JPH0789408B2 - Magnetic disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic disk such as a floppy disk having a structure in which a magnetic layer formed by dispersing and binding magnetic powder in a binder is provided on a base.

[Conventional technology]

In this type of magnetic disk, with the recent demand for high-density recording, the surface of the disk is smoothed, and the gap between the magnetic disk and the magnetic head during recording and reproduction tends to be as small as possible. In particular, in order to reduce the size and weight of the disk drive, especially in the Floppy disk, this drive uses a direct motor drive system with a low drive torque and has a magnetic head that is always in contact with the magnetic disk without a head load solenoid. Things are being used more and more.

In such a magnetic disk, as a peculiar problem not found in other magnetic recording media such as a magnetic tape, the magnetic disk and the magnetic head are attracted to each other, and this attraction causes the drive with the low drive torque to occur. There is a problem that it becomes difficult to rotationally drive the magnetic disk. Further, even if such a problem does not occur, the adsorption may damage the magnetic layer of the magnetic disk and the magnetic head, resulting in deterioration of electromagnetic conversion characteristics.

As a countermeasure against this, conventionally, the surface roughness of the magnetic disk and the amount of the lubricant contained in the magnetic layer are empirically known, and by managing this, the slip of the interface between the magnetic disk and the magnetic head can be prevented. We are taking measures to improve it (literature unknown). However, such measures are unavoidable not only causing the production cost of the magnetic disk to increase, but also reducing the reliability of the product and the difficulty of guaranteeing it.

[Problems to be solved by the invention]

The present invention does not take the above-mentioned problem of the attraction between the magnetic disk and the magnetic head without taking the conventional measures, that is, the problems such as increase of production cost, lack of reliability, and difficulty of guarantee are involved. It is an object of the present invention to provide a highly reliable magnetic disk which can be easily solved to meet the recent demands for high-density recording and the demands for smaller and lighter disk drives.

[Means for solving problems]

In order to achieve the above-mentioned object, the inventors of the present invention have made extensive studies and as a result, used a specific resin as a binder component of the magnetic powder constituting the magnetic layer of the magnetic disk, and also specified abrasive particles in the magnetic layer. By including it, it was found that the above-mentioned adsorption phenomenon can be well prevented, and thereby, the rotational drive of the magnetic disk at the time of recording / reproducing can be performed easily and stably, and the present invention has been completed. That is, the gist of the present invention is that magnetic powder is dispersed and bound to a binder containing a fibrous resin on a base, and α-Al ₂ O ₃ powder is included as abrasive particles having a Mohs hardness of 6 or more. The magnetic disk is characterized in that a magnetic layer is formed.

[Constitution / Operation of Invention]

A typical example of the fibrous resin used as the binder of the magnetic powder in the present invention is nitrocellulose having an average degree of polymerization of about 20 to 200. The reason why such a resin helps prevent the phenomenon of adsorption between the magnetic layer and the magnetic head is not always clear. However, since the slip between the magnetic layer and the magnetic head using this resin is very good, it is considered that this good slip property is very useful for preventing the adsorption phenomenon.

In the present invention, other binder components may be used together with the above fibrous resin, if necessary. Other binder components that can be used together include a wide range of polyvinyl chloride resins, polyester resins, polyacetal resins, polyurethane resins, polyisocyanate compounds and the like that are commonly used as binder components for magnetic tapes and the like. The content of these other binder components is preferably 80% by weight or less, preferably 60% by weight or less of the total amount of the binder, that is, 60% by weight or less, and the effect of the present invention is lost if too much is used.

The magnetic disk of the present invention is prepared, for example, by preparing a magnetic coating material in which magnetic powder is dispersed in a binder which essentially includes the above-mentioned fibrous resin, and the magnetic coating is applied to one side or both sides of a base such as a polyester film to have a dry thickness. 0.5 ~ on one side
It can be obtained by coating and drying so as to have a thickness of 3.0 μm to form a magnetic layer, and then subjecting it to calendering treatment and punching treatment by a conventional method.

As the magnetic powder used above, γ-Fe ₂ O ₃ powder, magnetite powder, oxide-based magnetic powder such as Co-containing magnetic iron oxide, Fe, Co, Ni or other metal or alloy magnetic powder is used. It is possible. The average particle size of magnetic powder is 0.1-1.0μ
The thickness is about m, preferably 0.2 to 0.6 μm.

Abrasive particles having a Mohs hardness of 6 or more,
Various known additives such as lubricants, antistatic agents, surfactants and pigments may be optionally contained, whereby a magnetic layer containing the above-mentioned additives and having a function corresponding thereto is formed. be able to.

