Method for laser processing a workpiece

Abstract

The invention relates to a method for laser processing a workpiece (104) by means of a processing beam (114), the workpiece (104) comprising a material (102) which is transparent for the wavelength λ of the processing beam (114), in which method material modifications (142) are formed in the material (102) along a predetermined processing line (134) by the action of the processing beam (114) on the material (102), a first group (144a) of spaced-apart material modifications (142) being formed in the material (102), the mutually adjacent material modifications (142) of the first group (144a) being formed one after the other in time. and having a distance (d0) of at least 0.25*λ and / or at most 2.5*λ between each other, and in the method, a second group (144b) of spaced-apart material modifications (142) is formed in the material (102), mutually adjacent material modifications (142) of the second group (144b) being formed one after the other in time and having a distance (d0) of at least 0.25*λ and / or at most 2.5*λ between each other, and the shortest distance (d1) between the material modifications (142) of the first group (144a) and the material modifications (142) of the second group (144b) is at least 5 μm.

Description

Technical Field

[0001] The invention relates to a method for laser processing of a workpiece by means of a processing beam, the workpiece comprising a material that is transparent to the wavelength λ of the processing beam. Background Art

[0002] DE 10 2014 116 958 B4 discloses an optical system for shaping a laser beam for processing a material that is largely transparent to the laser beam, with which the laser beam is focused into an elongated focal region oriented parallel to the propagation direction of the laser beam.

[0003] DE 10 2019 128 362 B3 discloses a diffractive optical beam-shaping element for imparting a phase distribution to the lateral beam profile of a laser beam, which can be used to form a Bessel-like beam with an asymmetric and, in particular, elliptical cross section.

[0004] DE 10 2019 218 995 A1 discloses a method for modifying a material that is at least largely transparent to the laser beam by means of a laser beam, wherein a focal region of a single pulse of the laser beam directed in the beam propagation direction interacts with the material, and the interaction of the single pulse with the material produces a channel through the material from a first end face to a second end face, and the channel has a channel width dimension of at most 1 μm.

[0005] EP 3 597 353 A1 discloses a method for separating transparent materials by means of an elongated focal region of a laser beam.

[0006] EP 3 227 241 B1 discloses a method for separating transparent materials by means of a plurality of parallel non-diffracting laser beams.

[0007] EP 3 872 041 A1 discloses a method for separating a glass element into at least two glass sub-elements along an impact surface, at least in certain areas, wherein line focusing is used to form a tension zone within the glass element, an initial damage is introduced into the glass material in the tension zone to form at least one crack, and the crack advances in the tension zone to form a separation surface and separate the glass elements.

[0008] EP 3 487 656 B1 discloses a method for separating dielectric or semiconductor materials, wherein a laser beam is focused in two spatially spaced focal zones, and the spaced focal zones are applied to the material, resulting in microcracks in the material extending between the focal zones. Summary of the Invention

[0009] The object of the present invention is to provide a method of the type mentioned at the outset which makes it possible to modify the material in such a way that cracks are formed, the preferred direction of which is oriented substantially parallel to a predetermined processing line.

[0010] According to the invention, this object is achieved in that material modifications are formed in the material along a predetermined processing line by the action of a processing beam on the material, a first group of spaced-apart material modifications being formed in the material, mutually adjacent material modifications of the first group being formed one after the other in time and having a distance of at least 0.25*λ and / or at most 2.5*λ between one another, and a second group of spaced-apart material modifications being formed in the material, mutually adjacent material modifications of the second group being formed one after the other in time and having a distance of at least 0.25*λ and / or at most 2.5*λ between one another, and the shortest distance between the material modifications of the first group and the material modifications of the second group being at least 5 μm.

[0011] Transparent materials can be separated, for example, by laser processing the material to form a material modification that mechanically weakens the material along a predetermined processing line. The material modification includes mechanical cracks that are arranged in the region of the processing line and allow the material to be separated there. For example, the cracks form a "predetermined breaking point" at which mechanical separation of the material is possible.

[0012] The processing line thus defines the separation line and / or separation surface produced during material separation. For high separation quality, it is important that the cracks formed run as parallel as possible to the processing line and / or to the distance between adjacent material modifications formed. This allows for the smoothest possible separation surface. Furthermore, potential damage to the separated workpiece segments (unit segments), which could be caused, for example, by uncontrolled crack formation, can be reduced.

[0013] By means of the method according to the invention, material modifications can be formed in the material that are associated with or cause the formation of cracks, and the preferred direction of the cracks can be controlled. It has been shown that the temporal formation of spaced-apart material modifications having the aforementioned distance range one after the other results in the formation of cracks in the material that extend at least approximately parallel to the processing line and / or parallel to the distance between adjacent material modifications.

[0014] Providing a minimum distance of 5 μm between mutually adjacent groups of material modifications is beneficial for the strength of the glass edge after cutting.

[0015] In particular, when the method according to the invention is performed, cracks are formed, and / or the method according to the invention is performed so that cracks can be formed, at least some portions of each of the cracks extending between a particular group of material modifications, and / or at least some portions of each of the cracks extending between adjacent, closest groups of material modifications, for example, between a first group and a second group. The preferred direction and / or main direction of extension of the formed cracks is oriented at least approximately parallel to the processing line.

[0016] In particular, it can be provided that the processing beam is a pulsed laser beam, preferably an ultrashort pulsed laser beam. In this case, for example, a corresponding laser pulse or a pulse train consisting of a plurality of laser pulses, also referred to as a "burst," is introduced into the material in order to form a specific material modification with the aid of the processing beam.

[0017] For example, the machining beam comprises laser pulses having a pulse duration of at least 0.3 ps and / or at most 20 ps.

