JPH01169729A - Method for manufacturing magnetic recording media - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a disk-shaped magnetic recording medium subjected to high-density recording.

[Conventional technology]

In recent years, flexible disk-shaped magnetic recording media have been widely used in the computer world, such as flexible disks as recording devices and magnetic sheets for still video cameras.

However, when using this type of magnetic recording medium, the magnetic head moves along the circumference to read and write records, whereas normally manufactured magnetic recording media Since the magnetic powder that forms the magnetic layer is not oriented in a circumferential manner, the squareness ratio is poor and the residual magnetization is smaller than that of magnetic tape, which has oriented magnetic powder. . Therefore, in this disk-shaped magnetic recording medium, in order to obtain sufficient output, the track width has to be widened, which hinders high density recording.

In addition, when using a magnetic powder with a large axis ratio of 31, which is normally used for tapes, it is possible to apply 4B, dry [non-magnetic +'] [support sheet without using an orientation device]. Because it receives R-machine orientation in the 11 direction (for example, the length direction), even if a signal with a constant amplitude is recorded circumferentially on a disk-shaped punched object, the residual magnetization will be in the longitudinal direction. There was also the problem that the envelope waveform was not constant and the output fluctuated periodically due to the large amplitude.

[The problem that the invention attempts to solve]

Therefore, in the currently dominant floppy disks and video floppies, the mechanical orientation is weakened during coating, or magnetic powder with a small axial ratio is used to create an envelope. ing. However, such a method suppresses the original characteristics of the acicular magnetic powder. This point will be clarified by comparing it with metal tape.

The axial ratio of the metal magnetic powder of the metal tape can be selected from about 5 to 11, but usually about 7 to 9 is used. The squareness ratio of a tape using such long needle-shaped magnetic powder is about 0.6 to 0.65 in the case of non-oriented tape after 0.55 planes when mechanical orientation is added. Furthermore, as disclosed in Japanese Patent Publication No. 34-2536, magnetic field orientation is applied using a device in which a solidified +if magnetic paint coated sheet passes between two plate magnets with the same W1 rod facing each other. If this is done, the squareness ratio will decrease by 1 to about 0.8 to 0.85. - Magnetic line mechanical orientation with a numerically large shape anisotropy, that is, a large axial ratio, is likely to be bent, and a large squareness ratio can be obtained as a result of the orientation. On the other hand, the squareness ratio in the circumferential direction of a metal video floppy whose orientation is suppressed is 0.6.
~0.65 and compared to tape, the output is 3dll
decreases as much as possible.

Many methods have been proposed to remove such mechanical orientation before coating 11i and to achieve circumferential (concentric) orientation. For example, Japanese Patent Publication No. 40-23626 discloses a method of circumferential orientation using an externally applied magnetic field. In this method, in a state where the magnetic paint is not solidified, the axis of rotation of the rotating magnetic pole surface is kept stationary relative to the original fabric, the magnetic pole surfaces are brought close to each other, and the magnetic powder is oriented in a concentric solid state. & Separation. In the example of the same method, a rotating magnetic field is applied from one side of the original fabric, but in the case of tape,
As shown in Publication No. 6, in the case of disks as well, it is better to install rotating magnetic pole surfaces that face the same magnetic pole on opposite sides of the original fabric. A conceptual diagram of such a device is shown in Japanese Unexamined Patent Publication No. 53-62505.

In the orientation caused by these rotating magnetic fields, the magnetic field self-aligning blade is
Basically, it is the same at any position on the circumference. On the other hand, as mentioned earlier, the machine-aligned blade has a strong orientation in the direction in which the web runs, so even after applying a magnetic field, the orientation in the seven-line direction and the direction perpendicular to the running direction within the plane of the web remain unchanged. There remains a difference in orientation between the two directions. As a result, the squareness ratio at any position in the circumferential direction in a disk-shaped magnetic recording medium obtained by the conventional orientation method is 0.75 to 0.8, and the squareness ratio in the longitudinal direction in the case of magnetic tape etc. is 7. , the resulting squareness ratio (0
, 8 to 0.85) and are not sufficiently oriented. This is extremely difficult because in order to orient the ferromagnetic particles aligned in the longitudinal direction in the circumferential direction using mechanical orientation, the ferromagnetic particles must be rotated up to 90 degrees in the width direction of the ribbon. This is for a reason.

The present invention is free from the influence of mechanical orientation and has a - degree of orientation in the circumferential direction.
- It is an object of the present invention to provide a disc-shaped magnetic recording medium which has a high degree of orientation equivalent to the longitudinal orientation of a magnetic tape.

