WO2018134039A1

WO2018134039A1 - Device and method for printing films which deform under thermal loads

Info

Publication number: WO2018134039A1
Application number: PCT/EP2018/025007
Authority: WO
Inventors: Clemens PÖRNBACHER; Philipp GUTGSELL
Original assignee: Durst Phototechnik Ag
Priority date: 2017-01-19
Filing date: 2018-01-13
Publication date: 2018-07-26
Also published as: EP3571052B1; EP3571052A1; IT201700005292A1

Abstract

The invention relates to a method for printing a film (100), having the following steps: a) providing a printing device with at least one means for receiving at least one film region, comprising a receiving surface (103) which is paired with a printing module (105a... 105d) comprising at least one nozzle row that lies opposite the receiving surface at a distance therefrom, b) placing the film region which has a temperature T1 on the receiving surface which has a temperature T2 so as to define a temperature difference TU, and c) printing the film region which is in contact with the receiving surface with drops of ink, wherein the film region which is in contact with the receiving surface undergoes a temperature change under the effect of a change in energy, said temperature change being produced when energy is supplied and/or drawn in such a manner that the temperature difference TU between the film region and the receiving surface is increased, and at the same time holding forces are applied to the film region via the receiving surface, said holding forces at least partly compensating, preferably compensating, and particularly preferably overcompensating, for at least the deformation forces produced parallel to the receiving surface by the temperature change in the film region so as to counteract same.

Description

Apparatus and method for printing under thermally stress-deforming films

The present invention relates to a printing apparatus and a method for printing under thermally stress-deforming films according to the preambles of claims 1 and 14.

A printer for printing on films is known from the prior art, comprising: I) a rotatable about an axis pressure roll with cylindrical roll shell, which a printing module in the direction of rotation of the pressure roller four successively arranged rows of nozzles, which are the roll shell spaced from each other assigned is, with the respective rows of nozzles different colors can be printed; II) means for tempering the roll shell to a temperature between 20 and 90 degrees Celsius, wherein the printer is adapted to be able to print on the film during which the film is moved across the roll shell away.

US 6 154 232 A describes a printing apparatus for printing on paper sheets comprising: I) a printing drum having a drum outer surface for receiving a paper sheet associated with a printing module comprising two sets of two rows of nozzles opposed to the drum outer surface, the width of a printing strip being the same ink printed on the paper sheet substantially corresponds to the sum of the print strips of two nozzle rows of the first set; II) means for driving the printing drum in a first direction of rotation, wherein the printer is adapted to be able to print on paper during which the printing drum is rotated in the direction of rotation. The printing drum in (I) is formed as a vacuum drum to secure the paper sheet during rotation in the direction of rotation from falling down. For this purpose, the printing drum is perforated with vacuum openings which extend between the interior of the printing drum and the drum outer surface and can be acted upon by negative pressure.

From DE102009007565A1 a guide device for guiding available as a material web or sheets of material flexible sheet material such as paper or plastic film, with at least one guide surface known about which can run away from the sheet and lead to serving to blow out air or other gases Gasausblaskanäle.

DE102013007300B4 also discloses a web guiding device for guiding a material web consisting of a flexible flat material, with at least one web deflecting unit.

The documents DE102009007565A1 and DE102013007300B4 are therefore only concerned with web guiding devices for deflecting flexible flat materials. On the other hand, the present invention is a printing apparatus for printing a film.

Different factors influence the printing process of a film. These include, among other things, the temperature, the heat capacity, the mass, the geometric dimensions and the material composition of the film used, as well as the energy that is supplied or withdrawn depending on their distribution on the film of the film. It should be noted that these factors influence each other.

Another factor influencing the printing process is the thermal expansion coefficient of a material of a film to be printed. A problem which causes low print quality when printing films having relatively high coefficients of thermal expansion is that they readily expand or contract during processing when subjected to thermal stresses.

The inventors have observed that printing a film with a prior art device with ink drops at a low selected temperature of the drops than the film increases the distortion and thus the deterioration of the printed image. On the other hand, it can be observed that at higher supplied energy in the form of, for example, IR and / or NIR irradiation during the printing process to at least partially vaporize and / or harden the ink drops, the distortion of the printed image also increases.

It can therefore be said in general terms that a temperature increase or decrease of the film resulting from the above-described influences during the printing process can lead to an image deterioration which results in an image deterioration Deformation of the film is due, whereby the ink drops can no longer hit their intended target positions in the stepwise construction of the printed image. This means that in the prior art, a temperature change of the film during the printing process must be avoided or at least kept as low as possible in order to obtain a handsome print image.

If one notes in a stepwise construction of a printed image, for example, during a single-pass printing process with a single-pass printing device, a film with a film width of 500 mm at a dot density of 600 dpi, d. H. is printed at a drop-to-drop distance of 42 μηι, while initially experiencing a shrinkage of 2 millimeters and then an extension of 3 millimeters, it will immediately clear what negative effects the deformation will have on the appearance of the print motif ,

In the context of this description, a single-pass printing device is understood to mean a printing device having a printing module for printing a film, in which the film is continuously moved in the operating mode and the printing module sees a region of the film only once, wherein the printing module does not act according to FIG known scanning method (ie line by line back and forth moving a pressure module) is operated, but is arranged stationary.

