Patent Grant
11667145
The present invention relates to a data carrier comprising at least one security element according to claim 1, a security document comprising such a data carrier according to claim 14, and a method of producing such a data carrier according to claim 15.
It is a common desire to protect data carriers being comprised in or constituting security documents such as identity cards, passports, credit cards, bank notes and the like against forgery. In this context color laser imaging technology that is applied onto a data carrier comprising a polycarbonate has been considered as the grail for identification documents for a long time. For example, Lasink and CLS are two main technologies that are known in the art and which are based on said technology. However, this technologies suffer from the drawbacks that the generated images are of a low resolution and the associated manufacturing costs are rather high.
Optical variable devices such as DOVIDs are known and useful features to assess easily by naked eye if a data carrier or a security document is genuine or not. However, counterfeiters manage to remove such DOVIDs by back-grinding and then recombine it with a new personalized core and a backside from another data carrier or security document.
It is an object of the present invention to overcome the drawbacks of the prior art. It is in particular an object to provide a data carrier comprising at least one security element that provides a high protection against counterfeits and which can be easily produced.
This object is achieved with a data carrier according to claim 1. In particular, a data carrier is provided, which comprises at least one optically variable element, at least one surface element, and at least one security element comprising at least part of the at least one optically variable element and at least part of the at least one surface element. The at least one optically variable element is arranged after the at least one surface element when seen along an extension direction. The at least one surface element is configured to guide impinging electromagnetic radiation towards the at least one optically variable element. The data carrier is configured such, that electromagnetic radiation is impinging on the at least one surface element under at least a first arrival angle when the data carrier is seen under a first observation angle. The data carrier is further configured such, that electromagnetic radiation is impinging on the at least one surface element under at least a second arrival angle being different from the first arrival angle when the data carrier is seen under a second observation angle being different from the first observation angle. The at least one optically variable element is configured to reflect at least a first reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the first arrival angle, whereby the at least one security element appears according to at least a first appearance. The at least one optically variable element is further configured to reflect at least a second reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the second arrival angle, whereby the at least one security element appears according to at least a second appearance being different from the first appearance.
That is to say, the present invention proposes a data carrier that comprises at least one security element that is formed by an optically variable element and a surface element. The optically variable element preferably corresponds to at least one of a multi-layer optical film, preferably a thin-film-interference film, a colour film, an optically variable ink, a diffractive element, a grating such as a resonant waveguide grating, optical absorbers, and a plasmonic structure. That is, the optically variable element preferably corresponds to an element that has color-shifting, i.e. wavelength-shifting attributes depending on the incidence angles of impinging electromagnetic radiation. Examples of interference films include Gemalto Thin Color Mirror Films, Gemalto Clear to Cyan Films, and 3M Dichroic Glass Finishes. That is, the optically variable element preferably corresponds to a commercially available element that is well-known in the art. The present invention makes use of this wavelength-shifting attributes associated with the optically variable element by providing at least one surface element that guides impinging electromagnetic radiation towards the optically variable element under different guiding angles depending on the observation angle under which an observer observes the data carrier. Consequently, electromagnetic radiation is impinging on the optically variable element under different impingement angles, such that the optically variable element reflects electromagnetic radiation of different wavelengths depending on the observation angle of the data carrier, whereby the security element appears with different appearances. In other words, by tilting the data carrier the electromagnetic radiation being impinging on the optically variable element has a different incidence angle, i.e. impingement angle. The reflected electromagnetic radiation, i.e. the reflection spectrum, is constituted by wavelengths that are changed accordingly. In this way, the data carrier produces a color variation in accordance with the tilt angle. Said tilt angle in turn is determined by the observation angle under which the observer observes the data carrier. The optically variable element results in a security element having a bright color appearance with high saturation in reflection at a specific observation angle. Furthermore, the security element has a high level of security because it is composed of elements that interplay with one another. If a forger manipulates the data carrier by removing the surface element, for example, this interplay is destroyed and the forgery becomes evident. In this regard it should be noted that the security element can be provided in various designs. For example, the security element could correspond to a machine-readable security element. However, it is likewise conceivable that the security element is configured to be human readable.
