JPS61924A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the coefft. of friction of a protective film and to improve running property by forming the plasma-polymerized protective film on the surface of a thin ferromagnetic metallic film provided on a non-magnetic substrate then subjecting the protective film to an oxygen plasma treatment. CONSTITUTION:The plasma-polymerized film is formed as the protective film 13 on the surface of the thin ferromagnetic metallic film 12 deposited and formed on the non-magnetic substrate 6. The film 13 is thereafter subjected to the oxygen plasma treatment. More specifically, glow discharge is executed in an oxygen atmosphere and a physicochemical surface treatment is applied to the film by the generated oxygen plasma. The film 13 having the extremely small coefft. of friction is thus obtd. and the running property is improved. The durability of a magnetic recording medium is eventually improved.

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 c and residual magnetic flux density Br.

Conventionally, a ferromagnetic metal thin film such as a Co-Ni alloy is deposited directly on a non-magnetic support such as a polyester film using vacuum evaporation or sputtering, and this is made magnetic. 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 has a coercive force Hc and a residual magnetic flux density B
Not only is r large, but the thickness of the magnetic layer can be made extremely thin, so the thickness loss during recording demagnetization and reproduction is extremely small. The packing density of ferromagnetic metal materials can be increased because there is no need to mix them, etc.
It has a number of advantages in terms of magnetic properties.

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, i.e. 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 gradually becomes more susceptible to magnetic heads, etc. There are many problems in terms of durability, uniformity, film thickness, etc., such as the fact that it is scraped off and its 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 this allows an extremely thin polymer film to be formed, which is effective in improving the runnability and durability of the above-mentioned magnetic recording medium.

However, the polymer film obtained by the plasma polymerization described above has a rather high coefficient of friction, and in order to improve running properties, it is desired to reduce this coefficient of friction.

[Purpose of the invention]

Therefore, the present invention was proposed in response to the above-mentioned needs in the technical field, and it is possible to produce a magnetic recording medium with excellent running properties by producing a plasma polymerized film with a small coefficient of friction. The purpose of this invention is to provide a method for manufacturing a magnetic recording medium.

[Means for solving problems]

That is, the method for manufacturing a magnetic recording medium according to the present invention includes forming a protective film by plasma polymerization on the surface of the ferromagnetic metal thin film of a magnetic recording medium in which a ferromagnetic metal thin film is provided on a nonmagnetic support, and then applying the protective film to the surface of the magnetic recording medium. The film is characterized by subjecting the film to oxygen plasma treatment, and the surface of the protective film formed by plasma polymerization is further surface-treated by oxygen plasma treatment to lower the friction coefficient of the protective film. This is an attempt to improve the running performance 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,
Examples include vinyl resins such as polyvinylidene chloride, plastics such as polycarbonate 1 to polyimide, and boramidimide. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum. Alternatively, it may be a so-called heart disk using an aluminum plate or the like as a nonmagnetic support.

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

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

The above-mentioned vacuum evaporation method
The ferromagnetic metal material is evaporated by resistance heating, high-frequency heating, electron beam heating, etc. in a vacuum of and vertical evaporation methods. 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. In the vertical deposition method, Bi, TI3, 8b is deposited on a non-magnetic support in advance in order to improve deposition efficiency and productivity and to obtain high coercive force.

A base metal layer such as Ga or Ge is formed in advance, and the ferromagnetic metal material is vertically deposited on the base metal layer. The above-mentioned ion blating method is also a type of vacuum evaporation method, in which DC claw discharge and F glow discharge are generated in an inert gas atmosphere of 10-' to 10-8 Torr, and the ferromagnetic metal is evaporated during the discharge. It is something. In the above sputtering method, glow discharge is caused in an atmosphere mainly composed of argon gas at 10 to 10' Torr, and the generated argon ions are used to knock out atoms on the target surface. There are three-pole sputtering method, high-frequency sputtering method, and Macnetron sputtering method using Macnetron discharge.

