JPH034975Y2 - - Google Patents

Description

[Detailed explanation of the idea]

Industrial Application Field The present invention relates to magnetic recording media.
In particular, it relates to magnetic recording media of the type used for angular or rotational control. Prior Art Conventionally, as a magnetic recording medium used for angle or rotational control, a circular base made of plastic or metal with a magnetic layer applied to the outer periphery, inner periphery, or flat surface has been used. There is. When recording or reproducing data on these magnetic recording media, the magnetic head or magnetic sensor is placed slightly away from the surface of the magnetic layer, for example, from several μm to several hundred μm, or the magnetic head or sensor is placed in contact with the magnetic layer with low pressure. I let him do it. However, when recording and reproducing without contact, it is necessary to keep a small gap between the magnetic head or sensor and the magnetic layer of the magnetic recording medium constant during rotation in order to obtain stable output. The dimensional accuracy of the magnetic recording medium is required to be highly accurate in order to prevent vibration, which poses the problem of making the magnetic recording medium itself expensive.In addition, considering temperature expansion and contraction, the magnetic layer and magnetic head of the magnetic recording medium must be highly accurate. Another problem is that the distance between the sensor and the sensor cannot be made very close, making it difficult to obtain a large output. On the other hand, in the type in which the magnetic head is brought into contact with the magnetic layer of the magnetic recording medium, there is a problem in that the magnetic layer and the head wear out when used continuously. Purpose of the invention The purpose of the invention is to solve the problems of the prior art as described above, and to provide an inexpensive magnetic recording medium that does not require much dimensional accuracy, can obtain a large reproduction output, and has extremely low wear. That's true. Structure of the invention The magnetic recording medium according to the invention is characterized by having a magnetic layer on the surface of the base with a rubber hardness of 30° to 90°. Just by bringing the heads into contact with a slight pressure, sufficient head contact is maintained and a stable and large output can be obtained. Embodiments Next, the present invention will be described in more detail with regard 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 is made by integrally molding a circular base 1 and a material obtained by kneading a magnetic material and a resin having rubber elasticity on the outer peripheral surface of the circular base 1 according to JISK6301-1971.
The magnetic layer 2 has a rubber hardness in the range of 30° to 90°. FIG. 2 is a perspective view showing another embodiment of the magnetic recording medium according to the present invention. The magnetic recording medium of this embodiment is JISK6301-1, which is made by integrally molding a disk-shaped substrate 3 and a material obtained by kneading a magnetic material and a resin having rubber elasticity on the upper surface of the disk-shaped substrate 3.
1971, the magnetic layer 4 has a hardness within the range of 30° to 90°. In the embodiments shown in FIGS. 1 and 2, the magnetic layer is provided on the outer peripheral surface of the circular base or the upper surface of the disc-shaped base, but in the case of a cylindrical base, etc., the magnetic layer is provided on the inner peripheral surface of the cylinder. It is also possible to form a magnetic layer on the magnetic layer, and the present invention also includes such a case. Next, an example of a method for manufacturing 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 body 6 is preferably one that is less deformable and light, such as plastic, fiber-reinforced plastic, inorganic material-added reinforced plastic, metal, etc., such as polyphenylene sulfide, nylon, etc.
Polycarbonate, iron, aluminum, copper, steel, etc. may be used. 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 having rubber elasticity. 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. Also,
The magnetic material is not particularly limited, but one with a small particle size is preferable, such as r-
Fe ₂ O ₃ , Fe ₃ O ₄ , Co−rFe ₂ O ₃ , Co−Fe ₃ O ₄ ,
CrO ₂ , Ba ferrite, Sr ferrite, rare earth magnet materials (SmCo ₅ , Sm ₂ Co ₁₇ , etc.) are used. The resin having rubber elasticity to be kneaded may be any of various rubbers or a mixture of resin and rubber, such as silicone rubber, urethane rubber, SBR, NBR, etc. In particular, silicone rubber has excellent recovery properties and is resistant to heat and heat.
It is preferable because it has good chemical stability and can form a high-performance magnetic layer. Further, the magnetic material and the resin may be kneaded by, for example, a conventional mixing device such as a kneader or a three-roll mill for an appropriate time. After that, the upper mold 8 is placed over the lower mold 5, and these are inserted between the flat pressure heat presses 11A and 11B with a built-in heater 10, and the resin is solidified and molded by applying pressure and heating. good. It is preferable to form a recess 8A 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 kneaded material 7. The magnetic recording medium thus formed was
Figures A and B show a plan view and a front view, respectively. In order to investigate the relationship between the rubber hardness of the magnetic layer in the magnetic recording medium of the present invention, the eccentricity of the magnetic recording medium, and the output fluctuation, experiments were conducted by forming various magnetic recording media as shown in the perspective view in Fig. 5. saw. The magnetic recording medium shown in FIG. 5 has a base body 12 with a diameter of 50 mm and a thickness of 5 mm, a magnetic layer 13 with a thickness of 1.5 mm on the outer peripheral surface, and a rotating shaft 14 fixed in the center. The rotating shaft 14 is fixed and rotated by shifting it by a predetermined amount with respect to the center of the base 12, and the eccentricity is adjusted in various ways. FIG. 6 shows the results of measuring the playback output by contacting the device. Figure 6 shows the results of measurements at a magnetic head contact pressure of 5 g, a recording density of 100 FRPI, and a rotation speed of 180 rpm. The horizontal axis represents the amount of runout (eccentricity) μm.
The output fluctuation percentage is plotted on the vertical axis. In FIG. 6, curve A shows the case where the rubber hardness of the magnetic layer 13 is 90° or more, curve B shows the case where the rubber hardness is 60°, curve C shows the case where the rubber hardness is 40°, Curve D shows the case where the rubber hardness is 30°. Experiments have shown that the lower the rubber hardness of the magnetic layer, the better the followability when the head is brought into contact with the magnetic layer, and the magnetic layer exhibits good head contact even with a highly eccentric medium at low head pressure. As is clear from the curve in FIG. 6, the lower the rubber hardness of the magnetic layer, the smaller the output fluctuation. It was observed that the higher the head pressure, the lower the output fluctuation. However, when the rubber hardness exceeded 90°, almost no effect was observed.
There is a correlation between rubber hardness and the minimum required head pressure to obtain sufficient head touch; the lower the hardness, the lower the head pressure. As for wear, a lower head pressure is often more advantageous, but if the rubber hardness of the magnetic layer is significantly lowered, the wear resistance may be lowered. If the rubber hardness is less than 30°, the mechanical strength will decrease significantly. Therefore, the rubber hardness of the magnetic layer should be selected to an appropriate value within the range of 30° to 90° depending on the application, for example, the contact pressure of the magnetic head. Next, a specific example of a prototype of the magnetic recording medium according to the present invention will be explained. A magnetic recording medium having the shape and dimensions shown in FIG. 5 was fabricated using aluminum for the base 12, iron for the rotating shaft 14, and magnetic layer 13 as follows. Composition of magnetic layer: Magnetic material rFe ₂ O ₃ (MRM400 Toda Kogyo Co., Ltd.) 60 parts Silicone rubber (KE78VBS Shin-Etsu Chemical Co., Ltd.) 40 parts Rubber hardness: 50° The magnetic recording medium according to the present invention The runout at the outer periphery was set at 10μ as a reference. On the other hand, as a comparative sample, in the composition of the magnetic layer,
A magnetic recording medium similar to the above-mentioned magnetic recording medium was prepared except that unsaturated polyester was used instead of silicone rubber. Regarding these magnetic recording media according to the present invention and comparative samples, the recording density was determined by the magnetic head.
Magnetic recording was performed at 100 FRPI, rotation speed 180 rpm, and head pressure 5 g, and reproduction was performed using a magnetic head at 5 g head pressure, and the results shown in the following table were obtained. Silicone rubber is an appropriate material for the present invention because it has excellent recovery properties after compression and also has good physical properties such as weather resistance, chemical resistance, dimensional stability, and heat resistance.

[Table] Comparing a comparison sample using unsaturated polyester with the magnetic recording medium of the present invention using silicone rubber, it was found that in the former, the adjustment of the head position to obtain the highest and uniform output was delicate and took a long time. However, the latter was able to obtain sufficient output with almost no fine-tuning. This is because, as shown in FIGS. 7A and 7B, which planarly shows the relationship between the medium and the magnetic head, the comparison sample having the magnetic layer 15 with high hardness has a high relationship between the magnetic layer 15 and the magnetic head 17. Since this is a line contact (see Figure 7A), even a slight deviation will create a gap and cause a decrease in output. However, in the magnetic recording medium of the present invention, the magnetic layer 1
6 has appropriate rubber elasticity, so that the magnetic head 17 bites into the magnetic layer 16 (see FIG. 7B).
Since slight deviations are absorbed, there is no need for delicate head positioning adjustments. This indicates that the magnetic recording medium of the present invention is easier to adjust the head position to obtain a stable output when mounted, and is superior in mass production than conventional products. Effects of the invention As is clear from the above, when the magnetic recording medium according to the invention is used in the contact playback method, the magnetic layer has appropriate rubber elasticity, so the head can be brought into contact with only a slight pressure. A sufficient head touch can be obtained, stable writing and reading are possible, and even if the medium is eccentric, it can be flexibly adapted to the head, and therefore the dimensional accuracy of the medium does not need to be very high. It can be made inexpensive. Further, when the magnetic recording medium according to the present invention is used in a non-contact reproduction method, the same effects as described above can be obtained during writing. That is, when using a magnetic drum with some eccentricity, if the magnetic head is made non-contact for both writing and reproducing (both writing and reproducing are affected by the eccentricity, output fluctuations are superimposed and become large). First, the influence of eccentricity occurs during writing, and the recording magnetization strength becomes uneven, strong in areas where the head approaches and weak in areas farther away.Furthermore, during playback, changes in the distance between the head and the medium cause the recorded magnetization strength to become uneven. The output changes accordingly. However, if the magnetic drum of the present invention is used, the heads can be brought into contact during writing even if there is some eccentricity, so the recording magnetization strength will be strong and uniform over the entire circumference. If non-contact is used during playback, the output will fluctuate as the distance between the head and the medium changes, but the magnitude of this will be limited only to the effect during playback. The following table shows an example of the results of comparing and measuring the degree of level fluctuation due to such eccentricity between the magnetic drum of the present invention and a conventional magnetic drum.

[Table] Sample A: Magnetic drum of the present invention: Rubber hardness 60° Sample B: Magnetic drum with binder made of unsaturated PET with no rubber elasticity The dimensions and shape are the same as in Figure 5. Conditions: Recording density 100FRPI Rotation speed 180rpm Head-medium distance: 20μ (nearest distance)

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the magnetic recording medium according to the present invention, FIG. 2 is a perspective view showing another embodiment of the magnetic recording medium according to the present invention, and FIG. 3 is a perspective view showing the magnetic recording medium according to the present invention. A schematic sectional view for explaining an example of the manufacturing method, FIGS. 4A and 4B are a plan view and a front view, respectively, of a magnetic recording medium formed by the manufacturing method explained in connection with FIG. 3, and FIG. A perspective view showing the shapes of various trial magnetic recording media manufactured to investigate the performance of the magnetic recording media of the invention. Figure 6 shows the amount of runout and output fluctuations that are the results of various measurements on the magnetic recording media shown in Figure 5. FIG. 7A is a schematic plan view showing the relationship between the comparative sample and the magnetic head, and FIG. 7B is a schematic plan view showing the relationship between the magnetic recording medium and the magnetic head according to the present invention. . 1, 3, 6, 12...Base, 2, 4, 7, 13
...Magnetic layer, 14...Rotating shaft, 15, 16...Magnetic layer, 17...Magnetic head.

Claims (1)

[Claims for Utility Model Registration] (1) A magnetic recording medium characterized by having a magnetic layer on the surface of a substrate with a rubber hardness of 30° to 90°. (2) The magnetic recording medium according to claim 1, wherein the magnetic layer is formed by integrally molding a material obtained by kneading a magnetic material and a resin having rubber elasticity onto the surface of the substrate. . (3) The magnetic recording medium according to claim 2, wherein the resin is silicone rubber.