Optically variable security element
10081213 · 2018-09-25
Assignee
Inventors
Cpc classification
B42D25/328
PERFORMING OPERATIONS; TRANSPORTING
B42D25/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
B42D25/00
PERFORMING OPERATIONS; TRANSPORTING
B42D25/328
PERFORMING OPERATIONS; TRANSPORTING
Abstract
An optically variable security element for securing valuable articles that viewing-angle-dependently displays a motif having at least one curve depiction that, from a first viewing direction, is visible as an initial curve having two or more connected, non-collinear segments and that, when the security element is tilted about a predetermined axis, splits into the individual segments in that the segments of the initial curve move alternatingly in different directions away from the initial curve. Each of the segments has associated with it one movement segment in the form of a sub-region of an areal motif region, such that, from the first viewing direction, the segments display the initial curve having the connected segments and that, from viewing directions tilted about the predetermined axis, they display curve depictions in which, with increasing tilt angle, the segments lie alternatingly in different directions increasingly further away from the initial curve.
Claims
1. An optically variable security element for securing valuable articles that viewing-angle-dependently displays a motif having at least one curve depiction that, from a first viewing direction, is visible as an initial curve having two or more connected, non-collinear segments, and that, when the security element is tilted about a predetermined axis, splits into individual segments in that the segments of the initial curve move alternatingly in different directions away from the initial curve, having an areal motif region having a plurality of optically effective elements, each of which directs incident light in a preferred direction, the segments of the initial curve in the areal motif region each having associated with it one movement segment in the form of a sub-region of the areal motif region, in which sub-region the optically effective elements are arranged and aligned in such a way that, from the first viewing direction, they display the initial curve having the connected segments and that, from viewing directions tilted about the predetermined axis, they display curve depictions in which, with increasing tilt angle, the segments lie alternatingly in different directions increasingly further away from the initial curve.
2. The security element according to claim 1, wherein at least one curve depiction splits into three or more segments when the security element is tilted.
3. The security element according to claim 1, wherein the initial curve of at least one curve depiction displays an alphanumeric character, a symbol or another information-bearing character.
4. The security element according to claim 1, wherein the movement segments of the curve depictions have a width that is between 10% and 100% of the dimension of the initial curve of the curve depiction.
5. The security element according to claim 1, wherein the movement segments of at least one curve depiction all have the same width.
6. The security element according to claim 1, wherein the optically effective elements are formed by ray-optically effective facets whose orientation is characterized in each case by an inclination angle against the plane of the areal motif region and by an azimuth angle in the plane of the areal motif region.
7. The security element according to claim 1, wherein the optically effective elements are formed by diffraction-optically effective grating fields having a grating pattern composed of parallel grating lines.
8. The security element according to claim 1, wherein the optically effective elements are formed by groove- and/or rib-shaped structural elements that lie adjacent to one another and extend along a longitudinal direction.
9. The security element according to claim 1, wherein the areal motif region is developed to be reflective such that the initial curve and the split of the initial curve into individual segments are visible in reflection.
10. The security element according to claim 1, wherein the optically effective elements are formed by reflection elements that are cast in an embossing lacquer and provided with a reflection-increasing coating.
11. The security element according to claim 10, wherein the reflection-increasing coating has a color-shift effect, especially in that the coating consists of a thin-film interference layer system having a reflector, a dielectric spacing layer and an absorber.
12. The security element according to claim 1, wherein the areal motif region is at least partially transmissive such that the initial curve and the split of the initial curve into individual segments are visible in transmission.
13. The security element according to claim 1, wherein the optically effective elements are formed by transmission elements in the form of transparent or semitransparent diffraction patterns, transparent or semitransparent prism patterns or transparent or semitransparent microrelief patterns.
14. The security element according to claim 1, wherein the motif includes at least a second curve depiction that, from a second viewing direction, is visible as a second initial curve having two or more connected, non-collinear segments, and that, when the security element is tilted about the predetermined axis, splits into the individual segments in that the segments of the second initial curve move alternatingly in different directions away from the second initial curve, the segments of the second initial curve in the areal motif region each having associated with it one second movement segment in the form of a sub-region of the areal motif region, in which sub-region the optically effective elements are arranged and aligned in such a way that, from the second viewing direction, they display the second initial curve having the connected segments and that, from viewing directions tilted about the predetermined axis, they display curve depictions in which, with increasing tilt angle, the segments lie alternatingly in different directions increasingly further away from the second initial curve.
15. The security element according to claim 14, wherein the movement segments of the first and second curve depiction do not overlap.
