JPH0855323A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent electromagnetic conversion characteristics and good durability by controlling the thickness of an oxide film between a metal thin film type magnetic film and a protective film to <5nm. CONSTITUTION:A Co-based (Co-Ni (90 at%-10at%)) metal magnetic film 22 is formed to 160nm thickness by vapor deposition on a 6-mum thick PET film 21 as a supporting body by using an oblique vapor deposition device. During the vapor deposition, oxygen gas is blown to the vapor deposition part through a gas supply nozzle of the oblique vapor deposition device. After the film is formed, the surface of magnetic columns 22a which constitute the metal magnetic film 22 is coated with an oxide film of >10nm thickness. This raw sheet having the metal magnetic film 22 is subjected to such a treatment that half or more of the oxide film 22b covering the magnetic columns 22a is removed by using a plasma etching device and a plasma CVD device to 2nm thickness. Then a diamond-like carbon film 23 is formed to 6nm thickness by using a plasma CVD device, on which a perfluoropolyether soln. is applied by die coating method to obtain 20Angstrom dry film thickness and then dried to form a lubricant layer 24.

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 and its manufacturing method.

[0002]

BACKGROUND OF THE INVENTION Magnetic recording media such as magnetic tapes are of a coating type in which a magnetic coating is prepared by coating a film, which is a non-magnetic support, with a magnetic powder and a lubricant together with a binder in a solvent. , A metal thin film type in which metal magnetic particles are deposited on a film without using a binder.

Among these, the metal thin film type magnetic recording medium is said to be suitable for high-density recording because the magnetic layer does not contain a binder and therefore has a high packing density of the magnetic material. And, such a metal thin film type magnetic recording medium is generally obtained by an oblique vapor deposition apparatus as shown in FIG. In FIG. 3, 1 is a non-magnetic support such as polyethylene terephthalate (PET), 2a
Is a supply-side roll, 2b is a winding-side roll, and the support 1 is configured to run between them. 3 is a cooling can roll, 4 is a shielding plate, 5 is a crucible, 6 is a magnetic metal,
Reference numeral 7 is an electron gun, 8 is a vacuum container, and 9 is a gas supply nozzle for irradiating oxygen to the film deposited on the support 1 guided by the cooling can roll 3. In forming the film, oxygen gas is supplied from the gas supply nozzle 9 for the purpose of improving the magnetic characteristics, so that the obtained magnetic recording medium is constructed as shown in FIG. That is, a layer made of a non-magnetic oxide is formed on the surface of the metal magnetic film.
In FIG. 5, 31 is a PET film, 32 is an oblique vapor deposition method while introducing oxygen gas, and has a thickness of 200.
nm is a metal magnetic film, 32a is an oxide film on the surface of the metal magnetic film 32, 33 is a diamond-like carbon film (protective film), 34 is a lubricant film, and 35 is a back coat film.

Such a magnetic recording medium has a metal magnetic film 3
Since oxygen is irradiated during the film formation of No. 2, the magnetic properties such as coercive force are improved.

[0005]

DISCLOSURE OF THE INVENTION According to the research conducted by the inventor of the present invention, it has been found that the improvement of the magnetic characteristics is not largely dependent on the presence or absence of the oxide film on the surface layer of the metal magnetic film 32. That is, as shown in FIG. 5, the oxide film is the diamond-like carbon film 3
Not only on the side of 3, but also on the side of the magnetic column,
It has been found that the latter oxide film sufficiently improves the magnetic characteristics. Not only was it found that the oxide film 32a on the surface layer of the metal magnetic film 32 was not necessary, but the revelation was obtained that the absence of the oxide film 32a would give a better result. That is, the thickness of the oxide film 32a in the surface layer portion of the metal magnetic film 32 formed in an oxidizing atmosphere in order to improve the magnetic characteristics is 10 nm or more. Therefore, the gap between the metal magnetic film 32 and the magnetic head is increased. It has been found that the pacing loss becomes large, which is not preferable. In particular, when a diamond-like carbon film is provided on the metal magnetic film 32 for the purpose of improving durability, it can be said that the oxide film 32a on the surface layer of the metal magnetic film 32 is unnecessary. I understand.

The present invention has been achieved on the basis of such knowledge, and an object of the present invention is to provide a magnetic recording medium having excellent electromagnetic conversion characteristics and excellent durability. An object of the present invention is a magnetic recording medium in which a metal thin film type magnetic film is provided on a support, and a protective film is provided on the support, and the magnetic recording medium is provided between the metal thin film type magnetic film and the protective film. This is achieved by a magnetic recording medium characterized in that a certain oxide film has a thickness of 5 nm or less.

The metal thin film type magnetic film of this magnetic recording medium contains an O component. This improves the magnetic characteristics. Also, a metal magnetic film forming step of depositing metal magnetic particles while supplying an oxidizing gas onto the support,
An oxide film removing step of removing an oxide film in the surface layer portion of the metal magnetic film formed in the metal magnetic film forming step, and a protective film forming step of providing a protective film after the oxide film removing step are provided. And a magnetic recording medium manufacturing method.

