JPH03201216A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain the effect of a lubricant and to improve wear resistance by coating a magnetic recording layer with a mixture liquid of a solvent containing silicon and a material which can be easily thermally decomposed, baking the coating film as in such a state that the solvent has projected parts from its film surface along the material which can be easily thermally decom posed. CONSTITUTION:A mixture liquid containing silicon and liquid paraffin is applied on a magnetic film 1 by spin coating, and the coating film thus formed has projections 7 projecting from the middle level L and recesses 8 lower than the level L. Namely, by applying the mixture liquid, the liquid paraffin forms into spheres as shown by (a) in the figure since the liquid paraffin easily volatilizes by heat, and lots of particles of the liquid paraffin appear on the mixture liquid (b) since these particles repel one another. By baking the film in this state to cure the mixture liquid (b), the particles of liquid paraffin easily decompose and evaporate to leave the residual film with concave recesses 8 and projections 7 like volcanos. Thereby, a lubricant can be held for a longer time on the medium and the wear resistance against sliding can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a magnetic recording medium used in a magnetic disk device, etc., and particularly to a method for manufacturing a magnetic recording medium for use in a magnetic recording and reproducing device using a C3S type floating magnetic head. This invention relates to a manufacturing method suitable for improving media.

[Technology background]

Magnetic disk devices used in data processing equipment, etc.
In recent years, there has been a rapid increase in data recording density and capacity, and there is a trend toward smaller devices in terms of speed and economy.

With the demand for such high recording density, recording media are changing from conventional coated films to continuous magnetic films.

In other words, conventionally magnetic powder was mixed into a binder such as synthetic resin,
This is spin-coded onto an aluminum substrate to form a coating film, which constitutes the magnetic film of the magnetic recording medium. Continuous magnetic films, on the other hand, are made by forming magnetic materials such as iron or iron-cobalt alloys on a substrate using methods such as sputtering, vapor deposition, or plating, and since they do not contain a binder, they are continuous. It is called a continuous magnetic film (continuous magnetic medium). This continuous magnetic film has better magnetic properties than a discontinuous magnetic film containing a binder such as a synthetic resin, such as a conventional coated film, and the manufacturing process is simpler. In addition, recording density has improved significantly, and media with excellent characteristics as high-density recording media have been obtained. In particular, ferrite oxide films are hard materials and have good corrosion resistance, making them extremely suitable for magnetic recording media. It has been rated as good.

By the way, similar to conventional magnetic disk devices, magnetic disk devices that use this continuous magnetic film also have C3S (Con
tact 5tart 5top) method is adopted.

Therefore, normally the magnetic head levitates above the disk surface to read and write, but when a floating edge is not generated, such as when the magnetic recording medium starts or stops rotating, the surface of the magnetic recording medium and the slider of the magnetic head are Contact and slide.

As a result, the surface of the magnetic recording medium in the head landing zone where the magnetic head makes sliding contact is worn, and abrasion particles are spread over the entire surface of the magnetic recording medium, causing a head crash. Therefore, it is necessary to prevent wear on the surface of the magnetic recording medium as much as possible.

[Conventional technology]

Conventionally, the following methods have been employed to prevent wear of the magnetic recording layer.

■On the surface of the magnetic recording layer, apply silicon oxide (
A protective film such as SiO□) or resin is provided.

■To reduce wear when the magnetic head contacts and slides,
A lubricant is applied on the magnetic recording layer or protective film to improve the sliding of the magnetic head slider.

■When the lubricant is applied, the magnetic head slider is exposed to the lubricant.
sticks to the surface of the magnetic recording medium, and when the magnetic recording medium starts rotating, there is a risk of damaging the support mechanism of the magnetic head or causing a head crash.

Therefore, in order to prevent this adhesion, JP-A-56-2
Figure 1 (a) was created using the method described in Publication No. 2221, etc.
As shown in FIG. 2, numerous protrusions 3 are provided on the surface of the protective film 2 provided on the magnetic recording layer l. The gaps between the protrusions 3 are impregnated with lubricant, and the lubricant film between the slider and the magnetic recording medium becomes thinner, eliminating adhesion and reducing the coefficient of friction compared to a smooth surface. Note that 4 is an aluminum substrate, and 5 is an alumite layer formed on the surface thereof.

■As the protective film 2 on the magnetic recording layer, a porous film is used, or minute holes 6 are formed on the surface of the protective film by a method such as photo-etching, as shown in FIG. 1 (b). Impregnate with lubricant. Furthermore, as described in JP-A No. 5,622,219, fine irregularities for retaining lubricant are created in coating-type magnetic recording media by kneading and applying paraffin particles to magnetic paint and baking the mixture. A method of directly forming the magnetic coating on the surface has been proposed.

