JPH09326114A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sliding resistant reliability of a magnetic recording medium and to embody a high recording density. SOLUTION: This medium consists of a magnetic layer 3 consisting of a ferromagnetic material allay thin film arranged on a substrate 1, a protective layer 4 mainly composed of the carbon arranged on this magnetic layer 3 and a lubricating layer 5 arranged on this protective layer 4. The protective layer 4 has baron covalent bonded to the carbon and nitrogen and the wave number of the main peak of its Raman spectra is set within a range from 1,500 to 1,565cm<-1> . The protective layer 4 may further contain hydrogen. The lubricating layer 5 preferably consists of a component strongly fixed to the protective layer and that weakly fixed thereto.

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 used for a main storage device of information equipment.

[0002]

2. Description of the Related Art Magnetic disk devices have become indispensable as main storage devices for information devices such as computers, and have a larger capacity as the need for high-speed processing of large amounts of data such as images and sounds increases. Moreover, it is necessary to speed up recording and reproduction. For this purpose, it is indispensable to further increase the recording density and read and write at high speed. Regarding the recording density, the actual distance from the element of the recording / reproducing head to the recording film of the magnetic disk that is the recording medium should be shortened as much as possible to narrow the track width.For high-speed operation, high-speed rotation and high-speed seek as well as high-speed data processing. is necessary. Along with these improvements, the magnetic head and the magnetic disk, which have conventionally been operating with a sufficiently long interval, are forced to operate in a so-called intermittent contact state in which the magnetic head and the magnetic disk move at high speed while being almost in contact with each other. Moreover, in order to shorten the substantial distance between the magnetic head element and the magnetic disk recording film as described above, the protective layer and the lubricating layer between them are made as thin as possible, for example, the protective layer is 10 nm or less, and the lubricating layer is 2 nm or less. The average distance between the magnetic disk surface and the magnetic head should be 30 or less.
nm or less, and contact may possibly occur. In order to obtain a magnetic disk that can be put to practical use under such extremely severe conditions, the key point is how to design the materials and shapes of the protective layer, the lubricating layer, and the contact portion of the head.

The protective layer and the lubricating layer of a magnetic disk have been conventionally improved from the viewpoint of improving wear resistance, sliding resistance, corrosion resistance and the like. As the protective layer, an amorphous carbon film formed by sputtering graphite in an Ar atmosphere, a hydrogenated amorphous carbon film formed by sputtering graphite in an Ar + H ₂ or Ar + CH ₄ atmosphere, and the like are in practical use. In addition to this, diamond-like carbon is formed by plasma CVD of hydrocarbon gas, or carbon film or S added with various elements such as Si, Ti, W, and Fe.
iO _2, such as a variety of protective film has been studied.

Of these protective layers, the protective layer in which hydrogen is added to carbon has improved wear resistance, but its effect is limited and cannot be used with a film thickness of 10 nm or less. Further, the protective layer to which TiC or WC is added has a drawback that it crashes instantly when the lubricating action is cut off. All of these are considered to occur because they partially block the strong bond between carbon atoms. That is, in the case of hydrogenation, when hydrogen atoms are bonded, the sp2 bond, which is a graphite-like bond of carbon, is reduced at first, so the strength is improved, but when hydrogen is added to a certain extent, -C
This is because the carbon atom bond network is terminated in the form of H ₃ , or the polymer structure in the form of — (CH ₂ ) n— is increased and the strength is weakened. Further, when an element that forms an interstitial carbide such as Ti or W is mixed, the heat is generated during sliding to remove carbon and leave a metal, resulting in a very weak film at high temperature.

On the other hand, Japanese Patent Laid-Open No. 63-102017 discloses a protective film of graphite-like carbon to which a covalent bond element such as boron, nitrogen or Si is added. Further, as a protective film having excellent wear resistance and corrosion resistance, boron,
An example using diamond-like carbon containing Si and the like is described in JP-A-60-29936.

On the other hand, for the lubricating layer, perfluoropolyether type lubricating oil having an adsorptive functional group at the end is mainly used, and many lubricants having an end group having improved binding property with the protective layer are known. Has been.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The conventional technique described in No. 936 has a problem that lubricity is inferior and therefore sufficient durability cannot be obtained. Also,
The conventional technique described in JP-A-63-102017 is as follows.
Since the carbon itself is combined with the graphite-like carbon, the strength of the carbon itself is insufficient, and there is a problem that it is difficult to withstand practical use, especially with an extremely thin film of 10 nm or less.

An object of the present invention is to provide a highly reliable magnetic recording medium suitable for high-density recording and high-speed rotation, which has a protective film excellent in corrosion resistance and abrasion resistance even if the film thickness is thin. To provide.

[0009]

In order to achieve the above object, a magnetic recording medium of the present invention has a magnetic layer made of a ferromagnetic alloy thin film arranged on a non-magnetic substrate, and arranged on this magnetic layer. And a lubricating layer disposed on the protective layer, the protective layer having boron and nitrogen covalently bonded to carbon, and the wavenumber of the main peak of the Raman spectrum. Is 1500 cm ^-1 to 156
It is designed to be in the range of 5 cm ^-1 .

The carbon contained in the protective layer is substantially free of carbon having a graphite structure and is amorphous diamond-like carbon. Raman spectra should be measured to confirm that the carbon contained in the protective layer does not have a graphite structure. That is, Ar
When the Raman spectrum measured by the light source of the ion laser with a wavelength of 514.5 nm is peak-separated, it has a graphite structure if the main peak is near 1580 cm ^-1, and the graphite component if it is below 1565 cm ^-1. It can be thought of as virtually nothing. In addition, it is difficult to produce a material having a main peak having a wave number of less than 1500 cm ⁻¹ by an ordinary method.

The atomic ratio of boron to nitrogen is preferably 5 to 25%. The protective layer of this magnetic recording medium may further contain hydrogen. At this time, the atomic ratio of hydrogen is preferably 0.1 to 30%.
However, the total of boron, nitrogen, and hydrogen is preferably less than 50%, that is, carbon is preferably 50% or more.
The thickness of the protective layer is preferably 4 to 10 nm.
The density of the protective layer is preferably 1.7 to 2.5 g / cm ³ .

The lubricating layer preferably comprises 65% or more and 96% or less of the components strongly adhered to the protective layer and 4% or more and 35% or less of the components weakly adhered to the protective layer, and the former component is 70%. More than 95%, less than 5% of the latter 30
% Or less is more preferable.

[0013]

FIG. 1 shows an example of a cross-sectional structure of a magnetic disk of the present invention. Further, other examples of the magnetic disk of the present invention are shown in FIGS. As seen in each figure, the magnetic disk of the present invention comprises a hard layer 1'on the substrate 1 if necessary.
And a base layer 2, a magnetic layer 3, a protective layer 4, and a lubricating layer 5 are sequentially laminated. In FIG. 1, the interface between the protective layer 4 and the magnetic layer 3 is substantially flat, and the surface of the protective layer 4 has irregularities. On the other hand, in FIGS. 2 to 4, there are irregularities under the magnetic layer 3, and the protective layer 4 having a uniform film thickness is formed thereon.

First, the structure of the magnetic disk of the present invention will be described with reference to FIG. The substrate 1 is a disc-shaped substrate having a hole in the center, and usually, an aluminum-magnesium alloy plated with NiP as a hard layer 1 ′ or a glass substrate subjected to a strengthening treatment for increasing strength is used. In the present invention, the material is not specified, but the surface is preferably as smooth as possible, and the center line average roughness is several nm or less, preferably 1 nm or less.

The underlayer 2 is for improving the crystallinity of the magnetic layer 3 and is not necessarily required, but for example, Cr or its alloy can be used. Of course, a multi-layer structure is also possible. The magnetic layer 3 is for recording signals, and is made of, for example, a Co-based alloy material. CoC
rTa, CoCrPt, CoCrV, CoNiCr, C
A ternary alloy such as oNiV is often used, but it is possible to add a fourth element or an oxide to these. Further, it may have a multilayer structure, or a non-magnetic layer may be sandwiched between a plurality of magnetic layers. None of these relate to the essence of the present invention. The materials of the protective layer 4 and the lubricating layer 5 will be described later.

In FIG. 1, fine irregularities are formed on the protective layer 4, which reduces the contact area with the magnetic head,
To reduce the frictional force, the height is about 10 to 20
It is preferable to provide the hill-shaped projections having a diameter of 0.1 nm and an average diameter of 0.1 to 10 μm as uniformly as possible. In order to form the unevenness, for example, fine particles are dispersed and adsorbed on the surface of the magnetic disk on which the protective layer 4 is formed, and the protective layer 4 is etched to a certain depth by performing plasma etching using the fine particles as a mask. The particle mask should be washed away. In addition to this, after forming a flat film up to the magnetic layer 3, another substance may be deposited in an island shape, and the protective layer 4 may be formed thereon with a uniform thickness.

2 to 4 show an example in which unevenness is formed under the base layer 2, which also has the effect of reducing the contact area of the disk surface and reducing the frictional force with the head. In FIG. 2, a method for making fine scratches on the surface of the NiP plating layer, which is the hard layer 1 ′, by machining, etc.
This is an example in which the surface of the plating layer is partially melted and unevenness is created by utilizing the undulations 6 generated. Further, FIG. 4 is an example in which the island-shaped deposit 7 is formed under the base layer 2. This is of course the same even if it is provided between the magnetic layer 3 and the underlayer 2.

In any case, the shape of the irregularities on the surface of the protective layer has a maximum height of 10 nm to 20 nm and a contact point density of 1 × 1.
It is preferable that the number of contact points is 0 ³ pieces / mm ² to 1 × 10 ⁵ pieces / mm ² , and the average diameter of the contact points is 0.1 to 10 μm. If the contact point is less than the above range, the protrusions are easily broken due to one-sided contact with the magnetic head or the stress per contact point is large, and if the contact point exceeds the above range, the magnetic head attracts and the frictional force becomes large and the surface does not float stably. . If the average diameter of the contact points is large, the attraction force with the magnetic head is too large.

The protective layer 4 is composed of carbon, boron and nitrogen, and optionally further contains hydrogen. Carbon is an amorphous diamond-like carbon and has a structure substantially having no graphite component. That is, it has almost no hexagonal network structure composed of sp2 bonds of carbon atoms. Of course, it is sufficient if it does not have a hexagonal sp2 structure at all, but even if it is contained slightly, it does not have to have the physical properties peculiar to graphite. That is, it suffices if it does not have the property of being easily plastically deformed and having low resistance. The property of being easily plastically deformed occurs because the interlayer bond of graphite is very weak, and makes a great contribution to the lubricating characteristics of graphite-like carbon.
On the contrary, when the actual film thickness is 10 nm or less, it is a major cause of strength deterioration. Therefore, it is preferable not to include this as much as possible.

In order to confirm that the carbon contained in the protective layer 4 does not have a graphite structure, it is preferable to measure the Raman spectrum. That is, 1000c measured with a light source having a wavelength of 514.5 nm of an Ar ion laser.
When the Raman spectrum in the wave number region of m ^{-1 to} 1800 cm ^-1 is separated into peaks, it is found that the graphite structure is present when the main peak is near 1580 cm ^-1, and the graphite structure is found when it is below 1565 cm ^-1. It can be considered to be substantially free of ingredients.

