EP4088945B1 - Security element with volume hologram and additional effects - Google Patents

Description

The invention relates to a security element for increasing the protection against forgery of security documents, such as banknotes, securities, identity cards, credit cards, debit cards or the like, wherein the security element consists of a substrate on which an exposable layer is arranged, wherein the exposable layer has a volume hologram.

To protect against imitation, especially with color copiers or other reproduction methods, security documents are equipped with optically variable security elements. The protection against forgery is based on the fact that the visually and easily and clearly recognizable optically variable effect is not reproduced or is only reproduced inadequately by the above-mentioned reproduction devices.

Holograms and hologram-like grating images as optically variable security elements in banknotes, particularly in window banknotes, are known from the state of the art. These holograms and hologram-like grating images can be present as light-dark transmission holograms or light-dark transmission gratings, surface structure holograms or surface structure gratings or volume holograms or Bragg gratings.

A volume hologram or Bragg grating is produced by exposing an exposable layer and is made, for example, of EP 2362275 A1 known. The exposable layer is several times as thick as the wavelength of light. In the exposable layer, exposure and fixation create a sequence of layer areas with different refractive indices, so that information in the form of a pattern, an alphanumeric character or a graphic image is stored.

Other conventional security elements are also in DE19611383-A1 , DE10-2007-005416 , DE10-2017-003795-A1 , WO2018-188784-A1 , EP2686172-A1 and DE10-2007-061828-A1 revealed.

The invention is based on the object of developing a generic security element in such a way that the protection against counterfeiting is further increased.

This object is achieved by the features of the independent claim. Further developments of the invention are the subject of the dependent claims.

According to the invention, an embossed layer is arranged on the substrate adjacent to the exposure layer, in the surface of which facing away from the substrate an embossed structure in the form of a refractive optical element is introduced. A coating is applied at least partially to the surface of the exposure layer facing away from the substrate and to the embossed structure, wherein the coating overlaps the exposure layer and the embossed structure and has optically recognizable information in the form of a pattern, an alphanumeric character or a graphic image. The coating has at least one recess above the exposure layer, so that the volume hologram is visible through the at least one recess and not visible outside the recess. Of course, the coating can also have at least one recess above the embossed layer.

Adjacent in the sense of this invention means that the exposable layer and the embossed layer are arranged next to each other on the same side of the substrate and at least partially touch each other or are arranged so close to each other that an observer at a normal viewing distance of about 20 cm without optical aids, such as a magnifying glass, no distance can be seen between the exposable layer and the embossed layer. It is also possible for the exposable layer and the embossed layer to overlap in the area where the exposable layer and the embossed layer are adjacent to one another. It must only be ensured that there are areas in which the exposable layer and the embossed layer do not overlap and are arranged next to one another.

A particular advantage of the invention is that a security element is created that is very difficult to counterfeit and at the same time is very attractive due to its pronounced luminous and dynamic effects. The high level of protection against counterfeiting is achieved in particular by arranging two areas of the security element, which were created using different technologies (volume hologram and embossed structures), next to each other. These are particularly preferably recognized by a viewer together with the coating as a meaningful, complementary design element.

According to a preferred embodiment, it is provided that the exposable layer consists of a photopolymer and/or the embossing layer consists of an embossing lacquer which is printed onto the substrate.

According to a preferred embodiment, the coating consists of a single-layer or multi-layer structure. In a multi-layer structure, the respective layers are arranged one above the other, viewed perpendicular to the surface of the substrate.

According to an advantageous embodiment, a single-layer structure consists of a layer with a high refractive index, preferably a thin layer of zinc sulphide (ZnS). A layer of metal, a layer of thin metallic or metallic-coloured pigments, which Structure following the embossed structure, or a printing ink with effect pigments is possible. The coating is preferably vapor-deposited or printed.

According to a further advantageous embodiment, a single-layer structure consists of a color layer that contains platelet-shaped metallic particles whose longest edge length is 15 nm to 1000 nm and whose thickness is 2 nm to 100 nm, so that the color layer shows a metallic color in reflected light and a colorful color in transmitted light. The platelet-shaped metallic particles preferably have a longest edge length of 15 nm to 600 nm and particularly preferably 20 nm to 500 nm and a thickness of 2 nm to 40 nm and particularly preferably 4 nm to 30 nm. Such a color layer is for example made of the WO 2011/064162 A2 and is also called gold-blue color.

According to a further advantageous embodiment, a two-layer structure consists of two thin layers of different metals applied one on top of the other. A particular advantage is that with a transparent embossing varnish, a viewer can see different metals or different colored metals on the top and bottom.

According to a further advantageous embodiment, a three-layer structure consists of a first metallic layer and a second metallic layer, between which a dielectric layer is arranged.

According to an advantageous embodiment, such a three-layer structure consists of a reflection layer, a dielectric layer and a partially transparent layer, wherein the dielectric layer is arranged between the reflection layer and the partially transparent layer. This Structure forms an interference-capable, multi-layer structure, as is the case for example in the WO 2005/108110 A1 or the WO 2005/038136 A1 is known. If the multilayer structure is viewed from the side of the partially transparent layer, the viewer perceives a certain color that changes as the viewing angle changes. The viewer perceives a color shift effect when the viewing angle changes.

According to a further advantageous embodiment, a multilayer structure has at least two semi-transparent mirror layers and at least one dielectric layer arranged between the at least two mirror layers, as is known for example from DE 10 2009 058 243 A1 is known. The at least two semi-transparent mirror layers of the reflection layer are preferably made of aluminum or an aluminum alloy, wherein the dielectric spacer layer with a thickness h and a refractive index v satisfies the relation 120 nm < hv < 190 nm, or of silver or a silver alloy, wherein the dielectric spacer layer with a thickness h and a refractive index v satisfies the relation 120 nm < hv < 170 nm or 340 nm < hv < 400. Such a structure shows an observer a golden color in reflected light, for example, and a blue color in transmitted light, for example, and is then also referred to as a gold-blue coating.

The embossed structure according to the invention is not a diffractive structure, such as a hologram. The lateral dimensions of the respective individual embossed elements that form the embossed structure are therefore smaller or larger than the wavelength of visible light, in particular smaller than 300 nm or larger than 1 µm.

According to an advantageous embodiment, the embossed structure consists of a plurality of achromatic microstructure elements having a lateral dimension of less than 1 mm, preferably between 3 µm and 100 µm.

• Sinus- oder Rechteckgitter,
• Sub-Wellenlängen- oder Mottenaugenstrukturen,
• Manhattenstrukturen bzw. ein unregelmäßiges Rechteckgitter mit unterschiedlichen Abständen, Breiten und Höhen der Gitterstrukturen,
• Mikrospiegel,
• Fresnel-Stukturen, Wölbstrukturen,
• Mattstrukturen,
• "Atztekenstrukturen" bzw. ein Raster aus einer Vielzahl von mikroskopischen Stufenpyramiden mit Substrukturen,
• Nanostrukturen,,
• Beugungsgitter nullter Ordnung (zero order device),
• "Tannenbaum-artige Strukturen" ("morpho rhetenor"),
• Opalstrukturen.

According to a further advantageous embodiment, the embossed structure consists of one or more of the following structures:

• sine or rectangular grid,
• sub-wavelength or moth-eye structures,
• Manhattan structures or an irregular rectangular grid with different distances, widths and heights of the grid structures,
• micromirrors,
• Fresnel structures, arched structures,
• matte structures,
• "Aztec structures" or a grid of a multitude of microscopic step pyramids with substructures,
• nanostructures,
• zero order diffraction grating (zero order device),
• "Christmas tree-like structures"("morphorhetenor"),
• opal structures.

According to a further advantageous embodiment, the embossed structure consists of a combination of the above-mentioned structures, whereby the structure types can be arranged adjacent to one another, rasterized, nested or even superimposed (substructures). For example, sinusoidal gratings can be present on a micromirror - or - moth-eye structures can be combined with diffractive structures.

According to a further advantageous embodiment, the volume hologram is designed as a reflection hologram, which requires a dark/black absorber in the background, or as a transmission hologram in a transparent window area without any dark absorbers.

According to a further advantageous embodiment, the volume hologram is designed in one or more colors or in true color.

According to a further advantageous embodiment, the volume hologram can have a color shift effect and could meaningfully complement/combine an existing color shift effect of the multilayer coating.

According to a further advantageous embodiment, the volume hologram can have a two-dimensional effect without depth effect and/or a three-dimensional effect with pronounced depth effect and/or dynamics when tilting.

According to a further advantageous embodiment, the volume hologram can be designed as a transmission hologram, whereby information can be seen/read out with coherent light (laser).

According to a further advantageous embodiment, the volume hologram can be designed as a white light reflection hologram.

An embossed structure can also serve as an exposure master for the volume hologram; in a preferred embodiment, the same embossed structure that is also used in the embossed layer, so that the same effects (color, dynamics, shape) can be seen in both areas.

