DE102016012625A1 - Security element and method for producing a security element - Google Patents

Abstract

The invention relates to a method for producing a security element (12) with a tilted image, comprising the following steps: providing a substrate (14) having a region with a laser-radiation-sensitive dye; Forming a plurality of microstructures (26) on the substrate (14), the microstructures (26) each being adapted to focus radiation incident on a front surface of the substrate (14) into the region; and irradiating a set (28) of parallel laser beams onto the microstructures (26) at a first angle to the substrate (14), the individual laser beams of the set (28) being arranged to produce a structure of a first tilt image (18) which is recognizable from the front side at a viewing angle associated with the first angle (a); wherein the laser-sensitive dye changes its color by irradiation with certain laser radiation; and wherein the first tilting image (18) shows a color effect due to the change of the color.

Description

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

Various variants are known to provide tilting images in security elements for value documents, such as banknotes. As a rule, a tilted image is visible to the viewer only 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. On a metallization microlenses are applied. The metallization layer is removed through the microlenses, so that a substrate lying below the metallization layer can only be seen at a predetermined viewing angle, which corresponds to the angle of the laser ablation.

The invention has for its object to provide a method for producing a security element, a security element and a corresponding device for manufacturing, so that a tilt image for the security element is particularly easily obtained.

This object is solved by the subject matter of the independent claims. The dependent claims describe preferred embodiments of the present solution.

In the present case, a method for producing a security element with a tilted image comprises the following steps: providing a substrate having a region with a laser-radiation-modifiable substance; Forming a plurality of microstructures on the substrate, each of the microstructures being configured to focus radiation incident on a front surface of the substrate into the region; and irradiating a set of parallel laser beams onto the microstructures at a first angle to the substrate to produce a first tilt image structure that is detectable from a front angle viewing angle range from the front side, the substance comprising a laser sensitive dye which changes its color by irradiation with certain laser radiation, and wherein the first tilting image shows a color effect due to the change of the color.

A security element comprises a substrate and a multiplicity of microstructures, which are formed on the substrate and focus radiation incident on a front side of the substrate into a region. The area has a laser-radiation-sensitive dye. The area is colored in a plurality of colored sections in such a way and the microstructures are each designed such that they focus radiation incident on the front side over a defined viewing angle range on the colored sections, so that a first tilted image in the predetermined viewing angle range can be recognized by the microstructures ,

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 by the said method. The security element can be provided for a carrier, such as a value document, that is, for example, applied to the carrier or integrated into the carrier. Likewise, the security element can be produced on the carrier, such as banknote or item to be secured. Accordingly, the carrier comprises the security element. As a carrier, any object may be formed, which is to be protected against counterfeiting.

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. By producing the first tilt image by irradiating the substrate over the microstructures and the microstructures focusing incident radiation onto the substrate, a color change in the substrate induced by the set of laser beams is less than an extension of the individual laser beams of the set. The substrate is only partially colored to produce a color effect of the first tilted image. The first tilt image is formed with gaps in the substrate, for which reason the first tilt image can only be seen from a certain first viewing angle range from the front side. The first viewing angle range may extend within an angular range of ± 3 °, ± 7 °, ± 15 ° or ± 30 ° about the first angle. The color changes in the substrate, which are sometimes referred to as color-changed sections, form the structure of the tilt image on the substrate. The use of a laser-sensitive dye makes the production of the first tilted image particularly simple, since the local dyeing by means of such a dye is associated with less effort than in the removal of a metal layer. In particular, it is not necessary in the method described here to apply a metal layer and to remove it again at corresponding points. The production of the security element thus requires fewer process steps than in DE 102014016009 A1 described method for making a tilted image. In addition, only a monochrome tilt image can be generated by the known local removal of a metal layer. Another advantage is thus the ability to produce brightness level or true color images.

The steps of the method according to the invention need not be carried out in the order given. For example, first of all the multiplicity of microstructures can 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 may be a (data) carrier for verification of authenticity, such as a security thread, a label, a transfer element or a security print. The substrate may be configured as any thin-surface element suitable for supporting the plurality of microstructures. For example, the substrate may be a paper, in particular a cotton paper, or a film of polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene (PP) or polyamide (PA). The paper may contain a proportion x of artificial polymer materials in the range of 0 <x <100% by weight. The film may be monoaxially or biaxially stretched. Among other things, the stretching of the film leads to it obtaining polarizing properties which can be used as a further authenticity feature. The tools required for exploiting 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 plurality of microstructures are embedded between two film layers.

