TESTING THE COERCIVE FIELD STRENGTH OF MAGNETIC PIGMENTS

Description

[0001] The invention relates to the testing of the coercive field strength of magnetic pigments of flat, such as sheet-shaped, samples, in particular of security documents, such as identity cards, or of valuable documents, such as banknotes, checks, cards, tickets, coupons.

[0002] It is known from the prior art to equip security or valuable documents with security elements, such as security strips or security threads, which contain magnetic pigments. The magnetic pigments can be applied to the security element either continuously or only in certain areas, for example in the form of a coding. For the magnetic coding of a security element, for example, a specific sequence of magnetic and non-magnetic areas that is characteristic of the valuable document is used. It is also known to use different magnetic pigments for magnetic coding. For example, different coercive magnetic pigments are used, from which low-coercive and high-coercive magnetic areas are formed that are arranged on the security element. However, magnetic security elements are also known for which magnetic pigments, possibly in a mixture with other pigments, are printed onto the documents.

[0003] Furthermore, it is known to mechanically verify magnetic security elements. In this process, valuable documents containing a magnetic security element are magnetized by subjecting them to one magnetic field or to two consecutive magnetic fields with different directions. The resulting magnetization is checked by one or more magnetic detectors to verify the authenticity or type of valuable document.

[0004] When manufacturing valuable documents with magnetic security elements, it may be necessary to test the coercive field strength of the magnetic pigments applied to the valuable document. This is intended, among other things, to ensure that the respective magnetic security element has the coercive field strength specified for the respective magnetic pigment. Typically, complex coercimeters are used to test the coercive field strength, in which the magnetic field strength can be variably adjusted using an electromagnet. Alternatively, devices are used in which the range of values ​​for the coercive field strength to be tested is very limited. It is often also necessary to destroy the object to be tested in order to measure its coercive field strength.

[0005] Examples of conventional methods for testing the coercive field strength of magnetic pigments in flat samples are described, for example, in DE102009039588-A1 and DE102011120972-A1.

[0006] The invention is therefore based on the object of proposing a possibility by which the coercive field strength of magnetic pigments can be tested in a simple manner and over a wide range of values.

[0007] This object is achieved by the subject matter of the independent claims. Advantageous developments and refinements of the invention are specified in dependent claims.

[0008] The invention relates to a method and a device for testing the coercive field strength of magnetic pigments in flat, such as sheet-shaped, samples, in particular security documents. For simplicity, the term "sample" is often used below instead of "flat sample." To test the coercive field strength of magnetic pigments contained in a magnetic region of a flat sample, the following steps are performed: a) Providing a magnetizing device with at least one magnet, preferably at least one permanent magnet, which provides a static magnetic field for magnetizing the magnetic pigments, and providing a testing device connected to the measuring device, which is designed to determine a test result relating to the coercive field strength of the magnetic pigments, b) Magnetizing the flat sample by the static magnetic field of the magnet of the magnetizing device or by a static magnetic field of another magnetizing device such that the magnetic pigments of the flat sample are magnetized in a magnetization direction until their magnetization is saturated, c) If necessary, measuring the remanence of the magnetization of the magnetized magnetic pigments after their magnetization with a measuring device,wherein the magnetic pigments are located outside the static magnetic field of the at least one magnet during the remanence measurement, d) first partial counter-magnetization of the magnetic pigments by the static magnetic field of the magnet of the magnetizing device such that the magnetic pigments are partially counter-magnetized by the static magnetic field, wherein for the first partial counter-magnetization, the flat sample and the magnet are moved towards each other until the magnetic pigments are positioned at a first magnetization distance from the magnet in the static magnetic field, in which the static magnetic field has a first magnetization field strength, e) first measurement of a first magnetization value of the partially counter-magnetized magnetic pigments with a / the measuring device, wherein the magnetic pigments are located outside the static magnetic field of the magnetizing device during the first measurement,f) if necessary, repeating the magnetization according to step b) and then, if necessary, further partial counter-magnetization according to step d) and further measurement according to step e) to measure a further magnetization value, wherein during the further partial counter-magnetization in the respective step d), for the partial counter-magnetization of the sample by the static magnetic field, the flat sample and the magnet are moved towards each other relative to each other until the magnetic pigments are positioned at a further magnetization distance from the at least one magnet in the static magnetic field, in which the magnetic field strength is greater or smaller than the first magnetization field strength present at the first magnetization distance, and wherein the magnetic pigments are located outside the static magnetic field of the at least one magnet during the measurement of the respective further magnetization value,g) transmitting the first magnetization value measured during the first measurement and, if applicable, the further magnetization value(s) of the partially counter-magnetized magnetic pigments measured during the further measurement(s) according to step f) from the measuring device to the testing device connected to the measuring device, in which a magnetic field profile of the magnetizing device is stored, or which is connected to another device in which a magnetic field profile of the magnetizing device is stored, h) testing the first and, if applicable, the further magnetization value(s) of the partially counter-magnetized magnetic pigments by means of the testing device to determine the test result relating to the coercive field strength of the magnetic pigments,i) transmitting the test result concerning the coercive field strength from the test device to an output device connected to the test device and outputting the test result concerning the coercive field strength of the magnetic pigments by the output device.

[0009] The stored magnetic field profile indicates the magnetic field strength of the static magnetic field of the magnetizing device as a function of the magnetization distance of the magnetic pigments from the at least one magnet. The magnetic field profile can be stored as a continuous function or in the form of several discrete values. The testing device can use the magnetic field profile of the magnetizing device to determine the test result relating to the coercive field strength. Additionally or alternatively, the testing device can use the magnetic field profile of the magnetizing device to determine the first magnetization distance and / or, if applicable, the at least one further magnetization distance to be selected between the magnetic pigments and the magnet for the first and / or, if applicable, the subsequent partial countermagnetization.The respective first / further magnetization distance can then be transmitted to the output device connected to the testing device, which is configured to output the respective first / further magnetization distance to an operator.

[0010] After magnetization, the flat sample is removed from the static magnetic field of the magnetizing device. Immediately before the first and, if applicable, before the renewed partial counter-magnetization according to step d), the flat sample is not positioned in the static magnetic field of the magnetizing device. For the first partial counter-magnetization and, if applicable, the renewed partial counter-magnetization, the flat sample can be moved towards the magnet or the magnet can be moved towards the flat sample in order to position the magnetic pigments at the first magnetization distance or at the further magnetization distance from the magnet in the static magnetic field. For example, for the first partial counter-magnetization and, if applicable,the renewed partial counter-magnetization according to step d), the flat sample is placed on a magnetizing surface of the magnetizing device and moved along the magnetizing surface of the magnetizing device towards the magnet of the magnetizing device (in the direction of the magnetic field gradient) and then moved away from the magnet of the magnetizing device (opposite to the magnetic field gradient). If the sample is moved while the at least one magnet remains stationary, this has the advantage that the attachment of the magnet is space-saving and cost-effective. Alternatively, if the at least one magnet is designed to be movable (while the sample remains stationary for partial counter-magnetization or is moved completely through the magnetizing device), both very large and very small magnetization field strengths for the partial counter-magnetization can be achieved by adjusting the magnet position.In addition, the position of at least one magnet can be adjusted more finely and read more easily than the position of the sample or the magnetic pigments on the sample.

[0011] For the first partial counter-magnetization, and if necessary for a further partial counter-magnetization, the flat sample is placed in the static magnetic field in such a way that the static magnetic field is directed at least approximately opposite to the magnetization direction of the magnetic pigments of the flat sample. Since the magnetization direction is a property of the magnetic pigments, the orientation of the flat sample and the magnetization distance of the flat sample from the magnet are selected accordingly so that the static magnetic field is directed opposite to the magnetization direction of the magnetic pigments of the flat sample. The magnetization resulting after the partial counter-magnetization can be directed in or opposite to the magnetization direction. The amount of magnetization achieved after the partial counter-magnetization can, for example,0% or 10% (or other proportions from 0% to 100%) of the remanent magnetization achieved during magnetization. For example, if the magnetization is counter-magnetized with exactly the coercive field strength, the achieved magnetization is negligible (corresponding to 0% of the remanent magnetization).

[0012] The partial counter-magnetization from step d) and the measurement from step e) to measure the further magnetization value are in some cases repeated or re-performed at least once according to step f), so that at least one further magnetization value is obtained. In particular, the partial counter-magnetization from step d) and the measurement from step e) to measure the further magnetization value are repeated or re-performed at least twice according to step f), with the further magnetization distance being varied so that at least two further magnetization values ​​are obtained at at least two further magnetization distances. This renewed or repeated measurement makes it possible to test the coercive field strength of the magnetic pigments using multiple magnetization values, even with short magnetic ranges.

[0013] In some embodiments, the flat sample has at least one long magnetic region in which the magnetic pigments are present, which is at least 1 cm, preferably at least 2 cm, long at least along its direction of extension. The magnetic pigments are preferably distributed essentially homogeneously, at least in sections, over this long magnetic region. The direction of extension can be, for example, the longitudinal direction, but also any other direction of the magnetic region in which it has a great length. For the first and, if necessary, for the repeated partial counter-magnetization, the flat sample is preferably positioned on the magnetizing device such that the direction of extension of the long magnetic region is parallel, antiparallel, or obliquely directed to the magnetic field gradient of the static magnetic field, i.e. along the distance coordinate of the stored magnetic field profile, but not perpendicular to the magnetic field gradient of the static magnetic field.As a result of the orientation of the long magnetic area parallel, antiparallel or oblique to the magnetic field gradient, the magnetic pigments located in different sections of the long magnetic area are counter-magnetized to different degrees (the sections closer to the magnet during counter-magnetization are more strongly magnetized than the sections further away).

[0014] In these embodiments, the measuring device is preferably configured to measure the magnetization as a function of the extension direction of the magnetic pigments on the sample. For example, the measuring device is configured to generate both a first magnetization value M(x0) (in a first section of the long magnetic region located at the first magnetization distance x0) during the first measurement (after the first partial counter-magnetization) and—without further partial counter-magnetization—one or more further magnetization values ​​M(x1), M(x2),..., which are measured in other sections of the long magnetic region. During the first partial counter-magnetization, the other sections were positioned at further magnetization distances x1, x2,... from the at least one magnet in the static magnetic field, in which the magnetic field strength of the static magnetic field is greater or smaller than at the first magnetization distance x0.Since a further partial counter-magnetization and a new measurement of the sample are then not necessary, a particularly fast test of the coercive field strength is possible.

[0015] In these embodiments, the testing device is preferably configured to determine a magnetization profile M(x) as a function of the magnetization distance x based on at least two further magnetization values ​​M(x1), M(x2),... of the magnetic pigments measured for different further magnetization distances x1, x2,... and / or based on the first magnetization value M(x0) measured for the first magnetization distance x0 and at least one further magnetization value M(x1) measured for a further magnetization distance x1, and to analyze the magnetization profile M(x) in order to determine a target magnetization distance xm at which the coercive field strength of the magnetic pigments was reached during the first partial counter-magnetization. When analyzing the magnetization profile M(x), the target magnetization distance xm is, for example,the magnetization distance is selected at which the magnetization M(x) as a function of the magnetization distance x or its first derivative M'(x)=dM(x) / dx as a function of the magnetization distance x has a zero crossing (M(xm)=0) or reaches a minimum or at which a standard deviation SM(x) of the magnetization M(x) has a minimum modulation (standard deviation of the magnetization measured at different y-positions but at the same x-position), e.g. in the case of magnetic serial numbers.

[0016] From the target magnetization distance xm, the testing device can determine the coercive field strength Km of the magnetic pigments based on the magnetic field profile K(x), e.g., by inserting the target magnetization distance xm into the function K(x). The coercive field strength Km of the magnetic pigments is then transmitted from the testing device to the output device, which is configured to output the coercive field strength Km of the magnetic pigments to an operator. Determining and outputting the coercive field strength (as opposed to simply confirming or denying a given coercive field strength) enables the operator to perform a more precise analysis of the sample, e.g., for classification, quantitative quality control, or defect analysis.

