EP1526963A1

EP1526963A1 - Laser-supported reproduction method

Info

Publication number: EP1526963A1
Application number: EP03790699A
Authority: EP
Inventors: Norbert Lutz
Original assignee: Leonhard Kurz GmbH and Co KG
Current assignee: Leonhard Kurz Stiftung and Co KG
Priority date: 2002-08-09
Filing date: 2003-08-08
Publication date: 2005-05-04
Also published as: CN1684818A; RU2005106263A; US20050269303A1; AU2003263129A1; WO2004020176A1; US7357075B2; RU2320483C2; CN100375673C; JP2005535483A

Abstract

The invention relates to a device and a method for the generation of a marking on a substrate. Said marked substrates are applied, for example, on documents such as credit cards, personal identity or banknotes, as security features for protection against forgery. Embodiments of said security features comprises diffractive or holographic structures. The generation of the markings is carried out by means of shaping with a die. A change in the embodiment of the marking is possible by means of a time-consuming change of the die. According to the invention, the novel device and the novel method permit the production of individualised markings on a substrate with little complex equipment. The novel device comprises a reproduction device (41), embodied as a reproducing roller, with a reproduction surface, a device for generating a radiation (30) and a counter-pressure device (42) with a counter-pressure surface. A substrate (43) is arranged between the reproduction surface of the reproduction device (41) and the counter-pressure surface of the counter-pressure device (42) such that a shaping region of the reproduction surface is shaped on the substrate (43) in a contact region (53) between the reproduction surface and the substrate (43).

Description

Laser-assisted replication process

The invention relates to a method for producing a marking, for example numbers, letters, surface patterns, surface images or decor, on a substrate, preferably a film, in particular transfer film, energy from a controllable energy source in the form of radiation, preferably laser radiation, into a replication surface Replication device for forming at least one impression area is introduced and the impression area of the replication surface is molded onto the substrate by the replication device contacts the substrate under pressure, as well as a device for generating a marking, for example numbers, letters, surface patterns, surface images or decor a substrate, preferably a film, in particular transfer film, with a replication device which has a replication surface, with a radiation-generating device, preferably a laser system, the radiation for forming at least one information area is directed to at least a portion of the replication surface, and with a counterpressure device having a counterpressure surface, the substrate being arranged between the replication surface of the replication device and the counterpressure surface of the counterpressure device in order to apply the impression region to the surface in a contact area between the replication surface and the substrate Imprint substrate. Protecting documents with security features has now become the standard for credit cards, ID cards and banknotes, for example. The counterfeit security of these features is based on the fact that a high level of specialist knowledge and extensive equipment are required for their manufacture. A particularly successful and difficult to imitate security feature is an optical variable device. Versions of this security feature have diffractive or holographic structures, which lead to an optical effect, such as a color change, a motif change, or a combination of both, when the light incidence or viewing angle changes during the visual check of the authenticity of the security label. The security feature can thus be checked for authenticity without further technical aids. An essential component of these security elements is a mostly thermoplastic or UV-curable layer, into which the diffractive or holographic structure is embossed in the form of a surface relief. This layer can be part of a transfer film, the security element being manufactured first and then being transferred to the document to be secured. This layer can also be formed as an additional layer directly on the object to be secured. Rotating embossing cylinders, such as are described, for example, in EP 0419773, or stamping dies, such as are disclosed in DE 2555214, are used to transfer the surface relief from a die to the thermoplastic layer. The production of the matrix is technically very demanding due to the fine diffractive or holographic structures and is also cost-intensive. To produce the matrices, templates, also called masters, are first produced, for example by interfering laser beams and etching processes or by electron beam writing, which are then usually electroplated.

For increased security against counterfeiting, the known methods aim to ensure that the same security feature is not applied to each document, but rather that the security features are applied to the respective document or to the

Identity of the holder of the document adjusted, i.e. individualized. There are two difficulties with the above methods: On the one hand, a large number of individualized masters would have to be produced, which is very cost-intensive, on the other hand, the matrices in the replication devices would have to be exchanged, which would lead to very long set-up times. As alternatives, methods and devices are known that only mold partial areas of a die in order to generate individualized security indicators.

CH 594495 describes a method for embossing a relief pattern into a thermoplastic information carrier, wherein only partial regions of the die are selectively molded into the thermoplastic layer. In terms of process engineering, these impression areas are selected either by heating these areas by means of heating tapes through which current flows, or by pressing only the selected impression areas onto the substrate by means of a counterpressure device which has height-adjustable partial areas. A high local resolution in the selection of the impression areas is not to be expected with this method, since the heat conduction during the long heating and cooling phase of the heating bands means that the limits of the impression areas can only be determined imprecisely or the dimensions of the impression areas can be determined by the dimensions of the bands or the dimensions of the height-adjustable sections are fixed. This method is therefore limited in that it has a low local resolution.

EP 0169326 describes a device for producing a marking on a substrate and the corresponding method. The device has a replication device in the form of an unheated embossing die, and a pressure plate, which is designed as a counterpressure device. The embossing die has a replication surface that is structured with microstructures to be molded. The device has a laser arrangement which generates a laser beam which is directed towards the substrate by the reverse direction. In the known method, the substrate is first pressed onto the printing plate by the embossing stamp. Due to the absorption of the laser beam directly incident on the substrate in the embossing area, the substrate is selectively heated locally and brought to a temperature at which it can be permanently deformed. By Positioning of the laser beam can be selected and transferred selectively.

With this method and this device, it has a restrictive effect that the replication device is designed as an embossing stamp. As a result, this process is limited to cyclical processing, which prevents high productivity.

The invention has for its object to provide a method and an apparatus that allow the production of preferably individualized markings on a substrate, preferably a film, with little equipment.

The object is achieved with the method according to claim 1 and the device according to claim 11.

With the method according to the invention, a marking is produced on a substrate, preferably a film, in particular a transfer film, the temperature of the replication surface being controlled at least in a partial area using an additional controllable energy source, an energy input by radiation from the radiation source and an energy input into the replication surface of the additional controllable energy source is introduced, so that at least a section of the replication surface is formed as a heat combination area, so that the impression area is molded onto the substrate, the section of the replication surface designed as a heat combination area or a section of the replication surface complementary to the heat combination area forming the impression area.

In the method according to the invention, the replication device is first heated with an additional energy source, so that regions or at least partial regions of the structured replication surface of the die have a first temperature. The replication surface of the replication device is then exposed to radiation, so that part of the radiation is absorbed by the replication surface and energy is introduced into the replication surface.

Due to the interaction of the heating of the replication device by the additional energy source and the selective heating by the radiation, areas with different temperatures, in particular at least two areas with different temperatures, are created on the replication surface. A part of the areas preferably has the first temperature, another part of the areas preferably has a second temperature, which is achieved by the additional energy input by the radiation. The areas with the second temperature can be called heat combination areas due to their origin.

The process can be carried out in such a way that either the first temperature or the second temperature corresponds to the working temperature of the molding process, so that in the case of an impression, either the partial areas with the first temperature or the partial areas with the second temperature are permanently molded onto the substrate.

The individualized marking preferably consists of the impressions of the partial areas of the replication surface which were selected for an impression by the temperature control described above. The individualization of the marking, i.e. the change in the selection of the molded areas can thus be made by changing the temperature distribution on the replication surface. Such a change can be made via the control of the radiation generating device, e.g. B. the laser system, or the corresponding beam guidance and beam shaping devices.

In a preferred development of the method the first temperature is in a plastic temperature range T _p ι _ast for the respective substrate and the second temperature in a flow temperature range Tfiiess for the respective substrate, wherein the flow temperature range is above the plastic temperature range. The first temperature is preferably at least 100 ° C., in particular at least 170 ° C.

The plastic temperature is the substrate-specific temperature at which an impression leads to a permanent marking in the substrate. The plastic temperature range preferably extends between +/- 2% of this substrate-specific temperature. A typical temperature range of this type would be, for example, 180 ° C +/- 3.6 ° C.

If the replication device is contacted with the substrate under pressure while there is a temperature in a partial area that is in the plastic temperature range, the structured replication surface is permanently molded from this partial area onto the substrate.

If the temperature is within a flow temperature range, after the die is separated from the substrate, the deformed material of the substrate will begin to flow. As a result, the surface textures molded into the substrate are smoothed, so that they are not retained as optically active structures on the substrate.

In this embodiment of the method, the subareas are molded onto the substrate that have been tempered to plastic temperature and that have not received any additional heat input from the radiation. The radiation can be used to make a negative selection of partial areas.

According to another preferred embodiment of the method, the first temperature is in an elastic temperature range T _e i _as t for the respective substrate and the second temperature in a plastic temperature range T _p ι _ast for the respective substrate, the elastic temperature range being below the plastic temperature range. The second temperature is preferably at least 100 ° C., in particular at least 170 ° C.

The subareas whose temperature is in the elastic temperature range only cause an elastic deformation of the substrate. After separation of the Replication devices from the substrate spring back the introduced surface structures elastically and the substrate takes on its original surface shape again approximately. There are no optically active structures on the substrate. In this execution of the method, the

Transfer heat combination areas. The additional heat input from the radiation thus represents a positive selection of partial areas.

The substrate can be made up of several layers. The specified temperatures or the specified temperature ranges of the substrate are in particular temperatures or temperature ranges of a thermoplastic layer which is part of the substrate. Additional layers of the substrate, e.g. the carrier layer of the substrate can have a different temperature.

In an advantageous development of the method, the replication device is designed as a replication roller, the radiation being introduced into the replication roller at a first angular position of the replication roller and the contact of the replication roller with the substrate at a second angular position. The intermediate angle between the first and second angular positions in the direction of rotation of the replication roller is so small that the heat combination area generated by the radiation in the first angular position still has sharp contours after rotation of the replication roller in the second angular position. This is the case, for example, if the blurring of the latent thermal image caused by thermal conduction is smaller than the reciprocal, desired resolution of the replication process. The definition of the unsharpness circle from the geometric optics can be used as a measure of the unsharpness.

In the limit, this intermediate angle can be in the range of 0 °, so that the two angular positions are arranged to overlap.

Furthermore, the object is achieved by a device according to claim 11, wherein the replication surface of the replication device is formed on an outside of a replication roller. The device according to the invention serves to apply or generate a marking on a substrate. The marking has a surface structure which preferably has a diffractive or holographic effect, or a preferably diffuse or directionally scattering matt structure which is introduced into a thermoplastic layer of a substrate, in particular a body, by means of replication processes. The substrate can have further layers with different layer materials as well as a carrier layer. The marking can be designed as a figure, number, character, surface pattern, surface image, lettering, numbering, security indicator or in any other form.

The marking can be introduced into the substrate by means of a replication device with a replication surface that has surface structures. The replication device can be designed as a replication roller with an at least partially cylindrical shape and rotatable about its coaxial axis of rotation. The cylinder surface, in particular the cylinder jacket, can be designed as a replication surface.

The substrate is arranged between the replication roller and a counter pressure device to form a contact area.

The back pressure device, e.g. can be designed as a counter-pressure plate or counter-pressure roller, has a counter-pressure surface on which the substrate is supported at least in the contact area, so that the replication roller can interact with the substrate in the contact area under pressure.

With the device according to the invention, the radiation can be used to selectively select partial areas of an embossing die for the impression, and the markings formed from the impressions of the partial areas can thus be designed individually. It is particularly advantageous here that the individualized marking in the form of the selection of the areas together with a security feature, namely e.g. B. the diffractive areas, through a common replication process be transmitted. Furthermore, the device according to the invention allows economical production due to the continuous, non-clocked mode of operation.

