EP1492679B2 - Security element comprising micro- and macrostructures - Google Patents

Abstract

A security element which is difficult to copy includes a layer composite which has microscopically fine, optically effective structures of a surface pattern, which are embedded between two layers of the layer composite. In a plane of the surface pattern, which is defined by co-ordinate axes x and y, the optically effective structures are shaped into an interface between the layers in surface portions of a holographically non-copyable security feature. In at least one surface portion the optically effective structure (9) is a diffraction structure formed by additive superimposition of a macroscopic superimposition function (M) with a microscopically fine relief profile (R). Both the relief profile (R), the superimposition function (M) and also the diffraction structure are functions of the co-ordinates x and y. The relief profile (R) is a light-diffractive or light-scattering optically effective structure and, following the superimposition function (M), retains the predetermined profile height. The superimposition function (M) is at least portion-wise steady and is not a periodic triangular or rectangular function. In comparison with the relief profile (R) the superimposition function (M) changes slowly. Upon tilting and rotation of the layer composite the observer sees on the illuminated surface portions light, continuously moving strips which are dependent on the viewing direction.

Description

The invention relates to a security element according to the preamble of claim 1.

Such security elements consist of a thin composite layer of plastic, wherein at least relief structures from the group of diffraction structures, light-scattering structures and planar mirror surfaces are embedded in the layer composite. The cut from the thin layer composite security elements are glued to objects to authenticate the authenticity of the objects.

The structure of the thin layer composite and the materials used for this purpose are, for example, in US 4,856,857 described. From the GB 2 129 739 A is also known to apply the thin layer composite with the aid of a carrier film on the object.

An arrangement of the type mentioned is from the EP 0 429 782 B1 known. The glued on a document security element has a example of the EP 0 105 099 A1 known, optically variable surface pattern of mosaic-like arranged surface parts with known diffraction structures. So that a forged document can not be provided with a counterfeit document cut out of a genuine document or detached from a genuine document in order to simulate an apparent authenticity, security profiles are embossed in the security element and in adjacent parts of the document. The real document is distinguished by the security profiles that extend seamlessly from the security element to adjacent parts of the document. The impressing of the security profiles interferes with the recognition of the optically variable area pattern. In particular, the position of the die on the security element varies from copy to copy of the document.

It is also known to equip the security elements with features that make copying or copying with conventional holographic means difficult or even impossible. For example, are from the EP 0 360 969 A1 and WO 99/38038 Arrangements of asymmetric optical gratings are described. The surface elements have gratings which, used at different azimuth angles, form a brightness-modulated pattern in the surface pattern of the security element. In a holographic copy, the brightness-modulated pattern is not reproduced. Are, like in the WO 98/26373 described, the structures of the lattice smaller than the wavelength of the light used for copying, such submicroscopic structures are no longer detected and thus not reproduced in the copy in the same manner.

The WO 01/80175 A1 describes a diffractive surface pattern formed as a visible mosaic composed of surface parts in a laminate of plastic. At least in one surface part, a "zero order microstructure" with a modulated lattice profile is formed whose spatial frequency f multiplied by a predetermined cutoff wavelength of the visible spectrum yields a product greater than or equal to one.

The documents mentioned in the examples EP 0 360 969 A1 . WO 98/26373 and WO 99/38038 described protection device against the holographic copying is bought with production technical difficulties.

The invention has for its object to provide a cost-effective, novel security element, which has a high resistance to counterfeiting attempts, e.g. by means of a holographic copying method.

This object is achieved by a security element according to claim 1.

Advantageous embodiments of the invention will become apparent from the dependent claims.

Figur 1

ein Sicherheitselement im Querschnitt,

Figur 2

das Sicherheitselement in Draufsicht,

Figur 3

Reflexion und Beugung an einem Gitter,

Figur 4

Beleuchtung und Beobachtung des Sicherheitselements,

Figur 5

Reflexion und Beugung an einer Beugungsstruktur,

Figuren 6

das Sicherheitsmerkmal unter verschiedenen Kippwinkeln,

Figur 7

eine Überlagerungsfunktion und die Beugungsstruktur im Querschnitt,

Figuren 8

das Ausrichten des Sicherheitselements mittels Kennmarken,

Figur 9

einen lokalen Neigungswinkel der Überlagerungsfunktion,

Figuren 10

das Ausrichten des Sicherheitselements mittels Farbkontrast im Sicherheitsmerkmal,

Figur 11

die Beugungsstruktur mit symmetrischer Überlagerungsfunktion,

Figuren 12

das Sicherheitsmerkmal mit Farbumschlag und

Figur 13

eine asymmetrische Überlagerungsfunktion.

Show it:

FIG. 1

a security element in cross section,

FIG. 2

the security element in plan view,

FIG. 3

Reflection and diffraction on a grid,

FIG. 4

Lighting and observation of the security element,

FIG. 5

Reflection and diffraction at a diffraction structure,

FIGS. 6

the security feature at different tilt angles,

FIG. 7

an overlay function and the diffraction structure in cross section,

FIGS. 8

the alignment of the security element by means of identification marks,

FIG. 9

a local tilt angle of the overlay function,

Figures 10

the alignment of the security element by means of color contrast in the security feature,

FIG. 11

the diffraction structure with symmetrical overlay function,

Figures 12

the security feature with color change and

FIG. 13

an asymmetric overlay function.

In the FIG. 1 3 denotes a layer composite, 2 a security element, 3 a substrate, 4 a cover layer, 5 an impression layer, 6 a protective layer, 7 an adhesive layer, 8 a reflective interface, 9 an optically active structure and 10 a transparent location in the reflective interface 8. The composite layer 1 consists of several layers of different, successively applied to a carrier film not shown here plastic layers and comprises in the order typically the cover layer 4, the impression layer 5, the protective layer 6 and the adhesive layer 7. The cover layer 4 and the impression layer 5 are transparent to incident light 11. If the protective layer 6 and the adhesive layer 7 are also transparent, indicia (not shown here, attached to the surface of the substrate 3) can be seen through the transparent location 10. The carrier film used in one embodiment, the cover layer 4 itself, in another embodiment, a carrier film is used to apply the thin layer composite 1 on the substrate 3 and is then removed from the layer composite 1, as for example in the aforementioned GB 2 129 739 A is described.