The fact is that common plastic materials, which are used for example in packaging films, but in fact almost always have a high coefficient of thermal expansion, which makes them very sensitive to temperature fluctuations during their processing, as shown in Table 1 below: Material Thermal material width SO ΔΤ1 AS1 ΔΤ2 AS2

Expansion [mm] [Kl [mm] [K] [mm] coefficient α [° K ¹ ]

Paper -13 x 10-6 500 10 0.065 40 0.26

Aluminum (Al) -23 X 10- ⁶ 500 10 0.115 40 0.46

Polyethylene ~ 80 x 10- ⁶ 500 10 0.4 40 1 6

Polyamide (nylon) -120 x 10 ⁶ 500 10 0.6 40 2.4

Polypropylene -150 x 0- ⁶ 500 10 0.75 40 3.0

Polyvinylchloride -175 x 10 ^"6 500 10 0.875 40 3.5

Polyethylene ^{(PE) -200 10- 6 500 10 1 40} 4.0

Table 1

The thermal expansion AS1 or AS2 typical plastic materials, for example, compared to paper, at the same temperature increase many times. For polyamide, polyvinyl chloride and polyethylene it is about 6 to 15 times that of paper.

Another factor that influences the printing process and plays a decisive role is the heat capacity of the film used. The heat capacity C of a substrate is by definition the ratio of the heat supplied to it (AQ) to the temperature increase (ΔΤ) caused thereby. The heat capacity of a substrate made of a homogeneous material can be calculated as the product of its specific heat capacity C and its mass m.

Since films naturally have relatively small thicknesses (ie thicknesses), typically in the range of 5 to 200 μιη, preferably in the range of 10 to 100 μι ^η , they are susceptible to temperature changes that are generated when energy is supplied to the film or withdrawn.

A combination of factors which further affects the printing of thermally stress-deforming films, when the film is a composite film consisting of several materials, in particular of these being layered. For example, this is the case when flexible films in addition to a plastic layer which carries the print motif, an effective barrier z. B. against migratory UV ink constituents is required. Such can be realized by providing a two-layer or multi-layer composite film comprising at least one metal layer, for example an aluminum layer. A problem that can occur when printing composite films with different coefficients of thermal expansion, is a deterioration of the print quality due to the so-called bimetallic effect, such that it bulges in prior art methods under thermal stress and the ink drops therefore no longer can get to their desired positions.

The composite film could even bulge so that it comes into contact with the usually only a few millimeters from the surface of the composite film opposing pressure nozzles, which z. B. would drag a smearing of the printing ink on the composite film with it.

There is therefore a need for an apparatus and a method for printing under thermally stress-deforming films having a relatively high thermal expansion coefficient, in which or in which the negative effects of thermal stress at least partially, preferably can be completely suppressed.

It is therefore an object of the present invention to provide an apparatus and a method for printing on thermally stress-deforming films having a relatively high coefficient of thermal expansion, in which the film or films despite thermal stress during a printing process can be kept substantially dimensionally stable.

This object is achieved by the device according to claim 1. Preferred embodiments of the device according to the invention are described in the subclaims.

According to claim 1, a printing device for printing on a thermally stress-deforming film is provided with at least one means for receiving at least a portion of a film having a receiving surface, the at least one printing module for printing the film with ink droplets comprising at least one row of nozzles which is spaced from the receiving surface opposite, is assigned, wherein the means for receiving comprises activatable holding means. According to the invention, the means for receiving means for controlling the temperature of the receiving surface.

Furthermore, the object is achieved by the method for printing on a thermally stress-deforming film according to claim 14, comprising the following steps:

Providing a printing device with at least one means for receiving at least one region of the film with a receiving surface, which is associated with at least one printing module comprising at least one row of nozzles which lies opposite the receiving surface at a distance,

Applying the region of the film having a temperature T1 to the receiving surface having a temperature T2, defining a temperature difference TU,

- Printing the area in contact with the receiving surface of the film with ink drops.

According to the invention, the procedure is such that a region of the film in contact with the receiving surface experiences a temperature change which is produced when energy is supplied and / or removed in such a way that an increase in the temperature difference TU occurs the area of the film and the receiving surface is effected, at the same time holding forces on the receiving surface are applied to the region of the film, which counteracts at least partially compensated, preferably compensated, and more preferably overcompensated at least the deformation forces caused by the temperature change in the region of the film parallel to the receiving surface ,

The film is thus, if it is subjected to thermal stresses on a receiving surface, held on the receiving surface by means of holding force in such a manner on the receiving surface, that the holding forces counteracting the parallel to the surface direction temperature-induced deformation forces counteracting at least partially compensated, preferably compensated, and particularly preferred overcompensated. The application of the holding forces thus serves not only and exclusively for the purpose of securing a substrate against possible dropping of the film from a receiving means, as is the case in US Pat. No. 6,154,232A, but serves according to the invention for the purpose of preventing the expansion described above and thus deformation of the applied to the receiving surface region of the film during the printing process, so that the film is held during its largely dimensionally stable. Only the above-disclosed solution can effectively avoid deterioration of print quality.