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

The plasma polymerization described above involves performing glow discharge in an organic monomer gas alone or in a mixture of the monomer gas and another gas (carrier gas), and depositing a polymer film derived from the excited monomer on a substrate in contact with the discharge region. For example, 1) it must have high adhesion to the ferromagnetic metal thin film that is the substrate, 2) it must have high density, 3) it must be heat resistant, and 4) it must be uniform. A polymeric film having various properties such as being produced as a protective film is formed as a protective film.

As the monomer gas used in the above plasma polymerization, any commonly used compound containing 31 atoms, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n -propylamine, trilopropylamine, n-methylamine, n-amylamine, rhohexylamine, laurylamine, ethylenecyamine, trimethylenediamine, hexamethylenediamine, ethanolamine, jetanolamine, allylamine, aniline, alanine, N-methylaniline, allyldimethylamine, 2-aminoethyl ether,
1-dimethylamine-2-chloroethane, cyclopropylamine, cyclohexylamine, ethyleneimine, 1
- Organic amine compounds such as methylethyleneimine, N,N-dimethylformamide, formamide, capronamide, diaminoacecool, benzylamine, piperidine, pyrrolidine, morpholine, trimethylchlorosilane,
Trimethylmethoxysilane, vinyldimethylchlorosilane, tetramethoxonerane, detraethoshisilane, trimethoxysilane, allyltriethoxysilane, phenyltrimethoxysilanetetraallyloxysilane, methyldichlorosilane, vinylmethyldichlorosilane and hydrolyzed wire metal products thereof Organosilicon compounds such as organosiloxane, ethylene, propylene, acetylene, vinyl chloride, vinylitine chloride, acrolein, allyl alcohol, maleic acid, acrylic acid, methyl methacrylate, cyclopentene, cyclohexene, cyclohexenol, 2,5-dihydro Furan, propadiene, 1.
2-Vtadiene, 1,3-butadiene, 1,7-ofcudiene, 1.

3,5-hex-1-liene, organic unsaturated compounds such as benzene, styrene, phthalic acid, phenol, aniline, dichlorobenzene, naphthalene, cyclohexadiene,
etc. are exemplified.

In particular, in order to form a highly durable protective film, (1)
Method (2) Using a silazane-based monomer gas as a monomer gas (2) A plasma polymerization reaction may be carried out by using a fluorocarbon having an unsaturated bond as a monomer gas and using oxygen, hydrogen, or nitrogen as a carrier gas.

The method (1) above involves performing a plasma polymerization reaction using a silazane compound, which is an organosilicon compound having an s I-N bond, as a monomer gas,
In this way, a highly durable polymer film can be obtained, but in particular, by mixing 20 to 40 volumes of an inert gas such as argon gas or oxygen to these silazane monomer gases, the degree of crosslinking is high and the ferromagnetic metal thin film is bonded to the silazane monomer gas. A polymer film with excellent adhesion is formed as a protective film. Here, the silazane compounds used include: ■ Tetramethylcyclodisilazane ■ 1,1,3,3-tetramethyldisilazane (CHs
)z-8i-N-8i-(CHa)t■ Hexamethylcyclotrisilazane■ Hexaphenyllecrotrisilazane■ Octamethylcyclotetrasilazane■ 1.3-bis(chloromethyl)tetramethyldisilazane (CHa)2 -5fi-N-8i-(CH8)2■
Hexamethoxydisilazane (CH20)! 1-8i -N-8i-(OCHsu8ω
) Hexamethyldisilazane (CHa)ssiNH8i (CHa)a, etc. are exemplified.

On the other hand, in the method (2) above, a fluorocarbon (having 2 to 4 carbon atoms) having an unsaturated bond, particularly preferably tetrafluoroethylene (02F4) or hexafluoropropylene (C8F6), is used as a monomer gas, and a carrier gas In this method, one of oxygen, hydrogen, and nitrogen is used as a gas, and claw discharge is performed in a mixed gas of these monomer gases and a carrier gas to perform a plasma polymerization reaction.

Here, the ratio of the monomer gas to the carrier gas is important, and when oxygen is used as the carrier gas, the monomer gas:carrier gas volume ratio is 75:25 to 8.
5:15, when using hydrogen as a carrier gas, the monomer:carrier gas ratio by volume is 5:9.
If nitrogen is used as the carrier gas, the monomer gas:carrier gas ratio by volume must be set at 50:50 to 80:20. Thus, by setting the ratio of the monomer gas to the carrier gas within a predetermined range, a polymeric film that is highly crosslinked and exhibits excellent durability is formed.

Further, the reaction apparatus used for carrying out the plasma polymerization reaction in the present invention may be of any type as long as it is commonly used. For example, two electrodes are disposed facing each other in a bell jar. It is possible to use an internal electrode type reaction apparatus in which a high frequency output is applied between the reactors, or an electrodeless type reaction apparatus in which discharge is caused from outside the reactor in an inductively coupled or capacitively coupled manner.

FIG. 1 shows an example of a reaction apparatus actually used in the present invention.

In this reactor, an inductively coupled electrodeless system is adopted because there is no electrode contamination and discharge stability is good, and the oscillation frequency of the applied high-frequency power is 13.
It is 55MHz. 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. An introduction pipe 5 for introducing monomer gas and carrier gas is connected to the reaction chamber 1, and the monomer gas or the mixed gas of monomer gas and carrier gas whose flow rate has been adjusted in advance using an evaporative mass flow controller is introduced into the reaction chamber 1. It is designed to be 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 the roll 1 a non-magnetic support 6 whose surface is coated with a ferromagnetic metal thin film, 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 configured.

The supply chamber 8 and the winding chamber 10 are each connected to a vacuum pump, so that the entire chamber including the reaction chamber 1 is maintained at a high vacuum.

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 10-2 Torr, and then the above-mentioned monomer gas or a mixed gas of monomer gas and carrier gas is introduced. The oscillator 3 is operated while being introduced into the reaction chamber 1 at a predetermined flow rate, R,
Apply F power to the coil 4 to discharge it. In order to cause good discharge, the plasma polymerization reaction is generally desirably carried out in a vacuum state of about 10 to 3 Torr, and usually about IQ Torr is employed.

As a result, a plasma polymerized film is formed as a protective film 13 on the surface of the ferromagnetic metal thin film 12 deposited on the nonmagnetic support 6, as shown in FIG.

In the present invention, after the protective film 13 is formed by the plasma polymerization described above, the protective film 13 is subjected to oxygen plasma treatment to modify its surface. According to experiments conducted by the present inventors, it has been found that by performing the oxygen plasma polymerization, the friction coefficient of the surface of the protective film 13 formed by the plasma polymerization reaction is significantly reduced.

In the oxygen plasma treatment, claw discharge is performed in an oxygen atmosphere, and the generated oxygen plasma is applied to the protective film 13.
This method applies physicochemical surface treatment to the surface, and a reaction apparatus similar to that used for the plasma polymerization reaction described above can be used. Therefore, for example, after forming the protective film 13 by the above-mentioned plasma polymerization reaction, the inside of the reaction apparatus is sufficiently degassed, and then only oxygen is introduced into the reaction apparatus and high frequency power is applied again to generate the oxygen plasma. Processing can be performed continuously.

Incidentally, the longer the oxygen plasma treatment time is, the more effective it is in reducing the friction coefficient of the protective film 13. However, if the treatment time is too long, there is a risk that the durability of the protective film 13 will be impaired. It is preferable to set it appropriately in consideration of the applied voltage during oxygen plasma treatment, the thickness of the protective film 13, etc.

As described above, after the protective film 13 is formed on the ferromagnetic metal thin film 12 by plasma polymerization, the protective film 13 with an extremely small coefficient of friction can be obtained by subsequently subjecting the protective film 13 to oxygen plasma treatment. Therefore, a ferromagnetic metal thin film magnetic recording medium with excellent running properties can be obtained. Furthermore, along with this improvement in running performance, the durability of the magnetic recording medium is also improved.

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 CO content of 8 cm) having a thickness of 1000 λ was deposited on a polyethylene terephthalate film by oblique evaporation.

