DE102016214407A1 - Optically variable security element - Google Patents

Abstract

The invention relates to an optically variable security element (1) having a relief layer (102) with a multiplicity of structurally identical individual optical elements (2), each having a single element surface (6) divided into partial surfaces (61, 62) facing different Have reflectivities, and the sub-surfaces (61, 62) are grouped such that each group includes a sub-surface (61, 62) of a single-element surface (6) and each group encodes an associated viewing-angle-dependent, naked-eye reflection motif, and at least a planar region (3) which extends between the individual optical elements (2) and which comprises diffraction gratings (31, 32) which produce at least one viewing angle dependent diffraction pattern visible to the naked eye through the predetermined directional illumination and viewing angle dependent reflection motifs and the at least one Viewing angle-dependent diffraction motifs generate viewing-angle-dependent overall motifs which are visible to the naked eye.

Description

The invention relates to an optically variable security element and a manufacturing method for an optically variable security element.

Optically variable security elements are well known in the art. For example, in the DE 10 2013 021 806 A1 a security element for displaying at least one optically variable information disclosed with a reflective layer, which is formed from a grid of optically active elements which are formed by embossing elements of identical basic shape. The raster of optically active elements contains at least one optically variable information that can be detected in reflected illumination without aids in reflection.

Besides that is from the DE 10 2013 001 734 A1 a security element for the production of value documents known with an upper side, on which a microrelief structure is formed, which has at least two subregions, each having a plurality of groove or rib-shaped, juxtaposed and extending along a longitudinal direction, reflecting or backscattering structural elements.

However, the security elements mentioned have the disadvantage that they only produce reflection images.

It is therefore an object of the present invention to provide a further developed optically variable security element which, in addition to reflection images, contains a further security element. It is another object of the invention to provide a manufacturing method for an optically variable security element according to the invention.

The object is achieved by an initially mentioned optically variable security element having the features of claim 1.

The invention makes use of the idea of combing together two security features distributed over an optically effective surface of a variable security element. For this purpose, a relief layer is provided, which extends along the optically active surface of the security element. The relief layer has a plurality of identical individual optical elements. Each individual element has a single element surface subdivided into sub-surfaces having different directional reflectivities, and the sub-surfaces are grouped such that each group comprises a sub-surface of a single-element surface, and each group of sub-surfaces is an associated viewing-angle-dependent, visible to the naked eye reflection image coded. The plurality of individual optical elements forms a security feature based on the formation of reflection images.

In addition, at least one planar region is provided in the relief layer, which extends between the individual optical elements and is provided with a diffraction grating structure applied over the at least one planar region, which generates viewing angle-dependent diffraction motifs visible to the naked eye through the predetermined directional illumination.

The invention thus makes use of the idea to provide a diffraction grating structure between the reflective individual elements. In the case of the same directional illumination, which also acts on the individual elements, the diffraction grating structure forms viewing angle-dependent diffraction motifs. According to the invention, the viewing angle-dependent diffraction motifs and the viewing angle-dependent reflection motifs form overall images which are likewise visible to the naked eye. Diffraction motifs and reflection motifs are interlaced with each other.

The disclosure of the post-published patent application DE 10 2015 202 106.8 is fully incorporated in this patent application.

With regard to the reflection motifs, a first reflection motif is divided into first sub-motifs. The first partial motifs are assigned first directional reflectances, which encode the reflection motif. These are preferably either partial surfaces with a high degree of reflection, preferably completely reflecting, or areas with a very low degree of reflection, preferably completely absorbing.

In this case, preferably each sub-motif is assigned an equal degree of reflection over the entire extent of the sub-motif. However, it is also conceivable that the degree of reflection changes over the extent of one or more or all partial motifs.

According to the invention, a relief layer is produced with a multiplicity of individual optical elements each having a single element surface. The individual optical elements may be arranged identically or differently or in two, three or any higher number of groups of similar elements in the relief layer.

Preferably, each of the single element surfaces is divided into disjoint sub-surfaces. In this case, preferably each of the Single element surfaces divided into identical and equally many sub-surfaces. Groups of sub-surfaces are formed, and the number of sub-surface groups suitably corresponds to the number of encoded reflection motifs. However, it is also conceivable that the number of reflection regions is greater than the number of coded motifs.

A first group of sub-surfaces of various single-element surfaces is assigned to the first reflection motif, and the first group of sub-surfaces associated with the first reflection motif is provided with the first directional reflectances. That is, the first reflection motif, which is divided into first sub-motifs, is coded into a first group of sub-surfaces. It is preferably provided to use reflection motifs, which are formed of black color on a white background, and then form the black and white motif in partial motifs and each of the partial motifs either completely black or completely white. If one of the sub-motifs consists exclusively of white background, it is assigned a very low degree of reflection over its entire extent. If the sub-motif is formed exclusively black, the sub-motif is assigned a high degree of reflection over its entire extent. If a sub-motif consists of areas of black color and white background, then the sub-motif is assigned different first directed reflectances.

Essential to the invention is that the sub-surfaces are provided with directional reflectances, the reflection is thus non-diffusive.

When reflecting light at interfaces, a distinction is made between directional reflection and diffuse reflection. Mostly a mixture of directional and diffuse reflection occurs. Specular reflection occurs in particular when the surface is sufficiently smooth compared to the wavelength of the light, i. H. the roughness structures are substantially smaller than the wavelength of the light. Curved surfaces and directional reflection are not mutually exclusive, for example a parabolic mirror of a telescope is given here. Directional reflection behaves according to "angle of incidence equals angle of reflection", whereby in curved surfaces the angle to the surface normal (normal of the tangential surface) is decisive.

