JPH11149631A - Magnetic record medium and magnetic storage device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the bonding strength of a lubricant by specifying the chemical compsn. of the surface of a protective layer contg. carbon, nitrogen and oxygen and further contg. at least one element selected from the group comprising silicon, boron and hydrogen. SOLUTION: The magnetic record medium has a magnetic layer on the substrate and a protective layer on the magnetic layer. The protective layer is a coating film contg. at least one element selected from the group comprising silicon, boron and hydrogen besides carbon, nitrogen and oxygen. The ratio of the number of nitrogen atoms to that of carbon atoms in the coating film is 0.005-0.3, the ratio of the number of oxygen atoms to that of nitrogen atoms in the surface of the coating film is 0.1-2.5 and the ratio of the number of silicon, boron or hydrogen atoms to that of carbon atoms in the surface is 0.07-0.28. Electron withdrawing groups are formed on the surface of the protective layer corresponding to the interface between the protective layer and a lubricative layer by the addition of nitrogen and oxygen having high electronegativity and the terminals of lubricant molecules bond tightly to the surface of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic storage device,
The present invention relates to a magnetic recording medium used therein, and more particularly to a highly reliable magnetic storage device having a recording density of 2 gigabits per square inch or more and a magnetic recording medium for realizing the same.

[0002]

2. Description of the Related Art A conventionally known protective layer for a magnetic disk is made of a material formed by sputtering a graphite target, is chemically stable, has a low coefficient of friction, and hardly generates abrasion powder during sliding. It has properties suitable for a protective layer, but contains a large amount of graphite-like carbon. For this reason, it is difficult to further increase hardness and wear resistance. On the other hand, measures have been proposed to prevent the formation of a graphite-like structure by adding another element to the above-mentioned protective layer made of only carbon, thereby achieving densification.

As elements to be added, metals, metal oxides and metal nitrides have been proposed in addition to hydrogen, boron, nitrogen, fluorine and silicon which are covalently bonded to carbon. In particular, the carbon-based protective layer to which nitrogen has been added has a higher average energy of multiple bonds of nitrogen and carbon than carbon and carbon, and β-C3N4 of the carbon-nitrogen single bond structure is comparable to diamond. It is expected to have high performance as a protective layer, for example, it is expected that the material will have a high hardness. To specifically illustrate the example where these are described,
There are JP-A-5-225556 and JP-A-7-320256.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 5-225556.
The technique disclosed in Japanese Patent Application Publication No. H10-115118 is to improve the durability by strengthening the protective layer by adding nitrogen to a graphite-like material containing a large amount of carbon. However, in the current situation where the magnetic head is becoming lighter, lower in flying height, and the protective layer is becoming thinner, the chemical action of the protective layer surface and the lubricant is more important than mechanical strength as a factor controlling the durability of the protective layer. Has become important, and the structure and chemical properties of the surface have become more important factors than the inside of the protective layer. Therefore, there is a problem that the durability of the magnetic disk cannot be improved only by increasing the mechanical strength of the protective layer.

On the other hand, the one described in the above-mentioned Japanese Patent Application Laid-Open No. 7-320256 is intended to enhance the bonding strength of a lubricant by adding a nitrogen element. If the chemical structure of the surface of the protective layer corresponding to the interface is not optimized, there is a problem that the effect of improving the durability of the magnetic recording medium is small.

A first object of the present invention is to solve the above-mentioned problems of the conventional protective film by focusing on chemical properties on the surface of the protective layer and increasing the mechanical strength. At the same time, the object is to increase the bonding force with the lubricant and improve the durability of the magnetic recording medium. A second object of the present invention is to provide a magnetic storage device having a high recording density and high reliability using the magnetic disk.