Among the above additives, the present inventors have found that when abrasive particles having a Mohs hardness of 6 or more are used, in addition to the inherent wear resistance improving function of the particles, the magnetic layer and the magnetic head aimed at by the present invention are formed. It has been found that good results can also be obtained for prevention of adsorption. That is, it has been known that the use of the particles and the fibrin-based resin in combination produces a synergistic effect in preventing the adsorption. The reason for this is not clear so far. The abrasive particles that are effective in preventing adsorption are α-Al ₂ O ₃ (alumina) powder,
Other various abrasive particles having a Mohs hardness of 6 or more such as Cr ₂ O ₃ and SiC powder can be used.

The average particle size of the abrasive particles is preferably about 0.1 to 2.0 μm. The amount used is about 1 to 30 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the magnetic powder. If too much is used, it is not preferable because the filling of the magnetic powder is reduced and the electromagnetic conversion characteristics are impaired.

Further, among the above additives, selective use of a lubricant can be recommended as a particularly preferable embodiment. That is, the lubricant gives a good result to the slipperiness between the magnetic layer surface and the magnetic head and helps prevent the adsorption phenomenon. Typical examples of such a lubricant include 2-ethylhexyl oleate, butyl stearate, butyl cellosolve stearate, butyl cellosolve oleate, oleyl oleate, oleic acid, stearic acid and the like. The amount of lubricant used is
It is usually preferable to add 1 to 20 parts by weight to 100 parts by weight of the magnetic powder.

The above-mentioned lubricant can be contained in the magnetic coating material, or after the magnetic layer is formed, the surface of the magnetic layer is made into a solution and sprayed or dipped to impregnate the inside of the magnetic layer. It doesn't matter.

〔The invention's effect〕

As described above, in the present invention, since the fibrin-based resin is used as the binder component of the magnetic powder and the specific abrasive particles are included in the magnetic layer, the adsorption of the magnetic layer and the magnetic head is achieved. Therefore, it is not necessary to take any measures if the surface roughness of the magnetic disk and the amount of the lubricant are strictly controlled as in the conventional case. That is, the surface of the disk, that is, the surface of the magnetic layer can have good smoothness so as to meet the demand for high density recording, and even when the lubricant is used as described above, its amount is relatively free. Can be decided.

Therefore, the recent demands for high-density recording and the compact size of the disk drive can be achieved without causing the problems of increase in production cost, lack of reliability, and difficulty of guarantee as seen in the above conventional measures. It is possible to provide a highly reliable magnetic disk that can easily meet the demand for weight reduction.

〔Example〕

Hereinafter, examples of the present invention will be described to more specifically describe. In the following, "parts" means "parts by weight".

Reference Example 1 Co-containing γ-Fe ₂ O ₃ powder 1,000 parts Carbon black (150 parts manufactured by Asahi Carbon Co., Ltd. HS-500) Nitrocellulose (trade name RSI manufactured by Daicel Chemical Industries 156 parts) Polyurethane resin (Dainippon Ink Co., Ltd. 156 parts Trade name HI 2000) Trifunctional isocyanate compound (Japan Poly 78 parts Urethane Industry Co., Ltd. trade name Coronate L) Oleyl oleate 100 parts Cyclohexanone 2,000 parts Toluene 2,000 parts Magnetic paint consisting of the above components A magnetic layer was formed by coating and drying on both sides of a polyester film having a thickness of 75 μm so that the dry thickness would be 1.3 μm on both sides, forming a magnetic layer, and then calendering and punching into a disc shape. .

Comparative Example 1 Instead of nitrocellulose, vinyl chloride-vinyl acetate-
Vinyl alcohol copolymer (trade name VAG manufactured by UCC, Inc. in the United States)
H) A magnetic disk was produced in exactly the same manner as in Reference Example 1 except that 156 parts was used.

Example 1 α-Al ₂ O ₃ powder (average particle size 0.8 μm) as a magnetic paint component
A magnetic disk was produced in the same manner as in Reference Example 1 except that 30 parts were added.

Comparative Example 2 α-Al ₂ O ₃ powder (average particle size 0.8 μm) as a magnetic paint component
A magnetic disk was produced in the same manner as in Comparative Example 1 except that 30 parts were added.

Each of the magnetic disks of the above-mentioned Reference Example, Example and Comparative Example was
Assembled into an inch compact floppy disc, mounted on a 3 inch compact floppy disc drive, run the same track for 4 hours in an environment of 40 ° C., and then examined the starting torque after stopping for 10 minutes. Also, the presence or absence of the adsorption phenomenon between the magnetic disk and the magnetic head at that time was observed. The results are as shown in the table below.

As is clear from the above table, the magnetic disk of the present invention is
It can be clearly seen that the starting torque is small and no adsorption with the magnetic head is observed.

Claims (1)

[Claims] 1. A magnetic layer comprising a base containing a fibrous resin and a magnetic powder dispersed and bound to the base and containing α-Al ₂ O ₃ powder as abrasive particles having a Mohs hardness of 6 or more. A magnetic disk characterized by that.