertical force component and a horizontal force component at the protruding portion, resulting in a deformation force with opposing effects on the glass ribbon, and the ratio of the horizontal deformation force component to the ratio of the vertical deformation force component increases toward the first and second ends. Here, the horizontal deformation force component prevents necking of the glass ribbon at the edge. This horizontal deformation force component stretches the glass ribbon horizontally, thereby reducing necking. The ratio of the horizontal deformation force component to the vertical deformation force component is controlled as intended by the curvature of the nozzle slit, for example with respect to the height of the nozzle slit, preferably with respect to the height of the protruding portion, by a specific shape or configuration of the nozzle slit, particularly a specific shape or configuration in the lateral region. Here, the radius of this curvature ideally decreases continuously linearly or exponentially toward the ends, however, a gradual transition of the nozzle, particularly towards the horizontal and / or linear central region, is also explicitly guaranteed to prevent irregularities in the thickness and width of the glass ribbon.

[0035] By using the described method, and especially by using the apparatus, particularly thin glass ribbons can be manufactured. By using a specially shaped nozzle with nozzle slits and protrusions that allow the tensile force acting across the width of the glass ribbon to be adjusted precisely and, in particular, individually for each region, edge rollers that could cause damage to the glass ribbon can be eliminated.

[0036] This apparatus and method are particularly suitable for the manufacture of thin and ultrathin glass. According to one embodiment, thin glass ribbons having a maximum thickness of 200 μm, preferably up to 100 μm, can be stretched. Even thinner glass ribbons can be stretched, for example, to a maximum thickness of 70 μm, preferably up to 50 μm, and particularly preferably up to 20 μm. Thicknesses of at least 5 μm, preferably at least 10 μm, are also conceivable. Such glass ribbon thicknesses are particularly advantageous for multilayer flexible or bendable covers, such as those found in flexible displays. A special configuration of the stretching nozzle makes it possible to manufacture glass ribbons of significantly different thicknesses, in particular, without changing the nozzle gap. Here, glass ribbons with thicknesses differing by at least 1.5 times, preferably at least 2 times, can be continuously drawn from the same nozzle. In this way, glass ribbons of thickness or different thicknesses can be manufactured without changing the nozzle and thus without interrupting the manufacturing process.

[0037] The present invention will now be described in more detail with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding components. [Brief explanation of the drawing]

[0038] [Figure 1] This is a schematic diagram of an apparatus for drawing glass ribbons from molten glass. [Figure 2] This is a top view of the nozzle slit and a schematic diagram of the thickness distribution along the width of the thin glass ribbon. [Figure 3] This is a top view of the nozzle slit and a schematic diagram of the thickness distribution along the width of the thin glass ribbon. [Figure 4] This is a schematic cross-sectional view of the lateral region of a nozzle having a protruding portion. [Figure 5] This is a schematic top view of the nozzle. [Figure 6] This is a schematic perspective view of the lateral region of a nozzle having a protruding portion and a short nozzle slit. [Figure 7]This is a schematic perspective view of the lateral region of a nozzle having a protruding portion and a short nozzle slit. [Figure 8] This is a schematic cross-sectional view of the lateral region of a nozzle having a protruding portion. [Figure 9] This is a schematic cross-sectional view of the nozzle. [Figure 10] This is a schematic diagram of an apparatus for drawing glass ribbons from molten glass. [Figure 11] This is a schematic diagram of a cooling reactor. [Figure 12] This is a schematic diagram of a molding region equipped with a heating unit or a cooling unit. [Figure 13] This is a schematic diagram of the crucible, discharge pipe, and extension tank.

[0039] Figure 1 is a schematic diagram of an apparatus 1 for stretching a glass ribbon 10 from a glass molten liquid 9. The apparatus comprises a stretching tank 2 and a cooling unit 3. A nozzle 4 is located below the stretching tank 2, and the glass ribbon 10 is cooled in the cooling unit 3. The glass molten liquid 9 is first sent to the stretching tank 2, where temperature control is performed, or the temperature of the glass molten liquid 9 is adjusted along the length and width of the stretching tank. Next, the glass molten liquid 9 enters the nozzle 4 and flows out of the stretching tank 2 through the opening of the nozzle 4. While passing through the nozzle, and especially as it flows out of the nozzle, the glass molten liquid 9 is formed into its final shape, the glass ribbon 10, in the molding region 14. The glass ribbon 10 is defined at its edges by a glass ribbon edge or edge 11.

[0040] After flowing out of nozzle 4, the glass ribbon 10 reaches a glass transition temperature T g The glass is cooled in or below the molding region 14 until it falls below a certain temperature. Advantageously, a stretch roller 15 is positioned below the cooling unit 3, i.e., advantageously in the low-temperature region, through which the tensile force is transmitted to the glass ribbon 10. Advantageously, the temperature of the glass at the point of contact with the stretch roller is at most 200°C, particularly preferably at most 100°C. The glass is cooled in the low-temperature region, i.e., T gIt has been found that contacting the stretch roller only at temperatures below a certain temperature, and particularly preferably up to 200°C, is preferable to reduce the probability of breakage. Furthermore, low temperatures offer greater flexibility in the selection of the stretch roller material. For example, the stretch roller can have an elastomer surface that exhibits only slight slipperiness.

[0041] Advantageously, at least two pairs of stretch rollers 15 are arranged lateral to the stretching direction Z, and each pair of stretch rollers grips the glass ribbon 10 from both sides in the region of the edge 11 between the two stretch rollers 15. Depending on the desired thickness of the glass ribbon 10, the tensile force transmitted by the stretch rollers 15 is adapted or adjusted. In this regard, according to one embodiment, when the thickness is small, the tensile force can be adjusted to be higher than when the desired thickness is large, i.e., when the glass ribbon 10 is thick. Thus, the glass ribbon 10 is drawn out of the nozzle 4 as molten glass 9, advantageously adjusted to the desired thickness by the tensile force transmitted by the stretch rollers 15.

[0042] Figures 2 and 3 show the shape of the nozzle slit in a top view, as well as a typical thickness distribution along the width of a thin glass ribbon. The nozzle 4 extends along the stretching direction Z along a width B, length L, and height H, and has an advantageously slit-shaped discharge opening, which is formed in particular as a nozzle slit 5. The nozzle slit is surrounded by the wall 6 of the nozzle 4. Here, the nozzle slit 5 has a first end 7a and a second end 7b, the first end 7a is located in the first lateral region 8a of the nozzle slit 5, and the second end 7b is located in the second lateral region 8b, and the two lateral regions 8a,8b extend substantially along a length L. Here, a central region 8c is located between the first lateral region 8a and the second lateral region 8b.

[0043] Figures 2 and 3 show, respectively, the thickness distribution along the width of the thin glass ribbon 10 in the parallel nozzle slits 5. Figure 2 shows a typical thickness distribution for thin glass ribbons 10 with a thickness of less than 300 μm or greater, while Figure 3 shows a typical thickness distribution for thin glass ribbons 10 with a thickness greater than 300 μm. It can be seen that the glass ribbon 10 with a thickness of less than 300 μm (Figure 2) is significantly thicker at the edges 11 than in the center between the edges. In contrast, the opposite effect is observed in the glass ribbon 10 with a thickness greater than 300 μm (Figure 3). In this case, the maximum value of the thickness distribution is in the center. This is mainly due to different cooling behaviors related to the stretching speed, or the formation of a temperature gradient across the width of the glass ribbon 10 of each thickness. The nozzle slits 5 are formed to be curved in order to equalize the stretching speed or throughput of the glass passing through the nozzle slits 5, which have an existing temperature gradient in the glass melt or a temperature gradient intentionally introduced to the nozzle 4. However, advantageously, the temperature gradient can be intentionally adjusted so that it exists from the center outward, i.e., increasing or decreasing particularly from the center of the nozzle slit towards the ends 7a, 7b. In particular, the first lateral region 8a and / or the second lateral region 8b are formed to be consistently nonlinear or advantageously curved with respect to its height H along the length L of the nozzle slit 5. Thus, ideally, particularly in the case of glass ribbons 10 having a thickness of less than 300 μm, the nozzle slit 5 has an oval, elliptical, or lenticular, or more generally convex, cross section perpendicular to the height, in order to reduce throughput at the edges 11, which is understood in particular to mean that the width Bs of the nozzle slit 5 decreases from the center towards the ends 7a, 7b.In contrast, for glass ribbons 10 having a thickness of more than 300 μm, a bone-like cross-section is preferred in order to reduce the throughput at the center of the glass ribbon 10 compared to the edges 11. Here, a bone-like cross-section is understood to be a cross-section that is advantageously formed in a concave shape, and therefore, in particular, the width Bs of the nozzle slit 5 increases from the center towards the ends 7a, 7b. Thus, in both cases, a uniform glass ribbon thickness can be achieved over the width of the glass ribbon ends 10 or over the length L of the nozzle slit 5 by adjusting the throughput based on the shape of the nozzle slit. Preferably, the curvature is consistent or even continuous, and in particular linear or exponential, in order to enable uniform forming along the length L.

