WO2009010244A1

WO2009010244A1 - Method for operating a laser engraving device

Info

Publication number: WO2009010244A1
Application number: PCT/EP2008/005698
Authority: WO
Inventors: Hans-Georg Schepers; Stephan Brüning
Original assignee: Schepers Gmbh + Co. Kg
Priority date: 2007-07-14
Filing date: 2008-07-11
Publication date: 2009-01-22
Also published as: DE102007032903A1

Abstract

The invention relates to a method for operating a laser engraving device (1) for engraving printing or embossing molds (2), wherein a surface of the printing or embossing molds (2) is separated into a plurality of surface points to be engraved, having a laser (10.1), having an acoustooptical or electrooptical modulator (11.1) connected downstream from the laser (10.1) for laser beam deflection, wherein a laser beam path leads from the modulator (11.1) into an absorber (12), wherein another laser beam path leads to a surface point (OP1) on the surface (20) of the printing or embossing mold (2) to be engraved, and wherein the laser beam on the other laser beam path experiences a deflection, or a further deflection, thus at least one further laser beam path being formed, which leads to at least one further surface point (OP2) also on the surface (20) of the printing or embossing mold (2). The novel method is characterized in that - the same is carried out for the engraving of rotary printing or embossing molds (2) while rotating the same, wherein a plurality of laser pulses or laser pulse strokes are applied to the surface (20) of the pressure or embossing mold (2) with each rotation thereof, - at least two laser pulses or laser pulse strokes are applied to each surface point (OP1, OP2, and so forth) of the printing or embossing mold (2) at an interval that is greater than the interval between two chronologically directly successive laser pulses or laser pulse strokes, and - two chronologically directly successive or two or more simultaneous laser pulses or laser pulse strokes are applied to two different surface points (OP1, OP2) that are positioned at a distance from each other.

Description

Description:

Method for operating a laser engraving device

The present invention relates to a method for operating a laser engraving device for the engraving of printing or embossing forms, wherein a surface of the printing or embossing forms is divided into a plurality of surface points to be engraved, with a laser, with a laser downstream acousto-or electro-optical A modulator for laser beam deflection, wherein from the modulator from a laser beam path leads into an absorber, wherein another laser beam path leads to a surface point on the surface of the engraved printing or embossing mold and wherein the laser beam on the other laser beam path undergoes a deflection or a further deflection, and at least one further laser beam path is thus formed, which also leads to at least one further surface point on the surface of the printing or embossing mold,

An engraving of the type indicated above is usually carried out on the basis of stored digital data, wherein the database represents an image resolved in pixels. In this case, e.g. each pixel is assigned a grayscale or intensity value between 0 and 255 at 8 bits of data depth. The modulator not only switches the laser beam off and on, but also intensity modulation of the laser beam in a number of intensity levels corresponding to the number of gray level or intensity values. In this case, the respectively required laser beam intensity can be adjusted from pixel to pixel to the respectively required value by the modulator.

From the document EP-A-1 245 326 a method of the type mentioned is known. The purpose of this known method is the optimal utilization of a part of the laser engraving device forming adjustment optics. For this purpose, a plurality of laser beam paths are generated which lead to a plurality of focus points on the surface. surface of a printing or embossing mold to be engraved. The focus points are arranged in the form of a two-dimensional dot matrix. In this way, several immediately adjacent surface points of the printing or embossing mold are engraved simultaneously, which allows rapid engraving.

A disadvantage of this method is that the closely adjacent and simultaneously occurring engraving of the dot matrix can affect each other unfavorable, so that the engraving does not always achieve the desired or required quality. An unfavorable influence occurs in particular when material is removed from the surface of the printing or embossing mold; in a mask exposure without material removal, there is no such disadvantage.

Document US-A-5 416 298 discloses another method of the kind set forth. Furthermore, it is characteristic of the method known from this document that every impingement of the laser beam on the surface of the printing or embossing mold there forms a depression in the form of a complete cell or a complete well. For this purpose, the laser beam is pulsed through the acousto-or electro-optical modulator. In order to introduce sufficient laser beam energy into the desired focal point for producing a complete cell or a complete cell, the laser beam is deflected in the direction of rotation of the rotating printing or embossing mold such that the focal point has the same speed as the printing plate surface in the circumferential direction , mitwandert with this. It is thereby achieved that the laser beam strikes the predetermined focal point on the printing plate surface for a longer time. Due to the incident for a relatively long time laser beam material is evaporated directly from the surface of the printing plate, wherein the surface according to the cited document is a ceramic surface.

A disadvantage is to look at this method that it comes to a considerable heat generation and action here due to the relatively long exposure time of the laser beam on the same surface point of the engraved printing or embossing form, leading to undesirable changes in the material of the printing or embossing mold in the environment Cell or cell comes. In addition, relatively large amounts of ablation residues are formed in gaseous form and there are stored relatively large and many particles blown off the surface in the surrounding area. the cell or well on the surface of the printing or embossing mold. As a result, only a limited quality of the engraving can be achieved.

Another laser engraving device is known from WO-A-97/19783. This document describes a laser engraving system for engraving a workpiece surface, comprising a laser beam source, a modulator arranged in the beam path of the laser beam source, an optics arranged downstream of the modulator, which is arranged at a distance from the workpiece surface, whereby optics and workpiece are moved relative to one another, and a control device, which controls the modulator with a control signal, so that its incident on the workpiece surface output radiation is modulated in accordance with the control signal and the workpiece surface processed accordingly deep. The workpiece may, for example, be a roller with a rubber or plastic coating. Furthermore, in this known laser engraving system, a second laser beam source is provided, which is controlled by the control device with a second control signal. In this case, the fine structures of the profile to be produced in the workpiece surface are to be formed by the first laser beam guided via the modulator, while the depth regions of the profile are to be formed by the laser beam of the second laser. For this purpose, the modulator on the one hand and the second laser beam source on the other hand driven by interconnected, but separate control signals. The two perpendicularly polarized laser beams from the modulator on the one hand and the second laser beam source on the other hand are transmitted or reflected by a selective mirror and passed together via an optical system to the workpiece surface to be machined.

Obviously, in this laser engraving device, the technical complexity is relatively high, since two lasers must be used. In addition, this laser engraving system is only economically usable when particularly large engraving depths are to be achieved, which are not achieved with the use of a single laser.

From EP-A-1 068 923 a method is known with which the intensity distribution of the laser beam in the focal point can be changed rapidly in a laser engraving device. For this purpose, at least two partial beams with different intensity distribution are used, which are combined to form a working beam. Due to the fact that the intensity of the partial beams can be changed individually, the - A -

intensity distribution within the focal point of the merged laser beam changed in the desired manner and adapted to different applications. Although this can be advantageously influenced in the production of printing cylinders, for example, the shape of Tiefdrucknäpfchen in the printing plate surface, but hereby an acceleration of the engraving is not achieved.

For the present invention, the task is to provide a method of the type mentioned above, in which the disadvantages set out above are avoided and in particular a very fast as well as high quality, reproducible engraving, even with a significant material removal from the surface to be engraved printing or embossing mold can be achieved.

The object is achieved according to the invention with a method of the type mentioned above, characterized in that

that the method for engraving rotary printing or embossing forms is carried out with their rotation, wherein with each revolution of the printing or embossing mold a plurality of laser pulses or laser pulse trains are applied to the surface thereof,

- That at each surface point of the printing or embossing mold at least two laser pulses or laser pulse trains with a time interval which is greater than the time interval between two temporally immediately successive laser pulses or laser pulse trains applied, and

- That each time two consecutive or two or more simultaneous laser pulses or laser pulse trains are applied to two different, spaced-apart surface points.

With the method according to the invention, it is advantageously achieved that the engraving of a rotary printing or embossing mold can take place at a high speed and at the same time with a high quality. Each surface point is not processed with a single laser pulse, but by multiple laser pulses or laser pulse trains that hit the specific surface point with time. Between the impingement of the individual laser pulses or laser pulse trains there is a certain period of time, which is so great that a mutual disturbance of the laser pulses or laser pulse trains striking the same surface point occurs is excluded. At the same time, the performance of the laser is well utilized by the application of two laser pulses or laser pulse trains, which follow one another directly in time, onto two different, spaced-apart surface points, thus avoiding unproductive dead times. The distribution of the energy for engraving a certain surface point on a plurality of laser pulses or laser pulse trains a thermal overstress and thereby possibly caused damage to the material of the printing or embossing mold is excluded. In this way results in a very fast engraving with very high quality engraving.

It is further provided according to the invention that the engraving of the rotary printing or embossing forms seamlessly along a helix and that the two different, spaced-apart surface points lie in two axially spaced circumferential tracks of the helix and / or are spaced apart in the circumferential direction of the printing or embossing molds. The engraving along a helix further contributes to a high engraving speed, since this type of engraving is much faster than a block engraving, in which a discontinuous feed movement from one circumferential track to the adjacent circumferential track is required. When engraving along a helical line, the movement of the laser engraving device can take place at a constant speed relative to the printing or embossing mold, which results in the mentioned faster engraving and also simplifies the execution of the method technically. With regard to the position of the two different, spaced-apart surface points, which are acted upon by two temporally successive or simultaneous laser pulses or laser pulse trains, there is a large freedom, since the distance can be in the circumferential direction, in the axial direction or in an intermediate direction.

The distance of the two spaced-apart surface points is expediently chosen such that the effects produced by the first laser pulse or laser pulse train, such as plasma formation, ablation residues in gaseous form or particles blown off the printing or embossing mold surface, do not cause any interference, in particular no absorption effect on the immediately following time exercise second laser pulse or laser pulse train. The actually selected distance is expediently determined in practice in such a way that the spatial extent of the effects produced by the first laser pulse or laser pulse train is determined by experiments and that then the distance is selected according to the aforementioned specifications. The distance is chosen as large as necessary and as small as possible in order to eliminate the interference while keeping the deflection of the laser beams as small as possible.

In a method embodiment, it is provided that the zero-order beam is guided into the absorber from the modulator via a first laser beam path and the first-order beam is guided to the surface of the printing or embossing mold via a second laser beam path. Here, therefore, the laser beam of the first order, that is the beam deflected in the modulator, is used for the engraving. The intensity of the laser beam for the engraving can thus be varied between zero and a maximum value, which depends on the effectiveness of the modulator, by means of a single modulator. The method in this embodiment can therefore be technically implemented relatively easily.

An alternative method embodiment proposes that further modulators are arranged in series with the modulator such that the beam of zeroth order is guided through all modulators through a first laser beam path to the surface of the printing or embossing mold and that from each modulator via a second laser beam path the first-order jet is conducted into the absorber as a common absorber or into its own absorber. When using very high laser power and / or modulators with low efficiency, it is advantageous not to use the first-order beam generated in the switched-on state of the modulator as a working or Abtragsstrahl but the actual beam of the laser beam source, which when turned off or not RF power applied modulators is transmitted. By the number of modulators the maximum extinction can be determined. The intensity of the Abtragsstrahls is determined by the RF power applied to the modulators, and thus can be controlled continuously. A structure for carrying out the method can be constructed as a single-beam or multi-beam system in combination with a downstream deflection unit, such as a polygon mirror. With an individual efficiency of a modulator of, for example, 60%, a minimum of 1.0% of the laser beam power is transmitted to the surface of the printing or embossing mold when, for example, five modulators are used. The number of modulators depends in particular on how far the laser beam intensity has to be reduced at most so that the minimum laser intensity does not cause any interference. kung causes more on the surface to be machined. In this process embodiment and structure, the laser beam properties are not affected by the diffraction of the modulators or by the RF power because the laser beam used for engraving is simply transmitted through the modulator crystal only. Thus, a particularly high overall efficiency is achieved here, since as maximum power practically the entire laser power, only reduced by low transmission losses in the modulators, reaches the surface to be processed. Furthermore, by this method, a more accurate intensity control possible.

Furthermore, the invention proposes that one or more ultra-short pulse lasers are used. The generated and applied ultrashort laser pulses or laser pulse trains contribute to a gentle engraving of the printing or embossing mold. Since the energy is applied in a very short period of time, there is a so-called "cold" erosion, in which the material hit by the laser pulse or Laserpulszug is completely and very quickly evaporated at the surface point of the printing or embossing mold, without it becoming a In addition, an undesirable liquid state of the material leading to crater edges or splashes of material in the vicinity of the surface point is virtually completely avoided.

In a further embodiment, it is preferably provided that laser pulses with a length between 0.1 and 100 picoseconds are applied in pulse trains through an external modulator / deflector.

A further contribution to achieving a high engraving speed is provided by the fact that preferably the Laserpυlse be applied with a repetition frequency between 1 MHz and several 100 MHz. This high repetition frequency of the laser pulses allows rapid engraving with a correspondingly high speed of the engraved printing or embossing mold, whereby the engraving time can be kept very short even with large printing or embossing forms.

Depending on the material of the printing or embossing mold to be engraved, different energies of the laser pulses are to be used and different surface point distances must be observed. To meet these requirements, For example, the invention proposes that the pulse train length, the surface point and the amplitude be controlled by the external modulator / deflector.

