Security element with magnetic coding, value document, production method and checking method

Abstract

The invention provides for at least one of the code cells (20) of the magnetic coding (16) to contain a partial region made of hard magnetic material with moderate coercive field strength (LoCo material) (30) and a partial region made of a soft magnetic material (32), the partial regions that contain LoCo material (30) and the partial regions that contain soft magnetic material (32) being arranged next to one another within the code cell (20).

Description

[0001] Security element with magnetic coding, valuable document,

[0002] Manufacturing processes and testing procedures

[0003] The invention relates to a security element with a magnetic encoding consisting of a plurality of code cells for securing security documents, valuables, and other data carriers. The invention also relates to a valuables document with such a security element, a method for manufacturing such a security element, and a method for testing a valuables document equipped with such a security element.

[0004] Data carriers, such as valuables or identification documents, but also other valuables, such as branded goods, are often equipped with security elements for protection, which allow verification of the authenticity of the data carriers and also serve as protection against unauthorized reproduction.

[0005] To enable automated authentication and, if necessary, further sensor-based detection and processing of the data carriers, the security features are often designed to be machine-readable. For this purpose, security features with machine-readable magnetic areas have long been used, the information content of which can be detected and evaluated by the magnetic sensor of a banknote processing system during authentication.

[0006] Based on this, the invention aims to further improve a security element of the type mentioned above and, in particular, to provide a reliably readable magnetic security element with extended coding possibilities and high counterfeit protection. This objective is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0007] The invention provides a security element with a magnetic coding consisting of a plurality of code cells, which serves to secure valuable documents.

[0008] At least one of the code cells of the magnetic encoding contains a section made of hard magnetic material with moderate coercivity and a section made of soft magnetic material. Hard magnetic material with moderate coercivity is also referred to in this description as "LoCo material," where "LoCo" stands for "Low Coercivity." The sections containing LoCo material and the sections containing soft magnetic material are arranged next to each other within the code cell.

[0009] In an advantageous embodiment, some of the code cells of the magnetic encoding contain a magnetic material, wherein the arrangement of the code cells with magnetic material and the code cells without magnetic material forms a coarse magnetic encoding, particularly for a first code with lower information content. The aforementioned code cells with magnetic material can, in particular, comprise LoCo material and / or HiCo material (hard magnetic material with high coercivity). The coarse encoding can, for example, represent a denomination, a series, a currency, and / or the authenticity of the security element or the security document it embosses.In this advantageous embodiment, at least one of the code cells containing magnetic material contains a sub-area of ​​LoCo material and a sub-area of ​​a soft magnetic material, wherein the sub-area containing LoCo material and the sub-area containing soft magnetic material are arranged next to each other within the respective code cell.

[0010] The arrangement of LoCo material and / or soft magnetic material within at least one of the code cells containing magnetic material forms a fine-grained magnetic encoding for a second magnetic code with additional information content. Additional information content means, in particular, information content in addition to the information content of the coarse-grained encoding, so that the second magnetic code has a higher information content than the first magnetic code. Therefore, the arrangement and type of code cells with fine-grained magnetic encoding and the code cells without magnetic material can form a second magnetic code with a higher information content than the first magnetic code.To further increase the information content of the second magnetic code, some of the magnetic code cells can also be made of material with high coercive field strength, in particular with a coercive field strength of 600 Oe (48 kA / m) or more, or contain corresponding material.

[0011] The code cells containing LoCo material and / or soft magnetic material all contain magnetic material, but can differ in their arrangement, particularly in the size and / or sequence of the sub-areas filled with LoCo or soft magnetic material. The different arrangements of LoCo material and / or soft magnetic material within a code cell thus form a fine-grained magnetic encoding, which in this description is also referred to as the "type" or "configuration" of the code cell.

[0012] The first code, with lower information content, is specifically a binary code where code cells containing magnetic material represent a bit "1" and code cells without magnetic material represent a bit "0". The second code, with higher information content, is specifically a multivalued code where code cells without magnetic material each represent a state "0", and code cells with magnetic fine encoding each represent one of several states "1" ... "n", with n > 2. The state "0" of the multivalued code corresponds to bit "0" of the binary code. The n states "1" to "n" of the multivalued code all correspond to bit "1" in the binary code, since the corresponding code cells each contain magnetic material. However, since n different states exist in the multivalued code for each bit "1" of the binary code, the multivalued code contains more information than the binary code.

[0013] Advantageously, the LoCo material and the soft magnetic material of the code cells are matched such that the magnetization of the LoCo sub-areas and the soft magnetic sub-areas of a code cell is essentially the same at a magnetic field strength HB, which is preferably either between 900 Oe (72 kA / m) and 1500 Oe (120 kA / m), particularly at about 1200 Oe (96 kA / m), or between 50 Oe (4 kA / m) and 500 Oe (40 kA / m), more preferably between 50 Oe (4 kA / m) and 250 Oe (20 kA / m). Essentially the same means, in particular, that the difference between the two magnetizations at the magnetic field strength HB is less than 10%, preferably less than 5%, of the higher magnetization value. Such a tuning eliminates a signal peak that would otherwise be present at the interface between the LoCo sub-areas and the soft magnetic sub-areas when reading data in a magnetic field of strength HB.As explained in more detail below, the absence of a signal peak at the interface can serve as a strong identifying feature, for example, as a mark of authenticity or as an identifier for the type of security element or the security document it embodies. Specifically, this identifying feature could be, for example, a denomination mark. The magnetic field strength HB, at which the magnetizations of the LoCo material and the soft magnetic material are essentially the same, is advantageously determined by the magnetization field strength of existing magnetic sensors, with the aforementioned magnetic field ranges being particularly well-suited for HB. The aforementioned magnetic field strength HB can, in particular, be provided by the readout field of a magnetic sensor intended for testing the security element or a security document it embodies.

