JPS6267724A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic characteristic by disordering the orientation of ferromagnetic particles then drying and solidifying the coating liquid thereby holding and fixing the pulverous ferromagnetic particles which are disordered in the orientation. CONSTITUTION:Multipolar permanent magnets M1-M6 are gradually changed in the angle with the conveying direction of a web and the intensity of the magnetic field thereof is gradually increased on the down stream side, by which the directions of the particles are largely changed with the uncured web contg. the ferromagnetic particles. The particles are thereby rotated and eventually the directions are made random and non-oriented. Since the angle is gradually changed according to the flow of the multipolar magnets in the above-mentioned manner, stripes in a coated layer are hardly generated. The electromagnetic characteristic is thus improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided on a non-magnetic support by a coating method, and more specifically, to The present invention relates to a method of manufacturing a disk-shaped or sheet-shaped magnetic recording medium in which the orientation of fine particles is disordered.

[Conventional technology]

Generally, flexible magnetic disks and magnetic sheets are manufactured by continuously transporting a strip-shaped non-magnetic support (polyethylene terephthalate, triacetylcellulose, diacetylceftzO-su, vinylidene chloride, polyzologylene, etc.) in the longitudinal direction of the support. Binders dissolved in solvents (e.g. vinyl chloride vinyl acetate copolymers, vinyl chloride acrylonitrile copolymers, acrylic ester acrylonitrile copolymers, acrylic ester vinylidene chloride copolymers, other copolymers with acrylic acid) , urethane distomer, nylon-silicone resin.

Nitrocellulose, polyvinyl chloride, vinylidene chloride acrylonitrile copolymer, polyamide resin.

Polyvinyl detyral, cellulose derivatives, styrene-butadiene copolymers, phenolic resins, engineered resins, polyurethaneurea resins, melamine resins.

Ferromagnetic fine particles (γ-Fe2O3, Fe
It is manufactured by coating with γ-Fe20s acoat doped with 3O4, Co, etc., but if ferromagnetic fine particles are arranged in a specific direction during manufacturing and anisotropy occurs in the magnetic recording medium, Anisotropy also occurs in magnetic and electromagnetic properties.

When the magnetic particles are arranged along the coating direction, if the magnetic recording medium is a magnetic disk, the reproduction output signal in the coating direction will be higher than that in the other direction, and as a result, the reproduction output signal level read from the magnetic disk will be Changes as the magnetic disk rotates.

[Problems to be solved by the invention] Therefore, 2. For example, when manufacturing a flexible magnetic disk (floppy disk) that is used by rotating, it is necessary to manufacture a general magnetic tape so that the ferromagnetic particles do not have linear directionality. In the process.

It is manufactured by physically removing the orientation of magnetic particles or by shielding the magnetic field, but even with these methods, linear directionality still occurs in the coating direction due to flow orientation during coating. As a result, fluctuations in the reproduction output level occur.

That is, in a floppy disk, it is originally desirable that the ferromagnetic fine particles 11 be random (non-oriented) within the plane of the magnetic recording medium 10, as shown in FIG. 3, but in extreme cases, as shown in FIG. In general, orientation progresses in the direction of web (medium) feed.

When a disk is punched out of the medium and the output characteristics are measured along with the rotation angle, the output changes with the orientation (Fig. 5).
When low-pass modulation) appears and the ratio between high level A and low level B becomes large, it cannot be used as a recording medium.

Therefore, it is necessary that the output level is high (or satisfies a certain level) and the ratio between B and B is extremely small, and as a floppy disk, the ratio A/B is
is not practical unless it is 1.05 or less.

The object of the present invention is to use non-orientation means (magnets).

Eliminating the orientation of ferromagnetic particles in the coating web conveyance direction in the production of flexible magnetic disks or magnetic sheets,
The object of the present invention is to provide a method for manufacturing a magnetic recording medium that improves electromagnetic properties by uniformly disordering the orientation of ferromagnetic fine particles.

[Failure to solve the problem]

The method for manufacturing the magnetic recording medium of the present invention involves coating a strip-shaped non-magnetic support in the longitudinal direction of the support with a coating solution in which fine ferromagnetic particles are dispersed in a binder dissolved in a solvent. In a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided by a method, before the applied coating liquid is dried and solidified,
It has a certain angle with respect to the conveyance direction of the coated web, and the angle θ increases as it goes downstream of the magnetic medium.

In order to form a magnetic field so that the magnetic field to the medium gradually decreases, a large number of magnets (one magnet
In this book, the orientation of one ferromagnetic particle is made disordered by a non-orientation means formed by arranging a large number of poles arranged alternately, and then the coating liquid is dried and solidified, so that the orientation is disordered. It is characterized by holding and fixing ferromagnetic fine particles.

That is, the present invention applies a coating solution in which a ferromagnetic material is dispersed in a binder dissolved in a solvent onto a strip-shaped non-magnetic support.
In this method of manufacturing a magnetic recording medium in which a magnetic recording layer is formed by coating along the longitudinal direction of the support, before the coating liquid applied to the support is dried and solidified, the coating liquid is applied along the longitudinal direction of the support. .

A plurality of multi-pole magnetized permanent magnets are arranged so that the angle gradually changes, and the strength of the magnetic field gradually decreases along the downstream direction of the conveyance direction of the support. This method of manufacturing a magnetic recording medium is characterized by randomizing the orientation of magnetic particles, and then drying and solidifying the coating liquid.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a side view schematically showing an apparatus for manufacturing a magnetic recording medium according to the present invention. In FIG. 2, 1 is a delivery section, 2 is a non-magnetic paste (support), and 3 is a coating device for applying a coating liquid to the support 2.

4 is a non-orientation means, 5 is a drying device, and 6 is a winding section.

FIG. 1 specifically shows the non-orientation means (magnet) 4 in FIG. 4, with (,)d being a top view and (b) being a side view thereof.

In FIG. 1, Ml, M2. M3. M4. M5゜M6
are permanent magnets, and M1 to M6 are exactly magnetized with multiple poles. 2M1 and M2 as shown in Figure 1(a),
M3 and M4, M5 and M6 are arranged in a T-V shape,
Its center is perpendicular to the conveyance direction of the web 2, and the central angle of the figure 7 is θ. , θ1. In the thickness direction of the web 2, the gap d0 between the web and the web is such that the magnetic field from the permanent magnet gradually decreases as the downstream side of the web 2 increases. dl, d
This is a configuration in which 2 is increased. That is, y d6 (d,
(d). Although there are differences depending on the type of ferromagnetic fine particles and the binder.

For oxide ferromagnets, a configuration is required that provides a magnetic field of 300 to 700 oersteds at the upstream tip and 5 to 50 oersteds at the downstream end.

Further, the length of the permanent magnets M1 to M6 is preferably at least as long as the diameter of the floppy disk.

In terms of manufacturing, it is more practical if the width W of the media web (see FIG. 1(, )) is also larger.

〔Effect of the invention〕

In this way, in the present invention, the angle of the multi-pole permanent magnet is gradually changed with respect to the web conveyance direction, and the strength of the magnetic field is gradually decreased on the downstream side, thereby producing a magnetic material containing ferromagnetic particles. In the cured web, the direction of the two particles is greatly changed and rotated, and as a result, the direction becomes random and becomes non-oriented.

Furthermore, since the angle of the multi-pole magnet is gradually changed according to the flow, stripes do not occur in the coating layer.

[Transformation]

The material of the permanent magnet used in the present invention is not limited.

Rare earth permanent magnets (samarium, cobalt magnets, neodymium, iron-based magnets), ferrite magnets, alnico magnets, and plastic magnets are applicable.

In addition, in Figure 1, permanent magnets are placed only on the top side, but
The upper and lower sides of the web may be opposed to each other.

There is no problem even if they are arranged alternately on both the upper and lower surfaces.

Further, there is no restriction on the number of permanent magnets.

Further, the permanent magnet M needs to be magnetized with multiple poles, so that non-orientation is uniformly performed over the entire area of the web.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the non-orientation means used in the present invention, in which (a) is a top view and (b) is a side view. FIG. 2 is a schematic side view of an apparatus for manufacturing a magnetic recording medium according to the present invention, FIGS. 3 and 4 are diagrams for explaining the orientation state of ferromagnetic fine particles on a magnetic recording medium, and FIG. 5 is a diagram showing the relationship between the rotation angle of a magnetic recording medium and the output radius. DESCRIPTION OF SYMBOLS 1... Delivery part, 2... Support body, 3... Coating device, 4... Non-orientation means, 5... Drying device, 6...
Winding section. M1 to M6...Permanent magnets.

Claims (1)

[Claims] 1) A magnetic recording layer is formed by applying a coating liquid consisting of a ferromagnetic material dispersed in a binder dissolved in a solvent onto a strip-shaped non-magnetic support along the longitudinal direction of the support. In a method for manufacturing a magnetic recording medium, before the coating liquid applied to the support is dried and solidified, a plurality of multi-pole magnetized permanent magnets are installed so that the angle gradually changes with respect to the conveying direction of the support. Randomize the orientation of the ferromagnetic particles through a non-orientation means that gradually decreases the strength of the magnetic field along the downstream direction of conveyance of the support, and then dry and solidify the coating liquid. A method of manufacturing a magnetic recording medium characterized by: