U.S. patent application number 12/696325 was filed with the patent office on 2010-06-03 for method of forming thick layer by screen printing and method of forming piezoelectric actuator of inkjet head.
This patent application is currently assigned to Samsung Electronics Co., Ltd. Invention is credited to Jae-woo Chung, Hwa-sun Lee, Kyo-yeol LEE, Tae-kyung Lee, Seung-mo Lim.
Application Number | 20100132176 12/696325 |
Document ID | / |
Family ID | 38427737 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132176 |
Kind Code |
A1 |
LEE; Kyo-yeol ; et
al. |
June 3, 2010 |
METHOD OF FORMING THICK LAYER BY SCREEN PRINTING AND METHOD OF
FORMING PIEZOELECTRIC ACTUATOR OF INKJET HEAD
Abstract
A method to form a thick layer by screen printing and a method
to form a piezoelectric actuator of an inkjet head. The method to
form the thick layer including forming a guide groove in a surface
to a predetermined depth, and forming the thick layer by applying a
material to the surface inside the guide groove through screen
printing. The method to form the piezoelectric actuator including
forming an insulating layer on a top surface of a vibration plate
and forming a guide groove in the top surface of the vibration
plate or an insulating layer to a predetermined depth at a position
corresponding to each of a plurality of pressure chambers, forming
a lower electrode on the top surface of the insulating layer;
forming a piezoelectric layer inside the guide groove by screen
printing, and forming an upper electrode on a top surface of the
piezoelectric layer.
Inventors: |
LEE; Kyo-yeol; (Yongin-si,
KR) ; Lee; Tae-kyung; (Suwon-si, KR) ; Chung;
Jae-woo; (Yongin-si, KR) ; Lee; Hwa-sun;
(Suwon-si, KR) ; Lim; Seung-mo; (Suwon-si,
KR) |
Correspondence
Address: |
STANZIONE & KIM, LLP
919 18TH STREET, N.W., SUITE 440
WASHINGTON
DC
20006
US
|
Assignee: |
Samsung Electronics Co.,
Ltd
Suwon-si
KR
|
Family ID: |
38427737 |
Appl. No.: |
12/696325 |
Filed: |
January 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11581334 |
Oct 17, 2006 |
7677707 |
|
|
12696325 |
|
|
|
|
Current U.S.
Class: |
29/25.35 |
Current CPC
Class: |
B41J 2002/14491
20130101; Y10T 29/42 20150115; H05K 3/1216 20130101; B41J 2/1646
20130101; H05K 3/107 20130101; B41J 2/1631 20130101; B41J 2/14233
20130101; B41J 2/161 20130101; B41J 2/1626 20130101 |
Class at
Publication: |
29/25.35 |
International
Class: |
H01L 41/22 20060101
H01L041/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2006 |
KR |
2006-15628 |
Claims
1. A method of forming a piezoelectric actuator on a vibration
plate of an inkjet head, the method comprising: forming an
insulating layer on a top surface of the vibration plate; forming a
guide groove at a top surface of the vibration plate or the
insulating layer to a predetermined depth at a position
corresponding to a pressure chamber of the inkjet head; forming a
lower electrode on the top surface of the insulating layer;
applying a piezoelectric material to a top surface of the lower
electrode inside the guide groove by screen printing to form a
piezoelectric layer; and forming an upper electrode on a top
surface of the piezoelectric layer.
2. The method of claim 1, wherein the piezoelectric material
comprises a paste.
3. The method of claim 1, wherein the guide groove is formed at the
top surface of the vibration plate, and then the insulating layer
is formed on the top surface of the vibration plate.
4. The method of claim 1, wherein the insulating layer is formed on
the top surface of the vibration plate, and then the guide groove
is formed at the top surface of the insulating layer.
5. The method of claim 1, wherein the insulating layer is a silicon
oxide layer.
6. The method of claim 1, wherein the forming of the lower
electrode comprises depositing a conductive metal on the top
surface of the insulating layer to a predetermined thickness.
7. The method of claim 6, wherein the forming of the lower
electrode comprises sequentially depositing a Ti layer and a Pt
layer through sputtering.
8. The method of claim 1, wherein the guide groove has the same
contour as a desired contour of the piezoelectric layer.
