EP3529084B1 - Method for producing a security element - Google Patents

Description

The invention relates to a method for producing a security element with a tilt image and a security element with a tilt image.

The most varied of variants are known for providing tilt images in security elements for documents of value, such as bank notes. A tilted image is generally only visible to the viewer from a given viewing angle range and is not visible from other viewing angles.

DE 102014016009 A1 describes a method for producing a security element with one or more tilt images. Microlenses are applied to a metallization layer. The metallization layer is removed through the microlenses, so that a substrate lying under the metallization layer can only be seen from a predetermined viewing angle which corresponds to the angle of the laser ablation.

In US 2012/0194916 A1 a laser beam with a scanning speed of 200 mm / s is guided over an optical film with a lens structure, microimages and one or more laser-sensitive layers. U.S. 4,032,691 and DE 33 11 882 call laser-sensitive substances. DE 85 29 297 U1 relates to an identity card with a lens structure and a laser-sensitive layer, the color of which can optionally be changed. To generate a tilted image with 3 partial images, a pulsed laser beam is guided over the lenses and activated three times per lens. DE 85 29 297 U1 shows the preamble of claim 1.

The invention is based on the object of providing a method for producing a security element so that a tilted image for the security element is obtained particularly easily.

This object is achieved by the subject matter of claim 1.

The dependent claims describe preferred configurations of the present solution.

A method according to the invention for producing a security element with a tilt image comprises the following steps: providing a substrate which has an area with a substance that can be modified by laser radiation; Forming a plurality of microstructures on the substrate, wherein the microstructures are each designed such that they focus radiation incident on a front side of the substrate into the region; and irradiating a set of parallel laser beams onto the microstructures at a first angle to the substrate, so that a structure of a first tilted image is generated, which can be seen from the front side at a viewing angle range associated with the first angle, the substance comprising a laser radiation-sensitive dye which changes its color when exposed to certain laser radiation, and wherein the first tilt image shows a color effect caused by the change in color. The parallel laser beams are controlled individually, in particular with regard to fluence and / or irradiation duration. The number of juxtaposed laser beams in the set is selected so that the structure of the tilt image is generated (or specified) simultaneously in at least one dimension, such as width or length.

A security element not claimed comprises a substrate and a multiplicity of microstructures which are formed on the substrate and which focus radiation incident on a front side of the substrate into an area. The area has a dye that is sensitive to laser radiation. The area is colored in a large number of colored sections and the microstructures are each designed in such a way that they focus radiation incident on the front side at a given viewing angle range on the colored sections, so that a first tilted image can be recognized through the microstructures in the given viewing angle range .

The preferred developments, advantages and variants described here with regard to the method for producing a security feature apply analogously to the security element.

A security element can be produced according to the method mentioned. The security element can be provided for a carrier, such as a document of value, that is to say, for example, applied to the carrier or integrated into the carrier. The security element can also be produced on the carrier, such as a bank note or an object to be secured. The carrier accordingly comprises the security element. Any object that is to be protected from counterfeiting can be designed as a carrier.

A preferred advantage of the invention is that the microstructures are used both for applying the first tilted image to the substrate and for viewing the first tilted image. Because the first tilt image is generated by irradiating the substrate via the microstructures and the microstructures focus incident radiation onto the substrate, a color change in the substrate induced by the set of laser beams is smaller than an extension of the individual laser beams of the set. The substrate is only colored in areas in order to generate a color effect of the first tilt image. The first tilt image is formed with gaps in the substrate, which is why the first tilt image can only be seen from the front under a specific first viewing angle range. The first viewing angle range can extend in an angular range of ± 3 °, ± 7 °, ± 15 ° or ± 30 ° around the first angle. The color changes in the substrate, some of which are also referred to as color-changed sections, form the structure of the tilt image on the substrate. The use of a dye that is sensitive to laser radiation makes the production of the first tilt image particularly easy, since the local dyeing by means of such a dye is associated with less effort than when removing a metal layer. It is particularly the case with the method described here it is not necessary to apply a metal layer and remove it again at the appropriate points. The production of the security element thus requires fewer process steps than that in FIG DE 102014016009 A1 described method for producing a tilt image. In addition, only a monochrome tilted image can be generated through the known local removal of a metal layer. Another advantage is the possibility of producing brightness level or true color images.

The steps of the method according to the invention do not have to be carried out in the order given. For example, the plurality of microstructures can first be formed on the substrate and then the laser radiation-sensitive dye can be introduced into the substrate or applied to the substrate.

The security element can be a (data) carrier for verification of authenticity, such as a security thread, a label, a transfer element or a security print. The substrate can be designed as any desired thin-surface element that is suitable for supporting the multitude of microstructures. For example, the substrate can be a paper, in particular a cotton paper, or a film made of polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene (PP) or polyamide (PA). The paper can contain a proportion x of synthetic polymer materials in the range of 0 <x <100% by weight. The film can be stretched monoaxially or biaxially. The stretching of the film leads, among other things, to the fact that it acquires polarizing properties that can be used as a further authenticity feature. The aids required to utilize these properties, such as polarization filters, are known to the person skilled in the art. In addition, the substrate can be a paper film composite or a film composite in which the substrate and the multitude of microstructures are embedded between two film layers.

