JPH0514331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording body, and particularly to a magnetic recording body for a magnetic encoder that enables high reliability and high coercive force.

In general, known magnetic recording media include magnetic tapes used in audio equipment and the like, magnetic disks and magnetic drums used in computers and the like. The magnetic film of these magnetic recording bodies has a very thin film thickness of 0.2 to several μm for high-density recording, and the magnetic powder used is fine particles with a major axis diameter of about 0.4 μm or less. On the other hand, magnetic recording bodies used in magnetic encoders require a large distance between the magnetic sensing element and the magnetic recording body (disk or drum), ranging from several μm to several hundred μm, so the magnetic film is required to have a high coercive force. Ru. In order to obtain a high coercive force, a metal whose main component is iron, cobalt, etc. is used as the magnetic material, and the film thickness is 50 to 100 μm.
Requires a film as thick as 1.0 m. On the other hand, in terms of reliability, since magnetic encoders are used in a wide range of environments, heat resistance of approximately 150°C or higher is required. In particular, in order to improve heat resistance, conventional magnetic powders can only guarantee temperatures up to about 80℃, and they also have problems such as film defects, film cracks, and difficulty in uniform coating when forming thick films. Therefore, it has been extremely difficult to obtain a magnetic film for a magnetic encoder with excellent reliability and heat resistance.

Accordingly, an object of the present invention is to provide a magnetic recording medium that allows a thick film and improves heat resistance by forming a magnetic film using a magnetic material with a large particle size.

The present invention will be explained in detail below using Examples.

In the present invention, a magnetic disk is prepared by cleaning a substrate made of a non-magnetic material such as Al, applying a magnetic paint containing magnetic powder to a thickness of about 80 μm using a spinner method, and aligning the substrate with a magnetic field. After baking, it is magnetized to complete the magnetic recording medium. In this case, the magnetic paint used an epoxy resin as a binder and toluene as a solvent, with a magnetic powder filling amount (weight ratio of magnetic powder in the coating film excluding solvent) of 65 wt%. As a result of repeated experiments and studies under various conditions, the inventor found that the size of the major axis diameter r of the magnetic powder added to the magnetic coating material greatly influences heat resistance. That is, as an experiment, various magnetic powders were made into paints by changing the long axis diameter r, and the output of the magnetic detection element was investigated against the life time in a high temperature (approximately 150°C) environment. As a result, the characteristics (r = 0.4μm),
As shown in characteristics (r = 0.6 μm), characteristics (r = 0.7 μm, characteristics (r = 0.8 μm), characteristics (r = 1.0 μm), characteristics (r = 1.2 μm), the long axis diameter r of the magnetic powder It was found that the range of 0.6 to 1.0 μm is optimal for obtaining an output higher than the comparison value. In this case,
If the long axis diameter r of the magnetic powder is less than 0.6 μm, a practically sufficient heat resistance effect cannot be obtained. If it exceeds 1.0 μm, the effect of facilitating thick film formation and magnetic field orientation can be obtained, but A problem arises in that the initial output (magnetic force) is insufficient. Therefore, considering the quality limit, the long axis diameter r of the magnetic powder is 0.7~
The optimal range was 0.8 μm, and when deviations (dispersions) were taken into consideration, the long axis diameter of 0.8 μm was the best value. In addition, the magnetic powder filling amount of magnetic paint is approximately
If it exceeds 70 wt%, cracks are likely to occur in the formed magnetic film, and if it exceeds about 60 wt%, bubbles will occur in the formed magnetic film. Therefore, considering the quality limit, the optimal range for the magnetic powder filling amount was 65±5 wt%. In addition, the magnetic film thickness is determined by a magnetization pitch of 0.1 as shown in Figure 2.
In the case of mm, it is proportional to the magnetic detection output, so when the film thickness is about 70 μm or more, the output becomes almost constant.
Therefore, in consideration of obtaining high output and process deviations, it is optimal to form a thick film of about 80 μm, which allows the output to be slightly saturated and the film thickness to be stable. However, if it exceeds 60 μm, there will be no practical problem.

In the above embodiment, a case was explained in which a disk was used as the magnetic recording medium, but the present invention is not limited to this, and it is of course possible to obtain exactly the same effect even if a drum is used. be.

As explained above, according to the present invention, approximately 150°C
Since it is possible to obtain a magnetic film that has the above heat resistance and can be formed into a thick film, it is possible to obtain an extremely excellent effect that a highly reliable magnetic encoder can be provided.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the output of the magnetic sensing element and the life time using the long axis diameter of the magnetic powder as a parameter, and FIG. 2 is a characteristic diagram showing the relationship between the output and the magnetic film thickness.

Claims (1)

[Claims] 1. Magnetism prepared by using toluene as a solvent and epoxy resin as a binder, and containing metal magnetic powder with a major axis diameter of 0.6 to 1.0 μm so that the weight ratio of the magnetic powder in the coating film excluding the solvent is 65 ± 5 wt%. 1. A method for manufacturing a magnetic disk, which comprises applying a paint onto an aluminum substrate using a spinner, aligning it in a magnetic field, and then baking it to a final film thickness of 60 μm or more.