JPS5817967B2 - Jiquitape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape, and its purpose is to reduce noise components generated when a magnetic tape recorded with FM modulation is played back in a general video tape recorder. The objective is to improve video S/N.

Fig. 1 shows an enlarged sectional view of a conventional magnetic tape, Fig. 2 shows a schematic configuration of a video circuit of a conventional video tape recorder, and Figs. 3 to 5 show video noise characteristics. A conventional example will be explained based on the drawings.

In addition, in all figures 3 to 5, the carrier frequency is 3 (MH, z
) with relative speed 1 ], (m/
s) Recorded and played back with a video tape recorder.

In current video tape recorders that employ the FM modulation method, when recording and reproducing are performed using a magnetic tape with the magnetic layer 1 provided only on one side of the support base 20 as shown in Fig. 1, as shown in Fig. 2. An input video signal is applied to a video input terminal 3 and amplified by a video intensifier 4, as shown in FIG.

The amplified signal is converted into an FM modulated wave by the FM modulator 5.

This signal is amplified by a recording amplifier 6, applied to a recording head 7, and recorded on a magnetic tape 8.

Further, during reproduction, a weak modulated wave induced in the reproduction head 7' by the magnetic tape 8' is amplified by the reproduction amplifier 9, and is sent to the demodulator 10 through the S-T.

Here, the FM modulated wave is demodulated and converted into an AM component.

The demodulated signal is amplified by a video amplifier 4' and output as a video signal of a predetermined voltage to a video output terminal 3'.

The output of the signal thus obtained from the regenerative amplifier 9 is analyzed by a spectrum analyzer, and the modulation noise component is drawn by an X-Y recorder.

Next, describe the device noise of the video tape recorder in the same manner as above without applying any input signal.

For each noise component, set the signal output I (VPP) to 0.
Figure 3 shows a comparison in terms of (dB).

This proves that among the generally known noise components of a video tape recorder, modulation noise A occupies a much larger proportion than amplifier noise, that is, device noise B, etc.

The modulation noise A is the carrier wave (3MHz) of the recorded signal.
) is particularly large in the vicinity.

This modulation noise consists of amplifier noise, demagnetization noise, tape modulation noise, etc., and the former (amplifier noise and demagnetization noise) is sufficiently smaller than the latter (tape modulation noise).

Therefore, consider that most of the modulation noise is tape modulation noise.

It is known that tape modulation noise is mainly caused by unevenness on the tape surface.

Figure 4 shows the modulation noise C and D of different types of tapes, that is, 5 different surface properties, and the reproduction output of the carrier signal in OdB.
This is a comparison of C/N expressed as .

Here, the modulation noise of the magnetic tape CrO2 is C, and the modulation noise of the magnetic tape γ-F1□03 is D.

The surface smoothness of the former is superior to that of the latter.

Video amplifier 4' after AM conversion (demodulation) of this signal
A comparison of the video output terminal 3' of the video output terminal 3' shows the result shown in FIG.

Noise level E of CrO2 tape with excellent surface smoothness is inferior to CrO2 tape with surface smoothness of γ-F120
This is lower than the noise level E of 3 tapes.

In other words, it can be seen that the S/N ratio is excellent.

In this regard, there are slight differences even between tapes of the same type.

Next, in order to understand the relationship between the recording signal wavelength and tape modulation noise, Figure 6 shows the measurement of the ratio of fluctuation of the reproduction output voltage to the amplitude of the envelope wave when the recording wavelength and recording current were changed. .

When the recording wavelength λ = 3.5 (μm), it is G, and λ-35 [
μm] is Hl; and λ-350 [μm] is ■.

As will be seen below, as the recording wavelength becomes shorter, the amplitude fluctuation rate becomes larger.

This means that the shorter the recording wavelength, the greater the influence of tape modulation noise.

Therefore, in recent years as high-density recording is progressing, the surface roughness of ordinary magnetic tapes is 0.3 to 0.4 [μm], whereas the surface roughness is around 0.1 [μm] or smaller. The tape surface is smoothed to reduce tape modulation noise.

However, despite efforts to improve the smoothness of the tape surface, tape modulation noise still accounts for a large proportion, and the development of technology for smoothing the tape surface, which requires advanced technology, has become a major issue.

The present invention has been made to address such problems,
In order to solve this problem, the magnetic tape of the present invention has a first magnetic layer on one side of the support base and a second magnetic layer on the other side.
A magnetic layer is provided, and the coercive force of the second magnetic layer is configured to be higher than the coercive force of the first magnetic layer. The magnetic flux generated by the magnetic component of the signal recorded on the second magnetic layer demagnetizes the magnetization component of the uneven portion of the tape surface, and the magnetization component of the uneven portion is demagnetized by the magnetization component of the uneven portion. Attenuates the tape modulation noise of the video signal to improve S/
N is improved.

Hereinafter, the present invention will be explained based on drawings showing embodiments.

