Method for Applying a Film

Abstract

A more versatile film transferring device for transferring image-forming layers from a transfer foil to printing sheets is provided. The device includes a coating device for applying a colored adhesive pattern.

Description

The invention relates to a method and to devices for transferring image-forming layers from a carrier film onto a material to be printed according to the preamble of Claim 1.

It is known to produce metallic layers on material to be printed by means of a film transfer method. For example, in EP 0 569 520 B1 a printing material and a printing device using this material are described. Here, a sheet-processing machine is shown that has a feeder and a delivery system, with printing units and a coating module being arranged between the two assemblies. In at least one of the printing units, an adhesive pattern is applied by means of a planographic printing method. This adhesive pattern is applied in a cold printing method and has a certain image-forming design. In the coating module following the printing unit, having an impression cylinder and a press roll, a film guide is provided. This is designed such that a film strip or a transfer film is guided from a film storage roll through the transfer gap of the coating module between the impression cylinder and the press roll. The film strip is rewound on the delivery side after leaving the coating module. The transfer film has a carrier layer, on which image-forming layers, such as metallic layers, for example, made from aluminum, can be deposited. Between the metallic layer and the carrier film there is a separating layer, which ensures that the metallic layer can be removed from the carrier layer.

When printing sheets are conveyed through the printing unit, each printing sheet is provided with an adhesive pattern. Then the printing sheet is guided through the coating module, wherein, the printing sheet on the impression cylinder is brought into contact with the film material by means of the press roll. Here, the metallic layer on the bottom enters into a tight connection with the areas on the printing sheet provided with adhesive. After the further transport of the printing sheet, the metallic layer adheres only in the area of the pattern provided with adhesive. Thus, the metallic layer is removed from the carrier film in the area of the adhesive pattern. The transfer film consumed in this way is then rewound. The printing sheet is delivered in the coated state.

It is known to use such coating modules, for example, in printing units of printing presses. A disadvantage of the known devices is that they are not flexible.

Therefore, the problem of the invention is to provide a device by means of which the transfer of an image-forming layer, e.g., a metallization layer, can be performed reliably, economically, and precisely onto a printing sheet, wherein the device should be easy to operate for an expanded spectrum of applications.

The solution of this problem follows from a device according to the features of Claim 1 and from a method according to the features of Claim 6.

Advantageously, the adhesive pattern for transferring the image-forming layer from the transfer film is created with a colored adhesive.

In this way, the image-forming layer on the transfer film can be transparent, semitransparent, opaque, or non-transparent.

The device can also be used to improve the use of the film, such that the transfer film is divided into one or more sub-film webs of smaller width. In combination with the previously mentioned method, different types of films can thus also be used adjacent to each other.

In this way, adhesive patterns with different colors could then be used.

Application devices for this purpose are generally known.

The effects that can be achieved in this way include the compensation of very small surface defects, the intensification of color effects, the combination or superposition of the color effects of the adhesive and the image-forming layer, or the support of the glossy effect of the image-forming coating.

For improving the glossiness, the image-forming layer can be applied by means of so-called UV ground tints. The UV ground tint is applied by means of the printing unit for the adhesive in a corresponding way via an offset printing plate.

Advantageously, it is also possible to provide several coating modules, one behind the other, within a sheet-processing machine. In this way, various image-forming coatings or metallization layers can be applied one after the other within a design. Here, it is possible to transfer the image-forming layers one next to the other by means of a single adhesive pattern with all of the image pattern elements. It is also possible to provide a first adhesive pattern in a first coating module with a first image-forming coating or metallization layer and, in an overlapping manner, to then deposit another adhesive pattern enclosing the first pattern and to provide another image-forming coating or metallization layer.

The invention is described in more detail below with reference to figures.

Shown are:

FIG. 1, a basic representation of a printing press with a film-transfer device, and

FIG. 2, the setup of a coating module with a film-transfer device, and

FIG. 3, a press roll of a coating module, and

FIG. 4, a variant for the design of an application unit.

