EP3288770B1 - Security element having a multilayer structure - Google Patents

Description

The invention relates to a security element for security papers, documents of value or the like, which consists of an interference-capable, multi-layered structure, wherein the interference-capable, multi-layered structure comprises a reflective layer, a dielectric layer and a partially transparent layer, wherein the dielectric layer between the reflective layer and the partially transparent layer is arranged.

A generic security element is for example from the WO 2005/108110 A1 or the WO 2005/038136 A1 known.

If the generic security element viewed from the side of the partially transparent layer, the viewer perceives a certain color, which changes with change of the viewing angle. The cause of the color shift is an interference effect between the light rays reflected from the surface of the outer partially transmissive layer and the light rays which pass through the outer partially transmissive and middle dielectric layers and are reflected back from the reflection layer to the partially transmissive layer. The light beams are then either transmitted to the outside or reflected again at the partially transparent layer, so that in this case the light beams are repeatedly reflected back and forth between the reflection layer and the partially transparent layer. Thus, the light beams that have passed through the thin film layer have traveled a longer distance than the light beams reflected on the surface of the thin film layer, so that they are out of phase with each other when interfering with them. If the light rays incident on the thin film layer encounter the thin film layer at different angles of incidence, the light beam is in the Thin-film layer traveled path of light rays of different lengths. This difference results from the path difference of the beams reflected multiple times within the thin film layer due to the angle of incidence. Therefore, the phase angle of the interfering light beams is different depending on the angle of incidence, so that depending on the angle of incidence different colors or hues of the resulting, perceived by the observer light beam result, a so-called color shift effect. Due to its mode of operation, such a generic security element is also referred to as a thin-film layer interference layer structure or as a color shift element.

For generating different optically variable effects in a generic security element in supervision and in review, it is for example from the WO 2009/149831 A2 It is known to introduce a plurality of recesses into the partially transparent layer and the reflective layer. However, these security elements are relatively expensive to produce and produce in transmitted light, viewed from the back, only a uniform gray hue

The patent document EP 2 708 371 A1 discloses a security element having the features of the preambles of claims 1 and 3.

The invention is therefore the object of developing a generic security element such that the disadvantages of the prior art is eliminated and the protection against counterfeiting is further increased.

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

According to the invention, the reflection layer of the interference-capable, multilayer structure is formed by a color layer or a further multilayer structure, wherein the color layer and the multilayer structure are configured such that they show a metallic hue in reflected light and a colorful hue in transmitted light.

For the purposes of this invention, a color layer with a metallic hue is a color layer which has a metallically reflecting surface with a metal-colored hue, which is preferably golden or golden, silver or silver-colored or bronze-colored.

For the purposes of this invention, a color layer with a colored hue is a color layer which has a single- or multi-colored surface, preferably a monochrome blue, a monochrome green or a monochrome red.

Transmitted light is present when the illumination of an object takes place from one side and the viewing from the other side. Incident light is when the illumination and viewing are from the same side of an object.

If the reflection layer is formed by a color layer, then the color layer 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 golden hue in reflected light and a blue hue 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 from the WO 2011/064162 A2 known and is also referred to as gold-blue color.

• Aluminium oder einer Aluminium-Legierung, wobei die dielektrische Abstandsschicht mit einer Dicke h und einem Brechungsindex v die Relation 120 nm < h ·v < 190 nm erfüllt oder
• Silber oder einer Silber-Legierung, wobei die dielektrische Abstandsschicht mit einer Dicke h und einem Brechungsindex v die Relation 120 nm < h ·v < 170 nm oder 340 nm < h ·v < 400 nm erfüllt.

