JPH10198941A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly adjust the crystal grains of a conductive thin film, to obtain high coercive force with impression of a bias voltage of a desired specific resistance and good efficiency and to enable a high-density recording by controlling the crystal grains to be included in the crystallization region of a nonmagnetic substrate having a specified heat resistance temp. or above and forming the conductive thin film reflecting in the crystal grains. SOLUTION: A crystallized glass substrate 1 which contains canasite as a main crystal, has a crystal grain size of 0.05μm, is precisely polished to 5Å in the surface roughness Ra of the main surface and has the heat resistance temp. of >=400 deg.C is formed. The IOT conductive thin films 2 are crystallized to reflect the crystal grain size of the crystallized glass continuously at 100nm film thickness on both main surfaces and flanks of this substrate. The crystal grain size thereof is 0.05μm and the surfaces maintain the surface roughness of 5Å and flatness. A raggedness control layer 3, a ground surface layer 4 consisting of a Cr film, a magnetic layer 5 consisting of CoPtCr film, a protective layer 6 consisting of a carbon film and a lubricating layer 7 consisting of a film of a liquid lubricant are successively formed thereon. As a result, the magnetic recording medium 10 which enables the high-density recording is obtd.

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 having a high coercive force and a high practicality, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the recording capacity of a magnetic recording device such as a hard disk has been remarkably improved, and accordingly, demands for high-density recording on a magnetic recording medium have been increasingly severe.

[0003] At present, many attempts have been made to achieve high-density recording of a magnetic recording medium from various elemental technologies that affect the recording density.

As one of the elemental technologies, when a magnetic layer is formed on a substrate, a bias voltage is applied to the substrate to form a magnetic film by a sputtering method, an ion plating method, or the like. It is known that high-density recording can be achieved. This is because when the magnetic layer is formed by a sputtering method or the like, the magnetic material is in a positively charged plasma state.By charging the substrate to a negative charge, plasma particles are injected into the substrate during sputtering. It is believed to be so powerful.

Here, in a general magnetic recording medium using an aluminum alloy substrate as a substrate, a bias voltage can be applied to the substrate when forming a magnetic layer because the substrate itself is a conductive material. .

However, aluminum alloy substrates have problems in physical and chemical durability such as mechanical durability, heat resistance, and corrosion resistance, and have high coercive force, enable high-density recording, and have high reliability in magnetic recording media. Was not obtained.

Recently, as a technique for solving the above-mentioned problems of the aluminum alloy substrate, a magnetic recording medium using glass or ceramics or the like having excellent mechanical, physical and chemical durability as a substrate has attracted attention.

However, since glass and ceramics are nonconductive (insulating) materials, a bias voltage cannot be applied directly to the substrate. Also, in order to achieve high-density recording, the magnetic head is made to fly low, and recording and reproduction are performed while simulating contact. CSS (contact)
start / stop) There is a problem in terms of durability.

Under these circumstances, a nonmetallic disk substrate such as glass or ceramic is coated with a metal film such as Ti or Mo to make the substrate surface a conductor, and a bias voltage is applied thereto to improve the coercive force. (Japanese Patent Laid-Open Publication No. 6-243452) has been proposed.

[0010]

However, the above-mentioned prior art has the following problems.

That is, in the magnetic recording medium described in JP-A-6-243452, since a conductive thin film of Ti, Mo, or the like is formed by a sputtering method, a main surface portion or side surface holding a substrate is provided. Since uncoated portions were formed in the portions and the like, a bias voltage could not be effectively applied to the substrate, and a magnetic recording medium having a high coercive force could not be obtained.

The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic recording medium having a high coercive force and capable of high-density recording, and a method of manufacturing the same.

[0013]

In order to achieve the above object, a magnetic recording medium according to the present invention comprises at least a conductive thin film on a non-conductive non-magnetic substrate having a heat-resistant temperature of 400 ° C. or higher;
A magnetic layer, wherein the non-magnetic substrate has a crystallized region including crystal grains at least on the substrate surface on which the conductive thin film is formed, and the conductive thin film is The nonmagnetic substrate is formed so as to be reflected on crystal grains contained in a crystallized region of the nonmagnetic substrate.

In the magnetic recording medium of the present invention, the average grain diameter of the crystal grains contained in the crystallized region of the non-magnetic substrate is 0.005 to 1 μm.
m, and the average crystal grain size of the conductive thin film is 0.005.
-1 μm, the average crystal grain size of the crystal grains contained in the crystallization region of the non-magnetic substrate is 0.01-0.1 μm, and the average crystal grain size of the conductive thin film is 0.01-0 .
1 μm, the non-magnetic substrate is made of crystallized glass, and the conductive thin film is made of In, Sn, Sb, M
g, a composition comprising an oxide containing at least one element selected from Zn, Ga, and Cd, wherein the conductive thin film is formed of indium tin oxide, tin antimony oxide, magnesium indate, zinc gallate, cadmium antimonate. , Indium-zinc oxide, a structure made of any one material selected from indium-gallium-zinc oxide, or the conductive thin film is formed by volatilizing a solvent of a solution containing a conductive precursor and baking. This is the configuration that has been done.

Further, in the method for manufacturing a magnetic recording medium of the present invention, the heat-resistant temperature is 400 ° C. or more, and the average particle size is at least 0.005 to 1 μm on the surface on which the magnetic layer is formed.
a step of preparing a non-conductive non-magnetic substrate having a crystallized region including crystal grains of m, and forming a conductive thin film to reflect the crystal grains contained in the crystallized region of the non-magnetic substrate And a step of applying a bias voltage to the non-magnetic substrate via the conductive thin film to form a magnetic layer.

Further, in the method for manufacturing a magnetic recording medium of the present invention, the method for manufacturing a magnetic recording medium of the present invention may be arranged such that an average crystal grain size of crystal grains contained in the crystallized region of the nonmagnetic substrate is 0.01. Wherein the step of forming the conductive thin film includes applying a solution containing a conductive precursor on the non-magnetic substrate, and evaporating a solvent in the solution to form a thin film. Or a step of heat-treating the thin film, or wherein the non-magnetic substrate is a crystallized glass substrate.

[0017]

According to the present invention, the crystal grains contained in the crystallized region of the non-magnetic substrate are controlled, and the conductive thin film is formed by reflecting the crystal grains. It can be adjusted and a conductive thin film having a desired specific resistance value can be obtained.

Hereinafter, the present invention will be described in detail.

First, the magnetic recording medium of the present invention will be described.

In the present invention, a non-conductive non-magnetic substrate having a crystallized region containing crystal grains on at least the surface of the substrate on which the conductive thin film is formed is used. The conductive thin film formed on the crystallization region is formed by reflecting the crystal grains included in the crystallization region.

As described above, when the conductive thin film is formed so as to reflect the crystal grains contained in the crystallized region of the non-magnetic substrate, it is possible to control the crystal grains contained in the crystallized region of the non-magnetic substrate. Accordingly, the crystal grain of the conductive thin film can be accurately adjusted even with respect to the conductive thin film formed by reflecting the crystal grain, so that a conductive thin film having a desired specific resistance value can be obtained.

On the other hand, for example, a chemically strengthened glass generally used as a glass substrate for a magnetic recording medium does not have a crystal structure. Therefore, for example, when a solution containing a conductive precursor is applied to the surface of the chemically strengthened glass substrate, the solvent in the solution is volatilized, and a heat-treated heat-treated liquid crystal thin film is formed. Are irregularly grown and the grain size of the crystal grains of the conductive thin film is varied, so that the movement of electrons at the grain boundary of each crystal grain is hindered, and the mobility decreases. Therefore, a conductive thin film having a desired resistance value cannot be obtained, and the conductivity of the conductive thin film deteriorates.

In the present invention, the average crystal grain size of the crystal grains contained in the crystallization region of the nonmagnetic substrate is set to 0.005 to 1 μm, and the average crystal grain size of the conductive thin film formed to reflect this is set to 0 to 1 μm. It is preferably set to 0.005 to 1 μm.

By controlling the crystal grain size of the conductive thin film in this way, a conductive thin film having good conductivity and flatness is maintained. Therefore, the magnetic layer can be formed while effectively applying a bias voltage to the substrate via the conductive thin film. Further, since the flatness is maintained, the magnetic layer has a high coercive force and a high density. A magnetic recording medium on which recording and reproduction can be performed is obtained.

If the crystal grain size of the conductive thin film is less than 0.005 μm, high conductivity cannot be obtained. This is because the number of crystal grains constituting the conductive thin film increases, and thus the number of crystal boundaries increases, so that when a voltage is applied to the conductive thin film, the scattering of electrons increases and the electron moving speed decreases. That is, it is considered that the mobility of electrons decreases. Therefore, a bias voltage cannot be effectively applied to the substrate, and a magnetic recording medium having a high coercive force cannot be obtained, which is not preferable. Also, the crystal grain size of the conductive thin film is 1
When the thickness exceeds μm, the flatness of the surface of the conductive thin film deteriorates, and the flatness of the surface of the magnetic recording medium reflected by the conductive thin film also deteriorates.

In the present invention, the average crystal grain size of the crystal grains contained in the crystallization region of the nonmagnetic substrate is set to 0.01 to 0.1 μm, and the average crystal grain size of the conductive thin film formed by reflecting the average crystal grain size Is more preferably 0.01 to 0.1 μm. By further controlling the crystal grain size of the conductive thin film, a conductive thin film having better conductivity can be obtained, so that a magnetic recording medium having a higher coercive force and capable of high-density recording and reproduction can be obtained. Can be

From the viewpoint of the flatness of the conductive thin film,
The crystal grain size of the conductive thin film is preferably 0.5 μm or less, more preferably 0.2 μm or less.
Thereby, the flatness (Rmax) is in the range of 0.1 μm or less.

In the present invention, the nonmagnetic substrate having a crystallized region on the substrate surface is preferably crystallized glass from the viewpoint of production cost and the like.

Here, as the crystallized glass, Li ₂ O
—SiO ₂ system, Na ₂ O—MgO—SiO ₂ system, Na ₂ O—
BaO-SiO _{2 system, K 2 O-MgO-SiO} 2 system, Li ₂
O—K ₂ O—ZnO—SiO ₂ system, Li ₂ O—MgO—Z
nO-SiO ₂ system, PbO-BaO-SiO ₂ system, PbO
—Nb ₂ O ₅ —SiO ₂ system, Li ₂ O—Ga ₂ O ₃ —SiO _{2
System, CdO-In 2 O 3 -SiO} 2 system, K ₂ O-TiO ₂ -
SiO ₂ system, Li ₂ O—Al ₂ O ₃ —SiO ₂ system, Na ₂ O—
Al ₂ O ₃ —SiO ₂ system, Li ₂ O—K ₂ O—Al ₂ O ₃ —S
iO ₂ system, MgO-Al ₂ O ₃ -SiO ₂ system, CaO-Al
₂ O ₃ —SiO ₂ system, BaO—Al ₂ O ₃ —SiO ₂ system, Pb
O-Al ₂ O ₃ -SiO _{2 system, MnO-Al 2 O 3 -SiO} 2
_{System, FeO-Al 2 O 3 -SiO} 2 system, CoO-Al ₂ O ₃
—SiO ₂ system, CaO—MgO—Al ₂ O ₃ —SiO ₂ system,
_{CaO-BaO-Al 2 O 3} -SiO 2 system, Li ₂ O-Mg
O-Al ₂ O ₃ -SiO _{2 system, Li 2 O-CaO-Al} 2 O 3
—SiO ₂ system, K ₂ O—MgO—Al ₂ O ₃ —SiO ₂ system,
Na ₂ O—MgO—Al ₂ O ₃ —SiO ₂ system, Na ₂ O—C
aO-Al ₂ O ₃ -SiO _{2 system, Li 2 O-ZnO-Al} 2
O ₃ —SiO ₂ system, Na ₂ O—CaO—MgO—Al ₂ O ₃
—SiO ₂ system, PbO—ZnO—B ₂ O ₃ system, PbO-Z
nO-B ₂ O ₃ -SiO ₂ system, MgO-P ₂ O ₅ -SiO
_{2 system, CaO-Al 2 O 3 -P} 2 O 5 -SiO 2 system, SiO ₂
—B ₂ O ₃ —Al ₂ O ₃ —MgOK—K ₂ OF—based.

The main crystal of the crystallized glass is L
i ₂ O.SiO ₂ , Li ₂ O.2SiO ₂ , 2MgO.2A
l ₂ O ₃ · 5SiO ₂ , α-cristobalite, β-spodumene solid solution, β-spodumene solid solution-mullite,
β-quartz solid solution, phlogopite solid solution, total fluorine mica, lithium mica, β-wollastonite, Na ₂ O.Al ₂ O ₃ .2
SiO ₂ , BaO.Al ₂ O ₃ .2SiO ₂ , (Ba, S
_{r, Pb) Nb 2 O 6} , alkali silicates, Pb, Zn-
Borate, hexacelsian, spinel, mullite, canasite, garnite, potassium fluororichterite, forsterite, rutile enstatite, aggrelite, CaO.SiO ₂ , Ca10 (P ₂ O ₅ ) 6O ₂ ,
Examples include aluminum and silicate crystals.

In the present invention, as a nonmagnetic substrate having a crystallized region on the substrate surface, at least the surface of a substrate made of known quartz glass or ceramics on which a magnetic layer is formed is coated with the above-mentioned crystallized glass. Alternatively, a crystallized region may be formed on the surface of the glass substrate by subjecting only the side of the crystallizable glass substrate on which the conductive thin film is formed to a crystallization treatment by heat treatment or the like.

In the present invention, a substrate having a heat resistant temperature of 400 ° C. or more is used as a non-conductive non-magnetic substrate.