By contrast, deformations of the film before application to the receiving surface described above or after detachment of the film from the same receiving surface are unavoidable-on the contrary, they may even be desirable or at least not disturbing.

At the same time, the invention overcomes another problem inherent in conventional methods for printing on films having relatively high coefficients of thermal expansion when the region of the film undergoes an inhomogeneous temperature distribution due to energy input and / or output, since even this negative effect is achieved by the solution according to the invention largely prevented.

The cause of such an inhomogeneous temperature distribution can be based on different factors. These include, for example, the ink color and / or the ink application.

As is well known, dark inks heat up much more when exposed to heat than bright ones. The cause lies, inter alia, in the interaction of the ink concerned with the near infrared radiation (NIR), which, however, is not limited exclusively to the absorption of the electromagnetic radiation, in which the electromagnetic waves are converted into heat, but also to the heat radiation of the surface of the Ink, so the emission in the far infrared.

If a printed image according to the four-color printing and with an inhomogeneous color ink distribution was printed in the prior art and then exposed to IR and / or NIR irradiation, it inevitably experienced an inhomogeneous temperature distribution and thus an inhomogeneous deformation. The problem of an inhomogeneous temperature distribution occurring in the film during the printing process is thus also effectively remedied by the present invention.

The invention will now be described in detail and by way of example with reference to the figures.

Fig. 1 shows a schematic side view of a particularly preferred embodiment of the printing device according to the invention in cross section.

1 shows a roll-to-roll ink jet printing device for printing a film 100 with a means 101 for receiving a portion of the film 100 having a receiving surface 103, wherein the means for receiving 101 is formed as a rotatable about an axis pressure roller and wherein the receiving surface 103 is formed as a cylindrical roll shell.

The cylindrical rolling mantle is associated with four printing modules 105a, 105b, 105c, 105d, each comprising at least one row of nozzles (not shown) which are spaced apart from the rolling mantle. The respective printing modules 105a, 105b, 105c, 105d are each assigned an electromagnetic radiation source 106a, 106b, 106c, 106d for at least partial curing and / or at least partial evaporation of the ink drops applied to the film 100 in the direction of rotation (arrow) of the pressure roller downstream.

Advantageously, by using one or more electromagnetic radiation sources, such as, for example, an IR and / or NIR radiation source and / or UV radiation source, undesired wetting behavior of the ink droplets printed on the film can be avoided since they no longer have sufficient time to disperse to run or pull together (depending on the wetting behavior: no wetting, partial wetting, complete wetting).

For preheating the film 100, the printing device comprises a pre-tempering roller 115 with two associated nip rollers 117, which are designed to press the film 100 movable over the pre-tempering roller 115 against the pre-tempering roller 115.

Advantageously, the energy transfer from the roller to the film can be improved by this arrangement. The pre-tempering roller can be in a range between 20 and 100 degrees Celsius, preferably between 50 and 90 degrees Celsius, tempered.

As shown in Figure 1, the film 100 can by means of a unwinding device (not shown) of a film roll 127 via a device for tension control, which is designed as a dancer roller 133, and a pre-tempering roll 115, a guide roller 119, a pressure roller, another guide roller 121, a cooling roller 123 for cooling the film 100 and a second dancer roller 135 away and be rewound by means of a take-up device (not shown) as a film roll 129.

The rollers or rollers described are mounted on a frame 131 of the printing device, wherein feet 134 are attached to the frame.

The cooling roll 123 are also associated with three nip rolls 125 which are adapted to press the film 100 movable over the cooling roll 123 against the cooling roll 123.

The pressure roller with cylindrical roller shell comprises means for temperature control of the receiving surface 103 and activatable holding means which are formed by vacuum beauf bare suction channels and extending through a layer 104 to the cylindrical roll shell down and open on the cylindrical roll shell as suction openings (not shown). The layer 104 forms the receiving surface 103.

According to the invention, the activatable hardening agents are designed such that the area of the film 100 that is in contact with the receiving surface 103 undergoes a temperature change, which is generated when energy is supplied and / or extracted in such a way, at the same time as a result of an energy change Holding forces on the receiving surface 103 can be applied to the region of the film 100, which are so large that at least the deformation forces caused by the temporary temperature change in the region of the film 100 parallel to the receiving surface 103 at least partially compensated, preferably compensated, and particularly preferably overcompensated , The pressure roller is mounted on a hollow shaft 102, wherein the pressure roller and thus the cylindrical roller shell can be acted upon by a hollow shaft passing through the tube (not shown) by means of a vacuum generator (not shown) with a certain negative pressure. The cylindrical roll shell is either via a hollow shaft 102 passing through the second tube by means of a tempered liquid or current means (not shown) to an arbitrary temperature in a range between 20 and 100 degrees Celsius, preferably between 50 and 90 degrees Celsius, tempered.

An energy means may be a heating resistor that can convert electrical energy into thermal energy.

The printing device further comprises a drive means (not shown), which can act on the pressure roller directly or indirectly unidirectionally or bidirectionally with a predetermined torque.

The printing apparatus additionally comprises a control unit 132 for carrying out a printing method according to the invention.

