JPH01169724A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a disk-shaped magnetic recording medium which is uniform in the degree of orientation in a circumferential direction while eliminating the influence of mechanical orientation by disposing plural magnet groups arrayed alternately with N poles and S poles along the direction perpendicular to the carrying direction of a thin strip in such a manner that the intensity of magnetic fields decrease gradually along the carrying direction. CONSTITUTION:This method consists in subjecting a traveling broad thin band-shaped nonmagnetic base (raw sheet) 1 which is coated with a magnetic coating compd. in an undried state is subjected to disordering of orientation to eliminate mechanical orientation, then impressing a circumferentially orienting magnetic field thereto. The non-orienting magnetic fields 13-16 are so arranged that the N poles and S poles array alternately in the direction perpendicular to the carrying direction of the raw sheet 1 and the magnitude of the magnetic field increases in number from 13 to 16. The raw sheet 1 is fed by carrying rollers 2, 3 and is subjected to the non-orientation by the non-orienting magnets 13-16. The raw sheet passes between rotary drums 11 and 12 in succession thereto and are circumferentially oriented by the circumferentially orienting magnets 5, 6. The influence of the mechanical orientation is eliminated in such a manner and the degree of orientation is uniformized in the circumferential direction.

Description

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

[Conventional technology]

In recent years, flexible disk-shaped magnetic recording media have been widely used, such as flexible disks used as large-capacity storage devices for computers 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 Because the magnetic powder that forms the layer is not oriented in a circumferential manner, the squareness ratio is poor and the residual magnetization is lower than that of a magnetic tape in which the magnetic powder is oriented. Therefore, in this disk-shaped magnetic recording medium, there is an effect of widening the track width in order to obtain sufficient output, which hinders high density.

In addition, when using needle-like magnetic powder with a large axial ratio, such as those normally used in tapes, it is possible to avoid using an orientation device during the coating and drying process in the coating direction of the non-magnetic support sheet (e.g. Even if a signal with a constant amplitude is recorded circumferentially on a disk-shaped punched disk, the residual magnetization is larger in the longitudinal direction.
There was also the problem that the envelope waveform was not constant and the output fluctuated periodically.

[Problem that the invention seeks to solve]

Therefore, in the currently dominant floppy disks and video floppies, the mechanical orientation is weakened during the coating process, or magnetic powder with a small axial ratio is used to make the envelope as flat as possible. 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 0.55 in the case of no orientation, but becomes about 0.6 to 0.65 when mechanical orientation is added. Furthermore, as disclosed in Japanese Patent Publication No. 34-2536, magnetic field orientation is imparted using a device in which a sheet coated with magnetic paint before solidification is passed between two plate magnets with the same magnetic poles facing each other. For example, the squareness ratio increases to about 0.8 to 0.85. −
Magnetic powders with numerically larger shape anisotropy, that is, larger axial ratios, are more likely to be mechanically oriented, and as a result of orientation, a larger squareness ratio can be obtained. On the other hand, a metal video floppy whose orientation is suppressed has a squareness ratio in the circumferential direction of about 0.6 to 0.65, which lowers the output by about 3 dB when compared with tape.

Remove mechanical orientation before application, such as circumferential (concentric circles)
Many methods have been proposed in the past for orientation. For example, Japanese Patent Publication No. 40-23626 discloses a method of circumferentially orienting by 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 material, the magnetic pole surfaces are brought close together, the magnetic powder is oriented concentrically, and then separated. It is something. In the example of this method, a rotating magnetic field is applied from one side of the original material, but in the case of a tape, as shown in Japanese Patent Publication No. 34-2536, in the case of a disk, it is applied from the opposite side. It is better to install a rotary magnetic pole surface having the same magnetic pole on the opposite side of the web. A conceptual diagram of such a device is published in Japanese Unexamined Patent Application Publication No. 1986-
It is shown in the 62505 publication.

