JPH06231442A - Thin film magnetic disk and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To eliminate burrs and projections of a disk and to easily clean the disk after treatment by removing grooves formed by texturing of the surface of a Ni-P substrate and specifying the surface roughness of the plate CONSTITUTION:An aluminum substrate 1 (a) is used as a disk substrate, on which a Ni-P plating film 2 is formed to 10-30mum thickness by electroless plating (b). The surface of the plating film 2 is polished with a processing liquid containing an abrasive powder (c), and then cleaned to remove residual matter (d). Then the surface is treated with a surface treating liquid and treating cloth in the circumferencial direction (e). The residue after the treatment is washed out (f), and then a Cr base layer 3, Co magnetic film 4, and C protective film 5 of specified thickness are successively formed on the surface of the substrate 8 by sputtering (g). Further, dust or projections produced in this film forming process are treated with a surface processing machine using only a tape (h). No processing liquid is used. Then the surface is controlled by exposing to an atmosphere of satd. vapor pressure (i) so that a lubricant film can be easily adhered to the surface. A lubricant 6 is applied (j) and the disk is subjected to finish inspection (k). Since no burr or projection is produced in the process of surface treatment (e) or in other processes, nor abrasive powder is used, good cleaning can be easily done after treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic disk used as an external storage device such as a computer and a workstation, and a method for manufacturing the same, and more particularly to a magnetic medium excellent in head flying and magnetic characteristics.

[0002]

2. Description of the Related Art Storage devices utilizing magnetic recording technology, such as magnetic disks, are widely used as external storage devices such as computers and workstations. Is required. On the other hand, the shape of the apparatus itself is desired to be smaller and lighter, and in order to achieve both of them, it is essential to dramatically improve the recording density of the recording medium. In order to realize this, development of a magnetic disk in which a magnetic medium is continuously attached to the surface of the magnetic disk is under development. As the method, a Co-based magnetic film is applied to a Ni-P plated aluminum alloy substrate by a plating method, a Cr underlayer film, a Co-based magnetic film, a C protective film is formed by sputtering, and an aluminum alloy is anodized. However, a method of forming a film of gamma iron oxide by sputtering is the mainstream. These membrane configurations are also described in Clean Technology Symposium (1988). However, since the thin film magnetic disk does not have magnetic anisotropy in the circumferential direction only by depositing these media on a flat surface, the following processing is performed.

Prior to the formation of the magnetic film, a substrate surface of the magnetic disk or an N film which is previously provided as a base film on the substrate surface is used.
As shown in the partially broken perspective view of FIG. 8, the i-P plating is subjected to a process (hereinafter abbreviated as texturing) for making processing marks in a substantially concentric shape in the circumferential direction of the magnetic disk medium. There is.

Texturing is one of its advantages (1)
The effect of reducing the adsorption phenomenon between the magnetic head and the magnetic disk medium when the magnetic disk is stopped, and (2) by giving shape anisotropy to the magnetic film formed on the processed surface,
It has the effect of making the magnetic characteristics uniform in the circumferential direction.

On the other hand, however, since abrasive grains such as diamond and alumina are used for processing, burrs and protrusions are likely to occur on the surface, which causes non-uniform flying characteristics of the head and crystal growth of the magnetic medium. However, there is a problem that it cannot be expected to improve the recording density.

Note that, as a technique related to this type of texture processing, for example, Japanese Patent Laid-Open Nos. 63-42027 and 6-SHO6.
3-249933, JP-A-63-42019, JP-A-6-63
2-262227 etc. are mentioned.

[0007]

Therefore, the present invention has been made in view of the above situation, and an object of the present invention is to solve the problem of the conventional texture processing technique. It is an object of the present invention to provide a thin film magnetic disk having an improved surface treatment of a substrate that can improve the magnetic characteristics without impairing the flying characteristics, and a method for manufacturing the same.

[0008]

In order to achieve the above object, the present invention is characterized in that the surface of a Ni-P plated substrate is subjected to boundary polishing and then subjected to a circumferential surface treatment. More specifically, the above object is to provide a method for manufacturing a thin film magnetic disk including a step of sequentially forming a base film, a magnetic film, a protective film, and a lubricating film on a Ni-P plated substrate supporting a magnetic medium, The Ni-P-plated substrate was subjected to removal of irregularities and undulations using diamond abrasive grains, and then the surface of the Ni-P substrate which was subjected to boundary polishing was circumferentially treated with an abrasive-free surface treatment liquid and a surface treatment tape or surface treatment sheet. This is achieved by a method of manufacturing a thin film magnetic disk which is formed by adding a rubbing step.

