JPS6339134A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve sliding characteristic and attraction resistance and to assure a long life by forming grooves having a specific depth and width at >=1 pieces per 10mum concentrically to the surface of a hard underlying film. CONSTITUTION:Liquid is held in the concentrical grooves if the many grooves are formed on the surface of the above-mentioned film. The dissipation of the liquid by centrifugal force is then decreased and the deterioration in the sliding characteristic is obviated. However, if the grooves are as deep as >=0.1mum, the magnetic field of a head does not reach the magnetic film in the bottom and the overwrite characteristic of the output decreases to >=30dB. Such depth is, therefore, undesirable. The effect of the grooves is low if the grooves is as shallow as <=0.01mum. The width of the grooves is stipulated to >=0.1mum and <=1Xm from the size of abrasive grains for working. The effect of decreasing the attraction characteristic by the decrease in the actual contact area between the disk and the head is obtd. if the concentrical grooves are formed to the distribution density of at least one piece per 10mum as the width of the slider is about 0.1-0.8mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk used as a storage device for an electronic computer.

[Conventional technology]

The magnetic disks that are currently widely used are called coated type disks, which are made by mirror-finishing aluminum alloy and then coating magnetic powder together with resin (film thickness: 0.5 to 1 μm). This is because the magnetic powder is discontinuously dispersed within the resin, which causes large noise in the recording and reproduction output, making it impossible to increase the recording density.

Therefore, a disk called a thin film type, in which a magnetic material is continuously applied in a thin layer (film thickness of 0.2 μm or less) by sputtering or plating, has been developed and is in some use.

The head of a magnetic disk drive is used during recording and playback.

It floats on a rotating, smooth disk via a film of air, but when not in use, it is grounded on a disk that has stopped rotating. Coated type disks reduce the impact caused by contact with the disk during contact sliding when the head starts and stops rotating by coming into contact only with the head and a hard substance mixed in the resin, but thin film type Since the disk cannot be coated with a hard material that discontinuously discontinuizes the magnetic material, a hard base film (e.g., anodic oxide film or electroless nickel plating film) with no unevenness defects of φO, L μm or more is used under the magnetic material. It is used with the .

However, if the frictional force at the time of contact between the head and the disk during sliding is large, the head may cause pitching vibration and damage the disk, so it is necessary to apply a liquid lubricant on top of the magnetic film or protective film. There are many things.

The method for applying the liquid lubricant is to use a solution (abbreviated as liquid) of the liquid lubricant and its solvent.

(a) A method in which the substrate is immersed in a liquid (dip method) (b) A method in which the substrate is rotated at high speed and the liquid is supplied from the inner circumference and coated using centrifugal force (spin cord method) (C) A method in which the liquid is uniformly applied to the substrate (d) A method of applying a mist (spray method); (d) A method of spreading the liquid applied by these methods by pressing it with gauze or the like before it dries (rubbing method).

[Problem that the invention seeks to solve]

Any of the above methods can apply a practically sufficient amount of liquid lubricant to a coating type disk. Since the resin of the coating type is porous, it is impregnated with liquid, and if the amount of liquid applied is set to the lowest level, the excess amount is soaked in the old soak so that the amount of liquid that comes out on the surface is almost constant. Therefore, the sliding properties of the head during sliding are good and the coefficient of dynamic friction μ is as small as 0.1 or less. If there is too much, the adsorption force will be large when the head is stopped, and the static friction force will be large when starting up, deforming the gimbal. However, the slider surface of the head will only come into contact with the hard material that is exposed on the resin, and the actual head and disk will be in contact with each other. Since the contact area is small, if it is placed at a certain lowest position, there will be fewer adsorption accidents.

However, thin-film disks have a smooth magnetic film with no unevenness, so if the amount of liquid applied is small, scratched areas will occur and the frictional force will be large (for example, μ = 0.5), which makes it difficult to protect the disk when sliding. This may wear out the film or damage the magnetic film. In addition, if a large amount of liquid is applied, a smooth slider surface with a large contact area (Rmaxo, 02 μm) and a smooth disk surface (Rmaxo,
xo, 1 μm) is easily adsorbed when the head is stopped, and the force to peel it off can reach 40 gf.

Note that in the thin film type, the liquid is not retained in the resin as in the coating type, and in addition, the disk surface is smoother, so the liquid often dissipates due to centrifugal force. Long-term sliding tests (for example, CSS (Contact Start Stop) tests on thin film types.

When conducting a test in which the head takes off and lands intermittently, μ is initially as small as 0.1 and no friction occurs, but 2
From about 0,000 times, μ becomes large to 0.4 and wear may become large. As described above, unless the minimum allowable lubricant film thickness is determined in consideration of changes over time, collisions in which the head wears out the disk cannot be avoided.

As described above, the sliding and adsorption properties of thin film type disks are significantly more sensitive than those of coated type disks, depending on the thickness of the liquid-wet film.

[Means for solving problems]

After considering the above problems, we found that on the surface of the hard base film,
It was found that if concentric grooves are provided, the effect of film thickness on sliding adsorption is reduced. In other words, by providing many concentric grooves, the liquid is retained in the grooves, and dissipation due to centrifugal force is prevented. This prevents deterioration in sliding properties. Also, by adding grooves, the number of concave surfaces increases, which improves the adhesion of liquid. By retaining the excess liquid in the groove, the range of allowable liquid amount is widened, making it easier to embellish.

By providing grooves, the actual contact area between the disk surface and the slider surface of the head is reduced, so the adhesion is also reduced.

However, if the groove is deeper than 0.1 μm, the magnetic field of the head will not reach the bottom magnetic film, and the output override characteristic (
Overwriting characteristics) is 30dB (R60m, 2F=2.5M
Hz, IFl, 25M I(z) or less, which is not preferable. Moreover, if the groove is shallow, such as 0001 μm or less, the above effect is small. The depth of the groove was determined by measuring the cross section with a transmission electron microscope or obliquely observing the surface with a SEM.

The width of the groove can be defined as O, 1 μm or more and 1 μm or less, based on the size of the processing abrasive grains used to obtain the above depth. If the deviation (concentricity) between the rotation center when the disk is installed in the actual device and the processing center where the concentric grooves are made is within 1■, it will have a great effect of avoiding dissipation due to centrifugal force, and the distribution density of the concentric grooves will be Since the slider width is approximately 0.1 to 0.8 mm, if there is at least one slide per 10 μm, the effect of lowering the adsorption property due to the reduction in the actual contact area between the disk and the head can be obtained.

〔Example〕

Aluminum alloy (Mg4.5% Others Si, Fe,
0.02% in total of Mn, Cu, etc.) with an outer diameter of 130 nm,
After finishing it by turning into a shape with an inner diameter of 40 m and a plate thickness of 1.9051 mm, anodization was performed using chromic acid solution to form an anodic oxide film with a thickness of 13 μm. The surface is smoothed with alumina abrasive grains with an average grain size of 0.3 μm (Ra=0.007 pm), and after cleaning, a tape with white alumina abrasive grains (average grain size of about 5 μm) fixed to the surface is rotated. Concentric grooves were created by pressing the Thereafter, it was immediately washed, and a Co--Ni magnetic film and a carbon protective film were applied by sputtering, and a fluorinated oil-based liquid lubricant was applied using a spin cord to produce a magnetic disk.

In addition, in order to investigate the difference in the hard base film, a 15 μm thick electroless nickel plating film was applied instead of the anodic oxide film, and the same type of processing was applied. For comparison, we also produced a model without grooves.

In addition, the groove depth can be adjusted by changing the size of the alumina abrasive grains used for groove processing.
The film thickness was varied by changing the concentration of the liquid lubricant used in spin coding. The groove depth was measured by SEM, and the film thickness was measured by FT.
The absorbance of the liquid lubricant in an IR (Fourier transform infrared spectrometer) was calibrated to the film thickness using an ellipsometer.

For evaluation, the sliding property was measured after 20,000 C5S tests, the presence or absence of abrasion of the carbon in the protective film, and the adsorption resistance of the 9 heads after being left in an environment with 60% humidity for 5 days after applying liquid lubricant. If the override characteristic is 2F2.5M71 due to frictional force
Each test was conducted at a value of F1.25 MHz. Passing was defined as no wear, 5 gf or less, and 30 dB or more.

The head used is the Minwin Chester head.

The experimental results are shown in Table 1. Liquid lubricant film thicknesses that have good sliding properties but have poor adhesion resistance (D, E), and thin or non-existent films that have poor sliding properties but good adsorption resistance (A, B, I). )
Intermediate films (C, J), etc., which are bad on both WI sides, can be made to satisfy both (F,
G.K.

L), of course, if the groove is too deep (H, N) or the film is too thick (M), the override characteristics and adhesion resistance will not be satisfied. The disk device has excellent sliding properties and adhesion resistance, and a long life is guaranteed.Table 1. It can improve the sliding and adsorption properties of the disk and head.

Claims (2)

[Claims] (1) A hard base film is applied on an aluminum alloy substrate, a continuous magnetic film with a thickness of 0.2 μm or less is applied on top of the hard base film, a protective film is placed on top of it as necessary, and a film with a thickness of 0.02 μm is placed on top of that as necessary.
In a magnetic disk having a liquid lubricant film of not more than m, grooves with a depth of 0.01 μm or more and 0.1 μm or less and a width of 0.1 μm or more and 1 μm or less are formed on the surface of the hard base film when the disk is incorporated into a device. At least 10 μm on the head sliding area in a concentric circle with a circumference of 1 mm or less around the rotation center of the
A magnetic disk characterized in that each magnetic disk has one or more disks. (2) The magnetic disk according to item 1 above, wherein the hard underlayer film is an anodic oxide film.