JPH0648536B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium used in a magnetic disk device or the like, and more particularly to a magnetic recording for a magnetic recording / reproducing apparatus using a CSS type flying magnetic head. The present invention relates to a manufacturing method suitable for improving a medium.

[Background of technology]

The magnetic disk device used for data processing equipment,
In recent years, the data recording density has been rapidly improved and the capacity has been increased, and the device tends to be miniaturized in terms of high speed and economy.
With the demand for such a high recording density, the recording medium is changing from a conventional coating film to a continuous magnetic film.

That is, conventionally, magnetic powder was mixed with a binder such as synthetic resin,
This is spin-coated on an aluminum substrate to form a coating film, which constitutes the magnetic film of the magnetic recording medium. On the other hand, the continuous magnetic film is formed by forming a magnetic material such as iron or an iron-cobalt-based alloy on the substrate by a method such as sputtering, vapor deposition, or plating, and does not include a binder (binder) so that it is continuous. It is called a magnetic film (continuous magnetic medium). The continuous magnetic film has better magnetic characteristics than the conventional continuous film, which includes a binder such as synthetic resin, and the manufacturing process is simplified. In addition, the recording density has been remarkably improved, and one having excellent characteristics as a high recording density medium has been obtained. Especially, the ferrite oxide film is hard in terms of material and has good corrosion resistance, which makes it extremely useful as a magnetic recording medium. Is rated as good.

By the way, as in the conventional magnetic disk device, the CSS (Contact
Start Stop) method is adopted. Therefore, normally, the magnetic head floats above the disk surface for reading and writing,
When the floating force is not generated, such as when the magnetic recording medium starts and stops rotating, the surface of the magnetic recording medium and the slider of the magnetic head come into contact with each other and slide. Therefore, the surface of the magnetic recording medium in the head landing zone where the magnetic head is in sliding contact is abraded, and the abrasion powder diffuses over the entire surface of the magnetic recording medium, causing a head crash. Therefore, it is necessary to prevent wear of the surface of the magnetic recording medium as much as possible.

[Conventional technology]

In order to prevent the wear of the magnetic recording layer, the following method has been conventionally adopted.

A protective film such as silicon oxide (SiO ₂ ) or resin is provided on the surface of the magnetic recording layer so that the distance between the magnetic head and the magnetic recording layer does not become too large.

In order to reduce wear during contact sliding of the magnetic head,
A lubricant is applied to the magnetic recording layer or the protective film to improve the sliding of the magnetic head slider.

When the lubricant is applied, the lubricant causes the magnetic head slider to adhere to the surface of the magnetic recording medium, which may damage the support mechanism of the magnetic head or cause a head crash when the magnetic recording medium starts to rotate. Therefore, in order to prevent this adhesion, the surface of the protective film 2 provided on the magnetic recording layer 1 as shown in FIG. 1 (a) by the method described in JP-A-56-22221. Are provided with innumerable protrusions 3 ... A lubricant is impregnated into the gaps between the projections 3 and the lubricant film between the slider and the magnetic recording medium becomes thin, so that adhesion is eliminated and the friction coefficient is smaller than that of a smooth surface. 4
Is an aluminum substrate, and 5 is an alumite layer formed on the surface thereof.

As the protective film 2 of the magnetic recording layer 1, a porous film is used, or a first film is formed on the surface of the protective film by a method such as photoetching.
As shown in the figure (b), minute holes 6 are provided to impregnate the lubricant. Further, as described in JP-A-56-22219, in a coating type magnetic recording medium, a paraffin particle is kneaded and applied to a magnetic coating material, and baked to obtain a fine lubricant holding agent. There has been proposed a method of forming irregularities directly on the surface of a magnetic coating film.

[Problems to be Solved by the Invention]

However, all of these methods have the following problems. That is, abrasion cannot be prevented by simply providing a protective film as described above. Since the alumite surface of the substrate is mirror-finished and the magnetic film is provided thereon, the surface of the magnetic film also becomes a mirror-finished surface. Therefore, the protective film on the magnetic film is also smooth, and when the magnetic head is not in a floating state and is in sliding contact with the protective film, dust is generated due to abrasion of the protective film, causing a head crash that is a fatal obstacle. May trigger.

When the lubricant is applied to improve the slippage as described above, the friction coefficient is small during the initial period and is effective, but when the lubricant is consumed over time, the lubricating action is reduced and abrasion powder is generated. However, if a large amount of lubricant is applied, the slider will stick to the magnetic recording medium surface when the magnetic recording medium stops and is in contact with the slider, so that the next time the magnetic recording medium starts rotating. In addition, the magnetic head may be abruptly peeled off from the surface of the magnetic recording medium, causing a head crash or damaging the gimbal supporting the magnetic head.