[0007]

In order to achieve the first object, a magnetic recording medium of the present invention has a magnetic layer on a base material and a protective layer formed on the magnetic layer. Consists of a film containing at least one element selected from the group consisting of silicon, boron, and hydrogen while containing at least carbon, nitrogen, and oxygen, and the nitrogen / carbon atomic ratio of the film is 0.05 to 0.3.
And the atomic ratio of oxygen / nitrogen on the surface of the coating is in the range of 0.1 to 2.5, and the atomic ratio of silicon, boron or hydrogen / carbon at this time is in the range of 0.07 to 0.28. It is characterized by being in.

The magnetic recording medium of the present invention for achieving the first object has a center line average roughness Ra of 1n.
m or less. Here, the definition of the center line average roughness conforms to the provisions of the Japanese Industrial Standards (JIS-B0601).

A magnetic storage device for achieving the second object has a magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head including a recording unit and a reproducing unit, and the magnetic head. A magnetic storage device comprising: means for causing relative movement with respect to a magnetic recording medium; and recording / reproduction signal processing means for performing signal input to the magnetic head and reproduction of an output signal from the magnetic head. Is a magnetoresistive magnetic head, and the magnetic recording medium contains at least carbon, nitrogen and oxygen and at least one selected from the group consisting of silicon, boron and hydrogen.
Containing the elements of the species, the atomic ratio of nitrogen / carbon is 0.05-0.3,
And the atomic ratio of oxygen / nitrogen on the surface of the film is 0.1
The protective layer is characterized in that the protective layer has an atomic ratio of silicon / carbon, boron / carbon or hydrogen / carbon within a range of 0.07 to 0.28.

A magnetic storage device for achieving the second object has a magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head including a recording unit and a reproducing unit,
A magnetic storage device comprising: means for moving the magnetic head relative to the magnetic recording medium; and recording / reproducing signal processing means for reproducing a signal input to the magnetic head and an output signal from the magnetic head. A magnetic head is formed on a magnetic head slider having an air bearing surface rail area of 1.25 mm2 or less and a mass of 2 mg or less, and the magnetic recording medium contains at least carbon, nitrogen and oxygen, and silicon,
Boron, containing at least one element selected from the group consisting of hydrogen, the atomic ratio of nitrogen / carbon is 0.05 to 0.3, and,
The atomic ratio of oxygen / nitrogen on the surface of the coating is 0.1 to 2.5.
And the atomic ratio of silicon / carbon, boron / carbon or hydrogen / carbon at this time is in the range of 0.07 to 0.28.

According to the method of manufacturing a magnetic recording medium of the present invention, a step of forming a magnetic layer on the surface of a base material and a step of forming a magnetic layer containing at least carbon, nitrogen and oxygen on the surface of the magnetic layer are performed at the same time. Forming a protective layer containing at least one selected element; and irradiating the surface of the protective layer with ultraviolet light in the air.

According to another aspect of the present invention, there is provided a method of manufacturing a magnetic recording medium, comprising: forming a magnetic layer on a surface of a base material; A step of forming a protective layer containing at least one element selected from the group consisting of silicon, boron, and hydrogen; and performing a plasma treatment on a surface of the protective layer in an oxygen atmosphere.

Next, the above configuration will be functionally described. In the magnetic recording medium having the above configuration, nitrogen and oxygen having a large electronegativity are added to the surface of the protective layer at the interface between the protective layer and the lubricating layer to form a strong electron-withdrawing group. Strongly binds to the surface. In particular, if a nitro group consisting of nitrogen and oxygen is bonded to an aromatic ring or conjugated double bond, the transfer of π electrons becomes a stronger electron-withdrawing group, and furthermore, it is strongly bonded to a lubricant, and the durability of the magnetic disk is improved. It contributes to the improvement of performance. Such electron-withdrawing groups due to nitrogen or oxygen are formed by the reaction with oxygen in the atmosphere, but the oxygen / nitrogen atom is adjusted by adjusting the film formation method and conditions, or by performing surface treatment. By optimizing the ratio, the bonding force with the lubricant is further strengthened. For example, surface treatment using oxygen plasma or ultraviolet irradiation is also an effective means for optimizing the chemical composition of the surface. Moreover, irradiation with an oxygen plasma treatment or ultraviolet irradiation is effective in removing organic contaminants by reaction with oxygen radicals and ozone, and in mitigating unevenness by ashing or photoetching.
However, even when nitrogen and oxygen are contained, the durability may be deteriorated, for example, the lubricant molecules may be easily decomposed depending on the chemical state of the surface. Therefore, in order to improve the durability of the magnetic disk, it is necessary to optimize the surface element ratio of the protective layer as necessary. The lubricant used is not particularly limited, but fluoropolymers such as perfluoropolyethyl, perfluoropolyether, and perfluorocarboxylic acid are preferred.

