JPH02301016A - Magnetic disk medium - Google Patents

Abstract

PURPOSE:To obtain the medium having high S/N by mixing two kinds of Al2O3 having a different grain size into a coating film in a specified ratio and allowing the grains having a different diameter to play a different role in reinforcing the coating film. CONSTITUTION:The magnetic grains of gamma-Fe2O3 or Co-coated gamma-Fe2O3 and the Al2O3 grains for reinforcing the coating film obtained by mixing the grains having 0.05-0.2mum average diameter and the grains having 0.4-1mum average diameter in the volume ratio of (9:1)-(5:5) in the amt. to control the volume content when the coating film is formed after coating and baking to 0.5-5% based on the coating film volume are mixed, kneaded and dispersed in the resin and solvent to obtain a magnetic coating to be applied on a magnetic disk substrate. The coating is applied on a nonmagnetic substrate in desired thickness by spin coating and baked, and then the surface is lapped. Since the two kinds of Al2O3 having a different grain diameter are incorporated to reinforce the coating film and allowed to play a different role in reinforcing the coating film, the durability of the coating film is improved, and a medium excellent in S/N is obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for producing a magnetic material on a disc-shaped non-magnetic substrate such as an aluminum alloy.
This invention relates to a magnetic disk medium coated with a magnetic paint in which magnetic iron oxide powder, non-magnetic particles, etc. are dispersed in a resin and a solvent.

[Conventional technology]

Conventionally, magnetic disk coatings include γ-Fe in resin.
Magnetic particles such as 20s and Co-coated 7-Fe20s and alumina (A
z2os) particles are used. A
The particle diameter of fil 20 s is 0.5 to 1 μm, and the volume content is 1 to 10%.

[Problem to be solved by the invention]

From the viewpoint of mechanical strength of the coating film, it must be durable against sliding between the floating surface of the magnetic bed and the disk surface when the disk starts and stops rotating, and it also needs to be durable against the sliding of the floating surface of the magnetic bed and the surface of the disk when the disk rotates. It is necessary for the coating film to be able to sufficiently withstand so-called head crashes, in which the stable floating state of the head is disturbed, the coating film contacts the head, and the coating film is destroyed. It is not possible to reduce or reduce the particle size. On the other hand, from the viewpoint of signal-to-noise ratio (S/N), A 12 t 01 particles are the main cause of media noise generation, and it is desirable to reduce the amount of mixed particles and reduce the particle size. As described above, it is currently impossible to fully satisfy both coating film durability and S/N ratio.

[Means to solve the problem]

The present invention provides two types of A II z O3 with different particle sizes.
are mixed into the coating film at a predetermined ratio, and A of each particle size is mixed.
By assigning different coating film strengthening roles to the 4201 particles, a high density magnetic disk medium having excellent coating film durability and high S/N ratio can be obtained.

That is, the present invention uses γ-Fe2O3 or Co-coated-Fe2Og magnetic particles as a magnetic paint to be applied to a magnetic disk substrate, and A (120s particles, fine particles with an average particle size of 0.05 to obtain coating strength). ~0.2 μm A II 203, relatively large particle size 0.4-1 μm
m's A A! 20 s in volume ratio from 9:1 to 5:5
The mixture is mixed and dispersed in the resin and solvent, and mixed and dispersed in the resin and solvent, and then applied to the non-magnetic substrate. It is characterized in that it is formed by applying the film to a desired thickness using a spin code method, and then polishing the surface after baking.

[Effect]

One effect of A 1220 i particles on coating strength is that they promote the polymerization reaction of the resin during coating baking and improve the strength of the resin itself, and the other is that their high hardness reduces contact when the head contacts the coating. It may cause you to bear the load.

For the former, it is desirable that a large number of fine particles of A II 20 s be dispersed in the resin so that the contact area with the resin is large. For the latter, relatively large A II 20s particles having a particle size approximately equivalent to the coating thickness are desirable.

