Magnetic head

Details Magnetic head Magnetic head

2001-07-17

2004-11-23

Heinz, A. J. (Department: 2653)

Dynamic magnetic information storage or retrieval

Head

Core

C360S122000

Reexamination Certificate

active

06822828

ABSTRACT:

CROSS REFERENCES TO RELATED APPLICATIONS
The present document is based on Japanese Priority Document JP 2000-235281, filed in the Japanese Patent Office on Jul. 31, 2000, and amended on Dec. 26, 2000, the entire contents of which being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head for recording and reproducing an audio signal, a video signal, or an information signal such as a data signal to or from a magnetic recording medium.
2. Description of the Related Art
A typical conventional video tape recorder (VTR), a digital audio tape recorder (DAT) or a digital data recording-reproducing device using a magnetic tape or the like as a magnetic recording medium has a magnetic head for writing information signals in a magnetic signal form into recording tracks on such magnetic tape, or for reading recorded information signals in a magnetic signal form from the recording tracks.
Such magnetic head generally has a magnetic core composed of two magnetic core halves joined with each other, and such magnetic core is processed to have a slide-contact plane with which a magnetic tape comes into contact.
The slide-contact plane has a magnetic gap embedded therein, and such magnetic gap is formed by joining two magnetic core halves while being interposed with a magnetic film or a gap material.
The magnetic gap is responsible for limiting the extending range of the magnetic field on the magnetic tape during recording, and for introducing magnetic flux from the magnetic tape during reproduction.
A specific constitution of such magnetic head is shown in
FIG. 12. A
magnetic head
10
comprises a magnetic core halves
11
a
and
11
b
. The magnetic core halves
11
a
,
11
b
have metal magnetic thin films
12
a
and
12
b
fabricated therein to thereby complete a magnetic circuit. Joining such magnetic core halves
11
a
and
11
b
, individually having the metal magnetic thin films
12
a
and
12
b
formed thereon, while providing a gap material therebetween will produce a magnetic gap g.
Sliding motion of a magnetic tape across the magnetic gap g allows recording and reproduction of information signals between such magnetic tape and the magnetic head
10
.
The upper end and the lower end of the magnetic gap g along the vertical direction in
FIG. 12
are referred to as “edges”, where misalignment or sagging of the joined metal magnetic thin films
12
a
,
12
b
may occur. Such misalignment or sagging of the metal magnetic thin films
12
a
,
12
b
will produce unnecessary leakage magnetic field from the edges of the magnetic gap g, which undesirably disturbs recording patterns on the magnetic tape moving on the slide-contact plane of the magnetic head
10
.
This raises a tough problem in particular for the case that the recording system of information signals is based on the overwrite system as shown in
FIG. 13
, since S/N ratio in the recording tends to be degraded due to so-called side-erasing effect, which prevents all recording tracks on the magnetic tape from being effectively used.
To avoid such problem, a groove
33
is formed, as shown in
FIG. 12
, on the lower edge side of the magnetic gap g of the magnetic head
10
, which is corresponded with the overwriting side, so as to prevent the misalignment or sagging at the edge of the magnetic gap g on the side responsible for the overwriting.
The groove
33
is filled with a glass
33
a
. This successfully prevents clogging of the groove
33
with the magnetic powder dropped from the magnetic tape, or chipping of the edge of the magnetic gap g, which ensures stable running of the magnetic tape.
Filling the glass
33
a
into the groove
33
of the magnetic head
10
, however, tends to generate bubbles entrained in such glass
33
a
in the vicinity of the metal magnetic films
12
a
and
12
b
and along the magnetic core halves
11
a
and
11
b
. Such bubbles entrained in the glass
33
a
will undesirably catch the magnetic powder to be clogged during the tape run.
Oxygen plasma cleaning or block annealing of the groove
33
under an oxygen atmosphere before being filled with the glass
33
a
was only partially effective in reducing such bubbles entrained along the magnetic core halves
11
a
and
11
b
, and was not effective at all in reducing those along the metal magnetic films
12
a
and
12
b
, which makes it difficult to bring the magnetic head
10
into mass production.
Considering the above, it is therefore an object of the present invention to provide a magnetic head which allows simple filling of a non-magnetic material such as glass, and allows suppression of the bubble generation within such non-magnetic material.
SUMMARY OF THE INVENTION
The present invention provides a magnetic head comprising a slide-contact plane with which a magnetic recording medium comes into contact, which is provided on a magnetic core; a magnetic gap provided in the slide-contact plane by forming thereon at least a magnetic film; a groove portion provided at one end or each of both ends of the magnetic gap so as to be aligned approximately in parallel to a moving direction of the magnetic recording medium; and a non-magnetic material provided in the groove portion; wherein the groove portion has a non-magnetic oxide film and a chromium film formed on an inner surface thereof and has the non-magnetic material formed on such chromium (Cr) film so as to fill the groove portion.
In an embodiment, the groove portion has on the inner surface thereof a non-magnetic oxide film which can prevent the non-magnetic material and the magnetic film from reacting with each other and thus can prevent the bubbles from being generated within such non-magnetic material. The non-magnetic oxide film is further covered with the chromium (Cr) film. The bubble generation is also caused by rare gas which are once occluded in the non-magnetic oxide film during the formation thereof typically by sputtering into the groove portions, and then released into the non-magnetic material during filling thereof due to elevated temperature. The chromium (Cr) film can block such release of the rare gas.
In an embodiment, the non-magnetic material is a glass, and the filling of such glass is carried out under a nitrogen (N
2
) atmosphere added with oxygen.
Using a highly weatherproof glass is preferable for ensuring reliability of the magnetic head, but has been disadvantageous in that filling of such highly weatherproof glass into the groove portion requires heating typically at 540° C. or above. This is because such glass can flow to thereby successfully fill the groove portion only when heated to such high temperature region.
Raising the temperature of such highly weatherproof glass to 540° C. or above, however, produces deposition within the glass, so that it has actually been difficult to use the highly weatherproof glass in the groove portion.
In an embodiment, the non-magnetic material is a highly weatherproof glass which is filled under a nitrogen atmosphere added with oxygen, which improves wettability of the glass and thus allows the glass to flow smoothly into the groove portion to thereby fill thereof even at a relatively low temperature. Such low temperature is not causative of the deposition within the glass.
Hence the highly weatherproof glass, which has been unavailable previously, can be filled in the groove portion to thereby improve the reliability of the magnetic head.
In an embodiment, the non-magnetic oxide film has a thickness of 0.1 &mgr;m or above, and the chromium film has a thickness of 0.01 to 0.1 &mgr;m. According to the constitution of claim
3
, the non-magnetic oxide film as thick as 0.1 &mgr;m or above can completely prevent the reaction between the highly weatherproof glass and the magnetic film, which successfully prevents the highly weatherproof glass from generating the bubbles.
The chromium film has a thickness of 0.01 to 0.1 &mgr;m. The thickness of 0.01 &mgr;m or above is preferred since a thickness less than such value may result in corrosion of the chromium fi

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