16. The security element according to claim 14, wherein the first and second viewing direction include an angle of at least 5.
17. The security element according to claim 14, wherein at least one segment of the first curve depiction is also a segment of the second curve depiction such that, when the security element is tilted, the second curve depiction is at least partially composed of segments of the split first curve depiction.
18. The security element according to claim 1, wherein the security element is a security thread, a tear strip, a security band, a security strip, a patch or a label for application to a security paper, value document or the like.
19. A data carrier having a security element according to claim 1.
20. A method for manufacturing an optically variable security element according to claim 1, in which a desired initial curve having two or more connected, non-collinear segments is defined, for each of the segments of the initial curve, movement segments are defined in which the segments of the initial curve move when the security element is tilted, and in an areal motif region in the defined movement segments, optically effective elements are arranged and aligned in such a way that, from the first viewing direction, they display the initial curve having the connected segments and that, from viewing directions tilted about the predetermined axis, they display curve depictions in which, with increasing tilt angle, the segments lie alternatingly in different directions increasingly further away from the initial curve.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention further includes a method for manufacturing an optically variable security element of the kind described above, in which a desired initial curve having two or more connected, non-collinear segments is defined, for each of the segments of the initial curve, movement segments are defined in which the segments of the initial curve move when the security element is tilted, and in an areal motif region in the defined movement segments, optically effective elements are arranged and aligned in such a way that, from the first viewing direction, they display the initial curve having the connected segments and that, from viewing directions tilted about the predetermined axis, they display curve depictions in which, with increasing tilt angle, the segments lie alternatingly in different directions increasingly further away from the initial curve.
(2) Further exemplary embodiments and advantages of the present invention are explained below by reference to the drawings, in which a depiction to scale and proportion was dispensed with in order to improve their clarity.
(3) Shown are:
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DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
(13) The invention will now be explained using the example of security elements for banknotes. For this,
(14) The security strip 12 has a metallic appearance and, when viewed perpendicularly from above, displays the value numeral 50 multiply spaced apart one on top of another. Each depiction of the value numeral 50 consists of two curve depictions 14A, 14B that are each formed by connected polylines 5 and 0, respectively. The curve depictions 14A, 14B, when viewed perpendicularly from above, are perceptible as light polylines against the somewhat darker, but likewise metallically gleaming background of the security strip 12. Said visual impression when viewed perpendicularly from above is depicted again in greater detail in
(15) When the banknote 10 is tilted 16A, 16B about its longitudinal axis, the security strip 12 displays a striking optical effect: The originally connected curve depictions 14A, 14B, frequently also referred to below as initial curves, split for the viewer into a plurality of individual segments 18 that, with increasing tilt, move alternatingly in different directions away from the respective initial curve.
(16) For illustration,
(17) Proceeding from the connected depiction of the initial curves 14A, 14B in
(18) The occurrence of this striking splitting effect will now be explained in greater detail with reference to
(19) As is clearly visible in the curve depictions 14A, 14B in
(20) The movement segments 22 extend perpendicularly substantially the same distance from the initial curve on both sides, the width of the segments advantageously being between 20% and 50% of the dimension of the initial curve.
(21) As shown in the detailed section in
(22) Here, the facets 32 each arranged in the middle of the movement segments 22A and 22B have an inclination angle =0 against the plane of the areal motif region 20 and therefore, when light incidence is perpendicular, reflect substantially perpendicularly upward. The facets 34 in the movement segment 22A that are offset in the +y-direction from the facets 32 have increasing inclination angles up to an inclination angle =+20 at the upper edge 24-O of the movement segment, while the facets 36 that are offset in the y-direction have decreasing inclination angles up to an inclination angle =20 at the lower edge 24-U of the movement segment.
(23) In the immediately adjacent movement segment 22B, the inclination angles of the facets change inversely, that is, starting from the facets arranged in the middle having a tilt angle =0, the facets 36 that are offset in the +y-direction have a decreasing inclination angle up to an inclination angle =20 at the upper edge 26-O of the movement segment 22B, while the facets 34 that are offset in the y-direction have an increasing inclination angle up to an inclination angle =+20 at the lower edge 26-U of the movement segment 22B.
(24) If the security element 12 having the surface region 20, starting from perpendicular top view, is now tilted a few degrees downward (tilt direction 16A), then the reflection condition angle of incidence equals angle of reflection is fulfilled in the movement segment 22A for facets 34 that are offset upward (in the +y-direction), and in the movement segment 22B for facets 34 that are offset downward (in the y-direction). The reverse applies for a tilt a few degrees upward in tilt direction 16B. The segments 18 that are visible in the movement segments 22A, 22B of the curve depiction 14A thus proceed for the viewer, upon tilting in the opposite direction, away from the initial curves and move away from each other.
