EP1268211A1

EP1268211A1 - Method of printing and corresponding print machine

Info

Publication number: EP1268211A1
Application number: EP01940100A
Authority: EP
Inventors: Udo Lehmann
Original assignee: Aurentum Innovationstechnologien GmbH
Current assignee: Aurentum Innovationstechnologien GmbH
Priority date: 2000-03-30
Filing date: 2001-03-28
Publication date: 2003-01-02
Anticipated expiration: 2021-03-28
Also published as: US20030156178A1; US7137697B2; CA2404328C; JP4353452B2; DE50111796D1; JP2003528751A; CA2404328A1; WO2001072518A1; DE10191123D2; AU2001273816A1; ATE350220T1; EP1268211B1

Abstract

The invention relates to a printing method, for the transfer of printing substances (8), from a colour support (2), onto a printing substrate, whereby the printing substance undergoes a volume- and/or position-change, by means of an induced process of an energy-releasing device and, thus, the transfer of a printed point, onto the printing substrate occurs. The aim of the invention is to provide a printing method and printing device, operable with low energy requirement, easily refillable with the printing substance and, furthermore, overcoming the difficulties above, whereby the printing substance (8) is coated on the colour support, forming an essentially complete film.

Description

Printing process and printing machine therefor

The present invention relates to a printing method for transferring printing substance from an ink carrier to a printing substrate, whereby the printing substance undergoes a change in volume and / or position by means of an induced process of an energy-emitting device and thereby a printing point is transferred to the printing substrate, as well as a printing measure. seem for this.

A printing process is primarily understood to mean a process for reproducing text and / or image templates as often as desired by means of a printing form which is recolored after each printing. In general, a distinction is made between four fundamentally different printing processes. On the one hand, the high-pressure process is known, in which the printing elements of the printing form are raised, while the non-printing parts are deepened. This includes, for example, letterpress printing and so-called flexo or anil printing. Furthermore, planographic printing processes are known in which the printing elements and the non-printing parts of the printing form lie essentially in one plane. This includes offset printing, but also more methods known in the artistic field, such as. B. the stone print. In the case of offset printing, the colored drawing on the printing plate is not actually printed directly on the printing material, but is first transferred to a rubber cylinder or a rubber blanket and only then is the printing material printed on. If we are talking about printing stock in the following, the actual printing stock, i.e. the material to be printed, as well as any transfer medium, e.g. a rubber cylinder can be understood. A third process is the so-called gravure printing process, in which the printing elements of the printing form are recessed. This includes a number of manual techniques, such as B. the engraving and the etching. A gravure printing process is an industrially applied gravure printing process. Finally, a printing process, which is sometimes also referred to as a screen printing process, is known in which the ink is transferred to the printing material at the printing points through screen-like openings in the printing form.

These printing processes are all characterized by the fact that they require a printing form which is more or less complex, so that these printing processes only work economically in the case of very long runs, usually well over 1000 pieces. For example, in high-pressure form production, a raster film of the template to be printed must first be produced, which is copied onto the material of the printing form by means of a light-sensitive layer. Since the non-printing parts of a high-pressure form must be recessed compared to the printing parts, the metallic printing forms are then etched or plastic printing forms are selected. rule. However, these printing forms can only be used for printing a specific template. If another template is to be printed, a new high-pressure form must be produced.

Printers are already used for printing short runs and are generally connected to an electronic data processing system. These generally use digitally controllable printing systems that are able to print individual printing points on demand. Such printing systems use different processes with different printing substances on different substrates. Some examples of digitally controllable printing systems are: laser printers, thermal printers and inkjet printers. Digital printing processes are characterized by the fact that they do not require any printing forms.

For example, from GB 2 007 162 an electrothermal ink printing process is known in which the water-based ink is briefly heated to boiling by electrical impulses in a suitable ink nozzle, so that a gas bubble develops in a flash and an ink drop is shot out of the nozzle , This process is generally known under the term "bubble jet". However, these thermal ink printing processes have the disadvantage that on the one hand they consume a great deal of energy for printing a single printing dot and on the other hand they are only suitable for printing inks which are water-based. In addition, each individual pressure point must be controlled separately with the nozzle. Piezoelectric ink printing processes, on the other hand, suffer from the disadvantage that the nozzles required clog easily, so that only very special and expensive colors can be used for this.

Furthermore, it is known from DE 195 44 099 that with the aid of a laser beam or an electrothermal heating, solid printing substances can be melted and can thereby be transferred. A transparent cylinder is homogeneously provided with small cups on the surface. These cells are then filled with molten liquid paint and knife-coated using conventional methods. Subsequently, the ink to be printed is melted in a targeted manner from the inside through the cylinder by laser beam bombardment or by electro-thermal processes and thus emptied, thereby setting a pressure point. In this method too, the selection of the printing substance is severely restricted, since it is necessary for the printing process that the printing substance shows a phase transition from the solid to the liquid phase as quickly and in an energy-saving manner. In addition, the filling of the cells with meltable ink is problematic in this printing process.

Finally, it is known from DE 197 46 174 that a laser beam induces a process by means of very short pulses in a printing substance which is in the cups of a printing roller, so that the printing substance undergoes a change in volume and / or position. As a result, the printing substance grows over the surface of the printing form and the transfer of a printing point to a printing material approximated to it is possible. However, this method has the disadvantage that printing material approximated to this is possible. However, this method has the disadvantage that the filling of the cells is very difficult due to the small diameter of the cells.

The present invention is therefore based on the object of providing a printing method and a printing press which can be operated with very low energy, allow easy refilling of the printing substance and also overcome the disadvantages mentioned above.

According to the invention, this object is achieved with respect to the method in that the printing substance is applied to the ink carrier, essentially forming a homogeneous film. Because the printing substance forms a homogeneous film, it is achieved that due to the adhesion or the capillary force between the printing substance, ink carrier and optionally the printing form, a simple filling of any wells or openings is achieved. This is apparently u. a. remember that no air pockets form when printing substance is added to the ink carrier.

For example, a cylindrical body is used as the ink carrier, which preferably rotates about its own axis. The substrate, e.g. B. paper, plastic film, metal foil, but also rigid materials such as glass or metal, moved past with a transport speed that corresponds approximately to the peripheral speed of the cylindrical body. However, it is understood that the peripheral speed of the cylindrical body can also be greater than the feed speed of the printing material.

