METHOD AND DEVICE FOR PROCESSING GLASS ELEMENTS

Description

[0001] The invention relates generally to the processing of glass by cutting the glass along a desired dividing line. In particular, the invention relates to a laser-assisted method for introducing dividing lines.

[0002] To separate glass panes along a predetermined line, the scoring method is often used. In this process, the glass is first scored along a line and then broken by applying a bending stress along the line. However, a problem arises with this method, particularly with thicker glass, where the resulting edge surface can become misaligned and no longer be perpendicular to the side surfaces.

[0003] US patent 2016 / 009586 A1 discloses a method in which a pulsed laser with a beam focal length between 0.1 mm and 100 mm induces at least one perforation line in a glass article and a glass separation station downstream of the glass cutting station is configured to remove a portion of the glass article across the perforation line, particularly after heating and cooling, to produce a laser-cut glass article.

[0004] US 2018 / 057390 A1 describes a method for laser processing of glass workpieces, which includes focusing a pulsed laser beam into a laser beam focal line that is aligned along the beam propagation direction and directed into the glass, wherein the laser beam line creates an induced absorption within the material and the induced absorption creates a defect line at a temperature above the annealing or tempering temperature of the glass along the laser beam line within the glass.

[0005] A method for laser cutting of display glass is known from WO 2015 / 095088 A1. In this method, after an overflow fusion forming process of a glass ribbon, the edge of the glass ribbon is removed, the glass ribbon is cut to length, and then cut to the desired formats to obtain the desired contour and size of glass panes. The cutting can be carried out with an ultrashort pulse laser. WO 2015 / 095091 A1 describes a similar process.

[0006] The process according to US 2015 / 165560 A1 involves the use of an ultrashort pulse laser to create perforations or holes in thin substrates made of transparent materials, followed by a CO₂ laser beam to promote complete separation around the perforation line. Additionally, a high-velocity auxiliary gas can be blown through a nozzle surrounding the CO₂ laser, which helps to force the detached glass material out of the larger substrate.

[0007] US9975799 and WO 2016 / 007843 describe, among other things, the separation of a vial formed from a glass ribbon by blow molding (so-called string-ribbon process) by filamenting along the neck of the vial and subsequent separation of the vial along the filamentation line by applying mechanical or thermal stresses, in particular by a CO₂ laser. The separation process takes place shortly after the hot forming process.

[0008] The above-mentioned writings have in common that an ultrashort pulse laser process is carried out following the hot forming process, whereby a clear temporal separation between fracture preparation in the hot state and separation of the substrate in the cold state is not provided for.

[0009] Since filamentation is a thermally based process, it depends not only on material properties such as the coefficient of thermal expansion, but also on the workpiece temperature during processing. It has been observed that there are significant differences when filamentating brittle materials at room temperature and the same material at high temperatures: Because the local temperature difference ΔT generated by the filamentation process decreases with increasing workpiece temperature, significantly lower stresses are generated in the filamentation area at high workpiece temperatures than at lower substrate temperatures. Consequently, the degree of damage to the material is also lower at high temperatures.This difference in the degree of damage around the produced filaments is evident in significantly higher breaking forces (during filament production at high workpiece temperatures), which also exhibit a significantly higher scatter.

[0010] It was surprisingly found that with increasing processing temperature during the filamentation process, the fracture forces required to open the filamentation line and their dispersion increase. This effect continues up to the glass's transformation temperature, at which point the cleavage of the resulting material damage drops dramatically. This effect is of considerable importance for the application of the filamentation process in inline production, especially at high temperatures near or within the hot forming area.

[0011] The invention is therefore based on the objective of facilitating and making more reliable the separation of glass elements following a hot process, such as hot forming. This objective is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the respective dependent claims.

[0012] The effect of decreased cleavage at the cleavage line at high temperatures can be counteracted by increasing the number of pulses in a burst and / or the burst frequency, thereby generating more extensive damage and—consequently—lower fracture forces. However, the invention is based on the understanding that the fracture force and its dispersion can be significantly reduced by rapid cooling in the area of ​​the laser-induced damage. The effect of reducing the fracture force and its dispersion through forced cooling immediately following the filamentation process in the area of ​​the modified material is more pronounced the higher the cooling rate: the higher the cooling rate, the greater the reduction in fracture force.

[0013] Accordingly, the invention provides a method for processing glass elements in which a perforation line for separating the glass element is inserted into a glass element during or after a hot processing process at an elevated temperature of at least 100°C, preferably at least 200°C, particularly preferably at least 300°C, by inserting filament-shaped defects spaced apart along the predetermined course of the perforation line into the glass element with a pulsed laser beam of an ultrashort pulse laser, and wherein, during the insertion of the filament-shaped defects, the glass element is cooled with a cooling fluid in such a way that a temperature gradient is created which induces a mechanical stress at the filament-shaped defects, thereby reducing the breaking force required to separate the glass element along the perforation line.

[0014] A suitable device for processing glass elements includes A device for hot processing the glass elements, and a device for inserting a perforation line into the glass element in order to separate the glass element along the perforation line, wherein the device for inserting a perforation line includes an ultrashort pulse laser, which is arranged and aligned such that it shines onto a glass element in a region of the device for processing glass elements, in which the glass element has a temperature of at least 100 °C before heating during processing in the device for hot processing the glass elements, and wherein the glass element has a temperature of at least 100 °C after processing in the device for hot processing the glass elements, and wherein a movement device is provided to move the point of impact of the laser beam along a predetermined path of the perforation line. wherein the ultrashort pulse laser is configured to introduce filament-shaped defects into the glass element, and wherein the device for processing glass elements comprises a cooling device, the cooling device comprising a nozzle for emitting a cooling fluid jet or a device for quenching the glass element in a liquid, which is arranged and configured such that it cools the glass element during the introduction of the filament-shaped defects, creating a temperature gradient which induces mechanical stress at the filament-shaped defects, thus reducing the breaking force required to separate the glass element along the separation line, as well as typically its scattering. In this way, breaking force and scattering are reduced compared to filamentation at high temperatures; with suitable cooling, a reduction compared to filamentation at room temperature can even be achieved.The invention thus not only reduces the breaking force but also narrows the statistical distribution typical for the breakage of brittle materials. This is very advantageous for increasing the reliability of separating the glass element and / or reducing the probability of uncontrolled breakage.

[0015] The elevated temperature at which the perforation line is inserted can be selected not only as an absolute temperature, as described above. According to one embodiment of the invention, the temperature of the glass is selected based on the interval between room temperature and the glass transition temperature. In a further embodiment, a perforation line for separating the glass element is inserted during or after a hot processing process at an elevated temperature, whereby the temperature is increased by at least half the temperature difference between room temperature and the glass transition temperature compared to room temperature (20°C). For example, if the glass has a glass transition temperature of 520°C, half the difference to Tg corresponds to a temperature increase of 250°C. Therefore, the perforation line is inserted at a temperature of at least room temperature (20°C) + 250°C, i.e., at least 270°C.According to further training, the perforation line is inserted at a temperature that is at least room temperature plus three-quarters of the temperature interval between room temperature and the glass transition temperature. In the example above, this would therefore be a temperature of at least 20 °C + (3 / 4)*500 °C = 395 °C.

[0016] The invention is particularly preferred for hot processing processes in the form of hot forming processes. According to a preferred embodiment, the device for hot processing glass elements thus comprises a device for hot forming glass elements. In particular, the hot forming can include shaping the glass element from a melt.

[0017] To effectively reduce fracture forces through forced cooling, cooling methods associated with laser-based thermal cutting, such as cutting with a CO₂ laser, can be used. Examples include blowing with air, other gaseous media, or air / gas-liquid mixtures (aerosols), or quenching by immersion in a liquid. Quenching can also be achieved by a liquid curtain from a casting nozzle through which the glass element passes. A key advantage of cooling is that the contact of the modified area of ​​the substrate results in at least local cooling of the area with the filamentous defects. This creates a local thermal stress that enlarges microcracks around the filament modification or filamentous defect, thus further weakening the material.The choice of cooling method can be made according to the requirements of the existing production conditions and process parameters.

[0018] Local quenching leads to an increase in stresses and thus to an increased formation or lengthening of microcracks, so that the fracture stress required for subsequent separation is reduced as a result of the greater pre-damage.

[0019] A neodymium-doped yttrium aluminum garnet laser with a wavelength of 1064 nanometers is particularly suitable as an ultrashort pulse laser for the purposes of the invention. This laser can be used for all embodiments described in this disclosure. The average power of an ultrashort pulse laser suitable for the invention is preferably in the range of 20 to 300 watts. To achieve the filament-shaped damage, a pulse energy in the burst of more than 400 microjoules is used according to an advantageous embodiment of the invention; furthermore, a total burst energy of more than 500 microjoules is advantageously used.