Further, it is preferable that boron and nitrogen contained in the protective layer 4 form a strong covalent bond network together with carbon. To investigate this, the bond of carbon, nitrogen and boron is determined by photoelectron spectroscopy. You can analyze the condition. That is, each atom is C-N, C = N, C-
It can be seen that if B and B-N are connected, they form a three-dimensional network. On the other hand, the bond is -C
If it is a terminal such as ≡N or N≡N, it means that the network is broken. Further, in order to quantify whether or not this network is strong, a minute hardness may be measured, and an indentation hardness of 15 GPa or more is preferable.

In order to form the protective layer 4 of the present invention, direct current or alternating current magnetron sputtering is preferably used. At that time, when a target made of C, B, N is used as a target material and when a target made of C, B is used. There is a case where sputtering is used in an atmosphere containing nitrogen gas. Either method may be used, but if the ternary target material cannot be used stably, the latter method is inexpensive and preferable. When hydrogen is further contained, in the latter case, sputtering may be performed in an atmosphere containing a mixed gas of nitrogen and hydrogen or a mixed gas of nitrogen and a hydrocarbon gas such as methane. In addition, compounds consisting of nitrogen, hydrogen and carbon, such as CH ₃
You may use CN etc. In any case, Ar, He, Ne, Xe or the like can be used as the inert gas, and it is industrially preferable to use Ar because it is inexpensive.

On the other hand, for the lubricating layer 5, it is preferable to apply a commonly used perfluoropolyether type lubricating oil very thinly, and a trade name AM2001R or other commercially available lubricating oil may be used. Since the protective layer of the present invention has many functional groups consisting of nitrogen and boron on the surface, it has an affinity for water, and it is not preferable that excessive moisture is adsorbed in view of corrosion resistance and sliding characteristics. In order to eliminate this, it is preferable to use a lubricant that firmly adheres to the above-mentioned functional group and lowers the surface energy. Examples of this include a fluorinated polyalkyl or fluorinated alkyl polyether having a hydroxyl group, an alcohol group, an ester group, a carboxyl group, an amino group, an amine base, an amide group or the like at the terminal. The lubricating layer may be composed of the same kind of lubricant molecules or a plurality of different lubricant molecules.

In order to further improve the effect of the present invention, it is preferable that the lubricating layer is composed of a component strongly fixed to the surface of the protective layer and a component weakly fixed to the surface of the protective layer. That is, the strongly adhered component is a component that is fixed by strong adsorption or chemical bonding with the surface functional group of the protective layer and does not move under the normal use condition of the magnetic disk, and covers the functional group on the surface of the surface of the disk itself. It serves to keep energy low.
The weakly adhered component is a component that is fixed by interaction with the surface of the protective layer or by entering into a minute gap of the surface shape, and can be relatively easily moved by a temperature rise caused by heating or sliding.

These may be the same type of lubricant molecule. The amount of the above-mentioned functional group on the surface limits the amount of the component strongly adhered to the surface of the protective layer, so that the lubricant molecules other than this amount exist as weakly adhered components. Also, by combining a lubricant having a polar functional group at the terminal, a lubricant having no polar functional group, and two kinds of lubricants,
The former adheres strongly to the surface of the protective layer, and the latter adheres weakly.
In the present invention, the method for forming the lubricating layer is not particularly limited, and a dip method, a spin coating method or the like which is commonly used can be used.

The combination of the protective layer and the lubricating layer as described above is suitable for the following reason. First, regarding the material of the protective layer, a thin film having a thickness of 10 nm or less must be dense and have a low defect in order to ensure corrosion resistance and strength against scratches and the like when foreign matter is mixed. Since a crystalline substance is apt to form a gap between grains and causes defects, it is necessary to use an amorphous, stable and smooth material.

