EP2055479A2 - Transfer printing procedure - Google Patents

Abstract

The method involves tangentially guiding a transfer foil (5) of a pressing device of a coating module (2) such that the transfer foil is guided with a printed sheet through a transfer gap (6) under pressure. Coating or parts of the coating of the transfer foil is provided at the printed sheet after the discharge of the printed sheet from the transfer gap. An optical effective structure of the coating on the transfer foil is applied to an associated print image or print image elements printed on the printed sheet.

Description

The invention describes a pictorial transfer printing method for use in sheet-fed rotary printing presses according to the preamble of patent claim 1 and a printed product according to the preamble of claim 14.

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 image-providing 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 image-giving 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 the further transport of the printing sheet, the transferred layer adheres only in the area provided with the adhesive pattern. 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. Both patents 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 replaced at points of the carrier film of the transfer film, where 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.
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. The known transferable holograms or hologram-like structures are based on embossed metal layers or layers, which are based on a combination of lacquer and metal layer. The disadvantage is that such layers can not be applied to a printed image because they have no transparency. Among other things, conventional production methods are based on the fact that a hologram or a diffractive optical structure is produced by embossing.

Optical effects include optical gratings, lenses and diffractive structures for the design of optical effects in transparent materials. Optical gratings are also referred to as diffraction gratings and consist for example of a plurality of longitudinal structures at a uniform distance. The light of the single column interferes and forms an interference pattern. This results in a series of diffraction reflections whose arrangement corresponds to that which is found at the double slit with equal intervals. Due to the dependence of the reflections on the wavelength, optical gratings are used to separate different wavelengths. Optical lenses occur in the as collecting lenses or diverging lenses. The diffractive optic exploits the diffraction of the light. Diffraction effects occur on quasi-dimensional forms (for example, a lattice structure) with sufficiently small structures (gap width on the order of the wavelength of the light used).

The so-called lenticular images are images which have changeable light effects in the viewing angle. On a Drucksujet, which is composed of one or more frames, a film is applied. This film has lenticular elevations with convex or cylindrical elevation structures (lenticular elements). Basically, a distinction is made between horizontal and vertical lenses. As a generic representative of such a lenticular structure, the US 6,795,250 B2 be used. The patent discloses the development of an elliptically shaped lenticular grid and includes the differences in line screens.
The patent publication US 2004/0219302 A1 discloses a method for producing partially arranged lenticular images. First, the printed image is printed. The printed strip images are not distributed over the entire sheet, but only in individual places. Subsequently, paint is applied and dried using a paint unit partially at the points where a lenticular image is to be formed. The disadvantage is that depending on the desired effect several layers of paint must be applied. Also, with this method, no diffractive structures, but only relatively rough structures can be produced. The optical precision is also limited, since the liquid paint runs something after the order on the substrate.
The patent publication DE 10 2006 003 798 A1 is concerned with a method and a device for generating viewing angle-dependent changeable image effects on a printing substrate. The optically effective lacquer layer is structured by the use of lacquers of different surface tensions.
The patent publication WO 2004/057382 A1 involves the creation of a micro-optical grating on a substrate surface. The grid is introduced by embossing on the substrate surface or in the coating layer located on the substrate. Viewing angle dependent holographic or similar effects are created in the eye of the beholder. Depending on the viewing angle, the intensity and color of the effect change. In this case, an embossed lacquer layer may appear completely transparent even under certain viewing angles.

In the US 5,585,144 discloses a reflection hologram in which printed fonts or images are combined with a microscopically fine, embossed structure. The structure includes a reflective film on the surface of which the holographic effect and the printed fonts and / or images can be seen. The disadvantage is that such a hologram is not transparent and thus can not be placed over a printed image. In addition, the inline production of holograms in the printing machine by embossing because of the low contact forces is very difficult.

The above publications disclose transparent optical structures that can be overlaid on a printed image. The disadvantage, however, that the production of such structures require relatively high contact forces, which are difficult to apply in a printing press. In addition, the embossing in a transparent lacquer on a fiber-based printing material has the disadvantage that it has a certain elasticity and thus requires a higher embossing force to apply the structures. The mechanical stability of the printing material can be attacked.

The object of the invention is therefore to further develop the production process known per se for the cold foil transfer so that a transfer of holographic, diffractive or other optically transparent structures as a transparent layer on a printed image is possible.

The object is achieved with the features of a method according to claim 1 and the features of a printed product according to claim 14.

By combining a transparent optically effectively structured layer with a pre-printed layer, the printed product is provided with viewing angle-dependent optical effect. The connection of the transparent structure with the printed image takes place inline during a printing pass or Offline during a second pass through the press by the press using the cold foil transfer process.

According to the invention, a printed image consisting of fonts, logos and / or images is printed in the printing press with printing ink. After the color printing, a highly transparent adhesive with an offset or flexographic printing unit is then applied to the printed image over a plane or partially. Thereafter, the sheet is passed through the coating unit, being brought by means of the press roller on the impression cylinder resting sheet with the film transfer material in combination. In this case, the downwardly lying, transparent layer, which carries optically active structures, a close connection with the adhesive provided areas. After the further transport of the printing sheet, the transferred layer adheres only in the area provided with the adhesive pattern. 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.

This produces a printed product which consists of a substrate, a pictorial layer or layers located thereon, consisting of text, logos and / or images, and a transparent optical structure applied thereto.

The film material for the cold film transfer consists of a carrier film, a release layer thereon and a transparent transfer layer, which is removed during the transfer process by the adhesive layer on the substrate. According to the invention, the transfer layer has an optically active structure, which is preferably a diffractive structure. The optically active structure can be introduced into the transfer layer by exposure methods. The structure is preferably introduced by a microoptical embossing. The generation of the optical structure can be outside the printing press, for example, during the production of the transfer films, or by a stamping mill, which is integrated in the film feed to the press nip, are generated.

In the context of the invention, a transparent, optically active layer which is applied in the cold-film transfer process is understood as meaning a layer in which the texts located underneath are readable or images can be seen at certain viewing angles.

The advantage of the invention is that in the area of packaging and magazine impression, optical effects can be applied to a printed product without limiting the space for text and image. The application of an embossed transfer layer to a printed image also provides excellent protection against product counterfeiting, since such a protected packaging can hardly be reproduced again with the classic precursor processes. In addition, such printed products produce a high attention value, so that the advertising effectiveness of the printed product increases significantly.

• Ein leerer, vorbehandelter oder mit einem ein- oder mehrfarbigen Druckbild vorbedruckter Druckbogen wird zunächst mit einem flächigen Klebstoffauftrag oder einem bildgebenden Klebstoffmuster versehen (erstes Druckwerk als Auftragwerk 1).
• In dem darauf folgenden Druckwerk wird der Druckbogen dann gemeinsam mit einer Transferfolie 5 unter Pressung durch einen Transferspalt 6 geführt, (zweites Druckwerk als Beschichtungswerk 2)
• Und in einem weiteren Folgedruckwerk 50 oder Lackierwerk 51 kann schließlich auf den nunmehr mit einer Folienapplikation beschichteten Druckbogen über diese noch eine Druckfarben- oder Lackschicht aufgetragen werden.

The coating method on which the invention is based is referred to as cold foil transfer and can be used in a device as shown in FIG FIG. 1 be executed.
FIG. 1 shows for this purpose parts of a sheet-fed rotary printing press, in the example, three printing units 1, 2 and 50 are shown. The printing units 1, 2 and 50 can be used in cold foil transfer for the following purposes:

• An empty, pretreated or pre-printed with a single- or multi-color printed image sheet is first provided with a two-dimensional adhesive application or an adhesive pattern (first printing unit as an applicator 1).
• In the following printing unit, the printed sheet is then passed together with a transfer film 5 under pressure through a transfer nip 6 (second printing unit as coating unit 2).
• And in a further follow-on printing unit 50 or coating unit 51 can finally be applied to the now coated with a film application sheet over this still an ink or varnish layer.