The substrate may be transparent, translucent or opaque. Under opaque in the sense of the application is understood to mean a material which transmits a maximum of 5%, in particular a maximum of 2%, of the visible light. In the context of the application, transparent or translucent means 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 the fact that an image can be recognized through the transparent material - the image information remains after passing through the transparent material - with a translucent material this is not the case - the image information is lost due to scattering due to the translucent material ,

The laser-sensitive dye may optionally be applied as a layer to the substrate or provided in the substrate as a layer. The laser-sensitive dye changes color when irradiated with the particular laser radiation. The properties of the particular laser radiation may relate to the wavelength of the laser radiation, the intensity of the laser radiation or the polarization of the laser radiation. By local application of the specific laser radiation, the color of the substrate can thus be locally changed, resulting in color differences and thus a color effect. By varying the intensity of the particular laser radiation, the fluence or the residence time of the laser radiation at a certain location, the degree of color change can be influenced, so that gradations in the discoloration of the substrate can be adjusted.

The parallel laser beams are preferably individually controlled, 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 may be generated by, for example, 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. More preferably, the lasers are in two or more rows arranged side by side. The individual lasers of this diode laser array can be switched on or off individually or controlled individually in the intensity of the radiation to be emitted. For example, such a diode laser array has a resolution of 200 dpi to 500 dpi. By selectively turning on or turning off individual lasers of the diode laser array, the arrangement of the set of parallel laser beams can be adjusted and thus different tilt images can be generated. Preferably, each diode laser generates a laser beam of the set of parallel laser beams. The first angle of the irradiation direction of the set of parallel laser beams can be adjusted by the spatial arrangement of the laser sources or by deflection of 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 onto the substrate. The individual microstructures can be designed as microlenses or micro-hollow mirrors. The microstructures can be designed as elliptical or oval structures that are circular in cross-section perpendicular to the normal, or as line-shaped elements for focusing the laser radiation. Accordingly, the substrate has a linear color change when using linear microstructures, and a lattice-shaped color change when using circular, oval or elliptical microstructures.

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

The number of juxtaposed laser beams in the set is preferably selected such that the structure of the tilt image can be simultaneously generated (or given) in at least one dimension, such as width or length. In the ideal case, sufficient laser beams are provided in such a way that the entire structure of the tilted image can be generated (or predetermined) by the set. The tilting image can also be generated in partial images. In particular, a series of juxtaposed laser beams may be used, which extends across a dimension of the tilt image (such as width or length of the tilt image) to sequentially generate the tilt image in the correspondingly different dimension (length or width) in sub-images. Two rows of parallel laser beams are particularly preferably used in the set, wherein the two rows (in the sense of an overall denser beam arrangement) are arranged offset from one another by half a laser beam width.

The microlenses may be applied to a foil or formed integrally with a foil; the film may be applied to the substrate to form the microstructures on the substrate. The microlenses may 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 region in which the laser-sensitive dye is provided may extend over the entire substrate or may be only a partial region of the substrate. In particular, the area may have an outline that matches the outline of the first tilted image. That is, the area in which the laser-sensitive dye is provided approximately coincides with the extent of the tilt images to be applied.

To produce a tilt image, which is constructed, for example, from color or gray levels, it is optionally provided that the laser beams of the set have the specific laser radiation, wherein a fluence of the determined laser radiation and / or an irradiation time per unit area are set locally differently. The tilting image is preferably locally changed differently in color, so contains a color effect. The fluence may be varied by varying the intensity of the individual laser beams of the set or by differentially focusing the individual laser beams of the set. The irradiation time can be changed by switching on the individual laser beams of the set for different times. By varying the above-mentioned irradiation parameters, a larger or smaller proportion of the laser-radiation-sensitive dyes is activated per unit volume, whereby a different color change can be produced. For example, the higher the fluence, the greater the color change. In this way, the degree of color change can be graded.

The present color change may be a monochrome color change, ie, for example, a change in brightness and / or color saturation. Alternatively or additionally, the color change may include a color change, so for example a change in the color value.

