JP3475533B2 - Thin-film magnetic disk - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic disk suitable for high density recording used in a magnetic storage device of a computer. In particular, the present invention relates to a thin-film magnetic disk built in a portable small computer and requiring a high degree of shock resistance.

[0002]

2. Description of the Related Art In recent years, the market for portable computers has been expanding due to the miniaturization and speeding up of computers. A high degree of shock resistance is required for these types of computers. Therefore, the magnetic disk used as the storage medium of the external storage device of such a computer is required to have high impact resistance. In a high-density magnetic disk, a magnetic recording medium formed on a non-magnetic disk substrate is a conventional coating film in which magnetic powder is bound with resin, and a magnetic metal is plated on the disk substrate by a plating method, an evaporation method, a sputtering method, or the like. It has been transferred to the thin magnetic metal film formed by. And in general, when the magnetic disk is operating, the magnetic head floats above the disk surface,
A so-called CSS (contact start stop) method of contacting the disk surface when stopped is adopted.

FIG. 3 is a sectional view of an example of a known magnetic disk. In FIG. 3, reference numeral 1 is a non-magnetic substrate, for example, an aluminum alloy disc and a Ni-P formed thereon by electroless plating or the like.
It is composed of a base layer such as an alloy layer. In order to prevent the magnetic head from adsorbing, fine groove-like irregularities called texture are generally formed in the rotating circumferential direction on the surface of the underlayer. The base film 2 is formed on the substrate, and an island structure is formed between them by a vacuum deposition method, a sputtering method, or fine particles are arranged by a coating method or the like. , May form texture. Base film 2
Is generally formed to improve the magnetic characteristics of the magnetic film and the adhesion of the magnetic film. For example, Cr or Cr formed by a method such as a plating method, an ion plating method, a vacuum deposition method, or a sputtering method is used. A film made of an alloy or compound containing Cr as a main component is used.

A magnetic film 3 is formed on the base film 2. The magnetic film 3 is formed of, for example, a plating method, an ion plating method, a vacuum deposition method, a sputtering method, or the like, and is a ferromagnetic metal such as Co, Fe, or Ni, or a ferromagnetic material containing these elements as a main component. Membranes made of alloys are commonly used. Since it is necessary to reduce the distance between the center of the thickness of the magnetic film and the magnetic head, it is desirable that the magnetic film 3 be as thin as possible within the range that satisfies the required magnetic characteristics.

A protective film 4 is formed on the magnetic film 3 because the magnetic film 3 is susceptible to oxidative corrosion in air and has poor wear resistance. As the protective film 4, for example, a carbon-based protective film produced by a sputtering method, a hydrogenated carbon-based protective film produced by introducing hydrogen or hydrocarbon during film formation by sputtering, a SiO ₂ -based protective film, etc. are generally used. It is used. The protective film 4 is preferably thinner as it is necessary to reduce the distance between the magnetic film 3 and the magnetic head. However, from the viewpoint of preventing corrosion of the magnetic film and improving wear resistance when sliding with the magnetic head, a film thickness of a certain amount or more is required. Texture may be formed by forming irregularities on the protective film 4 itself by an ion plating method, a sputtering method or the like, or by dispersing fine particles in the protective film 4 by using a coating method.

A lubricant layer 5 is formed on the protective film 4 for the purpose of improving the sliding resistance at the time of contact with the magnetic head. The lubricant layer 5 is, for example, FOMBLIN A manufactured by Montefluos of Italy.
Perfluoroalkyl ether type lubricants such as M2001, FOMBLINZ-DOL, KRYTOX 143 manufactured by DuPont, and Demnum series manufactured by Daikin are generally used. A magnetic disk having a magnetic film 3 which is a continuous magnetic thin film made of such a metal or a metal compound is
The magnetic film can be made extremely thin as compared with a coating type magnetic disk, and is widely used as a magnetic disk suitable for high recording density.

[0007]

However, when the conventional magnetic disk is applied to a portable magnetic disk device with a built-in small computer, some of the recorded information is lost due to an impact such as a drop. It is known to cause problems. This missing information is
The magnetic head is struck against the magnetic disk by an impact such as dropping, and the substrate is plastically deformed. Therefore recently, for the purpose of improving the impact resistance, the type of substrate, when the same stress acts, has begun to be studied to change to a more materials such as glass hardly occurs deformation. However, as a result of investigations by the inventors regarding this, although the impact resistance of the magnetic disk is considerably improved by changing the substrate to a material such as glass that does not easily deform, the impact of dropping or the like is not sufficient. It was revealed that the impact resistance was not sufficient to withstand. An object of the present invention is to provide a thin film magnetic disk having excellent impact resistance.

[0008]

Means for Solving the Problems The present invention, at least moth
A lath substrate, a base film formed on the surface of the glass substrate, a magnetic film formed on the base film, a protective film formed on the magnetic film, and a lubricant layer formed on the protective film. A thin-film magnetic disk having the Vickers hardness of the glass substrate surface of 1200 or more (excluding 1200) and including the underlayer film interposed between the glass substrate surface and the magnetic film. The sum of the film thickness and the film thickness of the magnetic film is 80
It is a thin-film magnetic disk characterized by having a thickness of nm or less.

[0009] If it is dropped the magnetic disk apparatus incorporating the magnetic to Disk from a high position, the magnetic disk may sometimes an error occurs with considerable probability. This is when the amount of deformation a of the substrate itself due to the collision of the magnetic head in FIG. 4 is large, and the base film and the magnetic film formed on this substrate are plastically deformed. That is, the amount of depression b on the surface of the protective film becomes large, so that in the collision mark area during normal driving of the magnetic disk,
The distance between the center of the thickness of the magnetic film and the magnetic head becomes larger than the initial design value, the output decreases, and an error occurs. The present inventor has studied and considered the above phenomenon, and the reason why the present invention has been achieved will be described below. Conventionally, a magnetic disk having a structure as shown in FIG. 3 has been used. When a shock such as a drop is applied to the magnetic disk device using the magnetic disk having such a structure, especially when the magnetic disk is in operation, the magnetic head is strongly struck against the magnetic disk. As a result, collision marks are formed on the surface of the magnetic disk. FIG. 4 conceptually shows a cross-sectional view of this collision mark. In the figure, 1 is Al alloy substrate formed with the Ni-P alloy layer in electroless solution plating or the like, 2 base film, 3 is a magnetic film, the protective film 4, and 5 is a lubricating layer. Due to the collision of the magnetic head, the magnetic disk substrate is mainly deformed, so that the magnetic film and the like formed on the magnetic disk substrate are also depressed. In such a collision mark area, when the magnetic disk is normally driven, the distance between the center of the thickness of the magnetic film and the magnetic head becomes larger than the initial design value, and the output decreases and an error occurs.

The present inventor uses a glass substrate having a large surface hardness and hardly deforming as the non-magnetic substrate, and
It has been found that the amount of deformation of these films can be reduced by making the film thicknesses of the underlayer film and the magnetic film below a certain value. I.e. during operation of the magnetic to Disk device incorporating a magnetic disk was subjected to impact test for applying a variety of acceleration, surprisingly error accordance sum of the thickness of the base film and the magnetic film is reduced We have found that the probability of occurrence is decreasing. At this time, in the area where the collision mark is generated, when the magnetic disk is normally driven,
It has been found that the distance between the center of the magnetic film thickness and the magnetic head has a smaller expansion width with respect to the initial design value, and hence has a smaller decrease in output and a smaller error probability.

The glass substrate in the present invention must have a surface Vickers hardness of 600 or more. If the Vickers hardness is less than 600, when the magnetic head is struck by the impact on the magnetic disk,
The surface of the substrate is deformed, and the impact resistance cannot be sufficiently improved. The surface hardness of the substrate itself is preferably higher in order to minimize the amount of deformation of the substrate itself. The surface hardness of the substrate itself is more preferably 800 or more in Vickers hardness, and particularly preferably 1200 or more. Examples of such a material include glass, crystallized glass, amorphous carbon, and SiC . Among these materials, especially the surface flatness to minimize the flying height of the magnetic head,
Glass is preferably used in terms of material cost and workability. The composition of the glass is not particularly limited, but aluminosilicate glass excellent in weather resistance and low cost soda lime silicate glass are preferably used. These glass substrates are chemically strengthened for the purpose of improving their mechanical strength.

In the magnetic disk of the present invention, a base film is formed on a glass substrate which is a non-magnetic substrate. The base film is generally formed to improve the magnetic properties of the magnetic film and the adhesion of the magnetic film, and is formed by a method such as a plating method, an ion plating method, a vacuum deposition method, a sputtering method, or the like. A film made of Cr or an alloy containing Cr as a main component, a compound, or a W film is used. In particular, an alloy containing Cr as a main component is preferably used from the viewpoint of improving magnetic properties. Further, the method using a polishing tape or a polishing abrasive grains known conventionally generally, upon adoption of the non-magnetic substrate such as glass it is difficult to form a texture, while the non-magnetic substrate and the base film , Forming an island structure by a vacuum vapor deposition method, a sputtering method, or arranging fine particles by a coating method,
It is performed Nde good to form the texture. Also,
For purposes to facilitate the texture formation, or magnetic properties may be further formed intermediate film between the base film and the non-magnetic substrate for the purpose of improving.

In the present invention, a magnetic film is formed on the base film. The magnetic film is formed of, for example, a plating method, an ion plating method, a vacuum deposition method, a sputtering method, or the like, which is a ferromagnetic metal such as Co, Fe, or Ni, or a ferromagnetic material containing these elements as a main component. Membranes made of alloys are commonly used.

In the present invention, the above-mentioned magnetic film is prone to oxidative corrosion in air and has poor wear resistance, so that a protective film is formed on the magnetic film. As this protective film, for example, a carbon-based protective film produced by a sputtering method, a hydrogenated carbon-based protective film produced by introducing hydrogen or hydrocarbon during film formation by sputtering, a SiO ₂ -based protective film, etc. are generally used. To be The thickness of this protective film is preferably thinner because it is necessary to reduce the distance between the magnetic film and the magnetic head. However, from the viewpoint of preventing corrosion of the magnetic film and improving wear resistance when sliding with the magnetic head, a film thickness of a certain amount or more is required. The texture may be formed by forming irregularities on the protective film itself by a sputtering method or by dispersing fine particles in the protective film by a coating method.

In the present invention, a lubricant layer is formed on the protective film for the purpose of improving the sliding resistance when it comes into contact with the magnetic head. This lubricant layer is, for example, FOMBLI of Montefluos of Italy.
Perfluoroalkyl ether type lubricants such as NAM2001, FOMBLIN Z-DOL, KRYTOX 143 of DuPont, and Demnum series of Daikin are preferably used.

In the present invention, that the surface of the glass substrate, the thickness of all films that exist until magnetic layer present on the glass substrate, the total thickness of the magnetic film is 80nm or less is necessary. From the surface of the glass substrate, the moth
If the sum of the film thicknesses of all the films existing up to the magnetic film existing on the lath substrate and the film thickness of the magnetic film exceeds 80 nm, the impact resistance decreases. From the viewpoint of increasing the impact resistance, the surface of the glass substrate, the thickness of all films that exist until magnetic film present on the glass substrate,
The total thickness of the magnetic film is more preferably 50 nm or less, further preferably 30 nm or less.
To ensure the magnetic properties of the magnetic film, the thickness of the magnetic film is 1
The thickness of the underlayer film is preferably 5 nm or more in order to improve the crystal structure of the magnetic film and improve the magnetic characteristics.
The above is preferable. Therefore, it is preferable that the total thickness of the magnetic film and the thickness including the thickness of the underlayer film interposed between the surface of the glass substrate and the magnetic film is 20 to 80 nm, and more preferably 20 to 50 nm. Preferably 2
Most preferably, it is from 0 to 30 nm.

[0017]

In the present invention, the surface Vickers hardness is 1200.
Using the above glass substrate (excluding 1200) ,
In addition, the total thickness of all the films existing from the surface of the glass substrate to the magnetic film and the film thickness of the magnetic film is set to 80 nm or less. Therefore, the depth of the collision mark generated when the magnetic head is struck against the magnetic disk by an impact such as a drop is minimized, and the error occurrence probability is extremely reduced.

[0018]

EXAMPLES Next, examples of the present invention will be described. ( Embodiment 1 ) FIG. 1 is an enlarged partial sectional view of an embodiment of a magnetic disk according to the present invention. The inner diameter of the disk substrate 11 is 20
Using an aluminosilicate glass plate having an outer diameter of 64 mm and an outer diameter of 64 mm, the surface roughness (Rmax) was smooth-polished to 1 nm or less. Then, a thickness of about 10 is obtained on the chemically strengthened and cleaned substrate.
nm CrV-based metal underlayer 12, Co about 30 nm thick
The PtCr-based magnetic films 13 were sequentially formed by the sputtering method. On top of this, a coating method of about 20n thick is used.
A SiO ₂ protective film 14 of m and a texture layer 15 having a large number of hemispherical projections made of SiO ₂ having a height of about 40 nm were formed. Further, a 3 nm-thick organic polymer fluorine compound (product name AM2001) was formed thereon as a lubricating layer 16 by a dipping method. Here, the Vickers hardness of the surface of the chemically strengthened aluminosilicate glass substrate is about 1400 (however, the Vickers hardness is NEC.
It was converted from the result of measurement with a micro hardness meter NECMHA-400 manufactured by Ultra Co., Ltd. under a load of 1 mN. )Met. As a comparative example of Example 1, CrV-based metal base film 12
A magnetic disk having the same structure as in Example 1 was prepared except that the film thickness was 100 nm, and a sample of Comparative Example 1 was obtained. Further, as a comparison with Example 1, a magnetic disk having the same configuration as in Example 1 was prepared except that an aluminum alloy plate having a Ni-P alloy layer formed on the surface thereof by an electroless plating method was used as a substrate. Then, a sample of Comparative Example 2 was obtained. Here, Ni on the surface
The Vickers hardness of the surface of the aluminum alloy substrate on which the -P alloy layer was formed was about 400 (however, the measuring method is the same as in Example 1).

[0019] constitute a magnetic disk device using the three types of magnetic disks, by falling from various heights predetermined number of times the disk operating state the entire device, the impact test for applying a variety of acceleration went. Table 1 shows the relationship between the acceleration applied at this time and the number of errors generated by the impact.

[0020]

[Table 1]

However, the error is counted as one if it is continuous regardless of the size of the error. From this, it can be seen that an error has already occurred at an acceleration of 150 G in the magnetic disk of Comparative Example 1 and at an acceleration of 100 G or less in the magnetic disk of Comparative Example 2.
It can be seen that in the magnetic disk of Example 1, no error occurred even at an acceleration of 250 G, and good impact resistance could be realized. In particular, as is clear from the results of Comparative Example 2, it is clear that impact resistance is not improved if the hardness of the substrate surface is low even if the thickness of the film existing between the substrate surface and the magnetic film is reduced. Be recognized.

( Embodiment 2 ) FIG. 2 is an enlarged partial sectional view of another embodiment of the magnetic disk according to the present invention. As the disk substrate 21, a soda lime silicate glass plate having an inner diameter of 20 mm and an outer diameter of 64 mm was used, and the surface roughness (Rmax) was smoothed to 25 nm or less. Then chemically strengthened and surface roughness (Rmax)
A Ti film 22 having a thickness of about 5 nm was formed on a substrate which had been precisely polished to 1 nm or less and washed, and island-shaped Al grains 23 having a height of about 40 nm were formed on the Ti film 22 to form a texture. At this time, the average thickness of the Al film calculated from the amount of sputtering was 2 nm. On top of this, a Cr-based metal base film 24 having a thickness of about 20 nm and a thickness of about 2
0 nm CoPtCr magnetic film 25, thickness about 20 nm
The carbon protective film 26 of 1 was sequentially formed by the sputtering method. Furthermore, a lubricating film 27 having a thickness of 3 n
AM2001 of m was formed by the dipping method to obtain the sample of Example 2. Here, the Vickers hardness of the soda lime silicate glass substrate surface subjected to chemical strengthening is about 1300 (however, the Vickers hardness, the load 1 by the NEC ultra thin films for micro hardness meter NECMHA-400
It was converted from the result measured in mN. )Met. As a comparison with the second embodiment, the thickness of the Cr-based metal base film 12 is set to 100.
except that the nm, to prepare a sample of Comparative Example 3 of the magnetic disk of the same film structure as in Example 2. The same impact test as in Example 1 was performed on the two types of magnetic disk samples of Example 2 and Comparative Example 3. Table 2 shows the relationship between the acceleration applied at this time and the number of errors generated by the impact. Therefore, in the magnetic disk of Comparative Example 3, 1
It can be seen that, while an error occurred under the acceleration condition of 50 G, the magnetic disk of Example 2 did not generate an error even under the acceleration of 250 G, and good impact resistance was realized.

[0023]

[Table 2]

[0024] (Example 3) disc substrate 11, an inner diameter of 20 mm, an outer diameter of 64mm
Surface roughness (Rm
ax) was smooth-polished to 1 nm or less. Then, on the chemically strengthened and washed substrate, a CrV-based metal underlayer film 12 having various thicknesses and a CoPtCr-based magnetic film 13 having a thickness of about 20 nm are provided.
Were sequentially formed by the sputtering method. On top of this, a SiO ₂ protective film 1 having a thickness of about 20 nm is formed by a coating method.
4 and a texture layer 15 having a large number of SiO ₂ hemispherical protrusions having a height of about 40 nm were formed. Further, an AM2001 having a thickness of 3 nm was formed thereon as a lubricating layer 16 by a dipping method. Here, the Vickers hardness of the surface of the chemically strengthened aluminosilicate glass substrate was about 1400 (however, the Vickers hardness was calculated from the result of measurement with a load of 1 mN using NEC's ultra-thin film microhardness meter NECMHA-400. )Met. The thickness of the CrV-based metal base film was changed to 5, 10, 20, 50, 100 nm. A magnetic disk device was constructed using these five types of magnetic disks, and the same impact test as in Example 1 was performed. Table 3 shows the relationship between the acceleration applied at this time and the number of errors generated by the impact. From this, it is shown that the best impact resistance is 300 G when the sum of the film thicknesses of the underlayer and the magnetic film is 25 nm, and 250 G when the sum of film thicknesses is 30 and 40 nm and 200 G when the film thickness is 70 nm. It showed excellent impact resistance. On the other hand, the sum of the film thickness is 120
In the case of nm, it is considerably deteriorated to 100G. Considering that the shock resistance during operation required for a magnetic disk that normally requires such portability is about 200 G, a shock resistance that can be practically applied by setting the sum of film thicknesses to 80 nm or less. Sex is obtained.