[Means for solving the problem] [-1 of L] is to apply a magnetic paint containing magnetic powder to a running wide thin strip-shaped non-magnetic support, and to apply a magnetic layer after drying the coating. In a method for manufacturing a magnetic recording medium by punching out a disk shape after forming the thin strip, the thin strip that has been coated with magnetic paint and has not yet been dried and solidified is subjected to an orientation treatment in the longitudinal direction. A part of the width of the portion that has been oriented is subjected to an orientation treatment in the width direction, and further, the ribbon is centered at one point of the portion where the orientation treatment has been performed in the width direction.
This can be achieved by a method for manufacturing a magnetic recording medium characterized by including step 1 of magnetically oriented in a circumferential manner.

The present invention first performs pseudo-circumferential alignment of the magnetic material in an unsolidified state, and then applies a circumferential alignment magnetic field to achieve alignment at any position on the track without the influence of mechanical alignment. A disk-shaped magnetic recording medium with the same degree of orientation is manufactured, and thereby the degree of orientation is increased to the same level as that of a magnetic tape oriented by a magnetic field in the longitudinal direction.

In the present invention, in particular, pseudo-circumferential orientation is performed as described in -F, so even if the diameter of the disk to be manufactured changes,
This can be easily done by simply changing the widthwise oriented magnet.

Hereinafter, typical aspects of the method for manufacturing a magnetic recording medium of the present invention will be explained in more detail with reference to the drawings.

Pseudo-circumferential orientation is important for the present invention, and FIG. 1(a) shows a typical example of the mutual arrangement of the magnetic original fabric sheet 3, the longitudinally oriented magnets 1, and the widthwise oriented magnets 2 in this process. It is a schematic perspective view.

The longitudinally oriented magnets 1 are arranged so that the same poles face each other, and the widthwise oriented magnet 2 has a head shape and is arranged ahead of the longitudinally oriented magnet 1.

A magnetic paint 4i containing ferromagnetic powder, a binder, and a solvent as -IE components is applied between the pair of longitudinally oriented magnets 1. Fi, dry solidification 11'' original fabric sheet 3 is passed through the tank 1 [
i width). At this time, the strength of the orienting magnetic field varies depending on the viscosity of the magnetic paint, coating speed, etc., but it is set so that the magnetic field is about 1 to 5 times the coercive force of the magnetic powder used.

The raw sheet 3 thus longitudinally oriented is oriented in the width direction by the widthwise oriented magnet 2 by the magnetic pole spacing g.

The magnetic pole spacing g is set to have the following relationship with the center track radius r of the disc-shaped magnetic recording medium to be manufactured. This is because it is desirable that the ratio of orientation in the length direction and the width direction be approximately the same.

g<2r (preferably 8%5r) The strength of the alignment magnetic field in this case is also set in the same way as in the case of alignment in the navigation direction.

The orientation pattern of the magnetic layer thus subjected to orientation treatment is schematically represented as shown in FIG. 1(b).

In the present invention, the raw sheet 3 thus pseudo-circumferentially oriented is then subjected to circumferential orientation. The center of the circumferential orientation is the 0 point in FIG. 1(b).

FIG. 2 is a side view showing an example of an apparatus used to carry out the steps described above. The transport rolls 9 and 10 can move the raw sheet 3 at a constant speed in the direction of the arrow 4. A belt conveyor or caterpillar-shaped orientation magnet holding traveling device 11 that holds the circumferential orientation magnets 5 bands a, 5b, 5C, etc. rotates in the direction of arrow 8 at a constant circumferential speed that is synchronized with the web traveling speed. .

Circumferentially oriented magnets 6a, 6 are arranged symmetrically across the original fabric sheet 3.
An orientation magnet holding traveling device 12 for holding the magnets b, 6C, . The circumferentially oriented magnet 5.6 moves and hangs so as to maintain a stopped state relative to the original fabric sheet 3. Orienting magnet holding device 11.1
In front of the magnet 2, the longitudinally oriented magnet 1 and the widthwise oriented magnet 2 shown in FIG. 1 are provided.

When this device is operated, the original sheet 3 is transferred to the conveying roller 9
．． 10, and is subjected to pseudo-circumferential orientation by the longitudinal direction oriented magnet 1 and the width direction oriented magnet 2. Subsequently, the original fabric sheet 3 is moved to a rotating orientation magnet holding device 11.1.
A circumferential orientation device 5.6 held at the stone 2 causes the stone 2 to be oriented circumferentially around a point on the center line of the magnetic pole gap g of the stone 2 in the width direction.