[0020] When operating an ultrashort pulse laser in burst mode, the repetition rate is the number of times a burst is emitted. The pulse duration is essentially independent of whether the laser is operated in single-pulse mode or in burst mode. The pulses within a burst typically have a similar pulse length to a single pulse in single-pulse mode. The burst frequency can range from 15 MHz to 90 MHz, preferably from 20 MHz to 85 MHz. For example, the burst frequency might be 50 MHz, with the number of pulses in the burst ranging from 1 to 10, e.g., 6 pulses.

[0021] According to one embodiment of the invention, the average distance between adjacent filament-shaped defects is generally 1µm to 10µm, preferably 3-8µm.

[0022] To generate sufficient mechanical stress at the filamentous defects to facilitate the subsequent separation process, one embodiment provides for the glass element to be cooled at a rate of at least 50 °C per second, preferably at least 100 °C. This need not apply to the entire cooled area, preferably to the surface, but at least to the location of the filamentous defects. Preferably, the cooling is also carried out in such a way that a temperature gradient of at least 50 °C per millimeter is established at the location of the filamentous defects at least once. This temperature gradient can be located along the surface and / or within the volume of the glass. For example, quenching the glass would cool the surface over a large area, creating a temperature gradient from the surface into the interior of the glass.The gradient then runs in the longitudinal direction of the filamentous damage.

[0023] The invention will be explained in more detail below with reference to the attached drawings. Brief description of the characters

[0024] Fig. 1 shows a device for processing glass elements. Fig. 2 shows one variant of the device. Fig. 3 represents a device for the production of float glass. Fig. 4 shows an arrangement for inserting a perforation line into a glass tube. Fig. 5 This is a diagram of the measured breaking forces when the perforation lines break. Fig. 6 and Fig. 7 show devices for the production of glass tubes according to the Danner and Vello processes. Fig. 8 shows a processing head. Fig. 9 shows an arrangement with cooling of the side opposite the point of impact of the laser beam. Detailed description of the invention

[0025] Fig. 1 Figure 2 shows an exemplary embodiment of a device 2 for processing glass elements. For the purposes of this disclosure, the term "processing" generally also includes their manufacture. A typical processing method is the hot forming of glass elements. Fig. 1This is an example of such processing. Here, a glass element in the form of a continuous glass ribbon 100 is drawn from a glass melt 111 through a downward-facing, slot-shaped nozzle 20. This hot forming process for glass ribbons or glass sheets is also known as the down-draw process. Hot forming using the overflow fusion process is also possible. As the distance from the nozzle 20 increases, the temperature of the glass decreases until the glass transition temperature Tg is reached at position 21. In general, without being limited to the specific example shown, a preferred embodiment provides that the perforation line is inserted at a glass temperature below the glass transition temperature. However, it is even possible to insert the perforation line, at least partially, above the glass transition temperature.The upper limit is then considered to be the melting temperature, or rather a temperature at which the glass viscosity has a value of 10⁴ < dPa·s. Filamenting at a temperature below the glass transition temperature is advantageous, however, to avoid influencing the shape and position of the filaments after insertion. This condition can also be met at temperatures below the softening point, i.e., the temperature at which the viscosity has a value of 10⁷.6 < dPa·s, since the glass is already dimensionally stable below this temperature.According to a further development of the invention, it is therefore provided that the insertion of the perforation line 3 takes place at a temperature of the glass below the temperature at which the glass has a viscosity of 10⁴ < dPa·s, preferably at a temperature below the softening point, in particular below the deformation temperature at a viscosity of 10⁻¹¹.5 < dPa·s, particularly preferably at a temperature below the upper cooling point at a viscosity of the glass of 10⁻¹³ < dPa·s and most preferably below the glass transition temperature.

[0026] The device 2 generally comprises a device 13 for inserting a perforation line 3 into the glass element 1. The perforation line 3 represents a controlled point of failure or weakening of the material, so that the glass element 1 can later be easily separated along the perforation line 3. The device 13 comprises an ultrashort pulse laser 7, which is arranged and aligned such that it shines onto the glass element 1, here the glass ribbon 100, in a region of the device 2 used for processing glass elements 1, where the glass element 1 still has a temperature of at least 100 °C.

[0027] As can be seen from the figure, the point of impact of the laser beam 5 is preferably located at a position further away from the nozzle than position 21, at which the glass reaches its glass transition temperature. The temperature of the glass is therefore generally in a range between 100°C and the glass transition temperature.

[0028] In general, a beam-shaping optic 4 can be provided, as shown, to adapt the laser beam. In particular, the beam-shaping optic 4 can focus the laser beam 5 to increase the power density in the glass. The individual filament-shaped defects 9 run transversely, preferably perpendicularly to the surface of the glass element 1, following the propagation direction of the laser beam 5.