The electromagnetic radiation being impinging on the data carrier, in particular on the at least one surface element, preferably corresponds to ultraviolet light and/or visible light and/or infrared light. In the case of ultraviolet light and infrared light a corresponding ultraviolet source such as a black lamp or an infrared source such as an infrared heater are conceivable irradiation sources for irradiating the electromagnetic radiation onto the data carrier. Visible light can be provided by ambient light such as day light or a regular light source such as a flash lamp, for example.
The first and second observation angles preferably correspond to the viewing angles under which an observer is observing the data carrier.
It should be noted that the expressions “electromagnetic radiation” and “spectrum” as used herein can in each case be constituted by a single wavelength only. More preferably, however, said electromagnetic radiation and/or spectrum in each case comprises two or more, in particular several wavelengths. Depending on the characteristics of the surface element, see further below, electromagnetic radiation being composed of two or more wavelengths is therefore guided by or impinging on the surface element or the optically variable element under a set of angles, which can be referred to as a cone of angles. Within one set of angles or within one cone of angles the individual angles associated with the individual wavelengths constituting the electromagnetic radiation or the spectrum can be different from one another.
Hence, the at least one surface element is preferably configured to guide impinging electromagnetic radiation towards the at least one optically variable element such, that said electromagnetic radiation is impinging on the optically variable element under at least a first impingement angle (or a first set or cone of impingement angles) when the data carrier is seen under the first observation angle. The at least one surface element is preferably further configured to guide impinging electromagnetic radiation towards the at least one optically variable element such, that said electromagnetic radiation is impinging on the optically variable element under at least a second impingement angle (or a second set or cone of impingement angles) being different from the first impingement angle (or first set or cone of impingement angles) when the data carrier is seen under the second observation angle. The at least one optically variable element is preferably configured to reflect the first reflection spectrum upon impingement of the electromagnetic radiation under the first impingement angle (or first set or cone of impingement angles) and to reflect the second reflection spectrum upon impingement of the electromagnetic radiation under the second impingement angle (or second set or cone of impingement angles).
The observation angles and the arrival angles are preferably linked to tilting angles by which the data carrier is tilted. In particular, if the data carrier is tilted, the electromagnetic radiation is incident on the optically variable element under a different impingement angle as compared to a non-tilted data carrier. The reflection spectrum is changed accordingly. That is, the data carrier enables a colour variation of the security element according to the tilting angle. Thus, if the observer is looking at the data carrier in an untilted state, then said first observation angle is e.g. about 60° with respect to a (imaginary) plane that runs through a top surface of the data carrier. Said top surface corresponds to the surface on which the surface element is arranged or formed from. If the observer is looking at the data carrier in a tilted state, for example by tilting the data carrier by about 20° with respect to said plane, then said second observation angle corresponds to the difference between the first observation angle and the tilting angle, i.e. here to the difference between 60° and 20°, thus to 40°.
Hence, the observation angles, and therefore the viewing angles, can be defined as the angles that are formed between the viewing direction and a plane of the data carrier that extends perpendicularly to the extension direction. The impingement angle under which the electromagnetic radiation is impinging on the optically variable element in turn depends on the arrival angle of the electromagnetic radiation on the surface element.
The optically variable element is preferably configured such, that it is transparent for impinging electromagnetic radiation constituting a first impingement spectrum and that it is reflective for impinging electromagnetic radiation constituting a second impingement spectrum being different from the first impingement spectrum.
An optically variable element being transparent for electromagnetic radiation being composed of certain one or more wavelengths is understood as being an element through which impinging electromagnetic radiation can travel without being reflected or absorbed.
Such a transparent optically variable element can also be referred to as a transmissive optically variable element. An optically variable element being reflective for electromagnetic radiation being composed of certain one or more wavelengths is understood as being an element that reflects at least part of the impinging electromagnetic radiation.
The optically variable element is preferably arranged within the data carrier with respect to the extension direction such, that the optically variable element lies above or below or essentially at a focus of the electromagnetic radiation being guided from the surface element to the optically variable element. Additionally or alternatively a vertical distance between the surface element and the optically variable element with respect to the extension direction is preferably such, that a focus of the electromagnetic radiation being guided from the surface element to the optically variable element lies above or below or essentially at the optically variable element with respect to the extension direction.
