JPH10255252A - Magnetic recording disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording disk having the running durability which realizes ultra-high density recording at a high speed rotation and an excellent ferro-magnetic metal thin film magnetic layer for head. SOLUTION: This magnetic recording disk is formed by sequentially forming a non-magnetic metal lower layer and a ferro-magnetic metal thin film at least on one surface on a flexible non-magnetic carrier. An internal stress of the non-magnetic metal lower layer is turned in the vertical direction to the flexible non-magnetic carrier and in the tensile direction (direction becoming far from the flexible non-magnetic carrier) and an internal stress of the ferromagnetic metal thin film is turned in the vertical direction to the flexible non-magnetic carrier and in the compressing direction (direction coming close to the flexible non-magnetic carrier) and an internal stress of the film as a whole combining the non-magnetic metal lower layer and ferromagnetic metal thin film is within the range of -1×10<9> to +1×10<9> N/m<2> and moreover amount of curl of the magnetic recording disk is 3mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removable magnetic recording medium used for an auxiliary recording device of a computer, an image recording device, and the like, and relates to a flexible recording medium having a high recording density of 1 gigabit per square inch or more. The present invention relates to an ultra-high-density floppy disk (FD) having a magnetic layer formed of a ferromagnetic metal thin film formed on a non-magnetic support by a vacuum film forming method such as evaporation or sputtering.

[0002]

2. Description of the Related Art In recent years, there has been a demand for an ultra-high-capacity recording medium with an increase in the amount of information. Digital video tapes have been used as ultra-high-density magnetic recording media, but disk media are now used from the viewpoint of recording and reproduction speed. There are two types of disk media, a fixed installation type and a removable type. HD (glass or aluminum disk) is used as a substrate for both magnetic recording media. A removable high-density recording medium is going to be used as a recording medium for a professional digital video camera, which is replaced with a tape because of its easy handling. However, since HD is used for the removable medium substrate, when an impact is applied to the apparatus, a head crash occurs, and the medium and the head are greatly damaged. The problem of shock resistance has not been solved yet, and the spread of disk digital cameras has been hindered. When a flexible material is used as the support, there are advantages such as a reduction in the weight of the recording unit and a reduction in the damage caused by an impact at the time of contact between the head and the medium. Therefore, a high-density removable magnetic recording medium using a flexible non-magnetic support as a substrate and having excellent impact resistance is desired.

A flexible non-magnetic support has excellent properties in terms of impact resistance and head damage because it is smooth. On the other hand, there are major problems in the magnetic properties of the magnetic layer, the head contact between the medium and the head, and the durability. Even if the same lubricant and protective layer formulation as in HD and ME, for which the technology has been established for durability, is applied to FD, it cannot be put to practical use, and a major problem remains. I think this is due to curl,
Although the development of an FD with a small curl was performed, the durability was hardly improved contrary to expectation.

The prior art relating to the curl of a perpendicular magnetization recording medium is disclosed by the present applicant and is disclosed in, for example, JP-A-61-153818 and JP-A-61-151829.
And JP-A-61-91822. In high-density recording, it is important to keep the head contact between the head and the medium, that is, the flying height low and constant. When a flexible medium is rotated at a high speed, the disk is fluttered due to the curl of the disk and the deformation of the substrate itself during the manufacturing process. Therefore, it is important to stabilize the head contact in order to put a flexible substrate to practical use. .

[0005] The present researcher suggested that to improve the durability of a disc,
We thought that it was necessary to reduce not only the curl but also the internal stress itself. The underlayer / magnetic layer formed in a vacuum has internal stress in the layer. In a normal medium, since the underlayer and the magnetic layer formed under the same conditions are provided on both surfaces, the curl amount is reduced by balancing the forces on both surfaces. Alternatively, it is also possible to balance the internal stresses of the entire medium by forming films having different thicknesses on both sides, or by balancing the internal stresses of the magnetic layer and the underlayer on one side.

