Method and apparatus for cutting glass sheets

Abstract

The object on which the present invention is based is to reliably separate even thin glass with stable handling. For this purpose, a method is provided in which a glass sheet having a thickness of at most 300 μm is provided and irradiated with a pulsed laser beam of an ultrashort pulse laser, wherein the light intensity of the laser beam in the glass sheet is high enough that the laser beam leaves filamentous damage along the path through which it passes through the glass sheet, and wherein the laser beam and the glass sheet are moved relative to each other such that, under the action of the pulses of the laser beam, filamentous damage is introduced adjacent to each other along a path extending on the glass sheet, and wherein, during the introduction of the filamentous damage, a tensile stress acting on the glass at the filamentous damage and preferably in a direction transverse to the path of the adjacent filamentous damage is applied to at least one surface of the glass sheet such that the glass sheet separates along the path during the introduction of the filamentous damage.

Description

[0001] This application claims priority to German application No. DE102020123928.9, the entire content of which is incorporated herein. In particular, the applicant reserves the right to revert to the disclosure of DE102020123928.9 in this application and / or claim rights to the subject matter based on that disclosure. Field of the Invention

[0002] The present invention generally relates to the cutting of thin glass. In particular, the present invention relates to a method and apparatus for cutting glass by laser irradiation. Background Art

[0003] The separation of thin glass is typically carried out using conventional scribing and breaking processes. These processes have at least two stages. First, surface damage is introduced using a scribing tool (such as a scribe wheel or diamond), and then the glass plate is separated along the surface damage by mechanical bending or the introduction of thermo-mechanical stress (such as by a CO 2 laser).

[0004] A cutting process for introducing cracks using a diamond or similarly shaped engraving tool is known from DE 10 2018 131 179 A1. Using this process, very strong edges can be produced. On the other hand, the diamond as a scribing tool is very sensitive and can be damaged, especially when placed on the glass.

[0005] Laser-induced tension-crack-separation is known from US2013 / 0126576A1, WO2011 / 026074A1, and US6327875B1. These processes are generally unstable for thin glass because it is difficult to establish a large enough temperature gradient between the top and bottom of the glass. In addition, even the smallest temperature gradient can lead to unstable three-dimensional deformation ("bulging"). WO2016 / 156235A1 proposes an asymmetric beam waveform to obtain a steeper temperature gradient. Similarly, WO2016 / 156234A provides a particular beam waveform in which two sub-regions of the laser action area are laterally spaced from a dividing line and frame a portion in the action area through which the dividing line extends, such that the regions of the thin glass near the dividing line and in this spaced portion are heated to a higher degree than the region on the dividing line.

[0006] Furthermore, DE102017100015A1 discloses a method for separating a glass substrate, in which a pulsed laser beam is used to introduce damage into the substrate along a predetermined separation line at a certain distance from each other, wherein the average distance between adjacent damages and the number of laser pulses generating one damage are selected such that the fracture stress for separating the substrate is less than a reference stress, and thereby the edge strength of the separation edge obtained after separation is greater than a second reference stress depending on the corresponding substrate. After introducing the damage, the substrate can be separated along the separation line by applying a tensile force. However, especially for thin substrates, there is a problem that the glass substrate whose strength has been weakened by perforation may separate in an uncertain manner during handling (such as transportation). As a result, in terms of the edge profile, it will separate in an uncontrolled manner, and thus may also lead to a reduction in edge strength. The reason is that thin glass is prone to deformation under the action of handling forces due to its low inherent stiffness, and thus may inadvertently introduce tensile stresses higher than the forces required for cutting. In particular, if these stresses do not act along the pre-prepared line but deviate at an angle from this line, uncontrolled fracture or a reduction in edge strength may occur. Summary of the Invention

[0007] Therefore, the object of the present invention is to reliably separate even thin glass in a stable process. This problem is solved by the subject matter of the independent claims. Advantageous embodiments are specified in the respective dependent claims. Accordingly, a method for separating a glass sheet is provided, wherein

[0008] - a glass sheet with a thickness of at most 300 μm is provided, and

[0009] - the glass sheet is irradiated with a pulsed laser beam from an ultrashort pulse laser,

[0010] - the light intensity of the laser beam in the glass sheet is high enough such that the laser beam leaves filamentous damage along its path through the glass sheet, and

[0011] - the laser beam and the glass sheet are moved relative to each other such that, under the action of the pulses of the laser beam, filamentous damages are introduced adjacent to each other along a path extending on the glass sheet, and wherein

[0012] - during the introduction of the filamentous damages, a tensile stress acting on the glass at the filamentous damages and preferably in a direction transverse to, in particular perpendicular to, the path of adjacent filamentous damages is applied to at least one surface of the glass sheet such that

[0013] - during the introduction of the filamentous damages, the glass sheet separates along the path.

[0014] Preferably, the thickness of the glass sheet is at most 200 μm, more preferably at most 100 μm. In particular, the present invention can also be applied to very thin glass sheets with a thickness of 50 μm or less, especially at most 35 μm. In one embodiment, a glass sheet with a thickness of 30 μm is processed.

[0015] The glass sheet should be understood as a very thin glass plate with low inherent stiffness due to its small thickness.

[0016] Preferably, if the glass of the glass sheet is transparent relative to the wavelength of the laser beam, the laser beam can pass through the glass sheet.

[0017] In addition, the laser beam can be focused with focusing optics. Therefore, due to the focusing, the light intensity of the laser beam inside the glass sheet can become high enough so that the laser beam leaves filamentous damage along its path through the glass sheet.

[0018] Applying a tensile stress during the introduction of the filamentous damage can be to apply the tensile stress while introducing the filaments. However, generally, the tensile stress can be applied during a time period that overlaps with the time period of introducing multiple filaments, so that during this time overlap, the introduction of the filaments and the application of the tensile stress are carried out simultaneously.

[0019] For simplicity, the filamentous damage will hereinafter be referred to simply as filaments. The filamentous damage can be a continuous, thin, open passage. Similarly, there may be only filamentous or more precisely linear shape changes in the material. A hybrid type is also feasible, where cavities or material changes extend along a line. For example, one type can include short damages arranged in rows along a line in a chain-like manner generated by the periodic self-focusing of a strong laser beam.

[0020] Surprisingly, it has been found that the process of perforating or pre-damaging with pulses of an ultrashort pulse laser can be carried out directly continuously with the separation, and thus, these processes can be combined in a defined manner in a common process step. Thereby, perforations are made in the glass while the glass of the glass sheet is subjected to a defined tensile stress. By combining the tensile stress with the perforation and the resulting pre-weakening, the substrate can be weakened and directly separated in a defined manner in a single setup or configuration. Therefore, an ultrashort pulse laser can be used to achieve the usually and desired edge quality from an established separation process in one step.

[0021] Especially under the influence of the tensile stress, usually after introducing new filaments, cracks jump from one filament to the next. Therefore, this not only eliminates the usually two stages of separation with scratches and subsequent fracture. Since the cracks move continuously from filament to filament, it also avoids the cracks crossing the rows of filaments that have already been introduced and then continuing to expand in an uncontrolled manner. This enables good control of the crack progression.

[0022] If the glass sheet is bent to produce a tensile stress transverse to the path, particularly good control of crack propagation will be achieved. For this purpose, the glass sheet is placed on a support having protrusions such that the glass sheet is bent over the protrusions. Preferably, the protrusions are elongate, and the path of the filaments arranged in rows extends along the longitudinal direction of the protrusions.

[0023] The separation of the glass sheet can in particular also be used to customize glass elements having the desired dimensions. Thus, pretreatment can be carried out by separating the glass sheet from the glass ribbon. Then, the separation edge resulting from the separation from the glass ribbon does not have to be of high quality.

[0024] For example, the separation edge does not have to be strictly at right angles to the edge of the glass ribbon. Since the separation line strictly follows the path of the filaments arranged one after another, a high degree of shape accuracy is achieved by laser-supported separation. Thus, in one embodiment of the method, it is provided that a continuous glass ribbon is produced in a thermoforming process, in which the glass sheet is separated from the glass ribbon, and in which the glass element is separated from the glass sheet by introducing filamentous damage and arranging it in rows.

[0025] A particular advantage of the method described herein is the use of straight dividing lines as well as intersecting dividing lines. Basically, curved dividing lines (corner radii) are also conceivable.

[0026] The invention will now be explained in more detail with reference to the accompanying drawings. Description of the Drawings

[0027] Figure 1 An apparatus for separating a glass plate is shown.

[0028] Figure 2 Shows Figure 1 a variant of the apparatus shown in

[0029] Figure 3 Shows Figure 1 a further variant of the apparatus shown, which has a conveying device for the glass sheet.

[0030] Figure 4 A glass sheet separated from a glass ribbon is shown.

[0031] Figure 5 A glass sheet with two perforation paths having different starting points is shown.

[0032] Figure 6 A glass sheet with two intersecting laser beam paths is shown.

[0033] Figure 7 Different beam profiles of the laser beam are shown.

