JP2543938B2 - Magnetic recording media - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium having a magnetic pattern. For example, it can be applied to cards having a magnetic bar code, an information record carrier using a magnetic bar, and the like.

[Prior Art] Some securities, cards, and the like that are widely used today have a magnetic pattern for authenticity determination. By detecting this with a magnetic sensor, authenticity determination is performed, and security is added and improved.

In magnetic recording media in general, such as securities and cards, codes are constructed using magnetic patterns,
Further, when recording some information, the information may be recorded as binary information of "0" or "1".

FIG. 5 is an explanatory diagram of a case where binarized information is configured using a conventional magnetic recording medium.

As shown in the figure, in order to record the binarized information according to the magnitude of the detected voltage by the conventional method, it is necessary to change the thickness of the magnetic pattern 102 formed on the base material 101 according to the binarized information. was there. That is, a thick magnetic pattern 102b is formed to obtain a high level output, and a thin magnetic pattern 102a is formed to a low level output.

By scanning such a magnetic pattern, a detection voltage corresponding to the thickness of the magnetic pattern is obtained from the detection coil 62 of the magnetic head 6, and the binary information is reproduced.

[Problems to be Solved by the Invention] However, when the binarized information is formed by the magnitude of the detection voltage of the conventional magnetic pattern, the thickness of the magnetic pattern must be changed as described above. For this,
There is a problem that the manufacturing process becomes complicated, and the magnetic pattern is easily visible, which is disadvantageous in terms of security.

The present invention is intended to solve such a problem, and it is possible to increase the detection voltage, record binarized information, and easily detect information without changing the thickness of the magnetic pattern. The purpose is to provide a magnetic recording medium.

[Means for Solving the Problems] In order to achieve the above object, the magnetic recording medium according to the present invention is characterized by having a magnetic pattern having a line width smaller than 1 mm.

[Operation] When a magnetic pattern with a line width smaller than 1 mm is detected by the magnetic head, the detection voltage is significantly increased compared to the case with a line width of 1 mm or more. Especially when the line width is 0.5 mm or less, the detection voltage is 3
0% to 110% higher and a remarkable effect.

Therefore, with the above structure, it is possible to record information only by changing the line width, the manufacturing is easy, and the thickness is uniform, so that it is hard to see and the security is improved.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

4A to 4D are manufacturing process diagrams of an embodiment of the magnetic recording medium according to the present invention.

First, as shown in FIG.
A substrate 1 of a polyethylene terephthalate film having a thickness of μm is prepared.

Next, as shown in FIG. 1B, magnetic ink patterns 2a and 2b were printed on the base material 1. Pattern 2a has a line width
The magnetic bar is 1 mm or more, and the pattern 2b is a magnetic bar whose line width is thinner than 1 mm. The arrays of patterns 2a and 2b correspond to the binary information to be recorded. The length of both patterns is 10.0 mm.

The magnetic ink patterns 2a and 2b are printed by screen printing, and the screen mesh is Tetron 25
It is line 0.

The stock solution of the magnetic ink is 48 parts by weight of carbonyl iron (weight part, the same applies hereinafter), modified polyester resin solution (solid content 50
% By weight), 7 parts isophorone, 7 parts butyl cellosolve, 7 parts cyclohexanone and 7 parts Solvesso 100.
Part, and kneaded with a roll mill for 2 hours. Its viscosity was about 100 poise. Carbonyl iron has a density of 3.0 to 3.2 g / cm ³ , a particle size of 1.5 to 1.8 μm, and a coercive force of about 10
(Oe) was used.

Here, carbonyl iron is spherical iron powder having a uniform particle size obtained by reducing iron carbonyl, and usually two types are present depending on the reduction method. The first type is carbon,
It contains nitrogen and oxygen and has a high Vickers hardness Hv of about 900. The second type has a low content of carbon, nitrogen and oxygen and high purity, and the Vickers hardness Hv is about 150. In this example, the first kind of carbonyl iron was used in which the particles did not deform when formed into an ink and remained spherical, and the coercive force hardly changed.

On the other hand, the reduced iron powder obtained by reducing the oxide and the electrolytic iron powder obtained by iron electrorefining have an irregular shape, a wide particle size distribution, and a particle size of several tens of μ.
Since it is m or more, it is difficult to form an ink. Further, the magnetic ink pattern using these has a larger output fluctuation at the time of detection than the case of using carbonyl iron.

When the magnetic ink stock solution using carbonyl iron was used as it was and printed with 250 lines of screen mesh, the film thickness of pattern 2 was about 9 μm. This sample is hereinafter referred to as sample A.

Also, 1 part isophorone, 1 part butyl cellosolve,
Using a thinner containing 1 part of cyclohexanone and 1 part of Solvesso 100, 10 parts of the above magnetic ink was diluted with 1 part of thinner, and the diluted magnetic ink was printed with 250 lines of a screen mesh to give a film thickness of about 7.5. became μm.
This is sample B.

When 10 parts of the magnetic ink is diluted with 2 parts of the thinner and screen-printed under the same conditions, the film thickness is 5.
It was 5 μm. This is sample C.

A magnetic field of up to 5000 (Oe) was applied to this magnetic ink pattern using a sample vibrating magnetometer (VSM) to measure the magnetic flux density and coercive force, which were approximately 4400 Gauss and 10.1 (Oe), respectively.
e).

Next, as shown in FIG. 3C, a silver ink layer 3 is formed to conceal the formed magnetic ink pattern 2. The pigment of silver ink is scaly and has a thickness of 1-2 μm.
Sufficient concealing property can be obtained even at a certain level. Here, the thickness of the silver ink layer 3 is about 1 μm. As such a pigment, there is a scale-like aluminum pigment.

Next, as shown in FIG. 3D, the overcoat layer 4 is formed on the silver ink layer 3. The overcoat layer 4 is
It is provided to withstand the friction of the magnetic head when detecting the magnetic ink pattern 2, and is formed to a thickness of about 2 μm.

The thus formed product was processed into a commuter pass size of 57.5 mm × 85 mm to prepare a sample card 5 of this example.

FIGS. 1A to 1C are explanatory diagrams showing the relationship between the magnitude of the output voltage and the line width of the magnetic ink pattern when the magnetic head scans the present embodiment.

In the figure (A), the magnetic head 6 has a gap of 30 μm.
m, the track width is 1 mm, and has a bias coil 61 and a detection coil 62.

First, a DC bias current of about 20 mA is passed through the bias coil 61 to generate a leakage magnetic field of about 1000 (Oe).
Then, the card 5 is conveyed in the direction of the arrow in the figure to detect the magnetic ink pattern. At this time, in order to prevent the output level from decreasing, the scanning direction of the gap of the magnetic head 6 and the end sides of the patterns 2a and 2b are set to be substantially vertical. Further, the transportation speed of the card 5 was set to about 45 cm / sec.

When the card 5 is conveyed and the magnetic head 6 passes over the magnetic ink pattern, magnetic coupling is caused to change the magnetic flux, and as shown in FIG. A reverse output voltage is generated at the terminal.

However, this output voltage is significantly higher in the case of the pattern 2b thinner than 1 mm as compared with the case of the pattern 2a having a line width of 1 mm or more. By utilizing this phenomenon, it is possible to reproduce low-level binary information from the pattern 2a and high-level binary information from the pattern 2b.

Next, the phenomenon in which the output voltage changes depending on the line width will be demonstrated using Samples A, B and C above. Sample A was printed with the above stock solution of magnetic ink and had a pattern with a thickness of 9 μm, Sample B was printed with magnetic ink diluted to 10: 1 and had a pattern with a thickness of about 7.5 μm, and Sample C was 1
It is printed with magnetic ink diluted 0: 2 and has a pattern with a thickness of about 5.5 μm.

FIG. 2 is a graph showing the relationship between the line width of the magnetic bar and the detected voltage. The vertical axis of the graph represents the maximum value of the output voltage on each pattern of the magnetic head as a relative value. Further, the magnetic head, the transport speed of the card 5 and the like are the same as the above-mentioned conditions.

As shown in the graph, in any of Samples A, B, and C, the output voltage hardly changed when the line width was between 10.0 mm and 1.0 mm, but significantly increased when the line width became thinner than 1 mm. , Shows the maximum value near the line width of 0.3 mm. When comparing this maximum value with the average output when the line width is 10.0 mm to 1.0 mm, it is about 30% for sample A and about 85% for sample B.
%, Sample C has an increase of about 110%.

Although the output is reduced at a line width of 0.2 mm, this line width is close to the limit of silk screen printing, and it is possible that this is a phenomenon caused by the influence. Therefore, the line width is 0.3 mm
It cannot be said that it became clear that the maximum value was obtained in the vicinity.

However, it was confirmed that the output voltage was increased by reducing the line width, and it was clearly demonstrated that the output voltage increased by at least 110% was obtained in the sample C.

Therefore, the change in the output can be made to correspond to the binary information "0" and "1". For example, sample B
Then, when the line width is 0.3 mm, the relative output level is 120 and the line width is 1.
Since it is 61 in the case of 0 mm, permanent magnetic recording can be performed by arranging the line widths of 0.3 mm and 1.0 mm according to the binarized information.

Furthermore, by utilizing the fact that the output voltage hardly changes when the line width is 1.0 mm to 10.0 mm, information is placed on the line width itself and the output voltage caused by the line width, and both are formed in a single printing process. Is also possible.

For example, in the case of line widths of 1 mm and 2 mm, the line widths are doubled but the output voltages are about the same. Therefore, information can be placed on the line width itself. Conversely, line width 0.5 mm
In the case of and 1 mm, the line width is also twice as large, but the output is significantly higher when the line width is 0.5 mm. Therefore, information can be placed on the level of the output voltage.

FIG. 3 is an explanatory diagram showing the structure of a magnetic pattern in another embodiment of the present invention.

As shown in the figure, in the present embodiment, a magnetic pattern 2a having a line width of 1 mm or more and a magnetic pattern 2b having a line width of less than 1 mm are mixed with a dummy pattern 2c of a specific magnetic material.

No output voltage appears on the dummy pattern 2c because the magnetic flux of the magnetic head 6 does not change. Therefore, the recorded information cannot be read from the apparent pattern, and the security is improved.

Regarding security, this embodiment is advantageous as described below.

When a magnetic pattern is detected by the magnetic head 6 shown in FIG. 1 (A), residual magnetization occurs in a magnetic ink pattern having a coercive force exceeding 30 (Oe). For this reason, the magnetic ink pattern can be easily viewed with a commercially available magnetic viewer or the like. Conventionally, in order to prevent this, it is necessary to perform degaussing every time, which leads to a complicated system.

However, the carbonyl iron powder used in this example has a coercive force of about 10 (Oe) and no residual magnetization is generated, so that it is difficult to visually observe with the magnetic viewer or the like. This is important for security.

The present invention is not limited to the above embodiment, but can be applied to general magnetic recording media having a magnetic pattern.

[Effects of the Invention] As described in detail above, the magnetic recording medium according to the present invention can record information only by changing the line width of the magnetic pattern, is easy to manufacture, and has a uniform thickness. Therefore, security is also improved.

[Brief description of drawings]

FIGS. 1 (A) to 1 (C) are explanatory diagrams showing the relationship between the magnitude of the output voltage and the line width of the magnetic ink pattern when a magnetic head scans an embodiment of the magnetic recording medium according to the present invention. FIG. 2 is a graph showing the relationship between the line width of the magnetic bar and the detected voltage, and FIGS. 3 (A) and 3 (B) are explanatory views showing the configuration of the magnetic pattern in another embodiment of the present invention. FIGS. 4 (A) to 4 (D) are manufacturing process diagrams of this embodiment, and FIGS. 5 (A) and 5 (B) are explanations in the case where binarized information is formed using a conventional magnetic recording medium. It is a figure. 1 ... Substrate 2a, 2b ... Magnetic ink pattern 2c ... Dummy pattern 3 ... Silver ink layer 4 ... Overcoat layer 5 ... Card 6 ... Magnetic head 61 ... Bias coil 62 ... Detection coil

Claims (3)

(57) [Claims] 1. A magnetic recording medium having a magnetic pattern having a line width smaller than 1 mm. 2. A magnetic recording medium comprising a first magnetic pattern having a line width of less than 1 mm and a second magnetic pattern having a line width of 1 mm or more. A magnetic recording medium comprising: 3. A magnetic recording medium in which binarized information is recorded by the first and second magnetic patterns.