However, simply reducing the internal stress makes it difficult for the ultra-high-density recording disk to sufficiently secure a large number of revolutions for a high transfer rate, durability for the same, and head contact. there were.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording disk having a ferromagnetic metal thin-film magnetic layer which is excellent in running durability, capable of recording at ultra-high density at high speed rotation, and excellent in head contact. .

[0008]

That is, the object of the present invention is to
In a magnetic recording disk having a non-magnetic metal underlayer and a ferromagnetic metal thin film formed on at least one surface of a flexible non-magnetic support in this order, the internal stress of the non-magnetic metal underlayer is The direction perpendicular to the magnetic support and in the pulling direction (the direction away from the flexible non-magnetic support), and the internal stress of the ferromagnetic metal thin film is applied to the flexible non-magnetic support. With respect to the vertical direction and the compression direction (the direction approaching the flexible non-magnetic support),
In addition, the magnitude of the internal stress of the entire film including the nonmagnetic metal base layer and the ferromagnetic metal thin film is −1 × 10 ⁹ to + 1 ×
In the ¹⁰⁹ range of N / m ^2, it can be achieved by a magnetic recording disk, wherein the further magnetic curling amount of the recording disk is less than 3mm.

[0009] The present researcher has proposed a method for improving the amount of curl and durability of a disk by using a non-magnetic metal underlayer (hereinafter simply referred to as “underlayer”).
), The internal stresses of the ferromagnetic metal thin film (hereinafter also referred to as “magnetic layer”) are in the tensile direction and the compressive direction, respectively, and the sum of these internal stresses is (−1 to +1) × 1.
The reason we thought it was necessary to be in the range of ⁹ N / m ² was
It is as follows.

When the internal stresses of the underlayer and the magnetic layer are balanced so that the sum of the internal stresses of the underlayer and the magnetic layer falls within the above range, the amount of curl of the disk is reduced, and the flatness of the disk is improved. Surface runout during rotation is reduced. In addition, by considering the direction of the force acting from each layer on the boundary surface between the magnetic layer and the underlayer, the underlayer is pulled and the magnetic layer is designed to have a compressive stress, thereby significantly improving the durability. In this state, a compressive force is applied to the interface between the underlayer and the magnetic layer. If a head crash occurs and a strong force greater than the film elasticity and adhesion between the underlayer and the magnetic layer is applied to the boundary surface, the film is cracked and peeled off at the boundary surface. If a compressive force is constantly acting on the interface, the magnetic layer and the underlayer will be pressed against each other. The force for joining the magnetic layer and the underlayer acts strongly against subsequent damage, and peeling of the film can be suppressed.
On the other hand, when the underlayer is compressed and the magnetic layer is tensile, a tensile force is constantly acting on the boundary surface, and when damage is applied again, the magnetic layer and the underlayer are more likely to peel off, resulting in greater disk damage.

In the present invention, the contribution of the internal stress of the protective layer to the stress of the entire medium is considered to be small.
The object of the present invention can be achieved by limiting the sum of these internal stresses to a specific range. The present invention solves the problems of durability and impact resistance by providing the above configuration, and provides an ultra-high recording density FD.

Constituting the film of the magnetic recording disk of the present invention
When the underlayer is "L₁”And the magnetic layer _Two"
The protective layer to be_ThreeAnd the film consisting of the underlayer and
Also referred to as “L”. L₁, L_Two, And L_ThreeIs a flexible non-magnetic
Provided on at least one side, preferably both sides, of the support
You. Also, L₁The internal stress of L_1f, L_TwoThe internal stress of L
_2f, L_ThreeThe internal stress of L_3f, L internal stress_fToss
You.

Each of the above internal stresses is measured in a direction perpendicular to the film surface. To measure the internal stress, an underlayer, a magnetic layer, and a protective layer are formed on a flexible nonmagnetic support (polyimide) on a strip. The layer is formed and derived from the variables of the entire disc before and after formation. The method of measuring and deriving each internal stress is as follows. 50μ cut out on a strip (25 × 5mm ² )
2 are prepared. The strips are arranged so that a film is formed on the 0 side (back side) and 1 side (front side), and the strips are fixed so that the length of the flexible non-magnetic support is 15 mm. First, the deformation of the flexible non-magnetic support itself (deformation due to the internal stress of the support itself before film formation) is measured for the 0 plane and 1 plane (both sides). Assuming that the deformation amount of surface 0 is α, one surface is naturally measured in the opposite direction.
−α.

Next, a film to be measured is separately formed under the same conditions on only one of the 0 plane and 1 plane. The amount of deformation measured at this time is the total amount of deformation of the medium, and the details of the amount of deformation are the amount of deformation (α) due to the internal stress of the support itself before the film formation, and the amount of the support Is the amount of deformation due to internal stress (β: actually deformed by heat), and the amount of deformation (γ) of the formed film due to internal stress.

That is, the amount of deformation when a film is formed on the zero plane is α +
Assuming that β + γ, when a film is formed on one surface, −α−β +
Since it is measured as γ, the sum of them is divided by 2 to obtain γ. Γ is obtained from the total deformation amount of the medium when the films are separately formed on the 0 plane and the 1 plane, and the internal stress σ of the film is derived by the Stoney equation.

Σ = Eb ² X / 3 (1-v) dl ² E: Young's modulus of the support, b: thickness of the support, X: deformation γ, v: Poisson's ratio of the support, d: membrane The internal stress “−” means the direction from the membrane surface to the support surface, that is, the compression direction (the direction approaching the flexible non-magnetic support), and “+” indicates the thickness of the support. It refers to the direction from the support surface to the membrane surface, that is, the pulling direction (the direction away from the flexible non-magnetic support).

Accordingly, in the present invention, L_1fThe sign of
"+" And L_2fMust be "-"
Is L_fMay be "-" or "+" within the above range.
But preferably zero rather than "+" or "-"
No. L_fIs L_1f+ L_2fBecomes L_fIs (-1 to +1)
× 10⁹N / m^Two, Preferably (-0.7 to +0.7)
× 10⁹N / m^TwoAnd more preferably (−0.3 to +0.
3) x 10⁹N / m^TwoAnd L_1fIs preferably
Is (+0.7 to +1.5) × 10⁹N / m^Two, Even more preferred
Or (+0.0 to +0.7) × 10⁹N / m^TwoRange
And L_2fIs preferably (−0.7 to −1.5) ×
10⁹N / m ^Two, More preferably (−0.0 to −0.
7) × 10⁹N / m^TwoRange.

Incidentally, L _3f is usually (−7.0 to +8) ×
10 ⁸ N / m ² , preferably (−3 to +3) × 10 ⁸ N
/ M ² , more preferably (−1 to +1) × 10 ⁸ N / m
It is in the range of ² . In the present invention, the method for controlling the internal stress is not particularly limited, but preferably includes, for example, the following method.

As a means for forming the underlayer and the magnetic layer or the protective layer on the flexible non-magnetic support, a vacuum film forming method is preferable, and among them, a sputtering method is preferable, and various conditions of the sputtering method are selected. This makes it possible to control the internal stress. A sputtering method is preferable because a film can be formed without changing the composition of many elements. Also,
It is preferable that both layers are formed without breaking the vacuum state.

The conditions include adjusting the sputter pressure by a sputter gas such as Ar, the input power, and the like for each layer. The sputtering pressure by a sputtering gas such as Ar is equal to the sputtering pressure in the vicinity of the target / support, and is different from the indicated value of the vacuum gauge of the sputtering apparatus. Therefore, it is necessary to vapor-deposit a target sputter substance for each apparatus and to set a sputter gas pressure at which the film stress can be set to an optimum value by a vacuum gauge of each apparatus. For example, sputtering pressure by Ar sputtering gas as a (hereinafter, also referred to as Ar sputtering pressure), the formation of L ₁ is preferably 0.2~20mTor
r, more preferably 0.7 to 10 mTorr.
r, and the formation of L ₂ is preferably from 0.2 to
10 mTorr, more preferably 0.7 to
5 mTorr, and the formation of L ₃ is usually 1 to
8 mTorr, preferably in the range of 2 to 5 mTorr.

The input power is usually 400 to
It is in the range of 2000W, preferably 700-1600W. When a film was formed using the two types of sputtering apparatuses of the present applicant under the same conditions (Ar sputtering pressure, input power, etc.), the internal stress did not show the same tendency. Thus, since the indicated value of the vacuum gauge and the degree of vacuum near the target / support differ for each apparatus, it is necessary to set the Ar sputtering pressure in each apparatus.

The curl amount is measured as follows. After forming a ferromagnetic metal thin film on a flexible non-magnetic support, it is punched into an FD having an outer diameter and an inner diameter of a desired size, an inner peripheral portion is inserted into a projection, and the FD is vertically fixed to each other. The distance between the contact between one of the parallel surfaces and the most protruding part of the FD and the contact between the other vertical surface and the most recessed part of the FD is measured with a micrometer, This is performed by obtaining the curl amount.

The present invention solves the problems of durability, impact resistance and head contact by controlling the internal stress and the amount of curl of each of the underlayer, the magnetic layer and the protective layer as described above. A density FD can be provided. Examples of the flexible non-magnetic support used in the present invention include polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide imide, and polybenzoxazole. The thickness of these supports is
Usually, it is 30 to 120 μm, preferably 40 to 70 μm. If the thickness is too large, head damage is large, and if it is too thin, the output becomes unstable due to deformation of the disk, which is not preferable.

The temperature of the support during vacuum film formation is 50 to 17
0 ° C, preferably in the range of 70 to 160 ° C. When the temperature of the support is lower than 60 ° C., the magnetostatic properties of the magnetic layer are poor, the noise of the medium increases, and the performance of the medium decreases. On the other hand, when the temperature exceeds 170 ° C., thermal deformation of the support occurs, and the durability and head contact are significantly deteriorated. In order to improve the flatness and heat resistance of the support, an undercoat layer may be provided on the flexible non-magnetic support.

[0025] In addition, a fine non-magnetic support
Protrusions may be provided, for example, SiO 2 _Two, Al_TwoO_Three, T
iO_TwoEtc. or a coating containing organic fine particles together with a binder resin.
Coating on the undercoat layer or separately on the support
Thereby, the projection can be provided. Magnetic recording of the present invention
For disks, the underlayer and magnetic layer are deposited by vacuum deposition.
Preferably, the underlayer is a Cr alloy based film,
The magnetic layer is a CoCr alloy film and is protected on the magnetic layer
Preferably, a layer and a lubricating layer are formed.

The material of the Cr alloy-based film includes Cr alone, and a Cr alloy such as Cr and Ti, W, Mo, V,
1 selected from Ta, B, Si, Nb, Zr and Mo
Alloys with more than one kind. In the present invention, since a flexible non-magnetic support is used, it is necessary to select an optimum underlayer element in order to obtain good magnetic properties at a low heating temperature. Chromium said additive metal added as a host as an underlying layer elements to examine the Ar sputtering pressure dependence of the magnetic properties and L _1. As a result, even when the Ar sputtering pressure was changed, the stable value of the coercive force showed a high value because Cr-T
i, a magnetic recording disk using a Cr-W alloy as an underlayer. When Cr is used as the underlayer, Cr-
The coercive force was smaller than the Ti and Cr-W alloys. For the above reasons, most desirable is Cr or an alloy of Cr and Ti and / or W. The concentration of W and Ti (including only one) is usually 8 to 22 atomic%, preferably 10 to 20 atomic%. Atomic% range.

The thickness of the underlayer is usually 5 nm to 500 n.
m, particularly preferably 10 to 100 nm. If the thickness of the underlayer exceeds 100 nm, the grain size of the magnetic layer increases, and noise increases. As the magnetic material of the CoCr alloy-based film, if it is an alloy containing at least CoCr,
Although there is no particular limitation, in particular, Pt, Ta, Si, B, Ni,
Alloys with Pd and O, specifically Co-Cr, Co-Cr
-Ni, Co-Cr-Ta, Co-Cr-Pt, Co-
Cr-Pt-Ta, Co-Cr-Pt-Si, Co-C
r-Pt-B or the like can be used. In particular, Co-Cr-Pt, Co-Cr-Pt-Ta for improving the electromagnetic conversion characteristics.
Is preferred.

The thickness of the magnetic layer is preferably from 10 to 30.
0 nm, particularly preferably 10 to 50 nm. In the magnetic recording disk of the present invention, the protective layer is preferably provided on the magnetic layer by a vacuum film forming method. Among them, preferable film forming methods are a sputtering method and a CVD method. The sputtering method is a relatively simple process and has high practicality.
The CVD method has an advantage that a protective film having high strength and high elasticity can be obtained.

As the protective layer, oxides such as silica, alumina, titania, zirconia, cobalt oxide and nickel oxide; nitrides such as titanium nitride, silicon nitride and boron nitride; carbides such as silicon carbide, chromium carbide and boron carbide;
Examples of the protective layer include carbon such as graphite and amorphous carbon. As the protective layer, a hard film having a hardness equal to or higher than that of the head material is preferable, and a layer that hardly causes seizure during sliding and has a stable and stable effect is most preferable. Examples include a hard carbon film.

The carbon protective layer is formed by a plasma CVD method,
Amorphous and graphite created by the sputtering method, etc.
Or diamond structures, or a mixture of these.
Carbon film, particularly preferably a diamond film.
It is a hard carbon film called dry carbon. This
Hard carbon film has a Vickers hardness of 1000 kg / mm ^Two 
Above, preferably 2000 kg / mm^Two Hard charcoal over
It is a base film. The crystal structure is amorphous.
And non-conductive. And in the present invention
The structure of diamond-like carbon film was analyzed by Raman spectroscopy.
1520-1560 cm when measured^-1To pea
This can be confirmed by detecting a lock. Charcoal
If the structure of the film deviates from the diamond-like structure,
Peaks detected by optical spectroscopy are out of the above range
And the hardness of the carbon film decreases.

This hard carbon protective layer comprises methane, ethane,
Plasma C made from a carbon-containing compound such as an alkane such as propane or butane, an alkene such as ethylene or propylene, or an alkyne such as acetylene.
It can be formed by VD, sputtering in a hydrogen or hydrocarbon atmosphere using carbon as a target, or the like.

H, F, N, O, V, W
May be included. If the thickness of the hard carbon protective layer is large, the electromagnetic conversion characteristics are deteriorated and the adhesion to the magnetic layer is reduced. If the thickness is small, abrasion resistance is insufficient.
5 to 30 nm is preferable, and particularly preferably 5 to 10 n
m. Preferably, the surface of the hard carbon protective layer may be surface-treated with an oxidizing or inert gas for the purpose of further improving the adhesion with the lubricant provided on the hard carbon protective layer.

In the magnetic recording disk of the present invention, a lubricant can be used in order to improve running durability and corrosion resistance, and the lubricant can be provided on the protective layer or the magnetic layer. In the present invention, it is preferable to further provide a rust preventive. As the lubricant, known hydrocarbon-based lubricants, fluorine-based lubricants, extreme pressure additives and the like can be used.