[Problem to be solved by the invention]

However, all of these methods have the following problems. That is, simply providing a protective film as shown in (2) cannot prevent wear. Since the alumite surface of the substrate is finished to a mirror finish and the magnetic film is provided on it, the surface of the magnetic film also becomes a mirror-like and extremely smooth surface. Therefore, the protective film on the magnetic crotch is smooth, and if the magnetic head is not floating and is in sliding contact with the protective film, the protective film will wear out and generate dust, causing a fatal head crash. There is a risk that

Applying a lubricant to improve slippage as in (2) is effective in the initial stage because the coefficient of friction is small, but as the lubricant wears out over time, the lubricating effect decreases and wear particles are generated. However, if a large amount of lubricant is applied, the lubricant will cause the slider to stick to the surface of the magnetic recording medium when the magnetic recording medium is stopped and in contact with the slider, causing problems when the magnetic recording medium starts rotating next time. Furthermore, there is a risk that the impact when the magnetic head is suddenly peeled off from the surface of the magnetic recording medium may cause a head crash or damage the gimbal that supports the magnetic head.

If countless protrusions 3 are provided on the surface of the magnetic recording medium as shown in (2), the lubricant will be impregnated into the gaps between the protrusions, so the problem with the method (2) will be alleviated to some extent, but centrifugal force will cause It flows and disappears. Therefore, the impregnating agent cannot be held stably and uniformly over the entire surface. Therefore, the life of the lubricant is short and cannot withstand long-term use.

If the protective film is made porous as in (2), the lubricant will be difficult to move and the lubricant will last longer, but since the surface of the protective film is smooth, the wear resistance during sliding will decrease.

Furthermore, with the method of patterning using a mask, it is impossible to form holes with a target diameter of about 1 μm;
You can only get something of a high degree.

In addition, in the method of kneading and baking paraffin particles in a magnetic paint as described in JP-A-56-22219, in addition to the presence of non-magnetic resin in the magnetic film, paraffin particles Since cavities are generated due to the traces, the characteristics of the magnetic film are deteriorated, and this method is not applicable to media with high recording density. Moreover, since the magnetic paint has a high viscosity, it is difficult to uniformly disperse paraffin particles, and cavities may be concentrated, resulting in problems such as bit errors and a decrease in the S/N ratio. Since magnetic paint has a high viscosity, it is difficult to use surface tension to form protrusions along the ridges of paraffin particles. 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 into a magnetic paint cannot be applied.

The technical problem of the present invention is to solve these problems with conventional magnetic recording media, and to achieve long lubricant retention, wear resistance, and magnetic properties even in continuous magnetic film type or high recording density media. The object is to make it possible to realize a magnetic recording medium with excellent characteristics.

[Means to solve the problem]

The technical means of 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 lubricating the protective crotch. A method for manufacturing a magnetic recording medium, which includes a step of coating a solvent, and the step of forming a protective film includes: mixing a silicon-containing solvent with a thermally decomposable or thermally evaporable substance; The mixed solution is applied onto the magnetic recording layer so that the solvent is raised along the surface of the substance above the surface of the solvent film, and then baked to harden the solvent and cure the heat-resistant layer. The method is characterized by the simultaneous decomposition and evaporation of decomposable or thermally evaporative substances.

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

[Operation] According to this method, traces of evaporated liquid paraffin become recesses and protrusions. In other words, a solvent containing silicon has a low viscosity and tends to bulge along the spheres of liquid paraffin etc. due to surface tension. An independent concave portion recessed from the film surface is formed. Because easily heat-decomposable or heat-evaporable substances such as liquid paraffin are mixed with a low-viscosity silicon-containing solvent, they can be easily and uniformly dispersed in the solvent, creating uniform unevenness over the entire surface of the protective film. Can be formed.

In addition, by appropriately selecting the amount of liquid paraffin added and its ingredients, the depth of the liquid paraffin's evaporation traces and the height of the protrusions form various irregularities, resulting in countless protrusions higher than the surface of the protective film and the protective film. Numerous recesses lower than the surface can be obtained.

Unlike the conventional method of kneading paraffin particles into magnetic paint and baking them, the continuous magnetic film medium is It can also be applied to

Furthermore, even when the method of the present invention is applied to a medium with a discontinuous magnetic film such as a coated film type media, no cavities are formed in the magnetic film. There is no increase in area and deterioration of magnetic properties.
Suitable for high recording density media.

