JPH06111270A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Structure] A magnetic layer formed by oblique vapor deposition on a substrate, and a lubricating layer formed on the surface of the magnetic layer, and the conditions (1) to (4) below. A magnetic recording medium that satisfies the requirements. (1) The thickness of the magnetic layer is 1000 to 2000Å. (2) The surface roughness of the magnetic layer is 1 to 4 mm. (3) The magnetic layer contains Co, Ni and O in a specific ratio. (4) The thickness of the lubricating layer is 50Å or less. [Effect] The output at high frequency is good, and the durability and corrosion resistance are excellent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic recording medium.
More specifically, it relates to a vapor-deposited magnetic recording medium having excellent durability and corrosion resistance.

[0002]

2. Description of the Related Art As a magnetic recording medium, a coating type magnetic recording medium manufactured by coating a magnetic paint containing magnetic powder on a substrate (film) made of polyethylene terephthalate or the like has been known. However, the coating type magnetic recording medium has a limit to the filling property of the magnetic powder, and it is difficult to increase the density and improve the thinness of the magnetic recording medium.

In order to achieve this high density, a magnetic recording medium of a type in which a thin film of a magnetic material is directly formed on a substrate has been proposed, and this type has characteristics which a coating type magnetic recording medium does not have. .

A magnetic recording medium of the type in which a magnetic layer is directly formed on a substrate is manufactured by depositing a magnetic material on the substrate and forming the magnetic layer directly on the substrate.
There is a so-called vapor deposition type magnetic recording medium. This type of magnetic recording medium is usually manufactured by running a substrate on a cylinder under a reduced pressure condition and evaporating a magnetic material heated by an electron beam or the like onto the substrate. Japanese Patent Publication No. 41-1938
No. 9 discloses that the coercive force of a magnetic recording medium is improved by obliquely depositing a magnetic metal material.

However, when it is actually used as a video tape or the like, it cannot be put into practical use unless it is excellent in high output at high frequency and durability in addition to the coercive force. Although the magnetic recording medium described in Japanese Patent No. 19389 has an improved coercive force, it is insufficient in terms of high output and durability.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted intensive studies to enable high output at high frequencies of a vapor-deposited magnetic recording medium and to improve durability and corrosion resistance. As a result, the present invention was completed. I arrived.

That is, the present invention has a magnetic layer formed by oblique vapor deposition on a substrate and a lubricating layer formed on the surface of the magnetic layer, and satisfies the following conditions (1) to (4): The present invention provides a satisfying magnetic recording medium. (1) The thickness of the magnetic layer is 1000 to 2000Å. (2) The surface roughness value (Ra) of the magnetic layer is 1 to 4 mm. (3) The magnetic layer contains Co, Ni and O, and the ratio of Co, Ni and O in the magnetic layer is at 75% ≦ Co, 5%
It is in the range of ≦ Ni ≦ 25%, 5% ≦ O ≦ 15%. (4) The thickness of the lubricating layer is 50Å or less.

In the magnetic recording medium of the present invention, the magnetic layer essentially containing Co, Ni and O is formed on the substrate by oblique vapor deposition. The method of oblique vapor deposition conforms to the known technique. The inclusion of Co, Ni and O in the magnetic layer improves durability and corrosion resistance. The ratio of Co, Ni, and O 2 in the magnetic layer is at 75% ≤ Co, 5% ≤ Ni ≤ 25%, 5% ≤ O ≤ 15%
Is. If the ratio is out of this range, the output at high frequency is reduced and the corrosion resistance is also reduced.

Generally, as the recording wavelength becomes shorter, the magnetic layer may be thinner, but since the video and audio signals have a band, each has an appropriate thickness. In the magnetic recording medium of the present invention, the thickness of the magnetic layer formed by oblique vapor deposition is 10
It is from 00 to 2000Å. If the thickness of the magnetic layer is out of this range, high output at high frequencies cannot be obtained.

The surface roughness value (Ra) of the magnetic layer is 1
~ 4 mm. If Ra deviates from this range, high output at high frequencies cannot be obtained. Ra is measured by non-contact optical interferometry.

In the magnetic recording medium of the present invention, in order to further improve durability and corrosion resistance, a lubricating layer is formed on the surface of the magnetic layer obliquely deposited as described above. Usually, a vapor deposition type magnetic recording medium has a lubricating layer formed thereon, but they have a thickness of about 200Å, and in the present invention, the thickness of the lubricating layer must be 50Å or less. If the thickness of the lubricating layer exceeds 50Å, the output at high frequencies will decrease. The thickness of the lubricating layer is preferably 5-20Å. The lubricating layer is formed by a conventional method such as die coating. The lubricating layer is preferably made of perfluoropolyether. As the perfluoropolyether, those having a molecular weight of 2000 to 5000 are suitable, and examples thereof include "FOMBLIN Z DIAC" [carboxyl group-modified, manufactured by Nippon Montedison Co., Ltd.], "FOMBLIN Z DOL".
A commercially available product under the trade name of [alcohol modified, manufactured by Nippon Montedison Co., Ltd.] can be used. Since these have a hydroxyl group or a carboxyl group at the terminal, they can enhance the binding between the lubricant and the magnetic layer, and are therefore particularly preferably used in the present invention. Note that other fluorine-based lubricants can also be used. Fluorine-based lubricants are particularly preferably used in the present invention because they improve not only durability but also corrosion resistance as compared with fatty acid-based lubricants.

As the base material used in the magnetic recording medium of the present invention, an ordinary non-magnetic support can be used. Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate and cellulose diester. Cellulose derivatives such as acetate; polycarbonate; polyvinyl chloride; polyimide; plastics such as aromatic polyamide are used. The thickness of these substrates is 3-50
It is about μm.

A method of manufacturing the magnetic recording medium of the present invention will be briefly described. FIG. 1 is a schematic view showing an example of a manufacturing apparatus used for forming a magnetic layer by vapor deposition according to the present invention. Vacuum container 1
The inside is maintained at a vacuum of about 10 ^-4 to 10 ^-7 Torr by a vacuum pump. The film 3 serving as the substrate travels from the unwinding roll 4 on the vapor deposition cylinder (can) 2, and metal atoms vaporized by the electron gun 10 are obliquely vapor deposited on the film surface. The scattering plate 8 can control the scattering range of metal atoms. Oxygen gas inlet pipe 11
Oxygen can be included in the magnetic layer by treating the film having the magnetic layer formed therein with oxygen gas or by flowing oxygen gas at the same time when the magnetic layer is formed. As a result, a magnetic layer containing Co, Ni and O is formed. The oxygen gas introduction tube is preferably installed at the end of the reach of vapor deposition atoms (A in the figure). By controlling the flow rate of oxygen gas, the amount of oxygen in the magnetic layer can be manipulated, and the ratio of cobalt, nitrogen and oxygen can be set to a desired value. The film treated with oxygen gas is the take-up roll 5
Is wound up in. Then, perfluoropolyether is applied to the surface of the magnetic layer of this film by a conventional method such as die coating to form a lubricating layer having a thickness of 50 Å or less.

In the magnetic recording medium of the present invention, if a lubricating layer is formed on the surface of the magnetic layer, an undercoat layer having a thickness of about 0.01 to 0.2 μm, a protective layer having a thickness of about 10 to 100 Å,
Or the thickness of which carbon black is the main component 0.2 to 1.0
A back coat layer having a thickness of about μm may be formed.
As a raw material for forming these layers, conventionally known materials can be appropriately used.

[0015]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A back coating layer was formed by applying a binder coating mainly composed of carbon to the back surface of a polyethylene terephthalate film having a thickness of 9.2 μm by a conventional method so that the thickness after drying was 0.5 μm. Then, this film was attached to the device shown in Fig. 1, and Co-Ni alloy (Co: Ni = 90:10 atomic%) was applied on the surface.
A magnetic layer was formed by oblique vapor deposition while flowing oxygen in a vacuum of 1.5 × 10 ^-5 Torr. The thickness of the magnetic layer was 1500Å. This film is taken out into the air, and fluorine-based perfluoropolyether (grade: FOMBLIN Z DIAC carboxyl group-modified, manufactured by Nippon Montedison Co., Ltd.) is applied as a lubricant by die coating, dried and the thickness is 20Å. Of the lubricating layer was formed. Then, this film is cut into a width of 8 mm, placed in a cassette for 8 mm VTR, and commercially available
Luminance signal output at 7MHz and 10MHz was measured by using the modified device. The measured values of the luminance signal output are shown in Table 1 in dB units with reference to an 8 mm reference tape manufactured by Sony Corporation. Moreover, the physical property values in the table were measured as follows. -Thickness of lubricating layer: Measured by FTIR (Fourier transform infrared) spectrum. Elemental analysis in magnetic layer: Measured by Auger electron spectroscopy. Tape surface roughness: Ra value was measured by non-contact optical interference method. -Durability: Still durability was measured and used as a guideline for durability. The still durability was measured by measuring the decrease in output when still for 1 hour. -Corrosion resistance: The reduction rate of the saturation magnetic flux density when the tape was left for 1 week under the conditions of 60 ° C and 90% RH was evaluated. The results are shown in Table 1.

Example 2 In Example 1, the atomic percentage of the Co--Ni alloy was Co: Ni = 80:
20, the thickness of the magnetic layer is 1000Å, and fluorine-based perfluoropolyether (grade: FOMBLIN
A magnetic recording medium was manufactured in the same manner as in Example 1 except that Z DOL alcohol-modified, manufactured by Nippon Montedison Co., Ltd. was used, and the same evaluation was performed. The results are shown in Table 1.

Example 3 In Example 1, a magnetic recording medium was manufactured in the same manner as in Example 1 except that the flow rate of oxygen was increased so that the thickness of the magnetic layer was 2000 Å, and the same evaluation was performed. The results are shown in Table 1.
Shown in.

Comparative Example 1 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the lubricating layer was not formed after the magnetic layer was formed in Example 1, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 2 In Example 1, a magnetic recording medium was manufactured in the same manner as in Example 1 except that the flow rate of oxygen was increased to make the thickness of the magnetic layer 3000 Å, and the same evaluation was performed. The results are shown in Table 1.
Shown in.

Comparative Example 3 In Example 1, a magnetic recording medium was manufactured in the same manner as in Example 1 except that the thickness of the lubricating layer was 80Å, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 4 In Example 1, the flow rate of oxygen was increased, the atomic percentage in the magnetic layer was Co: Ni: O = 72: 8: 20, Ra was 6.0, and the other conditions were the same as in Example 1. A magnetic recording medium was manufactured by the above method, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 5 In Example 1, the atomic percentage of the Co--Ni alloy was changed to Co: Ni = 9.
The flow rate of oxygen is increased to 5: 5, and atomic% in the magnetic layer is changed to C
A magnetic recording medium was manufactured in the same manner as in Example 1 except that o: Ni: O = 80.8: 4.2: 15, Ra was 5.0, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 6 In Example 1, a magnetic recording medium was manufactured in the same manner as in Example 1, except that oxygen was not flowed to form a magnetic layer containing no oxygen. I did. The results are shown in Table 1.

Comparative Example 7 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the magnetic layer containing no Ni was formed in Example 1, and the other evaluations were made. The results are shown in Table 1.

[0026]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for performing oblique vapor deposition on a film substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Vapor deposition cylinder (can) 3 ... Film 4 ... Unwinding roll 5 ... Winding roll 6 ... Magnetic metal 7 ... Crucible 8 ... Shielding plate 9 ... Vacuum pump (exhaust system) 10 ... Electron gun 11 ... Oxygen Gas inlet pipe

Claims (2)

[Claims] 1. A magnetic layer formed by oblique vapor deposition on a substrate, and a lubricating layer formed on the surface of the magnetic layer,
A magnetic recording medium that satisfies the following conditions (1) to (4). (1) The thickness of the magnetic layer is 1000 to 2000Å. (2) The surface roughness value (Ra) of the magnetic layer is 1 to 4 mm. (3) The above magnetic layer contains Co, Ni and O, and the ratio of Co, Ni and O in the magnetic layer is at 75% ≦ Co, 5%
It is in the range of ≦ Ni ≦ 25%, 5% ≦ O ≦ 15%. (4) The thickness of the lubricating layer is 50Å or less. 2. The magnetic recording medium according to claim 1, wherein the lubricating layer is made of perfluoropolyether.