Depending on the focusing properties of the surface element and/or the distance by which the optically variable element is separated from the surface element the impingement angle under which the electromagnetic radiation impinges on the optically variable element and consequently the appearance of the security element can be tuned. In particular, if the focusing properties and/or the distance are chosen such, that electromagnetic radiation is impinging on the optically variable element under various impingement angles, then a range of the wavelengths being reflected from the optically variable element and transmitted through the surface element towards an outside can be reduced. For example, if the focus of the electromagnetic radiation lies below the optically variable element with respect to the extension direction, electromagnetic radiation will impinge on the optically variable element under different impingement angles or under a set or cone of impingement angles that differ from one another. Said difference preferably is more than 10°, more preferably more than 20°, particularly preferably about 30°. Consequently, the reflection spectrum that is comprised of electromagnetic radiation being reflected from the optically variable element also comprises different wavelengths, i.e. different colors. For example, it is conceivable to provide a data carrier wherein the colors red, green and blue are reflected. If the focusing properties of the surface element are changed such as increasing its focal length then the range of impingement angles under which the electromagnetic radiation is impinging on the optically variable element is reduced. As a result, the reflection spectrum being reflected from the optically variable element comprises essentially one or a few wavelengths. For example, it is conceivable to provide a data carrier wherein only the color green is reflected. A vertical distance between a surface of the data carrier on which the surface element is arranged on and the optically variable element with respect to the extension direction is preferably between 0 to 800 micrometer, more preferably about 150 micrometer.
The optically variable element is preferably configured such, that the electromagnetic radiation that impinges on the surface element under the at least one first arrival angle and the electromagnetic radiation constituting the at least one first reflection spectrum are essentially the same or different from one another. Additionally or alternatively the optically variable element is preferably configured such, that the electromagnetic radiation that impinges on the surface element under the at least one second arrival angle and the electromagnetic radiation constituting the at least one second reflection spectrum are essentially the same or different from one another.
To this end a difference could manifest itself in different one or more wavelengths that constitute the impinging electromagnetic radiation and the reflection spectrum, and/or a different intensity or intensity distribution of the impinging electromagnetic radiation and the reflection spectrum, and/or a different polarization or polarization distribution of the impinging electromagnetic radiation and the reflection spectrum, for example.
The optically variable element is preferably configured to transmit at least part of the electromagnetic radiation upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the at least one first arrival angle as at least a first transmittance spectrum, and wherein the at least one first transmittance spectrum differs from the at least one first reflection spectrum. Additionally or alternatively the optically variable element is preferably configured to transmit at least part of the electromagnetic radiation upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the at least one second arrival angle as at least a second transmittance spectrum, and wherein the at least one second transmittance spectrum differs from the at least one second reflection spectrum.
Hence, and as has been already mentioned above, the optically variable element can be configured to have its own transmittance spectrum that depends on the incidence angle, i.e. the impingement angle under which the electromagnetic radiation impinges on the optically variable element. At any impingement angle, the ratio for each wavelength is given by:
T=1−R−A,
wherein T refers to the transmittance spectrum,
wherein R refers to the reflection spectrum, and
wherein A refers to the absorption spectrum, i.e. electromagnetic radiation being absorbed by the optically variable element.
In the event that no absorption takes place within the optically variable element, then said ratio is given by:
T=1−R.
Hence, if no absorption takes place inside the optically variable element then the transmittance spectrum and the reflection spectrum are complementary to one another.
The data carrier, in particular the surface element, preferably comprises at least one blocking element, and wherein said blocking element is configured to block impinging electromagnetic radiation, whereby a further impingement of said electromagnetic radiation on the optically variable element is prevented and/or whereby electromagnetic radiation being reflected from the optically variable element is blocked.
The blocking element preferably corresponds to at least one of a laser marking and an opaque material such as a foil or layer that preferably comprises a metal-compound.
