JP2846036B2 - Magnetic disk, method of manufacturing the same, and magnetic disk device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium used as an external storage device such as an electronic computer or a workstation, and particularly to a magnetic recording medium having a protective film structure excellent in sliding resistance. About the disk.

[Conventional technology]

2. Description of the Related Art A storage device using a magnetic recording technology such as a magnetic disk is widely used as an external storage device such as a computer and a work station. On the other hand, as for the shape of the device itself, a smaller and lighter one is desired, and a drastic improvement in the recording density of a recording medium is indispensable to achieve both. For example, in a magnetic disk, a magnetic head floats above the disk with a certain floating space, thereby performing high-speed read / write and preventing wear destruction of the medium caused by the head rubbing the medium. However, in order to improve the recording density, the flying space must be further reduced, and the frequency of contact between the head and the disk increases due to fluctuations in the head attitude, irregularities on the medium surface, and undulation during rotation. It is expected to be. Further, in order to perform recording and reproduction at a high speed, the rotation speed of the disk becomes higher than the current state. Therefore, it is necessary that both the head and the disk have sufficient strength against such high-speed contact.

By the way, in order to improve the recording density of a magnetic disk, a sputtered magnetic disk has recently been developed in which a thin film is formed by sputtering a Co-based alloy or the like. In such a thin-film magnetic disk, since the sliding resistance of the magnetic layer is inferior to that of a so-called coated magnetic disk in which conventional magnetic powder is mixed with a resin called a binder, a protective film such as a carbon film is formed. It has strength. However, as described above, if the distance between the head and the disk is reduced in the future and the chance of contact with each other is increased, it is apparent that the conventional carbon film cannot sufficiently protect the magnetic layer. For this reason, various methods for improving the protective film have been disclosed,
Nothing has been found to have a sufficient effect on the required abrasion resistance. For example, Japanese Patent Application Laid-Open No. 1-23520 discloses a magnetic recording medium provided with a protective film having a laminated structure of hard carbon and soft carbon, and Japanese Patent Application Laid-Open No. A magnetic recording medium provided with a provided protective film is disclosed. It is conventionally known that roughening the surface as in the latter example reduces the actual contact area and produces an effect of lowering the friction coefficient. However, the part in contact with the head on the roughened disk surface is the foremost part of the unevenness, and this part is easily worn due to extremely high surface pressure, and eventually the contact area increases. For this reason, there was a problem that the friction coefficient gradually increased in a CSS (contact start / stop) test in which the durability was repeated by repeating takeoff and landing of the head.

[Problems to be solved by the invention]

The present invention has been made in view of the above situation, and has as its object to provide a protective film structure capable of exhibiting high wear resistance even at low flying spacing, and to significantly improve the durability of a magnetic recording medium. It is what it was.

[Means for solving the problem]

In order to achieve the above object, in the present invention, particles mainly composed of diamond microcrystals are grown on the surface of the magnetic medium, and then the surface is coated with a very thin hard amorphous carbon film. As a result, the stress deformation at the tip of the convex portion which comes into contact with the head is reduced, and the hard amorphous carbon layer has a property as a solid lubricating film, which has an effect of further improving sliding resistance.

FIG. 1 schematically shows a cross section of a magnetic recording medium provided with a protective film according to the present invention.
For example, in the case of a magnetic disk, the surface of an aluminum substrate is NiP plated to a thickness of about 10 μm and the surface is mirror-polished, the aluminum substrate is heat treated and an alumite layer is provided, or tempered glass, ceramics, etc. Which is processed to a surface roughness (Ra) of about 5 nm or less. In particular, a glass substrate or a ceramic substrate is preferably used because the substrate must have heat resistance to grow diamond.

The base film 2 is made of, for example, a thin nonmagnetic metal such as Cr or an alloy thereof, or ceramics.
Of course, depending on the material used for the substrate, the underlayer may be omitted, or it may be better to form a composite film of two or more layers.

The magnetic layer 3 is a thin film made of a material having ferromagnetism,
For example, alloys such as Co and Co oxides, Co-Ni and Co-Cr, and composite alloys obtained by adding a third or fourth element selected from Ti, Mo, Zr, V, PtSi, Nb, W, etc. It is mainly used, but in addition, Fe, γ-Fe203, iron nitride, or a material obtained by adding an additive thereto can also be used.

A feature of the present invention is the structure of the protective layer, which further comprises particles 4 mainly composed of diamond microcrystals and a protective film 5 further covering the particles. Further, a lubricating layer 6 may be further provided thereon.

