Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-03-08
2002-03-26
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603210, C219S069150, C219S069170
Reexamination Certificate
active
06360429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head which performs recording or reproduction of information signals on a magnetic recording medium, a method for producing the same, and a magnetic recording/reproduction apparatus using the same. It relates particularly to a narrow-track magnetic head for high density magnetic recording used in a digital VCR or the like, a method for producing the same, and a magnetic recording/reproduction apparatus using the same.
2. Description of the Related Art
In order to record/reproduce a large amount of information signals such as found in digital VCR, it is necessary to employ high density magnetic recording/reproduction techniques such as the narrow-track technique and the short-wavelength technique. Generally, it is known that for the realization of high density magnetic recording/reproduction, it is better to increase the coercive force of a recording medium or to increase the saturation magnetic flux density (hereinafter, referred to as a “Bs”) of a magnetic head.
However, a ferrite material, which has mainly been used in the prior art as a material for a magnetic head, has a Bs of about 0.5 T, which is not sufficiently large. Therefore, when a prior art magnetic head made of the ferrite material is used on a metal tape having a high coercive force of 80 kA/m or more, there occurs magnetic saturation so that a recording and reproduction of information might not be conducted with certainty.
To resolve the situation, magnetic heads have currently been suggested which are made of a new material having a Bs larger than that of the ferrite material, such as a Sendust alloy film (Bs: about 1.0 T) or a Co type amorphous film (Bs: about 0.8 T to about 1.1 T), or other materials having a Bs of about 1.3 T or more, such as a Co type superstructure nitriding alloy film, an Fe type superstructure nitride film or an Fe type nitride film. Among these, research has been vigorously conducted particularly on a composite magnetic head, or so-called MIG head, in which the main core is made of ferrite and a magnetic thin film is disposed on the surface of the main core at least in the vicinity of the front gap.
FIG. 13
is a perspective view illustrating an example of a configuration of a prior art MIG head.
In the prior art MIG head
500
shown in
FIG. 13
, a pair of convex or bevelled magnetic cores
502
and
503
are disposed opposite to each other with a magnetic gap
501
being therebetween. The magnetic core
502
includes a convex or bevelled core body
504
(hereinafter, simply referred to as the “core body
504
”) made of ferrite and a magnetic film
506
which is formed on the surface of the core body
504
and has a high saturation magnetic flux density. Similarly, the magnetic core
503
includes a convex or bevelled core body
505
(hereinafter, simply referred to as the “core body
505
”) made of ferrite and a magnetic film
507
which is formed on the surface of the core body
505
and has a high saturation magnetic flux density. The magnetic films
506
and
507
are formed so as to cover the projection end faces of the core bodies
504
and
505
, respectively, facing the magnetic gap .
01
, and also completely cover both of the side faces therefrom. The magnetic gap
501
is provided with a nonmagnetic film (referred to as “gap member”) not shown in FIG.
13
. The magnetic cores
502
and
503
are butted to each other with the magnetic gap
501
including the gap member inserted therebetween. Furthermore, the magnetic cores
502
and
503
butted as such are coupled to each other with a pair of glass blocks
508
and
509
which are disposed at both sides of their butting ends. A winding window
510
for coils to pass is provided at the middle of the side faces of the MIG head
500
.
In view of the narrow-track technique, the MIG head
500
described above may not be formed with sufficient accuracy with respect to a track width due to a production error such as butting accuracy of the two magnetic cores
502
and
503
, or due to the influence of a roundness at the track edge of the magnetic films
506
and
507
. Moreover, since the track width cannot be determined unambiguously, sufficient accuracy may not be obtained during the adjustment steps for the track height during assembly. Consequently, a decrease in the yield may result in the production of the MIG head
500
.
In order to solve these problems, the applicant of the present application has suggested an MIG head as disclosed in Japanese Laid-Open Patent Publication No. 7-220218, which corresponds to pending U.S. patent application Ser. No. 08/313,594 filed on Sep. 29, 1994. In
FIG. 14
, a configuration of the top face of the MIG head
600
, i.e., the sliding surface for a magnetic tape, is schematically illustrated.
A fundamental configuration of the MIG head
600
is similar to that of the MIG head
500
described before. A pair of convex or bevelled magnetic cores
602
and
603
are disposed opposite to each other with a magnetic gap
601
being therebetween. The magnetic core
602
includes a convex or bevelled core body
604
(hereinafter, simply referred to as the “core body
604
”) made of ferrite and a magnetic film
606
which is formed on the surface of the core body
604
and has a high saturation magnetic flux density. Similarly, the magnetic core
603
includes a convex or bevelled core body
605
(hereinafter, simply referred to as the “core body
603
”) made of ferrite and a magnetic film
607
which is formed on the surface of the core body
605
and has a high saturation magnetic flux density. The magnetic films
606
and
607
are formed so as to cover the projection end faces of the core bodies
604
and
605
, respectively, facing the magnetic gap
601
, and also completely cover both of the side faces therefrom. The magnetic gap
601
is provided with a nonmagnetic film as a gap member. The magnetic cores
602
and
603
are butted to each other with the magnetic gap
601
including the gap member inserted therebetween. Furthermore, the magnetic cores
602
and
603
butted as such are coupled to each other with a pair of glass blocks
608
and
609
which are disposed at both sides of their butting ends.
The magnetic tape sliding face of the MIG head
600
is provided with notches
613
a
and
614
a
over both of the magnetic cores
602
and
603
in addition to a convexly processed part
639
which regulates the track width. By having these notches
613
a
and
614
a
, a track misalignment associated with the butting accuracy of the magnetic cores
602
and
603
within the magnetic head
600
is eliminated, and degradation of accuracy due to a roundness of the track edge, or so-called fringe, is also reduced considerably.
However, since a number of processes are also conducted after processing steps for the notches
613
a
and
614
a
in the production of the MIG head
600
, there may result a track misalignment between the magnetic cores
602
and
603
on a microscopic level, and it may be the case that an initial track width cannot be maintained with sufficient accuracy.
Furthermore, the side faces of the convexly processed or bevelled part
639
of the magnetic cores
602
and
603
are provided with an antireaction film
640
made of a material such as SiO
2
, ZrO
2
, Ta
2
O
5
, glass, Cr, or a composite thereof, at the interfaces between the glass blocks
608
and
609
and the magnetic films
606
and
607
. Thus, a chemical reaction between the magnetic cores
602
and
603
(more precisely the magnetic films
606
and
607
) and the glass blocks
608
and
609
, respectively, is inhibited. However, the interfaces between the magnetic films
606
and
607
and the glass blocks
608
and
609
at the notches
613
a
and
614
a
are not provided with such antireaction films
640
. Consequently, the chemical reaction may occur therebetween and, as a result, problems such as a blur at the track edge may occur.
Due to problems described above, even with the MIG head
600
illustrated in
FIG.
Renner Otto Boisselle & Sklar
Tugbang A. Dexter
Young Lee
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