[0017] The invention also relates to a device for testing coercive field strength, comprising the aforementioned measuring device and the aforementioned testing device, i.e., without the aforementioned magnetizing device, which is provided separately. The measuring device and testing device can be separate devices or housed together in one device, e.g., in the same housing. The device can also comprise an input device connected to the testing device and / or an output device connected to the testing device.

[0018] The measuring device is designed to carry out the first and, if applicable, the respective further measurement in such a way that the magnetic pigments are not located in a magnetic field suitable for magnetizing the magnetic pigments during the first measurement and, if applicable, during the respective further measurement, in particular outside the static magnetic field of the magnetizing device, i.e. so far away from the latter that the magnetic field strength of the magnetizing device at the location of the measurement is negligibly small. Preferably, the measuring device has a holder for holding the flat sample, which is positioned in such a way that the flat sample is not located in a magnetic field suitable for magnetizing the magnetic pigments during the first and, if applicable, the at least one further measurement, in particular outside the static magnetic field of the magnetizing device. During the first measurement and, if applicable,During the further measurement(s), the magnetic pigments are preferably not in a magnetic field suitable for their magnetization, ie at most in a very weak magnetic field (e.g. the earth's magnetic field), which can change the magnetization of the magnetic pigments by less than 1%.

[0019] The measuring device is designed to carry out a first measurement of a first magnetization value of the magnetic pigments that are partially counter-magnetized by the first magnetization field strength after the first partial counter-magnetization, and optionally at least one further measurement to measure at least one further magnetization value of the magnetic pigments that are partially counter-magnetized during a possibly repeated partial counter-magnetization, if these are partially counter-magnetized with a further magnetization field strength opposite to the magnetization direction, which is greater or smaller than the first magnetization field strength with which the magnetic pigments were counter-magnetized at the first magnetization distance. The measuring device is designed to compare the at least one first orfurther magnetization value of the partially counter-magnetized magnetic pigments to be transmitted to the testing facility.

[0020] If necessary, the operator can also specify one or more regions of interest (ROIs) in which the magnetic pigments to be tested are located on the respective flat sample. The measuring device can then limit itself to measuring the magnetization in this ROI. The testing device can be configured to use the information about the ROI on the sample to select the magnetization values ​​measured by the measuring device, which are used to determine the test result concerning the coercive field strength of the magnetic pigments. The testing device selects, for example, one or more specific magnetization values ​​from the ROI or averages the magnetization values ​​across the ROI.

[0021] The testing device is configured to test the first and, if applicable, the further magnetization value(s) of the partially counter-magnetized magnetic pigments to determine a test result relating to the coercive field strength of the magnetic pigments, and to transmit the test result relating to the coercive field strength of the magnetic pigments to the output device connected to the testing device. The testing device is programmed, for example, with appropriate software with the aid of which it can determine the test result relating to the coercive field strength of the magnetic pigments. A magnetic field profile K(x) of the magnetizing device is preferably stored in the testing device. Alternatively, the testing device can also be connected to another device in which a magnetic field profile K(x) of the magnetizing device is stored.In particular, the testing device has a memory area in which a magnetic field profile K(x) of the magnetizing device is stored as a function of the distance from the magnet of the magnetizing device (as a function of the magnetization distance x of the magnetic pigments). The magnetic field profile K(x) can be determined empirically prior to the test using an appropriate measuring device, calculated by mathematical simulation, or empirically determined using magnetic objects with a known coercive field strength.

[0022] If necessary, a correction of the magnetic field profile K(x) obtained in this way can be carried out based on a calibration measurement of a corresponding calibration medium, which - analogous to the flat sample - is first magnetized, then counter-magnetized using the magnetizing device, and then measured using the measuring device. The calibration medium is, for example, flat and has one long (at least 1 cm long, preferably at least 2 cm long) or preferably several long magnetic regions (at least 1 cm long, preferably at least 2 cm long), each of which has magnetic pigments of a specific coercive field strength throughout and is spatially separated from one another on the calibration medium, wherein the coercive field strength of the various long magnetic regions is selected to be different.During partial counter-magnetization, the calibration medium is positioned on the magnetizing device such that the long magnetic regions extend parallel, anti-parallel, or obliquely to the magnetic field gradient of the static magnetic field. This design of the calibration medium enables calibration of the magnetic field profile K(x) based on a single measurement, analogous to the measurement of a sample with a long magnetic region. The calibration medium can also be used for a comparison measurement in which the calibration medium and the flat sample (containing magnetic pigments of an unknown coercive field strength) are attached to one another, counter-magnetized in one step using the magnetizing device, and measured in one step using the measuring device, whereby both a magnetization profile of the flat sample M(x) and a magnetization profile of the calibration medium are measured.The coercive field strength of the flat sample can then be checked by comparing the measured magnetization curves.

[0023] The testing facility is particularly designed to to use the magnetic field profile K(x) of the magnetizing device to determine the test result relating to the coercive field strength of the magnetic pigments, and / or to use the magnetic field profile K(x) of the magnetizing device to determine a magnetization distance to be selected between the magnetic pigments and the magnet for the first and / or, if applicable, the renewed partial counter-magnetization and to transmit this first / further magnetization distance to the output device.

[0024] The testing device can be configured to receive, from an input device connected to the testing device or via an interface connected to the testing device, an operator input concerning a target coercive field strength to be verified with the testing device and / or an indication of a target coercivity range including the target coercive field strength (e.g., a tolerance around the target coercive field strength). Based on the operator input, the testing device can then determine, based on the magnetic field profile K(x) of the magnetizing device, the first magnetization distance to be selected between the magnetic pigments and the magnet for the first partial countermagnetization.The testing device can then transmit the first magnetization distance to the output device connected to the testing device, which is configured to output the respective first magnetization distance to an operator of the magnetizing device, e.g., by visually displaying it to the operator or outputting it acoustically. This embodiment allows for a particularly simple testing of a predetermined target coercive field strength, for example, for the quality control of security documents or for their authenticity testing.

[0025] In some embodiments, the test result determined during testing, which relates to the coercive field strength of the magnetic pigments, comprises a confirmation (or a negation) of whether the magnetic pigments have a predetermined target coercive field strength or whether their coercive field strength lies in the target coercivity range including the target coercive field strength.

[0026] In some embodiments, the testing device is configured to check, when testing the first magnetization value of the partially counter-magnetized magnetic pigments, whether the first magnetization value corresponds to a magnetization of zero or lies within a magnetization acceptance range surrounding a magnetization of zero. According to the hysteresis curve of the magnetic pigments, the acceptance range corresponds to the target coercivity range (including the target coercivity). If yes, the testing device transmits to the output device the confirmation that the magnetic pigments have the specified target coercivity or that the coercivity of the magnetic pigments lies within the specified target coercivity range. If no, a corresponding negative response is transmitted.If necessary, the output device will prompt the operator to repeat partial countermagnetization and measure again to determine at least one additional magnetization value. If the test device automatically selects the additional magnetization distance, this will also be displayed for the operator. Alternatively, the operator can select an additional magnetization distance of their own choosing and enter it on an input device or via an interface.

[0027] In some embodiments, the testing device is configured to receive an operator specification from an input device or interface relating to a coercivity range to be examined with the testing device, and to determine, on the basis of the operator specification and using the magnetic field profile K(x) of the magnetizing device, the first and at least one (preferably several) further magnetization distances to be selected between the magnetic pigments and the magnet for the renewed partial counter-magnetization. The testing device transmits the respective first or further magnetization distance to the output device connected to the testing device, which is configured to output the respective first or further magnetization distance for an operator of the magnetizing device. The operator specification relating to a coercivity range to be examined with the testing device contains, for example,the coercivity range itself and, if necessary, an additional step size for the coercivity field strength or a number of test steps within the coercivity range. The testing device is particularly designed to select one or more coercivity field strengths that lie within the coercivity range specified by the operator and to insert these into the magnetic field curve K(x) in order to determine the further magnetization distances x1, x2. The upper and lower limits of the coercivity range and, if necessary, coercivity field strengths lying in between are selected. The testing device can select these equidistantly or automatically according to the specified number or step size for the coercivity field strength. This procedure enables accelerated measurement if the coercivity field strength of the sample is approximately known.

[0028] In some embodiments, the test result determined during testing, which relates to the coercive field strength of the magnetic pigments, includes a value for the coercive field strength of the magnetic pigments (and possibly also an accuracy specification therefor).

[0029] The testing device can be configured to approximately determine or estimate the actual coercive field strength of the magnetic pigments on the basis of the first magnetization value and optionally at least one of the further magnetization values ​​using a look-up table which specifies discrete values ​​for the magnetic field profile K(x) as a function of the magnetization distance x, e.g. by determining the smallest measured magnetization value and looking up the associated coercive field strength or an associated coercivity range in the look-up table.

[0030] Alternatively or additionally, the testing device can be configured to determine a target magnetization distance xm, at which the magnetization, as a function of the magnetization distance, crosses zero or at least reaches a minimum (and is thereby vanishingly small), based on at least two of the further magnetization values ​​or on the first magnetization value and at least one of the further magnetization values. From the target magnetization distance xm, the testing device can determine the coercive field strength of the magnetic pigments based on the magnetic field profile K(x), e.g. by inserting the target magnetization distance xm into the function K(x). The testing device then transmits the coercive field strength of the magnetic pigments to the output device connected to the testing device, which is configured to output the coercive field strength of the magnetic pigments to an operator, e.g. a numerical value of the coercive field strength, if necessary.with an accuracy specification.

[0031] To determine the target magnetization distance at which the magnetization crosses zero as a function of the magnetization distance, the testing device can be configured to determine a magnetization curve M(x) as a function of the magnetization distance based on the further magnetization value(s) and, if applicable, the first magnetization value, and to automatically analyze the magnetization curve. It can transmit the magnetization curve M(x) to the output device, which is configured to output the magnetization curve M(x) to the operator for further analysis, e.g., by displaying it.

[0032] For example, the testing device can be configured to determine the target magnetization distance at which the magnetization M(x) has a zero crossing (M(xm)=0) as a function of the magnetization distance x, by fitting, extrapolating, or interpolating the first magnetization value and at least one of the further magnetization values, or by fitting, extrapolating, or interpolating at least two of the further magnetization values. Two or more magnetization values ​​are used for the fitting, extrapolation, or interpolation.

[0033] In some embodiments, the testing device is configured to automatically determine a further magnetization distance on the basis of the first magnetization value (measured in step e)) transmitted by the measuring device, wherein the further magnetization distance closer to the magnet of the magnetizing device than the first magnetization distance is selected (higher magnetic field strength) if the first magnetization value suggests that the magnetization of the magnetic pigments resulting after their partial counter-magnetization still points in the magnetization direction (despite the counter-magnetization), and further away from the magnet of the magnetizing device than the first magnetization distance is selected (lower magnetic field strength) if the magnetization of the magnetic pigments resulting after their partial counter-magnetization points opposite to the magnetization direction.Since in this case the magnetic field strength used for the renewed partial counter-magnetization is lower than that used for the first partial counter-magnetization, the magnetization must be repeated before the renewed partial counter-magnetization, during which the magnetic pigments of the flat sample are magnetized in the magnetization direction until their magnetization is saturated.

[0034] The test device then transmits the additional magnetization distance to the output device, which is configured to prompt the operator to repeat partial countermagnetization and re-measure the magnetic pigments for the additional magnetization distance, so that the operator can determine a further magnetization value using the measuring device. Based on the first magnetization value and the additional magnetization value, additional magnetization distances can be automatically determined and output if necessary, so that the operator can determine further magnetization values ​​of the magnetic pigments by repeating partial countermagnetization and measuring again.

[0035] The invention also relates to an arrangement for magnetizing the respective flat sample and for testing the coercive field strength of the magnetic pigments of the respective flat sample using the aforementioned magnetizing device and the aforementioned apparatus, which comprises the aforementioned measuring device and the aforementioned testing device. The magnetizing device and the measuring device are separated from one another, so that the magnetic pigments are located outside the static magnetic field of the magnetizing device during the first measurement and, if applicable, during the respective subsequent measurement. This has the advantage that the magnetic field strength used for partial counter-magnetization can be flexibly changed without influencing the measurement of the measuring device.

[0036] The magnetizing device has, for example, a magnetizing surface for receiving the flat sample and at least one magnet that provides a static magnetic field configured to partially counter-magnetize the magnetic pigments of the flat sample. The magnetizing device is configured, for example, so that the flat sample (placed on the magnetizing surface) and the at least one magnet can be moved toward each other for a first partial counter-magnetization of the magnetic pigments until the magnetic pigments are positioned at a first magnetization distance from the at least one magnet, at which the static magnetic field has a first magnetization field strength.For the partial re-magnetization of the magnetic pigments, the flat sample and the at least one magnet can be moved relative to each other until the magnetic pigments are positioned at a further magnetization distance from the at least one magnet, at which the magnetic field strength of the static magnetic field is greater or smaller than the first magnetization field strength (prevailing at the first magnetization distance). The magnetizing device according to the invention enables well-defined magnetization of the magnetic pigments at very different magnetic field strengths. With the achievable magnetic field strengths, both low-coercivity magnetic pigments with a coercivity of a few oersteds and high-coercivity magnetic pigments with a coercivity of up to 3500 oersteds (of course also magnetic pigments with coercivity in between) can be counter-magnetized.In addition, the magnetic field strength used for partial counter-magnetization can be adjusted very easily with the magnetizing device according to the invention by appropriate positioning of the magnetic pigments or the magnet.

[0037] The magnetizing surface of the magnetizing device is preferably large enough that the flat sample can be placed on the magnetizing surface and moved along the magnetizing surface towards the magnet of the magnetizing device. The magnetizing surface is preferably wider and - viewed along the direction of movement of the sample - longer than the sample. The at least one magnet of the magnetizing device is arranged, for example, such that a gap is formed between the magnetizing surface and the at least one magnet, into which gap the flat sample can be inserted for magnetizing its magnetic pigments, wherein the gap perpendicular to the magnetizing surface is larger than the thickness of the flat sample. In this way, the widest possible range of magnetic field strengths can be used to magnetize the sample.The sample can be passed completely through the gap for magnetization and into the gap for partial counter-magnetization.

[0038] In a first embodiment of the magnetizing device, the sample is guided into the gap for partial counter-magnetization until the magnetic pigments have reached the desired magnetization distance from the magnet. In a second embodiment of the magnetizing device, the sample is guided into the gap for partial counter-magnetization until the magnetic pigments are located in the gap (centrally below the magnet or slightly offset to the side of the magnet) and then the distance of the magnet from the magnetizing surface is reduced until the desired magnetization distance between the magnet and the magnetic pigments of the sample is reached. In the first embodiment of the magnetizing device, the test device orThe magnetic field profile of the magnetizing device stored in the other device indicates the magnetic field strength present on the magnetizing surface as a function of the position (in the predetermined direction of movement of the sample) along the magnetizing surface, parallel or antiparallel to the magnetic field gradient of the static magnetic field. In this first embodiment, the static magnetic field of the magnetizing device is unchangeable (with respect to the magnetizing device) or remains unchanged during the magnetization and testing of the magnetic pigments. In the second embodiment of the magnetizing device, the magnetic field profile of the magnetizing device stored in the testing device or in the other device indicates the magnetic field strength present on the magnetizing surface as a function of the (variable) position of the at least one magnet perpendicular to the magnetizing surface and, if applicable,additionally as a function of the position of the sample along the magnetizing surface, parallel or antiparallel to the magnetic field gradient.

[0039] The magnetizing surface of the magnetizing device is designed to hold the sample during the first and, if applicable, during the respective subsequent partial counter-magnetization of its magnetic pigments (and, if applicable, also during the magnetization). The magnetizing surface is configured so that the flat sample held by the magnetizing surface is guided in a predetermined direction of movement along the magnetizing surface for the partial counter-magnetization (with the sample touching the magnetizing surface during its movement). By being guided along the magnetizing surface, the flat sample can be moved toward the magnet (and, if applicable, into the gap formed between the magnetizing surface and the at least one magnet).The magnetizing surface has an input side, which - viewed along the predetermined direction of movement of the sample - is arranged in front of the at least one magnet, and an output side, which - viewed along the predetermined direction of movement of the sample - is arranged after the at least one magnet. Preferably, the magnetizing surface extends, at least on its input side - viewed along the predetermined direction of movement - from its edge to the at least one magnet at least over the length of the flat sample, e.g., at least over 10 cm. This allows the flat sample to be conveniently positioned during partial counter-magnetization, and a high level of positioning accuracy is achieved. Preferably, the magnetizing surface of the magnetizing device is delimited on one or both sides by a guide that extends along the predetermined direction of movement (and is designed, e.g., as a step).This makes it possible to avoid twisting of the sample and thus increase the positioning accuracy of the sample during partial counter-magnetization.

[0040] To provide the static magnetic field, the magnetizing device has at least one magnet. The at least one magnet extends - parallel to the magnetizing surface and viewed in the direction perpendicular to the predetermined direction of movement of the sample - at least across the width of the flat sample so that the sample can be magnetized uniformly and continuously perpendicular to its direction of movement. On the input side of the magnetizing device (i.e., along the predetermined direction of movement on this side of the at least one magnet), the static magnetic field is directed in the opposite direction than on the output side of the magnetizing device (i.e., along the predetermined direction of movement beyond the at least one magnet).The magnetizing device has either a single (correspondingly long) magnet or several (preferably identical) magnets arranged in a row perpendicular to the direction of movement of the sample, which are also installed in the same direction. The at least one magnet is preferably arranged such that either its magnetic north pole or its magnetic south pole points towards the magnetizing surface at the end, and the respective other magnetic pole faces away from the magnetizing surface. In a row of magnets, either all magnetic north poles or all magnetic south poles point towards the magnetizing surface at the end. This end-to-end arrangement of the magnetic poles has the advantage that the magnetic field provided by the at least one magnet for magnetizing the sample on the magnetizing surface has a large magnetic field component that is directed parallel or antiparallel to the predetermined direction of movement of the sample.On the output side of the magnetizing device, the magnetic field component directed parallel or antiparallel to the predetermined direction of movement of the sample is directed in the opposite direction to that on the input side (parallel on the input side and antiparallel on the output side, or antiparallel on the input side and parallel on the output side). Compared to this magnetic field component, the magnetic field component of the static magnetic field perpendicular to the predetermined direction of movement of the sample is negligibly small. On the magnetizing surface of the magnetizing device, the magnetic field component of the static magnetic field directed perpendicular to the magnetization direction is preferably less than 10% of the magnetic field component of the static magnetic field directed parallel or antiparallel to the magnetization direction.Such an orientation of the magnetic field enables partial countermagnetization with a low-intensity magnetic field. Furthermore, the measurement and evaluation of the magnetization values ​​is simplified, since it is sufficient to consider only the magnetization component in one spatial direction, namely the magnetization direction.

[0041] The magnetizing device preferably has a scale that is readable by an operator, from which the operator can read a measure of the magnetization distance between the magnetic pigments and the magnet of the magnetizing device. The distance of the sample's front or rear edge from the magnet can be read from the scale, from which - taking into account the distance of the magnetic pigments from the front or rear edge of the flat sample - the magnetization distance of the magnetic pigments from the magnet can be automatically calculated. The readable scale can extend along the predetermined direction of movement, e.g., be applied to a lateral guide of the magnetizing device. This can be useful in both the first and the second embodiment of the magnetizing device. If a mechanical stop is provided, the distance of the mechanical stop from the magnet can then also be read from the scale.

[0042] In the second embodiment of the magnetizing device, the magnetizing device preferably has an adjustment device with which the operator can adjust the distance of the at least one magnet from the magnetizing surface in order to change the distance between the magnetic pigments and the magnet of the magnetizing device when the magnetic pigments are positioned between the magnet and the magnetizing surface (in the gap). This adjustment device can also have a scale that can be read by the operator, from which the operator can read a measure of the magnetization distance between the magnetic pigments and the magnet of the magnetizing device.

[0043] The magnetizing device can also include a mechanical stop that can be moved along the magnetizing device along the predetermined direction of movement of the flat sample. The stop is placed flush with the lateral guide, for example, and the flat sample is moved to the front edge of the mechanical stop until the front edge of the flat sample touches the stop. This allows for better definition of the position and orientation of the flat sample.

[0044] The invention is explained below by way of example with reference to the following figures. Fig. 1 an example of an arrangement for magnetizing and testing the coercive field strength of flat samples, Fig. 2 an example of a measuring device for measuring the magnetization of the flat samples, Fig. 3 an example of a magnetizing device for magnetizing the flat samples ( Fig. 3a), an example of the magnets of the magnetizing device,( Fig. 3b ), a flat sample positioned on a magnetizing device ( Fig. 3c ) and a flat sample at different distances from the magnet of the magnetizing device ( Fig. 3d ), Fig. 4 a hysteresis curve of magnetic pigments with a coercive field strength K0' ( Fig. 4a ), a magnetic field profile K(x) of the magnetizing device ( Fig. 4b ), the measured magnetization M(x) as a function of the magnetization distance x ( Fig. 4c ), Fig. 5a a magnetizing device with a movable mechanical stop and a readable scale, Fig. 5b,c a magnetizing device with a vertically adjustable magnet, Fig. 6 a flat sample positioned on a magnetizing device, the magnetic region of which extends parallel to the magnetic field gradient ( Fig. 6a ), or extends obliquely to the magnetic field gradient ( Fig. 6d), the magnetization curve M(x) of the magnetic area Fig. 6a as a function of the magnetization distance x ( Fig. 6b ) and its first derivative ( Fig. 6c ) and the first derivative of the magnetization curve M'(x) of the magnetic area from Fig. 6d as a function of the magnetization distance x ( Fig. 6e ), Fig. 7 a flat sample positioned on a magnetizing device, the magnetic serial number of which is oriented antiparallel to the magnetic field gradient ( Fig. 7a ) and the determination of the target magnetization distance xm using the standard deviation ( Fig. 7b, c ).

[0045] Based on Figure 1The test of the coercive field strength of magnetic pigments of a flat sample 1 is explained as an example. The magnetic pigments are present in a magnetic region of the sample 1, which in this example is formed by a magnetic security thread 2. The magnetic pigments can be applied continuously along the security thread or only locally, e.g. as part of a magnetic coding consisting of high-coercive and / or low-coercive magnetic regions h, l, cf. Fig. 2 The magnetic area of ​​the magnetic pigments can also be formed by another security element, such as a magenta imprint. In this example, the flat sample is designed as a security document.

[0046] For magnetization, the magnetic pigments are first magnetized using a magnetizing device that provides a static magnetic field. Fig. 1shown magnetizing device 7 may be used or another magnetizing device 7', which provides a magnetic field with a greater magnetic field strength. For magnetizing the sample, for example, another magnetizing device 7' (with a greater magnetic field strength) is used if the magnetic field of the magnetizing device 7 exceeds the coercive field strength of the sample, but is not sufficient to saturate its magnetization. For magnetizing, the sample 1 is pushed by an operator 30 along the arrow direction completely through the magnetizing device 7 (or 7'), which is even more precisely with respect to Fig. 3aDuring magnetization, the sample 1 is magnetized in a magnetization direction (here directed along the arrow) until its magnetization is saturated. The sample is then removed from the static magnetic field of the magnetizing device. Preferably, the magnet of the magnetizing device has a magnetic field strength that exceeds the (expected) coercive field strength of the sample by a factor of 2, particularly preferably by a factor of 5. For example, the magnet of the magnetizing device has a magnetic field strength of at least 0.75 T, preferably of at least 1 T.

[0047] To obtain a reference value for subsequent magnetization measurements, the magnetization achieved by magnetization can be measured (remanence measurement). However, the magnetization values ​​described below can also be evaluated without such a reference value. The respective measurement of the respective magnetization value, which is performed after the respective partial counter-magnetization of sample 1, is performed using a measuring device 4. The optional remanence measurement can also be performed using measuring device 4.

[0048] To measure the magnetization of the sample 1, for example, a measuring device 4 is used which is contained in a device 10 and is accessible from the outside to the operator 30 of the device 10 through a hinged window 5. In this example, the measuring device 4 has a drum 23 onto which the operator places the magnetized sample 1, cf. Fig. 2The sample is sucked onto the drum for attachment. A magnetic detector 20 is mounted on a scanning device (not shown) which can be transported along the y-direction at a short distance from the drum 23. The drum 23 can be rotated about an axis A which runs parallel to the y-direction. By rotating the drum 23, the sample 1 can be repeatedly transported past the magnetic detector 20 along the circumference of the drum 3. With each drum rotation, the magnetization of those magnetic regions h, l of the security thread 2 can be detected which, depending on the y-position of the magnetic detector 20, are currently located in the detection range of the magnetic detector 20. By slowly moving the magnetic detector 20 along the y-direction and simultaneously rotating the drum 23 quickly, the magnetization of different sections or magnetic regions h, l of the security thread can be detected one after the other.The magnetization is measured without the influence of a magnetic field.

[0049] The device 10 and the magnetizing device 7 are arranged within reach of the operator 30, who feeds the sample 1, if necessary alternately, to the magnetizing device 7 and the measuring device 4 of the device 10. The device 10 has a testing device 3 connected to the measuring device 4, which is set up to evaluate the magnetization values ​​measured by the measuring device 4 and in which a magnetic field profile K(x) of the magnetizing device 7 is stored, which is used to test the coercive field strength of the magnetic pigments. The device 10 also has an output device, e.g. a display device, and an input device for the operator 30. In the device 10, both are present together as an input and output device 6, e.g. in the form of a touchscreen. Furthermore, another device 8, e.g. a computer, can be connected to the device 10, in which the magnetic field profile K(x) of the magnetizing device 7 can be stored and which, if necessary,used to evaluate the measurement results. The measuring device 4 and the testing device 3 do not need to be housed in a common device 10, but can also be independent. Magnetizing device

[0050] In Fig. 3a, a magnetizing device 7 is shown by way of example, which provides a magnetizing surface 77 for receiving the sample 1, which is designed to receive the sample during the magnetization of its magnetic pigments. For the purpose of magnetizing the sample 1, the operator 30 places the sample 1 on the input side (right) onto the magnetizing surface 77 and guides it along the magnetizing surface (if necessary into the gap 76) in a predetermined direction of movement of the sample (here the -x direction). The sample slides as it is guided along the magnetizing surface 77. The magnetizing surface 77 is delimited on both sides by guides 73, 74, which are designed as steps and extend along the predetermined direction of movement -x. The magnetizing device 7 has at least one magnet 71, the magnetic north pole (alternatively south pole) of which points towards the magnetizing surface 77 at the end.Only a single, wide magnet 71 or several, aligned and similar magnets 71 arranged in a row perpendicular to the direction of movement -x of the sample can be used, the magnetic north poles (alternatively south poles) of which point towards the magnetizing surface 77. The at least one magnet 71 extends - parallel to the magnetizing surface 77 and viewed in the direction perpendicular to the direction of movement -x of the sample - across the entire width of the sample, thereby achieving a homogeneous magnetization of the sample 1 across its entire width.

[0051] Opposite the magnet 71, at least one further magnet 72 can be arranged, which is oriented mirror-inverted to the magnet 71, so that its magnetic north pole (alternatively the south pole) also points towards the magnetizing surface 77. Analogous to the magnet 71, several magnets 72 with the same direction can also be used. The magnetic field B provided by the magnets 71, 72 for magnetizing the sample on the magnetizing surface 77 therefore has a magnetic field component that is parallel or antiparallel to the direction of movement of the sample. The magnetizing surface 77 has (right) an input side, which - viewed along the predetermined direction of movement (-x) of the sample - is arranged in front of the at least one magnet, and (left) an output side, which - viewed along the predetermined direction of movement of the sample - is arranged after the at least one magnet. On the (in Fig. 3aOn the input side of the magnetizing device 7 (located on the right), this magnetic field component points in the positive x-direction. Fig. 3a On the output side of the magnetizing device 7 (located on the left), this magnetic field component points in the negative x-direction, i.e. it is directed in the opposite direction to that on the input side of the magnetizing device 7, cf. Fig. 3b .

[0052] Instead of the opposing magnets 71, 72, the magnetizing device can also be equipped with one or more magnets on one side only (either magnet(s) 71 above or magnet(s) 72 below the magnetizing surface 77). The magnetic field B thus generated on the magnetizing surface 77 is then not exactly parallel or antiparallel to the x-direction, but also has a component in the z-direction. However, the evaluation of the magnetization values ​​can be limited to the x-direction if the test device 3 is only sensitive to magnetization in the x-direction.

[0053] The at least one magnet 71 is located in a crossbar 75, which is arranged at a small (z-)distance above the magnetizing surface 77. The distance between the crossbar 75 and the magnetizing surface is at least the thickness of the sample 1. The at least one magnet 72 is arranged below the magnetizing surface 77, cf. Fig. 3aBetween the magnetizing surface 77 and the crossbar 75, in which the at least one magnet 71 is located, a gap 76 is formed, into which the flat sample 1 can be inserted for the magnetization of its magnetic pigments. For magnetization, the sample 1 can be completely (in Fig. 3a from right to left) through the gap 76. Since the magnetic field B on the output side of the magnetizing device points in the negative x-direction, the magnetic pigments are magnetized in the negative x-direction until saturation. For partial counter-magnetization, sample 1 is moved, starting from the input side (right), in the direction of the crossbar 75 (in the -x-direction) until the magnetic pigments are at the desired magnetization distance x0 from the magnets 71, 72, cf. Fig. 3c. When the movement of sample 1 is stopped, the magnetic pigments to be subjected to partial counter-magnetization are located to the right of the magnets 71, 72 and thus in the section of the magnetic field B in which the magnetic field direction is directed in the positive x-direction, cf. Fig. 3b, 3c Depending on the position of the magnetic pigments on sample 1 and the selected magnetization distance x0, it may be necessary for the sample (its front edge) to be partially guided into the gap 76. The magnetic field strength of the magnetic field B decreases - starting from the position x=0, where the magnets 71, 72 are located - to the right, according to the Fig. 3csketched lines of constant magnetic field L (in the xy plane). If the magnetic pigments are present in a long magnetic region on sample 1, the magnetization distance x0 is considered to be the magnetization distance of a representative part of the magnetic region, e.g., the center of the respective magnetic region or the point of the magnetic region closest to the magnet.

[0054] In Fig. 4b The magnetic field profile K(x) of the magnetizing device 7 is sketched as an example, ie the profile of the x-component of the magnetic field strength of the magnetic field B as a function of the magnetization distance x, cf. Fig. 3cAt point x=0, i.e., directly beneath magnet 71, the x-component of magnetic field B is negligible, but even at small magnetization distances x (at the edge of magnet 71), the magnetic field strength increases sharply and then decreases monotonically with increasing magnetization distance x. For partial countermagnetization, the magnetic pigments are brought into a magnetization distance that lies in the monotonically decreasing branch of the magnetic field curve K(x), at most up to the point at which the maximum of the magnetic field curve K(x) is reached. Partial counter-magnetization

[0055] After magnetization (and if necessary after the remanence measurement), the first partial counter-magnetization of the magnetic pigments is carried out, in which the magnetic pigments of the sample are partially counter-magnetized by the static magnetic field of the magnets 71, 72. For the first partial counter-magnetization, the sample is placed on the magnetizing surface 77 of the magnetizing device 7 and the magnetic pigments are introduced into the static magnetic field B in such a position that the static magnetic field B is directed in the positive x-direction, i.e. opposite to the magnetization direction of the sample (negative x-direction), i.e. at a magnetization distance on the positive x-axis. The sample and the magnet are moved towards each other relative to each other until the magnetic pigments are positioned at a first magnetization distance from the magnet in the static magnetic field.For positioning, the sample 1 can be moved towards the magnet 71 (in the embodiment to . Fig. 3d and 5a ). In addition, if necessary, the magnet 71 can be moved towards the sample 1 (in the embodiment to Fig. 5b,5c ). After this partial counter-magnetization, the sample is moved in the opposite direction, ie in the positive x-direction, away from the magnet 71, 72 and removed from the static magnetic field B.

[0056] The resulting magnetization of the magnetic pigments after partial countermagnetization can be negligible or directed in or opposite to the magnetization direction, depending on whether the coercive field strength KO of the magnetic pigments is present at the magnetization distance x0 to which the sample is brought for partial countermagnetization, or whether the coercive field strength of the magnetic pigments is exceeded or undershot at the magnetization distance. If the coercive field strength is exactly reached at the selected magnetization distance x0, the magnetic pigments are countermagnetized during partial countermagnetization so that their resulting magnetization is negligible or, ideally, zero.If the selected magnetization distance is x>x0, a magnetic field strength K <K0 erreicht, die geringer ist als die Koerzitivfeldstärke K0, so dass die Magnetpigmente beim teilweisen Gegenmagnetisieren weniger als zur Hälfte gegenmagnetisiert werden und die resultierende Magnetisierung der Magnetpigmente weiterhin in die Aufmagnetisierungsrichtung (negative x-Richtung) weist. Falls der gewählte Magnetisierungsabstand bei x<x0 liegt, wird beim teilweisen Gegenmagnetisieren eine Magnetfeldstärke K> K0 is reached, which is greater than the coercive field strength K0, so that the magnetic pigments are more than half counter-magnetized during partial counter-magnetization and the resulting magnetization of the magnetic pigments points in the opposite direction to the magnetization direction, i.e. in the positive x-direction.

[0057] After the first partial counter-magnetization of sample 1, a first magnetization value is measured by the measuring device 4, which is characteristic of the partial counter-magnetization of the magnetic pigments achieved at the selected magnetization distance. During the measurement of the first magnetization value, the magnetic pigments are located outside the static magnetic field of the magnetizing device (i.e., at such a large distance from the magnetizing device that its static magnetic field causes no or negligible magnetization). Fig. 4a an example of the measured first magnetization value M(x0') is shown, which was achieved by the first partial counter-magnetization by means of the magnetizing device 7 at a magnetization distance x0'. Optional re-partial counter-magnetization and measurement

[0058] The partial counter-magnetization described above and the subsequent measurement of a magnetization value can be repeated or re-performed if necessary, e.g., depending on the previously measured first magnetization value. The partial counter-magnetization and the subsequent measurement of a further magnetization value are performed again, for example, if the magnetic range of the magnetic pigments whose coercive field strength is being tested extends perpendicular to the magnetic field gradient of the magnetizing device. The repeated partial counter-magnetization and measurement can be omitted if the magnetic range of the magnetic pigments extends parallel or antiparallel to the magnetic field gradient or to the x-direction.

[0059] Depending on the magnetization distance selected for the renewed partial countermagnetization, a repeat magnetization may be necessary (before the partial countermagnetization). This is the case if the magnetic field strength used for the renewed partial countermagnetization is lower than that used during the previous partial countermagnetization. However, if the magnetic field strength used for the renewed partial countermagnetization is higher than that used during the previous partial countermagnetization, a repeat magnetization is not necessary.

[0060] During the renewed partial countermagnetization - as during the first partial countermagnetization - the sample is placed on a magnetizing surface 77 of the magnetizing device 7 and the sample 1 and the magnet 71 are moved towards each other relative to each other until the magnetic pigments are positioned at a further magnetization distance x1 from the magnet (different from the first magnetization distance x0) in the static magnetic field, in which the magnetic field strength is greater or smaller than at the first magnetization distance (and greater or smaller than during a possibly previously performed renewed partial countermagnetization). After the renewed partial countermagnetization of the sample 1, a further magnetization value is measured by means of the measuring device 4, which is characteristic of the partial countermagnetization of the magnetic pigments achieved at the magnetization distance selected during the renewed partial countermagnetization.Here too, the magnetic pigments are outside the static magnetic field of the magnet during the further measurement(s). Test equipment and test result

[0061] The first magnetization value measured during the first measurement and, if applicable, the further magnetization value(s) of the partially counter-magnetized magnetic pigments measured during the subsequent measurement(s) are transmitted from the measuring device 4 to the testing device 3 connected to the measuring device. The transmission can take place after each individual measurement, i.e. before the renewed partial counter-magnetization, or only after the end of the renewed measurements. A magnetic field profile K(x) of the magnetizing device 7 is stored in the testing device 3. For example, the testing device has a memory area 9 in which the magnetic field profile K(x) of the magnetizing device is stored as a function of the distance x from the magnet of the magnetizing device, cf. Fig. 1. The test device 3 checks the first magnetization value measured during the first measurement (and, if applicable, the further magnetization value(s) of the partially counter-magnetized magnetic pigments measured during the further measurement(s)) in order to determine a test result relating to the coercive field strength of the magnetic pigments.

[0062] In a first exemplary embodiment, this test result includes, for example, confirmation of a predetermined target coercive field strength or a predetermined target coercivity range. In this first exemplary embodiment, the magnetic field profile of the magnetizing device 7 is used to determine one (and optionally at least one further) magnetization distance to be selected for the first (and optionally the further) counter-magnetization between the magnetic pigments and the magnet. This magnetization distance is output to the operator of the magnetizing device, e.g., by display on the input and output device 6 connected to the test device.

[0063] In other embodiments (2-7), the test result includes a numerical value of the coercive field strength, which is determined during testing by the testing device 3. In these other embodiments 2-7, the magnetic field profile K(x) of the magnetizing device is used to determine the test result concerning the coercive field strength.

[0064] The test result concerning the coercive field strength of the magnetic pigments, in particular the confirmation of a predetermined target coercive field strength or a predetermined target coercivity range or the numerical value of the coercive field strength, is then output by an input and output device 6 connected to the test device 3, to which the test device transmits the test result. First embodiment

[0065] In the first embodiment, it is checked whether the magnetic pigments have a specified target coercive field strength K0'. The following steps are performed: Specifying a target coercive field strength K0' by the operator 30, if necessary by selecting one of several predefined magnetic pigment types that the operator selects at the input and output device 6. Alternatively, the operator can select the magnetic pigment type indirectly by selecting the sample or valuable document type for which the coercive field strength of the respective magnetic pigment and, if necessary, the respective position of the respective magnetic region on the sample is stored in the testing device 3. For example, the operator receives a corresponding input prompt at the input and output device 6. Ideally, with partial counter-magnetization of the magnetic pigments with exactly the coercive field strength, a (first) magnetization value of zero is to be expected.Automatic determination of the magnetization distance x0' to be selected for the respective magnetic pigment with the target coercive field strength K0', at which the magnetic pigments are to be positioned by the magnet 71 and at which the partial counter-magnetization should ideally lead to a resulting magnetization of the magnetic pigments of zero. This magnetization distance x0' is automatically determined by the test device 3 based on the stored magnetic field profile K(x). For this purpose, the magnetization distance x0' at which the magnetic field strength corresponds to the target coercive field strength K0' is selected based on the magnetic field profile K(x), cf. Fig. 4b . The magnetization distance x0' to be selected for the selected magnetic pigments is displayed to the operator 30 on the input and output device 6. Magnetization of the magnetic pigments until their magnetization is saturated using the magnetizing device 7 or 7' by the operator. Partial counter-magnetization of the magnetic pigments at the previously determined magnetization distance x0' using the magnetizing device 7 by the operator. The operator places the sample, e.g., on the far right of the magnetizing device and moves it in the negative x-direction until the magnetic pigments, e.g., the security thread 2, have a magnetization distance x0' from the magnet 71. The sample is then withdrawn in the positive x-direction, lifted from the magnetizing device 7, and inserted into the device 10 to measure the magnetization M(x0'), cf. Fig. 4a. The test device 3 receives the magnetization value M(x0') from the measuring device 4 and then checks whether the magnetization M(x0') disappears or lies within an acceptance range A around zero. If so, the test device 3 causes the input and output device 6 to output a confirmation that the magnetic pigments have the specified target coercive field strength K0'. In the example from Fig. 4a the first magnetization value M(x0') is not zero, but in the acceptance range A. Such a confirmation is therefore output at the input and output device 6 of the device 10.

[0066] Otherwise, if the test device 3 has determined that the first magnetization value lies outside the acceptance range A, the input and output device 6 of the device 10 outputs that the magnetic pigments do not have the specified target coercive field strength K0'. If the test device 3 has determined that the measured magnetization still points in the direction of magnetization despite partial countermagnetization (if M(x0') lies above the acceptance range A, see Fig. 4a ), it can also be output that the coercive field strength of the magnetic pigments is greater than the specified coercive field strength K0'. If the measured magnetization after partial counter-magnetization points opposite to the magnetization direction (if M(x0') is below the acceptance range A, cf. Fig. 4a ), it can be output that the coercive field strength of the magnetic pigments is lower than the specified coercive field strength K0'.

[0067] Optionally, the operator can also specify the acceptance range A for the (first) magnetization value to be measured. The acceptance range A includes the ideally expected magnetization value of zero and indicates how large the deviation of the measured (first) magnetization value from zero may be so that the coercive field strength of the magnetic pigments is confirmed—despite an (acceptable) deviation from zero, see [see figure]. Fig. 4a . The deviation can arise, for example, due to fluctuations in the magnetic pigments themselves or due to measurement inaccuracies, or due to positioning inaccuracies of the sample on the magnetizing device 7. Alternatively, the acceptance range A can also be fixed. The acceptance range A can also be selected or specified via a coercivity range K', which corresponds to the acceptance range A according to the hysteresis curve of the respective magnetic pigments, cf. Fig. 4a .

[0068] In a further development of the first embodiment, in the event that the testing device has determined that the measured magnetization is not within the acceptance range A despite partial counter-magnetization, the partial counter-magnetization and measurement are carried out again with the aim of determining the actual coercive field strength of the magnetic pigments examined, as described below: For this purpose, the partial counter-magnetization is repeated or carried out again with a further magnetization distance x1' instead of the magnetization distance x0' and then a further magnetization value is measured with the measuring device 4.The further magnetization distance x1' is selected closer to the magnet 71 (higher magnetic field strength) if the first magnetization value still points in the direction of magnetization despite partial counter-magnetization, and further away from the magnet 71 (lower magnetic field strength) if the first magnetization value points opposite to the magnetization direction. The further magnetization value M(x1') is then checked to see whether it disappears or lies within the acceptance range A around zero. If necessary, the partial counter-magnetization and subsequent measurement of a further magnetization value can be repeated several times while varying the magnetization distance x, e.g., until a further magnetization value is reached that is vanishingly small or lies within the acceptance range A around zero.For this magnetization distance, the corresponding coercive field strength is then determined based on the magnetic field curve K(x) and output to the operator.

[0069] After one or more magnetization measurements, the test device automatically checks, based on a termination criterion, whether the coercive field strength can be determined based on the previous magnetization measurements. For example, the test device can check whether sufficient magnetization values ​​are available to calculate the coercive field strength with sufficient accuracy, e.g., at least two very low magnetization measurements (e.g., <20% of the remanence). Another termination criterion can be whether consecutive magnetization measurements result in magnetization values ​​with opposite signs.

[0070] In the first embodiment, a predetermined coercive field strength was checked and the first magnetization distance used for the first partial counter-magnetization was specifically selected so that the magnetic pigments are exposed to a magnetic field strength that is approximately the (alleged) coercive field strength of the magnetic pigments. Second embodiment

[0071] In the second embodiment, however, the first magnetization distance used for the first partial counter-magnetization is deliberately chosen differently.

[0072] First, the magnetic pigments are magnetized by the operator until their magnetization is saturated using the magnetizing device 7 or 7', as described above. Analogous to the first embodiment, the operator selects a coercive field strength K* that the operator suspects for the magnetic pigments to be examined. However, unlike the first embodiment, two partial counter-magnetizations and measurements are then performed at two magnetization distances x0 and x1, which lie on either side of the magnetization distance x* that corresponds to the specified coercive field strength K* according to the magnetic field profile K(x), cf. Fig. 4bFor example, the first magnetization distance x0 is chosen such that, after the first partial counter-magnetization, a significant amount of magnetization remains in the magnetization direction, and the subsequent measurement measures a correspondingly large first magnetization value M(x0) that is significantly greater than zero. A second partial counter-magnetization is then performed, which generates significant magnetization opposite to the magnetization direction, and the subsequent measurement measures a correspondingly large additional magnetization value M(x1) that is significantly below zero. To increase accuracy, further partial counter-magnetizations can be performed at different magnetization distances and measurements to obtain additional "support points" of magnetization values.

[0073] Then, the first and at least one further magnetization value M(x0), M(x1) are interpolated to determine the desired target magnetization distance xm at which the magnetization M(x) is equal to zero, cf. Fig. 4c . From the target magnetization distance xm thus determined, the testing device 3 can determine the actual coercive field strength Km of the magnetic pigments using the magnetic field profile K(x), cf. Fig. 4b , which is then output at the input and output device 6. Third embodiment

[0074] In the third embodiment, two magnetization distances for partial counter-magnetization are specified by the operator and the coercive field strength is automatically determined based on the measured magnetization values.

[0075] First, the operator magnetizes the magnetic pigments until their magnetization is saturated using the magnetizing device 7 or 7', as described above. If necessary, the remanent magnetization R is first measured, which is reached after the magnetic pigments have been magnetized to saturation (remanence measurement). A first magnetization value M(x0) is then measured after partial counter-magnetization at a first magnetization distance x0, and a further magnetization value M(x1) is measured after partial counter-magnetization at a further magnetization distance x1. The magnetization distances x0 and x1 can be selected by the operator, who enters them into the input and output device 6 for the testing device.

[0076] The first and further magnetization values ​​can be related to the previously measured remanent magnetization R according to the formula GM(x)=(RM(x)) / 2R and thus given as a percentage of the remanent magnetization, cf. Fig. 4c . For the left scale GM(x) in Fig. 4c GM=0% corresponds to a magnetization value equal to the remanent magnetization R, and GM=100% means that saturation and thus remanent magnetization in the opposite direction has been achieved during partial countermagnetization, ie M(x)=-R. The value GM=50% corresponds to a magnetization value M(x)=0.

[0077] From the first and subsequent magnetization values ​​M(x0) and M(x1), the testing device determines the target magnetization distance xm, at which the magnetization curve M(x) crosses zero (M(xm)=0 or GM=50%). The desired target magnetization distance xm can be determined, for example, by interpolating the magnetizations M(x0), M(x1) of the magnetic pigments measured for the two magnetization distances x0, x1, cf. Fig. 4c If both magnetization values ​​are on the same side of the zero crossing, an extrapolation is performed. From the target magnetization distance xm thus determined, the testing device can then determine the actual coercive field strength Km of the magnetic pigments based on the magnetic field profile K(x), see. Fig. 4b , and output at the input and output device 6. Fourth embodiment

[0078] In the fourth embodiment, an unknown coercivity is determined by specifying a coercivity range to be tested. The operator specifies, for example, a coercivity range C in which he or she expects the coercivity of the magnetic pigments to be tested to be. Fig. 4b , e.g. by entering a lower and upper limit of the coercivity range C at the input and output device 6.

[0079] First, the magnetic pigments are magnetized by the operator until their magnetization is saturated using the magnetizing device 7 or 7', as described above. Based on the magnetic field profile K(x), the testing device determines two or more than two magnetization distances x0, x1, ... , at which the operator should place the magnetic pigments on the magnetizing device 7 for the respective partial counter-magnetization. For example, the magnetization distances of the boundaries of the specified coercivity range C are selected (in Fig. 4b These are x0 and x1). Then, further measurements of the respective further magnetization values ​​can be carried out by varying the magnetization distance x=x0, x1, x2,... step by step, as shown in Fig. 3d is outlined. Between x0 and x1, additional magnetization distances can also be selected for repeated partial counter-magnetizations, covering the range x0 to x1, for example, equidistantly, and corresponding measurements can be performed. As already described, at least a first magnetization value M(x0) is measured after the first partial counter-magnetization at the first magnetization distance x0, and a further magnetization value M(x1) is measured after the repeated partial counter-magnetization at the second magnetization distance x1, as well as, if necessary, further magnetization values ​​M(x2),... after the repeated partial counter-magnetization at further magnetization distances x2,....

[0080] As in the third embodiment, the first and the at least one further magnetization value are then interpolated in order to determine the desired target magnetization distance xm at which the magnetization M(x) is equal to zero, cf. Fig. 4c . From the target magnetization distance xm thus determined, the testing device 3 can determine the actual coercive field strength Km of the magnetic pigments using the magnetic field profile K(x), cf. Fig. 4b , which is then output at the input and output device 6. Fifth embodiment:

[0081] In the fifth embodiment, an unknown coercive field strength is determined without requiring any operator input.

[0082] First, the magnetic pigments are magnetized by the operator until their magnetization is saturated using the magnetizing device 7 or 7', as described above. The testing device automatically sets a first magnetization distance x0 for the first partial counter-magnetization, e.g., in the middle between the crossbar and the right edge of the magnetizing device 7 or at a specific magnetization distance from the magnet 71, which corresponds to a standard coercive field strength or the last measured coercive field strength. The testing device 3 outputs this magnetization distance x0 to the operator at the input and output device 6.

[0083] After magnetizing the magnetic pigments until their magnetization is saturated, the operator uses the magnetizing device 7 to partially counter-magnetize the magnetic pigments at the automatically determined magnetization distance x0. The sample is then placed in the device 10 in order to measure the magnetization M(x0) using the measuring device 4. The testing device 3 receives the magnetization value M(x0) from the measuring device 4 and then checks whether the magnetization M(x0) disappears or lies within the acceptance range A around zero. If so, the testing device 3 uses the magnetic field curve K(x) to determine the coercive field strength K0 corresponding to the magnetization distance x0, cf. Fig. 4b , and causes the input and output device 6 to output information that the magnetic pigments have the coercive field strength K0.

[0084] However, if the magnetization M(x0) does not disappear or does not lie within the acceptance range A around zero, another magnetization distance x1 is automatically determined. This distance is selected closer to magnet 71 (higher magnetic field strength) if the magnetization M(x0) measured in the previous step still points in the direction of magnetization despite partial countermagnetization (M(x0)>>0), and further away from magnet 71 (lower magnetic field strength) if the magnetization M(x0) measured in the previous step points opposite to the magnetization direction (M(x0)<<0). In the latter case, the magnetization of the magnetic pigments of the flat sample must be repeated until their magnetization is saturated before further partial countermagnetization.Then the partial counter magnetization is carried out again at the further magnetization distance x1, a further magnetization value M(x1) is measured and checked to see whether this disappears or lies within the acceptance range A around zero. If so, the test device 3 uses the magnetic field profile K(x) to determine the coercive field strength K1 corresponding to the magnetization distance x1, cf. Fig. 4b , and causes the input and output device 6 to output information that the magnetic pigments have the coercive field strength K1.

[0085] If this is not the case, the partial counter-magnetization and subsequent measurement of a further magnetization value M(x) is carried out again while varying the magnetization distance x, until a further magnetization value (e.g. M(xm)) is reached which is vanishingly small or lies within the acceptance range A around zero. With each variation, a further magnetization distance x2, x3... is automatically determined, which is selected closer to the magnet (higher magnetic field strength) if the magnetization measured in the previous step still points in the direction of magnetization despite partial counter-magnetization, and which is selected further away from the magnet (lower magnetic field strength) if the magnetization measured in the previous step points opposite to the magnetization direction. If the direction of the steps has to be reversed when varying the magnetization distances (i.e.In this case (i.e., first reducing the magnetization distance and then increasing it in the next step, or vice versa), the step size of the magnetization distance is preferably chosen smaller than in the previous step. This allows the desired target magnetization distance xm to be achieved in just a few steps.

[0086] As soon as a measurement has been carried out in which the further magnetization value disappears or lies in the acceptance range A around zero, the test device 3 uses the magnetic field profile K(x) to determine the coercive field strength Km corresponding to this target magnetization distance xm, cf. Fig. 4b , and causes the input and output device 6 to output information that the magnetic pigments have the coercive field strength Km. Sixth embodiment

[0087] In the sixth embodiment, an unknown coercive field strength of the magnetic pigments of one or more long magnetic regions in which the magnetic pigments are homogeneously contained is determined. For partial countermagnetization, the magnetic region is placed on the magnetizing device 7 along the magnetic field gradient or along the distance coordinate x of the magnetic field profile K(x) or at an angle thereto.

[0088] The long magnetic area can, for example, be a magnetic security thread that is continuously and homogeneously provided with the same magnetic pigment. However, the security thread can also have several magnetic areas of the same magnetic pigment, in each of which the magnetic pigment is preferably homogeneously distributed, as in the example from Fig. 6a shown. The security thread 2 from Fig. 6ahas a magnetic coding consisting of five magnetic areas 22 of the same coercive field strength. As an alternative to magnetic security threads, other long magnetic areas can also be tested in the manner described below.

[0089] First, the operator magnetizes the magnetic pigments until their magnetization is saturated using the magnetizing device 7 or 7', as described above. For this purpose, the sample is placed on the input side of the magnetizing device 7 such that the long magnetic region is oriented along the magnetic field gradient (-x direction) and extends from right to left under the crossbar 75. Subsequently, a remanence magnetization curve R(x) of the magnetized magnetic pigments can be measured along the distance coordinate x on the sample using the measuring device 4, if necessary.

[0090] The security thread 2 is also used for partial counter-magnetization in Fig. 6aplaced on the magnetizing device 7 parallel to the direction of movement, i.e., oriented parallel to the magnetic field gradient, i.e., the security thread runs along the distance coordinate x of the magnetic field profile K(x). The position of the sample 1 can be determined automatically or by the operator. For example, the front edge of the long magnetic area 2 is positioned at the edge of the crossbar 75 (x=d), cf. Fig. 6a Due to this orientation of the long magnetic region, the magnetic pigments located in different sections of the long magnetic region are counter-magnetized to varying degrees. During partial counter-magnetization, the sections closer to magnet 71 are counter-magnetized more strongly than the sections further away.

[0091] Subsequently, a magnetization curve M(x) of the partially counter-magnetized magnetic pigments is measured along the distance coordinate x on the sample using the measuring device 4, cf. Fig. 6b . In contrast to the previous embodiments, the measured magnetization M(x) is a continuous function of the distance x. The magnetization curve M(x) contains a first magnetization value M(x0) and many further magnetization values ​​M(x1), M(x2),... along the long magnetic region. The first magnetization value M(x0), for example, is considered to be the magnetization at the front edge of the long magnetic region (x=d). The further magnetization values ​​correspond to magnetization distances of x>d. In the example of the security thread 2 with five magnetic regions 22, the magnetization M(x) curves as in Fig. 6bshown. A peak is generated for each magnetic region 22 as a function of the magnetization distance. Due to their short distance from the magnet 71, the two left-hand magnetic regions 22 were partially counter-magnetized to such an extent that their magnetization points opposite to the magnetization direction (M negative). Due to their large distance from the magnet 71, the two right-hand magnetic regions 22 were only partially counter-magnetized to a slight extent, so that their magnetization still points in the magnetization direction (M positive). Very low magnetization values ​​were measured for the middle magnetic region 22. This middle magnetic region 22 was therefore counter-magnetized approximately with the coercive field strength of the magnetic pigments. The position of the middle magnetic region therefore corresponds at least approximately to the target magnetization distance xm, at which the magnetization curve M(x) has a minimum or a zero crossing (M(xm)=0).

[0092] The test device 3 can automatically determine the target magnetization distance xm using a corresponding signal evaluation of the curve M(x), e.g., by selecting the peak with the lowest height or by interpolating between the two lowest peaks. If necessary, the (minimum) magnetization value found at the target magnetization distance xm can be compared with a remanence measurement value R of the remanence measurement (e.g., with the maximum of the measured function R(x)) to ensure that its absolute height is indeed very low (e.g., below a threshold). This ensures that the counter-magnetization magnetic field at the found magnetization minimum actually approximately corresponds to the coercive field strength.The testing device 3 can then determine the actual coercive field strength Km of the magnetic pigments from the target magnetization distance xm thus determined using the magnetic field profile K(x), which is then output at the input and output device 6.

[0093] Alternatively, the first derivative of the magnetization curve M'(x)=dM(x) / dm with respect to the coordinate of the magnetization distance x can be used to determine the desired target magnetization distance xm and its lowest peak can be determined, cf. Fig. 6cInstead of a one-dimensional magnetization curve M(x), the measuring device 4 can also measure a two-dimensional distribution of the magnetization M(x, y) and evaluate it with the aid of image processing in order to determine xm. Alternatively, the testing device can also output only the magnetization curve M(x), its first derivative M'(x) or a two-dimensional distribution of the magnetization M(x, y) or its first derivative M'(x,y), e.g. as a grayscale image, to the input and output device and the determination of xm can be carried out by the operator, e.g. by setting a corresponding mark on the lowest peak of M(x) or M'(x) or M(x,y) or M'(x,y) with a cursor on the input and output device 6.

[0094] If the measured magnetization curve M(x) or M(x,y) does not show a zero crossing or a minimum (e.g., because the long magnetic region was not positioned at an appropriate magnetization distance during partial countermagnetization or has an unusual coercive field strength), the partial countermagnetization can be repeated in a different region of the magnetizing device 7, in which different magnetization distances and thus different coercive field strengths are achieved for the long magnetic region. The measurement of the magnetization curve M(x) or M(x,y) and the evaluation described above are then also performed again.

[0095] If the security thread additionally has magnetic areas of a different coercive field strength, the procedure just described can simply be repeated, whereby the partial countermagnetization—corresponding to the different coercive field strength—may need to take place in a different area of ​​the magnetizing device 7. The operator specifies separate ROIs on the flat sample for the magnetic areas of different coercive field strengths. The measurement of the magnetization curve M(x) or M(x,y) and its evaluation is carried out analogously to the above for the magnetic areas of the different coercive field strength.

[0096] Fig. 6dshows the orientation of the long magnetic region 2 chosen for partial counter-magnetization in a modification of the sixth embodiment. There, the magnetic region 2 does not run parallel to the magnetic field gradient (-x direction), but obliquely to it at an angle α to the x direction. Furthermore, the magnetic region here has magnetic pigments continuously along its extension direction. Here, too, the long magnetic region 2 extends over such a large section of the static magnetic field that the magnetic region 2 covers a multitude of magnetization distances x0, x1, x2, ... The magnetization of the magnetic pigments takes place in the same oblique orientation, by pulling the sample under the crossbar 75. Fig. 6eThe first derivative of the magnetization curve M'(x) measured after the first partial counter-magnetization is shown with respect to the magnetization distance x. The magnetization distance x is obtained from the coordinate p along the (oblique) magnetic area 2 using the relationship x=d0+p▪cos(α). Using the first derivative from Fig. 6e the desired target magnetization distance xm can be determined, which in this case lies at a local minimum of M'(x) (the large peaks of the function M(x) mark the beginning and the end of the continuous magnetic region 2). Seventh embodiment

[0097] As in the sixth, in the seventh embodiment, an unknown coercive field strength of the magnetic pigments of a long magnetic region is determined. However, in this case, the magnetic region is not homogeneously coated with the magnetic pigment, but rather finely structured. As an example, a serial number 25 made of magnetic printing ink is considered, as it is shown in Fig. 7a is shown.

[0098] First, the magnetic pigments are magnetized by the operator until their magnetization is saturated using the magnetizing device 7 or 7', as described above. Subsequently, the course of the remanent magnetization R(x) of the magnetized magnetic pigments along the distance coordinate x on the sample can be measured using the measuring device 4. Fig. 7b The standard deviation SR(x) of the remanent magnetization R(x) in the y-direction (i.e., the standard deviation calculated perpendicular to the serial number direction) is shown. In the region of the serial number, this shows continuous modulations, which are due to the fine structure of the serial number.

[0099] For partial counter magnetization, the sample 1 is placed on the magnetizing device 7 in such a way that the magnetic serial number is parallel, antiparallel or oblique to the magnetic field gradient, e.g. analogous to Fig. 6a or Fig. 6dDue to this orientation of the serial number, the magnetic pigments located in different sections of the serial number are counter-magnetized to different degrees.

[0100] Subsequently, the magnetization values ​​of the partially counter-magnetized magnetic pigments are measured along the distance coordinate x on the sample using the measuring device 4 with the magnetization curve M(x) and the standard deviation SM(x) of the magnetization M(x) in the y-direction is determined again, cf. Fig. 7cThe standard deviation SM(x) does not show a continuous modulation; rather, the modulation is minimal or interrupted in the region of position xm, with the standard deviation SM also assuming relatively low values. The weak modulation at xm and the low SM values ​​indicate that the serial number has a low magnetization at this position xm, i.e., the partial countermagnetization was performed with approximately the coercive field strength.

[0101] Testing device 3 can automatically determine the target magnetization distance xm using a corresponding signal evaluation of the curve SM(x). If necessary, the curve SR(x) can also be used for comparison during the evaluation. Testing device 3 can then determine the actual coercive field strength Km of the magnetic pigments from the thus determined target magnetization distance xm based on the magnetic field profile K(x), which is then output to the input / output device 6. First embodiment of the magnetizing device

[0102] The Fig. 5a The magnetizing device 7 shown is based on the Fig. 3a, but additionally has a scale 88 which is readable by an operator and on which the operator can read off a measure of the distance between the magnetic pigments and the magnet 71 of the magnetising device, in particular the magnetisation distance x0, x1, x2, .... The scale extends, for example, along one of the (or both) lateral guides 74, 75. If the position of the magnetic pigments on the sample is visible to the operator, the position of the magnetic pigments and thus the magnetisation distance can be read off the scale directly and with millimetre precision.

[0103] If the operator does not know the position of the magnetic pigments on the sample, he can alternatively read the position of the sample front edge d0 or the position of the sample back edge on the scale, from which - based on the distance p0 of the magnetic pigments from the front or back edge of the sample - the magnetization distance of the magnetic pigments x0, x1, x2,... can be determined, cf. Fig. 3c. Several values ​​for p0 for different samples can be stored in the test device 3 so that it can automatically convert the leading edge positions d0, d1, d2, which can be easily determined by the operator, into the magnetization distance x0, x1, x2, ... or vice versa.

[0104] For those in Fig. 5aIn the magnetizing device shown, an adjustable mechanical stop 80 can optionally be additionally provided, which facilitates the positioning of the flat sample 1 on the magnetizing device 7. The mechanical stop 80 preferably extends over the entire width of the magnetizing surface 77 and is so small that it can be inserted into the gap 76 between the crossbar 75 and the magnetizing surface 77, e.g., if the front edge of the sample 1 is to be positioned under the crossbar. It is preferably removable from the magnetizing device 7. In certain cases, markings 85 on the mechanical stop are also useful, the position of which along the scale can be read as an alternative to the position of the front edge of the sample or the stop, e.g., if the front edge is covered by the crossbar 75.

[0105] The mechanical stop 80 may have a vertical plate 81 on its underside, the position of which can be varied along the stop 80. To change the position, this plate 81 is moved along an elongated hole 84 using one or more adjusting screws 83. Coarse and fine adjustment may be provided, allowing positioning with an accuracy of at least 0.5 mm. The vertical plate 81 prevents the mechanical stop 80 from slipping during partial counter-magnetization of the magnetic pigments. Second embodiment of the magnetizing device

[0106] In Fig. 5b,c another magnetizing device 7 is shown, in which the position of the upper magnet 71 is vertically adjustable, cf. the arrow pointing in the z-direction in Fig. 5c. Fig. 5c shows a section along the line QQ in Fig. 5bThe position of the lower magnet 72 can also be vertically adjustable. The magnets 71, 72 extend in the y-direction across the entire width of the magnetizing surface 77. If necessary, both magnets 71, 72 (mechanically coupled) are adjusted so that they always have the same z-distance from the magnetizing surface 77, so that the static magnetic field present in the magnetizing surface 77 points as far as possible in the x-direction.

[0107] The opposing magnets 71, 72 are each located in a shaft in which they are floatingly mounted. Their position is determined by two adjusting screws 93, which press on the respective magnet 71, 72 from above and below. The adjusting screws 93 are provided with a readable scale, for example, from which the operator can read off a measure of the magnetization distance of the magnetic pigments. A discrete grid is preferably specified for the z-positions of the magnets 71, 72, which can be set by the operator, so that the number of magnetic field curves to be stored for each one remains manageable. The magnets can be fixed solely by repulsion forces. To prevent tilting, the shafts are lined with a lubricious material. A thin steel plate can be attached between the adjusting screw and the magnet.Alternatively, the entire crossbeam 75 can be moved relative to the magnetizing surface 77, leaving the magnets 71, 72 stationary in the shaft. Alternatively, the z-movement of the magnet 71 or both magnets 72 can also be achieved with the aid of a laterally movable adjustment profile, the lateral movement of which causes a z-movement of the magnets 71, 72. A readable scale can be attached to the adjustment profile, providing a measure of the magnetization distance.

[0108] For partial counter-magnetization, the sample 1 is preferably positioned so that the magnetic region 2 with the magnetic pigments is not exactly under the magnet 71, but slightly offset in the x-direction, e.g. under the right edge of the crossbar 75, cf. Fig. 5cThis is advantageous compared to positioning directly beneath magnet 71, as the x-component of the static magnetic field is relatively small there. The adjusting screw 93 is then moved until the desired magnetization distance is reached. For any subsequent partial counter-magnetizations, the magnetic pigments can be brought to the same x-position (e.g., beneath the right-hand edge of crossbeam 75) and only the adjusting screw 93, i.e., the z-position of magnet 71, can be adjusted accordingly. Alternatively, the z-position of magnet 71, after having been initially set, can remain unchanged, and different x-positions of the magnetic pigments can be selected for the partial counter-magnetizations.

[0109] The magnetic field profile K(x) stored in the test device 3 indicates the magnetic field strength as a function of the magnetization distance x. In the case of the magnetizing device, the magnetization distance x includes Fig. 5b,cHowever, not only the x-position of the magnetic pigments along the x-direction, but also the z-position of the magnet 71 (and possibly also that of the magnet 72) to be varied. The magnetization distance x0, x1, x2 of the magnetic pigments therefore results from the z-position of the adjusting screws 93 and the selected x-position of the magnetic pigments. In the case of a magnetizing device that has a magnet that can be adjusted in the z-direction, the magnetic field profile K is therefore preferably stored in the testing device not only as a function of the x-position, but also as a function of the z-position of the magnet. This can also be a function K(x, z). Or, in the testing device 3, several magnetic field profiles K(z) can be stored for several discrete x-positions of the magnetic pigments, or several magnetic field profiles K(x) for several discrete z-positions of the magnet. These stored magnetic field profiles can be determined empirically in advance of the magnetic pigment test.

[0110] Alternatively, sample 1 can be partially counter-magnetized by pulling it through the magnetizing device—as with magnetization—to achieve the desired partial counter-magnetization. The magnetic field extreme value on the negative x-axis is x=-f (cf. Fig. 4b) is crucial for the resulting magnetization. For example, the sample can be pulled through the magnetizing device 7 for the first time to be magnetized. For the first partial counter-magnetization, the sample is rotated by 180° (front and back edges swapped), pulled through the magnetizing device 7 a second time, and then a first magnetization value is measured. The z-position of the magnet 71 is then adjusted downwards, the sample is pulled through the magnetizing device 7 a third time in the same orientation, and a second magnetization value is measured. From the two magnetization values, the z-position of the magnet can be determined, for example by extrapolation or interpolation, at which a magnetization value of zero is to be expected. From this - based on the magnetic field curve K(-f, z) applicable for the position x=-f - the corresponding coercive field strength of the sample can be determined.

Claims

1. Method for checking the coercive field strength of magnetic pigments of a planar sample (1) which are contained in a magnetic region of the planar sample, comprising the following steps: a) providing a magnetizing device (7) having at least one magnet (71, 72) which provides a static magnetic field for magnetizing the magnetic pigments, b) magnetizing the planar sample by the static magnetic field of the magnet of the magnetizing device or by a static magnetic field of another magnetizing device in such a way that the magnetic pigments of the planar sample are magnetized in a magnetizing direction up to the saturation of their magnetization, c) if appropriate, remanence measurement of the magnetization of the magnetized magnetic pigments after their magnetization with a measuring device (4), wherein the magnetic pigments are located outside the static magnetic field of the at least one magnet during the remanence measurement, d) first partial counter-magnetization of the magnetic pigments by the static magnetic field of the magnet of the magnetizing device in such a way that the magnetic pigments are partially counter-magnetized by the static magnetic field, wherein for the first partial counter-magnetization the planar sample and the magnet are moved relative to each other towards each other until the magnetic pigments are positioned at a first magnetization distance (x0, x0') from the magnet in the static magnetic field, at which the static magnetic field has a first magnetization field strength, e) first measurement of a first magnetization value (M(x0), M(x0')) of the partially counter-magnetized magnetic pigments with a / the measuring device (4), wherein the magnetic pigments are located outside the static magnetic field of the magnetizing device (7) during the first measurement, f) if appropriate, repeating the magnetizing according to step b) and subsequently, if appropriate, renewed partial counter-magnetization according to step d) and renewed measurement according to step e) for measuring a further magnetization value, wherein upon the renewed partial counter-magnetization in the respective step d), for the partial counter-magnetization of the planar sample by the static magnetic field, the planar sample and the magnet are moved relative to each other towards each other until the magnetic pigments are positioned at a further magnetization distance (x1) from the at least one magnet in the static magnetic field, at which the magnetic field strength is greater or less than the first magnetization field strength, and wherein the magnetic pigments are located outside the static magnetic field of the at least one magnet during the measurement of the respective further magnetization value, g) transmitting the first magnetization value measured during the first measurement and, if appropriate, the further magnetization value(s) of the partially counter-magnetized magnetic pigments measured during the renewed measurement(s) according to step f) from the measuring device (4) to a checking device (3) connected to the measuring device, in which checking device a magnetic field profile (K(x)) of the magnetizing device (7) is stored or which checking device is connected to another device (8) in which a magnetic field profile (K(x)) of the magnetizing device (7) is stored, h) checking the first and, if appropriate, the further magnetization value(s) of the partially counter-magnetized magnetic pigments by means of the checking device (3) for ascertaining a check result which relates to the coercive field strength of the magnetic pigments, i) transmitting the check result relating to the coercive field strength from the checking device to an output device connected to the checking device and outputting the check result relating to the coercive field strength of the magnetic pigments by the output device, wherein the checking device (3) is configured in particular - to use the magnetic field profile (K(x)) of the magnetizing device (7) to ascertain the check result relating to the coercive field strength, and / or - to use the magnetic field profile (K(x)) of the magnetizing device (7) to ascertain the first magnetization distance (x0) and / or, if appropriate, the at least one further magnetization distance (x1), which is to be chosen between the magnetic pigments and the magnet for the first and / or, if appropriate, the renewed partial counter-magnetization.

2. Method according to Claim 1, characterized in that for the first partial counter-magnetization and, if appropriate, for the renewed partial counter-magnetization, the planar sample (1) is moved towards the magnet (71, 72) and / or the magnet (71, 72) is moved towards the planar sample (1) in order to position the magnetic pigments at the first or at the further magnetization distance (x0, x1) from the magnet in the static magnetic field.

3. Method according to either of the preceding claims, characterized in that for determining the magnetic field profile (K(x)) of the magnetizing device (7) a calibration measurement of a planar calibration medium is carried out, which calibration medium has a long magnetic region, which throughout has magnetic pigments of a specific coercive field strength, wherein the calibration medium preferably has a plurality of long magnetic regions which are spatially separated from each other on the calibration medium and each throughout have magnetic pigments of a specific coercive field strength, wherein the coercive field strength of the various long magnetic regions is chosen differently in each case.

4. Method according to any of the preceding claims, characterized in that - the planar sample has a long magnetic region (2, 25) containing the magnetic pigments, and in that during the first partial counter-magnetization the planar sample is positioned on the magnetizing device (7) in such a way that the long magnetic region (2, 25) extends parallel, antiparallel or obliquely with respect to a magnetic field gradient of the static magnetic field, and - in that the measuring device (4) is configured for measuring the magnetization as a function of an extension direction of the long magnetic region on the planar sample and is configured in particular to generate both the first magnetization value (M(x0)) and at least one of the further magnetization values (M(x1), M(x2)) already during the first measurement, wherein the first magnetization value is measured from a first portion of the long magnetic region located at the first magnetization distance (x0), and wherein the respective further magnetization value is measured from a further portion of the long magnetic region, which, during the first partial counter-magnetization, was positioned at a further magnetization distance (x1, x2) from the at least one magnet in the static magnetic field, at which the magnetic field strength of the static magnetic field is greater or less than at the first magnetization distance (x0).

5. Method according to Claim 4, characterized in that the checking device is configured - on the basis of at least two further magnetization values (M(x1), M(x2)) of the long magnetic region measured for different further magnetization distances (x1, x2), and / or on the basis of at least one further magnetization value (M(x1)) of the long magnetic region measured for a further magnetization distance (x1) and on the basis of the first magnetization value M(x0) measured for the first magnetization distance (x0), to ascertain a magnetization profile (M(x)) as a function of the magnetization distance (x) and, on the basis of the magnetization profile M(x), to determine a target magnetization distance (xm) at which the coercive field strength (Km) of the magnetic pigments was attained during the first partial counter-magnetization, and - to determine the coercive field strength (Km) of the magnetic pigments from the target magnetization distance (xm) on the basis of the magnetic field profile (K(x)), - to transmit the coercive field strength (Km) of the magnetic pigments to the output device (6) connected to the checking device, which output device is configured to output the coercive field strength (Km) of the magnetic pigments.

6. Apparatus (10) for checking the coercive field strength of magnetic pigments of a planar sample, in particular according to a method according to any of Claims 1 to 5, wherein the magnetic pigments of the planar sample (1) were magnetized in a magnetizing direction up to saturation of their magnetization and were partially counter-magnetized oppositely to the magnetizing direction by a first magnetization field strength provided by a magnetizing device (7) during a first partial counter-magnetization, wherein the apparatus comprises a measuring device (4) and a checking device (3) connected to the measuring device, wherein: - the measuring device (4) is configured ∘ to carry out a first measurement of a first magnetization value (M(x0), M(x0')) of the magnetic pigments partially counter-magnetized after the first partial counter-magnetization, and, if appropriate, to carry out at least one further measurement for measuring at least one further magnetization value (M(x1)) of the magnetic pigments partially counter-magnetized during a renewed partial counter-magnetization, in which these were partially counter-magnetized oppositely to the magnetizing direction with a further magnetization field strength, which is greater or less than the first magnetization field strength, ∘ to carry out the first and, if appropriate, the respective further measurement such that the magnetic pigments are located outside the static magnetic field of the magnetizing device (7) during the first measurement and, if appropriate, during the respective further measurement, ∘ to transmit the first magnetization value of the partially counter-magnetized magnetic pigments measured during the first measurement, and, if appropriate, the at least one further magnetization value measured during the at least one further measurement, to the checking device (3), and - the checking device (3) connected to the measuring device is configured ∘ to check the first and, if appropriate, the at least one further magnetization value of the partially counter-magnetized magnetic pigments for ascertaining a check result which relates to the coercive field strength of the magnetic pigments, and ∘ to transmit the check result relating to the coercive field strength of the magnetic pigments to an output device (6) connected to the checking device, - wherein a magnetic field profile (K(x)) of the magnetizing device is stored in the checking device (3) or the checking device is connected to another device (8) in which a magnetic field profile (K(x)) of the magnetizing device (7) is stored, and wherein the checking device is configured in particular ∘ to use the magnetic field profile (K(x)) of the magnetizing device for ascertaining the check result relating to the coercive field strength of the magnetic pigments, and / or ∘ to use the magnetic field profile of the magnetizing device to ascertain a magnetization distance which is to be chosen between the magnetic pigments and the magnet for the first partial counter-magnetization and / or, if appropriate, for the renewed partial counter-magnetization of the magnetic pigments.

7. Apparatus according to Claim 6, characterized in that the checking device (3) is configured - to receive an operator specification which relates to a desired coercive field strength (K0') to be verified with the checking device and, if appropriate, an indication of a desired coercivity range (K') including the desired coercive field strength, and - on the basis of the operator specification, with the aid of the magnetic field profile (K(x)) of the magnetizing device, to ascertain the first magnetization distance (x0') which is to be chosen between the magnetic pigments and the magnet for the first partial counter-magnetization, and - to transmit the first magnetization distance (x0') to an output device (6) connected to the checking device, which output device is configured to output the first magnetization distance for an operator of the magnetizing device.

8. Apparatus according to Claim 7, characterized in that the checking device (3) is configured, when checking the first magnetization value of the partially counter-magnetized magnetic pigments, to check whether the first magnetization value (M(x0)) corresponds to a magnetization of zero and / or to check whether the first magnetization value (M(x0)) is in a magnetization acceptance range (A) which lies around a magnetization of zero and which corresponds to the desired coercivity range (K') according to a hysteresis curve of the magnetic pigments, and, if so, to transmit to the output device the confirmation that the magnetic pigments have the specified desired coercive field strength (K0') or that the coercive field strength of the magnetic pigments is within the specified desired coercivity range (K').

9. Apparatus according to either of Claims 7 and 8, characterized in that the check result ascertained during checking, which relates to the coercive field strength of the magnetic pigments, comprises a confirmation or a denial of whether the magnetic pigments have the specified desired coercive field strength (K0') and / or whether their coercive field strength is in the desired coercivity range (K') including the desired coercive field strength.

10. Apparatus according to any of Claims 6 to 9, characterized in that the check result ascertained during checking, which relates to the coercive field strength of the magnetic pigments, comprises a value for the coercive field strength of the magnetic pigments.

11. Apparatus according to Claim 10, characterized in that the checking device is configured to receive an operator specification which relates to a coercivity range (C) to be examined with the checking device, and, on the basis of the operator specification, with the aid of the magnetic field profile (K(x)) of the magnetizing device (7), to ascertain the first (x0) and at least one further magnetization distance (x1, x2) which is to be chosen between the magnetic pigments and the magnet for the first partial counter-magnetization or for the renewed partial counter-magnetization, and to transmit the respective first and further magnetization distance (x1, x2) to the output device (6) connected to the checking device, which output device is configured to output the respective first (x0) and the at least one further magnetization distance (x1, x2) for an operator of the magnetizing device.

12. Apparatus according to Claim 10 or 11, characterized in that the checking device is configured - on the basis of at least two of the further magnetization values (M(x1), M(x2)) or on the basis of the first magnetization value M(x0) and at least one of the further magnetization values (M(x1)), to determine a target magnetization distance (xm) at which the magnetization as a function of the magnetization distance (x) has a zero crossing (M(xm)=0) or at least assumes a minimum, and - to determine the coercive field strength (Km) of the magnetic pigments from the target magnetization distance (xm) on the basis of the magnetic field profile (K(x)), and - to transmit the coercive field strength (Km) of the magnetic pigments to an output device (6) connected to the checking device, which output device is configured to output the coercive field strength (Km) of the magnetic pigments, wherein the checking device is configured in particular to determine the target magnetization distance (xm), at which the magnetization M(x) as a function of the magnetization distance (x) has the zero crossing (M(xm)=0), by fitting or extrapolation or interpolation of the first magnetization value M(x0) and at least one of the further magnetization values (M(x1)), or by fitting or extrapolation or interpolation of at least two of the further magnetization values (M(x1), M(x2)).

13. Apparatus according to any of Claims 10 to 12, characterized in that the checking device is configured to automatically determine a further magnetization distance (x1) on the basis of the first magnetization value (M(x0)) transmitted by the measuring device, wherein the further magnetization distance (x1) - is chosen to be closer to the magnet of the magnetizing device (7) than the first magnetization distance (x0) if the magnetization of the magnetic pigments still points in the magnetizing direction after their first partial counter-magnetization, and - is chosen to be further away from the magnet of the magnetizing device (7) than the first magnetization distance (x0) if the magnetization of the magnetic pigments points counter to the magnetizing direction after their first partial counter-magnetization, and the checking device is configured to transmit the further magnetization distance (x1) to an / the output device (6), which is configured to request the operator to effect the renewed partial counter-magnetization of the magnetic pigments at the further magnetization distance (x1) and to effect the renewed measurement of the magnetic pigments that have undergone renewed partial counter-magnetization, in order to determine the further magnetization value (M(x1)) by means of the measuring device (4).

14. Apparatus according to any of Claims 6 to 13, characterized in that the measuring device (4) has a receptacle (23) for receiving the planar sample, which is configured to receive the planar sample during the first and, if appropriate, the at least one further measurement such that the planar sample is located outside the static magnetic field of the magnetizing device (7) during the first and, if appropriate, during the at least one further measurement.

15. Arrangement for magnetizing a planar sample and for checking the coercive field strength of magnetic pigments of the planar sample, in particular according to a method according to any of Claims 1 to 5, wherein the arrangement comprises: - an apparatus (10) for checking the coercive field strength of magnetic pigments of a planar sample according to any of Claims 6 to 14, and - a magnetizing device (7) having a magnetizing surface (77) for receiving the planar sample and at least one magnet (71, 72) which provides a static magnetic field configured for partial counter-magnetization of the magnetic pigments of the planar sample, wherein ∘ the magnetizing device (7) is configured so that the planar sample placed onto the magnetizing surface (77) and the at least one magnet (71, 72), for the first partial counter-magnetization of the magnetic pigments, are movable relative to each other towards each other until the magnetic pigments are positioned at a first magnetization distance (x0) from the at least one magnet (71, 72), at which the static magnetic field has a first magnetization field strength, and ∘ wherein the planar sample and the at least one magnet, for the renewed partial counter-magnetization of the magnetic pigments, are movable relative to each other towards each other until the magnetic pigments are positioned at a further magnetization distance (x1) from the at least one magnet (71, 72), at which the magnetic field strength of the static magnetic field is greater or less than the first magnetization field strength.

16. Arrangement according to Claim 15, characterized in that the at least one magnet (71, 72) is arranged in such a way that a gap (76) is formed between the magnetizing surface (77) and the at least one magnet, into which gap the planar sample (1) can be inserted for magnetizing its magnetic pigments, wherein the gap (76) perpendicular to the magnetizing surface (77) is greater than the thickness of the planar sample.

17. Arrangement according to either of Claims 15 and 16, characterized in that the magnetizing surface (77) has an entrance side, which - viewed along a predetermined direction of movement of the planar sample - is arranged before the at least one magnet (71, 72), and has an exit side, which - viewed along the predetermined direction of movement of the planar sample - is arranged after the at least one magnet (71, 72), wherein preferably - the magnetizing surface (77) of the magnetizing device - viewed along the predetermined direction of movement - on the entrance side and / or on the exit side extends at least over the length of the planar sample, in particular over at least 10 cm, and / or - the magnetizing surface (77) of the magnetizing device is delimited on one side or on both sides by a guide (73, 74) which extends along the predetermined direction of movement of the planar sample.

18. Arrangement according to any of Claims 15 to 17, characterized in that the magnetizing device (7) has at least one magnet (71, 72) whose magnetic north pole or whose magnetic south pole faces the magnetizing surface (77) with its end face.

19. Arrangement according to any of Claims 15 to 18, characterized in that the magnetizing device (7), in particular a guide (73, 74) delimiting the magnetizing surface (77) of the magnetizing device, or an adjustment device (93) of the magnetizing device, has a scale that can be read by an operator, from which the operator can read a measure of the magnetization distance between the magnetic pigments and the magnet (71, 72) of the magnetizing device.

20. Arrangement according to any of Claims 15 to 19, characterized in that the magnetic field profile (K(x)) of the magnetizing device (7) stored in the checking device (3) or in the other device indicates the magnetic field strength present on the magnetizing surface as a function of the position along the magnetizing surface, in particular parallel or antiparallel to the magnetic field gradient of the static magnetic field.

21. Arrangement according to any of Claims 15 to 19, characterized in that the magnetizing device has an adjustment device (93), with the aid of which an operator of the magnetizing device can adjust the distance between at least one of the magnets (71, 72) and the magnetizing surface (77), and in that the magnetic field profile (K(x)) of the magnetizing device stored in the checking device (3) or in the other device indicates the magnetic field strength present on the magnetizing surface in particular as a function of the position (z) of the at least one magnet (71, 72) perpendicular to the magnetizing surface (77).