JP6550587B2 - Magnetic line sensor and discrimination device using the same - Google Patents

Description

  The present invention provides a magnetic line sensor device that accurately detects a two-dimensional magnetic image of a magnetic substance printed on paper sheets such as banknotes, and further, by comparing the outputs obtained from the line sensors It is possible to distinguish the type (hard magnetic material and soft magnetic material) and the magnetization state.

The present invention relates to the authenticity determination of valuables such as banknotes and securities.
With the remarkable performance improvement of recent printing technology and copying technology, forgery of banknotes, securities, credit cards, etc. is becoming more and more sophisticated, and proper identification and exclusion of them maintain social order It is regarded as important. In particular, in machines that handle bills such as ATMs and bill processors (hereinafter referred to as financial instruments), a high-speed, high-performance discrimination system for determining authenticity is strongly required.
As a method for discriminating these bills and securities, pattern identification by an optical line sensor device and magnetic ink identification by a magnetic line sensor are used. The present invention relates to a magnetic line sensor used to determine the authenticity of banknotes and valuables.

For valuables such as banknotes and securities (hereinafter referred to as media), magnetic ink containing magnetic material is used in fibers and threads inserted inside the printing section and media for the purpose of preventing forgery, and magnetic properties are applied to specific parts. Measures are taken to prevent forgery.
Magnetic line sensors are mounted in various financial instruments to detect this magnetic substance, and various magnetic resistance elements (magnetic resistance elements: MR, anisotropic magnetic resistance elements: AMR, giant magnetic resistance) are used as magnetic line sensors. Element: SMR, tunnel type magnetoresistive element: TMR element, etc., a magnetic impedance element, a differential coil, and a sensor in which a Hall element, etc. are arranged in a direction perpendicular to the moving direction of the medium are used. Electrical changes due to ink are detected.

Japanese Patent No. 4267271

  However, according to the current detection method using the magnetic line sensor, it is considered that the detection capability of the magnetic ink is still insufficient, and a new high performance magnetic line sensor is required. For example, the magnetic line sensor using the existing magnetoresistive element has a large element shape of about 10 mm, and it can not be said that the necessary magnetic information of the medium can be accurately acquired.

  From this situation, more recently, attempts have also been made to detect magnetic images of media by arranging compact AMR, SMR, and TMR elements on a line at high density. In the method using these magnetoresistive elements, the dynamic fluctuation of the magnetic quantity when the medium passes is output (hereinafter abbreviated as differential output), and the magnetic field of the mounted magnet is also arranged parallel to the moving direction of the medium It is done. This method has a problem that the magnetic information directly on the medium cannot be accurately detected due to the output fluctuation due to the moving speed of the medium.

Furthermore, in the differential output method, only the periphery of the magnetic pattern of the scanned medium is output as a signal, and it is difficult to distinguish the entire image of the magnetic pattern of the medium due to differential output at portions with large area of magnetic ink area or fine pitch. have. That is, there is a problem that the magnetic information of the medium immediately above the sensor unit can not be accurately detected.
A magnetic impedance element (hereinafter referred to as an MI element) is easy to miniaturize and has high sensitivity, and it is possible to directly detect the magnetic strength of the medium, but the hysteresis and dynamic range to the applied magnetic field are small. There are problems such as causing output saturation.

  The present invention has been made in view of the above situation, and a magnetic line sensor capable of detecting a two-dimensional image including a magnetic material printed on a sheet with high resolution and high accuracy, and the same An object is to provide a discrimination device.

As a result of examining the solution of the problem of such a magnetic line sensor and repeatedly examining it for the purpose of development of a magnetic line sensor that can directly read the magnetic pattern and magnetization intensity of the medium, the magnetic pattern of the medium is read accurately and further Found a magnetic line sensor configuration that can also determine the magnetization intensity, and reached the present invention.
That is, the present invention is a magnetic line sensor that directly detects a two-dimensional magnetization density pattern according to the magnetization intensity of a medium including a magnetic material printed on a paper sheet such as a bill. In the present invention, a special Hall element capable of directly reading the magnetization intensity of the medium is used, and this is arranged at high density, and a long (rod-like) plastic magnet is loaded so as to continue directly under it. It is a new magnetic line sensor that can directly read the magnetization pattern of the medium by applying By attaching this to a financial instrument etc., it will be possible to further strengthen anti-counterfeit measures.

  The Hall element is used in a sensor or the like that measures a magnetic field by applying the Hall effect, which is a phenomenon in which an electromotive force appears in a direction orthogonal to both current and magnetic field when a magnetic field is applied perpendicularly to the current. As the Hall element, a material having a large Hall electromotive force and a low temperature dependency is preferred, and germanium, silicon, indium / antimony, indium arsenide, gallium arsenide, and the like are used.

  However, while the Hall element has a large dynamic range and excellent linearity, the sensitivity is smaller than that of the magnetoresistive element or the MI element. Therefore, there is a problem that it can not be detected unless the signal output obtained from the medium is amplified several thousand times in order to be used for the purpose of the present invention, and all Hall elements described above are required to obtain a large S / N signal. It can not be used.

  Furthermore, in the present invention, in order to read out a magnetic image, a large number of Hall elements are mounted at a pitch (arrangement pitch) of 0.5 pieces / mm or more, preferably 1 piece / mm or more. Therefore, miniaturization is possible, and the current consumption per Hall element is as low as possible. The heat generation and current consumption of the entire magnetic line sensor should not exceed the practical range.

  The inventor focused on an indium-antimony compound semiconductor (hereinafter abbreviated as InSb) having a high electron mobility and hence the highest sensitivity as a result of earnestly examining a Hall device suitable for the purpose, and in particular this single crystal It has been found that a Hall element using a thin film is suitable for the present invention. That is, the Hall element in the present invention is composed of a single crystal thin film made of an indium / antimony compound semiconductor film formed on a substrate.

  InSb is a material that has a large electron mobility and is most suitable for a Hall element, and is widely applied to motor rotation detection, open / close sensors, geomagnetic sensors, and the like. However, when precise magnetic force is detected as in the present invention, it is necessary to select the fine structure of InSb appropriately. For example, in the case of polycrystalline material, the influence of grain boundaries becomes large and the linearity is bad, and the occurrence of hysteresis or There is a drawback that noise is mixed into the signal output due to shock such as vibration. Although the above problems can be solved by using a single crystal element, the impedance of the Hall element itself becomes small because the bulk resistance is small, and the output voltage to the magnetic field of the sensor becomes low. In order to increase the output voltage, it is necessary to increase the current applied to the element. However, in the case of the present invention where the number of elements is large, the operating current of the sensor is extremely increased, and heat generation and power capacity are practical. The problem of became clear.

  From the above reasons, as a result of searching for an optimum Hall element, it was found that the balance between sensitivity and resistance is suitable for the purpose of the present invention by using an InSb single crystal thin film. Specifically, it is a Hall element consisting of an InSb single crystal thin film epitaxially grown on a gallium arsenide single crystal substrate, and in consideration of the effects of additives such as film thickness and doping, hole sensitivity is preferably 6 mV / mT or more. Is 8 mV / mT or more, and heat generation is performed while securing sensitivity and S / N by selecting a Hall element having a resistance value (DC resistance of each Hall element) of at least 70 Ω, preferably 100 Ω or more. It was found that a small magnetic line sensor can be constructed.

  The magnetic component of the magnetic ink applied to the medium by printing etc. includes a magnetized permanent magnet type (hereinafter abbreviated as hard magnetic material) and a high permeability magnetic material (hereinafter abbreviated as soft magnetic material) that is magnetized by the surrounding magnetic force. There are two types, and it is required that these can be separated.

  Various attempts have been made to solve the above problems. For example, as a magnetic line sensor using Hall elements, the Hall elements are arrayed as described in Patent Document 1 (Japanese Patent No. 4267271). A method for detecting a magnetic pattern of a valuable material has been proposed. According to the above patent, a Hall element array to which a magnetic bias (a permanent magnet is disposed below the sensor unit) and a Hall element array to which no magnetic bias is applied are arranged in two rows at right angles to the moving direction of the medium. A method has been proposed in which the hard magnetic material and the soft magnetic material contained in the magnetic ink are separated by reading the difference between the outputs of the Hall element sensor arrays. Since the Hall element arrays are arranged in two rows, the structure is larger and more expensive than the currently used magnetic line sensor. Thus, it has been shown that the dead zone can be eliminated with a small number of Hall elements by devising a magnet. Furthermore, in order to arrange the Hall elements at a high density and detect the magnetic image, there is a problem that the two-row arrangement is not practical.

  On the other hand, the present invention has a structure in which only one row of high-sensitivity Hall elements is arranged at a high density, and a bias magnetic field is applied to the passage portion of the medium by a plastic magnet to detect magnetic information immediately above the Hall element array. It is. As a result, the magnetic amount of magnetic material such as magnetic ink on the medium is directly detected by each Hall element, and the output signal of each Hall element is taken out as a line signal to make the magnetic pattern of the medium a density pattern corresponding to the magnetic amount. It can be read. The performance effect and economic merit of the present invention are considered to be extremely large.

  Furthermore, an anisotropic magnetic body that is polarized in the in-plane direction may be disposed in the thread portion, and when read by the magnetic line sensor of the present invention, the upper part shows magnetism opposite to the applied magnetic field, It was confirmed that it could be detected as a negative magnetic quantity.

  In magnetic ink used for banknotes and valuables, magnetite (Fe3O4) as a magnetic substance for preventing forgery, permanent magnet type (hard magnetic substance) magnetic powder such as γ-iron oxide, barium or strontium ferrite and the like In many cases, high magnetic permeability soft magnetic materials such as nickel zinc ferrite, manganese zinc ferrite and nickel zinc / copper ferrite are used depending on the location.

  The inventor of the present invention pays attention to the fact that the saturation magnetic flux density of these hard magnetic materials is smaller than the saturation magnetic flux density of soft magnetic materials, and assumes that the output difference of the magnetic line sensor appears in an appropriate magnetic field. The As a result, by setting the surface magnetic flux density on the magnetic line sensor to 100 mT or more, more preferably 150 mT or more, particularly preferably 180 mT or more, the output difference of the sensor is largely developed, and a branch point is provided in the output. It has been found that the magnetic substance and the soft magnetic substance can be clearly distinguished. As described above, by appropriately setting the magnetic flux density at the interface in contact with the medium in the upper portion of the Hall element, the magnetization intensity of the magnetic body of the medium can be determined.

  The hard magnetic substance contained in the magnetic ink has a saturation magnetic flux density in the range of 100 to 200 mT, and the soft magnetic substance is magnetized much larger than the hard magnetic substance by the magnet mounted on the magnetic line sensor. It can be easily confirmed as the output difference of the line sensor.

  Thereby, in the case of the hard magnetic material, the saturation magnetic flux density of the material itself is smaller than that of the soft magnetic material, and thus the magnetic sensitivity tends to be saturated. Also, in the case of a soft magnetic material, the magnetic sensitivity can be proportionally increased correspondingly to the strength of the bias magnetic field, so the present invention can be classified as a clear output difference by using a Hall element with high sensitivity and excellent linearity. I can do it.

Specifically, the following new effects can be realized by the configuration of the magnetic line sensor of the present invention.
1. The pitch of the magnetic line sensor can be easily made finer, and the magnetic pattern can be read out directly as an image.
2. Since the differential output method was not used, the output fluctuation due to the moving speed of the medium, which was a problem, was small, and precise correction was easily possible, leading to the improvement of the S / N ratio of the magnetic signal.
3. The Hall element has a feature that the dynamic range is large and the linearity of the magnetic amount is excellent, which makes it possible to precisely measure the magnetic characteristics of the magnetic ink, and as a result, the strength of the ink magnetized by the magnetic field The distinction made it possible to distinguish the ink containing the permanent magnet and the soft magnetic material.

The bias magnetic field can be applied by an electromagnet and a permanent magnet, but for the purpose of reducing the power consumption and stabilization and temperature dependency of the magnetic field, a permanent magnet, particularly an Alnico and rare earth magnet having a small temperature change of the magnetic force is used. preferable.
The rare earth magnet can generate a strong magnetic field, and alloys such as samarium-cobalt and iron-neodymium-boron are well known. However, although plastic magnets of strong magnetic force can be obtained when these are used as plastic magnets for magnetic line sensor applications of the present invention, they are easily oxidized by oxygen and moisture in the atmosphere and difficult to handle, and There is a problem that the fluctuation is large, and furthermore, since the powder to be a raw material is formed by grinding, the dispersion of the particle size is large and the fluctuation of the magnetic distribution of the plastic magnet is likely to occur. From this point of view, the rare earth cobalt nitride which can obtain a homogeneous fine powder directly by the nitriding reaction is extremely stable even in the atmosphere, tends to be given a strong magnetic field and a uniform magnetic field, and has a smaller temperature dependency than a ferrite magnet. Therefore, it turned out that it is optimal for the plastic magnet made into the object of the present invention.
That is, it is preferable that the plastic magnet in the present invention contains magnetic powder composed of rare earth cobalt alloy nitride powder, and it is more preferable that the magnetic powder is samarium cobalt nitride powder.
The rare earth cobalt nitride powder can be kneaded with a plastic serving as a binder and molded into a desired shape by injection or extrusion while giving a magnetic field. Further, in order to generate a desired magnetic force, it is necessary to mix magnetic powder of at least 70% by weight or more of the weight of the molded product, and for the purpose of cost reduction, oxide ferrite within a range not affecting performance. Other magnetic powders such as may be mixed. The plastic used as the binder can be appropriately selected from the viewpoints of the filling property, the moldability and the heat resistance, and is not particularly limited, but usually polypropylene, 6 or 12 nylon, polyacetal, polyphenylene sulfide and the like are preferable.
The powder particles of the magnetic powder contained in the plastic magnet are subjected to a process of orienting the respective magnetization axes in a predetermined direction in the molding step, and become a magnet having a strong magnetic force. If the shape of the magnet is arranged individually for each Hall element, the positional accuracy and the variation of the magnetic field become large, which is disadvantageous in terms of cost, and it is not preferable. Magnetic distribution is obtained by using a long plastic magnet mixed with a magnetic substance of rare earth compound. It is particularly preferable because the stabilization and correction of

  An output voltage corresponding to the magnetic field of a plurality of Hall elements arranged on a straight line can be obtained as a magnetic output on a continuous line using an integrated circuit, and this is sequentially repeated in the direction in which the medium moves. It is possible to obtain a magnetic image.

  As the distance between the medium to be detected and the sensor can be increased as close as possible, the upper surface of the arrayed Hall elements is covered with a thin plate made of nonmagnetic material with wear strength, and this thin plate is placed on this thin plate A favorable magnetic output can be obtained by moving the medium. The material of the thin plate is preferably a metal such as brass, nonmagnetic stainless steel material, ceramic material, carbon fiber composite material, etc., but it is not particularly limited as long as it is nonmagnetic material.

  Hereinafter, the present invention will be described in more detail by way of examples, but of course the present invention is not limited to the examples.

  According to the present invention, a two-dimensional image including a magnetic material printed on a paper sheet is detected with high resolution and high accuracy. An apparatus for the same is also provided. There will be no doubt that such a magnetic image can be one of the techniques needed to further upgrade the anti-counterfeiting measures for paper sheets. Therefore, the present invention will greatly contribute to further progress in measures for preventing counterfeiting of paper sheets.

The output example of the magnetic line sensor of this invention is contrasted with the output of a conventional sensor. It is a schematic sectional drawing of the discrimination apparatus provided with the magnetic line sensor 1 which concerns on 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows roughly the structure of the magnetic line sensor 1 which concerns on 1st Embodiment of this invention, and the mode of the magnetic field generate | occur | produced in it. FIG. 1 is a schematic perspective view showing a part of a magnetic line sensor 1 according to a first embodiment of the present invention. It is the schematic plan view which expanded and showed the holding substrate partially. It is a schematic bottom view of the holding substrate of FIG. 5A.

FIG. 1 shows an output example of the magnetic line sensor of the present invention in comparison with the prior art.
A medium is produced by sequentially printing a magnetic ink containing a nickel zinc ferrite soft magnetic material, a barium ferrite hard magnetic material, and a rare earth magnetic powder having a large coercive force, and the medium is scanned in the direction of the arrow by a magnetic line sensor. The sensor output of is illustrated.
As described in the text, in the differential output by the magnetoresistive sensor of the comparative example, the magnetic fluctuation of the edge of the magnetic ink is obtained as the output, and in particular, when the pitch of the printing portion becomes finer, the entire image of the printing portion becomes difficult to distinguish.
On the other hand, as shown in the embodiment, the sensor output of the present invention directly detects the magnetic intensity of the magnetic ink on the upper part of the sensor as the output, so the magnetic ink of fine pitch is also output as the pattern. In the case of a large magnetic body, it is not magnetized by the magnetic force of the magnetic line sensor and can be detected as a negative output as it is.
Then, the output of the magnetic line sensor of the present invention can be easily output as a two-dimensional magnetic pattern image simply by combining the line signals as in the optical line sensor.

  FIG. 2 is a schematic cross-sectional view of a discrimination device including the magnetic line sensor 1 according to the first embodiment of the present invention. The discrimination device is a device for discriminating the medium S including a magnetic body (magnetic image M) printed on a paper sheet such as a bill. A magnetic image M is printed on the medium S using, for example, magnetic ink, a magnetic thread, and the like. The magnetic line sensor 1 detects the magnetic image M included in the medium S.

  The conveyance path 2 is formed in the conveyance direction D1 at an interval G and a width slightly larger than the width of the medium S. The medium S is sent into the transport path 2 by the upstream transport roller 21 and further transported toward the downstream transport roller 22 by the sensor facing roller 23 facing the magnetic line sensor 1. The sensor facing roller 23 also has a function of pressing down in the direction opposite to D3 so that the medium S approaches the magnetic line sensor 1. In this way, the magnetic material of the medium S is detected while the medium S passes over the magnetic line sensor 1. Next, the medium S is discharged from the conveyance path by the downstream conveyance roller 22.

  FIG. 3 is a cross-sectional view schematically showing the configuration of the magnetic line sensor 1 and the state of the magnetic field generated therein. FIG. 4 is a schematic perspective view showing the magnetic line sensor 1. The magnetic field generation unit 3 is usually composed of a permanent magnet and forms a bias magnetic field. In this example, the magnetic field generation unit 3 is provided below the Hall element 4 so that the N pole is on the upper side and the S pole is on the lower side. A loop-shaped magnetic flux as shown in FIG. 3 is formed around the magnetic field generation unit 3, and in particular, in the vicinity of the Hall element 4, a bias magnetic field perpendicular to the transport direction D 1 of the medium S (see FIG. 2). Is formed. In general, the Hall element has a higher output and higher sensitivity as the bias magnetic field is stronger. Therefore, a plastic magnet in which samarium cobalt nitride powder having high magnetism and high retention rate is mixed as magnetic powder is used as the permanent magnet. . High retention is necessary to retain magnetic properties even at high temperatures. The plastic magnet contains 70% by weight or more of samarium cobalt nitride powder, and the magnetization axis (axis of easy magnetization) of each powder particle is oriented in a certain direction. However, samarium cobalt nitride powder is only an example of magnetic powder, and other rare earth cobalt alloy nitride powder may be used as magnetic powder.

  A plurality of Hall elements 4 are provided in the bias magnetic field, and a plurality of Hall elements 4 are provided to detect the magnetic flux formed in the orthogonal direction D3 to the medium S. Each Hall element 4 is formed of a single crystal thin film of an iridium-antimony compound semiconductor deposited on a substrate, and its Hall sensitivity needs to be 6 mV / mT or more and its direct current resistance be 70 Ω or more. The plurality of Hall elements 4 are arranged in a direction (width direction) D2 orthogonal to the transport direction (movement direction) D1 of the medium S. The plurality of Hall elements 4 constitute a sensor unit (hall element array) 40, and convert the strength of the bias magnetic field generated by the magnetic field generation unit 3 into an electric signal. The plastic magnet that constitutes the magnetic field generation unit 3 is rod-like (long), and is directly below the sensor unit 40 in a direction parallel to the transport direction D1. The sensor unit (hall element array) 40 and the magnetic field generation unit 3 (plastic magnet) have a structure for detecting magnetic information immediately above the sensor unit 40. That is, when the medium S passes over the Hall element 4, the bias magnetic field is changed by the magnetic material included in the medium S. The Hall element 4 detects this changed bias magnetic field. Since the Hall element provides an electric signal proportional to the intensity of the bias magnetic field, even the density of the magnetic image M can be detected. A two-dimensional magnetization density pattern (magnetic image according to the magnetization intensity of the medium S is obtained by acquiring electric signals from the plurality of Hall elements 4 arranged in the width direction D2 while conveying the medium S in the conveyance direction D1. M) can be detected directly.

  In the present embodiment, the arrangement pitch of the Hall elements 4 along the width direction D2 is set to 0.5 / mm or more, and preferably 1 / mm or more. In the present embodiment, the arrangement pitch of the Hall elements 4 is set to 0.5 to 2 / mm, for example. The pitch is set equal to or less than the magnetic field detection range in the D2 direction of the Hall element 4. Thereby, when the medium S is conveyed, the magnetic field change on the entire surface of the medium S can be detected without any gap. The Hall sensitivity of each Hall element 4 is 6 mV / mT or more, preferably 8 mV / mT, and the direct current resistance is 70 Ω or more, preferably 100 Ω or more.

