Metal working – Piezoelectric device making
Reexamination Certificate
1999-04-06
2001-12-25
Young, Lee (Department: 3729)
Metal working
Piezoelectric device making
C029S890100, C427S100000, C216S027000
Reexamination Certificate
active
06332254
ABSTRACT:
TECHNICAL FIELD
This invention relates to a laminated ink-jet recording head, a process for making the head and an apparatus such as a printer having the recording head; in particular, the invention relates to a laminated ink-jet recording head or the like that comprise a nozzle plate, pressure generating members and a diaphragm in superposition and which have piezoelectric vibrators of a flexural vibrating mode mounted on a surface of the diaphragm.
BACKGROUND ART
Laminated ink-jet recording heads have heretofore been known that comprise a nozzle plate, pressure generating compartments and a diaphragm in superposition and which have piezoelectric vibrators of a flexural vibrating mode mounted on a surface of the diaphragm (for example, Unexamined Published Japanese Patent Application (kohyo) No. Hei 5-504740). Typically, most of the members that constitute the laminated ink-jet recording head are formed of ceramics.
Hence, by sintering the aforementioned members in the form of superposed green sheets (claey sheets), those members can be fixed without using an adhesive. The resulting advantage of this feature is that the step of joining the individual layers together can be eliminated to thereby simplify the manufacturing process.
However, with the aforementioned conventional art laminated ink-jet recording head, two operations are necessary, one for superposing the green sheets of the respective members and the other for sintering them. It should here be noted that since the aforementioned respective members are made of ceramics comprising different ingredients, the diaphragm and the piezoelectric vibrator that have different coefficients of thermal expansion are superposed and sintered. Hence, due to the thermal expansion mismatch between the two members, deformation may occur after sintering or warpage and the like may prevent complete joining of the two members.
Under the circumstances, the present inventors conducted intensive studies and obtained a novel finding in that the above-mentioned problems could advantageously be solved by producing piezoelectric vibrating elements utilizing a hydrothermal method (hereunder sometimes referred to as a “hydrothermal synthesis method”). This hydrothermal method has heretofore been generally known since it has been proposed by, for example, Unexamined Published Japanese Patent Application (kokai) Nos. Hei 5-136476, Hei 6-206787, and Hei 6-314821; however, neither of these patents give consideration to the utilization of the hydrothermal. method in the manufacture of laminated ink-jet recording heads.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a laminated ink-jet recording head that has a strong joint between the diaphragm and the piezoelectric vibrating element and which can be driven on low voltage. Another object of the invention is to provide a process for producing the laminated ink-jet recording head. Yet another object of the invention is to provide an apparatus such as a printer that is equipped with the recording head.
In order to attain these objects, the present invention provides a laminated ink-jet recording head including a spacer in which a pressure generating chamber is formed, a diaphragm that closes one side of the pressure generating chamber and which has a piezoelectric vibrating element of a flexural vibrating mode secured to the surface, and a nozzle plate that closes the other side of the pressure generating chamber and which has a nozzle orifice bored for the issuance of ink drops, the head including a lower electrode on the diaphragm in at least a region that corresponds to the pressure generating chamber, the lower electrode being overlaid with the piezoelectric vibrating element formed by a hydrothermal method, the piezoelectric vibrating element in turn being overlaid with an upper electrode, and the piezoelectric vibrating element having a film thickness of not less than 1 &mgr;m but not more than 10 &mgr;m. This structure can provide a laminated ink-jet recording head that has a strong joint between the diaphragm and the piezoelectric vibrating element and which can be driven on low voltage.
If the film thickness of the aforementioned piezoelectric vibrating element is less than 1 &mgr;m, the voltage necessary to issue the ink may potentially exceed the withstand voltage of the piezoelectric vibrating element; If the film thickness exceeds 10 &mgr;m, the distance between adjacent pressure generating chambers is increased in order to prevent interference with the displacement of the piezoelectric vibrating element, which is by no means suitable for an inkjet recording head of a high-density type.
The aforementioned diaphragm may be made of an electrically conductive material. By so doing, it can serve as both a conductive sheet and a lower electrode. In addition, at least that part of the aforementioned lower electrode which faces the piezoelectric vibrating element may be formed of a titanium layer. Further in addition, the aforementioned lower electrode may have a multilayer structure consisting of a titanium layer and another electrically conductive layer. And in addition, the aforementioned lower electrode may be formed of a titanium layer.
This titanium layer may have a film thickness of not less than a tenth but not more than twice the film thickness of the aforementioned piezoelectric vibrating element.
In addition, the aforementioned titanium layer may be formed such that the portion formed in the region corresponding to the pressure generating chamber has a smaller film thickness than the portion formed in the other region. By so doing, ink can be efficiently issued from the pressure generating chamber.
If the film thickness of the titanium layer is less than a tenth or more than twice the film thickness of the aforementioned piezoelectric vibrating element, the rigidity of the titanium layer prevents efficient issuance of the ink.
In addition, the aforementioned lower electrode may comprise a plurality of titanium films in superposition.
In addition, the aforementioned spacer may be formed of an electroformed article. And this electroformed article may be made of an alkali resistant material. Further in addition, the aforementioned spacer and the diaphragm may be made of the same material and united into one. In addition, the spacer and the diaphragm may be united as an electroformed article.
In addition, the aforementioned spacer may be made of a silicon substrate enclosed with a silicon dioxide film.
And in addition, at least part of the aforementioned piezoelectric vibrating element may be located within a recess formed in the aforementioned lower electrode in such a way that it is formed with a clearance provided to form a gap from both sidewalls of the recess.
Further in addition, a titanium oxide layer may be formed between the aforementioned diaphragm and the lower electrode. By so doing, the adhesion between the diaphragm and the lower electrode can be further improved.
In addition, the present invention provides a laminated ink-jet recording head including a spacer in which a pressure generating chamber is formed, a diaphragm that closes one side of the pressure generating chamber and which has a piezoelectric vibrating element of a flexural vibrating mode secured to the surface, and a nozzle plate that closes the other side of the pressure generating chamber and which has a nozzle orifice bored for the issuance of ink drops, the diaphragm being made of an electrically conductive material so as to function as an electrode.
The aforementioned spacer may be made of an electroformed article. In addition, the laminated ink-jet recording head of the invention may be of such a structure that the aforementioned spacer is joined to the aforementioned diaphragm. And in addition, the aforementioned diaphragm may be made of a titanium layer.
It should be noted that the aforementioned upper electrode may be formed on the entire surface of the aforementioned diaphragm. In addition, the aforementioned lower electrode may also be formed by a film forming technique.
I
Murai Masami
Nishiwaki Tsutomu
Shimada Masato
Sumi Kouji
Usui Minoru
Seiko Epson Corporation
Sughrue & Mion, PLLC
Tugbang A. Dexter
Young Lee
LandOfFree
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