JPH0443324B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a magnetic recording medium having a magnetic recording layer made of a ferromagnetic metal thin film suitable for high-density magnetic recording. Conventional Structures and Problems With the increasing demand for high-density recording in recent years, various fields are actively investigating the practical application of magnetic recording media in which the magnetic recording layer is composed of a ferromagnetic metal thin film. Since such a medium aims at high-density recording, the space loss has a dominant effect on reducing the reproduction output at short wavelengths, so the surface of the magnetic recording layer naturally becomes smooth. Therefore, not only high-speed sliding with the magnetic head but also friction with the traveling mechanism members increases, and countermeasures are required. Therefore, as shown in FIG. 1, Co-Ni-O, Co-Ni-P, A general structure is a magnetic recording medium 4 having a magnetic recording layer 2 made of a ferromagnetic metal thin film such as Co--Cr, and a protective layer 3 disposed thereon. As mentioned above, due to space loss constraints, the protective layer must have a thickness of 1000 Å or less, preferably about 100 Å to 200 Å, to achieve its purpose. The use of thin coatings of esters, silicone oils, fluorine oils, etc., and the sputtering method using Teflon as a target are being considered, but these methods do not provide sufficient running performance in various environments with varying temperature and humidity. There is nothing to ensure that. In particular, silicone-based plasma polymerized membranes have satisfactory performance, but are thick at about 1000 Å, and improvements have been desired. Purpose of the Invention An object of the present invention is to provide a manufacturing method that can exhibit the advantages of plasma polymerized films even in the thin film area, and to enable the manufacturing of magnetic recording media having a practical ferromagnetic metal thin film as a magnetic recording layer. . Structure of the Invention The present invention provides a method for forming a plasma polymerized film on a moving ferromagnetic metal thin film, by determining the moving direction of the thin film,
It is characterized in that the directions of plasma spraying are opposite to each other, and a sufficient effect as a protective film can be obtained in a thickness region of 200 Å or less where space loss can be ignored. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows the method used to carry out the method of the present invention.
FIG. 2 is a configuration diagram of main parts of a protective layer forming apparatus. The ferromagnetic metal thin film 5 (of course, this is formed on the substrate, but for convenience of explanation it is shown as shown in the figure) is moved from the feeding shaft 6 to the winding shaft 7 by the arrow 8.
is configured to move in the direction of The winding system is arranged inside the vacuum chamber 9, and a plasma injection nozzle 11 is arranged to penetrate from the atmosphere into the vacuum through a part of the constituent wall 10 of the vacuum chamber. The nozzle 11 has an excitation coil 12 wound around it in the atmosphere, and introduces the monomer gas 13 alone or simultaneously with the carrier gas,
The gas 14 is plasma-polymerized and is injected in a polymerized state. 15 is the holding flange and 16
is an O-ring seal. The excitation coil 12 is connected to a high frequency power source via a matching circuit. It goes without saying that the plasma generation method for producing a plasma polymerized film is not limited to this example. It goes without saying that the formation of the magnetic recording layer and the formation of the protective layer may be performed continuously. The ferromagnetic metal thin film used in the present invention includes:
Co, Co-Ni, Co-Cr, Co-Ti, Co-W, Co-
It may be Mo, Co--Ni--O, etc., and may be used for so-called longitudinal recording or perpendicular recording, and does not depend on the manufacturing method. High frequencies from 1MHz to 30MHz are often used.
As the carrier gas, argon or the like is used as necessary, and as the monomer gas, CF ₄ , C ₃ F ₈ ,
CF ₃ Cl perfluorocyclobutane, vinyltrimethylsilane, hexamethyldisiloxane, octamethylcyclotetrasiloxane, etc. are used as appropriate. The present invention will be explained in detail below using more specific examples, but it goes without saying that the present invention is not limited to these examples. Example 1 Co-Ni (Ni 20wt%) was deposited at an incident angle on polyethylene terephthalate with a thickness of 10 μm and a surface roughness of 200 Å.
Diagonal deposition was performed at an angle of 40° or more. Vacuum degree is 1×10 ^-6 Torr
After exhausting the air to a temperature of 2×10 ^-5 Torr, oxygen was introduced.
I made it. Co−Ni is evaporated by electron beam heating,
The deposition rate was approximately 3000 Å/sec, and the film thickness was controlled to 0.1 μm. The cases of the present invention were compared with the case where the plasma was blown in a direction that corresponded to the moving direction of the vapor deposited film (Comparative Example 1), the case where the plasma was blown almost perpendicularly to the vapor deposited film (Comparative Example 2). For plasma, CF ₄ gas was introduced at 4c.c./min, high frequency was 13.56MHz, 1200W after injection, reflected wave
It was 90W. The moving speed of the deposited film was 6 m/min. The thickness of the protective film was unified to 120 Å. The resulting magnetic tapes were compared in three tests. In test 1, we prepared a deck capable of evaluating video tapes with a tape width of 8 mm with a running system equivalent to that of a commercially available video tape recorder (for example, Matsushita Electric's NV-3000), ran it repeatedly in various environments, and detected tape squeals. The presence or absence of was investigated. Judgments were made on a three-level scale: A (no problem at all), B (a slight effect on the screen, but at a practical level), and C (an impractical level). Test 2 is the protective effect against resistance, 60
Test 1 after being stored in an environment of ℃ 80% RH for one week.
The previous value was set as 1 and compared before and after adding the dropout to the environment. The surface condition was also observed using a light microscope. Test 3 used the deck from Test 1 to observe the screen in a still state, and compared the time it took for the S/N to deteriorate by 3 dB. (The magnetic head used was a ring-shaped ferrite head with a gap of 0.3 μm.)

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[Table] From the above test results, the magnetic recording medium having the plasma polymerized film obtained by the method for forming a protective film of the present invention has stable running performance, and can also play other roles as a protective film. It is understood that certain ferromagnetic metal thin films can be protected from corrosion and that the still life when used as a videotape is also good. The reason for this is not necessarily clear, but it is thought to be mainly due to the fact that when the plasma polymerized film adheres to the ferromagnetic metal thin film, the direction of movement is opposite, so that the so-called orientation effect is effective. Conceivable. This can also be inferred from the fact that the same can be said for other materials and is not an effect unique to fluorine-based plasma polymerized films. Example 2 A Co-Cr (Cr20wt%) film of 0.2 μm thickness was formed on polyamideimide 10.5 μm (average roughness 150 Å) by high-frequency sputtering method, and a polymerized film of hexamethyldisiloxane was added on top of it by gas introduction. Dicyclosan 5 c.c./min, argon 2 c.c./min
The high frequency is 13.56MHz, and the incident wave is
A reflected wave of 140 Å was formed under the conditions of 1350 W and 105 W. Place this tape on an amorphous head (gap).
Evaluation was made using the deck used in Example 1, which was replaced with 0.26 μm). In the product of the present invention, the plasma gas introduction direction and the moving direction of the ferromagnetic film are opposite (moving speed 7.5 m/min), whereas in Comparative Example 1, the moving direction of the ferromagnetic film and the plasma gas introduction direction are the same, and the plasma Comparative Example 2 is a case where the gas is introduced at right angles. The same test as in Example 1 was conducted.

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[Table] Effects of the Invention The present invention, when forming a plasma-polymerized film as a protective film on a ferromagnetic metal thin film, reverses the direction of plasma spraying to the moving direction of the ferromagnetic metal thin film, thereby making it easier to use repeatedly. It becomes possible to manufacture a practical magnetic recording medium for high-density recording that does not generate noise in the running system, has a long still life, and does not increase dropouts due to corrosion.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium, and FIG. 2 is a diagram showing the main part of a protective film forming apparatus for carrying out the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Magnetic recording layer (ferromagnetic metal thin film), 3... Protective film, 11... Plasma injection nozzle, 12... Excitation coil.

Claims (1)

[Claims] 1. A method for manufacturing a magnetic recording medium, characterized in that when a plasma polymerized film is formed on a moving ferromagnetic metal thin film, the moving direction of the thin film and the plasma spraying direction are opposite to each other.