WO2013185920A2

WO2013185920A2 - Method for indirectly applying printing liquid to a printing substrate

Info

Publication number: WO2013185920A2
Application number: PCT/EP2013/001750
Authority: WO
Inventors: Bernard Beier; Martin Greive; Peter Hachmann; Axel Hauck; Rolf Kündgen; Albert Maul; Rolf Müller; Heiner Pitz; Achim Scheurer; Matthias Schlörholz; Michael Schwandt
Original assignee: Heidelberger Druckmaschinen Ag
Priority date: 2012-06-15
Filing date: 2013-06-13
Publication date: 2013-12-19
Also published as: WO2013185920A3

Abstract

The invention relates to a method for indirectly applying printing liquid (45) to a printing substrate (43), wherein an intermediate support (2), preferably a circulating belt, is provided, a liquid conditioning agent (47) comprising a first substance is provided and is applied to the intermediate support (2), a printing liquid (45), in particular an inkjet ink, comprising a second substance, is provided and is applied to the conditioning agent on the intermediate support (2), the printing liquid (45) is present in the form of drops or a layer substantially on the conditioning agent and the drops or the layer form on the underside thereof a contact area with the conditioning agent, the printing liquid (45) is heated, preferably by means of a drier (19 and/or 23), and the printing liquid is transferred from the intermediate support (2) to the printing substrate (43).

Description

Method for the indirect application of printing fluid to a printing substrate

The present invention relates to a method for the indirect application of

Printing fluid on a substrate.

Various methods and devices for so-called indirect inkjet are known from the prior art. In this case, a plurality of inkjet inks or inks are consumed by means of successive inkjet printheads on a circulating subcarrier corresponding to the printed image, i. aufgejettet. From this intermediate carrier, e.g. a transfer belt or a

Transfer cylinder, the inks or the multi-color printed image on the substrate, e.g. a paper sheet or a paper web. The paint is thus not directly, but indirectly over the surface of a transfer device to the substrate. This surface must therefore be so designed or treated that the necessary color transfer is possible, i. E. it must take on the color and the - possibly treated, e.g. hardened - can give off color again.

In US 2008/0166495 Al, e.g. discloses such a machine for indirect inkjet printing. This comprises a central circulating transfer belt as an intermediate for the inks, which are jetted by four printheads on the tape. Before the ink is applied by means of a separate applicator a

Coating liquid applied to the tape. After ink application, the ink on the belt is exposed to radiation from a radiation source and hardened. Subsequently, the transfer of the inks or the printed image takes place in a heated printing gap on a substrate web, on which the ink finally again

is heat treated. The tape is cleaned by a cleaning device before re-inking.

From US 2007/0058022 AI a similar machine is known, however, has a central transfer cylinder instead of a band. In the above devices and methods of the prior art, the problem may be that the ink does not completely or substantially completely detach from the intermediate carrier and be transferred to the substrate. It is therefore necessary to provide additional measures to assist in the removal of the ink. Such and other measures are already known from the prior art.

Against this background, it is an object of the present invention to provide a comparison with the prior art improved method, which makes it possible to remove printing ink from an intermediate carrier completely or at least almost completely and transfer from this to a substrate.

This object is achieved by a method having the features of claim 1. Advantageous developments and other features of this invention will become apparent from the related claims and from the following description and the accompanying drawings.

An inventive method for the indirect application of printing fluid to a substrate, wherein an intermediate carrier is provided, a liquid

Conditioner, comprising a first substance, provided and on the

Subcarrier is applied, a pressure fluid, comprising a second substance, provided and applied to the conditioning agent on the intermediate carrier, the pressure fluid as a drop or layer substantially on the

Conditioner is located and form the drops or the layer on its underside with the conditioning a contact area, the pressure fluid is heated, and the printing fluid is transferred from the intermediate carrier to the substrate, characterized in that the first substance of the liquid conditioning agent, the viscosity of the Increases pressure fluid on the intermediate carrier in the contact region by a reaction with the second substance of the hydraulic fluid and thereby the

Pressure fluid forms a film in the contact area, and that the pressure fluid outside the contact area has a lower viscosity than within the

Has contact area. By providing the features according to the invention can be achieved in an advantageous manner that the printing fluid using the film formed completely or at least almost completely detached from the intermediate carrier and on the

Substrate can be transferred. An advantage is in particular given by the fact that not the entire pressure fluid is changed by a reaction in its viscosity, but only the contact area of the pressure fluid to the conditioning, thus only a portion of the droplets or a sub-layer of the layer of pressure fluid. The remainder of the pressure fluid, which is located outside the contact area in the droplet or the layer, is not or only marginally affected by the reaction, while maintaining a lower viscosity. As a result, the pressure fluid in this area remains fluid and possibly sticky and adhering the pressure fluid to the substrate and thus a detachment of the pressure fluid from the intermediate carrier is improved.

One for the detachment of the pressure fluid or the droplets or the layer

Pressure fluid from the intermediate carrier advantageous and therefore preferred

Further development of the method according to the invention may be distinguished by the fact that the contact region has a layer thickness of less than 10 nanometers. In this way, only a very thin film is formed on an outer surface of the printing liquid and a substantial remainder of the printing liquid substantially remains in the state of original viscosity. Even such a thin film can advantageously improve the detachment of the printing fluid from the intermediate carrier

A further development of the method according to the invention, which is advantageous with regard to the detachment of the pressure fluid from the intermediate carrier and therefore preferred, may be distinguished by the fact that the viscosity takes place by hardening the pressure fluid. Alternatively, the increase in viscosity can also be achieved by crystallizing or gelling the pressure fluid.

A development of the method according to the invention that is advantageous and therefore preferred on account of the simple provision and application can be distinguished by the fact that the conditioning liquid is applied as an aqueous solution. It can be provided in particular that the liquid conditioning agent a Forming layer with a thickness of about one micron, but at least less than about 5 microns. Such a thin, aqueous layer is already sufficient to cause the reaction according to the invention and thereby advantageously to improve the detachment of the printing fluid from the intermediate carrier. In this way, high print quality can be achieved with little use of consumables.

A development of the method according to the invention which is advantageous and therefore preferred for hardening the pressure fluid in the contact region can be distinguished by the fact that the pressure fluid is applied as a polyacrylic liquid. It may be advantageous and therefore preferred, the liquid

Conditioner as a multivalent cation, in particular Ca (2+) or Al (2+), to apply having liquid. It can be effected in this way flocculation of the polyacrylic acid and therefore caused a change in viscosity. Due to the controllability of the change in viscosity, it is advantageous and therefore preferred to activate the first substance by radiation for reaction with the second substance according to a development of the method according to the invention. A radiation-activatable first substance advantageously makes it possible to start both the reaction at a given time and to influence the intensity of the reaction and thus the result thereof by the irradiation.

In the context of the invention is also to be seen a printing press according to the invention, which is designed by providing appropriate components to carry out the process steps of the above-mentioned inventive method and thereby to provide the necessary substances.

In the prior art, there may be a problem that the ink drops on the

Do not sufficiently spread intermediate carriers, i. run to be able to train full areas. To such a sufficient spreading of the hydraulic fluid on the

To achieve intermediate carrier, the surface energy of the subcarrier must be adjusted accordingly Against this background, it is an object of the present invention to provide a comparison with the prior art improved method which allows a complete or at least almost complete transfer of the printing fluid from the intermediate carrier to the substrate.

This object is achieved by a method having the features of claim 11. Advantageous developments of this invention will become apparent from the accompanying dependent claims and from the following description and the accompanying drawings.

An inventive method for the indirect application of printing fluid to a substrate, wherein an intermediate carrier is provided, a liquid release agent is provided and applied to the intermediate carrier, a pressure fluid is provided and applied to the intermediate carrier, the pressure fluid is heated, and the pressure fluid from the Intermediate carrier is transferred to the substrate, characterized by the fact that the release agent has a boiling point which is higher than the boiling point of the solvent of the hydraulic fluid.

The inventive solution of the problem allows in an advantageous manner, the

Transfer printing fluid completely or at least almost completely from the intermediate carrier to the substrate. For this purpose, the pressure fluid is heated. This heating can be done for example by the application of hot air or infrared radiation. Since the pressure fluid is above the release agent on the intermediate carrier, the heating of the pressure fluid will usually lead to a heating of the release agent. In the context of the invention it was recognized that the

Providing a release agent boiling temperature which is higher than the boiling temperature of the solvent of the pressure fluid, is advantageous. A correspondingly high

Boiling temperature of the release agent makes it possible to evaporate solvent from the pressure fluid, without causing evaporation of the release agent at the same time. In this way it can be ensured according to the invention and in an advantageous manner that the release agent below the printing fluid, preferably as a release layer obtained remains and its separating effect when transferring the pressure fluid from

Subcarrier can unfold on the substrate.

A preferred embodiment of the method according to the invention that is advantageous and therefore preferred in terms of the media used can be characterized in that the release agent comprises alcohol, in particular glycol or glycerol or glycol ether. By the

Provision of said substances, the boiling temperature can be set to a value higher than the boiling temperature of the solvent of the hydraulic fluid. In addition to the substances mentioned, comparable organic liquids with a mediating effect between oleophilic and hydrophilic liquids can also be used.

Another embodiment of the method according to the invention which is advantageous and therefore preferred with regard to the media used can be distinguished by the fact that the separating agent comprises an aqueous gel. Alternatively, the release agent may also comprise a non-aqueous gel. It is preferably provided in both cases that the release agent also comprises a thickener. As such a thickener, for example, pectin, Argar Argar or cellulose may be provided. A preferred embodiment of the method according to the invention, which is preferred on account of its particularly advantageous separating effect, can be distinguished by the fact that the separating agent is applied to the intermediate carrier as a separating layer, in particular as one

Separating layer with a thickness between about 1 μηι and about 10 μιη. A further development of the method according to the invention, which is likewise preferred on account of its advantageous separating effect, can be distinguished by the fact that the separating agent substantially completely wets the surface of the intermediate carrier. Furthermore, it can be provided in an advantageous manner that the printing liquid spreads sufficiently on the separating layer, so that the printing liquid of the individual printing dots of a particular printing ink on the separating layer can converge to form a solid surface, if desired. For this purpose, it may also be necessary, the pressure points Apply sufficiently close to each other and with sufficient amount of pressure fluid on the intermediate carrier.

A further advantageous and therefore preferred embodiment of the method according to the invention with an advantageous separation effect can be characterized in that the transfer of the printing fluid to the printing material by a cleavage of the

Separating layer takes place. The printing fluid is transferred completely or at least almost completely from the intermediate carrier to the printing material by this cleavage within the separating layer. The separation layer itself can be partially transferred. Remains of the release layer on the intermediate carrier can be removed by a cleaning and / or supplemented with new release agent to form a new complete release layer.

Another embodiment of the method according to the invention that is advantageous with regard to an achievable good print quality and therefore preferred may be characterized in that a further layer of another liquid is applied to the separating layer, the further liquid influencing the spreading behavior of the printing liquid on the separating layer. As mentioned above, when printing on solid surfaces, it may be necessary to take action that is applied

Pressure fluid or the individual pressure points run into each other. For this purpose, the spreading behavior of the pressure fluid on the separating layer must be adjusted accordingly. This adjustment can be achieved by providing a further layer on the release layer. The spreading behavior of the printing fluid on the separating layer can be effected in particular by matching the surface energies of the media used to one another. If the separating layer itself or the further layer applied to the separating layer has a sufficiently high surface energy, then the set pressure points of printing fluid are formed with a sharp edge, while with sufficiently low surface energy, a running of the pressure points into one another can be achieved.

An advantageous with respect to the order process and therefore preferred embodiment of the method according to the invention may be characterized in that the Printing liquid is a printing ink and is applied to the intermediate carrier in the ink jet process and / or that the release agent in the ink jet method on the

Subcarrier is applied. If both media are applied by the ink jet method, it is furthermore advantageously possible to apply the release agent only in those areas in which printing ink has also been applied. In other words: In this case, the release agent can be applied to the printed image and thereby save considerable amount of release agent, especially in those cases where large areas in the printed image represent non-image areas.

A preferred and therefore preferred for the setting of the boiling temperature of the release agent v and therefore preferred embodiment of the method can be characterized in that the pressure fluid comprises a substance, in particular a solvent or an additive which enters the separation layer and the boiling temperature of the mixture of release agent and substance increased above the boiling point of the hydraulic fluid. The penetration of the substance into the separating layer can take place for example by diffusion. In the illustrated areas, d. H. In such areas, in which pressure fluid comes to rest on the release agent, thus creating a mixture or solution of the substance of the pressure fluid and the release agent and by this mixing or dissolution, the boiling temperature of the resulting mixed or dissolved separation layer is increased compared to the originally applied release layer , According to the invention on the boiling point of the solvent of the pressure fluid.

Finally, a development of the method according to the invention which is advantageous and therefore preferred with regard to the media used can be distinguished by the fact that the separating agent is water and that the substance is a solvent of the pressure fluid other than water. The solvent other than water of the printing liquid is expelled upon heating of the printing fluid and mixes with the release agent of the originally applied release layer. The mixture thus formed in turn has a higher boiling point than the water according to the invention. This solution according to the invention has the advantage that the applied Separation layer of water is retained only in the areas after heating, in which also pressure fluid was applied to the release layer.

In the context of the invention, a printing machine can be seen by providing appropriate components and by providing a corresponding

Control is able to perform the above-mentioned inventive method.

In the known devices, which operate on the indirect inkjet printing process, the intermediate carrier usually has an outer layer of plastic,

Rubber or silicone rubber or similar materials which provide a complete transfer of the aufjetteten on the surface and then on the intermediate carrier

dried or solidified printing fluid to enable the substrate. These materials have a comparatively poor thermal conductivity. Maybe under this layer is still a foam layer, the

Improve compression behavior of the intermediate carrier and thermally practically acts as an insulating layer. In the indirect inkjet with water-based printing inks, therefore, the energy required to evaporate the water from the ink is generally supplied by radiation and hot air from the outside, as described, for example, in US Pat. No. 7997717 B2.

In a rubber layer, however, temperature differences also do not equalize or only very slowly in the lateral direction, ie in the plane of the surface of the intermediate carrier. Now, if printed images are printed with a relatively large ink coverage, especially when working with water-based inks, the following problem: Due to the evaporation of water from the printing liquid, the surface of the intermediate carrier cools in the areas with large color occupancy significantly stronger than in Areas with low color usage. In this way, the surface of the subcarrier is quasi a thermal image inscribed that the properties of the tape in terms of ink acceptance or uniform acceptance of release agent, the properties of only a very small distance above the belt inkjet nozzles, but also the transmission properties of the tape in the transmission of the Print image on the substrate can affect. Furthermore, it is difficult for print jobs with high ink coverage to couple all the energy required into the ink to vaporize the water. If the amount of energy is insufficient, the ink at the pressure points is not sufficiently dry enough to be completely transferred from the subcarrier to the substrate. However, since the methods of indirect inkjet are based on the fact that with each rotation of the subcarrier, the printed image or the solid ink droplets completely from the subcarrier on the

Print substrate, even small residues that remain on the intermediate carrier, unacceptable because they interfere with the subsequent image and cause waste.

On the other hand, areas of the intermediate carrier that are not filled with pressurized fluid are heated up unnecessarily, which not only means a waste of energy but, as explained below, also thermally stresses the inkjet heads.

For methods of direct inkjet, in which the ink is applied directly to a printing substrate, it is known that the printed image on the z. B. paper directly after the

To be dried with the help of spatially resolved applied laser radiation by only the printed areas are irradiated by the laser. Such methods are described for example in EP 993378 Bl of US 6,857,734 B2 and US 2004/085423 AI. In most cases, the process is used in conjunction with so-called UV inks which are cured with ultraviolet radiation. In such processes, the above-mentioned problem of cooling occurs

Subcarrier surface in the image areas not on, because there is on the one hand no intermediate carrier and on the other hand, these inks are not water-based. Insofar as reference is made in US 2004/0085423 AI to so-called "infrared curable inks", these are also inks which are cured by crosslinking of acrylic resins, but not water-based inks, in which high amounts of energy are required in order to achieve the evaporate the water contained in the ink.

It is therefore an object of the present invention to provide a method and to provide a device for indirect inkjet printing with water-based inks, by which the aforementioned disturbing influences are avoided or at least reduced. This object is achieved by a method having the features of claim 28 and a device having the features of claim 33.

Advantageous developments will become apparent from the respective dependent claims and the following description and from the figures of the accompanying drawings.

The method according to the invention is characterized in that the intermediate carrier is locally heated only at the image locations by radiation before the inking of the ink and / or directly in front of the printing gap.

The method according to the invention leads to the above-described negative effect of inscribed "thermal images" in the intermediate carrier surface being avoided

Direction of movement of the subcarrier in front of the Inkjetköpfen z. B. by means of a correspondingly controlled infrared laser diode array a positive thermal image in the

Subcarrier surface is inscribed, on which the droplets begin to evaporate after Aufjetten, if necessary, evaporated even before the inkjet heads applied water-based conditioner. In the course of the evaporation process then cools the inscribed positive thermal image and takes about the same

Temperature on like the non-image areas to which no ink is aufgejettet. This also has the advantage that the nozzles of the inkjet heads located directly above the intermediate carrier in the non-image areas, which are used much less frequently than the nozzles in the image areas, surface areas of the band with relatively low temperature

are opposite. In this way, the danger of so-called "clocking" is reduced, that is, adding not just needed inkjet nozzles, a danger that increases with increasing temperature.

Thus, with the method described, the intermediate carrier, for example a belt or coated or covered cylinder, can be heated precisely at the point at which a pixel is to be applied. This has the advantage that the

Intermediate carrier is energized only where it is actually needed, that is, in fact applied with ink that requires energy to evaporate. This saves energy and reduces the thermal impact on the printheads at the locations of the nozzles that do not print. However, the method is also suitable for pinning, curing, drying or completely drying conditioning liquids, primers or functional coatings which are applied to the intermediate carrier prior to printing the ink, and precisely at the image locations where this is required, namely where the ink is then jetted.

On the other hand, however, the object stated at the beginning can also be solved in that the already solidified print image, which has clearly cooled in the course of the evaporation of the water in the ink prior to the transfer from the intermediate carrier to the printing substrate with respect to the surrounding non-image areas, is targeted only at the image locations Radiation energy is heated.

In this way too, the negative thermal image already written into the strip surface by evaporation of the solvent or water of the ink is raised to the temperature level of the surrounding non-image areas via the radiation which is additionally applied only at these points. Add to that one more on the

Transfer behavior of the subcarrier on the printing substrate positive effect effect, namely that the solidified ink of the image locations in a desired

Temperature range is heated in, for the transfer of the ink image from the intermediate carrier to the z. B. Paper is optimal.

In this way, the viscosity or the state of aggregation of the pressure points to be transmitted can be adjusted before they are transferred to the printing material in the nip. In this case, it may be expedient to arrange the device, which irradiates the intermediate carrier before the printing nip, depending on the image, in accordance with the speed of movement of the intermediate carrier in such a way that a defined finite time between the

Irradiation and the inlet is maintained in the nip, the z. B. is typical of a glass transition for the polymer, from which the pressure fluid in the evaporated state ultimately exists. If then the polymer is melted exactly at the inlet into the nip, Dubliereffekte, conditionally prevented for example by touching the nip paper sheet. In order to be able to fully utilize the advantages of the method, it may be necessary to design the printing fluids and / or the coatings of the intermediate carrier sufficiently light-absorbing. If IR radiation is used in a targeted manner in front of the nip, absorptive substances which absorb radiation in the infrared or near infrared can be added to the hydraulic fluids. However, it may also be sufficient, the surface of the intermediate carrier itself with the required

Absorption capacity in the infrared or near infrared. In this case, z. B. Infrared radiation through the already solidified polymer particles through which the pressure fluid after evaporation of its water content still exists, and heats the underlying surface of the intermediate carrier. So can be dispensed with absorbent additives in the printing fluids or inks.

It is particularly advantageous to combine the two measures with one another, that is to say already impress a positive thermal image in the surface of the intermediate carrier before it reaches the inkjet heads and in addition, the resulting in the course of evaporation of the water component of the color negative thermal image before the printing gap To neutralize radiation or to heat the solidified pressure fluid there.

It may also be appropriate to the intermediate carrier in the area between the pressure nip d. H. After the transfer of the ink image to the print substrate and before applying a new image on the intermediate carrier to cool then in the following area under the print heads controllable, not set too high temperatures for the subcarrier. In the case of using a tape as an intermediate carrier can be z. B. by cooled guide rollers, over which the intermediate carrier or the intermediate carrier belt is guided with a large wrap angle.

in which case it is primarily important that the cylinder contacting the surface of the intermediate carrier strip consists of good heat-conducting material such as, for example, a metal, heat-conducting ceramic or thermally conductive plastic, and is cooled. In the event that the intermediate carrier consists of a cylinder, it is expedient the cylinder surface of the intermediate carrier in contact with a cooled or tempered good heat conducting tape, z. B. brought a metal strip. In this way can be removed by the areal contact effectively very large amounts of heat from the outer layer of the intermediate carrier.

Various methods are suitable for carrying out the process according to the invention

Radiation sources. On the one hand, light emitting diodes can be used in the infrared, which are also available as a diode array in sufficient resolution to heat only the image locations on the subcarrier. However, it is also possible to use lasers, for example pulsed lasers for this purpose, which are operated in the scanning mode d. H. scan the subcarrier transversely to the process direction and be switched on only where there is also a pixel. Furthermore you can

Edge emitter diode laser arrays or VCSEL arrays are used or on

Fiber bundles coupled laser, in which the coupling is released only for the fibers, the end of which meets a pixel.

Against the background of the prior art, it is an object of the present invention to provide a process for the indirect application of printing fluid to a printing material that is improved over the prior art of indirect inkjet, which allows printing fluid to be completely or at least almost completely removed from an intermediate carrier to transfer to the substrate. It is also a further object of the present invention to provide an improved over the prior art of the so-called indirect inkjet device for the indirect application of printing fluid to a substrate, which shows corresponding advantages.

These objects are achieved according to the invention by a method having the features of claim 40 and a device having the features of claim 43.

Advantageous developments of these inventions will become apparent from the respective dependent claims and from the following description and from Figure 1. An inventive method for the indirect application of printing fluid to a substrate, wherein an intermediate carrier is provided, a liquid release agent is provided and applied to the intermediate carrier, provided a printing fluid and applied to the intermediate carrier a printed image only at the printing locations, the heated printing fluid will and the

Pressure fluid is transferred from the intermediate carrier to the substrate, characterized in that the intermediate carrier with a metallic coating

is provided and that the release agent is applied as a molecular coating on the metallic coating.

The method according to the invention advantageously permits the so-called indirect inkjet, wherein a complete or at least almost complete transfer of printing fluid from the intermediate carrier to the printing material can be ensured. For this purpose, the intermediate carrier according to the invention with a metallic

Provided coating and applied to this metallic coating a molecular assignment. This molecular assignment is designed so that the molecules develop an adhesive effect, which allows the pressure fluid to adhere to the molecularly occupied surface of the intermediate carrier. At the same time, however, the molecular assignment is also designed in such a way that the pressure fluid now adhering to the intermediate carrier returns in a pressure gap from the surface of the

Intermediate carrier detached and can be transferred to the substrate. This can be achieved, for example, by the fact that the adhesive effect of the printing ink on the surface of the printing material in the printing gap exceeds the adhesive effect of the molecular coverage and thereby the printing fluid or the printing fluid formed by it

Print layer is detached from the surface of the intermediate carrier. At a

For example, water-based printing fluid can be achieved by molecules that hydrophilize the surface of the intermediate carrier so that it adopts and adheres to the water-based printing fluid. The same applies to oil-based printing inks. However, since the printing fluid still has a certain stickiness on its surface and is pressed in the nip against the surface of the printing material, the forces acting thereon on the printing liquid exceed the forces mediated by the hydrophilicity or hydrophobicity / oleophilicity of the molecules the printing fluid and this or the layer formed by it is transferred from the surface of the intermediate carrier to the surface of the printing material completely or at least almost completely. One advantageous in terms of the medium used and therefore preferred

Further development of the method according to the invention may be distinguished by the fact that the molecular assignment comprises an amphiphilic organic compound. Particular preference is given to molecular assignments containing phosphonic acid or

Hydroxamic acid.

An inventive device for the indirect application of printing fluid to a substrate with an intermediate carrier, a first application device which applies a liquid release agent to the intermediate carrier, a second

Applicator which applies a printing fluid according to a printed image only at the printing locations on the intermediate carrier, a heater which heats the printing fluid, and a printing nip, in which the printing fluid is transferred from the intermediate carrier to the printing material, characterized in that the Intermediate carrier has a metallic coating and that the release agent is applied as a molecular coating on the metallic coating.

With the device according to the invention benefits go hand in hand, as already described above with respect to the inventive method. It will

According to the invention applied with the first application device, a liquid release agent, wherein the release agent is applied as a molecular coating on a metallic coating. The applied molecular assignment on the metallic

Coating of the intermediate carrier, in turn, ensures that the printing liquid adheres to the surface of the intermediate carrier from the point of application of the printing liquid up to the point of transfer of the printing liquid to the printing material in a printing gap on the intermediate carrier. At the same time, the molecular assignment ensures that the printing fluid in the nip can be completely or at least almost completely detached from the surface of the intermediate carrier and transferred to the surface of the printing substrate. A refinement of the device according to the invention which is advantageous and therefore preferred in terms of the construction of the device for the indirect inkjet with a plurality of printheads arranged one after the other can be distinguished by the fact that the metallic coating is applied to a flexible carrier strip of the intermediate carrier. This carrier tape can be passed around cylinders and adjacent to a run of the carrier tape, the plurality of print heads for the indirect inkjet can be arranged. One advantageous for attaching the molecular occupancy and therefore preferred

Development of the device according to the invention may be characterized in that the metallic coating and its surface are oxidized. It is particularly preferred that the metallic coating comprises oxidized titanium, oxidized stainless steel, oxidized aluminum, titanate or zirconate.

A development of the device according to the invention that is advantageous and therefore preferred for heat-treating the printing fluid on the intermediate carrier may be distinguished by the fact that the intermediate carrier comprises an absorption layer and / or a buffer layer and / or a thermal insulation layer. It can the

Absorbent layer be formed such that it absorbs irradiated infrared or near infrared radiation particularly well, thereby heating the

Subcarrier allows, so that the heat generated to heat up the

Pressure fluid and drying the pressure fluid can be used. For this purpose, the absorption layer absorption centers or absorbers, which are set to the Wellenläge the incident infrared radiation include. If the absorption layer does not itself have a sufficient buffer effect for the coupled thermal energy, it may be advantageous to have one of the. Below the absorption layer

Absorbing layer to provide a separate buffer layer, which is designed due to a sufficiently high heat capacity selected to buffer the coupled thermal energy for a short time. At the same time, this buffer layer and also possibly a thermal insulation layer underneath should be designed with regard to its thermal conductivity so that a heat flow in the lateral direction and downwards in the Intermediate carrier is effectively prevented. In other words: the coupled

Heat energy should be maintained as possible at the points of the subcarrier, where was directly coupled. In this way, it becomes possible to digitally dry the printing fluid on the intermediate carrier with a digitally controllable dryer, d. H. using the data of the printed image to dry. In this case, heat energy is coupled only at the points at which hydraulic fluid is present on the intermediate carrier. Therefore, it may be advantageous to prevent a heat flow in the lateral direction. Preventing the flow of heat into the subcarrier should be avoided since it can select heat radiation sources that have lower power.

Especially with strong ink coverage of the subcarrier with aqueous inks can be difficult to apply the required heat energy to evaporate the water content of the ink on the intermediate carrier. Here, it proves to be an advantage if the metallic intermediate carrier or the metallic coating contains ferromagnetic material. Because then it is possible to heat the subcarrier near its surface by magnetic induction and in this way effectively very high

To couple energy quantities into the intermediate carrier. One advantageous with regard to the media used and therefore preferred

Development of the device according to the invention may be distinguished by the fact that the molecular assignment comprises an amphiphilic organic compound. Particularly preferred is a molecular occupancy containing phosphonic acid or

Hydroxamic acid.

A refinement of the device according to the invention which is advantageous and therefore preferred for indirect inkjet printing is finally distinguished by the fact that the second application device for the printing fluid is designed as an inkjet head. Accordingly, when printing multicolor images, multiple printheads are provided. It is an object of the present invention to provide a method with which

remaining disturbing paint residues on the surface of an intermediate carrier in indirect inkjet can be removed as gently as possible without excessive effort.

This object is achieved with the features characterized in the claims 54 and 64, respectively.

According to the invention, a mechanical stress on the surface of the

Intermediate carrier avoided, which goes beyond what the intermediate carrier learns anyway when transferring the cached inkjet image on the printing substrate. Instead, it will be detected pollution or regular

Periods of a cleaning procedure, in which remaining parts of the ink are printed on a special dedicated area. This can be a surface on which the already solidified parts of the image adhere better than on the surface of the substrate currently being used. However, this can also be done by further improving their adhesion to the printing material by covering the untransferred parts of the inks again with ink and then printing these together with the non-transferred parts of the ink onto the surface provided for this purpose.

The latter surface can be suitably formed by a printing substrate itself to which the particular very small-area remaining parts of the untransfered solidified ink just after a large area coverage just then adhere. In the former case, it is expedient to use a printing substrate having slightly different surface properties than the printing material used for the printing job, for example a special "cleaning sheet" made of paper with a coated surface or in the form of a plastic film instead of the uncoated paper used for the printing job can be introduced, for example, at regular intervals or as needed in the transport path of the substrate, then takes the passage through the nip due to its high affinity for the solid color residues, this from the intermediate carrier and is then discharged as a spoiling sheet from the paper transport again. However, it is also possible to realize the intended for the printing of the non-transferred parts of the ink surface by a engageable paper or plastic wrap or a cleaning roller, which with the same surface or

Circumferential speed as the surface of the subcarrier itself contacts this and decreases the transferred to them residual color, and then in turn to be cleaned, which in turn is easily possible, since their surface can be sufficiently resistant to a cleaning process formed.

For example, the area provided for printing the ink residue may be formed by the outer surface of the impression cylinder, of which the normally

Printing substrate is brought into contact with the surface of the intermediate carrier, expediently in such a modified form that the impression cylinder for the purpose of removing residual color from the intermediate carrier has a spanned on him, preferably vorspulbaren elevator, which then in turn assumes the residual color.

In the event that remaining ink residues are covered again with ink applied in the course of the cleaning procedure, it is expedient to perform the coverage only in the image areas in which the ink application is actually incomplete on the printing substrate. To detect this, the surface of the subcarrier is electronically imaged by the image sensor after image transmission to the printing substrate and subjected to image processing by means of which the extent and location of contamination of the surface of the subcarrier is detected. However, it is also possible to cover the dirty areas of the subcarrier over the entire surface, which then not necessarily by the inkjet heads of the device for the indirect

Inkjet must be done, but can also be done by full-surface spraying by means of fewer spray nozzles or by full-surface application by means of rollers.