[0034] Figures 8 to 11 A further embodiment of the apparatus for separating a glass sheet is shown. Detailed implementation mode

[0035] In Figure 1 is shown a device 4 for performing the method described herein. Generally, and not limited to what is shown in the specific example, the device 4 for separating a glass sheet 1 having a thickness of at most 300 μm includes

[0036] - an ultrashort pulse laser 3 that irradiates the glass sheet 1 with a pulsed laser beam 5, wherein the glass is transparent with respect to the wavelength of the laser beam 5 such that the laser beam 5 can pass through the glass sheet 1, and

[0037] - a focusing optical device 7 that focuses the laser beam 5 such that the light intensity of the laser beam 5 within the glass sheet 1 becomes high enough so that the laser beam 5 leaves a filamentous damage 9 along its path through the glass sheet 1, and

[0038] - a device 21 for moving the laser beam 5 and the glass sheet 1 relative to each other such that the pulses of the laser beam 5 introduce the filamentous damages 9 adjacent to each other along a path 11 extending on the glass sheet 1, and

[0039] - a device for applying a tensile stress on the glass sheet 1 during the introduction of the filamentous damages 9, wherein the tensile stress acts on the glass at the filamentous damages 9 and in a direction transverse to the path 11 of the adjacent filamentous damages 9 such that during the introduction of the filamentous damages 9, the glass sheet 1 separates along the path 11.

[0040] According to one embodiment, the ultra-short pulse laser 3 can be operated in a so-called burst mode. In this operating mode, the laser pulses are not emitted as single pulses, but as a series of pulses emitted in rapid succession. These pulses together form a pulse packet, i.e., a so-called burst. The pulse frequency within the burst is significantly higher than the repetition frequency of the burst. The energy of such a pulse packet is typically slightly higher than that of a single pulse in normal single-shot operation. However, the pulses within the burst contain much less energy than a single pulse. The pulse energy within the burst does not have to be constant, but can also decrease or increase. A suitable laser for the method described herein is, for example, a neodymium-doped yttrium aluminum garnet laser operating at a wavelength of 1064 nm. According to one embodiment, the ultra-short pulse laser 3 operates at a repetition frequency in the range from 1 kHz to 1000 kHz, preferably in the range from 10 kHz to 400 kHz, and most preferably in the range from 30 kHz to 200 kHz. The repetition frequency and the scanning speed at which the laser beam 5 moves above the glass sheet 1 along the provided path 11 can be selected such that a desired distance between adjacent filamentary damages 9, also referred to as "pitch", is achieved. The suitable pulse duration of the laser pulses is in the range of less than 100 picoseconds, preferably less than 20 picoseconds. The typical average power of the ultra-short pulse laser 3 is preferably in the range from 50 to 500 watts. According to an advantageous development of the invention, it is advantageous to use a pulse energy of more than 400 microjoules in the burst to generate filamentary damages 9 in the glass, and furthermore, it is advantageous for the total burst energy to exceed 500 microjoules.

[0041] The filamentary damages 9 are preferably spaced apart from each other by a certain distance, i.e., the pitch is in the range from 1 μm to 10 μm, preferably in the range from 3 μm to 8 μm.

[0042] When the pulsed laser 3 operates in burst mode, the repetition frequency is the repetition frequency at which the burst is emitted. Generally, the pulse duration is substantially independent of whether the laser operates in single-pulse mode or burst mode. Thus, the burst typically has a pulse length similar to that of the pulses in single-pulse mode. The frequency of the individual pulses within the burst can be in the range from 15 MHz to 90 MHz, preferably in the range from 20 MHz to 85 MHz, and is, for example, 50 MHz. The number of pulses in the burst can be between 2 and 10 pulses, for example 6 pulses. The preferred repetition frequency, i.e., the frequency at which the burst repeats, is in the range from 50 kHz to 500 kHz.

[0043] As shown in the example, the device 4 preferably includes a support 15 on which the glass sheet 1 is placed. The support 15 can have a support surface 16 with protrusions such that the glass sheet 1 is bent over the protrusions. The tensile stress is generated by the bent portion of the glass sheet 1 over the protrusions.

[0044] According to one embodiment, the support 15 includes a support surface 16 on which the rod 17 is placed. The rod 17 forms an elongated protrusion, and the placed glass sheet 1 is bent on the protrusion.

[0045] The bending of the glass sheet 1 on the protrusion (such as the rod 17) results in a bending axis 13 extending in the longitudinal direction of the protrusion. The direction of the tensile stress on the glass surface caused by the bending extends transversely to, in particular perpendicular to, the bending axis 13, and thus also transversely to the longitudinal axis of the protrusion.

[0046] The device 21 for moving the laser beam 5 and the glass sheet 1 relative to each other is represented by the crossbeam in Figure 1 where the ultrashort pulse laser 3 together with the focusing optics 7 moves on the crossbeam above the glass sheet 1. As an alternative or in addition to the movement of the laser, the glass sheet 1 can also be moved relative to the fixed laser beam 5 in order to guide the laser beam 5 along the provided path 11 above the surface of the glass sheet 1. In order to achieve the spontaneous and controllable separation of the glass sheet 1 along the predetermined path 11 of the aligned filamentous damages 9, the path 11, and thus the moving direction of the laser beam 5 above the glass sheet 1, extends in the longitudinal direction of the protrusion, or more generally, along the bending axis 13 of the bent portion of the glass sheet 1. Due to the bending on the rod 17, the bending axis 13 of the bent portion is also parallel to the longitudinal axis of the rod 17, or more generally, parallel to the longitudinal axis of the elongated protrusion.

