JPH11259845A - Magnetic record medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high coercive force corresponding to high recording density by forming a thin ferromagnetic metal film having a specified range of coercive force as a base layer of a thin metal magnetic film formed on a nonmagnetic supporting body. SOLUTION: A thin film comprising a ferromagnetic metal having 200 to 500 (kA/m) coercive force is formed as a base layer by vapor deposition on a nonmagnetic supporting body, and further a thin metal magnetic film is formed thereon. As for the ferromagnetic metal material to form the base layer, for example, Pt-Co and Y-Co are used. As for the thin metal magnetic film, for example, a ferromagnetic metal material such as Fe, Co and Ni is used. By forming the thin ferromagnetic metal film having high coercive force as the base layer and then forming the thin metal magnetic film thereon, the coercive force of the thin metal magnetic film can be increased, which suppresses such a phenomenon that magnetization flips during recording. Moreover, orientation property can be controlled, good electromagnetic conversion characteristics are obtd., and higher recording density can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium and a method for manufacturing the same. More specifically, the present invention relates to improvement of an underlayer of a metal thin film type magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media include ferromagnetic powders such as oxide magnetic powders and alloy magnetic powders and binders such as vinyl chloride-vinyl acetate copolymers, polyester resins, urethane resins and polyurethane resins. A so-called coating type magnetic recording medium in which a magnetic layer is formed by applying a magnetic paint composed of an organic solvent on a non-magnetic support, is widely used.

On the other hand, with the increasing demand for high-density recording, Co, Co-Ni alloy, Co-Cr alloy,
A metal magnetic material such as Co-O is directly deposited on a non-magnetic support such as a polyester film, a polyamide film, and a polyimide film by plating or a vacuum thin film forming technique (vacuum deposition method, sputtering method, ion plating method, etc.). Thus, a so-called metal magnetic thin film type magnetic recording medium in which a magnetic layer is formed has been proposed and attracted attention.

The magnetic recording medium of the metal magnetic thin film type has excellent magnetic properties such as coercive force and squareness ratio as compared with a coating type magnetic recording medium, and has excellent electromagnetic conversion characteristics in a short wavelength region. Since the thickness of the layer can be made extremely thin, the thickness loss during recording and reproduction is extremely small, and there is no need to mix a binder, which is a non-magnetic material, into the magnetic layer. It has a number of advantages, such as being able to increase the packing density of the material.

In such a magnetic recording medium of the metal magnetic thin film type, the magnetic layer is obliquely deposited at the time of forming the magnetic layer in order to further improve the electromagnetic conversion characteristics and to obtain a larger output. So-called oblique deposition has been proposed.

[0006]

By the way, in the metal thin-film type magnetic recording medium as described above, a high coercive force is required due to a demand for higher recording density. Means for introducing oxygen when obliquely depositing the metal magnetic thin film have been proposed, but have not been able to sufficiently meet the demand for higher recording density.

Accordingly, the present invention has been proposed in view of the above circumstances, and provides a magnetic recording medium having a high coercive force capable of coping with a further increase in recording density and a method of manufacturing the same. What you want to do.

[0008]

To solve the above-mentioned problems, a magnetic recording medium according to the present invention is a magnetic recording medium comprising a non-magnetic support and a metal magnetic thin film formed on a non-magnetic support. A coercive force of 200 (kA /
m) to 500 (kA / m) of a ferromagnetic metal thin film.

As described above, the coercive force of the underlayer is 200
When a ferromagnetic metal thin film having a high coercive force of (kA / m) to 500 (kA / m) is formed as an underlayer, a phenomenon in which magnetization is reversed during recording in a metal magnetic thin film formed thereon. Can be suppressed.

That is, in the present invention, the above-described phenomenon is suppressed by forming the base layer of the metal thin film from a ferromagnetic metal thin film having a larger coercive force than the metal thin film. The coercive force of the metal magnetic thin film is usually about 100 (kA /
m) to 130 (kA / m), if the coercive force of the ferromagnetic metal thin film serving as the underlayer is less than 200 (kA / m), the difference in coercive force between these metal magnetic thin films and the ferromagnetic metal thin film Therefore, the effect of the present invention cannot be sufficiently obtained.

The coercive force of the ferromagnetic metal thin film is 500
If it is larger than (kA / m), it may adversely affect the reproducing apparatus such as noise. Further, with the current magnetic head, it is difficult to write information on a metal magnetic thin film having a base layer of a ferromagnetic metal thin film having a coercive force of more than 500 (kA / m). Furthermore, it is difficult at present to realize a ferromagnetic metal thin film having a coercive force of more than 500 (kA / m).

Incidentally, as a method of manufacturing a magnetic recording medium as described above, a coercive force of 200 (k) is applied on a nonmagnetic support.
(A / m) to 500 (kA / m), a thin film made of a ferromagnetic metal is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed thereon by vapor deposition.

Specific examples of vapor deposition as a means for forming the underlayer include vapor deposition by electron beam melting and vapor deposition by sputtering.

The ferromagnetic metal material for forming the underlayer may be any material as long as it satisfies the above conditions, but is not limited to Pt-Co, Y-Co, La-Co, Ce-C
o, Pr-Co, Sm-Co, and the like.

Further, the metal magnetic thin film may be formed of a material used for an ordinary metal magnetic thin film type magnetic recording medium. For example, ferromagnetic metal materials such as Fe, Co, and Ni, Fe—Co, Co—Ni, Fe—Co—Ni, and F
e-Cu, Co-Cu, Co-Au, Co-Pt, Fe
-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr,
Ferromagnetic alloy materials such as Co-Ni-Cr and Fe-Co-Ni-Cr are exemplified. For example, the vicinity of the surface of the metal magnetic thin film may be an oxide for improving corrosion resistance and the like.

Further, in the magnetic recording medium of the present invention, a protective film may be formed on the metal magnetic thin film, and the protective film is generally used as a protective film forming material of the metal magnetic thin film type magnetic recording medium. What is necessary is just to form by what is performed. Such materials include, for example, carbon, Cr
O ₂ , Al ₂ O ₃ , BN, Co oxide, MgO, SiO
_{2, Si 3 O 4, SiN} X, SiC, SiN X -SiO
₂ , ZrO ₂ , TiO ₂ , TiC and the like. When this protective film is formed, it may be a single-layer film, a multilayer film, or a composite film with a metal made of the above materials.

Further, the structure of the metal magnetic thin film type magnetic recording medium to which the present invention is applied is not limited to this. For example, if necessary, a back coat layer may be formed, a lubricant, The formation of a layer such as a rust agent does not matter at all. In this case, any of conventionally known materials can be used as the nonmagnetic pigment, resin binder or lubricant contained in the back coat layer, and the material contained in the rust preventive layer.

In the magnetic recording medium and the method of manufacturing the same according to the present invention, the coercive force on the non-magnetic support is 200 (kA /
m) to 500 (kA / m), a thin film made of a ferromagnetic metal is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed thereon by vapor deposition. And the orientation is also controlled, so that its electromagnetic conversion characteristics are good.

[0019]

Embodiments of the present invention will be described below.

The magnetic recording medium according to the present invention has a coercive force of 200 (kA / m) to 500 (kA / m) on a nonmagnetic support.
m) An underlayer, which is a ferromagnetic metal thin film, is formed, and a metal magnetic thin film is further formed thereon.

The ferromagnetic metal material for forming the underlayer may be any material as long as it satisfies the above conditions, but Pt--Co, Y--Co, La--Co, Ce--Co,
Pr-Co, Sm-Co and the like are exemplified.

The metal magnetic thin film may be formed of a material used for a normal metal magnetic thin film type magnetic recording medium. For example, ferromagnetic metal materials such as Fe, Co, and Ni, Fe—Co, Co—Ni, Fe—Co—Ni, and F
e-Cu, Co-Cu, Co-Au, Co-Pt, Fe
-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr,
Ferromagnetic alloy materials such as Co-Ni-Cr and Fe-Co-Ni-Cr are exemplified. Then, for example, the vicinity of the surface of the metal magnetic thin film may be an oxide for improving corrosion resistance.

Further, in the magnetic recording medium of the present invention, a protective film may be formed on the metal magnetic thin film, and the protective film is generally used as a material for forming a protective film of a metal magnetic thin film type magnetic recording medium. What is necessary is just to form by what is performed. Such materials include, for example, carbon, Cr
O ₂ , Al ₂ O ₃ , BN, Co oxide, MgO, SiO
_{2, Si 3 O 4, SiN} X, SiC, SiN X -SiO
₂ , ZrO ₂ , TiO ₂ , TiC and the like. When this protective film is formed, it may be a single-layer film, a multilayer film, or a composite film with a metal made of the above materials.

