Patent Publication Number: US-2010128076-A1

Title: Droplet jet head and droplet jet apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional patent application of U.S. Ser. No. 11/354,619 filed Feb. 15, 2006, claiming priority to Japanese Patent Application No. 2005-043513, filed Feb. 21, 2005, all of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a droplet jet apparatus, and in particular, it relates to a compact droplet jet head having multiple high-density rows of nozzles and ejection chambers, and a droplet jet apparatus including the same. 
     2. Description of the Related Art 
     As recent electrostatic inkjet printers are increasing in the number of nozzles and rows of the inkjet head for high-speed printing and multicolor printing of high-resolution images, the number of nozzles per row and ejection chambers increase, thus increasing the length of the nozzle rows. The nozzle rows generally eject different colors of ink (e.g., red, green, blue, etc.) row by row. 
     Known droplet jet heads and droplet jet apparatuses mount device-control ICs directly on the surface of a substrate having ink channels and thermoelectric transducers, and has a flexible printed circuit (FPC) for supplying an input signal for driving the device-control ICs on the substrate (e.g., refer to Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-210969, FIGS. 1 and 2). 
     However, in the known droplet jet heads and droplet jet apparatuses (e.g., Patent Document 1), the device-control IC constitutes part of the nozzle surface, which requires a layer for protecting the surface of the device-control IC from ink, posing the problem of complicating the structure and manufacturing process. 
     Also, because the device-control IC is exposed, it is susceptible to outside air and vibrations, resulting in low durability. 
     Furthermore, the device-control IC is closer to print paper than the nozzles. This results in a long spread distance of ink droplets, so that the ink droplets cannot reach predetermined positions, making it difficult to achieve high-definition printing. 
     Since the ink channel and the FPC are disposed in opposite sides with the IC therebetween, the droplet jet head becomes large when the number of nozzle rows is increased. 
     SUMMARY 
     Accordingly, it is an advantage of some aspects of the present invention to provide a compact and high-durability droplet jet head having multiple high-density rows of nozzles and ejection chambers, and a droplet jet apparatus including the same. 
     A droplet jet head according to a first aspect of the invention includes: a nozzle substrate having a plurality of nozzle holes that eject droplets; a cavity substrate having recesses whose bottoms serve as diaphragms, and the recesses serving as ejection chambers for storing the droplets; an electrode substrate having separate electrodes opposed to the diaphragms and driving the diaphragms; a reservoir substrate having a recess serving as a common droplet chamber for supplying droplets to the ejection chambers, through holes for transferring the droplets from the common droplet chamber to the ejection chambers, and nozzle communicating holes for transferring the droplets from the ejection chambers to the nozzle holes; and a driver IC that supplies a driving signal to the separate electrodes. The cavity substrate has a first hole, and the reservoir substrate has a second hole. The first hole and the second hole communicate with each other to form a housing, and the driver IC being housed in the housing. 
     Since the cavity substrate has a first hole, the reservoir substrate has a second hole, and the first hole and the second hole communicate with each other to form a housing, in which the driver IC is housed, the droplet jet head can be made compact. This decreases the distance between print paper and the nozzle to allow high-definition printing. Furthermore, since the surface on which the nozzles are formed can be made flat, wiping (the process of removing unnecessary droplets) can be facilitated. 
     Since the droplet jet head is constructed of four layers of the nozzle substrate, the reservoir substrate, the cavity substrate, and the electrode substrate, a large capacity of the reservoir for storing droplets can be provided to allow reduction in the resistance of a droplet channel. 
     In the droplet jet head, it is preferable that the first hole pass through the cavity substrate; the second hole pass through the reservoir substrate; and the housing is closed by the nozzle substrate, the cavity substrate, the reservoir substrate, and the electrode substrate. 
     Since the first hole passes through the cavity substrate, and the second hole passes through the reservoir substrate, the housing can have large capacity, allowing a relatively large driver IC to be housed therein. 
     Since the housing is closed by the nozzle substrate, the cavity substrate, the reservoir substrate, and the electrode substrate, there is no need to provide a separate layer for protecting the driver IC from droplets, and from outside air. 
