Patent Publication Number: US-7219981-B2

Title: Ink-jet head and producing method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink-jet head for squirting ink at recording medium for recording a formed image and the like. 
     2. Description of the Related Art 
     In the ink-jet head, ink from an ink tank is supplied to a pressure chamber through a common ink chamber, to impart squirting energy to the ink in the pressure chamber and then the energized ink is squirted from a nozzle. The head is provided with an actuator for imparting the squirting energy to the ink in the pressure chamber. The actuator is electrically connected to a flexible printed circuit (FPC). The actuator is driven under driving signal fed from a driver IC through the FPC. 
     A variety of actuators are in use, including a piezoelectric actuator and a capacitance type actuator. In the piezoelectric actuator, the actuator is disposed opposite to the pressure plate to form a partition wall of the pressure chamber, so that when the actuator is mechanically deformed, the pressure chamber is changed in volume to thereby impart the squirting energy to the ink in the pressure chamber. In the capacitance type actuator, a vibrating sheet is disposed to form a partition wall of the pressure chamber and the actuator is arranged to be spaced apart from and opposite to the vibrating sheet. When the vibrating sheet is deflected by electrostatic force generated by the drive of the actuator, the pressure chamber is changed in volume to thereby impart the squirting energy to the ink in the pressure chambers, as is the case with the piezoelectric actuator mentioned above. 
     Although there are presented a variety of actuators, including those as mentioned above, the existing actuators all suffer from the problem that when the ink adheres to the actuator, the ink squirting capability of the actuators reduces or fails. In order to minimize this problem, various techniques have been developed. Take an actuator having such a structure that FPC is bonded to the actuator and is further drawn to an outside of the head, for example. For this type of actuator, there has been proposed a technique of mounting a sealing member at a location where the FPC is drawn out, because the ink enters into the head from that location easily. According to this technique, the sealing member prevents the entry of the ink into the head, thus preventing the adhering of the ink to the actuator. 
     However, according to this technique, although the adhering of the ink to the actuator can be prevented, there is a possibility that the sealing member may enter into the head to cause adherence of the sealing member to the actuator. When the sealing member adheres to the actuator, the deformation of the actuator, the piezoelectric actuator in particular, is deteriorated. Further, in other types of actuators, such as a capacitance type actuator, as well, when the sealing member adheres to the actuator, the function of the actuator may deteriorate, as is the case with the actuator of the type noted above. Therefore, the existing techniques mentioned above are unsatisfactory for solving the problem of reduction of the ink squirting capability of the actuator. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an ink-jet head that can release or minimize reduction of an ink squirting capability of the actuator by preventing adhesion of ink, a sealing member and the like to the actuator, and a producing method thereof. 
     In accordance with a first aspect of the present invention, there is provided an ink-jet head comprising: a passage portion in which a plurality of ink ejecting nozzles are formed, the passage portion including a plurality of individual ink passages running to the nozzles through pressure chambers, a spaced portion spaced apart from and opposite to the passage portion, a driving portion, bonded to a surface of the spaced portion facing the passage portion, for imparting squirting energy to ink in the pressure chambers, a power supply member electrically connected with the driving portion, for supplying driving signals to the driving portion, a protrusion provided in at least either of the surface of the spaced portion facing the passage portion and the surface of the passage portion facing the spaced portion, and a sealing member disposed adjacent to the protrusion, for sealing a spaced between the passage portion and the spaced portion. 
     In the construction mentioned above, the protrusion is presented at one side of the driving portion serving as the actuator. While a construction having no protrusion can allow an easy entry of the ink into the head from the other side, the construction of the invention having the protrusion can prevent the entry of the ink into the head by the protrusion. Thus, the construction of the invention can prevent the adhering of the ink to the actuator, thus releasing or minimizing the problem of reduction of the ink squirting capability of the actuator. Further, when the sealing member is employed as in the existing technique mentioned above, since the sealing member is prevented from adhering to the actuator by the protrusion, the problem of reduction of the ink squirting capability of the actuator can be even more released. 
     In accordance with a second aspect of the present invention, there is provided an ink-jet head comprising; a passage unit in which a plurality of ink ejecting nozzles are formed, the passage unit including a plurality of individual ink passages running to the nozzles through pressure chambers, a reservoir unit including an ink reservoir in which ink is stored and from which the stored ink is fed to the passage unit, an actuator unit, bonded to the passage unit, for imparting squirting energy to the ink in the pressure chambers, and a power supply member electrically connected with the actuator unit, for supplying driving signals to the actuator unit, wherein the reservoir unit has a bonded surface bonded to the passage unit and a spaced surface extended across and spaced apart from the actuator unit, wherein a protrusion is provided in an area of the spaced surface of the reservoir unit, the area is opposite to the bonded surface with respect to an area facing the actuator unit, and wherein the power supply member is in abutment with both of the protrusion and the passage unit, and a sealing member for sealing a space between the passage unit and the reservoir unit is disposed at the abutment portion. 
     In the construction mentioned above, the actuator unit is bonded to the passage unit, and the reservoir unit is bonded to the passage unit so that the reservoir unit is extended to bridge over the actuator unit and spaced apart therefrom. This construction including the protrusion provided in said area can also provide the same effect as in the first aspect of the invention. 
     In accordance with a third aspect of the present invention, there is provided a producing method of an ink-jet head comprising: the step of producing a passage unit in which a plurality of ink ejecting nozzles are formed, the passage unit including a plurality of individual ink passages running to the nozzles through pressure chambers, the step of producing a protruding member having a first protrusion and a second protrusion protruding in the same direction as the direction in which the first protrusion protrudes by a half-etching, the step of producing an actuator unit for imparting squirting energy to the ink in the pressure chambers, the step of bonding the actuator unit to the passage unit, the step of electrically connecting between a power supply member for supplying driving signals to the actuator unit and the actuator unit, the step of bonding together the passage unit and the protrusion member in such a manner that a front end of the first protrusion serves as a bonded surface bonded to the passage unit; that the protrusion member has a spaced surface spaced apart from and extended across the actuator unit and that a second protrusion is located in an area which is spaced apart from the bonded surface across an opposite area of the spaced surface to the actuator unit and is not opposite to the actuator unit, and the step of disposing a sealing member for sealing a space between the passage unit and the protrusion member at an abutment portion between the power supply member and the protrusion. 
