JPS6341132B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic field orientation apparatus used when manufacturing perpendicular magnetic recording media, and particularly to a magnetic field orientation apparatus for manufacturing perpendicular magnetic recording media that can manufacture recording media with a high orientation rate. Magnetic recording generally relies on a method that uses magnetization in the in-plane longitudinal direction of a recording medium. However, in a recording method that uses magnetization in the in-plane longitudinal direction,
If an attempt is made to increase the recording density, the demagnetizing field within the recording medium will increase, so the recording density cannot be improved that much. Therefore, in order to eliminate such problems,
In recent years, perpendicular magnetic recording methods have been proposed that use magnetization in a direction perpendicular to the surface of a recording medium. In this perpendicular magnetic recording method, the demagnetizing field in the recording medium decreases as the recording density increases, so it can be said to be a recording method essentially suitable for high-density recording. However, in order to employ such a perpendicular magnetic recording method, a magnetic recording medium having an axis of easy magnetization in a direction perpendicular to the surface is required. Conventionally, as a recording medium that satisfies these demands, the recording film was made of Co-Cr.
There have been proposed methods in which the recording film is formed from a sputtered film and a recording film formed from a coated layer of magnetic fine particles. By the way, in the case where the recording film is formed by a coating layer of magnetic fine particles, the following manufacturing method can be considered. That is, as magnetic fine particles, for example
A hexagonal ferrite such as BaFe ₁₂ O ₁₉ is used (see, for example, Japanese Patent Application Laid-open No. 86103/1983). The reason for using hexagonal ferrite is that this ferrite has a flat plate shape and the axis of easy magnetization is perpendicular to the plate surface, so it can be easily vertically aligned by magnetic field alignment treatment or mechanical treatment. It is.
After mixing such magnetic fine particles of hexagonal ferrite and a binder and coating this on the surface of a non-magnetic tape, for example, this coated layer is placed in a magnetic field so that the surface is perpendicular to the direction of the magnetic field. A recording medium suitable for perpendicular magnetic recording can be obtained by arranging the easy axis of magnetization of each magnetic fine particle so that it coincides with the direction of the magnetic field and then drying the paint. However, when manufacturing a perpendicular magnetic recording medium by the above-mentioned so-called coating method, the following points need to be taken into consideration. In other words, in order to clarify the advantages of perpendicular magnetic recording compared to conventional longitudinal magnetic recording, it is necessary to make the minimum recording unit on the order of submicrons. It is necessary to use it. Such small-sized magnetic particles have a single domain structure,
In other words, since they become minute magnets, they are easily magnetically coupled to each other. Therefore, care must be taken to ensure uniform distribution within the binder. Furthermore, even if a desired magnetic paint with uniform dispersion is obtained, the following phenomenon may occur when such a magnetic paint is applied onto a substrate and vertically aligned using a magnetic field orientator. It often happens. In other words, when a substrate coated with magnetic paint is placed between the magnetic poles of a magnetic field orientator with NS poles facing each other, and its surface is placed perpendicular to the magnetic field, the axis of easy magnetization of the magnetic fine particles in the paint coincides with the direction of the magnetic field. Rotate and orient as shown. After being oriented in this way, if you stop applying the magnetic field or try to take the substrate out of the magnetic field, the magnetic poles remaining on both sides of the coating will cause the magnetic field to move in the opposite direction to the direction of the oriented magnetic field. A demagnetizing field is generated, and the magnetic particles forming an angle with the direction of the magnetic field of this demagnetizing field are subjected to a torque in the in-plane direction, and as a result, the vertical orientation obtained by the magnetic field orientator is significantly inhibited. .
The recording characteristics of perpendicular magnetic recording media are closely related to the ratio (orientation rate) of the easy magnetization axes of the magnetic particles in the coating film that are perpendicular to the substrate surface.
The higher the orientation rate, the higher the reproduction output and the higher density recording possible. For these reasons, the reality is that there is a strong desire for a magnetic field orientation device that can obtain a high orientation rate during the orientation process. The present invention has been made in view of the above circumstances, and its purpose is to reliably prevent the re-rotation of magnetic fine particles due to a demagnetizing field, and to produce a recording medium with a high orientation rate. Another object of the present invention is to provide a magnetic field alignment apparatus for manufacturing perpendicular magnetic recording media, which has a simple overall configuration. That is, the present invention provides a non-magnetic member between the magnetic pole faces of a magnet that generates an orientation magnetic field, and also provides a temperature control mechanism that controls this member to a desired temperature. , the paint is dried while a magnetic field is maintained in that direction to increase its viscosity to, for example, 10 ⁴ CP or more, thereby preventing the rotation of the magnetic particles and increasing their orientation. The non-magnetic member and temperature control mechanism used in the present invention are those that circulate hot water at a desired temperature inside a copper container or aluminum container, or a carbon-dispersed planar electric heating element. Those that use a Nesa glass heating element, those that use an endless rubber belt (preheated with a heating medium outside the magnetic field), and those that use a sheet heating element with a heating element such as nichrome wire embedded, but those that use a heating element made of Nesa glass, etc. As long as it satisfies the condition that the part is planar, there is no problem in using other materials than those mentioned above. Further, the non-magnetic member may not be in the form of a flat plate but may be formed in a cylindrical shape, and there are no restrictions on the shape as long as it meets the purpose of the present invention. Further, it is more effective if the non-magnetic member is one in which the temperature of the guide surface is given an appropriate temperature gradient by a temperature control mechanism. It is also effective to use a combination of a plurality of non-magnetic members and temperature control mechanisms for the purpose of providing this temperature gradient, that is, for the purpose of arbitrarily changing the rate of viscosity increase. Examples of the present invention will be described below. In the figure, reference numeral 1 is an orientation magnet consisting of a permanent magnet (an electromagnet may be used) with its NS poles facing each other. A running mechanism 4 that runs a tape-shaped substrate 3 made of a non-magnetic material, one surface of which is covered with an undried coating layer 2 containing magnetic fine particles, at a constant speed in the direction of the arrow X in the figure with a constant tension. , 5, and 6 are provided. Thus, between the magnetic pole faces of the magnet 1, a non-magnetic member 8 whose upper surface contacts the lower surface of the running tape-shaped base 3 and positions the surface of the tape-shaped base 3 perpendicular to the direction of the magnetic field. is fixed. This non-magnetic member 8 is composed of, for example, a carbon-dispersed planar electrothermal heating element, and is formed so that the amount of heat generated increases as the tape-shaped substrate 3 moves in the running direction. The input end thereof is connected to a power source (not shown). With such a configuration, one surface of the carbon-dispersed planar electrothermal heating element constituting the non-magnetic member 8 is covered with the undried coating layer 2 containing magnetic fine particles while the input end is connected to a power source. When the tape-shaped substrate 3 is run as shown in the drawing by the running mechanisms 4, 5, and 6, the magnetic fine particles P in the coating layer 2 are transferred to the magnetic surfaces 1a,
The axis of easy magnetization is oriented in the same direction as the direction of the magnetic field at the position where it enters the magnetic field between 1b. As mentioned above, the tape-shaped substrate 3 is guided by the non-magnetic member 8 so that the substrate surface is perpendicular to the direction of the magnetic field, so the axis of easy magnetization of each magnetic fine particle P is oriented perpendicular to the substrate surface. will be done. and,
The magnetic fine particles P oriented as described above are fixed in the above-mentioned oriented state by the drying of the paint due to the heat supply from the non-magnetic member 8 while traveling in the magnetic field, and are moved out of the magnetic field. This is where perpendicular magnetic recording media are manufactured. In this case, the paint is dried in the magnetic field to increase its viscosity and the vertically oriented magnetic fine particles P are immobilized in their oriented state. Even if this occurs, the magnetic fine particles will not be rotated by this demagnetizing field, and as a result, a recording medium with a high orientation rate can be manufactured. As shown in the embodiment, the configuration can be simplified if the non-magnetic member 8 has both the function of guiding the tape-shaped substrate and the function of drying the paint. It is also possible to make only the function appear. Next, the results of actually manufacturing a recording medium using the apparatus shown in the figure will be explained. A recording medium was manufactured by using a Nesa glass heating element as the non-magnetic member 8 and varying the amount of heat generated by this heating element. The relationship between the paint viscosity and orientation ratio of the paint film that came out through the magnetic field was investigated, and the results shown in Table 1 were obtained.

[Table] However, the orientation rate is the ratio of the residual magnetization Mr to the saturation magnetization Ms, which is obtained by correcting the demagnetizing field from the magnetization curve obtained by mounting the surface of the coating medium perpendicular to the measuring magnetic field. Calculated from. As shown in Table 1, when the viscosity of the paint is 10,000 CP or less, the orientation rate is in the 70% range, which is not practical, but when the viscosity of the paint is 10,000 CP or more, the orientation rate is over 80%. It is clear that Therefore, when using this device, the viscosity of the paint coming out of the vertically oriented magnetic field is 10 ⁴ CP.
It is necessary to control the amount of heat generated by the non-magnetic member 8 to the amount of heat generated above. Note that similar results were obtained when a carbon-dispersed sheet electrothermal heating element was used instead of the Nesagalas heating element.

[Brief explanation of the drawing]

The figure is a schematic side view of a magnetic field orientation device according to an embodiment of the present invention. 1... Magnet, 3... Tape-shaped substrate, 4, 5, 6
...Traveling mechanism, 8...Temperature-controlled non-magnetic member.

Claims (1)

[Scope of Claims] 1. An orienting magnet with both magnetic pole faces facing each other, and a non-woven material whose one surface is covered with an undried coating layer containing magnetic fine particles so as to pass between the magnetic pole faces of this magnet. Perpendicular magnetic recording characterized by comprising means for running a magnetic substrate, a non-magnetic member provided between the magnetic pole faces, and a temperature control means for controlling the temperature of the non-magnetic member to a set temperature. Magnetic field orientation device for media production. 2. The non-magnetic member has a guiding function of coming into contact with the non-magnetic substrate passing between the magnetic pole surfaces and constantizing the angle formed between the surface of the non-magnetic substrate and the direction of the magnetic field. A magnetic field orientation apparatus for manufacturing perpendicular magnetic recording media according to claim 1.