JPH0350330B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary of the Invention] After applying a magnetic paint to a non-magnetic substrate, pre-baking and post-baking are performed. By performing this within the range of +10% ±10% from the peak of the chevron characteristic curve of solvent resistance for baking conditions such as baking temperature and time, it is possible to prevent the durability of the media from decreasing even if the characteristics of the magnetic paint change. prevent it from happening.

[Industrial application field]

The present invention relates to a method for manufacturing a magnetic recording medium in a magnetic disk device used as an auxiliary storage device in an information processing system, and in particular a method for manufacturing a magnetic recording medium for a magnetic recording/reproducing device using a CSS type floating magnetic head. Regarding.

[Conventional technology]

CSS (contact start
In a stop-type magnetic recording/reproducing device, the floating magnetic head comes into contact with the medium and slides when the rotation of the medium starts and ends. As a result, the surface of the medium that comes into sliding contact with the magnetic head is worn, and abrasion powder is scattered over the entire surface of the medium, causing head crash.

In order to prevent such wear during sliding, a lubricant has been applied to the surface of the medium to improve the sliding of the magnetic head slider.

However, if lubricant is applied, the magnetic head slider will stick to the medium surface due to the lubricant, and when the medium starts rotating, there is a risk of damaging the gimbal, which is the means for supporting the magnetic head, or causing head crash. This sticking occurs because a large amount of lubricant is present on the medium surface, and will not occur if a suitable amount of lubricant is present on the medium surface. Therefore, it is effective to form countless voids on the surface of the medium and impregnate the lubricant therein so that the lubricant oozes out onto the surface little by little.

The impregnating properties and durability of such lubricants are
It depends on the characteristics of the magnetic paint and the processing conditions after applying the magnetic paint to the substrate.

The medium is manufactured by applying a magnetic paint in which ferromagnetic powder such as γ-Fe ₂ O ₃ is dispersed in a polymeric binder onto a non-magnetic substrate such as aluminum, and then baking it. FIG. 4 is a diagram showing a conventional method for manufacturing a medium in the order of steps. First, in step 1, magnetic powder such as γ-Fe ₂ O ₃ , resin, phenol, solvent, etc. are kneaded for about 24 hours, and then in step 2, solvent, resin, acrylic, melamine, etc. are added and kneaded again for about 24 hours. Knead. In step 3, the solution is further diluted with a solvent, and then subjected to centrifugal coating in step 4.

In this way, magnetic paint is made by combining acicular magnetic powder such as γ-Fe ₂ O ₃ and a polymer binder such as phenol, mainly epoxy, melamine, or acrylic, in a solvent such as xylene, toluene, or cellosolve. Dispersed materials are used. To disperse this magnetic paint, kneading is generally carried out using a ball mill or a 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.

In step 4, while the non-magnetic substrate is being rotated at high speed, magnetic paint is sprayed from a nozzle onto a position close to the center of the substrate. Then, the sprayed magnetic paint spreads around the outer circumference of the substrate due to centrifugal force, and the magnetic paint is spin-coated on both the front and back sides of the substrate. Since the magnetic paint is diluted with a volatile solvent, the magnetic paint film begins to dry as soon as it is applied.

Next, in step 5, a prebaking process using hot air is performed.
Then, in a polishing step 6, the surface of the magnetic coating film is polished, and in a post-baking step 7, the magnetic coating film is baked again with hot air, and then in a burnishing step 8, it is burnished for a final finish. Finally, in a veneer test step 9, a veneer test is performed for each medium to check whether there are any defects in the medium.

Pre-baking and post-baking are carried out by putting a large number of media into a baking furnace at the same time and using hot air.However, a sufficient crosslinking temperature cannot be obtained, the baking effect is insufficient, and the hardness of the magnetic coating film is low. The surface becomes rough or scratched during polishing or burnishing. Also, when baking with hot air, it takes about 1 hour for the temperature inside the furnace to rise to the baking temperature, 30 minutes for baking time, and about 1 hour for the temperature to cool down to room temperature. In this way, it takes a long time to raise the temperature to the baking temperature, and the baking time is also long, so the synthetic resin that is the binder deteriorates before the magnetic paint crosslinks, so the magnetic coating film after baking deteriorates. It is thought that sufficient strength cannot be obtained. On the other hand, as shown in Figure 6, if pre-baking and post-baking are performed with far infrared rays instead of baking with hot air, a medium with high magnetic coating strength and sufficient lubricant impregnation can be produced. be able to. This makes it possible to bake in an extremely short period of time, and the crosslinking reaction of the synthetic resin that is the binder for the magnetic powder proceeds in a short period of time, so there is no time for the synthetic resin to deteriorate, resulting in extremely high strength. A magnetic coating is obtained.

[Problem that the invention seeks to solve]

By the way, the viscosity of the magnetic paint, the drying conditions of the solvent,
Subtle control methods, such as the degree of dispersion between solvent, resin, and magnetic powder, greatly affect the film quality of magnetic coatings. Furthermore, the dispersion of the solvent and the resin or magnetic powder is also affected by seasonal changes in temperature and humidity (atmosphere, surface temperature, cooling water temperature, etc.). Therefore, it is extremely difficult to maintain a homogeneous magnetic coating at all times, but if there are variations in film quality from lot to lot, there will be variations in durability such as the strength and weather resistance of the film surface. Therefore, efforts are being made to maintain the atmosphere and environment as constant as possible, but this is too costly and it is nearly impossible to maintain constant dispersion conditions.

The technical problem of the present invention is to solve these problems in the conventional method of manufacturing magnetic disk media,
The object of the present invention is to realize a manufacturing method that is not affected by variations in the degree of dispersion of magnetic paint.

[Means for solving problems]

The technical means of the present invention is to apply post-baking when manufacturing a magnetic disk medium by applying a magnetic paint to a non-magnetic substrate and performing pre-baking, then surface treatment and then post-baking. By managing the conditions of
Measures are taken to maintain the quality of the media. That is, when performing the post-baking treatment, the solvent resistance with respect to the post-baking temperature was evaluated, and it was found that the solvent resistance characteristic was a chevron-shaped characteristic curve a with respect to the post-baking temperature. On the other hand, the hardness characteristic b of the medium film surface shows a tendency to gradually increase as the temperature of post-baking increases.
Therefore, +10% ±10 from the peak p of the Yamagata characteristic curve.
%, solvent resistance and mechanical strength can be satisfied. Furthermore, since the solvent resistance exhibits a chevron characteristic with respect to the baking time, the baking time is also set in a region slightly past the peak value of the chevron characteristic curve.

[Effect] When we evaluated the solvent resistance against temperature during post-baking treatment, we found that up to a certain temperature,
Solvent resistance improves depending on the post-baking temperature, but when that temperature is exceeded, solvent resistance gradually decreases.
By evaluating the solvent resistance, it is possible to know the weather resistance of the magnetic film, general mechanical properties such as impact and bending, and the degree of adhesion of the magnetic film to the substrate. On the other hand, the mechanical hardness characteristics of the media film surface tend to gradually increase as the post-baking temperature increases, as shown by curve b. Therefore, from the peak p of the Yamagata characteristic curve, +
By performing post-baking in a temperature range of 10%±10% w, solvent resistance and mechanical hardness can be satisfied.

Furthermore, when the post-baking temperature was kept constant and the solvent resistance was evaluated against the post-baking time, it was found that the sample had a chevron-shaped characteristic curve, similar to the case of the solvent resistance characteristic against the post-baking temperature. That is, until a certain time,
Solvent resistance improves as the post-baking time increases, but once that time is exceeded, solvent resistance gradually decreases.
The hardness characteristics of the media film surface also show a tendency to gradually increase as time elapses during post-baking. Therefore, by performing the post-baking at a temperature that is slightly higher than the peak of the chevron-shaped characteristic curve for the post-baking time, both solvent resistance and mechanical hardness can be satisfied.

〔Example〕

Next, examples will be used to explain how the method for manufacturing a magnetic disk medium according to the present invention is actually implemented.

Figure 2 shows the measurement results of the durability characteristics against the post-baking temperature when baking was carried out in a hot air oven, where a represents the solvent resistance and b represents the continuous drag strength representing the mechanical hardness of the film surface. are shown respectively. The horizontal axis is the post-baking temperature, and the processing time is 30 minutes.

Solvent resistance was evaluated by impregnating a cotton swab with MEK (methyl ethyl ketone) and applying lubricant to the inner, center, outer, and
In the area between 10 mm in the radial direction per circumference,
Rub the cotton swab back and forth at a 20 degree angle. The number of durability until the coating film peeled off is expressed on the vertical axis. This MEK test allows evaluation of weather resistance, adhesion of the coating film to the substrate, and general mechanical strength.

The continuous drag strength test for evaluating the mechanical hardness of the film surface was performed when the outer circumferential speed of the media disk after lubricant application was at its maximum (128 mm radius disk, 3600 rpm).
Next, turn the alumina slider in the opposite direction so that it does not float up, and slide it. The vertical axis represents the durability time (minutes) until the membrane surface is damaged. Note that you can also use Safaya as the slider for evaluation. In addition, 1 g is applied to a stylus with a diameter of several μm.
It is also possible to evaluate the mechanical hardness of the film by moving it under a certain amount of load and looking at the depth of the scratches at that time.

As shown by curve a, the solvent resistance peaks at about 270° C. in the example and exhibits chevron-shaped characteristics. Further, the continuous drag strength gradually improves as the temperature rises, as shown by curve b.
This is due to excessive baking, which causes deterioration.
This is caused by the thinner and shallower scratches on the membrane during head crushing. Therefore, in order to satisfy both solvent resistance and continuous drag strength, the temperature should be slightly over the peak p of the mountain-shaped characteristic curve of solvent resistance.
Post-baking is ideal. In reality, it is impossible to maintain the ideal temperature all the time, so it is effective to perform post-baking in the temperature range wt of peak temperature +10°C±5°C.

When post-baking is performed with far infrared rays, the baking time is shorter than that of hot air baking, usually less than 20 minutes, but the characteristics of solvent resistance and continuous drag strength with respect to baking temperature tend to be the same as shown in Figure 2. It was confirmed that

FIG. 3 shows an example of post-printing using far infrared rays, and the horizontal axis indicates the printing time (minutes). As in the case of FIG. 2, curve a shows the solvent resistance property, and curve b shows the continuous drag strength. Although the temperature characteristics shown in FIG. 2 are gentler, the solvent resistance shows a chevron-shaped characteristic, and the continuous drag strength also improves with the elapse of baking time.

Therefore, in this case as well, the optimum condition is approximately several minutes (Wm) centered on the time when the peak p of the mountain-shaped characteristic curve of solvent resistance is slightly exceeded, as shown in the figure. When post-baking with hot air,
Although the treatment time is longer, the trends in solvent resistance and continuous drag strength with respect to treatment time are the same.

For both baking temperature and baking time, the commonly optimal baking conditions are approximately +10% ± 10% from the peak p of the chevron characteristic curve of solvent resistance against baking temperature and baking time. It is.

〔Effect of the invention〕

As described above, according to the present invention, by maintaining the optimum conditions for the post-baking treatment, variations in durability caused by variations in the degree of dispersion of the magnetic paint can be eliminated. Further, since the post-baking conditions can be maintained constant regardless of the season or environment, it is easy to maintain the optimum processing conditions.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram explaining the basic principle of the method for manufacturing a magnetic disk medium according to the present invention, FIG.
The figures show an example of the method for manufacturing magnetic disk media according to the present invention. Figure 2 shows the durability against temperature when post-baking is performed in a hot air oven, and Figure 3 shows the durability against temperature when post-baking is performed using far infrared rays. Figure 4 is a diagram showing the durability against baking time when baking is performed. Figure 4 is a diagram showing the process order of a conventional method for manufacturing magnetic disk media using a hot air oven. Figure 5 is a diagram showing the manufacturing method of magnetic disk media using conventional far infrared rays. It is a figure showing a manufacturing method in process order. In the figure, 1 and 2 are the kneading process, 3 is the dilution process, 4 is the centrifugal coating process, 5 is the pre-baking process, 6 is the polishing process, 7 is the post-baking process, a is the solvent resistance curve, and b is the continuous drag strength. The curves are shown respectively.

Claims (1)

[Scope of Claims] 1 Post-baking treatment when manufacturing a magnetic disk medium by applying a magnetic paint to a non-magnetic substrate and performing pre-baking, surface treatment, and then post-baking. A method for producing a magnetic recording medium, characterized in that the process is carried out within a range w of +10%±10% from a peak p of a chevron-shaped characteristic curve a of solvent resistance with respect to baking conditions such as post-baking temperature and time.