JP4508675B2 - How to read paper with magnetic material - Google Patents

Description

This invention relates to method of reading magnetic necessity paper. More particularly, to magnetic necessity paper reading method comprising crowded liked magnetic threads being formed by stacking two kinds of magnetic material having different coercive forces. By combining two kinds of magnetic materials having different magnetic characteristics, authenticity can be determined by a special reading method, and security can be improved.
There are various methods for reading such paper with magnetic materials such as license, passport, resident registration card, identification card, credit card and prepaid card, gift certificate, stock certificate, gift certificate, ticket, voting ticket, ticket, label, etc. Can be used for security media.

As a measure for preventing counterfeiting of various security media, there is a method of winding a magnetic thread into a sheet. Since the magnetic thread is inserted into the paper with the magnetic material in the paper manufacturing stage, it is difficult to forge by color copying, scanner taking, plate making printing, or the like.
There are Patent Document 1 and Patent Document 2 as techniques for inserting a magnetic thread into a sheet and performing a true / false determination with a dedicated reader. Both relate to anti-counterfeit thermal paper and ticket paper in which thread elements coated with a magnetic film are embedded.
These are ones in which one type of magnetic thread is embedded in a strip on a ticket, and a unique magnetic characteristic is read and determined by a dedicated magnetic head. However, since there is one detection method for one type of thread, there is a problem that the authenticity determination method is simplified.

In addition, Patent Document 3 discloses a unique magnetization in which an irregular magnetic change occurs in each period of the excitation magnetic field in a region where the large Barkhausen phenomenon occurs immediately before the saturation magnetization region with respect to the excitation magnetic field in which the magnetic field strength periodically changes. A reading method using a ferromagnetic material that generates noise has been proposed.
Patent Document 4 also proposes a method of changing the excitation magnetic field and analyzing the frequency component of the magnetic hysteresis characteristics. The magnetic material is peculiar and security is considered high.
However, these have complicated determination processing, and there is a problem that the production of such a special magnetic material is expensive.
Patent Document 5 describes an anti-counterfeit paper in which a thread formed by laminating two ferromagnetic layers is formed on a base paper, but its reading method is not particularly devised. .

JP 2001-315478 A JP 2001-316998 A Japanese Patent Laid-Open No. 11-16110 JP-A-8-199498 JP 2002-242097 A

  Thus, the present invention has been completed by studying the form of a magnetic material-containing paper whose reading of magnetic properties is not simplified and its reading method.

In order to solve the above problems, the present invention includes a magnetic material formed by interposing a magnetic thread formed by laminating two kinds of magnetic materials having coercive forces Hc1 and Hc2 and Hc1 ≧ 2 × Hc2. A method for reading a sheet, wherein a magnetic field that changes in time series in a range in which the amplitude of an excitation magnetic field of a magnetic head is larger than Hc1 and smaller than Hc2 is applied to the magnetic thread, and the detection coil of the magnetic head An irregular signal corresponding to the excitation magnetic field is caused to appear, and authenticity is determined based on the signal, whereby a magnetic material-containing paper reading method is provided .

The magnetic paper used in the reading method of the present invention has a magnetic thread formed by laminating two types of magnetic materials having a squareness ratio of 0.4 or more and different coercive forces. Therefore, it is difficult to manufacture the magnetic material-containing paper itself, which has a remarkable anti-counterfeit effect.
In the method for reading a sheet with magnetic material according to the present invention, when the reading is performed by a reader, the excitation magnetic field of the magnetic head is not a sine wave or rectangular wave having a constant amplitude, but a waveform in which the excitation magnetic field changes in time series. An irregular signal according to the excitation magnetic field can be obtained, and authenticity determination can be ensured.

The magnetic material-containing paper of the present invention relates to a paper obtained by winding a magnetic thread into a base paper.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a paper containing magnetic material according to the present invention, FIG. 2 is a perspective view showing a magnetic thread used for the paper containing magnetic material, and FIG. 3 is a diagram showing a hysteresis curve of the magnetic material. 4 is a diagram showing a state in which a magnetic thread is fed into a sheet, and FIG. 5 is a diagram showing a paper storage tank at the time of winding.