The substrate can be transparent, translucent or opaque. In the context of the application, opaque is understood to mean a material which transmits a maximum of 5%, in particular a maximum of 2%, of the visible light. Transparent or translucent in the sense of the application is understood to mean that a material transmits at least 50%, in particular between 70%, preferably 90%, and 100%, of the visible light. Transparent and translucent materials differ in that an image can be seen through the transparent material - the image information is retained after passing through the transparent material - this is not the case with a translucent material - the image information is lost through the translucent material due to scattering .

The laser radiation-sensitive dye can optionally be applied as a layer to the substrate or be provided in the substrate as a layer. The laser radiation sensitive dye changes its color when it is irradiated with the specific laser radiation. The properties of the specific laser radiation can relate to the wavelength of the laser radiation, the intensity of the laser radiation or the polarization of the laser radiation. By locally applying the specific laser radiation, the color of the substrate can thus be changed locally, which results in color differences and thus a color effect. By changing the intensity of the specific laser radiation, the fluence or the dwell time of the laser radiation at a specific location, the degree of color change can be influenced so that gradations in the discoloration of the substrate can be set.

The parallel laser beams are controlled individually, in particular with regard to fluence and / or irradiation duration.
The arrangement of the individual parallel laser beams of the set of parallel laser beams produces the local structuring of the color change of the substrate. The set of parallel laser beams can be generated, for example, by an array of lasers, such as a diode laser bar or a diode laser stack. The lasers are preferably arranged as a row arranged next to one another. The lasers are more preferably present in two or more rows arranged next to one another. The individual lasers of this diode laser array can be switched on or off individually, or the intensity of the radiation to be emitted can be controlled individually. For example, such a diode laser array has a resolution of 200 dpi to 500 dpi. By selectively switching on or off individual lasers of the diode laser array, the arrangement of the set of parallel laser beams can be adjusted and different tilt images can thus be generated. Preferably, one diode laser in each case generates one laser beam of the set of parallel laser beams. The first angle of the direction of incidence of the set of parallel laser beams can be set by the spatial arrangement of the laser sources or by deflecting the laser radiation by means of mirrors. The first angle is z. B. measured with respect to a normal to the substrate.

The multitude of microstructures focuses the incident radiation on the substrate. The individual microstructures can be designed as microlenses or micro-concave mirrors. The microstructures can be designed as circular, elliptical or oval structures with a cross section perpendicular to the normal or as linear elements for focusing the laser radiation. Accordingly, the substrate has a linear color change when linear microstructures are used and a lattice-like color change when circular, oval, or elliptical microstructures are used.

The number of microstructures is optionally greater than the number of laser beams, so that a laser beam (from a single diode laser) strikes several microstructures. The single laser beam of the set is larger in extent than the microstructure. This has the advantage that the individual laser beams do not have to be precisely aligned with the respective microstructures, but rather a laser beam always completely illuminates at least one microstructure due to the large extent of the individual laser beams compared to the diameter of the microstructures. In this way it can be ensured that every laser beam causes a discoloration on the substrate.

The number of juxtaposed laser beams in the set is selected so that the structure of the tilt image is generated (or specified) simultaneously in at least one dimension, such as width or length. Ideally, sufficient laser beams are provided over a large area so that the entire structure of the tilt image can be generated (or specified) by the sentence. The tilt image can also be generated in partial images. In particular, a series of juxtaposed laser beams can be used that extend over one dimension of the tilt image (such as width or length of the tilt image) in order to generate the tilt image in the corresponding other dimension (length or width) in partial images one after the other. Two rows of parallel laser beams are particularly preferably used in the set, the two rows (in the sense of an overall denser beam arrangement) being offset from one another by half a laser beam width.

The microlenses can be applied to a film or formed in one piece with a film; the film can be applied to the substrate to form the microstructures on the substrate. The microlenses can be made of a transparent material such as polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene (PP) or polyamide (PA).

The area in which the laser radiation-sensitive dye is provided can extend over the entire substrate or only be a partial area of the substrate. In particular, the area can have an outline that matches the outline of the first tilt image. This means that the area in which the laser radiation-sensitive dye is provided corresponds approximately to the extension of the tilt images to be applied.

To produce a tilted image, which is made up of color or gray levels, for example, it is optionally provided that the laser beams of the set have the specific laser radiation, a fluence of the specific laser radiation and / or an irradiation duration per unit area being set locally differently. The color of the tilt image is preferably changed locally differently, that is, it contains a color effect. The fluence can be changed by varying the intensity of the individual laser beams in the set or by differently focusing the individual laser beams in the set. The duration of the irradiation can be changed by switching on the individual laser beams of the set for different lengths of time. By varying the above-mentioned irradiation parameters, a larger or smaller proportion of the laser radiation-sensitive dyes is activated per unit volume, as a result of which a different degree of color change can be produced. For example, the color change stronger the greater the fluence. In this way, the degree of color change can be graded.

The present color change can be a monochrome color change, for example a change in brightness and / or color saturation. Alternatively or additionally, the color change can include a color change, that is to say, for example, a change in the color value.

In particular as a grayscale, color gradation or true color image, the tilt image contains a gradual (or gradual) change in color, which is preferably a chromatic color.