9. The method of claim 1, wherein the forming of the guide groove
comprises forming a guide groove having a same contour as a desired
contour of the piezoelectric layer after the lower electrode is
formed at the top surface of the insulating layer.
10. The method of claim 8, wherein the guide groove has a width
corresponding to the width of the pressure chamber.
11. The method of claim 1, wherein the applying of the
piezoelectric material comprises applying a piezoelectric material
paste inside the guide groove in such a manner that the width of
the piezoelectric material paste applied is smaller than the width
of the guide.
12. The method of claim 11, wherein the applying of the
piezoelectric material paste further comprises: allowing the
piezoelectric material paste applied inside the guide groove to
spread laterally to have a width corresponding to the width of the
guide groove.
13. The method of claim 11, wherein the applying of the
piezoelectric material paste further comprises: allowing the
piezoelectric material paste applied inside the guide groove to
spread laterally to have a uniform thickness, a uniform width, and
a straightened vertical outer edge.
14. The method of claim 1, wherein the forming of the upper
electrode comprises applying an electrode material paste to the top
surface of the piezoelectric layer by screen printing.
15. The method of claim 14, further comprising: sintering the
piezoelectric layer and the upper electrode.
16. The method of claim 1, wherein the forming of the upper
electrode comprises depositing a conductive metal on the top
surface of the piezoelectric layer to a predetermined thickness by
sputtering.
17. The method of claim 16, further comprising: sintering the
piezoelectric layer prior to the forming of the upper
electrode.
18. A method of forming a piezoelectric actuator, the method
comprising: forming guide grooves at a first surface of a vibration
plate; forming a lower electrode along the first surface of the
vibration plate, including the guide grooves; applying a
piezoelectric material to the lower electrode at the guide grooves;
and forming an upper electrode over the piezoelectric material.
19. The method of claim 18, wherein the piezoelectric material is a
paste.
20. The method of claim 18, wherein the applying of the
piezoelectric material includes spreading the piezoelectric
material along an entire surface of the guide groove.
21. The method of claim 20, wherein the applying of the
piezoelectric material comprises screen printing the piezoelectric
material to form a piezoelectric layer.
22. The method of claim 18, further comprising: forming an
insulating layer over the first surface of the vibration plate
before forming the lower electrode along the first surface of the
vibration plate.
23. The method of claim 22, wherein: the forming of the guide
grooves at a first surface of the vibration plate comprises forming
of guide grooves at a surface of the insulating layer; and the
forming of the lower electrode along the first surface of the
vibration plate, including the guide grooves comprises forming a
lower electrode along a top surface of the insulating layer,
including the guide grooves.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of prior application Ser.
No. 11/581,334, filed Oct. 17, 2006, in the U.S. Patent and
Trademark Office, which claims the benefit under 35 U.S.C.
.sctn.119 of Korean Patent Application No. 10-2006-15628, filed on
Feb. 17, 2006, in the Korean Intellectual Property Office, the
disclosure of which is incorporated herein in its entirety by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present general inventive concept relates to a method of
forming a thick layer more uniformly by screen printing, and a
method of forming a piezoelectric actuator of an inkjet head using
the method of forming the thick layer.
[0004] 2. Description of the Related Art
[0005] Inkjet heads are devices for printing an image on a printing
medium by ejecting ink droplets onto a desired region of the
printing medium. Depending on an ink ejecting method, the inkjet
heads can be classified into two types: thermal inkjet heads and
piezoelectric inkjet heads. A thermal inkjet head generates bubbles
in an ink to be ejected by using heat and ejects the ink utilizing
an expansion of the bubbles, and a piezoelectric inkjet head ejects
an ink using a pressure generated by deforming a piezoelectric
material.
[0006] FIG. 1A is a sectional view illustrating a conventional
piezoelectric inkjet head, and FIG. 1B illustrates a sectional view
taken along line A-A' of FIG. 1A. The conventional piezoelectric
inkjet head illustrated in FIGS. 1A and 1B is formed by a
conventional screen printing method.
[0007] Referring to FIGS. 1A and 1B, a manifold 11, a plurality of
restrictors 12, and a plurality of pressure chambers 13 forming an
ink flow channel are formed in a flow channel plate 10 of the
conventional piezoelectric inkjet head. A vibration plate 20, which
can be deformed by piezoelectric actuators 40, is bonded to a top
surface of the flow channel plate 10, and a nozzle plate 30 in
which a plurality of nozzles 31 are formed is bonded to a bottom
surface of the flow channel plate 10. The vibration plate 20 can be
formed integrally with the flow channel plate 10, and the nozzle
plate 30 can also be formed integrally with the flow channel plate
10.
[0008] The manifold 11 is an ink passage for supplying ink from an
ink reservoir (not illustrated) to the respective pressure chambers
13, and the restrictors 12 are ink passages allowing inflow of ink
from the manifold 11 to the pressure chambers 13. The pressure
chambers 13 are filled with and eject the supplied ink and are
arranged at one side or both sides of the manifold 11. The nozzles
31 are formed through the nozzle plate 30 and are connected to the
respective pressure chambers 13. The vibration plate 20 is bonded
to the top surface of the flow channel plate 10 to cover the
pressure chambers 13. The vibration plate 20 is deformed by the
operation of the piezoelectric actuators 40. Thus, pressures in the
respective pressure chambers 13 change and the ink is ejected from
the pressure chambers 13 by the operation of the piezoelectric
actuators 40. Each of the piezoelectric actuators 40 includes a
lower electrode 41, a piezoelectric layer 42, and an upper
electrode 43 that are sequentially stacked on the vibration plate
20. The lower electrode 41 is formed on the entire surface of the
vibration plate 20 as a common electrode. The piezoelectric layer
42 is formed on the lower electrode 41 above each of the pressure
chambers 13. The upper electrode 43 is formed on the piezoelectric
layer 42 as a driving electrode for applying a voltage to the
piezoelectric layer 42.
[0009] In the conventional piezoelectric inkjet head, the
piezoelectric actuator 40 is usually formed as follows. The lower
electrode 41 is formed by sputtering a metal to a predetermined
thickness on a top surface of the vibration plate 20. The
piezoelectric layer 42 is formed by applying a piezoelectric
ceramic material paste to a predetermined thickness to a top
surface of the lower electrode 41 through screen printing, and by
sintering the applied piezoelectric ceramic material paste. The
upper electrode 43 is formed by applying a conductive material to a
top surface of the piezoelectric layer 42 by screen printing and
sintering the applied conductive material.
[0010] When forming the piezoelectric layer 42, the piezoelectric
ceramic material paste is applied to the lower electrode 41 to a
thickness of several tens of micrometers, and then the
piezoelectric ceramic material paste is dried and sintered to
obtain a thick layer for the piezoelectric layer 42. However, since
the piezoelectric ceramic material paste applied to the lower
electrode 41 is thick, the piezoelectric ceramic material paste
spreads outward with time. This makes the piezoelectric layer 42
relatively thicker at a center portion and thinner at edge portions
as illustrated in FIG. 1B, such that a thickness and a width of the
piezoelectric layer 42 are not uniform. Further, an outer edge of
the piezoelectric layer 42 can be curved although a straight outer
edge is preferable. Accordingly, the overall shape of the
piezoelectric layer 42 can be irregularly curved.
[0011] Furthermore, due to the unevenness of the piezoelectric
layer 42, the thickness and the width of the upper electrode 43
formed on the piezoelectric layer 42 may not be uniform. In
addition, the distance between the lower electrode 41 and the upper
electrode 43 is not constant because of the uneven thickness of the
piezoelectric layer 42, and thus an electric field cannot be
uniformly formed between the lower electrode 41 and the upper
electrode 43.
[0012] Additionally, nozzle density should be high to realize
high-quality printing such as high-resolution and high-speed
printing. The nozzle density is usually denoted using "cpi (channel
per inch)," and the resolution of an image is usually denoted using
"dpi (dot per inch)." To increase the nozzle density, the distance
between adjacent pressure chambers 13 should be reduced.
Accordingly, the distance between adjacent piezoelectric layers 42
should be reduced. However, as described above, since the
piezoelectric layer 42 formed by a conventional method has an
uneven width, the piezoelectric layer 42 may easily make contact
with an adjacent piezoelectric layer 42 when they are formed closer
to each other, making it difficult to increase the nozzle density
much more.