     A droplet jet head according to a second aspect of the invention includes: a nozzle substrate having a plurality of nozzle holes that eject droplets; a cavity substrate having recesses whose bottoms serve as diaphragms, the recesses serving as ejection chambers for storing the droplets; an electrode substrate having separate electrodes opposed to the diaphragms and driving the diaphragms; a reservoir substrate having a recess serving as a common droplet chamber for supplying droplets to the ejection chambers, through holes for transferring the droplets from the common droplet chamber to the ejection chambers, and nozzle communicating holes for transferring the droplets from the ejection chambers to the nozzle holes; and a driver IC that supplies a driving signal to the separate electrodes. The cavity substrate has a hole; and the driver IC is housed in the hole. 
     Since the cavity substrate has a hole, in which the driver IC is housed, the droplet jet head can be made compact. This decreases the distance between print paper and the nozzle to allow high-definition printing. Furthermore, since the surface on which the nozzles are formed can be made flat, wiping (the process of removing unnecessary droplets) can be facilitated. 
     Since the droplet jet head is constructed of four layers of the nozzle substrate, the reservoir substrate, the cavity substrate, and the electrode substrate, a large capacity of the reservoir for storing droplets can be provided to allow reduction in the resistance of a droplet channel. 
     In the droplet jet head, it is preferable that the hole pass through the cavity substrate, and the hole be closed by the cavity substrate, the reservoir substrate, and the electrode substrate. 
     Since the hole is closed by the cavity substrate, the reservoir substrate, and the electrode substrate, there is no need to provide a separate layer for protecting the driver IC from droplets, and from outside air. 
     A droplet jet head according to a third aspect of the invention includes: a nozzle substrate having a plurality of nozzle holes that eject droplets; a cavity substrate having recesses whose bottoms serve as diaphragms, the recesses serving as ejection chambers for storing the droplets; an electrode substrate having separate electrodes opposed to the diaphragms and driving the diaphragms; and a driver IC that supplies a driving signal to the separate electrodes. The cavity substrate has a hole; and the driver IC is housed in the hole. 
     Since the cavity substrate has a hole, in which the driver IC is housed, the droplet jet head can be made compact. This decreases the distance between print paper and the nozzle to allow high-definition printing. Furthermore, since the surface on which the nozzles are formed can be made flat, wiping (the process of removing unnecessary droplets) can be facilitated. 
     In the droplet jet head, it is preferable that the hole pass through the cavity substrate, and the hole be closed by the nozzle substrate, the cavity substrate, and the electrode substrate. 
     Since the hole is closed by the nozzle substrate, the cavity substrate, and the electrode substrate, there is no need to provide a separate layer for protecting the driver IC from droplets, and from outside air. 
     In the droplet jet head, it is preferable that the driver IC be placed on the electrode substrate, and connects to the separate electrodes. 
     If the driver IC is disposed on the electrode substrate, and is connected directly to the separate electrodes, wiring of the separate electrodes (wiring for connection) becomes unnecessary. Thus the droplet jet head can be made compact and the number of separate electrodes of the electrode rows, to be described later, can be increased. 
     In the droplet jet head, it is preferable that the electrode substrate have a plurality of rectangular separate electrodes having long sides and short sides, the separate electrodes be arranged in such a manner that the long sides are parallel to each other to form a plurality of electrode rows extending along the short side of the separate electrodes, and the driver IC connect to two of the electrode rows. 
     Since the separate electrodes are disposed in parallel to form multiple electrode rows, and the driver IC connects to two electrode rows, a driving signal can be supplied from the driver IC to the two electrode rows, facilitating multiple number of electrode rows. Since the number of the drive ICs can be decreased, cost reduction can be achieved, and the droplet jet head can be made compact. 
     A droplet jet apparatus according to a third aspect of the invention includes one of the above-described droplet jet heads. 
     Since one of the droplet jet heads is mounted, a high-durability droplet jet apparatus capable of high-definition printing can be provided. 
     It is preferable that the droplet jet apparatus further include a flexile printed circuit (FPC) for supplying an external input signal to the driver IC, the driver IC connect to the FPC, and the FPC be connected to the driver IC in such a manner that a direction of a length of the FPC is parallel to a direction of the short sides of the separate electrodes that form the electrode rows. 
     Since the FPC connects to the driver IC in parallel to the short side of the separate electrode rows, the droplet jet head having multiple electrode rows and the FPC can be connected compactly. 
     In the droplet jet apparatus, it is preferable that the cavity substrate have a common electrode for applying voltage to the diaphragms, and the common electrode connect to the flexile printed circuit. 