There has been disclosed a printing apparatus for printing a thermally stress-deforming film 100 having at least one means 101 for receiving 101 at least a portion of a film 100 having a receiving surface 103 comprising at least one printing module 105a, 105b, 105c, 105d for printing the film with ink droplets comprising at least one row of nozzles, which is spaced from the receiving surface 103, is associated, wherein the means for receiving 103 comprises activatable holding means.

According to the invention, the means for receiving 101 comprises means for controlling the temperature of the receiving surface 103.

In a preferred embodiment of the invention, the activatable holding means are designed so that during exposure of the receiving surface 103 in contact area of the film 100 undergoes a change in temperature caused by a change in energy, which is generated when energy supplied in such a manner and / or At the same time holding forces can be applied over the receiving surface 103 on the region of the film 100, which are so large that at least by the temporary temperature change in the region of the film 100 parallel to the receiving surface 103 caused deformation forces counteracting at least partially compensated, preferably compensated, and more preferably overcompensated.

In a further preferred embodiment of the invention, the activatable holding means are formed by suction channels which can be acted upon by vacuum and which extend from the interior of the means for receiving 101 to the receiving surface 103 and open at the receiving surface 103 as suction openings.

In a particularly preferred embodiment of the invention, the means for receiving 101 comprises a layer 104, which comprises the suction channels, wherein the layer 104 forms the receiving surface 103.

The layer 104 is preferably formed of nano- and / or microporous material.

The suction openings may be formed as nano and / or micro-openings.

If in the context of the invention of micro-openings is spoken, as are openings with a size between 1 pm to 200 yim, preferably 1 μιη understood to 100 μητι. If, on the other hand, nano-apertures are used, they are understood as meaning openings with a size smaller than 1 [im.

In a particularly preferred embodiment of the invention, the at least one means 101 for receiving a portion of the film 100 is formed as a rotatable about an axis pressure roller and the receiving surface 103 is formed as a cylindrical roll shell, wherein the pressure roller is adapted to rotate the film 100 in a rotational direction , whereby a feed direction of the film 100 is defined.

In a further particularly preferred embodiment of the invention, the pressure roller is mounted on a hollow shaft 102, wherein the pressure roller and thus the cylindrical roller shell can be acted upon by means of a hollow shaft by means of vacuum means with a certain negative pressure via a hollow shaft. he cylindrical roll mantle can either by means of a hollow shaft 102 passing through the second tube by means of a tempered liquid or by means of current to an arbitrary temperature in a range between 20 and 100 degrees Celsius, preferably between 50 and 90 degrees Celsius, tempered. In a preferred embodiment, at least two, preferably at least four, pressure modules 105a, 105b, 105c, 105d are arranged at a distance from one another in the direction of rotation relative to one another.

In a further preferred embodiment, at least one corresponding electromagnetic radiation source 106a, 106b, 106c, 106d for the at least partial curing and / or at least partial vaporization of the film applied to the film is or downstream of the pressure modules 105a, 105b, 105c, 105d in the direction of rotation of the pressure roller downstream Associated with drops of ink.

The at least one electromagnetic radiation source 106a, 106b, 106c, 106d can be embodied as an IR and / or NIR radiation source.

The at least one IR and / or NIR radiation source can be arranged between at least two pressure modules 105a, 105b, 105c, 105d.

In a particularly preferred embodiment, the printing device comprises a pre-tempering device for pre-tempering the film 100, which is preferably tempered in a range between 20 and 100 degrees Celsius, more preferably between 50 and 90 degrees Celsius, wherein the pre-tempering in the feed direction of the film 100 relative to the pressure roller is arranged upstream. The pretempering device is preferably designed as a pre-tempering roller 115.

In a further particularly preferred embodiment, the printing device comprises a cooling device for cooling the film 100, which is preferably tempered in a range between 20 and 40 degrees Celsius, wherein the cooling device is arranged in the feed direction of the film 100 relative to the pressure roller downstream. The cooling device is preferably designed as a cooling roller 123.

In another particularly preferred embodiment, the printing device comprises a final curing and / or evaporation device for complete curing and / or evaporation of the printed ink drops. This can be part of an aftertreatment device. In a further particularly preferred embodiment of the invention, the printing device comprises a roll-to-roll printing device, in particular a roll-to-roll ink jet printing device.

In a preferred embodiment, the printing device comprises a drive means which can act on the pressure roller directly or indirectly unidirectionally or bidirectionally with a predetermined torque. The drive means may be an electric drive motor.

The roll-to-roll printing device may comprise a device for unwinding and / or winding the film in the form of a continuous film web from or to a winding core, which preferably each comprises a drive means which directly or indirectly uni or bidirectionally the respective winding core can act on a predetermined torque.

In a particularly preferred embodiment, the printing device comprises at least two successive pressure rollers each having a cylindrical roll shell.

In a particularly preferred embodiment, the printing device or the roll-to-roll printing device is designed as a single-pass printing device.

It should be pointed out here that the printing apparatus may additionally comprise means for cleaning the film of soiling and / or means for aligning the film or film web and / or means for pretreating the film, such as a corona treatment unit.

For the sake of order, it should be pointed out that for a better understanding of the construction of the printing device, these or their components have been shown partly unevenly and / or enlarged and / or reduced in size.

With reference to FIG. 1, a particularly preferred embodiment of the method according to the invention for printing under thermally stress-deforming films is described below.

In a first step, a printing device with a means for receiving 101 at least a portion of a film 00, which is formed as a pressure roller, provided. The pressure roller comprises a receiving surface 103, which is formed as a cylindrical roll shell, the four printing modules 105a, 105b, 105c, 105d comprising at least one nozzle row (not shown) which are spaced from the receiving surface 103, associated.

In the exemplary process, a pressure roller with a cylindrical roller shell with a diameter of 1.4 meters was provided as the pressure roller.

In a second step, the film 100 is pre-tempered by means of a pre-tempering roller 15 to a temperature of 88 degrees Celsius and in a third step on the roll shell at a temperature T1 of 88 degrees Celsius, which roll jacket is heated to a temperature T2 of 90 degrees Celsius , applied. Temperature T1 and temperature T2 define a temperature difference TU of 2 degrees Celsius.

In a fourth step, the area of the film 100 in contact with the roll shell is printed by the ejection of water-based ink droplets at a temperature of 40 degrees Celsius from the nozzles of the nozzle rows of the four printing modules 105a, 105b, 105c, 105d.

In a fifth step, the ink drops are successively at least partially vaporized by means of the electromagnetic radiation sources disposed downstream of the pressure modules 105a, 105b, 105c, 105d as IR and / or NIR radiation sources 106a, 106b, 106c, 106d.

During this, the area of the film 100 in contact with the roll shell undergoes a temperature change, which is produced when energy is removed by printing with ink droplets of a lower temperature than the area of the film 100 in contact with the roll shell and at the same time at least partially drying the water-based ink droplets printed on the area of the film 100 in contact with the roll shell by IR and / or NIR irradiation, so that an increase in the temperature difference TU between the area of the film 100 and the receiving surface 103 is effected; At the same time holding forces are applied to the region of the film 100 via the receiving surface 103, which at least counteracts at least the deformation forces caused by the temperature change in the region of the film 100 parallel to the receiving surface 103 partially compensated, preferably compensated, and most preferably overcompensated.

A method has been disclosed for printing on a thermally stress-deforming film 100, comprising the following steps: a) providing a printing device having at least one means for receiving 101 at least a portion of the film 100 having a receiving surface 103, the at least one printing module 105a 105b, 105c, 105d comprising at least one row of nozzles which is opposite the receiving surface 103, b) applying the region of the film 100 having a temperature T1 to the receiving surface 103 having a temperature T2, defining a temperature difference TU, c) printing of the area of the film 100 in contact with the receiving surface 103 with ink droplets

According to the invention, while the area of the film 100 in contact with the receiving surface 103 undergoes a temperature change, which is generated when energy is supplied and / or extracted in such a way that an increase in the temperature difference TU between the region the film 100 and the receiving surface 103 is effected at the same time holding forces on the receiving surface 103 applied to the region of the film 100, which counteracts at least partially compensated by the deformation in the film 100 parallel to the receiving surface 103 caused deformation forces at least partially, preferably compensated, and particularly preferably overcompensated.

A preferred embodiment of the method according to the invention is characterized in that, at the same time, the region of the film 100 in contact with the receiving surface 103 is supported by a reduction of a current temperature difference TU by the action of an additional energy change by energy exchange between the receiving surface 103 and the region of the film 100. and preferably, thereby at least partially re-equalizing a current temperature of the region of the film 100 is supported to the temperature T2, and preferably takes place.

In a preferred embodiment of the method, the holding forces are applied as vacuum holding forces via holding means, which are formed by vacuum acted upon suction channels extending from the interior of the means for receiving the receiving surface 103 and open at the receiving surface 103 as suction openings.

In a further preferred embodiment of the method, the means for receiving as means for receiving comprising a layer 104 is provided which comprises suction channels, wherein the layer 104 forms the receiving surface 103 and wherein the layer is preferably formed of nano- and / or microporous material.

The receiving surface 103 can be provided as a receiving surface 103, the suction openings are chosen so small that the areas of the film 100 directly affected by the suction openings can be kept dimensionally stable with respect to the action of vacuum holding forces, i. the affected areas of the film 100 are not plastically deformed by the vacuum holding forces (suction forces).

In a particularly preferred embodiment of the invention, the receiving surface 103 is provided as a receiving surface 103, the suction openings are formed as nano and / or micro-openings.

The area of the film 100 can be pre-tempered prior to application to the receiving surface 103 so that it has a temperature T1 at the moment of application to the receiving surface 103, which compared to the temperature T2 a temperature difference TU in a range between at least 0 and 10 degrees Celsius , preferably between 0 and 5 degrees Celsius.

In some embodiments of the method according to the invention, in particular when the film 100 is printed with ink drops of a lower temperature than the film 100, it may be advantageous if the film 100 has a slightly lower temperature at the moment of application to the receiving surface 103. As a result, stronger deformation forces, due to the lower temperature difference, prevent it during the printing process.

The area of the film 100 can therefore be pre-tempered prior to application to the receiving surface 103 so that it has a temperature T1 at the moment of application to the receiving surface 103, which in relation to the temperature T2 in a range between at least 2 and 10 degrees Celsius, preferred tempered between 2 and 5 degrees Celsius lower.

In a preferred embodiment, the holding forces can be determined as a function of a predetermined maximum temperature change and taken into account in the control of the holding forces in a manner that the counteracting deformation forces at least partially compensated, preferably compensated, and more preferably overcompensated.

In a particularly preferred embodiment, printing is carried out with ink drops of a lower temperature than the region of the film 100 that is in contact with the contact surface 103, so that the temperature change in the region of the film 100 is produced by energy removal. The cause of the energy deprivation is thus the ink with its lower temperature compared to the film.

In a preferred embodiment, according to a method step d), an at least partial evaporation and / or hardening of the ink droplets printed on the area of the film 100 in contact with the receiving surface 103 takes place by IR and / or NIR irradiation, so that the temperature change is generated by energy input.

In a further preferred embodiment, according to a process step e), instead of the process step d) or supporting it, air at a temperature between 15 and 180 ° C by means of a blowing air on the printed on the receiving surface 103 in contact area of the film 100 printed Blown ink drops, so that the temperature change is generated accordingly by energy extraction or energy supply. This approach is advantageous because, inter alia, an insulating air layer covering the ink can be eliminated more quickly. The steps d) and e) can be performed separately or simultaneously.

The hardening of the ink droplets can take place instead of or in addition to step d) in a step f) by UV irradiation.

In a preferred embodiment of the method according to the invention, the receiving surface 103 before step b) by means for temperature control to a certain temperature 12 in a range between 50 and 100 degrees Celsius, preferably between 60 and 100 degrees Celsius, more preferably between 80 and 100 degrees Celsius tempered and at least during the following steps b) and c) maintained at this temperature at least partially constant, preferably kept constant.

In a particularly preferred embodiment, a water-based ink is used as the ink.

Water-based inks make it possible to realize thinner cured ink films on a substrate than the conventional acrylate-based UV inks, which consist largely of one or more monomers. Advantageously, it is also possible to save expensive acrylate monomer as starting material.

The temperature of the ink drops may be lower than the current temperature of the area of the film 100 lower temperature in the range between 20 and 60 degrees Celsius, preferably 30 and 50 degrees Celsius.

As the water-based ink, a water-based hybrid ink comprising as components (a) water, (b) UV-curing oligo- and / or polymer having ethylenically unsaturated functional groups, (c) a humectant and (d) a radical-forming photoinitiator can be used.

When used in the context of this specification, an oligomer is understood to mean a molecule having a molecular weight in the range of between 1,000 and 10,000 inclusive. If, however, spoken in the context of this description of a polymer, so is a molecule with a molecular weight greater than 10,000 to understand.

A preferred hybrid ink comprises the following component: (a) 20 to 70%, preferably 40 to 70% component (a),

(b) 5% to 50%, preferably 05 to 25% component (b),

(c) 02 to 40%, preferably 05 to 30% component (c),

(d) 0.1 to 05%, preferably 0.5 to 3.0% component (d)

For the purposes of this description, the percent sign "%" is used in terms of weight percentages.

The application of the film 100 to the receiving surface 103 may take place under a predetermined first drawing tension in a first direction and a second drawing tension vertically opposite to the first direction, wherein the first and second pulling tension is zero or non-zero.

In a particularly preferred embodiment, the application of the film to the receiving surface 103 takes place under a first drawing tension of <1500 N, in particular <700 N and a second drawing tension of preferably <300 N, in particular <200 N.

The film 100 may be provided as an elastically deformable film 100.

The film 100 may be provided as a film 100 comprising a thermoplastically deformable plastic.

The film 100 may be provided as a multilayer composite film comprising at least one thermoplastically deformable plastic layer and optionally at least one metal layer and / or at least one paper layer.

In a preferred embodiment, the film 100 used is a film 100 with at least one layer which has a thermal expansion coefficient α of at least 40 * 10 ^-6 * "K ^{" 1} , preferably at least 70 * 10 ⁶ * ° K " ¹ .

The film 100 is typically provided with a thickness between 5 and 200 μιτι, preferably 10 and 100 μιη.

In a particularly preferred embodiment, the method comprises the following steps: Providing a pressure roller rotatable about an axis 102 as a means for receiving 101 with a cylindrical roller shell as a receiving surface 103,

Driving the pressure roller in a direction of rotation, wherein during the rotation a synchronous entrainment of the film 100 takes place in the direction of rotation of the pressure roller,

- Printing the film 100 with drops of ink

The printing device may be provided as a roll-to-roll printing device, in particular as a roll-to-roll ink jet printing device, such that the film 100 is processed in the form of a continuous film web from the roll and continuously applied to the cylindrical roll shell.

The pre-tempering can take place by means of a pre-tempering device, which is preferably designed as a pre-tempering roller (115), over which the film 100 is guided.

Typically, a film 100 having a width in a range between at least 100 mm and 1000 mm is provided as film 100.

