JPS63217528A - Production of magnetic coating compound - Google Patents

Abstract

PURPOSE:To greatly improve the defect rate of a magnetic disk medium by using a filter of an internal capturing type having 40-100mum mesh size, passing a magnetic coating compd. through said filter by its own weight, then filtering the compd. with a precision filter having the finer mesh size and coating such compd. on a substrate. CONSTITUTION:A filter component 13 of the filter F1 is formed of a fiber material such as PP having excellent chemical resistance like sponge to constitute the internal capturing type filter. This filter has 40-100mum mesh size to allow passage of the magnetic coating compd. by its own weight and to prohibit the passage of a gel-like dispersion by its own weight. The precision filter F2 is provided after the filter F1 to remove the magnetic material powder and foreign matter larger than the target magnetic material powder. The defect rate of the magnetic disk medium is thereby greatly improved.

Description

Detailed Description of the Invention [Summary] After the magnetic paint is passed through an internal capture type filter with a mesh diameter of 40 to 1100 tI under its own weight to remove gel-like undispersed matter and coarse foreign matter, it is passed through a precision filter. By filtering and applying with a filter, gel-like undispersed substances can be surely removed.

[Industrial application field]

A magnetic disk medium of a magnetic disk device used as an external storage device in an information processing system is manufactured by applying magnetic paint to a disk made of aluminum or the like.

The present invention relates to a method of manufacturing a magnetic coating material for forming a magnetic coating film on such a magnetic disk medium.

[Overview of magnetic disk media]

FIG. 4 is a diagram showing a magnetic disk medium coated with a magnetic paint manufactured by the method of the present invention, (a) is a perspective view;
(9) is a sectional view. The magnetic disk medium l has a mounting hole 2 in the center, and is attached to the spindle of a magnetic disk device through the hole 2, and information is recorded/reproduced by a magnetic head while rotating at high speed. Ru.

That is, as shown in the figure (b), a thin magnetic coating film 4.4 of 1 μm or less is formed on both the front and back surfaces of a non-magnetic base tfi3 such as aluminum, and information is recorded in this magnetic chamber 114.4.

This magnetic coating film 4.4 is made by applying a magnetic paint made by dispersing ferromagnetic powder such as γ-FezO, etc. in a polymeric binder and a solvent onto a non-magnetic substrate 3 such as aluminum. You can get it by doing.

[Prior Art] Mixing and dispersing of magnetic coating materials is carried out using a ball mill or a sand mill. However, magnetic paints kneaded by a ball mill, sand mill, etc. usually contain foreign substances such as ferromagnetic powder and binder, and incompletely dispersed undispersed substances. Therefore, in order to remove these, the kneaded magnetic paint is filtered and then applied onto a substrate to form a thin magnetic coating.

FIG. 5 is a diagram showing the entire structure of the magnetic paint manufacturing apparatus. 5
is a paint tank, which contains a magnetic paint 6 in which magnetic powder, polymer bonding side such as acrylic, epoxy, phenol, or melamine, and a solvent such as toluene, xylene, or cellosolve are stirred and dispersed using a ball mill or the like; The magnetic powder is stirred by a propeller 7 to prevent it from settling. This magnetic paint is sent by a pump 8 through a filter 9 to a storage tank 10. and from the storage tank 10.

It is supplied to the coating nozzle 12 by the pump 11 and coated on the substrate 3.
It is applied by centrifugal coating method.

6 and 7 are enlarged sectional views of elements of a conventional filter 9. FIG. FIG. 6 shows a surface capture type filter (membrane filter), which has holes with a constant mesh diameter, and the thickness d in the direction in which the magnetic paint passes is extremely small. On the other hand, the internal capture type filter shown in Figure 7
It is made of fibers such as cellulose and has a thickness D of about 15 to 20 IllIll in the direction in which the magnetic paint passes.

[Problem that the invention seeks to solve]

The surface-trapping type filter shown in FIG. 6 is thin and has a short path in the direction in which the magnetic paint passes, so gel-like undispersed substances can easily pass through it. In other words, incompletely dispersed particles contained in the magnetic paint after kneading take on a gel-like appearance, and phenol resins in particular tend to gel.

In general, gel-like undispersed substances are amorphous, flexible, and have good fluidity, so they can be freely deformed and passed through a filter. After coating, the particles become a lump of incompletely dispersed particles, which forms protrusions on the magnetic coating.

On the other hand, if the mesh diameter is made small so that gel-like undispersed matter cannot pass through, a problem arises in that even the magnetic powder is blocked.

The internal capture type filter shown in Figure 7 has a long passage path for the magnetic paint in the filter, so it seems suitable for capturing gel-like undispersed substances. If pressure is not applied, it will be difficult for the magnetic paint to pass through.

However, when pressure is applied, the gel-like undispersed material can pass through the filter while deforming along the filter holes, making it impossible to obtain the expected effect.Furthermore, this filter is highly flexible; Hard foreign substances such as coarse particles of
It pushes the mesh of the filter wider and passes through it. In order to prevent this, if the mesh diameter of the filter is made small, the problem arises that magnetic powder is also trapped, as in the case of surface trapping type filters.

There is also a method of filtering the resin material before stirring and dispersion using a precision filter, but this method is not perfect because gel-like undispersed matter is generated during the subsequent stirring and dispersion step.

Even if a magnetic paint filtered through a filter is used, gel-like undispersed substances cannot be removed, so undispersed substances such as ferromagnetic powder, re-agglomerated substances, and other undispersed substances in the paint cannot be removed. There are protrusions several micrometers in size made of insoluble matter, etc.
This often causes magnetic defects such as bit errors and flying problems in floating magnetic heads.

In recent years, with the increase in recording density of magnetic disk media, the thickness of the coating film has become thinner and thinner, and the flying gap of floating magnetic heads has also become smaller, so that uniform coating without such protrusions can be achieved. The key to achieving high-density recording is how to form such a coating film.

For example, in a magnetic disk medium with a recording density of 64008 PI, when a magnetic paint is applied onto an aluminum substrate using a centrifugal coating method, the thickness of the coating film at the inner circumference is approximately 1.5 μm.
m, approximately 2.0 μm at the outer periphery, and baking is approximately 1.0 μm at the inner periphery and approximately 1.5 μm at the outer periphery due to grinding after hardening.
It is formed into a thin film called m. Furthermore, the flying gap of the magnetic head is extremely small, approximately 0.35 μm, and even a 1 μm protrusion may come into contact with the magnetic head, which may even lead to permanent destruction of the coating film.

Therefore, especially in the case of magnetic paints used in high-density recording magnetic disk media, it is necessary to be able to reliably separate and remove gel-like undispersed substances.

The technical problem of the present invention is to eliminate such problems in the conventional manufacturing method of magnetic paint for magnetic disk media, and to make it possible to reliably separate even gel-like undispersed substances. .

[Means for solving problems]

FIG. 1 is a diagram illustrating the basic principle of the method for producing magnetic paint according to the present invention. Fl has a mesh diameter of 40 to 1100
1z is a coarse internal capture type filter, and F2 is a precision filter with a fine mesh diameter.

In the present invention, in the coarse internal capture type filter F1 with a mesh diameter of 40 to 100 μm, the magnetic paint is passed through by its own weight without being pressurized by a pump. After this filtration process, the magnetic paint is applied to the substrate 3 after being filtered through a precision filter F2 with a fine mesh diameter. At this time, the magnetic paint is not pressurized by a pump, but is passed through the filter by the weight of the magnetic paint. As a result, the gel-like undispersed material is not pushed by the pump pressure, so it becomes deformed and difficult to pass through the filter mesh.

On the other hand, magnetic powder and the like can easily pass through the filter even if it is not pressurized by a pump because the mesh diameter of the filter is coarse.

However, the mesh diameter is coarse, allowing objects larger than the target magnetic powder to pass through. Therefore, particles larger than the target magnetic powder are removed by the precision filter F2 before the powder is applied. Note that the gel-like undispersed matter has already been removed by the coarse mesh filter F1, so it does not pass through the fine filter F2.