1A and 1B are diagrams showing an embodiment of a sheet containing magnetic material according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line AA in FIG. is there.
As shown in FIG. 1, the magnetic material-containing sheet 1 of the present invention has one magnetic thread 2 inserted therein, but it may be two or more. In the case of FIG. 1 (A), the magnetic thread 2 is made visible by the exposed portion (window) 11 provided periodically, but the exposed portion may not be present.
As shown in the cross-sectional view of FIG. 1B, the magnetic material-containing paper 1 has a two-layer structure of a paper material, and a magnetic thread 2 is inserted between the first layer 1a and the second layer 1b. ing.
Since the magnetic thread 2 is drawn at the paper making stage, it is usually inserted in a straight line parallel to the paper making direction.

The magnetic thread 2 used for the magnetic material-containing paper 1 of the present invention is obtained by forming a magnetic layer on a resin film substrate.
FIG. 2 is a perspective view showing the magnetic thread, and a cross section is shown at the end in order to show the layer structure of the thread.
As shown in FIG. 2, in the magnetic thread 2, two types of magnetic layers 22 and 23 having different coercive forces are formed on a base material 21 made of a resin film by a vacuum film forming method, a coating method, or a printing method.
As the vacuum film forming method, vapor deposition, sputtering, ion plating, or the like can be used. As the coating method, various coating methods such as roll coating or gravure coating can be used. Moreover, offset printing, gravure printing, etc. can be used as a printing method. In the case of vacuum film formation, the thickness is a thin film of 1 μm or less, usually 10 nm to 300 nm, whereas in the coating method or printing method, the film thickness is 0.3 μm to 30 μm after drying, Is usually 1.0 μm to 10 μm.

  There is preferably a non-magnetic layer 24 between the magnetic layers 22 and 23, and the layer is also formed by an equivalent means. The nonmagnetic material layer 24 is effective for relaxing the interaction between a plurality of magnetic layers. The nonmagnetic layer 24 is necessary particularly when the plurality of magnetic layers are thin films formed by vacuum film formation. When the magnetic layer is formed only by a coating method or a printing method, or when the magnetic layer is formed by a coating method, a printing method, and a vacuum film forming method, the nonmagnetic material layer can be omitted. This is because the resin material contained in the printing ink serves as a non-magnetic layer.

  The coercive forces Hc1 and Hc2 of the magnetic layers 22 and 23 of the magnetic thread 2 can have various coercive force combinations by using different coercive forces. When reading with a magnetic head, different peak waveforms can appear due to different coercive forces, which is highly effective in preventing counterfeiting. The squareness ratio of the magnetic material is preferably 0.4 or more.

In addition, an adhesive layer is formed on the surface of the base 21 on which the magnetic layer is not formed or the outermost surface of the magnetic layer, if necessary. This brings about the effect which raises adhesive force, when it crawls into a base paper and it is set as the paper containing a magnetic body. In the case of FIG. 2, only the adhesive layer 25 on the lower surface side of the substrate 21 is shown.
The width W of the magnetic thread 2 is not particularly limited, but is generally about 0.2 mm to 5.0 mm depending on the purpose of use of the paper 1.

As the resin film substrate 21, a solvent-resistant and heat-resistant resin film can be used. In general, other polyester resin films such as a polyethylene terephthalate (PET) resin film, a polyamide resin film, a polyimide resin film, Examples include polycarbonate resin films, polystyrene resin films, polypropylene resin films, polysulfone resin films, polyphenylene sulfide resin films, cellulose resin films, and polyethylene naphthalate (PEN) resin films.
As thickness of the resin film base material 21, about 4-20 micrometers is preferable.

The total thickness of the magnetic thread 2 is suitably about 5 to 100 μm, but is more preferably about 10 to 25 μm in consideration of the workability of the magnetic film and the degree of swelling when embedded in the paper. That is, if the thickness is less than 4 μm, it is difficult to apply coating or the like in terms of machinability, and if the thickness exceeds 25 μm, unevenness occurs when embedded in thin paper. The width of the magnetic thread 2 is preferably in the range of 0.3 to 4 mm, and more preferably 0.5 to 1.5 mm from the viewpoint of easy detection of magnetic properties. The thickness of the paper to be rolled in is required to be about three times the thickness of the thread.
Although the detection of the magnetic characteristics depends on the size of the head gap of the magnetic head, even if the paper thickness is up to about 150 μm, there is no problem from both the front and back sides.

