JPH1116110A - Information recording medium and apparatus for deciding authenticity thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an information recording medium having high safety by sticking, printing or embedding a ferromagnetic material alone which has a specific magnetization noise characteristic in a region where a large Barkhausen phonomenon just before a saturation magnetization region occurs with respect to an excitation magnetic field periodically changing in the intensity of a magnetic field or a small piece, wire-shaped, film-shaped or powdery body thereof stuck to a resin, etc., to a paper or resin substrate. SOLUTION: A ferromagnetic material piece is embedded in the paper of a bond 5. A ferromagnetic material filament 4 is formed by applying a ferromagnetic material on a chemical resin, such as polyethylene, and is capable of recording data having meanings. The ferromagnetic material is an amorphous alloy consisting of COx Zry M1z M2 (1-x-y-z) material. M1 is a transition metal selected from Ti, Cr, Mn, Fe, Ni, Cu, M2 is a transition metal selected from Mo, Nd, Tc, Ag or a nonmetal alloy selected from Si, Be, Se, Sb and (x), (y), (z) are compounding ratios. A thin film made amorphous by a sputtering process is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, such as securities or cards, which requires forgery prevention and a device for judging the authenticity thereof.

[0002]

2. Description of the Related Art Conventionally, as countermeasures against counterfeiting of securities and cards, special printing techniques, such as hologram printing, which are generally difficult to forge, bar codes and patterns printed with magnetic ink, ultraviolet rays, infrared rays, etc. Known are those using printing with a reactive special ink and those employing a configuration in which a resin piece, a thread, or a metal piece is embedded in paper or resin. In order to determine the authenticity of such a specially printed information recording medium, a method of visually comparing the information recording medium with a genuine product, a method of detecting the amount of reflection and absorption from ink by irradiating ultraviolet rays and infrared rays, There are known a method of detecting an absorption amount, a method of detecting a magnetic amount or a pattern applied by a magnetic sensor, and the like.

[0003] Further, the present invention uses a structure in which safety assurance data is stored using a ferromagnetic foil or thread in a safety filament previously proposed by the inventors of the present invention. There is a method for judging the authenticity of security paper by using unique magnetic characteristics (Japanese Patent Laid-Open No. 7-32778, "Security paper and its authenticity determination device"). When a ferromagnetic material is used as a part of an information recording medium, a change in magnetic strength or a change in magnetic characteristics due to heat, slit width, etc. is detected by a magnetic head or a magnetic coil and the change is used as meaningful data. (Japanese Unexamined Patent Publication No. Hei 8-127997, "Safety protection paper and its authenticity determination device"). Further, as one of the methods for determining the unique magnetic characteristics of the ferromagnetic material, there is also a method of determining the authenticity using the magnetic hysteresis characteristics of the ferromagnetic material due to the change in the intensity of the exciting magnetic field (Japanese Patent Laid-Open No. Hei 8-199498). "Safety protection paper and its authenticity determination device").

[0004]

Problems to be Solved by the Invention
In the issue of “Safety protection paper and its authenticity judgment device”, a special alloy ratio and a special manufacturing method are used to embed ferromagnetism that is formed to have unique magnetic properties that cannot be easily forged, so that paper can be safely protected. It is shown that if a protective paper is made, a genuine product and a counterfeit product can be easily distinguished by examining the magnetic hysteresis characteristics of the embedded ferromagnetic material based on the change in the exciting magnetic field strength. In this case, the magnetic material used for preventing forgery has a unique magnetic characteristic that is not common, and the more the detection means is more specific, the higher the security can be. From this point of view, those using the magnetic hysteresis characteristic have high security with a special alloy ratio and a special manufacturing method, but the magnetic hysteresis characteristic itself is generally known in a dedicated magnetic characteristic measuring device. Can be measured as magnetic properties
It can be a clue to forgery. Therefore, unless it is a magnetic material that is generally rarely used and has unique magnetic characteristics and cannot be determined without special detection means, the information recording medium to be used is We cannot increase safety. Conventionally, no magnetic material that sufficiently satisfies such conditions has been provided.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides an extremely high-security information recording medium and a device for judging the authenticity thereof.