     Since the FPC is connected also to the common electrode, a driving signal can be supplied to both of the separate electrodes and the diaphragms using one FPC. 
     It is preferable that the droplet jet apparatus further include a common-electrode IC for supplying a driving signal to the common electrode, and the common-electrode IC be disposed in other than the flexile printed circuit and the droplet jet head. 
     Since the common-electrode IC is disposed in other than the FPC and the droplet jet head, the driver IC can be made compact, so that the droplet jet head can also be made compact. 
     In the droplet jet apparatus, it is preferable that the driver IC supply a driving signal to the common electrode. 
     Since the driver IC supplies a driving signal to the separate electrodes and the common electrode, the droplet jet head can serve multiple functions. 
     In the droplet jet apparatus, it is preferable that the FPC have a driving-signal supply wire for supplying a driving signal from the driver IC to the common electrode. 
     Since the FPC has a driving-signal supply wire for supplying a driving signal from the driver IC to the common electrode, there is no need to have wiring in the droplet jet head, facilitating supply of a driving signal to the common electrode. 
     In the droplet jet apparatus, it is preferable that the FPC have a common-electrode IC for supplying a driving signal to the common electrode. 
     Since the FPC has a common-electrode IC for supplying a driving signal to the common electrode, the driver IC can be made compact, so that the droplet jet head can also be made compact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a droplet jet head according to a first embodiment of the invention; 
         FIG. 2  is a longitudinal sectional view of the droplet jet head of  FIG. 1  in an assembled state; 
         FIG. 3  is a schematic block diagram of the control system of a droplet jet apparatus having the droplet jet head shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic block diagram showing an example of the internal structure of a driver IC and a COM generating circuit; 
         FIG. 5  is an exploded perspective view of a droplet jet head according to a second embodiment of the invention; 
         FIG. 6A  is an exploded perspective view of a droplet jet head according to a third embodiment of the invention; 
         FIG. 6B  is a perspective view of the droplet jet head according to the third embodiment; 
         FIG. 7  is a perspective view of a droplet jet head according to a fourth embodiment of the invention; 
         FIG. 8  is a longitudinal sectional view of a droplet jet head according to a fifth embodiment in an assembled state; 
         FIG. 9  is a longitudinal sectional view of a droplet jet head according to a sixth embodiment in an assembled state; and 
         FIG. 10  is a perspective view showing an example of a droplet jet apparatus having the droplet jet head according to one of the first to sixth embodiments. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       FIG. 1  is an exploded perspective view of a droplet jet head according to a first embodiment of the invention, including part of a flexible printer circuit (FPC) for supplying a driving signal.  FIG. 2  is a longitudinal sectional view of the droplet jet head of  FIG. 1  in an assembled state, taken along line A-A of  FIG. 1 . 
     The droplet jet head shown in  FIGS. 1 and 2  is of a face ejection type that ejects droplets from nozzle holes provided on the surface of the nozzle substrate, and employs an electrostatic system. The structure and operation of the droplet jet head according to the first embodiment will now be described with reference to  FIGS. 1 and 2 . 
     As shown in  FIG. 1 , the droplet jet head  1  according to the first embodiment has not a three-layer structure, unlike general electrostatic droplet jet heads, but is constructed of four substrates of an electrode substrate  2 , a cavity substrate  3 , a reservoir substrate  4 , and a nozzle substrate  5 . One surface of the reservoir substrate  4  connects to the nozzle substrate  5 ; the other surface connects to the cavity substrate  3 . The surface of the cavity substrate  3  opposite to the surface that connects to the reservoir substrate  4  connects to the electrode substrate  2 . In other words, the substrates are joined in the order of the electrode substrate  2 , the cavity substrate  3 , the reservoir substrate  4 , and the nozzle substrate  5 . 
     The droplet jet head  1  according to the first embodiment has a driver IC  20  for supplying a driving signal to separate electrodes  7 , to be described later. The driver IC  20  will be described later. 
     The electrode substrate  2  is made of glass such as borosilicate glass. Although the electrode substrate  2  is made of borosilicate glass in the first embodiment, the electrode substrate  2  may be made of monocrystal silicon. 
