JPH10208228A - Magnetic recording medium and magnetic storage device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To isolate a lubricant from dangling bonds and contaminants on the surface of a protective film and to obtain a magnetic recording medium not deteriorating its lubricating performance and having stable sliding characteristics and weather resistance over a long period of time by forming a self-textured monomolecular film on the protective film and then forming a thin org. lubricant film on the monomolecular film. SOLUTION: A Cr film 5, a magnetic recording film 4 and a protective film 3 of amorphous carbon are successively formed on a glass substrate 6 in a device for continuously forming a film by successively. The resultant magnetic disk is taken out of the device, dipped in a soln. of dodecanethiol in ethanol and successively rinsed with ethanol and pure water to form a self-textured monomolecular film 2. A fluorine-contg. org. lubricant film is then formed on the monomolecular film 2 by a soln. dip-coating method. The densely self- textured monomolecular film of dodecanethiol bonds chemically to the protective film through sulfur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a magnetic storage device, and more particularly, to a hard disk,
The present invention relates to a laminated structure of a magnetic recording medium such as a floppy disk, a magnetic tape, and the like, in which a head comes into contact temporarily or constantly, and a magnetic storage device.

[0002]

2. Description of the Related Art For example, a magnetic recording disk (hereinafter, referred to as a magnetic disk) used as a large-capacity storage device such as a large-sized computer, a personal computer, a network server, a movie server, etc. A high ferromagnetic thin film is formed by a sputtering method or the like. Further, it is common practice to form a protective film made of amorphous carbon thereon, and further apply a fluorine-based lubricant on the protective film in order to enhance sliding resistance and corrosion resistance. .

In this case, in order to obtain stable lubricating properties, it is necessary to use a lubricant which is thermally and chemically stable and has excellent splash resistance. In addition, it is necessary to maintain these lubrication characteristics over time. Further, in recent years, it has become necessary to reduce the distance between the recording head and the magnetic disk in order to improve the recording density, which means that the sliding conditions of the magnetic disk become more severe. Therefore, in magnetic disks, perfluoropolyether, which is a synthetic lubricant that has already been used as a lubricant for aerospace equipment, is generally used. However, in the case of ordinary perfluoropolyether, there is a tendency that the lubricant is scattered by sliding with the head, or the lubricant disappears from the sliding surface under high temperature conditions, and the lubricating performance is reduced.

In order to solve such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 61-4727, a lubricant such as perfluoroalkyl ether containing a terminal group having an irritating function is coated on the protective film. Has been proposed. IEEE Transactions on Magnetics, 3
1 Vol. 2922-2924 (1995) reports a magnetic disk in which a 3 nm-thick gold thin film is formed on a protective film and a self-assembled monomolecular film is formed thereon.

[0005]

The prior art (I)
EEE Transactions on Magnetics, 31 Vol. 2922-2
924 (1995) report that sufficient sliding resistance could not be obtained because the gold thin film under the self-assembled monolayer was soft. In addition, even if only a self-assembled monolayer is formed, the coefficient of friction is high due to lack of lubricity itself. And proceed.

Further, the above-mentioned other prior art (Japanese Unexamined Patent Publication No.
In Japanese Patent Application Laid-Open No. 1-4727, the terminal group of the lubricant adheres to the surface of the protective film by an irritating function, and exhibits excellent scattering resistance and sliding resistance. However, with the recent decrease in the flying height of the head and the increase in the rotation speed, the sliding resistance tends to be insufficient. The thinning of the lubricating film also spurred the loss of the lubricant due to sliding. It is due to a mechanism called chemical lubricant molecule destruction. That is,
Usually, amorphous carbon formed by a sputtering method or a CVD method necessarily has many bonds whose terminals are not chemically terminated. This is called a dangling bond and has been detected experimentally.
The dangling bond serves as an active site for the adsorption of the terminal group of the lubricant. On the other hand, it has recently been revealed that the dangling bond acts as a catalyst to decompose the lubricant. This is because the dangling bond may interact directly with the lubricant molecule, or the dangling bond and the water molecule or hydrocarbon-based contaminant adsorbed on the surface by the adsorption may react to form a new active intermediate. It produces seeds, which can break down lubricant molecules. Such a decomposition process of the lubricant caused by the dangling bond is particularly remarkable in a recent magnetic disk in which the lubricating film thickness is reduced in order to reduce the flying height and prevent sticking.

An object of the present invention is to provide a magnetic recording medium which does not cause a lubricant decomposition reaction caused by these dangling bonds, exhibits good long-term sliding resistance, and has excellent durability and reliability. Is to do. Another object of the present invention is to reduce the flying height of the magnetic head and the rotation of the magnetic disk so that a uniform molecular film is densely formed on the protective film so that a true contact point does not occur during sliding between the magnetic head and the magnetic disk. Provided is a magnetic recording medium corresponding to a higher speed.

