Abstract:
A piezo-electric actuator is rigidly mounted for a portion of one surface and provided with opposing electrodes for application of a bias. Because the mounted portion is constrained from deformation, the piezo-electric actuator deforms in a bending manner upon application of a bias. The actuator is provided with a mirror surface for selective reflection of an incident light beam in accordance with a bending deformation of the actuator. The actuator can also modulate a light beam by selectably deflecting into the light path to thereby block the light beam.

Description:
RELATED APPLICATIONS 
     This application is a division of copending application Ser. No. 08/587,844, filed Jan. 11, 1996, claiming priority from Japanese Patent Application Nos. 7-003502, filed Jan. 12, 1995, 7-003504, filed Jan. 12, 1995, 7-055719, filed Mar. 15, 1995 and 7-078659, filed Apr. 4, 1995 each of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to an ink jet recording apparatus. More particularly, the invention concerns an electro-mechanical transducer employed in the ink jet recording apparatus. 
     2. Background of the invention 
     Conventionally, an electro-mechanical transducer having piezo-electric members is employed in an ink jet recording device. The piezo-electric member vibrates in different vibrating modes depending upon its shape, the direction that the member is polarized, or the direction that an electronic field applied thereto. For example, where the piezo-electric member is in the form of plate which is rectangular in cross-section and is polarized in a direction along its transverse direction, applying an electronic field along its polarized direction makes the piezo-electric member contract along its longitudinal direction and expand along its transverse direction, while applying an electronic field to the piezo-electric member reverse to the polarized direction makes the piezo-electric member expand along its longitudinal direction and contract along its transverse direction. A vibration along the longitudinal direction will be referred to as “a d( 31 ) mode” while a vibration mode along the transverse direction will be referred to as “a d( 33 ) mode”. Further, applying the electronic field to the piezo-electric member perpendicular to its polarized direction introduces therein a shear stress along its surface. This vibration mode is referred to as “a d( 15 ) mode” hereinafter. 
     Each prior art electro-mechanical transducer employs one of these vibration modes, the d( 33 ) or d( 31 ) mode being mainly employed among them. Further, a prior art ink jet recording device includes the electro-mechanical transducer. Each transducer has therein an ink chamber in which an elongated piezo-electric member is arranged. The piezo-electric member is vibrated according to image signals. Then, in response to displacements of the piezo-electric member and the resultant energy generated in the ink, ink droplets are ejected from the ink chamber through a nozzle formed in a wall of the chamber. 
     For instance, U.S. Pat. No. 4,752,788 discloses an ink jet head which is shown in FIG.  1 . This ink jet head  10  includes a piezo-electric member  11  in which a plurality of parallel slots  12  are formed, and a plate  13  for covering the slots  12  to define respective ink chambers  14 . Each slot  12  has at its bottom portion a pair of slits extending in a longitudinal direction thereof so as to define therebetween an elongated mount  15 . An electrode  16  is arranged on the upper surface of the mount  15 , and another electrode  17  is provided on a lower surface of the piezo-electric member  11  opposing electrode  16 . In operation of the head  10  thus constructed, applying a voltage between the electrodes  16  and  17  causes the mount  15  to deform, which varies a volume of the ink chamber  14 . This energizes ink in the chamber  14  so that a droplet of the ink is ejected through a nozzle which is not shown. 
     Further, Japanese Patent Laid-Open Publication No. 6-143563 discloses another ink jet head  20  depicted in FIG.  2 . The head  20  has a first base plate  21 . The plate  21  includes a plurality of parallel slots  22  which are covered by a compliant film  23  to define a plurality of corresponding ink chambers  24 . The head  20  also has a second base plate  25 . This plate  25  has thereon a plurality of mutually spaced piezo-electric vibrators  26  for drive as well as a dummy piezo-electric vibrator  27 . These piezo-electric vibrators  26  and  27  are constructed by superimposing piezo-electric thin layers and electrode layers alternately. The second base plate  25  is arranged on the first base plate  21  so that each vibrator  26  contacts with the compliant film  23  over the ink chamber  24 . The drive and dummy vibrators  26  and  27  are typically formed by first bonding a layered piezo-electric plate on the plate  25  and second forming grooves in the plate at equal intervals. The first base plate  21 , compliant film  23 , and the second base plate  25 , including the vibrators  26  and  27 , are held securely by rigid plates  28  and  29  using bolts. In operation of the ink jet head  20  thus constructed, applying voltage on the vibrator  26  causes it to deform, which moves the complaint film  23  to force the ink so that the volume of the ink chamber  24  varies and then an ink droplet is ejected through a nozzle which is not shown. 
     However these prior arts ink jet heads employs one of d( 31 ), d( 33 ), or d( 15 ) vibration modes, each of which provides for only a small deformation with the piezo-electric member. Therefore, the ink is not sufficiently energized in response to the image signals. 
     Further, in the above mentioned systems, the vibration of one piezo-electric member is transmitted to the neighboring ink chambers and piezo-electric members, i.e., a cross-talk from chamber to chamber is occurred, which results in unexpected ink ejections from those ink chambers so that the resultant image of a recording device is damaged. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved piezo-electric transducer which is capable of providing a piezo-electric member with a large deformation to eject an ink droplet vigorously. 
     Another object of the invention is to provide an improved piezo-electric transducer which is capable of ejecting ink droplets vigorously. 
     Further object of the invention is to provide an improved ink jet recording apparatus which employs a piezo-electric transducer capable of providing a piezo-electric member with a large deformation and then ejecting ink droplets vigorously. 
     In accordance with these objects, the present invention provides an ink jet recording apparatus which includes an ink chamber in which an ink is filled, said ink chamber having a nozzle from which the ink is ejected; a strip member which is provided along with said ink chamber, said strip member being extending in an extending direction from a first portion corresponding to said ink chamber to a second portion not corresponding to said ink chamber; and driver which is connected with said strip member to induce a displacement of said first portion in a direction orthogonal to the extending direction. 
     Further the present invention provides an electro-mechanical device which includes a base member; a piezo-electric member which has a strip shape extending in an extending direction, said piezo-electric member having a first surface along with said extending direction and a second surface opposing to said first surface, a part of said first surface being fixedly connected with said base plate, said second surface having at least one groove; a first electrode which is disposed on said first surface; and a second electrode which is disposed on said second surface throughout said groove. 
     Furthermore the present invention provides an electro-mechanical device which includes a strip member which has a strip shape extending in an extending direction, said strip member having a surface along the extending direction; a piezo-electric member which is fixedly connected with said surface at an edge portion of said strip member with respect to said extending direction; and a pair of electrodes which is provided on said piezo-electric member. 
     Moreover the present invention provides an electro-mechanical device which includes a piezo-electric member having a length ( 1 ) in an extending direction, said piezo-electric member having a first surface parallel to said extending direction, and having a second surface opposing to said first surface; a first electrode which is provided on said first surface; a second electrode which is provided on a first portion of said second surface, said first portion having a length (t) with respect to said extending direction from a first edge of said piezo-electric member; a base member on which a second portion of said piezo-electric member is fixedly connected, said second portion having a length (s) with respect to said extending direction from a second edge of said piezo-electric member, said second end being opposing to said first edge, wherein the lengths ( 1 ), (s) and (t) satisfy the following formations, 
     
       
         ( 1 )&gt;(t) 
       
     
     
       
         ( 1 )&gt;(s). 
       