When a myriad of protrusions 3 ... Are provided on the surface of the magnetic recording medium as described above, the gap in the protrusions is impregnated with the lubricant, so that the problem in the method of (1) can be alleviated to some extent. To do. Therefore, the impregnating agent cannot be stably and uniformly held on the entire surface. Therefore, the lubricant has a short life and cannot withstand long-term use.

When the protective film is made porous as described above, the lubricant does not easily move and the holding property of the lubricant is improved, but since the surface of the protective film is smooth, the abrasion resistance during sliding is reduced. Also, with the technique of patterning using a mask, it is impossible to form a target hole of about 1 μm, and only a large hole of about 10 μm can be obtained.

In the method of kneading and baking paraffin particles in a magnetic coating as described in JP-A-56-22219, in addition to the presence of a non-magnetic resin in the magnetic film,
Since cavities due to the traces of paraffin particles are generated, the characteristics as a magnetic film are deteriorated, and it is not applicable to a medium having a high recording density. Moreover, since the magnetic paint has a high viscosity, it is difficult to uniformly disperse the paraffin particles, and the cavities are concentrated, resulting in bit errors and S.
There is a problem such as a decrease in the / N ratio. Since the magnetic paint has a high viscosity, it is also difficult to form protrusions along the ridges of paraffin particles by utilizing surface tension. In particular, in the case of a medium in which a continuous magnetic film is formed by a method such as sputtering or vapor deposition as in the present invention, the method of kneading paraffin particles in a magnetic paint cannot be applied.

The technical problem of the present invention is to solve the above problems in the conventional magnetic recording medium, and even in a continuous magnetic film type medium or a medium having a high recording density, the lubricant has a long holding property, and the wear resistance and the magnetic characteristics are high. It is also possible to realize an excellent magnetic recording medium.

[Means for Solving the Problems]

The technical means according to the present invention taken to solve this technical problem includes a step of forming a magnetic recording layer on a substrate, a step of forming a protective film on the magnetic recording layer, and a step of forming a protective film on the protective film. A method of manufacturing a magnetic recording medium including a step of applying a lubricant, wherein the step of forming the protective film comprises mixing a solvent containing silicon and an easily thermally decomposable or easily thermally evaporated substance, The mixed solution is applied on the magnetic recording layer, and the solvent is made to be in a state of being raised along the surface of the substance more than the film surface of the solvent. The method is characterized in that decomposition and evaporation of a thermally decomposable or easily heat-evaporable substance are carried out simultaneously.

Liquid paraffin is suitable as the easily decomposable or easily heat-evaporable substance.

[Action]

According to this method, the traces of liquid paraffin that have evaporated become depressions and projections. That is, since the solvent containing silicon has a low viscosity and easily rises along a sphere of liquid paraffin or the like due to surface tension, after the liquid paraffin or the like decomposes and evaporates, a protrusion protruding from the flat protective film surface and the protection Independent recesses that are recessed from the film surface are formed. A solvent containing silicon with low viscosity is mixed with an easily thermally decomposable or easily thermally evaporated substance such as liquid paraffin, so it can be easily and uniformly dispersed in the solvent, and unevenness is evenly distributed over the entire surface of the protective film. Can be formed.

In addition, by appropriately selecting the amount and composition of liquid paraffin, the depth of evaporation traces of liquid paraffin and the height of protrusions form various irregularities. Innumerable recesses lower than the surface can be obtained.

Unlike the conventional method in which paraffin particles are kneaded and baked in a magnetic paint and baked, in the step of forming the protective film on the magnetic film, unevenness is formed on the surface of the protective film. Can also be applied to. Further, even when the method of the present invention is applied to a medium of a discontinuous magnetic film such as a coating type medium,
Since no cavities are formed in the magnetic coating film, it is suitable for a medium having a high recording density without causing a non-magnetic region in the magnetic coating film to increase and the magnetic characteristics to deteriorate unlike the conventional method.

Example of Invention

Next, practical examples of how the method for manufacturing a magnetic recording medium according to the present invention is embodied will be described. FIG. 2 shows a first embodiment of a magnetic recording medium manufactured by the method of the present invention, (a) is a sectional view and (b) is an enlarged sectional view. The surface of the aluminum substrate 4 is oxidized to form an alumite layer 5, and γ-FeO ₃ or the like is provided as the magnetic film 1 on the surface by a method such as sputtering. Innumerable protrusions 7 and recesses 8 are formed on the magnetic film 1. L is the position of a planar protective film surface formed at a position separated from the magnetic film 1 by a predetermined film thickness, and the position of this protective film surface is hereinafter referred to as an intermediate level. For this intermediate level L, the protrusion 7 ...
Are raised like a crater, and the spherical recesses 8 ... Have a recessed shape with respect to the intermediate level L.

