JPH09326113A - Magnetic recording medium and magnetic recording and reproducing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium capable of improving an overwriting characteristic while maintaining high electromagnetic conversion characteristics. SOLUTION: This magnetic recording medium formed with a magnetic layer 3 on a film-like base 2 by coating this case with magnetic powder of a metal system consisting essentially of Fe is so set that the saturation magnetic flux density Bm in its traveling direction L of the magnetic recording medium is within a range of 3,500 to 5,000G (gauss), the coercive force Hc is >=2,000Oe (oersted), the surface roughness SRa of the magnetic layer described above is <=2nm, the thickness (t) of the magnetic layer is within a range of 0.1 to 0.2μm, the saturation magnetization quality σS of the magnetic powder is within a range of 160 to 200emu/g, the major axis length of the magnetic powder is within a range of 0.05 to 0.2μm and the inversion magnetic field distribution SFD of the magnetic layer is <=0.45. As a result, the overwriting characteristic is improved while the electromagnetic conversion characteristics are highly maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium and a recording / reproducing system thereof, and in particular,
The present invention relates to a magnetic recording medium that realizes excellent characteristics for high-density digital recording and a recording / reproducing method thereof.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium is composed of a magnetic tape or a magnetic disk, and is used in
Since it is widely used in many fields such as computer-related products and the amount of information to be handled is increasing, there is an increasing demand for improvement in magnetic characteristics in order to realize high density recording. Specifically, in order to improve the magnetic characteristics for increasing the recording density, improvement of the saturation magnetic flux density Bm of the medium magnetic layer, improvement of the coercive force Hc, and the like have been attempted.
Along with this, in order to prevent a decrease in signal output due to a spacing loss that occurs during recording and reproduction of a signal, the medium plane is made smoother to suppress the spacing as much as possible.

[0003]

By the way, as a result of improving various magnetic characteristics as described above, one of the characteristics is to improve the coercive force Hc.
There is a contradictory relationship that deteriorates the overwrite characteristic, which is one of the important characteristics. That is, the overwrite characteristic indicates a recording characteristic when a signal is overwritten on a recorded magnetic medium without erasing the previous information, and when the coercive force Hc is improved, the previous signal is overwritten. Will tend to remain. As one of the measures for preventing such deterioration of the overwrite characteristic, for example, as disclosed in Japanese Patent Laid-Open No. 62-121902, a medium and a head gap which are suppressed to a coercive force (coercive force) of 750 Oe or less are defined. Use a specific magnetic head, or make the magnetic layer very thin, for example 0.1 μm.
It is proposed to set it to m or less.

However, the current situation is that sufficient overwrite characteristics cannot be obtained by the above measures. For example, the signals recorded on the magnetic recording medium are not only short-wavelength signals, but also long-wavelength signals such as control signals.
Regarding such a signal, the reproduction output becomes extremely low in the above-mentioned magnetic layer having a small thickness. In addition, the output at the time of recording and reproducing of the short wavelength signal is not sufficient with the one currently put to practical use and the one proposed. Furthermore, as described above, the durability of the coating film deteriorates in a medium having a single magnetic layer of 0.1 μm or less.

The present invention has been devised in order to effectively solve the above-mentioned problems. An object of the present invention is to provide a magnetic recording medium and a magnetic recording / reproducing system capable of improving overwrite characteristics while maintaining high electromagnetic conversion characteristics.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a magnetic film comprising a film-like support coated with metal magnetic powder containing Fe as a main component to form a magnetic layer. In the recording medium, the saturation magnetic flux density Bm in the running direction of the magnetic recording medium is in the range of 3500 to 5000 G (Gauss), the coercive force Hc is 2000 Oe (Oersted) or more, and the surface roughness SRa of the magnetic layer is 2 nm or less, The thickness t of the magnetic layer is in the range of 0.1 to 0.2 μm, the saturation magnetization amount σs of the magnetic powder is in the range of 160 to 200 emu / g, and the major axis length of the magnetic powder is 0.05 to 0.2 μm. Within this range, the switching field distribution SFD of the magnetic layer is set to 0.45 or less.

