Patent Publication Number: US-8118413-B2

Title: Liquid ejecting head, image forming apparatus, and method for manufacturing liquid ejecting head

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent specification claims priority from Japanese Patent Application No. 2008-192205, filed on Jul. 25, 2008 in the Japan Patent Office, which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that is equipped with a recording head for ejecting ink droplets. 
     2. Discussion of the Background 
     As an image forming apparatus, such as a printer, a facsimile machine, a plotter, or a multifunction machine including at least two of these functions, a liquid-ejecting image forming apparatus such as an inkjet recording device that uses a recording head for ejecting ink droplets is known. (It is to be noted that imaging, recording, and printing are synonymous with “image forming” in the descriptions below.) 
     There are two types of the liquid-ejecting image forming apparatus. A serial type image forming apparatus forms images using a recording head that ejects ink droplets while moving in a main scanning direction. A line type image forming apparatus forms images using a recording head that remains stationary while ejecting ink droplets. In either case, the liquid-ejecting image forming apparatus forms images by ejecting the ink droplets from the recording head onto a sheet of recording media while the sheet is being transported past the head. Therefore, transport characteristics of the image forming apparatus profoundly affect imaging performance. 
     Such a recording head, or liquid ejecting head, typically includes a compression chamber and an actuator for generating pressure to compress ink contained in the compression chamber, so that ink droplets are discharged from a nozzle connected to the compression chamber and onto the sheet. 
     As a pressure generating mechanism, the actuator itself may be of several types. There are known liquid ejecting heads that use a piezo-electric actuator composed of an appropriate piezo-electric element, a thermal actuator composed of a heating resistance member, and an electrostatic actuator that generates an electrostatic force. The actuator compresses individual liquid paths (hereinafter “compression chambers”) to eject the ink. 
     Currently, there is market demand for an image forming apparatus capable of outputting high-quality images at high speed. To accommodate such demand, at present, the size of the individual liquid droplets is reduced and/or the nozzles are packed more densely together on the recording head to provide the required high resolution. At the same time, to increase the speed of image formation, a driving frequency with which the liquid is ejected is enhanced and a long liquid ejecting head, such as a line-type head that includes more nozzles per head unit, is used. 
     To increase the number of nozzles by using a long liquid ejecting head, compression liquid members that form complicated liquid paths are often formed not of silicon, which is difficult and costly to work into long pieces, but metal plates or resins. 
     In particular, in one known approach, a vibration plate and a liquid path plate are simultaneously formed as a single multi-layered element (laminated material), in which multiple metal plates are connected with a single resin plate in advance. 
     However, connecting the individual metal layers together using adhesive requires many connection processes and high connection accuracy, which increases production costs and is susceptible to plate misalignment. Further, in general, a multi-layered configuration that requires connecting stainless steel plate with another material is not preferable because stainless steel is not easily adhered to other materials. 
     There is an additional difficulty. In the above-described approach, two metal materials that can be etched and which are located on both sides of an etching-resistant member are simultaneously etched, and thus interior partition walls of the liquid chambers (liquid paths) and convex portions (e.g. a connection portion) connecting to the piezo-electronic element are simultaneously formed. At this time, because the amounts of etching of the metal members that can be etched are adjusted by using materials having different speeds of etching, the thickness of members that can be etched needs to be calculated based on the etching rate, respectively. Therefore, getting dimensions and shapes that have sufficient quality for a liquid ejecting head is difficult. 
     Further, as described above, when the vibration plate is formed with the laminated material that includes the multiple metal plates connected with the resin plate in advance, one metal plate serves as a portion that forms the partition wall of the liquid chambers (an interior partition wall through liquid path), and the other metal plate serves as a portion that forms a connection portion connected with a driving mechanism (e.g. a piezo-electronic element). 
     Then, when one metal plate forms thick (higher) partition wall of the liquid chambers, it is preferable that the thin connection portion be formed in a shorter time than the other metal plate is even if the accuracy is relatively lower, and that, even if it takes a relatively long time, the connection portion connecting to piezo-electronic element be formed at high accuracy. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, one illustrative embodiment of the present invention provides a liquid ejecting head including multiple nozzles to eject liquid droplet, a vibration unit including a vibration plate that forms at least one wall face of multiple liquid paths that communicate with the respective nozzles, and a driving member to move the vibration plate. The vibration unit is formed of a laminated multi-layered member that includes a resin layer to form the vibration plate, a first metal layer located on a first side of the resin layer, and a second metal layer located on a second side of the resin layer opposite the first side of the resin layer. The first and second metal layers are formed of different metals, with the first metal layer having an ionization tendency higher than that of hydrogen and the second metal layer has an ionization tendency lower than that of hydrogen. 
     In view of the foregoing, one illustrative embodiment of the present invention provides an image forming apparatus that includes a transport mechanism disposed facing the recording head and to transport a sheet, and the ink ejecting described above. 
     In view of the foregoing, one illustrative embodiment of the present invention provides a manufacturing method for a liquid ejecting head including the steps of: forming the vibration unit with a laminated multi-layered member including a resin layer to form the vibration plate, a first metal layer located on a first side of the resin layer, and a second metal layer located on a second side of the resin layer opposite the first side of the resin layer; etching the first metal layer and the second metal layer using different etching liquids; and forming predetermined patterns on the respective sides of the resin layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram illustrating a configuration of an image forming apparatus according to embodiments of the present invention; 
         FIG. 2  is a plan view of the image forming apparatus shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a liquid ejecting head along a longitudinal direction of a compression chamber thereof, according to a first embodiment; 
         FIG. 4  is a cross-sectional view of the liquid ejecting head shown in  FIG. 3  along a shorter side of the compression chamber thereof; 
         FIGS. 5A through 5E  are cross section diagrams illustrating respective manufacturing processes of a vibration unit of the liquid ejecting head according to the first embodiment; 
         FIG. 6  is a cross-sectional view of a liquid ejecting head taken along a shorter side of the compression chamber, according to a second embodiment; 
         FIG. 7  is a cross-sectional view of a liquid ejecting head taken along a shorter side of the compression chamber, according to a third embodiment; 
         FIGS. 8A through 8E  are cross-sectional diagrams illustrating respective manufacturing processes of the vibration unit of the liquid ejecting head according to a fourth embodiment; 
         FIG. 9  is a cross-sectional view of a liquid ejecting head taken along a longitudinal direction of a compression chamber thereof, according to a fifth embodiment; and 
         FIG. 10  is a cross-sectional view of the liquid ejecting head shown in  FIG. 9  taken along a shorter side of the compression chamber. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve a similar result. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and particularly to  FIGS. 1 and 2 , an image forming apparatus using a liquid ejecting head according to an illustrative embodiment of the present invention is described. 
     It is to be noted that, in the present application, “image forming apparatus” means the device that ejects the ink to a recording medium, such as paper, thread, fiber, textile, metal, plastic, glass, ceramic, etc., so as to form images thereon, and “image forming” includes both forming on the recording medium an image including a pattern, etc., that has no commonly understood meaning as well as image including a letter and/or an illustration that does have a given meaning. Further, “ink” is not limited to only the materials generally called “ink” but also used as a generic term for the liquid, such as recording-liquid, fixing liquid, other liquid, etc., which can form images, such as, recording liquid, fixing processing liquid, a DNA sample, a registration, and pattern materials. 
     Moreover, “transfer sheet” includes not only paper but also any materials onto which ink can adhere, such as, an overhead projector (OHP) sheet, textile, etc., and is used as a generic term for a recording medium, recording paper, a recording sheet, etc. 
       FIG. 1  is a schematic view of an image forming apparatus  200 . The image forming apparatus  200  includes an image forming device  201 , a paper tray  202 , a feed roller  243 , a separation pad  244 , a guide  245 , a counter roller  246 , a conveyance guide  247 , a pressing member  248 , a conveyance belt  251 , a conveyance roller  252 , a tension roller  253 , a charging roller  256 , a separation nail  261 , output rollers  262  and  263 , an output tray  203 , a duplex unit  271 , and a bypass tray  272 . 
     The pressing member  248  includes a leading edge pressing roller  249 . The image forming device  201  includes a main guide rod  231 , a sub guide rod  232 , a carriage  233 , recording heads  234 , and sub tanks  235 . The paper tray  202  includes a sheet loading portion  241 . 
