RU2790680C1 - Hidden marking method - Google Patents

Abstract

FIELD: luminescent compositions.

SUBSTANCE: luminescent compositions based on β-diketonates of boron difluoride, suitable for hidden marking of material objects. The method of hidden marking is proposed, which consists in the formation of a film containing polycarbonate and 0.05-1 wt.% of diarylmethanate or arylacetonate of boron difluoride by the solution method, followed by applying a protective image by irradiating the film with a source of high-intensity UV radiation in the range of 360-410 nm and subsequent verification of the image.

EFFECT: proposed method for marking polymer films, in which marking and activation of a luminescent dye does not require the use of technically complex equipment, and identification of protective marking is possible using a compact ultraviolet flashlight or UV lamp.

1 cl, 1 dwg, 1 tbl, 11 ex

Description

The invention relates to luminescent compositions based on boron difluoride β-diketonates, suitable for hidden marking of material objects and can be used to determine the authenticity of goods.

Smuggling and counterfeit trade affect a variety of goods and influence the economic development of many countries. Manufacturers that operate within the legal field are looking for ways to combat this threat. One of the effective methods of such struggle is covert labeling, which helps to track products at all stages of the life cycle. This allows you to reliably determine the ownership of products and can be used to prove the fact of unfair competition.

To protect against counterfeiting, luminescent inks designed for hidden marking are actively used. They can be either visible to the naked eye, disguised as ordinary ink, or completely transparent, but luminescent under the influence of electromagnetic radiation of a certain wavelength. The advantage of using luminescent ink is that manufacturers can put their own invisible characters on tax stamps, labels or paper packaging of goods without risking confusion with the main marking, or protect themselves from competitors' claims due to counterfeit products that visually resemble the original. . The method of marking includes the application of luminescent substances invisible to the naked eye in the composition of the ink by means of typographic printing on documents, labels or packaging protected from forgery. Verification is carried out under certain illumination visually or using devices for recording luminescence.

Rare earth elements are widely used to ensure the luminescence of ink applied by printing on a marked paper surface in the form of a symbol invisible in natural light. It is visualized by illumination with a source of infrared and / or ultraviolet radiation, causing a glow of a certain color. Next, the document is identified and a conclusion is made about its authenticity or falsification.

Thus, a fine-crystalline luminescent composition for marking and a method for identifying a document using this composition are known [US Pat.RU No. 2253665, publ. 06/10/2005]. To obtain it, gadolinium oxysulfide activated with terbium, having an average crystal size of 1.1 μm, and yttrium oxysulfide, activated with ytterbium and erbium, having an average crystal size of 1.3 μm, are mixed in a vibrating mixer in a ratio of 2:1 to 1:2. The resulting composition with crystalline particles of not more than 1.5 microns is introduced into printing ink and applied by printing on the surface of the excise stamp in the form of a marking invisible under normal conditions. The marking is visualized by illuminating the surface of the excise stamp with radiation in the ultraviolet region of the spectrum (λ=254 nm) or LED radiation (λ=960 nm), causing it to glow green.

The main disadvantage of the known invention is that the powders of fine-crystalline phosphors have a sufficiently large particle size and, when the ink dries, can be deposited on the equipment, thereby necessitating its cleaning, which will lead to additional production costs. In addition, the use of expensive compounds of rare earth elements significantly increases the cost of marking.

An aqueous ink composition for thermal inkjet printing is proposed for protecting documents and containing at least one luminescent water-soluble lanthanide complex [U.S. Pat. EA No. 21513, publ. November 30, 2012]. The rare earth complexes of the present invention are selected from luminescent complexes of trivalent rare earth metal ions with three tridentate 5- or 6-membered heteroaryl ligands bearing a double negative charge. The above result is achieved by using a stable water-soluble tris complex of the trivalent rare earth cation Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and mixtures thereof, with a ligand selected from the group of pyridine, imidazole, triazole , pyrazole, pyrazine, having at least one carbonyl group, which absorbs radiation in the ultraviolet and/or blue region of the electromagnetic spectrum. The luminescent emission of these lanthanide complexes is due to internal transitions to the f-sublevel, for example, ⁵ D ₀ → ⁷ F ₁ and ⁵ D ₀ → ⁷ F ₂ for Eu ³⁺ .

The main disadvantage of the known luminescent inks is the presence of phosphor crystals in their composition, and heating during printing can cause particles to settle on the nozzles of the print heads, clog them and, thereby, lead to the need to replace the heads with the impossibility of full use of the cartridges, which is negative affects the cost of printing. In addition, the use of expensive compounds of rare earth elements can significantly increase the cost of labeling.

Organic luminescent substances have good solubility in common organic solvents, as well as high luminescence intensity.

A luminescent additive based on organic compounds of europium and terbium in ink for hidden marking of valuable material objects in order to protect against counterfeiting is proposed in [US Pat.RU No. 2373211, publ. November 20, 2009]. The additive is a compound di(nitrato)acetylacetonatobis(1,10-phenanthroline) lanthanide(III) of the general formula [Ln(NO ₃ ) ₂ Acac(Phen) ₂ ]⋅H ₂ O, where Ln - Tb _x Er _1-x , 0<x<1, Acac - acetylacetonate ion, Phen -1,10-phenanthroline, and is characterized by three protective properties that can be controlled independently of each other. The first protective property is the ability to luminesce green light when exposed to UV radiation. The second protective property is the ability to luminesce green light when exposed to X-rays (X-ray luminescence). The third protective property is thermoluminescence, which is the ability to store the energy of UV and X-ray radiation indefinitely and emit a green glow upon subsequent heating.

The disadvantage of the proposed additive is that the known invisible ink is suitable for application on paper and is not implemented for use in films, which limits the range of applications. The presence of rare earth elements, which are characterized by high cost, significantly increases the cost of marking.

In [US Pat. US No. 7147801, publ. 12.12.2006] describes a multi-component composition of ink suitable for inkjet printing, containing a luminescent compound, a solvent, an energetically active substance and, optionally, a non-luminescent dye. An energetically active compound, when exposed to an effective amount of energy, forms one or more active substances that can react with the phosphor, changing one or more of its characteristics and/or non-luminescent dye. A preferred luminescent dye refers to lanthanide complexes that include chelated organic ligands, such as rare earth coordination complexes. Other possible ligands include oxo-, amino-, pyridino-, sulfoxo ligands such as beta-diketonates; bipyridines and others. Known ink is easily applied to a paper substrate, dries quickly, and the impact of energy on the substrate when the security pattern is identified triggers a cascade of photochemical reactions, as a result of which a change in the pattern is visible to the naked eye. Moreover, both "fading" and "burning up" of luminescence are possible.

The main disadvantage is the multicomponent and high cost of some compounds of the composition. In addition, the specified composition and method is applicable for marking documents and the source of information does not consider options for applying to a polymer matrix, which can affect the luminescence of a number of substances.

Known compositions of luminescent polymers of a large number of diketonates [h. WO No. 2011011646, publ. 01/27/2011] for use as imaging agents, probes, easily processed photosensitizers, sensors (e.g., oxygen, temperature, humidity, pH), laser dyes, optical fibers, waveguides, light guides, photoactivated oxidizers, emitting materials for displays, solvatochromic, photodegradable, lithographic materials, as well as dyes, inks, reactive dyes. Compositions can be included in matrices, including polymer ones, namely, polyacrylates, polymethacrylates, polylactide, polyamide, polyvinyl chloride, polyvinylidene chloride, polyethylene glycol, poly(ethylene terephthalate), polysiloxanes, silicones.

The disadvantage of the invention is the lack of information on the use of diketonates, including boron difluoride diketonates, for latent labeling, since the source describes only options for using known compounds and compositions of luminescent dyes in cell biology in a method for determining oxygen, which is carried out without the use of invasive methods.

Complexes of boron difluoride for surface marking attract interest due to the intense absorption of radiation in the visible region, the high quantum yield of photoluminescence and high chemical stability. So, in [Xiaolin Zhu et al. "An AIE-active boron-difluoride complex: multi-stimuli-responsive fluorescence and application in data security protection" // Chem. Commun., 2014, V.50, pp. 12951-12954] proposed to use as a cryptographic ink a complex of boron difluoride containing a flat structure of the azaboro-dichinomethene core and two N-substituted phenothiazine chromophores. The technology of encryption and decryption of information includes writing characters with a solution of a well-known boron difluoride complex saturated with HCl vapor on filter paper. The paper is then immersed in a tartrazine dye solution for 20 seconds and dried at room temperature, which makes the inscription invisible under normal or ultraviolet light. At the stage of decoding, the yellow fluorescence of the applied symbols is visualized by exposing the paper to hydrochloric acid or triethylamine vapors for 10 minutes.