The covering of the ink residues can be done in principle with the same ink with which the inkjet image is printed on the intermediate carrier. Appropriately, however, when the overlap of the ink residues is not done with the inkjet heads themselves, but by other means such as spray nozzles or applicator rolls, a fluid can be used which improves the transfer behavior during printing and optionally another solidification mechanism works like the ink used to make the inkjet image. For the cleaning procedure, it is therefore expedient to spray a fluid which contains radiation-hardening constituents onto the untransferred color residues and is irradiated with UV radiation in the course of the cleaning procedure. In this way, then forms a solidified film on the

Subcarrier surface, which "takes along" the underlying paint residue adhering to the film and transfers it to a cleaning sheet in the printing nip.

In the indirect inkjet with water-based printing inks, the energy required to evaporate the water from the ink is generally supplied by radiation and hot air from the outside, as described, for example, in US Pat. No. 7997717 B2. In this device, although an additional heating roller is provided in the interior of the intermediate carrier cylinder to enter further heat energy in the intermediate carrier. However, this rolls off in linear contact on the interior of the intermediate carrier. It is not suitable at this point to equalize temperature differences on the surface of the intermediate carrier and also the energy transfer to the intermediate carrier is poor because of the linear contact. It is therefore the object of the present invention to provide a method and to provide a device by which the aforementioned disturbing influences are avoided or at least reduced.

This object is achieved by a method having the features of claim 69 and a device having the features of claim 74.

The method according to the invention is characterized in that thermal energy is applied or introduced onto or into the outer layer of the intermediate carrier by direct contact with a surface with high thermal conductivity and / or the heat energy already applied to the layer or introduced into it is made uniform over the surface of the intermediate carrier. The inventive method eliminates by the contact of the outer subcarrier layer with materials of good thermal conductivity, the above-described negative effect of inscribed "thermal images" in the

Between the support surface. This is expediently achieved, for example, by the fact that the intermediate carrier surface in direct contact with rolls or strips of good heat conducting materials made of metal such. As copper, aluminum, stainless steel, nickel or thermally conductive ceramics such as A1 ₂ 0 ₃ or aluminum nitride is or is brought after the printed image has been transferred to the substrate to be printed. Since the direct inkjet printing method yes works with complete transfer of the ink to the printing substrate, at this point, the surface of the intermediate carrier is free of color and can therefore be brought into good contact with metal cylinders or a metal band without disturbing themselves through this contact Influences are exerted on the sensitive surface of the subcarrier. In this way, temperature differences in the surface of the intermediate carrier are made uniform, so that disturbing thermal inhomogeneities are eliminated before the intermediate carrier is newly coated or imaged by the inkjet heads.

Then, if the intermediate carrier consists of a band, it is expedient to provide at least one metal cylinder over which the intermediate carrier belt with a large

Umschlingungswinkel is led, whereby it is primarily important that the

Surface of the intermediate carrier band contacting cylinder made of good heat conducting material such as a metal thermally conductive ceramic or

thermally conductive plastic and / or is heated. To support or increase the temperature of the temperature entry in the intermediate carrier, however, it may be expedient to heat the other involved in the wrapping cylinder, rollers or rollers with which the underside of the intermediate carrier belt comes into contact.

In the event that the intermediate carrier consists of a cylinder, the cylinder surface of the intermediate carrier is expediently in contact with a heated or tempered good heat-conducting tape, for. B. brought a metal strip. In this way, the large-area contact can effectively dissipate very large amounts of heat into the outer layer enter the intermediate carrier and even out the existing temperature differences of the subcarrier surface.

Another way to reduce or eliminate the above-described thermal effects on the surface of the subcarrier is to build the subcarrier itself in a multi-layered manner so as to directly under a relatively thin, outer layer that is optimized in terms of ink acceptance and transfer behavior a metal layer follows. This metal layer then causes the lateral equalization of the temperature differences in the overlying the temperature relatively poorly conductive plastic, rubber or silicone rubber layer in which a temperature compensation otherwise would only be very slow.

In this variant of the invention, thermal energy for heating the intermediate carrier can be entered directly into the outer layer via a metallic contact. For if the underlying metal layer has ferromagnetic properties, it can be very contactlessly and at any point by there arranged induction heaters provide very effectively with heat energy.

In the foregoing, the invention has been described in a device for indirect inkjet printing. However, it is also in an electrophotographically working

Can be used, which operates with an intermediate carrier on which the electrophotographically generated toner image is printed before it is transferred to the actual printing substrate is reversed. The invention can be used in particular even in such printing devices that work with liquid toner, the actual toner is thus dispersed in an oil or hydrocarbon mixture (Isopar).

When printing with water-based inks in the indirect inkjet printing process, considerable amounts of water must be evaporated within a short time in order to dry the printing liquid so that the unvaporized residue in the printing nip can be transferred to the printing substrate or the paper. As a rule, this is a polymer which carries the dye or the pigments dispersed therein or adhering thereto. These amounts of energy are supplied by heat, infrared radiation, etc. and heat the surface of the subcarrier on strong. The inkjet head, however, or its nozzle openings have only a very small distance of typically 1mm to

This causes the ink in the nozzles, which are not constantly ejecting ink, to become highly viscous because the water evaporates and clogs the nozzles, and accordingly, additional so-called "purging" of ink in Pressure-free areas resistant to ink eject through the nozzles to keep the nozzles clear, increasing ink consumption. Attempted nozzles are attempted to be "blown free" by an increase in pressure, since otherwise the inkjet head locks, ie the nozzles remain irreversibly closed, which results in expensive replacement of the heads.

One could now try to solve the above problem by the ink jet heads are thermally shielded from the subcarrier or cooled or

to be tempered to the usual range for aqueous inkjet printing

Keep temperatures below 40 ° C. However, this is not easy to realize, especially because of the very small distance between the heads and the

Intermediate carrier, and would if at all possible only with very high technical equipment use. In addition, you then create additional problems, since the moisture of the evaporating water content from the ink is then on the cooled inkjet head

precipitates, adversely affects the jet behavior of the nozzles or causes water marks in the inkjet image.

It is therefore an object of the present invention to provide a method, in particular for indirect inkjet printing with water-based printing fluids, with which avoid the problems described above or at least mitigate, for example, the time between the "purging" sequences significantly extended and the risk of irreversible Blocking the inkjet heads is significantly reduced.

This object is achieved by a method with the features of claim 91. A suitable printing fluid or ink is in

Claim 96 specified. Advantageous developments of this invention will become apparent from the accompanying dependent claims and from the following description and the accompanying drawings. According to the invention, therefore, a completely different approach is taken and instead the inkjet head or the inkjet heads are operated at temperatures above 70 degrees and the pressure fluid is adapted to this temperature range by adding boiling solvents above 120 degrees. Such water-soluble solvents are expediently selected from the following compounds: alkylic alcohols, glycol or oligomers thereof, alkylated mono- or polyglycol ethers, cyclic ethers, dioxolanes, pyrolidones or mixtures thereof. Especially suitable for this

Ethyl glycol, diethylene glycol, propylene glycol, dipropylene glycol and their methoxy or ethoxy derivatives, diglyme, 1-alkanols, 2-alkanols, 1, n-alkanediols, polyols of the form HOCH2 [CH (OH)] n CH20H with n <4, glycerol , Glycerol formal.

Of course, it is also possible to mix several different of the substances and substance classes mentioned with water, it may be useful if individual components of this aqueous solvent mixture can form azeotropic mixtures and that advantageously those that are accompanied by an increase in the boiling point.

All this helps to protect the operated at the high temperature inkjet head or its nozzles from blocking or to significantly extend the times between the purging sequences.

In the following, the invention will be described in more detail with reference to the figures of the attached drawings. The drawings show: FIG. 1 schematic view of a preferred embodiment of a

The device according to the invention and the process steps according to the invention which can be carried out by the method according to embodiments of the method according to the invention, FIGS. 1 a and 2 a show schematic views of exemplary embodiments of a device according to the invention

Device for the indirect inkjet, FIG. 3 a, on a greatly enlarged scale, sections through the outer layers of intermediate carriers;

FIG. 1b shows a schematic view of an exemplary embodiment of an apparatus for indirect inkjet printing,

Figures 2b to 5b show in relation to Figure lb on an enlarged scale different

Embodiments as an alternative to the impression device 60 to 65 in Figure lb,

Figures ld and 2d are schematic views of embodiments for a

Device for the indirect inkjet,

Figures 3d and 4d greatly enlarged sections through the outer layers of subcarriers,

Figure 5d a cooling device and

FIG. 6d shows a doctor device.

The device 1 in FIG. 1 comprises a circulating belt 2, which is guided around two cylinders 3 and 4 as well as via a guide surface 5. At least one of the two cylinders is driven by a motor 6 and in turn drives the belt. The guide surface serves to stabilize the run of the tape in the area of the print job.

The printing material is transported in the form of individual sheets from a system stack 7 to a delivery stack 8. The transport takes place via sheet guides shown in simplified form as lines 9 and 10 (in fact, it may be one or more

Transport cylinder act) and by means of the sheet transport cylinder 11, 12 and 13th

The latter have gripper systems 42 for the printing material 43. Each individual sheet 43 passes through a pressure gap 44 between the cylinder 13 and one at this Employed press roller 14. Drive this sheet transport system via at least one motor 15th

Adjacent to the run of the tape 2, a plurality of print heads 16a to 16d are arranged consecutively, e.g. Printheads for the usual colors cyan, magenta, yellow and black. Each printhead produces color drops 45 that are jetted onto the ribbon to create color dots. In this way, multicolored rasterized printed images can be created. However, it can also be provided that the color drops of a color run at least in places into one another and therefore form closed color areas. Since the printheads are arranged consecutively in the direction of the tape, the different color dots come to lie partly on each other. It may be provided that the printheads 16a to 16d are provided with a post-treatment device 16e, e.g. for painting or paint application, downstream. Also adjacent to the belt 2 is a belt handling device 17, e.g. for plasma treatment, arranged. By means of the plasma or a corona discharge, the strip surface can be cleaned and added to a surface state defined for application of liquid media with respect to the surface energy. Furthermore, adjacent to the belt 2, a device 18 for applying conditioner is provided. The conditioner ensures that the belt surface accepts the ink, that the ink does not undesirably spread or bead on the belt, that the ink adheres to the belt during belt transport, and that the ink in the nip 44 can be transferred to the substrate 44. The applied to the tape 2 ink 46 is at least partially dried by a hot air jet of a hot air dryer 19 by water and / or

Solvent is evaporated from the ink. The hot air is supplied via a feed 20 and the steam produced by the drying is removed via an integrated into a housing 21 Luftabsaugung 22.

For further treatment, a further dryer 23, preferably an infrared dryer, is provided, which contains the printing ink, the conditioner 47 and / or the belt 2 heated immediately before and / or in the region of the pressure nip. This heating and the concomitant influence on the adhesion of the ink on the belt and the printing material 44 ensures that the printing ink and thus also the

Essentially completely detached from the tape and deposited on the substrate. Optionally, another, the printing gap 44 downstream dryer 24 may be provided which further heats the transferred ink and thereby dried and / or cured.

Since it is advantageous for the overall process to maintain the printing ink 46 at or above a certain temperature level, optionally heating means 25, 26, 27 and / or 28 can be provided, which temper the cylinders 3 and 4 from inside or outside. Likewise, the press roll 14 may be heated.

A device 29, e.g. a camera for inspection of the image is also disposed adjacent to the belt 2. With her can be determined via an image acquisition and evaluation, whether the printed image produced on the tape 2 meets the quality requirements or set, for example. has unwanted errors. Resulting insights can be used to improve the printing process, e.g. the order of the

Conditioner 47, the order of the ink drops 45 and / or the performance of the dryer 19 adapt or regulate.

Optionally, devices 30a to 30d for intermediate inspection, eg cameras, or intermediate treatment, eg drying, may be provided between the print heads 16a to 16d or these respectively directly downstream. Furthermore, optionally in the field of sheet feed or removal devices 31 and 32 for inspection of the sheet and / or a device 33 for pretreatment of the sheet, for example by a primer application, and / or a device 34 for the treatment of the sheet, for example by further drying , provided. An apparatus 35 for cleaning the belt 2 is arranged adjacent to the belt and is used to remove possible soiling of the belt. These may be residues of the primer, the printing substrate, the conditioner and / or the printing inks originate. The cleaning device then comprises a belt engageable cleaning roller with a cleaning liquid supply.

The liquids intended for consumption in the device 1 are provided in respective storage containers: reservoir 36 for cleaning liquid,

Storage tank 37 for conditioning fluid, reservoir 38 for several

Pressure fluids, e.g. Inks, and reservoir 39 for primer fluid. The containers and the associated application devices are connected via supply lines, not shown.

A device 40, e.g. a central computer for controlling the device 1 controls the individual components of the device, in particular the print heads 16a to 16d and the dryer 19 and 23. The control device is preferably with all components 6, 15 to 20, 22 to 39 and 41 on not shown data lines in connection.

Component 41 is a device for changing the band 2, which makes it possible, with decreasing band quality, to exchange the previous band for a new one.

The method steps of the method according to the invention with regard to the device shown in Figure 1 will be described in more detail below. As an intermediate carrier, the band 2 is provided. As a liquid conditioning agent, the conditioner 47 is provided by the applicator 18. In the conditioner 47, the first substance is already contained or added to it. The pressurized fluid is provided in reservoirs 38. In multicolor printing, a plurality of different pressure fluids are provided, each comprising the second substance or different second substances. The hydraulic fluid or the

Printing fluids are applied to the surface of the intermediate carrier 2 by means of the printing heads 16a to 16d.

After the application of the conditioning agent 47 and the pressure fluids 45, the pressure fluid is present as a drop or as a layer essentially on the

Konditioniennittel. In other words, the conditioner is between the pressure fluids (top) and the belt 2 (bottom). At the bottom of the drops or the layer of the respective pressure fluid 45, the pressure fluid forms a contact area with the conditioning agent 47. In other words: You have to imagine the sequence from the bottom up in such a way that at the bottom of the band 2 comes to rest, then the conditioning liquid 47, then the contact area of the

Pressure fluid with the conditioning agent and finally at the top of the rest of the pressure fluid outside the contact area.

The printing fluid is heated by the dryer 19 and / or the dryer 23. By heating with the dryer 19 solvent is expelled from the hydraulic fluid 45 and discharged through the air suction 22. The warming by the

Dryer 19 can also cause the activation of the first substance and thereby start the film formation in the contact area. However, it may alternatively be provided, the film formation by a separate irradiation, for. B. of infrared or

Ultraviolet radiation, to start.

The printing fluid 45 is transferred in the printing nip 44 from the intermediate carrier 2 to the printing substrate 43, which is shown as an arc in the exemplary embodiment.

By superimposing the conditioning agent and the pressure fluid and the contact area thereby forming, the reaction described below can be limited to this contact area. The following happens: The first

Substance of the liquid conditioning agent 47 increases the viscosity of the pressure fluid 45 on the intermediate carrier 2 in the contact area by a reaction with the second substance of the pressure fluid 45. The pressure fluid 45 thereby forms a film in the contact area. Pressure fluid outside the contact area instead has a lower viscosity than pressure fluid within the contact area, or

Preferably, the pressure fluid maintains its original viscosity.

The layer formed by the conditioning agent on the intermediate carrier 2 can also be regarded as a functional intermediate layer. It is particularly preferred to roll up this functional intermediate layer by means of an aqueous solution on the surface of the intermediate carrier 2 and thereby with a thin and homogeneous as possible layer a thickness of about 1 μη, but at least less than about 5 μηι to form. The applied layer of the conditioning agent is guided by the circulating belt 2 through the effective ranges of the respective print heads 16a to 16d, so that the printing fluid or the hydraulic fluids can be applied to the conditioning agent.

In a preferred embodiment, the print heads 16a to 16d apply polyacrylic printing fluid. Upon contact of such a printing fluid with the functional intermediate layer, the printing fluid or this type of ink reacts in such a way that only its outer surface indicative of the conditioning agent, i. H. a layer only a few nanometers thick, hardens. This layer is more preferably less than 10 nanometers thick. The polyacrylic thus forms the second substance contained in the pressure fluid. As the first substance in the conditioning agent, polyvalent cations, for example, Ca (2+) or Al (3+) are provided. These cause e.g. a flocculation of the dissolved

Polyacrylic acid. At the same time, the polymer molecules are crosslinked in the contact area and thereby lose their thermoplastic property. In this way it can be achieved that the pressure fluid in a subsequent reflow process, for example in the effective range of the dryer 19 and / or the dryer 23, is not melted and remains in the pressure gap 44 in the solid state during the transfer process. After the transfer to the substrate 43, these networked areas now do not form a lowermost layer but rather an uppermost layer and thus come to lie outside. The printing liquid layer is thereby not sticky even at a later heating of the printed product above the glass transition temperature of the polyacrylic acid.

Instead of rolling up the conditioning agent, it may also be provided to spray it on. Furthermore, it can be provided to dissolve the conditioning agent prior to its application in organic or partially organic solvent. Alternatively, however, it may be envisaged to apply the conditioning agent without solvent.

As the first substance in the conditioning agent can also acids, bases or

Catalysts may be provided. Also adjacent to the belt 2 is a device 17 for belt treatment, eg for plasma treatment. By means of the plasma or a corona discharge, the strip surface can be cleaned and added to a surface state defined for application of liquid media with respect to the surface energy. Furthermore, adjacent to the belt 2, a device 18 for applying conditioner is provided. The conditioner ensures that the belt surface accepts the ink, that the ink does not undesirably spread or bead on the belt, that the ink adheres to the belt during belt transport, and that the ink in the nip 44 can be transferred to the substrate 44.

The applied to the tape 2 ink 46 is at least partially dried by a hot air jet of a hot air dryer 19 by water and / or

For further treatment, a further dryer 23, preferably an infrared dryer, is provided, which heats the printing ink, the conditioner 47 and / or the belt 2 immediately before and / or in the region of the printing gap. This heating and the concomitant influence on the adhesion of the ink on the belt and the printing material 44 ensures that the printing ink and thus also the

Since it is advantageous for the overall process to maintain the printing ink 46 at or above a certain temperature level, optionally heating means 25, 26, 27 and / or 28 can be provided, which temper the cylinders 3 and 4 from inside or outside. Likewise, the press roll 14 may be heated. A device 29, for example a camera, for inspecting the image is also arranged adjacent to the belt 2. With her can be determined via an image acquisition and evaluation, if the printed image generated on the tape 2 meets the quality requirements or, for example, has undesirable errors. The resulting knowledge can be used to improve the printing process, eg the order of the

Optionally, between the printheads 16a to 16d or immediately downstream therefrom are devices 30a to 3dd for intermediate inspection, e.g. Cameras, or intermediate treatment, e.g. Drying, be provided. Furthermore, optionally in the area of sheet feeding or removal, devices 31 and 32 for inspecting the sheets and / or a device 33 for pretreating the sheets, e.g. by a primer application, and / or a device 34 for post-treatment of the sheet, e.g. by further drying, provided.

An apparatus 35 for cleaning the belt 2 is arranged adjacent to the belt and is used to remove possible soiling of the belt. These can result from residues of the primer, the printing substrate, the conditioner and / or the printing inks. The cleaning device then comprises a belt engageable cleaning roller with a cleaning liquid supply.

Storage tank 37 for conditioning fluid, reservoir 38 for several

Pressure fluids, such as inks, and storage tank 39 for primer fluid. The containers and the associated application devices are connected via supply lines, not shown. A device 40, for example a central computer, for controlling the device 1 controls the individual components of the device, in particular the print heads 16a to 16d and the dryers 19 and 23. The control device is preferably provided with all components 6, 15 to 20, 22 to 39 and 41 via unillustrated data lines in conjunction.

Component 41 is a device for changing the band 2, which makes it possible, with decreasing band quality, to exchange the previous band for a new one. The inventive method is in several process steps as follows

carried out. There is provided an intermediate carrier 2, in particular the band shown or alternatively a cylinder. A liquid release agent 47, in particular the illustrated conditioner, is provided in a storage container 37 and applied by a device 18 to the surface of the intermediate carrier 2.

Preferably, the release agent is sprayed through the device 18 and wets the surface of the intermediate carrier 2 at least in the print image areas completely and forms there a release layer. One or more printing fluids, in particular the printing inks cyan, magenta, yellow and black, are provided in the storage containers 38 and applied to the printed image in the form of drops 45 on the wetted surface of the intermediate carrier 2 with the print heads 16a to 16d. With the hot air dryer 19 and / or with the infrared dryer 23, the applied pressure fluid is heated on the rotating intermediate carrier 2. The separating agent entering the effective range of the respective driers 19 and / or 23 or the separating layer formed by it has a boiling temperature which is higher than that

Boiling temperature of the solvent of the applied pressure fluid or the applied pressure fluids. In this way it is possible that solvent, in particular water, is expelled from the hydraulic fluid without the

Release agent or the separating layer formed by it is negatively influenced in their separation effect. The expulsion of the solvent from the printing liquid is preferably carried out with the dryer 19 and the air extraction 22. In other words: After leaving the effective range of the dryer 19 is under the pressure liquid still sufficient release agent, so that a complete or almost complete transfer of Pressure fluid can be carried out by cleavage within the release layer in the region of the pressure gap 44.

It can be further advantageously provided that the separator 23 is used to increase the release agent to a temperature which is higher than the boiling point of the Release agent is located. This heating of the release agent before or in the area of

Pressure gap 44 may be the complete or almost complete detachment of the

Support hydraulic fluid from the intermediate carrier 2 in an advantageous manner. Hereinafter, some concrete examples are given as embodiments:

example 1

As an intermediate carrier 2, a rubber band, preferably constructed comparable to an offset blanket provided. Then about a μπι thick layer TPnB is applied over a spray bar 18 (tripropylene glycol n-butyl ether,

for example the product Dowanol TPnB). Finally, a water and binder based ink is applied.

Example 2

As intermediate carrier 2, a Teflon-coated transfer belt is provided. Then an approximately 4 μπι thick layer DPM is applied as a release layer (dipropylene glycol methyl ether, such as the product Dowanol DPM). The order can be made via a roller system, in particular similar to an offset dampening unit. Subsequently, an about 0.1 to about 1 μηι thin dispersion varnish layer is applied, which is dried and thus forms a skin on the DPM. For this purpose, a separate dryer may be provided, which is not shown in Figure 1 but the

Applicator 18 may be directly downstream. Finally, a water- and binder-based ink is applied, in particular a so-called latex ink. Example 3

As an intermediate carrier 2, a belt or a cylinder elevator is used, which is comparable in its material to a known offset blanket. Then an approximately 0, 1 to about 1 μηι thin oil layer is applied as a release layer, in particular a vegetable oil such as sunflower oil. Finally, an organic solvent-based ink is applied.

Example 4 As an intermediate carrier 2, a silicone coated band or a cylinder surface or a cylinder lift is provided, which otherwise resembles an offset blanket in its material. Then, an approximately six microns thick layer of a release fluid and then a hot-melt ink is applied.

Example 5

As an intermediate carrier, a belt or a cylinder elevator is used, which is comparable in its material with a known Offsetgummituch. Then a thin layer of colorless or pigment-free offset printing ink or color base is applied as a release layer about 0.1 to about 2 μηι thin layer. The surface tension is approximately between 0.01 N / m and 0.04 N / m. The viscosity of this ink can be between 40 and 100 Pa s. Typical geometry factors for the gap between the roller applying the release agent and the intermediate carrier belt are between 0.001 and 0.1. This results in printing speeds between 5 and 2 m / s surface roughness of the colorless release agent layer with a period of between 0.1 and 1.5 μιη. Then printing fluid is applied in the form of a water-based inkjet image, wherein the ink contains between 2 and 8% solids d. H. Polymer particles, which serve as a carrier for the dye or the pigments. The polymer particles and / or the pigments may have dimensions in the nanometer range.

In the above five embodiments, there are the following advantages:

If a compressible intermediate carrier, z. As a rubber band is used, this allows the printing of various substrates and in particular of rather rough natural papers. The use of, for example, Dowanol TPnB (with a boiling point of 274 ° Celsius) as a release layer leads to an outstanding release effect. This substance is a strong film-forming assistant and therefore improves the spreading of the

Pressure liquid drops. It is partially water soluble and miscible with most organic solvents. The same applies to Dowanol DPM. The use of water-based and binder-based inks is also advantageous, in particular the use of so-called latex inks or acrylate dispersions. These promise similar good mechanical resistance as UV inks, z. B. against scrubbing. They are also dry at relatively low temperatures, at about 60 to about 150 ° Celsius. If the release agent used is a transparent printing ink on which the water-based ink droplets jetted on it do not sufficiently spread or after which

If the impact does not remain sufficiently spread, a surface roughness caused by color splitting serves for pinning the overlying inkjet image. The same roughness is set again as part of a continuous process with each rotation of the intermediate carrier, there is no wear and color splitting when transferring the image on the substrate ensures a complete transition of the inkjet image, the transparent release agent protects the printed image and the gloss level this cover layer can be adjusted.

A device 29, for example a camera, for inspecting the image is also arranged adjacent to the belt 2. With her can be determined via an image recording and evaluation, whether the printed image produced on the tape 2 meets the quality requirements or, for example, has undesirable errors. The resulting knowledge can be used to improve the printing process, eg the order of the Conditioner 47, the order of the ink drops 45 and / or the performance of the dryer 19 adapt or regulate.

Optionally, between the printheads 16a to 16d or immediately downstream therefrom are devices 30a to 30d for intermediate inspection, e.g. Cameras, or intermediate treatment, e.g. Drying, be provided. Furthermore, optionally in the area of sheet feeding or removal, devices 31 and 32 for inspecting the sheets and / or a device 33 for pretreating the sheets, e.g. by a primer application, and / or a device 34 for post-treatment of the sheet, e.g. by further drying, provided.

Storage tank 37 for conditioning fluid, reservoir 38 for several

Pressure fluids, e.g. Inks, and reservoir 39 for primer fluid. The containers and the associated application devices are connected via supply lines, not shown. A device 40, e.g. a central computer for controlling the device 1 controls the individual components of the device, in particular the print heads 16a to 16d and the dryer 19 and 23. The control device is preferably with all components 6, 15 to 20, 22 to 39 and 41 on not shown data lines in connection.

The device 1 according to the invention for the indirect application of printing fluid 45 to a printing substrate 43 has the belt 2 as an intermediate carrier. According to the invention provided on the intermediate carrier 2, a metallic coating. This metallic coating can be done for example by vapor deposition of a flexible carrier tape. As a result, a very thin metallic coating can be produced on the carrier tape 2, whereby the flexibility of the tape remains substantially unaffected. The metallic coating of the tape 2 has the advantage that irradiated

Heat radiation at the surface of the metallic coating can be reflected and thereby both the incident beam and the outgoing beam of the

Radiation respectively through the pressure fluid 45 and the layer formed by it passes. In this way, the effect of heat radiation, for example, in the intended drying of the printing fluid, can be improved.

As a first application device according to the invention, the device 18 may be provided which applies a liquid release agent 47 to the intermediate carrier 2. According to the invention, the release agent 47 is applied as a molecular coating to the metallic coating of the intermediate carrier 2. The molecular assignment has the advantage that on the one hand very little medium is used and therefore costs and also

Cleaning costs can be reduced. On the other hand, however, it also has the advantage that a molecular assignment sufficient but relatively little

Media with separating effect in the printing fluid or on the substrate passes and thereby possibly reduces the print quality. The amount of medium at a molecular occupancy is essentially negligible. The application of a molecular coating can be carried out by applying the molecules in an aqueous solution to the metallic surface and then evaporating the aqueous solution by coupling in thermal energy. Also, rolling over with a drying roller is possible. Thus, the molecular coverage is applied in aqueous solution and immediately reduced to a nanoscopic, especially less than 50 or less than 10 nanometers thick layer.

As a second application device according to the invention, the print heads 16a to 16d can be provided, which apply the printing liquid 45 to the printed image corresponding to the printed image only at the printing locations on the metallic coating of the intermediate carrier 2. Thus, while in the prior art, the molecular occupancy by means of laser radiation is imaged using image data, e.g. B. at the non-printing sites, the molecular assignment is removed, the molecular occupancy is not structured according to the invention and instead the order of the printing fluid in a structured manner, ie a printed image corresponding performed.

As a heating device according to the invention, the hot air dryer 19 and / or the dryer 23, in particular an infrared dryer, may be provided. With this

Heating device, the hydraulic fluid is heated. Here, as already described above, the metallic coating of the intermediate carrier 2 may be advantageous due to its reflectivity with regard to the electromagnetic radiation.

As pressure gap according to the invention, the pressure gap 44 between the press roller 14 and the cylinder 13 may be provided for the sheet transport, in which the

Pressure fluid 45 is transmitted from the intermediate carrier 2 to the substrate 43. This transfer takes place according to the invention completely or at least almost completely, so that the printing fluid is located after the nip on the substrate and the surface of the intermediate carrier 2 advantageously not, only slightly or rarely needs to be cleaned. It may be advantageous to provide the intermediate carrier 2 with a thermally insulating layer on which the metallic coating is applied. Furthermore, it may be advantageous if this thermally insulating layer at the same time a strong absorption with respect to radiated electromagnetic radiation for heating the

Pressure fluid has. Such a thermally insulating and at the same time buffering layer is, for example, formed as a layer consisting of yttrium-stabilized zirconium oxide, aluminum chromium nitride or of aluminum titanium bentonitrile.

Particularly preferred is a layer of titanium aluminum nitride, which is characterized by a columnar material structure and is a good thermal insulator. Such layers are in connection with the laser imaging of printing plates in offset printing in the not yet published German patent application with the

Reference 10 2011 1 10 014.1 discloses. Above, the invention has been described with reference to an embodiment in which the intermediate carrier 2 is formed as a circulating belt. However, it is also possible to form the intermediate carrier in the manner of a cylinder elevator, which on a

Support cylinder is clamped and under the printheads 16a-e or arranged at the periphery of the cylinder process stations is moved past.

The device 1 in Figure la comprises a circulating belt 2, which is guided over a plurality of cylinders 4, 14, 51, 52, 53 and via a guide surface 5. At least one of the cylinders 4, 14, 51, 52, 53 is driven by a motor 6 and in turn drives the belt. The guide surface serves to stabilize the run of the tape in the area of the print job.

Transport cylinder act) and by means of the sheet transport cylinder 1 1, 12 and 13th

The latter have gripper systems 42 for the printing material 43. Each individual sheet 43 passes through a pressure gap 44 between the cylinder 13 and a press roll or cylinder 14 attached thereto. The drive of this sheet transport system takes place via at least one motor 15.

Adjacent to the run of the tape 2, a plurality of print heads 16a to 16d are arranged consecutively, e.g. Printheads for the usual colors cyan, magenta, yellow and black. Each printhead produces ink drops 45 of a water-based ink which are jetted onto the ribbon to create color dots. In this way, multicolored rasterized printed images can be created. Since the printheads are arranged consecutively in the direction of the tape, the different color dots come to lie partly on each other. It may be provided that the printheads 16a to 16d are provided with a post-treatment device 16e, e.g. for painting or for

Varnish order, is subordinate. Also adjacent to the belt 2 is a device 17 for belt treatment, eg for plasma treatment. By means of the plasma or a corona discharge, the strip surface can be cleaned and added to a surface state defined for application of liquid media with respect to the surface energy. Furthermore, adjacent to the belt 2, a device 18 for applying conditioner is provided. The conditioner ensures that the belt surface accepts the aqueous ink, that the ink does not undesirably spread or bead on the belt, that the ink adheres to the belt during belt transport, and that the subsequently solidified ink in the nip 44 impacts the print substrate 44 can be transferred.

The ink 45 applied to the belt 2 is heated by a jet of hot air

Heißlufttrockners 19 at least partially dried by water and / or

By this heating, the water contained in the ink evaporates, and a film 46 of the thermoplastic polymer particles contained in the ink, in which the dye or pigments of the ink are dissolved or adhered to the pigments, is formed. For further treatment of the resulting colored polymer layer (ink layer 46), a further dryer 23, preferably an infrared dryer, is provided which heats the ink layer 46 and / or the belt 2 immediately before and / or in the region of the printing nip. This dryer 23 consists of one or more consecutively

arranged arrays of IR radiation emitting diodes with an upstream lens array for focusing the radiation to the passing below pixels, which is controlled by means of the data stored in the controller 40 data of the prepress. The control takes place in such a way that according to the position values of the

Subcarrier tape 2, which provides a division on the inside of the tape 2 scanning encoder 28, at the right moment only the locations of the tape 2 are irradiated, on which there are evidence of the pre-stage data and pixels. About the like

Adjusting the viscosity of the ink layer 46 and, associated therewith, the adhesion of the ink layer to the belt and to the printing material sheet 44, is achieved the ink layer and thus also the print image substantially completely detached from the tape and deposited on the substrate 43.

Since it is advantageous for the overall process, the color layer 46 during the

Drying process on the belt 2 to keep at or above a certain temperature level, optionally further heating means may be provided, of which the surface of the intermediate carrier belt 2 is heated (not shown).

Optionally, between the printheads 16a to 16d or immediately downstream therefrom are devices 30a to 30d for intermediate inspection, e.g. Cameras, or intermediate treatment, e.g. Drying, be provided. Furthermore, optionally in the area of sheet feeding or removal, devices 31 and 32 for inspecting the sheets and / or a device 33 for pretreating the sheets, e.g. by a primer application, and / or a device 34 for post-treatment of the sheet, e.g. by further drying, be provided. The liquids intended for consumption in the device 1 are provided in respective storage containers: reservoir 36 for cleaning liquid,

Storage tank 37 for conditioning fluid, reservoir 38 for several

Pressure fluids, such as inks, and storage tank 39 for primer fluid. The containers and the associated application devices are connected via supply lines, not shown. A central computer 40 controls the individual components of the device 1, in particular the print heads 16a to 16d and the dryers 19, 23 and 25. The computer 40 is preferably connected to all components 6, 15 to 20, 22 to 39 via data lines not shown in connection ,

In particular, the computer 40 also controls a further heating device 25, preferably with the same or similar construction as the dryer 23 described above. The heating device 25 likewise consists of an array of radiation-emitting diodes and an upstream lens array for focusing the infrared radiation onto the surface of the latter passing below Subcarrier 2. The heater 25 is controlled with the data of the prepress and according to the position values supplied by the encoder 28 in such a way that at the right moment, only the points of the subcarrier belt 2 are supplied with radiant energy to those of the

Inkjet printheads 16a-d also pixels are aufgejettet. On these preheated areas, the conditioning liquid 47 evaporates immediately, the ink droplets 45 jetted by the inkjet heads 16a to 16d then find there a conditioned strip surface which allows the ink drops to spread and hold on the surface of the strip. At the same time, the amount of water contained in the ink drop then begins to evaporate and the viscosity increases to such an extent that when the next color is jetted by the next head (eg 16b), the ink drops are prevented from flowing into one another.

In the area between the pressure nip 44 and the plasma treatment station 17, where the transport direction of the intermediate carrier belt 2 is reversed, the belt 2 is guided in a loop over three deflection cylinders 53, 52 and 51, wherein the cylinder 51 contacts the surface of the belt 2. Around this cylinder 51, the band 2 is guided with a relatively large wrap angle, wherein in the course of the wrap, the band 2 contacts about 50% of the cylinder surface. The cylinder 51 is cooled or tempered with a temperature Tz, which is slightly below the target temperature Ts ₀ n, which should have the band 2 or its outer layer 71 (Figure 3), if it

Conditioning device 18 reached. This temperature should be below 70 ° C, so that the not or rarely driven nozzles of the printheads 16a-d, yes are only about 1-2 mm above the surface of the belt 2, are not subject to thermal stress or to prevent the drying or sticking of the nozzle openings. Optionally, the deflection cylinders 51 and 52 may be cooled, but this is not required. Because the band 2 usually has a structure as shown in Figure 3 and as it is quite similar known for the blankets in offset printing. Over a textile-reinforced support layer 73 is a layer 72 of resilient rubber material, such as foam rubber, which conducts heat very poorly due to the material used and the porous structure. In addition, the outer layer 71 of relatively firm and compared to the layer 72 better heat conductive rubber material applied, here materials such as silicone rubber or nitrile rubber are used, which ensure that the printed inkjet image can be fully transferred to the printing substrate 43 in the printing nip 44.

The exemplary embodiment of a device for the indirect inkjet printing according to FIG. 2a differs from that according to FIG. 1a on the one hand by using a cylinder 102 instead of a belt as the intermediate carrier, which is externally provided with a sleeve or a rubber blanket, which in principle is the same has structure described in Figure 3a. The individual components and components of the device in this

Embodiments are arranged on the periphery of the cylinder surface and have in principle the same structure and the same function as in

Embodiment of Figure la. They are provided with an increased reference numeral 100 and should not be explained again in detail at this point.

However, in view of the present invention, reference should be made to the following: The surface of the cylinder 114 coated with a flexible, poorly heat-conductive rubber layer 102 which serves as an intermediate support for the printing heads 1 16a-1 16d im

Inkjet method printed images, after passing through the printing gap 144 has an inhomogeneous temperature profile. This is because the ink jetted on the subcarrier surface 102 by the heads 116a-d cools more at the image positions after expelling the water content with the hot air drier 119 than in the surrounding non-image parts. This inhomogeneous temperature profile is still present when the subcarrier under the device 1 17 for the plasma treatment of Surface passes through and applied to the surface of the conditioner 125 onditionierer. Between the conditioning device 125 and the first inkjet printhead 116a, an infrared laser diode array 125, for example a VCSEL array, is arranged, which is the surface of the poorly conductive outer

Rubber layer 102 of the intermediate carrier only at the points where later the printed image is aufgejettet, acted upon by high-energy laser radiation and so the surface of the intermediate carrier at the image locations a higher Temperaturprofü inscribes, as at the surrounding non-image areas. For this purpose, the laser diode array 118 is connected to the controller 140, which knows both the prepress data and the current angular position of the cylinder 114 (which is interrogated by an encoder, not shown). On the thus preheated image areas, the water or solvent evaporates in the ink jetted by the heads 116a-16d, at least to such an extent that the then increased viscosity of the ink droplets will intermingle or prevent each other from mixing by mixing the different colors before they are finally removed from the

Hot air dryer 119 are dried to a remaining polymer film (ink layer 146), which is then transferred as an image in the printing gap 144 on the printed product 143.

The device 1 in Figure lb comprises a circulating belt 2, which is guided over a plurality of cylinders 3, 4, 14 and a guide surface 5. At least one of the cylinders 3, 4, 14 is driven by a motor 6 and in turn drives the belt. The

Guide surface serves to stabilize the run of the tape in the area of the print job.

The latter have gripper systems 42 for the printing material 43. Each individual sheet 43 passes through a pressure gap 44 between the cylinder 13 and a pressure roller 14 placed against it. The drive of this sheet transport system takes place via at least one motor 15. Adjacent to the run of the tape 2, a plurality of print heads 16a to 16d are arranged consecutively, for example, print heads for the usual colors cyan, magenta, yellow and black. Each printhead produces ink drops 45 of a water-based ink which are jetted onto the ribbon to create color dots. In this way, multicolored rasterized printed images can be created. However, it can also be provided that the color drops of a color run at least in places into one another and therefore form closed color areas. Since the printheads are arranged consecutively in the direction of the tape, the different color dots come to lie partly on each other. It can be provided that the printing heads 16a to 16d, a device 16e for post-treatment, eg for painting or for

Paint order, downstream, which is either also designed as an inkjet head or is designed as a conventional painting device that the paint job on

Application rollers or using less spray nozzles causes and thus covers the surface of the belt 2 over the entire surface with paint or other fluids. The varnish can be pigment-free ink, which otherwise has the same properties, in particular drying properties, as the ink 45, which is jetted onto the band 2 by the heads 16a-d.

Also adjacent to the belt 2 is a belt handling device 17, e.g. for plasma treatment, arranged. By means of the plasma or a corona discharge, the strip surface can be cleaned and added to a surface state defined for application of liquid media with respect to the surface energy. Furthermore, adjacent to the belt 2, a device 18 for applying conditioner is provided. The conditioner ensures that the belt surface accepts the aqueous ink, that the ink does not undesirably spread or bead on the belt, that the ink adheres to the belt during belt transport, and that the subsequently solidified ink in the nip 44 impacts the print substrate 44 can be transferred.

The ink 45 applied to the belt 2 is heated by a jet of hot air

Heißlufttrockners 19 at least partially dried by water and / or

Solvent is evaporated from the ink. The hot air is supplied via a feed 20 supplied and the steam resulting from the drying is discharged via an integrated into a housing 21 air extraction 22.

For further treatment, a further dryer 23, preferably an infrared dryer, is provided, which heats the ink, the optionally applied paint, the conditioner 47 and / or the belt 2 immediately before and / or in the region of the printing gap. As a result of this heating, the water contained in the ink or paint evaporates and a sticky film is formed. About the concomitant influence on the adhesion of the film on the tape and the printing material 44 is achieved that the film and thus also the printed image substantially completely detached from the tape and is deposited on the substrate. Optionally, another, the pressure nip 44th

Subordinate dryer 24 may be provided which further heats the already dried paint film and thereby dries and / or z. B. cures by radiation. Since it is advantageous for the overall process to remove the dried ink film, i. In order to maintain the printing ink 46 at or above a certain temperature level, heating means 25, 26, 27 and / or 28 may optionally be provided, which temper the cylinders 3 and 4 from the inside or outside. Likewise, the pressure roller 14 may be heated. At this point it should be mentioned that the arrangement and the type of the various

Heating devices can be chosen differently in order to optimize the overall printing process. For example, the hot air dryer 20 may be arranged in the strip running direction in front of the device 16e for post-treatment in order to dry the image on the intermediate carrier 2 first, before this then z. B. varnish is coated.

Conditioner 47, the order of the ink drops 45 and / or the performance of the dryer 19 adapt or regulate. Optionally, devices 30a to 30d for intermediate inspection, eg cameras, or intermediate treatment, eg drying, may be provided between the print heads 16a to 16d or these respectively directly downstream. Furthermore, devices 31 for inspecting the sheets or behind the printing nip 44 may optionally be provided for inspecting the strip surface after the impression and / or a device 33 for the pretreatment of the sheet, for example by a primer application, and in the field of sheet feeding or removal / or a device 34 for the post-treatment of the sheet, for example by further drying.

The liquids intended for consumption in the device 1 are provided in respective storage containers: cleaning liquid storage tank, conditioner liquid storage tank 37, multiple ink storage tank 38, e.g. Inks, and reservoir 39 for primer fluid. The containers and the associated

Application devices are connected via supply lines, not shown.

A central computer 40 controls the individual components of the device 1, in particular the print heads 16a to 16d and the dryers 19 and 23. The computer 40 is preferably connected to all components 6, 15 to 20, 22 to 39 and 41 via data lines, not shown in connection , Component 41 is a device for changing the band 2, which makes it possible, with decreasing band quality, to exchange the previous band for a new one.

In the area between the pressure nip 44 and the transport roller 3, where the transport direction of the intermediate carrier belt 2 is reversed, means 60 to 65 are optionally inserted, with the help of remaining remaining, not in the nip 44 on the sheet 43 transferred parts of the ink 46 of the surface of the tape 2 can be printed. This device has a counter-roller 62, over which a plastic belt 65 is guided, which is unwound from a winding 64 and wound on a winding 63. The film 65 consists either of smooth coated paper or a plastic such. As polyamide or polycarbonate with good ink-absorbing properties and high surface energy compared to the surface of the tape 2, made of silicone rubber, Teflon o. Ä. Another material with lower

Surface energy exists, the ink takes less well or gives off easier.

If the camera 32 determines that color residues are still present on the surface of the belt 2 due to insufficient transfer in the print nip, or that these exceed a certain level, first the jetting of the ink droplets 45 is interrupted once, d. H. no new print image is being jetted onto the intermediate carrier tape 2. As soon as the last image has been transferred from the intermediate carrier 2 in the printing nip 44 to the paper sheet 43, the cleaning procedure is initiated. This can begin with the fact that the machine is first stopped and optionally the pressure provision is turned off at the printing gap 44, so that the band 2 can then move freely between the impression cylinder 13 and the pressure roller 14 therethrough. Then the actual cleaning procedure begins. In this case, the tape and the film 65 are symbolized by a pressure roller 60 on the back of the belt 2 as brought into contact with each other, d. H. the tape surface is pressed against the film 65. The belt 2 and the film 65 are then moved forward at the same speed in mutual contact. For this purpose, the cores of the winding 63 and 64 are provided with drives which are also moved by the controller 40 in synchronism with the motor 6 of the tape drive, namely until the entire length of the tape 2 is once passed between the rollers 60 and 62. In this case, all remaining on the tape 2 color residues are transferred to the film 65. The camera 32 monitors the success of the cleaning procedure in a second pass, so that if no further ink residues are detected, the printing process can be resumed.

The separate pressure roller 60 can be dispensed with if the remaining components of the device are arranged as shown in FIG. 2 d. H. be moved into the area under the guide roller 3. In this case, the elastic roller 162 through which the cleaning sheet 165 is guided, movable in the direction of arrow 161 and presses at the beginning of the cleaning sequence, the film 165 against the underside of the guide roller 3 and thus against the surface of the overlying belt 2. Otherwise the

Operation is the same as described with reference to Figure lb. It is also possible to arrange the cleaning impression device in the region of the belt 2 between the deflection roller 4 and the pressure gap 44, if, for example, the infrared dryer 28 assumes the function of the dryer 23.

The paper or plastic belt 65 or 165 can be rewound and rewound several times until it has taken up so many ink residues that the reel 63 is to be replaced. However, especially if only occasional cleaning procedures with low color residues have to be performed, an endless belt may be used instead of a ribbon wrap.

In the embodiment according to FIG. 3b, a separate film which can be wound up and unwound in order to remove the ink residues from the strip surface is dispensed with in comparison to FIG. 2b. Instead, below the guide roller 3, a roll 172 which can be attached to this or the belt 2 placed above it, is provided which consists of a good ink-accepting material, such as e.g. As copper or Rilsan exists. On the surface of this roller 162 is located on a knife blade 174, which scraps the paint residues from the surface of the roller 172 and in a

Collecting container 173 collects. This "Farbabnahmewalze 172" rotates with the same

Circumferential speed as the guide roller 3 and the tape laid over it 2 and therefore exerts no great mechanical stress on the belt surface. The force of symbolized by the arrow 261 adjusting movement of the roller 172 and

Contact pressure, which the roller 172 exerts on the belt surface, can be adjusted or regulated so that paint residues are reliably removed from the belt 2, but to a value which is not higher than absolutely necessary.

In the alternative embodiment according to FIG. 4b, the device 60 to 65 in FIG. 1b is dispensed with. Instead, the impression cylinder denoted by 13 in FIG. 1, which conveys the sheet 43 to be printed, is replaced by a special one

Counter-pressure cylinder 113 replaced. This counter-pressure cylinder 1 13 has in its interior two pairs of coils 263a / 264a and 263b / 264b, from which a roll of smooth paper on the two opposite cylinder segments is placed, which normally held by the grippers 81a and 81b, to be printed sheet 43rd against the Press the surface of the belt 2. By a device not shown here, the respective paper tape from the one coil, for. B. 263a, unwound and on the

receiving coil 264a wound in a similar manner as that in US RE. 36,275 of the applicant for an offset printing film in a directly imageable

Sheet-fed flat printing machine is described.

If the camera 32 in the device according to FIG. 1b recognizes color residues on the surface of the belt 2, the pressure for the next number of sheets located on the belt surface is interrupted, and the corresponding amount of sheet 9 to be printed is interrupted, depending on the length of the belt withheld on the stack 7. As soon as the last printed sheet 43 has passed the printing nip 44, the surface of the belt 2 in the printing nip 44 no longer finds a sheet 43 to be printed, but instead the smooth surface of the cleaning paper roll which has been drawn over the respective cylinder segment. The color residues are then deposited on this smooth paper surface, whereupon the surface of the strip 2 is again free of color and, in addition, can fully fulfill its function as an intermediate carrier. As soon as the paper reel has picked up enough residual ink over the cylinder segments after several cleaning sequences, the drives for the reels 263a / 264a and 264b and 263b are actuated and fresh paper is stretched over the cylinder segments.

In the embodiment of Figure 5b is dispensed with the installation of paper reels in the impression cylinder 13 and 1 13th Instead, the segments of the impression cylinder 13 have a very smooth surface 13a, 13b of a color good-accepting material such. B. Rilsan or copper, similar to the roller 172 of Figure 3b. Instead, as in the preceding description of FIG. 4, the interfering residual color is printed off the strip surface 2 during a cleaning sequence on these surfaces. The surfaces 13a, 13b of the impression cylinder 13 are then removed at regular intervals by an underlying cloth washing device. The cloth washing device has the following structure: In a box 360 arranged below the impression cylinder 13, there are two rolls 363 and 364, the roll 364 being the supply roll from which a wash cloth 365 is unwound and wound up by the roll 363. The washcloth 364 is from Cleaning liquid in a tank 366 moistened. For the purpose of cleaning the surface of the impression cylinder 13 of the strip 2 removed paint residues a pressure roller 362 is moved in the direction of the fold 361 on the impression cylinder and pushes the wash cloth 365 against the surface while the impression cylinder 13 moves on and also the wash cloth 365 with lower

Speed is further to absorb the color of the outer surfaces 13a, 13b of the cylinder segments.

However, instead of the cloth washing means, a brush washer or other washing means may be used which, in good mechanical contact with the resistive surface of the impression cylinder, returns it to a clean, ink-accepting condition.

In this case, the cleaning procedure is as follows: At longer intervals or when the camera sensor 32 (Figure lb) detects contamination of the surface of the belt 2, the paper transport from the stack 7 is interrupted and for as many sheets as can be printed in one band pass if the entire band is to be cleaned, or for correspondingly fewer sheets, if only a part of the band is to be cleaned. Synchronously with this interruption, the banding of the strip surface with the ink droplets 45 is also interrupted so that the last printed sheet 43 still passing the printing gap 45 still decreases the last image present on the strip surface. Subsequently, the band 2 continues to run and remaining paint residues put on the strong ink-removing surfaces 13a, 13b of the

Counterpressure cylinder 13 on which collects the pollution. If the

Surface of the belt 2 is cleaned, the printing process continues with the decrease of the sheets 9 from the stack 7 and the further printing. Before this happens, the

Surface of the impression cylinder 13 are cleaned by the washing device 360 to 366 in order to avoid any loss of ink residues located on the impression cylinder on the back of the then transported by him substrate ie the sheet 43 in the nip. This cleaning of the impression cylinder 13 may be omitted or only in larger

Be necessary distances if, with a suitable choice of the material of the surface of the impression cylinder 13 is ensured that the ink residues remain on it and are not transferred to the back of the paper sheets to be covered 43.

According to further process variants of the invention can under certain

Preconditions to the above-described cleaning facilities are completely dispensed with. The first further variant of the invention consists in that, if the stack 7 in FIG. 1b contains uncoated paper, the sheets 9, 43, 10 removed therefrom thus have a relatively rough surface and the ink residues remaining on the strip surface and detected by the camera 32 due in particular to this rough printing material surface, the following procedure takes place at regular intervals. Upon detection of impurities instead of an uncoated paper sheet, or more sheets in a row, depending on the length of the belt 2 used, a printing substrate with different surface properties in the

Paper transport path introduced and transported by the cylinders 11, 13, 12 through the pressure gap 44. This can be, for example, smooth coated paper or foils. On these so-called spoil sheets then the impurities of the

Ribbon surface are printed because they show a much better color reduction behavior compared to the uncoated paper. It is now possible to proceed in such a way that the inkjet printing is stopped in the course of the cleaning procedure, or also that the inkjet printing is continued and the contaminants of the tape together with the image printed above are requested and discharged as waste. In this case as well, the device 60 to 65 according to FIG. 1 can be dispensed with. For safe transfer of the ink residues in the nip 44 on this spoiling sheet they can be reheated with the help of the infrared dryer 23 just before the pressure nip 44 to improve the decrease behavior through the spoiling sheet.

In an additional variant of the method according to the invention, in particular when the remaining paint residues on the surface of the strip 2 are not on the

The use of uncoated paper as printing substrate can be done as follows: The color remainders become after they of the Camera sensor 32 were recognized in terms of location and size, again coated in the course of the cleaning sequence of the inkjet heads 16a to 16d in a larger area in ink that combines with the color residues and is then solidified by the dryer 19, 27, 28, 23 as described , In the nip 44, then, these larger contiguous areas of the ink can be safely transferred to the sheet 43 to be printed, which is then also discarded as a spoiling sheet.

In a further variant, the surface of the strip 2 can also be sprayed over the whole area via the device 16e for post-treatment, for example a spraying device inserted at the point, relatively thickly with a fluid which is either dried by heat as described above or

Radiation-hardening substances containing, then from one in place of

Hot air dryer 19 arranged UV lamp is cured. Thus, a solid film thicker than the entire, but at least the soiled portion of the tape surface is formed on the tape surface, and this film can then be readily transferred in the printing nip 44 from the ink-repellent surface of the tape 2 to the ink-accepting sheet. In this way, all remaining contaminants are removed from the belt 2 and also to a

Transfer waste paper. In this process variant, it is also possible, instead of the waste sheets one of the devices shown in Figures lb to 5b, z. B. to use the figure 3b for removing the cured film from the strip surface. In that case, after the roller 172 has been set, the cured film adheres to the

Strip surface on the surface of the roller 172 and is withdrawn therefrom with the adhering to the film residual contaminants from the belt surface. The doctor blade 172 then peels off the cured film from the roller 172.

The cleaning procedure in this case is such that, at intervals or after contamination of the tape surface by the camera sensor 32 is detected

Paper transport and the printing of the tape 2 is exposed for a number of sheets and with the belt running on instead the above-described heat or radiation curing fluid is applied to the tape 2, and after stopping Counterpressure cylinder 13 and adjusting the roller 172 is subtracted from this, the film of the cured fluid from the belt 2.

The device 1 in FIG. 1 d comprises a circulating belt 2, which is guided over a plurality of cylinders 4, 14, 51, 52, 53 and via a guide surface 5. At least one of the cylinders 4, 14, 51, 52, 53 is driven by a motor 6 and in turn drives the belt. The guide surface serves to stabilize the run of the tape in the area of the print job. The printing material is transported in the form of individual sheets from a system stack 7 to a delivery stack 8. The transport takes place via sheet guides shown in simplified form as lines 9 and 10 (in fact, it may be one or more

The latter have gripper systems 42 for the printing material 43. Each individual sheet 43 passes through a pressure gap 44 between the cylinder 13 and a press roll 14 placed against it. The drive of this sheet transport system takes place via at least one motor 15.

Adjacent to the run of the tape 2, a plurality of print heads 16a to 16d are arranged consecutively, e.g. Printheads for the usual colors cyan, magenta, yellow and black. Each printhead produces ink drops 45 of a water-based ink which are jetted onto the ribbon to create color dots. In this way, multicolored rasterized printed images can be created. However, it can also be provided that the color drops of a color run at least in places into one another and therefore form closed color areas. Since the printheads are arranged consecutively in the direction of the tape, the different color dots come to lie partly on each other. It may be provided that the printheads 16a to 16d are provided with a post-treatment device 16e, e.g. for painting or for

Varnish order, is subordinate.

Also adjacent to the belt 2 is a device 17 for belt treatment, eg for plasma treatment. By means of the plasma or a corona discharge For example, the surface of the belt can be cleaned and placed in a surface state defined for liquid media application. Furthermore, adjacent to the belt 2, a device 18 for applying conditioner is provided. The conditioner ensures that the belt surface accepts the aqueous ink, that the ink does not undesirably spread or bead on the belt, that the ink adheres to the belt during belt transport, and that the subsequently solidified ink in the nip 44 impacts the print substrate 44 can be transferred.

The ink 45 applied to the belt 2 is heated by a jet of hot air

Heißlufttrockners 19 at least partially dried by water and / or

Solvent is evaporated from the ink. The hot air is supplied via a feed 20 and the steam produced by the drying is removed via an integrated into a housing 21 Luftabsaugung 22. For further treatment, a further dryer 23, preferably an infrared dryer, is provided which heats the ink, the conditioner 47 and / or the belt 2 immediately before and / or in the region of the printing nip. As a result of this heating, the water contained in the ink evaporates and a sticky film is formed. About that

accompanying influence on the adhesion of the ink to the tape and the printing material sheet 44 is achieved that the ink and thus also the printed image substantially completely detached from the tape and is deposited on the substrate. Optionally, another, the pressure nip 44 downstream dryer 24 may be provided which further heats the already dried ink film and thereby drying and / or z. B. cures by radiation.

Since it is advantageous for the overall process to keep the dried ink 46 at or above a certain temperature level, optionally heating means 25, 26, 27 and / or 28 may be provided, which temper the cylinders 3 and 4 from inside and outside. Likewise, the press roll 14 may be heated.

A device 29, for example a camera, for inspecting the image is also arranged adjacent to the belt 2. With her can be determined about an image acquisition and evaluation be whether the printed image produced on the tape 2 meets the quality requirements set or, for example, has undesirable errors. The resulting knowledge can be used to improve the printing process, eg the order of the

Onditionierers 47, the order of the ink drops 45 and / or the performance of the dryer 19 adapt or regulate.

Optionally, between the printheads 16a to 16d or immediately downstream therefrom are devices 30a to 30d for intermediate inspection, e.g. Cameras, or intermediate treatment, e.g. Drying, be provided. Furthermore, optionally in the area of sheet feeding or removal, devices 31 and 32 for inspecting the sheets and / or a device 33 for pretreating the sheets, e.g. by a primer application, and / or a device 34 for post-treatment of the sheet, e.g. by further drying, provided. An apparatus 35 for cleaning the belt 2 is arranged adjacent to the belt and is used to remove possible soiling of the belt. These can result from residues of the primer, the printing substrate, the conditioner and / or the printing inks. The cleaning device then comprises a belt engageable cleaning roller with a cleaning liquid supply.

Storage tank 37 for conditioning fluid, reservoir 38 for several

A central computer 40 controls the individual components of the device 1, in particular the print heads 16a to 16d and the dryers 19 and 23. The computer 40 is preferably connected to all components 6, 15 to 20, 22 to 39 and 41 via data lines, not shown in connection , Component 41 is a device for Changing the band 2, which allows to replace the previous band with a new band quality with decreasing band quality.

In the area between the pressure nip 44 and the plasma treatment station 17, where the transport direction of the intermediate carrier belt 2 is reversed, the belt 2 is guided in a loop over three deflection cylinders 53, 52 and 51, wherein the cylinder 51 contacts the surface of the belt 2. To this metal cylinder 51, the band 2 is guided with a relatively large wrap, wherein in the course of wrap the band 2 contacts about 50% of the cylinder surface. The cylinder 51 is heated or

tempered with a temperature T _z , which is slightly above the target temperature Ts ₀ u, which should have the band 2 or its outer layer 71 (Figure 3d) when it reaches the conditioning device 18. This temperature can well be above 100 ° C, typically at 120 ° C. For tempering are known in the graphic arts industry for controlling the temperature of rollers or cylinders in printing machines tempering, which are used with high-boiling bath liquids such. B. glycol to heat the cylinder 51 on its surface to temperatures of about 120 degrees. Optionally, the deflection cylinders 51 and 52 may be heated in order to provide the intermediate carrier belt 2 with a certain thermal base load, but this is not necessary. Because the band 2 usually has a structure as shown in the figure 3d and as he is quite similar known for the blankets in offset printing. Over a textile-reinforced support layer 73 is a layer 72 of resilient rubber material, such as foam rubber, which conducts heat very poorly due to the material used and the porous structure. In addition, the outer layer 71 of relatively firm and compared to the layer 72 better heat conductive

Applied rubber material, in which case materials such as silicone rubber or

Nitrile rubber are used, which ensure that the printed inkjet image can be completely transferred to the printing substrate 43 in the printing nip 44.

Via the cylinder 51 can be lateral temperature differences of 20 ° C in the outer layer 71 to a no longer disturbing amount of ± 2 ° C on the

Remove the surface of the layer 71 of the intermediate carrier 2. The exemplary embodiment of an apparatus for indirect inkjet printing according to FIG. 2d differs from that according to FIG. 1d in that, instead of a belt, a cylinder 102 which is externally provided with a sleeve or a rubber blanket, which in principle is the same, is used as intermediate carrier has structure described in Figure 3d. The individual components and components of the device in this

Embodiment of Figure ld. They are provided with an increased reference numeral 100 and should not be explained again in detail at this point.

To equalize the temperature differences on the surface of the cylinder 102, due to the drying of the printed image by means of the dryer 20, 28 and 23, after the printing gap 144 and after the cleaning device 135, a metal belt 151 placed over two rotatable rollers 152 and 153 is arranged that the surface of the

Cylinder 102 in the area between the two rollers 152 and 153 a large area touched. The existing lateral temperature differences on the surface of the cylinder 102 are effectively degraded in this way. The metal strip 151 is also tempered and is heated to a temperature slightly above the set temperature Ts ₀ ii with heaters, which may be inside one or both of the rollers 152 and 1 3 or in the area between the rollers, as indicated by the dashed Presentation is indicated. This heating device can be infrared heating bars which, in cooperation with an absorbent inner coating of the metal strip 151, ensure very good heat transfer to the metal strip 151 and, in turn, to the outer layer 71 of the intermediate carrier cylinder 102.

In a further exemplary embodiment of the invention, the outer layers of the intermediate carrier strip 2 from FIG. 1 d and the intermediate carrier cylinder 102 from FIG. 2 d have the structure described in FIG. 4 d. This differs from the structure of Figure 3d in that between the foam rubber layer 72 and the outer z. B.

Silicone rubber layer 71 a metal layer 74 is inserted. This metal layer 74 ensures lateral temperature transport in the plane of the surface of the intermediate carrier 2 or 102. In such a structure can therefore on the guide rollers 51/52 in FIG ld or the metal strip 151 are dispensed with according to Figure 2d. This solution also has the advantage that the lateral temperature transport takes place in the plane of the intermediate carrier over its entire surface, ie even in the area in which the dryers ink the water-based ink drops jetted by the inkjet heads 16a-d or 16a-d That is, where the temperature inhomogeneities begin to form, they evaporate.

Moreover, if the metal layer 74 is made of ferromagnetic material, it is also possible to use it directly for heating the outer layer 71 of the intermediate carrier 2 or 102. For this purpose, then the hot air dryer 19 can be omitted and instead replaced by a dryer which heats the metal layer 74 by induction. In this way, a considerable amount of energy can be coupled into the outer layer of the intermediate carrier above the poorly heat-conducting foam rubber layer 72, so that in this way the water-based ink droplets 45 on the intermediate carrier 2 or 102 are dried with certainty before they reach the pressure gap 44.

In the embodiments described above, it is assumed that the

Temperature of the subcarrier surface then, when the subcarrier passes under the inkjet heads, should already be relatively high, so that there the jetted

Evaporate the ink drops immediately. In another selected type of process management, in which the subcarrier surface is not supposed to have this high temperature, but runs "cold" under the heads, for example, especially at heights

Resolutions clogging the then very narrow nozzles of the inkjet head to avoid, can also be done differently. In that case, it is expedient to cool the temperature of the intermediate carrier 2 or 102 between the pressure gap 44 and the point 5, from which then the fluid application takes place. This example is described in FIG. 5d. In this case, a tempering device 61 is provided, which supplies the deflection cylinder 51, which contacts the surface of the intermediate carrier 2, with coolant via the lines 66a and 66b. The heat absorbed by the cylinder 51 is also supplied via the lines 68 a and 68 b to a heat exchanger 67, which the

removed heat of the subcarrier 2 reused. This is the

Heat exchanger 67 in the supply air between the supply air pipe 67 a and the fan 20th installed for the hot air dryer 19. In this way, the heat loss caused by the cooling and reheating of the intermediate carrier tape 2, kept within tolerable limits. The procedure described can also be with a structure for the

Intermediate carrier 2 combine, as shown in Figure 4d. Depending on

Process management, that is, as described above, the intermediate carrier 2 after the pressure gap by the deflection cylinder 51 heats or cools is the

Heat capacity of the layer 74 selected, which is below the color-accepting

Functional layer 71 is located. This layer 74 serves not only the heat balance or the equalization of temperature differences in the outer ink-accepting layer 71. For the high temperature case, the case that the intermediate carrier 2 is to pass through under relatively high temperature under the Inkjetköpfen is by a correspondingly high heat capacity then serving as a heat storage layer 74 ensured that the z. B. in front of the nip 44 by the heater 23 introduced heat in the intermediate carrier 2 is maintained and under the inkjet heads 16a-d cooling the intermediate carrier surface 71 when jetting the aqueous ink 45 is prevented. In the other case, however, when the intermediate carrier 2 is cooled by the deflection cylinder 51 as described with reference to Figure 5d at the point, is instead a

Used intermediate carrier 2, in which the layer 74 has a comparatively low heat capacity under the thinnest possible anti-adhesive covering layer 71, on which the ink is jetted. Because then the surface of the intermediate support 2 can be sufficiently well and deeply and permanently cool in its wrap around the deflection cylinder 51, without subsequent heat from the deeper layers of the intermediate carrier tape 2 heats the surface layer 71 immediately before it is heated under the inkjet heads 16a. d went through. The thermal conductivity of the layer 71 can be adjusted on the thickness and the choice of material in addition to the heat capacity of the underlying layer 74 so that under the inkjet heads 16a-d, the required amount of heat can flow, which for the Evaporation or thickening of the hydraulic fluid before the hot air dryer 19 is required.

Furthermore, when working with the exemplary embodiment according to FIGS. 1d, 4d and 5d, it has been found that the deflection cylinder 51 with its preferably metallic surface assumes a very good color. Since it rests in the region of the wrap angle of the intermediate carrier 2 at the top, remaining, not in the nip transferred to the substrate color remains stick to him, so it also serves to clean the surface of the intermediate carrier 2 of paint residues. For this purpose, as shown in Figure 6d, measures taken to exploit this effect. On a longitudinal direction of the arrow 171 in the direction of the deflection cylinder engageable support 120 is a collecting container 172 with a knife blade 173, which is employed by the feed movement to the surface of the deflection cylinder 51. This can be done either continuously or at intervals during printing. In this way, the removed from the surface of the subcarrier tape 2, not transferred color residues from the

Printing process removed. The separate cleaning device designated in FIG. 1d with 35 or in FIG. 2d with 135 can then be dispensed with.

The ink printed by the printheads 16a-d is on its way from the

Reservoir 38 to the printheads 16a-d in Figure 1 when using

Hochtemperaturtinte on a not shown here tempering on the

Operating temperature of preferably 80 ° C heated at which the printheads 16a to 16d are operated. Also not shown are the usual filters used in inkjet printing and means for degassing the ink which cause the Pressure heads can perform their function smoothly and the nozzles can not be clogged by particles or prevented by gas bubbles on their pumping function. Although the printheads 16a to 16d can also separately on their

Operating temperature to be tempered, but it has been shown that by a

Tempering the ink itself, for example, between the heads and the

Tempering device is pumped back and forth in the ring flow, and outgoing from the about 120 ° C hot strip 2 temperature radiation in the printheads 16a-d sets a temperature equilibrium, which can be easily maintained in a range between 70 ° C and 90 ° C. without requiring special shielding measures between the belt 2 and the printheads 16a-d.

The ink printed by the printheads 16a to 16d in Figure 1 suitably has the following composition: 5 to 20% of a dye or pigment, 5 to 20% of a polymer in which the pigment or dye is dissolved or dispersed, 60 to 90% a polar solvent mixture with a water content between 20 and 80%. As usual with inkjettinten here are 0.05 to 3% of an antifungal agent such. B. benzoic acids or sulfonic acids added prevent the transferred to the sheet 43 components of the printing fluid primarily the solidified polymer containing the dyes or pigments are attacked by fungi. In one embodiment of the ink, the following composition was chosen:

14.6% pigment,

10% of a styrene-methacrylic acid copolymer with polyethylene glycol side chains, 75% of an aqueous solvent consisting of its mixture of isoamyl alcohol,

Water and 1-methoxy-2-propanol in the ratio 1: 1: 1, and

0.4% benzoic acid.

With these and functionally similar compositions of the ink, the device for indirect inkjet printing described with reference to FIG. 1 can be operated such that a purge of the nozzles of the print heads 16a-d is required only at very large intervals, without the inkjet nozzles clogging. The times are now in the double digits Minute range compared to times in the two-digit second range, as occurred in the prior art.

LIST OF REFERENCE NUMBERS

1 facility

2 band

3 cylinders for tape guidance

4 cylinders for belt guidance

5 guide surface for Bandfuhrung

6 motor for the belt guide

7 investment piles

8 delivery stacks

9 bowing

10 bow guide

1 1 cylinder for sheet transport

12 cylinders for sheet transport

13 cylinders for sheet transport

14 press roll

15 engine for sheet transport

16a-d printheads

16e Post-treatment device, e.g. Painting or embossing

17 Belt treatment device, e.g. plasma

18 Apparatus for applying conditioner

19 hot air dryer

20 hot air supply

21 housing

22 air extraction

23 dryers, e.g. IR dryer

24 dryers, e.g. IR dryer

25 heater inside

26 heater outside

27 heater inside

28 heater outside

29 Apparatus for inspecting the image ad Intermediate Inspection or Intermediate Inspection Device for sheet inspection

Device for inspecting the printed image

Apparatus for pretreating the sheet, e.g. Primer application Post-treatment device for the sheet, e.g. Drying, 135 Device for cleaning the belt

Reservoir for cleaning fluid

Reservoir for conditioning fluid

Reservoir for hydraulic fluid, e.g. ink

Storage container for primer liquid

Device for controlling the device

Device for changing the band

gripper systems

bow

nip

color drops

printing ink

conditioner

, 53 deflection cylinders

a, b lines for cooling fluid

deflecting cylinder

a, b lines for cooling fluid

, 362 pressure roller

temperature control

, 162 Counter role

, 64, 163, 164 wraps

, 165 plastic strap

a, b; 68a, b lines

heat exchangers

a Supply air duct heat exchanger

outer layer

Foam rubber layer / layer 73 base course

74 metal layer

81a, b gripper

102 rubber layer on cylinder

1 13 impression cylinder

1 14 cylinders

143 printing substrate

144 pressure gap

161, 261, 361 arrow

151 metal band

152 roller

153 roller

170 carriers

171 arrow

172 copper roller, container

173 collection container, doctor blade

174 knife scraper

263a, b paper wrapping

264a, b paper wrapping

360 washing facility

364 washcloth wraps

365 washcloth

366 tank for washing liquid

Claims

claims

1. A method for the indirect application of printing fluid to a substrate, wherein

an intermediate carrier (2) is provided,

a liquid conditioning agent (47) comprising a first substance, provided and applied to the intermediate carrier (2),

a pressure liquid (45) comprising a second substance is provided and applied to the conditioning means (47) on the intermediate carrier (2),

the pressure liquid (45) is present as a drop or layer essentially on the conditioning means (47) and the drops or the layer form on the underside thereof with the conditioning means (47) a contact area,

- That the pressure fluid (45) is heated, and

the printing fluid (45) is transferred from the intermediate carrier (2) to the printing material (43),

characterized,

- That the first substance of the liquid conditioning agent (47) increases the viscosity of the pressure fluid (45) on the intermediate carrier (2) in the contact area by a reaction with the second substance of the pressure fluid (45) and thereby the pressure fluid (45) in the contact area a film trains, and

- That the pressure fluid (45) outside the contact area a lower

Viscosity than within the contact area.

2. The method according to claim 1,

characterized,

the contact region has a layer thickness of less than 10 nanometers.

3. The method according to claim 1 or 2,

characterized,

the viscosity is increased by hardening the pressure fluid (45).

4. The method according to claim 1 or 2,

characterized,

the viscosity is increased by crystallizing the pressure fluid (45).

5. The method according to claim 1 or 2,

characterized,

the viscosity is increased by gelling the pressure fluid (45).

6. The method according to any one of the preceding claims,

characterized,

the conditioning liquid (47) is applied as an aqueous solution.

7. The method according to claim 6,

characterized,

the conditioning liquid (47) comprises a layer having a thickness of about 1

Micrometer forms.

8. The method according to any one of the preceding claims,

characterized,

the liquid conditioner (45) is applied as a polyacrylic liquid.

9. The method according to any one of the preceding claims,

characterized,

in that the liquid conditioning agent (47) has polyvalent cations, in particular Ca (2+) or Al (2+).

10. The method according to any one of the preceding claims,

characterized,

that the first substance by radiation to react with the second substance is activated.

11. A method for the indirect application of printing fluid to a substrate, wherein

an intermediate carrier (2) is provided,

a liquid release agent (47) is provided and applied to the intermediate carrier (2),

a pressure fluid (45) is provided and applied to the intermediate carrier (2),

- The pressure fluid (45) is heated, and

characterized,

in that the separating means (47) has a boiling temperature which is higher than the boiling temperature of the solvent of the pressure fluid (45).

12. The method according to claim 11,

characterized,

that the release agent (47) alcohol, in particular glycol or glycerol, or

Includes glycol ether.

13. The method according to claim 11,

characterized,

the release agent (47) comprises a gel and / or a thickener.

14. The method according to claim 11,

characterized,

in that the release agent (47) is an oil-based release agent, preferably a colorless or transparent printing ink, preferably offset printing ink or flexographic ink. WO 2013/185920 ^{"ΙΔ '} PCT / EP2013 / 001750

15. The method according to claim 14,

characterized by

the offset printing ink contains one or more of the following substances: mineral oil, vegetable oil, resins, waxes, esters.

16. The method according to any one of the preceding claims 11 to 15,

characterized,

in that the release agent (47) is applied as a release layer to the intermediate carrier (2), in particular as a release layer having a thickness of between about 1 micron and about 10 microns.

17. The method according to any one of the preceding claims 11 to 16,

characterized,

in that the separating means (47) substantially completely wets the surface of the intermediate carrier (2).

18. The method according to any one of the preceding claims 11 to 17,

characterized,

in that the transfer of the printing fluid (45) to the printing substrate (43) is effected by a cleavage of the separating layer.

19. The method according to any one of the preceding claims 11 to 18,

characterized,

a further layer of a further liquid is applied to the separating layer, the further liquid influencing the spreading behavior of the printing liquid (45) on the separating layer.

20. The method according to any one of the preceding claims 15 to 19,

characterized,

the printing fluid (45) is a preferably water-based printing ink and is applied to the intermediate carrier (2) in the inkjet method.

21. The method according to any one of the preceding claims 11 to 20,

characterized,

that the release agent is applied as a rough layer on the intermediate carrier (2).

22. The method according to claim 21,

characterized,

the roughness and / or decay time of the surface roughness of the separating layer (122) is adjusted by way of the viscosity and / or surface tension of the separating liquid (47), taking into account the subsequent heating or drying of the printing liquid (46) applied thereto, such that during transfer of the the release layer (122) applied optionally dried or

solidified printing fluid (46) on the substrate (43) as possible

achieve full carryover.

23. The method according to claim 21,

characterized,

the roughness and / or decay time of the surface roughness of the separating layer (122) is adjusted via the viscosity and / or surface tension of the separating liquid so that a pressure fluid (46) applied to the separating layer (122) spreads sufficiently well and / or can be pinned and or a certain gloss of the release layer (122a) on the print substrate (43) can be achieved.

24. The method according to any one of claims 21 to 23,

characterized,

the release agent (47) is applied with a roller (118) as the release agent layer (122).

25. The method according to any one of claims 21 to 23,

characterized,

in that the release agent (47) is sprayed or fogged onto the intermediate carrier (2) or applied by inkjet.

26. The method according to claim 25,

characterized,

that the sprayed or atomized droplets of the release agent (47) are cooled.

27. The method according to claim 21,

characterized,

in that the degree of gloss of the printed image (46) transferred to the printing substrate (43) is adjusted by the time and / or given printing speed by the location at which the part (122a) of the separating layer (122) remaining on the printed image (46) is dried is, and / or by intensity and duration of

Influence of the heat or radiation applied for the drying.

28. Method for the indirect application of printing fluid to a printing substrate,

- wherein on an intermediate carrier (2, 102), which has an outer layer with relatively low thermal conductivity, a printing fluid (45, 145) is applied to a printed image corresponding only to printing sites,

- The pressure fluid (45, 145) is heated and

- The pressure fluid (45, 145) or their evaporated ink remaining layer (46) in a printing nip of the intermediate carrier (2, 102) is transferred to a substrate (43),

characterized,

that the intermediate carrier is heated locally before the application of the printing fluid and / or before the printing nip (44, 144) locally at the points at which the printed image is subsequently applied, or is already applied.

29. The method according to claim 28,

characterized,

that the intermediate carrier (2, 102) before the application of the printing fluid at the expected image locations of an infrared (laser) controlled according to the image data and the current position of the subcarrier surface - Radiation device (25, 125) is heated.

30. The method according to claim 28,

characterized,

that the surface of the intermediate carrier (2) directly in front of the printing nip (44) optionally at a distance which takes into account the melting time of the already evaporated ink layer (46), only at the image locations of an infrared radiation source controlled according to the image data and the instantaneous position of the subcarrier surface ( Laser array 23) is heated directly or indirectly.

31. The method according to claim 30,

characterized,

the heating of the intermediate carrier (2, 102) takes place directly through the ink layer (46, 146).

32. The method according to claim 30,

characterized,

the heating of the intermediate carrier (2, 102) takes place indirectly by heating the absorbing ink layer (46, 146).

33. Device for the indirect application of printing fluid to a substrate with

an intermediate support (2, 102) having one or more relatively low thermal conductivity layers (71, 72),

- An applicator device (16 a to 16 d), a pressure fluid (45) a

Applies print image to the intermediate carrier (2, 102) only at printing locations

- A heater (19, 23, 25, 119, 125), which heats the pressure fluid (45) and

a pressure nip (44, 144) in which the printing fluid (45) or the ink film remaining after evaporation thereof is transferred from the intermediate carrier (2, 102) to the printing material (43, 143), characterized,

that

- The heating device (23, 25, 125) comprises one or more beam sources, which heats the surface of the intermediate carrier (2, 102) and / or the printing fluid (45) or the ink layer (46) at the print image locations, wherein the radiation sources in Movement direction of the intermediate carrier (2, 102) in front of the printing nip (44, 144) and / or in front of the applicator device (16a to 16d) are arranged.

34. Device according to claim 33,

characterized,

the radiation sources (25, 125) are arranged directly in front of the application device (16a-d) in front of or behind a conditioning device (18, 118) arranged there.

35. Device according to claim 33,

characterized,

in that the radiation sources (23) are arranged in front of the printing gap (44, 144).

36. Device according to claim 35,

characterized,

in that the distance of the radiation sources (23) from the printing gap (44, 144) is dimensioned such that, taking into account the materials used for the ink layer (46), the belt speed and the radiation power of the radiation sources (23), the color layer (46) for the Transfer from the intermediate carrier (2, 102) to the

Substrate (43, 143) has reached optimum temperature and / or viscosity.

37. Device according to claim 33,

characterized,

in that the radiation sources of the heating device (23, 25, 125) are connected to a controller in which the print image data and their position are stored on the intermediate carrier (2, 102) and the controller (40, 140) is connected to an encoder (28) is, which emits a signal characterizing the actual situation of the subcarrier.

38. Device according to claim 33,

characterized,

the radiation sources of the heating device (23, 25, 125) comprise one or more of the following types of radiation sources: lasers, pulsed lasers,

Laser diode arrays, VCSEL arrays, high power LEDs or LED arrays, where the radiation sources emit infrared radiation.

39. Device according to claim 38,

characterized,

the surface of the intermediate carrier (2, 102) and / or the color layer (46) contains absorber substances whose absorption properties are matched to the wavelength of the radiation sources (23, 25, 125).

40. Method for the indirect application of printing fluid to a printing substrate, wherein

an intermediate carrier (2) is provided,

a printing fluid (45) is provided and applied to the intermediate carrier (2) corresponding to a printed image only at printing locations,

- The pressure fluid (45) is heated, and

characterized,

- That the intermediate carrier (2) is provided with a metallic coating, and

- That the release agent (47) as a molecular assignment to the metallic

Coating is applied.

41. The method according to claim 40,

characterized, the molecular occupancy comprises an amphiphilic organic compound.

42. The method according to claim 41,

characterized,

that the molecular occupancy comprises phosphonic acid or hydroxamic acid.

43. Device for the indirect application of printing fluid to a substrate, with

an intermediate carrier (2),

a first application device (18) which applies a liquid release agent (47) to the intermediate carrier (2),

- A second application device (16a to 16d), which applies a printing fluid (45) corresponding to a printed image only at printing locations on the intermediate carrier (2)

- A heater (19, 23) which heats the pressure fluid (45), and

- A pressure nip (44), in which the pressure fluid (45) of the

Subcarrier (2) is transferred to the substrate (43),

characterized by

- That the intermediate carrier (2) has a metallic coating, and

- That the release agent is applied as a molecular coating on the metallic coating.

44. Device according to claim 43,

characterized,

that the metallic coating on a flexible carrier tape of the

Subcarrier (2) is applied.

45. Device according to claim 44,

characterized,

that the metallic coating is oxidized on its surface.

46. Device according to claim 45,

characterized,

the metallic coating comprises oxidized titanium, oxidized stainless steel, oxidized aluminum, titanate or zirconate

47. Device according to one of claims 44 to 46,

characterized,

the intermediate carrier has an absorption layer.

48. Device according to one of claims 44 to 47,

characterized,

the intermediate carrier has a buffer layer.

49. Device according to one of claims 44 to 48,

characterized,

the intermediate carrier has a thermal insulation layer.

50. Device according to one of claims 44 to 49,

characterized,

the molecular occupancy comprises an amphiphilic organic compound.

51. Device according to claim 50,

characterized,

that the molecular occupancy comprises phosphonic acid or hydroxamic acid.

52. Device according to one of claims 44 to 51,

characterized,

in that the second application device (16a to 16d) is designed as an ink-jet head.

53. Device according to one of claims 44 to 52,

characterized,

that the printing fluid is a water-based ink.

54. A method for cleaning the intermediate carrier (2) of an apparatus (1) for indirect inkjet printing, in which

an ink (45) is jetted onto the intermediate carrier (2),

the ink (45) is heated and thereby at least partially evaporated and / or solidified,

the evaporated or solidified part of the ink (45) is transferred from the intermediate carrier (2) to the printing material (43),

characterized,

the subcarrier is subjected to a cleaning procedure after known contamination or at intervals, in which at least the surface areas of the subcarrier (2), which carry untransferred parts of the ink, are covered again with ink or a solidifiable or vaporizable fluid and these are then covered together with the untransferred parts of the ink are printed on a designated area.

55. The method according to claim 54,

characterized,

the area provided for this is formed by a printing substrate itself.

56. The method according to claim 54,

characterized,

that the designated area by an engageable paper web or

Plastic film (65, 165) or a cleaning roller is formed.

57. The method according to claim 54,

characterized,

in that the area provided for this purpose is formed by a preferably pre-windable elevator (265) mounted on the impression cylinder (113) of the device for indirect inkjet printing.

58. The method according to claim 54,

characterized,

that the surface provided for this purpose is defined by the surface (13a, b) of the

Counterpressure cylinder (13) itself is formed, which is continuously cleaned at intervals or on demand in turn.

59. The method according to any one of claims 54 to 58,

wherein the repeated application of ink during the cleaning procedure on part of the surface only on those parts of the surface of the intermediate carrier (2), which are dirty.

60. The method according to claim 59,

wherein the surface of the intermediate carrier (2) is electronically imaged and subjected to image processing by an image sensor (32) to detect the contamination.

61. The method according to any one of claims 54 to 58,

wherein the covering of the soiled areas of the intermediate carrier (2) takes place over the entire surface.

62. The method according to claim 61,

wherein the re-application of ink using the inkjet heads (16a-d) of the device, by full-surface spraying or by applying a solidifiable fluid over the entire surface by means of a roller.

63. The method according to any one of claims 61 or 62,

wherein in the course of the cleaning procedure, a different liquid is applied than during the normal printing operation, preferably a liquid containing the

Improves transfer performance during printing and optionally works on another hardening mechanism (UV curing).

64. Method for cleaning the intermediate carrier (2) of an apparatus (1) for indirect inkjet printing, in which

an ink (45) is jetted onto the intermediate carrier (2),

characterized,

the subcarrier is subjected to a cleaning procedure after known contamination or at intervals during which remaining evaporated or solidified parts of the ink (46) are printed on a designated area (65, 165, 172, 263/264, 13a, b) the better adhered to the evaporated or solidified parts than on the surface of the printing substrate (43).

65. The method according to claim 64,

characterized,

if necessary or at regular intervals, a printing substrate with different surface properties than the printing material (43) reaches the printing gap (44) of the printing substrate (43)

Device to be supplied.

66. The method according to claim 65,

wherein the print substrate for cleaning is a smooth-surfaced paper or plastic film (which has a stronger affinity for the solidified ink (46) than the surface of the intermediate carrier (2).

67. The method according to claim 64,

wherein the intended surface (65, 165, 172, 265) to be printed on is the part of an engageable paper or plastic roll (63/64, 163/164, 263a, b / 264a, b) or a engageable cleaning roller (162) acts.

68. The method according to claim 64,

the surface (13a, b) of the counter-pressure cylinder (13) being itself or the elevator (263a, b, 264a, b) mounted thereon preferably being able to be pre-spooled.

69. A method for the indirect application of printing fluid to a printing substrate, wherein an intermediate carrier (2, 102, 202) is provided which has an outer layer with relatively low thermal conductivity

- A pressure fluid (45, 145) on the intermediate carrier (2, 102, 202) a

Printed image is applied accordingly only at printing sites,

- The pressure fluid (45, 145) is heated and

- The pressure fluid (45, 145) or their evaporated ink film remaining from the intermediate carrier (2, 102, 202) is transferred to the substrate (43), characterized

that on or in the outer layer of the intermediate carrier (2, 102, 202) by direct contact with a preferably metallic surface with high

Thermal conductivity is applied or registered or discharged, and / or in the outer layer (71) already registered

Heat energy over the surface of the intermediate carrier (2, 102, 202) is made uniform.

70. The method according to claim 69,

characterized,

in that the direct contact takes place via at least one cylinder (51) or a band (151).

71. The method according to claim 70,

characterized,

the cylinder (51) or the belt (151) additionally serves to remove paint residues from the intermediate carrier (2, 102, 20) and is preferably tempered or cooled.

72. The method according to claim 69,

characterized,

the cylinder or belt is cleaned permanently or at intervals.

73. The method according to claim 69,

characterized,

the direct contact is realized by a metal layer (74) of the intermediate carrier (2, 102, 202) directly under the outer layer (71).

74. Device for the indirect application of printing fluid to a substrate, with

- An intermediate carrier (2, 102, 202), which consists of one or more layers (71, 72, 73) with relatively low thermal conductivity, an applicator (16a to 16d), the printing fluid (45) corresponding to a printed image only to be printed Places on the intermediate carrier (2, 102, 202),

- A heater (19, 23, 119, 123), which heats the pressure fluid (45) and

a pressure gap (44, 144) in which the printing fluid (45) or the ink film remaining after evaporation thereof is transferred from the intermediate carrier (2, 102, 202) to the printing material (43, 143),

characterized,

that

- The outer layer (71) of the intermediate carrier (2, 102, 202) at least at one point has direct surface contact with a surface of a material (51, 74, 151) having high thermal conductivity, via the heat energy in the layer (71) applied or added or removed, or is evened on the intermediate carrier already applied or registered heat energy over the flat contact.

Device according to claim 74,

characterized, in that the surface with high thermal conductivity is arranged by a directly under the outer layer (71) of the intermediate carrier (2, 102, 202)

Metal layer (74) is realized.

76. Device according to claim 75,

characterized,

the metal layer (74) has ferromagnetic properties.

77. Device according to claim 76,

marked by

a heater directly heating the metal layer (74) by induction.

78. Device according to claim 74,

characterized,

in that the surface with high thermal conductivity is realized by metal cylinders (51, 52) contacting the intermediate carrier (2, 102, 202) or a metal strip (151).

79. Device according to claim 78,

characterized by

the cylinders (51, 52) or the belt (151) are connected directly or indirectly to one or more heating devices or cooling or cooling devices.

80. Device according to one of claims 78 or 79,

characterized,

in that the intermediate carrier (2, 102, 202) consists of a band and is guided over at least one cylinder (51) with a large angle of wrap.

81. Device according to claim 80,

characterized,

wherein the at least one cylinder (51) has a heated or tempered or cooled metal surface. WO 2013/185920 ^"öo" PCT / EP2013 / 001750

82. Device according to one of claims 75 to 79,

characterized,

in that the intermediate carrier (102) consists of a cylinder and the cylinder surface is in contact with a heated or tempered or cooled metal strip (151).

83. Device according to one of claims 78 to 82,

characterized,

that the intermediate carrier (2, 102) is constructed in multiple layers and over one

Insulation layer (72) has a layer (74) with greater thermal conductivity than the outer, the ink or ink (46) receiving layer (71), wherein the

Heat capacity of the layer (74) is adapted to the ink transfer process.

84. Device according to claim 83,

wherein, in the event that the intermediate carrier (2, 102) in the region (5), in which the hydraulic fluid is applied, a relatively low temperature to take, the cylinder (51) or the belt (151) is cooled and the Layer (74) has a comparatively low heat capacity.

85. Device according to claim 83,

wherein, in the event that the intermediate carrier (2, 102) in the region (5), in which the hydraulic fluid is applied, a relatively high temperature to take, the cylinder (51) or the band (151) is heated and the Layer (74) has a comparatively high heat capacity.

86. Device according to one of claims 74 to 85,

characterized,

in that the application device (16a to 16d) comprises one or more inkjet heads.

87. Device according to one of claims 74 to 86,

characterized,

the printing fluid (45) applied by the application device (16a to 16d) is a water-based ink.

88. Device according to one of claims 74 to 85,

characterized,

the application device (16a to 16d) comprises one or more devices for the application of liquid toner.

89. Device according to claim 88,

characterized,

that the pressure fluid is an oil-based or isopar-based liquid toner.

90. Device according to one of claims 78 to 89,

characterized by a cleaning device (170 to 173) for cleaning the surface of the cylinder (51) or belt (151).

91. Method for the indirect application of printing fluid to a substrate, wherein

a water-based printing fluid (45) with one or more inkjet heads is applied to an intermediate carrier (2),

- The pressure fluid (45) is heated and at least the proportion of water in the pressure fluid is evaporated,

- The printing fluid (45) or the non-evaporated remaining components from the intermediate carrier (2) is transferred to the substrate (43),

characterized,

that

- The or the inkjet heads are operated at temperatures above 70 ° C and

- The pressure fluid (45) contains water-miscible solvents whose

Boiling point is above 110 ° C. WO 2013/185920 ^"öö" PCT / EP2013 / 001750

92. The method according to claim 91,

characterized,

in that the pressure fluid above 120 ° C boiling polar solvents preferably comprises alcohols or ethers.

93. The method according to claim 91,

characterized,

that the printing fluid at least one of the following water-miscible

Solvents include: alkylic alcohols, glycol or oligomers thereof, alkyl single or multiple glycol ethers, cyclic ethers, dioxolanes, pyrolidones or mixtures thereof.

94. The method according to claim 93,

characterized,

the printing fluid contains one or more of the following water-miscible solvents: ethyl glycol, diethylene glycol, propylene glycol, dipropylene glycol and their methoxy or ethoxy derivatives, diglyme, 1-alkanols, 2-alkanols, 1,1-alkanediols, polyols of the formula HOCH2 CH (OH)] n CH20H with n <4, glycerol, glycerol formal.

95. The method according to claim 94,

characterized,

that the pressure fluid (45) or individual components thereof can form an azeotropic mixture.

96. hydraulic fluid for carrying out the method according to one of claims 91 to 95,

characterized by the following components:

5 to 20% of a dye or pigment

5 to 20% of a polymer in which the pigment or dye is dissolved or dispersed,

60 to 90% of a polar solvent mixture with a water content between 20 and 80%.

97. Pressure fluid according to claim 96,

with an addition of an antifungal agent between 0.05% and 3%.

98. printing fluid according to claim 97,

characterized,

that individual components of the pressure fluid can form an azeotropic mixture.