JPH06275883

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DESCRIPTION JPH06275883
[0001]
The present invention relates to a piezoelectric / electrostrictive actuator, and more particularly,
an ink jet print head, a microphone, a sounding body (speaker etc.), various vibrators and
oscillators, a bend of unimorph type or the like used in a pump etc. The present invention relates
to a piezoelectric / electrostrictive actuator of a type that generates displacement.
[0002]
BACKGROUND ART In recent years, a vibrating wall is formed in each of a plurality of spaces
provided inside a base, and a part of the vibrating wall is vibrated by the operation of a
piezoelectric / electrostrictive element provided in the vibrating wall. Piezoelectric /
electrostrictive actuators are known. Such an actuator is used, for example, as an ink pump of a
print head used for an ink jet printer, and is supplied with ink to raise the pressure in the filled
space by displacement of the piezoelectric / electrostrictive element. Thus, ink particles
(droplets) are ejected from the nozzle holes communicating with the space and printed.
[0003]
Specifically, FIGS. 5 and 6 show an example of this type of ink jet print head. In these figures, 16
is an ink nozzle member, and a metallic nozzle plate 4 provided with a plurality of nozzle holes 2
and a metallic orifice plate 8 provided with a plurality of orifice holes 6 flow It is formed by being
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stacked and joined with the passage plate 10 interposed therebetween, and the ink ejection flow
passage 12 for introducing the ink to the nozzle hole 2 and the ink supply flow for introducing
the ink to the orifice hole 6 therein. A passage 14 is formed. Further, 25 is an actuator, and the
nozzle holes 2 and the orifice holes 6 of the ink nozzle member 16 are formed in the base 24
formed by laminating the closing plate 18 and the spacer plate 20 made of metal or synthetic
resin. The plurality of spaces 26 corresponding to each other are provided, and the vibration wall
portion 32 is formed in each of the spaces 26. Then, on the outer surface of the closing plate 18,
the piezoelectric / electrostrictive element 28 is fixed at a position corresponding to each
vibrating wall portion 32. Then, the ink nozzle member 16 and the actuator 25 are overlapped
and bonded and integrated to form an ink jet print head, and by operating the piezoelectric /
electrostrictive element 28, the vibrating wall portion 32 is formed. By deforming, pressure can
be generated in the space 26.
[0004]
By the way, when the ink nozzle member 16 and the actuator 25 are bonded and integrated, a
pressing operation is usually performed to improve adhesion. When the actuator 25 is
pressurized, as shown in FIG. 7, the piezoelectric / electrostrictive element 28 is raised on the
outer surface of the base 24 by an amount corresponding to the thickness of the piezoelectric /
electrostrictive element 28. It is easy to apply pressure to the However, since the piezoelectric /
electrostrictive element 28 has low strength, it has a problem that it is easily broken by such
pressure. Therefore, at the time of pressing in bonding, in order to prevent breakage of the
piezoelectric / electrostrictive element 28, it is necessary to transmit the pressing force only to
the area other than the piezoelectric / electrostrictive element 28. (1) A method of pushing only
the peripheral part of the actuator 25 or (2) A method of setting a pushing plate having a portion
corresponding to the piezoelectric / electrostrictive element 28 set in the actuator 25 and
pushing is adopted.
[0005]
However, originally, it is necessary to firmly seal the adjacent spaces 26, 26 with each other by
adhesion so that the ink does not leak. There is a problem that the force to press the partition
wall 30 is insufficient, adhesion failure occurs, and leakage easily occurs. Further, in the method
(2), it is necessary to precisely position the pressing plate so as not to be applied to the
piezoelectric / electrostrictive element 28. However, in order to highly integrate and arrange the
piezoelectric / electrostrictive element 28, The width of the partition 30 between the spaces 26
and 26 is very narrow, 0.05 to 0.5 mm, and the piezoelectric / electrostrictive element 28
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protrudes, making it difficult to position and causing a problem of poor workability. is there.
Furthermore, when the position of the pressing plate is shifted, the piezoelectric / electrostrictive
element 28 may be pushed and damaged.
[0006]
Here, the present invention has been made against the background described above, and the
problem to be solved by the present invention is that a plurality of outer surfaces of the base are
provided corresponding to the positions of the respective vibrating walls of the base. When
bonding a piezoelectric / electrostrictive actuator provided with a piezoelectric / electrostrictive
element to another member such as an ink nozzle member, it is possible to improve adhesion
while preventing damage to the piezoelectric / electrostrictive element, and also to improve
adhesion workability. To improve.
[0007]
In order to solve the above-mentioned problems, according to the present invention, a base on
which vibrating walls are respectively formed in a plurality of spaces provided inside, and each
vibrating wall of the base are provided. The vibrating wall comprises the lower electrode film, the
piezoelectric / electrostrictive film, and the piezoelectric / electrostrictive element consisting of
the upper electrode film sequentially formed by a film forming method at the corresponding
position on the outer surface, and the vibrating wall by the piezoelectric / electrostrictive
element. In the piezoelectric / electrostrictive actuator in which a part of the portion is vibrated, a
terrace is formed between the adjacent piezoelectric / electrostrictive elements on the outer
surface of the base at a height projecting by a predetermined dimension than the piezoelectric /
electrostrictive element. A piezoelectric / electrostrictive actuator characterized in that a shape
interference portion is provided is the gist of the present invention.
[0008]
In summary, in the piezoelectric / electrostrictive actuator according to the present invention, a
terrace-like interference portion higher than that is provided between adjacent piezoelectric /
electrostrictive elements on the outer surface of the base.
As a result, when the actuator is pressed against and bonded to another member such as an ink
nozzle member, it is easy to apply a pressing force to the most projecting terrace-like
interference portion, making it difficult to apply a force to the piezoelectric / electrostrictive
element And the piezoelectric / electrostrictive element can be protected.
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And, in the case of setting the pressing plate in which the portion corresponding to the
piezoelectric / electrostrictive element is set, the positioning can be performed roughly, and the
bonding workability can be improved, and a simple without a hole. By using a flat pressing plate,
it is also possible to press only the terrace-like interference portion, and adhesion becomes easy.
In addition, pressing force is effectively applied to the terrace-like interference portion, and
adhesion of the partition portion between adjacent spaces inside the base can be performed well,
and breakage of the piezoelectric / electrostrictive element is effectively performed. By being
prevented, excellent operation characteristics can be stably exhibited in the piezoelectric /
electrostrictive actuator according to the present invention.
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In order to clarify the present
invention more specifically, an embodiment using the piezoelectric / electrostrictive actuator
according to the present invention as an ink pump of an ink jet print head will be described in
detail with reference to the drawings. I will explain.
[0010]
First, FIGS. 1 and 2 schematically show an example of an ink jet print head using the piezoelectric
/ electrostrictive actuator according to the present invention, and FIG. 3 shows an exploded
perspective view thereof. It is done.
The ink jet print head 40 shown therein is formed by joining and integrating the ink nozzle
member 42 and the actuator 44, and the ink supplied to the space 46 inside the base 70 of the
actuator 44 The ink is jetted through a nozzle hole 54 provided in the ink nozzle member 42.
[0011]
More specifically, in the ink nozzle member 42, the nozzle plate 48 and the orifice plate 50, each
having a thin flat plate shape, are overlapped with the flow path plate 52 interposed
therebetween, and are integrally joined by an adhesive. It has the following structure.
[0012]
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A plurality of (three in this embodiment) nozzle holes 54 for jetting ink are formed in the nozzle
plate 48, and positions corresponding to the nozzle holes 54 are provided in the orifice plate 50
and the flow path plate 52. In the above, through holes 56 and 57 penetrating in the thickness
direction are formed with an inner diameter larger than the nozzle hole 54 by a predetermined
size.
Further, a plurality of (three in this embodiment) orifice holes 58 for supplying ink are formed in
the orifice plate 50, and the window portion 60 provided in the flow path plate 52 includes the
nozzle plate 48 and the orifice plate. At 50, the ink supply flow path 62 communicated with each
orifice hole 58 is formed by covering from both sides. Further, the orifice plate 50 is provided
with a supply port 64 for supplying the ink led from the ink tank to the ink supply flow path 62.
[0013]
The material of each plate 48, 50, 52 constituting the ink nozzle member 42 is not particularly
limited. However, in order to form the nozzle hole 54 and the orifice hole 58 with high
dimensional accuracy, generally, plastic or Preferably, metals such as nickel, stainless and the
like are employed. Further, the orifice hole 58 is formed with, for example, a tapered shape
whose diameter decreases in the ink flow direction, as illustrated, in order to exert an action like
a check valve on the supplied ink. Is desirable.
[0014]
On the other hand, the actuator 44 comprises a base 70 formed by overlapping a closed plate 66
and a spacer plate 68 each having a thin flat plate shape, and a piezoelectric / electrostrictive
element 80 having a film formed on the outer surface of the closed plate 66. It consists of Then,
a space 46 of a predetermined size is provided inside the base 70.
[0015]
More specifically, in the spacer plate 68 constituting the substrate 70, a long rectangular window
portion at a position corresponding to the through hole 56 and the orifice hole 58 formed in the
orifice plate 50 of the ink nozzle member 42. A plurality of (two in this embodiment) 72 are
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formed. The partition wall 73 between the adjacent windows 72 and 72 is preferably set to a
width of about 0.03 to 0.5 mm in order to dispose the piezoelectric / electrostrictive element 80
in a highly integrated manner. The closure plate 66 is superimposed on the spacer plate 68 to
cover the opening of the window portion 72 of the spacer plate 68 to provide a space 46 inside
the base 70, and further, the closure plate corresponding to the space 46. The vibrating wall
portion 67 is formed at the portion 66.
[0016]
In addition to being formed of metal, synthetic resin or the like as in the prior art, the substrate
70 can also be formed as an integral fired product of ceramics. When a ceramic base is
employed, perfect sealing performance can be stably obtained on the overlapping surface of the
plates 66 and 68 without adding a special adhesion process or the like.
[0017]
In addition, the specific manufacturing method of the ceramic substrate first uses a general
apparatus such as a doctor blade apparatus or a reverse roll coater apparatus from a ceramic
slurry prepared from a ceramic raw material, a binder, a liquid medium, etc. Form the sheet.
Then, as necessary, the green sheet is subjected to processing such as cutting, cutting, punching,
etc. to form the windows 72 and the like, and the precursors of the plates 66 and 68 are formed.
Then, by laminating the respective precursors and firing, an integral ceramic substrate can be
obtained.
[0018]
Further, the material of the ceramic is not particularly limited, but in view of formability and the
like, a material containing alumina, zirconia or the like as a main component is preferably
adopted. Further, it is desirable to use, for the closing plate 66 and the spacer plate 68, green
sheets having substantially the same ceramic composition and particle size distribution from the
viewpoint of the sintering property and the thermal expansion matching. Furthermore, in such a
ceramic substrate, the plate thickness of the closing plate 66 is preferably 50 μm or less, more
preferably 3 to 12 μm, and the plate thickness of the spacer plate 68 is preferably 50 μm or
more, more preferably 100 μm or more It is assumed.
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[0019]
The piezoelectric / electrostrictive element composed of the lower electrode film 74, the
piezoelectric / electrostrictive film 76, and the upper electrode film 78 is provided on the outer
surface of the base 70 corresponding to each vibrating wall portion 67 of the closing plate 66.
80 are provided by film formation. In addition, between adjacent ones of the piezoelectric /
electrostrictive elements 80, a terrace-like interference portion 82 is provided by a film forming
method at a height which protrudes by a predetermined dimension from the piezoelectric /
electrostrictive elements 80. . Particularly preferably, as the piezoelectric / electrostrictive
element 80, the piezoelectric / electrostrictive element proposed by the applicant of the present
invention in Japanese Patent Application Nos. 3-203831 and 4-9742 is employed. The Rukoto.
[0020]
The respective electrode films (upper and lower electrode films 78 and 74) of the piezoelectric /
electrostrictive element 80 and the piezoelectric / electrostrictive film 76 are formed by various
known film forming methods such as screen printing, spraying, dipping, coating, etc. It is formed
by a thin film forming method such as a film forming method, ion beam, sputtering, vacuum
evaporation, ion plating, CVD, plating and the like. Then, in the present embodiment, as shown in
FIG. 4, after the lower electrode film 74 and the piezoelectric / electrostrictive film 76 are
formed, a terraced interference portion 82 is formed between the adjacent piezoelectric /
electrostrictive films 76. The upper electrode film 78 is formed so as to cover the surfaces of the
piezoelectric / electrostrictive film 76 and the terraced interference section 82 by the film
forming method.
[0021]
In the case where the substrate 70 is made of a ceramic, the film formation thereof can be
performed before or after the blocking plate 66 (substrate 70) is sintered. Furthermore, although
the upper electrode film 78, the lower electrode film 74, and the piezoelectric / electrostrictive
film 76 of the piezoelectric / electrostrictive element 80 are heat-treated as necessary, such heat
treatment is carried out each time the respective films are formed. , Or after forming all the films,
it may be performed simultaneously.
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[0022]
Moreover, as a material of the electrode film (upper and lower electrode films 78 and 74)
constituting the piezoelectric / electrostrictive element 80, a conductor capable of withstanding a
high temperature oxidizing atmosphere at a heat treatment temperature or a baking temperature
(when the substrate 70 is made of ceramic) No particular limitation is imposed on the material,
and it may be, for example, a single metal or an alloy. Furthermore, there is no problem even if it
is a mixture of insulating ceramics, glass, etc., and a metal, an alloy, or even conductive ceramics.
On the other hand, as a material of the piezoelectric / electrostrictive film 76, any material can be
adopted as long as it is a material exhibiting an electric field induced strain such as a
piezoelectric or an electrostrictive effect, and it is a crystalline material. Alternatively, it may be
an amorphous material. Moreover, even if it is a semiconductor material, a dielectric ceramic
material or a ferroelectric ceramic material, there is no problem, and even if it is a material that
requires polarization processing, it is an unnecessary material. It is good.
[0023]
Furthermore, the thickness of the piezoelectric / electrostrictive element 80 is generally 100 μm
or less. The thickness of each electrode film (upper and lower electrode films 78 and 74) is
generally 20 μm or less, preferably 5 μm or less, and the thickness of the piezoelectric /
electrostrictive film 76 is large displacement at low operating voltage It is desirable that the
thickness be 50 μm or less, and more preferably 3 μm or more and 40 μm or less, in order to
obtain the same.
[0024]
Since the piezoelectric / electrostrictive element 80 formed in this manner uses the closing plate
66 as a substrate, mechanical strength and toughness can be advantageously secured even at a
thin plate thickness. In addition, since it is formed by the film forming method, many pieces can
be formed on the closing plate 66 at fine intervals simultaneously and easily without using an
adhesive or the like.
[0025]
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On the other hand, the terrace-like interference portion 82 is desirably formed of a material
having a sufficient Young's modulus so as to withstand the pressing force when the actuator 44
is adhered to the ink nozzle member 42. Further, when the pedestal interference portion 82
contacts the upper electrode film 78 and the lower electrode film 74, an insulating material such
as an insulating resin is used to prevent a short circuit. The insulating resin which can be used is
not particularly limited as long as it is a resin having a predetermined hardness and being
capable of applying a film forming method such as screen printing and having insulating
properties, but preferably the Young's modulus is preferably used. A material of 1 kg / mm 2 or
more and 1000 kg / mm 2 or less is selected, and among them, thermosetting resins such as
acrylic resin and epoxy resin are preferably employed. In addition, for example, various solder
resists are preferably used from the viewpoint of the insulating property and the film forming
property. In the case where there is no fear that the terrace-like interference portion 82 comes in
contact with the upper and lower electrode films 78 and 74, a conductive material such as a
metal material can also be used.
[0026]
The terrace-like interference portion 82 is formed to have a height protruding by a
predetermined dimension from the piezoelectric / electrostrictive element 80, and in particular,
the pressure when bonding the actuator 44 to the ink nozzle member 42. In order to ensure that
the piezoelectric / electrostrictive element 80 is well protected at the same time, the terrace-like
interference portion 82 is formed to project 5 .mu.m or more, more preferably about 10 .mu.m or
more, from the piezoelectric / electrostrictive element 80. The Rukoto.
[0027]
Thus, the piezoelectric / electrostrictive element 80 and the terrace-like interference portion 82
are integrally provided on the outer surface of the closing plate 66 of the base body 70, whereby
the target actuator 44 is configured.
Then, the actuator 44 is superposed on the ink nozzle member 42 as shown in FIG. 1, and is
bonded and integrated using an appropriate adhesive, thereby achieving the target ink jet print
head 40 are formed.
[0028]
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Adhesives that can be used at that time include vinyl, acrylic, polyamide, phenol, resorcinol, urea,
melamine, polyester, epoxy, furan, polyurethane, silicone, rubber, Any of polyimide type,
polyolefin type, etc. may be used. However, when the print head is configured as in the present
embodiment, an adhesive having durability against ink is selected.
[0029]
In addition, the form of the adhesive is, from the viewpoint of mass production, either a
dispenser-based application or a highly viscous paste-type that allows screen printing, or a sheettype that can be punched out. Short hot melt adhesive or room temperature cure adhesive is
more desirable. Furthermore, as a highly viscous paste type, it is also possible to use one in
which a filler is mixed in an original adhesive to increase the viscosity. And, from the above
points, an elastic epoxy adhesive or silicone adhesive capable of screen printing, or a sheetshaped hot melt type polyolefin adhesive or polyester adhesive capable of being punched is
particularly preferably used. It will be In addition, it is also possible to selectively use those
various adhesives on a part of adhesion surface, and another part, respectively.
[0030]
Then, when bonding the actuator 44 and the ink nozzle member 42, an adhesive is applied to the
bonding surface of the actuator 44, and after overlapping on the ink nozzle member 42, pressing
is performed to obtain good adhesion. However, in the actuator 44 as described above, since the
terrace-like interference portion 82 higher than that is provided between the piezoelectric /
electrostrictive elements 80 on the outer surface of the base body 70, the most projecting
plateau-like interference portion While the force can be effectively applied to 82, the
piezoelectric / electrostrictive element 80 can be effectively protected. In addition, when setting a
pressing plate in which a portion corresponding to the piezoelectric / electrostrictive element 80
is set, positioning can be performed roughly, and a simple flat plate-shaped pressing plate
without a hole is used. It is also possible to push only the terrace-like interference unit 82.
[0031]
Therefore, while preventing breakage of the piezoelectric / electrostrictive element 80, an
effective pressing force is applied to the terrace-like interference portion 82, and adhesion of the
partition wall 73 between the adjacent spaces 46, 46 can be performed well. As a result, the
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adhesion workability is enhanced and good adhesion and sealability can be obtained. Thus, based
on the fact that excellent operation characteristics can be stably exhibited in the piezoelectric /
electrostrictive actuator 44, excellent ink ejection characteristics can be stably obtained in the
ink jet print head 40.
[0032]
Although the representative embodiments of the present invention have been described above in
detail, these are merely exemplifications, and the present invention should not be construed as
being limited to such specific embodiments.
[0033]
For example, the piezoelectric / electrostrictive actuator according to the present invention is
used as an ink pump for ink jet print heads of various structures other than those having the
above-mentioned structure, and also micropumps, piezoelectric speakers, sensors, vibrators,
oscillators, It can also be used as a filter or the like.
[0034]
In the embodiment, the base 70 of the actuator 44 is composed of the closing plate 66 and the
spacer plate 68, but a three-layer structure in which the spacer plate 68 is further superimposed
on the surface opposite to the closing plate 66. The present invention is also applicable to an
actuator using the above-described substrate.
In the above embodiment, the upper electrode film 78 of the piezoelectric / electrostrictive
element 80 is provided so as to integrally cover the surfaces of the piezoelectric / electrostrictive
film 76 and the terrace-like interference portion 82, but The configuration is not essential, and
the upper electrode film 78 may be formed only on the surface of the piezoelectric /
electrostrictive film 76.
[0035]
Further, the structure and the material of the ink nozzle member 42 are not limited to those of
the embodiment described above, and the whole or a part is integrally molded by injection
molding of synthetic resin material etc. or other molding method. It is also possible to use
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Furthermore, the formation position and the formation number of the nozzle holes 54 and the
orifice holes 58 of the ink nozzle member 42, and the formation position and the formation
number of the space 46 of the actuator 44 and the vibrating wall portion 67 are limited to those
of the embodiment It is not something to be done.
[0036]
In addition, although not listed one by one, the present invention can be implemented in an
embodiment to which various changes, modifications, improvements, etc. are added based on the
knowledge of those skilled in the art, and such an embodiment is the present invention. It is a
matter of course that all are included in the scope of the present invention unless they deviate
from the spirit of the invention.
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