Reflectance is the ratio of the reflected to the incident light intensity. The directional reflectance referred to below is the ratio of the directionally reflected to the incident light intensity. The directional reflectance can also be called the degree of reflection. For applications as an optically variable security element, the directional reflection levels in the visible wavelength range of the light (about 400 nm-700 nm) are of particular interest. Particularly high reflectivities here metals, z. As aluminum, silver, gold, copper, etc. This is particularly interesting because thin, smooth, highly reflective layers can be produced by vapor deposition, electroplating or by printing with a metal pigment paint.

The optical variable security element according to the invention is based on different directional reflection. Therefore, it is particularly advantageous if the maximum directional reflectance of an optically variable security element according to the invention is particularly high, preferably at least in a visible wavelength range of more than 5%, preferably more than 10%, preferably more than 50% and optimally more than 90%. is.

The illumination of the optically variable security element is preferably non-diffuse.

Diffusion is defined as illumination which impinges on the optically variable security element uniformly from all directions, for example outdoor daylight in the case of cloudy weather or an extensive surface light source or indirect light generated by a large illuminated surface. Non-diffuse lighting is referred to, which strikes the optically variable security element from a small and medium solid angle range, for example a point light source, a spotlight, a light bulb, a lamp, a neon tube, a window or sunlight.

It should be noted that the distinction between non-diffuse and diffuse light source is quite fluent and quite a non-diffused lighting can be realized by a cloudless sky in the sunshine and a diffuse lighting in a cloudy sky. Whether the optically variable behavior according to the invention of switching between the motifs sets in depends also on the size of the reflection regions, which can be chosen to be smaller the more non-diffuse the incident light is.

The invention is based on the directed reflection of light on curved surfaces. When a directionally-reflective curved surface is illuminated by a non-diffuse light source, a viewer may recognize a reflection of the light source on the directionally-reflective curved surface at a location on the surface at which the surface normal to the surface is parallel to the bisector of the angle between a straight line of FIG the light source is the location on the surface and a line from the viewer to the location on the surface. This corresponds to the law of reflection " Angle of incidence is equal to the angle of incidence "and, depending on the curvature, can be fulfilled in several places on a curved surface, so that a viewer can perceive several specular reflections at different positions The places where reflective reflections are perceived depend on the position of the light source and the position of the viewer relative to the curved surface for a curved surface, and changing these locations will also change the locations the surface, where a specular reflex is perceived, so that, for example, different reflective reflections can be perceived from different viewing positions.

According to the invention, the curved surface and the differently directed reflecting sub-surfaces are coordinated so that a viewer perceives different reflection motifs from different viewing angles. These reflection motifs are composed of specular reflections. An advantage of the invention is that a specular reflection of light can have a high brightness depending on the degree of reflection, and thus also the composite reflection motif. The greater the maximum directional reflectance of the surface, the brighter the reflection motif appears.

The invention has significant advantages over the prior art. Conventional optically variable security elements, in which the information layer directly adjoins the relief structure, are based on shading. As a result, the angle range needed to represent two different images separately must be very large. To completely separate two images by shading, they must be placed on surfaces at 90 ° to each other. If the angle is reduced, the shading is no longer complete. As a result, not many different motifs can be coded in an optically variable security element. In the case of quadrilateral pyramids, these are z. B. only four, in the case of corrugated metal structures only two.

A shadowing proves surprisingly not necessary according to the invention. The observer sees from a certain viewing angle the specular reflections from which the reflection motif is assembled for this viewing angle. In addition, in principle, all or some other sub-surfaces can also be seen in this viewing angle (not shaded), ie. H. the groups of sub-surfaces of different reflectance intended for different viewing angles. In this respect, a superimposition of several reflection motifs should actually be perceived. However, the disturbing reflection motifs are so dark in comparison to the specular reflections that they are only perceived as a homogeneous background. This perception as a homogeneous background is further enhanced by the small lateral size of the structures, which is preferably smaller than the resolving power of the human eye.

Preferably, positions of the first group of sub-surfaces on the single-element surfaces are determined by determining a position of visible reflection of a light source on each of the single-element surfaces from a given first viewing angle and the first group associated with a first reflection motif around the positions of the reflexes of the directed reflections is arranged on sub-surfaces. The first group of sub-surfaces, which is assigned to a first reflection motif, is thus distributed on the individual element surfaces such that first reflections of a preferably virtual point light source or a real non-diffuse light source are formed from a given viewing angle at a certain angle to the optically variable security element and the first group of partial surfaces is formed around the first reflexes, to which the partial motifs of the first reflection motif are then distributed.

The optically variable security element according to the invention is preferably formed when at least one further motif is divided into further sub-motifs, each of which is assigned further directed reflectances, which respectively encode the further reflection motif, and the individual element surfaces are subdivided into further groups of sub-surfaces and further groups of sub-surfaces different individual element surfaces are each assigned to a further reflection motif and the at least one further reflection motif associated further groups are provided on sub-surfaces with the respective other directional reflection degrees. Here, as in the following, more than a single further motif, namely also two, three or any even higher number of motifs, is to be understood as a further reflection motif.

Not only a first reflection motif, but also at least one further reflection motif is coded on the optically variable security element, wherein at least one further viewing angle deviating from the first viewing angle is chosen and at least one further position of at least one further directed reflection of the light source on each of the individual Element surfaces is determined and the at least one further position of the at least one further directed reflections around which the at least one further reflection motif associated further group is arranged on sub-surfaces. Multiple reflection motifs can be formed in a two-dimensional relief layer or a one-dimensional relief layer, as will be explained below.