(25) The furnishing with optically variable elements described by way of example for the movement segments 22A, 22B is carried out accordingly also for the other movement segments 22 of the surface region 20, such that the inclination angles of the facets 30 each change inversely in adjacent movement segments. In this way, the segments 18 of the initial curves 14A, 14B each proceed for the viewer alternatingly in different directions along the initial curves such that the initial curves appear to split when the security element is tilted.
(26) In the exemplary embodiment in
(27) For illustration,
(28) In the exemplary embodiment, the orientation parameter k progresses within each of the movement segments 22 alternatingly either from 1 to +1 or from +1 to 1. For example, the orientation parameter in the movement segment 22A progresses from the lower to the upper edge from 1 to +1, while in the adjacent movement segment 22B, it progresses from the lower to the upper edge from +1 to 1. As shown in
(29) In the realization of the optically effective elements by the facets 30, the inclination angle of the facets in the y-direction was obtained through the relationship
(k)=k.Math.20,1k1(F1)
from the orientation parameter k. If k varies between 1 and +1, then the inclination angle changes accordingly between 20 (downward inclination) and +20 (upward inclination).
(30) Through a two-dimensional specification of the orientation parameter k as in
(31) Coming back to the depiction in
s=5/(220)=
of the size of the movement segments results.
(32) The k values for a desired motif can be specified via suitable mathematical algorithms, the k value, for example, can increase in proportion to the distance of the segments from the initial curve. Alternatively, the values can also be produced by hand by a designer, for instance as a color gradient in a design sheet. The value of the orientation parameter preferably increases in proportion to the distance of a segment from the initial curve to the edge of the movement region to +1 or decreases to 1, as shown, for instance, in the exemplary embodiment in
(33) In principle, the connection between the orientation parameter and the distance from the initial curve can, of course, also be non-linear. As a result, especially the line width or the movement dynamics can be varied dependent on the tilt angle. For example, the k values around the k value of the initial curve can vary very strongly such that a sharp depiction of the initial curve is achieved. Toward the edge of the movement segments, the k value can then vary more slowly, causing the line width to become larger and the dynamic to increase.
(34) In some embodiments, it can also be provided that the k value does not progress through the entire range between 1 and +1 in all segments. If the k value in one segment progresses, for example, only up to a k value of +0.5, then the segment appears, when tilted in viewing angles that correspond to k values above 0.5, to disappear, since then no optically effective elements are present that direct incident light toward the viewer at these viewing angles.
(35) For the above-indicated relationship (F1) between the inclination angles of reflective facets and the orientation parameter k, the facets can, of course, also be chosen to be steeper or flatter, or be inclined, alternatively or additionally, in the x-direction instead of in the y-direction. What is essential is merely that, when tilted about a specified tilt axis, the optically effective elements having k=1 to k=+1 are visible in sequence, for example become light, dark or colored and not visible again, such that a corresponding movement effect results for the segments.
(36) If small hologram grating regions are used as optically effective elements, the orientation parameter k can be linked, for example, with the azimuth angle and/or the grating period p of the hologram grating regions, for example in the form
(k)=k.Math.30,1k1(F2)
for azimuth angles between +30 and 30 or
p(k)=1000 nm+k.Math.500 nm,1k1(F3)
for grating periods between 500 nm and 1.5 m.
(37) In further embodiments, as optically effective elements, also microrelief patterns having groove- and/or rib-shaped structural elements can be used, as are described, for example, in document WO 2014/117938 A1, whose disclosure is incorporated in the present application by reference. In this case, the orientation parameter k can be linked, for example, with the azimuth angle of the structural elements.
(38) It is understood that, besides reflective facets, hologram gratings and microrelief patterns, also other optically effective elements can be used. Within the scope of the present invention, it is important only that, when tilted, the described moving segments appear to a viewer, regardless of whether said segments are light, dark, colored or visible in another manner, and whether this occurs in top view or when looked through.
(39) Thus, according to a further design possibility, as optically effective elements, also microlens or concave microreflector grids can be used that, together with line patterns, effect moir magnification effects. For this, the line patterns have approximately the same period as the microlens or concave microreflector grids and are arranged, for instance, in the focus plane of the microlenses or concave microreflectors. The microlenses or concave microreflectors direct incident light viewing-angle-dependently in a direction onto or next to the lines such that they appear to a viewer either in the color of the lines or in the color of the gaps. In this case, the orientation parameter k indicates how far the line pattern is shifted locally compared with the grid of the microlenses or concave microreflectors. For example, the center point of the lines of the line grid can, for a k value of 1, lie at a first edge of the individual microlenses or concave microreflectors, and for a k value of +1, at a second edge, opposite the first edge, of the microlenses or concave microreflectors.