[0047] By introducing perforations made of filaments 9 arranged in rows along the tensile stress lines generated by the bent portion, the glass sheet 1 is immediately separated in the perforation process step. Separation can also occur if the geometric bending line and the perforation line deviate from each other within the usual manufacturing tolerances. Preferably, the deviation is in the range of less than 1 mm, preferably less than 0.5 mm, and particularly preferably less than 0.3 mm.

[0048] It is advantageous to produce a defined bent portion, which is ensured by placing the bent portion on a support of a corresponding shape. In addition, it is generally advantageous that the laser beam 5 impinges on the glass substantially perpendicularly, thereby forming perforations or laser filaments in the glass. Preferably, the deviation of the incident direction from the direction perpendicular to the surface is preferably less than 5°.

[0049] It is assumed that the fracture occurring during separation jumps from one filamentous damage 9 to the next along the path 11. This ensures that the fracture does not overtake the laser beam 5 guided above the glass sheet 1, because the fracture stops at the last introduced filament 9 due to the absence of another filament in front. If the fracture were to overtake a row of continuously introduced filaments, the fracture edge might exhibit an uncontrolled process due to the lack of guidance along the filaments.

[0050] One parameter in the context of the separation process described herein is the tensile stress in the glass sheet 1, which is applied, for example, by rods 17 of different diameters. Thus, a round rod with D = 6 mm and a 30-μm-thick glass of type AS87 can generate a maximum tensile stress of 360 MPa, which is an order of magnitude higher than the usual separation strength (usually 15 - 35 MPa, depending on the laser process). Adjusting the laser line and mechanical bending in one step enables a controllable separation process for very thin glass.

[0051] Generally, not limited to the illustrated examples or even to generating tensile stress through bends, according to one embodiment, a tensile stress is provided that is generated on at least one surface of the glass sheet 1 in the region of path 11 and is at least 75 MPa, preferably at least 150 MPa, and most preferably at least 250 MPa. On the other hand, too high a tensile stress can be disadvantageous as it may lead to self-fracture. Preferably, the maximum tensile stress applied to the glass sheet 1 is at most 750 MPa.

[0052] The following table lists exemplary embodiments with which the influence of the diameter of the rod 17 on the quality of the separation edge generated in the glass sheet 1 was investigated:

[0053] Test number Rod diameter [mm] Quality of the fracture edge Comment 1 2 Good 2 2 Good 3 2 Bad Lateral offset (2mm) 4 2 Bad Lateral offset (1mm) 5 2 Good 6 2 Medium 7 2 Medium 8 3 Very good 9 3 Good 10 3 Good 11 4 Very good 12 4 Good 13 6 Good 14 6 Very good 15 6 Very good 16 8 Good 17 8 Very good

[0054] The experiments were carried out on a 30-μm-thick glass sheet 1 made of AS87 glass. According to the results listed in the table, the best edge is obtained using a rod with a diameter of 6 mm.

[0055] According to an alternative or additional embodiment, the glass sheet 1 is bent on a step 18 in the support 15, where a filamentary damage 9 is introduced along a path 11 that extends along the step 18. Since the substrate forms a ramp on the step 18, a defined tensile stress is exerted. According to this embodiment, Figure 2 shows a variant of the device 4 according to Figure 1 This device can be advantageous for continuously separating the glass sheet 1 with parallel incisions by moving the glass sheet 1 forward over the step 18 after the separation process (subsequent to another separation).

[0056] Figure 3 shows Figure 1 a further variant of the illustrated device, which further variant has a feed device or conveying device 23. The glass sheet 1 is moved by this feed device or conveying device 23. The principle of this embodiment is based on the fact that the conveying device 23 is designed such that the glass sheet 1 is bent on the conveying device 23, where the bending axis 13 of the bend of the glass sheet 1 is oriented transversely to, in particular perpendicular to, the feed direction 24 of the conveying device 23. The bending of the glass sheet 1 is achieved in particular by the arrangement and design of various conveying elements. Figure 3The example shown includes two conveyor belts 25 as conveying elements. These two conveyor belts are arranged at different levels so as to form steps similar to Figure 2 the embodiment shown, on which the glass sheet 1 extends.

[0057] Figure 4 Illustrates a typical application of the method. The method or the device 4 for implementing the method can be used respectively to remove the glass element 2 from the glass sheet 1. Therefore, the glass sheet 1 has a bead 19. The bead 19 represents a thickened edge region on two opposite sides. Such a glass sheet 1 is obtained when the glass sheet 1 is separated from the glass ribbon as multiple parts, where the glass ribbon is produced in a continuous thermoforming process. In a preferred embodiment, the glass ribbon is produced in a down-draw process, where the glass ribbon is pulled out from a downward-opening nozzle. The bead 19 is caused by the soft glass that is still thermally shrinking after being pulled out from the nozzle. This shrinkage mainly occurs at the edges of the glass ribbon. Due to the bead 19, the glass sheet 1 has a higher stiffness in the case where the bending axis 13 of the bending portion intersects the bead 19 compared to the case where the bending axis 13 of the bending portion is parallel to the longitudinal direction of the bead 19.

