Patent Publication Number: US-7900355-B2

Title: Ink-jet head and method for manufacturing the same

Description:
This is a Division of application Ser. No. 10/796,140 filed Mar. 10, 2004. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink-jet head that ejects ink onto a recording medium to conduct recordings, and also to a method for manufacturing the ink-jet head. 
     2. Description of Related Art 
     An ink-jet head used in an ink-jet recording apparatus such as ink-jet printers has a passage unit provided with many pressure chambers and many nozzles communicating with the pressure chambers. Ink is distributed from an ink tank to the pressure chambers, and pressure is selectively applied to each pressure chamber, so that the volume of each pressure chamber is changed and ink is ejected through a corresponding nozzle. In order to apply pressure to the respective pressure chambers, an actuator is disposed on a face of the passage unit that has the pressure chambers formed thereon. 
     In general, the passage unit and the actuator are adhered to each other through the steps of: forming an adhesive layer on wall portions defining the pressure chambers in the passage unit; positioning the actuator onto the passage unit; disposing a pressurizing member such as a heater on the actuator; and then performing pressure application and heating. When a thickness of the adhesive layer between the passage unit and the actuator is nonuniform, there may arise a problem that the pressure chambers vary from each other in pressure generated therein and therefore the nozzles exhibit different ink ejection characteristics from each other to result in deterioration in image quality. In an extreme case, an ink leakage between the pressure chambers can be caused. Accordingly, for a prevention of a variation in ink ejection characteristics, it has been desired that the adhesive layer has a uniform thickness. 
     A piezoelectric element is typically adopted as the actuator. In this case, an electrode as a surface electrode is formed on the piezoelectric element and a drive signal is outputted to the surface electrode, to thereby deform the piezoelectric element and accordingly change the volume of the pressure chamber. In this technique, sometimes, a surface electrode is formed individually for each pressure chamber, and each surface electrode includes a main body having a slightly smaller area than a pressure chamber area and an extension extending to an outside of the pressure chamber area, i.e., extending to a position opposing a wall portion that defines the pressure chamber (see Japanese Patent Laid-Open No. 11-34323). In this construction, a contact between the surface electrode and another member such as a flexible flat cable is formed on the extension of the surface electrode. An electrical connection between the surface electrode and the cable is achieved by soldering the cable to the contact or pressing against the contact a contact member such as a terminal. 
     In the above-described construction, however, the contact with the cable is formed on the extension of the surface electrode. Consequently, when the cable is disposed on the piezoelectric element, there is formed only a relatively narrow space between the cable and the piezoelectric element. When, under such a condition, the cable is soldered onto the extension of each surface electrode, overflow of a solder tends to cause a short circuit between neighboring surface electrodes. This problem becomes prominent particularly when the pressure chambers are densely arranged in the passage unit. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an ink-jet head and a method for manufacturing the ink-jet head having a structure in which a piezoelectric element acting as an actuator is disposed on a passage unit having pressure chambers formed therein, wherein an adhesive layer formed between the passage unit and the piezoelectric element has a uniform thickness, and wherein surface electrodes formed on the piezoelectric element can be connected to a cable member with high reliability. 
     According to an aspect of the present invention, there is provided an ink-jet head comprising a passage unit that has a plurality of pressure chambers and a plurality of nozzles communicating with the respective pressure chambers, an actuator unit that is adhered to the passage unit and changes the volume of the pressure chambers to thereby eject ink through the nozzles, and a cable member that supplies a drive signal to the actuator unit. The actuator unit includes a piezoelectric element sandwiched by a common electrode and a plurality of surface electrodes, the plurality of surface electrodes being formed on the piezoelectric element at positions corresponding to the respective pressure chambers, a plurality of first lands formed on the piezoelectric element to be connected to the respective surface electrodes, the first lands having a higher height from a surface of the piezoelectric element than that of the surface electrodes and being connected to the cable member, and a plurality of second lands formed on the piezoelectric element to be spaced from the respective surface electrodes, the second lands having substantially the same height from the surface of the piezoelectric element as that of the first lands. 
     According to the aforementioned aspect, the actuator unit including the piezoelectric element is arranged on the passage unit including the pressure chambers, and on the piezoelectric element, formed are not only the surface electrodes corresponding to the respective pressure chambers but also the first lands and the second lands corresponding to the respective surface electrodes. The first lands are connected to the respective surface electrodes, and the second lands are spaced from the respective surface electrodes. Both lands have substantially the same height from the surface of the piezoelectric element, which is higher than that of the surface electrodes. Like this, a total of two or more lands are provided for one surface electrode. As a result, when the actuator unit is adhered to the passage unit, pressure applied by a pressurizing member such as a heater can be dispersed. More specifically, the pressurizing member becomes in contact only with the first and second lands, and pressure of the pressurizing member is dispersed relatively well, through the first and second lands, over planes of the piezoelectric element and the passage unit. This makes uniform a thickness of an adhesive layer formed between the passage unit and the piezoelectric element, and accordingly prevents a variation in ink ejection characteristics. 
     In addition, the first lands are shaped into protrusions and their height from the surface of the piezoelectric element is higher than that of the surface electrodes. Consequently, when the cable member is disposed on the piezoelectric element, a relatively large space can be ensured between the cable member and the piezoelectric element. Further, the space can more surely be ensured by providing the second lands in addition to the first lands. This allows a stable connection of the first lands and the cable member, thereby suppressing overflow of a solder and thus preventing a short circuit between the neighboring surface electrodes. That is, the surface electrodes can be connected to the cable member with high reliability. 
     According to another aspect of the present invention, there is provided a method for manufacturing an ink-jet head comprising the steps of forming a passage unit that has a plurality of pressure chambers, a plurality of nozzles communicating with the respective pressure chambers, and a plurality of wall portions separating the pressure chambers from each other, and forming an actuator unit that changes the volume of the pressure chambers to thereby eject ink through the nozzles. The step of forming the actuator unit includes the steps of disposing, at a piezoelectric element, a plurality of surface electrodes and a common electrode opposing the plurality of surface electrodes, forming a plurality of first lands on the piezoelectric element to be connected to the respective surface electrodes, the first lands having a higher height from a surface of the piezoelectric element than that of the surface electrodes, and forming a plurality of second lands on the piezoelectric element to be spaced from the respective surface electrodes, the second lands having substantially the same height from the surface of the piezoelectric element as that of the first lands. The method for manufacturing an ink-jet head further comprises the steps of forming an adhesive layer on the wall portions of the passage unit, and positioning the actuator unit onto the passage unit such that the surface electrodes oppose the respective pressure chambers and both the first and second lands oppose the wall portions, and then disposing a pressurizing member on the actuator unit to press and adhere the actuator unit to the passage unit. 
     According to the aforementioned method, in the step of adhering the actuator unit to the passage unit, the first lands serving basically as contacts with the cable member are utilized and further the second lands are also utilized for dispersing pressure applied by the pressurizing member. Thus, an ink-jet head having the above-described effects can efficiently be manufactured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other and further objects, features and advantages of the invention will appear more fully from the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an ink-jet head according to an embodiment of the present invention; 
         FIG. 2  is a sectional view taken along a line II-II of  FIG. 1 ; 
         FIG. 3  is a plan view of a head main body included in the ink-jet head illustrated in  FIG. 1 ; 
         FIG. 4  is an enlarged view of a region enclosed with an alternate long and short dash line illustrated in  FIG. 3 ; 
         FIG. 5  is an enlarged view of a region enclosed with an alternate long and short dash line illustrated in  FIG. 4 ; 
         FIG. 6  is a partial sectional view of the head main body illustrated in  FIG. 3  as taken along a line VI-VI of  FIG. 5 ; 
         FIG. 7  is a partial exploded perspective view of the head main body illustrated in  FIG. 6  and a flexible printed circuit attached to the head main body; 
         FIG. 8A  is a plan view of a space that forms an ink passage illustrated in  FIG. 6 ; 
         FIG. 8B  is a perspective view of the space that forms the ink passage illustrated in  FIG. 6 ; 
         FIG. 9  is an enlarged view of a region enclosed with an alternate long and short dash line illustrated in  FIG. 6 ; 
         FIG. 10  is a plan view showing a shape of one individual electrode formed on a surface of an actuator unit, and shapes of a land and a dummy land corresponding to that individual electrode; 
         FIG. 11A  is a partial plan view showing individual electrodes, lands, and dummy lands arranged on the surface of the actuator unit; 
         FIG. 11B  is a partial enlarged view showing one of the individual electrodes illustrated in  FIG. 11A , and the lands and the dummy lands surrounding that individual electrode; 
         FIG. 12  is an enlarged sectional view showing a state where a terminal of the flexible printed circuit is connected to the land of the actuator unit; 
         FIG. 13  is a sectional view showing a step of adhering the actuator unit to a passage unit; 
         FIGS. 14A ,  14 B, and  14 C are sectional views stepwisely showing an exemplary step of connecting the terminal of the flexible printed circuit to the land; and 
         FIG. 15  is a partial plan view of a modification of the individual electrodes, the lands, and the dummy lands arranged on the surface of the actuator unit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, a general structure of an ink-jet head according to an embodiment of the present invention will be described with reference to  FIGS. 1 ,  2 , and  3 . 
     An ink-jet head  1  is used in an ink-jet printer of line-printing type. As illustrated in  FIGS. 1 and 2 , the ink-jet head  1  has a head main body  1   a  and a base  71  that supports the head main body  1   a . The head main body  1   a  has, in a plan view, a rectangular shape extending in one direction, as a main scanning direction. The base  71  comprises a base block  75  partially bonded to the head main body  1   a , and a holder  72  bonded to an upper face of the base block  75  for supporting the base block  75 . 
     The base block  75 , made of a metal material such as stainless steel, is a substantially rectangular parallelepiped member having substantially the same length as a longitudinal length of the head main body  1   a . The base block  75  functions as a light-weight structure for reinforcing the holder  72 . The holder  72  is made up of a holder main body  73  disposed near the head main body  1   a , and a pair of holder supporters  74  each extending from the holder main body  73  in a direction opposite to a head main body  1   a  side. Each holder supporter  74  is configured as a flat plate member. These holder supporters  74  extend along a longitudinal direction of the holder main body  73  and are disposed in parallel with each other at a predetermined distance therebetween. 
     An elastic member  83  such as a sponge is adhered to an outer side face of each holder supporter  74 . A flexible printed circuit (FPC)  50  as a cable member or flexible flat cable is arranged along the outer side face of each holder supporter  74  with the elastic member  83  interposed between them. A driver IC  80  is fixed to the FPC  50  so as to confront the elastic member  83 . The FPC  50  is electrically connected to both the driver IC  80  and a later-described actuator unit  21 . A heat sink  82  is disposed in close contact with an outer side face of the driver IC  80 . The heat sink  82  of nearly rectangular parallelepiped shape efficiently dissipates heat generated in the driver IC  80 . 
     A substrate  81  is placed outside the FPC  50  above the heat sink  82 . Above the substrate  81 , disposed is a controller (not illustrated) that conducts a general control over the ink-jet head  1 . The driver IC  80 , which is connected to the substrate  81 , is capable of individual potential controls over each of many pressure chambers  10  (see  FIG. 5 ) that are formed in a passage unit  4  as will be described later. 
     As illustrated in  FIG. 2 , seal members  84  are arranged between the heat sink  82  and the substrate  81  and between the heat sink  82  and the FPC  50 . They are secured to each other with interposition of the seal member  84 . 
     As illustrated in  FIG. 2 , a pair of skirt portions  73   a  protruding downward is formed at both ends of the holder main body  73  in a sub scanning direction, i.e., in a direction perpendicular to the main scanning direction (see  FIG. 1 ). Each skirt portion  73   a  is formed throughout a whole length of the holder main body  73 , thereby defining a substantially rectangular parallelepiped groove  73   b  on a lower face of the holder main body  73 . 
     The base block  75  is received in the groove  73   b  of the holder main body  73 , and has its upper face bonded to a bottom face of the groove  73   b  with an adhesive and the like. Within the base block  75 , formed are two ink reservoirs  3  serving as passages for ink to be supplied to the head main body  1   a . The ink reservoirs  3  are two substantially rectangular parallelepiped spaces or hollow regions extending along a longitudinal direction of the base block  75 . The two ink reservoirs  3  are arranged along the longitudinal direction of the base block  75  in parallel with each other at a predetermined distance with interposition of a partition  75   a  formed along the longitudinal direction of the base block  75 . In  FIG. 3 , the ink reservoirs  3  formed in the base block  75  are conceptionally illustrated with broken lines. 
     Referring to  FIG. 2 , an opening  3   b  (see  FIG. 3 ) communicating with the ink reservoir  3  is formed at a lefthand position, as corresponding to the ink reservoir  3 , on a lower face  75   b  of the base block  75 . As illustrated in  FIG. 3 , pairs of openings  3   b  are arranged in a zigzag pattern in an extending direction of the ink reservoirs  3  in areas where the later-described actuator unit  21  is not placed. Each opening  3   b  is provided with a filter (not illustrated) for catching dust and dirt that may be contained in ink. In the lower face  75   b  of the base block  75 , a vicinity of the opening  3   b  protrudes downward from surroundings thereof, as illustrated in  FIG. 2 . 
     As illustrated in  FIG. 3 , each ink reservoir  3  communicates at one end thereof with an opening  3   a . Ink is suitably supplied from an ink tank (not illustrated) via the opening  3   a  to each ink reservoir  3 , so that the ink reservoir  3  is always filled up with ink. 
     As illustrated in  FIG. 2 , the head main body  1   a  supported below the base block  75  comprises a passage unit  4  and a plurality of actuator units  21  (only one of which is illustrated in  FIG. 2 ) that are adhered to an upper face of the passage unit  4 . The base block  75  is bonded to the head main body  1   a , in more detail, bonded to the passage unit  4  of the head main body  1   a , only at a vicinity  75   c  of each opening  3   b  of the lower face  75   b . An area of the lower face  75   b  of the base block  75 , other than the vicinity  75   c  of each opening  3   b , is spaced from the head main body  1   a . The actuator units  21  are disposed within this space. Thus, the actuator units  21  and the base block  75  are kept out of contact with each other. 
     As illustrated in  FIG. 3 , each actuator unit  21  has, in a plan view, a trapezoidal shape having parallel opposed sides, i.e., upper and lower sides, extending along the longitudinal direction of the head main body  1   a . The actuator units  21  are arranged between the pairs of openings  3   b  in a zigzag pattern. Neighboring oblique sides of the actuator units  21  overlap each other in a widthwise direction of the head main body  1   a . Areas of a lower face of the passage unit  4  corresponding to regions adhered to the actuator units  21  are made into ink ejection regions. A large number of nozzles  8  (see  FIG. 4 ) are arranged on a surface of the ink ejection regions, as will be described later. Although  FIG. 4  illustrates only a part of the nozzles  8 , the nozzles  8  are arranged over a whole region corresponding to the region adhered to the actuator unit  21 . The FPC  50  is jointed to a surface of the actuator unit  21 , which will be described later. 
     As illustrated in  FIG. 2 , a seal member  85  is disposed around a tip end of the skirt portion  73   a  of the holder main body  73 . This seal member  85  secures the FPC  50  to the passage unit  4  and the holder main body  73 . As a result, the FPC  50  is hardly bent even if the head main body  1   a  becomes longer. Moreover, an interconnecting portion between the actuator unit  21  and the FPC  50  can be prevented from receiving stress, and the FPC  50  can be securely held in place. 
     Referring to  FIG. 1 , in a vicinity of each lower corner of the ink-jet head  1  along the main scanning direction, six protruding portions  30   a  are disposed at a regular interval along a sidewall of the ink-jet head  1 . As illustrated in  FIG. 2 , these protruding portions  30   a  are provided at both ends, in the sub scanning direction, of a nozzle plate  30  (see  FIG. 6 ) that is a lowermost layer of the head main body  1   a . That is, the nozzle plate  30  is bent at an angle of approximately 90 degrees along a boundary between each protruding portion  30   a  and the other portion. The protruding portions  30   a  are formed at positions corresponding to vicinities of both ends of various-sized papers to be used for printing. Since bent portions of the nozzle plate  30  are not right-angled but rounded, there is hardly caused a paper jam, which may occur because a leading edge of the paper having been transferred to the head  1  is stopped by a side face of the head  1 . 
     Next, a construction of the passage unit  4  is detailed with reference to  FIGS. 4 to 8 . 
     In the passage unit  4 , formed are manifold channels  5  (as illustrated with broken lines in  FIG. 4 ) communicating with the openings  3   b  so that ink reserved in the ink reservoirs  3  of the base block  75  may be introduced into the manifold channels  5 . Front end portion of each manifold channel  5  branches into two sub-manifold channels  5   a . In a region corresponding to one actuator unit  21 , two sub-manifold channels  5   a  extend from each of two openings  3   b  located on both sides of that actuator unit  21  in the longitudinal direction of the ink-jet head  1 . That is, in a region of the passage unit  4  corresponding to one actuator unit  21 , four sub-manifold channels  5   a  in total extend along the longitudinal direction of the ink-jet head  1 . A location, in a sectional view, of each sub-manifold channel  5   a  in the passage unit  4  is as illustrated in  FIG. 6 . 
     Referring to  FIG. 6 , many openings to serve as the pressure chambers  10  are formed in an uppermost plate in the passage unit  4 , i.e., a later-detailed cavity plate  22 , to a surface of which the actuator units  21  are to be adhered. Within the ink ejection regions that correspond to areas adhered to the actuator units  21 , the pressure chambers  10   a  are arranged adjacently to each other on the surface of the passage unit  4 , as illustrated in  FIGS. 4 and 5 . 
     As illustrated in  FIG. 6 , the pressure chamber  10  communicates with the sub-manifold channel  5   a  through an aperture  12 . The aperture  12  is for restricting ink flow and thus applying a suitable passage resistance, to thereby stabilize an ink ejection. The aperture  12  is elongated in parallel with the pressure chamber  10 , i.e., in parallel with the surface of the passage unit  4 . As illustrated in  FIG. 5 , one end of the aperture  12  is located in a region of the sub-manifold channel  5   a , and the other end thereof is located at an acute-angled portion of the pressure chamber  10  having a substantially rhombic shape. 
     Further, referring to  FIG. 6 , many openings serving as the nozzles  8  are formed in the nozzle plate  30  that is the lowermost layer of the passage unit  4 . As illustrated in  FIGS. 4 and 5 , the nozzles  8  are arranged within the ink ejection region corresponding to the area adhered to the actuator unit  21 . The nozzles  8  are positioned outside the ranges of the sub-manifold channels  5   a , and substantially correspond to one acute-angled portion of the respective pressure chambers  10  of rhombic shape. 
       FIGS. 4 and 5  show the lower face of the passage unit  4 , and therefore should illustrate with broken lines the pressure chambers  10  and the apertures  12 , which are however illustrated with solid lines for easy understanding. In a plan view, one pressure chamber  10  overlaps two apertures  12 , as illustrated in  FIG. 5 . This arrangement is achieved by providing the pressure chambers  10  and the apertures  12  at different levels from each other, as illustrated in  FIG. 6 . This enables a highly dense arrangement of the pressure chambers  10 , and also a high-resolution image formation using the ink-jet head  1  that occupies a relatively small area. 
     Here will be described an arrangement of the pressure chambers  10  and the nozzles  8  in a plane parallel to the surface of the passage unit  4 . 
     Within the ink ejection regions, both the pressure chambers  10  and the nozzles  8  are arranged in a matrix in two directions, i.e., a direction along a length of the ink-jet head  1  as the first arrangement direction and a direction slightly inclined relative to a width of the ink-jet head  1  as the second arrangement direction. The first and second arrangement directions form an angle theta, θ, somewhat smaller than the right angle. The nozzles  8  are arranged at 50 dpi in the first arrangement direction. The pressure chambers  10  are, on the other hand, arranged such that one ink ejection region corresponding to the area adhered to one actuator unit  21  may contain twelve pressure chambers  10  at the maximum in the second arrangement direction. An amount of shift in the first arrangement direction caused by arranging twelve pressure chambers  10  in the second arrangement direction is equivalent to one pressure chamber  10 . Therefore, throughout a width of the ink-jet head  1 , twelve nozzles  8  exist within a range that corresponds to an interval between two neighboring nozzles  8  in the first arrangement direction. At both ends of each ink ejection region in the first arrangement direction, i.e., at portions corresponding to oblique sides of each actuator unit  21 , one ink ejection region is complementary to another ink ejection region corresponding to an actuator unit  21  located opposite in the widthwise direction of the ink-jet head  1 , to thereby satisfy the above-mentioned condition. 
     Accordingly, the ink-jet head  1  can perform printing at 600 dpi in the main scanning direction by sequentially ejecting ink droplets through the many nozzles  8  arranged in the first and second arrangement directions, in association with relative movement of a paper along the sub scanning direction of the ink-jet head  1 . 
     Referring to  FIGS. 6 and 7 , the passage unit  4  has a layered structure including nine plates in total, i.e., from the top, a cavity plate  22 , a base plate  23 , an aperture plate  24 , a supply plate  25 , manifold plates  26 ,  27 , and  28 , a cover plate  29 , and a nozzle plate  30 . These plates  22  to  30  are made of metal such as stainless steel, etc. 
     Many substantially rhombic openings to serve as the pressure chambers  10  are formed in the cavity plate  22 . Portions of the cavity plate  22  having no openings formed therein constitute wall portions  22   a  that define the respective pressure chambers  10 . In the base plate  23 , both of one communication hole between a pressure chamber  10  and a corresponding aperture  12  and one communication hole between a pressure chamber  10  and a corresponding nozzle  8  are provided for each pressure chamber  10  formed in the cavity plate  22 . In the aperture plate  24 , both of one opening to serve as an aperture  12  and a communication hole between a pressure chamber  10  and a corresponding nozzle  8  are provided for each pressure chamber  10  formed in the cavity plate  22 . In the supply plate  25 , both of one communication hole between an aperture  12  and a sub-manifold channel  5   a  and one communication hole between a pressure chamber  10  and a corresponding nozzle  8  are provided for each pressure chamber  10  formed in the cavity plate  22 . In each of the manifold plates  26 ,  27 , and  28 , in addition to an opening to serve as the sub-manifold channel  5   a , one communication hole between a pressure chamber  10  and a corresponding nozzle  8  is provided for each pressure chamber  10  formed in the cavity plate  22 . In the cover plate  29 , one communication hole between a pressure chamber  10  and a corresponding nozzle  8  is provided for each pressure chamber  10  formed in the cavity plate  22 . In the nozzle plate  30 , one tapered opening to serve as a nozzle  8  is provided for each pressure chamber  10  formed in the cavity plate  22 . 
     In the passage unit  4 , formed are ink passages  32  (see  FIG. 6 ) each extending from the ink tank (not illustrated), through the ink reservoir  3 , the manifold channel  5 , the sub-manifold channel  5   a , the aperture  12 , and the pressure chamber  10 , to the nozzle  8 . The ink passage  32  firstly extends upward from the sub-manifold channel  5   a , then extends horizontally in the aperture  12 , then further extends upward, then again extends horizontally in the pressure chamber  10 , then extends obliquely downward to a certain extent away from the aperture  12 , and then extends vertically downward toward the nozzle  8 . 
       FIGS. 8A and 8B  show a plan view and a perspective view, respectively, of a configuration of a space that forms the ink passage  32  in the passage unit  4  illustrated in  FIG. 6 . In  FIGS. 8A and 8B , shown is a filter  13  provided at a boundary between the aperture  12  and the sub-manifold channel  5   a . The filter  13  is for removing dust contained in ink. 
     A construction of the actuator unit  21  will then be detailed with reference to  FIGS. 9 and 10 . 
     The actuator unit  21 , including four piezoelectric sheets  41 ,  42 ,  43 , and  44  put in layers, is adhered onto the cavity plate  22  as the uppermost layer of the passage unit  4  with an adhesive layer  70  (see  FIG. 9 ) interposed between them. These piezoelectric sheets  41  to  44  constitute a piezoelectric element. Each of the piezoelectric sheets  41  to  44  has a thickness of approximately 15 μm, and is made of a lead zirconate titanate (PZT)-base ceramic material, which has good workability and ferroelectricity. 
     The piezoelectric sheets  41  to  44  are formed into a piece of layered flat plate spanning the many pressure chambers  10  formed within one ink ejection region in the ink-jet head  1 . As a result, mechanical rigidity of the piezoelectric sheets  41  to  44  can be kept high, and further the ink-jet head  1  obtains improved responsiveness for ink ejection. 
     Individual electrodes  35  as surface electrodes having a thickness of approximately 1 μm are formed on the uppermost piezoelectric sheet  41 . The individual electrodes  35  correspond to the respective pressure chambers  10 . As illustrated in  FIG. 10 , the individual electrode  35  has a main electrode portion  35   x  and a connecting portion  35   y . The main electrode portion  35   x  opposes the pressure chamber  10 , and has, in a plan view, a substantially rhombic shape with a length of 850 μm and a width of 250 μm similar to that of the pressure chamber  10 . One acute-angled portion of the main electrode portion  35   x  extends out to form the connecting portion  35   y  that opposes the wall portion  22   a  of the cavity plate  22 . 
     A common electrode  34  having a thickness of approximately 2 μm is interposed between the piezoelectric sheet  41  and the piezoelectric sheet  42  disposed under the piezoelectric sheet  41  (see  FIG. 9 ). The common electrode  34  is a single conductive sheet extending over substantially an entire surface of one actuator unit  21 . Both the individual electrodes  35  and the common electrode  34  are made of, e.g., an Ag—Pd-base metallic material, and serve to change the volume of the pressure chambers  10  by applying an electric field to the piezoelectric sheet  41  for deformation, as will be described later. 
     No electrode is disposed between the piezoelectric sheet  42  and the piezoelectric sheet  43  disposed under the piezoelectric sheet  42 , between the piezoelectric sheet  43  and the piezoelectric sheet  44 , and under the piezoelectric sheet  44 . 
     As shown in  FIGS. 4 and 5 , a region of the surface of the actuator unit  21  where the individual electrodes  35  are formed is enclosed, over its whole circumference, with circular ground electrodes  38 . In other words, many ground electrodes  38  are formed at substantially the same interval around an outer periphery of the surface of the piezoelectric sheet  41  of a trapezoidal shape. All the ground electrodes  38  are connected to the common electrode  34  via through holes (not illustrated) formed in the piezoelectric sheet  41 , although  FIG. 9  has no illustration thereof. 
     A driving method of the actuator unit  21  will here be described. 
     The piezoelectric sheets  41  to  44  included in the actuator unit  21  have been polarized in their thickness direction. Portions of the piezoelectric sheet  41  sandwiched between the individual electrodes  35  and the common electrode  34  act as active portions. In this case, when an individual electrode  35  is set at a different potential from that of the common electrode  34  to apply an electric field in a polarization direction to a corresponding active portion of the piezoelectric sheet  41 , the active portion expands or contracts in its thickness direction, and, by a transversal piezoelectric effect, contracts or expands in its plane direction that is perpendicular to the thickness direction. On the other hand, the other three piezoelectric sheets  42  to  44  are non-active layers having no region sandwiched between electrodes, and therefore cannot deform by themselves. That is, the actuator unit  21  has a so-called unimorph structure in which an upper piezoelectric sheet  41  distant from the pressure chamber  10  is a layer including active portions and the lower three piezoelectric sheets  42  to  44  near the pressure chamber  10  are inactive layers. 
     In this construction, when an electric field is applied in the polarization direction to an active portion of the piezoelectric sheet  41 , the active portion expands in the thickness direction and contracts in the plane direction while the other three piezoelectric sheets  42  to  44  exhibit no deformation. At this time, since a lowermost face of the piezoelectric sheets  41  to  44  is fixed to upper faces of the wall portions  22   a  of the cavity plate  22  as illustrated in  FIG. 9 , the piezoelectric sheet  41  to  44  as a whole deform to protrude toward a pressure chamber  10  side (i.e., unimorph deformation) in association with the deformation of the active portion of the piezoelectric sheet  41 . This reduces the volume of the pressure chamber  10  and raises pressure of ink in the pressure chamber  10 , and thereby the ink is ejected through the nozzle  8 . Then, when the individual electrode  35  is again set at the same potential as that of the common electrode  34 , the piezoelectric sheets  41  to  44  restore their original shape of flat plate. At this time, the volume of the pressure chamber  10  increases, and accordingly ink in the sub-manifold channel  5   a  is introduced into the pressure chamber  10 . 
     In another possible driving method, all the individual electrodes  35  are in advance kept at a different potential from that of the common electrode  34  so that the piezoelectric sheets  41  to  44  as a whole deform to protrude toward the pressure chamber  10  side. Then, upon every ejection request, a corresponding individual electrode  35  is once set at the same potential as that of the common electrode  34 . Thereafter, at a predetermined timing, the individual electrode  35  is again set at the different potential from that of the common electrode  34 . In this case, at a timing when the individual electrode  35  and the common electrode  34  have the same potential, the piezoelectric sheets  41  to  44  restore their original shape of flat plate, and a corresponding pressure chamber  10  thereby increases in volume as compared with its initial state, where the piezoelectric sheets  41  to  44  as a whole deform to protrude toward the pressure chamber  10  side. As the pressure chamber  10  increases in volume, ink in the sub-manifold channel  5   a  is introduced into the pressure chamber  10 . Thereafter, at a timing when the potentials of the individual electrode  35  and the common electrode  34  become different from each other, the piezoelectric sheets  41  to  44  as a whole deform to protrude toward the pressure chamber  10  side. This reduces the volume of the pressure chamber  10  and raises pressure of ink in the pressure chamber  10 , and thereby the ink is ejected through the nozzle  8 . 
     When, on the other hand, an electric field perpendicular to the polarization direction is applied to an active portion of the piezoelectric sheet  41 , the active portion expands in its plane direction and contracts in its thickness direction. At this time, the piezoelectric sheets  41  to  44  as a whole deform to be concaved on the pressure chamber  10  side. This increases the volume of the pressure chamber  10 , and thereby ink in the sub-manifold channel  5   a  is introduced into the pressure chamber  10 . Then, when a potential of the individual electrode  35  returns to its initial value, the piezoelectric sheets  41  to  44  restore their original shape of flat plate. This reduces the volume of the pressure chamber  10  and raises pressure of ink in the pressure chamber  10 , and thereby the ink is ejected through the nozzle  8 . 
     Then, a description will be given to a land  36  and a dummy land  37  as a second land both formed on the surface of the piezoelectric sheet  41  to correspond to each individual electrode  35 . 
     The land  36  is disposed on the surface of the piezoelectric sheet  41  as illustrated in  FIG. 9 , and more specifically disposed at an end of the connecting portion  35   y  distant from the main electrode portion  35   x  as illustrated in  FIG. 10 . That is, the land  36  is so provided as to oppose the wall portion  22   a  and to be connected to the individual electrode  35 . The land  36  is shaped into a column having a diameter of approximately 160 μm and a thickness of approximately 10 μm, and made of, e.g., gold including glass frits.  FIG. 9  shows that a height of the land  36  from the surface of the piezoelectric sheet  41  is higher than that of the individual electrode  35 . Since the land  36  has the thickness of approximately 10 μm and the individual electrode  35  has the thickness of approximately 1 μm, the height of the land  36  from the surface of the piezoelectric sheet  41  is approximately 11 μm. 
     As shown in  FIGS. 9 and 10 , a dummy land  37  and a land  36  make a pair, and are positioned symmetrically with respect to a center of a corresponding pressure chamber  10 . The dummy land  37  is, similarly to the land  36 , so provided as to oppose the wall portion  22   a , made of gold including glass frits, and has substantially the same diameter of approximately 160 μm and substantially the same thickness of 10 μm as those of the land  36 . Since the land  36  is formed on the individual electrode  35 , there exists 1 μm difference between the land  36  and the dummy land  37  in height from the surface of the piezoelectric sheet  41 , however, the difference is in permissible variation in manufacturing the land  36 , the dummy land  37 , and the FPC  50 , etc. The dummy land  37  is spaced from the individual electrode  35  without electrical connection thereto, while the land  36  is connected to the individual electrode  35 . 
     Referring to  FIGS. 11A and 11B , each of the individual electrodes  35  is surrounded with the corresponding land  36  and dummy land  37  in a pair, and is also surrounded with lands  36  and dummy lands  37  corresponding to other individual electrodes  35  adjacent to the individual electrode  35 . Referring to  FIG. 11B , further, around each individual electrode  35 , disposed are six lands  36  and dummy lands  37  including the lands  36  and dummy lands  37  corresponding to other individual electrodes  35  adjacent to the individual electrode  35 . The three lands  36  and the three dummy lands  37  make pairs, and each pair is positioned symmetrically with respect to a center of a corresponding pressure chamber  10 . The three lands  36  and the three dummy lands  37  are arranged in a hexagonal formation. 
     Next, a construction of the FPC  50  will be described in detail with reference to  FIG. 12 . 
     The FPC  50  includes a base film  51 , a plurality of conductive patterns  53  formed on a lower face of the base film  51 , a cover film  52  covering substantially an entire lower face of the base film  51 , and terminals  54  protruding from a lower face of the cover film  52 . The base film  51 , the conductive patterns  53 , and the cover film  52  have thicknesses of approximately 25 μm, 9 μm, and 20 μm, respectively. A plurality of through holes  52   a , each having a smaller area than that of the conductive pattern  53 , are formed in the cover film  52 . Each through hole  52   a  corresponds to each of the plurality of conductive patterns  53 . The base film  51 , the conductive patterns  53 , and the cover film  52  are positioned in layers such that a center of each through hole  52   a  may correspond to a center of each conductive pattern  53  and the cover film  52  may cover outer peripheries of the conductive patterns  53 . 
     The base film  51  and the cover film  52  are insulative sheet members. The base film  51  is made of a polyimide resin, and the cover film  52  is made of a photosensitive material. Like this, by making the cover film  52  from a photosensitive material, the many through holes  52   a  can easily be formed. 
     The conductive patterns  53  are made of a copper foil. The conductive patterns  53  are wirings for transmitting to the actuator units  21  drive signals outputted from the driver IC  80  (see  FIGS. 1 and 2 ). The conductive patterns  53  are connected to the driver IC  80 , and form predetermined patterns on the lower face of the base film  51 . 
     The terminals  54 , made of a conductive material such as nickel, are connected through the through holes  52   a  of the cover film  52  to the conductive patterns  53 . More specifically, the terminal  54  is so formed as to close the through hole  52   a , to cover an outer periphery of the through hole  52   a  on a side of the lower face of the cover film  52 , and to protrude toward a piezoelectric sheet  41  side. A diameter of the terminal  54  is approximately 50 μm, and a protrusion length of the terminal  54  from the lower face of the cover film  52  is approximately 30 μm. 
     Each terminal  54  corresponds to one of the lands  36 . A terminal  54  and a corresponding land  36  are connected to each other with a solder  60 . Since the terminal  54  is connected to the conductive pattern  53 , each individual electrode  35  electrically connected to the corresponding land  36  becomes in connection with the driver IC  80  through the conductive pattern  53  formed independently of one another on the FPC  50 . This allows individual potential controls over each of the pressure chambers  10 . 
     The FPC  50  has no terminals to correspond to the dummy lands  37 . This is because, as mentioned above, the dummy lands  37  are not electrically connected to the individual electrodes  35 . 
     In addition to the above-described conductive patterns  53 , the FPC  50  has ground conductive patterns (not illustrated) as well. Terminals of the ground conductive patterns (not illustrated) are connected to the above-mentioned ground electrodes  38  (see  FIGS. 4 and 5 ), so that the common electrode  34  connected to the ground electrodes  38  is kept at the ground potential equally in its region corresponding to any pressure chamber  10 . 
     Next, an example of methods for manufacturing the ink-jet head  1  will be described. 
     When forming the head main body  1   a , in this example, the passage unit  4  and the actuator unit  21  are prepared separately from each other and subsequently adhered to each other. 
     In order to manufacture the passage unit  4 , first, each of the nine plates  22  to  30  is subjected to etching with a mask of patterned photoresist, thereby forming openings and recesses as illustrated in  FIGS. 6 and 7  in each of the plates  22  to  30 . Subsequently, the plates  22  to  30  are overlaid on and bonded to one another with an adhesive such that they may form the ink passage  32  as illustrated in  FIG. 6 . 
     In order to manufacture the actuator unit  21 , first, a conductive paste to develop into the common electrode  34  is printed in a pattern on a green sheet of a ceramic material to develop into the piezoelectric sheet  42 . The four piezoelectric sheets  41  to  44  are then positioned and overlaid on one another using a jig, and formed into one piece through firing at a predetermined temperature. Subsequently, a conductive paste to develop into the individual electrodes  35  is printed in a pattern on the piezoelectric sheet  41 . Thereafter, a firing process is performed. Further, a conductive paste to develop into each land  36  is printed in a pattern on one end of the individual electrode  35 , more specifically on the connecting portion  35   y  of each individual electrode  35 . A conductive paste to develop into each dummy land  37  is printed in a pattern at a position substantially symmetric to a land  36  paired therewith with respect to a center of their corresponding pressure chamber  10 . The pastes are sintered through a subsequent firing process. As a result, the individual electrodes  35 , the lands  36 , and the dummy lands  37  are formed on the surface of the piezoelectric sheet  41 . 
     Then, the passage unit  4  and the actuator unit  21  formed through the aforementioned steps are adhered to each other. In this adhering step, a thermosetting adhesive layer  70  (see  FIG. 13 ) is formed on the wall portions  22   a  of the cavity plate  22  of the passage unit  4  using an appropriate method such as transferring. The actuator unit  21  is then positioned and arranged on the passage unit  4 , and a ceramic heater  100  as a pressurizing member is disposed on the actuator unit  21  to apply pressure and heat. Consequently, the passage unit  4  and the actuator unit  21  are fixed to each other, and the head main body  1   a  is prepared. At this time, the heater  100  is in contact only with the lands  36  and the dummy lands  37  without any contact with the piezoelectric sheets  41  to  44  and the individual electrodes  35 . 
     Then, the terminals  54  of the FPC  50  are connected to the lands  36  in order to feed electric signals to the individual electrodes  35 , and manufacture of the ink-jet head  1  is completed through further predetermined steps. 
     Here, an exemplary step of connecting the terminals  54  of the FPC  50  to the lands  36  will be described with reference to  FIGS. 14A ,  14 B, and  14 C.  FIGS. 14A ,  14 B, and  14 C stepwisely show the step of connecting the terminal  54  to the land  36 . 
       FIG. 14A  shows the head main body  1   a  formed by adhering the actuator unit  21  to the passage unit  4  as described above. First, the solder  60  having a thickness of approximately 10 μm is put to cover an entire surface of the terminal  54  of the FPC  50  (see  FIG. 14B ). The FPC  50  is then positioned such that the terminal  54  may confront the land  36 , and, in this condition, the FPC  50  is brought closer to the actuator unit  21  to eventually reach a contact between the terminal  54  and the land  36  (see  FIG. 14C ). When, e.g., a ceramic heater (not illustrated) is disposed on an upper face of the base film  51  of the FPC  50  and pressure and heat are applied, the solder  60  melts into such a shape as to cover an entire circumference of the terminal  54 , i.e., from the lower face of the cover film  52  to a surface of the land  36 , to thus provide a complete connection of the terminal  54  and the land  36 . Subsequent curing of the solder  60  completes the connection of the terminal  54  and the land  36 , and as such the FPC  50  is electrically connected to the individual electrode  35 . 
     Although the FPC  50  and the dummy land  37  are out of contact with each other in  FIG. 14C , they may be brought into contact when the FPC  50  is bent or distorted. In any case, however, the FPC  50  never contacts with the piezoelectric sheets  41  to  44  and the individual electrodes  35 , with a space ensured between the FPC  50  and the piezoelectric sheet  41 . 
     As described above, the ink-jet head  1  of this embodiment has a structure in which the actuator unit  21  including the piezoelectric sheets  41  to  44  is arranged on the passage unit  4  including the pressure chambers  10 , wherein on the piezoelectric sheets  41 , formed are not only the individual electrodes  35  corresponding to the respective pressure chambers  10  but also the lands  36  and the dummy lands  37  corresponding to the respective individual electrodes  35 . The lands  36  are connected to the respective individual electrodes  35 , and the dummy lands  37  are spaced from the respective individual electrodes  35 . Both of the lands  36  and the dummy lands  37  have substantially the same height from the surface of the piezoelectric sheet  41 , which is higher than that of the individual electrodes  35 . Like this, since two protrusions in total, i.e., a land  36  and a dummy land  37  are provided for one individual electrode  35 , pressure applied by the heater  100  can be dispersed when the actuator unit  21  is adhered to the passage unit  4 . More specifically, the heater  100  becomes in contact only with the lands  36  and the dummy lands  37 , and its pressure is dispersed relatively well, through the lands  36  and the dummy lands  37 , over planes of the piezoelectric sheets  41  to  44  and the passage unit  4 . This makes uniform a thickness of the adhesive layer  70  formed between the passage unit  4  and the piezoelectric sheet  44 , and accordingly prevents a variation in ink ejection characteristics. 
     In addition, the lands  36  are shaped into protrusions and their height from the surface of the piezoelectric sheet  41  is higher than that of the individual electrodes  35 . Consequently, when the FPC  50  is disposed on the piezoelectric sheet  41 , a relatively large space can be ensured between the FPC  50  and the piezoelectric sheet  41 . Further, the space can more surely be ensured by providing the dummy lands  37  in addition to the lands  36 . This allows a stable connection of the lands  36  and the FPC  50 , thereby suppressing overflow of the solder  60  and thus preventing a short circuit between the neighboring individual electrodes  35 . That is, the individual electrodes  35  can be connected to the FPC  50  with high reliability. 
     From the viewpoint of effects of the manufacturing method of this embodiment, in the step of adhering the actuator unit  21  to the passage unit  4 , the lands  36  serving basically as contacts with the FPC  50  are utilized and further the dummy lands  37  are also utilized for dispersing the pressure applied by the heater  100 . Thus, the ink-jet head  1  having the above-described effects can efficiently be manufactured. 
     Further, also in the step of connecting the terminals  54  of the FPC  50  to the lands  36 , the lands  36  and the dummy lands  37  are utilized for ensuring a space between the FPC  50  and the piezoelectric sheet  41 . Thereby, the connecting can be performed in a stable manner. 
     Further, one mentionable effect obtained by surely ensuring the space between the FPC  50  and the piezoelectric sheet  41  is that external force can be prevented from acting on the individual electrodes  35 . That is, even when the FPC  50  is bent or distorted, the FPC  50  is never in contact with the individual electrodes  35 , because each individual electrode  35  is surrounded with the lands  36  and the dummy lands  37  so that a space is surely ensured particularly around each individual electrode  35 . Deformation of the individual electrodes  35  caused by external force may deteriorate deformability of the actuator unit  21 , but such a problem can be prevented in this embodiment. 
     If the lands  36  and the dummy lands  37  are arranged to oppose the pressure chambers  10  instead of the wall portions  22   a ; when the lands  36  and the dummy lands  37  receive force during, e.g., pressure application by the heater  100 , the piezoelectric sheets  41  to  44  tend to be damaged due to cavities of the pressure chambers  10  located thereunder. In this embodiment, on the other hand, the foregoing problem of damage to the piezoelectric sheets  41  to  44  can be relieved, because both the lands  36  and the dummy lands  37  are arranged at positions opposing the wall portions  22   a  as illustrated in  FIG. 9 . 
     One mentionable effect obtained by arranging the lands  36  to oppose the wall portions  22   a  and by suppressing the overflow of the solder  60  as mentioned above is that the solder  60  can be prevented from flowing into regions opposing the pressure chambers  10 . When the solder  60  flows into the regions opposing the pressure chambers  10 , deformability of the actuator unit  21  may deteriorate. However, such a problem can be prevented in this embodiment. 
     In this embodiment, further, each of the individual electrodes  35  is provided with a corresponding one of the lands  36  and a corresponding one of the dummy lands  37  that make a pair and are positioned symmetrically with respect to a center of a corresponding one of the pressure chambers  10 , as illustrated in  FIG. 10 . Therefore, pressure applied by the heater  100  can effectively be dispersed particularly around the pressure chamber  10 , to thereby more surely uniformalize the thickness of the adhesive layer  70  around the pressure chamber  10 . 
     As illustrated in  FIGS. 11A and 11B , the pressure chambers  10  are formed adjacently to each other on the surface of the passage unit  4 , and each of the individual electrodes  35  is surrounded with the corresponding land  36  and the corresponding dummy land  37  in a pair, and is also surrounded with lands  36  and dummy lands  37  corresponding to other individual electrodes  35  adjacent to the individual electrode  35 . In this case, not only the land  36  and the dummy land  37  corresponding to the individual electrode  35  but also lands  36  and dummy lands  37  corresponding to other adjacent individual electrodes  35  contribute to force transmission to the adhesive layer  70  around a corresponding one of the pressure chambers  10 . As a result, since pressure applied by the heater  100  is more efficiently dispersed particularly around the pressure chambers  10 , the thickness of the adhesive layer  70  can reliably be made uniform. 
     Like this, since the individual electrode  35  is surrounded not only with the corresponding land  36  and dummy land  37  but also with lands  36  and dummy lands  37  corresponding to other individual electrodes  35 , the space between the FPC  50  and the piezoelectric sheet  41  can more surely be ensured particularly around the pressure chambers  10 , so that a solder joint can more stably be performed to advantageously prevent a short circuit. 
     Moreover, the lands  36  and the dummy lands  37  are, as illustrated in  FIG. 11B , arranged around each individual electrode  35  in a symmetrical manner with respect to the center of a corresponding pressure chamber  10 . More specifically, the pressure chambers  10  each having a rhombic shape are formed on the surface of the passage unit  4 , and three lands  36  and three dummy lands  37  are arranged in a hexagonal formation around each individual electrode  35  corresponding to each pressure chamber  10 . In this case, pressure applied by the heater  100  is transmitted to the piezoelectric sheets  41  to  44  and the adhesive layer  70  via six lands  36  and dummy lands  37  positioned at vertexes of the hexagon. As a result, the pressure is dispersed more efficiently and more uniformly, particularly around the pressure chambers  10 . Therefore, the thickness of the adhesive layer  70  can more reliably be made uniform. 
     The plurality of pressure chambers  10  are formed in a matrix on the surface of the passage unit  4 , which contributes to an excellent densification of the pressure chambers  10 , i.e., high resolution. When the pressure chambers  10  are densely arranged in the passage unit, a problem of short circuit between neighboring individual electrodes  35  becomes prominent. In this embodiment, however, densification of the pressure chambers  10  results in a cyclic arrangement pattern of the lands  36  and the dummy lands  37 , so that the space is more surely ensured between the FPC  50  and the piezoelectric sheet  41  and therefore the solder joint can be performed in a more stable manner. That is, a short circuit can be prevented effectively even when the pressure chambers  10  are arranged at a high density. Moreover, the cyclic arrangement pattern of the lands  36  and the dummy lands  37  makes uniform the thickness of the adhesive layer  70 . 
     The pressurizing member used in the step of adhering the actuator unit  21  to the passage unit  4  is not limited to the heater  100 . The actuator unit  21  may be adhered to the passage unit  4  without the application of heat, for example. In such a case, the adhesive layer  70  need not have a thermosetting property. 
       FIG. 15  shows a possible modification of how to arrange the pressure chambers  10 , the individual electrodes  35 , the lands  36 , and the dummy lands  37 . This modification differs from the aforementioned embodiment in shape and arrangement direction of the pressure chambers  10  and the individual electrodes  35  (see  FIGS. 5 and 11A ). As for the shape, the pressure chambers  10  and the individual electrodes  35  in the aforementioned embodiment are longer and thinner than in this modification. As for the arrangement, the pressure chambers  10  in the aforementioned embodiment are not arranged along both longer and shorter diagonals of a rhomboid forming the pressure chamber  10 , while the pressure chambers  10  in this modification are arranged along these two diagonals. In the aforementioned embodiment, in particular, the pressure chambers  10  are not arranged along the shorter diagonal of the rhomboid forming the pressure chamber  10 . Due to such a difference in arrangement of the pressure chambers  10 , etc., six lands  36  and dummy lands  37  arranged around each individual electrode  35  are in a regular-hexagonal formation in this modification while they are not in such a formation in the aforementioned embodiment. Such a balanced formation of the lands  36  and the dummy lands  37  arranged around each individual electrode  35  makes more uniform the thickness of the adhesive layer  70 . Thus, the modification shown in  FIG. 15  is more preferable to realize the uniform thickness of the adhesive layer  70 . 
     However, the formation of the lands  36  and the dummy lands  37  arranged around each individual electrode  35  is not limited to hexagons. In addition, the lands  36  and the dummy lands  37  arranged around each individual electrode  35  may not necessarily be positioned symmetrically with respect to a center of a corresponding pressure chamber  10 . 
     Further, it is not always necessary that each individual electrode  35  is surrounded with lands  36  and dummy lands  37  corresponding to other individual electrodes  35  adjacent to the individual electrode  35 . That is, each individual electrode  35  can be surrounded only with a land  36  and a dummy land  37  corresponding to that individual electrode  35 . Alternatively, arbitrarily-formed dummy lands can be arranged, as described later. 
     In the aforementioned embodiment, a single land  36  is provided for one individual electrode  35 . However, this is not limitative, and a plurality of lands  36  can be provided for one individual electrode  35 . In such a case, however, there is involved increased number of connection of the land  36  and the terminal  54 , and at the same time an electrical connection system becomes complicated. 
     In the aforementioned embodiment, the lands  36  are formed on surfaces of the individual electrodes  35 , and more specifically on surfaces of the connecting portions  35   y . However, a location of the lands  36  is not limited thereto as long as the height of the lands  36  from the surface of the piezoelectric sheet  41  is higher than that of the individual electrodes  35 . For example, the lands  36  can be formed on the surface of the piezoelectric sheet  41 . 
     Similarly, although a single dummy land  37  is provided for one individual electrode  35  to make a pair with the land  36 , this is not limitative. For example, two or more dummy lands  37  can be provided for one individual electrode  35 . In addition, the dummy lands  37  can be formed at any arbitrary positions on the surface of the piezoelectric sheet  41  except positions where the individual electrodes  35  and the dummy lands  36  are formed. 
     Shapes of the lands  36  and the dummy lands  37  can also be variously changed. 
     Although, in the aforementioned embodiment, both the lands  36  and the dummy lands  37  are made of gold including glass frits, this is not limitative. However, it is preferable to form the lands and the dummy lands from the same material, because they can be formed at one time and the manufacturing process can thereby be simplified. 
     Moreover, it is not always necessary to use the solder  60  to connect the terminals  54  to the lands  36 . For example, metallic binders made of tin, ACP (Anisotropic Conductive Paste) of thermosetting resins, and any other materials may be used for the connection. 
     Although, in the aforementioned embodiment, the dummy lands  37  are not connected to the FPC  50 , the FPC  50  can be provided with terminals for the dummy lands  37  to connect these terminals to the dummy lands  37 . In such a case, since the FPC  50  is not easily separated from the actuator  21 , the FPC  50  and the actuator  21  can be bended to each other with increased reliability. 
     The actuator unit is, further, not limited to the one illustrated in the aforementioned embodiment. For example, a common electrode may be disposed between the piezoelectric sheets  43  and  44 , or additional individual electrodes may be disposed between the piezoelectric sheets  42  and  43 . The common electrode  34  of the aforementioned embodiment is a single conductive sheet spanning the entire surface of the piezoelectric sheet. However, a common electrode having a larger area than that of the pressure chamber  10  can be provided for each pressure chamber  10  so that a projective region of each common electrode in a thickness direction of the sheets may cover an area of each pressure chamber  10 . Alternatively, a common electrode having a slightly smaller area than that of the pressure chamber  10  can be provided for each pressure chamber  10  so that a projective region of each common electrode in a thickness direction of the sheets may fall within an area of each pressure chamber  10 . In such cases where each pressure chamber  10  is provided with its own common electrode, the common electrodes need be electrically connected to one another so that all the common electrodes may have the same potential in their portions corresponding to the respective pressure chambers  10 . 
     A planar shape of the pressure chamber is not limited to a quadrilateral such as rhomboid but may variously be changed, e.g., into circles, ellipses, and the like. In addition, the arrangement of the pressure chambers  10  on the surface of the passage unit  4  is not limited to a matrix arrangement. 
     The ink-jet head according to the present invention can be used not only in a line-type ink-jet printer that performs printing by conveying a paper relative to a fixed head main body as in the aforementioned embodiment, but also in a serial-type ink-jet printer that performs printing by, for example, conveying a paper and at the same time reciprocating a head main body perpendicularly to a paper conveyance direction. 
     Further, an application of the ink-jet head according to the present invention is not limited to ink-jet printers, and it is also applicable to, for example, ink-jet type facsimiles or copying machines. 
     While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.