EP2718911B1 - Method for verifying a security document having a security feature in the form of a fluorescent printing element and use of such a corresponding arrangement - Google Patents

Description

The invention relates to a method and a use of an arrangement for verifying a security document with a security feature in the form of at least one fluorescent printing element. In particular, such a method can be performed with a smartphone or such an arrangement can be an integral part of a smartphone.

From the state of the art it has long been known to provide security documents with security features in the form of luminescent substances in order to make them counterfeit-proof or verifiable. Security documents within the meaning of the invention are, in particular, banknotes, passports, ID cards, driver's licenses, tickets and similar documents or objects in which the need for forgery-proofing exists.

The EP 1 673 231 B1 describes a value document with a value document substrate having at least two different feature substances for checking the value document. At least one of the feature substances is formed by a luminescent substance or a mixture of luminescent substances. The feature substance can be irradiated with visible or infrared radiation, with emission taking place in the infrared spectral range. The authenticity check is performed based on the detected emission.

The EP 0 977 670 B1 shows a printed value document with an authenticity feature in the form of a luminescent substance based on a rare earth-doped host lattice. The host lattice absorbs almost in the entire visible spectral range, so that all lines in the visible spectral range of the luminescent substance are suppressed. The excitation range of the luminescent substance coincides with the radiation range of strong light sources, such as halogen lamps, flash lamps or the like. However, it can also be excited with light from the visible range.

The EP 0 991 522 B1 includes a document of value with luminescent substances which have emission spectra which are so far in the IR spectral range that they can be detected with conventional detectors only with high metrological effort, if they are added to the value document in maximum, but the document not changing amount. Suitable substances are substances based on holmium-doped host lattices.

The EP 0 053 183 B1 shows a security document in the form of luminescent and absorbing substances which are excitable with invisible and / or visible light and luminesce only in the invisible region of the optical spectrum.

Furthermore, should still on the EP 0 052 624 B1 . EP 0 053 124 B1 . EP 0 053 148 B1 . EP 0 975 468 B1 and EP 0 975 469 B1 where value documents with luminescent authenticity features are also described. The excitation of the phosphors can be done both in the visible and in the non-visible spectral range. As an additional safety factor pointed out that as much as possible no emissions in the visible range should occur.

For verification of security documents usually special detection devices are needed, which are usually operated stationary and only a limited user group are available. In addition, there are efforts for some time, detectors also for mobile applications to provide.

The WO 2006/056268 A1 and the DE 10 2004 056 007 A1 include a mobile verification device for authenticity verification of travel documents. The verification device comprises an identification device for identifying an authorized user, a release device for releasing the verification device on the basis of a signal of the identification device, an optical reading unit for reading image-based or alphanumeric information contained on the pages of the travel document, a data processing device for processing the optical reading unit supplied signals according to a predetermined algorithm, a display unit for displaying the read-out data and the Verifikationsergebnisses and a communication unit for the encrypted transmission of the read data or the verification result to a central location. According to a preferred embodiment, a mobile telephone can serve as a graphic display unit, data processing unit and communication unit. As an optical reading unit, for example, a camera is used, which preferably has a lighting device with modulatable, in particular pulsable light sources, such as LEDs or laser diodes. By using such lighting systems, the security elements contained in pigments of printing inks can be stimulated and the signals obtained are also used for authenticity testing.

In the CN 1462010 A For example, a system for identifying forged banknotes using a cellular phone is described. The banknotes are encrypted by means of infrared barcode. The barcode is recorded in a central computer database. After the banknotes are in circulation, the authenticity of banknotes can be checked by means of a banknote recognition function of the mobile radio telephone implemented via suitable software. For this purpose, the central database is accessed via mobile connection.

The CN 101252612 A shows a mobile telephone with a system for checking the authenticity of banknotes. The system includes a CCD camera mounted on the mobile phone as well as light sources located on the same side as the CCD camera. The light sources preferably comprise an infrared light source and an ultraviolet light source. The system may further comprise an infrared filter and an ultraviolet filter which can be pushed onto the infrared light source or ultraviolet light source by means of a transfer mechanism. Through the described system, the CCD camera conventionally used in mobile telephones can detect security features of banknotes. A disadvantage of the solution described is that additional modifications, such as the attachment of light sources, are required on the mobile telephone.

From the US 2006/0279732 A1 is a mobile phone with an integrated spectroscopic sensor known. The spectroscopic sensor comprises a light source and a photosensor, the existing flash and the CMOS / CCD image sensor the mobile phone as a light source or as a photo sensor use. By means of a mobile phone, an authenticity check of objects such as banknotes, jewels, etc. is to be carried out. However, the wavelength ranges of the radiation to be used are not described in detail.