As an absorber for a reflective volume hologram, which is viewed from above, a dark, preferably black absorber is required for better perception. This can be produced with a black body color, but also with a microstructure color, e.g. moth eye structures. Alternatively, a reflective reflector (e.g. aluminum) can be used, whereby the volume hologram is then preferably seen outside the gloss angle, i.e. when viewed at a very angle.

According to a further advantageous embodiment, the security element is applied as a film element in the form of strips or patches on a substrate (paper, polymer) or in a film-paper composite substrate or for embedding as a security thread in a substrate. The film element can also be applied/introduced onto or into a polymer substrate with ("L-element") or without ("T-element") a carrier film.

According to a further advantageous embodiment, the security element according to the invention can be combined with further machine-readable security elements. For example, one of the layers can contain one of the following elements or combinations thereof in regions or over the entire surface: magnet, IR, UV, phosphor, THz.

According to a further advantageous embodiment, the security element according to the invention can be combined with other printing and/or effect inks, such as super silver, gold color printing, iriodin, colored ink.

For both volume hologram and embossed layer, the following optically variable effects can be used when tilting or changing the viewing angle or changing the illumination angle: Depth effects (=stereoscopic effects), running, flipping, morphing effects, colour shift effect (top view), colour change effect ("trans-colour shift" when viewed through)

According to a further advantageous embodiment, the security element according to the invention can be designed as a window element with a different visual impression on two sides, particularly suitable as a window element, e.g. for polymer notes in a transparent area or for paper/foil composite banknotes in a window area.

According to a further advantageous embodiment, the security element according to the invention can have hidden information ("varifeye effect"). For example, the volume hologram is a reflection hologram and has no absorber in some areas in a transparent window. The hidden message of the volume hologram can only be recognized when the volume hologram is placed on a dark/black background.

According to a further advantageous embodiment, the volume hologram and the embossed layer are arranged at least partially overlapping in a window area, so that a viewer sees clearly different information or complementary motifs from the front and back.

Transmitted view occurs when the substrate is illuminated from one side and viewed from the other side. Top view occurs when the substrate is illuminated and viewed from the same side.

An optically variable element within the meaning of this invention is an element whose visual appearance changes when the element is tilted or rotated. For example, when the optically variable element is tilted or rotated, its color changes, a bar appears to move from one side of the element to the other side, different characters are displayed when tilted or rotated, or a so-called pumping effect occurs in the form of an enlarged or reduced outline of an image motif.

The substrate of the security element according to the invention particularly preferably consists of a plastic film or of paper made of cotton fibers, as is used for banknotes, for example, or of other natural fibers or of synthetic fibers or a mixture of natural and synthetic fibers. The substrate also preferably consists of a combination of at least two different substrates arranged one above the other and connected to one another, a so-called hybrid. The substrate here consists, for example, of a combination of plastic film-paper-plastic film, i.e. a substrate made of paper is covered on each of its two sides by a plastic film, or of a combination of paper-plastic film-paper, i.e. a substrate made of a plastic film is covered on each of its two sides by paper.

Valuable documents for which a security element according to the invention can be used are in particular banknotes, shares, bonds, certificates, vouchers, checks, high-value admission tickets, but also other papers at risk of forgery, such as passports and other identification documents, as well as cards, such as credit or debit cards, the card body of which has at least one layer of security paper, and also product security elements, such as labels, seals, packaging, folding boxes, package inserts and the like.

The simplified term “value document” includes all of the above-mentioned materials, documents and product security devices.

According to the invention, the coating that overlaps the exposable layer and the embossed structure has optically recognizable information in the form of a pattern, an alphanumeric character or a graphic image. Information in the sense of this invention is a pattern-shaped and visually perceptible representation. This can, for example, form an alphanumeric character sequence of numbers and/or letters, a graphic image, an image, text or other characters. The information particularly preferably consists of positive and/or negative motifs. In the case of a positive motif, a motif element itself is applied to the exposable layer and the embossed structure, whereas in the case of a negative motif, the area surrounding the motif element is applied to the exposable layer and the embossed structure. A positive motif is, for example, a letter printed in dark color on the light substrate. A negative motif is, for example, an area applied in dark color on the light substrate, which has an unprinted area in the form of a letter within the area.

It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations without departing from the scope of the present invention, as long as this is covered by the scope of protection of the claims.

The advantages of the invention are explained using the following embodiments and the supplementary figures. The embodiments represent preferred embodiments, to which the invention is not intended to be limited in any way. Furthermore, the representations in the figures are highly schematic for the sake of better understanding and do not reflect the actual conditions. In particular, the proportions shown in the figures do not correspond to the conditions in reality and are intended solely to improve clarity. Furthermore, the embodiments described in the following exemplary embodiments are reduced to the essential core information for the sake of better comprehensibility. In practical implementation, much more complex patterns or images can be used.

Fig. 1

ein erfindungsgemäßes Sicherheitselement gemäß einem ersten Ausführungsbeispiel,

Fig. 2

ein erfindungsgemäßes Sicherheitselement gemäß einem zweiten Ausführungsbeispiel,

Fig. 3

ein erfindungsgemäßes Sicherheitselement gemäß einem dritten Ausführungsbeispiel.

In detail, the following diagrams are shown:

Fig. 1

a security element according to the invention according to a first embodiment,

Fig. 2

a security element according to the invention according to a second embodiment,

Fig. 3

a security element according to the invention according to a third embodiment.

Fig. 1 shows schematically a security element according to the invention with a substrate 1, which consists for example of a transparent polymer film. An exposable layer 2 with a volume hologram and an embossed layer 3 adjacent to it are arranged on the substrate 1. The embossed layer 3 has on its surface facing away from the substrate 1 a non-diffractive embossed structure, which in this example consists of a triangular structure with oblique flanks. On the surface of the exposed layer 2, which faces away from the substrate 1, and a coating 4 is applied to the embossed structure of the embossed layer 3, which has a recess 5 above the exposed layer 2. A viewer from the front or top side of the security element sees the volume hologram in the exposed layer 2 through the recess 5.

The coating 4 has optically recognizable information in the form of a pattern, an alphanumeric character or a graphic image, which is not shown in the figure. For example, the outline of the coating 4 or the recess 5 can form the information.

Fig. 2 shows the security element Fig. 1 , in contrast to Fig. 1 the coating 4 also has recesses 6 and 7 above the embossed layer 3.

Fig. 3 shows the security element Fig. 1 , in contrast to Fig. 1 the coating 4 consists of a three-layer structure with the thin layers 4.1, 4.2 and 4.3.

For example, layer 4.1 consists of a reflective material, layer 4.2 of a transparent dielectric and layer 4.3 of a partially reflective or semi-transparent material. Together, the three layers form a thin-film element that shows a color shift effect, for example from magenta to green, when the viewing or illumination angle changes.

Claims (9)

1. Security element for increasing protection against forgery for security documents such as banknotes, valuable papers, identity cards, credit cards, debit cards or the like, wherein the security element consists of a substrate (1) with an exposable layer (2) arranged thereon, wherein the exposable layer (2) has a volume hologram, wherein adjacent to the exposable layer (2) an embossing layer (3) is arranged on the substrate (1), a non-diffractive embossing structure being introduced into the surface of said embossing layer facing away from the substrate (1), wherein at least partly a coating (4) is applied to the surface of the exposable layer (2) facing away from the substrate (1) and to the embossing structure, wherein the coating (4) overlaps the exposable layer (2) and the embossing structure and has optically recognizable information in the form of a pattern, an alphanumeric character or a graphical image representation, and wherein the coating (4) has at least one cutout (5) over the exposable layer (2).
2. Security element according to Claim 1, characterized in that the exposable layer consists of a photopolymer.
3. Security element according to Claim 1 or 2, characterized in that the embossing layer consists of an embossing lacquer.
4. Security element according to any of the preceding claims, characterized in that the coating consists of a monolayer or multilayer construction.
5. Security element according to Claim 4, characterized in that a monolayer construction consists of a layer having a high refractive index, preferably a thin vapour-deposited layer of zinc sulphide (ZnS).
6. Security element according to Claim 4, characterized in that a monolayer construction consists of a colour layer containing platelet-type metallic particles having a longest edge length of 15 nm to 1000 nm and a thickness of 2 nm to 100 nm, such that the colour layer exhibits a metallic hue in reflected light and a chromatic hue in transmitted light.
7. Security element according to Claim 4, characterized in that a two-layered construction consists of two thin layers of different metals applied one over the other.
8. Security element according to Claim 4, characterized in that a multilayered construction consists of a first metallic layer and a second metallic layer with a dielectric layer arranged between them.
9. Security element according to any of the preceding claims, characterized in that the embossing structure is formed from a plurality of achromatic microstructure elements having a lateral dimension of less than 1 mm, preferably between 3 µm and 100 µm.

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