EP1527902A2 - Method for producing a web of material - Google Patents

Abstract

Method for preparing a material (A), in the form of an endless belt, having a relief structure, preferably a diffraction structure. Method for preparing a material (A), in the form of an endless belt, having a relief structure, preferably a diffraction structure, comprises coating a substrate, at least on some regions, with a layer of radiation-hardenable lacquer (I) and forming the relief structure in (I). The new feature is that, up to the time when the structure is formed, (I) has a degree of hardness below the gel point. Independent claims are also included for the following: (1) (A) produced by the new method; (2) safety element prepared using (A); (3) safety document that includes an element of (2); and (4) apparatus for preparing (A).

Description

The present invention relates to a method and a device for Production of sheet-like materials with a relief structure and after web-shaped materials and security elements produced by this process.

Value documents such as banknotes, checks, identity cards, credit cards and the like, often have security features with diffractive structures that have an optically variable effect. That is, when the viewing angle changes the perceptible information and / or color changes the information. Since a copier only under a certain Viewing angles display visible information and / or color can provide such security elements high counterfeit protection. Due to the appealing visual effects and the high copy protection Such security elements are also widely used in the field of Product fuse used. The security elements are either applied directly to the object of value or its packaging.

To ensure an economical production of such security elements to be able to, the diffraction structures are usually in a relief structure implemented, which is introduced into the surface of a stamping tool. With this embossing tool, suitable layers in continuous Processes are characterized and thus provided with the diffraction structures.

EP 1 310 381 A1 describes a method for producing such security elements with diffraction structures. This is a slide with a UV-curable lacquer coated, which is pre-cured to the gel point. In This pre-cured paint is then impressed the diffraction structure and the paint during the embossing process by UV irradiation on hardened. After the embossing process, the paint with the relief structure subjected to a post-curing.

The pre-cure to the gel point ensures that the paint at the time the embossing already has a certain strength. This has the disadvantage that the fine relief structures, whose dimensions are usually in the range the wavelength of visible light, not with sufficient acutance can be played back. This loss of sharpness leads to loss of brilliance on the finished optically variable element.

The invention is therefore based on the object, a method and a Device to provide a higher acutance of the Molded relief structure ensures and thus the production of optically variable security elements with increased brilliance allows.

This object is solved by the features of the independent claims. Advantageous embodiments and further developments of the invention are Subject of the dependent claims.

When curing a varnish, the liquid varnish passes through crosslinking polymerization in the solid state about. Sales at which the liquid properties and the solid state properties have the same level, is called a gel point. There occur for the first time insoluble, so-called "Gel particles" on.

According to the invention, the relief structure is in a radiation-curable Paint layer introduced, wherein the paint layer at the time of introduction has a degree of cure below the gel point.

The invention is based on the finding that below the gel point the liquid properties of the coating outweigh and thus the embossed structures without loss of sharpness 1: 1 imprinted in the paint can be. This increases the brilliance of the finished product.

In the inventive method for producing sheet-like materials with a relief structure, in particular a diffraction structure in a first step, a substrate at least partially, preferably coated over the entire surface with a radiation-curable varnish layer. Of the Radiation-curable varnish can be applied by any printing method are preferably, screen, gravure or flexographic printing process used. The flexographic printing process is used in particular if the radiation-curing lacquer is not full-surface, but only partially is applied to the substrate. The paint can, however, also with other coating systems, such as roll coaters, spray nozzles or paint spray systems, respectively. The thickness of the applied lacquer layer is in of the order of 1 to 10 microns, preferably in the range of 1 to 5 microns, more preferably in the range of 2 to 4 microns.

As a substrate is preferably a plastic film, in particular a transparent plastic film, used. A particularly preferred material is polyester, but also other plastics such as PE, PP, MOPP, PPS, PGEK, PEK, PGE, PSO, PAEK, LCP, PEN, PPT, PET, PA, PC, COC, POM, ABS and PVC, can be used. The thickness of the plastic film lies in the Order of 4 to 30 microns, preferably from 6 to 25 microns, especially preferably from 12 to 23 microns.

This substrate may be radiation-curable before coating Lacquer be pretreated in further process steps. This can happen to act pure pretreatments, such as corona discharge, the adhesion properties affect between substrate and paint. The substrate but can also provide at least partially with other coatings be that also adjust the Ablöse- or adhesion properties or the web-shaped material provided with other security features. These may be, for example, layers with luminescent and / or magnetic and / or electrical and / or optically variable and / or thermochromic properties.

