Patent Publication Number: US-7707701-B2

Title: Method for manufacturing a piezoelectric element

Description:
The entire disclosure of Japanese Patent Application No. 2005-089167, filed Mar. 25, 2005 is expressly incorporated by reference herein. 
   BACKGROUND 
   1. Technical Field 
   The present invention relates to piezoelectric elements and methods for manufacturing the same, ink jet recording heads and ink jet printers. 
   2. Related Art 
   Ink jet printers are known as printers that can realize high image quality and high speed printing. In order to improve the characteristics of piezoelectric elements in ink jet recording heads for ink jet printers, it is important to control the crystal orientation of the piezoelectric layers. 
   As a method to control the crystal orientation, Japanese Laid-open patent application JP-A-2000-158648 describes a control method using an MgO (100) single crystal substrate. However, according to this method, the process for manufacturing an ink jet recording head may become complex. 
   SUMMARY 
   In accordance with an advantage of some aspects of the invention, piezoelectric elements that can obtain good piezoelectric characteristics and methods for manufacturing such piezoelectric elements can be provided. In accordance with another advantage of some aspects of the invention, ink jet recording heads and ink jet printers that use the piezoelectric elements described above are provided. 
   In accordance with an embodiment of the invention, a method for manufacturing a piezoelectric element includes the steps of: forming a first electrode above a substrate; forming above the first electrode a piezoelectric layer composed of a piezoelectric material having a perovskite structure; and forming a second electrode above the piezoelectric layer, wherein the step of forming the first electrode includes forming a lanthanum nickelate layer oriented to a cubic (100) by a sputter method, and a ratio of nickel to lanthanum (Ni/La) in a target used for the sputter method is greater than 1 but smaller than 1.5. 
   According to the method for manufacturing a piezoelectric element, a piezoelectric element having good piezoelectric characteristics can be provided because of the following reasons. 
   Basically, lanthanum nickelate would likely be self-oriented to (100). However, for example, if the ratio of nickel to lanthanum in a target used for the sputter method is less than 1 or greater than 1.5, the crystallinity of the lanthanum nickelate deteriorates. In contrast, according to the method for manufacturing a piezoelectric element in accordance with the present embodiment, the ratio of nickel to lanthanum in a target is set to be greater than 1 but smaller than 1.5, whereby the lanthanum nickelate layer is oriented to (100). In this manner, because the lanthanum nickelate layer is oriented to (100), the piezoelectric layer succeeds the crystal orientation of the lanthanum nickelate layer and can be oriented to (100), when the piezoelectric layer is formed above the lanthanum nickelate layer. Accordingly, the piezoelectric element has the piezoelectric layer having a higher piezoelectric constant and exhibits a greater strain to an impressed voltage. In other words, according to the piezoelectric element, much better piezoelectric characteristics can be obtained. 
   It is noted that, in the descriptions concerning the invention, the term “above” may be used, for example, as “a specific element (hereafter referred to as “A”) is formed ‘above’ another specific element (hereafter referred to as “B”).” In this case, the term “above” is assumed to include a case in which A is formed directly on B, and a case in which A is formed above B through another element. 
   In the method for manufacturing a piezoelectric element in accordance with an aspect of the embodiment, the step of forming the first electrode may include forming a low resistivity layer composed of a conductive material having a lower specific resistance compared to lanthanum nickelate. 
   In the method for manufacturing a piezoelectric element in accordance with an aspect of the embodiment, the conductive material may include at least one of a metal, an oxide of the metal, and an alloy of the metal, and the metal may be at least one of Pt, Ir, Ru, Ag, Au, Cu Al and Ni. 
   In the method for manufacturing a piezoelectric element in accordance with an aspect of the embodiment, the lanthanum nickelate layer may be formed above the low resistivity layer. 
   In the method for manufacturing a piezoelectric element in accordance with an aspect of the embodiment, the lanthanum nickelate layer and the piezoelectric layer may be formed in contact with each other. 
   In the method for manufacturing a piezoelectric element in accordance with an aspect of the embodiment, the piezoelectric material is composed of a rhombohedral crystal or a mixed crystal of tetragonal and rhombohedral crystals, and may be oriented to (100). 
   A piezoelectric element in accordance with an embodiment of the present invention may be obtained by the method for manufacturing a piezoelectric element described above. 
   An ink jet recording head in accordance with an embodiment of the invention has any one of the piezoelectric elements described above. 
   An ink jet printer in accordance with an embodiment of the invention has the ink jet recording head described above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view schematically showing a piezoelectric element in accordance with a first embodiment of the invention. 
       FIG. 2  is a 2θ-θ scanning X-ray diffraction pattern of a lanthanum nickelate layer in accordance with an experimental example. 
       FIG. 3  is a cross-sectional view schematically showing a modified example of the piezoelectric element in accordance with the first embodiment. 
       FIG. 4  is a schematic structural diagram of an ink jet recording head in accordance with a second embodiment of the invention. 
       FIG. 5  is a schematic exploded perspective view of the ink jet recording head in accordance with the second embodiment. 
       FIG. 6  is a view for describing operations of an ink jet recording head. 
       FIG. 7  is a view for describing operations of the ink jet recording head. 
       FIG. 8  is a view schematically showing a structure of an ink jet printer in accordance with a third embodiment of the invention. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Preferred embodiments of the invention are described below with reference to the accompanying drawings. 
   1. First Embodiment 
   1-1. First, a piezoelectric element  10  in accordance with a first embodiment is described. 
     FIG. 1  is a cross-sectional view of the piezoelectric element  10 . The piezoelectric element  10  includes a substrate  1 , a stopper layer  2  formed on the substrate  1 , a hard layer  3  formed on the stopper layer  2 , a first electrode  4  formed on the hard layer  3 , a piezoelectric layer  5  formed on the first electrode  4 , and a second electrode  6  formed on the piezoelectric layer  5 . 
   For example, a silicon substrate with a (110) orientation may be used as the substrate  1 . For example, a layer of silicon oxide may be used as the stopper layer  2 . The stopper layer  2  can function as an etching stopper, for example, in the step of etching the substrate  1  from its back surface side for forming a cavity  521  of an ink jet recording head  50  (see  FIG. 4 ). Also, the stopper layer  2  and the hard layer  3  function as an elastic layer  55  in the ink jet recording head  50 . As the hard layer  3 , for example, a layer of yttria stabilized zirconia, cerium oxide, zirconium oxide, or the like can be used. 
   The first electrode  4  may include a low resistivity layer  40 , and a lanthanum nickelate layer  42  formed on the low resistivity layer  40 . The first electrode  4  is one of electrodes for impressing a voltage to the piezoelectric layer  5 . The first electrode  4  may be formed in the same plane configuration as that of, for example, the piezoelectric layer  5 . 
   The low resistivity layer  40  is composed of a conductive material having a lower specific resistance, compared to lanthanum nickelate. The conductive material can include at least one of, for example, a metal, an oxide of the metal, an alloy composed of the metal. It is noted that, for example, at least one of Pt, Ir, Ru, Ag, Au, Cu, Al and Ni can be used as the metal. For example, IrO 2  and RuO 2  may be enumerated as the oxide of the metal. For example, Pt—Ir, Ir—Al, Ir—Ti, Pt—Ir—Al, Pt—Ir—Ti and Pt—Ir—Al—Ti may be enumerated as the alloy composed of the metal. In accordance with the present embodiment, the crystal orientation of the conductive material is not particularly limited, and, for example, can be in a (111) orientation. The film thickness of the low resistivity layer  40  may be, for example, about 50 nm-150 nm. 
   The lanthanum nickelate layer  42  is in contact with the piezoelectric layer  5 . Lanthanum nickelate composing the lanthanum nickelate layer  42  can be expressed by a chemical formula, LaNiO y  (2≦y≦3). Lanthanum nickelate is oriented to (100). It is noted that the crystal orientation of lanthanum nickelate in the in-plane direction is random. Lanthanum nickelate would likely be self oriented to (100). The film thickness of lanthanum nickelate layer  42  may be, for example, about 10 nm-140 nm. 
   The piezoelectric layer  5  is composed of a piezoelectric material having a perovskite structure. The piezoelectric layer  5  is in contact with the lanthanum nickelate layer  42 . The piezoelectric material composing the piezoelectric layer  5  may preferably be in a rhombohedral crystal or a mixed crystal of tetragonal and rhombohedral crystals, and may preferably be oriented to (100). The piezoelectric layer  5  composed of such a piezoelectric material has a high piezoelectric constant. 