The disadvantage of these inks is, first of all, the complex verification procedure, which can only be carried out in laboratory conditions using hazardous chemicals.

As can be seen from the prior art, the use of luminescent ink in printing processes is not always economically feasible and convenient for hidden labeling of goods. Sometimes security elements need to be included in the polymer matrix of the product itself or invisible symbols must be applied to its packaging.

Thus, a composition for protection against forgery based on a polymeric, non-conductive material and an electrically conductive pigment and an organic luminescent compound distributed in it, which, in the presence of a conductive pigment, is capable of excitation, is known [US Pat. EA No. 28223, publ. October 31, 2017]. In a particular case of implementing the invention, 5 wt.% of the electroluminescent compound iridium(III)tris(2-(4-totyl)pyridinato-N,C2), 10 wt.% of the material providing electron transport N,N'-bis( 3-methylphenyl)-N,N'-bis(phenyl)benzene, 25 wt.% semiconductor 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole and 60 wt. % polystyrene. The total concentration of these four substances is 2.5 wt.% of the finished organic solution. To produce the security element, a known composition is printed on a polycarbonate film with a thickness of about 100 μm by means of inkjet or screen printing. The printed film after drying contains 0.5 wt.% luminescent substance, 90 wt.% organic polymer matrix material, 8 wt.% conductive fillers. The patterned polycarbonate film thus obtained is laminated with a polycarbonate film layer without the use of adhesives. The layers cannot be separated from each other, resulting in a particularly high mechanical protection against impact on the protection element. Visualization is carried out using non-contact excitation of luminescence in an electric alternating field.

The disadvantage of the known material is a large number of specific and expensive components and layering, which can affect the cost of manufacturing materials. In addition, the need to use equipment for activating luminescence complicates the widespread implementation of this method of latent marking.

Known composition of a transparent nanofluorescent material and its covert application to protect against counterfeit goods [US Pat. CN No. 102002365, publ. 21.08.2013]. EFFECT: invention provides obtaining a material with a transparency of more than 50% at wavelengths of 390-650 nm. It consists of the following nanofluorescent materials: fluorescent powder of inorganic rare earth nanooxide, organic dye with unsaturated bonds, organic light-emitting small molecules, semiconductor fluorescent quantum dots and molecules of organic metal complexes that contain rare earth elements, while the average particle diameter of nanofluorescent materials is not more than 400 nm. To create a hidden marking with transparent printing ink, a security symbol is applied to the surface of known packaging materials - biaxially oriented polypropylene film or polymer films made of polyvinyl chloride or polyethylene. At the same time, the film containing the security symbol must have significant transparency under natural light. The badge is visualized when exposed to ultraviolet radiation (>320 nm), observing a fluorescent glow visible to the eye and / or two types of different visible fluorescence colors when using several phosphors in the paint composition.

The disadvantage of the invention lies in the multicomponent composition, which increases the number of operations to obtain it, and the inclusion of expensive lanthanide luminescent complexes leads to an increase in the cost of labeling.

Based on the prior art, the task was set to develop a method for hidden marking of material objects using luminescent compositions of boron difluoride β-diketonates, based on their long-term delayed excimer fluorescence induced by UV radiation at high intensity at room temperature.

The technical result of the claimed invention is an inexpensive, simple method for marking polymer films with the possibility of applying any desired symbols. Hidden marking and activation of the luminescent dye do not require the use of expensive, bulky and technically complex equipment, and it is possible to identify the protective marking using a compact ultraviolet flashlight or UV lamp. Another advantage is that the inventive marking can be used in a wide temperature range and has a long service life.

The technical result is achieved by the hidden marking method, which consists in preparing a solution of polycarbonate and diarylmethanate or arylacetonate of boron difluoride in a chlorinated hydrocarbon at a concentration of 0.05-1 wt.% in the finished film, forming the film by the solution method, drying it in air, applying a protective image by irradiation films with a source of high-intensity UV radiation in the wavelength range of 360-410 nm and subsequent image verification using low-intensity UV radiation in the wavelength range of 360-410 nm.

The claimed invention is based on the use of diarylmethanates or arylacetonates of boron difluoride, which are mentioned in the text as compounds 1-10 and are shown in the following figure: FIG. Fig. 1. Structural formulas of diarylmethanates and arylacetonates of boron difluoride used for covert labeling.

