JPH01303610A - Magnetic head - Google Patents

Abstract

PURPOSE:To surely detect a tracking error with a pilot system by providing the narrow gap part for recording and reproducing, in which the track width and the gap length are smaller than the wide gap part, in the internal part of a wide gap part for reproduction. CONSTITUTION:The title head has a wide gap part 8 in which a track width Tw is specified by track width regulation grooves 7 and 7 and in the internal part, a narrow gap part 10 of a track width TN facing two ferromagnetic metallic thin films 9 and 9 is formed. The gap length is smaller than the 1/2 of the minimum recording wavelength of a video signal and a signal detected by a PCM signal and so forth. The gap length of the wide gap part 8 is larger than the 1/2 of the maximum recording wavelength of the signal to be detected and smaller than the minimum recording wavelength of the pilot signal. Thus, at the time of recording, the narrow gap part 10 only functions, at the time of reproduction, the narrow gap part 10 detects respective signals on a scanning track and the wide gap part 8 detects only the signal of the wavelength signal on the adjoining track of the scanning track.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetic head used in a magnetic recording/reproducing device such as a VTR.

(b) Prior Art Conventionally, there is a pilot method detection means as one of tracking error detection means in magnetic recording and reproducing apparatuses such as VTRs (video tape recorders) and DATs (digital audio tape recorders). This pilot method detecting means detects the video signal track of the tape pattern and the PC.
This method utilizes the strength of crosstalk from adjacent tracks when reproducing a pilot signal recorded on an M signal track in a superimposed manner or divided into areas. Furthermore, Bt
In the case of rtmVTR and R-DAT, signal tracks are recorded azimuthally without guard bands.

Since video signals and PCM signals have short wavelengths, crosstalk from adjacent tracks is quite small due to the effect of azimuth loss even without a guard band.

Further, since the pilot signal has a long wavelength, the effect of azimuth loss is small, and crosstalk from adjacent tracks can be sufficiently detected without a guard band. In order to take advantage of this feature, the track width of the recording/reproducing head is generally 1.2 to 1.2 times larger than the pitch of the track pattern.
It is designed to be about 1.5 times larger.

On the other hand, the 12th magnetic head compatible with high coercive force metal tape developed to realize high-density recording is
Mn-
A ferromagnetic metal thin film (3a) such as sendust having a high saturation magnetic flux density is placed near the gap (2) between a pair of magnetic cores made of ferromagnetic oxide such as Zn ferrite (la) and (lb).
) (3b) A so-called composite magnetic head has been proposed. In addition, (4) is the magnetic core half-off (la) (l
(b) is the glass for joining, and (5) is the winding groove.

Conventionally, when using the composite magnetic head shown in FIGS. 12 and 13 in, for example, an 81111 VTR, the track width was set to 25 m for a track pitch of 20 scales for the reasons described above.
When used for R-DAT, the track width is designed to be about 20 scales for the track pinch 14M, and trunking errors are detected by a pilot method.

However, as mentioned above, if you perform azimuth recording by making the track width of the magnetic head larger than the track pitch of the tape pattern, it will be possible to record short-wavelength video signals and
Crosstalk from adjacent tracks of CM signals is small,
Although the crosstalk of long-wavelength pilot signals from adjacent tracks becomes large, it is not sufficient to perform good tracking error detection.

(c) Problems to be Solved by the Invention The present invention has been made in view of the drawbacks of the above-mentioned conventional examples.
It is an object of the present invention to provide a magnetic head that can reliably detect tracking errors using a pilot method.

(d) Means for Solving the Problems The magnetic head of the present invention has a narrow gap section for recording/reproduction, which has a track width and gap length smaller than the wide gap section, inside the wide gap section for reproduction. Features.

(E) Effect According to the above configuration, only the narrow gap section works during recording, and during reproduction, the narrow gap section detects each signal on the scanning track, and the wide gap section detects each signal on the track adjacent to the scanning track. Detect only the signal.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the tape sliding surface of the magnetic head of this embodiment, and the same parts as in FIG. 13 are given the same reference numerals, and their explanation will be omitted.

The magnetic head of this example has a track width regulating groove <7) (
7) has a wide gap part (8) whose track width Tw is defined by 7), and inside the wide gap part (8) there is a track width in which ferromagnetic metal thin films (9) (9) are opposed to each other. A narrow gap portion (10) of T8 is formed and machined. The gap length gN of the narrow gear/pitch section (10) is smaller than the minimum recording wavelength of the signal to be detected such as a video signal or PCM signal, and the gap length gw of the wide gap section (8) is It is larger than the maximum recording wavelength of the signal to be detected and smaller than the minimum recording wavelength of the pilot signal.

In general, the frequency f and recording wavelength of 8mn VTR, DAT video signals, PCM signals, and pilot signals are as follows:
Within the range shown in the table. In Table 1, ν is the head
This is the relative running speed between tapes. Incidentally, the relational expression ^-shi/f holds true.

Table 1 When the magnetic head of this embodiment is used in the above-mentioned 81TfflVTR or R-DAT, the gap length gs of the narrow gap portion (10) and the gap length &
1 may be set to the values shown in Table 2 below, for example.

Table 2 also shows that the track width T of the narrow gap portion (10) is within the range of 1 to 1.5 times the track pitch, and the track width Tw of the wide gap portion (8) is within the range of 1 to 1.5 times the track pitch. It is within the range of 1 to 1.5 times the track width TN.

In general, it is known that the relationship between reproduction output due to gap loss and gear ratio/wavelength is as shown in Figure 2 (see Figures 7 and 14 of "R Magnetic Recording" published by Soyam Publishing Co., Ltd., 2118). It can be seen that if the gap length is smaller than the wavelength, efficient reproduction can be performed, and if the gap length is larger than the wavelength, the reproduction output will drop significantly.

That is, in the magnetic head of this embodiment, the narrow gap portion (10
) is the video signal recorded on the scanning track, PCM
The wide gap section (8) efficiently reproduces only the pilot signal recorded on the track adjacent to the scanning track, and the pilot signal recorded on the adjacent trunk. video signal,
PCM signals are hardly reproduced.

Next, a method of manufacturing the above magnetic head will be explained with reference to FIGS. 3 to 7. In addition, in Figures 4 to 7 (
(a) is a side view of the substrate 11) shown in FIG. 3 as viewed from the direction of arrow A, and (b) is a side view of the substrate (11>) as viewed from the direction of arrow B.

First, a pair of substrates (11) made of a ferromagnetic oxide such as ±M n -Z n ferrite as shown in FIG. 3 is prepared, and the upper surfaces of the substrates (11) are mirror-polished.

Next, as shown in FIGS. 4(a) and 4(b), the substrate (11
) A ferromagnetic metal thin film (9) such as sendust is deposited several times thicker by sputtering etc. on the upper surface of the above-mentioned tonic metal thin film (9), and then a gap spacer (12) of 5tot etc. is sputtered on the upper surface of the above-mentioned toronic metal thin film (9). A thickness of several n111 is formed by the following steps.

Next, as shown in FIGS. 5(a) and 5(b), a narrow track width T is formed on the upper surface of the gap spacer (12). After forming a resist pattern (13) in a portion corresponding to , ion beam etching is performed to remove an excess gap spacer (12) and a ferromagnetic metal thin film (9) as shown in FIGS. 6(a) and (b). remove. In this example, the etching depth of the ion beam etching is the ferromagnetic metal thin film (9).
and the gap spacer (12).

The gap length gN of the narrow gap portion (10) is equal to twice the film thickness of the gear 7 bus baser (12), and the gap length gw of the wide gap portion (8) is equal to the etching depth of the aforementioned ion beam etching. Equals twice.

Next, a track width that regulates the track width T of the wide gap part as shown in FIG. Regulation groove (7
) will be established.

Next, out of the pair of substrates formed in the steps from FIG. 3 to FIG. 7(a), winding grooves (5 ) and glass rod insertion groove (
14).

Next, the pair of substrates formed in the above steps are glass-bonded by abutting each other so that the narrow gap forming surfaces (Is) (15) face each other, and then this bonded body is cut in a well-known manner. , by applying R polishing, slicing, etc.
The shiki head of this embodiment having a tape sliding contact surface as shown in FIG. 1 is completed.

In the above manufacturing method, the etching depth of the ion beam etching is adjusted between the ferromagnetic metal thin film (9) and the gap spacer (
12), but it does not necessarily have to be the same as the total film thickness; even if a part of the ferromagnetic metal thin film (9) remains, it may also extend to a part of the substrate (11). At this time, the tape sliding surface will have the shape shown in FIG. 8 or 9.

Further, - the manufacturing method of the magnetic head of the above embodiment is not limited to the manufacturing method described above; for example, a track width regulating groove for regulating the track Tw is formed on a substrate, and after filling the line groove with glass, the substrate The top surface is mirror-polished, a ferromagnetic metal thin film and a gear spacer are deposited, and then the track width TN is regulated by etching, and winding grooves, glass welding, cutting, rounding, and slicing are performed. It may be formed by performing.

In the magnetic head as described above, recording of video signals, PCM signals, and pilot signals is performed only in the narrow gap section (10), and the optimum recording current for the narrow gap section (10) is There is very little recording magnetic flux from the gap part (8), and during reproduction, each signal on the scanning track is detected in the narrow gap part (10), and the pilot signal on the adjacent track is detected in the wide gap part (8). Detected in At this time, the video signal and PCM recorded on the adjacent track
Since the signal has a short wavelength, it is not detected by the wide gap section (8), and the wide gap section (8) detects only the pilot signal on the adjacent track, so that tracking error detection by the pilot method is performed with high accuracy. In addition, in the track width direction, the wide gap part (8) and the narrow gap part (l
The more the centers of O) coincide, the better the tracking error can be detected.

In addition, in the magnetic head of the embodiment described above, the magnetic core is half-dead (
There is a risk that the interface between la) (lb) and the ferromagnetic metal thin [(9) (9) may become a pseudo gap, and a pseudo signal may be detected during reproduction, but this problem has already been solved, for example, in a patent application filed before the present invention. As shown in Japanese Patent Application No. 62-194893, after applying chemical etching and reverse sputtering to the upper surface of the substrate, a heat-resistant thin film (16) of 510 m or more is formed with a narrow gap of 1 nm or more. Gap length T8
This can be solved on the upper back by depositing the tape so that it is within a range of less than 100 mL, and then forming a ferromagnetic metal thin film to form a magnetic nodule having a tape sliding surface as shown in FIG. 1O.

Furthermore, if we do not place emphasis on supporting metal tapes with high coercive force, there will be no ferromagnetic metal thin film in the vicinity of the gap, as shown in Figure 11, and the gap spacer (12) will not be present in the narrow gap area (10). Through the magnetic core half (la
) (lb) are facing each other,
During reproduction, only pilot signals on adjacent tracks are detected in the wide gap section (8), and tracking errors can be detected accurately using the pilot method.

(G) Effects of the Invention According to the present invention, video signals and PC signals having short wavelengths can be used for signals recorded on tracks adjacent to the scanning track.
It is possible to provide a magnetic head that hardly detects the M signal, efficiently detects only the long-wavelength pin signal, and can satisfactorily detect tracking errors using a pilot method.

[Brief explanation of the drawing]

FIGS. 1 to 11 relate to the present invention, and FIGS.
Figures 9, 10 and 11 are diagrams showing the tape sliding surface of the magnetic head, Figure 2 is a diagram showing reproduction output characteristics, Figures 3, 4, 5 and 6 respectively. and FIG. 7 are diagrams each showing a method of manufacturing a magnetic head. 12 and 13 relate to a conventional example, with FIG. 12 being a perspective view showing the external appearance of the magnetic head, and FIG. 13 being a view showing the tape sliding surface. (8)...Wide gap portion, (9)...Ferromagnetic metal thin film, (10)...Narrow gap portion.

Claims (4)

[Claims] (1) A magnetic head characterized in that a narrow gap section for recording/reproduction is provided inside a wide gap section for reproduction, the track width and the gap length of which are smaller than the wide gap section. (2) The narrow gap section detects a signal recorded on a scanning track, and the wide gap section detects a pilot signal recorded on a track adjacent to the scanning track. 1. The magnetic head according to 1. (3) The gap length of the narrow gap portion is 1/2 or less of the minimum recording wavelength of the signal to be detected, and the gap length of the wide gap portion is 1/2 of the maximum recording wavelength of the signal to be detected.
3. The magnetic head according to claim 2, wherein the wavelength is 1/2 or more and 1/2 or less of the minimum recording wavelength of the pilot signal. (4) Claims 1 and 2 characterized in that the core material regulating the gap length of the narrow gap portion is a ferromagnetic metal thin film.
Or the magnetic head according to 3.