RU2359328C2 - Method for counterfeit protection and authentication of valuables - Google Patents

Abstract

FIELD: physics, alarm.

SUBSTANCE: invention is related to methods for counterfeit protection of valuables and may be used for counterfeit protection of museum valuables, including paintings, jewellery, and also costly medications, intellectual property objects, banknotes, credit and other securities, and also for provision of possibility for their further authentication with application of technical facilities. In process of method realisation, on valuable item passive protective facility of specified structure is created, and possibility is provided for its authentication and detection of availability. Material of passive protective facility used represents particles of nanosize level substance, at least of three different sizes, at that possibility for control of availability and authentication of protective facility is provided by method of analysis by optical effects in process of external action of probing electromagnet radiation of visible optic range and detection of informative criteria in optic response of protective facility to mentioned external action with further visual and automatic comparison of registered parametres of informative criteria to informative criteria contained in database of detection facility. Material of nanosize level particles is silicon or porous silicon. Probing electromagnet radiation used is laser radiation readjusted in frequency and power in near infrared and visible optical range of wave lengths. Detected informative criteria used are represented by contrast photoluminescence of protective mark elements.

EFFECT: provides for guaranteed counterfeit protection of valuables and provides for possibility to determine their authenticity with the help of simple technical facilities.

5 cl, 4 dwg

Description

The invention relates to methods for protecting valuable products from counterfeiting and can be used to protect against museum counterfeit property, including paintings, jewelry, as well as expensive medicines, intellectual property, banknotes, credit and other securities, as well as to enable subsequent determining their authenticity using technical means.

Technical solutions of a similar nature are well known in the art.

So, from the prior art, individual means of protecting documents are known in the form of perforations, the pattern of which has recognizable irregularities. The perforation is carried out using a laser beam, based on the usual drawing, while the laser is controlled by a computer in such a way that each perforation has an individual irregularity depending on the initial value, see, for example, description of application DE No. 0368353, B44F 1/12, 1988 [1].

The disadvantages of this method can be attributed to the fact that they can be quite easily reproduced with a high degree of compliance with the original using modern means, widely known and available to a wide range of specialists.

So the prior art method of protection against counterfeiting and authenticity control of valuable products, disclosed in the description of the patent of the Russian Federation No. 2074420, G07D 7/00, G01N 24/08, 02/27/1997 [2]. The method consists in introducing into the material of the protected object or applying a mark on it, which is used as a stable isotope osmium-187 or its compound, and the determination of its presence is carried out by nuclear magnetic properties. The introduction into the material of the protected object or the deposition of the stable osmium-187 isotope on it can be carried out in a chemical compound that provides constant orientation of the magnetic moments of the electron shells of osmium-187 atoms. This method allows you to simplify and reduce the cost of protection against counterfeiting banknotes, securities and documents while ensuring a high degree of security.

However, from the prior art there is a known method of protection against counterfeiting of valuable products, disclosed in the description of the patent of the Russian Federation No. 2144216, G07D 7/00, G07D 7/06, G06K 19/08, 10.01.2000 [3]. According to this method, an isotopic indicator based on a mixture of stable isotopes is used as a means of protection. A protective label is formed by the said isotope indicator in such a way that it is possible to control its presence on the protected product (upon detection) by at least one of the spectral analysis methods (for example, X-ray fluorescence or luminescent methods). This security tag can be formed directly on the protected product or independently of it in any known form and using known technologies.

In addition, technologies of a similar purpose disclosed in the descriptions of foreign security documents, for example, GB 1193511, JP 9119867, US 4533244, are known from the prior art.

Also known from the prior art is a method of protection against counterfeiting and authenticity control of valuable products, disclosed in the description of the patent of the Russian Federation No. 2276409, G07D 7/06, G06K 19/14, 05/10/2006 [4] (the closest analogue). According to this method, a passive protective means of a given structure is formed on the product, which provides the ability to control the presence and authenticity of the said means by a physical method for analyzing resonance effects during external exposure to it by probing electromagnetic radiation of a given radio frequency and detecting parameters of certain informative features in the resonant response of the protective means to mentioned external impact followed by automatic matching registered OF DATA parameters of these informative features with reference values. As a passive protective agent, a metallized at least three-layer resonant filter structure is used. The microwave frequency is used as the probing radiation, and characteristic peak values of the frequency response of the direct transmission and back reflection coefficients are used as informative signs.

The disadvantages of all of the above analogues should include their lack of reliability. This is due, first of all, to the fact that the current level of development of computational, analytical and multiplying equipment allows reproducing with a high degree of identity almost any security paper in unlimited quantities at a relatively low material cost.

The problem to which the invention is directed is to increase the level of reliability of protection against counterfeiting and copying valuable products.

When implementing this invention, several technical results are achieved, one of which is to increase the degree of complexity of a protective agent on a valuable product while reducing the possibility of counterfeiting, copying, changing it.

This problem is solved by the fact that in the method of protection against counterfeiting and authenticity of valuable products on a valuable product form a passive protective agent of a given structure, provide the ability to control its presence and authenticity, while particles of a substance of nanoscale level, at least, are used as a material of a passive protective agent at least three different sizes, while the ability to control the presence and authenticity of the protective agent is provided by the method of analysis of optical effects in the process of external the action of probing electromagnetic radiation of the visible optical range on it and the detection of informative features in the optical response of the protective agent to the mentioned external influence, followed by visual and automatic comparison of the recorded parameters of the informative features with the informative features contained in the database of the detection tool.

At the same time, silicon or porous silicon can be used as a substance of particles of a nanoscale level.

In addition, it is possible to use laser radiation tunable in frequency and power in the near infrared and visible optical wavelength ranges as probing electromagnetic radiation.

In addition, as detectable informative features, it is possible to use contrast photoluminescence of security label elements.

The invention is based on the following principle. The essence of the method is to use the physically unique optical properties of silicon particles of nanoscale level and porous silicon to identify the authenticity of valuable products [1, 2, 3]. The term “unique” by physicists means properties that are not characteristic of either bulk substance or the molecules and atoms of which the bulk substance consists.

These physically unique properties are:

- strong photoluminescence of nanoparticles at room temperature (about 300K),

- the dependence of the photoluminescence spectrum on the size of the nanoparticles ("blue" shift),

- frequency shift of the spectral lines of excitation and photoluminescence,

- dependence of the intensity of photoluminescence on the power of the probe radiation.

As you know, luminescence is the absorption of energy by a substance with its subsequent re-emission in the visible or close to the visible range [1].

The luminescence of a substance can be excited by exposure to energy sources of various physical nature (light, electricity, heat, etc.). The method under consideration involves the use of laser radiation energy in the near IR and visible wavelength spectra to excite luminescence, therefore, the term “photoluminescence” corresponding to the physics of the phenomenon is used below.

Ordinary silicon has a weak photoluminescence between 0.96 and 1.20 eV, i.e. at energies close to the band gap of 1.125 eV at room temperature. Such photoluminescence in silicon is a consequence of electron transitions through the band gap. However, nanosized silicon particles exhibit strong light-induced photoluminescence with energies noticeably greater than 1.4 eV at 300 K (see FIG. 1). The position of the peak in the emission spectrum is determined by the size of the nanoparticles [1, 2, 3].

Interest in nanoparticles is due to the strong influence of their size on optical properties. For example, there is a so-called “blue” shift, i.e. shift of spectral lines towards higher energies with a decrease in the size of nanoparticles.

An illustration of this effect is the photoluminescent emission spectra (see FIG. 3) of seven quantum dots with sizes from 1.5 to 4.3 nm [1].

A quantum dot is a nanoparticle with nanoscale sizes across all three dimensions. The epithet “quantum” is used due to the subordination of the properties of such nanoparticles to the laws of quantum mechanics.

In the general case, the photoluminescence excitation technique can consist in scanning the frequency of the exciting light and detecting the emission in a very narrow spectral range. Figure 2 illustrates the excitation and photoluminescence spectra of CdSi nanoparticles with a size of 5.6 nm [1]. It is important to note the observed frequency shift of the spectral line of excitation relative to the spectral line of photoluminescence.

In this case, excitation by high-energy photons (greater than the width of the energy gap) can be most effective in studying the photoluminescence of bulk materials. However, in the case of nanomaterials, it was found that, at high incident photon energies, the photoluminescence efficiency decreases. In this case, nonradiative excitation relaxation paths begin to dominate.

The following is a description of the graphic materials, in no way limiting all possible embodiments of the invention.

Figure 1 illustrates the dependence of the photoluminescence intensity of porous silicon nanoparticles on the time of electrochemical etching of a silicon wafer, which determines the size of the nanoparticles. The smaller the size of the nanoparticles (shorter etching time), the higher the intensity of photoluminescence [1, 2].

In figure 2. The spectra of quantum dots from CdSe 5.6 nm in diameter at a temperature of 10 K are shown: a) absorption spectrum (solid line) and photoluminescence (dashed line) obtained upon excitation at 2.655 eV (467 nm); b) the excitation spectrum obtained at the emission frequency shown by the down arrow in the upper graph. A frequency shift of the spectral line of excitation relative to the spectral line of photoluminescence is observed [1].

In figure 3. normalized photoluminescence excitation spectra for seven quantum dots with sizes from 1.5 nm (upper spectrum) to 4.3 nm (lower spectrum) are given [1].

Figure 4 presents an example block diagram of a device for detecting a security tag and verifying its authenticity. The following abbreviations are used to indicate blocks:

PL - tunable laser

UCHI - a device for controlling the frequency of submarine radiation

LL - laser beam,

OL1, 2 - optical lenses 1 and 2,

OF - optical filter,

UUOF - PF control device,

UOF1, 2, 3 - narrow-band OF 1, 2 and 3, respectively,

UUUOF - control unit UOF 1-3

EMC1, 2 - electromechanical systems 1 and 2 of the "inclusion" OF and

UVF 1-3 respectively

ЗМ - protective label (barcode),

ZI - protected product,

ZLI - probing laser radiation,

PHISM - photoluminescent image of a protective label,

XRF - recording equipment,

EVU - electronic computing device,

MEVU - EVU monitor,

BDSHZM - database of security label templates.

As an example of a possible principle for the formation of a security label, the use of a barcode made using one, two or three nanoparticles of substantially different but selected sizes can be considered. The mentioned barcode can contain information, for example, about the denomination of a banknote, series and number indicating the year of issue, etc., duplicated or tripled for further detection by two or three sizes of nanoparticles, respectively.

The authentication of the security label is carried out in two stages.

First step.

When exposed to the indicated label of the probe laser radiation with a frequency and power characteristic of exciting the photoluminescence used in the formation of the barcode of the nanoparticles, a contrast photoluminescent image of the barcode appears on one, second and third “resonant”, i.e. causing photoluminescence, the frequency of the exciting laser radiation (in the case of using three sizes of nanoparticles).

Second phase.

When exposed to the indicated label of the probe laser radiation with a frequency characteristic of the photoluminescence excitation used in the formation of the barcode of the nanoparticles, but with an increased power, the contrast of the photoluminescent image of the barcode decreases or it almost completely “disappears” from the protected object due to an increase in the number of nonradiative excitation relaxation paths.

The suppression of the background illumination at the radiation frequency of the laser exciting the photoluminescence is ensured by the use of narrow-band (for example, diffraction) optical filters.

To implement the considered method of protecting valuable products, in particular, banknotes, credit documents and other securities, choose the structure of the security label that is most suitable for the protected device. Various known from the prior art options and methods for forming and applying a protective label can be used.

Since specific methods of applying images, for example, to banknotes of various denominations, are protected by the state, and their choice does not limit the scope of the proposed method, we assume that the security label is in the form of the above barcode, which is applied to the protected object with a stamp, screen or other in a known manner. By the way, the stability of the image made using nanoparticles on the surface of the paper itself is high. This phenomenon can be explained by their deep penetration into the structure of the material. Guaranteed durability of a protective label based on nanoparticles can be obtained by using various types of plasticizers at various stages of the manufacture of protected objects, primarily banknotes, credit and other securities.

The current state of the art makes it possible to carry out equipment for a protective mark detection device both in stationary and portable versions. An embodiment of a block diagram of a device for authenticating a protected object is shown in FIG. 4.

As submarines, for example, Al ₂ O ₃ : Ti ³⁺ and forsterite crystals (Mg ₂ SiO ₄ : Cr ⁴⁺ ) can be used to convert the lasing energy of the fundamental frequency and second harmonic YAG (YLF ): Nd lasers with a modulated Q-factor of the resonator into tunable narrow-band radiation of the near IR, ultraviolet, and visible spectral regions [4].

In principle, instead of a tunable laser, several independent lasers can be used, the number and frequency of radiation of which should correspond to the number of standard sizes used to create ZM nanoparticles.

The control of the laser radiation power and the suppression of background illumination at the radiation frequency of the laser exciting the photoluminescence can be performed, for example, by introducing the appropriate optical (dimming and narrow-band) filters into the optical circuit.

As photoluminescence recording photographic equipment, for example, a digital camera similar to that used for fingerprinting (see above) or another device, for example, based on charge-coupled devices (CCD), can be used.

Optical elements: lenses, a filter to attenuate the power of laser radiation and narrow-band, for example diffraction, filters have no special features.

The sequence of operation of the detection device ZM in accordance with the previously described steps and the identification of the authenticity of the program provides the EVU.

Let nanoparticles of three sizes be used to form ZM. To identify the ZM, the protected product is placed in a device for its detection. The initial state of the OF optical filter is “on”, i.e. it was installed using EMC1 along the path of the LL (position 1a in Fig. 4), as a result of which the radiation power of the submarines is reduced to a working level that provides the required photoluminescence intensity of the nanoparticles.

The first stage of identification of ZM.

An electronic computing device generates a signal of the first "level", which enters the UCHI of a tunable laser. As a result of this, UCHI provides parameters of the PL at which the frequency of its radiation corresponds to that necessary for the excitation of photoluminescence of nanoparticles of the first size. In this case, OL1 is designed to disperse LL to the surface of the ZM, and OL2 ensures the operation of the XRF.

“On” (position 1b in FIG. 4), using EMC2 and UUUOF, the UVB narrowband filter UV1 is configured to transmit the photoluminescence wavelength of first-size nanoparticles, which provides a “cut-off” of background radiation with a laser generation frequency that excites the photoluminescence of these particles. A photographic equipment recording a photoluminescent image of a ZM in a known manner converts it into a digital one, which is fed to an EVU. In the EVU, a correlation comparison of the digital image of the ZM with the corresponding template stored in the BDSM takes place. At the same time, a digital image of the ZM is displayed on the EVU monitor for visual control and comparison with the templates given in the relevant instructions or with the templates already mentioned, the image of which can also be displayed on the EVU monitor.

Then the EVU sequentially generates the signals of the second and third “levels” at the input of the LEARNING, while at the same time providing UV2 and then UV3 through the UVUF and EMC2. In this case, the process of correlation comparison is repeated a second and third time.

The results of the first stage can be the following:

- there is no photoluminescence of ZM,

- a contrast photoluminescent EM image is recorded at all excitation frequencies.

The first result indicates that the ZM on the protected product is either absent or made using non-nanoparticles or nanoparticles of other sizes. The second result for the first stage is positive.

The second stage of identification of ZM.

The electronic computing device generates a signal that is fed to the input of the UMI. In accordance with this signal, EMC1 “turns off” the OF, removing it from the LL path (position 2a in Fig. 4), and the power of the probe laser radiation increases.

The identification process described above is sequentially repeated a fourth, fifth, and sixth time.

A positive result of the second stage is a noticeable decrease in contrast or the disappearance of the photoluminescent image of ZM for each of the excitation frequencies. Additional control is provided by visual observation of the contrast changes in the photoluminescent image on the MEA.

Thus, the application of the proposed method, based on the use of physically unique optical properties of particles of a substance of nanoscale level, provides guaranteed protection of valuable products from counterfeiting and the possibility of subsequent determination of their authenticity with high reliability both visually and automatically using technical means.

Literary sources

1. C. Pool, F. Owens. The world of materials and technology. Nanotechnology. M., Technosphere, 2004.

2. P.K. Kashkarov. Unusual properties of porous silicon. Soros Educational Journal, Volume 7, No 1, 2001.

3. S.P. Zimin. Porous silicon is a material with new properties. Soros Educational Journal, Volume 8, No 1, 2004.

4. Production of the LOTIS company (Lasers - Optics - Technology and Systems) at the Institute of Physics of the Academy of Sciences of Belarus.

Claims (5)

1. A method of protecting against counterfeiting of valuable products and controlling their authenticity, in which a passive protective label of a given structure is formed on a valuable product, it is possible to control its presence and authenticity, characterized in that particles of silicon or nanosized silicon are used as the material of the passive protective label level of at least three different sizes, while the ability to control the presence and authenticity of the protective mark is provided by the method of analysis according to the effects of luminescence in the process of external actions of probing electromagnetic radiation of the visible optical range on it and detecting informative signs of the protective mark in its optical response to the mentioned external influence, followed by visual and automatic comparison of the registered parameters of the informative signs of the protective mark with the informative signs contained in the database of the detection means, and probing electromagnetic radiation form, for each size, nanoparticles of said substance at first with frequency and power, characteristic for the excitation of luminescence of a nanoparticle of the corresponding size, and then with an increased power, providing a decrease in the contrast of luminescence. 2. The method according to claim 1, characterized in that the laser radiation in the near infrared and visible optical wavelength ranges is used as a probe electromagnetic radiation. 3. The method according to claim 1, characterized in that the contrast photoluminescence of the security label elements is used as detected informative features. 4. The method according to claim 1, characterized in that the contrast photoluminescence of the security label elements is used as detected informative features. 5. The method according to claim 2, characterized in that the contrast photoluminescence of the security label elements is used as detected informative features.

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