RU2635212C2 - Method of protecting documents, securities or articles by using semiconductor filamentary nanocrystals - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: in the method, a label is placed in or into the security document, security paper or article containing semiconductor filamentary nanocrystals with the predetermined parameters that can be detected by using various detecting devices. The heterostructured filamentary nanocrystals thus obtained are made on the basis of a combination of materials with different forbidden bands, as well as structures with a combined dimension such as quantum dots inside the filamentary nanocrystals, which will ensure that these documents can be encoded by using them, as well as the simplicity of verification.

EFFECT: increasing the security of these documents and articles and simplifying the procedure for the authenticity verification.

4 cl, 2 dwg

Description

The invention relates to the field of protection of products, securities and documents. A method of protecting documents, securities and products using semiconductor whisker nanocrystals is that a label is inserted or applied to the security document, security paper or product that contains semiconductor whisker nanocrystals with predetermined parameters that can be detected using various detecting devices .

The trend towards continuous improvement of effective technological means of protecting securities, documents and products has not yet lost its relevance and is inextricably linked to the development and accessibility of methods for faking them. For example, the advent and widespread use of laser digital printing made it necessary to have several additional degrees of document protection, as traditional printing methods began to lose their significance. Today, there are various ways to protect documents and securities, based on the use of completely different technological approaches. The use of special grades of paper, including those with built-in protective elements, such as metal threads, ferromagnetic elements, etc., can now be sufficiently imitated. The ongoing development of printing technology, primarily microprinting, also no longer provides much protection. Of particular interest are the methods associated with the creation of new types of ink and inks used to protect documents. The introduction of nanoparticles with certain optical or magnetic (in the case of using ferromagnetic materials) properties into their composition can represent significant advantages over other methods of protection. However, these protection methods can also be reproduced, since they usually have a certain specific response depending on the materials used. For example, the possibility of using osmium isotopes or nanodiamonds with active NV centers for coding documents is currently being widely discussed. The presence of a certain band in the radiation spectrum, in the case of nanodiamonds, in fact, represents a unique signature of the document. However, it cannot be changed, and therefore, there is a non-zero probability of its copying. In turn, the development of labels based on semiconductor whisker nanocrystals (NOCs) opens up great opportunities for creating labels for specific customer requirements. Varying the technological parameters during the synthesis of NWs allows one to obtain NWs, on the one hand, with certain geometric dimensions, which also allows varying degrees of protection, and on the other, various physical properties. A wide spectral range of NW radiation, which can be obtained by varying the materials used - from ultraviolet to terahertz units, allows you to create labels with predetermined optical properties. Including a combination of different NWs in one label under different spectral ranges is possible. Synthesis of heterostructures based on NWs, i.e. the combination of materials with different forbidden zones, as well as structures with a combined dimension such as quantum dots inside the NOC also provides broad prospects for coding documents, while it becomes possible to create unique degrees of protection for a particular document. Thus, the implementation of security labels based on NOCs represents a fundamentally new approach that can significantly change the degree of security of securities, documents, and products.

Closest to the proposed method of protecting documents, securities or products using semiconductor whisker nanocrystals and adopted as prototypes of the present invention are the following methods.

PCT International Application for the Invention “Luminescent Ink and Methods of Authenticating Products” (WO 2013/066202 (PCT RU 2012/000132), IPC C09K 11/08, B44F 1/12, B82B 1/00, B82B 3/00, B82Y 40 / 00, B82Y 99/00, C09D 11/16, D21H 21/48, publ. 05/10/2013).

The invention relates to compositions for coating, namely, printing inks containing luminescent protective inks for the cryptographic protection of documents and products from fakes, to methods for their application, as well as to methods for verifying the authenticity of documents and products containing luminescent ink. Depending on the method of cryptographic protection, and / or the material of the product, and / or the method of applying a protective mark on the surface, luminescent inks contain various types and amounts of semiconductor nanocrystals, solvents, and surfactants. To verify the authenticity of documents and products containing a visible and / or invisible eye protective label, sources of visible or ultraviolet radiation are used, followed by identification of the fluorescent signals described in the reference document during visual determination or available in the database during machine determination. The implementation of the methods provides additional protection for twenty years and the ability to assess the authenticity of documents and products by simple technical means.

