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DESCRIPTION JPH06350155

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DESCRIPTION JPH06350155
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric / electrostrictive film type element (hereinafter referred to as an element), mainly
an ink jet print head, a microphone, a sound generator (speaker etc.), various vibrators and
oscillators, Furthermore, the present invention relates to a unimorph-type or bimorph-type
element used for a sensor or the like which generates a bending displacement. The term
"element" as used herein refers to an element that converts electrical energy into mechanical
energy, that is, mechanical displacement or stress or vibration, as well as an element that
performs the reverse conversion. In addition to the piezoelectric / electrostrictive characteristics,
the element of the present invention also has dielectric properties, and can therefore be used as a
film-like capacitor element or the like.
[0002]
2. Description of the Related Art In recent years, in the fields of optics and precision processing,
displacement elements for adjusting the optical path length and position on the order of
submicrons and detection elements for detecting micro displacement as electrical changes have
become desirable. As a response to this, development of an actuator using displacement based on
the inverse piezoelectric effect or the electrostrictive effect that occurs when an electric field is
applied to a piezoelectric / electrostrictive material such as a ferroelectric, or the reverse is
advanced. There is.
[0003]
Among such fields, in the ink jet print head etc., as a structure of the actuator, a unimorph type
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bending displacement type conventionally known is suitably adopted, and the printing quality,
printing speed and the like of the printer In order to meet the demand for improvement,
developments are in progress for achieving downsizing and high density of actuators, low voltage
operation, and high speed response.
[0004]
In order to improve each of these characteristics, it is important to reduce the thickness of the
substrate to be the diaphragm of the actuator. However, if the entire substrate is thinned, the
characteristics described above will be improved but the strength of the substrate will decrease.
There is a contradictory relationship of
Therefore, the applicant of the present application has proposed an element capable of achieving
both the improvement of element characteristics and the improvement of substrate strength in
the earlier application (Japanese Patent Application Laid-Open No. 5-49270).
As shown in the partial cross-sectional view of FIG. 8, the element includes a ceramic substrate
(16) having a cavity or a recess and a thin, flat ceramic substrate (17). The lower electrode film
(2a), the piezoelectric / electrostrictive film (2b), and the thin film portion (17a) of the concave
portion (5) of the cavity substrate formed by laminating in the state of a green sheet and firing
and integrating A piezoelectric / electrostrictive actuating portion (hereinafter referred to as an
actuating portion) (2) formed by sequentially laminating the upper electrode film (2c) is
provided. Therefore, according to this structure, only the portion functioning as the actuating
portion, that is, only the diaphragm is thin, and both sides of the diaphragm are formed thick, so
that the function of the actuating portion can be sufficiently exhibited. Also, the strength of the
entire substrate can be sufficiently secured, and the above-mentioned conventional problems can
be solved.
[0005]
However, as shown in FIG. 9A, when a plurality of operating parts are provided on the same
substrate surface to constitute an element as a result of the subsequent examination, as shown in
FIG. When only the actuating portion (21) is actuated, the thin portion (17a) curves downward as
shown. At that time, the side wall (16b) of the recess (5) is slightly deformed inward, and the thin
portion is effectively bent. However, as shown in FIG. 6 (b), when the adjacent operating parts
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(22) are also operated simultaneously, the thin walled part (17a) provided with each operating
part is continuously formed through the thick part, The forces pulling on each other act to make
it difficult to bend the thin portion. That is, the displacement was reduced as compared with the
case where the device was operated alone, and it was revealed that the characteristics inherent to
the device could not be sufficiently exhibited, and the reduction rate was also different among
the devices. .
