Apparatus and method for segmenting material

Abstract

The invention relates to a method for separating a workpiece (1) having a transparent material, wherein ultrashort laser pulses from an ultrashort pulse laser (2) are used to introduce a material modification (5) into the transparent material of the workpiece (1) along a separation line (4), and then the material of the workpiece (1) is separated in a separation step along the material modification surface (50) thus produced, wherein the laser pulses enter the workpiece (1) with an angle of incidence (α), the material modification (5) is a type III modification, which is associated with crack formation in the material of the workpiece (1).

Description

Technical Field

[0001] This invention relates to an apparatus and method for dividing materials using ultrashort laser pulses. Background Technology

[0002] In recent years, the development of lasers with very short pulse lengths (especially those below one nanosecond) and high average power (especially in the kilowatt range) has led to a new type of materials processing. The short pulse length and high pulse peak power, or high pulse energy from a few microjoules to 100 µJ, can cause nonlinear absorption of the pulse energy within the material, resulting in the ability to process materials that are virtually transparent or essentially transparent to the laser wavelength used.

[0003] The specific application of this laser radiation lies in the cutting and processing of workpieces. In this process, the laser beam is preferably introduced into the material perpendicularly, as this minimizes reflection losses at the material surface. However, for processing materials at a certain angle of attack, such as chamfering material edges or creating chamfered and / or beveled structures with angles of attack greater than 30°, unresolved problems remain, especially because the large angle of attack at the material edges causes significant aberrations in the laser beam, making it impossible to achieve the target energy deposition within the material. Summary of the Invention

[0004] Based on known prior art, the objective of this invention is to provide an improved apparatus for dividing workpieces, and also to provide a corresponding method.

[0005] This objective is achieved by the method for dividing workpieces as described in this application. Advantageous extensions of this method are derived from this specification and the accompanying drawings.

[0006] Accordingly, a method for segmenting a workpiece comprising a transparent material is proposed, wherein an ultrashort laser pulse from an ultrashort laser is used to introduce material modification into the transparent material of the workpiece along a segmentation line, and then the workpiece is segmented along the resulting material-modified surface in a segmentation step. According to the invention, the laser pulse enters the transparent material of the workpiece at an angle of attack, and the material modification is a Type III modification associated with crack formation in the transparent material.

[0007] Here, an ultrashort pulse laser provides ultrashort laser pulses. "Ultrashort" can mean a pulse length, for example, between 500 picoseconds and 10 femtoseconds, and particularly between 10 picoseconds and 100 femtoseconds. Here, the ultrashort laser pulses move along the laser beam composed of these ultrashort laser pulses in the beam propagation direction.

[0008] When an ultrashort laser pulse is focused into the material of a workpiece, the intensity in the focused volume can induce nonlinear absorption, for example, through multiphoton absorption and / or electron avalanche ionization processes. This nonlinear absorption results in the generation of an electron-ion plasma, which, upon cooling, can induce permanent structural changes within the workpiece material. Because energy can be transferred into the volume of the material through nonlinear absorption, these structural changes can be generated within the sample without affecting the workpiece surface.

[0009] Here, transparent material should be understood as a material that is substantially transparent to the wavelength of the laser beam of an ultrashort pulse laser. The terms “material” and “transparent material” are used interchangeably herein, that is, the material specified herein should always be understood as a material that is transparent to the laser beam of an ultrashort pulse laser.

[0010] Material modification introduced into transparent materials via ultrashort laser pulses can be subdivided into three distinct categories; see K. Itoh et al. „Ultrafast Processes for Bulk Modification of Transparent Materials“ MRS Bulletin, vol. 31 p.620 (2006): Type I is isotropic refractive index change; Type II is birefringent refractive index change; and Type III is so-called void or cavity. In this respect, the resulting material modification depends on laser parameters such as pulse duration, wavelength, pulse energy, and laser repetition frequency, on material properties such as electronic structure and coefficient of thermal expansion, and also on the focused numerical aperture (NA).

[0011] Type I isotropic refractive index changes can be traced back to site-constrained fusion via laser pulses and rapid re-solidification of transparent materials. For example, when quartz glass is rapidly cooled from a higher temperature, it has a higher material density and refractive index. Therefore, if the material in the focused volume melts and is subsequently rapidly cooled, the quartz glass has a higher refractive index in the modified surface than in the unmodified region.

[0012] Type II birefringence refractive index changes can occur, for example, due to interference between an ultrashort laser pulse and the electric field of the plasma generated by the laser pulse. This interference leads to periodic modulation in the electron plasma density, which results in birefringence properties of transparent materials during curing, i.e., direction-dependent refractive index. Type II modification is also accompanied, for example, by the formation of so-called nanogratings.

[0013] For example, type III modified voids (cavities) can be generated at high laser pulse energies. Here, void formation is attributed to the explosive expansion of highly excited evaporated material from the focusing volume into the surrounding material. This process is also known as micro-explosion. Because this expansion occurs within the material mass, micro-explosions result in less dense or hollow (void) microscopic defects, or submicron or atomic-level defects, which are encapsulated by a dense material. Considering the compaction at the impact front of the micro-explosion, stresses are generated in transparent materials that may lead to spontaneous crack formation or may promote crack formation.

[0014] In particular, void formation can also accompany Type I and Type II modifications. For example, Type I and Type II modifications can occur in smaller stress regions around the introduced laser pulse. Correspondingly, in the case of Type III modification, there is always a less dense or hollow or defective component. For example, it is not a cavity, but a lower-density region generated in the sapphire by micro-explosions produced by Type III modification. This modification also often accompanies or promotes crack formation due to the material stress generated in the case of Type III modification. When Type III modification is introduced, the formation of Type I and Type II modifications cannot be completely suppressed or avoided. Therefore, it is unlikely to find “pure” Type III modification.

[0015] At high laser repetition rates, materials cannot cool completely between pulses, allowing the cumulative effect of heat introduced from pulse to pulse to potentially affect material modification. For example, the laser repetition frequency may be higher than the reciprocal of the material's thermal diffusion time, causing heat accumulation due to continuous absorption of laser energy to occur in the focal region until the material's melting temperature is reached. Furthermore, due to heat transfer to areas surrounding the focal region, regions larger than the focal region can fuse. The heated material cools rapidly after the introduction of the ultrashort laser pulse, and thus the density and other structural properties of the high-temperature state are fixed within the material.

[0016] Material modification is introduced into the material along the dividing line. The dividing line describes the incident line of the laser beam on the workpiece surface. For example, the laser beam and the workpiece move relative to each other at a feed rate due to the feed, causing the laser pulses to be incident on the workpiece surface at different locations over time. Here, the feed rate and / or repetition rate of the laser are chosen such that the material modification in the workpiece material does not overlap, but exists separately in the material. Here, being able to move relative to each other means that not only can the laser beam be translated relative to the workpiece at a fixed location, but the workpiece can also move relative to the laser beam. Alternatively, both the workpiece and the laser beam can move. During the relative movement of the workpiece and the laser beam, the ultrashort pulse laser emits laser pulses into the workpiece material at its repetition frequency.

[0017] Because the material modification manifests in the workpiece material along the beam propagation direction, it creates a surface in which all material modification exists, and this surface intersects the workpiece surface along the dividing line. The surface in which material modification exists is called the material modification surface. In particular, the material modification surface can also be curved, such that material modification forming, for example, the outer surface of a cylinder or cone, is also located within the material modification surface.

[0018] The laser pulse is introduced into the workpiece material at a so-called angle of attack. Here, the angle of attack is given by the angular difference between the laser beam and the surface normal of the workpiece to be divided. When the angle of attack is not zero, the material modification surface is also inclined relative to the surface normal of the workpiece. It is important to consider that, in the case of a non-translational angle of attack, according to Snell's law, the laser beam is refracted according to the corresponding refractive indices of the surrounding medium, preferably air, and the workpiece material. Therefore, the beam propagation direction in the workpiece material can differ from the beam propagation direction before entering the workpiece material. In particular, the material modification surface can therefore also be inclined relative to the surface normal at an angle different from the angle of attack.

