JPH01169706A - Magnetic recording and reproducing system - Google Patents

Abstract

PURPOSE:To disable a read with a signal from one track and to prevent the use of a counterfeit of a magnetic card, etc., by executing a special recording and a special reading by using a magnetic recording medium of two-layer constitution in which the coercive force of a lower layer is larger than that of the upper layer and two pieces of heads. CONSTITUTION:Two or more tracks are provided by coating a magnetic recording medium of coercive force in the upper and the lower layers 2b, 2a from the base film 3 side, which is made a magnetic card, etc. Multi-track heads 11, 12 are used as recording and reproducing magnetic heads; security signals and recording signals are recorded on separate tracks 212, 222 on the magnetic recording surface in inverse phases, thereafter, the recording layer 2a only is unified by a DC magnetic field, so that arbitrary recording pitch signals are recorded in superimposition on the track 212. At the time of reading, a security signal and a recording signal are concurrently read simultaneously from the plural tracks, and their output sum is outputted so that only the recording signal is detected.

Description

[Detailed Description of the Invention] [Overview of the Field] The present invention relates to a magnetic recording medium having a two-layer structure with different magnetic properties,
The present invention relates to a new magnetic recording and reproducing system configured using two sets of magnetic heads.

[Contents and problems of conventional technology]

Recently, magnetic cards such as credit cards have become popular, and it is said that the age of cards has arrived. With the spread of magnetic cards, so-called magnetic card readers, which are devices that can write signals to and read signals from magnetic cards, are also being used, and it is easy for the general public to use magnetic card writers to write signals to magnetic cards. It has become available.

For this reason, there is an urgent need for measures to prevent counterfeiting of magnetic cards for credit cards.

Conventional measures to prevent counterfeiting of magnetic cards have been taken by improving the recording signal method used when recording signals on the magnetic card, or by improving the structure of the magnetic head and the medium of the card. However, since there is currently no recording method that is completely reliable by itself, anti-counterfeiting measures are being taken that combine the above-mentioned methods.

[Purpose of the invention]

The present invention is based on the conventional counterfeit prevention method, which records one magnetic recording signal on one track on a magnetic card, whereas the present method uses multiple magnetic heads on the magnetic recording surface. The purpose of the present invention is to provide a magnetic recording method with high security by recording a plurality of magnetic recording signals.

[Structure of the invention]

The present invention uses two types of magnetic recording media with different coercive force values on the magnetic recording surface, and the two layers are coated with a magnetic recording medium with high coercive force on the base film side and a magnetic recording medium with low coercive force on top of it. A magnetic recording medium having a structure, a multi-track head with two or more tracks is used as a magnetic head for recording and reproduction, a security signal and a recording signal are recorded on separate tracks on the magnetic recording surface, and overlapping recording is performed, When reading, this is a magnetic recording and reproducing method in which security signals and recorded signals are simultaneously read out from multiple tracks in parallel, and only the original recorded signal is read.

The present invention will be explained with reference to the drawings in the case of a two-track example.

FIG. 1(a) shows a two-track magnetic head used in the present invention, in which magnetic heads having the same characteristics are arranged in parallel at regular intervals. FIG. 1(C) is a perspective view of a two-layer magnetic recording medium (magnetic card) used in the present invention, viewed from the magnetic recording surface side, and FIG. 1(b) is a cross-sectional view of the two-layer magnetic recording medium. It shows. On the non-magnetic base film 3 are magnetic recording medium layers 2a, 2 made of hard magnetic material and having different characteristics.
b are each laminated. At this time, in order to implement the method of the present application, the characteristics of the magnetic recording medium layers 2a and 2b are such that the upper layer (2a) is higher than the lower layer (2a) in terms of coercive force (He).
b) lower than that, and for values of magnetic flux (φ),
It is important that the upper layer (2a) is selected to be smaller than that of the lower layer (2b).

In the example of the present invention, the lower magnetic recording medium layer 2b has a coercive force of 3
000 oersted material is used for the upper magnetic recording medium layer 2.
A barium ferrite recording medium with a coercive force of 10 QO Oersted is used for a.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, an embodiment of the present invention will be described with reference to the drawings regarding magnetic recording and reading methods when two magnetic heads are used and magnetic recording is performed on two tracks.

The magnetic recording according to the present invention uses two magnetic heads in the first step shown in FIG. The recording magnetic flux reaches the magnetic medium layer of the two tracks, and the signals 222.221 and 212.211 of the upper and lower tracks of the two magnetic recording layers are respectively recorded as the same signal.

At this time, the signals recorded on the magnetic recording medium surface using the two magnetic heads are as shown in (C).

Next, as a second step, the recording signal of FIG. 1(C) is transferred to the upper magnetic recording layer 2a at 212.222
Only the signals are uniformly recorded using a DC magnetic field.

When a DC current is applied to each magnetic head in the same phase as shown in Fig. 2(a), and only the upper layer is made uniform by a DC magnetic field as shown in Fig. 2(b), the recording surface becomes as shown in Fig. 2(c). The recording surface will look like this. At this time, on the surfaces of the two magnetic recording tracks, only a small amount of magnetic flux leaks from the remaining recording signals recorded in the lower magnetic recording layer.

Next, as a third step, a recording signal is recorded only in the upper layer on the first track 212 of the two recording tracks, for example, as shown in FIGS. 3(b) and 3(C). The recording signal is recorded at an arbitrary recording pitch regardless of the recording pitch performed in the first step. This completes the recording process.

Next, as a reading method, two recorded tracks are simultaneously read with two magnetic heads, and the sum of the outputs of the two tracks is output. By doing so, only the recording signal can be detected.

As mentioned above, the magnetic recording medium used in the present invention has two layers coated with two media with different coercive forces, and the magnetic recording layer has a double structure. The amount of magnetic flux depends on the size of the lower recording layer, so the third
In the state where the signal shown in Figure (C) is recorded, magnetic flux is generated on the magnetic recording surface in the form that the magnetic signal recorded in the first track 212 is added with the magnetic signal recorded in the first step. For example, even if the first track is read by one magnetic head, the output signal will be completely different from the recording signal written as the recording signal. In addition, the signal appearing on the magnetic recording surface for the second track is a magnetic recording signal different from the recorded signal, and when the first track and the second track are read simultaneously and the output sum is calculated, A normal output signal is obtained only when the recorded signals cancel each other out.

That is, if the track on which the recording signal is recorded is the first track, the output voltage of the second track will be [loss due to security signal amount and upper layer thickness]. Further, the output voltage of the first track becomes [-recorded signal output due to loss due to security signal quantity sumo wrestler upper layer thickness]. Therefore, when the outputs of the two tracks are summed, only the recording signal can be detected.

Therefore, with this recording method, even if the signal of only one track can be read, the recorded # signal cannot be analyzed, making it possible to prevent forgery.

In the embodiments of the present invention, two tracks are used in one magnetic recording medium. However, in practical use, since magnetic recording is performed using multiple tracks, a combination of two of the multiple tracks is used. This increases confidentiality.

〔Effect of the invention〕

As described above, the present invention makes it possible to provide a magnetic recording and reproducing system which has the advantage of preventing forgery since it is impossible to read recorded signals using only the signals for each track.

Below margin

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the magnetic method according to the present invention, and is a diagram showing write recording signals in the first step. (a) is a diagram in which recording is performed in opposite phases using two sets of magnetic heads that perform recording and reproduction. (b) is a cross-sectional view showing simultaneous recording on a two-layered magnetic recording medium. (C) is a diagram showing signals recorded in opposite phases by two magnetic heads using the respective magnetic heads. FIG. 2 is a diagram in which only the upper layer of the two-layered magnetic recording layer of the magnetic recording signal recorded in FIG. 1(C) is canceled by the DC magnetic field of the magnetic head. (a) is a diagram showing the direction of current flowing through the magnetic head. (b) is a diagram showing a state in which only the upper layer of the two-layer magnetic recording medium is demagnetized. (C) is a diagram showing a lower layer magnetic recording signal slightly appearing on the surface through a demagnetized upper layer recording medium. FIG. 3 is a diagram for writing a recording signal into the upper layer of a two-layered magnetic recording medium. (a) shows two sets of magnetic heads. (b) is a diagram showing a magnetic recording number written on the upper layer recording medium. (C) is a diagram in which magnetic recording signals are written on one track. 11, 12...Magnetic heads for recording and reproduction. 3...Base film. 2a... Upper magnetic recording medium layer. 2b... Lower magnetic recording medium layer. 4...Writing magnetic field created by the magnetic head. 211...Magnetic recording signal written on the lower layer recording medium of the first track. 212...Magnetic recording signal written on the upper layer recording medium of the first track. 221...Magnetic recording signal written on the lower layer recording medium of the second track. 222...Magnetic recording signal written on the upper layer recording medium of the second track. A: Direction of movement of the magnetic head. S, N... Polarity of recording signal. Figure 2 in the margin below

Claims (1)

[Claims] A lower magnetic recording medium layer is formed on a non-magnetic base plate, and an upper magnetic recording medium layer is formed on top of the lower magnetic recording medium layer, and the coercive force of the lower magnetic recording medium is larger than that of the upper layer, and the magnetic flux of the lower magnetic recording medium is A two-layered magnetic recording medium whose amount is selected to be larger than that of the upper layer and two magnetic heads are used, and signal currents with opposite phases are passed through the two magnetic heads to separate the lower and upper magnetic recording media. The first magnetic recording is performed by simultaneously reversing the magnetization of the two layers and recording a signal on the two-layer magnetic recording medium, and the magnetic recording of the upper layer is performed using the same phase DC magnetic field on the same two recording tracks where the first magnetic recording was performed. A second magnetic recording is performed in which the recording signals on the medium are aligned with the same polarity, and then a third magnetic recording is performed in which the recording signal is written in the upper layer of one of the recording tracks recorded with the same polarity. A magnetic recording and reproducing system that reads a recording track simultaneously with two magnetic heads and outputs the sum of the outputs of the two magnetic heads.