WO2003001446A1

WO2003001446A1 - Marker device and method for reading said marker device

Info

Publication number: WO2003001446A1
Application number: PCT/EP2002/006542
Authority: WO
Inventors: Jan Morenzin; Daniel Schondelmaier
Original assignee: Forschungszentrum Jülich GmbH
Priority date: 2001-06-25
Filing date: 2002-06-14
Publication date: 2003-01-03
Also published as: DE10130553A1

Abstract

The invention relates to a marker device (1) for the identification of objects by means of a code, which has areas (4 to 8) with different characteristics. Said device is characterised in that it has areas (4 to 8) of varying maximum coercivity. The invention also relates to a method for reading the inventive marker device.

Description

Description;

Marking device and method for reading out the marking device

The invention relates to a marking device for marking objects with a coding that identifies areas with different magnetic properties.

Magnetic encodings are often used for marking and thus individual assignment and securing of credit cards, credit cards, access cards, electronic keys or the like, often in the form of a so-called magnetic strip. A permanent magnetic layer is selected for the coding, i.e. magnetized in areas such that areas of different magnetization arise, which also include non-magnetized areas, that is to say those with magnetization 0. With appropriate magnetic field sensors, the magnetic signature or coding can be detected and then processed according to the respective purpose.

Magnetic strips are described in EP 0 650 142 A1 and DE 40 28 202, in which two magnetic layers of different coercivity are applied to a carrier. The spatial training of the highly coercive The magnetic layer is homogeneous in all magnetic strips, so that identification is only possible by writing. In addition, the coding and thus the information in the highly coercive magnetic layer can be changed by appropriate devices, so that only limited protection is provided against unauthorized production or manipulation.

In addition, DE 198 52 368 describes a marking device in which a permanent magnetic base layer and at least one magnetic coding layer are first applied to a carrier, an intermediate layer having a thickness such that regions are not parallel between the base layer and coding layer or antiparallel coupling. A disadvantage of this marking device is that its production is associated with a number of process steps.

The invention is based on the object of designing a marking device of the type mentioned at the outset in such a way that it is tamper-proof, permits an authenticity check and is also simple to produce.

This object is achieved in that areas of different maximum coercivity are present in the marking device. The maximum coercivity is to be understood as the greatest value for the coercivity, which is found in all directions when read out results, usually in the direction of the easy magnetic axis.

The advantage of the invention is that the regions of different coercivity generate a spatial distribution that represents the stored information or coding, and that the regions simultaneously form a distribution of the saturation magnetization or remanent magnetization, via which an authenticity test is possible. The definition of the information or coding in the spatial structure of the hysteresis properties takes place during the manufacture of the marking device and ensures a high level of protection against intentional or unintentional manipulation of the coding, because the sequence of the areas with different coercivities or remanence is after completion of the Manufacturing no longer changeable. The authenticity of the structure can simply be tested mechanically by reading out the magnetization states of the areas in a spatially resolving manner. By evaluating the distribution of the saturation magnetization or the remanent magnetization after suitable magnetization and comparison with a reference, it is possible to differentiate with certainty whether it is an original structure or whether there is a simulation of the magnetic structure. The authenticity check can be carried out automatically and without the control of a person. The readout unit can be encapsulated and protected against access from outside. An authenticity check is possible without an external data connection. The readout unit can be inexpensive and compact with using conventional magnetic reading technology.

In order to produce particularly strong flow changes at the boundaries of the regions, regions of different coercivity should adjoin one another in at least one direction. The proposal serves the same purpose that the magnetically easy axes of the regions point in one direction, preferably the readout direction and thus also the direction in which the regions expediently adjoin one another.

Basically, there is the possibility of providing areas with a large number of different coercivities. However, it simplifies the production to provide only two different coercivities, that is to say regions with high and equally large coercivities and regions with low and likewise equally high coercivities. It is expedient to provide a clear distance between high and low coercivity in order to produce flow changes that can be read out reliably. The low-coercive areas should not fall below a value of 5 Oersted so that they are stable in their magnetization state, that is to say they are not influenced by external magnetic interference or stray fields from adjacent magnetic areas.

As far as saturation magnetization or remanent magnetization is concerned, there is basically the possibility of areas of different saturation magnetization or to provide retentive megnetization so that a spatial structure of the saturation magnetization or retentive magnetization is created and can be evaluated. It can then be compared to a reference structure for the authenticity test. A simpler evaluation results, however, if the areas all have values of the same size for the saturation magnetization or remanent magnetization, since only a reference value then has to be compared.

The invention further relates to a method for reading out the above-described marking device. It is read out in such a way that areas with different coercivities are acted upon by a first magnetic field, that only part of the areas are remagnetized, and that the resulting pattern of flux changes is read out and used. With this type of reading, only the low-coercive areas u are magnetized, while the high-coercive areas maintain their magnetization state. The first magnetic field is so small that it is unable to re-magnetize the highly coercive areas.

If the low-coercivity areas have low magnetic stability, i.e. the coercivity is less than 5 Oersted, the flux changes should be read out under the action of a second magnetic field, which stabilizes the magnetization level of the u-magnetized areas, but is so low that no re-magnetization the non-magnetized, ie higher-coercive areas. The first and second magnetic fields can be of the same size and rectified. The stabilization with the second magnetic field prevents interactions with external magnetic interference or stray fields.

For the authenticity test, provision is made for the areas before and / or after the reading to be subjected to a third magnetic field which is so large and directed that all areas are then magnetized in one direction, and the areas are then magnetized evaluated and compared with a reference. If the highly coercive areas have already been magnetized during manufacture and have such a high coercivity that the magnetization is stable to external influences, it is sufficient if the third magnetic field is just so strong that the low coercive areas are in the direction of the magnetization of the highly coercive areas are magnetized. However, in order to be on the safe side with regard to the highly coercive areas, it is recommended to generate such a large third magnetic field that a saturation magnetization of all areas is brought about.

If the authenticity test is carried out before the remagnetization and the readout of the flux changes, it is particularly expedient if the highly coercive areas are not sufficiently stable against external influences, that the areas before the remagnetization with a fourth magnet field that is so large that a saturation magnetization of all areas is effected. Subsequently, the magnetization of the low coercive areas with the first magnetic field can then take place.

In particular, if the low-coercive areas have only a low stability, the authenticity test should be carried out in such a way that the areas are subjected to a fifth magnetic field after magnetic reversal and reading, which is so strong and so directed that all areas subsequently are magnetized in one direction, and the magnetization of the regions is then evaluated under a sixth magnetic field and compared with a reference that stabilizes the state of magnetization caused by the fifth magnetic field. The fifth and sixth magnetic fields can be rectified and the same size. For both magnetic fields, it is sufficient if the magnetization of the low-coercive areas is adapted to that of the high-coercive areas, that is, they are magnetized in the same direction until saturation. The direction of magnetization is opposite to that of the first magnetic field.

Finally, it is provided according to the invention that the second and the fifth and / or sixth magnetic field are of the same size, but directed in opposite directions.

The production, ie lining up of the areas of different coercivity, can be achieved by a non-homogeneous Material composition of one or more layers take place. Evaporation in a high vacuum is particularly suitable for applying the layers. The local growth properties of individual or multiple layers can be influenced, for example by local doping of the interfaces or the bulk material, local temperature differences, external magnetic field distribution, local ion or electron bombardment, locally different roughness of the support or other process parameters. Instead of vapor deposition, pigment systems can also be printed on, in which magnetizable particles are embedded in a binder matrix.

Alternatively, it can be provided that the structure consists of at least one ferromagnetic or ferrimagnetic layer and at least one further layer made of a magnetic or non-magnetic material. At least one of these additional layers is designed such that a spatially varying coercivity of the overall layer system is generated. Another possibility consists in the homogeneous formation of one or more ferro- or ferrimagnetic layers, which are influenced after the completion of the production in such a way that locally different coercivities result.

Two manufacturing examples are described below:

Example A; An alloy of 81% Ni and 19% Fe is evaporated in a first pattern to form spaced first areas on a support, these areas having a coercivity of <10 Oersted. The spatial distribution of the areas is specified by a mask. Subsequently, pure Co is vapor-deposited into the spaces between the first areas on the carrier with the aid of a second mask, so that first and second areas alternate in one direction. The second areas have a coercivity of> 50 Oersted. The layer thicknesses are chosen so that the saturation magnetization of all areas are the same. The field strength for U magnetizing the low coercive areas is between 10 and 50 Oersted.

Example B

Two dispersions with different magnetic particles are produced, the first particles having a coercivity of <500 Oersted and the second particles having a coercivity> 3000 Oersted. The dispersions are printed on a carrier in such a way that low-coercive areas and high-coercive areas alternate. To remagnetize only the low-coercive areas, the field strength must be between 500 and 3000 Oersted.

In the drawing, the invention is illustrated in more detail using an exemplary embodiment. Show it: 1 shows a marking device with a graphic representation of the different hysteresis loops;

FIG. 2 shows the marking device according to FIG. 1 in saturation magnetization;

3 shows the marking device according to FIGS. 1 and 2 during the remagnetization of the low-coercive areas and

4 shows the marking device according to FIGS. 1 to 3 with saturation magnetization in the opposite direction according to FIG. 2.

In FIG. 1, an oblique view shows a marking device 1, consisting of an elongated carrier layer 2 and a magnetic layer 3 applied thereon. The magnetic layer 3 is divided into five areas 4, 5, 6, 7, 8, which are arranged one behind the other in the longitudinal direction of the magnetic layer 3 and have different extensions in the longitudinal direction. The darker areas 4, 6, 8 alternate with the lighter areas 5, 7. The lighter areas have a low coercivity, as is illustrated by the illustration of the narrow hysteresis loop 9. The darker areas, 6, 8 have a high coercivity, symbolized by the second hysteresis loop 10. The two hysteresis loops fen 9, 10 it can also be seen that the remanent magnetizations and the saturation magnetizations are the same in all areas 4 to 8.

FIG. 2 shows the magnetization of the areas 4 to 8. A magnetic field aligned in the direction of the arrow 11 with a field strength H _lf which is greater than the field strengths H _CItιax and H _{c # ιrιin} , in which the areas 4, 5, 6, 7, 8 act in one direction, acts on the areas 4 to 8 be magnetized. In this way it is ensured that all areas 4 to 8 are magnetized in a direction indicated by the arrows on areas 4 to 8.

FIG. 3 shows the influence of an opposite magnetic field of the field strength H ₂ symbolized by the arrow 12. The field strength H ₂ is less than H _x and also as ^H _c , _m _ _x r but greater than the field strength H _{C / tnin} . In this way, the low-coercive areas 5, 7 are remagnetized in the direction of the arrow 12 compared to the state according to FIG. 2, so that the highly coercive areas 4, 6, 8 magnetized in one direction with the oppositely reversed areas 5, 7 with lower Alternate coercivity. Flux changes occur at the respective common boundaries of the areas 4 to 8, which can be read out by means of conventional magnetic field sensors. Because of their spacing, a characteristic pattern results which represents the stored information, that is to say represents the coding. It can then be evaluated depending on the task. If the magnetic field is strengthened with the field strength H ₂ in the direction of arrow 12, the situation shown in FIG. 4 results. The field strength H ₃ _c has the same absolute value as the field strength E is therefore greater than _cma ^H ^{and H,} _m i _n - ^The magnetic field is, however, (arrow 12) directed opposite. In this way, the highly coercive areas 4, 6, 8 are remagnetized, so that all areas 4 to 8 are magnetized in the same direction. The river changes at the borders of areas 4 to 8 disappear. Since all areas 4 to 8 have the same saturation magnetization, this magnetization can be detected by the magnetic field sensor and compared with a reference value. If the two values match, the marking device 1 is "genuine", ie the authenticity check has a positive result.

The authenticity check can also be carried out by a field which is greater than H _{C / min} and <H _{C (max} , but is directed opposite the field H ₂ used to activate the readout state. This field therefore points in the magnetization direction of the highly coercive areas 4, 6, 8. Due to the action of this field, only the low-coercive areas 5, 7 are folded over in the direction of the high-coercive areas 4, 6, 8, so that the flux change structure disappears.

It goes without saying that the above-described authenticity check can also be carried out with the magnetization shown in FIG. 2, since even then all rich 4 to 8 are saturation magnetized. In this case, the step shown in FIG. 4 can be omitted.

The flow changes can be read out with sufficiently stable, low-coercive areas 5, 7 without the influence of the magnetic field. If the coercivity of the areas 5, 7 is very low, the magnetic field with the field strength H ₂ or another field strength that lies between H _{C (inax} and H _{Crmln) can} also act on the readout, thereby stabilizing the low-coercivity areas in their magnetization direction.

Claims

Claims: marking device and method for reading out the marking device

1. Marking device (1) for the identification of objects with a coding, the areas (4 to 8) with different properties, characterized in that areas (4 to 8) of different maximum coercivity are present.

2. Marking device according to claim 1, characterized in that areas (4 to 8) of different coercivity adjoin each other in at least one direction.

3. Marking device according to claim 1 or 2, characterized in that the magnetically easy axes of the areas (4 to 8) point in one direction.

4. Marking device according to one of claims 1 to 3, characterized in that the regions (4, 6, 8) with high coercivity and the regions (5, 7) with low coercivity each have the same saturation magnetization and / or remanent magnetization.

5. Marking device according to claim 4, characterized in that the areas with low coercivity have a coercivity of at least 5 Oersted.

6. A method for reading out the marking device (1) according to one of claims 1 to 5, characterized in that areas (4 to 8) with different coercivity are acted upon by a first magnetic field (H ₂ ), which reverses magnetization of only a part of the areas (4 to 8), and that the resulting pattern of river changes is read out and used.

7. The method according to claim 6, characterized in that the reading of the flux changes takes place under the action of a second magnetic field (H ₂ ), which stabilizes the magnetization state of the magnetized areas (5, 7), but is so low that no magnetization of the magnetized not Areas (4, 6, 8) is effected.

8. The method according to claim 7, characterized in that the first and second magnetic fields (H ₂ ) are the same size and rectified.

9. The method according to any one of claims 6 to 8, characterized in that the areas (4 to 8) before and / or after reading with a third magnet _Field (H _ιr H ₃ ) are applied, which is so large and directed that all areas (4 to 8) are then magnetized in one direction, and that the magnetization of the areas (4 to 8) is then evaluated and with a reference is compared.

10. The method according to claim 9, characterized in that the third magnetic field (R _lf H ₃ ) is so large that a saturation magnetization of all areas (4 to 8) is effected.

11. The method according to any one of claims 6 to 10, characterized in that the areas (4 to 8) are subjected to a fourth magnetic field (H _x ) prior to remagnetization, which is so large that a saturation magnetization of all areas (4 to 8 ) is effected.

12. The method according to any one of claims 6 to 11, characterized in that the areas (4 to 8) are subjected to a fifth magnetic field after the magnetic reversal and the reading, which is so strong and so directed that all areas (4 to 8) are magnetized in one direction and that the magnetization of the regions (4 to 8) is then evaluated under a sixth magnetic field and compared with a reference which stabilizes the magnetization state caused by the fifth magnetic field.

13. The method according to claim 12, characterized in that the fifth and sixth magnetic fields are rectified and the same size.

14. The method according to any one of claims 6 to 13, characterized in that the first and / or second and the fifth and / or sixth magnetic field are the same size, but are directed in opposite directions.