JPS59192918A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an inexpensive magnetic recording medium with high precision and superior in mass productivity by providing a magnetic layer formed in one body with the material kneaded with a magnetic material and a resin for a base body and a surface thereof. CONSTITUTION:A base body 6 having a desired shape is provided previously in a bottom force 5 of a metallic mold. Next, the material 7 kneaded with the magnetic material and the resin is packed in the gap between the inner circumferential surface of the force 5 and the outer circumferential surface of the body 6. Rare earth magnetic material, etc. of small particle size and thermosetting resin are used as the magnetic material and the kneading resin respectively. Then, a top force 8 is covered against the force 5, these are inserted between heat pressing plane plates 11A and 11B containing a heater 10, pressed and heated to harden and mold the resin. It is preferable to form a dent 8A for escaping the material 7 at the position corresponding to the vicinity of the outer circumference of the body 6 at the lower surface of the force 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium and a method for manufacturing the same, and in particular to a type of magnetic recording medium used for angle or rotational control and a method for manufacturing the same. .

Prior Art Conventionally, magnetic recording media used for angle or rotational control include those with a magnetic coating formed on the outer periphery of a circular metal base (while still being flat), circular glass magnets), etc. There is one in which a sintered ring magnet is glued. This type of magnetic recording medium has its magnetic part magnetized with equally spaced magnetization and turns, and is attached to a rotating system and magnetized with a magnetic head or magnetoresistive element. It is used to detect turns and to indicate the number of rotations and all angles of rotation.

However, conventional magnetic recording media on which magnetic coatings are formed have disadvantages of poor productivity and high cost because they require grinding. This is because - Spraying is generally used as the coating method, but to obtain the required film thickness of 30 to 700μ gold, multiple coatings are required, and drying is required after each coating, which reduces productivity. is inferior. In addition, the surface of the coating film becomes rough, and the coating becomes rough and requires grinding to reduce noise.

Furthermore, in the case of a star magnetic recording medium in which a conventional circular glass magnet is bonded, it is difficult to obtain high dimensional accuracy, so there is a drawback that high-precision characteristics cannot be obtained. In other words, the dimensional accuracy of the plastic magnet itself can be improved, but when it is bonded to a metal base, misalignment and deformation occur, so it is necessary to limit its roundness and center runout to within 700μ. It's difficult.

By grinding the surface of the magnet after adhering it, it is possible to improve the roundness and accuracy, but this increases the cost.

Furthermore, in the case of a conventional magnetic recording medium with a ring magnet bonded to it, a sintered molded magnet is used, but it has the disadvantage that it requires grinding after molding, which complicates the process and increases costs. Furthermore, when mounting on a rotating system, alignment is sometimes difficult and it is difficult to keep the runout within 100 microns, which is the same drawback as in the case of the plastic magnet described above.

In recent years, as this type of magnetic recording medium, a kneaded type magnetic recording medium has been developed in which the entire body including the base is formed by injection molding from a material such as nylon resin kneaded with a magnetic material such as barium ferrite. . However, since these kneaded type magnetic recording media have a uniform composition as a whole, it has been difficult to satisfy the conflicting properties of mechanical strength and magnetic properties. This is because a higher content of magnetic material is better for magnetic properties, but this results in brittleness and a decrease in mechanical strength. Therefore, in such cases, it has been necessary to compromise on a composition that provides both magnetic properties and mechanical strength to a certain degree.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide an inexpensive magnetic recording medium with high precision and excellent mass productivity, and a method for manufacturing the same.

Structure of the Invention The magnetic recording medium according to the present invention is characterized by comprising a base body and a magnetic layer formed by integrally molding a material obtained by kneading a magnetic material and a resin onto the surface of the base body.

Further, according to the present invention, in such a magnetic recording medium, a substrate to which a magnetic layer is to be applied is placed in a mold in advance, and a magnetic material and a thermosetting material are placed in the gap between the surface of the substrate and the mold. After filling a material kneaded with a resin, the resin is hardened and molded by applying pressure and heating to form a magnetic M on the surface of the substrate.
'fr Manufactured by integrally forming.

Embodiments Next, the present invention will be described in more detail with reference to embodiments of the present invention based on the accompanying drawings.

FIG. 1 is a perspective view showing an embodiment of a magnetic recording medium according to the present invention. The magnetic recording medium of this embodiment includes a circular base 1 and a magnetic layer 2 formed by integrally molding a material obtained by kneading a magnetic material and a resin onto the outer peripheral surface of the circular base 1.

FIG. 1 is a perspective view showing another embodiment of the magnetic recording medium according to the present invention. The magnetic recording medium of this embodiment includes a disc-shaped substrate 3 and a magnetic layer 4 formed by integrally molding a material obtained by kneading a magnetic material and a resin onto the upper surface of the disc-shaped substrate 3. It has become.

In the embodiments shown in section 1 and FIG. 2, the magnetic layer is provided on the outer circumferential surface of the circular substrate or the upper surface of the disc-shaped substrate, but in the case of a cylindrical substrate, etc., the magnetic layer is provided on the inner circumferential surface of the cylinder. It is also possible to form the magnetic layer integrally with the magnetic layer, and the present invention also includes such a case.

Next, an embodiment of the method for fabricating a magnetic recording medium according to the present invention will be described with reference to FIG.

As shown in a schematic cross-sectional view in FIG. 3, a base body 6 having a desired shape is placed in advance in the lower mold 5 of the mold. The material for forming the base 6 is preferably one that is less deformable and light, such as glass, fiber-reinforced plastic, reinforced plastic with added inorganic materials, metal, etc., such as EVA, polyphenylene sulfide, nylon, polycarbonate, iron, aluminum, copper, etc. Brass etc. is fine. Next, the gap between the inner circumferential surface of the lower mold 5 and the outer circumferential surface of the base body 6 is filled with a material 7 obtained by kneading a magnetic material and a resin. In this case, it is preferable to apply a mold release material 9 such as silicone to prevent adhesion on the inner peripheral surface of the lower mold 5. Further, the magnetic material is not particularly limited, but preferably has a small particle size, such as r
-Fe203+ Fe3O4゜Co-rFe OCo-
Fe3O41CrO2, Ba ferrite, 2 3+ Sr ferrite, rare earth magnet material (SmCo 5
r Sm2Co 17 etc.) are used. The resin to be kneaded is preferably a thermosetting resin that is initially in a liquid state and solidified by pressure heat treatment due to the manufacturing method.
For example, unsaturated polyester, acrylic resin, epoxy resin, urethane resin, etc. may be used. Further, the magnetic material and the resin may be kneaded for a suitable time using a conventional mixing device such as a kneader, a three-neck machine, or a Lumir. after that,
The upper mold 8 is placed over the lower mold 5, and these are connected to the heater 10.
The resin may be hardened and molded by inserting it between the flat-pressure heat lugs 11A and 11B, which have a built-in unit, and pressurizing and heating the resin. It is preferable to form a recess 8Ai on the lower surface of the upper die 8 at a position corresponding to the vicinity of the outer periphery of the base body 6 for escape of the interfering material 7.

The magnetic recording medium formed in this way is shown in Fig. q (A).
and (B) are shown in a plan view and a front view, respectively.

According to such a pressure and heat molding method, the magnetic layer can be made homogeneous, and since the stress applied to the substrate during forming is low, distortion such as deformation of the substrate can be prevented. Instead of such a pressure and heat molding method, it is possible to use an injection molding method, but this method involves injecting a material made by kneading molten resin and magnetic material into the gap between the mold and the base, and then cooling and hardening. Since the fluidity state differs near the injected dart, it is difficult to avoid uneven distribution or orientation of the magnetic material, resulting in areas with uneven magnetic properties.Also, because the injection pressure is high, This is not preferable because it has the disadvantage of being subject to strong stress and being easily deformed.

A magnetic recording medium having a shape specifically shown in FIG. q was fabricated using the creation method explained with reference to FIG. 3 and the following specifications.

Magnetic layer forming material Magnetic material: rFe 203 (MRM 'Iθ0 Toda Kogyo ■) 60 parts Resin: Unsaturated polyester
Base material: polyphenylene sulfide (PPS)
Resin (Shin-Etsu Chemical) Dimensions: Outer diameter φHere...! ;tntn thickness
S magnetic layer thickness /, S order compression molding pressure: 100 kg7cm2 Molding temperature near 6
A magnetic recording medium prototyped with specifications longer than 0° (molding time) was able to obtain good characteristics as described below.

Magnetic characteristics Coercive force 2g θ00e Residual magnetic flux density: 900G Electromagnetic conversion characteristics As shown by the solid curve A in the left diagram, a uniform and sufficient output was obtained.

Dimensional accuracy Roundness: /μ or less Runout (runout of the outer periphery based on the center hole): ±/θ
A dotted curve B in the figure below μ shows the output waveform of a magnetic recording medium similar to the above-mentioned magnetic recording medium prototyped according to the present invention and formed by the above-mentioned injection molding method. As shown by B' of this dotted curve B, in injection molded magnetic recording media, large output fluctuations occur at the weld portion of the magnetic layer caused by injection molding. By comparing these curves A and B in FIG. 5, it can be seen that the reproduction output waveform of the magnetic recording medium according to the present invention has much less fluctuation, and the magnetic recording medium according to the present invention has better magnetic properties. In addition to being uniform, it also has excellent dimensional accuracy.

If the entire magnetic layer of the medium manufactured as described above is polished, it is possible to obtain a medium with even less center runout and high accuracy.

Effects of the Invention Compared to conventional kneaded type magnetic recording media, the magnetic recording medium according to the present invention has a two-layer structure consisting of a base and a magnetic layer, so the magnetic properties are determined only by the magnetic properties, and the mechanical properties are determined by the base. This provides flexibility in that materials satisfying both characteristics can be selected as the magnetic layer material and the substrate material, respectively, independently of each other. In addition, regarding the overall weight, the specific gravity of conventional mixed-in magnetic recording media, in which a magnetic material (for example, ferrite with a specific gravity of about 5) is kneaded throughout, is 3 to 5 da. In the magnetic recording medium according to the invention, the heavy magnetic material is contained only in the surface magnetic layer, so the overall weight can be reduced, and its specific gravity is 8S-λ, about 1/2 the weight of the conventional kneaded type. can do.

Furthermore, the magnetic recording medium according to the present invention has an advantage over conventional coating-type magnetic recording media in that the thickness of the magnetic layer can be arbitrarily selected. That is, the magnetic layer thickness is an important factor for magnetic recording, and the optimum thickness must be determined depending on the conditions.

If it is thin, the playback output will be low, and if it is too thick,
This has the disadvantage that the reproduction output decreases due to peak shift (distortion of reproduced waveform) and film thickness loss. From this point of view as well, the present invention is advantageous in that it is possible to select the magnetic layer thickness within a wide range, so that a magnetic layer having an optimum thickness can be formed in many cases. In addition, according to the method for manufacturing a magnetic recording medium of the present invention, it is possible to mass-produce a magnetic layer having homogeneous magnetic properties,
Various shapes, dimensions, etc. can be selected over a wide range, and there is no deformation or noise of the base, making it possible to provide inexpensive magnetic recording media that are highly mass-producible.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a perspective view showing another embodiment of a magnetic recording medium according to another embodiment of the present invention, and FIG. 3 is a perspective view showing a magnetic recording medium according to another embodiment of the present invention. 9(A) and 9(B) are a schematic cross-sectional view for explaining one embodiment of the method for manufacturing a magnetic recording medium, and FIGS. The front view of FIG. 5 is a diagram showing an example of a waveform reproduced from the magnetic recording medium of FIG. 1.3.6...Base, 2.4.7...Curved magnetic layer, 5...Bottom mold, 8... ... Upper die, 11A, 11B... Curve... Flat pressure heat press Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A magnetic recording medium comprising a substrate and a magnetic layer formed by integrally molding a material obtained by kneading a magnetic material and a resin onto the surface of the substrate. (2) Place the substrate to which the magnetic layer is to be applied in advance in the mold,
A magnetic layer is formed on the surface of the substrate by filling the gap between the surface of the substrate and the mold with a material obtained by kneading a magnetic material and a thermosetting resin, and then hardening and molding the resin by applying pressure and heating. A method of manufacturing a magnetic recording medium, characterized in that it is integrally formed.