The US 2005/0100204 A1 shows a method and a device for the detection of fluorescent particles for the authenticity verification of documents. The device comprises a mobile telephone with an integrated light source and a photosensor.

The US 2010/144387 A1 shows a multifunctional portable electronic device with integrated verification function. The device can z. B. be a mobile phone or a PDA. For verification of value documents such as banknotes, the corresponding area is excited, for example, with red or blue-violet light from a light source of the device. The resulting emissions can be evaluated with the naked eye and further detected by means of camera module. By means of a central processing unit, a comparison is made with predetermined data. The verification result is output on a display unit.

The EP 1 986 162 A1 describes an apparatus and a method for checking the authenticity, in which a target area containing an authenticity feature is excited with visible or non-visible light and the emissions lying in the visible or non-visible spectral range are detected by means of a photosensor.

The EP 1 672 668 A1 deals with fluorescent security features that emit in the visible spectral range. For excitation, a lighting unit with an array of LEDs can be used, which can emit light in different spectral ranges.

The WO 2008/113963 A1 shows a portable device for authentication with two oppositely arranged LEDs that emit visible light, which is focused by Fresnel lens and meets a group of security elements. The light emitted by the security elements light is detected by image sensor and further processed by a processor. The emitted light is in the visible spectral range. The result of the test is signaled optically or acoustically.

The WO 2010/100378 A2 describes a method for the optical analysis of a substance on an object or a document. The object or document is irradiated with visible light to excite the substance, whereupon the substance emits visible light. In order to visualize a characteristic chromatic radiation, which is not detectable in visible light, a corresponding filter element is used.

An object of the present invention is to provide a use of an arrangement and a method for verifying a security document. The arrangement should be characterized in particular by the fact that it consists of simple, generally available components and is inexpensive to implement compared to conventionally used verification arrangements. In particular, the aim is the arrangement and the method for verification of such security documents so that they can be easily integrated into mobile phones, smart phones and similar devices.

To achieve the object of the invention is a method for verifying a security document according to the accompanying claim 1. To achieve the object of the invention is also a use of an arrangement for verification of a security document at, according to claim 3.

The method according to the invention for verifying a security document comprises the steps described below: First, the pigment-like fluorescent printing element, which is arranged in a test area of the security document, is excited by means of a light source emitting in the visible spectral range. The light source used is preferably an LED light which is used as a flash or photographic light, as it is used in particular on modern mobile telephones. However, the excitation can also be done via a continuous light source, such as neon tubes, halogen lamps or LED lighting. Likewise, an excitation can also be realized via natural sunlight. To excite the preferably used fluorescent printing element is usually sufficient blue light. As a result of the excitation, light is emitted from the fluorescent printing element. The emission of the pigment-like fluorescent printing element is detected by a photosensor and subsequently evaluated. The evaluation takes place via a specific application program, which also takes into account the different light sources. The photosensor is preferably an image sensor of a mobile phone and the application program can be installed as a so-called app on a smartphone.

In the context of this evaluation, a comparison with the remaining surface of the security document, on which no fluorescent printing element is arranged (comparison area), or with a pictorial image of the non-excited fluorescent printing element. The comparative data are usually stored in a database, the z. B. stored in the mobile phone or is available online. However, it is also possible to generate the data required for comparison during the process by illuminating a comparison region of the security document by means of the exciting light source and detecting the emission of the comparison region. Alternatively, the fluorescent printing element can also be detected in the unexcited state and used for comparison.

In the last method step, the verification result is output, preferably on the display of the mobile telephone. If necessary, the verification result can be transmitted from the mobile phone to a remote receiver.

The security document to be verified by means of the method according to the invention has a security feature in the form of at least one pigment-like fluorescent printing element which can be excited in a first wavelength range of electromagnetic radiation in order to emit electromagnetic radiation in a second wavelength range, the first and the second wavelength range in the visible spectral range lie.

As a fluorescent printing element, it is particularly preferred to use a fine-grained inorganic LED conversion luminescent material in a modified form, which is used in printing inks, printing inks or Printing pastes is incorporated. Included in this group are conversion phosphors used in the manufacture of LEDs to convert at least a portion of the emission of the semiconductor in the blue region to another color region to produce white light.