     The electrode substrate  2  has a recess  6  with a depth of 0.3 μm. Inside the recess  6 , the separate electrodes  7  are formed so as to face a diaphragm  11 , to be described later, at fixed intervals by the sputtering of, e.g., indium tin oxide (ITO) to a thickness of 0.1 μm. In the above example, the space between the separate electrode  7  and the diaphragm  11  becomes 0.2 μm after the electrode substrate  2  and the reservoir substrate  4  have been joined together. One end of the separate electrodes  7  connect to the driver IC  20 , from which a driving signal is supplied. Part of the recess  6  is shaped in a somewhat large pattern similar to the shape of the separate electrode  7  so as to mount it; the other part (the central part in  FIG. 1 ) is shaped in a pattern so that the driver IC  20  can be mounted on the electrode substrate  2 , on which the driver IC  20  is mounted. 
     In the first embodiment, after the electrode substrate  2  and the cavity substrate  3  have been joined together, a sealer  17  is applied to the space between the separate electrode  7  and the diaphragm  11  to prevent foreign matter (refer to  FIG. 2 ). 
     The electrode substrate  2  has droplet supply ports  10   a . The droplet supply ports  10   a  pass through the electrode substrate  2 . 
     In the droplet jet head  1  according to the first embodiment, each of the separate electrodes  7  is shaped like a rectangle having long sides and short sides. The separate electrodes  7  are arranged in such a manner that the long sides are parallel to each other to form two rows of electrodes along the short side of the separate electrode  7 . For example, when the short side of the separate electrode  7  tilts relative to the long side to form a long parallelogram, an electrode row extending in the direction perpendicular to the long side may be formed. 
     In the droplet jet head  1  according to the first embodiment, the driver IC  20  is disposed between two electrode rows, and connects to both of the electrode rows. This allows the driver IC  20  to supply a driving signal to the two electrode rows, facilitating multiple electrode rows. Since the number of driver ICs  20  can be decrease, cost can be reduced and the droplet jet head  1  can be made compact. 
     Although the droplet jet head  1  shown in  FIG. 1  has two driver ICs  20 , it may have one IC or three or more ICs. 
     The cavity substrate  3  is made of, e.g., monocrystal silicon, and has multiple recesses  12   a  whose bottom walls are the diaphragms  11  and serving as ejection chambers  12 . The recesses  12   a  are arranged in two rows in correspondence with the separate electrodes  7  (electrode rows). The cavity substrate  3  has a first hole  21  between the electrode rows, the first hole  21  passing through the cavity substrate  3 , and common electrodes  22  for applying voltage to the diaphragm  11 . The common electrodes  22  connect to a FPC  30 . 
     In the first embodiment, the cavity substrate  3  is made of monocrystal silicon, all over which is formed a 0.1-μm insulating film (not shown) made of tetraethyl orthosilicate (TEOS) by plasma chemical vapor deposition (CVD). This is to prevent dielectric breakdown and short circuit when the diaphragm  11  is driven and to prevent the cavity substrate  3  from being etched by droplets of ink etc. 
     The cavity substrate  3  also has droplet supply ports  10   b  that pass through the cavity substrate  3 . 
     The diaphragm  11  of the droplet jet head  1  may be made of a high-concentration boron-doped layer. When dopant is boron, the rate of etching of monocrystal silicon using alkaline solution such as potassium hydroxide is extremely low in high concentrations of about 5×10 19  atoms/cm 3  or more. Accordingly, when the diaphragm  11  is made of a high-concentration boron-doped layer, and the recesses  12   a  serving as the ejection chamber  12  is formed by anisotropic etching using alkaline solution, the boron-doped layer is exposed to decrease the etching rate significantly, which is called an etching stop technique, the diaphragm  11  can be formed in a desired thickness. 
     The reservoir substrate  4  is made of, e.g., monocrystal silicon, and has two recesses  13   a  serving as common droplet chambers  13  for supplying droplets to the ejection chamber  12 . In the bottom of the recesses  13   a , through holes  14  for transferring droplets from the common droplet chamber  13  to the ejection chamber  12  are provided. 
     The bottom of each recess  13   a  has a droplet supply port  10   c  that passes therethrough. The droplet supply ports  10   c  of the reservoir substrate  4 , the droplet supply ports  10   b  of the cavity substrate  3 , and the droplet supply ports  10   a  of the electrode substrate  2  connect to each other with the reservoir substrate  4 , the cavity substrate  3 , and the electrode substrate  2  joined together, to form droplet supply ports  10  for supplying droplets from the exterior to the common droplet chamber  13  (refer to  FIG. 2 ). 
