JPS58141437A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the influence of demagnetizing fields and to permit high density recording by setting the orienting direction of magnetic particles in the magnetic coating film on a substrate in the direction inclining with respect to the traveling direction. CONSTITUTION:The orienting direction of magnetic particles is set in the direction inclining in the traveling direction (a) with respect to a magnetic head, and recording and reproducing are performed along the direction (a). If the magnetic tape and magnetic particles are oriented in such a way that the orientation direction attains >=theta=10 deg. with respect to the longitudinal direction, the influence of demagnetizing fields is decreased and the reproduced outputs begin to be improved as compared to conventional magnetic tapes oriented to the above- mentioned theta=0 deg.. At theta=60 deg., the magnetic fluxes that the magnetic head can sense decrease and conversely the reproduced outputs are decreased. Therefore, the range of the theta is preferably 10-60 deg., more preferably 15-45 deg., at which the magnetic recording medium deals suffciently with recording at short wavelengths without receiving the influence of demagnetizing fields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording media such as magnetic tape.

In this type of recording medium, such as a magnetic tape, the magnetic particles are oriented approximately in the longitudinal direction (travel direction) during the process of applying magnetic paint. It is customary to forcibly orient the particles in the longitudinal direction (arrow & direction) using a repelling magnet or a solenoid coil (not shown) while the applied coating film 2 is still dry. is also carried out along this direction.

By the way, recording media such as magnetic tapes need to be able to sufficiently support high recording density, so-called short wavelength recording, but the magnetic particles oriented in the longitudinal direction have a limit for short wavelength recording. There is.

That is, as shown in Fig. 1, in a short wavelength recording state, when the wavelength λ becomes very short and becomes smaller than the thickness t of the magnetic coating (about 4μ), for example, when it becomes less than 1μ, the magnetic particles will not interact with each other. The demagnetizing field related to the model number becomes stronger, causing a state in which magnetization is not orderly in the longitudinal direction (a), and as a result, it becomes impossible to obtain an appropriate reproduction output.

For this reason, it has been devised to avoid the above-mentioned adverse effects of the demagnetizing field by orienting the magnetic particles in the thickness direction of the magnetic tape, that is, in the vertical direction (b), as shown in Figure 2. In the case of short wavelength recording where wavelength/thickness of magnetic coating film is 115 or less, alignment in the vertical direction or recording/reproduction described above is preferable to alignment in the longitudinal direction or recording/reproduction described above. would be much more advantageous.

However, when magnetic particles are oriented in the vertical direction, since the particles are acicular in shape, the magnetic coating tends to have a flat or rough surface, which requires high surface processing accuracy. In addition, there is a problem in that the magnetic particles tend to tilt during the above-mentioned surface preparation and other steps, in other words, it is difficult to maintain the magnetic particles in a proper vertical posture throughout the entire process.

In view of these circumstances, as a result of extensive research, the inventors set the orientation direction of the magnetic particles to be inclined to the traveling direction a with respect to the magnetic head, as shown in FIG. By performing recording and reproducing along the traveling direction, we have discovered a magnetic recording medium that can reduce the influence of demagnetizing fields, making it compatible with high-density recording, and in particular, allows easy orientation of the magnetic particles.

By the way, the demagnetizing field is expressed by the following formula.

Demagnetizing field - NxBr (However, N is the demagnetizing field coefficient and Br is the residual magnetic flux density.

) As shown in FIG. 4, the demagnetizing field coefficient N is approximately proportional to cos θ, where θ is the angle of the magnetization direction H with respect to the longitudinal direction.

Therefore, assuming that the residual magnetic flux density is constant, the demagnetizing field can be made smaller as the angle θ approaches 90°. However, as θ approaches 90°, the magnetic flux that can be detected by the magnetic heads disposed in the longitudinal direction decreases, resulting in a problem that the reproduction output decreases.

Therefore, from the viewpoint of practicality, in order to find a preferable angle θ, we decided to use a conventional magnetic tape that is easily affected by demagnetizing fields (θ = θ°, that is, oriented along the running direction) and a magnetic tape that has a different orientation direction of magnetic particles. Recording and playback were performed along the length of the tape at a recording wavelength of 0.5μ, and a comparison was made with the output at this time.
As a result, when the orientation is offset by θ-10° or more with respect to the longitudinal direction, the influence of the demagnetizing field is reduced and the above θ
It was found that the reproduction output began to improve compared to the conventional magnetic tape oriented at -08, and that when θ=60° or more, the magnetic flux that the magnetic head could sense decreased, and the reproduction output conversely decreased. Therefore, the range of θ is preferably 10° to 60°, preferably 15° to 45°, in which case short wavelength recording can be sufficiently supported without being affected by the demagnetizing field.

At the same time, examples of the present invention will be described.

Example 1 Particle size 0.4μ, major axis/minor axis ratio 8, coercive cuff 00 Oersted CO-containing iron oxide magnetic powder 100f, vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer resin (U-C0C
A magnetic paint was prepared by mixing and dispersing in a ball mill 12 pieces of VAGH (manufactured by Co., Ltd.), 8 pieces of urethane prepolymer (Takenate, made by Narita Pharmaceutical Co., Ltd.), 100 g of methyl isobutyl ketone, and 100 g of toluene.

After applying the above paint onto a 12μ thick polyester film to a dry thickness of 4μ to form a magnetic coating film, apply an opposing magnetic field at an angle of 15° with respect to the longitudinal direction while the paint is still wet. The magnetic tape of the present invention was obtained by applying a certain amount of pressure to the magnetic tape for orientation.

Example 2 After forming a magnetic coating film in the same manner as in Example 1 above, an opposing magnetic field was applied at 30° to the longitudinal direction while the film was still wet.
The magnetic tape of the present invention was obtained by applying an inclined force for orientation.

Example 3 A magnetic coating film was formed in the same manner as in Example 1 above, and while it was still wet, an opposing magnetic field was applied to it by 45° in the longitudinal direction.
The magnetic tape of the present invention was produced by applying and aligning the magnetic tape at an angle of .degree.

Comparative Example A magnetic coating film was formed in the same manner as in Example 1, and then oriented in the longitudinal direction, ie, θ=θ°, to produce a magnetic tape while it was still undried.

For each of the magnetic tapes of the above Examples, short wavelength recording of 0.5μ was performed in the longitudinal direction of the tape, and each output when this was reproduced was compared to the magnetic tape obtained in the Comparative Example above in the longitudinal direction of the tape. The output was compared with the output when recording and playing back in the direction. The results were as shown in the table below.

As is clear from the above table, the magnetic tape of the present invention can obtain superior output compared to the comparative example, and in other words, even when the wavelength in short wavelength recording becomes shorter, it can sufficiently cope with this. Moreover, not only the orientation can be easily performed, but also the recording method is simple.

[Brief explanation of the drawing]

1 and 2 are perspective views showing the orientation of magnetic particles in the magnetic coating film of a conventional magnetic tape, and FIG. 3 shows the orientation state of magnetic particles in the magnetic coating film of the magnetic tape of the present invention. The perspective view and FIG. 4 are plan views for explaining the relationship between the magnetization direction and the demagnetizing field in the magnetic tape. ]...Substrate, 2...Magnetic coating film, a Running direction C longitudinal direction). Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] +11 A magnetic recording medium in which the orientation direction of magnetic particles in a magnetic coating film coated on a substrate is set in a direction inclined with respect to the running direction of the substrate.