The device is advantageously further developed when the radiation is supplied by the counterpressure device. The radiation transmits the

Back pressure device or parts of the back pressure device before the radiation impinging on the replication surface to form the impression areas.

The counterpressure device can also be made transparent in this development of the device. The area jerk or parts of the

Counter jerk device, in particular the sections belonging to the counter pressure surface, can have omissions and / or inserts transparent to the radiation and / or can consist of a material transparent to the radiation.

In modified embodiments, the counter pressure device is implemented as a counter pressure roller. The counter pressure roller is preferably cylindrical, the cylinder surface being designed as a counter pressure surface. In particular, the counter-pressure roller is rotatably mounted about its coaxial axis of rotation.

If the counterpressure device is designed as a counterpressure roller, the radiation can be supplied, for example, in the following different ways: In a first type, the radiation can be arranged outside the counterpressure roller and the substrate preferably has an angle to the back and / or front of the Transmit substrate-oriented beam propagation direction and then hit the replication surface.

In a second type, the radiation can transmit the counter-pressure roller along the entire radial extent of the counter-pressure roller, the radiation entering through the counter-pressure surface in a region of the counter-pressure roller facing away from the contact area and exiting again through the counter-pressure surface in the contact area. In the further course, the radiation can leave the substrate aligned preferably at right angles to the rear and / or front of the substrate Transmit the beam propagation direction and preferably hit the replication roller in the contact area.

In a third type, if the counter-pressure roller is designed as a hollow body, preferably as a hollow cylinder, the radiation can also emanate from the cavity in the hollow body through a wall of the hollow body, in particular through the

Transmit cylinder wall, so that the radiation preferably exits in the contact area through the counter pressure surface. In the further course, the radiation can transmit the substrate with the beam propagation direction preferably oriented at right angles to the rear and / or front side of the substrate and can strike the replication roller preferably in the contact area.

The device is particularly advantageously developed for the last embodiment if a radiation-generating unit, preferably a laser system, or parts thereof or a beam deflection unit is provided within the counter-pressure device.

In a further advantageous development of the device or the method, the radiation is fed to the replication surface to form the impression areas through the substrate. The radiation enters on a rear surface of the substrate and emerges on an opposite front surface of the substrate and subsequently strikes the replication surface. The substrate is preferably transparent to the radiation. In modified embodiments, the substrate can partially or almost completely absorb the radiation in one or more layers. The direction of propagation of the radiation within the substrate can be oriented perpendicular to the front and / or the back of the substrate. In modifications, the substrate is irradiated obliquely, the direction of propagation of the radiation within the substrate being oriented at an angle, in particular at an angle between 60 ° and 90 °, with respect to the front and / or back of the substrate.

The device is advantageously further developed if a cooling device is provided for cooling the replication surface, by means of which, in particular, an introduced latent thermal image can be deleted or somehow modified. The cooling device can be designed as a blower, with an air flow generated by the blower being directed onto the replication surface and cooling it. A similar function can be performed by gas stream cooling, in which case a gas stream, preferably a noble gas or nitrogen gas stream, strikes the replication surface and also cools it.

In further embodiments, the cooling device can be implemented as a cooling roller, which is offset parallel to the replication roller and makes contact with it along a linear surface. The thermal contact between the replication roller and the cooling roller results in heat dissipation and thus the cooling of the replication roller.

When using a replication roller, the cooling device is preferably arranged such that it acts on the replication surface in an area which lies in the direction of rotation of the replication roller between the contact area of the replication device and the substrate and the point of incidence of the radiation on the replication surface.

In a further embodiment of the device, the radiation-generating device is designed as a laser system. This laser system can expediently have a scanner system and / or a mask projection system. When using a scanner system, the laser beam is shaped in such a way that the diameter of the laser spot when it hits the replication device is preferably in a range between 0.05 mm and 2.0 mm. This laser spot can be passed through the scanner system sequentially in writing over the replication device. The scanner system can be a system with deflection devices, for example deflection mirrors, or a system with flying optics. The position of the laser spot on the replication device can be changed by the user by means of a controller, preferably a path controller, so that different geometric shapes, images, letters and numbers can be written flexibly on the replication device with the laser spot. In other embodiments, the replication device can be exposed areally by a mask projection system. Here, the beam shaping can be designed in such a way that a mask, for example by a 4f structure, is imaged on the replication device in such a way that the shape of the laser spot Form of the omissions in the mask matches. The mask can be a rigid mask or a matrix arrangement of elements that transmit or extinct in a controlled manner the laser beam, which can be, for example, movable mirrors or liquid crystal elements.

There is an advantageous embodiment if a control device, in particular a freely programmable control device, is provided which preferably controls the selection of the radiation areas by controlling the radiation-generating device. In this advantageous development, the patterns of the markings are preferably digital information, e.g. provided as a file, which were generated by image processing programs, by computer-aided methods or the like. This information is converted by the control device, in particular by activating the laser system, into a time-dependent change in the area power density of the radiation impinging on the replication device. The impression areas and thus the pattern of the marking are determined by the controlled selection of the irradiation areas.

The control of power, beam direction and / or surface power density of the laser beam enables several operating modes of the laser beam.

In a first operating mode, the laser beam is switched on and off in control sequences, so that markings that are separated from one another are generated on the substrate. The design of these different markings can be the same in each case or can vary from marking to marking through individualized features, for B. distinguish by consecutive numbering.

In a second mode of operation of the laser beam, the laser beam is switched on continuously and the point of incidence of the laser beam is moved on the replication roller. The point of impact moves along or counter to the replication roller and parallel to the axial extension of the replication roller. The movement is caused by a parallel displacement of the laser beam to itself or by an angular deflection of the laser beam.