The applicator 1 may be a per se known offset printing unit with an inking unit 11, a plate cylinder 12 and a blanket cylinder 13. The blanket cylinder 13 cooperates with an impression cylinder 4 and transmits a generated by means of the inking unit and the printing plate on the plate cylinder 12 adhesive image on the sheet.

The coating unit 2 can also be formed by an offset printing unit. The transfer nip 6 in the coating unit 2 is formed by a press roll 3 and an impression cylinder 4. The press roll 3 may correspond to the blanket or blanket cylinder. The press roll 3 may also correspond to the forme cylinder of a paint module. Within the coating unit 2 used for the film transfer, a web guide 14 for transfer films is shown. The transfer film 5 is thereby switched on and executed by protective devices 15 of the coating unit 2.

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 for the continuous controlled feeding of the transfer film to the coating unit 2. In the film feed deflection or tension rollers for guiding the transfer film 5 may be provided in a substantially constant tension against the press roller 3. On the downstream side of the printing unit, a film collecting roller 9 is provided for the used sheet material. A rotary drive 7 on the film collecting roller 9 is always advantageous. It can even be provided that the transfer film 5 is conveyed on the outlet side by means of the rotary drive 7 and held taut on the inlet side by means of a brake.

The press roll 3 (blanket or form cylinder or separate press roll) carries on its surface a compressible, e.g. also provided with a compressible intermediate layer element. For this purpose, the press roll 3 can be provided with a press fabric 10, for example as a plastic cover, comparable to a blanket or blanket, which is held in a cylinder channel on clamping devices.

To ensure the efficiency of the coating process can be provided, the film feed of the transfer film 5 from the film supply roll 8 to the transfer nip 6 and the film collection roller 9 is gradually controlled, the transfer film 5 is then stopped, if no transfer of imaging or covering layers should take place.
The associated device preferably includes a corresponding feed control for the transfer sheet 5, which ensures that at least the lying in the region of the press roller 3 and the impression cylinder 4 part of the film web is stationary as long as the cylinder channel passes.
A further improvement of the film utilization of the type described results when the transfer film 5 is divided into one or more Teilfolienbahnen lesser width.

Furthermore, dryer 16 can be provided in the film application module thus formed from the applicator 1 and the coating unit 2, by means of which the adhesive application or the entire film coating can be dried. Here, for example, UV dryers come into question.
Furthermore, an intermediate dryer 16 is provided in a follow-on printing unit 50, which adjoins the coating unit 2. The intermediate dryer 16 may also be arranged in or in connection with sheet guiding elements 19, 20. As a sheet guiding element, a pneumatically assisted sheet guide path 20 or a sheet guiding drum 19 may be provided, with the aid of which the foil-coated printing sheets B are conveyed from the coating unit 2 to the printing unit 50. The sheet guide path 20 may be below a Bow guide drum - shown here in training as a skeleton drum 19 - be arranged.

In the follow-on printing unit 50, which is designed as an offset printing unit, form a impression cylinder 40 and a blanket cylinder (blanket cylinder) 41 with a blanket (blanket) 42 a printing nip 60. The print image to be printed by a inking / dampening unit 49 via a plate cylinder 43 by means of a Pressure plate 44 generated and transmitted via the blanket cylinder 41 on the sheet. For this purpose, a Druckbeistelleinrichtung 45 is provided on the rubber cylinder 41, which allows adjustment of the pressure of the sheet in the printing gap 60. Furthermore, a pressure supply device 46 for adjusting the pressing pressure in the transfer nip 6 is provided on the press roller 4. This results in indicated by arrows pressing adjustment, which are indicated as Druckbeistellung 47 at the printing nip 60 and as Druckbeistellung 48 at the transfer nip 6.

Furthermore, the film application module may include a monitoring device 17 for scanning the printing surface of the coated printing sheet.

With the device described above, it is possible to coat substrates or partially or completely coated substrates or to laminate or laminate or even to provide a particularly resistant surface layer. For this purpose, the device for the film transfer in a printing units of a sheet-fed printing machine downstream printing or coating plant is arranged. In such an arrangement, the surface of the fresh print is finished or protected by means of the film coating.

In FIG. 2 is a sheet-fed press with a sheet feeder AN, a plurality of offset printing units 50, a coating unit 51 and a sheet delivery AU shown. The printing process runs in the sheet transport direction from the sheet feeder AN to the sheet delivery AU. All printing units 50 have plate cylinder 43 and a color / dampening 49. The equally available everywhere rubber cylinder 41 and impression cylinder 40 each form a pressure gap 60. Between the last Printing unit 50 and the coating unit 51 are arranged two printing units, which are configured as a commissioning unit 1 and 2 as a coating unit. For this purpose, an essay with holders for a film supply roll 8 and a film collecting roll 9 is assigned to these two printing units. In the coating unit 2, the printed sheets are guided with a transfer film web 5 through a transfer nip 6 between a press roll 3 (rubber, blanket cylinder) and the impression cylinder 4. Thereafter, in the coating unit 51 by means of the forme cylinder 52, an additional coating on the finished with the transfer sheet signature. This additional coating can be carried out as a full-surface or partial coating.

The process according to the invention is in FIG. 3 outlined. First, in the first three printing units 50, a color image printing is performed. For this purpose, two printed images are schematically shown as first pressure D1 and second pressure D2.
The print D1 is shown in bold, indicating that this is a normal color print.
The pressure D2 is shown grayed out. This means that the print D2 is not visible, imperfectly visible or quasi in the form of a coded image. Therefore, when the first pressure D1 is superposed by the second pressure D2, the first pressure D1 would remain completely visible.

As a third process step, the application of a smooth or structured film layer from a transfer film web 5 is provided as printing D3 or film transfer. This is done in the cold foil transfer process as described above. In this case, the adhesive in the applicator 1 corresponding to the exact fit to the print image D2 or to the combination of D1 and D2, the transfer film 5 is assigned to the combined print image of pressure D1 and D2 accordingly.
If the application of a structured film or a film with an optically active pattern is desired, this can be done by two methods. The patterning or the pattern can be in the film web 5 in its supply to the transfer nip 6 by means of a stamping unit 53 (see Fig. 1 and 2 ) are introduced as microembossing.

Furthermore, embossing on the finished product can take place in a coating module 51 downstream of the coating unit 2, in which case the forme cylinder 52 can then be converted in a manner known per se for embossing. An approach in this way can also be done in a follow-up printing unit 50 by means of appropriate equipment of the blanket cylinder 41.

This results in the fourth printed image D4 in which the superimposed representation of D1 and D2 under the action of the applied in D3 film layer or structural film layer now gives a modified representation. The film layer or structured film layer, which rests on the combination print on the printing sheet B and which has been obtained from the transfer film 5, now brings the elements of the printed image D2 with respect to the printed image D1 through their computational or resolution effect.

This special function for visualizing latently present information can be used for security features, optical additional effects for advertising media, playful effects on packaging or printing or content elements that can be differently used and evaluated. In this case, the orientation of the underlying printed images to the overlying optically effective embossed or structured foil layers can be influenced by a register device. Thus, even fine structures can be generated and applied to one another on the substrate.

The resulting printed product can be well protected against counterfeiting, since the optically active layer is firmly connected to the substrate. It protects the printed samples optically and mechanically against scanning. Upon detachment of the optical layer, the image layer would be destroyed and the printed security pattern in turn can not be copied.

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

Dryer / intermediate dryer / UV dryer

17

monitoring system

18

dancer roll

19

Sheet transport drum / skeleton drum

20

Sheet guiding element / sheet guiding path

40

Impression cylinder

41

rubber cylinder

42

blanket

43

plate cylinder

44

printing plate

45

Druckbeistelleinrichtung

46

Druckbeistelleinrichtung

47

printing pressure

48

printing pressure

49

Inking / dampening unit

50

printing unit

51

Painting works

52

form cylinder

53

stamping

60

nip

D1

first pressure

D2

second pressure

D3

third pressure

D4

fourth pressure

B

Sheet / foil sheet

Claims (15)

Transfer printing method in an offset printing machine, preferably a sheetfed offset printing press, comprising a coating module (2) comprising at least one impression cylinder (4) and a pressing device which form a common transfer nip (6), wherein a transfer film (5) at least in the press nip (6 ) is guided past touching, such that the transfer film (5) rests with a wear side bearing on the impression cylinder (4) provided with an imagewise adhesive layer printed sheet and is passed under pressure together with the signature through the transfer nip (6) , wherein the coating or parts of the coating of the transfer film (5) remain on the printing sheet after the exit of the printing sheet from the transfer nip (6), and the transfer film (5) carries an optically active structure, such as a hologram
characterized,
in that the optically active structure of the coating on the transfer film (5) (transfer layer) is applied to a printed image or printed image elements thereof printed on the print sheet. Transfer printing method according to claim 1,
characterized,
in that the optically effective coating on the transfer film (5) is applied by means of the transfer film (5) through a pre-printed transparent adhesive or adhesive ink on a printing substrate printed with a printed image and / or text and / or figures. Transfer printing method according to claim 1 or 2,
characterized,
that the optically effective coating carries a diffractive structure. Transfer printing method according to claim 1, 2 or 3,
characterized,
in that the optically active coating is applied by means of the transfer film (5) through partial or full-surface through a pre-printed transparent adhesive or adhesive ink on a printed with a printed image and / or text and / or figures substrate, wherein the coating is applied so that they adheres to the pre-printed adhesive and that the printed image located on the substrate after the film transfer at certain viewing angles is still recognizable by the transferred in the transfer printing process layer. Transfer printing method according to claim 1, 2, 3 or 4,
characterized,
that the optically active coating is applied by means of the transfer foil (5) by a partial picture elements associated with pre-printed transparent adhesive or adhesive color on a printed with a print image and / or text and / or figures printed material, said foil elements attached to the pre-printed adhesive parts so that the optical effect of the transfer film (5) influences the printed image on the substrate after the film transfer so that the printed image or parts of the printed image are recognizable or not recognizable. Method according to claims 1 to 5,
characterized,
that in a printing pass through a printing machine, first a single- or multi-color printed image is printed, then that the transparent adhesive and then in the coating module (2) of the transfer step of the optical structures takes place, which can be followed by further finishing steps, all printing and coating operations "Inline" done in a single pass. Method according to claims 1 to 5,
characterized,
that by combining a transparent visually effectively structured Layer with a pre-printed layer, the printed product is provided with a viewing angle dependent occurring optical effect. Method according to claims 1 to 7,
characterized,
that in the printing press, the printing before the coating by means of the transfer foil (5) is printed by means of printing ink with a print image consisting of fonts, logos and / or images. Method according to claim 8,
characterized,
that after the color printing, a surface or partially arranged and highly transparent adhesive application by means of an offset or flexographic printing on the printed image. Method according to claims 1 to 9,
characterized,
in that the optically active structure is introduced into the transfer layer of the transfer film (5) by exposure methods. Method according to claims 1 to 9,
characterized,
in that the optically effective structure is introduced by a microoptical embossing into the transfer layer in connection with the transfer film (5) or into the transfer layer after the cold foil transfer onto the printed sheet. Method according to claims 1 to 9,
characterized,
that the production of the optically effective structure outside of the printing press during production of the transfer foils (5) or in an offline process takes place. Method according to claims 1 to 9,
characterized,
that the production of the optically effective structure within the printing machine during the production of the printing sheet in the cold foil transfer by application of the transfer foils (5) is effected by an embossing unit which is integrated in the sheet feeding to the press nip (6). Printed product produced in a process according to one or more of claims 1 to 13,
characterized,
that the printed product consists of a substrate, one or more pictorial layers consisting of text, logos and / or images, and a transparent optically active structure applied thereon, the transparent optically active layer being applied by the cold foil transfer method and under certain conditions Viewing angles underneath makes picture elements readable or recognizable. Printed product according to claim 14,
characterized,
in that, by non-detachable bonding of an optically active embossed transfer layer to a printed image, features for protection against product counterfeiting are applied.

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