  The plurality of Hall elements 4 are held by a holding substrate 5. The holding substrate 5 is a printed circuit board in which a circuit pattern is printed with a conductive foil such as copper foil on the surface of a rigid substrate formed of an insulating resin such as glass epoxy resin, for example. On the surface of the holding substrate 5 in the present embodiment, a plurality of Hall elements 4 and a connector 51 for electrically connecting the holding substrate 5 to another member are mounted.

  The detection unit 7 is connected to the holding substrate 5 via the flexible substrate 6. That is, one end of the flexible substrate 6 is detachably connected to the connector 51 mounted on the holding substrate 5, and the other end of the flexible substrate 6 is connected to the connector 71 mounted on the drive substrate constituting the detection unit 7. By being detachably connected, the circuit on the holding substrate 5 and the detection unit 7 are electrically connected.

  A drive voltage is applied to each Hall element 4 from the detection unit 7 via the flexible substrate 6, and an output signal from each Hall element 4 is input to the detection unit 7 via the flexible substrate 6. From the output of the Hall element 4, the detection unit 7 extracts only the change of the bias magnetic field due to the magnetic substance contained in the medium S, and detects the magnetic substance of the medium S with high accuracy.

  The flexible substrate 6 is a flexible printed circuit board, and has a configuration in which a conductor foil such as copper foil is covered with a polyimide material that is a film-like insulator. The flexible substrate 6 constitutes a connection unit 60 that connects the sensor unit 40 (Hall element 4) and the detection unit 7. In the present embodiment, a plurality of Hall elements 4 are collectively connected to the detection unit 7 by one flexible substrate 6. As a result, compared to the configuration in which each Hall element 4 is connected to the detection unit 7 individually by wiring, a large number of Hall elements 4 can be arranged and connected to the detection unit 7.

  With this configuration, since the plurality of Hall elements 4 are provided separately from the detection unit 7, the Hall elements 4 are placed in a relatively narrow space between the transport path 2 and the magnetic field generation unit 3. It becomes possible to provide.

  The end of the flexible substrate 6 on the side of the detection unit 7 is divided into a plurality of connection pieces 61 by forming a cut or a cut out portion. Each connection piece 61 is connected to the detection unit 7 via an individual connector 71. That is, by connecting the plurality of connection pieces 61 to the detection unit 7, the plurality of Hall elements 4 can be collectively connected to the detection unit 7 using one flexible substrate 6. There is. Furthermore, when the end of the flexible substrate 6 on the side of the detection unit 7 is divided, deformation due to thermal expansion is less likely to occur than in the case where the flexible substrate 6 is not divided. As a result, the influence of the deformation of the end on the end on the opposite side (Hall element 4 side) can be suppressed, so that the positional deviation of each Hall element 4 due to the deformation of the flexible substrate 6 is unlikely to occur. In this example, the end of the flexible substrate 6 is divided into three connection pieces 61. However, the present invention is not limited to this. The flexible substrate 6 may be divided into two connection pieces 61, or four or more connection pieces 61. It may be divided.

  The holding case 8 is a housing that holds the magnetic field generation unit 3, the Hall element 4, the holding substrate 5, and the flexible substrate 6. The magnetic field generation unit 3, the Hall element 4 and the holding substrate 5 are fixed by the holding case 8 so that their positional relationship does not move in a substantially sealed state. The flexible substrate 6 is adhesively fixed to the holding case 68 fixed to the magnetic field generation unit 3, the Hall element 4 and the holding substrate 5. This adhesion fixing is performed using a material containing an epoxy resin such as an epoxy adhesive.

  The magnetic field generator 3 and the holding substrate 5 are connected by the holding case 8. In this example, connecting members 81 are provided at both ends in the width direction D2 of the magnetic field generating unit 3, and the holding case 8 and the holding substrate 5 are connected to both ends in the width direction D2 by the connecting members 81. Specifically, the connecting member 81 is a protrusion that protrudes from the holding case 8 toward the holding substrate 5, and positioning holes 52 are formed at both ends of the holding substrate 5 at positions facing each protrusion.