[0044] Figures 4 and 5 show schematic cross-sections of the lateral region 8b, respectively. Here, Figure 4 shows the lateral region 8b of the nozzle 4 having a projection 20, which is understood to be a depth of the nozzle slit 5, or a depth that provides additional volume for accommodating the glass molten 9. The projection is preferably defined by a bottom wall 21, an end wall 22, and preferably further at least one, preferably two or more, side walls 25. The side walls may be linear or curved in shape with respect to the height H of the nozzle 4, the width Bv of the projection 20, and optionally the length of the projection 20. The bottom wall 21 advantageously extends between the side walls 25 in width Bv and is defined longitudinally, in particular by the end wall 22.

[0045] However, in order to obtain an effect against the forces acting on the glass ribbon 10 during stretching, the lower wall 21 is formed to be curved, and in particular, to be continuously, and preferably linearly or exponentially curved along the length L and with respect to the height H. In this way, a consistently curved shape can be achieved, in which the lower wall 21 of the projection 20 ideally forms a smooth transition to the lower boundary 30 of the central region 8c of the nozzle slit 5. In the best case, the lower wall 21 and the lower boundary 30 of the central region 8c form a uniform surface, preferably such that the curvature of the lower wall 21 begins in the lateral region 8b and extends to the lower end 23 of the projection. At the lower end 23, the lower wall 21 is in contact with the end wall 22 and may be connected to it by one or two pieces.

[0046] Advantageously, the lower wall 21 and / or lower boundary 30 close the nozzle 4 or the stretching tank 2 downward, with the lower boundary 30 in particular extending horizontally. In this case, the nozzle slit is positioned in the lower boundary 30 and the lower wall 21 so that the molten glass 9 can flow out from the lower end 23 or at least be drawn out, thereby allowing the glass ribbon 10 to be stretched in the width direction at the edge 11 of the lower end 23. Thus, the nozzle slit 5 can also extend beyond the lower end in its length L direction, as shown in Figure 7.

[0047] The radius R is determined by the height H of the nozzle 4 from the lower end 23 to the upper wall 24 and the length Lv of the protrusion 20 in the lateral regions 8a and 8b. The protrusion 20 is set to a height of 20 mm to 40 mm in order to adjust the radius R of the curvature of the nozzle slit 5 or the lower wall 21 to a value of 160 mm to 200 mm, which ideally decreases toward the lower end 23. Another important correlation is the ratio of the height H of the nozzle 4 to the width Bv of the protrusion 20, which is also shown in a schematic diagram in Figure 5. The smaller the width Bv, the higher the pressure loss that the incoming glass must clear. On the other hand, if the width of the protrusion 20 is too wide, the path of heat conduction through the glass to the cooling walls 21 and 22 of the protrusion becomes longer, resulting in poorer cooling of this glass volume. Therefore, the ratio of the height H of the nozzle 4 to the width Bv in the internal space of the protrusion 20 is ideally 0.8 to 1.2. Since the nozzle slit 5 is substantially oval or elliptical, the nozzle slit 5 may be defined by the variation in its width Bs. For example, to manufacture glass with a thickness of 50 μm, the difference from the center to the outer surface of the nozzle slit width Bs may exceed 3 mm. In this case, the nozzle slit width may vary in both the lateral regions 8a, 8b, i.e., the region of the protruding portion 20, and the central region 8c of the nozzle 4.

[0048] To define or provide the optimal internal space of the protrusion 20 and thereby adjust the viscosity of the glass melt 9, the width Bv of the protrusion 20 is calculated based on the nozzle slit width Bs.

[0049] Bv = 2 × Bs ~ 5 × Bs

[0050] Along its length, the projection 20 preferably extends beyond the lower end 23 so that the end wall 22 can extend from the upper wall 24 in an oblique and / or curved manner. Advantageously, the upper opening of the upper wall 24 of the nozzle 4 is wider and / or longer than the lower wall 21, and in particular wider and / or longer than the width Bs of the nozzle slit.

[0051] Figures 6 and 7 show two embodiments of the nozzle slit 5 of the nozzle 4 in perspective views. In one embodiment (Figure 6), the nozzle slit 5 is shown to be slightly shorter than in the embodiment of Figure 7, and therefore the nozzle slit 5 still ends in the downwardly curved region of the projection 20. Thus, in this embodiment, the nozzle slit 5 is always curved downward to its end. In the embodiment shown in Figure 7, the nozzle slit is shown to be slightly longer. Thus, the nozzle slit 5 extends beyond the lower wall 21 of the projection 20 to the lower end 23, or even further beyond. Advantageously, the curvature of the nozzle slit 5 has an inflection point W in the transition region from the lower wall 21 to the lower end 23, and therefore the inclination, in particular, decreases again, or may even reverse. The nozzle slit 5 may also have a bend at the inflection point.

[0052] Figure 8 illustrates the force distribution at the protrusions 20. The force generated when the glass ribbon 10 is pulled in the stretching direction is divided into a vertical force component Fv and a horizontal force component Fh at one or more protrusions 20 due to the curvature of the nozzle slit 5. As a result, the lateral component of the tensile force continuously increases towards the nozzle end at the downwardly curved portion 8b of the nozzle slit 5 or the lower wall 21. In other words, the smaller the radius R is in the direction of the lower end 23, the larger the horizontal component Uh of the deformation force when stretching the glass ribbon 10 becomes, and this component is very important for stretching the glass ribbon 10 and keeping it wide. The reaction force of the high-toughness glass plays a role in deformation processing, i.e., thinning of the glass material. Therefore, here as well, the horizontal component Uh pulls the glass being deformed outward, i.e., in the width direction, especially at the edge 11, and thus proceeds to necking, while the vertical component Uv of the deformation force pulls the glass downward in the stretching direction Z. In the glass ribbon 10, the force resulting from the sum of the horizontal and vertical force components is denoted as Fz for tensile force and as Uz for deformation force.

[0053] Depending on the desired width and / or tensile force of the glass ribbon 10, the radius R of curvature of the nozzle slit 5 may be uniform, that is, advantageously, not decreasing towards the lower end. However, since "bent sections" result in a point-like, non-uniform or non-same force distribution, it is particularly important that "bent sections" do not occur at the transition from the lower wall 21 to the lower boundary 30 of the central region 8c. In particular, non-uniform force distributions of deformation forces Uh and Uv can lead to localized changes in the thickness or width of the high-toughness glass, making it impossible to guarantee a stable deformation process or uniform parameters or glass properties across the width of the glass ribbon 10.

[0054] Overall, by using a nozzle 4 in which the nozzle slit 5 is curved in length L, width B, and height H, it is considered possible to manufacture wider glass ribbons from a given stretching tank width compared to a nozzle without curvature. It is also possible to stretch glass thicknesses of less than 100 μm, and even less than 50 μm. Figure 9 illustrates the change in the width of the glass ribbon 10 caused by the curved slit, compared to a nozzle slit 5 that extends parallel in all directions. Here, the dashed edge line 11 shows the width Bp of the glass ribbon 10 manufactured using the parallel nozzle slit 5, and the solid edge line 11 shows the width Bk of the glass ribbon 10 that can be manufactured using the curved nozzle slit 5. Although merely illustrative, some typical data for the nominal width of glass ribbons 10 of various thicknesses produced by a nozzle slit 5 with a length of 700 mm is shown below, as well as the change in width that may occur when using a curved nozzle slit 5.

[0055] [Table 1]

[0056] With respect to the embodiment of apparatus 1 shown in Figure 1, Figure 10 shows a schematic diagram of apparatus 1 having further embodiments relating to a cooling unit 3 and / or a stretching tank 2. According to one of these embodiments, the cooling unit 3 comprises at least one cooling furnace 40, through which the glass ribbon 10 is moved, particularly through the inlet and outlet openings of the cooling furnace 40. The cooling furnace 40 is advantageously located below the forming region 14 of the glass ribbon 10, thereby cooling the formed glass ribbon 10 to a desired temperature, such as room temperature, and especially slowly in a controlled manner, thereby avoiding or reducing stress on the glass ribbon 10.

[0057] To cool the glass ribbon 10 with particular precision across its width, the cooling furnace 40 may be provided to have a plurality of cooling and / or heating units 41 arranged side by side / overlapping, and advantageously adjacent to one another. At least one cooling and / or heating unit 41, preferably a plurality, more preferably all cooling and / or heating units 41, are equipped with thermocouples 42 for measuring and controlling the temperature. Preferably, the cooling and / or heating units 41 are arranged side by side in a tiled manner, particularly in a tiled style. This is understood to mean that the cooling and / or heating units are formed as tiles, or are rectangular, square, or hexagonal, so that they can be arranged adjacent to one another without any free space between them. Such embodiments are shown, for example, in Figure 11. The cooling and / or heating units 41 may be provided to have different sizes. For example, cooling and / or heating units 41 located particularly in the area of ​​the edge 11 or the edge of the cooling furnace may be formed to be larger or smaller than those located in the central part of the cooling furnace 40 or the glass ribbon 10. In this way, specific regions of the glass ribbon 10 can be locally cooled and / or heated strongly or weakly, thereby providing individual cooling and / or heating methods for each glass ribbon width and glass ribbon shape. Therefore, it is also conceivable that the cooling and / or heating section 41 is formed to be larger or smaller in the lower region of the cooling furnace 40 than in the upper region of the cooling furnace 40.

