High speed magnetic coil for magneto-optical head

Details High speed magnetic coil for magneto-optical head High speed magnetic coil for magneto-optical head

2000-11-01

2003-06-24

Dinh, Tan (Department: 2653)

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

Magnetic field and light beam

C369S013170

Reexamination Certificate

active

06584045

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a magnetic head coil suitable for recording an information signal at a high speed, a magnetic head using it, and a magneto-optical recording apparatus.
BACKGROUND ART
A conventionally known magneto-optical recording apparatus applies a magnetic field modulated by an information signal to a magneto-optical recording medium such as a magneto-optical disk, and irradiates the medium with light to record an information signal. This magneto-optical recording apparatus comprises a magnetic head for applying a magnetic field. The magnetic head may be one of various types of heads. For example,
FIG. 17
is a perspective view showing a magnetic head disclosed in Japanese Laid-Open Patent Application No. 4-74335, and
FIG. 18
is a sectional view showing the magnetic head.
Reference numeral
50
denotes a flat coil component (to be referred to as a coil hereinafter) formed from a flexible printed wiring board; and
51
, a core made of a magnetic material such as ferrite. The coil
50
is constituted by a flexible base
52
made of polyimide or polyester, a spiral coil pattern
53
serving as a conductor pattern made of a copper foil formed on the base
52
, and terminals
54
a
and
54
b
. The coil
50
is bonded to the core
51
with an adhesive
55
.
The terminals
54
a
and
54
b
of the coil
50
are connected to the magnetic head drive circuit of a magneto-optical recording apparatus. The magneto-optical recording apparatus comprises an optical head. To record an information signal, the optical head irradiates the magnetic recording layer of a magneto-optical recording medium with a laser beam so as to converge the laser beam to a small light spot. At the same time, the magnetic head drive circuit supplies a current to the coil pattern
53
to generate a magnetic field modulated by an information signal from the center of the coil pattern
53
, and vertically applies the magnetic field to the laser beam irradiation position of the magnetic recording layer.
Conventionally, like this prior art, only a conductor pattern serving as a path for positively supplying a current, i.e., a conductor pattern necessary for an electrical function is formed on components using conductor patterns including a flat coil component for a magnetic head.
In recent years, as demands have arisen for a higher information signal recording speed, the flat coil component used in the magnetic head must be downsized. Along with this, the dimensional precision and flatness of the flat coil component must be increased to adjust the relative position to the optical head and the distance from the magneto-optical recording medium at higher precision. The magnetic field must be accurately, efficiently applied to the light spot position on the magnetic recording layer of the magneto-optical recording medium. However, the above-described flat coil is low in rigidity and mechanical strength, readily deforms in manufacturing a magnetic head, and is difficult to be adjusted to an accurate position. Thus, the above demands cannot be met. This problem will be explained in detail.
To more efficiently generate a magnetic field in the above magnetic head, the coil pattern
53
must be formed very close to the core
51
. For this purpose, the base
52
must be as thin as possible. To efficiently apply a magnetic field to the magneto-optical recording medium, the surface of the coil
50
must be brought very close to the magneto-optical recording medium.
Although not described in the above reference, the base
52
constituting the coil
50
is made of a 20-&mgr;m thick polyimide sheet. Since the thin resin material sheet is very flexible, the coil
50
is insufficient in rigidity, posing the following problem in manufacturing a magnetic head.
More specifically, in bonding the coil
50
and the core
51
, the coil
50
cannot resist an operating force and readily deforms, e.g., bends at a portion where no coil pattern
53
is formed. As a result, the attaching position of the coil
50
is not accurately determined, causing an error. The relative position to the optical head deviates, so an information signal cannot be normally recorded.
A conductor pattern for connecting the coil pattern to the terminal
54
b
is formed to protrude from the base
52
on a surface of the coil
50
facing the core
51
. Thus, the surface of the coil
50
facing the core
51
is not flat. In bonding the coil
50
to the core
51
, part of a surface of the coil
50
facing the magneto-optical disk readily deforms, e.g., protrudes or inclines. This inhibits the surface of the coil
50
facing the magneto-optical recording medium from coming very close to the magneto-optical recording medium so as to efficiently apply a magnetic field.
To increase the information signal recording speed, the magnetic field modulation frequency must be increased. However, the RF loss on the core
51
and coil pattern
53
increases in almost proportion to the modulation frequency, so that the temperature of the magnetic head rises. The magnetic material such as ferrite forming the core
51
decreases in saturation flux density Bs along with the temperature rise. As the magnetic field modulation frequency increases, the saturation flux density Bs of ferrite forming the core
51
decreases to be equal to the internal flux density of the core
51
. If the magnetic field modulation frequency further increases, the internal flux density of the core
51
decreases together with the saturation flux density Bs, and the strength of a magnetic field generated by the magnetic head also decreases. As a result, a magnetic field applied to the magneto-optical recording medium weakens, failing to record an information signal.
If the temperature of the magnetic head exceeds the heat resistance limit of its building member, deformation or electrical insulation failure may occur.
Under these circumstances, an increase in modulation frequency is limited, and the information signal recording speed cannot be further increased.
DISCLOSURE OF INVENTION
In the present invention, a flat coil (to be referred to as a coil hereinafter) for a magnetic head is made up of at least a coil pattern serving as a conductor pattern made of a conductive material film, and a terminal for supplying a current to the coil pattern. The coil pattern is a spiral conductor pattern capable of supplying a current so as to flow around the magnetic field generation center. In the present invention, a region where this coil pattern is formed is defined as an “effective region” where an effective current contributing to generation of a magnetic field can be supplied. A region outside the coil pattern where at least the conductor pattern capable of supplying a current so as to flow around the magnetic field generation center is not formed is defined as an “ineffective region”. In the following description, conductor patterns formed in the ineffective region except for a conductor pattern serving as a current supply path to the coil pattern, such as a conductor pattern for connecting terminals to each other and a terminal to the coil pattern, will be referred to as a “dummy pattern”.
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide a flat coil for a magnetic head in which a conductor pattern is formed in the ineffective region, and a conductor occupation ratio R (ratio of the total area of all conductor patterns formed from a conductive material film in a given region, to the total area of the region) is defined within a predetermined range in accordance with the distance from the coil pattern, thereby improving the mechanical strength, flatness, and dimensional precision without degrading the electrical characteristics of the coil, a magnetic head using the flat coil, and a magneto-optical recording apparatus.
The present inventors have made extensive studies to find that the above problem can be solved when, letting S be the distance from the outer edge of the coil pattern (outer edge of the effective region), P be

Affiliated with

Also associated with

Rating

High speed magnetic coil for magneto-optical head does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with High speed magnetic coil for magneto-optical head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High speed magnetic coil for magneto-optical head will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3118260