JP2752332B2 - Magnetic recording media - Google Patents

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 magnetic disk drive or the like.

[0002]

2. Description of the Related Art In recent years, the amount of information recorded on a magnetic recording medium in a magnetic disk device or the like has increased remarkably, and the characteristics required for the magnetic recording medium have become increasingly severe. This magnetic recording medium has a magnetic layer with excellent magnetic properties and electromagnetic conversion properties, a low frictional force when contacting and sliding with the magnetic head, high abrasion resistance, hard to cause head crash, and corrosion resistance. An excellent protective layer is required.
Therefore, recently, a magnetic recording medium is often formed by forming a magnetic layer on a nonmagnetic substrate, forming a protective layer, and further forming a lubricating layer as necessary. For example, in Japanese Patent Application Laid-Open No. 61-73227, after a CoNiP magnetic layer is provided on an Al substrate on which a Ni-P layer is provided in advance, a particle size of 30 nm is obtained.
There is disclosed a magnetic recording medium provided with a silicon oxide polymer protective layer in which hard fine particles of 0-500 angstroms of γ-alumina fine particles are dispersed, and further provided with a perfluoropolyether lubricating layer in order. This Japanese Patent Application Laid-Open
JP-A-73227 describes that the hardness of the protective layer is increased and the durability to a contact start / stop (hereinafter referred to as CSS) test is improved by using the above-described structure of the magnetic recording medium. Here, the CSS test means that the rotation of the magnetic recording medium is started in a state where the magnetic recording medium and the magnetic head are in contact with each other, and the rotation causes the magnetic head to fly while sliding on the magnetic recording medium, and for a predetermined time. After the rotation, the rotation of the magnetic recording medium is stopped, and the magnetic head is again brought into contact with the magnetic recording medium. Thereafter, the rotation start / stop is repeated, and the magnetic recording medium has passed several CSS times. After that, it is a test for examining whether a breakage or an increase in friction coefficient is caused, and evaluating the durability of the magnetic recording medium.

[0003]

However, when the durability of a magnetic recording medium having the above-described structure is evaluated by a CSS test in a low humidity atmosphere (hereinafter referred to as CSS durability), the magnetic recording medium exhibits appropriate CSS durability. C in an atmosphere with high humidity, for example, an atmosphere at a relative temperature of 90% and a temperature of 30 ° C.
When the SS durability is evaluated, the CSS durability remarkably decreases. For example, the coefficient of static friction with the magnetic head starts to increase when the number of CSSs is several hundred, and when the number of CSSs is several thousand, the magnetic head comes to the surface of the magnetic recording medium. The phenomenon of sticking occurs, and a head crash often occurs.

If such a magnetic recording medium having no CSS durability is used in a humid environment, such as in the rainy season or summer in Japan, the magnetic disk device becomes unusable. Was a problem.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a magnetic recording medium having excellent durability even in a high humidity environment.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and comprises a magnetic layer and a protective layer formed sequentially on a non-magnetic substrate, wherein the protective layer is formed of a metal oxide. In a magnetic recording medium comprising a film and hard fine particles dispersed in the metal oxide film, in the protective layer, the thickness of the region of the metal oxide film where no hard fine particles exist between the hard fine particles Is 50 to 400 angstroms, and the hard fine particles include a plurality of types of hard particles having different particle diameters.
A magnetic recording medium comprising fine particles .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG.

Embodiment 1 FIG. 1 is a partial sectional view of a magnetic recording medium according to the present embodiment. The magnetic recording medium comprises an underlayer 2, a magnetic layer 3, and a protective layer 4 on a non-magnetic substrate 1. And a lubricating layer 5. The protective layer 4 includes a metal oxide film 6 using silicon oxide as a metal oxide, and hard fine particles dispersed in the metal oxide film 6. 2 having different average particle sizes
The hard fine particles (silica fine particles) are composed of various kinds of hard fine particles, that is, silica fine particles 7 having an average particle diameter of 300 angstroms and silica fine particles 8 having an average particle diameter of 3000 angstroms. (Ie, the average size of a group of hard fine particles (silica fine particles) including hard fine particles (silica fine particles) having different diameters in the vertical and horizontal directions).