     Furthermore, between the common droplet chambers  13  of the reservoir substrate  4  is provided a second hole that passes through the reservoir substrate  4 . 
     As shown in  FIG. 2 , the first hole  21  of the cavity substrate  3  and the second hole  23  of the reservoir substrate communicate to form a housing  24 . The housing  24  accommodates the driver IC  20 . 
     The part of the reservoir substrate  4  other than the recesses  13   a  has nozzle communicating holes  15  that communicate with the ejection chambers  12 , for transferring droplets from the ejection chambers  12  into nozzle holes  16  (to be described later). The nozzle communicating holes  15  pass through the reservoir substrate  4  to the end opposite to the end with which the through hole  14  of the ejection chamber  12  communicate (refer to  FIG. 2 ). 
     The nozzle substrate  5  is formed of a silicon substrate of, e.g., 100 μm in thickness, and has a plurality of nozzle holes  16  communicating with the respective nozzle communicating holes  15 . In the first embodiment, the nozzle holes  16  are disposed in two steps to improve the linearity at the time of ejection of droplets (refer to  FIG. 2 ). 
     For the connection of the electrode substrate  2 , the cavity substrate  3 , the reservoir substrate  4 , and the nozzle substrate  5 , the silicon substrate and the borosilicate glass substrate can be connected by anode coupling; the silicon substrates can be connected by direct coupling, or with an adhesive. 
     As shown in  FIG. 2 , in the droplet jet head  1  according to the first embodiment, the driver IC  20  is housed in the housing  24 , and the housing  24  is closed by the nozzle substrate  5 , the cavity substrate  3 , the reservoir substrate  4 , and the electrode substrate  2 . Specifically speaking, the housing  24  is closed in such a manner that the nozzle substrate  5  forms the upper surface of the housing  24 ; the electrode substrate  2  forms the lower surface of the housing  24 ; and the cavity substrate  3  and the reservoir substrate  4  form the sides of the housing  24 . It is preferable that the housing  24  be closed for protect the driver IC  20  from droplets or outside air. 
     The operation of the droplet jet head shown in  FIGS. 1 and 2  will now be described. To the common droplet chamber  13 , droplets such as ink are supplied from the exterior through the droplet supply ports  10 . To the ejection chamber  12 , droplets are supplied from the common droplet chamber  13  through the through holes  14 . To the driver IC  20 , a driving signal (pulse voltage) is supplied from the controller (not shown) of the droplet jet apparatus via an IC wire  31  of the FPC  30  and a lead  25  (refer to  FIG. 1 ) disposed on the electrode substrate  2 . A pulse voltage ranging from 0 V to about 40 V is applied from the driver IC  20  to the separate electrodes  7  to charge the separate electrodes  7  positively. A driving signal (pulse voltage) is supplied to the diaphragm from the controller (not shown) of the droplet jet apparatus via a common-electrode wire  32  (refer to  FIG. 1 ) to charge it negatively. At that time, the diaphragm  11  is distorted toward the separate electrode  7  under the suction by an electrostatic force. When the pulse voltage is then turned off, the electrostatic force applied to the diaphragm  11  is lost to recover the diaphragm  11 . At that time, the pressure in the ejection chamber  12  increases abruptly to force the droplets in the ejection chamber  12  to be ejected from the nozzle holes  16  through the nozzle communicating holes  15 . Then droplets are supplied from the common droplet chamber  13  into the ejection chamber  12  through the through holes  14  to return the droplet jet head to the initial state. 
     The supply of droplets to the common droplet chamber  13  of the droplet jet head  1  is made, e.g., through a droplet supply tube (not shown) connected to the droplet supply port  10 . 
     In the first embodiment, the FPC  30  connects to the driver IC  20  in such a manner that a direction of the length of the FPC  30  is parallel to a direction of the short sides of the separate electrodes  7  that forms an electrode row. For example, when the short side of the separate electrode  7  tilts relative to the long side to form a long parallelogram, the FPC  30  may be connected in the direction perpendicular to the long side of the separate electrode  7 . This allows compact connection of the droplet jet head  1  having multiple electrode rows and the FPC  30 . 