As described above, it is essential for the method according to the invention for the point of impact of the laser pulses or laser pulse trains to "jump" on the surface of the printing or embossing mold. that a signal fed into the acousto-or electro-optical modulator for laser beam deflection is varied, and thus a deflection angle of the laser beam and the surface point of the printing or embossing form hit by the laser beam are changed. In this way, the laser beam on which the laser pulses or laser pulse trains reach the surface of the printing or embossing mold can be deflected without any mechanical aids, which ensures a very fast and precise deflection.

Another embodiment of the method provides that instead of the acousto-electro-optical or electro-optical modulator or in addition to the acousto-or electro-optical modulator laser beam deflection is performed by a rotating polygon mirror. When using only the acousto-or electro-optical modulator with its relatively limited maximum deflection angle, the productivity of the process depends essentially on a maximum possible speed of the printing or embossing mold to be processed, the achievable speed is on the order of about 2,0007min. With the rotating polygon mirror, the maximum possible deflection angle becomes many times greater, so that a very high productivity can be achieved even at reduced speed of the printing or embossing mold. Due to the large deflection angle, a large number of laser pulses or laser pulse trains can be applied to a surface point in the case of a helical feed. The high technical effort for the most accurate possible fast turning of the printing or embossing mold can therefore be reduced, which makes the implementation of the method and equipment for easier and less expensive. With the same productivity, for example, the speed of the pressure or embossing mold can be reduced to about one-tenth of the otherwise necessary speed. Thus, it is also possible to economically process molds which are large and heavy and / or are subject to imbalances which are caused, for example, by heating and / or cooling devices arranged in the mold interior. A low speed of the printing or embossing mold also advantageously reduces the air turbulence Lungs near the mold surface, which is favorable for an effective suction of Abtragsrückständen.

In this case, it is expedient to further provide for the rotating polygon mirror, as seen in the laser beam direction, to be arranged behind the optionally used acoustoelectronic or electro-optical modulator. An angularly large fanning of the laser beam is so advantageous only shortly before the surface of the printing or embossing mold to be processed.

In order to ensure high accuracy and reproducibility, the rotation of the polygon mirror, a rotation of the printing or embossing mold and an axial feed of the laser engraving device are synchronized with each other.

For this purpose, it is specifically suggested that each rotation and the feed are detected via at least one associated electronic encoder with an accuracy of at least 1 micron.

Another way to increase the productivity of the method is that two or more laser beams are supplied to the polygon mirror. If necessary, the polygon mirror can be cooled to avoid thermal overload.

A contribution to the widest possible working range on the surface of the printing or embossing mold is that preferably the two or more laser beams are supplied to the polygon mirror at different angles of incidence.

Furthermore, it is preferably provided that, in addition to the laser beam or the laser beams, at least one measuring beam of a measuring device for an optical surface measurement of the printing or embossing mold is guided over the polygon mirror. In this way, an additional benefit of the polygon mirror is achieved.

A further development proposes that with the measuring device a separate surface measurement of the printing or embossing mold after completion of the mate- rialabtrag is made. Thus, the material removal can be documented, which is advantageous for a secure quality control.

Alternatively, the measuring device can be used to perform an integrated surface measurement of the printing or embossing mold during material removal, and measurement results of the measuring device can then be used for active control of the material removal. Thus, the current machining operation can be constantly monitored and corrected for deviations from a target value. This leads to particularly high qualities of processing and avoids rejects due to no or too late noticed processing errors.

The above-described use of the polygon mirror is preferred for the method according to the invention. Alternatively, however, it is also possible for a mechanical mirror (galvanomirror) or a miniature mirror array or an electro-optical modulator to be used instead of the rotating polygon mirror.

Since due to the deflection of the laser beam, this no longer in each case perpendicular to the surface of the engraved printing or embossing mold, but can also strike at a certain oblique angle, there is a misplacement of the laser focus; To prevent this, the invention proposes that the focus of the laser beam is tracked by a lens system with adapted lens design as a function of its current deflection angle. This ensures that the focus of the laser beam is always exactly at the point of impact on the surface of the printing or embossing mold and not in front of or behind it. In this way, the maximum possible resolution and accuracy of the engraving is guaranteed. Here, e.g. an F-theta lens can be applied, in which by the entrance angle a certain location on the printing or embossing mold, which may be a cylinder in particular, is achieved. The lens design is designed so that focus points on the working range of this lens in a plane, so on the printing form surface lie.

In the case of engraving with a material removal from the surface of the printing or embossing mold, it is often expedient or necessary for the adjacent circumferential traces to overlap. Since a laser beam is round in its profile and has a Gaussian beam profile, such a overlap of the tracks would result in a linear structure running in the direction of the circumferential tracks of the soil of an ablation. Thus, a continuous engraving would lead to a strong groove formation. To avoid this unwanted groove formation, it is proposed that the engraving along the helix is superimposed on a stepless variation of an axial position of the point of impact of the laser beam on the printing or embossing mold surface. By this variation of the axial position of the point of impact of the laser beam, the aforementioned groove formation is excluded, because not only exactly along the circumferential tracks, but also in areas between these material removal takes place. This also allows larger three-dimensional structures without disturbing groove formation, so produce a low surface roughness, low.

Another measure for achieving a particularly accurate and reproducible engraving result is that the engraving is superimposed on a cleaning process, with which each surface point is cleaned after applying a laser pulse or laser pulse train before another laser pulse or laser pulse train is applied to the same surface point.

The cleaning process is preferably carried out by brushing, also ultrasound-assisted brushing, or by sand blasting or by means of a plasma cleaning process. A combination of different cleaning processes is of course possible.

Due to physical conditions, the working range of an acousto or electro-optical modulator / deflector is limited in terms of the maximum possible deflection angle of the laser beam. Commercially available acoustoelectronic or electro-optical modulators / deflectors have, for example, a working range with regard to the fed-in modulation frequency of 30 MHz, in which a constant efficiency is achieved. The bandwidth of the frequency of 30 MHz corresponds to a maximum deflection angle of 1 to 3 °, depending on the material of the acoustoelectronic or electro-optical modulator. For some engravings, such a deflection angle may be too small, since the maximum possible deflection angle also determines the maximum possible distance between two surface points which are acted upon by laser pulses or laser pulse trains which follow one another directly or simultaneously in time. In order to allow a larger deflection angle, it is proposed that the laser beam after passing through the acousto-or electro-optical modulator by at least one connected in series another acousto or electro-optical modulator is performed. With a second acousto-or electro-optical modulator, the deflection angle can be doubled. With even more modulators, a further increase in the deflection angle can be achieved, if necessary.

In a further embodiment, it is proposed that the laser beam is guided by two identically constructed modulators, the deflection of the second modulator being inverted for the deflection of the first modulator. This ensures that the laser beam diffracted or deflected by the first modulator can no longer be influenced by the second modulator. Thus, on the surface of the printing or embossing mold two spaced impact points, wherein the deflection angles add and a large distance between the surface points hit by the laser pulses or laser pulse trains, is achieved.

An alternative development of the method provides that the laser beam is divided by a first polarization beam splitter into two sub-beams, that each sub-beam is guided by a respective acousto-or electro-optical modulator and that then the sub-beams are superimposed by a second polarization beam splitter back to a laser beam. The fact that each partial beam is guided by its own acousto-or electro-optical modulator, the modulation bandwidth can be doubled, which also means a doubling of the deflection angle. Thus, the distance of the surface points, which are acted upon by two temporally directly successive laser pulses or laser pulse trains, can be doubled. Since this type of division behaves like the use of two discrete lasers, two points can advantageously also be controlled simultaneously on the printing or embossing form.

In a further development of the embodiment of the method described above, it is proposed that the laser beam is directed by angular displacement of the second polarization beam splitter to desired surface points of the printing or embossing mold. This has the advantage that the positioning of the point of impact of the laser beams on the surface of the printing or embossing form is not only possible by varying the modulation frequency and thus the deflection angle of the acousto-electro-optical modulator, but can also be done by the second polarization beam splitter positioning , In a concrete further embodiment, it is provided that the laser beam is guided through two birefringent crystals which each serve as polarization beam splitters, the second crystal being arranged inversely to the first crystal. Concretely, the crystals may be, for example, calcite crystals.

The laser engraving device can basically be operated with a single laser. In some applications, the use of multiple lasers may be useful to achieve higher laser pulse energy or higher productivity. In this case, mutually identical or different lasers can be used. For these cases, the method according to the invention provides that a laser beam is generated by a plurality of lasers, that the laser beams generated by the lasers are each guided by an associated acousto-optical or electro-optical modulator / deflector and that the individual laser beams behind the modulators become a laser beam be merged, which impinges on the printing or embossing mold surface. Furthermore, the beams can also be merged quasi. They differ only in their propagation angle, whereby they are mapped to two different locations in the focusing plane. Due to the difference in angle, these rays diverge; with discrete optics but such a small distance would not be possible. A small distance is desirable in order to keep the f-number high and to achieve the greatest possible depth of focus.

In a further embodiment, the laser beams generated by the plurality of lasers have mutually different wavelengths. In particular, a reduction in the dependence of the removal rate on the absorption behavior of the material of the printing or embossing mold can be achieved. It consists, e.g. the ability to use two different resolution lasers, i. different spot size of the focus at the point of impact on the printing or embossing mold, and / or different power use. The laser beam of the first laser can then be used to create a "rough texture" and the second laser to create a "fine texture".

In order to combine the individually generated laser beams of the different lasers into a single laser beam, the invention proposes that the laser beams are converted by means of their respective dichroic mirrors into one another. be steered. The number of lasers is not limited to two, as in the prior art with a polarization beam overlay, but may advantageously be greater than two.

It is further proposed that the converged laser beam is directed by angular adjustment of at least one of the dichroic mirror to desired surface points of the printing or embossing mold. This adjustment of the at least one mirror advantageously achieves an additional, static possibility of deflecting the combined laser beam in addition to the dynamic deflection by the acoustoelectronic or electrooptical modulators associated with the lasers. For mirror adjustment, e.g. a piezoelectric actuator can be used, which is electrically controllable and with which an adjustment with an accuracy in the nanometer range is possible.

In order to produce a suitable laser beam for the method according to the invention, it is preferably provided that the laser beam or the laser beams are transmitted through one or more fiber lasers, e.g. Yterbium fiber laser, by one or more disk lasers, e.g. Yterbium vanadate laser, by one or more rod lasers, e.g. Titanium sapphire laser, and / or by one or more gas lasers, e.g. Eximer laser, is generated / are. With such lasers laser radiation with wavelengths of about 700 nm to 2,100 nm is possible, which allows a correspondingly high resolution in the engraving, which can go into the range of the wavelength of the laser radiation, that is, of just below 1 micron.

For cases where even higher resolution is desired, the method provides that the frequency of the laser radiation be multiplied by a frequency multiplier system within the laser or lasers. According to the frequency multiplication, the wavelength of the laser radiation decreases, whereby a corresponding increase in the resolution of the engraving can be achieved.

For a high engraving quality, it is not only essential that the points of impact of the laser pulses or laser pulse trains on the surface of the printing or embossing mold are precisely determined with respect to their location, but also in terms of the depth of the engraving compliance with exact removal depths is essential. To take this point into account, the invention proposes that before an engraving process by a calibration of the material of the printing or embossing mold dependent Abtragstiefe per laser pulse or laser pulse train is determined and that determined according to the determined Abtragstiefe per laser pulse or Laserpulszug the number of applied to a predetermined depth to be engraved surface point of the printing or embossing mold laser pulses or laser pulse trains becomes.

The inventive method can be used for a variety of engraving tasks. A first preferred use of the method provides that with this two-dimensional or three-dimensional mask layers are removed or exposed to printing or embossing forms. Such mask layers are required in particular if an etching process or a galvanic coating process is carried out in a further step of the engraving.

Another possible use of the method according to the invention is that with this a three-dimensional material removal of metallic or non-metallic printing or embossing mold surfaces is made. In this application, a printing or embossing mold surface can be made entirely with the laser engraving device operated by the method according to the invention; an etching process is not required here.

In a further embodiment, it is provided that the three-dimensional removal of material takes place in the form of a cell pattern and that a screen or engraved printing roll is thus produced. Due to the achievable with the novel high resolution engraving raster or gravure rolls can be produced with very small pitches and thus a very high resolution reliable and economical.

Another favorable application of the method is that with this embossing forms for embossing holograms can be produced. Embossing molds for embossing holograms require a high resolution, which can be easily achieved with the method according to the invention. In addition, since the removal rate of each individual laser pulse or laser pulse train is adjustable, a very small Abtragsrate per laser pulse or laser pulse train necessary for the production of hologram embossing can be easily adjusted to a required degree. A further field of application of the method is that the method produces embossing forms, for example for embossing leather structures for the automotive sector.

In order to carry out the method according to the invention economically and safely, it is provided that it is executed under the control of an electronic control unit in accordance with stored retrievable digital engraving data containing information about the position and the engraving depth of each surface point of the printing or embossing mold.

Finally, the invention also proposes that with the control unit the / each laser, the / each modulator, the polygon mirror, / each polarization beam splitter, the / each dichroic mirror, a rotary drive for the rotation of the printing or embossing mold and / or a Linearverfahreinrichtung for a method of the laser engraving device in the axial direction of the printing or embossing mold is controlled.

In the following, embodiments of the invention will be explained with reference to a drawing. The figures of the drawing each show in a schematic representation:

FIG. 1 shows a laser engraving device together with a printing or embossing mold during its engraving,

2 shows the laser engraving device in a first embodiment, with a

Laser and a first laser beam guide,

3 shows the laser engraving device in a second embodiment with a

Laser, with a modified laser beam guide,

4 shows the laser engraving device in a third embodiment, with a

Laser, whose beam is split and reunited,

Figure 5 shows the laser engraving device in a fourth embodiment, with several

Lasers whose laser beams are combined

6 shows the laser engraving device in a fifth embodiment, with a

Laser and a polygon mirror, 7 shows the laser engraving device in a sixth embodiment, with several lasers and a polygon mirror,

8 shows the laser engraving device in a seventh embodiment, with several lasers, a polygon mirror and a separate surface measurement, FIG.

9 shows the laser engraving device in an eighth embodiment, with several

Lasers, a polygon mirror and an integrated surface measurement, and

10 shows the laser engraving device in a ninth embodiment, with several modulators in series.

1 shows below in a purely schematic representation of a laser engraving device 1, which is used for engraving a printing or embossing mold 2 shown in the upper part of Figure 1, for example a printing cylinder.

The laser engraving device 1 can be moved parallel to the axial direction 24 of the printing or embossing mold 2 by means of a linear positioning device 15. The printing or embossing mold 2 is displaceable about its central axis 21 in rotation by means not shown here bearing means and a rotary drive. During the rotation, the surface 20 of the printing or embossing mold 2 moves in the circumferential direction 23.

The laser engraving device 1 generates by means of at least one laser provided therein a laser beam, which causes the desired engraving of the surface 20 of the printing or embossing mold 2 in the form of laser pulses or laser pulse trains. For this purpose, the surface 20 is subdivided into a multiplicity of surface points spaced apart in the circumferential direction 23 and in the axial direction 24. In each of these surface points, a desired influencing, in particular exposure or removal, of the material of the surface 20 of the printing or embossing mold 2 takes place. The engraving of the printing or embossing mold 2 takes place endlessly along a helical line 22 that runs around the outer circumference of the mold 2, that is to say helically, resulting in a multiplicity of adjacent circumferential tracks. To perform the engraving along this helical line 22, the linear motion Device 15 moves at a constant speed parallel to the axial direction 24 of the simultaneously rotating mold 2 in the direction of the arrow on the Linearverfahreinrichtung 15, here from left to right.

Each surface point of the printing or embossing mold 2 is applied for its engraving with at least two, in practice with a generally much larger number of laser pulses or laser pulse trains. Each laser pulse or laser pulse train, when engraving with material removal, ensures that material is vaporized from the surface 20 of the mold 2. Thus, the effects resulting from the impact of a laser pulse or laser pulse train on a first surface point OP1, in particular a plasma formation, ablation residues in gaseous form or particles blown off the surface, the application of the other or further laser pulses or laser pulse trains not by their absorption before reaching the surface 20, the laser beam is deflected so that it "jumps" between surface points OP1 and OP2 which are sufficiently far apart from each other. The laser beam or the laser pulses or laser pulse trains forming the laser beam thus reach the surface 20 of the mold 2 on two different laser beam paths L1 and L2 With an appropriate choice of the distance between the surface points OP1 and OP2, the engraving processes at the individual surface points OP1 and OP2 do not interfere with each other, thus causing problems with absorption of laser pulses or laser pulse trains by a previously formed surface plasma or by gaseous ablation residues avoided. It is also possible here to carry out a cleaning operation between two laser pulses or laser pulse trains on the same surface point OP1 or OP2, with which solid residues, in particular particles blown off from the surface, are removed.

In the example shown in FIG. 1, the two surface points OP1 and OP2 are spaced apart in the axial direction 24 of the mold 2. In accordance with differently directed deflection of the laser beam, the surface points OP1 and OP2 can also be spaced apart in the circumferential direction 23 or in a direction extending between the circumferential direction 23 and the axial direction 24. If necessary, it is also possible to choose the distance between the surface points OP1 and OP2 greater than shown in FIG. 1; In FIG. 1, the distance of the surface points OP 1 and OP 2 corresponds to the distance between two circumferential tracks 22. 1 and 22. 2 in the axial direction 24. stood between the surface points OP1 and OP2 and a multiple of the distance between two adjacent circumferential tracks 22.1 and 22.2 amount. A greater distance between the surface points OP 1 and OP 2 is achieved by an increased deflection between the two laser beam paths L 1 and L 2.

FIG. 1 shows the helical line 22 and the peripheral tracks 22.1 and 22.2 in a purely schematic, non-scale representation, so that the principle becomes recognizable. In practice, the distance between the circumferential tracks 22.1 and 22.2 seen in the axial direction 24 can be down to about 1 micron. A correspondingly small distance between adjacent surface points can also be present in the circumferential direction 23, so that a very high engraving resolution is achieved. The maximum resolution is determined by the wavelength of the laser used in the laser engraving device 1. Here, e.g. Fiber laser used, the laser radiation has a wavelength of about 1 micron.

FIG. 2 shows a schematic representation of the laser engraving device 1 in a first embodiment. By means of a laser 10.1, a pulsed laser beam L is generated. The laser pulses are preferably ultrashort with a time length between 0.1 and 100 picoseconds. In addition, the laser pulses are generated at a very high repetition rate of up to several 100 MHz. This allows a very fast engraving.

The laser beam L passes through an acousto-or electro-optical modulator 11.1. This results in two laser beam paths, both of which lead into a further, connected in series with the first modulator 11.1 acousto-or electro-optical modulator 11.2. At the output of the second modulator 11.2 then arise three laser beam paths. The laser beam path LO leads into an absorber 12.1. The two further laser beam paths L1 and L2 pass by the absorber 12.1 and are guided to the surface of the printing or embossing mold, not shown here.

By appropriate selection of modulation frequencies and feeding the modulation frequencies into the acousto-electro-optical modulators 11.1 and 11.2, the distance of the laser beam paths L1 and L2 on the surface of the printing or embossing mold can be determined and influenced. In the case of the laser engraving device 1 in FIG. 2, the two modulators 11.1 and 11.2 have the same deflection direction, so that the two laser beam paths L1 and L2 pass by on the same side of the absorber 12.1.

