JP2538003B2 - Magnetic disk drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device suitable for high density recording used in a magnetic storage device of a computer.

2. Description of the Related Art As a thin film magnetic disk using a metal thin film or a metal oxide thin film as a magnetic layer, a vacuum film forming method or plating is usually applied to a substrate whose surface is an aluminum alloy plate that has been subjected to alumite treatment, nickel-phosphorus plating treatment, or the like. A thin film magnetic layer formed by a method or the like has been put into practical use. In general, a so-called contact start stop (CSS) method is adopted in which the magnetic head floats above the disk surface when the magnetic disk is in operation and contacts the disk surface when stopped. In this case, in order to withstand the sliding contact between the magnetic head slider and the disk surface at the time of start or stop, or when exposed to a high humidity environment at the time of stop, the magnetic head slider may move to the disk In order to prevent the so-called adsorption phenomenon that is fixed to the surface, the disk surface is usually provided with a protruding shape having grooves parallel to the running direction of the magnetic head generated by the texturing of the substrate surface. A protective film mainly composed of graphite, SiO _2, etc. is provided on the thin film, and a lubricant layer is provided on the surface thereof.

Problems to be Solved by the Invention In order to improve the recording density, it is necessary to reduce the flying distance of the magnetic head. At that time, the height of the projection shape generated by the texturing is reduced to improve the surface property. As a result, the CSS durability and the magnetic head attracting property are sacrificed by that amount, making it difficult to secure practical performance.

Further, the texturing is usually a process in which minute scratches are generated in the disk circumferential direction due to abrasive wear caused by abrasive grains, and the projection shape is a gradient such as a mountain range ridge in the circumferential direction. It's very loose. Such a gentle slope is easily deformed and destroyed by the impact force of the magnetic head slider,
Further, when the magnetic head slider slides, surface contact is likely to occur, and the coefficient of friction tends to be higher than in the case of point contact.

The present invention has been invented in view of the above-mentioned problems. By making two kinds of minute protrusions having a large number of steep gradients on the disk surface and making the contact with the magnetic head slider a point contact, It is an object of the present invention to provide a magnetic disk device that solves the above problems.

Means for Solving the Problems In order to achieve the above object, the present invention provides a surface with a height of 10
0 to 300Å, height: length ratio in the plane direction of 0.1 or more, density of 1 × 10 ⁷
~ 1 x 10 ⁹ pieces / mm ² of the first micro-projection group, height 400 ~ 800
Å, height: length ratio in the plane direction 0.1 or more, density 1 × 10 ³ to 1 ×
A thin-film magnetic disk in which a magnetic layer, a protective layer, and a lubricant layer are sequentially formed on a non-magnetic substrate having a minute protrusion group of 10 ⁶ pieces / mm ² and recording on this thin-film magnetic disc. A magnetic disk device comprising a magnetic head slider having a magnetic head for reproducing.

Here, in the thin film magnetic disk, the thickness of the magnetic thin film is about 500 in a metal system such as CoP, CoNi, CoNiP, CoNiCr, and CoCr.
Å, Approximately 1000Å for oxides such as γ-Fe ₂ O ₃ , and the total thickness is about 2000Å even if an underlayer and a surface protective layer are added to these, so the shape of the substrate surface is almost the same as the disk surface shape. Is reflected in. The greatest feature of the present invention is that two kinds of granular fine projections having a steep slope are arranged on the surface of the substrate, instead of the projections having an average gentle slope as seen in the texture processing which is conventionally used in the substrate. There is something I did.

It is important that the ratio of the height of the minute protrusions employed in the present invention to the length in the plane direction is 0.1 or more in any protrusion. It is difficult to obtain the desired CSS life outside this range. The height of the first micro-projection group is the average value of the maximum heights.
Range 100~300Å are suitable, its density 1 × 10 ⁷ ~
1 × 10 ⁹ pieces / mm ² is suitable. If the density is out of this range or the height is less than 100Å, the CSS durability will decrease. Further, when the height is 300 Å or more, the output is greatly reduced and it is difficult to obtain a high recording density. The height of the second micro-projection group is suitable in the range of 400 to 800Å as the average value of the maximum height, and its density is 1 ×.
10 ⁴ to 1 × 10 ⁶ pieces / mm ² is suitable. Density is 1 × 10 ⁴ pieces /
If it is less than mm ² , CSS durability will be reduced. Furthermore, the height is 400Å
Below, the effect of preventing adsorption is reduced. 800 Å or higher in height,
On the other hand, if the density is 1 × 10 ⁶ pieces / mm ² or more, the output is greatly reduced and it is difficult to obtain a high recording density.