The laser marking is preferably achieved by means of a standard laser engraving process, wherein laser radiation is irradiated onto the data carrier so as to produce a preferably black laser marking in the data carrier. If an opaque material is provided in the data carrier, said opaque material is preferably selectively removed, e.g. again by means of an irradiation of laser radiation, whereby the remaining opaque material constitutes the blocking element. For example, in order to produce personalizable color images at a specific observation angle, one could use standard laser engraving processes as they are known in the art. Indeed by the help of a laser source, a local darkening of the data carrier can be achieved. Therefore, by choosing properly the location of the darkening, one can prevent certain wavelengths, i.e. colors, from being reflected from the data carrier towards an outside or from being impinging on the optically variable element. In order to perform an engraving at a precise location, one can use one or more registration marks located somewhere on the data carrier. Said registration marks can be used for the alignment of the engraving system. It is furthermore preferred if the blocking element corresponds to a pixel of at least one of an alphanumeric character and an image. That is, it is preferred to provide blocking elements, wherein each blocking element corresponds to one pixel of an image or an alphanumeric character, and wherein each pixel participates in the selective blocking of a particular wavelength or wavelengths, i.e. of a particular colour. The form of each pixel can be approximated as a round shape, wherein a pixel size is preferably between 10 micrometer and 100 micrometer, more preferably between 20 micrometer and 50 micrometer, particularly preferably around 40 micrometer. The one or more blocking elements are preferably generated in a region of the surface element, for example on a top surface of the surface element or below said top surface. The provision of one or more blocking elements brings additional value since they allow a personalization of the data carrier after the data carrier production.
It is preferred when two or more surface elements are provided in an array and/or according to a pattern, in particular a pixelated pattern.
That is to say, the data carrier preferably comprises two, even more preferably a plurality of surface elements, wherein said surface elements are preferably arranged in a particular relationship to one another. For example, they can be arranged as a one-dimensional or two-dimensional array that extends along a transverse direction running perpendicularly to the extension direction. Alternatively, said surface elements can be distributed according to a pattern within a plane that runs perpendicularly to the extension direction. A pixelated pattern is understood here as a pattern of surface elements, wherein each surface element is associated with the generation of one or more particular colours being reflected from the data carrier. For example, surface elements that result in the reflection of red, green and blue colours could be provided, which can be used as red-green-blue (RGB) pixels in order to produce a coloured image at high resolution. By generating one or more blocking elements, said coloured image could be personalized as described above. Furthermore, said blocking elements can be used to block certain colours.
The data carrier preferably further comprising at least one further surface element that is configured to guide impinging electromagnetic radiation towards the optically variable element, wherein the data carrier is further configured such, that electromagnetic radiation is impinging on the at least one further surface element under at least a further first arrival angle when the data carrier is seen under the first observation angle, and wherein the at least one optically variable element is configured to reflect at least a further first reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one further surface element under the further first arrival angle that is different from the first reflection spectrum, whereby the at least one security element appears according to at least a further first appearance that is different from the first appearance. Additionally or alternatively the data carrier is preferably further configured such, that electromagnetic radiation is impinging on the at least one further surface element under at least a further second arrival angle when the data carrier is seen under the second observation angle, and wherein the at least one optically variable element is configured to reflect at least a further second reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one further surface element under the further second arrival angle that is different from the second reflection spectrum, whereby the at least one security element appears according to at least a further second appearance that is different from the second appearance.
That is to say, it is conceivable that the data carrier comprises at least one further surface element that results in a second reflection spectrum being different from the first reflection spectrum, and therefore in a second appearance of the security element being different from the first appearance, when the data carrier is observed under the first observation angle and/or under the second observation angle.
Any explanations provided with respect to the one or more surface elements likewise apply to the one or more further surface elements.
For example, the two or more further surface elements can be provided in a further array and/or according to a further pattern, in particular a further pixelated pattern. To this end it is also conceivable that at least one surface element and at least one further surface element are provided in a combined array and/or according to a combined pattern, in particular a combined pixelated pattern. It is furthermore conceivable that one of (i) a vertical distance between the surface element and the optically variable element with respect to the extension direction equals to or is different from a further vertical distance between the further surface element and the optically variable element with respect to the extension direction, and (ii) the surface element and the further surface element are arranged immediately adjacent to one another or at a horizontal distance from one another with respect to a transverse direction running perpendicularly to the extension direction.
The surface element and/or the further surface element preferably comprises or consist one or more lenses. Furthermore, the one or more lenses preferably are of a cylindrical lens shape and/or of a spherical lens shape.
Moreover, a shape, in particular a focal length and/or an angular aperture of the lens being provided by the surface element(s) and of the lens being provided by the further surface element(s) are the same or different from one another.
Hence, it is preferred that the one or more surface elements and/or the one or more further surface elements correspond to lenses. A focal length of the lenses constituting the surface elements and a focal length of the lenses constituting the further surface elements can be the same or different from one another. Additionally or alternatively it is preferred that an f-number associated with the lenses constituting the surface elements and an f-number associated with the further surface elements are the same or different from one another. It is particularly preferred that a focal length of the lenses constituting the surface elements is in the range of 50 micrometer to 3000 micrometer, in particular 150 micrometer, and/or that a focal length of the lenses constituting the further surface elements is in the range of 50 micrometer to 3000 micrometer, in particular 300 micrometer, and/or that an f-number associated with the lenses constituting the surface elements is in the range of 1.0 to 10.0, in particular 1.2, and/or that that an f-number associated with the lenses constituting the further surface elements is in the range of 1.0 to 10.0, in particular 2.4.
Furthermore, at least two of the surface elements, in particular lenses, are arranged such that, when the data carrier is seen under the first observation angle and/or under the second observation angle, impinging electromagnetic radiation impinges on the data carrier via one of these two surface elements and is reflected from the data carrier via the other of these two surface elements, and wherein a lateral distance between these two surface elements with respect to a transverse direction running perpendicularly to the extension direction is between 50 micrometer to 3000 micrometer, preferably about 125 micrometer.
The same applies in the event that two or more further surface elements, in particular lenses, are present on the data carrier.
These at least two surface elements and/or at least two further surface elements are referred to as two involved lenses.
For a given optically variable element and at a given observation angle the wavelengths that are out-coupled from the data carrier are dictated by the f-number of the lenses, the lenses focal lengths, a vertical distance between the top surface of the data carrier and the optically variable element, and a lateral distance between two involved lenses, i.e. between a lens that guides impinging electromagnetic radiation towards the optically variable element and a lens through which the reflected electromagnetic radiation is out-coupled from the data carrier as just explained. In other words, by appropriately choosing one or more of these parameters it is possible to provide a data carrier with a security element having a desired appearance.
It is furthermore preferred to provide one or more lenses, wherein each lens is configured to produce one particular color at one particular pixel. To this end the geometry of the lens is preferably selected such, that it results in the generation of one particular color. It is furthermore preferred to distribute different types of lenses such, that the lenses result in the generation of red, green and blue colors. In other words, it is preferred to distributed the lenses as RGB pixels. Alternatively, it is conceivable to provide one or more lenses which are in each case configured to generate two or more colours.
The surface element and/or the further surface element preferably comprise or consist of a polymer, preferably a thermoplastic polymer, particularly preferably polycarbonate. Any further components, with the exception of the optically variable element, preferably likewise comprise or consist of a polymer, preferably a thermoplastic polymer, particularly preferably polycarbonate.
The data carrier preferably further comprises a transparent region, wherein the security element, preferably the optically variable element and the surface element and/or the further surface element, is arranged within said region and/or before said region with respect to the extension direction and/or after said region with respect to the extension direction.
The transparent region can be understood as a window region or windowed embodiment. The transparent region is preferably provided by means of transparent plastics, particularly preferably by transparent thermoplastics such as polycarbonate. If a white region is placed below the transparent region and therefore below the optically variable element with respect to the extension direction, the white region results in a reflection of electromagnetic radiation being transmitted through the optically variable element and the transparent region and being impinging on said white region. If a black region is placed below the transparent region and therefore below the optically variable element with respect to the extension direction, said black region will absorb any electromagnetic radiation that is transmitted through the optically variable element and the transparent region and which is impinging on the black region. If a coloured region is placed below the transparent region and therefore below the optically variable element with respect to the extension direction, said coloured region participates in the formation of an overall reflected colour comprising emitted radiation from the coloured region upon its excitation with the impinging electromagnetic radiation according to the additive color mixing scheme.
The data carrier preferably further comprises at least one masking element, wherein said masking element is arranged before the optically variable element with respect to the extension direction, and wherein said masking element is configured such that, depending on the electromagnetic radiation being reflected from the optically variable element, the masking element is invisible or visible to an observer.
The masking element preferably is coloured and particularly preferably corresponds to a coloured print.
In a further aspect a security document comprising or consisting of at least one data carrier as described above is provided the security document preferably being an identity card, a passport, a credit card, a bank note or the like. That is, the data carrier per se can correspond to a security document. Or, the data carrier can be part of a security document. For example, in the case of a passport it is conceivable to incorporate the data carrier into a page of the passport.
In a further aspect a method of producing a data carrier, preferably a data carrier as described above, is provided, wherein the method comprising the steps of (i) providing at least one optically variable element, (ii) providing at least one surface element, and (iii) providing at least one security element comprising at least part of the at least one optically variable element and at least part of the at least one surface element. The at least one optically variable element is arranged after the at least one surface element when seen along an extension direction. The at least one surface element is configured to guide electromagnetic radiation that is impinging on the at least one surface element to the at least one optically variable element. The data carrier is configured such, that electromagnetic radiation is impinging on the at least one surface element under at least a first arrival angle when the data carrier is seen under a first observation angle. The data carrier is further configured such, that electromagnetic radiation is impinging on the at least one surface element under at least a second arrival angle being different from the first arrival angle when the data carrier is seen under a second observation angle being different from the first observation angle. The at least one optically variable element is configured to reflect at least a first reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the first arrival angle, whereby the at least one security element appears according to at least a first appearance. The at least one optically variable element is further configured to reflect at least a second reflection spectrum upon impingement of the electromagnetic radiation being impinging on the at least one surface element under the second arrival angle, whereby the at least one security element appears according to at least a second appearance being different from the first appearance.
Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,
Hence, the data carrier 1 according to the invention comprises at least one optically variable element 2 and at least one surface element 3a. The optically variable element 2 is arranged after the surface element 3a when seen along an extension direction E extending from the surface element 3a towards the optically variable element 2. The surface element 3a is configured to guide impinging electromagnetic radiation EM towards the optically variable element 2. In fact, the data carriers 1 depicted in the figures comprise a plurality of surface elements 3a which form arrays and which are furthermore arranged according to a pattern.
In addition, said surface elements 3a are arranged immediately adjacent to one another with respect to a transverse direction T extending perpendicularly to the extension direction E. In addition, the surface elements 3a correspond here to lenses which are in each case of a cylindrical shape. The optically variable element 2 corresponds to at least one of a multi-layer optical film, preferably a thin-film-interference film, a colour film, an optically variable ink, a diffractive element, a grating such as a resonant waveguide grating, optical absorbers, and a plasmonic structure. That is, the optically variable element 2 corresponds to an element that is configured to reflect and/or transmit electromagnetic radiation EM in dependency of an observation angle γ1, γ2 under which the data carrier 1, and therefore the optically variable element 2, is observed by an observer. At least a part of the optically variable element 2 and at least a part of the surface element 3a participate in the formation of at least one security element 4. Hence, by selectively providing one or more surface elements 3a in combination with the optically variable element 2 it is possible to select specific electromagnetic radiation EM that is reflected from and/or transmitted through the optically variable element 2. This phenomenon shall be further illustrated by means of
That is,
Hence, when the data carrier 1 is tilted, the electromagnetic radiation EM is incident on the surface element 3a under a different arrival angle β1as compared to the arrival angle α1 associated with the non-tilted data carrier 1. The reflection spectrum R2a and/or the transmission spectrum T2a and therefore an appearance A2a of the security element 4 is changed accordingly. That is, the data carrier 1 enables a color variation of the security element 4 according to the tilt angle. The electromagnetic radiation being impinging on the data carrier 1, in particular on the lens elements 3a, preferably corresponds to ultraviolet light, visible light, or infrared light. In the case of ultraviolet light and infrared light a corresponding ultraviolet source such as a black lamp or an infrared source such as an infrared heater are conceivable irradiation sources for irradiating the electromagnetic radiation onto the data carrier. Visible light can be provided by ambient light such as day light or a regular light source such as a flash lamp, for example. Depending on the optical properties of the optically variable element 2 and the angle under which it is impinged by the electromagnetic radiation EM, the optically variable element 2 is configured to reflect and/or transmit electromagnetic radiation EM corresponding to ultraviolet light, visible light, or infrared light. As is readily evident from these figures, the first and second observation angles γ1, γ2 preferably correspond to the viewing angles under which an observer is viewing the data carrier 1. The observation angles γ1, γ2, and therefore the viewing angles, can be defined as the angles that are formed between the viewing direction and a (fictitious) normal N to a (fictitious) plane P of the data carrier 1 that extends perpendicularly to the extension direction E. Said plane P runs through an uppermost surface 9 of the data carrier 1, on which the at least one surface element 3a is arranged. In the present examples, the plane P is indicated by dashed lines at a location in the data carrier 1 where the lens elements 3a are formed. Similarly, the first and the second arrival angle α1, β1 are defined here in each case as the angle which is formed between the light rays of electromagnetic radiation EM being impinging on the lens elements 3a and the normal N to said plane P.