First, basic experiments related to the present invention will be explained.

FIG. 7 shows the mechanism of a small rotary two-head video tape recorder, and in this experiment a special post 12 was added.

In FIG. 7, 14 is a head drum section, 15 is a full-width erasing head, 16 is an audio erasing head, 17 is an audio and control head, 18 and 18' are tape guide posts, 19 is a head rotation motor, and 20 is a capstan. , 21 is a pinch roller, 22 and 22' are tension arms, 23 is a take-up reel, 23' is a supply reel, 2
4 is a winding torque motor, 24' is a supply torque motor,
25 is a cap stan motor.

Note that the magnetic head portion is omitted.

First, Co -F1□ with coercive force Hc-1400 (Qe)
A 1 (MHz) signal is recorded on the 03 tape by a video tape recorder that is a mirror image of the recording pattern on the magnetic tape obtained by a general-purpose unified video tape recorder.

In this case, the relative speed between the tape and head is V = 11
(m/s).

Next, after cutting this tape, it was wound around the post 12 of the tape running section with the magnetic surface facing outward, as shown in FIG. 7 and 11.

On the other hand, r-F120 with coercive force Hc=340 (Qe)
3 tape 13 with a general-purpose unified video tape recorder.
After recording a signal of (MHz), the tape was run in contact with the magnetic surface of the recorded tape 11 on the post 12.

Then, the output C/N of the reproduction amplifier 9 of the γ-F1203 tape 13 was measured and compared when the tape 11 was provided on the post 12 and when it was not provided.

This data is shown in FIG. C/N after wrapping the recorded tape 11 on the post 12 and running it
(K) is considerably improved compared to C/N (J') after running without wrapping the tape 11.

The improvement is remarkable near carrier wave 3 (MHz).

This is due to γ, which is the main cause of modulation noise, as shown in Figure 9.
-F1203 The magnetization component 26 in the uneven surface of the tape 13 is the signal magnetization component 27 of the carrier wave 3 (MHz)
This is because it partially follows.

Figure 10 shows the video amplifier 4 after demodulating these signals.
' This shows the noise spectrum at the video output terminal 3' of the video output 1 (Vp-P).
Here, the noise level M when the tape 11 is wound and run and the noise level L when the tape 11 is run without being wound are considered as image noise, that is, the first Comparing frequencies below 1 (MHz), which are more likely to occur, the noise level of the former is lower.

In other words, the S/N ratio is improved.

Next, set the frequency to be recorded on the γ-F1203 tape 13 to 3.
(MHz), the wavelength of the signal recorded on the tape 11 wound on the post 12 was changed, and the same experiment as the above was carried out. 11 and 12 compare how the noise level and signal level of No. 13 change.

Note that video output 1 (VPP) is OdB.

In FIG. 11, the recording wavelength of the tape 11 is 2.2 (μm).
FIG. 12 shows the case of 3.7 (μm).

Solid lines N and R in FIGS. 11 and 12 indicate post 1
2 without wrapping the tape 11 on γ-F1203
The noise level when the tape 13 is running, and the circles P and T are the signal output level of the reproduction amplifier 9 in this case.

The broken lines O and S indicate the noise level when the tape 11 is wound around the post 12 and the γ-F1203 tape 13 is run, and the triangle marks Q and S indicate the signal output level of the regenerative amplifier 9 in this case. .

The next step is to wrap tape 1 around post 12.
The shorter the wavelength of the signal recorded in 1, the better the S/H improvement rate.

As shown in FIG. 11, when the wavelength of the signal recorded on the tape 11 is 2.2 (μm), the signal component level P
is hardly attenuated to Q, and only the level of the noise component is
On the other hand, as shown in FIG. 12, the wavelength of the signal recorded on the tape 11 is 3.7 (μ
In case m), not only the noise component is attenuated from R to S (the signal component is also attenuated from T to U).

Therefore, the former is more effective in improving S/H than the latter.

Figure 13 shows the strength of the magnetic field generated from the magnetic tape when the distance in the direction perpendicular to the magnetic tape surface is changed for each magnetic tape with recorded signals of different wavelengths. become.

In FIG. 13, the solid line V indicates the recording wavelength of 22 (μm), W
is 11 (μm), X is 3.7 (μm), Y is 2.75
(μm), 2 indicates the case of 2.2 (μm).

As we will see, the shorter the wavelength, the shorter the distance that the magnetic field generated from the magnetic tape can reach.

From the above, the following can be said about the experimental results shown in FIGS. 11 and 12.

As shown in FIG. 14, when the frequency of the magnetic field 28 generated from the tape 11 wound around the post 12 is high, that is, the wavelength is short, the unevenness of the tape surface which is a noise component of the γ-F■203 tape 13 Only the magnetization component 26 in the portion γ is demagnetized by the magnetic flux 28' generated by the magnetization component 28 of the signal recorded on the magnetic tape 11, and γ
- It hardly affects the magnetic flux 27' of the carrier wave component located deep in the thickness direction of the F1203 tape 13.