     
     Still further the present invention provides an electro-mechanical device which includes a piezo-electric member which has a first portion which is polarized in a predetermined direction and a second portion which is not polarized; and a base member on which said second portion is fixedly connected. 
     Furthermore, the present invention provides an ink jet recording device which includes an ink chamber in which ink is filled, said ink chamber having a aperture and a nozzle from which ink is ejected; a strip member a portion of which is inserted into said ink chamber from said aperture; a filling material which is provided a gap between said aperture and said strip member to prevent leakage on the ink. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This and other objects and features of the present invention will become clear from the following description taken in conjunction with a preferred embodiment thereof with reference to the accompanying drawings throughout which like parts are designated by like reference numerals, and in which: 
     FIG. 1 is a transverse sectional view of a prior art electro-mechanical transducer; 
     FIG. 2 is a transverse sectional view of another prior art electro-mechanical transducer; 
     FIG. 3 is an elevation view of an electro-mechanical transducer of the present invention; 
     FIG. 4 is a graph which shows a relationship between a distance from a fixed position and a displacement of a piezo-electric member in the electro-mechanical transducer in FIG. 3; 
     FIG. 5 is an elevation view of a modification of the electro-mechanical transducer; 
     FIG. 6 is an elevation view of another modification of the electro-mechanical transducer; 
     FIG. 7 is a cross-sectional view of a printer in which the electro-mechanical transducer of the present invention is installed; 
     FIG. 8 is a perspective view of the ink jet head in which the electro-mechanical transducer of the present invention is installed; 
     FIG. 9 is a transverse sectional view of the electro-mechanical transducer of the first embodiment; 
     FIG. 10 is a longitudinal sectional view of the electro-mechanical transducer of the first embodiment; 
     FIGS. 11A-11C shows a process for manufacturing a second plate and piezo-electric members in the electro-mechanical transducer of the first embodiment; 
     FIGS. 12A-12C show a process for manufacturing a first plate in the electro-mechanical transducer of the first embodiment; 
     FIGS. 13A-13C show a process for assembling the electro-mechanical transducer of the first embodiment; 
     FIGS. 14-14B show a process for assembling the electro-mechanical transducer of the first embodiment; 
     FIG. 15 is a perspective view of the ink jet head which includes the electro-mechanical transducer of the first embodiment; 
     FIGS. 16A-16D illustrates pulse forms to be applied to electrodes in the electro-mechanical transducer; 
     FIG. 17 shows a deformation of the piezo-electric member which is bonded at its entire longitudinal surfaces to a base plate; 
     FIG. 18 shows a deformation of the piezo-electric member which is bonded at its entire longitudinal surface to a base plate; 
     FIG. 19 is a transverse sectional view of the electro-mechanical transducer of the first embodiment in which the deformation of the piezo-electric member is illustrated; 
     FIGS. 20A-20C show modifications of the piezo-electric members, in each of which an individual electrode has a different length from a common electrode; 
     FIG. 21 shows another modification of the piezo-electric member which has a trapezoid cross-section; 
     FIGS. 22A-22B show an integrated piezo-electric unit in the form of fork; 
     FIG. 23 shows another modification of the piezo-electric member in which a plurality of piezo-electric layers are superimposed; 
     FIG. 24 is a perspective view of an electro-mechanical transducer of the second embodiment; 
     FIG. 25 is a transverse sectional view of the electro-mechanical transducer of the second embodiment; 
     FIG. 26 is a longitudinal sectional view of the electro-mechanical transducer of the second embodiment; 
     FIGS. 27A-27G illustrate pulse forms to be applied to electrodes in the electro-mechanical transducer of the second embodiment; 
     FIGS. 28A-28B show modifications of drivers to be used in the electro-mechanical transducer of the second embodiment; 
     FIGS. 29A-29B show other modifications of the electro-mechanical transducer of the second embodiment; 
     FIGS. 30A-30B show other modifications of the electro-mechanical transducer in which piezo-electric member has plurality of layers; 
     FIG. 31 shows a close-up of the plurality of layers of the piezo-electric member; 
     FIG. 32 is a transverse sectional view of the ink jet head of the third embodiment; 
     FIG. 33 is a longitudinal sectional view of the ink jet head of the third embodiment; 
     FIGS. 34A-34B illustrate a process of assembling a second plate and other elements arranged thereon; 
     FIGS. 35A-35C illustrate a process of manufacturing the piezo-electric members of the third embodiment; 
     FIGS. 36A-36C illustrate a process of manufacturing a first plate of the third embodiment; 
     FIGS. 37A-37C illustrate a process of assembling the first and second plates of the third embodiment; 
     FIGS. 38A-38B illustrate a process of assembling the electro-mechanical transducer of the third embodiment; 
     FIG. 39 is a perspective view of the ink jet head of the third embodiment; 
     FIGS. 40A-40C illustrate pulse forms to be applied to electrodes in the electro-mechanical transducer; 
     FIG. 41 shows a deformation of the piezo-electric members of the electro-mechanical transducer of the third embodiment; 
     FIG. 42 shows a deformation of a partition wall in the electro-mechanical transducer of the third embodiment; 
     FIG. 43 shows a modification of the electro-mechanical transducer of the third embodiment; 
     FIG. 44 shows an integrated unit of the drivers of the third embodiment; 
     FIG. 45 is a longitudinal sectional view of an electro-mechanical transducer of the fourth embodiment; 
     FIG. 46 is a transverse sectional view of the electro-mechanical transducer of the fourth embodiment; 
     FIG. 47 illustrates a modification of piezo-electric member; 
     FIGS. 48A-48B show an integrated driver used in the electro-mechanical transducer of the fourth embodiment; 
     FIG. 49 is a perspective view of a semi-gould type ink jet head in which the electro-mechanical transducer of the present invention is used; 
     FIG. 50 is a cross-sectional view of a cyronics type ink jet head in which the electro-mechanical transducer of the present invention is used; 
     FIG. 51 is a cross-sectional view of a stemme type ink jet head in which the electro-mechanical transducer of the present invention is used; 
     FIG. 52 shows a beam scanner in which the electro-mechanical transducer of the present invention is used; 
     FIG. 53 shows a display device in which the electro-mechanical transducer of the present invention is used; 
     FIG. 54 shows a deformation of an electro-mechanical transducer in the display device FIG. 53; 
     FIG. 55 shows an electro-photographic printer in which the electro-mechanical transducer of the present invention is used; and 
     FIG. 56 shows an photographic colort printer in which the electro-mechanical transducer of the present invention is used. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     (I) ELECTRO-MECHANICAL TRANSDUCER 
     A discussion is made to an electro-mechanical transducer of the present invention. Referring to FIG. 3, which illustrates a structure of an electro-mechanical transducer of the invention, a reference numeral  101  generally indicates a piezo-electric transducer. This transducer  101  comprises a base plate  102  made of non-piezo-electric material and an elongated piezo-electric member  103 . The piezo-electric member  103 , preferably being a rectangular cross section, is polarized in its transverse direction indicated by an arrow P. Provided on the surfaces of the member  103 , i.e., on surfaces through which the arrow P extends, are electrodes  104  and  105 , respectively, made of electrically conductive material. The piezo-electric member  103  is bonded to the base plate  102  for a specific region S along the electrode  105 . This bonded region S extends from one end of the member  103  for a predetermined distance so that the opposite end of the member  103  can bend upward. While the electrode  105  extends over all of the length of the member  103 , the other electrode  104  extends only for a region T which positioned outside the bonded region S. This region T is referred to as un-bonded region hereinafter. The electrodes  104  and  105  are electrically connected to a power supply  106  to apply a predetermined voltage between the electrodes  104  and  105 . 
     In operation, upon turning on the power supply  106  to apply a voltage between the electrodes  104  and  105  so that an electronic field is formed in a direction indicated by an arrow E which is parallel to the polarized direction P, the opposite or free end of the piezo-electric member  103  in the un-bonded region T deforms to bend upward as illustrated by dotted lines. This is because the piezo-electric member  103  is secured to the base plate  102  only in the bonded region S, and it is not secured to the base plate  102  along the un-bonded region T. If instead, the piezo-electric member were bonded to the base plate over all of the length thereof, the piezo-electric member would contract in the longitudinal direction and expand in the traverse direction according to the d( 33 ) vibration mode. Each displacement of the bent portion increases as the distance from the bonded region S increases as shown in FIG. 4, and the maximum displacement of the piezo-electric member is far greater than that of d( 33 ) mode. 
     Upon turning off the power supply  106  to eliminate the electronic field, the piezo-electric member  103  in the un-bonded region returns its original position as depicted by riveting solid lines. 
     Although bonding is employed for securing the piezo-electric member  103  to the base plate  102  in the previous embodiment, the member  103  may be secured by rivetting, molding, or the like. Alternately, as shown in FIG. 5, the member  103  may be secured by first bonding it to a retaining member  107  and then holding the piezo-electric member  103  together with the base plate  102 , and finally holding the retaining member  107  firmly using, for example, clamps without bonding the member  107  to the base plate  102 . Furthermore, it is not necessary to bond the piezo-electric member  103  either to the base plate  102  to or the retaining member  107 , because the member  103  may be secured by clamping it between the base plate  102  and the retaining member  107 , as illustrated in FIG.  6 . 
     (II) INK JET RECORDING DEVICE 
     A. FIRST EMBODIMENT 
     A first preferred embodiment of an ink jet recording device of the present invention will be described below. Referring to FIG. 7, a reference numeral  110  generally designates an ink jet recording device of the invention. The ink jet recording device  110  generally includes a power circuit  111  having a plug  112 , a driving source  113 , a first controller  114 , a memory  115 , a second controller  116 , an ink supply, a scan carriage  118 , a sheet feeder  119 , a housing  120 , and an operation panel  121 . The scan carriage  118  is so mounted as to scan in a direction which intersects perpendicularly to a direction indicated by arrow A, along which a sheet  122  from the feeder  119  advances. The carriage  118  houses four ink jet heads  123  having black, cyan, magenta, and yellow inks, respectively. These heads  123  are arranged along the sheet transporting direction with ink ejecting nozzles not shown being directed downward. Ink supply  117  supplies ink to heads  123 . 
     FIG. 8 shows the ink jet head  123 . This Head  123  includes a base plate  124  on which an ink ejector  125 , a terminal plate  126 , and a connector  127  are arranged sequentially from one end of the plate  124 . As best shown in FIGS.  9  and  10 , the ink ejector  125  has a first plate  128  made of non-piezo-electric material such as aluminum. The first plate  128  has a plurality of slots  129 . Each slot  129  extends parallel in a longitudinal direction of the plate  128  leaving specific separation from neighboring slots. Also, each slot  129  has a predetermined width. The ink ejector  125  further includes a second plate  130 , which is attached to the surface of the first plate  128  so as to cover the slots  129  to define corresponding ink chambers  131 , respectively. 
     Mounted on the second plate  130  are a plurality of piezo-electric members  132  extending parallel in a longitudinal direction of plate  130 . The piezo-electric member  132  is made of, for example, lead zuconate titanate (PZT) piezo-electric material and preferably has a rectangular cross-section. The piezo-electric members  132  are arranged at equal intervals as the slots  129 . Therefore, upon assembling the first and second plates  128  and  130  into an integrated unit, each piezo-electric member  132  is accommodated in and along the slot  129  leaving specific spaces from either side walls of the slot  129 . Each piezo-electric member  132  has an individual electrode  133  on one surface and a common electrode  134  on the other surface. Also, each piezo-electric member  132  is polarized in a direction indicated by an arrow B, which is identical to the direction along which an electronic field will be formed when biasing a voltage between the individual and common electrodes  133  and  134 . As best shown in FIG. 10, the piezo-electric member  132  is bonded at its rear region, i.e., right hand side thereof, indicated by region S, to the second plate  130  by an electrically conductive adhesive so that the front region can bend. Therefore, upon application of a biasing voltage between the individual and common electrodes  133  and  134  to form the electronic field in the piezo-electric member  132 , the front side portion of the piezo-electric member  132  will deform and bend, which energizes an ink (not shown) in the ink chamber  131 . 
     Although, the front portion of the piezo-electric member  132  is spaced a gap apart from the second plate  130  by a gap in a region outside the region S, the gap can be eliminated by shaving off a rear surface of second plate  130  in region S to form a thin recess having a depth of approximately several microns (um) for positioning the adhesive therein. 
     The integrated unit of the first and second plates  128  and  130  has at its front end a nozzle plate  135  made of, for example, polyimide film of approximately  25 - 200  μm in thickness. This nozzle plate  135  has a plurality of nozzles  136  positioned in a line, each axis of the nozzles  136  being spaced the same distance as that of ink chambers  131  from each other. Suitably the distance is, for example, about 42.3-254 μm where a pixel density is from 600-100 dpi. 
     The first plate  128  has at its rear portion an opening  137  which extends in the transverse direction to cross the ink chambers  131 . Either side of this opening  137  is closed by a side plate  138  as best shown in FIG.  8 . Further, rear end openings of the ink chambers  131  are closed by a back plate  139 . Furthermore, the first plate  128  has thereon a manifold  140  which communicates through the opening  137  to the ink chambers  131  for supplying ink into the chamber  131 . 
     As shown in FIG. 8, each piezo-electric member  132  is extended out beyond the back plate  139  from the ink chamber  131 . The individual electrode  133  is connected through a conductive member  141 , the drive IC  142 , a conductive member  143 , and a connector  127  to the controller  112  (see FIG.  7 ). The common electrodes  134  are connected each other through the electrically conductive adhesive which bonds the piezo-electric member  132  to second plate  130 . This conductive adhesive is further connected to an electrically conductive member  144 . Further, the member  144  is connected to a conductive member  145  by wire-bonding technique, then to a connector  127 . 
     Referring to FIGS. 11 through 15, a process for manufacturing the ink jet head  125  will be described below. FIGS. 11A-11C shows a process for making the piezo-electric members  132  on the second plate  130 . In this process, first a rectangular plate  150  of PZT is processed to form electrode layers of about 10-0.1 μm in thickness, on both sides thereof, by an electroless plating or sputtering. Advantageously, Au/Ni is preferably used for the electroless plating while Au/Ni or Au/Cr is used for sputtering. Next, the PZT plate  150  is placed on the second plate  130  preferably having the same size as PZT plate  150 . These two plates are bonded each other by applying adhesive in a specific region indicated by the region S. Then, the PZT plate is cut at equal intervals into a folk-like configuration using a dicing saw  151  so that a plurality of mutually spaced piezo-electric members  132  and slots therebetween are formed side by side. Last, an entire surface of the piezo-electric member  132  is applied with a specific resin such as polyimide and then heated at 180° C. for about an hour to form a protection layer. This protection layer prevents moisture in the atmosphere from penetrating into the piezo-electric member to degrade performance. Accordingly, the piezo-electric member keeps its original deformation rate even though it is exposed to moisture. Note that this process can be eliminated if the piezo-electric member is made of another piezo-electric material having greater resistance to moisture. 
     The first plate  128  is manufactured as shown in FIGS. 12A-12C. Plate  128  is made from a rectangular plate  152  of non-piezo-electric material, for example, aluminum, or ceramic. The rectangular plate  152  is first cut to form grooves on one side by a dicing saw  153  so that a plurality of parallel slots  129  are formed at the same interval as that of piezo-electric members  132  on the second plate  130 . Each slot  129  has a width greater than that of piezo-electric member  132  so that piezo-electric member  132  can be inserted therein. On the opposite side of plate  152  is formed a slot or opening  137  which runs in the transverse direction so that this opening  137  communicates with each of slots  129 . 
     As shown in FIGS. 13A-13C, these plates  128  and  130  thus manufactured are assembled and bonded each other while positioning each piezo-electric member  132  in the corresponding slot  129 . Further, the nozzle plate  135  is bonded to the front end of the integrated plates, with each of the nozzles  136  being positioned at the center of the corresponding ink chamber  131 . 
     Further, as best shown in FIGS. 14A and 14B, the manifold  140  is attached on the first plate  128  to cover the opening  137 , and then the side plates  138  are attached on both sides of first plate  128  to enclose the opening  137 . Still further, the back plate  139  is bonded to the rear end of the integrated plates to enclose the ink chambers  131 . 
     Furthermore, as shown in FIG. 15, the ink ejector  125 , the terminal plate  126  having thereon the drive IC  142  and the conductive members  141  and  143 , the connector  127  are bonded on the base plate  124  having conductive member  145 . Then the individual electrode  133  of piezo-electric member  132  is connected to the corresponding conductive members  141  while the conductive adhesive extended from the common electrode  134  is connected to the conductive member  145 . The conductive members  141  are connected through the drive IC  142  to the corresponding terminals in the connector  127  while the conductive member  145  is connected to the associated terminal in the connector  127 . Finally, resin molding is provided over the base plate  124  so that the elements on the base plate  124  are covered except nozzles  136 . 
     A discussion will be made next to an ejection of ink. The ink is supplied from the ink supply  117  through the manifold  140  into the ink chambers  131 . Upon applying a pulse voltage (see FIG. 16A) between the individual and common electrodes  133  and  134  according to an image signal, an electric field is generated in the direction parallel to the polarized direction indicated by the arrow B in FIG.  9 . As a result, because the piezo-electric member  132  is bonded to the second plate  130  only in the region S, the un-bonded free portion of the piezo-electric member  132  deforms and bends upward in a instance(see FIG.  18 ). Displacement of the piezo-electric member  132  above the second plate  130  increase gradually along the length of piezo-electric member  132  with a maximum displacement at the distal end of the piezo-electric member  132 . 
     Note that, as shown in FIG. 17, if a piezo-electric member is bonded to the plate in its entire longitudinal length S′, upon biasing to form an electric field in the direction indicated by an arrow B, the piezo-electric member contracts in the longitudinal direction indicated by an arrow X while it expands in the transverse direction indicated by an arrow Y. 
     Tests were made to compare the displacements of the piezo-electric member bonded to the plate only in the region S (see FIG. 18) and the piezo-electric member bonded to the plate in the entire region S′ thereof (see FIG.  17 ). The results showed that the displacement of the piezo-electric member of the present invention ( FIG. 18) is  100  times larger than that of piezo-electric member of FIG.  17 . 
     This deformation of piezo-electric member pressurizes the ink in ink chamber  131  so that an ink droplet is ejected from the ink chamber  131  through the nozzle  136 . This droplet deposits on the sheet moving past in front of the nozzle. 
     Upon turning off the biasing voltage between the individual and common electrodes  133  and  134  to eliminate the electric field, the piezo-electric member  132  moves back to its original position. At this time, a negative pressure is generated in the ink chamber  131 , which permits ink to enter via manifold  140  to prepare for next ink ejection. 
     Note that a pulse form as shown in FIG. 16B is preferably used rather than that shown in FIG.  16 A. The reason is, if the biasing voltage is decreased instantly, the piezo-electric member returns to its original position very quickly. This introduces a negative pressure in the ink which sucks in through the nozzle. Further, once air is aspirated, little or no ink can be subsequently ejected from the nozzle because the pressure in the ink generated by the deformation of piezo-electric member is absorbed in the aspirated air bubbles. 
     Therefore, to prevent aspiration of air, it is desirable to use a pulse form as shown in FIG. 16B, in which the voltage drops gradually to zero as fast as possible to the extent that no air is sucked into the chamber. 
     Ejection of the ink is carried out at the same time for each ink chamber  131  in response to the image signals, thereby one line of image is reproduced. This is done repeatedly in synchronism with the movement of the sheet, thereby a whole image is reproduced on the recording sheet. 
     In the ink jet head  125  above described, the piezo-electric member  131  is bonded to second plate  130  only along the restricted region S, not along entire length. Accordingly the vibration of biased piezo-electric member  132  is not transmitted to the neighboring piezo-electric members through plate  130 . Therefore no ink is energized or ejected from the neighboring ink chamber in which the piezoelectric member is not biased. That is, no cross-talk from chamber to chamber occurs so that the ink droplet is ejected only from the ink chamber in which the piezo-electric member is biased. Consequently, a quality of the reproduced image is improved. 
     Furthermore, because the piezoelectric member is bonded in a restricted region, the maximum displacement of the piezo-electric member is increased in proportion to the applied bias voltage. Therefore, a lower voltage can eject the same amount of ink with the same speed as that of prior art printers, which reduces costs of the driver. Also, a size of the ink droplet can be adjusted by controlling the voltage applied to the piezo-electric member, thereby controlling the displacement thereof, which improves the reproductivity of half-tone color images. 
     The length of the bonded region of the piezo-electric member should be shorter to the extent that no cross-talk from chamber to chamber occurs, which increases an energy derived from the deformation of the piezo-electric member. This achieves a stable ejection of ink droplets and improves high frequency response allowing increased printing speed. 
     To prevent the cross-talk from chamber to chamber while maintaining stable bonding of the piezo-electric member to the plate, the length of the bonded region S should be selected as follows: 
     