The particles 4 mainly composed of diamond microcrystals are grown with a uniform distribution over the entire surface of the substrate, and occupy 0.01% to 10% of the total surface area of the magnetic film, and more preferably. Of the total surface area of the magnetic film
It has been made to account for 0.1% to 1%.
The height of the microcrystal from the magnetic film surface is 0.00% on average.
It is designed to be in the range of 1 μm to 0.05 μm, and more preferably in the range of 0.005 to 0.02 μm.

The following methods are known for growing the above-mentioned particles 4 mainly composed of diamond microcrystals, and among them, it is preferable to select them in consideration of the production rate, the upper limit of the settable substrate temperature, and the like.

1) A microwave plasma is generated using a mixed gas of a hydrocarbon gas and hydrogen as a raw material, and a substrate is formed.
Heat to 300-700 ° C. When a magnetic field is applied to the above-mentioned plasma region and the treatment is carried out under conditions that cause a phenomenon called so-called eclectron cyclotron resonance, the plasma density increases, and the growth rate of diamond particles can be increased. Although the growth rate is lower than the above, high-frequency plasma or DC plasma may be used instead of the microwave plasma.

2) The substrate is heated to about 700 ° C. to 1000 ° C., a mixed gas of hydrocarbon gas and hydrogen gas is introduced, and diamond particles are generated on the substrate surface by a thermal reaction.

3) A mixed gas of a hydrocarbon gas and a hydrogen gas is maintained at a pressure lower than the atmospheric pressure, and a raw material gas is reacted by utilizing a thermoelectron generated by applying a current to a filament such as tungsten disposed close to the substrate.

4) The hydrocarbon molecules are ionized and collide with the substrate at an energy of 300V to 2000V.

5) The substrate is arranged at the reducing flame portion of the hydrocarbon gas combustion flame under atmospheric pressure, and diamond particles are generated on the substrate surface.

In addition, these methods often produce amorphous carbon in addition to diamond at the same time. This is because amorphous carbon often has a low density and is brittle, and a hard amorphous Unlike carbon, in some cases, it has an adverse effect on the improvement of the sliding resistance aimed at by the present invention. Therefore, in such a case, it is better to remove the amorphous portion by ashing or etching with O2 or H2 plasma.

The raw material used in the above method for producing diamond particles is mainly a molecule composed of carbon and hydrogen, and may contain oxygen and other atoms. Specifically, methane, ethane, propane butane, pentane, saturated hydrocarbons such as hexane, ethylene, acetylene, propene,
Unsaturated hydrocarbons such as butene, benzene, toluene,
Aromatic hydrocarbons such as xylene, alcohols such as methanol, ethanol and propanol, ketones such as acetaldehyde, acetone and methyl ethyl ketone;
Ethers such as dimethyl ether, methyl ethyl ether and diethyl ether are used. Further, a mixed gas of two or more of these, or Xr, Ar, He, Ne, O
A mixed gas with 2, H2O, N2, or the like may be used.

The above-mentioned particles may have a random distribution with respect to the magnetic film surface, but particularly preferably have a certain distribution in the circumferential direction. FIG. 2 is a schematic diagram showing the growth of particles having a random distribution, and FIG. 3 is a schematic diagram showing the growth of particles having a uniform distribution in the circumferential direction. In particular, in order to have a selective distribution in the circumferential direction as described above,
A very thin amorphous film is provided on the surface of the magnetic layer, and the surface is scratched in the circumferential direction by machining, etc., and the underlying magnetic layer is partially exposed to selectively expose the magnetic layer. Preferably, diamond particles are grown. The above-mentioned amorphous film can be formed by sputtering or plasma CVD, particularly preferably the same amorphous carbon film used after the diamond particle generation step in the present invention, and its thickness Is preferably set to 0.001 to 0.005 nm. In addition, it is also possible to form a thin film of Si, W, Mo, Ti, Ta, Ge, or the like by sputtering or the like, apply a shallow circumferential processing flaw to the surface thereof, and selectively grow diamond microcrystals thereon. In this case, since the adhesion between the diamond particles and the amorphous carbon thin film and the thin film is good, separation is prevented, and the life is further extended.

The protective film 5 in the present invention is a hard and amorphous film mainly composed of carbon. When the protective film 5 is formed to a thickness of, for example, 1 μm or more, it has a micro Vickers hardness of about 10 μm.
It is more than 00Hv. Such a carbon film can be formed by sputtering using, for example, graphite as a target. However, according to the following method, a film having higher hardness and higher wear resistance can be obtained.