   The piezoelectric material can be expressed by, for example, a general formula ABO 3 . It is noted here that A may include Pb, and B may include at least one of Zr and Ti. Further, B may also include at least one of V, Nb and Ta. In this case, the piezoelectric material can include at least one of Si and Ge. More concretely, the piezoelectric material may include at least one of lead zirconate titanate (Pb (Zr, Ti)O 3 ), lead zirconate titanate niobate (Pb (Zr, Ti, Nb)O 3 ), lead lanthanum titanate ((Pb, La) TiO 3 ), lead lanthanum zirconate titanate ((Pb, La) Zr TiO 3 ), lead magnesium niobate titanate (Pb(Mg, Nb)TiO 3 ), lead magnesium niobate zirconate titanate (Pb(Mg, Nb)(Zr, Ti)O 3 ), lead zinc niobate titanate (Pb (Zn, Nb) TiO 3 ), lead scandium niobate titanate (Pb (Sc, Nb) TiO 3 ), lead nickel niobate titanate (Pb(Ni, Nb) TiO 3 ), and lead indium magnesium niobate titanate (Pb (In, Mg, Nb) TiO 3 ). 
   Also, the piezoelectric material may include at least one of (Ba 1-x  Sr x )TiO 3  (0≦x≦0.3), Bi 4 Ti 3 O 12 , SrBi 2 Ta 2 O 9 , LiNbO 3 , LiTaO 3  and KNbO 3 . The film thickness of the piezoelectric layer  5  may be, for example, about 0.4 μm-5 μm. 
   The second electrode  6  includes a conductive oxide layer  46  and another low resistivity layer (hereafter referred to as a “second low resistivity layer”)  47  formed on the conductive oxide layer  46 . The second electrode  6  is the other of the electrodes for impressing a voltage to the piezoelectric layer  5 . As the second electrode  6  includes the conductive oxide layer  46  and the second low resistivity layer  47 ; the second electrode  6  and the first electrode  4  are generally placed symmetrical with each other with respect to the piezoelectric layer  5 . In other words, the symmetric property of the piezoelectric element  10  can be made better. It is noted that the second electrode  6  can be formed from either the conductive oxide layer  46  or the second low resistivity layer  47 . The second electrode  6  may be formed in the same plane configuration as that of the piezoelectric layer  5 . 
   The conductive oxide layer  46  may be composed of conductive oxide having a perovskite structure. The conductive oxide may include, for example, at least one of CaRuO 3 , SrRuO 3 , BaRuO 3 , SrVO 3 , (La, Sr) MnO 3 , (La, Sr) CrO 3 , (La, Sr) CoO 3 , LaNiO y  (2≦y≦3), and a solid solution composed of at least two of the foregoing materials. The film thickness of the conductive oxide layer  46  may be, for example, about 0 nm-200 nm. 
   The second low resistivity layer  47  may be composed of, for example, a conductive material with a lower specific resistance compared to the conductive oxide that composes the conductive oxide layer  46 . The conductive material may be composed of, for example, the conductive material composing the low resistivity layer  40  described above. The film thickness of the second low resistivity layer  47  may be, for example, about 0 nm-200 nm. 
   1-2. Next, a method for manufacturing the piezoelectric element  10  in accordance with the present embodiment is described with reference to  FIG. 1 . 
   First, a silicon substrate with a (110) orientation is prepared as a substrate  1 . 
   Next, a stopper layer  2  is formed on the substrate  1 . The stopper layer  2  may be formed by, for example, a thermal oxidation method, a CVD method or the like. 
   Next, a hard layer  3  is formed on the stopper layer  2 . The hard layer  3  may be formed by, for example, a CVD method, a sputtering method, a vacuum evaporation method or the like. 
   Next, a low resistivity layer  40  is formed on the hard layer  3 . As described above, in accordance with the present embodiment, since the crystal orientation of a conductive material that composes the low resistivity layer  40  is not particularly limited, conditions and method for fabricating the low resistivity layer  40  can be optionally selected. The low resistivity layer  40  may be formed by, for example, a sputter method, a vacuum vapor deposition method or the like. Also, the temperature at which the low resistivity layer  40  is formed may be, for example, room temperature to 600° C. 
