U.S. patent application number 17/104153 was filed with the patent office on 2021-06-03 for method for producing piezoelectric actuator.
The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Takanori AIMONO, Yasuhiro ITAYAMA, Harunobu KOIKE, Masao NAKAYAMA, Toshihiro SHIMIZU, Koji SUMI, Motoki TAKABE.
Application Number | 20210167276 17/104153 |
Document ID | / |
Family ID | 1000005287113 |
Filed Date | 2021-06-03 |
United States Patent
Application |
20210167276 |
Kind Code |
A1 |
KOIKE; Harunobu ; et
al. |
June 3, 2021 |
Method for Producing Piezoelectric Actuator
Abstract
A method for producing a piezoelectric actuator including
forming a vibration plate, forming a first electrode on the
vibration plate, forming a piezoelectric layer on the first
electrode, and forming a second electrode on the piezoelectric
layer, wherein the forming the vibration plate has a single layer
forming step including forming a metal layer containing zirconium
by a gas phase method, and forming a metal oxide layer by firing
the metal layer, the single layer forming step is repeated, thereby
forming the vibration plate in which the metal oxide layers are
stacked, and the metal oxide layer has a thickness less than 200
nm.
Inventors: |
KOIKE; Harunobu; (Matsumoto,
JP) ; AIMONO; Takanori; (Matsumoto, JP) ;
NAKAYAMA; Masao; (Shiojiri, JP) ; TAKABE; Motoki;
(Shiojiri, JP) ; SUMI; Koji; (Shiojiri, JP)
; ITAYAMA; Yasuhiro; (Kai, JP) ; SHIMIZU;
Toshihiro; (Fujimi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
1000005287113 |
Appl. No.: |
17/104153 |
Filed: |
November 25, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 14/5806 20130101;
C23C 14/185 20130101; H01L 41/29 20130101; H01L 41/35 20130101;
C23C 14/34 20130101 |
International
Class: |
H01L 41/35 20060101
H01L041/35; H01L 41/29 20060101 H01L041/29; C23C 14/18 20060101
C23C014/18; C23C 14/34 20060101 C23C014/34; C23C 14/58 20060101
C23C014/58 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2019 |
JP |
2019-216461 |
Claims
1. A method for producing a piezoelectric actuator, comprising:
forming a vibration plate; forming a first electrode on the
vibration plate; forming a piezoelectric layer on the first
electrode; and forming a second electrode on the piezoelectric
layer, wherein the forming the vibration plate has a single layer
forming step including forming a metal layer containing zirconium
by a gas phase method, and forming a metal oxide layer by firing
the metal layer, the single layer forming step is repeated, thereby
forming the vibration plate in which the metal oxide layers are
stacked, and the metal oxide layer has a thickness less than 200
nm.
2. The method for producing a piezoelectric actuator according to
claim 1, wherein the metal oxide layer has a thickness of 50 nm or
more.
3. The method for producing a piezoelectric actuator according to
claim 1, wherein the metal oxide layer has a thickness of 150 nm or
less.
4. The method for producing a piezoelectric actuator according to
claim 1, wherein the metal oxide layer has a columnar crystal
structure.
5. The method for producing a piezoelectric actuator according to
claim 1, wherein the metal oxide layer is a zirconium oxide layer,
and in X-ray diffraction of the metal oxide layer, a ratio of an
intensity of a peak attributed to a (-211) plane to an intensity of
a peak attributed to a (-111) plane is 0.36 or less.
6. The method for producing a piezoelectric actuator according to
claim 5, wherein a position of the peak attributed to the (-111)
plane is 28.1.degree. or more and 28.5.degree. or less, and a
position of the peak attributed to the (-211) plane is 40.4.degree.
or more and 41.4.degree. or less.
7. The method for producing a piezoelectric actuator according to
claim 5, wherein an intensity of a peak attributed to a (111) plane
is higher than the intensity of the peak attributed to the (-211)
plane, and a position of the peak attributed to the (111) plane is
29.5.degree. or more and 30.5.degree. or less.
Description
[0001] The present application is based on, and claims priority
from JP Application Serial Number 2019-216461, filed on Nov. 29,
2019, the disclosure of which is hereby incorporated by reference
herein in its entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a method for producing a
piezoelectric actuator.
2. Related Art
[0003] There has been known a piezoelectric element actuator that
deforms a vibration plate by a piezoelectric element. Such a
piezoelectric actuator is used in, for example, a liquid ejection
head or the like.
[0004] For example, JP-A-2005-168172 (Patent Document 1) describes
a piezoelectric actuator including a vibration plate composed of a
silicon dioxide film with a thickness of 1 .mu.m and a zirconium
oxide film with a thickness of 200 nm.
[0005] However, in Patent Document 1, the zirconium oxide film has
a thickness of 200 nm, which is thick, and therefore, when it is
exposed to a high temperature and high humidity environment, the
zirconium oxide film is sometimes peeled from the silicon dioxide
film.