In the protective layer 4, the thickness of the region of the metal oxide film 6 where the hard fine particles (silica fine particles 7, 8) do not exist between the hard fine particles is limited in the range of the present invention (50 to 50). 40
0 Å), and the density of the silica fine particles 7 is 20 particles / 1.
The existing density of the μm square and the silica fine particles 8 is 0.1 / μm square.

This magnetic recording medium was manufactured as follows. That is, an aluminum alloy plate having a diameter of 130 mm, a central hole diameter of 40 mm, and a thickness of 1.9 mm (surface roughness: 80 Å), both of whose main surfaces are mirror-polished first.
Is prepared by alumite treatment, and a 1000 Å thick C film is formed on the substrate 1 by a sputtering method using a Cr target and Ar gas.
An underlayer 2 made of an r film was formed.

Next, a film thickness of 6 is formed on the underlayer 2 by a sputtering method using a CoNiCr target and Ar gas.
A magnetic layer 3 made of a 00 Å CoNiCr film was formed.

Next, a metal alkoxide, tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ), water, methanol, acetic acid and formamide are mixed at a molar ratio of 1/2/10 / 0.1 /
0.1 and a solution having an average particle size of 3
00 angstroms (the average particle size is a particle size distribution analyzer Coulter Counter N4 manufactured by Coulter Counter Co., Ltd.)
Was measured. The same applies hereinafter) to a solution obtained by dispersing 15% by weight of each of the silica fine particles 7) and silica fine particles 8 having an average particle diameter of 3000 Å in methanol at a ratio of 100/1, and mixing the resulting mixed liquid. After spin coating on the magnetic layer 3, 29
Heat treatment at 0 ° C. for 30 minutes to convert tetraethoxysilane, which is a metal alkoxide, to silicon oxide, which is a metal oxide, to form a metal oxide film 6. The protective layer 4 in which the fine particles 8 were dispersed was obtained. The thickness of the region of the metal oxide film 6 in the protective layer 4 where the silica fine particles are not present between the hard fine particles is about 150 angstroms as described above, and the density of the silica fine particles measured by the scanning electron microscope is as follows. And silica fine particles 7 having an average particle size of 300 Å as described above.
About 20 pieces / 1 μm square, average particle size 300
0.1 Å for silica fine particles 8 of 0 Å
Pieces / μm square.

Next, a fluorinated oil (KRYTOX 157 manufactured by DuPont) is applied on the protective layer 4 by spin coating.
FSH) was applied to form a lubricating layer 5 having a thickness of about 15 angstroms, thereby obtaining a target magnetic recording medium.

The obtained magnetic recording medium of this embodiment was subjected to a CSS test, and the output voltage of the magnetic head was measured. These results will be described later in detail together with the results of the magnetic recording media of Comparative Examples 1 to 3 described later.

Comparative Example 1 Only silica fine particles having an average particle size of 300 Å were used as the hard fine particles, and the existing density was 50 particles / 1.
A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1 except that the square was set to μm square.

Comparative Example 2 Only fine silica particles having an average particle size of 2000 Å were used as the hard fine particles, and the existing density was 10 particles /
A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1 except that the square was 1 μm.

Comparative Example 3 Only fine silica particles having an average particle size of 4000 Å were used as the hard fine particles, and the density of the fine particles was 10 particles /
A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1 except that the square was 1 μm.

Next, for each of the ten magnetic recording media of Examples 1 and 2 and Comparative Example 1,
Using a magnetic head having an iC slider, a CSS test was performed in an atmosphere having an average relative humidity of 90% and an average temperature of 30 ° C., and the results of evaluating the CSS durability were as follows.

The magnetic recording medium of the first embodiment not only withstands the number of CSSs of 10,000 or more for all ten sheets,
Even after 10,000 CSS cycles, the coefficient of static friction with the magnetic head was an extremely small value of about 0.5 on average. In addition, the magnetic head did not stick to the surface of the magnetic recording medium, and no head crash occurred.

On the other hand, the magnetic recording medium of Comparative Example 1
The coefficient of static friction with the magnetic head starts to increase from about 100 times of CSS, and 500 out of four out of ten sheets.
With a CSS count of ~ 1000, the static friction coefficient is
The torque value of the motor of the durability evaluation device was larger than the value obtained by dividing the torque between the rotation axis of the motor and the magnetic head, and the measurement became impossible. The remaining six cards caused a head crash at the CSS count of 500 to 1000 times. The coefficient of static friction with the magnetic head immediately before the head crash was 2.0 or more.

From the above results, it was clarified that the magnetic recording medium of Example 1 was excellent in CSS durability even in an atmosphere having a higher humidity than that of Comparative Example 1.

Next, with respect to the magnetic recording medium of Example 1 and the magnetic recording media of Comparative Examples 2 and 3, to evaluate the degree of spacing loss (decrease in recording density due to an increase in the distance between the head and the magnetic recording medium), The output of the magnetic head was measured. In this measurement, an RD008 media certifier (using a monolithic type magnetic head) manufactured by Adelphi Corporation in the United States was used as a measuring instrument, and the distance between the head and the surface of the magnetic recording medium (so-called flying height) was set to 2000 Å. . As a result, Example 1
Magnetic recording medium, the output voltage of the magnetic head is 0.4
In contrast, in the case of the magnetic recording media of Comparative Examples 2 and 3, the output voltage of the magnetic head was 0.25 mV,
0.15 mV, indicating that the spacing loss of the magnetic recording medium of Example 1 was smaller than that of the magnetic recording medium of Comparative Example.

While the present invention has been described with reference to the embodiment, the present invention includes the following modifications and application examples.

(1) In the examples, tetraethoxysilane was used as a raw material for forming a metal oxide film made of silicon oxide, but a partial or complete hydrolyzate thereof may be used. As long as a silicon oxide is formed by a sol-gel method, another silicon alkoxide or a partial or complete hydrolyzate thereof may be used. Such examples include tetraalkoxysilanes such as tetramethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, and tetra-tert-butoxysilane. And silicon alkoxides such as monoalkyl trialkoxy silanes, dialkyl dialkoxy silanes and trialkyl monoalkoxy silanes in which 1 to 3 of the alkoxy groups of these tetraalkoxy silanes are substituted with alkyl groups, and partial or complete hydrolysates thereof Is mentioned.

The metal oxide film may be formed of aluminum oxide, and the film made of this aluminum oxide is also formed by a sol-gel method using aluminum alkoxide or its partial or complete hydrolyzate. Examples of these include aluminum triethoxy, aluminum trimethoxy, aluminum tri-n-propoxy,
Trialkoxyaluminums such as tri-i-propoxyaluminum and tri-n-butoxyaluminum, and one of the alkoxy groups of these trialkoxyaluminums
Alkoxides of aluminum such as monoalkyldialkoxyaluminum and dialkylmonoalkoxyaluminum, in which .about.2 are substituted with alkyl groups, and partially or completely hydrolyzed products thereof. Further, as the metal alkoxide, an alkoxide such as tantalum, tungsten, tin, zirconium, and titanium and a partial or complete hydrolyzate thereof may be used to form a metal oxide film. Here, metal oxides include semi-metal oxides including the above-described silica oxides and the like.

The film made of a metal oxide such as silicon, aluminum, tantalum, tungsten, tin, zirconium, and titanium may be formed by a method other than the sol-gel method using a metal alkoxide. Note that two or more kinds of metal oxides constituting the metal oxide film may be used.

In the embodiment, a mixture of tetraethoxysilane, water, methanol, acetic acid and formamide is used for forming a metal oxide film made of silicon oxide. One or both of acetic acid and formamide are used. Can be omitted. Alternatively, a solution containing a hydrolyzate of a metal alkoxide may be obtained by taking in water (steam) in the atmosphere without actively using water. Ethyl alcohol, butyl alcohol, or the like may be used instead of methanol.

(2) In the examples, silica fine particles were used as the hard fine particles dispersed in the metal oxide film. However, other inorganic fine particles may be used as long as they have hardness. Examples include alumina, zirconia, titania,
Fine particles such as silicon carbide and tungsten carbide can be used. Two or more different types of hard fine particles can be used.

(3) In the embodiment , the hard fine particles in the protective layer
Although the thickness of the region of the metal oxide film hard particles do not exist between was 150 Å, in the present invention,
This thickness is limited to the range of 50-400 Angstroms.

The reason is that if the thickness is less than 50 angstroms, the metal oxide film becomes too thin and the force for holding the hard fine particles is reduced, and the CSS durability is deteriorated. If it exceeds 400 angstroms, the spacing loss is reduced. This is because a problem occurs.

(4) In the examples, hard fine particles having an average particle diameter of 300 angstroms were used as hard fine particles having a small average particle diameter, and hard fine particles having an average particle diameter of 3000 angstroms were used as hard fine particles having a large average particle diameter.
The former hard fine particles having a small average particle size have an average particle size of 200 to
The hard fine particles having a large average particle size can be selected in the range of 1000 Å, and the latter hard fine particles having a large average particle size can be selected in the range of 1,000 to 5,000 Å (however, both hard fine particles having an average particle size of 1000 Å must be used. Can not).

The density of the hard particles having an average particle diameter of 200 to 1000 angstroms was set to 20 particles /
Although 1 μm square was used, in the present invention, the existence density is preferably in the range of 10 to 500 pieces / 1 μm square.

The reason is that if the number of squares is less than 10 pieces / 1 μm square, CSS under high humidity (for example, 90% relative humidity)
In the test, the coefficient of static friction starts to increase rapidly after several hundred CSS cycles, and when it exceeds 500 pieces / μm square, the coefficient of static friction tends to increase due to the continuation of the CSS test, and there is a problem of spacing loss. Because it may

The density of the hard particles having an average particle diameter of 1,000 to 5,000 angstroms was set to 0.1 particles / 1 μm square in the examples, but the density of the hard particles is 0.01 to 10 particles / 1 μm in the present invention. It is preferably within the range of square. The reason is 0.01 /
If it is less than 1 μm square, the hard fine particles are displaced by the continuation of the CSS test and the coefficient of static friction tends to increase, and if it exceeds 10 particles / 1 μm square, a problem of spacing loss may occur. is there.

That is, by setting the range of the average particle size and the range of the existence density of the two types of hard fine particles having different average particle sizes as described above, the increase in the coefficient of static friction is extremely small even when the CSS frequency is repeated. It is possible to obtain a magnetic recording medium that is particularly excellent in durability and has a particularly small spacing loss.

(5) In the examples, two types of hard fine particles having different average particle diameters were used as the hard fine particles.
Hard particles of more than one kind can also be used.

(6) In the embodiment, the aluminum alloy plate is used as the non-magnetic substrate, but other materials such as metal other than aluminum alloy, glass, alumina, ceramic, plastic and the like can also be used. .

(7) In the embodiment, CoNi is used as the magnetic layer.
Although the Cr film is formed, the magnetic layer may be made of another Co-based alloy such as CoNi, CoPt, and CoP, or a magnetic material such as Fe ₂ O ₃ .

(8) In the embodiment, the underlayer made of the Cr film is provided. However, as the material of the underlayer, Mo, Ti,
A non-magnetic material such as Ta can be used. The underlayer is not an essential layer, and its formation may be omitted in some cases.

(9) In the embodiment, the protective layer is formed directly on the magnetic layer. However, one or more metal films such as Cr or metal oxide films such as chromium oxide are provided between the magnetic layer and the protective layer. The chemical durability of the magnetic layer may be further improved by interposing the layer.

(10) In the embodiment, the fluorinated oil is used as the material of the lubricating layer. However, a fluorocarbon liquid lubricant or a lubricant comprising an alkali metal salt of sulfonic acid may be used. The lubricating layer is not an essential layer, and its formation may be omitted in some cases.

[0042]

As described above in detail, according to the present invention, the thickness of the protective layer in the region where the hard fine particles are not present is selected to a predetermined value, so that the CSS has excellent CSS durability under high humidity, and A magnetic recording medium free from spacing loss has been provided.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a magnetic recording medium according to a first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 2 Underlayer 3 Magnetic layer 4 Protective layer 5 Lubrication layer 6 Metal oxide film 7,8 Silica fine particles

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/72 G11B 5/66

Claims (2)

(57) [Claims] A magnetic layer and a protective layer are sequentially formed on a non-magnetic substrate, wherein the protective layer comprises a metal oxide film and hard fine particles dispersed in the metal oxide film. In the magnetic recording medium, in the protective layer, the thickness of the region of the metal oxide film in which the hard fine particles are not present between the hard fine particles is 50 to 400 Å, and the hard fine particles have a plurality of types having different particle diameters. Hard fine particles
The magnetic recording medium characterized in that it consists of. 2. The magnetic recording medium according to claim 1, wherein irregularities are formed on the surface of the protective layer .