If, on the other hand, the reflection layer is formed by a further multilayer structure, then the further multilayer structure has at least two semitransparent mirror layers and at least one dielectric layer arranged between the at least two mirror layers, as described, for example, in US Pat DE 10 2009 058 243 A1 is known, so that the security element consists of an interference-capable, multi-layered structure of at least five superimposed layers. The reflection layer exhibits a resonance with a half-value width of 70 nm to 150 nm when measuring the transmission of unpolarized light in the blue wavelength range from 420 nm to 490 nm. Preferably, the resonance of the reflection layer is the only resonance in the visible range. The at least two semitransparent mirror layers of the reflection layer are preferably formed from:

• Aluminum or an aluminum alloy, wherein the dielectric spacer layer having a thickness h and a refractive index v satisfies the relation 120 nm <h v <190 nm or
• Silver or a silver alloy, wherein the dielectric spacer layer having a thickness h and a refractive index v, the relation 120 nm <h · v <170 nm or 340 nm <h · v <400 nm.

Further embodiments and specific thickness specifications for the layers used of the further multilayer structure are known from DE 10 2009 058 243 A1 to which reference is hereby made.

The invention thus replaces the reflection layer of a color shift element known from the prior art by a color layer with platelet-shaped metallic particles or by a further multilayer structure of at least two semitransparent mirror layers and at least one arranged between the at least two mirror layers dielectric layer. In reflected light, both the color layer with platelet-shaped metallic particles and the further multi-layered structure show a golden hue, thus reflecting the incident light and acting like a reflection layer. Thus, the security element according to the invention in reflected light shows the color-shifting effect known from the prior art. In transmitted light, however, both the color layer with platelet-shaped metallic particles and the further multi-layered structure show a blue hue and reflect the incident light not or only insignificantly. In transmitted light, the security element according to the invention thus shows a blue hue and no color shift effect.

According to a preferred embodiment, it is provided that at least one of the dielectric layers of the interference-capable, multilayer structure consists of silicon dioxide (SiO ₂ ). The partially transparent layer of the interference-capable, multilayer structure preferably consists at least of chromium and / or nickel. Alternatively, a dielectric layer may consist of a transparent printing layer having a constant thickness.

The invention further relates to a see-through security element for security papers, documents of value and the like, with a carrier and a security element according to the invention applied to the carrier. Such a carrier is in particular a transparent or translucent plastic film.

Particularly preferably, a lacquer layer can be arranged between the security element and the carrier, which preferably consists of an embossing lacquer. Such an embossing lacquer may be, for example, a UV lacquer, i. a lacquer which cures under the action of ultraviolet light, or a thermoplastic embossing lacquer. Diffractive structures, holograms or micromirrors are preferably embossed in this embossing lacquer. The thickness of this lacquer layer is 1 μm to 12 μm, preferably 2 μm to 7 μm.

Translucency in the sense of this invention means that an object, such as the substrate or the plastic film, can transmit incident light in a certain proportion. If light strikes one side of the object, a certain portion of the light is transmitted to the other side of the object and exits there again. The greater the percentage of transmitted light, with respect to the incident light, the more translucent the object is. If the percentage is at least 90%, i. If the object allows the incident light to pass through almost unattenuated, as in the case of a window, the object is called transparent. An object, on the other hand, which transmits less than 10% and preferably about 0% of the incident light, i. where the amount of light passing through, with respect to the incident light, is low, close to or equal to zero, is said to be opaque or non-translucent.

A security paper, document of value or the like is particularly preferably made of a substrate made of paper from cotton fibers, as used for example for banknotes, or from other natural fibers or from synthetic fibers or a mixture of natural and synthetic fibers, or from at least one plastic film. Further preferably, the substrate consists of a combination of at least two superimposed and interconnected different substrates, a so-called hybrid. Here, the substrate is made of, for example, a combination of plastic film-paper plastic film, ie a paper substrate is covered on both sides by a plastic film, or a combination of paper-plastic film paper, ie a substrate made of a plastic film on each of its covered by paper on both sides.

Information on the weight of the substrate used are, for example, in the Scriptures DE 102 43 653 A9 specified, the statements of which are fully incorporated in this application in this regard. The font DE 102 43 653 A9 in particular states that the paper layer usually has a weight of 50 g / m ² to 100 g / m ² , preferably from 80 g / m ² to 90 g / m ² . Of course, depending on the application, any other suitable weight can be used.

