EP3497679B1 - Method and device for identifying at least one security element of at least one security feature of a security product - Google Patents

Description

The invention relates to a method and a device for identifying at least one security element of at least one security feature of a security product.

Security products such as valuables and/or security documents are usually equipped with security features that can consist of various security elements. These security features make it more difficult or prevent counterfeiting of these products. Furthermore, the security features or security elements used therein can be used to verify or authenticate the security product. Valuable and/or security documents can be, for example, banknotes, checks, credit cards, stocks, passports, identification documents, driving licenses, entrance tickets, tokens or the like.

Security products are preferably provided with various security features, each of which can be assigned to different security levels. It can be advantageous here if several security elements are put together in or into a security feature in such a way that they have different security levels for verification or authentication in such a way that the same security element can be assigned to several security levels at the same time.

It is also known to use substances with electroluminescent properties as security elements in valuable and/or security documents. This is for example in the EP 1 151 057 B1 as well as in the DE 10 2013 114 496 A1 described. Substances with electroluminescent properties can generally be understood to mean those powdery materials which, when excited with an alternating electric field, emit radiation preferably in the visible region of the optical spectrum. If electroluminescent substances are used, in particular to protect against counterfeiting of security products, powdery, zinc sulfide electroluminophores are preferably used. These can be printed on or in the matrix of the respective security products using standard printing technology, for example gravure printing, offset printing or screen printing processes to be ordered. The safety products can consist of paper, plastic, but also other suitable materials. The electroluminophores provided in this way can then be excited, preferably in a contactless manner, with an alternating electrical field. This is in the EP 0 964 791 B1 described.

Such electroluminescent security elements can form a so-called Level 3 feature. This means that they have a very high level of security. Proof of authenticity of corresponding security documents involves a comparatively high level of effort and high demands on the detection technology used. This applies both to stationary testing and in particular to the non-stationary high-speed detection of electroluminescence signals, which is the aim in numerous applications.

When using electroluminescent security elements, it has proven to be advantageous to combine the electroluminescent pigments used with so-called field displacement elements and to arrange this combination, for example in the form of a pigment mixture, on or in the security product. This is for example in the EP 1 631 461 B1 and in the EP 1 748 903 B1 described.

The field displacement elements can, for example, be designed as transparent or semi-transparent dielectric or electrically conductive pigments or include such pigments. The dielectric pigments have a comparatively high permittivity, for example a permittivity greater than 100, in order to be able to effectively displace the electric field. In an initial state, such dielectric pigments are not electrically conductive or are only electrically conductive to a very small extent (σ ≤ 10 ^-7 S/m). Alternatively, the field displacement elements can also be designed as conductive pigments with comparatively low electrical conductivity or can include such pigments. Electrically conductive field displacement elements have an electrical conductivity in the range of 10 ^-3 -10 ^-2 S/m.

The field displacement elements can cause an amplification or concentration of the local alternating electric fields effective on the surface of the electroluminescent elements and thus an increase in the intensity of the electroluminescence radiation emitted due to the field-induced excitation. They can do this Electrically conductive particles cause significantly higher amplification of the local field compared to dielectric particles.

From the EP 1 748 903 B1 It is also known to use optically variable effect pigments, in particular so-called multilayer effect pigments, as field displacement elements, which, in addition to the explained amplification of the local electric field, can also generate verifiable optical effects, in particular interference effects. These effect pigments can preferably contain at least some metal oxide layers, such as those made of titanium oxide.

If, as described in the publication, optically variable effect pigments are combined with the powdered zinc sulfide electroluminophores to increase the effective local strength of the exciting electric field, the resulting security feature can also have a corresponding level 1 characteristic in addition to its level 3 characteristic. In particular, the optical effect, which can consist of a color or gloss change that is perceptible to the viewer at different lighting and/or viewing angles, can also be evaluated as an additional criterion for authenticity verification.

The disadvantage, however, is that when using the security features described in valuable and/or security documents, despite the presence of field displacement elements, comparatively extremely high excitation voltages are required in order to generate a sufficiently strong local alternating electric field, which is sufficient to efficiently excite the electroluminescence and thus also ensuring reliable detection of the corresponding electroluminescence signal. This is due, among other things, to the extremely special and unconventional arrangement of the electroluminescent elements in the valuable and/or security documents compared to the conventional technical application of electroluminophores in electroluminescent films with classic capacitor construction, as well as to the contactless excitation with an alternating electric field, particularly in the case of high-speed detection of the electroluminescent signals and the also preferably contactless detection of these signals. High-voltage alternating fields are therefore required in order to be able to operate under the circumstances described powdery zinc sulfide pigments to stimulate electroluminescence and to ensure a sufficiently high signal strength.