The radiation-curing coating itself may also contain such security features. Alternatively, the paint can also be dyed with any printing inks. Preferably, however, transparent paints are used. The radiation-curable lacquer used is preferably UV-curable lacquers. But it could also be used other radiation-curing paints. It is also possible to use lacquers with a plurality of photoinitiators which trigger the polymerization process when irradiated in different wavelength ranges. This can have various advantages, as will be explained in more detail below. A lacquer which can be used in the context of the process according to the invention can have, for example, the following composition: 26.5% polyester 6.6% Epoxy novolac acrylate in trimethylolpropane triacrylate / hydroxyethyl methacrylate 26.5% hexafunctional aliphatic urethane acrylate 5.31% Mixture of pentaerythritol tri- and tetracrylate 21.2% Trimethylethylolpropantriacrylat 6.6% tertiary amine 6.9% Darocure (initiator for the short-wave UV range) 0.2% BAPO (initiator for the short-wave UV range)

In a further step, the relief structure is introduced into the lacquer layer, wherein the lacquer layer substantially at the time of introduction has a degree of cure below the gel point.

For the introduction of the relief structure, the lacquer layer is preferably brought into contact with an embossing tool, which on its surface the Relief structure has. This embossing tool can be a Die of any shape act. Preferably, a stamping cylinder used, the entire cylinder surface with the surface to be transferred Relief structure is provided. The production of this embossing cylinder can be done in different ways. In the case of diffraction structures becomes the diffractive motif as a so-called master structure in a nickel foil provided. Using this master structure, recombinant techniques can be used and subsequent molding, preferably galvanic molding, Metal foils, in particular nickel foils, are produced, the their entire surface is seamlessly provided with the master structure. These Metal foils are welded and formed, for example, with a laser the cylinder jacket of the embossing tool, which is mounted on a clamping cylinder becomes.

At the time of introduction of the relief structure, i. at the time, where the lacquer layer is brought into contact with the embossing tool, the lacquer layer may be substantially uncured or already on one Curing degree be pre-cured below the gel point. If the lacquer layer is precured, this precuring preferably takes place directly before the embossing process. That is, leaves the coated with the resist layer substrate by means of a corresponding transport system, the means for Pre-hardening and is after a suitably dimensioned transport route transported directly into the device for the embossing process. Important is, that between the pre-curing process and the embossing process, the film is not exposed to UV radiation or other curing radiation a non-reproducible, unintentional pre-hardening of the embossing lacquer avoid. For this purpose, the film is in a light-tight shaft between Commissioned work and embossing plant. The length of the transport route is like this to choose that for a given web speed, the paint enough time has to run evenly over the surface and a homogeneous smooth Paint film to form.

The pre-hardening is preferably carried out from the paint side. Thereby It is possible to cure only the surface of the paint to tackiness to reduce the varnish in this surface area, leaving a Adhesion of the paint on the stamping tool is avoided. Because only the surface of the varnish is hardened, the varnish in the volume retains its Flowability and can therefore still the relief structure with the necessary Take acutance.

Preferably, the paint is also during the embossing process in a hardened main hardening step. That is, while the lacquer layer In contact with the stamping tool is the paint layer preferably through the substrate by exposure to radiation a degree of cure> 50%, preferably between 80 and 98%, cured.

In certain embodiments of the method according to the invention It may also be necessary, the paint layer after the introduction of the relief structure For example, aftercure by further exposure to radiation. This post-curing has the advantage that reproducible coating properties be generated, which further processing of the substrate with the embossed lacquer layer and blocking the web material when winding up avoid.

For the mentioned curing steps - pre-, main-, post-curing - the same or different radiation can be used. At this Radiation can be any light or particle radiation. If electromagnetic radiation is used, it is preferably visible Light or UV radiation used. IR radiation, in particular heat radiation, but it is also possible. As radiation sources are particularly suitable Mercury vapor lamps, also referred to as Hg lamps, the characterized by a high proportion of ultraviolet radiation. The respective required wavelength ranges can by appropriate Doping the Hg lamps, for example with Ga, Fe, Ga / Pb, realized. However, depending on the used paint and its composition Other sources of radiation, such as fluorescent tubes or lasers, advantageous be.

The emitted wavelength or the wavelength range of the radiation sources can be monitored at certain intervals or continuously, as the radiation sources age and the radiation spectrum can change. For better light output, the radiation sources with reflectors, preferably parabolic or free surface reflectors.

The described method steps preferably run in a continuous manner Process off. For the device used, this means that the individual devices for coating the substrate, the introduction the relief structure and the different curing processes in a row arranged and connected via a common transport system are. In this case, preferably transport rollers are used, which is the web-shaped material continuously through the individual bodies of the Guide device.

However, the device may have other facilities suitable for the Control and control of the individual process parameters are necessary. So is For example, it is advantageous, the temperature of the radiation-curable varnish controlled throughout the process to make sure that the paint in each step has the optimum viscosity.

However, the device can also have other processing devices, which are not needed directly for the method according to the invention, but with regard to the further processing or the intended use of the sheet-like material are useful. Thus, the device before the Inventive institutions preferred facilities for Surface treatment of the substrate, the later liability or Determine the release properties of the paint. This may be a corona discharge device or if a coating is applied should act to a printing unit or a coating device.

Also in the wake of the inventive devices can more Processing facilities, such as a printing unit arranged be. Such devices are particularly advantageous when placed to the introduced relief structure further preferably partial coatings should be applied. So can register to the relief structure a soluble ink is printed in the form of a pattern. This soluble ink may after full-scale metallization dissolved and removed the web-shaped material. Because the overlying thin metal layer is removed with, arise in the metal layer recognizable recesses in the form of previously with the soluble ink applied pattern, which serve as an additional security feature.

The relief structures according to the invention are preferably around diffraction structures. So that the stored in the diffraction structures Information can be visually recognized well, the web-shaped Material after the introduction of the relief structure over the entire surface or area provided with a metal layer or a dielectric layer. Of course, also following the inventive Process steps further security features on the web-shaped Material to be applied.

The sheet-like material according to the invention can then be used for the production of security elements for any valuables, such as banknotes, ID documents, passports, ID or credit cards, or any Goods used for product safety.

If the web-shaped material as a transfer material, in particular hot stamping foil, used, the layer sequence of the security element in the reverse order, as later on the object of value to be secured comes to rest, prepared on the substrate and then by means of an adhesive or lacquer layer in the desired outline shapes transfer the valuable asset. The outline is thereby by the Shape of the applied adhesive or lacquer layer or one preferably heated transfer punch defined. In the so-called hot stamping process Using the transfer stamp is only part of the Adhesive layer activated and thus anchored to the object of value. The remaining web-shaped material can then be effortlessly removed. The substrate may also be different from the layer structure after transfer of the security element or as a protective layer as solid Part of the security element remain on the layer structure. The individual security elements may be on the substrate as separate individual elements be prepared in the outline to be transmitted. alternative becomes the layer sequence of the security elements in continuous form provided on the substrate.

Will the web-like material be used as label material or security thread material used, so must be for a solid bond between the substrate and the layered structure of the security element applied thereto be taken care of. The sheet material is in this case in threads or cut desired security elements of any outline shape and applied to the object to be secured, preferably glued. The security threads are commonly used during papermaking embedded in a security paper at least partially.

Further embodiments and advantages of the invention will become apparent of the figures explained. The figures show only schematically the essential Aspects and do not represent a detailed illustration.

Fig.1 bis 3

verschiedene Ausführungsformen der erfindungsgemäßen Vorrichtung bzw. des erfindungsgemäßen Verfahrens.

Show it:

Fig.1 to 3

various embodiments of the device or the method according to the invention.

Fig. 1 shows a first embodiment of the method according to the invention. Here, a transparent plastic film is used as substrate 1 which a radiation-curable lacquer 2 at least partially by means of a Lackauftragswerks 3, here a printing unit, is applied. Subsequently is the still moist uncured paint 2 via a transport system 4 to transported a corresponding embossing 5. In the example shown there is the embossing 5 essentially of a stamping cylinder 6, on the Surface is arranged to be transferred relief structure 7. When bringing in contact of the varnish 2 with the embossing cylinder 5 becomes the relief structure 7 transferred to the paint 2. To fix the relief structure 7 in the paint, located in the immediate vicinity of the embossing 5 a curing device 8, which has at least one radiation source 9. These Radiation source 9 irradiates the paint 2 through the substrate 1, the must be at least partially transparent to this radiation. The radiation of Radiation source 9 cures the paint during the embossing process to a Degree of cure> 50%, preferably between 80 and 98%. This process forms the main hardening of the varnish 2.

By embossing in the still wet paint layer 2 gives an excellent Embossing quality, since the fine relief structures 7 of the embossing tool. 6 100%. Usually, the paint is after the embossing process however still soft, so that during transport by subsequent facilities the device, the relief structure 7 can be damaged. Because the embossed paint surface comes in the further course of processing again and again with transport wheels and similar facilities Device in contact, which can impress the soft paint surface. Since this leads to a visible loss of brilliance on the finished product or Security element leads, the paint 2 after embossing in a another curing device 10, preferably a further radiation source 11, post-hardened. This is preferably on the embossed lacquer side of the substrate 1, so that the embossed lacquer layer 2 unhindered is acted upon by the corresponding radiation.

This method is particularly suitable for sheet-like materials, in which the substrate 1 has a good adhesion to it Layer structure should have. This is especially true for label materials and security threads of the case. Because in this case, the paint 2 has a greater adhesion to the substrate 1 than to the embossing tool 6, so that the danger the paint deposit on the embossing tool 6 is relatively low.

For the radiation sources 9 and 11 of the respective curing devices 8, 10, the same radiation sources can be used. As radiation sources UV lamps are preferably used.

Alternatively, however, different sources of radiation for the various curing devices 8, 10 are used. In this Case 2 contains two different photoinitiators. The first photoinitiator speaks to the radiation of the radiation sources 9 during the Main curing of the paint 2 and there initiates the polymerization of the paint 2. The second photoinitiator, however, speaks only to radiation of Radiation source 11, which is used for the post-curing of the paint 2 becomes. For example, the first photoinitiator can be specific for emission bands be sensitive in the visible range, for example by Ga- or Fe-doped mercury lamps emit. The second photoinitiator, on the other hand, can For example, react to UV radiation of short wavelength, so that for the radiation source 11 in the post-curing device a radiation source with appropriate emission band is selected.

Fig. 2 shows a further embodiment of the method according to the invention or the device according to the invention. The procedure presented here or the device shown are largely identical to the in Fig. 1 already explained method steps or facilities. The procedure differs only in that before the embossing 5 a Pre-curing device 12 is arranged, which preferably at least one Radiation source 13 has. For this is on a Nachhärtungseinrichtung 10 waived. This pre-curing device 12 is located immediately before the embossing unit 5, so that the precured lacquer layer 2 in direct connection transported to the pre-hardening device 12 in the embossing unit 5 becomes. The pre-curing device 12 is preferably on the lacquer-coated Side of the substrate 1 is arranged so that the radiation of the Radiation source 13 hits the paint without hindrance. This has the advantage that for the radiation source 13 and radiation sources are used can, whose radiation would be absorbed by the substrate 1.

In the pre-hardening device 12, the lacquer layer 2 becomes a degree of hardening Pre-cured below the gel point. Preferably is through the pre-hardening process only selectively hardens the paint surface, so that she loses her stickiness. This has the advantage that the paint 2 is not adheres to the embossing cylinder 6. At the same time the paint 2 in volume still so soft that the relief structure 7 unimpeded 1: 1 transferred to the paint 2 can be.

Analogous to the embodiment already described with reference to FIG. 1 can here for the radiation sources 9 and 13 identical or different Radiation sources are used. Likewise, the paint 2 contain appropriate photoinitiators, which are used on the respective Radiation of the radiation sources 13 and 9 are adjusted.

Fig. 3 shows a further embodiment of the invention. She represents one Combination of the methods and devices shown in FIGS. 1 and 2 Because here the paint is both pre- and post-cured. This has the advantage that the pre-hardening reduces the stickiness of the paint can be to avoid contamination of the embossing cylinder 6. By post-curing in the Nachhärtungseinrichtung 10, the relief structure 7 stabilized in the paint 2. In addition, can be with the help of the post-curing produce reproducible paint properties for further processing the film, such as another printing, necessary are. Finally, the post-hardening also prevents blocking of the sheet-like Material when winding up.

By splitting the lacquer hardening into at least two hardening processes In addition, the risk of embrittlement of the paint is too strong Significantly reduce radiation exposure. Furthermore, there is a significant greater flexibility in the choice of receptors of the paints that are on This way much better suited to the specific requirements of the security elements to be provided valuables or the other Processing steps can be adjusted. This way you can also the processing speed can be increased.

According to a specific embodiment, so-called dual-cure paint formulations are also suitable for complete curing in addition to the Radiation fraction (pre-hardening and main hardening or only pre-hardening) completely harden by later exposure to heat. In this case the post-curing device 10 is equipped with a heat radiator.

Claims (35)

Method for producing sheet-like materials having a relief structure, such as a diffraction structure, characterized by the following steps: at least partially covering a substrate with a radiation-curable lacquer layer, Introducing the relief structure in the lacquer layer, wherein the lacquer layer at the time of introduction substantially has a degree of cure below the gel point. A method according to claim 1, characterized in that the paint layer is brought into contact with the introduction of the relief structure with an embossing tool having on its surface the relief structure. A method according to claim 2, characterized in that a stamping cylinder is used as embossing tool. Method according to at least one of claims 1 to 3, characterized in that the lacquer layer at the time of introduction of the relief structure is substantially uncured. Method according to at least one of claims 1 to 3, characterized in that the lacquer layer is pre-cured before the introduction of the relief structure to a degree of cure below the gel point. A method according to claim 5, characterized in that the pre-hardening takes place directly before the introduction of the relief structure. A method according to claim 5 or 6, characterized in that the precuring takes place from the paint side. Method according to at least one of claims 1 to 7, characterized in that a lacquer is used which contains at least two photoinitiators. Method according to at least one of claims 1 to 8, characterized in that a UV-curable lacquer is used. Method according to at least one of claims 1 to 9, characterized in that the method comprises a main hardening step, in which the lacquer layer is hardened during the introduction of the relief structure by the action of radiation. Method according to at least one of claims 1 to 10, characterized in that the lacquer layer during the main hardening to a degree of cure> 50%, preferably cured between 80 and 98%, is. Method according to at least one of claims 1 to 11, characterized in that the main hardening takes place through the substrate. Method according to at least one of claims 1 to 12, characterized in that during the pre-curing, the surface of the paint is cured. Method according to at least one of claims 1 to 13, characterized in that the lacquer layer is post-cured after the introduction of the relief structure by the action of radiation. Method according to at least one of claims 1 to 14, characterized in that all curing steps with the same radiation, preferably UV or electron radiation occur. Method according to at least one of claims 1 to 14, characterized in that different radiations are used for the different curing steps. Method according to at least one of claims 1 to 16, characterized in that the relief structure represents a diffraction structure. Method according to at least one of claims 1 to 17, characterized in that a preferably transparent plastic film is used as the substrate. Method according to at least one of claims 1 to 18, characterized in that a plastic film having a thickness in the range from 10 to 30 μm, preferably 12 to 23 μm, is used as the substrate. Method according to at least one of Claims 1 to 18, characterized in that the substrate absorbs UV radiation in the short-wave range up to approximately 400 nm. Method according to at least one of claims 1 to 20, characterized in that the substrate is pretreated prior to the application of the lacquer layer in order to adjust the detachment or adhesion properties. A method according to at least one of claims 1 to 21, characterized in that the web-like material is provided over the entire surface or partially with a metal layer or a dielectric layer after the introduction of the Rieliefstruktur. Method according to at least one of claims 1 to 22, characterized in that the web-shaped material is provided with further security features. Web-shaped material produced by a method according to at least one of claims 1 to 23. Web-shaped material according to claim 24, characterized in that it is a transfer material, label material or security thread material. Security element, characterized in that a web-shaped material according to claim 24 or 25 is used for its production. Security document, characterized in that it comprises a security element according to claim 26. Apparatus for producing web-shaped materials having a relief structure, such as a diffraction structure, with a device for applying a lacquer to a substrate, a device for precuring the lacquer and a device for introducing the relief structure into the lacquer, characterized in that the device for pre-curing the lacquer Paint is arranged directly in front of the device for introducing the relief structure. Apparatus according to claim 28, characterized in that the means for introducing the relief structure is a stamping mill. Apparatus according to claim 29, characterized in that the embossing unit has an embossing cylinder. Device according to at least one of claims 28 to 30, characterized in that the device has a device for the main curing of the paint. Apparatus according to claim 31, characterized in that the means for main hardening is arranged in the embossing mill, so that the main hardening takes place during the embossing process. Device according to at least one of claims 28 to 32, characterized in that the means for precuring and the means for main hardening are arranged on opposite sides of the varnish-coated substrate. Device according to at least one of claims 28 to 33, characterized in that the device for pre- and / or main hardening is a radiation source. Apparatus according to claim 34, characterized in that the radiation source is an electron beam, a laser, a fluorescent tube, a mercury vapor lamp or a doped Hg lamp, preferably a Ga, Fe or Ga / Pb-doped Hg lamp is used.

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