COMPLEMENTARY PARTS OF A PLAN GLASS ELEMENT

Description

[0001] The description generally discloses the laser-assisted separation of a section from a planar glass element. Specifically, the description relates to the laser-assisted separation of a section from the interior of a planar glass element. The invention relates to the product manufactured using the laser process.

[0002] WO 2012 / 006736 A2 discloses that irreversible damage in the form of filaments can be caused in a glass substrate using high-energy laser pulses, and that the sequence of such damage within the glass enables its separation. A filament is formed by an ultrashort laser pulse, during which self-focusing occurs within the glass due to the Kerr effect until the energy density at a point becomes so high that a plasma is ignited. This results in a plasma explosion, causing irreversible damage to the glass around the plasma point of origin. Further radiation emanates from this point, undergoing self-focusing and culminating in another plasma explosion. This effect is repeated multiple times, depending on the intensity. The energy decreases across the entire thickness of the glass, meaning the initial plasma spots have the highest energy and also produce the most extensive damage.

[0003] Document US 2014 / 027951 A1 concerns a method for separating brittle materials such as glass, ceramics, or sapphire using laser radiation. The method can separate thin substrates with a thickness of less than 500 µm.

[0004] Document US 2015 / 165560 A1 concerns a laser process that enables the removal of an inner piece from a glass substrate. The process is used to create holes in a thin glass substrate with a thickness of 0.7 mm.

[0005] To remove an inner contour, it is proposed to create additional parting lines and break off individual pieces. An alternative embodiment involves melting and thereby removing the inner contour by heating it.

[0006] Document US 2015 / 166393 A1 also concerns a laser-assisted method for removing a piece from a glass element. The glass element has a thickness of 0.4 or 0.7 mm.

[0007] Singulation can be achieved by applying a bending force. Another embodiment provides an additional CO2 laser that traces the separation line and locally generates thermal stresses, which are intended to lead to a gradual separation.

[0008] Finally, document EP 2 754 524 A1 relates to a method for laser-based processing of planar substrates made of glass or conductor wafers using a laser source. The material is separated along the separation line either by the material's inherent stress or by applied forces.

[0009] Document US 2015 034613 describes a method for introducing continuous laser filaments into transparent materials using focused laser pulses. The laser pulses are focused to generate sufficient energy density within an extended area of ​​the material to support the formation of a continuous filament without causing optical breakthrough. Filaments formed using this method can reach lengths of up to 10 mm.

[0010] Document US 2015 118522 A1 also discloses a non-ablative process that describes filamentation using pulse bundles from ultrashort pulse lasers. This process allows, for example, glass blanks to be cut so precisely that the edges of the blank do not need to be ground.

[0011] DE 10 2012 110 971 A1 describes a method for preparing transparent workpieces for separation, in which filament structures extending transversely through the workpiece are generated by ultrashort laser pulses along a separation line. The material is thereby perforated and pre-damaged along this separation line. In a subsequent step, the workpiece is separated.

[0012] If specific sections of a workpiece need to be completely separated, the material is typically divided into two distinct areas by the dividing line. After the material has been filamented along this dividing line, applying a suitable tension in a subsequent step allows the material to be cut along the resulting predetermined breaking line, i.e., along the dividing line, resulting in the separated section and a remaining main part. The separated section can typically be referred to as the inner part, and the remaining main part as the outer part.

[0013] If the dividing line is straight, the subsequent separation after laser processing is straightforward. Separation becomes more difficult, however, if the dividing line is curved, has several sections at angles to each other, or even forms a closed line. The latter case occurs, for example, when an internal contour or a hole is to be created. This is the case, for instance, when a window is to be cut into a glass pane. It also occurs when a glass part is to be produced whose outer contour is completely defined by the dividing line.

[0014] Separating glass along generally curved, sectionally angled or even closed dividing lines is therefore difficult because a sufficient bending moment cannot easily be exerted on the glass at the dividing line.

[0015] One method for cutting internal contours from planar substrates can be found in EP 2 781 296 A1. In the process described therein, after crack lines have been introduced along a contour line (contour definition step), the section to be separated from the substrate is thermally deformed or melted using high laser power (material deformation or ablation step), making it easier to separate from the substrate. To aid separation, additional crack lines, such as spiral or V-shaped ones, can be introduced into the section to be removed, allowing it to be extracted in smaller pieces. Disadvantages of this method include the high cost, which reduces its economic benefit, and the destruction of the section to be removed, which, due to its precise fit with the remaining main part of the substrate, may be of interest.Further disadvantages of destroying the section include the resulting particles and splinters, and the increased cleaning effort.

[0016] The present invention is therefore based on the objective of enabling an efficient and clean, in particular splinter-free, separation of a section from a planar glass element along non-straight dividing lines, so that neither the separated section nor the remaining main part of the glass element is further damaged.

[0017] One aspect of the task is to enable such separation of internal sections along closed dividing lines.

[0018] Another aspect of the task is to enable such separation while minimizing the risk of harmful cracking both in the separated section and in the remaining main part of the glass.

[0019] The problem is already solved by the subject matter of the independent claims. Advantageous embodiments and further developments of the invention are given in the respective independent claims.

[0020] The disclosed method for separating a section from a planar glass element along a designated separation line, which divides the glass element into a section to be separated and a main part to remain, is based on the creation of filament-shaped defects in the volume of the glass element side by side along the separation line, and the defects are created by laser pulses of an ultrashort pulse laser, wherein the material of the glass element is transparent to the laser pulses, and the laser pulses generate a plasma in the volume of the glass element which causes the filament-shaped defects, and the points of impact of the laser pulses on the glass element are moved across its surface along the separation line.and after the insertion of the filament-shaped defects arranged side by side along the separation line, the glass element in the area of ​​the main part is heated and expanded and / or cooled and contracted in the area of ​​the section, so that the section detaches from the main part along the separation line at the adjacent filament-shaped defects, with the section and the main part each remaining intact.

[0021] The expansion of the main part and / or the contraction of the sub-part causes the sizes of these parts to change relative to each other. For example, when the sub-part cools, it shrinks compared to the main part. This relative change in size causes the sub-part to separate from the main part.

[0022] Preferably, after the insertion of filament-shaped defects arranged side by side along the separation line, a laser beam, preferably from a carbon dioxide laser, is moved across the surface of the glass element along the separation line, thus inducing local tensile stresses in the glass along the separation line to cause cracking between adjacent filament-shaped defects. This process step is also referred to as a cleaving step. This cleaving step can also be supported by local cooling after heating to increase the tensile stresses generated in the material.

[0023] A cleaving step serves for pre-separation. The glass element is preferably irradiated with a CO₂ laser along the separation line to generate thermomechanical stresses in the glass element at the separation line. This can create a crack formation along the separation line that connects the filament-like defects, thus resulting in at least partial separation along the separation line, although generally without the segment detaching from the main part. Therefore, the cleaving step is preferably carried out before the process step of heating the area of ​​the main part and / or cooling the area of ​​the segment.

[0024] Both the filament structures themselves and additional cracks in the material caused by a cleaving step represent pre-damage in the material that runs along the separation line.

[0025] The invention provides that the main part and the sub-section are each retained as wholes. An advantage of retaining the main part and the sub-section as wholes is that both parts can be reused. Depending on the purpose for which the separation process is used, either the main part, the sub-section, or both parts may be the focus of interest. If the main part is of primary interest, retaining the sub-section is advantageous because fewer remnants and splinters are produced, and the sub-section can be reused as raw material without having to be melted down. If both parts are of interest, an advantage can lie in the precise complementary shape of the two parts. Furthermore, the process effort is significantly reduced compared to a process in which a part to be separated is divided into several smaller pieces.

[0026] The precision separation process used for the invention, in which defined damage is created in a material in the smallest space by laser pulses of an ultrashort pulse laser, is based on the local destruction of the material in the interaction zone with the laser light with the creation of closely spaced submicron hollow channels, i.e. hollow channels with diameters of less than 1 micrometer.

