JP2897156B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
In particular, the present invention relates to a magnetic recording medium having a lubricant layer that has a low friction coefficient between the magnetic recording medium and the magnetic head, does not decompose by a catalyst at the time of local heating, and does not easily attract the magnetic head under high temperature and high humidity.

[0002]

2. Description of the Related Art In a thin film type magnetic recording medium, a ferromagnetic metal or an alloy thereof is formed on a nonmagnetic substrate by sputtering, vapor deposition, electroless plating, or the like, and carbon is mainly formed on the metal magnetic layer. A protective film layer is formed.

In a start / stop method using a contact start / stop (CSS) using a floating magnetic head,
The magnetic head comes into contact with the surface of the magnetic recording medium when the disk rotation starts and stops. As the protective film layer, various materials have been proposed, but a protective film layer mainly composed of carbon having excellent sliding characteristics and oxide ceramics of SiO ₂ and ZrO ₂ have been generally used. Was. However, with only the protective film layer, as the number of CSSs increases, the coefficient of kinetic friction at the time of sliding contact between the magnetic recording medium and the magnetic head significantly increases, causing a head crash. Therefore, a lubricant layer is provided on the protective film layer. As the above lubricant, perfluoropolyethers (PerfluoroPolyethers)
In particular, a lubricant having a polar group at the molecular end of perfluoropolyether is generally used for the purpose of enhancing the bonding force (fixing property) to the protective film layer.
As such a lubricant, for example, Japanese Patent Publication No. 6-4644
No. 1

Embedded image Product name "Fomblin Zett Doll (F
OMBLIN ZDOL)] [Audimont (AUSI
MONT), or

Embedded image Product name "DEMNUM S (DEMNU
MSA) "(manufactured by Daikin Industries, Ltd.) and the like are generally known.

[0004]

The above-mentioned "Fomblin Zetdall" has CH ₂ OH groups at both ends of the molecule, and therefore has a strong bond with the surface of the protective film layer (= fixing property is low). High) and provide excellent sliding resistance. However, “Fomblin Zetdall” is described in the literature (“Degradation of perfluoropolyethers catalyzed b
y aluminum oxide ”, Paul H. Kasai, Wing T. Tang and P
atrick Wheeler, Applied Surface Science, 51 (1991)
As shown in 201~ 211), O-CF ₂ in a molecule
Since it has a bond of —O unit, it is easily decomposed at a temperature of about 200 ° C. in the presence of aluminum oxide (α-Al ₂ O ₃ ) which is a component of the magnetic head. However, at the time of CSS, the local instantaneous temperature becomes 90 to 450 ° C. or more due to contact between the magnetic recording medium and the magnetic head. Therefore, aluminum oxide, which is a component of the slider portion of the magnetic head, acts as a catalyst, and decomposition of “fomblin zett doll” occurs. Part of the lubricant decomposed in this way adheres to the magnetic head, causing a decrease in reproduction output by increasing the flying height of the head, or the head adsorbed on the surface of the recording medium due to the adhesion of the decomposed component to the magnetic head. There has been a problem that the lubricant film thickness is reduced due to evaporation or volatilization of the decomposed lubricant to increase the dynamic friction coefficient.

On the other hand, the above-mentioned "Demnam S.A."
Is chemically stable because it does not have a bond of O-CF ₂ -O unit in the molecule and does not cause decomposition by local high heat, but has a CH ₂ OH group only at one end of the molecule. Is not enough, the bond with the surface of the protective film layer is not enough,
When the magnetic disk is rotated at high speed at a high temperature, the lubricant is easily scattered (spin-off test), and the thickness of the lubricant decreases. For this reason, there was a problem that the dynamic friction coefficient at the time of CSS was large. Therefore, a lubricant which is chemically stable even at a locally high temperature and has excellent wear resistance has been desired.

[0006]

The present invention SUMMARY OF THE INVENTION It is an proposed in view of the above, the in the molecule, such as "Fomblin Zdol" does not include the structure of the O-CF ₂ -O units, yet the molecular As a result of examining a lubricant having a structure having CH ₂ —OH groups at both ends, it was found that in a magnetic recording medium in which at least a ferromagnetic thin film layer and a protective film layer were provided on a non-magnetic substrate, the protective film layer was a carbon-based or oxidized film. It is selected from ceramics, and has a chemical formula on the surface of the protective film layer.

Embedded image It is an object of the present invention to provide a magnetic recording medium having a lubricant layer comprising a fluorine-containing polyalkyl ether diol compound represented by the formula:

In the above compound, p is an integer of 2 to 10. When p is less than 2, there is a danger of decomposition due to weak acetal bond. On the other hand, when p exceeds 10, it is not preferable because of fluidity as a lubricant and maintenance of coatability.

When a carbonaceous film is used as the protective film layer to which the lubricant is applied, a hydrogenated or nitrogenated carbon film is preferable. When an oxide ceramic is used, SiO ₂ and ZrO ₂ are preferable.

In the present invention, the thickness of the lubricant layer is
The thickness is preferably 50 ° or less, and if the thickness exceeds this, the magnetic head will be attracted, which causes a problem in running properties. still,
The method of forming the lubricant layer, that is, the method of applying the lubricant, may be performed by any known method such as a dipping method, a spin method, and a spray method.

[0010]

According to the magnetic recording medium of the present invention, the lubricant layer comprises:
Since it does not contain the structure of O-CF ₂ -O unit in the molecule and is composed of a compound having CH ₂ OH groups at both ends of the molecule, it is chemically stable even at local high temperature, and the friction coefficient is In comparison, the magnetic head is hardly attracted. Therefore, the reliability of the magnetic recording medium is dramatically improved.