Then, hexafluoropropylene (C8Pe) was used as the monomer gas and hydrogen (H2
), the ratio CaFa:Hz of these monomer gas and carrier gas was set to be 25 near 5 in terms of volume ratio, the total flow rate was 1 oomy/=, and the pressure was 5.

O X 1 0-”Torr, high frequency output (frequency 13
．． A plasma polymerization reaction was carried out under the conditions of 56MHz) and 600W to form a plasma polymerized film with a thickness of 200λ on the Co-Ni alloy film.

Next, the amount of oxygen introduced is 100 m//kaku, the pressure is 5.0 x 1 Q.
Torr, high frequency output (frequency 1 3.5 6MHz
) The above plasma polymerized film was subjected to oxygen plasma treatment under the condition of 400 W to prepare a sample tape.

When we measured the friction coefficient of the sample tape obtained, we found that
It was extremely small at 0.15. In addition, as shown in FIG. 3, the above-mentioned coefficient of friction is determined by contacting the sample tape 22 over % of the circumference of the stainless steel drum 21, and suspending a weight W (weight 50 g) from the lower end of the sample tape 22. A strain gauge 23 is attached to the other end, and the sample tape 22 is moved in the direction of the arrow X. It was determined by running at a speed of jl/tea and measuring the value after running 100 times.

Example 2 A Co--Ni alloy thin film (with a Co content of 8 mm) having a thickness of 1000 Å was deposited on a polyethylene terephthalate film by oblique deposition.

Then, hexamethylcinlazan [
(CHs)a8iNH8i (CHa)3], argon (Ar) was used as the carrier gas, the volume ratio of monomer gas to carrier gas was set to 70:30, the total flow rate was 3Qm//m+++, and the pressure was 2. OXI
Q-2Torr high frequency output (frequency 1 3.5 6MH
2) Perform a plasma polymerization reaction under the conditions of 600W (7) to form a film with a thickness of 150 to 250A on the Co-Ni alloy film.
A plasma polymerized film was formed.

Subsequently, the amount of oxygen introduced was 109 m//y, the pressure was 5.0 x 1
0-2 Torr, high frequency output (frequency 1 3.5
The plasma polymerized film was subjected to oxygen plasma treatment under the conditions of 5 MHz') 600 W. Sample 1 was prepared by changing the treatment time of the oxygen plasma treatment as shown in Table 1.
Sample 5 was prepared.

The friction coefficient and still characteristics of each sample obtained were measured. The results are shown in Table 1.

In this Table 1, Comparative Example 1 shows a sample that was not provided with a plasma polymerized film and therefore was not subjected to oxygen plasma treatment, and Comparative Example 2 is a sample that was provided with a plasma polymerized film but was not subjected to oxygen plasma treatment. show. In addition, the above-mentioned still characteristics are based on 4. It shows the still time until a 2 MHz video signal is recorded and the playback output attenuates to a factor of 50, and is a measure of the durability of the magnetic tape.

ζ From Table 1, it can be seen that the friction coefficient of the sample tape obtained by oxygen plasma treatment becomes significantly smaller. In particular, the oxygen plasma treatment time was 10
It can be seen that the still characteristics are also improved from one second to one minute.

〔Effect of the invention〕

As is clear from the explanation of the above-mentioned examples, in the present invention, the surface of the protective film formed by plasma polymerization is further treated with oxygen plasma, so that a protective film with an extremely small coefficient of friction can be produced. Therefore, it is possible to manufacture a magnetic recording medium with excellent running properties.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a plasma reaction device used in the present invention, and FIG. 2 is an enlarged view of the main part showing the configuration of a ferromagnetic thin film magnetic recording medium on which a plasma polymerized film is formed. FIG. FIG. 3 is a schematic diagram illustrating a method of measuring the coefficient of friction.

Claims (1)

[Claims] A magnetic recording medium comprising a ferromagnetic metal thin film provided on a non-magnetic support is characterized in that after a protective film is formed on the surface of the ferromagnetic metal thin film by plasma polymerization, the protective film is subjected to oxygen plasma treatment. A method for manufacturing magnetic recording media.