The common contact area between the impression layer 5 and the protective layer 6 is the interface 8. The optically active structures 9 having a structure height H _{St of} an optically variable pattern are formed in the impression layer 5. Since the protective layer 6 fills the valleys of the optically active structures 9, the interface 8 has the shape of the optically active structures 9. In order to obtain a high efficiency of the optically active structures 9, the interface 8 is provided with a metal coating, preferably from the elements of Table 5 of the aforementioned US 4,856,857 , in particular aluminum, silver, gold, copper, chromium, tantalum, etc., which separates the impression layer 5 and the protective layer 6 as a reflection layer. The electrical conductivity of the metal coating causes a high reflectivity for visible incident light 11 at the interface 8. However, one or more layers of one of the known, transparent inorganic dielectrics, for example, in Tables 1 and 4 of the above-mentioned are suitable instead of Metallbelags US 4,856,857 or the reflective layer has a multi-layered interference layer, such as a two-layered metal-dielectric combination or a metal-dielectric-metal combination. The reflection layer is structured in one embodiment, ie it covers the interface 8 only partially and in predetermined zones of the interface 8.

The composite layer 1 is produced as a plastic laminate in the form of a long film web with a multiplicity of juxtaposed copies of the optically variable pattern. For example, the security elements 2 are cut out of the film web and joined to a substrate 3 by means of the adhesive layer 7. The substrate 3, usually in the form of a document, a banknote, a bank card, a passport or other important or valuable object, is provided with the security element 2 in order to authenticate the authenticity of the object.

The FIG. 2 shows a section of the substrate 3 with the security element 2. By the cover layer 4 (FIG. Fig. 1 ) and the impression layer 5 ( Fig. 1 ) through a surface pattern 12 is visible. The surface pattern 12 lies in a plane spanned by the coordinate axes x, y and contains a security feature 16 of at least one surface part 13, 14, 15 easily recognizable in the contour with the naked eye, ie the dimensions of the surface part are greater than in at least one direction 0.4 mm. The security feature 16 is in the drawing of FIG. 2 double framed for illustrative reasons. In another embodiment, the security feature 16 of a mosaic of surface elements 17 to 19 of the above-mentioned EP 0 105 099 A1 surrounded mosaic described. In the surface parts 13 to 15 and optionally in the surface elements 17 to 19, the optically active structures 9 (FIG. Fig. 1 ), such as microscopically fine diffractive gratings, microscopically fine, light-scattering relief structures or even mirror surfaces in the interface 8 (FIG. Fig. 1 ) molded.

Based on FIG. 3 describes how this affects the interface 8 (FIG. Fig. 1 ) incident light 11 is reflected by the optically active structure 9 and deflected in a predetermined manner. The incident light 11 falls in the diffraction plane 20 which is perpendicular to the surface of the layer composite 1 with the security element 2 (FIG. Fig. 1 ) and contains a surface normal 21, on the optically active structure 9 in the composite layer 1 a. The incident light 11 is a parallel bundle of light rays and includes with the surface normal 21 the angle of incidence α. If the optically active structure 9 is a plane mirror surface parallel to the surface of the layer composite 1, the surface normal 21 and the direction of the reflected light 22 form the legs of the reflection angle β, where β = -α. If the optically effective structure 9 is one of the known grids, the grating deflects the incident light 11 into different diffraction orders 23 to 25 determined by the spatial frequency f of the grating, provided that the grating vector describing the grating lies in the diffraction plane 20 , The wavelengths λ contained in the incident light 11 are deflected at the predetermined angles into the different diffraction orders 23 to 25. For example, the grating simultaneously deflects violet light (λ = 380 nm) as beam 26 into the plus 1st diffraction order 23 as beam 27, into the minus 1 diffraction order 24 and as beam 28 into the minus 2 diffraction order 25. Light components with longer wavelengths λ of the incident light 11 will emerge in directions with larger diffraction angles to the surface normal 21, for example red light (λ = 700 nm) in the directions indicated by the arrows 29, 30, 31. The polychromatic incident light 11 is fanned out due to the diffraction at the grating in the light rays of the different wavelengths λ of the incident light 11, ie the visible part of the spectrum extends in the region between the violet light beam (arrow 26 and 27 and 28) and the red light beam (arrow 29 or 30 or 31) in each diffraction order 23, 24 and 25, respectively. The light diffracted into the zeroth diffraction order is the light 22 reflected by the angle of reflection β.

The FIG. 4 shows a in the surface elements 17 ( Fig. 2 ) until 19 ( Fig. 2 ) shaped diffraction grating 32, the microscopically fine relief profile R (x, y), for example, has a sinusoidal, periodic profile cross section of constant profile height h and with the spatial frequency f. The averaged relief of the diffraction grating 32 defines a central surface 33 arranged parallel to the cover layer 4. The parallel incident light 11 penetrates the cover layer 4 and the impression layer 5 and is applied to the optically effective structure 9 (FIG. Fig. 1 ) of the diffraction grating 32 deflected. The parallel diffracted light beams 34 of the wavelength λ leave the security element 2 in the line of sight of an observer 35, who in the illumination of the surface pattern 12 (FIG. Fig. 2 ) with the parallel incident light 11, the colored, brightly radiating surface elements 17, 18, 19 sees.

In the FIG. 5 lies the diffraction plane 20 in the plane of the drawing. In at least one of the surface parts 13 (FIG. Fig. 2 ) to 15 ( Fig. 2 ) of the security feature 16 ( Fig. 2 ), a diffraction structure S (x, y) is formed, the central surface 33 of which is arched or inclined locally to the surface of the layer composite 1. The diffraction structure S (x, y) is a function of the coordinates x and y in the plane of the surface pattern 12 parallel to the surface of the layer composite 1 (FIG. Fig. 2 ), in which the surface parts 13, 14 ( Fig. 2 ), 15 lie. In each point P (x, y), the diffraction structure S (x, y) determines a distance z parallel to the surface normal 21 to the plane of the surface pattern 12. More generally, the diffraction structure S (x, y) is the sum of the relief profile R (x, y). x, y) ( Fig. 4 ) of the diffraction grating 32 ( Fig. 4 ) and a well-defined overlay function M (x, y), the midplane 33, where S (x, y) = R (x, y) + M (x, y). For example, the relief profile R (x, y) generates the periodic diffraction grating 32 with the profile of one of the known sinusoidal, asymmetrical or symmetrical sawtooth or rectangular shapes.

In another embodiment, the microscopically fine relief profile R (x, y) of the diffraction structure S (x, y) is a matte structure instead of the periodic diffraction grating 32. The matte structure is a microscopically fine stochastic structure having a predetermined scattering characteristic for the incident light 11, wherein in an anisotropic matt structure instead of the grid vector, a preferred direction occurs. The matte structures scatter the perpendicularly incident light into a scattering cone having an aperture angle predetermined by the scattering power of the matte structure and the direction of the reflected light 22 as the cone axis. The intensity of the scattered light is e.g. on the cone axis largest and decreases with increasing distance from the cone axis, wherein the deflected in the direction of the generatrices of the scattering cone light is barely visible to an observer. The cross section of the scattering cone perpendicular to the cone axis is rotationally symmetric in a matt structure referred to here as "isotropic". On the other hand, if the cross section in the preferred direction is compressed, i. elliptical deformed with the short major axis of the ellipse parallel to the preferred direction, the matte structure is here called "anisotropic".

Because of the additive or subtractive overlay, the profile height h ( Fig. 4 ) of the relief profile R (x, y) in the region of the overlay function M (x, y) is not changed, ie the relief profile R (x; y) follows the overlay function M (x, y). The uniquely defined superimposition function M (x, y) is at least piecewise differentiable and curved at least in partial areas, ie ΔM (x, y) ≠ 0, periodic or aperiodic and is not a periodic triangular or rectangular function. The periodic superposition functions M (x, y) have a spatial frequency F of at most 20 lines / mm. For good visibility, links between two adjacent extreme values of the overlay functions M (x, y) are at least 0.025 mm long. The preferred values for the spatial frequency F are limited to at most 10 lines / mm and the preferred values for the distance between adjacent extreme values are at least 0.05 mm. The superimposition function M (x, y) thus varies as a macroscopic function in the continuous range slowly compared to the relief profile R (x, y).

One on the plane of the surface pattern 12 ( Fig. 2 ) projected intersection line of the diffraction plane 20 with the center plane 33 lays a track 36 (FIG. Fig. 2 ) firmly. The superimposition function M (x, y) has a gradient 38, grad (M (x, y)) at each point P (x, y) on the sections lying parallel to the track 36 with continuous sections. In general, the gradient 38 means the component of the degree (M (x, y)) in the diffraction plane 20, since the observer 35 defines the optically effective diffraction plane 20. The diffraction grating 32 has, in each point of the surface part 13, 14, 15, a gradient γ predetermined by the gradient 38 of the superposition function M (x, y).

The deformation of the central surface 33 causes a new, advantageous optical effect. This effect is explained by the diffraction behavior at transmission points A, B, C of the surface normal 21 and normal 21 ', 21 "to the central surface 33, eg along the track 36. The refraction of the incident light 11, the reflected light 22 and the diffracted light Light rays 34 at the boundary surfaces of the layer composite 1 is the sake of simplicity in the drawing of FIG. 5 not shown and not included in the following calculations. In each piercing point A, B, C, the inclination γ is determined by the gradient 38. The normals 21 'and 21 ", the grating vector of the diffraction grating 32 ( Fig. 4 ) and a viewing direction 39 of the observer 35 lie in the diffraction plane 20. In accordance with the angle of inclination γ, the angle of incidence α ( Fig. 3 ), which are enclosed by the dashed lines 21, 21 ', 21 "and the white, parallel incident light 11. This also changes the wavelength λ of the diffracted light beams 34 deflected in a predetermined viewing direction 39 to the observer 35. If the normal 21' tilted away by the viewer 35, the wavelength λ of the diffracted light beams 34 is greater than when the normal 21 "to the observer 35 is tilted. In the example shown by way of illustration, for the observer 35, the light beams 34 diffracted in the region of the piercing point A have a red color (λ = 700 nm). The diffracted in the region of the piercing point B light rays 34 are of yellow-green color (λ = 550 nm) and the diffracted in the region of the piercing point C light rays 34 have a blue color (λ = 400 nm). Since in the example shown, the inclination γ changes continuously over the curvature of the central surface 33, for the observer 35 along the track 36, the entire visible spectrum on the surface part 13, 14, 15 visible, whereby color bands of the spectrum on the surface part 13, 14, 15 extend perpendicular to the track 36. So that the color bands of the spectrum can be seen by the observer 35 at a distance of 30 cm, at least 2 mm in length or more must be selected for the distance between the throughput points A and C. Outside the visible spectrum, the surface of the surface part 13, 14, 15 has a faint gray. When tilting the layer composite 1 about a tilt axis 41 perpendicular to the plane of the FIG. 5 the angle of incidence α changes. The visible color bands of the spectra shift continuously in the region of the overlay function M (x, y) along the track 36. When tilting, for example in a clockwise direction about the tilting axis 41 of the layer composite 1, the color of the diffracted light beam 34 changes in the piercing point A ins Yellow-green, the color of the diffracted light beam 34 in the piercing point B to the blue and the color of the diffracted light beam 34 in the piercing point C in violet. The observer 35 perceives the change in the colors of the diffracted light 34 as migration of the color bands in a continuous manner over the surface part 13, 14, 15.

This consideration is true for any diffraction order. The number of color bands of how many diffraction orders the observer sees on the surface part 13, 14, 15 simultaneously depends on the spatial frequency of the diffraction grating 32 and the number of periods and the amplitude of the superposition function M (x, y) within the surface part 13, 14, 15 from.

In another embodiment, where one of the matte structures is substituted for the diffraction grating 32, the observer 35 sees in the direction of the reflected light 22 only a bright, white-gray band instead of the ribbons. In contrast to the color bands, the bright, whitish-gray band is visible to the observer 35 as a function of the scattering power of the matt structure, even if the color band is flat over the surface of the surface part 13, 14, 15 Viewing direction 39 is oblique to the diffraction plane 20. The following is therefore with "strip 40" ( Fig. 6a ) meant both the color bands of a diffraction order 23, 24, 25 and the bright white-gray band produced by the matt structure.