1) A hydrocarbon gas is used alone or mixed with another gas to form a raw material, a plasma is generated, and CVD (chemical vapor deposition) is performed under such conditions that the substrate surface has a potential drop of 100 V or more with respect to the plasma potential. . Most simply, a substrate to be processed is used as one electrode, and a high frequency voltage such as a commercial high frequency (13.56 MHz) is applied between the electrode and a sufficiently large area to generate plasma, thereby generating a plasma near the substrate. It is preferable to form a film so that ions are accelerated by a bias voltage.

2) A hydrocarbon gas is used alone or mixed with another gas to form a raw material. This gas is ionized in an ionization chamber, and the generated ions are accelerated by an electric field to about 100 to 1000 V to collide with a substrate.

If the thickness of the film mainly composed of hard amorphous carbon is too large, the substantial interval between the head and the magnetic layer is increased and S / N
Is preferably 50 nm or less, since this causes a decrease in Moreover, in order to prevent an increase in the contact area due to abrasion at the tip of the convex portion, which is the object of the present invention, it is better that the thickness is even thinner.
The range of 0 nm is good.

When the lubricating layer 6 made of a linear organic polymer is provided on the surface of the protective layer, the sliding characteristics can be further improved. The lubricant used has a main chain composed of, for example, perfluoropolyether or perfluoroalkyl, and at least one terminal is substituted with a polar group such as an ether group, an ester group, a hydroxyl group, a carbonyl group, an amino group, or an amide group. It is best to use one with a molecular weight of about 1,000 to 10,000.
In addition, saturated fatty acids and derivatives thereof, higher alcohols and derivatives thereof, and the like can also be used.

[Action]

According to the structure of the present invention, the convex portion of the disk surface with which the head mainly comes into contact is composed of diamond particles having high hardness, and an amorphous carbon thin film which is hard, lubricious and has high wear resistance. Can be made smaller. In addition, since the amorphous carbon thin film hardly generates wear particles that cause abrasive wear, accelerated wear due to this is also unlikely to occur. In addition, since the diamond particles grow from the surface of the magnetic layer, the particles are separated by abrasion and serve as abrasive grains to prevent the adverse effect of breaking the film.

Further, according to the present invention, since the diamond particles are present in a dispersed state, the air flow is not disturbed during the floating of the head, and a floating space is formed at a distance between the surface of the carbonaceous protective film in a portion substantially free of diamond particles and the bottom of the head. Decided.
Moreover, since the head hardly contacts this portion, the film pressure can be reduced, and the floating space can be reduced.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to specific examples.

(Example 1) The surface of a disk for a glass disk was cleaned, and a Cr underlayer and a magnetic layer of a Co-based alloy were formed on both surfaces thereof by a sputtering process to a thickness of about 200 nm and 50 nm, respectively. The substrate was set in a reaction chamber of a microwave plasma generator, and the inside of the reaction chamber was evacuated to 1 × 10 −5 Torr or less.
Thereafter, the substrate was heated to 500 ° C., a mixed gas of methane and hydrogen having a volume ratio of 5:95 was introduced into the reaction chamber, the gas pressure was set to 50 mTorr, and microwaves were introduced to generate plasma, which was maintained for 1 minute. When the substrate was taken out and observed with an electron microscope, it was observed that granular substances having a particle size of about 50 nm were sparsely formed at a density of about 100 particles per cm 2. Electron diffraction confirmed that the particles contained a diamond structure. Next, the substrate on which the diamond-containing particles were generated as described above was set on the electrode of the high-frequency plasma CVD apparatus, and a negative bias voltage was applied to the electrode on the side where the substrate was set so that the plasma was produced using methane gas as a raw material. And an amorphous thin film mainly containing carbon was formed to a thickness of about 10 nm. The magnetic disk created in this way was subjected to a CSS tester, and the flying height of the head was
Repeated CSS at 0.1 μm did not crash up to 30k times and hardly increased the wear coefficient between head and disk. In addition, no wear marks that could be observed with an optical microscope were found in the observation of the disk surface. Furthermore, this disc was coated with a perfluoropolyether having an average molecular weight of 2,000 substituted with an ester group by an ester method using a wet method, and the same CSS test was carried out. The dirt on the head has been reduced.