Next, the effect of silicon, boron or hydrogen will be described. Since hydrogen, boron and silicon all form a single bond with carbon, the formation of a graphite-like structure can be prevented. In particular, when silicon is included in the protective layer, silicon forms a tetrahedral skeleton by forming a single bond with carbon, so that the protective layer has a dense film structure, improves the hardness of the film, and has excellent wear resistance. Therefore, it becomes a protective layer excellent in sliding characteristics at the time of low flying. On the other hand, when boron is contained in the protective layer, boron combines with oxygen to generate B ₂ O ₃ molecules during abrasion during sliding, so that no abrasion residue is left on the surface of the protective layer. Therefore, scratches and the like due to abrasive wear are unlikely to occur, and the protective layer has excellent sliding characteristics at low flying height.
Further, when hydrogen is contained in the protective layer, a polymer is formed on the protective layer, so that strain is released at a portion terminated by bonding with hydrogen, and there is an effect of relaxing stress in the film. Therefore, by adding hydrogen to the protective layer having high hardness to relieve stress, a protective layer having excellent adhesion can be obtained. As described above, by using a protective layer containing at least one element selected from the group consisting of silicon, boron, and hydrogen, a magnetic storage device having high recording density and high reliability can be achieved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a magnetic recording medium according to the present invention and a method for manufacturing the same will be described with reference to the drawings. FIG. 1 is a configuration diagram of a magnetic recording medium for a hard disk that best illustrates the features of the present invention, and FIG. 3 is a Raman spectrum of a protective layer having a nitrogen / carbon atomic ratio of 0.48 formed by sputter deposition under a high gas pressure by a high-frequency magnetron method shown in one embodiment of the present invention, and FIG. 4 shows one embodiment of the present invention. Raman spectrum of a protective layer with an atomic ratio of nitrogen / carbon of 0.055 formed by sputter deposition under a low gas pressure using a high-frequency magnetron method, and FIG. 5 shows the wear of the protective layer after 10M seeks in a seek test shown in this example. FIG. 6 is a diagram showing the relationship between the atomic number ratios of the samples having an amount of 3 mm or less, FIG. 6 is a configuration diagram of a magnetic storage device having the magnetic recording medium of the present invention, and Tables 1, 2, and 3 shown below are respectively Measured by X-ray photoelectron spectroscopy A surface element ratio representative protecting layer of Example.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[Embodiment] FIG. 1 shows the configuration of a typical magnetic recording medium of this embodiment. This magnetic recording medium has a Cr underlayer 2, a magnetic layer 3 made of a CoCr-based alloy on a non-magnetic base magnetic disk substrate 1, a protective layer 4 containing nitrogen and oxygen in carbon,
It is composed of a multilayer film in which perfluoropolyethyl-based lubricating layers 5 are sequentially laminated.

This magnetic recording medium is formed as samples having different atomic ratios of nitrogen / carbon and oxygen / nitrogen on the surface of the protective layer by sputter deposition of a graphite-like target of the type shown in Examples 1-3 below. did. The film thickness in each case
7 nm.