   Next, a lanthanum nickelate layer  42  is formed on the low resistivity layer  40 . The lanthanum nickelate layer  42  is formed by a sputtering method. The ratio of nickel to lanthanum (Ni/La) in a target used for the sputtering method is greater than 1 but smaller than 1.5. As the target, for example, a target formed by mixing La 2 O 3  powder and NiOx powder, and sintering the mixture may be used. The ratio of nickel to lanthanum in the target may be set to a desired value by, for example, adjusting the mixing ratio between La 2 O 3  powder and NiOx powder. If the lanthanum nickelate layer  42  is formed by, for example, a RF sputtering method, the RF power may be set to, for example, 500-3 kW. Also, the ratio of oxygen in a mixture of argon and oxygen (O 2 /(Ar+O 2 ) may be set to, for example, 0%-50%. By the steps described above, the first electrode  4  is formed. 
   Next, a piezoelectric layer  5  is formed on the lanthanum nickelate layer  42 . The piezoelectric layer  5  may be formed by, for example, a sputtering method, a sol-gel method or the like. 
   Next, a conductive oxide layer  46  is formed on the piezoelectric layer  5 . The conductive oxide layer  46  may be formed by, for example, a sputtering method, a sol-gel method or the like. 
   Next, a second low resistivity layer  47  is formed on the conductive oxide layer  46 . The second low resistivity layer  47  may be formed by, for example, a sputter method, a vacuum evaporation method or the like. By the steps described above, the second electrode  6  is formed. 
   By the process described above, the piezoelectric element  10  in accordance with the present embodiment can be formed. 
   1-3. Next, experimental examples are described. 
   With the present experimental example, the ratio of nickel to lanthanum (Ni/La) in each target used for a sputtering method was changed, whereby the lanthanum nickelate layer  42  was formed. Concretely, a sample A with the ratio of Ni/La being 1, a sample B with the ratio being 1.2, a sample C with the ratio being 1.5, and a sample D with the ratio being 1.8 were formed. It is noted that a silicon substrate with a (110) orientation was used as the substrate  1 , a laminated layer film of silicon oxide and titanium oxide (TiO x ) as the stopper layer  2 , and a platinum layer as the low resistivity layer  40 . It is noted that the hard layer  3  was not formed. Also, the lanthanum nickelate layer  42  was formed by a RF sputtering method. The RF sputtering method was conducted under conditions with the RF power being 1 kW, the substrate temperature being 250° C., and the ratio of O 2 /(Ar+O 2 ) being 10%. The film thickness of each of the layers was as follows. The silicon oxide layer was 1000 nm thick, the titanium oxide layer was 400 nm thick, the low resistivity layer  40  was 100 nm thick, and the lanthanum nickelate layer  42  was 80 nm thick. 
     FIG. 2  is a 2θ-θ scanning X-ray diffraction pattern of the lanthanum nickelate layers  42  in accordance with the experimental examples. As shown in  FIG. 2 , with the sample A, broad peaks derived from the fact that lanthanum nickelate was oriented to (100) were observed. In the fabrication of the sample A, because the conductivity of the target (with Ni/La=1) used for the sputtering method was higher compared to the other targets used for forming the other samples, abnormal discharge occurred, which made it difficult to fly atoms from the target. When the RF power was increased to fly atoms from the target, cracks would be generated in the target. In this manner, in the formation with the target A, it is believed that, because it was difficult for atoms to fly from the target, the raw material was not sufficiently supplied, and the crystallinity of the lanthanum nickelate layer  42  was deteriorated, which resulted in the broad peaks. 
   On the other hand, with the sample B, as shown in  FIG. 2 , only sharp peaks derived from the fact that lanthanum nickelate was oriented to (100) were observed. It is believed that, because nickel was sufficiently supplied from the nickel-rich target (with Ni/La=1.2) in the case of the sample B, nickel in the lanthanum nickelate layer  42  was moderately secured, which resulted in a good crystal orientation. 
   In contrast, with the sample C, as shown in  FIG. 2 , a peak of lanthanum nickelate (110) was observed. It is believed that, because nickel was excessively supplied from the nickel-rich target (with Ni/La=1.5) in the case of the sample C, nickel in the lanthanum nickelate layer  42  became excessive, and the crystal orientation was disturbed. 
