WO2018072881A2

WO2018072881A2 - Security element, and method for producing a security element

Info

Publication number: WO2018072881A2
Application number: PCT/EP2017/001226
Authority: WO
Inventors: André Gregarek; Christian Fuhse; Steffi JAHN; Veronika RACK; Patrick Renner; Georg Depta; Josef Schinabeck; Annett Bähr
Original assignee: Giesecke+Devrient Currency Technology Gmbh
Priority date: 2016-10-21
Filing date: 2017-10-19
Publication date: 2018-04-26
Also published as: DE102016012625A1; EP3529084B1; CN109562635B; CN109562635A; WO2018072881A3; EP3529084A2

Abstract

The invention relates to a method for producing a security element (12) comprising a flip image, the method comprising the following steps: providing a substrate (14) having a region with a dye that is sensitive to laser radiation. forming a plurality of microstructures (26) on the substrate (14), each microstructure (26) being formed such that it focuses radiation incident on a front face of the substrate (14) onto said region; and irradiating the microstructures (26) with a set (28) of parallel laser beams at a first angle to the substrate (14), the individual laser beams of the set (28) being arranged such that a structure of a first flip image (18) is created, which image can be discernible from the front face at a viewing angle associated with the first angle (α); wherein the dye that is sensitive to laser radiation changes its colour by irradiation with a specific laser radiation; and wherein the first flip image (18) displays a colour effect caused by the colour change.

Description

S e c tio n a tio n s an d v e rc e s

C o n n e c o n t i o n s s e c tio n s s e t i o n s

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 tilting 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, the microstructures each 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 so as to produce a structure of a first tilt image that is recognizable from the front side at a viewing angle range associated with the first angle, wherein the

Substance has a laser-sensitive dye, which changes its color by irradiation with certain laser radiation, and wherein the first tilting image shows a caused by the change of color color effect.

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, in the case of the method described here, It is not necessary to apply a metal layer and to remove it at corresponding points. The production of the security element thus requires fewer process steps than the method described in DE 102014016009 A1 for producing a tilted image. In addition, by the known local removal of a metal layer only a monochrome

Tilting image can be generated. 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 specified sequence. For example, first the

Variety of microstructures are formed on the substrate and then the laser-radiation-sensitive dye is 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 may have a paste Pierfolienverbund 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 that an image can be recognized through the transparent material - the image information remains after passing through the transparent material - this is not the case with a translucent material - the image information passes through the translucent material Scattering lost.

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 can be the wavelength of the laser radiation, the

Intensity of the laser radiation or the polarization of the laser radiation relate. 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 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 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 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 (of a single diode laser) falls on several 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 exactly aligned with the respective microstructures, but rather because of the large size of the individual laser beams compared to the diameter of the microstructures

Laser beam always fully illuminates at least one microstructure. 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 can be used, which extends over one dimension of the tilt image (such as width or length of the tilt image) to produce the tilt image in the correspondingly different dimension (length or width) in sub-images one after the other. 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 tilted 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 a different period 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, whereby a different color change can be produced. For example, the color The greater the fluence, the greater the 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. Thus, from EP 2528742 Bl a laser-sensitive substance is known, which 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 it is part of a continuing It is preferred that the laser-radiation-sensitive dye is changeable in terms of its color in a modification process comprising at least two stages, wherein laser radiation is radiated in both stages and the stages differ with respect to a wavelength of the 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 random incident on the security element radiation, such as visible light or UV radiation, it is preferred in one embodiment that the one activation of the substance is effected in the two stages and the other of the two stages effects the color change of the substance. For example, in the

EP 2528742 B1 described dye can be used. For activation of the dye in the first stage, a wavelength in the near infrared or in the infrared can be used, for example, a Nd: Y AG laser with a wavelength of 1.064 μιη. 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 for both the structure and the intensity of the color change to be determined by means of the activation, as described above, by 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 In this case, the second color change step of the substance can be irradiated with over the range 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 through the microstructures, a disturbing chromatic aberration during focusing can be avoided.

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 sub substance. Laser radiation-sensitive dyes may be partially changed in color in several irradiation steps (or steps). It is also known for such dyes 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 side and second color change from the front or rear side with optional final deactivation from the front or rear side (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 to specify a negative structure of the tilting image, backside 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. 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 irradiation for color change of the substance laser radiation is radiated (front or back and, where appropriate, 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 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 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 tilting image, in particular according to one of the described described methods, comprises an arrangement region for arranging a security element, to the substrate of which a multiplicity of microstructures are applied, which radiation incident on a front side of the security element has on it focus on 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, which is directed to the front of a security element in the array area. A control unit controls at least the laser units 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 also 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, which is directed simultaneously with the first set on the front of the security element, and / or

a second laser source, which can be configured as a group of independently controllable laser units whose laser radiation is directed onto the rear side 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 can 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 two laser diodes are coupled so 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 any 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 / is above or below a threshold value for the color change.

This produces an optical impression in which, when the viewing angle is identical or nearly identical to the first angle of the incident laser radiation for the third and / or second stage, by the third and / or second color level visible color change in the first image is recognizable. 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 angle range in which the tilt 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 represent 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 generates a second tilt image is irradiated by irradiating a group of parallel laser beams at a second angle to the substrate on the front surface thereof.

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 tilting 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 regarding the first tilted image, the preferred development and the advantages can be applied analogously. Specially in

In connection with the gradual color change, the second tilt 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 tilting image is recognizable under the second color. 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 not possible because considerable heat is often generated during demetallization, so that a simultaneous removal of the metallization layer to produce 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, the set of parallel laser beams being irradiated onto the entire area with the substance which can be modified by the laser radiation. The regular image is recognizable from the front side next to the first tilted 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 changes into a regular image could possibly be adjusted by other means. In particular, an imprint by means of a shutter effect (for example, by applying a foil with directed lamellas) could become a partially tilting image with adjacent regular partial image. Preference is therefore present in the regular

Picture another, to the tilting picture only complementary or associated motif represented (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, a second (third or further) tilting image is particularly preferably generated in the present case by means of the microstructures. 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 produced in the section in which the microstructures are arranged, and in the section in which the microstructures are not arranged, a visible from many viewing angles, regular image. 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 prevent 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. For example, if a paper is used for the substrate, the laser-radiation-sensitive dye can be added to the fabric for running 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 from 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 modifying bare substance contained in the substrate material or be 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. 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. 1a-1c show a plan view of a document of value under various

Viewing angles;

FIG. 2 shows a plan view of a further embodiment of a value document; FIG.

Fig. 3 is a sectional view taken along the line I-I of Fig. La;

4 is a sectional view of another embodiment of the

Value document;

5 is a sectional view of another Ausführungsf

Value document; and Fig. 6 is a sectional view for illustrating a manufacturing method for the document of value.

In FIGS. 1 and 2, portions of various embodiments of a value document 10 are shown. The value document 10 can be, for example, a banknote and comprises a security element 12. A regular image 16 can be seen in a plan view on a substrate 14 of the security element 12. The regular image 16 is shown in FIGS. 1 and 2 as a triangle or detail of a quadrilateral, but may 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 wide viewing angle range, for example from 0 ° to 70 ° or 80 ° with respect to a normal, in top view of the document of value 10, as shown in FIGS. 1b and 1c.

If the value document 10, in particular the security element 12, is viewed under a first viewing angle range, as shown in FIG. 1 b, a first tilt image 18 can be seen in addition to the regular image 16. The first viewing angle range is clearly 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 tilting image 18 is shown in FIG. 1b as a quadrilateral, which complements the regular image 16 to form an overall image, the regular image 16 and the first tilting image 18 being in perfect registration with one another.

If the document of value 10, in particular the security element 12, viewed under a second viewing angle range, as shown in Fig. Lc, in addition to the regular image 16, a second tilt image 20 can be seen, which as well as the first tilt image 18 in perfect registration to the re - gular picture 16 stands. The second viewing angle range may be ± 3 °, ± 7 °, ± 15 ° or ± 30 ° of the second angle β. The first tilting image 18 and / or the second tilting image 20 can / may have any desired shape in addition to the illustrated quadrilaterals and in particular represent persons, objects or animals. For example, the overall picture is a coat of arms and the tilting pictures 18, 20 represent parts of the coat of arms that can be seen from the respective viewing angle. The first tilting image 18 and / or the second tilting image 20 can, as shown in FIG. 2, be composed of non-contiguous sections which optionally complement each other with the regular image 16 to form an overall image. 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 mode of operation of the value document 10 or of the security element 12 will be explained with reference to the sectional views in FIGS. 3-6. The value document can also be regarded as a security element in a broader sense.

The embodiment of the security element 12 shown in FIG. 3 has, in addition to the substrate 14, a color layer 22 with laser-radiation-sensitive dyes contained therein, an optional carrier layer 24 and a large number of microstructures 26. The substrate 14 is made in the embodiment shown from paper, in particular cotton paper. In addition, the substrate 14 may 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 is a separately applied to the substrate 14 layer. 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 and the color layer 22, the carrier layer 24 is applied, on which the microstructures 26 are formed. The carrier layer 24 consists of a transparent film, for example polyethylene (PE) or polypropylene (PP). The microstructures 26 are formed as, optionally circular, microlenses and in the embodiment shown made in one piece with the carrier layer 24. However, it is also possible for the plurality 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 region of the substrate 14 in which the laser-radiation-sensitive dye is provided. Among other things, the sections of the tilting image 18 shown in Figure 2 can be realized by different configurations. In one variant, the microstructure 26 is present only in the subsections, per subsection, in the sense of FIG. 3, a film element 24 with microstructures 26 is applied to the substrate 14. In a preferred variant, not shown, which is described only with the example of FIG. 2, the microstructures 26 are embedded in the substrate 14 on the carrier layer 24. In particular, if the microstructures are present on a security thread, the microstructures, optionally as in FIG. 2 as a pendulum thread, can be embedded in the substrate. In FIG. 3, the partial region 24, 26 would be an element integrated in the substrate 14, wherein the color layer 22 of the partial region 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 are optional at different times with laser radiation active dyes, possibly in a color layer, can be provided.

The production of the value document 10 or of the security element 12 is in one embodiment as follows: First, in the region of the regular image 16 and the later first tilt image 18, the laser-radiation-sensitive dye is introduced into the substrate 14, for example by impregnating the substrate 14 with a liquid, like glue that contains the laser-sensitive dye. In this way, the color layer 22 is provided with an extension which corresponds to the later regular image 16 and the first tilt image 18. In the area of the first tilting image 18 and the second tilting image 20, the carrier layer 24 with the plurality of microstructures 26 arranged thereon is applied. Subsequently, a set 28 of laser beams is irradiated at a first angle α to a normal to the substrate 14. The individual laser beams of the set 28 have an extension that 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 tilt image 18 result therefrom in that in the ink layer 22 at the locations where the set of laser beams 28 the color layer 22 hits, a color change occurs. In the embodiment shown in FIGS. 1 and 2, the individual laser beams of the set 28 have an equal intensity and an equal exposure duration, so that the regular image 16 and the first tilt image 18 appear as homogeneous surfaces. However, since the laser beams of the set 28 are spaced from each other, there is no continuous color change in the color layer 22. Specifically, by focusing the laser beams of the set 28 through the microstructures 26, colored portions 30 result in the ink layer 22 having a width b. In between there are non-colored sections 32 in the color layer 22, in which no color change was caused. If one now considers the security element 12 from the front side at a viewing angle which is approximately equal to the first angle α, then the eye of the observer receives radiation which originates from the colored sections 30. The first tilting image 18 is thus recognizable. If the security element 12 is viewed from the front side from a viewing angle which differs from the first angle α, then the radiation reaching the eye of the observer originates from the non-colored sections 32, so that the first tilted image 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. 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 tilting image 20 take place analogously to the first tilting image 18, except that a group 34 of laser beams is irradiated at a different, second angle β to produce the second tilting image 20, as shown in FIG. 5. With the group 34 of laser beams, a different area of the substrate 14 from the colored portions 30 is colored. The irradiation of the group 34 of laser beams may be simultaneous with that of the set 28 of laser beams or sequentially.

Another embodiment of the value document 10 or security element 12 is shown in FIG. 4. This is true except for the following In the embodiment shown in FIG. 4, the microstructures 26 are designed as micro-hollow mirrors which focus incident laser beams onto the ink layer 22. The ink layer 22 is in the embodiment shown in FIG provided separately from the substrate 14 and may be formed, for example, as a film in which laser-sensitive dye is mixed. The mode of action and method of production is analogous to the value document 10 shown in FIG. 3. The laser-sensitive dye of the color layer 22 and / or the laser radiation are adapted such that the laser-sensitive dye does not react to the unfocussed radiation, ie is transparent to it. Only the radiation focused by the microstructures produces the color change.

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

FIG. 6 shows a further embodiment of the value document 10 or security element 12, which corresponds to the embodiment shown in FIGS. 3 and 5. Here, a laser-sensitive dye is used, which can be changed in terms of its color in a modification process comprising at least two stages. In a first stage, the set 28 of laser beams at the first angle α is irradiated through the microstructures 26. The wavelength of the laser radiation is, for example, in the infrared, in particular 1.064 μιη. The laser radiation for the first stage is used to activate the laser radiation-sensitive dye. To the actual Now color change is irradiated laser radiation with one of the set 28 of laser radiation of different wavelength, for example, with a wavelength in the ultraviolet. Since the focus of the laser radiation through 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. The intensity of the laser radiation for the second stage is homogeneous in the illustrated embodiment over the area of the regular image 16 and the first tilt image 18. To produce different shades (gray levels) and structures, the set 28 of laser beams for the first stage is modified accordingly. 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 to provide, for example, a third stage (or a third step of irradiating laser radiation) for producing a further color effect in the laser-radiation-sensitive dye according to the embodiment of FIG. 6. 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 be re-irradiated through the microstructures 26, in particular again at the first angle a.

More preferably, the fluence and the duration of irradiation of the laser-sensitive dye for the (second or) third stage are selected such that the color change within (each) of the colored portion 30 is different. This can be caused, for example, by the fact that, due to the focusing through the microstructures 26, a Gaussian intensity distribution in the ink layer 22 or in the substrate 14 results. Due to this, a gradual color change results in the inked portion 30, and in the middle of the inked portion 30, the color of the color change of the (second or) third stage and at the edges of the inked portion 30 does not result in color change by this stage. In FIG. 6, only the color of the second stage of the color change is correspondingly present at the edges of the respectively colored sections 30. Upon viewing the value document 10 at an angle slightly greater or smaller than the first angle α, the first tilt image 18 with the color for the second stage becomes recognizable. 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.

Claims

Patent claims

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

Providing a substrate (14) having a region with a laser-radiation-modifiable substance,

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

Generating a structure of the first tilting image (18), so that the first tilting image (18) is recognizable te 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.

2. The method according to claim 1, characterized in that the parallel laser beams, in particular with respect to fluence and / or irradiation time, are individually controlled.

3. The method of 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 2 -

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.

4. The method according to any one of claims 1 to 3, characterized in that the generation of the first tilting image (18) comprises at least two steps of irradiating laser beams, including the irradiation 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 sub-steps 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 d) deactivation of the substance.

6. The method of 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 is provided for a second color change.

7. The method according to any one of claims 4 to 6, characterized in that at least the step of irradiating the set (28) takes place from the front and another of the at least two steps takes place from the back.

8. The method according to any one of claims 1 to 7, characterized in that the laser beams of the set (28) have the specific laser radiation and the color change of the substance according to the structure Bewir- - 3 -

ken, wherein preferably a fluence of the determined laser radiation and / or an irradiation time per unit area are set locally differently.

9. The method according to any one of claims 1 to 7, characterized

the set (28) of laser beams causes an activation of the substance according to the structure, and in a second step of irradiation for color change of the activated substance the laser radiation is radiated onto a rear side of the substrate (14) and / or

the set (28) of laser beams causes a deactivation of the substance outside the structure and that in a second step of the irradiation for the color change of the substance laser radiation is irradiated.

10. The method according to any 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 which is irradiated onto the front side of the substrate (14), wherein preferably the fluence and / or the irradiation time for the second color change are adjusted such that on each substrate ( 14) a gradual color change is produced.

11. The method according to any one of the preceding claims, characterized in that a second, at a - a second angle (ß) corresponding - second viewing angle range of the front visible tilting image (20) is generated by a second set (34) of parallel laser beams at the second angle (β) to the substrate (14) is irradiated, - 4 -

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 one of the preceding claims, character- ized in that the microstructures (26) cover a part of the range with the laser radiation modifiable substance, wherein - preferably the set (28) of parallel laser beams - on another part of the area with the irradiated so that from the front next to the first tilting image (18), a regular image (16), which is visible in a relation to the first viewing angle range larger viewing angle range is visible.

13. A device for producing a security element (12) with a first tilted image (18), in particular according to a method according to one of claims 1 to 12, wherein the device comprises:

an array region for disposing 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 - 5 -

a second laser source that may be configured as a group of independently controllable laser units whose 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 for generating the first tilting image by irradiation of a security element in the arrangement area.

14. 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 an area,

characterized in that

the area has a laser-sensitive dye and the area is colored in a plurality of colored sections (30) and the microstructures (26) are each designed such that they impinge on the colored areas (30) under a first predetermined viewing angle range on the front side ), so that a first tilting image (18) in the predetermined viewing angle range can be recognized by the microstructures (26).

15. The security element according to claim 14, wherein the first tilting image (18) is present in a part of the area with laser-radiation-sensitive dye and a regular image (16), which is recognizable in a larger viewing angle range than the first viewing angle area, in another part of the area laser-sensitive dye is present, wherein the first tilt image (18) and the regular image (16) by means of a - are timed at a first, the viewing angle associated angle - irradiated set (28) of parallel laser beams register with each other are generated.