Further, in each of the examples, in order to change the atomic ratio of oxygen / nitrogen on the surface of the protective layer, oxygen plasma treatment and ultraviolet irradiation in the air were also performed. In the oxygen plasma treatment, plasma was generated at a power of 150 W from a high-frequency power supply in an atmosphere in which oxygen gas was introduced at 100 mTorr, and the sample was left for 4 minutes. For UV irradiation, a high-pressure mercury lamp equipped with a reflecting mirror was installed at a position 50 mm from the surface of the sample, and treatment was performed for 4 minutes at a power of 10 kW. By performing such a surface treatment, oxygen /
The atomic ratio of nitrogen was improved to 1.2 to 2 times before the treatment.

Example 1 In this example, a protective layer was formed by a reactive sputter deposition method using a DC magnetron electrode under the following conditions.

[0023]

[Table 4]

Comparative Example 1 A protective layer was formed using the same sputter deposition method using a DC magnetron electrode as in Example 1 under the condition that nitrogen gas was not introduced.

Example 2 In this example, a protective layer was formed by a reactive sputter deposition method using a high-frequency magnetron electrode under the following conditions. In this embodiment, the operating pressure during film formation was 30 mTorr and 5 mTorr. However, operating pressure is 5mTorr
Since the discharge in the gas phase is insufficient due to the lack of electrons in the gas phase, the operating pressure for one second from the start of the discharge was set to 30 mTorr.

[0026]

[Table 5]

[Embodiment 3] In this embodiment, a protective layer was formed by a reactive sputter deposition method using an asymmetric magnetron electrode under the following conditions. The sputter deposition using the asymmetric magnetron electrode used in this example is a method of controlling the magnet and the arrangement of the magnetron electrode and using the effect of the magnetic flux spreading between the electrodes to generate plasma. Electric current flowed.

[0028]

[Table 6]

Tables 1, 2, and 3 show the results of X-ray photoelectron spectroscopy measurements of the surface element ratios of the representative protective layers formed in Examples 1 to 3, respectively. These values were measured at photoelectron take-out angles of 90 and 30 degrees. The values shown in parentheses are values at an electron extraction angle of 30 degrees, and correspond to the element ratio near the outermost surface.

As a result, the nitrogen concentration of the sample of Example 2 when formed at a high gas pressure was the highest, about 30 at%
The value of was shown. This is because active nitrogen molecules were generated at a high concentration during sputter deposition by high-frequency discharge. In the sample of Example 2, one in which the operating pressure at the time of film formation was lowered,
The nitrogen concentration was 15-20at% due to the etching effect by the self-bias generated on the substrate.

Next, a perfluoropolyethyl-based lubricant was applied to a thickness of 2 nm on the magnetic disks provided with the protective layers formed in Examples 1 to 3 and Comparative Example 1. Thereafter, the disk was rotated at 6300 rpm in an atmosphere reduced to 0.5 atm, and the magnetic head was pressed with a load of 3 g to perform a seek test at a speed of 20 Hz. FIG. 2 summarizes the results of measurement of the wear amount of the protective layer after a seek operation of 10M by an ellipsometer by a seek test. From now on, the atomic ratio of nitrogen / carbon of the protective layer is 0.0
The wear resistance was remarkably improved in the samples of 5 to 0.3.

On the other hand, in the sample having an atomic ratio of nitrogen / carbon exceeding 0.30, scratch marks were generated on the protective layer immediately after the start of the seek test. Therefore, the atomic ratio of nitrogen / carbon is
When the Raman spectrum was measured for a sample exceeding 0.3, emission of fluorescence due to the released nitrogen compound was observed. For example, FIG. 3 shows a Raman spectrum measured with a protective layer having an atomic ratio of nitrogen / carbon of 0.48. The background was greatly inclined due to the fluorescence emitted from the free nitrogen compound. This sample was sputter-deposited under a high gas pressure with a high-frequency magnetron electrode, and the abrasion resistance by the seek test was extremely short because the continuity of the protective layer was lost due to the presence of the free nitrogen compound. However, in the sample formed at a low operating pressure even by reactive sputtering deposition using a high-frequency magnetron, no background gradient due to Raman spectrum fluorescence was observed as shown in FIG. 4, and the nitrogen / carbon atomic ratio was 0.2 or less. Met.
If the operating pressure is lowered even in the high-frequency discharge, a self-bias is generated in the substrate, and the free nitrogen compound is decomposed by the ion bombardment during the sputter deposition, so that the durability in the seek test is improved.

Generally, in a low-load seek test using a lightweight head for a protective layer having a thickness of 10 nm or less, the main factor governing the sliding resistance is not the mechanical strength but the chemical property of the protective layer surface and the lubricant. Action. Therefore, it is necessary to pay more attention to the structure and chemical properties of the surface than to the inside of the protective layer. Therefore, increasing the mechanical strength of the protective layer is not enough to improve the durability of the magnetic disk, and it is necessary to optimize the chemical composition of the surface of the protective layer at the interface between the protective layer and the lubricating layer.

FIG. 5 shows the results of plotting the atomic ratios of the samples in which the protective layer abrasion after 10M seeks was 3 ° or less in the seek test of this embodiment. As described above, in the seek test using the magnetic head, the effect of the interaction between the protective layer and the lubricating layer is large, and in addition to the atomic ratio of nitrogen / carbon in the protective layer, the chemical effect on the surface of the protective layer at the interface between the lubricating layer and the protective layer. The life was also changed by the difference in composition. As a result, in the seek test, the wear ratio of the protective layer after the 10M seek operation was 3 mm or less, and the nitrogen / carbon atomic ratio of the sample was 0.05 to 0.3, and
The atomic ratio of oxygen / nitrogen on the surface is in the range of 0.5 to 1.0, and the atomic ratio of silicon, boron, hydrogen and carbon is each 0.1.
It was in the range of 07-0.28. Another feature of the sample with high durability in the seek test is that the center line average roughness of the untextured surface is low.
It was extremely smooth at 1 nm or less.

Embodiment 4 An embodiment of the present invention will be described with reference to FIG. This device comprises a magnetic head 6 and a driving unit 7 thereof.
And a recording / reproducing signal processing means 9 for the magnetic head 8, a magnetic recording medium 10, and a driving unit 11 for rotating the magnetic recording medium 10. The magnetic head 6 is a composite head having both an electromagnetic induction type magnetic head for recording and a magnetoresistive effect type magnetic head for reproduction. In this magnetic storage device, a magnetic recording medium of the conditions in which the number of seeks exceeds 10M among the first, second, and third embodiments of the present invention is incorporated, and a head flying height of 30 is provided.
nm, linear recording density of 210 kBPI, track density of 9.6 kTPI was evaluated for recording and reproduction.
Good recording and reproducing characteristics were obtained for a recording density of 2 gigabits per square inch. In addition, the number of bit errors after 10 million head seek tests from the inner circumference to the outer circumference is 10 bits / surface or less for any magnetic recording medium, and the MTBF
In 150,000 hours.

Next, using a magnetic head 12 formed on a magnetic head slider having an air bearing surface rail area of 1.25 square mm or less and a mass of 2 mg or less, the head flying height 30
The recording and reproduction were evaluated at nm, a linear recording density of 210 kBPI, and a track density of 9.6 kTPI. Also in this case, in the seek test shown in Examples of the present invention, good recording / reproducing characteristics were obtained at a recording density of 2 gigabits per square inch with respect to a magnetic recording medium having a protective layer abrasion of 3 mm or less after 10M seeks. Was done. Also, the number of bit errors after 10 million head seek tests from the inner circumference to the outer circumference was 10 bits / surface or less in any of the magnetic recording media, and 150,000 hours of MTBF could be achieved.

As described above, in Examples 1, 2, and 3 of the present invention, in the magnetic storage device incorporating the magnetic recording medium in which the wear amount of the protective layer after 10M seeks in the seek test is 3 mm or less, the protective layer However, high reliability was obtained even when the recording density became thin and the recording density became high.