The ink carrier is preferably translucent, so that the energy-emitting device can emit energy, for example in the form of light, from the side of the ink carrier facing away from the printing substance through the ink carrier directly into the printing substance. The energy-emitting device is preferably a laser beam-emitting device, the laser beam preferably being focused on a selected point on the ink carrier. The translucent transparent cylinder could, for example, have depressions in the form of cups, so that by focusing the laser beam of the energy-emitting device on a specific cup, a change in position and / or volume of the printing substance in the relevant cup takes place, so that the printing substance here over the Extends the outer circumference of the transparent ink carrier and a transfer of the printing substance to the printing material can take place.

As an alternative to this, a preferably translucent transfer cylinder can also advantageously be provided, which is approximated to the ink carrier at one section and comes into contact with the actual printing material at another section. A laser beam can then pass through with the aid of a laser beam emitting device arranged inside the transfer cylinder the translucent transfer cylinder can be focused on a selected point on the ink carrier. As a result, the printing substance experiences a change in position and / or volume and the printing substance is transferred from the ink carrier to the transfer cylinder. If the transfer cylinder is now rotated, the printing substance adhering to the transfer cylinder is brought into contact with the actual printing material at some point and transferred to it.

In the embodiment with cups, however, the printing material may not touch the ink carrier during the transfer of the printing point. Rather, it is sufficient if the printing material is at least approximated to the ink carrier so that by inducing a change in position or volume of the printing substance, the printing substance can move so far in the direction of the printing material that an ink transfer takes place.

The energy can be transferred directly to the printing substance. However, this presupposes that the printing substance is able to absorb the energy. In order to increase the diversity of the printing substances that can be used, it is therefore advantageous if the energy is first transferred from the energy-emitting device to a switching material and then from the switching material to the printing substance. The mediation material is preferably a light-absorbing material, which is advantageously arranged in the form of a layer on the ink carrier. The energy transfer from the mediation material to the printing substance can take place, for example, by transferring thermal energy. That is to say that the mediating material is first heated by the energy-emitting device at the desired location in question, which in turn emits thermal energy to the printing substance. However, it is also possible for the energy transfer to take place by means of a pulse transfer. That is, here a change in position and / or volume of the material is induced within the mediation material, so that an impulse is transmitted to the printing substance by the movement or expansion of the mediation material. In this indirect printing method, the energy-absorbing layer is preferably matched as optimally as possible to the absorption of the energy beam, so that the energy to be used for the transmission of a pressure point can be further reduced.

It should be emphasized at this point that a printing form in the classic sense is not absolutely necessary for the method according to the invention. It is indeed possible to provide the cylindrical ink carrier with depressions which form a printing form, the so-called cups, which are essentially applied to the outer surface of the ink carrier, but which have a connection to one another, so that the printing substance, which is located in adjacent depressions who has a connection. However, it is also possible to completely dispense with special shaped elements. For example, it is possible to design the cylindrical ink carrier without depressions. By emitting a focused laser beam to a selected location, a change in volume and / or position of the printing substance is induced locally, so that a color droplet is formed separates locally from the essentially homogeneous color layer. The detachment does not have to take place solely on the basis of the induced energy, rather it is sufficient if the printing substrate is sufficiently close to the printing substance if the induced energy causes the printing substance to change its position, so that the printing substance is collected locally this touches the printing material and detachment occurs.

Due to the inertia of the remaining printing substance, the “printing form” is quasi formed by the surrounding printing substance.

The thickness of the pressure point can preferably be set here by varying the laser energy and / or by varying the pulse length.

Alternatively or in combination, it is possible for the diameter of the pressure point to be set via the variation of the laser energy and / or via the variation of the pulse length.

The resolution of the printing process can therefore be set almost arbitrarily. In addition, the positioning of the pressure point can be chosen freely. In contrast to this, in the known method only defined positions, namely the positions of the cells, are available. Even if the number of wells on the color support can be more than 100 million with good resolution, the dot pitch and the size of the dots are predetermined by such a color support. In the event that such shaping elements are completely dispensed with, a distance is preferably maintained between the ink carrier and printing material or printing substance on the ink carrier and printing material, which is preferably at least 10 μm, particularly preferably approximately 50 μm. In contrast to the known methods, the printing material does not touch the “printing form” or the ink carrier. This has the advantage that complex doctor blade devices are not required.

The pulse length of the laser pulse used is advantageously less than 1 μs, preferably less than 500 ns, particularly preferably between 100 to 200 ns. Due to the very short pulse length (with sufficient total energy), the laser energy is very well localized and you can achieve a clean printing of printing dots without the capillary forces of the printing substance forming a continuous film being negatively noticeable. Even laser pulses with a pulse duration of a few femtoseconds have been used with advantage.

In the printing method described, a laser beam is focused on the ink carrier or in the printing substance. If the laser light is absorbed, heat is generated in the printing substance, which leads to the solvent evaporating almost suddenly and a part of the printing substance being flung away from the ink carrier. In order for the process to function optimally, care must be taken to ensure that the energy from the laser beam into the printing substance is fast and This energy transfer can take place either by using printing inks that are not absorbing for the laser beam, e.g. pigmented inks, since the laser surface is directly absorbed on the pigment surface of the printing substance, or an absorption layer must be provided that the laser backing first absorbed and then the energy transferred to the printing substance

When using a translucent ink carrier, in which the laser beam is focused from the inside onto the absorption layer by the ink carrier, it has been shown in some cases that either the energy transferred to the printing substance is not sufficient to release a drop of ink from the printing substance , or there is a risk that the absorbed layer will be detached from the ink carrier due to the amount of energy transferred,

Therefore, the energy-emitting device is advantageously arranged in such a way that the light beam is not directed through the ink carrier but from the side of the ink carrier which is contaminated with printing substance onto the absorption layer. In this case, the light beam is first directed through the (non-absorbing) printing substance and then strikes the absorption layer It has surprisingly been found that with such an arrangement the risk of the absorption layer becoming detached from the ink carrier is significantly reduced

Furthermore, it has also been shown, surprisingly, that the direction of movement of the energy-absorbing ink droplet depends only very slightly on the angle at which the light beam strikes the surface of the printing substance. It is therefore not absolutely necessary, as in the embodiment described above, for the case that the ink carrier is arranged opposite a translucent transmission means through which the light beam is guided so that it strikes approximately perpendicular to the surface of the printing substance

Rather, as is also shown in connection with the embodiments shown in the figures, the laser beam can be “oblique”, ie with the normal on the surface of the printing substance, an angle greater than 0 ° and preferably less than 75 °, particularly preferably less than 60 ° To ensure an optimal transfer of the printing point to the printing material or the transfer medium, the distance between the focal point of the light beam and the location of the printing point to be set on the printing medium or transfer medium becomes less than 2 mm, preferably less than 1 mm, particularly preferably even less than 0 , 5 mm selected

With regard to the printing press, the above-mentioned object is achieved by a printing press for printing on a printing substrate with an ink carrier or an energy-emitting device, which is arranged and designed such that energy can be transferred to specific areas of the ink carrier, the ink carrier being provided for this purpose, Print substance to form essentially a homogeneous or continuous film Color carrier advantageously formed as a cylindrical body, which is preferably designed as a hollow cylinder with an essentially smooth surface.

As an alternative to this, however, it can be advantageous for some applications if the ink carrier is a flat plate. In principle, both the design as a cylinder and as a flat plate are possible, in the case of the hollow cylinder the refilling of the printing substance is easily possible, while in the case of the flat plate the supply of the printing material is easily realized.

The ink carrier is advantageously made of translucent material, preferably glass. This makes it possible to use light-emitting devices as energy-emitting devices, which emit the energy, for example, from the interior of the hollow cylinder through the translucent material directly into the printing substance.

In an expedient embodiment, the ink carrier has a thickness between 1 mm and 20 mm, preferably between 2 mm and 10 mm and particularly preferably about 5 mm.

In a preferred embodiment, the ink carrier designed as a cylinder has a maximum deviation from the ideal cylindrical shape below 200 μm, preferably below 100 μm, in particular below 80 μm.

In particular in the event that the printing substrate and ink carrier or printing form are arranged at a distance from one another during the printing process, a defined distance is preferably maintained very precisely. It is therefore provided in an expedient embodiment that the cylindrical ink carrier has an external bearing. This external storage allows the distance between the substrate and the ink carrier to be set exactly. A generally existing ovality of the cylindrical ink carrier is absorbed by the external storage. The external bearing can, for example, consist of at least one, preferably two, particularly preferably 3 rollers or rollers on which the cylindrical ink carrier rests. The external storage is preferably carried out with such precision that the distance between the ink carrier and the substrate varies during the rotation of the ink carrier by less than 50 μm, preferably less than 20 μm and particularly preferably by less than 10 μm. In addition, it is of course advantageous to produce the cylindrical outer surface of the ink carrier (printing drum) with the smallest possible tolerances, especially for smooth running and maintaining a constant distance. However, the outer bearing could probably only be dispensed with if the tolerance deviations of the outer surface can be kept below the variation values given above, preferably below 10 μm, for transparent hollow cylinders with an outer diameter of the order of magnitude of 300 mm Of course it is possible to transfer the energy directly into the printing substance. However, this presupposes that the printing substance is able to absorb light energy, for example. In order to increase the variety of usable printing substances, it is therefore provided in a preferred embodiment that an absorption layer is arranged on the ink carrier, which preferably has a thickness that is less than 10 μm, preferably less than 5 μm, particularly preferably less than 1 μm or even better is less than 0.5 μm.

In particular, in those applications in which a higher ink layer thickness is desired on the printing material, it has been shown that the surface of the portion of the ink carrier which receives the printing substance is not as completely smooth as possible (in the sense of optically glossy), but is somewhat matt or roughened , This can be done, for example, by using frosted glass. Particularly good results have been achieved with surfaces which have an arithmetic mean roughness of at least 0.1 μm, preferably between 0.5 μm and 5 μm, particularly preferably approximately between 1 μm and 2 μm. In the context of the present invention, such ink carrier surfaces are also considered to be “substantially smooth”, in contrast to surfaces provided with macroscopic depressions (cups or grooves) or elevations. In these embodiments with matted surfaces, several ink layers can also be “printed” in succession. Due to the fact that the surface of the ink carrier is not completely smooth, the ink carrier is able to absorb an increased amount of printing substance. "Printing" a dot then has the result that there is still enough printing substance on the ink carrier at the same location remains to print further pressure points.

For some applications, however, it can be advantageous if a printing form is additionally provided. This printing form serves to give the individual pressure points their form. In a preferred embodiment, the printing form has a multiplicity of cups and / or grooves which are provided for receiving printing substance, and in particular can absorb considerably more printing substance per unit area than smooth or matt surfaces.

Alternatively, the printing form can also be designed in the form of a network, so that so-called meshes are provided instead of cells or grooves. The network form has the advantage that the connection of the individual meshes to one another is produced automatically, without corresponding connection channels having to be provided. In other words, the print substance also forms an essentially continuous film along the ink carrier.

The formation of the printing medium in such a way that the printing substance forms a continuous, coherent layer, the energy transfer required to detach a pressure drop taking place so briefly that the drop detaches in a well-defined shape and size, enables the use of a wide variety of printing substances. The printing form is fastened, for example, on a cylindrical and transparent printing ink support in such a way that the color support is enclosed by the printing form. It is possible that the printing form and the ink carrier are integrally formed with each other, and that the printing form is releasably attachable to the ink carrier. An alternative embodiment provides that the printing form is designed as a band, preferably as an endless band. In this case, the ink carrier does not necessarily have to rotate, provided that the printing substance is supplied in another way.

The energy-emitting device preferably consists of at least one laser source. Under certain circumstances, arrangements of laser diodes can also be used as laser sources, but “classic” lasers with a power in the order of magnitude of 50-100 W or even more are still preferred at present. A practical embodiment also provides a focusing device that does The laser beam is focused on a predetermined point on the color carrier. This focusing device can be f-theta optics, for example. Of course, all other corresponding focusing devices can also be used.

In particular, in the event that the ink carrier consists of a transparent hollow cylinder with only a small diameter, it is structurally very difficult to arrange the energy-emitting device within the hollow cylinder. In this case, the arrangement of a deflection device can be of great advantage, with the aid of which the laser beams, which are emitted by the energy-emitting device, are redirected to the printing substance.

The deflection device can be, for example, a deflection mirror, the solder on the reflecting surface and the solder on the printing substrate plane preferably enclosing an angle of approximately 45 ° at the time of printing.

This arrangement has the advantage that the laser beam can be aligned essentially parallel to the axis of rotation of the ink carrier and thus the energy-emitting device can be arranged next to the ink carrier.

In a preferred embodiment, an addressing device is provided which is separate from the energy-emitting device and is controlled in order to image the laser beam on the corresponding point on the printing medium. This addressing device can have, for example, a polygon mirror that can be rotated about its axis. This has the advantage that the energy-emitting device does not have to be moved for addressing the individual pressure points.

In principle, a facet on a polygon mirror with eight facets angled evenly (at 45 °) allows the deflection of a laser beam between a minimal and a maximum angle that include a range of 90 °. However, for the use of the f-theta optics the laser beam used has to be expanded considerably and the polygon mirror is of course finite in size, whereby the laser energy can only be fully used if the expanded beam is completely on the currently active facet of the polygon mirror incident. The laser beam that is in principle available in continuous operation (even if it may be a pulsed laser with ultra-short pulses and correspondingly short pulse intervals) cannot be used, or at least not with its full power, as long as the expanded beam strikes the corner area between two neighboring facets. With the expansions used in practice and a reasonably manageable size of the polygon mirror, this ultimately means that only a deflection area of the laser beam on the polygon mirror of approximately 45 ° can be used (in the case of a polygon mirror with eight facets), so that within this 45 ° area is a complete print line or must be scanned. During the further rotation of the polygon mirror, during which the laser beam sweeps over a corner area between two adjacent facets, the laser beam cannot be used, ie there is a brief pause in printing.

In a special embodiment of the present invention, it is therefore provided that the laser beam is split in a type of "time-division multiplexing method" or guided via two different paths, the one beam part being directed in such a way that it is then precisely from a correspondingly selected and preferably 20 ° to 80 ° offset direction hits the relevant polygon facet completely, while the other branch of the beam would hit a corner area at the transition between two facets Switching between the two beam branches, preferably at an angle of 45 ° relative to each other Impinging on the polygon mirror can be done, for example, by a mirrored shutter disc (interrupter disc) which has alternating through openings and mirror surfaces and which is appropriately synchronized with the rotation of the polygon mirror, so that the beam is either passed through or through a mirror Shutter disk is deflected so that it runs on a different path than the beam that passes through the corresponding gaps of the shutter disk and strikes the shutter mirror on a first path.

Alternatively, instead of the shutter disk, it would also be possible to use a polarized laser beam in conjunction with an electro-optical modulator. The electro-optical modulator rotates the direction of polarization of the laser light, which is then either reflected by a polarization filter by 90 ° or is passed completely through the filter if the direction of polarization of the laser is suitable. In this way, too, an alternate guidance or redirection of the beam along two different paths can be realized, which in turn is synchronized with the rotation of the polygon mirror by corresponding electronic control of the electro-optical modulator, so that at any time one of the two beams is fully on a facet surface of the polygon mirror, while the beam otherwise strikes the other path a transition area would hit between two polygon facets. In this way, the duty cycle of the laser beam, which due to practical restrictions is otherwise only about 0.5, can be increased to the maximum value 1.

It goes without saying that a laser array can also be used instead of a single laser.

The absorption layer is preferably made of crystalline material, the size of the individual crystals should be as small as possible. As an absorption layer is advantageously nanocrystalline material such. B. carbon or so-called "gas soot" was used, the size of the individual crystals being approximately between 10 and 1000 nm. The size of the individual crystals is advantageously chosen to be smaller than the wavelength of the laser light used.

The absorption layer is preferably attached to the print carrier with polysilicate.

In the event that the light-emitting device is arranged within the color carrier designed as a transparent hollow cylinder, the light beam is focused through the transparent hollow cylinder onto the absorption layer. On the one hand, the absorption layer must be active enough to absorb the light and, at the same time, be able to pass on as much of this energy as possible directly to the printing substance. On the other hand, the absorption layer must be such that it is not detached from the light carrier by the color carrier.

It may therefore be advantageous for some embodiments if the light-emitting device is arranged in such a way that the light beam is guided through the printing substance onto the absorption layer. This has the advantage that the pulse transmission transmitted by the laser beam to the absorption layer presses the absorption layer onto the ink carrier and does not - as in the first case - detach the absorption layer from the ink carrier.

Surprisingly, it has been shown that the light beam does not necessarily have to strike the absorption layer or the color support perpendicularly. The volume and / or position change induced by the light beam usually runs essentially in the direction of the normal on the surface of the ink carrier.

Further advantages, features and possible uses of the present invention will become clear from the following description of preferred embodiments and the attached figures. Show it:

Figure 1 a) and 1 b) 2 shows a schematic sectional view of a section through the ink carrier including printing form,

2a) to 2d) schematic representations of the printing process for different embodiments,

Figure 3a) and 3 b)

Section views for two alternative embodiments,

4a) and 4b) different embodiments of a printing unit,

5a) and 5b) are sectional views of alternative embodiments,

FIG. 6 shows a schematic illustration of a deflection optics,

Figure 7 schematically shows a beam path along two paths to increase the duty cycle and

FIG. 8 shows a basic illustration of a further alternative printing arrangement,

FIG. 9 shows a schematic illustration of a printing arrangement which is based on the principle shown in FIG. 8 and

Figure 10 is a schematic diagram of a further alternative printing arrangement and

Figure 11 a) and 11b) is a schematic representation of a printing arrangement based on the principle shown in Figure 10.

FIGS. 1 a) and b) and FIGS. 2 a) to d) show different embodiments of the ink carrier with and without a printing form. In FIGS. 1 a) and b), the ink carrier 2 is covered by a printing form 1 which has so-called antechambers 5 on the side facing the ink carrier, which are filled with an absorption material 10. The antechambers 5 are separated from the wells 6, which are filled with pressure substance 8, by an elastic membrane 4. The cups 6 are separated here by so-called webs 3 on the side facing the printing material, which is not shown in detail. In addition, the individual cells are connected tion channels (not shown here) connected to each other, so that the printing substance can form an essentially homogeneous film that extends over several cells. The section shown in FIG. 1 b) differs from section 1 a) in that the printing form 1 has no prechambers 5 separate from the cups 6, but in this case anchors the absorption material 10 in the printing form 1 at the bottom of the cups 6 is so that the energy beam 7 is first converted into heat by an absorption material 10. The absorption material does not necessarily have to be arranged in separate chambers, but can, for example, also be designed as a continuous layer.

An energy-emitting device, here in the form of a laser arrangement, which is able to address each well 6 by at least one beam, is located within the ink carrier 2, which is cylindrical in the embodiment shown. The laser light can be controlled so that the width of the ink carrier 2 in the area of the printing nip, ie. H. In the area in which the printing material is approximated to the ink carrier or the printing form, the printing substance 8 located on the surface of the printing form 1 can be controlled selectively.

Further embodiments are shown in FIGS. 2a) to d). In these embodiments, the printing substance 8 is applied to the ink carrier. In Figure 2a) is the energy-inducing process, d. H. the printing process, shown. The wells 6 are filled with printing substance 8, absorption material 10 being introduced into the printing substance 8 as a dispersion. It should be emphasized at this point that the absorbent material 10 is not absolutely necessary if suitable printing substances are used accordingly. Only in the event that the printing substance is unable to absorb the energy introduced is the use of an absorbent, e.g. B. as a continuous layer or by mixing the absorption material into the printing substance, necessary.

The energy beam 7 is focused into the well 6 in FIG. 2 a). The absorption bodies 10 located in the printing substance 8 absorb the energy of the energy beam 7 and convert it into heat, so that the solvent located in the printing substance 8 evaporates. Due to this sudden evaporation of the solvent, the pressure substance 8 is thrown out of the cup 6.

In the embodiments with a membrane shown in FIGS. 1 a) and b), the energy transfer need not necessarily take place by heat transfer. Rather, it is also possible that the absorption medium heated by the laser beam expands and transmits an impulse to the printing substance via the membrane 5, which ensures that the printing substance 8 rises above the outer contour of the ink carrier or the printing form. In Figure 2 b) essentially the same process is shown as in Figure 2 a) Here, however, the Absorptionsmateπal 10 is not introduced into the printing substance 8, but arranged as a solid layer on the cup base in the printing form 1 It is clear that the Absorptionsmit - Tel does not necessarily have to be separated from the printing substance 8 by a membrane 5. The energy beam 7 is here converted into heat by the layer-shaped absorption material 10, which in turn brings the solvent in the printing substance 8 to a boil. This sudden evaporation of the solvent causes the Printing substance 8 thrown out of the cup 6

FIG. 2 c) shows an embodiment without a separate printing form. Here only the printing substance 8 is located as a homogeneous film on the printing ink carrier 2. Here, too, a laser pulse 7 leads to a movement of the printing substance 8 beyond the outer contour of the ink carrier. In other words, printing can be done of dots even without printing form 1, which leads to a sort of portioning of the printing substance 8, the control of the amount of pressure points and its expansion is then carried out by controlling the pulse energy and the pulse length

FIG. 2 d) shows an embodiment with specially shaped cups 6. It can clearly be seen that the cups essentially consist of a channel that widens on both sides. Because, as in the middle illustration in FIG. 2 d), is shown, the laser beam is focused in the extended area of the channel, which faces the ink carrier 2, the relatively weak gas bubble formation in the printing substance 8 is intensified and, due to the nozzle-like shape, is oriented in the direction of the printing material the cup can reduce the energy required for printing

FIG. 3 a) shows an embodiment with a printing form, in which the connection of the individual cups can be seen. The printing form 1 has a roughened side 16 on the side facing the ink carrier 2, so that there is a gap between the ink carrier 2 and the printing form 1 13, which ensures a homogeneous distribution of the printing ink 8 of the wells 9 due to capillary forces occurring between printing form 1, ink carrier 2 and printing substance 8. Furthermore, air pockets are prevented and a homogeneous and defined filling of the wells with printing substance is possible

In the embodiment shown in FIG. 3 b), a printing form 1 is also arranged on the ink carrier 2. However, the printing form 1 is designed here as a network 18 and therefore has so-called meshes 15 instead of the cups. The network here also allows a homogeneous distribution of the printing substance 8 through the gap 13

The cylindrical ink carrier 2 is shown as a whole in FIG. 4 a), the printing form 1 seamlessly enclosing the cylindrical printing cylinder or the ink carrier 2. The laser arrangement 7 is located in the interior of the printing cylinder 2 Alternatively, the printing form 1 can also run around the cylindrical printing cylinder or the ink carrier 2 as a band, as shown in FIG. 4 b). Here too, the laser arrangement 7 is located inside the printing cylinder 2.

As shown in the embodiment in FIG. 4 c), the ink carrier 2 need not necessarily be designed as a rotating cylinder. Here, however, the printing form 1 runs as a tape past a firmly anchored print head 16. A laser arrangement 17 is arranged in the interior of the printhead 16 and, owing to the limited space, can be based on semiconductor technology.

In the embodiment of Figure 5 a), the ink carrier 2 is cylindrical. No printing form 1 is connected to the ink carrier 2, but the printing substance 8 is applied to the ink carrier 2 as a homogeneous film. However, a printing form 1 is provided here, which is arranged separately from the ink carrier 2 and which here has the shape of an aperture. By rotating the ink carrier 2, the supply of the printing substance is secured with the aid of a standardized ink system. In this embodiment it should be noted that the distance of the diaphragm-like printing form 1 from the ink carrier 2 corresponds approximately to the layer thickness of the printing substance film. This measure ensures that too much printing substance 8 is never fed to the actual printing process and thus swelling of the printing substance 8 is avoided.

In Figure 5 b), the ink carrier 2 is designed as a flat disc, so that the printing substance 8 is located as a homogeneous film on the underside of the flat ink carrier 2. The printing form 1 is also separated from the ink carrier 2 and also has an aperture shape. The supply of the printing substance is secured here by periodically moving the flat printing medium 2 back and forth.

Finally, FIG. 6 shows a diverting optic which is advantageously used together with the printing press according to the invention. However, it goes without saying that this diversion optics is not limited to the printing method according to the invention described, but can be used for all printing methods in which a laser beam is to be imaged specifically on a specific point on an ink carrier.

6 shows the ink carrier 2, which is designed as a cylinder. A deflection mirror 21 is located within the cylinder, which here encloses an angle of 45 ° with the central axis of the cylinder 2. The laser beam 7 is first directed at a first deflecting mirror 24, which does not necessarily have to be present, to the addressing unit 23, which is designed here as a polygonal mirror. The addressing unit 23 can be controlled so that the deflection of the laser beam 7 can be determined with the aid of the polygonal mirror 23. After the laser beam 7 has been deflected by the addressing device 23, it passes through a focusing device which is designed here as an f-theta arrangement and which bears the reference number 22. Then he meets the steering mirror 21 and is focused on the surface of the ink carrier 2. Two alternative beam profiles 7 ′ are shown as examples, which could result from an appropriately set addressing device 23. By driving the polygonal mirror 23, each point can be driven a line that runs parallel to the axis of rotation of the ink carrier 2 on the surface of the ink carrier 2 without the actual laser having to be moved. More precisely, the focus point of the laser runs through every point of this line during the rotation of the polygon mirror, and it can be switched on or off at any point (or pixels according to the possible resolution).

7 shows a laser source 32 which generates a laser beam which is split into two different laser beams 7 and 7 '. However, this splitting does not take place with a conventional beam splitter, which would produce continuous beams 7 or 7 'of half the power, but from a mirrored interrupter disc (shutter), which alternately has gaps for passing a laser beam 7 and mirrored surfaces for deflecting the laser beam 7 '. The gaps and mirrored surfaces preferably occupy angle sectors of equal length and alternate with one another. In the preferred embodiment, in which an eight-faceted polygon mirror 23 is also used, the interrupter disk 28 also has eight passage openings and eight mirrored surfaces, which are evenly distributed around the circumference of the interrupter disk 28. The drive 29 for the interrupter disk 28 is suitably synchronized with the rotation of the polygon mirror 23 via a synchronizing device 33, the exact type of synchronization being described below.

Analogous to data transmission, one could also speak of a time-division division of the laser beam into beams 7, 7 ', which, however, has nothing to do with the high-frequency switching on and off of the laser beam for addressing the individual pressure points of a scanning line, which is due to the comparatively low-frequency beam interruption and redirection is superimposed.

After the beam splitting, a beam widening takes place in the units 30 and 31, which is only required later in the f-theta optics 22, which is no longer shown in FIG. 7 but is shown in FIG. 6.

The one partial beam 7 runs through a gap in the interrupter disk 28 and the beam expansion 31, strikes a mirror 27 and is reflected from there at a fixed angle (corresponding to the position of the mirror 27) onto the polygon mirror 23, which is perpendicular to the paper axis central axis rotates. The beam 7 'is first deflected upwards by the mirrored segments of the interrupter disk 28, passes through the beam widening 30, then strikes a mirror 25 and from there hits a mirror 26, which in turn directs the beam onto the polygon mirror 23. It should be noted that the mirrors are only shown schematically here and the mirror 26 is in any case oriented such that the beam is directed onto the polygon mirror 23 falls. However, the points of incidence of the steels 7 and 7 'on the polygon mirror are selected such that they are offset relative to one another by half the length of a facet surface, measured in the circumferential direction of the polygon mirror.

It is assumed that the polygon mirror 23 rotates counterclockwise, the laser beams 7, 7 'always being broken down into individual packets, which corresponds to the alternating interruption of the two beams, although realistically the individual "packets" are significantly longer and with correspondingly larger gaps would have to be shown. The interrupted beam representation in FIG. 7 therefore corresponds more to the individual pressure point pulses which are directed onto the print carrier in a scanning line.

FIG. 7 shows a state where the laser beam 7 still passes through a gap in the interrupter disk 28 and strikes one of the facet surfaces via the mirror 27. The length of the gap or interruption in the interrupter disk 28 is dimensioned such that the facet of the polygon mirror in question passes almost completely through the area on which the beam 7 impinges. That is, the beam 7 strikes the relevant facet of the polygon mirror for the first time when the preceding corner between adjacent facets has just passed this area. As the polygon mirror continues to rotate, the relative orientation of the polygon mirror facet to the laser beam 7 changes, which leads to the laser beam 7 reflected by the polygon mirror sweeping over an angular range that extends approximately from a horizontal to a 45 ° angle , this 45 ° angle being almost reached in the momentary representation according to FIG. 7.

Shortly before the laser beam 7 strikes the next corner at the transition to the next facet, the beam 7 is interrupted by the interrupter disk 28, so that the beam 7 'is now directed onto the facet in question, and initially immediately behind the corner to the preceding facet strikes the same facet that was previously covered by the beam 7. The same process takes place here as in the case of beam 7, i.e. starting from a deflection, the beam 7 'is pivoted about 45 ° downwards from a horizontal to approximately a horizontal, while the polygon mirror continues to rotate counterclockwise. Then the next corner for the transition of the next facet has passed the point of incidence of the beam 7 and at the same time the interrupter disk 28 in turn releases the beam 7, so that the beam 7 'disappears and the beam 7 now strikes the next facet. As already mentioned, the representation in FIG. 7 is only schematic and the positions and angles shown need not exactly match those of a realistic construction of the positions and angles.

The main reason for this configuration is that the beams 7, 7 'are relatively widened in relation to the effective length of the individual facets and cannot be used as long as If the full beam cross-section does not strike one of the facets, the duty cycle of the laser is therefore only about 50% or 0.5. However, by dividing the laser beam into the two partial beams 7, 7 ', a duty Cycle of 1 (duty cycle 1) can reach, i.e. while one beam must be inactive because it passes the area of a corner at the transition between two facets, the other beam, the point of impact of which can be at least by the amount of the beam diameter or beam width, and for example, offset by about half a facet length, be active so that the essentially continuously available laser energy is also used continuously. It goes without saying that the interruption of the beam with the aid of the interrupter disk is independent of the other addressing interruption, with which the individual points of a print image are controlled

In addition, a polarization filter can be used instead of the interrupter disc if the laser works with polarized light, an electro-optical modulator being connected in front of a corresponding polarization filter, which is capable of rotating the polarization plane by 90 °, depending on whether the electro-optical Modulator is active, then let the polarization filter pass the laser radiation unhindered or reflect it through a corresponding arrangement by 90 °, so that one can obtain exactly the same division into beams 7, 7 'as was described with reference to the interrupter disk

In the embodiments shown so far, the energy or the laser beam was focused by the (transparent) ink carrier into the absorption layer or into the printing substance. In FIG. 8, on the other hand, it is shown that this is not absolutely necessary. Rather, the laser beam can also be seen from the other side, ie be focused from the side of the ink carrier with the printing substance into the printing substance or the absorption layer

In FIG. 8, the laser beam 7 is focused through the printing ink 8 through a transparent glass cylinder, which serves here only as a transfer means, onto the absorption layer 10 applied to the ink carrier 2 at point 9. The absorption layer 10 absorbs at least part of the energy from the laser beam 7 and passes this into the printing substance 8. This leads to an abrupt local heating of the printing ink and an ink drop 11 is detached explosively from the printing ink layer 8. This ink drop 11 reaches the glass cylinder 12. In this way a glass cylinder could be printed the printing point placed on the glass cylinder 12 must be transferred to the printing material 34

FIG. 9 schematically shows the construction of a printing press that uses the arrangement just described. A laser beam 7 is focused through the glass cylinder 12 onto the ink carrier 2, optionally provided with an absorption layer 10, which is designed here in the form of a roller equipped with a printing form 1, so can Touch glass cylinder 12 and ink carrier 2. However, if the ink carrier does not have a specially designed printing form 1, but is only wetted by the printing substance 8, the glass cylinder 12 and ink carrier 2 should be spaced apart, as described above.