[0013] As mentioned above, in the conventional method of forming a
thick layer by screen printing, the thickness and width of the
piezoelectric layer 42 of the piezoelectric actuator 40 cannot be
uniformly formed. Further, the conventional method makes it
difficult to increase the nozzle density of the inkjet head.
SUMMARY OF THE INVENTION
[0014] The present general inventive concept provides a method of
forming a thick layer by screen printing and a method of forming a
piezoelectric actuator of an inkjet head using the method of
forming the thick layer. The method allows a piezoelectric layer to
have a uniform width and thickness, and also allows the nozzle
density of the inkjet head to be increased.
[0015] Additional aspects and advantages of the present general
inventive concept will be set forth in part in the description
which follows and, in part, will be obvious from the description,
or may be learned by practice of the general inventive concept.
[0016] The foregoing and/or other aspects and utilities of the
present general inventive concept may be achieved by providing a
method of forming a thick layer on a surface by screen printing,
the method including forming a guide groove in the surface to a
predetermined depth, and applying a paste material inside the guide
groove formed on the surface through screen printing.
[0017] The guide groove may have the same contour as a desired
contour of the thick layer.
[0018] A width of the material applied to the inside of the guide
groove may be smaller than the width of the guide groove such that,
the paste material is allowed to spread laterally inside the guide
groove and the paste material has a width corresponding to the
width of the guide groove and a uniform thickness.
[0019] The amount of the paste material applied to the inside of
the guide groove may be such that a thick layer of the paste
material has a uniform thickness.
[0020] A thick layer formed of the paste material may have a
thickness of about several tens of micrometers.
[0021] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
a method of forming a piezoelectric actuator on a vibration plate
of an inkjet head, the method including forming an insulating layer
on a top surface of the vibration plate, forming a guide groove at
a top surface of the vibration plate or the insulating layer to a
predetermined depth at a position corresponding to a pressure
chamber of the inkjet head, forming a lower electrode on the top
surface of the insulating layer, applying a piezoelectric material
to a top surface of the lower electrode inside the guide groove by
screen printing to form a piezoelectric layer, and forming an upper
electrode on a top surface of the piezoelectric layer.
[0022] The piezoelectric material may be a paste.
[0023] The guide groove may be formed at the top surface of the
vibration plate, and then the insulating layer may be formed on the
top surface of the vibration plate.
[0024] The insulating layer may be formed on the top surface of the
vibration plate, and then the guide groove may be formed at the top
surface of the insulating layer.
[0025] The insulating layer may be a silicon oxide layer.
[0026] The forming of the lower electrode may include depositing a
conductive metal on the top surface of the insulating layer to a
predetermined thickness.
[0027] The forming of the lower electrode may include sequentially
depositing a Ti later and a Pt layer through sputtering.
[0028] The guide groove may have the same contour as a desired
contour of the piezoelectric layer.
[0029] The forming of the guide groove may include forming a guide
groove having a same contour as a desired contour of the
piezoelectric layer after the lower electrode is formed at the top
surface of the insulating layer.
[0030] The guide groove may have a width corresponding to the width
of the pressure chamber.
[0031] The applying of the piezoelectric material may include
applying the piezoelectric material paste inside the guide groove
in such a manner that the width of the piezoelectric material paste
applied is smaller than the width of the guide groove.
[0032] The applying of the piezoelectric material paste may further
include allowing the piezoelectric material paste applied inside
the guide groove to spread laterally to have a width corresponding
to the width of the guide groove.
[0033] The applying of the piezoelectric material paste may further
include allowing the piezoelectric material paste applied inside
the guide groove to spread laterally to have a uniform thickness, a
uniform width, and a straightened vertical outer edge.
[0034] The forming of the upper electrode may include applying an
electrode material paste to the top surface of the piezoelectric
layer by screen printing.
[0035] The method may also include sintering the piezoelectric
layer and the upper electrode.
[0036] The forming of the upper electrode may include depositing a
conductive metal on the top surface of the piezoelectric layer to a
predetermined thickness by sputtering.
[0037] The method may also include sintering the piezoelectric
layer prior to the forming of the upper electrode.
[0038] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
a method of forming a piezoelectric actuator, the method including
forming guide grooves at a first surface of a vibration plate,
forming a lower electrode along the first surface of the vibration
plate, including the guide grooves, applying a piezoelectric
material to the lower electrode at the guide grooves, and forming
an upper electrode over the piezoelectric material.
[0039] The piezoelectric material may be a paste.
[0040] The applying of the piezoelectric material may include
spreading the piezoelectric material along an entire surface of the
guide groove.
[0041] The applying of the piezoelectric material may include
screen printing the piezoelectric material to form a piezoelectric
layer.
[0042] The method may further include forming an insulating layer
over the first surface of the vibration plate before forming the
lower electrode along the first surface of the vibration plate.
[0043] The forming of the guide grooves at a first surface of the
vibration plate may include forming of guide grooves at a surface
of the insulating layer, and the forming of the lower electrode
along the first surface of the vibration plate, including the guide
grooves may include forming a lower electrode along a top surface
of the insulating layer, including the guide grooves.
[0044] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
a piezoelectric inkjet head including a flow channel plate having a
plurality of pressure chambers, a vibration plate bonded to a top
surface of the flow channel plate to cover the pressure chambers,
an insulating layer formed on a top surface of the vibration plate,
a nozzle plate having a plurality of nozzles corresponding to the
pressure chambers, bonded to a bottom surface of the flow channel
plate, and a plurality of piezoelectric actuators bonded to a top
surface of the insulating layer to provide ink-ejecting forces to
the respective pressure chambers by deforming the vibration plate,
wherein a top surface of the insulating layer or a top surface of
the vibration plate has a plurality of guide grooves of a
predetermined depth and width, and the plurality of guide grooves
are disposed in positions corresponding to the plurality of
pressure chambers.
[0045] The top surface of the vibration plate may have the
plurality of guide grooves.
[0046] The top surface of the insulating layer vibration plate may
have the plurality of guide grooves.
[0047] The plurality of piezoelectric actuators may include a lower
electrode formed on a top surface of the insulating layer as a
common electrode, a plurality of piezoelectric layers formed inside
each of the plurality of guide grooves on a top surface of the
lower electrode, and a plurality of upper electrodes, each formed
on a top surface of the plurality of piezoelectric layers as
driving electrodes.
[0048] The piezoelectric layer may have a uniform width, a uniform
thickness, and a straightened vertical outer edge.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] These and/or other aspects and advantages of the present
general inventive concept will become apparent and more readily
appreciated from the following description of the embodiments,
taken in conjunction with the accompanying drawings of which:
[0050] FIG. 1A is a sectional view illustrating a conventional
piezoelectric inkjet head, and FIG. 1B illustrates a sectional view
taken along line A-A' of FIG. 1A;
[0051] FIGS. 2A through 2E illustrate a method of forming a
piezoelectric actuator of an inkjet head using a method of forming
a thick layer by screen printing according to an embodiment of the
present general inventive concept; and
[0052] FIGS. 3A through 3C illustrate a method of forming a
piezoelectric actuator of an inkjet head using a method of forming
a thick layer by screen printing according to another embodiment of
the present general inventive concept.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] Reference will now be made in detail to the embodiments of
the present general inventive concept, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present general inventive
concept by referring to the figures.
[0054] FIGS. 2A through 2E illustrate a method of forming a
piezoelectric actuator of an inkjet head using a method of forming
a thick layer by screen printing according to an embodiment of the
present general inventive concept.
[0055] Referring to FIG. 2A, the piezoelectric inkjet head may
include a plurality of plates forming an ink flow channel. For
example, three plates may be used: a flow channel plate 110, a
vibration plate 120, and a nozzle plate 130. A manifold (not
illustrated), a plurality of restrictors (not illustrated), and a
plurality of pressure chambers 113 may be formed in the flow
channel plate 110, and the vibration plate 120 may be bonded to a
top surface of the flow channel plate 110 to cover the pressure
chambers 113. The nozzle plate 130 may be bonded to a bottom
surface of the flow channel plate 110. A plurality of nozzles 131
are formed through the nozzle plate 130 corresponding to the
pressure chambers 113. The flow channel plate 110 may be formed
with a manifold (not illustrated) and a plurality of restrictors
(not illustrated). Meanwhile, the vibration plate 120 can be formed
integrally with the flow channel plate 110, and the nozzle plate
130 can also be formed integrally with the flow channel plate
110.