As the surface treatment liquid, those containing alcohol or a hydrophilic treatment liquid such as a surfactant as a main component are preferable, and these may be used alone or in combination of both. Examples of alcohols include polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, and glycerin, or higher alcohols having an appropriate viscosity. As the surfactant, for example, one containing a polyoxyethylene-based nonionic surfactant as a main component is preferable, and one having an etching action, for example, EDT
It is preferable to use a compound to which a chelating agent such as A (ethylenediaminetetraacetic acid disodium salt) is added, because the effect of the surface treatment is further improved. Similarly, it is effective to add a component having an etching action to a treatment liquid of alcohols such as ethylene glycol. For the surface-treated tape or sheet, it is preferable to use synthetic fibers such as aliphatic polyamide such as nylon, polyester, cellulose and the like. Further, the pressing pressure when rubbing the Ni-P surface is preferably 1 to ²⁰ kg / cm ² .

[0010]

Function The surface of the substrate after the boundary polishing has a flat surface macroscopically, but microscopically random processing marks remain. Therefore, magnetic anisotropy cannot be obtained even if a magnetic medium is formed on this substrate. Therefore, the surface treatment liquid is applied to the plain substrate and rubbed in a circumferential direction with a tape or a sheet to reduce random processing marks to form a smoother and flat surface, and to correct the rubbed direction. In the correction here, the atoms on the pole surface before the treatment are random, but they are rearranged by rubbing in the circumferential direction with regularity in the rubbing direction. In this case, a rearranged state of atoms having magnetic anisotropy in the circumferential direction can be obtained. In this way, by performing a surface treatment in the circumferential direction, magnetic anisotropy appears in the circumferential direction in the magnetic substance formed on the surface, and by cutting with abrasive grains such as texturing. Since no burrs or protrusions are generated, the flying characteristics of the head are improved.

Further, unlike the texture processing, since abrasive grains are not used to form a processing groove of more than ten and several nm on the surface, burrs and protrusions generated by cutting or the like are not generated at all. Therefore, the flying characteristics of the head are improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a film structure of a thin film magnetic disk of the present invention, FIG. 2 is a process diagram showing an example of its manufacturing process, and FIGS. 3, 4, 5, and 6 are devices for realizing surface treatment. FIG. 7 is a schematic perspective view, FIG. 7 is a magnetic characteristic of the substrate manufactured by the manufacturing process of the present invention, FIG. 8 is a film configuration diagram of a conventional thin film magnetic disk, and FIG. 9 is a configuration diagram of the thin film magnetic disk of Example 3. FIG. 10 shows a process drawing for making unevenness on the protective film.

Example 1 FIG. 1 shows the structure of a thin film magnetic disk of the present invention. A conventional sputter magnetic disk is shown in FIG.
As shown in (1), since the Ni-P plating film and the base film are texture-processed, the shape on the surface of the protective film from the bottom appears as it is. Also, since it is textured, burrs and protrusions appear in places. In the present invention, since no texture processing is performed, as shown in FIG.
A near-ideal surface flat shape is obtained. Next, the structure of the magnetic disk and the role of each will be described in detail.

The structure of the thin film magnetic disk of the present invention is shown in FIG.
As shown in FIG. 3, an aluminum alloy substrate 1 for supporting the magnetic medium, a Ni—P plated underlayer film 2 for giving the substrate an appropriate hardness, an underlayer film 3 for imparting magnetic anisotropy of the magnetic medium, and a magnetic film 4. The magnetic film is composed of a protective film 5 for protecting the magnetic head from sliding with respect to the magnetic head, and a lubricating film for reducing the wear coefficient. However, in this embodiment, the Ni—P plating base film 2 of FIG. 1 is not textured.

(Manufacturing Method) Next, a method of manufacturing the thin film magnetic disk of the present invention will be described with reference to the process chart of FIG.

In step (a), an aluminum substrate 1 is prepared as a disc substrate.

In step (b), the Ni-P plating 2 is applied to the substrate 1 by electroless plating to a thickness of 10 to 30 μm.

In step (c), the surface of the Ni-P plating 2 is surface-polished using a working liquid containing abrasive grains and the like.

In step (d), processing residues such as abrasive grains, polishing powder and processing liquid attached to the substrate surface are washed.

In the step (e), the surface is treated in the circumferential direction with the surface treatment liquid and the treated cloth. This surface treatment method is a feature of the present invention and will be described in detail later.

In step (f), the treatment residue attached after the surface treatment is washed.

In step (g), a Cr underlayer 3, Co magnetic layer 4, C having a predetermined thickness are formed on the surface of the substrate 8 by a sputtering method.
The protective film 5 is sequentially formed.

In order to remove dust, projections, etc. generated during the film formation in the step (h), the surface processing apparatus shown in FIGS. 3 and 4 is used.
Surface treatment is done only with tape. In this case, the processing liquid is not used.

In step (i), surface adjustment such as exposure to an atmosphere of saturated water vapor pressure is carried out so that a lubricating film is easily attached to the surface.

In step (j), the lubricant 6 is applied.

A final inspection is performed in step (k).

Next, the most characteristic step (e) of the present invention
Two methods for the surface treatment will be described.

(Treatment Method 1) As one method of surface treatment, as shown in FIGS. 3A and 3B, the substrate is rotated by pressing the treatment tape with the contact roller 10 to rub the surface. As for the method of supplying the treatment liquid, the treatment liquid is dropped between the substrate and the treatment tape as shown in (a), or the treatment liquid is sprayed onto the substrate as shown in (b). Also,
It is also conceivable to carry out this treatment in the treatment liquid as in (c).

In the case of double-sided processing, a processing device having the same mechanism as in (a) may be installed on the back surface.

The contact roller 10 may have a width smaller than the radius of the substrate 8, the same width as the radius, or the same width as the diameter of the substrate. However, in this case, the width of the processing tape 9 needs to be the same as or wider than the width of the roller. The substrate surface can be uniformly processed by swinging the contact roller and the processing tape.

The pressing pressure of the tape depends on the width and material of the roller,
In this experiment, for example, when a polyurethane-based φ20 mm roller having a width of 45 mm is used, it changes depending on hardness and the like.
It was performed at 2.5 kgf. The pressing pressure in this case is at least 1
kgf is required. The rotation speed of the disc is 100.
The range is up to 1000 rpm, but in this experiment 600r
pm.

The treatment tape may be a plastic fiber such as nylon, polyester or cellulose.

(Processing Method 2) FIGS. 5A and 5B show a surface processing method using a processing sheet. (A) shows the substrate 8
The processing disc 13 having the treatment sheet 12 attached thereto is rotated while being pressed against the fixed plate 11 holding the treatment disc, or conversely, the treatment disc 13 having the treatment sheet 12 attached thereto as shown in (b).
Then, the surface treatment is performed by rotating the pressing plate 11 holding the substrate 8 while pressing it. Further, a method of combining (a) and (b) and fixing the substrate 8 to the substrate fixing jig 14 as shown in FIG.

The processing sheet naturally needs to be larger than the substrate. The processing liquid is the processing sheet 1 as shown in FIG.
It is also possible to make a hole in the center of the processing disk 13 to which 2 is attached and to supply from there, or to immerse the entire processing section in the processing liquid as in the case of FIG. 4C.

The material of the processing sheet and the rotation speed of the substrate or the processing disc may be the same as those in the processing method 1. However, the pressing pressure must be 1 kgf / cm ² or more.

The treatment method 2 can treat the entire surface of the substrate at once as compared with the treatment method 1, and since the structure is simple, a large amount of treatment can be performed.

By the above surface treatment, there are no processing marks, burrs, protrusions and the like, and the surface roughness is 2 nmRa or less, so that the head flying height can be 0.1 μm or less.

(Treatment Liquid) The method of surface treatment has been described above. Next, the treatment liquid will be described.

In the surface treatment, a hydrophilic treatment liquid is preferable because it gives a sliding state between the substrate and the treatment tape and a treatment effect on the substrate surface. For example, as the main component of the treatment liquid, ethylene glycol, polyethylene glycol, propylene glycol,
Polyhydric alcohols such as polypropylene glycol and glycerin, higher alcohols having appropriate viscosity, and surfactants can be used. The main component of the surfactant is preferably a polyoxyethylene-based nonionic surfactant or the like. In the case of a surfactant, the effect of the surface treatment is further improved by using one having an etching action. Similarly, for other treatment liquids such as ethylene glycol, the surface treatment effect is further improved by adding a liquid having an etching action. As the liquid having an etching action, for example, EDTA
You may use what added the chelating agent like (ethylenediamine tetraacetic acid disodium). However, the etching effect does not appear unless the treatment liquid in this case is alkaline. Considering the cleaning that also serves as rinsing after the surface treatment, the process is easier when the surfactant is used.

The substrate thus obtained enhances the crystal orientation of the Cr underlayer film and the Co magnetic film formed on the substrate, and a thin film magnetic disk having good magnetic characteristics can be obtained.

Next, the magnetic characteristics of the substrate of the present invention will be described.

FIG. 7 shows the substrate 8 surface-treated in the step (e).
9 shows the results of measuring the magnetic anisotropy of the magnetic disk having the Cr underlayer film, the Co magnetic film, and the C protective film formed by the sputtering method in the step (g). The vertical axis represents the coercive force Hc (θ) in the circumferential direction and the coercive force Hc (R) in the radial direction.
The ratio of When Hc (θ / R) is 1, there is no magnetic anisotropy, and the larger this value is, the more magnetic anisotropy is and the better the magnetic properties are. As a result, it can be seen that the surface treatment of this example has markedly higher magnetic anisotropy than the untreated (plain substrate) substrate prepared for comparison. The surface treatment A according to the present example uses propylene glycol as a main component of the treatment liquid, and the treatment liquid of surface treatment B also uses a detergent containing a polyoxyethylene-based surfactant as a main component. Shows.

<Embodiment 2> Since conventional texturing is performed by using abrasive grains such as diamond and alumina, burrs and protrusions are apt to occur on the substrate surface, which causes the levitation characteristics of the magnetic head and the magnetic medium. Crystal growth becomes uneven,
Although improvement in magnetic properties such as coercive force could not be expected, even in such a case, if the surface treatment step of the present invention is adopted after texture processing, the surface condition is modified and the magnetic properties are improved. That is, this example is the same as the step (e) of Example 1.
The surface of the Ni-P plating 2 is textured by a well-known method, and then the same surface treatment as the step (e) of Example 1 is performed.

<Embodiment 3> In Embodiment 1, the structure of a flatter surface is used, but an appropriate surface roughness is required for the head to stably fly and stop. This is because when a flat object is placed on a flat surface in a stationary state, moisture or the like from the air agglomerates on the contact surface, which causes the object to cause an adsorption phenomenon. In the past, texture processing was used to make small grooves in the circumferential direction on the surface to prevent adhesion between the head and the substrate. However, there is a problem that burrs, protrusions, and the like are generated in the texturing, and the head collides with the protrusion and the head crashes, and it is difficult to control the surface roughness. Therefore, in order to prevent the adhesion between the head and the substrate in the first embodiment, the height is controlled to form unevenness on the protective film.

FIG. 9A shows the sectional structure of the substrate of Example 3 in which the height of the irregularities is controlled. The structure is the same as that of Example 1 except the shape of the C protective film. That is, C protective film 5
There are countless small irregularities scattered on the surface of so as to prevent the adsorption phenomenon even with a flat head. The convex shape may be on the circumference of the circle as shown in (b), or may be a radial shape, or may be radially attached from the center of the circle to the outside of the circle.
It may be a small dot-shaped convex as shown in. What is needed here is to make the area of the convex hill smaller than the area of the head. The height is preferably high considering the wear caused by the sliding of the head and the protective film, but it is better to reduce the height in order to increase the recording density.
100 nm is good.

As the method of forming the unevenness, a method is used in which the substrate manufactured up to the step (g) of the process drawing of Example 1 is provided with a resist as shown in FIG. Alternatively, as shown in the process diagram (b), fine particles or the like may be uniformly applied to a substrate provided with a protective film, and the particles may be used as a mask to make unevenness by an etching action of oxygen plasma or ultraviolet rays and ozone. (B) is desirable for simplification of the process.

As described above, by using the thin film magnetic disk of the present invention, a magnetic disk device having a high recording density can be realized.

[0049]

As described above, according to the present invention, since abrasive grains are not used for processing unlike texture processing,
Since the surface treatment of the substrate surface was simply performed by rubbing it with the treatment liquid and the treatment tape, the conventional problems could be solved and the intended purpose could be achieved. That is,
(1) No burrs or protrusions are generated (2) Abrasive grains are not used, resulting in good cleanability after treatment. (3) Only surface treatment is required without using a machining liquid containing abrasive powder such as abrasive grains. Cleaning after the treatment is simplified, and (4) magnetic anisotropy is added, and the flying characteristics of the head are improved.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a structure of a thin film magnetic disk according to a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of the thin-film magnetic disk of the first embodiment as well.

FIG. 3 is a perspective view schematically showing an example 1 of an apparatus that also realizes the surface treatment method.

FIG. 4 is a perspective view schematically showing an example 1 of an apparatus that also realizes the surface treatment method.

FIG. 5 is a perspective view schematically showing an example 2 of an apparatus that also realizes the surface treatment method.

FIG. 6 is a perspective view schematically showing an example 2 of an apparatus that also realizes the surface treatment method.

FIG. 7 is a characteristic diagram showing the magnetic coercive force ratio Hc (θ / R) in the circumferential direction (θ) and the radial direction (R) as magnetic characteristics.

FIG. 8 is a partially cutaway perspective view showing the structure of a conventional thin film magnetic disk.

9A and 9B are a cross-sectional view and a perspective view showing the structure of a thin film magnetic disk of Example 3 of the present invention.

FIG. 10 is a process drawing of similarly forming irregularities on the protective film of Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Aluminum substrate, 2 ... Ni-P base film, 3 ... Base film, 4 ... Magnetic film, 5 ... Protective film, 6 ... Lubrication film, 7 ... Treatment liquid, 8 ... Ni-P substrate, 9 ... Treatment tape, 10 ... Contact roller, 11 ... Fixed plate, 12 ... Treatment sheet, 13 ... Treatment disc, 14 ... Substrate fixing jig.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Fumioka 2880 Kozu, Odawara, Kanagawa Hitachi Storage Systems Division (72) Inventor Noriyuki Takeo 2880 Kozu, Odawara, Kanagawa Hitachi Storage Systems Co., Ltd. (72) Inventor Kenji Furusawa, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock Engineering Institute, Hitachi, Ltd.

Claims (13)

[Claims] 1. A thin-film magnetic disk in which a base film, a magnetic film, a protective film, and a lubricating film are sequentially formed on a Ni-P plated substrate that supports a magnetic medium, and there is no textured groove on the surface of the Ni-P substrate. A thin film magnetic disk having a flat surface with a surface roughness of 2 nm Ra or less. 2. The thin-film magnetic disk according to claim 1, wherein an aluminum substrate is plated with Ni-P, and then the substrate surface is surface-polished, and after cleaning, a base film, a magnetic film, and a protective film are formed by sputtering, A method of manufacturing a thin-film magnetic disk, comprising applying a lubricating film. 3. In the surface polishing of the manufacturing method according to claim 2, first of all, most irregularities and undulations are removed with a working fluid containing abrasive grains and a polishing cloth, and then surface treatment is performed. A method for manufacturing a thin film magnetic disk characterized by the above. 4. The method of manufacturing a thin film magnetic disk according to claim 3, wherein the surface of the Ni—P is rubbed in a circumferential direction with a treatment liquid and a treatment cloth. 5. The method for manufacturing a thin film magnetic disk according to claim 4, wherein a hydrophilic liquid is used as the working liquid and the processing liquid. 6. The method of manufacturing a thin film magnetic disk according to claim 4, wherein the treated cloth is made of a plastic fiber such as aliphatic polyamide (nylon), polyester or cellulose. 7. The method for manufacturing a thin film magnetic disk according to claim 3 or 4, wherein the working liquid and the processing liquid have an appropriate viscosity and have an etching action. 8. The production method according to claim 5, wherein the main component of the treatment liquid is a polyhydric alcohol such as ethylene glycol, polyethylene glycol or glycerin, a higher alcohol having an appropriate viscosity, and a surfactant. A method of manufacturing a thin-film magnetic disk, which comprises using a hydrophilic treatment liquid. 9. The method of manufacturing a thin film magnetic disk according to claim 3, wherein the surface treatment is performed by rubbing the surface of the substrate while the treated cloth relatively rotates about the center of the substrate surface. 10. The thin film magnetic disk according to claim 1, wherein a protective film is provided with irregularities. 11. A thin film magnetic disk according to claim 10, wherein a protective film is formed by sputtering and then fine particles are uniformly applied, and the protective film is etched by using the fine particles as a mask to form irregularities. Manufacturing method of magnetic disk. 12. A method for manufacturing a thin film magnetic disk according to claim 11, wherein the protective film is etched by oxygen plasma, ozone and ultraviolet rays. 13. A magnetic disk device, wherein the thin film magnetic disk according to claim 1 or 10 is used in a magnetic disk device for recording data with a head-magnetic disk spacing of 0.1 μm or less.