Claims

Claims:

A printing device for printing a film (100) which deforms under thermal load, having at least one means for receiving (101) at least one region of a film (100) having a receiving surface (103) which has at least one printing module (105a, 105b, 105c, 105d) for printing the film with ink droplets comprising at least one row of nozzles, which is opposite the receiving surface (103) spaced apart, wherein the means for receiving (103) activatable holding means comprises, characterized in that the means for receiving (101) means for temperature control the receiving surface (103).

2. Printing device according to claim 1, characterized in that the activatable holding means are designed so that while the receiving surface (103) in contact area of the film (100) undergoes a change in temperature under the action of a change in energy, which is generated when energy in such a manner fed and / or withdrawn, at the same time holding forces on the receiving surface (103) on the region of the film (100) can be applied, which are so large that at least by the temporary temperature change in the region of the film (100) deformation forces caused parallel to the receiving surface (103) counteracting at least partially compensated, preferably compensated, and more preferably overcompensated.

3. A printing device according to claim 1 or 2, characterized in that the activatable holding means are formed by vacuum acted upon suction channels extending from the interior of the means for receiving the receiving surface (103) out and open on the receiving surface (103) as suction openings on the by means of a vacuum generator, a negative pressure on the film (100) can be acted upon.

4. Printing device according to claim 3, characterized in that the means for receiving (101) comprises a layer (104) comprising the suction channels, wherein the layer (104) forms the receiving surface (103), wherein the layer is preferably made of nano- and or microporous material is formed.

5. Printing device according to claim 3 or 4, characterized in that the suction openings are designed as nano and / or micro-openings.

6. A printing device according to at least one of the preceding claims, characterized in that the at least one means for receiving (101) of the region of the film (100) is designed as a rotatable about an axis pressure roller and the receiving surface (103) is formed as a cylindrical roll shell, wherein the pressure roller is adapted to rotate the film (100) in a rotational direction, thereby defining a feeding direction of the film (100).

7. A printing device according to claim 6 characterized countersigns, that the pressure roller is mounted on a hollow shaft (102), wherein the pressure roller and thus the cylindrical roller shell can be acted upon by means of a hollow medium by means of vacuum means with a certain negative pressure via a hollow shaft.

8. A printing device according to claim 6 or 7 characterized countersigns that the cylindrical roll shell either via a hollow shaft (102) passing through the second tube by means of a tempered liquid or flow means at least the cylindrical roll shell to an arbitrary temperature in a range between 20 and 100 degrees Celsius, preferably between 50 and 100 degrees Celsius, more preferably between 60 and 100 can be tempered.

9. Printing device according to at least one of claims 6 to 8, characterized in that at least two, preferably at least four printing modules (105a, 105b, 105c, 105d) are arranged spaced apart in the direction of rotation.

10. Printing device according to at least one of claims 6 to 9, characterized in that the printing module or the printing modules (105a, 105b, 105c, 105d) in the direction of rotation of the pressure roller downstream at least one corresponding electromagnetic radiation source (106a, 106b, 106c, 106d) for at least partial hardening and / or at least partial evaporation of the ink droplets applied to the film (100) is or are associated with, wherein the electromagnetic radiation source is preferably formed as an IR and / or NIR radiation source.

11. Printing device according to at least one of claims 6 to 10, characterized in that the printing device for pre-tempering the region of the film (100) comprises a pre-tempering device, which is preferably designed as Vortemperierwalze (115), which preferably in a range between 20 and 100 Degrees Celsius, more preferably between 50 and 90 degrees Celsius is temperature-controlled, and which is arranged in the feed direction of the film (100) opposite the pressure roller upstream.

12. Printing device according to at least one of the claims, characterized in that the printing device is a roll-to-roll printing device, in particular a roll-to-roll ink jet printing device.

13. Printing device according to at least one of claims 6 to 12, characterized in that the printing device comprises a control unit for carrying out a method according to at least one of claims 14-36.

14. A method for printing on a thermally stress-deforming film (100) comprising the steps of: a) providing a printing device with at least one means for receiving (01) at least a portion of the film (100) having a receiving surface (103) Printing module (105a, 105b, 105c, 105d) comprising at least one row of nozzles, which is associated with the receiving surface (103) spaced opposite, b) applying the region of the film (100) having a temperature T1 on the receiving surface (103) having a temperature T2 , defining a temperature difference TU, c) printing the area of the film (100) in contact with the receiving surface (103) with ink droplets, during which the area of the film (100) in contact with the receiving surface (103) is exposed to a Energy change undergoes a change in temperature, which is generated when energy is supplied and / or withdrawn in such a way that a vergr Greater temperature difference TU between the region of the film (100) and the receiving surface (103) is effected at the same time holding forces on the receiving surface (103) are applied to the region of the film (100), at least by the temperature change in the region of the film (100) parallel to the receiving surface (103) caused deformation forces counteracting at least partially compensated, preferably compensated, and more preferably overcompensated.

15. The method according to claim 14, characterized in that at the same time with the receiving surface (103) in contact area of the film (100) under the action of an additional energy change by energy exchange between the Receiving surface (103) and the region of the film (100) a reduction of a current temperature difference TU is supported, preferably carried out, whereby at least partially re-equalization of a current temperature of the region of the film (100) is supported to the temperature T2, preferably.

16. The method according to any one of claims 14 or 15, characterized in that the holding forces are applied as vacuum holding forces via activated holding means which are formed by vacuum acted upon suction channels extending from the interior of the means for receiving (101) to the receiving surface (103) and open at the receiving surface (103) as suction openings.

17. The method according to at least one of the preceding claims 14 to 16, characterized in that the region of the film (100) prior to application to the receiving surface (103) is preheated so that it at the moment of applying to the receiving surface (103) a temperature T1, which compared to the temperature T2 has a temperature difference TU in a range between 0 and 10 degrees Celsius, preferably between 0 and 5 degrees Celsius.

18. The method according to at least one of the preceding claims 14 to 17, characterized in that the region of the film (100) prior to application to the receiving surface (103) is preheated so that it at the moment of application to the receiving surface (103) a temperature T1, which is tempered lower than the temperature T2 in a range between at least 2 and 10 degrees Celsius, preferably between 2 and 5 degrees Celsius lower.

19. The method according to at least one of the preceding claims 14 to 18, characterized in that the holding forces determined in response to a predetermined maximum temperature change and these are taken into account in the control of the holding forces in such a way that the induced deformation forces counteracting at least partially compensated, preferably compensated , and most preferably overcompensated.

20. The method according to at least one of the preceding claims 14 to 19, characterized in that the printing with ink drops of a lower temperature than the contact surface with the contact surface (103) in contact Film (100) takes place so that the temperature change in the region of the film (100) is produced by energy removal.

21. Method according to claim 14, characterized in that the method comprises a further step: d) at least partial evaporation and / or curing of the ink drops printed on the area of the film (100) in contact with the receiving surface IR and / or NIR irradiation and / or UV irradiation so that the temperature change is generated by energy input.

22. The method according to claim 21, characterized in that in a step e), either instead of the process step d) or supportive, air at a temperature between 15 and 180 ° C by means of a blown air on the in contact with the receiving surface 103 in contact Area of the film 100 printed ink drops is blown, so that the temperature change is generated accordingly by energy extraction or energy supply.

23. The method according to at least one of the preceding claims 14 to 22, characterized in that the receiving surface (103) before step b) by means for temperature control to a certain temperature T2 in a range between 50 and 100 degrees Celsius, preferably between 60 and 100 degrees Celsius, more preferably tempered between 80 and 100 degrees Celsius and at least during the following steps b) and c) held at this temperature at least partially constant, preferably kept constant.

24. The method according to claim 14, characterized in that the temperature of the ink drops is a temperature which is lower than the current temperature of the region of the film (100) in the range between 20 and 60 degrees Celsius, preferably 30 and 50 degrees Celsius, is.

25. The method according to at least one of the preceding claims 14 to 24, characterized in that a water-based ink is used as the ink.

26. The method according to at least one of the preceding claims 25, characterized in that the water-based ink is a water-based hybrid ink comprising as components (a) water, (b) UV-curable oligo- and / or polymer having ethylenically unsaturated functional groups, (c) a humectant and (d) a radical-forming photoinitiator.

27. The method according to claim 14, characterized in that the foil (100) is applied to the receiving surface (103) under a predetermined first drawing tension in a first direction and a second drawing tension vertically opposite to the first direction first and second pull tension is zero or nonzero, the application of the film (100) to the receiving surface (103) preferably below the first pull tension of <1500 N, in particular <700 N and the second pull tension of preferably <300 N, in particular < 200 N takes place.

28. Method according to claim 14, wherein the film is provided as an elastically deformable film.

29. The method according to at least one of the preceding claims 14 to 28, characterized in that the film (100) is provided as a film (100) comprising a thermoplastically deformable plastic.

30. The method according to at least one of the preceding claims 14 to 29, characterized in that the film (100) is provided as a multilayer composite film, comprising at least one thermoplastically deformable plastic layer and optionally at least one metal layer and / or at least one paper layer.

31. The method according to at least one of the preceding claims 14 to 30, characterized in that as a film (100) a film (100) is selected with at least one layer having a thermal expansion coefficient α of at least 40 * 10 ^"6 * ⁰ K ^" , preferably at least 70 * 10 ' ^{6 *} ° K ^{' 1} .

32. The method according to at least one of the preceding claims 14 to 31, characterized in that the film (100) with a thickness between 5 and 200 μιη, preferably 10 and 100 pm is provided.

33. The method according to at least one of the preceding claims 14 to 32, characterized in that the method comprises the following steps:

Providing a pressure roller rotatable about an axis (102) as a means for receiving (101) with a cylindrical roller casing as a receiving surface (103),

- Driving the pressure roller in a rotational direction, wherein during rotation, a synchronous entrainment of the film (100) takes place in the direction of rotation of the pressure roller,

- Printing the film (100) with ink drops

34. The method according to claim 33, characterized in that the printing device is provided as a roll-to-roll printing device, in particular as a roll-to-roll ink jet printing device, so that the film (100) is processed in the form of a continuous film web from the roll and continuously on the cylindrical roll shell is applied.

35. The method according to at least one of the preceding claims 14 to 34, characterized in that the Vortemperierung by means of a Vortemperiereinrichtung, which is preferably designed as Vortemperierwalze (115) takes place, via which the film (100) is guided.