JPH0259524B2 - - Google Patents

Description

[Detailed description of the invention]

[Summary] By using a kneading ball made of zirconium oxide with 6% by weight or less of Ittria added and sintered, and by kneading and dispersing acicular magnetic powder, the amount of wear on the kneading ball can be reduced and the wear amount can be reduced. By miniaturizing the kneading balls, we aim to extend the life of the kneading balls and improve the magnetic properties of the recording medium. [Industrial Application Field] Magnetic disk media of magnetic disk devices used as external storage devices in information processing systems are manufactured by applying magnetic paint to disks made of aluminum or the like. The present invention relates to a method for producing a magnetic coating material for forming a magnetic coating film on such a magnetic disk medium. [Prior Art] FIG. 3 is a diagram showing a magnetic disk medium coated with a magnetic paint produced by the method of the present invention, in which A is a perspective view and B is a sectional view. Magnetic disk medium 1
A mounting hole 2 is drilled in the center, and the disc is attached to the spindle of a magnetic disk device through the mounting hole 2, and information is recorded/reproduced by a magnetic head while rotating at high speed. That is, as shown in FIG. 2, thin magnetic coatings 4, 4 of 1 μm or less are formed on both the front and back surfaces of a non-magnetic substrate 3, such as aluminum, and information is recorded on these magnetic coatings 4, 4. These magnetic coatings 4, 4 are magnetic paints in which ferromagnetic powder such as γ-Fe ₂ O ₃ is dispersed in a polymer binder such as epoxy, phenol, or melamine, and a solvent such as xylene, toluene, or cellosolve. It can be obtained by coating on a non-magnetic substrate 3 such as aluminum. To disperse this magnetic paint, kneading is generally performed using a ball mill or sand mill, and alumina, glass, zirconia, etc. are used as the dispersion medium for these. Glass is commonly used in sand mills because of its low specific gravity. [Problems to be solved by the invention] The important points required of a dispersion medium are specific gravity, wear resistance, and size of abrasion powder.Alumina balls, which are generally used most often, There are drawbacks in terms of durability and size of abrasion powder. In other words, if the alumina balls are kneaded for a long time or at high speeds in order to improve dispersibility, too much abrasion powder will be generated, and when applied to a disc and used as a magnetic disk medium, protrusions of the alumina powder will occur, resulting in bit errors. It can cause sagging and hemorrhoids. Zirconia (zirconium oxide, ZrO ₂ ) balls, which have been used to solve this problem, have a specific gravity of
5.5, alumina (aluminum oxide, Al ₂ O ₃ )
Since it is larger than 3.6, the kneading properties are good, the amount of wear on the kneading balls is small, and the size of the abrasion powder is small. However, recently, recording density has increased and the area per bit has become smaller and smaller. For this reason, the amount and size of abrasion powder generated from kneading balls during the production of magnetic paints has become an even bigger problem, and even zirconia balls are becoming insufficient. The technical problem of the present invention is to further reduce the amount of abrasion powder generated from the kneading balls in order to solve these problems in the conventional magnetic paint manufacturing method and to manufacture a magnetic paint suitable for high-density recording. , and to reduce the size of wear particles. [Means for solving the problem] The technical means of the present invention taken to solve this problem is to mix a polymeric binder, a solvent, and acicular magnetic powder with a kneading ball to create a magnetic paint. When manufacturing, balls containing zirconium oxide as a main component are used as kneading balls. That is, this kneading ball is made by sintering zirconium oxide with the addition of yttria (Y ₂ O ₃ ) as an auxiliary agent, and the proportion of yttria is 6% or less. [Function] According to this technical means, since the amount of zirconium oxide is smaller than that of conventional zirconia balls, the specific gravity is higher than that of alumina balls and somewhat lower than that of conventional zirconia balls. Therefore, the magnetic paint is dispersed smoothly and uniformly, so there is no need to spend a long time dispersing as with conventional alumina balls.The kneading ball itself has excellent abrasion resistance, and it also prevents abrasion powder. The size is also small. As a result, the kneading ball can be used repeatedly, and in particular, the amount of abrasion powder is reduced and the size of the abrasion powder is small, so that bit errors and head crashes of the magnetic disk medium are reduced, and the magnetic properties are also improved. [Example] Next, how the method for producing a magnetic paint according to the present invention is actually implemented will be explained using examples.
FIG. 1 is a manufacturing process diagram in the method of the example. First, the substrate is processed by rough machining and finishing with a diamond tape on an aluminum disk, and then pretreatment such as cleaning is performed. Then, the magnetic paint produced by the method of the present invention is applied by centrifugal force, and an orientation process is performed to align the direction of the magnetic powder using a magnet. An example of manufacturing this magnetic paint will be described in detail later. After magnetic paint coating and orientation treatment, place in a furnace at 270℃
After baking for 6 minutes, polishing with polishing tape and baking again at 270°C for 6 minutes. The magnetic disk medium is then completed by applying lubricant using the dip method, and finally cleaning it by burnishing and then testing it on a single plate. The magnetic paint applied in the coating process was manufactured under the following conditions. Binder: Acrylic, epoxy paint PWC: 55% Magnetic powder: γ-Fe ₂ O ₃ or more materials were kneaded for 48 hours in a 50 ball mill containing 90 kg of balls. Furthermore, what is PWC?
This is the ratio (weight ratio) of magnetic powder to the entire magnetic paint. The balls used at this time were made of zirconium oxide with 6% of ittria (Y ₂ O ₃ ) added, and had a ball size of about 1200
It had a diameter of 5 mm and was sintered at ℃ for one week. The conditions after the magnetic paint application step are as follows. Coating method: Spin coating using centrifugal force Finishing method: Tape polish Substrate used: Aluminum disk finished with diamond tape The thickness of the magnetic coating after finishing the magnetic disk media is as follows: Magnetic disk media with a diameter of 5 inches In the case of , the inner 4i was 0.5±0.05 μm and the outer 4o was 0.6±0.5 μm. The characteristics of the magnetic paint obtained by kneading magnetic powder using the zirconia balls according to the present invention manufactured under these conditions were compared with those obtained by kneading magnetic powder using conventional alumina balls and conventional zirconia balls, respectively. Figure 2 shows a comparison with the characteristics of the magnetic paint we tested. Also, in the same figure,
Curves ●−● indicate alumina balls, △−△ indicate zirconia balls, and ×−× indicate zirconia balls containing ittria. This figure shows the extra pulse characteristics and missing bit characteristics as magnetic characteristics, and the horizontal axis is the slice level (%),
The vertical axis is the number of errors (errors/one side). The measurement magnetic head used was one for 10,000 BPI and 900 TPI. To evaluate the extra pulse characteristics, once information is recorded on the magnetic coating of the magnetic disk medium,
DC erasure is performed by applying a DC magnetic field. Then, all the magnetization in the magnetic coating is aligned in a certain direction, and even when reproduced with a magnetic head, no magnetization is detected in the normal region. However, if there are scratches or protrusions, those ends act as magnetic poles, generating magnetic flux, and extra pulses are detected. Therefore, the smaller the extra pulse, the better. Missing bit characteristics: When information is recorded on a magnetic coating and reproduced by a magnetic head, under normal conditions, an alternating current wave of constant amplitude is detected. However, if there is a defect in the magnetic coating, the output decreases and the amplitude of the detection pulse decreases. Therefore, the larger the value of this missing bit, the better. Such a missing bit check is performed over all bits. In the characteristic diagram of FIG. 2, the curve on the left side shows the extra pulse characteristic, and the curve on the right side shows the missing bit characteristic. Looking at the extra pulse characteristics, compared to alumina balls and conventional zirconia balls, the zirconia balls containing ittriya according to the present invention do not generate errors even when the slice level is reduced to about 15%. Looking at the missing bit characteristics, the slicing level is approximately 79%.
Even when I raised it to a certain level, no error occurred. The magnetic coating film thus produced by the method of the present invention is
With the extra pulse characteristic, no error will be detected even if the slice level is made sufficiently small, and with the missing bit characteristic, no error will be detected even if the slice level is made sufficiently large. This is thought to be due to the fact that the amount of abrasion from the kneading balls is small and the amount of abrasion powder is small. table. 1 shows the amount of wear and life (usable years) when each of the above balls is used, and is compared based on the number of errors with each ball. The No. 1 alumina ball has a wear rate of 10%,
The content of the zirconia balls is 1.5%, and the content of the zirconia balls containing ittria according to the present invention is 0.3%.
Since conventional alumina balls are easily worn out, their usable life is extremely short at 0.3 years. Conventional zirconia balls have a reduced wear rate of 1.5%, which improves their usable life, extending them to two years. However, the amount of wear of the ittria-containing zirconia ball according to the present invention is further reduced, and as a result, the usable life is significantly increased to 9.9 years.

[Table] Next, when using the balls of the present invention, the magnetic powder has good dispersibility, so the rotation speed of the ball mill can be slowed down, so there is less breakage of the acicular magnetic powder, and the magnetic powder has excellent orientation. . That is, during or immediately after applying the magnetic paint, a strong magnetic field is applied to the magnetic paint film to align all the mixed magnetic particles in the same direction. If the magnetic powder remains intact and long without breaking, it will be easier to align in a certain direction, and the magnetic properties when recording/reproducing information will also improve. Ball mills usually have 20
Kneading is carried out at ~30 rpm, but when the ball of the present invention was used, sufficient kneading was possible even at low speed rotation of 10 rpm or less. As a result, the degree of orientation is improved and the squareness ratio
Br/Bs was 0.9, which was an extremely good value. In addition, the S/N was 50 dB, and the surface roughness was 0.02 Ra (no whisker-like projections). [Effect of the invention] As described above, according to the present invention, the main component is zirconium oxide, and the proportion of zirconium oxide is 6.
When the amount is less than % by weight, the amount of wear of the kneading balls is small and the amount of abrasion powder is small, so that the kneading balls have a long life. Therefore, the manufacturing conditions for magnetic paint are stabilized, and variations in properties between lots are eliminated. In addition, magnetic disk media coated with this magnetic paint have excellent magnetic properties because the amount of abrasion powder mixed into the magnetic paint is small, and the abrasion powder mixed into the magnetic paint is small, so there is no risk of causing bit errors or head crashes. Nor. Because of its excellent kneading properties, the speed of the ball mill can be slowed down to prevent breakage of the magnetic powder and further improve magnetic properties.
N etc. are improved.

[Brief explanation of drawings]

Figure 1 is a process diagram of an example of implementing the method for manufacturing magnetic paint according to the present invention, and Figure 2 is a comparison of the magnetic properties of magnetic paint manufactured by the method of the present invention and magnetic paint manufactured by the conventional method. FIG. 3 is a perspective view and a sectional view of a magnetic disk medium coated with magnetic paint. 2 is a mounting hole, 3 is a non-magnetic substrate, and 4 is a magnetic coating film.

Claims (1)

[Scope of Claims] 1. When manufacturing a magnetic paint by kneading a polymer binder, a solvent, and acicular magnetic powder using a kneading ball, Ytturia (Y ₂ O ₃ ) is added to zirconium oxide as a kneading ball. 1. A method for producing a magnetic coating for magnetic recording, characterized in that it is added and sintered, and the proportion of ittria is 6% by weight or less.