As the hydrocarbon lubricant, stearic acid,
Carboxylic acids such as oleic acid, esters such as butyl stearate, sulfonic acids such as octadecylsulfonic acid, phosphoric esters such as monooctadecyl phosphate, alcohols such as stearyl alcohol and oleyl alcohol, and carboxylic acids such as stearamide. Examples thereof include acid amides and amines such as stearylamine.

Examples of the fluorine-based lubricant include lubricants in which part or all of the alkyl group of the hydrocarbon-based lubricant is substituted with a fluoroalkyl group or a perfluoropolyether group. Examples of the perfluoropolyether group include a perfluoromethylene oxide polymer, a perfluoroethylene oxide polymer, a perfluoro-n-propylene oxide polymer (CF ₂ CF ₂ CF ₂ O) _n , and a perfluoroisopropylene oxide polymer (CF (CF
₃ ) CF ₂ O) _n or a copolymer thereof.

Examples of extreme pressure additives include phosphoric esters such as trilauryl phosphate, phosphites such as trilauryl phosphite, thiophosphites and thiophosphoric esters such as trilauryl trithiophosphite, and the like. And sulfur-based extreme pressure agents such as dibenzyl sulfide. The above lubricants are used alone or in combination of two or more. As a method of applying these lubricants on the magnetic layer or the solid protective layer, the lubricant is dissolved in an organic solvent and applied by a wire bar method, a gravure method, a spin coating method, a dip coating method, or a vacuum evaporation method. May be attached.

The amount of the lubricant to be applied is 1 to 30 mg / m
² is preferable, and 2 to 20 mg / m ² is particularly preferable. Benzotriazole, as a rust inhibitor that can be used in the present invention,
Nitrogen-containing heterocycles such as benzimidazole, purine and pyrimidine, and derivatives having an alkyl side chain introduced into their mother nucleus, and nitrogen and sulfur such as benzothiazole, 2-mercaptobenzothiazole, tetrazaindene ring compounds and thiouracil compounds Heterocycles and derivatives thereof.

[0038]

Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. Examples and Comparative Examples Example 1: Undercoated 90 μm as an alloy thin film medium
Titanium is used as an underlayer on a PEN flexible non-magnetic support.
60n chromium alloy containing 0 atomic% by DC sputtering
m. Next, a cobalt alloy thin film having a thickness of 30 nm and containing 20 atomic% of chromium and containing 12 atomic% of platinum was coated on the underlayer as a magnetic layer by DC sputtering. The support temperature at the time of forming the underlayer and the magnetic layer was 150 ° C. The Ar sputtering pressure at the time of forming the underlayer: 8 mTorr, the input power was 1400 W, and the Ar sputtering pressure at the time of forming the magnetic layer:
Assuming 1.5 mTorr and input power of 1400 W, L _1f
+ 4.2 × 10 ⁸ N / m ² , and L _2f −0.9 × 10 ⁸
N / m ² and L _f were set to + 3.2 × 10 ⁸ N / m ² . Next, a carbon protective layer was formed by a sputtering method. The sputtering conditions were as follows: Ar sputtering pressure: 3 mTorr, and input power: 700 W. The obtained carbon protective film was amorphous and had a thickness of 20 nm. L _3f −0.1
× 10 ⁸ N / m ² .

Next, an underlayer, a magnetic layer and a protective layer were provided on the opposite side of the support provided with the above layers under the same conditions as above, and the curl amount was measured. The curl amount was 2.7 mm. Example 2: The thickness of the underlayer was 60 n in Example 1.
A magnetic recording disk was prepared in the same manner as in Example 1 except that the value was changed to m. Comparative Example 1 A magnetic recording disk was prepared in the same manner as in Example 1, except that the thickness of the underlayer was changed to 180 nm.

