JPH08172007A - Method of manufacturing magnetic powder - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a magnetic card that has an excellent anti-counterfeiting effect that can easily record information without preparing a special magnetic recording / reproducing device and that does not easily erase existing information. [Structure] A nitrate having a weight ratio of strontium nitrate represented by the chemical formula Sr (NO ₃ ) ₂ and iron nitrate represented by the chemical formula Fe (NO ₃ ) ₃ is 1: x (5 ≦ x ≦ 20) is prepared. The chemical formula for this nitrate is H ₂ NCH ₂ COOH
The amino acid represented by is mixed so that the weight ratio of nitrate and amino acid is 1: y (0.4 ≦ y ≦ 0.6) to prepare a solution. This solution is heated and reacted at a temperature not lower than its boiling point and not higher than 1100 ° C. to produce magnetic powder. Using this magnetic powder, the magnetic layer 3 is formed on the main surface of the card substrate 2.
To form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing magnetic powder used in magnetic recording media such as magnetic cards.

[0002]

2. Description of the Related Art In recent years, as a kind of magnetic recording medium, a magnetic card used as a ticket such as a magnetic ticket or a magnetic commuter pass, a telephone card, or a prepaid card is known. This magnetic card is provided with a magnetic layer made of a paint containing magnetic powder for recording information on a substrate such as resin or paper. Then, the content of information already magnetically recorded on the magnetic layer is rewritten by a predetermined device every time the magnetic card is used.

The information recorded on the magnetic layer of this type of magnetic card is usually readable by a magnetic viewer or the like. Therefore, there is a possibility that the magnetic card may be forged or altered and used illegally. Various measures have been taken to prevent the unauthorized use, such as providing a protective layer or a shielding layer on the magnetic layer.

Further, a method of forming a magnetic layer on a plurality of magnetic recording media having different coercive forces, and the combined use of a bar code or the like with the magnetic recording media are being studied. However, the materials generally used conventionally as magnetic recording media are mostly γ-iron oxide-based, cobalt-doped γ-iron oxide-based, barium-based, and chromium oxide-based ferrite powders, and their magnetic characteristics have a coercive force of 4 kOe or less. Therefore, it is possible to easily write and read the recorded information by using a generally used magnetic head.

The magnetic card is constructed, for example, on a substrate made of polyethylene terephthalate (PET) resin or paper, magnetic powder of barium ferrite having a coercive force of 2 to 3 kOe together with a dispersant such as stearic acid, vinyl chloride, It is formed by dispersing it in a resin binder such as vinyl acetate to prepare a magnetic paint and applying it to the surface of the substrate.

As a measure for preventing unauthorized use of the magnetic card thus constructed, it has been considered to form a plurality of magnetic layers to be coated on the base body or to punch holes in the magnetic card. However, even with these, there is a limit to the prevention of illegal use, and it is required to improve the magnetic characteristics of the magnetic recording medium.

[0007]

Recently, along with the widespread use of magnetic cards, magnetic recording / reproducing apparatuses for recording and reproducing information on magnetic cards have been developed, and information recorded on magnetic cards can be easily read, and further, Information can be written easily. Therefore, the conventional magnetic card has a drawback that it cannot effectively prevent forgery and alteration. Specifically, all information including new information generated each time the magnetic card is used is rewritten each time in a form of overwriting old information. It is possible to easily rewrite information and thereby forge the recorded contents of the magnetic card.

The reason for permitting forgery and alteration of the magnetic card is that the coercive force of the magnetic layer is as low as 2 to 3 kOe so that it can be rewritten by the conventional magnetic recording / reproducing apparatus. That is, when the coercive force of the magnetic layer is low, information can be easily rewritten by a conventional magnetic recording / reproducing apparatus, and a magnetic card can be forged or altered.

A recording magnetic head used in a conventional magnetic recording / reproducing apparatus can generate a magnetic field of about 5 kG. The coercive force of the magnetic layer of a magnetic card that can be magnetized (recordable) by this magnetic head is about 2 to 3 kOe, which is about half the magnetic field generated by the magnetic head. When the coercive force of this magnetic layer is larger than this, rewriting (overwriting) cannot be performed. That is, each time the magnetic card is used, the existing record information is overwritten, and the existing record information is erased, and new information such as the remaining amount and the used amount is written. When the coercive force of the magnetic layer is large, conventional magnetic recording
The playback device cannot record new information.

Forgery that makes writing and reading information difficult
In order to prevent unauthorized use of alteration, it is necessary to improve the magnetic characteristics of the magnetic layer. Especially, it is to improve the coercive force among the magnetic properties.

However, it is necessary to increase the productivity without complicating the manufacturing process of the magnetic recording medium. Further, it is necessary to form a magnetic layer that does not complicate the writing / reading device of the magnetic card.

Therefore, an object of the present invention is to provide a magnetic card which has an excellent anti-counterfeiting effect, in which information can be easily recorded without preparing a special magnetic recording / reproducing apparatus, and existing information is hard to erase. Another object of the present invention is to provide a method for producing magnetic powder suitable for forming a magnetic layer of the magnetic card.

[0013]

According to the present invention, the weight ratio of strontium nitrate to iron nitrate is 1: x (5≤x≤2).
Amino acid is mixed with the nitrate which becomes 0) so that the weight ratio of nitrate and amino acid is 1: y (0.4 ≦ y ≦ 0.6) to prepare a solution, and the solution is There is obtained a method for producing magnetic powder, which is characterized by producing a magnetic powder by heating and reacting at a temperature not lower than the boiling point and not higher than 1100 ° C.

Here, the strontium nitrate has the chemical formula S
Preferably, the iron nitrate is represented by r (NO ₃ ) ₂ , the iron nitrate is represented by the chemical formula Fe (NO ₃ ) ₃ , and the amino acid is represented by the chemical formula H ₂ NCH ₂ COOH.

Further, the magnetic powder is added at a temperature of 700 to 1100.
It is preferable to perform heat treatment at ° C.

A magnetic card can be obtained by applying a magnetic layer to the main surface of the card base using the magnetic powder.

[0017]

The magnetic characteristics of the magnetic powder are that the magnetic flux rises quickly and the coercive force is large. Therefore, the effect of preventing falsification and forgery of the information once recorded is high. Furthermore, the magnetic powder manufacturing method is not a complicated manufacturing process, and it is possible to improve the magnetic characteristics only by adding a specific heat treatment process.

[0018]

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

FIG. 1 is a sectional view of a magnetic card according to an embodiment of the present invention. The magnetic card 1 is used as a ticket such as a ticket, a telephone card, or a prepaid card. In this magnetic card 1, a magnetic layer 3 is formed on one main surface of a card base 2 made of polyethylene terephthalate (PET) resin by applying a magnetic paint described later, and a protective layer is further formed thereon as needed. 4 is formed.

FIG. 2 is a plan view for explaining the magnetic recording method according to the embodiment of the present invention, as viewed from the surface on which the magnetic layer 3 is formed. The magnetic layer 3 of the magnetic card 1 is provided with a stripe-shaped information recording area 5 extending between both ends in the longitudinal direction (predetermined direction) of the magnetic card 1. Although the information recording area 5 is described so as to be clearly visible in FIG. 2 for the sake of convenience, it is desirable that the information recording area 5 is provided in a form that cannot be actually viewed.

Next, an example of a method of manufacturing magnetic powder for forming the magnetic layer 3 of the magnetic card 1 and a magnetic card having the magnetic layer 3 will be described.

Example 1 Strontium nitrate represented by the chemical formula Sr (NO ₃ ) ₂ (hereinafter referred to as Sr (NO ₃ ) ₂ ) and iron nitrate represented by the chemical formula Fe (NO ₃ ) ₃ (hereinafter Fe ( The weight ratio of NO ₃ ) ₃ ) is 1: 1, respectively.
Prepare nitrates containing Sr (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ weighed and blended so as to be 3, 1: 5, 1:10, 1:20, 1:30. Of the amino acid (chemical formula:
H ₂ NCH ₂ COOH) was weighed and the nitrate and amino acid were dissolved in pure water to obtain a solution. 1000 ℃ the solution
The powder was obtained by spraying into the atmosphere heated to 100 ° C. to cause a heating reaction.

The magnetic properties of the obtained powder were examined using a vibrating sample magnetometer (hereinafter referred to as VSM).
Table 1 shows the results.

[0024]

[Table 1]

From the results shown in Table 1, Sr of Fe (NO ₃ ) ₃
When the weight ratio to (NO ₃ ) ₂ was 3 or less, the strength of magnetization was low, and when it was 30 or more, the coercive force was low.

A magnetic paint was prepared by using the above-mentioned magnetic powder with the composition shown in Table 5 to be described later, and the above-mentioned magnetic paint was applied to a card substrate made of polyethylene terephthalate (PET) resin so that the thickness became 20 μm. Coating,
I made a magnetic card.

On the magnetic layer of the magnetic card thus obtained, a magnetic head (generated magnetic field of about 5 kG) was used to perform recording in the longitudinal direction of the card by the FM system. When the recorded information was read as it was using a conventional magnetic card reader / writer, Sr (NO of Fe (NO ₃ ) _3
3 ) All the recorded information could be read except a part of the recorded information of the magnetic card using the powder having the weight ratio of 3 to ₂ .

Next, new information was overwritten on the existing information recording area of the magnetic layer of the magnetic card in which this information was recorded by using a magnetic card reader / writer. When the information of this magnetic card was read by the head of the magnetic card reader / writer, existing recorded information was recorded except for the magnetic card using the powder whose weight ratio of Fe (NO ₃ ) ₃ to Sr (NO ₃ ) ₂ is 30. It was confirmed that it was readable and new information could not be overwritten.

Example 2 Sr (NO ₃ ) ₂ and Fe (N
Prepare a nitrate in which Sr (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ are weighed and mixed so that the weight ratio with O ₃ ) ₃ is 1:10, and then, with respect to the total amount of this nitrate, The weight ratio is 1: 0.3, 1: 0.4, 1: 0.5,
Amino acids were weighed so that the ratio was 1: 0.6 and 1: 0.7. Then, the nitrate and the amino acid were dissolved in pure water to obtain a solution. The solution was sprayed into the atmosphere heated to 1000 ° C. and reacted by heating to obtain a powder.

The obtained powder was vibrated sample magnetometer (V.
S. M) was used to investigate the magnetic properties of the powder. The results are shown in Table 2.

[0031]

[Table 2]

From the results shown in Table 2, the coercive force decreased when the weight ratio of amino acid to nitrate was 0.3% or less or 0.7 or more.

Example 3 Sr (NO ₃ ) ₂ and Fe (N
Prepare a nitrate in which Sr (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ are weighed and mixed so that the weight ratio with O ₃ ) ₃ is 1:10, and then, with respect to the total amount of this nitrate, The amino acids were weighed so that the weight ratio was 1: 0.5, respectively. Then, the nitrate and the amino acid were dissolved in pure water to obtain a solution. The solution is heated to temperatures of 80 ° C and 200 ° C, respectively.
℃, 400 ℃, 600 ℃, 800 ℃, 1000 ℃, 12
The powder was obtained by spraying in the air heated to 00 ° C. to cause a heating reaction. However, at a temperature of 80 ° C., no reaction occurred and the liquid remained. The obtained powder was vibrated sample magnetometer (VS.
M) was used to investigate the magnetic properties of the powder. The results are shown in Table 3.
Shown in

[0034]

[Table 3]

From the results shown in Table 3, the reaction temperature of the powder was 1200.
The coercive force became low at ℃ or higher.

<Embodiment 4> The powder obtained in the above-mentioned Embodiment 3 was treated at 600 ° C, 700 ° C, 900 ° C and 110 ° C, respectively.
A heat treatment was performed by leaving it in the atmosphere at 0 ° C. and 1200 ° C. for 1 hour.

The obtained powder was vibrated sample magnetometer (V.
S. M) was used to investigate the magnetic properties of the powder. The results are shown in Table 4.

[0038]

[Table 4]

From the results of Table 4, it was confirmed that the magnetic properties of the powder did not change by the heat treatment at a temperature of 600 ° C. or lower, and that the magnetic properties of the powder deteriorated by the heat treatment at a temperature of 1200 ° C.

In the above four embodiments, the strontium powder powder production equipment and heat treatment equipment may be general general-purpose equipment, and since no special atmosphere is used, it is an inexpensive and safe production method.

A magnetic coating material having the composition shown in the following Table 5 is obtained by using the magnetic powder in the composition value range described above and by the manufacturing method of the above-mentioned embodiment.

[0042]

[Table 5]

As shown in FIG. 1, the magnetic coating material having the composition shown in Table 5 is applied on the card substrate 2 made of PET resin so as to have a thickness of 20 μm to form the magnetic layer 3.

On the magnetic layer 3 of the magnetic card 1 thus obtained, a magnetic head (generated magnetic field of 5 kG) was used, and some unrecorded portions were left in the longitudinal direction of the card, and recording was performed by, for example, the FM system. . When this was read as it was using a conventional magnetic card reader / writer, the written record information could be read.

Next, erasing of all recordings on the magnetic card was performed using a magnetic head of a general magnetic card reader / writer (generated magnetic field of about 5 kG), and the magnetic card after the erasing process was read using the magnetic head. , All existing records
It was confirmed that it was not erased even by the erasing process. That is, it was confirmed that new information cannot be overwritten.

[0046]

As described above, according to the present invention,
It is possible to provide a magnetic card having magnetic characteristics such that information cannot be rewritten or written for the purpose of forgery, and a manufacturing method for inexpensively manufacturing magnetic powder suitable for forming a magnetic layer of the magnetic card.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic card according to an embodiment of the present invention.

FIG. 2 is a plan view of the magnetic card shown in FIG.

[Explanation of symbols]

 1 magnetic card 2 card base 3 magnetic layer 4 protective layer 5 information recording area

Claims (5)

[Claims] 1. Amino acid to nitrate in which the weight ratio of strontium nitrate and iron nitrate is 1: x (5 ≦ x ≦ 20), and the weight ratio of nitrate and amino acid is 1: y (0.4 ≦ y ≦
0.6) to prepare a solution by mixing and dissolving the solution, and heating the solution to react at a temperature not lower than its boiling point and not higher than 1100 ° C. to prepare a magnetic powder. Production method. 2. The strontium nitrate has the chemical formula Sr.
The compound according to claim 1, which is represented by (NO ₃ ) ₂ , the iron nitrate is represented by the chemical formula Fe (NO ₃ ) ₃ , and the amino acid is represented by the chemical formula H ₂ NCH ₂ COOH. Method for producing magnetic powder. 3. The magnetic powder is further added at a temperature of 700 to 110.
The method for producing magnetic powder according to claim 1, further comprising a step of heat treatment at 0 ° C. 4. A method for manufacturing a magnetic card, characterized in that a magnetic layer is provided on the main surface of a card base using the magnetic powder manufactured by the method according to claim 1. 5. A magnetic card manufactured by the manufacturing method according to claim 4.