EP1839894A1 - Pictographic transfer printing process - Google Patents

Abstract

The method involves guiding a transfer foil (5) around or tangentially over a pressing device. A coating or ingredients of the coating is remained on the transfer foil after the withdrawal of a printing sheet from a transfer gap (6). Image-moderate motives e.g. alphanumeric characters, structures, picture motives, hologram, metallic structures, or special partially applied coatings, are partially included in the transfer foil, where the transfer foil is not holohedrally coated. Independent claims are also included for the following: (1) a transfer foil for utilization in a pictographic transfer printing method (2) a transfer printing system.

Description

The invention describes a pictorial transfer printing process for use in sheet-fed rotary printing presses.

As a transfer process in the printing industry, the so-called hot foil stamping has found widespread use. In hot foil stamping a transfer film is used, which usually has a wax layer as a release layer. The imaging layers, usually metallic layers, are then applied to this release layer. By means of a heated embossing stamp, the metallic layers are partially transferred from the carrier material to the printing substrate.

Due to the relatively low resolution of the image structures and the low processing speed, cold transfer processes have become widely accepted in the printing industry. So is in the EP 0 569 520 B1 a printing material and a printing apparatus using this material are described. In this case, a sheet-processing printing machine is shown, which has a feeder and a boom, wherein printing units and coating units are arranged between the two units. In at least one of the printing units, an adhesive pattern is applied by means of the planographic printing process. This adhesive pattern is applied in a cold printing process and has a specific imaging subject. In the printing unit following coating unit with a counter-pressure cylinder and a press roller a film guide is provided. This is designed in such a way that from the film supply roll, a film strip or a transfer film is passed through the nip between the impression cylinder and press roll. When transporting the sheets through the printing unit, each sheet is provided with an adhesive pattern. Thereafter, the sheet is passed through the coating unit, wherein by means of the press roller resting on the impression cylinder printed sheet with the film material in combination is brought. The downwardly lying, mostly metallic layer forms a close connection with the areas provided with adhesive. After further transporting the printing sheet, the transferred layer adheres only in the area of the pattern provided with adhesive. The carrier film is thus removed only the transfer layer in the region of the adhesive pattern. The used in this way transfer film is wound up again. It is known to use such coating units, for example in printing units of printing presses. It is also known to use as a press roll, for example, the blanket cylinder or printing cylinder of a printing unit.

The disadvantage of this type of device that they work with two printing units. That's why it shows WO 2005/100028 a further development of the cold foil transfer process by the method is carried out using the individual elements in a printing unit. In a first embodiment, an adhesive pattern is applied directly to the film. Thereafter, the image-forming layer is transferred in the desired subject with a press nip directly to the substrate. It is also proposed in the said patent specification to control the film advance in such a way that the transfer film is stopped when there is no transfer of the imaging or metallization layer. The two publications EP 0 569 520 B1 and WO 2005/100028 It is common that the image-wise structuring is carried out by the adhesive application and the transfer layer is detached at points from the carrier film of the transfer film, at which the transfer film comes into contact with the imagewise structured adhesive application.

However, it is obvious to anyone that with the method of cold foil transfer only relatively thin transfer layers can be transferred, since otherwise the adhesive force is no longer sufficient to replace the layer to be transferred. However, a thicker layer would also mean that the internal relationship of the transfer layer is higher. An edge-to-edge peeling, as required in the printing sector, would therefore not be possible with most materials. Rather, a detachment of larger areas is to be expected if the adhesive force of the adhesive is even sufficient to replace the transfer layer.

In addition to a lack of edge sharpness, this leads to particles which are not firmly connected to the printing substrate outside the area of the adhesive application. This can lead to disturbances in the printed image and to machine pollution.

However, many applications are known in which a higher layer thickness would be required. An example is the transfer of tactile surfaces, the transfer of scratch-offs to the facile coverage of loose fields or conductive layers in Locost electronics applications.

The cold foil transfer process, as described in the patents EP 0 569 520 B1 and WO 2005/100028 is disclosed, is also only conditionally suitable for a transfer of high-quality security elements, since they require complex manufacturing processes that can not be represented with the simple elements of the known cold foil transfer process. However, holograms can be transferred to substrates using transfer methods, as many applications show. Usually, the hot foil stamping method is used for the transfer of such holograms and other expensive security elements. Also, the known cold foil transfer method is a static printing method, that is, the transfer of variable image data is not possible. Variable image data can be, for example, numbering, but also personalized texts or changing images.

The object of the invention is to further develop the known methods of cold foil transfer so that the transfer of high layer thicknesses with these methods is possible. In a further development, the process is developed further, so that security elements, such as holograms, can be transmitted.

The transmission of high layer thicknesses in a cold foil transfer process essentially takes place in that the image motif, for example an image, a circuit, an antenna, an alphanumeric text or a haptic Structure, is printed, this external printed motif is guided around the press roller. The transfer of the printed motif takes place after an adhesive application to the printing substrate in a press nip between the press roller and the impression cylinder. The adhesive application to the printing substrate can be carried out by a printing unit or another suitable device, for example a spray nozzle, in front of the press nip between the press roll and the impression cylinder, the adhesive being applied in a planar, partial or motif-related manner. In a further embodiment of the invention is not applied, as in the aforementioned embodiment, the adhesive to the printing substrate, but the adhesive is applied directly to the transfer belt before passing through the press nip. For the application of adhesive to the transfer belt known devices, such as roller units, flexographic printing units, spray nozzles and all suitable devices can be used.

The application of the image motif on the transfer belt can be carried out with a flexographic printing unit, in particular a flexographic printing unit with chambered doctor blade and anilox roller, with one or a multiplicity of inkjet devices, with a flat screen printing unit, a rotary screen printing unit or a gravure printing unit.
The press roller may be a separate roller which is set against the impression cylinder of a printing machine during the transfer operation or the press roller is a blanket cylinder of a printing unit or a forme cylinder of a coating unit.

In an advantageous development of this claim of the invention, the printed motif is dried or transferred from the transfer belt to the printing substrate. This has the advantage that the printing layer is not crushed in the press nip between the press roll and impression cylinder. A dry print on the transfer ribbon can be achieved by using a fast-drying paint or coating. Such a paint or coating could be, for example, a waxy ink or coating, a solvent-containing ink or coating. Alternatively, the print motif may also be replaced by a drying or curing device after application be dried or cured on the transfer belt. Examples of such drying devices would be hot air dryers (convection dryers), infrared dryers, radiation dryers, such as UV or electron beam dryers or microwave dryers.

According to the invention, after the transfer of the print motif from the transfer belt to the printing substrate in the press nip between the press roller and impression cylinder, the transfer belt can be rolled up again. The transfer belt is thus consumed used and disposed of after the transfer. In a further development of the claim of the invention, the transfer belt can also be used circumferentially, that is, the transfer belt is optionally cleaned after the transfer and newly provided with a motif. In both cases, it is advantageous to synchronize the transfer belt with the printing press so that the print image printed in the printing machine and the transferred image fit together. Synchronization can be achieved by evaluating one or more measuring marks on the transfer belt with a suitable sensor, for example an optical sensor. Detected deviations can be adjusted and corrected by means of dancer rolls or electric drives. Also, a mechanical synchronization is conceivable by the transfer belt has lateral rows of holes by engaging pins of a synchronization roller.

In the following the invention is illustrated in more detail with reference to drawings:

Figur 1:

eine grundsätzliche Darstellung einer Bogen verarbeitenden Maschine mit einer Vorrichtung zur Durchführung des Transferdruckverfahrens

Figur 2:

eine Vorrichtung zur Durchführung des Transferdruckverfahrens in einer Arbeitseinheit und

Figur 3:

eine Vorrichtung zur Durchführung des Transferdruckverfahrens mit einem umlaufenden Transferfolienband

Showing:

FIG. 1:

a basic illustration of a sheet-processing machine with a device for carrying out the transfer printing process

FIG. 2:

a device for carrying out the transfer printing process in a working unit and

FIG. 3:

a device for carrying out the transfer printing process with a circulating transfer ribbon

In principle, according to the invention, the described transfer printing processes are provided in all devices according to FIGS. 1 to 3.

In one exemplary embodiment, documented in FIG. 1, the embodiment of the embodiment according to the invention with a consumable transfer belt is to be explained. In contrast, the representation of the embodiment according to the invention with a circulating transfer belt has been dispensed with, but it is clear to anyone skilled in the art that in this case the up and unwind stations 8 and 9 are dispensed with and the transfer belt 5 can be operated circumferentially via deflection rollers. The circulating transfer belt has the advantage that the elimination of the film supply roll 8 and the film collection roll 9 makes it easier to integrate a more complex printing unit, such as a flexo or a screen printing unit. As shown in Fig. 1, the transfer belt 5 is unrolled from the film supply roll 8 and then printed with a printing device 27, shown here as an ink jet device. After printing with the printing device 27, the ink or coating applied to the transfer belt is optionally dried or cured by a drying or curing device 28. The position of the transfer belt relative to the cylindrical position of the blanket cylinder 3 is evaluated in this example by one or more sensors 29, which determine the position of the transfer belt 5 from the front or back or both sides based on measuring marks or other characteristic properties. A possible correction of the position of the transfer belt can be carried out by the dancer roller control, wherein the dancer rollers can be introduced at any point in the tape run of the transfer belt. The position can also be synchronized with the roller drive 7. Advantageously, the deflection rollers 14 would also be designed as dancer rollers in order to be able to carry out the corrections as close as possible to the transfer nip 6. In the case of a mechanical synchronization, the guide rollers 14 would be laterally equipped with thorns, which in lateral rows of holes on the transfer belt 5 intervene. Each roller, which is in contact with the transfer belt 5, can be used in the sense of the invention for synchronization.

In a further embodiment of the invention, a transfer belt, which consumingly works with a winding and unwinding or circulating, printed with a wax-like ink from a heated printing device. This waxy ink has the advantage that it hardens relatively quickly and therefore can not run. The transfer of the printed image on the transfer belt can then be done by the pressure roller, which operates against the impression cylinder, is heated and the color dissolves. Alternatively or additionally, the print motif can be heated on the transfer belt by a heating device. This makes it easy to transfer the print image to the substrate. This solution also allows variable data printing in an excellent manner. In a direct printing of a sheet in a sheet-fed printing machine with a variable data printer, for example, an inkjet printer, there is always the problem that the distance between the printing device, for example, the printhead of an ink jet device and the printing substrate is not always constant, since just in rigid substrates the Have a tendency that the bow end can stand out. By the selected device with transfer belt and pressure roller, which simultaneously serves the sheet guide, this problem can be avoided, since the distance between the transfer belt and printing device can be kept constant by simple devices. Residual stocks of wax-containing printing ink of the print motif can also be easily removed from the transfer belt by suction sponge rollers or scrapers by the ink residues are heated shortly before the cleaning station by one or more heating devices or by contact with one or more heated rollers.

In a further embodiment, the transfer belt is printed with one or more sublimation inks. Sublimation printing processes are printing inks containing one or more dyes, which, with the application of heat and optionally pressure from a solid without a transition into a gaseous Go state and penetrates the gaseous dye or gaseous dyes in the product to be decorated. The gaseous dye or gaseous dyes revert to a solid state in the product or printing substrate to be decorated and remain there. This method is known as sublimation printing or sublimation. Similar methods are also used in the thermal sublimation printing process. In this case according to the invention, the press roll 3 makes contact with the printing substrate and is heated in such a way that the sublimation of the dyes into the printing substrate can take place. The transfer belt 5 may be preheated by a suitable heating or drying device 28 before passing through the transfer nip 6 to a temperature just below the temperature at which the sublimation process begins.

In a further embodiment of the invention, the so-called decalcomania method is used. In this case, a motif is printed on the transfer belt with a printing ink that can be activated by water or steam. In this case, the printed image is moistened before passing through the transfer belt 5 in the transfer nip 6 by a suitable device. This may be a water vapor device, a spray device or a roller mill.

In many cases, however, the pictorial motif on the transfer belt can not be produced economically and technically in the printing machine. For example, this applies to holograms used for product safety. Such holograms go through multi-level, complex manufacturing processes, which are difficult to use in the production environment of a printing press. Another example is antennas for RFID (radio frequency identification device) applications can be used. Such antennas are today etched in most cases, a process that runs slowly and therefore is not compatible with the high production speeds of modern printing presses. Also wet-chemical plants are not conceivable for reasons of safety at work in the environment of a printing press. Also the complete transfer of labels, for For example, if these have advanced functionality, it makes perfect sense. Another application example would be the transfer of pre-printed high-opacity layers used in scratch-offs. Printing inks used for this purpose generally contain solvents to a high degree, so that a pressure of such layers would entail high expenses for a solvent disposal, for example a vacuum with afterburning. In such cases, it makes sense to pre-print such layers in specialized printing presses.

In the latter embodiments according to the invention, the film supply roll 8 on the transfer belt contains a pre-printed or prefabricated motif, hologram or label. These possibilities of various applications, pre-printed motif, prefabricated motif, hologram or label are summarized in the following under the term transfer motif simplifying. This transfer motif is transferred to the printing substrate with the press roll 3 or a pressure roller 21 in the transfer nip 6. The transfer motif located on the transfer belt may be provided with an adhesive which is activated by pressure and / or heat. The transfer motif may be provided with a glue that is activated by the application of moisture before passing through the transfer nip 6. This application of moisture can be done by a device that directs water vapor onto the transfer belt or by the direct application of water by means of suitable devices, such as roller mechanisms or spray nozzles. Alternatively, any adhesive may be applied to the transfer belt 5 prior to passing the transfer nip 6 by means of such a device. Of course, the order of an adhesive can be done by an offset printing unit or a flexographic printing, which is upstream of the transfer nip 6 in the sheet running direction of the printing press. In either case, a solution is preferred in which the transfer belt is clocked to transfer the transfer motif to the correct location on the print substrate. Ideally, these are one or more, independently operable transfer belts, which are arranged side by side in the axial direction of the impression cylinder 4 are, and each cover only a portion of the print width.

LIST OF REFERENCE NUMBERS

1

commissioned

2

coating module

3

press roll

4

Impression cylinder

5

Transfer foil / foil web

6

transfer nip

7

roller drive

8th

Film supply roll

9

Foil composite role

10

Press covering

11

Inking / dampening unit

12

plate cylinder

13

Rubber / impression cylinder

14

guide

15

Verschutzung

16

UV dryer

17

monitoring system

18

dancer roll

19

cylinder gap

20

21

pressure roller

22

deflecting

23

deflecting

24

form cylinder

25

application system

26

dosing

27

printing system

28

dryer system

29

Sensors for registering register marks

Claims (38)

Transfer film for use in a transfer printing process in an offset printing machine, preferably a sheet-fed offset printing machine, wherein the printing press comprises a coating module (2) containing at least one impression cylinder (4) and a pressing device which form a common transfer nip (6), wherein a transfer film ( 5) is guided around the pressing device or slightly tangentially past the pressing device, such that the transfer foil rests with the coated side on the printing sheet guided on the impression cylinder (4) and under pressure together with the printed sheet through the transfer gap (6). between the pressing device and impression cylinder (4) is guided and wherein the coating or ingredients of the coating remain on the transfer sheet after the exit of the sheet from the transfer nip (6) on the sheet,
characterized,
that the transfer film partially contains a pictorial motif, for example alphanumeric characters, structures, motifs, holograms, metallic structures or special partially applied coatings and is not coated over the entire surface. Transfer printing method using a transfer film according to claim 1,
characterized,
that the transfer film is printed before passing through the transfer gap (6) at least with a suitable printing device (27) with a motif, and this image is transferred to at least partially in the transfer gap (6) on the printed sheet. Transfer printing method according to claim 2,
characterized,
that the printing device (27) is one or more flat screen printing devices, one or more rotary screen printing devices, one or more gravure printing devices, or one or more ink jet devices, or a combination of any or all of the mentioned printing devices. Transfer printing method according to claims 2 and 3,
characterized,
that the by the printing device (27) is cured composition applied to the transfer belt (5) motif prior to passing the transfer nip (6) by a suitable curing or drying device (28) and / or dried. Transfer printing method according to claim 4,
characterized,
that the curing or drying device (28) is formed by a convection dryer, an infrared dryer, a UV dryer, a microwave dryer, an electric beam dryer, or any combination of the above drying or curing devices. Transfer printing method according to claim 1,
characterized,
in that the film supply roll (8) is formed as a whole roll or a plurality of transfer rolls (5) arranged side by side in the axial direction of the counterpressure cylinder (4), which has been provided in advance with a transfer motif in a separate processing station, then transferring the transfer film 5 from the supply roll ( 8) is unrolled in the printing operation and the transfer nip (6) is supplied, in which the transfer motif located on the transfer or the transfer film is then transferred to the sheet. Transfer printing method according to claim 6,
characterized,
that the transfer motif is alphanumeric characters and / or Image motifs acts. Transfer printing method according to claim 6,
characterized,
that the transfer motif is holograms. Transfer printing method according to claim 6,
characterized,
that it is in the transfer of motive to antennas or electrically conductive or semi-conductive layers. Transfer printing method according to claim 6,
characterized,
that the transfer motif is a single-layer or multi-layer label. Transfer printing method according to claim 6,
characterized,
that the transfer motif as last external, in the transfer nip (6), the impression cylinder (4) facing layer comprises an adhesive layer, which before passing the transfer sheet (5) through the transfer gap (6) is activated by a suitable device. Transfer printing method according to claims 6 and 11,
characterized,
that the adhesive layer on the transfer motif is a glue which is activated by passing the transfer film through the transfer nip (6) by applying steam to the transfer film or by spraying the transfer film with water, the transfer film is contacted by a roll mill Water is applied, Transfer printing method according to claims 6 and 11,
characterized,
in that the adhesive layer on the transfer motif is a thermally activatable adhesive which is activated by one or more suitable heating devices, for example an infrared radiator and / or a supply of heated air, before passing through the transfer gap (6). Transfer printing method according to claim 4 or 6 in combination with at least one of claims 7 to 10,
characterized,
in that on the side of the transfer film (5), which is directed in the transfer nip (6) against the impression cylinder (4), before passing through the transfer film by transfer nip, an adhesive is partially or extensively applied by a suitable device, and the adhesive / glue for adhesion the transfer motif on the sheet is used. Transfer printing method according to claim 14,
characterized,
that the device for the glue / adhesive application is a roll coater, which is in contact with the transfer foil. Transfer printing method according to claim 14,
characterized,
that the device for the glue / adhesive application is a non-contact spraying device. Transfer printing method according to claim 4 or 6 in combination with at least one of claims 7 to 10,
characterized,
