JPH08306027A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having high reproduction output and fit for high density recording by regulating the total thickness of all magnetic films to a prescribed value and the thickness of a magnetic film as the top layer positioned farthest from the substrate to a prescribed value. CONSTITUTION: A magnetic film 2 of metal Co as a lower layer is formed on one side of a substrate 1, e.g. by an oblique vapor deposition means and a magnetic film 3 of metal Co as an upper layer is formed on the film 2 by oblique vapor deposition or other means. A protective film 4 of diamondlike carbon, boron carbide, silicon nitride, etc., is formed on the film 3 in about 50-200Åthickness, a fluorine-contg. lubricant such as perfluoro-polyether is applied on the film 4 in about 20-70Å thickness and a back coating film is formed on the other side of the substrate 1. The total thickness of all the magnetic films 2, 3 is regulated to 800-3,000Å and the thickness of the magnetic film 3 as the top layer positioned farthest from the substrate 1 is regulated to 1/6-1/3 of the total thickness. The objective magnetic recording medium fit for high density recording and having high reproduction output is obtd.

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 having a plurality of metal thin film type magnetic films.

[0002]

BACKGROUND OF THE INVENTION In the field of magnetic recording, it is required to improve the recording density year by year. As a means for achieving the purpose in line with this demand, it is proposed that the magnetic film is composed of a plurality of magnetic films and the thickness per magnetic film is thin (Japanese Patent Laid-Open No. 2-152007, etc.). Has been done.

However, there is a demand for higher density.

[0004]

DISCLOSURE OF THE INVENTION In order to increase the recording density, the recording wavelength must be a short wavelength. From this point of view, the upper magnetic film may be used as a magnetic film for high density. And to reduce self-demagnetization,
The magnetic film should be thin. Further, since only a short wavelength signal is not used for recording, a magnetic film may be provided under the high density recording magnetic film and a long wavelength signal may be recorded on this magnetic film.

That is, at least two magnetic films are provided,
If the upper magnetic film is made to carry out recording at a short wavelength and the lower magnetic film is made to carry out recording at a long wavelength, it is possible to carry out recording with high output over a wide area. The present invention has been made as a result of earnestly conducting research in view of such a viewpoint, and an object of the present invention is to provide a magnetic recording medium having a high output over a wide area.

An object of the present invention is a magnetic recording medium in which a plurality of metal thin film type magnetic films are laminated on a support,
The total magnetic film has a thickness of 800 to 3000Å, and the thickness of the uppermost magnetic film farthest from the support is 1/6 to 1/3 of the total magnetic film. And a magnetic recording medium. The upper magnetic film preferably has a larger coercive force than the lower magnetic film. For example, the coercive force of the lowermost magnetic film is 1000 to 1800 Oe, while the coercive force of the uppermost magnetic film is 1500 to 20.
It is preferable that the upper magnetic film has a larger coercive force as described as 00 Oe.

In the present invention, the total magnetic film has a thickness of 800.
The thickness of the uppermost magnetic film located farthest from the support is set to ⅙ to ⅓ of the total magnetic film thickness in order to expect a high reproduction output. . For example,
If the thickness of the total magnetic film is too thin, less than 800 Å, the characteristics in the low range deteriorate and the durability deteriorates.
If the thickness of the total magnetic film exceeds 3000 Å and is too thick, it is not preferable in consideration of higher recording density and higher capacity.
It was set to 00Å. The preferred thickness is 1500 to 2500Å.

If the thickness of the uppermost magnetic film is less than ⅙ of the thickness of the total magnetic film, durability and magnetic characteristics are deteriorated, and conversely, the thickness of the total magnetic film is reduced. If it is thicker than 1/3 of the above, high output in the high range cannot be expected. For this reason, the thickness of the uppermost magnetic film is set to ⅙ to ⅓ of the total magnetic film. In the present invention, the coercive force of the lowermost magnetic film is 1000 to 1800 Oe, while the coercive force of the uppermost magnetic film is 1500 to 2000 Oe.
As described above, it is preferable to increase the coercive force of the upper magnetic film in order to expect a high output in a high range.