This is because the heat treatment for obtaining a conductive thin film having a low specific resistance value is usually at least 400 ° C., and the substrate must be able to withstand the heat resistance. Also,
This is because the heat resistant temperature of the substrate is also important in terms of heat treatment performed for improving the magnetic properties of the magnetic layer.

As the non-conductive non-magnetic substrate having a heat-resistant temperature of 400 ° C. or higher, there are various materials, and there is no particular limitation.

Examples of such a substrate include crystallized glass (heat-resistant temperature of about 750 ° C.), quartz glass (heat-resistant temperature of about 1000 ° C.), oxynitride glass (heat-resistant temperature of about 950 ° C.), and high silicate glass. (Heat-resistant temperature about 800
C) or ceramic (heat-resistant temperature of about 150
0 ° C.), silicon (heat-resistant temperature of about 1000 ° C.), and carbon (heat-resistant temperature of about 1200 ° C.). In the case of glass and ceramics, the heat resistance temperature is slightly different depending on the composition.

In the present invention, as the material of the conductive thin film,
An oxide containing at least one element selected from In, Sn, Sb, Mg, Zn, Ga, and Cd is preferable.

As such an oxide, for example, indium tin oxide (ITO (In ₂ O ₃ —Sn
O ₂ )), tin-antimony oxide (SnO ₂ —Sb)
₂ O ₃ ), magnesium indate (MgIn ₂ O ₄ ), zinc gallate (ZnGa ₂ O ₄ ), cadmium antimonate (CdSb ₂ O ₄ ), indium zinc oxide (In
₂ O ₃ (ZnO) m) and indium gallium zinc oxide (InGaZnO ₄ ).

In the present invention, the conductive thin film is preferably formed by volatilizing and baking the solvent of the solution containing the conductive precursor.

In this case, it is preferable to form the conductive thin film by a coating method such as a spin coating method, a dipping method, and a spraying method. The conductive thin film formed by these methods is uniform and uneven on the main surface of the substrate (refers to one surface or both surfaces of the glass substrate for a magnetic recording medium, on which the magnetic layer is formed). This is because there is no conductive thin film.

Further, by forming a conductive thin film continuously on the main surface and the side surface of the substrate, the conductive thin film on the main surface side on which the magnetic layer is formed and the conductive thin film on the side surface of the substrate become conductive. Therefore, if a terminal to which a voltage is applied is brought into contact with the conductive thin film on the side surface of the substrate, a magnetic layer can be formed on the entire main surface of the substrate.

The side surface includes an outer peripheral side surface and an inner peripheral side surface.
A conductive thin film may be formed on one of them, or a conductive thin film may be formed on both.

In the present invention, the conductive thin film may be formed on the main surface of the substrate, and the conductive thin film need not always be formed on the side surface.

The thickness of the conductive thin film is preferably from 10 nm to 1 μm.

If the thickness of the conductive thin film is smaller than 10 nm, the surface resistance (sheet resistance) of the film becomes large, so that a bias voltage is not effectively applied and a magnetic recording medium having a high coercive force can be obtained. It is not preferable because it cannot be performed. When the thickness of the conductive thin film exceeds 1 μm, cracks occur in the conductive thin film and the film is peeled off, which is not preferable.

The layers other than the non-magnetic substrate and the conductive thin film in the magnetic recording medium of the present invention are not particularly limited, and conventionally known techniques can be employed.

As other layers, in terms of function, an unevenness forming layer, an underlayer, a magnetic layer, a protective layer, a lubricating layer, and the like can be mentioned.
It is formed as needed. Various thin film forming techniques are used to form these layers.

In the present invention, an unevenness forming layer for controlling unevenness on the medium surface can be formed. The formation position of the unevenness forming layer is not particularly limited.

In the case of a magnetic recording medium for a non-contact recording type magnetic disk device, the unevenness forming layer forms unevenness due to the unevenness of the unevenness forming layer on the surface of the medium. It is formed for the purpose of preventing attraction between the magnetic recording medium and the magnetic recording medium and improving CSS durability.

In the case of a magnetic recording medium for a contact recording type magnetic disk drive, the surface of the medium is preferably as flat as possible to avoid damage to the magnetic head and the magnetic recording medium. No need.

The surface roughness of the unevenness forming layer is Ra = 10 to 5
Preferably, it is 0 Å. A more preferred range is Ra = 10 to 30 angstroms.

When Ra is less than 10 angstroms,
Since the surface of the magnetic recording medium is nearly flat, the magnetic head and the magnetic recording medium are attracted to each other, and the magnetic head and the magnetic recording medium are damaged, or the head crashes due to the attracting, resulting in fatal damage. On the other hand, if Ra exceeds 50 angstroms, the glide height becomes large and the recording density is lowered, which is not preferable.