In principle, the invention works with arbitrary reliefs, ie curved surfaces containing areas of different directed reflectance. Even completely random freeform surfaces are possible. In this case, the calculation of which surface elements are covered by which reflectance is very complex and must be determined using 3D programs and simulations. The production of such elements also proves to be very complex. For this reason, reliefs are preferred which, at least in some areas, have repetitive individual structures. In principle, one can distinguish between two-dimensional and essentially one-dimensional individual structures in the repetitive individual structures.

In repetitive two-dimensional individual elements, each one of the M repeating individual elements is considered as a multiple motive point. The perceived brightness of a partial surface of the multiple motif points depends on the position and position of the light source, the security element and the observer as well as the directional reflectance at the point where the reflex appears. The M multiple motif points are each subdivided into N sub-surfaces, each of the N sub-surfaces of the M multiple-motif points corresponding to one of M sub-motives of one of N subjects. The directional reflectance of the N sub-surfaces of the M multiple-subject points is adjusted according to the brightness of the corresponding sub-motif of the subject. Has z. B. the corresponding sub-motif a low brightness, a lower-reflectance is set and vice versa. Each of the N subjects can then be perceived by a viewer from a different viewing angle through specular reflexes.

Advantageously, the two-dimensional structures are repeated in a regular two-dimensional grid. Such a grid may be orthogonal, hexagonal or otherwise regular. The individual elements can be concave, convex or convex / concave. For example, the individual elements consist of hemispheres, spherical sections, semi-ellipsoids, ellipsoidal sections, parabolic sections or structures with slight deviations therefrom or otherwise arched individual elements.

Substantially one-dimensionally, individual elements of the optically variable security element are designated whose length is significantly greater than their width and whose sectional image is essentially the same perpendicular to the long axis along this axis in the longitudinal direction.

In repetitive, essentially one-dimensional individual elements, each of the K repeating individual elements is regarded as a motif line. This motive line is divided into M multiple motive points parallel to the one-dimensional structure. The perceived brightness of a partial surface of the multiple motif point depends on the position and location of the light source, the individual element and the observer as well as the directional reflectance at the point where the reflex appears. The light source in this case should have a minimum extension that corresponds to the size of the optically variable security element. Each of the M sub-surfaces of the M multiple-subject points corresponds to one of M sub-motives of one of N subjects. The directional reflectance of the N reflection areas of the M multiple subject points is adjusted according to the brightness of the corresponding multiple subject point of the subject. Has z. For example, if the corresponding multiple subject point has a low brightness, a lower reflectance is set and vice versa. Each of the N motifs can then be perceived by a viewer from another position through reflective reflections.

Advantageously, the one-dimensional individual elements are repeated in a regular grid. The individual elements can be concave, convex or convex / concave. For example, the sectional images of the individual elements consist of semicircles, circular sections, elliptical sections, parabolic sections or structures with slight deviations therefrom or otherwise arched structures.

Advantageously, positions of the first group of sub-surfaces on the single-element surfaces are determined by determining from a given first observer position a position of a first reflection of visible directional reflection of a light source on each of the single-element surfaces, and surrounding the positions of the first reflections of the directed reflections first group associated with the first motif is arranged on sub-surfaces.

In the case of several motifs, which can be perceived from different observer positions and preferably only from exactly these observer positions, one of the first Viewer position selected different observer position and determines a position of a further reflection of a further directed reflection of the light source on each of the individual element surfaces, and around the positions of the further reflections of the further directed reflection around the further motif associated further reflection regions are arranged.

A non-diffused light emitting light source generates reflections on the individual element surfaces. The reflections are bright when the reflectance is high and low when the reflectance is low. The position of the reflections on the single element surface depends on the observer angle with which the viewer looks at the optically variable security element at a predetermined position of the security element and a predetermined relative to the security element arrangement of the light source. Depending on the viewing angle, the reflections travel along the individual element surfaces. The group of partial surfaces assigned to a reflection motif is fundamentally chosen such that further reflections associated with a further reflection motif can not be perceived from the first viewer position and, conversely, first reflections associated with the first reflection motif can not be perceived from a further viewer position can.

Furthermore, it is preferably provided that the reflection regions and the further reflection regions reflect incident light in a directed manner.

Conveniently, the profile layer is formed such that the first and the further reflection areas in non-diffuse light incidence from the other observer position or the first observer position are not visible and diffuse light incidence both the first and the further reflection motif both from the first and can be seen from the other observer position.

The first and the further reflection areas are favorably arranged so that they do not shade each other, ie lie together in the viewing area of the viewer in preferably each of the observer positions. Reflections, however, are only recognizable to the viewer in directed reflection when it is in the first or in the further observer position.

Compared with known reliefs, the relief layer according to the invention can have very low relief heights in order to achieve the desired alternating effect or tilting effect. Conveniently, the dimensions of the individual elements are on the order of less than the resolution of the eye, which is 80 μm.

Individual elements having a diameter of 40 μm have already been produced, which rise at a height of 2.5 μm to 3 μm over a plane of the security element in the case of a spherical-segment-shaped shape of the individual elements. With such a small height of a spherical section, apart from extreme angles of view of 0 ° above the plane of the security element, almost the entire single element surface can be seen.

An information layer is desirably applied to the relief layer by printing only the reflective areas of high reflectance with a metal-containing resist. In another embodiment of the method according to the invention, the relief layer is first metallized completely and then the information layer is formed by demetallizing reflection regions with a low degree of reflection. The demetallization can preferably be carried out with a laser lithograph. Used laser lithographs are focused focused on the metallized layer. In practical embodiments, a diameter of the focused laser beam about 8 .mu.m, so that five different sub-motives can be applied to individual elements with a diameter of about 40 microns.

In another embodiment of the method according to the invention, the relief layer is coated with a release lacquer in reflection regions with a low degree of reflection, the relief layer is then completely mirrored, and the release lacquer is subsequently washed out. Alternatively, the relief layer can be coated with an adhesion-promoting lacquer in the areas of reflection having a high degree of reflection, the relief layer then being completely mirrored, and the mirroring of the relief layer in the reflection areas being washed out without an adhesion-promoting lacquer.

According to the invention planar areas are provided between the individual elements. These planar regions may be contiguous or non-contiguous. The planar areas contain a diffraction grating structure. The diffraction grating structure may include diffraction gratings of a first group of diffraction gratings and diffraction gratings of plural groups of diffraction gratings. A group of diffraction gratings is defined by the same diffraction grating type, so that they have the same diffraction properties, ie in particular have the same lattice constant or the same lattice constants. The diffraction grating may be a line grid or a grid.

It may be one group or several groups of diffraction gratings, each group of diffraction gratings characterized in that it has diffraction gratings of the same diffraction grating type.

The diffraction gratings of a group can form a continuous or multiple diffraction grating. Each group of partial diffraction gratings encodes a diffraction motif.

Both the diffraction motifs and the reflection motifs are visible to the naked eye. The optically variable security element is illuminated both with respect to the diffraction grating structure and with respect to the individual elements with the same directional illumination source and viewed from the same viewing angle with the naked eye.

According to the geometry and the arrangement of the individual elements and the geometry and arrangement of the diffraction gratings are coordinated so that the viewing angle-dependent reflection motifs and the viewing angle-dependent diffraction motions generate viewing angle-dependent overall motifs that are visible to the naked eye. By concealing the individual elements and the diffraction grating or the diffraction grating, the reflection motifs and the diffraction motifs can be seen along the same optically active surface of the optically variable security element. They can be arranged directly next to each other, alternating and complementing each other.

The concept of the overall motive is to be understood broadly here. On the one hand, these are to be understood as overall motifs which comprise at least one diffraction motif and at least one reflection motif in the same viewing angle. When the viewer sees from a viewing angle on the optically variable security element, he perceives both a diffraction and a reflection motif simultaneously. Different forms of simultaneous interaction are conceivable. The diffraction and the reflection motif can be arranged side by side and thereby form each readable motifs; For example, both the diffraction and the reflection motif each have a letter or a sequence of letters, a number or a sequence of numbers or mixtures of both o. Ä. and the overall motif is a word, a security code, or the like, made up of the individual letters, letter sequences, numbers, or the sequences of numbers of both types of motifs.

Another variant would be that even the single letter, the single number itself consists partly of a diffractive motive and partly of a reflection motif. The reflection motifs and diffraction motifs do not form any self-explanatory motifs. The overall motif becomes readable only when the two motifs interact simultaneously.

The concept of the overall motif also includes a sequence or sequence of diffraction and reflection motifs. The result is obtained by changing the viewing angle, for example by tilting the optically variable security element. The temporal duration of tilting creates a temporal sequence of successive motifs. Depending on the viewing angle, another subject, either a diffractive or a reflection motif, will be visible, or one of the combinations of motifs described above will be visible at the same viewing angle. The viewer is presented as a total motive a sequence of motifs. In a first viewing angle is a first subject to see in a second viewing angle, a second motif, etc. for the viewer. The first motif may be a reflection motif and the second motif may be a diffractive motif. There are almost any consequences conceivable. It is also conceivable that both a diffraction and a reflection motif are arranged within the sequence in a viewing angle.

An overall motif is therefore to be understood as meaning both a static overall motif which was described first and a dynamic overall motif in the form of a sequence, as described below.

The diffraction grating structure is provided between the individual elements in planar areas. It is particularly advantageous that the planar and curved areas are provided alternately and are thus interlocked with each other. Advantageously, the diffraction grating structure contains groups of diffraction gratings with the diffraction properties which are the same in the groups but different from each other; these are the diffraction angles of the diffraction gratings and the individual diffraction angles. These are determined by the lattice constant of the diffraction gratings.

The diffraction characteristics depend on the microstructure of a diffraction grating, which may be a rectangular structure, a sawtooth structure or a sinusoidal structure. They depend on whether they are phase or amplitude gratings or a mixed form of them. They depend on whether they are line grids or cross gratings. The diffraction gratings may also be blazed gratings which have substantially exactly one diffraction order. Important for the diffraction properties is especially the lattice constant, d. H. the repetition rate of diffractive microstructures. The lattice constant essentially determines the angles at which diffraction orders occur.

In a preferred embodiment, the planar areas contain groups of diffraction gratings of the same diffraction property. In this case, each of the group of diffraction gratings of the planar regions forms a diffraction motif that is visible in the diffraction angles and thus viewing angle dependent. The areas with diffraction gratings correspond to the motif, ie where the subject has bright areas, there are diffraction gratings of the associated group and where the image has dark areas, there are no diffraction gratings. Where the image has medium brightness, the image can be divided into light and dark areas by a halftoning process, as is known in the art of printing. An image composed of diffraction gratings will be called a diffraction image hereinafter.

As is known, diffraction gratings cause a color splitting of white light, since the diffraction angle is dependent on the ratio of the wavelength of the light to the lattice constant. As a result, diffraction patterns appear when illuminated with white light in rainbow colors, they shimmer. The perceived color depends in particular on the illumination or viewing angle. If the viewing angle is increased in comparison to the surface normal, the diffraction pattern is first perceived in blue, then in green, then in orange / yellow and finally in red.

In the places where the individual elements of the relief structure are located, no diffraction gratings are provided, and thus there are no diffraction patterns at these locations. It has been found, however, that the diffraction motifs are nevertheless very clearly recognizable to a viewer, in particular if the size of the individual elements of the structure is close to or at least in one dimension, or preferably below the resolution limit of the human eye.

In a further embodiment, the planar regions N include groups with diffraction gratings with N different diffraction properties. In this case, subareas of the planar regions having the same diffraction property assigned to the groups form a diffraction motif which is visible in the respective diffraction angles and thus viewing angle-dependent, resulting in the totality of N diffraction images. In turn, these N diffraction motifs are interlaced or superposed in the planar areas.

Preferably, at least one of the overall motifs arranged next to one another at a viewing angle has a complete reflection motif and a complete diffraction motif. In this overall motif, a complete reflection motif, for example a company logo, a number, a letter, a word, and a complete diffraction motif, likewise a company logo, a number, a letter, a word, can be recognized simultaneously in the viewing angle.

The object is achieved in its other aspect by a manufacturing method of one of the above-described optically variable security elements.

According to the invention, first a master is produced with a negative of a relief layer having a multiplicity of identically constructed individual elements and with at least one planar region between the individual elements. The structure, the height profile of the relief layer, is formed negatively in the master. This can be z. B. done by lithographic techniques or by machining diamond machining. Subsequently, the relief layer is embossed by the master into a carrier substrate, for. B. by a hot stamping process or by a UV embossing process. It is preferably a rotary embossing process. Thereafter, the carrier substrate is coated with the embossed relief layer with a metal layer. The different reflectivities of sub-surfaces of single-element surfaces and partial regions with diffraction gratings are produced in a laser lithography method by processing the metal layer of the carrier substrate. Parts with low reflectance are demetallised.

Preferably, the partial regions are produced with diffraction gratings by demetallizing intermediate surfaces between grids of the diffraction grating. The diffraction grating has a grid or line structure with equal lattice constants in one direction. These are elevations or subsidence in the carrier layer. The grids themselves remain metallized so that they can diffract the incident light, but the interfaces between the grids are demetallised. The laser lithography process must be aligned exactly with the embossed structures to obtain the desired effects. Laser lithography is particularly advantageous when producing a series of security elements in which each individual security element is individualized or serialized, i. H. z. B. carries its own serial number, which is shown optically variable.

In a particularly preferred production process, the master already contains diffraction gratings in the planar regions between the individual elements, which are also transferred into the material in the embossing process. In this case, the subregions are provided with diffraction gratings by covering, destroying or demetallizing the pre-embossed diffraction gratings at the locations where no diffraction grating is provided.

In a particularly preferred manufacturing process, an embossing cylinder is produced directly by diamond turning a raw cylinder. In this case, it is particularly preferred that the structures are essentially one-dimensional. The geometry of the individual elements of the relief structure is in this case preferably predetermined by the diamond tool. Also, the diffraction gratings in the planar areas can be made directly by turning a raw cylinder diamond by z. B. the grid lines are screwed directly with a diamond tool. In this case, the grid lines and the individual elements are arranged parallel to each other.

The demetallization can preferably be carried out with a laser lithograph. Used laser lithographs are focused focused on the metallized layer. In practical embodiments, a diameter of the focused laser beam about 1 micron to 20 microns, so that up to forty different sub-motives can be applied to individual elements with a diameter of about 40 microns.

Compared with known reliefs, the relief layer according to the invention with its individual elements can have very low relief heights in order to achieve the desired alternating effect or tilting effect. Conveniently, the dimensions of the individual elements are on the order of less than the resolution of the eye, which is about 80 μm.

Individual elements with a diameter of 40 μm have already been produced, which rise at a height of 2.5 μm to 3 μm over a plane of the optically variable security element in the case of a spherical-segment-shaped shape of the individual elements. With such a small height of a spherical section, apart from extreme angles of view of 0 ° above the plane of the optically variable security element, almost the entire single element surface can be seen.

The invention will be illustrated with reference to some embodiments in FIGS. Showing:

1a a schematic section of an optically variable security element according to the invention,

1b a schematic view of a single element with adjacent planar portion,

2 nine figures showing the intermingling of two reflection motifs with a diffraction motif in a two-dimensional grid of individual elements,

3 five figures representing the formation of two diffraction motives in two partial areas of the planar area in a two-dimensional grid of individual elements,

4 10 figures illustrating the intermeshing of three reflection motifs and one diffraction motif in a one-dimensional grid of individual elements,

5a an example of a motif sequence with two diffraction motives arranged outside of the reflection motifs,

5b an example of a motif sequence with two diffraction motifs arranged within the reflection motifs,

5c an example of a motif sequence with a diffraction motif arranged within the reflection motifs,

6 an example of a motif sequence with diffraction and reflection motifs visible in two viewing angles at equal viewing angles,

7 three examples of a combination of diffraction and reflection motifs,

8th an example of a motif sequence with a diffraction motif visible in different colors and reflection motifs visible at the same viewing angles,

9 a further example of a sequence of motifs with a diffraction motif visible in different colors and reflection motifs which are visible at the same viewing angles,

10 Layer structure of an optically variable security element,

11 Refraction behavior of a beam path of a diffraction and a reflection motif.

1a schematically shows a sectional view of an optically variable security element according to the invention 1 , 1a shows a relief structure with four periodically repeating single elements 2 with planar areas between them 3 ,

In the 1b are one of the individual elements 2 and an adjacent planar region 3 shown schematically and both on the single element 2 as well as on the planar area 3 striking directional light 4 , At the single element 2 becomes the light 4 in a large angular range by reflection on a single element surface 6 in accordance with the law of reflection "angle of incidence equals angle of reflection" measured on a surface normal reflected at a reflection point.