FIG. 3 is a diagram showing a hysteresis curve of a generally well-known magnetic material. Bm is the saturation magnetic flux density, Br is the remaining magnetic flux density, and Hc is the holding force. The squareness ratio Rsq is
Rsq = Br (residual magnetic flux density) / Bm (saturated magnetic flux density).
The magnetic material used in the present invention is preferably a ferromagnetic material. However, the magnetic material is not limited to one having an extremely high squareness ratio, and one having a squareness ratio in the range of about 0.4 to 1.0 can be selected and used. . Moreover, it is necessary to use a thing with a different coercive force. In the case of FIG. 3, the magnetic body 1 has a coercive force Hc1, and the magnetic body 2 has a smaller coercive force Hc2.
The ferromagnetic material used in the present invention has an Hc (coercive force) of 40 to 8000 A / m (0.5 to
100 oersted) and Rsq (square ratio) are preferably 0.4 to 1.0.

Next, when the ferromagnetic layer 22 is formed by a vacuum film forming method, it may be crystalline or amorphous, and any one of iron (Fe), cobalt (Co), and nickel (Ni). Alternatively, a magnetic material composed of a combination of two or more types is used as a main component, and boron (
B), carbon (C), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), titanium (Ti), vanadium (V), chromium (Cr), manganese ( Mn), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (Pd), silver (Ag), indium (In), tin ( Consists of additives of several metals or non-metallic elements selected from Sn, tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), gold (Au), lead (Pb) ing.

In the case of the vacuum film-forming method, the ferromagnetic layer is formed by vapor deposition, sputtering, ionization using a material composed of an alloy composed of iron, cobalt, nickel as a main component and an additive element or a mixture thereof as a target material or a vapor deposition source. It is formed by a film forming method using a vacuum process such as plating. In the case of the vacuum film formation method, the thickness is a thin film of 1 μm or less, usually 10 nm to 300 nm.
The reason why the layer thickness of 10 nm is the lower limit in the vacuum film formation method is that the magnetic layer 22 is thin, so that the saturation magnetic flux decreases with a decrease in the absolute amount of the magnetic material, and the magnetic signal becomes small. This is because the thickness of the magnetic material is required to be 10 nm or more in order to obtain a magnetic signal used for authenticity determination. The reason why the upper limit is 300 nm is to make a clear distinction from a magnetic layer (usually having a thickness of 1 μm or more) produced by another method, and it is preferable to avoid increasing the thickness further. . Furthermore, if the thickness is greater than this, the characteristics of the magnetic thread may deteriorate due to curling due to internal stress of the film, and wrinkles and cracks may occur.

Next, when the magnetic layer 22 is formed by a coating method, the ink used here includes a magnetic substance as a pigment, and is composed of a binder and a solvent for dispersing the pigment. When formed by a printing method, an offset ink using a magnetic substance as a pigment and using an oxidation polymerization type or ultraviolet curable resin can be used.
As the magnetic material, powder having a wide particle diameter from 10 nm to several tens of μm can be used. The particle size is preferably several μm or less in view of application suitability and printability. There is no problem with the shape of the powder as long as the powder is within the above particle size range and the magnetic properties, application suitability, and printability are maintained. In the case of the coating method and the printing method, the film thickness of 0.3 μm is the lower limit because it is a limit for stably mechanically attaching a layer having a uniform thickness, and the upper limit of 30 μm is that This is because stable application is difficult and not necessary.
The magnetic material may be metal powder, oxide powder, nitride powder, or oxynitride powder. In the case of using metal powder, the same material as that formed by the above vacuum film forming method may be used. In the case of an oxide or nitride ferromagnet, the above metal oxide or nitride compound is used.

For the nonmagnetic layer 24, a nonmagnetic metal or nonmetal can be used. For example, aluminum (Al), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), gold (Au), silicon (Si), titanium (Ti), vanadium (V), Chromium (Cr) or an alloy thereof, or an oxide, nitride, or oxynitride powder thereof can be used.
When the magnetic layer 22 is formed by printing, the binder of the printing ink also serves as the nonmagnetic material layer, so there is no need to separately provide the nonmagnetic material layer 24 adjacent to the printing layer.

The adhesive layer is used to increase the adhesive strength with the paper when the magnetic thread 2 is rolled into the paper containing the magnetic material. The adhesive layer is a contact made of a water-soluble binder having a heat melting temperature of 60 to 80 ° C. The agent layer 25 can be provided on the back surface of the substrate 21, the upper surface (front surface) of the ferromagnetic layer, or both. Alternatively, it may be a hot melt adhesive having a heat melting temperature of 60 to 80 ° C.
An adhesive made of starch, casein, carboxymethyl cellulose (CMC), or the like, which is water-soluble, can also be used.
The coating thickness may be within a few μm.

Next, the manufacturing state of the paper with magnetic material will be described.
Such a paper containing a magnetic material can be made by a two-tank type circular paper machine.
FIG. 4 is a diagram showing an apparatus for winding a magnetic thread into a sheet, which is a case of using a two-tank type circular net paper machine. FIG. 5 is a diagram showing the paper stock tank at the time of pouring.
The circular net paper machine makes paper by drawing paper stock from a tank onto a rotating cylindrical wire mesh surface immersed in a pulp tank. If the tape is affixed to the wire mesh surface at a predetermined size and interval to close the mesh, the exposed portion (window) of the thread can be formed.

The paper machine 100 includes a wire part 110, a press part 130, a dryer part 140, and a reel part 150.
The wire part 110 is a part that winds the magnetic thread 2 at the same time as making paper. The press part 130 is a part for compressing and dewatering the stacked paper, the dryer part 140 is a part for drying the paper after paper making, and the reel part 150 is a part for winding up the paper.

As shown in FIG. 4, the wire part 110 includes a first circular net 114 arranged in a column and a first paper tank 111 that holds the first circular net 114, a second circular net 115, and a second circular net that holds the first circular net 114. It is composed of a paper tank 112, and squeezing rollers 104 and 105 provided via respective circular nets and felt 117.
A thread unwinding device 121 is provided between the first paper tank 111 and the second paper tank 112.

As shown in FIG. 5, the first circular net 114 is rotatably supported by the first paper stock tank 111 and is in contact with the pressing roller 104 with the felt 117 interposed therebetween. The first paper stock tank 111 has a housing shape with an open top, and includes a semi-cylindrical wall portion 51 that rotatably accommodates the first circular net 114, and a paper stock wall 52, 53 is formed, and a paper supply port 54 is formed.
The first circular net 114 is a cylindrical cylinder. The mesh is formed by a known method such as spirally winding a wire around a support rod passed to the peripheral edge of the cylinder.
The relationship between the second circular net 115, the second paper tank 112, the felt 117, and the pressing roller 105, the third circular net 116, the third paper tank 113, the felt 117, and the pressing roller 106, This is the same as above.

  Next, a process of manufacturing a base paper using the above circular paper machine 100 and winding a magnetic thread will be described with reference to FIGS. 4 and 5.

As shown in FIG. 5, the first stock tank 111 is supplied with a stock prepared by adjusting necessary additives such as a pulp raw material, an acidic sizing agent, and water from a stock supply port 54. The supplied paper material flows between the first circular net 114 and the semi-cylindrical wall portion 51 over the paper material wall 53, passes through the paper material wall 52, and is discharged from a paper material discharge port (not shown). Reflux as necessary. When the first circular mesh 114 is rotated by a driving device (not shown), the stock is filtered by the mesh.
Thereby, pulp raw materials etc. stop on a mesh, water flows in into the cylinder of the 1st circular mesh 114, and the 1st wet paper web layer is formed on a mesh.
At this time, if the tape is affixed to the cylindrical metal mesh surface of the circular mesh at a predetermined size (for example, 10 mm × 10 mm) and an interval (for example, an interval of 20 mm) and the mesh is closed, the exposed portion of the thread (window ) Can be formed.

The place where the first web 114 rotates and the first wet paper layer rises from the liquid surface of the paper is squeezed by the squeezing roller 104 through the felt 117, and the first wet paper layer is transferred to the felt 117. . As described above, the first wet paper web layer formed on the first circular mesh 114 is transferred to the felt 117 by the squeezing roller 104, and then the second circular mesh together with the felt 117 that moves by the rotation of the roller 118. 115.
When the first wet paper layer moves to the felt 117, the magnetic thread is supplied from the thread unwinding device 121 in accordance with the position of the exposed portion (window) on the wet paper.
The second stock tank 112 is also supplied with the same stock as the first stock tank 111 and is driven in the same manner as the first stock tank.

  Then, the second wet paper layer formed on the mesh of the second circular mesh 115 is squeezed by the squeezing roller 105 through the felt 117, and the first wet paper web is squeezed through the felt 117. The second wet paper web layer is laid over the layer (on the second circular mesh 115 side).