SUMMARY
[0006] A method for producing a piezoelectric actuator according to
one aspect of the present disclosure includes forming a vibration
plate, forming a first electrode on the vibration plate, forming a
piezoelectric layer on the first electrode, and forming a second
electrode on the piezoelectric layer, wherein the forming the
vibration plate has a single layer forming step including forming a
metal layer containing zirconium by a gas phase method, and forming
a metal oxide layer by firing the metal layer, the single layer
forming step is repeated, thereby forming the vibration plate in
which the metal oxide layers are stacked, and the metal oxide layer
has a thickness less than 200 nm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a cross-sectional view schematically showing a
piezoelectric actuator according to an embodiment.
[0008] FIG. 2 is a cross-sectional view schematically showing metal
oxide layers of the piezoelectric actuator according to the
embodiment.
[0009] FIG. 3 is a flowchart for illustrating a method for
producing a piezoelectric actuator according to an embodiment.
[0010] FIG. 4 is a cross-sectional view schematically showing a
step of producing a piezoelectric actuator according to the
embodiment.
[0011] FIG. 5 is a cross-sectional view schematically showing a
step of producing a piezoelectric actuator according to the
embodiment.
[0012] FIG. 6 is an exploded perspective view schematically showing
a liquid ejection head according to an embodiment.
[0013] FIG. 7 is a plan view schematically showing the liquid
ejection head according to the embodiment.
[0014] FIG. 8 is a cross-sectional view schematically showing the
liquid ejection head according to the embodiment.
[0015] FIG. 9 is a perspective view schematically showing a printer
according to an embodiment.
[0016] FIG. 10 is a table showing evaluation results of
Experimental Examples.
[0017] FIG. 11 is a graph showing XRD measurement results of
Experimental Examples.
[0018] FIG. 12 is a graph showing XRD measurement results of
Experimental Examples.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0019] Hereinafter, preferred embodiments of the present disclosure
will be described in detail with reference to the drawings. Note
that the embodiments described below are not intended to unduly
limit the contents of the present disclosure described in the
appended claims. Further, not all the configurations described
below are necessarily essential components of the present
disclosure.
1. Piezoelectric Actuator
[0020] First, a piezoelectric actuator according to this embodiment
will be described with reference to the drawings. FIG. 1 is a
cross-sectional view schematically showing a piezoelectric actuator
100 according to this embodiment.
[0021] As shown in FIG. 1, the piezoelectric actuator 100 includes
a vibration plate 10 and a piezoelectric element 20. The vibration
plate 10 is provided on a basal plate 2.
[0022] The basal plate 2 is, for example, a silicon substrate. In
the example shown in the drawing, the basal plate 2 is provided
with an opening portion 4. The opening portion 4, for example,
passes through the basal plate 2.
[0023] The vibration plate 10 has flexibility and is deformed by
the action of the piezoelectric element 20. The vibration plate 10
has, for example, a silicon oxide layer 12 and a metal oxide layer
14.
[0024] The silicon oxide layer 12 is provided on the basal plate 2.
The silicon oxide layer 12 may be an SiO.sub.2 layer. The thickness
of the silicon oxide layer is, for example, 30 nm or more and 3
.mu.m or less.
[0025] The metal oxide layer 14 is provided on the silicon oxide
layer 12. The metal oxide layer 14 contains zirconium. The metal
oxide layer 14 is, for example, a zirconium oxide layer. The metal
oxide layer 14 may be a ZrO.sub.2 layer.
[0026] A thickness T of the metal oxide layer 14 is less then 200
nm, and preferably 10 nm or more and 180 nm or less, more
preferably 50 nm or more and 150 nm or less. The thickness T of the
metal oxide layer 14 can be measured by, for example, observing the
cross section of the piezoelectric actuator 100 using a scanning
electron microscope (SEM).
[0027] As the metal oxide layer 14, a plurality of layers are
provided. In the example shown in the drawing, as the metal oxide
layer 14, two layers are provided, however, the number of layers is
not particularly limited, and for example, 2 or more layers and 10
or less layers, preferably, 2 or more layers and 5 or less layers.
The thicknesses T of the plurality of metal oxide layers 14 may be
the same or different.
[0028] The metal oxide layer 14 has a columnar crystal structure.
Here, FIG. 2 is a cross-sectional view schematically showing the
metal oxide layers 14 and is a view for illustrating the columnar
crystal structure. As shown in FIG. 2, the "columnar crystal
structure" refers to a structure in which the shape of a crystal
grain G is a columnar shape, and a grain boundary GB is continuous
from a lower face 14a to an upper face 14b of the metal oxide layer
14. As shown in FIG. 2, in the two metal oxide layers 14, the grain
boundary GB of one of the metal oxide layers 14 and the grain
boundary GB of the other metal oxide layer are shifted in a lateral
direction (a direction orthogonal to a perpendicular line of an
upper face 2a of the basal plate 2). In the example shown in the
drawing, the grain boundary GB is linearly provided.
[0029] When X-ray diffraction (XRD) measurement is performed for
the metal oxide layer 14, for example, a peak P.sub.(-1111)
attributed to a (-111) plane of the metal oxide layer 14 and a peak
P.sub.(-211) attributed to a (-211) plane of the metal oxide layer
14 are confirmed. Further, a peak P(111) attributed to a (111)
plane of the metal oxide layer 14 may be confirmed. The peak
P.sub.(-1111) and the peak P.sub.(-2111) are attributed to the
metal oxide layer 14 that is a monoclinic crystal system. The peak
P.sub.(111) is attributed to the metal oxide layer 14 that is a
tetragonal crystal system.