Generally, a carbon film used as a protective film for a magnetic disk is formed of carbon having a graphite structure in an argon atmosphere or a mixed gas atmosphere of argon and hydrogen, methane or the like. The structure of is not completely decomposed to the atomic state, and particles having carbon of several atoms to several tens of atoms bonded with the graphite skeleton are directly sputtered, so such a structure was included. Will be things. The structure of graphite is soft and not only deteriorates wear resistance due to plastic deformation, but also causes defects by being contained in the film in a large lump. Further, if the substrate temperature during film formation is increased in order to improve the performance of the magnetic film, the structure of graphite further grows, and irregularities easily occur. The inclusion of hydrogen hinders the growth of such a graphite structure, but it cannot reduce the native graphite crystallites.

The protective film of the present invention contains almost no such graphite fine crystals as described above, and further, boron and nitrogen are uniformly mixed in the carbon matrix, which hinders the growth of the graphite structure even at high temperatures, and thus has high wear resistance. Is obtained.

However, if the graphite structure of the protective layer is substantially eliminated, a decrease in lubricity is expected. Furthermore, functional groups containing nitrogen and boron are present on the surface in a considerable concentration, which causes deterioration of corrosion resistance and sliding resistance due to reaction with water, adsorption or contamination of organic substances. To prevent this, a lubricating layer was provided on the surface of the protective layer. This lubricating layer not only reduces the frictional force in contact with the head, improves the sliding characteristics by preventing heat generation, but also lowers the surface energy of the protective layer and prevents contamination and moisture adsorption. . On the other hand, the boron, nitrogen, and functional groups of oxygen bonded to them on the surface have a high bond strength with the lubricant and are chemically stable in the bonded state, so the lubricant is less likely to decompose, resulting in a shorter service life. Can be dramatically increased.

In the present invention, the reliability of the magnetic disk is further improved by forming the lubricating layer as a composite layer of a strong fixed component and a weak fixed component. That is, the strongly fixed component binds to the hydrophilic group of the protective layer to chemically protect the surface and is fixed and does not move during normal sliding. On the other hand, the weakly adhered component does not move in the stationary state, but when the temperature rises due to sliding etc., the fixed part starts to move and starts moving, and this moving component reattaches to the part where the lubrication layer has partially peeled from the surface of the protective layer due to damage etc Then, the lubricating effect is exhibited again by covering it, and as a result, the reliability of the magnetic disk is dramatically improved. In the present invention, one of the functional group containing nitrogen and the functional group containing boron existing on the surface of carbon forms a strong bond and the other forms a weak bond, so that the above-mentioned 2
It is believed that a magnetic disk with components can be constructed. Note that a firmly fixed lubricant does not peel even if it is baked at a temperature of 150 ° C. and then washed with a fluoroether solvent, and a weakly fixed lubricant does not peel and is washed with the above solvent. It does not peel, but it peels when it is baked at a temperature of 150 ° C. and then washed with the solvent.

Example 1 The surface of an Al--Mg alloy disk substrate having an outer diameter of 3.5 inches and plated with non-magnetic NiP was smooth-polished, and finely machined grooves in the circumferential direction were provided on both surfaces thereof. . The surface roughness Ra after processing was about 10 nm. After the substrate was washed to remove foreign matters and organic contamination and dried, film formation was performed using a continuous multilayer film forming apparatus.
In the film forming step, the substrate was introduced into a vacuum from a load lock chamber, heated to 300 ° C. with an infrared heater, and then a Cr underlayer, a CoCrPt magnetic layer, and a protective layer were sequentially formed.
The thickness of each is 20 nm for the Cr underlayer and CoCrPt.
The conditions were adjusted so that the magnetic layer had a thickness of 20 nm and the protective layer had a thickness of 10 nm. Here, when forming the protective layer, carbon containing 20% of boron was used as a target, argon containing 40% of nitrogen was used as an atmosphere gas, and DC planar magnetron sputtering was performed at a gas pressure of 5 mTorr and a power density of 10 W / mm ² for 10 times. Sputtered for a second. After removing this substrate from the vacuum chamber, about 1.5 n of a lubricant having a perfluoropolyether skeleton having polar end groups was prepared by a dip method.
It was applied so that the average thickness was m.