[0008]

An object of the present invention is to provide at least a magnetic recording film and a protective film provided thereon, wherein a self-assembled monolayer is formed on the protective film. This is attained by a magnetic recording medium in which a thin film made of an organic lubricant is formed on a monomolecular film.

The self-assembled monolayer may be a monolayer having a horizontal translational symmetry in which the horizontal molecular intervals are arranged at substantially constant intervals of not less than 0.2 nm and not more than 1 nm on the protective film. desirable. From the viewpoint of ease of formation, the molecular spacing in the horizontal plane of the self-assembled monolayer is 0.4 nm to 0.6 n.
m is desirable.

Here, the self-assembled monomolecular film is desirably formed from an alkanethiol having 3 to 30 carbon atoms in which sulfur atoms are oriented to the protective film side, from the viewpoint of ease of formation. Further, the self-assembled monolayer may be formed from two or more kinds of alkanethiols having different carbon numbers.

In addition, the terminal methyl group on the opposite side of the alkanethiol protective film of the self-assembled monolayer is substituted with one or more of a hydroxyl group, an amino group and a methyl fluoride group. You may.

Further, the alkane thiol of the self-assembled monolayer is composed of two kinds of alkane thiols having a methyl group and a methyl fluoride group at the end opposite to the sulfur atom, and an alkane thiol having a methyl fluoride group. Has more carbon atoms than the alkanethiol having a methyl group. In this case, the number of molecules of the alkanethiol having a methyl fluoride group is desirably 5% to 80% of the total number of molecules of the self-assembled monolayer.

[0013] As the fluorine-containing organic lubricant, it is desirable that the main chain structure is composed of a perfluoropolyether polymer, a hydrocarbon or a fluorocarbon, or a mixture of two or more thereof. In this case, if the thickness of the thin film made of the fluorine-containing organic lubricant is less than 0.2 nm, a uniform film is not obtained. If the thickness is more than 10 nm, an adverse effect of meniscus adhesion occurs. It is desirable that: However, as the lubricant, other organic lubricants and inorganic lubricants may be used as long as they have stable sliding and durability.

The protective film is preferably made of any of amorphous carbon, silicon-containing amorphous carbon, nitrogen-containing amorphous carbon, boron-containing amorphous carbon, silicon oxide, zirconium oxide and cubic boron nitride. These amorphous carbon protective films may be formed by sputtering in an inert gas targeting graphite, or a mixed gas of an inert gas and a hydrocarbon gas such as methane, or a hydrocarbon gas, Alcohol, acetone, organic compounds such as adamantane alone or mixed with hydrogen gas, inert gas, etc., by a method of forming by plasma CVD, or by ionizing the organic compound, applying a voltage, accelerating, and colliding with the substrate And the like.

As the substrate of the magnetic recording medium, for example, a non-magnetic substrate such as an aluminum substrate, a glass substrate or a graphite substrate is used. The surface of the aluminum substrate may be plated with nickel or phosphorus. In addition, by pressing diamond abrasive grains or polishing tape while rotating the substrate, fine concentric grooves are formed on the substrate to improve the floating characteristics of the head and control the magnetic anisotropy. Things are also done. Further, the surface of the glass substrate may be chemically etched with a chemical such as a strong acid to form fine irregularities, to reduce the area in contact with the head, and to reduce the tangential force during sliding. In these, the same effect can be expected even if the surface of the protective film is masked with fine particles and etched.

Before forming the magnetic recording film, a base film such as chromium may be formed on the substrate of the magnetic recording medium by a sputtering method or the like in order to improve the magnetic properties of the recording film. . As the magnetic recording film on the substrate, a material obtained by mixing a small amount of platinum, tantalum, vanadium, samarium, or the like with cobalt / nickel, cobalt / chromium, or cobalt / chromium is used.

Also, the magnetic recording medium, a drive unit for driving the magnetic recording medium in a recording direction, a magnetic head comprising an electromagnetic induction type recording unit and a magnetoresistive effect type reproducing unit, and a magnetic head for the magnetic recording medium By constructing a magnetic storage device using a means for causing relative movement by means of a recording and reproducing signal processing means, etc., a recording density of 3 gigabits per square inch or more can be realized.

According to the present invention, by forming a self-assembled monolayer on the protective film and forming a thin film made of an organic lubricant on the self-assembled monolayer, the dangling on the surface of the protective film is reduced. The bond is isolated from the lubricant, and the decomposition reaction of the lubricant molecule due to the dangling bond can be prevented. Furthermore, the self-assembled monolayer forms a tightly packed monolayer while eliminating contaminants and adsorbed water on the surface during formation, making it possible to remove contaminants and water from the protective film surface. Become. This makes it possible to prevent deterioration of the lubricant and viscosity due to water and contaminants. Sulfur atom oriented to the protective film side, carbon number 3 or more 3
Alkanethiols of 0 or less have strong self-organizing power and are most suitable for this purpose.

Further, by forming an organic thin film having lubricity on the self-assembled monolayer, surface lubricity which cannot be realized only by the self-assembled monolayer can be obtained. That is, the lower self-assembled monolayer plays a role of regularity, smoothness, and chemical stability, and the upper organic lubricating film exhibits lubricating performance.

Further, when the self-assembled monolayer is formed of two or more kinds of alkanethiols having different carbon numbers, concavities and convexities having a molecular level can be formed on the surface. The unevenness can be freely controlled by changing the ratio and size of the alkanethiol to be mixed.
By forming these irregularities, the state of accumulation of the lubricating film to be applied thereon can be controlled, so that the frictional force can be controlled. Furthermore, the unevenness makes it possible to suppress the scattering of the lubricant due to the rotation. Up to now, changing the shape under such a lubricant has been done by texturing the substrate or etching the surface of the protective film, but in any case, the shape of the unevenness is on the order of μm, and the process Dependency was large and control was difficult. Self-assembled monolayers are the first method that can simultaneously control the surface chemistry and shape at the molecular level.

The terminal methyl group on the opposite side of the alkanethiol protective film of the self-assembled monolayer is a hydroxyl group, an amino group,
Substitution with any one or more of the methyl fluoride groups provides more aggressive control of surface chemistry. These can control the scatterability of the lubricant surface when a type of perfluoropolyether having a terminal functional group is used as the lubricant.

Further, the alkanethiol of the self-assembled monolayer has two kinds of alkanethiols each having a methyl group and a methyl fluoride group at the end opposite to the sulfur atom.
If the number of carbon atoms of the alkanethiol having a methyl fluoride group is larger than the number of carbon atoms of the alkanethiol having a methyl group, the convex portion has a small friction coefficient, and the concave portion exerts a self-organizing force. In this case, if the number of molecules of the alkanethiol having a methyl fluoride group is 5% or more and 80% or less of the total number of molecules of the self-assembled monolayer, the friction coefficient of the convex portion can be reduced without impairing the self-assembly force. Can be lowered.

Further, when the magnetic recording medium of the present invention is combined with a magnetic head using a magnetoresistive element in the reproducing section, a highly reliable magnetic disk device having a higher recording density than the conventional one can be realized. Becomes possible. That is, although the magnetoresistive head has high sensitivity, it is generally necessary to form a protective film of carbon or the like on the slider surface in order to prevent electrostatic breakdown and the like. The thickness of the protective film formed on the slider surface is usually about 10 to 20 nm.
When the flying height of the head is constant, the output is reduced because the distance between the medium and the magnetically sensitive part of the head is increased by the thickness of the protective film on the slider surface, and the output is reduced. It is difficult to bring out the full performance of the. In contrast, when the magnetic recording medium of the present invention having a lubricant layer on a self-assembled monolayer as a medium is used, since deterioration of the lubricant due to dangling bonds is suppressed,
The flying height of the head can be reduced, and the performance of a highly sensitive magnetoresistive head can be sufficiently brought out to realize a high recording density.

The tribo-resistant chemically reactive lubricating thin film forming technique of the present invention can be applied to a magnetic recording medium such as a magnetic disk, a magnetic tape, or a magnetic card, or an optical disk when a head which may come into contact with the disk is used. The present invention can be applied to various types of mechanical parts and sliding parts that require permanent lubrication.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. As a recording medium, a magnetic disk (hard disk, floppy disk), a magnetic tape, and the like are well known, but in the following description, a magnetic disk is used as a representative example.

Embodiment 1 FIG. 1 is a schematic sectional view of a magnetic recording medium according to a first embodiment of the present invention. In the figure, 1 is a thin film made of an organic lubricant, 2
Denotes a self-assembled monomolecular film, 3 denotes an amorphous carbon protective film formed by a sputtering method, 4 denotes a cobalt-nickel alloy magnetic recording film, 5 denotes a chromium film, and 6 denotes a glass substrate (2.5 inches in diameter). ). The organic lubricant has an average molecular weight of 3000 in which a copolymer of perfluoromethylene oxide and perfluoroethylene oxide segments has an alcohol functional group as a terminal group.

The magnetic disk having this configuration was manufactured by the following method. First, a 20-nm-thick chromium / titanium alloy base film 5, a 25-nm-thick cobalt-chromium-platinum alloy film 4, and a 20-nm-thick amorphous carbon protective film are formed on a substrate 6 by a known continuous sputtering film forming apparatus. Film 3 was formed sequentially. Thereafter, the magnetic disk was taken out of the sputtering apparatus, and an ethanol solution of dodecanethiol (concentration:
(0.001 mol / l) for 10 minutes, followed by rinsing with ethanol and pure water in this order.
Was formed. Then, a lubricating film of a fluorine-containing organic substance was formed on the self-assembled monolayer by a solution immersion coating method. The application conditions were as follows. The magnetic disk was immersed for 4 minutes in a solution in which the perfluoropolyether lubricant was dissolved in a fluorocarbon-based solvent at a concentration of 0.0005 mol / l, and pulled up at a speed of 0.5 mm / sec. Was.