       FIG. 3  is a schematic block diagram of the control system of a droplet jet apparatus having the droplet jet head shown in  FIGS. 1 and 2 . Assume that the droplet jet apparatus is a general inkjet printer. Although the control system of the droplet jet apparatus having the droplet jet head  1  will be described with reference to  FIG. 3 , the control system of the droplet jet apparatus having the droplet jet head  1  is not limited to the system shown in  FIG. 3 . 
     The droplet jet apparatus having the droplet jet head  1  shown in  FIGS. 1 and 2  includes a droplet-jet-head drive control unit  41  for controlling the drive of the droplet jet head  1 . The droplet-jet-head drive control unit  41  includes a controller  42  constituted primarily of a CPU  42   a . The CPU  42   a  is provided with print information from an external device  43  such as a personal computer via a bus  43   a , and connects to a ROM  44   a , a RAM  44   b , and a character generator  44   c  via an internal bus  42   b.    
     The controller  42  executes a control program stored in the ROM  44   a  using the memory region in the RAM  44   b  as working region to generate a control signal for driving the droplet jet head  1  on the basis of character information generated by the character generator  44   c . The control signal is converted to a drive control signal corresponding to print information via a logic gate array  45  and a driving-pulse generating circuit  46 , and is supplied to the driver IC  20  in the droplet jet head  1  via a connector  47 , and also to a COM generating circuit  46   a . To the driver IC  20 , also a print-driving pulse signal V 3 , a control signal LP, a polarity-reverse control signal REV, and other signals are supplied. The COM generating circuit  46   a  is constituted of a common-electrode IC (not shown) for generating a driving pulse, for example. 
     The COM generating circuit  46   a  outputs a driving signal (driving-voltage pulse) to be applied to the common electrodes  22  of the droplet jet head  1 , that is, to the diaphragms  11 , from its common output terminal COM (not shown) in response to the above-described signals supplied. The driver IC  20  outputs a driving signal (driving-voltage pulse) to be applied to the separate electrodes  7  from separate output terminals SEG of a number corresponding to the separate electrodes  7 , according to the supplied signals and a driving voltage Vp supplied from a supply circuit  50 . The potential difference between the output of the common output terminal COM and the output of the separate output terminals SEG is applied between the diaphragms  11  and the separate electrodes  7  opposed thereto. To drive the diaphragms  11  (to eject droplets), a driving potential waveform in a designated direction is applied; not to drive the diaphragm  11 , no driving potential is applied. 
       FIG. 4  is a schematic block diagram showing an example of the internal structure of the driver IC  20  and the COM generating circuit  46   a . One set of the driver IC  20  and the COM generating circuit  46   a  shown in  FIG. 4  supply a driving signal to 64 separate electrodes  7  and diaphragms  11 . 
     The driver IC  20  is a 64-bit high-pressure-proof driver for CMOS that operates at high-voltage driver voltage Vp and logic-circuit driver voltage Vcc supplied from a supply circuit  50 . The driver IC  20  applies one of a drive-voltage pulse and a GND potential to the separate electrodes  7  in response to a drive control signal supplied. 
     The driver IC  20  has a 64-bit shift register  61 . The shift register  61  is a static shift register that shifts up serial data in a 64-bit-length DI signal sent from a logic gate array  45  using an XSCL pulse signal that is a basic clock signal that synchronizes with the DI signal, and stores it in the register in the shift register  61 . The DI signal is a control signal that indicates selection information for selecting an electrode from among 64 separate electrodes  7  by switching between on and off. The signal is sent as serial data. 
     The driver ID  20  includes a 64-bit latch circuit  62 . The latch circuit  62  is a static latch that latches the 64-bit data stored in the shift register  61  according to a control signal (latch pulse) LP to store it, and signals the stored data to a 64-bit inverter circuit  63 . The latch circuit  62  converts the DI signal of the serial data to a 64-bit parallel signal for 64-segment output for driving the diaphragms  11 . 
     The inverter circuit  63  outputs the exclusive OR of the signal input from the latch circuit  62  and an REV signal to a level shifter  64 . The level shifter  64  is a level interface circuit that converts the voltage level of the signal from the inverter circuit  63  to a logic voltage level (5-V level or 3.3-V level) to a head-driving voltage level (0- to 45-V level). 
     An SEG driver  65  serves as a 64-channel transmission gate, and outputs a driving voltage pulse or a GND potential in response to the segmented output of SEG 1  to SEG  64  by the level shifter  64 . A COM driver  66  in the COM generating circuit  46   a  outputs a driving voltage pulse or a GND potential to the COM in response to the input of an REV signal. 
     The XSCL-, DI-, LP-, and REV-signals are at a logic voltage level, and are sent from the logic gate array  45  to the driver IC  20 . 
     With the structure of the driver IC  20  and the COM generating circuit  46   a , the driving voltage pulse for driving the diaphragms  11  of the droplet jet head  1  and the GND can easily be switched even when the number of segments (the number of the diaphragms  11 ) to be driven increases. 
     In the first embodiment, the cavity substrate  3  has the first hole  21  and the reservoir substrate  4  has the second hole  23  to form the housing  24 , in which the driver IC  20  is housed. Accordingly, the droplet jet head  1  can be made compact. This decreases the distance between print paper and the nozzle holes  16  to allow high-definition printing. Furthermore, since the surface on which the nozzle holes  16  are formed can be made flat, wiping (the process of removing unnecessary droplets) can be facilitated. 
     Also, since the housing  24  is closed by the nozzle substrate  5 , the cavity substrate  3 , the reservoir substrate  4 , and the electrode substrate  2 , there is no need to provide a separate layer for protecting the driver IC  20  from droplets, and from outside air. 
     Since the separate electrodes  7  are arranged in parallel to form multiple electrode rows, and the driver IC  20  connects to two electrode rows, a driving signal can be applied from the driver IC  20  to the two electrode rows, so that multiple electrode rows can easily be achieved. Since the number of the driver IC  20  can be decreased, cost reduction can be achieved, and the droplet jet head can be made compact. 
     Second Embodiment 
       FIG. 5  is an exploded perspective view of a droplet jet head according to a second embodiment of the invention, including part of an FPC for supplying a driving signal. 
     In the droplet jet head  1  according to the second embodiment, the driver IC  20  serves also as the function of the COM generating circuit  46   a  in  FIG. 3 , and so supplies a driving signal to the common electrode  22  in addition to the separate electrodes  7 . The FPC  30 , which connects to the lead  25  and the common electrode  22 , has a driving-signal supply wire  33  for supplying a driving signal from the driver IC  20  toe the common electrode  22 , in place of the common-electrode wire  32 . 
     The other structure and operation are the same as those of the droplet jet head  1  according to the first embodiment shown in  FIGS. 1 and 2 , and their description will be omitted here. Components the same as those of the droplet jet head  1  according to the first embodiment are given the same reference numerals. 
     According to the second embodiment, the driver IC  20  supplies a driving signal to the separate electrodes  7  and the common electrode  22 . Accordingly, the droplet jet head  1  can serve many functions. 
     The FPC  30  has the driving-signal supply wire  33  for supplying a driving signal from the driver IC  20  to the common electrode  22 . This eliminates the necessity for wiring in the droplet jet head  1 , facilitating supplying a driving signal to the common electrode  22 . Other advantages are the same as those of the droplet jet head  1  according to the first embodiment. 
     Third Embodiment 
       FIG. 6A  is an exploded perspective view of a droplet jet head  1  according to a third embodiment of the invention; and  FIG. 6B  is a perspective view of the droplet jet head  1 . 
     The droplet jet head  1  according to the third embodiment has six rows of separate electrodes  7 , and corresponding six rows of recesses  12   a  serving as ejection chambers  12 . Two driver ICs  20  are disposed for every two electrode rows, and so provide a driving signal to the electrode rows on both sides of the driver IC  20 . 
     The other structure and operation are the same as those of the droplet jet head  1  according to the first embodiment shown in  FIGS. 1 and 2 , and their description will be omitted here. Components the same as those of the droplet jet head  1  according to the first embodiment are given the same reference numerals. 
     Since the third embodiment has six rows of electrodes, multiple colors can easily be ejected if different colors of ink are ejected from each ejection chambers  12  according to different electrode rows (the rows of the separate electrodes  7 ). Other advantages are the same as those of the droplet jet head  1  according to the first embodiment. 
     Fourth Embodiment 
       FIG. 7  is a perspective view of a droplet jet head  1  according to a fourth embodiment of the invention. In the droplet jet head  1  according to the fourth embodiment, the FPC  30  has a common electrode  34 . The common electrode  34  has the function of the COM generating circuit  46   a  in  FIG. 3 , and so supplies a driving signal to the common electrode  22 . The other structure and operation are the same as those of the droplet jet head  1  according to the third embodiment shown in  FIG. 6 , so that their description will be omitted here. Components the same as those of the droplet jet head  1  according to the third embodiment are given the same reference numerals. 
     In the fourth embodiment, since the FPC  30  has the common electrode  34  for supplying a driving signal to the common electrode  22 , the driver IC  20  can be made compact, so that the droplet jet head  1  can also be made compact. Other advantages are the same as those of the droplet jet head  1  according to the third embodiment. 
     Fifth Embodiment 
       FIG. 8  is a longitudinal sectional view of a droplet jet head  1  according to a fifth embodiment in an assembled state. In the droplet jet head  1  according to the fifth embodiment, the reservoir substrate  4  has no second hole  23 , and the cavity substrate  3  has a hole  26  corresponding to the first hole  21 . The driver IC  20  is housed in the hole  26 . The hole  26  is closed in such a manner that the reservoir substrate  4  forms the upper surface of the hole  26 ; the electrode substrate  2  forms the lower surface of the hole  26 ; and the cavity substrate  3  forms the sides of the hole  26 . 
     The other structure and operation are the same as those of the droplet jet head  1  according to the first embodiment shown in  FIGS. 1 and 2 , and their description will be omitted here. Components the same as those of the droplet jet head  1  according to the first embodiment are given the same reference numerals. 
     The advantages are substantially the same as those of the droplet jet head  1  according to the first embodiment. 
     Sixth Embodiment 
       FIG. 9  is a longitudinal sectional view of a droplet jet head  1  according to a sixth embodiment in an assembled state. 
     The droplet jet head  1  according to the sixth embodiment has a general three-layer structure, and has no reservoir substrate  4 , but is principally constructed of the electrode substrate  2 , the cavity substrate  3 , and the nozzle substrate  5 . The recesses  13   a  serving as the common droplet chamber  13  are formed in the cavity substrate  3 . The common droplet chamber  13  and the ejection chamber  12  communicate with each other through an orifice  27  formed in the nozzle substrate  5 , in place of the through holes  14 . The orifice  27  may be formed in the cavity substrate  3 . 
     The droplet jet head  1  according to the sixth embodiment has two rows of separate electrodes  7 . The cavity substrate  3  has the hole  26 , as with the droplet jet head  1  according to the fifth embodiment. The hole  26  accommodates the driver IC  20 . The electrodes may be arranged in three rows, as with the droplet jet head  1  according to the third embodiment. The hole  26  is closed in such a manner that the nozzle substrate  5  forms the upper surface of the hole  26 ; the electrode substrate  2  forms the lower surface of the hole  26 ; and the cavity substrate  3  forms the sides of the hole  26 . 
     The other structure and operation are the same as those of the droplet jet head  1  according to the first embodiment shown in  FIGS. 1 and 2 , and their description will be omitted here. Components the same as those of the droplet jet head  1  according to the first embodiment are given the same reference numerals. 
     The advantages are substantially the same as those of the droplet jet head  1  according to the first embodiment. 
     Seventh Embodiment 
       FIG. 10  is a perspective view showing an example of a droplet jet apparatus  100  incorporating the droplet jet head  1  according to one of the first to sixth embodiments. The droplet jet apparatus  100  shown in  FIG. 10  is a general inkjet printer. 
     The droplet jet head  1  according to the first to sixth embodiments are compact and has excellent durability, and whose substrates are joined together with one FPC  30 , as described above. Therefore, the droplet jet apparatus  100  is also compact and has high durability. 
     The droplet jet head  1  according to the first to sixth embodiments can also be applied to manufacture of color filters of a liquid crystal display, formation of the light emitting element of an organic EL display, ejection of biofluid, and so on through alternations of droplets, in addition to the inkjet printer shown in  FIG. 10 . 
     It is to be understood that the droplet jet head and the droplet jet apparatus of the invention is not limited to the foregoing embodiments of the invention, but may be modified within the scope and spirit of the invention. For example, the separate electrodes  7  may be arranged in one row. Although in to the first embodiment the common IC (COM generating circuit  46   a ) is disposed in the controller  42 , it may be disposed in other than the FPC  30 , the droplet jet head  1 , and the controller  42 .