In FIG. 1, a sheet-processing machine is shown, here a printing press, which is composed of at least two printing units. The two printing units are used for the following purposes:

• • A printing sheet to be coated is provided in a first processing step with an image-forming adhesive pattern. The coating of the adhesive is realized in a device configured as an application unit 1, e.g., a conventional printing unit of an offset printing press, by means of inking and dampening units 11, a printing plate on a plate cylinder 12, a blanket or rubber cylinder 13, and an impression cylinder 4. Similarly, application units in the form of flexographic printing units or varnishing units can be used here. A variant to such an embodiment is shown in FIG. 4. The adhesive is there transferred by means of a metering system 21 via a screen roller 22 and a transfer roller 23 to a form cylinder 24. In this case, the form cylinder carries a relief printing plate for creating the image-forming adhesive coating.
  • Then, in a second step, a transfer film 5 is guided together with a printing sheet through a transfer gap 6, with the transfer film 5 being pressed against the printing sheet in the transfer gap 6. Here, a coating module 2 is used, which can correspond to a printing unit or an inking module or a base unit or some other kind of processing station of an offset sheet printing press.
  • The transfer gap 6 in the coating module 2 is formed by a press roll 3 and an impression cylinder 4.

Here, the press roll 3 can correspond to a blanket cylinder and the impression cylinder 4 can correspond to an impression cylinder of a known offset printing unit.

Furthermore, the press roll 3 can correspond to a form cylinder and the impression cylinder 4 can correspond to an impression cylinder of a varnishing module of a sheet printing press.

• • Furthermore, there can be a so-called calendering unit downstream of the coating module 2, if the coated printing sheets are to be lapped under elevated pressure to increase the adhesion of the coating or to increase the smoothness and gloss of the printing sheet.

Within the coating module 2 used for the film transfer, a web lead is shown for transfer films 5.

Transfer films 5 that can be used for the processing have a multi-layer construction. They have a carrier layer on which an image-forming layer is deposited over a separating layer. The separating layer is used for easier removal of the image-forming layer from the carrier layer. The image-forming layer can be, e.g., a metallized layer or a gloss layer or a textured layer or an inked layer or a layer containing one or more image patterns.

The film storage roll 8 is assigned to the coating module 2 on the side of the sheet feeder. The film storage roll 8 has a rotary drive 7. The rotary drive 7 is required for continuously regulated feeding of the transfer film 5 to the coating module 2 and is therefore controllable.

Furthermore, in the area of the film feeder and delivery system, there are guide devices 14, such as deflection or tension rolls, pneumatically activated guide means, guide plates, or the like. Thus, the film web of the transfer film 5 can always be guided smoothly without distortion and can be held at the same tension relative to the press roll 3. The guide devices 14 can also contain aids for introducing the transfer film 5. Here, automatic drawing-in aids for the film web of the transfer film 5 can also be used.

In this way, film feeding in the area of protective devices 15 surrounding the coating module 2 is simplified. The protective function of the protective devices 15 is simultaneously completely preserved.

Here, the transfer film 5 can be guided around the press roll 3, with the transfer film 5 advantageously being fed and discharged only from one side of the coating module 2 to the press gap 6 (see the dotted line representation). Unlike the illustration of FIG. 1, and depending on the space conditions, the film web can also advantageously be run on one side of the coating module 2, with the incoming and outgoing strands running parallel and close to one another.

In another embodiment, the transfer film 5 can also be fed and discharged to the press gap 6 passing the press roll 3 essentially tangentially or wrapped around this roll only over a small circumferential angle. For this purpose, the transfer film 5 is fed from one side of the coating module 2 and discharged to the opposite side of the coating module 2.

A film collecting roll 9 is shown on the delivery side of the printing unit. The used film material is wound up again onto the film collecting roll 9. Here, a controllable rotary drive 7 should also be provided for optimized production. Essentially, the transfer film 5 could also be moved by the rotary drive 7 on the delivery side and could be held taut on the feeding side by means of a brake.

For the transfer process of the image-forming, e.g., usable layer from the transfer film 5 to the printing sheet in the transfer gap 6 between the press roll 3 and the impression cylinder 4, it is essential that the surface of the press roll 3, that is, the blanket cylinder or the form cylinder, be equipped with a compressible, cushioning element.

The press roll 3 is therefore provided with a press covering 10 or as a roll with a corresponding coating. The press covering 10 or press coating can be configured, for example, as a plastic coating, comparable to a rubber blanket or printing blanket. The surface of the press covering 10 or press coating is preferably very smooth. It can also be formed from anti-adhesive material or structures. Here, for example, a relatively rigid structure can be used in the form of very fine spherical segments. A press covering 10 is held on the press roll 3 in a cylinder channel using tensioning devices.

The press covering 10 can be equipped with a specific elasticity for improving the transfer characteristics in the transfer gap 6. This covering can optionally be active in a compressible intermediate layer. This compressibility is preferably similar to or less than in conventional rubber blankets or printing blankets, which can also be used at this position.

The mentioned compressibility can be produced by means of a conventional compressible printing blanket. Furthermore, combination coverings made from a hard printing blanket and a soft bottom layer can also be used.

Furthermore, a delimited press surface area can be provided directly on the press roll 3 or on the press covering 10. This can be machined from the surface of the press covering 10 or it can also be fixed to the press roll 3 as a subsurface consisting of the material of the press covering 10.

To improve the economic efficiency of the coating method, the film advance of the transfer film 5 from the film storage roll 8 to the transfer gap 6 and to the film collecting roll 9 is controllable, such that as much as possible the transfer film 5 is stopped when there is no transfer of an image-forming layer:

Here, the transfer film 5 can be controlled so that the film advance is stopped when passing a cylinder channel holding a gripper of the sheet-guiding impression cylinder 4. The grippers hold the printing sheet on the impression cylinder 4. The press roll 3 has a corresponding cylinder channel 19 (see FIG. 3), in which a press covering 10 is held. In the area of the corresponding cylinder channels, the transfer film 5 is not pressed between the press roll 3 (printing blanket cylinder) and the impression cylinder 4. The press roll 3 then continues to run smoothly on the transfer film 5, while the transfer film 5 is set in tension not touching anything between the press roll 3 and the impression cylinder 4. This state lasts until the so-called printing start of the cylinder channel 19 ends and the transfer film 5 is clamped again between the press roll 3 and the impression cylinder 4 under the inclusion of a printing sheet. Then the transfer film 5 is transported further. The clocking of the film advance can begin or stop somewhat earlier than allowed by the channel edges of the cylinder channel according to a necessary acceleration or braking of the film storage roll 8 or film collecting roll 9. For fast-reaction clocking systems by means of so-called dancer rolls 18, as drawn, for example, in FIG. 1, control of the rotary drives 7 of the film storage rolls 8 or film collecting rolls 9 is optionally not required. Likewise, the required film tension is maintained by means of the dancer rolls 18.

A further improvement in the use of the film of the described type is given by dividing the transfer film 5 into one or more sub-film webs of smaller width. In this way, for a corresponding control with the help of the device or devices for clocking the film advance for each of the sub-film webs, the use of the transfer film 5 can also be improved for coating areas within a sheet with different lengths from zone to zone. In this way, each sub-film web is precisely forwarded only into the area where the image-forming surface layer is to be applied. In the areas not to be coated, each sub-film web can be stopped independent of the other sub-film webs, so that there is no unnecessary use of film.

Furthermore, for improving the coating method, a dryer 16 is provided in the area of the adhesive coating and in the area of the film coating. In this way, especially by means of a UV drying process, the adhesive layer applied like an image is dried by means of a first dryer 16 (intermediate dryer I), so that the usable layer of the transfer film 5 adheres better. Furthermore, the adhesive effect of the usable layer pressed onto the printing sheet can be improved by means of a second dryer 16 (intermediate dryer II), in that the drying of the adhesive is further accelerated.

Finally, the quality of the coating can be controlled by means of an inspection or monitoring device 17 after the film coating. For this purpose, the inspection device 17 is directed towards a sheet-guiding area of the coating module 2 after the transfer gap 6 and is optionally separated from the dryer 16 or is directed towards a sheet-guiding area of another sheet-guiding module arranged after the coating module 2. The coated printing sheet passing by at this location can then be checked for completeness and quality of the coating. Printing sheets identified as defective can be marked or sorted out as waste in a sorting device.

According to FIG. 2, the coating module can be provided with devices for conditioning the transfer film, in order to improve the layer transfer and the coating result. In this way, the film web 5 can be influenced by means of the film guiding device 14.

To support the visual effect of the layer application of the transfer films, according to the invention the adhesive layer taking on the application of the image-forming layer can contain a color. For this purpose, the adhesive layer can be colored with a gray tint for silver-colored or silver-luster films. For the use of gold-colored or gold-luster metal foils, the adhesive layer can be colored, for example, in a yellow tint. Thus, the effect of the image-forming layer relative to the color of the underlaying surface on the material to be printed is supported in the desired way.