Incidentally, the circumferentially oriented magnet 5.6 may be either a permanent magnet or an electromagnet. Further, these circumferentially oriented magnets can be used either in a method using rotating magnetic poles or in a method using fixed magnetic poles. However, as long as it achieves the same objective, that is, it can form a circumferential magnetic field, it is limited to these (not J. In addition, in the example of Fig. 2, the original The effect of circumferential alignment can be obtained even if the circumferential alignment magnetic field of the same 6th bar is applied from both sides of the sheet 3 or only from the C side.

The strength of the applied magnetic field during the circumferential orientation in the present invention varies depending on various factors, but is usually about 1 to 5 times the coercive force of the magnetic powder used.

〔Example〕

Example 1 Acicular magnetic metal powder (Fe-Ni alloy, major diameter 0.25μ
, axial ratio 10, l1c14500e) 100 parts by weight, 25 parts of binder (6=4 mixture of vinyl chloride-vinyl acetate-vinyl alcohol copolymer and polyurethane elastomer), lecithin (dispersant) liTuit part,
A magnetic paint made by dispersing and mixing α-alumina (abrasive, particle size 0°4) with a magnetic field and 240 parts of solvent (1=1 mixture of methyl ethyl ketone and toluene) in a dry thickness of 3 μm This is a coated band on a PET sheet.

Next, using the apparatus shown in FIG. 2, the orientation treatment was performed as described above, and punching was performed to obtain a disk-shaped magnetic recording medium (diameter 47+
+m).

In addition, the longitudinal direction, width direction, and circumferential orientation are all 3000 0
A magnetic field of e is applied, and the magnetic pole gap of the widthwise oriented magnet is 25+
It was set as nm.

Comparative Example 1 A disc-shaped magnetic recording medium was produced in the same manner as in Example 1, except that no orientation by a magnetic field was performed.

Comparative Example 2 Same as Example 1 except that pseudo circumferential orientation was not performed.
A disc-shaped magnetic recording medium was fabricated.

Comparative Example 3 A disk-shaped magnetic recording medium was produced in the same manner as in Example 1, except that circumferential orientation was not performed.

Example 2 A magnetic recording medium was produced in the same manner as in Example 1, except that the magnetic field of the circumferentially oriented magnet was changed to 3800 0 C.

(Evaluation) Characteristics such as squareness ratio and residual magnetization of Examples, Comparative Examples, and Reference Examples were investigated. The results are shown in Table 1.

This table clearly confirms the effect of the present invention.

〔Effect of the invention〕

As explained in Section 1, according to the manufacturing method of the present invention, the degree of orientation is constant in the circumferential direction with little or no influence of mechanical orientation, and the degree of orientation is constant in the circumferential direction, which is equivalent to the longitudinal orientation in magnetic tape. A disk-shaped magnetic recording medium having a high degree of orientation and a high squareness ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1(a) shows the pseudo-circumferential orientation [phase t of the magnetic original sheet, longitudinally oriented magnets, and widthwise oriented magnets in the culm].
FIG. 1(b) is a schematic perspective view showing an example of one arrangement, FIG. 1(b) is a schematic diagram showing a pattern of pseudo circumferential orientation according to FIG. 1(a),
FIG. 2 is a schematic side view showing one embodiment of the magnetic field orientation device used in the present invention. 1: Longitudinal orientation magnet 2: Width orientation magnet 3: J-paper sheet 4: Raw sheet running direction 5.6: Circumferential orientation magnet 7.8: Belt or caterpillar running direction 9.10:
Conveying rollers 11.12: Orienting magnet holding and traveling device Patent applicant Canon Co., Ltd. Representative Tadashi Wakabayashi 4 months, 1 G, V running, 3 pieces? Sheet 12a
12b 12c m12g 12h 12i 12a-i Distribution $+f9-So(b) Figure 1

Claims (1)

[Scope of Claims] 1) Magnetic recording made by applying a magnetic paint containing magnetic powder onto a running wide thin strip-shaped non-magnetic support, drying it to form a magnetic layer, and punching it out into a disk shape. In a method for manufacturing a medium, the thin ribbon coated with magnetic paint and before being dried and solidified is subjected to an orientation treatment in the longitudinal direction, and then a part of the width of the portion oriented in the longitudinal direction is oriented in the width direction. 1. A method of manufacturing a magnetic recording medium, comprising the steps of: performing a treatment, and further magnetically orienting the ribbon in a circumferential manner around one point in a portion of the ribbon that has been subjected to the orientation treatment in the width direction.