JP2752331B2 - 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-mentioned object, and comprises a magnetic layer formed by sequentially forming a magnetic layer, a first protective layer and a second protective layer on a non-magnetic substrate. In the recording medium, the first protective layer includes at least one film selected from chromium and chromium oxide,
The second protective layer includes a plurality of types of hard fine particles having different particle sizes.
A magnetic recording medium comprising a metal oxide film containing in a dispersed state .

[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 has an underlayer 2, a magnetic layer 3, a first protective layer A layer 4a, a second protective layer 4b, and a lubricating layer 5 are sequentially provided. The first protective layer 4a is made of a chromium film having a thickness of 50 angstroms. The second protective layer 4b includes a metal oxide film 6 using silicon oxide as a metal oxide, and two types of hard fine particles dispersed in the metal oxide film 6 and having different average particle diameters, It is composed of silica fine particles 7 having an average particle size of 300 angstroms and silica fine particles 8 having an average particle size of 3000 angstroms. (Here, the average particle size means an average size of hard fine particles (silica fine particles), that is, a vertical size. And the width mean 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 second protective layer 4b, the thickness of the region of the metal oxide film 6 where the hard silica particles 7, 8 are not present is 150 angstroms, and the density of the silica particles 7 is 20 particles / 1 μm square. The existing density of the silica fine particles 8 is 0.1 particles / 1 μ.
m 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 50 angstrom thick Cr film is formed by sputtering using a Cr target and Ar gas.
A first protective layer 4a made of a film was formed. The first protective layer 4a is used for removing the moisture contained in the outside air into the lubricating layer 5 and the second protective layer 4b.
The magnetic layer 3 is provided to prevent the magnetic layer 3 from entering the magnetic layer 3 through the layer and to further improve the chemical durability of the magnetic layer.

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 to the following), and a solution obtained by dispersing 15% by weight of each of the silica fine particles 7 and the silica fine particles 8 having an average particle diameter of 3000 angstrom in methanol at a ratio of 100 wt. Is applied on the first protective layer 4a by spin coating, and then heat-treated at 290 ° C. for 30 minutes to convert tetraethoxysilane, which is a metal alkoxide, to silicon oxide, which is a metal oxide. Was formed to obtain a second protective layer 4b in which silica fine particles 7 and silica fine particles 8 were dispersed in the metal oxide film 6. The thickness of the region of the metal oxide film 6 in which the silica fine particles do not exist in the second protective layer 4b is:
As described above, the density of the silica fine particles measured by a scanning electron microscope is about 150 angstroms. As described above, the silica fine particles 7 having an average particle diameter of 300 angstroms have a size of 20 particles / 1 μm square and an average particle diameter of 3
Regarding the silica fine particles 8 of 000 angstroms, the size was 0.1 / μm square.

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

Next, a CSS test was performed on each of the ten magnetic recording media of Example 1 in an atmosphere having an average relative humidity of 90% and an average temperature of 30 ° C. using a magnetic head having an AlTiC slider. As a result, the magnetic recording medium of Example 1 was found to have a total of 1
Each of the 0 sheets not only endured the number of CSSs of 10,000 or more, but even after the number of CSSs of 10,000, 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.

From the above results, it was clarified that the magnetic recording medium of Example 1 had excellent CSS durability even in a high humidity atmosphere.

Next, for the magnetic recording medium of Example 1, the output of the magnetic head was measured in order 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). In this measurement, a RD008 media certifier manufactured by Adelphi Corporation (using a monolithic magnetic head) was used as a measuring device.
And the distance between the head and the surface of the magnetic recording medium (the so-called flying height) was set to 2000 angstroms. As a result, in the case of the magnetic recording medium of Example 1, the output voltage of the magnetic head was 0.4 mV, and it became clear that the magnetic recording medium of Example 1 had a small spacing loss.

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

(1) In the embodiment, tetraethoxysilane was used as a raw material for forming a metal oxide film made of silicon oxide in the second protective layer, but a partial or complete hydrolyzate thereof was used. Alternatively, any other silicon alkoxide or its partial or complete hydrolyzate may be used as long as it forms a silicon oxide by a so-called sol-gel method. Such examples include tetramethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-
tetra-alkoxy silanes such as sec-butoxy silane and tetra-tert-butoxy silane, and monoalkyl trialkoxy silanes, dialkyl dialkoxy silanes and trialkyls in which 1 to 3 of the alkoxy groups of these tetraalkoxy silanes are substituted with alkyl groups Examples include silicon alkoxides such as monoalkoxysilanes and their partial or complete hydrolysates.

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, the metal oxide film includes a metal oxide such as a silicon oxide as described above.

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. However, 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 embodiment, silica fine particles are used as the hard fine particles dispersed in the metal oxide film, but other inorganic fine particles may be used as long as they have a hard property. 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 thickness of the first protective layer is set to 50
Although the thickness was set to be Å, it is preferable that the thickness be in the range of 30 to 80 Å. The reason is,
If the thickness is less than 30 angstroms, the function of protecting the magnetic layer tends to decrease, and if it exceeds 80 angstroms, the spacing loss increases and the porcelain characteristics tend to deteriorate.

Further, in the embodiment, the thickness of the region of the metal oxide film in which the hard fine particles are not present in the second protective layer is set to 150 Å, but this thickness is preferably set in the range of 50 to 400 Å. .

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 becomes small, and the CSS durability may be deteriorated. This is because a pacing loss problem may occur.

(4) In the examples, hard fine particles having an average particle size of 300 Å were used as the hard fine particles having a small average particle size, and hard fine particles having an average particle size of 3,000 Å were used as the hard fine particles having a large average particle size.
The former hard fine particles having a small average particle size have an average particle size of 200 to
The hard hard fine particles having a large average particle diameter can be selected from the range of 1000 angstrom.
It can be selected in the range of 00 angstroms.

The density of the hard fine 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 is set to 0.1 particles / 1 μm square in the embodiment, but in the present invention, the density is 0.01 to 10 particles / 1 μm. 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 diameter and the range of the existing density of the two types of hard fine particles having different average particle diameters as described above, the increase in the coefficient of static friction is extremely small even if 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 kinds of hard fine particles having different average particle diameters were used as the hard fine particles. However, other than the above two kinds of hard fine particles, other hard fine particles may be used as long as the object of the present invention is not impaired.
Hard particles of more than one kind can also be used. Also, one kind of hard fine particles can be used.

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

(7) In the embodiment, the magnetic layer is made of CoNi.
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 Cr metal film is formed as the first protective layer on the magnetic layer. However, one or more chromium oxide films may be provided.

(10) Although the fluorinated oil is used as the material of the lubricating layer in the embodiment, a fluorocarbon-based liquid lubricant or a lubricant composed of 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.

[0037]

As described in detail above, according to the present invention, the provision of the first protective layer prevents moisture contained in the outside air from entering the magnetic layer via the second protective layer. The chemical durability of the layer is maintained. As a result, a magnetic recording medium having excellent CSS durability under high humidity and having no problem of spacing loss was 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 4a First protective layer 4b Second protective layer 5 Lubricating 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] 1. A magnetic recording medium in which a magnetic layer, a first protective layer and a second protective layer are sequentially formed on a non-magnetic substrate, wherein the first protective layer is at least one selected from chromium and chromium oxide. The second protective layer comprises a plurality of types of hard fine particles having different particle sizes.
A magnetic recording medium comprising a metal oxide film containing in a dispersed state . 2. The magnetic recording medium according to claim 1, wherein irregularities are formed on the surface of the protective layer .