As explained in more detail below on the basis of various variants, the generation of the first tilt image can comprise at least two steps of irradiating laser beams. Radiation of the set of parallel laser beams is one of the two steps, but not necessarily the first of those steps. The wavelength of the laser radiation can differ for the at least two steps of irradiation. The at least two steps can also take place from different sides of the security element. The at least two steps can be carried out for different purposes: color change of the substance, activation of the substance for a subsequent color change, deactivation of the substance to prevent a color change.

The procedure according to the invention can also be used with a laser radiation-sensitive dye which changes its color in several stages. So is from the EP 2528742 B1 a laser-sensitive substance known that is colored with a multi-stage, here a three-stage process. Two-stage systems are also known to the person skilled in the art, so that in a further development It is preferred that the color of the laser radiation-sensitive dye can be changed in a modification process comprising at least two stages, with laser radiation being irradiated in both stages and the stages differing in terms of a wavelength of the laser radiation. For example, the laser radiation for the two stages can be generated with a laser array which has two different laser diodes for each laser beam, so that each laser beam of the set can comprise two wavelengths. By switching on the laser diodes of the laser array accordingly, a multicolored image can be generated.

In order to avoid unwanted discolouration of the security element, which can arise from a color change occurring in the laser radiation-sensitive dye due to radiation randomly incident on the security element, such as visible light or UV radiation, it is preferred in one development that one of the two Stages activate the substance and the other of the two stages causes the substance to change color. For example, the in the EP 2528742 B1 described dye can be used. A near-infrared or infrared wavelength can be used to activate the dye in the first stage, for example an Nd: YAG laser with a wavelength of 1.064 µm. The color change of the second stage can be generated with laser radiation in the ultraviolet wavelength range, for example with an excimer laser. It is possible here for both the structure and the intensity of the color change to be established by means of the activation, in that, as described above, the fluence and / or the irradiation time of the laser beams are / is varied to activate the laser radiation-sensitive dye; a larger or smaller proportion of the laser radiation-sensitive dye is thus activated. In In this case, the second stage for changing the color of the substance can then be irradiated with laser radiation that is homogeneous over the region, since the degree of the color change was determined by the variation in the activation.

In a variant, the fluence and irradiation duration of the laser beams of the first stage for activating the laser radiation-sensitive dye are kept constant. The variation of the color effect is produced in that the fluence and / or the irradiation time of the laser beams of the second stage are / is set differently in order to produce local color differences.

Since the laser radiation for the first stage and the second stage have a different wavelength, the focal length of the microstructures for the activation and the color change is different, so that guiding the laser beams of the first stage and the second stage through the microstructures leads to a longitudinal color error can. To avoid this, it is preferred in a development that in the first stage the set of laser beams activates the substance according to the structure and that in the second stage further laser radiation is radiated onto a rear side of the substrate to change the color of the substance. The activation of the dye and the excitation of the dye thus take place from different sides. Since the laser radiation for the second stage is not guided through the microstructures, an annoying color error during focusing can be avoided.

• Farbänderung und abschließende Deaktivierung (a, d),
• Farbänderung von der Vorderseite und zweite Farbänderung von der Vorder- oder Rückseite mit optional abschließender Deaktivierung von der Vorder- oder Rückseite (a, b, d),
• rückseitige Aktivierung, anschließend (erste) vorderseitige Farbänderung, optional zweite Farbänderung mit optional abschließender Deaktivierung (c, a, (b, d)), oder
• vorderseitige Aktivierung zur Vorgabe der Struktur des Kippbildes und rückseitige, vollflächige Bestrahlung zur Farbänderung mit optional abschließender Deaktivierung (c, a, d), oder
• vorderseitige Deaktivierung zur Vorgabe einer Negativ-Struktur des Kippbildes, rückseitig vollflächige Aktivierung der Substanz und danach (vorderseitige oder rückseitige) Bestrahlung zur Farbänderung mit optional abschließender Deaktivierung (d, c, a).

Auch sofern soeben nicht explizit vorgesehen, ist eine vorhergehende Aktivierung oder eine zweite Farbänderung jeweils zusätzlich möglich. Der Satz von Laserstrahlen kann insbesondere eine Deaktivierung der Substanz außerhalb der Struktur des Kippbildes bewirken, so dass in einem zweiten Schritt des Einstrahlens zur Farbänderung der Substanz Laserstrahlung eingestrahlt wird (vorder- oder rückseitig und gegebenenfalls nach Aktivierung).In each of the above-mentioned at least two steps of irradiating laser radiation, one of the following substeps a to d can take place: a) a first color change of the substance, b) a second color change of the substance, c) an activation of the substance or a d) deactivation the substance. Laser radiation-sensitive dyes can sometimes be changed in color in several irradiation steps (or stages). It is also known for such dyes that the dyes must first be activated by irradiation (or in some other way) before they can be changed in color by means of laser radiation. For activated dyes, the laser radiation of the specific wavelength triggers the color change. The color of the non-activated dyes is not changed by the laser radiation of the specific wavelength. The deactivation is usually irreversible, can take place at the end or, alternatively, can be used to specify the structure of the tilted image. Technically preferred processes can include the sub-steps in the following order:

• Color change and final deactivation (a, d),
• Color change from the front and second color change from the front or back with optional final deactivation of the front or back (a, b, d),
• rear activation, then (first) front color change, optional second color change with optional final deactivation (c, a, (b, d)), or
• Front activation to specify the structure of the tilted image and rear, full-surface irradiation for color change with optional final deactivation (c, a, d), or
• Deactivation on the front to specify a negative structure of the tilt image, activation of the substance over the entire area on the rear and then (front or rear) irradiation to change the color with optional final deactivation (d, c, a).