[0006]
Furthermore, in order to heat-process and integrate an action | operation part and a diaphragm,
in addition to the said subject, the following subjects exist. Since the chemical component of the
material differs depending on the purpose of the piezoelectric / electrostrictive film and the
diaphragm constituting the actuating portion, there is a difference in the thermal expansion
coefficient (each component will be described later). In the cooling process in the heat treatment
process of the piezoelectric / electrostrictive film, a difference occurs in thermal contraction, and
a residual stress corresponding to the contraction difference is generated in the piezoelectric /
electrostrictive film. Furthermore, since the firing shrinkage of the piezoelectric / electrostrictive
film is hindered by the diaphragm, the piezoelectric / electrostrictive film can not achieve its
original shrinkage when the rigidity of the ceramic substrate forming the piezoelectric /
electrostrictive working portion increases. In the inside of the piezoelectric / electrostrictive film,
a direction opposite to contraction, that is, a tensile force continues to be present as a residual
stress. And, as apparent from the experimental results described later, this residual stress
degrades the material properties of the piezoelectric / electrostrictive film, resulting in the
inability to fully utilize the material properties that the piezoelectric / electrostrictive film
material originally has. .
[0007]
In particular, as shown in FIG. 10, in the case of the ceramic substrate in which the closed
substrate (7) is formed on the opening side of the recess, the substrate rigidity is increased
compared to the ceramic substrate in which the closed substrate is not formed. It has become
clear that the actuating portion and the inner wall of the recess become more difficult to displace,
and the material characteristics also deteriorate. Therefore, for example, when this element is
applied to an ink jet print head, the discharge amount and the discharge speed of the ink filled in
each concave portion are reduced, and the dispersion thereof is caused, and good print quality
can not be obtained. .
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[0008]
Therefore, the object of the present invention is to firstly lower the substrate rigidity around the
portion where the piezoelectric / electrostrictive working portion is to be formed so that the
piezoelectric / electrostrictive film is thermally treated in the piezoelectric / electrostrictive film.
It is an object of the present invention to reduce the residual stress generated so that the material
properties originally possessed by the piezoelectric / electrostrictive film can be fully utilized.
Second, the reduction in displacement of each operating part when the plurality of operating
parts are simultaneously operated on the same substrate is reduced, and the variation in
displacement among the operating parts is reduced.
[0009]
SUMMARY OF THE INVENTION The present invention has been developed to solve each of the
above-mentioned problems, and the gist of the invention is a ceramic substrate having at least
one or more windows of a predetermined size. The ceramic substrate is laminated on the surface
of the ceramic substrate, and at least one recess of a predetermined size is formed on the same
surface, or on the bottom outer surface of each recess of the ceramic substrate or on the same
substrate surface. On the bottom outer surface of each recess of the ceramic substrate in which
at least one recess of the size is formed or on the bottom surface of the recess of the ceramic
substrate And an electrode film and a piezoelectric / electrostrictive film composed of an
electrode film and a piezoelectric / electrostrictive film are integrated by firing, or alternatively,
the electrode film and the piezoelectric / electrostrictive film are sequentially laminated by firing
together. In the piezoelectric / electrostrictive film type element, at least one groove of an
appropriate length which is deeper than the thickness of the bottom of the recess from the
surface of a predetermined thick portion around the outer surface of the bottom of each recess is
included in the recess They are formed along the wall surface and at appropriate intervals from
the inner wall surface.
[0010]
In order to further enhance such effects, each ceramic substrate contains at least one compound
of yttrium oxide, cerium oxide, magnesium oxide and calcium oxide, and thereby the crystal
phase is completely stabilized or partially stabilized. It is desirable to be made of a material
having the above-mentioned zirconium oxide as a main component.
[0011]
Further, a material wherein the piezoelectric / electrostrictive film is composed mainly of lead
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magnesium niobate, lead zirconate and lead titanate or lead nickel niobate, lead magnesium
niobate, lead zirconate and lead titanate It is desirable to be composed of a material whose main
component is a component consisting of
[0012]
Furthermore, it is desirable that the thickness of the bottom of each of the recesses is 50 μm or
less.
[0013]
[Operation] Since a thick portion around the bottom corresponding to the diaphragm of each
recess is formed with a groove having an appropriate length which is deeper than the thickness
from the surface to the bottom, a piezoelectric / electrostrictive working portion is formed The
rigidity of the substrate around the portion is low and the structure is easy to deform.
