JPS60263333A - 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 and carrier gas of hydrogen 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 hydrogen as the carrier gas are selected at 5:95-40:60 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] [Field of Industrial Application] 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 tape, and more specifically to a method for improving durability and runnability. The present invention relates to an improvement in a method for forming a protective film provided for the purpose of

[Background technology and its problems]

In the field of magnetic recording, higher recording density and shorter wavelength recording signals are being recorded, and in response to this, the coercive force H
There is a demand for magnetic recording media with large e and residual magnetic flux density Br.

Conventionally, a ferromagnetic metal thin film such as a Co-Ni alloy is deposited directly on a non-WMJE support such as a polyester film using a method such as a vacuum deposition method or a spunter method. A ferromagnetic metal thin film type magnetic recording medium has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has high coercive force He and residual magnetic flux density Br, but also has extremely low thickness loss during recording demagnetization and reproduction because the thickness of the magnetic layer can be made extremely thin. It has 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 layer. are doing.

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

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, at first the friction coefficient is reduced and running properties are improved, but since the lubricant has a weak adhesion force to the ferromagnetic metal thin film, the lubricant is gradually scraped away by the magnetic head, etc. There are many problems in terms of durability, uniformity, film thickness, etc., such that the effectiveness decreases rapidly.

On the other hand, attempts have been made to form the above-mentioned protective film by plasma polymerization. It has been reported that a thin polymer film can be obtained and is effective in improving the running properties of the above-mentioned magnetic recording medium.

However, the polymerized film obtained by the plasma polymerization described above has a problem of insufficient durability due to insufficient crosslinking degree, and there is a need to further improve this durability in order to put it into practical use. ing.

[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, thereby achieving a practical level. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that can manufacture a ferromagnetic single-metal thin film type magnetic recording medium having a durability of .

[Means for solving problems]

That is, in the method for manufacturing a magnetic recording medium according to the present invention, in 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, a monomer gas is Plasma polymerization is carried out using fluorocarbon having an unsaturated bond as a fluorocarbon, hydrogen as a carrier gas, and a monomer gas:carrier gas volume ratio of 5=95 to 40:60. By selecting the type and mixing ratio of monomer gas and carrier gas during plasma polymerization, the degree of crosslinking of the resulting polymer film can be increased and durability can be greatly improved. By doing so, it is intended to improve the durability and runnability of a ferromagnetic metal thin film type magnetic recording medium.

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 butyrate, polyvinyl chloride, polyvinylidene chloride, etc. Examples include plastics such as vinyl resin, polycarbonate, polyimide, and polyamideimide. In addition, the form of the above-mentioned non-magnetic support is 4-, a film, a tape, a sheet, a disk, a card,
Any device such as a drum may be used.

The above-mentioned ferromagnetic metal materials include iron Fe, cobalt Co1
Metal such as Niskel Ni or Co-Ni alloy, Fe
-Co alloy, Fe-Ni alloy, Co-N1-Fe-B alloy, and other alloys.

The means for depositing the ferromagnetic metal material include vacuum evaporation,
Examples include ion brating method and spanner method.

In the vacuum evaporation method, the ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-4 to 10''8 Torr, and the evaporated metal (ferromagnetic metal This method is divided into two methods: oblique deposition method and vertical deposition method. In the above-mentioned oblique deposition method, the ferromagnetic metal material is obliquely deposited on a non-magnetic support in order to obtain a high coercive force. It also includes things that are done. The above vertical deposition method improves deposition efficiency and productivity, and in order to obtain high coercive force, old, TJ, and Sb are deposited on a nonmagnetic support in advance.

A base metal layer of Ga, Ge, etc. is formed in advance, and the ferromagnetic metal material is vertically deposited on the base metal layer. The above-mentioned ion brating method is also a type of vacuum evaporation method, in which DC dull discharge and RF glow discharge are caused in an inert gas atmosphere of 10-4 to 1O-3 Torr, and the above-mentioned ferromagnetic metal is evaporated during the discharge. It is. The above sputtering method uses 1o-3 to 10-' Torr.
A glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon ions are used to knock out atoms on the target surface. There is also a magnetron sputtering method using magnetron discharge.

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

□ 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 must have high adhesion to the ferromagnetic metal thin film that is the base, 2) it must have high density, 3) it must be heat resistant, and 4) it must be uniform. A polymeric film having certain characteristics such as being formed as a protective film is formed as a protective film.

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

First, as the monomer gas, fluorocarbon (
CnF2n (2≦
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. There is.

Similarly, the above-mentioned fluorocarbon must have an unsaturated bond, and if it does not have this unsaturated bond, not only will the degree of crosslinking of the resulting polymer film be insufficient, but the formation of the film will be extremely slow. In some cases, there is a possibility that a polymer film may not be obtained.

Particularly preferred monomer gases include tetrafluoroethylene (CF2=CF2) and hexafluoropropylene (CF2=CF CFa).

On the other hand, hydrogen is used as the carrier gas. In a plasma polymerization reaction, when a fluorocarbon monomer is alone in a plasma state, fluorine radicals are generated in a polymer film? On the other hand, it may extend or prevent the degree of crosslinking from increasing.However, when hydrogen is added as a carrier gas, this hydrogen is effective in removing the above-mentioned harmful fluorine radicals, creating a strong structure with a high degree of crosslinking. It was found that a polymer film could be obtained.

The monomer gas and carrier gas must be mixed at a predetermined ratio before use, and according to the inventor's experiments, the volume ratio of monomer gas to carrier gas is 5.
It was found that by setting the ratio within the range of 95 to 40:60, a polymer film with extremely excellent durability was produced.

That is, if the proportion of the carrier gas is less than 60% by volume or exceeds 95% by volume, a polymer film with sufficient durability cannot be obtained, and therefore the ferromagnetic metal thin film type magnetic recording medium cannot be used. It is difficult to raise the durability to a fully practical level.

Plasma polymerization is carried out using the above-mentioned monomer 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 introduction pipe 5 for introducing monomer gas and carrier gas is connected to the reaction chamber 1, and the monomer gas and carrier gas, whose flow rates have been adjusted in advance by, for example, a mass flow controller, are mixed at the above-mentioned mixing ratio. The components are mixed together and introduced into the reaction chamber 1. Further, on both sides of the reaction chamber 1, there is a supply chamber 8 in which a non-magnetic support 6 having a ferromagnetic metal thin film coated on its surface is fed out from a roll 7, and a supply chamber 8 in which the non-magnetic support 6 is fed into the reaction chamber 1. A winding chamber 10 for winding the non-magnetic support 6 onto the roll 9 is connected to the winding chamber 10 for winding the non-magnetic support 6 onto the roll 9.
The entire chamber, including the reaction chamber 1, is maintained at a high vacuum while being continuously driven via a plasma pump.

Using the reactor configured as described above, first, the residual air in the reaction chamber 1 is sufficiently removed to reduce the pressure to about 10''2 Torr, and then the monomer gas and carrier gas are mixed in a predetermined mixture. The oscillator 3 is operated while gas is introduced into the reaction chamber 1 at a predetermined flow rate, and RF power is applied to the coil 4 to cause discharge. In addition, the above plasma polymerization reaction is generally carried out at a temperature of 10-3 to 10-3 to cause good discharge.
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 obtained magnetic recording medium has a ferromagnetic metal thin film 12 on a non-magnetic support 6, as shown in FIG.
are laminated, and a polymeric film obtained by the plasma polymerization described above is further laminated as a protective film 13 on the surface of this ferromagnetic metal thin film 12.

The thickness of the protective film 13 obtained by the above plasma polymerization reaction is preferably in the range of 50 to 500 Å, and more preferably in the range of 50 to 150 Å. If the film thickness is less than 50A, the lubricity imparting effect and durability will be insufficient, and if it exceeds 500A', the spacing loss (thickness loss) will increase when the tape is made to slide on the surface of the magnetic head. Put it away.

As mentioned above, in the present invention, fluorocarbon having unsaturated bonds is used as the monomer gas, hydrogen is used as the carrier gas, and the ratio of the monomer gas and the carrier gas is set at a predetermined ratio.
A highly crosslinked and highly durable polymeric film can be formed by plasma polymerization reaction, and by depositing this polymeric film as a protective film 13 on the ferromagnetic metal thin film 12, a magnetic recording medium with excellent durability can be obtained. This makes it possible to manufacture .

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-Ni alloy film with a thickness of 1000A (Co content 8
0% by weight, Ni content 20% by weight) was formed by vapor deposition.

Next, tetrafluoroethylene (
C2F4)' and hydrogen (
The ratios of these monomer gases and carrier gas used in H2)' were set as shown in Table 1, and the total flow rate was 100 ml, /mlH% pressure 5. OX10T
orr,, high frequency output (frequency 13.56MHz)
The entire plasma polymerization reaction was carried out under the condition of 500W, and the above Co
This figure shows the case where no plasma polymerized film is provided on the -Ni alloy film.

Methyl special for each sample obtained and the valley comparison sample! - Measured. The results are shown in Table 1.

The above-mentioned methyl characteristic indicates the still time until the reproduction output attenuates to 50% after recording a 4.2 MHz video signal, and serves as a measure of the durability of the magnetic tape.

Table 1 This Table 1 shows that by setting the ratio of monomer gas and carrier gas within a predetermined range, a polymer film with excellent durability can be formed, and the durability of the resulting magnetic recording medium can be greatly increased. I can see that it will improve.

Example 2 A Co--Ni alloy film (Co content: 8 Å) was formed on a polyethylene terephthalate film by oblique evaporation to a thickness of 1000 Å.

Next, hexafluoropropylene (C3F6) was used as the monomer gas, and hydrogen (H2) was used as the carrier gas.
), the ratios of these monomer gases and carrier gases were set as shown in Table 2, and the total flow rate was 100 mJ/min and the pressure was 5. OX 1 0-
2Torr, high frequency output (frequency 13.5 6MHz
) All plasma polymerization reactions were carried out under the conditions of 500 W, and the above C
Samples 5 to 8 and Comparative Samples 4 to 6 were prepared by forming plasma polymerized films on o-Ni alloy films.

Still characteristics were measured for the obtained valley sample and valley comparison sample.

The results are shown in Table 2.

Table 2 As is clear from Table 2, the magnetic recording media (Samples 5 to 8) on which the plasma polymerized film was formed according to the present invention have excellent durability, especially stealth resistance. I know that there is.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to produce a plasma polymerized film that is highly crosslinked and has excellent durability, and therefore it is possible to produce a magnetic recording medium that has excellent durability. It is possible.

[Brief explanation of drawings]

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...Protective film Patent applicant Nny Co., Ltd. Agent Patent attorney Koike Mimuki 1) Sakae Mura −

Claims (1)

[Claims] In forming a protective film on the surface of the ferromagnetic metal thin film of the magnetic recording medium by plasma polymerization, a fluorocarbon having an unsaturated bond is used as a monomer gas, hydrogen is used as a carrier gas, and the monomer gas:carrier gas is mixed at a volume ratio of 5. A method for producing a magnetic recording medium, characterized in that plasma polymerization is performed at a ratio of: 95 to 40:60.