JPH03189931A - Manufacture of coating film type - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] A method of manufacturing a magnetic disk in a magnetic disk device used as a file device of an information processing system, particularly a method of manufacturing a coated magnetic disk, without heating and in a short time. The aim is to make it possible to efficiently produce coated magnetic disks with excellent magnetic properties by making the magnetic paint hardenable. In the method for manufacturing a magnetic disk of the coating type, which is coated on a non-magnetic substrate, a magnetic paint containing a multifunctional ultraviolet curable resin, an organic solvent, and magnetic powder is cross-dispersed, and then coated on a non-magnetic substrate. The magnetic paint is cured by irradiating it with ultraviolet light.

[Industrial application field]

The present invention relates to a method of manufacturing a magnetic disk in a magnetic disk device used as a file device of an information processing system, and particularly to a method of manufacturing a coated magnetic disk.

[Conventional technology]

FIG. 2 shows a coated magnetic disk, in which (a) is a perspective view and (b) is a sectional view. The magnetic disk 1 has a mounting hole 2 drilled in the center, and is attached to a 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. It will be done.

That is, as shown in Figure (b), a thin magnetic coating film 4.4 of 1 μm or less is formed on both the front and back surfaces of a non-magnetic substrate 3 such as aluminum, and information is recorded on this magnetic coating film 4.4. .

This magnetic coating 4.4 is usually made by dispersing ferromagnetic powder such as γ-Fez03 in a polymeric 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 or the like and curing it.

FIG. 3 is a diagram showing the manufacturing method of this coated film type magnetic disk in the order of steps. First, the substrate is processed by rough processing and finishing processing using a diamond tape on an aluminum disk, and then pretreatment such as cleaning is performed. Then, the magnetic paint is applied using centrifugal force, and an orientation process is performed to align the direction of the magnetic powder using a magnet. After that, place it in a furnace and heat it for 30 minutes at 200-300°C, then polish it with Borinsh tape to adjust the film thickness, and then heat it again at 200-300°C for 30 minutes. After a minute of baking process. Then apply lubricant and finally clean with burnishing, then
A coated magnetic disk is completed by testing a single plate.

The magnetic paint to be applied is made of a thermosetting resin such as acrylic or epoxy resin, a solvent, and 7-FezO.

It can be obtained by cross-dispersing magnetic powder such as.

After applying this magnetic paint, the temperature is 200-300°C.
By heating and baking at a relatively high temperature, a coated magnetic disk can be obtained.

[Problem to be solved by the invention]

However, heating at such high temperatures deteriorates the magnetic properties of the magnetic powder. FIG. 4 is a diagram showing the temperature dependence of the magnetic properties of magnetic materials. The horizontal axis is the heating temperature, and the vertical axis is the magnetic properties. The solid line (■) is the magnetic iron oxide powder coated with cobalt, and the broken line (■) is the magnetic property of the metal iron powder.

As is clear from this figure, the magnetic properties of both decrease as the heating temperature increases, especially at 150°.
It is noticeable from around C.

However, in the process of manufacturing coated magnetic disks as described above, heat treatment is carried out twice at high temperatures of 200 to 300°C for several tens of minutes, which causes the magnetic material mixed in the magnetic paint to deteriorate. This means that the magnetic properties have significantly deteriorated. As a result, the coercive force, which is one of the magnetic properties, is only about 820 (Oe). FIG. 5 shows the relationship between the coercive force of a magnetic material and the reproduction output, where the horizontal axis is the coercive force and the vertical axis is the reproduction output. As is clear from this figure, as the coercive force increases, the reproduction output when recording/reproducing information with the magnetic head increases. In the case of the conventional coated magnetic disk mentioned above, the coercive force is 820 (Oe).
Since there are limits in the front and back, the reproduction output can only be about 0.7 mV.

As described above, in the conventional method of manufacturing a coated magnetic disk, magnetic properties are sacrificed because a thermosetting resin is used to harden and bake the magnetic paint.

On the other hand, as a magnetic recording material, metal iron powder is promising as a material with higher coercive force, but it is extremely unstable against heat and cannot be applied to coated magnetic disks that use thermosetting resin. .

On the other hand, a method is known in which a curing agent is used and heated at a low temperature for a long time to accelerate the reaction and harden the material, but the drawback is that the life of the magnetic coating is short. Also, although the temperature is low, 1
Since it must be heated to about 0.000°C, the magnetic properties are also deteriorated to some extent.

Furthermore, both when using a curing agent and when using a thermosetting resin, production efficiency is poor because heating must be performed for a long time of 30 minutes or more.

The technical problem of the present invention is to focus on such problems and to make it possible to harden magnetic paint in a short time without heating, thereby efficiently producing coated magnetic disks with excellent magnetic properties. The aim is to make it possible to produce

=6 [Means for Solving the Problem] FIG. 1 is a process diagram illustrating the basic principle of the method for manufacturing a coated magnetic disk according to the present invention. (1) is the finishing process of a non-magnetic substrate, in which a magnetic paint containing a polyfunctional ultraviolet curable resin, an organic solvent, and a magnetic powder is cross-dispersed using the method of the present invention on the final-finished non-magnetic substrate. Apply magnetic paint.

After this coating step (2) is completed, the applied magnetic coating film is irradiated with ultraviolet light to be cured by ultraviolet light.

[Effect]

According to the method of the present invention, a magnetic paint is cured by using an ultraviolet curable resin and irradiating it with ultraviolet rays, without using a thermosetting resin or curing agent that requires heating. Heat of several tens of degrees Celsius is generated during ultraviolet irradiation, but the temperature is extremely low compared to active heating, so the magnetic properties of the magnetic material in the magnetic paint may be demagnetized by heating. Never. Therefore, a coated magnetic disk with excellent magnetic properties can be obtained, and when used as a magnetic disk device, sufficient reproduction output can be obtained.

In addition, since the method of the present invention uses a polyfunctional UV-curable resin as the UV-curable resin, the hardness of the magnetic coating film after UV curing is sufficient, and the magnetic head comes into contact with the magnetic coating surface. Even if the magnetic recording medium is rubbed or slid, it can maintain good magnetic properties for a sufficiently long period of time, and a long-life magnetic recording medium can be obtained.

〔Example〕

Next, examples will be used to explain how the method for manufacturing a coated magnetic disk according to the present invention is actually implemented. To obtain the magnetic paint, first, 500 g of metal iron powder was added to a solution of UV curable resin (polyfunctional epoxy system 'I LOOG) in 3500 g of an organic solvent consisting of toluene, xylene, ethyl cellosolve acetate, and butyl cellosolve acetate. Mix and disperse in a sand mill for 4 hours. Next, add 600 g of ultraviolet curable resin (polyhydric phenol) and 1 sensitizer.
0g and 8700g of an organic solvent having the same composition as above were added and kneaded for further 3 hours to obtain a magnetic paint.

Next, after cleaning, the above-described magnetic paint is applied to a thickness of about 0.7 μm on an aluminum substrate that has been chemically treated with tannic acid, and metal iron powder is oriented in the circumferential direction. Next, after sufficiently drying, the film is irradiated with ultraviolet rays for about 20 seconds in an ultraviolet irradiation device to be cured, and then polished to a film thickness of about 0.40 μm. Thereafter, it was cured with ultraviolet light again in an ultraviolet irradiation device to obtain a magnetic coating film.

Table 1 shows the magnetic properties and electromagnetic conversion properties of the ultraviolet curable magnetic disk thus obtained and the conventional thermosetting magnetic disk. In both cases, metal iron powder was used as the magnetic material.

Table 1: To measure the magnetic properties, a BH) laser (applied magnetic field of 5000
0e), and the electromagnetic conversion characteristics were measured under the following conditions: core width of the magnetic head: 711.5 μm, gap length: 0.6 μm, gap depth: 6 μm, measurement frequency near, 5 MHz, and write current value: 12 mA.