[0029] In the example shown, the processing of the glass element 1 includes its separation into individual glass panes 101. The perforation lines 3 ensure a controlled, clean break. To create the perforation lines 3, which in this example run perpendicular to the plane of representation and perpendicular to the longitudinal direction of the glass strip 100, consisting of adjacent filament-shaped defects 9, the laser beam 5 is moved accordingly perpendicular to the longitudinal direction across the strip 100. For this purpose, a movement device 15 is provided to move the point of impact of the laser beam 7 along a predetermined path of the perforation line 3. The laser beam can be guided over the glass, or the glass can be guided past the laser beam. A combination of both methods is also possible. To move the laser beam 5 perpendicular to the direction of movement of the glass strip 100, a galvanometer scanner, for example, can be used.Since the glass ribbon 100 continues to move, the motion device 15 can guide the laser beam 5 slightly obliquely across the glass element 1 to compensate for the movement of the glass ribbon. The galvanometer scanner is therefore shown here positioned at a slight angle. In order to ensure a cutting path perpendicular to the edge of the glass ribbon in this embodiment, the inclination of the scanner mirror depends on the speed of the glass ribbon and can be adjusted if necessary.

[0030] Due to the special environmental conditions near the hot forming process, particularly when forming from molten glass as in the illustrated example, it is advantageous if, as shown, the beam forming optics 4 and optionally other components of the device 13 are arranged in a cooled enclosure 8. In particular, the laser 7 and / or the motion device 15 can also be arranged in the cooled enclosure 8. A cooled enclosure can advantageously be used generally for a device 2, without being limited to the example shown. Fig. 1 be planned.

[0031] After the perforation lines 3 have been introduced from adjacent filament-shaped defects 9, the individual glass panes 101 can finally be separated. One advantage of the method is that the distance the glass travels can be shortened, since the preparation for separation is carried out on the hot glass. At the high temperatures of the glass, the introduced filament-shaped defects are generally not as pronounced as when processed at room temperature, as explained above. In order to nevertheless achieve reliable and easy separation, the glass element 1 is spatially confined during the introduction of the filament-shaped defects 9, i.e.,The glass element 1 is cooled near the filament-shaped defects to create a temperature gradient. This gradient induces mechanical stress at the filament-shaped defects 9, thereby reducing the breaking force required to separate the glass element 1 along the perforation line 3. For this purpose, the device 2 for processing glass elements 1 includes a cooling unit 17, which is arranged to cool the glass element 1 during the insertion of the filament-shaped defects 9, creating the aforementioned temperature gradient. A high cooling rate is particularly advantageous for thin glass to generate sufficient stress. The cooling rate is preferably at least 50 °C per second.

[0032] According to the invention, the cooling device 17 comprises a nozzle 20 for dispensing a cooling fluid jet 18. Cooling can be achieved, for example, by blowing air, other gaseous media, or aerosols (gas-liquid mixtures), preferably with air as the carrier. The cooling fluid can also be a liquid jet. Therefore, according to one embodiment of the invention, and not limited to the specific example shown, cooling is achieved by blowing air or an aerosol, or by spraying a liquid.

[0033] In a further embodiment, cooling is carried out by quenching in a cooler liquid, preferably at a temperature lower than room temperature, and particularly preferably lower than 0°C. This embodiment can be performed as an alternative or in addition to blowing. For example, after an initial, more cautious cooling by blowing, rapid cooling by quenching can be carried out.

[0034] Fig. 2 shows an alternative or additional embodiment of the embodiment according to Fig. 1 In this embodiment of the device 2 for processing glass elements 1, a continuous glass ribbon 100 is also drawn from a nozzle 20, particularly in the form of a thin glass ribbon. The drawing can be carried out using the down-draw process, as shown, or the overflow fusion process. Another generally applicable hot-forming process is the redraw process, in which a preform is heated and drawn. The thickness of the glass ribbon is generally, and without limitation to the examples and drawing processes shown, preferably in the range of 0.01 mm to 20 mm, more preferably in the range of 0.05 mm to 10 mm, particularly in the range of 0.1 mm to 4 mm, and most preferably in the range of 0.1 mm to 2 mm.

