U.S. patent application number 09/879781 was filed with the patent office on 2001-11-22 for magnetic head and manufacturing method therefor.
Invention is credited to Inaguma, Teruo, Inoue, Yoshihiko, Ogata, Seiichi, Saito, Tadashi, Takahashi, Shinji.
Application Number | 20010042300 09/879781 |
Document ID | / |
Family ID | 27276445 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042300 |
Kind Code |
A1 |
Ogata, Seiichi ; et
al. |
November 22, 2001 |
Magnetic head and manufacturing method therefor
Abstract
A magnetic head having optimum recording/reproducing
characteristics and a method for producing the magnetic head. A
pair of magnetic core halves 2, 3, each having a substrate 4 and a
thin magnetic metal film 6 formed obliquely on it, are bonded
together via a non-magnetic material C for defining a magnetic gap.
A portion of the substrate faces a junction surface 8 of the
magnetic core halves 2, 3. The substrate portion is arranged for
facing an end face of the magnetic meta film 6 of the opposite side
magnetic core half facing the junction surface 8.
Inventors: |
Ogata, Seiichi; (Miyagi,
JP) ; Saito, Tadashi; (Miyagi, JP) ; Inaguma,
Teruo; (Miyagi, JP) ; Takahashi, Shinji;
(Miyagi, JP) ; Inoue, Yoshihiko; (Miyagi,
JP) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL
P.O. BOX 061080
WACKER DRIVE STATION
CHICAGO
IL
60606-1080
US
|
Family ID: |
27276445 |
Appl. No.: |
09/879781 |
Filed: |
June 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09879781 |
Jun 12, 2001 |
|
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09006460 |
Jan 13, 1998 |
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6278576 |
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Current U.S.
Class: |
29/603.2 ;
29/603.07; 29/603.15; 29/603.16; G9B/5.043; G9B/5.057 |
Current CPC
Class: |
G11B 5/314 20130101;
Y10T 29/49046 20150115; G11B 5/1276 20130101; Y10T 29/49048
20150115; Y10T 29/49055 20150115; G11B 5/53 20130101; G11B 5/1878
20130101; Y10T 29/49032 20150115 |
Class at
Publication: |
29/603.2 ;
29/603.07; 29/603.15; 29/603.16 |
International
Class: |
G11B 005/127; H04R
031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 1997 |
JP |
P09-004753 |
Feb 25, 1997 |
JP |
P09-040906 |
Jun 30, 1997 |
JP |
P09-173352 |
Claims
What is claimed is:
1. A magnetic head in which a pair of magnetic core halves, each
having a substrate and a magnetic metal film formed obliquely
thereon, are bonded together via a non-magnetic material for
defining a magnetic gap, characterized in that a portion of the
substrate faces the junction surface of the magnetic core halves,
said substrate portion being arranged for facing an end face of the
magnetic meta film of the opposite side magnetic core half facing
the junction surface.
2. The magnetic head as claimed in claim 1 wherein said substrate
is formed of a non-magnetic material.
3. The magnetic head as claimed in claim 1 wherein an underlying
layer is provided between said substrate and said magnetic metal
film.
4. The magnetic head as claimed in claim 3 wherein said underlying
layer is colored differently from the substrate and the thin
magnetic metal film.
5. The magnetic head as claimed in claim 1 wherein said thin
magnetic metal film is made up of plural magnetic metal layers
layered via non-magnetic layers.
6. The magnetic head as claimed in claim 5 wherein said the
uppermost one of the plural magnetic metal layers is thinner in
film thickness than other magnetic metal layers.
7. The magnetic head as claimed in claim 1 wherein said thin
magnetic metal film has a portion in the vicinity of the junction
surface cut out so that the film is progressively reduced in
thickness towards the junction surface.
8. The magnetic head as claimed in claim 1 wherein at least one of
the thin magnetic metal films is formed on an abutting surface to
the other thin magnetic metal film with a coil-forming recess in
which is formed a coil formed by the thin film forming process.
9. A method for producing a magnetic head in which a pair of
magnetic core halves, each having a substrate and a thin magnetic
metal film formed obliquely thereon, are bonded together via a
non-magnetic material for defining a magnetic gap, comprising:
obliquely forming a thin magnetic metal film on the substrate and
subsequently grinding the junction surface for exposing the
substrate on the unction surface; and bonding the magnetic core
halves so that a portion of one of the substrates facing the
junction surface faces the end face of the thin magnetic metal film
of the other magnetic core half facing the junction surface.
10. The method for producing a magnetic head as claimed in claim 9
wherein said substrate is formed of a non-magnetic material.
11. The method for producing a magnetic head as claimed in claim 9
wherein an underlying layer is formed between the substrate and the
thin magnetic metal film and the magnetic core halves are bonded
together with this underlying layer and the end face of the thin
magnetic metal film as reference.
12. The method for producing a magnetic head as claimed in claim 9
wherein said thin magnetic metal film is made up of plural magnetic
metal layers layered together with non-magnetic layers
in-between.
13. The method for producing a magnetic head as claimed in claim 12
wherein an uppermost one of the plural magnetic metal layers is
thinner in film thickness.
14. The method for producing a magnetic head as claimed in claim 12
wherein the magnetic core halves are abutted to each other with the
second upper one of the plural magnetic metal layers formed on one
of the magnetic core halves and the lowermost one of the magnetic
metal layers formed on the other magnetic core half as
reference.
15. The method for producing a magnetic head as claimed in claim 9
wherein said magnetic metal layer is ground so as to have a portion
thereof in the vicinity of the junction surface cut out so that the
film is progressively reduced in thickness towards the junction
surface.
16. The method for producing a magnetic head as claimed in claim 9
wherein at least one of the thin magnetic metal films is formed on
a abutting surface to the other thin magnetic metal film with a
coil-forming recess in which is formed a coil formed by the thin
film forming process.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a magnetic head having a magnetic
path formed by a magnetic metal film, and a manufacturing method
therefor.
[0003] 2. Description of Related Art
[0004] In a magnetic recording/reproducing apparatus, such as a
video tape recorder, researches in digitizing signals and recording
the resulting digitized signals for improving the picture quality,
are under way. In keeping pace therewith, researches in increasing
the recording density and the recording frequency, are also
progressing.
[0005] Meanwhile, with the increased magnetic recording density and
increased recording frequency, a magnetic head loaded on the
magnetic recording/reproducing apparatus is required to have a high
output and a low noise in the high frequency range. For example, in
a compound metal-in-gap magnetic head used frequently as a magnetic
head for VTR, in which a magnetic metal film is formed on a ferrite
material and a coil is placed thereon, has a large inductance and a
low output per inductance, as a result of which the output is low
in the high frequency range. Thus, it is difficult to cope
sufficiently with digital picture recording for which a high
frequency and a high density are required.
[0006] Under these circumstances, a so-called thin film type
magnetic head, fabricated by the thin film forming step, is being
investigated as a magnetic head for coping with the high
frequency.
[0007] This thin film type magnetic head is formed by connecting a
pair of magnetic head halves having magnetic metal films via a gap
material in-between. In the magnetic head halves is embedded a
magnetic metal film having its connecting surface formed by a
non-magnetic material, such as glass, and substantially
rectangular-shaped coil-forming recesses are formed at mid portions
thereof. In the coil-forming recesses of the magnetic head halves
is placed a coil formed by a thin film forming technique, such as
photolithography. These magnetic head halves are joined together
via a non-magnetic gap material in-between for forming the magnetic
gap between the magnetic metal films.
[0008] With the above-described thin-film type magnetic head, it
has been difficult to form the magnetic metal films in position for
facing each other on a sole substrate. That is, in the
above-described magnetic head, one of the thin magnetic metal films
becomes offset relative to the other film, as shown in FIG. 1. The
magnetic head shown in FIG. 1 undergoes so-called track offset,
with an offset angle being .theta.. In the present magnetic head,
an azimuth angle is represented by .alpha..
[0009] In the above-described magnetic head, an angle defined
between the counter-azimuth direction shown by arrow R in FIG. 1
and the bisector of the angle of track offset shown at Q in FIG. 1
becomes small. The result is that, in the conventional magnetic
head, neighboring recording tracks are reproduced, thus producing
the noise. That is, this magnetic head suffers from high playback
fringing.
[0010] With the present magnetic head, it may be premeditated that,
as shown in FIG. 2, one of the thin magnetic metal films 100 be
relatively offset to the other metal film in an opposite direction
to that shown in FIG. 1. With this magnetic head, the angle .times.
between the opposite azimuth direction R and the bisector Q of the
angle of track offset in this case becomes larger thus suppressing
the playback fringing to a smaller value. However, in the magnetic
head shown in FIG. 2, the track offset angle .theta. is of a
smaller value.
[0011] In a magnetic head, the larger the angle of track offset
.theta., the smaller is the recording fringing value. That is, in
the present magnetic head, if the track offset angle .theta. is
small, signals are recorded on the neighboring recording track,
thus partially erasing the signals of the neighboring track. Thus,
if the thin magnetic metal films 100 are relatively offset, as
shown in FIG. 25, the recording fringing is of a higher value,
because the track offset angle .theta. is small.
[0012] The above-mentioned defects in the recording/reproducing
characteristics due to relative position offset of the magnetic
thin film 100 can be evaded by setting the magnetic thin metal
films in position relative to each other. That is, in the
conventional magnetic head, the track offset angle .theta. can be
set so as to be as large as 90.degree. or more by bonding the
paired magnetic metal films in position for facing each other. This
renders it possible to suppress the recording fringing and the
reproducing fringing to a lower value thus achieving optimum
recording/reproducing characteristics.
[0013] However, it is extremely difficult to bond the paired
magnetic metal films in position for facing each other. For
correctly positioning the paired thin magnetic metal films in
position, the manufacturing device needs to be improved in accuracy
significantly, which is not a realistic method for solution. It may
also be premeditated to remove track offset by laser trimming after
bonding the paired magnetic thin metal films. In this case, laser
trimming is applied to each magnetic head in the manufacturing
process of simultaneously fabricating plural magnetic heads, thus
not only complicating the manufacturing process but also requiring
excess working time.
SUMMARY OF THE INVENTION
[0014] It is therefore an object of the present invention to
overcome the above-mentioned problems in the conventional magnetic
head and to provide a magnetic head having optimum
recording/reproducing characteristics.
[0015] It is another object of the present invention to overcome
the above-mentioned problems in the conventional magnetic head and
to provide a magnetic head having optimum recording/reproducing
characteristics.
[0016] In one aspect, the present invention provides a magnetic
head in which a pair of magnetic core halves, each having a
substrate and a magnetic metal film formed obliquely thereon, are
bonded together via a non-magnetic material for defining a magnetic
gap, wherein a portion of the substrate faces the junction surface
of the magnetic core halves. This substrate portion is arranged for
facing an end face of the magnetic meta film of the opposite side
magnetic core half facing the junction surface.
[0017] With the present magnetic head, the track offset angle
becomes larger at all times even if the magnetic core halves are
bonded together without correctly positioning the thin magnetic
metal films formed on the respective substrates. That is, with the
present magnetic head, since the magnetic core halves are bonded
together so that the thin magnetic metal film on one of the
substrates faces the opposite side substrate, the track offset
angle becomes larger even if magnetic core halves are bonded
together without correctly positioning the thin magnetic metal
films. Thus, the present magnetic head is reduced in recording
fringing thus exhibiting optimum recording characteristics.
[0018] Moreover, with the present magnetic head, since the thin
magnetic metal film on one of the substrates faces the opposite
side substrate, the angle between the counter-azimuth direction and
the bisector of the track offset angle can be increased, so that
the playback fringing is reduced to assure optimum reproducing
characteristics.
[0019] With the present magnetic head, thin magnetic metal film may
have a portion in the vicinity of the junction surface cut out so
that the film is progressively reduced in thickness towards the
junction surface.
[0020] With the present magnetic head, the magnetic flux density is
concentrated towards the magnetic gap, so that the magnetic head
has an improved output during recording/reproduction.
[0021] In another aspect, the present invention provides a method
for producing a magnetic head in which a pair of magnetic core
halves, each having a substrate and a thin magnetic metal film
formed obliquely thereon, are bonded together via a non-magnetic
material for defining a magnetic gap the method includes the steps
of obliquely forming a thin magnetic metal film on the substrate
and subsequently grinding the junction surface for exposing the
substrate on the junction surface, and bonding the magnetic core
halves so that a portion of one of the substrates facing the
junction surface faces the end face of the thin magnetic metal film
of the other magnetic core half facing the junction surface.
[0022] With the present manufacturing method for manufacturing the
magnetic head, the magnetic core halves are bonded together so that
a portion of the substrate is exposed to the junction surface and
the exposed portion of the substrate faces the thin magnetic metal
film on the opposite side substrate. Thus, with the present
technique, the track offset angle can be increased even if the
paired thin magnetic metal films are not positioned correctly.
Moreover, if the paired thin magnetic metal films are bonded
together by this technique, the angle between the counter-azimuth
direction and the bisector of the track offset angle can be
increased, so that the playback fringing is reduced to assure
optimum recording/reproducing characteristics.
[0023] With the present method, the thin magnetic metal film may
have a portion in the vicinity of the junction surface cut out so
that the film is progressively reduced in thickness towards the
junction surface.
[0024] With the present method, the magnetic flux density is
concentrated towards the magnetic gap, so that the magnetic head
may be manufactured which has an improved output during
recording/reproduction.
[0025] With the magnetic head and the manufacturing method
according to the present invention, the substrate is exposed on a
portion of the thin magnetic metal film on the junction surface
defining the magnetic gap and the substrate thus exposed on the
junction surface faces the magnetic metal film of the opposite side
substrate. Thus, the track offset angle can be increased, while the
angle between the counter-azimuth direction and the bisector of the
track offset angle can be increased, thus suppressing recording
fringing and playback fringing for assuring optimum
recording/reproducing characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a plan view showing a conventional magnetic
head.
[0027] FIG. 2 is a plan view showing another conventional magnetic
head.
[0028] FIG. 3 is a perspective view showing essential portions of a
magnetic head according to the present invention.
[0029] FIG. 4 is a plan view showing essential portions of the
magnetic head shown in FIG. 3.
[0030] FIG. 5 is a plan view showing essential portions of another
magnetic head according to the present invention.
[0031] FIG. 6 is a plan view showing essential portions of still
another magnetic head according to the present invention.
[0032] FIG. 7 is a graph showing the elation between the film
thickness of an underlying layer and recording fringing in a
magnetic head shown in FIG. 4.
[0033] FIG. 8 is a plan view showing essential portions of still
another magnetic head according to the present invention.
[0034] FIG. 9 is a graph showing the elation between the film
thickness of an uppermost magnetic metal layer and recording
fringing in the magnetic head shown in FIG. 6.
[0035] FIGS. 10 to 18 are perspective views showing the
manufacturing process for manufacturing a magnetic head according
to the present invention.
[0036] FIG. 19 is a perspective view showing the manufacturing
process for manufacturing another magnetic head according to the
present invention.
[0037] FIG. 20 is a plan view showing essential portions of a
sample A used in evaluating the recording fringing and reproducing
fringing of a magnetic head according to the present invention.
[0038] FIG. 21 is a plan view showing essential portions of a
sample B used in evaluating the recording fringing and reproducing
fringing of the magnetic head according to the present
invention.
[0039] FIG. 22 is a plan view showing essential portions of a
sample C used in evaluating the recording fringing and reproducing
fringing of a magnetic head according to the present invention.
[0040] FIG. 23 is a plan view showing essential portions of a
sample D used in evaluating the recording fringing and reproducing
fringing of a magnetic head according to the present invention.
[0041] FIG. 24 is a plan view showing essential portions of a
sample E used in evaluating the recording fringing and reproducing
fringing of an other magnetic head according to the present
invention.
[0042] FIG. 25 is a plan view showing essential portions of a
sample F used in evaluating the recording fringing and reproducing
fringing of the other magnetic head according to the present
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0043] Referring to the drawings, preferred embodiments of a
magnetic head according to the present invention will be explained
in detail.
[0044] A magnetic head 1 according to the present invention is made
up of a pair of magnetic head halves 2, 3 bonded together with a
non-magnetic gap material G in-between, as shown in FIGS. 3 and 4.
These magnetic head halves 2, 3 are each made up of a non-magnetic
substrate 4 and a magnetic metal film 6 formed thereon. On at least
one of the paired magnetic head halves 2, 3 is formed a coil 7 for
magnetic excitation or detection of an induced voltage. In this
magnetic head 1, the magnetic metal film 6 forms a magnetic core in
such a state in which the paired magnetic head halves 2, 3 are
bonded together with the gap material G in-between. On the magnetic
head 1 is slid a magnetic recording medium in a direction shown by
arrow A in FIG. 3, with the magnetic head halves 2, 3 being bonded
together, thus reproducing the signal magnetic field recorded on
the magnetic recording medium or recording the signal magnetic
field on the magnetic recording medium.