[0038]

As described above, according to the present invention, the chemical reaction on the surface of the protective layer containing at least one element selected from the group consisting of silicon, boron and hydrogen while containing carbon, nitrogen and oxygen is performed. By optimizing the composition, the bonding force of the lubricant can be strengthened, so that a highly reliable magnetic recording medium can be provided even when the protective layer is thin and has a high recording density.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a magnetic recording medium of the present invention.

FIG. 2 is a view showing the results of measurement of the wear amount of a protective layer after a 10M seek operation by an ellipsometer in a seek test shown in Examples of the present invention.

FIG. 3 shows a nitrogen / nitrogen film formed by sputter deposition under a high gas pressure by a high-frequency magnetron method showing an embodiment of the present invention.
Raman spectrum of a protective layer having a carbon atom ratio of 0.48.

FIG. 4 shows a nitrogen / nitrogen film formed by sputter deposition under a low gas pressure by a high-frequency magnetron system showing an embodiment of the present invention.
Raman spectrum of a protective layer having a carbon atom ratio of 0.15.

FIG. 5 is a diagram showing the relationship between the atomic ratios of samples in which the amount of wear of the protective layer after 10M seeks was 3 ° or less in the seek test shown in Examples of the present invention.

FIG. 6 is a configuration diagram of a magnetic storage device of the present invention using the magnetic recording medium of the present invention.

[Explanation of symbols]

1 ... substrate, 2 ... Cr-based underlayer, 3 ... CoCr-based magnetic layer, 4 ... Protective layer containing carbon, nitrogen and oxygen and at least one element selected from the group consisting of silicon, boron and hydrogen ,Five…
Lubricating layer, 6: magnetic head, 7: magnetic head driving unit, 8: recording / reproducing signal processing system, 9: magnetic recording medium, 10: magnetic recording medium driving unit, 11: base.

Claims (7)

[Claims] 1. A magnetic recording medium having a magnetic layer on a substrate and a protective layer formed on the magnetic layer, wherein the protective layer contains at least carbon, nitrogen and oxygen, and further comprises silicon, boron,
A film containing at least one element selected from the group consisting of hydrogen, wherein the nitrogen / carbon atomic ratio of the film is 0.05
A magnetic recording medium, wherein the atomic ratio of oxygen / nitrogen on the surface of the film is in the range of 0.1 to 2.5. 2. The method according to claim 1, wherein the silicon / carbon atomic ratio is 0.07 or more and 0.28 or more.
2. The magnetic recording medium according to claim 1, wherein: 3. The method according to claim 1, wherein the atomic ratio of boron / carbon is 0.07 or more and 0.28 or more.
2. The magnetic recording medium according to claim 1, wherein: 4. The method according to claim 1, wherein the atomic ratio of hydrogen / carbon is 0.07 or more and 0.28 or more.
2. The magnetic recording medium according to claim 1, wherein: 5. The magnetic recording medium according to claim 1, wherein the thickness of the protective layer is 10 nm or less, and the center line average roughness Ra of the surface is 1 nm or less. 6. A magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head comprising a recording unit and a reproducing unit, means for moving the magnetic head relative to the magnetic recording medium, In a magnetic storage device having recording / reproduction signal processing means for performing signal input to a magnetic head and reproduction of an output signal from the magnetic head, a reproduction unit of the magnetic head is constituted by a magnetoresistive magnetic head, and A magnetic storage device comprising the magnetic recording medium according to claim 1, 2, 3, 4 or 5. 7. A magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head comprising a recording unit and a reproducing unit, means for moving the magnetic head relative to the magnetic recording medium, In a magnetic storage device having recording / reproduction signal processing means for performing signal input to a magnetic head and reproduction of an output signal from the magnetic head, the magnetic head has an air bearing surface rail area of 1.25 mm2 or less and a mass of 2 mg or less. A magnetic storage device formed on a magnetic head slider, wherein the magnetic recording medium is constituted by the magnetic recording medium according to claim 1, 2, 3, 4, or 5.