FIGS. 3 and 4 are schematic views showing the surface state of the magnetic recording medium in order to explain another embodiment of the magnetic recording medium. (A) is a sectional view and (b) is a partial sectional view. It is a perspective view.
Innumerable protrusions 7 ... And innumerable recesses 8 ... Are formed on the protective film 2 provided on the magnetic film 1. In FIG. 3, the protrusion 7 ...
All have a constant shape and height, and the recesses 8 ...
All have a constant shape and a constant depth. On the other hand, in the case of FIG. 4, as shown by the protrusion 7e, the protrusion has a stepped shape. Similarly, the recesses 8 may have a stepped shape by changing the depth from the middle.

The protrusion 7b is lower than the other protrusions 7 and 7a, and thus the heights of the protrusions may be different.
Further, the depth of each recess 8 does not have to be constant.

In this way, the structure is provided with innumerable protrusions protruding from a certain intermediate level L having a planar shape and innumerable recesses recessed from the intermediate level L. Therefore, since the lubricant is impregnated into the innumerable independent recesses 8 ..., The lubricant does not move and is stably held. As a result, the lubricating action is maintained for a long period of time, and the generation of abrasion powder due to the abrasion of the protective film is prevented. Further, even if a small amount of abrasion powder is generated, it will not be a factor of head crash because it will be accumulated on the protective film surface of the intermediate level L between the protrusions 7.

At the time of recording / reproducing information, since the magnetic head slider makes sliding contact with the top ends of the protrusions 7 ..., 7a ..., the protective film 2 is smooth as shown in FIG. The friction coefficient is smaller and wear is reduced compared to the one that closely adheres to.

Next, an embodiment of the method of the present invention for obtaining a protective film having innumerable independent spherical concave portions depressed from the protective film surface as shown in FIG. 2 will be described. As described with reference to FIG. 2, a magnetic film 1 having a γ-
After providing FeO ₃ or the like by a method such as vapor deposition, processing is performed in the following order.

(1) Application of mixed solution: A mixed solution containing silicon (Si) and liquid paraffin is spin-coated on this magnetic film 1 at 1000 rpm as follows.

Silicon resin that belongs to polysilsesquioxane (with relatively few ladder parts), called glass resin (trademark of Owens Inline Corporation): 2% Ethylene glycol monoethyl ether acetate: 50% Xylene: 17% Acetic acid Ethyl: 31% Liquid paraffin: 0.3% of the total amount (2) Baking: After applying the mixed solution, bake at 200 ° C to 350 ° C for 1 to 5 hours.

As a result, protrusions 7 protruding from the intermediate level L and concave portions 8 recessed from the intermediate level L are formed. That is, when the liquid mixture having the above composition is applied, as shown in FIG. 5 (a), the liquid paraffin that is a heat-evaporable substance becomes spherical as shown by a, and the liquid paraffin balls a ... Repel each other. Because of matching, innumerable spheres a of liquid paraffin are generated on the mixed liquid b. The mixed liquid b contains a small amount of silicone resin such as about 2%,
Due to its low viscosity, it has high fluidity unlike magnetic paints. Therefore, it is easily adsorbed by the liquid paraffin sphere a due to the surface tension, and a spherical depression is formed at the contact portion with the liquid paraffin sphere a, and the outer periphery of the depression rises like a crater. Therefore, when baking is performed to cure the mixed solution b, the solvent such as ethylene glycol monoethyl ether acetate, xylene, and ethyl acetate in the mixed solution b is decomposed and evaporated, and Si (OH) ₄ in the glass resin is changed. As a result, only SiO ₂ remains and the SiO ₂ protective film 2 is formed. Also, when baking
Since the spherical liquid paraffin a, which is an easily heat-evaporable substance, is easily decomposed and evaporated, the traces thereof remain as the crater bottom-shaped spherical concave portion 8 and the crater edge-shaped raised portion 7. The spherical concave portion 8 is recessed from the planar intermediate level L, and the protrusion 7 formed of a raised portion is projected from the planar intermediate level L.

In a practical example, 2 μ on an aluminum substrate
magnetic material α-Fe ₂ O ₃ on the ground alumite film of m.
Of 0.2 μm was sputtered and subjected to reduction oxidation treatment to form a magnetic film. As a protective film, apply a mixed solution of the above composition onto a film sputtered with SiO ₂ (50 Å) to a film thickness of about 800 Å, bake at 300 ° C for 1 hour, and then add fluorinated oil. A liquid diluted to 0.03% with Fluorinert was applied as a lubricant to obtain a magnetic disk. When this magnetic disk medium was subjected to a high-speed high-load reverse rotation test, which is a conventional acceleration evaluation method, it showed a strength of 50 times or more. Compared to the conventional magnetic disk medium that could not withstand even once, the strength of the protective film is significantly improved, and the CSS of the magnetic head is
The protective film is not damaged even if the operation is repeated frequently. Further, fluorinated oil such as Krytox (trademark of DuPont) cannot be applied to the conventional continuous magnetic film in terms of strength and friction, but it is protected by the method of the present invention. The film was ready for application. Moreover, it does not cause stickiness and is highly resistant to seismic wear.

By changing the solvent such as ethylene glycol monoethyl ether acetate, xylene, ethyl acetate, etc., the surface shape and thickness of the protective film will be various due to the difference in the boiling point of the solvent used, Even if the weight of paraffin is small, it can be changed. In addition to the above, methyl isobutyl ketone, diacetone alcohol, butanol, air mill alcohol, cyclohexanol and the like can be used as the solvent. Glass resin is a silicon compound containing Si (OH) ₄ having a Milanol structure in a solvent of ethanol and ethyl acetate as a main component.
It is a solvent containing.

As an application of this embodiment, Si is sputtered on the magnetic film 1.
The adhesion of the magnetic head can be further improved by applying about 50 to 300Å O ₂ and then performing the above treatment.

〔The invention's effect〕

As described above, according to the present invention, in order to obtain a protective film having innumerable minute protrusions higher than a certain intermediate level and minute independent concave portions depressed from the intermediate level on the surface of the magnetic recording layer, After coating a mixed solution containing a solvent containing silicon (Si) and an easily thermally decomposable or easily heat-evaporable substance such as liquid paraffin on the recording layer, baking is performed to harden and cure the mixed solution. It employs a method of simultaneously decomposing and evaporating a thermally decomposable or easily heat-evaporable substance.

Therefore, only by applying and baking the mixed solution, the vaporized traces of the liquid paraffin form innumerable protrusions protruding from a certain intermediate level L having a planar shape and innumerable independent recesses recessed from the intermediate level L. Moreover, both a protrusion protruding from the protective film surface and an independent concave portion recessed from the protective film surface can be formed at once by a single process, which facilitates manufacturing.

Further, as compared with the conventional method of mixing and baking paraffin particles in a magnetic paint, the viscosity of a solvent for mixing a substance that is easily heat decomposable or easily heat evaporated is low, and a method of mixing it in a magnetic paint is also used. Unlike the above, free adjustment of the composition and ratio of the solvent does not affect the characteristics of the magnetic coating film. Therefore, the solvent having a low viscosity bulges along the ridges such as liquid paraffin, so that the protrusions protruding from the protective film surface can be formed reliably and smoothly.

Unlike the method in which paraffin particles are mixed with magnetic paint, a recess is formed in the protective film on the magnetic film, so the non-magnetic area does not increase and the magnetic characteristics of the magnetic film do not deteriorate, so high recording is achieved. It is suitable for a medium having a high density and is particularly effective for a medium having a continuous magnetic film such as a thin film magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a surface state of a conventional magnetic recording medium, FIG. 2 and the following show an embodiment of a method for manufacturing a magnetic recording medium according to the present invention, and FIG. 2 is a surface of the magnetic recording medium. 3 is a sectional view showing another surface state of the magnetic recording medium and a partial sectional perspective view, and FIG. 5 is a sectional view showing a method of manufacturing the magnetic recording medium according to the present invention. It is a figure. In the figure, 1 is a magnetic film, 2 is a protective film, 4 is an aluminum substrate, 5 is an alumite layer, 7, 7a and 7b are protrusions, 8
Represents a concave portion, L represents an intermediate level (protective film surface), a represents a liquid paraffin sphere, and b represents a mixed liquid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Kan, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, within Fujitsu Limited

Claims (1)

[Claims] 1. A magnetic recording medium comprising: a step of forming a magnetic recording layer on a substrate; a step of forming a protective film on the magnetic recording layer; and a step of applying a lubricant on the protective film. In the manufacturing method, in the protective film forming step, after mixing a solvent containing silicon and an easily thermally decomposable or easily thermally evaporable substance, the mixed solution is applied onto the magnetic recording layer, and The solvent is made to bulge along the surface of the substance more than the film surface of the solvent, and then baked to cure the solvent and decompose and evaporate the easily thermally decomposable or easily thermally evaporated substance. The method for manufacturing a magnetic recording medium is characterized by: