JP2002334426A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard disk type magnetic recording medium using a resin substrate which effectively suppresses production of cracks in the resin substrate, shows preferable environmental storage characteristics against high temperature and high humidity and is suitable as a hard disk system. SOLUTION: A first nonmagnetic base film, second nonmagnetic base film, magnetic information recording film, protective film and lubricant are successively deposited on a resin substrate. The first nonmagnetic base film consists of an alloy essentially comprising Cr and containing Nb, Ta or W by >=12 at.% and <=40 at.%. The first nonmagnetic base film is formed to >=1 nm and <=20 nm thickness. Further, oxygen atoms are incorporated into the surface of the resin substrate.

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 mounted on various magnetic recording devices such as an external storage device of a computer, in particular, a magnetic information recording film formed on a resin substrate through at least a base film. The present invention relates to a magnetic recording medium formed.

[0002]

2. Description of the Related Art Hard disk systems have been widely used as computer storage devices. This hard disk system generally includes a base plate mainly composed of Cr, a Co-Pt-Cr film on a metal plate of aluminum or the like whose surface is polished with high precision, or a substrate made of glass or the like.
A magnetic disk formed with a magnetic information recording film such as an alloy, a protective film mainly composed of C, and the like is used as a magnetic recording medium. In the hard disk system, a flying slider on which a magnetic head is mounted is floated by a predetermined flying height on a signal recording area of the magnetic disk to write and / or read signals.

[0003] By the way, as such hard disk systems are widely spread, further lower prices are required. In order to respond to the demand for lower prices,
As a substrate of a magnetic disk, application of a resin (plastic) disk substrate generally used in an optical disk or the like has been studied.

[0004] If a resin material is used as the substrate material of the magnetic disk, the cost of the material itself is greatly reduced, and servo signals and the like can be easily preformatted by injection molding. The manufacturing cost of the magnetic disk can be greatly reduced.

However, when a resin material is used as the substrate material of the magnetic disk, the following problems have occurred. First, when a metal film is laminated on a resin magnetic disk substrate (resin substrate), cracks may occur in the resin substrate due to internal stress. When a crack occurs in the magnetic disk substrate, the magnetic recording medium not only inhibits proper recording and reproduction of signals, but also has a problem that the quality of the magnetic recording film is increased. Therefore, if a crack occurs in the magnetic disk substrate, there arises a problem that not only the place where the crack occurs but also the entire magnetic disk, that is, the entire magnetic recording medium becomes defective.

For example, when a crack is generated due to an internal stress of pulling when a base film of Cr or a Cr alloy or the like in contact with a resin substrate is formed, a cross section of the laminated film is exposed, and Co atoms in the magnetic information recording film are removed. There is a concern that it may cause problems such as deposition on the film surface to form projections and hydration of Co causing the MR head to rust. For this reason, it is necessary to control the internal stress of a film such as Cr or a Cr alloy.

As a method for solving such a problem of the occurrence of cracks, the internal stress of a laminated film (base film, magnetic information recording film, protective film, etc.) laminated on a resin substrate is reduced to 0.3 G.
It is known that cracking can be suppressed by setting the pressure to Pa or less (Japanese Patent Laid-Open No. 2000-293893).
No.).

According to this method, the internal stress is reduced to 0.3 GP.
By setting the value to a or less, cracks having a size of a level observed with an optical microscope disappear. However, as a result of a detailed study, it was found that an AFM (Atomic Force Mi) was used.
(crossscope) and SEM (Scanning E)
Observation using an electric microscope revealed that finer cracks (approximately 1 μm) were generated, and it was found that the conventional technology was not sufficient.

Second, when the magnetic disk is stored in a high-temperature, high-humidity state, moisture intervenes between the substrate and the underlying film (metal film) due to the moisture absorption of the resin substrate, thereby floating the underlying film on the substrate. There was a case. When the base film on the resin substrate floats, the deformation height of the film becomes about 200 nm or more, which is very low relative to the magnetic disk (about 25 nm).
(Approximately below) and comes into contact with the floating magnetic head, causing the magnetic head to crash and thus failing to function as a hard disk drive.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional situation, and has as its object to crack a resin substrate in a hard disk type magnetic recording medium using the resin substrate. An object of the present invention is to provide a magnetic recording medium suitable for a hard disk system, in which generation is effectively suppressed and good environmental preservation characteristics against high temperature and high humidity are exhibited.

[0011]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that a metal laminated film such as a base film formed on a resin substrate, especially a resin laminated film. It has been found that when the internal stress of the metal base film formed directly on the substrate is large, cracks are generated in the resin substrate due to this.

Further, the present inventors have conducted intensive studies in order to solve the problem that moisture intervenes between the substrate and the metal film due to the moisture absorption of the resin substrate, thereby floating the underlying film on the substrate. As a result, they have found that by including oxygen atoms on the surface of a resin material used for a resin substrate, the durability against high temperature and high humidity, that is, the environmental storage resistance can be improved.

The magnetic recording medium according to the present invention has been created based on the above knowledge, and has a first non-magnetic base film, a second non-magnetic base film, An information recording film, a protective film, and a lubricant are laminated at least sequentially, and the first nonmagnetic underlayer is made of Nb, Ta, or W.
Is contained in an alloy containing 12 at% or more and 40 at% or less, and is mainly composed of Cr. Here, as the resin substrate, a substrate made of a polycycloolefin hydrocarbon is preferable, and the thickness of the first nonmagnetic underlayer is preferably 1 nm or more and 20 nm or less.

According to the present invention, with respect to the first non-magnetic underlayer, the internal stress caused by the pulling of the metal film during the formation of the film made of Cr or a Cr alloy is such that Cr is Nb,
By adding Ta and W in an amount of 12 atomic% or more and 40 atomic% or less, it is possible to control to 0.1 GPa or less.

That is, by setting the internal stress to 0.3 GPa or less, the occurrence of cracks at a level observable with an optical microscope can be suppressed, but an AFM (Atomic Force M) is used.
Scope) or SEM (Scanning)
Regarding fine cracks (about 1 μm) observed in Electric Microscope, it is necessary to control the internal stress to 0.1 GPa or less.

Since the internal stress is governed by the internal stress of the underlying film directly in contact with the substrate (resin substrate), the internal stress of the laminated film, ie, the first non-magnetic underlying film is 0.1 G
By setting the pressure to Pa or less, the occurrence of cracks on the resin substrate of the magnetic recording medium is effectively suppressed.

The average crystal grain size of the underlayer is usually 5n.
The thickness is preferably in the range of m to 15 nm, and if it exceeds 15 nm, the S / N of the information recording film may be significantly reduced, which is not desirable. In order to make the particle diameter in the range of 5 nm to 15 nm, for example, the gas pressure and the like are adjusted at the time of forming each film to be formed on the resin substrate by the sputtering method, and the conditions are set to optimal conditions. .

Furthermore, by including oxygen atoms on the surface of the resin substrate, it is possible to exhibit good environmental storage durability as a magnetic disk.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Here, an example in which the present invention is applied to a magnetic disk configured as a magnetic recording medium of a hard disk system will be described. However, the magnetic recording medium according to the present invention is not limited to this example, and is not limited to this example. The present invention is applicable to any magnetic recording medium in which a laminated film including at least a base film and a magnetic information recording film is formed.

FIG. 1 is an enlarged sectional view of a main part of a magnetic disk applied to the present invention. Magnetic disk 1 shown in FIG.
Is used as a magnetic recording medium of a hard disk system, and includes a resin substrate 2 formed by molding a resin material into a disk shape.
2a, a first non-magnetic base film 3 and a second non-magnetic base film 3 'which are bases of the magnetic information recording film 4, a magnetic information recording film 4, and protection for protecting the magnetic information recording film 4 Membrane 5,
The lubricant 6 is sequentially laminated in this order. And
The magnetic disk 1 is rotated by a spindle motor or the like, and a signal is written to the magnetic information recording film 4 by a magnetic head mounted on a slider that floats on the magnetic disk 1 by a predetermined flying height. The signal written on the magnetic information recording film 4 is read.

The resin substrate 2 is preferably made of a resin material such as a thermoplastic resin, for example, a material made of a polycycloolefin hydrocarbon. By selecting such a material, it is suitable for molding by a method such as injection molding, and the obtained substrate has excellent dimensional stability, excellent surface smoothness, and excellent environmental resistance such as humidity. ing.

The resin substrate 2 is formed in a disk shape by injection molding or the like. On one main surface 2a of the resin substrate 2, it is preferable that irregularities indicating servo signals and the like are formed in advance. . When the resin substrate 2 is injection-molded, the irregularities are formed by a stamper having a reverse pattern of the irregularities.
Alternatively, it can be formed by using a mold.

The surface roughness of the resin substrate 2 is preferably 2 nm or less, and the maximum projection height is preferably 20 nm or less. By improving the surface smoothness of the resin substrate 2 in this way, even if the gap between the magnetic disk 1 and the magnetic head is reduced, the magnetic disk 1 and the magnetic head do not come into contact with or collide with each other, and recording and reproduction can be performed stably. .