Further, the configuration of the metal magnetic thin film type magnetic recording medium to which the present invention is applied is not limited to this. For example, a back coat layer may be formed as necessary, The formation of a layer such as a rust agent does not matter at all. In this case, any of conventionally known materials can be used as the nonmagnetic pigment, resin binder or lubricant contained in the back coat layer, and the material contained in the rust preventive layer.

In the magnetic recording medium of the present invention, a ferromagnetic metal thin film having a high coercive force of 200 (kA / m) to 500 (kA / m) is used as an underlayer, and a metal magnetic thin film is formed thereon. In this metal magnetic thin film, the coercive force increases, the phenomenon of magnetization reversal during recording is suppressed, the orientation is controlled, and the electromagnetic conversion characteristics are improved. Therefore, it is possible to sufficiently cope with higher recording density.

As a method for manufacturing the magnetic recording medium as described above, a coercive force of 200 on a non-magnetic support is used.
There is a method in which a thin film made of a ferromagnetic metal (kA / m) to 500 (kA / m) is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed thereon by vapor deposition.

Specific examples of the vapor deposition as means for forming the underlayer include vapor deposition by electron beam melting and vapor deposition by a sputtering method.

Therefore, an example of a magnetic recording medium manufacturing apparatus which employs vapor deposition by electron beam melting and which can cope with the magnetic recording medium manufacturing method of the present invention will be described.

As shown schematically in FIG. 1, this magnetic recording medium manufacturing apparatus has a vacuum chamber 1 which is evacuated from exhaust ports 13 provided at the head, bottom, and side portions to form a vacuum inside. A feed roll 3 rotating at a constant speed in the clockwise direction in the figure and a winding roll 4 rotating at a constant speed in the clockwise direction in the figure are provided therein. The non-magnetic support 2 is configured to run sequentially.

A cooling can 5 having a diameter larger than the diameter of each of the rolls 3 and 4 is provided in the middle of the movement of the non-magnetic support 2 from the feed roll 3 to the winding roll 4. I have. The cooling can 5 is provided so as to pull out the nonmagnetic support 2 to the right in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 3, the take-up roll 4, and the cooling can 5 each have a cylindrical shape having a length substantially equal to the width of the nonmagnetic support 2. Further, a cooling device (not shown) is provided in the cooling can 5 so that deformation and the like of the nonmagnetic support 2 due to a temperature rise can be suppressed.

Accordingly, the non-magnetic support 2 is sequentially sent out from the feed roll 3 as shown by an arrow M ₁ in the drawing.
Further, it passes through the peripheral surface of the cooling can 5 and is wound up by the winding roll 4. In addition, guide rolls 6 and 7 are provided between the feed roll 3 and the cooling can 5 and between the cooling can 5 and the take-up roll 4, respectively. A predetermined tension is applied to the non-magnetic support 2 running from the cooling can 5 to the take-up roll 4 so that the non-magnetic support 2 runs smoothly. A crucible 8 is provided in the vacuum chamber 1 below the cooling can 5, and the crucible 8 is filled with a thin film forming material 9. The crucible 8 has substantially the same width as the width of the cooling can 5 in the longitudinal direction.

On the other hand, an electron gun 10 for heating and evaporating the thin film forming material 9 filled in the crucible 8 is attached to the side wall of the vacuum chamber l. This electron gun 10
Is disposed at a position where an electron beam emitted from the electron gun 10 and indicated by an arrow X in the figure is irradiated on the thin film forming material 9 in the crucible 8. The thin film forming material 9 evaporated by the electron gun 10 is deposited on the non-magnetic support 2 running at a constant speed on the peripheral surface of the cooling can 5 so that a thin film is deposited. Further, a shutter 11 is provided between the cooling can 5 and the crucible 8 and near the cooling can 5. This shutter 1
The shutter 1 is formed so as to cover a predetermined area of the non-magnetic support 2 running at a constant speed on the peripheral surface of the cooling can 5.
The thin film forming material 9 evaporated by the step 1 is obliquely deposited on the nonmagnetic support 2 at a predetermined minimum incident angle. Further, at the time of such vapor deposition, oxygen gas is supplied from the pump 14 to the surface of the non-magnetic support 2 through the oxygen gas inlet 12 provided through the wall on the bottom side of the vacuum chamber 1, and Improvements in characteristics, durability, and weather resistance are achieved. The oxygen gas inlet 12 is provided such that its jet port opens between the shutter 11 and the peripheral surface of the cooling can 5.

