JPH0696436A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To stabilize the coefft. (mu) of friction of a magnetic recording medium and to enhance the reliability and durability by regulating the amplitude of the surface waviness of the surface of the medium having a prescribed wavelength and the surface roughness to a specified range each. CONSTITUTION:A magnetic recording layer and a protective film covering this recording layer are formed on the surface of a nonmagnetic substrate and surface roughening is carried out so as to attain <=50nm amplitude of surface waviness having 0.3-3.0mm wavelength, 2-7nm surface roughness Ra and 10-60nm Rmax. The coefft. of friction is reduced and floating stability, that is, grind characteristics are improved because floating height is reduced. Products are made free from unevenness and the quality can be considerably enhanced.

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 having a surface provided with fine grooves or irregularities called a texture.

[Prior art]

The surface roughness of the texture of the magnetic recording medium is disclosed in JP-A-62-219227 and JP-A-64.
No. 55738, No. 01-251428, No. 01-303601, No. 02-3.
It is disclosed in Japanese Patent No. 1324, Japanese Patent Laid-Open No. 03-95727, and the like.

Further, Japanese Patent Laid-Open No. 63-197030 discloses a groove interval.

Further, Japanese Patent Laid-Open No. 64-23419 discloses a maximum height Rp and a maximum depth Rv.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since the minute waviness on the surface is not specified, it is arbitrarily set. Therefore, the friction coefficient μ, which is one of the CSS characteristics on the surface of the magnetic recording medium, is not stable, and reliability and durability are poor.

Further, the waviness is not specified, and stable glide characteristics cannot be obtained.

The inventor has found a relationship between this waviness and the glide characteristic which is the low flying characteristic of the slider. An object of the present invention is to maintain a small friction coefficient on the surface of a magnetic recording medium, to have excellent CSS characteristics, and at the same time to have stable glide characteristics.

[0008]

In a magnetic recording medium in which at least a magnetic recording layer and a protective film layer for covering the magnetic recording layer are provided on the surface of a non-magnetic substrate and the surface is roughened, a wavelength of 0.3 to The amplitude of the surface waviness of 3.0 mm is 50 nm or less, and Ra is 2 to 7 n for the surface roughness.
It is to define m and Rmax to be 10 to 60 nm.

[0009]

Embodiments of the present invention will be described in detail with reference to FIGS. The undulation amplitude and Ra and Rmax are measured with a stylus type surface roughness meter with a stylus tip radius of 2.5 μm. The amplitude is measured by 3 mm, and Ra and Rmax are measured by the measured length. Was 1 mm.

FIG. 1 is an explanatory view of undulations and amplitudes relating to the surface shape of a magnetic recording medium. A roughness curve showing the roughness in the radial direction of the magnetic recording medium was measured, and the waviness component of the roughness curve was determined and used as the waviness curve. The maximum amplitude of this waviness curve was represented by Wt, and this value was defined as the amplitude.

Example 1 A substrate A of aluminum alloy having a diameter of 65 mm containing about 4 wt% of Mg was ground and
A NiP film having a thickness of 10 to 15 μm is formed on the surface thereof to form a substrate B. Then, the surface roughness Ra of this substrate B is polished to 1 nm or less, and then texture processing is performed using free abrasive grains. The same applies to processing using a tape alone or processing combining free abrasive grains and tape.

FIG. 2 is a schematic diagram of texturing.
The substrate C is fixed on the turntable 1 and the rotation speed is 100 to 150 rp.
It was rotated at m. While dropping the loose abrasive grains 2 onto the substrate C, the quill pack 3 rotating at 10 to 50 rpm was pressed against the substrate C at a pressing force of 20 N for 20 to 50 seconds. After texture processing, a magnetic film of about 60 nm and
A carbon protective film of m was formed by sputtering, and then a liquid lubricant was applied.

Various trial productions of magnetic recording media were made within the above range. FIG. 1 shows the undulation amplitude Wt and the surface roughness Ra and Rmax. Wt is 10 to 100 nm, Ra
Is distributed in the range of 3 to 6 nm, and Rmax is distributed in the range of 30 to 60 nm.