It should also be noted that security features, especially those based on luminescence phenomena, are exposed to numerous aging processes during the period of their use. These can be caused, for example, by intense sunlight, dirt, mechanical abrasion, contact with water or organic solvents and by numerous other influencing factors. Therefore, when checking the authenticity of security and valuable documents in circulation with an electroluminescent security feature, it can be assumed that the signal strengths of electroluminescence resulting from constant excitation conditions will become increasingly lower over the life cycle of the security and valuable documents.

On the other hand, however, it is not possible to increase the strength of the luminescence signals and thus the reliability of detection by further increasing the excitation voltage. In particular, the level of the excitation voltage is limited by the dielectric strength (against voltage breakdown, arc, sparks) of the surrounding medium. In the case of air as the ambient medium, this means that the electric field generated by the excitation voltage must not exceed values of 3.3 V/µm. Excessively high voltage thus disadvantageously reduces operational reliability due to possible breakdowns.

The DE 10 2008 034 022 A1 which includes the preamble of claims 1 and 8, discloses a method for producing a security and/or valuable product, in particular a security and/or valuable document, with the following method steps: a substrate is coated with a marking layer containing a luminescent substance, from a A character string is formed by the pattern formed by the luminescence emission of the luminescent substance, and the character string is legibly applied to the security and/or valuable product as an identification character string and/or readably integrated therein.

The WO 2015/024619 A1 discloses a printed image on a substrate, in particular a printed image which contains platelet-shaped effect pigments and shows striking matt-gloss effects.

The WO 2015/091237 A1 discloses a powdery, zinc sulfide phosphor which, as an electroluminophore, can be excited by an electric field and also has special luminescence properties.

The DE 197 08 543 A1 discloses security documents with graphically designed security features, preferably in gravure printing, which can be made to glow in the form of dots, lines and/or areas, with wavelengths in the invisible UV range up to the range of typically 360 to the human eye 780 nm but also in the infrared range can be aimed for and implemented.

The technical problem therefore arises of creating a method and a device for identifying at least one security element of at least one security feature of a security product, which, with sufficient operational reliability, enables a more reliable identification of the security element over the entire life cycle of the security product, in particular identification with low excitation voltages or when using a substance with electroluminescent properties in low concentration.

The solution to the technical problem results from the objects with the features of claims 1 and 8. Further advantageous embodiments of the invention result from the subclaims.

It is a basic idea of the invention to use a combination of a substance with electroluminescent properties and a further substance with electrical conductivity that can be changed by high-energy irradiation, with this high-energy irradiation, namely UV irradiation, increasing the conductivity of the further substance before exposure an alternating electric field is changed in such a way that a sufficiently strong local excitation field is generated during the subsequent exposure to the alternating electric field, which in turn generates an electroluminescence radiation with sufficient intensity for identification. The basic idea is particularly suitable for a security feature which consists at least partially of a mixture of powdered electroluminophores and optically variable effect pigments.

What is proposed is a method for identifying at least one security element of at least one security feature of a security product.

A security element refers to a substance. The security feature includes substances.

The security product can in particular be a valuable or security document. Any document that is a physical entity that is protected against unauthorized production and/or falsification by security features can be referred to as a security document. Security features are features that make falsification and/or duplication at least more difficult than simple copying. Security elements can therefore designate physical entities that form a security feature.

A security document can include multiple security features and/or multiple security elements.

Value documents are documents that represent value. Documents of value can also be security documents. Examples of security documents, which also include documents of value, include, for example, passports, identity cards, driving licenses, identity cards, access control cards, health insurance cards, banknotes, postage stamps, bank cards, credit cards, smart cards, tickets and labels.

The security feature can in particular be a machine-readable security feature. Furthermore, the security feature or security elements of the security feature can be arranged at least partially or completely on a surface of the security product or in the security product.

For the purposes of this disclosure, the term identification also includes detection of the security element. An identification can therefore mean that it is detected whether the security element is present in the security feature or in the security product or whether the security feature is present in the security product or not. Identification can also mean that it is detected whether or not the at least one security element is contained in the security feature or product to a predetermined extent, for example in a predetermined amount or concentration.

The security feature includes at least a first substance with electroluminescent properties. This first substance can therefore be a first security element of the security feature. The first substance can in particular be a powdery substance or a substance that can be provided in powder form. The first substance is preferably powdery, zinc sulfide electroluminescent materials, which can also be referred to as electroluminescent pigments or electroluminophores. After excitation in an alternating electric field, the first substance emits luminescent radiation, in particular luminescent radiation with wavelengths in the visible range of the optical spectrum.

Electroluminescent materials suitable for the first substance are in the publications mentioned at the beginning, in particular in EP 1 151 057 B1 , the DE 10 2013 114 496 A1 as well as in the printed matter EP 1 631 461 B1 as well as EP 1 748 903 B1 described. Reference is therefore made in full to the disclosure content of these publications regarding the electroluminescent substance. The security feature further includes at least one further substance. In combination with the first substance, this causes an increase in the local electric field effective on the surface of the first substance when the alternating electric field is applied and thus an increase in the signal strength of the emitted electroluminescent radiation. This further substance can also be a further security element of the security feature.

The security feature consisting at least of the first and further substances can be applied to the entire or partial area of the security product. This can be done, for example, using a printing ink that consists of at least the first and the further substance in a common printing process.

According to the invention, the further substance is a substance with an electrical conductivity that can be changed, namely increased, by high-energy irradiation. The high-energy irradiation can be carried out with radiation whose maximum wavelength is smaller than the minimum wavelength of visible light, i.e. in particular smaller than 400 nm. The high-energy radiation is UV radiation. Radiation with wavelengths from a wavelength range of 5 nm to 380 nm, preferably from a wavelength range of 100 nm to 380 nm, can be used here. In the following, the high-energy radiation is therefore also referred to as UV radiation.

Without UV irradiation, the further substance can have a conductivity of an undoped semiconductor element, i.e. a rather low conductivity. The further substance is preferably a dielectric substance, i.e. a substance with a dielectric constant greater than 10, preferably greater than 100.

The further substance can preferably be transparent or semi-transparent with respect to the electroluminescent radiation emitted by the first substance. This means that the further substance is transparent to the electroluminescent radiation or that this radiation does not attenuate more than a predetermined level, for example not more than 50%, preferably not more than 10%.

The further substance is a non-electroluminescent substance. The further substance preferably consists of a substrate acting as a carrier material, which consists of different transparent or semi-transparent materials, for example synthetic or natural mica, SiO2, glass or other materials, as well as at least one transparent or semi-transparent metal oxide layer, which preferably consists of titanium oxide layer (TiO2 layer). In particular, the metal oxide layer can be a layer whose electrical conductivity can be changed induced by radiation.

Some metal dioxides, especially TiO2, show a strong increase in electrical conductivity after and during exposure to high-energy radiation, especially UV radiation. The reason for this may be a combination of photo effect and photocatalysis. With a band energy of approximately 3.0 - 3.2 eV, TiO2 is an effective photoconductor. The energy of 3.0 eV corresponds to a wavelength of approximately 390 nm. According to the invention, the security feature consisting of a combination of at least one electroluminescent security element and another security element with variable electrical conductivity is irradiated with high-energy radiation, namely UV radiation. For this purpose, the security feature can be arranged in an irradiation area of a device for generating this irradiation. The irradiation can take place at a fixed intensity for a predetermined period of time.

UV irradiation is preferably carried out at wavelengths that are smaller than 400 nm. Irradiation with UV irradiation devices that emit radiation in the so-called UV-A range, for example in the range of 365 nm. Both UV discharge lamps and UV LEDs can be used as irradiation devices.

Furthermore, the security feature is subjected to an alternating electrical field.

The alternating electric field can be generated by applying an excitation voltage to a means for generating the alternating field, for example at least one electrode. For this purpose, the security feature can be arranged in an exposure area of a device for generating the alternating electric field. The application of the alternating electric field serves to excite electroluminescent radiation. Furthermore, an electroluminescence radiation emitted by the first substance, which is emitted during and/or after exposure to the alternating electric field, is detected. The electroluminescent radiation can be detected in particular using a device for detecting radiation.

It has been shown that by irradiating the security feature with high-energy radiation, namely UV radiation, a significant increase in the intensity of the electroluminescent radiation can be achieved while the excitation voltage remains the same, or the same intensity of the electroluminescent radiation can be achieved with a significant reduction in this excitation voltage. This connection becomes apparent when UV irradiation of a combination of a first substance made of electroluminescent pigments with a further substance made of field displacement elements, which are designed as optical effect pigments or include such effect pigments.

In particular when using another substance with a metal oxide layer, it can be assumed that the UV irradiation leads to an increase in the conductivity of the metal oxide layer and thus causes an increase in the local electric excitation field in the area of electroluminescent pigments. This increases the intensity of the electroluminescence radiation, especially if powdery zinc sulfide electroluminophores are used as the first substance.

The radiation-related increase in the intensity of the electroluminescent radiation depends in particular on the irradiation dose, i.e. on the radiation energy and the duration of the UV irradiation.

In particular, the electrical conductivity of the further substance and thus the intensity of the electroluminescent radiation can increase in proportion to the irradiation dose or to the irradiation energy. For example, compared to excitation without prior UV irradiation, the electroluminescence intensity can increase by approximately 30% if the irradiation energy is 4 mJ or increase by approximately 85% if the irradiation energy is 18 mJ.

The effect mentioned can be exploited in an advantageous manner for simpler and more reliable identification of the first substance and/or the further substance. In particular, it leads to a stronger measurement signal, which enables more reliable identification of the electroluminescence and/or a reduction in the excitation voltage. In this way, proof of authenticity can also be secured for those valuable and security documents with electroluminescent security features that have been exposed to various aging processes over the course of their life cycle that impair the signal strength of the electroluminescence. A further option may also consist of reducing the concentration of the first substance in the security feature.

In order to achieve good machine readability with sufficiently high electroluminescence intensity, it has so far been essential that both the electroluminescent substance and the field displacement elements are present in the security feature, in particular in a fixed mixing ratio. Furthermore, comparatively extremely high alternating voltages were necessary in order to achieve the required local field strength and thus the desired electroluminescence intensity. The UV irradiation according to the invention now makes it possible to achieve the same or a similar high electroluminescence intensity with an excitation voltage that is 15-25% lower in comparison. If the same excitation voltage is used, there is a significant increase in the electroluminescence intensity, for example by over 100%.

The electrical conductivity of the additional substance can decrease again after UV irradiation has ended. The reduction of the electrical conductivity to the initial level before UV irradiation can take place in a predetermined period of time, for example a period of up to 10-15 minutes. The effect of increasing electrical conductivity through UV irradiation is therefore a reversible effect. After the electrical conductivity has been reduced, it can be increased again by further irradiation.

Furthermore, depending on at least one property of the electroluminescent radiation, the first substance and/or the further substance is identified, in particular detected. The property can in particular have an intensity of electroluminescent radiation. The property can then be determined using an evaluation device.

The evaluation device also carries out the identification.

For example, the first substance can be identified if at least one property-dependent criterion is met, for example if the intensity of the electroluminescent radiation is higher than a first predetermined threshold value. Otherwise the first substance cannot be identified.

For example, the further substance or a component of the further substance, in particular TiO2, can be identified if at least one further property-dependent criterion is met, for example if the intensity of the electroluminescent radiation is higher than a further predetermined threshold value. Otherwise the other substance cannot be identified. The further threshold value can be different from the first threshold value, in particular higher than this.

Alternatively or cumulatively, the first or the further substance can be identified depending on a change in properties, in particular a change in the intensity of the electroluminescent radiation. In this case, the change in property can be an increase or decrease in the intensity of the electroluminescence depending on the intensity and duration of the UV irradiation.

For example, the security feature can be subjected to an alternating electrical field before UV irradiation. The intensity of the electroluminescent radiation can then be determined without prior UV irradiation. The security feature can then be irradiated. After this UV irradiation has ended, the security feature can be subjected to the alternating electric field again, preferably with the same field strength. The intensity of the electroluminescence radiation can then be determined with previous UV irradiation.

The further substance can be identified if the intensity with previous UV irradiation is greater, in particular more than a predetermined amount greater, than the intensity without previous UV irradiation. Otherwise the further substance can cannot be identified.

It is therefore possible to identify a specific substance (substance type or species) introduced into the security feature according to the invention in addition to the electroluminescent pigments with changeable conductivity depending on the intensity of the detected electroluminescence, or its change. For example, other substances, which, for example, consist of different materials or have different material compositions, can be assigned to different properties of the electroluminescence radiation, in particular to different threshold values of intensities. It is therefore possible that various other substances lead to different changes in the intensity of the electroluminescent radiation.

This change can therefore be substance type-specific, in particular material or material composition-specific. It may therefore be possible to determine a type of further substance or at least several possible types of further substances depending on the change in intensity of the electroluminescent radiation.

Of course, the security feature can also be identified, in particular detected, depending on the at least one property of the electroluminescent radiation.

The method described can be used to verify or authenticate the security feature. In particular, the security feature can be verified if the first and/or the further substance has been identified. Alternatively or cumulatively, the security feature can be verified if at least one criterion, which depends on the property of the electroluminescent radiation, is met. For example, the security feature can be verified if the intensity is higher than a predetermined threshold value.

If the first and/or the further substance is not identified and/or the at least one property-dependent criterion is not met, the security feature cannot be verified.

In summary, by changing the electrical conductivity of the further substance, in particular by increasing it, the strength of the electrical excitation field in the area of the substance with electroluminescent properties can be increased, which in turn increases the intensity of the emitted electroluminescent radiation. In other words, this means that the electroluminescence radiation is increased by the previous UV irradiation (amplification effect). This amplification effect can be maintained for a predetermined period of time even after UV irradiation has ended.

The use of the combination of the two substances described advantageously results in the generation of electroluminescent radiation with comparatively low excitation voltages. This enables energy-saving but also reliable identification and ensures sufficient operational safety due to the reduction in the risk of puncture. The electroluminescent radiation for identification can also be generated reliably over the entire life cycle of the security feature.

In a preferred embodiment, the security feature is irradiated with UV radiation before it is exposed to the alternating electric field. This means that the UV irradiation begins before exposure to the alternating electric field. Preferably, the security feature is only exposed to the alternating electrical field after the UV irradiation has ended. In particular, the start of exposure to the alternating electric field can take place with a time duration of less than 1 second after the end of the UV irradiation.

However, it is also possible for the exposure to the alternating electric field to begin while the security feature is being exposed to UV radiation.

Preferably, the electroluminescent radiation generated due to exposure to the alternating electric field is only detected after the UV irradiation has ended, since the UV irradiation can additionally generate undesirable photoluminescent radiation of the first substance.

This advantageously results in the electroluminescence being measured as unfalsified as possible, in particular not distorted by photoluminescence effects.

In a further embodiment, a period of time between the end of the UV irradiation and the start of exposure to the alternating electric field is longer than 0 seconds. Alternatively or cumulatively, the time period is shorter than 600 seconds.

In a further embodiment, the further substance comprises at least one effect pigment. Of course, the further substance can comprise a large number of effect pigments.

Such effect pigments are explained at the beginning EP 1 748 903 B1 described.

The effect provided by the additional substance can also or additionally be used to verify the security feature and thus the security product. This advantageously increases the reliability of the verification.

In a preferred embodiment, the further substance has at least a portion of a metal oxide layer. This layer preferably consists at least partially of titanium dioxide. However, other metal oxides can also be used.

This advantageously results in the radiation-related change in conductivity explained.

In a further preferred embodiment, the metal oxide consists at least partially of TiO ₂ . Layers consisting of TiO ₂ or other metal oxides exhibit an increase in electrical conductivity when irradiated with high-energy radiation, in particular with UV radiation, and thus lead to a significant increase in electroluminescent radiation.

In particular, it can therefore also be identified whether a further substance consists of a desired material, in particular a metal oxide, particularly TiO ₂ .

In a further embodiment, in addition to identifying the first substance and/or the further substance, at least one effect generated by the effect pigment is detected depending on at least one property of the electroluminescent radiation. The effect pigment is further identified depending on the effect created. In other words, the effect pigment can be identified, in particular in addition to depending on the property of the electroluminescent radiation, depending on an effect generated by the effect pigment.

The effect can in particular be one of the optical effects explained above.

To detect the effect, the security feature can be illuminated at different illumination angles, in particular with radiation of a predetermined wavelength, radiation from a predetermined wavelength range or with radiation from different wavelength ranges. Alternatively or cumulatively, the radiation reflected or emitted by the security feature under the illumination can be detected at different detection angles or viewed at different viewing angles.

Furthermore, it can be detected whether a predetermined, desired effect occurs under the explained illumination and/or the explained observation or detection. If the predetermined effect occurs, the effect pigment and, if necessary, a type of effect pigment can be identified. Furthermore, if the effect pigment or a type of effect pigment is identified, the security feature can be verified. If the effect pigment or a predetermined type of effect pigment cannot be identified, the security feature cannot be verified.

It is also possible to identify the further substance depending on the properties of the electroluminescent radiation and depending on the effect produced. For example, the further substance can only be identified if the property and/or the increase in the electroluminescent radiation and/or if the effect generated can be assigned to the further substance.

This results in a more reliable identification of another substance and thus a more reliable verification of the security feature.

A device for identifying at least one component, in particular a substance, of at least one security feature of a security product is also proposed. The device is used to carry out a method according to one of the embodiments described in this disclosure. The device is therefore designed in such a way that the corresponding method can be carried out using the device.

The device comprises at least one device for generating high-energy radiation, namely UV radiation, at least one device for generating an alternating electric field, at least one device for detecting electroluminescent radiation and at least one evaluation device. The device for generating high-energy radiation is in particular a device for generating UV radiation. This can in particular be designed as a UV discharge lamp, as a UV LED or as a high-performance UV LED.

Furthermore, the at least one security feature can be irradiated, namely by the device for generating UV radiation. Furthermore, the security feature can be acted upon by an alternating electrical field, in particular by a device for generating an alternating electrical field. The device for generating an alternating electric field can be designed as an electrode or comprise at least one electrode. Furthermore, electroluminescent radiation emitted by the first substance can be detected, in particular by the device for detecting electroluminescent radiation. The device for detecting electroluminescence radiation can be, for example, a photodetector, a spectrometer or an image capture device. In addition to the suitable sensors, this or the device can also have suitable filter elements.

Furthermore, the first and/or the further substance of the security feature can be identified, namely by the evaluation device, depending on at least one property of the electroluminescent radiation. For this purpose, the evaluation device can record the property of the electroluminescent radiation. This was explained previously.

In a further embodiment, an irradiation area of the at least one device for generating UV radiation is from an exposure area of the at least one device for generating the alternating electric field different. This can mean that there is a spatial distance between the UV irradiation area and the exposure area. Furthermore, the security feature can be transported from the UV irradiation area into the exposure area, for example by means of a transport device. The device can include the transport device.

It is possible for security products to be transported through the device along a transport direction. In this case, the UV irradiation area can be arranged in front of the exposure area in the transport direction. In this case, it is also possible to arrange a series connection of several devices for generating UV radiation along the transport direction.

It is also possible for security products to be transported through the device at a predetermined speed, for example up to 10 m/s, with both the UV irradiation, the exposure to the excitation field and the detection of the electroluminescent radiation taking place during the movement. In this case, the parameters of the UV irradiation, in particular a time period, an irradiation energy and/or an irradiation direction of the irradiation, can be adjusted such that during transport through the UV irradiation area the irradiation dose is sufficient to achieve a desired electroluminescence intensity or a desired electroluminescence intensity change subsequent exposure to the alternating electric field.

In a further embodiment, the device comprises at least one device for generating, detecting and evaluating an effect generated by an effect pigment. The device can include several sub-devices, each of which can be used for generation, recording and/or evaluation. For example, the device can include a device for generating radiation from a predetermined wavelength range. The device for generating this radiation can be different from the device for generating radiation explained above. Furthermore, the device can comprise a partial device for detecting the radiation reflected by the at least one effect pigment. This can be designed, for example, as an image capture device. This image capture device can be different from the device for detecting electroluminescent radiation or the same as this device.

The device can further comprise a device for evaluating or determining at least one property of the radiation reflected or emitted by the at least one effect pigment. This evaluation device can be different from the previously explained evaluation device for evaluating the property of the electroluminescent radiation or the same as this device.

Fig. 1

ein schematisches Blockschaltbild einer erfindungsgemäßen Vorrichtung,

Fig. 2

ein schematisches Blockschaltbild einer erfindungsgemäßen Vorrichtung in einer weiteren Ausführungsform,

Fig. 3

ein Flussdiagramm eines erfindungsgemäßen Verfahrens,

Fig. 4

eine schematische Darstellung eines Sicherheitsmerkmals,

Fig 5

eine schematische Darstellung der Elektrolumineszenzintensität in Abhängigkeit der Bestrahlungsdosis, für zwei erfindungsgemäße Sicherheitsmerkmale mit unterschiedlichen Mischungsverhältnissen der ersten und der weiteren Substanz

Fig. 6

eine schematische Darstellung der Zunahme der Elektrolumineszenzintensität in Abhängigkeit der UV-Bestrahlungsdosis und

Fig. 7

eine schematische Darstellung der Reduktion der Elektrolumineszenzintensität nach Beendigung der UV- Bestrahlung.

The invention is explained in more detail using an exemplary embodiment. The figures show:

Fig. 1

a schematic block diagram of a device according to the invention,

Fig. 2

a schematic block diagram of a device according to the invention in a further embodiment,

Fig. 3

a flowchart of a method according to the invention,

Fig. 4

a schematic representation of a security feature,

Fig 5

a schematic representation of the electroluminescence intensity as a function of the irradiation dose, for two security features according to the invention with different mixing ratios of the first and the further substance

Fig. 6

a schematic representation of the increase in electroluminescence intensity as a function of the UV irradiation dose and

Fig. 7

a schematic representation of the reduction of the electroluminescence intensity after the end of UV irradiation.

Below, the same reference numbers designate elements with the same or similar technical features.

In Fig. 1 is a schematic block diagram of a device 1 for identifying at least one component of a security feature 2 of a security document 3. The security document 3 forms a security certificate. The security document 3 lies on a support surface 4.

The device 1 includes a device 5 for generating UV radiation, a device 6 for generating an alternating electric field, a device 7 for detecting electroluminescent radiation and a control and evaluation device 8. The control and evaluation device 8 can be designed as a microcontroller or include one. The device 5 for generating UV radiation can be designed as a UV LED. The device 6 for generating an alternating electric field can be designed as an electrode or comprise at least one electrode. The device 7 for detecting electroluminescent radiation can be designed, for example, as an image capture device, and in this case in particular as a CCD camera.

The device 6 for generating the alternating electric field and the device 7 for detecting electroluminescent radiation can preferably be arranged in such a way that the security document 3, in particular the security feature 2 of the security document 3, is arranged between these devices 6, 7.

The devices 5, 6, 7 can thus be arranged on different pages of the security document 3, with at least two of the devices 5, 6, 7 being able to be arranged on one side of the security document 3. However, this is not mandatory. All devices 5, 6, 7 can also be arranged on the same page of the security document 3. It is important that the electroluminescence radiation generated by the security feature 2 when exposed to the alternating electric field generated by the device 6 can be detected by the device 7. It is also important that the UV irradiation occurs from the side of the security document 3 on which the security feature 2 is arranged.

The security feature 2 includes a first substance, not shown, with electroluminescent properties and at least one further substance, the electrical conductivity of the further substance being changeable by UV irradiation. The first substance is in particular a powdery zinc sulfide electroluminophore. The further substance includes in particular optical effect pigments, in particular mica pigments coated with titanium dioxide.

Preferably, but not necessarily, the device 5 for generating UV radiation, the device 6 for generating an alternating electric field and the device 7 for detecting electroluminescent radiation are arranged and/or designed in such a way that a security feature 2 is, if possible, simultaneously with UV radiation irradiated and subjected to an alternating electric field and the electroluminescent radiation can be detected.

In a method for identifying the first and/or the further substance, the security feature 2 can be irradiated with UV radiation by the device 5 for generating UV radiation. After the start of irradiation with UV radiation, the security feature 2 can be acted upon by the device 6 for generating an alternating electric field with an alternating field, which can also be referred to as an excitation field. The electroluminescence radiation generated due to the excitation field can be detected after the UV irradiation has ended. In particular, the application of an alternating electric field can also take place after the UV irradiation has ended. If the security feature 2 is excited with the alternating electric field, the first substance emits electroluminescent radiation, which is detected by the device 7 for detecting this electroluminescent radiation. The control and evaluation device 8 can determine a property, in particular an intensity, of this electroluminescent radiation.

Depending on the property, it can be identified whether the security feature includes the first substance. For example, this can be identified when the intensity is greater than a first predetermined (low) threshold value.

Furthermore, depending on the property, it can be identified whether the security feature 2 includes the additional substance. For example, the further substance can be identified if the intensity is higher than a further predetermined threshold value, the further predetermined threshold value being higher than the first predetermined threshold value. The further predetermined threshold value can here be dependent on the strength of the alternating electric field. For a certain strength of the alternating electric field, the intensity of the electroluminescent radiation will be higher in the case in which the security feature 2 includes the further substance than in the case in which the security feature 2 does not include the further substance.

Depending on the at least one property, in particular the intensity, a type of further substance, in particular a material or a material composition, can also be determined. For different types of other substances, the electrical conductivity and thus the intensity of the electroluminescent radiation can change in various ways, in particular under and/or after UV irradiation.

The method described can be used to verify the security feature 2 and thus the security document 3. For example, the security feature 2 can be verified when both the first substance and the further substance have been identified. In addition, the security feature 2 can only be identified if a predetermined type of further substance has been identified.

Fig. 2 shows a schematic block diagram of a device 1 according to the invention in a further embodiment. In contrast to that in Fig. 1 In the embodiment shown, the device 5 for generating UV radiation, the device 6 for generating an alternating electric field and the device 7 for detecting the electroluminescent radiation are arranged in such a way that the irradiation area of the device 5 does not overlap with the exposure area of the device 6. Thus, after UV irradiation, the security document 3 with the security feature 2 is transported by the device 5 into the exposure area of the device 6, for example by means of a transport device, not shown. For example, the support surface 4 can be the surface of a conveyor belt.

In Fig. 3 a schematic flowchart of an identification method according to the invention is shown. A security feature 2 (see e.g Fig. 1 ), which comprises a first substance with electroluminescent properties and at least one further substance, the further substance being changeable by UV irradiation has electrical conductivity, an alternating electrical field is applied in a first step S1 and the intensity of the emitted electroluminescence radiation is recorded (Signal1).

In a second step S2, the security feature 2 is irradiated for a predetermined period of time with UV irradiation of a predetermined radiation energy, i.e. with a predetermined UV dose. In a third step S3, the security feature 2 is again subjected to the same alternating electrical field as in the first step S1 and the intensity of the emitted electroluminescent radiation is detected again (signal 2).

In a fourth step S4, the ratio between the intensities (Signal2/Signal1) detected in the third step S3 and the first step S1 is determined and compared with a predetermined ratio. If the ratio is greater than a predetermined threshold value, the further substance is identified, the threshold value being greater than one. This was explained previously. Furthermore, the first substance can also be identified in the fourth step if the intensity determined in the third step is greater than a predetermined threshold value.

Fig. 4 shows a schematic cross section through a security feature 2 of a security document 3. The security feature 2 is arranged on a paper layer 9 of the security document 3. Also shown is a device 6 for generating an electric field. Also shown is a glass plate 10 under which two electrodes 11 are arranged, with epoxy resin 12 being arranged in a space between the electrodes 11 under the glass plate 10. Air 13 is arranged between the paper layer 9 and the glass plate 10.

The security feature 2 comprises electroluminescent pigments 14 as a first substance and optical effect pigments 15 as a further substance. The electroluminescent pigments 14 are pigments 14 of a powdery, zinc sulfide electroluminophore. The optical effect pigments 15 are mica-based pigments that are coated with a TiO2 layer.