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

As explained in more detail below with reference to various variants, the generation of the first tilted image may comprise at least two steps of irradiating laser beams. The irradiation of the set of parallel laser beams is one of the two steps, but not necessarily the first of these steps. For the at least two steps of the irradiation, the wavelength of the laser radiation may differ. Likewise, the at least two steps can take place from different sides of the security element. The at least two steps may be 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 out of the EP 2528742 B1 a Laser-sensitive substance, which is colored with a multi-stage, here a three-stage process. Two-stage systems are also known to those skilled in the art, so that it is preferred in a development that the laser-sensitive dye in a modification process comprising at least two stages is changeable in terms of its color, wherein irradiated in both stages laser radiation and the steps with respect to a wavelength of Distinguish laser radiation. For example, the laser radiation for the two stages may be generated with a laser array having two different laser diodes for each laser beam so that each laser beam of the set may comprise two wavelengths. By correspondingly switching on the laser diodes of the laser array, a multicolored image can thus be generated.

In order to avoid unwanted discoloration of the security element, which may be caused by a color change occurring in the laser radiation-sensitive dye by incident on the security element incident radiation, such as visible light or UV radiation, it is preferred in one embodiment that one of the two Stages an activation of the substance and the other of the two stages causes the color change of the substance. For example, in the EP 2528742 B1 described dye can be used. For activating the dye in the first stage, a near infrared or infrared wavelength may be used, for example, a Nd: YAG laser having a wavelength of 1.064 μm. The color change of the second stage can be generated with a laser radiation in the ultraviolet wavelength range, for example with an excimer laser. In this case, it is possible by means of the activation to determine both the structure and the intensity of the color change by, as described above, varying the fluence and / or the irradiation duration of the laser beams for activating the laser-radiation-sensitive dye; Thus, a larger or smaller proportion of the laser-radiation-sensitive dye is activated. In this case, the second color change step of the substance may be irradiated with the region of homogeneous laser radiation since the degree of color change is determined by the variation of the activation.

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

Thus, since the laser radiations for the first stage and the second stage have a different wavelength, the focal length of the microstructures for activation and color change is different, so that guiding the first and second stage laser beams through the microstructures results in a longitudinal chromatic aberration can. In order to avoid this, it is preferred in a development that in the first stage the set of laser beams causes the activation of the substance according to the structure and that in the second stage for color change of the substance further laser radiation is irradiated onto a back side of the substrate. The activation of the dye and the excitation of the dye thus takes place from different sides. Since the laser radiation for the second stage is not guided by the microstructures, a disturbing color error in the 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).

In each of the above-mentioned at least two steps of irradiating laser radiation, one of the following sub-steps 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 may be partially changed in color in several irradiation steps (or steps). Also, for such dyes, it is also known that the dyes must first be activated by irradiation (or otherwise) before they can be changed in color by means of laser radiation. For activated dyes, the laser radiation of the particular wavelength triggers the color change. The non-activated dyes are not changed in color by the laser radiation of the particular wavelength. The deactivation is usually irreversible, may be final or alternatively used to specify the structure of the tilt image. Technically preferred processes may comprise, for example, the partial steps in the following sequence:

• 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 from the front or back (a, b, d),
• - back activation, then (first) front color change, optionally second color change with optional final deactivation (c, a, (b, d)), or
• - Front activation for specifying the structure of the tilting image and back, full-surface irradiation for color change with optional final deactivation (c, a, d), or
• - Front deactivation for specifying a negative structure of the tilting image, the back full-surface activation of the substance and then (front or back) irradiation for color change with optional final deactivation (d, c, a).

Even if not explicitly provided, a previous activation or a second color change is additionally possible in each case. In particular, the set of laser beams can bring about a deactivation of the substance outside the structure of the tilted image, so that in a second step of the irradiation for the color change of the substance, laser radiation is irradiated (front or rear side and optionally 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 by means of mirrors to the rear side. In another embodiment, another diode laser or an array of diode lasers may be used to generate the further laser radiation. The further laser radiation may 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 on the area in which the laser-radiation-sensitive dye is provided. This variant can be used in particular if a variation of the intensity is set by means of the set of laser radiation in the first stage.

An apparatus for producing a security element with a first tilted image, in particular according to one of the present described methods, comprises an arrangement region 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 acts on the laser-radiation-sensitive dye focus provided substrate. A first group of independently controllable laser units, each generating a laser beam, and arranged side by side to form a first set of parallel laser beams in a first direction, which is directed to the front of a security element in the array area. A control unit controls at least the laser units of the first group for generating the first tilting image by irradiation of a security element in the arrangement area.

In the present case, the device now further comprises either a second group of independently controllable laser units, each generating a laser beam, and arranged side by side to form a second set of parallel laser beams in a second direction coincident with the first set on the front of the security element is directed, and / or a second laser source, which may be configured as a group of independently controllable laser units, the laser radiation is directed to the back of the security element.