The arrangement comprises a freely programmable mobile telephone with a light source for emitting light in the visible spectral range and with a photosensor for recording or measuring light in the visible spectral range. The free programmable mobile phone is configured to compare the radiation received by the photosensor with measured data emitted by the pigmented fluorescent printing element with predetermined data and to signal over-match or deviation to verify the security features of the security document being examined.

A significant advantage of the verification arrangement is that only a correspondingly configured mobile phone is needed. Thus, a simple and also inexpensive solution for the authenticity check of security documents is available. The verification arrangement can be made available to a broader user group, which can carry out a review of security documents in a location-independent manner.

The freely programmable mobile phones include smartphones, which can be individually upgraded with additional functions by the user via additional programs (so-called apps). The required light source for verification and the photo sensor are standard on smartphones, so that the existing hardware does not change must become. Smartphones usually have an LED light source to realize a flash or lighting function. With the help of this so-called LED flash excitation of serving as a security indicator fluorescent pressure element can be done. A smartphone photosensor, such as a CCD, CMOS or Foveon sensor, is equipped with a shutter system in the range of 10 ms to 50 ms, in particular in the range of 33 ms in the wavelength range of about 360 nm to 1100 nm. Such photosensors are usually equipped with RGB color filters and IR cut filters, since they are sensitive to about 1100 nm and in particular in the non-visible range from 780 nm to 1100 nm have a high sensitivity.

An essential advantage of the invention is that emission takes place in the visible spectral range as a result of the fluorescent printing element used as security marking. This emission, because it is in the visible spectral range, can be detected with little effort and without special detectors, for example by means of a color image sensor of a smartphone. In the previously known from the prior art solutions instead emissions are usually caused by the phosphors used in the non-visible area, the detection is much more expensive.

According to an advantageous embodiment, the first wavelength range used for exciting the fluorescent printing element is between 380 nm and 500 nm. The middle wavelength of the first wavelength range is preferably in the visible spectral range, wherein it is also preferably in the wavelength range between 380 nm to 500 nm. For some embodiments, a mean wavelength has between 420 nm to 470 nm or between 450 nm to 470 nm proved to be favorable.

The fluorescent printing element emits in a second wavelength range whose wavelength is preferably in the visible spectral range. The wavelength or average wavelength of the second wavelength range is preferably between 490 nm and 780 nm or between 550 nm and 780 nm in the visible spectral range.

The security feature is usually applied to the security document by printing or integrated into the security document. The printing inks, printing inks or printing pastes used preferably have a polymeric binder matrix in which the fluorescent printing element is homogeneously dispersed. The printing inks, printing inks or printing pastes are applied to the security document by means of suitable application methods, such as intaglio printing, gravure printing, offset printing, flexographic printing, screen printing, inkjet printing, transfer printing, re-transfer printing, laser transfer printing, pad printing or numbering or integrated into the security document by printing on inner layers and subsequent lamination.

According to an advantageous embodiment, the pigment-like fluorescent printing element has a d50 pigment distribution in the range from 1 μm to 20 μm. The d50 value is the measure of the average pigment size. d50 means that 50% of the pigments are smaller than the specified value. In other embodiments, a d50 pigment distribution in the sub-micron range, especially in the nanoscale range has proved favorable. Here are advantageous d50 pigment distributions in the range of 3 nm to 30 nm or in the range of 100 nm to 500 nm.

The fluorescent printing element is formed by a nitridic phosphor having a host lattice of the structure M-Si-N, M-Si-ON, M-Al-N, M-Si-Al-N or M-Si-Al-ON and is doped with Eu ²⁺ as an activator, or has a host lattice of the structure M-Si-N, La-Si-N, M-Si-Al-N or M-Si-Al-ON and with Ce ³⁺ as activator is doped. M is a metal, which is preferably formed by Ca, Sr and / or Ba.

