RU62463U1 - RELIEF DIFFRACTION STRUCTURE - Google Patents

Abstract

The utility model can be used in optics and printing, for example, in the manufacture of documents of special importance in order to protect them from counterfeiting. The proposal is aimed at solving the problem of creating a relief diffraction structure, the complication of which, on the one hand, would make it difficult to reproduce, and on the other, would allow simple and effective control of its authenticity. The relief diffraction structure contains a substrate (1) with an aluminum layer (2) deposited on it, in which a relief (3) of a low-frequency diffraction grating is formed. On the surface of the relief (3), a relief (4) of the high-frequency diffraction grating is formed. In this case, the relief (3) of the low-frequency diffraction grating is preserved. Placed on any document, the proposed relief diffraction structure serves as reliable protection of this document from forgery. Since the low-frequency and high-frequency reliefs are combined with each other in this structure, each of which is a separate image visible with the naked eye, the authenticity of such a structure is easily and effectively controlled. 3 s.p. f-ly, 1 ill.

Description

The proposed utility model relates to diffractive optical elements, including holographic ones, and can be used both in optics and in printing, for example, in the manufacture of documents of special importance, banknotes, checks, etc., as well as packaging or labeling of goods in order to protect them from counterfeiting and unauthorized copying.

It is known that the quality of protection of documents from counterfeiting is significantly improved if these documents are additionally provided with labels (stickers) or laminated with polymer films that have a relief diffraction structure, for example, a hologram, diffraction grating, or other elements that allow reproducing the optical effect, which varies depending on from the viewing angle. Such elements cannot be copied by any of the standard printing methods; making copies of them requires highly qualified personnel and special equipment. In most cases, relief-phase holograms are used for protection purposes, replicated by embossing a thermoplastic relief-transmitting layer using a metal matrix. To increase the degree of security of such a hologram label or laminate, two approaches are used: complicating the topographic image, including the introduction of hidden marks, combined images, etc., or using such a holographic image structure that cannot be separated from the protected product in order to copy its relief and stick again.

There are various technical solutions aimed at complicating the holographic image, based on the use of diffraction gratings of different frequencies to form the latter.

So, in US patent No. 4094575 on different parts of the surface of the carrier substrate are applied lattices of different frequencies. To increase the angle of rotation of the substrate, at which diffraction can be observed, gratings of the same frequency can be superimposed.

US Pat. No. 4,304,809 describes pseudo-color diffraction images characterized in that at a certain viewing angle, different parts of the image are painted in different colors. Such pseudo-color images can be created using masks used to expose individual gratings that mimic a particular color (US Patent No. 4,788,116). Further improvement of this kind of hologram image is proposed in US patent No. 5291317. According to this patent, a plurality of hologram diffraction gratings in the form of a dot (pixel) raster is created on the substrate. Each pixel contains a diffraction grating of a given frequency and orientation of the strokes. A set of pixels forms a picture (image).

US Pat. No. 5,428,479 proposes a holographic image in the form of a regular set of pixels, each of which is an individual diffraction grating. At the same time, the pixels are arranged so that when they try to reflectively copy them, the resulting copy of the image in the zero diffraction order is heavily contaminated with moire or the Talbot effect (self-reproduction effect). At the same time, pixels make it possible to obtain an optically variable image.

RF patent No. 2193232 proposes a relief surface structure with N distinguishable shapes (usually from 6 to 30), each of which has a different lattice parameter. At a certain position of the structure, the observer sees only one structure, while turning, another. A structure made in a specific configuration is extremely difficult to fake.

In the patent of the Russian Federation No. 2155380 a diffraction structure is described, consisting of several surface regions. The optical depth of the lattice structure is constant over the entire length of one surface section, however, differs from the optical depth of the lattice structure of another surface section and, in addition, for individual surface sections made with identical (except for the “optical depth” parameter) lattice structures, the latter mutually offset by a fraction of the lattice period. Due to the fact that regions with different optical depths have maximum diffraction efficiency in different regions of the spectrum, interference copying of such a structure using a coherent light source is very difficult.

The prototype of the proposed technical solution selected relief diffraction structure containing at least two independent optical elements of different frequencies: a higher frequency (hereinafter referred to as high-frequency) and lower frequency (hereinafter referred to as low-frequency) - see RF patent No. 2162240 .

According to the prototype, the structure consists of a substrate - a carrier with faces applied to it, for example, a square pyramid. Such a structure is a combination of independent optical elements and their corresponding reliefs: low-frequency — in the form of faces of a pyramid and high-frequency — in the form of a diffraction grating formed on each face with a period shorter than the wavelength corresponding to the perceived color. Opposite faces capture and redirect light with a shorter wavelength than diffracted light. This structure allows one to observe grating diffraction in a wide range of viewing and illumination angles. Moreover, the color of the observed diffraction image is practically independent of the angle of observation, which distinguishes this structure from a typical rainbow hologram. However, as in all of the above analogues, the prototype is a

a purely diffractive structure, the image created by it obeys the properties of diffraction images and is not visible to the naked eye.

The disadvantages of the prototype of the claimed relief diffraction structure, as well as its analogues described above, are its insufficient degree of protection against falsification and the impossibility of a simple and effective control of its authenticity. The latter is explained by the fact that the authentication of holograms and other diffractive security elements is possible only by a person with special knowledge and is associated with the use of special equipment.

This useful model is aimed at solving the problem of creating a relief diffraction structure, the complication of which, on the one hand, would make it difficult to reproduce in order to avoid unauthorized copying, and on the other hand, would allow simple and effective control of its authenticity.

To achieve the technical result, in a known relief diffraction structure containing at least two independent optical elements of different frequencies, the relief of an optical element of one frequency is placed on the relief of an optical element of a different frequency, while the underlying relief is preserved.

In addition, the claimed technical solution has a number of features characterizing the proposed relief diffraction structure in particular cases of its implementation, specific forms of its material embodiment, namely:

- the relief of the high-frequency optical element can be placed on the relief of the low-frequency optical element;

- the relief of the low-frequency optical element can be placed on the relief of the high-frequency optical element;

- a diffraction grating can be selected as an optical element.

The applicant is not aware of any technical solutions having the same set of features as the claimed one. This allows us to conclude that the proposed relief diffraction structure satisfies the condition of "novelty."

Due to the implementation of the distinctive features of the claimed device (relief diffraction structure) in combination with the features common with its prototype, the claimed object has new properties: the proposed relief diffraction structure is a combination of at least two optical elements with different spatial frequencies or with different manifestation of diffraction. In this case, the relief of the high-frequency optical element is applied directly to the relief of the low-frequency optical element (or vice versa) so that the formed relief is the sum of two reliefs, each of which is a separate image visible to the naked eye.

The essence of the utility model is illustrated by the drawing, which shows the relief diffraction structure (first embodiment), which is a combination of two diffraction gratings, low-frequency and high-frequency.

The structure contains a substrate 1 made of polymethimethacrylate with an aluminum layer 2 deposited on the sky, in which a relief 3 of a low-frequency diffraction grating 70 × 70 mm in size is formed with a triangular line shape with a frequency of 50 lines / mm. On the surface of the relief 3, a relief 4 of a high-frequency diffraction grating is formed, which, without distorting the relief 3, completely repeats its contour.

The proposed relief diffraction structure works as follows. The structure is placed on some important document, for example, a credit card. During the operation of the document, the relief diffraction structure exhibits simultaneously the properties of high-frequency and low-frequency gratings. Due to complexity

reproduction of such a structure, it serves as reliable protection of this document from forgery. Since the proposed structure combines low-frequency and high-frequency reliefs, each of which is a separate image visible to the naked eye, the authenticity of such a structure is easily and effectively controlled.

The advantage of the proposed relief diffraction structure is that it can only be obtained by using a relatively rarely used inorganic photoresist. Only the vacuum method of applying a photoresist, thermal evaporation or spraying, leads to a layer whose relief exactly reproduces the relief of the substrate, whose role in the claimed utility model is played by the underlying relief. The complexity of the manufacturing technology of the proposed relief diffraction structure determines the complexity of its reproduction and, accordingly, a high degree of protection against falsification.

The inventive utility model can be widely used both in optics for creating combined optical elements with unique properties, and for the manufacture of diffractive anti-counterfeit elements, the authenticity of which can be easily and effectively verified without the use of special knowledge and equipment.

The proposed technical solution can be implemented using well-known materials and technologies, which determines, according to the applicant, compliance with his condition of "industrial applicability".

Claims (4)

1. Relief diffraction structure containing at least two independent optical elements of different frequency, characterized in that the relief of the optical element of one frequency is placed on the relief of the optical element of a different frequency, while the underlying relief is preserved. 2. The structure according to claim 1, characterized in that the relief of the high-frequency optical element is placed on the relief of the low-frequency optical element. 3. The structure according to claim 1, characterized in that the relief of the low-frequency optical element is placed on the relief of the high-frequency optical element. 4. The structure according to any one of claims 1 to 3, characterized in that a diffraction grating is selected as an optical element.