Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-13
2002-06-25
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06409320
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet printer head using a piezoelectric device to jet ink, and an ink jet printer.
Ink jet printers are printers of the type that liquid ink is jetted into air in droplets, a liquid column or a spray to print letters, graphs, pictures, etc. on recording papers. It has motivated practice of the ink jet printers that the ink jet printers can have noises reduced, be smaller-size and lightened.
Heads for use in the ink jet printers are mainly of bubble type which generates air bubbles generated by a heater in a pressure chamber to jet ink from a nozzle by a force of the air bubbles, and piezoelectric type which has an oscillation plate on the bottom of a pressure chamber to press the oscillation plate by a piezoelectric material to jet ink from a nozzle.
The bubble type of these two types has limits to printing speed and print quality because performance of the head is determined substantially by characteristics of ink, which makes it difficult to meet higher speed and higher print quality. On the other hand, the piezoelectric type is expected to have higher performance than the bubble type because the piezoelectric type can easily meet higher speed, control ability and ink characteristics but has disadvantages of the complicated structure and being expensive.
As an ink jet printer head which solves these disadvantages of the piezoelectric type the applicant proposes in Japanese Patent Laid-Open Publication No. 192513/1996 a piezoelectric type ink jet printer head comprising a channel plate
110
for defining a plurality of discrete ink channels
112
and a piezoelectric device
100
which is parts of the walls of the discrete ink channels
112
, which are connected with each other (see FIG.
8
). Because this structure is very simple and has a small number of parts, this type could be inexpensive comparably with the bubble type. However, drive portions
106
of the piezoelectric device
100
opposed to the discrete ink channels
112
are restricted by the side surfaces and the bottom surfaces, whereby the drive portions
106
have poor displacing efficiency. In addition, each drive portions
106
is affected by the other drive portions
106
, whereby a stroke of a displacement amount is large. The characteristics of the ink jet printer head are not satisfactory for an ink jet printer head.
Japanese Patent Publication No. 33087/1995 discloses an ink jet printer head having respective drive portions
140
divided by grooves
138
to thereby improve displacement efficiency (see FIG.
9
). In this ink jet printer head, drive portions
140
of a piezoelectric device
130
corresponding to discrete ink channels
152
are separated by the grooves
138
and accordingly are not little restricted in displacement, so that large displacement amounts can be obtained in comparison with those of the conventional head shown in FIG.
8
. However, on other hand, the bottoms of the drive portions
140
are connected to the base of the piezoelectric device
130
, and disadvantageously displacements of the drive portions
140
are conducted to the other drive portions
140
.
That is, when a voltage is applied to the drive portions
140
, the drive portions
140
are extended upward by the vertical piezoelectric effect while being diminished widthwise by the lateral piezoelectric effect. Displacements of the drive portions
140
by the lateral piezoelectric effect, the bottoms of which are not separated from the base of the piezoelectric device
130
therebelow, cause the base contacting the drive portions
140
to diminish. Accordingly, a tensile stress is exerted to the rest part of the base and restricts displacements of the other drive portions
140
. Thus, as a number of drive pins is larger, the drive pins restrict displacements each other to thereby vertical displacement amounts for pressing the respective ink channels
152
are decreased. In addition, displacements by the lateral piezoelectric effect become a huge stress at the forward ends of the grooves
138
due to stress concentration, which results in breaking devices and in decreasing reliability.
Furthermore in the head shown in
FIG. 9
, the piezoelectric layers
136
of the drive portions
140
are sandwiched by the drive electrodes
134
. Generally adhesion strength between piezoelectric materials and electrode materials is low, and the electrode material and the piezoelectric material tend to peel off each other in their interface when the grooves
138
are processed. The same peeling tends to occur while being driven or after driven due to stresses generated when driven. Reliability is poor.
Additionally in the head shown in
FIG. 9
, the drive electrodes
134
and the piezoelectric layers
136
are formed not considering the drive portions
140
and the non-drive portions
142
, and are divided by processing the grooves
138
, and accordingly the drive electrodes
134
are also formed in the non-drive portions
140
. A tensile stress is applied to the non-drive portions
142
when a voltage is applied to the drive portions
140
to press the ink channels, and the peeling tens to take place in the electrodes-ceramics interfaces whose strength is low.
For higher nozzle density it is necessary that the non-drive portions
142
have a width as small as possible, and the presence of the drive electrodes
134
in the non-drive portions
142
is a problem in view of reliability in processing the grooves
138
and driving.
As described above, the conventional ink jet printer heads are not satisfactory to meet both requirements of reduction of crosstalk and higher reliability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a ink jet printer head having little crosstalk, high reliability and high performance, and an ink jet printer of high performance using the ink jet printer head.
The above-described object is achieved by an ink jet printer head comprising: a piezoelectric device including: a stress removing electrode formed on a substrate; a stress removing piezoelectric layer formed on the stress removing electrode; and a drive layer having a pair of drive electrodes and a piezoelectric layer disposed between the pair of drive electrodes, the drive layer being divided in a plurality of drive portions and a plurality of non-drive portions by grooves which reach the stress removing piezoelectric layer; and a channel plate jointed to the piezoelectric device on a side where the drive layer is formed, and having a plurality of discrete ink channels formed in parts thereof respectively opposed to said plural drive portions, corresponding to nozzles for jetting ink.
In the above-described ink jet printer head, it is possible that the drive electrode and/or the stress removing electrode has all region thereof or a part of the region formed in a mesh.
In the above-described ink jet printer head, it is possible that a prescribed voltage is applied between the lowermost drive electrode and the stress removing electrode when the drive portions are driven to thereby mitigate a stress exerted to the stress removing piezoelectric layer.
In the above-described ink jet printer head, it is possible that a voltage to be applied to the drive electrode and a voltage to be applied to the stress removing electrode have equipotential.
The above-described object is also achieved by an ink jet printer head comprising: a piezoelectric device formed on a substrate, and including a drive layer having a pair of drive electrodes and a piezoelectric layer disposed between the pair of drive electrodes, the drive layer being divided in a plurality of drive portions and non-drive portions by grooves which reach the substrate; and a channel plate jointed to the piezoelectric device on a side where the drive layer is formed, and having a plurality of discrete ink channels formed in parts thereof respectively opposed to said plural drive portions, corresponding to nozzles for jetting ink, the non-drive portions having all regions thereof or parts of the regions where the drive el
Kurihara Kazuaki
Kutami Michinori
Armstrong, Westerman and Hattori, LLP
Barlow John
Tran Ly T
LandOfFree
Ink jet printer head and ink jet printer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet printer head and ink jet printer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet printer head and ink jet printer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2931835