JPH06325315A - Magnetic head and its production - Google Patents

Abstract

PURPOSE:To provide a magnetic head which can be positioned with good accuracy with tracks even in a recording and reproducing system of a small track pitch and is excellent in reproduction efficiency as well. CONSTITUTION:A pair of core half bodies 16, 17 arranged to face each other via a magnetic gap 15 are connected by a pair of glassy blocks 18, 19 disposed on both sides thereof. The core half body 16 has a projecting part 22 projecting from the base part. Track width regulating grooves 20, 21 orthogonal with a magnetic gap 15 exist on both sides of this projecting part 22. The spacings between the track width regulating grooves 20a, 21a on both sides of the base part are formed so as to be gradually larger the furtherer from the projecting part. The projecting length 23 of the projecting part 22 is set at 5 to 15mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head used in a magnetic recording / reproducing apparatus and a manufacturing method thereof.

[0002]

2. Description of the Related Art The track width of a magnetic head and the track pitch of a magnetic tape in a recent magnetic recording / reproducing apparatus have become extremely small in order to record / reproduce data at a high density. Even with tracking control, the conventional V
The method of using the control head found in HS-type VTRs cannot be fully supported, and DAT (Digital Audito Tape)
ATF servo system, etc., which is applied to (1) is introduced.

An outline of the ATF servo system is shown in FIG.
In this method, the effective track width a of the magnetic head 1 is set wider than the track pitch b of the magnetic tape 2. The magnetic head 1 (azimuth angle: -A) is a regular track 3 on the magnetic tape 2.
When the recording data of (azimuth angle: -A) is reproduced, the recording signals of the adjacent tracks 4 and 5 (azimuth angle: + A) located on both sides of the track 3 are also reproduced at the same time. Long-wavelength signals for tracking control (servo) are recorded on the adjacent tracks 4 and 5, and the reproduced signals on the adjacent tracks 4 and 5 are compared with each other. Then, by the tracking control by the signal of the difference, the relative alignment between the regular track 3 and the magnetic head 1 is performed. When the magnetic head 1 moves in the track width direction (X direction), the reproduction signal level of the adjacent tracks 4 and 5 changes. This state is shown in FIG. Here, La is the reproduction signal level of the track 4, Lb
Indicates the reproduction signal level of the track 5. When the magnetic head moves in the (+) direction, La increases, and when it moves in the (-) direction, Lb increases. The difference L (= La−Lb) is taken in FIG. 15B.

Assuming that signals from adjacent tracks 4 and 5 flow into the magnetic head 1 for some reason, the curve of La shifts to the (-) side as shown in FIG. The curve of Lb shifts to the (+) side. This is equivalent to expanding the track width of the magnetic head in reproducing the servo signal. When the amount of the shift becomes extremely large, the area where L does not change even if the magnetic head moves as shown in FIG.
Occurs in the vicinity of = 0 (on-track state), and the tracking accuracy decreases.

Conventional MIG (Met
The sliding surface of an al In Gap) type magnetic head is illustrated. The width of each of the pair of core halves 7 and 8 arranged so as to be opposed to each other via the magnetic gap 6 is formed to be the smallest on the magnetic gap 6 side in order to enhance the magnetic efficiency, and gradually increase as the distance from the magnetic gap 6 increases. ing. In addition, here 7
Reference numerals a and 8a denote high saturation magnetic flux density film portions, 7b and 8b denote track width regulating grooves, and 9 and 10 denote a pair of vitreous blocks.

FIG. 19 schematically shows the relationship between the magnetic head and recording tracks. In the magnetic recording / reproducing apparatus adopting the azimuth recording, when the azimuth angle becomes large, the track width regulation groove 7 on one side on the tape slide surface of each core half is formed.
b and azimuth recorded pattern 1 of adjacent track 4
Since the opening angle θ with respect to 1 becomes small, it becomes easy to be influenced by the recording signal of the adjacent track 4. For example, when the azimuth angle is 20 degrees and the track width regulating groove 8b is inclined at an angle of 60 degrees with respect to the magnetic gap 6, the angle θ is 20.
It becomes degree. In this case, the long-wavelength signal recorded for the servo is reproduced more than necessary and is additionally input. This means that La and Lb are displaced from each other in FIG. 15, and accurate tracking control cannot be obtained.

When the actual amount of the deviation was measured, the results shown in FIGS. 20 and 21 were obtained. That is, the pattern 11 recorded at an azimuth angle of 20 degrees is replaced with the magnetic head 1 having an azimuth angle (-) of 20 degrees.
It was examined how the reproduced signal level changes depending on the moving amount of the track when reproduced at 2. Then, the position at which the reproduction signal level is half the maximum value is deviated from the theoretical value, and the evaluation is made (this is the spread amount of the track). Specifically, the recording track width was 10 μm, the recording wavelength was 36 μm, and the track width of the magnetic head was 10 μm. FIG. 21 schematically shows the measurement result in this case. The solid line is the measured value and the dotted line is the theoretical value. It can be seen that the measured value is wider than the theoretical value. Even if the average value of the two spread amounts 13 and 14 is taken as the spread amount, depending on the sample, 10 μ
Some of them showed a spread amount of about m.

As described above, even if the ATF servo system is introduced, the tracking accuracy may be deteriorated depending on the conditions to which the ATF servo system is applied.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to efficiently reproduce a signal from a recording track and to be less susceptible to a signal from an adjacent track, that is, to the azimuth of the recording signal. It is an object of the present invention to provide a magnetic head capable of suppressing the spread amount from a theoretical value as small as possible when off-tracking with a reproducing magnetic head of reverse azimuth, and a manufacturing method thereof.

[0010]

In order to achieve the above-mentioned object, the present invention has projecting portions each projecting from a base portion in a convex shape, and these projecting portions face each other via a magnetic gap. And a pair of core halves arranged opposite each other as shown in FIG.
A pair of vitreous blocks interconnecting a pair of core halves, each projecting portion having track width regulating grooves for determining a track width on both side surfaces substantially orthogonal to the magnetic gap, and each base portion. The track width direction length is gradually increased as it goes away from the protruding portion, and the protruding length of the protruding portion is 5 μm to 15 μm.

Further, a step of forming a predetermined track groove on the mirror-polished magnetic body block to obtain a core half having a protruding portion protruding from the base portion, and at least one of the pair of core halves. And a step of butting a pair of core halves so that their protruding portions face each other through the magnetic gap forming film, and a pair of core halves on both sides thereof. A method of manufacturing a magnetic head, comprising: a step of connecting the glassy blocks to each other to obtain a composite body; and a step of cutting and separating the composite body into chips. .

[0012]

Since the track width regulating groove near the magnetic gap is substantially orthogonal to the magnetic gap, the opening angle between the pattern of the signal recorded on the adjacent track and the track width regulating groove becomes large. Therefore, the azimuth effect makes it difficult to receive a signal from an adjacent track. Also,
The protruding length of the protruding portion of the core half is 5 μm to 15 μm
Since it is set to 1, it is possible to obtain an excellent reproducing efficiency, a magnetic head which is hardly influenced by an adjacent track, and which has excellent reproducing efficiency.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a plan view of the magnetic head as seen from the sliding surface side. A pair of core halves 16 and 17 facing each other through a magnetic gap 15 are made of ferrite or another magnetic material. It is integrally connected by a pair of glassy blocks 18 and 19 provided on the sides. The core half body 16 has a protruding portion (hatched portion) 22 on the magnetic gap 15 side, and both side surfaces of the protruding portion 22 form track width regulating grooves 20 and 21. Protruding part 22
The width of the track determines the track width TW, and the protrusion length 23 is from 5 μm to
It is 15 μm. The width of the remaining portion of the core half body 16 other than the protruding portion 20 gradually widens as the distance from the protruding portion 22 increases, and along with this, the track width regulating groove 20 following each of the two track width regulating grooves 20 and 21.
The mutual distance between a and 21a also gradually increases. The other core half body 17 is also formed in the same shape as the core half body 16.

If the angle 24 formed by the track width regulating grooves 20a, 21a and the magnetic gap 15 is large, the area of the glass blocks 18, 19 occupying the sliding surface becomes large, which is not preferable in terms of wear resistance. On the other hand, if it is too small, it will be easily affected by the signals of the adjacent tracks. For this reason, it is desirable to set the azimuth angle 25 to about 25 to 50 degrees for a magnetic head having an angle of 20 degrees. As described above, the opening angle 24 between the track width regulating grooves 20a and 21a and the magnetic gap 15 has an appropriate value depending on the azimuth angle of the magnetic head, and as the azimuth angle increases, the preferable value of the angle 24 decreases. .

FIG. 2 shows an embodiment in which the present invention is applied to a MIG type magnetic head, and a pair of core halves 16 and 17 is used.
Has high saturation magnetic flux density films (soft magnetic material films) 16a and 17a, respectively, on the surface on the magnetic gap 15 side.

In this MIG type magnetic head, various types of protrusions 23 having different protrusion lengths 23 were made as prototypes.
The measurement was performed according to the procedure shown in FIG. The relationship between the amount of spread with respect to the theoretical value and the protruding length of the protruding portion was investigated.
As a result, as shown in FIG. 3, the angle formed between the track width regulating groove of the prototype magnetic head and the gap surface is 45 degrees.

Also here, the evaluation was performed by how much the position where the reproduction signal level becomes half the maximum value deviates from the theoretical value. The width of the recording track is 10 μm, and the azimuth angle is +20 degrees for the recording pattern and −2 for the magnetic head.
The recording wavelength is 0 degree and 36 μm. The measurement magnetic head is an average of eight each. Since it is difficult to measure the protruding length of the protruding portion with an actual magnetic head, the protruding length of the protruding portion is defined by the method shown in FIG. That is, the distance from the position where the extension lines of the track width regulating grooves 20 and 20a intersect to the magnetic gap. Here, when the left and right track width regulation grooves have different lengths, the shorter length is defined. In conclusion, the protruding length 23 of the protruding portion 22 is 5 μm
From the above, it can be seen that the spread with respect to the theoretical value hardly changes. The value of the spread is about 6 μm when the protrusion length 23 is 5 μm, and about 5 μm when the protrusion length is 20 μm.

The permissible values of the spread amount in the actual recording / reproducing apparatus are the track pitch (TP) and the track width (TW).
It depends on the following equation, though it depends on the formula.

(Permissible value) = TP- (TW-TP) / 2 In a recording / reproducing apparatus with TP of 10 μm, TW is about 15 μm.
Assuming that the above magnetic head is used, the permissible value of the width of spread is 7.5 μm. It can be seen that as TP becomes even narrower, this allowable value becomes smaller and smaller.

Further, when the spread angle between the track width regulating grooves 20a and 21a and the magnetic gap 15 becomes large,
The width of the spread becomes smaller, and conversely, the spread becomes larger as the spread angle becomes smaller.

Next, the results of measuring the reproducing characteristics of the magnetic heads manufactured by changing the track width and the protruding length of the protruding portion will be shown. Track width is 15μm and 10
The measurement was performed with a micrometer. A signal recorded at a relative velocity of 5 m / s and a frequency of 10 MHz (-20 ° for azimuth) was reproduced and the outputs were compared. The measurement was performed with eight magnetic heads each. Fig. 5 shows the result when the track width is 15 μm.
The case where the track width is 10 μm is shown in FIG. The output of the magnetic head is expressed with the unit output being 0 dB when the protrusion length of the protrusion is 1 μm. Track width is 15μm,
In both cases of 10 μm, when the protruding length of the protruding portion is 20 μm, the reproduction output is about −1 dB, and the reproduction characteristic is deteriorated.

Next, a method of manufacturing the magnetic head according to the present invention will be described with reference to FIGS.

(A) First, the ferrite or other magnetic material block 26 having a predetermined shape shown in FIG. 7 is mirror-polished. The variation in thickness is kept to about 5 μm or less. Since the protruding length of the protruding portion is 5 μm to 15 μm, it is desirable to control the thickness with such accuracy in consideration of the target error. (B) As shown in FIG. 8 or 9, track processing is performed so as to obtain a desired track width 27 and projection length 28.

(C) As shown in FIG. 10 or FIG.
A soft magnetic film 29 is formed on the surface on the magnetic gap side by a sputtering method, and a film (not shown) as a spacer for forming the magnetic gap is formed of SiO ₂ or glass.

(D) As shown in FIG. 12, a pair of core halves 31, 32 are butted against each other via a magnetic gap 30.
The glass material 33 is welded and connected. Reference numeral 34 indicates a winding groove. (E) As shown in FIG. 13, chips are cut and separated at a desired azimuth angle and head width. 35 shows a cutting line.

[0027]

As described above, according to the present invention, even in a recording / reproducing system having a small track pitch, it is possible to accurately position a track and to obtain a magnetic head excellent in reproducing efficiency.

[Brief description of drawings]

FIG. 1 is a plan view of a magnetic head according to an embodiment of the present invention.

FIG. 2 is a plan view of a magnetic head according to another embodiment of the invention.

FIG. 3 is a plan view of a reproduction output characteristic in the embodiment of the present invention.

FIG. 4 is a view for explaining a measurement standard of a core half body.

FIG. 5 is a plan view of reproduction output characteristics according to the embodiment of the present invention.

FIG. 6 is a plan view of a reproduction output characteristic in the embodiment of the present invention.

FIG. 7 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 8 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 9 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 10 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 11 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 12 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 13 is a perspective view of a manufacturing process according to an embodiment of the present invention.

FIG. 14 is a schematic explanatory diagram of an ATF servo system.

FIG. 15 is a schematic explanatory diagram of an ATF servo system.

FIG. 16 is a schematic explanatory diagram of an ATF servo system.

FIG. 17 is a plan view of a conventional magnetic head.

FIG. 18 is a plan view of a conventional magnetic head.

FIG. 19 is a diagram schematically showing a relative relationship between a magnetic head and a recording track.

FIG. 20 is an explanatory diagram of reproduction output of the ATF servo system.

FIG. 21 is an explanatory diagram of reproduction output of the ATF servo system.

[Explanation of symbols]

 15 magnetic gap 16 and 17 core half body 18 and 19 vitreous block 20 and 21 track width regulation groove 22 projecting portion 23 projecting length

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Ninomiya 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A pair of core halves, each having a protruding portion protruding in a convex shape from a base portion, the protruding portions facing each other through a magnetic gap, and a pair of core halves. Consists of a pair of vitreous blocks that are welded to both side surfaces of the core half body to connect a pair of core half bodies to each other, and each projecting portion has a track width on both side surfaces substantially orthogonal to the magnetic gap. It has a track width regulating groove to be determined, and the length of each base portion in the track width direction is gradually increased with increasing distance from the projecting portion, and the projecting length of the projecting portion is 5 μm to 15 μm. Magnetic head. 2. A step of forming a predetermined track groove in a mirror-polished magnetic body block to obtain a core half having a protruding portion protruding from a base portion, and at least one of a pair of core halves. A step of attaching a gap forming film to each other, a step of butting a pair of core halves so that their respective protruding portions face each other through the magnetic gap forming film, and a pair of core halves on both sides thereof. 2. A method of manufacturing a magnetic head, comprising: a step of connecting the glassy blocks to each other to obtain a composite body; and a step of cutting and separating the composite body into chips.