The method claimed in the present invention includes several steps. First, a polymer matrix is prepared with boron difluoride β-diketonate. To do this, a portion of the phosphor compounds of the series 1-10 based on the content in the finished polymer matrix of 0.05-1 wt.% and a portion of polycarbonate based on the content in the finished polymer matrix of 99-99.95 wt.% are dissolved in a suitable chlorinated hydrocarbon, for example, dichloromethane, trichloromethane, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane. Solution methods, such as pneumatic spraying of a solution onto a substrate, centrifugal casting (centrifugation method), pouring from a solution onto a flat surface, followed by drying in air, produce a polymer luminescent composition based on diarylmethanate or arylacetonate of boron difluoride with a final concentration of 0.05-1 wt .%. The thickness of the resulting film is 0.01-0.3 mm.

On the finished matrix, which can serve as a label, label or part of the package, without the use of any printing equipment, high-intensity short-wave irradiation in the range of 360-410 nm is applied with a laser pattern invisible in natural light or by irradiating through a stencil using a UV lamp.

To confirm the origin, the product is subjected to UV irradiation, as a result of which a protective image appears on the polymer matrix due to delayed excimer fluorescence in the form of a long green afterglow of the protective image. For visualization, a UV flashlight or UV lamp with a range of 360-410 nm is used. The effect of green afterglow persists in air for a long time, at least 9 months.

The essence of the claimed invention lies in the fact that boron difluoride β-diketonates are characterized by large extinction coefficients and high polarity of molecules. This causes the tendency of these compounds to self-organized aggregation and self-assembly, which, among other things, is manifested by the formation of excimers with a coplanar (sandwich) arrangement of molecular planes. The planar geometry of boron difluoride β-diketonate molecules promotes the formation of J-aggregates in the ground state and excimers in the excited state, which thereby makes it possible to achieve mutual compensation of the dipole moments of neighboring molecules.

When polymer films containing boron difluoride β-diketonates are irradiated with intense excitation radiation, the polymer matrix is heated and the free volume increases, as a result of which the nearest dye molecules in the irradiation zone form excimers in a self-organized manner. In this case, the rigid matrix prevents the quenching of triplet states. As a result, excimer delayed fluorescence is activated precisely in the zones of films irradiated with high-intensity radiation.

After the end of exposure to intense exciting radiation, the molecules of boron difluoride β-diketonate, clamped in the polymer matrix, continue to maintain a planar geometry, which is favorable for the formation of excimers. Thus, locally formed centers of delayed fluorescence remain active for an extremely long time, and their excitation is possible even with a low-intensity source of UV radiation. Heating the film or exposure to solvent vapors allows the protective image to be removed if necessary.

The absorption spectra of the polymer films were recorded with a Shimadzu UV-2550 spectrometer. Stationary excitation and luminescence spectra were obtained using a Shimadzu RF5301 spectrometer. Afterglow spectra were recorded using an R-Aero VISION2GO VIS-ER spectrometer. The afterglow kinetics was measured using a Horiba Fluorolog 3 spectrofluorimeter.

The claimed invention is implemented in the following examples.

Example 1

A polycarbonate polymer film containing boron difluoride diarylmethanate with structure 1 was prepared as described above based on a phosphor concentration in the film of 0.8 wt.%. 1,2-dichloroethane was used as a solvent. The film was formed in a Petri dish by pouring from a solution followed by drying in air for 1 day.

A local area of the film in the form of a triangle was irradiated with a laser with a wavelength of 375 nm. At the site of film irradiation with a laser, a green afterglow in the form of a triangle with a wavelength of λ=503 nm was observed with the naked eye for 6 seconds. Then, when the film was illuminated with a UV flashlight (365 nm), a pattern in the form of a triangle was observed, which stood out against the background of a uniform blue glow of the film (λ=418 nm).

After 1 month after drawing the pattern with a laser, an image in the form of a triangle was observed when the film was illuminated with a UV flashlight (365 nm).

Example 2

Polycarbonate film containing boron difluoride diarylmethanate with structure 4 was prepared as described in Example 1.

A laser with a wavelength of 405 nm was irradiated with a local section of the film in the form of a square for 10 seconds. At the point where the film was irradiated with a laser, a green afterglow of a local area in the form of a square was observed with the naked eye. Recorded luminescence parameters: λ=508 nm, glow time recorded by the eye, about 5 s. Then, when the film was illuminated with a UV lamp (365 nm), a square pattern was observed, which stood out against the background of a uniform blue glow of the film (λ=440 nm).

After 1 month after drawing the pattern with a laser, a square figure was observed by illuminating the film with a UV lamp (365 nm) with the naked eye.

Example 3

A polycarbonate polymer film containing boron difluoride diarylmethanate with structure 2 was prepared as described above based on a phosphor concentration in the film of 0.05 wt.%. Dichloromethane was used as a solvent. The film was formed on a glass slide by centrifugal casting using a spincoater followed by drying in air for 1 day.

A laser with a wavelength of 375 nm irradiated a local section of the film in the form of a circle. At the point where the film was irradiated with a laser, a green afterglow (λ=504 nm, the glow time recorded by the eye is about 4 s) of a local section of the film in the form of a circle was observed with the naked eye. Then, when the film was illuminated with a UV flashlight (365 nm) or a UV lamp (365 nm), a circular pattern was observed, which stood out against the background of a uniform blue glow of the film (λ=425 nm).

After 1 month after drawing the pattern with a laser, a circle figure was observed with the naked eye when the film was illuminated with a UV flashlight (365 nm) and a UV lamp (365 nm).

Example 4

Polycarbonate polymer film containing diarylmethanate boron difluoride with structure 2 was prepared as described in example 3 based on the concentration of the phosphor in the film 0.2 wt.%.

A high-intensity UV lamp with a wavelength of 365 nm was used to irradiate a local area of the film through a stencil with a circle shape for 10 seconds.

A green afterglow (λ=504 nm, glow time recorded by the eye, about 5 s) of a local area of the film in the form of a circle was observed at the film irradiation site. Immediately after application, when the film was illuminated with a UV flashlight with a wavelength of 365 nm, a circular pattern was observed, which stands out against the background of a uniform blue glow of the film (with a luminescence wavelength of λ=427 nm).

After 1 month after drawing the pattern, a circle-shaped image was observed when the film was illuminated with a UV lamp (365 nm) with the naked eye.

Example 5

A polycarbonate polymer film containing boron difluoride arylacetonate with a structure of 10 was prepared as described in the general part, based on the concentration of the phosphor in the film of 0.8 wt.%. Trichloromethane was used as a solvent. The film was formed in a Petri dish by pouring from a solution followed by drying in air for 1 day.

A high intensity UV lamp with a wavelength of 365 nm was used to irradiate a local area of the film through a rectangular stencil for 10 seconds. At the site of film irradiation with a laser, a green-yellow afterglow (λ=535 nm, glow time recorded by the eye, about 7 s) of a local area of the film in the form of a rectangle was observed with the naked eye. Then, when the film was illuminated with a UV flashlight (365 nm) or a UV lamp (365 nm), a pattern in the form of a rectangle was observed, which stands out against the background of a uniform blue glow of the film (λ=442 nm).

After 1 month after drawing the pattern with a laser, a rectangle shape was observed with the naked eye when the film was illuminated with a UV flashlight (365 nm) or a UV lamp (365 nm).

Example 6

Polycarbonate polymer film containing diarylmethanate boron difluoride with structure 7 was prepared as described in example 1 based on the concentration of the phosphor in the film 1 wt.%. Labeling and visualization was carried out as described in example 1.

At the point where the film was irradiated with a laser, a blue-green afterglow in the shape of a triangle with a wavelength of λ=491 nm was observed with the naked eye for 6 seconds. Then, when the film was illuminated with a UV flashlight (365 nm), a pattern in the form of a triangle was observed, which stood out against the background of a uniform blue glow of the film (λ=542 nm).

Examples 7-11.

Polycarbonate polymer films with compounds of structures 3, 5, 6, 8, 9 were prepared as described in example 1. The luminescence characteristics are summarized in the table:

Compound Concentration, wt.% Wavelength after marking, nm Afterglow color Picture shape Wavelength during visualization, nm 3 0.8 502 Green Triangle 427 5 0.8 517 Green Square 450 6 0.8 520 Green Circle 449 8 0.8 490 blue green Square 399 9 0.8 520 Green Circle 412

Claims (1)

Covert labeling method, which consists in preparing a solution of polycarbonate and diarylmethanate or arylacetonate of boron difluoride in a chlorinated hydrocarbon with a concentration of 0.05-1 wt.% in the finished film, forming the film by the solution method, drying it in air, applying a protective image by irradiating the film with a high-intensity source UV radiation in the wavelength range of 360-410 nm and subsequent image verification using low-intensity UV radiation at a wavelength of 360-410 nm.

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