EP3781408A1 - Smartphone-verifiable, luminescent-material-based security feature and assembly for verification - Google Patents

Abstract

The invention relates to a smartphone-verifiable security feature (01) containing a luminescent material which can be excited to luminescence by visible electromagnetic radiation generated by a smartphone and, after termination of the excitation, exhibits an emission which can be detected by means of an image-capturing unit of the smartphone for a decay time in the range of 1 ms to 100 ms. The invention also relates to an assembly for verifying a security document (02) which comprises such a security feature (01).

Description

 Smartphone verifiable, fluorescent-based

 Security feature and arrangement for verification

The present invention relates to a security feature with a phosphor that can be verified with the aid of a commercially available smartphone. The invention also relates to an arrangement for verifying a security document with such a security feature.

From the prior art, it has long been known, equipped with luminescent substances (phosphors)

Use security features to protect and authenticate security and value-added documents. They are mostly used as so-called Level 2 features. Your

Presence can be detected by the excitable with simple handsets (UV or IR radiation sources) and usually taking place in the visible spectral emission of the phosphors. In addition, they serve the copy protection. On the other hand, luminescent security features equipped with particularly high counterfeit security are also used as machine-readable level 3 features. The authenticity verification of such features is usually associated with a high technical complexity.

There is an increasing amount of security and value documents as well as product protection

Interest in the use of authenticity features that have a high level of security (level 2 ⁺ or level 3 characteristics), but can be tested with little technical effort.

Thus, from WO 2012/083469 Al a device for

Authentication of marked with photochromic systems Documents known. The photochromic security feature shows a change in color and / or a change in shape under the effect of a flashlight excitation. It is further described that the security feature is based on a retinal protein.

From DE 10 2015 219 395 A1 an identification feature with at least two identification elements arranged in a defined limited area for the identification of an object is known. After irradiating the surface with visible light, a first identification element consisting of ink or ink is visually visible and a second identification element is not visually visible.

WO 2013/034471 A1 and DE 10 2011 082 174 A1

describe a device for recognizing a document that incorporates a phosphor-based security feature

having designated wavelength conversion characteristics. For this purpose, a light generating device (for example, an LED flash unit) is provided which irradiates the security feature with excitation light, as well as an image recording device (for example, a digital camera of a mobile communication device), which is to receive the light emitted by the security feature light. However, it has been shown that the disclosed phosphors regularly have cooldowns that far with an evaluation of the emission

common devices, in particular a genuineness check with the help of commercially available smartphones do not allow.

WO 2013/034603 A1 describes a method for verifi cation of a security document with a security feature in the form of a fluorescent printing element. The method provides that the pressure element by means of a light source is excited and it emits an electro-magnetic radiation as a result of this excitation, which can be detected in a further step by means of a sensor. By comparing with given data, the collected data is evaluated. The verification result is given in a further step depending on the result of the comparison. In particular, the method should be performed with a smartphone, wherein the flash module of the smartphone as excitation source and the photo sensor of the camera of the smart phone come as a detection unit for use. As phosphors for the pigment-like fluorescent printing element inorganic phosphors are called, namely nitride phosphors; Europium-doped alkaline earth orthosilicate and alkaline earth oxyorthosilicate phosphors; Cerium-doped rare earth-metal-gallium-garnet phosphors; red light emitting (Ca, Sr) S: Eu ²⁺ ; and green emitting SrGa ₂ S ₄ : Eu ²⁺ . The proposed phosphors are extremely fast decaying so-called LED conversion phosphors. However, it has been shown that it is practically impossible to reliably detect the luminescence signals of these rapidly decaying phosphors directly during the flashlamp excitation because the luminescence signals have far too low an intensity compared to the excitation light and are covered by the high-intensity stimulating flashlight of the smartphone become.

In the practical application of the phosphors described in the aforementioned prior art, two previously unsolved problems have been shown. These known phosphors are regularly used as so-called conversion phosphors for the production of white LED, so that these phosphors are regularly included as radiation-converting components in the flash LED of the standard smartphones. This means that the excitation radiation of the flash units of the smartphones used as the excitation source with high probability has the same luminescence signals as are expected from the security feature to be examined. A secure proof of authenticity equipped with such security features value and security documents is already excluded for this reason.

A second problem results from the fact that the designated in the art for use as security features phosphors usually have just as short decay times in the ns to ys range, as applicable for the reasons mentioned for the flash LED are. If flashed by a smartphone, the emissions from the security feature are either completely superimposed by the flash, or they have already faded before being captured.

It is an object of the present invention, based on the prior art, to provide an improved fluorescent based security feature which is verifiable solely by means of a smartphone or a comparable multi-functional, widely used computing device. Another task of the present

The invention is to provide an arrangement for verifying such a security feature.

