JPS63119019A - Magnetic disk medium - Google Patents

Abstract

PURPOSE:To provide a titled medium which is suitable for ultrahigh density recording and has high durability, wear resistance and reliability by forming a magnetic film on a substrate, forming a thin inorg. compd. film of 30-200Angstrom on the magnetic film and further forming a lubricating agent film on the surface thereof. CONSTITUTION:The thin inorg. compd. film of 30-200Angstrom is formed on the surface of the disk on which the magnetic film is formed and further, the lubricating agent film is formed on the surface thereof. SiO2 is formed at 30-200Angstrom on the magnetic film and the lubricating agent is coated thereon, by which the magnetic recording medium having no spacing loss and having good wear resistance is obtd. The value as small as coefft. of friction (muk)=0.15-0.19 is obtd. at >=30Angstrom film thickness of SiO2 at the time of lubrication. Lubricity is obtd. only by the SiO2 film and the coefft. of friction (muk) does not decrease to <=0.2 if the film thickness of SiO2 is in a 30-100Angstrom range but said coefft. can be decreased to as small as muk=0.15-0.19 by making combination use of the lubricating agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk medium that is suitable for ultra-high density recording, has high durability, wear resistance, and high reliability.

Magnetic recording media for magnetic disk drives, which are generally used as external storage devices for information processing devices, are required to have increasingly higher recording density and higher reliability as the amount of information increases.

In order to improve the recording density, improvements in magnetic properties such as higher coercive force and higher magnetic flux density of the magnetic film attached to the surface of the hunting disk, thinning of the magnetic film itself, and improvement of electromagnetic conversion characteristics are required. Because it is necessary to reduce the distance between the magnetic head and the magnetic film of the magnetic recording medium (hereinafter referred to as spacing), the magnetic film surface must be free of surface roughness, protrusions, etc. Good smoothness is required.

Magnetic disks such as C that are oriented towards high recording densities range from conventionally commonly used coated magnetic films containing magnetic powder and binder to continuous magnetic films (continuous magnetic films containing no binder). Since magnetic media (magnetic media) have a high magnetic storage energy and are advantageous, iron or iron-cobalt alloys can be made non-magnetic by sputtering or vapor deposition in a vacuum or in an atmosphere of argon gas mixed with oxygen. Various methods have been proposed for ferrite oxide magnetic films (hereinafter referred to as ferrite oxide films) and metal magnetic films that are continuously deposited on a substrate.

Also, g! by electrodeposition method! The production of L-based films has also been conventionally performed. Magnetic recording media created by these methods are high recording density media with excellent properties. In particular, ferrite oxide films are hard materials and have good photocorrosion resistance, making them suitable as magnetic recording media. is rated as very good.

As described above, the properties of the magnetic film have been very good for a long time, and in this way, magnetic recording media have sufficient durability and resistance to the sliding of the magnetic head so that they can withstand actual usage conditions. Treating the surface of a magnetic film to improve its abrasion resistance has become an important issue.

In other words, in a magnetic disk device, during normal operation, the magnetic head flies above the magnetic film surface of the magnetic recording material.
The magnetic head does not come into direct contact with the magnetic film, but as recording density improves, a lower flying height is required to reduce the spacing. A type in which the head makes sliding contact with the magnetic recording medium, that is, a contact start-stop (
Hereinafter, this method will be referred to as the C8S method. ) method is now being adopted, so sufficient durability and abrasion resistance are required.

Conventionally, the following methods have been employed to improve the durability and wear resistance of such magnetic recording media.

One method is to form a lubricant film directly on the magnetic recording medium to reduce the total friction caused by sliding between the magnetic head and the magnetic recording medium.

For example, by applying a diluted solution of KryTox Jin-D (trademark of Dejima Bon Co., Ltd.) as a lubricant to the surface of a magnetic disk, the surface of the recording medium becomes slippery, which makes it difficult for the magnetic head to slide.
Efforts are being made to reduce wear and improve wear resistance.

