JPH06267055A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium being excellent in an overwrite characteristic and a reproduction output by providing a magnetic layer of a prescribed thickness on the surface of a base material. CONSTITUTION:The magnetic recording medium is a coating type metal magnetic recording medium tape having a magnetic layer 1 and a backing layer 3 provided by coating on a nonmagnetic base film 2. The coating type metal magnetic recording medium tape is better in productivity and durability than an evaporated metal magnetic recording medium tape and, besides, has no waveform distortion. In order to obtain this tape, the magnetic layer 1 is provided by coating on the surface of the base film 2 and the thickness of this magnetic layer 1 is made 0.10 to 0.13mum. Thereby a magnetic recording medium being excellent in an overwrite characteristic and a reproduction output is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used in digital VTRs, floppy disk devices and the like.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium is formed by laminating a magnetic layer on the surface of a base film made of a nonmagnetic material having a backing layer laminated on the back surface by coating or vapor deposition. By the way, there are various factors that determine the quality of the magnetic recording medium, but there are fundamental and important factors such as overwrite characteristics, reproduction output, shortest recording wavelength, etc., which can be set appropriately according to the purpose of use. Therefore, various values have been conventionally proposed.

FIG. 16 is an explanatory view showing the relationship between the shortest recording wavelength and the thickness of the magnetic layer in a conventionally proposed magnetic recording medium. The horizontal axis represents the shortest recording wavelength (μm) and the vertical axis represents the magnetic layer. The thickness (μm) is shown. In the figure, □ indicates the conventional product A (trade name Hi8VTR coated metal magnetic recording medium: M
P tape), △ mark are other conventional products B (brand name Hi8VTR
Evaporation-type metal magnetic recording medium: ME tape), X mark is a conventional product also used for home digital VTRs, ○ mark is a computer hard disk (Magnetic Recording Vol)
2 PP22).

By the way, the magnetic layer thickness of the conventional product indicated by □ is
0.3 μm, 0.2 μm for the conventional product indicated by Δ, 0.2 μm for the conventional product indicated by ×, and 0.9, 0.8, 0.63, 0.63, 0.17 μm for the conventional product indicated by ○. The shortest recording wavelength of the conventional product shown by □ is 0.49 μm, that of the conventional product shown by Δ is 0.5 μm, that of the conventional product shown by × is 0.49 μm,
0.5, 0.55, 0.67 μm, that of the conventional product shown by ○ is 8.0, 6.
2, 5.8, 5.0, 3.6 μm.

In addition, although audio recorders and those for floppy disk devices have been commercialized, the thickness of the magnetic layer in each of these magnetic recording media is 1 μm.
It is more than m.

FIG. 17 is an explanatory diagram showing the relationship between the shortest recording wavelength and the magnetic layer thickness / shortest recording wavelength in the conventional product shown in FIG. 16, where the horizontal axis represents the shortest recording wavelength (μm) and the vertical axis represents the shortest recording wavelength. The magnetic layer thickness / shortest recording wavelength is shown. Figure 17 □
The mark, △ mark, ○ mark, and X mark are all conventional products as shown in FIG. By the way, the magnetic layer thickness / shortest recording wavelength of the conventional product shown by □ is 0.61, and that of the conventional product shown by △ is 0.4.
The conventional products shown by 1 and X are 0.29 or more, and those of the conventional product shown by O are 0.15 or less.

[0007]

By the way, the magnetic layer thickness of the magnetic recording medium tends to become thinner with the downsizing of the magnetic recording / reproducing apparatus, the digitization of signals, the high density recording, etc., but 1.0 μm or less. The magnetic recording medium having a thin magnetic layer has a problem that the reproduction output of a short wavelength signal is reduced.

Further, in the hard disk, since the magnetic layer is thin, recording demagnetization occurs when a magnetic field more than necessary is applied to the magnetic layer to saturate the magnetic layer at the time of recording a short wavelength signal in order to improve overwrite characteristics. Not to mention long wavelength signals,
The reproduction output of the short wavelength signal also becomes small. In particular, the MP (coated metal) tape has a thicker magnetic layer than the ME (vapor-deposited metal) tape, so that the reproduction output of short-wavelength signals decreases more.

On the other hand, in a home digital VTR or the like, since the magnetic layer of the magnetic recording medium is thicker than the shortest recording wavelength, recording demagnetization similarly occurs, and the reproduction output becomes small. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic recording medium capable of ensuring a well-balanced overwrite characteristic and reproduction output characteristic.