In this way, two types of A420 s particles with different particle sizes are mixed into the coating film at a predetermined ratio, and A420 s particles of each size are mixed into the coating film.
Large A increases media defects and media noise by allowing i7□o3 particles to take on different coating strengthening roles.
The number of 42o3 particles can be reduced compared to conventional media, and S/N and coating film durability can be improved.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, the disk coating composition is as shown in Table 1: magnetic powder 1, large particles and small particles A 12.
A magnetic paint was prepared by cross-dispersing the 20s particles 2 and 3 in a resin 4 and a solvent. After coating it on a cholerachromate-treated aluminum alloy substrate 5 by a spin cord method, it was baked at 200°C for 2 hours. A lubricant was applied to the surface of the finished disk by polishing to a film thickness of 0.6 μm. Two types of A (1203 particles 2 and 3 with average particle diameters of 0.1 μm and 0.55 μm were used.

Table 1 FIG. 1 shows the cross-sectional structure of the disk coating film of the present invention thus obtained. Further, as a comparative example, a magnetic paint was prepared so that the composition of the disk coating film was as shown in Table 2, and a lubricant was applied to the finished disk surface in the same manner as described above to a coating thickness of 0.6 μm.

Table 2 FIG. 2 shows the cross-sectional structure of a disk coating film of a comparative example.

Figure 3 shows the contact start/stop (C, S, S,) test in which the disk starts rotating and stops repeatedly, and the disk surface and magnetic head flying surface repeatedly slide, until the paint film is scratched. S,S.

The number of times is shown for each of the five discs.

Figure 4 also shows the results of a seek test in which the head continuously reciprocated at high speed from the outer periphery to the inner periphery of the disk.The relative speed between the disk and the head was 40 m/see, and the flying height of the magnetic head was 0.15 μm.One seek speed was 3 m. The number of seeks until the paint film becomes scratched under the following conditions is shown for each of the five discs. FIG. 5 shows the signal-to-noise ratio at a recording density of 400 FRPI. C, S, S, the coating film strength for the test is 40,000 times or more for the inventive medium and 30,000 to 40,000 times for the comparative medium, and the coating film strength for the seek test is 150,000 times or more for the present invention medium and for the comparative medium. It is 50,000 to 100,000 times. On the other hand, S/N
is 29.5 to 30.9 dB for the medium of the present invention.

The comparison medium was 26.3 to 28.5 dB.

From the above results, it can be seen that the disk media of Examples produced by the method of the present invention had sufficient coating film durability and also had an excellent signal-to-noise ratio.

〔Effect of the invention〕

As explained above, the present invention provides A42 for strengthening coating films.
To improve coating film durability and obtain excellent S/N by mixing Alzos with different particle sizes as 0 s particles and having each A II z Os share a different role of strengthening the coating film. I can do it.

[Brief explanation of drawings]

FIG. 1 shows a sectional view of a disk coating film in an example of the present invention, and FIG. 2 shows a sectional view of a disk coating film in a comparative example. ■...Magnetic particles, 2...Large particle size A II 20s, 3...Small particle size 1x
os, 4...Resin (binder), 5...
...Nonmagnetic substrate. FIG. 3 is a graph showing the C, S, S test results, and shows the C, S, S, and number of times the paint film is scratched. FIG. 4 is a graph showing the seek test results, and shows the number of times of seeking that causes scratches on the coating film. Figure 5 shows a recording density of 400FRP.
1 is a graph showing signal-to-noise ratio in I (flux inversion/inch); Agent Patent Attorney Susumu Uchihara Figure 1 Figure 2 Invention 4 (Book Figure 3)

Claims (1)

[Claims] γ-Fe_2O_3, cobalt (Co) coated γ-Fe
In a disc coating film coated with a magnetic paint in which _2O_3 iron oxide powder or Fe-Co alloy powder and alumina particles, which are non-magnetic particles, are dispersed in a resin, the average particle diameter is 0.
Alumina particles of 0.05 to 0.2 μm and an average particle size of 0.05 to 0.2 μm.
Alumina particles of 4 to 1 μm in a volume ratio of 9:1 to 5
A magnetic disk medium characterized in that the magnetic disk medium is contained at a ratio of 0.5% to 5% with respect to the total coating film volume.