JPS60263334A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of a protective film to be formed on the surface of a thin ferromagnetic metallic film by selecting the gaseous monomer of fluorocarbon having an unsatd. bond are carrier gas of nitrogen at a specific volumetric ratio and executing plasma polymn. CONSTITUTION:A high-frequency coil 4 connected to a frequency oscillator 3 is wound around a reaction chamber 1 for plasma polymn. reaction. An introducing pipe 5 for introducing the gaseous monomer and carrier gas is connected to the chamber 1. A supply chamber 8 which lets off a non-magnetic base 6 on which the thin ferromagnetic metallic film 12 is deposited from a roll 7 and a take-up chamber 10 which takes up the base on a roll 9 are provided on both sides of the chamber 1. The residual air in the chamber 1 is removed and the inside thereof is evacuated; thereafter the fluorocarbon having the unsatd. bond as the gaseous monomer and the nitrogen as the carrier gas are selected at 50:50-80:20 volumetric ratio and are introduced into the chamber then the plasma polymn. is executed to form the protective film 13. The protective film which is highly crosslinked and is highly durable is thus formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ferromagnetic metal thin film type magnetic recording medium such as a so-called vapor-deposited tape1, and more specifically to a method for improving durability and running properties. This paper relates to improvements in the forming force of a protective film provided for the purpose of protecting the protective film.

[Background technology and its problems]

In the field of magnetic recording, efforts are being made to increase the recording density and shorten the wavelength of recording signals, but in response to stiffness, the coercive force H
Magnetic recording media with large c and residual magnetic flux density Br are desired1.
ing.

Conventionally, a ferromagnetic metal thin film such as a ferromagnetic metal material such as a C□-N L alloy is directly deposited on a non-magnetic support such as a polyester film using a method such as a vacuum deposition method or a subactor method. A ferromagnetic metal thin film type magnetic recording medium in which n is used as a magnetic layer has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium does not have a large coercive force HC or residual magnetic flux density Br, and the thickness of the magnetic layer can be made extremely thin, so the thickness loss during recording demagnetization and reproduction is extremely small. , there are many advantages in terms of magnetic properties, such as the ability to increase the packing density of ferromagnetic metal materials because there is no need to mix resin binders such as vinyl chloride-vinyl acetate copolymer or polyurethane resin into the magnetic layer. have.

However, the above-mentioned ferromagnetic metal thin film type magnetic recording medium has many drawbacks in terms of durability, runnability, etc., and improvement thereof remains a major challenge.

For example, attempts have been made to improve the durability and runnability by coating the surface of the magnetic layer of the magnetic recording medium, that is, the ferromagnetic metal thin film, with a lubricant or the like to form a protective film. In this case, the coefficient of friction is initially reduced and running properties are improved, but since the adhesion of the lubricant to the ferromagnetic metal thin film is weak, this lubricant is gradually removed by a magnetic head, etc. There are many problems in terms of durability, uniformity, film thickness, etc., such that the effectiveness decreases rapidly due to overheating.

On the other hand, attempts have been made to form the above-mentioned protective film by plasma polymerization. It has been reported that an extremely thin polymeric film can be obtained and is effective in improving the runnability of the above-mentioned magnetic recording media! I have been informed.

However, the polymer film obtained by the above plasma polymerization has a problem of insufficient durability due to insufficient crosslinking degree.
There is a need for people to be more internal.

[Purpose of the invention]

Therefore, the present invention was proposed in response to the above-mentioned needs in the technical field, and provides a plasma polymerization method capable of producing a polymer film with excellent durability and runnability. The object of the present invention is to provide a method for manufacturing a magnetic recording medium that can manufacture a ferromagnetic metal thin film type magnetic recording medium that has a practical level of durability.

[Means for solving problems]

That is, the method for producing a magnetic recording medium according to the present invention includes forming a protective film by plasma polymerization on the surface of a ferromagnetic metal thin film of a magnetic recording medium in which a ferromagnetic metal thin film is provided on a nonmagnetic support. , plasma polymerization is carried out by using a fluorocarbon having an unsaturated bond as a monomer gas, using nitrogen as a carrier gas, and selecting a monomer gas:carrier gas volume ratio of 50:50 to 80:20. By selecting the type and mixing ratio of monomer gas and carrier gas during plasma polymerization, it is possible to increase the degree of crosslinking of the resulting polymer film, greatly improving durability and reducing surface energy. The purpose of this invention is to reduce friction by reducing friction, and to improve the durability and runnability of ferromagnetic metal thin film type magnetic recording media by using n as a protective film.

The magnetic recording medium to which the present invention is applied is a so-called ferromagnetic metal thin film type magnetic recording medium in which a ferromagnetic metal material is directly deposited on a nonmagnetic support and a ferromagnetic metal thin film is formed as a magnetic layer. .

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate cutylate, polyvinyl chloride, polyvinylidene chloride, etc. Examples include plastics such as vinyl resin, polycarbonate, polyimide, and polyamideimide. Furthermore, the form of the non-magnetic support is as follows:
Any material such as film, tape, sheet, disk, card, drum, etc. is fine.

The above-mentioned ferromagnetic metal materials include iron (Fe, cobal) Co,
Co-N = gold alloy Fe such as nickel NJJ
-Co alloy, Fe-N=gold alloy co-NL-Fe-B alloy, and other alloys.

The means for depositing the ferromagnetic metal material include vacuum evaporation,
Examples include the ion blating method and spac 'fb'4. The above vacuum evaporation method uses 10-4 to 10" Torr
The ferromagnetic metal material is evaporated by resistance heating, high-frequency heating, electron beam heating, etc. in a vacuum, and the evaporated metal (ferromagnetic metal material) is deposited on the non-magnetic support. It is broadly divided into two methods: vertical deposition method and vertical deposition method. The above-mentioned oblique deposition method is a method in which the above-mentioned ferromagnetic metal material is obliquely deposited on a non-magnetic support in order to obtain a high coercive force.
This also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force. In the above-mentioned vertical deposition method, a base metal layer such as BL, Tz, Sl), Ga, Ge, etc. is formed in advance on a non-magnetic support in order to improve deposition efficiency and productivity and obtain high coercive force. Then, the ferromagnetic metal material is vertically deposited on the underlying metal layer. The above ion blating method is also a vacuum evaporation method.
D in an inert gas atmosphere of 10-' to 1o-3 Torr
C glow discharge or RF glow discharge is caused, and the ferromagnetic metal is evaporated during the discharge. The above sputtering method involves generating glow discharge in an atmosphere mainly composed of argon gas at 10-3 to 10'-' Torr, and using the generated argon ions to knock out atoms on the target surface. Examples include DC two-pole and three-pole sputtering methods, high-frequency sputtering methods, and magnetron sputtering methods that utilize magnetron discharge.

In the present invention, a protective film is formed by plasma polymerization on the surface of the ferromagnetic metal thin film of the above-mentioned magnetic recording medium.

In the above plasma polymerization, glow discharge is usually performed in an organic monomer gas alone or in a mixture of the monomer gas and another gas (carrier gas), and a polymer film derived from the excited monomer is brought into contact with the discharge region. For example, 1) it should have high adhesion to the thin ferromagnetic metal film formed on the substrate, 2) it should have high density, and 3) it should have good heat resistance. 4) It is difficult to form a uniform film because a polymeric film is formed as a protective film.

In the present invention, a polymeric film is formed by glow discharge in a mixed gas of a seven-layer liquid and a carrier gas.
Here, the type and mixing ratio of the monomer gas and carrier gas used are important.

First, as the monomer gas mentioned above, fluorocarbon (
Among them, CnF2n C2≦
A fluorocarbon having an unsaturated bond represented by the general formula (n≦4) is used. The number of carbon atoms in the fluorocarbon having unsaturated bonds is preferably 4 or less; if the number of carbon atoms exceeds 4, the degree of crosslinking may be insufficient and a polymer film with sufficient durability may not be obtained. . Similarly, the above-mentioned fluorocarbon must have an unsaturated bond, and if it does not have this unsaturated bond, the degree of crosslinking of the polymerized film obtained may be insufficient, or the film formation will be extremely slow. In such cases, there is a possibility that polymerized J model may not be obtained. A particularly preferred monomer gas is tetrafluoroethylene (
Examples include CF2=CF or hexafluoropropylene (CF2=CF-CF3).

On the other hand, nitrogen is used as the carrier gas. As a result of analysis, it is estimated that this nitrogen forms a network structure together with the above-mentioned 7-mer during the plasma polymerization reaction and contributes to improving the degree of crosslinking of the polymerized film, improving the durability of the resulting polymeric film and improving the surface It has been found that this method is extremely useful for improving film quality by reducing energy consumption and lowering the coefficient of friction.

The monomer gas and the carrier gas need to be mixed at a predetermined ratio, and according to the inventor's experiments, the volume ratio of the monomer gas to the carrier gas is 5.
By setting within the range of 0:50 to 80:20, r,
It was found that a polymer film with extremely high durability was produced. That is, if the proportion of the carrier gas is less than 20% by volume, or exceeds 50% by volume, a polymer film with sufficient durability cannot be obtained, and therefore ferromagnetic metal thin film type magnetic recording It is difficult to raise the durability of media to a practical level.

Plasma polymerization is carried out using the above-mentioned 7-mer gas and carrier gas. Next, an example of a reaction apparatus used for carrying out plasma polymerization in the present invention will be explained.

FIG. 1 is a schematic diagram showing the configuration of a reaction apparatus actually used in the present invention.

This reactor uses an electrodeless system because there is no contamination of the electrodes and good discharge stability, and it is an inductively coupled system, and the plasma oscillation frequency is 13.56M.
It is Hz. The reaction apparatus is equipped with a reaction chamber 1 for plasma polymerization reaction, and a high-frequency coil 4 connected to a frequency oscillator 3 via a matching network 2 is wound around the reaction chamber 1. has been done. Further, an inlet pipe 5 for introducing a monomer gas, a carrier gas, and a carrier gas is connected to the reaction chamber 1, and the monomer gas and the carrier gas are all adjusted in advance by a mass flow controller, for example. The gas is mixed with the above-mentioned mixing ratio and introduced into the reaction chamber 1. Further, on both sides of the reaction chamber 1, there is a supply chamber 8 for feeding out from a roll 7 a non-magnetic support 6 having a ferromagnetic metal thin film deposited on its surface, and a supply chamber 8 for feeding the non-magnetic support 6 into the reaction chamber 1. The non-magnetic support 6 is continuously driven via a guide roller 11 to deposit a polymer film formed by a plasma polymerization reaction. It is composed of den. The supply chamber 8 and the winding chamber 10 are connected to a vacuum pump so that the entire chamber, including the reaction chamber 1, is maintained at a high vacuum Vζ.

Using the reaction apparatus configured as described above, first, the residual air in the reaction chamber 1 is sufficiently removed to reduce the pressure to about to-''rorr, and then the monomer gas and carrier gas are mixed at a predetermined mixing ratio. Gas is supplied to reaction chamber 1 at a predetermined flow rate.
The oscillator 3 is activated while introducing the RF power into the coil 4, and the RF power is applied to the coil 4 to discharge it. In addition, in order to cause the above plasma polymerization reaction to occur in a good discharge condition, generally 10-3~
It is desirable to carry out the process in a vacuum state of 3 Torr, and usually about 10-2 Torr is employed.

As a result, a plasma polymerized film is grown on the surface of the ferromagnetic metal thin film deposited on the non-magnetic support 6 as a protective film. That is, the magnetic recording medium obtained is
As shown in the figure, a ferromagnetic metal thin film 1 is placed on a non-magnetic support 6.
2f: A layered layer is formed, and a polymer film obtained by the plasma polymerization described above is further applied to the surface of the ferromagnetic metal thin film 12 as a protective film 13.
It is constructed by laminating layers.

1 m of the protective film 13 obtained by the above plasma polymerization reaction
The thickness is preferably in the range of 50 to 50 mm, more preferably 50 to 150 mm.

If the above film thickness is less than 50 λ, the lubricating effect and durability will be insufficient, and if it exceeds 500 λ, spacing loss (thickness loss) will occur when the tape is slid on the magnetic head surface 7''. ) becomes large.

As described above, in the present invention, a fluorocarbon having an unsaturated bond is used as a monomerus, nitrogen is used as a carrier gas, and the ratio of the monomerus and the carrier gas is set at a predetermined ratio.
A highly crosslinked and highly durable polymeric film with low surface energy and small friction coefficient can be formed by plasma polymerization reaction, and this polymeric film is used as a protective film 13 to cover the ferromagnetic metal thin film 12. By forming an adhesive, it becomes possible to manufacture a magnetic recording medium with excellent durability and running properties.

Next, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

〔Example〕

Example 1 A Co--N=alloy alloy film having a CCo content of 8 mm was formed on a polyethylene terephthalate film by lateral deposition with a thickness of 1 mm.

Next, using hexafluoropropylene (C3F6) as a monomer gas and using nitrogen N2 as a carrier gas, the ratios of these monomer gases and carrier gases were set as shown in Table 1, and the total flow rate was 10.
0 'lnf/lni n , pressure 5.0×1 0-
2 Torr, high frequency output (frequency 1 3.5 6 M
A plasma polymerization reaction was performed for 1 minute under the condition of 500 W (Hz) to form a plasma polymerized film on the above CO-NL alloy film, thereby producing Samples 1 to 4 and Comparative Samples 1 to 6. Note that Comparative Sample 1 here shows the case where no plasma polymerized film was provided.

The stealth characteristics and friction characteristics were measured for each sample that could not be obtained and each comparative sample. The results are shown in Table 1. The above methyl characteristic indicates the methyl time it takes for a 4.2 MHz video signal to be recorded and the playback output to attenuate to a factor of 50, and is a measure of the durability of the magnetic tape. . Further, the above-mentioned frictional characteristics were measured using a stainless steel drum and showed a value of 100 times 1].

Table 1 As is clear from Table 1, the magnetic recording media (Samples 1 to 4) produced by the manufacturing method according to the present invention have excellent durability, especially methyl resistance. Moreover, since the friction characteristics are good, it can be seen that the running properties are also excellent.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to produce a plasma polymerized film that is highly cross-linked, has excellent durability, has low surface drag, and has a small coefficient of friction9.
Therefore, it is possible to manufacture a magnetic recording medium with excellent durability and running properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a plasma reaction apparatus used in the present invention, and FIG. 2 is an enlarged sectional view of a main part showing the structure of a magnetic recording medium obtained by the present invention. 6...Nonmagnetic support 12...Ferromagnetic metal thin film 13...Holding film

Claims (1)

[Claims] In order to form a protective group by plasma polymerization on the surface of the ferromagnetic metal thin film of a magnetic recording medium comprising a ferromagnetic metal thin film provided on a non-magnetic support, a fluorocarbon having an unsaturated bond is used as a monomer gas. A method for producing a magnetic recording medium, characterized in that plasma polymerization is carried out by using nitrogen as a carrier gas and selecting a monomer gas:carrier gas volume ratio of 50:50 to 80:20.