[0056] A plurality of piezoelectric actuators 140 provide
ink-ejecting forces to the respective pressure chambers 113 by
deforming the vibration plate 120 (refer to FIG. 2E). The plurality
of piezoelectric actuators 140 can be formed on the vibration plate
120 through the following operations.
[0057] Referring again to FIG. 2A, an insulating layer 121 is
formed on the entire top surface of the vibration plate 120. The
insulating layer 121 can have a thickness of about 1 .mu.m to about
2 .mu.m. When the vibration plate 120 is formed of silicon, the
insulating layer 121 may be formed of a silicon oxide.
[0058] Referring to FIG. 2B, a plurality of guide grooves 125 are
formed in a top surface of the insulating layer 121 to a
predetermined depth. The guide grooves 125 may be formed by
partially removing the insulating layer 121 through a removal
method such as etching, using a patterned photoresist as an etch
mask. For example, when the insulating layer 121 has a thickness of
about 1 .mu.m to about 2 .mu.m as described above, the guide
grooves 125 can have a depth approximately equal to half the
thickness of the insulation layer 121 (i.e., about 0.5 .mu.m to
about 1 .mu.m). The guide grooves 125 are formed in the insulating
layer 121 at locations corresponding to the respective pressure
chambers 113. The guide grooves 125 may be formed to have the same
contour as a desired contour of the piezoelectric layers 142 (refer
to FIG. 2D) of the piezoelectric actuators 140, or may be formed to
have the same contour as a desired contour of the piezoelectric
layer 142 taking into consideration the formation of the lower
electrode 141, as described below. The width of the guide grooves
125 may be substantially the same as that of the pressure chambers
113.
[0059] Referring to FIG. 2C, the lower electrode 141 is formed on
the insulating layer 121 as a common electrode. The lower electrode
141 may be formed by depositing a conductive metal on an entire top
surface of the insulating layer 121 to a predetermined thickness.
Although the lower electrode 141 can be formed of a single metal
layer, the lower electrode 141 may also be formed of two metal
layers such as Ti and Pt layers. For example, the Ti metal layer
can be formed to a thickness of about 400 .ANG. by sputtering, and
the Pt metal layer can be formed to a thickness of about 5000 .ANG.
by sputtering.
[0060] Referring to FIG. 2D, the piezoelectric layers 142 are
formed on the lower electrode 141 inside the guide grooves 125. In
detail, a piezoelectric material paste, such as a lead zirconate
titanate (PZT) ceramic material paste, may be applied to the lower
electrode to a predetermined thickness (e.g., about 30 .mu.m to
about 60 .mu.m) by screen printing. While a piezoelectric material
paste may be used, the current present general inventive concept is
not limited thereto, and other forms of piezoelectric material may
be used which result in the intended general inventive concept. The
piezoelectric material paste may be applied in such a manner that a
width of the piezoelectric layers 142 is slightly smaller than that
of the guide grooves 125. Since the applied piezoelectric material
paste may laterally spread with time, the piezoelectric layers 142
are leveled and widened into a more uniform shape as illustrated in
FIG. 2D. The width of the piezoelectric layers 142 is restricted by
the width of the grooves 125, such that the width of the
piezoelectric layers 142 can be uniform. Further, a thickness of
the piezoelectric layers 142 can be relatively uniform when
compared with the related art. The piezoelectric layers 142 may be
dried naturally or dried forcibly by using a hot plate heated up to
about 100.degree. C. Other suitable drying methods can be selected
depending on characteristics of the piezoelectric material paste
applied, such as a viscosity of the piezoelectric material
paste.
[0061] Referring to FIG. 2E, upper electrodes 143 are formed on the
respective piezoelectric layers 142 as driving electrodes. The
upper electrodes 143 may be formed by applying an electrode
material, paste, such as an Ag--Pd paste, to top surfaces of the
piezoelectric layers 142 by screen printing and drying the applied
electrode material paste. Then, the piezoelectric layers 142 and
the upper electrodes 143 may be sintered at a temperature of about
900.degree. C..about.1200.degree. C. After that, the piezoelectric
layers 142 may shrink to a thickness of about 10 .mu.m to about 30
.mu.m.