The ink carrier 2 is integrated in an inking unit 20 which, in addition to the ink carrier 2, also has an immersion roller 19 and a printing substance bath 8. The outer contour of the dipping roller 19 dips into the pressure substance bath 8. If the dipping roller 19 is rotated, this ensures that the surface of the dipping roller 19 is contaminated with pressure substance. The dipping roller is at least so close to the ink carrier 2 that the printing substance 8 is transferred from the dipping roller 19 to the printing carrier 2.

The inking unit 20 thus ensures that printing substance 8 is always on the surface of the ink carrier 2. If the laser beam hits the surface of the ink carrier 2, a change in volume and or position of the printing substance 8 is induced locally, either directly or via an absorption layer 8, so that a drop of printing substance 8 from the ink carrier 2 onto the glass cylinder 12 is transferred. The glass cylinder is rotated clockwise in the arrangement shown in FIG. 9, so that the surface section of the glass cylinder 12 onto which the droplet of printing substance has been transferred comes into contact at some point with the printing material web 34 running between the support cylinder 35 and the glass cylinder 12. Similar to offset printing, the printing ink is therefore first positioned on the glass cylinder 12 and only positioned on the actual printing material 34 in a subsequent step.

Since in general the printing substance 8 is not completely transferred from the glass cylinder to the printing material 34, a cleaning roller 14 is advantageously used with which the glass cylinder 12 is cleaned.

As already stated, it is not absolutely necessary for the laser beam 7 to strike the ink carrier 2 perpendicularly. Another arrangement is therefore shown in FIG. Here the laser beam 7 forms an angle α with the normal on the ink carrier surface. Surprisingly, it has been shown that the angle β between the ink carrier surface and the direction of the ink dot detached from the printing substance is almost independent of the angle α. In FIG. 10, the printing material 34 is therefore approximated to the ink carrier 2, the laser beam 7 being concentrated laterally between the printing material 34 and the ink carrier 2 onto the focal point 9 in the absorption layer 10 or the printing substance 8 in order to print a printing point. A drop 11 of the printing substance 8 experiences a change in volume and / or position due to the heat development in the printing substance 8, so that it leaves the printing substance film 8 almost perpendicular to the ink carrier surface. FIGS. 11a) and 11b) show an example of a printing press that realizes the laser arrangement just described. An inking roller 2 is integrated in an inking unit which, in addition to the inking roller 2, also includes the transfer roller 36 and the supply bath with printing ink 8. The inking unit ensures that the ink carrier roller 2 is always wetted with printing substance 8 on its surface. The laser beam 7 is directed directly onto the printing substance or the absorption layer on the ink carrier roller 2. In contrast to the arrangements described above, the laser beam 7 is not first passed through a transparent body, so that it strikes the surface of the printing substance or the absorption layer below it perpendicular to the surface.

As is shown enlarged in FIG. 11 a), the laser beam 7 strikes the absorption layer of the ink carrier roller 2, which is continuously colored with a printing ink that is transparent to the laser beam. The focus of the laser beam 7 is projected onto the surface of the ink roller at a certain angle. This angle is advantageously chosen so that the distance between the focal point and the substrate is optimal. The laser beam is then guided line by line over the inking roller in the manner described and the information or the pressure points are transmitted by switching the laser on and off. When the laser is switched on, the laser light is absorbed in the absorption layer, the solvent evaporates in the printing ink, and a change in volume and / or position of the printing substance is induced locally, so that the resulting ink drop sets the desired printing point. The web support roller guides the printing material in such a way that the distance between the printing material and the focal point is as small as possible, but the printing material neither interrupts the laser beam nor touches the inking roller. The ink carrier roller 2 advantageously has a smaller diameter than the web support roller 35.

The inventive method and the printing presses according to the invention provide a digital printing method that enables almost all conceivable printing substances or substrates to be printed or printed. For example, conductive coatings or caustic substances can also be applied to printed circuit boards. Rapid prototyping is another possible application. The inking rollers can - at least in the event that the energy is not transmitted through the inking roller - be made of almost all materials, preferably of metal or ceramic. Furthermore, they can be porous or have rough surfaces. LIST OF REFERENCE NUMBERS

1 printing form

2 color carriers

3 bridges

4 elastic membrane

5 antechambers

6 cells

7, 7 'laser beam

8 printing substance

9 focus point

10 absorbent material

1 1 printing substance drop

12 glass cylinders 13 gap

14 cleaning roller

15 stitches

16 roughened side

17 laser arrangement

18 network

19 dipping roller

20 inking unit

21 deflecting mirror

22 f-theta arrangement (optics)

23 addressing device

24 deflecting mirror

25 mirrors

26 mirrors

27 mirrors

28 breaker disc

29 Drive of the breaker disk

30 Device for beam expansion

31 Device for beam expansion

32 laser source

33 synchronization device

34 printing material or printing material web

35 support cylinders

36 transfer roller

Claims

Patent claims

1. Printing process for the transfer of printing substance (8) from an ink carrier (2) to a printing material or a transfer medium, in which the printing substance (8) undergoes a change in volume and / or position and thereby a transfer by means of an induced process of an energy-emitting device Printing point on the printing material or the transfer medium, characterized in that the printing substance (8) is applied essentially forming a continuous film on the ink carrier (2).

2. Printing method according to claim 1, characterized in that a cylindrical body is used as the ink carrier (2), which is preferably rotated about its own axis.

3. Printing method according to claim 2, characterized in that the printing material is moved past the ink carrier (2) at a transport speed which is matched to the peripheral speed of the cylindrical body.

4. Printing method according to one of claims 1 to 3, characterized in that a translucent ink carrier (2) is used as the ink carrier (2), wherein the energy-emitting device energy in the form of light from the side facing away from the printing substance

Ink carrier (2) through the translucent ink carrier (2) induces a change in volume and / or position of the printing substance (8).

5. Printing method according to one of claims 1 to 4, characterized in that a laser radiation (7) emitting device is used as the energy-emitting device, the laser beam (7) directed to selected points on the ink carrier (2) to be printed and is preferably focused.

6. Printing method according to one of claims 1 to 5, characterized in that energy is transmitted directly from the energy-emitting device into the printing substance (8).

7. Printing method according to one of claims 1 to 6, characterized in that energy from the energy-emitting device is first transferred to a mediation material and then from the mediation material to the printing substance (8).

Printing method according to claim 7, characterized in that a light-absorbing material is used as the mediating material, which is preferably arranged in the form of a layer on the ink carrier (2).

9. Printing method according to one of claims 5 to 8, characterized in that the energy is released by emission of a laser pulse.

10. Printing method according to claim 9, characterized in that the thickness of the printing point is set via the variation of the laser energy and / or via the variation of the pulse length.

11. Printing method according to claim 9 or 10, characterized in that the diameter of the pressure point is set via the variation of the laser energy and / or via the variation of the pulse length.

12. Printing method according to one of claims 1 to 1 1, characterized in that a distance is maintained between the ink carrier (2) and printing material, which is preferably at least 10 microns, particularly preferably about 50 microns.

13. Printing method according to one of claims 1 to 12, characterized in that a laser pulse with a pulse length of less than 1 μs, preferably less than 500 ns, particularly preferably less than 200 ns, is used for energy transmission.

14. Printing method according to one of claims 1 to 12, characterized in that the laser beam is directed at short time intervals alternately over two different paths and from different directions and to points offset by at least the beam width up to about half a facet length on the polygon mirror, wherein connect the angular ranges of the partial beams deflected by the polygon mirror to one another.

15. Printing method according to one of claims 1 to 3 or 5 to 14, characterized in that a transmission means (12) is provided, which is designed to be translucent, the energy-emitting device energy in the form of light through the transmission means through to the printing substance side of the ink carrier (2) and thereby induces a change in volume and / or position of the printing substance (8).

16. Printing method according to one of claims 1 to 3 or 5 to 14 and 7, characterized in that the energy-emitting device emits energy in the form of light through the printing substance on the mediation material and thereby a change in volume and / or position of the printing substance (8th ) induced

17 printing machine for printing a printing material with an ink carrier (2) and an energy-emitting device, which is arranged such that energy can be transferred to specific areas of the ink carrier (2), characterized in that the Far carrier (2) is intended to accommodate printing substance (8) essentially forming a continuous film.

18. Printing machine according to claim 17, characterized in that the ink carrier (2) is a cylindrical body which is preferably designed as a hollow cylinder or is a flat plate.

19. Printing machine according to one of claims 17 to 18, characterized in that the ink carrier (2) consists of translucent material, preferably of glass.

20. Printing machine according to claim 19, characterized in that the ink carrier (2) has a thickness between 1 mm and 20 mm, preferably between 2 mm and 10 mm, particularly preferably about 5 mm.

21. Printing machine according to one of claims 17 to 20, characterized in that an absorption layer (10) is arranged on the ink carrier (2), which preferably has a thickness which is less than 10 microns, preferably less than 5 microns, particularly is preferably less than 1 μm.

22. Printing machine according to one of claims 17 to 20, characterized in that the surface of the portion of the ink carrier (2) receiving the printing substance (8) has an arithmetic mean roughness of at least 0.1 μm, preferably between 0.5 μm and 5 μm, particularly preferably has between 1 μm and 2 μm.

23. Printing machine according to one of claims 17 to 21, characterized in that the surface of the ink carrier has a large tolerance deviation from an ideal flat or cylindrical surface of at most 20μ, preferably at most 5μm.

24. Printing machine according to one of claims 17 to 23, characterized in that a printing form (1) is provided.

25. Printing machine according to claim 24, characterized in that the printing form (1) has a plurality of cups and / or grooves which are provided for receiving printing substance (8).

26. Printing machine according to claim 24 or 25, characterized in that the printing form (1) has approximately network shape.

27. Printing machine according to one of claims 24 to 26, characterized in that a plurality of depressions of the printing form (1), which serve to hold printing substance (8), are connected to one another.

28. Printing machine according to one of claims 24 to 25, characterized in that the printing form (1) on the ink carrier (2) is arranged fastened.

29. Printing machine according to claim 28, characterized in that the printing form (1) and the ink carrier (2) are integrally formed.

30. Printing machine according to claim 28, characterized in that the printing form (1) is releasably attachable to the ink carrier (2).

31. Printing machine according to one of claims 24 to 28 or 30, characterized in that the printing form (1) is designed as a belt, preferably as an endless belt.

32. Printing machine according to claim 24, characterized in that the printing form (1) has the shape of an aperture which is arranged separately from the ink carrier (2) and between this and the printing material.

33. Printing machine according to one of claims 17 to 23, characterized in that no printing form (1) is provided.

34. Printing machine according to one of claims 17 to 33, characterized in that the energy-emitting device consists of at least one laser source.

35. Printing machine according to claim 34, characterized in that a focusing device (22) is provided which focuses the laser beam (7) on a predetermined point on the ink carrier (2).

36. Printing machine according to claim 35, characterized in that the focusing device is an f-theta lens (22).

37. Printing machine according to one of claims 34 to 36, characterized in that a deflection device (21) is provided.

38. Printing machine according to claim 37, characterized in that the deflection device (21) is a deflection mirror (21), preferably the solder on the reflecting surface and form an angle of approximately 45 ° on the substrate at the time of printing.

39. Printing machine according to one of claims 34 to 38, characterized in that an addressing device is provided.

40. Printing machine according to claim 39, characterized in that the addressing device has a polygon mirror rotatable about its axis.

41. Printing machine according to claim 40, characterized in that a deflection device is provided, through which the laser beam is guided at short time intervals alternately over two different paths and by deflecting mirrors alternately from two different directions and in the circumferential direction of the polygon mirror to at least the beam width and for example points offset by approximately half a facet length are directed onto the polygon mirror.

42. Printing machine according to claim 41, characterized in that the deflection device is a shutter disk which can be synchronized with the polygon mirror and which has alternately mirrored surfaces and passage openings.

43. Printing machine according to claim 41, characterized in that the laser is a polarized laser and the deflection device consists of an electro-optical modulator in combination with one or more polarization filters.

44. Printing machine according to one of claims 17 to 43, characterized in that the ink carrier designed as a cylinder is mounted on its outside, and preferably has bearing elements in the angular range in which the printing material also reaches the smallest distance from the surface of the ink carrier.

45. Printing machine according to one of claims 17 to 44, characterized in that a transmission means (12) is provided, which preferably consists of translucent material.

46. Printing machine according to one of claims 17 to 45, characterized in that the energy-emitting device is arranged such that it has a light beam under a

Angle α to the normal on the printing substance surface of greater than 0 ° and preferably less than 75 °.