With this configuration, the overwrite characteristic can be improved while maintaining the electromagnetic conversion characteristic at a high level. Further, in order to record and reproduce on this magnetic recording medium, a magnetic head having a saturation magnetic flux density Bs of 13,000 gauss or more is used. The magnetic recording medium may be a single magnetic layer or a multi-layered medium having a nonmagnetic layer having a thickness of 0.5 to 3 μm as an underlayer. This multilayer structure makes it possible to further improve the overwrite characteristic. The material of the magnetic head may be iron nitride, ferrite, sendust, or amorphous type.
Further, the structure of the magnetic head is not particularly limited, but a laminated type and a MIG (Metal In Gap) type are particularly effective, and a known shape and structure may be used. Here, the upper limit of the coercive force Hc is preferably about 3000 Oe, the lower limit of the surface roughness SRa is about 1 nm, and the lower limit of the switching field distribution SFD is about 0.4. The upper limit of the saturation magnetic flux density of the magnetic head is about 20000 Gauss.

[0008]

DETAILED DESCRIPTION OF THE INVENTION A magnetic recording medium and a magnetic recording / reproducing system according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional view showing a magnetic recording medium of the present invention, and FIG. 2 is a view showing a state in which recording and reproduction are performed on the magnetic recording medium shown in FIG. 1 by using a magnetic head. The magnetic recording medium 1 has a basic structure by coating the magnetic layer 3 on the support 2 formed in a film shape. The upper part of the support 2 is not limited to a single layer provided with only a magnetic layer, but may be a multilayer structure, for example, a magnetic layer 3 and an underlayer 6.
You may make it a layered structure. Further, a back coat layer 4 may be provided on the surface of the support 2 opposite to the magnetic layer 3.

As a material for the support 2, a PET (polyethylene terephthalate) film or the like can be used. The thickness t of the magnetic layer 3 is 0.1 to 0.2 μm.
Is made thin. In order to realize high electromagnetic conversion characteristics, it is effective to use fine magnetic powder having high magnetic characteristics as the magnetic powder in the magnetic layer 3. In the present invention, the magnetic metal powder containing Fe as a main component and having a saturation magnetization σs in the range of 160 to 200 emu / g is used. Saturation magnetization amount s
Is less than 160 emu / g, a sufficient saturation magnetic flux density Bm cannot be realized after forming the medium, and when the saturation magnetization σs is more than 200 emu / g, the corrosion resistance of the magnetic powder is significantly deteriorated. However, handling at the time of manufacturing the medium becomes extremely bad, and the medium cannot be completed. About the major axis length of the magnetic powder, 0.05 ~
The range of 0.2 μm is preferable, and when it is larger than 0.2 μm, the output and C / N in the high frequency range are deteriorated, and 0.0
If it is less than 5 μm, not only the dispersibility of the magnetic powder at the time of producing the medium is deteriorated, but also the orientation property when a magnetic field is applied is deteriorated, and as a result, the one having excellent electromagnetic conversion characteristics cannot be obtained.

A recording medium was manufactured using the above magnetic powder, and the saturation magnetic flux density Bm of the magnetic layer 3 at this time was 3500.
Set within the range of up to 5000 G (Gauss). If the saturation magnetic flux density Bm is less than 3500G, a high output cannot be obtained, and if it is greater than 5000G, so-called powder falling, such as lack of magnetic powder, occurs.
The coercive force Hc in the longitudinal direction of the medium, that is, the medium running direction, needs to be 2000 Oe (Oersted) or more, and if the coercive force Hc is less than 2000 Oe, the output in the high range is not good. The upper limit of this coercive force Hc is
About 3000 Oe is preferable. Surface roughness S of magnetic layer 3
Ra needs to be 2 nm or less. If the roughness SRa is larger than 2 nm, the spacing loss at the time of recording / reproducing a signal increases, and particularly the output in the high frequency range decreases. The lower limit of the surface roughness SRa is preferably about 1 nm. The thickness t of the magnetic layer 3 is 0.1 to 0.
Within the range of 2 μm, and if it is smaller than 0.1 μm, the reproduction output decreases over the entire range, and conversely, this is 0.
If it is larger than 2 μm, the distortion of the waveform at the time of recording and reproducing the pulse signal increases, and the overwrite characteristic also deteriorates.
The switching field distribution SFD is set to 0.45 or less,
When this exceeds 0.45 and becomes large, the overwrite characteristic deteriorates. The lower limit of this switching field distribution SFD is
About 0.4 is preferable. Further, compared with the recording medium having the conventional structure, in the present invention, it is possible to obtain sufficiently excellent coating film durability even when the magnetic layer has a single layer structure. Further, the multi-layer structure of the magnetic layer and the underlayer makes it possible to further improve the overwrite characteristic.

Using the magnetic head 5 as shown in FIG.
To perform recording and reproduction on the magnetic recording medium 1 as described above, a magnetic head having a saturation magnetic flux density Bs of 13000 G is used. In a magnetic head having a saturation magnetic flux density Bs of less than 13000G, the overwrite characteristic is deteriorated. The upper limit of the saturation magnetic flux density Bs is preferably about 20000G. As the material of the magnetic head 5, iron nitride, ferrite, sendust, or amorphous material can be used. The shape and structure of the magnetic head 5 are not limited and may be known ones.
A G type head is effective. When recording and reproducing were performed on the magnetic recording medium 1 formed as described above,
Both the electromagnetic conversion characteristics and the overwrite characteristics could be significantly improved.

<Example> Next, a concretely manufactured example of the present invention and a comparative example will be described in comparison. First, the composition shown in Table 1 below was used as a magnetic coating material for forming the magnetic layer 3.

[0013]

[Table 1]

The mixture having the composition shown in Table 1 was mixed and dispersed by a sand mill to prepare a magnetic coating material. The magnetic powder used here is of 10 types with different characteristics,
Its characteristics are shown in Table 2.

[0015]

[Table 2]

In Table 2, the arrow ↑ means the same numerical value as in the upper column. A magnetic tape was produced by applying the magnetic coating material produced as described above to a film-shaped support. The thickness and surface property of the magnetic layer were controlled by adjusting the coating conditions and the calendering conditions in the process of forming a tape. The switching field distribution SFD was adjusted by changing the distribution of Hc of the magnetic powder.

A back coat layer containing carbon black as a main component was provided on the surface of the support on the side opposite to the magnetic layer in the thus-produced one. Here, a PET film having a thickness of 6.0 μm was used as the support, and the thickness of the back coat layer was 0.5 μm. In addition, in Examples 6 and 7,
An underlayer having the following composition was provided between the support and the magnetic layer. This film-shaped medium was first cut to a width of 3.81 mm to obtain a DAT magnetic tape. A DAT deck, XD-Z505 manufactured by Victor Company of Japan, was used to evaluate the magnetic tape. The electromagnetic conversion characteristics were evaluated by modifying the deck. The recording / playback system was modified by modifying the head amplifier to enable direct signal input to the head from the outside and direct observation of the head signal. The runnability was evaluated at a temperature of 25 ° C and a humidity of 6
Evaluation was performed by running 100 times repeatedly in an environment of 0%. Regarding the electromagnetic conversion characteristics, sine wave signals of 1 MHz and 7 MHz were recorded respectively, and the reproduction output was measured. The overwrite characteristic was obtained by recording a 1 MHz signal, then erasing this signal, overwriting the same track with a 7 MHz signal, and measuring the decrease in the 1 MHz signal. Table 3 shows the magnetic powders used and the characteristics of the media.
The recording medium of the present invention is manufactured in Examples 1 to 7, and Comparative Examples 1 to 8 are prepared for comparison therewith.
Was produced. Base coating composition α-Fe ₂ O ₃ ... 100 parts by weight carbon black ... 5 parts by weight vinyl chloride ... 8 parts by weight urethane ... 5 parts by weight isocyanate ... 5 parts by weight palmitic acid ... 2 parts by weight methyl ethyl ketone ... 100 parts by weight cyclohexanone ... 100 parts by weight Department

[0018]

[Table 3]

In Table 3, portions outside the range specified in claim 1 are underlined. Examples 1 to 7
Table 4 shows the evaluation results of Comparative Examples 1 to 8.

[0020]

[Table 4]

In Table 4, the arrow ↑ means the same numerical value as in the upper column. Further, the head type A indicates an iron nitride type laminated magnetic head, and the head type B indicates a ferrite type M.
1 shows an IG magnetic head.

In the above evaluation, 1 MHz and 7 MHz
The reproduction output of Example 1 was represented using Example 1 as a reference (0 dB). Overwrite characteristics of -30 dB or less are OK
And The runnability was evaluated as ○, the tape that was run but the tape was damaged was evaluated as △, and the tape that was stopped during the running was evaluated as ×. In addition, in the comprehensive evaluation, those having all good characteristics were evaluated as ◯, and those having even one bad characteristic were evaluated as x. Further, the two examples in the bottom column of Table 4 are the results when the magnetic recording medium of Example 1 was changed and the magnetic head was evaluated.

