JP2003187419A - Magnetic recording medium and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium and its manufacturing method that can make the magnetic head floating low and reduce its friction coefficient by forming a roughened layer on a magnetic recording medium and precision controlling its roughness. <P>SOLUTION: The magnetic recording medium has a closely adhered non- magnetic metal layer 2 made of metal, such as Cr and a roughened non-magnetic metal deposit layer 3 made of metal, such as Al containing oxygen on the surface of an non-magnetic base 1. The roughened non-magnetic metal layer 3 is not made uniformly thick over the whole non-magnetic layer 2, but its metal is agglomerated locally and distributed in island-like manner to form the asperity. When forming the roughened layer 3 through sputtering, it is desirable that the maximum diameter of the insular projections be made 10 to 200 nm but not smaller or larger and the surface roughness (Ra) 0.3 to 3.0 nm but not smaller or larger, by supplying oxygen gas to obtain a partial pressure of 0.01 to 20 percent but not smaller or larger with respect to the partial pressure of Ar. <P>COPYRIGHT: (C)2003,JPO

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 hard disk drive or the like and a method for manufacturing the same, and more particularly, to a magnetic head of a magnetic head by forming fine irregularities on the outermost surface of the magnetic recording medium. The present invention relates to a magnetic recording technology that achieves high flying density and high durability to increase the recording density of a magnetic recording medium.

[0002]

2. Description of the Related Art Recently, the demand for recording density of magnetic recording media used in hard disk drives and the like has been increasing. In order to achieve a strict requirement for higher recording density, it is necessary to reduce the flying height of the magnetic head from the surface of the magnetic recording medium, and the surface roughness of the magnetic recording medium must be suppressed to some extent. .

On the other hand, regarding the durability due to the rubbing between the magnetic head and the surface of the magnetic recording medium, it is also required to reduce the friction coefficient between the magnetic head and the magnetic recording medium at the same time, so that the surface roughness of the magnetic recording medium is rough. Need to face.

In order to satisfy the requirements of both parties,
It is necessary to precisely control the surface roughness. In the conventional aluminum substrate medium or the like, a texture processing is applied to the surface of the non-magnetic substrate to provide mechanical uneven grooves.

[0005]

However, when a conventional texture processing is applied to a non-magnetic substrate made of a resin such as polycarbonate or polyolefin, the rigidity of the substrate is low, so that the surface roughness can be uniformly and precisely controlled. Difficult to do. As a means to solve it,
This can be avoided by prolonging the processing time, but this leads to an increase in manufacturing cost, and there is also a problem that goes against the cost reduction.

The present invention has been made in view of the above problems, and an object thereof is to provide a magnetic recording medium with a concavo-convex forming layer to precisely control the surface roughness of a magnetic head. It is an object of the present invention to provide a magnetic recording medium having both a low floating property and a low friction coefficient and a method for manufacturing the same.

[0007]

In order to achieve such an object, the invention according to claim 1 provides a nonmagnetic substrate, at least an unevenness forming layer, a nonmagnetic underlayer, and
In the magnetic recording medium, a granular magnetic layer including crystal grains containing Co and having ferromagnetism and a non-magnetic grain boundary surrounding the crystal grains, a protective film and a liquid lubricant layer are sequentially laminated, Is a non-magnetic metal deposit containing oxygen, and has an island-shaped convex shape discretely distributed on the surface of the non-magnetic metal adhesion layer.

The invention described in claim 2 is the same as claim 1.
In the invention described in [1], the concavo-convex forming layer is made of Al, C
u, Zn, Ag, Au, Pb, Ti, Si, Zr, Cr
It is characterized by being one kind of metal or two or more kinds of alloys selected from the group consisting of.

The invention described in claim 3 is the same as claim 1
Alternatively, in the invention described in Item 2, the non-magnetic substrate is made of a resin such as polycarbonate or polyolefin.

The invention according to claim 4 is the same as claim 2
Alternatively, in the invention described in Item 3, there is provided a non-magnetic metal adhesion layer that improves adhesion between the non-magnetic substrate and the unevenness forming layer.

The invention described in claim 5 is the same as claim 1.
In the invention according to any one of 1 to 4, the unevenness forming layer is Al, and the maximum diameter of the island-shaped protruding portion is 10 nm.
200 nm or less and a surface roughness (Ra) of 0.3 nm
It is characterized by being in the range of at least 3.0 nm.

The invention according to claim 6 is the same as claim 1.
5. The method for manufacturing a magnetic recording medium according to any one of items 1 to 5, characterized by comprising sputtering for forming the unevenness forming layer by sputtering in a mixed sputtering gas atmosphere of Ar and oxygen.

The invention according to claim 7 is the same as claim 6
In the invention described in above, the concavo-convex forming layer is Al, and the partial pressure ratio of oxygen to Ar in the mixed sputtering is in the range of 0.01% to 20%.

The invention described in claim 8 is the invention according to claim 7.
In the invention described in (3), the film forming process is performed without heating the non-magnetic substrate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. A method of controlling the surface roughness, which has low floating characteristics and low friction characteristics and further realizes cost reduction, can be produced by forming an unevenness forming layer by sputtering. For example, when forming the concavo-convex forming layer by sputtering, the partial pressure ratio of oxygen to Ar is 0.01%.
By controlling to 20% or less, three-dimensional island-like growth is promoted and a precise uneven shape can be easily obtained.

By using the concavo-convex shape obtained by this method, a magnetic recording medium having low flying characteristics and low friction characteristics can be obtained. Further, the nonmagnetic metal adhesion layer inserted between the unevenness forming layer and the nonmagnetic substrate has the function of improving the adhesion of the unevenness forming layer and improving the durability.

FIG. 1 is a sectional view for explaining an embodiment of the magnetic recording medium of the present invention. In a magnetic recording medium, a non-magnetic metal adhesion layer 2 of Cr or the like and an unevenness forming layer 3 of a non-magnetic metal deposit such as Al containing oxygen are formed on the surface of a non-magnetic substrate 1.
Are formed. The concavo-convex forming layer 3 is not formed with a uniform film thickness on the entire metal of the non-magnetic metal adhesion layer 2, but the non-magnetic metal is locally aggregated and discretely distributed. It takes the shape of an island. The nonmagnetic metal adhesion layer 2 has a function of improving the adhesion of the unevenness forming layer 3.

Next, a structure in which a non-magnetic underlayer 4, a granular magnetic layer 5 and a protective film 6 are sequentially formed on the metal deposit unevenness forming layer 3 is further formed. The liquid lubricant layer 7 is formed. For the purpose of controlling the crystal orientation of the nonmagnetic underlayer 4 or the granular magnetic layer 5 and other structures, a nonmagnetic seed layer may be provided between the concavo-convex forming layer 3 and the nonmagnetic underlayer 4, or a nonmagnetic underlayer may be provided. Four
Even if a non-magnetic intermediate layer is provided between the granular magnetic layer 5 and the granular magnetic layer 5, the effect of the present invention can be exhibited and more excellent characteristics can be obtained.

As the non-magnetic substrate 1, an inexpensive substrate prepared by injection molding polycarbonate, polyolefin or other resin is used, and the film forming process is performed without heating.

As the non-magnetic underlayer 4, any material can be used as long as it can control the crystal orientation, grain size, grain boundary segregation structure or other fine structure of the magnetic layer. For example, Cr or an alloy mainly composed of Cr as used in the conventional magnetic recording medium can be preferably used, and Ru, O which has a great effect on the granular magnetic layer.
Metals such as s and Re or alloys mainly containing them can also be used. The film thickness is not particularly limited, and a necessary and sufficient film thickness is required in consideration of the structure control effect of the granular magnetic layer, productivity and cost.

The magnetic layer 5 is a so-called granular magnetic layer which is composed of crystal grains having ferromagnetism and non-magnetic grain boundaries surrounding the crystal grains, and the non-magnetic grain boundaries are composed of metal oxides or nitrides. The material forming the crystal having ferromagnetism is not particularly limited, but a CoPt-based alloy can be preferably used. In particular, it is desirable to add Cr, Ni, Ta or the like to the CoPt alloy in order to reduce the medium noise.

On the other hand, as the material for forming the non-magnetic grain boundary, nitride can be used, but Cr, Co, S
The use of oxides of elements such as i, Al, Ti, Ta, Hf, and Zr is particularly desirable for forming a stable granular structure. The film thickness of the magnetic layer is not particularly limited, and a necessary and sufficient film thickness for obtaining a sufficient head reproduction output during recording and reproduction is required.

As the protective film 6, for example, a thin film composed mainly of carbon formed by a sputtering method or a CVD method is used. Further, for the liquid lubricant layer 7, for example, a perfluoropolyether lubricant can be used.

Next, an embodiment of a method of manufacturing a magnetic recording medium will be described. Oxygen gas is added so as to have a partial pressure ratio of 0.01% or more and 20% or less with respect to the Ar partial pressure when the unevenness forming layer 3 is formed by sputtering, and the maximum diameter of the island-shaped convex portion is 10 nm or more and 200 nm or less, Surface roughness (R
It is preferable that a) is 0.3 nm or more and 3.0 nm or less.

According to the present embodiment, when manufacturing the magnetic recording medium shown in FIG. 1, the texture processing step of forming the mechanical uneven groove included in the conventional method of manufacturing the magnetic recording medium is omitted. Therefore, the manufacturing cost can be reduced with the simplification of the manufacturing process.

Example 1 A 3.5 ″ φ disk-shaped substrate obtained by injection-molding a polycarbonate resin was used as the non-magnetic substrate 1, which was cleaned and then introduced into a sputtering apparatus at 30 mT.
The nonmagnetic metal adhesion layer 2 made of Cr is formed to a thickness of 20 nm under an Ar gas atmosphere of orr. After that, the unevenness forming layer 3 made of Al is subsequently formed. Ar film forming gas
And a mixed gas of oxygen are used, and the pressure of the film forming atmosphere is 30 mT.
The film formation is performed by changing the amounts of Ar and oxygen introduced while keeping the orr constant.

At that time, the atmosphere in the vacuum chamber was set to a quadrupole mass spectrometer and the partial pressure ratio of oxygen to Ar was set to 0.
The introduction amount is controlled so as to be a predetermined partial pressure ratio between 001% and 50%. Subsequently, the non-magnetic metal underlayer 4 made of Ru was added to 30 n in an Ar gas atmosphere of 30 mTorr.
m formed.

Further, subsequently, Ar of 15 mTorr
10 mol% of SiO ₂ was added under a gas atmosphere. Co
A granular magnetic layer 55 having a thickness of 15 nm was formed by an RF sputtering method using a Cr ₁₂ Pt ₁₂ target. Next, the carbon protective layer 6 was laminated to a thickness of 10 nm, taken out from the vacuum, and a sample was prepared. The substrate was not heated prior to film formation.

FIG. 2 is a diagram showing the relationship between the partial pressure ratio of oxygen gas when forming the concavo-convex forming layer 3, the crystal grain size D (diameter) of the island-shaped convex portion, and the surface roughness (Ra). . The crystal grain size D and the surface roughness (Ra) were quantified using an atomic force microscope (hereinafter referred to as AFM). As shown in FIG. 2, it is understood that the crystal grain size D (diameter) and the surface roughness (Ra) tend to increase as the partial pressure ratio of oxygen gas increases.

FIG. 3 is a schematic diagram showing a result of observing a cross section of a sample formed in an atmosphere having a partial pressure ratio of oxygen gas of 0.001% using a transmission electron microscope (TEM).
It can be seen that the Al deposit becomes an amorphous single film and has a fine uneven structure.

FIG. 4 shows a cross section of a sample formed in an atmosphere having a partial pressure ratio of oxygen gas of 10% by a transmission electron microscope (T
It is a schematic diagram which shows the result observed using EM). It can be seen that by increasing the oxygen partial pressure ratio, island-shaped convex portions of the crystalline phase grow in an island-like state in a scattered distribution, and the surface becomes uneven as a whole.

[Embodiment 2] Based on the result of the structural analysis confirmed in Embodiment 1, a 3.5 ″ φ disc-shaped substrate obtained by injection-molding polycarbonate resin is used as the non-magnetic substrate 1. After cleaning, it is introduced into the sputter device and 30m
The nonmagnetic metal adhesion layer 2 made of Cr is formed to a thickness of 20 nm in an Ar gas atmosphere of Torr. After that, the unevenness forming layer 3 made of Al is subsequently formed. Ar film forming gas
And a mixed gas of oxygen are used, and the pressure of the film forming atmosphere is 30 mT.
The film formation is performed by changing the introduced amounts of Ar and oxygen with orr kept constant.

At that time, the atmosphere in the vacuum chamber was set to a partial pressure ratio of oxygen to Ar of 0.0 using a quadrupole mass spectrometer.
The amount of introduction is controlled so that a predetermined partial pressure ratio is obtained between 01% and 50%. Subsequently, a nonmagnetic metal underlayer 4 made of Ru was formed to a thickness of 30 nm in an Ar gas atmosphere of 30 mTorr.

Further, subsequently, Ar of 15 mTorr
CoC with 10 mol% of SiO ₂ added in a gas atmosphere
A granular magnetic layer 5 having a thickness of 15 nm was formed by an RF sputtering method using an r ₁₂ Pt ₁₂ target. Then, the carbon protective layer 6 was laminated to a thickness of 10 nm, taken out from the vacuum, and then the liquid lubricant 7 was applied to a thickness of 1.5 nm to manufacture a magnetic recording medium having the structure shown in FIG. The substrate was not heated prior to film formation.

FIG. 5 is a diagram showing the relationship between the crystal grain size D of the magnetic recording medium produced by changing the partial pressure ratio of oxygen gas and the floating characteristic of the magnetic head. It is measured using a spin stand tester using a thin film magnetic head. Figure 5
As shown in (1), it is understood that the flying height of the magnetic head tends to increase as the crystal grain size D increases.

From this relationship, it can be seen that the upper limit of the crystal grain size D is determined in response to the demand for low floating characteristics. Further, since the crystal grain size D and the surface roughness (Ra) are in a proportional relationship, the same change is shown also in the surface roughness (Ra). Therefore, the crystal grain size D for obtaining good floating characteristics is 200 n
m or less, and the surface roughness (Ra) is 3.0 nm or less.

FIG. 6 is a diagram showing the relationship between the crystal grain size D of the magnetic recording medium produced by changing the partial pressure ratio of oxygen gas and the friction coefficient μ with the magnetic head. It is measured using a spin stand tester using a thin film magnetic head. As shown in FIG. 6, it is understood that the friction coefficient μ tends to decrease as the crystal grain size D increases.

From this relationship, it can be seen that the lower limit of the crystal grain size D is determined in response to the demand for low friction characteristics. Since the crystal grain size D and the surface roughness (Ra) are in a proportional relationship,
A similar change is shown for the surface roughness (Ra). Therefore, the crystal grain size D with which good friction characteristics are obtained is 10 nm or more, and the surface roughness (Ra) is 0.3 nm or more.

[0039]

As described above, according to the present invention, it becomes possible to control the surface roughness of the non-magnetic substrate by providing the concavo-convex forming layer, and it is possible to meet the requirements of low floating characteristics and low friction characteristics. It becomes possible to do. Specifically, the crystal grain size range is 10 nm or more and 200 or less, and the surface roughness range is 0.3 nm or more and 3.0 or less.