In these orientation methods using a rotating magnetic field, the magnetic field orientation force is
Basically, it is the same at any position on the circumference. On the other hand, as mentioned earlier, the mechanical orientation force is strong in the direction of fabric running, so even after applying the magnetic field orientation, the alignment method in the direction parallel to the running direction of the fabric is perpendicular to the running direction within the plane of the fabric. Differences with the orientation method in direction remain. As a result, the squareness ratio at any position in the circumferential direction of a disc-shaped magnetic recording medium obtained by the conventional orientation method is 0.75 to 0.8, and the squareness ratio obtained by longitudinal direction orientation in the case of magnetic tape, etc. is 0.75 to 0.8. squareness ratio (0
, 8 to 0.85) and are not sufficiently oriented. This is extremely difficult because in order to orient the ferromagnetic particles arranged in the elongated direction in the circumferential direction by mechanical orientation, the ferromagnetic particles must be rotated up to 90'' in the width direction of the ribbon. Therefore, it is an object of the present invention to provide a disk-shaped magnetic recording medium which has a constant degree of orientation in the circumferential direction without being affected by mechanical orientation, and has a degree of orientation as high as the longitudinal direction orientation in a magnetic tape. purpose.

c. Means for Solving Problems] The above purpose is to apply a magnetic paint containing magnetic powder onto a running wide thin strip-shaped non-magnetic support, dry it to form a magnetic layer, and then apply it to a disk. In a method for manufacturing a magnetic recording medium punched into a shape, an N-pole is formed along the direction perpendicular to the direction of conveyance of the thin strip coated with magnetic paint and before drying and solidification, so as to form a magnetic field perpendicular to the direction of conveyance. , a plurality of magnet groups in which Si is arranged alternately are arranged so that the strength of the magnetic field gradually decreases along the conveyance direction, and the orientation of the magnetic paint is disordered by the magnet groups arranged in this way. This can be achieved by a method for manufacturing a disc-shaped magnetic recording medium, which is characterized by including a step of magnetically orienting it in a circumferential manner.

The present invention disorderizes the orientation of the magnetic paint in an unsolidified state, removes the mechanical orientation, and then applies a circumferential orientation magnetic field. This method produces a disk-shaped magnetic recording medium with an equal degree of orientation in the magnetic field, and thereby increases the degree of orientation to the same level as that of a magnetic tape oriented by a magnetic field in the longitudinal direction.

In particular, since magnetic non-orientation is performed using a magnetic field whose strength gradually decreases, it is possible to form a coating film with less local unevenness in non-orientation and less surface roughness.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

The magnet used in the present invention, which forms a magnetic field perpendicular to the conveying direction of the ribbon, has N poles and S poles arranged alternately on substantially the same plane, as shown in FIG. 1(a). Can be made by combining multiple magnets. The thin strip (original fabric 1) coated with magnetic paint is passed above or below the magnet, or at a position sandwiched between the top and bottom as shown in Fig. 1(b), in a direction perpendicular to the drawing. , all you have to do is arrange it.

In order to reduce the magnetic field in the conveyance direction of the web 1, as shown in Fig. 2 (a) to (C), several magnet groups (each with a magnetic field strength of (different ones) can be arranged in order of magnetic field strength (Fig. 2 (a) to (
In C), the conveyance direction is from the top to the bottom of the drawing. ).

In the present invention, the magnetism of the magnetic paint is made non-oriented using the magnet as described above, and then the magnetic paint is oriented in a circumferential manner. An example of an apparatus for this purpose is shown in FIG. 3(a).

The conveying roll 2.3 can move the original fabric 1, which has a magnetic coating applied to the base film 2 and is not solidified, in the direction of the arrow 4 at a constant speed. Circumferentially oriented magnet 5a,
5b, 5C, . . . rotates in the direction of an arrow 8 about the rotating shaft 7 at a constant circumferential speed that is synchronized with the web traveling speed.

Circumferentially oriented magnets 6a, 6b, 6 are arranged symmetrically across the original fabric 1.
A rotating drum 12 holding C... is installed,
This also rotates around the rotating shaft 9 in the direction of the arrow 10 at the same circumferential speed as the rotating drum 11.

The non-oriented magnets 13 to 16 are the magnets shown in FIG. 1(a), and are arranged so that the magnitude of the magnetic field decreases as the number increases.

When this device is operated, the original fabric 1 is conveyed by the conveying roller 2.3 and is rendered non-oriented by the non-oriented magnets 13-16. Subsequently, the web 1 that has passed between the rotating drums 11.12 is oriented in a circumferential manner by the opposing circumferential orientation magnets 5.6.

In the example of FIG. 3(a), the circumferential oriented magnet 5.6 is held on a rotating drum and rotated, and as shown in FIG. 3(b), the circumferential oriented magnet 5. It may be held and conveyed to a magnet holding and traveling device 17,18. In this case, the circumferentially oriented magnets 5.6 can remain stationary relative to the original web 1 for a longer period of time.

It should be noted that either a permanent magnet or an electromagnet can be used as the circumferentially oriented magnet 5.6. Furthermore, these circumferentially oriented magnets may be of a type using rotating magnetic poles or of a type using fixed magnetic poles. It is not limited to. Furthermore, in the examples shown in Figures 3(a) and (b), a circumferential orienting magnetic field with the same magnetic poles was applied from both sides of the original fabric, but the effect of circumferential alignment cannot be obtained even if it is applied only from one side. It will be done.

The strength of the magnetic field applied in the present invention varies depending on various factors, but in general, for non-orientation, it ranges from 1/3 to 1 times the coercive force of the magnetic powder to 1/3 of the coercive force of the magnetic powder.
4 or less, and the circumferential orientation may be approximately 1 to 5 times the coercive force of the magnetic powder.

(Example) Example 1 100 parts by weight of acicular metal magnetic powder (Fe-Ni alloy, major axis 0.25 scales, axial ratio 10, HCl 450 0e) was mixed with 25 parts of binder (vinyl chloride-vinyl acetate). 6=4 mixture of alcohol copolymer and polyurethane elastomer), 1 part by weight of lecithin (dispersant), α-
Alumina (abrasive, particle size 0゜4u) 10 parts by weight and 2
A magnetic paint obtained by dispersing and mixing 40 parts by weight of a solvent (a 1=1 mixture of methyl ethyl ketone and toluene) was applied onto a polyester sheet to a dry thickness of 3 μm.

Next, using the apparatus shown in FIG. 3(b), the material was oriented as described above and then punched out to obtain a disk-shaped magnetic recording medium (diameter 47 m+n). In addition, for non-orientation, magnets 13 to
16 was assembled in the format shown in FIG. 2(b), and the magnetic fields on the ribbon were set to 800, 600, 400, and 2000e, respectively. Also, the magnetic field in the circumferential direction is 3000 0e
It was set to

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

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 Magnetic field for non-orientation is 1200.900.600.3000
e A magnetic recording medium was produced in the same manner as in Example 1 except that the method was changed.

Example 3 The magnetic field for non-orientation is 600.450.300.1, respectively.
A magnetic recording medium was produced in the same manner as in Example 1 except that the thickness was changed to 500e.

(evaluation) Characteristics such as squareness ratio and residual magnetization of Examples and Comparative Examples were investigated.

The results are shown in Table 1. From this table, the effects of the present invention can be clearly confirmed.

〔Effect of the invention〕

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

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are views of an example of a magnet group used in the non-oriented processing apparatus of the present invention, and FIG. 2(a)
, (b) and (c) are views of an example of the non-orientation processing apparatus according to the present invention, and FIGS. 3(a) and (b) are
FIG. 3 is a schematic side view showing one embodiment of an orientation device used in the present invention. Original fabric 2.3: Conveyance roller 4: Original fabric running direction 5a, 5b, 5c=, 6a, 6b, 6c...: Circumferential orientation magnet 7.9: Rotating shaft (a) (b) 1st FIG. (c) Fig. 2 5.6 2. Circumferential Muji G Jeki Seki 13.14.15.16: Nothing but another stone (a) Fig. 3 (b) Fig. 3

Claims (1)

[Scope of Claims] 1) Magnetic recording by applying a magnetic paint containing magnetic powder onto a running wide thin strip-shaped non-magnetic support, drying the coating to form a magnetic layer, and punching out the disk-shaped material. In a method for manufacturing a medium, N poles and S poles are arranged alternately along the direction perpendicular to the direction of conveyance of the thin strip coated with magnetic paint and not dried and solidified so as to form a magnetic field perpendicular to the direction of conveyance. A plurality of magnet groups are arranged so that the strength of the magnetic field gradually decreases along the conveyance direction, and after the magnet groups arranged in this way disorder the orientation of the magnetic paint, magnetic paint is applied in a circumferential manner. 1. A method of manufacturing a disc-shaped magnetic recording medium, the method comprising the step of orienting.