In the following Table 1 and in the following Table 2 important representatives of the Eu ²⁺ - or Ce ³⁺ -doped nitride phosphors are given specifying their characteristic emission wavelengths. <b> Table 1 </ b> Eu ²⁺ doping Emission wavelength in nm M = Ca Sr Ba M-Si-N MSiN ₂ 620-625 630-700 550-650 M ₂ Si ₅ N ₈ 605-615 610-680 570-680 MSi ₇ N ₁₀ - - 660 MYSi ₄ N ₇ - 550-570 505-540 M-Si-ON MSi ₂ O ₂ N ₂ 560 530-570 490 M ₃ Si ₂ O ₄ N ₂ 510 - - M ₃ Si ₆ O ₁₂ N ₂ - - 480-580 LaMSi ₂ O ₂ N ₃ - 650 - M-Al-N M ₃ Al ₂ N ₄ - 700-750 - M-Si-Al-N MSiAlN ₃ 660 - - MSi ₁₀ Al ₂ N ₁₆ 560-580 - - M-Si-Al-ON M _{x / 2} Si _{12- (x + y)} Al _{(x + y)} O _y N _16-y (α-sialon) 550-600 - - Ce ³⁺ doping Emission wavelength in nm M = Ca Sr Ba M-Si-N MSiN ₂ (Li ⁺ -, Na ⁺ -coded) 540-640 450-600 450-550 M ₂ Si ₅ N (Li ⁺ -, Na ⁺ -codotiert) 470 555 450 La ₃ Si ₆ N ₁₁ 550-590 550-590 550-590 M-Si-Al-N MSiAlN ₃ 565 - - M-Si-Al-ON M _{x / 2} Si _{12- (x + y)} Al _{(x + y)} O _y N _16-y (α-sialon) 485-540 - -

The exemplary naming of different phosphors is not intended to be limiting. Other suitable phosphors which emit in the visible after excitation in the blue or visible spectral range and mixtures of different phosphors can also be used. In addition, a preferred embodiment is to modify in particular those conversion phosphors which are also used for the production of white light-emitting LEDs in a suitable manner by varying the lattice composition, the activator concentration and / or by co-doping with other, different rare earth ions and in this form to use as a fluorescent printing element according to the invention.

Claims (6)

1. Method for verifying a security document using a freely programmable mobile phone, wherein the security document includes at least one pigment-like fluorescent print element as a security feature, which element is mounted in a test area and is excitable in a first wavelength range of electromagnetic radiation to emit electromagnetic radiation in a second wavelength range, wherein the first and second wavelength ranges are both in the visible spectral range, and wherein the pigment-like fluorescent print element is formed by a nitride fluorescent material with a host lattice which has a structure M-Si-N, M-Si-O-N, M-Al-N, M-Si-Al-N or M-Si-Al-O-N and is doped with Eu²⁺ as activator, or with a host lattice which has a structure M-Si-N, La-Si-N, M-Si-Al-N or M-Si-Al-O-N and is doped with Ce³⁺ as activator, wherein M stands for a metal, comprising the following steps:

   - exciting the fluorescent print element by means of a light source emitting in the first wavelength range;

   - detecting the emission of the fluorescent printing element with a photosensor;

   - evaluating the emission of the fluorescent printing element detected in the second emission wavelength range by comparison with predetermined data;

   - outputting the result of verification depending on the result of the comparison performed.
2. Method according to claim 1, characterized in that it further comprises the steps of:

   - illuminating a comparison area of the security document by means of the light source emitting in the visible spectral range, wherein the comparison area does not contain the fluorescent print element located in the in the test area;

   - detecting the emission of the comparison area with the photosensor;

   - applying the detected emission of the comparison range as predetermined data which is used when evaluating the detected emission of the fluorescent print element.
3. Use of an apparatus comprising a freely programmable mobile phone having a light source for irradiating a test area of the security document with visible light in a first wavelength range and having a photosensor for capturing visible light, wherein that mobile phone is configured to compare the radiation emitted by the fluorescent print element in the second wavelength range and captured by the photosensor with predetermined data and to report a match for the purpose of verifying a security document that has a security feature in the form of at least one pigment-like fluorescent print element, wherein the pigment-like fluorescent print element is formed by a nitride fluorescent material with a host lattice which has a structure M-Si-N, M-Si-O-N, M-Al-N, M-Si-Al-N or M-Si-Al-O-N and is doped with Eu²⁺ as activator, or with a host lattice which has a structure M-Si-N, La-Si-N, M-Si-Al-N or M-Si-Al-O-N and is doped with Ce³⁺ as activator, wherein M stands for a metal, wherein the fluorescent print element is applied in a test area of the security document, is excitable in a first wavelength range in the visible spectral range, and in consequence of this excitation electromagnetic radiation is emitted in a second wavelength range in the visible spectral range.
4. Use according to claim 3, characterized in that the first wavelength range is between 380 nm and 500 nm and/or the second wavelength range is between 490 nm and 780 nm.
5. Use according to claim 3 or 4, characterized in that the security feature is applied to and/or integrated in the security document using printing techniques, wherein the pigment-like fluorescent print element is dispersed homogeneously in a polymer binder matrix.
6. Use according to any one of claims 3 to 5, characterized in that the pigment-like fluorescent print element has a d50 pigment distribution in the range from 1 µm to 20 µm.