[0019] Currently, Type III modification is used to create fracture sites in materials or to penetrate the material along the modified surface. Here, crack formation promoted by voids can be achieved, with crack propagation occurring between adjacent material modifications, as will be explained in more detail below. Preferably, this crack formation occurs within the modified surface, making the modified surface a dividing surface.

[0020] The segmentation along the material modification surface is carried out here through a segmentation step, so that the workpiece is divided into bulk parts and so-called workpiece segments.

[0021] Here, the partitioning step may include mechanical partitioning and / or etching processes and / or thermal application and / or self-partitioning steps.

[0022] For example, heat application can be achieved by heating the material itself or heating the dividing line. For instance, the dividing line can be locally heated using a continuous-wave CO2 laser, causing the material in the modified region to expand differently compared to the untreated or unmodified material. Alternatively, heat application can be achieved via a hot air stream, baking on a hot plate, or heating the material in an oven. In particular, a temperature gradient can be applied during the dividing step. Cracks promoted by the material modification then undergo crack growth, allowing the formation of a continuous and seamless dividing surface through which portions of the workpiece are separated from each other.

[0023] Mechanical splitting can be achieved by applying tensile or bending stresses, for example, by applying mechanical loads to the workpiece portions separated by a dividing line. For instance, tensile stresses can be applied if forces acting in opposite directions on the workpiece portions separated by the dividing line act at the respective points of force application within the material plane, with these opposing forces pointing away from the dividing line. If these forces are not oriented parallel or antiparallel to each other, this can contribute to the generation of bending stresses. Once the tensile or bending stress exceeds the binding force of the material along the dividing plane, the workpiece splits along the dividing plane. In particular, mechanical changes can also be achieved through pulse-like action on the portions to be split. For example, lattice vibrations can be generated in the material through impact. Therefore, tensile and compressive stresses that trigger crack formation can be generated through the deflection of lattice atoms.

[0024] Materials can also be segmented using a wet chemical solution through etching, where the etching process preferably adheres the material to a material modifier, i.e., selectively weakens the material. Since the weakened parts of the workpiece through material modification are preferably etched, this results in the workpiece being segmented along the dividing surface.

[0025] In particular, so-called self-splitting can also be performed through targeted crack guidance achieved by the orientation of material modification in the material. Here, the crack formation from material modification to material modification enables the splitting of the entire surface of two parts of the workpiece without having to perform an additional splitting step.

[0026] This has the following advantages: it allows for the selection of an ideal segmentation method for the corresponding material of the workpiece, resulting in high-quality segmentation edges.

[0027] In particular, the material modification can be configured to extend through both sides of the workpiece, which are located in an intersecting plane, and the formed edges are generated through a segmentation step, preferably chamfers and / or bevels.

[0028] If the surface normals of a plane are not oriented parallel to each other, the two side faces lie in intersecting planes. For example, in the case of a cuboid, if the two side faces can be connected by the edges of the cuboid, these side faces lie in intersecting planes. In the case of a disk-shaped material, the circumference of the disk lies to some extent in a plane that intersects with the upper and lower sides of the disk. At least locally, even in the case of a disk, a rectangular cross-section is produced in the incident plane of the laser beam.

[0029] Material modification penetrates two adjacent sides. Here, penetration means that material modification begins on one side and ends on the other side in the direction of beam propagation. However, this could also mean that the material modification extends only within the workpiece material to avoid material debris on the material surface. In this case, however, a larger portion of the laser path must be modified between the two sides with the material modification. For example, since the material modification is strategically meaningfully positioned within the material, it might be sufficient to introduce the material modification only over one-third of the path. However, the material modification could also be continuous throughout the entire path between the two sides.

[0030] Thus, a segment of the workpiece is created in the plane of incidence of the laser beam, the incident beam, and the refracted beam. For example, in the case of a cuboid, this segment can be triangular. The triangular segment of the workpiece has a so-called hypotenuse, which is opposite to the edge to be divided. Here, the length of the hypotenuse is given by the length of the material modification in the workpiece. Furthermore, the distance between the edge adjacent to the hypotenuse of the segment is given by the distance between the dividing line and the edge of the workpiece.

[0031] Because the material modification penetrates both sides of the material, it introduces a fracture point along the entire length of the hypotenuse. Consequently, the workpiece is split along the material-modified surface in the subsequent cutting step.

[0032] After segmentation, the material-modified surface becomes what are called the forming edges of the material. The forming edges of the workpiece are further subdivided into what are called chamfers and bevels. Here, the chamfer of the workpiece is understood as a bevel, in which the initial edge of the cuboid has been replaced by two edges. Thus, the initial edge is softened, or a transition region is achieved between the first cuboid side and the second cuboid side. A bevel is created if the bevel of the segment coincides with an edge of the workpiece, or generally if the side of the triangular segment has the same length as at least one side of the workpiece extending parallel to that side.

[0033] For example, the length of the hypotenuse of the chamfer and / or bevel is between 50 µm and 5000 µm, preferably between 100 µm and 200 µm.

[0034] This has the following advantages: the workpiece can be chamfered in a visually appealing and high-quality manner. Furthermore, relatively thick workpieces can also be chamfered. Additionally, providing shaped edges, chamfers, or bevels allows for more stable edges that are less prone to breakage during further processing, installation, or end-customer use compared to edges with 90° angles.

[0035] The laser beam can be a non-diffractive laser beam.

[0036] In particular, non-diffractive beams and / or Bessel-type beams should be understood as beams in which the transverse intensity distribution remains unchanged during propagation. Specifically, in the case of non-diffractive beams and / or Bessel-type beams, the transverse intensity distribution in the longitudinal direction and / or propagation direction of the beam is substantially constant.

[0037] The transverse intensity distribution should be understood as the intensity distribution located in a plane oriented perpendicular to the longitudinal direction and / or propagation direction of the beam. Furthermore, the intensity distribution is always understood as the portion of the laser beam's intensity distribution that exceeds a material modification threshold. For example, this could mean that only a fraction or a few of the maximum intensity values ​​of a non-diffractive beam can introduce material modification into the workpiece material. Accordingly, the phrase "focused region" can also be used for the intensity distribution to clarify that this portion of the intensity distribution is provided in a targeted manner, and that intensity enhancement in the form of the intensity distribution is obtained through focusing.

[0038] For the definition and properties of non-refractive light beams, please refer to the following book: "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M. Wördemann, Springer Science & Business Media (2012), ISBN 978-3-642-29322-1. Please refer to its entire contents.

[0039] Therefore, non-diffractive laser beams have the advantage that they can have an intensity distribution that is elongated in the beam propagation direction to a size significantly larger than the transverse dimension of the intensity distribution. In particular, this can result in material modifications that are elongated in the beam propagation direction, allowing these modifications to penetrate both sides of the workpiece particularly easily.

[0040] The laser beam can have a non-radial symmetrical transverse intensity distribution, wherein the transverse intensity distribution is elongated in the direction of the first axis compared to the second axis, wherein the second axis is perpendicular to the first axis.

[0041] Here, non-radial symmetry means that the transverse intensity distribution depends not only on the distance to the optical axis but also, at least, on the polar angle around the beam propagation direction. For example, a non-radial symmetric transverse intensity distribution can mean that the transverse intensity distribution is, for example, cross-shaped, triangular, or polygonal, such as a pentagon. A non-radial symmetric transverse intensity distribution can also include additional rotationally symmetric and mirror-symmetric beam cross sections. In particular, a non-radial symmetric transverse intensity distribution can also have an elliptical form, where the ellipse has a major axis A and a minor axis B perpendicular to that major axis. Accordingly, an elliptical transverse intensity distribution exists if the ratio A / B is greater than 1, particularly if A / B = 1.5. An elliptical transverse intensity distribution of a laser beam can correspond to an ideal mathematical ellipse. However, a non-radial symmetric transverse intensity distribution of a non-diffractive laser beam can also simply have the aforementioned ratio of the major axis to the minor axis and can have different profiles—for example, an approximate mathematical ellipse, a dumbbell shape, or any other symmetric or asymmetric profile enveloped by a mathematically ideal ellipse.

[0042] In particular, elliptical non-diffractive beams can be generated from non-diffractive beams. Here, the elliptical non-diffractive beam exhibits special characteristics, revealed by analysis of the beam intensity. For example, the elliptical non-diffractive beam has a principal maximum value that coincides with the center of the beam. Here, the center of the beam is given by the location where these principal axes intersect. In particular, an elliptical quasi-non-diffractive beam can be represented by the superposition of multiple intensity maximum values, where only the envelope of the relevant intensity maximum value is elliptical. In particular, each intensity maximum value need not have an elliptical intensity profile.

[0043] Due to the non-radially symmetric transverse intensity distribution, the material modification in a cross-section perpendicular to the beam propagation direction within the material will also be non-radially symmetric. Conversely, the shape of the material modification corresponds to the intensity distribution of the non-diffractive beam within the workpiece material.

[0044] In the case of non-diffractive beams, there are particularly high-intensity regions that interact with the material and introduce material modification, as well as regions below the modification threshold. Here, the non-radially symmetric transverse intensity distribution involves the maximum intensity above the modification threshold.

[0045] Accordingly, the non-radially symmetric Type III material modification has a preferred direction of extension parallel to the elongated axis of the material modification. Consequently, cracks typically form or are induced along this preferred direction. For example, cracks primarily propagate along the major axis of the elliptical Type III material modification because the profile of the material modification has a smaller curvature there, and therefore the stress peaks here preferably relax in the form of cracks in the material.

[0046] In particular, crack propagation can be promoted in a targeted manner by appropriate orientation of non-radial symmetric material modification in the material, such that, for example, due to the orientation of the preferred direction, crack formation is tangential to the dividing line.

[0047] For example, if the feed direction between the non-diffractive laser beam and the workpiece is parallel to the short axis of the transverse intensity distribution, adjacent material modification cracks are unlikely to meet because crack formation preferably extends perpendicular to the feed direction. In contrast, if the feed direction is parallel to the long axis, adjacent material modification cracks are more likely to meet and merge, and crack formation preferably occurs relative to that long axis. Due to the beam cross-section and / or workpiece orientation, targeted crack development can be ensured along the entire length of the cleaving line, even in the case of a curved cleaving line. This allows material to be cleaved along cleaving lines of any desired shape.

[0048] When a non-radially symmetrical transverse intensity distribution is projected onto the surface of a workpiece, the first axis and the second axis can appear to have the same dimensions due to the angle of attack.

[0049] A non-radially symmetric transverse intensity distribution projected onto the workpiece surface at an angle of attack can lead to distortion of the intensity distribution. Therefore, for example, a circular intensity distribution can be generated on the workpiece by initially projecting an elliptical intensity distribution. However, it is also possible, in particular, to achieve an elliptical projection onto the workpiece surface by initially projecting a circular intensity distribution. Thus, material modification with an intensity distribution generated by projecting onto the workpiece surface at an angle of attack is introduced into the material.

[0050] Thus, material modifications are introduced into the inverted material, and these material modifications have an intensity distribution that is projected onto the workpiece surface at an angle of attack.

[0051] It is also possible that the previously selected preferred direction of the non-radially symmetric transverse intensity distribution is distorted by projection, thus the preferred direction deviates from the actual effective intensity distribution.

[0052] In one embodiment, it is therefore preferable that the non-radially symmetrical lateral strength distribution is circular due to the angle of attack. Specifically, this means that, in the case of an initially elliptical lateral strength distribution, the major axis A and minor axis B of the projected ellipse appear to have the same size. This effectively induces a circular strength distribution for material modification.

[0053] The projection of a non-radial symmetric intensity distribution onto the workpiece surface can be elongated in the feed direction.

[0054] Thus, the distortion caused by the intensity distribution projected onto the workpiece surface can be controlled such that the preferred direction of the effective beam profile points towards the feed direction. Since the preferred direction points towards the feed direction and therefore extends parallel to the dividing line, the workpiece can be divided along the resulting material-modified surface with particular ease and high quality.

[0055] The ratio of the first axis to the second axis in a non-radially symmetric transverse intensity distribution can be greater than the reciprocal of the cosine of the angle of attack.

[0056] Assume a laser beam is incident on a surface at an angle of attack, where a first axis of the transverse intensity distribution extends parallel to the workpiece surface and perpendicular to the incident plane of the laser beam, and a second axis lies in the incident plane. Furthermore, the first axis is positioned as the major axis of a non-radial symmetric transverse intensity distribution, and the second axis is positioned as the minor axis of the same distribution. Then, because the second axis is projected onto the workpiece surface, the effective length increases by the reciprocal of the angle of attack.

[0057] For example, if the second axis is 10 µm and the angle of attack is 60°, then the projection of the second axis onto the workpiece surface is 10 µm / cos(60°) = 20 µm.

[0058] Furthermore, the first axis of the transverse intensity distribution does not increase in size through projection because it is perpendicular to the incident plane. Accordingly, the beam profile has a first axis of the same size.

[0059] For example, if the first axis in the above example is 20 µm, it will also be 20 µm in the projection. However, overall, this thus produces a circular beam shape on the workpiece surface.

[0060] For example, if the first axis in the above example is 15 µm, it will also be 15 µm in the projection, but the second axis has grown to 20 µm. Therefore, material modification with a preferred orientation located in the incident plane of the laser beam is achieved. In particular, due to the projection, the preferred orientation has been rotated from the first axis to the second axis.

[0061] Therefore, by selecting the ratio of the first axis to the second axis as greater than the reciprocal of the cosine of the angle of attack, the initial intended orientation of the intensity distribution is ensured even when the beam is projected onto the surface of the workpiece.

[0062] The ratio of the first axis to the second axis can be greater than [a certain value]. .

[0063] Therefore, especially at an angle of attack of 45°, it is ensured that the initial expected orientation of the lateral intensity distribution is maintained. In particular, 1 / cos(45°) = This allows for the selection of the axis ratio accordingly. Consequently, even when the light beam is projected onto the workpiece surface, the preferred orientation is maintained through material modification.

[0064] The material modification surface can be tilted relative to the surface of the workpiece at an angle of up to 35° in terms of quantity.

[0065] According to Snell's law, the product of the refractive index of the surrounding medium and the sine of the angle of attack is equivalent to the product of the refractive index of the material and the sine of the angle of refraction. Accordingly, based on the refractive index, the angle of attack can be selected such that the material modification surface is tilted no more than 35° relative to the workpiece surface. In particular, the angle specification relates to the material modification surface where the material modification is located, such that the angle directly corresponds to the angle of refraction.

[0066] The pulse energy of the laser pulse can be between 10 µJ and 5 mJ and / or the average laser power can be between 1 W and 1 kW and / or the laser pulse can be a single laser pulse or part of a laser burst and / or the wavelength of the laser can be between 300 nm and 1500 nm, especially 1030 nm.

[0067] This has the advantage of providing optimal laser parameters for a wide range of materials.

[0068] For example, an ultrashort pulse laser can provide a single laser pulse with a pulse energy of 100 µJ, where the average laser power is 5 W and the laser wavelength is 1030 nm.

[0069] A laser burst can include 2 to 20 laser pulses, wherein the laser pulses of the laser burst have a time interval of 10 ns to 40 ns, preferably 20 ns.

[0070] For example, a laser burst can consist of 10 laser pulses, with a time interval of 20 ns between the pulses. In this case, the repetition frequency of the laser pulses is 50 MHz. Alternatively, a laser burst can be emitted with a single laser pulse repetition frequency on the order of 100 kHz.

[0071] By using laser bursts, it is possible to generate shaped edges with exceptionally high surface quality by responding to the specific thermal properties of the material.

[0072] The incident laser beam can be polarized parallel to the incident plane.

[0073] The refraction of a laser beam as it transitions from the surrounding medium into a material depends not only on the angle of attack and the refractive index. The polarization of the laser beam also plays a crucial role. Using the so-called Fresnel equations, it can be shown that for an incident angle greater than 10°, the transmittance of a laser beam polarized parallel to the incident plane is always greater than that of a laser beam polarized perpendicular to the incident plane.

[0074] In particular, this allows for the minimization of reflection loss of a P-polarized laser beam, thereby achieving optimal energy output for the segmentation process within the material. Furthermore, when the laser beam is incident at a Brewster angle, a particularly advantageous energy input coupled into the material can be obtained.

[0075] The aforementioned objectives are also achieved by the apparatus for dividing workpieces according to this application. The advantageous development is readily apparent from the specification and accompanying drawings.

[0076] Accordingly, an apparatus for dividing a workpiece comprising a transparent material is proposed, the apparatus comprising: an ultrashort pulse laser configured to provide ultrashort laser pulses; a processing optical tool configured to introduce the laser pulses into the transparent material of the workpiece; and a feeding device configured to move a laser beam formed by the laser pulses and the workpiece relative to each other along a dividing line in a feed relative to each other, and to orient the optical axis of the processing optical tool at an angle of attack relative to the surface of the workpiece. According to the invention, the laser pulses are introduced into the transparent material of the workpiece at an angle of attack, and the material modification is a type III modification, associated with crack formation in the material of the workpiece.

[0077] For example, a machining fixture can be an optical imaging system. For example, a machining fixture can consist of one or more components. For example, a component can be a lens or an optical imaging freeform surface or a Fresnel zone plate. The machining fixture, in particular, allows for the determination of the depth to which the intensity distribution is introduced into the workpiece material. In a sense, this can set the arrangement of the focal zone in the beam propagation direction. For example, by adjusting the machining fixture, the focal zone can therefore be arranged on the surface of the workpiece, or preferably in the material of the workpiece. For example, this allows the focal zone to be set such that the laser beam penetrates two adjacent sides, and thus results in material modification that allows the entire area of ​​the workpiece to be segmented through a segmentation step.

[0078] For example, the feeding device here could be an XY stage or an XYZ stage to change the incident point of the laser pulse on the workpiece. Here, the feeding device can move the workpiece and / or the laser beam so that material modification can be introduced into the workpiece material adjacent to each other along the dividing line.

[0079] The feeding device can also be angle-adjustable, allowing the workpiece and laser beam to rotate relative to each other around all Euler angles. This in particular ensures that the angle of attack can be maintained along the entire dividing line.

[0080] In particular, the angle of attack is also understood as the angle between the optical axis of the machining tool and the surface normal of the workpiece material. Here, the angle of attack between the optical axis of the machining tool and the surface normal can be, for example, between 0 and 60°.

[0081] A beam-forming optical tool can shape a non-diffractive laser beam from a laser beam, wherein the transverse intensity distribution of the non-diffractive laser beam can be non-radially symmetric, wherein the non-radially symmetric transverse intensity distribution can be elongated along a first axis compared to a second axis, and wherein the second axis is perpendicular to the first axis.

[0082] For example, a beamforming optics can take the form of a diffractive optical element (DOE), a free-form surface or axial cone or micro-axial cone in a reflective or refractive embodiment, or may include a combination of multiple such components or functionalities. If the beamforming optics shapes a non-diffractive laser beam from a laser beam upstream of the processing optics, the depth to which the intensity distribution is introduced into the material can be determined by focusing the processing optics. However, the beamforming optics can also be configured such that the non-diffractive laser beam is generated solely by imaging with the processing optics.

[0083] A diffractive optical element is configured to influence one or more properties of an incident laser beam in two dimensions. A diffractive optical element is a fixed component that can be used to generate exactly one intensity distribution of a non-diffractive laser beam from an incident laser beam. Typically, a diffractive optical element is a specially formed diffraction grating in which the incident laser beam is diffracted into the desired beam shape.

[0084] An axial cone is a conically ground optical element that shapes a non-diffractive laser beam from an incident Gaussian laser beam as it passes through. Specifically, the axial cone has a cone angle α, calculated from the beam incident surface to the lateral surface of the cone. This causes the edge rays of the Gaussian laser beam to be refracted into a focal spot different from the paraxial rays. In particular, this produces an intensity distribution that is elongated in the beam propagation direction.

[0085] The machining optical tool may include a telescope system configured to introduce a laser beam of reduced and / or increased size into the material of the workpiece.

[0086] Increasing or decreasing the size of the laser beam or its lateral intensity distribution allows the laser beam intensity to be distributed over a large or small focusing area. Because the laser energy is distributed over a large or small area, the intensity is suitable such that it can also be selected between modification types I, II, and III by increasing and / or decreasing it.

[0087] In particular, material modification can be introduced into the workpiece material by increasing or decreasing the non-radially symmetric transverse intensity distribution. For example, by decreasing the transverse intensity distribution of an ellipse into the material, the radius of curvature of the resulting material modification is also reduced. In other words, a given curvature becomes sharper due to the reduction. This can promote crack formation in the workpiece material. Furthermore, the increase or decrease in the optical system can be adapted to given processing conditions, allowing for more flexible use of the equipment.

[0088] The feed device may include a shaft device and a workpiece holder, which are configured to allow the machining tool and the workpiece to translate relative to each other along three spatial axes and rotate about at least two spatial axes.

[0089] For example, the axis device could be a 5-axis device. Alternatively, the axis device could be a robotic arm that guides the laser beam onto a workpiece or moves the workpiece relative to the laser beam.

[0090] Because the laser beam and the workpiece move relative to each other to introduce material modification along the dividing line, it is necessary for either the laser beam or the workpiece to rotate locally together to maintain an angle of attack relative to the dividing line. Therefore, even when the dividing line is curved, the material modification surface can always have the same angle relative to the workpiece surface.

[0091] In particular, this axial device can simultaneously orient the non-radial symmetric transverse strength distribution relative to the dividing line, thereby producing a material modification in which the preferred direction extends parallel to the dividing line and promotes the formation of cracks along the dividing line.

[0092] Furthermore, the axial device may include fewer than five movable axes, provided that the workpiece holder can move about the corresponding number of axes. For example, if the axial device is movable only in the XYZ directions, the workpiece holder may, for example, have two rotational axes to allow the workpiece to rotate relative to the laser beam.

[0093] The laser beam component can be incident on the workpiece at an angle of attack of up to 80° relative to the surface normal of the workpiece.

[0094] Because of the machining tool, the laser pulse converges towards the optical axis, which is oriented at an angle of attack relative to the surface normal of the workpiece. Here, the sub-laser beams of the ray have an angle relative to the optical axis of the machining tool. In particular, due to the numerical aperture, these angles can be very large or very small.

[0095] Because these sub-laser beams enveloping the laser beam are incident on the workpiece surface at an angle of incidence no greater than 80°, large reflection losses can be avoided. According to Fresnel's formula, the reflection and transmission of the laser beam at the workpiece surface depend on the angle of attack and the refractive index. In the case of grazing incidence, only a small amount of laser light can couple into the material, causing effective material processing to stop. Furthermore, the shape of the non-diffractive beam may be negatively affected as a result.

[0096] A polarizing optical apparatus can be configured to adjust the polarization of a laser beam relative to, preferably parallel to, the plane of incidence of the laser beam. This polarizing optical apparatus preferably includes a polarizer and a waveplate.

[0097] Waveplates, especially so-called half-waveplates, can rotate the polarization direction of linearly polarized light by a selectable angle. This allows for the desired polarization of a laser beam.

[0098] For example, a polarizer can be a thin-film polarizer. Thin-film polarizers only transmit laser radiation with a defined polarization.

[0099] Therefore, the polarization state of laser radiation can always be controlled by combining waveplates and polarizers.

[0100] According to Fresnel's formula, laser beam polarization parallel to the incident plane has the following advantages: for angles of attack greater than 10°, the transmittance is always greater than when the laser beam is polarized perpendicular to the incident plane. In particular, compared to the case where the polarized light is perpendicular, the transmission is more constant and uniform over a larger range of angles of attack when the polarized laser beam is parallel. Therefore, machining tools with large numerical apertures can also be used. However, when the polarized laser beam is perpendicular, asymmetrical beam reflection occurs at the workpiece surface, causing optical aberrations that degrade the quality of material modification and the quality of the cleaved surface.

[0101] The beam guiding device can be configured to guide a laser beam to a workpiece, wherein beam guiding is achieved through a mirror system and / or optical fiber, preferably a hollow optical fiber.

[0102] So-called free beam steering uses a mirror system to guide a laser beam from a fixed ultrashort pulse laser to a beam-shaping instrument in various spatial dimensions. Free beam steering has the advantage that the entire optical path is accessible, allowing for the installation of additional components, such as polarizers and waveplates, without any problems.

[0103] Hollow-core fiber is a photonic fiber that can flexibly guide ultrashort pulse laser beams further into beam-shaping optical instruments. Using hollow-core fiber eliminates the need for adjustment of the emitting mirror optical instrument.

[0104] The regulating electronics can be configured to trigger the emission of laser pulses from the ultrashort pulse laser due to the relative position of the laser beam and the workpiece.

[0105] In cases where the feed path is curved or polygonal, a localized reduction in feed rate may be meaningful. However, with a constant laser repetition frequency, this could lead to overlapping of adjacent material modifications or undesirable heating and / or fusion of the material. For this reason, the control electronics are able to control pulse emission based on the relative position of the laser beam and the workpiece.

[0106] For example, the feeding device may include a location-resolved encoder that measures the position of the feeding device and the laser beam. Based on the location information, the pulse emission of the laser pulse in the ultrashort pulse laser can be triggered by adjusting the corresponding triggering system of the electronics.

[0107] Computer systems can also be used to achieve pulse triggering. For example, the location of laser pulse emission can be determined for the corresponding dividing line before processing the material, thus ensuring the optimal distribution of material modification along the dividing line.

[0108] This ensures that the material modification interval remains constant even with variations in feed rate. In particular, it also allows for the production of uniformly segmented surfaces and high-quality chamfers or bevels.

[0109] The workpiece holder may have a surface that does not reflect and / or scatter laser beams.

[0110] This in particular prevents the laser beam from being redirected back into the material after it has penetrated it, thus preventing further material modification. In particular, non-reflective and / or non-scattering surfaces also improve operational safety. Attached Figure Description

[0111] Preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, in which: Figure 1A , Figure 1B , Figure 1C , Figure 1D , Figure 1E A schematic diagram of the method is shown; Figure 2A , Figure 2B , Figure 2C A schematic diagram of chamfered and beveled structures is shown; Figure 3A , Figure 3B , Figure 3C , Figure 3D , Figure 3E , Figure 3F Further schematic illustrations of chamfered and beveled structures are shown; Figure 4A , Figure 4B A schematic diagram of a non-diffractive laser beam is shown; Figure 5A , Figure 5B , Figure 5C , Figure 5D , Figure 5E Another schematic illustration of a non-diffractive laser beam is shown; Figure 6A , Figure 6B A schematic diagram illustrating crack formation around material modification is shown; Figure 7A , Figure 7B A schematic illustration of a beam of light projected onto a material surface is shown. Figure 8A, Figure 8B , Figure 8C , Figure 8D Another schematic illustration of a beam projection on a material surface is shown; Figure 9 A graph showing the transmittance according to polarization and angle of attack is shown; Figure 10 A schematic diagram of an apparatus for implementing the method is shown; and Figure 11A , Figure 11B , Figure 11C Further schematic illustrations of an apparatus for implementing the method are shown. Detailed Implementation

[0112] Preferred embodiments are described below with reference to the accompanying drawings. Here, in different drawings, the same reference numerals are used for the same, similar, or identical elements, and repeated descriptions of these elements are omitted in part to avoid redundancy.

[0113] Figures 1A to 1E A method for dividing a workpiece 1, which includes a transparent material, is schematically shown. Figure 1A The image shows a cross-section of workpiece 1, onto which the laser beam 20 of an ultrashort pulse laser 2 is incident. Here, the laser beam 20 is introduced onto workpiece 1 at an angle of attack α, which corresponds to the optical axis of the machining fixture 3 shown below.

[0114] Upon transition to workpiece 1, the laser beam 20 is refracted at surface 10 of workpiece 1 according to Snell's law of refraction, causing the laser beam 20 to continue propagating in the material of workpiece 1 at an angle β relative to the surface normal N. As the laser pulse is introduced into workpiece 1 through the laser beam 20, the material of workpiece 1 is heated in the focusing region 220 of the laser beam 20. Here, the material of workpiece 1 evaporates in the focusing region, causing an explosive expansion of this plasma state in the surrounding material of workpiece 1. Material stress is generated due to compression at the impact front of this so-called micro-explosion, leaving a less dense or even empty space (void) in the initial focusing region 220 of the laser beam. The material modification of workpiece 1 in the focusing region 220 is referred to as material modification 5, where material modification 5 is specifically type III material modification. Due to material stress, crack formation in the material of workpiece 1 is ultimately favored.

[0115] Here, the pulse energy of the laser pulse can be between 10 µJ and 5 mJ, and / or the average laser power can be between 1 W and 1 kW, and / or the laser pulse can be a single laser pulse or part of a laser burst, and / or the wavelength of the laser can be between 300 nm and 1500 nm. Furthermore, it is possible that the laser burst comprises 2 to 20 laser pulses, wherein the laser pulses of the laser burst have a time interval of 10 ns to 40 ns, preferably 20 ns.

[0116] like Figure 1B As shown, during the output laser pulse of the ultrashort pulse laser 2, the laser beam 20 and the workpiece 1 move relative to each other with a feed V. This feed V is guided along a dividing line 4, which determines where the workpiece 1 should be divided on the upper side 10. Since the laser beam 20 propagates in the material of the workpiece 1 at an angle β, the material modification 5 is also introduced into the material of the workpiece 1 at an angle β. In particular, the material modification 5 can be shaped differently depending on the extension scale and configuration or intensity distribution of the focusing region 220, especially being elongated in the beam propagation direction.

[0117] As the material modification 5 is elongated along the beam propagation direction, the laser beam 20 simultaneously feeds V, creating a so-called material modification surface 50 in the material of the workpiece 1 where the material modification 5 is located. It will be observed that the material modification 5 does not overlap, but exists separately from each other. The material modification surface 50 divides the workpiece 1 into so-called bulk workpiece 1' and so-called segments 12. For example, the material modification surface 50 can be tilted relative to the surface 10 of the workpiece 1 at an angle β of up to 35° in magnitude.

[0118] Due to the material modification 5 in the material modification surface 50, the material of the workpiece 1 is perforated to a certain extent, so that the workpiece 1 and the segment 12 can be separated from each other particularly easily along the material modification surface 50.

[0119] True segmentation can be achieved through defined segmentation steps. For example, spontaneous crack growth can be induced by mechanical action on segment 12, allowing segment 12 to be segmented from the bulk workpiece 1' face.

[0120] like Figure 1C As shown, segment 12 could also be separated from bulk workpiece 1' in a chemical bath. For example, it is possible that the introduced material modification 5 is particularly susceptible to the effects of the etching solution, causing the etching process in the material-modified surface 50 to separate segment 12 from bulk workpiece 1'.

[0121] For example, it is also possible to separate section 12 from the bulk workpiece 1' through thermal action, such as... Figure 1DAs shown in the diagram. For this purpose, workpiece 1 is heated, for example, using a hot plate 42 or a heating laser (not shown here), causing thermal expansion of workpiece 1. Due to the thermal expansion of workpiece 1, cracks may form due to the material stress already present in the material modification surface 50, causing the bulk workpiece 1' and section 12 to be separated from each other in a faceted manner.

[0122] Similarly, it is possible that workpiece 1 could split without external influence due to spontaneous crack formation, a so-called self-splitting process. By introducing material stresses into workpiece 1 through type III material modification, these stresses are already associated with crack formation itself. Therefore, such spontaneous crack formation could also cause the bulk workpiece 1 and segment 12 to split.

[0123] like Figure 1E As shown, due to the above-described segmentation steps, so-called chamfers and / or bevels are generated on the bulk workpiece 1'. It is also known to chamfer workpiece 1 to form its shaped edges. The chamfer or bevel is formed by the material modification surface 50, such that the angle of attack α of the laser beam 20, the refractive index of the surrounding medium, and the refractive index of workpiece 1 yield the angle of refraction β, and thus also the orientation of the material modification 5 and the final orientation of the chamfer or bevel.

[0124] To create shaped edges, it is advantageous that material modification 5 penetrates the workpiece 1 to form those sides of the chamfered edges. For example, in Figure 1A The middle sides 10 and 11 form chamfered edges 110. In particular, the sides 10 and 11 of the workpiece 1 lie in intersecting spatial planes, wherein the line of intersection of these planes is precisely the edge 110 of the workpiece 1.

[0125] Figures 2A to 2C Different possible shaped edges of the material are shown. Figure 2A In the process, the material modification surface 50 intersects with the workpiece 1, wherein the height of the chamfer is less than the height of the side surface 11, and the width of the chamfer is less than that of the side surface 10. Correspondingly, by chamfering, the edge 110 is replaced by two edges 110' and 110" . Thus, the initial edge 110 becomes blunt or flattened.

[0126] exist Figure 2B In this example, the material-modified surface 50 intersects with the workpiece 1, wherein the height of the segment 12 is equivalent to the height of the side surface 11, and the material-modified surface 50 coincides with the edge 130 formed by the lower side 13 and the side surface 11 of the workpiece 1. In this example, the number of edges remains constant, but the angle at which the sides 13 and 11 intersect becomes sharper. Accordingly, the workpiece 1 can be made sharper and / or form a pointed tip by forming the bevel 12.

[0127] exist Figure 2CIn this process, the material modification surface 50 intersects with the workpiece 1, specifically intersecting not only the upper side 10 but also the lower side 13 of the workpiece 1. Consequently, the overall longitudinal extension dimension of the workpiece 1 decreases, and the workpiece 1 also becomes more pointed, as shown... Figure 2B As shown.

[0128] In each of the cases shown, the so-called hypotenuse H of segment 12 is given by the length of the material modification in the material.

[0129] Even though the description has been reduced to cube segmentation, this method can also be used to segment circular material 1 or rounded material. For example, Figure 3A , Figure 3B Workpiece 1 is shown in the form of a disc. The so-called incident plane is defined by the laser beam 20 incident at an angle of attack α and the laser beam 20 refracted at an angle β. The above description can be used verbatim within this incident plane.

[0130] also, Figure 3C It shows the Figure 3A , Figure 3B The disc is chamfered to produce a tapered element, so that different forms of shaped edges can be produced through the introduced material modification 5.

[0131] Figure 3D Another example is shown. Material modification 5 is introduced circumferentially into workpiece 1, wherein the dividing line 4 is curved and the angle of attack α in the incident plane is always kept constant. Thus, a rounded chamfer or bevel with high optical quality is produced after the dividing step.

[0132] Figure 3E Another example is shown below. (Compared to...) Figure 3D Unlike other methods, the rounded dividing line 4 is not used here. Workpiece 1 is successively chamfered on all four sides, resulting in crystalline chamfers at the corners of workpiece 1 after the dividing step. Therefore, this method is also suitable for giving workpiece 1 a particularly high-quality appearance.

[0133] Figure 3F It shows Figure 3D and Figure 3E The cross-section of material 1 clearly shows the formation of chamfer 14.

[0134] To produce a particularly simple material modification 5 that penetrates at least sectionally into workpiece 1, a so-called non-diffractive laser beam 20 is suitable. The non-diffractive beam 20 preferably has a focusing region 220 of length L that is elongated in the beam propagation direction. Since the length L of the focusing region 220 is greater than the length H of the desired hypotenuse of section 12, workpiece 1 can be chamfered particularly easily and effectively.

[0135] Figure 4AA laser beam 20 processed by a beam-shaping optical tool is schematically shown. Sub-laser beams 200 of the laser beam 20 are incident on the workpiece 1 at an angle α' relative to the optical axis 30, wherein each sub-laser beam 200 is refracted according to its angle α' relative to the optical axis 30. However, overall, the optical axis 30 in this example of the laser beam 20 is perpendicular to the surface 10 of the workpiece 1, such that the angle of attack is 0°. In the workpiece 1, the sub-laser beams 200 are superimposed to form a non-diffractive beam with an elongated focusing region 220 of length L.

[0136] When the laser beam 20 is incident at an angle, i.e., at a non-translational angle of attack α, aberrations occur in the material because the upper half of the beam is incident on the workpiece 1 at an angle α + α' and the lower half of the beam at an angle α - α'. Therefore, as... Figure 4B As shown, for an angle of attack of α = 15°, the focal region 220 may be shortened or deformed. However, even when using a laser beam without aberration correction, this method can produce material modification 5, wherein the hypotenuse H of the chamfer and / or bevel is between 50 µm and 5000 µm, preferably between 100 µm and 200 µm.

[0137] Figure 5A The transverse intensity distribution or focused region 220 of the non-diffractive laser beam 20 is shown. The non-diffractive laser beam 20 is a so-called Bessel-Gaussian beam, wherein the transverse intensity distribution in the xy plane is radially symmetric, such that the intensity of the non-diffractive laser beam 20 depends only on its radial distance from the optical axis 30. In particular, the diameter of the transverse intensity distribution is between 0.25 µm and 10 µm. Figure 5B The image shows the longitudinal beam cross-section, i.e., the longitudinal intensity distribution. The longitudinal intensity distribution has a high-intensity elongated region, which is approximately 3 mm long. Therefore, the longitudinal extension scale of the focusing region 220 is significantly larger than the lateral extension scale.

[0138] Figure 5C China and Israel are similar Figure 5A The method illustrates a non-diffractive laser beam with a non-radial symmetric transverse intensity distribution. In particular, the transverse intensity distribution appears to be stretched in the y-direction and is almost elliptical. Figure 5D The image shows the longitudinal intensity distribution of the laser beam 20, wherein the focal region 220 again has an extension scale of L = 3 mm. Figure 5E It shows Figure 5C The magnified local distribution of the transverse intensity is shown, where different intensity maxima are generated by the superposition of different sub-laser beams 200. In particular, the focusing region 220 is significantly elongated in the horizontal direction A relative to the vertical direction B, where the two directions are perpendicular to each other.

[0139] If a laser beam 20 with this focusing region 220 is introduced into the workpiece 1, the resulting material modification 5 will have the same form. This is in Figure 6A As shown in the diagram. In particular, the material modification 5 thus has a sharp side and a flat side, wherein the sharp side exists in the direction of the major axis A, and the blunt side exists in the direction of the minor axis B. Here, the crack formation 52 caused by the material modification 5 occurs in the direction of the major axis A, since the stress peak is greatest there.