Comparative Examples 2 to 6: In Example 1, a chromium alloy containing 8 atomic% of titanium was used as the underlayer, and a cobalt alloy containing 22 atomic% of chromium and 16 atomic% of platinum was used as the magnetic layer. Example 1 except for the conditions
A magnetic recording disk was prepared in the same manner as described above. Comparative Example 2 The Ar sputter pressure when forming the underlayer was 6 mTorr and the input power was 1400 W, and the Ar sputter pressure when forming the magnetic layer was 5 mTorr and the input power was 1400 W.

Comparative Example 3 The Ar sputtering pressure at the time of forming the underlayer was 10 mTorr. Comparative Example 4 The Ar sputtering pressure at the time of forming the underlayer was 8 m, as in Example 1.
Torr. Comparative Example 5 The Ar sputtering pressure at the time of forming the underlayer was 5 mTorr, and the Ar sputtering pressure at the time of forming the magnetic layer was 2 mTorr.

Comparative Example 6 The Ar sputtering pressure at the time of forming the underlayer was 4 mTorr, and the Ar sputtering pressure at the time of forming the magnetic layer was 1 mTorr. The resulting L _1f of the magnetic recording disk, L _2f, the L _f and the curl amount described in Table 1. Regarding L _1f and L _2f, it is also specified whether the direction of tension (+ sign) or the direction of compression (− sign). The curl amount was evaluated as ◎ to ×. ◎ indicates a curl amount of 0 to 3 mm, ○ indicates a curl amount of 3 to 5 mm,
Indicates that the curl amount is 5 to 7 mm, and X indicates 7 mm or more.

The obtained samples were evaluated as follows, and the results are shown in Table 1. 1Gbits / inch as described above
^{In order} to realize ^two classes of ultra-high recording density media, it is necessary to rotate the disk at high speed due to the problem of transfer speed. Therefore, high speed rotation (300
(0 rpm). The running durability of the FD is as follows: While rotating the disk using a spin stand, sandwich the try pad head from both sides of the FD, record at 130 KFRPI, run while monitoring the output, and pass until the output drops below the original 6 dB. The number was measured.

As a measurement per head, the tri-pad head was sandwiched from both sides of the FD while rotating the disk, and allowed to run for 3 minutes while monitoring the output. The difference between the minimum output value and the maximum output value was used as an index.

[0045]

[Table 1]

As a result of the above measurement, the examples in which the orientations of L _1f and L _2f and the value of L _f are within the range of the present invention are different from those of the comparative examples in which any of those internal stresses is out of the range of the present invention. It can be seen that the running durability and the head contact are excellent.

[0047]

According to the present invention, there is provided a magnetic recording medium comprising an FD using a flexible non-magnetic support which is compact and excellent in usability, has a very large recording capacity and is excellent in running durability. The disk can be stably provided by adjusting the directions of the internal stresses of the underlayer and the magnetic layer and the sum of the internal stresses of the two in a specific range.

Claims (2)

[Claims] In a magnetic recording disk having a non-magnetic metal underlayer and a ferromagnetic metal thin film formed on at least one surface of a flexible non-magnetic support in this order, the internal stress of the non-magnetic metal underlayer is In the direction perpendicular to the flexible non-magnetic support and in the pulling direction (the direction away from the flexible non-magnetic support), the internal stress of the ferromagnetic metal thin film is The entire film in a direction perpendicular to the non-magnetic support and in the compression direction (direction approaching the flexible non-magnetic support), and combining the non-magnetic metal base layer and the ferromagnetic metal thin film Of the internal stress of -1 ×
A magnetic recording disk in a range from 10 ⁹ to + 1 × 10 ⁹ N / m ² , wherein the curling amount of the magnetic recording disk is 3 mm or less. 2. The non-magnetic metal underlayer is a Cr alloy based film formed by a vacuum film forming method, and the ferromagnetic metal thin film is a CoCr alloy based film formed by a vacuum film forming method, 2. The magnetic recording disk according to claim 1, wherein a protective layer and a lubricating layer are formed on the ferromagnetic metal thin film.