(Example 2) A glass disk substrate provided with a base film and a magnetic film was set on a rotatable jig in the same manner as in Example 1, and a burner provided with a slit nozzle elongated in the radial direction was placed on the disk surface. Methane gas was flowed from the nozzle at a flow rate of about 500 sccm and ignited to form a combustion flame. When the disk was rotated at about 0.5 rpm while the reducing flame portion of the above combustion flame was in contact with the disk surface, particles containing diamond having a particle diameter of about 30 nm were 1 cm2.
Produced at tens of densities per. In addition to the granular product, a film-like product was also observed. When this substrate was ashed with oxygen plasma, most of the film-like product was ashed, and only the granular product remained. Next, in the same manner as in Example 1, an amorphous carbon thin film having a thickness of about 20 nm was formed on the substrate surface by high-frequency plasma CVD. When the magnetic disk manufactured in this manner was subjected to a CSS tester in the same manner as in Example 1, the increase in the coefficient of friction was not more than 1 g even after 30 k times of CSS, and there was no scratch on the disk surface and no contamination of the head. Almost never.

(Example 3) After forming the magnetic film in Example 1, Si was sputtered on the surface, and the surface was scratched in the circumferential direction with a polishing tape having diamond abrasive grains having a particle diameter of 1 micron embedded therein. Particles containing diamond crystallites were produced in the same manner as described above. Microscopic observation confirmed that the particles were arranged along the processing flaw. On this substrate, an amorphous carbon film was further formed in the same process as in Example 1, and a CSS test was performed.
The disk withstood 100k CSS cycles without lubricant and showed no increase in coefficient of friction and no scratches on the disk surface.

〔The invention's effect〕

As described above, according to the present invention, the sliding resistance of the magnetic disk can be dramatically improved, the recording density of the magnetic disk device can be improved, and high reliability can be ensured. The protective film structure of the present invention can be used as a wear-resistant coating not only on magnetic recording media other than magnetic disks but also on members requiring general sliding resistance such as bearings.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a sectional structure of a magnetic disk according to the present invention. FIG. 2 is a schematic diagram showing one embodiment of the present invention. FIG. 3 is a schematic view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... base film, 3 ... magnetic film, 4 ... particles containing diamond, 5 ... hard amorphous carbon film, 6 ...
Lubrication film.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ryo Kito 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Research Laboratory (56) References JP-A-1-260627 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G11B 5/72 G11B 5/84

Claims (12)

(57) [Claims] 1. A magnetic disk having at least a magnetic layer and a protective layer provided on a non-magnetic substrate, wherein the protective layer is dispersed on the surface of the magnetic layer so as to cover microcrystals mainly composed of diamond grown nuclei and the entire magnetic layer. A magnetic disk comprising: a film mainly formed of hard amorphous carbon; 2. The magnetic disk according to claim 1, wherein said microcrystals mainly composed of diamond cover 0.01% to 10% of the surface of the magnetic layer. 3. The magnetic disk according to claim 1, wherein the average height of the microcrystals mainly composed of diamond is in the range of 0.001 μm to 0.05 μm. 4. The magnetic disk according to claim 1, wherein the distribution of the microcrystals mainly composed of diamond is uniform in the circumferential direction. 5. The magnetic disk according to claim 1, wherein the thickness of the coating mainly composed of hard amorphous carbon is 0.005 μm to 0.05 μm. 6. The magnetic disk according to claim 1, wherein a lubricant layer mainly composed of a linear polymer is provided on the surface of the film mainly composed of hard amorphous carbon. A magnetic disk characterized by the above-mentioned. 7. The magnetic disk according to claim 6, wherein the main chain of the lubricant molecule is perfluoropolyether and has a polar group at at least one end thereof. disk. 8. A magnetic disk drive using the magnetic disk according to claim 1. 9. A step of forming at least a magnetic layer thin film having ferromagnetism on the surface of a non-magnetic substrate, and microcrystals containing diamond dispersed on the surface by applying plasma containing hydrocarbon to the surface of the magnetic layer. And a step of forming a layer mainly composed of hard amorphous carbon on the surface of the microcrystal containing diamond and the magnetic layer. 10. The method of manufacturing a magnetic disk according to claim 9, wherein a lubricant mainly composed of a polymer containing fluorine is applied after forming the layer mainly composed of amorphous carbon. Disc manufacturing method. 11. The method of manufacturing a magnetic disk according to claim 9, wherein a thin film made of an amorphous substance or Si, W is formed on the surface of the magnetic layer before growing the microcrystal mainly containing diamond. , Ti, V, Mo, forming a thin film of a material selected from Ge, by machining the surface of the thin film in the circumferential direction so that the fine crystal particles mainly containing diamond are mainly arranged in the circumferential direction. A method for manufacturing a magnetic disk, comprising: 12. A method for manufacturing a magnetic disk according to claim 10, wherein after mainly growing microcrystals containing diamond, amorphous carbon precipitated simultaneously with the microcrystals containing diamond is removed. A method for manufacturing a magnetic disk, comprising steps.