As is clear from Table 1, the coercive force is about 8200e in the case of the conventional thermosetting resin coating, but it is improved to about 13500e in the example of the present invention.

As a result, the reproduction output when recording/reproducing information on a magnetic disk with a magnetic head was 0.54 mV compared to the conventional coating.
In contrast, in the case of the embodiment of the present invention, it is 0.93
It has improved to mV.

Furthermore, the resolution, which is a measure of interference from adjacent tracks, is 72.1% for the conventional coating film, whereas it has been improved to 80.6% in the embodiment of the present invention. Furthermore, S/N
While the conventional coating film has a value of 18.8 dB, in the example of the present invention, it has been improved to 23.5 dB.

As is clear from the above measurement results, the coated magnetic disk coated with the magnetic paint using the polyfunctional ultraviolet curable resin of the present invention does not undergo any heating, so its magnetic properties do not deteriorate. , a magnetic disk suitable for high recording density can be obtained.

9 0 In the case of a normal coated magnetic disk, the coating surface is
The strength of the coating film has been improved to the extent that it does not cause scratches when scratched with an H pencil, but in the magnetic disk of the embodiment of the present invention, it does not scratch even when scratched with a 7 to 9 H pencil. There is. Therefore, even if the magnetic head contacts or slides during long-term use, there is no problem of wear and abrasion particles being emitted, and a long-life magnetic disk can be obtained.

Since the hardening time of the applied magnetic paint is about 10 to 20 minutes including both pre-curing and post-curing, manufacturing efficiency is greatly improved and mass production can be carried out efficiently.

In addition to the polyfunctional ultraviolet curable resins shown in the examples, urethane, acrylic, and the like can also be used. The cross-dispersion of magnetic paint is usually repeated in two or more times, but as a multifunctional ultraviolet curable resin, one with excellent dispersibility is used in the first stage, and one with excellent dispersibility is used in the later stages. It is best to use one that is easy to use.

〔Effect of the invention〕

As described above, according to the present invention, a multifunctional ultraviolet curable resin is used to cure the magnetic paint, and since it can be cured without heating and sufficient hardness can be obtained, the magnetic material is demagnetized by heating. Therefore, a magnetic disk with excellent magnetic properties and a long life can be obtained. In addition, metal iron powder, which is susceptible to heat demagnetization, can also be used, and by using metal iron powder, it is possible to use metal iron powder that is more susceptible to heat demagnetization.
A reproduction output 5 to 2.0 times greater can be obtained.

The curing process for conventional coated magnetic disks requires 3 steps in the entire process.
Although it required a long time of 0 minutes or more, the method using the polyfunctional ultraviolet curable resin of the present invention requires less than 10 to 20 minutes and can be efficiently mass-produced.

[Brief explanation of drawings]

Fig. 1 is a process diagram explaining the basic principle of the method for manufacturing a coated magnetic disk according to the present invention, Fig. 2 is a diagram showing the structure of a coated magnetic disk, and Fig. 3 is a process diagram explaining the basic principle of the method for manufacturing a coated magnetic disk according to the present invention. Fig. 4 shows the temperature dependence of the magnetic properties of the magnetic material; Fig. 5 shows the relationship between the coercive force of the magnetic material and the reproduction output. It is a diagram. In the figure, 1 is a coated magnetic disk, 2 is a mounting hole, 3 is a non-magnetic substrate, and 4 is a magnetic coating film.

Claims (1)

[Claims] A method for manufacturing a coated magnetic disk in which a magnetic coating obtained by kneading magnetic powder into a resin is applied to a non-magnetic substrate, comprising: a polyfunctional ultraviolet curable resin and an organic solvent; A method for manufacturing a coated magnetic disk, which comprises cross-dispersing a magnetic paint containing magnetic powder and applying it to a non-magnetic substrate, and then curing the magnetic paint by irradiating it with ultraviolet light.