JPH08181008A - Magnetic powder, magnetic recording medium, and magnetic recording method using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] A magnetic recording medium having improved surface properties, which enables higher recording density and transferability, and which has sufficient characteristics even when used as a mother tape for magnetic field transfer. Offer to,
Also, an optimum magnetic recording method for this magnetic recording medium is provided. [Structure] The magnetic powder contains at least Co, the Co content is 15 to 40% by weight, the coercive force is 160 kA / m or more, the saturation magnetization is 130 Am ² / kg or more, and the major axis length is 0. The thickness of the magnetic layer is 2 μm or less, the center line average roughness of the magnetic layer is 0.02 μm or less, and the coercive force of the magnetic recording medium is 165 kA / m or more. And
The recording wavelength when recording is 0.4 μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder suitable for use in a magnetic recording medium such as a mother tape for magnetic field transfer, and further to a magnetic recording medium using the magnetic powder, and this magnetic recording. The present invention relates to a magnetic recording method for a medium.

[0002]

2. Description of the Related Art Various magnetic recording media such as magnetic tapes and flexible disks have undergone various improvements for the purpose of increasing recording density. Then, as an example thereof, there is a method of improving the surface property of the magnetic layer of the magnetic recording medium to make the gap with the magnetic head as small as possible to reduce the gap loss. In order to improve the surface property of the magnetic layer of the magnetic recording medium as described above, improvement of the manufacturing technique of the magnetic layer,
That is, improvement of dispersibility of magnetic powder, improvement of coating technique, and improvement of surface molding technique are required.

Among the above magnetic recording media, in particular,
In the case of a mother tape for magnetic field transfer (so-called mirror mother tape), in addition to improving the surface property of the magnetic layer for higher recording density, the magnetic layer is closely adhered to the magnetic layer of the magnetic tape to be transferred to transfer the magnetic field. Therefore, it is also important to improve the surface property of the magnetic layer in order to enhance transferability. However, in the above-mentioned mirror mother tape, the surface property of the magnetic layer has been improved by improving the surface property of the non-magnetic support made of a plastic film without much reliance on the manufacturing technique of the magnetic layer.

As a method for achieving a high recording density of various magnetic recording media as described above, there is also a method of shortening the recording wavelength to be recorded on the magnetic recording medium to, for example, 0.4 μm or less. It is difficult to use the magnetic recording medium used.

[0005]

Therefore, the present invention has been proposed in view of the conventional circumstances, and a magnetic powder having sufficient characteristics to be used in a magnetic recording medium such as a mother tape for magnetic field transfer is provided. The purpose is to provide. Furthermore,
Provided is a magnetic recording medium having improved surface properties, which enables higher recording density and improved transferability, and has sufficient characteristics even when used as a mother tape for magnetic field transfer. An object is to provide an optimum magnetic recording method.

[0006]

In order to achieve the above object, the magnetic powder of the present invention contains at least Co.
O content is 15% to 40% by weight and coercive force is 1
It is characterized by having 60 kA / m or more and a saturation magnetization of 130 Am ² / kg or more.

Further, the magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer comprising at least a magnetic powder and a binder is formed on a non-magnetic support made of a plastic film, wherein the magnetic powder is the above-mentioned present invention. Magnetic powder, the major axis length of the magnetic powder is 0.2 μm or less, the center line average roughness of the magnetic layer is 0.02 μm or less, and the coercive force of the magnetic recording medium is 165 kA / m or more. It is characterized by being.

Furthermore, the magnetic recording medium of the present invention is a mother tape for magnetic field transfer.

The characteristics of the magnetic powder of the present invention are as follows.
If it is out of the above range, the magnetic recording medium using the magnetic recording medium does not have sufficient characteristics as a mother tape for magnetic field transfer. That is, when the Co content is small, the coercive force becomes small, which is not suitable as a mother tape for magnetic field transfer, and the saturation magnetization also becomes small, so that magnetic field transfer cannot be performed sufficiently.

Further, in the above magnetic powder of the present invention, the Co content is preferably 19% by weight to 40% by weight, the coercive force is 165 kA / m or more, and further 167.
It is preferably at least kA / m, and the saturation magnetization is 140
Am ² / kg or more, and further preferably not 145Am ² / kg or more. In the magnetic powder of the present invention, the coercive force from a practical point of view is 220 kA / m or less, it is preferable saturation magnetization is less than 220Am ² / kg.

As an example of such a magnetic powder, Fe-based acicular magnetic powder containing Co can be mentioned.
-Co, Fe-Co-Ni, Fe-Co-B, Fe-C
An acicular magnetic powder made of an alloy such as o-Cr-B or Fe-Co-V may be used. The magnetic powder of the present invention may contain an appropriate amount of a metal element such as Al, Si, Y, P or B used for the purpose of preventing sintering during reduction or maintaining the shape.

Further, in the above magnetic recording medium of the present invention, when the major axis length of the magnetic powder is out of the above range, the center line average roughness is also out of the above range, the surface property is not good, and the recording density is increased. If the coercive force of the magnetic recording medium is outside the above range, it is not suitable as a mother tape for magnetic field transfer.

Further, in the above magnetic recording medium of the present invention, the center line average roughness of the magnetic layer is 0.019 μm or less,
Further, it is preferably 0.017 μm or less, and the coercive force as a magnetic recording medium is 175 kA / m or more, 220
It is preferably kA / m or less.

Specific examples of the non-magnetic support made of a plastic film used in the magnetic recording medium of the present invention include polyesters, polyolefins, celluloses, vinyl resins, polyimides, polycarbonates and the like. There are things.

Further, as the binder forming the magnetic layer of the magnetic recording medium of the present invention, vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylic acid ester, methacrylic acid ester, styrene, butadiene, acrylonitrile and the like are added. Examples thereof include a combination, a copolymer in which two or more of these are combined, a polyester resin, an epoxy resin and the like.

At this time, examples of the magnetic recording medium of the present invention include a coating type magnetic recording medium in which a magnetic coating is applied to the surface of a non-magnetic support to form a magnetic layer by the coating film.
In the magnetic recording medium of the present invention, a dispersant, an abrasive, an antistatic agent, a rust preventive, etc. may be added as additives to the magnetic coating material forming the magnetic layer. It may be set according to the amount added in the magnetic paint used in the various magnetic recording media.

As a magnetic recording method of the present invention for recording on such a magnetic recording medium of the present invention, a recording wavelength of 0.4 μm or less can be mentioned. Thus, even if the recording wavelength is 0.40 μm or less, further 0.35 μm or less, the magnetic recording medium of the present invention can sufficiently cope with it, the recording wavelength can be shortened, and the recording density can be increased. It

At this time, the major axis length of the magnetic powder of the magnetic recording medium of the present invention is 0.16 μm or less, and further 0.14 μm.
When it is m or less, it becomes possible to cope with the shortening of the recording wavelength. At this time, from the practical viewpoint, the major axis length of the magnetic powder is preferably 0.01 μm or more.

The magnetic head for recording in the magnetic recording method of the present invention has a recording wavelength of 0.4 μm or less,
Further, the material, size, etc. are not limited as long as they can achieve 0.35 μm or less. Further, other conditions such as the width of the magnetic recording medium used are not particularly limited.

[0020]

In the magnetic recording medium of the present invention, the magnetic powder contains at least Co, the Co content is 15% by weight to 40% by weight, and the coercive force is 160 kA / m or more.
Saturation magnetization is 130 Am ² / kg or more and major axis length is 0.2μ
m or less, the center line average roughness of the magnetic layer is 0.02 μm or less, the coercive force as a magnetic recording medium is 165 kA / m or more, and the major axis length of the magnetic powder is small. Since the center line average roughness is small, the surface property is good, the recording density is increased and the transferability is improved, and the characteristics of the magnetic powder described above are sufficient characteristics even when used as a mother tape for magnetic field transfer. Exert.

In the magnetic recording medium of the present invention, since the major axis length of the magnetic powder is 0.2 μm or less, the recording wavelength at the time of recording is sufficiently compatible with the recording wavelength of 0.4 μm or less. A shorter wavelength is achieved.

[0022]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results.

Experimental Example 1 In this experimental example, when the magnetic recording medium of the present invention is used as a mother tape for magnetic field transfer and magnetic field transfer is performed on the transferred magnetic recording medium, the electromagnetic field of the transferred magnetic recording medium is changed. The conversion characteristics were investigated. In addition,
In this experimental example, the present invention is applied to a coating type magnetic tape.

[Preparation of Sample] Example 1 First, magnetic powder was manufactured. That is, α-Fe ₂ O ₃ obtained by heating acicular α-FeOOH containing 20% by weight of cobalt in a heating furnace was hydrogen-reduced to obtain a black ferromagnetic metal powder. Then, before the ferromagnetic metal powder was taken out of the heating furnace, the oxygen partial pressure in the heating furnace was gradually increased to carry out the gradual oxidation treatment. This ferromagnetic metal powder was used as a practical sample powder 1, and the magnetic properties and powder properties shown in Table 1 were investigated. The magnetic properties were measured with a sample vibrating magnetometer manufactured by Toei Industry Co., Ltd.

[0025]

[Table 1]

Next, a magnetic coating material was manufactured using the above-mentioned practical sample powder 1. That is, the above-mentioned practical sample powder 1
Was used as a magnetic powder, and a magnetic coating material having the following composition was kneaded and dispersed to produce a magnetic coating material.

(Paint composition) Magnetic powder 100 parts by weight Binder 20 parts by weight Abrasive (Al ₂ O ₃ ) 3 parts by weight Additive (carbon) 2 parts by weight Solvent Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Cyclohexanone 50 parts by weight Then, the above magnetic paint was applied onto a non-magnetic support made of a polyethylene terephthalate film, subjected to orientation treatment in a direct current magnetic field, and dried by sending hot air. After that, a calendering process was performed, and a magnetic tape was completed by slitting into a predetermined width. This magnetic tape is referred to as Example 1.

Embodiments 2 and 3 First, the same steps as those described in Embodiment 1 are carried out, and then Table 1
Ferromagnetic metal powders having magnetic properties and powder properties as shown in the inside were obtained, and were used as practical sample powders 2 and 3, respectively.

Further, using the above-mentioned sample powders 2 and 3 as the magnetic powder, magnetic coating materials were respectively manufactured through the same steps as those described in Example 1, and magnetic tapes were manufactured using these. These magnetic tapes were used in Example 2,
Called 3.

For comparison, the following magnetic powder and magnetic tape were also manufactured.

Comparative Examples 1 to 6 First, ferromagnetic metal powders having magnetic characteristics and powder characteristics as shown in Table 1 were obtained through substantially the same steps as those described in Example 1, and these were respectively obtained. Comparative sample powders 1-6
And

Using the above comparative sample powders 1 to 6 as the magnetic powder, a magnetic coating material was manufactured through the same steps as those described in Example 1, and the magnetic coating material was used to manufacture a magnetic tape. It should be noted that these magnetic tapes are used in Comparative Examples 1 to 6, respectively.
Called.

[Characteristic Evaluation] Next, the center line average roughness of the magnetic tapes of Examples 1 to 3 and Comparative Examples 1 to 6 and the magnetic characteristics of the items shown in Table 2 were investigated. The center line average roughness was measured by a surface roughness meter based on JIS B0601, and the magnetic characteristics were measured by a sample vibrating magnetometer manufactured by Toei Industry Co., Ltd. Table 2 shows the results.

[0034]

[Table 2]

Next, the above Examples 1 to 3 and Comparative Examples 1 to 6
The magnetic conversion characteristics of the transfer tape when the magnetic tape was transferred to the transfer tape by using this magnetic tape as a mother tape (mirror mother tape) for magnetic field transfer were investigated.

That is, first, signals were recorded in Examples 1 to 3 and Comparative Examples 1 to 6. At this time, as a video tape recorder, Sony MMV-5001V (VH
SPAL) (model name), the running speed of the magnetic tape is 23.4 mm / sec, the relative speed between the magnetic tape and the magnetic head is 4.85 m / sec, and the signal output is 4.5 MH.
z (wavelength: λ = 1.08 μm) and S / N was 50% white. The video tape recorder has an amorphous head for both recording and reproduction.

Then, Examples 1 to 3 and Comparative Examples 1 to 1
The signals recorded in No. 6 were magnetically transferred onto the transferred tape. In addition, as the above-mentioned transfer target tape, 1/2 inch V
A magnetic tape for HS was used.

As an apparatus for magnetically transferring a signal as described above, there is a magnetic field transferring apparatus as shown in FIG. The magnetic field transfer device includes a transfer drum 4 on which a mirror mother tape 1 which is a mother tape for magnetic field transfer and a slave tape 2 which is a transfer target tape run on a peripheral surface thereof, and a transfer which applies a bias magnetic field for magnetic field transfer. The transfer head 3 is composed of the head 3, and the transfer head 3 is arranged on the peripheral surface of the transfer drum 4 so that the magnetic gaps face each other.

When magnetic field transfer is carried out by such a magnetic field transfer device, the transfer drum 4 is such that the magnetic layers are in close contact with each other at positions where the transfer heads 3 face each other on the peripheral surface of the transfer drum 4.
A slave tape 2 and a mirror mother tape 1 are sequentially arranged on the upper side, and an appropriate amount of bias magnetic field is applied to the contact portion by the transfer head 3. Then, the signal of the magnetic layer of the mirror mother tape 1 is magnetically transferred to the magnetic layer of the slave tape 2.

In the magnetic field transfer device, the transfer drum 4 is rotated, for example, in the direction indicated by the arrow M in the figure to move the mirror mother tape 1 and the slave tape 2 along the peripheral surface of the transfer drum 4 in the figure. Magnetic field transfer is continuously performed by sequentially running in the directions indicated by m ₁ and m ₂ .

At this time, in order to increase the degree of close contact between the mirror mother tape 1 and the slave tape 2, the casing 8 having the air chamber 5 inside the transfer head 3 in the magnetic field transfer apparatus. And the compressed air 6 is blown against the peripheral surface of the transfer drum 4 through the air chamber 5 in the direction indicated by the arrow P in the figure. Further, in order to prevent the positional deviation between the mirror mother tape 1 and the slave tape 2, a drive tape 7 having no magnetic characteristics is arranged on the mirror mother tape 1 and run in the direction indicated by an arrow m ₃ in the figure. I have to.

Next, the above Examples 1-3 and Comparative Examples 1-6.
The electromagnetic conversion characteristics of the tape to which the signal of (1) was magnetically transferred were investigated. At this time, as a video tape recorder,
Sony MMV-5001V (VHS PA
L) (model name), the magnetic tape running speed is set to 23.
The relative speed between the magnetic tape and the magnetic head was 4.85 m / sec, and a spectrum analyzer manufactured by HP was used as a measuring instrument. The results are also shown in Table 2. However, the above-mentioned electromagnetic conversion characteristics are shown by relative comparison values when the electromagnetic conversion characteristics of the transfer tape to which the signal of Comparative Example 1 is magnetically transferred are set to 0.

As can be seen from the results shown in Tables 1 and 2,
At least Co is contained, and the Co content is 15 wt% to 4
0% by weight, the coercive force is 160 kA / m or more, the saturation magnetization is 130 Am ² / kg or more, and the major axis length is 0.2 μm or less. Center line average roughness of magnetic layer is 0.02 μm
And the coercive force as a magnetic recording medium is 165 kA.
/ M or more, in the magnetic tapes of Examples 1 to 3,
The electromagnetic conversion characteristics of the transfer-target tape to which the magnetic field is transferred are good.

This is because in Examples 1 to 3, since the particles of the magnetic powder are fine, the surface property is good, and when these are used as a mother tape for magnetic field transfer, the transfer property is good, and the magnetic powder is good. It is considered that this is largely due to the fact that the large amount of Co contained therein increases the amount of magnetization, and the coercive force and the saturation magnetization are sufficient as a mother tape for magnetic field transfer.

On the other hand, in Comparative Example 1, the major axis length of the magnetic powder was large and the particles were large, so the surface property was not so good, and when this was used as a magnetic tape for magnetic field transfer, magnetic field transfer was carried out. The electromagnetic conversion characteristics of the transferred tape are lower than those of Examples 1 to 3.

In Comparative Example 2, the major axis length of the magnetic powder was large and the particles were large, so that the surface property was not so good, and the Co content in the magnetic powder was small. When used as a magnetic tape for magnetic recording, the electromagnetic conversion characteristics of the magnetic field-transferred tape are lower than those of Examples 1 to 3.

Further, in Comparative Example 3, the coercive force of the magnetic powder was small, and when this was used as a magnetic tape for magnetic field transfer, the electromagnetic conversion characteristics of the magnetic field transferred transfer tape were from those of Examples 1 to 3. Will also be lower.

Further, in Comparative Example 4, the saturation magnetization of the magnetic powder was small, and when this was used as a magnetic tape for magnetic field transfer, the electromagnetic conversion characteristics of the magnetic field transferred tape were Examples 1 to 3. Will be lower than.

In Comparative Example 5, the content of Co in the magnetic powder was small, and when this was used as a magnetic tape for magnetic field transfer, the electromagnetic conversion characteristics of the magnetic field-transferred transfer tape were those of Example 1. Lower than ~ 3.

Further, in Comparative Example 6, since the center line average roughness is large and the surface property is not so good, when this is used as a magnetic tape for magnetic field transfer, the electromagnetic conversion in the magnetic field transferred tape is performed. Characteristics are from Example 1
Lower than 3.

<Experimental Example 2> In this experimental example, the electromagnetic conversion characteristics when recording was performed on the magnetic recording medium of the present invention while changing the recording wavelength was investigated. In addition, in the present experimental example as well, the present invention is applied to a coating type magnetic tape, and Examples 1 to 1 used in Experimental example 1 as the magnetic tape
Use 3. Further, Comparative Examples 1 to 6 used in Experimental Example 1 are also used for comparison.

First, in Examples 1 to 3 and Comparative Examples 1 to 6,
Recording wavelength is 0.49μm, 0.40μm, 0.35μm
Then, the signal was recorded by changing. The recording current at the time of signal recording is set to an optimum value.

Next, Examples 1 to 3 and Comparative Examples 1 to 6 in which signals were recorded were reproduced, and their electromagnetic conversion characteristics were investigated in the same manner as in Experimental Example 1. The results are shown in Table 3. In addition, the said electromagnetic conversion characteristic is shown by the relative value when the electromagnetic conversion characteristic in the comparative example 1 is set to 0.

[0054]

[Table 3]

As can be seen from the results shown in Tables 1, 2 and 3, at least Co is contained, the Co content is 15% by weight to 40% by weight, and the coercive force is 160 kA / m or more.
Saturation magnetization is 130 Am ² / kg or more, major axis length is 0.2μ
The magnetic powders of the practical sample powders 1 to 3 of m or less are used as the magnetic powder, and the center line average roughness of the magnetic layer is 0.0.
2 μm or less, and the coercive force as a magnetic recording medium is 16
The magnetic conversion characteristics of the magnetic tapes of Examples 1 to 3 having 5 kA / m or more are good.

This is because, in the above-mentioned Examples 1 to 3, since the particles of the magnetic powder are fine, the surface property is improved and the gap loss is reduced, and the magnetic powder contains a large amount of Co. It is thought that this is largely due to the large amount of magnetization. And in these Examples 1-3, even if the recording wavelength is shortened to 0.4 μm or less,
It is possible to sufficiently cope with it, and high recording density can be achieved.

On the other hand, in Comparative Example 1, since the major axis length of the magnetic powder is large and the particles are large, the surface property is not so good, and the electromagnetic conversion characteristics are lower than those of Examples 1 to 3.

In Comparative Example 2, the major axis length of the magnetic powder was large and the particles were large, so the surface properties were not very good, and the Co content in the magnetic powder was small, so the electromagnetic conversion characteristics were good. It becomes lower than Examples 1-3.

Further, in Comparative Example 3, the coercive force of the magnetic powder is small and the electromagnetic conversion characteristics are lower than those of Examples 1 to 3.

Furthermore, in Comparative Example 4, the saturation magnetization of the magnetic powder is small, and the electromagnetic conversion characteristics are lower than in Examples 1 to 3.

Further, in Comparative Example 5, the content of Co in the magnetic powder is small, and the electromagnetic conversion characteristics are lower than those in Examples 1 to 3.

Further, in Comparative Example 6, the center line average roughness is large and the surface property is not so good, so the electromagnetic conversion characteristics are lower than those of Examples 1 to 3.

[0063]

As is apparent from the above description, in the magnetic recording medium of the present invention, at least Co is contained as the magnetic powder, the Co content is 15 to 40% by weight, and the coercive force is Is 160 kA / m or more, saturation magnetization is 1
The major axis length of the magnetic layer is 30 Am ² / kg or more and the major axis length is 0.2 μm or less.
m or less, and the coercive force as a magnetic recording medium is 165 k
A / m or more, the major axis length of the magnetic powder is small, and the center line average roughness is small, so that the surface property is good, the recording density is improved and the transfer property is improved. Due to its characteristics, it exhibits sufficient characteristics even when used as a mother tape for magnetic field transfer.

In the magnetic recording medium of the present invention, since the major axis length of the magnetic powder is 0.2 μm or less, the recording wavelength at the time of recording is sufficiently compatible with recording at 0.4 μm or less. The wavelength can be shortened and the recording density can be increased.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a magnetic field transfer device.

[Explanation of symbols]

 1 ... Mother tape 2 ... Slave tape 3 ... Transfer head 4 ... Transfer drum

Claims (4)

[Claims] 1. At least Co, the Co content is 15% by weight to 40% by weight, and the coercive force is 160 kA /
A magnetic powder characterized by having m or more and a saturation magnetization of 130 Am ² / kg or more. 2. A magnetic recording medium comprising a non-magnetic support made of a plastic film and at least a magnetic layer made of a magnetic powder and a binder, wherein the magnetic powder is the magnetic powder according to claim 1. The major axis length of the magnetic powder is 0.2 μm or less, the center line average roughness of the magnetic layer is 0.02 μm or less, and the coercive force as a magnetic recording medium is 165 kA / m or more. Magnetic recording medium. 3. The magnetic recording medium according to claim 2, which is a mother tape for magnetic field transfer. 4. The magnetic recording method for recording on the magnetic recording medium according to claim 2, wherein the recording wavelength is 0.4 μm or less.