       FIG. 2  is a plan view of the image forming device  201 . The image forming device  201  includes a left side plate  221 A, a right side plate  221 B, ink cartridges  210 , supply tubes  236 , a maintenance-restoration mechanism  281 , and an ink collection unit  288 . 
     The recording heads  234  include recording heads  234 A and  234 B. The sub tanks  235  include sub tanks  235 A and  235 B. The ink cartridges  210  include ink cartridges  210 K,  210 C,  210 M, and  210 Y. The maintenance-restoration mechanism  281  includes caps  282 , a wiper blade  283 , and a preliminarily discharged droplet receiver  284 . The caps  282  include caps  282 A and  282 B. The ink collection unit  288  includes openings  289 . 
     The image forming apparatus  200  can be any of a copier, a printer, a facsimile machine, a plotter, and a multifunction printer including at least one of copying, printing, scanning, plotter, and facsimile functions. In this non-limiting exemplary embodiment, the image forming apparatus  200  functions as a serial-type printer for discharging liquid (e.g., ink or an ink droplet) to form an image on a recording medium (e.g., a recording sheet). 
     As illustrated in  FIG. 2 , the left side plate  221 A and the right side plate  221 B support the main guide rod  231  and the sub guide rod  232 . The main guide rod  231  and the sub guide rod  232  serve as guide members for guiding the carriage  233 . For example, the main guide rod  231  and the sub guide rod  232  support the carriage  233  in such a manner that the carriage  233  slides and moves on the main guide rod  231  and the sub guide rod  232  in a main scanning direction. A main scanning motor, not shown, moves the carriage  233  in the main scanning direction via a timing belt, not shown. 
     The recording heads  234 A and  234 B are mounted on the carriage  233  and serve as liquid ejecting heads for ejecting yellow, cyan, magenta, and black ink droplets, respectively. In each of the recording heads  234 A and  234 B, two nozzle rows, each of which is formed of a multiplicity of nozzles, extend in a sub-scanning direction perpendicular to the main scanning direction so that the multiplicity of nozzles discharges ink droplets downward. 
     Each of the recording heads  234 A and  234 B includes two nozzle rows. For example, in the recording head  234 A, one nozzle row discharges black ink droplets and another nozzle row discharges cyan ink droplets. In the recording head  234 B, one nozzle row discharges magenta ink droplets and another nozzle row discharges yellow ink droplets. According to this exemplary embodiment, the image forming apparatus  200  includes the two recording heads  234 A and  234 B for discharging ink droplets in the four colors. Alternatively, the image forming apparatus  200  may include four recording heads for discharging yellow, cyan, magenta, and black ink droplets, respectively. Yet alternatively, the image forming apparatus  200  may include a single recording head in which four nozzle rows, each of which includes a multiplicity of nozzles, discharge yellow, cyan, magenta, and black ink droplets, respectively. 
     The sub tanks  235 A and  235 B are mounted on the carriage  233  and correspond to the nozzle rows of the recording heads  234 A and  234 B to supply inks in corresponding colors to the recording heads  234 A and  234 B. The ink cartridges  210 K,  210 C,  210 M, and  210 Y contain black, cyan, magenta, and yellow inks, respectively. A supply unit, not shown, supplies the black, cyan, magenta, and yellow inks from the ink cartridges  210 K,  210 C,  210 M, and  210 Y to the sub tanks  235 A and  235 B via the supply tubes  236 , respectively. 
     As illustrated in  FIG. 1 , in the paper tray  202 , the sheet loading portion  241  (e.g., a pressure plate) loads sheets  242 . The feed roller  243 , having a half-moon-like shape, separates a sheet  242  from other sheets  242  loaded on the sheet loading portion  241  and feeds the separated sheet  242  toward the guide  245 . The separation pad  244  opposes the feed roller  243  and includes a material having an increased friction coefficient. The separation pad  244  is pressed against the feed roller  243 . The feed roller  243  and the separation pad  244  serve as a sheet supplier. 
     The guide  245  guides the sheet  242  fed by the sheet supplier toward the counter roller  246 . The counter roller  246  feeds the sheet  242  toward the conveyance guide  247 . The conveyance guide  247  guides the sheet  242  toward the pressing member  248 . The leading edge pressing roller  249  of the pressing member  248  presses the sheet  242  against the conveyance belt  251 . The conveyance belt  251  serves as a conveyer for conveying the sheet  242  at a position opposing the recording heads  234  by electrostatically attracting the sheet  242 . Thus, the sheet  242  fed by the sheet supplier is sent to a position under the recording heads  234 . 
     The conveyance belt  251 , having an endless belt-like shape, is looped over the conveyance roller  252  and the tension roller  253  to rotate in a direction of rotation R (e.g., the sub-scanning direction). The charging roller  256  serves as a charger for charging a surface of the conveyance belt  251 . The charging roller  256  contacts the surface of the conveyance belt  251  and is driven and rotated by rotation of the conveyance belt  251 . A sub-scanning motor, not shown, drives and rotates the conveyance roller  252  via a timing belt so that the conveyance roller  252  rotates the conveyance belt  251  in the direction of rotation R. 
     The separation nail  261  and the output rollers  262  and  263  serve as an output device for discharging the sheet  242  bearing an image formed by the recording heads  234 . For example, the separation nail  261  separates the sheet  242  from the conveyance belt  251 . The output rollers  262  and  263  discharge the sheet  242  onto the output tray  203  provided beneath the output roller  262 . 
     The duplex unit  271  is detachably attached to a rear portion of the image forming apparatus  200 . The duplex unit  271  receives the sheet  242  fed by the conveyance belt  251  rotating backward, reverses the sheet  242 , and feeds the sheet  242  toward a nip portion formed between the counter roller  246  and the conveyance belt  251 . A top surface of the duplex unit  271  serves as the bypass tray  272 . 
     As illustrated in  FIG. 2 , the maintenance-restoration mechanism  281  is disposed in a non-printing region provided in one end of the image forming device  201  in the main scanning direction in which the carriage  233  moves. The maintenance-restoration mechanism  281  serves as a maintenance-restoration device for maintaining and restoring a condition of the nozzles of the recording heads  234 . In the maintenance-restoration mechanism  281 , the caps  282 A and  282 B cap nozzle surfaces of the recording heads  234 A and  234 B, respectively. The wiper blade  283  wipes the nozzle surfaces of the recording heads  234 . The preliminarily discharged droplet receiver  284  receives ink droplets discharged preliminarily and thereby not used for forming an image on the sheet  242  to discharge ink droplets having an increased viscosity. 
     The ink collection unit  288  (e.g., a preliminarily discharged droplet receiver) is disposed in another non-printing region provided in another end of the image forming device  201  in the main scanning direction in which the carriage  233  moves. The ink collection unit  288  serves as a liquid collection container for receiving ink droplets discharged preliminarily and thereby not used for forming an image on the sheet  242  to discharge ink droplets having an increased viscosity during an image forming operation and the like. In the ink collection unit  288 , the openings  289  are arranged along the nozzle rows of the recording heads  234 . 
     Referring to  FIG. 1 , the following describes an image forming operation performed in the image forming apparatus  200  having the above-described structure. The feed roller  243  and the separation pad  244  feed sheets  242  loaded on the paper tray  202  one by one upward toward the guide  245 . The guide  245  guides the sheet  242  in a substantially vertical direction toward the nip portion formed between the counter roller  246  and the conveyance belt  251 . The counter roller  246  and the conveyance belt  251  nip the sheet  242  and feed the sheet  242  toward the conveyance guide  247 . The conveyance guide  247  guides a leading edge of the sheet  242  toward the leading edge pressing roller  249 . The leading edge pressing roller  249  presses the sheet  242  against the conveyance belt  251  so that the conveyance belt  251  turns a sheet conveyance direction of the sheet  242  by about 90 degrees. 
     The charging roller  256  receives an alternating voltage in which positive output and negative output are alternately repeated. Accordingly, the conveyance belt  251  has an alternating charge voltage pattern. For example, the conveyance belt  251  is charged in such a manner that a positively charged band and a negatively charged band having a predetermined length are alternately provided in the sub-scanning direction in which the conveyance belt  251  rotates. When the sheet  242  is sent onto the conveyance belt  251  charged alternately with positive and negative voltages, the conveyance belt  251  attracts the sheet  242 , and the rotating conveyance belt  251  conveys the sheet  242  in the sub-scanning direction. 
     While the carriage  233  moves, the recording heads  234  are driven according to an image signal. For example, the recording heads  234  eject ink droplets onto the sheet  242  stopped on the conveyance belt  251  to form an image of one line. After the conveyance belt  251  conveys the sheet  242  for a predetermined amount, the recording heads  234  form an image of a next one line. When the recording heads  234  receive an image formation completion signal or a signal indicating that a trailing edge of the sheet  242  reaches an image forming region, the image forming operation is finished, and the sheet  242  is output onto the output tray  203 . 
     Descriptions will be given below of various embodiments of a liquid ejecting head that can be used as the recording heads  234  in the image forming apparatus  200 , which functions as a printer. Alternatively, the liquid ejecting heads  300  though  304  may be used in an image forming apparatus which functions as a multifunction printer having at least one of copying, printing, plotter, and facsimile functions, for example. Further, the liquid ejecting heads  300  though  304  may be used in an image forming apparatus using liquid other than ink, fixing liquid, and/or the like. 
       FIG. 3  is a cross-sectional view of a liquid ejecting head  300  taken along a longitudinal direction of a compression chamber  7  thereof (orthogonal to a direction of nozzle alignment).  FIG. 4  is a cross-sectional view of the liquid ejecting head  300  taken along a shorter side of the compression chamber  7  (direction of nozzle alignment). 
     The liquid ejecting head  300  includes a base  1 , a laminated piezo-electric element member  2 , a frame  3 , a vibration unit  4 , a nozzle plate  5 , a nozzle  6  to eject ink droplets, the compression chambers  7 , a fluid resistance portion  8 , and a common liquid chamber  9 . In the laminated piezo-electric element member  2 , multiple laminated piezo-electric element rods  2 A and  2 B that serve as activation mechanisms are disposed on the base  1 . The frame  3  is disposed around the outer circumference of the base  1 . The vibration unit  4  is disposed on the piezo-electric element member  2 , and the nozzle plate  5  is disposed on the vibration unit  4 . The compression chamber  7  is a route through which the ink is carried to the nozzle, and the common liquid chamber  9  supplies the ink to the compression chamber  7  through the fluid resistance portion  8  that is located between the common liquid chamber  9  and the compression chamber  7  and is narrower than the compression chamber  7 . 
     The vibration unit  4  includes a vibration plate  10 , partition walls  11 , convex portions  12 , and thick-walled portions  13 . The vibration plate  10  is formed of an etching-resistant material that forms a bottom wall of the compression chamber  7 . 
     Each partition wall  11  of the compression chamber  7 , (a partition wall among liquid path) is a laminated structure disposed on an upper side of the vibration plate  10  and is formed of a material that can be etched. Each convex portion  12  is an island-shaped laminated structure (thick-wall portion) disposed on a lower side (outer surface) of the vibration plate  10  to connect to the piezo-electric element rod  2 A and is formed of a material that can be etched (such as metal). Each thick-walled portion  13  is formed with a material identical or similar to that forming the convex portion  12  and is connected to the frame member  3  as well as the piezo-electric element rod  2 B. 
     Each nozzle  6  is a hole formed in the nozzle plate  5 , and has a diameter within a range of from 10 μm to 30 μm and is continuous with the compression chamber  7 . 
     An ink ejecting surface of the nozzle plate  5  (nozzle surface side) is coated with a water-repellent film that is selected in accordance with the physical properties of the ink. For example, the water-repellent film is formed using PTFE (polytetrafluoroethylene)-Ni (nickel) eutectoid plating, electrocoating of fluorocarbon polymers, elaboration coating with evaporable fluorocarbon polymers (e.g., pitch fluoride), or baking after application of a solvent such as silicon resin, fluoroplastic, or the like. Thus, the shape of droplets and aerodynamics of the ink can be stabilized to provide high-quality imaging. 
     The piezo-electric element member  2  is located on the outer surface of the vibration plate  10  (opposite the compression chamber  7 ), and the position thereof corresponds to the compression chamber  7 . The piezo-electric element member  2  serves as an activation mechanism that vibrates the vibration plate  10 . The island convex portion  12  corresponding to piezo-electric element rod  2 A and a thick portion  13  corresponding to piezo-electric element rod  2 B contact the lower surface of the vibration plate  10 , which is opposite surface of the compression chamber  7 . A piezo-electric actuator that deforms the vibration plate  10  is formed with the vibration plate  10  and the piezo-electric element member  2 . 
     For example, the piezo-electric member  2  can be formed of alternating piezo-electric layers  54  and internal electrode layers  55 A and  55 B. Each piezo-electric layer  54  has a thickness ranging from about 10 μm to about 50 μm and includes lead zirconate titanate (PZT). Each of the internal electrode layers  55 A and  55 B has a thickness ranging from several micrometers and includes silver-palladium (AgPd). The internal electrodes  55 A and  55 B are electrically connected alternately to individual electrodes  57  (e.g., an end face electrode or an external electrode) and a common electrode  56 . 
     Then, the piezo-electric element member  2  is subjected to a slitting process without decoupling it, and thus the multiple piezo-electric rods  2 A and  2 B are formed. Each piezo-electric rod  2 A is used as a driving-piezo-electric element rod that applies a driving waveform, and each piezo-electric rod  2 B is used as not a driving piezo-electric element rod but a support rod corresponding to the partition wall  11 . A flexible printed circuit (FPC) cable  14  that transmits the driving waveform is connected to the external electrode  57  disposed on one edge surface of the piezo-electric rod  2 A in the piezo-electric element member  2 . 
     A displacement in either a d33 direction or a d31 direction may be used as a piezoelectric direction of the piezo-electric element member  2  to compress the ink in the compress liquid chamber  7 . According to this exemplary embodiment, the displacement in the d33 direction is used. 
     Further, it is preferred that the base  1  be formed of metal. When the base  1  is formed of metal, the piezo-electric element member  2  can be prevented from storing heat by self-heating. As the piezo-electric element member  2  is connected to the base  1  with adhesive, when the number of channels increases, the temperature of the piezo-electric element member  2  increases to close to 100° C. and the adhesive strength significantly decreases. When the temperature inside the liquid ejecting head  300  increases by self-heating, the liquid temperature increases. When the liquid temperature increases, the viscosity of the liquid decreases, substantially affecting ejecting characteristics. 
     Therefore, because the metal base  1  can prevent the piezo-electric element member  2  from storing heat from self-heating, the deterioration of the ejection characteristics caused by the decrease in the connection strength and the decrease in the liquid adhesive can be prevented. 
     On the FPC cables  14 , multiple drivers IC  15  are mounted to generate the driving waveforms (electrical signals) that drive each channel corresponding to each compression chamber  7 . 
     Further, the frame member  3  is connected to the outer circumference of the vibration unit  4  with adhesive. Then, in the frame member  3 , the common liquid chamber  9  via which the ink is supplied from the external device to the compression chamber  7  is formed so as to be arranged opposite the driver IC  15  across at least the FPC cable  14 . 
     The common liquid chamber  9  is continuous with the fluid resistance portion  8  and the compression chamber  7  via an ink supply port  17  in the vibration unit  4 . 
     In the common liquid chamber  9 , because a damper chamber  19  is formed by a diaphragm portion  18 , a pressure wave that is generated in the common liquid chamber  9  by ejecting liquid is attenuated, and thus, the liquid can be stably ejected. 
     In the above-described liquid ejecting head  300 , when the driving voltage is applied to the piezo-electric element member  2 , the piezo-electric element member  2  is moved in the laminated direction, and the vibration plate  10  is deformed and moved to the side of the compression chamber  7 . Thus, the capacity in the compression chamber  7  is decreased, and accordingly the pressure in the compression chamber  7  is increased, which causes the ink droplet to be ejected from the nozzle  6 . At that time, the ink in the compression chamber  7  tries to enter the common ink chamber  9  through the fluid resistance portion  8 . However, the fluid resistance portion  8  inhibits the ink from entering the common ink chamber  9 , and thus, the ink can be effectively ejected. 
     Then, as the ink ejecting process is finished, the pressure of the ink in the compression chamber  7  is decreased, and negative pressure in the compression chamber  7  is generated by inertia flow of the ink and the discharge process of the driving voltage. Subsequently, the process proceeds to the process of supplying ink, and the ink is supplied from the common ink chamber  9  to the compression chamber  7  through the fluid resistance portion  8 . 