It is desirable that the substrate surface of the resin substrate 2 contains oxygen atoms. If the substrate surface is not set, the resin substrate 2 and the first non-magnetic base film 3 formed on the resin substrate 2 by sputtering or the like may not sufficiently adhere to each other. When exposed to the environment and moisture intervenes between the resin substrate 2 and the first non-magnetic underlayer 3, the resin constituting the resin substrate 2 has a very small ability to absorb moisture, so that sputtering is performed. A phenomenon that the metal film formed in the step floats may occur.

The first non-magnetic underlayer 3 is for preventing the occurrence of cracks, for example, Cr or Cr-X.
A Cr alloy such as (X = Nb, Ta, W) is formed on one main surface 2a of the resin substrate 2 by sputtering.

When Nb, Ta, or W is selected as an element to be added to Cr forming the first nonmagnetic underlayer,
It has the effect of reducing internal stress, especially 12% against Cr.
By adding at least 40 atomic%, the internal stress becomes 0.1 GPa or less, and cracks can be prevented. However, if the amount of the added element is excessively increased, the S / N tends to decrease, and if it is added at 40 atomic% or more, the S / N tends to be lower than the required S / N.

The thickness of the first nonmagnetic underlayer 3 is 1 n
It is desirable that the thickness be in the range of not less than m and not more than 20 nm. If the thickness of the first nonmagnetic underlayer 3 is less than 1 nm, the effect of preventing the occurrence of cracks is not sufficiently exhibited. If the thickness of the first non-magnetic underlayer 3 exceeds 20 nm, the effect on the magnetic properties of the first non-magnetic underlayer 3 is increased, and the effect of the second non-magnetic underlayer 3 'is reduced. There is a disadvantage that it is done.

The second nonmagnetic underlayer 3 ′ aligns the magnetic field of the magnetic information recording film 4 in the in-plane direction of the magnetic information recording film 4.
For improving the magnetic properties of W, Mo and W-X (X = Cr, Ti, Mo).
One main surface 2 of resin substrate 2 by sputtering of alloy
a. The second non-magnetic underlayer 3 '
Are not formed directly on the first non-magnetic underlayer 3, that is,
It may be formed via a Ni-P film, a C film, or the like that becomes a seed layer.

The magnetic information recording layer 4 is composed of crystal grains having ferromagnetism and non-magnetic grain boundaries surrounding the ferromagnetic grains, and the non-magnetic grain boundaries are made of a metal oxide or nitride. It is a magnetic layer. Such a structure can be formed, for example, by forming a film by sputtering in a vacuum with a ferromagnetic metal containing an oxide constituting a nonmagnetic grain boundary as a target, or using a ferromagnetic metal as a target with an oxygen-containing Ar It can be manufactured by forming a film by reactive sputtering in a gas.

The material constituting the crystal having ferromagnetism is not particularly limited, but a Co-Pt alloy can be preferably used. In particular, it is desirable to add at least one element of Cr, Ni and Ta to the Co-Pt alloy in order to reduce the noise of the magnetic recording medium and to adjust the thickness of the residual magnetization. Alloys are preferred.

On the other hand, materials constituting the non-magnetic grain boundaries include Cr, Co, Si, Al, Ti, Ta, Hf, and Zr.
Of the oxides of at least one element,
It is particularly desirable to form a stable granular structure.

The thickness of the magnetic information recording layer is not particularly limited, and a thickness (usually about 5 to 25 nm) for obtaining a sufficient magnetic head reproduction output during recording and reproduction is required.

The protective film 5 protects the magnetic recording medium 1 from external stress such as wear and damage caused by contact with the magnetic head.
Provided to protect the Therefore, not only the magnetic recording medium 1 is protected, but also, for example, carbon (C) having a high hardness that does not damage the magnetic head.
A thin film mainly composed of, for example, is used.

The lubricant 6 forms a lubricating layer on the protective film 5, thereby reducing the friction coefficient of the surface of the magnetic recording medium 1 and improving the running property and durability of the magnetic recording medium 1. Is to improve. As the lubricant 6, for example, a perfluoropolyether-based lubricant can be used.

The magnetic disk 1 configured as described above has a first non-magnetic base film 3 and a second non-magnetic base film 3 ′ laminated on one main surface 2 a of the resin substrate 2. , The entirety including the magnetic information recording film 4, the protective film 5, the lubricant 6, and other films such as a Seed layer added between them (hereinafter, on one main surface 2a of the resin substrate 2). The overall stress of the film formed by lamination is referred to as a laminated film 7). In the magnetic disk 1, since the internal stress of the laminated film 7 is set to 0.1 GPa or less, inconveniences such as generation of cracks in the resin substrate 2 can be effectively prevented, and proper recording and reproduction of signals can be performed. Can be.