[0006]

In order to achieve the above object, an information recording medium according to the present invention has a large Barkhausen phenomenon immediately before a saturation magnetization region with respect to an excitation magnetic field in which the magnetic field intensity periodically changes. In the region where the magnetic field occurs, a single ferromagnetic material having a peculiar magnetization noise characteristic in which the magnetization changes irregularly in each cycle of the excitation magnetic field, or a small piece, a line, a film, or a powder made of a ferromagnetic material bonded to a resin or the like Is attached to paper or a resin substrate, and printed or embedded.

In order to determine whether or not such an information recording medium is genuine, exciting means for periodically exciting a ferromagnetic material having peculiar magnetization noise characteristics, which is pasted, printed and embedded, from the outside. A magnetic history characteristic capable of visually discriminating a specific magnetization noise characteristic of the excited ferromagnetic material, or an analog-to-digital converter for detecting a change in magnetic flux density detected from the ferromagnetic material. Means for digitizing the magnetization noise characteristics, and means for expressing the digitized magnetization noise characteristics as a numerical value of the result of the statistical processing. A configuration is adopted in which the authenticity is determined based on whether or not it matches the noise characteristic or the numerical value.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The information recording medium according to the present invention is suitable for objects requiring high security, such as securities and cards, which require forgery prevention. Forgery is difficult due to the presence of the ferromagnetic material and the detection method is special, so that the security is extremely high. In addition, since the authenticity determination device according to the present invention can easily and reliably perform the authenticity determination on the information recording medium according to the present invention as an object as described above, reliability in handling the information recording medium can be improved. It has the effect of significantly increasing.

[Principle of the Invention] Before describing the present invention, the basic principle of the present invention will be described. The magnetization mechanism of a ferromagnetic material is mainly based on spontaneous magnetization due to the magnetic moment of atoms of the constituent materials and the movement of magnetic domains formed by the aggregation. When the magnetic field strength of a ferromagnetic material in a changing magnetic field is increased, irreversible movement of the domain wall of each magnetic domain occurs, and the ferromagnetic material moves discontinuously from one stable region to another stable region. Also, in this region, the large Barkhausen effect is remarkable, and magnetization noise is generated due to irregular movement of the domain wall (literature: "Physics of Ferromagnetic Materials", written by Toshinobu Chikaku, published by Shokabosha). This phenomenon has been known for a long time, and recently, fluctuation noise of an amorphous magnetic core used in a magnetic amplifier (literature: “Magnetic Applied Engineering”, published by Koichi Murakami, published by Asakura Shoten) and noise reduction of the MR head (literature: Japan Applied Magnetics) Journal Vol.21 No4.2 1997 The mechanism is studied in "Waveform instability and magnetic domain structure of MR head" by Kazuhiro Nakamoto et al.).

In any case, the magnetization noise is unnecessary in producing a magnetic application product, and the emphasis is on how to reduce it. For this reason, the mechanism has not been clarified yet, and some theories have suggested that irregular physical oscillations may occur as dissipative chaos as nonlinear physical phenomena (Reference: Journal of Japan Society of Applied Magnetics) Vol 18 No251-256 1994 "Distribution and energy loss of domain wall motion chaos" Hikaru Okuno et al.)

Further, the magnetic properties used industrially are B
It is represented by a magnetic hysteresis characteristic called -H curve characteristic, and many instruments for measuring this characteristic are commercially available. However, many devices for measuring the BH curve characteristics average the original signal including the obtained noise without paying attention to the magnetization noise, and treat the averaged signal as an ideal signal with very little apparent noise. , Making it difficult to discover the presence of magnetization noise.

According to the results observed by the present inventor, a ferromagnetic material having a large squareness ratio and a small coercive force in a magnetic hysteresis characteristic has a magnetization which irregularly changes in an unstable region where the magnetization changes greatly. Noise is seen. Further, it has been confirmed that an amorphous alloy has a greater tendency to occur than a crystallized alloy, and appears more prominently in a thin film having a thickness of 0.2 μm or less. Also, the change can be seen greatly by selecting a special alloy material and manufacturing process.

According to the present invention, it has been found that, in an amorphous alloy containing cobalt (Co) metal as a main component, an amorphous alloy in which a certain kind of transition metal is mixed generates the above-mentioned peculiar magnetization noise. Based on the idea, the present invention is not based on the discovery of an alloy material, but on the application of the magnetization noise characteristic inherent to the material to security.

FIGS. 1 (a) and 1 (b) are amorphous alloys each having the same thickness and substantially the same magnetic hysteresis characteristics mainly composed of Co metal. The transition metal (1) and the transition metal ( 2) it is obtained by adding a different metal, to convert the differential value of the magnetization strength of the material when the intensity of the excitation field E was varied as shown in the amplitude of the magnitude of the voltage V _d, overwrite each measurement FIG. (A) the magnetization less noise, the same magnetization intensity each time despite the overwrite is the waveform of the peak or the like in the voltage output V _d because of the stably generated clearly visible. FIG. 6B shows the magnetic material according to the present invention, and the waveform detected every time is not fixed because a large magnetization noise that causes irregular magnetization change occurs regardless of the magnitude of the exciting magnetic field. Therefore, the overwritten waveforms do not pass through the same place, and thus appear as a solid portion. As described above, since the magnitude of the generated magnetization noise with respect to the intensity of the excitation magnetic field differs depending on the alloy material, by inspecting this characteristic,
It can be determined whether the magnetic material is true or counterfeit.

As a method of inspecting the magnitude of the magnetization noise as described above, there is a method of visual inspection using a display.
Also, a numerical value obtained from the result of the statistical processing of the magnetization noise signal is determined in advance as a value specific to the ferromagnetic material, and is compared with a similar numerical value for the magnetic material to be detected. Whether the magnetic material is genuine or not can be easily and accurately determined.

[0016]

EXAMPLES Next, specific examples will be described. FIG. 2 shows a first embodiment of the present invention, wherein 1 is a prepaid card on which a barcode is printed. Reference numeral 2 denotes a bar code, which is a bar code formed by printing ferromagnetic filaments on a printing surface of the transfer ink.

FIG. 3 shows a second embodiment, wherein reference numeral 3 denotes a security in which a ferromagnetic piece is embedded in paper. Reference numeral 4 denotes a ferromagnetic filament formed by applying a ferromagnetic substance to a chemical resin such as polyethylene, and can record meaningful data. Any ferromagnetic also _{Co x Zr y Ml z M2 (} 1-x-y-
z) An amorphous alloy made of a material. Where M1
Is a transition metal selected from the group including Ti, Cr, Mn, Fe, Ni, Cu, and M2 is Mo, Nd, Tc, A
a transition metal or Si selected from the group containing
This is a nonmetallic alloy selected from the group including B, Se, and Sb, and x, y, and z are compounding ratios. Compound metal M1,
The thin film which has been made amorphous by a sputtering method by appropriately selecting M2 and the ratios x, y and z has a remarkably large magnetic noise in an unstable region where the magnetization greatly changes, and furthermore, a magnetic noise inherent to the material. It has specificity with characteristics. The magnetization noise characteristics referred to here are (1) generated region, (2) generated magnetization intensity, and (3)
Includes statistical distribution characteristics.

FIG. 4 is a characteristic diagram. (1) Generation region Among the magnetic hysteresis characteristics shown in FIG. 4A, the region where the large Barkhausen phenomenon occurs immediately before the saturation magnetization region is the region where the magnetization noise is most unstable and the magnetization noise is generated. Whether it accounts for the percentage depends on the material. (2) Magnetization intensity generated Magnetization intensity of the magnetization noise is shown in FIG.
As shown in (1), it is detected by a voltage as a differential value of the magnetic flux density. The variation in the peak value has a distribution as shown in FIG. 4C, and the distribution state differs depending on the material. (3) Statistical distribution characteristics The simplest is a standard deviation value, which is a measure of deviation from the average value, and indicates the magnitude of magnetization noise that varies depending on the material. In addition, the statistical distribution state of the magnetization noise (for example, Poisson distribution, Cows distribution, etc.) can also be used as an indicator of the characteristics.

FIG. 5 is a conceptual diagram of the authenticity determining apparatus of the present invention used for determining the authenticity of the information recording medium according to the present invention. Reference numeral 5 denotes a current source flowing through the exciting coil. In this embodiment, excitation is performed by a 4 kHz sine wave. Reference numeral 6 denotes an exciting coil for exciting the object 11 to be determined, which is a ferromagnetic material. Although a single excitation coil is shown in the conceptual diagram, it may be integrated with the magnetic head 7 for detecting the magnetization intensity. Reference numeral 7 denotes a magnetic head for detecting a change in the magnetization intensity of the excited ferromagnetic material. The magnetic head 7 may be any type other than the coil type, as long as it can detect a change in magnetic flux density, and a Hall element, an MR element, or a magnetic sensing element utilizing the Kerr effect can be used. Reference numeral 8 denotes an amplifier for amplifying a signal detected by the magnetic head 7. Reference numeral 9 denotes a display for displaying the amplified detection signal. The display 9 may use an oscilloscope. In order to easily see the noise, a peak hold function for always storing and displaying the maximum value using a digital storage oscilloscope (DSO) may be used. The characteristics shown in FIGS. 1A and 1B are DS
This is an example observed by this function of O. Reference numeral 10 denotes a statistical processing calculator for performing statistical processing and determination, and may use a microcomputer or the like.

FIG. 6 is a block diagram of the statistical processing calculator 10. 10-1 is an analog / digital converter (A / D converter) for digitizing an analog signal from the amplifier 8;
-2 is a memory device for storing digitized signals. Numeral 10-3 is an arithmetic unit for performing a statistical processing operation. The memory device 10-2 and the statistical processing arithmetic unit 10-3 are provided independently, or the main control unit (microcomputer) 10-
4 may be provided inside. When the microcomputer 10-4 is provided with an arithmetic unit, the microcomputer 10-4 performs a statistical operation, compares the result with an expected statistical value stored in advance, and checks if the result matches the statistical value. The determined information storage medium is genuine, and if different, it is determined to be counterfeit. Further, the judgment output can be taken out to an external device.

Next, the algorithm of the statistical operation will be described. Since the object to be detected is excited by a sine wave having a period T,
Average value bar x of detected voltage x at time (t + nT)
And its standard deviation σ (t) is as in the following equation (1).

(Equation 1) If n is made sufficiently large, α can be regarded as the variation at time t, that is, the magnitude of the magnetization noise. Moreover, as a characteristic of the ferromagnetic material, its value changes depending on the excitation voltage (magnetic field intensity), and has a specific value depending on the alloy material and the manufacturing method.
Assuming that the measurement is performed N times, the memory device 10-2 stores the following two-dimensional array. Where s
Is the number of samples.

(Equation 2)

Therefore, the average value bar x (t) and the standard deviation σ (t) of each column are obtained from the above equation (1). This can be expressed by the following equation (2).

Σ (t) = (σ1, σ2, σ3,... Σs) (2) Here, when a comparison value for authenticity determination is represented by C (t), the following expression (3) is obtained. is there.

C (t) = (c1, c2, c3,... Cs) (3) The cross-correlation R between the measured σ (t) and the comparison value C (t) is given by the following equation (4). Desired.

R = 1 / sΣ | C (t) −σ (t) | t = 1 to s (4) Here, if the measured value is close to the comparison value, it becomes almost zero. However, since there is a variation, a determination is made as “false” if R> M and “true” if R ≧ M, and a display or an appropriate process is performed.

FIG. 7 shows an example actually measured. FIG.
(A), (b) and (c) are graphs of the average value of the magnetization intensity detected by exciting different alloy materials and the standard deviation sequence which is the magnetization noise of the same thickness having a large Barkhausen effect. It is. Here, when one kind of material was used as a standard value and the difference in R value between the respective combinations was compared, the results shown in the following Table 1 were obtained.

[0024]

[Table 1]

That is, it has been proved that the magnetization noise inherent in the material can be used as a quantified value as an evaluation value for authenticity determination. In the embodiment, the algorithm of the statistical processing is based on the standard deviation, but other than that, a statistical processing method using a probability density function or a cross-correlation function is also effective for evaluating the occurrence of magnetization noise, It is possible to select what kind of statistical processing is to be used depending on the purpose of use.

[0026]

As described above in detail, according to the present invention, the ferromagnetic multi-layer embedded in, attached to, or printed on an information recording medium such as securities or cards that require forgery prevention is excited and detected. The inherent magnetic characteristics of the ferromagnetic material can be accurately determined by visually observing the generated magnetization noise or performing statistical processing. Therefore, if a ferromagnetic material having a specific magnetization noise that cannot be easily manufactured is generally used, it is difficult to detect a genuine product, so that forgery is difficult.
The effect is high.

[Brief description of the drawings]

FIG. 1 is a magnetization intensity differential waveform diagram when a magnetic field is externally applied to a ferromagnetic material used in the present invention.

FIG. 2 is a perspective view showing an embodiment of the present invention applied to a card on which a ferromagnetic material is printed.

FIG. 3 is a perspective view showing an embodiment of the present invention applied to an example in which a ferromagnetic material is embedded in a security.

FIG. 4 is a waveform diagram for explaining magnetization noise generated from a ferromagnetic material used in the present invention.

FIG. 5 is a block diagram showing a configuration example of a true / false determination device according to the present invention.

FIG. 6 is a block diagram illustrating a configuration example of a statistical processing device used in the authenticity determination device according to the present invention.

FIG. 7 is a characteristic diagram showing a result of statistical processing of magnetization noise measured by the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Prepaid card 2 Barcode with a ferromagnetic line 3 Securities 4 Ferromagnetic line 5 Excitation power supply 6 Excitation coil 7 Magnetic head 8 Amplifier 9 Display 10 Statistical processing apparatus 10-1 A / D converter 10-2 Memory device 10-3 Statistical processing arithmetic unit 10-4 Main control unit (microcomputer)

Claims (3)

[Claims] In a region where a large Barkhausen phenomenon occurs immediately before a saturation magnetization region with respect to an excitation magnetic field in which the strength of a magnetic field changes periodically, a unique magnetization that undergoes irregular magnetization change in each period of the excitation magnetic field. An information recording medium in which a ferromagnetic material that generates noise is in the form of a line, a plate, a film, or a powder, and is embedded or attached to a base material such as paper or plastic, or transferred and printed. 2. In a region where a large Barkhausen phenomenon occurs immediately before a saturation magnetization region with respect to an excitation magnetic field in which the intensity of a magnetic field periodically changes, a unique magnetization that undergoes irregular magnetization change in each period of the excitation magnetic field. For an information recording medium using a ferromagnetic material that generates noise, an excitation unit for periodically exciting the ferromagnetic material, and a change in magnetization of the ferromagnetic material due to the exciting magnetic field are detected. And magnetic characteristic display means for displaying the characteristics of the magnetization noise from the detected signal, and determining whether or not the characteristics of the displayed magnetization noise properly match the characteristics of the inherent magnetization noise determined in advance. An authenticity determination apparatus for an information recording medium configured to be able to determine whether the information recording medium is genuine or counterfeit. 3. In a region where a large Barkhausen phenomenon occurs immediately before a saturation magnetization region with respect to an excitation magnetic field in which the intensity of a magnetic field periodically changes, a unique magnetization that undergoes irregular magnetization change in each period of the excitation magnetic field. For an information recording medium using a ferromagnetic material that generates noise, an excitation unit for periodically exciting the ferromagnetic material, and an irregular magnetization change of the ferromagnetic material due to the excitation magnetic field. Means for detecting the corresponding magnetization noise, an analog-to-digital converter for digitizing the detected signal, a memory device for temporarily storing the digitized signal, and the digital signal temporarily stored in the memory device The information recording medium described above depends on whether or not the statistical processing result obtained by the computing device and the statistical processing result obtained by the computing device appropriately match the statistical result specific to the ferromagnetic material. Authenticity determination apparatus of the information recording medium and a means for determining that the one or counterfeit is true.