JP2807478B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used in a magnetic recording device and the like and a method of manufacturing the same, and more particularly, to a magnetic recording medium having a magnetic thin film and a method of manufacturing the same.

[Conventional technology]

A magnetic recording device reads, writes, and erases information using a magnetic recording medium and a magnetic recording / reproducing head or a transducer. With the advance of technology, high-density recording and high-speed recording are required, and the gap between the magnetic recording medium and the magnetic head is becoming narrower, and the relative movement speed between the two is increasing. As a result, collision and contact of the magnetic head with the magnetic recording medium, and accompanying wear and damage of the magnetic recording medium are inevitable. Further, in a general magnetic recording device, when the device is stopped, the magnetic recording medium and the magnetic head are in stationary contact, and the magnetic head is lifted from the surface of the magnetic recording medium by airflow when the device is driven, so-called contact start / stop (CSS). The method is adopted. This method causes contact and friction between the magnetic head and the magnetic recording medium and causes sticking when the two come into stationary contact with each other, and sometimes damages the magnetic recording medium when the two are separated when the apparatus is driven.

In order to prevent such abrasion and damage of the magnetic recording medium due to collision, contact, friction and the like between the magnetic recording medium and the magnetic head, a protective film is provided on the surface of the magnetic recording medium, and the mechanical strength of the protective film is further reduced. For the purpose of improvement, it has been studied to improve the adhesion of the protective film layer and to improve its hardness.

The magnetic recording medium described in JP-A-62-109222 uses a carbon layer as a protective film, and a silicon layer is provided between the magnetic layer and the protective film in order to improve the adhesion between the two. is there.

Also, by reducing the effective contact area at the time of contact between the magnetic recording medium and the magnetic head, an underlayer, a magnetic film layer,
It is common practice to provide a protective film layer. For example, IEE, Transaction on Magnetics, MAG23, pp. 3405-3407
Page (1987) (IEEE, Trans.Mgnetics, MAG 23, pp3405-34)
07 (1987)) reduces the coefficient of friction by optimizing the surface roughness.

Further, a lubricant is applied to the surface of the magnetic recording medium for the purpose of, for example, reducing the friction coefficient of the surface. Japanese Patent Publication No. 60-10368 proposes a method of firmly attaching an organic liquid lubricant to the surface of a magnetic recording medium.

[Problems to be solved by the invention]

The above prior art does not sufficiently consider the minute shape of the surface of the protective film to which the lubricant adheres and the method of attaching the lubricant, reduce the adhesive force between the magnetic recording medium and the magnetic head, and reduce the wear of the magnetic recording medium. However, there is a problem that the reduction of damage is not satisfied at the same time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium in which the adhesive strength between the magnetic recording medium and a magnetic head is reduced, and the magnetic recording medium is reduced in abrasion and damage, and a method of manufacturing the same.

[Means for solving the problem]

In order to achieve the above object, a magnetic recording medium of the present invention has a base film, a magnetic thin film, and a non-magnetic protective film on a substrate, and a lubricant is provided on the non-magnetic protective film. The surface has irregularities formed by crystal growth of a base film and a magnetic thin film, and the average diameter of the projections is in the range of 10 nm to 40 nm. The height of this unevenness is 25
It is preferably not more than nm.

In order to achieve the above object, a method of manufacturing a magnetic recording medium of the present invention includes forming a base film and a magnetic thin film on a substrate by sputtering, further forming a non-magnetic protective film on the magnetic thin film, Provide irregularities formed by crystal growth of the underlayer and magnetic thin film on the surface of the nonmagnetic protective film, adjust the average diameter of the convexities to be in the range of 10 nm to 40 nm, and attach a lubricant to the surface of the nonmagnetic protective film After that, it is washed with a solvent to remove a part thereof.

[Action]

The convex portion of the unevenness on the surface of the protective film functions as a contact surface when the magnetic head and the magnetic recording medium are in static contact. At the time of static contact, the contact area is small, and the magnetic head rarely comes into full contact with the attached lubricant, so that the adhesive force, that is, the attraction force of the magnetic head to the magnetic recording medium does not increase. . The adhesive force may increase due to the lubricant moving to the contact interface due to the meniscus effect, but the increase in the adhesive force is not large because the number of contact portions is small.

When the magnetic head and the magnetic recording medium come into strong contact during the relative movement, the contact surface pressure increases, and the convex portions of the surface irregularities are deformed or damaged. At this time, a large amount of the lubricant adheres to the surface of the magnetic head, so that the lubricating effect increases and damage to the magnetic recording medium can be reduced.

However, if the convex portions of the surface irregularities are too high, the surface pressure at the contact surface with the magnetic head becomes extremely high, and the medium surface is easily worn. This is presumed to be due to the fact that the abrasion powder generated in contact increases and eventually adheres to the magnetic head to promote abrasion by the abrasion powder, so that the lubricant functions to collect the abrasion powder. As described above, the height of the unevenness on the surface of the protective film also has a preferable range.

Since the magnetic recording medium of the present invention operates as described above,
The abrasion resistance can be improved while the adhesive force is kept small, and the lubrication characteristics can be improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. A plurality of substrates were prepared in which an N ₂ -P hard film was formed on an aluminum plate by plating, and the surface of which was given a surface roughness in the circumferential direction by texture processing. The average surface roughness Ra of the substrate is 5 to 8 nm. A Cr film is placed on these multiple substrates
Each layer was formed into various thicknesses of 50 to 500 nm by C-planar magnetron sputtering to form base films. Next, a CoNi alloy was formed to a thickness of 50 nm on each sample by DC planar magnetron sputtering to form a magnetic film, and a carbon film was formed to a thickness of 50 nm in the same manner as a protective film to obtain a magnetic recording medium. Was.

The size of the crystal grain size (columnar diameter) on the magnetic film surface and the fine roughness of the crystal grain exposure irregularities are changed independently of the surface roughness of the texture processing depending on the conditions for forming the Cr underlayer and the CoNi alloy magnetic film. be able to. The surface of the protective film has substantially the same shape as the irregularities on the surface of the lower magnetic film.

The unevenness on the surface of the protective film was obtained by observing the cut magnetic recording medium with a transmission electron microscope (TEM) and a tunnel microscope (STM). The size of the surface crystal grains was measured by a scanning electron microscope. FIG. 4 shows the relationship between the crystal grain size on the surface of the protective film of the sample and the height of the surface irregularities.

On the other hand, the magnetic recording medium was immersed in a 0.1 to 0.3% solution of a perfluoroalkylpolyether-based lubricant in trichlorotrifluoroethane, and slowly lifted into the atmosphere, whereby the lubricant was deposited on the protective film. The lubricant was then rinsed off with undiluted trichlorotrifluoroethane.

Lubricant is locally adhered to the concaves and convexes on the surface of the protective film of the magnetic recording medium because the lubricant is applied to the entire surface to some extent and impregnated with the lubricant to the inside of the concaves. A method of removing a part of the lubricant under such conditions can be used. To apply the lubricant over the entire surface, the magnetic recording medium may be immersed in a lubricant solution.
Further, another method such as spraying the solution on a magnetic recording medium may be used. Part of the lubricant can be removed by immersing the magnetic recording medium coated with the lubricant over the entire surface in a solvent containing no lubricant. Further, other chemical or mechanical methods may be used.

FIG. 5 shows a magnetic recording medium coated with a lubricant (circled in FIG. 5).
The results of comparing the adhesive strength of a magnetic recording medium (marked with △ in the figure) with the amount of lubricant to the magnetic recording medium manufactured by adding the above-mentioned washing step are shown. Lubricant amount is Fourier transform infrared spectrometer (FTIR)
From the peak value of the absorbance of the fluorine group. In addition, the adhesive force was applied to a sample with a magnetic head of Mn-Zn monolithic type applied with a load of 10 gf in the air at room temperature and normal humidity.
After standing for 24 hours, the measurement was performed. As shown in the results in FIG. 5, it is clear that the sample having the lubricant cleaning step has a lower adhesive strength despite the same amount of the attached lubricant.

In addition, a magnetic recording medium without lubricant application, a magnetic recording medium with lubricant applied, and a magnetic recording medium manufactured by adding a cleaning process are prepared, and the protective film is taken out.
Observation was performed by TEM. FIG. 2 shows a state of the magnetic recording medium manufactured by adding the cleaning step. A scale-like pattern corresponding to the irregularities of the crystal grains on the surface of the protective film and an adhering substance at the boundary were observed. The adhering substance at this boundary was a magnetic recording medium not coated with a lubricant. Was not observed. In addition, in the magnetic recording medium with the lubricant applied, an adhering substance is observed, but the contrast is small,
Spread and not localized.

As described above, in the magnetic recording medium of the present embodiment, as shown in FIG. 1, the lubricant 1 is locally applied to the concave and convex concave portions 6 of the protective film 2 caused by the crystal grain growth of the base film 4 and the magnetic film 3. It is considered that they are already filled.

Next, a magnetic recording medium was prepared in which the crystal grain size was changed by changing the sputtering film forming conditions of the base film and the magnetic film, and the size of the irregularities on the surface of the protective film was changed, and the adhesive strength and the wear rate were measured. In the manufacture of the magnetic recording medium, a lubricant washing step was added. The lubricant amount of the sample is 3 relative lubricant amounts shown in FIG.
Corresponds to. The abrasion speed was calculated by pressing a sapphire spherical surface of R30 μm against the sample surface, reciprocating, and measuring the time until the protective film was scraped off. The relationship between the crystal grain size and the height of the surface irregularities is the same as that shown in FIG. It became clear that the smaller the crystal grain size, the lower the wear rate, but the greater the adhesive strength. From this result, it is preferable that the diameter of the irregularities on the surface of the protective film caused by crystal growth at the time of forming the underlayer and the magnetic film is in the range of 10 nm to 40 nm.

Next, the conditions for forming the sputtering film for the base film and the magnetic film were changed, the size of the crystal grains was set to approximately 50 nm, and magnetic recording media having different heights of the crystal grain irregularities were prepared, and the wear rates thereof were measured. In the manufacture of the magnetic recording medium, a lubricant washing step was added. The lubricant amount of the sample corresponds to the relative lubricant amount 3 in FIG. The results are shown in FIG. It was clarified that even with the same crystal grain size, the higher the height of the irregularities, the faster the wear rate. From this result, it is preferable that the height of the unevenness is 25 nm or less.

In the above embodiment, carbon is used as the protective film. However, the same effect can be obtained even if the numerical value of the surface roughness changes with respect to the protective film of another material.

In the above embodiment, the case of the hard disk type magnetic recording medium has been described. However, the same effect can be obtained in the case of the flexible type magnetic recording medium.

〔The invention's effect〕

From the above results, the magnetic recording medium in which the lubricant mainly adheres to the concave portion of the surface roughness of the protective film and is locally filled has a low adhesive force with the magnetic head, a low wear rate, and a low magnetic head. The resistance to collision impact and sliding at the time of contact with steel has been improved.

[Brief description of the drawings]

1 is a partially enlarged longitudinal sectional view of a magnetic recording medium according to one embodiment of the present invention, FIG. 2 is a surface state diagram thereof, and FIG. 3 is a magnetic film of the magnetic recording medium according to one embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the adhesive strength and the wear rate with respect to the crystal grain size of the magnetic film, FIG. 4 is a diagram showing the relationship between the crystal grain size of the magnetic film and the surface irregularities, and FIG. FIG. 6 is a diagram showing the relationship between the crystal surface irregularities and the wear rate. DESCRIPTION OF SYMBOLS 1 ... Lubricant, 2 ... Protective film 3 ... Magnetic film, 4 ... Under film 5 ... Substrate, 6 ... Recess

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironori Tani 2880 Kozu, Kozuhara, Odawara City, Kanagawa Prefecture Inside the Odawara Plant, Hitachi, Ltd. 56) References JP-A-63-175225 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/72 G11B 5/66 G11B 5/84

Claims (3)

(57) [Claims] 1. A magnetic recording medium comprising a substrate, a base film, a magnetic thin film, and a non-magnetic protection film sequentially provided thereon, the non-magnetic protection film having irregularities on its surface, and a lubricant on the non-magnetic protection film. 3. The magnetic recording medium according to claim 1, wherein the irregularities are irregularities formed by crystal growth of the base film and the magnetic thin film, and the average diameter of the convexities is in a range of 10 nm to 40 nm. 2. The magnetic recording medium according to claim 1, wherein the height of the unevenness is 25 nm or less. 3. A base film and a magnetic thin film are formed on a substrate by sputtering, a non-magnetic protective film is formed on the magnetic thin film, and the surface is formed by crystal growth of the base film and the magnetic thin film. Irregularities, the average diameter of the convex portion is provided with irregularities in the range of 10 nm to 40 nm, after attaching a lubricant to the surface of the non-magnetic protective film, washing with a solvent to remove a part thereof. A method for manufacturing a magnetic recording medium, comprising: