JPH06309661A - Orienting method of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having good oblique orientation even when the application time of a magnetic field for oblique orientation is short. CONSTITUTION:Before a coating film is dried, a magnetic field to orient magnetic particles in the plane direction is applied by a longitudinally orienting magnetic field generators 2, 3, 4. Then, an oblique magnetic field slanted from the plane direction to the perpendicular direction of the film is applied by an obliquely orienting magnetic field generator 5 to dry the film. Thereby, even though the application time for oblique orientation is decreased, good oblique orientation magnetic recording medium can be produced. Thus, coating facilities can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for orienting a coating type magnetic recording medium prepared by applying a magnetic coating material onto a non-magnetic support, and particularly to make magnetic particles in a coating film in a good oblique orientation state. The present invention relates to an alignment method.

[0002]

2. Description of the Related Art Generally, in order to increase the output of a magnetic recording medium, a method of orienting magnetic particles in one direction is used. This is because by aligning the directions of the magnetic moments, it is possible to increase the effective amount of magnetization with respect to the recorded signals and to help increase the reproduction signal strength. For a long magnetic recording medium, this has been done by applying while applying a horizontal magnetic field along its longitudinal direction.

However, in the magnetic recording medium thus oriented in the film surface direction, when the recording wavelength becomes short, the recording magnetization faces the adjacent recording magnetization with the same poles, so that a strong demagnetizing field is generated, As a result, there is a problem that the recording magnetization becomes small and the short wavelength recording / reproducing characteristics deteriorate.

On the other hand, in the perpendicular magnetization recording method, since recording is performed perpendicularly to the film thickness direction of the medium, excellent short wavelength characteristics can be obtained without the same poles of adjacent recording magnetizations facing each other. In order to realize this in the coating type magnetic recording medium, the magnetic particles are oriented perpendicularly to the coating film. However, although the magnetic recording medium of the coating type perpendicular recording system thus obtained is excellent in short wavelength recording and reproducing characteristics,
In the recording process by the ring-type head, the direction of the easy axis of magnetization of the magnetic particles oriented perpendicular to the magnetic field generated by the head is too different, so sufficient recording cannot be performed in the long-wavelength characteristic region, and in the long-wavelength region. However, there is a problem that the characteristics of (3) deteriorate.

Therefore, in order to provide these characteristics together and obtain good recording density characteristics from the long wavelength region to the short wavelength region, diagonal alignment has been proposed. In order to perform this oblique orientation, it is necessary to apply an oblique magnetic field from the film surface direction to the film surface vertical direction in the orientation process of the magnetic particles after applying the magnetic coating on the non-magnetic support. To this end, an orienting magnetic field generator in which the same poles of permanent magnets face each other is arranged diagonally, a solenoid for generating a magnetic field in the film surface direction, and a permanent magnet for generating a magnetic field in the film surface vertical direction. A combination of the above can be considered. However, since the application angle of the orientation magnetic field can be relatively freely changed after the installation, the oblique orientation magnetic field generator in which electromagnets are arranged above and below the solenoid is useful.

[0006]

However, when the magnetic particles are oriented obliquely using only the above-mentioned oblique orientation magnetic field generator, the magnetic particles are oriented in one direction, that is, along the longitudinal direction of the film surface and in the direction inclined to the direction perpendicular to the film surface. In order to uniformly orient all the magnetic particles, it is necessary to continuously apply the oblique orientation magnetic field for a long time.

This will be described in detail with reference to FIG. FIG. 4A shows the state of the magnetic particles M in the undried coating film. In the figure, the X direction represents the longitudinal direction of the medium, the Y direction represents the width direction of the medium, and the Z direction represents the direction perpendicular to the film surface of the coating film. Immediately after coating, the magnetic particles M oriented in the X direction as shown in FIG. 4 (a) are oriented by applying an orientation magnetic field in the H direction in the figure, and the magnetic particles M rotate in this direction. . However,
Immediately after coating, the magnetic particles M oriented in the Y direction as shown in FIG.
As shown in (c), it rotates in a plane including the Y axis and the H direction of this orientation magnetic field, and tries to move in the direction of the orientation magnetic field. At this time, the angle of rotation of the magnetic particles M is larger than that in the case of FIG. Therefore, in order to orient all the magnetic particles M in the orientation direction, it is necessary to continuously apply the oblique orientation magnetic field until the magnetic particles M are fully oriented.

By the way, the coating type magnetic recording medium needs to have a high coating speed in order to improve the mass productivity, and in order to obtain a sufficient time for the alignment in the alignment step, it depends on the coating speed. Long orientation zones are required. However, in general, a device that generates an oblique orientation magnetic field has a complicated structure in order to apply a magnetic field in the film surface longitudinal direction and the film surface vertical direction,
To apply an oblique orientation magnetic field over a long distance,
There is a problem that the device becomes large-scale.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide a method for orienting a magnetic recording medium that enables good oblique orientation even when the application time of the oblique orientation magnetic field is short.

[0010]

The orientation method of the present invention comprises applying a magnetic coating mainly composed of magnetic particles and a binder onto a non-magnetic support, and then magnetically applying the magnetic coating in the film surface direction before the coating is dried. After applying a magnetic field for orienting the particles, the magnetic particles in the coating film are orientated obliquely by applying while applying an oblique magnetic field inclined from the film surface direction to the film surface vertical direction.

[0011]

According to the above-mentioned structure of the present invention, in order to orient the magnetic particles in the film surface direction, for example, a solenoid or the like can be used to apply an orienting magnetic field over a sufficiently long distance with relatively simple equipment. , Most of the magnetic particles can be directed in one direction of the film surface, and then by applying a desired oblique magnetic field, it can be obliquely aligned with the minimum rotation from the film surface direction. Even if the time is short, good oblique alignment is possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic recording medium orientation method of the present invention will be described below with reference to FIGS.

First, a coating apparatus for carrying out the orientation process is shown in FIG.
Will be described with reference to. Longitudinal orientation magnetic field generators 2, 3, 4 that generate an in-plane magnetic field along the longitudinal direction of a path along which a long non-magnetic support 1 coated with a magnetic coating travels.
Is provided. Each longitudinal orientation magnetic field generator 2, 3, 4
Is equipped with a solenoid, and about 6000 at the center of the solenoid
It is configured to generate a Gaussian magnetic field. Behind the last longitudinal alignment magnetic field generator 4, an oblique alignment magnetic field generator 5 is arranged, and before and after it, blowing nozzles 6 and 7 for drying are arranged. Behind the oblique orientation magnetic field generator 5, a drying zone 8 for performing main drying is arranged.

In FIG. 1, 9 is a raw roll of the non-magnetic support 10 and 11 is a magnetic paint. The magnetic paint 11 is applied to the surface of the non-magnetic support 10 by a gravure 12, and the magnetic paint is applied. The non-magnetic support 1 is formed. Also,
The magnetic recording medium exiting the drying zone 8 is the take-up reel 1
It is rolled up at 3.

As shown in FIG. 2, the oblique orientation magnetic field generator 5 includes an iron magnetic core 2 for amplifying a vertical magnetic field above and below a solenoid 21 for generating a horizontal orientation magnetic field.
2, 23 are arranged, and the coil 24 is wound around these magnetic cores 22, 23 in the same winding direction. This coil 24
The magnetic cores 22 and 23 are made into electromagnets by passing an electric current through
Generates a vertical magnetic field. The yokes 25 and 26 are disposed on the side surfaces of the upper and lower magnetic cores 22 and 23, and the structure is configured to reduce the magnetic flux leaking from the rear of the magnetic cores 22 and 23 and improve the efficiency. Reference numeral 27 is a DC power source for the coil 24, and 28 is a DC power source for the solenoid 21. Then, the vector sum of the horizontal and vertical magnetic fields generated by the solenoid 21 and the magnetic cores 22 and 23 can generate an oblique orientation magnetic field in the tape running portion in the central portion of the device. The intensity of the orientation magnetic field in the horizontal and vertical directions can be adjusted independently by the applied current, and therefore the angle of the orientation magnetic field as the vector sum can also be adjusted freely.

Example 1 Table 1 shows the material composition of the magnetic paint used in the experiment.

[0017]

[Table 1]

As the magnetic powder, acicular metal magnetic powder having a coercive force of 1440 oersted and a saturation magnetization of 125 emu / g was used.
These materials were sufficiently kneaded and dispersed to obtain a magnetic paint having a solid content ratio of 29%. This magnetic paint is applied to PET with a thickness of 15 μm
A (polyethylene terephthalate) film was coated on the film so that the layer thickness when dried was 3 μm, and passed through the alignment step of FIG. 1 to prepare a sample.

As Example 1, a sample was prepared with the longitudinal orientation magnetic field generators 2, 3 and 4 set to a central magnetic field of 6000 gauss and the oblique orientation magnetic field generator 5 set to 3,000 gauss in the longitudinal direction and 1730 gauss in the vertical direction. A was produced. In this state, in the oblique orientation magnetic field generator 5, a magnetic field inclined by 30 degrees from the film surface direction in the direction perpendicular to the film surface is generated.

(Comparative Example 1) As Comparative Example 1, a sample B was prepared using only the oblique orientation magnetic field generator 5 with all the longitudinal orientation magnetic field generators 2, 3 and 4 stopped.

(Comparative Example 2) As Comparative Example 2, the oblique orientation magnetic field generator 5 was stopped and the longitudinal orientation magnetic field generator 2,
Sample C was prepared using only 3 and 4.

The coating speed was the same for all of the samples A, B and C, and it took about 1 second to pass through all the alignment magnetic field generators 2, 3, 4 and 5.

(Comparative Example 3) As Comparative Example 3, a sample D was prepared using only the oblique orientation magnetic field generator 5 with all the longitudinal orientation magnetic field generators 2, 3 and 4 stopped. However,
Unlike Comparative Example 2, the coating speed was slowed down so that it took about 1 second to pass through the oblique orientation magnetic field generator 5.

After hardening and calendering, each sample was slit into a 1/2 inch width to obtain a tape-like sample.

[0025]

[Table 2]

Table 2 shows the measurement results of the magnetic properties of Samples A, B, C and D. From the squareness ratio measured in the longitudinal direction of sample C in Table 2, it can be seen that the magnetic paint used in the experiment can be oriented up to a squareness ratio of 0.86 by the longitudinal orientation magnetic field generators 2, 3, and 4. Sample A that has undergone the same longitudinal orientation process as this also has a squareness ratio of 0.8.
Although it should be oriented up to 6, it is actually 0.80. This is because Sample A was oriented to a squareness ratio of 0.86 immediately after passing through the longitudinal orientation magnetic field generators 2, 3 and 4, and thereafter the magnetic particles were oriented obliquely by the oblique orientation magnetic field generator 5, so that the longitudinal direction This is because the squareness ratio of is decreased. The squareness ratio of Sample B in the longitudinal direction is 0.78, which is lower than that of Sample A, but since it has not passed the orientation process in the longitudinal direction, the state of the magnetic particles immediately after coating (the magnetic particles are oriented in random directions) It is obliquely oriented only by the oblique orientation magnetic field. Therefore, the squareness ratio in the tape width direction is the largest in the sample, and the magnetic particles are not aligned in the longitudinal direction and oriented obliquely with respect to the film surface, but are oblique but in the tape longitudinal direction. You can see that is not available. However, the sample D oriented by applying only the oblique orientation magnetic field for a long time shows the same magnetic characteristics as the sample A. From this, it is understood that good oblique alignment can be achieved only by the oblique alignment magnetic field if the application time is sufficient.

That is, it can be seen that the same effect can be obtained by the alignment method in which the magnetic fields in the longitudinal direction and the oblique direction are combined and the alignment method in which only the oblique magnetic field is applied for a long time.

Next, the results of examining the electromagnetic conversion characteristics of these four samples are shown in FIG. For the measurement, the sample was wound around a drum having a diameter of 70 mm, and the magnetic head was contacted from the outside of the drum, that is, a so-called drum tester was used. As the magnetic head, an MIG head (metal in gap head) using sendust was used. The magnetic head was run in the direction in which the magnetic particles in the magnetic recording medium were tilted with respect to the direction perpendicular to the film surface (so-called forward direction), and the electromagnetic conversion characteristics were measured. As can be seen from these results, although samples A and D are slightly inferior to sample C, which is a longitudinal alignment medium, in the long wavelength region, they exhibit very good short wavelength characteristics and can realize a good oblique alignment state. Can be said. On the other hand, it can be seen that Sample B exhibits better characteristics than Sample C in the slightly shorter wavelength region, but is inferior to Samples A and D.

[0029]

According to the present invention, as described above, after applying a magnetic field for orienting magnetic particles in the film surface direction before the coating film is dried, the film is inclined from the film surface direction to the film surface vertical direction. By drying while applying an oblique magnetic field, it is possible to produce a good alignment medium even when the application time of the oblique alignment magnetic field is short. Therefore, an oblique alignment magnetic field that requires a device with a complicated configuration is sufficient. The coating equipment can be simplified as compared with the case of applying for a long time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of coating equipment for carrying out an alignment method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration of an oblique orientation magnetic field generator in the same Example.

FIG. 3 is a electromagnetic conversion characteristic diagram with respect to wavelengths in Examples and Comparative Examples.

FIG. 4 is an explanatory diagram of rotational movement of magnetic particles due to an orientation magnetic field.

[Explanation of symbols]

 1 Non-magnetic support coated with magnetic paint 2 Longitudinal orientation magnetic field generator 3 Longitudinal orientation magnetic field generator 4 Longitudinal orientation magnetic field generator 5 Oblique orientation magnetic field generator

Claims (1)

[Claims] 1. A film after applying a magnetic paint mainly composed of magnetic particles and a binder on a non-magnetic support and applying a magnetic field for orienting the magnetic particles in the film surface direction before the film is dried. A method for orienting a magnetic recording medium, which comprises drying while applying an oblique magnetic field inclined from a surface direction to a direction perpendicular to the film surface to obliquely orient magnetic particles in a coating film.