FIG. 3 shows a modified embodiment of the laser engraving device 1 from FIG. 2, in which, unlike FIG. 2, it is now provided that the deflection of the second modulator 11. 2 is inverted for the deflection of the first modulator 11. Hereby it is achieved that the deflection angle between the two laser beam paths L1 and L2 leading to the surface of the printing or embossing mold is doubled, while on the bisector at the angle between L1 and L2 the laser beam path LO leads into the absorber 12.1 ,

FIG. 4 likewise shows a purely schematic representation of a further embodiment of the laser engraving device 1. In this embodiment of the device 1, a laser beam L is also initially generated by means of a laser 10.1. The laser beam L is guided on a polarization beam splitter 13.1, whereby the laser beam L is split into two sub-beams. The first sub-beam runs in a straight line through the polarization beam splitter 13.1 into a first acousto-optical or electro-optical modulator 11.1. The second partial beam is deflected by the polarization beam splitter 13.1 and then guided via a deflecting mirror 16.1 into a second acousto-optical or electro-optical modulator 11.2. In each acousto-or electro-optical modulator 11.1, 11.2 takes place a deflection of the laser beam on two different beam paths, namely in each case a beam path LO, which leads in each case an absorber 12.1, 12.2, and a beam path through which a first partial beam LT1 and second partial beam LT2 runs, the latter being passed past the absorber 12.1 or 12.2. The first partial beam LT1 is deflected by a deflection mirror 16.2 and guided to a second polarization beam splitter 13.2. On this polarization splitter 13.2 and the second partial beam LT2 is performed. By means of the second polarization beam splitter 13.2, the two partial beams LT1 and LT2 are combined again to form a laser beam L, which is then guided onto the surface of the printing or embossing mold to be engraved. Since each partial beam LT1, LT2 can be deflected in a separate acousto-electro-optical modulator 11.1, 11.2, the combined laser beam L results in a doubled maximum deflection angle, which corresponds to a correspondingly larger distance between two surface points on the print which are processed in temporally successive or simultaneously - or embossing form allowed. Figure 5 of the drawing shows a fourth embodiment of the laser engraving device 1, again in a purely schematic representation. In this embodiment, the laser engraving device 1 comprises a plurality of lasers 10.1, 10.2, 10.3 to 10, the number of lasers is not fixed. The lasers 10.1 to 10 may be identical to one another; In the example shown in FIG. 5, the lasers 10.1 to 10 are distinguished by the wavelength of the laser radiation generated by them, with the laser 10.1 having the wavelength 1070 nm, the second laser 10.2 1090 nm, the third laser 10.3 1110 nm, etc can amount.

Each laser 10.1 to 10 generates a laser beam L, which is guided in each case its own associated acousto-or electro-optical modulator 11.1 to 11.n. In each acousto-to-optical modulator 11.1 to 11.n, beam deflection takes place on two laser beam paths LO and L1. In this case, the laser beam path LO leads in each case into an associated absorber 12.1 to 12. n. The respectively other laser beam path L1 leads past the respective absorber 12.1 to 12.n.

The laser beam on the beam path L1 of the first laser 10.1 is here deflected at right angles via a deflection mirror 16.1. The laser beams on the beam paths L1 of the second, third and subsequent lasers 10.2 to 10.n are each directed to a dichroic mirror 14.1 to 14.n, causing a superposition of all previously generated individual laser beams L1 to a laser beam L. This one laser beam L is then guided to the surface of the engraved printing or embossing mold.

Since each laser beam L, which is generated by one of the lasers 10.1 to 10.n, has its own modulator 11.1 to 11.n, a correspondingly large deflection angle can be realized.

In addition, a further, static deflection can take place via an adjustment of the dichroic mirrors 14.1 to 14.n. In this way, the laser engraving device 1 in its embodiment according to FIG. 5 offers particularly large deflection angles and thus enables, on the one hand, a particularly wide range of variations with regard to the position of the applied surface points relative to the laser engraving device and, on the other hand, particularly large distances between surface points, which are temporally unmitigated. be acted upon in succession or simultaneously by a laser pulse or laser pulse train.

FIGS. 6 to 9 show embodiments of the laser engraving device 1, for which it is characteristic that they have a polygon mirror 16 downstream of an acousto-optic or electro-optical modulator or an acousto-optical or electro-optical modulator.

FIG. 6 shows an embodiment in which a single laser beam is guided on a laser beam path L1 to the rotatable polygon mirror 16. The polygon mirror 16 deflects the incident laser beam L1 and leads it to the surface 20 of the below in Figure 6 visible in a small section print or embossing mold 2. Between the polygon mirror 16 and the printing or embossing mold 2 is still a conventional focusing and adjustment optics 17 arranged.

By the use of the polygon mirror 16, a large deflection angle is made possible, which results in a parallel to the axial direction of the printing or embossing mold 2 measured length a for the deflection region. Within the length a, all surface points of the surface 20 of the mold 2 can be processed, whereby a large processing width (corresponding to the length a) is achieved. In another orientation of the polygon mirror 16, the Abenkbereich may also run differently than in the axial direction of the mold 2.

This laser engraving device 1 and its large deflection range allow a slower rotation of the printing or embossing mold 2 about its longitudinal central axis, which makes the rotation of the mold 2 technically much easier. At the same time, despite the slower rotation of the printing or embossing mold 2, at least the same or even greater productivity of the method and of the laser engraving device 1 is achieved.

FIG. 7 shows an embodiment of the laser engraving device 1 in which a plurality of laser beams are guided on the laser beam paths L1, L2, Ln to the polygon mirror 16. The different laser beam paths L1, L2, Ln strike the polygon mirror 16 at different angles of incidence, which leads to a large deflection range and to a correspondingly large removal width. After reflection at the rotating polygon mirror 16 and passing through the focus and adjustment optics The laser beams, which also here preferably have the form of laser pulses or laser pulse trains, reach the surface points of the surface 20 of the printing or embossing mold 2 to be processed. By using a plurality of laser beams, which are preferably also generated by a plurality of lasers, a laser beam is produced Increased removal of material from the surface 20 of the printing or embossing mold 2 in the same time possible, which is another contribution to high productivity of the process and the laser engraving device 1.

In the embodiment according to FIG. 8, the laser engraving device 1 is designed as such in FIG. 7 and supplemented by a measuring device. The measuring device allows a separate measurement of the machined surface 20 of the printing or embossing mold 2. For this purpose, the measuring device not otherwise shown sends a measuring beam M from the laser beam paths LO, L1, Ln side facing away from the polygon mirror 16. From the polygon mirror 16 is the Measuring beam M is directed onto the surface 20 of the mold 2 and reflected from there as a reflected measuring beam M 'to the polygon mirror 16. From the polygon mirror 16, the reflected measuring beam M 'is reflected again and so again guided to the measuring device, in which an evaluation is carried out. As a result, the evaluation provides measured values about the shape of the surface 20 of the printing or embossing mold 2 in the processed state, i. after the removal process by the laser irradiation.

Finally, FIG. 9 shows an embodiment of the laser engraving device 1, which in itself also corresponds to the embodiment according to FIG. 7 and which is also equipped with a measuring device. In contrast to the example according to FIG. 8, the laser engraving device 1 according to FIG. 9 is designed so that with the associated measuring device an integrated surface measurement of the surface 20 of the printing or embossing mold 2 already takes place during processing by one or more laser beams. For this purpose, a measurement beam M from the same side, from which the laser beam paths L1 to Ln lead to the polygon mirror 16, this polygon mirror 16 is supplied. The polygon mirror 16 directs the measuring beam M together with the laser beams to the surface 20 of the printing or embossing mold 2 within the area of the surface 20 being processed. From the surface 20 the measuring beam is reflected as a reflected measuring beam M 'back to the polygon mirror 16 and from there Reflected here not specifically shown measuring device. In this embodiment, therefore, an integrated surface measurement of the surface 20 of the printing or embossing mold 2 during the removal of material from the surface 20 is possible, so that the measurements provided by the measuring device can be used for direct control of the removal, for example by the laser power accordingly the measurement results is changed. Hereby a particularly high quality of the surface processing, here the engraving, the form 2 can be achieved.

An alternative to the above-described examples laser engraving device 1 according to the figure 10 provides that in series with the modulator 11.1 further modulators, here four other modulators 11.2 to 11.5, are arranged that through all the modulators 11.1 to 11.5 through a first laser beam path LO the zeroth-order beam is guided to the surface 20 of the printing or embossing mold 2 and that from each modulator 11.1 to 11.5 in each case via a second laser beam L1 the first-order beam is guided into the absorber 12.1 as a common absorber or into its own absorber. The output laser beam generates here a single laser 10.1; a multi-beam system with two or more lasers is possible instead.

The laser beam which is used here for engraving the surface 20 is thus the beam of the zeroth order transmitted by the modulators 11.1 to 11.5. Its further deflection onto the different surface points OP1, OP2 and optionally further is effected by a deflection unit arranged downstream of the modulator row, in this case a polygon mirror 16, as has already been explained with reference to FIGS. 6 to 9. Instead of the polygon mirror 16, other deflection units, as already mentioned above, usable.

LIST OF REFERENCE NUMBERS

Sign label

1 laser engraving device

10.1 - 1O.n laser

11.1 -11.n acousto-or electro-optical modulators

12.1 -12.n absorber

13.1, 13.2 polarization beam splitter

14.1 -14.n dichroic mirrors

15 linear positioning device

16 polygon mirrors

17 Focusing and adaptation optics

2 printing or embossing mold

20 surface

21 axis of rotation

22 helical line

22.1, 22.2 Circumference traces

23 circumferential direction

24 axial direction

LO first laser beam path

L1 second laser beam path

L2 third laser beam path

Ln further laser beam path

M measuring beam

M ¹ reflected measuring beam

0P1, OP2 surface points

Claims

Patent claims:

1. Method for operating a laser engraving device (1) for engraving printing or embossing forms (2), a surface of the printing or embossing forms (2) being divided into a large number of surface points to be engraved, with a laser (10.1), with an acousto- or electro-optical modulator (11.1) arranged downstream of the laser (10.1) for laser beam deflection, a laser beam path leading from the modulator (11.1) into an absorber (12), with another laser beam path leading to a surface point (OP 1) on the surface (20) of the printing or embossing form (2) to be engraved and the laser beam undergoes a deflection or a further deflection on the other laser beam path and so at least one further laser beam path is formed which leads to at least one further surface point (OP2). also leads to the surface (20) of the printing or embossing mold (2), which means there is no marking,

- that the method for engraving rotary printing or embossing molds (2) is carried out while rotating them, with several laser pulses or laser pulse trains being applied to its surface (20) with each revolution of the printing or embossing mold (2),

- that at least two laser pulses or laser pulse trains are applied to each surface point (OP1, OP2, etc.) of the printing or embossing mold (2) with a time interval that is greater than the time interval between two laser pulses or laser pulse trains that immediately follow one another and

- that two immediately consecutive or two or more simultaneous laser pulses or laser pulse trains are applied to two different, spaced-apart surface points (OP1, OP2).

2. The method according to claim 1, characterized in that the engraving of the rotary printing or embossing molds (2) takes place seamlessly along a helical line (22) and that the two different, spaced apart surface points (OP1, OP2) in two axially spaced circumferential tracks (22.1, 22.2) lie on the helical line and/or lie at a distance from one another in the circumferential direction (23) of the printing or embossing molds (2).

3. The method according to claim 1 or 2, characterized in that the distance between the two spaced surface points (OP1, OP2) is chosen to be so large that effects generated by the first laser pulse or laser pulse train, such as plasma formation, ablation residues in gaseous form or from the pressure Particles blasted off from the surface of the embossing mold or embossing mold do not have any disruptive effect, in particular no absorption effect, on the second laser pulse or laser pulse train that immediately follows.

4. Method according to one of claims 1 to 3, characterized in that the zero-order beam is guided into the absorber (12) from the modulator (11.1) via a first laser beam path (LO) and the beam via a second laser beam path (L1). first order is guided to the surface (20) of the printing or embossing mold (2).

5. The method according to one of claims 1 to 3, characterized in that further modulators (11.2 - 11.n) are arranged in series with the modulator (11.1) so that through all modulators (11.1 - 11.n). A first laser beam path (LO) guides the zero-order beam to the surface (20) of the printing or embossing mold (2) and that the first-order beam comes out of each modulator (11.1 - 11.n) via a second laser beam path (L1). the absorber (12) is guided as a common absorber or in its own absorber.

6. Method according to one of the preceding claims, characterized in that one or more ultra-short pulse lasers are used.

7. The method according to claim 6, characterized in that laser pulses with a length between 0.1 and 100 picoseconds are applied in pulse trains by an external modulator / deflector.

8. Method according to one of the preceding claims, characterized in that the laser pulses are used with a repetition frequency between 1 MHz and a few 100 MHz.

9. Method according to one of claims 7 and 8, characterized in that the pulse train length, the surface point and the amplitude are controlled by the external modulator / deflector.

10. The method according to any one of the preceding claims, characterized in that a signal fed into the acousto- or electro-optical modulator (11.1) for deflection of the laser beam is varied and thus a deflection angle of the laser beam and the surface point (OP 1, OP2) hit by the laser beam are the pressure - or embossing mold (2) can be changed.

11. The method according to any one of the preceding claims, characterized in that instead of by the acousto- or electro-optical modulator (11.1) or in addition to the acousto- or electro-optical modulator (11.1), a laser beam deflection is carried out by a rotating polygon mirror (16).

12. The method according to claim 11, characterized in that the rotating polygon mirror (16) is arranged behind the acousto- or electro-optical modulator (11.1) as viewed in the laser beam direction.

