Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2000-09-26
2004-01-27
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06683760
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head to be used for a helical scan type magnetic recording and reproducing apparatus, particularly to a magnetoresistive magnetic head for use in a reproducing a magnetic head.
2. Description of the Related Art
FIG. 24
shows a perspective view of the rotary drum of the conventional helical scan type magnetic recording and reproducing apparatus;
FIG. 25
is a plane view for describing the recording method in the helical scan type magnetic recording and reproducing apparatus;
FIG. 26
is a plane view showing the construction of the composite type magnetic head;
FIG. 27
is a perspective view showing the construction of the magnetic head mounted on the base board of the rotary drum;
FIG. 28
is a plane view of the construction of the magnetic head mounted on the rotary drum viewed from the sliding face side of the recording medium;
FIG. 29
includes an enlarged construction of the area X in
FIG. 28
, and shows a plane view for describing the elevation adjustment of respective MR layers of the two magnetic heads;
FIG. 30
shows a plane view of the reproduction track during reproduction when respective MR layers of the two magnetic heads have different elevations one another; and
FIG. 31
a plane view showing how mounting errors occur when the magnetic head is mounted on the base board.
A line of information has been recorded and reproduced by a helical scan method in the magnetic recording and reproducing apparatus such as a VCR (Video Cassette Recorder) and a recording and reproducing unit for a computer using a magnetic tape as a magnetic recording medium. A plurality of the magnetic heads have been used in the helical scan type magnetic recording and reproducing apparatus in order to improve recording density and data transfer rate, wherein two magnetic heads
70
and
80
are mounted on a rotary drum
61
at two opposed positions on the outer circumference face as shown, for example, in FIG.
24
.
Signals are recorded on the magnetic tape
63
wound on the rotary drum
61
, or the signals recorded on the magnetic tape
63
are reproduced using these magnetic heads
70
and
80
. As shown in
FIG. 25
, for example, signals are recorded by a so-called guard-band-less method so that a recording track T
12
is made to partially overlap an area of another track T
11
where signals have been recorded by the magnetic heads
70
immediately before recording with the magnetic head
80
, when the rotary drum
61
is driven to rotate to record the signals from the magnetic head
80
on the magnetic tape
63
. On the other hand, respective magnetic heads
70
and
80
sequentially scan the corresponding recording tracks T
11
and T
12
for reproduction.
A MIG (Metal-In-Gap) type head and a lamination type head have been used for the magnetic heads
70
and
80
to be used for the helical scan type magnetic recording and reproducing apparatus.
Track width has been narrowed or the recording frequency has been increased for realizing high density recording on the magnetic recording medium in the data recording and reproducing apparatus for use in the VTR and computer. As a result, the magnetic gap is also required to be narrow in compliance with narrowing the track width.
However, it is difficult to make the MIG head small size because the magnetic gap is formed by mechanical cutting to make it impossible to meet the requirement of narrowing the track width. While a high polishing accuracy of the abutting faces is required for forming the magnetic gap meeting the requirement of narrowing the track width, the polishing accuracy for the fine magnetic gap has been hardly improved. While inductance should be also low for complying with the requirement of making the recording frequency high, on the other hand, it is impossible to lower the inductance in the MIG head and lamination type head. Furthermore, the MIG head and lamination type head also have a drawback that their reproduction outputs cannot be made to be sufficiently high when one attempts to increase the recording density.
In the magnetic recording and reproducing apparatus such as a hard disk device, on the other hand, various thin film magnetic heads have been used. Commonly used thin film magnetic heads mainly comprise an induction type magnetic head (an inductive head) and reproducing magnetic heads include a magnetoresistive magnetic head (a MR head). A composite type magnetic head formed by laminating the inductive head and the MR head has been also frequently used.
Such thin film magnetic heads as described above are advantageous in that they are suitable for mass production in one lot by using a thin film deposition process, and that they are able to meet the requirement of making the dimension fine for narrowing the magnetic gap for use in the track having a narrow width. The MR head is particularly suitable for high frequency recording since it is not dependent on the relative velocity of the magnetic recording medium to enable it to directly respond to the signal magnetic field to obtain a high reproduction output, besides its inductance is considerably lower as compared with the MIG head and lamination type head.
Accordingly, use of the thin film magnetic head described above as a magnetic head is also desirable in the helical scan type magnetic recording and reproducing apparatus.
When the composite type magnetic head is applied for the magnetic heads
70
and
80
of the helical scan type magnetic recording and reproducing apparatus, for example, the magnetic head
70
is composed of a MR head
71
and an inductive head
72
as shown in FIG.
26
. The MR heads
71
is formed by sequentially laminating an insulation layer
71
b
, a lower shield layer
71
c
, a lower gap layer
71
d
, a MR layer
71
e
, an upper gap layer
71
f
and an upper shield layer
71
g
on a base board
71
a
. Pulled-out electrodes and hard layers are not shown in the drawing. The inductive head
72
is constructed by sequentially laminating a gap layer
72
b
, an upper core layer
72
c
and an insulation layer
72
d
on a lower core layer
72
a
that also serves as the upper shield layer. The portion inserted between the lower shield layer
71
c
and the upper shield layer
71
g
serves as a read magnetic gap Ga′ of the MR head
71
. The portion inserted between the lower core layer
72
a
and the upper core layer
72
c
serves as a write magnetic gap Gb′ of the inductive head
72
.
The magnetic head
70
is mounted on a base board
62
by being slanted at an azimuth angle àx′, and the base board
62
on which the magnetic head
70
is mounted is attached at a prescribed position on the outer circumference face of the rotary drum
61
.
Likewise, the magnetic head
80
is composed of a MR head
81
having a MR layer
81
e
and an inductive head
82
as shown in
FIG. 29
, and has a read magnetic gap Ga″ and a write magnetic gap Gb″. The magnetic head
80
is also mounted on the base board
62
by being slanted at an azimuth angle Ay as shown in
FIGS. 24 and 29
, and the base board
62
on which the magnetic head
80
is mounted is attached at a prescribed position on the circumference face of the rotary drum
61
.
Since the magnetic heads
70
and
80
are alternately used for continuous recording and reproduction in the helical scan type magnetic recording and reproducing apparatus making use of the magnetic heads
70
and
80
comprising the foregoing thin film magnetic head, it is required that the MR layer
71
e
of the MR head
71
is located at an approximately the same elevation as that of the MR layer
81
e
of the MR head
81
from the base board
62
as shown in FIG.
29
. In other words, the elevation h
1
as measured from the base board
62
to the end of the MR layer
71
e
is approximately equal to the elevation h
2
as measured from the base board
62
to the end of the MR layer
81
e
. The reason will be described below.
When the elevation h
1
as measured from the base board
62
to the
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Tupper Robert S.
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