On the other hand, when the frequency of the magnetic field generated from the magnetic tape 11 is low, that is, the wavelength is long, as shown in FIG.
The magnetic flux 29' generated not only from the magnetization component 26 of the uneven portion of the tape surface, which is a noise component of the γ-F1203 tape 13, but also from the magnetization component 29 of the signal recorded on the tape 11, is generated in the thickness direction of the tape 13. This also affects the magnetization component 27 of the signal component, thereby attenuating the magnetic flux 27' generated from this.

From the above, in order to attenuate the noise components of a recorded tape, it is necessary to create the conditions for the former case of the above experiment in some way before playback to reduce the noise components of the uneven parts of the tape surface. Just attenuate it.

Note that 26' is a magnetic flux generated from the magnetization component 26.

FIG. 16 shows a sectional view of the magnetic tape of the present invention.

This is because the coercive force of the second magnetic layer 32 for demagnetizing noise components of the magnetic layer 31 is higher than the coercive force of the first magnetic layer 31 on which the video signal, which is the main signal, is recorded. te℃・ru.

This is to prevent the signal of the magnetic layer 32 from being demagnetized by the signal of the magnetic layer 31.

The second magnetic layer 32 is for recording short wavelength components, and its thickness may be as thin as about 2 to 8 (μ771).

Reference numeral 30 denotes a support. Generally, when a video tape recorder is configured as shown in FIG. 7, when the tape is fast-forwarded or rewound, a slip phenomenon occurs between the tapes on the reel 35, as shown in FIG. 17, and the tape tension changes. This causes the adjacent tapes to move relative to each other in the directions of arrows 33 and 340, which is the same situation as in the experiment described above.

Therefore, before reproducing the video signal of the first magnetic layer 31, a component with a shorter recording wavelength than that of the video signal recorded on the first magnetic layer 31, for example, as in this experiment, is added to the second magnetic layer 32. The wavelength of the video signal of the magnetic layer 31 is 11 (μm).
Alternatively, in the case of about 37 (μm), by recording a signal with a wavelength of about 22 (μm), only the noise component of the magnetic layer 31 can be attenuated, and the magnetic tape of the present invention can be implemented as described above. Since it is a magnetic tape, a magnetic layer is provided on the back side of the magnetic tape to reproduce the video signal, which is the main signal component.

By recording a signal on this magnetic layer before reproducing the video signal, it is possible to greatly attenuate the tape modulation noise generated by the magnetization component of the uneven portion of the tape surface under the current tape surface condition. Wear.

In other words, video S/N can be improved.

“

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional magnetic tape; Fig. 2 is a block diagram of a general-purpose video tape recorder; Fig. 3 is a characteristic diagram of the modulation and device noise spectrum of the video deck; Fig. 4 is a cross-sectional view of a conventional magnetic tape. A characteristic diagram of the noise spectrum when a 31VIHz signal is recorded and played back. Figure 5 is a characteristic diagram of the noise spectrum of the video output when the signal in Figure 4 is demodulated. Figure 6 is the wavelength of the recorded signal and the reproduced output voltage. FIG. 1 is a diagram showing the configuration of a general-purpose video tape recorder using an experimental sample according to the present invention, and FIG. 8 is a diagram showing the ratio of variation to the amplitude of the envelope wave.
/H characteristic principle diagram, Figure 9 is an enlarged view of the simple sparse pattern of magnetic tape, Figure 10 is a noise spectrum characteristic diagram of the output when the signal in Figure 8 is demodulated, and Figure 11 is noise component demagnetization. Figure 12 shows the video S/N characteristic diagram at the recording frequency of 5 (MHz) for the video recording frequency 3 (MHz).
Figure 13 shows the video S/N characteristic diagram for each magnetic tape recorded at different wavelengths.
A diagram showing the intensity of the magnetic field generated from the tape at different distances from the magnetic tape, FIG. 14 shows the Co-γ-F12o3 tape and r-F1203 tape in the case of FIG. 11.
FIG. 15 is an enlarged view of the magnetization model in the state of contact with the tape; FIG. 15 is the case of FIG. 12; an enlarged view of the magnetization model showing the same state as FIG. 14; FIG. 16 is a cross-sectional view of the magnetic tape according to the present invention. , FIG. 17 is an enlarged sectional view of the magnetic tape stored in the reel. 30...Support base, 31...First
magnetic layer, 32... second magnetic layer.

Claims (1)

[Claims] 1 A first magnetic layer is provided on one side of the support base, a second magnetic layer is provided on the other side, and the coercive force of the second magnetic layer is set to the first magnetic layer.
The coercive force of the second magnetic layer is higher than the coercive force of the second magnetic layer.
A magnetic tape characterized in that a signal having a relatively shorter wavelength than a video signal recorded on a first magnetic layer is recorded.