[0045] In the present magnetic head 1, the magnetic metal film 6 is
formed obliquely at a pre-set angle on the non-magnetic substrate
4. Thus, when the paired magnetic head halves 2, 3 are bonded
together via a gap material G in-between, the magnetic core is
arranged obliquely relative to the sliding direction of the
magnetic recording medium.
[0046] In the present magnetic head 1, the magnetic metal film 6 is
made up of three magnetic metal layers 6B, layered together via
non-magnetic layers 6A in-between. The magnetic metal films 6
formed on the paired magnetic head halves 2, 3 are bonded together
for facing each other via a gap material G for forming a magnetic
gap. The magnetic head of the present invention is, however, not
limited to the three magnetic metal layers 3B layered together as
in the present embodiment.
[0047] When the magnetic metal films 6 in the magnetic head 1 are
bonded together via the gap material G, these magnetic metal films
6 are offset relative to one another, as shown in FIG. 4. On a
junction surface 8, forming the magnetic gap, the non-magnetic
substrate 4 is exposed to one end 6C of the magnetic metal film 6,
so that, when the paired magnetic head halves 2, 3 are bonded
together via the gap material G, the magnetic metal film 6 of the
magnetic head half 2 faces the non-magnetic substrate 4 of the
opposite side magnetic head half 3 exposed on the junction surface
8.
[0048] The portion of the magnetic metal film 6 exposed to outside
of the magnetic recording medium facing surface is cut out so as to
reduced in width and is formed with a coil-forming recess, not
shown, for forming the coil 7. The coil 7 is formed of an
electrically conductive metal material by a thin film forming
technique, such as an electrolytic plating method.
[0049] In the magnetic head halves 2, 3, the non-magnetic substrate
4 is formed of a non-magnetic material, for example, MnO--NiO based
material, only by way of an example. That is, it suffices if the
non-magnetic substrate 4 is formed of calcium titanate, barium
titanate, zirconium oxide (zirconia), alumina, alumina titanium
carbide, SiO.sub.2, Zn ferrite, crystal glass or hard glass. The
magnetic metal film 6 may be of a magnetic metal material, such as
Fe--Al--Si alloy (sendust), only by way of example. Thus, it
suffices if the magnetic metal film 6 is formed of crystal alloys,
such as a Fe--Al alloy, Fe--Si--Co alloy, a Fe--Ga--Si alloy,
Fe--Ga--Si--Ru alloy, Fe--Al--Ge alloy, Fe--Ga--Ge alloy,
Fe--Si--Ge alloy, Fe--Co--Si--Al alloy or a Fe--Ni alloy.
Alternatively, it may be a metal-metalloid based amorphous alloy,
typified by an alloy comprised of one or more of elements Fe, Co
and Ni and one or more elements P, C, B and Si, or an alloy mainly
composed of these elements and also containing Al, Ge, Be, Sn, In,
Mo, W, Ti, Mn, Counter-azimuth direction R, Zr, Hf and Nb, or an
amorphous alloy, typified by a metal-metal based amorphous alloys,
mainly composed of transition metals, such as Co, Hf or Zr and
rare-earth elements.
[0050] In recording signals on a magnetic recording medium or
reproducing a signal magnetic field by the above-described magnetic
head 1 of the present embodiment, a magnetic core is defined by a
front gap 9 and a back gap 10 which are formed on bonding the
above-mentioned paired magnetic metal films 6.
[0051] In the present embodiment of the magnetic head, the paired
magnetic metal films 6 are bonded together with a shift (offset)
relative to each other, as described above. In the magnetic head 1,
the azimuth angle and the counter-azimuth angle are denoted by
.alpha. and -.alpha., respectively. The counter-azimuth angle
herein means an angle having the same value as the azimuth angle
.alpha. and the direction perpendicular to the medium sliding
direction on the medium sliding surface as an axis of symmetry.
[0052] In the present magnetic head 1, the magnetic metal films 6
are bonded together with a relative shift or offset therebetween.
By this shift, a track offset angle .theta. (FIG. 4) is produced.
In this magnetic head 1, a non-magnetic substrate 4 is exposed at
an end 6C of the magnetic metal film 6 on a junction surface 8
defining the magnetic gap. That is, in the present magnetic head 1,
the magnetic metal film 6 exposed on one junction surface 8 faces
the non-magnetic substrate exposed to the opposite side junction
surface 8. The result is that this magnetic head 1 has a large
track offset angle .theta..
[0053] If the magnetic head 1 has this large track offset angle
.theta., the recording fringing can be suppressed to a lower value.
Therefore, the magnetic head 1 is free from such an inconvenience
that neighboring tracks are simultaneously reproduced during
reproduction, thus assuring superior playback characteristics.
[0054] Moreover, with the present magnetic head 1, since the paired
magnetic metal films 6 are bonded together with a relative shift in
a pre-set direction, as described above, it becomes possible to
increase the angle defined between the counter-azimuth direction
indicated by a straight line R in FIG. 4 and the bisector of the
track shift angle indicated by a straight line Q in FIG. 4.
[0055] With the larger angle between the counter-azimuth direction
R and the bisector Q of the track shift angle, the playback
fringing of the magnetic head 1 can be suppressed to a lower value.
Thus, the present magnetic head 1 is free from an inconvenience
that neighboring tracks are reproduced during playback thus
assuring superior reproducing characteristics.
[0056] The magnetic head of the present invention is not limited to
the above-described embodiment. Thus, the magnetic head 1 may be
progressively reduced in thickness towards the junction surface to
the magnetic metal film 6. That is, with the present magnetic head,
a cut-out 6D is formed on an end of the magnetic metal film 6
opposite to its end in contact with the non-magnetic substrate 4.
In this case, the magnetic head 1 again has a structure in which
the magnetic metal film 6 making up one 2 of the magnetic head
halves faces the non-magnetic substrate 4 of the opposite side
magnetic head half exposed to the junction surface 8. Moreover,
with the present magnetic head 1, since the magnetic metal film 6
is progressively reduced in thickness towards the junction surface
8, the magnetic flux density is concentrated towards the magnetic
gap.
[0057] With the magnetic head 1 shown in FIG. 5, similarly to the
magnetic head of the previous embodiment, the recording fringing
and playback fringing can be suppressed to smaller values. Also, in
the present magnetic head 1, since the magnetic flux density is
concentrated towards the magnetic gap, not only can the magnetic
field of low intensity be detected, but the high-density magnetic
field can be produced. Thus, the magnetic head 1 has high
sensitivity suitable for high density recording.
[0058] Also, in the magnetic head 1 of the present invention, an
underlying layer 11 may be provided between the magnetic metal film
6 and the non-magnetic substrate 4, as shown in FIG. 6. This
underlying layer 11 operates as an index layer for high-accuracy
positioning of the magnetic metal film 6 formed on each of the
magnetic head halves 2, 3 when bonding these magnetic head halves
together.
[0059] This underlying layer 11 may be enumerated by oxide films,
such as Al.sub.2O.sub.3, SiO, SiO.sub.2, ZrO.sub.2 or
Cr.sub.2O.sub.3, a glass film, metal films, such as Au or Cu films,
either singly or as layered structures.
[0060] FIG. 7 shows the relation between the film thickness of the
underlying layer 11 and recording fringing. As may be seen from
FIG. 7, the film thickness of the underlying layer 11 is preferably
0.3 .mu.m to 4.0 .mu.m and more preferably 0.5 to 1.5 .mu.m. If the
underlying layer 11, acting as an index layer, has a film thickness
less than 0.3 .mu.m, difficulties are encountered as to
distinguishment form the non-magnetic substrate 4. If the
underlying layer 11 has a film thickness larger than 4.0 .mu.m,
recording fringing is undesirably increased.
[0061] Similarly to the above-described magnetic head, the magnetic
head shown in FIG. 6 is superior in playback fringing and in
recording fringing, and hence in recording/reproducing
characteristics.
[0062] Also, the underlying layer 11 is preferably formed of a
material colored differently from the non-magnetic substrate 4 or
the magnetic metal films 6. This assures more reliable
distinguishment of the underlying layer 11 from the non-magnetic
substrate 4 or the magnetic metal films 6.
[0063] It is also possible for the magnetic head of the present
invention to have the magnetic metal films 6 the uppermost layer of
which is reduced in thickness as compared to the remaining layers,
as shown in FIG. 8. The present magnetic head, shown in FIG. 8, has
four magnetic metal films 6 that are formed of the above-mentioned
materials. That is, the present magnetic head has, on the
non-magnetic substrate 4, a first magnetic metal layer 12, a second
magnetic metal layer 13, a third magnetic metal layer 14 and a
fourth magnetic metal layer 15, layered in this order with a
non-magnetic layer 6B between the neighboring layers 12 to 15.
[0064] With the present magnetic head, the fourth magnetic metal
layer 15 is thinner in thickness than the first magnetic metal
layer 12, second magnetic metal layer 13 or the third magnetic
metal layer 14. Specifically, the first to third magnetic metal
layers 12 to 14 are 4.0 .mu.m in thickness, whereas the fourth
magnetic metal layer 15 is 1.0 m in thickness, with the
non-magnetic layer 6B being 1.0 .mu.m in thickness.
[0065] With the present magnetic head, the uppermost one of the
plural magnetic metal layers is reduced in thickness, so that, when
bonding the magnetic head halves 2 and 3 together, the magnetic
metal films 6 formed thereon can be abutted against each other with
improved accuracy.
[0066] FIG. 9 shows the relation between the film thickness of the
uppermost magnetic metal layer and recording fringing of the
above-described magnetic head. As may be seen from FIG. 9, the film
thickness of the uppermost magnetic metal layer is preferably 0.3
.mu.m to 4.0 .mu.m and more preferably 0.5 m to 2.0 .mu.m. If, with
the present magnetic head, the film thickness of the uppermost
magnetic metal layer is less than 0.3 .mu.m, magnetic properties of
the magnetic metal films are lowered.
[0067] Similarly to the above-described magnetic head, the magnetic
head shown in FIG. 8 is superior in playback fringing and recording
fringing and hence in recording/reproducing characteristics.
[0068] The method for manufacturing the magnetic head 1 according
to the above-described embodiment is now explained by referring to
the drawings.
[0069] For manufacturing the magnetic head 1, plural magnetic head
halves 2, 3 are formed on one substrate. A pair of the substrates
are bonded together and the resulting unit is sliced into plural
magnetic heads 1.
[0070] For manufacturing the magnetic head 1, a substantially
flat-plate-shaped substrate 21 is provided, as shown in FIG. 10.
This substrate 21 proves to be a non-magnetic substrate 4 of the
magnetic head 1 and is formed of, for example, a non-magnetic
material, such as MnO--NiO. This substrate 21 is approximately 2 mm
in thickness and approximately 30 mm in length and width.
[0071] Next, first grooving is applied to one of the major surfaces
21A of the substrate 21, as shown in FIG. 11. During this first
grooving, plural magnetic core forming grooves 24, inclined by, for
example, 45.degree., are formed in the major surface 21A by, for
example, a grindstone, for extending parallel to one another.
Plural inclined surfaces 24A are formed by these magnetic core
forming grooves 24 prepared by the first grooving.
[0072] Although the inclined surfaces 24A are preferably inclined
by 25 to 60.degree., the inclination angle of 35 to 50.degree. is
more preferred in view of the pseudo-gap and track width precision.
The magnetic core forming groove 24, prepared by the first
grooving, is 130 .mu.m n depth and 150 m in width.
[0073] Then, a magnetic metal film 25, formed of the
above-mentioned materials, is then formed on the surface of the
substrate 21 formed with the inclined surfaces 24A. During this
film-forming process, the magnetic metal film 25 is formed to the
uniform film thickness on the major surface formed with the
inclined surfaces 24A. The magnetic metal film 25 is formed so that
three layers of the magnetic metal material will be layered with
non-magnetic layers in-between. This film-forming process is
carried out by, for example, a PVD method, such as magnetron
sputtering, or a CVD method.
[0074] The magnetic metal film 25 may also be formed by a single
magnetic metal layer, instead f by plural magnetic metal layers If,
in the present embodiment, the magnetic metal film 25 is formed by
plural layers, it is made up of three Fe--Al--Si alloy layers,
formed by alternately layered Fe--Al--Si (sendust) each being 4
.mu.m in thickness and alumina layers each being 0.15 .mu.m in
thickness. If the magnetic metal film 25 is made up of plural
layers, the non-magnetic layer is formed of alumina, SiO.sub.2 or
SiO, either singly or in combination. The non-magnetic layer needs
to be of a film thickness assuring insulation between magnetic
metal layers disposed on its both sides.
[0075] If this technique is used for manufacturing the magnetic
head as shown in FIG. 6, an underlying layer is formed between the
magnetic metal film 25 and the substrate 21.
[0076] Also, if this technique is used for manufacturing the
magnetic head as shown in FIG. 8, the film thickness of the
uppermost magnetic metal layer of the magnetic metal film 25 is
selected to be thinner than that of other magnetic metal
layers.
[0077] Then, as shown in FIG. 13, second grooving is applied to the
surface of the substrate formed with the magnetic metal film 25 in
a direction substantially perpendicular to the magnetic core
forming groove 24. During this second grooving, a number of
separating grooves 26 are formed for separating the substrate into
plural magnetic cores of desired size. Also, a winding slot 27 is
formed in each magnetic core for forming a coil-forming recess.
[0078] This separating groove 26 is used for magnetically
separating the magnetic core on the substrate 21 in the
fore-and-aft direction for delimiting the magnetic core for forming
a closed magnetic path in each magnetic core. Although two
separating grooves 26 are formed in the embodiment of FIG. 13, it
is necessary to from a number of the separating grooves 26 equal to
the number of columns of the magnetic head halves 2, 3. Also, the
separating groove 26 needs to be formed to a depth sufficient to
permit severing the magnetic metal film 25 for magnetically
separating the magnetic cores arranged in the fore-and-aft
direction. Specifically, the separating groove 26 needs to be
deeper by 150 .mu.m from the bottom side of the magnetic core
forming groove, that is 280 .mu.m in depth.
[0079] On the other hand, the winding slot 27 needs to be of a
depth such as not to sever the magnetic metal film 25, in order to
form the magnetic core having the front gap 9 and the back gap 10
and for forming the coil-forming recess. The winding slot 27,
having its shape determined responsive to the lengths of the front
gap 9 and the back gap 10, is of the width of the order of
approximately 140 .mu.m, with the front gap 9 and the back gap 10
being approximately 300 .mu.m and approximately 85 .mu.m,
respectively. The winding slot 27 of a depth not severing the
magnetic metal film 25 suffices. If the winding slot 27 is of an
excessive depth, the magnetic flux transmission efficiency tends to
be lowered due to the increased magnetic path length. The depth of
the winding slot 27, which depends on the thickness of the coil 7
formed by the process which will be explained subsequently, is
herein set to approximately 20 .mu.m. Although the winding slot 27
is not limited to any specific shape, the surface 27 thereof
towards the front gap 9 is herein designed as an inclined surface
of approximately 45.degree.. This gives a structure of the magnetic
metal film 6 in which the magnetic flux is concentrated towards the
front gap 9 thus assuring improved sensitivity.
[0080] Then, as shown in FIG. 14, a low melting glass 29 is charged
onto a major surface of the substrate 21 formed with the magnetic
core forming groove 24, separating groove 26 and the winding slot
27, as explained previously. Then, surface planarizing is applied
to the major surface of the substrate 21 charged with the
low-melting glass 29.
[0081] In the manufacturing method for the magnetic head according
to the present invention, grinding is applied to the major surface
charged with the low-melting glass, using a grindstone, thereby
planarizing the major surface. This planarizing is carried out
substantially until the substrate is exposed to the front gap
9.
[0082] If the substrate 21, exposed by this grinding process, is of
a larger width, the etching rate for the substrate 21 differs from
that for the low-melting glass, such that a step difference tends
to be produced on the boundary between the substrate 21 and the
low-melting glass. Therefore, the width of the substrate 21 exposed
by this grinding process is preferably smaller than the width of
the innermost rim of the coil 7 formed by the process which will be
explained subsequently.
[0083] Then, as shown in FIG. 15, a terminal groove 30 is formed by
grinding using a grindstone. This terminal groove 30 is formed so
as to directly overlie the above-mentioned separating groove 26 and
is approximately 100 .mu.m in both width and depth. Within this
terminal groove 30 is charged a good electrically conductive
material, such as Cu, by e.g., a plating method. Next, the
planarizing is applied.