13. The method according to claim 11 or 12, characterized in that the rotation of the polygon mirror (16), a rotation of the printing or embossing mold (2) and an axial feed of the laser engraving device (1) are synchronized with one another.

14. The method according to claim 13, characterized in that each rotation and the feed are recorded via at least one assigned electronic encoder with an accuracy of at least 1 μm.

15. The method according to any one of claims 11 to 14, characterized in that two or more laser beams are supplied to the polygon mirror (16).

16. The method according to claim 15, characterized in that the two or more laser beams are supplied to the polygon mirror (16) at different angles of incidence.

17. The method according to one of claims 11 to 16, characterized in that in addition to the laser beam or laser beams, at least one measuring beam (M, M ') of a measuring device for an optical surface measurement of the printing or embossing mold (2) via the polygon mirror (16) to be led.

18. The method according to claim 17, characterized in that a separate surface measurement of the printing or embossing mold (2) is carried out with the measuring device after the material has been removed.

19. The method according to claim 17, characterized in that an integrated surface measurement of the printing or embossing mold (2) is carried out with the measuring device during material removal and that measurement results of the measuring device are used for active control of the material removal.

20. The method according to any one of claims 11 to 19, characterized in that instead of the rotating polygon mirror (16), a mechanical mirror (galvano mirror) or a miniature mirror array or an electro-optical modulator is used.

21. Method according to one of the preceding claims, characterized in that the focus of the/each laser beam is tracked depending on its current deflection angle by a lens system with an adapted lens design.

22. The method according to any one of claims 2 to 21, characterized in that a stepless variation of an axial position of the point of impact of the laser beam on the printing or embossing mold surface (20) is superimposed on the engraving along the helical line (22).

23. The method according to one of claims 1 to 22, characterized in that the engraving is superimposed on a cleaning process with which each surface point (OP1, OP2, etc.) is cleaned after the application of a laser pulse or laser pulse train before the same surface point (OP1, OP2, etc.) another laser pulse or laser pulse train is applied.

24. The method according to claim 23, characterized in that the cleaning process is carried out by means of brushing or ultrasonic brushing or by means of sandblasting or by means of a plasma cleaning process.

25. Method according to one of the preceding claims, characterized in that the laser beam (L) after passing through the acousto- or electro-optical modulator (11.1) is guided through at least one further acousto- or electro-optical modulator (11.2) connected in series therewith.

26. The method according to claim 25, characterized in that the laser beam (L) is guided through two identical modulators (11.1, 11.2), the deflection of the second modulator (11.2) being inverted to the deflection of the first modulator (11.1).

27. The method according to any one of the preceding claims, characterized in that the laser beam (L) is divided into two partial beams (LT1, LT2) by a first polarization beam splitter (13.1), that each partial beam (LT1, LT2) is divided by an acoustic or electro-optical modulator (11.1,

11.2) and that the partial beams (LT1, LT2) are then superimposed again to form a laser beam (L) by means of a second polarization beam splitter (13.2).

28. The method according to claim 27, characterized in that the laser beam (L) is directed to desired surface points (OP1, OP2) of the printing or embossing mold (2) by angularly adjusting the second polarization beam splitter (13.2).

29. The method according to claim 27 or 28, characterized in that the laser beam (L) is guided through two birefringent crystals each serving as polarization beam splitters (13.1, 13.2), the second crystal being arranged inversely to the first crystal.

30. The method according to one of claims 1 to 29, characterized in that one laser beam (L) is generated by several lasers (10.1, 10.2, 10.n), that the laser beam (10.1, 10.2, 10.n) is generated by the lasers (10.1, 10.2, 10.n). generated laser beams (L) are each guided through an assigned acousto- or electro-optical modulator/deflector (11.1, 11.2, 11.n) and that the individual laser beams behind the modulators (11.1, 11.2, 11.n) form a laser beam ( L) are brought together, which hits the printing or embossing mold surface (20).

31. The method according to claim 30, characterized in that the laser beams (L) generated by the plurality of lasers (10.1, 10.2, 10.n) have wavelengths that are different from one another.

32. The method according to claim 30 or 31, characterized in that the laser beams (L) are deflected via a dichroic mirror (14.1, 14.2, 14. n) to bring them together.

33. The method according to claim 32, characterized in that the combined laser beam (L) is directed to desired surface points (OP1, OP2) of the printing or embossing mold (2) by angularly adjusting at least one of the dichroic mirrors (14.1, 14.2, 14.n). is directed.

34. The method according to any one of the preceding claims, characterized in that the laser beam (L) or the laser beams (L) are transmitted by one or more fiber lasers, for example yterbium fiber lasers, by one or more disk lasers, for example yterbium vanadate lasers or more- re rod laser, for example titanium-sapphire laser, and/or is/are generated by one or more gas lasers, for example eximer laser.

35. Method according to one of the preceding claims, characterized in that the frequency of the laser radiation is multiplied by a frequency multiplication system within the laser (10.1) or the lasers (10.1 - 10.n).

36. The method according to any one of the preceding claims, characterized in that before an engraving process, a removal depth per laser pulse or laser pulse train, which is dependent on the material of the printing or embossing mold (2), is determined by calibration and that in accordance with the determined removal depth per laser pulse or laser pulse train Number of laser pulses or laser pulse trains to be applied to a surface point to be engraved (OP1, OP2) of the printing or embossing mold (2) is determined.

37. Method according to one of claims 1 to 36, characterized in that two-dimensional or three-dimensional mask layers are removed or exposed to printing or embossing molds (2) using the method.

38. The method according to one of claims 1 to 36, characterized in that the method is used to remove three-dimensional material from metallic or non-metallic printing or embossing mold surfaces (20).

39. The method according to claim 38, characterized in that the three-dimensional material removal takes place in the form of a cell grid and that a screen or gravure printing roller is thereby produced.

40. The method according to any one of claims 1 to 36, characterized in that the method is used to produce embossing molds for embossing holograms.

41. The method according to one of claims 1 to 36, characterized in that the method is used to produce embossing molds, for example for embossing leather structures for the automotive sector.

42. The method according to one of the preceding claims, characterized in that it is under the control of an electronic control unit in accordance with stored, retrievable digital engraving data, the information about the position and the engraving depth of each surface point (OP1, OP2, etc.) of the printing or embossing form (2) included, is executed.

43. The method according to claim 42, characterized in that with the control unit the / each laser (10.1 - 10.n), the / each modulator (11.1 - 11. n), the polygon mirror (16), the / each polarization beam splitter (13.1 , 13.2), the/each dichroic mirror (14.1 - 14. n), a rotary drive for the rotation of the printing or embossing mold (2) and/or a linear displacement device (15) for moving the laser engraving device (1) in the axial direction (24 ) of the printing or embossing form (2) is controlled.