Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-05-25
2003-02-04
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S069000
Reexamination Certificate
active
06513916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to ink jet heads and, more specifically, to an ink jet head which has been improved to enable reliable connection of an external electrode and an electrode connecting portion by wire bonding or the like. The invention also relates to a method of manufacturing such an ink jet head.
2. Description of the Background Art
In recent years, a non impact printer such as an ink jet type printer which is adapted to provide colorization and higher gray scale level is rapidly diffused taking the place of an impact printer. Among such printers, a drop on demand type printer which ejects only a required amount of ink for printing has received a great deal of attention because of its high printing efficiency, low cost and low running cost and the like. A Kaiser type printer using a piezoelectric element or a thermal jet type printer is primarily used.
However, a Kaiser type printer is not readily reduced in size and thus unsuitable for greater integration. A thermal jet type printer is suitable for greater integration, but must meet strict requirements for long-lasting ink since it utilizes for ejection the energy of bubbles produced in the ink by a heater. In addition, in the thermal jet type printer, the heater life is limited and power consumption is considerable.
To solve the above mentioned problems, an ink jet type printer utilizing a shear mode of a piezoelectric material has been proposed. In this printer, an electric field is applied in the direction orthogonal to the polarizing direction of the piezoelectric material with use of an electrode formed on an ink channel wall of the piezoelectric material to deform the channel wall in the shear mode, so that ink droplets are ejected by pressure vibration caused at the time. As such, the ink jet type printer is adapted to provide higher density of nozzles, lower power consumption, and higher driving frequency. The structure of such an ink jet head utilizing the shear mode will be described with reference to FIG.
20
.
Referring to
FIG. 20
, the ink jet head includes a base member
1
having a plurality of grooves
4
formed in a piezoelectric material which has been subjected to a polarization process in the vertical direction, a cover member
2
including an ink supply port
21
and a common ink chamber
22
, and a nozzle plate
9
having nozzles
10
, which members are bonded together to define ink channels
4
. On the upper half portion of the channel wall
3
, an electrode
5
is formed for application of an electric field. The rear end portion of the ink channel is formed in an R shape corresponding to a diameter of a dicing blade used for groove formation. The portion denoted by
6
has a shallow groove as an electrode connecting portion which is also formed by the dicing blade for connection with respect to an external portion. The electrode formed in shallow groove portion
6
is connected to an external electrode
8
such as a flexible printed circuit board at the rear end portion of shallow groove portion
6
by a bonding wire
7
.
Now, a manufacturing method of the ink jet head shown in
FIG. 20
will be described with reference to
FIG. 21 and 22
.
As shown in
FIG. 21
, a dry resist film
11
allowing a dicing process is laminated on a piezoelectric material
12
which has been vertically subjected to a polarization process.
Then, as shown in
FIG. 22
, a groove to be ink channel
4
as well as, shallow groove portion
6
(slope) are formed by the dicing blade. Thereafter, diagonal vapor deposition is performed in the A and B directions in
FIG. 22
, with the incident direction set in such a way that a metal to be an electrode adheres only to the upper half portion of channel wall
3
. Then, dry resist film
11
is lifted off to provide a base material
1
as an actuator having a metal film
5
formed on the upper half portion of channel wall
3
and in shallow groove portion
6
as shown in FIG.
20
.
Returning to
FIG. 20
, cover member
2
has ink supply port
21
and common ink chamber
22
which are formed by machining or sand blasting. If the sand blasting is employed, it may be performed after masking the portion excluding ink supply port
21
and common ink chamber
22
with a resist film or a metal mask.
If nozzle plate
9
is formed of a polymeric material, nozzles, each having a prescribed size, are formed by an excimer laser process Alternatively, nozzles may be formed in a metal material by punching or the like. Thus manufactured base member
1
, cover member
2
and nozzle plate
9
are bonded together by an adhesive in a desired positional relationship.
Thus manufactured ink jet head has ink supply port
21
connected to an external ink storage tank (not shown) and common ink chamber
22
through which ink is supplied to the plurality of ink channels
4
. The electrode formed on the upper half portion of channel wall
3
is connected at the R-shape portion of the ink channel rear end portion to provide the same potential in respective ink channel
4
and connected to external electrode
8
through shallow groove portion
6
. The electrodes formed at respective ink channels
4
are individually connected to external electrode
8
.
A voltage is applied by external electrode
8
such that a prescribed ink channel is selected in accordance with printing data and an electric field is applied in the direction orthogonal to the polarizing direction of channel wall
3
. Channel wall
3
supplied with the voltage is subjected to shear deformation. As a result, pressure wave is caused in the ink channel to eject ink droplets from nozzle
10
. Note that although in
FIG. 20
the electrode connecting portion and the external electrode are connected by bonding wire
7
, the connection may be made with use of an anisotropic conductive film (ACF) as is conventionally known.
A conventional ink jet head uses a metal film formed in shallow groove portion
6
as the electrode connecting portion. Thus, the metal film is positioned in the shallow groove. Further, the metal film is formed when forming the metal film to be the electrode on the upper half portion of channel wall
3
. Thus, there is dry resist film
11
to be a mask at the portion excluding the shallow groove. As a result, a metal film of a sufficient thickness cannot be formed at the bottom of shallow groove portion
6
because of shadowing with diagonal vapor deposition.
The aforementioned problems are discussed in the following.
FIG. 23
is a cross sectional view of shallow groove portion
6
shown in conjunction with formation of the metal film. Assume that the width of the channel formed in base member
1
, the depth of the channel, and the thickness of dry resist film
11
are respectively 81 &mgr;m, 300 &mgr;m, and 30 &mgr;m. Then, the incident angle for diagonal vapor deposition would be about 24° with respect to the normal line when forming the metal film on the upper half portion of the channel wall. In this case, diagonal vapor deposition would be performed on shallow groove portion
6
of
FIG. 20
with the same incident angle as shown in FIG.
23
.
FIG. 24
is a photograph showing a cross section of the metal film formed on the shallow groove portion when the depth of the shallow groove portion, the thickness of the dry resist film, and the incident angle for diagonal vapor deposition with respect to the normal line are respectively 25 &mgr;m, 30 &mgr;m, and 24°. Note that
FIG. 24
shows the metal film after the dry resist film is lifted off.
Referring to
FIG. 24
, with the depth of the shallow groove portion of 25 &mgr;m, in the middle of the shallow groove bottom, the metal film is formed to have a step in the region with a width of about 32 &mgr;m. Thus, in wire bonding, bonding must be made in the middle of the step. The positioning failure of the bonding wire with respect to the step causes falling or inclining of the wire, and therefore accurate positioning must be ensured.
The height electrode portion is smaller than that of base member
1
. The small
Isono Hitoshi
Nakajima Yoshinori
Sharp Kabushiki Kaisha
Vo Anh T. N.
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