In order to produce a multicolored tilt image, it is provided in a development that the laser-radiation-sensitive dye further comprises a third stage, which allows a further color change of the substance. The third stage is activated by additional laser radiation, which is optionally irradiated through the microstructures on the front side of the substrate. The additional laser radiation may, 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, preferably, the laser radiation for the first stage and the laser radiation for the third stage may be applied through the microstructures.

The additional 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. Again, the variation of the color change in the third stage can be caused by the fact that the fluence and / or the irradiation time in the first stage varies / varies and the third radiation is homogeneously irradiated or that the laser beams of the first stage are homogeneous and the fluence and / or the irradiation time is varied in the laser radiation of the third stage according to the tilting image.

In order to generate a color-changing first tilted image when changing the viewing angle within the first viewing angle range, it is preferred in one development that the fluence and / or the irradiation duration for the third and / or second stage be set such that Microstructure on the substrate a gradual color change is generated. 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 is / are selected for the third and / or second stage in such a way that the color change in the third stage is produced depending on the Gaussian distribution on the substrate, the color changes for each microstructure according to the Gaussian distribution. A color-changed section thus has (not as previously described a uniform color, but) a gradual color change. This is achieved by virtue of the fact that, depending on the Gaussian distribution, the fluence and / or the irradiation duration are / above a threshold value for the color change. This produces an optical impression in which, if the viewing angle is identical or nearly identical to the first angle of the incident laser radiation for the third and / or second stage, the color change visible in the first image can be recognized by the third and / or second color level , If one deviates slightly from this viewing angle in one or the other direction, one looks at the edge regions 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 another Coloring has produced.

Such or similar second or third step of the irradiation of laser radiation can also be done with the aim of better visibility of the tilting image. Another particularly coloring laser irradiation step may lead to an increased width of the color-changed portion by slight variation of the wavelength (eg + - 5 (or 10) nm) and / or the angle of incidence (eg + - 0.5 (, 1 or 2) degrees) , An increased width of the color-changed sections causes an enlargement of the angular range in which the tilting image is visible.

In a further variant, the intensity distribution within a laser beam can be varied to produce the above-mentioned effect. This is an option, in particular, when the intensity change in the focus caused by the focusing is low. Such color changes dependent on the viewing angle are particularly desired in the case of tilt images which represent symbols, letters or characters. The change in the color of the first tilted image depending on the viewing angle can be a security feature of the security element.

In order to further increase the security against forgery of the security element, it is provided in a development 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 under two viewing angles. When the viewing angle is changed, the tilting image is visible in a first viewing angle range, then invisible and again identically visible in a second viewing angle range. This can be realized, for example, by generating the set of parallel laser beams and the group of parallel laser beams from the same laser diode array and directing them onto the substrate by means of a beam splitter or mirror at different angles. Moreover, 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 is recognizable from the front side at a second viewing angle range corresponding to the second angle. Analogously, a third tilt image or further tilt images can be generated. In preferred embodiments, a second (third or further) tilt image is generated with a second (third or further) laser diode array.

Further, the second (or any other) tilt image may be different than the first tilt image. The second, third or each further tilt image can be generated in a similar way as the first tilt image. In particular, the considerations made with regard to the first tilted image, preferred development and advantages can be applied analogously. Especially in connection with the gradual color change, the second tilted image can be adjusted such that, with increasing viewing angle, first the first tilted image under a first color, then under a second color, then the second tilted image under the first color and then the second tilted image under the second Color is recognizable. The second tilt image may also be generated with a diode laser array that is different from the diode laser array for generating the set of parallel laser beams.

In order to further increase the speed of the production of the security element, optionally the first tilt image and the second tilt image can be generated simultaneously. In a 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 no or only a small heat generation, the first tilt image and the second tilt image can be generated simultaneously, without resulting in thermal damage to the substrate. This would be in the demetallization for generating the tilt image, as shown in the DE 102014016009 A1 is described, not possible, since often considerable heat is generated in demetallization, so that a simultaneous removal of the metallization layer for generating the first and second tilt image is not possible.

The security against forgery of the security element can be further increased by combining a regular image with a tilt image into a forest. In a development, it is provided that the microstructures cover only a part of the area with the laser-radiation-modified substance, wherein the set of parallel laser beams is irradiated onto the entire area with the substance which can be modified by laser radiation. The regular image is recognizable from the front side next to the first tilted image and is visible under a larger viewing angle range than the first and / or second viewing angle range. 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 changes into a regular image could possibly be adjusted by other means. In particular, an imprint by means of a shutter effect (eg by applying a foil with directed lamellas) could become a partially tilted image with adjacent regular field. In the present case, therefore, another motif that is complementary or related to the tilting image is preferably displayed in the regular image (distinguishable partial images). A Venetian blind film could hardly be applied with the required register accuracy on a print with such distinguishable partial images. Therefore, as already described, it is particularly preferred that a second (third or further) tilting image is generated by means of the microstructures in the present case. Under a single microstructure are thus sections of different tilt images. For the viewer, the tipping pictures are (at least overlapping) in the same place. Creating a second tilt image for the viewer at the same location is not possible with the technologies available to a counterfeiter by means of blinds effects.

The microstructures may, for example, be applied to a carrier foil or formed in a carrier foil, wherein the carrier foil is arranged on the part of the region with the laser-radiation-modifiable substance. The carrier film may be strip-shaped. If now the set of laser beams is irradiated onto the area with the laser-radiation-sensitive substance, a tilted image is formed in the section in which the microstructures are arranged, and in the section in which the microstructures are not arranged, a view visible from many viewing angles, regular picture. Since the tilt image and the regular image are generated with the same set of parallel laser beams, they are in perfect registration with each other. It is possible that the portion of the area where the tilt image is provided is additionally illuminated with the group of parallel laser beams for producing the second tilt image.

In order to prevent the separation of the tilting 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 in the preparation of the substrate with their starting materials. If z. B. a paper is used for the substrate, the laser-sensitive dye can be added to the head box in the trough of the paper machine. Furthermore, it is possible to add the laser-radiation-sensitive dye to a liquid, for example a glue, with which the paper is soaked. In both cases, the laser-sensitive dye is firmly bonded to the paper, so that a targeted or accidental separation of the tilting image of the substrate is impossible.

The substrate may, as already described, comprise a plurality of partial regions which comprise the laser-radiation-modifiable substance. The microstructures are present in the first subregion and a regular image can be generated in a second subregion without microstructures. The subregions of the substrate may comprise different or the same substrate material. By way of example, the substrate may comprise a plastic film in the first partial region and a paper substrate in the second partial region. In both subregions, the laser-radiation-modifiable substance can be contained in the substrate material independently of one another or provided as a coating. The same laser-radiation-modifiable substance can be introduced into the subregions at different times. Particularly preferably, the first subregion is 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.

• 1a-1c eine Draufsicht auf ein Wertdokument unter verschiedenen Betrachtungswinkeln;
• 2 eine Draufsicht auf eine weitere Ausführungsform eines Wertdokuments;
• 3 eine Schnittdarstellung entlang der Linie I-I von 1a;
• 4 eine Schnittdarstellung einer weiteren Ausführungsform des Wertdokuments;
• 5 eine Schnittdarstellung einer weiteren Ausführungsform des Wertdokuments; und
• 6 eine Schnittdarstellung zur Illustration eines Herstellungsverfahrens für das Wertdokument.

Further embodiments and advantages of the invention will be explained below with reference to the figures, in the representation of a true-to-scale and proportionate reproduction has been omitted in order to increase the clarity. Show it:

• 1a - 1c a plan view of a document of value at different viewing angles;
• 2 a plan view of another embodiment of a document of value;
• 3 a sectional view taken along the line II of 1a ;
• 4 a sectional view of another embodiment of the value document;
• 5 a sectional view of another embodiment of the value document; and
• 6 a sectional view illustrating a production method for the document of value.

In the 1 and 2 become sections of various embodiments of a value document 10 shown. The value document 10 For example, it may be a banknote and includes a security element 12 , On a substrate 14 of the security element 12 is a regular picture in supervision 16 recognizable. The regular picture 16 is in the 1 and 2 However, as a triangle or section of a quadrilateral shown, but any subject, such as an outline of a person, an animal, an object or a symbol represent. The regular picture 16 is from a wide viewing angle range, for example from 0 ° to 70 ° or 80 ° to a normal, in supervision of the document of value 10 recognizable as in 1b and 1c is shown.

Will the value document 10 , in particular the security element 12 , viewed under a first viewing angle range, as shown in FIG 1b is shown next to the regular picture 16 a first tilt picture 18 recognizable. 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 may be ± 3 °, ± 7 °, ± 15 ° or ± 30 ° of the first angle α. The first tilt picture 18 is in 1b shown as a rectangle that matches the regular picture 16 added to an overall picture, taking the regular picture 16 and the first tilt picture 18 in perfect registration with each other.

Will the value document 10 , in particular the security element 12 , viewed under a second viewing angle range, as shown in FIG 1c is shown next to the regular picture 16 a second tilt picture 20 recognizable, as well as the first tilting picture 18 in perfect registration to the regular picture 16 stands. The second viewing angle range may be ± 3 °, ± 7 °, ± 15 ° or ± 30 ° of the second angle β. The first tilt picture 18 and / or the second tilt image 20 can / may have any shape in addition to the illustrated squares and in particular represent persons, objects or animals. For example, the overall picture is a coat of arms and the tipping pictures 18 . 20 represent parts of the coat of arms, which are recognizable under the respective viewing angle. The first tilt picture 18 and / or the second tilt image 20 can / can as in 2 represented, composed of non-contiguous sections, which optionally with the regular image 16 to complement each other to an overall picture. The sections of the tilting image can be formed, for example, in the respective visible parts of a pendulum thread in the value document.

The structure, the method of production and the operation of the value document 10 or the security element 12 are based on the sectional views in 3 - 6 explained. The value document can also be regarded as a security element in a broader sense.

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

On the substrate 14 or the color layer 22 is the carrier layer 24 applied to the the microstructures 26 are formed. The carrier layer 24 consists of a transparent film, such as polyethylene (PE) or polypropylene (PP). The microstructures 26 are formed as, optionally circular, microlenses and in the embodiment shown in one piece with the carrier layer 24 produced. However, it is also possible that the multitude of microstructures 26 prepared separately and on the carrier layer 24 is applied. 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 others the in 2 shown sections of the tilting image 18 can be realized by different configurations. In one variant lie the microstructure 26 only in the subsections before, per subsection is within the meaning of 3 a foil element 24 with microstructures 26 on the substrate 14 applied. In a preferred variant, not shown, which only the example of 2 are described, the microstructures 26 on the carrier layer 24 in the substrate 14 embedded. In particular, if the microstructures are present on a security thread, the microstructures, optionally as in FIG 2 as a pendulum thread, embedded in the substrate. In 3 would be the subarea 24 . 26 one in the substrate 14 integrated element, wherein the color layer 22 of the subarea without microstructures could possibly be arranged in the same plane with the microstructures. Generally speaking, a substrate can thus comprise subregions of different substrate material, which can optionally be provided with laser radiation-active dyes, optionally in a color layer, at different times.

The production of the value document 10 or the security element 12 is in one embodiment as follows: First, in the area of the regular image 16 and the later first flip picture 18 the laser-sensitive dye in the substrate 14 introduced, for example by impregnating the substrate 14 with a liquid, such as glue, which contains the laser-radiation-sensitive dye. In this way the color layer becomes 22 provided with an extension which is the later regular image 16 and the first tipping picture 18 equivalent. In the area of the first tilted image 18 and the second tilt image 20 becomes the carrier layer 24 with the plurality of microstructures arranged thereon 26 applied. Following this is a sentence 28 of laser beams at a first angle α to a normal to the substrate 14 irradiated. The individual laser beams of the sentence 28 have an extension greater than a diameter of the microstructures 26 so that a laser beam of the sentence 28 on several microstructures 26 falls. The individual laser beams of the sentence 28 have an arrangement and an intensity such that this results in the regular image 16 and the first tilt picture 18 this results by adding in the color layer 22 in the places where the sentence 28 of laser beams on the paint layer 22 meets, a color change occurs. In the in the 1 and 2 illustrated embodiment, the individual laser beams of the sentence 28 an equal intensity and an equal exposure time, so that the regular picture 16 and the first tilt picture 18 appear as homogeneous surfaces. However, since the laser beams of the sentence 28 spaced apart, there is no continuous color change in the ink layer 22 , In particular, by focusing the laser beams of the sentence 28 through the microstructures 26 arise colored sections 30 in the color layer 22 with a width b. In between there are undyed sections 32 in the color layer 22 in which no color change was caused.

Looking now at the security element 12 from the front side at a viewing angle which is approximately equal to the first angle α, the eye of the observer receives radiation from the colored sections 30 comes. The first tilt picture 18 is thus recognizable. Looking at the security element 12 from the front side, a viewing angle different from the first angle α, the radiation entering the eye of the observer originates from the non-colored sections 32 so that the first tipping picture 18 is not recognizable. Only the color of the uncoloured substrate 14 is visible or the base color of the laser-sensitive layer, which may well have an intrinsic color. As above the regular picture 16 no microstructure 26 are arranged, is the regular picture 16 recognizable from all viewing angles.

The generation and the mode of action of the second tilted image 20 takes place analogously to the first tilted image 18 except that for generating the second tilt image 20 a group 34 is irradiated by laser beams at another, second angle β, as shown in FIG 5 is shown. With the group 34 of laser beams becomes one of the colored sections 30 different area of the substrate 14 inked. The radiation of the group 34 of laser beams can be simultaneous with that of the sentence 28 done by laser beams or sequentially.

Another embodiment of the value document 10 or security elements 12 is in 4 shown. This is true except for the following differences with the value document 10 according to 3 agree: The microstructures 26 are in the in 4 shown embodiment designed as a micro-hollow mirror, which incident laser beams on the ink layer 22 focus. The color layer 22 is in the in 4 shown embodiment separated from the substrate 14 provided and may be formed, for example, as a film in which laser-sensitive dye is mixed. The mode of action and production method is analogous to that in 3 shown value document 10 , The laser-sensitive dye of the color layer 22 and / or the laser radiation are adjusted so that the laser-sensitive dye does not react to the unfocused radiation, that is transparent to it. Only the radiation focused by the microstructures produces the color change.

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

6 shows a further embodiment of the value document 10 or security elements 12 that with the 3 and 5 corresponds to the embodiment shown. Here, a laser-sensitive dye is used, which is changeable in terms of its color in a modification process comprising at least two stages. In a first stage, the sentence becomes 28 of laser beams at the first angle α through the microstructures 26 irradiated. The wavelength of the laser radiation is for example in the infrared, in particular 1.064 microns. The laser radiation for the first stage is used to activate the laser-radiation-sensitive dye. The actual color change will now be laser radiation with one of the set 28 irradiated by laser radiation of different wavelengths, for example with a wavelength in the ultraviolet. Because of the different wavelengths, the focusing of the laser radiation through the microstructures 26 changes, the laser radiation for the second stage is not from a front side of the substrate 14 but radiated from a back. The intensity of the laser radiation for the second stage is in the illustrated embodiment over the area of the regular image 16 and the first flip picture 18 homogeneous. To produce different shades (grayscale) and structures, the sentence becomes 28 modified accordingly by laser beams for the first stage. The substrate and / or the wavelength of the back irradiated laser radiation are chosen so that the substrate for the laser radiation is sufficiently transparent.

Moreover, it is possible, for example, a third stage (or a third step of irradiating laser radiation) to produce a further color effect in the laser-radiation-sensitive dye according to the embodiment of 6 provided. For generating the color effect in the third stage, laser radiation having a wavelength similar to the wavelength for the first stage is used. Therefore, the laser radiation for the third stage can again through the microstructures 26 are irradiated, in particular again at the first angle α.

Particularly preferably, the fluence and the duration of irradiation of the laser-sensitive dye for the (second or) third stage are chosen such that the color change within (each) of the colored portion 30 is different. This can for example be caused by the fact that due to the focus through the microstructures 26 a Gaussian intensity distribution in the color layer 22 or in the substrate 14 results. Due to this, a gradual color change results in the inked portion 30 , wherein in the middle of the colored section 30 the color of the color change of the (second or) third stage and at the edges of the colored portion 30 no color change through this stage results. In 6 lies accordingly at the edges of the respective colored sections 30 only the color of the second stage of the color change before. Looking at the value document 10 at an angle which is a little larger or smaller than the first angle α, the first tilting image 18 recognizable with the color for the second stage. By changing the viewing angle to the first angle α, the color gradually changes from the color of the second stage to the color of the third stage.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014016009 A1 [0003, 0010, 0043]
• EP 2528742 B1 [0026, 0027]

Claims (15)

Method for producing a security element (12) with a first tilted image (18), comprising the steps: Providing a substrate (14) having a region with a laser-radiation-modifiable substance, - Forming a plurality of microstructures (26) on the substrate (14), wherein the microstructures (26) are each formed so that they focus on a front side of the substrate (14) incident radiation in the area, and - Producing a structure of the first tilting image (18), so that the first tilting image (18) is recognizable in a first viewing angle range from the front, wherein generating the first tilting image (18) comprises simultaneously irradiating a set (28) of parallel laser beams onto the microstructures (26) at a first angle (a) to the substrate (14), the substance has a laser-radiation-sensitive dye, which changes its color by irradiation with certain laser radiation, and the first tilting image (18) shows a color effect caused by the change in color. Method according to one Claim 1 , characterized in that the parallel laser beams, in particular with respect to fluence and / or irradiation time, are individually controlled. Method according to Claim 1 or 2 , characterized in that the individual laser beams of the set (28) have a greater extent than a microstructure (26) and / or in the set (28) of laser beams sufficient laser beams are arranged side by side to the structure of the tilting image in at least one dimension, like width or length, to completely generate. Method according to one of Claims 1 to 3 characterized in that generating the first tilt image (18) comprises at least two steps of irradiating laser beams, including irradiating the set (28) of parallel laser beams. 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: 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 of the substance Substance. Method according to Claim 4 or 5 , characterized in that for the at least two steps of the irradiation, the wavelength of the laser radiation differs, wherein in particular a first specific wavelength for a first color change and a second specific wavelength for a second color change is provided. Method according to one of Claims 4 to 6 characterized in that at least the step of irradiating the set (28) is from the front and another of the at least two steps is from the back. Method according to one of Claims 1 to 7 , characterized in that the laser beams of the set (28) have the specific laser radiation and cause the color change of the substance according to the structure, wherein preferably a fluence of the determined laser radiation and / or an irradiation time per unit area are set locally different. Method according to one of Claims 1 to 7 , characterized in that the set (28) of laser beams causes activation of the substance according to the structure and that in a second step of irradiation for color change of the activated substance, the laser radiation is irradiated to a back side of the substrate (14) and / or that Set (28) of laser beams causes a deactivation of the substance outside the structure and that is irradiated in a second step of the irradiation for color change of the substance laser radiation. Method according to one of Claims 1 to 9 , characterized in that a second color change of the substance in a second and / or third step of irradiating laser radiation is effected, which is irradiated to the front side of the substrate (14), wherein preferably the fluence and / or the irradiation time for the second color change be set so that a gradual color change is produced per microstructure on the substrate (14). Method according to one of the preceding claims, characterized in that a second, at a second angle (β) corresponding to - second viewing angle range from the front visible tilting image (20) is generated by a second set (34) of parallel laser beams under 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. Method according to one of the preceding claims, characterized in that the microstructures (26) cover a part of the area with the laser-radiation-modifiable substance, wherein - preferably the set (28) of parallel laser beams - is irradiated to another part of the range with the laser radiation modifiable substance, so that from the front next to the first tilting image (18), a regular image (16) in a relation to the first viewing angle range larger viewing angle range is visible, is visible. Device for producing a security element (12) with a first tilted image (18), in particular according to a method according to one of the Claims 1 to 12 wherein the device comprises: - a positioning region for arranging a security element, to the substrate (14) of which a plurality of microstructures (26) are applied, which focus radiation incident on a front side of the security element (14) onto the substrate provided with laser-sensitive dye; a first group of independently controllable laser units, each generating a laser beam, and arranged side by side to form a first set of parallel laser beams in a first direction directed towards the front of the security element (14); a second group of independently controllable laser units, each generating a laser beam, and arranged side by side to form a second set of parallel laser beams in a second direction, which is directed simultaneously with the first set on the front of the security element (14), and / or a second laser source, which may be configured as a group of independently controllable laser units, the laser radiation is directed to the back of the security element (14); and a control unit which controls at least the laser units of the first group to generate the first tilted image by irradiating a security element in the arrangement area. Security element with a tilting image, in particular produced according to a method according to one of Claims 1 to 12 comprising - a substrate (14) and - a plurality of microstructures (26) formed on the substrate (14) and focusing radiation incident on a front surface of the substrate (14) into a region, characterized in that - the region comprises laser-dye-sensitive dye and - the area in a plurality of colored sections (30) is colored in such a way and the microstructures (26) are each designed such that they focus on a front irradiation incident radiation to the colored portions (30) at a first predetermined viewing angle range in that a first tilting image (18) in the predetermined viewing angle range can be recognized by the microstructures (26). Security element after Claim 14 wherein the first tilting image (18) is in one part of the laser-sensitive dye region and a regular image (16) recognizable in a wider viewing angle range than the first viewing angle region is in another part of the laser-radiation-sensitive dye region first tilted image (18) and the regular image (16) by means of a - at the same time at a first, the viewing angle associated angle - irradiated set (28) of parallel laser beams are generated in register with each other.

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