Therefore, residual stress caused by the difference in thermal expansion coefficient between the
substrate material and the piezoelectric / electrostrictive film material, which is generated in the
heat treatment process for integrating the piezoelectric / electrostrictive working portion with
the substrate, or the piezoelectric / electrostrictive film The force that hinders the firing
shrinkage can be kept low because the substrate can easily follow the thermal shrinkage
behavior of the piezoelectric / electrostrictive film working part, and the material characteristics
intrinsic to the piezoelectric / electrostrictive film material can be sufficiently extracted. It is
possible.
In addition, since the grooves are formed between the adjacent operating parts, the forces of the
bottoms of the adjacent recesses can mutually absorb each other, and the interference due to the
displacement of the other operating parts can be reduced. Therefore, it becomes possible to draw
out the original displacement of the actuating portion.
[0014]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The actuator of the present
invention will be described in detail below with reference to the drawings.
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In addition, in order to make an understanding easy, the same code | symbol shall be attached |
subjected to what has the same structure and function through each drawing.
[0015]
FIG. 1 is an external perspective view of an element according to the present invention in which a
plurality of operating parts (2) are provided on a cavity substrate (14), FIG. 2 is an explanatory
sectional view taken along line AA of FIG. FIG. 3 (b) is an explanatory view showing a method of
forming the cavity substrate (14), and FIG. 3 (b) is a sectional explanatory view in which the
formed cavity substrate is cut along line B-B in FIG. 3 (a).
The cavity substrate (14) is a ceramic substrate (8) and a substrate (4) on a ceramic closed
substrate (7) by using a method of multilayer lamination of green sheets as shown in FIG. 3 (a).
Are sequentially laminated. A plurality of windows (5) are formed on the substrate (8), and
grooves (6a) are provided on both sides of each window along the inner wall (8b) and at
appropriate intervals from the inner wall It is formed toward the thick portion (7a) of the closed
substrate (7). The substrate (4) (4a) corresponds to the bottom of the recess that is to be the
diaphragm of the element, on which the actuating portion (2) is integrally formed. (6b) is a
groove formed in the same size at a position corresponding to the groove (6a). A groove (6)
shown in FIG. 3 (b) is formed by the groove (6a) and the groove (6b). As shown in FIG. 2 (a), the
operating portion (2) is formed by sequentially laminating the lower electrode film (2a), the
piezoelectric / electrostrictive film (2b) and the upper electrode film (2c), and the diaphragm (4a)
) Is integrally formed on. The hole (7b) formed in the closed substrate (7) is a hole for
introducing the ink used in the ink jet print head into the cavity or discharging the ink out of the
cavity.
[0016]
The length (L1) of the groove (6) shown in FIG. 3 (a) is at least 1/8 or more, preferably 1/4 or
more, of the longitudinal side edge of the window (5) along the groove Preferably, the
longitudinal center of the groove is formed on an extension from the longitudinal side edge
center of the window (5b). In addition, the depth (D2) of the groove (6) preferably exceeds at
least the thickness (D1) of the ceramic substrate (4), and more preferably the depth shown in
equation 1 is exceeded. It is desirable to do.
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[0018]
Even more preferably, it is formed to have the depth shown in equation 2.
[0020]
The shape of the groove may be V-shaped, trapezoidal or the like, in addition to the one formed
in the vertical direction with respect to the substrate surface as in this embodiment.
[0021]
The thickness of the bottom (4a) of each recess serving as the diaphragm is generally 50 μm or
less, preferably 30 μm or less, and more preferably 10 μm or less, in order to obtain high-speed
response and large displacement of the actuating portion. .
[0022]
The element according to the present invention has the cavity substrate in which the groove is
processed in the thick part around the working part as described above, so the diaphragm is
easily bent, so the diaphragm and the working part are integrated by heat treatment. In this case,
since the diaphragm easily follows the contraction of the piezoelectric / electrostrictive film, the
contraction force of the piezoelectric / electrostrictive film is blocked by the diaphragm, which is
a force generated inside the piezoelectric / electrostrictive film, that is, residual Stress can be
reduced.
Therefore, various characteristics including the relative dielectric constant of the piezoelectric /
electrostrictive film become large, and the material characteristics originally possessed by the
piezoelectric / electrostrictive film material can be extracted.
[0023]
As a result, as shown in FIG. 2 (b), each diaphragm tends to be largely curved, and the inner walls
(8b) and (8b) of the recess (5) are also displaced inward with displacement of the diaphragm.
Therefore, compared to the conventional one in which only the diaphragm is displaced, the
volume change in the recess can be performed easily and quickly.
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In addition, even if the plurality of operating parts operate at the same time, the force that the
diaphragms pull each other is buffered, so that the variation in displacement of each diaphragm
can be reduced.
[0024]
Therefore, when this element is applied to an ink jet print head, the inner wall surface of the
concave portion is also easily displaced inward in addition to the large displacement of the
actuating portion, thereby increasing the discharge amount of the ink filled in the concave
portion. In addition, interference between adjacent operation parts, that is, crosstalk can be
reduced, and the discharge performance of the ink, for example, the discharge speed and the
discharge amount also by the difference in the operation state such as multiple simultaneous
operation or single operation. Are not easily affected, and good print quality can be obtained.
[0025]
Incidentally, even in the case of the element in which the closed substrate as shown in FIG. 4 is
not formed, it is needless to say that the material characteristic which the piezoelectric /
electrostrictive film material originally has can be extracted by forming the groove in the thick
portion. is there.
[0026]
FIG. 5 is a partial cross-sectional view of the element according to the present invention in which
two grooves deeper than the thickness of the diaphragm are formed in each thick portion.
According to this structure, even when the pitch between the actuating portions is wide and the
width of the thick portions is designed wide, the substrate rigidity around the actuating portions
can be reduced, and in addition, the element having the above-mentioned one groove is formed
In comparison with the above, it is possible to obtain further excellent device characteristics,
which is preferable.
[0027]
FIG. 6 (a) is a cross-sectional view of the element of the present invention to which the operating
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part used in the element (Japanese Patent Application No. 5-75414) proposed by the applicant of
the present invention in the previous application is applied.
As shown in FIG. 6 (b), the actuating portion covers the lower electrode film on the piezoelectric /
electrostrictive film (9b) on the lower electrode film (9a), and the end portion is the second
ceramic substrate (4 ) It is a structure with a size that overhangs upward.
An incomplete joint (11) is formed between the overhang (10) and the second ceramic substrate
(4). Here, the incomplete connection means that the connection between the projecting part (10)
and the second ceramic substrate (4) is incomplete, and the operation part (9) can sufficiently
exhibit the required performance. I say the state. (12)Is a resin layer formed to smoothly guide
the upper electrode film onto the ceramic substrate (4) in order to prevent the disconnection of
the upper electrode film (9c). With this structure, alignment of the lower electrode film and the
upper electrode film for short circuit prevention can be facilitated by this structure, and the
productivity of the element can be improved, and at the same time, the overhang portion and the
second ceramic substrate There is no limitation on the bending displacement or generated force
of the piezoelectric / electrostrictive film. Therefore, as shown in FIG. 6A, if the present invention
is constituted by this actuating portion, in addition to the improvement of the element
performance, the productivity of the element can also be improved. In each of the above
embodiments, the case where the plurality of operating portions are provided on the substrate
has been described, but even in the case where only one operating portion is provided, the same
groove is formed in the thick portion of the substrate Of course, the material properties of the
piezoelectric / electrostrictive film can be sufficiently obtained, resulting in an increase in
displacement.
[0028]
Next, in order to sufficiently exhibit the material properties of the piezoelectric / electrostrictive
film of the element according to the present invention, the ceramic substrate contains at least
one compound of yttrium oxide and cerium oxide, and magnesium oxide and calcium oxide. It is
desirable that the crystalline layer be composed of a material based on zirconium oxide in which
the crystal layer is completely stabilized or partially stabilized.
