JPH03189928A - Magnetic card and recording and reproducing method thereof - Google Patents

Abstract

PURPOSE:To assure the stable holding of recording information and the recording at a higher density by providing a magnetic layer consisting of hexagonal ferrite as a magnetic material on a substrate and specifying the surface roughness of the magnetic layer to <=0.015 mum center line average height. CONSTITUTION:The hexagonal ferrite has a high coercive force and can stably maintain the recording information against external magnetic fields. In addition, this ferrite has the extremely large Kerr rotating angle of reflected light and contributes largely to the improvement in reproduced output. The surface roughness thereof is specified to <=0.015 mum center line average height. Namely, the quantity of the reflected light from the surface of the magnetic layer is insufficient and the Kerr rotating angle decreases if the surface roughness larger than this value is adopted. A decrease in the reproduced output is then resulted. The Kerr rotating angle of the reflected light is increased in this way and the high reproduced output is expected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic force used in ID cards, private cards, etc., and a recording and reproducing method thereof.

[Conventional technology]

BACKGROUND ART In recent years, various magnetic cards such as credit cards, cash cards, and private cards have been used in a wide range of fields.

These magnetic cards usually have a magnetic layer on a substrate, and use a magnetic head to record information on this layer, and also use the magnetic head to read information. In this case, since the same part is slid over and over again, the magnetic layer is subject to significant wear. To prevent this and to stably retain recorded information, a protective film is usually formed on the magnetic layer. There is.

[Problem to be solved by the invention]

However, although such a protective film protects the magnetic layer from damage due to sliding, it also increases the distance between the magnetic layer on which information is recorded and the magnetic head that reproduces the information. As a result, the output reproduced by the magnetic head becomes small, causing the problem that high-density recording is not possible.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional circumstances, it is an object of the present invention to provide a magnetic card and a recording/reproducing method therefor that can easily maintain recorded information stably and achieve high-density recording by improving reproduction output.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventors of the present invention found that information is first recorded on a magnetic card using a magnetic head, but reproduction is performed using rotation of the polarization plane of laser light. In other words, he came up with a method that takes advantage of the fact that the rotation angle of the plane of polarization of light, that is, the Kerr rotation angle, is different between magnetized and unmagnetized parts, and detects this with a photodetector to read information. Ta.

This is because in reproduction using such laser light, the wear of the magnetic layer due to the sliding of the magnetic head is limited to only during recording.
In addition, this wear during recording can be suppressed by providing a protective film on the magnetic layer, and on the other hand, the existence of this protective film itself does not directly cause a reduction in the reproduction output, thus ensuring stable retention of recorded information and high performance. This is because it was expected that density recording would be achieved relatively easily.

However, despite detailed experimental studies conducted by the inventors in line with this expectation, a large Kerr rotation angle could not be obtained even if such a reproducing method using laser light was adopted for conventionally known magnetic cards. However, it was found that the reproduction output was never satisfactory.

Therefore, as a result of repeated trial-and-error experiments and dissections to find out how to increase the Kerr rotation angle mentioned above, we found that we specifically used hexagonal ferrite as the magnetic material to be included in the magnetic layer. When the surface of the magnetic layer is made very smooth so that the amount of laser light reflected from the surface of the magnetic layer is increased, the Kerr rotation angle increases significantly and the reproduction output can be greatly improved. Having discovered this fact, we have finally completed the present invention.

That is, the first aspect of the present invention is that a magnetic layer made of hexagonal ferrite as a magnetic material is provided on a substrate, and the surface roughness of this magnetic layer is 0.015 μm in center line average surface roughness.
The present invention relates to a magnetic card having the following characteristics.

A second aspect of the present invention is that information is recorded on the magnetic layer of the magnetic card using a magnetic head, and the information is reproduced using rotation of the polarization plane of light such as a laser beam. The present invention relates to a method for recording and reproducing magnetic cards.

