JPS6334734A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain circumferentially orientated disk-like magnetic recording media by perpendicularly crossing two rod-like magnets slightly longer than the diameter of each disk-like magnetic recording medium at the center of respective magnetic axes so that the magnetic axes are parallel with a thin band surface and have equal distances from the thin band surface and arranging the magnets so that the same poles of a pair of magnets are arranged in the traveling direction of the thin band. CONSTITUTION:The rod-like magnets 1, 2 have the length (d) slightly longer than the diameter of a disk-like magnetic recording medium to be formed. The pair of magnets 1, 2 are arranged so that respective magnetic axes are crossed at right angles and the same poles are arranged in the traveling direction of an original plate in case of observing the pair of magnets from one surface of the original plate 3. Respective magnets 1, 2 are orientated by traveling the original plate 3 in an arrow 4 direction while keeping respective magnets 1, 2 parallel with the original plate 3 at an equal distance g/2. The original plate sheet having a magnetic layer orientated by said procedure is punched as shown by a dotted circle with a diameter 2r(2r<d) to obtain a disk-like magnetic recording medium.

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 suitable for high-density recording.

[Prior Art] In recent years, flexible disk-shaped magnetic recording media have been widely used, such as flexible disks as large-capacity storage devices for computers, magnetic sheets for two-still video cameras, and the like.

However, in this type of magnetic recording medium, the magnetic head slides along the circumference to read and write records, whereas in normally manufactured magnetic recording media, magnetic powder that forms the magnetic layer is used. Since the magnetic particles are not oriented in a circumferential manner, the squareness ratio is poor and the residual magnetization is lower than that of magnetic tapes in which magnetic powder is oriented. Therefore, in this disc-shaped magnetic recording medium, it is necessary to widen the track width in order to obtain sufficient output, which is an obstacle to increasing the recording density.

In addition, when using needle-shaped magnetic powder with a large axial ratio, which is normally used in tapes, it is possible to adjust the direction of application of the non-magnetic support sheet (for example, in the long direction) without using an orientation device during the coating and drying process. Even if a signal with a constant amplitude is recorded circumferentially on a disk-shaped punched disk, the envelope waveform will not be constant because the residual magnetization is larger in the longitudinal direction. However, there was also a problem that the output fluctuated synchronously.

On the other hand, as a circumferentially oriented magnetic recording medium that eliminates the above-mentioned problems, there is also a hard disk obtained by spin coating. However, in the case of spin coating, since the support is formed into a disk shape and each recording medium is coated one by one, there are problems in that mass production is poor and the cost is high.

In addition, although some methods of circumferential orientation using a magnetic field have been devised, for example as disclosed in Japanese Patent Publication No. 40-23828, the conventional method using magnetic field orientation is Currently, it has not been put into practical use because it requires extensive modification.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above and provides a method for manufacturing a circumferentially oriented disc-shaped magnetic recording medium easily and with good mass productivity. The purpose is to

[Means and effects for solving the problem] The above problem can be solved by coating a magnetic coating on a wide thin strip-shaped non-magnetic support that runs in one direction to form a magnetic layer, and drying it by one-surface molding, etc. In a method for manufacturing an RA% recording medium that is punched out into a disk shape after passing through the process, the ribbon coated with magnetic paint and before drying and solidification is sandwiched between the thin strips, which are slightly smaller than the diameter of the disk-shaped magnetic recording medium to be manufactured. Each long bar-shaped magnet is orthogonally crossed at the center of each magnetic axis so that the magnetic axes are parallel to and equidistant from the ribbon surface, and the same poles of the pair of magnets are aligned in the ribbon running direction. After arranging the thin strip and the rod-shaped magnet, the distance between the thin strip and the rod-shaped magnet is kept constant, the thin strip is run for orientation, and after drying and surface shaping, one point on the line through which the center of the pair of magnets has passed. This problem is solved by a method for manufacturing a magnetic recording medium, which is characterized by punching out a disk shape with a center.

A more detailed explanation will be given below with reference to the drawings.

FIG. 1 is a plan view of a magnetic field orientation device used in the present invention, and FIG. 2 is a side view. Reference numeral 1.2 is a bar-shaped magnet, which is placed across the original fabric 3 that has not yet been dried and solidified after being coated with magnetic paint. The bar magnet 1.2 is similar and has a length d slightly larger than the diameter of the disc-shaped magnetic recording medium to be manufactured. When this pair of magnets is viewed from the direction of one surface of the web 3, the magnets are arranged so that their magnetic axes are orthogonal to each other and the same poles are lined up in the running direction of the web. Furthermore, as shown in Fig. 2, each magnet 1.2 is parallel to the web 3, and the web 3 is moved along the arrow 4 while maintaining the distance Mg/2 to the web 3.
Orientation is carried out by running it in the direction of .

At this time, the magnet spacing g is set so that a magnetic field approximately 1 to 5 times the coercive force of the magnetic powder used is applied, although it varies depending on the viscosity of the magnetic paint and the coating speed.

After the orientation, the orientation of the obtained magnetic layer is fixed by solidifying the magnetic layer by heat evaporation or heat curing as soon as possible.

FIG. 3 is a schematic diagram of the orientation pattern of the magnetic layer subjected to the orientation treatment, in which the end portions of the original fabric remain oriented in the longitudinal direction due to mechanical orientation, and the central portion is oriented in the width direction by the above-mentioned orientation device. As a result, when the web 3 is made to run in the direction of the arrow 4, a magnetization pattern as shown by the arrow is formed in the magnetic layer of the web 3.

Next, the raw sheet having the magnetic layer oriented in this manner is punched out as shown by a dotted circle with a diameter of 2 r (2 red) in FIG. 3 to obtain a disk-shaped magnetic recording medium. At this time, by positioning the punching so that the center of the disk is on the extension line (indicated by a straight dotted line in the figure) of the center point of the magnet used for orientation, the magnetic layer is oriented in a circumferential manner. A disc-shaped magnetic recording medium according to the present invention having the following characteristics is obtained.

The above example is a case where a pair of magnets are used as an orientation device, but if the width of the original film 3 is sufficiently larger than the diameter 2r of the disc-shaped recording medium 7a to be manufactured, some pairs of magnets are used as the orientation device. It is also possible to align a large number of sets simultaneously in the width direction of the bar magnets 1 and 2. In addition to permanent magnets, electromagnets can also be used as the bar magnets 1 and 2.

[Example] Acicular magnetic metal powder (Fe-Xi gold alloy major diameter 0.25g
tm, axial ratio 8, Hc 14500e) 100 parts by weight and 25 parts by weight of binder (vinyl chloride-vinyl acetate-
(6:4 mixture of vinyl alcohol copolymer and polyurethane elastomer), 1 part by weight of lecithin (dispersant), α
- Magnetic paint prepared by dispersing and mixing 10 parts by weight of alumina (abrasive material 1 particle size 0.4 L 1) and 240 parts by weight of a solvent (1=1 mixture of methyl ethyl ketone and toluene) to a dry thickness of 3 tiles. Apply it so that it becomes
The magnetic properties of a disc-shaped magnetic recording medium (diameter 47 mm) obtained by orientation treatment and punching as described above using the apparatus shown in the figure were compared with those of a conventional disc obtained in the same manner except that orientation treatment was not performed. Along with that of magnetic recording media,
A summary is shown in Table 1. For orientation, a magnetic field of 30,000 e was applied using a unit magnet with a magnetic pole width of 50+ am. The magnetic properties were measured using a Sendust head for recording and a ferrite head for reproduction at a relative velocity fi of 8 m.

Table 1 [Effects of the Invention] As explained above, according to the present invention, it is possible to easily manufacture a circumferentially oriented disk-shaped magnetic recording medium with good mass productivity.

[Brief explanation of drawings]

FIG. 1 is a plan view of a magnetic field orientation device used in the manufacturing method of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a schematic diagram of an orientation pattern of a magnetic layer subjected to orientation treatment according to the present invention. 1.2... Rod-shaped oriented magnet, 4... Original fabric running direction, g... Magnet spacing, d... Magnet length.

Claims (2)

[Claims] (1) A magnetic recording medium that is formed by coating a magnetic coating on a wide thin strip-shaped nonmagnetic support that runs in one direction to form a magnetic layer, and then punching it out into a disk shape after going through processes such as drying and surface shaping. In the manufacturing method, one bar-shaped magnet slightly longer than the diameter of the disc-shaped magnetic recording medium to be manufactured is placed between the thin ribbon coated with magnetic paint and not dried and solidified, so that the magnetic axis is on the surface of the thin ribbon. The magnetic axes of the respective magnetic axes are orthogonal to each other at the center so that they are parallel and equidistant from each other, and the magnets are arranged so that the same poles of the magnet pair are lined up in the ribbon running direction, and the distance between the ribbon and the bar magnet is A magnetic recording medium characterized in that the ribbon is orientated by running while being held constant, dried and surface formed, and then punched out into a disk shape centered on a point on a line through which the center of the pair of magnets passes. manufacturing method. (2) Two or more pairs of magnets are arranged in the width direction of the ribbon so that the distance between the centers is larger than the diameter of the disc-shaped magnetic recording medium to be manufactured. A method for manufacturing a magnetic recording medium.