Patent Publication Number: US-8985748-B2

Title: Liquid ejection head and method of manufacturing liquid ejection head

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid ejection head that ejects liquid and a method of manufacturing the same. 
     2. Description of the Related Art 
     A liquid ejection head for ejecting ink is generally mounted onto an ink jet recording apparatus for recording an image on a recording medium by ejecting the ink. As a mechanism for causing the liquid ejection head to eject ink, there is known a mechanism using a pressure chamber that is shrinkable in volume by a piezoelectric element. In this mechanism, the pressure chamber shrinks due to the deformation of the piezoelectric element to which a voltage is applied, and thus the ink inside the pressure chamber is ejected from an ejection orifice communicated to one end of the pressure chamber. As one liquid ejection head including such a mechanism, there is known a so-called shear mode type in which one or two inner wall surfaces of the pressure chamber are formed of the piezoelectric element, and the pressure chamber is caused to shrink by shear deformation of the piezoelectric element instead of extension or contraction deformation thereof. 
     Regarding ink jet apparatus for industrial applications or the like, there is a demand for use of high viscosity liquid. In order to eject high viscosity liquid, a large ejection force is required for the liquid ejection head. To satisfy this demand, there has been proposed a liquid ejection head called a Gould type, in which the pressure chamber is formed of a tubular piezoelectric member having a circular or rectangular sectional shape. In the Gould type liquid ejection head, the piezoelectric member extends or is deformed by contraction in the inward and outward directions (radial direction) about the center of the pressure chamber. In this manner, the pressure chamber expands or shrinks. In the Gould type liquid ejection head, the entire wall surface of the pressure chamber deforms, and this deformation contributes to the ink ejection force. Therefore, as compared to the shear mode type in which one or two wall surfaces are formed of the piezoelectric element, a larger ink jet force can be obtained. The method of manufacturing a Gould type liquid ejection head is disclosed in Japanese Patent Application Laid-Open No. 2007-168319. 
     In the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, first, multiple grooves all extending in the same direction are formed in each of multiple piezoelectric plates. After that, the multiple piezoelectric plates are stacked so that the grooves are directed in the same direction, and are cut in a direction orthogonal to the direction of the grooves. The groove part of the cut piezoelectric plate forms an inner wall surface of the pressure chamber. After that, in order to separate the respective pressure chambers, the piezoelectric member present between the pressure chambers is removed to a certain depth. On upper and lower sides of the piezoelectric plate having the completed pressure chambers, a supply path plate and an ink pool plate, and a printed circuit board and an ejection orifice plate are respectively connected. In this manner, the liquid ejection head is completed. With this manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, the pressure chambers can be arranged in matrix, and hence the pressure chambers can be arranged in high density. Further, with this manufacturing method, because forming a groove in the piezoelectric plate is better in processing than opening a hole in the piezoelectric plate, the pressure chambers can be formed with high accuracy. 
     A technology of staggering multiple ejection orifices in a specific direction is known as a way to accomplish high-density recording with a liquid ejection head. In the liquid ejection head of Japanese Patent Application Laid-Open No. 2007-168319, however, the pressure chambers are arranged in two directions that intersect each other at right angles. If the technology is applied to this liquid ejection head, the liquid ejection head may not be able to eject ink from the ejection orifices because how the ejection orifices are arranged does not match how the pressure chambers are arranged. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above, and an object of the present invention is therefore to provide a liquid ejection head capable of ejecting liquid from ejection orifices irrespective of a mismatch between how the ejection orifices are arranged and how pressure chambers are arranged, and a method of manufacturing the liquid ejection head. 
     In order to achieve the above-mentioned object, according to an exemplary embodiment of the present invention, there is provided a liquid ejection head, including: 
     multiple ejection orifices for ejecting liquid; 
     multiple pressure chambers that communicate with the respective ejection orifices, and are arranged in a first direction and a second direction that intersect each other, the multiple pressure chambers including first electrodes formed on inner walls of the multiple pressure chambers; 
     a piezoelectric block including the multiple pressure chambers and multiple air chambers, the multiple air chambers being arranged in the first direction and the second direction alternately with the multiple pressure chambers, the multiple air chambers including second electrodes formed on inner walls of the multiple air chambers, the inner walls of the respective pressure chambers being deformable by application of voltage between the first electrodes and the second electrodes to cause liquid to flow out of open ends of the respective pressure chambers; 
     an orifice plate in which the multiple ejection orifices are arranged; and 
     a plate-like member that is interposed between the piezoelectric block and the orifice plate and is pierced by multiple flow paths, the multiple flow paths allowing the open ends of the respective pressure chambers to communicate individually to the respective ejection orifices. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a liquid ejection head according to Embodiment 1 of the present invention. 
         FIG. 2  is a perspective view of the liquid ejection head of  FIG. 1 . 
         FIG. 3  is a flow chart illustrating steps of manufacturing the liquid ejection head according to Embodiment 1 of the present invention. 
         FIG. 4  is a flow chart illustrating steps of a first-piezoelectric substrate processing step. 
         FIG. 5  is a flow chart illustrating steps of a second-piezoelectric substrate processing step. 
         FIG. 6  is a diagram illustrating the first-piezoelectric substrate processing step. 
         FIGS. 7A ,  7 B,  7 C,  7 D,  7 E,  7 F,  7 G, and  7 H are diagrams illustrating the first-piezoelectric substrate processing step. 
         FIGS. 8A ,  8 B,  8 C,  8 D,  8 E,  8 F,  8 G, and  8 H are sectional views illustrating an electrode patterning method that uses lift-off. 
         FIG. 9  is a plan view of how the second piezoelectric substrate looks after groove processing is performed. 
