Magnetic head

Details Magnetic head Magnetic head

2000-06-09

2003-02-25

Dinh, Tan (Department: 2651)

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

Magnetic field and light beam

C369S013230

Reexamination Certificate

active

06526001

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a magnetic head for applying magnetic fields that vary with recorded information with respect to a heated portion in a recording region in a recording medium.
BACKGROUND OF THE INVENTION
The following description will explain an example of a magnetic head used in a MiniDisk (hereinafter referred to as MD) device, while referring to
FIGS. 6 through 9
.
FIG. 6
illustrates an arrangement of a magnetic head, while
FIG. 7
is an enlarged view of a magnetic core part and a coil part of the magnetic head.
FIG. 8
illustrates an arrangement of a magneto-optical recording medium, and
FIG. 9
illustrates an arrangement of a magneto-optical recording-reproducing device.
First, the following description will explain an arrangement of a magnetic head while referring to FIG.
6
.
FIG. 6
is a cross-sectional view of a magnetic head used with a magneto-optical disk. The magnetic head includes a magnetic field generating section composed of a central magnetic pole
11
that is made of a magnetic material such as Mn—Zn ferrite or the like, a coil
22
, and a bobbin
21
made of an insulating material, around which the coil
22
is wound in helical fashion.
This magnetic field generating section is fixed to a magnetic core holder
23
that is a contact-sliding member. Thus, a magnetic head is arranged. The magnetic core holder
23
has a sliding part
24
that is brought into contact with a magneto-optical recording medium (not shown in FIG.
6
). The sliding part
24
is formed by molding with a material with a low friction coefficient which is for example a polymer material such as polyarylate, nylon, or polyester, or alternatively, ceramic. The sliding part
24
may be formed with another material, and a tape-like material with a low friction coefficient may be applied to a surface that is brought into contact with a magneto-optical recording medium.
Next, the foregoing magnetic field generating section will be described with reference to FIG.
7
.
The magnetic core has an “E”-like shape, composed of a central magnetic pole
11
and yokes
13
on the sides. The yokes
13
are positioned relatively close to the central magnetic pole
11
, so as to increase the intensity of the magnetic fields.
The coil section is formed by winding the coil
22
around the bobbin
21
, and by attaching it to the central magnetic pole
11
of the E-shape magnetic core. The coil
22
is a wire plated with enamel or a magnetic material (diameter: 80 &mgr;m) and made of a conductive material. The bobbin
21
is aimed to make the height of the coil
22
uniform, and to prevent the coil
22
from being brought into direct contact with the central magnetic pole
11
.
FIG. 8
illustrates an arrangement of a magneto-optical recording medium
40
. The magneto-optical recording medium
40
is formed by providing a magneto-optical recording film
43
on a transparent substrate
41
made of polycarbonate (PC) or the like, though a dielectric film
42
made of SiN, AlN, or the like is provided between the magneto-optical recording film
43
and the transparent substrate
41
. The dielectric film
42
and a reflection film
44
made of Al or the like are provided on the magneto-optical recording film
43
, and on top of that, a resin protective layer
45
made of an UV curing resin is provided.
In the case of an MD, since a contact-sliding-type magnetic head is used, a lubrication film
46
made of silicon oil or the like that has a high lubricity is formed on the resin protective film
45
. Incidentally, a film that constitutes a single layer implementing the functions of both the resin protective film
45
and the lubrication film
46
has been developed.
A magnetic field modulating method is explained below, with reference to FIG.
9
. As shown in
FIG. 9
, an optical pick-up
50
for projecting laser light is provided on one side to the foregoing magneto-optical recording medium
40
, while a magnetic head section
20
that is provided inside the aforementioned magnetic core holder
23
which moves according to a position of a laser spot is provided on the other side to the magneto-optical recording medium
40
. The direction of the magnetic fields generated by the magnetic head section
20
is inverted in accordance with recording signals (recording information), whereby signals (information) are recorded on the magneto-optical recording medium
40
.
Furthermore, to arrange the magnetic head section
20
and the magnetic core holder
23
so as to be capable of moving appropriately in spite of, if any, fluctuations of the magneto-optical recording medium
40
and dusts and projections on the same, the magnetic head section
20
and the magnetic core holder
23
are supported by a thin elastic member
31
made of metal, normally 30 &mgr;m to 100 &mgr;m in thickness, to which a pressure of 3 mN (milli-newton) to 10 mN is previously applied. An end of the elastic member
31
is fixed by an elastic member fixing member
32
. The elastic member fixing member
32
is supported by a connecting arm
33
in a substantial “L” shape, so as to be connected to the aforementioned pick-up
50
.
Magnetic fields generated by the magnetic head section
20
vary depending on the distance from a magnetic pole face (end surface) of the central magnetic pole
11
to the magneto-optical recording medium
40
. In other words, as the distance increases, greater electric current need flow through the coil
22
in order to generate magnetic fields with a predetermined intensity to be applied to the magneto-optical recording medium
40
. In the case where the distance is set constant, the intensity of the magnetic fields is proportional to the electric current. Therefore, in the case of a recording medium that for recording requires magnetic fields of a great intensity, greater electric current need be made to flow through the coil
22
. This leads to a rise of the temperature in the magnetic head, that develops into serious problems such as a decrease of the intensity of the magnetic fields due to heat, and damage to the coil
22
. For this reason, as the recording medium used in the magnetic field modulation recording, a recording medium requiring small recording magnetic fields has been selected, as compared with that in the case of a light intensity modulation recording medium.
Besides, also in the case where the distance between the magneto-optical recording medium
40
and the magnetic pole face of the central magnetic pole
11
greatly fluctuates, the electric current need be increased for the fluctuation, thereby leading to the same result as above. To keep constant the distance between the magneto-optical recording medium
40
and the magnetic pole face of the central magnetic pole
11
, the magnetic core holder
23
for holding the magnetic field generating section composed of the central magnetic pole
11
and the coil
22
need be made of a material that allows smooth sliding, and the magnetic core holder
23
is arranged so that a level difference between the sliding part
24
and the magnetic pole face of the central magnetic pole
11
should be normally in a range of 20 &mgr;m to 100 &mgr;m.
By bringing the sliding part
24
into contact with the lubrication film
46
while preventing the central magnetic pole
11
from being brought into direct contact with the lubrication film
46
of the magneto-optical recording medium
40
, it is made possible to keep constant the distance between the magnetic pole face of the central magnetic pole
11
and the magneto-optical recording medium
40
, without a complex structure. Such a magnetic head, called as a sliding-type magnetic head, is generally used in an MD device.
Recently improvement of the recording speed and the recording density have been demanded, and to achieve it, it is required to drive the magnetic head at a higher frequency. However, when driving at a frequency exceeding several MHz, a magnetic loss of a magnetic material increases, and heat generation increases.
In a conventional magnetic head, the central magnet

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