In the Fig. 6a is the displacement of the strip from the observer 35 (FIG. Fig. 5 ) easier to recognize when a reference to the security feature 16 is present. Serve as a reference on the surface portion 13, 14, 15, for example, on the central surface portion 14, arranged identification marks 37 ( Fig. 2 ) and / or a predetermined boundary shape of the surface part 13, 14, 15. Advantageously, the reference specifies a predetermined viewing condition, which is determined by tilting the layer composite 1 (FIG. Fig. 1 ) is adjustable so that the strip 40 is positioned predetermined against the reference. In the region of the identification marks 37, the optically active structure 9 (FIG. Fig. 1 ) of the interface 8 ( Fig. 1 ) is advantageously embodied as an optically active structure 9, a diffractive structure, mirror surface or light-scattering relief structure, which is formed when the surface pattern 12 is replicated in register with the surface parts 13, 14, 15. However, a light-absorbing imprint on the security feature 16 can also be used as a reference for the movement of the strip 40, or the identification mark 37 is produced by means of the structured reflection layer.

In a further embodiment of the security feature 16 according to the FIGS. 6 serve the adjacent on both sides of the central surface portion 14, adjacent surface portions 13 and 15 as a mutual reference. The adjacent surface parts 13 and 15 both have a diffraction structure S * (x, y). In contrast to the diffraction structure S (x, y), the diffraction structure S * (x, y) is the difference RM from the relief function R (x, y) and the superimposition function M (x, y), ie S * (x, y) = R (x, y) - M (x, y). The color bands produced by the diffraction structure S * (x, y) exhibit a reversed color gradient with respect to the color bands of the diffraction structure S (x, y), as shown in the drawing of FIGS FIG. 6a is indicated by a fat longitudinal boundary of the strip 40. For a good visibility of the optical effect without aids, the security feature 16 along the coordinate axis y or the track 36 has a dimension of at least 5 mm, preferably more than 10 mm. The dimensions along the coordinate axis x are more than 0.25 mm, but preferably at least 1 mm.

In the execution of the security feature 16 according to the FIGS. 6a to 6c the oval surface part 14 has the diffraction structure S (y) dependent only on the coordinate y, while the surface parts 13 and 15 with the diffraction structure S * (y) dependent only on the coordinate y on both sides of the oval surface part 14 along the coordinate y extend. The superposition function is M (y) = 0.5 • y ² • K, where K is the curvature of the center surface 33. The gradient 38 ( Fig. 5 ) and the grating vector of the diffraction grating 32 (FIG. Fig. 4 ) or the preferred direction of the "anisotropic" matt structure are aligned substantially parallel or anti-parallel to the direction of the coordinate y.

In general, the azimuth φ of the grating vector or the preferred direction of the matt structure is related to a gradient plane which is determined by the gradient 38 and the surface normal 21. The preferred values of the azimuth φ are 0 ° and 90 °. In this case, deviations in the azimuth angle of the grating vector or the preferred direction of δφ = ± 20 ° to the preferred value are admissible in order to regard the grating vector or the preferred direction as being substantially parallel or perpendicular to the gradient plane in this region. As such, the azimuth φ is not limited to the said preferred values.

The smaller the curvature K, the higher the speed of movement of the strips 40 in the direction of that in the drawing FIGS. 6 a and 6c are not designated arrows per angular unit of rotation about the tilting axis 41. The strip 40 is in the drawing of FIGS. 6a to 6c Narrow drawn to clearly show the movement effect. The width of the strips 40 in the direction of the unsigned arrows depends on the diffraction structure S (y). Particularly in the case of the color bands, the spectral color gradient extends over a larger part of the surface part 13, 14, 15, so that the movement of the strips 40 can be observed on the basis of the wandering of a detail in the visible spectrum, for example the red color band.

The FIG. 6b shows the security feature 16 after rotation about the tilting axis 41 in a predetermined tilt angle, below which the strips 40 of the two outer surface portions 13, 15 and the central surface portion 14 lie on a line parallel to the tilting axis 41. This predetermined tilt angle is determined by the choice of the overlay structure M (x, y). In an embodiment of the security element 2 ( Fig. 2 ) is on the surface pattern 12 ( Fig. 2 ) to see a predetermined pattern only when in the security feature 16, the strip or strips 40 occupy a predetermined position, ie when the observer 35 views the security element 2 under the viewing conditions determined by the predetermined tilt angle.

In the FIG. 6c are after a further rotation about the tilting axis 41, the strips 40 on the security feature 16 again diverge, as the non-designated arrows in the FIG. 6c suggest.

Of course, sufficient for the security feature 16 in another embodiment, an adjacent arrangement of the central surface portion 14 and one of the two surface portions 13, 15 from.

The FIG. 7 shows a cross section along the track 36 ( Fig. 2 ) through the layer composite 1, for example in the region of the surface part 14 (FIG. Fig. 2 ). So that the layer composite 1 is not too thick and thus difficult to manufacture or use, the structural height H _St ( Fig. 1 ) of the diffraction structure S (x; y). In the not to scale drawing of FIG. 7 is an example of the overlay function M (y) = 0.5 • y ² • K left of the coordinate axis z, in which the height of the layer composite 1 expands, shown in section alone. In each point P (x, y) of the surface part 14, the value z = M (x, y) is limited to a predetermined stroke H = z ₁ -z ₀ . As soon as the superimposition function M (y) at one of the points P ₁ , P ₂ ,..., P _{n has reached} the value z ₁ = M (P _j ) for j = 1, 2,..., N the superposition function M (y) on a discontinuity point at which on the side remote from the point P _0, the value of the overlay function M (y) is reduced by the value H to the height z ₀ , that is in the diffraction structure S (x; y) value of the overlay function M (x; y) is the function value $$\mathrm{z}=\left\{\mathrm{M}\left(\mathrm{x}\mathrm{y}\right)+\mathrm{C}\left(\mathrm{x};\mathrm{y}\right)\right\}\mathrm{modulo}\mathrm{H}\mathrm{u}\mathrm{b}\mathrm{H}-\mathrm{C}\left(\mathrm{x};\mathrm{y}\right)\mathrm{,}$$

The function C (x; y) is limited in terms of amount to a range of values, for example to half the value of the structure height H _ST . The discontinuities of the function {M (x; y) + C (x; y)} modulo Hub H-C (x; y) generated for technical reasons are not to be counted as extreme values of the superposition function M (x; y). Likewise, in certain implementations, the values for the hub H may be locally smaller. In one embodiment of the diffraction structure S (x; y), the locally varying stroke H is determined by the distance between two consecutive points of discontinuity P _n not exceeding a predetermined value in the range from 40 μm to 300 μm.

In the surface parts 13 ( Fig. 2 ), 14, 15 ( Fig. 2 ), the diffraction structure S (x, y) extends on both sides of the coordinate axis z and not only as in the drawing of FIG FIG. 7 is shown, to the right of the coordinate axis z. Because of the superposition, the structure height H _{St is} the sum of the stroke H and the profile height h (FIG. Fig. 4 ) and equal to the value of the diffraction structure S (x, y) at point P (x; y). The structure height H _St is advantageously less than 40 μm, preferred values of the structure height H _{St being} <5 μm. The stroke H of the overlay function M (x, y) is limited to less than 30 μm and is preferably in the range H = 0.5 μm to H = 4 μm. The matte structures have microscopic scale fine relief features that determine the scattering and can only be described with statistical parameters, such as average roughness R _a , correlation length I _c , etc., wherein the values for the average roughness R _a in the range 200 nm to 5 microns with preferred values of R _a = 150 nm to R _a = 1.5 μm, while the correlation lengths I _{c are} at least in one direction in the range of 300 nm to 300 μm, preferably between I _c = 500 nm to I _c = 100 μm. In the case of the "isotropic" matt structures, the statistical parameters are independent of a preferred direction, while in the case of the "anisotropic" matt structures, relief elements with the correlation length I _c are aligned perpendicular to the preferred direction. The profile height h of the diffraction grating 32 (FIG. Fig. 4 ) has a value from the range h = 0.05 μm to h = 5 μm, the preferred values being in the narrower range of h = 0.6 ± 0.5 μm. The spatial frequency f of the diffraction grating 32 is selected from the range f = 300 lines / mm to 3300 lines / mm. From about F = 2400 lines / mm, the diffracted light is 34 ( Fig. 5 ) only in the zeroth diffraction order, ie in the direction of the reflected light 22 (FIG. Fig. 5 ), observable.

Further examples of the overlay function M (x, y) are: $$\mathrm{M}\left(\mathrm{x}\mathrm{y}\right)=\mathrm{0}.\mathrm{5}•\left({\mathrm{x}}^{\mathrm{2}}+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">y</figure-callout>}}^{\mathrm{2}}\right)•\mathrm{K}.\mathrm{M}\left(\mathrm{x}\mathrm{y}\right)=\mathrm{a}•\left\{\mathrm{1}+\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">sin</figure-callout>}\left(\mathrm{2}{\mathrm{\pi F}}_{\mathrm{x}}•\mathrm{x}\right)•\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">sin</figure-callout>}\left(\mathrm{2}{\mathrm{\pi F}}_{\mathrm{y}}•\mathrm{y}\right)\right\}.$$

M (x, y) = a • x ^1.5 + b • x, M (x, y) = a • {1 + sin (2πF _y • y)}, where F _x or F _{y is} the spatial frequency F of the Overlay function M (x, y) in the direction of the coordinate axis x and y, respectively. In another embodiment of the security feature 16, the overlay functions M (x, y) are periodically composed of a predetermined section of another function and have one or more periods along the track 36.

In the FIG. 8a form the superposition function M (x, y) = 0.5 • (x ² + y ² ) • K, ie a spherical cap, and the relief structure R (x, y), ie an "isotropic" matt structure, the diffraction structure S (x , y) ( Fig. 7 ) in, for example, circularly bounded surface part 14. The observer 35 (FIG. Fig. 5 ) detects in daylight according to the viewing direction 39 ( Fig. 5 ), a bright white-gray spot 42 against a dark gray background 43, wherein the position of the spot 42 in the surface part 14 with respect to the identification mark 37 and the contrast between the spot 42 and the background 43 are dependent on the viewing direction 39. The extent of the stain 42 is determined by the scattering power of the matte structure and the curvature of the superposition function M (x, y). The security element 2 ( Fig. 2 ) is, for example, by tilting about the tilting axis 41 (FIG. Fig. 5 ) and / or rotating about the surface normal 21 (FIG. Fig. 5 ) of the layer composite 1 ( Fig. 5 ) like in the FIG. 8b in such a way to align the predetermined viewing direction 39, that the spot 42 is located within the identification mark 37, which is arranged for example in the center of the circularly surrounded surface portion 14.

The FIG. 9 shows the diffractive effect of the diffraction structure S (x, y) ( Fig. 7 ) in the diffraction plane 20. The relief structure R (x, y) ( Fig. 4 ) is the diffraction grating 32 (FIG. Fig. 4 ) with an eg sinusoidal profile and with a spatial frequency f less than 2400 lines / mm. The grating vector of the relief structure R (x, y) lies in the diffraction plane 20. The superposition function M (x, y) in the surface part 13 (FIG. Fig. 2 ), 14 ( Fig. 2 ), 15 ( Fig. 2 ) of the security feature 16 is determined by the effect of the diffraction structure S (x, y), wherein the light 11 incident perpendicularly on the layer composite 1 is deflected into the positive diffraction order 23 at a predetermined viewing angle + θ or -θ. Fig. 3 ) or in the negative diffraction order 24 ( Fig. 3 ) is distracted. In the diffraction plane 20, first beams 44 having the wavelength λ ₁ with the incident light 11 include the viewing angle θ and second beams 45 having the wavelength λ ₂ include the viewing angle -θ. The observer 35 (FIG. Fig. 5 ) sees the surface portion 13, 14, 15 at the viewing angle θ in the color with the wavelength λ ₁ . After rotation of the layer composite 1 in its plane by 180 °, the observer 35 sees the surface part 13, 14, 15 at the viewing angle -θ in the color of the wavelength λ ₂ . If the central surface 33 has the local inclination γ = 0 °, the wavelengths λ ₁ and λ ₂ do not differ. For other values of the local inclination γ, the wavelengths λ ₁ and λ ₂ differ. The dotted line normal 21 'on the inclined central surface 33 encloses the angle α with the incident beam 11, where α = -β = γ. The first beams 44 and the normal 21 'include the diffraction angle ξ ₁ , the second beams 45 and the normal 21' the diffraction angle ξ ₂ .

woraus folgt, dass für vorbestimmte Werte des Betrachtungswinkels ϑ und der Spatialfrequenz f die Summe der beiden Wellenlängen λ₁, λ₂ der Strahlen 44, 45 proportional zum Kosinus des lokalen Neigungswinkels γ ist. Die Gleichung (1) ist für andere Ordnungszahlen m leicht herzuleiten. Die Ordnungszahlen m und der Betrachtungswinkel ϑ für eine bestimmte, beobachtbare Farbe sind durch die Spatialfrequenz f bestimmt.Because ξ _k = asin (sin α + m _k • λ _k • f) and α = γ, the relationship for the two first diffraction orders 23, 24, ie for m _k = ± 1, results $$\mathrm{f}•\left({\mathrm{<figure-callout\; id="1"\; label="\lambda "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}_{\mathrm{2}}\right)=\mathrm{2}•\sin \left(\mathrm{\theta }\right)•\cos \left(\mathrm{\gamma }\right)$$

From this it follows that for predetermined values of the viewing angle θ and the spatial frequency f, the sum of the two wavelengths λ ₁ , λ _{2 of} the beams 44, 45 is proportional to the cosine of the local tilt angle γ. Equation (1) is easy to deduce for other atomic numbers m. The ordinal numbers m and the viewing angle θ for a particular observable color are determined by the spatial frequency f.

In the Figures 10a and 10b is an example of an embodiment of the security feature 16, wherein in the FIG. 10a the security element 2 against the security element 2 in the FIG. 10b rotated in its plane by 180 °. The diffraction plane 20 ( Fig. 9 ) is shown with its track 36. In the Figures 10a and 10b The security feature 16 comprises the three surface parts 13, 14, 15 with the diffraction structure S (x, y) = R (x, y) + M (x, y), wherein in the three surface parts 13, 14, 15 the diffraction structures S (x, y) by means of the equation (1) determined values of the local inclinations γ of the superposition function M (x, y) and the spatial frequency f of the relief profiles R (x, y) differ. A background field 46 adjoins at least one surface part 13, 14, 15 and has the diffraction grating 32 (FIG. Fig. 4 ) with the same relief profile R (x, y) and the background field 46 own Spatialfrequenz f. The grating vector of the relief profile R (x, y) is aligned parallel to the track 36 in the surface parts 13, 14, 15 and in the background field 46. With vertical illumination of the security element 2 with white light 11 ( Fig. 9 ) shine in the security feature 16 in the orientation of the FIG. 10a under the viewing angle + θ, the surface parts 13, 14, 15 and the background field 46 in the same color, and the observer 35 (FIG. Fig. 5 ) the security feature 16 appears to illuminate without contrast in a uniform color, for example, the deflected first beams 44 (FIG. Fig. 9 ) the wavelength λ ₁ , eg 680 nm (red), on. In the in the FIG. 10b the entire security feature 16 is observed under the viewing angle -θ. For example, the first surface part 13 shines in the second rays 45 (FIG. Fig. 9 ) of the wavelength λ ₂ , for example λ ₂ = 570 nm (yellow), the second surface portion 14 in the second beam 45 of the wavelength λ ₃ , for example λ ₃ = 510 nm (green) and the third surface portion 15 in the second beam 45 of Wavelength λ ₄ , eg λ ₄ = 400 nm (blue). In the background field 46, in which the middle surface 33 (FIG. Fig. 9 ) of the diffraction grating 32 ( Fig. 4 ) the inclination γ ( Fig. 9 ) with the value γ = 0, for symmetry reasons the second beams 45 are also of the wavelength λ ₁ , ie the background area 46 again shines in the red color. The advantage of this embodiment is the conspicuous optical behavior of the security feature 16, namely the color contrast visible under a single predetermined orientation of the security element 2 after a 180 ° rotation of the security element 2 around the surface normal 21 (FIG. Fig. 3 ) changes or disappears. The security feature 16 thus serves to define a predetermined orientation of the security element 2 with the non-holographically copied security feature 16.

For the sake of simplicity only, a uniform color, ie a constant inclination γ, has been assumed in each surface part 13, 14, 15 as an example. In general, the surface part 13, 14, 15 has a section of the superimposition function M (x, y), so that the inclination γ in the surface part 13, 14, 15 continuously changes in a predetermined direction and the wavelengths of the second rays 45 out an area on both sides of the wavelength λ _k originate. Instead of the similarly limited surface portions 13, 14, 15 form a plurality of arranged on the background field 46 surface portions 13, 14, 15 a logo, a lettering, etc.

In the FIG. 11 the diffraction structure S (x, y) is more complicated. The superimposition function M (x, y) is a symmetric, piecewise continuous, periodic function whose value varies along the coordinate axis x according to z = M (x, y), while M (x, y) along the coordinate axis y a constant value z having. The eg rectangular surface part 13, 14 (FIG. Fig. 10 ), 15 ( Fig. 10 ) is aligned with its longitudinal side parallel to the coordinate x and divided into narrow sub-areas 47 of the width b, whose longitudinal sides are aligned parallel to the coordinate axis y. Each period 1 / F _{x of} the overlay structure M (x; y) extends over a number t of the partial surfaces 47, eg the number t is in the value range from 5 to 10. The width b should not fall below 10 μm, since otherwise the diffraction structure S (x, y) is not defined enough on the partial surface 47.

The diffraction structures S (x, y) of the adjacent sub-areas 47 differ in the summands, the relief profile R (x, y) and the section of the superimposition function M (x, y) assigned to the subarea 47. The relief profile R _i (x, y) of the i-th partial surface 47 differs from the two relief profiles R _{i + 1} (x, y) and R _i-1 (x, y) of the adjacent partial surfaces 47 by at least one lattice parameter, such as Azimuth, spatial frequency, profile h ( Fig. 4 ), etc. If the spatial frequency F _x or F _{y is} at most 10 lines / mm but not less than 2.5 lines / mm, the observer 35 (FIG. Fig. 5 ) on the surface part 13, 14, 15 with the naked eye no subdivision by the periods of the superposition function M (x, y) recognize more. The subdivision and the occupation of the sub-areas 47 with the diffraction structure S (x, y) are repeated in each period of the superposition function M (x, y). In another embodiment of the security feature 16, the relief profile R (x, y) changes continuously as a function of the phase angle of the periodic overlay function M (x, y).

The in the FIG. 11 shown diffraction structures S (x, y) are in the embodiment of the in Figures 12 shown security feature 16 deployed, which unfolds a novel, optical effect in the illumination with white light 11 when the security feature 16 is tilted about the coordinate axis y parallel to the tilting axis 41. The security feature 16 comprises the triangular first surface part 14, which is arranged in the rectangular second surface part 13. In the first surface part 14, the diffraction structure S (x, y) is characterized in that the spatial frequency f of the relief profile R (x, y) in the direction of the coordinate axis x within each period of the superposition function M (x, y) is gradual or continuous a predetermined Spatialfrequenz- area changed δf, wherein the spatial frequency f _i in the ith subarea 47 ( Fig. 7 ) is greater than the spatial frequency f _i-1 in the preceding (i-1) -th sub-area 47. Thus, in each period, the first sub-area 47 has the spatial frequency f with the value f _A. For the sub-area 47 in the minimum of the period, the spatial frequency f = f _M and for the end of the period sub-area 47 is the value of the spatial frequency f = f _E , where f _A <f _M <f _E , where δf = f _E - f _A. In the second surface part 13, the diffraction structure S (x, y) is characterized in that the spatial frequency f of the relief profile R (x, y) in the direction of the coordinate axis x within a period of the superimposition function M (x, y) of the one face 47 to the next stepwise or continuously reduced. In one embodiment, by way of example, the diffraction structure S ** (x, y) = R (-x, y) + M (-x, y) of the second surface part 13 is the diffraction structure S mirrored at the plane spanned by the coordinate axes y, z (x, y) of the first surface part 14. The grating vectors and the track 36 (FIG. Fig. 11 ) of the diffraction plane 20 ( Fig. 9 ) are aligned in two surface portions 13, 14 substantially parallel to the tilting axis 41. The gradient 38 is substantially parallel to the plane spanned by the coordinate axes x and z.

In the FIG. 12a the security feature 16 lies in the x - y plane spanned by the coordinate axes x and y, the viewing direction 39 (FIG. Fig. 5 ) forms a right angle with the coordinate axis x. In the case of perpendicular white light 11 ( Fig. 1 ), the partial areas 47 are illuminated in the region of the minima of the superposition function M (x, y). Since these partial surfaces 47 in both diffraction structures S (x, y), S ** (x, y) have the same relief profile R (x, y) and the same inclination γ ≈ 0 °, the two surface parts 13, 14 in the viewing direction 39 diffracted light beams 34 ( Fig. 5 ) from the same region of the visible spectrum, eg green, so that the color contrast on the security feature 16 between the first surface part 14 and the second surface part 13 disappears. When tilting the security feature 16 about the tilt axis 41, the color contrast with increasing tilt angle occurs more clearly, as shown in the FIG. 12b is shown. When tilting to the left, the color of the first surface part 14 shifts in the direction of red, since the surface portions 47 (FIG. Fig. 11 ) with the relief profiles R (x, y), in which the spatial frequency f is less than f _M. The color of the second surface part 13 shifts in the direction of blue, since the partial surfaces 47 become effective, in which the spatial frequency f of the relief profile R (x, y) is greater than f _M. In the FIG. 12c is the security feature 1 of the in the FIG. 12a shown tilted position about the tilting axis 41 to the right. Even when tilting to the right, the color contrast is clear, but with reversed colors. The color of the first surface part 14 shifts in the direction of blue, since the partial surfaces 47 become effective, in which the spatial frequency f of the relief profile R (x, y) is greater than the value f _M , while the color of the second surface part 13 in the direction Red shifts because the faces 47 ( Fig. 11 ), in which the spatial frequency f of the relief profile R (x, y) of the diffraction structure S ** (x, y) decreases with respect to the value f _M.

In another embodiment of the diffraction structure S (x, y) of the FIG. 11 For example, the relief profile R (x, y) in the sub-areas 47 of each period 1 / F _{x has the} same spatial frequency f, but the relief profile R (x, y) differs from sub-area 47 to sub-area 47 by its azimuth angle φ of the grid vector relative to the coordinate axis y. Within a period 1 / F _x , the azimuth angle φ changes, for example, in the range δφ = ± 40 ° with φ ≈ 0 ° in the minimum of each period, stepwise or continuously. The azimuth angle φ is dependent on the local inclination γ ( Fig. 5 ) of the central surface 33 ( Fig. 5 ) is selected from the range δφ such that, on the one hand, the diffraction structure S (x, y) of the first surface part 14 (FIG. Fig. 12a ) at all tilt angles about the tilt axis 41 (FIG. Fig. 12b, c ) diffracted light beams 34 ( Fig. 5 ) of the color range predetermined by means of the spatial frequency f, for example from the green region, into the viewing direction 39 (FIG. Fig. 5 On the other hand, the second surface part 13 (12a) in which the mirrored diffraction structure S ** (x, y) is formed is ejected only at a single predetermined tilt angle in the predetermined color, for example, in a mixed color generated from the green region. lights. At other angles of tilt, the second surface part 13 is dark gray. For the azimuth angle range δφ = ± 20 ° given here by way of example, the green range extends from the wavelength λ = 530 nm (φ≈0 °) to the wavelength λ = 564 nm.

In the FIG. 13 For example, the overlay function M (x, y) employed in the diffraction structure S (x, y) is an asymmetric function in the coordinate axis x direction. The overlay function M (x, y) increases aperiodically within the period 1 / Fx from a minimum value to a maximum value, eg like the function y = const • x ^1.5 . The spatial frequency F _x or F _y is in the range of 2.5 lines / mm to and 10 lines / mm. Not shown are the points of discontinuity caused by Operation Modulo Hub H ( Fig. 7 ) arise. The above-described "anisotropic" matt structure with the preferred direction substantially parallel to the coordinate axis x is used as a relief profile R (x, y). The incident light 11 ( Fig. 5 ) is therefore scattered mainly parallel to the coordinate axis y fanned out. In the first surface part 14 (FIG. Fig. 12a ) diffraction structure S (x, y) = R (x, y) + M (x, y) and in the second surface part 13 (FIG. Fig. 12a ), the diffraction structure S ** (x, y) = R (-x, y) + M (-x, y) is formed. Based on FIG. 12a is the optical effect of the security feature 16 with light 11 incident perpendicular to the x - y plane (FIG. Fig. 9 ) explained. If the security feature 16 lies in the x-y plane, the incident light 11 is scattered with great intensity by the matt structure in the region of the minima of the superposition function M (x, y), the scattering effect of the remaining surface parts 47 of the diffraction structures S (x, y ), S ** (x, y) is negligible. The light backscattered by the surface parts 13, 14 has the color of the incident light 11 (FIG. Fig. 5 ) and has in both surface parts 13, 14 the same surface brightness, so that no contrast between the two surface parts 13, 14 can be seen. In the FIG. 12b meets the incident light 11 ( Fig. 5 ) at an angle of incidence α on the security feature 16, which is tilted to the left about the tilting axis 41. Only in the second surface part 13 is the incident light 11 (FIG. Fig. 5 ). In this illumination condition, the surface brightness of the first surface part 14 is smaller by orders of magnitude than in the second surface part 13, so that the first surface part 14 stands out as a dark surface against the bright second surface part 13. In the FIG. 12c is the security feature 16 tilted away to the right, now the surface brightness of the two surface parts 13, 14 are reversed.