   Also, with the sample D, as shown in  FIG. 2 , no peak of lanthanum nickelate was observed. In other words, with the sample D, nickel was excessively supplied from the nickel-rich target (with Ni/La=1.8) in the case of the sample D, and the lanthanum nickelate did not crystallize. 
   From the results of the experimental examples, it was confirmed that, by setting the ratio of nickel to lanthanum (Ni/La) in a target used for a sputter method to be greater than 1 but smaller than 1.5, the lanthanum nickelate layer  42  is oriented to (100). 
   1-4. According to the method for manufacturing a piezoelectric element  10  in accordance with the embodiment, the piezoelectric element  10  can be provided with excellent piezoelectric characteristics. The reasons are as follows. 
   Basically, lanthanum nickelate would likely be self oriented to (100). However, as shown by the experimental examples described above, for example, if the ratio of nickel to lanthanum in a target used for a sputtering method is smaller than 1 or greater than 1.5, the crystallinity of the lanthanum nickelate layer  42  is deteriorated. In contrast, according to the method for manufacturing a piezoelectric element  10  in accordance with the present embodiment, as described above, by setting the ratio of nickel to lanthanum in a target used for a sputtering method to be greater than 1 but smaller than 1.5, the lanthanum nickelate layer  42  becomes oriented to (100). This does not depend on the crystal orientation of the conductive material that forms the base layer, i.e., the low resistivity layer  40 . Due to the fact that the lanthanum nickelate layer  42  is oriented to (100), when the piezoelectric layer  5  is formed on the lanthanum nickelate layer  42 , the piezoelectric layer  5  can succeed the crystal orientation of the lanthanum nickelate layer  42 , thereby being oriented to (100). As a result, the piezoelectric element  10  can have the piezoelectric layer  5  that has a higher piezoelectric constant, and exhibits a greater deformation to a voltage impressed. In other words, by the piezoelectric element  10  in accordance with the present embodiment, better piezoelectric characteristics can be obtained. 
   Also, in the piezoelectric element  10  in accordance with the present embodiment, the first electrode  4  has the low resistivity layer  40 . The low resistivity layer  40  is composed of a conductive material with a lower resistance compared to lanthanum nickelate. By this, for example, when the case where the first electrode  4  does not have a low resistivity layer  40  and the case where the first electrode  4  has a low resistivity layer  40  are compared to each other, with the first electrodes  4  being in the same configuration, the first electrode  4  has a lower resistivity as a whole in the case where the first electrode  4  has the low resistivity layer  40  (in other words, in the case of the present embodiment). Accordingly, the piezoelectric element  10  in accordance with the present embodiment, excellent piezoelectric characteristics can be obtained. 
   1-5. Next, a modified example of the piezoelectric element  10  in accordance with the present embodiment is described with reference to the accompanying drawings. It is noted that features different from those of the piezoelectric element  10  described above and shown in  FIG. 1  are described, and descriptions of similar features are omitted.  FIG. 3  is a cross-sectional view schematically showing an example of the modified example of the piezoelectric element  10 . 
   For example, as shown in  FIG. 3 , it is possible that a first electrode  4  does not have a low resistivity layer  40 . In other words, the first electrode  4  may be composed of a lanthanum nickelate layer  42  alone. 
   Also, for example, as shown in  FIG. 3 , a second electrode  6  may be composed of a conductive oxide layer  46  alone. Also, for example, although not shown, the second electrode  6  may be composed of a second low resistivity layer  47  alone. In these cases, the second electrode  6  and the first electrode  4  can be provided generally symmetrical with each other with respect to a piezoelectric layer  5 . 
   It is noted that the modified examples described above represent merely examples, and the invention is not limited to these modified examples. For example, the lamination order and the number of the layers laminated can be optionally changed. 
   2. Second Embodiment 
   2-1. Next, an ink jet recording head in accordance with an embodiment having a piezoelectric element  10  of the first embodiment is described.  FIG. 4  is a side cross-sectional view schematically showing a structure of an ink jet recording head in accordance with the present embodiment, and  FIG. 5  is an exploded perspective view of the ink jet recording head. It is noted that  FIG. 5  shows the ink jet recording head upside down with respect to a state in which it is normally used. 
   The ink jet recording head (hereafter also referred to as the “head”)  50  is equipped with a head main body  57  and piezoelectric sections  54  provided above the head main body  57 , as shown in  FIG. 4 . It is noted that each of the piezoelectric sections  54  shown in  FIG. 4  corresponds to a section having the first electrode  4 , the piezoelectric layer  5  and the second electrode  6  of the piezoelectric element  10  in accordance with the first embodiment. 
   Also, the stopper layer  2  and the hard layer  3  in the piezoelectric element  10  in accordance with the first embodiment correspond to an elastic layer  55  in  FIG. 4 . Also, the substrate  1  composes a main portion of the head main body  57 , in  FIG. 4 . 
   The head  50  is equipped with a nozzle plate  51 , an ink chamber substrate  52 , an elastic layer  55 , and piezoelectric elements (vibration sources)  54  that are bonded to the elastic layer  55 , which are housed in a base substrate  56 , as shown in  FIG. 5 . The head  50  forms an on-demand type piezoelectric jet head. 
   The nozzle plate  51  is formed from, for example, a rolled plate of stainless steel or the like, and includes multiple nozzles  511  formed in a row for jetting ink droplets. The pitch of the nozzles  511  may be appropriately set according to the printing resolution. 
   The ink chamber substrate  52  is fixedly bonded (affixed) to the nozzle plate  51 . The ink chamber substrate  52  is formed with the substrate  1  described above (see  FIG. 1 , for example). The ink chamber substrate  52  has a plurality of cavities  521 , a reservoir  523 , and supply ports  524 , which are defined by the nozzle plate  51 , side walls (partition walls)  522  and the elastic layer  55 . The reservoir  523  temporarily reserves ink that is supplied from an ink cartridge  631  (see  FIG. 8 ). The ink is supplied from the reservoir  523  to the respective cavities  521  through the supply ports  524 . 
   Each of the cavities  521  is provided in a manner to correspond to each of the corresponding nozzles  511 , as shown in  FIGS. 4 and 5 . The cavity  521  has a volume that is variable by vibrations of the elastic layer  55 . The cavity  521  is formed to eject ink by the volume change. 
   As a base material for obtaining the ink chamber substrate  52  (see  FIG. 1 , for example), for example, a silicon single-crystal substrate with a (110) orientation is used. Because the silicon single-crystal substrate with a (110) orientation is suitable for anisotropic etching, the ink chamber substrate  52  can be readily and securely formed. 
   The elastic layer  55  is disposed on the ink chamber substrate  52  on the opposite side of the nozzle plate  51 . Also, a plurality of piezoelectric sections  54  are provided on the elastic layer  55  on the opposite side of the ink chamber substrate  52 . A communication hole  531  that penetrates the elastic layer  55  in its thickness direction is formed in the elastic layer  55  at a predetermined position. Ink is supplied from an ink cartridge  631  to the reservoir  523  through the communication hole  531 . 
   Each of the piezoelectric sections  54  is electrically connected to a piezoelectric element driving circuit to be described below, and is structured to operate (vibrate, deform) based on signals provided by the piezoelectric element driving circuit. In other words, each of the piezoelectric sections  54  functions as a vibration source (piezoelectric element). The elastic layer  55  vibrates (deforms) by vibration (deformation) of the piezoelectric section  54 , and functions to instantaneously increase the inner pressure of the cavity  521 . 
   The base substrate  56  is formed from, for example, any one of various resin materials, any one of metal materials, or the like. The ink chamber substrate  52  is affixed to and supported by the base substrate  56 , as shown in  FIG. 5 . 
   2-2. Next, operations of the ink jet recording head  50  in accordance with the present embodiment are described. In the head  50  in accordance with the present embodiment, in a state in which a predetermined jetting signal is not inputted through the piezoelectric element driving circuit, in other words, in a state in which no voltage is applied across the first electrode  4  and the second electrode  6  of the piezoelectric section  54 , no deformation occurs in the piezoelectric layer  5 , as shown in  FIG. 6 . Therefore, no strain occurs in the elastic layer  55 , and no volume change occurs in the cavity  521 . Accordingly, no ink droplet is discharged from the nozzle  511 . 
   On the other hand, in a state in which a predetermined jetting signal is inputted through the piezoelectric element driving circuit, in other words, in a state in which a predetermined voltage is impressed across the first electrode  4  and the second electrode  6  of the piezoelectric section  54 , a deflection deformation occurs in the piezoelectric layer  5  in its minor axis direction (in a direction indicated by an arrow s shown in  FIG. 7 ). By this, the elastic layer  55  flexes, thereby causing a change in the volume of the cavity  521 . At this moment, the pressure within the cavity  521  instantaneously increases, and an ink droplet  58  is discharged from the nozzle  511 . 
   In other words, when the voltage is impressed, the crystal lattice of the piezoelectric layer  5  is extended in a direction perpendicular to its surface (in a direction indicated by an arrow d shown in  FIG. 7 ), but at the same time compressed in a direction along the surface. In this state, a tensile stress f works in-plane in the piezoelectric layer  5 . Therefore, this tensile stress f bends and flexes the elastic layer  55 . The larger the amount of displacement (in an absolute value) of the piezoelectric layer  5  in the direction of the minor axis of the cavity  521 , the more the amount of flex of the elastic layer  55  becomes, and the more effectively an ink droplet can be discharged. 
   When an ejection of ink has been completed, the piezoelectric element driving circuit stops application of the voltage across the first electrode  4  and the second electrode  6 . By this, the piezoelectric section  54  returns to its original shape, shown in  FIG. 6 , and the volume of the cavity  521  increases. It is noted that, at this moment, a pressure (pressure in a positive direction) works on the ink in a direction from the ink cartridge  631  toward the nozzle  511 . For this reason, air is prevented from entering the cavity  521  from the nozzle  511 , and an amount of ink matching with the jetting amount of ink is supplied from the ink cartridge  631  through the reservoir  523  to the cavity  521 . 
   In this manner, by inputting jetting signals successively through the piezoelectric element driving circuit to the piezoelectric sections  54  at positions where ink droplets are to be jetted, arbitrary (desired) characters and figures can be printed. 
   2-3. Next, an example of a method for manufacturing the ink jet recording head  50  in accordance with the present embodiment is described. 
   First, a base material that becomes an ink chamber substrate  52 , in other words, a substrate  1  composed of a silicon single-crystal substrate with a (110) orientation, is prepared. Then, as shown in  FIG. 1 , for example, layers for a stopper layer  2 , a hard layer  3 , a first electrode  4 , a piezoelectric layer  5  and a second electrode  6  are successively formed over the substrate  1 . 
   Next, the second electrode  6 , the piezoelectric layer  5  and the first electrode  4  are patterned in a manner to correspond to each of the cavities  521 , as shown in  FIG. 6 , thereby forming piezoelectric sections  54  in the number corresponding to the number of the cavities  521 , as shown in  FIG. 4 . 
   Next, the base material (substrate  1 ) that becomes an ink chamber plate  52  is patterned, thereby forming concave sections that become the cavities  521  at positions corresponding to the piezoelectric sections  54 , and concave sections that become a reservoir  523  and supply ports  524  at predetermined positions. 
   In the present embodiment, because a silicon substrate with a (110) orientation is used as the base material (substrate  1 ), a wet etching (anisotropic etching) using a highly concentrated alkaline solution is preferably used. In the case of wet etching with a highly concentrated alkaline solution, the stopper layer  2  can function as an etching stopper, as described above. Therefore the ink chamber plate  52  can be more readily formed. 
   In this manner, the base material (substrate  1 ) is removed by etching in its thickness direction to the extent that the elastic layer  55  is exposed, thereby forming the ink chamber substrate  52 . It is noted that, in this instance, portions that remain without being etched become side walls  522 . 
   Next, a nozzle plate  51  formed with a plurality of nozzles  511  is bonded such that each of the nozzles  511  is aligned to correspond to each of the concave sections that become the respective cavities  521 . By this, the plurality of cavities  521 , the reservoir  523  and the plurality of supply ports  524  are formed. For bonding the nozzle plate  51 , for example, a bonding method using adhesive, a fusing method, or the like can be used. Next, the ink chamber substrate  52  is attached to the base substrate  56 . 
   By the process described above, the ink jet recording head  50  in accordance with the present embodiment can be manufactured. 