Security papers, documents of value or the like in which a security element according to the invention can be used are, in particular, banknotes, stocks, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other papers that are subject to counterfeiting, such as passports and other identity documents, as well as cards such as credit - or debit cards whose card body has at least one layer of security paper and also product securing elements, such as labels, seals, packaging and the like.

The simplified term value document includes all the above materials, documents and product safeguards.

The terms "front side" or "back side" of a substrate, security paper, or value document are relative terms, which may also be referred to as "the one" and "the opposite" sides, and which constitute the overwhelming portion of the overall surface of the substrate, security paper, or value document. Specifically, these terms do not include the side surfaces of a substrate, security paper, or value document which are negligibly small, and usually not with security elements, in a thickness of a substrate or value document which is only about a millimeter in card bodies or fractions of a millimeter in banknotes Coatings can be provided or can be. In particular, no see-through effects can be achieved with the side surfaces.

According to a preferred embodiment, the security element according to the invention shows an observer in incident light and in transmitted light information. Information in the sense of this invention is a pattern-shaped and visually perceptible coating. This can, for example, form a graphic image, an image, a number, a letter, a text or other characters. Particularly preferably, the information consists of positive and / or negative motives. In the case of a positive motif, in this case a motif element is itself applied to the substrate, whereas in the case of a negative motif the area surrounding the motif element is applied to the substrate. For example, a positive subject is a letter printed in dark color on the light substrate. A negative motif is, for example, a surface applied in a dark color to the 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 yet to be explained below can be used not only in the specified combinations but also in other combinations, without departing from the scope of the present invention, insofar as this is covered by the scope of the claims.

Reference to the following embodiments and the additional figures, the advantages of the invention will be explained. The embodiments represent preferred embodiments, to which, however, the invention should not be limited in any way. Furthermore, the representations in the figures of the better understanding are highly schematized and do not reflect the realities. In particular, the proportions shown in the figures do not correspond to the conditions present in reality and serve exclusively to improve the clarity. Furthermore, the embodiments described in the following exemplary embodiments are reduced to the essential core information for the sake of clarity. In the practical implementation much more complex patterns or images can be used.

Fig. 1

ein erfindungsgemäßes Sicherheitselement, dessen Reflexionsschicht aus einer Farbschicht besteht,

Fig. 2

ein erfindungsgemäßes Sicherheitselement, dessen Reflexionsschicht aus einem weiteren mehrschichtigen Aufbau besteht,

Fig. 3

das erfindungsgemäße Sicherheitselement aus Fig. 1, das mit einer Lackschicht auf einem Träger befestigt ist.

Specifically, each in side view schematically show:

Fig. 1

a security element according to the invention whose reflection layer consists of a color layer,

Fig. 2

a security element according to the invention whose reflection layer consists of a further multilayer structure,

Fig. 3

the security element according to the invention Fig. 1 , which is fastened with a layer of varnish on a support.

Fig. 1 shows a side view of an inventive security element with a partially transparent layer 3 and a reflective layer 1, between which a dielectric layer 2 is arranged. These three layers together form a thin film layer interference layer structure. The reflection layer 1 consists of a color layer which 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 this color layer shows a golden hue in reflected light and a blue hue in transmitted light.

An observer 9, looking at the security element from the front 7 of the security element, looks at the partially transparent layer 3 of the interference-capable, multi-layered construction. Thus, the viewer 9 sees in incident light, i. with a lighting 11 from the front 7, a color shift effect, in which the color of the security element changes when tilting the security element, for example, from purple to green. In transmitted light, i. E. when illuminated 12 from the back 8 of the security element, the color shift effect disappears and the viewer 9 sees the security element in a blue color.

A viewer 10 looking at the security element from the back 8 of the security element looks at the color layer with platelet-shaped metallic particles. Thus, the viewer sees 9 in incident light, ie with a lighting 12 from the back 8, the security element in a golden color and in transmitted light, ie with a lighting 11 from the front 7, the security element in a blue color.

