JPS63188826A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a magnetic flux density by providing a 1st magnetic coated film essentially consisting of a magnetic material having an axis of easy magnetization within the plane on a nonmagnetic base and providing a 2nd magnetic coated film essentially consisting of a magnetic material having an axis of easy magnetization perpendicular to the film plane thereon. CONSTITUTION:The coated film 1 essentially consisting of the magnetic material having the axis of easy magnetization within the plane is provided as the 1st magnetic layer on the nonmagnetic base 2 of a magnetic recording medium for a magnetic revolution sensor. The coated film 3 essentially consisting of the magnetic material having the axis of easy magnetization perpendicular to the film plane is further provided as the 2nd magnetic layer thereon. Formation of the films into 3-layered structure by providing a nonmagnetic coated film 7 between the coated film 1 and the coated film 3 is equally satisfactory. A 3rd magnetic layer which is subjected to a magnetic field orientation treatment by a floating magnetic field from the coated film 3 and is thereby oriented toward the direction of the magnetic flux of an underlaying film more strongly than in the coated film 3 may be further provided on the coated film 3 at the time of magnetizing the coated film 3 to some magnitude in the forming stage of the coated films 1, 3 and providing the 3rd magnetic coated film thereon. The magnetic flux density is increased to about two-fold the magnetic flux density of the conventional medium by such constitution, by which the assembly of the magnetic sensor is facilitated and the reliability at the time of the assembly is enhanced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium in a magnetic rotation sensor for a rotary encoder. [Prior Art] A magnetic rotation sensor uses a magnetic recording medium on which a predetermined magnetic pattern is written. is attached to a rotating body, and this magnetic pattern is read by a magnetoresistive element or the like to detect the rotational state of the rotating body, that is, the rotation angle, one rotational speed, or the stop position. At this time, the larger the magnitude of the floating magnetic field generated from the magnetic recording medium, the easier it is to assemble the magnetoresistive element, so it is desirable that the floating magnetic field be large.

Conventional recording media for magnetic rotation sensors are disclosed in Japanese Patent Application Laid-Open No. 60-529.
As described in Japanese Patent No. 28, a magnetic recording medium was prepared by applying one layer or 2M of magnetic paint using a thermosetting binder.

[Problem that the invention seeks to solve]

However, when several layers of the same type of magnetic paint are applied as described above, the stray magnetic field on the surface of the magnetic recording medium does not become large enough. As shown in FIG. 5, for example, in a film having in-plane anisotropy, when this recording medium is magnetized, stray magnetic fields become magnetic flux 4 and magnetic flux 5 and are generated on both sides of the medium. Of these, the magnetic flux 4 is distributed within the nonmagnetic support 2, and therefore does not become a magnetic flux detected by a magnetoresistive element or a magnetic head. In this way, the magnetic flux that can be detected by the detection element is about half of the magnetic flux generated from the recording medium.

For this reason, it is necessary to increase the amount of magnetic flux, but for example, in a method of improving the magnetic properties of magnetic paint, increasing the amount of magnetic flux by only about 10% of the conventional amount is foolish, and a significant improvement cannot be expected.

An object of the present invention is to provide a magnetic recording medium having a structure that increases the amount of magnetic flux generated from the surface of the recording medium to approximately twice that of the conventional magnetic recording medium.

[Means for solving problems]

The present invention is a magnetic recording medium that has a two-layer structure consisting of an upper layer (surface-side magnetic layer) and a lower layer (support-side magnetic layer), and is characterized in that the directions of easy axes of magnetization of the upper layer and the lower layer are different.

In the present invention, the upper layer is a magnetic recording medium having an easy axis of magnetization in the perpendicular direction, and the lower layer is a magnetic recording medium having an easy axis of magnetization in the in-plane direction. When this recording medium is magnetized, of the magnetic flux generated from the upper layer 1, the magnetic flux generated on the lower layer side passes through the inside of the lower layer recording medium, forming a magnetic path that connects the north pole and the south pole with the shortest path. do. As a result, all the magnetic flux generated from one pole in the upper layer toward the lower layer passes through the lower layer and is absorbed by the dissimilar poles in the upper layer, and almost no magnetic field appears inside the nonmagnetic support. . Therefore, the stray magnetic field appears only on the recording medium film surface side, and all the magnetic flux that appeared on the non-magnetic support side in step 1 heads towards the film surface side and contributes to the generation of the stray magnetic field. The size is approximately twice as large as that of the conventional method.

