JPS5841563B2 - Method for manufacturing magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a magnetic recording medium such as a magnetic disk, and more particularly to a method of manufacturing a magnetic recording medium that improves the method of manufacturing a magnetic coating material to be applied to a substrate.

Magnetic recording media such as magnetic disks are widely used as storage media for computers.

For such magnetic recording media, there is a need to manufacture a medium that is particularly capable of high-density recording.

Generally, such magnetic recording media are produced by manufacturing a magnetic paint in which magnetic powder is dispersed in a binder, and applying the manufactured magnetic paint to a substrate.

The characteristics of a magnetic recording medium depend on the characteristics of such a magnetic coating material, and the method of manufacturing such magnetic coating material is an important factor.

Conventionally, the following method has been used to manufacture this magnetic paint.

Prepare a binder made by dissolving acrylic epoxy resin, which is a thermosetting resin, with thinner and magnetic powder such as γF e 203. In order to uniformly disperse the magnetic powder in the binder, the binder and the binder are placed in a pot containing ball material. Add magnetic powder and mix.

In the ball mill method, the magnetic powder is dispersed in the binder by rotating the pot or vibrating the pot from side to side.

Furthermore, the mixture other than the ball material in the pot is taken out to obtain a magnetic paint in which magnetic powder is dispersed in a binder.

In such conventional manufacturing methods, pots made of alumina or metal and balls made of alumina or metal were used.

However, since alumina is hard, the magnetic powder collides with the balls and pots when dispersed using the ball mill method, resulting in large stress, which impairs the magnetic properties of the magnetic powder.

In addition, metal pots and balls wear out in the form of metal ions, which are mixed into the magnetic paint and deteriorate the strength of the paint film.

An object of the present invention is to provide a method for manufacturing a magnetic recording medium in which balls or pots do not impair the magnetic properties of magnetic powder in the step of dispersing magnetic powder in a binder.

Another object of the present invention is to provide a magnetic recording medium with an excellent degree of orientation and fewer protrusions on the surface.

To achieve this objective, the method for producing a magnetic recording medium of the present invention includes storing magnetic powder, a binder, and a cross-wire ball in a pot, and rotating or vibrating the pot to disperse the magnetic powder in the binder. , in the method for producing a magnetic recording medium in which a magnetic coating material having magnetic powder dispersed in the binder is obtained by removing the cross-conducting balls, the inner wall of the pot is covered with polyamide resin, or the cross-conducting balls are surrounded by polyamide resin around the core material. It is characterized by being composed of a resin-coated ball.

That is, the inventor investigated the collision phenomenon between the inner wall of the pot and the ball and the magnetic powder, and found that the hardness of the inner wall of the pot and the ball affected the finished coating film.

If the inner wall of the pot and the ball are made of metal, the hardness is too low and metal ions are mixed in, and alumina is too hard and has a negative effect on the magnetic powder, so it is necessary to use a material with an appropriate hardness. was also found to be preferable.

The present inventor focused on the fact that resins have this possibility, and after examining various resins, selected a resin that satisfies the condition of not reacting with the thermosetting resin of the binder and the solvent.

Among these selected resins, polyethylene resin is abraded by magnetic powder, and there is a problem that the abrasive material gets mixed into the binder and impairs the smoothness of the coating film, so the present inventor found that polyamide resin is the most preferable. It is something that

The present invention will be explained below based on examples.

FIG. 1 shows a cross-sectional view of an embodiment of a pot used in the manufacturing method of the present invention, in which 1 is a pot base, 2 is a pot lid, and 3
indicates the internal capsule.

The pot used in the ball mill method shown in FIG. 1A consists of a pot base 1 in the form of a bottle and a lid 2 that closes the inlet thereof, and the pot base 1 and the lid 2 are made of stainless steel.

The inner walls of the pot base 1 and lid 2 are coated with an inner coating 3 made of polyamide resin.

Further, as shown in FIG. 1, the bottle-shaped pot base 4 and lid 5 may be made of polyamide resin.

In the normal ball mill method, balls are introduced, and then binder and magnetic powder are introduced from the pot entrance.

At this time, it is appropriate that the mixture of the binder, magnetic powder, and balls be about 7 times higher than the height of the pot.

In the ball mill method, the pot is rotated or vibrated from side to side to stir the mixture.

FIG. 2 shows a cross-sectional view of one embodiment of the ball used in the manufacturing method of the present invention, where 4 represents the core material and 5 represents the outer coating.

The core material 4 is used to obtain the weight of the ball, and can be made of either metal or non-metal material, but is preferably made of non-magnetic material.

For example, as the core material 4, stainless steel, steel,
Metals such as stainless steel or sintered oxides such as alumina and zirconia are preferable.

An outer coating 5 is provided around the core material 4, and the outer coating 5 is made of polyamide resin.

If the weight of one ball is less than 5 g, the dispersibility of the magnetic powder will be insufficient, and if it is more than 25 g, the stress applied to the magnetic powder will be too strong.

Therefore, the weight of one ball is preferably 5 g or more and less than 259 g.

Further, the size of the ball is preferably 5 mm or more and less than 25 mm in diameter from the viewpoint of dispersibility of the magnetic powder.

The polyamide resin used for these is based on the following molecular structure.

Polyamides containing heterocycles such as aliphatic and aromatic rings such as hexane rings, pyridine nuclei, piperazine nuclei, and vanzimidazole rings are also effective, and have hydroxyl groups and carboxyl groups in the side chains, and fluorine, phosphorus, and Polyamides containing silicon are also effective.

Next, examples of the present invention will be described.

γFe2O3 was used as the magnetic powder, acrylic epoxy resin with thinner as a solvent was used as the binder, and the following five combinations of balls and pots were used.

As the polyamide resin, Monomaron (trade name), which is a polyamide-based nylon resin, was used.

The capacity of each pot was 107, and the volume ratio of the binder containing γFe2O3 to the balls was 1:2.

Additionally, the mixture of balls and binder containing rFe2O3 was configured to occupy half the volume of the pot.

The configuration of the polyamide resin pot shown in Figure 1 was used.

In this state, the mixture was stirred by a ball mill method. The ball milling conditions were a rotation speed of 25 rpm and a ball milling time of 50 hours.

After ball milling, the balls were removed, and the obtained magnetic coating material was applied to an alumina substrate to a thickness of about 1.2 μm using a spin cord method, and then the surface was polished with a tapered finish.

When the surface of the magnetic recording medium obtained from each sample was measured using a surface roughness meter, the surface distribution was as shown in FIG. 3.

In FIGS. 3a, b, c, d, and e, the horizontal axis indicates the position of the medium, and the vertical axis indicates the height of the surface.

As shown in Figure 3a, the surface distribution of sample 1 is extremely 0.
There are many protrusions with a height of 25μ, and the surface distribution according to sample 2 is the third
As shown in the figure, the height of the protrusions is low and the number of protrusions is also small.

The surface distribution of sample 3 has almost no protrusions as shown in FIG. 3C, and the surface distribution of sample 4 has no protrusions as shown in FIG. 3d.

Further, the surface distribution of sample 5 had many protrusions as shown in Figure 3e, and as a result of microscopic observation, many polyethylene abrasions were observed within the coating film.

Such protrusions affect the head, especially in the head contact start/stop mechanism of the disk, and it is desirable that there be no protrusions.

Therefore, it was found that when polyamide resin was used for one or both of the pot and the ball as in Samples 2, 3, and 4, the protrusions were reduced.

Furthermore, when the squareness ratio (Br/Bs) of the coating film of sample 1 was measured after applying magnetic field orientation to the coating film obtained for each sample, the coating film of sample 1 was 0.7.
6. The coating film of sample 2 is 0.81, and the coating film of sample 3 is 0.85.
The coating film of sample 4 was 0.90, and it was found that the squareness ratio was also improved by using the polyamide resin.

Further, as another example, a coating film was formed under the same conditions using a pot having the structure as shown in FIG. 1a, and the same results as Samples 2 and 4 were obtained.

It has also been found that the thickness of the polyamide resin coating of the ball and the material of the core material of the ball do not significantly affect the above-mentioned properties.

From the above, the present invention has the effect that by using a polyamide resin for the inner wall of the pot or the ball, a coating film with fewer protrusions and an improved squareness ratio can be obtained, and in particular, a polyamide-based nylon resin having elasticity is suitable.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an example of a pot used in the manufacturing method of the present invention, Figure 2 is a cross-sectional view of an example of a ball used in the manufacturing method of the present invention, and Figure 3 is a distribution map of the coating surface roughness of each sample. In the figure, 1 and 4 are the pot base, 2 and 5 are the lid,
3 indicates the inner coat, 6 indicates the heartwood, and 7 indicates the outer coat.

Claims (1)

[Scope of Claims] 1. Magnetic powder, binder, and mixing balls are placed in a pot, the pot is rotated or vibrated to disperse the magnetic powder in the binder, and the kneading balls are removed and mixed in the binder. In the method for producing a magnetic recording medium for obtaining a magnetic paint having magnetic powder dispersed in A method of manufacturing a magnetic recording medium, characterized in that: 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the polyamide resin is a polyamide-based nylon resin.