[0140] Therefore, preferably, the long axis A of the non-radially symmetrical transverse strength distribution is oriented along the dividing line 4, for example, tangentially relative to the dividing line 4, such that the resulting crack formation follows the dividing line 4. If now as Figure 6B As shown, if the material modification 5 is oriented on the dividing line 4 such that the cracks 52 of adjacent material modifications 5 overlap, then the division can be achieved particularly easily through the division step.

[0141] If a laser beam 20 with a circular or non-radially symmetrical transverse intensity distribution is projected onto the surface 10 of the workpiece 1 at an angle of attack α, this results in a distortion of the intensity distribution in the incident plane. This... Figure 7A and Figure 7B As shown in [the image]. Figure 7A , Figure 7B In this process, the laser beam 20 is incident on the surface 10 of the workpiece 1 with a non-radial symmetric transverse intensity distribution. For example, the minor axis B can be located in the incident plane, while the major axis A of the beam profile is parallel to the feed direction. This allows crack formation 52 to preferably extend in the feed direction. However, since the minor axis B is projected onto the surface 10, the intensity distribution of the minor axis B is along the length B / cosα, causing the minor axis B to lengthen with increasing angle of attack due to this projection. In particular, this allows the projection of the minor axis B to be equivalent to the length of the major axis A. The resulting material modification 5 no longer has a preferred direction for crack formation.

[0142] For example, at an angle of attack of 45°, the minor axis grows to Therefore, if the ratio A / B before projection is greater than... Then, during projection, the orientation of the long axis A relative to the dividing line 4 remains unchanged.

[0143] Figures 8A to 8D Another example of the effects of projection is shown. Figure 8A The middle shows Figure 5A A Bessel-Gaussian beam incident perpendicularly on surface 10 of workpiece 1. In the case of a non-translational angle of attack α, such as... Figure 8BAs shown, the radially symmetrical intensity distribution on the surface 10 of workpiece 1 becomes an elongated intensity distribution in one direction, resulting in a preferred orientation for the material modification 5. Accordingly, the preferred orientation of the material modification 5 can be adjusted or changed by projecting the laser beam 20 onto the surface 10 of workpiece 1. Figure 8C The middle shows Figure 5C The Bessel beam is projected onto the surface 10 of the workpiece 1 to maintain the orientation of the major axis A, so that the orientation of the preferred direction of crack propagation resulting from the material modification 5 remains unchanged. Here, A / B is less than the reciprocal of the cosine of the angle of attack α.

[0144] The laser beam 20 can be polarized, preferably parallel to the incident plane, in order to minimize reflection loss. Therefore, Figure 9 The transmission of laser radiation through workpiece 1, polarized parallel and perpendicular to the incident plane, is depicted according to Fresnel's formula. Here, the angle of attack α is plotted specifically on the X-axis, but according to... Figure 4A The sub-laser beam 20 has a convergence angle α' relative to the optical axis 30.

[0145] For example, with an angle of attack α = 50° and a convergence angle α' = 20°, the sub-laser beam 200 is incident on the surface 10 of the workpiece 1 at an angle ranging from α - α' = 30° to α + α' = 70°. Thus, in the case of parallel incidence, the transmittance is between 96% and 94%, while in the case of perpendicular incidence, the transmittance varies between 95% and 70%. Therefore, the variation of the laser beam 200 polarized perpendicular to the incident plane is significantly stronger than the variation of light polarized parallel to the incident plane. Therefore, to reduce reflection loss, it is particularly advantageous for the sub-laser beam 200 to be incident on the workpiece 1 at an angle of less than 80° relative to the surface normal N.

[0146] Figure 10 An embodiment of the apparatus for implementing the method is shown. Here, the laser pulse is provided by an ultrashort pulse laser 2 and deflected by a polarizing optical apparatus 32 and a beam-shaping optical apparatus 34. The laser beam 20 is deflected from the beam-shaping optical apparatus 34 onto the workpiece 1 via a telescope system 36, wherein the optical axis 30 of the processing optical apparatus 3 is oriented at an angle α relative to the surface normal N of the workpiece 1.

[0147] Here, the polarizing apparatus 32 may include a polarizer that polarizes the laser beam 20 emitted by the ultrashort pulse laser 2, such that the laser beam has only a defined polarization. Then, a subsequent half-wave plate can ultimately rotate the polarization of the laser beam 20, so that the laser beam 20 can be introduced into the workpiece 1 preferably with a polarization parallel to the plane of incidence.

[0148] In the example shown, the beam-forming fixture 34 is an axonocone to shape the incident laser beam 20 into a non-diffractive laser beam. However, the axonocone can also be replaced by other elements to generate a non-diffractive beam. The axonocone generates a conically focused laser beam 20 from a preferably collimated input beam. Here, the beam-forming fixture 34 can also impose a non-radial symmetric intensity distribution on the incident laser beam 20. Finally, the laser beam 20 can be imaged into the workpiece 1 via a telescope fixture 36, which is here composed of two lenses 360, 362, wherein the imaging can be either magnified or reduced. A portion of the telescope fixture 36, particularly lens 360, can also be integrated into the beam-forming fixture 34. For example, an axonocone with a refracting free-form surface or a spherically polished back side can have both the lens function of lens 360 and the beam-forming function of beam-forming fixture 34.

[0149] Figure 11A The image shows a feed device 6, configured to move the machining fixture 3 and the workpiece 1 translationally along three spatial axes and rotate about two spatial axes. The laser beam 20 of the ultrashort pulse laser 2 is deflected onto the workpiece 1 by the machining fixture 3. Here, the workpiece 1 is arranged on a support surface of the feed device 6, wherein the support surface preferably neither reflects nor absorbs laser energy not absorbed by the material, nor strongly scatters the laser energy back into the workpiece 1.

[0150] In particular, the laser beam 20 can be coupled into the processing optical tool 3 via a beam guiding device 38. Here, the beam guiding device can be a free-space path with a lens and mirror system, such as... Figure 11A As shown in the figure. However, the beam guiding device 38 can also be a hollow fiber with coupling-in and coupling-out optical ducts, such as Figure 11B As shown in the image.

[0151] exist Figure 11A In the current example, the laser beam 20 is deflected toward the workpiece 1 by a mirror structure and introduced into the workpiece 1 by a machining fixture 3. In the workpiece 1, the laser beam 20 causes material modification 5. The machining fixture 3 can be moved and adjusted relative to the material by means of a feed device 6, such that, for example, a preferred direction or axis of symmetry of the lateral intensity distribution of the laser beam 20 can be adapted to the feed trajectory and thus to the dividing line 4.

[0152] Here, the feed device 6 can move the workpiece 1 below the laser beam 20 with a feed V, so that the laser beam 20 introduces material modification 5 along the desired dividing line 4. In particular, in the illustrated... Figure 11AIn this device, the feed device 6 has a first axis system 60, by which the workpiece 1 can move along the XYZ axes and, if necessary, rotate. In particular, the feed device 6 may also have a workpiece holder 62 configured to hold the workpiece 1. If necessary, the workpiece holder may also have degrees of freedom of movement, such that the major axis of the non-radially symmetrical transverse intensity distribution perpendicular to the beam propagation direction can always be tangentially oriented relative to the desired dividing line 4.

[0153] For this purpose, the feeding device 6 can also be connected to a regulating electronics 64, which translates user commands from the device's user into control commands for the feeding device 6. In particular, predefined cutting patterns can be stored in the memory of the regulating electronics 64 and the process can be automatically controlled by the regulating electronics 64.

[0154] The regulating electronics 64 can also be connected to the ultrashort pulse laser 2. Here, the regulating electronics 64 can request or trigger the output of laser pulses or laser bursts. The regulating electronics 64 can also be connected to other mentioned components and thus can coordinate material processing.

[0155] In particular, a position-controlled pulse trigger can be implemented in such a way that, for example, the shaft encoder 600 of the feed device 6 is read and the shaft encoder signal is interpreted as location information by the regulating electronics 64. Therefore, the regulating electronics 64 can automatically trigger the emission of laser pulses or laser bursts, for example, if the internal adder unit, which sums the lateral path lengths, reaches a certain value and then resets to 0. Thus, for example, laser pulses or laser pulse sequences can be automatically emitted into the workpiece 1 at regular intervals.

[0156] Since the feed speed and feed direction can also be processed in the adjustment electronics 64, and thus the dividing line 4 can be processed, laser pulses or laser pulse sequences can be automatically emitted.

[0157] The regulating electronics 64 can also calculate the distance or location of the laser pulse sequence or laser pulses to be emitted based on the measured speed and the fundamental frequency provided by the laser 2. This, in particular, allows for the material modification 5 to not overlap within the workpiece 1.

[0158] Since the emission position of laser pulses or pulse sequences is controlled, the time-consuming segmentation process programming can be eliminated. Furthermore, freely selectable processing speeds can be easily achieved.

[0159] Figure 11C Also shown is the feed device 6, in which the machining tool is guided on the workpiece 1 by a 5-axis arm to introduce the material modification 5 into the workpiece 1. The combination of rotating arms enables the machining tool to move along three spatial axes and rotate about two spatial axes.

[0160] Within the scope of application, all the various features presented in the exemplary embodiments may be combined and / or interchanged with each other without departing from the scope of the invention.

[0161] List of reference numerals 1. Workpiece 1' Bulk workpiece 10 Surface 11 upper side 110 edge 12 sections 13. Lower side 130 edge 14. Chamfer 2. Ultrashort pulse laser 20 laser beams 200 sub-laser beams 220 Focus Area 3. Machining optical tools 30 optical axes 32 Polarizing optical tools 34 Beam shaping optical tools 36 Telescopes 38 Beam Guiding Device 360 First Lens 362 Second Lens 4 dividing lines 40 chemical bath 42 Hot Plate 5. Material Modification 50 Material Modification Surface 52 Cracks 6. Feeding equipment 60-axis equipment 62 Workpiece Holder 64. Adjustment electronic device α Angle of attack β angle of refraction A First Axis B Second Axis N-face normal V feed H hypotenuse

Claims

1. A method for dividing a workpiece (1) having a transparent material, wherein, Material modification (5) is introduced into the transparent material of the workpiece (1) along the dividing line (4) using an ultrashort laser pulse from an ultrashort laser (2), and then the material of the workpiece (1) is divided along the resulting material modification surface (50) using a dividing step. Wherein, the laser pulse is introduced onto the workpiece (1) at an angle of attack (α), the material modification (5) is a type III modification associated with the crack formation of the material of the workpiece (1), the material modification (5) penetrates the two sides of the workpiece (1) located in intersecting planes, generates an oblique angle through the segmentation step, and the size of the hypotenuse (H) of the oblique angle is between 50 µm and 5000 µm, characterized in that the laser beam (20) composed of ultrashort laser pulses is a non-diffractive laser beam and has a non-radially symmetric transverse intensity distribution (220), wherein the transverse intensity distribution (220) is elongated in the direction of the first axis (A) compared with the second axis (B), wherein the second axis (B) is perpendicular to the first axis (A), wherein the first axis (A) is parallel to the feed direction (V), and wherein the ratio of the first axis (A) to the second axis (B) of the non-radially symmetric transverse intensity distribution (220) is greater than the reciprocal of the cosine of the angle of attack (α).

2. The method according to claim 1, characterized in that, The segmentation step includes mechanical segmentation and / or etching processes and / or thermal application and / or self-segmentation steps.

3. The method according to any one of the preceding claims, characterized in that, The hypotenuse (H) of the angle is between 100 µm and 200 µm.

4. The method according to claim 1 or 2, characterized in that, The pulse energy of the laser pulse is between 10 µJ and 5 mJ, and / or The average laser power is between 1 W and 1 kW, and / or The laser pulse is a single laser pulse or part of a laser burst, wherein a laser burst comprises 2 to 20 laser pulses, wherein the laser pulses of the laser burst have a time interval of 10 ns to 40 ns, and / or The wavelength of the laser is between 300 nm and 1500 nm.

5. The method according to claim 4, characterized in that, The laser pulses of the laser burst have a time interval of 20 ns.

6. The method according to claim 4, characterized in that, The wavelength of the laser is 1030 nm.

7. The method according to claim 1 or 2, characterized in that, The laser beam (20) is polarized parallel to the incident plane.

8. An apparatus for dividing a workpiece (1) comprising a transparent material, the apparatus comprising: An ultrashort pulse laser (2), the ultrashort pulse laser being configured to provide ultrashort laser pulses; The feeding device (6) has a workpiece holder (62) on which a workpiece (1) comprising a transparent material is held; and a processing optical tool (3), wherein the processing optical tool is configured to introduce these laser pulses into the material of the workpiece (1), The feeding device is configured to move the laser beam (20) formed by these laser pulses relative to the workpiece (1) along the dividing line (4), and to align the optical axis (30) of the processing fixture (3) at an angle of attack (α) relative to the surface (10) of the workpiece (1). The laser pulse is introduced into the workpiece (1) at an angle of attack (α), the material modification (5) is a type III modification associated with crack formation in the material of the workpiece (1), the material modification (5) penetrates two sides of the workpiece (1) located in intersecting planes, and an oblique angle is generated by a segmentation step, wherein the hypotenuse (H) of the oblique angle is between 50 µm and 5000 µm, characterized in that... The beam-shaping fixture (34) of the device shapes a non-diffractive laser beam (20) from the laser beam (20), wherein the transverse intensity distribution (220) of the non-diffractive laser beam (20) is non-radially symmetric. The non-radially symmetrical lateral strength distribution (220) is elongated in the direction of the first axis (A) compared to the second axis (B), wherein the second axis (B) is perpendicular to the first axis (A), wherein the first axis (A) is parallel to the feed direction, and wherein the ratio of the first axis (A) to the second axis (B) of the non-radially symmetrical lateral strength distribution (220) is greater than the reciprocal of the cosine of the angle of attack (α).

9. The device according to claim 8, characterized in that, - The processing optical tool (3) includes a telescope system (36) configured to introduce the laser beam (20) into the workpiece (1) in a decreasing and / or increasing manner, and / or - The feed device (6) includes a shaft device (60) and a workpiece holder (62), the shaft device and the workpiece holder being configured to move the machining tool (3) and the workpiece (1) relative to each other in a translating manner along three spatial axes and in a rotational manner about at least two spatial axes.

10. The device according to claim 8 or 9, characterized in that, - The angle of attack (α) of the machining tool (3) is between 0° and 60°, and / or - The sub-laser beam (200) of the laser beam (20) illuminates the workpiece (1) at a maximum angle of attack of 80° relative to the surface normal (N) of the workpiece (1).

11. The device according to claim 8 or 9, characterized in that, The polarizing optics (32) is configured to adjust the polarization of the laser beam (20) relative to the incident plane of the laser beam (20).

12. The device according to claim 11, characterized in that, The polarizing apparatus (32) is configured to adjust the polarization of the laser beam (20) parallel to the incident plane.

13. The device according to claim 11, characterized in that, The polarizing optical tool (32) includes a polarizer and a waveplate.

14. The device according to claim 8 or 9, characterized in that, - A beam guiding device (38) is configured to guide the laser beam (20) to the workpiece (1), wherein the beam guiding is achieved via a mirror system and / or optical fiber, and / or - The regulating electronics (64) are configured to trigger the emission of laser pulses from the ultrashort pulse laser (2) due to the relative position of the laser beam (20) and the workpiece (1), and / or - The workpiece holder (62) has a surface that does not reflect and / or scatter the laser beam (20).

15. The device according to claim 14, characterized in that, The optical fiber is a hollow-core optical fiber.

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