[0035] Due to the process, a so-called rim (i.e., a "bulge-like" thickening) forms at both edges of the glass ribbon. This rim can be removed, for example, by a laser process using a CO₂ laser or an ultrashort pulse laser. Because of the high fracture forces applied during the separation process, cracks can propagate into the glass ribbon, potentially leading to its destruction. Therefore, as shown in the example, the glass ribbon emerging from the hot forming zone is filamented in the rim area using two ultrashort pulse lasers 7 and locally cooled on one or both sides along the perforation line 3 by means of cooling devices 17 in the form of cooling nozzles.Here, the cooling rate can be adjusted to the process parameters (glass strip temperature and feed rate) of the respective hot forming process by regulating the flow rate of the cooling fluid, in order to prevent any influence on the glass strip 100 in the quality area (creating stresses in the glass strip). The glass strip 100, prepared in this way, can be cut in its cold state (for example, during or after deflection into a horizontal section of the production line) by applying mechanical stress. One possibility for this is to guide the perforation line 3 over a crowned roller.

[0036] The borders 102 run along the edges of the glass strip 100 in the longitudinal direction. Accordingly, the perforation lines 3 are also inserted in the longitudinal direction of the glass strip near the edges. In this embodiment of the invention, the laser beam 5 can remain essentially stationary. The movement device 15 here comprises, in particular, drawing rollers 25, which pull the glass strip 100 away and thus move it past the device 13 for inserting the perforation line 3, in particular past the one or more ultrashort pulse lasers.

[0037] In general, without being limited to the specific example shown, one embodiment provides a hot processing device 11 in the form of a hot forming device 110 for drawing a glass element 1 in the form of an elongated glass strip 100, wherein the device 13 for inserting a perforation line 3 is configured to insert perforation lines in the longitudinal direction of the glass strip 100, at which strip-shaped edge areas, each having a thickened border 102, can be separated. As shown, the movement device 15 can comprise a drawing device, in particular drawing rollers 25. The embodiment is analogously applicable to other drawing processes, such as the up-draw process, the overflow fusion process, and the redraw process, as well as to tube drawing processes, in particular the Danner or the Vello process.

[0038] Another variant shows Fig. 3The device 2 for processing glass elements 1 shown here is again a device for producing a glass ribbon 100. The hot processing device 11 comprises a float tank 31. The molten glass 111 flows into the float tank 31 from a melting tank 29 and is distributed there by drawing rollers and drawn out into a glass ribbon 100 floating on a tin bath 33. The glass ribbon 100 then passes through a cooling furnace 35. The device 13 for inserting a perforation line 3 is preferably arranged at the outlet of the cooling furnace 35. However, it is also possible to insert the perforation line before or inside the cooling furnace. The cooling device 17 can be integrated into the device 13. For example, the cooling device 17 can again comprise one or more cooling nozzles, or a liquid bath, or a casting nozzle for a liquid jet or curtain for local quenching of the glass.

[0039] Even at the in Fig. 3 In the illustrated embodiment, the device 13 can serve to insert longitudinal perforation lines 3 along the edge of the glass strip 100 in order to separate the edges 102 of the glass strip 100. A separating device 37, for example in the form of the aforementioned convex rollers, can generally be provided for this purpose. The edge 102 separates from the rest of the glass strip 100 at the separating device 37 and can then be collected in a cullet container. The glass strip 100 is transported through the cooling oven 35 by means of transport rollers 39, which accordingly form part of the movement device 15 by which the laser beam is guided over the glass element 1, or the glass strip 100.

[0040] Preferably, the temperature at the outlet of the annealing oven is between 100 °C and 400 °C. This is also a generally preferred temperature range, regardless of the hot processing method. It is also preferred to insert the perforation line 3 at a temperature at or below the lower cooling point, i.e., at a temperature at which the viscosity of the glass is at least 10<13 dPa·s. This condition is typically met at the outlet of the annealing oven. By maintaining a temperature below the lower cooling point, the build-up of undesirable permanent stresses during cooling by the cooling device 17 can be avoided. According to a further embodiment of the invention, the perforation line 3 is therefore inserted at a position on the glass element 1 where at least one of the aforementioned conditions is met, i.e., a temperature in the range between 100 °C and 400 °C or below the lower cooling point.This further development of the invention is of course not limited to the float process, but the mentioned temperature ranges can be used in all hot processing processes when inserting the perforation line.

[0041] The float process is particularly suitable for manufacturing thicker glasses with thicknesses in the range of 0.3 mm to 8 mm, preferably up to 4 mm. However, such thicker glasses can also be produced using the other drawing processes mentioned. Generally speaking, without being limited to those mentioned in the Figs. 1 to 3 In the illustrated special embodiments, the device 110 for hot forming comprises a device for producing a glass ribbon 100 using the down-draw process, the overflow fusion process, the redraw process or the float process.