〔Example〕

The present invention will be explained based on examples. FIG. 1 shows one embodiment of the present invention. A magnetic coating film 1 having an in-plane easy axis of magnetization is formed on a non-magnetic support 2. Next, a magnetic coating film 3 having an axis of easy magnetization perpendicular to the film surface is formed thereon. In the case of magnetic coating 1, the paint is made by mixing thermosetting resin with materials that are relatively easy to have in-plane orientation, such as acicular iron oxide powder and metal magnetic powder, and then It is cured to form a film. On the other hand, in the case of the magnetic coating film 3, a thermosetting resin is mixed with magnetic powder, such as Ba ferrite, which tends to have an axis of easy magnetization perpendicular to the film surface, and after coating, it is cured to form a film. When this film is magnetized, the inside of the recording medium 5 is magnetized, and magnetic poles are generated on both sides of the film. On the surface that is in contact with the medium 1, a magnetic pole having an opposite polarity is induced in the medium 1 depending on the type of magnetic pole of the medium 3. As a result,
The magnetic flux 6 flows from the N pole of the surface magnetic pole of the medium B to the S pole in contact with @, forming a closed loop. Therefore, almost no magnetic flux enters the nonmagnetic layer at locations other than the coating surface, and because the magnetic flux is concentrated, the magnetic flux density increases and the stray magnetic field increases to about twice that of the conventional one. FIG. 2 is an example of increasing the stray magnetic field with the aim of concentrating the leakage magnetic flux using the same principle as in FIG. 1. The difference is that a nonmagnetic layer 7 with a thickness of 50 μm or less is provided between the medium 1 and the medium 2. This /i17 is used to increase the bonding force between medium 1 and medium 2, and to prevent medium 1 and medium 2 from melting together at the interface during coating, and from mixing magnetic materials with different easy axis directions at the interface. exist. Therefore, it is necessary to apply this layer as thinly as possible so as not to prevent the magnetic flux from forming a closed loop.

Further, the bonding film 7 is made of a thermosetting resin whose viscosity is adjusted in order to improve the adhesion between the medium 1 and the medium 2.

In the case of Fig. 3, unlike Fig. 1, the medium 1 does not have an axis of easy magnetization in the in-plane direction, but instead, the coating film support is a support having magnetism. , for example Fe
, Ni, Co + Gd By coating the medium 3 on a support having metals as components, it is possible to make the flow of magnetic flux into a closed loop and increase the magnetic flux density in the same way as in Figure 1 and Figure 2. . In FIG. 4, a medium 1 having an easy axis in the direction of the film surface is coated on a non-magnetic support 2, and a medium 6 having an easy axis in the perpendicular direction is coated thereon. Next, this recording medium is magnetized with a predetermined signal to generate a floating magnetic field in the air from the surface of the medium film. Finally, in this state, a paint having an axis of easy magnetization in the perpendicular direction is applied to form the medium 9. In the medium 9 coated in this manner, the magnetic powder particles within the υ material are easily oriented by the magnetic field generated by the base, so that the easy axis direction is further strengthened in the perpendicular direction. In the medium having the structure shown in FIG. 4, the closed loop of the magnetic flux is not impaired, so the concentration of the magnetic flux increases the magnetic flux density and the stray magnetic field.

〔Effect of the invention〕

As explained above, according to the present invention, a magnetic recording medium in which the magnetic flux density is approximately twice as high as that of conventional media is manufactured, so that assembly of a magnetic sensor is extremely easy. Reliability can be significantly increased.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of embodiments of the present invention. Figures 5 and 3 are cross-sectional views 01 of conventional embodiments...
Magnetic recording medium 2 having an in-plane easy magnetization axis...Nonmagnetic support 6...Magnetic recording medium 4 having an easy magnetization axis in the direction perpendicular to the film surface...Support side magnetic flux 5 ...Membrane surface side magnetic flux 6 ... Circulating magnetic flux 7 ... Non-magnetic coating 8 ... Magnetic support 9 ... Perpendicular to the film surface Magnetic recording medium with easy magnetization axis Fig. 7 Fig. 5 Fig. 2 Fig. 3

Claims (1)

[Claims] (1) As a magnetic recording medium formed on a non-magnetic support and used in a magnetic rotation sensor, on the non-magnetic support,
A coating film made of a magnetic material with an in-plane axis of easy magnetization was provided as the first magnetic layer, and a coating film made of a magnetic material with an easy axis of magnetization perpendicular to the film surface was provided on top of it as the second magnetic layer. A magnetic recording medium characterized by being provided with a coating film. (2) In the magnetic recording medium according to claim 1, between the first magnetic layer coating having an in-plane easy axis of magnetization and the second magnetic layer coating having an easy axis of magnetization perpendicular to the film surface. 2. The magnetic recording medium according to item 1 above, wherein the magnetic recording medium has a three-layer structure by providing a non-magnetic layer coating. (6) In the magnetic recording medium according to claim 1, the second magnetic layer is magnetized to a certain degree when the coating films of the first magnetic layer and the second magnetic layer are formed. When a third magnetic layer is provided thereon, the third magnetic layer is subjected to a magnetic field orientation treatment by a stray magnetic field from the second magnetic layer, and is oriented more strongly in the direction of the magnetic flux of the underlying film than the second magnetic layer. A magnetic recording medium characterized by having: (4) The magnetic recording medium according to any one of claims 1 to 3, characterized by having a magnetic layer having an axis of easy magnetization perpendicular to the film surface on a support that can have magnetism. magnetic recording media.