U.S. patent application number 12/042999 was filed with the patent office on 2008-09-11 for piezoelectric device, process for producing the same, and liquid discharge device.
Invention is credited to Takamichi FUJII, Yoshikazu Hishinuma, Takayuki Naono.
Application Number | 20080218559 12/042999 |
Document ID | / |
Family ID | 39540695 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080218559 |
Kind Code |
A1 |
FUJII; Takamichi ; et
al. |
September 11, 2008 |
PIEZOELECTRIC DEVICE, PROCESS FOR PRODUCING THE SAME, AND LIQUID
DISCHARGE DEVICE
Abstract
A piezoelectric device includes a substrate; and a laminated
film formed above the substrate. The laminated film includes a
lower electrode layer, a piezoelectric layer, and an upper
electrode layer formed in this order, and the lower electrode layer
is a metal electrode layer containing as one or more main
components one or more nonnoble metals and/or one or more nonnoble
alloys. Preferably, the one or more main components are one or more
of the metals Cr, W, Ti, Al, Fe, Mo, In, Sn, Ni, Cu, Co, and Ta,
and alloys of the metals.
Inventors: |
FUJII; Takamichi;
(Ashigarakami-gun, JP) ; Naono; Takayuki;
(Ashigarakami-gun, JP) ; Hishinuma; Yoshikazu;
(Ashigarakami-gun, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
39540695 |
Appl. No.: |
12/042999 |
Filed: |
March 5, 2008 |
Current U.S.
Class: |
347/68 ; 216/17;
310/357; 310/364 |
Current CPC
Class: |
H01L 41/1876 20130101;
H01L 41/0477 20130101; B41J 2202/03 20130101; H01L 41/0475
20130101; H01L 41/316 20130101; Y10T 29/42 20150115; B41J 2/14233
20130101; H01L 41/0478 20130101; H01L 41/0973 20130101 |
Class at
Publication: |
347/68 ; 310/364;
310/357; 216/17 |
International
Class: |
H01L 41/047 20060101
H01L041/047; B41J 2/045 20060101 B41J002/045; H01L 41/08 20060101
H01L041/08; H01L 41/22 20060101 H01L041/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2007 |
JP |
055664/2007 |
Claims
1. A piezoelectric device comprising: a substrate; and a laminated
film being formed above said substrate, and including, a lower
electrode layer, a piezoelectric layer formed on said lower
electrode layer, and an upper electrode layer formed on said
piezoelectric layer; wherein said lower electrode layer is a metal
electrode layer containing as one or more main components one or
more of nonnoble metals and nonnoble alloys.
2. A piezoelectric device according to claim 1, wherein said lower
electrode layer contains as one or more main components one or more
of metals Cr, W, Ti, Al, Fe, Mo, In, Sn, Ni, Cu, Co, and Ta, and
alloys of the metals.
3. A piezoelectric device according to claim 2, wherein said lower
electrode layer contains as one or more main components one or more
of iron and alloys of iron.
4. A piezoelectric device according to claim 1, wherein said lower
electrode layer is formed by vapor phase epitaxy.
5. A piezoelectric device according to claim 3, wherein said lower
electrode layer is formed by vapor phase epitaxy.
6. A piezoelectric device according to claim 1, wherein said lower
electrode layer is patterned by use of wet etching.
7. A piezoelectric device according to claim 3, wherein said lower
electrode layer is patterned by use of wet etching.
8. A piezoelectric device according to claim 1, wherein said
piezoelectric layer is formed of a perovskite oxide, and is (100)
oriented.
9. A piezoelectric device according to claim 3, wherein said
piezoelectric layer is formed of a perovskite oxide, and is (100)
oriented.
10. A piezoelectric device according to claim 1, wherein said
piezoelectric layer has spontaneous polarization with a
negatively-polarized side and a positively-polarized side, the
negatively-polarized side of the spontaneous polarization is
oriented toward the lower electrode layer, the positively-polarized
side of the spontaneous polarization is oriented toward the upper
electrode layer, said upper electrode layer realizes a grand
electrode to which a fixed voltage is applied, said lower electrode
layer is separated into address electrodes, and variable voltages
are applied to the address electrodes.
11. A piezoelectric device according to claim 3, wherein said
piezoelectric layer has spontaneous polarization with a
negatively-polarized side and a positively-polarized side, the
negatively-polarized side of the spontaneous polarization is
oriented toward the lower electrode layer, the positively-polarized
side of the spontaneous polarization is oriented toward the upper
electrode layer, said upper electrode layer realizes a grand
electrode to which a fixed voltage is applied, said lower electrode
layer is separated into address electrodes, and variable voltages
are applied to the address electrodes.
12. A piezoelectric device according to claim 10, further
comprising a driver which drives said address electrodes so as to
vary the voltages applied to the address electrodes.
13. A piezoelectric device according to claim 11, further
comprising a driver which drives said address electrodes so as to
vary the voltages applied to the address electrodes.
14. A piezoelectric device according to claim 10, wherein said
piezoelectric layer is formed at 400.degree. C. to 600.degree.
C.
15. A piezoelectric device according to claim 11, wherein said
piezoelectric layer is formed at 400.degree. C. to 600.degree.
C.
16. A piezoelectric device according to claim 14, wherein said
piezoelectric layer is formed by vapor phase epitaxy using plasma
under a condition that the difference between a floating potential
and a plasma potential in plasma generated during formation of the
piezoelectric layer is 10 to 35 V.
17. A piezoelectric device according to claim 15, wherein said
piezoelectric layer is formed by vapor phase epitaxy using plasma
under a condition that the difference between a floating potential
and a plasma potential in plasma generated during formation of the
piezoelectric layer is 10 to 35 V.
18. A piezoelectric device according to claim 14, wherein said
piezoelectric layer is formed under a condition satisfying
inequalities, -0.2Ts+100<Vs-Vf.ltoreq.-0.2Ts+130, and
10.ltoreq.Vs-Vf.ltoreq.35, where Ts represents in degrees
centigrade a value of film-formation temperature, and Vs-Vf
represents in volts a difference between a floating potential and a
plasma potential in plasma generated during formation of the
piezoelectric layer.
19. A piezoelectric device according to claim 15, wherein said
piezoelectric layer is formed under a condition satisfying
inequalities, -0.2Ts+100<Vs-Vf.ltoreq.-0.2Ts+130, and
10.ltoreq.Vs-Vf.ltoreq.35, where Ts represents in degrees
centigrade a value of film-formation temperature, and Vs-Vf
represents in volts a difference between a floating potential and a
plasma potential in plasma generated during formation of the
piezoelectric layer.
20. A process for producing said piezoelectric device according to
claim 1, comprising the steps of: (a) forming a first film for said
lower electrode layer; (b) patterning said first film; (c) forming
a second film for said piezoelectric layer; and (d) patterning said
second film.
21. A process for producing according to claim 20, wherein said
step (b) and said step (d) are concurrently performed after said
step (a) and said step (c) are performed.
22. A process for producing according to claim 21, wherein said
step (b) and said step (d) are performed by use of wet etching.
23. A liquid discharge device comprising: said piezoelectric device
according to claim 1; and a discharge member being formed
integrally with or separately from said substrate in the
piezoelectric device, and including, a liquid-reserve chamber which
reserves liquid, and a liquid-discharge outlet through which said
liquid is externally discharged from the liquid-reserve chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a piezoelectric device, a
process for producing the piezoelectric device, and a liquid
discharge device using the piezoelectric device.
[0003] 2. Description of the Related Art
[0004] Currently, piezoelectric devices constituted by a
piezoelectric layer and upper and lower electrode layers are used,
for example, as actuators installed in inkjet recording heads. In
the piezoelectric devices, the piezoelectric layer expands and
contracts in correspondence with increase and decrease in the
strength of an electric field applied from the upper and lower
electrode layers to the piezoelectric layer.
[0005] The inkjet recording heads have a basic structure in which a
piezoelectric device as above and a diaphragm are attached to an
ink-nozzle member. The ink-nozzle member has a plurality of ink
chambers and a plurality of ink-discharge outlets. The ink chambers
reserve ink, and the ink is externally discharged from the ink
chambers through the ink-discharge outlets. Normally, the
piezoelectric layer is patterned into separate pieces corresponding
to the plurality of ink chambers.
[0006] The perovskite oxides such as PZT-based oxides are known as
materials suitable for the piezoelectric layer, where PZT stands
for lead titanate zirconate. The PZT-based piezoelectric layer can
be formed, for example, by vapor phase epitaxy such as sputtering.
Depending on the composition and the material of the dopant, some
types of PZT-based piezoelectric layers formed by vapor phase
epitaxy such as sputtering normally have spontaneous polarization
oriented upward (i.e., the negatively-polarized side of the
PZT-based piezoelectric layer is the lower side, and the
positively-polarized side of the PZT-based piezoelectric layer is
the upper side) unless special polarization processing is performed
immediately after the formation of the PZT-based piezoelectric
layers.
[0007] As disclosed in Japanese Unexamined Patent Publication No.
2005-209912, noble metals such as iridium (Ir) and platinum (Pt)
are widely used in the lower electrode layers of the conventional
piezoelectric devices. However, the noble metals such as Ir and
platinum Pt are expensive. That is, use of the noble metals is not
preferable from the viewpoint of the cost. In addition, the noble
metals such as Ir are uneasy to etch. Specifically, the noble
metals such as Ir cannot be etched by wet etching, and can be
etched by only ion etching among various types of dry etching, so
that patterning of the noble metals such as Ir is difficult.
[0008] Therefore, conventionally, the lower electrode layer is not
patterned, and is formed to have a uniform film structure, and each
of the PZT-based piezoelectric layer and the upper electrode layer
is patterned into separate pieces corresponding to a plurality of
ink chambers. In this case, it is necessary that the lower
electrode layer be a grand electrode (to which a fixed voltage is
applied), and the upper electrode layer realize address electrodes
(to which variable voltages are applied). The drivers for driving
the piezoelectric devices are usually positive-output drivers.
Thus, conventionally, polarization-inversion processing is
performed in order to make the spontaneous polarization oriented
downward (i.e., so that the negatively-polarized side of the
piezoelectric layer becomes the upper side, and the
positively-polarized side of the piezoelectric layer becomes the
lower side) before the upper electrode layer is driven by
positive-output drivers.
[0009] However, in the case where a PZT-based piezoelectric layer
has upward spontaneous polarization after formation of the
PZT-based piezoelectric layer unless special polarization
processing is performed, it is inefficient to perform
polarization-inversion processing of the PZT-based piezoelectric
layer, and the polarization-inversion processing may not be able to
realize sufficient piezoelectric performance which the PZT-based
piezoelectric layer can intrinsically exhibit. In view of the above
circumstances, the present inventors consider that if the lower
electrode layer can be patterned into address electrodes and the
address electrodes can be driven by positive-output drivers, the
polarization-inversion processing of the PZT-based piezoelectric
layer can be dispensed with, and it is possible to achieve the
sufficient piezoelectric performance which the PZT-based
piezoelectric layer can intrinsically exhibit.
SUMMARY OF THE INVENTION
[0010] The present invention has been made in view of the above
circumstances.
[0011] The first object of the present invention is to provide a
piezoelectric device having a lower electrode layer which exhibits
satisfactory etching performance and can be patterned at low
cost.
[0012] The second object of the present invention is to provide a
process for producing the above piezoelectric device.
[0013] The third object of the present invention is to provide a
liquid discharge device using the above piezoelectric device.
[0014] (I) In order to accomplish the above first object, a
piezoelectric device according to the first aspect of the present
invention is provided. The piezoelectric device according to the
first aspect of the present invention comprises a substrate; and a
laminated film formed above the substrate. The laminated film
includes a lower electrode layer, a piezoelectric layer formed on
the lower electrode layer, and an upper electrode layer formed on
the piezoelectric layer, and the lower electrode layer is a metal
electrode layer containing as one or more main components one or
more nonnoble metals and/or one or more nonnoble alloys.
[0015] In this specification, the term "nonnoble metals" means the
metals other than noble metals.
[0016] Preferably, the piezoelectric device according to the first
aspect of the present invention may further have one or any
possible combination of the following additional features (i) to
(ix).
[0017] (i) The lower electrode layer contains as one or more main
components one or more of metals Cr, W, Ti, Al, Fe, Mo, In, Sn, Ni,
Cu, Co, and Ta, and alloys of the metals.
[0018] In this specification, the term "main component" means a
component the content of which is 50% or higher by weight.
[0019] (ii) The lower electrode layer contains as one or more main
components one or more of iron (Fe) and alloys of iron.