As has already been mentioned, the lens elements 3a are configured to guide impinging electromagnetic radiation EM towards the at least one optically variable element 2. In fact, the lens elements 3a are preferably configured such, that said electromagnetic radiation EM is impinging on the optically variable element 2 under at least a first impingement angle δ1 when the data carrier 1 is seen under the first observation angle γ1 and under at least a second impingement angle ε1 being different from the first impingement angle δ1 when the data carrier 1 is seen under the second observation angle γ2. Said first and second impingement angles δ1, ε1 are defined here again as the angle which is formed between the light rays of electromagnetic radiation EM coming from the lens elements 3a and the normal N to the plane P. To this end it should be noted that, when the data carrier 1 is observed under the first observation angle γ1, the electromagnetic radiation EM coming from the lens elements 3a can impinge on the optically variable element 2 under two or more first impingement angles δ1, wherein said two or more first impingement angles δ1 can be the same or different from one another. If electromagnetic radiation EM impinges on the optically variable element 2 under two or more first impingement angles δ1, said two or more first impingement angles δ1 can be said to form a set of first impingement angles or a cone of first impingement angles. Likewise, if the data carrier 1 is observed under the second observation angle γ2, the electromagnetic radiation EM coming from the lens elements 3a can impinge on the optically variable element 2 under two or more second impingement angles ε1, wherein said two or more second impingement angles ε1 can be the same or different from one another. If electromagnetic radiation EM impinges on the optically variable element 2 under two or more second impingement angles ε1, said two or more second impingement angles ε1 can be said to form a set of second impingement angles or a cone of second impingement angles. The set of second impingement angles or cone of second impingement angles differs from the set of first impingement angles or cone of first impingement angles. Hence, by tilting the data carrier 1, electromagnetic radiation EM impinges on the optically variable element 2 under different impingement angles. Consequently, the reflection spectra R1a, R2a and/or the transmission spectra T1a, T2a and thus the appearance A1a, A2a of the security element 4 are changed accordingly.
Additionally or alternatively a vertical distance va between the surface element 3a and the optically variable element 2 with respect to the extension direction E can be such, that a focus F of the electromagnetic radiation EM being guided from the surface element 3a to the optically variable element 2 lies above or below or essentially at the optically variable element 2 with respect to the extension direction E.
As follows from
The corresponding first transmittance spectrum T1a constitutes a spectrum being essentially complementary or complementary to the first reflection spectrum R1a. That is, if no absorption takes place inside the optically variable element 2 then the first reflection spectrum R1a is comprised of a first beam R1 of green light, a second beam R2 of red light and a third beam R3 of blue light, then the first transmittance spectrum is comprises of a first beam being T1=1−R1, a second beam being T2=1−R2, and a third beam being T3=1−R3, respectively. In this case, the first transmittance spectrum T1a is complementary to the first reflection spectrum R1a. However, it is conceivable that absorption takes place within the optically variable element 2, in which case the first transmittance spectrum T1a is comprised of a first beam being T1=1−R1−A, a second beam being T2=1−R2−A, and a third beam being T3=1−R3−A, wherein “A” denotes those wavelengths of the electromagnetic spectrum which are absorbed by the optically variable element 2. In this case, the first transmittance spectrum T1a is said to be essentially complementary to the first reflection spectrum R1a.
The data carriers 1 depicted in
As follows from
To this end it is particularly preferred to provide the blocking elements 5 as pixels of an image or alphanumeric character one wishes to generate in or on the data carrier 1. In fact, each blocking element 5 can correspond to one pixel of an image or alphanumeric character, wherein each blocking element 5 participates to selectively block a color. This phenomenon is illustrated in
It should be noted that a different appearances such as change in the reflection spectrum can also be obtained in other ways. Namely, and as follows from
| Number | Name | Date | Kind |
|---|---|---|---|
| 20170173990 | Cape | Jun 2017 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20220161590 A1 | May 2022 | US |