[Embodiments of the invention]

Next, examples will be used to explain how the method for manufacturing a magnetic recording medium according to the present invention is actually implemented. FIG. 2 shows a first embodiment of a magnetic recording medium manufactured by the method of the present invention, in which (a) is a cross-sectional view and (b) is an enlarged cross-sectional view. Oxidize the surface of the aluminum substrate 4 to form an alumite layer 5
is formed, and y-FeO or the like is provided on the surface thereof as a magnetic film 1 by a method such as sputtering. On this magnetic film 1, numerous protrusions 7 and recesses 8 are formed. 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 hereinafter the position of this protective film surface will be referred to as an intermediate level. The protrusions 7 . . . are raised like craters with respect to the intermediate level L, and the spherical recesses 8 .

3 and 4 schematically show the surface state of a magnetic recording medium in order to explain other embodiments of the magnetic recording medium, (a) is a cross-sectional view, and (b) is a partial cross-section. FIG.

The protective film 2 provided on the magnetic film 1 has countless protrusions 7...
and countless recesses 8... are formed. In Figure 3,
All of the protrusions 7... have a constant shape and height, and the recesses 8... also have a constant shape and a constant depth. On the other hand, in the case of FIG. 4, the protrusion has a stepped shape, as shown by the protrusion 7a. Similarly, the depth of the recesses 8 may be changed from the middle to have a stepped shape.

The protrusion 7b is lower than the other protrusions 7.7a, and the heights of the protrusions may vary in this way.

Furthermore, the depth of each recess 8 does not need to be constant.

In this way, it has a configuration including innumerable protrusions protruding from a certain planar intermediate level L and innumerable recesses recessed from the intermediate level L. Therefore, since the lubricant is impregnated into the numerous independent recesses 8, the lubricant does not move and is stably held. As a result, the lubricating effect is maintained over a long period of time, and the generation of abrasion powder due to wear of the protective film is prevented. Also, even if a small amount of wear powder is generated, the protrusion 7
. . . Since it accumulates on the protective film surface at the intermediate level L between them, it does not become a cause of head crash.

When recording/reproducing information, each protrusion 7..., 7a...
Because the magnetic head slider comes into sliding contact with the top end of Small and reduces wear.

Next, an embodiment of the method of the present invention for obtaining a protective film having numerous crater-like protrusions and independent spherical recesses recessed from the surface of the protective film as shown in FIG. 2 will be described. As explained in FIG. 2, γ-
After FeOz or the like is provided by a method such as vapor deposition, the following steps are performed.

(1) Application of mixed liquid: On this magnetic film 1, apply a mixed liquid containing silicon (Si) and liquid paraffin at 11,000 ml as follows.
Spin code with rp.

Silicone resins belonging to the polysilsesquioxanes (those with a relatively small amount of ladder fraction) called glass resins (trademark of Owens-Illinois Company):
2% acetic acid ethylene glycol monoethyl ether: 5oz xylene: 17% ethyl acetate: 31% Liquid paraffin: 0.3% of the total amount (2
) Baking: After applying the mixture, 1 to 200"C to 350℃
Bake for 5 hours.

As a result, protrusions 7 protruding from the intermediate level L and recesses 8 concave from the intermediate level L are formed.

That is, when a liquid mixture having the above composition is applied, as shown in FIG. 5(a), liquid paraffin, which is a heat-labile evaporable substance, becomes spherical as shown by a, and each liquid paraffin sphere a...
Because they repel each other, countless liquid paraffin balls a.
... occurs on top of the mixed liquid. The mixed liquid contains only about 2% silicone resin and has a low viscosity, so it has high fluidity unlike magnetic paint. Therefore, it is easily adsorbed by the liquid paraffin spheres a due to surface tension, and a spherical depression is formed at the contact area with the liquid paraffin sphere a, and the outer periphery of the depression is raised in the shape of a crater. Therefore, when the mixed liquid is cured by baking, the solvents such as acetic acid ethylene glycol monoethyl ether, xylene, and ethyl acetate in the mixed liquid are decomposed and evaporated, and the Si (OH
)4 changes and only SiO□ remains, forming SiO□ protective film 2.
is formed. In addition, during baking, the spherical liquid paraffin a, which is a substance that undergoes thermal evaporation, easily decomposes and evaporates, leaving traces of it as a spherical concave portion 8 shaped like a crater eave and a raised portion 7 shaped like a crater rim. The spherical recess 8 is recessed from the planar intermediate level L, and the protrusion 7 consisting of a raised portion protrudes from the planar intermediate level L.