FIG. 3 shows the relationship between the number of CSS times and the friction coefficient μ. In the conventional magnetic recording medium in which the maximum amplitude Wt of the waviness curve is larger than 50 nm, the friction coefficient μ increases faster as the number of CSS increases. Further, the magnetic recording medium of the present invention has a Wt of 50 nm or less and a general CSS of 30k times.
It is satisfied that the friction coefficient after the number of times is 0.8 or less.

In FIG. 4, a slider is levitated on each magnetic recording medium shown in FIG. 3, and the flying height of this slider is 0.2.
It shows the number of collisions at each flying height when it is reduced from μm. The number of collisions was counted as the number of pulse waves from the piezoelectric element provided on the back surface of the slider.

In a conventional magnetic recording medium having a waviness amplitude Wt of more than 50 nm, a flying height of 0.07 μm or less does not allow stable flying. In the present invention having an amplitude of 50 nm or less, the number of collisions is small and the slider flies stably even at a flying height of 0.07 μm or less.

(Embodiment 2) FIG. 5 shows that in the texture processing of Embodiment 1, the quill pack 3 is set to 30 rpm,
The pressing force was 10 to 60N. The results of Wt, Ra, Rmax, and CSS durability test of each magnetic recording medium are shown. As in Example 1, the sample NO. In (1), (2), and (3), the friction coefficient increases faster as the number of CSS increases. Sample No. (1), (2), (3)
Sample No. 1 having Ra and Rmax of 5 nm and 50 nm, respectively. The characteristics of (2) are good. From this, Wt
Indicates that the swell amplitude is important for the CSS characteristics. On the other hand, the sample NO.
(a), (b), (c) showed good characteristics.

Particularly, Ra and Rmax are 5 nm and 50, respectively.
sample NO. (b) shows good characteristics. Incidentally, W
When t is 50 nm or less, Ra is 2 to 7 nm and Rmax is 10 to 60 nm, and particularly good characteristics are exhibited. Ra, Rmax
When R is small, the magnetic recording medium and the slider are easily attracted to each other, and when Ra and Rmax are large, local wear and damage are likely to occur on the surface of the magnetic recording medium.

As described above, the wavelength of 0.3 to
In the present invention in which the amplitude of the surface waviness of 3 mm is 50 nm or less, the friction coefficient is small, and the floating stability, that is, the glide characteristic is improved in the low flying height region. Reliability and durability are greatly improved. Further, by setting the values of the amplitude of undulation and the surface roughness (Ra, Rmax) within a specific range, a more preferable effect can be obtained. By defining the minute waviness on the surface, the product variation is eliminated and the quality is greatly improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of undulations and amplitudes relating to the surface shape of the present invention.

FIG. 2 is a schematic diagram of texture processing that is Embodiment 1 of the present invention.

FIG. 3 is a CSS for Example 1 of the present invention and a conventional example.
Relationship diagram between the number of CSS times and the friction coefficient by the durability test

FIG. 4 is a diagram showing the relationship between the flying height of the slider and the number of collisions in the glide test for the first embodiment of the present invention and the conventional example.

FIG. 5 is a CSS for a second embodiment of the present invention and a conventional example.
Relationship diagram between the number of CSS and the friction coefficient by the durability test

[Explanation of symbols]

 A substrate B substrate C substrate 1 rotary table 2 loose abrasive grains 3 quill pack

Claims (2)

[Claims] 1. A magnetic recording medium in which at least a magnetic recording layer and a protective film layer covering the magnetic recording layer are provided on the surface of a non-magnetic substrate to roughen the surface, and the wavelength is 0.3 to 3.
A magnetic recording medium having an amplitude of surface waviness of 0 mm of 50 nm or less. 2. Surface roughness Ra = 2 to 7 nm, Rmax
The magnetic recording medium according to claim 1, wherein: 10 to 60 nm.