JPH0258688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium, and more particularly to a method of manufacturing a magnetic recording medium that improves its durability and homogeneity.

(b) Background of the technology Recently, in order to improve the magnetic recording density, a method has been developed to reduce the flying height of the magnetic head by using the magnetic head as close as possible to the magnetic recording medium, and also to reduce the flying height of the magnetic head when starting and stopping the magnetic disk. The so-called contact, start, stop (CSS) method, in which the recording medium and the recording medium come into contact with each other, has come into use. In the magnetic recording medium used in this type of system, since the magnetic head slides directly on the magnetic recording medium, the recording medium is easily damaged, so there is a strong demand for durability of the medium.

(c) Prior art and problems Conventionally, magnetic recording media such as magnetic disks are made by kneading magnetic powder made of r-Fe ₂ O ₃ and a binder made by dissolving thermosetting resin such as epoxy resin in an organic solvent. A magnetic paint made of aluminum is applied uniformly to the desired film thickness on a non-magnetic substrate made of an aluminum (Al) alloy by a spin coating method using a spinner or the like, and then the binder is hardened in a firing furnace. After the firing process, the specified surface roughness,
It is manufactured by performing surface processing such as polishing to obtain the desired film thickness.

However, there is a problem in that the durability of magnetic recording media formed by such manufacturing methods is not necessarily sufficient to meet the ever-increasing demand for improved durability.

As a result of various investigations into magnetic recording media formed in this way, the inventors of the present invention found that even if the coating films for magnetic recording media were manufactured using the same magnetic paint and firing conditions such as firing temperature and time, After firing the coating film, when processing the surface of the coating film through a process such as polishing,
The results showed that when the machining allowance was increased, the durability decreased, and when the machining allowance was small, the durability was good. The reason for this is that the hardening reaction of the binder takes place sufficiently in the areas near the surface of the coating film for magnetic recording media after firing, but as it reaches the interior of the coating film, the curing reaction becomes insufficient. it is conceivable that. Therefore, it has been found that when the surface layer of the coating film is removed by surface polishing or the like, the inner layer of the coating film is exposed and the durability is reduced. In other words, it has been found that the durability of the magnetic recording medium varies depending on the variation in the machining allowance during surface polishing after firing the coating film.

(d) Purpose of the Invention The present invention was made in view of the above-mentioned knowledge, and an object of the present invention is to provide a method for producing a magnetic recording medium that has good durability and is homogeneous. It is.

(e) Structure of the Invention In order to achieve the above object, the method for manufacturing a magnetic recording medium of the present invention involves coating a non-magnetic substrate with a magnetic paint made by kneading magnetic powder and a thermosetting resin to form a magnetic coating film. After formation, the entire surface of the magnetic coating is heated and baked to harden the entire surface of the magnetic coating, the magnetic coating is polished and washed, and then the entire surface of the magnetic coating is heated and baked again to cure the entire surface of the magnetic coating. This method is characterized by including a step of curing the exposed surface of the magnetic coating film.

(f) Embodiment of the Invention An embodiment of the present invention will be described in detail below with reference to the drawings. As mentioned above, magnetic powder made of γ-Fe ₂ O ₃ , a binder made by dissolving epoxy resin etc. in an organic solvent, and fine powder made of alumina (Al ₂ O ₃ ) are filled in a ball mill etc. and then kneaded to form a magnetic paint. Form. Thereafter, the magnetic coating material is uniformly spin-coated onto a non-magnetic disc made of aluminum alloy or the like using a spinner or the like. Thereafter, the substrate is fired for the first time using a hot air firing furnace or the like. This firing operation is carried out to such an extent that the entire surface of the magnetic coating is heated and baked to harden the magnetic coating and the components of the thermosetting resin constituting the binder are cured. Next, the heated and fired coating film is ground or polished on a polishing plate using a polishing powder such as alumina, so that the surface of the coating film has a predetermined surface roughness and a predetermined film thickness. do. Thereafter, the surface of the substrate is washed with water or a solvent such as isopropyl alcohol. In the conventional manufacturing method for magnetic recording media, after completing this cleaning process, a levitation test, a magnetic property test, a magnetic defect test, etc. The point is that a second firing step is further added to the method. That is, a step is added in which the magnetic recording medium that has undergone the cleaning step is heated again using a hot air firing furnace or the like. In this way, the surface layer with good durability is removed in the coating film surface processing step after the first firing step, and the portion of the surface of the magnetic recording medium where the parts with weak durability are exposed becomes the second layer. It hardens again during the firing process, improving durability.

In addition to the above embodiments, a cleaning process for removing dirt from the surface of the magnetic recording medium may be added after the second firing process described above, or a magnetic recording medium formed by the second firing process may be added. This patent also includes polishing the surface layer, which has good durability, to the extent that it becomes light and smooth.

Using a winchiester type test head with a slightly stronger spring pressure than in normal use, the surface of the magnetic recording medium thus formed was tested.
contact. start. The durability of the recording medium was evaluated by conducting a stop (CCS) test and visually inspecting the number of times CCS was repeated until a scratch appeared on the medium. When conducting the above test, an appropriate amount of a fluorinated lubricant (trade name: KRYTOX, manufactured by DuPont) was applied to the surface of the recording medium.
The results of the tests conducted in this manner are shown in FIGS. 1 to 3. In the figure, Figure 1 is a diagram comparing the durability test results of magnetic recording media formed by the conventional manufacturing method and the manufacturing method of the present invention, and Figure 2 is a diagram comparing the durability test results of magnetic recording media formed by the conventional manufacturing method. This is a diagram showing the durability test results when the second firing process of the invention is added. Figure 3 shows the durability test results when the medium subjected to the second firing process of the invention is further subjected to surface processing such as polishing. It is a figure which shows the test result of the durability of this medium. First of all
The figure shows a comparison of the number of CSS durability between magnetic recording media formed by the conventional manufacturing method and magnetic recording media formed by the manufacturing method of the present invention. Bar graphs 1, 2, and 3 with diagonal lines are the ones manufactured by the present invention. Bar graphs 4, 5, 6, 7, 8, and 9 without diagonal lines indicate magnetic recording media formed by the conventional method. In the figure, the vertical axis shows the number of samples,
The horizontal axis shows the number of CSS operations until a scratch occurs. still
CSS counts are rounded off if they are less than 5 digits. As shown in the figure, the magnetic recording medium formed by the method of the present invention has a peak at about 10,000 times of CSS, and has 2.5 times as many CSS times as the magnetic recording medium formed by the conventional method. It can be seen that the material is durable and has little variation. Moreover, the bar graphs 11, 12, 13, and 14 in FIG. 2 are the bar graphs 4, 5, and 6 without diagonal lines in FIG.
This graph shows the CSS durability when magnetic recording media Nos. 7, 8, and 9 are subjected to secondary firing according to the method of the present invention. They have nearly identical profiles, indicating that the method of the invention is reproducible. Also, bar graphs 21, 22, 23, 2 in Figure 3
4 and 25, the surfaces of magnetic recording media shown in bar graphs 1, 2, and 3 formed by the method of the present invention shown in FIG. 1 were polished by about 0.1 to 0.2 μm, and then the magnetic recording media were subjected to a CSS test. As shown in the diagram, the number of CSS operations almost matches the bar graphs 4, 5, 6, 7, 8, and 9 formed by the conventional method in FIG. 1. In other words, if the fired processed layer on the surface is polished after performing the second firing of the present invention, the durability will not be improved, and it will be necessary to lightly polish the surface to remove dirt.

In the above embodiments, as a magnetic recording medium,
I explained about magnetic disks, but magnetic tape,
The method of the present invention can also be applied to flexible disks and the like.

(g) Effects of the Invention As described above, the method of the present invention has the advantage that a magnetic recording medium with excellent durability can be obtained, and the method of the present invention is extremely effective when applied to the construction of magnetic disks, etc. It's large.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a comparison of the durability test results of magnetic recording media formed by the conventional manufacturing method and the manufacturing method of the present invention, and FIG. This is a diagram showing the test results of the durability of the recording medium when the second firing process is performed.
The figure shows the results of a durability test when a recording medium subjected to the second firing step of the present invention was further surface-treated. In the figure, 1, 2, 3 are bar graphs showing the durability of recording media formed by the method of the present invention, 4, 5,
6, 7, 8, 9 are bar graphs showing the durability of recording media formed by conventional methods, 11, 12, 13, 1
4 is a bar graph showing the durability of a recording medium formed by the conventional method when subjected to a secondary firing process, and 21, 22, 23, 24, and 25 are bar graphs showing the durability of the recording medium formed by the method of the present invention. It is a bar graph showing the durability of a recording medium when the surface layer is polished.

Claims (1)

[Claims] 1. A magnetic paint made by kneading magnetic powder and a thermosetting resin was applied to a non-magnetic substrate to form a magnetic coating, and then the entire surface of the magnetic coating was heated and baked to harden the entire surface of the magnetic coating. After that, the magnetic coating film is polished and washed, and then the entire surface of the magnetic coating film is heated and fired again to harden the surface of the magnetic coating film exposed by the polishing. Production method.