Further, in this vacuum vapor deposition apparatus, a dividing plate 15 for dividing the inside of the vacuum chamber 1 into a lower right portion in the figure where a crucible 8 and the like are provided and a portion where a feed roll 3 and a take-up roll 4 are provided is provided with a cooling can 5. It is provided so as not to impair the rotation of.

That is, in order to carry out the method for producing a magnetic recording medium of the present invention by the above-mentioned apparatus for producing a magnetic recording medium, it is necessary to carry out vapor deposition in two stages.

First, an underlayer is formed. The inside of the vacuum chamber 1 is kept at, for example, a degree of vacuum of 133.322 × 10 ⁻⁴ (Pa),
SmCo ₅ alloy 100 (wt%) as thin film forming material 9
Using the incident angle as 45 ° to 90 °, the non-magnetic support body 2 as described above, as shown by arrow M _1, sequentially feed from the feed roll 3, passed through the peripheral surface of the cooling can 5 Then, the film is wound on a winding roll 4 to perform vacuum deposition, and a thin film having a thickness of 100 (nm) is formed as a base layer.

Next, a metal magnetic thin film is formed. Therefore, once the winding to the direction showing the nonmagnetic support 2 wound underlayer on the roll 4 is formed in FIG. 1 in an arrow M ₁ take heart roll 3 wound feed by traveling in the opposite direction. Then, the inside of the vacuum chamber 1 is set to, for example, 133.322 × 10
^-4 (Pa), and Co100 is used as the thin film forming material 9.
(Wt%), the incident angle is set at 45 ° to 90 °, and the nonmagnetic support 2 is supplied as described above while supplying oxygen gas at a flow rate of 250 (cc / min) from the oxygen gas inlet 12. as shown by arrow M _1, sequentially feed from the feed roll 3, passed through the peripheral surface of the cooling can 5, and vacuum vapor deposition by a take-up roll 4 wound taken, the thin film having a thickness of 200 (nm) It is formed as a metal magnetic thin film.

[0037]

EXAMPLES Next, in order to confirm the effects of the present invention, a magnetic recording medium was actually manufactured and its characteristics were examined.

That is, first, polyethylene terephthalate having a width of 150 (mm) and a thickness of 10 (μm) was prepared as a nonmagnetic support. Then, an undercoat layer was formed on one main surface side of the nonmagnetic support. This undercoat layer is made of a water-soluble latex containing acrylic acid ester as a main component.
000 (10,000 / mm ² ).

Next, a ferromagnetic metal thin film serving as an underlayer was formed on the undercoat layer. That is, using the magnetic recording medium manufacturing apparatus shown in FIG. 1 above, the degree of vacuum on the crucible 8 side partitioned by the dividing plate 15 in the vacuum chamber 1 is kept at 7 × 10 ^-2 (Pa), and the winding roll The degree of vacuum on the 4 side is 9 × 10 ^-1 (Pa)
And SmCo ₅ alloy 100 as the thin film forming material 9
(Wt%) and the incident angle is 45 ° to 90 °,
As described above, the non-magnetic support 2 is sequentially fed from the feed roll 3 at a speed of 60 (m / min) as shown by an arrow M ₁ in the drawing, passed through the peripheral surface of the cooling can 5, and
To form a thin film having a thickness of 100 (nm) as an underlayer.

At this time, the coercive force of the ferromagnetic metal thin film serving as the underlayer was 240 (kA / m).

Next, a metal magnetic thin film was formed. Therefore, the retaking roll 3 wound feed by traveling in a direction opposite to the direction indicated nonmagnetic support 2 underlayer taken up by the take-up roll 4 once is formed in FIG. 1 in an arrow M _1. Then, the degree of vacuum on the side of the crucible 8 partitioned by the dividing plate 15 in the vacuum chamber 1 is maintained at 7 × 10 ⁻² (Pa), and the degree of vacuum on the side of the winding roll 4 is set at 9 × 10 ⁻¹ (Pa). Keep, thin film forming material 9
Is used, the incident angle is set to 45 ° to 90 °, and oxygen gas is supplied from the oxygen gas inlet 12 to 25%.
While supplying a flow rate of 0 (cc / min), as described above in the non-magnetic support member 2 as shown by arrow M ₁ at a speed of 60 (m / min), sequentially feed from the feed roll 3, cooling The thin film having a thickness of 100 (nm) was formed as a metal magnetic thin film by passing through the peripheral surface of the can 5 and winding it on the winding roll 4 to perform vacuum deposition.

Subsequently, the non-magnetic support on which the ferromagnetic metal thin film and the metal magnetic thin film are formed is taken out of the magnetic recording medium manufacturing apparatus, and the main surface of the non-magnetic support on which the thin films are not formed has carbon and urethane binders. Was applied to form a back coat layer. The back coat layer is formed by using a coating apparatus used in the manufacture of this type of magnetic recording medium so that the feed speed of the nonmagnetic support is 150 (m / min) and the coating thickness is 0.6 (μm). Formed.

Further, a protective film was formed by applying perfluoropolyether on the metal magnetic thin film. Finally, the magnetic recording medium was cut to a width of 8 (mm) to complete the magnetic recording medium, which was used as a working sample.

Next, for comparison, a magnetic recording medium was completed in the same manner as in Working Example 1 except that a ferromagnetic metal thin film serving as an underlayer was not formed, and this was designated as Comparative Sample 1.

For comparison, the thickness of the underlayer was set to 40
(Nm) except that the magnetic recording medium was manufactured in the same manner as in the working sample 1 to complete the magnetic recording medium.
And At this time, the coercive force of the ferromagnetic metal thin film serving as the underlayer was 162 (kA / m).

Then, the magnetic recording characteristics and the electromagnetic conversion characteristics of these working samples and comparative samples 1 and 2 were investigated.
As the magnetic characteristics, a sample vibration type magnetic characteristic measuring device (V
SM) to determine the saturation magnetization (Ms) and the coercive force (Hc). Further, as the electromagnetic conversion characteristics,
Sony's video tape recorder EV-S900
The reproduction output (Y-out) and the noise ratio (Y-C / N) are to be investigated using the modified model (model name), and the result of the comparative sample 1 is a relative value when the result is set to zero (dB). It was decided to display. Table 1 shows the results. Table 1 also shows the coercive force of the ferromagnetic thin films serving as the underlayers of the working sample and the comparative sample 2.

[0047]

[Table 1]

As can be seen from the results in Table 1, Comparative Sample 1 in which the ferromagnetic metal thin film serving as the underlayer was not formed.
Comparative sample 2 in which a ferromagnetic metal thin film serving as an underlayer and a coercive force of 162 (kA / m) are formed.
Comparing the above, although the saturation magnetization (Ms) has changed, the electromagnetic conversion characteristics have not improved much. However, in a working sample in which a ferromagnetic metal thin film serving as an underlayer is formed and its coercive force is 240 (kA / m), the saturation magnetization (Ms) changes and the electromagnetic conversion characteristics are greatly improved. doing.

That is, from these results, the coercive force on the non-magnetic support was 200 (kA / m) to 5 as in the present invention.
When a thin film made of a ferromagnetic metal of 00 (kA / m) is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed thereon by vapor deposition, the coercive force of the metal magnetic thin film is increased, and the orientation is improved. It was also confirmed that the recording characteristics were also controlled, and the electromagnetic conversion characteristics were good, and it was possible to sufficiently cope with a further increase in recording density.

[0050]

As described above, in the magnetic recording medium of the present invention and the method of manufacturing the same, the ferromagnetic metal having a coercive force of 200 (kA / m) to 500 (kA / m) is formed on the nonmagnetic support. Is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed on the base layer by vapor deposition.Therefore, the coercive force of the metal magnetic thin film is increased, the orientation is controlled, and the electromagnetic conversion characteristics are improved. Thus, the recording density is good, and it is possible to sufficiently cope with higher recording density.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part schematically showing a magnetic recording medium manufacturing apparatus.

[Explanation of symbols]

1 vacuum chamber, 2 non-magnetic support, 3 feed roll, 4
Winding roll, 5 cooling can, 6, 7 guide roll, 8 crucible, 9 thin film forming material, 10 electron gun

Claims (2)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a metal magnetic thin film formed on a non-magnetic support, wherein a coercive force is 200 (kA) as an underlayer of the metal magnetic thin film.
/ M) to 500 (kA / m) of a ferromagnetic metal thin film. 2. A coercive force of 200 (kA) on a non-magnetic support.
/ M) to 500 (kA / m), wherein a thin film made of a ferromagnetic metal is formed as a base layer by vapor deposition, and a metal magnetic thin film is formed thereon by vapor deposition to form a layer.