The present invention is, for example, polyester such as PET, polyamide, polyimide, polysulfone, polycarbonate, olefin resin such as polypropylene,
A metal thin film type magnetic film is provided on a support made of a polymer material such as a cellulose resin or a vinyl chloride resin, an inorganic material such as glass or ceramics, or a metal material such as an aluminum alloy. The metal thin film type magnetic film is, for example, a vapor deposition method using an oblique vapor deposition apparatus as shown in FIG. 3, a DC sputtering method, an AC sputtering method, a high frequency sputtering method, a DC magnetron sputtering method, a high frequency magnetron sputtering method, an ion beam sputtering. It is formed by a dry plating means called a method. Then, for example, oxygen gas is introduced when forming the metal thin film type magnetic film. This improves the magnetic characteristics. Examples of the material forming the metal thin film type magnetic film include Co—Ni alloys, Co—Pt alloys, and Co—Ni in addition to metals such as Fe, Co, and Ni.
-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-
Co-Ni alloy, Fe-Co-B alloy, Co-Ni-F
An e-B alloy, a Co-Cr alloy, or those containing a metal such as Al is used. Other than this, an appropriate one can be used.

In the present invention, since the metal magnetic film is formed in an oxidizing gas atmosphere for the purpose of improving the magnetic characteristics, a thick oxide film is formed on the surface layer side of the metal magnetic film as described above. It However, since this thick oxide film is unnecessary when a hard protective film such as a carbon film is specially provided, it is removed. The amount of removal varies depending on the thickness of the oxide film that has been formed, but the amount of removal is removed by etching so that the thickness of the remaining oxide film is about 5 nm or less, preferably 4 nm or less, and more preferably 3 nm or less. Of course, the thickness of the oxide film may be zero. The oxide film is not clearly defined as an oxide film from this position, and gradually changes as shown in the Auger spectrum in FIG. The side is an oxide film. Therefore, referring to the Auger spectrum shown in FIG. 2, Time / s
It is considered that the oxide film is on the side of 0 when ec is about 1000. Therefore, in the case of the Auger spectrum shown in FIG.
The thickness of the oxide film on the surface side of Time / sec of about 1000 is 0 to 5 nm.

Various means can be mentioned as means for removing the oxide film on the surface layer of the metal magnetic film. As an example thereof, plasma etching using a plasma CVD apparatus as shown in FIG. 4 is used. Besides, a Kauffman type ion gun, an ECR type ion gun or the like is also used. After removing the oxide film on the surface layer of the metal magnetic film, a protective film is provided. The protective film is made of a hard carbon thin film typified by diamond-like carbon, amorphous carbon, glass-like carbon, etc., and is harder than an oxide film. As a means for providing such a protective film, a chemical vapor deposition (CVD) means is generally adopted. The thickness of this protective film is roughly 3 to 2 although it varies depending on the quality of the film formed.
It is about 0 nm.

A lubricant is provided on the protective film. Lubrication
The agent is composed by applying a solution containing it
It The thickness of the lubricant layer is preferably 10-200Å
Good Particularly preferred is 20 to 50Å. Used
The lubricant used is perfluoropolyether, for example-(C (R)
F-CF₂-O)_p-(However, R is F, CF₃, CH₃Such as
Group), especially HOOC-CF₂(O-C₂F_Four)_p(OCF₂)_q -OCF₂-COOH,
F- (CF₂CF₂CF₂O)_n-CF₂CF ₂Carboxy like COOH
Sil group modified perfluoropolyether, HOCH₂-CF ₂(O-C₂
F_Four)_p(OCF₂)_q -OCF₂-CH₂OH, HO- (C₂H_Four-O)_m-CH₂-(O-
C₂F_Four)_p(OCF₂)_q-OCH₂-(OCH₂CH₂)_n-OH, F- (CF₂CF₂CF
₂O)_n-CF₂CF₂CH₂Alcohol-modified par such as OH
Fluoropolyether, Perfluorostearic acid, Pa
-Fluoromyristic acid, perfluorooctanoic acid,
-Examples include fluoroalaragic acid.

A back coat layer is provided on the surface of the support opposite to the magnetic film. This back coat layer is made of Al
It may be a metal thin film type such as. Further, a type in which a coating material containing carbon black and a binder resin is applied may be used. Further, in the magnetic recording medium configured as described above, the unnecessary portion of the oxide film introduced to improve the magnetic characteristics is removed, so that the spacing loss can be reduced and the reproduction output becomes large. It was

The present invention will be described below with reference to specific examples.

[0014]

1 is a schematic sectional view of a magnetic recording medium according to the present invention. First, the Co-based (Co-Ni (90a) is formed on the support by the oblique vapor deposition apparatus A as shown in FIG.
t% -10 at%)) of the metal magnetic film. That is, as shown in FIG. 1, a PET film 2 having a thickness of 6 μm
A metal magnetic film 22 having a thickness of 160 nm is provided on the surface 1 by oblique vapor deposition means.

When forming the metal magnetic film 22, oxygen gas is blown toward the vapor deposition portion at a rate of 55 sccm from the gas supply nozzle 9 in the oblique vapor deposition apparatus shown in FIG. Therefore, immediately after this film formation, the surface of the magnetic column 22a forming the metal magnetic film 22 is covered with the oxide film 22b having a thickness of 10 nm or more.

The original sheet provided with the metal magnetic film 22 is
Plasma etching apparatus B and plasma C shown in FIG.
The VD device C is suspended between the supply side roll 11a and the winding side roll 11b of the device provided side by side. Then, the plasma etching apparatus B removes more than half of the oxide film 22b on the front surface side of the magnetic column 22a forming the metal magnetic film 22 with respect to the original fabric running along the cooling can roll 12. That is, the oxide film 22b has a thickness of about 2 nm.

After that, a diamond-like carbon film 23 having a thickness of 6 nm is provided on the surface of the metal magnetic film 22 (remaining oxide film 22b) by the plasma CVD apparatus C. In FIG. 4, 13 is an electromagnet. After this, perfluoropolyether (FOM of Montecatini Co., Ltd. was applied by die coating method.
BLIN Z DOL 0.05 wt% solution (solvent is fluorine-based inert liquid (SV11 by Montecatini)
0)) was applied so that the thickness after drying would be 20Å, and then dried at room temperature to form a lubricant layer 24.

Reference numeral 25 is a back coat layer having a thickness of 0.5 μm. Comparative Example 1 The same procedure as in Example 1 was performed except that the plasma etching apparatus B was not operated and the oxide film 22b on the surface side of the magnetic column 22a was not removed at all.
Therefore, the protective film is thicker than that of the first embodiment because it is a laminated type of the oxide film and the diamond-like carbon film. The oxide film thickness + diamond-like carbon film thickness = 16 nm.

Comparative Example 2 In Example 1, the plasma etching apparatus B and the plasma CVD apparatus C were not operated, the oxide film 22b on the surface side of the magnetic column 22a was left as it was, and a lubricant layer was formed on this oxide film. Configured.
Therefore, since the protective film is only the oxide film, it is thinner than that of Comparative Example 1. The oxide film thickness is 10 nm.

[Characteristics] The magnetic tape of each of the above examples was slit into a width of 8 mm and mounted on a commercially available modified 8 mm VTR machine.
The C / N and output characteristics at 7 MHz were examined, and the results are shown in Table-1. Also, still reproduction was performed to examine the durability. The durability was shown by the output reduction (in each case, the initial output was 0 dB) in dB after still reproduction for 10 hours.

Table-1 C / N output durability Example 1 2.3 dB 2.0 dB 0.2 dB Comparative example 1 0.0 dB 0.0 dB 0.1 dB Comparative example 2 2.0 dB 2.0 dB The magnetic layer was scraped, Unmeasurable * C / N and output are displayed as values based on Comparative Example 1 * C / N is displayed as a ratio to noise at 6 MHz, which is 1 MHz lower than the carrier at 7 MHz. It can be seen that the electromagnetic conversion characteristics of the magnetic recording medium are excellent because the spacing loss is small and the durability is also high.

On the other hand, in Comparative Example 1, the oxide film 22b remaining on the metal magnetic film 22 has a large thickness, and the electromagnetic conversion characteristics are not so good. Also, in Comparative Example 2,
The electromagnetic conversion characteristics are not bad, but the durability is poor.

[0023]

[Effect] According to the present invention, it is possible to obtain the one having excellent electromagnetic conversion characteristics and excellent durability.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetic recording medium according to the present invention.

Fig. 2 Graph of Auger spectrum

FIG. 3 is a schematic view of an oblique deposition apparatus.

FIG. 4 Plasma etching and plasma CVD apparatus

FIG. 5 is a schematic view of a conventional magnetic recording medium.

[Explanation of symbols]

 21 PET film 22 Metal magnetic film 22a Magnetic column 22b Oxide film 23 Diamond-like carbon film 24 Lubricant layer 25 Back coat layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigemi Wakabayashi 2606, Akabane, Kai-cho, Haga-gun, Tochigi Prefecture Kao Co., Ltd.Institute of Information Sciences (72) Inventor Akira Shiga, 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Kao-sha ceremony Company Information Science Laboratory

Claims (3)

[Claims] 1. A magnetic recording medium comprising a metal thin film type magnetic film on a support, and a protective film provided thereon, wherein an oxidation is present between the metal thin film type magnetic film and the protective film. Membrane 5
A magnetic recording medium having a thickness of not more than nm. 2. The magnetic recording medium according to claim 1, wherein the metal thin film type magnetic film has an O component. 3. A metal magnetic film forming step of depositing metal magnetic particles on a support while supplying an oxidizing gas, and oxidation in a surface layer portion of the metal magnetic film formed in this metal magnetic film forming step. A method of manufacturing a magnetic recording medium, comprising: an oxide film removing step of removing a film; and a protective film forming step of providing a protective film after the oxide film removing step.