In this operating mode, a marking can be formed with a pattern that varies in the feed direction of the substrate. Above all, this operating mode allows that control sequences of movements of the laser beam for generating a single marking can take place over several rotations of the replication roller, that is to say over several working cycles. For example, this makes it possible to create any desired lettering in the feed direction on the substrate. If this operating mode is modified, the laser beam is switched on continuously and the beam profile of the laser beam is changed as a function of time. A combination of the above operating modes is also possible.

The device is expediently developed if the replication surface is structured with a surface relief. This surface relief is the negative for the structures that are transferred to the substrate during the molding process. The replication surface can be partially or completely structured. The depth of the surface relief is preferably between almost 0 and 20 μm, in particular between 0.1 and 0.5 μm. The surface relief can, in particular to form a diffractive or holographic structure on the substrate, be designed in partial areas or over the entire surface in a lattice shape. The grid spacing, that is to say the spatial frequency, is preferably between 4000 lines per mm and 10 lines per mm, in particular 1000 lines per mm. The replication surface can also be divided into partial areas, the dimensions of which are preferably smaller than 0.3 mm, and which differ from one another by the spatial frequency, the lattice orientation, lattice type or other parameters.

In a further advantageous embodiment of the invention, these partial areas can be arranged periodically repeating, in particular alternating. Possible embodiments are that an arrangement of different partial areas, for example an arrangement of two to six, preferably three partial areas, forms a pixel unit. A large number of pixel units can be arranged to form a surface image. The three sub-regions mentioned by way of example preferably represent the three basic colors due to their grid structure. This pixel unit or the partial areas can on the Replication surface to be arranged regularly or periodically repeating, for example lattice-shaped or alternating.

The surface relief can also be provided with surface structures that have a stochastic or quasi-stochastic distribution, in particular for producing a matt structure on the substrate. A matt structure on a substrate creates a diffuse scattering of the light incident on the substrate as a special optical effect. For the creation of a matt structure, the surface relief has surface structures, e.g. Grooves, grooves, craters, holes, etc., the respective shapes and / or orientations of which are each of the same or any other design and which can be distributed uniformly, stochastically or quasi-stochastically on the replication surface. For example, the surface relief can be designed with a structure similar to a brushed surface.

In a further advantageous embodiment, the replication device has a pressure die made of metal foil, in particular of nickel or of a nickel compound. The use of metal foils made of nickel or of nickel compounds makes the galvanic molding of a diffractive structure of a master easier. As an alternative to these materials, a material can also be used which has a particularly high absorption, in particular a higher absorption than nickel, for the wavelength of the laser radiation used. It is advantageous in this embodiment that the irradiated energy required to generate the latent thermal image on the replication device, preferably on the replication surface, is significantly reduced. Accordingly, less powerful and therefore less expensive lasers could be used in the device.

It is a particular advantage of the device and method to be able to cast different markings from a single die, for example also document-specific or person-specific, onto a substrate, partial areas of this die being selectively activated or deactivated for the molding process. Exemplary embodiments of the method and exemplary embodiments of devices for generating a marking are described below using figures. Show:

FIG. 1 a shows a first exemplary embodiment of a device for applying a marking to a substrate in a sectional view,

1b shows the temperature profile on the replication surface of the replication device in FIG. 1a in a coordinate system and a marking in the substrate corresponding to the temperature profile in FIG

Sectional view

2a shows the first embodiment of the device in FIG. 1a with a modification of the method in the same representation as in FIG. 1a,

Figure 2b shows the temperature profile on the replication surface of the replication device in Figure 2a and a marking corresponding to the temperature profile in the substrate in a representation similar to Figure 1b,

Figure 3 shows the heat distribution in a section of the replication device in

FIG. 1a shows a schematic sectional illustration when exposed to the laser beam,

4a, b are schematic representations to illustrate the principle for generating a negative or positive image,

5a, b each show a section of the surface of the replication device in FIG. 1a and a marking generated by the replication device, each as a top view in a schematic representation,

6a shows a second exemplary embodiment of a device for applying a marking to a substrate in the same representation as FIG. 1a, 6b shows the temperature profile on the replication surface of the replication device in FIG. 6a and a marking in the substrate corresponding to the temperature profile in a representation similar to FIG. 1b.

FIG. 1 a shows a schematic sectional illustration of the structure of an exemplary embodiment of a device for producing a marking on a substrate 43. The device has a replication roller 41 and an as

Counter pressure roller trained counter pressure device 42, which is arranged axially parallel to the replication roller 41 and offset vertically downwards. The film-like substrate 43 is provided in a horizontal orientation between the replication roller 41 and the counterpressure device 42. A laser beam 30 crosses the substrate 43 and strikes the replication roller 41. The alignment of the course of the laser beam is described in more detail below.

The metallic or metallic-coated replication roller 41 is designed in the form of a cylinder, the corresponding cylinder jacket as a replication surface with surface structures in the form of

Diffraction embossed structures 46 is executed. The diffraction embossing structures 46 have a depth of preferably almost 0 μm to 20 μm and have line spacings or local frequencies from 10 lines per millimeter to 4000 lines per millimeter. The replication roller 41 is controlled by a controllable inner, i.e. the heat source acting on the inside is heated so that the entire area of the replication surface which has the diffraction embossing structures 46 can be tempered.

The area jerking device 42 is designed as a roller in the form of a cylinder and is made of rubber or has a casing made of rubber. The corresponding cylinder jacket forms a counter pressure surface which interacts with the replication surface of the replication roller 41. The film-like substrate 43 has a front surface 103 pointing upwards in FIG. 1a to the replication roller 41 and a rear surface 102 pointing downwards in FIG. 1a to the counterpressure device 42 and is designed as a multilayer composite with a thickness of less than 1 mm. The multilayer composite comprises a thermoplastic layer 51, a carrier film 50 and optionally one or more further, in particular different layers 52 such as, for example, B. metallization layers, interference layers, protective lacquer layers, release layers, carrier material layers or adhesive layers.

An arrow 48 and an arrow 49 indicate the respective directions of rotation of the replication roller 41 and the counterpressure device 42, the replication roller 41 in FIG. 1a rotating clockwise and the counterpressure device 42 rotating counterclockwise. An arrow 47 points in the direction of advance of the substrate 43, which moves to the left in FIG. 1a. The replication roller 41, the substrate 43 and the counter pressure device 42 cooperate in such a way that the replication surface with the diffraction embossing structures 46 is pressed onto the substrate 43 under a certain, adjustable pressure during the rotation of the replication roller 41 and the counter pressure device 42. The contact area between replication roller 41, counterpressure device 42 and substrate 43 forms the replication gap 53.

In Figure 1a, the laser beam 30 is shown as an arrow coming obliquely from the bottom right. The illustrated course of the laser beam 30 begins in an area that lies below the substrate 43, i.e. is arranged on the side of the rear surface 102 of the substrate 43, and on the substrate-incoming side of the device. The

Laser beam 30 is aligned with the replication roller 41, the laser beam 30 being arranged over the entire course outside the counterpressure device 42. The laser beam 30 enters the substrate 43 through the rear surface 102 with an entry angle of less than 30 °. The entry point of the laser beam 30 into the substrate 43 is arranged in the feed direction of the substrate 43 in front of the replication gap 53. The entry angle is measured against the surface normal of the substrate 43 at the entry point. The laser beam 30 traverses the substrate 43, emerges through the front surface 103 of the substrate 43 and strikes the replication surface. Sub-areas are identified on the replication surface as replication surface sections 70a, b. It is the area of the replication surface treated with the laser beam.

In the position of the device shown in FIG. 1a, a first replication surface section 70a is located in the direction of rotation of the replication roller 41 in a position before entry into the replication nip 53, specifically in a position in which the replication surface section 70a exits from the substrate 43 Laser beam 30 is being irradiated.

During the operation of the device, the replication roller 41 continuously rotates clockwise and the replication surface section 70 a is passed through the replication gap 53 after the irradiation. This is where the irradiated replication surface section 70 a is molded as a marking in the substrate 43.

The second replication surface section 70 b is in the position of the device shown in FIG. 1 a in the direction of rotation of the replication roller 41 in a region after the replication nip 53. This replication surface section 70 b has already passed through the phases of the irradiation before the replication nip 53 and the impression in the replication nip 53 , The shaped marking 45 corresponding to the replication surface section 70b is accordingly located in a region of the substrate 43 which is arranged after the replication gap 53 in the feed direction of the substrate 43.

In the embodiment of the method shown in FIG. 1 a, the replication surface is brought to a temperature by the internal controllable heat source which lies within the elastic temperature range T _e i _a st.

The replication surface sections 70 a, b are further heated by the additional energy inputs by means of laser beam 30 during the irradiation. Through the combination of the energy input through the heating with the inner Heat source and the additional energy input due to the irradiation with the laser beam 30 form in the area of the replication surface sections 70 a, b heat combination areas. These heat combination areas represent latent thermal images, which can be designed as a simple geometric shape, such as a circle, polygon, closed polygon, but also as a letter, number or symbol.

The energy inputs are sized in the example of Figure 1a that the heat combination regions, ie, the replication surface 70a, b, when in contact with the substrate 43 in the replication 53 have a temperature within the plastic temperature range T _p ι _as t. These areas are permanently molded into the substrate 43.

The remaining areas on the replication surface have temperatures below the temperature in contact with the substrate 43 in the replication gap 53

Plastic temperature range T _p ι _as t. So in Elastiktemperaturbereich T _e iast on. These areas are not permanently molded into the substrate 43.

After taking the impression in the replication gap 53, it may be desirable for the current latent thermal image to be erased and for the replication surface to be brought into a state so that a new latent thermal image can be introduced.

A cooling area is provided in the direction of rotation of the replication roller 41 after the replication nip 53 for deleting the current latent thermal image. The replication surface runs through this cooling area and interacts with a cooling device, not shown in FIG. 1a. The replication surface is thereby cooled to a temperature below the temperature range T _p ι _as t.

The replication surface is then tempered again to a temperature within the temperature range T _e i _ast -

The latent thermal image is therefore erased by a controlled change in the temperature of the replication surface. Alternatively or additionally, the latent thermal image is deleted independently by conduction in the sense of fading of the latent thermal image.

The principle of the method for producing a marking 45 on the substrate 43, as used in FIG. 1 a, is to be clarified again with reference to FIG. 1 b.

FIG. 1b shows a coordinate system 20, which shows the temperature of the replication surface as it passes through the replication gap 53

Temperature profile T shows. Furthermore, the area of the substrate 43 is shown in an enlarged sectional view in FIG. 1a, which carries the marking 45 corresponding to the temperature profile T.

In the coordinate system 20, the temperatures of the replication surface during the molding process are plotted in the replication gap 53 on the vertical Y axis. The corresponding positions are plotted on the replication surface along the circumference of the replication roller 41 on the horizontal X axis of the coordinate system 20.

The temperature scale on the Y-axis is high divided into three areas: the first area is the Elastiktemperaturbereich T _e iast- The overlying the temperature range at higher temperatures is the plastic temperature range T _p ι _as t- The illustrated on this lying highest temperature range is the flow temperature range Tfiieß.

To illustrate the effects of the temperature on the replication surface during the molding process on the result of the molding process, the section of the substrate 43 corresponding to the temperature profile T is shown below the coordinate system 20. The substrate 43 is oriented parallel to the X axis of the coordinate system 20 in its longitudinal extent. The temperature profile of the replication surface shown along the X axis is divided into three areas I, II, III.

In the regions I and III, the replication surface while passing through the replication 53 temperatures within the Elastiktemperaturbereichs T ias _e _t. In area II, the temperature as it passes through the replication gap 53 lies within the plastic temperature range T _p ι _ast -

When the replication surface comes into contact with the substrate 43, the structures in the region I are introduced into the substrate 43 as elastic deformations. After separation of the replication surface and substrate 43, the substrate 43 resumes its original shape in these regions in an elastically resilient manner and no surface structures remain in the substrate 43.

