DE102011113508A1 - Device for introducing a marking onto a substrate by means of a laser beam - Google Patents

Abstract

The invention relates to a device for introducing a marking on and / or in a substrate, wherein at least one laser beam acts on the substrate and on at least one of the surfaces of the substrate causes a change in the material of the substrate or its coating, wherein the substrate via a rotatable stored cylinder is guided and the laser beam acts on the substrate while the substrate is at least partially in contact with the cylinder. According to the invention, the surface of the cylinder, which is in contact with the substrate, at least temporarily ablated particles, which detach due to the laser radiation from that side of the substrate, which is in contact with the cylinder, so that the ablated particles not again attached to the or a subsequent substrate.

Description

The invention relates to a device for introducing a marking on and / or into a substrate by means of a laser beam. At least one laser beam acts on the substrate and causes a change in the material of the substrate or a coating of the substrate on at least one of the surfaces of the substrate. In this case, the substrate is guided over a rotatably mounted cylinder, while the laser beam acts on the substrate. The substrate is at least partially in contact with the cylinder.

Such a generic device is known from the prior art. For example, with such a device, a mark in the form of individual information on a security, in particular a banknote, or a security sheet, on which there are several printed securities or banknotes, applied. The individualized information is, for example, a serial number of the security or security sheet that is different for each security or security sheet.

One way of applying a mark to the substrate of the security or security sheet is by means of a numbering machine. Among other things, the numbering machine consists of carrier disks and numbering units on these carrier disks, several numbering units being mounted on a carrier disk and several of these carrier disks being mounted on a shaft and the shaft being driven by at least one drive element with at least one rotary encoder. Each of these numbering machines prints the individual information on the security or the security sheet, whereby the individual information is changed in the next printing operation. For example, the value of the serial number when printing individual securities after printing is increased or decreased by one.

With a numbering machine, however, only predetermined characters, in particular letters and numbers, can be printed on the security.

Another way of applying a mark or individual mark to the substrate of the security or security sheet is by means of a laser beam. Here, the laser beam performs irreversible changes in the substrate of the security or security sheet, for example, by blackening of the substrate or ablation of substrate fabric or ink, which was previously printed on the substrate, wherein on the substrate or in the ink laser-sensitive materials are can be changed or ablated by the laser radiation. Furthermore, in this embodiment, it is possible to introduce a marking also in the interior of the substrate, wherein the substrate is irreversibly changed in its interior, for example by a rearrangement of particles of the substrate or by blackening. Furthermore, it is also possible to apply a marking to the back side of the substrate from its front side through the substrate. In this case, laser-sensitive materials are located only on the back side of the substrate, so that the laser radiation passes through the substrate almost unhindered and leads to a change in the substrate or a coating or ablation of particles only on its rear side.

Out EP 1641627 A1 For example, a method for generating at least one identity mark on the front and back sides of a substrate of a security document is known in which the part of the identity mark on the back side of the substrate is generated by the laser beam of a laser marking station arranged on the front side of the substrate. A portion on the back side of the substrate is here provided with a layer of a material which absorbs the laser radiation emitted by the laser beam. When the laser beam is directed onto the layer of absorbing material from the front side, the corresponding part of the identity mark is produced through the substrate on the back side of the substrate. The substrate hereby preferably consists of paper, wherein the layer of absorbing material is a color, metal or ink layer. The identity mark on the substrate is generated while the substrate is being transported on the same processing roller or processing cylinder.

The laser marking can thus also be carried out simultaneously on the front and rear side in or on the substrate or in coatings on the substrate, for example a printing ink with laser-sensitive materials.

An optional markable coating of the substrate can be applied, inter alia, by the following methods: offset printing, letterpress printing, indirect high pressure, intaglio, intaglio printing, screen printing, OVD patch application, OVD strip application, metallization or vapor deposition. If in this document the marking of the substrate is mentioned, the possibility of marking a coating of the substrate on its front and / or rear side is always included.

Furthermore, the laser marking can only on the front or even on the back of the Substrate or the coating can be performed. This means that the laser marking takes place in one case on the laser beam facing and in another case on the side facing away from the laser beam.

Advantage of the marking by means of laser beam is that any geometric shapes can be placed on or in the substrate. In particular, not only letters and numbers of any type, but also, for example, also drawings or images in arbitrary configurations can be introduced onto or into the substrate.

A device known from the prior art, which applies a laser beam mark to the substrate of a security or securities sheet, exists according to FIG 1 or 2 from a laser 3 that the laser beam 4 generated and a device that the focus of the laser beam 4 in relation to the substrate 2 at least in the transverse direction of the substrate 2 moved, preferably in the direction of the thickness of the substrate 2 and in and against the direction of travel of the substrate. A device for moving the focus of the laser beam 4 is for example a deflection of the laser beam 4 by means of moving mirrors or lenses or a displacement of the laser 3 even by means of spindle or belt.

The laser beam 4 then hits in the area 5 on the substrate 2 on, in which the substrate 2 from a cylinder 1 is guided and on the surface of the cylinder 1 rests. In a roll-shaped or web-shaped substrate 2 according to 1 becomes the substrate 2 unwound from a roll (not shown), passed over the cylinder and wound onto another roll (not shown). In an arcuate substrate 2 according to 2 , such as a security sheet, becomes the substrate 2 of grabs 6 on the cylinder 1 held, leaving the substrate 2 during the process of laser marking on the cylinder 1 can not slip and the distance of the laser to the substrate is kept almost constant and thus defined. This is necessary for adjusting the focus of the laser on the substrate.

The cylinder 1 usually consists of a counter-pressure cylinder on which a coating is applied. The coating usually consists of an elastomer, such as a vulcanized on the impression cylinder rubber in a web press or a clamped blanket or fabric cloth in a sheetfed press. The blanket consists of a fabric layer, applied to the at least one layer of an elastomer, preferably vulcanized.

However, upon the introduction of the mark onto or into the substrate, it has been found that not only at a mark on the back side of the substrate which is in contact with the cylinder, but even at a mark on the front side of the substrate the laser radiation is facing, particles, fibrous components and / or dust-like substances are ablated from the back of the substrate and on the coating of the impression cylinder, in particular a blanket or a tissue cloth, get. From the coating, these particles, etc. are transferred back to the back of the substrate and thus lead to undesirable contamination of the substrate.

It has also been found in practice that, depending on the selection of the coating, a non-reversible damage, in particular removal of the coating due to the laser marking acting through the substrate, can occur.

The invention is therefore the object of developing a generic security element such that the disadvantages of the prior art are eliminated.

This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, the surface of the cylinder which is in contact with the substrate absorbs ablated particles which, due to the laser radiation, detach from the side of the substrate which is in contact with the cylinder, so that the ablated particles do not return to the substrate Adhere substrate and not be transferred to a subsequent substrate.

According to a preferred embodiment it is provided that the cylinder consists of a counter-pressure cylinder on which a printing plate is clamped instead of a blanket. In this case, the printing form absorbs the ablated particles which, due to the laser radiation, detach from the side of the substrate which is in contact with the printing form.

As a printing for example, a printing plate, a full-surface coated cylinder, a blanket with a special surface, a structured cylinder or a sleeve are used.

Particularly preferred is the use of a printing plate. In this case, a printing plate is understood to mean a coating which can be fixed on the impression cylinder and which has partial depressions. The attachment can, for example with tensioning rails or by means of double-sided adhesive tape on the impression cylinder. The pressure plate may have a support material for stability reasons, such as. As aluminum sheet, steel or polyester film. The printing plates are preferably washable photopolymer plates, laser- or mechanically engravable plates or blankets, strippable rubber blankets.

The printing plate may either be elastic on the surface, for example a flexographic printing plate Gold A from Flint Group, or hard, for example a high-pressure plate or Nyloprint plate from Flint Group.

Instead of a pressure plate, it is also possible to coat a cylinder over the entire surface and to produce the recess in a further working step, for example by means of a laser, cutting tool, etching process or milling cutter. Another variant is to provide the cylinder with a photosensitive layer, to expose and then wash. The exposed areas are hardened and therefore can not be washed out.

Another possibility is to structure a cylinder directly, for example by means of engraving tool or laser.

Furthermore there is the possibility to create a sleeve. This is a sleeve with a coating which already has the desired recesses and is clamped on a clamping cylinder.

If the printing plates or the cylinders vary in thickness and it is not possible to compensate for the differences in thickness by means of backing materials, then inevitably results in different peripheral speeds on the printing plate surface despite the same production or angular velocity. By taking into account a distortion factor for the images to be introduced in the laser marking, it is possible to arrive at a non-distorted laser mark on the substrate.

The uptake of the particles by the printing form preferably takes place by means of two embodiments:
According to the first embodiment, the printing forme at least in the region in which the laser beam acts on the substrate, at least one recess in which collect the ablated particles. The bottom of the recess on the printing form is not in contact with the substrate, so that the ablated particles that collect in the recess, such as in a cavity or a cavity, not in contact with the substrate or a subsequent Substrate can come.

For large recesses, for example, have an area of more than 25 mm ² , and in particular for very large recesses, for example, have an area of 400 mm ² , it is also useful if at least one support point is arranged in at least one of the recesses on which the substrate rests. In the case of large recesses, in the absence of the support points, depending on the substrate quality, for example the stiffness, the substrate may be placed in the recesses of the recess, thereby causing contamination of the substrate due to direct contact with the recess deposited particles, comes.

Furthermore, the required constant distance to the laser and thus the positioning of the substrate relative to the focus of the laser beam can thus no longer be maintained and assumes an undefined position. The invention solves this problem by the substrate rests on the at least one support point, which is arranged in the interior of the recess, and is thereby held in the desired or required position relative to the focus distance. Preferably, the support point is arranged in the geometric center of gravity of the surface of the recess. For particularly large recesses, a plurality of support points are preferably arranged within the recess, which are particularly preferably arranged like a grid, wherein they either have a constant distance from one another and a regular arrangement or are arranged distributed irregularly or stochastically.

The contact point or the contact surface of the support point is chosen as small as possible in order to minimize the backside contamination of the substrate by ablated particles. Advantageously, a grid point with a round contact surface is used as a base, which has a diameter of 0.05 mm to 2 mm, preferably from 0.2 mm to 2 mm. Instead of a grid point and support lines can be used. If more than one support point is used, the ratio of the total contact area of the support points to the total area of the intervening recesses should be less than 50%, preferably less than 20% and particularly preferably less than 10%.

Furthermore, it is advantageous if the support points are below the level of the remaining contact surface of the printing plate, ie the surface spanned by the upper edge of the support points lies below the lower edge of the surface, which is spanned by the rest of the printing plate. This level distance is preferably between 0.02 mm and 1 mm, more preferably between 0.1 mm and 0.3 mm.

The size and shape of the recess is preferably matched to the size and shape of the geometrical shape to be applied to or introduced into the substrate and projects slightly beyond it. Due to the process tolerances in upstream printing and coating processes and the mechanical tolerances in the field of substrate guidance, for example by investors and grippers in a sheetfed machine, the supernatant or the enlargement of the recess to the motif of laser marking between 0.1 mm and 5 mm, preferably between 2 mm and 5 mm and more preferably between 3 mm and 5 mm to each adjacent edge.

If the shape and size of the recesses change depending on the security or security sheet, the printing form can be completely rastered, the substrate in the area in which the mark is to be placed, not fully over the printing form or the cylinder, but exclusively on Supporting points rests. These support points have a certain distance from each other and are preferably arranged like a grid. A preferred raster has a resolution of 4 to 60 points or lines per cm, preferably from 20 to 60 points or lines per cm, and an area coverage of between 3% and 50%, preferably from 5% to 30% and particularly preferably 10 % to 20%. In this embodiment, the ablated particles accumulate between the support points.

In a further embodiment, the recess in the bottom area is not smooth, but is enlarged in the surface by fissures (eg wave-shaped or a hemispherical array) in order to better temporarily fix the ablated particles.

According to a further embodiment, at least one recess reflects the incident laser radiation which impinges on the recess through the substrate, retroreflectively or diffusely. At least the bottom of the respective recess, preferably also the surface between the recesses and / or the flanks of the recesses are configured diffusely reflecting or retroreflecting. In a diffuse reflection or reflection, the corresponding area of the printing form, for example, white particles such. As TiO _2, which absorb the incident electromagnetic radiation of the laser beam, and radiate again in nearly all spatial directions. In order to produce a surface which is reflective for the laser radiation on the printing form, it can also be equipped with a mirror coating or thin-film reflection matched to the wavelength of the laser. In a retroreflective mirroring, however, the corresponding area of the printing form has, for example, background-mirrored microspheres, so-called Lüneburg lenses, or angular reflectors, so-called triple mirrors or cat's eyes, which reflect the incident electromagnetic radiation of the laser beam back in the direction from which the radiation originated or onto the retroreflective mirror Element has hit. Both embodiments have the advantage that an additional marking can be introduced on the rear side of the substrate and the energy requirement for producing a marking on the back side of the substrate can be lowered.

According to the second embodiment, the surface of the printing form at least in the area in which the laser beam acts on the substrate, a higher adhesion for the ablated particles than the substrate. This means that the printing form for the ablated particles has a higher adhesiveness or a greater tack than the substrate, so that the ablated particles adhere to the surface of the printing plate and not to the substrate.

Both embodiments can also be combined with each other. For example, the printing plate can have not only recesses in which the ablated particles collect, but also a higher adhesion for the ablated particles than the substrate. Particularly preferably, at least the recesses have a higher adhesion to the ablated particles than the substrate, so that the ablated particles are not only collected in the recesses, but also at least temporarily fixed.

So that the coating of the cylinder is not or only slightly affected by the laser beam, changed in properties or at least partially ablated, it is advantageous to use materials for the coating, which has the lowest possible absorption for electromagnetic radiation in the wavelength range of the laser beam used show or have a particularly good reflection for laser radiation of the wavelength used.

The ability of the cylinder or printing plate to collect the ablated particles is inevitably limited. At some point, the recesses are filled with ablated particles or the adhesive surface is covered with ablated particles. Therefore, particularly preferably, a cleaning device again removes the ablated particles that have accumulated on the cylinder or printing form from the surface of the cylinder or of the printing forme.

This cleaning device preferably consists of a suction device, which sucks the ablated particles from the cylinder by means of negative pressure. In this case, a type of vacuum cleaner moves along the surface of the cylinder or the printing plate and absorbs the accumulated ablated particles, which has been replaced by the laser beam from the substrate or the printing plate.

• – eine Überdruckvorrichtung, die ein Gas oder Gasgemisch, wie beispielsweise Luft, aus einer Düse ausstößt, wobei die Düse so auf die Oberfläche des Zylinders bzw. der Druckform ausgerichtet ist, dass der Gasstrom die ablatierten Partikel von dem Zylinder bzw. der Druckform in Richtung zur Absaugvorrichtung löst,
• – eine mechanische Reinigungsvorrichtung, bei der beispielsweise eine rotierende Bürste oder ein relativ zur Oberfläche des Zylinders bzw. der Druckform bewegtes Band mit einer textilen Oberfläche die ablatierten Partikel von dem Zylinder bzw. der Druckform löst,
• – ein entsprechend bewegter Schaber, der die ablatierten Partikel von einer glatten Oberfläche, beispielsweise einer Druckform ohne Vertiefung bzw. Aussparungen, löst,
• – eine Flüssigkeitsreinigungsvorrichtung, bei der beispielsweise ein Flüssigkeitsstrahl, ein Flüssigkeitsbad, eine rotierende Bürste mit integriertem Flüssigkeitsstrahl oder ein mit Flüssigkeit getränktes Band die ablatierten Partikel von dem Zylinder bzw. der Druckform löst.

The ablated particles can be released from the cylinder or the printing forme immediately before the suction process by means of one of the following devices, so that they can be absorbed by the suction device with less energy or more effectively;

• An overpressure device which ejects a gas or gas mixture, such as air, from a nozzle, the nozzle being aligned with the surface of the cylinder or the printing forme so that the gas flow directs the ablated particles from the cylinder or the printing plate in the direction to the suction device,
• A mechanical cleaning device in which, for example, a rotating brush or a belt with a textile surface moved relative to the surface of the cylinder or the printing forme dissolves the ablated particles from the cylinder or the printing form,
• A correspondingly moving scraper, which dissolves the ablated particles from a smooth surface, for example a printing plate without a depression or recesses,
• A liquid cleaning device in which, for example, a liquid jet, a liquid bath, a rotating brush with integrated liquid jet or a liquid-soaked strip dissolve the ablated particles from the cylinder or printing plate.

According to a further embodiment, an electrostatic cleaning device, for example an electrostatically charged drum or brush or an electrostatically charged strip, dissolves the ablated particles from the cylinder or printing plate. The ablated particles are either electrostatically charged by ablation or are electrostatically charged prior to their removal from the cylinder or printing plate by means of a prior art device, such as a belt generator, a drum generator, or an influential machine. The drum, brush or belt of the electrostatic cleaning device is charged with the opposite electrostatic charge so that it attracts and holds the electrostatically charged ablated particles on its surface.

The cleaning device may continuously remove the ablated particles from the surface of the cylinder or printing plate after each revolution or, with only a slight accumulation of ablated particles on the surface of the cylinder or the printing plate, after every n-th revolution, for example after every 5th, 10th or 20th turn. Particularly preferably, a sensor monitors the degree of contamination of the surface of the cylinder or the printing plate and activates the cleaning device when a predetermined limit value of the degree of contamination is exceeded.

In another embodiment, a sensor monitors the contamination in the region of the laser mark on the substrate and activates the cleaning device, which then removes the ablated particles from the surface of the cylinder or the printing plate.

The cleaning can take place both during and without substrate transport through the cylinder or the printing forme.

In a further embodiment, bores or apertures are introduced into the recesses in which the ablated particles collect. These holes or openings establish a connection between the respective recess and the hollow interior of the cylinder. In the hollow interior of the cylinder is compared to the ambient pressure in the outer space of the cylinder at the recesses on a negative pressure, which sucks the ablated particles from the recess into the interior of the cylinder.

In a preferred embodiment, the negative pressure in the interior of the cylinder is temporarily not applied in the areas in which the laser marking takes place at the same time in order to avoid sucking the substrate into the recesses or recesses. With a suitable number of bases, the suction of the substrate can be avoided in the wells, so that in this case the negative pressure in the interior of the cylinder does not have to be turned off.

The above-mentioned embodiments of the cleaning devices are preferably also combinable with each other.

Thus, in a first preferred embodiment, at least in the region where the laser beam acts on the substrate, the coating has at least one recess and the impression cylinder has small holes. In the area of the recess are also small holes, which are brought to the largest possible with the small holes of the impression cylinder in Passerung. An appropriate control ensures that the ablated particles have a Vacuum be sucked or sucked in the cylinder. Immediately before the cleaning device removes the ablated particles from the surface of the coating, the vacuum is turned off.

According to a second preferred embodiment, the coating has at least one recess at least in the region in which the laser beam acts on the substrate. The counter-pressure cylinder is charged electrostatically so that the ablated particles are temporarily fixed in the depressions or recesses via electrostatic forces. In the area of the cleaning device, the electrostatic charge is dissipated or neutralized, so that a discharge of the ablated particles from the surface of the coating is made possible.

According to a further embodiment, the device according to the invention for introducing the marking generates the recesses in the coating of the cylinder. In that case, the coating or, in the case of a multilayer coating, at least the uppermost layer of the coating must consist of a laser-sensitive material which can be ablated in the wavelength range of the laser beam from the coating.

The coating is preferably at least one two-ply layer structure consisting of at least one laser-sensitive layer and a non-laser-sensitive support. An example of such a coating is the standard blanket of the printing machine "Supernumerota" KBA, which consists of a doped with carbon black and thus laser-sensitive rubber layer and a white, non-laser-sensitive fabric cloth.

First, a file with the coordinates of the recesses is loaded into the control software of the device according to the invention for introducing the marking. Subsequently, the device according to the invention integrated on the printing machine generates the recesses by ablation of the laser-sensitive layer directly on the cylinder without substrate running.

By doing so, it is possible to avoid the high expense of setting up a printing plate. Furthermore, the separate process step of printing plate production is eliminated. Another advantage is the exact registration of the recess for laser marking, since the structuring of the printing plate takes place on the same cylinder.

Reference to the following embodiments and the additional figures, the advantages of the invention will be explained. The embodiments represent preferred embodiments, to which, however, the invention should not be limited in any way. Furthermore, the representations in the figures of better understanding are highly schematized and do not reflect the realities. In particular, the proportions shown in the figures do not correspond to the conditions present in reality and serve exclusively to improve the clarity. Furthermore, the embodiments described in the following exemplary embodiments are reduced to the essential core information for the sake of clarity. In the practical implementation much more complex patterns or images can be used.

The various embodiments are not limited to use in the form described, but can be combined to increase the effects with each other.

In detail, the figures show schematically in:

1 a device of the prior art for introducing a laser marking on a roll-shaped or web-shaped substrate,

2 a device of the prior art for introducing a laser marking on an arcuate substrate,

3 a detail of the cross section through a cylinder according to the invention with a recess,

4 a detail of the cross section through a cylinder according to the invention with a recess and a support point in this recess,

5 a detail of the cross section through a cylinder according to the invention with a recess and a plurality of support points in this recess, which are arranged like a grid,

6 a detail of the cross section through a cylinder according to the invention with a reflective or adhesive coating,

7 a detail of the cross section through a cylinder according to the invention with a recess and an adhesive coating at the bottom of the recess,

8th an inventive cleaning device in the form of a suction device which sucks ablated particles or dirt from the surface of the cylinder,

9 the cleaning device off 8th , combined with a rotating brush that dissolves the ablated particles or dirt,

10 the cleaning device off 8th combined with an overpressure device that dissolves the ablated particles or dirt,

11 the cleaning device off 10 , combined with another suction device,

12 a cleaning device according to the invention in the form of a circulating belt which receives the ablated particles or dirt.

3 schematically shows a section of the cross section through a cylinder according to the invention 1 , This cross section is an enlargement of the cross section, as it is also in 1 and 2 is shown, in 3 the area around the laser 3 and the contact area 5 on which the substrate 2 on the cylinder 1 rests, is shown enlarged. The cylinder 1 is shown in this and in all subsequent figures not arcuate, but straight for the sake of clarity. The actually arcuate portion of the cylinder is thus shown simplified straight or bent to a straight line. Since elbows for the limiting case opening angle α → 0 pass into the tangent to them and thus into a straight line, this simplification is not an unacceptable restriction on the general public.

The cylinder 1 consists in this embodiment of an impression cylinder 7 on which a printing plate in the form of a printing plate 8th is clamped in place of a rubber blanket known from the prior art. On the printing plate 8th lies the substrate 2 on, for example, a security, a security sheet or an endless belt from a roll of paper. Such a security is, for example, a banknote, a securities sheet, for example a sheet of paper, on which several banknotes, so-called benefits, are printed side by side.

On the substrate 2 is a printed image on the front 10 applied, in this printed image 10 a first laser mark is introduced. Also on the back of the substrate 2 may preferably be a printed image 11 be applied to the printed image 10 corresponds in shape and color or represents another printed image. In the print picture 11 a second laser mark is introduced. Of course, it is also possible to apply only a printed image on the front or only a printed image on the back, in which case a laser marking is introduced only on the front side or only on the back.

Alternatively, no printed image on the substrate 2 be applied, ie neither front nor on the back, in which case the mark directly on the surface or in the volume of the substrate 2 is introduced or introduced, for example by material rearrangement or material displacement, by blackening or by ablation of the substrate 2 ,

A laser 3 generates a laser beam 4 who is in the field 5 on the substrate 2 or the print images 10 and 11 incident. Will the mark by the laser beam 4 in the print image 11 through the substrate 2 introduced, it is obvious that particles are ablated from the back of the substrate, for example, color particles of the printed image 11 , But even in the event that the laser beam 4 the mark in the printed image 10 on the front of the substrate 2 can introduce particles from the back of the substrate 2 be solved, for example, particles of the substrate 2 themselves. These ablated or detached particles become according to the embodiment 3 in a recess 9 the printing plate 8th collected so that they do not return to the substrate 2 can get back. The depression 9 acts like a sort of "collection container" for the ablated particles.

Exceeds the surface of the recess 9 a certain limit based on the thickness and deformability of the substrate 2 depends, the substrate bends 2 in the recess 9 into it, that the focus of the laser beam 4 no longer at the desired or predetermined location of the substrate 2 to come to rest. The introduced mark appears in this case, for example, blurred or is in a different layer depth of the substrate 2 introduced as required. To avoid this, the pressure plate points 8th according to 4 a support point 12 on that in the recess 9 is arranged. On this support point 12 lies the substrate 2 on and is held by this, so it is not in the recess 9 can bend into it.

Is a support point 12 not sufficient alone, several support points can be arranged in the recess.

5 shows a further embodiment in which on the surface of the printing plate 8th a grid 13 is arranged by support points which support the substrate. This has the particular advantage that the marking, for example, in the printed image 10 should be introduced, not on the shape of the recess 9 is limited, but can take any form.

6 shows an embodiment in which a coating 14 on the surface of the printing plate 8th is applied. This coating has more preferably for the ablated particles, a higher adhesion than the substrate 2 so that the ablated particles adhere to the coating 14 attach and not on the substrate 2 ,

7 shows a combination of the embodiments 3 and 6 , This is at the bottom of the recess 9 a partial coating 15 attached, as well as the coating 14 particularly preferably for the ablated particles has a higher adhesion than the substrate 2 so that the ablated particles adhere to the coating 15 adhere.

Alternatively or additionally, the coating 14 or the partial coating 15 be provided with retroreflective or diffuse reflective elements that reflect the incident laser radiation accordingly.

8th shows a cleaning device that on the pressure plate 8th accumulated ablated particles 16 by means of a suction device 17 from the recess 9 sucks. The suction device 17 becomes along the direction of movement 18 led to the pressure plate and sucks, as soon as they ablate on particles 16 meet this.

Adhere to the ablated particles 16 very tight in the recess 9 and therefore allow yourself to be removed from the suction device 17 The ablated particles are very hard to peel off 16 loosened or detached before they are subsequently removed from the suction device 17 be sucked off. 9 to 11 show embodiments for such loosening or detachment of the ablated particles 16 from the printing plate 8th ,

9 shows a rotating brush 19 through which the ablated particles 16 in the recess 9 loosened or detached and in the direction of the suction device 17 be whirled up. Alternatively, the brush can of course also be in the running direction in front of the suction device.

In the embodiment according to 10 leads a blowing device 20 an air jet or a liquid steel on the ablated particles 16 , The detached or loosened ablated particles 21 are then sucked up by the suction device. Spray the blowing device 20 a jet of liquid or water on the ablated particles 16 so sucks the suction device 17 a mixture of liquid and loosened particles 21 one.

The embodiment according to 11 shows the device 10 , which is another suction device 17 is supplemented. Both suction devices 17 take the detached or loosened ablated particles 21 at the same time, so that the cleaning device in a shorter time over the surface of the printing plate 8th or the recess 9 can be performed. Of course, it is possible to use several of the above-mentioned devices for loosening or detaching the ablated particles 16 and combine several suction devices together.

The embodiment of 11 can be particularly preferably adapted to the effect that the blowing device 20 is disposed within a suction device. The blowing device 20 is completely surrounded by a suction device, with the exception of the exhaust opening itself, so that all ablated particles 16 be sucked off reliably, regardless of which direction they are from the blowing device 20 be loosened or blown away. Of course, it is also possible here, instead of the blowing device 20 one or more of the above or below devices for loosening or detachment of the ablated particles 16 to use.

12 shows a cleaning device in the form of a circulating belt, over the ablated particles 16 to be led. The surface of the strip is designed in such a way that it contains the ablated particles 16 not only from the depression 9 replaces, but also absorbs. This is done, for example, by electrostatic attraction between an electrostatically charged band and oppositely charged ablated particles 16 or over an absorbent surface of the tape. It is also possible to impregnate the surface of the belt with a cleaning fluid containing the ablated particles 16 detached, binds and absorbed by the tape again.