Even if not explicitly provided, a previous activation or a second color change is also possible. The set of laser beams can in particular cause a deactivation of the substance outside the structure of the tilted image, so that in a second Step of irradiating to change the color of the substance laser radiation is irradiated (on the front or back and, if necessary, after activation).

The further laser radiation can be generated, for example, by the diode laser array which generates the set of laser beams and whose radiation is directed onto the rear side by means of mirrors. In another embodiment, a further diode laser or an array of diode lasers can be used to generate the further laser radiation. The further laser radiation can be a single laser beam, by means of which the entire area or a part of the area in which the laser radiation-sensitive dye is provided is illuminated. Optionally, the further laser radiation is homogeneous in the area in which the laser radiation-sensitive dye is provided. This variant can be used in particular when a variation in the intensity is set by means of the set of laser radiation in the first stage.

• entweder eine zweite Gruppe von unabhängig steuerbaren Lasereinheiten, die jeweils einen Laserstrahl erzeugen, und nebeneinander angeordnet sind, so dass ein zweiter Satz paralleler Laserstrahlen in einer zweiten Richtung entsteht, der gleichzeitig mit dem ersten Satz auf die Vorderseite des Sicherheitselements gerichtet ist, und/oder
• eine zweite Laserquelle, die als Gruppe von unabhängig steuerbaren Lasereinheiten ausgestaltet sein kann, dessen Laserstrahlung auf die Rückseite des Sicherheitselements gerichtet ist.

A device that is not claimed for producing a security element with a first tilt image, in particular according to one of the presently described methods, comprises an arrangement area for arranging a security element, on the substrate of which a multiplicity of microstructures are applied, which radiation incident on a front side of the security element on the with Focus on the substrate provided with a dye sensitive to laser radiation. A first group of independently controllable laser units which each generate a laser beam and are arranged next to one another so that a first set of parallel laser beams is produced in a first direction which is directed onto the front of a security element in the arrangement area. A control unit controls at least the laser units the first group for generating the first tilt image by irradiating a security element in the arrangement area.
In the present case, the device now also includes

• either a second group of independently controllable laser units which each generate a laser beam and are arranged side by side so that a second set of parallel laser beams is produced in a second direction, which is directed simultaneously with the first set onto the front of the security element, and / or
• a second laser source, which can be configured as a group of independently controllable laser units, the laser radiation of which is directed onto the rear side of the security element.

In order to generate a multicolored tilted image, it is provided in a further development that the laser radiation-sensitive dye also has a third stage which enables a further color change of the substance. The third stage is activated by additional laser radiation, which is optionally radiated onto the front side of the substrate through the microstructures. The additional laser radiation can, for example, have a wavelength in the near infrared or in the infrared. Optionally, the laser radiation for the third stage is overlapping or equal to the wavelength range of the laser radiation of the first stage, so that the focus shift caused by the differences in the wavelength of the laser radiation is small. Thus, the laser radiation for the first stage and the laser radiation for the third stage can preferably be applied through the microstructures.

The further laser radiation for the third stage can be applied as homogeneous laser radiation. In a further variant, the laser diode array can generate two different wavelengths for each laser beam, for example, by coupling two laser diodes in such a way that they emit a laser beam. Here, too, the variation of the color change in the third stage can be caused by the fact that the fluence and / or the irradiation time vary / varies in the first stage and the third radiation is irradiated homogeneously or that the laser beams of the first stage are homogeneous and the fluence and / or the irradiation time for the laser radiation of the third stage can / will be varied according to the tilted image.

In order to generate a color-changing first tilt image when the viewing angle changes within the first viewing angle range, it is preferred in a further development that the fluence and / or the irradiation duration for the third and / or second stage are set in such a way that per Microstructure on the substrate creates a gradual color change. In particular, when the microstructures strongly focus the incident laser radiation, a Gaussian intensity profile of the incident radiation results due to the optical laws. If the fluence of the laser beams and / or the duration of the irradiation are selected for the third and / or second stage in such a way that the color change in the third stage is caused depending on the Gaussian distribution on the substrate, the color changes for each microstructure according to the Gaussian distribution. A section that has been changed in color therefore has a gradual change in color (not a uniform color, as previously described, but). This is achieved in that, depending on the Gaussian distribution, the fluence and / or the irradiation time are / is above or below a threshold value for color change. This creates an optical impression in which, if the viewing angle is identical or almost identical to the first angle of the incident laser radiation for the third and / or second stage, the through the third and / or second color level is visible color change in the first image. If one deviates slightly from this viewing angle in one direction or the other, one looks at the edge areas of the color change on the substrate per microstructure in which the color change for the third and / or second stage was not or not so strongly effective and thus a different one Has produced coloring.

Such or a similar second or third step of irradiating laser radiation can also take place with the aim of improving the visibility of the tilted image. Another, in particular coloring, laser irradiation step can lead to an increased width of the color-changed section by slightly varying the wavelength (e.g. + - 5 (or 10) nm) and / or the angle of incidence (e.g. + - 0.5 (, 1 or 2) degrees) . An increased width of the color-changed sections increases the angular range in which the tilted image is visible.

In a further variant, the intensity distribution within a laser beam can also be varied to produce the above-mentioned effect. As an option, this is particularly advantageous if the change in intensity in the focus caused by the focusing turns out to be small. Such color changes, which are dependent on the viewing angle, are particularly desirable in the case of tilt images that represent symbols, letters or characters. The change in the color of the first tilt image depending on the viewing angle can represent a security feature of the security element.

In order to further increase the security element's security against forgery, a further development provides that a second tilt image is generated by irradiating a group of parallel laser beams at a second angle to the substrate on its front side.

The second tilt image can optionally be identical to the first tilt image, so that identical tilt images can be seen from two viewing angles. When the viewing angle is changed, the tilted image is visible in a first viewing angle range, then invisible and again identically visible in a second viewing angle range. This can be implemented, for example, in that the set of parallel laser beams and the group of parallel laser beams are generated by the same laser diode array and are directed onto the substrate at different angles by means of a beam splitter or mirror. In addition, it is possible to activate the laser diode array identically at two different angles, so that two identical tilt images are generated. The second tilt image can be seen from the front at a second viewing angle range corresponding to the second angle. A third tilt image or further tilt images can be generated analogously. In preferred configurations, a second (third or further) tilt image is generated with a second (third or further) laser diode array.

Furthermore, the second (or any further) tilt image can be different from the first tilt image. The second, third or any further tilt image can be generated in a similar manner to the first tilt image. In particular, the considerations, preferred further developments and advantages put forward with regard to the first tilt image can be applied analogously. Specifically in connection with the gradual change in color, the second tilt image can be set in such a way that, with increasing viewing angle, first the first tilt image under a first color, then under a second color, then the second tilt image under the first color and then the second tilt image can be seen under the second color. The second tilt image can also be generated with a diode laser array that differs from the diode laser array for generating the set of parallel laser beams.

In order to further increase the speed of production of the security element, the first tilt image and the second tilt image can optionally be generated simultaneously. In a further development, it is therefore preferred that the set of laser radiation and the group of laser beams are irradiated simultaneously. For this purpose, the methods described above for generating the first tilt image and the second tilt image can be used. Since the color change of the laser radiation-sensitive dye usually brings little or no heat generation with it, the first tilt image and the second tilt image can be generated simultaneously without causing thermal damage to the substrate. This would be in the demetallization to generate the tilt image, as in the DE 102014016009 A1 is not possible, since considerable heat is often generated during demetallization, so that simultaneous removal of the metallization layer for generating the first and second tilted image is not possible.

The forgery-proof security element can be further increased by combining a regular image with a tilt image to form an overall structure. In a further development, it is provided that the microstructures only cover part of the area with the laser-radiation-modified substance, the set of parallel laser beams being irradiated onto the entire area with the laser-radiation-modifiable substance. The regular image can be seen from the front side next to the first tilt image and is under one opposite the first and / or second viewing angle range larger viewing angle range visible. The viewing angle for the regular image is optionally 50%, 100%, 200% or 500% larger than the first and / or second viewing angle range.

A tilted image that merges into a regular image could possibly also be reproduced by other means. In particular, an imprint by means of a blind effect (e.g. by applying a film with directed lamellas) could become a partially tilting image with an adjacent regular partial image. In the present case, therefore, a different motif that only supplements or belongs to the tilted image is preferably shown in the regular image (distinguishable partial images). A blind foil could hardly be applied to an imprint with such, distinguishable partial images with the required registration accuracy. Therefore, as already described, a second (third or further) tilt image is particularly preferably generated by means of the microstructures. Sections of different tilt images are thus located under a single microstructure. For the viewer, the tilt images are (at least overlapping) in the same place. Generating a second tilt image for the viewer at the same place is not possible with the technologies available to a forger using blinds.

The microstructures can for example be applied to a carrier film or formed in a carrier film, the carrier film being arranged on the part of the area with the substance that can be modified by laser radiation. The carrier film can be strip-shaped. If the set of laser beams is then irradiated onto the area with the laser radiation-sensitive substance, a tilted image is created in the section in which the microstructures are arranged, and in the section in which the microstructures are arranged are not arranged, a regular image visible from many viewing angles. Since the tilt image and the regular image are generated with the same set of parallel laser beams, they are in perfect register with each other. It is possible that the section of the area in which the tilted image is provided is additionally illuminated with the group of parallel laser beams for generating the second tilted image.

In order to exclude the separation of the tilt image from the substrate and thereby avoid counterfeiting attacks and / or unwanted damage to the security element, it is preferred in a development that the laser radiation-sensitive dye is distributed over a volume of the substrate. For example, the laser radiation-sensitive dye can be mixed with its starting products during the production of the substrate. If z. If, for example, paper is used for the substrate, the laser-radiation-sensitive dye can be added to the headbox in the trough of the paper machine. It is also possible to add the laser radiation-sensitive dye to a liquid, for example a glue, with which the paper is impregnated. In both cases, the laser-sensitive dye is firmly bonded to the paper, so that deliberate or inadvertent separation of the tilt image from the substrate is impossible.

As already described, the substrate can comprise a plurality of partial regions which comprise the substance which can be modified by laser radiation. The microstructures are present in the first partial area and a regular image can be generated in a second partial area without microstructures. The subregions of the substrate can comprise different or the same substrate material. For example, the substrate can comprise a plastic film in the first partial area and a paper substrate in the second partial area. In both sub-areas, the laser radiation-modifiable Substance contained in the substrate material or provided as a coating. The same substance that can be modified by laser radiation can be introduced into the subregions at different times. The first partial area is particularly preferably a part of an independent security feature, such as a thread, strip or the like, which is embedded in a carrier substrate, in particular paper. The embedded security feature, for example as a pendulum thread, preferably forms the surface of the carrier only in partial areas.

Fig. 1a-1c

eine Draufsicht auf ein Wertdokument unter verschiedenen Betrachtungswinkeln;

Fig. 2

eine Draufsicht auf eine weitere Ausführungsform eines Wert-dokuments;

Fig. 3

eine Schnittdarstellung entlang der Linie I-I von Fig. 1a;

Fig. 4

eine Schnittdarstellung einer weiteren Ausführungsform des Wertdokuments;

Fig. 5

eine Schnittdarstellung einer weiteren Ausführungsform des Wertdokuments; und

Fig. 6

eine Schnittdarstellung zur Illustration eines Herstellungsverfahrens für das Wertdokument.

Further exemplary embodiments as well as advantages of the invention are explained below with reference to the figures, in the representation of which a true-to-scale and true-to-proportion reproduction has been dispensed with in order to increase the clarity. Show it:

Figures 1a-1c

a plan view of a value document from different viewing angles;

Fig. 2

a plan view of a further embodiment of a value document;

Fig. 3

a sectional view along the line II of Fig. 1a ;

Fig. 4

a sectional view of a further embodiment of the value document;

Fig. 5

a sectional view of a further embodiment of the value document; and

Fig. 6

a sectional view to illustrate a production method for the value document.

In the Figs. 1 and 2 Excerpts of different embodiments of a value document 10 are shown. The value document 10 can be, for example, a bank note and comprises a security element 12. A regular image 16 can be seen on a substrate 14 of the security element 12 in plan view. The regular image 16 is in the Figs. 1 and 2 Shown as a triangle or section of a square, but can represent any motif, for example an outline of a person, an animal, an object or a symbol. The regular image 16 can be seen from a large viewing angle range, for example from 0 ° to 70 ° or 80 ° relative to a normal, in a plan view of the value document 10, as in FIG Figures 1b and 1c is shown.

If the value document 10, in particular the security element 12, is viewed from a first viewing angle range, as shown in FIG Figure 1b is shown, a first tilt image 18 can be seen in addition to the regular image 16. The first viewing angle range is significantly smaller than the viewing angle range of the regular image 16. For example, the first viewing angle range can be ± 3 °, ± 7 °, ± 15 ° or ± 30 ° of the first angle α. The first tilt image 18 is in Figure 1b shown as a square, which complements the regular image 16 to form an overall image, the regular image 16 and the first tilt image 18 being in perfect register with one another.

If the value document 10, in particular the security element 12, is viewed from a second viewing angle range, as shown in FIG Figure 1c is shown, in addition to the regular image 16, a second tilt image 20 can be seen which, like the first tilt image 18, is in perfect register with the regular one Picture 16 stands. The second viewing angle range can be ± 3 °, ± 7 °, ± 15 ° or ± 30 ° of the second angle β. The first tilt image 18 and / or the second tilt image 20 can have any shape in addition to the illustrated rectangles and in particular represent people, objects or animals. For example, the overall image is a coat of arms and the tilting images 18, 20 represent parts of the coat of arms that can be recognized from the respective viewing angle. The first tilt image 18 and / or the second tilt image 20 can / can as in FIG Fig. 2 shown, are composed of non-contiguous sections, which optionally complement the regular image 16 to form an overall image. The sections of the tilt image can be formed, for example, in the respectively visible parts of a pendulum thread in the value document.

The structure, the production method and the mode of operation of the document of value 10 or of the security element 12 are illustrated in FIG Fig. 3-6 explained. The value document can also be viewed as a security element in the broader sense.

In the Fig. 3 In addition to the substrate 14, the illustrated embodiment of the security element 12 has a color layer 22 with laser radiation-sensitive dyes contained therein, an optional carrier layer 24 and a multiplicity of microstructures 26. In the embodiment shown, the substrate 14 is made of paper, in particular cotton paper. In addition, the substrate 14 can also be produced from a film. The color layer 22 is part of the substrate 14 in which the laser radiation-sensitive dye is distributed. However, it is also possible for the color layer 22 to be a layer applied separately to the substrate 14. The laser-sensitive dye is a dye that changes color depending on the fluence of the incident radiation and the duration of the exposure.

The carrier layer 24, on which the microstructures 26 are formed, is applied to the substrate 14 or the color layer 22. The carrier layer 24 consists of a transparent film, for example made of polyethylene (PE) or polypropylene (PP). The microstructures 26 are designed as, optionally circular, microlenses and, in the embodiment shown, are produced in one piece with the carrier layer 24. However, it is also possible for the multiplicity of microstructures 26 to be produced separately and applied to the carrier layer 24. The microstructures 26 are also made of a transparent material, for example polyethylene (PE) or polypropylene (PP). The microstructures 26 lie in a plane above the area of the substrate 14 in which the laser radiation-sensitive dye is provided.

Among other things, the in Figure 2 The illustrated subsections of the tilt image 18 can be implemented by different configurations. In one variant, the microstructure 26 is only present in the subsections; per subsection is in the sense of Figure 3 a film element 24 with microstructures 26 is applied to the substrate 14. In a preferred variant, not shown, which is only based on the example of Figure 2 is described, the microstructures 26 on the carrier layer 24 are embedded in the substrate 14. In particular when the microstructures are present on a security thread, the microstructures can optionally be as shown in FIG Figure 2 as a pendulum thread, embedded in the substrate. In Figure 3 the sub-area 24, 26 would be an element integrated into the substrate 14, the colored layer 22 of the sub-area without microstructures possibly being arranged in the same plane with the microstructures. Generally speaking, a substrate can thus comprise partial regions made of different substrate materials, which are optional can be provided with laser radiation-active dyes, possibly in a color layer, at different times.

In one embodiment, the production of the document of value 10 or the security element 12 is as follows: First, in the area of the regular image 16 and the later first tilted image 18, the laser radiation-sensitive dye is introduced into the substrate 14, for example by soaking the substrate 14 with a liquid, like glue, which contains the laser radiation sensitive dye. In this way, the color layer 22 is provided with an extent which corresponds to the later regular image 16 and the first tilt image 18. The carrier layer 24 with the plurality of microstructures 26 arranged thereon is applied in the region of the first tilt image 18 and the second tilt image 20. Subsequently, a set 28 of laser beams is irradiated at a first angle α with respect to a normal to the substrate 14. The individual laser beams of the set 28 have an extent which is greater than a diameter of the microstructures 26, so that a laser beam of the set 28 falls on a plurality of microstructures 26. The individual laser beams of the set 28 have an arrangement and an intensity such that the regular image 16 and the first tilted image 18 result therefrom by placing in the color layer 22 at the points where the set 28 of laser beams hit the color layer 22 hits, a color change occurs. In the Figs. 1 and 2 In the illustrated embodiment, the individual laser beams of the set 28 have the same intensity and the same exposure time, so that the regular image 16 and the first tilted image 18 appear as homogeneous surfaces. However, since the laser beams of the set 28 are spaced from one another, there is no continuous color change in the color layer 22. In particular, the focusing of the laser beams of the set 28 through the microstructures 26 results in colored sections 30 in the color layer 22 with a width b. In between there are non-colored sections 32 in the colored layer 22, in which no color change was caused.

If the security element 12 is now viewed from the front at a viewing angle which is approximately equal to the first angle α, radiation that originates from the colored sections 30 is fed to the viewer's eye. The first tilt image 18 can thus be seen. If the security element 12 is viewed from the front from a viewing angle that differs from the first angle α, the radiation entering the viewer's eye comes from the non-colored sections 32, so that the first tilt image 18 cannot be seen. Only the color of the uncolored substrate 14 is visible or the basic color of the laser-sensitive layer, which can certainly have its own color. Since no microstructure 26 is arranged above the regular image 16, the regular image 16 can be seen from all viewing angles.

The generation and the mode of operation of the second tilt image 20 are analogous to the first tilt image 18, except that to generate the second tilt image 20 a group 34 of laser beams is radiated at a different, second angle β, as shown in FIG Fig. 5 is shown. With the group 34 of laser beams, a region of the substrate 14 different from the colored sections 30 is colored. The irradiation of the group 34 of laser beams can occur simultaneously with that of the set 28 of laser beams or one after the other.

A further embodiment of the value document 10 or security element 12 is shown in FIG Fig. 4 shown. This is true except for the following differences with the value document 10 according to Fig. 3 agree: The microstructures 26 are in the in Fig. 4 The embodiment shown is designed as a micro-concave mirror, which focuses incident laser beams onto the color layer 22. The color layer 22 is in the in Fig. 4 The embodiment shown is provided separately from the substrate 14 and can, for example, be designed as a film into which laser-sensitive dye is mixed. The mode of operation and production method is analogous to that in Fig. 3 The value document 10 shown. The laser-sensitive dye of the colored layer 22 and / or the laser radiation are adapted in such a way that the laser-sensitive dye does not react to the unfocused radiation, that is to say is transparent to it. Only the radiation focused by the microstructures creates the color change.

Fig. 5 shows an enlarged illustration of a further embodiment of the value document 10. The embodiment according to FIG Fig. 5 agrees with the embodiment according to Fig. 3 except for the following difference: The laser radiation-sensitive dye is in accordance with the embodiment Fig. 5 distributed completely in the substrate 14, so that no separate color layer 22 is formed. Depending on the opacity of the substrate 14, the colored section 30 extends further into the substrate 14.

Fig. 6 shows a further embodiment of the value document 10 or security element 12, which with the Fig. 3 and 5 embodiment shown matches. A laser radiation-sensitive dye is used here, the color of which can be changed in a modification process comprising at least two stages. In a first stage, the set 28 of laser beams is irradiated through the microstructures 26 at the first angle α. The wavelength of the laser radiation is, for example, in the infrared, in particular 1.064 μm. The laser radiation for the first stage is used to activate the laser radiation-sensitive dye. To the actual Color change, laser radiation is now radiated with a wavelength different from the set 28 of laser radiation, for example with a wavelength in the ultraviolet. Since the focusing of the laser radiation by the microstructures 26 changes due to the different wavelengths, the laser radiation for the second stage is not radiated from a front side of the substrate 14 but from a rear side. In the embodiment shown, the intensity of the laser radiation for the second stage is homogeneous over the area of the regular image 16 and the first tilted image 18. The set 28 of laser beams is modified accordingly for the first stage in order to generate different color tones (gray levels) and structures. The substrate and / or the wavelength of the laser radiation radiated in from the rear are selected such that the substrate is sufficiently transparent for the laser radiation.

In addition, it is possible, for example, to use a third stage (or a third step of irradiating laser radiation) for generating a further color effect in the case of the laser radiation-sensitive dye according to the embodiment of FIG Fig. 6 to be provided. To create the color effect in the third stage, laser radiation with a wavelength that is similar to the wavelength for the first stage is used. The laser radiation for the third stage can therefore be irradiated again through the microstructures 26, in particular again at the first angle α.

The fluence and the duration of the irradiation of the laser-sensitive dye for the (second or) third stage are particularly preferably selected such that the color change within (each) of the colored section 30 is different. This can be caused, for example, by the fact that, due to the focusing by the microstructures 26, there is a Gaussian intensity distribution in the color layer 22 or in the substrate 14 results. As a result, there is a gradual color change in the colored section 30, the color of the color change of the (second or) third stage in the middle of the colored section 30 and no color change resulting from this stage at the edges of the colored section 30. In Figure 6 accordingly, only the color of the second stage of the color change is present at the edges of the respectively colored sections 30. When viewing the document of value 10 at an angle that is a little larger or smaller than the first angle α, the first tilted image 18 with the color for the second stage can be recognized. By changing the viewing angle toward the first angle α, the color gradually changes from the color of the second level to the color of the third level.

Claims (12)

1. A method of manufacturing a security element (12) with a first tilt image (18), comprising the steps of:

   - supplying a substrate (14) which has a region with a laser-radiation-modifiable substance,

   - forming a plurality of microstructures (26) at the substrate (14), the microstructures (26) being respectively configured such that they focus radiation incident on a front side of the substrate (14) into the region, and

   - producing a structure of the first tilt image (18) so that the first tilt image (18) is recognizable from the front side in a first viewing angle range, wherein
   the substance has a laser-radiation-sensitive dye which changes color when irradiated with certain laser radiation, and
   the first tilt image (18) shows a color effect caused by the change in color, ch
   aracterized in that
   producing the first tilt image (18) comprises simultaneously irradiating a set (28) of parallel laser beams onto the microstructures (26) at a first angle (α) to the substrate (14),
   the parallel laser beams are controlled individually, and
   in the set (28) of laser beams, sufficient laser beams are arranged side by side to completely produce the structure of the tilt image in at least one dimension, such as width or length.
2. The method according to claim 1, characterized in that the parallel laser beams are individually controlled with respect to fluence and/or irradiation duration.
3. The method according to claim 1 or 2, characterized in that the individual laser beams of the set (28) have a larger extension than a microstructure (26).
4. The method according to any of claims 1 to 3, characterized in that the producing of the first tilt image (18) comprises at least two steps of the irradiating of laser beams, including the irradiating of the set (28) of parallel laser beams.
5. The method according to claim 4, characterized in that in each of the at least two steps of irradiating one of the following substeps a to d is effected: a) a first color change of the substance, b) a second color change of the substance, c) an activation of the substance or d) deactivation of the substance.
6. The method according to claim 4 or 5, characterized in that for the at least two steps of the irradiating the wavelength of the laser radiation differs, in particular a first certain wavelength is provided for a first color change and a second certain wavelength is provided for a second color change.
7. The method according to any of claims 4 to 6, characterized in that at least the step of irradiating the set (28) is effected from the front side and another one of the at least two steps is effected from the back side.
8. The method according to any of claims 1 to 7, characterized in that the laser beams of the set (28) have the certain laser radiation and induce the color change of the substance according to the structure, preferably a fluence of the certain laser radiation and/or an irradiation duration per unit area being adjusted locally differently.
9. The method according to any of claims 1 to 7, characterized in that the set (28) of laser beams induces an activation of the substance according to the structure and that, in a second step of irradiating for changing the color of the activated substance, the laser radiation is irradiated onto a back side of the substrate (14) and/or that the set (28) of laser beams induces a deactivation of the substance outside the structure, and that, in a second step of irradiating for changing the color of the substance, laser radiation is irradiated.
10. The method according to any of claims 1 to 9, characterized in that a second color change of the substance is induced in a second and/or third step of irradiating laser radiation which is irradiated onto the front side of the substrate (14), preferably the fluence and/or the irradiation duration for the second color change being adjusted such that per microstructure on the substrate (14) a gradual color change is produced.
11. The method according to any of the preceding claims, characterized in that a second tilt image (20) visible from the front side at a second viewing angle range - corresponding to a second angle (β) - is produced by irradiating a second set (34) of parallel laser beams at the second angle (β) to the substrate (14),
    wherein the first set (28) of parallel laser beams and the second set (34) of parallel laser beams are preferably irradiated simultaneously.
12. The method according to any of the preceding claims, characterized in that the microstructures (26) cover a part of the region with the laser-radiation-modifiable substance, wherein - preferably the set (28) of parallel laser beams - is irradiated onto another part of the region with the laser-radiation-modifiable substance, so that from the front side next to the first tilt image (18) a regular image (16) is visible which is recognizable in a viewing angle range larger than the first viewing angle range.

Images