According to the invention, the object is achieved by a verifiable with a smartphone, fluorescent-based safety feature according to the appended claim 1 and by an arrangement for verification of such a security feature according to the attached independent claim 11th A general solution to the mentioned object, which the invention implements, consists first of all in the fact that a security feature is equipped with a specific phosphor which avoids the problems described above. This phosphor must be configured so that it is on the one hand with a light source of a smartphone or a similar mobile computing device, ie in particular a flash LED of a smartphone, excitable. At the same time, the phosphor must be one

Have luminescence, which makes it possible to detect the luminescence even after completion of the excitation process still with high reliability with the help of Bildfassungsein unit of the same smartphone (mobile data processing device). This requires in addition to a high

Efficient of spectral excitability and high

Luminescence yield above all adapted to the exceptional speed of the image acquisition unit of the smartphone cooldown of the phosphor according to the invention.

The invention provides a reliably evaluable security feature which allows exclusive luminescence properties such as the spectral emission and

To include the decay characteristics of the special phosphors used to produce the security feature as authenticity criteria in the test. In addition, it is of great advantage that the decaying luminescence signals of the security feature according to the invention are neither visible to the human eye during nor after completion of the excitation. It has been found that the choices for the provision of suitable phosphors for the realization of the presented inventive solution are severely limited. This applies in particular to the required decay characteristic. The invention provides a Level-3 feature or at least one Level-2 + functionality feature, as disclosed in U.S. Patent Nos. 4,666,866 and 5,200,264

Security and value documents can be used for authenticity verification. Such features are invisible to the human eye as a rule, for example, even after excitation with UV or IR light sources. Your

Characteristics can so far only with high technical

Expense, for example, with the help of high speed sorting machines to be tested. The present invention makes it possible for the first time to verify the authenticity of such exclusive features with the aid of commercially available smartphones.

The security feature according to the invention can be applied to or in a value or security document and comprises a phosphor which can be excited to luminescence with an electromagnetic radiation of predetermined wavelength, as can be generated by a lighting unit of a smartphone, whereupon the phosphor is one of the Camera device of a smartphone emitted detectable radiation. The emission of the phosphor has a decay time in the ms range. Preferably, the cooldowns in the range between 1 to 100 ms, more preferably in the range between 5 to 50 ms, more preferably selected between 10 and 30 ms.

The decay process (decay process) basically characterizes the time-dependent decrease in the intensity of the radiation emitted by a luminous substance. The decay curve can often use a simple exponential equation of the form

I = Io ^{e_ (t / T) will be} described. The decay constant T contained therein denotes that period of time up to which the intensity of the emission after switching off the excitation source has fallen to 36.79% (= 1 / e-tel) of the output intensity is. However, it has turned out that not all

luminescent substances have a mono-exponential decay. Rather, multi ^¬ exponential resulting from the superposition under schiedlicher relaxation processes, if appropriate (for example, bi- or triexponential) decay curves.

And Mn ²⁺ - - as a particularly useful class of phosphors for the safe ^¬ integrated feature is Ce ³⁺ have co-doped silicate garnet phosphors (CSS) proved that having the formula:

Ca3Sc2Si30i2: Ce ^3+, Mn ²⁺

can be described. Such phosphors are characterized by a high absorption strength at 450 nm, a high luminescence intensity and efficient energy transfer between the ^¬ Ce ³⁺ and Mn ²⁺ ions.

According to an alternative notation, the phosphor having the formula:

_(X Cai_ _Ce _{x) 3} (Sci_ _z Mn _{z) 2} Si ₃ 0i ₂

It is frequently assumed on the basis of the known ionic radii in the literature that the Ce ³⁺ ions are preferably incorporated onto Ca ²⁺ and the Mn ²⁺ ions are preferably incorporated on Sc ³⁺ lattice positions.

In experimental studies it has been surprisingly found that phase-pure, highly efficient and more stable Ca3Sc2Si30i2: Ce ^3+, Mn ²⁺ phosphors are primarily formed when the starting materials is assumed when calculating the weights that the Mn ²⁺ ions both Ca ²⁺ and Sc ³⁺ squares are built into the grid. Particularly good results are achieved if the weighing calculations are made on the assumption that About 75% of the Mn ²⁺ coactivators have the Ca ²⁺ and about 25% the

Replace Sc ³⁺ ions as lattice constituents.

Particularly preferred is the phosphor by the following

general chemical formula describable:

(CAI _xy Ce _x Mn _{y) 3} (Sci_ _z Mn _{z) 2} Si ₃ 0i ₂

with 0 <x <0, l; 0 <y <0.8; 0 <z <0.8

where a y / z ratio of ~ 2 is preferred.

Considering the stoichiometric factors, this corresponds to the stated ratio for the occupation of the Ca ²⁺ or Sc ³⁺ lattice sites by Mn ²⁺ co-activator ions.

With the described Ca ₃ Sc ₂ Si ₃ 0i ₂ : Ce ³⁺ , Mn ²⁺ materials, particularly advantageous phosphors are provided which

Emissions with decay times between 5 and 30 ms and their luminescence signals even after completion of the flash light excitation with high certainty using the

Camera modules of standard smartphones can be detected.

The emission spectra of the phosphors according to the invention consist of three bands each, the direct luminescence of the Ce ³⁺ activator ions (band with an X _max of about 505 nm), as well as on the Ce ³⁺ - Mn ²⁺ energy transfer enabled emissions of the different lattice sites

positioned Mn ²⁺ coactivators can be assigned. The maxima of the latter emission bands are approximately at 570 nm (Mn ²⁺ on Ca ²⁺ space) and at around 700 nm (Mn ²⁺ on Sc ³⁺ space).

The relative intensities of the different emission bands can be determined by the concentrations of the activator and coactivator ions as well as by the respective concentration levels. Ratios are varied and adjusted. In addition, the individual emissions have different spectral decay times. While the decay time of the Ce ³⁺ emission allowed by quantum mechanics is in the nanosecond range, cooldowns in the two Mn ²⁺ emission bands resulting from quantum-mechanically forbidden optical transitions are reduced

in the single-digit (Mn ²⁺ to Ca ²⁺ space) or in the tens of milliseconds range (Mn ²⁺ to Sc ³⁺ space).

The fact that the emission bands to be applied in the green spectral range overlap to a great extent with maxima at about 505 and 570 nm due to their comparatively large half-widths also leads to a superposition of the decay curves of these emissions. Nevertheless, the modified CSS phosphors are characterized by different spectral decay curves with distinct cooldowns

characterized. On the other hand, this results

Constellation that in the event that at the decay

measurements the entire visible spectral range is detected, a significant color shift of the decaying luminescence of the phosphors results. Furthermore, it has been shown that the individual emission bands due to their

Characteristic overlays have no mono-exponential decay curves. Characteristic are bi- or triexponential decay curves.

The described special decay behavior contributes to a high degree to the exclusivity of the invention

Ca3Sc2Si30i2: Ce ³⁺ , Mn ²⁺ phosphors included. In addition, there are other properties that these phosphors for use in luminescent security features whose presence and authenticity can be verified with the help of standard smartphones recommend. On the one hand, the named luminaires Substances in the ultraviolet spectral range are practically non-excitable and, secondly, the body color of the corresponding luminescent pigments is such that it easily adapts to the color designs of the security and value documents to be protected (banknotes, identity cards, passports, driver's licenses, etc.).

adapted or covered by the printing inks used to make these documents. This means that the presence of the CSS: Ce ³⁺ , Mn ²⁺ luminescent substances introduced as a security feature into the security documents can not be detected by the observer either with the naked eye or with the aid of conventional UV excitation sources.

On the other hand, it is a particular embodiment of

Invention that in UV excitation effectively luminescent, rapidly evanescent phosphors are added to the emitting almost exclusively in the visible spectral range, preferably at 450 nm excitable phosphors with delayed decay behavior. The clearly visible in UV excitation stationary photoluminescence of the corresponding additional components can be used as a security increasing

Masking of the security documents integrated

Serve security features.

Although the choices for providing the required for the realization of the inventive solution shown phosphors are severely limited, there are next to the Ca3Sc2Si30i2: Ce ³⁺ , Mn ²⁺ phosphors but some other materials that used due to their Abklingverhaltens for producing inventive security features could become. In the table below are some of the tested for their suitability according to the invention phosphor compositions including those for the inventive Application relevant Lumineszenzeigenschaften put together.

 In particular, the table contains information on the measured maxima of the respective emission bands and on the decay times. To evaluate the luminescence yield and the spectral excitability at 450 nm was a verbal

 Scaling used.

The phosphors listed are essentially Ce ³⁺ - and Mn ²⁺ - codoped silicate garnets or

Germanate garnets to activate with Mn ²⁺ ions and, if appropriate, additionally with certain rare earth ions (Ce ³⁺ , Eu ²⁺ , Dy ³⁺ ) co-activated complex silicate or phosphatic

Basic lattice, Cr ³⁺ -activated gallate compounds, and the Mn ⁴⁺ -activated phosphors BaGeF _g : Mn ⁴⁺ and K ^ SiFgiMn ⁴⁴ . This listing has no final character. It can be assumed that there are more

suitable phosphors for realizing the features specified in the patent claims are available.

In this context, it is to be regarded as extremely advantageous to consider suitable phosphors to be suitable by deliberately changing their chemical composition, i. by deliberately made substitutions in the cation and / or Anionenteilgitter, so to modify that their luminescence properties, in particular their characteristic decay times, clearly from those in the literature

differentiate between described data. In this way, the exclusivity of the delayed evanescent luminescent

Materials and the anti-counterfeiting security of the corresponding security features can be significantly increased.

Another embodiment of the invention is characterized in that for creating the security features

Phosphor mixtures are used, the individual, preferably exclusive components have different and sensory distinguishable cooldowns. Also in this case results in an increase in the security against forgery of the security features of the invention.

Preferably, the phosphor has a cooldown in a one-digit or two-digit ms range, so that the

Emission of the phosphor with an image capture unit, in particular with a camera of a smartphone can be detected. Currently known smartphone cameras have a frame rate in the range of 240 fps (frames per second) up to 960 fps. Higher frame rates are conceivable especially in future devices, which is the use of the invention described here but does not conflict. With the currently known image frequencies, the smartphone camera records a first image after about 4.2 ms or, in exceptional cases, after 1 ms.

The frame rate of the image sensor used (in particular smartphone camera) determines a lower limit for the

Cooldown of usable in the context of the invention luminescent substances. In the event that the security feature in terms of the realization of a particularly high level of security is not to be recognized by the human eye, an upper limit is given by the physiology of human vision. In particular, the decay time of the luminescent substance in this case should be less than 1 s, since a luminescent of the phosphor, which lasts longer than 1 s from the human normal observer can be perceived.

In a preferred embodiment, the phosphor is a Ce ³⁺ or Mn ²⁺ co-doped silicate garnet phosphor. The stationary luminescence of the phosphor has excitation with the light of white emitting LED, preferably at a maximum wavelength of 450 nm, a broadband emission spectrum with multiple emission maxima in the visible spectral range. These maxima are around

505 nm (assignable to the emission of Ce ³⁺ ions)

dodecahedral Ca ²⁺ sites),

570 nm (attributable to the sensitized emission of Mn ²⁺ ions on dodecahedral Ca ²⁺ sites),

700 nm (attributable to the sensitized emission of Mn ²⁺ ions on octahedral Sc ³⁺ sites).

The spectral decay times of the different emission bands are in the order listed in the ns, in the single-digit or in the two-digit ms range. Preferably, the decay time of the phosphor of the security feature is in the range of 1 ms to 50 ms. Especially before given to the phosphor of the security feature a

Decay time from 10 ms to 30 ms.

So that the security feature can be detected solely by means of a smartphone, the phosphor is configured so that it can be excited in the visible spectral range, in particular in the blue spectral range, so that the flash light source of the smart phone can deliver this excitation radiation. Furthermore, the phosphor is configured to be visible

Spectral range emitted to ensure that it is detectable with the camera module of a standard smartphone. In addition, the phosphor is configured so that its

Luminescence fades in the ms range after completion of the flashlamp excitation, so that a safe verification after

Termination of the suggestion is possible.

The white light of a lighting unit of a smartphone is generated by an LED which consists of an LED semiconductor chip emitting, for example, at approximately 450 nm and one or more LED conversion phosphors placed above the LED semiconductor chip. These conversion luminescent substances are able to convert the emission of the blue LED proportionally into longer-wavelength visible luminescence radiation (broadband emissions in the green, yellow and red spectral range) with an emission maximum of, for example, about 560 nm. The white light of the LED, which is available as a lighting unit for conventional smartphones, results from the additive color mixing of the individual described

Luminescence components, wherein the blue spectral component has the much higher intensity. This means that the For the provision of the security feature according to the invention usable phosphor must preferably be configured so that it has a high efficiency of the spectral excitability, in particular in the range between 420 nm to 470 nm. Particularly preferably, the maximum of the spectral excitability of the phosphor is about 450 nm.

For detecting the luminescence signals of the phosphor, the smartphone camera is available as image capture unit. Preferably, the image capture unit is equipped with a CMOS sensor and an IR filter. She has one

Spectral sensitivity, which covers the entire visible spectral range to about 750 nm. By means of the image capture unit, individual images, image series or video recordings can be recorded. This means for the

Creation of the security feature used phosphor that it must be configured so that emitted after the successful excitation with the highest possible intensity preferably in the spectral range between 480 nm and 750 nm.

The mobile terminal used according to the invention for the verification of the security feature is preferably a conventional smartphone. It is understood by those skilled in the art that the same functionality can also be integrated into a tablet or a similar multifunctional data processing device, for which it must be equipped with a camera with image capture unit and / or lighting unit and a data processing unit. Such devices having the same effect should also be included in the invention. The data processing unit is preferably a processor, in particular a microprocessor. Preferably, the phosphor in the security feature is so

arranged to form a pattern. The phosphor pigments are preferably applied as a defined pattern on a support. The pattern may be arranged as a shape, for example a triangle or a star. Alternatively, the security feature pattern formed by the phosphor itself may contain data and be arranged as a code, such as a QR code. The luminescent pigments are printed as a security feature, for example on a security document. The printing or application can with

known printing methods such as gravure, flexographic, offset or screen printing done. Furthermore, the phosphor can be applied to the security document by coating methods or lamination methods or introduced into the security document. The particle size distribution of the luminescent pigments is preferably adapted to the respective printing and application method.

The security feature, in particular the phosphor, preferably has a high processing stability. In particular, the phosphor has a high thermal and mechanical stability. The phosphor preferably has a high aging resistance to environmental influences. Stability and aging resistance are required to ensure secure verifiability of the security feature throughout the lifecycle of the security document.

An advantage of the security feature according to the invention, which comprises a phosphor, can be seen in the fact that the

Security feature due to the specially configured

Luminescence characteristics of the phosphor can be excited by means of a smartphone flash light and its emission can be detected by the smartphone camera, resulting in a simple, fast and user-friendly verification of the security feature. An authenticity check and / or integrity check can be carried out. It has proven to be advantageous to select for the provision of the security feature a special phosphor with cooldowns in the ms range, the luminescence signals are still safe to measure even after completion of the excitation process. The verification advantageously does not exclusively refer to the proof of the presence of the security feature; it also includes the emissions as authenticity criteria

spectrum, the concrete form of the decay curve (decay

characteristic) and that by the phosphor pigments

trained patterns in the authenticity check. Another advantage of the security feature is that it can not be visually perceived by humans.

The arrangement according to the invention comprises a security feature according to the invention in one of the previously described

Finishes attached to a value or security document or into a security and value document

is introduced. In addition, the arrangement comprises a smartphone, which comprises a lighting unit, an image acquisition unit and a data processing unit.

It has been found that an advantageous approach to be able to reliably measure the decaying luminescence of the phosphors after completion of the excitation processes, is to use as a detection method, a combination of single flash and serial or video recordings, the duration of the series or Video recordings of the

stimulating flash light must exceed clearly. At the same time, the recording time is based on the cooldown of the

used to adapt phosphor. At the last

Recording, ie at the last frame, the emission intensity of the phosphor should be zero as it was before flashlamp excitation. Then, this frame can be used as a reference for calculating the image differences (Bi-R; B ₂ -R;... B _n -R). The analysis of the image differences, the contrast adjustment to be made and the consideration and inclusion of further image analysis methods (histogram analysis of the different color channels) can be regarded as an essential prerequisite for detecting, with the help of the smartphone, not only the presence of a selected inventive phosphor, but at the same time as well to verify the spectral emission and the exclusive decay characteristic.

Furthermore, it has been shown that it is extremely advantageous to keep the distance between the smartphone and the security feature to be tested as low as possible during the authenticity verification of the security document. In this way, the intensity can be increased flash stimulation and the disturbing influence of extraneous light can be significantly reduced. In particular, the distance between the detection

device and the security document are chosen to be less than the shaft adjustment range of the smartphone; for the exception and verification of the diffuse luminescence signals no sharp images are needed.

For example, the smartphone must be configured with an app in such a way that at least the following steps are carried out for the verification of the security feature: In a first method step, the security feature is excited by means of the illumination unit of the smartphone, preferably by triggering a single flash of the LED flash module for luminescence, so that the security feature emits an electromagnetic radiation in the visible spectral range.

In a second method step, the decaying luminescence signals of the phosphor of the security feature according to the invention, which occur after termination of the excitation, are detected parallel to the individual lightning excitation by means of the image acquisition unit, that is to say with the aid of the camera module of the smartphone.

In a further method step, the luminescence characteristics in the captured images are evaluated by means of the data processing unit and with reference data

to verify the security feature and verify the authenticity of the security document.

Further details, advantages and developments of

Invention will become apparent from the following description of preferred embodiments of the invention, with reference to the drawings. Show it:

1 shows a schematic representation of an embodiment of a security feature according to the invention on a security document in the form of a banknote;

Fig. 2 is a schematic representation of components of an inventive arrangement for verification of

Security feature; Fig. 3 is a schematic representation of the arrival and Abkling behavior of a phosphor of the security feature in flash excitation;

4 is a flowchart for performing the verification of

 Security feature with the inventive arrangement;

5 shows an excitation spectrum of the 700 nm emission band of a phosphor according to the invention according to embodiment 1;

Fig. 6 is an emission spectrum of excited at 450 nm

 stationary photoluminescence of the phosphor according to Embodiment 1;

Fig. 7 spectral decay curves of the different

 Emission bands of an inventive phosphor described in Embodiment 1;

Fig. 8 shows a color shift over the entire visible

 Spectral range detected, decaying luminescence of the phosphor according to Embodiment 1, shown on the basis of the time course of the x-y color coordinates in the CIE standard color chart;

FIG. 9 shows emission spectra of the stationary photoluminescence of the phosphors excited at 450 nm in accordance with FIG

 Embodiments 2 and 3;

10 shows decay curves of the main emission bands of the phosphors excited at 450 nm according to embodiments 2 and 3;

1 shows a security feature 01 according to the invention, which symbolizes on a value document, namely one shown security document 02 is applied in the form of a banknote. The security feature is the authenticity proof of the security document 02. The security feature 01 here has a star shape. It is positioned below a visible feature 03, in this case the face value of the banknote. The security feature 01 consists of a means of the illumination unit of a smartphone before preferably in the blue spectral range in the ms range

decaying luminescence-stimulable phosphor, as disclosed above in the context of the description of the invention.

Fig. 2 shows a schematic representation of an arrangement for verifying the security feature 01, wherein the safety feature by means of a lighting unit 04 of an image pickup unit 06 of a mobile terminal, namely a smartphone 07, is excited to luminescence by the

Lighting unit 04 excitation light, in particular white LED flash 08 produced with a spectral maximum of about 450 nm. The flash 08 has an intensity I _A. During the excitation, the phosphor of the security feature 01 emits a stationary electromagnetic radiation in the visible spectral range, which decays in the ms range after the end of the excitation. The decaying emission I _{E of} the phosphor is detected by a camera 09 of the image acquisition unit 06 of the smart phone 07 by triggering a serial or video recording. Furthermore, the camera 09 operating as a detector detects an ambient radiation Io of the daylight or room light impinging on the security feature 01 and the banknote 02 and reflected there. The influence of the ambient radiation Io can be kept low in the inventive method, that a distance d between the security feature 01 and the smartphone 07 is kept low. Due to the small distance d, which is preferably below the focal point Area of the image pickup unit 06 is located, the smartphone 07 shields the ambient radiation Io largely from. For the reliable verification of the diffuse luminescence signals of the security feature namely no sharp Bildauf are needed.

Fig. 3 shows a schematic representation of the arrival and

Decay behavior of the phosphor used in security feature 01. The diagram shows an emission curve 11 of the luminescence-stimulated security feature 01 along a time axis t. Furthermore, a flashlamp excitation curve 12 is plotted along the time axis. When the single flash is generated by the smartphone 07 (Fig. 2), the LED flash excitation curve 12 steeply rises, holds its level for a short time, and then drops to zero in the ns to ys range. By the electromagnetic radiation of the flash light of the phosphor of the security feature 01 is excited to luminescence, wherein the emission curve 11 increases almost simultaneously with the flash light excitation curve 12. The emission of the phosphor 11 sounds after completion of the

Flash excitation 12 much slower than the exciting radiation of preferably with white emitting LED

equipped lighting unit of the smartphone. The decay time of the phosphor is according to the invention in the ms- range.

Below the time axis, individual images 13 of the security feature 01 captured by the detector 09 of the smartphone 07 (FIG. 2) are shown in FIG. The image recordings 13 show the decaying emission intensity of the security feature 01 on the basis of the decreasing with time Hellig speed of the example used star pattern. After substantially complete decay of the emission of the luminous Stoffes can be detected as the last image of the recorded image sequence, a reference image 14b. Depending on the evaluation method, an additional reference image 14a (start image) can also be recorded before the activation of the excitation radiation (triggering of the flash). Optionally, to secure the availability of a reference image required for the calculation of the image differences, a starting image 14a may already be available as an additional reference image prior to triggering the series or video recordings which are decisive for the detection of the decaying luminescence signals of the security feature

be recorded.

4 shows in a simplified form the basic sequence of the verification of the security feature 01 using the arrangement shown in FIG. 3. In one

Positioning step 41, the secure document to be verified is positioned so that it can be reliably detected by the image capture unit of the smartphone. In an optional reference check step 42, the start image 14a of the security feature is generated even before the triggering of the flashlight excitation of the smartphone. In a detection step 43, with the aid of the image recording unit

Lighting unit of the smartphone triggered a single flash and a continuous shooting or video recorded to the present after the end of the flash excitation existing and in the ms range decaying luminescence signals for the

Creation of the security feature used phosphor to record. Finally, in an emission analysis step 44, the recorded image series and the reference images are compared by means of the data processing unit. In addition to the calculation of the image differences and their analysis, other methods of image processing such as for example the contrast adjustment and the histogram analysis the different color channels used in order in this way both the spectral emission and the exclusive decay characteristics of the invention

used phosphor to verify. By comparing the calculated parameters with the authenticity parameters of the security feature preferably stored in the data memory of the smartphone, the authenticity of the checked security document can be confirmed in a release step 45. In particular, verification of the security feature on the security document can provide authenticity and security

Integrity of the security document.

Fig. 5 shows an excitation spectrum 121 of the 700 nm emission band of a phosphor according to embodiment 1. For the preparation of this phosphor are 0.2822 g CaCCb, 0.5335 g SC2 (C2O4) 3 · 10, 723H ₂ 0, 0.1803 g SiC > 2, 0.0052 g Ce0 ₂ , and 0.0358 g MnC ₂ 04 -2H ₂ 0 completely homogenized by mortars with the addition of acetone. After evaporation of the solvent, the dry powder mixture is transferred to a corundum crucible. The sample is first precalcined in a box furnace at 500 ° C for 2 h in an air atmosphere and then annealed in a furnace at 1400 ° C for 4 h in 5% H ₂ /95% N ₂ atmosphere. The resulting product is then sieved. This

Phosphorus has the formula (Ca _2, 82Ceo, 03Mn ₀ , 15) (Se, ₉₅ Mn _0, 05) S13O12. The excitation spectrum makes it clear that the exemplary inventive phosphor has a maximum spectral excitability in the range from 440 to 450 nm.

FIG. 6 shows a corresponding emission spectrum 111 of the phosphor according to exemplary embodiment 1 at 450 nm excitation. It turns out that the above about the phosphor _Z composition and the selected preparation conditions specifically

configured phosphor broadband emissions over the has entire visible spectral range. Three emission bands are visible with maxima at about 505 nm, 570 nm and about 700 nm, with the band having the highest relative intensity with a maximum of about 700 nm. As already described, these bands can be the direct luminescence of the Ce ³⁺ activator ions (Ce ³⁺ on Ca ²⁺ site), as well as the emission of the Mn ² positioned on the different lattice sites via the Ce ³⁺ - Mn ²⁺ energy transfer ⁺

Coactivators (Mn ²⁺ on Ca ²⁺ site or Mn ²⁺ on

Assign Sc ³⁺ place).

Fig. 7 shows the spectral decay curves of the individual

Emission bands. The curve 1311 is the decay curve for the

505 nm emission, curve 1312 is the decay curve for the

570 nm emission, and curve 1313 is the decay curve for the 700 nm emission. It can be clearly seen that the spectral decay curves for the individual emissions

distinguish significantly. As already explained, for the emission with a maximum of about 505 nm, a decay in the nanosecond range is found, while the

Luminescence bands with maxima of about 570 and about 700 nm cooldowns in the single-digit or double-digit

Millisecond range. In addition, it is obvious to the person skilled in the art that the individual decay curves are unlikely to proceed exponentially. Rather, the measured curves seem multi-exponential

Show decay characteristics.

Figure 8 illustrates the color shift resulting when the evanescent luminescence is visible throughout

Spectral range is detected. FIG. 8 initially shows a schematic representation of a CIE standard color block 15 of the CIE standard valence system. The CIE standard system was 1931 defines a relationship between human color perception and the physical causes of the color stimulus, and typically captures the entirety of all perceptible colors, with color perception being that of a defined normal observer. Any color or any emission spectrum of a self-illuminator is governed by a single xy coordinate in the CIE standard

displayed. The color coordinates of the luminescence signals, which are measured integrally as a function of the time of decay, are shown in FIG. 8 by reference numerals 140 to

147 elements shown. At the same time, the data determined for a phosphor according to exemplary embodiment 1 can be taken from the following table.

The color shift, which tends to lead from the green to the red spectral range, results from the superimposition of the emission bands shown in FIG

Differences and the superposition of the corresponding decay curves of the invention shown in FIG

Phosphor according to embodiment 1. The described special decay behavior contributes to a high degree Exclusivity of Ca3Sc2Si30i2 invention: Ce ^3+, Mn ²⁺ - with phosphor.

FIG. 9 shows the emission spectra 1123, 113 of the stationary photoluminescence of the phosphors excited at 450 nm according to embodiments 2 and 3. FIG

associated decay curves 132, 133 of the main emission bands of the 450 nm excited phosphors according to the

Exemplary embodiments 2 and 3.

For the preparation of the phosphor according to Embodiment 2 will be 0.2898 g CaCO> 3, 0.1362 g Sc2O3, 0.1803 g SiC> 2, 0.0130 g of Ce (N0 ₃₎ 3 .6H ₂ 0, 0, 0179 g MnC ₂ 0 ₄ -2H ₂ 0 and 1.8170 g

Tris (hydroxymethyl) aminomethane completely dissolved with stirring and heating on a hot plate in a mixture of 10 ml of nitric acid and 100 ml of water. Subsequently, the

The liquid is evaporated until the remaining gel ignites and a black foam is formed. This foam is first dried at 150 ° C in a drying oven, then finely ground and transferred to a porcelain crucible. In a first heating step, the mixture is calcined for the purpose of decomposition of remaining organic constituents for 2 h at 1000 ° C in the air atmosphere of a chamber furnace. Subsequently, this is now a white body color

Combined annealing mixed with two percent by mass of boric acid and annealed again this time for 4 h at 1300 ° C in a 5% Formiergas- atmosphere. The resulting phosphor has the composition (Ca2, ₈₉ sCeo, 03Mn ₀ , 075) (Se, 9 ₇₅ Mh _0, 025) SZ3O12. The curve 112 in FIG. 9 shows the emission spectrum of this phosphor. In FIG. 10, the curve 132 denotes the decay curve for this preferably in the green

Spectral region emitting phosphor. For the preparation of the phosphor according to embodiment 3 with the composition (Ca _{2, 7} 45Ce _{0, 0} 3Mn ₀ , _{225) (} Sei _{, 925} Mn _{0, 075)} Si ₃ 0i ₂ are 0.2747 g CaCCg, 0.1227 g Sc ₂ C> 3, 0.1803 g Si0 _2, 0.0130 g of Ce (NO3) 3 · 6H ₂ 0, 0.0537 g MnC ₂ 0 ₄ -2H ₂ 0 and 1.8170 g of tris (hydroxymethyl) aminomethane with Stir and heat in a mixture of 10 ml of nitric acid and 100 ml of water. The liquid is then evaporated until the resulting gel ignites. The resulting black foam is dried at 150 ° C in a drying oven, then finely mortared and transferred to a porcelain crucible. After a first

two-hour annealing at 1000 ° C in the air atmosphere of a chamber furnace and the subsequent addition of two percent by weight of boric acid to the cooled annealing a renewed four-hour thermal treatment at 1100 ° C in a 5% Formiergas atmosphere. The measured at 450 nm excitation emission spectrum of the resulting phosphor is shown in the curve 113 of FIG. 9, the associated

Decay curve is the curve 133 of FIG. 10 can be seen.

The two exemplary embodiments and the associated figures once again clearly show that the Ca3Sc ₂ Si30i ₂ : Ce ³⁺ , Mn ²⁺ phosphors are a particularly suitable class of phosphors for the formation of a security feature according to the invention. Omposition by varying the fluorescent _Z and the preparation conditions can be numerous exclusive phosphor compositions with different decay and distinguishable

Emission spectra and create a very high level of security and authenticity for this reason. The exclusive properties of the luminescent materials that can be used to protect value and safety documents in the form of security features can be securely verified with the help of standard smartphones. LIST OF REFERENCE NUMBERS

01 security feature

 02 Security document / banknote

 03 nominal value

 04 lighting unit

 05

 06 image recording unit

 07 Smartphone

 08 flashlight

 09 camera / detector

 10

 11 emission curve

 12 flash light excitation curve

 13 Image of the security feature 01 14a Start image

 14b Reference image

 15 CIE standard color chart

41 45 process steps

111 emission spectrum of the phosphor according to

 Embodiment 1

 112 emission spectrum of the phosphor according to

 Embodiment 2

 113 Emission spectrum of the phosphor according to

 Embodiment 3

 121 excitation spectrum of the phosphor according to

 Embodiment 1

 1311 Decay curve for the 505 nm emission of the phosphor according to embodiment 1

 1312 Decay curve for the 570 nm emission of the phosphor according to embodiment 1

 1313 Decay curve for the 700 nm emission of the phosphor according to embodiment 1

 132 Decay curve of the predominantly green emission of the

 Phosphor according to embodiment 2

 133 Decay curve of the predominantly green emission of the

 Phosphor according to embodiment 3

 140 147 x-y color coordinates of the decaying integral

 Luminescence of the phosphor according to

 Embodiment 1

Claims

claims 1. Smartphone-verifiable security feature with one  Phosphor which is exposed to visible electromagnetic radiation generated by a smartphone  Luminescence is excitable and after completion of the excitation over a decay time in the range 1 ms to 100 ms a  Emission shows which is detectable by means of an image capture unit of the smartphone. 2. Security feature according to claim 1, characterized in that the phosphor is selected from the following group: (CAI _xy Ce _x Mn _{y) 3 (Sci_ z /} Mn _{z) 2} Si ₃ 0i _2;  with 0 <x <0, l; 0 <y <0.8; and 0 <z <0.8; and y / z ~ 2; Ca ₃ Sc ₂ Si ₃ 0i ₂ : Ce ³⁺ , Mn ²⁺ . 3. Security feature according to claim 1 or 2, characterized in that the phosphor after completion of the excitation, a cooldown of 1 ms to 50 ms, preferably a  Decay time of 10 ms to 30 ms, in which its emission in the visible spectral region has a luminescence characteristic that is detectable by the image acquisition unit of the smartphone. 4. Security feature according to one of claims 1 to 3, characterized in that the emission and the decay time of the phosphor is selected based on the spectral and temporal resolving power so that it is not visually perceptible by humans. 5. Security feature according to one of claims 1 to 4, characterized in that the phosphor can be excited by means of a white light emitting flash LED of the smartphone for luminescence. 6. Security feature according to one of claims 1 to 5,  characterized in that the phosphor exhibits emission during the decay time with maxima in the range from 470 nm to 500 nm and / or from 650 nm to 750 nm. 7. Security feature according to one of claims 1 to 6,  characterized in that the phosphor as a  Fluorescent mixture is configured, the phosphor components after completion of the excitation have different, sensory distinguishable cooldowns. 8. Security feature according to claim 7, characterized in that the phosphor mixture in UV excitation  contains luminescent, rapidly evanescent phosphor, its visually perceptible stationary photoluminescence as a masking of the emission of the as a security feature  serving phosphor acts. 9. Security feature according to one of claims 1 to 8,  characterized in that the phosphor is formed as a processable in a printing process phosphor pigments. 10. Security feature according to claim 9, characterized in that the phosphor pigments depict a predetermined pattern in the security feature. 11. An apparatus for verifying a security document (02), comprising:  a security feature (01) attached to the security document (02), containing a phosphor excitable for emission, and designed according to any one of claims 1 to 10,  a smartphone (07) with a lighting unit (04) for exciting the phosphor of the security feature, with a camera (09) for detecting the emission of the phosphor after completion of the excitation during a predetermined decay time by taking a pictures serie and with a data processing unit for evaluating the Series of pictures, whereby the emission recorded during the cooldown is stored with  Reference values to verify the security document. 12. The arrangement according to claim 11, characterized in that an application (App) on the smartphone (07) is installed, which controls the lighting unit (04), the camera (09) and the data processing unit. 13. Arrangement according to claim 11 or 12, characterized in that the recording time for recording the series of images is chosen so that the last image of the series of pictures is taken after the end of the cooldown, the security document (02) only verified as real becomes, if in this last picture no emission of the phosphor is detectable. 14. Arrangement according to one of claims 11 to 13, characterized  in that the distance between the smartphone and the security document to be checked is selected to be less than or equal to the focusing range of the smartphone.