that the sheet before passing through the transfer nip (6) by a or a plurality of printing units is surface or partially provided with an adhesive which detaches the transfer motif from the transfer sheet and ensures the adhesion of the transfer motif on the sheet. Transfer printing method according to claim 17,
characterized,
that the adhesive is applied to the sheet by an offset printing unit. Transfer printing method according to claim 17,
characterized,
that the adhesive is applied to the sheet by a flexo or coating unit. Transfer printing method according to claims 1 and 2,
characterized,
that printed on the transfer film motif containing one or more sublimation dyes. Transfer printing method according to claim 6,
characterized,
that the subject is located on the transfer film contains one or more sublimation dyes. Transfer printing method according to claim 20 or 21,
characterized,
in that the pressing device, for example the pressing roller (3) or the pressure roller (21), is heated in such a way that the sublimation ink layer, which is on transfer film on the side facing the counter-pressure cylinder (4), is heated above the sublimation temperature and the sublimation dyes are heated in one go over in the gaseous state and in the on the impression cylinder (4) pressure sheet penetrate. Transfer printing method according to claim 22,
characterized,
that the pressing device is heated by the flow of a heated device. Transfer printing method according to claim 22,
characterized,
that the pressing device is electrically heated. Transfer printing method according to claim 22,
characterized,
that the pressing device is heated indirectly by heat radiation. Transfer printing method according to claim 20 or 21 and 22,
characterized,
that the transfer film before the transfer nip (6) is heated by a suitable heating device just below the sublimation, so that only the differential temperature must be transmitted to the sublimation by the heated pressing device. Transfer printing method according to claims 1 and 2,
characterized,
that is printed on the transfer film motif is formed from one or more moisture-printing inks ( "Inks for the transfer process"). Transfer printing method according to claim 6,
characterized,
that the motif on the transfer film is formed from one or more moisture-activatable printing inks ("printing inks for the decal process") , Transfer printing method according to claim 27 or 28,
characterized,
that the transfer film is subjected to moisture before passing through the transfer nip (6). Transfer printing method according to claim 29,
characterized,
that the moisture impact of the transfer film by Wasserdampfbeaufschlagung, condensation is accomplished by cooling the transfer film, or by a spraying device. Transfer printing method according to claim 29,
characterized,
that the moisture is applied by a roller application device. Transfer printing method using a transfer film according to claim 27 or 28,
characterized,
that the printing sheet located on the counter-pressure cylinder (4) is partially or extensively exposed to moisture prior to passing through the transfer nip (6), and the decal formed by the moisture-activatable ink is transferred to the printing sheet in the transfer nip (6). Transfer printing method according to claim 1 and 2 or 6,
characterized,
in that the transfer film is unwound from a film supply roll (8), is fed to the transfer nip (6) and is rolled up again onto a film collection roll after the transfer. Transfer printing method according to claims 1 and 2,
characterized,
that the transfer film forms a circumferential band that via guide means (14) and / or deflection rollers (22/23) is moved past supplied to the printing devices (27) and optionally further devices the transfer nip (6) and from there back via guide devices (14) again for re-coating by the printing device (27) is supplied. Transfer printing system according to claim 34,
characterized,
that the transfer sheet (5) outside the printing area laterally continuous rows of holes or other openings, serve in the pins or pegs to ensure the register of the position of the transferred motif on the sheet, the pins or pins either on one or more guiding devices, on a or a plurality of guide rollers (22) or (23) or on the pressing device, and engage the pins or pins during the circulation of the film in the lateral rows of holes or openings. A circulating belt transfer printing system according to claim 34,
characterized,
in that the transfer film band (5) contains register marks on the rear side and / or on the front side which are detected by sensor systems (29) arranged on one or both sides of the film web shortly before the transfer nip (6) and the signals obtained for controlling the position of the transfer film web ( 5) can be used in the transfer nip by adjusting the motor control and / or adjusting the position of the transfer film (5) in the transfer nip (6) via dancer rolls (18). Transfer printing method according to claim 1 and 2 or 6,
characterized,
that the transfer film or the transfer films in the transfer operation continuously be transported through the transfer nip (6). Transfer printing method according to claim 1 and 2 or 6,
characterized,
that the transfer film or the transfer films are transported in transfer operation clocking through the transfer nip (6).

Images