Since the surface of the magnetic recording medium, that is, the surface of the magnetic film, has very good smoothness, a phenomenon occurs in which the magnetic head is attracted to the recording medium. Adsorption here refers to the phenomenon in which the magnetic head adheres to the disk surface. This adsorption is a type of adhesion using lubricant as an intermediary, and in the C8S method, stick slip (5tick-slip) occurs during sliding contact. This causes a head crash in the FF1IIIJL, causing damage to the magnetic head and scratches on the abrasive surface.

Applying a lubricant to the surface of a magnetic recording medium in this way reduces the frictional force, but conversely it causes an adsorption phenomenon, so it is not very effective in improving the wear resistance of the surface of the recording medium. I couldn't do it.

This head stick can be alleviated by applying a thin layer of lubricant on the magnetic recording medium, but on the other hand, from the perspective of reducing frictional force, we cannot expect much of an effect. The control has a small variable range of film thickness and is extremely reproducible.

Lack of manufacturability is nearly impossible in the mass production process.

As another method for improving the wear resistance of the surface of a magnetic recording medium, a method of forming a protective film on a magnetic film has been conventionally carried out using a gold F14al film, and many protective film materials have been proposed.

However, 1-1 In general, the protective film in the case of a gold-aminous film also has the purpose of improving corrosion resistance in addition to wear resistance.
In the following protective films, in order to prevent pinholes from forming in the protective film, a protective film having a thickness of 400 to 800 Å is usually used, since no effect on corrosion resistance can be expected.

It is also common practice to apply a lubricant on top of this protective film. It is true that the abrasion resistance of the protective film reaches a practical level, but as mentioned above, when using a protective film with such a large thickness, the spacing loss is caused by an electric current and e13, and the original performance of the magnetic film is exerted. I wanted to be able to do that.

However, even if the protective film is thinned without considering corrosion resistance, if the protective film is less than 400 Å, the abrasion resistance will be significantly reduced and it will break. The purpose is to form a thin film of 30 to 200 inorganic compounds on the surface of the disc where the magnetic film is formed, and further form a lubricant film on the surface. This can be achieved by a magnetic recording medium characterized by having a structure of:

The present invention will be explained below based on Examples.

FIG. 1 shows the characteristics of the magnetic disk medium according to the present invention, in which the horizontal axis shows the thickness of the inorganic compound thin film +5 iOt) and the vertical axis shows the number of times of sliding.

The number of sliding movements is determined by placing an alumina head slider (tapered flat) on the surface of the magnetic recording medium (same root shape).
Rotate the medium at low speed (1![1st speed 40~8 ocIL
/S) indicates the number of head passes until scratches appear on the media surface in an accelerated abrasion test. The head load is 2097-
It is.

Therefore, it is shown that the more the hole is slid, the better the wear resistance is.

The nine items indicated by solid lines in Figure 1 are Krytchus (Krytx).
Tox) 143AD (trademark of Demebon Co., Ltd.) diluent'
This is a lubricant applied to the SiO weave provided on the t-magnetic film, and the broken line indicates the state without lubrication.

Furthermore, each line width indicates the variation in measured values.

As is clear from the figure, the thicker the 5iotal provided on the magnetic film, the better the wear resistance, and the thinner the StO film, the lower the wear resistance, regardless of whether it is lubricated or not. In addition, wear resistance is generally lower when not lubricated than when lubricated.

What we need to pay attention to here is tx, sio, and wear resistance when the film thickness is around 300A. When the SiO* film thickness is around 300, there are large variations in the measured values of wear resistance.

Another major feature is that during lubrication, the variation becomes large, and some measured values of Vck are lower than when no lubrication is performed. This large variation in the vicinity of 300 is thought to be due to the fact that as the Sing film becomes thinner, the strength of the Sin film decreases markedly and the adsorption effect due to lubrication is added.

For abrasion resistance at a current practical level, it is necessary that the number of sliding operations is N-2000 or more in this accelerated test. It has been confirmed that this value can withstand C3.32 million cycles or more. This condition is stably satisfied when the SiO rich film thickness is 400 Å or more during lubrication.

Next, a detailed measurement was carried out when the film thickness of 5iO1 was around 300λ, and the results as shown in FIG. 2 were obtained.

What should be noted here is that when the film thickness of the frame and Sing is 300 people, the number of sliding times N is the lowest as shown in Figure 1, and when it is 300A or less, the variation becomes smaller and the wear resistance is improved. Naturally, the wear resistance is also the same as above.