There are various known materials and methods for forming the concavo-convex forming layer, and there is no particular limitation. As the material of the unevenness forming layer, Al, Ti, Cr, Ag, Nb, Ta, Bi, S
i, Zr, Cu, Ce, Au, Sn, Pd, Sb, G
Metals such as e, Mg, In, W, and Pb and alloys thereof, or oxides, nitrides, and carbides of these metals and alloys can be used. From the viewpoint of easy formation, etc., A
l Simple substance, Al alloy, Al oxide (Al ₂ O ₃ etc.), A nitride
It is desirable to use a metal mainly containing Al, such as 1 (AlN or the like).

The concavo-convex forming layer may be a continuous texture film or may be composed of discretely distributed island-like projections. The height of the island-like projections is preferably 100 to 500 Å, and more preferably 100 to 300 Å.

The surface roughness and the height of the unevenness (projections) of the unevenness forming layer can be controlled by the material and composition of the unevenness forming layer, heat treatment conditions and the like.

As other methods for forming unevenness, there are texture processing by mechanical polishing, texture processing by chemical etching, texture processing by energy beam irradiation, and the like, and these methods can be combined.

Incidentally, it is of course possible to make the conductive thin film itself also have a function as a concavo-convex forming layer.

The material of the magnetic layer is not particularly limited.

As the magnetic layer, specifically, for example, C
CoPt, CoCr, CoNi, Co mainly containing o
NiCr, CoCrTa, CoPtCr, CoNiP
t, CoNiCrPt, CoNiCrTa, CoCrP
Magnetic thin films such as tTa and CoCrPtSiO may be used. Further, the magnetic layer is formed of a non-magnetic film (for example, Cr, CrM).
o, CrV, etc.) to reduce noise (for example, CoPtCr / CrMo / CoPtC)
r, CoCrTaPt / CrMo / CoCrTaPt).

The magnetic layer may be made of, for example, ferrite, iron-rare earth, SiO 2
₂ , Fe, Co, CoF in a non-magnetic film such as BN
e, granular having a structure in which magnetic particles such as CoNiPt are dispersed. The magnetic layer may be either an in-plane type or a vertical type.

The underlayer in the magnetic recording medium is appropriately selected according to the magnetic layer. As the underlayer, for example, C
An underlayer made of at least one material selected from non-magnetic metals such as r, Mo, Ta, Ti, W, V, B, and Al is exemplified. In the case of a magnetic layer containing Co as a main component, it is preferable to use Cr alone or a Cr alloy from the viewpoint of improving magnetic properties. The underlayer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, Cr / Cr, Cr / CrMo, Cr
/ CrV, and a multi-layer underlayer such as CrV / CrV.

Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a hydrogenated carbon film, a carbon nitride film, a zirconia film, and a silica film. These protective films can be continuously formed with an underlayer, a magnetic layer, and the like by an in-line or stationary facing sputtering apparatus.
Further, these protective films may be a single layer, or may be a multilayer structure composed of the same or different films.

Another protective layer may be formed on the protective layer or in place of the protective layer. For example, instead of the above-mentioned protective layer, colloidal silica fine particles may be dispersed and applied while diluting tetraalkoxylan with an alcohol-based solvent, and then baked to form a silicon oxide (SiO ₂ ) film. . In this case, it functions as both the protective layer and the unevenness forming layer.

Although various proposals have been made for a lubricating layer, generally, a perfluoropolyether (PF) is generally used.
A liquid lubricant composed of PE) or the like is applied to the surface of the medium by a dipping method (immersion method), a spin coating method, a spray method, or the like, and is formed by performing a heat treatment as needed.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described.

In the method of the present invention, a non-conductive non-magnetic substrate having a crystallized region containing crystal grains having an average grain size of 0.005 to 1 μm formed on at least the surface on which the magnetic layer is formed is prepared. Since the conductive thin film is formed so as to reflect the crystal grains contained in the crystallization region of the non-magnetic substrate, the crystal grains of the conductive thin film can be controlled easily and with high accuracy, and the reliability is improved. A magnetic recording medium with high performance can be obtained.

The crystal grains of the conductive thin film can be easily and precisely controlled by the type, size and heating conditions of the crystal grains contained in the crystallization region of the non-magnetic substrate. This is because crystallization of the conductive thin film can be achieved by faithfully reflecting the crystal grains contained in the crystallization region of the nonmagnetic substrate. The average crystal grain size of the crystal grains contained in the crystallization region of the non-magnetic substrate is set to 0.005 to 1 μm, more preferably 0.01 to 0.1 μm (10 to 100 nm). desirable. The reason for setting the grain size of the crystal grains in this range is as described above.

In the method of the present invention, a conductive thin film is coated on a nonmagnetic substrate with a solution containing a conductive precursor, the solvent in the solution is volatilized to form a thin film, and the thin film is heat-treated. It is preferable to form by a process.

Thus, a conductive thin film can be easily formed continuously and uniformly on the main surface and side surfaces of the non-magnetic substrate. By continuously forming the conductive thin film on the main surface and the side surfaces of the non-magnetic substrate in this manner, the conductive thin film on the main surface side on which the magnetic layer is formed and the conductive thin film on the side surfaces of the substrate are electrically connected. Then, the magnetic layer can be formed on the entire main surface of the substrate by bringing the contact for applying voltage into contact with the conductive thin film on the side surface of the substrate.

It is extremely difficult to form a conductive thin film on the side surface of the substrate by sputtering or the like. If no conductive thin film is formed on the side surface of the substrate, the contact to which a bias voltage is applied becomes a magnetic layer. Undesirably covers the main surface of the substrate on the side where the magnetic layer is formed, and places where the magnetic layer is not formed on the main surface of the substrate.

The heat treatment of the conductive thin film is performed for the purpose of crystallizing the conductive thin film. The heat treatment temperature of the conductive thin film differs depending on the material of the conductive thin film and is appropriately adjusted.

The method of the present invention has a step of forming a magnetic layer by applying a bias voltage to the non-magnetic substrate via the conductive thin film.

In the method of the present invention, a step of heat-treating the magnetic layer can be provided.

The other steps in the method for manufacturing a magnetic recording medium according to the present invention are not particularly limited, and conventionally known techniques can be employed.

[0074]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on examples.

Embodiment 1

First, the magnetic recording medium according to the first embodiment will be described.

FIG. 1 is a schematic sectional view showing the structure of a magnetic recording medium according to one embodiment of the present invention.

As shown in FIG. 1, the magnetic recording medium 10 of the present embodiment has an ITO conductive thin film 2 continuously formed on both main surfaces and side surfaces of a crystallized glass substrate 1, an unevenness forming layer 3,
It comprises an underlayer 4, a magnetic layer 5, a protective layer 6, and a lubricating layer 7.

The crystallized glass substrate 1 is expressed by weight%
iO ₂ is 62.9%, CaO is 18.3%, Na ₂ O is 7.6%, K ₂ O is 8.4%, Al ₂ O ₃ is 2.0%, M
It is composed of crystallized glass containing 0.1% of gO and 5.2% of F, containing canasite as a main crystal, and having a crystal grain size of 0.05 μm.

The crystallized glass substrate 1 has an outer diameter of 65 m.
It is formed in a disk shape having a diameter of mφ, an opening diameter of 20 mmφ at the center, and a thickness of 0.65 mm, and at least both main surfaces thereof are precisely polished so that the surface roughness Ra is 5 Å.

The ITO conductive thin film 2 is made of In ₂ O ₃ : 90
%, SnO ₂ : A conductive thin film composed of 10% of ITO and having a thickness of 100 nm, formed on both main surfaces and side surfaces of the crystallized glass substrate 1 continuously and uniformly.

This conductive thin film is a thin film which is crystallized by reflecting the size of crystal grains of crystallized glass, and has a crystal grain size of 0.05 μm and a surface roughness Ra of 5 μm.
Angstrom and flatness are maintained.

The unevenness forming layer 3 is a continuous texture film having an average film thickness of 10 nm and a surface roughness Ra of 20 Å.

Since the unevenness forming layer has good flatness of the conductive thin film, it is a continuous texture film having no unevenness in unevenness. If the flatness of the conductive thin film is poor,
Not only cannot the surface roughness of the unevenness forming layer be accurately controlled, but also the unevenness of the unevenness forming layer occurs, and the risk of causing a head crash increases.

The underlayer 4 is a Cr film having an average film thickness of 15 nm.

The magnetic layer 5 is made of CoPt having an average thickness of 20 nm.
It is a Cr film. Here, the composition of CoPtCr is atomic%.
And Co: Pt: Cr = 84: 10: 16.

The protective layer 6 is a carbon film having an average thickness of 10 nm.

The lubricating layer 7 is a liquid lubricant film made of perfluoropolyether having an average film thickness of 0.8 nm.

Next, a method of manufacturing the magnetic recording medium according to the first embodiment will be described.

[0090] The composition after manufacture glass of crystallized glass, in weight percentages, SiO ₂ is 62.
9%, CaO 18.3%, Na ₂ O 7.6%, K ₂ O
8.4%, Al ₂ O ₃ 2.0%, MgO 0.1%,
The batch adjusted so that F became 5.2% was melted in a platinum crucible or the like for several hours, sufficiently homogenized, and then formed into a plate shape. This plate-shaped glass is held at 600 ° C. for 1 hour,
A nucleus was formed by generating a crystal nucleus of canasite as a crystal source in the glass (primary crystallization treatment).

Further, the glass was kept at 1000 ° C. for 2 hours to crystallize the glass (secondary crystallization treatment).

Thereafter, the crystallized glass was gradually cooled to obtain a crystallized glass having a main crystal of canasite and having an average particle diameter of 0.05 μm, and this was cut into a disk shape. Polishing etc., outer diameter 65mmφ, center opening diameter 20mmφ, thickness 0.65mm, surface roughness R
The crystallized glass substrate 1 having a of 5 Å was obtained.

Production of Magnetic Recording Medium Next, indium propoxide (In (OC ₃ H ₇ ) ₃ ) was used.
And tin propoxide (Sn (OC ₃ H ₇ ) ₄ ) were mixed at a molar ratio of 9: 1, and this was dissolved in alcohol.
Hydrolyze to make a coating solution. The crystallized glass substrate 1 was immersed in the coating solution and pulled up at a constant speed to form a coating film on the crystallized glass substrate 1.

This substrate was dried at 100 ° C. for 10 minutes, and then baked at 400 ° C. for 60 minutes in the air to form a uniform ITO conductive film continuously formed on both main surfaces and side surfaces of the crystallized glass substrate 1. A glass substrate on which the conductive thin film 2 was formed was obtained.

The ITO conductive thin film had a crystal structure, and the crystal grain size was 0.05 μm as reflected by the crystal grains of the crystallized glass. The obtained ITO conductive thin film had a thickness of 100 nm and a specific resistance of 0.01 Ωc.
m.

Next, the glass substrate 1 on which the ITO conductive thin film 2 was formed was placed on a holder having terminals for applying a voltage by using an in-line type sputtering apparatus.
Are disposed so that the side surfaces of the substrate are in contact with each other, and an average film thickness of 1
0 nm, A having an average surface roughness Ra of 20 Å
1 An unevenness control layer 3 and a Cr underlayer 4 having a thickness of 15 nm were sequentially formed. Subsequently, while applying a bias voltage of −300 V to the ITO conductive thin film 2 formed on the substrate,
nm of CoPtCr (Co: 84 at%, Pt 10 at
%, Cr: 16 at%).
C., Ar gas pressure: formed under an inert gas atmosphere of 2 mtorr.

Here, when the coercive force of the magnetic layer was measured, it was 2500 Oe.

Finally, a 10 nm-thick carbon protective layer 6 and a 0.8 nm-thick perfluoropolyether lubricating layer 7 were sequentially formed on the above substrate to obtain a magnetic recording medium.

Evaluation The magnetic recording medium obtained above was subjected to a 50% slider and a load of 3 at room temperature and normal humidity.
A 5 g CSS durability test was performed 100,000 times, but the magnetic head and the magnetic recording medium did not stick.

Further, a glide test was performed on the obtained magnetic disk. As a result, a hit (the head touches a protrusion on the surface of the magnetic disk) and a crash (the head hits a protrusion on the surface of the magnetic disk) were recognized. Did not.

The average particle diameters of the crystallized glasses of Examples 2 to 6 and Comparative Examples 1 and 2 were each 0.004 μm.
(Comparative Example 1), 0.005 μm (Example 2), 0.01
μm (Example 3), 0.1 μm (Example 4), 0.5 μm
m (Example 5), and a magnetic recording medium was manufactured in the same manner as in Example 1 except that the thickness was changed to 1 μm (Example 6) and 2.0 μm (Comparative Example 2).

The crystal grain size, specific resistance value,
Coercive force of magnetic recording medium, CSS of obtained magnetic recording medium
Table 1 shows the results of the durability test. FIG. 2 shows the relationship between the crystal grain size and the specific resistance of the ITO conductive thin film, and FIG. 3 shows the relationship between the specific resistance and the coercive force.

[0103]

[Table 1]

As can be seen from Table 1, FIG. 2 and FIG. 3, when the crystal grain size of the conductive thin film is 0.005 to 1 μm, the specific resistance value is low and the conductivity is high, so that the bias is effectively applied to the substrate. It can be seen that a voltage can be applied, a magnetic recording medium having a high coercive force can be obtained, and a magnetic recording medium free from head crash can be obtained.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments.

For example, instead of a crystallized glass substrate, a glass substrate having a crystallized region on the surface where a conductive thin film is formed as shown in FIG. 4 or a substrate such as quartz glass as shown in FIG. A substrate having a surface coated with crystallized glass may be used. In FIG. 4, the depth of the crystallization region can be appropriately adjusted, and the crystallization level of the substrate surface is high and the crystallization level gradually decreases toward the inner surface of the substrate (in the depth direction). it can.