[0062] As illustrated in FIG. 2E, after the above-described
operations the piezoelectric actuators 140 can have a sequentially
stacked structure formed by the lower electrode 141, the
piezoelectric layers 142, and the upper electrodes 143. The
piezoelectric layers 142 of the piezoelectric actuators 140 can
have a relatively uniform width and thickness, and outer vertical
edges of the piezoelectric actuators can be straightened owing to
the guide grooves 125.
[0063] While the upper electrodes 143 can be formed by screen
printing as described above, the present general inventive concept
is not limited thereto and the upper electrodes 143 can also be
formed by sputtering. For example, the piezoelectric layers 142 may
be sintered before the upper electrode layers 143 are formed. Then,
an electrode material, such as a conductive metal like Au or Pt, is
deposited on the piezoelectric layers 142 to a predetermined
thickness by sputtering, thereby forming the upper electrodes 143
as illustrated in FIG. 2E.
[0064] FIGS. 3A through 3C illustrate a method of forming a
piezoelectric actuator of an inkjet head using a method of forming
a thick layer by screen printing according to another embodiment of
the present general inventive concept. The method illustrated in
FIGS. 3A through 3C is similar to the method illustrated in FIGS.
2A through 2E, except that guide grooves are formed in a top
surface of a vibration plate. Thus, the current embodiment will now
be described briefly referencing similar processes illustrated in
FIGS. 2A through 2E.
[0065] Referring to FIG. 3A, a plurality of guide grooves 126 are
formed in a top surface of the vibration plate 120 to a
predetermined depth. The guide grooves 126 may be formed by
partially removing the top surface of the vibration plate 120
through a removal method, such as etching, using a patterned
photoresist as an etch mask. Since the vibration plate 120 may have
a thickness of about 10 .mu.m to about 20 .mu.m, depending on the
size of pressure chambers 113, the vibration plate 120 is not
affected by the guide grooves 126 when a depth thereof is about 0.5
.mu.m about 1 .mu.m. The guide grooves 126 are formed in the
vibration plate 120 at locations corresponding to the respective
pressure chambers 113. The guide grooves 126 may be formed to have
the same contour as a desired contour of the piezoelectric layers
142 (refer to FIG. 3C) of the piezoelectric actuators 140 or may be
formed to have the same contour as a desired contour of the
piezoelectric layer 142 taking into consideration the formation of
an insulating layer 121 and a lower electrode 141, as described
below. The width of the guide grooves 126 may be substantially the
same as that of the pressure chambers 113.
[0066] Referring to FIG. 3B, an insulating layer 121 and a lower
electrode 141 are sequentially formed on the entire top surface of
the vibration plate 120. The insulating layer 121 and the lower
electrode 141 are formed in the same way as for the embodiment
illustrated in FIGS. 2A through 2E.
[0067] Referring to FIG. 3C, piezoelectric layers 142 are formed on
the lower electrode 141 inside the guide grooves 126 by screen
printing, and upper electrodes 143 are formed on the piezoelectric
layers 142 by screen printing or sputtering. The piezoelectric
layers 142 and the upper electrodes 143 are formed in the same way
as in the embodiment illustrated in FIGS. 2A through 2E.
[0068] As illustrated in FIG. 3C, after the above-described
operations, the complete piezoelectric actuators 140 can have a
sequentially stacked structure formed by the lower electrode 141,
the piezoelectric layers 142, and the upper electrodes 143.
[0069] According to the present general inventive concept, a
piezoelectric layer of a piezoelectric actuator can be uniformly
formed and a more uniform electric field can be formed between the
lower electrode and the upper electrode since the distance between
the lower electrode and the upper electrode is more uniform.
Further, the width of the piezoelectric layer can be uniformly
controlled, so that the nozzle density of the inkjet head can be
easily increased.
[0070] Although a few embodiments of the present general inventive
concept have been shown and described, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
general inventive concept, the scope of which is defined in the
appended claims and their equivalents.
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