[0020] (iii) The lower electrode layer is formed by vapor phase
epitaxy.
[0021] (iv) The lower electrode layer is patterned by use of wet
etching.
[0022] (v) The piezoelectric layer is formed of a perovskite oxide,
and is (100) oriented, although the piezoelectric layer may contain
inevitable impurities.
[0023] (vi) The piezoelectric layer has spontaneous polarization,
the negatively-polarized side of the spontaneous polarization is
oriented toward the lower electrode layer, the positively-polarized
side of the spontaneous polarization is oriented toward the upper
electrode layer, the upper electrode layer realizes a grand
electrode to which a fixed voltage is applied, the lower electrode
layer is separated into address electrodes, and variable voltages
are applied to the address electrodes.
[0024] (vii) In the piezoelectric device having the feature (vi),
the piezoelectric device may further comprise a driver which drives
the address electrodes so as to vary the voltages applied to the
address electrodes.
[0025] (viii) In the piezoelectric device having the feature (vi),
the piezoelectric layer is formed at 400.degree. C. to 600.degree.
C.
[0026] (ix) In the piezoelectric device having the feature (vi),
the piezoelectric layer is formed by vapor phase epitaxy using
plasma under a condition that the difference between a floating
potential Vf and a plasma potential Vs in plasma generated during
formation of the piezoelectric layer is 10 to 35 V.
[0027] Japanese Unexamined Patent Publication No. 62 (1987)-165381
discloses a piezoelectric device using plates of stainless steel as
electrodes. In the piezoelectric device, bulk electrodes (realized
by the plates of stainless steel) and bulk piezoelectric bodies are
alternately piled. That is, none of the electrodes and the
piezoelectric bodies in the disclosed piezoelectric device are
films as the upper and lower electrode layers and the piezoelectric
layer in the piezoelectric device according to the first aspect of
the present invention. Further, the electrodes and the
piezoelectric bodies in the disclosed piezoelectric device are not
patterned.
[0028] (II) In order to accomplish the above second object, a
process according to the second aspect of the present invention is
provided. The process according to the second aspect of the present
invention is a process for producing the piezoelectric device
according to the first aspect of the present invention. The process
comprises the steps of: (a) forming a first film for the lower
electrode layer; (b) patterning the first film; (c) forming a
second film for the piezoelectric layer; and (d) patterning the
second film.
[0029] Preferably, the process according to the second aspect of
the present invention may further have one or any possible
combination of the following additional features (x) and (xi).
[0030] (x) The step (b) and the step (d) are concurrently performed
after the step (a) and the step (c) are performed.
[0031] (xi) The step (b) and the step (d) are performed by use of
wet etching.
[0032] (III) In order to accomplish the above third object, a
liquid discharge device according to the third aspect of the
present invention is provided. The liquid discharge device
according to the third aspect of the present invention comprises:
the piezoelectric device according to the first aspect of the
present invention; and a discharge member being formed integrally
with or separately from the substrate in the piezoelectric device,
and including, a liquid-reserve chamber which reserves liquid, and
a liquid-discharge outlet through which the liquid is externally
discharged from the liquid-reserve chamber.
[0033] (IV) The present invention has the following advantages.
[0034] In the piezoelectric device according to the first aspect of
the present invention, the lower electrode layer is a metal
electrode layer containing as one or more main components one or
more nonnoble metals and/or one or more nonnoble alloys. Therefore,
the etching performance of the lower electrode layer is
satisfactory, so that the lower electrode layer can be patterned
into address electrodes at low cost by using an inexpensive
technique such as wet etching. Thus, it is unnecessary to perform
the polarization-inversion processing even in the case where the
negatively-polarized side of the spontaneous polarization is
oriented toward the lower electrode layer. Consequently, according
to the present invention, it is possible to produce, at low cost, a
piezoelectric device which exhibits satisfactory piezoelectric
performance.
DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a cross-sectional view schematically illustrating
a cross section of an essential portion of an inkjet recording head
(as a liquid discharge device) having a piezoelectric device
according to an embodiment of the present invention.
[0036] FIG. 2 is a diagram indicating results of XRD measurement of
PZT films and Nb-PZT films which are formed by vapor phase epitaxy
using plasma, where the abscissa corresponds to the film-formation
temperature Ts, and the ordinate corresponds to Vs-Vf.
[0037] FIG. 3 is a schematic diagram of an example of an inkjet
recording apparatus using the inkjet recording head of FIG. 1.
[0038] FIG. 4 is a top view of a portion of the inkjet recording
apparatus of FIG. 3.
[0039] FIG. 5 is an XRD (X-ray diffraction) profile of a
piezoelectric film in a concrete example.
[0040] FIG. 6 is an XRD profile of a piezoelectric film in a
comparison example.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0041] Preferred embodiments of the present invention are explained
in detail below with reference to drawings.
1. Piezoelectric Device and Inkjet Recording Head
[0042] Hereinbelow, the structure of an inkjet recording head (as
an embodiment of the liquid discharge device according to the third
aspect of the present invention) containing a piezoelectric device
(as an embodiment of the piezoelectric device according to the
first aspect of the present invention) is explained with reference
to FIG. 1, which is a cross-sectional view schematically
illustrating a cross section of an essential portion of the inkjet
recording head. In FIG. 1, the dimensions of the illustrated
elements are differentiated from the dimensions of the elements of
the actual inkjet recording head for clarification.
[0043] In outline, the inkjet recording head 3 illustrated in FIG.
1 is constituted by a piezoelectric actuator 2 and an ink-nozzle
member 20, and the piezoelectric actuator 2 is constituted by a
piezoelectric device 1 and a diaphragm 17.
[0044] The piezoelectric device 1 is constituted by a substrate 11
and a laminated film 16 formed on the substrate 11. The laminated
film 16 is produced by forming on the substrate 11 a lower
electrode layer 12, a piezoelectric layer 13, and an upper
electrode layer 14 in this order so that an electric field in the
thickness direction can be applied to each portion (corresponding
to a pixel or an ink chamber) of the piezoelectric layer 13 through
the lower electrode layer 12 and the upper electrode layer 14.
[0045] The piezoelectric actuator 2 is produced by attaching the
diaphragm 17 to the back surface of the substrate 11 of the
piezoelectric device 1 so that the diaphragm 17 can vibrate in
correspondence with expansion and contraction of the piezoelectric
layer 13.
[0046] The inkjet recording head 3 is produced by attaching the
ink-nozzle member 20 to the back surface of the piezoelectric
actuator 2. The ink-nozzle member 20 is a member for reserving and
discharging ink, and comprises ink chambers 21 (as the
liquid-reserve chambers) and ink outlets 22 (as the
liquid-discharge outlets). Each of the ink chambers 21 is connected
to the corresponding one of the ink chambers 21. Each of the ink
chambers 21 reserves the ink, and the ink held in the ink chamber
is discharged out of the ink chamber through the corresponding ink
outlet.
[0047] Alternatively, it is possible to process portions of the
substrate 11 into the diaphragm 17 and the ink-nozzle member 20,
instead of separately preparing the diaphragm 17 and the ink-nozzle
member 20 and attaching the diaphragm 17 and the ink-nozzle member
20 to the piezoelectric device 1. For example, the ink chambers 21
can be formed by etching the corresponding portions of the
substrate 11 from the bottom surface of the substrate 11, and the
diaphragm 17 and the structures of the ink-nozzle member 20 can be
produced by processing the substrate 11 per se.
[0048] In the above inkjet recording head 3, the strength of the
electric field applied to each portion (corresponding to a pixel or
an ink chamber) of the piezoelectric device 1 is increased or
decreased so as to expand or contract each portion of the
piezoelectric device 1 and control the discharge of the ink from
the corresponding one of the ink chambers 21 and the discharge
amount of the ink.
[0049] In the piezoelectric device 1 according to the present
embodiment, the spontaneous polarization of the piezoelectric layer
13 is oriented upward. That is, the negatively-polarized side of
the spontaneous polarization of the piezoelectric layer 13 is
oriented toward the lower electrode layer 12, and the
positively-polarized side of the spontaneous polarization of the
piezoelectric layer 13 is oriented toward the upper electrode layer
14. In addition, the upper electrode layer 14 realizes a grand
(GND) electrode to which a fixed voltage is applied, the lower
electrode layer 12 is separated into address electrodes, and
variable voltages are applied to the address electrodes. The
piezoelectric actuator 2 operates in a deflection vibration mode,
and the lower electrode layer 12 and the piezoelectric layer 13 are
patterned so that the driving voltage applied to an address
electrode corresponding to each ink chamber 21 can be independently
varied. Further, the piezoelectric device 1 is provided with
drivers 15 which drive the piezoelectric device 1 by varying the
voltages applied to the address electrodes constituting the lower
electrode layer 12.
[0050] The material for the substrate 11 is not specifically
limited. For example, the substrate 11 may be made of silicon,
glass, stainless steel, YSZ (yttrium stabilized zirconia),
SrTiO.sub.3, alumina, sapphire, silicon carbide, or the like. In
addition, the substrate 11 may be realized by a laminated substrate
such as the SOI (silicon-on-insulator) substrate, which is produced
by alternately forming on a surface of a silicon substrate one or
more oxide films of SiO.sub.2 and one or more Si active layers.
Further, it is possible to arrange a buffer layer, an adhesion
layer, and the like between the substrate 11 and the lower
electrode 12. The buffer layer is provided for realizing
satisfactory lattice matching between the substrate 11 and the
lower electrode layer 12, and the adhesion layer is provided for
realizing satisfactory adhesiveness between the substrate 11 and
the lower electrode layer 12.
[0051] The lower electrode layer 12 is a metal electrode layer
containing as one or more main components one or more nonnoble
metals and/or one or more nonnoble alloys. Specifically, the lower
electrode layer 12 contains as one or more main components one or
more of metals Cr, W, Ti, Al, Fe, Mo, In, Sn, Ni, Cu, Co, and Ta,
and alloys of these metals. In this case, the etching performance
of the lower electrode layer is satisfactory, so that the lower
electrode layer 12 can be easily patterned by wet etching. In
particular, it is preferable that the lower electrode layer 12
contain as one or more main components one or more of iron (Fe) and
alloys of iron. For example, a main component of the lower
electrode layer 12 may be a stainless steel.
[0052] The main component of the upper electrode layer 14 is not
specifically limited, and may be, for example, one or a combination
of metals such as Au, Pt, and Ir, metal oxides such as TrO.sub.2,
RuO.sub.2, LaNiO.sub.3, and SrRuO.sub.3, and the same materials as
the above examples of the main component of the lower electrode 12.
Further, the thicknesses of the lower and upper electrode layers 12
and 14 are not specifically limited, and are preferably 50 to 500
nm.
[0053] The material for the piezoelectric layer 13 is not
specifically limited. For example, it is preferable that the
piezoelectric layer 13 be basically formed of one or more
perovskite oxides, although the piezoelectric layer 13 may contain
inevitable impurities. It is further preferable that the
piezoelectric layer 13 be basically formed of one or more
perovskite oxides having the composition expressed by the
compositional formula,
A.sub.aB.sub.bO.sub.3, (P)
where A represents one or more A-site elements, B represents one or
more B-site elements, and O represents oxygen atoms. The one or
more A-site elements are one or more elements including lead (Pb),
and the one or more B-site elements are one or more of the
lanthanide series of elements and the elements of Ti, Zr, V, Nb,
Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, and Ni.
Although normally a=1.0 and b=1.0, the value of each of a and b may
deviate from 1.0 within a range in which the composition expressed
by the compositional formula A.sub.aB.sub.bO.sub.3 can form a
perovskite structure. Specifically, the one or more perovskite
oxides for the piezoelectric layer 13 may be:
[0054] (1) lead compounds such as lead titanate, lead titanate
zirconate (PZT), lead zirconate, lead lanthanum titanate, lead
lanthanum titanate zirconate, zirconium magnesium niobate-lead
titanate, zirconium nickel niobate-lead titanate, and the like;
[0055] (2) nonlead compounds such as barium titanate, bismuth
sodium titanate, bismuth potassium titanate, sodium niobate,
potassium niobate, lithium niobate, and the like; and
[0056] (3) one or more mixed crystals of the perovskite oxides
having the composition expressed by the compositional formula
(P).
[0057] Furthermore, it is preferable that the piezoelectric layer
13 be basically formed of one or a mixed crystal of PZT and the
B-site substituted PZTs having the composition expressed by the
compositional formula,
Pb.sub.a(Zr.sub.b1Ti.sub.b2X.sub.b3)O.sub.3, (P-1)
where X represents one or more of the Group V and Group VI metal
elements, a>0, b1>0, b2>0, and b3.gtoreq.0. Although
normally a=1.0 and b1+b2+b3=1.0, the value of each of a and
b1+b2+b3 may deviate from 1.0 within a range in which the
composition expressed by the compositional formula
Pb.sub.a(Zr.sub.b1Ti.sub.b2X.sub.b3)O.sub.3 can form a perovskite
structure.
2. Process for Producing Piezoelectric Device
[0058] Hereinbelow, an example of a process for producing the
piezoelectric device 1 is explained.
[0059] In the first step, the substrate 11 is prepared, and the
lower electrode layer 12 is formed on the substrate 11. It is
possible to form a buffer layer and/or an adhesion layer before the
formation of the lower electrode layer 12, when necessary. After
the formation of the lower electrode layer 12, the piezoelectric
layer 13 is formed on the lower electrode layer 12 in the second
step, and then the piezoelectric layer 13 and the lower electrode
layer 12 are patterned in the third step so that a portion of the
piezoelectric device 1 corresponding to each of the ink chambers 21
can be independently actuated. Thereafter, the upper electrode
layer 14 is formed over the patterned piezoelectric layer 13 in the
fourth step, and the controllers 15 and necessary wirings are
formed in the fifth step. Thus, production of the piezoelectric
device 1 is completed.
[0060] The techniques used for formation of the lower electrode
layer 12, the piezoelectric layer 13, and the upper electrode layer
14 are not specifically limited. For example, the techniques may be
vapor phase epitaxy using plasma such as sputtering, ion beam
sputtering, ion plating, plasma CVD (chemical vapor deposition),
and the like.
[0061] The piezoelectric layer 13 is effectively expanded and
contracted in response to increase and decrease in the strength of
the electric field applied to the piezoelectric layer 13 when the
direction of the electric field coincides with the orientation of a
vector component of the spontaneous polarization axis in the
piezoelectric layer 13. Therefore, it is preferable to use as the
piezoelectric layer 13 an oriented film in which variations in the
orientation of the spontaneous polarization axis are small.
[0062] The crystal structure of the piezoelectric layer 13 is not
specifically limited. In the case where the PZT-based materials are
used, the crystal structure of the piezoelectric layer 13 may be a
tetragonal structure, a rhombohedral structure, or a mixture of the
tetragonal and rhombohedral structures. For example, in the case
where the piezoelectric layer 13 is formed of
Pb.sub.1.3Zr.sub.0.52Ti.sub.0.48O.sub.3, the crystal structure of
the piezoelectric layer 13 can be a monocrystal tetragonal
structure, a mixture of the tetragonal and rhombohedral structures,
or a monocrystal rhombohedral structure according to the film
formation condition.
[0063] As mentioned before, according to the present invention, the
spontaneous polarization is oriented upward. That is, the
negatively-polarized side of the spontaneous polarization of the
piezoelectric layer 13 is oriented toward the lower electrode layer
12, and the positively-polarized side of the spontaneous
polarization of the piezoelectric layer 13 is oriented toward the
upper electrode layer 14. Since the polarization-inversion
processing of a PZT-based piezoelectric layer may not be able to
realize sufficient piezoelectric performance of the PZT-based
piezoelectric layer, it is preferable that the PZT-based
piezoelectric layer have upward spontaneous polarization
immediately after formation of the PZT-based piezoelectric layer
even when no special polarization processing is performed.
[0064] For example, in the case where the piezoelectric layer 13
contains a rhombohedral phase (i.e., in the case where the
piezoelectric layer 13 is formed of a rhombohedral structure or a
mixture of tetragonal and rhombohedral structures), it is
preferable that the piezoelectric layer 13 be (100) oriented. Since
the spontaneous polarization of the rhombohedral crystal is
oriented along the <111> direction, the spontaneous
polarization has a vector component in the upward direction when
the piezoelectric layer 13 is (100) oriented.
[0065] As mentioned in the "Description of the Related Art,"
conventionally, the patterning of the lower electrode layer is
difficult. Therefore, conventionally, the PZT-based piezoelectric
layer and the upper electrode layer are patterned into separate
pieces corresponding to a plurality of ink chambers, the lower
electrode layer is used as the grand electrode, and the separate
pieces of the upper electrode layer are used as address electrodes
to be driven. Further, conventionally, polarization-inversion
processing is performed so as to make the spontaneous polarization
of the PZT-based piezoelectric layer oriented downward, and the
upper electrode layer is driven by positive-output drivers.
[0066] On the other hand, according to the present embodiment, the
lower electrode layer 12 is a metal electrode layer containing as
one or more main components one or more nonnoble metals and/or one
or more nonnoble alloys. Such a metal electrode layer exhibits
satisfactory etching performance, and can be easily patterned by
the wet etching, which is less expensive than the dry etching. For
example, in the case where the main component of the lower
electrode layer 12 is stainless steel as iron alloy, the
piezoelectric layer 13 can be easily patterned by wet etching
using, for example, a 1:1:3 mixture of 37 weight percent
hydrochloric acid, 70 weight percent nitric acid, and water.
Therefore, the lower electrode layer 12 can be patterned into
desired pieces so as to produce the address electrodes. Thus,
according to the present embodiment, it is possible to process the
lower electrode layer 12 into the address electrodes without
performing the polarization-inversion processing, and produce the
piezoelectric device 1, in which the address electrodes
constituting the lower electrode layer can be driven by
positive-output drivers.
[0067] As explained above, it is preferable that the lower
electrode layer 12 and the piezoelectric layer 13 be patterned by
wet etching. The patterning of the lower electrode layer 12 and the
piezoelectric layer 13 may be performed either concurrently or
separately. However, it is preferable that the lower electrode
layer 12 and the piezoelectric layer 13 be concurrently patterned
from the viewpoint of reduction of the number of process steps.
[0068] In the case where the piezoelectric layer 13 is formed by
vapor phase epitaxy such as sputtering, the film-formation
temperature is preferably 400.degree. C. to 600.degree. C. It is
difficult to stably grow perovskite crystals below 400.degree. C.
In the case where the piezoelectric layer 13 of a lead-containing
material such as a PZT-based material is formed, lead is likely to
be lost when the film-formation temperature is above 600.degree. C.