         FIGS. 10A ,  10 B,  10 C, and  10 D are perspective views illustrating steps of the second-piezoelectric substrate processing step that follow the groove processing step. 
         FIGS. 11A ,  11 B,  11 C, and  11 D are sectional views illustrating another electrode patterning method that uses lift-off. 
         FIGS. 12A and 12B  are perspective views illustrating a stacking step. 
         FIG. 13  illustrates another mode of a substrate  511  of  FIG. 12B . 
         FIG. 14  is a sectional view of a piezoelectric block  303  of  FIG. 12B . 
         FIG. 15  is a perspective view illustrating an end face electrode forming step. 
         FIGS. 16A ,  16 B,  16 C, and  16 D are sectional views taken along the line A-A of  FIG. 15 . 
         FIG. 17  is a sectional view taken along the line  17 - 17  of  FIG. 15 . 
         FIG. 18  is a perspective view illustrating a rear-end face electrode forming step. 
         FIGS. 19A ,  19 B,  19 C, and  19 D are sectional views taken along the line A-A of  FIG. 18 . 
         FIG. 20  is a perspective view of the liquid ejection head of Embodiment 1 of the present invention, which is viewed from the back. 
         FIG. 21  is a top view and sectional view of a rear throttle plate. 
         FIG. 22  is a frontal view of a plate-like member. 
         FIGS. 23A and 23B  are diagrams illustrating an orifice plate. 
         FIG. 24  is a perspective view illustrating a wiring/packaging step. 
         FIGS. 25A and 25B  are enlarged views of a region R of  FIG. 12B . 
         FIG. 26  is a sectional view illustrating how the piezoelectric block, the plate-like member, and the orifice plate are joined to one another. 
         FIG. 27  is a sectional view illustrating a mode in which two plate-like members are used. 
         FIG. 28  is a sectional view illustrating the structure of a principal part of a liquid ejection head according to Embodiment 2 of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     (Embodiment 1) 
     Embodiment 1 of the present invention is described.  FIG. 1  is an exploded perspective view of a liquid ejection head according to Embodiment 1.  FIG. 2  is a perspective view of the liquid ejection head of  FIG. 1 . In the liquid ejection head of  FIGS. 1 and 2  that is denoted by  101 , an orifice plate  304 , a plate-like member  401 , a piezoelectric block  303 , which is made of a piezoelectric material, a rear throttle plate  302 , and a common liquid chamber  301  are stacked on top of one another. The piezoelectric block  303  is provided with multiple pressure chambers  307  whose side walls are made of a piezoelectric material, and multiple air chambers  308 . The common liquid chamber  301  communicates to each pressure chamber  307  of the piezoelectric block  303  via the rear throttle plate  302 . Wiring lines from the piezoelectric block  303  to the outside are led out from the piezoelectric block  303  by a first flexible cable  310  and a second flexible cable  311 . Multiple ejection orifices  309  from which pressurized ink (liquid) is ejected are formed in the orifice plate  304 . The ejection orifices  309  individually communicate with the pressure chambers  307  via flow paths  402  that pierce the inside of the plate-like member  401 . 
     A method of manufacturing the liquid ejection head of this embodiment is described below.  FIG. 3  is a flow chart illustrating steps of manufacturing the liquid ejection head according to this embodiment. 
     A first-piezoelectric substrate processing step and a second-piezoelectric substrate processing step (Step S 1 ) are described first.  FIG. 4  is a flow chart illustrating steps of the first-piezoelectric substrate processing step.  FIG. 5  is a flow chart illustrating steps of the second-piezoelectric substrate processing step. The first-piezoelectric substrate processing step is described first. 
     As illustrated in  FIG. 4 , the first-piezoelectric substrate processing step includes a groove processing step (Step S 101 ), an electrode forming step (Step S 102 ), a polarization step (Step S 103 ), and a chip separating step (Step S 104 ). 
       FIG. 6  and  FIGS. 7A to 7H  are diagrams illustrating the first-piezoelectric substrate processing step.  FIG. 6  illustrates five sets of first grooves  503  and second grooves  504  that correspond to five nozzles made up of the pressure chambers  307  and the air chambers  308 .  FIGS. 7A to 7H  illustrate one set of the first grooves  503  and the second grooves  504 . 
     (Groove Processing Step) 
     The groove processing step (Step S 101 ) is described.  FIG. 7A  illustrates a first piezoelectric substrate  501  having a flat plate shape. The first piezoelectric substrate  501  can be, for example, a lead zirconate titanate (PZT) substrate. First exposure-use alignment grooves  514  (see  FIG. 6 ) are formed in the first piezoelectric substrate  501  by grinding that uses a super abrasive wheel. The first exposure-use alignment grooves  514  may be positioned based on the distance from one end of the first piezoelectric substrate  501 , or may be positioned with the use of a metal pattern or the like that is formed by photolithography to serve as a guide. 
       FIG. 7B  illustrates the first piezoelectric substrate  501  in which multiple first grooves  503  have been formed. The first grooves  503  respectively function as the pressure chambers  307  described above. As illustrated in  FIG. 7B , the first grooves  503  are open-ended on a first side face  804 , and are closed-ended on a second side face  805 , which is opposite from the first side face  804 . In the groove processing step, first alignment grooves for joining  513  (see  FIG. 6 ) that serve as an alignment guide in the chip separating step are formed as well. 
       FIG. 7C  illustrates the first piezoelectric substrate  501  in which multiple second grooves  504  have been formed. The second grooves  504  are side by side with and alternate with the first grooves  503 . The second grooves  504  are closed-ended on the first side face  804 , and are open-ended on the second side face  805 . The second grooves  504  run parallel to the first grooves  503  and function as the air chambers  308  described above. 
