JPH07244845A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a magnetic recording medium having excellent flying characteristics, CSS characteristics, and adsorption characteristics. In a method for manufacturing a magnetic recording medium in which a magnetic layer is formed on a substrate, free abrasive grains and a polishing tape are used on the surface of the substrate, and the peripheral velocity at the innermost periphery of the substrate is 0.25 m /
A method for producing a magnetic recording medium, which comprises performing a texturing under a condition of not less than a second to form a cross pattern having an angle of striations of 10 to 40 ° on a substrate surface and then forming a magnetic layer. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium. Specifically, by performing surface processing on the substrate, the surface characteristics are improved and the floating characteristics, lubricity,
And a method for producing a magnetic recording medium having excellent wear resistance.

[0002]

2. Description of the Related Art In recent years, with the development of information processing technology for computers and the like, magnetic recording media such as magnetic disks have been used as external storage devices. Conventionally, as a magnetic recording medium, an aluminum alloy substrate is subjected to alumite treatment or Ni-
A non-magnetic plating treatment such as P plating is applied, followed by coating an underlayer such as Cr, then a magnetic thin film layer of a Co-based alloy, and a carbonaceous protective film. .

With the increase in density of the magnetic recording medium (magnetic disk), the distance between the magnetic disk and the magnetic head, that is, the flying height, has become smaller and smaller.
It is about m or less. As described above, since the flying height of the magnetic head is extremely small, a protrusion on the magnetic disk surface may cause a head crash, which may damage the disk surface. Further, even minute protrusions that do not lead to head crashes are likely to cause various errors when reading and writing information.

On the other hand, magnetic disks are being miniaturized in parallel with the increase in capacity and density, and motors for spindle rotation are becoming smaller and smaller. For this reason, the torque of the motor is insufficient, and the phenomenon that the magnetic head does not fly while being fixed to the magnetic disk surface is likely to occur. As a means for preventing the sticking of the magnetic head by reducing the contact between the magnetic head and the surface of the magnetic disk, surface treatment called texture processing for forming fine grooves on the substrate surface of the magnetic disk is performed. It is being appreciated.

As a method of performing the above-mentioned texture processing, there is, for example, slurry grinding using free abrasive grains, and in Japanese Patent Laid-Open No. 147518/1993, a porous material is vibrated in the radial direction with respect to the magnetic disk surface. While letting
A method is described in which a slurry liquid containing loose abrasive grains is supplied to perform texture processing.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the slurry grinding according to Japanese Patent No. 518, because of low speed grinding, when forming a cross pattern, processing defects such as burrs and burrs remain. As a result, stable flight of the head is hindered when the magnetic disk device is driven, or a head crash easily occurs at the contact start stop (CSS) when the magnetic disk device is started or stopped. In order to avoid such a phenomenon, a method of reducing the surface roughness of the substrate, a method of strengthening the finishing processing of the substrate surface, etc. are taken, but when the surface roughness of the substrate is made too small. Alternatively, if the finishing process of the substrate surface is strengthened too much, the adsorption property becomes poor, and the problem that the head and the disk are attracted when the magnetic disk device is stopped and becomes immobile tends to occur. there were.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted flight stability of a magnetic head by texture-processing the substrate surface under specific conditions. The inventors have found that a magnetic disk having excellent CSS characteristics and adsorption characteristics can be provided, and completed the present invention.

That is, the gist of the present invention is to provide a method for manufacturing a magnetic recording medium in which a magnetic layer is formed on a substrate, by using free abrasive grains and a polishing tape on the surface of the substrate to form the innermost periphery of the substrate. Texture is applied under the condition that the peripheral speed is 0.25 m / sec or more, and the angle at which the scratches intersect on the substrate surface is 1
A method for producing a magnetic recording medium, which comprises forming a magnetic layer after forming a cross pattern of 0 to 40 °;
Exist in.

The present invention will be described in more detail below.
As the non-magnetic substrate of the magnetic recording medium in the present invention, a disk-shaped substrate generally made of an aluminum alloy is processed to a predetermined thickness, and then the surface thereof is mirror-finished, and then a non-magnetic metal such as Ni-P alloy, or A Ni-Cu-P alloy or the like formed as a surface layer having a film thickness of about 5 to 20 m by electroless plating is used. It is general that the surface layer of the above substrate is subjected to a polishing process and then subjected to a texture process to form specific unevenness and streak patterns. The polishing process is performed, for example, by sandwiching the substrate between polishing pads having free abrasive grains soaked in and impregnated with them, and polishing the liquid while replenishing a polishing solution such as a surfactant aqueous solution. The surface is mirror-finished to have an average surface roughness Ra of 50 Å or less, preferably 30 Å or less. As the loose abrasive grains, typically, an alumina slurry polyplastic 700 is used.
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, Surfin100 and SurfinXXX
-5 (both are registered trademarks of Fujimi Incorporated Co., Ltd.) or the like, and urethane foam or the like is used.

In the texturing in the present invention, a polishing tape and loose abrasive grains are used to perform slurry grinding of the surface layer of the substrate under specific conditions. Buff tape such as nylon pile or polyester pile is preferably used as the polishing tape used for the above-mentioned texture processing. WA (white alumina) -based, SiC-based, diamond-based, and the like can be used as the loose abrasive grains, preferably diamond abrasive grains having a diameter of 2 to 4 μm are used. It is used as a polishing liquid in the form of a liquid slurry suspended in a water-based liquid) with a dispersant.

An example of the above texture processing will be described in detail with reference to FIG. In FIG. 1A, four polishing tapes 2 are provided on both front and back surfaces of a disk-shaped substrate rotating in the direction of arrow A.
Is pressed by the contact roller 3 to perform polishing. The contact roller 3 presses the polishing tape against the surface of the substrate 1 by a roller pressing cylinder 4 with a predetermined force. The polishing tape is running in the direction of arrow B, and polishing is performed with a new tape surface always in contact with the surface of the substrate. Further, the polishing tape can reciprocate (vibrate) in the direction of arrow C by the reciprocating movement of the contact roller 3 to polish the entire surface of the substrate, and the scratches A formed by polishing the substrate with the polishing tape intersect. The angle (cross angle) θ has an angle of about 10 to 40 °. Furthermore, FIG.
As shown in (b), the polishing liquid in which the above-mentioned free abrasive grains are suspended is supplied from the polishing nozzle 5 to the polishing surface side of the polishing tape.

In the present invention, as the grinding conditions for the above-mentioned texturing, the concentration of the slurry in which free abrasive grains are suspended is 0.05 to 0.4 wt%, and the peripheral speed when the substrate is rotated is 0 on the basis of the innermost periphery of the substrate. 0.25 m / sec or more, preferably 0.28
~ 0.60 m / sec, the number of reciprocating movements of the polishing tape in the radial direction of the disk (oscillation frequency) is 500 times / min or more, preferably 1000-3000 times / min, and the pressing force of the cylinder is 1.0- 3.0 kg / cm ² , polishing time 5
The tape feed speed is 1 to 10 mm / s, and the oscillation width is 0 to ± 3 mm.

The peripheral velocity at the innermost periphery of the substrate is 0.2
If it is less than 5 m / sec, the improvement of the floating property will be insufficient, and if the reciprocating speed of the polishing tape is less than 500 times / min, the improvement of the CSS property will be insufficient. In the present invention, the average roughness Ra of the substrate surface is 120 Å or less, preferably 30 by performing the texturing under the above specific conditions.
To 120Å, more preferably 40 to 100Å, and the maximum projection height Rp is 400Å or less, preferably 20.
The angle at which the unevenness of 0 to 400Å intersects with the formed scratches (cross angle) is 10 to 40 °, preferably 10 to 35
The surface shape of the streak pattern is formed.

The surface shape of the substrate in the present invention is
The definition defined by JIS surface roughness (B0601) is used. The surface average roughness Ra and the maximum protrusion height Rp are determined by the slurry grinding conditions, in particular, the disk peripheral speed (rotation speed), the tape feeding speed, the reciprocating speed of the polishing tape (oscillation frequency), the pressing pressure of the cylinder, This can be achieved by appropriately adjusting the polishing time and the like within the above range.

On the other hand, the angle at which the texture streaks intersect (cross angle) can be achieved by adjusting the disk peripheral speed and the reciprocating frequency (oscillation frequency) of the polishing tape within the above range. . Then, the surface of the substrate after the above texture processing is subjected to a second stage texture finishing processing, whereby the floating characteristics and the like can be further improved. The processing method for the texture finishing is not particularly limited, and may be WA-based, GC-based.
(Green carbon) type fixed abrasive polishing tape,
Alternatively, a polishing tape or the like using free abrasive grains such as WA-based, SiC-based, and diamond-based is used.

The second stage texture finishing process is as follows:
Protrusions such as burrs and burrs formed on the substrate surface are selectively removed by polishing without substantially changing the surface average roughness Ra or the cross angle formed in the first-step texture processing, and the surface is The maximum projection height Rp can be preferably set to about 200 to 300Å. When free abrasive grains and a polishing tape are used for the second stage finishing treatment, a nonwoven tape of cellulose, nylon, rayon or the like is preferably used as the polishing tape used for the finishing treatment, and as the free abrasive grains. Is, for example, 0.5
-6 μm WA-based, SiC-based, diamond-based, etc. abrasive grains are used, and the free abrasive grains are used as a polishing liquid in the form of a liquid slurry suspended with a dispersant in a water-based liquid. As the second-stage texture device, a device similar to that shown in FIG. 1 is used. The slurry grinding conditions are not particularly limited, and are usually a disk rotation speed of 50 to 300 rpm, a reciprocating motion of the polishing tape (oscillation frequency) of 50 to 400 times / min, and a pressing pressure of the cylinder of 1.0 to 3.0 kg / cm ² , polishing time 3 to 3
It is carried out within the range of 0 seconds.

On the surface of the substrate that has been subjected to the above-mentioned electrolytic treatment, chromium is formed as a secondary underlayer by sputtering.
The thickness of the chromium underlayer is usually in the range of 50 to 2000 Å. As the metal magnetic thin film layer formed on the Cr underlayer of such a substrate, Co--Cr, Co--Ni,
A magnetic thin film layer of a Co-based alloy represented by Co-Cr-X, Co-Ni-X, Co-W-X or the like is suitable. Here, X is Li, Si, Ca, Ti, V, Cr, Ni,
As, Y, Zr, Nb, Mo, Ru, Rh, Ag, S
b, Hf, Ta, W, Re, Os, Ir, Pt, Au,
Examples include one or more elements selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, and Eu. The metal magnetic thin film layer made of such a Co alloy is
Usually, it is deposited and formed on the base layer of the substrate by means such as sputtering. The film thickness of the metal magnetic thin film layer is usually in the range of 100 to 1000Å.

A carbonaceous film is preferred as the protective thin film layer formed on the metal magnetic thin film layer, and the carbonaceous protective thin film layer is usually in the atmosphere of a rare gas such as argon or He or in the presence of a small amount of hydrogen. Then, an amorphous carbon film, a hydrogenated carbon film or the like is deposited by sputtering using carbon as a target. The thickness of the protective thin film layer is
It is usually in the range of 50 to 500Å. Further, a lubricating film may be further formed on the protective thin film layer in order to reduce the coefficient of friction.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

[0020]

【Example】

Examples 1 to 4 Polished Dia abrasive grains “WAM3” (abrasive grain size 3 μm) manufactured by Fujimi Incorporated and buff tape (made of nylon pile) sold by Maruishi Sangyo Co., Ltd. were used for commercially available Ni-P alloy plated disk substrates. Textured. Processing conditions are: disk rotation speed: 300 rpm (inner circumference reference peripheral speed: 0.39 m / s), oscillation frequency: 1
Grinding was performed under the conditions of 900 times / min, oscillation width: ± 1 mm, processing time: 25 seconds, adjusting the pressing pressure and tape speed so that the surface shape shown in Table 1 was obtained. A Cr underlayer film (1000
Å), a Co—Cr—Ta magnetic film (500 Å) and a C protective film (200 Å) were formed, and then cleaning treatment was performed to produce a magnetic disk.

Comparative Examples 1 to 3 Using the same abrasive grains and polishing tape as in Examples 1 to 4, texturing was carried out. Processing conditions are: disk rotation speed: 80 rpm (inner circumference reference peripheral speed: 0.11 m
/ S), oscillation frequency: 480 times / minute, oscillation width: ± 1 mm, processing time: 25 seconds, grinding is performed by adjusting the pressing pressure and tape speed so that the surface shape shown in Table 1 is obtained. went.

In the same manner as in Examples 1 to 4, Cr underlayer film (1000 Å) and Co-Cr-Ta were sequentially formed on the surface of the above substrate.
Form magnetic film (500Å), C protective film (200Å),
A magnetic disk was produced. Surface average roughness (Ra)
And the maximum protrusion height (Rp) are the surface roughness meter (Kosaka Research Laboratory ET-30H, ET-30H, which has a stylus with a 0.5 μm conical tip in the radial direction of the surface on an arbitrary inner straight line on the substrate.
K) was measured with a measurement length of 250 μm and evaluated.

[0023]

[Table 1]

FIG. 3 shows Rp of the substrate surface plotted against Ra for each of the examples shown in Table 1.
From FIG. 3, it can be seen that in the example using the disk peripheral velocity of 0.39 m / s, a surface shape with a smaller Rp value for the same Ra can be obtained as compared with the comparative example.

Examples 5 to 7 As the oscillation frequency, the texture processing was carried out under the conditions shown in Table 2, and then the second step of finishing processing was carried out by the abrasive grain WA4 manufactured by Fujimi Corporation.
Disk rotation speed: 100 using μm and non-woven tape
Magnetic disks were manufactured in the same manner as in Examples 1 to 4 except that the processing was carried out under the conditions of rpm and processing time of 20 seconds. In addition, commercially available fluorocarbon lubricant (25Å)
Table 2 shows the results of measuring the stable flying height of the head and the CSS characteristics after applying the. The evaluation of each characteristic was performed by the following methods.

<Stable Flying Height of Head (μm)> Measurement was carried out by a commercially available glide tester, and the height at which the head started to collide with one protrusion was defined as the flying height of the head. <CSS characteristics> Evaluation was made by using a 5 g weighted AlTiC head slider and measuring the friction coefficient after 20,000 CSS cycles.

Comparative Examples 4 to 7 Oscillation frequency: 480 times / min., Texture processing was carried out using the conditions shown in Table 2 as the disk rotation speed, and as the disk rotation speed for the second stage finish processing. , 210 rpm (Comparative Examples 4 and 5) and 100 rpm (Comparative Examples 6 and 7) were used to manufacture magnetic disks in the same manner as in Examples 5 to 7. The results of measuring each surface characteristic are shown in Table 2.

From Table 2, it is possible to perform texture processing at a substrate peripheral speed of 0.25 m / sec or more and a tape frequency of 500.
It can be seen that the magnetic recording medium in which both the flying characteristic and the CSS characteristic of the head are improved can be obtained by performing the operation under the condition of the number of times per minute or more.

[0029]

[Table 2]

[0030]

EFFECTS OF THE INVENTION By subjecting the surface of the substrate to the texturing by the method of the present invention, it is possible to remove the protrusions such as burrs and burrs without substantially changing the scratches of the cross pattern. Therefore, the flying characteristics of the head, the CS
Since it is possible to provide a magnetic disk having excellent S characteristics and adsorption characteristics, it has high industrial utility value.

[Brief description of drawings]

FIG. 1 (a) is a partial schematic front view of components of a magnetic disk surface processing apparatus of the present invention. (B) It is a schematic side view of (a).

2 is a partial schematic perspective view of the components of the apparatus of FIG. 1. FIG.

FIG. 3 shows the R of the substrate surface for each of the examples shown in Table 1.
It is the figure which plotted p with respect to Ra.

Claims (6)

[Claims] 1. A method of manufacturing a magnetic recording medium in which a magnetic layer is formed on a substrate, wherein free abrasive grains and a polishing tape are used on the surface of the substrate, and the peripheral velocity at the innermost periphery of the substrate is 0.25.
A magnetic recording medium is characterized in that a magnetic layer is formed after a texture pattern is formed under a condition of m / sec or more to form a cross pattern having an angle of striations of 10 to 40 ° on the substrate surface. Production method. 2. The peripheral velocity at the innermost periphery of the substrate is 0.28 to
The method for producing a magnetic recording medium according to claim 1, wherein the magnetic recording medium has a rate of 0.60 m / sec. 3. The polishing tape is 5 minutes per minute in the radial direction of the disk.
A method of manufacturing a magnetic recording medium, characterized in that a texture process is performed under the condition of reciprocating more than 100 times. 4. The polishing tape is 1 in the radial direction of the disk per minute.
A method for producing a magnetic recording medium, which comprises subjecting the material to texturing under the condition of reciprocating 000 to 3000 times. 5. The substrate surface after texture processing has a surface average roughness Ra30 to 120Å and a maximum protrusion height Rp.
The method for manufacturing a magnetic recording medium according to claim 1, which has a surface shape of 200 to 400 Å. 6. A substrate surface that has been textured,
6. The magnetic recording medium according to claim 1, wherein a magnetic layer is formed after a finishing treatment is performed using a non-woven tape and loose abrasive grains having an abrasive grain size of 0.5 to 6 μm. Production method.