[0025]

[Table 3]

( Embodiment 4 ) The disk substrate 11 has an inner diameter of 20 mm and an outer diameter of 64 mm.
Of the surface roughness (Rm
ax) was smooth-polished to 1 nm or less. Then, on the cleaned substrate, Ti with a thickness of about 5 nm is formed by a sputtering method.
A film 22 is formed, and island-shaped Al having a height of about 40 nm is formed on the film 22.
Grain 23 was formed and used as a texture. At this time, the average thickness of the Al film converted from the amount of sputtering is 2
was nm. On top of this, a Cr-based metal base film 24 having a thickness of about 6 nm and a CoPtCr-based magnetic film 2 having a thickness of about 20 nm are formed.
5. The hydrogenated carbon protective film 26 having a thickness of about 20 nm was sequentially formed by the sputtering method. Further, an AM2001 having a thickness of 3 nm was formed thereon as a lubricating layer 27 by a dipping method. Here, the Vickers hardness of the surface of each substrate is NECMH, a microhardness meter for ultra-thin films NECMH
The load was measured with A-400 at a load of 1 mN, and the results were converted to obtain. The same impact test as in Example 1 was conducted on magnetic disks manufactured using these various substrates. Table 4 shows the relationship between the acceleration applied at this time and the number of errors generated by the impact. From this, it is understood that the substrate has sufficient impact resistance when the Vickers hardness of the substrate is 600 or more.

[0027]

[Table 4]

From the above examination results, in order to improve the impact resistance of the magnetic disk, the thickness including the thickness of the underlayer film interposed between the surface of the glass substrate and the thin film magnetic film and the film of the thin film magnetic film. The total thickness is set to be less than 80 nm, and the glass substrate has a Vickers hardness of 1200 or more (however, 1200
It is understood that it is sufficient to use the ones other than () .

[0029]

According to the present invention, it is possible to provide a magnetic disk having excellent impact resistance, which is suitable for portable computer applications.

[Brief description of drawings]

FIG. 1 is an enlarged partial cross-sectional view for explaining a film structure of an embodiment of the present invention.

FIG. 2 is an enlarged partial sectional view for explaining a film structure of another embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of an embodiment of the present invention.

4 is an enlarged partial sectional view of a magnetic to Disk schematically shown in order to explain the deformation of the magnetic to Disk that received by the impact.

[Explanation of reference numerals] 1, 11, 21 ... Glass substrate, 2, 12, 24 ...
-Underlayer film, 3, 13, 25 ... Magnetic film, 4, 14, 2
6 ... Protective film, 5, 16, 27 ... Lubrication film, 15 ...
..Texture layer, 22 ... Ti film, 23 ... Texture composed of island-shaped Al particles

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/82

Claims (6)

(57) [Claims] And 1. A least a glass substrate, an underlying film formed on the glass substrate, and a magnetic film formed on the lower ground layer, and a protective film formed on the magnetic film, the protective film In a thin film magnetic disk having a lubricant layer formed on the glass substrate, the glass substrate surface has a Vickers hardness of 1200 or more (however,
And 1200 is the exception), and wherein the total thickness of the film thickness and magnetic film comprising a lower fabric layer interposed between the surface and the magnetic film of the glass substrate is 80nm or less Thin film magnetic disk. 2. A thin-film magnetic to Disk according to claim 1 sum of the film thickness is 20nm or more. 3. A thin-film magnetic to Disk according to claim 2 sum of the film thickness is 50nm or less. 4. A thin-film magnetic to Disk according to claim 2 sum of the film thickness is 30nm or less. 5. The film thickness of the magnetic film is 15nm or more, the thin film magnetic to Disk according to any one of claims 1 to 4 the thickness of the lower fabric layer is 5nm or more. 6. The thin film type magnetic to Disk according to any one of claims 1 to 5 lower land film is a film made of a metal mainly composed of Cr or Cr.