JPH02137120A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve CSS durability by consisting a protective layer of a metal oxide film and specific fine hard particles dispersed in the metal oxide film. CONSTITUTION:This recording medium is constituted by providing an underlying layer 2, a magnetic layer 3, the protective layer 4, and a lubricating layer 5 successively on a nonmagnetic substrate 1 and the protective layer 4 consists of the metal oxide film 6 in which a silicon oxide is used as the metal oxide and two kinds of the fine hard particles which are dispersed in the metal oxide film 6 and very in average grain size. Namely, the thickness in the region of the metal oxide film 6 where the fine hard particles in the protective layer 4 do not exist is 50 to 400Angstrom and the fine hard particles are constituted of at least two kinds of the fine hard particles 7, 8 which contain the fine hard particles 7 having 200 to 1,000Angstrom average grain size and the fine hard particles 8 having 1,000 to 5,000Angstrom average grain size and vary in the average grain sizes. The fine hard particles 7 of 200 to 1,000Angstrom average grain size are made to exist in the protective layer 4 at 10 to 500 pieces per 1mum<2> and the fine hard particle 8 of 1,000 to 5,000Angstrom average grain size are made to exist at 0.01 to 10 pieces per 1mum<2> therein. The excellent durability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium used in a magnetic disk device or the like.

[Prior Art] In recent years, the amount of information recorded on magnetic recording media in magnetic disk drives and the like has increased significantly, and the characteristics required of magnetic recording media have become increasingly strict. This magnetic recording medium has a magnetic layer with excellent magnetic properties and electromagnetic conversion properties, low frictional force during contact with the magnetic head and sliding, high wear resistance, less head crash, and corrosion resistance. An excellent protective layer is required. For this reason, recently, a magnetic recording medium is often constructed by forming a magnetic layer on a nonmagnetic substrate, then forming a protective layer, and further forming a lubricating layer if necessary. For example, JP-A-61-73227
In the publication, Co is deposited on an A1 substrate on which an N1-P layer is provided in advance.
After forming the N1P magnetic layer, the γ-
A magnetic recording medium is disclosed in which a silicon oxide polymer protective layer in which hard fine particles made of fine alumina particles are dispersed is provided, and a perfluoropolyether lubricating layer is sequentially provided. This Japanese Patent Application Laid-Open No. 61-73227 discloses that by making the magnetic recording medium as described above, the hardness of the protective layer is increased, resulting in contact start/stop (hereinafter referred to as C8S).
It is stated that durability against tests is improved. Here, the C8S test means that the magnetic recording medium starts to rotate with the magnetic recording medium and the magnetic head in contact with each other, and this rotation causes the magnetic head to float while sliding on the magnetic recording medium, and then for a predetermined period of time. After the rotation, the rotation of the magnetic recording medium is stopped and the magnetic head is brought into contact with the magnetic recording medium again. From then on, this rotation start and stop is repeated, and it is determined how many C8S cycles the magnetic recording medium has undergone. This is a test to evaluate the durability of a magnetic recording medium by examining whether damage or an increase in the coefficient of friction occurs after the magnetic recording medium.

[Problems to be Solved by the Invention] However, when the magnetic recording medium having the above-mentioned configuration is evaluated for durability by a C8S test (hereinafter referred to as C8S durability) in a low-humidity atmosphere, it shows a reasonable C8S durability. In a humid atmosphere, for example at a relative temperature of 3.
When evaluating C8S durability in an atmosphere of 0'C, C8S
Durability decreases significantly, for example, after several hundred C8S cycles, the coefficient of static friction with the magnetic head begins to increase, and
After 00 C8S cycles, a phenomenon occurs in which the magnetic head sticks to the surface of the magnetic recording medium, and head crashes often occur.

And such C8S non-durable magnetic recording media,
This has become a serious problem, especially when used in a humid environment such as during the rainy season or summer in Japan, as the magnetic disk drive becomes unusable.

The present invention has been made to solve these problems, and its purpose is to provide a magnetic recording medium that has excellent durability even in a humid environment.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and includes a magnetic layer and a protective layer formed sequentially on a non-magnetic substrate, the protective layer being made of a metal oxide. A magnetic recording medium comprising a film and hard fine particles dispersed in the metal oxide film, wherein the thickness of the region of the metal oxide film in which the hard fine particles are not present in the protective layer is 50 to 400 mm. and the hard fine particles have an average particle size of 200 to 1000 hard fine particles and an average particle size of 1
Consisting of at least two types of hard fine particles with different average particle sizes, including hard fine particles of 000 to 5000 people,
In the protective layer, the former hard fine particles with an average particle size of 200 to 1000 particles are 10 to 500 particles per 1 μm, and the latter hard fine particles with an average particle size of 1000 to 5000 particles are 1 μm0.
This is a magnetic recording medium characterized by the presence of 0.01 to 10 pieces.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to FIG.

Example 1 FIG. 1 shows a partial cross-sectional view of a magnetic recording medium according to this example. The protective layer 4 includes a metal oxide film 6 using silicon oxide as a metal oxide, and two types of particles having different average particle sizes dispersed in the metal oxide film 6. Silica fine particles 7 with an average particle size of 300, included in hard fine particles with an average particle size of 200 to 100OX defined in the present invention.
and silica fine particles 8 with an average particle size of 3000 particles, which are included in the hard fine particles with an average particle size of 1000 to 5000 particles defined in the present invention. This means the average size of a group of hard fine particles (silica fine particles), including hard fine particles (silica fine particles) that have different diameters in the vertical and horizontal directions.

In addition, in the protective layer 4, silica fine particles 7 which are hard fine particles
．． The thickness of the region of the metal oxide film 6 where 8 does not exist is 150 people included in the limited range of the present invention (50 to 400 500 pieces/200 pieces included in 1μm0)
1 m0, the density of silica fine particles 8 is within the limited range of the present invention (0°01 to 10 particles/1 μm0).
1 μm CI.

This magnetic recording medium was manufactured as follows. That is, first, an aluminum alloy plate (surface roughness: 180 mm) with a diameter of 130 mm, a central hole diameter of 40 mm, and a thickness of 1.9 m, whose ambidextrous surface was mirror polished, was anodized to prepare a special nonmagnetic substrate 1. Then, a film with a thickness of 1000 mm was formed on this substrate by sputtering using a Cr target and Ar gas.
A base layer 2 made of a human Cr film was formed.

Next, a Co film with a thickness of 600 nm was deposited on this underlayer 2 by sputtering using a CoNiCr target and Ar gas.
A magnetic layer 3 made of a NiCr film was formed.

Next, metal alkoxide tetraethoxysilane (S
i(OC2H5) 4), water, methanol, acetic acid, and formamide in a molar ratio of 1/2/1010.110.1
A solution prepared by mixing the following and silica fine particles 7 with an average particle size of 300 (the average particle size was measured using a particle size distribution analyzer Coulter Counter N4 manufactured by Coulter Counter Co., Ltd.) and a solution obtained by dispersing silica fine particles 8 with an average particle size of 3000 in methanol at a ratio of 15 wt % each, and the resulting mixed solution was applied onto the magnetic layer 3. After coating by a spin code method, a heat treatment is performed at 290° C. for 30 minutes to convert tetraethoxysilane, which is a metal alkoxide, into silicon oxide, which is a metal oxide, to form a metal oxide film 6. A protective layer 4 in which silica fine particles 7 and silica fine particles 8 were dispersed in 6 was obtained. The thickness of the area of the metal oxide film 6 in which no silica particles are present in the protective layer 4 is approximately 150 mm as described above, and the density of silica particles measured by a scanning electron microscope is the average thickness as described above. Particle size 30
For silica fine particles 7 of 0 people, the average particle diameter was 200 pieces/1 mO1, and for silica fine particles 8 of 3000 people, the average particle size was 0.1 pieces/1 μm0.

Next, a fluorinated oil (KRYTOX 157 FSH manufactured by DuPont) was applied onto the protective layer 4 by a spin code method.
) was coated to form a lubricating layer 5 with a thickness of approximately 15 mm, thereby obtaining the desired magnetic recording medium.

The obtained magnetic recording medium of this example was subjected to a C8S test, and the output voltage of the magnetic head was measured. These results will be detailed later together with the results for the magnetic recording media of Comparative Examples 1 to 4, which will be described later.

Comparative Example 1 A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1, except that only silica fine particles having an average particle size of 300 particles were used as hard fine particles, and the density was 500 particles/1 m0. .

Comparative Example 2 As hard fine particles, the average particle size was 200 to 1000.
Example 1 except that human silica particles with an average particle size of 300 and human silica particles with an average particle size of 800, which are contained in human hard particles, were used, and their density was set to 20 particles/1 μm0.
A magnetic recording medium of this comparative example was obtained in the same manner as described above.

Comparative Example 3 A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1, except that only silica fine particles having an average particle diameter of 2000 were used as the hard fine particles, and the density was set to 10 pieces/1 μm0.

Comparative Example 4 A magnetic recording medium of this comparative example was obtained in the same manner as in Example 1, except that only silica fine particles having an average particle size of 4000 were used as hard fine particles, and the density was set to 10 pieces/1 μm0. .

Next, ten sheets of each of the obtained magnetic recording media of Example 1 and Comparative Example 1.2 were heated to an average relative humidity of 90 using a magnetic head having an Aj2TiC slider.
%, the C8S test was conducted in an atmosphere with an average temperature of 30° C., and the results of evaluating the C8S durability are as follows.

The magnetic recording medium of Example 1 has a total capacity of 10,000 for all 10 sheets.
Not only did it withstand more than 10,000 C8S cycles, but even after 10,000 C8S cycles, the coefficient of static friction with the magnetic head was an extremely small value of about 0.5 on average. Furthermore, the magnetic head did not stick to the surface of the magnetic recording medium, and no head crash occurred.

On the other hand, for the magnetic recording medium of Comparative Example 1, the coefficient of static friction with the magnetic head started to increase after about 100 C8S cycles, and 4 of the 10 media stopped coming to a standstill after 500 to 1000 CSS cycles. The friction coefficient became larger than the value obtained by dividing the motor torque value of the C8S durability evaluation device by the distance between the motor's rotating shaft and the magnetic head, making it impossible to measure it. The remaining 6 cards caused head crashes after 500 to 1000 CSS cycles. In addition, the coefficient of static friction of the magnetic helad immediately before causing a head crash was 2.0 or more. In addition, in the magnetic recording medium of Comparative Example 2, the increase in the coefficient of static friction was more gradual than in Comparative Example 1, but 5 out of 10 had a C8S frequency of about 10.
At 00 times, the coefficient of static friction became greater than 2.

Of the remaining five discs, three had static friction coefficients exceeding 2 after 5,000 C8S cycles, and two suffered head crashes after approximately 5,000 cycles.

The above results revealed that the magnetic recording medium of Example 1 has superior C8S durability even in a humid atmosphere compared to that of Comparative Example 1.2.

Next, with respect to the magnetic recording medium of Example 1 and the magnetic recording medium of Comparative Example 3.4, in order to evaluate the degree of spacing loss (a decrease in recording density due to an increase in the distance between the head and the magnetic recording medium), The output was measured. The measuring device used in this measurement was RDOO manufactured by Adelphi Corporation in the United States.
A 8-media certifier (using a monolithic type magnetic head) was used, and the distance N between the head and the surface of the magnetic recording medium (so-called flying height) was set to 2000.

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, whereas in the case of Comparative Example 3.4.
In the case of the magnetic recording medium, the output voltage of the magnetic head was 0.25 mV and 0.15 mV, respectively, and it became clear that the magnetic recording medium of Example 1 had less bassing loss than that of the comparative example. .

Although the present invention has been described above with reference to Examples, the present invention includes the following modifications and applications.

(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 of tetraethoxysilane may also be used, or a so-called sol-gel method may be used. Other silicon alkoxides and their partial or complete hydrolysates may be used as long as they form silicon oxides. Examples of such include tetraalkoxysilanes such as tetramethoxysilane, tetra-n-propoxysilane, tetra-1-propoxysilane, tetra-n-butoxysilane, tetra-5ec-butoxysilane, and tetra-tert-butoxysilane. and silicon alkoxides such as monoalkyltrialkoxysilanes, dialkyldialkoxysilanes, and trialkylmonoalkoxysilanes in which 1 to 3 of the alkoxy groups of these tetraalkoxysilanes are substituted with alkyl groups, and their partial or complete hydrolysates. can be mentioned.

Further, the metal oxide film may be formed of aluminum oxide, and the film made of aluminum oxide is also formed by a sol-gel method using aluminum alkoxide or a partial or complete hydrolyzate thereof. Examples of these include trialkoxyaluminums such as triethoxyaluminum, trimethoxyaluminum, tri-n-propoxyaluminum, tri-n-propoxyaluminum, tri-n-butoxyaluminum, and 1 to 2 alkoxy groups of these trialkoxyaluminums. Alkoxides of aluminum such as monoalkyldialkoxyaluminum and dialkylmonoalkoxyaluminum in which is substituted with an alkyl group, and partial or complete hydrolysates thereof can be mentioned. Furthermore, a metal oxide film may be formed by using alkoxides such as tantalum, tungsten, tin, zirconium, and titanium, and partial or complete hydrolysates thereof as the metal alkoxide.

Films made of metal oxides such as silicon, aluminum, tantalum, tungsten, tin, zirconium, titanium, etc.
It may be formed by a method other than the above-mentioned sol-gel method using a metal alkoxide.

Note that two or more types of metal oxides may be used as the metal oxides constituting the metal oxide film.

In addition, in the examples, a mixture of tetraethoxysilane, water, methanol, acetic acid, and formamide was used to form a metal oxide film made of silicon oxide, but one or both of acetic acid and formamide may be used. Can be omitted.

Alternatively, a solution containing a metal alkoxide hydrolyzate may be obtained by taking in water (steam) from the atmosphere without actively using water. Moreover, ethyl alcohol, butyl alcohol, etc. may be used instead of the methanol.

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

(3) In the example, the thickness of the region of the metal oxide film in which hard fine particles are not present in the protective layer is 150 mm, but in the present invention, this thickness is limited to a range of 50 to 400 mm. .

The reason for this is that if there are fewer than 50 people, the metal oxide film becomes too thin and its ability to hold hard fine particles decreases, resulting in C8
This is because S durability deteriorates, and if the number of people exceeds 400, a problem of spacing loss will occur.

(4) In the examples, hard fine particles with an average particle size of 300 mm were used as hard fine particles with a small average particle size, and hard fine particles with an average particle size of 3000 mm were used as hard fine particles with a large average particle size. Hard fine particles with a small particle size can be selected with an average particle size of 200 to 1000 particles, and the latter hard fine particles with a large average particle size can be selected with an average particle size of 1000 to 500 particles.
(However, it is not possible to use hard fine particles with an average particle size of 1000 particles for both hard particles.)

In the example, the density of the former hard fine particles having an average particle size of 200 to 1000 particles is 200 particles/1 m.

However, in the present invention, its density is 10 to 50
It is limited to a range of 0 pieces/1 μm0.

The reason for this is that if the number of particles is less than 100 pieces/1m0, the C8S test under high humidity (e.g. 90% relative humidity)
The coefficient of static friction begins to increase rapidly when the number of C8S is 0, and when it exceeds 500 pieces/1 μmo, the coefficient of static friction tends to increase due to the continuation of the C8S test, which inevitably causes the problem of spacing loss. It is.

In addition, the density of the latter hard fine particles with an average particle size of 1000 to 5000 particles was set to 0.1 particles/1 μma in the example,
In the present invention, the abundance density is 0.01 to 10 pieces/1
limited to the range of μm'. The reason is 0.01/1
If it is less than μm0, the hard particles are likely to be scraped by the continuation of the C8S test and the coefficient of static friction will tend to increase, and if it exceeds 100 particles/1m0, a problem of spacing loss will occur.

In other words, by setting the average particle size range and existing density range of the two types of hard fine particles with different average particle sizes as described above, the increase in the coefficient of static friction is extremely small even after repeated C8S cycles, and the CSS durability is maintained. An excellent magnetic recording medium with small spacing loss can be obtained.

(5) In the examples, two types of hard fine particles with different average particle diameters were used as the hard fine particles, but in addition to the above two types of hard fine particles, one or more types of Hard fine particles can also be used.

(6) In the embodiment, an aluminum alloy plate was used as the nonmagnetic substrate, but other materials such as metals other than aluminum alloy, glass, alumina, ceramics, and plastics may also be used.

(7) In the example, a CoNiCr film was formed as the magnetic layer, but other Co such as CoNi, CoPt, CoP, etc.
The magnetic layer may be made of a magnetic material such as a magnetic alloy or Fe2O3.

(8) In the embodiment, a base layer made of a Cr film was provided, but as a material for the base layer, other than Cr, non-magnetic materials such as MOTi, Ta, etc. can be used. Note that the base layer is not an essential layer, and its formation may be omitted depending on the case.

(9) In the examples, the protective layer was formed directly on the magnetic layer, but one or more layers of a metal film such as Cr or a metal oxide film such as chromium oxide may be interposed between the magnetic layer and the protective layer. The chemical durability of the magnetic layer may be further improved.

(10) In the examples, fluorinated oil was used as the material for the lubricant layer, but a fluorocarbon-based liquid lubricant or a lubricant made of an alkali metal salt of sulfonic acid may also be used. Note that the lubricating layer is not an essential layer, and its formation may be omitted depending on the case.

[Effects of the Invention] As detailed above, according to the present invention, a magnetic recording medium having excellent C8S durability and free from the problem of spacing loss was provided.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of the magnetic recording medium of Example 1.

Claims (1)

[Claims] (1) A magnetic layer formed by sequentially forming a magnetic layer and a protective layer on a non-magnetic substrate, where the protective layer is composed of a metal oxide film and hard fine particles dispersed in the metal oxide film. In the recording medium, a region of the metal oxide film in which hard fine particles are not present in the protective layer has a thickness of 50 to 400 Å, and the hard fine particles include hard fine particles with an average particle size of 200 to 1000 Å and hard fine particles with an average particle size of 1000 to 5000 Å. The protective layer is composed of at least two types of hard fine particles having different average particle diameters, including hard fine particles of 200 to 1000 Å, and the former hard fine particles have an average particle size of 1 μm/μm.
1. A magnetic recording medium characterized in that there are 0.01 to 10 hard fine particles per μm° with an average particle diameter of 1000 to 5000 Å.