In area II, when the replication surface comes into contact with the substrate 43, a permanently remaining marking is molded into the substrate 43. The marking shown in FIG. 1b corresponds to the marking 45 in FIG. 1a.

In area III, analogous to area I, no surface structuring is produced in substrate 43 when the replication surface comes into contact with substrate 43.

The method shown in FIGS. 1a and 1b creates a marking 45 on the substrate 43, in which only the replication surface sections 70a, b irradiated with the laser beam 30, that is to say the heat combination regions, are molded. A marking 45 formed in this way is also referred to below as a positive image.

A time-dependent side effect of the method illustrated in FIGS. 1a, b and its compensation is described below:

In FIG. 1 a, the energy input into the replication surface section 70 a takes place by means of a laser beam 30 in an area on the rotating replication roller 41 in front of the replication nip, in a position that unites with the replication nip 53 Rotation angle distance of approximately 20 °. The spatial distance between the irradiation position and the impression position results in a time interval between the irradiation process and the impression process.

The time interval leads to heat losses (energy losses) in the

Heat combination areas, e.g. B. due to heat conduction. In extreme cases, this effect can lead to the fact that the heat combination areas in the replication gap 53 have a temperature below the plastic temperature range T _p ι _as t.

To compensate for the heat losses of the energy input is increased accordingly by the laser beam 30 so that in the heat combining areas a temperature within the plastic temperature range T _p ι _ast during passage through the replication 53 is ensured. The increase can so be such that the heat combination areas after irradiation _f initially a temperature within the flow temperature range T comprise n _ESS and to reach the Replizierspalts cooled 53 to a temperature within the plastic temperature range T _p ι _as t.

The described side effect can occur not only in connection with the temperature or the temperature range T _p ι _ast , but also analogously or similarly at other temperatures or temperature ranges, for example T _f | j _es s, T _e ι _as t. The compensation can be carried out analogously to the procedure described above.

FIG. 2a shows the same exemplary embodiment of the device as in FIG. 1a with a second embodiment of the method, the difference between the embodiments of the method being the temperature control.

In the example shown in Figure 2a the replication process is brought up through the inner controllable heat source to a temperature which is within the plastic temperature range T _p ι _ast.

The irradiated replication surface sections 70 a, b are further heated by the additional energy input by means of laser beam 30. The energy inputs are like this dimensioned so that the replication surface sections 70a, b have a temperature within the flow temperature range T _f üeα in contact with the substrate 43 in the replication gap 53.

Only the non-irradiated areas have a temperature in the temperature range T _p ι _as t in contact with the substrate 43 in the replication gap 53, the irradiated areas have a temperature there within the temperature range T measurement.

In this second embodiment of the method, only those regions of the replication surface are molded which are complementary to the replication surface sections 70a, b irradiated with the laser beam 30, that is to say complementary to the heat combination regions.

The deletion of a latent thermal image generated in this way on the replication surface can be carried out analogously to the deletion described in connection with FIG. 1a.

The principle of the implementation of the method according to FIG. 2a is illustrated again schematically in FIG. 2b in the same representation as FIG. 1b, the temperature profile T thus being designed differently than in FIG. 1b.

The temperature profile T in figure 2b, the replication surface while passing through the replication 53 is located in the regions I and III in the plastic temperature range T _p i _a st. whereas in area II the temperature is within the flow temperature range _f iieß.

In area I, when the replication surface comes into contact with the substrate 43, a permanently remaining marking is molded into the substrate 43.

When the replication surface comes into contact with the substrate 43, the structures in the region II are first introduced into the substrate 43 as plastic deformations. After separation of the replication surface and substrate 43, the substrate material begins to flow, so that the surface structures introduced into the substrate 43 do not remain permanently. In area III, analogous to area I, when the replication surface comes into contact with the substrate 43, a surface structuring is generated in the substrate 43.

The substrate 43 in FIG. 2b has a surface structuring in regions corresponding to regions I and III, whereas in a region corresponding to region II the surface profile has healed again and the surface is almost flat or has a stochastic structure. In any case, areas II and areas I and III are visually distinguishable

A marking 45 is produced on the substrate 43 by the method shown in FIGS. 2a and 2b, in which only the regions are formed which have not been irradiated with the laser beam 30. Such markings are also referred to below as negative images.

FIG. 3 is a sectional illustration of a replication device 35, which corresponds to the replication roller 41 in FIG. 1a. The replication device 35 is provided with surface structures 36 on its replication surface. The heat distribution in the replication device in the area of the surface structuring 36 is illustrated by isotherms 32. To simplify, there are only three

Isotherms 32 are shown, which demarcate regions with different temperatures Ti, T ₂ and T ₃ . Furthermore, the laser beam 30 is shown, which is directed onto the replication surface with the surface structuring 36 and strikes it, as well as a schematic identification of the absorption volume 31.

In a first method step, the replication device 35 in the vicinity of the replication surface with the surface structure 36 is set to a first temperature Ti by the controllable heat source in the regions I, II and III shown here.

In the next method step, which can also overlap in time with the first method step, the replication device 35 is exposed in region II with the laser beam 30. Here, the laser beam 30 on the Replication surface with the surface structure 36 absorbed in an absorption volume 31. The energy input in the absorption volume 31 causes the absorption volume to increase further from the temperature Ti to a temperature T ₃ . Thermal conduction shifts the temperature range Ti further into the replication device and results in a heat distribution as shown in FIG. 3. Depending on the initial temperature Ti and the energy input as well as the position and the extent of the laser beam 30, a temperature profile according to FIG. 1b for a positive image or a temperature profile according to FIG. 2b for a negative image can be generated on the replication surface.