[Structure and operation of the invention]

As the hexagonal ferrite in the present invention, one represented by the following general formula (%) is preferably used. A in the formula is Ba
, Sr, Pb, and Ca; M is Ni, Zn, Co, and TiZ;
at least one element selected from r, Sn, In, Ge, Cu, and Mn; X has a value of 0.01 to 0°15;
n is a value from 4 to IO. Note that the element represented by M above is usually added to adjust the coercive force, but it may not be added. In this case, the element represented by the general formula A0.6FezO
: Hexagonal ferrite represented by + is particularly preferably used.

Such hexagonal ferrite is usually 700 to 5.00
It has a high coercive force of 0 oersted, which has the advantage of stably retaining recorded information against external magnetic fields.In addition, it has a higher coercive force than other magnetic materials with high coercive force, such as Co-modified iron oxide. It has a feature that the Kerr rotation angle of the light is extremely large, which greatly contributes to improving the reproduction output.

In the present invention, the above-mentioned hexagonal ferrite can be used alone as the magnetic material, or may be used in combination with other magnetic materials such as Co-modified iron oxide, if necessary. However, the content of these other magnetic materials is preferably 50% by weight or less based on the total amount with hexagonal ferrite, and if the amount is too large, the Kerr rotation angle cannot be expected to be improved.

In the present invention, a magnetic layer using such a magnetic material may be directly provided on a non-magnetic substrate, such as a polyester film, usually having a thickness of about 150 to 500 μm, by vapor deposition or sputtering. Alternatively, a magnetic coating may be prepared in which magnetic particles containing at least hexagonal ferrite particles are dispersed in a binder, and this may be applied onto the same substrate as described above and dried to form a magnetic layer.

The above magnetic particles have an average particle diameter of 0°06~
The diameter is preferably in the range of 2 μm; if it is too small, the reproduction output will be reduced due to poor dispersibility, and if it is too large, it will be difficult to set the surface roughness of the magnetic layer within the specific range of the present invention. Binders for dispersing magnetic particles include ordinary binders for magnetic cards, such as vinyl chloride-vinyl acetate resins, polyurethane resins, polyester resins, cellulose resins, polyhinyl butyral resins, and various types of ultraviolet curing resins. In addition to mold resins, a wide variety of resins including polyisocyanate compounds as crosslinking agents can be used.

The thickness of the magnetic layer formed in this way is approximately 5 to 30 μm depending on the purpose of use of the magnetic pad, but its surface roughness is 0.015 μm or less in terms of center line average surface roughness. It is essential to be present. That is, if the surface roughness is greater than this, the amount of reflected light from the magnetic layer surface will not be sufficient to be detected as a signal, and the Kerr rotation angle will become small, resulting in a reduction in reproduction output.

The above-mentioned surface roughness of the magnetic layer can be set by, for example, selecting the size of the magnetic particles used in a method of applying and drying a magnetic paint, or by applying pressure using a calendar after being applied to a substrate, or by applying pressure using a calendar, etc. This can be easily achieved by adding appropriate means such as forming a protective film with good surface smoothness on the magnetic layer.

The magnetic card of the present invention is characterized by having the above-mentioned specific magnetic layer provided on the base, and may have the same structure as a conventional magnetic card other than this. An ultraviolet curable resin may be formed as a protective film to a thickness of about 0.1 to 2 μm, or a printing layer, a pattern layer, etc. may be arbitrarily formed on the same side or the opposite side of the magnetic layer.

To record information using the magnetic card of the present invention, a conventionally known method using a magnetic head may be used (on the other hand,
The reproduction can be carried out by, for example, irradiating the surface of the magnetic layer with light such as a laser beam, and detecting the reflected light with a photodetector through a polarized beam stabilizer.

In other words, in this reproduction method, the reflected light from the magnetized part is polarized, and the reflected light from the unmagnetized part is not polarized. By adjusting the polarization angle, recorded signals can be reproduced with high sensitivity.

[Effects of the Invention] As described above, according to the magnetic card and the recording and reproducing method of the present invention, the wear of the magnetic layer due to the sliding of the magnetic head is limited to only during recording, and the wear of the brackets during recording is also caused by the magnetic layer. This can be suppressed by providing a protective film on the layer, but on the other hand, the presence of such a protective film does not directly cause the reduction in reproduction output, and as mentioned above, it is possible to suppress the reduction by using a specific magnetic material for the magnetic layer. By making the surface roughness within a specific range, the Kerr rotation angle of the reflected light can be increased, and high reproduction output can be expected.

Therefore, according to the present invention, stable retention of recorded information and high-density recording by improving reproduction output can be easily achieved, and the present invention can be widely applied to various magnetic cards such as credit cards, cash cards, and brivate cards. can do.

〔Example〕

Next, examples of the present invention will be described in more detail. In addition, hereinafter, parts are parts by weight.

Example 1 As a magnetic material, the average particle diameter was 0.32 μm, the coercive force was 2.
530 Oersted barium ferrite (B a F
A magnetic coating composition having the following composition was prepared using the 6120 Iq) particles.

Barium ferrite particles 75 parts Methyl isobutyl ketone 75 parts Toluene
75 parts Next, apply this magnetic paint to a thickness of 190 μm.
A magnetic card was prepared by coating and drying the magnetic layer on a polyester film having a thickness of about 13 μm and a centerline average surface roughness of 0.014 μm.

Example 2 As a magnetic material, an average particle diameter of 0.12 μm, a coercive force f,
910 Oersted's S [rontium ferrite (S
A magnetic card having a magnetic layer with a thickness of about 13 μm and a center line average surface roughness of 0.0] and 077 m was produced in the same manner as in Example 1, except that the r Fe 12019) particles were used. .

Example 3 The same procedure as Example 1 was carried out, except that after the magnetic paint was applied and dried, the surface was smoothed using a calendar at 80°C, and the thickness was about 13 μm, and the center line average surface roughness was 0. .0
A magnetic card having a magnetic layer of 0.09 μm was produced.

Comparative Example 1 As a magnetic material, the average particle diameter is 1.2 μm, and the coercive force is 1.7.
The same procedure as in Example 1 was carried out except that barium ferrite particles of 80 oersted were used, with a thickness of about 13 μm and a center line average surface roughness of 0. 0], a magnetic card having a magnetic layer of 8 μm was produced.

Comparative Example 2 As a magnetic material, average particle diameter is 0.30 μm, coercive force is 95
A magnetic card having a magnetic layer having a thickness of about 13 μm and a center line average surface roughness of 0.008 μm was produced in the same manner as in Example 1 except that CO-containing -Fe2O1 particles of 0 oersted were used. did.

The Kerr rotation angle of each of the magnetic cards of the above Examples and Comparative Examples was examined in the following manner. The results are shown in Table 1 below along with the coercive force and centerline average surface roughness of the magnetic layer.

<Kerr rotation angle> The polarization angle of light was determined when light with a wavelength of 780 was irradiated to the residual magnetized state after applying a magnetic field of 10 kiloersted.

1 2 First, the recorded signal was reproduced. As a result, the magnetic cards of Examples 1 to 3 could be reproduced with good sensitivity, but the magnetic cards of Comparative Examples 1.2 could not be reproduced well.

As is clear from the above table, all of the magnetic cards of Examples 1 to 3 of the present invention have large Kerr rotation angles, except for the magnetic quadrangle and hexagonal ferrite particles of Comparative Example 1, which have a rough surface roughness of the magnetic layer. It can be seen that a large Kerr rotation angle was not obtained with the magnetic card of Comparative Example 2 using the magnetic material.

Claims (2)

[Claims] (1) A magnetic material characterized in that a magnetic layer made of hexagonal ferrite as a magnetic material is provided on a substrate, and the surface roughness of the magnetic layer is 0.015 μm or less in center line average surface roughness. card. (2) Information is recorded on the magnetic layer of the magnetic card according to claim (1) using a magnetic head, and the information is reproduced using rotation of the polarization plane of light such as a laser beam. A method for recording and reproducing magnetic cards.