Fig. 2 shows a side view of a security element according to the invention, in which the reflection layer 1 in contrast to the security element from Fig. 1 consists of a further multilayer structure comprising two semitransparent mirror layers 4 and 6 and at least one dielectric layer 5 arranged between the two mirror layers. The two semitransparent mirror layers 4 and 6 preferably each consist of a thin layer of aluminum and the dielectric layer 5 of SiO ₂ . For a viewer results in incident and transmitted light both from the front 7 and 8 from the back of the same effect as for the viewer Fig. 1 ,

Fig. 3 shows the security element according to the invention Fig. 1 , which is fastened with a lacquer layer 15 on a support 16. The lacquer layer 15 here preferably consists of a UV lacquer, the support 16 preferably made of a plastic film. According to Fig. 3a the security element is attached to the reflective layer 1 on the lacquer layer 15 on the support 16 and according to Fig. 3b with the partially permeable layer 3.

Claims (10)

1. Security element for security papers, valuable documents or the like, which consists of a multi-layered construction capable of interference, wherein the multilayered construction capable of interference comprises a reflection layer (1), a dielectric layer (2) and a partly transmissive layer (3), wherein the dielectric layer (2) is arranged between the reflection layer (1) and the partly transmissive layer (3), characterized in that the reflection layer (1) consists of a colour layer containing laminar metallic particles whose longest edge length is 15 nm to 1000 nm and whose thickness is 2 nm to 100 nm, such that the colour layer exhibits a metallic hue in reflected light and a chromatic hue in transmitted light.
2. Security element according to Claim 1, characterized in that the laminar metallic particles have a longest edge length of preferably 15 nm to 600 nm and particularly preferably 20 nm to 500 nm, and a thickness of preferably 2 nm to 40 nm and particularly preferably 4 nm to 30 nm.
3. Security element for security papers, valuable documents or the like, which consists of a multi-layered construction capable of interference, wherein the multilayered construction capable of interference comprises a reflection layer (1), a dielectric layer (2) and a partly transmissive layer (3), wherein the dielectric layer (2) is arranged between the reflection layer (1) and the partly transmissive layer (3), characterized in that the reflection layer (1) consists of a further multilayered construction comprising at least two semi-transparent mats (4, 6) and at least one dielectric layer (5) arranged between the at least two mirror layers, such that the security element consists of a multilayered construction capable of interference and composed of at least five layers arranged one above another, wherein upon measurement of the transmission of unpolarized light in the blue wavelength range of 420 nm to 490 nm, the reflection layer (1) exhibits a resonance having a full width at half maximum of 70 nm to 150 nm, such that the further multilayered construction exhibits a metallic hue in reflected light and a chromatic hue in transmitted light.
4. Security element according to Claim 3, characterized in that the resonance is the sole resonance in the visible range.
5. Security element according to Claim 3 or 4, characterized in that the at least two semi-transparent mirror layers (4, 6) are formed from aluminium or an aluminium alloy and the dielectric spacer layer having a thickness h and a refractive index v satisfies the relation 120 nm < h · v < 190 nm.
6. Security element according to Claim 3 or 4, characterized in that the at least two semi-transparent mirror layers (4, 6) are formed from silver or a silver alloy and the dielectric spacer layer having a thickness h and a refractive index v satisfies the relation 120 nm < h · v < 170 nm or 340 nm < h · v < 400 nm.
7. Security element according to at least one of the preceding claims, characterized in that at least one of the dielectric layers (2, 5) consists of a transparent printed layer or of silicon dioxide.
8. Security element according to at least one of the preceding claims, characterized in that the partly transmissive layer (3) consists at least of chromium and/or nickel.
9. See-through security element for security papers, valuable documents and the like, comprising a carrier (16) and a security element according to any of Claims 1 to 8 that is applied on the carrier (16).
10. See-through security element according to Claim 9, characterized in that a lacquer layer (15) is arranged between the security element and the carrier (16), said lacquer layer preferably consisting of an embossing lacquer.

Images