Further, this is an alternative to the conventional texturing process for forming mechanical uneven grooves, and the process can be shortened and the manufacturing cost can be reduced.
Furthermore, since heating of the substrate can be omitted, inexpensive plastic can be used as the substrate.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining an embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a diagram showing a relationship between a partial pressure ratio of oxygen gas, a crystal grain size D (diameter) of an island-shaped convex portion, and a surface roughness (Ra) when forming the concave-convex forming layer 3.

FIG. 3 is a schematic diagram showing a result of observing a cross section of a sample formed in an atmosphere having a partial pressure ratio of oxygen gas of 0.001% using a transmission electron microscope (TEM).

FIG. 4 is a schematic diagram showing a result of observing a cross section of a sample formed in an atmosphere having a partial pressure ratio of oxygen gas of 10% using a transmission electron microscope (TEM).

FIG. 5 is a diagram showing the relationship between the crystal grain size D of a magnetic recording medium manufactured by changing the partial pressure ratio of oxygen gas and the flying characteristic of a magnetic head.

FIG. 6 is a diagram showing a relationship between a crystal grain size D of a magnetic recording medium manufactured by changing a partial pressure ratio of oxygen gas and a friction coefficient μ with a magnetic head.

[Explanation of symbols]

1 Non-magnetic substrate 2 Non-magnetic metal adhesion layer 3 Concavo-convex forming layer 4 Non-magnetic underlayer 5 Granular magnetic layer 6 protective film 7 Liquid lubricant layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoji Sakaguchi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Hiroyuki Uesumi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Tadaaki Oikawa             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Masaru Nakamura             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 5D006 BB01 BB02 BB06 BB07 CA01                       CA04 CA05 CB01 EA03                 5D112 FA04 FB20

Claims (8)

[Claims] 1. A non-magnetic substrate, at least an unevenness forming layer, a non-magnetic underlayer, and a granular magnetic layer comprising Co-containing ferromagnetic crystal grains and a non-magnetic grain boundary surrounding the crystal grains. A magnetic recording medium in which a protective film and a liquid lubricant layer are sequentially laminated, wherein the concavo-convex forming layer is a nonmagnetic metal deposit containing oxygen, and is discrete on the surface of the nonmagnetic metal adhesion layer. A magnetic recording medium having an island-shaped convex shape that is randomly distributed. 2. The concavo-convex forming layer is made of Al, Cu, Zn,
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is one metal or an alloy of two or more selected from the group consisting of Ag, Au, Pb, Ti, Si, Zr, and Cr. 3. The magnetic recording medium according to claim 1, wherein the non-magnetic substrate is made of resin such as polycarbonate or polyolefin. 4. The magnetic recording medium according to claim 2, further comprising a non-magnetic metal adhesion layer that improves adhesion between the non-magnetic substrate and the unevenness forming layer. 5. The irregularity forming layer is made of Al, and the maximum diameter of the island-shaped convex portion is in the range of 10 nm or more and 200 nm or less and the surface roughness (Ra) of 0.3 nm or more and 3.0 nm or less. The magnetic recording medium according to any one of claims 1 to 4, wherein 6. The method for manufacturing a magnetic recording medium according to claim 1, further comprising sputtering for forming the concavo-convex forming layer by sputtering in a mixed sputtering gas atmosphere containing Ar and oxygen. And a method for manufacturing a magnetic recording medium. 7. The unevenness forming layer is made of Al, and the partial pressure ratio of oxygen to Ar in the mixed sputtering is in the range of 0.01% or more and 20% or less. Manufacturing method of magnetic recording medium. 8. The method of manufacturing a magnetic recording medium according to claim 7, wherein the film forming process is performed without heating the non-magnetic substrate.