   2-4. In the inkjet recording head  50  in accordance with the present embodiment, the piezoelectric layer  6  of the piezoelectric section  54  has a high piezoelectric constant (d 3 1 ) and exhibits a greater strainto a voltage impressed, as described above in conjunction with the first embodiment. In other words, the piezoelectric section  54  has excellent piezoelectric characteristics. Accordingly, the amount of deflection of the elastic layer  55  can become greater, and the ink droplet can be discharged more efficiently. It is noted here that the term “efficiently” implies that an ink droplet in the same amount can be jetted by a lower voltage. In other words, the driving circuit can be simplified, and at the same time, the power consumption can be reduced, such that the nozzles  511  can be formed at a pitch with a higher density. Accordingly, a high density printing and a high-speed printing become possible. Furthermore, the length of the major axis of the cavity  521  can be shortened, such that the entire head can be miniaturized. 
   3. Third Embodiment 
   3-1. Next, an ink jet printer in accordance with an embodiment of the invention equipped with an ink jet recording head  50  of the second embodiment is described.  FIG. 8  is a view schematically showing a structure of an ink jet printer  600  in accordance with the present embodiment. The ink jet printer  600  can function as a printer capable of printing on paper or the like. It is noted that, an upper side in  FIG. 8  refers to an “upper section” and a lower side therein refers to a “lower section” in the following descriptions. 
   The ink jet printer  600  is equipped with an apparatus main body  620 , a tray  621  for holding recording paper P in an upper rear section thereof, a discharge port  622  for discharging the recording paper P to a lower front section thereof, and an operation panel  670  on an upper surface thereof. 
   The apparatus main body  620  is provided on its interior mainly with a printing device  640  having a head unit  630  that can be reciprocated, a paper feeding device  650  for feeding recording paper P one by one into the printing device  640 , and a control section  660  for controlling the printing device  640  and the paper feeding device  650 . 
   The printing device  640  is equipped with the head unit  630 , a carriage motor  641  that is a driving source for the head unit  630 , and a reciprocating mechanism  642  that receives rotations of the carriage motor  641  to reciprocate the head unit  630 . 
   The head unit  630  includes the ink jet recording head  50  equipped with multiple nozzles  511  in its lower section, ink cartridges  631  that supply inks to the ink jet recording head  50 , and a carriage  632  on which the ink jet recording head  50  and the ink cartridges  631  are mounted. 
   The reciprocating mechanism  642  includes a carriage guide shaft  644  with its both ends being supported by a frame (not shown), and a timing belt  643  that extends in parallel with the carriage guide shaft  644 . The carriage  632  is freely reciprocally supported by the carriage guide shaft  644 , and affixed to a portion of the timing belt  643 . By operations of the carriage motor  641 , the timing belt  643  is moved in a positive or reverse direction through pulleys, and the head unit  630  is reciprocally moved, guided by the carriage guide shaft  644 . During these reciprocal movements, the ink is jetted from the ink jet recording head  50 , to be printed on the recording paper P. 
   The paper feeding device  650  includes a paper feeding motor  651  as its driving source and a paper feeding roller  652  that is rotated by operations of the paper feeding motor  651 . The paper feeding roller  652  is composed of a follower roller  652   a  and a driving roller  652   b  that are disposed up and down and opposite to each other with a feeding path of the recording paper P (i.e., the recording paper P) being interposed between the two, and the driving roller  652   b  is coupled to the paper feeding motor  651 . 
   3-2. Because the ink jet printer  600  in accordance with the present embodiment is equipped with the ink jet recording head  50  with high performance, which is capable of arranging nozzles at a higher density, as described above in conjunction with the second embodiment, a high density printing and a high-speed printing become possible. 
   It is noted that the ink jet printer  600  in accordance with the present embodiment can also be used as a droplet discharge device that is used for industrial purposes. In this case, as ink (liquid material) to be jetted, a variety of functional materials may be used with their viscosity being appropriately adjusted by solvent, dispersion medium or the like. 
   The embodiments of the invention are described above in detail. However, those skilled in the art should readily understand that many modifications can be made without substantially departing from the novel matter and effects of the invention. Accordingly, those modified examples are also included in the scope of the invention. For example, the piezoelectric elements in accordance with the present invention are applicable not only to the devices described above, but also to a variety of other devices.