Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-07
2002-01-08
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06336717
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an ink jet recording head wherein a piezoelectric element is formed via a diaphragm in a part of each of pressure generating chambers communicating with nozzle openings for jetting ink drops and ink drops are jetted by displacement of the piezoelectric element, and an ink jet recording apparatus comprising the ink jet recording head.
The following two types of ink jet recording heads, each wherein a part of a pressure generating chamber communicating with a nozzle opening for jetting an ink drop is formed of a diaphragm and the diaphragm is deformed by a piezoelectric element for pressurizing ink in the pressure generating chamber for jetting an ink drop through the nozzle opening, are commercially practical: One uses a piezoelectric actuator in a vertical vibration mode in which the piezoelectric element is expanded and contracted axially and the other uses a piezoelectric actuator in a deflection vibration mode.
With the former, the volume of the pressure generating chamber can be changed by abutting an end face of the piezoelectric element against the diaphragm and a head appropriate for high-density printing can be manufactured, but a difficult step of dividing the piezoelectric element like comb teeth matching the arrangement pitch of the nozzle openings and work of positioning and fixing the piezoelectric element divisions in the pressure generating chambers are required and the manufacturing process is complicated.
In contrast, with the latter, the piezoelectric element can be created and attached to the diaphragm by executing a comparatively simple process of putting a green sheet of a piezoelectric material matching the form of the pressure generating chamber and baking it, but a reasonable area is required because deflection vibration is used; high-density arrangement is difficult to make.
On the other hand, to solve the problem of the latter recording head, Japanese Patent Publication No. 5-286131A proposes an art wherein an uniform piezoelectric material layer is formed over the entire surface of a diaphragm according to a film formation technique and is divided to a form corresponding to a pressure generating chamber according to a lithography technique for forming a piezoelectric element separately for each pressure generating chamber.
This eliminates the need for work of putting the piezoelectric element on the diaphragm and the piezoelectric element can be created by the lithography method, an accurate and simple technique. In addition, the piezoelectric element can be thinned and high-speed drive is enabled.
However, in the manufacturing method according to the thin-film technique and the lithography method described above, after thin film patterning, pressure generating chambers are formed. At the time, a diaphragm is deflected to the pressure generating chamber side by the effect of relaxation of the internal stresses in an upper electrode and piezoelectric layers and the deflection remains as the initial deformation of the diaphragm.
Further, in a piezoelectric vibrator manufactured by the thin-film technique and the lithography method, in which arm portions of a lower electrode are removed by the patterning, a piezoelectric layer becomes thinner. Thus, the strength of the dielectric breakdown on both sidewalls in width direction of the lower electrode becomes lower and thereby the dielectric breakdown occurs easily.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an ink jet recording head, wherein the dielectric breakdown of the piezoelectric layer is prevented and wherein the initial deflection amount of a diaphragm is decreased, and an ink jet recording apparatus comprising the ink jet recording head.
In order to achieve the above object, according to a first aspect of the present invention, there is provided an ink jet recording head comprising: a pressure generating chamber communicating with a nozzle opening; and a piezoelectric element a lower electrode provided on an area facing the pressure generating chamber via an insulating layer, a piezoelectric layer provided on the lower electrode, and an upper electrode provided on the piezoelectric layer, wherein at least both ends of the lower electrode in a width direction thereof are positioned within the area facing the pressure generating chamber, and the piezoelectric layer covers sides of both ends of the lower electrode in the width direction thereof.
In the first aspect, the both side wall of the lower electrode in the width direction thereof patterned in the pressure generating chamber are covered with the piezoelectric layer, thus the strength of the dielectric breakdown thereon is improved and the insulating layer and the piezoelectric layer are brought into intimate contact with each other, whereby the initial deflection amount of a diaphragm is decreased.
According to a second aspect of the present invention, in the ink jet recording head of the first aspect, crystal direction of the piezoelectric layer is preferentially oriented.
In the second aspect, the piezoelectric layer is formed in a thin film process, so that crystal is preferentially oriented.
According to a third aspect of the present invention, in the ink jet recording head of the second aspect, the piezoelectric layer has a columnar crystal structure.
In the third aspect, the piezoelectric layer is formed in a thin film process, so that the piezoelectric layer has a columnar crystal structure.
According to a fourth aspect of the present invention, in the ink jet recording head of the first to third aspect, the insulating layer in the area under the area where the lower electrode is formed is thicker than any other area.
In the fourth aspect, the piezoelectric layer is at a position distant from the neutral axis of bend caused by drive of the piezoelectric element, so that displacement efficiency is improved.
According to a fifth aspect of the present invention, in the ink jet recording head of any of the first to fourth aspects, the top of the insulating layer in a thickness direction thereof is made of an adhesive insulating layer made of a material having a good adhesion with the piezoelectric layer. The adhesive insulating layer is adhered with the piezoelectric layer covering sides of both ends of the lower electrode in the width direction thereof.
In the fifth aspect, the lower electrode in the area facing the pressure generating chamber is covered completely with the piezoelectric layer and the strength of the dielectric breakdown on the sidewall is furthermore improved.
According to a sixth aspect of the present invention, in the ink jet recording head of the fifth aspect, the material of the adhesive insulating layer is made of either one of an oxide or a nitride of at least one element selected from composite element of the piezoelectric layer.
In the sixth aspect, the intimate contact property between the insulating layer and the piezoelectric layer is improved.
According to a seventh aspect of the present invention, in the ink jet recording head of the sixth aspect, the adhesive insulating layer is made of zirconium oxide.
In the seventh aspect, the rigidity of the insulating layer is improved and the durability is enhanced.
According to an eighth aspect of the present invention, in the ink jet recording head of any of the fifth to seventh aspects, the insulating layer is made of the adhesive insulating layer.
In the eighth aspect, the insulating layer is formed easily and the manufacturing process is simplified.
According to a ninth of the present invention, in the ink jet recording head of the eighth aspect, the insulating layer is formed directly on a silicon monocrystalline substrate.
In the ninth aspect, the zirconium oxide film shows sufficient durability even solely.
According to a tenth aspect of the present invention, in the ink jet recording head of the eighth aspect, the insulating layer is formed on a silicon dioxide film formed on the silicon monocrystalline substrate. The portions of the silicon dioxide film corres
Furuhata Yutaka
Miyata Yoshinao
Moriya Souichi
Sakai Shinri
Shimada Masato
Nguyen Thinh
Seiko Epson Corporation
Sughrue & Mion, PLLC
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