[0058] The method can be particularly used to produce glass elements 2 that are precisely defined in terms of shape and size. As can be seen from Figure 4 the edges 98, 99 of the glass sheet 1 that intersect the bead 19 are not exactly at right angles to the edges 100, 101 with the bead. In particular, such a glass sheet 1 is obtained if the glass sheet 1 is separated from the continuous glass ribbon by introducing short scratches only at the edges of the glass ribbon. Then the edges 98, 99 are produced by the fracture starting from the scratches in the glass ribbon, so the scratches are not necessarily perfectly at right angles to the two longitudinal edges of the glass ribbon. On the other hand, such a pre-cutting method allows for rapid and rough cutting, thus enabling a high feed rate of the glass ribbon. Therefore, without being limited to the examples described herein, in an embodiment of the method, a continuous glass ribbon is produced in a thermoforming process, where the glass sheet 1 is separated from the glass ribbon by introducing scratches at the edges of the glass ribbon, and where the glass sheet 1 is separated by a fracture that starts from the crack and transversely cuts the glass ribbon. Then, as described, the glass element 2 can be separated from the glass sheet 1 by introducing the filamentous damage 9 along one or more predetermined paths 11 and arranging them in rows.

[0059] In Figure 4In the example shown, a path 11 extending in the outer contour of the glass sheet 1 is divided into smaller paths or portions 111, 112. The path 11 as a whole encompasses the contour of the glass element 2 to be removed from the glass sheet 1. To facilitate bending of the glass sheet 1 to generate tensile stress for separation during perforation with a laser beam 5, it is generally advantageous to first separate the glass sheet 1 at the portion 111 extending along the bead edge 19, and then separate the glass sheet 1 at the portion 112 extending transversely to the bead edge 19. That is, the glass sheet 1 can be easily bent on the protrusion extending parallel to the bead edge 19, while in the case where the protrusion intersects the bead edge 19, the very hard bead edge 19 also has to bend. Preferably, the portion 111 extending along the bead edge 19 is guided along at least one edge of the glass sheet 1. In the example shown, the two portions 111 even extend across the two lateral edges 98, 99 of the glass sheet 1. If the bead edge 19 is separated, the glass sheet 1 can also be easily bent in a direction perpendicular to the bead edge 19. Without being limited to the example shown, an embodiment generally provides a glass sheet 1 that includes two opposite edges 100, 101, the two opposite edges 100, 101 including bead edges 19 in the form of thickened regions extending along these edges, wherein the glass sheet 1 is first separated along two paths 111 that extend in the direction of the edges 100, 101 with the bead edges 19, and wherein the glass sheet 1 is then separated along at least one additional path 112 that extends transversely to the two paths 111 in the edge direction. Preferably, as shown, the separation also occurs along two paths 112 that extend transversely to the edges 100, 101 with the bead edges 19. The paths 111 in the direction of the edges 100, 101 with the bead edges 19 preferably extend parallel to these edges 100, 101. However, depending on the desired shape of the glass element 2 separated in this way, these paths can also be at an angle to the edges. However, in this case, the path 112 or its extension preferably does not intersect the bead edge 19 to avoid the bead edge 19 also having to bend and generating tensile stress. Similarly, as Figure 4 shown, the path 112 extending transversely to the edges 100, 101 with the bead edge 19 extends perpendicular to the edges 100, 101. Using the paths 111 or 112 (one extending parallel and one extending perpendicular), a rectangular glass element 2 can be separated from the glass sheet 1 in this way.

[0060] For stable process guidance, it is generally advantageous that the tensile stress at the cutting edge of the glass sheet 1 (e.g., a part of the glass ribbon with a beaded edge 19) does not exceed the edge strength present there, so that uncontrollable fractures do not occur. The edge strength can be determined by performing fracture tests on samples produced in a similar manner. The average value of the tensile stress at which the sample fractures can be used as the edge strength. Generally, not limited to the examples shown in the drawings, the tensile stress applied to the glass sheet 1 is thus provided to be lower than the average value of the tensile stress, i.e., the average fracture stress at which tearing occurs at one edge of the glass sheet 1. Preferably, the applied tensile stress does not exceed about 2 / 3 of the average fracture stress, preferably not more than half of the average fracture stress.

[0061] During the use of the ultrashort pulse laser, this method can especially have two versions. Referring to Figure 5 These variants of the method are explained in more detail. Figure 5 A glass sheet 1 with two perforated paths 111, 112 (i.e., filamentous damage 9 arranged in a row) is shown. The two paths 111, 112 differ in the starting point 113. According to an embodiment of the method, the path of the laser beam crosses two opposite edges 100, 101 of the glass sheet 1. Thus, perforations (laser lines or paths 11) are continuously introduced on the edge of the glass sheet 1, i.e., having a forward stroke and a subsequent stroke. However, it is possible that, depending on the cutting process, the stress at the blank glass sheet 1 or at the edge of the glass sheet 1 may be uncertain, such that the fracture starts in an uncertain manner. However, this continuous perforation implemented in the example of the path 111 is advantageous in order to produce a continuous, clearly defined separating edge.

[0062] Another possibility is the applied perforation implemented through the path 112. Thus, the starting point 113 of the path 112 of the laser beam is positioned on the glass sheet 1 and is thus at a certain distance from all the edges of the glass sheet 1. Thus, the perforation (laser line or path 11) initially starts within the glass sheet 1 and preferably only has a corresponding subsequent stroke. Then, in this case, the first unperforated part is unexpectedly and usually separated in a controlled manner by itself due to the fracture mechanism occurring in the remaining area under tensile stress. According to an embodiment, the distance to the nearest edge is 1 - 2 mm. Then preferably, at the end, the laser beam is guided above one of the edges of the glass sheet 1, so that the path 112 of the laser beam accordingly crosses one of the edges (in this case the edge 101).

[0063] The two embodiments can also be combined, especially two forms of the paths 111, 112 can be introduced. In this way, a first discontinuous cut with a starting point on the glass can be introduced. Then, a second path crossing two opposite edges can cross this discontinuous cut or path and thus separate the glass element 2. This embodiment is inFigure 6 is shown. In this case, the glass sheet 1 does not therefore have to break spontaneously between the starting point 113 of the path 112 and the edge 100.

[0064] The separability of the glass sheet 1 and thus the tensile stress to be applied can be influenced by a plurality of parameters, such as the spacing, i.e., the mutual spacing of the filamentous damages 9. One possibility of reducing the tensile stress is to set a specific beam profile of the laser beam 5. According to one embodiment, a focusing optical device 7 is provided for this purpose. The focusing optical device 7 produces a beam profile of the laser beam 5 in the glass sheet 1. This beam profile is greater in the direction along the path 11 than in the direction perpendicular to this path. By irradiating the glass sheet 1 with the laser beam 5 having such a beam profile, a preferred direction of the microcracks can be produced, which promotes separability or allows separation at a lower tensile stress. Without loss of generality, Figure 7 Examples of different beam profiles of the laser beam 5 are shown, which, as described above, extend more in the direction of the path 11 than in the direction perpendicular to the path 11. The local image (a) shows the laser beam 5 having an elliptical beam profile, the major semi-axis of which is oriented in the direction of the path 11. In the beam profile according to the local image (b), the beam profile is divided into two separate light spots, which are spaced apart in the direction along the path 11. Due to this distance, the beam profile also extends more in the direction of the path 11 than in the direction perpendicular to the path 11. A beam profile that is asymmetric with respect to the mirror axis perpendicular to the path 11 can also be provided. An example related thereto is shown in the local image (c). The beam profile has an elongated droplet shape along the path 11. For example Figure 7 the elongated beam profiles exemplarily shown in can promote separation, especially in the case of a non-straight path 11.

[0065] Figures 8 to 10 Another embodiment of the device 4 for separating the glass sheet 1 is shown. Figure 8 is Figure 1 a variant of the example shown. Figure 8 is an example of an embodiment in which a support 15 with an elongated protrusion is provided, where the protrusion has an interruption in the region of the incidence point of the laser beam 5, such that the glass sheet 1 positioned on the support 15 is exposed at the incidence point of the laser beam 5. In Figure 8 the example of, the interruption is achieved by a groove 27 in the rod 17. The glass sheet 1 spans the groove 27. In this way, the laser beam 5 does not directly impinge on the rod 17 after passing through the glass sheet 1. This avoids damage to the rod 17.

[0066] In the exemplary embodiment shown currently, the bent portion of the glass sheet 1 generates tensile stress on the side of the glass sheet 1 facing the ultra-short pulse laser 3 or in the incident direction of the laser beam 5. However, it is generally also feasible to bend the glass sheet 1 such that tensile stress is generated on the side of the glass sheet 1 facing away from the ultra-short pulse laser 3. Figure 9 An example thereof is shown. Generally, without being limited to the example shown, in one embodiment, it is provided that the side of the glass sheet 1 facing the ultra-short pulse laser 3 is bent in a concave manner. To achieve this, a support 15 having a gap 29 can generally be provided, where the glass sheet 1 arches into the gap 29. In the example shown, a support 15 in the form of a conveying device or a feeding device 23 is provided, and the conveying device or the feeding device 23 has two conveyor belts 25 separated by the gap 29. The glass sheet 1 sags at the gap 29 and thus arches into it. One advantage of this embodiment is that when the glass sheet 1 sags due to its own weight, the tensile stress is distributed over a wide area on the opposite side of the glass sheet 1, so that this arrangement is less sensitive to the position of the path 11 or the incident point of the laser beam 5. In this way, a non-linear path or a separated edge can also be achieved in a simple manner. By moving the conveyor belts 25 in the opposite direction or more generally moving the moving device, the bending radius of the glass sheet 1 and thus the tensile stress can also be adjusted. However, in this case, the vertical position of the glass sheet 1 also changes relative to the laser beam 5.

[0067] In the embodiment described above with reference to the drawings, tensile stress is generated on at least one surface of the glass sheet 1 by bending the glass sheet 1. When bending, tensile stress is generated on the convex bending side, while compressive stress is generated on the opposite concave bending side. However, it is also possible to stretch the glass sheet 1 to generate tensile stress. Then, tensile stress is applied to the opposite two sides. It is obvious to those skilled in the art that the stretching of the glass sheet 1 advantageously occurs in a direction transverse to, preferably perpendicular to, the filament path.

[0068] Figure 10 An apparatus for implementing this embodiment is shown. A stretching device 30 (represented by two clamps in the figure) is provided. The stretching device 30 stretches the glass sheet 1 transverse to the path 11, thereby generating tensile stress on two opposite surfaces of the glass sheet 1.

[0069] Figure 11Another variant of the device 4 for separating glass sheets 1 is shown in a cutaway perspective view. With this device 4, the glass sheet 4 can be separated along a non-linear path 11. Generally, the device is based on the use of a stamp 32 and a protrusion, where the stamp 32 and the protrusion are offset from each other and placed together, with the glass sheet 1 being bent between these placed-together elements. In the example shown, the stamp 32 is plate-shaped and the protrusion is a ring 34. This creates an annular tensile stress zone, where the tensile stress acts in the radial direction along the glass surface. In this way, the glass sheet 1 can be separated along a generally annular path 11, such as along a circular path as shown. It is obvious to a person skilled in the art that the method and device are not limited to the specific exemplary embodiments described here, but can be modified within the scope of the subject matter of the appended claims. In particular, different embodiments can also be combined with each other. For example, Figure 3 the transport device 23 provided in Figure 1 the example can also be provided in

[0070] Reference numeral

[0071] 1 glass sheet

[0072] 2 glass element

[0073] 3 ultrashort pulse laser

[0074] 4 device for separating glass sheets

[0075] 5 laser beam

[0076] 7 focusing optics

[0077] 9 filamentary damage

[0078] 11, 111, 112 path

[0079] 13 bending axis

[0080] 15 support

[0081] 16 support surface

[0082] 17 rod

[0083] 18 step

[0084] 19 bead edge

[0085] 21 moving device

[0086] 23 Conveying equipment

[0087] 24 Feed direction

[0088] 25 Conveyor belt

[0089] 27 Groove

[0090] 29 Gap

[0091] 30 Pulling device

[0092] 32 Die

[0093] 34 Ring

[0094] 98, 99, 100, 101 Edges of the glass sheet

[0095] 113 Starting points of paths 11, 111, 112

Claims

1. A method for separating a glass sheet, wherein - a glass sheet (1) with a thickness of at most 300 μm is provided, and - the glass sheet (1) is irradiated with a pulsed laser beam (5) of an ultrashort pulse laser (3), - the light intensity of the laser beam (5) within the glass sheet (1) is high enough such that the laser beam (5) leaves filamentous damages (9) along its path through the glass sheet (1), and - the laser beam (5) and the glass sheet (1) are moved relative to each other such that, under the action of the pulses of the laser beam (5), filamentous damages (9) are introduced along a path extending on the glass sheet (1) at a spacing within the range of 1 μm to 10 μm from each other, and wherein - during the introduction of the filamentous damages (9), a tensile stress acting on the glass is applied to at least one surface of the glass sheet (1) at the filamentous damages (9) and in a direction transverse to the path of adjacent filamentous damages (9), such that - during the introduction of the filamentous damages (9), the glass sheet (1) separates along the path.

2. The method according to claim 1, characterized in that the fracture caused by the separation jumps from one filamentous damage (9) to the next along the path.

3. The method according to claim 1 or 2, characterized in that the glass sheet (1) is bent to generate a tensile stress oriented transverse to the path.

4. The method according to claim 3, characterized by at least one of the following features: - the glass sheet (1) is placed on a support (15) having a protrusion such that the glass sheet (1) bends over the protrusion, - a support (15) with a support surface (16) is provided, a rod (17) is placed on the support surface, the rod (17) forms an elongated protrusion, and the placed glass sheet (1) bends over the protrusion, - the glass sheet (1) bends on a step (18) in the support (15), the glass sheet (1) is placed on the support (15), wherein the filamentous damages (9) are introduced along a path extending along the step (18), - the glass sheet (1) is moved by means of a conveying device (23), wherein the conveying device (23) is designed such that the glass sheet (1) bends on the conveying device (23), and wherein the bending axis (13) of the bent portion of the glass sheet (1) is oriented transverse to the feed direction (24) of the conveying device (23).

5. The method according to claim 3, characterized in that the glass sheet (1) is moved by means of a conveying device (23), wherein the conveying device (23) is designed such that the glass sheet (1) bends on the conveying device (23), and wherein the bending axis (13) of the bent portion of the glass sheet (1) is oriented perpendicular to the feed direction (24) of the conveying device (23).

6. The method according to claim 1 or 2, characterized in that A continuous glass ribbon is produced in a thermoforming process, in which the glass sheet (1) is separated from the glass ribbon, and in which glass elements (2) are removed from the glass sheet (1) by introducing the filamentous damage (9) and arranging it in rows.

7. The method according to claim 1 or 2, characterized by at least one of the following features: - In the region of the path, a tensile stress of at least 75 MPa is generated on at least one surface of the glass sheet (1), - The maximum tensile stress applied to the glass sheet (1) is at most 750 MPa, - The applied tensile stress is at most 2 / 3 of the average fracture stress at the edge of the glass sheet (1), - The glass sheet (1) is pulled transversely to the path by a pulling device (30), thereby generating tensile stresses on two opposite surfaces of the glass sheet (1).

8. The method according to claim 1 or 2, characterized by at least one of the following features: - In the region of the path, a tensile stress of at least 150 MPa is generated on at least one surface of the glass sheet (1), - The applied tensile stress is at most half of the average fracture stress at the edge of the glass sheet (1).

9. The method according to claim 1 or 2, characterized in that: In the region of the path, a tensile stress of at least 250 MPa is generated on at least one surface of the glass sheet (1).

10. The method according to claim 1 or 2, characterized by one of the following features: - The path of the laser beam (5) intersects two opposite edges (100, 101) of the glass sheet (1), - The starting point (113) of the path of the laser beam is located on the glass sheet (1) such that the starting point is spaced from all edges of the glass sheet (1), - The glass sheet (1) is irradiated with a laser beam (5), and the beam profile of the laser beam in the glass sheet (1) is longer in the direction along the path than in the direction perpendicular to the path.

11. The method according to claim 1 or 2, characterized in that, A glass sheet (1) including two opposite edges is provided, the edges including bead edges (19) in the form of thickened regions extending along the edges, wherein the glass sheet (1) is first separated along two paths extending in the direction of the edges with bead edges (19), and then the glass sheet (1) is separated along at least one additional path extending transversely to the two paths in the direction of the edges.

12. An apparatus (4) for separating a glass sheet (1) having a thickness of at most 300 microns, the apparatus (4) comprising: - An ultrashort pulse laser (3) that irradiates the glass sheet (1) with a pulsed laser beam (5), wherein the glass is transparent with respect to the wavelength of the laser beam (5) such that the laser beam (5) can pass through the glass sheet (1), and - A focusing optical device (7) for focusing the laser beam (5) such that the light intensity of the laser beam (5) within the glass sheet (1) becomes high enough to leave a filamentary damage (9) along the path through which the laser beam (5) passes through the glass sheet (1), and - A device (21) for moving the laser beam (5) and the glass sheet (1) relative to each other such that the pulses of the laser beam (5) introduce filamentary damages (9) spaced apart from each other by a spacing within the range of 1 μm to 10 μm along a path extending on the glass sheet (1), and - A device for applying a tensile stress on the glass sheet (1) during the introduction of the filamentary damages (9), wherein the tensile stress acts on the glass at the filamentary damages (9) and in a direction transverse to the path of the adjacent filamentary damages (9) such that the glass sheet (1) separates along the path during the introduction of the filamentary damages (9).

13. The device (4) according to claim 12, characterized in that at least one of the following features: - The device (4) includes a support (15) having a protrusion such that the glass sheet (1) placed on the support bends on the protrusion, - The device (4) includes a support (15) having a step (18) such that the glass sheet (1) placed on the support bends on the step (18), - The device (4) includes a conveying device (23), wherein the conveying device (23) is designed such that the glass sheet (1) bends on the conveying device (23) such that the bending axis (13) of the bent portion of the glass sheet (1) is transverse to the feed direction (24) of the conveying device (23), - A pulling device (30) is provided, which pulls the glass sheet (1) transversely to the path, thereby generating a tensile stress on two opposite surfaces of the glass sheet (1).

14. The device (4) according to claim 12, characterized in that the device (4) includes a conveying device (23), wherein the conveying device (23) is designed such that the glass sheet (1) bends on the conveying device (23) such that the bending axis (13) of the bent portion of the glass sheet (1) is perpendicular to the feed direction (24) of the conveying device (23).

15. The device (4) according to any one of claims 12 to 14, characterized in that a focusing optical device (7) that generates a beam profile of the laser beam (5) in the glass sheet (1), the beam profile being longer in the direction along the path than in the direction perpendicular to the path.

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