[0014] The code cells can be freely arranged within the magnetic encoding. In an advantageous embodiment, the code cells are arranged along a first direction, forming a linear code, and the section made of LoCo material and the section made of soft magnetic material within each code cell are arranged side by side along a second direction. The second direction can coincide with the first direction; however, in advantageous embodiments, the second direction differs from the first. In particular, the second direction is perpendicular to the first direction, so that the direction of the fine encoding is perpendicular to the direction of the coarse encoding, meaning that the two encoding directions are as far apart as possible. In other embodiments, the second direction can form an angle between 15° and 75°, particularly between 30° and 60°, advantageously around 45°, with the first direction.If the second direction forms an angle with the first direction other than 0° and other than 90°, the magnetic coding, in particular the fine coding, can be read along different transport directions, for example perpendicular and parallel to the longitudinal axis of a security thread.

[0015] In addition to linear arrangements, the code cells can also form a two-dimensional code in advantageous configurations and can, for example, be arranged in a regular two-dimensional grid or an irregular two-dimensional arrangement.

[0016] In a further advantageous embodiment, it is provided that in at least one code cell, preferably in at least 50%, or even in at least 80% of the code cells, the sub-areas of the code cells made of LoCo material and soft magnetic material are arranged edge to edge or with a small gap of 0.5 mm or less, preferably 0.2 mm or less, and particularly preferably 0.1 mm or less. Small overlaps of the sub-areas made of LoCo material and soft magnetic material, in particular overlaps of less than 0.2 mm, preferably less than 0.1 mm, are also possible. However, due to the increased material thickness resulting from an overlap, overlap-free arrangements are preferred.With particular advantage, the sub-areas are printed with LoCo material and with soft magnetic material with a small design spacing d, which is dimensioned so that even if registration fluctuations of an amplitude Ad occur, neither an overlap nor an undesirably large distance between the sub-areas can occur.

[0017] The sections containing LoCo material and soft magnetic material are preferably separated by a boundary line, which may be straight, curved, bent, or jagged. Sinusoidal, quasi-sinusoidal, or completely arbitrary boundary line shapes are also possible. In a preferred embodiment, a straight boundary line runs perpendicular to the second direction. In another preferred embodiment, the boundary line runs obliquely, particularly at an angle between 15° and 75°, to the first direction.

[0018] In a further advantageous embodiment, the magnetic encoding comprises a magnetic code area formed from one magnetic code cell or from several immediately adjacent magnetic code cells, in which sub-areas containing LoCo material and sub-areas containing soft magnetic material follow one another both along the first direction or perpendicular to the first direction, as well as along a further, different direction. This can be achieved, for example, by a boundary line between LoCo material and soft magnetic material running obliquely (approximately between 15° and 75°) to the first direction.A stepped distribution of sections containing LoCo material and sections containing soft magnetic material is also possible, for example, in the form of a 2x2 grid, where sections containing LoCo material are arranged on one grid diagonal and sections containing soft magnetic material on the other. This advantageously allows for the fine coding of one and the same magnetic code area both during a security document check in transverse transport (transport direction of the security document parallel to the first direction / thread longitudinal direction) and during measurement in longitudinal transport (transport direction of the security document perpendicular to the first direction / thread longitudinal direction). The aforementioned LoCo material exhibits a pronounced hysteresis curve with high remanence and moderate coercive field strength.In this description, moderate coercive field strength means, in particular, that the LoCo material has a coercive field strength between 100 Oe (8 kA / m) and 500 Oe (40 kA / m), preferably between 100 Oe (8 kA / m) and 400 Oe (32 kA / m), and especially preferably between 100 Oe (8 kA / m) and 300 Oe (24 kA / m). The remanence of the LoCo material is expediently between 80% and 20%, and advantageously between 60% and 30% of the saturation magnetization.

[0019] The hysteresis curve of the aforementioned soft magnetic material passes through the origin or at least approximately through the origin, so that the coercive field strength and the remanence of the soft magnetic material are low. Specifically, the soft magnetic material advantageously exhibits a coercive field strength below 50 Oe (4 kA / m), preferably below 30 Oe (2.4 kA / m), particularly preferably below 20 Oe (1.6 kA / m), and most preferably below 10 Oe (0.8 kA / m). The remanence of the soft magnetic material is advantageously below 30%, preferably below 20%, and particularly preferably below 10% of the remanence of the LoCo material used.

[0020] In an advantageous embodiment, the code cells of the magnetic encoding are all of the same shape and size, which makes reading the code cells with a magnetic sensor particularly easy. For the same reason, the division of the code cells into sub-areas is also advantageously the same for all code cells of the magnetic encoding. However, designs with different shapes and sizes of code cells and / or with different divisions into sub-areas are also possible and advantageous in some applications. The code cells each form a contiguous area, except for a possible narrow gap along the boundary line of two sub-areas, with a generally arbitrary outline shape. Particularly preferred outline shapes are rectangles, squares, circles, and triangles. The outline shape of the code cells can also itself represent information, such as a letter, a number, text, or a symbol.

[0021] The code cells preferably have clear outlines with sharp edges, as this concentrates the magnetic field lines emanating from the edges, and the resulting stray field can be detected more effectively by a magnetic sensor. Code cells with frayed or ragged edges are advantageously avoided.

[0022] Preferably, the size of the code cells in the smallest dimension direction is at least 1 mm, particularly preferably between 2 mm and 6 mm. They thus occupy essentially the entire width of a typical security thread.

[0023] The code cells of the magnetic coding system can be directly adjacent to one another, but are advantageously spaced apart. This facilitates the reading of the magnetic codes and also allows for the inclusion of additional human characteristics, such as negative identifiers, in the spaces between the code cells. The distance between adjacent code cells is advantageously 2 mm or more.

[0024] In an advantageous embodiment, the thickness of the magnetic material of the code cells is the same for all code cells, so that the sections of the same material exhibit essentially the same remanence. In other embodiments, further coding can be provided by using different thicknesses of the magnetic materials. Magnetic sections of different thicknesses differ in their remanence, which can be detected with suitable magnetic sensors.

[0025] The magnetic materials of a code cell are preferably formed by printed magnetic inks with suitable magnetic pigments. The amount of magnetic material determines the magnetic flux of the tape, which is advantageously between 50 nWb / m and 600 nWb / m, preferably around 400 nWb / m.

[0026] A particular advantage of magnetic coding is that it does not contain code cells that consist solely of soft magnetic material. Therefore, if a code cell does contain any magnetic material at all (states "1" to "n"), it advantageously contains at least one LoCo material and, optionally, an additional soft magnetic material. The absence of purely soft magnetic code cells in magnetic coding allows for reliable reading of the simple, first code even with basic magnetic sensors, since these sensors often cannot distinguish code cells containing only soft magnetic material from code cells containing no magnetic material at all.

[0027] Preferably, each code cell of the security element containing magnetic material comprises LoCo material. This has the advantage that each of these magnetic code cells can then be detected by magnetic sensors that test the security element not in a magnetic field, but without an applied magnetic field during measurement. Optionally, each magnetic code cell can also contain additional high-coercive magnetic material, which does not interfere with the detectability of the LoCo material.

[0028] In an advantageous embodiment of the invention, the magnetic encoding does not include code cells containing hard magnetic material with high coercivity (hereinafter also referred to as "HiCo material," where "HiCo" stands for "High Coercivity"), in particular hard magnetic material with a coercivity of 600 Oe (48 kA / m) or more. Eliminating the use of hard magnetic material with high coercivity allows for simpler reading of the magnetic encoding, as no high-coercivity magnetic material needs to be remagnetized or brought into a defined magnetization state.

[0029] Simple sensors are generally unable to remagnetize magnetic HiCo elements because their (pre-)magnetization units are usually too weak. Therefore, HiCo elements are magnetized in an undefined manner for such sensors. This can cause the resulting field to disappear when interacting with softer magnetic materials, or the magnetization of the HiCo elements may be oriented in such a way that inductive read heads cannot detect a signal. If a HiCo element is not magnetized, magnetoresistive sensors with weak supporting fields cannot magnetize it and therefore cannot detect a signal.

[0030] In an alternative, equally advantageous embodiment of the invention, it is provided that some of the code cells of the magnetic encoding contain a hard magnetic material with a high coercive field strength, in particular a coercive field strength of 600 Oe (48 kA / m) or more. In this embodiment, reliable reading of the magnetic encoding requires a more complex, sophisticated magnetic sensor, such as that described, for example, in EP 2791 919 Bl. However, the advantage is that the number of possible encodings is significantly increased, since three different magnetic materials (soft magnetic material, LoCo material, HiCo material) are then available for encoding.

[0031] According to an advantageous embodiment, the security element includes one or more camouflage layers that cover the magnetic coding to reduce its visual visibility. For example, in the case of a security thread visible from both sides, the magnetic coding can be covered on both sides with a camouflage layer. If the security element is located on an opaque area of ​​a substrate, it may also suffice to cover only the side of the magnetic coding facing the viewer. A suitable camouflage layer may, for example, comprise a metal layer, a layer system comprising one or more metal layers, a metallically pigmented topcoat, a white topcoat, or a combination of such layers. The magnetic coding can also be camouflaged by encapsulating the magnetic pigments of the magnetic paints in a white or at least light-colored covering material.

[0032] In addition to magnetic coding, the security element can contain other machine-readable security features, for example, based on fluorescence, phosphorescence, or IR-absorbing materials. Furthermore, a combination of magnetic coding with optically variable features is advantageous. These can include, for example, holograms, microlenses, rod lenses, microconcave mirrors in spherical and lenticular designs, micromirrors, Fresnel elements for displaying curved surfaces, nanostructures, liquid crystals, CGHs (computer-generated holograms), and the like, also in combinations arranged one above the other and side by side. An optically variable element is advantageously positioned so that, when viewed, it lies between the observer and the magnetic coding, which is preferably camouflaged and thus not, or not easily, visible. Such camouflage is preferably provided on both the front and back of the security element.

[0033] In an advantageous embodiment, the security element is a security thread, wherein the aforementioned first direction preferably forms the longitudinal direction of the thread. However, the security element can also be, for example, a security strip, a patch, or a label.

[0034] Furthermore, the security element can not only be a separate security feature to be attached to or embedded in a security document, but can also be printed on or an integral part of the document. Such designs are particularly suitable for security documents with plastic substrates, where traditional security threads cannot be embedded. The security element can also be advantageously incorporated into a printed area on a security document, such as a banknote.

[0035] The invention also includes a security document with a security element of the type described. The security document can be, in particular, a banknote, for example a paper banknote, a polymer banknote or a foil-laminated banknote, a share certificate, a bond, a certificate, a voucher, a check, a seal, a tax stamp, a high-quality admission ticket, but also an identification card, such as a credit card, a bank card, a cash payment card, an authorization card, an identity card or a passport personalization page.The invention further includes a method for manufacturing a security element of the described type, in which a magnetic coding is generated from a plurality of code cells by providing at least one of the code cells of the magnetic coding with a partial area of ​​hard magnetic material with moderate coercive field strength (LoCo material) and a partial area of ​​soft magnetic material, wherein the partial areas containing LoCo material and the partial areas containing soft magnetic material are arranged next to each other within the code cell.

[0036] Finally, the invention also includes a method for examining a security document of the described type, comprising the following steps:

[0037] Magnetizing the security element of the security document using one or more magnets,

[0038] Transporting the valuable document past a magnetic sensor,

[0039] Detecting magnetic signals from the magnetized security element using the magnetic sensor while the valuable document is transported past the magnetic sensor, and

[0040] Verification of the security document based on the detected magnetic signals, particularly with regard to the authenticity and / or the type of security document.

[0041] The transport of the security document past the magnetic sensor can occur, in particular, along the first direction or perpendicular to the first direction. If the security element is a security thread, the transport can occur, in particular, along the thread's longitudinal direction or perpendicular to the thread's longitudinal direction.

[0042] The magnetization process is advantageously carried out in two steps, particularly when dealing with magnetic fields of different strengths and / or orientations. Additionally or alternatively, two detection steps can be performed, and the detection signal from both steps evaluated together to verify the document. For example, an additional magnetization step can be performed between two detection steps. An example of this is described in publication EP 2 791 919 Bl.

[0043] The preferred embodiments and their advantages presented with reference to the respective method according to the invention apply accordingly to the safety element according to the invention. The components of the safety element according to the invention are each configured to perform the respective steps of the method.

[0044] Further features of the invention will become apparent from the claims, the figures, and the figure description. Exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings. In the figures, identical or functionally equivalent elements are designated with the same reference numerals.

[0045] This shows:

[0046] Fig. 1 shows a schematic representation of a banknote with a security element according to the invention in the form of a security thread provided with a magnetic code, Fig. 2 shows in (a) a section of the magnetic code of a security thread with a plurality of code cells and in (b) the subdivision of the code cells into two sub-areas,

[0047] Fig. 3 shows the MH hysteresis curves of the hard and soft magnetic materials involved.

[0048] Fig. 4 schematically shows a security thread with a magnetic coding with different configurations of code cells,

[0049] Fig. 5 in (a) and (b) shows a first measurement step when reading the magnetic encoding of Fig. 4 at a magnetic field of HA ~ 0,

[0050] Fig. 6 (a) and (b) a second measurement step when reading the magnetic coding of Fig. 4 with a magnetic field of HB = 1200 Oe (96 kA / m) applied in the transport direction,

[0051] Fig. 7 in (a) to (c) Coding examples of a safety thread,

[0052] Fig. 8 shows another magnetic encoding,

[0053] Fig. 9 shows a security thread with extended geometries and coding possibilities of code cells, and

[0054] Fig. 10 schematically shows the cross-sectional structure of a security thread according to the invention. The invention will now be explained using the example of banknotes. Fig. 1 shows a schematic representation of a banknote 10 with a security element according to the invention in the form of a security thread 14 provided with a magnetic code 16. The security thread can be applied to the surface of the banknote 10 or partially or completely embedded in the banknote paper 12.

[0055] The magnetic encoding 16 of the security thread 14 is usually concealed by a covering (not shown in the figure), for example, a metal coating, a metallic-pigmented topcoat, or a white opaque layer, so that the presence of the magnetic encoding 16 is not readily apparent. Furthermore, in addition to the magnetic encoding, the security thread 14 may have other security features, such as optically variable counterfeit indicators, which dominate the visual appearance of the security thread.

[0056] The magnetic encoding 16 allows machine reading of the security thread 14, for example, during a banknote 10 authentication check. The special design of the magnetic encoding 16 allows reading with both simple and advanced magnetic sensors, with the latter capturing a larger amount of information. The magnetic encoding 16 contains a coarse encoding, a first magnetic code with a low information content that can be reliably read even with simple magnetic sensors. More advanced sensors can also detect a fine encoding contained within the magnetic encoding 16, thereby extracting a second magnetic code with a higher information content from the same magnetic encoding 16, which can be used, for example, for further authentication.The principle of storing two magnetic codes with different information density in a magnetic encoding 16 according to the invention will now be explained in more detail with reference to Figures 2 to 6.

[0057] Figure 2(a) schematically shows a section of the magnetic coding 16 of the security thread 14 of Fig. 1 with a plurality of code cells 20 arranged next to each other in a first direction 26.

[0058] As illustrated in Fig. 2(b), each of the code cells 20 is identically subdivided into two sub-areas 22, 24, which are arranged one above the other in a second direction 28 perpendicular to the first direction 26. The width b of the code cells corresponds to the width of the security thread 14 and is, for example, 2 mm. In the exemplary embodiment, the two sub-areas 22, 24 are of equal size with a height ai = a2 = b / 2.

[0059] Some of the code cells 20 contain a hard magnetic material 30 exhibiting a moderate coercive field strength of, for example, 270 Oe (LoCo material). The LoCo material 30 can fill either only the lower sub-area 22 (cells of configuration 2 or 4), only the upper sub-area 24 (cells of configuration 3 or 5), or both sub-areas 22 and 24 (cells of configuration 1). Some code cells 20 (cells of configuration 0) contain no magnetic material. The configuration 0, 1, 2, ... 5 of the code cells 20 is indicated below the respective code cell in Fig. 2(a).

[0060] The sequence of code cells 20 with LoCo material (one of configurations 1-5) and without magnetic material (configuration 0) forms a coarse magnetic encoding in the first direction 26 for a first code with lower information content. The first code is a binary code, which in the exemplary embodiment represents the bit sequence "1011001110001111", where code cells with LoCo material represent a bit "1", and code cells without magnetic material represent a bit "0".

[0061] Some of the code cells 20 (cells of configuration 2 or 3) contain, in addition to the LoCo material 30, a soft magnetic material 32 in the other sub-area 22 or 24, such that in these code cells the sub-area containing a LoCo material 30 and the sub-area containing a soft magnetic material are arranged side by side in the second direction 28. The code cells 20 of type 2 or 3 differ from the code cells of type 4 or 5 by the presence of the soft magnetic material 32, and also differ from each other by the sequence in which the two magnetic materials 30 and 32 follow one another.

[0062] The arrangement of LoCo material 30 and / or soft magnetic material 32 within a code cell 20 thus forms a magnetic fine coding of the code cells with 5 different configurations or 5 different types of code cells. Including this fine coding, the magnetic coding 16 therefore contains six different code cell configurations and thus forms a second code with higher information content. In the embodiment of Fig. 2, the second code forms, for example, the number sequence "102300450002345", where the numbers each indicate the configuration (0-5) of the corresponding code cell 20.

[0063] Another special feature, which provides an additional identification or authentication mark when reading the magnetic encoding 16 with a sophisticated magnetic sensor, is illustrated in the diagram in Fig. 3, which shows the MH hysteresis curves of the two magnetic materials 30 and 32 involved. For the soft magnetic material 32, the hysteresis curve 34 essentially passes through the origin; therefore, the following applies:

[0064] M soft (H=0) « 0.

[0065] Therefore, the coercive field strength and the remanence of the soft magnetic material 32 are also small. For example, the coercive field strength of the soft magnetic material 32 is less than 20 Oe (1.6 kA / m) and the remanence is less than 10% of the remanence of the LoCo material 30.

[0066] In contrast, the LoCo material 30 exhibits a pronounced hysteresis curve 36 with high remanence and moderate coercive field strength. For example, the coercive field strength of the hard magnetic material 30 lies between 200 Oe (16 kA / m) and 300 Oe (24 kA / m), and the remanence lies between 60% and 30% of the saturation magnetization.

[0067] The hysteresis curves 34, 36 of the two materials are matched so that they coincide when a specific applied magnetic field HB is applied, which corresponds to a preselected measuring magnetic field of a highly developed magnetic sensor, i.e.

[0068] Mweich (H — Hß) — Mhart (H — Hß) applies. This agreement ensures that the two magnetic materials 30, 32 have the same magnetization M under the measuring magnetic field HB.

[0069] Figures 4 to 6 illustrate how the various code cells 20 of configurations 0 to 5 can be detected and distinguished from one another using a sophisticated magnetic sensor, for example, of the type described in EP 2 791 919 B1. Figure 4 schematically shows a security thread 14 with a magnetic coding 16 that contains precisely the six different configurations of code cells 20-0 to 20-5 described above. Code cell 20-0 contains no magnetic material, code cells 20-1, 20-4, and 20-5 contain only LoCo material 30, and code cells 20-2 and 20-3 contain both LoCo and soft magnetic material 30, 32 in different sequences. In code cells 20-4 and 20-5, the LoCo material 30 only fills one of the two sub-areas 22 and 24, while in code cell 20-1 the entire code cell is filled with LoCo material 30.

[0070] A highly developed magnetic sensor can distinguish these 6 different configurations by measuring at two magnetic field strengths, for example at HA = 0 and the measuring magnetic field HB = 1200 Oe (96 kA / m).

[0071] For the purposes of this explanation, it is assumed that the security thread 14 is guided through the magnetic sensor in a direction designated as transport direction x (pointing downwards in Figs. 5 and 6), and that the magnetic sensor contains a plurality of identical magnetosensitive elements, each arranged in a row, with which the magnetization of the code cells 20 of the security thread 14 can be read.

[0072] In the highly developed magnetic sensor, a premagnetization takes place in a preparatory step when the safety thread 14 enters the sensor, which aligns the magnetic moments with remanence against the transport direction x (arrow 40 in Fig. 5).

[0073] In the following first measurement step of Fig. 5, the code cells are

[0074] 20 is then read out at a magnetic field HA ~ 0. Under these conditions, the soft magnetic areas of the code cells 20-2, 20-3 show no magnetization, while the LoCo areas of the code cells 20-1 to 20-5 contribute to the measured signal after premagnetization 40 through their remanence (arrows 42), as shown in Fig. 5(a).