[0084] Then, as shown in FIG. 16, a coil 7, centered about the back
gap 10, is formed, in a manner not shown in FIG. 16. For forming
this coil 7, a coil-forming recess 31 having a depth of, for
example, 5 .mu.m, is formed in the planarized low-melting glass 29
by e.g., etching.
[0085] Within this coil-forming recess 31 is then formed the
photoresist patterned to a desired coil shape. The coil 7 is then
formed, using e.g., electrolytic plating using an electrically
conductive material such as Cu. The desired col 7 is formed by
removing the resist. At this time, the coil 7 is formed so as to be
electrically connected to the good conductor charged in the
terminal groove 30 formed in the above-mentioned step. The coil 7
can be formed by sputtering or vapour deposition, without being
limited to the method described above.
[0086] Then, a protective layer, not shown, for protecting the coil
7 from contact with atmosphere is formed. This protective layer is
formed for burying the coil-forming recess 31 formed for producing
the coil 7. Then, planarizing is applied to the surface formed with
the protective layer. This generates a coil contacting portion
electrically connecting the front gap 9, back gap 10 and the coil 7
so that the coil contacting portion will be exposed to outside.
[0087] The substrate 21 is then sliced so that the plural magnetic
head halves 6, formed simultaneously, will be arrayed transversely
in a line, for forming magnetic head half blocks 32.
[0088] A pair of the magnetic head half blocks 32 are bonded
together, as shown in FIG. 17. At this time, the paired magnetic
head half blocks 32 are positioned so that the major surfaces
thereof formed with the protective layers 31 will face each other
and so that the back gap 9 and a coil connection terminal 7A will
face a pre-set portion. With this metal diffusion bonding method,
the portions of the paired magnetic head half blocks 32 that need
to be electrically connected to each other can be connected
reliably.
[0089] In the present embodiment of the manufacturing method for
manufacturing the magnetic head, the paired magnetic head half
blocks 32 are connected together so that the portion of the
substrate 21 exposed to the front gap 9 of one of the magnetic head
half blocks 32 will face the portion of the magnetic metal film 25
exposed to the front gap 9 of the other magnetic head half block
32. That is, with this technique, the paired magnetic head half
blocks 32 are bonded together with one of the magnetic head half
blocks 32 shifted in the direction of the inclined surfaces
24A.
[0090] If, in the present technique, the magnetic head half blocks
formed with underlying layers are used, the underlying layer formed
on one of the magnetic head half blocks and the uppermost magnetic
metal layer formed on the opposite side magnetic head half block
are brought into registration correctly with each other when
bonding the paired magnetic head half blocks. This gives paired
magnetic head half blocks shaped as shown in FIG. 6.
[0091] Conversely, if there is formed no underlying layer, it may
be an occurrence that the relative shift opposite to that shown in
FIG. 4 is produced. That is, if the paired magnetic head half
blocks 32 are bonded together with the respective magnetic metal
layers as reference, the boundary between the magnetic metal layers
and the substrate is difficult to recognize such that difficulties
are met in improving the bonding accuracy.
[0092] Thus, the paired magnetic head half blocks can be bonded
together more easily and to higher accuracy by employing magnetic
head half blocks formed with the underlying layer.
[0093] If, in the present technique, the film thickness of the
uppermost magnetic metal layer is smaller than that of the other
magnetic metal layer, specifically, if the magnetic head shown in
FIG. 8 is produced, it suffices if the magnetic head half blocks
are abutted to each other with the first magnetic metal layer 12 of
one of the magnetic head halves 2 and the third magnetic metal
layer 14 of the opposite magnetic head half 3 as reference and with
the third magnetic metal layer 14 of one of the magnetic head
halves 2 and the first magnetic metal layer 12 of the opposite side
magnetic head half 3 as reference.
[0094] Since the third magnetic metal layer 14 of one of the
magnetic head halves 2 and the first magnetic metal layer 12 of the
opposite side magnetic head half 3 are abutted to each other, the
magnetic gap is of the desired size, even if the third magnetic
metal layer 14 and the first magnetic metal layer 12 become offset
in any direction, because of the presence of the fourth magnetic
metal layer 15. The paired magnetic head half blocks 32 can be
connected to each other to higher accuracy by setting the reference
used when connecting the paired magnetic head half blocks 32 to
each other.
[0095] Then, as shown in FIG. 18, a magnetic head block 33,
produced on connecting the paired magnetic head half blocks 32 to
each other, as described above, is separated into individual
magnetic heads. At this time, the magnetic head block 33 is sliced
along lines B-B in FIG. 18. This gives a magnetic head 1 having a
magnetic gap between the front gaps 9. The medium sliding surface
of the magnetic head 1 is then ground, in a manner not shown, so as
to produce a cylindrical surface. The medium sliding surface is
also formed with an abutment controlling groove for assuring
optimum abutment characteristics against the magnetic recording
medium. This abutment controlling groove is formed so as to be
substantially parallel to the sliding direction of the magnetic
recording medium for controlling the friction against the magnetic
recording medium.
[0096] In the above-described manufacturing method for the magnetic
head, grinding is applied, at the time of the planarizing
processing following the charging of the low-melting glass 29, so
that the substrate 21 will be exposed to the front gap 9. When
bonding the magnetic head half blocks 32 together, part of the
substrate 21 exposed to the front gap 9 faces part of the magnetic
metal film 25 exposed to the opposite side front gap 9.
[0097] Thus, with the present technique, the magnetic head 1 can be
produced which has a large track offset angle .theta. and a large
angle between the counter-azimuth direction R and the bisector Q of
the track offset angle. Thus, with the present technique, the
magnetic head 1 can be produced which is optimum in recording
fringing and playback fringing and superior in
recording/reproducing characteristics.