The wet paper layer in which a plurality of layers are wound together circulates in a state of being attached to the felt 117, is transferred to the next felt 131, and is guided to the press part 130. In the press part, the wet paper web layer is compressed and dehydrated when moving between the pair of press rollers.
Next, the wet paper layer guided to the dryer part 140 is dried by moving on a dryer cylinder (not shown), and wound up by a winding roller to obtain a sheet.
As described above, the production of the paper with a magnetic material according to the present invention is not limited to the one using a circular net-making machine. It can also be manufactured by a method of laminating. Therefore, it is not limited by the manufacturing method.

Next, a method for reading a sheet containing magnetic material according to the present invention will be described.
FIG. 6 is a diagram illustrating the reading device, FIG. 7 is a diagram illustrating a reading state, and FIG. 8 is a diagram illustrating a chart example in which a sheet containing magnetic material is read.
The reading device of FIG. 6 shows a device that detects by comparing the output waveform of the reference coil 44 with the output waveform of the detection coil 43 by passing a current (5 to 10 kHz, 2 to 5 Vpp) through the exciting coil 42. Is preferably used.

When reading a sheet containing magnetic material, the magnetic characteristics are measured by applying the magnetic head 45 to the side close to the surface of the paper layer 1a of the magnetic thread 2 as shown in FIG. At this time, an excitation magnetic field in which the amplitude from the head gap 41 changes in time series is applied to the magnetic thread 2.
The fact that the amplitude changes in time series means that the peak value of the excitation magnetic field waveform is not constant and changes with respect to the time axis, as shown in FIG. This is because the amplitude of the exciting magnetic field can be changed continuously by changing the amplitude of the current flowing through the exciting coil of the magnetic head 45 in time series.
The magnetic film A and the magnetic film B are magnetized according to the change of the excitation magnetic field, but the point is to make the intensity of the excitation magnetic field larger or smaller than the coercive force of each magnetic layer. That is, by changing the magnitude of the exciting magnetic field, it is possible to selectively obtain the output from each layer, and determine whether the obtained output pattern matches the normal output.

Hereinafter, the principle of obtaining the above signal will be described with reference to FIGS. As shown in FIG. 6, the magnetic head 45 includes three coils (excitation coil 42, reference coil 44, and detection coil 53). As shown in FIG. 7, this magnetic head is fixed on the magnetic films A and B, an alternating current whose amplitude is changed is applied to the exciting coil 42, and an alternating exciting magnetic field H is applied through the head gap 41. .
The magnetic flux density of each magnetic layer changes nonlinearly with respect to the alternating magnetic field, and the change in the magnetic flux density is detected by the detection coil 43 and the reference coil 44 of the magnetic head. When N is the number of turns of the coil, μo is the magnetic permeability in the atmosphere, and μe is the magnetic permeability of the magnetic layer,
The voltage Ve detected from the detection coil 43 is
Ve = −d / dt (N · ∫ (μe + μo) HdV) (1)
It becomes. On the other hand, the voltage from the reference coil 44 is
Vo = −d / dt (N · ∫ (μo · HdV) (2)
It has been adjusted to be. Taking the difference between the sensing coil and the reference coil,
(1)-(2) Ve−Vo = −d / dt (N · ∫ (μe · HdV) (3)
The change in magnetic flux density from the magnetic films A and B can be detected according to the change in the alternating magnetic field.
When the squareness ratio of the film is high, a sharp pulse is observed in synchronism with the period of the exciting AC magnetic field.
For example, in FIG. 8 (A), the magnetic film A, the excitation magnetic field exceeds the coercive magnetic force B is applied, the output signal of Ve-Vo is, as shown in FIG. 8 (B), has two peaks Waveform is observed. Also the application of a coercive magnetic force following excitation field of the magnetic film magnetic film exceeds the coercive magnetic force of A B, the output signal of Ve-Vo is not observed only waveform having one peak.

The output signal Ve-Vo will be described in more detail with reference to FIG.
FIG. 8A shows the waveform of the excitation magnetic field, and FIG. 8B shows the output waveform of the difference between the detection coil 43 and the reference coil 44. Magnetic film A shown in FIG. 8, if the B excitation field not exceeding any of the coercive magnetic force is applied, the output signal is not detected as shown in FIG. 8 (B) ( "no output").
Magnetic film A, if large excitation field than any of the coercive magnetic force B is applied, the output signal having two peaks are detected ( "output A + B") The coercive magnetic magnetic film A beyond the force, and the output signal excitation field does not exceed the coercive magnetic force of the magnetic film B is applied not only observed waveform having one peak ( "output a").