[0029]
The amount of additives for stabilizing or partially stabilizing zirconium oxide is 1 mol% to 30
mol% with respect to yttrium oxide, 6 mol% to 50 mol% for cerium oxide, magnesium oxide or
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calcium oxide On the other hand, it is preferable to set it to 5 mol% to 40 mol%, and it is
particularly preferable to set it to 2 mol% to 4 mol% with respect to yttrium oxide.
This is because zirconium oxide to which yttrium oxide is added in these ranges partially
stabilizes the crystal layer and exhibits particularly excellent substrate properties.
[0030]
In addition, although a sintering aid such as clay may be added to the substrate material, silicon
oxide, boron oxide, phosphorus oxide, germanium oxide or the like may be added to at least the
second ceramic substrate constituting the thin portion. It is desirable to adjust the composition
and the addition amount of the auxiliary so that the easily vitrifiable material is not contained in
1% by weight or more. The reason is that when the material that easily vitrifies is contained in
the substrate, a reaction easily occurs during heat treatment with the piezoelectric /
electrostrictive film, and control of the composition of the piezoelectric / electrostrictive film
becomes difficult.
[0031]
By the way, such a ceramic substrate can effectively receive the operating characteristics of the
operating portion formed thereon, in other words, the distortion and force generated there, and
to effectively perform the reverse operation. The surface roughness represented by the formula
is adjusted to be in the range of 0.03 to 0.9 .mu.m. Such adjustment of the surface roughness: Ra
is also effective in securing the strength of the thin substrate.
[0032]
In addition, although the first ceramic substrate and the second ceramic substrate are finally in a
sintered form, they are previously heated to 1000 ° C. to 1800 ° prior to the formation of the
piezoelectric / electrostrictive operation part. The substrate may be sintered at about C, and may
be sintered after forming an operation part by a film forming method described later using a
green sheet of a substrate material, but among them, in advance, among them, A sintered
substrate can be advantageously used because the warpage of the element can be made smaller
and the pattern dimension accuracy can be obtained.
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[0033]
Each groove can be formed both in the green substrate and in the sintered substrate, and various
methods are adopted in that case.
For example, laser, electron beam, slicing, blasting, ultrasonic processing and the like, and in the
case of a substrate in a green state, a punching process using a die, a die, and the like are further
suitably adopted. These processes can be performed either before forming each film or after
forming the whole film. Among these processing methods, laser processing is preferably
employed, in which relatively complicated processing is easily possible, but in that case, thermal
stress is minimized to prevent cracking and breakage of the ceramic substrate. You need to make
it smaller. In order to reduce this thermal stress, there are various processing conditions. For
example, when processing as in this application, a YAG laser is used as a laser light source, and
the pulse width is 140 nsec or less, preferably 100 nsec. In the following, it is possible to
perform pulse control (for example, 3.6 KHz) by the Q switch, and further, the beam diameter of
the laser light is φ50 μm or less, preferably φ5 to φ10 μm by lens focusing, and the
processing speed is 1.0 mm / sec or less However, it is desirable to adopt TEM 00 single mode
resonance with Gaussian distribution (normal distribution) as energy distribution in the laser
beam.
[0034]
Then, a predetermined lower electrode film (2a), upper electrode film (2c) and piezoelectric /
electrostrictive film (2b) are provided on such a ceramic substrate to form a piezoelectric /
electrostrictive working portion (2). And various film forming methods known in the art are
suitably adopted. For example, thick film forming methods such as screen printing, spraying,
dipping, coating, etc., thin film forming methods such as ion beam, sputtering, vacuum
evaporation, ion plating, CVD, plating Is selected appropriately. In particular, in order to form the
piezoelectric / electrostrictive film (2b), a thick film forming method by screen printing, spraying,
dipping, coating or the like is suitably adopted. This is because, according to those thick film
forming methods, using a paste or slurry mainly composed of ceramic particles of piezoelectric /
electrostrictive material having an average particle diameter of 0.01 μm to 5 μm, preferably
0.05 μm to 3 μm. It is because a film can be formed on a ceramic substrate and good device
characteristics can be obtained. Moreover, as the shape of such a film, in addition to forming a
pattern using a screen printing method, a photolithography method or the like, an unnecessary
part is formed using a laser processing method, a machining method such as slicing or ultrasonic
processing. It may be removed and patterned.
