JPH07272259A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in chemical durability of the magnetic layer by forming two protective layers having mutually different compsns. CONSTITUTION:An underlayer 2, a magnetic layer 3, a 1st protective layer 4a, a 2nd protective layer 4b and a lubricative layer 5 are successively formed on a nonmagnetic substrate 1 to obtain the objective magnetic recording medium. The 1st protective layer 4a is made of a Cr film having 50Angstrom thickness and the 2nd protective layer 4b consists of a metal oxide film 6 using silicon oxide as the metal oxide, fine silica particles 7 having 300Angstrom average particle diameter and fine silica particles 8 having 3,000Angstrom average particle diameter dispersed in the film 6. In the 2nd protective layer 4b, the thickness of the metal oxide film 6 in the region where the fine silica particles 7 and 8 do not exist is 150Angstrom , the existence density of the particles 7 is 20 per 1mum<2> and that of the particles 8 is 0.1 per 1um<2>. Since the 1st protective layer 4a prevents moisture contained in the open air from entering the magnetic layer 3 through the 2nd protective layer 4b, the chemical durability of the magnetic layer 3 is maintained and spacing loss can be prevented.

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 in a magnetic disk device 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 significantly increased, and the characteristics required for the magnetic recording medium have become more and more severe. This magnetic recording medium has a magnetic layer with excellent magnetic characteristics and electromagnetic conversion characteristics, a small frictional force at the time of contact with the magnetic head and sliding, high wear resistance, head crash does not easily occur, and corrosion resistance An excellent protective layer is required.
Therefore, recently, a magnetic recording medium is often constructed by forming a magnetic layer on a non-magnetic substrate, then forming a protective layer and, if necessary, a lubricating layer. For example, in Japanese Patent Laid-Open No. 61-73227, a CoNiP magnetic layer is provided on an Al substrate on which a Ni-P layer is provided in advance, and then the grain size is 30.
A magnetic recording medium is disclosed in which a silicon oxide polymer protective layer in which hard fine particles of γ-alumina fine particles of 0 to 500 angstrom are dispersed is provided, and further a perfluoropolyether lubricating layer is sequentially provided. This JP-A-61
JP-A-73227 describes that the hardness of the protective layer is increased and the durability against a contact start stop (hereinafter referred to as CSS) test is improved by using the above-described magnetic recording medium. Here, the CSS test is to start rotation of the magnetic recording medium 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, the magnetic head is brought into contact with the magnetic recording medium again, and thereafter, this rotation start / stop is repeated, and the magnetic recording medium has passed CSS times. This is a test for evaluating the durability of the magnetic recording medium by investigating whether damage or increase in friction coefficient will occur later.

[0003]

However, the magnetic recording medium having the above-mentioned structure shows a suitable CSS durability when evaluated by CSS test durability (hereinafter referred to as CSS durability) in an atmosphere of low humidity. C in a high humidity atmosphere, for example, in an atmosphere with a relative temperature of 90% and a temperature of 30 ° C.
When the SS durability is evaluated, the CSS durability is remarkably lowered. For example, the static friction coefficient with the magnetic head starts to increase after several hundred CSS times, and the magnetic head reaches the magnetic recording medium surface after several thousand CSS times. The phenomenon of adsorption occurs, and head crash often occurs.

When such a magnetic recording medium having no CSS durability is used in a high humidity environment such as the rainy season and summer of Japan, the magnetic disk device becomes unusable, which is a serious problem. It was a problem.

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

[0006]

The present invention has been made in order to achieve the above-mentioned object, and is 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 comprises at least one film selected from chromium and chromium oxide,
The second protective layer is a magnetic recording medium comprising a metal oxide film containing hard particles having a particle size distribution.

[0007]

Embodiments of the present invention will be described below in detail with reference to FIG.

Example 1 FIG. 1 is a partial cross-sectional view of a magnetic recording medium of this example. The magnetic recording medium comprises a non-magnetic substrate 1, an underlayer 2, a magnetic layer 3, and a first protective layer. The layer 4a, the second protective layer 4b, and the lubricating layer 5 are sequentially provided. The first protective layer 4a is made of a chromium film having a thickness of 50 Å. The second protective layer 4b is composed of a metal oxide film 6 using silicon oxide as a metal oxide, and two kinds of hard fine particles having different average particle diameters dispersed in the metal oxide film 6, that is, It is composed of 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 (here, the average particle diameter means an average size of hard fine particles (silica fine particles), that is, a vertical direction. Means the average of the diameters of a group of hard particles (silica particles), including hard particles (silica particles) that differ in diameter between and. 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 Å, and the density of the silica particles 7 is 20 pieces / 1 μm square. The existence density of the silica fine particles 8 is 0.1 piece / 1 μ
It is m square.

This magnetic recording medium was manufactured as follows. That is, first, both main surfaces were mirror-polished, and 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 angstrom).
A nonmagnetic substrate 1 obtained by alumite treatment is prepared, and a C film having a film thickness of 1000 angstrom is formed on the substrate 1 by a sputtering method using a Cr target and Ar gas.
The underlayer 2 made of the r film was formed.

Next, a film thickness 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 CoNiCr film of 00 angstrom was formed.

Then, a Cr film having a film thickness of 50 angstrom is formed by a sputtering method using a Cr target and Ar gas.
The first protective layer 4a made of a film was formed. The first protective layer 4a contains moisture contained in the outside air as the lubricating layer 5 and the second protective layer 4b.
It is provided in order to prevent the magnetic layer 3 from entering into the magnetic layer 3 via the magnetic field and further improve the chemical durability of the magnetic layer.

Next, tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) which is a metal alkoxide, water, methanol, acetic acid and formamide are mixed at a molar ratio of 1/2/10 / 0.1 /.
The solution obtained by blending so as to be 0.1, and the average particle size is 3
00 angstrom (The average particle size is Coulter Counter N4 manufactured by Coulter Counter Co., Ltd.)
It was measured at. The same shall apply hereinafter) and a solution obtained by dispersing 15 wt% of silica fine particles 8 having an average particle diameter of 3000 angstrom in methanol at a ratio of 100/1 are mixed to obtain a mixed liquid. After being coated on the first protective layer 4a by a spin coating method, it is heat-treated at 290 ° C. for 30 minutes to convert tetraethoxysilane, which is a metal alkoxide, into silicon oxide, which is a metal oxide. To obtain a second protective layer 4b in which the silica fine particles 7 and the silica fine particles 8 are 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 silica fine particles is about 150 Å, and the density of the silica fine particles measured by a scanning electron microscope is 20 particles / μm square and the average particle size is 3 for the silica fine particles 7 having an average particle size of 300 Å as described above.
With respect to the silica fine particles 8 of 000 angstrom, the number was 0.1 pieces / 1 μm square.

Then, a fluorinated oil (KRYTOX manufactured by DuPont) is formed on the second protective layer 4b by a spin coating method.
157 FSH) to form a lubricating layer 5 having a film thickness of about 15 angstroms to obtain a desired magnetic recording medium.

Next, for each of the 10 magnetic recording media obtained in Example 1, a CSS test was conducted 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 of evaluating the CSS durability, the magnetic recording medium of Example 1 was 1
Not only did 0 sheets withstand the number of CSS times of 10,000 times or more, but the static friction coefficient with the magnetic head was a very small value of about 0.5 even after passing the number of CSS times of 10,000 times. Further, the magnetic head did not stick to the surface of the magnetic recording medium, and head crash did not occur.

From the above results, it has been clarified that the magnetic recording medium of Example 1 has excellent CSS durability even in an atmosphere of high humidity.

Next, with respect to 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 increase in the distance between the head and the magnetic recording medium). In this measurement, the RD008 media certifier (monolithic type magnetic head is used) manufactured by Adelphi, USA
The distance between the head and the surface of the magnetic recording medium (so-called flying height) was set to 2000 angstroms. As a result, it was revealed that in the case of the magnetic recording medium of Example 1, the output voltage of the magnetic head was 0.4 mV, and the magnetic recording medium of Example 1 had less spacing loss.

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

(1) In the examples, tetraethoxysilane was used as a raw material for forming the metal oxide film made of silicon oxide in the second protective layer, but a partial or complete hydrolyzate thereof was used. Other silicon alkoxides or partial or complete hydrolysates thereof may be used as long as they form a silicon oxide by the so-called sol-gel method. Such examples include tetramethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-
Tetraalkoxysilanes such as sec-butoxysilane and tetra-tert-butoxysilane, and monoalkyltrialkoxysilanes, dialkyldialkoxysilanes and trialkyls in which 1 to 3 of the alkoxy groups of these tetraalkoxysilanes are substituted with alkyl groups. Silicon alkoxides such as monoalkoxysilanes and their partial or complete hydrolysates are 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 are triethoxy aluminum, trimethoxy aluminum, tri-n-propoxy aluminum,
Trialkoxyaluminum such as tri-i-propoxyaluminum and tri-n-butoxyaluminum, and one of the alkoxy groups of these trialkoxyaluminums.
Examples include aluminum alkoxides such as monoalkyl dialkoxy aluminum and dialkyl monoalkoxy aluminum in which 2 to 2 are substituted with alkyl groups, and partial or complete hydrolysates thereof. Further, as the metal alkoxide, alkoxides of tantalum, tungsten, tin, zirconium, titanium and the like and partial or complete hydrolysates thereof may be used to form the metal oxide film. Here, the metal oxide film includes an oxide of a semimetal such as an oxide of silicon as described above.

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

Further, in the examples, a mixture of tetraethoxysilane, water, methanol, acetic acid and formamide was used in forming the metal oxide film made of silicon oxide, but one or both of acetic acid and formamide were used. Can be omitted. Further, without using water positively, water (steam) in the atmosphere may be taken in to obtain a solution containing the hydrolyzate of the metal alkoxide. Further, ethyl alcohol, butyl alcohol, or the like may be used instead of the 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 hardness. As an example, alumina, zirconia, titania,
Examples include fine particles of silicon carbide, tungsten carbide and the like. It is also possible to use two or more kinds of different hard particles.

(3) In the embodiment, the thickness of the first protective layer is 50.
Although the thickness is set to angstrom, it is preferable that the film thickness is in the range of 30 to 80 angstrom. The reason is,
If it is less than 30 angstroms, the protective function for the magnetic layer tends to deteriorate, and if it exceeds 80 angstroms, 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 particles are not present in the second protective layer is 150 angstrom, but this thickness is preferably in the range of 50 to 400 angstrom. .

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 particles becomes small, so that the CSS durability may deteriorate, and if it exceeds 400 angstroms. This is because the problem of pacing loss may occur.

(4) In the embodiment, hard fine particles having an average particle diameter of 300 Å are used as hard fine particles having a small average particle diameter, and hard fine particles having an average particle diameter of 3000 Å are 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-
It can be selected in the range of 1000 angstroms, and the latter hard hard fine particles having a large average particle size are 1000-50.
It can be selected in the range of 00 Å.

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

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

The density of the latter hard fine particles having an average particle size of 1000 to 5000 angstroms was set to 0.1 pieces / 1 μm square in the examples, but in the present invention, the existence density is 0.01 to 10 pieces / 1 μm. It is preferably in the square range. The reason is 0.01 /
If it is less than 1 μm square, the hard fine particles will be displaced due to the continuation of the CSS test, and the static friction coefficient will easily increase, and if it exceeds 10 pieces / μm square, the problem of spacing loss may occur. is there.

That is, by setting the range of the average particle size and the range of the existing density of the two types of hard fine particles having different average particle sizes as described above, the increase in the static friction coefficient is extremely small even if the CSS times are repeated, and the CSS is very small. It is possible to obtain a magnetic recording medium having excellent durability and 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, but other than the above two kinds of hard fine particles, other 1
It is also possible to use one or more kinds of hard fine particles. Also, one kind of hard fine particles can be used.

(6) In the embodiments, an aluminum alloy plate is used as the non-magnetic substrate, but other materials such as metal other than aluminum alloy, glass, alumina, ceramics, plastics, etc. 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 formed of another Co-based alloy such as CoNi, CoPt, or CoP or a magnetic material such as Fe ₂ O ₃ .

(8) In the embodiment, the underlayer made of a Cr film is provided, but as the material of the underlayer, in addition to Cr, Mo, Ti,
A non-magnetic material such as Ta can be used. The base layer 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, but one or more layers of chromium oxide film may be provided.

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

[0037]

As described above in detail, according to the present invention, by providing the first protective layer, it is possible to prevent the moisture contained in the outside air from entering the magnetic layer via the second protective layer and The chemical durability of the layer is retained. 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 drawings]

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

[Explanation 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

Claims (2)

[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 selected from chromium and chromium oxide. A magnetic recording medium comprising one kind of film, wherein the second protective layer is made of a metal oxide film containing hard particles having a particle size distribution. 2. The particle size distribution is a distribution in which irregularities are formed on the surface of the protective layer so as to suppress adsorption between the head and the magnetic recording medium surface in a high humidity environment. The magnetic recording medium described.