    As described above, in the reading method of the present invention, the appearance state of the peak waveform varies depending on the intensity of the excitation magnetic field. Therefore, if a magnetic material having a different coercive force is used, a unique peak can appear.

<Production of magnetic thread>
Embodiments of the present invention will be described below with reference to the drawings.
(Magnetic thread)
As the film base 21 of the magnetic thread, a polyethylene terephthalate film (“Lumirror S-28” manufactured by Toray Industries, Inc.) [thickness: 16 μm] having good smoothness is used. A Si-based magnetic film (square ratio 0.8, coercive force 1600 A / m) A was formed by a vacuum film formation method to a film thickness of 150 nm.
Subsequently, a magnetic film (square ratio 0.4, coercive force 3200 A / m) B having the following ink composition is coated on the first magnetic layer so as to have a film thickness of 8 μm by a gravure coating method. did. In addition, before the magnetic substance ink just after application | coating dried, a DC magnetic field was applied and the magnetic body was orientated. Finally, it was cut using a slitter machine to finish a magnetic thread having a width of 2 mm.

[Ink composition]
Granules: Permalloy (iron Fe-nickel Ni alloy)
(Scalar particles having an average particle length of 2 μm and an aspect ratio of 3) 36 parts by weight Binder; Urethane resin 12 parts by weight Colorant; Carbon 2 parts by weight Solvent; Toluene 20 parts by weight
MEK 15 parts by mass
MIBK 15 parts by mass Isocyanate-based curing agent 2 parts by mass

<Preparation of paper with magnetic material>
Using the circular net paper machine shown in FIG. 4 and FIG.
As shown in FIG. 1, the magnetic thread 2 is taped to a cylindrical metal mesh so that the exposed portion 11 is repeated at a size of 15 mm × width of 10 mm and the covering portion is repeated at a pitch of 15 mm so that the magnetic thread 2 appears on a sheet containing magnetic material. The machine was rolled into high-quality paper of 90 kg / sixth edition.

Using the apparatus shown in FIG. 6, an excitation magnetic field whose amplitude changes in time series was applied to the thread portion of the magnetic material-containing paper of the completed example, and the output signal was measured.
In the case of the example, there are a peak with an excitation magnetic field strength amplitude of 1600 A / m or less, a peak exceeding 1600 A / m and less than 3200 A / m, and a peak exceeding 3200 A / m as shown in FIG. A current was supplied to the exciting coil 42 so as to be obtained. The differential output between the detection coil 43 and the reference coil 44 is the output signal, and the waveform shown in FIG. 8B is obtained.

It is a figure which shows the Example of the paper with a magnetic body of this invention. It is a perspective view which shows the magnetic thread | sled used for the paper containing a magnetic body. It is a figure which shows the hysteresis curve of a magnetic body. It is a figure which shows the state which winds a magnetic thread | yarn into a paper. It is a figure which shows the paper supply tank at the time of papering. It is a figure explaining a reader. It is a figure which shows the state which reads the paper containing a magnetic body. It is a figure which shows the chart example which read the paper containing a magnetic body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic sheet 2 Magnetic thread 21 Base material 22, 23 Magnetic layer 24 Nonmagnetic layer 25 Adhesive layer 41 Head cap 43 Detection coil 44 Reference coil 45 Magnetic head 100 Paper machine 104, 105 Squeeze roller 114 1st circle Net 115 Second circular net 111 First paper tank 112 Second paper tank 117 Felt 121 Thread unwinding device

Claims (1)

A method of reading a paper containing magnetic material, in which magnetic threads formed by laminating magnetic materials of two kinds of coercive forces Hc1 and Hc2 are wound , Hc1 ≧ 2 × Hc2, and the squareness ratio is A magnetic field that changes in time series in a range in which the amplitude of the excitation magnetic field of the magnetic head is larger than Hc1 to a range smaller than Hc2 is applied to the magnetic thread that is 0.4 or more, and excitation is performed on the detection coil of the magnetic head. An irregular signal corresponding to a magnetic field appears and authenticity is determined based on the signal, and a method for reading a sheet containing magnetic material is provided.

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