[0018] For example, the processing beam comprises laser pulses having a pulse energy of at least 50 μJ and / or at most 500 μJ. Provision can be made for individual laser pulses, in particular individual laser pulses having this pulse energy, to be introduced into the material by means of the processing beam to produce a specific material modification, or for a pulse train consisting of a plurality of laser pulses to be introduced, the total energy of which is at least 50 μJ and / or at most 500 μJ, to produce a specific material modification. The pulse train can comprise, for example, 2 to 20 sub-pulses spaced approximately 20 ns apart.

[0019] For example, the machining beam comprises laser pulses with a repetition rate of at least 100 kHz and / or at most 300 kHz and preferably of approximately 200 kHz.

[0020] Advantageously, at least one additional group of spaced-apart material modifications is formed, wherein adjacent material modifications of the at least one additional group are formed one after the other in time and have a distance of at least 0.25*λ and / or at most 2.5*λ from one another, and the shortest distance between the material modifications of the at least one additional group and the material modifications of the group of material modifications adjacent to and closest to the at least one additional group is at least 5 μm. In particular, multiple additional groups of material modifications can be provided, each of which is arranged along a processing line. This makes it possible, in particular, to increase the total length of the crack formed in the material as desired. This allows cracks to be formed in the material along a processing line of variable length.

[0021] In the present case, the expressions "mutually adjacent material modifications" or "mutually adjacent groups" are to be understood as meaning mutually adjacent and closest (also called nearest neighbors) material modifications or groups, respectively, in particular without further material modifications or groups, respectively, being arranged between them.

[0022] Advantageously, the distance between adjacent material modifications assigned to a particular group is at least 0.5*λ and / or at most 2.0*λ, preferably at least 0.7*λ and / or at most 1.5*λ, particularly preferably at least 0.85*λ and / or at most 1.25*λ. For example, the distance is approximately 1.0*λ. This allows for optimal control of the alignment of the formed cracks so that they are aligned at least approximately parallel to the direction of the processing line and / or the distance between adjacent material modifications.

[0023] "A specific group" should be understood to mean, for example, the first group, the second group or at least one further group.

[0024] For example, a particular group of material modifications may have two or more adjacent and / or spaced-apart material modifications. A corresponding group preferably has or consists of two material modifications, e.g., a first material modification and a second material modification spaced-apart from the first material modification.

[0025] In particular, it can be provided that the wavelength λ of the processing beam is at least 300 nm and / or at most 1500 nm, preferably at least 1000 nm and / or at most 1100 nm, for example, a wavelength of approximately 1030 nm.

[0026] A material transparent to this wavelength is understood to mean in particular a material through which at least 70%, in particular at least 80%, in particular at least 90% of the laser energy of a laser beam incident on this material and having this wavelength is transmitted.

[0027] Advantageously, the material modifications are formed one after another along the processing line by means of the processing beam. In particular, the material modifications assigned to a specific group are formed one after another by means of the processing beam. This makes it possible, in particular, to form cracks in the region of the material modifications, which cracks extend at least partially between the material modifications and are oriented at least approximately parallel to the processing line.

[0028] Advantageously, mutually adjacent material modifications assigned to a particular group are formed at a time interval of at least 1 μs and / or at most 15 μs, preferably at least 2 μs and / or at most 8 μs, particularly preferably at least 3.5 μs and / or at most 6.5 μs. For example, the time interval is approximately 5 μs. This allows for optimal control of the alignment of the formed cracks so that they are aligned at least approximately parallel to the processing line and / or the distance between adjacent material modifications.

[0029] In the case of a pulsed laser beam, the aforementioned time intervals correspond in particular to the time intervals in which corresponding laser pulses or pulse trains consisting of a plurality of laser pulses are introduced into the material by means of the processing beam in order to form mutually adjacent material modifications.

[0030] Advantageously, the shortest distance between the material modifications of adjacent groups of closest material modifications is at least 7 μm and / or at most 40 μm, preferably at least 8.5 μm and / or at most 30 μm, particularly preferably at least 10 μm and / or at most 20 μm. For example, the distance is approximately 15 μm. This allows for optimal control of the alignment of the cracks formed, so that they are aligned at least approximately parallel to the processing line and / or the distance direction between adjacent groups.

[0031] Advantageously, the processing beam is moved relative to the material along the processing line at an advance speed, in particular a constant advance speed, of at least 50 mm / s and / or at most 400 mm / s, preferably at least 100 mm / s and / or at most 300 mm / s, particularly preferably at least 150 mm / s and / or at most 250 mm / s. For example, the advance speed is approximately 200 mm / s. Combined with the typical beam parameters of the processing beam, this makes it technically easy to produce material modifications with the aforementioned time intervals and spatial distances.

[0032] Advantageously, the processing beam has identical beam parameters for forming the material modifications assigned to a specific group. In particular, provision can be made for the processing beam to have identical beam parameters for forming all material modifications along the processing line. Consequently, there is no need for complex control and / or regulation of the beam parameters or for synchronizing the beam parameters with specific positions of the processing beam on the processing line. This makes the method easier to implement from a technical point of view.

[0033] In particular, in the case of a pulsed machining beam, provision can be made for the laser pulses for producing adjacent material modifications to have the same pulse energy.

[0034] In this case, specifically, the first pulse that creates the first material modification does not form any cracks, but it modifies the material and generates stress within it, which lowers the threshold for crack formation in adjacent areas. The second pulse that creates the second modification may then form cracks due to the lower threshold.

[0035] In an alternative variant, it is in principle also possible for the processing jet to have different beam parameters for forming mutually adjacent material modifications assigned to a specific group.

[0036] For example, in the case of a pulsed machining beam, it can be provided that the laser pulses for producing adjacent material modifications have different pulse energies.

[0037] In particular, the first pulse energy of the laser pulses or pulse train used to form a particular group of first material modifications is lower than the second pulse energy of the laser pulses or pulse train used to form the group of second material modifications adjacent to the first material modification. In particular, the first pulse energy is at least 40% and / or at most 95% of the second pulse energy, preferably at least 50% and / or at most 70% of the second pulse energy, particularly preferably at least 55% and / or at most 65% of the second pulse energy.

[0038] The pulse energy of a pulse train is understood to mean in particular the respective pulse energy of the laser pulses forming the pulse train.

[0039] In order to form mutually adjacent laser pulses, for example, laser pulses or pulse trains with a first pulse energy and laser pulses or pulse trains with a second pulse energy are respectively introduced alternately into the material.

[0040] In this case, the formation of the first material modification in the material is in particular not associated with the formation of cracks, whereas cracks are formed in the material when the second material modification is formed.

[0041] Advantageously, the beam parameters assigned to the machining beam are selected such that, when the machining beam acts on the material at a test location, wherein the material is not modified within a radius of approximately 5 μm or greater at the test location, the material modification formed at the test location by means of the machining beam is not associated with the formation of cracks in the material and / or the material modification formed by means of the machining beam is associated with a change in the refractive index of the material. In particular, the beam parameters assigned to the machining beam are selected such that, when the machining beam acts on the material at the test location, a Type I and / or Type II modification is formed.

[0042] The fact that the material is not modified within the aforementioned radius is understood to mean, in particular, that within the aforementioned radius, no material modification is produced in the material by means of the machining beam and / or no material modification is associated with a mechanical weakening of the material.

[0043] Advantageously, the beam parameters assigned to the machining beam are selected such that, when the machining beam acts on the material at a test location, wherein the material is not modified within a radius of approximately 5 μm or more than 5 μm for the test location, the material modification formed at the test location by means of the machining beam is associated with a local formation of mechanical stresses in the material in the region of the formed material modification.

[0044] The result of the aforementioned selection of beam parameters is that when forming a specific set of first material modifications, and in particular the first material modification, cracks do not form, but rather local mechanical stresses are generated in the material, particularly in the region of the first material modification. When forming a second material modification adjacent to the first material modification, the existing mechanical stresses are relieved, which is associated with the formation of cracks in the material in the region of the first and second material modifications. It has been shown that the cracks that form in this regard are oriented substantially parallel to the distance between the first and second material modifications—that is, in the case of a straight processing line, substantially parallel to the processing line. This leads to the advantages explained at the outset.

[0045] For technical details of the explained mechanism, reference is made to the scientific publication by Bradt, RC, “The Fractography and Crack Patterns of Broken Glass”, J Fail. Anal. and Preven, 11, 79-96 (2011), DOI: 10.1007 / s11668-011-9432-5.

[0046] For the same reason, it is advantageous if the beam parameters assigned to the processing beam are selected such that the formation of a first material modification of a particular group of material modifications is not associated with the formation of a crack in the material, and that a crack is formed in the material when a second material modification of the group, spaced apart from the first material modification, is being formed, the distance between the first and second material modifications being at least 0.25*λ and / or at most 2.5*λ. This makes it possible to optimally control the alignment of the formed cracks so that they are aligned at least approximately parallel to the processing line and / or the distance direction between adjacent material modifications.

[0047] A first material modification of a particular group is to be understood as meaning in particular the first material modification assigned to said group, said material modification being formed in particular in due course as the first material modification of said group.

[0048] In particular, at least some portions of the cracks formed during the formation of the second material modification extend between the first material modification and the second material modification, and in particular extend in a direction at least approximately parallel to the distance between the first material modification and the second material modification and / or a preferred direction of the processing line orientation.

[0049] Advantageously, the beam parameters assigned to the machining beam are selected such that, when forming the material modifications of the second group, cracks are formed in the material, at least some portions of which extend between the material modifications of the first group and the material modifications of the second group. This allows for optimal control of the alignment of the formed cracks so that they are aligned at least approximately parallel to the machining line and / or the distance direction between adjacent groups.

[0050] In particular, the above-mentioned crack formation in the material occurs upon formation of the second set of second material modifications.

[0051] The material modifications introduced into transparent materials by ultrashort laser pulses are subdivided into three different categories; see K. Itoh et al., “Ultrafast Processes for Bulk Modification of Transparent Materials,” MRS Bulletin, Vol. 31, p. 620 (2006): Type I is an isotropic refractive index change; Type II is a birefringent refractive index change; and Type III is so-called voids or cavities. The resulting material modifications depend on the laser parameters of the laser beam forming the focusing element, such as its pulse duration, wavelength, pulse energy, and repetition rate, and on the material properties, such as its electronic structure and thermal expansion coefficient, and also on the numerical aperture (NA) of the focus.

[0052] The formation of modifications of type I and type II is associated with a change in the refractive index of the material and in particular is not associated with the formation of cracks, whereas the formation of modifications of type III involves the formation of cracks in the material.

[0053] Advantageously, the machining beam has a focal zone, in particular an elongated focal zone, which is introduced into the material of the workpiece at least in certain sections and is moved relative to the material along the machining line. This makes it possible to modify the material of the workpiece in a region defined by the size of the focal zone introduced into the material.

[0054] In particular, it can be provided that the machining beam has a quasi-non-diffracting and / or Bessel-like beam profile in the focal region.

[0055] In particular, the term "focusing zone" should be understood to mean a focused radiation region of the processing beam, which in particular has a specific spatial extent. To determine the spatial size of the focusing zone, for example, its diameter, only intensity values ​​above a specific intensity threshold are considered. In this regard, for example, the intensity threshold is selected such that values ​​below this intensity threshold have such low intensities that they are no longer relevant for interaction with the material to form a material modification. For example, the intensity threshold is 50% of the global intensity maximum of the focusing zone.

[0056] In particular, the machining beam has been assigned a corresponding spatial interaction region, in which it interacts with the material of the workpiece when the machining beam is introduced into the material. In particular, the machining beam interacts with the material in the interaction region by nonlinear absorption. In particular, the interaction region is formed in and / or by means of the focal region of the machining beam.

[0057] In particular, the elongated focal zone extends over the thickness of the material and / or over the thickness of the section to be separated from the material. This modifies the material over the entire thickness, for example, so that the material can be separated.

[0058] In particular, the elongated focusing zone extends along a longitudinal center axis which is preferably oriented transversely and in particular perpendicularly to an outer side of the workpiece, in particular the outer side via which the focusing zone is coupled into the material of the workpiece.

[0059] For example, the longitudinal center axis of the focal region is oriented parallel to or transverse to the thickness direction of the material.

[0060] In particular, the longitudinal center axis of the focal region is oriented at least approximately parallel to the main propagation direction of the processing beam.

[0061] For example, the length of the focal zone oriented along the longitudinal central axis may be between 50 μm and 5000 μm, preferably between 100 μm and 1000 μm.

[0062] In particular, the processing beam and / or the focal region of the processing beam has a symmetrical transverse beam cross section.

[0063] For example, the transverse beam diameter of the machining beam and / or the focal zone may be between 0.2 μm and 5 μm. For example, the transverse beam diameter is approximately 1 μm.

[0064] The transverse beam cross section is to be understood as meaning, in particular, a cross section oriented perpendicularly to the main propagation direction of the processing beam and / or a cross section oriented perpendicularly to the longitudinal center axis of the focal zone. The transverse beam diameter is to be understood as meaning the diameter of the processing beam or of the focal zone in this cross section.

[0065] In particular, the machining beam and / or the focal zone are formed by shaping an input laser beam, in particular a Gaussian input laser beam, wherein the beam shaping particularly includes imparting a phase to the transverse beam cross section of the input laser beam. For example, the beam shaping is performed with the aid of a diffractive and / or refractive and / or reflective optical element, such as an axicon element.

[0066] The relative movement of the elongated focal zone of the processing beam through the material along the processing line in particular forms a processing surface corresponding to the processing line, at which the material is modified and / or a material modification is formed.

[0067] In particular, it can be provided that the processing line is straight at least in certain sections and / or that the processing line is curved at least in certain sections. For example, a shaped and / or rounded separating edge can be formed by means of a curved processing line.

[0068] In particular, the processing line is oriented parallel to the outer side of the workpiece.

[0069] In particular, it can be provided that the material of the workpiece is separable or is separable along a processing line and / or along a processing surface assigned to the processing line and having a material modification.

[0070] The material of the workpiece is preferably separated by applying thermal action and / or mechanical stress and / or by etching with the aid of at least one wet chemical solution. For example, the etching can be carried out in an ultrasound-assisted etching bath.

[0071] In particular, the expression "at least approximately" or "approximately" is generally to be understood as meaning a deviation of no more than 10%. Unless otherwise stated, the expression "at least approximately" or "approximately" is to be understood as meaning in particular that the actual value and / or distance and / or angle deviates from the ideal value and / or distance and / or angle by no more than 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The following description of the preferred embodiments is used to explain the present invention in more detail with reference to the accompanying drawings.

[0073] in:

[0074] Figure 1 A schematic diagram illustrating an exemplary embodiment of an apparatus for laser processing of a workpiece; and

[0075] Figure 2 One example of a workpiece material having material modifications formed thereon is shown, with a view of the outside of the workpiece shown, and the material modifications are arranged along a straight process line.

[0076] In all figures, elements that are identical or have equivalent functions are provided with the same reference numerals. DETAILED DESCRIPTION

[0077] An exemplary embodiment of an apparatus for laser processing of a workpiece is Figure 1 1 and denoted in this figure by 100. Apparatus 100 can be used to create local material modifications, such as submicron-scale or atomic-scale defects that weaken the material, in material 102 of a workpiece 104. Workpieces 104 can be separated at these material modifications.

[0078] The device 100 includes a laser beam source 106 that provides an input laser beam 108. The input laser beam 108 provided by the laser beam source 106 is in particular a pulsed laser beam and / or an ultrashort pulsed laser beam. For example, the input laser beam 108 provided by the laser beam source 106 has a Gaussian beam profile.

[0079] The laser beam source 106 includes a control device 110, by means of which pulse parameters of the laser pulses of the input laser beam 108 can be set. The pulse parameters are or include, for example, the pulse energy and / or the pulse duration and / or the repetition rate of the laser pulses.

[0080] In particular, the laser beam source 106 can have a pulse selection device 111 or the pulse selection device 111 can be assigned to the laser beam source 106 (at Figure 1 ). In particular, laser pulses can be coupled out of the laser beam source 106 at defined times and / or at defined time intervals by means of a pulse selection device 111 in order to introduce them into the material 102 of the workpiece 104. The pulse selection device 111 is to be understood as meaning in particular a “pulse picker”.

[0081] In particular, the pulse selection device 111 comprises an acousto-optic modulator and / or an electro-optic modulator. In particular, the pulse selection device 111 is in the form of an acousto-optic or electro-optic modulator.

[0082] The apparatus 100 further comprises a beam shaping device 112 for forming a machining beam 114 and focusing it into the material 102 of the workpiece 104 .

[0083] The beam shaping device 112 preferably comprises a beam shaping element 116 for forming a beam 118 having a quasi-non-diffracting and / or Bessel-like beam profile.

[0084] In the exemplary embodiment shown, a Gaussian input laser beam 108 is coupled into a beam shaping element 116 , and the input laser beam 108 is shaped using the beam shaping element 116 to form a beam 118 having a quasi-non-diffracting beam profile.

[0085] The beam is shaped by means of a beam shaping element 116 by applying a phase to the transverse beam cross section of the input laser beam 108 , wherein the application of the phase is selected such that the beam 118 is formed as a quasi-non-diffracting and / or Bessel-like beam.

[0086] It may be advantageous if the beam shaping element 116 has at least one diffractive optical element or is in the form of a diffractive optical element.In principle, the beam shaping element 116 can also be configured as a refractive and / or reflective optical element or can include a refractive and / or reflective optical element.

[0087] For example, the beam shaping element 116 is or includes an axicon element and / or a spatial light modulator (SLM).

[0088] For the definition and realization of quasi-non-diffracting and / or Bessel-like beams and the technical configuration of the beam shaping element 116, reference is made to the book "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M. Springer Science & Business Media (2012), ISBN 978-3-642-29322-1, and the scientific publications by I. Chremmos et al., “Bessel-like optical beams with arbitrary trajectories,” Optics Letters, Vol. 37, No. 23, 1 December 2012, and by K. Chen et al., “Generalized axicon-based generation of nondiffracting beams,” arXiv:1911.03103v1 [physics.optics], 8 November 2019.

[0089] In order to focus and / or project beam 118 into material 102 of workpiece 104, device 100 has a telescope arrangement 120, which is preferably arranged downstream of beam shaping element 116 and / or beam 118 with respect to main propagation direction 122. In the example shown, quasi-undiffracted beam 118 is focused and / or projected into material 102 by means of telescope arrangement 120.

[0090] The main propagation direction 122 is the main propagation direction of the input laser beam 108 and / or the beam formed from the input laser beam 108 and / or the beam 123 guided through the beam shaping device and / or the processing beam 114. In particular, the main propagation direction is to be understood as meaning the main spread direction and / or longitudinal direction of the aforementioned beams. A transverse direction is to be understood as meaning, in particular, a direction perpendicular to the main propagation direction 122.

[0091] The beam focused and / or coupled out from the beam shaping device 112 or the telescopic device 120 is referred to in the present case as the processing beam 114. Figure 1 As shown, for example, the machining beam 114 acts on the material 102 of the workpiece 104 , ie, the machining beam 114 is introduced into the material 102 .

[0092] exist Figure 1 In the illustrated embodiment, the telescope arrangement 120 includes a first lens element 124 and a second lens element 126 spaced apart from the first lens element 124 in the main propagation direction 122 .

[0093] The first lens element 124 is a long focal length lens element and / or an input lens element of the telescope arrangement 120. The second lens element 126 is an output lens element and / or a short focal length lens element of the telescope arrangement 120. In particular, the second lens element is in the form of an objective lens or has the function of an objective lens.

[0094] The beam shaping element 116 and / or the first lens element 124 and / or the second lens element 126 do not necessarily have to be formed in one piece. In particular, it can be provided that the beam shaping element 116 and / or the first lens element 124 and / or the second lens element 126 are each formed from or include multiple optical components.

[0095] The first focal length f1 of the first lens element 124 is greater than the second focal length f2 of the second lens element 126. In particular, the ratio f1 / f2 is at least 5 and / or at most 50.

[0096] In principle, first lens element 124 and / or the functionality of first lens element 124 may also be integrated into beam shaping element 116 .

[0097] In particular, main propagation direction 122 is oriented parallel to an optical axis 128 of telescope arrangement 120 and / or beam shaping arrangement 112 .

[0098] Due to the beam shaping performed by means of the beam shaping element 116, the processing beam 114 formed for laser processing the material 102 of the workpiece 104 has a quasi-non-diffracting and / or Bessel-like beam profile, i.e., the processing beam 114 has an elongated focal zone 130. The focal zone 130 extends along a longitudinal center axis 132, which is particularly oriented parallel to the main propagation direction 122 and / or parallel to the optical axis 128.

[0099] In the example shown, the longitudinal center axis 132 is a straight line. In principle, the longitudinal center axis 132 of the focal zone 130 can also be in the form of a curve and / or have a curved shape, at least in certain sections.

[0100] Regarding the formation and properties of quasi-non-diffracting and / or Bessel-like beams with curved shapes, reference is made to the scientific publication “Bessel-like optical beams with arbitrary trajectories” by I. Chremmos et al., Optics Letters, Vol. 37, No. 23, December 1, 2012.

[0101] Furthermore, reference is made to WO 2016 / 079062 A1 with regard to the focal region 130. This document describes the technical implementation and properties of the focal region 130 in detail.

[0102] In particular, the telescope arrangement 120 can be used to adjust the spatial dimensions of the focal region 130 for processing the material 102 of the workpiece 104, in particular the length of the focal region 130 parallel to the main propagation direction 122 and / or the optical axis 128 can be adjusted. Furthermore, for example, the transverse diameter of the processing beam 114 in the focal region 130 can be adjusted.

[0103] In particular, the focal zone 130 is to be understood as meaning a focal region and / or a spatially continuous region within which the laser radiation intensity is at least sufficiently great that, when the focal zone 130 is applied to the material 102 of the workpiece 104, material modifications are generated within the material 102, and in particular the material 102 can be separated at these material modifications.

[0104] The beam parameters of the machining beam 114 are selected such that when the machining beam 114 impinges on the material 102 in the focal zone 130, the material 102 absorbs the laser radiation focused therein nonlinearly. Due to this interaction in the form of nonlinear absorption, material modifications in the material 102 can be formed.

[0105] In particular, the intensity of the laser radiation in the focal zone 130 provided for laser processing of the material 102 is at least approximately constant along the longitudinal center axis 132 .

[0106] However, in principle, the intensity can also vary along the longitudinal center axis 132 and / or be zero at isolated points. In this case, the focal zone 130 is subdivided into, for example, a plurality of partial focal zones, which extend along the common longitudinal center axis. In this respect, the term "focal zone" can also include a focal zone consisting of a plurality of partial focal zones, provided that these partial focal zones are used to form a material modification in the direction of the longitudinal center axis that allows the material 102 to be separated and / or weakens the material 102 in a manner that makes the separation of the material possible.

[0107] In the example shown, longitudinal center axis 132 is a straight line. However, in principle, focal zone 130 can also extend along the longitudinal center axis in a curved shape. For example, the phase imparted to input laser beam 108 by beam shaping element 116 can occur in such a way that focal zone 130 is embodied in a curved shape.

[0108] The focal region 130 preferably has an at least approximately symmetrical intensity distribution in a cross section oriented perpendicular to the longitudinal center axis 132. For example, the intensity distribution in the cross section oriented perpendicular to the longitudinal center axis 132 is at least approximately radially symmetrical about the longitudinal center axis 132.

[0109] The input laser beam 108 and / or the processing beam 114 has a wavelength λ for which the material 102 is transparent. For example, the material 102 is or includes a glass material.

[0110] The workpiece 104 is mounted in such a manner that it can be moved relative to the processing beam 114. For laser processing of the workpiece 104, the material 102 is moved relative to the processing beam 114 along a processing line 134. For this purpose, the apparatus 100 comprises, for example, a movable holding device (not shown) for the workpiece 104, by means of which a corresponding relative movement relative to the processing beam 114 can be achieved.

[0111] For example, the holding device can be actuated by means of the control device 110 in order to move the processing beam 114 along the predetermined processing line 134 and in particular to couple laser pulses by means of the processing beam 114 into the material 102 at specific spatial positions on the processing line 134 .

[0112] The material 102 has a first outer side 136 and a second outer side 138 spaced apart from the first outer side 136, e.g., the first outer side 136 and the second outer side 138 are spaced apart parallel to a thickness direction 140 of the material 102. For example, the material 102 has an at least approximately constant thickness with respect to the thickness direction 140. For example, the workpiece 104 is in the shape of a plate and / or a panel.

[0113] The material 102 of the workpiece 104 intended for laser machining may, for example, have a thickness between 50 μm and 5000 μm and preferably between 100 μm and 1000 μm.

[0114] The method for laser processing a workpiece 104 by means of the device 100 is carried out as follows:

[0115] To laser process a workpiece 104, a processing beam 114 acts on the workpiece material 102, i.e., a focal zone 130 assigned to the processing beam 114 is introduced into the material 102. The processing beam 114 is moved relative to the material 102 along a predetermined processing line 134, along which the laser processing and / or modification of the material 102 takes place. At each position along the processing line 134, the advancement direction 141 of the processing beam 114 relative to the material 102 is always oriented parallel to and / or tangentially to the processing line 134.

[0116] The processing beam 114 is coupled into the material 102, for example, via a first outer side 136, with the longitudinal center axis 132 preferably being oriented transversely and, in particular, perpendicularly to the first outer side 136. In principle, the processing beam 114 can be coupled into the material 102 in such a way that the longitudinal center axis 132 is oriented at a specific contact angle relative to the first outer side 136. In particular, the orientation and / or the contact angle of the longitudinal center axis 132 relative to the first outer side 136 are constant, so that the entire material modification 142 is formed along the processing line 134.

[0117] The processing beam 114 and / or the focal zone 130 preferably extend over the entire thickness of the material 102 or the section to be separated from the material 102, respectively, and in particular extend uninterrupted over the entire thickness of the material 102 or the section to be separated. The length of the processing beam 114 and / or of the focal zone 130, oriented in the direction of the longitudinal center axis 132, is in particular selected such that it is at least as great as the thickness of the material 102 or the section to be separated.

[0118] For example, by means of the processing beam 114 configured as a pulsed laser beam and / or an ultrashort pulsed laser beam, material modifications 142 are formed, which are respectively positioned spaced apart from one another along the processing line 134 in the material 102 .

[0119] In particular, corresponding individual pulses or pulse trains are introduced into the material 102 by means of the machining beam 114 in order to form a specific material modification 142 .

[0120] The local locations of the material modifications 142 formed in the material 102 correspond to the local locations at which the machining beam 114 acts on the material and / or to the local locations at which individual pulses or pulse trains are introduced into the material 102 by means of the machining beam 114 .

[0121] exist Figure 2 In the example shown, the resulting material modifications 142 are represented as circles in a view from above the first outer side 136 of the material 102. Due to the elongated focal zone 130 assigned to the processing beam 114 and introduced into the material 102, the corresponding material modifications 142 extend parallel to the longitudinal center axis 132 of the focal zone 130, which in the example shown is oriented parallel to the thickness direction 140, through the material 102 (and are not formed solely on the surface of the first outer side 136 of the material 102). In particular, the material 102 is modified at specific material modifications 142 that are parallel to the thickness direction 140 and / or parallel to the longitudinal center axis 132 of the introduced focal zone 130, the modification region being defined by the spatial dimensions of the focal zone 130.

[0122] Therefore, a specific material modification 142 should be understood to refer to a modified region of the material 102 that is defined by the spatial dimensions of the focal zone 130 introduced into the material 102 and in particular extends at least a component in the thickness direction 140 of the material 102 .