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[0035]
The structure of the element produced here and the shape of the film-like operating part are not
limited at all, and any shape may be adopted according to the application, for example, a polygon
such as a triangle or a square, There is no problem even if it is a circle such as a circle, an ellipse,
an annular ring, a comb, a lattice, or a special shape combining them, and the groove formed in
the thick portion also corresponds to the shape of the actuating portion By the formation, the
effects of the present invention can be exhibited.
[0036]
In addition, the respective films (2a), (2b) and (2c) thus formed on the ceramic substrate by the
above method are heat-treated each time the respective films are formed, and are integrated with
the substrate. Alternatively, after forming all the films, heat treatment may be simultaneously
performed to integrally bond each film to the substrate at the same time.
Of course, in the case of forming the element shown in FIG. 6 using these forming methods, the
overhanging portion of the piezoelectric / electrostrictive film and the ceramic substrate are in
an incompletely coupled state. In the case of forming an electrode film by such a film forming
method, a heat treatment may not necessarily be necessary for integration. For example, before
forming the upper electrode film (2c), in order to ensure insulation with the lower electrode film
(2a), insulating coating is performed around the element with an insulating resin or the like, or as
shown in FIG. May form a resin layer (13) to prevent disconnection of the upper electrode film
(10c). In that case, heat treatment is required to form the upper electrode film (10c). Methods
such as vapor deposition, sputtering and sputtering are employed.
[0037]
Furthermore, as a heat treatment temperature for integrating the film thus formed and the
substrate, a temperature of about 900 ° C. to about 1400 ° C. is generally employed,
preferably in the range of about 1000 ° C. to about 1400 ° C. The temperature is
advantageously chosen. When heat treatment of the piezoelectric / electrostrictive film, heat
treatment is performed while controlling the atmosphere together with the evaporation source of
the piezoelectric / electrostrictive material so that the composition of the piezoelectric /
electrostrictive layer becomes unstable at high temperature. Is preferred. In addition, it is also
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recommended to adopt a method in which a suitable cover member is placed on the piezoelectric
/ electrostrictive film so that the surface is not directly exposed to the baking atmosphere, and
the baking is performed. In that case, as the cover member, the same material system as the
substrate is used.
[0038]
The material of the lower electrode film (2a) constituting the piezoelectric / electrostrictive
working portion manufactured by the above method is particularly restricted as long as it is a
conductor that can withstand a high temperature oxidizing atmosphere around the heat
treatment temperature and the sintering temperature. For example, it may be a single metal or an
alloy, or a mixture of an insulating ceramic with a metal or an alloy, or even a conductive
ceramic. . Furthermore, more preferably, an electrode material mainly composed of high melting
point noble metals such as platinum, palladium and rhodium, or an alloy such as silver-palladium,
silver-platinum and platinum-palladium, and a cermet of platinum and a ceramic substrate
material Preferably, a material, a cermet material of platinum, a substrate material and a
piezoelectric material is used, and among them, a material containing platinum as a main
component is more preferable. Further, as a material to be added to the electrode, a glass such as
silicon oxide is likely to cause a reaction during heat treatment with the piezoelectric /
electrostrictive film, which tends to cause deterioration of the actuator characteristics, so it is
desirable to avoid its use. The substrate material to be added to the electrode is preferably about
5 to 30% by volume, and the piezoelectric material is preferably about 5 to 20% by volume. On
the other hand, the upper electrode film material is not particularly limited.
[0039]
An electrode film formed using such a conductive material is generally formed to a thickness of
20 μm or less, preferably 5 μm or less.