       
         0.21L≦S≦0.91L 
       
     
     wherein L represents the entire length of the piezo-electric member. These limits are determined as follows. If the length of the bonded region S is less than 0.21L, the piezo-electric member is so weak in strength that it is easy to be damaged during its manufacturing or construction. On the other hand, if the length of the bonded region S is more than 0.91L, much of the vibration of the piezo-electric member is transmitted to neighboring piezo-electric members so that cross-talk from chamber to chamber occurs. Most advantageously, the length is determined as follows: 
     
       
         0.31L≦S≦0.71L 
       
     
     In the previous embodiment, the ink is ejected from the chamber and supplied by turning on and off the voltage. It is possible, however, that, by turning off and on the voltage, the ink could be supplied into the chamber and is ejected therefrom by using pulse forms illustrated in FIGS. 16C or  16 D. When using these pulse forms, by turning off the voltage the piezo-electric member returns its original position from its deformed position so that the ink is supplied into the chamber, while by turning on the voltage the piezo-electric member moves back to the bent position so that the ink is ejected from the chamber. To carry out this, it is desirable to keep a small gap of about several microns between the piezo-electric member and the lower plate. This can be achieved by increasing the thickness of the adhesive used for bonding the piezo-electric member to the plate. The pulse form shown in FIG. 16D having a gradual voltage drop is preferably used rather than that shown in FIG. 16C for the reason described above. 
     Although the piezo-electric member in the previous embodiment comprises individual and common electrodes having equal length and extending for the entire longitudinal length of the piezo-electric member, they may also have different lengths as shown in FIG. 20A and 20B. Also, as shown in FIG. 20C, the piezo-electric member may have a plurality of slits extending transverse to the length, in which the individual electrode is provided so as to make the overall length of the individual electrode longer than that of the common electrode. 
     Using the piezo-electric member shown in FIG.  17  and (referred to hereinafter as “type D”) the piezo-electric members shown in FIGS. 20A,  20 B and  20 C, (referred to hereinafter as types A, B, and C, respectively), experiments were made to estimate forces generated in the piezo-electric member and displacements at the distal ends thereof. In the experiment with respect to the force, a movement of the piezo-electric member was restricted to 1 μm by a restriction member and a force applied to the restriction member was measured. In the experiment with respect to the displacement, a 50 volt bias was applied to each piezo-electric member, and the displacement of the distal end was measured. The results are shown in Table 1. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Piezo-electric 
                 FORCE 
                 DISPLACEMENT 
               
               
                   
                 MEMBER 
                 (gf) 
                 (μm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 TYPE D 
                 86.5 
                 1.0 
               
               
                   
                 TYPE A 
                 240.0 
                 2.8 
               
               
                   
                 TYPE B 
                 693.6 
                 8.0 
               
               
                   
                 TYPE C 
                 1020.0 
                 11.8 
               
               
                   
                   
               
             
          
         
       
     
     As can be seen from the table, the piezo-electric members of types A, B, and C provided greater force and displacement than that of type D, which means that it is desirable to employ one of these types A, B, or C rather than type D in order to minimize the bias voltage and/or increase the efficiency of the ink ejection. 
     It should be noted that since the dicing process piezo-electric members may also have a trapezoidal cross-section as shown in FIG.  21 . The trapezoidal shape facilitates assembly of the upper plate and the lower plate. 
     The piezo-electric members may also be integrated into a unit as shown in FIGS. 22A and 22B. This unit  155 , in the form of fork, ha s a base  157  from which each piezo-electric member extend parallel. Also, the base  157  is preferably designed to be lower than piezo-electric members  156  as shown in FIG.  22 B. This unit is manufactured by dicing. In dicing, the dicing saw moves from one end of the original plate for forming each piezo-electric member and, once it reaches a base region, the dicing moves up with keeping its lower end within the plate, and then continues the cut toward the other end of the original plate so that grooves on the base  157  are formed. 
     According to this embodiment, each piezo-electric member has greater structural strength, which increases both durability and reliability of the ink jet head. Also, since the common electrodes can be extended over the base portion, the connection between the common electrode and the conductive line on the base plate will be readily done by wire-bonding or solder. Therefore, it is not necessary to connect each common electrodes to the conductive line, which facilitates assembly of the head. 
     The piezo-electric member may include a plurality of piezo-electric layers and electrode layers as shown in FIG.  23 . In this embodiment, the piezo-electric member  132  has three, i.e., upper, middle, and lower layers. An additional individual electrode  133  is positioned between the upper and middle layers, while an additional common electrode is positioned between the middle and lower layers. With this piezo-electric structure, the displacement at the distal end of the piezo-electric member further increased depending upon the number of the layers, which thereby decreases power consumption and the cost of the driver IC. 
     B. SECOND EMBODIMENT 
     A second embodiment of an ink jet head of the present invention will be described below. As shown in FIGS. 24,  25 , and  26 , an ink jet head of this embodiment has an first plate  200  made of non-piezo-electric material such as aluminum. The first plate  200  has a plurality of slots  201  made by, for example, dicing as previously described. Each slot  201 , which has a predetermined width, extends parallel in a longitudinal direction of the plate  200  leaving specific spaces from neighboring slots. The ink jet head  200  further includes a second plate  202 , which is adhered to the surface of the first plate  200  so as to cover the slots  201  to define corresponding ink chambers  203 . Preferably, the adherence between the first and second plates may be accomplished by, for example, bolts and nuts or by resin molding. 
     Referring to FIG. 26, the front side of the integrated plates  200  and  202 , i.e., right hand side in FIG. 26, has a nozzle plate  204  made of polyimide film, having a thickness of about 25-200 μm. The nozzle plate  204  has defined therein apertures, i.e., nozzles  205 , each of which has the same spacing between them as the ink chamber  23 . Normally this space is, for example, about 42.3-254 μm which corresponds to a pixel density of 600-100 dpi. It is preferable that the nozzles are formed using eximicer laser. The rear side of the integrated plates  200  and  202 , i.e., left hand side in FIG. 26, has a back plate  206 . The back plate  206  has at its lower portion a plurality of mutually spaced cut-outs  207  corresponding to the ink chambers  203 . Each cut-out  207  is sized so that each actuator  208  of driver  209 , described in detail below, can be arranged therethrough without difficulty. The first plate  200  also has defined therein an opening or ink inlet  210  at the opposite side remote from the ink chambers  203 . This inlet  210  runs in the transverse direction of the first plate  200  so that it communicates with each of the ink chambers  203 . Further, the ink inlet  210  is connected to a hollow manifold  211  having ink tube  212  through which an ink is supplied from the ink supply to the ink chambers  203 . 
     Referring to FIGS. 24 and 26, the second plate  202  has at its one side a recess  213  which is lower than an adjacent region confronting to the ink chambers  203 . On the recess  213  a plurality of drivers  209  are positioned corresponding to the ink chambers  203 . Each driver  209  generally includes the actuator  208  which extends its front portion into the ink chamber  203  through the cut-out  207 , and lower and upper, i.e., first and second, piezo-electric members  214  and  215  which cooperate each other to firmly hold the actuator  208 . 
     In this embodiment, the actuator  208  always contacts the ink at its front portion, which can degrade its durability by a penetration of the ink into the actuator. Therefore, it is preferable that the actuator is made of material having ink resistance. Further, it is more preferable that the widths of the slot  201  and actuator  208  are so sized that spaces between confronting side walls of slot  201  and actuator  208  is less than 30 μm. This keeps the ink from moving into the spaces which possibly decreases efficiencies of ink ejection. 
     Each of the first and second piezo-electric members  214  and  215  has a common electrode  216  on the surface confronting the actuator  208  and an individual electrodes  217  on the opposite surface. The common electrodes  216  are grounded, while the individual electrodes  217  are electrically connected to the controller  116  (see FIG. 7) via a driver IC, respectively. This permits each pair of piezo-electric members  214  and  215  to be provided with voltage in response to image signals. 
     Further, the first piezo-electric member  214  is electrically polarized in the direction indicated by arrow P which directs from the common electrode  216  to individual electrode  217  while the second piezo-electric member  215  is electrically polarized in the direction indicated by arrow P′ which directs from the individual electrode  217  to common electrode  216 . 
     Note that it is preferable that all the common electrodes are electrically connected to each other with an electrically conductive adhesive and then to the ground. Furthermore, where the electrically conductive adhesive is used for bonding the piezo-electric members to the actuator, the adhesive can be utilized as a common electrodes. 
     In this embodiment, although the driver  209  is bonded to the second plate  202  by the adhesive, alternatively be fixed on the second plate  202  by any other known means instead. 
     The driver  209  is preferably constructed by first holding an original plate of actuators  208  between two piezo-electric original plates, for example, PZT piezo-electric plates of the first and second piezo-electric members  214  and  215  and then cutting the integrated plates using, for example, a dicing saw such that each of the actuators  208  and piezo-electric members  214  and  215  has a column-like configuration of a rectangular cross-section. The common and individual electrodes  216  and  217 , preferably having a thickness of 0.1-10 μm, are pre-formed on the original piezo-electric plates by an electroless plating or sputtering. Advantageously, Au/Ni is preferably used for the electroless plating while Au/Ni or Au/Cr is used for sputtering. To prevent humidity in the air from penetrating into the piezo-electric members which decreasing deformation thereof when being biased, the piezo-electric members  214  and  215  are advantageously covered with polyimide by a spin-coat method and then cured by heating for about an hour at 180° C. This process can be eliminated if the piezo-electric member is made of material that has a great resistance to humidity. 
     Openings existing between the cut-outs  207  in the back plate  206  and the actuators  208  are sealed by sealing member  218 , e.g., fluoro-silicon rubber, to prevent ink in the ink chambers  203  from leaking therethrough. The sealing material is selected among elastic materials such that actuator  208  is capable of deforming freely at its portion in the ink chamber. 
     An ejection of ink from each ink jet head will be discussed in detail below. Ink is supplied from the ink supply  117  (See FIG. 7) to the ink tube  212 , which in turn feeds the ink to each ink chamber  203  through ink inlet  210 . When a positive pulse voltage, as shown in FIG. 27A, is applied between the first and second piezo-electric members  214  and  215  by the voltage biasing means, i.e., controller  116 , an electric field directed from the individual electrode  217  to the common electrode  216  is formed, which causes the piezo-electric members  214  and  215  to deform and vibrate. 
     Note that the first piezo-electric member  214  is polarized in the direction from the common electrode  216  to the individual electrode  217  while the second piezo-electric member  215  is polarized in the direction from the individual electrode  217  to the common electrode  216 . Accordingly, the piezo-electric members  214  and  215  deform in different directions. Especially, the first piezo-electric member  214 , if it is not restricted to deform, expands in the longitudinal direction and contracts in the transverse direction. This member  214 , however, is bonded at its sides to the base plate  202  and actuator  208 , respectively, so that it deforms at the its both ends to expand as best shown in FIG. 26 by dotted lines. On the other hand, the second piezo-electric member  215 , if it is not restricted to deform, contracts in the longitudinal direction and expands in the transverse direction. This member  215 , however, is bonded at its one side to the actuator  208 , which causes the member  215  to deform into a trapezoidal configuration shown in FIG. 26 by dotted lines. 
     The deformations of the first and second piezo-electric members  214  and  215  provide one surface of the actuator  208  confronting the first piezo-electric member  214  with a force which expands it and the other surface of the actuator  208  confronting the second piezo-electric member  215  with a force which contracts it. As a result, the free end portion of the actuator  208 , extending in the ink chamber  203 , is pivoted as shown in FIG. 26 by dotted lines in response to the pulse. As described above, since the sealing member  218  is made of elastic material, no restriction is provided with the actuator  208 . The movement of the actuator  208  pressurizes the ink in the ink chamber  203 , which causes an ink droplet to eject through the nozzle  205 . The ink droplet is then deposited on the sheet moving past under the head. 
     Upon turning off the biasing voltage to the individual electrode  217 , the electric field is eliminated. This permits the piezo-electric member  214  and  215  to return the original configuration. Upon returning to the original position, a negative pressure, i.e., suction, is generated in the ink chamber  203 , which causes the ink to be supplied into the ink chamber  203  through the manifold  211  and ink inlet  210  in preparation for the next ink ejection. 
     Note that a pulse form as shown in FIG. 27B is preferably used rather than that shown in FIG.  27 A. The reasoning behind that is, if the biasing voltage is decreased instantly, the piezo-electric member returns to its original position very quickly. This introduces a negative pressure in the ink which sucks air into the ink chamber through the nozzle. Further, once air is aspirated, due to bubbles of the air, little or no ink can be ejected from the nozzle because the pressure in the ink generated by the deformation of piezo-electric member is absorbed by the air. 
     Therefore, to prevent this, it is desirable to use a pulse form as shown in FIG. 27B, in which the voltage drops gradually to zero as fast as possible to the extent that no air is aspirated into the ink. 
     A volume or diameter of the ink droplet to be ejected can be changed by increasing or decreasing the width of the pulse which effects the resultant displacement of the actuator  208 . This permits half-tone images to be reproduced. For example, using a pulse having a smaller width as shown in FIG. 27C rather than that shown in FIG. 27A causes the diameter of the ink droplet to be decreased. 
     Another pulse form shown in FIG. 27D is advantageously used. This pulse form has a main pulse and a following small pulse of different polarity from the main pulse. Using this pulse form, an ink column following the ink droplet ejected by the main pulse is drawn back into the ink chamber  203  through the nozzle  205  by the small pulse, which decreases so-called satellite noise. 
     Another pulse form shown in FIG. 27E may also be used. This pulse form includes a small pulse and a following main pulse, both having the same polarity. Using this pulse form, the voltage of the main pulse may be reduced, which reduces a load of the driver IC. Therefore, this is economical to the device. 
     Ejection of ink is carried out for each ink chamber  203  at the same time in response to the image signals, thereby one line of image is reproduced. This is done repeatedly in synchronism with the movement of the sheet, thereby a whole image is reproduced on the sheet. 
     As described above, among members of the driver  25  for ejecting ink, only the actuator  208  is extended into the ink chamber  203  to contact with the ink, while the first and second piezo-electric members  214  and  215  are arranged outside the ink chamber  203  so as not to contact with the ink. Therefore, each of the piezo-electric members  214  and  215  can be applied with an effective voltage. Therefore, the piezo-electric members  214  and  215  deform to vibrate depending upon the voltages to be biased, which causes the ink to be ejected effectively. 
     Although the driver  209  is securely mounted on the base plate  202  via the first piezo-electric member  214 , the vibration of one driver  209  is not transmitted to the neighboring ones. Further, even if the vibration could be transmitted to neighboring ones, it is so small that no cross-talk from chamber to chamber occurs. Therefore, no ink is ejected unexpectedly, and ink flows in the chamber without being disturbed. Consequently, ink drops having a constant diameter will be ejected, which increases the quality of the reproduced image. 
     It should be noted that since the dicing process permits the ink chamber  203  and the drivers  209  to be formed readily and in high density, the number of the ink chambers and the associated nozzles can be increased, which accelerates the printing speed of the device. 
     With the present embodiment, the driver has a bimorph structure, i.e., the actuator  208  is held between the first and second piezo-electric members  214  and  215 , so that displacement of the piezo-electric member is amplified in the actuator  208 . Accordingly, an inexpensive driver IC for lower voltages can be employed, which decreases costs of driver IC. 
     Although, in the previous embodiment, the actuator  208  is deformed to bend by pulse voltage as shown in FIGS. 27A-27E, they may alternatively be deformed by polarizing the piezo-electric members in the opposite direction and arranging individual electrode  217  between the actuators  208  and the first and second piezo-electric members while arranging the common electrodes  216  on the opposite side of the first and second piezo-electric members, and applying biasing pulse voltages as shown in FIGS. 27F or  27 G. 
     Several modifications of the second embodiment will be described below. Note that only specific structure in the modifications and effects derived therefrom will be discussed below. 
     Referring to FIGS. 28A-28B, although the piezo-electric members  214  and  215  have the same length, the first member  214  may be shorter or longer than the other member  215 . This provides the actuator  208  with a larger displacement, which permits the driver to activate at lower voltage and further decreases the cost of the driver IC. 
     Although the second embodiment employs the first and second piezo-electric members  214  and  215 , the second piezo-electric member  215  can be eliminated as shown in FIG.  29 A. This modification also works as the second embodiment. In this modified embodiment, as shown in FIG. 29B, it is not necessary to bond the overall region that the piezo-electric member  214  contacts the actuator  208 , which causes the piezo-electric member  214  to deform to bend in its un-bonded region and further permits the actuator  208  to displace. 
     The piezo-electric member  214  or  215  may be multi-layered as shown in FIGS. 30A-30B This multi-layered piezo-electric member, which is made by superimposing individual electrode, piezo-electric member, and common electrode in order, may be used. According to this modified embodiment, larger displacement of the actuator  208  can be obtained as the number of the layers increase, which means that a lower biasing voltage is required which allows the driver IC cost to be reduced. Further, the ink droplets can be stably ejected. 
     Although, in the second embodiment, drivers  209  are separated from the other, as shown in FIG. 31, they may be integrated at the rear ends thereof with suitable connecters  219  into a fork-like configuration. The connecter  219  is formed together with piezo-electric members as an unit by cutting a large piezo-electric plate. In this cutting, the connecter is formed by moving the dicing saw up and down along a contour of the connecter  219  to define a shallow slot thereon. The individual electrodes  217  on the rear portion of the piezo-electric members  214  and  215  adjacent the connecters  219  are eliminated therefrom, which prevents the piezo-electric members  214  and  215  from deforming and vibrations of the piezo-electric members from being transmitted to the neighboring ones. 
     This fork-like configuration increases a structural strength of the driver, which increases the durability and responsibility of the device and handling in the forming and assembling. Further, this increases precision of the assembly, causing the detect rate to be reduced and decreases the cost of production. Due to the existence of the connecter  219 , common electrodes can be arranged between the actuator  209  and the first and second piezo-electric members  214  and  215 , which permits each of the common electrodes for the piezo-electric members  214  and  215  to be grounded by single electrical connection. 
     C. THIRD EMBODIMENT 
     Referring to the drawings, a third embodiment of the ink jet head will be described. As shown in FIGS. 32 and 33, the ink jet head  300  has a first plate  301  made from non-piezo-electric plate of, for example, aluminum. The plate  301  has its one surface a plurality of mutually spaced slots  302  extending longitudinal direction thereof. Bonded on the lower surface of the first plate  301  is a compliant partition wall  303  made of, for example, epoxy-resin to cover slots  302  so that a plurality of ink chambers  304  are formed. As best shown in FIGS.  34 A and  34 B, a pair of spacers  305  are secured by bonding at both sides of the lower surface of the first plate  301  via partition wall  303 . Referring back to FIGS. 32 and 33, a second plate  306  is secured by bonding under spacers  305 . As shown in FIG. 32, the second plate  306  has a recess  307  extending parallel along the slots  302 . the recess  307  has a width that covers all slots  302 . Note that spacers  305  and the second plate  306  are made of non-piezo-electric material like the first plate  301 . The second plate  306  has at its rear end, i.e., right hand side in FIG. 33, a support  308  for a plurality of piezo-electric members. This support  308  may be made of the same material as that of the second plate  306  or different materials. 
     Mounted on support  308  are a plurality of elongated piezo-electric members  310 , made of, for example, preferably PZT piezo-electric ceramic. The number of piezo-electric member corresponds to that of slots  302  and each piezo-electric member  310  is so arranged as to face each associated slot  302 . The piezo-electric member  310  has an individual electrode  311  on its one surface with leaving a small gap from the partition wall  303  and a common electrode  312  on the other surface. The piezo-electric member  310  is polarized in a direction indicated by an arrow B which corresponds to a direction of an electric field generated by biasing a voltage between the individual and common electrodes  311  and  312 . 
     Referring to FIG. 33, as previously discussed, piezo-electric member  310  is bonded to support  308  at its rear side of the head, i.e., right hand side thereof, and is extended freely therefrom toward the opposite side of the head while leaving a gap, corresponding to the thickness of the support  308 , from the second plate  306 . This is because, in the present embodiment, piezo-electric member  310  is so designed that, upon biasing a voltage between electrodes  311  and  312  to form an electronic field in piezo-electric member  310 , it first bends towards the second plate  308 , and then upon turning off the voltage to eliminate the electronic field, it returns toward its original position and further moves past the original position due to its inertia force to hit and move partition wall  303  into the ink chamber  304 , which pressurizes the ink in ink chamber  304 . Therefore, the gap between partition wall  303  and the piezo-electric member  310  should be smaller than the displacement towards the partition wall  303  of the piezo-electric member  310 . 
     Although the gap between the piezo-electric member and the second plate  306  is formed by using the support  308 , this gap may be provided by forming a wide recess or a plurality of recesses confronting piezo-electric members  310 , respectively. Further, the support  308  may be formed by adhesive for bonding the piezo-electric member  310  to the second plate  306 . 
     An integrated unit of the upper and lower plates  301  and  306  has at its front end a nozzle plate  313  made of, for example, polyimide film of approximately 25-200 μm in thickness. This nozzle plate  313  has a plurality of nozzles  314  positioned in a line, each axis of the nozzles  314  being spaced the same distance as that of ink chambers from each other. Suitably the distance is, for example, about 42.3-254 μm if a pixel density is from 600-100 dpi. 
     The first plate  301  has at its rear portion an opening  315 , extending in the transverse direction, which crosses ink chambers  304 . Both sides of this opening are closed by side plates  316  as best shown in FIG.  38 . Further, rear end openings of the ink chamber are closed by back plate  317 . Furthermore, the first plate  301  has thereon a manifold  318  which communicates with opening  315  to feed ink into ink chambers  304 . 
     As shown in FIG. 33, the piezo-electric member  310  is extended out beyond back plate  317 . Like the first embodiment, each individual electrode  311 , at its rear end, is connected through a wire bonding to a conductive member, the drive IC, a conductive member, and a connector to controller, while the common electrodes  312  are connected to each other through conductive adhesive which bonds piezo-electric member  310  to the second plate  306 . This conductive adhesive is further connected to the controller through the wire bonding and connecter. 
     Referring to FIGS. 34 through 38, a process for manufacturing ink jet head  30  of the present embodiment will be described hereinafter. As shown in FIGS. 34A and 34B, a plate made from non-piezo-electric material is prepared for the second plate  306 . On the second plate  306 , a pair of spacers  305  are mounted on both sides thereof and the support  308  is arranged between spacers  305 . The spacers  305  and support  308  are bonded to the second plate  306 . Also, an electrically conductive adhesive is applied on the support  308 . 
     Then, as shown in FIGS. 35A-35C, a rectangular plate  320  is arranged between the spacers  305  and bonded on the support  308 . This plate  320  is made from PZT having electrode layers of about 10-0.1 μm in thickness, on both upper and lower sides thereof. This electrode layer may be Au/Ni produced by electroless plating or Au/Ni or Au/Cr deposited by sputtering. 
     After that, PZT plate is cut at equal intervals using a dicing saw  321  so that a plurality of mutually spaced piezo-electric members  310  and slots therebetween are formed. Next, an entire surface of the piezo-electric member  310  is coated with a specific resin such as polyimide and then is heated at 180° C. for about an hour to form a protection layer. This protection layer prevents moisture in the atmosphere from penetrating into the piezo-electric member so that the piezo-electric member keeps its original deformation rate even though it is exposed to moisture. Note that this process can be eliminated if the piezo-electric member is made of another piezo-electric material having greater resistance to the humidity invasion. 
     The first plate  301 , on the other hand, is manufactured as follows. This plate  301  is manufactured from a rectangular plate of non-piezo-electric material, for example, aluminum, or ceramic. As shown in FIGS. 36A-36C, the rectangular plate  322  is cut by dicing saws so that a plurality of parallel slots  302  are formed on its one side at the same interval as that of piezo-electric members  310  on the second plate  306 . Each slot  302  has a width greater than that of piezo-electric member  310  so that the piezo-electric member  310  can be inserted therein. Formed in the opposite side of the plate  322  is another slot or opening  315  which runs in the transverse direction so that this opening communicates with the slots  302 . 
     As shown in FIGS. 37A-37C, these plates  301  and  306  thus manufactured are assembled and bonded to each other with each piezo-electric member  310  being positioned in the associated slot  302 . Further the nozzle plate  313  is bonded to the front end of the integrated plates with each of nozzles  314  being positioned at the center of the associated ink chamber  304 . 
     Further, as best shown in FIGS. 38A and 38B, the manifold  318  is attached on the first plate  301  to cover the opening  315 , and then the side plates  316  are mounted on both sides of the first plate  301  to enclose the opening  315 . The back plate  317  is bonded to the rear end of the integrated plates to enclose ink chambers  304 . 
     Furthermore, like first embodiment of the invention, as shown in FIG. 39, head  300  thus constructed is mounted on the base plate and each element is connected to the associated element on the base plate. Further, the elements of the head are preferably over molded by the suitable resin. 
     A discussion will be made next to ink ejection. Ink is supplied from the ink supply through the manifold  318  and filled in the ink chambers  304 . Upon applying a pulse voltage (see FIG. 40A) between the individual electrode  311  and common electrode  312  according to an image signal, an electric field is generated in the direction parallel to the polarization direction indicated by the arrow B, from the common electrode  312  to individual electrode  311 . As a result, as shown in FIG. 41, the piezo-electric member  310  bends towards the second plate  306  from an original position shown by dotted lines. Next, upon turning off the voltage, the piezo-electric member  310  returns toward the original position due to its elasticity, and after moving past the original position, the piezo-electric member  310  keeps moving to hit and force the partition wall  303 , which results in a reduction of the volume of the ink chamber  304  as shown in FIG.  42 . As a result, an ink droplet is ejected through nozzle  314  from the ink chamber  304  and then is deposited on a recording sheet not shown. 
     After that, the piezo-electric member  310  moves to the original position while the partition wall  310  returns to its original position shown in FIG. 32, which reduces pressure in the ink chamber  304  so that the ink is supplied through the manifold  318  to the ink chamber  304  in order to prepare for a next ink ejection. 
     Because no means are provided to restrict the free end portion of the piezo-electric member  310 , after moving back to its original position, it continues to move from upward to downward and vice versa, repeatedly. Also, at the very moment the bias voltage is applied to the electrodes, the piezo-electric member should be in its original position. Otherwise, the piezo-electric member fails to start deformation in a predetermined direction at the same time that the voltage is applied thereto, which results in a variation of diameters of ink droplets, a delay of ink ejection, or a reduction of image quality. Further, to wait until the piezo-electric member comes to a standstill will decreases the speed of printing. Therefore, according to this embodiment, it is desirable to apply a supplemental pulse voltage having opposite polarity as shown FIGS. 40B or  40 C, which causes the piezo-electric member to come to a stop in its original position in a short time. 
     According to the present embodiment, after bending the free end portion of the piezo-electric member  310  towards the second plate  306 , by turning off the voltage which has been applied to the electrodes, the piezo-electric member is released to hit the partition wall  303  due to its elasticity so that the ink chamber  304  is pressurized to eject ink therefrom. Further, the present embodiment receives less resistance and thus needs less voltage than to bias the piezo-electric member towards the partition wall. Furthermore, normally the piezo-electric member having a greater rigidity will provide the partition wall with a greater force, which generates a powerful energy for ejecting the ink. Consequently, according to the embodiment, the ink is efficiently ejected with a low voltage to be applied to the electrodes. Moreover, because the piezo-electric member  310  is positioned outside the ink chamber  304 , it keeps its electrical resistance, which ensures the stability and reliability of the ink jet head. 
     FIG. 43 shows a modification of the present embodiment, in which a second plate  330  has a plurality of mutually spaced slots  331  extending in a longitudinal direction thereof, each slot  331  confronting the ink chamber  304  via partition wall  303 . In this modification, the support  308  may be in the form of a fork, and the gap between the piezo-electric member  310  and the second plate  306  may be formed by providing steps in the respective slots  331 . 
     According to this modification, because the slot  331  serves as a guide for the piezo-electric member  310  housed therein, even when the piezo-electric member  310  includes a permanent deformation therein, the piezo-electric member will be correctly guided toward the partition wall  303 . Also, the partition wall  303  is held by the first and second plates  301  and  330  at an equal interval; therefore, no vibration of the partition wall  303  is transmitted to the neighboring ink chambers  304 . Further, a mechanical strength of partition wall is increased, which increases the durability of ink jet head. 
     Although, in the third embodiment, a small gap is provided between the partition wall  303  and the piezo-electric member  310 , the piezo-electric member  310  may be bonded directly to the partition wall  303  without leaving any gap therebetween. This allows the partition wall  303  to follow the movement of the piezo-electric member  310  even when pulse voltages of high frequency are applied to the piezo-electric member  310 , which improves an ability to response against high frequency image signals and a print speed. 
     If the piezo-electric member  310  is bonded to the partition wall  303 , moving the piezo-electric member  310  opposite to the ink chamber increases the volume of ink chamber  304 , which reduces the pressure in the ink chamber  304  to draw ink into the chamber. However, a very rapid increase of the volume of the ink chamber can suck air through nozzle into the ink chamber. Further, once air is aspirated, due to bubbles in the ink, little or no ink can be ejected from nozzle  314  because pressure in the ink generated by the deformation of piezo-electric member  310  is absorbed by the air. 
     Therefore, to prevent air from being aspirated into the ink chamber, it is desirable to determine the pulse form where the voltage drops gradually to zero as fast as possible to the extent that no air is aspirated into the ink, as shown in FIG.  40 C. Advantageously, a supplemental pulse having a different polarity with respect to that of a main pulse is applied after the main pulse. 
     The piezo-electric members may be integrated into a unit as shown in FIG.  44 . This unit  340 , in the form of fork, has a base  343  from which each piezo-electric member extended parallel to each other. Also, the base  343  is preferably designed to be lower than piezo-electric members  342 . This unit is manufactured by a dicing saw. In dicing, the dicing saw moves from one end of the original plate to form each piezo-electric member and, once it reaches a base region, the dicing moves up while keeping its lower end within the plate, and then continues to the other end of the original plate so that grooves on the base  343  are formed. 
     According to this embodiment, each piezo-electric member has a greater structural strength, which increases both durability and reliability of the ink jet head. Also, since the common electrodes can be extended over the base portion, the connection between the common electrode and the conductive line on the base plate may be readily done by wire-bonding or solder. Therefore, it is not necessary to connect each common electrode to the conductive line, which facilitates assembly of the head. 
     The piezo-electric member may include a plurality of piezo-electric layers and electrode layers. With this piezo-electric member, the displacement at the distal end of the piezo-electric member will be increased depending upon the number of the layers, which decreases power consumption and the cost of the driver IC. 
     D. FOURTH EMBODIMENT 
     Referring to the drawings, a fourth embodiment of the ink jet head will be described next. FIGS. 45 and 46 illustrate the ink jet head  400 . This ink jet head  400  includes a first plate  401  made of non-piezo-electric material such as aluminum. This plate  401  has therein a plurality of parallel slots  402  formed by a dicing operation. Each slot is spaced a predetermined distance from neighboring ones and extends in a longitudinal direction of the plate  401 . Arranged and bonded over the slots  402  is a partition wall  403 , made of resin such as aramid, thereby enclosing the slots  402  to define corresponding ink chambers  404 . 
     Mounted on the other side of the partition wall  403  is a second plate  405  which is made from a non-piezo-electric plate like first plate  401 . The second plate  405  has an its portion confronting the partition wall  403  a plurality of mutually spaced longitudial slots  406 , in the same interval as the slots  402  in the first plate  401 . These slots are preferably made by a dicing operation. The second plate  405  is secured to the first plate  402  so that the slots  406  confront the slots  402 , respectively on opposite sides of the partition wall  403 . A variety of means may be employed for securing plates  401  and  405  together, including such items as adhesive, screws, or resin molding. 
     Arranged in and along each slot  406  in the second plate  405  is an elongated piezo-electric member  407 . This piezo-electric member  407 , which has a rectangular cross-section, is made by cutting a plate of, for example, PZT piezo-electric ceramic by using a dicing saw. Preferably the piezo-electric member  407  has a height which is greater than that of the depth of the slot  406 , such that once the upper and lower plates  401  and  405  are integrated, the piezo-electric member  407  is held firmly between the bottom of the slot  406  and the partition wall  403  while in contact with the partition wall  403 . It is not necessary, however, to make the piezo-electric member higher than the slot, member  407  may be as high as the slot  406 . The piezo-electric member  407  is preferably bonded to the partition wall  403 , which causes the partition wall  403  to follow the vibration of the piezo-electric member  407 . This ensures a higher response to high frequency signals. A portion of the piezo-electric member  407  at least in the ink chamber  404 , however, is not bonded to the bottom of the slot  406 . 
     Preferably the piezo-electric member  407  is spaced 50 μm or less from either side of the walls of the slot  406 , more advantageously 20 μm or less. This prevents the ink in the chamber  404  from moving into slits defined between the piezo-electric member  407  and the walls when the piezo-electric member  407  deforms to pressurize the ink, which causes a pressure loss. 
     As shown in FIGS. 45 and 46, an individual electrode  408  is arranged between piezo-electric member  407  and partition wall  403  only in a region T where ink chamber  404  faces to the member  407 . Further, a common electrode  409  is arranged on the opposite entire surface of piezo-electric member  407 . These electrodes  408  and  409  are preferably films of Au/Ni made by an electroless plating or of Au/Ni or Au/Cr deposited by sputtering. The electrodes preferably have a thickness of 0.1-10 μm. Further, the piezo-electric member  407  is polarized in a direction from the individual electrode  408  to the common electrode  409  as shown in FIG. 45 by arrow P. The overall surface of piezo-electric member  407  is preferably protected by first applying polyimide resin by a spin-coat method, and second heating it over 180° C. for about an hour to cure polyimide prevents the piezo-electric member from absorbing moisture from the air, which results in a reduction of the deformation of the piezo-electric member when it is biased. This coating may be eliminated if the piezo-electric member is made of a material having great resistance to humidity invasion. 
     Attached to the front end, i.e., right hand side in FIG. 45, of an integrated unit is a nozzle plate  410  made of polyimide film having a thickness of, for example, about 25-200 μm. This nozzle plate  410  has a plurality of nozzles  411  formed at equal spacing intervals by, for example, an excimer laser. This spacing interval is about 42.3-254 μm corresponding to pixel density of 600-100 dpi. 
     The first plate  401  has a back plate  412  at its rear end. Further, the first plate  401  has a front plate  413  confronting the back plate  412 . Provided between back and front plates  412  and  413  is a channel  414  for supplying ink into the ink chamber  404 . This channel  414  communicates with ink chamber  404  through an ink inlet  415 . 
     Referring to FIG. 45, the piezo-electric member  407  is bonded to the bottom of the slot  406  only over a region S outside the ink chamber  404 . However, the piezo-electric member  407  is not bonded to the second plate  405  in a free end region T where ink chamber  404  confronts thereto. 
     The piezo-electric member  407  is extends out beyond the back plate  412 . Each individual electrode  408  is electrically connected to an electrically conductive adhesive which extends along the member and under back plate  412 . This adhesive is further connected through a driver IC and the controller  116  (see FIG. 8) to which the image signals are input. Therefore, voltages in response to image signals are applied through the controller  116  to piezo-electric member  407 . The common electrode  409 , on the other hand, is connected to the ground through a electrically conductive adhesive. 
     Ejection of ink droplets from the ink jet head  404  will be described below. The ink is supplied from the ink supply through the ink supply channel  414  and then ink inlet  415  to ink chamber  404 . When a positive pulse voltage is applied to the individual electrode  408  on the piezo-electric member  407  from the power supply means or controller  116 , an electric field is developed from the individual electrode  408  to the common electrode  409 , as illustrated by arrow E, which is parallel to the polarization direction as indicated by arrow P. As a result, the portion of piezo-electric member in the un-bonded free region T deforms as shown by dotted lines. Repetition of the pulses causes the piezo-electric member to vibrate. Further, when the piezo-electric member moves toward partition wall  403 , it forces the partition into the ink chamber  404 . This reduces the volume in the ink chamber  404 , which pressurizes the ink causing it to eject through nozzle  411  toward a sheet moving past under the nozzle  411 . 
     Upon turning off the voltage, the piezo-electric member  407  returns to its original position, while the partition wall  403  follows the piezo-electric member  407  maintaining contact therewith due to its elasticity. Consequently, the ink chamber  404  recovers to its original volume, thereby causing ink to be supplied through the ink inlet  415  to ink chamber  404  preparation for the next ink ejection. 
     Each nozzle  411  ejects ink droplets independently in response to image signals to produce an image line image. This could be repeated for each nozzle  411 , an image corresponding to the image signal is reproduced on the recording sheet. 
     According to the ink jet head  400  of this embodiment, as described because the portions of the piezo-electric member in the free region T as not bonded to the second plate  405 , but simply retained between the bottom of the slot  406  and partition wall  403 , no vibration of the piezo-electric member is transmitted to the neighboring piezo-electric members via plate  405 , which minimizes cross-talk from chamber to chamber. Also, no ink is ejected unintentionally, or no disturbance in the ink could occur, and thereby the ink is ejected stably. Consequently, no variation in size of ink dots occurs, which increases the quality of the printed images. 
     Further, the partition wall  403  keeps the piezo-electric member  407  from being in contact with the ink. Therefore, no ink is absorbed in the piezo-electric member, which keeps its original electronic resistance. Consequently, an ejection efficiency of the ink is improved so that a stability and reliability of ink jet head  400  is increased. 
     Although, in the previous embodiment, to prevent the piezo-electric member from deforming in the fixed regions, no common electrode is provided in that region, this can also be achieved by eliminating the polarization in that region or by bonding the piezo-electric member in the region using an adhesive which keeps its elasticity even after hardening to absorb the deformation of the member. 
     The piezo-electric member may have a single-layer or multi-layer structure as shown in FIG.  47 . It is well known that the multi-layered piezo-electric member  420  can be manufactured by a green-sheet method, in which the individual and common electrode layers can be arranged therein. This multi-layered piezo-electric member provides a greater deformation as the number of the layers increases and therefore the same amount of deformation can be obtained with less voltage than the single-layered piezo-electric member, which results in a cost reduction of the driver. 
     Although in this embodiment, each piezo-electric member is separated from others, the piezo-electric members may be manufactured as a single unit as shown in FIGS. 48A-48B. FIGS. 48A-48B show the piezo-electric unit  421  in the form of a fork, in which a number of parallel, mutually-spaced piezo-electric members are connected at one ends to a connecting portion  422 . The unit  421  is made from a single plate of piezo-electric material produced by a dicing process. In this dicing process, a cutter (not shown) is moved from one end to form a groove  423  toward the other end, and after moving past the connecting portion  422 , the cutter moves downward to separate each piezo-electric member  424  from others and then continues to the other end. This unit is placed on the lower plate with each piezo-electric member being positioned in a respective slot while the connecting portion occupies the fixing region. 
     E. APPLICATIONS OF ELECTRO-MECHANICAL TRANSDUCER 
     The electro-mechanical transducer of the present invention may be used not only for the ink jet recording apparatus as described above, but also for a piezo-electric vibrator to be used in another piezo-electric ink jet recording apparatus. Referring to the drawings, several embodiments of the piezo-type ink jet recording device will be described below. It should be noted that, in each embodiment described below, assume that arrangement of individual and common electrodes and polarizing direction of piezo-electric members are the same as the first embodiment shown in FIG. 5, except directions of the voltages to be applied to the electrodes. 
     FIG. 49 shows a Zoltan-type ink jet head  501 , in which the transducer is used as a piezo-electric vibrator. The ink jet head  501  includes a cylindrical nozzle  502  preferably made of glass. This nozzle  502  has defined an orifice  503  at its front portion. Also, the nozzle  502  is connected at its rear portion to a tube  504  for supplying ink into the nozzle. Mounted on and along an outer surface of the nozzle  502  is a piezo-electric vibrator  505  which is in the form of a column, having a rectangular in cross-section. This vibrator  505  is bonded on the nozzle at its rear end portion, which permits the other front end of the vibrator  505  to deform. 
     In operation, ink is supplied through tube  504  into the nozzle  502 . Upon applying a voltage to the piezo-electric vibrator  505  in response to an image signal, the piezo-electric vibrator  505  contracts and bends in its front portion to force the nozzle  505 , which causes the ink in the nozzle  505  to ejected from the orifice  502 . This ejected ink is then deposited on a recording medium (not shown). 
     FIG. 50 shows a Kyser-type ink jet head  511 , in which the transducer is used as a piezo-electric vibrator. The ink jet head  511  has a nozzle  512  in which an ink chamber  513  is defined. The ink chamber  513  has an opening  514 , an ink inlet  515 , and an ink outlet  516 . Further, the opening  514  is closed with a cover  517  preferably made of metal. Arranged outside and on the cover  517  is a piezo-electric vibrator  518  which is firmly supported by the ink chamber  512  at its one end. With this ink jet head  511 , ink is supplied through the ink inlet  515  into the ink chamber  513 . When a voltage is applied to the piezo-electric vibrator  518 , according to an image signal, the piezo-electric member  518  deforms and bends to force the metal cover  517 , which reduces the volume of the ink chamber  513  to eject the ink from the ink outlet  516 . This ejected ink is then deposited on the sheet (not shown). 
     FIG. 51 shows a stemme-type ink jet head  521 , in which the transducer is used as a piezo-electric vibrator. The ink jet head  521  has therein a pressure chamber  522  and an ink supply chamber  523 . These chambers  522  and  523  are connected to each other through a passage  524 . The pressure chamber  522  is closed by a cover  525 , while the ink supply chamber  523  has an ink inlet  526  and an ink outlet  527 . Further, arranged outside and on the cover  525  is a piezo-electric member  528  which is bonded -to the cover  525  at its one end portion. 
     In operation, ink is supplied through the ink inlet  526  into the ink chamber  523 . When a signal of an image is applied to the piezo-electric vibrator  528 , the piezo-electric vibrator  528  bends and presses the cover  525 , which pressurizes the ink in the pressure chamber  522 . This pressure is transmitted through the passage  524  to the ink supply chamber  523 , which causes the ink to move through the nozzle  527  to be ejected therefrom and then to be deposited on a sheet (not shown). 
     The following descriptions are embodiments of other recording apparatus other than inkjet printers in which the electro-mechanical transducers are employed therein. It should be noted that, in each embodiment described below, assume that the arrangement of individual and common electrodes and polarizing direction of piezo-electric members are the same as the first embodiment shown in FIG.  5 . 
     FIG. 52 illustrates a beam scanner  531  used in a surveying instrument. The scanner  531  includes a base plate  532  and a piezo-electric member  533 . This member  533  is secured at one end portion thereof and has an electrode-mirror  534  at the other end thereof. This electrode-mirror  534  is made on the surface of one electrode by polishing the surface by a diamond polisher and then depositing aluminum by sputtering. The beam scanner  531  further includes a laser device  535  which emits a laser beam therefrom toward the electrode-mirror  534  and an object, e.g., a cylindrical photoreceptor  536  to which the reflected laser beam from the electrode-mirror  534  is illuminated thereon. 
     With this beam scanner  531 , if a voltage is applied to the piezo-electric member  533 , the piezo-electric member  533  bends. As a result, the laser beam emitted from the laser device  535  which is polarized, is reflected from the electrode-mirror  534  and is scanned on the photoreceptor  536  to form an image such as electrostatic latent image. 
     FIG. 53 illustrates a display device  551  which is mounted on a head mount for virtual-reality. The device  551  includes three light sources  552   a ,  552   b , and  552   c , a first reflection mirror  553   a , a second mirror  553   b , a lens assembly  554 , and a galvanomirror or resonance mirror  555 . The light sources emit strip-like lights of red (R), green (G), and blue (B), respectively. The first mirror  553   a  reflects the R light from the light source  552   a  and permits the G light to move past, so that the R light and the G light are combined in the same plane. The second mirror  553   b  reflects the B light from the light source  552   c  and permits the combined R-G light to move past therethrough so that the B light and the combined R-G light are further combined in the same plane. The lens assembly concentrates the combined RGB light. The resonance mirror  555  reflects the concentrated RGB light toward an operator. 
     Arranged between the first mirror  553   a  and the light source  552   a , between the first mirror  553   a  and the light source  552   b , and between the second mirror  553   b  and the light source  552   c  are shutters  556   a ,  556   b , and  556   c . As shown in FIG. 54, each shutter  556   a ,  556   b , or  556   c  includes a number of piezo-electric members  558 . These members  558  may be arranged independently side by side or be integrated into a fork-like unit. Each electrode  558  is extended to an associated light passage and is inclined with respect to the light passage, such that, once a voltage is applied thereto, it deforms to block the associated light passage as shown by dotted lines. 
     The display device  551  analyzes the strip-like horizontal image light into a plurality of line image lights, i.e., pixels, the number of which corresponding to that of members  558 . Further, each of the piezo-electric members is biased so as to generate a specific color image corresponding to the pixel. Especially, if the pixel is to be reproduced in red color, the piezo-electric member  558  of the associated R shutter is not biased while the piezo-electric members  558  of the associated G and B shutters are biased. As a result, the R light from the light source  552   a  advances without being shut by the shutter  556   a  while the G and B lights from respective light sources  556   b  and  556   c  are shut. Therefore, only the R light is reflected by the second mirror  553   a , moves past the lens assembly  554 , again reflected by the galvanomirror  555 , and finally concentrated in front of the eyes of the operator. Further, other pixels are concentrated in front of the operator&#39;s eyes, which forms a line color image to be reproduced. Like this, different color line images are reproduced one by one. These line images are reproduced in different positions in space based upon a rotation of the galvanomirror  555 , thereby a plane image is reproduced on the eyes of the operator. 
     FIG. 55 shows an electrophotographic printer  561 . This printer  561  includes the electro-mechanical transducer as an image writing head  563  which illuminates a line image extending in a longitudinal direction to a photoreceptor  562  and which forms an electrostatic latent image thereon. The head  563  has a plurality of piezo-electric members  565 .  565  which are preferably integrated into a fork-like unit as described in the previous embodiment. Each free end portion thereof, i.e., electrode-mirror  564 , is directed toward the photoreceptor  562 . Illuminated on the electro-mirrors  564  is a strip-like light from a halogen light source (not shown) which is directed through a bundle of optical fibers  566 . The illuminated light from the optical fibers  566  is reflected by the electrode-mirror  564 . Then, if no voltage is applied to the piezo-electric member  565 , the reflected. light moves past a slit  567  and then illuminates the photoreceptor  562  at an exposing station. If a voltage is applied to the member  565 , the member  565  bends so that the reflected light is blocked by the slit  567  as shown by dotted lines. 