[0042] The following describes examples of glass tube cutting. Glass tubes (material: clear Fiolax; diameter: 6.85 mm; inner diameter: 4.85 mm) were heated to approximately 304°C in a tube furnace. The temperature was measured with a pyrometer. The glass tubes were then removed from the furnace and filamented directly along a circumferential circle while rotating on a motor-driven axis. Fig. 4Figure 1 schematically shows the arrangement of the tube on the axis 151, which serves here as a motion device 15 and is driven by a motor 152. The rotation during the application of the laser beam 5 creates a perforation line 3 circumferentially on the glass tube 103. An ultrashort pulse laser 7 with a wavelength of 1064 nm was used to generate the filament-shaped defects 9. The laser beam 5 is focused onto the glass element 1, or the glass tube 103, by a biconvex lens 40, which serves as beam-shaping optics 4 with a focal length of 20 mm. The raw beam diameter of the laser beam 5 was 12 mm. The ultrashort pulse laser was operated in burst mode with four bursts per pulse. The rotation speed and the repetition rate of the laser were set such that the filament-shaped defects along the perforation line on the outer surface have a spacing of 7 µm.

[0043] In a first series of measurements, the glass tubes 103, provided with a perforation line 3, were allowed to cool without active cooling. In a second series of measurements, the glass tubes 103 were quenched with water. As a comparative test, in a third series of measurements, the glass tubes were treated with an ultrashort pulse laser at room temperature. Finally, in a fourth series of measurements, the glass tubes 103, after filamenting at 304 °C, were forced-cooled with a cooling nozzle by applying an air / water cooling mixture or an air / water aerosol along the perforation line. The volume flow rate was 0.2 ml / min. At least 24 samples were tested in each series of measurements. The strength of the perforation lines 3 was determined in a modified flexural strength test according to DIN EN 843-1 by determining the mean fracture stress or the Weibull parameters.

[0044] Fig. 5The measurement results are shown in a diagram with double-logarithmic scaled axes. This diagram is a Weibull plot. The graphs of the measured values ​​for measurement series 1 to 4 are labeled M1 to M4. To better track the measurement series and to determine Weibull parameters, regression lines are plotted for each graph. The results are presented in the following table: Measurement series: Number of samples Average breaking strength scattering N N M1: Perforation line inserted at 304°C, slow cooling 24 154,86 49,12 M2: Perforation line inserted at 304°C, cooled by quenching. 24 118,08 34,44 M3: 25 94,06 2,66 M4: 30 42,49 4,41

[0045] It was found that with defined local forced cooling after filamentation in the hot state, the breaking forces are only half as high (with comparable scatter) as with filamentation at room temperature. With uncontrolled, area-wide cooling of the substrate after filamentation in the hot state, however, the breaking forces are on average increased by more than 50% compared to room temperature, but the values ​​are still significantly lower than the breaking forces that occur with slow cooling.

[0046] Only measurement series 2 showed a distribution of breaking force values ​​that approximates a Weibull distribution. For the mean value of 118 N and a standard deviation of 34 N, a characteristic value of 130 N and a Weibull modulus of 4.0 can be calculated. These examples demonstrate that the invention generally allows for significant reductions in breaking forces.

[0047] In the example of the Fig. 4 Cut glass tubes were processed. However, the process according to this disclosure can also be applied analogously to the following: Figs. 1 to 3 The examples described can also be applied to the hot forming of tubes from a glass melt 111. Fig. 6Figure 1 shows an example in which annular perforation lines 3 are inserted into a glass tube 103 continuously drawn using the Danner process. The glass tube 103 can then be cut into shorter sections along these perforation lines 3. In this process, the molten glass 111 flows onto a spindle 26, which is rotated by a motor 152 via a shaft 151. The rotation distributes the molten glass around the circumference of the spindle 26. Simultaneously, the resulting tube is drawn off the spindle 26. Compressed air can be supplied through the spindle 26 to prevent the tube from collapsing behind it. The rotation of the glass tube 103 ensures that the laser beam 5 is guided around the circumference of the glass tube and inserts an annular perforation line 3 into the still-hot glass. It is also advantageous to follow the laser 7 in the axial direction at the feed rate of the tube 103.

[0048] Fig. 7 Another example is shown. In the device 2 shown here, a continuous glass tube 103 is drawn using the Vello method. The method is similar to the down-draw method according to Fig. 1 , since the glass tube 103 is drawn downwards through a downwardly open nozzle 20. A mandrel 42 is arranged in the nozzle 20, resulting in an annular nozzle gap. The molten glass 111 flows along the mandrel and is drawn off as a tube at the end of the mandrel 42. Compressed air can be supplied through a central channel 44 in the mandrel 42 to prevent the initially soft tube from collapsing. Just as in the example of the Fig. 6 A ring-shaped perforation line 3 is inserted using the laser 7 and locally cooled by means of a cooling fluid jet 18 to reduce the breaking force.

[0049] The inventive method involving filamentation on hot glass and active cooling is implemented such that the insertion of the perforation line with the ultrashort pulse laser and the cooling occur simultaneously. The laser welding process can be used, in which the process gases are supplied to the working volume of the laser beam by a suitably designed welding head, and in this case, the appropriate coolant is supplied during filamentation instead of the process gases. According to one embodiment of an inventive device for processing glass elements, the device 13 for inserting a perforation line 3 comprises a head through which the laser light is directed and the cooling fluid, in particular the cooling jet, is directed onto the glass element 1. Such a processing head 130 is shown. Fig. 8The processing head 130 has a channel 131 directed towards the glass element 1, through which both the laser beam 5 and the cooling fluid jet 18 are guided, so that the point of impact of the laser beam 5 lies within the cooling fluid jet 18 and is surrounded by the cooling fluid. The configuration with a common channel is advantageous, but not mandatory. Regardless of the specific configuration, one embodiment of the invention provides that the device 13 for inserting the perforation line 3 comprises a processing head 130 through which both the laser beam 5 and the cooling jet are directed towards the glass element 1, so that the point of impact of the laser beam 5 on the glass element 1 lies within the cooling fluid jet 18.A compact arrangement, in which the cooling fluid generally cools the area processed by the laser beam 5 directly, is possible according to yet another embodiment, in which, by means of a suitably arranged cooling device 17, the cooling fluid jet 18 is directed onto the surface of the glass element 1 from which the laser beam 5 exits again, or in which the cooling jet is directed onto a surface of the glass element 1 that is opposite the surface on which the laser beam 5 strikes. An example of this variant is shown. Fig. 9 The laser beam is focused by the beam shaping optics 4 with lens 40 onto the surface 105, while the cooling fluid beam 18 is directed towards the opposite surface 106, but here also as in the embodiment according to Fig. 6 acts on the site of irradiation and creates a temperature gradient and thus a mechanical stress.

[0050] All the examples shown have in common that cooling during filament forming is locally confined. This is generally advantageous, without being limited to the specific examples shown, in order to avoid stresses in the glass.

[0051] The invention is not limited to the hot forming processes shown in the preceding figures. Further hot processing methods include the firing of ceramic colors or decorations, as well as coating processes in which the glass is held at an elevated temperature. Without being limited to specific embodiments, one embodiment of the invention provides that the hot processing method comprises at least one of the following processes: ceramicizing the glass element 1 to produce glass ceramics, forming a glass element in the form of a hollow, container, or tube glass, thermal tempering, firing of ceramic colors, and coating the glass element. Reference symbol list

[0052] Glass element 1 Device for processing glass elements 2 Perforation line 3 Beam-shaping optics 4 laser beam 5 Ultrashort pulse laser 7 Refrigerated enclosure 8 filamentous damage 9 Device for hot processing of glass elements 11 Setup for inserting a perforation line 13 Movement device 15 Cooling device 17 Cooling fluid jet 18 nozzle 20 Position with temperature T g 21 Pull roller 25 spindle 26 Float device 28 Melting tank 29 Floating tub 31 Tin bath 33 Cooling oven 35 Separation device 37 Transport roller 39 lens 40 mandrel 42 channel 44 Glass ribbon 100 glass pane 101 border 102 glass tube 103 Areas of 1 105, 106 Hot forming device 110 Glass melt 111 Processing head 130 channel 131 axis 151 Motor 152

Claims

1. A method for processing glass elements (1), which comprises introducing, into a glass element (1), a perforation line (3) during or after a hot processing process at an elevated temperature of at least 100 °C, for separating said glass element (1), by introducing, into the glass element (1), filament-like defects (9) which are spaced apart from one another along the predetermined course of the perforation line (3) using a pulsed laser beam (5) from an ultrashort pulse laser (7), characterised in that during the introduction of the filament-like defects (9), the glass element (1) is cooled with a cooling fluid in such a way that a temperature gradient is created which induces a mechanical stress at the filament-like defects (9), thereby reducing the breaking force required to separate the glass element (1) along said perforation line (3).

2. The method according to the preceding claim, characterised in that the hot processing process comprises hot forming, in particular the forming of the glass element (1) from a glass melt (111).

3. The method according to the preceding claim, characterised in that the hot forming comprises the production of a glass ribbon which preferably has a thickness in the range from 0.01 mm to 20 mm, preferably in the range from 0.05 mm to 10 mm, more particularly in the range from 0.1 mm to 4 mm, most preferably in the range from 0.1 mm to 2 mm.

4. The method according to any one of the preceding claims, characterised in that the introduction of the perforation line (3) is performed at a temperature of the glass below the temperature at which the glass has a viscosity of 104 dPa·s, preferably at a temperature below the softening point, most preferably at a temperature below the glass transition temperature.

5. The method according to any one of the preceding claims, characterised in that the cooling is performed by blowing air or an aerosol thereon or by spraying a liquid thereon.

6. The method according to any one of the preceding claims, characterised in that the cooling comprises quenching in a liquid.

7. The method according to any one of the preceding claims, characterised in that the glass element (1) is cooled at a cooling rate of at least 50 °C per second, preferably at least 100 °C per second.

8. The method according to any one of the preceding claims, characterised in that the cooling is performed in such a way that, at least at one point in time, a temperature gradient of at least 50 °C per millimetre is built up at the location of the filament-like defects (9).

9. The method according to any one of the preceding claims, characterised in that the perforation line (3) is introduced into the glass element (1) at a location at which at least one of the following conditions applies: - the temperature is between 100 °C and 400 °C; - the temperature is equal to or lower than the strain point of the glass.

10. The method according to any one of the preceding claims, characterised in that the hot processing process comprises at least one of the following processes: - ceramizing the glass element (1) to produce glass ceramics; - forming a glass element into the form of a hollow glass, glass container or glass tubing; - thermal toughening; - firing ceramic inks; - coating the glass element (1).

11. An apparatus (2) for processing glass elements (1), comprising - a device (11) for hot processing the glass elements (1); and - a device (13) for introducing a perforation line (3) into the glass element (1) for separating the glass element (1) along said perforation line (3), wherein said device (13) for introducing a perforation line (3) comprises - an ultrashort pulse laser (7) which is arranged and aligned so as to irradiate a glass element (1) within a region of the apparatus (2) for processing glass elements (1) where the glass element (1) is still at a temperature of at least 100 °C from the heating during the processing in said device (11) for hot processing the glass elements; and wherein - a motion device (15) is provided for moving the point of incidence of the laser beam (7) along a predetermined course of the perforation line (3); wherein the ultrashort pulse laser (7) is adapted to introduce filament-like defects (9) into the glass element (1); and wherein the apparatus (2) for processing glass elements (1) comprises - a cooling device (17), said cooling device (17) comprising a nozzle (20) for emitting a cooling fluid jet (18) or a means for quenching the glass element in a liquid, which is arranged and configured so as to cool the glass element (1) during the introduction of the filament-like defects (9) into the glass element (1) in such a way that a temperature gradient is created which induces a mechanical stress at the filament-like defects (9) such that a breaking force required to separate the glass element (1) along the perforation line (3) is reduced.

12. The apparatus (2) according to the preceding claim, characterised in that the device (11) for hot processing the glass elements (1) comprises a hot forming device (110), in particular for forming glass elements (1) from a glass melt (111).

13. The apparatus (2) according to the preceding claim, characterised in that the hot processing device (11) comprises a hot forming device (110) for drawing a glass element (1) in the form of an elongated glass ribbon (100), wherein the device (13) for introducing a perforation line (3) is adapted for introducing perforation lines longitudinally of the glass ribbon (100), along which strip-shaped edge portions, each having a thickened border (102), can be separated.

14. The apparatus (2) according to any one of claims 12 or 13, characterised in that the hot forming device (110) comprises a device for producing a glass ribbon (100) using a down-draw or up-draw process, an overflow fusion process, a redraw process or a float process; or a device for producing glass tubes, in particular by using Danner process or Vello process.

15. The apparatus (2) according to any one of the preceding claims 11 to 14, characterised in that the device (13) for introducing the perforation line (3) comprises a processing head (130) which directs both the laser beam (5) and the cooling fluid jet (18) onto the glass element (1), such that the point of incidence of the laser beam (5) on the glass element (1) lies within the cooling jet (18).

16. The apparatus (2) according to any one of the preceding claims 11 to 15, wherein the cooling device (17) is arranged such that a cooling fluid jet (18) is directed onto a surface of the glass element (1) which is opposite the surface on which the laser beam (5) is incident.