Analysis of the protective layer of the magnetic disk thus manufactured revealed that the ratio of carbon, boron and nitrogen was 7: 2: 1 respectively, and the peak of carbon in Raman spectrum was 1520 cm ^-1. It was found that there was almost no graphite component. Further, the electric resistance was measured and found to be 3 × 10 ⁹ Ωcm.
Further, when the bond between boron and nitrogen was examined by photoelectron spectroscopy, it was found that most of them were bonded to carbon atoms. Further, when the hardness and Young's modulus of this disk were measured with an indentation hardness meter having a minute depth, they were 25 GPa and 120 GPa, respectively.

The magnetic disk produced as described above was subjected to slider milling by ion milling on the bottom surface of a block made of Al ₂ O ₃ -TiC ceramics having a length of 2 mm, a width of 1.5 mm and a thickness of 0.4 mm. Using the manufactured test head, a continuous sliding test was performed at a load of 5 gf and a rotation speed of 5 m / s. As a result, as shown by the curve A in FIG. 5, the frictional force was 1.5 gf or less from the initial stage and there was no large change up to 100 k times. Further, when the slider was kept in contact with the slider after stopping for 1 day and the frictional force after rotation was measured, it was found to be about 2.5 gf, and the adhesive force was also small. The sliding portion of this disk and the slider surface of the test head were observed with an optical microscope and AFM, but no abrasion was detected. Further, when the amount of lubricant in the sliding portion of the disk was measured, it was about 95% of the non-sliding portion, and it was found that there was almost no decrease.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that graphite was used as the target during the formation of the protective layer and the atmosphere was pure argon. The carbon peak of the Raman spectrum was 1580 cm ^-1 , and it was found that the graphite component was contained. The electric resistance was 2 Ωcm, and the hardness and Young's modulus measured by the indentation hardness meter were 12 GPa and 90 GPa, respectively.
When this was subjected to a sliding test in the same manner as in Example 1,
The result is that the initial frictional force is 1.5 gf as shown by the curve B in FIG.
Although it was below, it increased with the number of rotations and crashed at 15k times.

Comparative Example 2 A magnetic disk was manufactured in the same manner as in Example 1 except that graphite was used as a target during the formation of the protective layer and argon was used as the atmosphere containing 20% of hydrogen. Raman spectrum has a carbon peak of 1
It was 568 cm ⁻¹ , and it was found that the graphite component was contained but the amount thereof was smaller than that of Comparative Example 1. The electric resistance was 1 × 10 ¹¹ Ωcm, and the hardness and Young's modulus measured by the indentation hardness meter were 15 GPa and 13 GPa, respectively. When this was subjected to a sliding test in the same manner as in Example 1, the result was that the initial frictional force was 1.5 as shown by the curve C in FIG.
It was less than gf and did not increase up to 30k times, but it increased with the number of revolutions thereafter, and 7.5g at 100k times.
reached f. Further, the slider was kept in contact with the slider after the suspension, and the slider was kept in contact with the slider for one day. Then, the frictional force after rotation was measured, and it was found to be about 15 gf.

When the sliding portion of the disk and the slider surface of the test head were observed with an optical microscope and AFM, the protective film was worn by about 5 nm on the disk surface, and the slider surface was also scratched. Further, a part where lubricant was collected was found at the end of the slider. Also, when the amount of lubricant in the sliding portion of the disk was measured, it was about 30% of the non-sliding portion.
It turns out that% is gone.