In the FIGS. 12a to 12c For example, instead of a single triangular first surface part 14 on the second surface part 13, a plurality of the first surface parts 14 may be arranged, which form a logo, a lettering, etc.

In a further embodiment, instead of the simple mathematical functions, relief images, as used on coins and medals, are also used as at least piecewise continuous superimposition function M (x, y) in the diffraction structure S (x, y), wherein advantageously the relief profile R (x, y) is an "isotropic" matte structure. The observer of the security element 2 in this embodiment receives the impression of a three-dimensional image with a characteristic surface structure. When rotating and tilting the security element 2, the brightness distribution in the image changes according to the expectation in a true relief image, but projecting elements do not cast a shadow.

Without deviating from the idea of the invention, all diffraction structures S are in their structural height to the value H _St ( Fig. 1 ), as indicated by the FIG. 7 was explained. The relief profiles R (x, y) and overlay functions M (x, y) used in the special embodiments described above can be combined as desired to form other diffraction structures S (x, y).

The use of the security features 16 described above in the security element 2 has the advantage that the security feature 16 forms an effective barrier against attempts to holographically copy the security element 2. In a holographic copy, the positional shifts or color shifts on the surface of the security feature 16 can be recognized only in a modified form.

Claims (15)

1. Security element (2) from a layer composite (1) with microscopically fine, optically active structures (9) of an area pattern (12) which are embedded between transparent layers (4; 5; 6) of the layer composite (1), wherein the optically active structures (9) are moulded in subareas (13; 14; 15; 46) of a security feature (16) in a reflective boundary layer (8) between the layers (5; 6) on a plane of the area pattern (12) that is spanned by coordinate axes (x; y), characterized in that at least one subarea (13; 14; 15) with dimensions of greater than 0.4 mm has a diffraction structure (S; S*; S**) which is formed by additive or subtractive superposition of a superposition function (M), which describes a macroscopic structure, with a microscopically fine relief profile (R), with the superposition function (M), the relief profile (R) and the diffraction structure (S; S**; S**) being functions of the coordinates (x; y) and the relief profile (R) describing a light-diffusing optically active structure (9) which retains the predetermined relief profile (R) following the superposition function (M), and in that a middle surface (33), which is defined by the at least partially continuous superposition function (M), is curved at least in partial regions and has in each point a local inclination angle (γ), which is predetermined by the gradient of the superposition function (M), is not a periodic triangular or rectangular function and changes gradually in comparison with the relief profile (R).
2. Security element (2) according to Claim 1, characterized in that the superposition function (M) is a partially continuous, periodic function with a spatial frequency (F) of at most 20 lines/mm.
3. Security element (2) according to Claim 1, characterized in that the superposition function (M) is an asymmetric, partially continuous, periodic function with a spatial frequency (F) in the range of 2.5 lines/mm to 10 lines/mm.
4. Security element (2) according to Claim 1, characterized in that, in the subarea (13; 14; 15), neighbouring extreme values of the superposition function (M) are spaced apart from each other by at least 0.025 mm.
5. Security element (2) according to one of Claims 2 to 4, characterized in that the relief profile (R) is an anisotropic matt structure having a preferential direction with an azimuth angle (ϕ).
6. Security element (2) according to Claim 5, characterized in that the security feature (16; 16') has at least two neighbouring subareas (13; 14; 15), and in that the first diffraction structure (S) is moulded in the first subarea (14) and the second diffraction structure (S*, S**), which differs from the first diffraction structure (S), is moulded in the second subarea (13; 15), wherein the preferential direction of the first relief profile (R) in the first subarea (14) and the preferential direction of the second relief profile (R) in the second subarea (13; 15) are aligned substantially parallel.
7. Security element (2) according to one of Claims 5 to 6, characterized in that, in the diffraction structure (S; S*; S**), the preferential direction of the relief profile (R) is substantially parallel to a gradient plane that is determined by the gradient (38) of the superposition function (M) and a surface normal (21) which is perpendicular to the surface of the layer composite (1).
8. Security element (2) according to one of Claims 5 to 7, characterized in that the first diffraction structure (S) is moulded in a first subarea (14), which first diffraction structure (S) is formed as a sum from the relief profile (R) and the superposition function (M), and in that the second diffraction structure (S*) is moulded in a second subarea (13; 15), which second diffraction structure is formed as a difference (R - M) from the same relief profile (R) and the same superposition function (M).
9. Security element (2) according to one of Claims 5 to 8, characterized in that, in the diffraction structure (S; S*; S**), the preferential direction of the relief profile (R) is substantially perpendicular to a gradient plane which is determined by the gradient (38) of the superposition function (M) and a surface normal (21) which is perpendicular to the surface of the layer composite (1).
10. Security element (2) according to Claim 5, characterized in that, in the first subarea (14), the first diffraction structure (S) is formed from the sum from the relief profile (R) and the superposition function (M), and in that, in the second subarea (13; 15), the diffraction structure (S**) is the first diffraction structure (S) which is mirrored at the plane of the area pattern (12
11. Security element (2) according to Claim 1, characterized in that the relief profile (R) is an isotropic matt structure.
12. Security element (2) according to Claim 11, characterized in that the superposition function (M) describes a relief image.
13. Security element (2) according to Claim 11, characterized in that the superposition function (M) describes a spherical cap.
14. Security element (2) according to one of Claims 1 to 13, characterized in that further area elements (17; 18; 19) with the optically active structures (9) are parts of the area pattern (12) and in that at least one of the area elements (17; 18; 19) adjoins the security feature (16).
15. Security element (2) according to one of Claims 1 to 14, characterized in that at least one identifying mark (37) with an optically active structure (9) that differs from the diffraction structure (S; S*; S**) is arranged on at least one of the subareas (13; 14; 15) and in that the identifying mark (37), which can be used as a reference for aligning the layer composite (1), has one of the optically active structures (9) from the group of the diffractive or diffusing relief structures or a mirror surface.

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