Abstract
The invention concerns a security element having a magnetic coding consisting of magnetic coding elements. At least one of the magnetic coding elements has a grid-shaped magnetic region which is formed by a plurality of mutually parallel grid strips made of magnetic material which respectively have a magnetic anisotropy. The grid strips lead, through their magnetic anisotropy, to the magnetization direction of the coding element being able to differ from the direction of the applied magnetic field. Since the resultant magnetic signals that the grid-shaped magnetic regions deliver cannot be simulated by conventional magnetic regions, said coding elements increase the anti-forgery security of the security element.
Claims
1. A security element for safeguarding value documents which has a magnetic coding with at least one magnetic coding element, wherein the magnetic coding element has a grid-shaped magnetic region which is formed by a plurality of mutually parallel grid strips made of magnetic material, with the grid strips of the magnetic coding element respectively having a magnetic anisotropy that is arranged to allow a magnetization direction of the magnetic coding element that differs from the direction of an applied magnetic field.
2. The security element according to claim 1, wherein the magnetic coding has at least two of the magnetic coding elements, which are arranged along a coding direction on or in the security element, with the grid strips of at least one of the coding elements extending at an acute angle to the coding direction of the security element, in particular at an angle between 20 and 70.
3. The security element according to claim 1, wherein the magnetic coding of the security element has at least a first magnetic coding element and at least a second magnetic coding element, with the first and the second magnetic coding element being arranged along the coding direction on or in the security element, and with the first magnetic coding element having a grid-shaped magnetic region which is formed by a plurality of mutually parallel grid strips made of magnetic material which respectively have a magnetic anisotropy, and the second magnetic coding element having a grid-shaped magnetic region which is formed by a plurality of mutually parallel grid strips made of magnetic material which respectively have a magnetic anisotropy, with the grid strips of the second magnetic coding element extending in another direction than the grid strips of the first magnetic coding element.
4. The security element according to claim 3, wherein the grid strips of the second magnetic coding element extend at an angle of 60 to 120 to the grid strips of the first magnetic coding element.
5. The security element according to claim 1, wherein the width and thickness of the grid strips, in particular the width and thickness of the grid strips of the first magnetic coding element and the width and thickness of the grid strips of the second magnetic coding element, are chosen so small that the grid strips respectively have a magnetic shape anisotropy whose preferential magnetic direction extends along the grid strips.
6. The security element according to claim 1, wherein the magnetic anisotropy of the grid strips of the respective magnetic coding element, in particular of the first and the second coding element, is configured such that the respective magnetic coding element, in particular the first and the second magnetic coding element, has in the magnetization direction parallel to the grid strips a magnetization characteristic with an open hysteretic shape, and has in the magnetization direction perpendicular to the grid strips a magnetization characteristic that has a negligibly small remnant magnetization, in comparison to the magnetization characteristic in the magnetization direction parallel to the grid strips.
7. The security element according to claim 1, wherein the magnetic anisotropy of the grid strips of the respective magnetic coding element, in particular of the first and the second coding element, is configured such that the magnetization characteristic with the open hysteretic shape that the respective magnetic coding element has in the magnetization direction parallel to the grid strips has a coercive field strength of at least 10 Oe, and the magnetization characteristic that the respective magnetic coding element has in the magnetization direction perpendicular to the grid strips has a negligibly small coercive field strength, in comparison to the magnetization characteristic in the magnetization direction parallel to the grid strips.
8. A foil material having the security element according to claim 1.
9. A value document having the security element according to claim 1.
10. A method for manufacturing the security element according to claim 1, wherein the grid strips of the respective coding element, in particular of the first and the second coding element, are respectively manufactured from a magnetic coating which is applied to a substrate of the security element using a coating method.
11. The method according to claim 10, wherein, for manufacturing the grid strips, the magnetic coating is applied to a grid-shaped surface relief which was previously incorporated into a layer of the security element, in particular embossed thereinto.
12. The method according to claim 10, wherein the grid strips are manufactured by a metal transfer method, wherein in a layer of a first substrate a grid-shaped surface relief is manufactured and the latter is subsequently coated with magnetic material, so that magnetic regions form both on the raised places and on the depressions of the grid-shaped surface relief, a second substrate which is furnished with a bonding-agent layer is connected to the first substrate, so that the bonding-agent layer of the second substrate comes in contact with the magnetic regions of the first substrate which are present on the raised places of the grid-shaped surface relief, the first and second substrates are subsequently mutually separated again, with the magnetic material of the raised places remaining adhering to the bonding-agent layer and being detached from the first substrate, in particular from the layer of the first substrate.
