JPH01251319A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To randomize the orientation of ferromagnetic perticulates, to minimize output fluctuation and to improve an electric characteristic by using a device in which a magnet is fixed on one side and a magnet is rotatably set in parallel with a supporting body on the other side. CONSTITUTION:The ferromagnetic perticulates contained in applied liquid 7 on a non-magnetic supporting body 2 which runs in a longitudinal direction by a rotating magnet 41 pass between the rotating magnet 41 and a fixed magnet 42 and thus, anisotropy generated along an applying direction is more disorientated (randomized) than the case in which only rotating magnet or only fixed magnet is used. The number of magnets to be set, their arrangement and combination can be selected suitably at will. Thus, the process to disorder the orientation of the magnetic particles of a magnetic layer is improved, the ferromagnetic particles can be disordered sufficiently and the occurrences of the reproducing output level fluctuation decreases.

Description

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

[Conventional technology]

Conventionally, magnetic recording media such as magnetic tapes or magnetic sheets are generally formed by coating a magnetic paint, which is a mixture of magnetic powder, a binder component, and other necessary components, on a non-magnetic support such as a polyester film. ing. In recent years, with the increasing demand for high-density recording magnetic recording media used in 8mm videos, electronic cameras, etc., metal magnetic powders made of iron, cobalt, etc., and various alloys, which have high coercive force and maximum residual magnetic flux density, have become popular. came into use. These ferromagnetic fine particles are made into a magnetic paint together with a binder and the like, and then coated on a non-magnetic support by methods such as top reverse coating, doctor coating, and gravure coating.

However, in the above coating method, the magnetic particles are arranged along the coating direction, resulting in anisotropy in the magnetic recording medium. When the medium is a magnetic disk, the reproduction output signal in the coating direction is higher than that in the other direction, and as a result, the reproduction output signal level read from the magnetic disk varies depending on the rotation of the magnetic disk.

For this reason, conventionally, in the manufacturing process, the orientation of the magnetic particles has been changed by (a) using a magnet that rotates the base film in parallel to randomize the orientation of the ferromagnetic particles, as shown in Figure 6. Methods of similarly removing anisotropy have been known, such as physically removing the anisotropy, or (b) applying a magnetic field in the width direction.

[Problem to be solved by the invention]

However, in (a) above, the mechanical orientation cannot be removed sufficiently, and in (b), it causes surface roughness and irregular constrictions of the envelope, resulting in direct directionality in the coating direction. As a result, there is a problem in that the reproduction output level fluctuates, and this tendency is particularly noticeable in ferromagnetic particles having a large coercive force, and disordering the orientation of ferromagnetic particles has been a major problem.

The present invention improves the process of disordering the orientation of magnetic particles in a magnetic layer, and even ferromagnetic particles can be sufficiently disordered. As a result, a magnetic recording medium with less variation in reproduction output level can be manufactured. This is what I tried to do.

[Means for Solving the Problems] According to the present invention, in a coating device that continuously coats magnetic paint on a non-magnetic support, a magnet is fixed on one side before the coating liquid is dried and solidified. , and the other side has a base film (
The orientation of the ferromagnetic particles is randomized by using a magnet that rotates parallel to the non-magnetic support (non-magnetic support), and then the orientation in the coating direction is removed by drying and solidifying the coating solution, resulting in uniform orientation of the ferromagnetic particles. Since this disorder is achieved, it becomes possible to manufacture a magnetic recording medium with excellent electrical properties.

The magnets used in the present invention are installed on both sides of the magnetic paint-coated support surface, one of which is fixed and the other rotated. A schematic side view of the device that best represents this feature is shown in FIG. The ferromagnetic fine particles contained in the coating liquid 7 on the non-magnetic support 2 that travels in the longitudinal direction by the rotating magnet 41 pass between the rotating magnet 41 and the fixed magnet 42, so that they are spread along the coating direction. The resulting anisotropy is
The orientation is more non-oriented (randomized) than when only rotating magnets or only fixed magnets are used.

Further, the number, arrangement, and combination of magnets to be installed can be freely selected as appropriate. An example is shown in FIGS. 2 to 5. The purpose of Figures 2 to 4 is to further increase the effect of the magnets by using two fixed magnets. Figure 2 shows the same poles arranged in the same direction, and Figure 3 shows In this case, magnets with different polarities are arranged in the same direction, and FIG. 4 shows fixed magnets arranged in parallel with the non-magnetic support 2, regardless of whether they have the same or different polarities. becomes even larger. FIG. 5 shows a large number of the devices shown in FIGS. 1 to 4 arranged side by side. By using a plurality of magnets, it is possible to prevent the randomization effect from decreasing in the vicinity of the introduction part and the derivation part to the magnet part, and it is possible to further strengthen the randomization effect. In this way, the combination of a fixed magnet and a rotating magnet is
It can be selected freely depending on the target support, etc., and contrary to FIGS. 1 to 5, the rotating magnet may be placed below the support.

In addition, both permanent magnets and electromagnets can be used as magnets, and the size, shape, magnetic field strength, gap to the support, rotation speed of the rotating magnet, etc. can be set freely as well, making it effective. Non-orientation can be achieved.

According to the above configuration, even when using ferromagnetic particles, non-orientation can be achieved, especially when the coercive force Hc 14
Effective non-orientation can be performed for those with a diameter of 000e or more. Thereafter, the non-oriented support coated with magnetic paint can be made into a desired magnetic recording medium by a conventional method.

[Example] Example 1 100 parts by weight of acicular metal magnetic powder exhibiting the coercive force Hc shown in the table was mixed with 25 parts by weight of a binder (vinyl chloride-vinyl acetate-vinyl alcohol copolymer and polyurethane elastomer in a 6:4 ratio). 1 part by weight of lecithin (dispersant), 10 parts by weight of alpha alumina (abrasive, particle size 0.4p) and 240 parts by weight of a solvent (1 to 1 mixture of methyl ethyl ketone and toluene). Immediately after coating the polyester film with the paint and smoothing the surface with a smoother, a non-orientation treatment was performed using a magnet having the configuration shown in the table, and thereafter a 47 mm diameter disc-shaped magnetic recording medium was obtained using a conventional method. When the modulation and squareness ratio of each recording medium obtained were measured, the results were as shown in the table.
6) had improved electrical properties, etc., compared to the conventional examples (NO, 1 to 2), and particularly when magnetic powder of He14000e or higher was used, the improvements were remarkable.

Table [Effects of the Invention] As explained above, the orientation of ferromagnetic fine particles can be made random by using a device that is installed parallel to a support such that a magnet is fixed on the negative side and rotated on the other side. turned into
As a result, a magnetic recording medium with small output fluctuations and improved electrical characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a typical non-orientation means of the present invention, FIGS. 2 to 5 are schematic side views showing other non-orientation means of the present invention, and FIG. 6 is a conventional non-orientation means. FIG. 7 is a schematic side view showing the orientation means, and FIG. 7 is a schematic side view of the manufacturing apparatus in the present invention. 1 is a feeding section 2 is a non-magnetic support 3 is a coating device 4 is a non-orientation means 5 is a drying device 6 is a winding section 7 is a coating liquid 41 is a magnet (for rotation) 42 is a magnet (for fixation) 43 is a shaft Patent applicant Canon Co., Ltd.

Claims (2)

[Claims] (1) A magnetic recording layer is formed by applying a coating liquid consisting of fine ferromagnetic particles dispersed in a binder dissolved in a solvent onto a strip-shaped non-magnetic support along the longitudinal direction of the support. In the method of manufacturing a magnetic recording medium, before the coating liquid applied to the support is dried and solidified, a fixed plate holding a magnet on one side is rotated parallel to the non-magnetic support on the other side. A method for producing a magnetic recording medium, comprising making ferromagnetic fine particles random (non-oriented) by using a magnet, and then drying and solidifying the coating liquid. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the ferromagnetic fine particles have an Hc of 14,000e or more.