Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Physical deformation
Reexamination Certificate
2002-08-05
2004-09-21
Nguyen, Cuong Q (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Physical deformation
Reexamination Certificate
active
06794723
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a matrix type piezoelectric/electrostrictive device. More particularly, the present invention relates to a matrix type piezoelectric/electrostrictive device which is used for an optical modulator, optical switch, electrical switch, microrelay, microvalve, transportation device, image display device such as a display and a projector, image drawing device, micropump, droplet discharge device, micromixer, microstirrer, microreactor, various types of sensors, and the like, generates large force and large displacement, allows a piezoelectric/electro-strictive substance to generate expansion/contraction displacement or expansion/contraction vibration in a direction perpendicular to a main surface of a ceramic substrate by a transverse effect of an electric field induced strain of the piezoelectric/electrostrictive substance, and applies action such as pushing, distorting, moving, striking (impacting), or mixing to an object of action or operates when such action is applied, and to a method of manufacturing the matrix type piezoelectric/electrostrictive device.
In recent years, displacement control elements capable of adjusting the length or position of an optical path on the order of sub-microns have been demanded in the field of optics, precision machining, manufacture of semiconductors, and the like. To deal with this demand, development of piezoelectric/electrostrictive devices such as actuators or sensors which utilize strain based on a reverse piezoelectric effect or an electrostrictive effect occuring when an electric field is applied to ferroelectrics or antiferroelectrics has progressed. The displacement control elements utilizing an electric field induced strain are capable of easily controlling minute displacement, decreasing power consumption due to high mechanical/electrical energy conversion efficiency, and contributing to a decrease in the size and weight of a product due to ultraprecise mounting capability in comparison with a conventional electromagnetic method or the like using a servomotor or a pulsemotor. Therefore, application fields of displacement control elements are expected to be expanded steadily in the future.
Taking an optical switch as an example, use of a piezoelectric/electrostrictive device as an actuator for switching a transmission path of introduced light has been proposed. FIGS.
2
(
a
) and
2
(
b
) show an example of an optical switch. An optical switch
200
shown in FIGS.
2
(
a
) and
2
(
b
) includes alight transmitting section
201
, an optical path change section
208
, and an actuator section
211
. The light transmitting section
201
includes a light reflecting surface
101
provided on part of a surface which faces the optical path change section
208
, and light transmitting paths
202
,
204
, and
205
provided in three directions from the light reflecting surface
110
. The optical path change section
208
includes a light introducing member
209
which is moveably provided close to the light reflecting surface
101
in the light transmitting section
201
and formed of a light transmitting material, and a light reflecting member
210
which totally reflects light. The actuator section
211
includes a mechanism which is displaced by an external signal and transmits the displacement to the optical path change section
208
.
As shown in FIG.
2
(
a
), the actuator section
211
operates (displaces) by applying an external signal such as a voltage. The optical path change section
208
is separated from the light transmitting section
201
by the displacement of the actuator section
211
. Light
221
introduced into the light transmitting path
202
in the light transmitting section
201
is totally reflected by the light reflecting surface
101
in the light transmitting section
201
, of which the refractive index is adjusted at a specific value. The reflected light
221
is transmitted to the light transmitting path
204
on the output side.
As shown in FIG.
2
(
b
), the actuator section
211
returns to the original position when the actuator section
211
enters a non-operating state, whereby the light introducing member
209
in the optical path change section
208
comes in contact with the light transmitting section
201
at a distance equal to or less than the wavelength of the light. As a result, the light
221
introduced into the light transmitting path
202
is introduced into the light introducing member
209
from the light transmitting section
201
and transmitted through the light introducing member
209
. The light
221
transmitted through the light introducing member
209
reaches the light reflecting member
210
. The light
221
is reflected by the light reflecting surface
102
of the light reflecting member
210
and transmitted to the light transmitting path
205
, differing from the light reflected by the light reflecting surface
101
in the light transmitting section
201
.
As described above, the piezoelectric/electro-strictive device is suitably used as the actuator section of the optical switch having a function of changing the optical path. In particular, in the case of forming a matrix switch which switches between a plurality of channels, a piezo-electric/electrostrictive device in which a plurality of uni-morph or bi-morph piezoelectric/electrostrictive elements (hereinafter may be referred to as “bending displacement elements”) are arranged, as disclosed in Japanese Patent No. 2693291 issued to the applicant of the present invention, is suitably employed. The bending displacement element consists of a diaphragm and a piezoelectric/electrostrictive element, and generates bending displacement by converting only a small amount of expansion/contraction strain of the piezoelectric/electrostrictive element produced when applying an electric field into a bending mode. Therefore, a large displacement is easily obtained in proportion to the length of the piezo-electric/electrostrictive element.
However, since the bending displacement element converts strain, stress which causes the strain of the piezoelectric/electrostrictive element cannot be directly utilized. Therefore, it is very difficult to increase displacement and force generation at the same time. Moreover, since the resonance frequency is inevitably decreased as the length of the element is increased, it is also difficult to satisfy a desired response speed.
In order to further improve the performance of the above type of optical switch, there have been at least the following two demands. Specifically, an increase in ON/OFF ratio (contrast) is demanded. In the case of the optical switch
200
, it is important to securely perform contact/separation operations between the light transmitting section
201
and the optical path change section
208
. Therefore, the actuator section preferably has a large stroke, specifically, generates large displacement.
The other demand is to minimize a loss caused by switching. In this case, it is important to increase a substantial contact area between the optical path change section
208
and the light transmitting section
201
while increasing the area of the optical path change section
208
. However, since an increase in the contact area causes reliability relating to separation to be decreased, a piezoelectric/electrostrictive device capable of generating a large force is necessary as the actuator section. Specifically, a piezoelectric/electrostrictive device capable of generating displacement and force at the same time is demanded as the actuator section in order to improve the performance of the optical switch.
It is preferable that each of the piezoelectric/electrostrictive elements be formed independently. This means that each of the piezoelectric/electrostrictive elements does not interfere with the others, specifically, does not restrict displacement and force generated by other piezoelectric/electrostrictive elements.
For example, a piezoelectric/electrostrictive device
145
shown in
FIG. 3
shows bending displacement by
Kawaguchi Tatsuo
Kimura Koji
Takeuchi Yukihisa
Watanabe Masashi
Burr & Brown
NGK Insulators Ltd.
Nguyen Cuong Q
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