13. The method according to claim 10, wherein the magnetic coating is applied to a substrate of the security element, and the applied magnetic coating is subsequently removed in the intermediate regions of the grid strips, in particular by etching or by means of a washing-ink method or by means of a photoresist lift-off method or by irradiation with a laser.
14. The method according to claim 10, wherein a magnetic coating is applied to a substrate of the security element, and that the grid strips of the coding element are manufactured by embossing the magnetic coating.
15. A method for checking a value document which has a security element according to claim 1, using a magnetic sensor which detects magnetic signals of the security element, wherein, for magnetizing the magnetic coding elements, there acts on the security element before and/or during the detection of the magnetic signals a magnetic field whose direction extends at an acute angle to the grid strips of at least one of the magnetic coding elements.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Hereinafter the invention will be explained by way of example with reference to the following figures. There are shown:
(2) FIGS. 1a-b magnetization of a grid-shaped magnetic region by a magnetic field extending perpendicular to the grid strips (FIG. 1a) or parallel to the grid strips (FIG. 1b),
(3) FIG. 1c magnetization characteristic of the grid-shaped magnetic region in the cases of FIGS. 1a and 1b,
(4) FIGS. 2a-c first exemplary embodiment of the security element according to the invention (FIG. 2a), its magnetization by a magnetic field H.sub.x (FIG. 2b), and vectorial breakdown of the magnetization (FIG. 2c),
(5) FIG. 3a two-dimensional representation of the magnetic signals of the security element from FIGS. 2a-b, detected in the z direction,
(6) FIG. 3b course of the magnetic signals detected in the z direction, along the y direction at the position x=x0,
(7) FIG. 4 arrangement for checking the magnetic signals of the security element,
(8) FIGS. 5a-b second (FIG. 5a) and third (FIG. 5b) exemplary embodiments of the security element according to the invention,
(9) FIG. 6 fourth exemplary embodiment of the security element according to the invention,
(10) FIGS. 7a-d cross-sectional representations for a first preferred manufacturing method, with the grid strips extending perpendicular to the drawing plane,
(11) FIGS. 8a-b cross-sectional representations for a second preferred manufacturing method, with the grid strips extending perpendicular to the drawing plane.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
(12) In FIG. 1a is shown an example of a grid-shaped magnetic region 2. It has a plurality of grid strips 3 made of magnetic material and interjacent non-magnetic regions 4. The grid strips 3 have a length a which is preferably at least three times greater than their width b. The width b of the grid strips is e.g. in the m range or there below. The grid strips have a magnetic shape anisotropy which leads to the grid strips 3 being magnetizable differently in dependence on the magnetic-field direction.
(13) Through a magnetic field H.sub. extending parallel to the direction of the grid strips 3, cf. FIG. 1b, a magnetization of the grid-shaped magnetic regions 2 is obtained. As a function of the strength of a magnetic field H.sub. that is applied in the direction parallel to the grid strips, the grid-shaped magnetic region 2 has a magnetization characteristic M(H.sub.) with an open hysteretic shape which has a coercive field strength K.sub. of about 200 Oe, cf. FIG. 1c. Even after removal of the grid-shaped magnetic region 2 from the magnetic field H.sub. there remains a great remanent magnetization R.sub..
(14) Through a magnetic field H.sub. extending perpendicular to the direction of the grid strips 3, cf. FIG. 1a, the grid-shaped magnetic regions 2 are magnetized distinctly more weakly, in contrast. As a function of the strength of a magnetic field H.sub. that is applied in the direction perpendicular to the grid strips, the grid-shaped magnetic region 2 has a flat and nearly closed, substantially linearly extending magnetization characteristic M(H.sub.) with negligibly smaller coercive field strength (K.sub.), cf. FIG. 1c. After removal of the grid-shaped magnetic region 2 from the magnetic field H.sub. there remains in this case only a negligibly small remanent magnetization R.sub.. The latter is preferably at least a factor of 5 smaller than the remanent magnetization R.sub..
(15) In FIG. 2a is shown a plan view of a security element 1 of a first exemplary embodiment. Along the longitudinal direction y of the security element, the security element 1 has a magnetic coding comprising four different sorts of magnetic coding elements 2a, 2b, 2d, 2e. Between the coding elements 2a-d there is no magnetic material. The coding elements 2a, 2b and 2d respectively have a grid-shaped magnetic region, but with the direction of the grid strips 3 being different in said coding elements. The magnetic coding element 2e has a conventional magnetic region which has no grid strips but rather in which the magnetic material is applied continuously areally. The grid strips 3 of the coding elements 2a and 2b respectively extend at an acute angle to the longitudinal direction y of the security element 1. Viewed along the longitudinal direction y, the grid strips 3 of the coding element 2a extend to the right and the grid strips 3 of the coding element 2b to the left. In the shown example, the grid strips of the coding element 2b extend approximately perpendicular (y90) to those of the coding element 2a and the two acute angles amount to approximately 45. The grid strips 3 of the coding element 2d, in contrast, extend parallel to the longitudinal direction y of the security element 1.
(16) The security element 1 is magnetized e.g. by a magnetic field H.sub.x that is applied along the x direction, i.e. perpendicular to the longitudinal direction y of the security element 1. With the conventional coding element 2e, the magnetic field H.sub.x leads to a magnetization M along the x direction, i.e. parallel to the magnetic field H.sub.x. After removal of the security element 1 from the magnetic field H.sub.x there remains with the coding element 2e a remanent magnetization parallel to the previously applied magnetic field H.sub.x, which is indicated in FIG. 2b by an arrow on the coding element 2e. In accordance with the remanent magnetization, the magnetized coding element 2e has a magnetic south pole (marked as S) at one edge (above in FIG. 2b) and a magnetic north pole (marked as N) at the opposing edge (below in FIG. 2b). In contrast, there results with the coding elements 2a, 2b and 2d having a grid-shaped magnetic region a completely other magnetization behavior.
(17) The coding element 2d whose grid strips extend perpendicular to the magnetic field H.sub.x is not magnetized, or magnetized only to a negligibly small degree, in the x direction by the magnetic field H.sub.x, in accordance with the magnetization characteristic M(H.sub.) from FIG. 1c. Hence, with said coding element 2d there remains only a negligibly small remanent magnetization (no arrow in FIG. 2b or 2c). Additionally, the security element 1 can also have further coding elements, e.g. a coding element having a grid-shaped magnetic region whose grid strips extend parallel to the magnetic-field direction x. With regard to its magnetization in the x direction, such a coding element behaves qualitatively like the conventional coding element 2e.
(18) The magnetic field H.sub.x can be broken down vectorially into a magnetic-field component H.sub.1 extending parallel to the grid strips 3 of the coding element 2a and into a magnetic-field component H.sub.2 extending perpendicular to the grid strips 3 of the coding element 2a, cf. FIG. 2a on the left. Due to the magnetic shape anisotropy of the grid strips 3, the coding element 2a is magnetized by the magnetic-field component H.sub.1 directed in the direction of the grid strips, while the magnetic-field component H.sub.2 directed perpendicular thereto hardly influences or does not at all influence the magnetization M of the coding element 2a. In contrast, the magnetization M of the coding element 2b is hardly or not at all influenced by the magnetic-field component H.sub.1, but rather the coding element 2b is magnetized by the magnetic-field component H.sub.2. The magnetization of the coding elements (marked with arrow in FIG. 2b) extends both with the coding element 2a and with the coding element 2b along the respective grid strips, i.e. not parallel to the magnetic field H.sub.x but rather at an acute angle to H.sub.x. In accordance with the magnetization, the grid strips 3 of the coding elements 2a, 2b respectively have a magnetic north pole at one of their ends and a magnetic south pole at the opposing end. In contrast to the conventional coding element 2e, a magnetic north pole and south pole are formed not only at the upper and lower edges of the coding elements 2a, 2b, but also at the right and left edges of the coding elements 2a, 2b, cf. FIG. 2b.
(19) The magnetization M of the coding elements 2a and 2b can be broken down vectorially into a magnetization component M.sub. parallel to the magnetic field H.sub.x and into a magnetization component M.sub. perpendicular to the magnetic field H.sub.x, cf. FIG. 2c. The two coding elements 2a and 2b whose grid strips 3 form an acute angle to the magnetic field H.sub.x therefore have not only a magnetization component in the direction parallel to the applied magnetic field (x direction), but also a magnetization component perpendicular to the applied magnetic field (y direction). In contrast, the magnetization M of the conventional coding element 2e only has a magnetization component parallel to the applied magnetic field (x direction) and no magnetization component in the direction perpendicular to the applied magnetic field (y direction), cf. FIG. 2c on the right.
(20) After the security element was magnetized by the magnetic field H.sub.x, magnetic signals of the security element are detected by a magnetic sensor in order to check the magnetic properties of the security element 1. Depending on the kind of magnetic sensor, a magnetic field can also act on the security element during the detection of the magnetic signals. In the following example it will be assumed that no magnetic field acts on the security element during detection.
(21) FIG. 4 shows an arrangement for checking the magnetic properties of the security element 1 or of the value document 10. The shown arrangement is contained e.g. in an apparatus for value-document processing to which the value documents 10 are inputted singly or in stacks, subsequently checked, sorted and outputted again or stored in the apparatus for value-document processing. A value document 10 is transported along a transport path T first past a magnetization device 5, for supplying the magnetic field H.sub.x, and thereafter past a magnetic sensor 7 having a sensor line 6. The magnetic field H.sub.x is supplied e.g. by two mutually opposing magnets 30, 40 between which the value document 10 is transported through. The poles N, S of the magnets 30, 40 are so aligned that there results therebetween a magnetic field H.sub.x parallel to the transport direction T (x direction). However, other orientations of the magnetic poles are also possible. Alternatively, the first magnetization device 5 can also be arranged only on one side of the transport path S, as long as this achieves a sufficiently great magnetic field strength for magnetizing the magnet material. For example, the magnetic field H.sub.x can also be supplied by only one magnet.
(22) After magnetization by the magnetic field H.sub.x, the value document 10 is transported past the magnetic sensor 7 which is installed in the apparatus for value-document processing so as to be spatially separate from the magnetization device 5. Therebetween there can be provided e.g. branchings or deflections of the transport path. The magnetic sensor 7 contains a sensor line 6 having a multiplicity of magnetosensitive elements 13 of the same kind, which are arranged in a line. Each of said magnetosensitive elements 13 delivers a magnetic signal as a function of time or as a function of the x position on the value document 10 transported past. The sensor line 6 is arranged in direct proximity to the transport plane of the value document 10. It can be provided that the value documents 10 transported past touch the surface of the sensor line, but there can also be provided a small distance between the surface of the sensor line 6 and the value document 10 transported past. The magnetosensitive elements 13 are e.g. respectively arranged on a common printed board (details not shown), and connected to an evaluation device 9 which evaluates the magnetic signals of the elements 13.
(23) The value document 10 from FIG. 4 has a security element 1, which in this example is configured as a security thread. However, the invention also concerns other kinds of magnetic security elements of value documents, e.g. foil elements which are applied to the value document and which have a magnetic coding. As an example it is assumed that the security element 1 has the magnetic coding shown in FIG. 2a. The magnetic field H.sub.x is oriented parallel to the transport direction x of the value document 10 and has a sufficient magnetic field strength to magnetize the grid strips 3 of the coding elements 2a, 2b of the security element 1. Through the magnetic field H.sub.x the coding elements 2a-c of the security element 1 are magnetized in accordance with the arrows shown in FIGS. 2b and 2c. Through the sensor line 6 there are detected magnetic signals that correspond to the remanent magnetization of the coding elements 2a-c. By the security element 1 being transported past the sensor line 6, the magnetic signals are detected both as a function of the x direction and as a function of the y direction. The value document 10 or the security element 1 is, in so doing, magnetically scanned two-dimensionally. The magnetosensitive elements 13 can be configured for detecting magnetic fields along the x or y or z direction (different sensitivity directions being possible).
(24) In the present example, the magnetosensitive elements 13 are configured for detecting the magnetic-field component that the coding elements 2 of the security element 1 bring about in the z direction. In FIG. 3a is represented the magnetic signal S.sub.z that the sensor line 6 detects upon magnetic scanning of the security element 1 from FIG. 2a as a function of the x and y coordinates. Positive values of the magnetic signal S.sub.z are shown black, while negative values of the magnetic signal S.sub.z are shown bordered in white. For illustration, FIG. 3a also shows the edges of the security element 1 dashed. The upper and left edges of the coding element 2a deliver a negative magnetic signal S.sub.z, in accordance with the magnetic south pole present at said two edges, cf. FIG. 2b. The lower and right edges of the coding element 2a deliver a positive magnetic signal S.sub.z, in accordance with the magnetic north pole present at said edges, cf. FIG. 2b. Conversely, the upper and right edges of the coding element 2b deliver a negative magnetic signal S.sub.z, in accordance with the magnetic south pole present at said two edges, cf. FIG. 2b. The lower and left edges of the coding element 2b deliver a positive magnetic signal S.sub.z, in accordance with the magnetic north pole present at said edges, cf. FIG. 2b. The conventional coding element 2e, in contrast, only delivers a negative magnetic signal S.sub.s (magnetic south pole) at its upper edge and a positive magnetic signal S.sub.z (magnetic north pole) at its lower edge. From the coding element 2d no, or only a negligibly small, magnetic signal S.sub.z is detected, due to the absence of remanent magnetization upon magnetization along the x direction.
(25) FIG. 3b indicates the course of the magnetic signal S.sub.z detected in the z direction, as a function of the position along the longitudinal direction of the security element 1 (y direction), which corresponds to the signal from FIG. 3a at the position x=x0. The position x0 is chosen here approximately in the middle of the security element 1viewed along the magnetic-field direction xsince that is where the differences of the magnetic signal of the coding elements 2a-c are especially distinct. The magnetic signal S.sub.z of the security element has a negative peak at the left edge of the coding element 2a and at the right edge of the coding element 2b. At the right edge of the coding element 2a and at the left edge of the coding element 2b it has a positive peak. At the y coordinates of the conventional coding element 2e no magnetic signal S.sub.z at all is detected at the position x=x0, just as in the region of the coding element 2d. The two coding elements 2a and 2b hence have magnetic signals S.sub.z which are completely different from those of the conventional coding element 2e. Such magnetic signals that the grid-shaped magnetic regions of the coding elements 2a, 2b deliver cannot be generated by conventional magnetic regions of other shape or size either. The coding elements 2a and 2b having a grid-shaped magnetic region hence increase the anti-forgery security of a security element having one or more of said coding elements.
(26) Furthermore, the two coding elements 2a and 2b are mutually distinguishable unambiguously on the basis of their different magnetic signals, cf. FIG. 3b. Such grid-shaped magnetic regions having a different grid direction can hence be advantageously employed for a magnetic coding of the security element 1 consisting of different coding elements. Thus, new basic elements for a magnetic coding are available that constitute a forgery-proof alternative to the basic elements of previous magnetic codings consisting of conventional high- and low-coercivity coding elements.
(27) To mutually distinguish the different magnetic signals of the different coding elements, magnetosensitive elements 13 with other sensitivity directions can also be employed. The magnetic signals can also be mutually distinguished by magnetosensitive elements whose sensitivity direction lies in the plane of the security element (x-y plane), e.g. the sensitivity direction can also be parallel, oblique or perpendicular to the longitudinal direction y of the security element 1. Instead of a magnetic field H.sub.x, other magnetic-field directions can also be employed for magnetization. However, the magnetic field preferably forms an acute angle with the direction of the grid strips.
(28) In FIG. 5a is shown a second exemplary embodiment of a security element 1 which has a conventional coding element 2e and has two coding elements 2b. The angle that the grid strips 3 of the coding elements 2b form with the longitudinal direction y of the security element 1 is an acute angle of about =30.
(29) In FIG. 5b is shown a third exemplary embodiment of a security element 1 which has two coding elements 2a. The angle that the grid strips 3 of the coding elements 2a form with the longitudinal direction y of the security element 1 is an acute angle of about =60.
(30) FIG. 6 shows a fourth exemplary embodiment of a security element 1 having a coding element 2d with grid strips 3 extending parallel to the longitudinal direction y of the security element 1, and a coding element 2c with grid strips 3 extending perpendicular to the longitudinal direction y of the security element 1. For magnetization, however, there is applied in this example a magnetic field H.sub.xy that extends obliquely to the axes x and y, e.g. at an angle of 45. The magnetic-field angle can also deviate from 45. The grid strips in turn enclose an acute angle with the applied magnetic field H.sub.xy. Through said magnetic field H.sub.xy there is generateddue to the anisotropic magnetizability of the respective grid strips 3a magnetization parallel to the y direction with the coding element 2d and a magnetization parallel to the x direction with the coding element 2c. Accordingly, the magnetic north pole N and the south pole S arise with the two coding elements on different sides of said coding elements, cf. FIG. 6. A conventional coding element 2e, in contrast, would respectively obtain a magnetic north pole on its right and lower sides and respectively a magnetic south pole on its left and upper sides. Accordingly, the magnetic signals that the two coding elements 2d and 2c deliver also differ both from each other and from that of a conventional coding element 2e.