[0058] To control the temperature of the glass ribbon 10, the apparatus 1 is provided to include at least one temperature measuring unit 45. The temperature measuring unit 45 is configured in particular to detect or measure the temperature of the glass ribbon 10, advantageously over the entire width of the glass ribbon. As shown in Figure 10, the temperature measuring unit 45 may be located above the molding area 14, particularly above the cooling furnace 40, so that, for example, the temperature of the glass ribbon 10 can be detected before it is cooled in the cooling furnace 40. In this way, an optimal cooling program for the glass ribbon 10 can be achieved. Similarly, the temperature measuring unit 45 or at least one or more additional temperature measuring units 45 may be part of the cooling furnace 40 and / or located within the cooling furnace, for example, in the central part.

[0059] In some cases, for example, when a nozzle 4 optimized for a certain glass thickness is used to manufacture a glass thickness that deviates from that, it may be necessary to already affect the temperature of the glass ribbon 10 in the molding region 14. Therefore, in a further embodiment, the apparatus 1 comprises at least one, in particular a plurality of, cooling and / or heating units 50 arranged spatially apart, these units being advantageously located within the molding region 14. In this case, the cooling and / or heating units 50 may be configured to locally heat and / or cool the glass ribbon 10 in at least specific regions as intended, so that the width of the glass ribbon 10 in the molding region 14 can be adjusted as intended. Thus, it is understood that cooling or heating can be performed locally in desired regions rather than across the entire width of the glass ribbon 10. Consequently, non-uniform and / or uniform cooling or heating can be achieved across the width of the glass ribbon.

[0060] Therefore, it is particularly preferable that the different heating and / or cooling units 50 are spatially separated, especially laterally, relative to the glass ribbon 10, in order to influence the local glass distribution within the glass ribbon 10 and to allow for fine adjustment of the glass distribution. In this case, the heating and / or cooling units 50 are, for example, separated and arranged across the entire surface of the molding region 14, and advantageously, separated at a height of more than 5%, preferably more than 10%, preferably more than 15%, of the length of the molding region 14, and / or at a height of less than 50%, preferably less than 30%, of the length of the molding region 14, in which case the length of the molding region 14 extends laterally with respect to the width of the glass ribbon 10. Here, the length of the molding region 14 can be 100 mm to 300 mm. In other words, the heating and / or cooling units 50 may be positioned between the nozzle 4 and the cooling furnace 40, for example, to allow for fine adjustment of the thickness of the glass ribbon 10. This makes it possible to stretch various glass ribbons with a wider range of glass thicknesses than the actual optimization range of the nozzle slit 5 using a single nozzle slit 5.

[0061] In this way, for example, in a thin glass having a concave thickness distribution in the center of the glass ribbon 10, different heating and / or cooling units 50 can be used to lower the glass temperature or increase the viscosity of the glass. This allows the molding to be completed earlier and prevents the glass from being drawn out in this region as it would be if these heating and / or cooling units 50 were not present. To allow for individual temperature control at desired locations on the glass ribbon 10, multiple heating and / or cooling units 50 may be arranged along the width of the glass ribbon 10, or aligned with respect to the width of the glass ribbon 10, and / or diagonally or laterally. Similarly, multiple heating and / or cooling units 50 may be arranged overlapping, particularly in the stretching direction. Depending on the application, for example, 2 to 6 heating and / or cooling units 50 may be provided, arranged side by side, overlapping, and / or diagonally to each other.

[0062] Advantageously, the heating and / or cooling units 50 may be configured as air-cooled or water-cooled cooling devices, respectively, and in particular can generate airflow, water jets, droplets, mist, and / or aerosols, as schematically shown in Figure 12, for example. These media can be directed particularly locally and, if necessary, directly onto the glass ribbon 10.

[0063] However, the heating and / or cooling unit 50 can also be configured as an indirect heating and / or cooling unit 50, for example, as a closed conduit system through which at least one medium circulates, thereby preventing the glass ribbon 10 from coming into contact with any further medium, such as water. In this case, each heating and / or cooling unit 50 is configured to release, absorb, or transport thermal energy. At least one conduit in such a conduit system may be aligned laterally or parallel to the extension direction. A temperature measuring unit 45 may be provided to detect the temperature, preferably the temperature of the medium and / or the glass ribbon, and this temperature measuring unit 45 may be located particularly on at least one, preferably one heating and / or cooling unit 50, so as to also measure the thermal energy drawn from the glass ribbon 10, for example. Combinations of direct and indirect heating and / or cooling units 50 can also be used, although not limited to the embodiments described above. Regardless of whether the heating or cooling by the heating and / or cooling unit 50 is indirect or direct, the cross-sectional shape of the heating and / or cooling unit 50 can be various, such as circular, oval, or polygonal shapes like rectangles or hexagons.

[0064] Here, the distance of the heating and / or cooling unit 50 from the glass ribbon 10 can be changed. This allows, for example, air cooling to be fine-tuned by adjusting the amount of air. In this case, the more air permeates per unit time, the thicker the glass becomes. A further very effective variation of air cooling is to mix in atomized water so that an aerosol is formed. This aerosol can transport considerably more thermal energy than mere dry air, depending on the amount of water, and it is also possible to effectively cool by mixing the aerosol, or atomized water, or another atomized liquid, with air or a specific gaseous composition.

[0065] When the heating and / or cooling unit 50 is used, for example, in the form of a water-cooled and / or air-cooled cooling device, its position or distance from the glass ribbon 10 can be changed. In this case, the smaller the distance between the water-cooled cooling device and the glass ribbon 10, the thicker the glass becomes. The heating unit has the same, but opposite, effect, and the heating unit makes it possible to make the glass ribbon 10 thinner in a desired area. Here, the heating unit may be formed as an air and / or heating coil-based heating unit. To allow for precise adjustment of the heating and / or cooling unit 50, a temperature measuring unit 45 may be provided, positioned between the nozzle 4 and the heating and / or cooling unit 50.

[0066] In a further embodiment, the apparatus 1 comprises a crucible 55 for containing and homogenizing clarified glass, the crucible 55 having at least one discharge pipe 56 having an advantageously specially adapted diameter, the discharge pipe 56 opening in particular to a stretching tank 2. Thus, the glass can be transported from the crucible 55 through the discharge pipe 56 to the stretching tank 2. Here, the apparatus may comprise at least one, advantageously more than one, or even more than one heating element 60, at least one heating element 60 positioned near the stretching tank 2, the discharge pipe 56 and / or the crucible 55. As shown in the example in Figure 13, multiple heating elements 60 may be positioned near the stretching tank 2, the discharge pipe 56 and / or the crucible 55, respectively, to allow for precise control of the temperature and the distribution of glass in the stretching tank 2.

[0067] In the sense of the present invention, the heating element 60 is understood as a device suitable for and intended to release energy to the stretching tank 2, the discharge pipe 56 and / or the crucible 55 and / or their contents. This energy can be released, for example, in the form of thermal energy, or even electrical energy, or, for example, magnetic energy. Here, the heating element 60 may comprise one or more heating coils and / or flanges, which can at least partially or completely surround the stretching tank 2, the discharge pipe 56 and / or the crucible 55 in at least one direction. Thus, in general, the stretching tank 2, the discharge pipe 56, the crucible 55 and / or their contents can be directly heated by the thermal energy supplied by the heating element 60, or the stretching tank 2, the discharge pipe 56 and / or the crucible 55 can be self-heated, for example, by induction or current supply, advantageously by at least one or more flanges in particular. Here, it is conceivable that currents flowing through the stretching tank 2, discharge pipe 56, and / or crucible 55 are generated by at least two flanges, or that a magnetic field is generated by at least one flange, thereby inductively supplying energy to the stretching tank 2, discharge pipe 56, and / or crucible 55. Therefore, advantageously, the stretching tank 2, discharge pipe 56, and / or crucible 55 can have materials that conduct heat and / or electric current, such as metal. In general, heating by the heating element 60 can be carried out particularly indirectly, advantageously over a wider area, and thus, for example, the formation of glass defects can be reduced. Fine-tuning of the temperature, particularly locally, is also possible.

[0068] Although not limited to the example in Figure 13, a heating element 60 is provided near the crucible 55, with one heating element 60 each at the upper inlet and lower outlet openings, thereby enabling the glass to be delivered to the discharge pipe 56 at a desired temperature. The discharge pipe 56 is equipped with three heating elements 60, with one heating element 60 each located in the upper third, the middle third, and the lower third. Advantageously, the discharge pipe 56 is thus divided into two to four electric heating circuits 61, which in particular allows for very fine temperature control and enables uniform distribution of the glass when it is already flowing into the stretching tank.

[0069] In a further embodiment, the stretching tank 2 comprises a plurality, particularly at least four, heating elements 60 such that the heating of the stretching tank (2) is advantageously divided into three electric heating circuits. The heating circuits can also be understood as spatially distinct or distinct heating zones of the stretching tank 2, each capable of heating a predetermined volume range of glass within the stretching tank. Here, the heating circuits 62 of the stretching tank 2 are advantageously arranged in line with respect to the length L of the nozzle slit 5, thereby influencing the glass distribution in the stretching tank 2 laterally or along the length L of the nozzle slit 5. Thus, the glass distribution in the nozzle slit 5 and the throughput of the amount of glass in the nozzle 4 can be adjusted by temperature control of the discharge pipe 56 and the stretching tank 2. Preferably, the heating elements 60 are arranged to form at least two or three, particularly more, heating circuits 62. In this case, at least two of the heating circuits 62 and / or heating elements 60 may be located on the side of the stretching chamber 2, and in particular, at least three heating circuits 62 may be formed, with at least one additional heating circuit 62 located in the center of the stretching chamber 2. Here, each heating circuit 62 may be surrounded, defined, or enclosed by at least two heating elements 60.

[0070] Therefore, the aforementioned problems can also be solved by an apparatus 1 for stretching a glass ribbon 10 from a glass molten 9, without being limited in general to the specific features of a particular embodiment, wherein the apparatus 1 comprises a crucible 55 for containing a clarified glass molten and a discharge pipe 56 for transporting the glass molten to a stretching tank 2, the stretching tank 2 comprising at least a plurality of heating elements 60, which are advantageously arranged laterally with respect to the length L of the nozzle slit 5 of the nozzle 4, so that the glass molten 9 can flow out downward through the nozzle 4, and the apparatus 1 comprises at least one, in particular a plurality of cooling and / or heating units 50 arranged in a forming area 14. Advantageously, in this embodiment as well, the nozzle slit 5 is curved downward in the stretching direction Z, particularly consistently or continuously, toward the ends 7a, 7b of the nozzle slit 5 in the first lateral region 8a and the second lateral region 8b, so that the ends 7a, 7b are located lower than the central region 8c of the nozzle slit 5, which is located between the ends 7a, 7b. For glass homogenization, the crucible 55 may be provided with a stirring unit, the rotation speed per unit time of which can be adjusted. [Explanation of symbols]

[0071] 1. Glass ribbon stretching device 2 Stretching tank 3 Cooling Unit 4 nozzles 5 Nozzle slits 6. The wall of the nozzle or nozzle slit 7a First end 7b Second end 8a First lateral region of the nozzle slit 8b Second lateral region of the nozzle slit 8c Central area of ​​the nozzle slit 9. Glass melt 10 Glass Ribbons 11 Edge 14 Molding area 15 Stretching roller 20 Protrusion 21 Lower wall of the protruding part 22 End wall of the protruding part 23 Lower end of the protruding part 24 Nozzle upper wall 25 Side wall 30 Lower boundary of the central region 40 Cooling furnace 41 Cooling and / or heating section 42 Thermocouples 45 Temperature Measurement Unit 50 Cooling and / or heating units 55 Crucible 56 Discharge pipe 60 heating elements 61 Heating circuit for the exhaust pipe 62 Heating circuit of the stretching tank B Width Bk Width of glass ribbon manufactured using a curved nozzle slit Bp Width of glass ribbon manufactured using parallel nozzle slits Bs Nozzle slit width Bv width of the protruding part H Nozzle height / Protruding part height L Nozzle slit length Lv (Length of protruding part) R radius of curvature Inflection point of W curvature Z stretching direction

Claims

1. An apparatus (1) for stretching a glass ribbon (10) from a glass molten liquid (9), wherein the apparatus (1) comprises a stretching tank (2) for containing the glass molten liquid (9), the stretching tank (2) comprises a nozzle (4) having a discharge opening (5), the glass molten liquid (9) can flow out downward through the nozzle (4), the discharge opening is formed as a nozzle slit (5) having two ends (7a, 7b), the length (L) of the nozzle slit (5) is greater than the width (B) of the nozzle slit (5) Furthermore, the nozzle slit (5) is curved downward in the stretching direction (Z) particularly consistently or continuously toward the ends (7a, 7b) of the nozzle slit (5) in the first lateral region (8a) and the second lateral region (8b), so that the ends (7a, 7b) are located lower than the central region (8c) of the nozzle slit (5) located between the ends (7a, 7b), and the width of the nozzle slit (5) changes from the central part toward the ends (7a, 7b). Apparatus (1), wherein the nozzle slit (5) exhibits a continuous curvature with respect to the height (H) and radius (R) in the first lateral region (8a) and the second lateral region (8b), and the height (H) extends parallel to the extension direction (Z).

2. The apparatus (1) according to claim 1, wherein the nozzle slit (5) tapers from the central portion toward the end, so that the width of the nozzle slit (5) in the central region (8c) is larger than that of the end portions (7a, 7b) of the nozzle slit (5).

3. The nozzle slit has the following features: - The nozzle slit (5) is always curved up to the end (7a, 7b), - The nozzle slit (5) is bent toward the end portion (7a, 7b), and the bend has an inflection point (W). The apparatus (1) according to claim 1 or 2, having at least one of the following.

4. The apparatus (1) according to any one of claims 1 to 3, wherein the nozzle slit (5) has an oval, elliptical, concave, or lenticular shape in the top view, that is, with respect to the length (L) and width (B).