When the surface of the magnetic disk was analyzed by FT-IR (Fourier transform infrared absorption spectroscopy), it was confirmed that the perfluoropolyether lubricating film having a thickness of 1 nm was formed on the protective film surface. Was done. In addition, the surface of the magnetic disk was observed by X-ray photoelectron spectroscopy and scanning tunneling microscope before forming the lubricating film. As shown in FIG. 1, dodecanethiol was densely self-organized and chemically bonded to the protective film via sulfur. It was confirmed that a monomolecular film was formed. The horizontal molecular spacing of this monolayer of dodecanethiol is about 0.4 nm.

The dynamic friction coefficient of the magnetic disk of this embodiment was measured using a head made of a slider made of aluminum / titanium carbide (AlTiC). The rotation speed of the magnetic disk at the time of measurement was 1 rpm, the load was 1.5 gf,
The tangential force applied to the head at a radius of 20 mm was measured with a strain gauge sensor to obtain a coefficient of dynamic friction. As a result, the dynamic friction coefficient of the magnetic disk of this embodiment is 0.01
Met.

To evaluate the sliding resistance, a contact start / stop test (hereinafter referred to as a CSS test) was performed. As is well known, the CSS test is a test in which a disk is rotated while the head is in contact with the disk surface, the head is floated, and then the disk is stopped again at regular intervals. Rotation rise time is 2
Second, constant speed high speed rotation time is 2 seconds, fall time is 2 seconds,
Stop time is 2 seconds, rotation speed at high speed is 10,000 rpm
m. As a result, no damage was observed on the surface of the magnetic disk even after 300,000 CSS repetitions. Further, when the above-mentioned dynamic friction coefficient was measured after 300,000 times of CSS repetition, it was 0.015, and it was confirmed that the increase in the dynamic friction coefficient was suppressed. This is because the lubricant is isolated from the dangling bonds on the surface of the protective film by the self-assembled monolayer, and the decomposition due to the tribochemical reaction that easily occurs during sliding with the head is suppressed. Things.

When the contact angle of the magnetic disk of this embodiment to water was measured, it was 107 degrees, indicating water repellency equivalent to that of polytetrafluoroethylene. Further, when an experiment was performed in which the magnetic disk of this example was left for 50 hours in a constant temperature and humidity environment of 80 ° C. and 90% RH, no corrosion point was observed on the surface of the magnetic disk after leaving. These results are the result of removing the organic contaminants and the adsorbed water on the surface of the protective film during the formation of the self-assembled monolayer, and improving the weather resistance of the lubricating layer.

Embodiment 2 FIG. 2 is a schematic sectional view of a magnetic recording medium according to a second embodiment of the present invention. In FIG. 2, 3 is an amorphous carbon protective film formed by a sputtering method, 4 is a cobalt-chromium-platinum alloy magnetic recording film, 5 is a chromium-titanium alloy film, and 6 is a glass substrate (2.5 mm in diameter). Inch), 1 is a perfluoropolyether lubricating film equivalent to that of Example 1, and 7 is a self-assembled monomolecular film composed of a mixture of two or more alkanethiols having different carbon numbers.

In the present embodiment, a magnetic disk in which a protective film was formed using the same continuous film forming apparatus and substrate as in Example 1 was prepared. Thereafter, the magnetic disks were placed in an ethanol solution of dodecanethiol and decanethiol (concentrations of 0.02 respectively).
005 mol / l) for 10 minutes, lifted and rinsed with ethanol and pure water in this order. In this way, a self-assembled monomolecular film 7 composed of a mixture of two or more alkanethiols having different carbon numbers was formed on the protective film. Then, a lubricating film of a fluorine-containing organic substance was formed on the self-assembled monolayer by a solution immersion coating method. The application conditions were as follows. The magnetic disk was immersed for 4 minutes in a solution in which the perfluoropolyether lubricant was dissolved in a fluorocarbon-based solvent at a concentration of 0.0005 mol / l, and pulled up at a speed of 0.5 mm / sec. Was.

Observation of the surface of the magnetic disk by X-ray photoelectron spectroscopy and scanning tunneling microscopy before the application of the lubricant revealed that the difference in the length of the two types of alkanethiols on the surface of the densely packed self-assembled monolayer. It was confirmed that irregularities of about 0.1 nm corresponding to were formed. After applying the lubricant, the thickness of the lubricating film was measured by FT-IR in the same manner as in Example 1, and it was 1 nm. The dynamic friction coefficient of the magnetic disk of this example was measured under the same head and measurement conditions as in Example 1, and was 0.01.

The coefficient of dynamic friction after 300,000 CSS tests equivalent to that of Example 1 was 0.016, and the dangling bond on the surface of the protective film was formed by a self-assembled monomolecular film of two different lengths of alkanethiol. Was masked, and it was confirmed that the decomposition reaction of the lubricant due to dangling bonds caused by sliding with the head was effectively prevented.

The contact angle of the magnetic disk of this embodiment to water was 108 degrees. A corrosion point was not observed in a standing test in a constant temperature and humidity environment under the same conditions as in Example 1.

Embodiment 3 FIG. 3 is a schematic sectional view of a magnetic recording medium according to a third embodiment of the present invention. 3, reference numeral 3 denotes an amorphous carbon protective film formed by sputtering, 4 denotes a cobalt-chromium-platinum alloy-based magnetic recording film, 5 denotes a chromium / titanium alloy film, and 6 denotes a glass substrate (2.5 mm in diameter). Inch), 1 is the same perfluoropolyether lubricating film as in Example 1, and 8 is a self-assembled monolayer. However, this self-assembled monolayer is formed of two types of molecules, an alkylthiol (trifluoromethylundecanethiol) and a decanethiol in which the terminal on the opposite side of sulfur is substituted with a methyl fluoride group.

Also in this embodiment, a magnetic disk in which a protective film was formed using a continuous film forming apparatus and a substrate equivalent to that of Embodiment 1 was prepared. Thereafter, the magnetic disk was placed in an ethanol solution of trifluoromethylundecanethiol and decanethiol (concentration 0.0005 mol / l each) for 10 minutes.
After immersion for a minute and lifting, it was rinsed in the order of ethanol and pure water. Thus, a self-assembled monolayer 8 was formed on the protective film. Then, a lubricating film of a fluorine-containing organic substance was formed on the self-assembled monolayer by a solution immersion coating method. As the application conditions, the above-mentioned perfluoropolyether lubricant was added to the fluorocarbon-based solvent at 0.0005 mol / l.
The magnetic disk was immersed for 4 minutes in a solution dissolved at each concentration and pulled up at a speed of 0.5 mm / sec.

Observation of the surface of the magnetic disk by X-ray photoelectron spectroscopy and scanning tunneling microscopy before the application of the lubricant revealed that the difference between the lengths of the two alkanethiols on the surface of the densely packed self-assembled monolayer. It was confirmed that unevenness of about 0.2 nm corresponding to was formed. The ratio was found to be 1: 1 from the comparison of the surface element concentrations of fluorine and carbon by X-ray photoelectron spectroscopy. Also, a comparison of the observations by a scanning tunneling microscope and a friction force microscope revealed that the methyl fluoride group was in the convex portion.

After the application of the lubricant, FT-
The thickness of the lubricating film measured by IR was 1 nm. The dynamic friction coefficient of the magnetic disk of this example was measured under the same head and measurement conditions as in Example 1, and was 0.01.

The coefficient of kinetic friction after 300,000 CSS tests equivalent to that of Example 1 was 0.017, and dangling bonds on the surface of the protective film were formed by a self-assembled monomolecular film of two kinds of alkanethiols having different lengths. Was masked, and it was confirmed that the decomposition reaction of the lubricant due to dangling bonds caused by sliding with the head was effectively prevented.

The contact angle of the magnetic disk of this embodiment to water was 108 degrees. A corrosion point was not observed in a standing test in a constant temperature and humidity environment under the same conditions as in Example 1.

Fourth Embodiment FIG. 4 is a schematic sectional view of a magnetic recording medium according to a fourth embodiment of the present invention. In FIG. 4, 3 is an amorphous carbon protective film formed by a sputtering method, 4 is a cobalt-chromium-platinum alloy magnetic recording film, 5 is a chromium-titanium alloy film, and 6 is a glass substrate (2.5 mm in diameter). Inch), 1 is a perfluoropolyether lubricating film, 9 is a self-assembled monolayer. However, this self-assembled monolayer is formed of two types of molecules, an alkyl thiol (hydroxyundecanethiol) and an undecanethiol in which the terminal on the opposite side of sulfur is substituted with a hydroxyl group.

In this embodiment, a magnetic disk in which a protective film was formed using a continuous film forming apparatus and a substrate equivalent to that of the first embodiment was prepared. Thereafter, the magnetic disk was immersed in an ethanol solution of hydroxyundecanethiol and undecanethiol (each having a concentration of 0.0005 mol / l) for 10 minutes, pulled up, and then rinsed in the order of ethanol and pure water. Thus, the self-assembled monolayer 9 is formed on the protective film.
Was formed. Then, a lubricating film of a fluorine-containing organic substance was formed on the self-assembled monolayer by a solution immersion coating method. As the application conditions, the magnetic disk was immersed for 4 minutes in a solution in which a perfluoropolyether lubricant was dissolved in a fluorocarbon-based solvent at a concentration of 0.0005 mol / l,
It was raised at a speed of 0.5 mm / sec. As the perfluoropolyether lubricant, one having a main chain structure of a copolymer of perfluoromethylene oxide and perfluoroethylene oxide (average molecular weight 2800) and having both ends of a piperonyl functional group was used.

Observation of the surface of the magnetic disk by X-ray photoelectron spectroscopy and scanning tunneling microscopy before the application of the lubricant reveals that two types of alkanethiols, one having a hydroxyl group exposed on the surface and one having a methyl group exposed on the surface. It was confirmed that a densely packed self-assembled monolayer was formed. The ratio was found to be 1: 1 from the comparison of the surface element concentrations of oxygen and carbon by X-ray photoelectron spectroscopy.

After the application of the lubricant, FT-
The thickness of the lubricating film measured by IR was 1 nm. The dynamic friction coefficient of the magnetic disk of this example was measured under the same head and measurement conditions as in Example 1, and was 0.01.

The coefficient of kinetic friction after 300,000 CSS tests equivalent to that of Example 1 was 0.018, and the dangling bond on the surface of the protective film was formed by a self-assembled monomolecular film of alkanethiol having two different lengths. Was masked, and it was confirmed that the decomposition reaction of the lubricant due to dangling bonds caused by sliding with the head was effectively prevented.

The contact angle of the magnetic disk of this embodiment to water was 106 degrees. A corrosion point was not observed in a standing test in a constant temperature and humidity environment under the same conditions as in Example 1.

[Embodiment 5] In this embodiment, a magnetic disk similar to that of Embodiment 1 whose sectional structure is schematically shown in FIG. 1 was manufactured. However, polybutene having 20 carbon atoms was used as the lubricant. The lubricating film thickness is 2 nm.

When the dynamic friction coefficient was measured using the AlTiC head in the same manner as in Example 1, it was 0.017. The value of the dynamic friction coefficient after 300,000 times of the CSS test under the same conditions as in Example 1 was 0.024. The contact angle of the magnetic disk of this example with water was 106 degrees. In a standing test in a constant temperature and humidity environment performed under the same conditions as in Example 1, no corrosion point was observed.

[Embodiment 6] In this embodiment, a magnetic disk similar to that of Embodiment 1 whose sectional structure is schematically shown in FIG. 1 was manufactured. However, a fluoroester having 16 carbon atoms was used as the lubricant. The lubricating film thickness is 1.5 nm.

When the dynamic friction coefficient was measured using the AlTiC head in the same manner as in Example 1, it was 0.016. The value of the coefficient of dynamic friction after 300,000 CSS tests under the same conditions as in Example 1 was 0.020. The contact angle of the magnetic disk of this example with water was 107 degrees. In a standing test in a constant temperature and humidity environment performed under the same conditions as in Example 1, no corrosion point was observed.

[Embodiment 7] FIGS. 5 (a) and 5 (a) are a schematic plan view and a schematic longitudinal sectional view of a magnetic storage device according to the present invention.
(B). This apparatus comprises a magnetic recording medium 10, a driving unit 11 for rotating the magnetic recording medium 10, a magnetic head 12 and its driving means 13, and a recording / reproducing signal processing means 1 for the magnetic head.
4 is a magnetic storage device having a known configuration including

FIG. 6 shows the structure of the magnetic head. This magnetic head is a composite type head having both an electromagnetic induction type magnetic head for recording and a magnetoresistive magnetic head for reproduction formed on the base 21. The recording head is a coil 18
The upper recording magnetic pole 19 and the lower recording magnetic pole / upper shield layer 17 sandwiching the magnetic recording medium, and the gap layer thickness between the recording magnetic poles is 0.3 μm.
m. Cu having a thickness of 3 μm was used for the coil. The reproducing head comprises a magnetoresistive sensor 15 and electrode patterns 20 at both ends thereof.
It is sandwiched between a lower recording magnetic pole / upper shield layer having a thickness of m and the lower shield layer 16, and the shield interlayer distance is 0.25 μm. In FIG. 6, the gap layer between the recording magnetic poles and the gap layer between the shield layer and the magnetoresistive sensor are omitted.

FIG. 7 shows a sectional structure of the magnetoresistive sensor.
The signal detection region 22 of the magnetic sensor includes a portion in which a lateral bias layer 24, a separation layer 25, and a magnetoresistive ferromagnetic layer 26 are sequentially formed on a gap layer 23 of Al oxide. A 20 nm NiFe alloy was used for the magnetoresistive ferromagnetic layer. Although 25 nm of NiFeNb was used for the lateral bias layer, NiF
Any ferromagnetic alloy having relatively high electric resistance such as eRh and having good soft magnetic properties may be used. The lateral bias layer is magnetized in an in-plane direction (lateral direction) perpendicular to the current by a magnetic field generated by a sense current flowing through the magnetoresistive ferromagnetic layer, and applies a lateral bias magnetic field to the magnetoresistive ferromagnetic layer. As a result, a magnetic sensor showing a linear reproduction output with respect to the leakage magnetic field from the medium can be obtained. For the separation layer for preventing the shunt of the sense current from the magnetoresistive ferromagnetic layer, Ta having relatively high electric resistance was used, and the film thickness was 5 nm.

At both ends of the signal detection area, there are tapered portions 27 which are processed into a tapered shape. The tapered portion includes a permanent magnet layer 28 for converting the magnetoresistive ferromagnetic layer into a single magnetic domain, and a pair of electrodes 20 formed thereon for extracting a signal.
Consists of The permanent magnet layer needs to have a large coercive force and the magnetization direction does not easily change.
A Pt alloy or the like is used.

As the magnetic recording medium 10, the medium described in the first embodiment was used. Here, a medium having a coercive force Hc of 2.7 kOe was used as a characteristic of the magnetic recording film. Using the magnetic storage device of this embodiment, the head flying height was 35 nm, and the linear recording density was 2
When the recording / reproducing characteristics were evaluated under the conditions of 30 kFCI and a track density of 13 kTPI, an apparatus S / N of 4.5 was obtained. Further, by performing an 8-9 code modulation process on the input signal to the magnetic head, recording and reproduction could be performed at a recording density of 3 gigabits per square inch. Moreover, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference was 10 bits / plane or less, and 150,000 hours could be achieved with MTBF.

[Embodiment 8] An embodiment of a magnetic storage device having the same structure as that of the embodiment 7 but different in the film configuration of the recording medium from the magnetoresistive sensor of the reproducing head will be described below.
As shown in FIG. 8, the magnetoresistive sensor has a T on the Al oxide layer 23 for causing the magnetic layer to have a (111) orientation.
a buffer layer 29 is 5 nm, 7 nm first magnetic layer 3
It has a structure in which a Cu intermediate layer 31 of 0 and 1.5 nm, a second magnetic layer 32 of 3 nm, and an Fe-50 at% Mn antiferromagnetic alloy layer 33 of 10 nm are sequentially formed. A Ni-20 at% Fe alloy was used for the first magnetic layer, and Co was used for the second magnetic layer. The magnetization of the second magnetic layer is fixed in one direction by the exchange magnetic field from the antiferromagnetic layer. On the other hand, the direction of magnetization of the first magnetic layer, which is in contact with the second magnetic layer via the non-magnetic layer, changes due to the leakage magnetic field from the magnetic recording medium, so that a resistance change occurs. Such a change in resistance due to a change in the relative direction of magnetization of the two magnetic layers is called a spin valve effect. In this embodiment, a spin valve magnetic head utilizing this effect is used as a reproducing head. The tapered portion has the same configuration as the magnetic sensor of the seventh embodiment.

The medium described in Example 1 was used as a magnetic recording medium. Here, the coercive force H is a characteristic of the magnetic recording film.
A medium having a c of 2.7 kOe was used. Using the magnetic storage device of this embodiment, a head flying height of 35 nm and a linear recording density of 230
When the recording / reproducing characteristics were evaluated under the conditions of kFCI and track density of 13 kTPI, an apparatus S / N of 4.5 was obtained.
Further, by performing an 8-9 code modulation process on the input signal to the magnetic head, recording and reproduction could be performed at a recording density of 3 gigabits per square inch. Moreover, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference was 10 bits / plane or less, and 150,000 hours could be achieved with MTBF.

[Comparative Example 1] A perfluoropolyether lubricant equivalent to that of Example 1 was applied to a magnetic disk having an amorphous protective film formed on the same substrate as that of Example 1 under the same conditions at 1 nm.
A solution dip-coated with a film thickness of 1 was prepared as Comparative Example 1.

When various evaluation tests equivalent to those in Example 1 were performed, the following results were obtained. (1) The coefficient of dynamic friction was 0.02. (2) The coefficient of kinetic friction after 300,000 times of CSS increased to 0.8. Wear marks were observed on the sliding track after 300,000 times of CSS. (3) The contact angle with water was 107 degrees. Further, the surface of the magnetic disk after the constant temperature and humidity test under the same conditions as in Example 1 showed very slight discoloration.

[Comparative Example 2] A rotary drive unit, a magnetic head and its driving means, a magnetic head recording / reproducing signal processing means, and a magnetic recording medium described in Comparative Example 1 are used. The configured magnetic storage device was created.
Here, as a characteristic of the magnetic recording film, the coercive force Hc is 3.2 kO.
e medium was used.

Using the magnetic storage device of this comparative example, the recording / reproducing characteristics were evaluated under the conditions of a head flying height of 35 nm, a shield layer interval of 0.35 μm or less, a linear recording density of 230 kFCI, and a track density of 13 kTPI. / N
was gotten. Further, by performing an 8-9 code modulation process on the input signal to the magnetic head, recording and reproduction could be performed at a recording density of 3 gigabits per square inch. However, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference is 800 bits / plane or more.
Was less than 90,000 hours.

[0064]

As described in detail above, according to the present invention,
In a magnetic recording medium having a magnetic recording film and a protective film,
By forming a self-assembled monolayer on the protective film and forming a thin film composed of an organic lubricant on the self-assembled monolayer, the lubricant becomes dangling bonds and contaminants on the protective film surface. Because it is isolated from the head, the decomposition of the lubricant induced by the tribochemical reaction caused by the sliding with the head is suppressed, and the sliding performance and weather resistance are stable for a long time without deterioration of the lubrication performance. A magnetic recording medium can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a magnetic disk according to the present invention.

FIG. 2 is a schematic sectional view of another example of the magnetic disk according to the present invention.

FIG. 3 is a schematic sectional view of another example of the magnetic disk according to the present invention.

FIG. 4 is a schematic sectional view of another example of the magnetic disk according to the present invention.

5A and 5B are schematic diagrams of a magnetic storage device, in which FIG. 5A is a schematic plan view, and FIG.

FIG. 6 is a schematic three-dimensional view showing a cross-sectional structure of a magnetic head.

FIG. 7 is a schematic diagram of a cross-sectional structure of a magnetoresistive sensor section of the magnetic head.

FIG. 8 is a schematic diagram of a cross-sectional structure of a magnetoresistive sensor section of the magnetic head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thin film made of an organic lubricant, 2 ... Self-assembled monomolecular film, 3 ... Amorphous carbon protective film, 4 ... Magnetic recording film, 5 ... Chromium film, 6 ... Glass substrate, 7 ... Different carbon number A self-assembled monolayer composed of two or more alkanethiols, 8
... Self-assembled monolayer containing two or more kinds of outermost surface chemical species having different carbon numbers, 9 ... Self-assembled monolayer containing two or more kinds of different chemical species on the outermost surface, 10 ... Magnetic recording medium, 11
... Magnetic recording medium drive unit, 12 ... Magnetic head, 13 ... Magnetic head drive unit, 14 ... Recording / reproducing signal processing system, 15 ... Magnetic resistance sensor, 16 ... Lower shield layer, 17 ... Upper shield recording magnetic pole combined layer, 18 ... Coil, 19: upper recording magnetic pole, 20: conductor layer, 21: base, 22: signal detection area,
23: gap layer between the shield layer and the magnetoresistive sensor;
Reference numeral 24: lateral bias layer, 25: separation layer, 26: magnetoresistive ferromagnetic layer, 27: tapered portion, 28: permanent magnet layer, 29:
Buffer layer, 30 first magnetic layer, 31 intermediate layer, 32
... second magnetic layer, 33 ... antiferromagnetic layer

Claims (10)

[Claims] 1. A self-assembled monomolecular film having at least a magnetic recording film and a protective film provided thereon, wherein an organic substance is formed on the self-assembled monomolecular film. A magnetic recording medium comprising a thin film formed of a lubricant. 2. A horizontal plane having at least a magnetic recording film and a protective film provided thereon, and having a substantially constant horizontal molecular interval of 0.2 nm or more and 1 nm or less on the protective film. A magnetic recording medium, wherein a self-assembled monolayer having translational symmetry is formed, and a thin film made of an organic lubricant is formed on the self-assembled monolayer. 3. The self-assembled monomolecular film according to claim 1, wherein said self-assembled monolayer is formed of an alkanethiol having 3 to 30 carbon atoms in which sulfur atoms are oriented toward said protective film. Magnetic recording medium. 4. The magnetic recording medium according to claim 1, wherein said self-assembled monolayer comprises a mixture of two or more alkanethiols having different numbers of carbon atoms. 5. The self-assembled monolayer, wherein the terminal methyl group on the side opposite to the alkanethiol protective film is substituted with one or more of a hydroxyl group, an amino group and a methyl fluoride group. 5. The method according to claim 3, wherein
The magnetic recording medium according to the above. 6. The alkanethiol is two kinds of alkanethiols having a methyl atom and a methyl fluoride group at the end opposite to the sulfur atom, and the alkanethiol having a methyl fluoride group has a methyl group. Alkanethiol having more than carbon number of alkanethiol and having methyl fluoride group is 5% of the total number of molecules of the self-assembled monolayer.
5. The magnetic recording medium according to claim 4, wherein said magnetic recording medium is at least 80%. 7. The organic lubricant according to claim 1, wherein the main chain structure of the organic lubricant comprises a perfluoropolyether polymer, a hydrocarbon or a fluorocarbon, or a mixture of two or more thereof. 7. The magnetic recording medium according to 6. 8. The magnetic recording medium according to claim 1, wherein the thickness of the thin film made of the organic lubricant is 0.2 nm or more and 10 nm or less. 9. The protection film according to claim 1, wherein the protective film is at least one selected from amorphous carbon, silicon-containing amorphous carbon, nitrogen-containing amorphous carbon, boron-containing amorphous carbon, silicon oxide, zirconium oxide, and cubic boron nitride. The magnetic recording medium according to any one of claims 1 to 8, wherein the magnetic recording medium is made of one material. 10. A self-assembled monolayer having at least a magnetic recording film and a protective film provided thereon, wherein an organic substance is formed on the self-assembled monolayer. A magnetic recording medium on which a thin film made of a lubricant is formed, and a drive unit for driving the magnetic recording medium in a recording direction,
A magnetic head including a recording unit and a reproducing unit, and a unit that relatively moves the magnetic head with respect to the magnetic recording medium;
A magnetic storage device comprising: a recording / reproducing signal processing unit.