These reasons are considered to be as follows.

When the film thickness of Sing is 300 Å or more, the film strength of Sing is high, so it is considered that even if adsorption occurs, it is unlikely to be scratched.

In addition, if the film thickness of S iQ1 is 300A or less,
The reason why the wear resistance is stable and improved despite the thin film thickness and low film strength is thought to be due to the prevention of adsorption.

In other words, adsorption is an adhesion phenomenon between the head and the medium with the lubricant as an intermediary, and the application t of the lubricant to the medium is vI4
! iL, you can prevent it by doing something. The problem here is the adhesion of the lubricant to the medium.

As shown in Table 1, it is clear from the good wettability that general lubricants have a greater adhesion force to inorganic compounds such as Sin than to magnetic films such as 7-elite.

Therefore, if a lubricant is applied to a magnetic film on which an inorganic compound is dotted and thoroughly wiped off, the lubricant can be left only on the surface of the inorganic compound.

Therefore, what is the amount of inorganic compounds dotted on the magnetic film? Naturally, if the amount of the lubricant is increased, the amount of lubricant applied will increase, and conversely, if the amount of the inorganic compound scattered is reduced, the amount of lubricant applied 1- can be reduced.

The amount of this inorganic compound dotted is 5i02 film thickness con)a-
This can be done by

That is, when the film thickness of 5 int becomes 300 mm or less, it is considered that the S 2 O film does not adhere continuously on the magnetic film but in a network to island form.

Therefore, as described above, it is possible to control the amount of lubricant applied. As shown in Figure 2, when the thickness of the Sin film is less than 300A, the amount of lubricant applied is controlled and becomes the optimum amount, eliminating adsorption and improving wear resistance due to the sliding effect of the lubricant. I can do things.

Based on this idea, the inventors of the present invention were able to control the amount of lubricant applied to the optimum level and obtain sufficient wear resistance without providing a relatively thick Siot film called a protective film. The film thickness of 5iO1 is found, and this film thickness is 3
It has been discovered that 0 to 200 A is the optimum value, and it has succeeded in obtaining practically sufficient wear resistance while making it possible to significantly improve spacing loss.

Hata KryTox 143AD (trademark of Demebon Co., Ltd.)
, 1μ of Freon dilution with a concentration of 5 x 10! The diameter of the drop after 9 minutes.

(Note) All film thicknesses are 100OOA.

FIG. 3 is a diagram showing the relationship between the thickness of the Sin film provided on the magnetic film and the coefficient of friction (μk) between the magnetic film and the ferrite head.

In the figure, the Q mark indicates that the SiQ film is not lubricated, and the * mark indicates that it is lubricated. This lubrication is performed using the aforementioned Kry'rox143.
AD1! This is the case when r is used.

As is clear from this figure, during lubrication, the film thickness of Sin is 30
A small friction coefficient cμk) of 0.15 to 0.19 was obtained above A. When the film thickness of Si0g is in the range of 30 to 100, the coefficient of friction (μk
) should not be less than 0.2, but by using a lubricant, μ can be reduced to 0.15 to 0.19.

The attached table shows the film thickness of S ion on the magnetic recording medium, the coefficient of friction between the magnetic head and the magnetic recording medium depending on whether or not a lubricant is applied, the C8S resistance, the rate of change in characteristics, and the sputtering conditions for forming the S ion film. It is something.

Sample numbers applicable to the present invention are 3 to 9 and 30 to 200.
The measurement results as shown in the attached table were obtained regarding the concentration of SiO.

As is clear from the table, when the lubricant of the present invention is applied with a film thickness of S io, the C3S resistance is approximately 20,000 times or more, and the spacing loss (rate of change in characteristics) is approximately 0, which is very high. Good results were obtained.

As described above, in the present invention, 30 to 200 A is applied on the magnetic film.
10. By forming a magnetic recording medium and applying a lubricant thereon, it is possible to provide a magnetic recording medium that does not have any visible loss and has good abrasion resistance.

In the present invention, the ferrite oxide magnetic film is formed by sputtering. However, the present invention is not limited to this. Electrodeposition method and spadume film are also used for metal magnetic models formed by vapor deposition method, such as disks that do not require corrosion resistance or corrosion resistance. It can be applied to discs without corrosion protection, and even discs that have been subjected to anti-corrosion treatment, as long as the adhesion (bonding strength) between the film, such as silicon dioxide, which provides lubricity to the surface of the disc and the disc surface is good.

The film that imparts lubricity to the surface of t1 has lubricity,
Silicon dioxide film (
Not limited to alumina (Sin, ) shown in Table 1 (Jt
A silicon nitride (SilN, ) film and a silicon nitride (SilN, ) film are also effective.

Furthermore, silicon dioxide-alumina oxide I7+7um (
S i O@-Al, o, -B eO) films can be used simultaneously. Various lubricants can also be used.

<Example> CI) Formation of ferrite oxide magnetic film: The surface of the alumina substrate was anodized in a sulfuric acid bath, and alumite 7@all 1
After forming the substrate to a thickness of ~2 μm, the substrate was cleaned and sputtered using a target mainly composed of iron containing cobalt in an atmosphere of 80 thiargon (Ar) and 20 thionic acid (0,0) to form a thin film on the substrate surface. 0.2 μm hematite (α-Fe
lOs)'It was formed.

This was heat-treated in a reducing atmosphere and magnetite (Fe,
0. ) and further heat-treated in the atmosphere to form ferrite oxide magnetic M of hematite (γ-Fe2O3).

CII) Formation of silicon dioxide film 100 y
(Ar) or 1-jso*Argon (Ar)-20'4 Oxygen (formed by sputtering in an atmosphere of zero). Conditions are shown in the attached table.

(2) Formation of lubricant film KryTox143 is used as lubricant A on the rotating disk by Nispin coating.
AD (Dejima Bon Co., Ltd. trademark), Lubricant B,! : L-IX
Apply looO (Canyon Products Company trademark),
Next, the surface was wiped with a rotating pad to which paper containing no oil valve was attached to form a lubricant film.

The lubricant was applied after the silicon dioxide film was formed and the sample was left in a decal for 20 hours.

Experimental Method> (1) The C8S resistance test was performed by repeating the cycle shown in FIG. 4, and was expressed as the number of C8S cycles until scratches appeared on the disk surface. Check for scratches by visual inspection.

The test was conducted twice for each sample, once on the inner circumference and once on the outer circumference.

The heads used were Winchester type and Taber 7 elite type Mn-Zu with a load of 3.2±0.21.
A new head was used for each test with a ferrite head.

The rate of change in electromagnetic transmissibility (characteristic change group) is the output difference when the solitary wave output in sample No. 2 in the attached table without the silicon dioxide film is set to 1, and is shown in "H".

The nine heads used to measure the characteristics had a flying height of 0.2 μm (
Measurements were carried out under the same conditions using the same tapered flat Zn ferrite head with a circumferential speed of 40 m/s).

Further, the friction coefficient indicates the friction coefficient (μk) immediately after the ferrite head and the magnetic recording medium slide. The friction coefficient values in the attached table are the average values of 5 times. The film thickness of 5iO1 is calculated from the sputtering rate, and the thickness ZQOA
In the following description, it is considered that the film is not a completely continuous film, but here it refers to the average shape film thickness obtained by dividing the deposition amount by the total area.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the film thickness of Siol and the number of times of sliding.
Figure 2 is a diagram showing the relationship between the number of times of sliding and the film thickness of Sin according to the present invention, Figure 4 is a diagram showing the conditions for repeating the start and stop of rotation of the magnetic recording medium, and Figure 3 is a diagram showing the relationship between the number of times of sliding and the thickness of the Sin film according to the present invention. FIG. 3 is a diagram showing the relationship between film thickness and friction coefficient. Sliding ω number (N) (xt6ri

Claims (1)

[Scope of Claims] A magnetic disk medium used in a magnetic disk device for recording and reproducing information by disposing a flying head on a rotating magnetic disk medium, comprising: a magnetic film formed on a substrate; On the membrane, 30-200
1. A magnetic disk medium comprising: a thin film of an inorganic compound having a thickness of 1.5 cm, and a lubricant film formed on the surface of the thin film of an inorganic compound.