[0098] The manufacturing method for the magnetic head according to
the present invention is not limited to the above-described method
for manufacturing the magnetic head 1 and may also be a method for
manufacturing the magnetic head shown in FIG. 5.
[0099] In this case, the magnetic core forming groove 24,
separating groove 26 and the winding slot 27 are similarly
produced, as shown in FIG. 13. The low-melting glass 29 is then
charged into these grooves. Then, grinding is applied to the outer
portion of the magnetic metal film 25, using a grindstone having
one face cut by approximately 35.degree., for forming a cut-out 40.
The portion of the substrate thus ground is then charged with the
low-melting glass 29.
[0100] In this state, planarization is applied as in the
above-described embodiment. This planarizes the connecting surface
while exposing a portion of the substrate on the connecting
surface. The magnetic head is then produced in the same way as in
the above-described manufacturing process.
[0101] With the above-described manufacturing method for the
magnetic head, a magnetic head can be produced in which recording
fringing and playback fringing can be suppressed to lower values.
In addition, by this technique, such a magnetic head can be
produced in which the magnetic metal film 25 is progressively
reduced in thickness towards the magnetic gap. Thus, with the
magnetic head, manufactured by this technique, since the magnetic
flux density can be concentrated towards the magnetic gap, the
magnetic head can be improved in recording/reproducing
sensitivity.
[0102] Tests were conducted on the magnetic head according to the
present invention and magnetic heads of comparative examples for
evaluating characteristics of the magnetic heads.
[0103] As a magnetic head embodying the invention, a sample A
having a track offset angle .theta. equal to 135.degree. and the
azimuth angle .alpha. equal to 20.degree. was produced, as shown in
FIG. 20. In this sample A, the angle defined between the
counter-azimuth direction R and the bisector Q of the track offset
angle was 27.5.degree..
[0104] For comparison with the magnetic heads of the comparative
examples, samples B to D were produced. The sample B was produced
by shifting paired magnetic head halves 2, 3 in an opposite
direction to the sample A. The samples C and D were fabricated so
that the substrate 4 is not exposed on the junction surface and so
that only the magnetic metal films 6 face each other.
[0105] In the sample B, the track offset angle .theta. is
45.degree., while the angle between the counter-azimuth direction R
and the bisector Q of the track offset angle is 62.5.degree., as
shown in FIG. 21. In the sample C, the track offset angle .theta.
is 90.degree., while the angle between the counter-azimuth
direction R and the bisector Q of the track offset angle is
5.degree., as shown in FIG. 22, whereas, in the sample D, the track
offset angle .theta. is 45.degree., while the angle between the
counter-azimuth direction R and the bisector Q of the track offset
angle is 62.5.degree., as shown in FIG. 23.
[0106] The recording fringing and the playback fringing were
measured of these samples A to D. The results are shown in Table
1.
1 TABLE 1 recording fringing playback fringing sample A 0.5 .mu.m
0.7 dB sample B 2.0 .mu.m 0.5 dB sample C 1.0 .mu.m 2.5 dB sample D
2.0 .mu.m 0.5 dB
[0107] The recording fringing was evaluated by measuring the
erasure width of neighbouring tracks using a digital camcorder for
household use. The playback fringing was evaluated, by measuring,
using a digital camcorder for domestic use, the difference in the
noise level between the case of reproducing a medium having signals
recorded in the neighboring tracks and the case of reproducing a
medium having no signals recorded in the neighboring tracks.
[0108] As may be seen from Table 1, the sample A according to the
present invention is low in both the recording fringing and
playback fringing and hence has superior recording/reproducing
characteristics.
[0109] The sample B is low in playback fringing because of a large
angle between the counter-azimuth direction R and the bisector Q of
the track offset angle. However, the recording fringing of the
sample B is of a high value because of the small track offset angle
.theta.. Thus, the sample B, having good playback characteristics,
is not superior in recording characteristics.
[0110] The sample C, having the large track offset angle .theta.
and hence the low recording fringing, has a higher playback
fringing value, because of a small angle defined between the
counter-azimuth direction R and the bisector Q of the track offset
angle. Thus, the sample C, having good recording characteristics,
is not optimum in playback characteristics.
[0111] The sample D has the angle defined between the
counter-azimuth direction R and the bisector Q of the track offset
angle .theta. and the track offset angle .theta. equal to those of
the sample B. Thus, the sample D has the recording fringing and
playback fringing equal in values to those of the sample B and
hence has good reproducing characteristics, without being optimum
in recording characteristics.
[0112] In connection with the magnetic head of an alternative
embodiment shown in FIG. 5, a sample E having a track offset angle
.theta. of 135.degree. and the azimuth angle .alpha. of 20.degree.
was produced. For comparison with the sample E, a sample F, having
an offset in the opposite direction to that of the sample E, as
shown in FIG. 25, was prepared as a comparative example. The
recording fringing and the playback fringing were measured of the
samples E and F in the same way as described above. The results are
shown in Table 2.
2 TABLE 2 recording fringing playback fringing sample E 0.5 .mu.m
0.7 dB sample F 2.5 .mu.m 0.5 dB
[0113] It is seen from Table 2 that, according to the present
invention, the recording fringing and the playback fringing can be
reduced even with a magnetic head configured for concentrating the
magnetic flux density towards the magnetic gap. Further, the
playback outputs of the samples E and F were measured, using a
digital camcorder, for measuring the sensitivities thereof.
[0114] It has become clear that the playback output of the sample E
is higher approximately 1 dB than in the sample A. Thus it is seen
that the sensitivity is improved if the magnetic metal film 6 is
progressively reduced in film thickness towards the junction
surface. Thus, the magnetic head is suitable for high-density
recording.
* * * * *