     The front end of the first protrusion is equivalent to the bonded surface of the second aspect of the invention. By forming both the first protrusion and the second protrusion as the protrusion in the first and second aspects of the invention by half-etching, manufacturing costs can be reduced. 
    
    
     
       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 an entire construction diagram showing an example of a printer including an ink-jet head according to an embodiment of the present invention, 
         FIG. 2A  is a partly cross-sectional view of the ink-jet head shown in  FIG. 1 , 
         FIG. 2B  is a partly enlarged view of a lateral side of a head body shown in  FIG. 2A , 
         FIG. 3  is an exploded perspective view of the head body shown in  FIG. 2A , 
         FIG. 4  is a plan view of the head body shown in  FIG. 2A , 
         FIG. 5  is an enlarged view of an area surrounded by a dashed line of  FIG. 4 , 
         FIG. 6  is a partly cross-sectional view corresponding to a pressure chamber of the head body shown in  FIG. 4 , 
         FIG. 7  is a plan view of an individual electrode formed on an actuator unit depicted in  FIG. 6 , 
         FIG. 8  is a partly cross-sectional view of the actuator unit depicted in  FIG. 6  taken along line VIII—VIII of  FIG. 7 , 
         FIG. 9A  is a partly cross-sectional view of a variant of the ink-jet head according to the present invention, which corresponds to  FIG. 2A , and 
         FIG. 9B  is a partly enlarged view of a lateral side of the head body shown in  FIG. 9A . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is an entire construction diagram showing an example of a printer including an ink-jet head according to an embodiment of the present invention. The ink-jet printer  1  of this embodiment is a color ink-jet printer having four ink-jet heads  2 . The ink-jet printer  1  has a paper feed portion  11  (left side when viewed in the illustration) and a paper discharge portion  12  (right side when viewed in the illustration). It also has in an interior thereof a paper carrier passage running from the paper feed portion  11  toward the paper discharge portion  12 . 
     A pair of paper feed rollers  5   a ,  5   b  are disposed on the directly downstream side of the paper feed portion  11 , to feed the paper of the recording medium from the left to right when viewed in the illustration. Two belt rollers  6 ,  7  and a loop carrier belt  8  extended between the both rollers  6 ,  7  are disposed in an intermediate portion of the paper carrier passage. 
     The carrier belt  8  has a two-layer structure comprising a polyurethane base material impregnated with urethane and a silicon rubber located on a carrying surface side of the carrier passage. The paper carried by the pair of paper feed rollers  5   a ,  5   b  is held on the carrying surface on the front side of the carrier belt  8  through absorption, while it is carried downstream of the carrying direction (toward the right side as viewed in the illustration) by the drive for rotation of one of the belt rollers  6  in the clockwise direction (in the direction indicated by an arrow  90 ). 
     Presser members  9   a ,  9   b  are disposed at locations where the paper is fed in and out with respect to the belt roller  6 . The presser members  9   a ,  9   b  serve to press the paper down on the carrying surface of the carrier belt  8  to hold it thereon, so as to ensure the carriage of the paper on the carrying surface. 
     A paper releasing mechanism  10  is arranged downstream of the carrying direction (toward the right side as viewed in the illustration) along the paper carrier passage. The paper releasing mechanism  10  is structured to release the paper held on the carrying surface of the carrier belt  8  by the aid of absorption from the carrying surface of the carrier belt  8  and feed it to a paper discharge portion  12  on the right side, 
     Four ink-jet heads  2  have head bodies  2   a  on their lower ends, respectively. The head bodies  2   a  each have a rectangular cross-section. The head bodies  2   a  are disposed adjacent to each other so that their longitudinal dimensions can correspond to the direction orthogonal to the paper carrying direction (vertical direction as viewed in  FIG. 1 ). In other words, this printer  1  is a line printer. Bottoms of the four head bodies  2   a  are opposite to the paper carrier passage, and a number of ink squirting ports or nozzles  13  having a very small diameter ( FIGS. 4 ,  5 ,  6 ) are arranged on the bottoms. The four head bodies  2   a  squirt four color inks of magenta, yellow, cyan, and black, respectively. 
     The head body  2   a  is set in place to define a small space between the lower surface of the head body and the carrying surface of the carrier belt  8 , and the paper carrier passage is formed in that space. Accordingly, when paper carried by the carrier belt  8  passes in sequence right under the head bodies  2   a , the head bodies  2   a  squirt their respective color inks at an upper surface (a printing surface) of the paper to form a desired color image on the paper. 
       FIG. 2A  shows a partly cross-sectional view of the ink-jet head  2  shown in  FIG. 1 . The ink-jet head  2  is mounted on an adequate member  14  provided in the printer  1  through a holder  15 . The holder  15  is formed in an inverted T-shape having a vertical portion  15   a  and a horizontal portion  15   b , when viewed from side. The vertical portion  15   a  is mounted on a member  14  by a screw  16 , while the head body  2   a  is fixed to a lower surface of the horizontal portion  15   b  of the holder  15  through a spacer  3 . 
     The head body  2   a  includes a passage unit (passage portion)  20  having a number of nozzles  13  formed on a bottom thereof, four actuator units (driving portion)  19  for imparting squirting energy to ink in the passage unit  20  (See  FIGS. 3 and 4 ), and a reservoir unit (protrusion member)  40  for feeding the ink to the passage unit  20 . Both the passage unit  20  and the actuator unit  19  have a laminated structure formed by lamination of a plurality of thin sheets. The reservoir unit  40  formed of metal material, such as stainless steel, has substantially the same plane form as the passage unit  20 . The actuator unit  19  and the reservoir unit  40  are both bonded to an upper surface of the passage unit  20 . 
     Now, reference is made of the construction of the reservoir unit  40 , with reference to  FIGS. 2A ,  2 B, and  3 . 
     The reservoir unit  40  is formed by lamination of two places of an upper sheet  41  and a lower sheet  42 . The lower sheet  42  has a depressed portion formed in an upper surface thereof. The depressed portion is formed to be enclosed completely by a half-etching. The depressed portion is covered with the upper sheet  41  having a flat lower surface, to define an ink reservoir  42   a . The ink reservoir  42   a  is a generally rectangular parallelepiped hollow region for storing the ink fed to the passage unit  20 . The ink reservoir  42   a  has a generally rectangular planar form extending along a direction of elongation of the head body  2   a.    
     In the bottom of the reservoir unit  40  or in the bottom  46  of the lower sheet  42 , a bonded portion  44  (a first protrusion) extending downwardly from a surrounding surface is formed in zigzag with respect to the direction of elongation of the reservoir unit  40  by the half-etching. All rears of the bottom  46  but the bonded portion  44  serve as a spaced portion  45  spaced apart from and opposite to the passage unit  20 . A front end of the bonded portion  44  serves as a bonded surface  44   a  bonded to the passage unit  20 . The bonded portion  44  is bonded to the passage unit  20  while supporting the spaced portion  45  to maintain a distance between the spaced portion  45  and the passage unit  20 . The spaced portion  45  includes the ink reservoir  42   a  (See  FIG. 2A ). 
     As shown in  FIGS. 3 and 4 , four actuator units  19  are staggered on the upper surface of the passage unit  20  in an area thereof opposite to the spaced portion  45 . In other words, the reservoir unit  40  has the bonded surface  44   a  bonded to the passage unit  20  and the spaced surface  45   a  (bottom of the spaced portion  45 ) spaced apart from the actuator unit  19  and extended to bridge over the actuator unit  19 . As seen from  FIG. 2A , an entire area of each actuator unit  19  is opposite to the spaced portion  45 . 
     Returning to  FIG. 2A , flexible printed circuits (FPC)  4  which are power supply members for supplying driving signals to the actuator unit  19  are bonded to an upper surface of the actuator unit  19 . Each FPC  4  is drawn out leftwards or rightwards and then drawn upwards along the head body  2   a.    
     In  FIG. 2B , a lateral side of the head body  2   a  shown in  FIG. 2A  at a location where the FPC  4  is drawn out is shown in an enlarged form. It is seen from  FIG. 2B  that a protrusion (a second protrusion)  45   e  projecting in the same direction (downwardly) as the bonded portion  44  is provided in a surface of the spaced portion  45  of the reservoir unit  40  opposite to the passage unit  20  at an end thereof on an opposite side to the bonded portion  44  with respect to the actuator unit  19 . In other words, the protrusion  45   e  is located in an area (a first area) which is spaced apart from the bonded surface ( 44   a ) across an opposite area of the spaced surface ( 45   a ) of the reservoir unit ( 40 ) to the actuator unit ( 19 ) and is not opposite to the actuator unit ( 19 ). The location where the protrusion  45   e  is provided corresponds to the location where the FPC  4  is drawn out. 
     Further, as shown in  FIG. 2B , the protrusion  45   e  is opposite to the passage unit  20  and also its front end is positioned below the upper surface of the actuator unit  19 . The front end of the protrusion  45   e  is spaced apart from the passage unit  20  to provide only a space for FPC  4  to be drawn out. For example in the case where the front end of the protrusion  45   e  and the upper surface of the passage unit  20  are spaced from each other at only a distance equal to a width of the FPC  4 , when the bonded portion  44  is bonded to the upper surface of the passage unit  20 , there is a possibility that FPC  4  may be brought into contact with the protrusion  45   e , to cause the bonded portion  44  located on the opposite side to the protrusion  45   e  to rise from the upper surface of the passage unit  20 . Accordingly, in the illustrated embodiment, the front end of the protrusion  45   e  and the upper surface of the passage unit  20  are spaced from each other at only a distance slightly larger than the width of the FPC  4 , in order to avoid the problem mentioned above. 
     A silicon-based adhesive (i.e., a sealing member)  36  is mounded on the lateral side of the head body  2   a  at the location where FPC  4  is drawn out. The adhesive  36  serves to fix the FPC  4  to the reservoir unit  40 ; reinforce it; and prevent the irk and the like from entering into an interior of the head  2  from the space between the FPC  4  and the reservoir unit  40 . 
     Further it is seen from  FIG. 2B  that the FPC  4  is in contact with at least a part of the protrusion  45   e . This can allow the positioning of the FPC  4  relative to the head body  2   a  with comparative ease, and as such can allow the FPC  4  to be fixed more stably. 
     Next, reference is made of the flow of ink through the head body  2   a . As shown in  FIGS. 2A and 3 , the upper sheet  41  of the reservoir unit  40  is provided with an ink supply passage  41   a  extending through the upper sheet  41  vertically formed at a location near one end thereof with respect to the direction of elongation of the upper sheet  41 . The ink supply passage  41   a  communicates between a supply port  41   b  formed in the surface of the reservoir unit  40  and an inlet  41   c  of the ink reservoir  42   a . The ink supplied from an ink tank (not shown) to the head body  2   a  enters into the ink supply passage  41   a  from the supply port  41   b  and arrives at the ink reservoir  42   a . In this embodiment, since the inlet  41   c  is formed at a location near one end thereof with respect to the direction of elongation of the ink reservoir  42   a , the ink, when entering into the ink reservoir  42   a  from the inlet  41   c , flows through the ink reservoir  42   a  toward the other end with respect to the direction of elongation of the ink reservoir. 