The magnetic disk 1 constructed as described above
For example, the first non-magnetic base film 3 and the second non-magnetic layer constituting the laminated film 7 are formed on one main surface 2a of the resin substrate 2 by an in-line type sputtering apparatus 10 as shown in FIG. It is manufactured by sequentially forming a base film 3 ', a magnetic information recording film 4, a protective film 5, and the like.

The in-line type sputtering apparatus 10 shown in FIG. 2 has a plurality of chambers 11, 12, 13, 14, 15 arranged in-line (on a straight line). These plurality of chambers 11, 12, 13, 14, 1
5 is provided with an exhaust port 16, and a vacuum pump 17 is connected through the exhaust port 16.
Each of these chambers 11, 12, 13, 14, 1
The inside of 5 can be evacuated to a predetermined degree of vacuum by a vacuum pump 17.

Further, a plurality of chambers 11, 12, 13,
Each of 14 and 15 is provided with a gas inlet 18, and a sputter gas supply source 19 is connected through the gas inlet 18. And each of these chambers 1
A sputtering gas such as Ar gas is supplied from 1, 12, 13, 14, 14, and 15 from a sputtering gas supply source 19.

The chamber 11 is provided with a cathode for performing plasma processing. Also, a plurality of chambers 1
A target holder 20 for holding a target is provided in each of 2, 13, 14 and 15. Each of these target holders 20 is connected to a target electrode (not shown).
For example, by applying a negative potential of 600 to 800 V, the target held by the target holder 20 can be sputtered.

Further, a plurality of chambers 11, 12, 13,
A pallet 21 on which a substrate is placed is arranged in one of the chambers 14 and 15. The pallet 21 has a plurality of chambers 11, 12, 13, 14, 15
You can move freely between them.

This in-line type sputtering apparatus 1
When the magnetic disk 1 is manufactured using the magnetic disk 1, first, an apparatus for performing plasma processing on the chamber 11, and a material for forming the first non-magnetic base film 3, for example, a target made of a Cr alloy, are provided on the target holder 20 of the chamber 12. And the target holder 20 of the chamber 13 holds a material of the second non-magnetic base film 3 ′, for example, a target of a W alloy, and the magnetic information recording film 4 is formed on the target holder 20 of the chamber 14. Material, for example, Co-Pt-Cr
-Holding a SiO ₂ -based target, and holding a material constituting the protective film 5, for example, a C target, in the target holder 20 of the chamber 15.

First, the resin substrate 2 is placed on the pallet 21, and the pallet 21 is moved into the chamber 11, so that one main surface 2a of the resin substrate 2 faces the cathode of the plasma generator. And each chamber 11, 12,
The insides of 13, 14, and 15 are evacuated by a vacuum pump 17 to a predetermined degree of vacuum, for example, about 2 × 10 ⁻⁵ Pa. afterwards,
A sputtering gas is supplied from the sputtering gas supply source 19 into the chamber 11 in which the cathode is disposed at a gas pressure of, for example, about 8.0 Pa.
Introducing a sputtering gas such as r gas, for example, 20
Plasma is generated by electric power of about 0 W, and the resin substrate 2
By performing the pre-treatment, an oxygen-containing functional group, for example, a hydroxyl group, a carbonyl group, a carboxyl group, or the like is formed on one main surface 2a of the resin substrate 2.

Next, the pallet 21 is moved while keeping the vacuum in the chamber 12 so that the one main surface 2a of the resin substrate 2 is kept at 84 at.
16 atomic% W (hereinafter, atomic% is omitted and 84Cr-16
Notated as W. Note that other compounds have the same notation.)
To the target. A sputtering gas such as Ar gas is introduced from the sputtering gas supply source 19 into the chamber 12 in which the 84Cr-16W target is disposed, for example, at a gas pressure of about 3.0 Pa, and the power is reduced to about 300 W, for example. The first nonmagnetic underlayer 3 is formed to a thickness of about 5 nm on one main surface 2a of the resin substrate 2 by sputtering an 84Cr-16W target.

Next, the pallet 21 is moved into the chamber 13, and one main surface 2 a of the resin substrate 2 on which the first non-magnetic base film 3 is formed is placed on the target holder 20. To the target. And
50Ti-50W from sputtering gas supply source 19
In the chamber 13 in which the target is provided, for example, 0.
A sputtering gas such as an Ar gas is introduced at a gas pressure of 6 Pa, and for example, 50 Ti-50 W is applied at a power of about 350 W.
The target is sputtered, and the first non-magnetic base film 3 formed on one main surface 2a of the resinous substrate 2
A second non-magnetic underlayer 3 'is formed to a thickness of about 0 nm.

Next, the pallet 21 is moved into the chamber 14, and the one main surface 2a of the resin substrate 2 on which the first non-magnetic base film 3 and the second non-magnetic base film 3 'are formed is targeted. 64Co-14Pt-10 held in the holder 20
Made to face the target Cr-12SiO _2. Then, from the sputtering gas supply source 19, 64Co-1
In a chamber 14 in which a 4Pt-10Cr-12SiO ₂ target is disposed, for example, a gas pressure of 0.9 Pa
Introducing a sputtering gas such as r gas, for example, 35
64Co-14Pt-10Cr-1 at power of about 0W
By sputtering a 2SiO ₂ target, a magnetic information recording film 4 having a thickness of about 12 nm is formed on a second non-magnetic base film 3 ′ formed on one main surface 2 a of the resin substrate 2.

Next, the pallet 21 is moved into the chamber 15, and the first non-magnetic base film 3, the second non-magnetic base film 3 ', and the resin substrate on which the magnetic information recording film 4 is formed. 2 with one main surface 2a held in the target holder 20 by C
To the target. Then, a sputtering gas such as an Ar gas is introduced from the sputtering gas supply source 19 into the chamber 15 in which the C target is provided, for example, at a gas pressure of about 0.6 Pa, and the C gas is supplied at a power of about 450 W, for example. The target is sputtered to form a protective film 5 on the magnetic information recording film 4 with a thickness of about 8 nm.

As described above, the first non-magnetic base film 3, the second non-magnetic base film 3 ', the magnetic information recording film 4, the protective film 5 are sequentially formed, and a lubricant 6 (for example, a fluorine-based lubricant) is applied on the protective film 5 by a dipping method or the like, so that the magnetic disk 1 used as a magnetic recording medium of the hard disk system is formed. Complete.

The magnetic disk 1 manufactured as described above
Is a first laminate formed on one main surface 2a of the resin substrate 2.
Non-magnetic base film 3, second non-magnetic base film 3 ', magnetic information recording film 4, protective film 5, and debris film 7 containing lubricant 6
Is set to 0.1 GPa or less,
The inconvenience of cracks in the resin substrate 2 is effectively prevented. In addition, this information recording medium can exhibit good environmental storage durability by performing a process of including oxygen atoms on the surface of the resin substrate.

[0049]

Embodiments of the present invention will be described below. Example 1 In order to confirm the effects of the present invention, the relationship between the internal stress of the laminated film and the occurrence of cracks was examined, and a magnetic disk was actually manufactured and stored in a high-temperature, high-humidity environment. The relationship with the film floating was investigated.

The resin substrate was manufactured as follows.
The same method as that used for the optical disk was used to form the pattern on the resin substrate. First, a resist was applied to the surface of a glass disk for producing a stamper, and a groove pattern was exposed on the resist based on cutting data. Next, after pattern exposure,
Development and cutting were performed to form a resist pattern. Thereafter, Ni plating was applied to the glass disk on which the resist pattern remained, and the back surface of the Ni plating was polished to a desired thickness to complete a stamper.
The same method is used when a pattern such as a groove is not required. In this case, only a resist is applied, Ni plating is applied thereon, and the back surface is polished to a desired thickness to complete a stamper. Let it.

Next, resin (plastic) molding was performed using this stamper to obtain a required 3.5-inch resin substrate (disk). The resin used for molding is polycycloolefin (ZEONEX manufactured by Zeon Corporation). The average surface roughness Ra of the obtained plastic substrate is:
AFM (Atomic Force Microsco
It was 0.352 nm from the measurement result of pe). In addition, the maximum projection height was 4.505 nm. This was almost equal to the surface roughness of the resist surface applied to the glass disk for the stamper.

The relationship between the internal stress of the laminated film and the occurrence of cracks is governed by the magnitude of the internal stress due to the pulling of the underlying film, and it has been found that cracks can be prevented by setting the magnitude to 0.3 GPa or less. I have. However, as a result of a subsequent study, it was found that when the internal stress was 0.1 to 0.3 GPa, a crack having a size of about 1 μm was generated.

A crack having a size of about 1 μm cannot be observed with an optical microscope.
c Force Microscope) or S
EM (Scanning Electric Micror)
osc)). For the measurement of internal stress, a film is formed on an optically flat glass plate by sputtering, the number of Newton rings formed at that time is measured, and based on the number of Newton rings, each of the following methods is used. The internal stress of the film was calculated.

By forming a thin film having a thickness d on a circular glass plate, the glass plate is deformed, and when a radius of curvature r is obtained, the internal stress α of the thin film formed on the glass plate is obtained.
It is the Young's modulus of the glass plate as ^{E (7.0 × 10 10 Pa)} , the thickness of the glass plate and ^{b (1.0 × 10 -4 m)} , the Poisson's ratio and [nu (0.2) , Is obtained by the following equation (1).

[0055] ^{α = Eb 2/6 (1} -ν) rd ··· (1) , where the radius of curvature r can be determined from the number n of the radius R and Newton rings of the glass plate. That is, as shown in FIG. 3, when the deformation height of the deformed glass plate is h, R · sin θ = h and r · sin θ = R · cos θ. Here, when θ ≒ 0, sin θ = tan θ =
θ, R · θ = h, r · θ = R, and r =
Represented as R ² / h.

Here, since the wavelength of the green filter used in this measurement is 546.1 nm, the deformation height h of the glass plate is represented by 546.1 × n (nm). Therefore, the radius of curvature r is obtained by the following equation (2).

[0057] ^{r ≒ R 2/546 · n} ··· (2) or the formula (1), and the equation (2), on the basis of the number of Newton's rings was calculated internal stresses of the respective films.

COMPARATIVE EXAMPLE 1 First, the dependency of the sputtering gas pressure on the internal stress and crack generation of the first nonmagnetic underlayer film 3, the magnetic information recording film 4, and the protective film 5 constituting the laminated film 7 shown in FIG. 10mm in diameter and 0.1mm in thickness to confirm the property
While changing the gas pressure of the sputtering gas (Ar gas) on the optically flat circular glass plate of
0 nm Cr film (corresponding to the first nonmagnetic underlayer 3), 25 nm thick Co-Pt-Cr film (64Co-14Pt)
-10Cr-12SiO ₂₎ (corresponding to the magnetic information recording layer 4), the film thickness was formed by sputtering 20nm of C film (corresponding to the protective film 5), respectively. FIG. 4 shows the relationship between the internal stress and the crack.

FIG. 4 shows that the internal stress of the Cr film greatly depends on the gas pressure of the sputtering gas, and that the Cr film formed under the condition that the gas pressure of the sputtering gas is 0.1 to 1.5 Pa: It turns out that a large tensile stress is working. In contrast, 64Co-14Pt-10Cr-
It can be seen that the internal stress of the 12SiO ₂ film and the C film does not depend much on the gas pressure of the sputtering gas, and a predetermined compressive stress always acts. However, in the Cr film, generation of microcracks is observed in any region of the sputtering gas pressure.

Next, the gas pressure of the sputtering gas was changed.
While the resin substrate was manufactured in the same manner as in Example 1.
2 and a Cr film is formed on the first non-magnetic base film 3.
On this Cr film, a Co-Pt-Cr film (64Co-
14Pt-10Cr-12SiO _TwoFilm) (magnetic information recording
Film 4) and a C film (corresponding to the protective film 5) are sequentially formed.
Thus, a laminated film was formed. The internal stress and crack
Effect of gas pressure of sputtering gas on the relationship with crack generation
I checked about it. The result is shown in FIG.

FIG. 5 shows that the Cr film and the 64Co-14Pt
And -10Cr-12SiO ₂ film, the laminated film and the C film are laminated, the tensile stress of the Cr film is largely acts,
As a whole, it can be seen that a tensile stress depending on the gas pressure of the sputtering gas at the time of forming the Cr film acts.
Then, only when the internal stress of the laminated film exceeds 0.3 GPa, it is recognized that a large crack is generated in the resin substrate, and a micro crack is generated in the entire region.

From the above results, it was found that cracks cannot be effectively prevented only by adjusting and controlling the gas pressure of the sputtering gas during the formation of the Cr film.

Example 2 The configuration of the first nonmagnetic underlayer 3 was fixed to 8 nm, the Ar pressure at the time of film formation was fixed to 2.0 Pa, and the structure according to FIG.
By changing the second element added to Cr, the first nonmagnetic underlayer 3
Is formed thereon, and 50Ti-50W is successively formed thereon as a second nonmagnetic underlayer 3 'by 10 nm (Ar pressure: 0.8 P).
a (6 mTorr)), 64C as the magnetic information recording film 4
o-14Pt-10Cr-12SiO ₂ at 10 nm
(Ar pressure: 1.1 Pa (8 mTorr)), protective film 5
Is 8 nm (Ar pressure: 0.67 Pa (5 mT
orr)) was formed to produce a magnetic recording medium (magnetic disk). FIG. 6 shows the result of examining the S / N of the obtained magnetic recording medium.

FIG. 6 shows that when Ti and Mo are selected as elements to be added to Cr forming the first non-magnetic underlayer, the effect of reducing internal stress is small, but Nb, Ta,
When W was selected, it was found that, in contrast, the internal stress was reduced. And it turned out that internal stress becomes 0.1 GPa or less by adding 12 atomic% or more, and a crack can be prevented. However, if the amount of the added element is excessively increased, the S / N becomes small, and if it is added in an amount of 40 atomic% or more, the S / N falls below the required S / N. Therefore, it was found that it is desirable to add Nb, Ta, and W as an additional element in an amount of 12 atomic% or more and 40 atomic% or less.

Example 3 Next, referring to FIG. 1, the composition of the first non-magnetic
4Cr-16W and the Ar pressure (2.0 Pa) were fixed, the film thickness was changed, and 50Ti-50W 10 nm as the second nonmagnetic underlayer 3 'and the magnetic information recording film 4 were sequentially formed thereon as the second nonmagnetic underlayer 3'. , 64Co-14Pt-10Cr-12S
A magnetic recording medium (magnetic disk) was manufactured by forming iO ₂ at 10 nm and forming C as the protective layer 5 at 8 nm.

FIG. 7 shows the results of an investigation on the dependency of the film thickness on the relationship between the internal stress and the occurrence of cracks, and the dependency of the film thickness on the relationship between the S / N and the occurrence of cracks.
From this figure, the thickness of the first non-magnetic film 3 is set to 3 nm to 2 nm in order to suppress the occurrence of cracks and maintain the necessary S / N.
It has been found that both characteristics can be compatible with each other within the range of 0 nm.

Example 4 A structure similar to that of FIG. 1 was used. On a resin substrate 2 made of ZEONEX, 84Cr-1 was formed as a first nonmagnetic underlayer 3.
6W to 3 nm (Ar pressure: 2.0 Pa), and 50Ti-50W as a second nonmagnetic underlayer 3 'thereon.
To 10 nm (Ar pressure: 0.8 Pa (6 mTorr)
r)), 64Co-14Pt as the magnetic information recording film 4
The -10Cr-12SiO ₂ 10nm, (Ar pressure:
1.1 Pa (8 mTorr)) and C as the protective layer 5 were formed under the conditions of 8 nm (Ar pressure: 0.67 Pa (5 mTorr)) to produce a magnetic recording medium (magnetic disk). After leaving this magnetic disk at 80 ° C. and a relative humidity of 80% for 4 hours, it was cooled down for 1 hour to -10 ° C.
An environmental test was conducted under the condition of cooling for 1 hour. As a result, a film float having a size of about 1 μm to 30 μm was observed. The height of the film floating at that time is 200 nm to 1000
It was confirmed that the height was nm. This height exceeded the flying height of the head.

Example 5 Before the film formation under the conditions of Example 4 described above, the resin substrate 2 was placed in a load chamber of a sputtering apparatus 10.
Plasma treatment was performed for 8.6 seconds at a power of 0.03 kW to 0.5 kW using a 20 kHz RF power source under the condition of Ar gas at 9.0 Pa. A part of the substrate after the treatment was taken out, and its surface was examined using FT-IR and compared with the untreated substrate surface. FIG. 8 shows an FT-IR diagram. as a result,
The substrate subjected to the plasma treatment has a functional group containing oxygen, that is, an absorption based on a hydroxyl group (—OH) in part A of FIG. 8, a carboxyl group (—COOH), and a carbonyl group (ＣＯCO) in part B of FIG. ) Were detected. Using this substrate, an environmental test was performed on a magnetic disk manufactured by forming a film under the same conditions as in Example 4. As a result, no film lifting was observed in any of the samples, and it was found that there was no problem with respect to the environmental test.

Next, FIG. 9 shows the S / N dependence on the RF power. As shown in FIG.
The S / N sharply decreases from kW. When the pretreated substrate at this time was analyzed by ESCA, RF
Al, which is the material of the cathode for performing the treatment, was detected. The slightly adhered Al is 84Cr-16W of the base film.
It is considered that the crystal orientation of Co was finally changed due to the influence of S and the S / N was reduced.

Example 6 A film was formed under the conditions shown in Table 1 below, and magnetic characteristics, electromagnetic conversion characteristics, and environmental tests were performed.

[0071]

[Table 1]

RF Glow treatment / 84Cr-16W / 50Ti on plastic substrate made of ZEONEX
-50W / Ru / 62Co-17.5Pt-8.5Cr
The film was formed in the order of -12SiO ₂ / C. The magnetic characteristics obtained at this time were measured using a VSM (vibration sample type magnetic characteristic measuring device) as follows: Mr · t = 0.4 mA, Hc = 255 kA
/ M, S ^* = 0.85 (S ^* : coercivity squareness ratio). The magnetic characteristics of the spinstand LS-90,
R / W Analyzer Guzik 1632A (manufactured by Kyodo Denshi) was used. The head is recording 0.5μ
m, reproduction 0.25 μm track width, floating 25 nm G
An MR nanoslider was used. Measuring radius 28.7mm,
The S / N at a rotational speed of 5400 rpm and a recording density of 250 kFCI was measured. As a result, the absolute value of S / N is 27
dB was obtained, and the S / N ratio of Example 5 was +1.0 dB. As a result of SEM measurement of this medium, it was confirmed that no crack was formed. In addition, this medium is referred to as Class 1
After leaving for 4 hours in an environment of 80 ° C. and 80% under a Clean environment of 00 or less, the temperature was lowered to −40 ° C. over 1 hour, left for 1 hour, and returned to room temperature over 4 hours. Thereafter, the film floating was observed with an optical microscope. However, no film floating occurred. In order to confirm that the disk was not deformed, flying was confirmed using the head with the spin stand LS90, but electromagnetic conversion characteristics could be confirmed without crash.

[0073]

According to the first aspect of the present invention, at least a first non-magnetic base film, a second non-magnetic base film, a magnetic information recording film, a protective film, and a lubricant are sequentially laminated on a resin substrate. The first nonmagnetic underlayer is made of Nb, Ta, or W.
, The internal stress of the laminated film is reduced to less than 0.1 GPa, and the occurrence of cracks in the resin substrate can be suppressed. A magnetic recording medium with a high recording density on the substrate is made possible.

According to the second aspect of the present invention, cracks can be suppressed and the required S / N can be maintained by setting the thickness of the first non-magnetic underlayer to 1 nm or more and 20 nm or less. And the respective characteristics can be compatible.

According to the third aspect of the present invention, the resin substrate is a substrate containing oxygen atoms on its surface, thereby improving the adhesiveness between the resin substrate and the base film and improving the adhesion of the base film to high temperature and high humidity. Environmental characteristics can be improved in order to prevent peeling and lifting.

According to the fourth aspect of the present invention, the resin substrate is a substrate made of a polycycloolefin-based hydrocarbon, which satisfies the function as a magnetic disk.
Good moldability and low cost make it possible to realize the practicality of a resin substrate.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a configuration of a magnetic disk.

FIG. 2 is a schematic view showing an in-line type sputtering apparatus.

FIG. 3 is a diagram illustrating a relationship between a radius of curvature and a deformation height.

FIG. 4 is a diagram showing a relationship between an internal stress of a constituent film and an Ar pressure.

FIG. 5 is a diagram showing a relationship between an internal stress of a constituent film and an Ar pressure.

FIG. 6 is a diagram showing the relationship between internal stress and S / N and the amount of added elements.

FIG. 7 is a diagram showing the relationship between internal stress, S / N, and Cr—W film thickness.

FIG. 8 is an FT-IR diagram showing a surface state of a resin substrate.

FIG. 9 is a diagram showing a relationship between an S / N ratio and RF power.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Resin substrate, 2a ... One main surface, 3 ... 1st non-magnetic base film, 3 '... 2nd non-magnetic base film, 4 ... Magnetic information recording film , 5 ... Protective film, 6 ...
Lubricant, 7 laminated film, 10 sputtering device,
11 ... chamber, 12 ... chamber, 13 ... chamber, 14 ... chamber, 15 ... chamber, 16 ... exhaust port, 17 ... vacuum pump, 18 ... gas inlet port, 19
…… Sputter gas supply source, 20 …… Target holder,
21 ... Palette

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Masaki 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 5D006 CA04 CA05 CA06 CB01 CB07 DA03 EA03 FA03 FA05

Claims (4)

[Claims] A first non-magnetic base film on a resin substrate;
At least a second nonmagnetic underlayer, a magnetic information recording film, a protective film, and a lubricant are sequentially laminated, and the first nonmagnetic underlayer contains Nb, Ta, or W in an amount of 12 atom% or more and 40 atom% or less. A magnetic recording medium comprising an alloy containing Cr as a main component. 2. The method according to claim 1, wherein said first nonmagnetic underlayer has a thickness of 1 nm.
2. The magnetic recording medium according to claim 1, wherein the thickness is 20 nm or less. 3. The magnetic recording medium according to claim 1, wherein the resin substrate is a substrate containing oxygen atoms on the surface. 4. The magnetic recording medium according to claim 1, wherein the resin substrate is a polycycloolefin hydrocarbon substrate.