On partial surfaces of the single element surfaces 6 With low reflectance or no reflection less or no light is reflected in the corresponding solid angle. On partial surfaces of the single element surfaces 6 With high reflectivity, a lot of light is reflected in the corresponding solid angle. The single element surface 6 is partially mirrored. On the sub-surfaces in which a lot of light is reflected, is a high reflectance, at sub-surfaces, where little light is reflected, is a low reflectance, so no mirroring provided.

In the planar areas 3 there are subregions with diffraction gratings that light 4 bend into a diffraction order or multiple diffraction orders.

2 shows the formation of the optically variable security element 1 with two reflection motifs, the letters F and T, and a diffraction motif, the letter L. The two reflection motifs and the one diffractive motif are in the first line of the 2 shown. The two reflection motifs F, T are in the different reflectance of the sub-surfaces of the periodically repeating individual elements in the X and Y directions 2 coded. For the individual elements 2 These are dome-shaped bulges or dome-shaped indentations. The inventive, repeating individual elements 2 are in the second row of the 2 shown on the left. Between the individual elements 2 are the planar areas 3 intended. It is the contiguous area between the cross-section parallel to the plane of the optically variable security element 1 circular single elements 2 ,

The second image of the second row shows how the individual surfaces 6 in sub-surfaces 61 . 62 be divided with different degrees of reflection. The sub-surfaces are in a first group of sub-surfaces 61 encoding the letter F and a second group of sub-surfaces 62 , which encode the letter T, split. Every single element surface 6 is disjoint in the sub-surfaces 61 . 62 divided into the first and second groups. Black indicates a high degree of reflection and white a very low reflectance, ie the sub-surfaces 61 . 62 of the single element surfaces 6 that are marked black are fully mirrored while the sub-surfaces 61 . 62 of the individual elements 1 that are marked in white, are anti-reflective. This gives the impression that when viewing the arranged in a grid plurality of individual elements 2 At a first viewing angle of the letter F and at a second viewing angle the letter T appears as a reflection motif.

According to the invention is now additionally in the subarea 31 of the planar area 3 , which according to the third illustration of the second line of 2 L-shaped extends, provided a diffraction grating, which is defined by a specific diffraction grating type. The letter L is therefore at the same directional illumination by the light 4 in a diffraction angle determined by the diffraction grating type.

The third line of the 2 shows how the letters F and T by individual reflections on the associated sub-surfaces 61 . 62 are each composed to a reflection motif and the letter L, here by the contiguous portion 31 of the planar area 3 is trained. If the size of the individual elements 2 Below the resolution of the human eye is located, so about below 50 microns, for the viewer creates the impression of continuous illuminated lines, and he no longer registers the individual reflections or holes in the diffraction pattern.

The schematic representations of 2 represent the basic principle of creating an optically variable security element according to the invention 1 For a real optically variable security element 1 the circumstances would be chosen differently. So z. B. a figure to be displayed 5 mm in size, while the individual elements z. B. would repeat in a grid of 50 microns. In this example, the number is 100 × 100 individual elements 2 whose size is again below the resolution limit of the eye. In this case, the human observer can not perceive the individual pixels separately from one another, which results in continuous individual images for him-both in the case of the reflection motifs F, T and in the diffraction motifs L.

3 shows an extension of the representation in 2 , In 3 is a second diffraction motif in the optically variable security element 1 integrated. It is the letter H, which is integrated in addition to the letter L as the second diffraction motif. This is the planar area 3 in two groups of subareas 31 . 32 divided as the second representation of the 3 shows.

The first group of subareas 31 is in contrast to the subsection of 2 no longer connected, but the first group of subareas 31 , which encodes the letter L, consists of five individual first diffraction grating types, as the left representation of the second Row in 3 2, which together produce the letter L in a diffraction motif when the light incidence is directed, while the letter H is in a second group of subregions 32 encoded in nine individual second diffraction grating types, such as the second representation of the second series in FIG 3 shows. Here are the first group of subareas 31 and the second group of subareas 32 also interlaced so that, depending on the viewing angle, the letter L appears when the viewing angle appears in the direction of a diffraction order of the first grating type and the letter H when the viewing angle corresponds to the diffraction order of the second grating type.

4 shows the formation of the optically variable security element 1 if the individual elements 2 are groove-shaped or semi-cylindrical or rib-shaped. This can be the single element 2 over an entire length L of the optically variable security element 1 extend while the single element 2 is repeated along a width B at periodic intervals. The left illustration of the first line of the 4 shows the basic design of the individual elements 2 , Each of the individual elements 2 is divided along its longitudinal direction into three rows of five pixels each. The pixels all have the same length extension and an equal but narrower extent along the width B of the individual element 2 , Each of the individual elements 2 is divided along the length L into five pixels and along the width B in three pixels.

4 shows the coding of the three reflection motifs F, T and N by appropriate choice of the reflectance of the first, second and third row of pixels and the one diffractive motif L. The diffraction motif L is in the planar region 3 between the elongated individual elements 2 in a first group of subareas 31 is encoded with a diffraction grating, while the three reflection motifs are each encoded in a group of sub-surfaces, the first group of sub-surfaces comprising the top row of pixels, the second group of sub-surfaces the middle pixels and the third group of sub-surfaces the bottom pixels of the single-element surfaces 6 includes. The dark mark again shows to what extent the individual element surfaces 6 are mirrored along their longitudinal direction.

In the 5a . 5b and 5c is given in each case an example of a possible sequence of motives. The scale indicates the viewing angle. The viewing angle θ is given in this example when the viewer is in the direction of the zeroth order of the diffraction grating.

In 5a For example, the reflection patterns are formed as an image sequence 1-2-3-4-5 that is visible in a certain viewing angle range, and the diffraction image B is visible at a viewing angle outside the viewing angle range of the reflection motif sequence.

Since, in this example, it is a symmetrical, non-blazed diffraction grating, the diffraction motif B is visible under at least two viewing angles that are symmetrical about the viewing angle.. It should be noted that this symmetry is not present in the reflection motif sequence. The numbers 1-2-3-4-5 and the letter B stand for any content of the motifs. The contents may be logos, texts, serial numbers, symbols, photos, etc. In particular, the image sequence 1-2-3-4-5 may be an animation, e.g. B. a motion or zoom animation. In the viewing angle outside the viewing angle range of the reflection motif sequence, other diffraction motifs may also be present.

In 5b For example, the first image information is an image sequence 1-2-3-4-5 that is visible in a certain viewing angle range except two viewing angles, and the diffraction image B is visible at the two recessed viewing angles.

In 5c 1, the reflection motif sequence 1-2-3-4-5-6 is shown, which is visible in a certain viewing angle range except for one viewing angle, and the diffraction image B is visible at the recessed viewing angle. Since this example is an asymmetric, blazed diffraction grating, the diffraction image B is visible under exactly one viewing angle.

In the embodiment according to 6 For example, the reflection images are visible as an image sequence 1-2-3-4-5-6-7 in a certain viewing angle range, and the diffraction image B is visible in two symmetrical diffraction angles. In this embodiment, the respectively visible image of the image sequence (image 3 and image 5) and the visible diffraction image B are matched to one another in the diffraction angles. The respective motifs may be the same in parts or disjoint in parts, or in parts or complementary content.

In 7 In the left picture two contents are shown: a customer logo "BRAND ^TM " as a reflection motif and a serial number "9 8 1 3 0" as a diffraction motif. The customer logo appears as a silvery font, while the serial number shimmers in rainbow colors. Both motifs essentially dive in the same area of the optical variable security element 1 and at the same viewing angle. To illustrate, the reflection motif is represented as filled in the representation and the diffraction motif as an outline. In the middle illustration, only one content is displayed as the overall motif, the content being divided between the reflection motif and the diffraction motif. The first three digits 9 8 1 of the serial number are shown as a reflection motif and the last two digits 3 0 of the serial number as a diffraction motif. In the last presentation of the 7 a content is displayed as an overall motif, the content being divided between the reflection and the diffraction motifs. The upper half of the serial number 9 8 1 3 0 is the reflection motif, while the lower half represents the diffraction motif.

In 8th are the reflection motifs as a motif sequence 1, 2, 3, 4, 5, 6, 7, which is visible in each case in a certain viewing angle range, shown, and the diffraction patterns are shown here as letter B. The letter B is visible in a diffraction angle range. Since the individual colors differs at the same diffraction grating type differently when the light incidence of white light, the diffraction angle of the different colors can be adapted to the viewing angle of the different reflection motifs, so that when the reflection motif "3" appears the letter B in blue, when the reflection motif "4" the letter B in green and the appearance of the reflection motif "5" the letter B in red perceived.

9 shows a similar example. In a viewing angle in which the diffraction motif, here the serial number 98130, gives a blue color impression, the content of the reflection image matched to it, that is to say in FIG 8th the third picture, the picture sequence visible. Here the text "blue" appears. At a viewing angle in which the diffraction information gives a green color impression, the content of the fourth image is matched according to 8th the image sequence visible in a text "green". At a viewing angle in which the diffraction information gives a red color impression, the content of the fifth image matched to it is in accordance with 8th the image sequence visible in a text "red".

10 shows an example of a layer structure of the invention. At the top is a substantially transparent carrier layer 100 made of polymer. Underneath is the relief structure, which is in one of the carrier layer 100 adjoining, essentially transparent lacquer layer 101 is impressed. Underneath is a metallized layer 102 in which the sub-surfaces with different reflectance and the sub-areas with diffraction gratings are located. Underneath is a contrasting layer 103 , which simultaneously acts as an adhesive layer. All layers 100 . 101 . 102 . 103 extend over the entire areal extent of the optically variable security element 1 ,

11 shows different beam paths over the metallized layer 102 over a planar area 3 and a single element 2 when a medium having a refractive index n over the metallized layer 102 located.

On the left side, an incident light beam is incident on a diffraction grating in the planar area 3 according to the formula sin (α) = λ / g diffracted, where α is the diffraction angle, λ is the wavelength in the medium and g is the lattice constant of the diffraction grating. The wavelength λ in the lacquer layer 101 with refractive index n is shortened by the factor 1 / n with respect to the wavelength in air. As a result, the sine of the diffraction angle in the medium is also smaller by a factor of 1 / n. Upon exiting the medium at the interface with air, the light beam undergoes a refraction corresponding to the refraction law sin (β) = n · sin (α). It is assumed that the refractive indices of the carrier layer 100 and the paint layer 101 are the same. The sine of the diffraction angle is thus increased by the factor n, which is outside the lacquer layer 101 gives a diffraction angle, as would occur in a diffraction grating without medium. It is thus for the diffraction angle of the optically variable security element 1 irrelevant, whether there is still a layer of paint over the diffraction grating 101 is located with a refractive index n.

On the right side, an incident light beam is reflected according to the law of reflection "angle of incidence equal to the angle of reflection", regardless of the refractive index n of the lacquer layer 101 , When exiting the lacquer layer 101 at the interface with air, the sine of the angle is increased by the factor n. If, therefore, a layer with a refractive index n is still located above the reflecting structure, the mirror angles and thus the angles at which the first image information according to the invention is visible are significantly increased. Again, to explain the reflection behavior for the sake of simplicity, the lacquer layer 101 and the carrier layer 100 as a layer, as a varnish layer 101 considered. Incidentally, it does not matter if the backing layer 100 a different refractive index than the lacquer layer 101 because of the refractive index of the carrier layer 100 repeals both the diffraction motif and the reflection motif.

According to the invention, in the generation of the optically variable security element 1 the refractive index n of the layer lying above the relief structure 101 by taking into account the angular magnification caused by the refractive index n Reflection motifs in the design of the optically variable security element 1 is compensated. A compensation can be done either by an adapted selection of the geometry of the individual elements 1 take place, wherein in general the curvatures of the geometry are reduced with a larger refractive index or the same geometry by changing or shifting the regions of different reflection.

LIST OF REFERENCE NUMBERS

1

 optically variable security element

2

 Single element

3

 planar area

4

 light

6

 Single element surface

31

 subregion

32

 subregion

61

 part surface

62

 part surface

B

 Wide single element

L

 Length single element

100

 support film

101

 paint layer

102

 relief layer

103

 contrasting layer

n

 refractive index

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102013021806 A1 [0002]
• DE 102013001734 A1 [0003]
• DE 102015202106 [0010]

Claims (18)

Optically variable security element ( 1 ) with a relief layer ( 102 ) with a large number of structurally identical individual optical elements ( 2 ), each having a single element surface ( 6 ) in sub-surfaces ( 61 . 62 ), which have different directional reflectivities, and the sub-surfaces ( 61 . 62 ) are grouped in such a way that each group has a sub-surface ( 61 . 62 ) of a single element surface ( 6 ) and each group encodes an associated viewing angle-dependent, visible to the naked eye reflection motif, and with at least one planar area ( 3 ), which extends between the individual optical elements ( 2 ) and the subareas ( 31 . 32 ) with diffraction gratings which produce at least one viewing angle dependent diffraction motif visible to the naked eye by the predetermined directional illumination, and the viewing angle dependent reflection motifs and the at least one viewing angle dependent diffraction motif produce viewing angle dependent overall motifs visible to the naked eye. Optically variable security element according to claim 1, characterized in that at least one of the overall motifs arranged next to one another at a viewing angle has a complete reflection motif and a complete diffraction motif. Optically variable security element according to claim 1 or 2, characterized in that at least one of the overall motifs is constructed in one part of a reflection motif and in another part of a diffraction motif. Optically variable security element according to claim 1, 2 or 3, characterized in that along a tilt axis increasing viewing angles successively reflection motifs and diffraction patterns are shown and the reflection motifs between the diffraction motives or the diffraction motifs between the reflection motifs are arranged. Optically variable security element according to one of claims 1 to 4, characterized in that the relief layer ( 102 ) individual elements repeating along a longitudinal direction ( 2 ) having. Optically variable security element according to one of claims 1 to 5, characterized in that the relief layer ( 102 ) individual elements repeating along a transverse direction ( 2 ) having. Optically variable security element according to one of claims 1 to 6, characterized in that the individual elements ( 2 ) are arranged in a grid. Optically variable security element according to one of claims 1 to 7, characterized in that the subregions are divided into groups and each group is assigned a diffraction grating type and each group codes an associated diffraction motif. Optically variable security element according to claim 8, characterized in that different diffraction grating types have different diffraction properties. Optically variable security element according to one of claims 1 to 9, characterized in that the individual elements ( 2 ) have a maximum diameter of less than 200 microns, preferably less than 100 microns, preferably less than 75 microns, preferably less than 50 microns. Optically variable security element according to one of Claims 1 to 10, characterized in that the planar region ( 3 ) an area fraction between 20% and 80% of an optically effective total area of the optically variable security element ( 1 ) occupies. Optically variable security element according to one of claims 1 to 11, characterized in that along the side facing the directional illumination of the relief layer ( 102 ) a transparent carrier layer ( 100 ) extends over the entire surface. Optically variable security element according to one of claims 1 to 12, characterized in that along the side facing away from the directed illumination of the relief layer ( 102 ) a contrasting layer ( 103 ) extends over the entire surface. Optically variable security element according to one of claims 1 to 13, characterized in that an adhesive layer over its entire surface along an underside of the optically variable security element ( 1 ). Optically variable security element according to one of Claims 1 to 14, characterized in that a protective layer ( 101 ) directly on the relief layer ( 102 is arranged with a refractive index (n), wherein a diffraction angle of the diffraction pattern to ambient air is independent of a size of the refractive index (n) and an angle of refraction of the reflection motif depends on the size of the refractive index (n), and the dependency is the diffraction characteristics of the diffraction gratings and / or the location of the sub-surfaces ( 61 . 62 ). Manufacturing method for an optically variable security element ( 1 ) according to claim 1, wherein a master with a negative of a relief layer ( 102 ) with a large number of identical individual elements ( 2 ) and at least one planar area ( 3 ) between the individual elements ( 2 ), the relief layer ( 102 ) is embossed by the master into a carrier substrate, the carrier substrate with the embossed relief layer (FIG. 102 ) is coated with a metal layer, different reflectivities of sub-surfaces ( 61 . 62 ) of single element surfaces ( 6 ) and partial regions with diffraction gratings are produced in a laser lithography process by processing the metal layer of the carrier substrate. Manufacturing method according to claim 16, characterized in that the subregions ( 31 . 32 ) are generated by diffraction gratings by demetallating interfaces between grid lines or grid points of the diffraction grating. Manufacturing method according to claim 16 or 17, characterized in that the subregions ( 31 . 32 ) are generated by diffraction gratings by diffraction gratings are introduced over the entire surface in the planar region of the master, are transferred by the embossing in the carrier substrate and demetallized portions in which no diffraction grating is provided.

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