JP2511702B2 - Method of manufacturing magnetic disk medium - Google Patents

Description

DETAILED DESCRIPTION [Outline] A method of manufacturing a magnetic disk medium (manufactured by applying a magnetic coating material to a non-magnetic substrate such as aluminum) of a magnetic disk device used as an external storage device in an information processing system. In order to realize a manufacturing method that has sufficient strength, can strengthen the magnetic coating film by adding a small amount, and can add a strengthening agent with a fine particle size, a material containing SiC can be sintered. The binder resin is kneaded with the medium to mix and the SiC fine powder is abraded and mixed, and then kneaded and dispersed with the magnetic powder and applied to a non-magnetic substrate to manufacture a magnetic disk medium.

[Industrial applications]

A magnetic disk medium of a magnetic disk device used as an external storage device in an information processing system is manufactured by applying a magnetic paint to a non-magnetic substrate such as aluminum. The present invention relates to a method for manufacturing such a magnetic disk medium.

[Conventional technology]

FIG. 11 is a view showing a magnetic disk medium, (a) is a perspective view and (b) is a sectional view. The magnetic disk medium 1 has a mounting hole 2 formed in the center thereof.
Then, the information is recorded / reproduced by the magnetic head while being mounted on the spindle of the magnetic disk device and rotating at a high speed.

That is, as shown in FIG. 2B, thin magnetic coatings 4 and 4 of 1 μm or less are formed on both front and back surfaces of the non-magnetic substrate 3 such as aluminum, and information is recorded on the magnetic coatings 4 and 4.

The magnetic coatings 4 and 4 are magnetic coatings prepared by dispersing ferromagnetic powder such as γ-Fe ₂ O _{3 in} a polymer binder such as epoxy, phenol and melamine and a solvent such as xylene, toluene and cellosolve. Is coated on a non-magnetic substrate 3 such as aluminum.

In such a coating type magnetic disk medium, in order to prevent the magnetic film from being destroyed when it collides with the magnetic head during high speed rotation, it is common to mix alumina powder into the coating film as a reinforcing agent. The most effective particle size is the same as the film thickness.

As a mixing method, a paint disperser such as a ball mill is used, and when the magnetic paint is kneaded into the resin serving as the binder, it is naturally mixed by abrasion from the dispersion media (balls), or a particle having an arbitrary particle size is previously prepared. Is added to the magnetic paint.

[Problems to be Solved by the Invention]

However, in recent years, as the recording density has increased, the magnetic film thickness has been reduced to 0.5 μm or less, and the flying height of the magnetic head has become extremely low.
There is a demand for an extremely sharp distribution with a concentration of 0.5 μm.

However, as shown in FIG. 3, the abrasion powder of the alumina dispersion medium has a wide distribution of 0.2 to 2.0 μm and has a large variation, which makes practical application difficult. On the other hand, there is no additive powder having a sharp particle size distribution other than high-purity alumina derived and synthesized from organic ammonium and aluminum sulfate.

However, since this high-purity alumina is a synthetic product and has a weak crystal structure and inferior mechanical strength, the addition and mixing ratio must be 1.5 to 2.0 times that of the conventional product. As a result, the density of the magnetic powder is lowered, the S / N ratio is lowered, and the like, which has been one of the obstacles for increasing the density of the coating medium.

The technical problem of the present invention is to solve the above problems in the conventional method for producing a magnetic disk medium, to have a sufficient strength, to strengthen the magnetic coating film by adding a small amount, and to strengthen the magnetic particles with a fine particle size. And to realize a manufacturing method in which the magnetic powder can be uniformly kneaded and dispersed to be applied.

[Means for solving the problem]

In the present invention, a dispersion medium is prepared by sintering a material containing SiC, and the SiC resin is used to knead the binder resin. As a result, the abrasion powder of SiC powder is mixed into the binder resin.

Next, the resin thus mixed with the SiC wear powder is put together with the magnetic powder in a ball mill having a blade for preventing the retention of dispersed media made of a chemical resistant resin on the inner wall of the drum, and kneaded and dispersed with the magnetic powder. , Create magnetic paint and apply it to non-magnetic substrate.

[Action]

SiC with sufficient hardness, fine particle size distribution and sharpness, and low price
Focused on (silicon carbide). SiC has a new Mohs hardness of 14 and the second highest hardness after diamond, but unlike the above-mentioned alumina, there is no method of generating crystals from the molecular state, and it is difficult to obtain a powder having a particle size distribution that can be added in advance.

Therefore, Si is formed into a spherical or pellet shape with a diameter of 3 to 10 mm.
C is sintered into media (balls), filled in a ball mill, and kneaded with a binder for magnetic paint for 100 to 200 hours. As a result, SiC becomes minute wear powder and is mixed in the binder. Thereafter, the magnetic powder and the binder are kneaded to prepare a magnetic coating material, and the magnetic coating material is applied to the non-magnetic substrate to manufacture a magnetic disk medium.

Alumina can be used in the same method, but the crystal size is more sticky than that of SiC, so the particle size that wears off is not constant. For SiC, the particle size can be controlled by adjusting the collision degree by adjusting the number of revolutions of the mill, the diameter of the sintered ball, the viscosity of the binder to be kneaded, and the mixing amount is proportional to the kneading time. However, when trying to achieve the same purpose when kneading with magnetic powder, the time required to mix SiC is several times longer than the appropriate time required to disperse magnetic powder, resulting in breakage of magnetic powder due to overdispersion. The point is to let me do it.

〔Example〕

Next, practical examples of how the method for manufacturing a magnetic disk medium according to the present invention is embodied will be described. Second
The figure is a cross-sectional view showing a state in which SiC abrasion powder is mixed in a binder resin by a ball mill. Reference numeral 5 is a ball mill drum, and the inner peripheral wall 6 is lined with a chemical resistant resin. A resin 7 serving as a binder and a medium 8 obtained by sintering SiC are placed in the drum 5, and the abrasion powder of the SiC medium 8 is mixed in the binder 7 by rotating the drum 5.

Sintered SiC media 8 was sintered in a spherical shape having a diameter of 5 mm, and a sinter SiC media 8 was used after passing a tentative standard with a wear reduction rate of 0.03% or less after 50 hours of the abrasion test using water.

Then, the mixture was kneaded for 120 hours under the conditions shown in Table 1, taken out from the mill, subjected to microfiltration in order to remove coarse particles and foreign matters, and then kneaded and dispersed with the magnetic powder to prepare a magnetic paint. This was applied on an aluminum alloy substrate to manufacture a magnetic disk medium.

The particle size distribution of the abrasion powder obtained here is shown by X in FIG. For comparison, the particle size distribution of wear powder of alumina sintered balls under the same conditions is shown by ●. As indicated by the cross,
The particle size of wear particles of SiC is fairly sharp, centered around 0.4 μm, as shown by the ● mark, the wear particles of alumina have a wide distribution, and a maximum particle size of 2 μm was also found. .

As is clear from this, the SiC abrasion powder is concentrated in 0.4 μm and is extremely suitable as a thin film for high density recording having a magnetic film thickness of 0.5 μm or less.

FIG. 4 is a diagram showing the strength of various reinforcing agents, where the vertical axis is the sliding resistance time and the horizontal axis is the reinforcing agent mixing ratio (%) with respect to the magnetic powder. × mark indicates abrasion powder by the SiC media according to the present invention, ○
The mark indicates wear powder from alumina media, and the mark indicates addition of alumina powder. As is clear from the test results,
Sliding resistance time is longer when SiC wear powder is mixed than when alumina wear powder is mixed, and half the amount of SiC wear powder is required to obtain the same sliding resistance time as when alumina wear powder is mixed. It only needs to be mixed. Therefore, the amount of the reinforcing agent can be suppressed to half or less, the S / N ratio is improved, and a highly reliable magnetic disk medium can be obtained. When high-purity alumina powder is added, the sliding resistance time becomes worse and the mixing ratio must be further increased, so the S / N ratio becomes worse.

FIG. 5 is a diagram showing the surface roughness of the magnetic coating film of the magnetic disk medium. (A) shows the case where the magnetic paint containing SiC wear powder according to the present invention is applied, and (b) shows the alumina wear powder. This is the case when the magnetic coating material is applied. Si shown in (a)
When C wear powder is mixed, the height of protrusions on the surface of the magnetic coating can be reduced by about 0.05 to 0.07 μm compared to the case where alumina wear powder is mixed as shown in (b). It was possible to improve the property. Similarly, the addition of high-purity alumina can suppress the surface roughness, but as shown in FIG.
It is necessary to add about 3 times as much as C wear powder, and the S / N ratio is further reduced.

[Example of ball mill]

Next, in order to knead and disperse the binder resin mixed with the SiC wear powder and the magnetic powder with a ball mill, as shown in FIG.
It is effective to provide the blade 9 on the inner peripheral wall 6 of the drum 5.

In order to produce a magnetic coating material for a coating type magnetic disk medium, a method of dispersing ferromagnetic particles, that is, magnetic powder in a binder using a dispersing machine such as a ball mill or a sand mill is used. The use of a ball mill, which is not efficient because it is necessary to considerably reduce the viscosity in response to the thinning of the film, but which can surely increase the dispersion even at a low viscosity, occupies the majority.

A ball mill puts spherical or roll-shaped ceramics as a dispersion medium in a drum-shaped container, puts materials such as magnetic powder and binder, and rotates the container for a certain period of time to disperse it. Because of the tendency to dislike, the inner wall is lined with resin with high chemical resistance.

On the other hand, media for dispersing magnetic powder are required to have high dispersive power and high wear resistance, and Si-based ceramics are mainly used. However, in order to reduce the wear of the dispersed media in this way, it is necessary to finish the surface of the medium 10 more smoothly. However, if it is too smooth, the medium 10 will be stuck on the inner wall of the ball mill as shown in FIG. It cannot follow up and stays in one place.

The dispersion in the ball mill follows the rotation of the drum 5, and the dispersion medium 10 is lifted to a certain height.
However, this is done when the surface rolls down like an avalanche. It is absolutely necessary for the media to follow the rotation of the mill in order to be carried out efficiently, but to prevent contamination, if the unevenness of the media surface is suppressed as much as possible to make it smooth, it will slip on the inner wall of the drum, As described above, the particles stay in one place, which significantly deteriorates the dispersion efficiency.

As described above, when the movement of the medium becomes poor, in addition to the deterioration of the dispersibility, problems such as the deterioration of the magnetic characteristics due to the partial destruction of the magnetic powder crystal occur.

In order to solve this problem, it is effective to provide the blade 9 for pumping the media on the inner peripheral wall of the drum 5 of the ball mill as described above. The blades are made of a chemically resistant resin and formed in a plate shape, and the dispersion efficiency can be improved by performing a treatment for preventing the retention of the media due to slippage during rotation of the mill.

However, the shape of the vane is one plate and the total length of the mill [L]
It is better to divide it into about 1/8 instead of covering it, and install it by shifting it by about 30 ° as shown in the developed view of FIG. With a single plate, the movement of the media becomes simple, which has the opposite effect. By subdividing into about 1 / 8L, the surface rolls down and the dispersion is sufficiently improved while the media moves in the same complicated way as when the media operates normally (when there is no prevention plate), and the retention of media Loss due to can be prevented.

Next, the dispersion effect of the magnetic powder by the example ball mill will be examined. First, as shown in FIG. 6 and FIG.
A ball mill having blade plates 9 attached at four locations at 90 ° intervals and a width of 1/8 of the ball mill length (L) and shifted by 30 ° to a total of 32 locations was prepared. A chemical resistant resin was used as the material of the blade. The same effect can be obtained with ceramics etc.,
Highly viscous chemical resistant resin is used to prevent wear of both sides due to collision with media as much as possible.

This ball mill was filled with about 50% of the mill volume of Si-based ceramics media and dispersed the magnetic coating material for magnetic disk media. I was able to get a good one.

Improved magnetic properties (due to reduced damage to magnetic powder crystals) (1). Static characteristics of magnetic film: HC680 increased to 720 Oe, 5%
The effect of up was obtained.

(2). Electromagnetic conversion characteristics (reproduction output): As shown in FIG. 9, it increased from 0.70 to 0.82 mV, and an effect of 10 to 15% up was obtained. FIG. 9 shows changes in reproduction output when the write current value is increased and the saturation current value is investigated. As shown by the ● mark, in both cases of 1.5F and 4F, it was confirmed that the regeneration output was higher than in the case of the conventional bladeless mill shown by the X mark.

Bit error reduction (dispersion improvement) (1). Number of errors (60% missing bit slices): The number of errors has dropped significantly from 35 / sheet to 3 / sheet.

(2). Infinite error occurrence slice level: 68% to 80%
Rose to. FIG. 10 shows the investigation of the error number increase state when the bit error slice level is made severe. As indicated by the ● mark, both the extra error and the missing error are higher in error quality, especially the missing error than the case of the conventional bladeless mill shown by the × mark.
It can be confirmed that the rise of errors (depression, chipping) is delayed, and that it is definitely improving.

〔The invention's effect〕

As described above, according to the present invention, in a medium formed by sintering a material containing SiC, by kneading the binder, after the SiC fine powder is abraded and mixed, it is kneaded and dispersed with the magnetic powder to obtain a non-magnetic material. Since the magnetic disk medium is manufactured by applying it to the substrate, the strength of the reinforcing agent is sufficient, and the magnetic coating film can be strengthened by adding a small amount. Further, since the particle size is fine and uniform, it is suitable for a magnetic disk medium for high density recording.

By providing blades on the inner wall of the ball mill to prevent retention of the magnetic powder dispersion medium, the magnetic powder and the above-mentioned binder containing SiC wear powder are effectively kneaded and dispersed, so that information is recorded / reproduced. When the error rate is improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic principle of a method for manufacturing a magnetic disk medium according to the present invention, FIG. 2 is a diagram showing a method for kneading a SiC medium and a binder by a ball mill, and FIG.
Fig. 4 is a diagram showing the particle size distribution of C abrasion powder and alumina abrasion powder, Fig. 4 is a diagram comparing the mixing ratios and strengths of different reinforcing agents, and Fig. 5 is SiC.
The figure which compares the surface roughness of the mixing membrane and the surface roughness of the alumina mixing membrane, Figure 6 is the figure which illustrates the ball mill which possesses the retention blade of the medium, Figure 7 is the figure which shows the conventional ball mill, and Figure 8 Is a diagram exemplifying the arrangement of media retention blades, FIGS. 9 and 10 are diagrams showing experimental results for confirming the effect of media retention blades, and FIG. 11 is a diagram showing the structure of a magnetic disk medium. is there. In the figure, 3 is a non-magnetic substrate, 4 is a magnetic coating film, 5 is a drum, 6 is an inner peripheral wall of the drum, 7 is a binder resin, and 8 is SiC.
A medium, 9 is a blade for preventing retention of the medium, and 10 is a magnetic powder dispersion medium.

Claims (2)

(57) [Claims] 1. A medium obtained by sintering a material containing SiC, kneading a binder resin to wear and mix SiC fine powder, then kneading and dispersing with magnetic powder, and applying it to a non-magnetic substrate. And a method for manufacturing a magnetic disk medium. 2. A binder resin is kneaded with a medium formed by sintering a material containing SiC to mix the SiC fine powder with abrasion to produce a binder resin containing SiC abrasion powder, and the inner wall of the ball mill drum is chemically resistant. A blade for preventing retention of dispersed media made of a conductive resin was provided, and the binder resin containing SiC wear powder, magnetic powder and dispersion media were placed in this drum, and the magnetic powder and binder resin containing SiC wear powder were kneaded and dispersed. Then, a method of manufacturing a magnetic disk medium, which comprises applying the magnetic disk medium to a non-magnetic substrate.