Furthermore, the colored adhesive layer supports the color effect of the image-forming coating. In this way, for one, the use of economical films is allowed. Thus, the image-forming layer can be completely transparent or semitransparent, opaque or non-transparent.

The effects that can be achieved in this way include the following possible applications:

• • the compensation of very small surface defects in the image-forming coating on the material to be printed, through visual compensation of the color effect or covering of the color of the underlying material to be printed,
  • the intensification of color effects in transparent or semitransparent image-forming coatings, through the additive effect of coloring the adhesive layer and the coating on the material to be printed,
  • the combination or superposition of color effects of the adhesive and the image-forming coating, through the mixture of color effects from coloring the adhesive layer and the coating on the material to be printed, or
  • the support of glossy effects of the image-forming coating, through the additional glossiness of the adhesive layer for transparent or translucent coatings on the material to be printed.

Consequently, the visual effect of the image-forming coating can also be influenced at a later time. Here, the spectrum of applications for standard transfer films 5 can advantageously be expanded for the creation of high-quality coatings with the cold foil stamping method.

To improve the glossiness, the application of the image-forming layer by means of an adhesive reacting with ultraviolet radiation is in this connection discussed again. Here, colorless or colorable UV ground tints are applied. This UV ground tint is applied by means of the application unit 1 for the adhesive in a corresponding way via an offset printing plate. In this way, an improved gloss, and thus the glossiness of the image-forming layer on the material to be printed, is produced. Thus the adhesive effect of the UV ground tint can be completely utilized and the smoothness of the coating is increased.

LIST OF REFERENCE SYMBOLS

• 1 Application unit
• 2 Coating module
• 3 Press roll
• 4 Impression cylinder
• 5 Transfer film/film web
• 6 Transfer gap
• 7 Roll drive
• 8 Film storage roll
• 9 Film collecting roll
• 10 Press covering
• 11 Inking/dampening unit
• 12 Plate cylinder
• 13 Printing blanket/rubber cylinder
• 14 Film guide device
• 15 Printing unit protective device
• 16 Dryer
• 17 Inspection device/monitoring system
• 18 Dancer roll
• 19 Cylinder channel
• 20 Press surface
• 21 Metering system
• 22 Screen roller
• 23 Transfer roller
• 24 Form cylinder

Claims

1-8. (canceled)

9. A device for transferring an image-forming layer from a transfer foil to a printing sheet comprising: an application unit for coating an image area of the printing sheet with an adhesive pattern; and a coating module for transferring the image-forming layer from the transfer foil to the printing sheet, the coating module including an impression cylinder and a press cylinder that define a transfer gap therebetween, the transfer foil being guidable through the transfer gap together with the printing sheet with a coated side of the transfer foil including the image-forming layer in contact with the printing sheet such that the image-forming layer is transferred to the image area of the printing sheet having the adhesive pattern; wherein the adhesive pattern has a color that enhances a visual effect of the image-forming layer when applied to the printing sheet.

10. The device according to claim 9 wherein the adhesive pattern is dryable using ultraviolet (UV) radiation.

11. The device according to claim 10 wherein the adhesive pattern includes a UV ground tint.

12. The device according to claim 11 wherein a UV dryer for at least partially drying the adhesive pattern including the UV ground tint is arranged the application unit and the coating module.

13. The device according to claim 12 wherein a second UV dryer is assigned to the coating module for drying the adhesive pattern including the UV ground tint after the image-forming layer is transferred to the printing sheet.

14. A method for transferring an image-forming layer from a transfer foil to a printing material in a sheet-processing machine comprising the steps of: coating an image area of the printing material with an adhesive in an application unit; guiding the transfer foil together with the printing material through a transfer gap in a coating module defined by an impression cylinder and a press cylinder, the transfer foil including a coating side having the image-forming layer that is in contact with the printing material as the transfer foil and printing material are guided through the transfer gap such that the image-forming layer is transferred to the image area of the printing material having the adhesive; wherein an adhesive is selected that enhances a visual effect of the image-forming layer when applied to the printing sheet.

15. The method according to claim 14 further including the step of drying the adhesive layer using UV radiation.

16. The method according to claim 15 further including the step of printing an image over the image-forming layer transferred onto the printing material in a printing unit arranged downstream of the coating module.