In addition, in the case where the piezoelectric layer 13 is formed
above 600.degree. C., regardlessly of inclusion or noninclusion of
lead, the difference in the thermal expansion coefficient between
the substrate 11 and the piezoelectric layer 13 imposes stress on
the piezoelectric layer 13, for example, during the operation of
forming the film or during the operation of cooling the
piezoelectric layer 13 after the film formation, so that cracks and
the like are likely to occur in the piezoelectric layer 13.
[0069] The present inventors have found that a preferable condition
for forming the piezoelectric layer 13 by vapor phase epitaxy using
plasma such as sputtering is that the difference Vs-Vf between the
floating potential Vf and the plasma potential Vs in plasma
generated during formation of the piezoelectric layer should be 10
to 35 V.
[0070] In this specification, it is assumed that the plasma
potential Vs and the floating potential Vf are measured by the
single-probe technique using the Langmuir probe. In order to
prevent inclusion of errors caused by adhesion of a portion of a
film being formed or the like to the probe, the tip of the probe is
maintained in the vicinity of the substrate (for example,
approximately 10 mm above the substrate) in the measurement, and
the measurement is completed in the shortest possible time. The
potential difference Vs-Vf between the plasma potential Vs and the
floating potential Vf, measured in volts (V), can be directly
converted into an electron temperature expressed in electron volts
(eV), where 1 eV corresponds to 11,600 K (Kelvin).
[0071] The present inventors have produced samples of the
piezoelectric layer by sputtering using targets of PZT
(Pb.sub.1.3Zr.sub.0.52Ti.sub.0.48O.sub.3) or Nb-PZT
(Pb.sub.1.3Zr.sub.0.43Ti.sub.0.44Nb.sub.0.13O.sub.3) at different
film-formation temperatures Ts with different potential differences
Vs-Vf, and evaluated the structures of the samples by performing
XRD (X-ray diffraction) measurement. The results of the evaluation
are indicated in FIG. 2. In FIG. 2, the abscissa corresponds to the
film-formation temperature Ts, and the ordinate corresponds to the
potential difference Vs-Vf. The marks at a plurality of points in
FIG. 2 indicate the evaluation results of the samples formed at the
respective temperatures Ts with the respective potential
differences Vs-Vf. The filled circles indicate that the samples are
evaluated as having a satisfactory structure, the filled triangles
indicate that the samples are evaluated as having a structure which
has a problem but is acceptable, and the crosses indicate that the
samples are evaluated as having an unsatisfactory structure.
Further, in FIG. 2, the samples formed at the film-formation
temperature Ts of 525.degree. C. are Nb-PZT films, and the samples
formed at the other temperatures are PZT films.
[0072] For example, among the samples formed under the condition
that the potential difference Vs-Vf is approximately 12, the XRD
result of the sample formed at the film-formation temperature Ts of
450.degree. C. indicates that the sample formed at 450.degree. C.
is mainly constituted by a pyrochlore phase, so that the sample
formed at 450.degree. C. is evaluated as being unsatisfactory. The
XRD result of the sample formed at the film-formation temperature
Ts of 475.degree. C. indicates that a pyrochlore phase begins to
appear in the sample formed at 475.degree. C., so that the sample
formed at 475.degree. C. is evaluated as having a problem but being
acceptable. The XRD results of the samples formed in the range of
500.degree. C. to 550.degree. C. indicate that perovskite crystals
having satisfactory crystal orientation are stably obtained in the
samples formed in the range of 500.degree. C. to 550.degree. C., so
that the samples formed in the range of 500.degree. C. to
550.degree. C. are evaluated as being satisfactory. The XRD results
of the sample formed at the film-formation temperatures of
575.degree. C. and 600.degree. C. indicate that the crystal
orientation begins to break in the sample formed at 575.degree. C.
Therefore, the sample formed at 575.degree. C. is evaluated as
having a problem but being acceptable, and the sample formed at
600.degree. C. is evaluated as being unsatisfactory.
[0073] Consequently, as indicated in FIG. 2, in the case where the
films of PZT or Nb-PZT are formed under the condition that the
film-formation temperature Ts (.degree. C.) and the difference
between the floating potential Vf (V) and a plasma potential Vs (V)
in plasma generated during film formation satisfy the
inequalities,
400.ltoreq.Ts.ltoreq.600,
-0.2Ts+100<Vs-Vf.ltoreq.-0.2Ts+130, and
10.ltoreq.Vs-Vf.ltoreq.35,
it is possible to stably grow perovskite crystals containing the
pyrochlore phase only in very small portions, and stably suppress
lead loss (Pb defect). Therefore, according to the present
embodiment, it is possible to stably form a high-quality
piezoelectric layer having satisfactory crystal structure and
composition.
[0074] As explained above, in the piezoelectric device 1 according
to the present embodiment, the lower electrode layer 12, the
piezoelectric layer 13, and the upper electrode layer 14 are formed
in this order on the substrate 11, and the lower electrode layer 12
is a metal electrode layer containing as one or more main
components one or more nonnoble metals and/or one or more nonnoble
alloys. Since such a metal electrode layer exhibits satisfactory
etching performance, and can be easily patterned by wet etching,
which is less expensive than dry etching, the lower electrode layer
12 can be patterned into the address electrodes. Therefore, it is
unnecessary to perform the polarization-inversion processing even
although the negatively-polarized side of the spontaneous
polarization of the piezoelectric layer 13 is oriented toward the
lower electrode layer 12. Consequently, according to the present
invention, it is possible to produce, at low cost, the
piezoelectric device 1 exhibiting satisfactory piezoelectric
performance.
3. Inkjet Recording Apparatus
[0075] Hereinbelow, an example of an inkjet recording apparatus
having the inkjet recording head 3 is explained with reference to
FIGS. 3 and 4. FIG. 3 is a schematic diagram illustrating an
outline of an example of an inkjet recording apparatus having the
inkjet recording head 3 of FIG. 1, and FIG. 4 is a top view of a
portion of the inkjet recording apparatus of FIG. 3.
[0076] As schematically illustrated in FIG. 3, the inkjet recording
apparatus 100 comprises a printing unit 102, an ink
reserve-and-load unit 114, a sheet feeding unit 118, a decurling
unit 120, a suction-type belt conveyer 122, a print detection unit
124, and a sheet output unit 126. The printing unit 102 comprises a
plurality of inkjet recording heads 3K, 3C, 3M, and 3Y
corresponding to inks of different colors (specifically, black (K),
cyan (C), magenta (M), and yellow (Y)). Hereinafter, the inkjet
recording heads may be referred to as heads. The ink
reserve-and-load unit 114 reserves the inks to be supplied to the
heads 3K, 3C, 3M, and 3Y. The sheet feeding unit 118 feeds a
recording sheet 116. The decurling unit 120 eliminates curl of the
recording sheet 116. The suction-type belt conveyer 122 is arranged
to face the nozzle faces (ink-discharge faces) of the printing unit
102, and conveys the recording sheet 116 while maintaining the
flatness of the recording sheet 116. The print detection unit 124
reads an image printed on the recording sheet 116 by the printing
unit 102. The sheet output unit 126 externally outputs a printed
recording sheet 116.
[0077] Each of the heads 3K, 3C, 3M, and 3Y constituting the
printing unit 102 corresponds to the inkjet recording head
according to the present embodiment as explained before. In order
to realize a linear head (explained later), each inkjet recording
head used in the inkjet recording apparatus 100 comprises a
plurality of ink chambers and a plurality of ink-discharge
outlets.
[0078] The decurling unit 120 performs decurling of the recording
sheet 116 by heating the recording sheet 116 with a heating drum
130 so as to eliminate the curl produced in the sheet feeding unit
118.
[0079] In the case where the inkjet recording apparatus 100 uses
roll paper, a cutter 128 for cutting the roll paper into desired
size is arranged in the stage following the decurling unit 120 as
illustrated in FIG. 3. The cutter 128 is constituted by a fixed
blade 128A and a round blade 128B. The fixed blade 128A has a
length equal to or greater than the width of the conveying path of
the recording sheet 116, and is arranged on the side opposite to
the print side of the recording sheet 116. The round blade 128B is
arranged opposite to the fixed blade 128A on the print side of the
recording sheet 116, and moves along the fixed blade 128A. In the
inkjet recording apparatuses using cut paper, the cutter 128 is
unnecessary.
[0080] After the roll paper is decurled and cut into the recording
sheet 116, the recording sheet 116 is transferred to the
suction-type belt conveyer 122. The suction-type belt conveyer 122
is constituted by rollers 131 and 132 and an endless belt 133. The
rollers 131 and 132 are placed apart and the endless belt 133 is
looped around the rollers 131 and 132 in such a manner that at
least portions of the endless belt 133 which face the nozzle faces
of the printing unit 102 and the sensor face of the print detection
unit 124 are flat and horizontal.
[0081] The endless belt 133 has a width greater than the width of
the recording sheet 116, and a great number of suction pores (not
shown) are formed through the endless belt 133. A suction chamber
134 is arranged inside the loop of the endless belt 133 at the
position opposite to the nozzle faces of the printing unit 102 and
the sensor face of the print detection unit 124, and suctioned by a
fan 135, so that a negative pressure is generated in the suction
chamber 134, and the recording sheet 116 on the endless belt 133 is
held by suction.
[0082] The power of a motor (not shown) is transmitted to at least
one of the rollers 131 and 132 so that the endless belt 133 is
driven clockwise in FIG. 3, and the recording sheet 116 held on the
endless belt 133 is moved from left to right in FIG. 3.
[0083] In the case of borderless printing, ink can be deposited on
the endless belt 133. Therefore, in order to clean the endless belt
133, a belt cleaning unit 136 is arranged at a predetermined
(appropriate) position outside the loop of the endless belt 133 and
the printing region.
[0084] A heating fan 140 is arranged on the upstream side of the
printing unit 102 above the conveying path of the recording sheet
116 (which is realized by the suction-type belt conveyer 122). The
heating fan 140 blows heated air to the recording sheet 116 before
printing so as to heat the recording sheet 116 and facilitate
drying of deposited ink.
[0085] Each of the heads 3K, 3C, 3M, and 3Y in the printing unit
102 is a so-called full-line type head, which is a linear head
having a length corresponding to the maximum width of the recording
sheet 116, and being arranged across the width of the recording
sheet 116 (i.e., in the main scanning direction perpendicular to
the feeding direction of the recording sheet 116) as illustrated in
FIG. 4. Specifically, each of the heads 3K, 3C, 3M, and 3Y is a
linear head in which the aforementioned plurality of ink-discharge
outlets (nozzles) are arrayed over a length exceeding the maximum
length of a side of the largest recording sheet 116 on which the
inkjet recording apparatus 100 can print an image. The heads 3K,
3C, 3M, and 3Y corresponding to the inks of the different colors
are arrayed upstream in this order along the feeding direction as
illustrated in FIG. 4. Thus, a color image can be printed on the
recording sheet 116 by discharging the inks of the different colors
while conveying the recording sheet 116.
[0086] The print detection unit 124 may be constituted by, for
example, a line sensor which takes an image formed of spots of the
inks discharged from the printing unit 102, and detects, from the
image taken by the line sensor, incomplete discharge, which can be
caused by clogging of a nozzle or the like.
[0087] A rear drying unit 142 for drying the printed surface of the
recording sheet 116 is arranged in the stage following the print
detection unit 124. For example, the rear drying unit 142 is
realized by a heating fan or the like. Since it is preferable to
avoid contact with the printed surface before the ink on the
printed surface is completely dried, it is preferable that the rear
drying unit 142 dry the ink on the printed surface by blowing
heated air.
[0088] In order to control the glossiness of the image printed on
the recording sheet 116, a heating-and-pressurizing unit 144 is
arranged in the stage following the rear drying unit 142. The
heating-and-pressing unit 144 comprises a pressure roller 145
having a surface having predetermined projections and depressions,
and transfers the predetermined projections and depressions to the
printed surface of the recording sheet 116 by pressing the printed
surface with the pressure roller 145 while heating the printed
surface.
[0089] Finally, the printed recording sheet 116 produced as above
is outputted from the sheet output unit 126. It is preferable to
separately output test prints and prints for practical use.
Therefore, the sheet output unit 126 includes a first output unit
126A for the prints for practical use and a second output unit 126B
for the test prints. Although not shown, the inkjet recording
apparatus 100 further comprises a sorting unit which sorts the
printed recording sheets 116 into the test prints and the prints
for practical use, and sends the test prints to the first output
unit 126B, and the prints for practical use to the second output
unit 126A.
[0090] Further, in the case where both of a test image and an image
for practical use are concurrently printed on a recording sheet
116, it is possible to arrange a cutter 148, and separate a first
portion of the recording sheet 116 on which the test image is
printed and a second portion of the recording sheet 116 on which
the image for practical use is printed.
4. Concrete Examples of the Present Invention
[0091] The present inventors have produced a concrete example of an
inkjet recording head having a piezoelectric device according to
the present invention and a comparison example of an inkjet
recording head having a conventional piezoelectric device as
indicated below.
4.1 Concrete Example
[0092] In the concrete example of the inkjet recording head
including a piezoelectric device according to the present
invention, a piezoelectric layer of PZT is formed by using a target
of Ph.sub.1.3Zr.sub.0.52Ti.sub.0.48O.sub.3 in the atmosphere of a
mixture of Ar and 1.0 voltage percent of O.sub.2 at the pressure of
0.5 Pa.
[0093] Before the formation of the PZT piezoelectric layer, a
substrate on which a lower electrode layer is formed is prepared.
Specifically, an adhesion layer of Ti having a thickness of 10 nm
and a lower electrode layer of the type 430 stainless steel (e.g.,
SUS430 according to Japanese Industrial Standard (JIS)) having a
thickness of 200 nm are formed in this order on a SOI
(Si/SiO.sub.2/Si/SiO.sub.2) substrate.
[0094] Thereafter, the piezoelectric layer is formed while the
substrate with the lower electrode layer is placed in a floating
arrangement and a ground is arranged at a position apart from the
substrate. At this time, the plasma potential Vs and the floating
potential Vf (i.e., the potential in the vicinity of the substrate
(approximately 10 mm above the substrate)) are measured, and the
potential difference Vs-Vf of approximately 35 V is obtained.
During the formation of the piezoelectric layer, the substrate
temperature is 480.degree. C., and the RF (radio frequency) power
is 500 W. The thickness of the formed piezoelectric layer is 4
micrometers.
[0095] FIG. 5 is an XRD (X-ray diffraction) profile of the
piezoelectric film in the concrete example. As indicated in FIG. 5,
the obtained piezoelectric layer is (100) oriented, and the degree
of orientation is 90% or higher.
[0096] The present inventors have measured the piezoelectric
constant d.sub.31 of the PZT piezoelectric film by using a
cantilever, and obtained the value of the piezoelectric constant
d.sub.31 as 130 pm/V. In addition, the present inventors have
confirmed that the negatively-polarized side of the spontaneous
polarization of the piezoelectric layer is oriented toward the
lower electrode layer, and the positively-polarized side of the
spontaneous polarization of the piezoelectric layer is oriented
toward the upper electrode layer.
[0097] After the piezoelectric film of PZT is formed, the
piezoelectric film is masked with photoresist, and then the
piezoelectric film of PZT and the lower electrode layer of the type
430 stainless steel are patterned by wet etching. A BHF (buffered
hydrogen fluoride) solution (e.g., a 1:6 mixture solution of a 40
weight percent ammonium fluoride solution and fluoric acid) is used
as an etchant solution in the etching of the piezoelectric film,
and a 1:1:3 mixture of 37 weight percent hydrochloric acid, 70
weight percent nitric acid, and water is used as an etchant
solution in the etching of the lower electrode layer.
[0098] Then, the upper electrode layer is formed on the patterned
piezoelectric film of PZT, and finally, ink nozzles including ink
chambers with the dimensions of 500.times.500 micrometers and
accompanying ink-discharge outlets are formed on the back side of
the SOI substrate by processing the back surface of the SOI
substrate by RIE (reactive ion etching) so that an active layer in
the SOI substrate can operate as a diaphragm. Thus, production of
the inkjet recording head is completed.
[0099] The present inventors have driven the inkjet recording head
by using the lower electrode layer as the address electrodes and
the upper electrode layer as the grand electrode, and using
positive-output drivers for driving the address electrodes. The
present inventors have confirmed that the inkjet recording head
produced as above operates satisfactorily.
4.2 Comparison Example
[0100] The comparison example of the inkjet recording head
including the conventional piezoelectric device is produced in a
similar manner to the above concrete example except that the lower
electrode layer is formed of iridium (Ir). FIG. 6 is an XRD profile
of the piezoelectric film in the comparison example. As indicated
in FIG. 6, the obtained piezoelectric layer in the comparison
example is (100) oriented, and the degree of orientation is 90% or
higher.
[0101] The present inventors have measured the piezoelectric
constant d.sub.31 of the PZT piezoelectric film in the comparison
example by using a cantilever, and obtained the value of the
piezoelectric constant d.sub.31 as 130 pm/V. In addition, the
present inventors have confirmed that the orientation of the
spontaneous polarization in the piezoelectric layer is similar to
the concrete example.
[0102] After the piezoelectric film of PZT is formed, the
piezoelectric film is masked with photoresist, and then the
piezoelectric film is patterned by wet etching under a similar
condition to the concrete example. However, the lower electrode
layer of Ir is difficult to wet etch. In addition, since it is
difficult to realize, in dry etching, a desirable ratio between the
etching rates of the lower electrode layer of Ir and the Si-based
substrate underlying the lower electrode layer, the lower electrode
layer of Ir is also difficult to satisfactorily dry etch.
Therefore, the lower electrode layer is not patterned, and is
uniformly formed.
[0103] Subsequently, the upper electrode layer and the ink nozzles
are formed in similar manners to the concrete example. Thereafter,
in order to drive the upper electrode layer as address electrodes,
polarization-inversion processing of the piezoelectric layer is
performed at room temperature. Thus, production of the inkjet
recording head as the comparison example is completed.
[0104] The present inventors have driven the inkjet recording head
as the comparison example by using the upper electrode layer as the
address electrodes and the lower electrode layer as the grand
electrode, and using positive-output drivers for driving the
address electrodes. The present inventors have observed that the
displacement achieved by the inkjet recording head as the
comparison example is as small as approximately one-third of the
displacement achieved by the inkjet recording head as the concrete
example according to the present invention.
5. Additional Matters
[0105] The piezoelectric devices according to the present invention
can be preferably used in piezoelectric actuators, diaphragms, and
the like which are mounted in the inkjet recording heads, the
magnetic recording-and-reproduction heads, MEMS (micro
electromechanical systems) devices, micropumps, ultrasonic probes,
and the like.
* * * * *