JPH04157614A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To make it possible to attain an excellent PCM audio characteristic by setting specific magnetic characteristics for an audio head of a ferrite head and the one of a metal heads respectively in the case when a video signal is recorded in superposition on a recorded audio signal. CONSTITUTION:In regard to a magnetic recording medium wherein a video signal is recorded in superposition on an audio signal recorded by an audio head, a magnetic characteristic is so set as to be expressed by a formula I when the audio head is a ferrite head and as to be expressed by a formula II when the head is a metal head, for an area S1 corresponding to a signal rewriting part in the superposed recording of the video signal and an area S2 corresponding to the other part on a coercive force distribution curve of the medium. When C/N (carrier/noise) corresponding to an error rate of the lowest limit for obtaining an excellent audio characteristic, a PCM audio characteristic in particular, is made to be lower-limit C/N, the magnetic characteristic is set so that a value of this lower-limit C/N or above can be ensured, according to this constitution. Thereby an excellent characteristic can be attained for a PCM audio signal as well, while a video signal characteristic is satisfied.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium on which audio signals and video signals are recorded in a superimposed manner, and is particularly suitable for magnetic recording media for improving characteristics of PCM audio signals. It's about the medium.

[Prior Art] For VTRs, especially home-use VTRs, for example, the Japanese Society of Television Engineers, Vol. 37. No. 12 (1983), P.
There is one disclosed in rVH8 (registered trademark) Hi-Fi VTRJ (Shuzo - Tsumachi) published in 1009-Pi013. According to this, an FM audio signal band is set between each frequency band of a luminance signal and a chrominance signal that form a video signal, and this FM audio signal is recorded in the deep part of a magnetic tape and superimposed thereon. A video signal is recorded on the surface layer of the magnetic tape.

In this deep recording method, there are two types of problems: unerased signals that occur when a magnetic field smaller than the saturation magnetic field is applied to a magnetic tape on which a -degree signal is recorded, and azimuth loss due to differences in the azimuth angle of the magnetic head gap. It's being used. First, the FM audio signal is recorded deep into the magnetic tape by the FM audio head. after that,
A portion of the surface layer of the magnetic tape is rewritten into a video signal by the video head. The reproduction of the FM audio signal is performed by reproducing the signals remaining in the deep portion of the magnetic tape without being rewritten.

Since the frequency of the FM audio signal is lower than the frequency of the video signal, it is recorded much deeper into the magnetic tape than the video signal, so it is hardly affected by the video signal. For this reason, the various characteristics required of magnetic tape are determined mainly by recording and reproducing video signals, and the required recording and reproducing characteristics of FM audio signals can be achieved without paying special attention to FM audio signals. Obtainable.

Incidentally, recently, with the aim of dramatically improving the audio performance of a VTR, a method for digitizing audio signals, particularly a method using PCM audio signals, has been proposed. For example, in Japanese Patent Application Laid-Open No. 63-288402, F
A three-layer recording method has been disclosed in which an FM audio signal is recorded on a magnetic tape by an M audio head, a PCM audio signal is superimposed and recorded by a PCM audio head, and a video signal is further superimposed and recorded on top of the PCM audio signal by a video head. There is. Furthermore, Japanese Patent Laid-Open No. 1-105301 discloses a deep-N recording method in which a multiplexed signal of an FM audio signal and a PCM audio signal is recorded on a magnetic tape by an audio head, and then a video signal is superimposed and recorded by a video head. has been done.

[Problem to be Solved by the Invention] However, when recording a PCM audio signal in this way, since the frequency band of the PCM audio signal is higher than the frequency band of the FM audio signal, the writing depth of the signal on the magnetic tape is limited. becomes shallow. Therefore, the proportion of audio signals that are rewritten due to superimposed recording of video signals increases. Therefore, conventional magnetic tapes manufactured with tape characteristics focused only on video signals have the disadvantage that satisfactory recording and reproducing characteristics of PCM audio signals cannot be obtained.

The present invention has been made in view of the above points, and aims to provide a magnetic recording medium that can obtain good characteristics even for PCM audio signals while satisfying video signal characteristics.
That is the purpose.

[! One aspect of the present invention is that in a magnetic recording medium in which a video signal is superimposed and recorded by a video head on an audio signal recorded by an audio head, the video signal in the coercive force distribution curve is When the audio head is a ferrite head, the magnetic characteristics are set so that the area S1 corresponding to the signal rewriting portion during signal superimposition recording + the area S2 of the other portion is S1+32, and the audio head is In the case of a metal head, the magnetic characteristic is set to be S1+82.

According to another invention, when the audio head is a ferrite head, the magnetic characteristics are set so that Hm≧930[Oe] with respect to the peak magnetic field Hm in the coercive force distribution curve, and the audio When the head for use is a metal head, the magnetic characteristics are set so that Hm≧850 [Oe].

According to still another invention, when the audio head is a ferrite head, the magnetic characteristics are adjusted so that, with respect to the effective magnetic field Hx and the peak magnetic field Hm during video signal recording in the coercive force distribution curve, m is obtained. is set, and if the audio head is a metal head, the magnetic characteristics are set so that m is set.

[Operation] According to the present invention, the C/N corresponds to the minimum error rate for obtaining good audio characteristics, especially PCM audio characteristics.
When (carrier/noise) is set as the lower limit C/N, the magnetic characteristics are set so as to ensure a value equal to or higher than this lower limit C/N.

Embodiments Hereinafter, embodiments of the magnetic recording medium according to the present invention will be described.
This will be explained with reference to the attached drawings. First, common matters in the following examples will be explained.

The coercive force in a magnetic tape generally has a distribution as shown in FIG. In the figure, the horizontal axis is the magnetic field or coercive force H applied to the magnetic tape, and the vertical axis is the differential value of the magnetization M of the magnetic tape with respect to the magnetic field H. In other words, the height of the vertical axis indicates the amount of magnetic particles in the magnetic tape.
In the illustrated example, magnetic particles having a coercive force Hm are included most.

By the way, in the above-described deep recording method, a PCM audio signal is first recorded on a magnetic tape by a preceding audio head, and then a video signal is superimposed and recorded by a video head. That is, the signal is superimposed and recorded through a process in which part of the PCM audio signal is rewritten into a video signal. Therefore, as a characteristic of the magnetic tape, the coercive force distribution characteristic shown in FIG. 3, which indicates the difficulty with which signals are erased, becomes important.

Here, the effective recording magnetic field obtained by averaging the magnetic field acting on the magnetic tape generated by the video head in the depth direction is considered, and its value is assumed to be HX. Then, H
The magnetization of the PCM audio signal recorded on the magnetic particles with a coercive force below xi is erased and rewritten into a video signal. However, PC of magnetic particles with coercive force larger than Hx
The M audio signal is not rewritten into a video signal, remains as it is, and contributes to playback.

In other words, the area below Hx (to the left of Hx in the figure) is 8
1. If the area above Hx (to the right of Hx in the figure) is 82, s1+s2 is proportional to the playback signal when only the PCM audio signal is recorded, and S2 is the PCM audio after being partially rewritten by the video signal. It will be proportional to the reproduced signal.

Therefore, Δ5=S2/(S1+S2) indicates the ratio of the PCM audio signal before writing the video signal to the PCM audio signal after rewriting.

Next, for the following examples, 11 magnetic tape samples shown in Table 1 below were prepared.

Table 1 In this table, the unit of coercive force He and Hm is [Oe]
It is. Further, SR is the squareness ratio, and ΔS is expressed in [%]. Furthermore, ΔH is (Hx-Hm)/
Hm is expressed as a ratio.

In this table, Sample 2 is the magnetic tape with the most average value, and the effective recording magnetic field Hx was determined based on this magnetic tape. When the amount of cancellation of the PCM audio signal in Sample 2 was measured, it was found to be =16.4 [dB]. Therefore, based on this value, 201og1o (S2
/ (S1 + 52)) = -16.4 When 81 and S2 are set, Hx = 1350 [Oe]. This means that magnetic particles with a coercive force of 1350 Oe or less are rewritten from a PCM audio signal to a video signal.

Therefore, when Hx=1350 EOe, Δ5=
S2/(S1+52)XIO○ [%] was determined for other samples as well, and the results are shown in Table 1 above. Also, when Hx=1350 [Oe], ΔH=
(Hx-Hm)/Hm was similarly measured to obtain the data shown in the same table.

Next, various characteristics will be explained when each of the sample magnetic tapes shown in the table above is set in a VTR capable of actually recording deep bias PCM audio signals. In addition,
Cases in which the PCM audio head is made of ferrite or metal will be described as a first embodiment and a second embodiment, respectively.

First Example (In case of ferrite head) First, P
The relationship between C/N [d Bl and block error rate (hereinafter referred to as rB, E, R, and J) for a CM audio signal was measured for each sample in Table 1.

FIG. 1(A) shows the measurement results. In the figure, the minimum error rate for obtaining good PCM audio characteristics is indicated by lower limits B, E, and R.

The C/N corresponding to this is set as the lower limit C/N.

That is, if a value equal to or higher than the lower limit C/N can be secured, good PCM audio characteristics can be obtained. In the same figure, the lower limits B, E, and R are expressed as "1" because they are used as standards.
Further, the lower limit C/N corresponding to this is expressed as rOJ.

