JPS5968820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve friction running stability, durability, rust-preventive properties, etc. in a magnetic recording medium of a thin metallic film by providing a layer contg. nitrogen and oxygen by a plasma treatment using gas contg. nitrogen and oxygen on the surface. CONSTITUTION:A plasma treatment method performs plasma treatment by mixing the electric discharge plasma of a carrier gas such as Ar, He, H2, N2 or the like and gas expressed by NxOy such as dinitrogen oxide or the like or mixing O2 or O3 with the electric discharge plasma of gas, and bringing the gaseous mixture or plasma into contact with the surface of a substrate. The inside of a reactor R is evacuated to <=10<-3>Torr, thereafter, the treating gas is supplied therein at 1-100ml/min and the carrier gas at 50-500ml/min flow rate in a mixed state. The inside of the vessel is controlled within 0.01-10Torr range degree of vacuum and a high-frequency power source 6 is turned on whereby the recording medium is plasma-treated. The plasma-treated layer is >=1Angstrom and <=100Angstrom .

Description

[Detailed Description of the Invention] The present invention relates to a magnetic recording medium, in particular a magnetic recording medium whose surface is plasma-treated with a gas containing nitrogen and oxygen for the purpose of low friction, running stability, durability, rust prevention, etc. It relates to magnetic recording media.

γ-Fθ20 γ-Fa, 04, C○ on a non-magnetic support
Impregnation-Fe20. It has been a long time since magnetic recording media with magnetic layers mainly composed of oxide-based magnetic powders such as oxide magnetic powders such as Co)Co-N
i, Fe-C.

-Ni, Fe-Co-8% Fe-Co-Cr-BXM
Magnetic recording media made of ferromagnetic powder such as n-'Bis Mn-Al, Fe-Co-V, and binders, and magnetic recording media whose magnetic layers are metal vapor-deposited thin films or sputtered thin films have been put into practical use. 0 These magnetic recording media, especially for magnetic tape and magnetic disk applications, have a low coefficient of friction, exhibit smooth and stable running properties, have excellent wear resistance, and can run stably for long periods of time. There is a strong demand for such materials to be able to perform various functions, to be stable under the environmental conditions in which they are placed, to be able to regenerate reliably at any time, and to be durable.

In addition to these demands, the surface of magnetic recording media using the above-mentioned ferromagnetic powder for high-density recording and magnetic recording media using vapor deposition or sputtering thin films is being made smoother, which increases the coefficient of friction. Since this is a trend, some kind of countermeasure is especially required to ensure smooth and stable running. Additionally, these magnetic recording media may show deterioration due to rust due to metal being exposed on the surface.0 Information recorded at high density can be stored for long periods of time and reliably reproduced at any time. As such, these high-density recording media are required to have even greater running stability, running smoothness, durability, and the like.

Conventionally, lubricating agents such as silicone oil and fluorine oil have been incorporated into the magnetic layer or coated on the surface thereof. Additionally, topcoating with a film layer tailored to a specific purpose has also been practiced. However, conventionally known methods are not satisfactory because it is difficult to mix or apply the lubricant uniformly, the lubricant and other effects deteriorate with use, and the lubricant is not durable. Furthermore, when the coating becomes thick, the output decreases due to the spacing cross.

As described above, it has been extremely difficult to form a thin, long-lasting film that exhibits the desired effects.

In view of the drawbacks of the prior art as described above, the present invention
For magnetic recording media in general, especially for metal thin film high-density magnetic recording media using vapor deposition and sputtering methods,
The object of the present invention is to provide a novel thin film layer that has surface characteristics such as low friction, running stability, durability, and rust prevention.

For this purpose, the present inventors have discovered that a very excellent effect can be achieved by plasma treating the surface of a metal thin film with a gas containing nitrogen and oxygen. Since this method is not a top coat method, it does not cause a decrease in the output of the magnetic recording medium due to spacing cloth, and is extremely advantageous. Furthermore, since plasma boration is a gas phase reaction,
It was found that nitride was formed uniformly only near the surface.

This phenomenon seems to play an important role in improving the rust prevention effect. In addition, since the plasma processing method allows continuous generation at high speed, it can be easily incorporated into the magnetic recording medium manufacturing process without hindering its productivity. ``The thin film produced by the plasma treatment method has the above-mentioned surface characteristics significantly improved without any loss in the magnetic properties, electrical properties, and recording density characteristics of the magnetic recording medium. This is an extremely significant point compared to conventional thin films.

The plasma treatment method is i) Ar, He5H,, N
Discharge plasma of 2nd grade carrier gas and dinitrogen oxide N2
0, -nitrogen oxide NO1 dinitrogen trioxide N, 03, nitrogen dioxide NO7, dinitrogen pentoxide NtOs, nitrogen trioxide NO
8. Mix the large dinitrogen oxide rope Nt 011 with the gas expressed by Nx0y, or ii) create a discharge plasma of the gas expressed by Nxoy.
Mix 02 or 03 with H3, NX0Y discharge plasma or! V) Ot, Os discharge plasma with N,,
The surface of the substrate is plasma-treated by mixing NHl and Nx0y and bringing the mixed gas or plasma into contact with the surface of the substrate.

To outline the principle, when a gas is kept at a low pressure and an electric field is applied, the free electrons present in a small amount in the gas are accelerated by the electric field and are accelerated by 5 to 1
Obtain a kinetic energy (electron temperature) of 0 eV. When these accelerated electrons collide with atoms and molecules, they disrupt atomic and molecular orbits and dissociate them into unstable chemical species such as electrons, ions, and neutral radicals. The dissociated electrons are accelerated again by the electric field and dissociate other atoms and molecules, but this chain reaction quickly turns the gas into a highly ionized state, which is called a plasma gas.

Gas molecules have fewer chances of collision with electrons, so they do not absorb much energy and are kept at a temperature close to room temperature. A system in which the kinetic energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called a low-temperature plasma. This creates a situation in which chemical reactions can proceed, and the present invention attempts to utilize this situation to plasma-treat the surface of a substrate. Since low-temperature plasma is used, there is no thermal effect on the substrate.

An example of an apparatus for treating the surface of a magnetic recording medium with plasma is shown in FIGS. 1 and 2. FIG. 1 shows a plasma processing apparatus using high frequency discharge, and FIG. 2 shows a plasma processing apparatus using microwave discharge.

In FIG. 1, a processing gas and a carrier gas are supplied from a processing gas source 1 and a carrier gas source 2 via mass flow controllers 3 and 4, respectively, and are mixed in a mixer 5 and then fed to a reaction vessel R. . The processing gas is a raw material for plasma processing in the reaction vessel, and in the present invention, it may be i) a gas expressed by Nx0y, 1i) a nitrogen-containing gas such as N2 or NH8, or! ! selected from oxygen-containing gases such as Ot 10a.

The carrier gas is appropriately selected from Ar, HeXH, N, etc. The processing gas is 1-100!4/min and the carrier gas is 50-500m! 'Control the flow rate range of juice. A magnetic recording medium support device to be processed is installed in the reaction vessel R, and here a feed roll 9 and a winding roll 10 are shown for the purpose of magnetic tape processing.

Various support devices can be used depending on the form of the recording medium to be processed, and for example, a mounted rotary support device can be used.

Opposite electrodes 7, 7' are provided between the magnetic tapes to be processed, one electrode 7 is connected to the high frequency power source 6, and the other electrode 7' is grounded at 8. Generally, a vacuum system for evacuating the inside of the reaction vessel R is provided, and this includes a liquid nitrogen trap 11, an oil rotary pump 12, and a vacuum controller 13. These vacuum systems maintain a vacuum level within the reaction vessel within the range of 0.01 to 10'I''orr.

In operation, the inside of the reaction vessel R is first heated to 10-” Torr.
Evacuate the inside of the container with an oil rotary pump until it reaches r.
Processing gas and carrier gas are then supplied in a mixed state into the container at a given miscarriage.

The vacuum inside the reaction vessel is controlled within the range of 0,01 to 1 Q Torr. Once the transfer rate of the magnetic tape to be processed and the flow rates of the oxidizing gas and carrier gas have stabilized, the radio frequency power source is turned on. In this way, the magnetic recording medium being transferred is plasma treated.

FIG. 2 shows a plasma processing apparatus using microwave discharge. The same components as in the KS1 diagram are given the same reference numerals.

Here, a discharge plasma chamber 15 is formed in the reaction vessel R, and a carrier gas from a carrier gas source 2 is supplied to the outer end of the chamber. After being supplied, the carrier gas is turned into plasma and stabilized by the oscillation of the magnetron 6.

Processing gas is introduced into the reaction vessel through a nozzle 16 that opens near the inner end of the plasma chamber 15 . A support device is mounted in alignment with the plasma chamber 15, in this case with the unwinding and winding rolls 9 and 10 oriented vertically. Other elements are the same as in FIG.

As the plasma generation source, in addition to the above-mentioned high frequency discharge and microwave discharge, any one of direct current discharge, alternating current discharge, etc. can be used.

As mentioned above, the magnetic recording medium treated by the single-line plasma treatment method has significantly improved low friction properties, running stability, durability, rust prevention effect, etc. by plasma treatment of the surface.

Next, an example in which the surface of a magnetic recording medium was plasma-treated using the apparatus shown in FIGS. 1 and 2 will be described.

Example 1 CoS portion and Ni 2 on a 10 μm thick base film
A magnetic tape on which a 0.1 μm magnetic layer was obliquely deposited from an ingot was subjected to plasma treatment using dinitrogen trioxide as a treatment gas. The equipment shown in Figure 1 was used. The plasma treatment conditions were as follows.

Dinitrogen trioxide gas: 2 parts mV Carrier gas 'N250vrt/min Vacuum degree
1.Q Torr high frequency power supply:
13.56MHz00W Magnetic tape running speed: 0.5 m7 Example 2 Co-Ni (
Composition C095%-Ni 5%) as raw material, 01μm
A magnetic tape was prepared by sputtering to a thickness of .

First, the interior of the reaction vessel R and the discharge plasma chamber 15 is pumped 1Q with the oil rotary pump 12 having an evacuation speed of 100j15).
The pressure was evacuated to below Torr. Nitrogen was introduced as carrier gas at a flow rate of 80114/min.

0.5 Tor by the vacuum controller 13 in the reaction vessel
It was managed to r. Frequency 24 due to oscillation of magnetron 6
A power of 500 W at 50 MHz was applied to stabilize the plasma. Next, nitrogen trioxide was supplied to the nozzle 16 at a flow rate of 30 cm. The magnetic tape was transferred from the feed roll 9 to the take-up roll 10 at a speed of 0.8 yrv%.

Example 3 In Example 1, dinitrogen oxide N20 was used instead of dinitrogen trioxide gas. NH3 gas was used instead of carrier gas. Other conditions were the same as in Example 1.

Example 4 In Example 2, oxygen was used instead of the carrier gas nitrogen. Nitric oxide was used instead of nitrogen trioxide. Other conditions were the same as in Example 2.

Comparative Example 1 In Example 1, the supply of dinitrogen trioxide was stopped and argon was used instead of the carrier gas N.

Other conditions were the same as in Example 1.

Comparative example 2 In Example 2, the tape running speed was 0.11 minutes.

The rest was the same as in Example 2.

The composition of the thin film was measured by ESCA and confirmed to be a layer containing nitrogen and oxygen. The thickness of the plasma-treated layer was measured by thickness direction analysis using ESCA and an ellipsometer.

The thickness of the treated layer is shown in the table below.

Even if the thickness of the layer containing oxygen and nitrogen exceeds 100 A, its effectiveness does not improve, but rather there is a tendency for electromagnetic conversion characteristics to deteriorate.

Performance Comparison Test The following three tests were conducted on the samples of Examples 1 to 3, Comparative Examples 1 and 2, and untreated magnetic tape samples.

(b) Dynamic friction coefficient μ: IEICE technical report R50-25 (1980)
Measured according to the method described. That is, a magnetic tape is wound around a wear ring corresponding to a magnetic head with the magnetic layer side facing inside, a weight is loaded on one end, and the other end is fixed to a load cell. The wear wheel is rotated and the frictional force of the magnetic tape is detected by a load cell.

Assuming friction crab T1 weight: W and wrapping angle: θ, calculate μk from the following formula.

The comparison results are as follows.

It can be seen that the magnetic recording medium of the present invention exhibits an extremely low friction coefficient, exhibiting a coefficient of friction less than half that of untreated tape.

(b) Still time It was measured as the time until no image appears when a still image is played back on a VTR.

The comparison results are as follows.

It can be seen that the present invention significantly improves wear resistance.

(c) Environmental resistance It is known that this type of tape has a phenomenon in which its magnetic properties deteriorate due to oxidation. In order to examine the degree of deterioration, the magnetic recording medium was left in an environment of 50° C. and 98% relative humidity for 72 hours, and changes in magnetic flux density were measured using a vibrating magnetometer. The rate of change in magnetic flux density was calculated as Br'-Br-X 100 (%) Br (Br: initial magnetic flux density Br': magnetic flux density after test). The comparison results are as follows. Relative values are shown with the untreated product set as 1.

This shows that the magnetic recording medium of the present invention has excellent durability and rust prevention properties.

As explained above, the present invention is applicable to various magnetic recording media that will require increasingly strict quality requirements and durability in the future.
This demand can be fully met by forming a completely different layer on the surface by plasma treatment using a gas containing nitrogen and oxygen.

[Brief Description of the Drawings] Fig. 1 is a schematic diagram of a high frequency discharge plasma processing apparatus, and Fig. 2 is a schematic diagram of a microwave discharge plasma processing apparatus. 0 1: Processing gas source 2: Carrier gas source 3.4: Mass flow controller 5: Mixer 6: High frequency power source 1 Magneto source 7.7': Electrode 9.10: Feeding and winding four wheel 11: Liquid nitrogen trap 12: Oil rotating trap 13: Vacuum controller R2 Reaction vessel"'-11 Procedural Sleeve Book November 1980 251-1 Commissioner of the Japan Patent Office Kazuo Wakasugi Indication of the case 1982 Patent Application No. 177569 Title of the invention Related patent applicant name (
306) Tokyo Denki Kagaku Kogyo Co., Ltd. Agent Address: 103 Address: 13-11, 3rd Floor, Nihonbashi, Chuo-ku, Tokyo Oil and Fat Industry Hall Telephone number: 273-6436 li+j Address: Same Upper demand auxiliary suspension → e-mail → H power 11 2nd edition - number of lines = + + li city's subject j section hand 4 l prefecture Mingzhu →・applicant's yuzu I・ specification invention invention medical country juxu glass taste 4 → ψ← detailed description of the invention Contents of column amendment The detailed description of the invention under examination will be amended as shown in the attached sheet. (1) On page 3, line 13 of the specification, "durability" will be corrected to "durability." Procedural amendment June 10, 1980 Director of the Japan Patent Office Kazuo Wakasugi Indication of the case 1982 Patent Application No. 177569 Title of the invention Relationship to the case of the person who amends the magnetic recording medium Patent applicant name (3
06) TDC Co., Ltd. Agent 〒103 ・－interest１１ζ－－－－－・ Contents of the amendment Subject to amendment As shown in the attached sheet, the detailed description of the invention in Part F is amended as follows. 1. On page 4, line 11 of the specification, "how to" is corrected to "process." 2. On page 8, line 12, "oxidation" has been corrected to "treatment."

Claims (2)

[Claims] (1) A special grade of metal thin film magnetic recording medium in which a layer containing nitrogen and oxygen is provided on the surface by plasma treatment with a gas containing nitrogen and oxygen. (2) The magnetic recording medium according to claim 1, wherein the plasma treated layer has a thickness of 1λ or more and 100λ or less.