In the actual example, 2μ on an aluminum substrate was used.
The magnetic material α-Fe,
0. was sputtered to a thickness of 0.2 μm and subjected to reduction-oxidation treatment to create a magnetic film. As a protective film, a mixed solution of the above composition was applied to a sputtered film of SiO□ (50 nitrides) so that the film thickness was about 800 nickels, and after baking at 300°C for 1 hour, fluorine A magnetic disk was obtained by applying a liquid obtained by diluting chemical oil to 0.03% with Fluorinert as a lubricant.

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. The strength of the protective film has been significantly improved compared to that of conventional magnetic disk media, which could withstand even a single time, and the protective film will not be damaged even if the C3S operation of the magnetic head is repeated frequently. . In addition, fluorinated oils such as Krytx (trademark of DuPont) cannot be applied to conventional continuous magnetic films due to strength and friction concerns, but the protective film textured using the method of the present invention can be applied to. Moreover, it does not cause adhesion and has excellent seismic abrasion resistance.

Note that by changing the solvents mentioned above, such as ethylene glycol monoethyl ether acetate, xylene, and ethyl acetate, the surface shape and thickness of the protective film can vary depending on the boiling point of the solvent used, and the fluidity of the added fluid can vary. It is also possible to change the weight of paraffin. In addition to the above-mentioned solvents, methyl isobutyl ketone, diacetone alcohol, butanol, airyl alcohol, cyclohexanol, and the like can be used. Glass resin is a silicon compound whose main component is St (OH) a having a ranol structure in the solvents of ethanol and ethyl acetate, and is a solvent containing silicon (Si).

As an application of this example, 5
If the above-mentioned treatment is performed after approximately 50 to 300 λ of in2 is deposited, the adhesion of the magnetic head can be further improved.

〔Effect of the invention〕

As described above, according to the present invention, in order to obtain a protective film having countless minute protrusions higher than a certain intermediate level and infinitesimal independent recesses recessed below the intermediate level on the surface of the magnetic recording layer, magnetic After coating a liquid mixture containing a solvent containing silicon (Si) and a substance that easily decomposes or evaporates easily by heat, such as liquid paraffin, on the recording layer, the mixture is hardened and easily evaporated by baking. A method is adopted in which the decomposition and evaporation of thermally decomposable or thermally evaporative substances occur simultaneously.

Therefore, by simply applying and baking the liquid mixture, countless protrusions protruding from a certain planar intermediate level L and countless independent recesses recessed from the intermediate level L are formed by traces of evaporated liquid paraffin. Moreover, both the protrusion protruding from the protective film surface and the independent recess recessed from the protective film surface can be formed at once in a single process, and manufacturing is easy.

In addition, compared to the conventional method of mixing paraffin particles in magnetic paint and baking it, the viscosity of the solvent used to mix easily thermally decomposable or thermally evaporable substances is lower, and the method of mixing paraffin particles into magnetic paint has a lower viscosity. Unlike conventional methods, freely adjusting the composition and ratio of the solvent does not affect the properties of the magnetic coating. Therefore, the low-viscosity solvent bulges along the ridges of liquid paraffin, etc., and can reliably and smoothly form protrusions that protrude from the surface of the protective film.

Unlike the method of mixing paraffin particles with magnetic paint, since recesses are formed in the protective film on top of the magnetic film, the non-magnetic area does not increase and the magnetic properties of the magnetic film do not deteriorate, resulting in high recording performance. It is suitable for high-density media, and is particularly effective for continuous magnetic film media such as thin-film magnetic recording media.

(stomach) 1st (B)

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional perspective view showing the surface condition of a conventional magnetic recording medium. FIG. 3 and 4 are cross-sectional views and partial cross-sectional perspective views showing other surface conditions of the magnetic recording medium. FIG. 5 is a cross-sectional view showing a method of manufacturing a magnetic recording medium according to the present invention. It is a diagram. 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, 7b are protrusions, 8
denotes a concave portion, L denotes an intermediate level (protective film surface), a denotes a ball of liquid paraffin, and b denotes a mixed liquid.

Claims (1)

[Claims] A magnetic recording medium comprising: forming a magnetic recording layer on a substrate; forming a protective film on the magnetic recording layer; and applying a lubricant on the protective film. In the manufacturing method, the protective film forming step includes: mixing a silicon-containing solvent and a thermally decomposable or thermally evaporable substance, and then applying the mixed liquid onto the magnetic recording layer; The solvent is raised along the surface of the substance above the surface of the solvent film, and then baked to harden the solvent and decompose the thermally decomposable or thermally evaporable substance. A method for manufacturing a magnetic recording medium, characterized by performing evaporation at the same time.