  Thus, the holding substrate 5 can be easily positioned with respect to the magnetic field generation unit 3 only by inserting the connecting member 81 into the positioning hole 52 formed in the holding substrate 5. In particular, in the case where the plurality of Hall elements 4 are held by the holding substrate 5 as in the present embodiment, the positioning of each Hall element 4 can be performed easily and accurately only by positioning the holding substrate 5. As it can, the assembly operation can be simplified.

  The number of connection members 81 is not limited to two, and three or more may be provided. Further, the connecting member 81 is not limited to the configuration in which the connecting member 81 is connected to the connecting member 81 at both end portions in the width direction D2 at one end portion of the holding substrate 6, and the holding substrate 5 is placed at other positions such as the center portion in the width direction D2. The connection member 81 may be configured to be connected. Furthermore, the connection member 81 is not limited to the configuration provided in the holding case 8, and may be provided, for example, in the magnetic field generation unit 3 or may be provided in another member.

  The protective cover 9 is a cover that protects the Hall element 4 from the medium S or the like conveyed into the conveyance path 2 and is made of a nonmagnetic material (for example, phosphor bronze). The spacer 10 and the attachment 11 are made of a nonmagnetic material for preventing the protective cover 9 from being deformed by the medium S conveyed into the conveyance path 2. The spacer 10 is configured higher than the Hall element 4 so that the Hall element 4 does not contact the protective cover 9 by the medium S conveyed into the conveyance path 2, and the spacer 10 and the holder 10 are not received vibration due to the conveyance of the medium S The substrate 5 is fixed by an elastic double-sided tape. Here, the elastic double-sided tape is only an example of the elastic member, and other elastic members can be used. Further, the flexible substrate 6 is sandwiched and fixed by the holding case 8 and the attachment 11. The magnetic flux density at the interface between the protective cover 9 and the medium S at the top of each Hall element 4 is 100 mT or more, preferably 150 mT or more. Thereby, the magnetization intensity of the magnetic body (magnetic image M) of the medium S can be determined.

  FIG. 5A is a schematic plan view showing the holding substrate 5 in a partially enlarged manner. FIG. 5B is a schematic bottom view of the holding substrate 5 of FIG. 5A. As shown in FIGS. 5A and 5B, circuit patterns 53 and 54 are formed on the front and back surfaces of the holding substrate 5. Circuit patterns 53 and 54 are formed on the surface of the holding substrate 5 at the mounting positions of the Hall elements 4, and the Hall elements 4 are mounted on the circuit patterns 53 and 54. The circuit pattern 53 is a signal pattern from the Hall elements 4 and extends from the output of each Hall element 4 to the connector 51 mounted on the holding substrate 5, and the flexible substrate 6 is attached to the connector 51.

  The circuit pattern 54 is a power supply pattern that applies a constant voltage to the Hall element 4, is routed by the circuit pattern 54 on the back surface from the connector 51 mounted on the holding substrate 5, and passes through the through-hole hole 55 of the holding substrate 5. Then, it is connected to the circuit pattern 54 on the surface. The power sources of all the Hall elements 4 are connected in parallel.

  In this example, the front surface is connected by a signal pattern and the back surface is connected by a power supply pattern. However, the configuration is not limited to this, and the circuit pattern 54 may be divided. In this embodiment, the Hall elements 4 are connected in parallel at a constant voltage. However, the power supply pattern of each Hall element 4 may be connected in series by using a power source that supplies a constant current.

  In the above description, the configuration in which the plurality of Hall elements 4 are held by the holding substrate 5 has been described. However, deformation in which the holding substrate 5 and the flexible substrate 6 are integrated can be easily considered. The flexible substrate 6 is generally constituted by one coated with polyimide, but in this case, for example, it is formed not by polyimide but by a solder resist with a small thermal expansion around each Hall element 4 May be By forming the periphery of the Hall element 4 with a solder resist, a positional shift around the Hall element 4 due to a temperature change is less likely to occur. Such easily conceivable variations should also be included in the present invention.

  According to the above description, a large number of small Hall elements 4 can be accurately arranged at a fine pitch, and even if the number of input / output terminals of the hall elements 4 and the detection unit 7 increases, the compact connection can be achieved. The magnetic line sensor 1 can be manufactured in which the distance between the magnetic field generator 3 and the transport path 2 and the Hall element 4 is as short as possible. Thereby, the sensitivity of the Hall element 4 is increased, and the magnetic image M included in the medium S can be detected with high resolution and high accuracy.

<Magnetic image detection method>
As a basic requirement for detecting a two-dimensional magnetic image M, in order to detect a magnetic field change in a direction orthogonal to the transport direction D1 of the medium S without gaps, the plurality of Hall elements 4 in the transport direction D1. It is necessary to arrange in the orthogonal direction at a pitch approximately equal to the magnetic field detection range of the Hall element 4 in that direction. The magnetic line sensor 1 of the present invention described above already satisfies this condition.
Furthermore, in order to detect the change in the magnetic field in the transport direction D1 of the medium S without gaps, the imaging operation by the Hall element 4 is substantially performed with the period during which the medium S passes the magnetic field detection range in the transport direction D1 of the Hall element 4 It is necessary to continuously repeat this cycle or a cycle of an integral fraction of this cycle. Such a circuit is basically the same as the circuit in the conventional optical image detection apparatus for detecting a continuous optical image, and thus is well known to those skilled in the art and detailed description will be omitted.
In order to increase the resolution of the magnetic image M, both the magnetic field detection range in the conveyance direction D1 of the Hall element 4 and its orthogonal direction (main scanning direction) D2 must be made smaller. Generally, the magnetic field detection range is small. As the sensitivity and the S / N ratio of the Hall element 4 decrease as much as possible, 25 to 50 dpi (0.5 to 2 elements / mm) is considered to be an appropriate pitch in consideration of the cost of the magnetic line sensor 1 and the obtained output. .
Using the magnetic line sensor 1 and the detection method of the magnetic image M described above, the magnetic image M of a bill such as a dollar, ruble, original, or euro was detected at conveying speeds of 1600 mm / sec and 4000 mm / sec. As a result, the resolution hardly changes depending on the transport speed. For example, the distribution of small circular marks in a magnetic thread, the numbers and characters printed with magnetic ink, and the design of a structure etc. and its shade etc. are continuously , For example, could be detected clearly at a resolution of about 25 dpi.

DESCRIPTION OF SYMBOLS 1 Magnetic line sensor 2 conveyance path 21 upstream conveyance roller 22 downstream conveyance roller 23 sensor opposing roller 3 magnetic field generation part 4 hall element 5 holding substrate 6 flexible substrate 7 detection part 8 holding case 9 protective cover 10 spacer 11 attachment 40 sensor part (hole Element array)
51 connector 52 positioning hole 53 signal pattern 54 power supply pattern 60 connecting portion 61 connecting piece 71 connector 81 connecting member

Claims (8)

A magnetic line sensor for directly detecting a two-dimensional magnetization density pattern corresponding to the magnetization intensity of a medium containing a magnetic material printed on a paper sheet,
A Hall element array in which a plurality of Hall elements are arranged in a direction perpendicular to the moving direction of the medium, and a rod-like plastic magnet continuous under the Hall element array, and the magnetism directly above the Hall element array It has a structure to detect information,
The Hall element is composed of a single crystal thin film made of an indium / antimony compound semiconductor film formed on a substrate,
A magnetic line sensor characterized in that the Hall sensitivity of each Hall element is 6 mV / mT or more, the direct current resistance is 70 Ω or more, and the arrangement pitch of each Hall element is 0.5 pieces / mm or more.   The magnetic line sensor according to claim 1, wherein the Hall sensitivity of each Hall element is 8 mV / mT or more.   3. The magnetic line sensor according to claim 1, wherein the direct current resistance of each hall element is 100Ω or more.   The magnetic flux density of the interface in contact with the medium at the upper portion of the Hall element of the Hall element array is 100 mT or more, and the magnetization intensity of the magnetic body of the medium can be determined. The magnetic line sensor according to item.   The magnetic line sensor according to any one of claims 1 to 4, wherein the magnetic powder of the plastic magnet is a rare earth cobalt alloy nitride powder.   The magnetic line sensor according to claim 5, wherein the magnetic powder of the plastic magnet is samarium cobalt nitride powder.   7. The magnetic line sensor according to claim 5, wherein 70% by weight or more of magnetic powder is contained in the plastic magnet, and the magnetization axis of each of the powder particles is oriented in a predetermined direction. A magnetic line sensor according to any one of claims 1 to 7,
And a conveying path for conveying the medium immediately above the Hall element array.

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