Action In the disk of the present invention, the contact between the magnetic head slider and the disk surface during CSS and at the stop mainly occurs on the second minute projection group on the disk surface.
The surface of the magnetic head slider comes into contact with the disk at many points, which reduces frictional resistance, has good CSS resistance, and suppresses the occurrence of adsorption. By the way, the surface of the magnetic head slider is originally made smooth, but during use, minute surface roughness may occur due to abrasion, or abrasion powder or the like may adhere to form minute protrusions. Further, a co-sliding phenomenon occurs due to the generated abrasion powder. The tips of the fine projections on the surface of the magnetic head slider and the abrasion powder during co-sliding contact the valleys of the second fine projections on the disk surface, that is, the first fine projections existing in the valleys. Become. Since the contact in this case is also point contact, the friction resistance is reduced, and good CSS resistance is secured without the occurrence of adhesion and fracture phenomena.

Further, the lubricant which is usually applied to the surface of the disk is held between the minute projections on the surface of the disk and is supplied to the tips of the minute projections by the action of surface tension.

After all, the first and second micro-projection groups effectively act on the CSS resistance, and the second micro-projection group effectively acts on the adsorption prevention.

Embodiment FIG. 1 is a partially enlarged view of a cross section in the thickness direction of a magnetic disk according to an embodiment of the present invention.

In the figure, 1 is a substrate, 2 is a first minute protrusion on the surface of the substrate 1, 3 is a second minute protrusion on the surface of the substrate 1, 4 is a magnetic thin film layer,
5 is a protective layer, 6 is a lubricant, 7 is a microprojection on the disk surface corresponding to the first microprojection 2 on the substrate surface, and 8 is the second microprojection.
It is a minute protrusion corresponding to the minute protrusion 3.

The substrate 1 used in the present invention is an aluminum or aluminum alloy plate, on which alumite treatment, NiP plating treatment, resin treatment such as polyimide or the like is applied, glass plate, ceramic plate, plastic molding plate, reinforced plastic molding Boards can be used.

As a method of forming protrusions on a smooth substrate 1, for example,
There is one in which a mixture of two kinds of fine particles having different average diameters is fixed on the substrate 1 with a resin binder. In this case,
As the fine particles, fine particles of inorganic compounds such as alumina, silica, titanium oxide, etc., polyester, polyamide, polyarylate, polysulfone, polyphenylene oxide, polyimide, epoxy, crosslinked styrene, crosslinked acrylic, crosslinked benziguanamine, crosslinked melamine and the like. , Carbon fine particles, metal alkoxide hydrolyzate fine particles, etc. can be used. As the resin binder, saturated polyester such as polyethylene terephthalate and polybutylene terephthalate, nylon 6, nylon 66, nylon 61
Polyamide, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, phenoxy resin, polyimide, polyamideimide, etc. , A mixture of various resins
A copolymer or the like can be used, and a crosslinkable resin such as an epoxy resin, a urethane resin, a silicone resin or a phenol resin can also be used. A coating liquid obtained by adding 50 to 300 parts by weight of the fine particles forming the first microprojection 2 group and 100 parts by weight of the fine particles forming the second microprojection 3 group to 100 parts by weight of the binder is applied and dried on the surface of the substrate 1. Let The method of forming a group of fine projections is not limited to the above, and a method of depositing a metal, an oxide, or the like in an island shape by a method such as sputtering, ion beam vapor deposition, or plating, or a method in which these are combined with the wet coating method is used. It can also be used in combination.

As the magnetic thin film layer 4, Co-Ni, Co-Ni-Cr, Co-Cr, Co-Ni
-P, γ-Fe ₂ O _{3 and} other known thin film layers obtained by sputtering, vapor deposition, plating, etc. can be used.
It is also possible to provide an underlayer such as i. A suitable thickness of the magnetic thin film layer 4 including the underlayer is 500 to 5000Å.

As the protective layer 5, thin films made of various inorganic and organic non-magnetic materials with a thickness of 50 to 500 Å can be used. In particular, various carbon thin films obtained by the sputtering method, CVD method, etc., SiO ₂ thin films obtained by the wet method, etc. Is suitable.

As the lubricant layer 6, perfluoroalkyl polyether and its derivative, a fluoroalkyl group-introduced fatty acid,
Suitable are fatty acid esters, fatty acid amides, metal soaps, silicone compounds, fluorine-based surfactants, etc., and the amount present is 0.1 to 100 mg per 1 m ² of the surface.

 Hereinafter, examples will be described with reference to specific examples.

(Specific example) A with a diameter of 95 mm and a thickness of 1.2 mm that was mirror-finished by buffing
l The surface of the substrate 1 obtained by forming a polyimide film having a thickness of 5 μm on the surface of the alloy plate by the wet coating method and smoothing the surface is applied to the surface of the substrate 1 by the following methods A to C in various shapes and various densities. Two microprotrusions 2 and 3 groups were formed.

A) Crosslinked resin emulsions of various particle sizes consisting of styrene-divinylbenzene copolymer (particle size: 400Å, 600Å, 800
Å) Diluted solutions are selected and combined to obtain a mixed solution (for example, a particle size of 400Å and a concentration of 3000ppm, and a particle size of
An equivalent mixture of 800 Å concentration of 500 ppm diluted solution) was applied on the substrate 1 and then heat-treated at 150 ° C. for 30 minutes. 400 by heat treatment
Particles of Å form protrusions with a height of 300 Å, particles of 600 Å form protrusions of 400 Å and 600 Å from 800 Å, and the height-to-face ratio is about 0.8.
Met.

B) A solution containing two kinds of polyarylate fine particles having an average diameter of 1000 Å and 4000 Å swollen and dispersed in a chloroform: benzene mixed solution, each of which has a different content ratio of the two kinds of particles, and then applied to each substrate. Heat treatment was performed at 10 ° C for 10 minutes. 20 from a particle with a diameter of 1000Å
From 0Å and 4000Å particles, 800Å protrusions were formed. The height: height ratio of the protrusions was 0.1.

C) A mixed solution obtained by selecting and combining polyvinyl alcohol aqueous solutions (silica colloid concentration 1000 ppm, polyvinyl alcohol concentration 500-2000 ppm) containing four types of silica colloids with average diameters of 50 Å, 100 Å, 200 Å, 400 Å, respectively. Was applied to the substrate and dried. In this case, the particle diameter and the projection height were almost the same value. The height ratio of the protrusions to the plane direction was 0.5 to 0.8.

From the SEM photographs of the surface and fracture surface of the sample obtained by these methods, the height of the microprotrusions, the length ratio in the height: plane direction, and the surface density were obtained. After that, the Cr underlayer (thickness 1200Å), CoNi magnetic layer 4 (600
Å) and carbon protective layer 5 (200 Å) are sequentially formed, and finally, perfluoropolyether lubricant is applied to the surface 1
A lubricant layer 6 was formed by applying 1 mg per m ² to prepare a sample. Then, CSS measurement and adsorption measurement were performed for each sample. CSS durability is the number of CSSs when the friction coefficient exceeds 1.0 or C when a head crash occurs.
The number of times of SS was evaluated, and these points were set as CSS life. In the adsorption test, when the disc was rotated in a 90% atmosphere at 40 ° C. with the slider fixed on the disc, when the force applied to the slider at the time of starting showed an abnormal value, it was considered that the adsorption occurred.

For each of the above samples, the contents of the samples and the results of the CSS test and adsorption test are summarized in Table 1.

In the table, the prototype disc numbers with () are comparative examples.

From Table 1, it is necessary that both the first and second groups 2 and 3 of microprotrusions are required [see Comparative Examples (7) and (8)], and the height of the first microprotrusions 2 must be 100Å or more. [Comparative example (1
3)], and its surface density is 1 × 10 ⁷ to 1 × 10 ⁹ pieces / mm ²
Is appropriate [see Comparative Examples (6), (12) and (20)], the height of the second micro-protrusions 3 must be 400 or more [see Comparative Example (21)], and its areal density is 1 x 10 ⁴ ~ 1
× 10 ⁶ pieces / mm ² is appropriate [Comparative example (2), (1
See 0) and (14).

In consideration of the above, it is clear from Table 1 that the CSS test result and the adsorption test result are all good within the scope of the claims of the present application. It should be noted that the magnetic layer 4 and the protective layer 5 are formed on the polyimide film of the substrate 1 after forming the protrusions by the conventionally known texture processing without forming the minute protrusion group.
When the maximum surface roughness was 1000Å, the CSS durability was 1000 times or less in the case where the above were formed in accordance with the above examples.

EFFECTS OF THE INVENTION According to the present invention, instead of the conventional texture shape, the first
By adopting the second group of microprotrusions, it is possible to ensure practical CSS durability and slider non-adhesiveness in an area where surface roughness is small and high recording density is possible. Of high value.

[Brief description of drawings]

FIG. 1 is a sectional view in the thickness direction of a thin film magnetic disk according to the present invention. 1 ... Substrate, 2 ... First minute protrusion, 3 ... Second minute protrusion, 4 ... Magnetic layer, 5 ... Protective layer, 6 ... Lubricant layer.

Claims (1)

(57) [Claims] 1. A first group of microprojections having a height of 100 to 300Å, a height: plane length ratio of 0.1 or more, and a density of 1 × 10 ⁷ to 1 × 10 ⁹ pieces / mm ² , and a height on the surface. 400-800Å, height: length ratio in the plane direction 0.
A magnetic layer on a non-magnetic substrate having a microprojection group having a density of 1 or more and a second microprojection group having a density of 1 × 10 ⁴ to 1 × 10 ⁶ pieces / mm ² .
A magnetic disk drive comprising: a thin film magnetic disk having a protective layer and a lubricant layer sequentially formed thereon; and a magnetic head slider having a magnetic head for recording and reproducing information on the thin film magnetic disk.