WO2021037520A1

WO2021037520A1 - Method and apparatus for cutting a workpiece by means of a laser beam

Info

Publication number: WO2021037520A1
Application number: PCT/EP2020/072180
Authority: WO
Inventors: Malte Kumkar; Jonas Kleiner; Daniel FLAMM
Original assignee: Trumpf Laser- Und Systemtechnik Gmbh
Priority date: 2019-08-29
Filing date: 2020-08-06
Publication date: 2021-03-04
Also published as: DE102019123239A1; DE102019123239B4

Abstract

The invention relates to the cutting of a workpiece (12) by local modification by means of a laser beam (16), the following steps being carried out: - generating a quasi-Bessel laser beam (16) which propagates in a propagation direction (28) after exiting a beam-shaping device (24); - radiating the quasi-Bessel laser beam (16) through a surface (30) of the workpiece (12) such that a focal zone (32) effective for cutting lies at least partially inside the material (14) of the workpiece (12); - displacing the focal zone (32) along a cutting curve (34) along the surface (30) of the workpiece (12); wherein the focal zone (32) is displaced such that, at least in a correction section of the cutting curve (34), the normal (36) of the surface (30) and the propagation direction (28) are inclined at an acute angle (α) to one other, wherein the value of the acute angle (α) is equal to or greater than the convergence angle (ß) which the quasi-Bessel laser beam (16) has on exiting the beam-shaping device (24). The invention also relates to a laser cutting apparatus.

Description

Title: Method and device for separating a workpiece by means of a laser beam

description

The invention relates to a method for cutting a workpiece according to claim 1 and to a laser cutting device according to claim 10.

With these techniques, transparent or partially transparent substrates can be separated or cut. Corresponding methods and devices are used, for example, when cutting glasses or other transparent substrates, in particular when Accurately fitting shapes are to be cut out of plate-like workpieces, for example in the production of displays.

WO 2012/006736 describes a laser cutting method in which a laser focus is irradiated through a surface of an in particular plate-like workpiece and is displaced along a cutting curve along the surface. The laser focus produces local modifications and / or material tensions in the material. Depending on the design of the separating curve, parts can thereby be separated or separated from the rest of the material.

In particular, Bessel-like laser beams can be used in laser processing. Such a Bessel-like laser beam or quasi-Bessel laser beam has an elongated focus zone in which the beam has non-diffractive properties, in the sense that the laser beam in the focus zone has an approximately propagation-invariant beam cross-section. The characteristic focus zone of the quasi-Bessel laser beam enables comparatively greater cutting depths and thus the separation of thicker pieces of material.

Bessel-like beams can be generated with optics (eg axicon) from a laser beam emitted by a conventional laser light source, for example from a Gaussian beam. The Bessel-like beam emerging from the optics generally initially has a convergence area in the beam path in front of its focus zone, in which the beam area initially tapers starting from the optics. In the material to be processed, the optical properties (in particular the refractive index) can change locally strongly or abruptly, for example at edges, in the area of already existing material modifications or in the area of other imperfections. Such material areas are referred to below as critical areas. In the critical areas, the Bessel-like beam can be disturbed and the shifting of the focus zone along the separation curve can be impaired, for example by the fact that the beam is shaded or reflected in the beam path in front of the focus zone and the focus zone can no longer penetrate into the material. As a result, the focus area cannot be brought close enough to the mentioned critical area. This can mean that it is not possible to separate the material in the critical areas.

The invention is based on the object of improving the reliability and efficiency of laser cutting processes.

This object is achieved by the method according to claim 1. By introducing local modifications into the material of a workpiece by means of a laser beam, areas are separated from the workpiece or areas are cut out of the workpiece. A workpiece is used that is at least partially transparent to the laser beam, e.g. glass.

According to the method, a Bessel-like beam (hereinafter referred to as a quasi-Bessel laser beam) is first generated. This can be done by means of an optical

Beam shaping device (for example comprising an axicon element) take place, which is described in more detail below. To When exiting the beam-shaping device, the quasi-Bessel laser beam propagates along a direction of propagation.

The quasi-Bessel laser beam is radiated into the material of the workpiece through a surface of the workpiece, so that the focus of the quasi-Bessel laser beam, which is effective for separation and, in particular, is elongated in the direction of propagation, lies at least partially within the material. The focus zone is then displaced along a separating curve along the surface of the workpiece, in particular parallel to the surface of the workpiece.

The focus zone is shifted in such a way that at least in some areas (in a so-called correction section of the separation curve) the normal to the surface with the direction of propagation encloses an acute angle in terms of amount. In terms of amount, the acute angle is equal to or greater than the convergence angle which the quasi-Bessel laser beam has when it emerges from the beam-shaping device. The acute angle is particularly included in an apex at an intersection of the direction of propagation with the surface of the workpiece with the local normal there, the acute angle being open in the direction of the beam shaping device (or a beam exit area of the beam shaping device).

A quasi-Bessel laser beam can be viewed as an approximate realization of an ideal Bessel beam.

The quasi-Bessel laser beam is generated, for example, from an entering laser beam by means of diffractive and / or refractive generated optical elements, as explained in more detail below. To generate such a quasi-Bessel laser beam, various beam components converge in a focus zone, which then has properties similar to a Bessel beam over a certain spatial area. In this respect, the quasi-Bessel laser beam initially has a convergence zone after its exit from the beam shaping device, which then merges into the focus area.

Due to the mentioned inclination in the correction section of the separation curve, an impairment of the Bessel-like focus zone by the critical areas in the material described at the beginning can be reduced or even compensated for. This makes it possible to relocate the focus zone effective for separation up to the critical areas or even into the critical areas. This enables complete separation even in materials with the critical areas mentioned. In addition, impairments of the focus zone due to refraction effects (for example on the surface) and / or diffraction effects (for example at points of interference) can be compensated for. Areas can also be reached from the focus zone which are not optically accessible without the described inclination. By irradiating the quasi-Bessel laser beam with the mentioned inclination, workpieces can also advantageously be detached from a surrounding material area, that is to say inner contours can be generated in material areas. For this purpose, a separating curve running in a correspondingly closed manner in the workpiece is selected. In addition, the inclination of the quasi-Bessel laser beam can cause an angle to the normal that is too large for an inclined workpiece can be avoided, for example with a three-dimensional component. This can reduce aberrations on the workpiece surface. These measures thus allow a larger tolerance range for machining without complex correction within the optics. Overall, the reliability and efficiency of the material separation is improved.

Depending on the type of critical areas and / or depending on the geometric conditions, the inclination of the direction of propagation to the surface with respect to a direction of web movement can be sluggish (direction of propagation in the direction of the local movement of the path inclined forwards) or piercing (direction of propagation inclined backwards against the local movement of the path) ).

In principle, the correction section can be extended over the entire separation curve, that is, the entire separation curve can be traversed with the described inclination. However, it can also be advantageous that the correction section is selected only in those areas in which faults, critical areas or other shading effects can occur. In this respect, the described inclination preferably only takes place in those areas of the material of the workpiece in which the refractive index of the material for the laser radiation changes spatially strongly, in particular changes abruptly. As explained, the critical areas also occur in the edge areas of the surface. In this case, it is advantageous if the correction section of the separating curve includes, in particular, any points of intersection or contact points of the separating curve with edge regions of the workpiece. For a further refinement, the focus zone can also be displaced parallel to the surface and at least in some areas also perpendicular to the surface along the separation curve. For this purpose, corresponding telescope optics can be provided in the beam path of the beam shaping device, by means of which the position of the Bessel-like zone can be varied within certain limits along the direction of propagation.

The quasi-Bessel laser beam is advantageously generated from a Gaussian beam, for example by an axicon element, in particular a conical lens, as will be explained in more detail below.

Said inclination can be achieved in various ways, in particular by tilting the workpiece in relation to the beam-shaping device or tilting the beam-shaping device in relation to the workpiece, or by forming a correspondingly inclined beam path when exiting the beam-shaping optics.

The named task is also carried out by a

A laser cutting device according to claim 10, which comprises an optical device for generating the laser beam and a workpiece holder for the needs-based arrangement (in particular holding and positioning) of the workpiece in relation to the laser beam.

The optical device comprises a laser light source for emitting an input laser beam and a beam shaping device, in particular comprising an axicon element, for converting the input laser beam into the quasi-Bessel laser beam. The beam shaping device has a beam exit area, for which an optical axis is defined. The quasi-Bessel laser beam exits through the beam exit area and spreads along a direction of propagation, the radiation initially converging at an angle of convergence (especially with respect to the optical axis) after the beam exit area in order to form the Bessel-like radiation zone. The workpiece is positioned in the workpiece holder in such a way that the quasi-Bessel laser beam can be irradiated onto a surface of the workpiece in such a way that the normal of the surface and the direction of propagation are inclined at an acute angle to one another, the amount of which is equal to or greater than the angle of convergence of the quasi-Bessel laser beam as it emerges from the beam shaping device. Such a laser cutting device is designed in particular to carry out the method described above.

To vary the focus zone, in particular to vary the position of the Bessel-like area in the material, for example along the direction of propagation, the optical device comprises in particular at least one telescope arrangement. For example, a first telescope arrangement for expanding the beam

Input laser beam may be provided, which is arranged in particular in the beam path in front of the beam shaping device. A second telescope arrangement can be provided, for example, in order to form a focal zone which is elongated in the direction of propagation and to vary its shape and / or orientation. Such a telescope arrangement is preferably arranged in the beam path after the beam shaping device. As explained, the inclination can be achieved by tilting the workpiece holder and the optical axis relative to one another, or also by forming an inclined radiation path in the optical device.

In this respect, the optical device can in particular comprise a wedge plate which causes the quasi-Bessel laser beam to be inclined with respect to the optical axis. The wedge plate is in particular rotatable in the

Laser separating device arranged so that the direction of the inclination of the quasi-Bessel laser beam can be changed, for example to follow a curved path movement by corresponding rotation of the inclination. The wedge plate is preferably arranged following the beam shaping device along the beam path and in front of the second telescope arrangement.

Advantageously, the optical device can comprise at least two wedge plates which cause the quasi-Bessel laser beam to be inclined relative to the optical axis, at least two of the wedge plates being arranged such that they can rotate relative to one another and / or together. The at least two wedge plates are preferably arranged following the beam shaping device along the beam path and in particular in front of the second telescope arrangement.

The inclined irradiation of the Bessel-like focus zone can be achieved, for example, by means of the second telescope arrangement. For this purpose, for example, at least one lens of the second telescope arrangement can be displaced transversely to the direction of propagation and / or transversely to the optical axis be arranged. The final lens of the second telescope arrangement can preferably be displaced in the aforementioned manner, for example the final lens of a micro-objective.

The inclination of the focus zone can also be changed in that the laser beam, inclined with respect to the optical axis, hits the lens of the second telescope arrangement which is in front in the beam path. This can be achieved, for example, by providing a variable / adjustable beam deflection device in the beam path in front of the second telescope arrangement, by means of which the direction of propagation of the laser beam in front of the second telescope arrangement can be changed. For example, the direction of propagation with respect to the optical axis on the first lens of the second telescope arrangement is changed by an angle alpha 'by means of a piezo-driven mirror. The mirror can also be designed as a reflective, diffractive optical element (DOE), which allows a very compact design.

To generate the Bessel-like radiation properties, the beam shaping device preferably comprises an axicon element and / or a diffractive optical element (DOE). In order to generate an inclination in the manner mentioned, the axicon element and / or the diffractive optical element can preferably be held inclinable with respect to the optical axis. By inclining the element, the quasi-Bessel laser beam or the Bessel-like focus can then be inclined relative to the optical axis.

For a further refinement, the axicon element and / or the diffractive optical element is mounted rotatably about the optical axis of the beam shaping device. This allows the direction of inclination of the beam path when passing through a curved path movement, so that, for example, the inclination in relation to the local path movement can always be kept constant.

The inclination of the beam path in the manner mentioned can also be achieved by means of an Alvarez lens system. The Alvarez lens system is preferably arranged along the beam path on the beam shape of the optical element and in front of the telescope arrangement. An Alvarez lens system preferably comprises two lens elements which are designed to continuously change the sphero-cylindrical effect, the two lenses being arranged in relation to one another in such a way that different spherical and / or cylindrical radii of curvature result when they are mutually displaced.

The invention is explained in more detail below with reference to the figures.