[0030] In the XRD of the metal oxide layer 14, the position of the
peak P.sub.(-111) is 28.1.degree. or more and 28.5.degree. or less.
The position of the peak P.sub.(-2111) is 40.4.degree. or more and
41.4.degree. or less. The position of the peak P.sub.(-1111) is
29.5.degree. or more and 30.5.degree. or less.
[0031] In the XRD of the metal oxide layer 14, a ratio R of an
intensity of the peak P.sub.(-2111) to an intensity of the peak
P.sub.(-1111) is, for example, 0.36 or less, preferably 0.31 or
less, more preferably 0.25 or less, further more preferably 0.20 or
less. The metal oxide layer 14 may be preferentially oriented to
(-111). The expression "preferentially oriented to (-111)" refers
to that the intensity of the peak P.sub.(-1111) is highest among
all the peaks attributed to the metal oxide layer 14. The intensity
of the peak P.sub.(111) may be higher than the intensity of the
peak P.sub.(-2111).
[0032] As shown in FIG. 1, the piezoelectric element 20 is provided
on the vibration plate 10. The piezoelectric element 20 has a first
electrode 22, a piezoelectric layer 24, and a second electrode
26.
[0033] The first electrode 22 is provided on the metal oxide layer
14. The shape of the first electrode 22 is, for example, a layer
shape. The thickness of the first electrode 22 is, for example, 3
nm or more and 200 nm or less. The first electrode 22 is, for
example, a metal layer such as a platinum layer, an iridium layer,
a titanium layer, or a ruthenium layer, an electrically conductive
oxide layer thereof, a lanthanum nickel oxide (LaNiO.sub.3:LNO)
layer, a strontium ruthenate (SrRuO.sub.3: SRO) layer, or the like.
The first electrode 22 may have a structure in which a plurality of
layers exemplified above are stacked.
[0034] The first electrode 22 is one of the electrodes for applying
a voltage to the piezoelectric layer 24. The first electrode 22 is
a lower electrode provided below the piezoelectric layer 24.
[0035] The piezoelectric layer 24 is provided on the first
electrode 22. In the example shown in the drawing, the
piezoelectric layer 24 is provided on the first electrode 22 and
the metal oxide layer 14. The piezoelectric layer 24 is provided
between the first electrode 22 and the second electrode 26. The
thickness of the piezoelectric layer 24 is, for example, 200 nm or
more and 2 .mu.m or less. The piezoelectric layer 24 can be
deformed by applying a voltage between the first electrode 22 and
the second electrode 26.
[0036] The piezoelectric layer 24 is, for example, a composite
oxide layer having a perovskite structure. The piezoelectric layer
24 is, for example, a lead zirconate titanate
(Pb(Zr,Ti)O.sub.3:PZT) layer, a potassium sodium niobate
((K,Na)NbO.sub.3:KNN) layer, or the like. To the piezoelectric
layer 24, an additive such as manganese, niobium, or silicon may be
added.
[0037] The second electrode 26 is provided on the piezoelectric
layer 24. Although not shown in the drawing, the second electrode
26 may be further provided on a side face of the piezoelectric
layer 24 and on the metal oxide layer 14 as long as the second
electrode 26 is electrically separated from the first electrode
22.
[0038] The shape of the second electrode 26 is, for example, a
layer shape. The thickness of the second electrode 26 is, for
example, 15 nm or more and 300 nm or less. The second electrode 26
is, for example, a metal layer such as an iridium layer, a platinum
layer, a titanium layer, or a ruthenium layer, an electrically
conductive oxide layer thereof, a strontium ruthenate layer, a
lanthanum nickel oxide layer, or the like. The second electrode 26
may have a structure in which a plurality of layers exemplified
above are stacked.
[0039] The second electrode 26 is the other electrode for applying
a voltage to the piezoelectric layer 24. The second electrode 26 is
an upper electrode provided on the piezoelectric layer 24.
2. Method for Producing Piezoelectric Actuator
[0040] Next, a method for producing the piezoelectric actuator 100
according to this embodiment will be described with reference to
the drawings. FIG. 3 is a flowchart for illustrating the method for
producing the piezoelectric actuator 100 according to this
embodiment. FIGS. 4 and 5 are each a cross-sectional view
schematically showing a step of producing the piezoelectric
actuator 100 according to this embodiment.
[0041] As shown in FIG. 3, the method for producing the
piezoelectric actuator 100 includes a vibration plate forming step
(Step S1) of forming the vibration plate 10, a first electrode
forming step (Step S2) of forming the first electrode 22, a
piezoelectric layer forming step (Step S3) of forming the
piezoelectric layer 24, and a second electrode forming step (Step
S4) of forming the second electrode 26.
[0042] In the vibration plate forming step (Step S1), as shown in
FIG. 4, for example, the basal plate 2 that is a silicon substrate
is thermally oxidized, whereby the silicon oxide layer 12 is
formed.
[0043] Subsequently, the metal layer 13 is formed on the silicon
oxide layer 12 by a gas phase method. As the gas phase method, for
example, a sputtering method is exemplified. The metal layer 13 is
a layer containing zirconium. The metal layer 13 is, for example, a
zirconium layer.
[0044] As shown in FIG. 5, the metal layer 13 is fired, whereby the
metal oxide layer 14 is formed. The metal layer 13 is oxidized and
converted into the metal oxide layer 14 by firing. The firing
temperature is, for example, 850.degree. C. or higher and
1000.degree. C. or lower, preferably 900.degree. C. or higher and
950.degree. C. or lower. When the firing temperature is 850.degree.
C. or higher, the metal oxide layer 14 can be prevented from
peeling from the metal layer 13. When the firing temperature is
1000.degree. C. or lower, occurrence of a crack in the metal oxide
layer 14 due to too high firing temperature can be prevented.
[0045] As shown in FIG. 1, by performing the step of forming the
metal layer 13 by a gas phase method and the step of forming the
metal oxide layer 14 by firing the metal layer 13, one metal oxide
layer 14 is formed (single layer forming step). By repeating the
step, the vibration plate 10 in which a plurality of metal oxide
layers 14 are stacked is formed. The number of repetitions of the
step of forming the metal oxide layer 14 is not particularly
limited.
[0046] In the first electrode forming step (Step S2), as shown in
FIG. 1, the first electrode 22 is formed on the vibration plate 10.
The first electrode 22 is formed by, for example, a sputtering
method, a chemical vapor deposition (CVD) method, a vacuum
deposition method, or the like. Subsequently, the first electrode
22 is patterned by, for example, photolithography and etching.
[0047] In the piezoelectric layer forming step (Step S3), the
piezoelectric layer 24 is formed on the first electrode 22. The
piezoelectric layer 24 is formed by, for example, a liquid phase
method such as a sol gel method or a metal organic deposition (MOD)
method, a chemical solution deposition (CSD) method, a sputtering
method, a CVD method, a laser abrasion method, or the like.
Subsequently, the piezoelectric layer 24 is patterned by, for
example, photolithography and etching.
[0048] In the second electrode forming step (Step S4), the second
electrode 26 is formed on the piezoelectric layer 24. The second
electrode 26 is formed by, for example, a sputtering method, a CVD
method, a vacuum deposition method, or the like. Subsequently, the
second electrode 26 is patterned by, for example, photolithography
and etching. The second electrode 26 and the piezoelectric layer 24
may be patterned in the same step.
[0049] Subsequently, the basal plate 2 is etched from a lower face
side, whereby the opening portion 4 is formed in the basal plate
2.
[0050] By the above steps, the piezoelectric actuator 100 can be
produced.
[0051] The method for producing the piezoelectric actuator 100 has,
for example, the following effects.
[0052] In the method for producing the piezoelectric actuator 100,
the vibration plate forming step (Step S1) has a single layer
forming step including forming the metal layer 13 containing
zirconium by a gas phase method, and forming the metal oxide layer
14 by firing the metal layer 13, and the single layer forming step
is repeated, thereby forming the vibration plate 10 in which the
metal oxide layers 14 are stacked. The thickness T of the metal
oxide layer 14 is less than 200 nm.
[0053] Therefore, as compared with a case where the thickness T of
the metal oxide layer is 200 nm or more, the piezoelectric actuator
100 in which the metal oxide layer 14 is less likely to be peeled
from the interface between the metal oxide layer 14 and the silicon
oxide layer 12 and the interface between the metal oxide layer 14
and the metal oxide layer 14 even if it is exposed to a high
temperature and high humidity environment can be produced (for
details, see the below-mentioned "5. Experimental Examples").
Further, as compared with a case where the metal oxide layer is
formed by a liquid phase method, the metal oxide layer is less
likely to be peeled. Therefore, the piezoelectric actuator 100
having high durability and reliability can be produced.
[0054] Further, in the method for producing the piezoelectric
actuator 100, a single layer of the metal layer 13 containing
zirconium is formed by a gas phase method, and therefore, the metal
oxide layer 14 has a columnar crystal structure. Further, in the
vibration plate forming step (Step S1), a step of forming the metal
oxide layer 14 by forming the metal layer 13 and then firing the
metal layer 13 is repeatedly performed. Therefore, as shown in FIG.
2, in the two metal oxide layers 14, the grain boundary GB of one
of the metal oxide layers 14 and the grain boundary GB of the other
metal oxide layer 14 are shifted in a lateral direction. A crack is
likely to occur along the grain boundary GB. Therefore, in the
piezoelectric actuator 100, the grain boundaries GB are shifted,
and therefore, even if a crack has occurred along the grain
boundary GB of one of the metal oxide layers 14, progress of the
crack can be stopped at the interface between the lower face 14a of
one of the metal oxide layers 14 and the upper face 14b of the
other metal oxide layer 14. For example, in the two metal oxide
layers, when the grain boundaries GB are aligned, progress of the
crack cannot be stopped, and the metal oxide layer is likely to be
peeled. Note that the single layer means a layer composed of one
layer.
[0055] Further, the metal oxide layer 14 has a columnar crystal
structure, and therefore, as compared with a case where a metal
oxide layer has a granular crystal structure, the ratio of the
grain boundaries GB in the metal oxide layer 14 can be decreased. A
gap is likely to be generated at the grain boundaries GB, and when
a gap is generated, a binding strength between the crystal grains G
is decreased. For example, moisture in the air penetrates along the
grain boundaries GB. Therefore, by adopting the columnar crystal
structure in which the ratio of the grain boundaries GB is small
for the metal oxide layer 14, peeling of the metal oxide layer 14
can be prevented. Note that when the metal oxide layer containing
zirconium is formed by a liquid phase method, the metal oxide layer
has a granular crystal structure.
[0056] In the method for producing the piezoelectric actuator 100,
the thickness T of the metal oxide layer 14 may be 50 nm or more
and 150 nm or less. Therefore, the piezoelectric actuator 100 in
which the metal oxide layer 14 is less likely to be peeled can be
produced. Further, if a metal oxide layer having a thickness T less
than 50 nm is tried to be formed, the cost is increased. Therefore,
by setting the thickness T to 50 nm or more, the increase in the
production cost can be suppressed.
[0057] In the method for producing the piezoelectric actuator 100,
the metal oxide layer 14 is a zirconium oxide layer, and in the XRD
of the metal oxide layer 14, the ratio R of the intensity of the
peak P.sub.(-211) to the intensity of the peak P.sub.(-111) may be
0.36 or less. When the ratio R is 0.36 or less, unevenness at the
interface between the metal oxide layer 14 and the silicon oxide
layer 12 can be prevented from occurring, and a gap is less likely
to be generated at the interface. Therefore, the metal oxide layer
14 is less likely to be peeled from the silicon oxide layer 12.
[0058] In the method for producing the piezoelectric actuator 100,
in the metal oxide layer 14, the intensity of the peak P.sub.(111)
may be higher than the intensity of the peak P(-211). Here, the
peak P.sub.(-111) and the peak P.sub.(-2111) are attributed to the
metal oxide layer 14 that is a monoclinic crystal system, and the
peak P.sub.(111) is attributed to the metal oxide layer 14 that is
a tetragonal crystal system. The metal oxide layer 14 that is a
tetragonal crystal system is converted into a monoclinic crystal
system by applying an external force and increases its volume. Due
to this, a crack occurs, and when a force is applied to the metal
oxide layer 14 that is a tetragonal crystal system, the metal oxide
layer 14 is converted from the tetragonal crystal system to a
monoclinic crystal system and increases its volume, and progress of
the crack can be stopped. Therefore, when the metal oxide layer 14
that is a tetragonal crystal system is present to such an extent
that the intensity of the peak P.sub.(111) is higher than the
intensity of the peak P.sub.(211), even if a crack occurs in the
metal oxide layer 14, progress of the crack can be stopped. When
the thickness T of the metal oxide layer 14 is set to 150 nm or
less, the crystal grains of the metal oxide layer 14 become dense.
Due to this, the ratio of the crystal grains attributed to a
monoclinic crystal system adjacent to the crystal grains attributed
to a tetragonal crystal system is increased, and the occurrence of
a crack is more easily suppressed.
3. Liquid Ejection Head
[0059] Next, a liquid ejection head according to this embodiment
will be described with reference to the drawings. FIG. 6 is an
exploded perspective view schematically showing a liquid ejection
head 200 according to this embodiment. FIG. 7 is a plan view
schematically showing the liquid ejection head 200 according to
this embodiment. FIG. 8 is a cross-sectional view taken along the
line VIII-VIII in FIG. 7 schematically showing the liquid ejection
head 200 according to this embodiment. In FIGS. 6 to 8, X axis, Y
axis, and Z axis are shown as three axes orthogonal to one another.
Further, in FIGS. 6 and 8, the piezoelectric element 20 is shown in
a simplified manner.
[0060] As shown in FIGS. 6 to 8, the liquid ejection head 200
includes, for example, a basal plate 2, a piezoelectric actuator
100, a nozzle plate 220, a protective substrate 240, a circuit
board 250, and a compliance substrate 260. In FIG. 7, illustration
of the circuit board 250 is omitted for the sake of
convenience.
[0061] In the basal plate 2, a pressure generating chamber 211 is
provided. The pressure generating chamber 211 is divided by a
plurality of partitions 212. The volume of the pressure generating
chamber 211 is changed by the piezoelectric element 20.
[0062] A first communication path 213 and a second communication
path 214 are provided at an end in the positive X-axis direction of
the pressure generating chamber 211 of the basal plate 2. The first
communication path 213 is configured such that an opening area
thereof becomes smaller by narrowing the end in the positive X-axis
direction of the pressure generating chamber 211 from the Y-axis
direction. The width in the Y-axis direction of the second
communication path 214 is, for example, the same as the width in
the Y-axis direction of the pressure generating chamber 211. In the
positive X-axis direction of the second communication path 214, a
third communication path 215 that communicates with a plurality of
second communication paths 214 is provided. The third communication
path 215 constitutes a part of a manifold 216. The manifold 216
becomes a liquid chamber common to the respective pressure
generating chambers 211. In this manner, in the basal plate 2, a
supply flow path 217 composed of the first communication path 213,
the second communication path 214, and the third communication path
215, and the pressure generating chamber 211 are provided. The
supply flow path 217 communicates with the pressure generating
chamber 211 and supplies a liquid to the pressure generating
chamber 211.
[0063] The nozzle plate 220 is provided at one face of the basal
plate 2. A material of the nozzle plate 220 is, for example, steel
use stainless (SUS). The nozzle plate 220 is joined to the basal
plate 2 using, for example, an adhesive, a heat-welding film, or
the like. In the nozzle plate 220, a plurality of nozzle holes 222
are provided along the Y axis. The nozzle holes 222 communicate
with the pressure generating chamber 211 and eject a liquid. A
vibration plate 10 is provided at the other face of the basal plate
2.
[0064] A plurality of piezoelectric elements 20 are provided. The
number of piezoelectric elements 20 is not particularly
limited.
[0065] In the liquid ejection head 200, by deformation of the
piezoelectric layer 24 having an electromechanical conversion
property, the vibration plate 10 and the first electrode 22 are
displaced. That is, in the liquid ejection head 200, the vibration
plate 10 and the first electrode 22 substantially have a function
as a vibration plate.
[0066] The first electrode 22 is constituted as an individual
electrode independent for each pressure generating chamber 211. The
width in the Y-axis direction of the first electrode 22 is narrower
than the width in the Y-axis direction of the pressure generating
chamber 211. The length in the X-axis direction of the first
electrode 22 is longer than the length in the X-axis direction of
the pressure generating chamber 211. In the X-axis direction, both
ends of the first electrode 22 are located across both ends of the
pressure generating chamber 211. To the end in the negative X-axis
direction of the first electrode 22, a lead electrode 202 is
coupled.
[0067] The width in the Y-axis direction of the piezoelectric layer
24 is, for example, wider than the width in the Y-axis direction of
the first electrode 22. The length in the X-axis direction of the
piezoelectric layer 24 is, for example, longer than the length in
the X-axis direction of the pressure generating chamber 211. The
end in the positive X-axis direction of the first electrode 22 is
located, for example, between the end in the positive X-axis
direction of the piezoelectric layer 24 and the end in the positive
X-axis direction of the pressure generating chamber 211. The end in
the positive X-axis direction of the first electrode 22 is covered
with the piezoelectric layer 24. On the other hand, the end in the
negative X-axis direction of the piezoelectric layer 24 is located,
for example, between the end at the negative X-axis direction side
of the first electrode 22 and the end in the positive X-axis
direction of the pressure generating chamber 211. The end at the
negative X-axis direction side of the first electrode 22 is not
covered with the piezoelectric layer 24.
[0068] The second electrode 26 is, for example, continuously
provided on the piezoelectric layer 24 and the vibration plate 10.
The second electrode 26 is constituted as an electrode common to
the plurality of piezoelectric elements 20.
[0069] The protective substrate 240 is joined to the basal plate 2
using an adhesive 203. In the protective substrate 240, a through
hole 242 is provided. In the example shown in the drawing, the
through hole 242 passes through the protective substrate 240 in the
Z-axis direction and communicates with the third communication path
215. The through hole 242 and the third communication path 215
constitute the manifold 216 to serve as a liquid chamber common to
the respective pressure generating chambers 211. Further, in the
protective substrate 240, a through hole 244 that passes through
the protective substrate 240 in the Z-axis direction is provided.
In the through hole 244, an end in the negative X-axis direction of
the lead electrode 202 is located.
[0070] In the protective substrate 240, an opening portion 246 is
provided. The opening portion 246 is a space for preventing
inhibition of driving of the piezoelectric element 20. The opening
portion 246 may be sealed or need not be sealed.
[0071] The circuit board 250 is provided on the protective
substrate 240. The circuit board 250 includes a semiconductor
integrated circuit (IC) for driving the piezoelectric element 20.
The circuit board 250 and the lead electrode 202 are electrically
coupled to each other through a coupling wire 204.
[0072] The compliance substrate 260 is provided on the protective
substrate 240. The compliance substrate 260 has a sealing layer 262
provided on the protective substrate 240, and a fixing plate 264
provided on the sealing layer 262. The sealing layer 262 is a layer
for sealing the manifold 216. The sealing layer 262 has, for
example, flexibility. In the fixing plate 264, a through hole 266
is provided. The through hole 266 passes through the fixing plate
264 in the Z-axis direction. The through hole 266 is provided at a
position overlapping with the manifold 216 when seen from the
Z-axis direction.
4. Printer
[0073] Next, a printer according to this embodiment will be
described with reference to the drawing. FIG. 9 is a perspective
view schematically showing a printer 300 according to this
embodiment.
[0074] The printer 300 is an inkjet-type printer. As shown in FIG.
9, the printer 300 includes a head unit 310. The head unit 310 has,
for example, a liquid ejection head 200. The number of liquid
ejection heads 200 is not particularly limited. In the head unit
310, cartridges 312 and 314 constituting a supply unit are
detachably provided. A carriage 316 on which the head unit 310 is
mounted is provided freely movable in an axial direction to a
carriage shaft 322 attached to a device body 320 and ejects a
liquid supplied from a liquid supply unit.
[0075] Here, the liquid may be any as long as it is a material in a
state when a substance is a liquid phase, and a material in a
liquid state like a sol, a gel, or the like is also included in the
liquid. Further, not only a liquid as one state of a substance, but
also a material in which particles of a functional material
composed of a solid such as a pigment or metal particles are
dissolved, dispersed, or mixed in a solvent, etc. are included in
the liquid. Typical examples of the liquid include an ink and a
liquid crystal emulsifier. The ink is assumed to include various
liquid compositions such as general aqueous inks and oily inks, gel
inks, and hot-melt inks.
[0076] In the printer 300, a driving force of a drive motor 330 is
transmitted to the carriage 316 through a plurality of gears (not
shown) and a timing belt 332, and thereby the carriage 316 on which
the head unit 310 is mounted is moved along the carriage shaft 322.
On the other hand, the device body 320 is provided with a
conveyance roller 340 as a conveyance mechanism for relatively
moving a sheet S that is a recording medium such as paper with
respect to the liquid ejection head 200. The conveyance mechanism
for conveying the sheet S is not limited to the conveyance roller,
and may be a belt, a drum, or the like.
[0077] The printer 300 includes a printer controller 350 as a
control unit that controls the liquid ejection head 200 and the
conveyance roller 340. The printer controller 350 is electrically
coupled to the circuit board 250 of the liquid ejection head 200.
The printer controller 350 includes, for example, a random access
memory (RAM) that temporarily stores various data, a read only
memory (ROM) that stores a control program or the like, a central
processing unit (CPU), and a drive signal generation circuit that
generates a drive signal to be supplied to the liquid ejection head
200, and the like.
[0078] The piezoelectric actuator 100 can be used in a wide range
of applications without being limited to a liquid ejection head and
a printer. The piezoelectric actuator 100 is favorably used in, for
example, an ultrasonic motor, a vibration-type dust remover, a
piezoelectric transformer, a piezoelectric speaker, a piezoelectric
pump, a pressure-electric converter, or the like.
5. Experimental Examples
[0079] 5.1. Preparation of Samples
[0080] An SiO.sub.2 layer was formed by thermal oxidation of a
silicon substrate. Subsequently, a Zr layer was formed on the
SiO.sub.2 layer by a sputtering method. Subsequently, the Zr layer
was converted into a ZrO.sub.2 layer by performing firing at 850 to
1000.degree. C. FIG. 10 is a table showing the configuration of the
ZrO.sub.2 layer prepared in Experimental Examples.
[0081] In Experimental Examples 1 to 5, as shown in FIG. 10, one
ZrO.sub.2 layer having a different thickness was formed. The
thickness of the Zr layer was set to a value obtained by dividing
the target thickness of the ZrO.sub.2 layer by 1.44. For example,
in Experimental Example 1, the target thickness of the ZrO.sub.2
layer was 50 nm, and therefore, the Zr layer having a thickness of
about 35 nm was formed.
[0082] In Experimental Examples 6 to 11, two ZrO.sub.2 layers were
formed by repeating formation of a Zr layer by a sputtering method
and oxidation of the Zr layer by firing. In each of the
Experimental Examples 6 to 11, the thickness of the ZrO.sub.2 layer
as the first layer and the thickness of the ZrO.sub.2 layer as the
second layer are different.
[0083] In Experimental Example 12, three ZrO.sub.2 layers were
formed by repeating formation of a Zr layer by a sputtering method
and oxidation of the Zr layer by firing.
[0084] In Experimental Example 13, four ZrO.sub.2 layers were
formed by repeating formation of a Zr layer by a sputtering method
and oxidation of the Zr layer by firing.
[0085] In Experimental Example 14, a ZrO.sub.2 layer as a first
layer was formed by formation of a Zr layer by a sputtering method
and oxidation of the Zr layer by firing, and thereafter, a
ZrO.sub.2 layer as a second layer was formed by a liquid phase
method. In the liquid phase method, a compound of Zr and an organic
substance was applied, followed by firing at 850.degree. C. to
1000.degree. C.
[0086] 5.2. Evaluation of Durability against Environmental
Change
[0087] With respect to the samples prepared as described above,
evaluation of durability against environmental change was
performed. Specifically, with respect to the samples exposed to a
dry environment at a temperature of 45.degree. C. and a humidity of
5% for 24 hours, and the samples exposed to a high temperature and
high humidity environment at a temperature of 45.degree. C. and a
humidity of 95% for 24 hours, a scratch test was performed. In the
scratch test, a pressure was increased until the ZrO.sub.2 layer
was peeled, and the pressure (mN) at which the ZrO.sub.2 layer was
peeled was recorded as a scratch strength. In the scratch test,
"CRS-5000" manufactured by RHESCA, Co., Ltd. was used.
[0088] In FIG. 10, evaluation of an amount of change in the scratch
strength in the dry environment and in the high temperature and
high humidity environment is shown as the evaluation of durability
against the environmental change. In the scratch test, the obtained
value was changed according to a parameter such as a curvature
radius of a tip of a needle used for scratching, and therefore,
relative comparison was performed using the amount of change. The
criteria for the evaluation shown in FIG. 10 are as follows.
[0089] A: The amount of change in the scratch strength is less than
3%.
[0090] B: The amount of change in the scratch strength is 3% or
more and less than 10%.
[0091] C: The amount of change in the scratch strength is 10% or
more.
[0092] Note that the amount of change in the scratch strength was
determined according to the following formula.
"Amount of change in scratch strength"=("Scratch strength in dry
environment"-"Scratch strength in high temperature and high
humidity environment")/"Scratch strength in dry
environment"-100
[0093] As shown in FIG. 10, for the samples in which the thickness
of the one ZrO.sub.2 layer is 200 nm or more, the evaluation of
durability is lower as compared with that for the samples in which
the thickness of the one ZrO.sub.2 layer is less than 200 nm. With
respect to the sample in which the thickness of the one ZrO.sub.2
layer is less than 200 nm, even if the ZrO.sub.2 layers are
stacked, the evaluation of durability is high. Accordingly, it was
found that by setting the thickness of one ZrO.sub.2 layer less
than 200 nm, the ZrO.sub.2 layer is less likely to be peeled.
[0094] In Experimental Example 14 in which the ZrO.sub.2 layer as
the second layer was formed by a liquid phase method, although the
thickness was 100 nm, the evaluation of durability was "C". When
the cross section of the ZrO.sub.2 layer as the second layer was
observed using an SEM, the ZrO.sub.2 layer as the second layer of
Experimental Example 14 had a granular crystal structure. On the
other hand, the ZrO.sub.2 layers formed by formation of a Zr layer
by a sputtering method and oxidation of the Zr layer all had a
columnar crystal structure. Accordingly, it was found that the
ZrO.sub.2 layer having a columnar crystal structure is less likely
to be peeled as compared with the ZrO.sub.2 layer having a granular
crystal structure.
[0095] In FIG. 10, in the samples for which the evaluation of
durability was "C", the ZrO.sub.2 layer was peeled at the interface
between the ZrO.sub.2 layer and the SiO.sub.2 layer or at the
interface between the ZrO.sub.2 layer and the ZrO.sub.2 layer, and
did not undergo fracture (brittle fracture) in which the surface of
the ZrO.sub.2 layer or the inside of the ZrO.sub.2 layer was
ruptured and broken.
[0096] Further, before performing the scratch test, the samples
were exposed to heavy water at 70.degree. C. to 80.degree. C. for
24 hours, and thereafter, secondary ion mass spectrometry (SIMS)
analysis was performed. As a result, in the samples for which the
evaluation of durability was "C", a reaction with heavy water was
observed in at least one of the interface between the ZrO.sub.2
layer and the SiO.sub.2 layer and the interface between the
ZrO.sub.2 layer and the ZrO.sub.2 layer. Accordingly, it was found
that by setting the thickness of the ZrO.sub.2 layer to 200 nm or
less and forming the Zr layer by a gas phase method, a gap can be
made less likely to be generated between the metal oxide layer and
the silicon oxide layer, and moisture that penetrates into the
interface between the metal oxide layer and the silicon oxide layer
can be reduced. Further, it was found that a gap can be made less
likely to be generated between the metal oxide layer and the metal
oxide layer, and moisture that penetrates into the interface
between the metal oxide layer and the metal oxide layer can be
reduced.
[0097] 5.3. XRD Measurement
[0098] Before performing the scratch test, XRD measurement
(out-of-plane measurement) was performed for the samples. In the
XRD measurement, "D8 Discover with GADDS" manufactured by Bruker
Corporation was used. In the XRD measurement, a Cu--K.alpha. ray
was used. In the XRD measurement, the acceptance angle was set as
follows: 2 theta: 20.degree. to 50.degree., gamma: -95.degree. to
-85.degree.. The device arrangement of XRD was set as follows:
frame angles: 2 theta: 35.degree., omega: 10.degree., phi:
0.degree., chi: 90.degree..
[0099] The XRD measurement was performed for Experimental Examples
1, 2, 4, 5, 11, and 13. FIG. 11 is a graph showing the XRD
measurement results of Experimental Examples 1, 2, 4, and 5. FIG.
12 is a graph showing the XRD measurement results of Experimental
Examples 11 and 13.
[0100] As shown in FIGS. 11 and 12, in Experimental Examples 1, 2,
4, 5, 11, and 13, a peak P.sub.(-111) attributed to a (-111) plane
of the ZrO.sub.2 layer and a peak P.sub.(-211) attributed to a
(-211) plane of the ZrO.sub.2 layer were confirmed. In FIG. 10, a
ratio R of an intensity of the peak P.sub.(-211) to an intensity of
the peak P.sub.(-1111) is shown.
[0101] As shown in FIG. 10, it was found that for the samples in
which the intensity ratio R is 0.36 or less, the evaluation of
durability is more favorable as compared with a case where the
intensity ratio R is larger than 0.36.
[0102] As shown in FIGS. 11 and 12, in Experimental Examples 1 and
2, an intensity of a peak P.sub.(111) attributed to a (111) plane
of the ZrO.sub.2 layer was higher than an intensity of a peak
P.sub.(-2111) attributed to a (-211) plane of the ZrO.sub.2
layer.
[0103] The present disclosure is not limited to the embodiments
described above, and various modifications may be made. For
example, the present disclosure includes substantially the same
configurations as the configurations described in the embodiments.
The substantially the same configurations are, for example,
configurations having the same functions, methods, and results, or
configurations having the same objects and effects. Further, the
present disclosure includes configurations in which non-essential
parts of the configurations described in the embodiments are
substituted. Further, the present disclosure includes
configurations having the same effects as in the configurations
described in the embodiments, or configurations capable of
achieving the same objects as in the configurations described in
the embodiments. In addition, the present disclosure includes
configurations in which a known technique is added to the
configurations described in the embodiments.
* * * * *