[0010]

A magnetic recording medium according to a first invention is a magnetic recording medium having a magnetic layer formed by coating a magnetic material on the surface of a base material,
The thickness of the magnetic layer is 0.10 to 0.13 μm.

A magnetic recording medium according to a second aspect of the invention is a magnetic recording medium having a magnetic layer formed by coating a magnetic material on the surface of a base material, wherein the thickness of the magnetic layer is the shortest recording wavelength. It is characterized by being 1/5 to 1/4.

[0012]

In the first and second inventions, the magnetic layer has a thickness of 0.
Range of 10 μm to 0.13 μm, or 1/5 to 1 / of the shortest recording wavelength
Within the range of 4, the overwrite characteristics as well as the reproduction output characteristics are excellent.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. (Embodiment 1) FIG. 1 is a sectional structural view showing the structure of Embodiment 1 of the present invention, in which 1 is a magnetic layer, 2 is a non-magnetic layer such as a base film, 3 is a backing layer, As a whole, it is constructed as an MP (coated metal magnetic recording medium) tape having a three-layer structure laminated in this order. The reason why it is configured as an MP tape is that it is superior in productivity and durability to ME (vapor-deposited metal magnetic recording medium) tape, and there is no waveform distortion peculiar to ME tape. This is because there is an advantage that an equalization circuit is not required.

The thickness of the magnetic layer 1 of the magnetic recording medium according to the present invention is set to 0.10 μm or more and 0.13 μm or less. The thickness of the magnetic layer 1 is 0.10 μm or more is 0.10 μm
If it is less than the above, sufficient reproduction output for long-wavelength signals and short-wavelength signals cannot be obtained. The reason why the thickness is set to 0.13 μm or less is that if the thickness exceeds 0.13 μm, the required overwrite erase rate cannot be obtained.

FIG. 2 is a correlation characteristic diagram of the overwrite erasing rate and the magnetic layer thickness obtained by computer simulation. The horizontal axis represents the thickness of the magnetic layer 1 of the magnetic recording medium, and the vertical axis represents the overwrite erasing rate. Is shown. The overwrite erasing rate α was calculated by the following formula. α = −20 log ₁₀ V ₁ / V ₁₀ where V _{1 is} a long-wavelength signal component before overwriting V _{10 is} a long-wavelength signal component after overwriting (erasing residual signal component)

As can be seen from FIG. 2, the overwrite erasure rate α sharply improves when the magnetic layer 1 is made thinner than 0.15 μm, and the erasure rate of 20 dB or more required for a home digital VTR depends on the magnetic layer thickness. It can be seen that it is realized at 0.13 μm or less.

FIG. 3 is a correlation characteristic diagram obtained by computer simulation of the thickness of the magnetic layer and the reproduction output of the long wavelength signal before overwriting. The horizontal axis shows the thickness (μm) of the magnetic layer and the vertical axis shows the magnetic layer thickness. The reproduction output of the long wavelength signal before overwriting is shown.

As is apparent from FIG. 3, if the thickness of the magnetic layer 1 of the magnetic recording medium is 0.10 μm or more, the reproduction output of the short wavelength signal before overwriting is secured. The output of the long-wavelength signal before overwriting decreases when the thickness of the magnetic layer 1 of the magnetic recording medium is thinner than 0.15 μm, but decreases by 2 dB when the thickness of the magnetic layer 1 of the magnetic recording medium is 0.10 μm or more. It turns out that it can be suppressed to the following.

FIG. 4 is a correlation characteristic diagram of the reproduction output of a short wavelength signal after overwriting and the thickness of the magnetic layer by computer simulation. The horizontal axis indicates the thickness (μ) of the magnetic layer 1 of the recording medium.
m) and the vertical axis represents the reproduction output (dB) of the short wavelength signal after overwriting. The reproduction output was set to 0 dB when the magnetic layer thickness was 0.21 μm. As is clear from FIG. 4, the reproduction output of the short wavelength signal has a magnetic layer thickness of 0.10.
It can be seen that a high value of 0.3 dB or more is obtained in the range of μm to 0.13 μm.

FIG. 5 is a correlation characteristic diagram between the overwrite erasing rate and the magnetic layer thickness shown in FIG. 2, and a correlation characteristic diagram between the reproduction output of the long wavelength signal before overwriting and the magnetic layer thickness shown in FIG. FIG. 5 is a diagram summarizing the correlation characteristic diagram between the reproduction output of the short wavelength signal after overwriting shown in FIG. 4 and the magnetic layer thickness. The abscissa indicates the thickness (μm) of the magnetic layer 1 of the magnetic recording medium,
The vertical axis shows the overwrite erase rate (dB) on one side and the reproduction output (dB) on the other side. In the figure, a shows the reproduction output characteristic of the long wavelength signal before overwriting, b shows the reproduction output characteristic of the short wavelength signal after overwriting, and c shows the overwrite erasing rate.

As is clear from FIG. 5, the shortest recording wavelength 0.5 μ
At m, if a coating type magnetic recording medium having a magnetic layer of 0.10 to 0.13 μm thickness is used, a magnetic recording medium having a well-balanced reproduction output characteristic and overwrite characteristic can be obtained. I understand.

6, FIG. 7, and FIG. 8 show the thickness of the magnetic layer 1 respectively.
FIG. 9 is a reproduction waveform diagram showing simulation results after overwriting on the magnetic recording medium in the case of 0.21, 0.15, and 0.10 μm, in which the vertical axis represents the reproduction output and the horizontal axis represents time. The reproduced waveforms when the thickness of the magnetic layer 1 is 0.21 and 0.15 μm are shown. Although low frequency distortion is observed in the waveforms in FIGS. 6 and 7, when the thickness of the magnetic layer 1 is 0.10 μm, low frequency distortion is hardly observed in the reproduced waveform in FIG. 8.

This low-frequency distortion is due to the signal having a recording wavelength of 2.0 μm recorded before overwriting. From this, it can be said that the magnetic recording medium having the thickness of the magnetic layer 1 of 0.21 and 0.15 μm is not suitable for overwriting.
Therefore, if the thickness of the magnetic layer 1 of the overwritten magnetic recording medium is 0.13 μm or less, it is easily estimated that good characteristics can be obtained.

FIGS. 9, 10, and 11 are magnetization pattern diagrams obtained by simulating the case where a signal having a recording wavelength of 2.0 μm is recorded on a magnetic recording medium (MP tape) in a non-recording state. The thickness of each magnetic layer 1 in FIGS. 9, 10 and 11 is 0.2.
It shows the case of 1, 0.15 and 0.10 μm. The direction and size of the arrow shown in the figure correspond to the magnetization direction and the size of the magnetization of the medium, and the magnetization pattern corresponds to a half wavelength of the recording wavelength of 2.0 μm.

The recording wavelength of 2.0 μ is shown in FIGS.
After overwriting the magnetic recording medium having the recording pattern of 0.5 μm on the magnetic recording medium recording the m signal, that is, after overwriting the magnetic recording medium having the magnetization pattern shown in FIGS. 9, 10 and 11. 3 is a magnetization pattern diagram of FIG. The thickness of each magnetic layer 1 in FIGS. 12, 13 and 14 is shown in FIG.
0.21, 0.15, and 0.10 μm, which are the same as in Fig. 10 and Fig. 11.

As is clear from FIG. 14, FIG. 13 shows that the region B of change of magnetization due to overwriting is only up to a depth of about 0.13 μm, and in the deeper region, it is due to the recording of the long wavelength signal recorded before overwriting. It can be seen that the magnetization remains. This 0.13 μm is approximately the same as the generally-known optimum recording depth of a recording wavelength of 0.5 μm, that is, a quarter of the recording wavelength of 0.5 μm. Therefore, a magnetic layer thickness of 0.13 μm or more in depth is rather It is presumed that there is a problem in overwrite characteristics.

Next, the contents of the simulation performed on the overwrite characteristic and the reproduction output as described above will be described. In the simulation method, the magnetization pattern of the magnetic recording medium was first obtained by recording a long wavelength signal, overwriting with a short wavelength signal was simulated based on the data of the magnetization pattern, and the magnetization pattern after overwriting was obtained.

The reason for overwriting after recording the long wavelength signal is as follows. The recording depths of the long-wavelength signal, the short-wavelength signal and the short-wavelength signal are magnetized deeper into the magnetic layer 1 of the recording medium when the long-wavelength signal is recorded, and the short-wavelength signal is recorded after the long-wavelength signal is recorded. This is because when overwriting is performed, the overwriting characteristics deteriorate, and this case was used as the simulation target.

In the recording process, the head magnetic field is expressed by the Karlqist equation,
The magnetization of the recording medium was calculated by the self-consistent method and simulated, and the reproducing process was simulated by the reciprocity theorem.

The computer simulation used this time is "COMPUTER SIMULATION OF THE DOUBULE-COMPONENT
MULTIPLE RECORDING METHOD OF VCRs ”, IEE Transactio
n on Consumer Electronics, Vol.38, No.3, AUGUST, 199
2, This is a proven method reported in PP247-252.

The simulation conditions are as follows. Recording medium: MP tape, coercive force 1700 Oe, residual magnetic flux density 3100G Recording wavelength for short wavelength: 0.5 μm Recording wavelength for long wavelength: 2.0 μm Recording current: Optimum current value for rectangular wave, short wavelength signal Spacing of medium and magnetic head : 0.03 μm Gap length of magnetic head: 0.2 μm Parameter: Thickness of magnetic layer 1 High-density magnetic recording with the shortest recording wavelength of 0.5 μm

The range of the thickness of the magnetic layer 1, which is a parameter, is 0.21 μm for the following reason.
Up to m As is clear from the magnetic pattern diagrams shown in FIGS. 10 and 11, when the thickness of the magnetic layer is 0.10, 0.15 μm, the entire thickness of the magnetic layer 1 is magnetized, but the thickness of the magnetic layer 1 is 0.21 μm. In the magnetization pattern diagram shown in Fig. 9, the recording by the signal with the recording wavelength of 2.0 μm is about 0.17 μm.
It can be seen that only the region A having a depth of m is magnetized. Therefore, the thickness of the magnetic layer 1 of the magnetic recording medium is 0.17 μm.
It is predicted that even if the thickness is thicker, the magnetic characteristics are not so different, and it can be said that the upper limit of the thickness of the magnetic layer of the magnetic recording medium to be simulated is 0.21 μm.

(Example 2) In the magnetic recording medium shown in the above Example 1, the thickness of the magnetic layer 1 was set to 0.10 to 0.13 µm, but this Example 2 shows that the thickness of the magnetic layer is the shortest. It is also a coating type magnetic recording medium having a thickness corresponding to 1/5 to 1/4 of the wavelength. 1/5 or more of the shortest recording wavelength is 1 /
This is because if it is less than 5, good reproduction output cannot be obtained. The reason for setting the wavelength to be 1/4 or less of the shortest recording wavelength is that if it exceeds 1/4, sufficient overwrite characteristics cannot be obtained.

Also in the second embodiment, the same overwrite characteristic and reproduction output characteristic as in the first embodiment can be obtained in a well-balanced manner. The reason is that the simulation shown in Example 1 is similar for all short recording wavelengths, and similar results can be obtained at other recording wavelengths. Further, even if the frequency characteristic of the efficiency of the magnetic head is taken into consideration, long-wavelength recording is only strengthened, and this effect can be ignored if the thickness of the magnetic layer is set within the above range.

(Embodiment 3) FIG. 15 is a block diagram showing the structure of a magnetic recording / reproducing apparatus for a magnetic recording medium shown in Embodiment 1 or 2. In FIG. 15, 11 is the coating type metal magnetic recording medium shown in Embodiment 1 or 2, and 12 is the magnetic head. The magnetic head 12 is selectively connected to the recording amplifier 13 side during recording and to the reproducing amplifier 15 side during reproduction by the recording / reproducing changeover switch SW. As a result, at the time of recording, the recording / reproduction changeover switch SW is turned on to the R side, and input information such as video, audio, data, etc.
The signal converted by is supplied as a recording current to the magnetic head 12 through the recording amplifier 13 and recorded on the coating type metal magnetic recording medium 11.

At the time of reproduction, the recording / reproduction changeover switch SW is turned on to the P side, and the magnetic head 12 senses the magnetic flux from the coating type metal magnetic recording medium 11 and converts it into a reproduction voltage. After that, it is converted into output information such as video, audio and data by the signal processing circuit 16 through the reproduction amplifier 15.

The coating type metal magnetic recording medium 11 is superior in productivity and durability to the vapor deposition type metal magnetic recording medium and has no waveform distortion peculiar to the vapor deposition type metal magnetic recording medium. As shown in 1, the magnetic layer thickness is 0.10 ~
Since the coating type metal recording medium is set to 0.13 μm and the thickness of the magnetic layer is regulated at the shortest recording wavelength in the second embodiment, a special waveform equalization is performed between the reproducing amplifier 15 and the signal processing circuit 16. Recording and reproduction can be performed by a magnetic recording / reproducing apparatus that does not require a circuit and does not use a waveform equalizing circuit. In the magnetic recording / reproducing apparatus configured as described above, since the waveform equalizing circuit does not exist, the circuit scale can be reduced, which is also advantageous for downsizing the apparatus.

[0038]

As described above, according to the first aspect of the invention, since the thickness of the magnetic layer is set to 0.10 to 0.13 .mu.m, the overwrite characteristic is excellent and the reproduction output is also excellent. Further, according to the second aspect of the invention, since the recording wavelength is set to 1/5 to 1/4, both the overwrite characteristic and the reproduction output can be satisfied similarly.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a magnetic recording medium of Example 1.

2 is a correlation characteristic diagram showing a simulation result of an overwrite erasing rate and a magnetic layer thickness in the magnetic recording medium shown in Example 1. FIG.

FIG. 3 is a correlation characteristic diagram showing a simulation result of a reproduction output of a long wavelength signal before overwriting and a magnetic layer thickness in the magnetic recording medium shown in Example 1.

FIG. 4 is a correlation characteristic diagram showing a simulation result of a reproduction output of a short wavelength signal after overwriting and a magnetic layer thickness in the magnetic recording medium shown in Example 1.

5 is a correlation characteristic diagram collectively showing simulation results of the long-wavelength signal before overwriting and the reproduction output after overwriting shown in FIGS. 2, 3, and 4, and the overwriting erasing rate and the magnetic layer thickness. .

FIG. 6 is a reproduction waveform diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.21 μm and then overwritten with a short wavelength signal.

FIG. 7 is a reproduction waveform diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.15 μm and then overwritten with a short wavelength signal.

FIG. 8 is a reproduction waveform diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.10 μm and then overwritten with a short wavelength signal.

FIG. 9 is a magnetization pattern diagram showing a simulation result when a long-wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.21 μm.

FIG. 10 is a magnetization pattern diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.15 μm.

FIG. 11 is a magnetization pattern diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.10 μm.

FIG. 12 is a magnetization pattern diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.21 μm and then overwritten with a short wavelength signal.

FIG. 13 is a magnetization pattern diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.15 μm and then overwritten with a short wavelength signal.

FIG. 14 is a magnetization pattern diagram showing a simulation result when a long wavelength signal is recorded on a magnetic recording medium having a magnetic layer thickness of 0.10 μm and then overwritten with a short wavelength signal.

FIG. 15 is a block diagram of a magnetic recording / reproducing apparatus used in the present invention.

FIG. 16 is an explanatory diagram showing the relationship between the shortest recording wavelength and the magnetic layer thickness of a magnetic recording medium in a conventional product.

FIG. 17 is an explanatory diagram showing the relationship between the shortest recording wavelength and the thickness of the magnetic layer of the magnetic recording medium / the shortest recording wavelength in the conventional product.

[Explanation of symbols]

 1 magnetic layer 2 non-magnetic layer 3 backing layer 11 coated metal magnetic recording medium 12 magnetic head 13 recording amplifier 14 signal processing circuit 15 reproducing amplifier 16 signal processing circuit SW recording / reproducing switch

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[Procedure amendment]

[Submission date] July 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. (Example 1) Usually, a coating type medium is a metal film such as a vapor deposition type medium.
In addition to being superior in productivity and durability compared to the medium,
It has the advantage that there is no waveform distortion that is peculiar to such animals. Less than
The coating medium will be described. FIG. 1 is a cross-sectional structure diagram showing the configuration of Example 1 of the present invention, in which 1 is a magnetic layer, 2 is a non-magnetic layer such as a base film, 3 is a backing layer, and in this order as a whole. MP with a stacked three-layer structure
(Coating metal magnetic recording medium) It is configured as a tape.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

The coated metal magnetic recording medium 11 is superior in productivity and durability when compared with the vapor-deposited metal magnetic recording medium, and , in addition, has no peculiar waveform distortion unlike the vapor-deposited metal magnetic recording medium. The thickness of the magnetic layer is set to 0.10 to 0.13 μm as shown in Example 1, and in Example 2, the coating type metal recording medium in which the thickness of the magnetic layer is regulated at the shortest recording wavelength is used. A special waveform equalizing circuit is not required between the signal processing circuit 16 and the signal processing circuit 16, and recording / reproducing can be performed by a magnetic recording / reproducing apparatus which does not use the waveform equalizing circuit. In the magnetic recording / reproducing apparatus configured as described above, since the waveform equalizing circuit does not exist, the circuit scale can be reduced, which is also advantageous for downsizing the apparatus.

Claims (2)

[Claims] 1. A magnetic recording medium comprising a magnetic layer formed by coating a magnetic material on the surface of a base material, wherein the magnetic layer has a thickness of 0.10 to 0.13 μm. recoding media. 2. A magnetic recording medium having a magnetic layer formed by applying a magnetic material to the surface of a base material, wherein the thickness of the magnetic layer is 1/5 to 1/4 of the shortest recording wavelength. A magnetic recording medium characterized by the following.