Show it:

Figure 1: sketched representation of a

Laser cutting device for performing the method described;

FIG. 2: sketched representation to explain the displacement of the quasi-Bessel laser beam along a separation curve;

Figures 3a 3b, 3c: sketched representations to explain the problems occurring in critical areas of the material when cutting by means of laser beams;

FIG. 4: a sketched representation to explain the beam path in a beam shaping device for a laser cutting device of the type described;

FIG. 5: a sketched representation to explain the quasi-Bessel laser beam as it emerges from the beam-shaping device;

Figure 6: Sketched representation to explain the

Inclination of the quasi-Bessel laser beam with respect to the normal to the surface of the workpiece;

FIG. 7: Sketched representation to explain the advantages that can be achieved by the measures described.

In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

FIG. 1 outlines a laser cutting device 10, by means of which areas of a workpiece 12 can be cut off, the workpiece 12 at least partially consisting of a material 14 that is transparent to a laser beam 16. The laser cutting device 10 comprises an optical device 18 for generating the laser beam 16 as well as a workpiece holder 20 for holding and positioning the workpiece 12.

The optical device 18 comprises a laser source 22 for emitting an input laser beam 16 ′, which is converted into the laser beam 16 by means of a beam shaping device 24 arranged in the beam path, by means of which the workpiece 12 is machined.

The beam shaping device 24 is designed to reshape the input laser beam 16 ′ in such a way that the laser beam 16 emerges in the manner of a quasi-Bessel laser beam from a beam exit region 26 of the beam shaping device 24. After the beam exit area 26, the quasi-Bessel laser beam spreads along a

Propagation direction 28 from. The workpiece 12 is received in the workpiece holder 20 in such a way that the quasi-Bessel laser beam is radiated into the material 14 through a surface 30 of the workpiece 12.

As sketched in FIG. 2, the quasi-Bessel laser beam initially converges after exiting the beam exit region 26 of the beam shaping device 24, wherein it spreads overall along the direction of propagation 28. The direction of propagation of the laser beam 16 can be established as a Poynting vector spatially averaged over the beam cross-section.

The beam shaping device 24 is designed in such a way that the quasi-Bessel laser beam 16 has a focus zone 32 which is elongated in particular along the direction of propagation 28 and in which the beam 16 has Bessel-like properties, thus propagated in particular along the direction of propagation over a certain area almost without diffraction.

As can be seen in FIG. 2, a local modification (e.g. melting) of the material 14 takes place in the area of the focus zone 32, which leads to a local separation of the material composite.

To separate the workpiece 12, the focus zone 32 is displaced along a separation curve 34 through the material 14 of the workpiece 12. The dividing curve 34 can run straight or curved. In particular, it is possible for the separating curve 34 to be a closed curve, so that a desired molded part can be cut out of the material 14.

When the focus zone 32 is displaced along the separating curve 34, problems can arise which impair the separation of the workpiece by modifying the material 14 in the focus zone 32, as described above.

The measures relevant to solving these problems can be explained in particular on the basis of geometric variables, such as the local normal 36 to the surface 30 and the direction of propagation 28 (cf. the illustration of these directions in FIG. 1).

FIG. 3 a sketches a case in which the separating curve 34 runs through an essentially undisturbed material section of the workpiece 12. In the example shown, the beam exit region 26 of the beam shaping device 24 is displaced essentially parallel to the surface 30, which is symbolized by a path movement 38 sketched with an arrow. A case is shown in which the The direction of propagation 28 is oriented essentially perpendicular to the surface 30, that is to say parallel to the normal 36. Along the path movement 38, the focus area 32 (see FIG. 2) produces local modifications in the material 14. Since there are no disruptive material areas, a separation along the separation curve can take place without any problems.

In the situation sketched in FIG. 3b, the separation curve (symbolized by the path movement 38) approaches an edge 40 of the workpiece 12 or its surface 30. At the edge 40, locally abrupt changes in the optical properties of the material 14 occur, in particular abrupt changes Change in the refractive index. As a result, local modifications can no longer be introduced over the entire area of the material 14 with the quasi-Bessel laser beam 16, since the focus zone 32 (FIG. 2) can no longer reach all areas of the material 14. Separation of the workpiece 12 in the area of the edge 40 is thus not possible. Even if the laser beam is irradiated directly at the edge 40, an optically inaccessible or “shaded area 42” remains, see FIG. 3c.

FIG. 4 shows, in a schematic representation, an embodiment of the beam shaping device 24 into which the input laser beam 16 ′ emitted by the laser source 22 is radiated. The laser source 22 emits, for example, a laser beam in the manner of a Gaussian beam, which does not have the properties of a Bessel-like beam. In this respect, the beam shaping device 24 comprises in particular an optical transformation element 44 for converting the

Input laser beam 16 'into a Bessel-like beam. in the In the example shown, the optical transformation element 44 is designed as an axicon element 46. In principle, however, other configurations are also possible. In general, Gaussian-like rays can be converted into Bessel-like rays, for example by conical lens means. Likewise, the optical transformation element can be designed as a diffractive optical element (DOE) or comprise one. In the example shown, the optical transformation element 44 is preceded by a first telescope arrangement 48 in the beam path. This can serve, for example, to widen the input laser beam 16 'before it is converted into a Bessel-like beam.

In the example shown, the beam shaping device 24 also comprises a second telescope arrangement 50 which is arranged in the beam path following the optical transformation element 44. The second telescope arrangement 50 can be designed, for example, to reduce the spatial extent of the focus zone 32 of the Bessel-like laser beam 16 generated or to shape it with a view to optimal material processing.

The second telescope assembly 50 comprises, for example, a first lens means 52 (e.g., converging lens) and an im

Closing lens means 54 following the beam path (e.g.

Converging lens). If necessary, further lens means can be provided between the lens means 52 and 54, depending on the design of the telescope optics.

The beam shaping device 24, in particular the second telescope arrangement 50, defines an optical axis 56 in the example shown. The beam shaping device 24 is preferably designed in such a way that the focus zone 32 of the quasi-Bessel laser beam 16 can be inclined in relation to the optical axis 56. For example, the closing lens means 54 of the second telescope arrangement can be displaced transversely with respect to the optical axis 56, as a result of which an axial offset of the focus zone 32 can be achieved.

An inclination of the Bessel-like focus zone 32 can also be achieved in that at least one wedge plate 58 is provided, which is preferably arranged in the beam path after the optical transformation element 44. The wedge plate 58 is formed in particular from a lens material and can incline the beam path for the formation of the quasi-Bessel laser beam 16 with respect to the optical axis 56. To this extent, the wedge plate 58 is preferably supported so as to be inclined with respect to the optical axis. In addition, the wedge plate 58 can also be held rotatably about the optical axis 56, so that an inclination of the Bessel-like focus zone 32 can be set both in terms of the angle of inclination and in the direction of inclination.

FIG. 5 sketches the geometric relationships of the radiation path, starting from the beam exit region 26 of the beam shaping device 24. The quasi-Bessel laser beam 16 is sketched schematically by enveloping marginal rays. Starting from the beam exit region 26, the quasi-Bessel laser beam initially has an angle of convergence β and, viewed as a whole, spreads along the

Propagation direction 28 from. In the example shown, the direction of propagation coincides with the optical axis, but this is not mandatory, as will be explained in more detail below. If in this configuration the quasi-Bessel If the laser beam 16 is radiated along the normal 36 onto the surface 30 of the workpiece 12, the problems explained in connection with FIGS. 3a, 3b, 3c can occur.

In order to remedy these problems, the quasi-Bessel laser beam 16 is preferably radiated through the surface 30 of the workpiece 12 in such a way that the (local) normal 36 in the area in which the quasi-Bessel laser beam 16 radiates through the surface 30 of the surface 30 and the direction of propagation 28 are inclined relative to one another in such a way that they enclose an acute angle in terms of amount. The apex of the acute angle lies on the surface 30, in particular formed by the point of intersection of the direction of propagation 28 with the local normal 36 there. The angle is in particular selected such that its absolute value is equal to or greater than the angle of convergence β.

As sketched in Figure 6, said inclination can be realized, for example, that workpiece 12 and beam shaping device 24 are arranged and oriented in relation to one another in such a way that the optical axis 56 of the beam shaping device 24 and the normal 36 on the surface 30 to each other by the angle are inclined. The direction of propagation 28 can then run on the optical axis 56. In this respect, in this embodiment it is not absolutely necessary for the Bessel-like laser beam 16 itself to be inclined with respect to the optical axis 56 of the beam-shaping device 24.

As an alternative or in addition to this, it is also possible for the Bessel-like laser beam 16 or the focus zone 32 to pass through the means described in connection with FIG. 4 are inclined to the optical axis.

The described inclination of the direction of propagation 28 and normal 36 to one another is preferably not provided in the entire area of the separating curve 34 (see FIG. 2). In particular, it may be sufficient to use the described inclination only in a correction section of the separating group 34, the correction section being selected such that all of the critical areas of the material described at the beginning which are traversed by the separating curve 34. However, a simple embodiment also results from the fact that the slope described is provided over the entire separation curve. In other words, the correction section can also be extended over the entire separation curve.

FIG. 7 outlines the effect achieved by the inclination described. In the example shown, the beam shaping device 24 is designed in such a way that the propagation direction 28 of the exiting quasi-Bessel laser beam 16 no longer runs on the optical axis 56 of the beam shaping device 24 (or the beam exit area 26), but that the propagation direction 28 is inclined to the optical axis 56 is. In particular, the inclination is selected such that the angle of inclination is included between the direction of propagation 28 and the normal to the surface 30. Since the inclination is at least as great as the convergence angle β (see FIG. 6), beam contributions also pass through the surface 30 in the edge regions of the quasi-Bessel laser beam 16 in such a way that they can always fully contribute to the formation of the focus zone 32. In particular, the angle of inclination can be selected such that no optically inaccessible areas occur in the material 14, in particular not in areas of the material 14 in which optical properties (eg refractive index) change abruptly. In the example of Figure 7 is

Irradiation of the quasi-Bessel laser beam 16 at the edge 40 of the workpiece 12 is shown.

Claims

1. A method for separating a workpiece (12) by local modification by means of a laser beam (16), the workpiece (12) comprising a material (14) that is at least partially transparent for the laser beam (16), the method comprising the steps:

- Generating a quasi-Bessel laser beam (16) by means of an optical beam shaping device (24), the quasi-Bessel laser beam (16) propagating along a propagation direction (28) after exiting the beam shaping device (24);

- Radiation of the quasi-Bessel laser beam (16) through a surface (30) of the workpiece (12) in such a way that a focus zone (32) effective for separating the quasi-Bessel laser beam (16) is at least partially within the material (14) the workpiece (12) lies;

- Shifting the focus zone (32) along a separating curve (34) along the surface (30) of the workpiece (12); wherein the shifting of the focus zone (32) takes place in such a way that at least in a correction section of the separation curve (34) the normal (36) of the surface (30) and the direction of propagation (28) are at an acute angle

(ex) are inclined to each other, the acute angle (ex) being equal in magnitude to or greater than the convergence angle (β) which the quasi-Bessel laser beam (16) has when exiting the beam-shaping device (24).

2. The method according to claim 1, wherein the separation curve (34) is traversed with a path movement (38) and in which Correction section of the separation curve (34) the direction of propagation (28) is inclined forward in the direction of the path movement (38).

3. The method according to claim 1, wherein the separation curve (34) is traversed with a path movement (38) and in the correction section of the separation curve (34) the direction of propagation (28) is inclined backwards against the path movement (38).

4. The method according to any one of the preceding claims, wherein the separation curve (34) runs through regions of the material (14) of the workpiece (12) in which the refractive index of the material (14) for the laser radiation changes spatially, in particular changes abruptly, and wherein the correction section of the separation curve (34) is selected in the said range.

5. The method according to any one of the preceding claims, wherein the separation curve (34) intersects an edge (40) of the surface (30) in at least one point of intersection and wherein the correction section is selected such that it includes the at least one point of intersection.

6. The method according to any one of the preceding claims, wherein the focus zone (32) is displaced along the separation curve (34) parallel to the surface (30) and at least in sections also perpendicular to the surface (30).

7. The method according to any one of the preceding claims, wherein the quasi-Bessel laser beam (16) is generated by means of an optical beam shaping device (24) from a Gaussian beam (16) emitted by a laser light source (22).

8. The method according to any one of the preceding claims, wherein the quasi-Bessel laser beam (16) is generated by means of a beam shaping device (24) which defines an optical axis (56), the direction of propagation (28) on the optical axis (56) ), and when the focus zone (32) is displaced along the separating curve (34) in its correction section, the workpiece (12) is arranged in relation to the optical axis (56) in such a way that the normal (36) of the surface ( 30) is inclined at the acute angle (ex) with respect to the optical axis (56).

9. The method according to any one of claims 1-7, wherein the generation of the quasi-Bessel laser beam (16) takes place by means of a beam shaping device (24) which defines an optical axis (56), wherein when moving the focus zone (32) along the Separation curve (34) in whose correction section the direction of propagation (28) is inclined with respect to the optical axis (56) with the acute angle (ex).

10. Laser cutting device (10) for cutting a workpiece (12) by means of a laser beam (16), the workpiece (12) comprising a material (14) that is at least partially transparent for the laser beam (16), with an optical device (18) for generating of the laser beam (16) and with a workpiece holder (20) for arranging the workpiece (12), the optical device (18) comprising:

- A laser source (22) for emitting a laser beam (16 ');

- A beam shaping device (24) for converting the laser beam (16 ') into a quasi-Bessel laser beam (16), wherein the beam shaping device (24) has a beam exit area (26) with an optical axis (56) and is designed in such a way that the quasi-Bessel laser beam (16) extends after the beam exit area (56) along a direction of propagation (28 ), the workpiece holder (20) being designed to position the workpiece (12) in such a way that the quasi-Bessel laser beam (16) can be irradiated onto a surface (30) of the workpiece (12), the normal (36) on the surface (30) and the

Propagation direction (28) are inclined to one another at an acute angle (), the acute angle (ex) being equal in magnitude to or greater than the convergence angle (ß) which the quasi-Bessel laser beam (16) exits the beam shaping device (24) having.

11. Laser cutting device (10) according to claim 10, the optical device (18) comprising a first telescope arrangement (48) for beam expansion of the laser beam (16 ').

12. Laser cutting device (10) according to claim 10 or 11, the optical device (18) comprising a second telescope arrangement (50) for generating a focus zone (32) elongated in a propagation direction (28) in the material to be processed (14).

13. Laser cutting device (10) according to one of claims 10-12, wherein the optical device (18) is designed and arranged in such a way that the direction of propagation (28) the optical axis (56), and the

The workpiece holder (20) is designed and arranged in such a way that the normal (36) of the surface (30) can be inclined at the acute angle (ex) with respect to the optical axis (56).

14. Laser cutting device (10) according to one of claims 10-12, characterized in that the optical device (18) is designed such that the

Propagation direction (28) relative to the optical axis (56) with the acute angle (ex) is inclined.

15. Laser cutting device (10) according to one of claims 10-14, wherein the optical device (18) comprises a wedge plate (58) which causes an inclination of the quasi-Bessel laser beam (16) relative to the optical axis (56), wherein the Wedge plate (58) is arranged in particular rotatable in order to change the direction of inclination of the quasi-Bessel laser beam (16).

16. Laser cutting device according to one of claims 10-14, characterized in that the optical device (18) comprises at least two wedge plates (58), the wedge plates (58) being designed to face an inclination of the quasi-Bessel laser beam (16) effect of the optical axis (56), the wedge plates (58) being arranged so as to be rotatable relative to one another and / or together with one another in order to change the inclination of the quasi-Bessel laser beam (16).

17. Laser cutting device (10) according to claim 12, characterized in that the second telescope arrangement (50) is designed such that the focus zone (32) in the material (14) elongates in the direction of propagation (28) and the elongated focus zone (32) is inclined with respect to the optical axis (56), with at least one lens (54) of the second telescope arrangement (50), in particular the lens (54) of the second telescope arrangement (50) terminating in the beam path, being transversely in this way can be displaced relative to the direction of propagation (28) so that the inclination of the elongated focus zone (32) can be changed.

18. Laser cutting device (10) according to claim 12, wherein a beam deflection device is provided in the beam path in front of the second telescope arrangement (50) such that the laser beam (16 ') inclined relative to the optical axis (56) onto a lens of the second arranged in the beam slope on the input side Telescope arrangement (50) can be irradiated.

19. Laser separating device (10) according to claim 10, wherein the beam-shaping device (24) comprises an axicon element (16) and / or a diffractive optical element (DOE) which is held inclinable with respect to the optical axis (56) in such a way that the inclination of the axicon element (46) and / or the diffractive optical element (DOE) causes the quasi-Bessel laser beam (16) to incline relative to the optical axis (56).

20. Laser cutting device (10) according to claim 19, wherein the axicon element (46) and / or the diffractive optical element (DOE) is mounted such that it is rotatable about the optical axis (56).