JPH0656649B2 - Magnetic tape - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape having a ferromagnetic metal thin film as a magnetic recording layer for magnetically recording and reproducing a signal by a rotary magnetic head, and the field of recording, recording, information processing, etc. Can be used for.

Structure of conventional example and its problems The technology for recording and reproducing audio signals and image signals on a magnetic tape by a rotating magnetic head has been developed more and more, and the kinds of recorded signals are not only analog signals but also digital signals. In addition, a metal thin film type magnetic tape having a ferromagnetic metal thin film as a magnetic recording layer tends to be used in order to shorten the wavelength of recording.

Since this metal thin film type magnetic tape has a large output at short wavelengths, it is possible to increase the areal recording density, and the magnetic recording layer is about 1/20 of the magnetic recording layer of the coating type tape currently in practical use. 100% metal despite being thin
Since it has a large Young's modulus, it is possible to reduce the total thickness including the thickness of the support by 30% to 50%. As a result, so-called volume recording density can be increased. Expected in the advanced information industry. However, in reality, when the total thickness of the tape is close to 10 μm, problems such as track deviation occur when repeatedly used, and the volume recording density cannot be increased as expected.

In order to solve the above problems, reduce the total thickness of the tape, and increase the mechanical strength of the polymer film as a support, it has been conventionally performed to strengthen the film in a specific direction. As this specific direction, the longitudinal direction of the magnetic tape (hereinafter referred to as MD) or the width direction orthogonal to this (hereinafter referred to as TD)
Either) is selected. In the so-called coating type tape in which γ-Fe ₂ O ₃ particles currently in practical use are coated on a support with a binder, from the viewpoint of preventing track deviation due to the bending phenomenon of the tape due to the position control posts during recording and reproduction, As the support becomes thinner, T
A method of strengthening in the D direction is adopted, but the strength of the polymer film used as a support decreases the dimensional stability as it strengthens, causing a signal shift between tracks, which is a so-called skew problem. Therefore, even in this case, there is a limit, and the limit is that a support of about 10 μm is actually used.

OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic tape which is thin and has a total thickness without causing a problem of skew even when recording and reproducing are repeatedly performed by a rotary magnetic head.

According to the magnetic tape of the present invention, the tape support having a ferromagnetic metal thin film for recording / reproducing with a rotary magnetic head as a magnetic recording layer,
It is characterized in that it is made of a polymer film that minimizes the elongation of the tape in the scanning direction of the rotary magnetic head.

The magnetic tape of the present invention uses a rotating magnetic head, and as shown in the figure, it does not match the MD direction (2) of the magnetic tape (1) or the TD direction (3) orthogonal to the MD direction, M
A large number of tracks (4) are recorded in parallel with the inclined direction AA 'indicated by the angle .theta. In the D direction and reproduced as necessary.

At the time of this recording / reproducing, the surface of the magnetic tape is in sliding contact with the rotary magnetic head at a high speed, and the friction phenomenon between the magnetic head and the magnetic tape is due to the external force acting in the AA ′ direction in the figure. The magnetic tape of is the elongation of the tape in the AA 'direction,
That is, the tape elongation Δd [cm] when receiving an external force F [g]
Since it is the smallest, the dimensional change in the track direction can be ignored, and problems such as output drop and dropout increase due to track deviation during repeated use can be eliminated. As high-density recording progresses, it is expected that alloy heads such as amorphous and sendust will be used as the rotary magnetic head, but in such a rotary magnetic head, the frictional force between the metal and the tape will be further increased. Therefore, the effect of the present invention described above becomes more remarkable as the high density recording progresses.

This is because it is thought that the conventional cause of track deviation is the bending phenomenon of the tape due to the position control post, and it is unpredictable from the fact that measures to strengthen and stretch in the width direction of the tape were taken as described above. , Is based on a new finding that sliding contact with a rotating head puts a burden on the tape, resulting in a magnetic tape by utilizing the large Young's modulus of a ferromagnetic metal thin film. It is particularly effective in reducing the total thickness of the.

Description of Examples Examples of a polymer film used as a holder for a ferromagnetic metal thin film of a magnetic tape of the present invention include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as nitrocellulose, polycarbonate, polychlorinated. Vinyl, polyamide, polyimide, etc. may be mentioned.

Further, the ferromagnetic metals that can be used as the magnetic recording layer of the present invention are Co, Fe, Co-Fe, Co-Ni, Co-Zn, Co-Ti, Co-Si, Co-M.
n, Co-Mg, Co-Cr, Co-Be, Co-Ru, Co-Pt, Co-Sn, Co-Ni-Cr, Co-
Ni-Mg, Co-O, Co-Ni-O, etc., and the magnetic recording layer may have an easy axis of magnetization parallel to, perpendicular to, or oblique to the support. May be a stack of
Further, a non-magnetic or soft magnetic underlayer may be provided.

Examples of means for providing the magnetic recording layer on the support include electron beam evaporation method, electric field evaporation method, ion plating method, sputtering method and electroless plating method.

Next, the results of a comparative test of the magnetic tape according to the present invention and the magnetic tape using the conventional film reinforced and stretched in the TD direction will be described.

First, a 7.5 μm thick polyethylene terephthalate film and a 6 μm thick polyethylene 2-6 naphthalate film were prepared. Both of these films are designed and manufactured so that the Young's modulus in the track direction becomes maximum when processed into a magnetic tape. Young's modulus of the track direction, polyethylene terephthalate is 680 kg / mm ^2, a polyethylene 2-6 Nafutareta is 790 kg / mm ^2, when the external force is 15g, respectively, and 0.3% with respect to the film of 8mm width 0.26
% Elongation. The Young's modulus of each film in the TD direction was 480 kg / mm ² , 520 kg / m.
It was m ² .

Next, as a comparative example, a thickness of 7.5 μm reinforced and stretched in the TD direction
Of polyethylene terephthalate film was prepared. This film has the minimum elongation in the TD direction, and when the external force is 15 g, the elongation of 0.25% occurs with respect to the film having a width of 8 mm.

The above-mentioned three types of films were processed by a winding vapor deposition machine to form a magnetic recording layer. That is, Co-Ni (Co80%, Ni20, Co80%, Ni20) obtained by electron beam heating was applied to a film to be moved along the peripheral side surface of a cylindrical can having a diameter of 1 m in 1 × 10 ⁻⁵ Torr oxygen.
%) Oblique vapor deposition due to vapor flow at a blocking incident angle of 46 °, coercive force of 950 [e], saturation magnetic flux density of 7200 [G], thickness of 0.13
A Co-Ni-O-based thin film of μm was formed. On the Co-Ni-O type thin film, a methyl isobutyl ketone solution containing 300 ppm of myristic acid was applied by a reverse roll coater and dried to obtain about 35Å
The myristic acid coating layer was prepared to improve the lubricity of the magnetic tape.

Each of these films was cut into a width of 8 mm, and recording and reproduction were repeated by a video tape recorder with a rotating cylinder having a diameter of 40 mm for comparison and examination.

The magnetic head is an amorphous alloy head with a gap length
Two types of 0.27 μm, track width 15 μm and 10 μm were prepared, and the recording wavelength was fixed at 0.65 μm.

The magnetic tape of the present invention using a polyethylene terephthalate film was designated as A, the magnetic tape of the present invention using a polyethylene 2-6 naphthalate film was designated as B, and the above-mentioned tape prepared as a comparative product was designated as C.

Test I After running each tape 50 times, record at 23 ℃, 60% RH,
Table 1 shows the results of relative comparison between the first-time playback output and the 50-th playback output when the vehicle was repeatedly run 50 times.

Test II Each tape was recorded at 5 ° C. and 80% RH, and then repeatedly reproduced at 40 ° C. and 80% RH, and the relative output at the first measurement and each measurement was compared. The results for a track width of 10 μm are shown in Table 2.

Test III The tapes used in Test I and Test II were compared in terms of still life. The life was determined when the output decreased by 3 dB from the initial output. The still life is 23 ℃, 60% RH.
Table 3 shows the results of the examination under the above environment and a head with a track width of 10 μm.

From the results of Test I to Test III described above, it is understood that the magnetic tape of the present invention is suitable for high density recording with a short recording wavelength and a narrow track width. It is also shown that the magnetic tape has durability against the large stress received by the magnetic layer from the magnetic head during repeated running even though the total thickness of the magnetic tape is small, and the problem of skew is almost eliminated. Can be ignored.

EFFECTS OF THE INVENTION The magnetic tape of the present invention is configured such that the elongation of the polymer film as a support is minimum in the direction in which the rotary magnetic head slides in contact at high speed and moves, that is, in the recording track direction. Even if the thickness of the polymer film is 10 μm or less, there is no increase in skew due to repeated use,
The volume recording density can be increased at the same time as the area recording density, and a large practical effect can be obtained.

[Brief description of drawings]

The figure shows a recording pattern on the magnetic tape of the present invention. (1) …… Magnetic tape, (4) …… Recording track.

Claims (1)

[Claims] 1. A ferromagnetic metal thin film for recording / reproducing a signal by a rotary magnetic head, and a support for the ferromagnetic metal thin film is a polymer film which minimizes tape elongation in the scanning direction of the rotary magnetic head. A magnetic tape characterized by having.