[0011]

【Example】

<Preparation of Test Magnetic Disk> [Example 1] FIG. 1 is a sectional view of a hard disk according to the present invention. An aluminum alloy substrate (1) is coated with a Ni-P plating film (2) as a hard underlayer at a thickness of 13 μm,
Next, Cr was used as a base film layer (3) by sputtering.
800 °, a Co—Cr—Ta alloy as the magnetic film layer (4) at 600 °, and hydrogenated carbon as the protective film layer (5) at 200 °. Further, on the upper surface thereof, a fluorinated solvent [(trade name) “PF5060”, manufactured by 3M Company]

Embedded image A compound having a number average molecular weight of 1,000 represented by
%, And applied by a dip method to a film thickness of 40 ° (measured using ESCA) to form a lubricant layer (6). Thus, a magnetic disk of Example 1 was obtained.

Example 2 Chemical Formula as Lubricant

Embedded image A magnetic disk of Example 2 was obtained in the same manner as in Example 1 except that a lubricant having a number average molecular weight of 3000 represented by was used.

[Example 3] Chemical formula as a lubricant layer

Embedded image A magnetic disk of Example 3 was obtained in the same manner as in Example 1 except that a lubricant having a number average molecular weight of 2000 represented by was used.

[Comparative Example 1] Chemical formula as lubricant layer

Embedded image The magnetic disk of Comparative Example 1 was obtained in the same manner as in Example 1 except that the product name “Fomblin ZDOL” (manufactured by AUSIMONT) having a number average molecular weight of 2,000 represented by Was.

Comparative Example 2 A chemical formula was used as a lubricant layer,

Embedded image The product name "Demnum with a number average molecular weight of 2000 represented by
A magnetic disk of Comparative Example 1 was obtained in the same manner as in Example 1 except that "SEM (DEMNUMSA)" manufactured by Daikin Industries, Ltd. was used.

<Test 1: CSS characteristic measurement> Example 1 above
The contact start / stop (CSS) characteristics of each of the magnetic disks of Comparative Examples 1 and 2 and Comparative Examples 1 and 2 were measured. C
A commercial CSS tester (manufactured by Matsubosha) is used for the SS tester.
The magnetic head was 10000 times the CSS using the Al ₂ O ₃ -TiC slider head. Obtained CSS
The characteristics are shown in FIG. As shown in FIG. 2, the magnetic disks of Examples 1 to 3 have a low dynamic friction coefficient of 0.3 to 0.4 even when the dynamic friction coefficient is 10,000 times. The value was as high as 0.9. When the magnetic head after completion of the CSS was observed using an optical microscope, the adhesion of the lubricant to the head of Comparative Example 1 was recognized, but the heads of Examples 1 to 3 and Comparative Example 2 were clean. Was.

<Test 2: Measurement of Coefficient of Static Friction> Next, the coefficient of static friction was measured using the magnetic disks of Examples 1 to 3 and Comparative Examples 1 and 2. The static friction coefficient was measured at 60 ° C x 8
Perform 5,000 times of CSS under 0% high temperature and high humidity atmosphere,
The test was performed after leaving the magnetic head fixed on the magnetic disk for 24 hours. Table 1 shows the obtained results.

[Table 1] From Table 1, the static friction coefficients of Examples 1 to 3 showed a low value of about 0.9, while the static friction coefficients of Comparative Examples 1 and 2 showed a high value of 1 or more.

<Test 3: Measurement of Amount of Reduction in Film Thickness> Next, the magnetic disks of Examples 1 to 3 and Comparative Examples 1 and 2 were rotated at a rotation speed of 7000 rpm for 72 hours at a temperature of 80 ° C. (spin-off). After that, the amount of decrease in the film thickness of the lubricant was examined. Table 2 shows the amount of reduction in film thickness at a radius of 20 mm.

[Table 2] From Table 2, Comparative Example 2 showed a remarkable decrease in film thickness because the lubricant was scattered at high speed rotation, but the film thicknesses of Examples 1, 2, 3 and Comparative Example 1 were stable.

The protective film layer is made of SiO ₂ or ZrO.
_In the case of using No. 2, the same results as in Examples 1, 2 and 3 and Comparative Examples 1 and 2 were obtained.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments, and can be implemented in any manner unless the configuration described in the claims is changed. it can.

[0021]

As described above, the magnetic recording medium of the present invention has a lubricant layer which is chemically stable even under local high temperature and high humidity and has excellent lubricating properties, so that it has excellent sliding resistance. The present invention can be applied to a magnetic recording device.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a hard disk according to the present invention.

FIG. 2 is a graph showing CSS test results of Examples 1, 2, 3 and Comparative Examples 1 and 2.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C10N 40:18 (72) Inventor Shujiro Yoko 1-1-1 Onodai, Midori-ku, Chiba-shi, Chiba Prefecture Showa Denko KK In-house (72) Inventor Hiroshi Sakai 3-1 Yawata Kaigandori, Ichihara-shi, Chiba Prefecture Inside the HD plant of Showa Denko KK (56) References JP-A-62-66417 (JP, A) JP-A-56-124127 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/66-5/71 C10M 105/54 C10M 107/38 C10N 40:18 CA (STN) WPI / L (QUESTEL)

Claims (1)

(57) [Claims] 1. A magnetic recording medium having at least a ferromagnetic thin film layer and a protective film layer provided on a non-magnetic substrate, wherein the protective film layer is selected from carbon-based or ceramic oxide-based. Chemical formula on the surface of the film layer A magnetic recording medium having a lubricant layer comprising a fluorine-containing polyalkyl ether diol compound represented by the formula: