Metal working – Piezoelectric device making
Reexamination Certificate
2002-03-27
2004-03-30
Arbes, Carl J. (Department: 3729)
Metal working
Piezoelectric device making
C029S890100, C347S071000, C347S068000, C427S100000, C427S126300
Reexamination Certificate
active
06711793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a method of producing a piezoelectric device used in ink jet recording heads, etc., and in particularly, to a method of producing a piezoelectric device, etc., by means of which crystallization of the entire layer-built structure can be performed all at once and productivity thereby raised, and its products.
2. Description of the Related Art
Piezoelectric devices are elements with electric equipment conversion capability and are made by sandwiching a piezoelectric ceramic such as crystalline lead zirconate titanate (PZT), etc., between electrodes. In order to produce this piezoelectric device, a diaphragm layer, bottom electrode layer, piezoelectric thin film layer, and a top electrode layer are formed in succession on a substrate. By means of methods of producing piezoelectric devices in general, a different method is used to produce each layer because the composition of each layer is different. For instance, the diaphragm is formed by the thermal oxidation method, while the electrode layers are formed by sputtering, etc. Moreover, the so-called sol-gel method is used to produce the piezoelectric thin film layer. By means of the sol gel method, a sol, or the organic metal precursor, is applied, the sol is dried and pyrolyzed, and finally, the product is heat treated at a high speed and thereby crystallized.
Methods of producing thin films in general are further discussed in, for instance, Phillips J. Res. 47('93), pp. 263-285, etc.
Nevertheless, by means of conventional methods of producing piezoelectric devices, the thin film of one layer is completed and then the film of the next layer is formed and therefore, there is a problem in that the structure of each layer is completely crystallized and adhesion between the layers is weak. When adhesion between the layers is poor, peeling occurs during the production process, leading to poor yield, and peeling occurs during use, resulting in poor reliability. Therefore, there is a demand for a method of production that results in strong adhesion.
Moreover, since each layer is as it is being crystallized, there are inevitably many processes needed to complete the piezoelectric structure. Because there are many processes, there is naturally an increase in the production cost. Therefore, there is a demand for a production method with few processes.
SUMMARY OF THE INVENTION
Thereupon, a method whereby a piezoelectric device of a piezoelectric ceramic that has been applied to a substrate and pyrolyzed is placed in a specific alkali solution and crystallized is recorded in “Application of Hydrothermal Mechanism for Tailor-Making Perovskite Titanate Films,” IEEE Proc. of the 9th Int'l Symp. on Electrets, Shanghai, China, September 25-30, pp. 617-622 (1996), W-ping Xu, Masanori Okuyama, et al. This method of crystallization in an alkali solution is called the hydrothermal method. When compared to the sol-gel method, crystallization at a relatively low temperature is possible by means of this hydrothermal method and therefore, there are a number of advantages to this method. The inventors of the present invention hit upon the idea that a piezoelectric device with a multi-layered structure could be crystallized all at once by using this hydrothermal method and successfully completed experiments with this production method confirming this point.
In light of the aforementioned facts, the first problem of the present invention is to present a functional thin film with high adhesion between layers and high reliability, a piezoelectric device, an ink jet recording head and a printer.
The second problem of the present invention is to present a method of producing a piezoelectric device and a method of producing an ink jet recording head, both of which have fewer production processes than conventional production methods and therefore have a lower production cost.
The invention that solves the aforementioned first problem is a functional thin film, characterized in that a mixed layer where the components of thin film layers made of different components are mixed together is formed between the respective thin film layers. This film is not only “functional thin film,” but also film that is used for any purpose for which many thin films are used. There is a region of a specific thickness where the components of two layers are mixed at the interface between the respective layers of the thin film structure.
Another invention that solves the aforementioned first problem is a piezoelectric device, characterized in that it comprises at least 1 piezoelectric thin film layer and 2 electrode layers, and a mixed layer that is a mixture of the components of adjacent layers is formed between the respective layers. The crystals of the two layers are intricately intertwined in the mixed layer and therefore, adhesion between the layers is high.
Still another invention that solves the aforementioned first problem is a piezoelectric device that further comprises at least 1 diaphragm layer, with a mixed layer that is a mixture of the components of the aforementioned diaphragm layer and the adjacent electrode layer formed in between the respective layers.
Thickness of the aforementioned mixed layers is, for instance, 5 nm or thicker. By means of conventional production methods, thickness of the part where the compositions are mixed was less than 3 nm and therefore, adhesion between layers is improved by the presence of this thick mixed layer.
For instance, the metal alkoxide that comprises the piezoelectric thin film layers is any piezoelectric ceramic selected from lead zirconate titanate (Pb(Zr, Ti)O
3
: PZT), lead lanthanum titanate ((Pb, La)TiO
3
), lead lanthanum zirconate ((Pb, La)ZrO
3
), lead lanthanum zirconate titanate ((Pb, La)(Zr, Ti)O
3
: PLZT), or lead magnesium niobate zirconate titanate (Pb(Mg, Nb)(Zr, Ti)O
3
: PMN—PZT).
For instance, the piezoelectric device of the present invention has 2 or more piezoelectric thin film layers and 3 or more electrode layers and is made by sandwiching at least one of the piezoelectric thin films between electrode layers. This type of structure is generally called a bimorph.
Still another invention that solves the aforementioned first problem is an ink jet recording head with the piezoelectric device of the present invention as the piezoelectric actuator. For instance, it has
a) a pressure chamber substrate that forms the pressure chamber,
b) a diaphragm on one side of the pressure chamber, and
c) a piezoelectric device that is placed facing the diaphragm in the pressure chamber and is made so that it deforms the aforementioned diaphragm.
Another invention of the present application that solves the aforementioned first problem is a printer that has the ink jet recording head of the present invention as a printing means. For instance, it has
a) a recording medium conveyor that is made so that it is possible to feed in and carry out the recording medium and
b) a head control circuit by means of which the ink jet recording head prints at any desired position on the recording medium that has been fed by the recording medium conveyor.
Still another invention that solves the aforementioned second problem is a method of producing a piezoelectric device with at least one piezoelectric thin film layer and at least 2 electrode layers, characterized in that it comprises
a) the process whereby amorphous piezoelectric thin film layers, which are the amorphous state of each of the piezoelectric thin film layers, are formed,
b) the process whereby amorphous electrode layers, which are the amorphous state of each of the electrode layers, are formed, and
c) the process whereby after each amorphous piezoelectric thin film layer and each amorphous electrode layer have been laminated, hydrothermal synthesis is performed to crystallize the amorphous piezoelectric thin film layers and the amorphous electrode layers.
Moreover, another invention that solves the abovementoned second problem is a method of producing a piezoelectric device that further
Arbes Carl J.
Nguyen Tai V
Seiko Epson Corporation
Sterne Kessler Goldstein & Fox P.L.L.C.
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