(40) The described movement effects can be produced, not only in top view, but also for viewing when looked through, both with facets and with hologram gratings and microrelief patterns. If the facets are not, for example, embedded in a material having the same or a very similar refractive index, then they act, when looked through, as small prisms, such that brightness differences in the transmitted light result and a movement effect according to the present invention can be produced in transmitted light.
(41) In particular, with a thin semitransparent coating, for example a thin metal layer, it can be achieved that the same embossing patterns, as reflective facets, produce, in top view, a movement effect according to the present invention and, simultaneously, with the effect of microprisms, when looked through, additionally a movement effect according to the present invention. In a similar manner, also the above-mentioned microrelief patterns and hologram gratings can, for looking through, be coated for example semitransparently, for instance with a very thin metal layer, or high-index transparently.
(42) The described concept is particularly advantageously used in so-called RollingStar security threads or LEAD strips having micromirrors, that is, in designs having facets or micromirrors that are embossed with embossing heights of a maximum of 5 m in an embossing lacquer and then metalized.
(43) The metalization is advantageously done with a thin metal film or a color-shifting thin-film coating having the layer sequence reflector/dielectric/absorber.
(44)
(45)
(46) Also in this exemplary embodiment, the depiction of the value numeral 50 includes the curve depictions 14A, 14B, already described in detail above, in the form of the numbers 5 and 0. The depiction of the letter string PL includes the curve depictions 54A, 54B in the form of the letters P and L. Since the initial curves in this exemplary embodiment are not intended to be visible from the same viewing directions, but rather from different ones, the initial curves are associated with different values of the orientation parameter k. Specifically, the initial curves of the value numeral 50 correspond to a k value of +0.5 and the initial curves of the lettering PL correspond to a k value of 0.5. Furthermore, the movement segments 22 of the segments 18 of the value numeral 50 include only k values between 0 and 1, while the movement segments 52 of the segments 58 of the letter string PL include only k values between 1 and 0, as illustrated in
(47) When the motif region 50 is tilted, the appearances shown in
(48) The segments 18 of the value numeral 50 are visible only when tilted downward, since the associated movement segments 22 include no k values greater than 0. Similarly, the segments 58 of the letter string PL are visible only when tilted upward, since the associated movement segments 52 include no k values less than 0. Overall, when the motif region is tilted from bottom to top, from initially unordered segments 58 is created the letter string PL that, when tilted further, splits again, while from other unordered segments 22, the value numeral 50 is created that, for its part, splits when tilted further upward (
(49) Such a movement effect is very memorable and dynamic, and stands out clearly from known tilt effects. A further distinctive feature compared with conventional tilt effects consists in that, besides the connected depictions of the value numeral 50 and the letter string PL in certain viewing directions, also in the viewing directions lying therebetween, high-contrast dynamic depictions are visible that, however, do not or hardly permit the original depictions to be perceived any longer, but rather display a chaotic pattern of unordered segments (such as
(50) In such depictions, the movement segments 22, 52 and the segments 18, 58 of the two sub-depictions are particularly advantageously coordinated with each other in such a way that individual segments continuously proceed from movement segments of the first depiction to movement segments of the second depiction. The aggregate depiction then includes a shared movement region in which one or more segments move in such a way that, from the first viewing directions, they are part of the first depiction, and from the second viewing directions, part of the second depiction. In this way, the visual impression can be produced that segments of the splitting first depiction reassemble to form the new second depiction.
(51) In the exemplary embodiment in
(52) The more segments are both part of the first and part of the second depiction, the more likely the impression will be created that the second depiction is recomposed of parts of the splitting first depiction.
LIST OF REFERENCE SIGNS
(53) 10 Banknote 12 Security element 14A, 14B Curve depictions 16A, 16B Tilt directions 18, 18C Segments 20 Areal motif region 22, 22A, 22B, 22C Movement segments 24-O, 24-U Edges of the movement segment 22A 26-O, 26-U Edges of the movement segment 22B 30, 32, 34, 36 Facets 40 Grayscale depiction 50 Areal motif region 52, 52C Movement segments 54A, 54B Curve depictions 56 Combined movement segment 58, 58C Segments 60 Grayscale depiction