Next, FIG. 3B shows the relationship between ΔS and the C/N for each sample. As mentioned above, the PC
The C/N value for the M audio signal must be greater than or equal to the lower limit C/N. Therefore, from this graph, it can be seen that this condition is satisfied if △S≧12.0[%].

Next, in the same figure (C), the C/N in each sample is shown.
The relationship between Hm and the peak magnetic field Hm is shown. Similarly, in order to obtain a C/N value higher than the lower limit C/N, Hm
≧930 COe].

Next, in the same figure (D), the C/N in each sample is shown.
The relationship between and ΔH is shown. Similarly, lower limit C/N
In order to obtain the above C/N value, it is necessary that ΔH≦0.45.

As is clear from the above measurement results, when the audio head is a ferrite head, (1) ΔS≧12.0C%] (2) Hm≧930[Oe] (3) ΔH≦0.45 If you satisfy the above condition, you will get B.

E and R have values within permissible limits, and good characteristics can be obtained not only for video signals but also for PCM audio signals.

Second Embodiment (Metal Head) Currently, the above-mentioned ferrite head is generally used as an audio head for a VTR. However, in recent years, metal heads have begun to be adopted in some areas. Therefore, similar measurements were performed using a metal head.

First, C/N [d BE and block error rate (hereinafter referred to as rB, E, R, J) for the PCM audio signal.
Measurements of the relationship were made for each sample in Table 1.

FIG. 2(A) shows the measurement results. In the same figure, the minimum error rate for obtaining good PCM audio characteristics is set to the lower limits B, E, R,
The C/N corresponding to this is set as the lower limit C/N.

Next, FIG. 3B shows the relationship between ΔS and the C/N for each sample. As mentioned above, the PC
The C/N value for the M audio signal needs to be lower than 1111 C/N. Therefore, from this graph,
HaboΔS≧7. ○ [%] indicates that this condition is satisfied.

Next, in the same figure (C), the C/N in each sample is shown.
The relationship between Hm and the peak magnetic field Hm is shown. Similarly, in order to obtain a C/N value higher than the lower limit C/N:
≧850 [Oel is required.

Next, in the same figure (D), the C/N in each sample is shown.
The relationship between and ΔH is shown. Similarly, lower 111i
In order to obtain a C/N value greater than or equal to C/N, ΔH≦0.
6 is required.

As is clear from the above measurement results, when the audio head is a metal head, (1) ΔS≧7.0 [%ko (2) Hm≧850 [Oeko (3) ΔH≦0.6] If either condition is satisfied, it is B.

E and R have values within permissible limits, and good characteristics can be obtained not only for video signals but also for PCM audio signals.

[Effects of the Invention] As explained above, according to the magnetic recording medium according to the present invention, since each of ΔS, Hm, and ΔH is set to a predetermined value for each type of head, the error rate is reduced. Therefore, even when deep recording of an audio signal with a relatively high frequency is performed, good audio characteristics, especially PCM audio characteristics, can be obtained.

Therefore, even compared to conventional FM audio, higher dynamic range and better frequency characteristics can be obtained.
It becomes possible to realize a VTR that plays digital sound similar to CDs.

[Brief explanation of drawings]

FIG. 1 is a graph showing a first embodiment of the magnetic recording medium according to the present invention, FIG. 2 is a graph showing a second embodiment of the present invention,
FIG. 3 is a graph showing a general coercive force distribution of a magnetic tape. Sl: Area corresponding to the signal rewriting portion during video signal superimposition recording, S2: Other area, Hm: Magnetic field at peak, Hx: Effective magnetic field during video signal recording. Patent applicant: Victor Japan Co., Ltd.

Claims (3)

[Claims] (1) On the audio signal recorded by the audio head,
In a magnetic recording medium on which a video signal is superimposedly recorded by a video head, the above-mentioned audio If the head is a ferrite head, S_2/(S_1+S_2)×100≧12.0[%]
When the audio head is a metal head, the magnetic characteristics are set so that S_2/(S_1+S_2)×100≧7.0[%]. magnetic recording media. (2) On the audio signal recorded by the audio head,
In a magnetic recording medium on which a video signal is superimposed and recorded by a video head, for the peak magnetic field Hm in the coercive force distribution curve,
When the audio head is a ferrite head, Hm
The magnetic properties are set so that ≧930 [Oe], and when the audio head is a metal head, Hm≧85
A magnetic recording medium characterized in that magnetic properties are set to be 0 [Oe]. (3) On the audio signal recorded by the audio head,
In a magnetic recording medium on which a video signal is superimposed and recorded by a video head, for the effective magnetic field Hx and peak magnetic field Hm during video signal recording in the coercive force distribution curve, when the audio head is a ferrite head, , (Hx-Hm)/Hm≦
0.45, and when the audio head is a metal head, the magnetic characteristics are set so that (Hx-Hm)/Hm≦0.60. magnetic recording media.