The disadvantage of the described invention is that despite the claimed document protection period of about 20 years, usually semiconductor quantum dots obtained by chemical synthesis have a fairly low photostability. This can lead to rapid degradation of the optical properties of structures. The proposed solution involving the use of silicone compounds may lead to a restriction when using this class of protective labels. In addition, the sizes of the quantum dots under consideration lie in the nanometer range, which makes it difficult to detect them without using transmission electron microscopy methods, which cannot be used for simplified verification of objects.

RF patent for invention No. 2503705 “Luminescent ink for cryptographic protection of documents and products from counterfeits, the method of their application, as well as methods for verifying the authenticity of such products” (IPC C09K 11/08, C09D 11/16, B44F 1/12, D21H 21/48 , B82B 1/00, B82B 3/00, B82Y 40/00, B82Y 99/00, publ. 10.01.2014).

The invention describes coating compositions, namely, printing inks containing luminescent protective inks for cryptographic protection of documents and products from counterfeit, methods for their application and methods for checking the authenticity of documents and products on which such luminescent inks are applied.

Luminescent protective inks contain a solvent and semiconductor nanocrystals dispersed in an organosilicon compound, consisting of sequentially arranged: semiconductor core 1, first 2 and second 3 semiconductor layers, as well as an outer 4 layer, the material of which is selected from an organosilicon polymer from a series including poly (aminoethyl ) trimethoxysilane, poly (methacryl) triethoxysilane, poly (methyl) triethoxysilane, poly (mercaptoethyl) trimethoxysilane, methyl phenyl polysiloxane, polyethoxysilane (Fig. 2). Semiconductor nanocrystals emit a fluorescence signal in the fluorescence wavelength range from 400 to 3000 nm under the influence of a visible or ultraviolet light source, the relative fluorescence quantum yield is not less than 80%. On the basis of luminescent protective ink, a protective mark is made, with the help of which the authenticity of the product is controlled by simple means. Provides additional protection for twenty years.

The disadvantages of this invention include the items listed in the analysis of the previous patent.

RF patent for invention No. 2530238 "Method for creating hidden luminescent labels" (IPC G06K 7/10, B82B 1/00, publ. 10.10.2014).

The invention relates to means for marking products, in particular to the manufacture of protective labels that can be used for covert marking of various objects in order to prevent unauthorized production of these objects and simplify the process of verifying their authenticity. The technical result is to increase the degree of protection of the marking. The method is based on the introduction of quantum nanorods into the track pores of polymer membranes and consists in creating photoinduced anisotropy of luminescence in the layer of nanorods. For this, in linearly polarized light, a selective effect of light of a certain wavelength on a part of the nanorods is carried out, the spatial orientation of which in the sample coincides with the direction of the electric vector of light acting on the sample. Thus, the problem of simplifying the manufacturing method, expanding the technological approach and reducing the accuracy requirements for monitoring the parameters of hidden labels with polarizing contrast in the process of their manufacture is solved.

The disadvantage of the described invention is not only the spread in the parameters of the pores and, as a consequence, the parameters of the nanorods, but also the problems associated with the direct formation of hidden labels based on this type of complex materials.

The problem solved by the present invention is the development of a new method for the protection of documents, securities and products.

The technical result that allows you to complete the task is to increase the reliability of protection of securities, documents, materials and various products.

The technical result is achieved due to the fact that in the protected document, security paper or product, a mark is inserted or applied, which contains semiconductor whisker nanocrystals with predetermined parameters that can be detected using various detecting devices. The proposed method is based on the fact that when changing the technological parameters of the synthesis, whisker nanocrystals can be obtained not only with certain geometric sizes (lengths from hundreds of nanometers to tens of micrometers), which also allows you to vary the degree of protection, but also a variety of physical properties. A wide spectral range of NW radiation, which can be obtained by varying the materials used - from ultraviolet to terahertz units, allows you to create labels with predetermined optical properties. Including a combination of different NWs in one label under different spectral ranges is possible. For example, a label can be made based on GaN NWs that emit in the UV spectral range. In turn, AlGaAs or InGaN are visible, while GaAs, InP, or InAs NWs have features in the IR range. Synthesis of heterostructures based on NWs, i.e. the combination of materials with different forbidden zones, as well as structures with a combined dimension such as quantum dots inside an NOC (for example, a GaAs quantum dot in an AlGaAs NOC), also provides broad prospects for coding documents, while it becomes possible to create unique degrees of protection for a particular document. Different types of whisker nanocrystals can be used in a single security label, which also increases the degree of protection. The direct synthesis of NWs can be carried out using various techniques, such as molecular beam epitaxy (MPE), gas phase epitaxy from organometallic compounds (HFEMO), etc. (see Fig. 1).

It should be noted that NWCs can be grown on semiconductor substrates used repeatedly after special processing procedures.

By simple operations, for example using the ultrasonization method, NWCs can be transferred from the substrates on which they were grown and placed in a solution (see Fig. 2). Based on the resulting solution, special labels can be made to protect products, securities and documents. Moreover, the content in the solution of NWs with different physical properties allows you to get tags with a high degree of protection of objects. Verification of the authenticity of documents, securities and products can be based on the use of various physical techniques (optical, x-ray, etc.).

FIG. 1 - schematically presented stages of the growth of whiskers by the mechanism of fatty acids. (a) preparing a semiconductor substrate, (b) applying a thin layer of a metal catalyst (most often gold), (c) forming an array of droplets — growth nuclei by thermal annealing of the sample, (d) the initial stage of growth of whiskers, (d ) - whiskers grown on a semiconductor substrate.

FIG. 2 is a diagram of creating solutions with whisker nanocrystals. (a) a substrate with synthesized whisker nanocrystals; (b) a solution with a sample placed; (c) a solution with whisker nanocrystals after the process of ultrasonization and removal of the substrate.

The process of forming semiconductor NWs using the mechanism of "vapor-liquid-crystal" (PZHK) is implemented in two stages. At the first stage, the preparation of the substrate is carried out, including purification from natural oxide, deposition of the buffer layer, etc. (Fig. 1a).

Then, a thin film of the catalyst metal can be deposited onto the prepared substrate (Fig. 1b) for its subsequent thermal annealing in order to create an array of drops of the eutectic solution from the catalyst atoms and the semiconductor substrate (Fig. 1c). An array of droplets can also be formed without first spraying a thin film of metal. To do this, it is sufficient to carry out the deposition of catalyst atoms on a heated substrate or to use dispersed metal particles. It is important that the drops do not wet the surface, which is a necessary condition for the nucleation of whiskers. It should be noted that the diameter of the NWC will correlate with the size of the droplets of growth catalysts. At the last stage, there is a direct growth of whiskers (Fig. 1d, d). By varying the composition of materials during the formation of NWs, it is possible to obtain NWs with built-in quantum dots, radial and axial p-n junctions, etc., possessing the required geometric dimensions, shape, and physical properties. At the same time, it becomes possible to create unique degrees of protection for a specific document.

Using the ultrasonization method, NWs can be transferred from the substrates on which they were grown and placed in a solution of both deionized water and ethyl alcohol (see Fig. 2).

Based on the resulting solution, special labels can be made to protect products, securities and documents. Mixing solutions with whisker nanocrystals with different physical (optical) properties will significantly increase the degree of protection of documents.

Claims (4)

1. A method of protecting documents, securities and products using semiconductor whisker nanocrystals, which consists in the fact that a security document, security paper or product is introduced or applied a label that contains semiconductor whisker nanocrystals with predetermined parameters that can be detected using various detecting devices. 2. A method for protecting documents, securities and products using semiconductor whisker nanocrystals according to claim 1, characterized in that when changing the technological parameters of the synthesis, whisker nanocrystals with various geometric sizes ranging from hundreds of nanometers to tens of micrometers can be obtained. 3. The method of protecting documents, securities and products using semiconductor whisker nanocrystals according to claim 1, characterized in that the synthesis of heterostructures based on whisker nanocrystals includes combinations of materials with various forbidden zones, as well as structures with a combined dimension such as quantum dots inside whisker nanocrystals. 4. A method for protecting documents, securities and products using semiconductor whisker nanocrystals according to claim 1, characterized in that different types of whisker nanocrystals are used in one security label.

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