As can be seen from Tables 2 to 4, the coercive force Hc is too low and the magnetic layer surface roughness SRa is too large with respect to the numerical values defined in claim 1. Comparative Example 3 which has a low output in the low range and a too thin magnetic layer has low output in the low range and has a problem in running property. Further, in Comparative Example 4 in which the magnetic layer is too thick, the output in the high range is low and the overwrite characteristic is poor. Comparative Example 5 with poor SFD has poor overwrite characteristics. Furthermore, in Comparative Example 6 where the saturation magnetization amount σs of the magnetic powder is too low and the saturation magnetic flux density Bm of the magnetic layer is too low, the output is low over the entire range. Comparative Example 7 in which the major axis length of the magnetic powder is small and the saturation magnetic flux density Bm of the magnetic layer is too low has a low output over the entire range and also has a problem in running property. In Comparative Example 8 in which the major axis length of the magnetic powder is too large, the magnetic characteristics of the tape are high, but the output in the high range is low.

On the other hand, Examples 1 to 7 satisfying the numerical values defined in claim 1 show good results with respect to reproduction output, overwrite characteristics, and runnability. Further, not only in the case of a single magnetic layer but also in the case of a two-layer structure (magnetic layer and underlayer) (Examples 6 and 7), good characteristics are shown. In particular, it is found that the overwrite characteristics can be further improved by forming a multilayer structure on the support as shown in Examples 6 and 7. Furthermore, the saturation magnetic flux density Bs is 13 with respect to the recording medium shown in Example 1.
Even when the evaluation was performed using a 000 G ferrite MIG magnetic head (second column from the bottom), good reproduction output, overwrite characteristics, and runnability were obtained. Therefore, it turns out that the good result is obtained regardless of the head type. On the other hand, when the recording medium shown in Example 1 was evaluated using the iron nitride laminated magnetic head having the saturation magnetic flux density Bs of 12000 G (bottom column), the output in the high range was too low. However, the overwrite characteristics are not good. Therefore, it is found that a magnetic head having a saturation magnetic flux density Bs of 13000 G or more must be used when performing recording and reproducing on the recording medium of the present invention.

[0025]

As described above, according to the magnetic recording medium and the magnetic recording system of the present invention, the following excellent operational effects can be exhibited. According to the magnetic recording medium of the present invention, it is possible to significantly improve the overwrite characteristic while maintaining the electromagnetic conversion characteristic and the running property at a high level. In recording and reproducing on the magnetic recording medium, particularly by using a magnetic head having a saturation magnetic flux density of 13,000 gauss or more, the overwrite characteristic can be particularly improved. Further, the overwrite property can be further improved by forming a multilayer structure on the support.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a magnetic recording medium of the present invention.

FIG. 2 is a diagram showing a state in which recording and reproduction are performed on the magnetic recording medium shown in FIG. 1 by using a magnetic head.

[Explanation of symbols]

1 ... Magnetic recording medium, 2 ... Support, 3 ... Magnetic layer, 5 ... Magnetic head, 6 ... Underlayer, L ... Medium running direction.

Claims (3)

[Claims] 1. A magnetic recording medium in which a magnetic support is formed on a film-like support by coating metal magnetic powder containing Fe as a main component to form a magnetic layer, and a saturation magnetic flux density Bm in the running direction of the magnetic recording medium is Within the range of 3500 to 5000 G (Gauss), the coercive force Hc is 2000 Oe (Oersted) or more,
The surface roughness SRa of the magnetic layer is 2 nm or less, the thickness t of the magnetic layer is in the range of 0.1 to 0.2 μm, the saturation magnetization σs of the magnetic powder is in the range of 160 to 200 emu / g,
The major axis length of the magnetic powder is in the range of 0.05 to 0.2 μm,
A magnetic recording medium, wherein the switching field distribution SFD of the magnetic layer is set to 0.45 or less. 2. A magnetic recording medium according to claim 1, wherein a non-magnetic layer is provided as an underlayer between the support and the magnetic layer to form a multilayer structure. 3. A magnetic recording / reproducing system for performing at least one of signal recording and reproduction using a magnetic head having a saturation magnetic flux density Bs of 13000 G (Gauss) or more on the magnetic recording medium according to claim 1. .