     As shown in  FIGS. 2A and 3 , the lower sheet  42  of the reservoir unit  40  is provided with ten connecting passages  42   b  for connecting between the ink reservoir  42   a  and the bottom of the reservoir unit  40 . Connecting ports  42   c  ( FIG. 2A ) which are openings of the connecting passages  42   b  facing the passage unit  20  are formed at locations to connect with the connecting ports  20   a  in the upper surface of the passage unit  20 . The ink in the ink reservoir  42   a  is supplied to the passage unit  20  through the ten connecting passages  42   b  and the ten connecting ports  20   a . The ink supplied to the passage unit  20  is ejected or squirted from the nozzles  13 . 
       FIG. 4  is a plan view of the head body  2   a  from which the reservoir unit  40  is excluded. The passage unit  20  has a generally rectangular plan form extended in one direction (in a main scanning direction). In  FIG. 4 , manifold channels  30  which are common ink chambers arranged in the passage unit  20  are depicted in broken lines. The ink is supplied from the ink reservoir  42   a  of the reservoir unit  40  into the manifold channels  30  through the ten connecting ports  20   a  arranged in the upper surface of the passage unit  20 . The manifold channels  30  are branched into a plurality of sub-manifold channels  30   a  extending in parallel with the direction of elongation of the passage unit  20 . The ten connecting ports  20   a  are arrayed in two lines along the direction of elongation of the head body  2   a , five connecting ports  20   a  for each line. 
     Four actuators  19  having a trapezoid planar form are staggered in two lines in such a manner as to pass over the connecting ports  20   a  and are adhesive bonded to the upper surface of the passage unit  20 . The actuator units  19  are disposed so that their parallel and opposite sides (upper side and lower side) run along the direction of elongation of the passage unit  20 . Oblique lines of adjacent actuator units  19  are partly overlapped with each other in a width wise direction of the passage unit  20 . 
     A bottom of the passage unit  20  opposite to the adhesive bonded area of the actuator unit  19  serves as an ink squirting area where a number of nozzles  13  are arranged in matrix. Groups of pressure chambers in which a number of pressure chambers  34  are arranged in matrix are formed in the surface of the passage unit  20  opposite to the actuator unit  19  (See  FIG. 5 ). 
       FIG. 5  is an enlarged view of an area surrounded by a dashed line of  FIG. 4 . As shown in  FIG. 5 , the passage unit  20  opposite to the actuator unit  19  includes four sub-manifold channels  30   a  extending in parallel with the direction of elongation of the passage unit  20 . The sub-manifold channels  30   a  connect with a number of individual ink passages  35  running from outlets of the sub-manifold channels to the nozzles  13  (See  FIG. 6 ).  FIG. 6  is a cross-sectional view showing the individual ink passage  35 . As seen from  FIG. 6 , each nozzle  13  communicates with the sub-manifold channel  30   a  through the pressure chamber  34  and an aperture  32 . Thus, in the head body  2   a , each pressure chamber  34  has the individual ink passage  35  running from the outlet of the sub-manifold passage  30   a  to the nozzle  13  through the aperture  32  and the pressure chamber  34 . 
     As seen from  FIG. 6  as well, the head body  2   a  with the exclusion of the reservoir unit  40  has a laminated structure wherein a total of ten sheet materials are laminated in the order of the actuator unit  19 , a cavity plate  21 , a base plate  22 , an aperture plate  23 , a supply plate  24 , manifold plates  25 ,  26 ,  27 , a cover plate  28 , and a nozzle plate  29 . The passage unit  20  is formed from nine sheet sheets of these ten sheet materials with the exclusion of the actuator unit  19 . 
     In the actuator unit  19 , four piezoelectric sheets  51 – 54  ( FIG. 8 ) are laminated and electrodes are arranged, as detailed later. Of these piezoelectric sheets, only an uppermost layer is in the form of a layer having an active layer portion that becomes an active layer when electric field is applied thereto (which is hereinafter simply referred to as “the layer having the active layer”) and the three remaining layers are in the form of a non-active layer. The cavity plate  21  is a metal plate having a number of generally diamond-shaped holes defining the space of the pressure chamber  34  which are formed in an adhesive bonded area of the actuator unit  19 . The base plate  22  is a metal plate having a communicating hole for communicating from the pressure chamber  34  to the aperture  32  and a communicating hole for communicating from the pressure chamber  34  to the nozzle  13  which are formed for each pressure chamber  34  of the cavity plate  21 . 
     The aperture plate  32  is a metal plate having a communicating hole for communicating from the pressure chamber  34  to the nozzle  13  in addition to a hole serving as the aperture  32  are formed for each pressure chamber  34  of the cavity plate  21 . The supply plate  24  is a metal plate having a communicating hole for communicating between the aperture  32  and the sub-manifold channel  30   a  and a communicating hole for communicating from the pressure chamber  34  to the nozzle  13  are formed for each pressure chamber  34  of the cavity plate  21 . Each of the manifold plates  25 ,  26 ,  27  is a metal plate having a communicating hole for communicating from the pressure chamber  34  to the nozzle  13  in addition to the sub-manifold channel  30   a  are formed for each pressure chamber  34  of the cavity plate  21 . The cover plate  28  is a metal plate having a communicating hole for communicating from the pressure chamber  34  to the aperture  32  formed for each pressure chamber  34  of the cavity plate  21 . The nozzle plate  29  is a metal plate having the nozzle  13  formed for each pressure chamber  34  of the cavity plate  21 . 
     These ten sheets  19 ,  21 – 29  are aligned and laminated each other so that the individual ink passage  35  can be formed, as shown in  FIG. 6 . The individual ink passage  35  extends upwards from the sub-manifold channel  30   a , first, and then extends horizontally in the aperture  32 . Then, it extends further upwards therefrom and then extends horizontally again in the aperture  32 . Then, it extends obliquely downwards in a direction of being away from the aperture  32  and then extends vertically downwards to the nozzle  13 . 
     As apparent from  FIG. 6 , the pressure chamber  34  and the aperture  32  are positioned at different level. This enables the aperture  32  communicating to one pressure chamber  34  in the passage unit  20  opposite to the actuator unit  19  to be arranged at the same position as an adjacent pressure chamber  34  and overlapped each other, when viewed from the top plan, as shown in  FIG. 6 . This enables the pressure chambers  24  to be disposed closely at a high density, thus enabling an image to be printed with high resolution by the ink-jet head  1  having a relatively small occupation area. 
     Returning to  FIG. 5 , the groups of pressure chambers each comprising a number of pressure chambers  34  are formed in the adhesive bonded area of the actuator unit  19 . The group of pressure chambers have a trapezoid form having substantially the same size as the adhesive bonded area of the actuator unit  19 . The group of pressure chambers are formed for each actuator unit  19 . 
     As apparent from  FIG. 5 , the each pressure chamber  34  belonging to the groups of pressure chambers is communicated to the nozzle  13  at one end of a long diagonal line thereof and is communicated to the sub-manifold channel  30   a  through the aperture  32  at the other end of the long diagonal line. As mentioned later, individual electrodes  45  ( FIGS. 7 ,  8 ) having a generally planar diamond form and slightly smaller than the pressure chamber  34  are arranged in matrix on the actuator unit  19  in such a manner as to be opposite to the pressure chambers  34 . In  FIG. 5 , the nozzles  13 , pressure chambers  34  and apertures  32  in the passage unit  20  which should be depicted in a broken line are depicted in a solid line, for the purpose of easy understanding of the illustration. 
     Next, reference is made of the construction of the actuator unit  19 . A number of individual electrodes  56  ( FIGS. 7 ,  8 ) are arranged in matrix on the actuator unit  19  to have the same pattern as in the pressure chamber  34 . The individual electrodes  56  are arranged in the positions opposite to the pressure chambers  34 , when viewed from the top plan. 
       FIG. 7  is a plan view of the individual electrode  56 . As shown in  FIG. 7 , the individual electrode  56  comprises a main electrode area  56   a  to be arranged in an opposite position to the pressure chamber  34 , when viewed from top, so as to be accommodated therein the pressure chamber  34  and an auxiliary electrode area  56   b  communicating to the main electrode area  56   b  and arranged in an opposite position to an outside of the pressure chamber  34 . 
       FIG. 8  is a partly cross-sectional view of the actuator unit depicted in  FIG. 6  taken along line VIII—VIII of  FIG. 7 . As shown in  FIG. 8 , the actuator unit  19  includes four piezoelectric sheets  51 ,  52 ,  53 ,  54  formed to have the same thickness of the order of 15 μm. These piezoelectric sheets  51 – 54  are formed into a layered continuous flat plate (continuous flat plate layer) to be arranged over a number of pressure chambers  34  formed in one ink squirting area in the head body  2   a . As a result of the piezoelectric sheets  51 – 54  being arranged in the form of the continuous flat plate layer over a number of pressure chambers  34 , the individual electrodes  56  can be arranged on the piezoelectric sheet  51  at a high density by using a screen printing technique, for example. Therefore, the pressure chambers  34  formed at the corresponding positions to the individual electrodes  56  can also be arranged at such a high density that an image can be printed with high resolution. The piezoelectric sheets  51 – 54  are made of lead zirconate titanate (PZT) ceramic material having ferroelectricity. 
     The main electrode area  56   a  of the individual electrode  56  formed on the uppermost layer of the piezoelectric sheet  51  has a generally diamond planar form similar to the form of the pressure chamber  34 , as shown in  FIG. 7 . The main electrode area  56   a  of a generally diamond form has a lower acutely-angled portion connected to the auxiliary electrode area  56   b  opposite to the outside of the pressure chamber  34 . The auxiliary electrode area  56   b  is provided, at its end, with a circular land portion  57  which is electrically connected with the individual electrode  56 . As shown in  FIG. 8 , the land portion  57  is opposite to the area where no pressure chamber  34  is formed in the cavity plate  21 . The land portion  57  is made of gold including glass frit, for example, and is formed on a surface of an extended area of the auxiliary electrode area  56   a , as shown in  FIG. 7 . The land portion  57  is electrically connected with a contact point in the FPC  4 , though the FPC  4  is omitted from the illustration of  FIG. 8 . When the land portion is bonded to the auxiliary electrode area  56   a , the contact point of the FPC  4  must be pressed against the land portion  57 . Since the pressure chamber  34  is not formed in the area of the cavity plate  21  opposite to the land portion  57 , the contact point of the FPC  4  can be pressed against the land portion  57  with sufficient pressing force to ensure the bonding. 
     A common electrode  58  having the same outer shape as the piezoelectric sheet  52  and a thickness of about 2 μm is interposed between the uppermost layer of piezoelectric sheet  51  and the piezoelectric sheet  52  immediately under the uppermost layer. The individual electrode  56  and the common electrode  58  are both formed of metal material such as Ag—Pd-based metal. 
     The common electrode  58  is connected to ground in an area not shown and thereby the common electrode  58  is kept at a ground potential equally in all area corresponding to the pressure chambers  34 . Also, the individual electrodes  56  are connected to the driver IC (not shown) through the FPC  4  including different independent lead lines for their respective pressure chambers  56  and the land portion  57  so that the potential can be controlled for the respective individual electrodes  56  corresponding to the pressure chambers  34 . 
     Next, reference is made of the driving method of the actuator unit  19 . A polarization direction of the piezoelectric sheet  51  of the actuator unit  19  corresponds to a thickness direction thereof. That is to say, the actuator unit  19  has a so-called unimorph structure wherein one upper piezoelectric sheet  51  (positioned to be away from the pressure chamber  34 ) is in the form of the layer having the active layer and three lower piezoelectric sheets  52 – 54  are in the form of a non-active layer. Accordingly, when the individual electrode  56  is set at a predetermined positive or negative potential, for example, if the direction of the electric filed and that of the polarization are the same, the area of the piezoelectric sheet  51  sandwiched between the electrodes acts as the active layer (pressure generating portion), so that the actuator unit is crimped in a direction orthogonal to the polarization direction by the piezoelectric transversal effect. 
     In this embodiment, the area of the piezoelectric sheet  51  sandwiched between the main electrode area  56   a  and the common electrode  58 , to which the electric field is applied, acts to the active layer. Accordingly, the area of the piezoelectric sheet  51  sandwiched between the main electrode area  56   a  and the common electrode  58  is crimped in the direction orthogonal to the polarization direction by the piezoelectric transversal effect. 
     On the other hand, since the piezoelectric sheets  52 – 54  are not influenced by the electric field, they are not deformed spontaneously. This causes difference in distortion in the direction orthogonal to the polarization direction between the upper layer of piezoelectric sheet  51  and the lower layers of piezoelectric sheets  52 – 54 . As a result, the entire piezoelectric sheets  51 – 54  are tried to deform in such a manner as to protrude toward the non-activity layer side (Unimorph deformation). At this time, as a result of the lower surface of the piezoelectric sheets  51 – 54  being fixed to the upper surface of the partition (cavity plate)  21  for defining the pressure chamber  34 , as shown in  FIG. 6 , the piezoelectric sheets  51 – 54  are deformed in such a manner as to protrude toward the pressure chamber side. Due to this, the volume of the pressure chamber  34  is reduced to cause an increased pressure against the ink, thus causing the ink to be squirted from the nozzle  13 . After that, when the individual electrode  58  is returned to the same potential as the common electrode  58 , the piezoelectric sheets  51 – 54  are turned to their original forms and the volume of the pressure chamber  34  is returned to their original volume, so that the ink is sucked from the sub-manifold channel  30   a  side. 
     Another driving method may be taken. For example, the individual electrode  56  is previously kept at a different potential from that of the common electrode  58  and is set at the same potential as that of the common electrode  58  for a while upon each ink squirting request and, thereafter, is set again at the different potential from that of the common electrode  58 . In this method, when the piezoelectric electrodes  51 – 54  are restored into their original forms at the timing when the individual electrode  56  and the common electrode  58  come to be the same potential, the volume of the pressure chamber  34  is increased, as compared with the initial state (the state in which the both electrodes are different in potential from each other), so that the ink is sucked into the pressure chamber  34  from the sub-manifold channel  30   a  side. Thereafter, the piezoelectric sheets  51 – 54  are deformed to protrude toward the pressure chamber side at the timing when the individual electrode  56  is set at a different potential from that of the common electrode  58 . Due to this, the volume of the pressure chamber  34  is reduced to cause an increased pressure against the ink, thus causing the ink to be squirted. 
     Next, reference is made of the producing method of the ink-jet head  2  of this embodiment. Reference is herein made of the producing method of only the head body  2   a  shown in  FIG. 2A . 
     The passage unit  20  of the head body  2   a  is produced in the following way. The plates are etched with patterned photoresists as masks, to form openings and recessed portions are formed in the respective plates  21 – 29 , as shown in  FIG. 6 . Thereafter, the nine plates  21 – 29  are laminated and bonded to each other while adhesive is interposed between adjacent plates, to form the individual ink passage  35  as shown in  FIG. 6 , to thereby produce the passage unit  20 . 
     On the other hand, the actuator unit  19  is produced in the following way. First, a pattern of a conductive paste serving as the common electrode  58  is printed on a green sheet of ceramic material serving as the piezoelectric sheet  52 . Then, the four piezoelectric sheets  51 – 54  are aligned with a jig and laminated to form a laminated member, and the laminated member thus formed is baked at a predetermined temperature. Then, the laminated member thus formed having no individual electrode  56  is adhesive bonded to the passage unit  20  to put the piezoelectric sheet  54  and the cavity plate  21  into contact with each other. Thereafter, a pattern of a conductive paste serving as the individual electrode  56  is printed on a surface of the piezoelectric sheet  51  and further a pattern of a conductive paste serving as the land portion  57  is printed at one end of the conductive paste serving as the individual electrode  56 . Thereafter, it undergoes a baking process to bake the paste. After this manner, the individual electrode  56  is formed on the surface of the piezoelectric sheet  51  and further the land portion  57  is formed on the auxiliary electrode area  56   b  of the individual electrode  56  at one end thereof. 
     Thereafter, the actuator unit  19  and the FPC  4  are bonded to each other by pressing the contact point of the FPC  4  against the land portion  57  in heating condition, after each contact point of the FPC  4  is positioned with a corresponding land portion  57 . The FPC  4  bonded to the upper surface of the actuator unit  19  is drawn out leftwards or rightwards of the head  2  and then is raised up along the head body  2   a , as shown in  FIGS. 2A and 2B . Further, it is connected with the driver IC (not shown) fixed to a lateral side of the member  14 , thus enabling the driving signals to be supplied to the individual electrode  56 . 
     On the other hand, the reservoir unit  40  is produced by two plates of the upper plate  41  and the lower plate  42  being laminated and bonded to each other. 
     Reference is herein made of the method for forming concavity and convexity in the bottom  46  of the lower plate  42 , in particular. First, the bottom of the lower plate  42  is etched by the first half-etching in the state in which its portion corresponding to the bonded surface  44   a  of the bonded portion  44  is masked. In this stage, the recessed portion having a length for the protrusion  45   e  to be protruded, or a depth for the FPC  4  to be drawn out, is formed in all areas of the lower plate  42  except the area corresponding to the bonded surface  44   a  of the bottom of the lower plate  42 . Then, a portion of the lower plate corresponding to the front end surface of the protrusion  45   e  is further masked, with the portion corresponding to the bonded surface  44   a  masked, and then the bottom of the lower plate  42  is etched by the second half-etching in this state. As a result, the recessed portion having a depth for the actuator unit  19  to be disposed is formed in the area of the spaced portion  45 , except the protrusion  45   e , as shown in  FIG. 2A . At the same time as this, the protrusion  45   e  is formed. The bonded portion  44  is formed in the masked portions in the two half-etching processes in total. 
     The reservoir unit  40  thus produced is bonded to the upper surface of the passage unit  20  in such a manner that the bonded surface  44   a  and the spaced surface  45   a  in the bottom  46  and the actuator unit  19  bonded to the upper surface of the passage unit  20  have the positional relationship as shown in  FIG. 2A . In this positional relationship, a space, which does not suppress the deformation of the actuator unit  19 , is formed between the actuator unit  19  and the spaced surface  45   a . Further, between the upper surface of the passage unit  20  and the protrusion  45   e , formed is a space, which prevents ink or the adhesive  36  having fluidity from entering into the head  2  while allowing the FPC  4  to be withdrawn outside of the head  2 . 
     As mentioned above, according to the ink-jet head  2  of this embodiment, the bonded portion  44  is presented at one side of the actuation unit  19  and the protrusion  45   e  is presented at the other side, as shown in  FIG. 2A . While a construction having no protrusion  45   e  can allow an easy entry of the ink into the head  2  from the other side, the construction of the invention having the protrusion  45   e  can prevent the entry of the ink into the head  2  by the protrusion  45   e . Thus, the construction of the invention can prevent the adhering of the ink to the actuator unit  19 , thus releasing or minimizing the problem of reduction of the ink squirting capability of the actuator unit. 
     Also, when the adhesive  36  is used as in this embodiment, since the adhesive  35  has comparatively large fluidity before solidified, it enters into the space between the FPC  4  and the reservoir unit  40  with ease. However, the provision of the protrusion  45   e  serves to prevent the entry of the adhesive  36  into the head  2  and the adherence to the actuator unit  19 . Thus, when the adhesive  36  is used for fixing the FPC  4  to the reservoir unit  40  or the passage unit  20 , the protrusion  45   e  prevents the adhering of the adhesive  36  to the actuator unit  19 , thus minimizing the problem of reduction of the ink squirting capability of the actuator unit. 
     Moreover, because the FPC  4  is partly in contact with both of the upper surface of the passage unit  20  and the protrusion  45   e , a space between the upper surface of the passage unit  20  and the protrusion  45   e  is minimized. Accordingly, by disposing the adhesive  36 , the advantage of preventing the entry of ink or the adhesive  36  having fluidity into the head  2  and also the advantage of preventing the adhering of the ink or the adhesive  36  to the actuator unit  19  are more effectively achieved. 
     Specifically, in the construction in which the pressure chambers  34  are arranged in matrix and the individual electrodes  56  of the actuator unit  19  are arranged opposite to the respective pressure chambers  34 , so that the FPC  4  supplies driving signals to the individual electrodes  56 , as in the construction of the illustrated embodiment, it is general that the FPC  4  is bonded in the interior of the head body  1   a  and is drawn out over the head  2  (See  FIGS. 2A and 2B ). In this construction in particular, the adhesive  36  enters into the head  2  easily. However, even in this construction, the entry of the adhesive  36  into the head  2  can be well prevented by the protrusion  45   e.    
     Also, the protrusion  45   e  is provided in the reservoir unit  40  forming the head body  1   a , not in an additional member other than the head body  1   a . Thus, the effect mentioned above can be obtained with a comparatively simple construction and without increasing the parts count. 
     Further, since a width of the passage unit  20  is not more than a width of the reservoir unit  40  and the protrusion  45   e  formed in the reservoir unit  40  is opposite to the passage unit  20  and also the front end of the protrusion  45   e  is positioned below the upper surface of the actuator unit  19 , as shown in  FIG. 2B , the effects mentioned above can be obtained while the head  2  can also be reduced in width, as compared with a variant ( FIG. 9 ) as mentioned later. 
     Also, the entire actuator unit  19  is opposite to the spaced portion  45  of the reservoir unit  40 . For example if a part of the actuator unit  19  is located in a position where it is not opposite to the spaced portion  45 , there is a possibility that the ink may adhere to the part of the actuator unit  19 . However, in the construction of this embodiment, since the entire actuator unit  19  is opposite to the spaced portion  45 , the effect of preventing the adhering of the ink to the actuator unit  19  provided by the protrusion  45   e  can be surely achieved. 
     As the FPC  4  is fixed to both of the protrusion  45   e  and the passage unit  20  facing the protrusion  45   e  by the adhesive  36 , even if some external force is added to the FPC  4 , reliability of electrical connection between the FPC  4  and the actuator unit  19  is ensured. 
     Further, according to the producing method of the ink-jet head  2  according to this embodiment, since the bonded portion  44  and the protrusion  45   e  are both formed by the half-etching when the concavity and convexity is formed in the bottom  46  of the lower plate  42 , the production cost can be reduced. 
     Reference is now made of a variant of the ink-jet head according to the present invention.  FIGS. 9A and 9B  are views showing the ink-jet head of the variant, which correspond to  FIGS. 2A and 2B . This variant differs from the embodiment mentioned above only in the construction of the reservoir unit or rather in the construction of the lower plate, and the remaining constructions are the same as those of the embodiment illustrated above. Accordingly, the description of the corresponding construction is omitted, while like reference numerals are labeled to corresponding parts. 
     As shown in  FIG. 9A , the reservoir unit  140  of the ink-jet head  102  according to this variant is formed by laminating the upper plate  41  and the lower plate  142  having a larger width than the upper plate  41 . The lower plate  142  is provided with the ink reservoir  42   a  and the connecting passage  42   b  ( FIG. 4 ) identical with those of the embodiment mentioned above. On the other hand, the lower plate  142  has a bonded portion (first protrusion)  144  and a spaced portion  145  formed on the bottom  146  by the half-etching. 
     The bonded portion  144  has a width with respect to a lateral direction of the head larger than that of the bonded portion  44  of the embodiment illustrated above (See  FIG. 2A ). Accordingly, a bonded surface  144   a  of the front end of the bonded portion  144  is not bonded to the upper surface of the passage unit  20  at one end thereof with respect to the lateral direction of the head. On the other hand, the spaced portion  145  has a protrusion (second protrusion)  145   e  protruding in the same direction as the bonded portion  144  (i.e., downwardly) which is formed in its opposite surface to the passage unit  20  at an end thereof opposite to the bonded portion  144  with respect to the actuator unit  19 . As shown in  FIG. 9B , the protrusion  145   e  of this variant is not opposite to the passage unit  20  and also the front end of the protrusion is positioned below the upper surface of the passage unit  20 . The spaced surface  145   a  of the spaced portion  145  has a width larger than the spaced surface  45   a  illustrated above and includes a portion that is not opposite to the passage unit  20 , as shown in  FIG. 9B . Also, it is seen from  FIG. 9B  that the FPC  4  is in abutment with at least a part of the protrusion  145   e , as is the case with the embodiment illustrated above. 
     Although depending on rigidity of the FPC  4 , protruding length of the protrusion  145   e , and the like, the FPC  4  withdrawn through the space between the passage unit  20  and the protrusion  145   e  is bended as in  FIG. 9B  and is surely in abutment with both of the protrusion  145   e  and an end portion of the passage unit  20 . Thereby, the entry of ink, the adhesive  36  and the like into the head  2  is more effectively prevented. 
     The ink-jet head  102  of this variant can provide the same effects as those of the embodiment illustrated above by the same construction as that of the embodiment illustrated above and can further provide the following effects. First, since the front end of the protrusion  145   c  is positioned below the upper surface of the passage unit  20 , the effect of preventing the entry of the ink or the adhesive into the head  102  can be provided effectively, as compared with the ink-jet head  2  of the embodiment illustrated above. Thus, the adhering of the ink, the adhesive and the like to the actuator unit  19  can be prevented more reliably. The farther the protrusion  145   e  protrudes, the more reliably the effect mentioned above can be achieved. 
     When the ink-jet head  102  of this variant is produced, or particularly when the concavity and convexity of the bottom  146  of the reservoir unit  140  is formed, the bonded portion  144  and the protrusion  145   a  can be both formed by the first half-etching. To be more specific, since the front end of the bonded portion  144  and the front end of the protrusion  145   a  are positioned at the same level, as shown in  FIG. 9A , the bottom of the lower plate  142  can be etched by the half-etching in the state in which its portions corresponding to the bonded surface  144   a  and the front end surface of the protrusion  145   e  are masked, to form the recessed portion having the spaced surface  145   a  as the bottom. All areas of the bottom of the lower plate  142  except the recessed portion are presented in the form of the bonded portion  144  and the protrusion  145   e . This can provide reduction in number of processes and thus in production costs. 
     The concavity and convexity of the reservoir unit  40 ,  140  may be formed in any proper methods, such as resin molding or cutting, without limitation to the half-etching. 
     Also, the protrusion may be provided in the passage unit  20 , rather than in the spaced portion  45 ,  145 . In this case, the protrusion may be provided at a width end of the passage unit  20  of the cavity plate  21  forming the uppermost layer of the passage unit  20  in such a manner as to protrude upwardly. In this configuration, in case a protruding length of the protrusion is the same as the height of the actuator unit  19 , the FPC  4  connected to the actuator unit  19  need not to be excessively bended. Therefore, such an advantage is obtained in addition to the above-mentioned advantage, that reliability of electrical connection between the actuator unit  19  and the FPC  4  is enhanced. Moreover, although depending on a size of the space between the spaced portion and the passage unit  20 , another protrusion is preferably provided on the separated portion so that the another protrusion faces the protrusion formed on the passage unit  20 , from the viewpoint of preventing the entry of ink, the adhesive  36 , and the like into the head  2 . The protrusion may be provided in a area of the passage unit  20  not facing the spaced portion  45 ,  145  so that a tip of the protrusion is placed upper of a level of the spaced portion  45 ,  145 . In this case, the FPC  4 , which is withdrawn outside with bended so as to pass a spaced between the protrusion and the spaced portion, is in abutment with both of the protrusion and the spaced portion. Thereby, the entry of ink, the adhesion  8 , and the like into the head  2  is more effectively prevented. 
     Further, the spaced portion spaced apart from and opposite to the passage unit  20  may be formed by another component, without limitation to the bottom of the reservoir unit  40 ,  140 , and the protrusion may be formed in that member. 
     Also, the driving portion for imparting squirting energy to the ink in the pressure chambers  34  is not limited to the member, like the actuator unit  19 , bonded to the passage unit  20  to be opposite to the pressure chambers  34 . For example, the vibrating plate, spaced apart from the driving portion, for defining the pressure chamber, like the vibrating plate of the capacitance type ink-jet head, may also be used as the driving portion. This means that the present invention is also applicable to the structure that the driving portion is bonded to the spaced portion. 
     The pressure chamber  34  need not necessarily be arranged in matrix. Also, the FPC  4  need not necessarily be constructed to supply driving signals to the respective individual electrodes  56  of the actuator unit  19 . 
     The FPC  4  may be in abutment with the passage unit  20 , rather than the protrusion  45   e ,  145   e , or may be in abutment with neither of them. 
     Further, the present invention is applicable, for example, to a serial printing type ink-jet printer wherein the head body  2   a  is moved in reciprocation in a direction orthogonal to the paper carrying direction for printing, as well as a line printing type ink-jet printer wherein the paper is carried with respect to the fixed head body  2   a ,  102   a  for printing, like the ink-jet head of the illustrated embodiments. 
     Also, the present invention is also applicable, for example, to an ink-jet type facsimile or copy machine, without limitation to the ink-jet printer. 
     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.