Instead of forming an unevenness control layer below the magnetic layer, an unevenness control layer may be formed on the magnetic layer as shown in FIG. 6, or unevenness may be formed on the conductive thin film itself. It may be formed to have a function as an unevenness control layer.

Further, the conductive thin film was not formed continuously on both the main surface and the entire side surface of the substrate, but as shown in FIG.
It may be formed continuously on one of the main surface and the outer peripheral side surface of the substrate.

In the case of manufacturing a magnetic recording medium for a contact type recording system or a dynamic load type magnetic disk device, the magnetic recording medium is almost flat without forming any unevenness or unevenness control layer. It can also be a medium.

[0110]

As described above, according to the present invention, the crystal grains contained in the crystallization region of the non-magnetic substrate are controlled, and the conductive thin film is formed by reflecting the crystal grains. Crystal grains of the conductive thin film can be accurately adjusted, and a conductive thin film having a desired specific resistance value can be obtained.

Further, since the specific resistance value of the conductive thin film is low,
Since a magnetic layer can be formed by efficiently applying a bias voltage to the conductive thin film, a magnetic recording medium having an extremely high coercive force can be obtained.

Further, since the flatness of the conductive thin film is maintained, a magnetic recording medium capable of high-density recording can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a magnetic recording medium according to one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a crystal grain size of a conductive thin film and a specific resistance value.

FIG. 3 is a diagram showing a relationship between a specific resistance value of a conductive thin film and a coercive force of a magnetic recording medium.

FIG. 4 is a view showing another embodiment of the non-magnetic substrate.

FIG. 5 is a view showing still another embodiment of the non-magnetic substrate.

FIG. 6 is a diagram showing an embodiment in which an unevenness control layer is formed on a magnetic layer.

FIG. 7 is a diagram showing an embodiment in which a conductive thin film is not formed on the entire surface of a substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Conductive thin film 3 Unevenness control layer 4 Underlayer 5 Magnetic layer 6 Protective layer 7 Lubricating layer 10 Magnetic recording medium

Claims (11)

[Claims] 1. A magnetic recording medium having at least a conductive thin film and a magnetic layer on a non-conductive non-magnetic substrate having a heat-resistant temperature of 400 ° C. or higher, wherein the non-magnetic substrate has at least the conductive property. A crystallization region including crystal grains on the surface of the substrate on which the conductive thin film is formed, wherein the conductive thin film is formed by reflecting the crystal grains included in the crystallization region of the non-magnetic substrate. A magnetic recording medium characterized by the above-mentioned. 2. An average crystal grain size of crystal grains contained in a crystallization region of the nonmagnetic substrate is 0.005 to 1 μm, and an average crystal grain size of the conductive thin film is 0.005 to 1 μm. The magnetic recording medium according to claim 1, wherein: 3. An average crystal grain size of crystal grains contained in a crystallization region of the nonmagnetic substrate is 0.005 to 0.1 μm, and an average crystal grain size of the conductive thin film is 10 to 100 nm.
The magnetic recording medium according to claim 1, wherein 4. The magnetic recording medium according to claim 1, wherein said non-magnetic substrate is made of crystallized glass. 5. The method according to claim 1, wherein the conductive thin film comprises In, Sn, Sb,
5. The magnetic recording medium according to claim 1, comprising an oxide containing at least one element selected from Mg, Zn, Ga, and Cd. 6. The conductive thin film according to claim 1, wherein the conductive thin film is selected from indium tin oxide, tin antimony oxide, magnesium indate, zinc gallate, cadmium antimonate, indium zinc oxide, and indium gallium zinc oxide. 6. The magnetic recording medium according to claim 5, wherein the magnetic recording medium is made of one material. 7. The magnetic recording medium according to claim 1, wherein the conductive thin film is formed by volatilizing and baking a solvent of a solution containing a conductive precursor. 8. A heat-resistant temperature of 400 ° C. or higher, and an average particle size of at least 0.04
A step of preparing a non-conductive non-magnetic substrate having a crystallized region containing crystal grains of 1 to 0.1 μm; A method for manufacturing a magnetic recording medium, comprising: forming a thin film; and applying a bias voltage to the non-magnetic substrate via the conductive thin film to form a magnetic layer. 9. The method for manufacturing a magnetic recording medium according to claim 8, wherein the average crystal grain size of the crystal grains contained in the crystallization region of the non-magnetic substrate is 0.05 to 0.1 μm. . 10. The step of forming the conductive thin film includes the steps of: applying a solution containing a conductive precursor on the non-magnetic substrate; and evaporating a solvent in the solution to form a thin film. 10. A method for manufacturing a magnetic recording medium according to claim 8, further comprising the step of: 11. The magnetic recording medium according to claim 8, wherein the non-magnetic substrate is a crystallized glass substrate.