Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-06-20
2003-09-23
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C310S328000, C310S366000
Reexamination Certificate
active
06623111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer piezoelectric device and a method of producing the same. More particularly, the present invention relates to a multilayer piezoelectric device used for producing a piezoelectric actuator including a plurality of separately drivable actuator units and a method of producing the multilayer piezoelectric device, and a piezoelectric actuator including such a multilayer piezoelectric device.
2. Description of the Related Art
Conventional print heads in inkjet printers generally are driven using a piezoelectric actuator. An example of such a piezoelectric actuator is disclosed in Japanese Unexamined Patent Application Publication No. 11-320881. The piezoelectric actuator described in this publication has an external shape shown in FIG.
13
and includes a multilayer piezoelectric device
31
.
The multilayer piezoelectric device
31
includes a piezoelectric layered body
37
, which is a rectangular ceramic sintered body, including a driving section
34
and a connecting section
36
. In the driving section
34
, a plurality of first driving internal electrodes
32
and a plurality of second driving internal electrodes
33
are alternately placed upon each other through a piezoelectric layer. In the connecting section
36
, a plurality of connecting internal electrodes
35
are placed upon each other through a piezoelectric layer. The piezoelectric layer of the driving section
34
is a portion that stretches and contracts along a lamination direction, called a d33 direction, in response to application of an alternating voltage thereto after it has been polarized.
As shown in
FIG. 13A
, which illustrates the multilayer piezoelectric device
31
viewed from one side thereof, end portions of the first driving internal electrodes
32
are exposed from only one of opposing side surfaces
37
a
and
37
b
of the piezoelectric layered body
37
, that is, from only the first side surface
37
a,
whereas end portions of the first driving internal electrodes
32
are not exposed from the second side surface
37
b.
As shown in
FIG. 13B
, which shows the multilayer piezoelectric device
31
viewed from the other side thereof, end portions of the second driving internal electrodes
33
are exposed from the second side surface
37
b,
whereas end portions are not exposed from the first side surface
37
a.
End portions of the connecting internal electrodes
35
are exposed from both the first side surface
37
a
and the second side surface
37
b
of the piezoelectric layered body
37
.
Driving-side external electrodes
38
and connection-side external electrodes
39
are each formed in parallel at the first side surface
37
a
of the piezoelectric layered body
37
through a gap
40
of a predetermined width. The first driving internal electrodes
32
and the connecting internal electrodes
35
are separately in electrical conduction with their corresponding external electrodes
38
and
39
. A common-side external electrode
41
is disposed at the second side surface
37
b
of the piezoelectric layered body
37
. The second driving internal electrodes
33
and the connecting internal electrodes
35
are all in electrical conduction with the common-side external electrode
41
.
Here, the common-side external electrode
41
is formed over the entire second side surface
37
b,
while the driving-side external electrodes
38
and the connection-side external electrodes
39
are formed after providing a gap
42
of a predetermined width in the bottom portion of the first side surface
37
a,
that is, after being separated through the gap
42
from the bottom surface of the piezoelectric layered body
37
. Therefore, as shown in
FIG. 14
, the driving section
34
of the multilayer piezoelectric device
31
has a cross-sectional structure such as that shown in FIG.
14
.
A piezoelectric actuator
45
having an external form shown in
FIG. 15
is produced using the multilayer piezoelectric device
31
. More specifically, the multilayer piezoelectric device
31
is secured to a supporting substrate
46
using, for example, an adhesive, and a plurality of slits
47
, which extend in a lamination direction X from the top surface to the bottom surface of the driving section
34
, are formed in the driving section
34
of the piezoelectric layered body
37
of the multilayer piezoelectric device
31
.
As shown in
FIG. 15A
, which shows the piezoelectric actuator
45
viewed from one side thereof, by dividing the first driving internal electrodes
32
and the second driving internal electrodes
33
, and the driving-side external electrodes
38
by the slits
47
, the driving section
34
is divided into a plurality of driving section portions in order to provide a plurality of separately drivable actuator units
48
. Obviously, by these slits
47
, the first driving internal electrodes
32
and the second driving internal electrodes
33
that have been placed upon each other in the driving section
34
are divided.
Here, since the driving-side external electrodes
38
are also divided, a plurality of unit external electrodes
49
corresponding to the separate actuator units
48
are formed. The portions between the connecting section
36
and the driving section
34
of the piezoelectric actuator
45
may be divided by the slits
47
.
FIG. 15B
shows the piezoelectric actuator
45
viewed from the other side thereof.
Although not shown, a flexible printed circuit drawn out from a driving signal source, installed externally of the piezoelectric actuator
45
, is connected to the piezoelectric actuator
45
including the actuator units
48
. By applying alternating voltage between each unit external electrode
49
and the common-side external electrode
41
, or, actually, between each unit external electrode
49
and each connection-side external electrode
39
, connected to the common-side external electrode
41
through each connecting internal electrode
35
, each actuator unit
48
is driven.
As described above, in the multilayer piezoelectric device
31
used for producing the piezoelectric actuator
45
, the driving-side external electrodes
38
and the connection-side external electrodes
39
are disposed at the first side surface
37
a
of the piezoelectric layered body
37
, and the common-side external electrode
41
is disposed at the second side surface
37
b
of the piezoelectric layered body
37
. As shown in
FIG. 16
, when forming these external electrodes
38
,
39
, and
41
, a deposition mask
50
for completely covering portions of the piezoelectric layered body
37
other than the side surfaces
37
a
and
37
b
is provided. After placing the piezoelectric layered body
37
inside the deposition mask
50
, an electrode formation process, that is, evaporation or sputtering, is carried out. The arrows shown in
FIG. 16
indicate the directions of film deposition.
However, when the piezoelectric layered body
37
is placed inside the deposition mask
50
, a gap
51
is formed between them, and the deposition mask
50
undergoes thermal deformation at the time of film deposition, so that a film-deposition precision of the order of only ±0.1 mm can be obtained. As shown in
FIG. 14
, the driving-side external electrodes
38
and the connection-side external electrodes
39
, disposed at the first side surface
37
a
of the multilayer piezoelectric device
31
having a height H of 1.0 mm, need to be separated from the bottom surface of the piezoelectric layered body
37
through the gap
42
having a width W of 0.1 mm. Therefore, problems such as those described below arise.
Since a high film-deposition precision cannot be achieved, the width W of the gap
42
becomes large or small, so that the heights of the locations where the driving-side external electrodes
38
and the connection-side external electrodes
39
are disposed become large or small. When the heights of the portions where the driving-side external electrodes
38
are disposed become large, so that the width W of the gap
Do An H.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Judy
LandOfFree
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