FIGS. 4a, b show the principle of how an individualized security feature can be generated by various embodiments of the method. On the left is a partial area of a replication surface, e.g. from the replication roller 41 from FIG. 1 a with a structured surface 2. On the right in plan view is a section 4 of a substrate after the molding process, e.g. shown from the substrate 43 in Fig. 1a.

In Fig. 4a 2, the k-shaped surface portion 3 of the surface to a temperature T, which _branch within the plastic temperature range T _p ι is the substrate. Outside this area, the surface 2 has a temperature which lies outside the plastic temperature range T _p ι _as t. In a molding process with this temperature distribution, a positive image 5 is formed on a substrate 43, the mirror-image-shaped k-shaped surface of which is filled with the impression of the surface structures of the structured surface 2.

In Fig. 4b, the k-shaped surface has a temperature T outside and the remaining areas of the surface 2 a temperature T within the plastic temperature range T _p ι _ast . The permanently remaining imprint on the substrate 43 resulting from this temperature distribution during a molding process is a negative image 6, the areas that are complementary to the mirror-image k-shaped surface being filled with the imprint of the surface structures of the structured surface 2. FIG. 5 a shows a section of the replication surface of the replication roller 41 in FIG. 1 a with a diffraction embossing structure 46, which is divided into different partial areas. These subregions have been formed from a limited number of diffraction patterns which differ with regard to the spatial frequency, the relief depth, the azimuth, the curvature of the grating, the profile shape or other parameters. In the representation in FIG. 5a, representative of the many possibilities, partial areas with three different diffraction patterns, in particular with different azimuth, are shown, namely 80, 81 and 82. Each partial area 80, 81, 82 has only one diffraction pattern. These different partial areas 80, 81, 82 are regularly arranged alternately as pixels. The partial areas 80, 81, 82 are preferably designed as delimited area fields with a square contour, for example with side lengths of less than or equal to 0.3 mm. By means of the method presented, it is now possible to activate or deactivate sub-areas 80, 81, 82 for the transfer from the replication roller to the substrate by exposure to radiation, in particular laser radiation, in order to give a positive or a negative image during a replication process produce. An image 85 generated in this way has partial area impressions 80 ', 81', 82 'of the partial areas 80, 81, 82. In this exemplary embodiment, the partial areas 80, 81, 82 of the diffraction embossing structure 46 were selected by the heat distribution in the replication device in such a way that 85 image areas 86, 87, 88 are formed in the image, each of which has only one type of diffraction pattern, that is to say only one Kind of partial area impressions 80 ', 81', 82 'are formed, namely the image area 86 exclusively from partial area impressions 81', the image area 87 exclusively from partial area impressions 82 'and the image area 88 exclusively

Sub-area impressions 80 ". When viewing the image 85, these image areas 86, 87, 88 consisting of individual separate sub-area impressions appear as full-area, homogeneous image areas as are known from conventionally produced images, with the difference that the image areas 86, 87, 88 are special have optical properties, for example holographic properties.

FIG. 5b shows on the left side in a similar representation as FIG. 5a another section of the replication surface of the replication roller 41 in FIG. 1a with a Diffraction embossed structure 46. The diffraction embossed structure again has different partial areas 80, 81, 82. On the right-hand side of FIG. 5 b, another image 95 created after the selection and molding of partial areas 80, 81, 82 according to the method presented is shown schematically. The image 95 has image areas 96, 98 and image areas 97, 99. The image areas 96, 98 are each in the form of a number, namely 1 and 5, and are filled with partial area impressions of a single type, namely the partial area impression 82 '. The image areas 97, 99, on the other hand, are formed as letters A and D and consist of a large number of partial area impressions 81 '. The sub-area impressions 81 'and 82' in FIG. 5b differ in that

Arrangement, in particular the azimuthal alignment, of the diffraction gratings, the diffraction gratings being arranged horizontally in the partial area impression 82 ′ and standing in the partial area impression 81 ′ in FIG. 5b. The different arrangement of the diffraction gratings leads to an angle-dependent diffraction effect, so that the image areas 96, 98 and 97, 99 also carry holographic information in addition to their geometric information, number or letter. With image 95 only the first characters 96, 98 are visible from a first viewing angle and only the second characters 97, 99 are visible from a second viewing angle.

FIG. 6a shows a second exemplary embodiment of a device for generating a marking in the same representation as the device in FIG. 1a. Analogously to the device in FIG. 1a, the device shown in FIG. 6a has an arrangement with a replication roller 41, a substrate 43 and a counterpressure device 42. In FIG. 6a, however, the counterpressure device 42 and the arrangement and the course of the laser beam 30 differ from FIG. 1a. The principle of the method already described in connection with FIG. 1b is illustrated again in FIG. 6b.

In the exemplary embodiment in FIG. 6a, the counterpressure device 42 is designed as a hollow cylinder with a cavity 101 and a cylinder wall 100, the outside of the cylinder wall 100 being designed as a counterpressure surface. The inner surface of the cylinder wall 100 is concentric with the counter pressure surface arranged. The cylinder wall 100 consists of a material which is transparent to the radiation, for example glass or plastic.

The laser beam 30 is directed from the cavity 101 onto the replication roller 41. Starting from the cavity 101, the laser beam 30 penetrates into the cylinder wall 100 through the inner surface, crosses the cylinder wall 100 and emerges from the cylinder wall 100 through the counterpressure surface. In the further course, the laser beam 30 crosses the substrate 43. After emerging from the substrate 43, the laser beam 30 irradiates a replication surface section 70 a, which is arranged in the region of the replication gap 53. In this exemplary embodiment, a heat combination region is therefore only formed directly in the region of the replication gap 53.

In further embodiments, parts of a laser source or an entire laser source, e.g. a diode laser, integrated in the replication roller 41 or the laser beam 30 is fed into the cavity 101, for. B. via one or more optical fibers or via an open, coaxial to the replication roller 41 beam guide. Beam guiding devices or beam shaping devices, e.g. Scanner devices can be provided in the replication roller 41.

The method for generating a marking and the control of the laser beam 30 as well as constructive or functional configurations are designed analogously to the explanations for the first exemplary embodiment of the device in FIG. 1a, so that it is also possible with the device in FIG. 6a to produce positive and negative images produce.

Claims

claims

Method of creating a mark (45) e.g. Numerals, letters, surface patterns, surface images or decor, on a substrate (43), preferably a film, in particular transfer film,

wherein energy from a controllable energy source is introduced in the form of radiation, preferably laser radiation (30), into a replication surface of a replication device (41) to form at least one impression area,

wherein the impression area of the replication surface is molded onto the substrate (43) by the replication device (41) contacting the substrate (43) under pressure,

characterized,

that the replication surface is tempered at least in a partial area using an additional controllable energy source,

that an energy input by radiation of the

Radiation source and an energy input of the additional controllable energy source is introduced so that at least a portion of the replication surface is formed as a heat combination area,

that the impression area is molded on the substrate, the as

Section of the replication surface formed in the heat combination area forms the impression area directly and / or indirectly. A method according to claim 1, characterized in that for the time of the molding process, the temperature of the replication surface outside the heat combination area is set to a temperature or a temperature range in the plastic temperature range of the substrate and the temperature of the replication surface within the heat combination area to a temperature or a temperature range in the flow temperature range of the Substrate is set.

3. The method according to claim 1, characterized in that the temperature of the replication surface outside the heat combination area to a for the time of the molding process

Temperature or a temperature range in the elastic temperature range of the substrate is set and the temperature of the replication surface within the heat combination range is set to a temperature or a temperature range in the plastic temperature range of the substrate.

4. The method according to any one of the preceding claims, characterized in that the radiation introduced to form the at least one impression area is supplied through the substrate (43), preferably outside the replication device or through the replication device.

5. The method according to any one of the preceding claims, characterized in that a rotating replication roller (41) having the replication surface on its outside is used as the replication device and that the radiation is introduced into the replication surface of the replication roller before and / or during the resulting heat combination area contacted the substrate (43) for molding.

6. The method according to claim 5, characterized in that a counter-pressure device, preferably a counter-pressure roller (42), which interacts with the replication roller (41), is used and the radiation for forming the at least one impression area by the counter-pressure device (42) or parts of the counter-pressure device ( 42) is fed into the replication surface of the replication roller (41).

7. The method according to any one of claims 5 or 6, characterized in that the introduction of the radiation into the replication surface of the replication roller (41) at a first angular position of the replication roller (41) and the molding process by contact of the replication surface of the replication roller (41) with the Substrate (43) takes place at a second angular position of the replication roller (41), an intermediate angle of less than 30 °, in particular less than 5 °, being set in the direction of rotation of the replication roller (41) between the first angular position and the second angular position.

8. The method according to any one of the preceding claims, characterized in that the radiation is sequential and / or punctiform sequentially on the replication surface e.g. acts on the replication surface of the replication roller (41).

9. The method according to any one of the preceding claims, characterized in that the position of the point of impact of the radiation on the replication surface can be controlled by one- or multi-dimensional movement of the radiation and / or that the area power density of the radiation at the point of impact of the Radiation on the replication surface is controllable.

10. The method according to claim 5 to 9, characterized in that a control sequence for controlling the radiation-generating

Device extends over more than one revolution of the replication roller (41).

11. A device, preferably for carrying out the method according to one of the preceding claims, for generating a marking (45), e.g. Numerals, letters, surface patterns, surface images or decor, on a substrate (43), preferably a film, in particular transfer film,

with a replication device (41) which has a replication surface,

with a device (30) generating radiation, preferably a laser system, the radiation (30) being directed to form at least one impression area on at least a section (70a, b) of the replication surface, and

with a back pressure device (42) having a back pressure surface, the substrate (43) being arranged between the replication surface of the replication device (41) and the back pressure surface of the back pressure device (42), in a contact area (53) between the replication surface and the substrate (43) molding the impression area onto the substrate (43),

characterized,

that the replication surface is formed on an outside of a replication roller (41).

12. The device according to claim 11, characterized in that the position in which the radiation acts on the portion of the replication surface during the irradiation process and the position of the contact area between the replication surface and the substrate (43) overlapping and / or in the direction of rotation of the replication roller (41 ) are arranged with a distance angle of less than 30 °.

13. Device according to one of claims 11 or 12, characterized in that the radiation (30) for forming the at least one impression area is supplied by the counterpressure device (42) or parts of the counterpressure device (42).

14. Device according to one of claims 11 to 13, characterized in that the counter pressure device (42), preferably in the region of the counter pressure surface, is transparent to the radiation (30).

15. Device according to one of claims 11 to 14, characterized in that the counter-pressure device is designed as a counter-pressure roller (42).

16. Device according to one of claims 11 to 15, characterized in that the counter-pressure device (42) completely or in sections as a hollow body, preferably hollow cylinder, in particular as a hollow glass cylinder, preferably with an inner surface parallel and / or concentric to the counter-pressure surface and in particular with one for the Radiation transparent cylinder wall (100) is formed.

17. Device according to one of claims 11 to 16, characterized in that the device (30) generating the radiation and / or a beam deflection unit is arranged within the counter-pressure device (42) or within the replication roller (41).

18. Device according to one of claims 11 to 17, characterized in that the radiation (30) for forming the impression areas is supplied through the substrate (43).

19. Device according to one of claims 11 to 18, characterized in that a device tempering the replication surface, e.g. a heating device and / or cooling device for heating or cooling the

Replication surface, in particular of partial areas of the replication surface, is provided, which is preferably designed as a blower, gas flow cooling, cooling roller, heating laser device, inductive heating device, resistance heating or as a device that generates heat radiation.