[0123] Due to the elongated focal zone 130 of the processing beam 114 which has been introduced into the material 102, the relative movement of the processing beam along the processing line 134 forms a processing surface assigned to the processing line 134, on the surface area of ​​which the material modification 142 is arranged and on which the material 102 can be separated. Figure 2 In the example of FIG, the machining surface is a plane parallel to the thickness direction 140 and extending through the machining line 134 .

[0124] Provision is made for the processing beam 114 to form first a first material modification 142a and then a second material modification 142b along the processing line 134 , which is spaced apart from the first material modification 142a by a distance d0 along the processing line 134 .

[0125] The first material modification 142a and the second material modification 142b form a first group 144a of material modifications or are assigned to the first group 144a of material modifications.

[0126] A second group 144b of material modifications is also formed, which likewise comprises a first material modification 142'a and a second material modification 142'b. In particular, provision can be made to form at least one further group 144c of material modifications, which likewise comprises two material modifications 142, for example.

[0127] In principle, a group 144 of material modifications can have two or more material modifications 142 .

[0128] The different groups 144 are spaced apart from each other along the processing line 134 by a distance d1 , which is understood to be the shortest distance between the material modifications 142 of the different groups 144 , ie the distance between the respective closest material modifications 142 of the different groups 144 . Figure 2 In the example shown, the distance d between the first group 144a and the second group 144b is l It should be understood to refer to the distance between the second material-modified portion 142b and the first material-modified portion 142'a.

[0129] The distances d0, d1 are to be understood as meaning in particular the distances based on the respective geometric center points of the respective material modifications 142, e.g. Figure 2 shown.

[0130] For example, the distance d0 between adjacent material modifications 142 within a particular group 144 is approximately 1.0 μm. For example, d0 is at least 0.25 μm, particularly at least 0.5 μm, particularly at least 0.75 μm, particularly at least 0.85 μm. For example, d0 is at most 2.5 μm, particularly at most 2.0 μm, particularly at most 1.5 μm, particularly at most 1.25 μm.

[0131] Mutually adjacent material modifications 142 or groups 144 are to be understood as meaning the closest adjacent material modifications 142 or groups 144 , respectively, in particular between which no further material modifications 142 or groups 144 are arranged.

[0132] For example, the distance d1 between the closest material modifications 142 of two adjacent groups 144 is approximately 15 μm, for example, d1 is at least 5 μm, in particular at least 7.5 μm, in particular at least 10 μm, for example, d1 is at most 40 μm, in particular at most 30 μm, in particular at most 20 μm.

[0133] The processing beam 114 has, for example, at least one of the following beam parameters: wavelength λ = approximately 1030 nm; pulse duration of a single pulse for forming the specific material modified portion 142: 0.3 ps to 20 ps; pulse energy of a single pulse or a pulse train for forming the specific material modified portion 142: 50 μJ to 500 μJ.

[0134] For example, the lateral diameter of the machining beam 114 in the focal zone 130 is approximately 1 μm.

[0135] For example, the advancing speed oriented parallel to the advancing direction 141 is approximately 200 mm / s.

[0136] For example, the repetition rate of the laser pulses of the machining beam 114 is approximately 200 kHz. At this repetition rate and a forward speed of approximately 200 mm / s, mutually adjacent material modifications 142 are formed, for example, at intervals of approximately 5 μs, i.e., the laser pulse for forming the second material modification 142 b is introduced into the material 102 approximately 5 μs later than the laser pulse for forming the first material modification 142 a.

[0137] The beam parameters of the machining beam 114 are specifically selected so that cracks are not formed in the material 102 when the respective first material modification portions 142a, 142′a of the specific groups 144a and 144b are formed, respectively, but are only formed in the material 102 when the respective second material modification portions 142b, 142′b of the respective groups 144a and 144b are formed, respectively.

[0138] exist Figure 2 In the example shown, first the first material modifications 142a of the first group 144a are formed, followed by the second material modifications 142b, with cracks 146 forming during the formation of the second material modifications 142b. These cracks 146 extend in the region of the first and second material modifications 142a, 142b and have a preferred direction 148 and / or a main extension direction that is oriented at least approximately parallel to the direction of the distance d0 between adjacent material modifications 142a, 142b. For example, the cracks 146 extend within a spatial region of approximately 3 μm to 5 μm around the material modifications 142a, 142b.

[0139] Then, the first and second material modification portions 142′a, 142′b assigned to the second group 144b are formed one after another, wherein cracks 146 are formed in the area around these material modification portions 142′a, 142′b during the formation of the second material modification portion 142′b (in a similar manner to the first group 144a).

[0140] In this manner, cracks 146 are formed between corresponding material modifications 142 of a particular group 144 and between material modifications 142 of different groups 144. In particular, material modifications 142 may be formed such that cracks 146 between different groups 144 join and / or overlap along process line 134.

[0141] The preferred direction 148 of the cracks 146 formed is at least approximately parallel to the distance d0 between adjacent material modifications 142 and / or the distance d1 between adjacent groups 144 (in Figure 2 In particular, it is preferred that direction 148 be oriented parallel to process line 134.

[0142] In particular, it is provided that the different material modifications 142 of a specific group 144 are formed with the same beam parameters of the processing beam 114. However, in principle, mutually adjacent material modifications 142 can also be formed with different beam parameters.

[0143] For example, it can be provided that, for forming the respective second material modification 142b, 142'b, the processing beam 114 has a higher energy and / or pulse energy than for forming the respective first material modification 142a, 142'a. For example, the pulse energy allocated to the processing beam 114 for forming the first material modification 142a, 142'a is approximately 60% (at Figure 2 are represented by circles of different sizes).

[0144] After the material modifications 142 and associated cracks 146 have been formed, the material 102 may be separated along the process line 134, such as by applying a mechanical force.