5. The apparatus (1) according to any one of claims 1 to 4, wherein the nozzle (4) is provided with one projection (20) in each of the first lateral region (8a) and the second lateral region (8b) for accommodating an additional volume of the glass molten liquid (9), the projection (20) extends along the extension direction (Z), and the internal space of the projection (20) determines the size of the additional volume of the additional volume of the liquid.

6. The apparatus (1) according to claim 5, wherein the ratio of the height (H) of the internal space of the protruding portion (20) to the width (B) of the internal space of the protruding portion (20) is greater than 0.2, preferably greater than 0.5, preferably greater than 0.8 and / or less than 2, preferably less than 1.6, preferably less than 1.

2.

7. The apparatus (1) according to claim 6, wherein the radius (R) of the curvature of the nozzle slit (5) is determined by the height (H) and the length (L) of the protruding portion (20).

8. The apparatus (1) according to claim 6 or 7, wherein the ratio of the length (L) of the protrusion (20) to the height (H) of the protrusion (20) is less than 2.8, preferably less than 2.6, and preferably less than 2.

4.

9. The apparatus (1) according to any one of claims 5 to 8, wherein the curved portion of the protrusion (20) in the first lateral region (8a) faces the curved portion of the protrusion (20) in the second lateral region (8b).

10. The apparatus (1) according to any one of claims 6 to 9, wherein the height (Hv) of the internal space of the protruding portion (20) is greater than 10 mm, preferably greater than 15 mm, preferably greater than 20 mm and / or less than 80 mm, preferably less than 60 mm, preferably less than 40 mm.

11. The apparatus (1) according to any one of claims 6 to 10, wherein the width (B) of the protruding portion (20) is given by the product of the width (B) of the nozzle slit (5), in particular the width (B) of the cross section of the discharge opening, and a value greater than 1 mm, preferably greater than 1.5 mm, preferably greater than 2 mm and / or less than 15 mm, preferably less than 10 mm, preferably less than 5 mm.

12. The apparatus (1) according to any one of claims 6 to 11, wherein the radius (R) of the curvature of the nozzle slit (5) is greater than 100 mm, preferably greater than 130 mm, preferably greater than 160 mm and / or less than 260 mm, preferably less than 230 mm, preferably less than 200 mm.

13. The apparatus (1) according to any one of claims 5 to 11, wherein the protruding portion (20) has a lower wall (21) that closes the internal space of the protruding portion (20) in the extension direction (Z), and the discharge opening is located on the lower wall (21).

14. The apparatus (1) according to any one of claims 1 to 13, wherein a plurality of heating elements (60) are arranged in the stretching tank (2) such that the heating of the stretching tank (2) is divided into an electric heating circuit (62), and the heating circuit (62) of the stretching tank (2) is preferably arranged in line with respect to the length L of the nozzle slit 5.

15. The apparatus (1) according to any one of claims 1 to 14, comprising at least one, in particular a plurality of, cooling and / or heating units (50) arranged spatially apart, wherein the cooling and / or heating units (50) are located within a molding region (14).

16. A method for stretching a thin glass ribbon (10) from a glass molten liquid (9), wherein glass is melted, the glass flows out of a stretching tank (2) through which the glass molten liquid (9) passes and which has a discharge opening, and a thin glass ribbon (10) is obtained by pulling the glass out so as to move downward in the stretching direction (Z), the thin glass ribbon (10) is cooled after flowing out of the discharge opening until it falls below the glass transition temperature Tg, the thin glass ribbon (10) is pulled out in the stretching direction (Z) by contact with a stretching roller (15) that transmits tensile force to the thin glass ribbon (10), the stretching roller (15) contacts the glass at a position where the temperature of the glass falls below the glass transition temperature Tg, and the apparatus (1) described in any one of claims 1 to 15 is used, the apparatus (1) is equipped with a nozzle (4) having a projection (20) that prevents necking of the glass ribbon (10).

17. The method according to claim 16, wherein the nozzle is formed such that the tensile force of the glass ribbon (10) generated below the discharge opening is divided at the protruding portion (20) into a vertical force component (Kv) and a horizontal force component (Kh), and a deformation force (Uz) having opposing effects is generated in the glass ribbon (10), and the ratio of the horizontal deformation force component (Uh) to the ratio of the vertical deformation force component (Uv) increases toward the first end (7a) and the second end (7b).

18. The following features: - A thin glass ribbon (10) having a thickness of up to 70 μm, preferably up to 50 μm, and more preferably up to 20 μm is stretched. - Continuously draw glass ribbons with thicknesses that differ by at least 1.5 times, and preferably at least 2 times, from the same nozzle. The method according to claim 16 or 17, comprising at least one of the above.

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