     With respect to a rotational direction of the photoreceptor, arranged on the upstream side from the exposing station are an eraser  568  and a charger  569  while arranged on the downstream side from the exposing station are a developer  570 , a transfer roller  571 , and a cleaner  572 . Further, a fixing roller  573  is arranged in the downstream region of the transfer roller  571  with respect to a traveling direction of the sheet. 
     With this printer  561 , during the rotation of the photoreceptor  562 , the eraser  568  eliminates residual electrical charge on the photoreceptor  562 . Then the charger  569  provides electrical charge on the photoreceptor  562 . Each piezo-electric member  565  is biased according to image signals, thereby an electrostatic latent image corresponding to the image signals is reproduced on the photoreceptor  562 . The electrostatic latent image is then developed into a toner image, which is transferred onto a recording sheet. The toner images on the sheet is fixed by the fixing roller  573 . The sheet is then fed out from the printer. The residual toner on the photoreceptor  562  is removed therefrom by the cleaner  572 . 
     FIG. 56 shows a photographic color printer  581 . The printer  581  includes a light writing head  582  which illuminates a strip-like writing light onto a printing paper to form an electrostatic latent image thereon, which is similar to the head  563  of the printer  561  shown in FIG.  55 . This head  582  has a light source in which a RGB filter (not shown) that is changeable by a controller  584  is mounted. 
     With this printer  581 , first the R filter is set by the controller  584  and the printing paper is transported by transfer rollers  585  in the direction shown by an arrow. Then, upon biasing a specific voltage to each piezo-electric member  586 , a R-image is reproduced on the paper. Next, the printing paper on which the image is reproduced is transported in the arrow direction, and then is developed, fixed, and finally dried. 
     F. MATERIALS 
     Next described are materials and the like that may be applied to the ink-jet heads of the above-described embodiments. 
     Materials for Piezo-electric Member 
     The following piezo-electric materials are applicable for the piezo-electric members: 
     (1) Piezo-electric Crystals 
     Crystals such as quarts (SiO 2 ), Rochelle salt (RS: NaKC 4 H 4 O 6 .4H 2 O), ethylenediamine tartrate (EDT: C 6 H 14 N 2 O 6 ), potassium tartrate (DKT: K 2 C 4 H 4 O 6 .1/2H 2 O), dibasic ammonium phosphate (ADP: NH 4 H 2 PO 4 ), perovskite type crystals (e.g., CaTiO 3 , BaTiO 3 , PLZT), tungsten bronze type crystals (e.g., Na x WO 3  (0.1&lt;X&lt;0.28)), sodium barium niobate (Ba 2 NaNb 5 O 15 ), lead potassium niobate (Pb 2 KNb 5 O 15 ), lithium niobate (LiNbO 3 ), lithium tantarate (LiTaO 3 ), and sodium chlorate (NaClO 3 ), tourmaline, zincblende. (ZnS), lithium sulfate (LiSO 4 .H 2 O), lithium methagallate (LiGaO 2 ), lithium iodate (LiIO 3 ), glycine sulfate (TGS), bismuth germanate (Bi 12 GeO 20 ), lithium germanate (LiGeO 3 ), barium germanium titanate (Ba 2 Ge 2 TiO 3 ) and the like. 
     (2) Piezo-electric Semiconductors 
     Wurtzite, BeO, ZnO, CdS, CdSe, AlN 
     (3) Piezo-electric Ceramics 
     Barium titanate (BaTiO 3 ), lead titanate zirconate (PbTiO 3 .PbZrO 3 ) , lead titanate (PbTiO 3 ), barium lead niobate ((Ba—Pb)Nb 2 O 6 ). 
     (4) Molded bodies of the dispersed powder of (1) piezo-electric crystals, (2) piezo-electric semiconductors or (3) piezo-electric ceramics in plastics may be used. 
     (5) Piezo-electric Polymers 
     Polyvinylidene fluoride PVDF (—CH 2 —CF 2 —) n , polyvinylidene fluoride/PZT, rubber/PZT, copolymers of trifluoroethylene and fluorinated vinylidene, copolymers of vinylidene cyanide and vinyl acetate, polyvinylidene tetrachloride and the like. 
     The piezo-electric materials listed above may be used through the process of polarizing them and then forming them into a piezo-electric member, or the process of forming them into a piezo-electric member and then polarizing. The piezo-electric members may be also laminated, as required, so that they can be driven at low voltage. 
     Overcoat Treatment of Piezo-electric Member 
     Overcoat treatment of the piezo-electric members can be performed by any of the following methods (1) to (5): 
     (1) Application of Plastics 
     Thermoplastic resins such as saturated polyester resin, polyamide resin, polyimide resin, acrylic resin, aramid resin, ethylene-vinyl acetate resin, ion cross-linked olefin copolymer (ionomer), styrene-butadiene block copolymer, polyacetal, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrol resin and the like. 
     Thermosetting resins such as epoxy resin, phenoxy resin, urethane resin, nylons, silicone resin, fluorinated silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin and the like. 
     Photoconductive resins such as polyvinyl carbazole, polyvinyl pyrene, polyvinyl anthracene, polyvinylol and the like. 
     These resins may be used singly or in combinations. 
     Other materials such as engineering plastics like liquid crystal polymers or mixtures of plastics with powder or whiskers may be conveniently used while photosensitive resins or photoresist resins for making thick films are also applicable. Bakelite, fluorinated resins or glass-epoxy resins (epoxy resin mixed with glass fillers) may also be used. Any application methods of liquids, such as coating, dipping or spraying, known in the art can be used for these materials. 
     Of these materials, polyimide resin, aramid resin, epoxy resin, phenoxy resin, fluorinated silicone resin, fluorinated resin and glass-epoxy resin show especially good effects. 
     (2) Deposition of Metal Oxide, Nitride or Sulfide Compounds 
     Metal oxide compounds (SiO 2 , SiO, CrO, Al 2 O 3  and the like), metal nitride compounds (Si 3 N 4 , AlN and the like), metal sulfide compounds (ZnS and the like) or alloys of them are used for coating by vacuum deposition or sputtering. 
     The plastics of (1) described above or Parylene resins may be applied by deposition. 
     Among the materials above, Al 2 O 3 , Si 3 N 4  or Parylene resins have excellent effects. 
     (3) Application of Hydrocarbon Compounds 
     Hydrocarbon compounds containing group IV elements represented by hydrocarbons, oxygen-containing hydrocarbons or sulfur-containing hydrocarbons, nitrogen-containing hydrocarbons, silicon-containing hydrocarbons, halogen-containing hydrocarbons represented by fluorine-containing hydrocarbons or hydrocarbons containing group III elements are applied by P-CVD (plasma CVD) for overcoat treatment. A mixed gas of these materials may be also used for application by P-CVD. 
     Fluorine-containing hydrocarbons have a good effect among the materials described above. 
     In forming coating films of the materials above, an appropriate undercoat by a-Si (amorphous silicon), a-SiC, a-SiN or the like must be applied depending on the compatibility for adhesion to the piezo-electric member. 
     (4) Instead of applying the plastics of (1) directly on the plate surface of the piezo-electric member in coating liquid state, the portion for forming a piezo-electric member is immersed in vacuum to replace the portion with the plastics, thereby forming a plastic-coated piezo-electric member. 
     (5) The surface of the plate of the piezo-electric member is subjected to surface treatment with an ink-repelling solvent. 
     When the properties of the overcoat films prepared by the methods described in (1) to (5) are compared with one another, the following characteristics are observed (wherein the films of (3) have an undercoat layer). 
     1 Strength: 
     Strong (2), (3)&gt;(1), (4)&gt;(5) Weak 
     2 Smoothness: 
     Good (1), (4)&gt;(2), (3), (5) No good 
     3 Adhesion (including vibration-resistance) 
     Strong (1), (4)&gt;(2), (3)&gt;(5) Weak 
     4 Durability (including ink-resistance) 
     Good (1), (4)&gt;(2), (3)&gt;(5) No good 
     The films of (5) are convenient to handle, lending themselves to post-treatment for (1) to (4). The films of (1) and (4) are particularly low cost. 
     The methods (1) to (5) described above may be used in appropriate combinations according to the piezo-electric member or the type of the ink. 
     Materials for Top Plate, Base Plate and Operating Member 
     Examples of the materials that can be used for the top-plate, base-plate and operating member are listed in (1) to (4) below. 
     (1) Ceramics 
     A 1   2 O 3 , SiC, C, BaTiO 3 , BiO 3 .3SnO 2 , Pb(Zr x , Ti 1−x )O 3 , ZnO, SiO 2 , (1&#39;X)Pb(Zr x , Ti 1−x )O 3 +(X)La 2 O 3 , Zn 1−x Mn x Fe 2 O 3 , γ-Fe 2 O 3 , Sr.6Fe 2 O 3 , La 1−x Ca x CrO 3 , SnO 2 , transition metal oxides, ZnO—Bi 2 O 3 , semiconductor BaTiO 3 , β-Al 2 O 3 , stabilized zirconia, LaB 6 , B 4 C, diamond, TiN, TiC, Si 3 N 4 , Y 2 O 2 S:Eu, PLZT, ThO 2 , —CaO.nSiO 2 , Ca 5 (F, Cl)P 3 O 12 , TiO 2 , K 2 O.nAl 2 O 3 . (2) Glasses 
     Element glass=Si, Se, Te, As 
     Hydrogen bonded glass=HPO 3 , H 3 PO 4 , SiO 2 , B 2 O 2 , P 2 O 5 , GeO 2 , As 2 O 3    
     Oxide glass=Sbo 3 , Bi 2 O 3 , P 2 O 3 , V 2 O 5 , Sb 2 O 5 , As 2 O 3 , So 3 , Zro 2    
     Fluoride glass=BeF 2 , Chloride glass=ZnCl 2    
     Sulfide glass=GeS 2 , As 2 S 3    
     Carbonate glass=K 2 CO 3 , MgCO 3    
     Nitrate glass=NaNO 3 , KNO 3 , AgNO 3    
     Sulfate glass=Na 2 S 2 O 3 .H 2 O, Tl 2 SO 4 , alum 
     Silicate glass=SiO 2    
     Silicate alkaline glass=Na 2 O—CaO—SiO 2    
     Potassium lime glass=K 2 O—CaO—SiO 2    
     Sodium lime glass=Na 2 O—CaO—SiO 2    
     Lead glass 
     Barium glass 
     Borosilicate glass 
     (3) Plastics 
     Thermoplastic resins such as saturated polyester resin, polyamide resin, polyimide resin, aramid resin, acrylic resin, ethylene-vinyl acetate resin, ion crosslinked olefin copolymer (ionomer), styrene-butadiene block copolymer, polyacetal, polyphenylene sulfide, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrol resin and the like. 
     Thermosetting resins such as epoxy resin, phenoxy resin, urethane resin, nylon resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin and the like. 
     Photoconductive resins such as polyvinyl carbazol, polyvinyl pyrene, polyvinyl anthracene, polyvinyrol and the like. 
     The materials listed in (1) to (3) above may be used singly or in combinations. 
     Other materials such as engineering plastics like liquid crystal polymers or mixtures of plastics with powder, whiskers, or glass fillers may also be used. 
     Photosensitive resins or photo-resist resins for making thick films may also be used while Bakelite, fluorinated resins or glass-epoxy resins (epoxy resins mixed with glass fillers) are also applicable. 
     (4) The Others 
     Rubbers and synthetic rubbers may also be used, while all kinds of metals are also applicable provided the side face adjacent to the ink chamber is coated with an insulating film. 
     The materials listed in (1) to (4) are machined or molded into the top-plate  20  after processing them into plate form, or they may be first formed into the top-plate  20  by pattern etching or photosetting. 
     Materials for Adhesives 
     The following materials (1) to (4) can be used for adhesives to assemble the ink-jet head. Electric conductance of the materials are, of course, required when the adhesive layer is used as a conductor for grounding the common electrodes. 
     (1) Thermosetting resin adhesives of epoxy resin, phenol resin, phenoxy resin, acrylic resin, furan resin, polyurethane resin, polyimide resin, silicone resin and the like. 
     (2) Thermoplastic resin adhesives of polyvinyl acetate, polyvinyl chloride, polyvinyl acetal, polyvinyl alcohol, polyvinyl butyrl and the like. 
     (3) UV setting resin adhesives 
     (4) Anaerobic setting adhesives 
     Materials for Partition Wall 
     Examples of the materials for the partition wall are as follows. 
     (1) Thermosetting resins such as epoxy resin, phenoxy resin, urethane resin, nylons, silicone resin, fluorinated silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin and the like. Of these, epoxy resin, phenoxy resin and fluorinated silicone resin are preferable for use. 
     (2) Thermoplastic resins such as saturated polyester resin, polyamide resin, acrylic resin, aramid resin, ethylene-vinyl acetate resin, ion cross-linked olefin copolymer (ionomer), styrene-butadiene block copolymer, polyacetal, polyphenylene sulfide, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, styrol resin and the like. 
     Of the materials above, aramid resin, polyimide resin, polyamide resin and ethylene-vinyl acetate resin are suitable for use. 
     (3) Liquid crystal polymers 
     (4) Photosensitive resin, photoresist resins for making thick films 
     (5) Rubber, synthetic rubber 
     (6) Thin plates of nickel, stainless steel, titanium, tungsten and the like. 
     The materials listed in (1) to (5) above may be used singly or in combinations. 
     Comparisons of the properties of the materials listed in (1) to (6) revealed that materials (1) to (3) are comparable with one another, while exhibiting the features as follows: 
     Superior (1) to (3)&gt;(4)&gt;(6)&gt;(5) Inferior 
     A thickness of the material of 100 μm or less, desirably 50 μm or less is preferable. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included in the scope of the following claims.