〔Example〕

Next, examples will be used to explain how the method for producing magnetic paint according to the present invention is actually implemented.

FIG. 2 shows an embodiment of the filter F1 in FIG. 13 is a filter element, which is made of a fiber material with excellent chemical resistance such as polypropylene.
It is formed like a sponge. That is, it is an internal capture type filter with a size of about 10 to 50 mm in the direction in which the magnetic paint passes. This filter allows the magnetic paint to pass through it by its own weight without being pressurized by a pump, so gel-like undispersed matter cannot pass through it due to its own weight, but the mesh diameter is large enough to allow normal magnetic powder to pass through. For this purpose, a mesh diameter of about 40 to 100 μm is suitable.

When such a filter element is used and the magnetic paint is passed through by its own weight without applying pump pressure, both gel-like undispersed matter and coarse hard foreign matter cannot pass through, as shown in 14, and are captured reliably. be done.

FIG. 3 is a diagram showing the characteristics of a magnetic disk medium coated with a magnetic paint manufactured by the method of the present invention and a magnetic disk medium coated with a magnetic paint manufactured by a conventional method. Lofts A, B, and C are the defect rates of magnetic disk media coated with magnetic paint manufactured by conventional methods, and nearly 20% of the media are defective. Loft D, E,
F is the defect rate of the magnetic disk medium coated with the magnetic paint produced by the method of the present invention. That is, after the magnetic paint is filtered by its own weight using the filter element 13 shown in FIG. 2, the magnetic paint passed through a precision filter is applied, and the defective media is reduced to about 5%. As described above, a magnetic coating film formed by applying a magnetic coating material manufactured by the method of the present invention has a significantly improved defect rate and eliminates the problem of flying the magnetic head.

Note that a precision filter F2 may be provided following the filter F1 for removing gel-like undispersed substances, but after filtering the stirred and dispersed magnetic paint with the filter F1 for removing gel-like undispersed substances, It may be stored in a paint tank 5 and passed through a precision filter during the coating process.

〔Effect of the invention〕

As described above, according to the present invention, the filter F1 with a coarse mesh diameter of about 40 to 1100 μ, through which the gel-like undispersed matter cannot pass under the weight of the magnetic paint, is used to allow the gel-like undispersed matter to pass under its own weight. Remove. After that, the precision filter F2 removes magnetic powder and foreign matter that are larger than the target magnetic powder, making it possible to reliably capture gel-like undispersed matter, significantly improving the defect rate of magnetic disk media. be done.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the basic principle of the method for producing magnetic paint according to the present invention, Fig. 2 is a diagram showing a filter element according to an embodiment of the present invention, and Fig. 3 is a diagram illustrating the magnetic paint produced by the method of the present invention. A diagram comparing the characteristics of paint and magnetic paint manufactured by conventional methods; Figure 4 is a diagram showing a magnetic disk medium;
FIG. 5 is a diagram showing the entire structure of a magnetic paint manufacturing apparatus, FIG. 6 is a diagram showing a conventional surface trapping type filter, and FIG. 7 is a diagram showing a conventional internal trapping type filter. In the figure, 3 is a substrate, 4 is a magnetic coating film, 6 is a magnetic paint,
8.11 is the pump, 12 is the nozzle, 9 is the filter, F
1 indicates a filter for removing gel-like undispersed matter with a coarse mesh diameter, and F2 indicates a precision filter. Patent Applicant: Fujitsu Co., Ltd. Sub-Agent, Patent Attorney: Yasushi Fukushima Basics of Japan H! Figure 1 Compensation can stop for magnetic pillow paint filter/finishing Figure 2 Comparison of notes (2) Crab harvesting filter Fig. 6 @D) - Conventional indoor recitation type filter Fig. 7

Claims (1)

[Claims] An internal capture filter (F1) with a mesh diameter of 40 to 100 μm is used, and the magnetic paint is passed through by its own weight without being pressurized by a pump. A method for producing a magnetic paint, which comprises applying it to a substrate after filtering it through a fine precision filter (F2).