For example, the coercive force of the uppermost magnetic film is set to 155
If the coercive force of the lowermost magnetic film is 0 Oe, such as 1630 Oe, a high reproduction output cannot be expected, and
C / N is not good either. In the above description, a general case where the magnetic film has two or more layers has been described, but the magnetic film is often composed of two layers. In the case of this two-layer magnetic film, the thickness of the upper magnetic film is 250 to 900Å (more preferably 400 to 700Å), and the coercive force of the upper magnetic film is 15
00-2000 Oe (more preferably 1600-190)
0 Oe), and the thickness of the lower magnetic film is 550 to 210.
0 Å (more preferably 1100 to 2000 Å), the coercive force of the lower magnetic film is 1000 to 1800 Oe (more preferably 1500 to 1700 Oe), and the total thickness of the upper magnetic film and the lower magnetic film is 800 to 3000 Å ( It is more preferable that the upper magnetic film has a thickness of 1/5 to 1/2 the thickness of the lower magnetic film, and the coercive force of the upper magnetic film is larger than that of the lower magnetic film.

The support used in the magnetic recording medium of the present invention may be either magnetic or non-magnetic, but is generally non-magnetic. Such a support is PET
Polyester such as polyester, polyamide, polyimide, polysulfone, polycarbonate, olefin resin such as polypropylene, cellulose resin, vinyl chloride resin, organic materials such as glass, ceramics such as glass, and other metal materials such as aluminum alloy. Used.
An undercoat layer for improving the adhesion of the metal magnetic film is appropriately provided on the surface of the support.

A first metal magnetic film (lower magnetic film) is provided on one surface of the support by, for example, oblique vapor deposition means.
As the material of the magnetic particles forming the lower magnetic film, for example, F
In addition to metals such as e, Co, and Ni, Co-Ni alloys and Co
-Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy,
Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Co-
B alloy, Co-Ni-Fe-B alloy, Co-Cr alloy,
Alternatively, a material in which a metal such as Al is contained is used. Also, Fe-N alloy, Fe-N-O alloy, Fe
-C alloy, Fe-CO alloy, etc. are also used. In order to separate the magnetic layer from the upper magnetic film, it is preferable to provide an oxidizing gas during the film formation of the lower magnetic film to oxidize the surface.

A second metal magnetic film (upper magnetic film) is provided on the first metal magnetic film by, for example, oblique vapor deposition means. As the material of the magnetic particles forming the upper magnetic film, for example, a metal such as Fe, Co, or Ni, a Co--Ni alloy,
Co-Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-C
An o-B alloy, a Co-Ni-Fe-B alloy, a Co-Cr alloy, or those containing a metal such as Al is used. In addition, Fe-N alloy, Fe-N-O alloy,
Fe-C alloy, Fe-C-O alloy, etc. are also used. The upper magnetic film and the lower magnetic film may use the same magnetic material or may use different magnetic materials.

50 to 20 made of diamond-like carbon, boron carbide, silicon nitride, etc. are formed on the upper magnetic film.
A protective film having a thickness of about 0Å is provided. On the protective film, a fluorine-based lubricant such as perfluoropolyether is provided with a thickness of about 20 to 70Å. Further, a so-called back coat film is provided on the other surface side of the support opposite to the side where the magnetic film is provided.

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

[0015]

【Example】

[Embodiment 1] FIG. 1 is a schematic view of an embodiment of a magnetic recording medium according to the present invention. The magnetic tape of this embodiment is obtained by using an oblique vapor deposition device. That is, the support 1
Is hung between the supply-side roll and the winding-side roll of the oblique vapor deposition apparatus and run along the cooling can roll. After evacuating the inside of the vacuum chamber to a degree of vacuum of about 10 ⁻⁴ to 10 ⁻⁶ Torr, the magnetic metal in the crucible is melted and evaporated by electron beam heating from an electron gun, and a thickness of 1300 is formed on the support 1.
Å The lower Co metal magnetic film 2 having a coercive force of 1570 Oe was formed. During the formation of the lower Co metal magnetic film 2, oxygen was supplied to oxidize the surface layer of the lower Co metal magnetic film 2 so as to improve the magnetic characteristics and to allow magnetic separation from the upper magnetic film.

After that, the winding-side roll around which the support 1 having the lower Co metal magnetic film 2 formed thereon is wound is set on the supply side, and the lower Co metal magnetic film 2 is formed in the same manner as the lower layer. The Co metal magnetic film 2 has a thickness of 500Å and a coercive force of 16
An upper Co metal magnetic film 3 of 50 Oe was formed. After this,
A diamond-like carbon film 4 having a thickness of 70Å was provided on the upper Co metal magnetic film 3.

A back coat film was provided on the other side of the support 1, and a film of a perfluoropolyether type lubricant was attached to the surface. [Example 2] In Example 1, the lower Co metal magnetic film 2 was used.
A magnetic tape was obtained in the same manner as in Example 1, except that the thickness was 1600 Å and the coercive force was 1540 Oe, and the upper Co metal magnetic film 3 was 600 Å and the coercive force was 1590 Oe.

[Embodiment 3] In Embodiment 1, the lower layer Co
The metal magnetic film 2 has a thickness of 1800Å and a coercive force of 1600O.
and the upper Co metal magnetic film 3 has a thickness of 500
Å A magnetic tape was obtained in the same manner as in Example 1 except that the coercive force was 1650 Oe. [Example 4] In Example 1, the lower Co metal magnetic film 2 was used.
A magnetic tape was obtained in the same manner as in Example 1 except that the thickness was 2000 Å and the coercive force was 1500 Oe, and the upper Co metal magnetic film 3 was 700 Å and the coercive force was 1600 Oe.

Comparative Example 1 In Example 1, the lower layer Co
The metal magnetic film 2 has a thickness of 1800Å and a coercive force of 1570O.
and the upper Co metal magnetic film 3 has a thickness of 1000
Å A magnetic tape was obtained in the same manner as in Example 1 except that the coercive force was 1600 Oe. [Comparative Example 2] In Example 1, the lower Co metal magnetic film 2 was used.
A magnetic tape was obtained in the same manner as in Example 1 except that the thickness was 1000 Å and the coercive force was 1600 Oe, and the upper Co metal magnetic film 3 was 1000 Å and the coercive force was 1600 Oe.

[Comparative Example 3] In Example 1, the lower layer Co
The metal magnetic film 2 has a thickness of 1000Å and a coercive force of 1630O.
and the upper Co metal magnetic film 3 has a thickness of 1300
Å A magnetic tape was obtained in the same manner as in Example 1 except that the coercive force was 1550 Oe. [Characteristics] In the magnetic tapes obtained in the above examples, 5 MH
The reproduction output and C / N at z, 10 MHz, and 20 MHz were examined, and the results are shown in Table-1.

Table-1 Output (dB) C / N (dB) 5 MHz 10 MHz 20 MHz 5 MHz 10 MHz 20 MHz Example 1 +0.4 +1.8 +3.1 +0.2 +2.1 +3.5 Example 2 +1.0 +1.9 +3.0 +0.8 +2.0 +3.2 Example 3 +1.2 +2.1 +3.4 +1.1 +2.3 +3.7 Example 4 +1.1 +1.8 +2.9 +0.9 +1.9 +3.2 Comparative Example 1 0 0 0 0 0 0 0 Comparative Example 2 -0.7 +0.2 +0.8 -0.8 +0.4 +0.6 Comparative Example 3 -0.4 -0.5 -0.7 -0.5 -0.6 -0.8 * Displayed as a relative value based on Comparative Example 1 * Measurement was carried out by the drum tester method. It is suitable for high-density recording and has high reproduction output.

[0022]

[Effect] It has a high reproduction output and is suitable for high density recording.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Support 2 Lower Co Metal Magnetic Film 3 Upper Co Metal Magnetic Film 4 Diamond-Like Carbon Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Shiga 2606 Akabane, Kai-cho, Haga-gun, Tochigi Prefecture Kao Corporation Company Information Science Laboratory

Claims (4)

[Claims] 1. A magnetic recording medium in which a plurality of metal thin film type magnetic films are laminated on a support, wherein the total magnetic film has a thickness of 800 to 3000 Å, and is located farthest from the support. A magnetic recording medium, wherein the thickness of the uppermost magnetic film is 1/6 to 1/3 of the thickness of the total magnetic film. 2. The magnetic recording medium according to claim 1, wherein the upper magnetic film has a larger coercive force than the lower magnetic film. 3. The coercive force of the lowermost magnetic film is 1000 to 1
800 Oe, the coercive force of the uppermost magnetic film is 1500 to 20
It is 00 Oe, Claim 1 or Claim 2 characterized by the above-mentioned.
Magnetic recording medium. 4. The magnetic recording medium according to claim 1, wherein the magnetic film is a magnetic film formed by oblique vapor deposition.