RU2266357C1 - Protection element for controlling genuineness - Google Patents

Abstract

FIELD: special-purpose paper types.

SUBSTANCE: device has light guide manufactured from optically transparent polymers as ribbon.

EFFECT: high protection quality.

18 cl, 3 dwg

Description

The invention relates to security elements and materials used in securities, banknotes, plastic cards and other documents to prevent counterfeiting and to ensure authenticity control.

The known security element [1] contains a fiber identified by a special feature, which may be optical.

A credit or identification card with a security element made in the form of a fiber having the property of conductivity and extending from one edge of the protected card to the other edge is also known. The specified fiber can be made of electrically conductive or light-guide materials, in particular, fiber-optic fiber can be used [2].

These protective elements using optical glass fibers have a low degree of protection against counterfeiting due to the fact that optical glass fibers are commercially available. In addition, the technology for manufacturing optical fiber fibers is owned by many technological centers and companies that are capable of producing such fibers with various sizes and properties, so that the potential danger is already created by this uncertainty of the circle of potential manufacturers of protective elements.

Optical fiber optic fibers are characterized by fragility and fragility, which makes it difficult to use them as security elements embedded in thin and flexible paper sheets, such as banknotes, securities, etc., in addition, the known security elements do not allow to obtain a variety of visually recognizable security features.

The technical result of the present invention is to increase the degree of protection against counterfeiting of securities, banknotes and documents and to obtain additional visually recognizable and modifiable signs of protection, as well as to increase durability when used in sheet materials.

To achieve the technical result in the known security element for checking the authenticity of securities, banknotes and documents, which is used as a fiber, consisting of a core and an outer shell, it is proposed to fabricate a fiber from optically transparent polymers in the form of a tape, while the shell polymer has a refractive index visible light is less than the refractive index of the core polymer.

The following enhancements to the security feature are provided:

- intermediate polymer shells are placed between the core of the ribbon waveguide and its cladding, while the refractive index of the polymer of the outer cladding is less than the refractive index of the polymer of each of the inner claddings;

- one of the surfaces of the outer sheath of the optical fiber has a metal layer;

- a dye with an absorption band in the optical region of the spectrum is introduced into the core of the fiber optic fiber;

- an organic phosphor is used as a dye;

- at least one additional optical fiber is embedded in the core of the tape fiber;

- a dye with an absorption band in the optical region of the spectrum is introduced into the cores of the additional optical fibers;

- a phosphor is used as a dye;

- phosphors introduced into the cores of additional fibers have different emission spectra;

- the phosphor of the fiber optic fiber has an emission band overlapping with the optical absorption band of the phosphors of the cores of the additional optical fibers;

- the security element contains at least one additional tape light guide;

- two tape optical fibers are combined into one combined optical fiber so that the planes are bonded to each other;

- a light-absorbing layer is placed between the tape fibers forming a combined light guide;

- between the tape fibers forming a combined light guide, a reflective layer is placed;

- organic phosphors with differing light emission spectra are introduced into the cores of the first and second tape fibers forming a combined fiber;

- at least one tape light guide is placed on a carrier polymer substrate;

- the carrier polymer substrate has a metal layer;

- phosphors having different emission spectra of light are introduced into the cores of at least two tape optical fibers.

The invention is illustrated by the accompanying drawings.

Figure 1 shows a cross section of a security element of various designs.

Figure 2 shows the absorption and emission spectra of luminescent dyes introduced into the cores of the tape and additional optical fibers.

Figure 3 shows a cross section of a combined optical fiber of various designs, composed of two tape optical fibers.

The security element for controlling the authenticity of securities, banknotes and documents consists of a light-conducting core 1 of a reflective shell 2, which are made of optically transparent polymers in the form of a tape.

In one embodiment of the invention shown in FIG. 1 (a), the light guide core 1 is surrounded by a light reflecting shell 2 having a refractive index n ₂ <n ₁ , where n ₁ is the light refractive index of the light guide core, n ₂ is the refractive index of the light reflecting shell. The condition n ₂ <n ₁ is a "condition of light conduction", that is, the propagation of light by "total internal reflection" along the light guide core. This condition is fulfilled for all presented embodiments of the invention. To provide the required mechanical and optical properties, for example, to increase the coefficient of light capture in total internal reflection, the reflective shell 2 can be made of several layers of polymers having different values of the refractive index.

Figure 1 (b) shows an embodiment in which a light guide consisting of a light guide core 1 surrounded by a reflective sheath 2 is placed on a carrier polymer substrate 3.

Figure 1 (c) depicts an embodiment of the invention in which several tape optical fibers consisting of light-conducting cores 1, ... 1, ^{n *} surrounded by reflective sheaths 2, ..., 2 ^{n *,} respectively, are placed on the carrier substrate 3.

Figure 1 (d) shows an embodiment of the invention in which several additional light guide fibers of a smaller cross section, consisting of light guide cores 4, ..., 4 ^{n *} surrounded by reflective shells 5, are inserted inside the light guide core 1 surrounded by the light reflecting sheath 2, ... 5 ^{n *,} respectively.

In other embodiments of the invention, various combinations of the options shown in FIGS. 1 (a) to (g) are possible.

To protect securities (or banknotes) using these tape fibers, at least one fiber on the substrate or without it is introduced into the paper web during its formation without gaps from one edge to another. The security element is located in the thickness of the paper web and may have sections extending to the surface of the paper web. In this case, a genuine protective tape conducts visible light from one end of the security to be protected to the other end. This security element can also be used in a plastic carrier.

Embodiments of the invention are possible in which organic dyes having an absorption band in the optical spectrum are introduced into the polymer matrices of the light-conducting cores 1, ... 1 ^{n *} shown in Figs. 1 (a) - (d). In this case, a genuine protective tape conducts visible light, in the spectrum of which there is a feature caused by the absorption band of the dye, from one end of the security to be protected to the other end.

Embodiments of the invention are possible in which organic phosphors having an absorption band in the optical spectrum are introduced into the polymer matrices of the light-conducting cores 1, ... 1 ^{n *} shown in Figs. 1 (a) - (d). The absorption of light by such a phosphor leads to the excitation of molecules and the appearance of luminescence, that is, the removal of the excitation of dye molecules by emission of light quanta. Part of the emission light (in the implemented versions, 6-10%), due to the fulfillment of the “light conduction condition”, is captured in full internal reflection, and transported along the light-conducting core to the end of the ribbon waveguide, and exits through its end. Light that excites phosphor molecules can penetrate the core of the fiber through the lateral surfaces of the ribbon. If the light evenly illuminates the side surface and all this light is absorbed by the phosphor contained in the core of the fiber, then under the condition that the side surface area exceeds the cross-sectional area of the fiber by 15-20 times, the brightness of the fiber end will exceed the brightness of the source illuminating the side surface of this fiber .

In one embodiment of the invention, the length of the fiber is 65 mm, the width is 1 mm, the thickness is 0.03 mm, the ratio of the areas of the lateral surface to the cross-sectional area is ~ 2200. Thus, ideally, the presented embodiment of the invention with a core doped with a phosphor makes it possible to achieve an increase in the brightness of the end face compared to the exciting light by a factor of ~ 100. Due to the small thickness of the core and limited concentration of the phosphor due to quenching of the luminescence, ~ 30% of the incident light is absorbed in it. This reduces the brightness increase to ~ 30 times. However, this is quite enough to create an easily identifiable visual sign of protection.

An implementation option is possible in which one of the side surfaces of the tape waveguide or one of the surfaces of the polymer carrier substrate is coated with a metal layer. Metallization increases the effective thickness of the light-absorbing layer of a phosphor solid solution in the polymer matrix of the core of the fiber optic fiber and approximately doubles the brightness of the fiber end. The metal layer can also serve as an additional security element. Moreover, it may have a special pattern and / or additional coatings.

When placing several optical fibers on a carrier substrate in accordance with FIG. 1 (c), it is possible to use phosphors with different emission spectra in all optical fibers or in some of them, which gives differently colored ends of the optical fibers.

To protect securities (or banknotes) using the proposed elements, at least one protective tape with a core containing a phosphor is introduced into the paper web without tears from one end to the other end. In addition, each type (or face value) of the security (or banknote) to be protected is characterized by a certain luminescence color of the end face of the protective tape or a combination of colors when using several tape optical fibers. The authentication of the protected product is carried out by identifying the optical fibers, which is carried out by checking the light conduction of the protective tape "in the light" from one end to the other end and, additionally, by the presence of luminescence light coming out through both ends of the protective tape when illuminating the area in the center of the paper to be protected, inside protective tape passes. The brightness enhancement described above allows reliable visual identification of a security feature.

In another embodiment of the invention, an additional polymer light guide fiber of a smaller cross section, the core of which also contains a phosphor, is introduced inside the core 1 of the ribbon waveguide containing the phosphor. Moreover, the emission spectrum 7 (FIG. 2 (a)) of the phosphor contained in the core 1 partially or completely overlaps with the absorption spectrum 8 (FIG. 2 (b)) of the phosphor contained in the core 4 of an additional optical fiber introduced into the core 1. When illuminating a tape optical fiber (Fig. 1 (d)) with a light-conducting core inserted inside its containing a phosphor with an absorption spectrum of 6 (Fig. 2 (a)) and emission spectrum 7 (Fig. 2 (a)), an additional optical fiber of a smaller cross-section, the core of which contains a phosphor with special absorption spectrum 8 (FIG. 2 (b)) and emission spectrum 9 (FIG. 2 (b)), through its lateral surface, phosphor molecules absorb part of the light in the range of absorption band 6 (FIG. 2 (a)) and emit light in the spectral interval 7 (figure 2 (a)). Part of the emission light is captured in total internal reflection and transported along the light guide core 1. In the process of light propagation through the core 1, part of it passes through the side surface of the internal additional fiber into the light guide core 5 and excites a phosphor with an absorption spectrum of 8 (Fig. 2 (b)) due to its overlap with the emission spectrum 7. The phosphor contained in the light guide core 5 of the internal additional fiber emits light of spectral composition 9 (Fig. 2 (b)), part of this light is captured is reported in the total internal reflection and is conveyed along the core 5 to the inner end of the additional fibers, which coincides with the end of the outermost belt waveguide and exits through the end face. In this case, against the background of the bright end of the outer tape, a bright luminous point of the end of the inner additional fiber with a longer wavelength than the surrounding light appears. When using several additional fibers introduced into the core of the external tape fiber in accordance with figure 1 (g), phosphors with different emission spectra can be used to dope their light-conducting cores. This allows for additional "color coding" of protected products. Moreover, each type (or face value) of the security (or banknote) to be protected is characterized by a certain luminescence color of the end face of the security thread or a combination of colors when using several tape luminescent optical fibers and additional fibers introduced into the light guide core of the optical fibers. The luminescent light guides are illuminated through the outer layer of the paper web of the security (or banknote) to be protected.

In a variant of use as a protective element of a combined optical fiber (Fig. 3), formed of two tape optical fibers interconnected by flat surfaces, an additional protective effect is achieved when the exposure conditions of the protective element are changed.

Embodiments of the invention are possible in which organic luminescent dyes having an absorption band in the optical spectrum and different optical emission spectra are introduced into the polymer matrices of the light-conducting cores 1 and 1` shown in FIGS. 3 (a) and (b). The absorption of light penetrating the side surfaces A and B of the combined fiber leads to the excitation of phosphor molecules and the appearance of luminescence. Due to the fulfillment of the “light conduction condition”, part of the light of the emission of phosphors is captured in total internal reflection and transported along its “own” light guide core to the end of the fiber and exits through the common end. The light exciting the phosphor molecules can penetrate into the cores of the combined fiber through different lateral surfaces: into fiber 1 (Fig. 3 (a), (b)) through surface A; in the light guide 1` (Fig. 3 (a), (b)) through the surface B. Between the light guides fastened to each other along the surface C, a layer of opaque material 10 is placed (Fig. 3 (a)), which protects the cores of the light guides from exposure through the surface C. To increase the utilization of light entering the cores of the optical fibers through surfaces A and B, the opaque layer 11 (Fig. 3 (b)) is made mirror-like. In this case, the light passes twice through the core of the ribbon waveguide, which makes it possible to increase the light absorption coefficient of the phosphor, and therefore the amount of emission light. If the light evenly illuminates both side surfaces A and B and this light is absorbed by the phosphors contained in the cores of the optical fibers 1 and 1`, then as a result of luminescence and the processes of the capture of light into total internal reflection, light emission with a spectral composition corresponding to the sum of the emission spectra of both phosphors (taking into account the "weight" of each spectrum) contained in cores 1 and 1`. One of the features of human color vision is the equivalence of the perception of a complex spectrum and monochromatic radiation, if they equally excite the color receptors of the eye. Therefore, visually the radiation from the end of the combined fiber will be perceived as light having an intermediate color with respect to the emission color of the phosphor core 1 and the phosphor core 1`. For example, a phosphor with an emission spectrum in the green region is introduced into core 1, and an orange region is introduced into core 1`. In this case, the eye will perceive the resulting end-face radiation as intermediate, that is, radiation of various shades of yellow (depending on the ratio of the brightness of the spectral components). The situation fundamentally changes if one of the surfaces A or B is protected from exposure to light. In this case, only one of the cores 1 or 1` of the combined fiber will be excited and luminesce. In this case, the end face will emit either green if surface A and, accordingly, core 1 are illuminated (Fig. 3 (a), (b)), or orange if surface B and core 1` are illuminated (Fig. 3 (a), (b)). When using a combined optical fiber to protect securities, the luminescent optical fibers are illuminated through the outer layer of the paper web of the security (or banknote) to be protected.

Sources of information

1. PCT Application No. WO98 / 38365 of 02.24.98; D 02 Q 3/00; D 06 H 1/00.

2. Application DE No. 2443967 from 09/11/74; D 21 H 5/10 - prototype.

Claims (18)

1. The security element for controlling the authenticity of securities, banknotes and documents, which is used as a light guide, consisting of a light guide core and a reflective sheath, characterized in that the light guide is made of optically transparent polymers in the form of a tape, while the polymer of the outer shell has a refractive index less than the refractive index of the core polymer. 2. The security element according to claim 1, characterized in that intermediate polymer layers are placed between the core of the ribbon waveguide and its cladding, while the refractive index of the polymer of the outer shell is less than the refractive index of the polymer of each of the inner layers. 3. The security element according to claim 1, characterized in that one of the surfaces of the outer layer of the sheath of the tape fiber has a metal layer. 4. The security element according to claim 1, characterized in that a dye with an absorption band in the optical region is introduced into the core of the tape fiber. 5. The security element according to claim 4, characterized in that a phosphor is used as a dye. 6. The security element according to claim 1, characterized in that at least one additional optical fiber is inserted into the core of the tape fiber. 7. The security element according to claim 6, characterized in that a dye with an absorption band in the optical region is introduced into the cores of the additional optical fibers. 8. The security element according to claim 7, characterized in that a phosphor is used as a dye. 9. The protection element according to claim 6, characterized in that phosphors with different light emission spectra are introduced into the cores of the additional optical fibers. 10. The security element according to claim 6, characterized in that the phosphor of the ribbon waveguide has a spectral band of light emission overlapping with a spectral band of optical absorption of phosphors introduced into the cores of additional optical fibers. 11. The security element according to claim 1, characterized in that it contains at least one additional tape light guide. 12. The security element according to claim 11, characterized in that it consists of two tape optical fibers combined into one combined optical fiber so that their planes are bonded to each other. 13. The security element according to claim 12, characterized in that a light-absorbing layer is placed between the tape fibers forming the combined light guide. 14. The security element of claim 12, wherein a reflective layer is placed between the tape fibers forming the combined light guide. 15. The security element according to claim 12, characterized in that organic phosphors with different emission spectra of light are introduced into the cores of the first and second tape optical fibers forming a combined optical fiber. 16. The security element according to claim 11, characterized in that at least one tape optical fiber is placed on a carrier polymer substrate. 17. The security element according to clause 16, wherein the carrier polymer substrate has a metal layer. 18. The security element according to clause 16, characterized in that phosphors having different emission spectra of light are introduced into the cores of at least two tape optical fibers.

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