EP1674260B1 - Transfer process - Google Patents

Description

The invention relates to a method and a device for transferring image-forming layers from a carrier film to printing sheet according to the preamble of patent claim 1.

It is known to produce metallic layers on printed sheets by means of a film transfer process. 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 machine is shown, which has a feeder and a boom, between which two units printing units and a coating unit are arranged. 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 the coating unit with a counter-pressure cylinder and a pressing cylinder a film guide is provided. This is designed in such a way that a film strip or a transfer film is guided through the transfer nip of the coating unit between the impression cylinder and the press cylinder from a supply roll of film. The foil strip is rewound on the outlet side after leaving the coating unit. The transfer film has a carrier layer on which imaging layers such as metallic layers, for example of aluminum, can be applied. Between the metallic layer and the carrier film, a separating layer is provided, which ensures that the metallic layer can be removed from the carrier layer.

When printing sheets are transported through the printing unit, each sheet is given an adhesive pattern. Thereafter, the sheet is passed through the coating unit, wherein by means of the pressing cylinder of the resting on the impression cylinder printed sheet with the film material in combination is brought. In this case, the downwardly lying metallic layer enters into a close connection with the areas provided with adhesive on the printed sheet. After the further transport of the printing sheet, the metallic layer adheres only in the area provided with the adhesive pattern. The carrier film is thus removed from the metallic layer in the region of the adhesive pattern. The used in this way transfer film is wound up again. The print sheet is laid out in the coated state.

So far, in other contexts, the protection of printed sheets against surface damage has become known. For this purpose, painting or powdering facilities are used, which require complex facilities in the machine, but protect the arch only imperfectly.

It is also known to apply special laminates to surface coatings, e.g. Lacquer in a UV process. Here, too, difficult processes result, so that the coating is always problematic to handle and the coating result is often imperfect.

So is out of the EP 0 945 280 A2 a method for a transfer printing without using a stamping die, which is carried out with the aid of heat. In this case, an adhesive is applied to a substrate, the adhesive is dried, the substrate is heated until the adhesive becomes adhesive, and a pigmented or metallic layer is transferred from a film to the substrate.

Furthermore, from the WO 01/085456 A1 a method and apparatus for applying a lacquer layer to the top of a print medium known. In this case, a coating layer is produced on a roller, dried there and the dried coating film thus produced is transferred to the wet surface of a fresh color print by permanent bonding. For this purpose, an adhesive layer may be used, wherein prior to the transfer of the paint film an adhesive applied to the printing medium, then the paint film will be applied.

The object of the invention is therefore to provide a device by means of which a protective coating can be done safely, economically and accurately, the device should be easy to handle.

The solution to this problem results in a method according to the features of claim 1.

Advantageously, a clear protective layer is applied to a finished printing sheet in the manner of a lamination by means of the described coating method of a transfer film. The method is economical because it can be executed in a printing unit and can thus be integrated inline into a printing process.

To ensure the efficiency of the coating process can be provided to control the film feed such that the transfer film is then stopped when no transfer of the protective layer takes place.

Advantageously, a control of the transfer film can be made such that when passing through a gripper of the sheet-guiding impression cylinder receiving cylinder channel of the film feed is stopped, wherein the pressing cylinder then passes under the transfer film sliding.
In a further embodiment, as the surface of the pressing cylinder, an elevated, contoured pressing surface may be provided, which is limited to the area to be coated. For this, a cut-out blanket, a plastic printing form or a stick-on press-on segment is suitable. Thereby, the feed of the transfer film can be stopped in a very advantageous manner, even if the area to be coated is within the image area of the sheet.
A further improvement of the film utilization results from the fact that the transfer film is divided into one or more Teilfolienbahnen smaller width.
In addition, partial coating of a printed sheet is possible in both aforementioned cases.
In combination with the above-mentioned method, it is thus also possible to use different types of film side by side. This makes it possible to produce surfaces of different film color or different smoothness.
To improve the gloss effect, the image-forming layer can be applied by means of so-called UV negative-pressure ink. The UV negative pressure ink is applied by means of the printing unit for the adhesive in a corresponding manner via an offset printing plate.
Within the sheet-processing machine receiving the coating unit, the coating unit can advantageously be placed anywhere on the machine. In this way, in the case of a printing press having a plurality of printing units, it is possible for imaging coatings or metallization layers to be applied both before, as well as after and also between the application of printing ink layers.
Advantageously, the coating unit is designed as a coating module in the manner of a transportable unit.
Advantageously, it is also possible to provide several coating units behind one another within a sheet-processing machine. Thus, the application of various coatings or metallization layers within of a subject in succession. It is also possible to provide a first adhesive pattern in a first coating unit with a first image-forming coating or metallization layer and, in the following, superimposing another, the first enclosing adhesive pattern and to provide it with a different coating or metallization layer.

In the following the invention is illustrated in more detail with reference to figures.

Figur 1

eine grundsätzliche Darstellung einer Druckmaschine mit einer Folientransfereinrichtung.

Showing:

FIG. 1

a basic representation of a printing machine with a film transfer device.

• Ein Druckbogen wird zunächst mit einem bildgebenden oder vollflächigen Klebstoffmuster versehen (Auftragwerk 1).
• Danach wird im Folgedruckwerk gemeinsam mit einem Druckbogen eine Transferfolie 5 durch einen Transferspalt 6 geführt, wobei die Transferfolie 5 im Transferspalt 6 gegen den Druckbogen gepresst wird (Beschichtungswerk 2).

Der Transferspalt 6 im Beschichtungswerk 2 wird durch einen Presszylinder 3 und einen Gegendruckzylinder 4 gebildet. Diese können dem Drucktuchzylinder und dem Gegendruckzylinder eines Offsetdruckwerkes entsprechen.
Weiterhin kann nachgeschaltet ein so genanntes Kalandrierwerk vorgesehen werden. Innerhalb des für den Folientransfer genutzten Beschichtungswerkes 2 ist eine Bahnführung für Transferfolien dargestellt.
Die Transferfolien 5 sind mehrschichtig aufgebaut. Sie weisen eine Trägerschicht auf, auf der mittels einer Trennschicht eine bildgebende Schicht bzw. Funktionsschicht aufgebracht ist. Die Trennschicht dient dem erleichterten Abheben der Funktionsschicht von der Trägerschicht. Die Funktionsschicht kann eine transparente Glanzschicht oder eine transparente Texturschicht oder eine eingefärbte Schicht sein.In FIG. 1 is a sheet-processing machine, here a printing press, shown, which consists of at least two printing units. The two printing units are used for the following purposes:

• A printed sheet is first provided with an imaging or full-surface adhesive pattern (applicator 1).
• Thereafter, a transfer sheet 5 is passed through a transfer nip 6 in the following printing unit together with a printing sheet, wherein the transfer sheet 5 is pressed in the transfer nip 6 against the sheet (coating unit 2).

The transfer nip 6 in the coating unit 2 is formed by a pressing cylinder 3 and an impression cylinder 4. These may correspond to the blanket cylinder and the impression cylinder of an offset printing unit.
Furthermore, downstream of a so-called calendering be provided. Within the used for the film transfer coating 2 a web guide for transfer films is shown.
The transfer films 5 have a multilayer structure. They have a carrier layer on which an imaging layer or functional layer is applied by means of a separating layer. The separating layer serves to facilitate the lifting of the functional layer from the carrier layer. The functional layer may be a transparent glossy layer or a transparent textured layer or a colored layer.

The film supply roll 8 is assigned to the coating unit 2 on the sheet feed side. The film supply roll 8 has a rotary drive 7. The rotary drive 7 is required for the continuous controlled feeding of the transfer film to the coating unit 2, and is therefore controllable. Furthermore, a deflecting or tensioning roller is provided in the region of the film feed. Thus, the film web of the transfer film is always held in the same voltage relative to the press cylinder 3. On the downstream side of the printing unit, a film collection roller 9 is shown. On the film collecting roll 9, the used film material is wound up again. Again, a rotary drive 7 is provided for the optimized production, which is controllable. In essence, the transfer film 5 could also be moved by the rotary drive 7 on the discharge side and kept taut on the inlet side by means of a brake.
The transfer process of a transparent protective layer on the printing paper takes place in the transfer nip 6 between the pressing cylinder 3 and the impression cylinder. The pressing cylinder 3 may be a blanket cylinder of an offset printing unit. The pressing cylinder 3 may also be the forme cylinder of a paint module. It is essential that the surface of the pressing cylinder 3 so the blanket cylinder or forme cylinder is equipped by means of a compressible, damping element.
Furthermore, a limited pressing surface can be provided directly on the pressing cylinder 3 or on the press fabric. This can be worked out of the surface of the press fabric or it can be additionally attached as a partial surface of the material of the press fabric on the press cylinder 3.

By means of such a device is provided to provide a printed sheet with a transparent protective layer. The coating process takes place in the manner described above and serves the full-surface or partial-area sealing of a printed surface. The method may be referred to as a laminating process within a printing press. The protective layer may be visible, invisible, clear, colorless or colored. Likewise, textured layers can be applied.
The protective layer can be applied directly to the color print or a painted color print.

It is also possible to apply several layers of different quality superimposed on one another.
Protective coatings of this type can be applied in a simple manner inline during a printing process or even offline for post-refinement.

• Hierzu kann eine Steuerung der Transferfolie 5 derart erfolgen, dass beim Durchlaufen eines Greifer des bogenführenden Gegendruckzylinders 4 aufnehmenden Zylinderkanales der Folienvorschub angehalten wird. Die Greifer halten den Druckbogen auf dem Gegendruckzylinder 4. Auch der Presszylinder 3 weist einen Zylinderkanal auf. Im Bereich des Zylinderkanals erfolgt keine Pressung der Transferfolie 5 zwischen dem Presszylinder 3 (Drucktuchzylinder) und dem Gegendruckzylinder 4. Der Presszylinder 3 läuft dann unter der Transferfolie 5 gleitend durch, während die Transferfolie 5 zwischen Press- und Gegendruckzylinder 4 frei gespannt ist. Nach dem Kanaldurchgang wird die Transferfolie 5 weiter transportiert. Bei reaktionsschnellen Taktungssystemen über so genannte Tänzerwalzen 18, wie sie beispielhaft in Figur 1 eingezeichnet sind, ist eine Steuerung der Drehantriebe 7 der Folienvorratsrollen 8 bzw. Foliensammelrolle 9 ggf. nicht erforderlich.

To ensure the economic efficiency of the coating process, it is provided that the film advance of the transfer film from the film supply roll 8 to the transfer nip 6 and the film collection roll 9 is controllable such that the transfer film 5 is stopped as far as possible if no transfer of the image-forming layer is to occur:

• For this purpose, a control of the transfer film 5 can be made such that the film feed is stopped when passing through a gripper of the sheet-guiding counter-pressure cylinder 4 receiving cylinder channel. The grippers hold the sheet on the impression cylinder 4. Also, the press cylinder 3 has a cylinder channel. In the region of the cylinder channel, there is no pressing of the transfer film 5 between the press cylinder 3 (blanket cylinder) and the impression cylinder 4. The press cylinder 3 then slides under the transfer film 5, while the transfer film 5 is tensioned freely between the press cylinder and impression cylinder 4. After the channel passage, the transfer film 5 is transported on. In reaction-fast timing systems via so-called dancer rollers 18, as exemplified in FIG. 1 are drawn, a control of the rotary actuators 7 of the film supply rolls 8 and film collecting roll 9 may not be necessary.

In a further embodiment, a contoured pressing surface can be provided as the surface of the pressing cylinder 3. For this purpose, instead of an all-over plastic layer, a pressing surface limited to the area to be coated is used on the pressing cylinder 3. For this purpose, for example, a cut-out printing blanket, an imageable plastic printing plate or a pressure pad which is preferably releasably fastened to a smooth base, possibly stickable or magnetically attachable, can be used to support the limited pressing surface.

A further improvement of the film utilization of the type described results from the fact that the transfer film 5 is divided into one or more Teilfolienbahnen lesser width.

To improve the gloss effect, the protective layer can be applied by means of an adhesive reacting to ultraviolet radiation. Here, so-called UV negative pressure ink by means of the applicator 1 for the adhesive applied in a corresponding Weise_über an offset printing plate. This results in improved smoothness and thus gloss effect of resting on the sheet protective layer. To carry out the UV technology, a UV dryer 15 is to be provided either after the applicator 1 for predrying the adhesive application. On the other hand, even after the transfer of the imaging layer in the coating unit 2, a protective layer penetrating the UV dryer 15, for example, on the impression cylinder 4 of the coating unit 2 are arranged.

In combination with known methods, the transfer of a first adhesive pattern in a first applicator 1 can also take place and be provided in a first coating unit 2 with an imaging metallization layer. Overlaying this, in a following application unit 1 another, the first enclosing or overlapping adhesive pattern can be applied and provided in a second coating unit 2 with the protective layer. In this way, for example, first an image pattern of a silver-colored layer and then a full-surface protective layer can be produced in a coating pass.

On the basis of the present embodiments, it is possible to transfer different types of coatings in the transfer process from a transfer film 5 to different substrate materials. The detailed embodiments of the invention are not limited to the possibilities given here, but may be interpreted beyond the skill of the art.

LIST OF REFERENCE NUMBERS

1

commissioned

2

coating plant

3

press cylinder

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

15

UV dryer

16

monitoring system

18

dancer roll

Claims (7)

1. A method for the transfer of function layers on a substrate film onto print sheets in a device having at least one application unit (1) for coating a print sheet with an adhesive and having a coating unit (2) for transferring a function layer from the substrate film onto the print sheet, wherein the coating unit (2) comprises an impression cylinder (4) and a press cylinder (3), which form a transfer gap (6), and wherein furthermore the substrate film can be guided past the press cylinder (3) in such a manner that with the coated side placed onto the print sheet guided on the impression cylinder (4) and under pressure it is guided through the transfer gap (6) jointly with the print sheet, so that the function layer following the exiting of the print sheet from the transfer gap (6) adhering to the print sheets in the regions provided with adhesive is lifted off the substrate film, characterized in that during a printing process for sealing a printed surface an adhesive layer over the full or part area is applied after the printing operation onto a print sheet provided with a colour print and in that from a substrate film a transparent protective layer over a full or part area is adheringly transferred in the transfer gap (6) onto the print sheet by means of the adhesive layer, wherein the full-area or part-area protective layer is applied onto a printed sheet after the application of the last colour layer or onto a printed and varnished sheet after the application of the last varnish layer.
2. The method according to Claim 1, characterized in that the protective layer is transparent, visible or invisible.
3. The method according to Claim 1, characterized in that the protective layer is coloured or textured.
4. The method according to Claim 1 to 3, characterized in that the protective layer is transferred from a substrate film that is divided into one or a plurality of part film webs of smaller width in one or a. plurality of part regions next to one another in the transfer gap (6).
5. The method according to Claim 1 to 4, characterized in that the protective layer of the part film webs are provided with characteristics that differ from one another, wherein layers of different colour and/or different glaze and/or different surface texture can be created.
6. The method according to Claim 1 to 5, characterized in that the protective layer is transferred onto a printed sheet in a sheet-processing machine, in particular a printing press having a plurality of printing couples and in that the coating operation is arranged before, between or after the printing couples.
7. The method according to Claim 1 to 6, characterized in that a protective layer is applied in multiple layers on a printed sheet in a plurality of coating operations in succession within a sheet-processing machine.

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