[0040]
In addition, as the piezoelectric / electrostrictive material constituting the working part, any
material can be adopted as long as it is a material exhibiting electric field induced strain such as
piezoelectric or electrostrictive effect, and it is crystalline. It may be a material or an amorphous
material, and even if it is a semiconductor material, a dielectric ceramic material or a ferroelectric
ceramic material, there is no problem and further polarization processing is necessary. Material,
or it may be an unnecessary material.
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[0041]
Furthermore, as the piezoelectric / electrostrictive material used in the present invention,
preferably, a material containing lead zirconate titanate (PZT based) as a main component, a
material containing lead magnesium niobate (PMN based) as a main component, nickel Material
mainly composed of lead niobate (PNN system), material mainly composed of magnesium lead
tungstate, material mainly composed of manganese niobate, material mainly composed of lead
antimony stannate, zinc niobate A material containing lead as a main component, a material
containing lead titanate as a main component, or a composite material of these materials is used.
In addition, oxides such as lanthanum, barium, niobium, zinc, cerium, cadmium, chromium,
cobalt, antimony, iron, yttrium, tantalum, tungsten, nickel, manganese, lithium, strontium,
magnesium, calcium, bismuth, etc. Or, even if materials containing other compounds of these as
additives, for example, materials containing PZT as a main component, lanthanum is added, and
the above-mentioned additives are appropriately added to the above materials so as to become
PLZT. No matter what.
The addition of glass materials such as silicon oxide should be avoided. The reason is that leadbased piezoelectric / electrostrictive materials such as PZT-based materials easily react with
glass, which makes it difficult to control the desired piezoelectric / electrostrictive film
composition and causes variations and deterioration of actuator characteristics. .
[0042]
Among these piezoelectric / electrostrictive materials, materials containing lead magnesium
niobate, lead zirconate and lead titanate as main components, or lead nickel niobate, lead
magnesium niobate, lead zirconate and titanate A material containing a component consisting of
lead as a main component is preferred, and in particular, a material containing a component
consisting of lead magnesium niobate, lead zirconate and lead titanate is particularly preferred as
a substrate material during heat treatment In particular, since the reaction between the overhang
and the ceramic substrate can be kept low to such an extent that the piezoelectric /
electrostrictive working part does not affect the required performance, the segregation of
components In combination with having a high piezoelectric constant, it is difficult to occur,
processing for maintaining the composition can be suitably performed, and the target
composition and crystal structure are easily obtained. Used in interest, screen printing, spraying,
dipping, is recommended as the material of the case of forming the piezoelectric / electrostrictive
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film in thick-film forming technique such as coating. In the case of a multi-component
piezoelectric / electrostrictive material, the piezoelectric characteristics change depending on the
composition of the components, but in the case of a ternary lead-free material of lead magnesium
niobate-lead zirconate-lead titanate which is suitably employed in the present invention
Preferably, the composition is near the phase boundary between pseudo cubic, tetragonal and
rhombohedral phases, in particular, lead magnesium niobate: 15 to 50 mol%, lead zirconate: 10
to 45 mol%, lead titanate: A composition of 30 mol% to 45 mol% is advantageously employed
because of its high piezoelectric constant and electromechanical coupling factor.
[0043]
Furthermore, the thickness of the working portion composed of the electrode film and the
piezoelectric / electrostrictive film formed as described above is generally 100 μm or less, and
the thickness of the piezoelectric / electrostrictive film is low. In order to obtain a large
displacement or the like by the operating voltage, it is desirable that the thickness be preferably
50 μm or less, more preferably 3 μm to 40 μm.
[0044]
Next, the effects of the present invention will be described based on experimental results.
In this experiment, in the piezoelectric / electrostrictive film type device having the same
actuating portion as shown in FIG. 11, the conventional cavity substrate and the cavity substrate
of the present invention are used for the structure of the substrate (15). The difference in the
element characteristics due to the difference in the structure of the cavity substrate was
determined. Table 1 shows the results of measuring the displacement and the relative dielectric
constant of the working part when the working part ~ was provided on each of the conventional
cavity substrate and the cavity substrate of the present invention. The cavity substrate used in
Comparative Example 1 has a structure according to the invention of the applicant of the present
applicant in which the closed substrate of FIG. 8 is not formed, and the one used in Comparative
Example 2 is the closed substrate of FIG. The formed structure according to the prior invention of
the present applicant and the one used in the present application A are the structure shown in
FIG. 2 and the groove depth is 100 μm.
[0046]
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From the experimental results shown in Table 1, the displacement of the actuating portion when
provided on the cavity substrate of the present application A is more than that of the
conventional one in which the closed substrate was formed although the closed substrate was
formed. It can be seen that not only a large displacement but a displacement comparable to that
in which the closed substrate is not formed is obtained. Also, although the relative dielectric
constant shows a larger value than any of the conventional ones, this is because the residual
stress existing in the piezoelectric / electrostrictive film is small and the material property itself
of the piezoelectric / electrostrictive film is improved. To support the
[0047]
Next, Table 2 shows the difference in displacement between when the actuating portions are
simultaneously actuated and when each actuating portion is independently provided, that is, the
displacement reduction rate is compared with the conventional cavity substrate and the cavity
substrate of the present invention And the result compared with. In the case of the cavity
substrate in which the closed substrate is formed and the groove (13) is formed with the same
thickness as the diaphragm and the depth of 10 μm as shown in FIG. 7, Comparative Example 3
is 50 μm in which the closed substrate is formed. In the case of using a cavity substrate having a
groove of a depth of. The present application C is a case where a cavity substrate in which two
grooves are formed with a depth of 100 μm as shown in FIG. 5 on which a closed substrate is
formed.
[0049]
As shown in the experimental results of Table 2, in the case of the conventional substrates shown
in Comparative Example 1, Comparative Example 2 and Comparative Example 3, when the
respective operating parts are operated at the same time, they operate independently at each
position. There is a large difference not only in the displacement but also in the displacement
reduction rate of each working part compared to the case where the present invention is applied,
the displacement of each working part is also large in the present invention B, the present
application A and the present application C It can be seen that there is no significant difference in
the displacement reduction rate. This proves that not only large displacement can be obtained by
the element of the present invention, but also that the element of the present invention is not
easily affected by the displacement of other working parts. Further, comparing Comparative
Example 2 and Comparative Example 3, the groove having the same depth as the thickness of the
diaphragm has almost no effect, but comparing the present application A with the present
application B, the groove has a thickness of the diaphragm It can be understood that the deeper
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one can obtain a large displacement of the working parts, and the variation in the displacement
between the working parts is also smaller. Furthermore, when the present application C and the
present application A are compared, it can be seen that the effect is larger in the case where two
grooves are provided.
[0050]
In the measurement of displacement, the displacement when the voltage application was
performed individually or simultaneously to each operating part was evaluated by a laser
Doppler vibrometer. Further, the thickness of the diaphragm was 10 μm, the total thickness of
the substrate (7) and the substrate (8) was 150 μm, and the working part was formed by a thick
film method. The applied voltage is 30V.
[0051]
The present invention is not limited to the above embodiments, and various changes,
modifications, and improvements can be made without departing from the scope of the present
invention.
[0052]
According to the present invention, since the residual stress generated inside the piezoelectric /
electrostrictive film can be reduced when the diaphragm and the actuating portion are integrated
by firing, the piezoelectric / electrostrictive film is inherently used. It is possible to sufficiently
bring out the material properties which it has.
Moreover, the material properties hardly deteriorate even if the rigidity of the substrate
increases. In addition, since it is possible to prevent the displacement of the diaphragm and the
interference between the operating parts, it is possible to realize the element characteristic with
no variation of the displacement in each operating part. Furthermore, since a large displacement
of the diaphragm can be maintained and the inner wall of the recess having the diaphragm at the
bottom can be largely displaced inward, the volume change in the recess can be easily and
quickly made with a small electric potential. It can be done to
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