[0075] Figure 5(b) schematically shows the measurement signal obtained by the magnetosensitive elements of the magnetic sensor in the different measurement tracks. The magnetosensitive elements each detect the z-component (perpendicular to the plane of the thread) of the resulting stray field of each code cell 20 and therefore produce a positive or negative signal peak at the entry and exit of a magnetized magnetic area into the measurement area, respectively.

[0076] As can be seen from measurement signals 44-0 to 44-5, code cell 20-0 can be identified by the absence of any signal peaks, and code cell 20-1 by a distance b between the two signal peaks, which corresponds to the thread width. Code cells 20-2 and 20-4 each generate measurement signals with two signal peaks spaced ai apart, while code cells 20-3 and 20-5 each generate measurement signals with two signal peaks spaced a2 apart.

[0077] Even if, as in the exemplary embodiment, ai = a2 = b / 2 is chosen, the measurement signals of code cells 20-2 and 20-4 on the one hand and code cells 20-3 and 20-5 on the other hand can be distinguished by the distance of the measurement peaks from the origin. The measurement signals of code cells 20-2 and 20-4, as well as of code cells 20-3 and 20-5, do not differ in the first measurement step.

[0078] In the second measurement step, illustrated in Fig. 6, the code cells 20 are read out under a magnetic field HB = 1200 Oe (96 kA / m) applied in the transport direction x (arrow 45 in Fig. 6(a)). The two magnetic materials 30, 32 are, as described above, matched to each other so that they exhibit the same magnetization under the HB measurement field. The resulting magnetization of the different sub-areas is illustrated in Fig. 6(a) by arrows 46.

[0079] Figure 6(b) schematically shows the measurement signal obtained from the magnetosensitive elements in the various measurement tracks when a magnetic field HB is applied. The hard and soft magnetic areas are now magnetized in the same direction and exhibit the same signal per unit area. As a result, signal peaks are generated at code cells 20-1 to 20-3 only at the entry and exit points of the cells into the measurement area, but not at the interface between the LoCo areas and the soft magnetic areas.

[0080] Accordingly, code cells 20-1 to 20-3 show the same measurement signals 48-1 to 48-3, while code cells 20-2 and 20-4 on the one hand, and code cells 20-3 and 20-5 on the other, can now be clearly distinguished: Code cells 20-2 and 20-3 produce two signal peaks at a distance b of the thread width, while code cells 20-4 and 20-5 produce two signal peaks at the smaller distance ai and a2, respectively. Furthermore, one of the signal peaks in each case has a different distance from the origin than the corresponding peak in code cells 20-2 and 20-3.

[0081] By combining the two measurement steps, the six code cell configurations 20-0 to 20-5 can be reliably distinguished from one another, allowing the second code with the higher information density to be read. The code cells can be identified solely by the distance between the signal peaks of the measurement signals.

[0082] The absence of a signal peak at the interfaces between LoCo and soft magnetic materials in code cells 20-2 and 20-3 represents a particularly strong security feature, as it requires a precise matching of the magnetic materials and thicknesses, which is difficult for a potential counterfeiter, as well as precise knowledge of the measuring field used in the magnetic sensor.

[0083] Simple magnetic sensors typically lack the capability to apply an external magnetic field during measurement or to perform two measurements with and without a magnetic field. Furthermore, they generally lack the spatial resolution required to distinguish between distances ai or a2 and b. However, simple magnetic sensors can detect the presence or absence of LoCo material 30 in a code cell 20. Accordingly, a simple magnetic sensor delivers the result "Bit 0" (no LoCo material 30 present) for code cell 20-0 and the result "Bit 1" (LoCo material 30 present) for each of the code cells 20-1 to 20-5.

[0084] Figure 7 shows some coding examples of a security thread 14 to illustrate the difference between the low-information-density code detectable by a simple magnetic sensor and the high-information-density codes detectable by a sophisticated magnetic sensor. The coding examples in Figure 7 utilize precisely the code cell configurations 20-0 to 20-5 described above.

[0085] All three encoding examples contain the same encoding "BABBAABBBAAABBBB" with bits A and B as shown in Fig. 7(a) as the first code with low information density.

[0086] The coding 50 of the security thread 14 in Fig. 7(a) is a comparative example and uses a simple code that only employs code cells 20-0 (displayed as configuration 0) and 20-1 (configuration 1). Configuration 0 corresponds to bit "A", and configuration 1 to bit "B" of the simple coding. Coding 50 contains no code cells with soft magnetic material and no second code with higher information content.

[0087] The coding 52 of the security thread of Fig. 7(b) uses a more complex code which, in addition to the code cells 20-0 and 20-1, also uses the code cells 20-2 (configuration 2), 20-3 (configuration 3) and 20-4 (configuration 4) in blocks.

[0088] Even more complex is the encoding 54 of the security thread of Fig. 7(c), which uses all 6 code cell configurations 20-0 to 20-5 and in which adjacent bits "B" are each encoded with a different code cell type.

[0089] A simple magnetic sensor detects only the simple encoding "BABBAABBBAAABBBB" in all three encoding examples 50, 52, 54 of subfigures (a), (b) and (c). With a sophisticated magnetic sensor, however, encodings 52, 54 can be distinguished from the simple, non-inventive encoding 50, since they each use different fine encodings for the bit "B".