     (Electrode Forming Step) 
     The electrode forming step (Step S 102 ) is described.  FIG. 7D  illustrates the first grooves  503  in which first electrodes  505  have been formed and the second grooves  504  in which second electrodes  506  have been formed. The first electrodes  505  and the second electrodes  506  are formed by patterning that uses lift-off, or by patterning that uses a laser or polishing, or by other methods.  FIGS. 8A to 8H  are sectional views illustrating an electrode patterning method that uses lift-off.  FIGS. 8A to 8D  are sectional views taken along the line A-A of  FIG. 7C .  FIGS. 8E to 8H  are sectional views taken along the line B-B of  FIG. 7C . 
       FIG. 8A  illustrates the first piezoelectric substrate  501  on which a film resist  902  has been stacked.  FIG. 8B  illustrates the film resist  902  that has been patterned by exposure and development. In lift-off, a resist pattern is formed by photolithography so that the resist remains in parts where the electrode pattern is not to be left.  FIG. 8C  illustrates a metal layer formed on the substrate by sputtering or vapor deposition to form electrodes.  FIG. 8D  illustrates the substrate from which the resist has been removed. Removing the resist causes the metal film formed on the resist to peel off along with the resist and, ultimately, a desired metal film pattern is obtained. 
     An electrode patterning method that uses a laser or polishing is described. First, a metal film is formed on the first piezoelectric substrate  501  through sputtering, vapor deposition, electroless plating, or the like. At this point, the metal film is formed on the first side face  804  and the second side face  805  as well. An unnecessary part of the metal film is then removed with the use of a laser or by polishing, and a desired electrode pattern is thus obtained. The first electrodes  505  and the second electrodes  506  establish electrical connection to each other via the parts of the metal film that are formed on the first side face  804  and the second side face  805 . 
       FIG. 7E  illustrates a rear face of the first piezoelectric substrate  501  (a face opposite from the one where the first grooves  503  and the second grooves  504  are formed) on which first common wiring  802  and second common wiring  803  have been formed. The first common wiring  802  and the second common wiring  803  are made from a metal film. The first common wiring  802  and the second common wiring  803  are divided from each other in a direction in which the first grooves  503  are arranged. The first common wiring and the second common wiring can be patterned by lift-off or etching of a photo resist that uses photolithography, or other similar methods. The first common wiring and the second common wiring can also be patterned by removing an unnecessary part with the use of a laser, or through dicing or milling. A step of patterning the first common wiring  802  and the second common wiring  803  by lift-off that uses photolithography is described with reference to  FIGS. 8E to 8H . 
     A film of a second resist  903  is formed over the entire rear face of the first piezoelectric substrate  501  (see  FIG. 8E ). The resist  903  is subsequently patterned (see  FIG. 8F ). A metal film is then formed on the patterned resist  903  and the rear face of the piezoelectric substrate  501  (see  FIG. 8G ). Lastly, the resist  903  is removed (see  FIG. 8H ). 
     The first common wiring  802  is electrically connected to the first electrodes  505  and the second electrodes  506  via the first side face  804 . The second common wiring  803 , on the other hand, is electrically connected to the first electrodes  505  and the second electrodes  506  via the second side face  805 . 
     (Polarization Step) 
     The polarization step (Step S 103 ) is described.  FIG. 7F  is a diagram illustrating the polarization step. In the polarization step, a high voltage is applied between the first common wiring  802  and the second common wiring  803 . At this point, the first electrodes  505  have a positive electric potential and the second electrodes  506  have a ground electric potential. The temperature condition is about 100 to 150° C., and the voltage condition is about 1 to 2 kV/mm. Polarization is desired to be performed in oil that is highly insulative (for example, silicone oil that is 10 kV/mm or more in dielectric breakdown voltage) in order to prevent atmospheric discharge and creeping discharge. Silicone oil can be removed after the polarization step with a hydrocarbon-based solvent such as xylene, benzene, or toluene, or a chlorinated hydrocarbon-based solvent such as methyl chloride, 1.1.1-trichloroethane, or chlorobenzene. 
     Aging processing may be performed after the polarization step. Specifically, the first piezoelectric substrate  501  on which polarization has been performed is kept at a raised temperature for a given period of time. The piezoelectric characteristics of the first piezoelectric substrate  501  are stabilized in this manner. 
     (Chip Separating Step) 
     The chip separating step (S 104 ) is described.  FIG. 7G  is a diagram illustrating the chip separating step. In the chip separating step, the first piezoelectric substrate  501  is cut with a super abrasive wheel  901  as illustrated in  FIG. 7G . Dicing, polishing, and laser abrasion can be given as other cutting method examples. The first grooves  503  need to be closed at both ends in order to function as the pressure chambers  307 . In this step, the first piezoelectric substrate  501  is cut in the manner illustrated in  FIG. 7G , with the result that the multiple second electrodes  506  are electrically isolated from one another and are also electrically isolated from the second common wiring  803 . 
     A step illustrated in  FIG. 7H  is a step of removing the part of the first common wiring  802  that is formed on the first side face  804 . Dicing, polishing, and laser abrasion can be given as removal method examples. Removing the part of the first common wiring  802  that is formed on the first side face  804  renders the multiple first electrodes  505  electrically isolated from one another. In the chip separating step, the five sets of piezoelectric substrates of  FIG. 6  are cut off for every five nozzles. Five chips are thus cut out of the first piezoelectric substrate  501 . 
     In the first-piezoelectric substrate processing step described above, polarization can be performed with the second grooves  504 , which function as the air chambers  308 , closed on the first side face  804 . 
     The second-piezoelectric substrate processing step is described next. As illustrated in  FIG. 5 , the second-piezoelectric substrate processing step includes a polarization step (Step S 201 ), a groove processing step (Step S 202 ), an electrode forming step (Step S 203 ), and a chip separating step (Step S 204 ). 
     (Polarization Step) 
     The polarization step (Step S 201 ) is described. A second piezoelectric substrate  502  can be a PZT substrate as is the case for the first piezoelectric substrate  501 . In the step of processing the first piezoelectric substrate  501 , the polarization step is executed after the groove processing step as illustrated in  FIGS. 7A to 7H . In the step of processing the second piezoelectric substrate  502 , on the other hand, the polarization step is conducted before the groove processing step. The polarization step is a step of respectively forming electrodes over the entire front face and rear face of the piezoelectric substrate having a flat plate shape, and applying a high electric field of about 1 to 2 kV/mm between the electrodes for a given period of time while the substrate is heated at about 100 to 150° C. Through the polarization, the piezoelectric substrate is polarized uniformly in a direction perpendicular to the principle surface of the piezoelectric substrate. The polarization may be conducted in insulative oil as is the case for the first piezoelectric substrate  501 , or in the air. The electrodes are removed from the front face by etching or polishing after the polarization. 
     (Groove Processing Step) 
     The groove processing step (Step S 202 ) is described.  FIG. 9  is a plan view illustrating the second piezoelectric substrate  502  on which groove processing has been performed. In  FIG. 9 , five sets of grooves are disposed to serve as the air chambers  308  that correspond to five nozzles. However, only one out of the five sets is discussed and illustrated in the following description of steps and drawings referred to in the description. 
       FIG. 9  illustrates second exposure-use alignment grooves  516  that are formed by grinding that uses a super abrasive wheel. The groove processing step uses the second exposure-use alignment grooves  516  as a reference for processing. The second exposure-use alignment grooves  516  may be positioned based on the distance from an end of the substrate, or may be positioned with the use of a metal pattern or the like that is formed by photolithography to serve as a guide. 
       FIGS. 10A to 10D  are perspective views illustrating steps of the second-piezoelectric substrate processing step that follow the groove processing step.  FIG. 10A  illustrates the second piezoelectric substrate  502  in which multiple third grooves  507  have been formed. The third grooves  507  function as the air chambers  308  that are adjacent to the pressure chambers  307  described above. In this embodiment, the third grooves  507  that are closed at one end in the longitudinal direction are formed by pulling up the super abrasive wheel  901  away from the piezoelectric substrate during grinding at some points on the piezoelectric substrate. 
     (Electrode Forming Step) 
       FIG. 10B  illustrates the third grooves  507  in which a fourth electrode  509  has been formed. The fourth electrode  509  has the same polarity as that of the second electrodes  506 . It is sufficient if the fourth electrode  509  is formed on at least the bottom faces of the third grooves  507 , and an electrode formed over the entire surface of the third grooves  507  may be used as the fourth electrode  509 . The fourth electrode  509  can be patterned by lift-off or polishing, or with the use of a laser. 
       FIGS. 11A to 11D  are sectional views illustrating an electrode patterning method that uses lift-off. The sectional views of  FIGS. 11A to 11D  are taken along the line A-A of  FIG. 10B .  FIG. 11A  illustrates the second piezoelectric substrate  502  on which the film resist  903  has been stacked.  FIG. 11B  illustrates the film resist  903  on which a resist pattern has been formed by photolithography so that the resist remains in parts where the electrode pattern is not to be left.  FIG. 11C  illustrates a metal layer formed on the substrate by sputtering or vapor deposition to form electrodes.  FIG. 11D  illustrates the substrate from which the resist has been removed. Removing the resist causes the metal film formed on the resist to peel off along with the resist and, ultimately, a desired metal film pattern is obtained. 
     The electrodes may also be patterned with the use of a laser or by polishing by the same method that has been described in the description of the electrode forming step (Step S 102 ) that is one of the steps of processing the first piezoelectric substrate  501 . 
       FIG. 10C  illustrates the second piezoelectric substrate  502  having a rear face on which a fifth electrode  512  has been formed from a metal film (the rear face of the second piezoelectric substrate  502  is a face opposite from the one where the third grooves  507  are formed). The pattern of the fifth electrode  512  is divided along borders between the third grooves  507 . The fifth electrode  512  can be patterned by lift-off or etching of a photo resist that uses photolithography, or other similar methods. The fifth electrode  512  can also be patterned by removing an unnecessary part with the use of a laser, or through dicing or milling. 
     (Chip Separating Step) 
     The chip separating step (Step S 204 ) is described.  FIG. 10D  is a diagram illustrating the chip separating step. In the chip separating step, a part of the second piezoelectric substrate  502  is cut. Dicing, polishing, and laser abrasion can be given as cutting method examples. In this embodiment, the second piezoelectric substrate  502  is cut so that the third grooves  507  are closed on one side face. The second piezoelectric substrate  502  is cut into pieces for every five nozzles similarly to the first piezoelectric substrate  501 . Five chips are thus cut out of the second piezoelectric substrate  502 . 
     (Stacking Step) 
     A stacking step (Step S 2 ) is described next with reference to  FIGS. 12A and 12B . The first grooves  503  and the second grooves  504  have been formed in the first piezoelectric substrate  501  through the first-piezoelectric substrate processing step and the second-piezoelectric substrate processing step (Step S 1 ) described above. The first electrodes  505  are formed on the inner walls of the first grooves  503  and the second electrodes  506  are formed on the inner walls of the second grooves  504 . A third electrode  508  is formed on the rear face of the first piezoelectric substrate  501 . In the second piezoelectric substrate  502 , on the other hand, the third grooves  507  are formed and the fourth electrode  509  that is substantially the same as the second electrodes  506  is formed on the inner walls of the third grooves  507 . A fifth electrode  512  is formed on the rear face of the second piezoelectric substrate  502 . 
     In the stacking step, one first piezoelectric substrate  501  and one second piezoelectric substrate  502  are first stacked and joined to each other as illustrated in  FIG. 12A . The piezoelectric substrates are joined with the use of, for example, an epoxy-based adhesive. In order to avoid filling the grooves formed in the respective piezoelectric substrates with the adhesive, it is desired to control the amount of the adhesive appropriately. The adhesive can be applied by forming a thin uniform adhesive layer on another flat substrate through spin coating, screen printing, or the like, pressing a surface to be joined against the adhesive layer, and then pulling the surface away. A thin uniform adhesive layer is thus formed on one of the piezoelectric substrates. After the adhesive is applied, the piezoelectric substrates are positioned with a minute gap left therebetween substrates, and the piezoelectric substrates are then bonded by pressure bonding. 
     To align the piezoelectric substrates for the stacking, an end face of each chip cut out of the piezoelectric substrates may be pushed against positioning pins. Alternatively, the piezoelectric substrates may be aligned with the use of a camera in order to improve the positioning accuracy. In the alignment with the aid of a camera, edges of the chips, grooves, alignment marks patterned when the electrodes are formed, or the like can be used as a guide. 
     In the stacking step, the stacked body of  FIG. 12A  constitutes one unit and multiple units are stacked and joined to one another. A substrate  510  is joined to the topmost layer of the multiple units (see  FIG. 12B ), and a substrate  511  is joined to the lowermost layer of the multiple units (see  FIG. 12B ). The piezoelectric block  303  is manufactured in this manner. The substrate  510  and the substrate  511  are flat plates on which no patterns are formed. The substrate  510  and the substrate  511  do not need to be piezoelectric substrates. In the case where heating is required to join the substrates, the substrate  510  and the substrate  511  are desired to be made from a material that has a thermal expansion coefficient close to those of the first piezoelectric substrate  501  and the second piezoelectric substrate  502 . The substrate  510  and the substrate  511  work to correct the overall warping of the stacked piezoelectric substrates. 
       FIG. 13  illustrates another mode of the substrate  511  of  FIG. 12B . When the substrate  511  of  FIG. 13  is used, the second piezoelectric substrate  502  is not placed on the lowermost layer of the stacked body of the first piezoelectric substrate  501  and the second piezoelectric substrate  502 . There is no particular need to form electrodes on inner walls of the substrate  511  of  FIG. 13 . 
       FIG. 14  is a sectional view of the piezoelectric block  303  illustrated in  FIG. 12B . In the piezoelectric block  303  of  FIG. 14 , the pressure chambers  307  (the first grooves  503 ) and the air chambers  308  (the second grooves  504  and the third grooves  507 ) are arranged in two directions that intersect each other. In the following, one of the two directions that is a direction in which the grooves are arranged in the respective piezoelectric substrates is referred to as “first direction” and the other direction that intersects the first direction is referred to as “second direction”. The second direction in this embodiment corresponds to a direction in which the first piezoelectric substrate  501  and the second piezoelectric substrate  502  are stacked. In other words, the second direction in this embodiment intersects the first direction at right angles. In the piezoelectric block  303  of this embodiment, the air chambers  308  and the pressure chambers  307  are arranged alternately in the first direction and the second direction. 
     (Polishing Step) 
     A polishing step (Step S 3 ) is described. The polishing step is a step of leveling both end faces of the piezoelectric block  303  (faces where the open ends of the pressure chambers  307  are located) by polishing. Abrasive grains are used for the polishing. It is preferred to give the end faces a surface roughness Ra of about 0.4 μm for subsequent electrode forming steps. It is also preferred to give each end face a levelness within 10 μm and to set the parallelism between the end faces to 30 μm or less in order to bond the orifice plate  304  and the rear throttle plate  302  with precision. 
     (Front End Face Electrode Forming Step) 
     A front end face electrode forming step (Step S 4 ) is described. The front end face electrode forming step is a step of forming, on a front end face of the piezoelectric block  303  (a face where ink flows out of the open ends of the pressure chambers  307 ), a wiring pattern that is electrically connected to the electrodes provided in the respective air chambers  308 .  FIG. 15  is a perspective view illustrating the front end face electrode forming step. Wiring  817  illustrated in  FIG. 15  is formed on a front end face  806  of the piezoelectric block  303 . A method of patterning the wiring  817  is described with reference to  FIGS. 16A to 16D .  FIGS. 16A to 16D  are sectional views taken along the line A-A of  FIG. 15 . First, a film resist  904  is stacked on the front end face  806  of the piezoelectric block  303  as illustrated in  FIG. 16A . Exposure and development are conducted next to expose the air chambers  308  and the peripheries of the air chambers  308  (see  FIG. 16B ). At this point, the pressure chambers  307  and the peripheries of the pressure chambers  307  are covered with the film resist  904 . The wiring  817  is further formed as illustrated in  FIG. 16C . The wiring  817  is thus electrically connected to the second electrodes  506  and the third electrode  508 . At this point, a film is formed with the use of a mask also on a top face  808  (see  FIG. 15 ) of the piezoelectric block  303 , to thereby form a packaged wiring connecting portion  815 . The film resist  904  is then removed as illustrated in  FIG. 16D , with the result that the wiring  817  is patterned to have a desired pattern by lift-off.  FIG. 17  is a sectional view taken along the line  17 - 17  of  FIG. 15 . The wiring  817  is electrically connected to the second electrodes  506  that are formed on the inner walls of the air chambers  308 , and is not electrically connected to the first electrodes  505  that are formed on the inner walls of the pressure chambers  307 . 
     The wiring  817  may be structured so that, for example, a Cr layer is formed as a base layer and an Au layer is formed as an electrode layer. To give another example, the wiring  817  may be structured so that a Pd layer is formed on a Cr layer serving as a base layer. The wiring  817  may also have a structure in which a Ni plating film is formed with a Pd layer as a seed layer and Ni on the surface is displaced with Au by displacement plating. 
     (Rear End Face Electrode Forming Step) 
     A rear end face electrode forming step (Step S 5 ) is described. The rear end face electrode forming step is a step of forming, on a rear end face  807  of the piezoelectric block  303 , a wiring pattern that is electrically connected to the electrodes provided in the respective pressure chambers  307 .  FIG. 18  is a perspective view illustrating the rear end face electrode forming step. Wiring  816  illustrated in  FIG. 18  is electrically connected to the packaged wiring connecting portion  814  formed above the rear end face  807  of the piezoelectric block  303 . The wiring  816  is electrically connected to the first flexible substrate  310  via the packaged wiring connecting portion  814  by a step described later. A method of patterning the wiring  816  is described with reference to  FIGS. 19A to 19D .  FIGS. 19A to 19D  are sectional views taken along the line A-A of  FIG. 18 . First, a film resist  905  is stacked on the rear end face  807  of the piezoelectric block  303  as illustrated in  FIG. 19A . Exposure and development are conducted next to expose the pressure chambers  307  and the peripheries of the pressure chambers  307  (see  FIG. 19B ). The wiring  816  is further formed as illustrated in  FIG. 19C . The wiring  816  is thus electrically connected to the first electrodes  505  and the fifth electrode  512 . The film resist  905  is then removed as illustrated in  FIG. 19D , with the result that the wiring  816  is patterned to have a desired pattern by lift-off. The wiring  816  can have the same structure as that of the wiring  817  described above. 
     The first electrodes  505  formed on the inner walls of the respective pressure chambers  307  are each individually connected to one wiring line  816 . Drive signals are applied to the respective wiring lines  816  to deform the inner walls of the pressure chambers  307  independently of one another. 
     (Rear Throttle Plate Joining Step) 
     A rear throttle plate joining step (Step S 6 ) is described.  FIG. 20  is an exploded perspective view of the liquid ejection head according to this embodiment. The perspective view of  FIG. 20  is viewed from the back of the liquid ejection head of this embodiment.  FIG. 21  is a top view and sectional view of the rear throttle plate. As illustrated in  FIG. 21 , the rear throttle plate  302  is provided with multiple openings  809  at points corresponding to the respective pressure chambers  307 . The openings  809  are a member for restricting ink from flowing back from the pressure chambers  307 . The rear throttle plate  302  in this embodiment is made from a silicon substrate. The openings  809  are formed by etching or the like so as to pierce the rear throttle plate  302 . The diameter of each opening  809  is smaller than the diameter of each pressure chamber  307 . It is preferred to form an insulating film on the surface of the rear throttle plate  302  by thermal oxidation or the like in advance in order to prevent the wiring lines formed in the piezoelectric block  303  from short-circuiting when the rear throttle plate  302  is joined to the piezoelectric block  303 . An epoxy-based adhesive, for example, is used to join the rear throttle plate  302  to the piezoelectric block  303 . In order to avoid filling the openings  809  with the adhesive when the rear throttle plate  302  is joined, the amount of the adhesive needs to be controlled appropriately. The adhesive can be applied by forming a thin uniform adhesive layer on another flat substrate through spin coating, screen printing, or the like, pressing a surface to be joined against the adhesive layer, and then pulling the surface away. A thin uniform adhesive layer is thus formed on the piezoelectric block. After the adhesive is applied, the throttle plate and the piezoelectric block are positioned with a minute gap left therebetween, and the throttle plate is then bonded to the piezoelectric block by pressure bonding. 
     Grooves  811  may be formed outside the openings  809  of the rear throttle plate  302  in order to prevent the adhesive from entering the openings  809 . 
     The alignment grooves for joining  513  (see FIG.  6 ) and alignment grooves for joining  515  (see  FIG. 9 ) are used as measures for positioning when the rear throttle plate  302  is joined to the piezoelectric block  303 . As illustrated in  FIG. 20 , the rear throttle plate  302  is provided with alignment holes  810  for positioning with respect to the alignment grooves for joining  513  and  515 . 
     The rear throttle plate  302  is bonded to the rear end face  807  of the piezoelectric block  303  so that the packaged wiring connecting portion  814  is exposed. 
     (Insulating Step) 
     An insulating step (Step S 7 ) is described. The insulating step is a step of forming an insulating film on the surface of the electrodes that have been formed on the inner walls of the pressure chambers  307 , the electrodes that have been formed on the inner walls of the air chambers  308 , and the electrode wiring lines. Of the electrode wiring lines, the insulating film is not formed on the packaged wiring connecting portions  814  and  815 . The packaged wiring connecting portions  814  and  815  are masked with tape or the like when the insulating film is formed. The insulating film is, for example, a thin film of parylene and is formed by chemical vapor deposition (CVD). Before the parylene film is formed, UV ozone treatment may be performed at room temperature for about five minutes in order to improve the adhesion of the parylene film. The adhesion may be enhanced further by applying a coupling agent after the UV ozone treatment. 
     (Plate-like Member Joining Step) 
     A plate-like member joining step (Step S 8 ) is described. The plate-like member joining step is a step of joining the plate-like member  401  of  FIG. 22  to the front end face  806  of the piezoelectric block  303 .  FIG. 22  is a frontal view of the plate-like member  401 . Multiple flow paths  402  are provided in the plate-like member  401 . The flow paths  402  are flow paths by which the pressure chambers  307  individually communicate with the ejection orifices  309 . The plate-like member  401  in this embodiment is made from a silicon substrate. The flow paths  402  are formed by opening through-holes in the plate-like member  401  by etching or the like. It is preferred to form an insulating film on the surface of the plate-like member  401  by thermal oxidation or the like in advance in order to prevent the wiring lines formed in the piezoelectric block  303  from short-circuiting when the plate-like member  401  is joined to the piezoelectric block  303 . An epoxy-based adhesive, for example, is used to join the plate-like member  401  to the piezoelectric block  303 . In order to avoid filling the flow paths  402  with the adhesive when the plate-like member  401  is joined, the amount of the adhesive needs to be controlled appropriately. The adhesive can be applied by forming a thin uniform adhesive layer on another flat substrate through spin coating, screen printing, or the like, pressing a surface to be joined against the adhesive layer, and then pulling the surface away. A thin uniform adhesive layer is thus formed on the piezoelectric block. After the adhesive is applied, the plate-like member and the piezoelectric block are positioned with a minute gap left therebetween, and the plate-like member is then bonded to the piezoelectric block by pressure bonding. 
     Grooves  406  may be formed around the flow paths  402  in order to prevent the adhesive from entering the flow paths  402  (see  FIG. 22 ). 
     The alignment grooves for joining  513  (see  FIG. 6 ) and the alignment grooves for joining  515  (see  FIG. 9 ) are used as measures for positioning when the plate-like member  401  is joined to the piezoelectric block  303 . As illustrated in  FIG. 22 , the plate-like member  401  is provided with alignment holes  405  for positioning with respect to the alignment grooves for joining  513  and  515 . 
     (Orifice Plate Joining Step) 
     An orifice plate joining step (Step S 9 ) is described. The orifice plate joining step is a step of joining the orifice plate  304  to the plate-like member  401 .  FIGS. 23A and 23B  are diagrams illustrating the orifice plate.  FIG. 23A  is a perspective view of the orifice plate  304 .  FIG. 23B  is a plan view and sectional view of one of the ejection orifices  309  formed in the orifice plate  304 . 
     Multiple ejection orifices  309  pierce the orifice plate  304 . The ejection orifices  309  individually communicate with the respective pressure chambers  307  via the flow paths  402  of the plate-like member  401 . Grooves  812  for preventing an adhesive from entering the ejection orifices  309  are provided in the orifice plate  304  on a side where the orifice plate  304  is joined to the plate-like member  401  (see  FIG. 23B ). The orifice plate  304  can be manufactured by, for example, electroforming of Ni. Ink repellent treatment may further be performed on a face of the orifice plate  304  that is opposite from the one where the orifice plate  304  is joined to the plate-like member  401 . Silane-based materials and fluorine-based materials are given as ink repellent material examples, and a film of one of these materials is formed on the orifice plate  304  by vapor deposition or the like. 
     The orifice plate  304  in this embodiment is joined to the plate-like member  401  with, for example, an adhesive. An epoxy-based adhesive can be given as an example of the adhesive. In order to avoid filling the ejection orifices  309  with the adhesive when the orifice plate  304  is joined, the amount of the adhesive needs to be controlled appropriately. The adhesive can be applied by forming a thin uniform adhesive layer on another flat substrate through spin coating, screen printing, or the like, pressing a surface to be joined against the adhesive layer, and then pulling the surface away. A thin uniform adhesive layer is thus formed on the piezoelectric substrate. After the adhesive is applied, the orifice plate and the plate-like member are positioned with a minute gap left therebetween, and the orifice plate is then bonded to the plate-shaped member by pressure bonding. 
     As illustrated in  FIG. 23A , the orifice plate  304  is provided with alignment holes  813  for positioning with respect to the alignment grooves for joining  513  and  515 . 
     In this embodiment, the piezoelectric substrates are stacked so that the open ends of the pressure chambers  307  on the ejection orifice side are arranged in the first direction and the second direction that intersect each other at right angles as illustrated in  FIG. 14 . The ejection orifices  309 , on the other hand, are arranged in the first direction and a third direction (see  FIG. 23A ). The third direction is a direction tilted from the second direction. Arranging the ejection orifices  309  in this manner enhances the recording density compared to a mode in which the ejection orifices  309  are arranged orthogonally as the pressure chambers  307  are. 
     Beading can be reduced by controlling ejection so that ink is not ejected successively from the ejection orifices  309  that are adjacent to one another. “Beading” herein refers to a phenomenon in which a drop of ink ejected first is not given time to be absorbed by a recording medium before the next drop of ink is ejected, and the resultant mixture of the ink drops causes density unevenness. 
     (Wiring/Packaging Step) 
     A wiring/packaging step (Step S 10 ) is described.  FIG. 24  is a perspective view illustrating the wiring/packaging step. As illustrated in  FIG. 24 , in the wiring/packaging step, the first flexible substrate  310  is bonded under pressure to the rear end face  807  of the piezoelectric block  303 , and the second flexible substrate  311  is bonded under pressure to the top face  808  of the piezoelectric block  303 . An anisotropic conductive film is used for the bonding under pressure. After the bonding under pressure, areas around where the respective flexible substrates are joined to the piezoelectric block  303  are reinforced with an adhesive. 
     (Common Liquid Chamber Joining Step) 
     A common liquid chamber joining step (Step S 11 ) is described. After the wiring/packaging step, the common liquid chamber  301  having an ink supply port  305  (see  FIG. 1 ) is joined to the rear throttle plate  302 . The common liquid chamber  301  in this embodiment is made from a stainless steel substrate. The ink supply port  305  is formed by machining. The common liquid chamber  301  is joined to the rear throttle plate  302  with an adhesive. 
     Lastly, other necessary components are assembled to complete the liquid ejection head. 
     (Driving) 
     The operation of driving the piezoelectric block  303  is described next.  FIGS. 25A and 25B  are enlarged views of a region R illustrated in  FIG. 12B . As illustrated in  FIG. 25A , each pressure chamber  307  (first groove  503 ) is defined by the air chambers  308  (the second grooves  504  and the third grooves  507 ) so that the chambers form a two-dimensional array pattern. The pressure chamber  307  is polarized in an outward polarization direction  601 .  FIG. 25B  illustrates how the pressure chamber  307  looks when voltage is applied. The voltage is applied between the electrodes with the first electrode  505  and the fifth electrode  512  that are formed on the inner walls of the pressure chamber  307  given a positive electric potential, and the second electrodes  506 , the third electrode  508 , and the fourth electrode  509  that are formed on the inner walls of the air chambers  308  given a ground electric potential. The voltage application causes the pressure chamber  307  to deform by shrinking in a manner illustrated in  FIG. 25B . The shrinking deformation enhances the pressure of ink filling the pressure chamber  307 . As a result, the ink flows out of the open end of the pressure chamber  307 . The flowing ink runs along the relevant flow path  402  to be ejected from the relevant ejection orifice  309 . On the other hand, the pressure chamber  307  deforms by expanding when drive voltage is applied with the first electrode  505  and the fifth electrode  512  given a GND electric potential, and the second electrodes  506 , the third electrode  508 , and the fourth electrode  509  given a positive electric potential (not shown). 
     In the liquid ejection head of this embodiment, how the ejection orifices  309  are arranged does not match how the pressure chambers  307  are arranged as described above. However, the flow paths  402  formed in the plate-like member  401  allow the pressure chambers  307  and the ejection orifices  309  to communicate with each other as illustrated in  FIG. 26 . The liquid ejection head can thus eject ink from the ejection orifices  309  despite the fact that how the ejection orifices  309  are arranged does not match how the pressure chambers  307  are arranged.  FIG. 26  is a sectional view illustrating the piezoelectric block  303 , the plate-like member  401 , and the orifice plate  304  that have been joined to one another. The flow paths  402  do not communicate with the pressure chambers  307  as illustrated in  FIG. 26 . 
     In the case where a gap P (see  FIG. 26 ) between one pressure chamber  307  and one air chamber  308  is narrow, a plate-like member  403  illustrated in  FIG. 27  may be inserted between the piezoelectric block  303  and the plate-like member  401  so that only the pressure chambers  307  and the ejection orifices  309  communicate with one another. The plate-like member  403  is pierced by flow paths  404 , which communicate with the flow paths  402 . The diameter of each flow path  404  is smaller than the diameter of each flow path  402 . 
     Other than stacking the two plate-like members  401  and  403 , a form similar to the one illustrated in  FIG. 27  can be manufactured with one plate-like member by adjusting the depth of the flow paths  402  through counterboring or the like. 
     (Embodiment 2) 
     Embodiment 2 of the present invention is described. The following description focuses on differences from the first embodiment described above.  FIG. 28  is a sectional view illustrating the structure of a principal part of a liquid ejection head according to Embodiment 2. In Embodiment 2, components similar to those described in Embodiment 1 are denoted by the same reference symbols that are used in Embodiment 1, and detailed descriptions thereof are omitted. 
     The liquid ejection head of Embodiment 2 is, similarly to the liquid ejection head of Embodiment 1, manufactured by following the steps of the flow chart of  FIG. 3 . In the stacking step (Step S 2 ) of Embodiment 1, the first piezoelectric substrate  501  and the second piezoelectric substrate  502  are stacked so that the pressure chambers  307  are arranged orthogonally. In this embodiment, on the other hand, the center of the open end of each pressure chamber  307  on the ejection orifice side is shifted in the first direction from the center of the open end of the pressure chamber that is adjacent to the pressure chamber in the second direction. 
     Arranging the pressure chambers  307  in the manner described above makes the flow paths  402  of the plate-like member  401  shorter than in Embodiment 1. The resistance of the flow paths  402  can accordingly be kept low. 
     In this embodiment, an opening width L 2  in the first direction of each air chamber  308  of the second piezoelectric substrate  502  needs to be wider than in Embodiment 1 in order to secure the displacement between the pressure chambers  307  that are adjacent to each other. Specifically, it is preferred for each pressure chamber  307  to satisfy the following Expression (1) when the displacement amount of the center of the pressure chamber  307  is represented by d (see  FIG. 28 ) and the opening width of the pressure chamber  307  in the first direction is represented by L 4  (see  FIG. 28 ).
 
 L 2&gt; L 4+ d    (1)
 
     However, when the opening width L 2  described above is wide, a gap L 1  between two air chambers each having the opening width L 2  is narrow. The gap L 1  that is narrow decreases the rigidity of the piezoelectric block  303 . In particular, the narrow gap L 1  decreases the rigidity of the second piezoelectric substrate  502  and makes the piezoelectric substrate susceptible to breakage in the electrode forming step and the stacking step. As the displacement amount d becomes larger, the drop in the rigidity of the piezoelectric block  303  is more noticeable. The drop in the rigidity of the piezoelectric block  303  also becomes noticeable as an opening width L 3  in the first direction becomes narrower in each air chamber  308  of the first piezoelectric substrate  501 . The displacement amount d is therefore preferred to be small. For instance, it is preferred if the displacement amount d satisfies the following Expression (2):
 
 d&lt;L 3− L 1 (or  L 3&gt; L 1+ d )   (2)
 
     When Expression (2) is satisfied, high-density recording can be accomplished while the rigidity of the piezoelectric block  303  is secured. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2012-140703 filed Jun. 22, 2012 which is hereby incorporated by reference herein in its entirety.