Comparative Example 3 A magnetic disk was prepared in the same manner as in Example 1 except that the target used for forming the protective layer was graphite containing boron as in Example 1 and the atmosphere was pure argon. The carbon peak of the Raman spectrum was 1570 cm ^-1 , and it was found that the graphite component was still contained. Electric resistance is 7 × 10 ⁴ Ω
cm, and the hardness and Young's modulus measured by an indentation hardness meter were 18 GPa and 16 GPa, respectively. When this was subjected to a sliding test in the same manner as in Example 1, the result was that the frictional force was 2 gf or more from the initial stage as shown by the curve D in FIG. 5, and then gradually increased to 5.8 gf at 100 k times. Reached In addition, when the slider was kept in contact with the slider after stopping for 1 day and the frictional force after rotation was measured,
It was about 9 gf and was found to be sticky.

Observation of the sliding portion of the disk and the slider surface of the test head with an optical microscope and AFM showed that the protective film was not worn on the disk surface.
The slider surface was scratched. Further, when the amount of the lubricant on the sliding portion of the disk was measured, it was found to be about 60% of the non-sliding portion, and it was found that the amount of the lubricant was reduced by about 40%.

<Examples 2 to 12> The protective film of Example 1 was changed in the same manner as in Table 1 except that the target composition and atmospheric gas components were changed to the same as in Table 1 to form a protective film, and a lubricant was applied. Then, a magnetic disk was produced. The results of ESCA analysis of the protective film composition at that time are also shown in Table 1. When these were subjected to the same sliding test as in Example 1, the results shown in Table 2 were obtained. Similarly, the magnetic disk of the comparative example shown in Table 3 was produced. The results of this sliding test and the like are shown in Table 4.

From these results, the protective film of carbon (amorphous diamond-like carbon) or hydrogenated carbon containing boron and nitrogen and having substantially no graphite component does not easily increase the frictional force, so that it comes into contact with the magnetic head. It can be seen that it does not stick easily even if left alone. Furthermore, the ratio of boron is 5 to 25
It has been found that those having a nitrogen content of 5 to 25% exhibit good characteristics. It was also found that the one having a higher nitrogen ratio is less likely to increase the frictional force after being left for one day.

The magnetic disks of this example and the comparative example were 5
After heating at 0 C for 1 hr, the product was immersed in a Fluorinert solvent, ultrasonically washed for 10 minutes, and then the lubricant reduction rate was examined. The results are shown at the right end of Tables 2 and 4. It was found that the smaller the decrease rate after heating, the smaller the increase in the frictional force after one day of standing after the sliding test of 100 k times.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

As described above, according to the present invention, it is possible to obtain a magnetic recording medium having sufficient strength and sliding resistance even with a thin protective film. Moreover, since the adhesion resistance of the lubricant can be improved, a magnetic recording medium having excellent reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of a magnetic disk of the present invention.

FIG. 2 is a sectional view showing the structure of another embodiment of the magnetic disk of the present invention.

FIG. 3 is a sectional view showing the structure of still another embodiment of the magnetic disk of the present invention.

FIG. 4 is a sectional view showing the structure of still another embodiment of the magnetic disk of the present invention.

FIG. 5 is a diagram showing the results of a sliding test of magnetic disks of the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 1 '... Hard layer 2 ... Underlayer 3 ... Magnetic layer 4 ... Protective layer 5 ... Lubricating layer 6 ... Waviness 7 ... Island deposit

Claims (3)

[Claims] 1. A magnetic layer composed of a ferromagnetic alloy thin film arranged on a non-magnetic substrate, a protective layer containing carbon as a main constituent and arranged on the magnetic layer, and a lubrication arranged on the protective layer. In the magnetic recording medium composed of layers, the protective layer has boron and nitrogen covalently bonded to carbon, and the Raman spectrum has a main peak wave number of 1500 cm ⁻¹ to 1 cm 1.
A magnetic recording medium having a range of 565 cm ^-1 . 2. The magnetic recording medium according to claim 1, wherein the protective layer further contains hydrogen. 3. The magnetic recording medium according to claim 1, wherein the lubricating layer strongly adheres to the protective layer of 65% or more and 96% or less and weakly adheres to the protective layer of 4% or more and 35% or less. A magnetic recording medium comprising the above component.