An excitation field can be generated by the electrode 11, which in turn leads to the emission of electroluminescent radiation. This electroluminescence radiation can then be detected, as explained above.

Figure 5 shows a schematic representation of the electroluminescence intensity as a function of the UV irradiation dose for two security features according to the invention with different mixing ratios of the first and the further substance

Here, the detected electroluminescence intensities after UV irradiation of a security feature, which comprises the first substance and the further substance in a first mixing ratio, are represented by circles. The irradiation dose is shown on the abscissa, while the height of the recorded electroluminescence intensities is shown on the ordinate.

The rectangles represent the recorded electroluminescence intensities after UV irradiation of a security feature which includes the first substance and the further substance in a further mixing ratio. The further mixing ratio is different from the first mixing ratio.

It can be seen that the recorded electroluminescence intensity at the same irradiation dose is very dependent on the specific composition of the security feature, i.e., among other things, on the mixing ratio of the combined electroluminescent pigments and the field displacement elements with variable conductivity. Furthermore, it can be seen that the electroluminescence intensity increases with increasing irradiation dose in both cases, with the increase having an approximately logarithmic increase and thus saturation occurs at irradiation doses above a predetermined limit value.

Fig. 6 shows a schematic representation of the increase in electroluminescence intensity as a function of the irradiation dose after UV irradiation of a security feature, which includes both the first and the further substance. It can be seen that the electroluminescence intensity increases with increasing irradiation dose, the increase having an approximately logarithmic course and thus the explained saturation of the recorded intensity is achieved.

Fig. 7 shows a schematic representation of the reduction in electroluminescence intensity after UV irradiation has ended. This shows that after UV irradiation with an energy of 45 mJ, the electroluminescence intensity has returned to the initial level before irradiation after more than 800 seconds, which is shown by a solid line.

Reference symbol list

1

contraption

2

Security feature

3

Security document

4

Support surface

5

Device for generating UV radiation

6

Device for generating an alternating electric field

7

Device for detecting electroluminescent radiation

8th

Control and evaluation device

9

paper layer

10

Glass plate

11

electrode

12

Epoxy resin

13

Air

14

electroluminescent pigment

15

Effect pigment

S1

first step

S2

second step

S3

Third step

S4

fourth step

Claims (10)

1. Method for identifying at least one security element of at least one security feature (2) of a security product, the security feature comprising (2) comprising a first substance and at least one further substance, the first substance being an electroluminescent substance, the further substance being a substance having an electrical conductivity which can be changed by UV irradiation
   characterized in that
   the at least one security feature (2) is irradiated with UV irradiation to amplify an electroluminescence radiation of the first substance, wherein an alternating electric field is applied to the security feature (2), wherein an electroluminescence radiation emitted by the first substance and amplified by the UV irradiation is detected, wherein the first substance and/or the further substance is identified as a function of at least one property of the amplified electroluminescence radiation.
2. Method according to claim 1, characterized in that the security feature (2) is irradiated in time before exposure to the alternating electric field.
3. Method according to claim 2, characterized in that a time duration between the end of the irradiation and the beginning of the exposure to the alternating electric field is longer than 0 seconds and/or shorter than 600 seconds.
4. Method according to any one of the preceding claims, characterized in that the further substance comprises a metal oxide layer at least in part.
5. Process according to claim 4, characterized in that the metal oxide consists at least partly of Ti02.
6. Process according to any one of the preceding claims, characterized in that the further substance comprises at least one effect pigment.
7. Method according to claim 6, characterized in that, in addition to the identification of the first and/or the further substance as a function of at least one property of the electroluminescence radiation, at least one effect produced by the effect pigment is detected, the effect pigment being identified as a function of this detected effect.
8. Device for identifying at least one security element of at least one security feature (2) of a security product, the device (1) comprising at least one device (5) for generating UV radiation, at least one device (6) for generating an alternating electric field, at least one device (7) for detecting electroluminescence radiation, and at least one evaluation device (8), characterized in that the at least one security feature (2) can be irradiated with UV irradiation to amplify electroluminescence radiation of the first substance, wherein an alternating electric field can be applied to the security feature (2), wherein an electroluminescence radiation emitted by the first substance and amplified by the UV irradiation can be detected, the evaluation device (8) being set up to identify the first and/or the further substance as a function of at least one property of the amplified electroluminescence radiation.
9. Device according to claim 8, characterized in that an irradiation area of the at least one device (5) for generating UV radiation is different from an application area of the at least one device (6) for generating the alternating electric field, the security feature (2) being transportable from the irradiation area into the application area.
10. Device according to claim 8 or 9, characterized in that the device comprises

    (1) comprises at least one device for generating, detecting and evaluating an effect produced by an effect pigment.

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