[0145] Reference Signs List

[0146] λ wavelength

[0147] d0 distance

[0148] d1 distance

[0149] 100 devices

[0150] 102 Materials

[0151] 104 workpieces

[0152] 106 laser beam source

[0153] 108 Input laser beam

[0154] 110 control device

[0155] 111 pulse selection device

[0156] 112 beam shaping device

[0157] 114 processing beam

[0158] 116 beam shaping element

[0159] 118 beam

[0160] 120 telescope device

[0161] 122 Main propagation direction

[0162] 123 beam

[0163] 124 first lens element

[0164] 126 second lens element

[0165] 128 optical axes

[0166] 130 Focus Area

[0167] 132 longitudinal center axis

[0168] 134 processing line

[0169] 136 First Outer Side

[0170] 138 second outer side

[0171] 140 thickness direction

[0172] 141 forward direction

[0173] 142 Material Modification Department

[0174] 142a First material modification unit

[0175] 142'a First material modification unit

[0176] 142b Second material modification unit

[0177] 142'b Second material modification unit

[0178] 144 groups

[0179] 144a Group 1

[0180] Group 144b

[0181] 144c Another group

[0182] 146 cracks

[0183] 148 preferred direction

Claims

1. A method for laser processing a workpiece by means of a processing beam, the workpiece comprising a material that is transparent to the wavelength λ of the processing beam, in which method a material modification is formed in the material along a predetermined processing line by the action of the processing beam on the material, a first group of spaced-apart material modifications being formed in the material, mutually adjacent material modifications of the first group being formed temporally one after the other and having a distance d0 of at least 0.25*λ and / or at most 2.5*λ between one another, and a second group of spaced-apart material modifications being formed in the material, mutually adjacent material modifications of the second group being formed temporally one after the other and having a distance d0 of at least 0.25*λ and / or at most 2.5*λ between one another, and a shortest distance d1 between the material modifications of the first group and the material modifications of the second group being at least 5 μm.

2. The method according to claim 1, wherein The processing beam is a pulsed laser beam and, by means of it, corresponding laser pulses or pulse trains consisting of a plurality of laser pulses are introduced into the material in order to produce a specific material modification.

3. The method according to claim 2, wherein: At least one further group of spaced-apart material modifications is formed, wherein mutually adjacent material modifications of the at least one further group are formed temporally one after the other and have a distance d0 of at least 0.25*λ and / or at most 2.5*λ between one another, and wherein the shortest distance d1 between the material modifications of the at least one further group and the material modifications of the group of material modifications adjacent to and closest to the at least one further group is at least 5 μm.

4. The method according to claim 3, wherein: The distance d0 between adjacent material modifications assigned to a particular group is in each case at least 0.5*λ and / or at most 2.0*λ.

5. The method according to claim 2, wherein: The distance d0 between adjacent material modifications assigned to a particular group is in each case at least 0.5*λ and / or at most 2.0*λ.

6. The method according to claim 2, wherein: The wavelength λ of the processing beam is at least 300 nm and / or at most 1500 nm.

7. The method according to claim 1, wherein At least one further group of spaced-apart material modifications is formed, wherein mutually adjacent material modifications of the at least one further group are formed temporally one after the other and have a distance d0 of at least 0.25*λ and / or at most 2.5*λ between one another, and wherein the shortest distance d1 between the material modifications of the at least one further group and the material modifications of the group of material modifications adjacent to and closest to the at least one further group is at least 5 μm.

8. The method according to claim 1, wherein The distance d0 between adjacent material modifications assigned to a particular group is in each case at least 0.5*λ and / or at most 2.0*λ.

9. The method according to claim 7, wherein: The distance d0 between adjacent material modifications assigned to a particular group is in each case at least 0.5*λ and / or at most 2.0*λ.

10. The method according to claim 1, wherein The wavelength λ of the processing beam is at least 300 nm and / or at most 1500 nm.

11. The method according to claim 1, wherein Mutually adjacent material modifications assigned to a specific group are formed at a time interval of at least 1 μs and / or at most 15 μs.

12. The method according to claim 1, wherein The shortest distance d between the material modification portions of a group of adjacent closest material modification portions l is at least 7 μm and / or at most 40 μm.

13. The method according to claim 1, wherein The processing beam is moved relative to the material along the processing line at a forward speed of at least 50 mm / s and / or at most 400 mm / s.

14. The method according to claim 1, wherein The material modifications are produced temporally one after the other along the processing line by means of the processing beam.

15. The method according to claim 1, wherein The processing beams have identical beam parameters for forming the material modification assigned to a specific group.

16. The method according to claim 1, wherein The beam parameters assigned to the machining beam are selected such that, when the machining beam acts on the material at a test location at which the material is not modified within a radius of more than 5 μm, the material modification formed at the test location by means of the machining beam is not associated with the formation of cracks in the material and / or the material modification formed at the test location by means of the machining beam is associated with a change in the refractive index of the material.

17. The method according to claim 1, wherein The beam parameters assigned to the machining beam are selected such that the formation of a first material modification of a specific group of material modifications is independent of the formation of cracks in the material, and wherein cracks are formed in the material during the formation of a second material modification of the group spaced apart from the first material modification, the distance between the first material modification and the second material modification being at least 0.25*λ and / or at most 2.5*λ.

18. The method according to claim 1, wherein The beam parameters assigned to the machining beam are selected such that, during formation of the second set of material modifications, cracks are formed in the material, at least some portions of the cracks formed in the material extending between the first set of material modifications and the second set of material modifications.

19. The method according to claim 1, wherein The machining beam has a focal region which is introduced into the material of the workpiece at least in certain sections and is moved relative to the material along the machining line.

20. The method according to claim 1, wherein The material of the workpiece can be separated along the processing line and / or along a processing surface assigned to the processing line and having a material modification.

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