JPH0817053A - Magnetic disk - Google Patents

Abstract

PURPOSE:To produce a magnetic disk excellent in sliding resistance characteristics such as CSS characteristics and levitation characteristics of a magnetic head with high reproducibility. CONSTITUTION:At least a magnetic layer and a protective layer are successively formed on the textured surface of a substrate to obtain the objective magnetic disk. The surface state of the protective layer of this disk is measured and the area of a figure defined by a contour line drawn at a height below the apex of each protrusion by 16Angstrom is calculated. When the radial direction and tangential direction of the substrate are expressed by X and Y axes, respectively, the total area of figures defined by all such contour lines present in the range of 10mum in the X-axis direction and 10mum in the Y-axis direction is within the range of 3-14mum<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk, and more particularly, to a magnetic disk suitable for high density recording, which has sliding resistance such as flying characteristics and CSS characteristics of a magnetic head. The present invention relates to a magnetic disk having an excellent surface shape.

[0002]

2. Description of the Related Art In general, a magnetic disk is formed by subjecting a surface of a non-magnetic substrate to alumite treatment or Ni-P electroless plating treatment, and then polishing the surface to a predetermined roughness by texturing. A base layer, a magnetic layer, and a protective layer are sequentially formed on the surface, and then a lubricating layer is further formed to manufacture.

In the magnetic disk device, in order to stably maintain a minute gap between the magnetic head and the magnetic disk, the magnetic head comes into contact with the magnetic disk surface at the time of stop and stops, and the magnetic head at the time of rotational driving. Employs a so-called contact start / stop (CSS) method in which a vehicle slides on a magnetic disk surface and levitates. The above C. S. The S method is required to have durability that can maintain a sliding friction coefficient between the magnetic disk and the magnetic head, which is generated at the time of starting and stopping the magnetic disk device, to be sufficiently small. There have been various proposals regarding.

For example, Japanese Patent Application Laid-Open No. 61-242334 proposes a magnetic disk in which fine irregularities are regularly formed in the circumferential direction of a substrate.
Japanese Patent Laid-Open No. Hei 1-1920 proposes a magnetic disk in which the tips of fine irregularities are flat and have a uniform surface.
Japanese Patent Publication No. 14 discloses a magnetic disk in which the shape of fine irregularities is defined by the average roughness and the depth of the groove.

[0005]

However, in the end, the above proposals make the surface rough to prevent adhesion of the magnetic head and to prevent the magnetic head flying characteristics from deteriorating. It only mentions that the shapes of the parts are made uniform, and it can be said that the surface shape of the magnetic disk is shown accurately and quantitatively from the relationship with the levitation characteristics of the magnetic head and the CSS tangential force required for the magnetic disk. Absent.

Therefore, under the present circumstances, the conditions for forming the surface of the magnetic disk are set by trial and error. For example, in the conventional magnetic disk whose surface shape is defined by the surface roughness Ra, even when the magnetic disk has the same Ra value, the result of the durability test has a large variation and is stable. It is difficult to reproducibly manufacture a magnetic disk having durability.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present inventors have made an evaluation item indicating the durability of a magnetic disk by quantitatively evaluating the surface shape on a magnetic disk substrate, and an evaluation method therefor. As a result of extensive studies, it was found that the durability of the magnetic disk can be quantitatively evaluated by a specific method, and a magnetic disk having excellent durability can be manufactured with good reproducibility based on the evaluation.

The present invention has been completed based on the above findings, and its purpose is to improve the flying characteristics of a magnetic head and CS.
An object of the present invention is to provide a magnetic disk which is excellent in sliding resistance characteristics such as S characteristics and can be manufactured with good reproducibility. The gist of the present invention is a magnetic disk in which at least a magnetic layer and a protective layer are sequentially provided on a textured surface of a substrate, the surface state of the protective layer of the magnetic disk is measured, and 16 Å from the apex of each protrusion. When the area of the figure surrounded by the contour lines obtained at the lower height is calculated and the radial direction of the substrate is the X axis and the tangential direction is the Y axis, the X axis direction is 10 μm and the Y axis direction is 10 μm.
A magnetic disk characterized by having a surface shape in which the total area of the figures surrounded by the contour lines existing in the range of μm is in the range of 3 to 14 μm ² .

The present invention will be described in detail below. FIG.
It is a typical sectional view of an example of a magnetic disk. Usually, as shown in FIG. 3, a magnetic disk is constructed by sequentially forming an electroless plating layer (2), an underlayer (3), a magnetic layer (4) and a protective layer (5) on a substrate (1). To be done. Underlayer (3),
The magnetic layer (4) and the protective layer (5) are usually formed by a film forming method such as sputtering. Then, on the protective layer (5), a lubricant such as fluorine is usually applied to form the lubricating layer (6).

In the magnetic disk of the present invention, in the above magnetic disk, the sliding surface with the magnetic head is observed and measured, the surface state of the protective layer is evaluated by a specific method, and the optimum sliding surface is determined. It was formed. First, a method of measuring the surface state of the substrate and a method of selecting contour lines based on the measurement result will be described. These are commonly adopted in the above inventions. (1) Method of Measuring Surface State of Substrate (Protective Layer) Using a scanning tunneling microscope (hereinafter abbreviated as STM) or atomic force microscope (hereinafter abbreviated as AFM),
The surface condition of the CSS zone area of the magnetic disk substrate is measured. This measurement is performed on the surface of the protective layer, and when the radial direction of the substrate is the X-axis and the tangential direction is the Y-axis, in the region of the substrate (XY plane) in the range of 10 μm × 10 μm, the X-axis direction ( About 400 to 600 points in 10 μm) and about 400 to 600 lines in the Y-axis direction (10 μm) (total about 1
60,000-360,000).

In the case of STM, a tunnel current of several m to 2 V is applied as a bias from the probe, and while detecting the tunnel current flowing between them, the tunnel current is detected while sequentially scanning the probe within the above range. To do. Thereby, a three-dimensional STM image of the microscopic surface state of the protective layer surface can be obtained. FIG. 1 is a photograph (magnification 1.8 × 10 ⁸ ) of the surface of the protective layer observed by STM, which was obtained by the above method. (2) Contour line selection method With respect to the three-dimensional STM image obtained in the above (1), the vertices of each projection are selected. The method of selecting vertices is as follows. That is, one point on the surface of the protective layer is selected, a virtual circle with that point as the center point is drawn, and if this center point is higher than any point in the virtual circle, it is regarded as a vertex, and this operation is performed for all measurement points. . However, the radius of the virtual circle is 0.5 μm
And Then, as shown in FIGS. 2A and 2B, contour lines are obtained at a height 16 Å below the apex of each selected protrusion. That is, a contour line cut by a section 16 Å below the apex of each protrusion is drawn.

Next, the magnetic disk according to the present invention will be described. This magnetic disk is characterized in that the total area of the figures surrounded by the contour lines, which is obtained based on the contour line area calculation method, is in the range of 3 to 14 μm ² . (3) Contour line area calculation method The area of each region surrounded by the contour lines is calculated from the contour map obtained in (2) above, and the area of the substrate (XY plane) is 10 μm.
The total area of the figures enclosed by the contour lines, which are completely contained within the range of m × 10 μm, is obtained. Hereinafter, the total of these areas will be referred to as the contour line area.

The magnetic disk according to the present invention has a surface shape having the contour line area in the range of 3 to 14 μm ² , and is excellent in sliding resistance characteristics such as flying characteristics and CSS characteristics of the magnetic head. The contour area in the above evaluation method is an index of the smoothness of the surface of the magnetic disk. If the contour line area is less than the lower limit, the surface of the protrusion is often sharp and the magnetic head easily collides with the protrusion, which deteriorates the CSS characteristics. On the other hand, when the upper limit is exceeded, the surface of the protrusion is too smooth and the magnetic head tends to attract, so that the head is easily worn and the CSS characteristics deteriorate.

Next, a method of manufacturing a magnetic disk based on each of the above evaluations in the present invention will be described. In the magnetic recording medium of the present invention, a disk-shaped nonmagnetic substrate made of an aluminum alloy or the like is usually used as the substrate. The substrate is used after being mirror-finished on its surface and then forming a non-magnetic metal layer, for example, a Ni-P alloy layer or a Ni-Cu-P alloy layer as a primary underlayer. The nonmagnetic metal layer is formed by electroless plating or the like, and its thickness is usually 5 to 20 μm.

Generally, the non-magnetic metal layer of the above-mentioned substrate comprises:
Polished and then textured. The polishing process is performed, for example, by sandwiching the substrate between polishing pads having free abrasive grains attached to the surface thereof and replenishing a polishing liquid such as a surfactant aqueous solution. Polishing is performed in a range of about 2 to 5 μm, and the surface is mirror-finished so that the average surface roughness (Ra) is usually 50 Å or less, preferably 30 Å or less.

The loose abrasive grains are typically alumina-based slurries "Polypla 700" and "Polypla 103".
(Both are registered trademarks of Fujimi Incorporated), diamond-based slurry, SiC-based slurry and the like are used. As a polish pad, typically,
"Surfin 100" and "Surfin XXX-5"
(Both are registered trademarks of Fujimi Incorporated.)
Foamed urethane or the like is used.

The contour area defined by the present invention can be adjusted by selecting the texturing conditions. Various methods and combinations are adopted as the texturing method, and specifically, one-step or two-step texturing can be adopted. The two-step texturing will be described in detail below. The first stage texturing is performed using a polishing tape and loose abrasive grains. The surface of the substrate (polished surface) is then subjected to slurry grinding under specific conditions or tape grinding using only a polishing tape.
Roughness and streak patterns are formed on. The unevenness is formed so that Ra is usually 20 to 150Å, preferably 40 to 100Å, and the maximum protrusion height Rp is usually 100 to 1000Å, preferably 200 to 400Å, and the streak pattern is a CSS zone. The cross angle at is usually 10
It is formed so as to be -40 °, preferably 10-30 °. Surface roughness R of the substrate after the first-stage texture processing
When a is lower than 20Å, the CSS characteristics deteriorate and Ra
Is higher than 150Å, it is not preferable because the floating characteristics are deteriorated.

Buff tape such as nylon pile or polyester pile is preferably used as the polishing tape used for the slurry grinding, and 0.3 is used as the loose abrasive grains.
Diamond-based abrasive grains of up to 4 μm are preferably used. The loose abrasive is used as a liquid slurry in which a dispersant is suspended in a liquid (water or a water-based liquid). In slurry grinding, the disk rotation speed is usually 30-450 rpm, and the polishing tape vibration frequency (reciprocating vibration).
60 to 3000 times / min, cylinder pressing pressure is 1.0
˜3.0 Kg / cm ² , and polishing time is 5 to 30 seconds.

A polishing tape used for tape grinding is usually alumina abrasive grains having a particle size of 0.5 to 3 μm or S.
Polishing tape carrying iC abrasive grains, specifically, products "WA # 4000" to "WA # 800" manufactured by Mypox.
An example is a polishing tape carrying 0 "white alumina abrasive grains. In tape grinding, the number of revolutions of the disk is usually 30 to less than 450 rpm, the frequency of the polishing tape (reciprocating vibration) is 80 to 300 times / min, the pressing pressure of the cylinder is 1.0 to 2.0 Kg / cm ² , and the polishing is performed. The time is 5 to 30 seconds.

The second stage texture processing is applied to the substrate surface after the first stage texture processing described above. The second stage texturing is done using a polishing tape or polishing tape and certain loose abrasive particles. Then, by grinding the surface of the substrate under specific conditions, protrusions such as burrs and burrs on the surface can be obtained without substantially changing the surface average roughness Ra and the cross angle after the first-step texturing. Is removed, and the maximum projection height (Rp) on the surface is usually 400 Å or less, preferably 100 to 250 Å.

The polishing tape used for the second-stage texturing has sufficient porosity so that the following liquid slurry can penetrate into the polishing tape, for example, non-woven tape such as nylon, cellulose, rayon, buff tape, etc. Woven tape or flocking tape such as nylon is preferably used, and the free abrasive grains are, for example, 0.3 to
6 μm white alumina-based abrasive grains are used, and a liquid slurry in which the loose abrasive grains are suspended in a water-based liquid together with a dispersant is used as a polishing liquid. The above tape impregnated with the liquid slurry is pressed against the surface of the rotating disk through a pressure roll to polish.
The loose abrasive grains in the polishing liquid are trapped at the contact area between the polishing tape and the disc and pressed against the disc surface to realize the desired polishing action. The conditions for slurry grinding in the second-stage texturing are not particularly limited, and usually disk rotation speed is 50 to 400 rpm, polishing tape vibration frequency (reciprocating frequency) is 50 to 200 times / minute, and cylinder pressing is performed. A pressure of 1.0 to 3.0 kg / cm ² and a polishing time of 3 to 20 seconds are used.

The maximum protrusion height Rp after the second-step texture processing is 400 Å or less, but if it is higher than 400 Å, the floating characteristic is deteriorated, which is not preferable. The substrate obtained by the two-step texture processing has a surface average roughness Ra of 20 to 150Å, preferably 40 to 100Å, and a maximum protrusion height Rp of 100 to 400Å, preferably 100.
To 250Å and the Rp / Ra ratio is 5 or less, and the cross angle θ is 10 to 40 °, preferably 10 to 3
It has a 0 ° shape.

In the present invention, by performing the two-step texture processing, adsorption of the magnetic head and the magnetic recording medium can be prevented, CSS characteristics are improved, and magnetic anisotropy is improved. Further, for example, by combining chemical etching with an acidic solution or electrolytic treatment with the above-mentioned texture processing, the contour line area defined in the present invention can be obtained. In this case, the texture processing is 1
It may be a step or a multi-step process such as two steps.

The case where the electrolytic treatment is combined after the above texture processing will be described in detail below. The electrolytic treatment is performed in an acidic electrolytic solution while applying a voltage such that a DC voltage or a current has a specific waveform (alternating waveform) on the textured substrate. As the electrolytic solution, for example, an aqueous solution containing one or more of sulfuric acid, nitric acid, hydrochloric acid, chromic acid, phosphoric acid, oxalic acid, acetic acid and the like is used. The concentration is usually 0.5 to 40% by weight, preferably 1 to 30% by weight. A phosphoric acid aqueous solution is particularly preferable.

In the electrolytic treatment, the liquid temperature is usually 10 to 70.
° C., a current density is usually 50 mA / cm ² or less, preferably 0.1~50mA / cm ^2, more preferably 0.5 to 4
5 mA / cm ² , electrolysis time is usually 1 to 400 seconds, preferably 2 to 200 seconds, quantity of electricity (product of current density and electrolysis time)
Is 10 to 1000 mA · sec / cm ² , preferably 50 to
It is selected from 600 mA · sec / cm ² .

As the alternating waveform current, an alternating waveform current obtained by alternately exchanging (converting) positive and negative polarities, that is, the polarities of the anode and the cathode, for example, sinusoidal single-phase alternating current and sinusoidal three-phase alternating current. , Square wave, triangular wave, trapezoidal wave, and other waveform currents. The frequency of the alternating waveform current is usually 0.1 to 500 Hz, preferably 0.1 to 300 Hz.

By the above electrolytic treatment, protrusions, burrs and the like on the surface of the substrate after texture processing are removed by etching, the surface of the substrate becomes a smooth surface state, and the floating characteristics and C
SS characteristics are significantly improved. In addition, after the electrolytic etching process is completed and prior to the formation of a secondary underlayer described later,
Finish by applying free abrasive grains to the surface of a non-woven fabric such as cellulose non-woven fabric and impregnating them, or tape that carries comparatively fine abrasive grains such as alumina, etc. against the substrate surface and re-texturing Processing may be performed.

A secondary underlayer, a magnetic layer, and a protective layer are sequentially provided on the surface of the substrate that has been subjected to the electrolytic treatment. These are formed by the sputtering method. Chromium is preferably used as the second underlayer, and its thickness is
It is usually 50 to 2000Å. The magnetic layer is Co-C
It is preferable to form a Co-based alloy represented by r, Co-Ni, Co-Cr-X, or the like. Where X is L
i, Si, Ca, Ti, V, Cr, Ni, As, Y, Z
r, Nb, Mo, Ru, Rh, Ag, Sb, Hf, T
a, W, Re, Os, Ir, Pt, Au, La, Ce,
Examples include one or more elements selected from the group consisting of Pr, Nd, Pm, Sm, and Eu. The thickness of the magnetic layer is usually 50 to 600Å.

As the protective layer, a carbonaceous protective thin film layer is suitable. In particular, an amorphous carbon protective layer or a hydrogenated carbon protective layer formed by using a carbon target in an atmosphere of a rare gas such as argon or He or an atmosphere of coexistence with a small amount of hydrogen is preferable. The thickness of the protective thin film layer is
It is usually set to 50 to 500Å. A lubricating film may be formed on the surface of the protective layer in order to reduce the coefficient of friction.

[0030]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Examples 1 to 6 First, Ni-P plating is performed to a thickness of 15 μm by an electroless plating method.
The surface of the aluminum alloy disk-shaped substrate having a thickness of about 100 nm was subjected to polishing to obtain a mirror surface having a surface average roughness (Ra) of about 20 to 30 Å. Then, as white alumina, "WA # 6000" manufactured by Mypox Co., Ltd.
Using a polishing tape carrying
Texture processing was performed under the conditions of pm, tape frequency 190 times / min, and polishing time 9 seconds to form fine grooves (concavities and convexities) having a surface average roughness (Ra) of about 85Å.

Next, electrolytic treatment was performed in a 10 wt% phosphoric acid aqueous solution under the conditions shown in Table 1 while applying a DC potential to the substrate. The liquid temperature was 20 ° C. Then, as white alumina, "WA # 4000" manufactured by Fujimi Co., Ltd.
Using loose abrasive grains (particle size 5 μm), surface finishing was performed by slurry grinding under the conditions shown in Table 1. Then, a general Cr underlayer, a magnetic layer made of a Co-Cr-Ta alloy, and a carbon protective layer were sequentially provided on the surface of the substrate by a sputtering method to manufacture a magnetic disk. The surface shape of the magnetic disk, the contour line area of the protrusions, the glide levitation characteristic, and the CSS characteristic were evaluated by the following methods. The results are shown in Table 1.
Shown in (1) Surface shape (surface average roughness (Ra), maximum protrusion height (Rp), peak count (Pc)>: 0.5 μ at the tip
Surface roughness meter with m-cone stylus (Kosaka Laboratory's "ET
-30HK ") was used and the measurement length was 250 μm. Ra and Rp were obtained by measuring in the radial direction the surface on an arbitrary straight line on the circumference of the substrate. Further, a count level parallel to the center line was provided 200 Å above the center line of the roughness curve, and the peak count at a measurement length of 250 μm was measured, which was designated as Pc200. (2) Contour area of protrusions: Determined by the method described above.
The surface state of the protective layer was measured by using STM, and 10 μm × 1 of the CSS zone area of the magnetic disk obtained above was measured.
400 points in the X-axis direction and 400 in the Y-axis direction in the range of 0 μm
A total of 160,000 points on the line were measured. (3) Glide levitation characteristics: "RG55" made by Hitachi DECO
The collision height between the magnetic head and the projection of the magnetic disk was detected by the PZT element using "0", and evaluated as the flying height of the external head. (4) CSS characteristics: A magnetic disk is incorporated into an actual drive, and start and stop are repeated,
The static friction coefficient between the magnetic head and the magnetic disk after 0 times was measured and evaluated as CSS characteristics.

[0032]

[Table 1] ──────────────────────────────────── Actual Example Ratio Comparative Example 1 2 3 1 2 3 <Electrolytic treatment> Current density (mA / cm ² ) 2 2 2 2 2 2 Treatment time (seconds) 23 90 180 23 90 180 <Second stage texture processing> Tape frequency (times / min) 70 70 70 70 − − Disk rotation speed (rpm) 150 150 150 300 − − Polishing time (seconds) 5 5 5 5 − − ───────────────────────── ──────────── Ra 92 99 109 78 79 93 Rp 347 434 371 241 514 356 Pc200 27 30 34 9 23 33 Contour area 3.5 8.3 5.3 17.2 1.4 2.2 Glide levitation characteristics (μm) 0.046 0.043 0.048 − − − CSS characteristics 0.17 0.14 0.15 0.25 0.24 0.37 ─────────────────────────────────────

[0033]

According to the present invention described above, there is provided a magnetic disk which is excellent in sliding resistance characteristics such as flying characteristics and CSS characteristics of a magnetic head and can be manufactured with good reproducibility.

[Brief description of drawings]

FIG. 1 is a photograph (magnification 1.8 × 10 ⁸ ) of the surface of a protective layer observed by STM.

FIG. 2 is an explanatory diagram of a contour line selection method.

FIG. 3 is a schematic sectional view of an example of a magnetic disk.

[Explanation of symbols]

 1: Substrate 2: Electroless plating layer 3: Underlayer 4: Magnetic layer 5: Protective layer 6: Lubricating layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Emiko Kojima, 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd. (72) Inventor Yoko Shimoji 1000-1, Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Prefecture Ryokasei Co., Ltd.

Claims (1)

[Claims] 1. A magnetic disk comprising at least a magnetic layer and a protective layer sequentially provided on a textured surface of a substrate, the surface state of the protective layer of the magnetic disk being measured,
Calculate the area of the figure enclosed by the contour line obtained at a height of 16 Å from each apex of each protrusion, and set X in the radial direction of the substrate.
A surface in which the total area of figures enclosed by all the above contour lines existing in the range of 10 μm in the X-axis direction and 10 μm in the Y-axis direction is 3 to 14 μm ² when the axis and the tangential direction are the Y-axis. A magnetic disk characterized by having a shape.