[0027] The filament-shaped defects created by the laser pulses preferably have a length of at least 200 micrometers, and particularly preferably at least 500 micrometers. Suitable pulse energies and durations are selected for this purpose. The specified minimum lengths of the filament-shaped defects are advantageous because they facilitate the removal of the section.

[0028] Operating the ultrashort pulse laser in so-called burst mode is particularly advantageous for generating long, filament-shaped lesions. In this operating mode, the laser pulse is not emitted as a single pulse, but as a sequence of pulses emitted in quick succession, which together form a pulse packet, a so-called burst. Accordingly, a further development of the invention provides for operating the ultrashort pulse laser by emitting laser pulses sequentially in the form of bursts or pulse packets, with each of these bursts preferably generating one of the filament-shaped lesions.

[0029] Such a pulse packet generally has a slightly higher energy than a single pulse in typical single-shot operation. However, the individual pulses within a burst contain significantly less energy than a single pulse. Furthermore, it is typical for the pulse energies of the individual pulses within a burst to decrease.

[0030] A suitable laser source according to the present invention is a neodymium-doped yttrium aluminum garnet laser with a wavelength of 1064 nanometers. The laser source operates, in particular, at a repetition rate between 10 kHz and 120 kHz, preferably between 30 kHz and 110 kHz, and most preferably between 35 kHz and 105 kHz. The scan speed can preferably be selected such that, depending on the repetition rate, the distance between adjacent filamentous defects is in the range of 4 micrometers to 10 micrometers.

[0031] The suitable pulse duration of a laser pulse is in the range of less than 100 picoseconds, preferably less than 10 picoseconds. The pulse duration can also be less than 1 picosecond. The typical power of the laser source is particularly advantageously in the range of 40 to 100 watts. To achieve the filament-shaped damage, a pulse energy of more than 200 microjoules is used in the burst, and furthermore advantageously a total burst energy of more than 500 microjoules.

[0032] When an ultrashort pulse laser is operated 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 or burst mode. The pulses within a burst typically have a similar pulse length to a single pulse in single-pulse mode.

[0033] In the microperforation method used for the invention, apart from minute quantities, no material is removed from the separation joint. After the insertion of the filament-like defects, both parts to be separated remain essentially connected.

[0034] After micro-perforation, a predetermined breaking line is present in the material along the separation line. While the material is not yet completely separated along this line, it can be easily separated if a suitable stress is applied. A cleaving step is particularly suitable for this purpose.

[0035] In principle, stresses in a flat glass substrate could also be created simply by bending the substrate. When bent, the material is stretched in one half of its volume, creating tensile stress in that half, while simultaneously it is compressed in the other half, creating compressive stress there. The two volume halves are separated by a plane located midway between the two surfaces of the substrate, also known as the neutral zone, as it experiences neither tensile nor compressive stress. Bending a glass substrate is suitable for separating it along a predetermined breaking line, but only if the predetermined breaking line is as straight as possible.

[0036] In contrast, heating the glass element in the main part and / or cooling it in the section allows tensile stresses to be generated in the element, which are present essentially throughout its entire thickness. This means that tensile stresses can be generated without simultaneously generating compressive stresses.

[0037] One possibility is to heat the element only in the area of ​​the main part, causing it to expand while leaving the area of ​​the sub-section unheated. This results in greater expansion in the area of ​​the main part than in the area of ​​the sub-section. This can create tensile stress in the glass element, causing the sub-section to separate from the main part along the dividing line. Furthermore, the sub-section detaches from the main part. Therefore, if internal sub-sections are to be separated from the element, the substrate can be heated, excluding the internal geometries. These internal geometries can then be removed once a specific temperature is reached.

[0038] One example of heating the glass element without creating internal geometries is to use a heating plate that is recessed in the internal geometries. However, many other possibilities exist for heating the glass element solely in the area of ​​the main part. For example, it can be heated by exposure to light while the section is covered. The main part can also be heated by blowing or irradiating a warm fluid or by using a CO2 laser passed over the main part.

[0039] A second possibility is to heat the element in the area of ​​the main part, causing it to expand, and then to cool the element in the area of ​​the sub-section, causing it to contract. In this way, the tensile stress in the material can be increased even further.

[0040] One example, in the case of internal sections, is to heat the glass element using a heating plate with cutouts for the internal geometries. Air is blown through these cutouts, thus cooling the element in the area of ​​the internal geometries. It is also possible to cool the element in the area of ​​the internal geometries using fluids other than air, or to use a cooling plate.

[0041] Heating the element in the main section and cooling it in the section can occur simultaneously, but this is not mandatory. For example, the entire glass element can be heated (consequently also heating the main section) and then cooled in the section. The reverse procedure, cooling the element completely and then heating it in the main section, is also possible.

[0042] A third possibility is to cause the sub-section to contract by cooling the element only in the area of ​​the sub-section, while the element in the area of ​​the main part is not cooled.

[0043] The section is separated from the main part without any additional auxiliary cuts within the section itself. The advantage of avoiding these additional cuts is that tensile stresses in the glass element, which can arise as a result of heating and / or cooling, are not distributed across such auxiliary cuts but rather exert their full effect at the desired separation line. Thus, neither the section nor the main part is damaged beyond the damage caused by inserting the filaments along the separation line. After separation, the main part and the section exhibit only the introduced damage at their cut edges.

[0044] The precision cutting process using micro-perforation achieves a very high edge quality at the cut edges. Since the condition of the glass edge is crucial for the bending strength of a glass element, high edge quality also leads to increased bending strength of the main part and the cut section. In other words, a clean glass edge with as few and as small as possible, preferably no chips, nicks, or other irregularities, helps to reduce the risk of glass breakage.

[0045] If the glass element is heated in the area of ​​the main part, this step can be integrated into a potentially subsequent tempering or ceramization process of the main part.

[0046] In a further development of the invention, the glass element is heated and expanded in the area of ​​the main part and / or cooled and contracted in the area of ​​the section, whereby a temperature difference of at least 150 degrees Celsius, preferably at least 200 degrees Celsius, and particularly preferably at least 300 degrees Celsius is created between the average temperature of the main part and the average temperature of the section.

[0047] In a further development of the invention, the glass element in the area of ​​the main part is heated and expanded, and after the section has detached from the main part along the separation line at the adjacent filament-shaped damages, the main part is thermally prestressed by utilizing the heating effect.

[0048] In this further development of the invention, the already heated parts of the glass element are directly prestressed, thus avoiding further high energy costs. This means that the main part is thermally prestressed in an energy-efficient manner. The prestressing of the heated parts immediately following the separation is made possible in particular by the precision separation process using filament forming, resulting in high edge quality. Therefore, it is not necessary to grind or otherwise process the edge produced by separating the section from the main part.

[0049] Furthermore, it is also possible to ceramicize the main part using the generated heat. In this way, the main part can be ceramicized in an energy-efficient manner, that is, transformed into a glass-crystal composite. Therefore, from an energy-saving perspective, it is advantageous to carry out the ceramicizing after the separation process.

[0050] A process chain can therefore be implemented, for example, as follows: First, the glass element is filamented, i.e., microperforated, along at least one defined separation line using laser pulses. At least one of these separation lines describes a non-linear separation line within the meaning of this invention—in this example, an inner contour is assumed, which represents the section. There can also be further separation lines, for example, outer contours, along which the glass element is initially separated in a different way than according to the disclosed method, for example, by applying stress to the glass element by bending or by irradiation with a CO₂ laser. The edges created by separating along these further separation lines can be ground after separation; for example, a so-called C-grind can be performed. Further optional steps can include cleaning and printing on the glass element.A cleaving step is then preferably performed along the separation line of the inner contour, whereby the filaments are joined together so that the inner contour separates from the main part without, however, detaching from the main part. The section is then detached from the main part using the disclosed method by heating the main part and causing it to expand. This process removes the inner contour, with both the cut edge of the section and the main part exhibiting very high edge quality, characterized in particular by chipping of less than 10 micrometers, more preferably less than 5 micrometers, and a roughness with an Rz value of less than 30 micrometers, preferably 20 micrometers, more preferably 10 micrometers. Finally, the main part is thermally prestressed, utilizing the heating already performed for separation.The main part can also be ceramicized using the heat that has been applied. The main and / or partial pieces of the glass element can then be packaged.

[0051] Thermal prestressing, or thermal hardening, is based on the process of quenching the glass element to be tempered. During this process, the surface of the element cools down first, while the interior remains warmer or softer. The temperature difference to the surrounding environment is then greater inside than outside. The interior of the glass element would subsequently contract more, but this is prevented by the already hardened surface. This results in tensile stress in the interior, while compressive stress develops on the surface.

[0052] One advantage of thermal tempering is that it is a comparatively inexpensive method for increasing strength. In this embodiment of the invention, an efficient method for separating and subsequently tempering is provided. This increases the economic benefit of this embodiment. On the other hand, thermally tempered glass elements are generally difficult to cut and separate. However, in this embodiment of the invention, micro-perforating, cutting, and separating after tempering is not strictly necessary, as all required separation steps can be performed beforehand in the untempered glass element.This applies – in accordance with the exemplary process chain described above – to separations along non-straight separation lines within the meaning of this invention, as well as, if applicable, further separation lines along which the separation can also be carried out using conventional methods.

[0053] The method described in EP 2 781 296 A1 can also be used for glass with tempered or prestressed surfaces. However, a disadvantage is that such glass—as explained above—can no longer be cut cleanly and tears more easily than untempered or non-prestressed glass, thus increasing the risk of harmful cracking during the contour definition step. Furthermore, the laser parameters, such as laser power and cutting speed, must be precisely controlled. These disadvantages are avoided by the described further development of the present invention.

[0054] In a further development of the invention, the material of the glass element has a coefficient of thermal expansion that is greater than 3×10 -6< K -1< , preferably greater than 4×10 -6< K -1< , particularly preferably greater than 7×10 -6< K -1< .

[0055] The coefficient of thermal expansion of a glass is a parameter that indicates how the dimensions of a given glass element change as a result of expansion or contraction due to temperature changes. The coefficient of thermal expansion is understood to be the linear coefficient of expansion a = (1 / L)(ΔL / ΔT), where ΔT denotes the temperature difference and ΔL the change along a linear dimension of the original length L.

[0056] The glass element has a thickness of at least 2 millimeters, preferably at least 3 millimeters, particularly preferably at least 4 millimeters, and even more preferably at least 5 millimeters. The disclosed method for laser-assisted separation of a section from a planar glass element is particularly suitable for planar elements with the aforementioned thicknesses. In contrast, separating glass along generally curved, sectionally angled, or even closed predetermined breaking lines using conventional separation methods, such as applying a bending moment, becomes increasingly difficult with increasing glass thickness. This is because, with conventional separation methods, the risk of tilting between the parts still in contact increases with increasing substrate thickness. Therefore, reliable separation using conventional methods can become difficult or even impossible with thicker glass elements.

[0057] The method described in EP 2 781 296 A1 involves causing the contour to be separated to form a gravity-induced droplet-shaped bulge due to thermally induced flow of the substrate material in the irradiated area, thereby creating a gap to the remaining substrate material. However, a disadvantage of this method is that it is only suitable for limited glass thicknesses. If the glass is too thick, the effect of gap formation due to material flow becomes increasingly weaker compared to expansion resulting from the heating of the contour to be separated in the plane of the substrate. In contrast, the presented method for laser-assisted separation of a section from a planar glass element is particularly suitable for thicker glass elements. Glass with a thickness exceeding 5 millimeters can also be processed, and in particular, thicknesses exceeding 8 millimeters can be successfully processed.

[0058] The glass element preferably has a thickness of at most 20 millimeters, more preferably at most 15 millimeters, and most preferably at most 10 millimeters. Glass with these maximum thicknesses in the aforementioned ranges is still well suited for cutting and reliably separating the parts using the disclosed method.

[0059] With thicker glass elements, it is often no longer possible, or at least impractical, to perform micro-perforation across the entire thickness in a single processing step, or by moving the laser beam's point of impact along the cutting line only once. To enable simple and reliable separation of the section, it is much more advantageous to perform two or more passes at different focal depths.

[0060] In a further development of the invention, it is provided that filament-shaped defects are produced side by side along an offset line spaced at least 5 and at most 50, preferably at most 40, particularly preferably at most 30 micrometers from the dividing line at each point of the dividing line, the projection of which onto the longitudinal direction of the filament-shaped defects produced along the dividing line has an overlap with the filament-shaped defects produced along the dividing line of less than 200, preferably less than 100, preferably less than 50 micrometers.

[0061] Furthermore, filament-shaped damage can be created in the volume of the glass element in an analogous manner along a second offset line, which is spaced apart from the first offset line.

[0062] In a further development of the invention, the section has a minimum dimension of at least 5 millimeters, preferably at least 10 millimeters, particularly preferably at least 20 millimeters, along a first lateral dimension, and a minimum dimension of at least 5 millimeters, preferably at least 10 millimeters, particularly preferably at least 20 millimeters, along a second lateral dimension which is orthogonal to the first lateral dimension.

[0063] It is advantageous if the section to be separated has a certain minimum extent along both lateral dimensions, that is, along the two dimensions that run parallel to the planar glass element, i.e., in the plane of the element. This is because the relative expansion of the main part in relation to the section (or the contraction of the section relative to the main part) induced in the present process leads to a greater tensile stress the larger the section to be separated is. A certain minimum extent is also advantageous in the case of an additional cleaving step, particularly for internal sections (internal contours), as will be explained below using an example.

[0064] This can be illustrated, for example, by assuming that the segment is already completely separated from the main part along the dividing line by a cleaving step, i.e., not just microperforated. If the segment is, for instance, a square with dimensions of 10 by 10 millimeters located inside the main part, expanding the main part or contracting the segment by 10 percent results in a total gap width of one millimeter in each lateral dimension, i.e., 0.5 millimeters all around the square segment. In contrast, if we assume that the segment has dimensions of only 1 by 1 millimeter, the resulting gap width would be only 0.05 millimeters.

[0065] The tensile stress (in the case without a cleaving step) or the resulting gap width (in the case with a cleaving step) generated by the temperature difference between the main part and the section is greater the larger the area of ​​the section. It has proven advantageous if the smallest dimension of the section along either of its two lateral dimensions is at least 5 millimeters, preferably at least 10 millimeters, and particularly preferably at least 20 millimeters. With such dimensions, detachment can be achieved in many glass materials by heating the material in the area of ​​the main part to a temperature below the glass transition temperature, while the material in the area of ​​the section remains at room temperature and is optionally cooled there by blowing air on it.

[0066] However, although advantageous, it is not absolutely necessary for the section to exceed the specified dimensions. The section can be cooled much more significantly, for example, by using special cooling fluids such as nitrogen, cooling plates, etc., so that sufficient tensile stress for separation is generated even in smaller sections. Depending on the type of glass, the glass transition temperature may also be high enough to allow for greater heating of the main section without permanent deformation, thus enabling the separation of even smaller sections.

[0067] Furthermore, it is also possible to heat the glass element unevenly in the main part and / or to cool it unevenly in the section. For example, extensions or tongues of the section can be cooled more.

[0068] The desired detachment of the segment from the main part within the disclosed process depends on various parameters. One important parameter is the smallest dimension L of the segment along the first or second lateral dimension. Another important parameter is the temperature difference ΔT in Kelvin that arises between the average temperature of the main part and the average temperature of the segment in the disclosed process. A further important parameter is the (linear) coefficient of thermal expansion a = (1 / L)(ΔL / ΔT) of the glass used. With these three parameters, the smallest gap width S that arises between the main part and the segment as a result of heating and / or cooling within the disclosed process can now be easily estimated: S = ΔL / 2 = L · ΔT · α / 2.Advantageously, the parameters L, ΔT, and α are matched such that the smallest gap width S is greater than the mean roughness R of the edge surface of the segment where the segment is detached from the main part. The mean roughness R, according to a common definition, represents the mean distance of a point on the edge surface to an averaging surface, where the averaging surface corresponds to the ideal edge surface, or—mathematically speaking—intersects the actual profile of the edge surface in such a way that the sum of the deviations of the actual profile relative to the averaging surface is minimized.

[0069] In a further development of the disclosed method, it is therefore provided that the smallest dimension L of the section in the plane of the planar glass element, the temperature difference ΔT in Kelvin, which is caused between the average temperature of the main part and the average temperature of the section, the coefficient of thermal expansion α, which the material of the glass element possesses, and the average roughness R of the edge surface of the section, at which the section separates from the main part, satisfy the inequality L·ΔT·α > R.

[0070] The glass element is divided by the dividing line in such a way that the main part assumes a two-dimensional shape in the plane of the planar glass element, which is not star-shaped in the mathematical-topological sense.

[0071] Separating glass along generally curved or sectionally angled predetermined break lines using conventional cutting methods becomes increasingly difficult the more the break line is curved or angled. Separating a section becomes particularly difficult—apart from an internal section with a closed break line—when the section is partially or almost internal, meaning the break line is not yet completely closed. One criterion for such a situation is that the two-dimensional region corresponding to the main part of the glass element is, mathematically speaking, no longer a star-shaped region. This means that within this two-dimensional region, there is no point from which any other point in the region can be reached by a straight line segment that lies entirely within the region.

[0072] While some conventional separation methods encounter particular difficulties when the main part of the glass element is not star-shaped in the mathematical-topological sense, the present invention is particularly suitable for such situations.

[0073] While the main part has a non-star-shaped form, it is advantageous—though not strictly necessary—for the segment to assume a star-shaped form for the cleanest possible separation. This is because the two-dimensional region corresponding to the segment then has at least one point from which any other point in the region can be reached by a straight line segment that lies entirely within the region. With respect to such a star point, the region can therefore be contracted without any entanglement with the region corresponding to the main part during the contraction. The described contraction of the region can be understood as analogous to the cooling of the segment.

[0074] Some exemplary, mathematically speaking, star-shaped two-dimensional forms that the segment can assume in the plane of the glass element are those of a regular polygon, a regular polygon with rounded corners, an oval, or a circle.

[0075] In a further development of the invention, the glass element is divided by the dividing line in such a way that the main part completely encloses the sub-section in the plane of the planar glass element.

[0076] Separating glass along closed lines, that is, separating a section located within the two-dimensional surface, or in other words, creating holes or cutouts in a planar glass element, presents a challenge for conventional separation methods. This is due, among other things, to the previously described problem of applying a bending moment, but also to the fact that sometimes little or no material is removed during micro-perforation by the laser pulses. The present invention, in contrast, is particularly suitable for such situations.

[0077] The present method can be applied to almost any shape of an internal section, or in other words, the inner contour or the closed dividing line. As explained above, for the cleanest possible separation, it is advantageous—though not strictly necessary—if the section has a two-dimensional, star-shaped form in the plane of the flat glass element. For example, round, simple, angular, or even more complexly shaped sections can be removed from the glass element.

[0078] In a further development of the invention, the laser pulses are directed obliquely onto the surface of the glass element, so that the direction of propagation of the laser pulses, and thus also the longitudinal direction of the filament-shaped defects, runs obliquely to the surface, and furthermore the dividing line runs obliquely, preferably perpendicular to the plane of incidence of the light. The plane of incidence of the light is defined by the direction of propagation of the laser beam and the surface normal.

[0079] In other words, the damage channels are inserted in such a way that their longitudinal direction deviates from the normal direction of the surface of the glass element. This results in an oblique cut or separation surface between the parts to be separated.

[0080] Creating obliquely filament-shaped damage, or in other words, angling the perforation into the material, can facilitate the removal of a section because, instead of a fit, a certain opening angle exists, which further reduces the risk of jamming.

[0081] When thicker glass is processed with multiple passes using a laser processing device, different focus depths are typically employed. This means that if the length of the generated filaments is insufficient to penetrate the entire thickness of the glass, multiple laser passes are made across the cut line to create filaments at varying depths. At greater focus depths—that is, the further the damaged channels are from the entry point in the glass—the lengths of the filament-like damage can become shorter. This is because portions of the laser radiation are reflected from the substrate surface due to the use of an angle of incidence. An angle of incidence is defined as a non-zero angle between the surface normal of the glass element and the direction of incidence of the laser pulses.Therefore, with thicker lenses, it is often advantageous to keep the angle of inclination small. Even at small angles of inclination, removal without risk of tilting is generally possible using the method according to the invention.

[0082] One of many applications of cutting out internal geometries is the production of hob tops from glass, for example soda-lime glass. In this process, the soda-lime glass is also prestressed as described above.

[0083] Using the disclosed method, a product according to the invention can be produced in the form of a set of two planar, i.e. plate- or disc-shaped, glass elements.

[0084] The set of two planar glass elements according to the invention is characterized in that the two-dimensional shape that one of the planar glass elements has in its plane is complementary to the two-dimensional shape that the other of the planar glass elements has in its plane, and wherein two edges of one planar glass element, which form the transition between the side surfaces and an edge surface connecting these side surfaces, each have the same shape as two edges of the other planar glass element, which form the transition between the side surfaces and an edge surface connecting these side surfaces, and wherein in these edge surfaces of the two planar glass elements there are filament-shaped defects running side by side, which form depressions in these edge surfaces, wherein the longitudinal direction of the filament-shaped defects runs in the direction from one edge to the other edge.

[0085] Theoretically, one flat glass element could therefore be fitted precisely together with the other flat glass element, if friction and tilting problems are disregarded.

[0086] In a further development of the invention, the two-dimensional shape that one of the planar glass elements has in its plane encloses the two-dimensional shape that the other of the planar glass elements has in its plane.

[0087] In a further development of the invention, one of the flat glass elements is thermally prestressed. In this further development, it can be provided that the prestressed flat glass element remains in a state of slightly increased expansion due to the thermal prestressing. Accordingly, in this further development of the invention, it can be possible not only theoretically but also practically to join one flat glass element precisely with the other, since friction and tilting problems caused by the slight enlargement of one flat glass element through prestressing are avoided. Such a set of two flat glass elements that can be joined precisely can fit together so accurately that it is liquid-tight. This can be used, for example, to manufacture liquid-tight glass closures.

[0088] It may also be possible to grind one or both of the flat glass elements on the edge surface that has filament-like damage. This can also make joining them possible in practice.

[0089] Furthermore, one of the planar glass elements of the set of two planar glass elements according to the invention can be ceramicized.

[0090] By further developing the disclosed method, in which several laser processing steps are used at different focus depths, a product according to the invention can be produced in the form of a planar, i.e. plate- or disc-shaped, glass element.

[0091] A planar glass element according to the invention is characterized in that filament-shaped defects running side by side are present in an edge surface, forming depressions in the edge surface, wherein the longitudinal direction of the filament-shaped defects runs in the direction from one edge to the other edge, which forms the transition between the edge surface and the side surfaces of the planar glass element, and wherein the edge surface has at least one offset running along the entire edge surface, which runs substantially perpendicular to the longitudinal direction of the filament-shaped defects, and wherein the offset represents a step of at least 2 micrometers and at most 30 micrometers.

[0092] A disclosed method for removing a section from a planar glass element according to yet another embodiment is based on defining a dividing line that separates the glass element into the section to be removed and a remaining main part, and generating filament-shaped defects side by side along the dividing line in the volume of the glass element, and generating the defects by laser pulses of an ultrashort pulse laser, wherein the material of the glass element is transparent to the laser pulses, and the laser pulses generate a plasma in the volume of the glass element which causes the filament-shaped defects, and the points of impact of the laser pulses on the glass element are moved across its surface along the dividing line, and after the insertion of the filament-shaped defects arranged side by side along the dividing line, the glass element is prestressed.and after the glass element is prestressed, cracking is triggered in the area of ​​the section, the propagation of which is limited by the adjacent filament-shaped defects arranged along the separation line, so that the section can be removed from the main part along the separation line at the adjacent filament-shaped defects, while the main part remains intact.

[0093] In the process for removing a section from a flat glass element, the entire substrate, i.e., the entire glass element, is tempered. Tempering can be carried out in various ways, for example, thermally or chemically. After tempering, self-fracture is induced within the section, with the filament structure acting as a propagation limit for the resulting cracks. As a result, only the sections break into small pieces of glass, as is known, for example, from thermally tempered single-pane safety glass. Preferably, the section has a simple, continuous shape in the plane of the flat glass element. While not necessary, a star-shaped or even convex shape can be advantageous.

[0094] The invention is explained in more detail below with reference to the enclosed figures. In the figures, identical reference numerals denote identical or corresponding elements.

[0095] They show: Fig.1 Schematic perspective view of a laser processing device for generating filament-shaped damage along various separation lines in the volume of a glass element, Fig.2 Schematic perspective view of a heating device for heating the glass element in the area of ​​the main part, Fig.3 a diagram of schematic graphs of temperature as a function of location with respect to the lateral dimensions of a planar glass element, Fig.4 Schematic representation of tensile stresses generated in a planar glass element by heating / cooling, as seen from above. Fig.5 Schematically shown in perspective view a filamentous glass element that has been heated in the area of ​​the main part so that the section can be removed, Fig.6 schematically shown in top view various forms of a dividing line and the corresponding main part and sub-section, Fig.7 Schematic perspective view of an alternative laser processing device for generating obliquely running filament-shaped damage. Fig.8 Schematic side view of glass elements after multiple laser processing. Fig.9 Schematic perspective view of glass elements after multiple laser processing along a separation line and additional offset lines. Fig.10 Schematic representation in perspective view of sets consisting of two flat glass elements each. Fig.11 Schematic representation of planar glass elements in perspective view with offset(s) in the edge surface.

[0096] The Fig.1 Figure 1 schematically shows a laser processing device 1 with which a glass element 2 can be microperforated by introducing filament-shaped damage 20 along a defined separation line 21 and thus prepared for subsequent separation.

[0097] The laser processing device 1 comprises an ultrashort pulse laser 10, the laser pulses 12 of which are directed at the glass element 2. The laser pulses 12 are focused onto the glass element 2 by means of a focusing device 11. The wavelength of the ultrashort pulse laser 10 is selected such that the laser pulses 12 can penetrate the glass element 2.

[0098] The laser pulses 12 generate a plasma within the volume of the glass element 2, which causes the filament-shaped defects 20. The points of impact 13 of the laser pulses 12 on the glass element 2 are successively moved across the surface 22 along the defined dividing line 21.

[0099] The dividing line 21 is defined in such a way that it completely divides the glass element 2 into a section to be separated 4 and a remaining main part 3.

[0100] In Fig.1 Several exemplary dividing lines are shown in Figure 21. Fig.1a shows a curved, non-straight dividing line that is not closed in itself. Fig.1b-d The self-contained dividing lines show 21 different shapes. Fig.1b shows a dividing line 21 of oval shape, Fig.1c shows a dividing line 21 in the form of a regular pentagon and Fig.1d shows a dividing line 21 in the form of a regular pentagon with rounded corners.

[0101] Fig.2 Figure 1 schematically shows an exemplary heating device 5 for heating the glass element 2 in the area of ​​the main part 3. For better illustration, the glass element 2 has been shown in the Fig.2 a clear distance from the heating device 5. In reality, however, the glass element 2 can be in contact with the heating device 5. The flat glass element 2 can therefore rest on the heating device 5 with the surface of its underside.

[0102] In Fig. 2 The planar glass element 2 has its longest dimensions along the x and y dimensions shown. The two dimensions running along the longest dimensions of the glass element 2 shall also be referred to as the first lateral dimension 6 and the second lateral dimension 7. Along the dimension that runs orthogonal to the lateral dimensions 6 and 7, the glass has a thickness of 23.

[0103] The in Fig.2 The heating device 5 shown as an example is designed as a flat surface and can therefore also be referred to as a heating plate. The surface of this heating plate is parallel to the two lateral dimensions 6 and 7 of the glass element 2, i.e., to the one shown in Fig.2 x and y dimensions shown.

[0104] The heating plate heats the glass element 2 in the area of ​​the main part 3. Generally, without being limited to the exemplary heating device, the heating plate can have a heating field 50 adapted to the shape of the main part 3. In the case shown, the heating field extends along the first lateral dimension 6 from the value x=0 to the value x=x3 and along the second lateral dimension 7 from the value y=0 to the value y=y2, with a recess in the center adapted to the section 4, which, for example, extends from x=x1 to x=x2 for the value y=y1. Accordingly, the glass element 2 is exposed to different temperatures on a surface extending in the plane of the two lateral dimensions (x and y dimensions), depending on its position on this surface (x and y values).

[0105] Fig.3 Figure 1 shows various schematic temperature profiles in the glass element 2, suitable for separating the section 4 from the main part 3. The temperature profiles are shown as functions of the position x of a first lateral dimension 6 at a fixed value y = y₁ of the second lateral dimension 7. The fixed value y = y₁ of the second lateral dimension is chosen such that the value x along the first lateral dimension includes positions both in the region of the main part 3 and positions in the region of the section 4. Fig.3a shows an idealized temperature profile for the case where the main part 3 has a constant temperature that is higher than the temperature of the section 4. Fig.3c shows a similar temperature profile in the case where a temperature gradient exists that runs across the predetermined breaking point described by the dividing line 21. Fig.3b und Fig.3d They also show temperature profiles for the case of existing temperature gradients, where the temperature gradient runs entirely within section 4 or main section 3. All in Fig.3a-d The temperature profiles shown have in common that the average temperature in the main part 3 is higher than the average temperature in the section 4. It is irrelevant whether the glass element 2 was heated in the area of ​​the main part 3 or cooled in the area of ​​the section 4, or whether both occurred simultaneously or with a time delay. What is decisive for the disclosed method is only that, as a result of the generated temperature profile, the glass element 2 expands in the area of ​​the main part 3 and / or contracts in the area of ​​the section 4.

[0106] Fig.4 Figure 2 shows the tensile stresses generated in glass element 2 by heating and / or cooling, i.e., in the case where no cleaving step was performed. The tensile stresses are schematically represented by arrows. Filament-shaped defects arranged along the dividing line 21 had previously been introduced into glass element 2. Fig.4a shows tensile stresses resulting from the heating of the glass element 2 in the area of ​​the main part 3, corresponding to a Fig.3d temperature profile shown. Fig.4b shows tensile stresses resulting from heating in the area of ​​the main part 3 according to a Fig.3c temperature profile shown. Fig.4c shows tensile stresses resulting from cooling in the area of ​​section 4, corresponding to a Fig.3b temperature profile shown. Fig.4d shows tensile stresses resulting from cooling in the area of ​​section 4, corresponding to a Fig.3c temperature profile shown. Fig.4e shows tensile stresses resulting from heating in the area of ​​the main part 3 according to a Fig.3d The temperature profile shown, during simultaneous or staggered cooling in the area of ​​section 4, corresponds to a [missing information]. Fig.3b temperature profile shown. Fig.4f shows tensile stresses resulting from heating in the area of ​​the main part 3 according to a Fig.3c The temperature profile shown, during simultaneous or staggered cooling in the area of ​​section 4, corresponds to a [missing information]. Fig.3b temperature profile shown. Fig.4g shows tensile stresses resulting from heating in the area of ​​the main part 3 according to a Fig.3d The temperature profile shown, during simultaneous or staggered cooling in the area of ​​section 4, corresponds to a [missing information]. Fig.3c temperature profile shown. Fig.4h shows tensile stresses resulting from heating in the area of ​​the main part 3 according to a Fig.3c The temperature profile shown, during simultaneous or staggered cooling in the area of ​​section 4, corresponds to a [missing information]. Fig.3c temperature profile shown.

[0107] Alone Fig.4a-h The illustrated variants for generating tensile stresses in the glass element 2 by heating and / or cooling can cause the section 4 to separate from the main part 3 along the separation line 21 at the adjacent filament-shaped defects.

[0108] Fig.5 The figure schematically shows a perspective view of a glass element 2 that has been heated and expanded in the area of ​​the main part 3. The glass element 2 has detached from the section 4 along the separation line at the adjacent filament-shaped defects of the main part 3. Section 4 can therefore be removed from the main part 3.

[0109] As long as the main part 3 is still heated, the removal of the section 4 is possible without any problems, i.e., in particular without jamming with the main part 3, damage, or permanent deformation of the section 4. This is because the relative expansion of the main part 3 compared to the section 4 not only results in separation along the separation line, but also creates a gap 24 between the main part 3 and the section 4 corresponding to the course of the separation line. This gap provides a certain degree of clearance, which makes it possible to remove the section 4 from the main part 3 without jamming.

[0110] While separation processes that involve applying bending moments or local heating by laser radiation, for example by CO2 lasers, become increasingly difficult as the thickness of the glass element 2 increases, the removal of the section 4 in the disclosed method is particularly easy even for glass elements 2 with a thickness 23 of at least 2 millimeters, preferably at least 3 millimeters, especially preferably at least 4 millimeters, and even more preferably at least 5 millimeters.

[0111] The width of the gap created by heating in the region of the main part 3 and / or cooling in the region of the section 4 depends, among other things, on the difference in the mean temperatures generated between the main part 3 and the section 4. The gap width also depends on the size of the area of ​​the section 4 along the two lateral dimensions 6 and 7. It is advantageous for the disclosed method if the section 4 has certain minimum dimensions along these two dimensions, in particular if the smallest dimension of the section 4 in a first lateral dimension 6 as well as the smallest dimension of the section 4 in a second lateral dimension 7 each have a minimum length. In a further development of the invention, this minimum length is 5 millimeters, preferably 10 millimeters, and particularly preferably 20 millimeters.

[0112] Alternatively, it is also possible that the smallest rectangle enclosing segment 4 in the plane spanned by lateral dimensions 6 and 7 has side lengths 41 and 42, each of which has a certain minimum length. Then both the maximum dimension of segment 4 in a first lateral dimension 6 and the maximum dimension of segment 4 in a second lateral dimension 7 each have a minimum length.

[0113] Fig.6 Figure 2 shows, in a top view of the glass element 2, different forms of a separation line 21 and corresponding main parts 3 and sub-pieces 4. The damage-free separation of the sub-piece 4 from the main part 3 – that is, separation in such a way that neither the main part 3 nor the sub-piece 4 suffers any further damage except for the micro-perforation at the separation edge – is easily possible if the separation line 21, as shown in Figure 2, is formed by the main part 3 and the sub-piece 4 without damage other than the micro-perforation at the separation edge. Fig.6a shown, is straight. In such a case, damage-free separation is possible with the disclosed method, but it can also be carried out with conventional separation methods such as applying a sufficient bending moment. The same applies to slightly curved or slightly angled separation lines 21, as shown in Fig.6b or Fig.6c shown.

[0114] Common separation methods encounter particular difficulties when the separation line 21 is strongly curved or sharply angled, that is, when the segment 4 can be described as predominantly or completely internal in the plane of the glass element 2, as is the case in Fig.6d or Fig.6e This is illustrated by example. The disclosed method, on the other hand, is very well suited for such cases.

[0115] Fig.6d Figure 3 shows a case in which the segment 4 lies predominantly inside the glass element 2. One criterion that can be applied to this case is that the two-dimensional shape of the main part 3 in the plane of the glass element 2 is not star-shaped in the mathematical-topological sense. This means that within the two-dimensional area corresponding to the main part 3, there is not a single point 31 that has the property of being a star point. The point 31 shown lacks this property because it is not possible to draw straight lines from point 31 to all other points within the two-dimensional area corresponding to the main part 3 that lie entirely within this two-dimensional area. Therefore, starting from point 31, the hatched areas within the area of ​​the main part 3 are not reachable in the manner shown.The region of main part 3 is therefore not star-shaped. The same applies to the region of in . Fig.6e The main part 3 shown is neither star-shaped nor simply connected. Part 4 is even completely internal, meaning it is entirely enclosed within the plane of the glass element 2. Such an internal part 4 is sometimes also referred to as an internal contour or internal geometry.

[0116] It is generally advantageous for the disclosed method if the two-dimensional shape of the section 4 in the plane of the glass element 2 is star-shaped, that is, if there is at least one star point 43 in the two-dimensional area corresponding to the section 4. This is in the Fig.6d und Fig.6e The situations shown are the case. In the Fig.6d und Fig.6e In the examples shown, every point of the area of ​​section 4 is even a star point. In other words, the areas of sections 4 are convex areas in these examples. It is advantageous for separation if sections 4 represent convex areas in the plane of the planar glass element 2. Therefore, in a general embodiment of the invention, and not limited to the examples shown, it is provided that sections are detached which have a two-dimensional shape of a convex area in the plane of the planar glass element.

[0117] However, it is not absolutely necessary for the functioning of the disclosed method that the shape of the section be star-shaped or even convex on the surface of the glass. This is because the separation along the predetermined breaking point, which runs according to the separation line 21, tends to progress once it has begun in certain areas. In addition, uneven cooling and / or heating of the main part 3 and / or the section 4 can also contribute to the separation of non-star-shaped sections 4.

[0118] Another exemplary case, in which neither the main part nor the section 4 is star-shaped or convex in the surface of the glass, is in Fig.6f shown. Here, the two-dimensional area corresponding to glass element 2 is neither star-shaped nor convex nor simply connected. Such a glass element 2, which has a hole, can, for example, result from separating an internal section, as shown in Fig.6e As shown, the dividing line 21 is closed in this case. Mathematically speaking, the section 4 defined by the dividing line 21 is no longer an internal section 4. However, in practice – depending on the size of the hole – it is not uncommon to still refer to an internal geometry. The non-star-shaped and non-simply connected section 4 can be separated from the non-star-shaped and non-simply connected main part 3 without damage or tilting using the disclosed method.

[0119] As shown by the Fig.7a As can be seen, in a further development of the invention, the laser pulses 12 can also be directed obliquely onto the surface 22 of the glass element 2, so that an angle exists between the surface normal 14 and the direction of the laser pulses 12. Thus, the longitudinal direction of the filament-shaped defects 20 also runs obliquely to the surface 22. Furthermore, the influence of the refraction of the laser light at the surface 22 of the glass element 2 must be taken into account.

[0120] To facilitate the separation of the section, the angle between the direction of incidence of the light and the surface normal 14 can be in the range of a few degrees to well over 10°. Preferably, an angle in the range of 3° to 15°, and even more preferably at least 5°, is set between the direction of incidence of the laser pulses 12 and the surface normal 14 of the surface 22 of the glass element 2.

[0121] As demonstrated by Fig.7a As can be seen, the laser pulses 12 are directed obliquely onto the surface 22 such that the plane of incidence 15 lies transversely, preferably perpendicularly, to the dividing line 21. Accordingly, the direction of movement along which the point of impact 13 is moved across the surface 22 is also transversely, preferably perpendicularly, to the plane of incidence 15. The plane of incidence 15 is defined by the direction of incidence and the surface normal 14. If the dividing line 21 is curved, for example circularly, as in the example shown, then the orientation of the dividing line 21 transversely to the plane of incidence 15 is to be understood as meaning that the tangent to the dividing line 21 is transversely, preferably perpendicularly, to the plane of incidence 15.

[0122] Fig.7b shows one of the Fig.7a Corresponding sectional view of the glass element 2. The angle between the longitudinal direction of the filamentary damage 20 and the normal on the surface 22 gives a preferred direction, indicated by the arrow, along which the section 4 can be separated from the main part 3.

[0123] Fig.8 illustrates glass elements in a to Fig.7b Analog section view after multiple laser processing at different focus depths. This means that after a processing step in which damage 20 is created in the volume of the glass element 2 by laser pulses 12 of an ultrashort pulse laser by moving the impact points 13 of the laser pulses 12 on the glass element 2 over its surface 22 along the dividing line 21, there are further processing steps in which, in an analogous manner, but with different focus depths of the laser pulses 12, damage 20', 20", etc. is created at other depths in the volume of the glass element 2.

[0124] Such multiple laser processing is particularly suitable for thicker glass elements 2, where it is often no longer possible or at least inconvenient to carry out the micro-perforation over the entire thickness 23 in a single processing step, or by moving the point of impact 13 of the laser beam 12 along the dividing line 21 only once.

[0125] One problem that can arise when repeatedly passing the laser beam at different focus depths is that the damage at different depths in the volume of the glass element 2 does not align perfectly.

[0126] Fig.8a Figure 2 illustrates, by way of example and schematically, a glass element 2 after two laser processing operations across its surface 22. In a first processing step, the defects 20 were created, while in a second step, the defects 20' were created at a deeper depth. The defects 20 and 20' are offset from each other, which typically exhibits statistical fluctuations due to the finite positioning accuracy. This offset makes it difficult to separate the section 4 from the main part 3 using the disclosed method. The offset results in a roughness R' of the cut edge that is higher than the roughness R inherent in the filamentation process itself.

[0127] In a further development of the invention, it is provided that the offset between damages 20 and 20' is brought about in such a way that for a separation of the part 4 from the main part 3 only the roughness R caused by the filamentation itself, but not the roughness R' of the edge surface which takes the offset into account, is decisive.

[0128] As in Fig.8b As shown, the defects 20', which are located deeper within the volume of the glass element 2 relative to surface 22, are designed such that the section 4 is slightly larger on the side opposite surface 22 than on the side facing surface 22. This results in a preferred direction, indicated by the arrow, along which the section 4 can be separated from the main part 3. Along this preferred direction, the roughness R, which is solely due to filamentation, is decisive for separation, while against the preferred direction, the roughness R', which also results from the offset between defects 20 and 20', is decisive for separation. The section 4 need not be entirely internal; rather, all previously mentioned shapes are possible.In the event that section 4 is a circular inner piece, it has, figuratively speaking, a pie-like shape due to the offset between damages 20 and 20'.

[0129] While the damages amounted to 20 according to Fig.1 by moving the impact points 13 of the laser pulses 12 on the glass element 2 across its surface 22 along the dividing line 21, the damage 20' is generated according to Fig.9a This is generated by moving the impact points 13 of the laser pulses 12 on the glass element 2 across its surface 22 along an offset line 21' slightly spaced away from the dividing line 21. Advantageously, the offset line runs entirely on one side of the dividing line 21; however, it is not necessary, although advantageous, for the distance between the offset line 21' and the dividing line 21 to be constant along the line.

[0130] The described further development of the invention is not limited to two laser processing passes. Three or even more passes with the laser can also be carried out. Fig.8c Figure 1 shows, by way of example and schematically, the section through a glass element 2 after three laser processing operations, which led to the damages 20, 20' and 20". Fig.8d This again shows how the offsets between the damages 20 and 20' and between the damages 20' and 20" can be generated in this further development of the invention in such a way that a preferred direction for separating the section 4 from the main part 3 is indicated by the arrow.

[0131] The damages are 20' according to Fig.9b The damage is generated by moving the impact points 13 of the laser pulses 12 on the glass element 2 across its surface 22 along a first offset line 21' slightly spaced from the dividing line 21. The damage 20" is further generated by moving the impact points 13 of the laser pulses 12 on the glass element 2 across its surface 22 along a second offset line 21" slightly further away from the dividing line 21 than the first offset line 21'. Advantageously, the second offset line 21" runs entirely on one side of the first offset line 21'; however, it is not necessary, although advantageous, for the distance between the second offset line 21" and the first offset line 21' to be constant along the lines.

[0132] More than two laser processing steps can also be performed. For this purpose, further offset lines, again spaced somewhat further away from the dividing line 21, can be defined, along which the points of impact 13 of the laser pulses 12 on the glass element 2 are moved across its surface 22.

[0133] The targeted control of one or more offsets between damages created by multiple laser processing with different focus depths can be combined with the in Fig.7 The laser processing shown involves directing the laser pulses 12 obliquely onto the surface 22 of the glass element 2. In practice, the angle between the direction of light incidence and the surface normal 14 cannot usually be set exactly to zero degrees. Therefore, strictly speaking, there is regularly a (very small) angle, so that the longitudinal directions of the damage channels also regularly exhibit a certain angle with respect to the surface normal 14 of the glass element 2. As with the positioning, a statistical deviation smaller than the alignment accuracy must also be assumed here.

[0134] Fig.8e Figure 2 shows oblique damage 20 and 20' caused by two laser treatments of a glass element 2. Again, the damage 20 and 20' are not exactly on the same line (or exactly on the same surface) but exhibit a certain offset from each other. This, in turn, makes it more difficult to separate the section 4 from the main part 3 using the disclosed method.

[0135] How Fig.8f As shown, the offset can be advantageously adjusted so that the preferred cutting direction indicated by the arrow results. Along this preferred direction, the section 4 can be separated from the main section 3 without the edges created by the offset having a disruptive effect.

[0136] The described further development of the invention is not limited to two laser processing steps with laser pulses 12 striking the surface 22 at an oblique angle. Three or more laser processing steps can also be carried out at different focus depths. Fig.8g Figure 1 shows, by way of example and schematic, the section through a glass element 2 after three laser processings with laser pulses 12 directed obliquely onto the surface, which lead to the damages 20, 20' and 20". Fig.8d Figure 1 shows how the offsets between the defects 20 and 20' and between the defects 20' and 20" can be arranged in this embodiment of the invention such that a preferred direction for separating the section 4 from the main part 3 is indicated by the arrow. In practice, the offsets do not need to be of the same size.

[0137] Fig.10 shows two sentences ( Fig.10a und Fig.10b ) consisting of two planar glass elements each, which can be produced using the disclosed method. During the in Fig.10b The set of two planar glass elements shown is designed such that the two-dimensional shape that one of the planar glass elements 2 has in its plane completely encloses the two-dimensional shape that the other of the planar glass elements 2' has in its plane, this is the case for the Fig.10a The set of two flat glass elements shown is not the case. For the one in Fig.10b The sentence shown means that glass element 2' is an inner piece that fits glass element 2. For the one in Fig.10a In the sentence shown, this means that the glass element 2' is a section that matches the glass element 2 and can be described here as being predominantly inside.

[0138] For both sentences shown ( Fig.10a und Fig.10b ) it is true that one flat glass element 2 could at least theoretically be joined to the other flat glass element 2' in a perfectly fitting manner.

[0139] Each planar glass element 2 (or 2') of a set has an edge surface 25 (or 25') in which adjacent filament-shaped defects 26 (or 26') are present, forming depressions in this edge surface 25 (or 25'). These filament-shaped defects can be produced by microperforating laser processing according to the disclosed method.

[0140] The longitudinal direction of the filament-shaped defects 26 (or 26') in an edge surface 25 (or 25') of a planar glass element of a set of two planar glass elements runs from one edge to the other, forming the transition between the edge surface 25 (or 25') and the side surfaces 29 (or 29') and 30 (or 30') of the glass element. When a glass element 2 (or 2') of a set of two glass elements is produced by the disclosed method, this longitudinal direction of the filament-shaped defects 26 (or 26') corresponds to the direction of propagation of the laser pulses.

[0141] If the two flat glass elements 2 and 2' of a set were fitted together precisely, their edge surfaces 25 and 25' would touch or come very close to each other. Edges 27 and 27' would also touch or come very close to each other, as would edges 28 and 28'. The two-dimensional surfaces in the planes of the flat glass elements 2 and 2' would fit together like two puzzle pieces when the two glass elements 2 and 2' are joined.

[0142] Preferably, the two planar glass elements of a set originate from the same separation process. That is, by applying the disclosed method, an original planar glass element is divided into a main part and a sub-part, which together form a set of planar glass elements according to the invention. If the two planar glass elements of a set originate from the same process, a particularly high degree of dimensional accuracy is ensured, which is even higher than if a series of sub-parts of equivalent sub-parts and a series of main parts of equivalent main parts are produced from several equivalent separation processes, and an arbitrary sub-part from the sub-part series and an arbitrary main part from the main part series result in a set of planar glass elements according to the invention.

[0143] In a further development of the invention, each planar glass element 2 (or 2') of a set of two planar glass elements has an edge surface 25 (or 25') in which at least one offset 32 ​​(or 32'), i.e., a step, is present, which runs transversely, preferably substantially perpendicularly, to the longitudinal direction of the adjacent filament-shaped defects 26 (or 26'). An illustration of such planar glass elements 2 shows Fig.11 .

[0144] The at least one offset 32 ​​(or 32') can lead to a roughness R' of the edge surface 25 (or 25') that is increased compared to the roughness R caused by the filament-shaped damage 26 (or 26').

[0145] The at least one offset represents a step that is not perceptible to the naked eye, so that it can still be referred to as a single edge surface 25 (or 25'). Preferably, the at least one offset represents a step of at least 5 micrometers and at most 50 micrometers.

[0146] Fig.11a Figure 2 shows a planar glass element 2 according to the invention, characterized in that adjacent filament-shaped defects 26 are present in an edge surface 25, forming depressions in the edge surface 25, wherein the longitudinal direction of the filament-shaped defects 26 extends from one edge 27 to the other edge 28, which form the transition between the edge surface 25 and the side surfaces 30 of the planar glass element 2, and wherein the edge surface 25 has an offset 32 ​​extending along the entire edge surface 25, which is substantially perpendicular to the longitudinal direction of the filament-shaped defects 26. The offset preferably extends with a deviation of 20 percent in the middle of the edge surface, that is, with a deviation of 20 percent midway between edges 27 and 28.

[0147] Fig.11b Figure 1 shows a further planar glass element 2 according to the invention, which is characterized in that the edge surface 25 has two offsets 32 extending along the entire edge surface 25, which run substantially perpendicular to the longitudinal direction of the filament-shaped defects 26. The two offsets preferably run with a deviation of 20 percent at a distance of one-third and two-thirds of the width 23 of the edge surface 25 from the surface 30 of the glass element 2, respectively. Bezugszeichenliste

[0148] 1 Laser processing device 10 Ultrashort pulse laser 11 Focusing device 12 Laser pulse 13 Points of impact of the laser pulses on the glass element 14 Surface normal of the glass element 15 Plane of incidence of the laser pulses 2 Planar glass element 2' Planar glass element 20, 20', 20" Filamentous damage 21, 21', 21" Dividing line 22 Surface of the glass element 23 Thickness of the glass element 24 Gap between the section and the main part 25 Edge surface in which adjacent filamentous damage is present 25' Edge surface in which adjacent filamentous damage is present 26 Filamentous damage on an edge surface 26' Filamentous damage on an edge surface 27, 28 Edges of a planar glass element which form the transition between the side surfaces and a These side surfaces connecting the edge surfaces form the 27', 28' edges of a planar glass element,which form the transition between the side surfaces and an edge surface connecting these side surfaces 29, 30 Side surfaces of a planar glass element 29', 30' Side surfaces of a planar glass element 32 Offset in an edge surface 3 Main part 31 Point in the two-dimensional area corresponding to the main part 4 Section to be separated 41 Maximum extent of the section along the first lateral dimension 42 Maximum extent of the section along the second lateral dimension 43 Point in the two-dimensional area corresponding to the section 5 Heating device 50 Heating field 6 First lateral dimension of the glass element 7 Second lateral dimension of the glass element,

Claims

1. A set comprising two planar glass elements (2, 2', 3, 4), wherein the two-dimensional shape that one of the planar glass elements (2) has in its plane is complementary to the two-dimensional shape that the other one of the planar glass elements (2', 3, 4) has in its plane, and wherein two edges (27, 28) of the one planar glass element (2), which define the transition between the faces (29, 30) and an edge surface (25) connecting these faces (29, 30), each have the same shape as two edges (27', 28') of the other planar glass element (2', 3, 4), which define the transition between the faces (29', 30') and an edge surface (25') connecting these faces (29', 30'), and wherein each of these edge surfaces (25, 25') of the two planar glass elements (2, 2', 3, 4) present filamentary damages (26, 26') which extend next to one another and form depressions in these edge surfaces (25, 25'), wherein the longitudinal extension of the filamentary damages (26, 26') is in a direction from one edge (27, 27') to the other edge (28, 28') in each case; characterised in that the shape of one of the planar glass elements (2, 2', 3, 4) is not star-shaped in a sense of mathematical topology, and that the glass elements (2, 2', 3, 4) have a thickness of at least 2 millimeters, and wherein the edge surfaces (25, 25') extend perpendicular to the normal direction (14) of the faces (29, 30, 29', 30') or form an angle of a few degrees therewith, or form an angle between 3 degrees and 15 degrees therewith.

2. The set comprising two planar glass elements (2, 2', 3, 4) according to the preceding claim, wherein the two-dimensional shape that the one planar glass element (2) has in its plane completely encloses the two-dimensional shape that the other planar glass element (2', 3, 4) has in its plane.

3. The set comprising two planar glass elements (2, 2') according to any one of the preceding claims, wherein the one of the planar glass elements (2) has been thermally toughened.

4. The set comprising two planar glass elements (2, 2') according to any one of the preceding claims, wherein each planar glass element (2, 2', 3, 4) of the set has an edge surface (25, 25') which includes at least one offset (32, 32') in the form of a step extending transversely to the longitudinal extension of the filamentary damages (26, 26') that extend next to one another .

5. The set comprising two planar glass elements (2, 2', 3, 4) according to the preceding claim, characterised in that the offset constitutes a step of at least 5 micrometers and at most 50 micrometers.

6. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the two preceding claims, characterised in that the edge surface (25) of one glass element (2) comprises an offset (32) extending along the entire edge surface (25), which extends substantially perpendicular to the longitudinal extension of the filamentary damages (26) that extend next to one another.

7. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that the filamentary damages have a length of at least 200 micrometers, preferably at least 500 micrometers.

8. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that the glass elements (2, 2') form a main part (2) and a portion (4), wherein neither the main part (2) nor the portion (4) is star-shaped in a mathematical-topological sense in the plane of the glass.

9. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that the filamentary damages (26, 26') are defined by submicron hollow channels having diameters of less than 1 micrometer.

10. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that one of the glass elements (2, 2', 3, 4) is ceramized.

11. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that the material of one glass element (2, 2', 3, 4) has a coefficient of thermal expansion of greater than 3 × 10-6 K-1, preferably greater than 4 × 10-6 K-1, most preferably greater than 7 × 10-6 K-1.

12. The set comprising two planar glass elements (2, 2', 3, 4) according to any one of the preceding claims, characterised in that the smallest dimension of the glass elements (2, 2', 3, 4), along one of the two lateral dimensions in each case, is at least 5 millimeters, preferably at least 10 millimeters, most preferably at least 20 millimeters.