The circulating belt here consists of a cleaning track, which passes through a cleaning roller 22 is diverted. The cleaning roller 22 pushes the tape against the ablated particles 16 , The clean cleaning track 23 runs on the cleaning roller 22 to, dissolves the ablated particles 16 and pick it up. The ones with the ablated particles 16 acted upon and thus polluted cleaning track 24 gets from the cleaning roller 22 away and preferably supplied to a cleaning station, which frees the cleaning path of the ablated particles, recycled and as a clean cleaning path 23 again the cleaning roller 22 supplies.

Of course, any other known from the prior art cleaning device can be used, which is suitable, the ablated particles 16 from the surface of the printing plate 8th to remove.

LIST OF REFERENCE NUMBERS

1

cylinder

2

substratum

3

laser

4

laser beam

5

Contact area Substrate 2 - Cylinder 1

6

grab

7

Impression cylinder

8th

printing plate

9

recess

10

Printed image for laser marking on the front of the substrate 2

11

Printed image for laser marking on the back of the substrate 2

12

support point

13

Grid of interpolation points

14

coating

15

partial coating

16

ablated particles

17

suction

18

movement direction

19

rotating brush

20

blower

21

through the blowing device 20 dissolved ablated particles 16

22

cleaning roller

23

clean cleaning track

24

dirty cleaning track

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1641627 A1 [0006]

Claims (10)

Apparatus for introducing a marking on and / or in a substrate, wherein at least one laser beam acts on the substrate and on at least one of the surfaces of the substrate causes a change of the material of the substrate or its coating, wherein the substrate is guided over a rotatably mounted cylinder and the laser beam acts on the substrate while the substrate is at least partially in contact with the cylinder, characterized in that the surface of the cylinder in contact with the substrate at least temporarily receives ablated particles due to the laser radiation detach from the side of the substrate that is in contact with the cylinder so that the ablated particles do not resuspend on the or a subsequent substrate. Apparatus according to claim 1, characterized in that the cylinder consists of a counter-pressure cylinder on which there is a coating which receives the ablated particles, which detach due to the laser radiation from that side of the substrate, which is in contact with the coating. Apparatus according to claim 1 and 2, characterized in that the coating does not or only slightly absorb the laser radiation, preferably with an absorbance of less than or equal to 50%, preferably less than or equal to 70%, of the incident energy amount to damage the coating by the laser beam to avoid. Apparatus according to claim 2 and 3, characterized in that the coating has at least in the region in which the laser beam acts on the substrate, at least one recess in which collect the ablated particles. Apparatus according to claim 4, characterized in that at least one support point is arranged in at least one of the recesses, on which the substrate rests. Apparatus according to claim 4 or 5, characterized in that a plurality of support points are arranged like a grid in at least one of the recesses. Device according to one of claims 4 to 6, characterized in that at least one recess, the incident laser radiation which impinges through the substrate on the recess, retroreflectively or diffusely reflected. Device according to at least one of the preceding claims, characterized in that the surface of the coating, at least in the region in which the laser beam acts on the substrate, a higher adhesion for the ablated particles than the substrate. Device according to at least one of the preceding claims, characterized in that a cleaning device removes the ablated particles, which are located on the cylinder or the coated counter-pressure cylinder and / or in the recesses of the coatings, from the cylinder. Apparatus according to claim 9, characterized in that the cleaning device consists of at least one of the following devices: - A suction device which sucks the ablated particles from the cylinder by means of negative pressure and / or An overpressure device which ejects a gas or gas mixture from a nozzle, the nozzle being aligned with the surface of the cylinder or pressure plate in such a way that the gas stream releases the ablated particles from the cylinder, A mechanical cleaning device in which, for example, a rotating brush, a belt with a textile surface or a scraper releases the ablated particles from the cylinder and / or A liquid cleaning device in which, for example, a liquid jet, a liquid bath or a liquid-soaked strip dissolves the ablated particles from the cylinder and / or An electrostatic cleaning device in which, for example, an electrostatically charged drum or brush or an electrostatically charged belt releases the ablated particles from the cylinder.

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