[0090] Figure 8 shows another magnetic encoding 56, which appears identical to the encodings in Figure 7 for a simple magnetic sensor, and which serves to illustrate further, as yet undescribed, code cell configurations. In the more general code cell configurations 6 to 15, the division into two vertically superimposed sub-areas is eliminated. The configuration of each code cell is indicated below the code cell. The code cell of configuration 6 contains parallel LoCo areas 30 and soft magnetic areas 32 in the transport direction (perpendicular to the thread's longitudinal direction), which can be distinguished with a sophisticated magnetic sensor if appropriately scaled, while the code cell, due to the proportion of hard magnetic material 30, can still be read as a magnetic "bit B" by simpler sensors.

[0091] The code cells of configurations 7 to 15 exhibit different angles of the boundary line between LoCo areas 30 and soft magnetic areas 32. With appropriate scaling between the size of the code cells and the resolution of the sensor, a continuous shift of the peaks from measurement track to measurement track can be detected, and the code cell configuration can be deduced from this. Due to the proportion of LoCo material 30, the code cells of configurations 7 to 15 can still be read as a magnetic bit "B" for simple sensors, so that encoding 56 represents the same encoding "BABBAABBBAAABBBB" for a simple sensor as encoding examples 50, 52, and 54.

[0092] Some extended geometries and coding possibilities of code cells are illustrated using the security thread 14 of Fig. 9 with the different code cells 60-1 to 60-10.

[0093] Each code cell 60 forms an area section that is contiguous except for a possible narrow gap along the boundary line and can, in principle, have any outline shape. Particularly preferred outline shapes are rectangles (code cell 60-1), squares (code cell 60-2), circles (code cell 60-3), ellipses, or triangles (code cell 60-4). The outline of the code cells 60 can itself represent information such as a letter, a number, text, or a symbol. In addition to different outline shapes and different divisions into areas, the code cells of a magnetic encoding can also have different sizes.

[0094] The code cells are advantageously arranged in the direction of the thread, but other arrangements, for example in the direction of the thread width, are also possible (code cell 60-5).

[0095] Adjacent LoCo areas 30 and soft magnetic areas 32 may, in practice, exhibit small gaps or overlaps due to manufacturing tolerances. The boundary line 36 between LoCo areas 30 and soft magnetic areas 32 preferably runs in a straight line, but it can also be curved, bent, jagged, sinusoidal, quasi-sinusoidal, or even completely arbitrary. Straight boundaries preferably extend parallel to the thread direction, perpendicular to the thread direction, at an angle of 45°, or more generally at an angle between 15° and 75°, or at any angle to the thread direction. (Code cells 60-2, 60-6, and 60-7).

[0096] In some configurations, a portion of the code cells can also contain a hard magnetic material with a high coercive field strength of 600 Oe (48 kA / m) or more ("HiCo material"). To illustrate this, Fig. 9 shows a code cell 60-8 with adjacent sub-areas containing a LoCo material 30 and a HiCo material 34. Code cell 60-9 contains adjacent sub-areas containing a soft magnetic material 32 and a HiCo material 34. In code cell 60-10, the soft magnetic material 32 and the HiCo material 34 are located in the same area. The inclusion of such a HiCo material increases the number of coding possibilities for sophisticated magnetic sensors, but also means that code cells with hard magnetic HiCo material often cannot be read reliably by simple sensors.

[0097] Figure 10 illustrates an exemplary cross-sectional structure of a security thread 14 according to the invention. In a thread or film structure, the hard or soft magnetic materials are advantageously concealed behind a camouflage layer, so that after the security thread 14 is embedded in banknote paper or a film is applied to a target substrate, no easily recognizable coding is visible to the naked eye. This is all the more critical because most magnetic colors are dark to black and therefore, without countermeasures, show through a thin layer of paper very clearly.

[0098] The security thread 14 of Fig. 10 contains a carrier film, for example a PET film 70, which is provided on its upper side with a primer / heat-seal lacquer layer 72. A UV lacquer layer 74 was first applied to the underside of the PET film 70, embossed with a desired relief structure 76, provided with a reflection-enhancing coating 78, and leveled with a primer layer 80. The reflection-enhancing coating 78 can, in particular, be a metal coating, for example made of aluminum, or a color-shifting multi-layer structure, for example with the layer sequence Cr / SiO₂ / Al.

[0099] The magnetic coding 16 is then printed with the code cells, using sections of soft magnetic ink 82 and sections of hard magnetic LoCo ink 84, and overprinted with a silver ink layer 86. The thread structure is completed by a further primer layer 88, an opaque white layer 90, and a final primer / heat-seal varnish layer 92. In this example, a first camouflage layer for the magnetic inks is formed by the reflection-enhancing coating 78, and a second camouflage layer by the combination of the silver ink layer 86 and the opaque white layer 90.

[0100] When the security thread 14 is viewed from above in the orientation shown in Fig. 10, the magnetic coding 16 is not visible because it is obscured by the reflection-enhancing coating 78. The coating 78 may also contain negative markings that are synchronized with the gaps between the code cells, so that the magnetic areas 82, 84 are also not visible there.

[0101] When a security thread 14 is registered with a magnetic code 16, i.e., with a predetermined position of the magnetic code relative to the banknote edges, and inserted into banknote paper, the number of possible codes increases. Registered insertion also has the advantage that the thicker thread sections resulting from the magnetic printing can be positioned in thinner paper areas.

[0102] The security element according to the invention can not only represent a separate security element, such as the security threads described so far, but can also represent a printed or integral part of a banknote or other security document.

Claims

Patent claims 1. Security element for securing valuable documents with a magnetic coding consisting of a plurality of code cells, characterized in that at least one of the code cells of the magnetic coding contains a sub-area made of hard magnetic material with moderate coercive field strength (LoCo material) and a sub-area made of a soft magnetic material, wherein the sub-areas containing LoCo material and the sub-areas containing soft magnetic material are arranged next to each other within the code cell.

2. Security element according to claim 1, characterized in that a portion of the code cells of the magnetic encoding contains a magnetic material, and the arrangement of the code cells with magnetic material and the code cells without magnetic material forms a coarse magnetic encoding, in particular for a first code with lower information content, at least one of the code cells containing magnetic material contains a partial area of ​​LoCo material and a partial area of ​​a soft magnetic material, wherein the partial area containing LoCo material and the partial area containing soft magnetic material are arranged side by side within the respective code cell, and the arrangement of LoCo material and / or soft magnetic material within at least one of the magnetic material The contained code cells form a magnetic fine coding for a second magnetic code with additional information content.

3. Security element according to claim 1 or 2, characterized in that the LoCo material and the soft magnetic material of the code cells are matched to each other such that the magnetization of the hard magnetic and soft magnetic sub-areas is essentially the same at a magnetic field strength which is preferably either between 900 Oe (72 kA / m) and 1500 Oe (120 kA / m), in particular at about 1200 Oe (96 kA / m), or between 50 Oe (4 kA / m) and 500 Oe (40 kA / m), preferably between 50 Oe (4 kA / m) and 250 Oe (20 kA / m).

4. Security element according to at least one of claims 1 to 3, characterized in that the code cells are arranged along a first direction and the part made of LoCo material and the part made of soft magnetic material are arranged next to each other within the respective code cell along a second direction, wherein the second direction advantageously differs from the first direction, in particular being perpendicular to the first direction.

5. Security element according to at least one of claims 1 to 4, characterized in that in at least one code cell, preferably in at least 50% or even in at least 80% of the code cells, the sub-areas with LoCo material and with soft magnetic material are arranged buttressed or with a small distance of 0.5 mm or less, preferably 0.2 mm or less, particularly preferably 0.1 mm or less.

6. Safety element according to at least one of claims 1 to 5, characterized in that the partial areas with LoCo material and with soft magnetic material are separated by a boundary line which, for example, is straight, bent, curved or jagged, wherein the boundary line is preferably oriented obliquely, in particular at an angle between 15° and 75°, to the first direction.

7. Security element according to at least one of claims 1 to 6, characterized in that the magnetic coding has a magnetic code area formed from a magnetic code cell or from several immediately adjacent magnetic code cells, in which sub-areas containing LoCo material and sub-areas containing soft magnetic material follow one another both along the first direction or perpendicular to the first direction, as well as along a further, different direction.

8. Safety element according to at least one of claims 1 to 7, characterized in that the LoCo material has a coercive field strength between 100 Oe (8 kA / m) and 500 Oe (40 kA / m), preferably between 150 Oe (12 kA / m) and 400 Oe (32 kA / m), particularly preferably between 200 Oe (16 kA / m) and 300 Oe (24 kA / m), and / or that the soft magnetic material has a coercive field strength below 50 Oe (4 kA / m), preferably below 30 Oe (2.4 kA / m), particularly preferably below 20 Oe (1.6 kA / m).

9. Security element according to at least one of claims 1 to 8, characterized in that the magnetic coding does not include code cells which contain only soft magnetic material as magnetic material.

10. Safety element according to at least one of claims 1 to 9, characterized in that the magnetic coding does not include code cells containing hard magnetic material with high coercive field strength, in particular with a coercive field strength of 600 Oe (48 kA / m) or more.

11. Security element according to at least one of claims 1 to 9, characterized in that part of the code cells of the magnetic coding contains a hard magnetic material with a high coercive field strength, in particular a coercive field strength of 600 Oe (48 kA / m) or more.

12. Security element according to at least one of claims 1 to 11, characterized in that the security element contains one or more camouflage layers that cover the magnetic coding in order to reduce the visual visibility of the magnetic coding.

13. Security element according to at least one of claims 1 to 12, characterized in that the security element represents a security thread, wherein the first direction preferably forms the longitudinal direction of the thread, or that the security element forms a printing area on a security document.

14. Security document comprising a security element according to at least one of claims 1 to 13.

15. Method for manufacturing a security element according to any one of claims 1 to 13, wherein a magnetic code is generated from a plurality of code cells by at least one of the code cells of the Magnetic coding is provided with a sub-area of ​​hard magnetic material with moderate coercive field strength (LoCo material) and a sub-area of ​​soft magnetic material, wherein the sub-areas containing LoCo material and the sub-areas containing soft magnetic material are arranged next to each other within the code cell.

16. Method for examining a security document according to claim 14, comprising the steps: Magnetizing the security element of the security document using one or more magnets, Transporting the valuable document past a magnetic sensor, Detecting magnetic signals from the magnetized security element using the magnetic sensor while the valuable document is transported past the magnetic sensor, and Verification of the security document based on the detected magnetic signals, particularly with regard to the authenticity and / or the type of security document.

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