     Then, when the vibration on the meniscus surface of the ink near the exit of the nozzle  6  is attenuated and the meniscus surface is returned to a steady state, the process proceeds to a subsequent ink ejecting process. 
     Next, a detailed configuration of the vibration unit  4  is described below with reference to  FIGS. 5A through 5E  in addition to  FIGS. 3 and 4 . Each of  FIGS. 5A through 5E  is a cross-sectional diagram illustrating a manufacturing process of the vibration unit  4  according to the first embodiment. It is to be noted that a different type of the vibration unit  4  is described below, and therefore, the configuration shown in  FIGS. 3A through 3E  is not necessarily the same as the configuration shown in  FIGS. 1 and 2 . 
     The vibration unit  4  is formed of a three-layered laminated member  20 . In center of the laminated member  20 , a resin layer  21  formed of etching-resistant material such as polyimide (PI) or polyphenylensulfide (PPS) is formed. As shown in  FIG. 5A , the resin layer  21  is sandwiched by a first metal layer  22  disposed on an upper side thereof and a second metal layer  23  disposed on a lower side thereof. 
     The first and second metal layers  22  and  23  are formed of different metals. As shown in  FIG. 5A , in the present embodiment, as the material of the laminated member  20 , the first metal layer  22  is formed of chromium (Cr) whose ionization tendency is higher than hydrogen (H), and the second metal layer  23  is formed of copper (Cu) whose ionization tendency is lower than hydrogen. 
     Initially, the entire surface of the laminated member  20  is coated with a photo-resist, and then patterning of the photo-resist is executed, as shown in  FIG. 5B . As a result, a resist pattern  24  opened at portions corresponding to the compression chambers  7  is formed on the side of the first metal layer  22 , and a resist pattern  25  opened at portions except the convex portions  12  and the thick-walled portions  13  is formed on the side of the second metal layer  23 . 
     Subsequently, as shown in  FIG. 5C , the second metal layer  23  is etched by ammonia water. Herein, as described above, the metal whose ionization tendency is higher than hydrogen is selected for the first metal layer  22 , and the metal whose ionization tendency is lower than hydrogen is selected for the second metal layer  23 . Because the first metal layer  22  whose ionization tendency is higher than hydrogen generally has higher resistivity against alkalinity, the first metal layer  22  is not etched. Therefore, only the second metal layer  23  can be etched without protecting the first metal layer  22 . The etching operation is stopped when the resin layer  21 , which is an etching-resistant member, is exposed, and thus the second metal layer  23  that can be etched is engraved. 
     Next, as shown in  FIG. 5D , the first metal layer  22  is etched by hydrochloric acid (HCl). Because the ionization tendency of the second metal layer  23  is lower than hydrogen, the second metal layer  23  can be resistant against acid and is not engraved. 
     Thereafter, as shown in  FIG. 5E , the resist patterns  24  and  25  are removed so that the partition walls  11  serving as structures and concave portions  7   a  each of which forms the compression chamber  7  are formed with the first metal layer  22 , the convex portion  12  and the thick-walled portion  13  are formed with the second metal layer  23 , and the vibration plate  10  is formed with the resin layer  21 . Thus, the vibration unit  4  is obtained. 
     The etching rate of the second metal layer  23  whose ionization tendency is lower than hydrogen is slower than that of the first metal layer  22  whose ionization tendency is higher than hydrogen. Therefore, the convex portion  12  and the thick-walled portion  13  can be formed with a higher degree of accuracy from the second metal layer  23  whose ionization tendency is lower than hydrogen, and the partition wall  11  and the concave portion  7   a  forming the compression chamber  7  can be formed in a shorter time even with their greater thickness. 
     As for the triple-layer laminated member  20 , for example, commercial triple-layered members, such as stainless steel-polyimide-copper layered members can be used. Alternatively, etching can be executed after the three layers are connected in advance. 
     In this case, whether the etching process was executed before the connection process or after the connection process can be relatively easily distinguished because, when the etching is executed after the three layers are adhered together, there are no or almost no protrusions of the adhesion layer on the edge portion of the pattern. 
     Further, regarding the connection between the etching-resistant layer and the layer that can be etched, a surface betterment layer that enhances connection force of the adhesive layer may be formed. In this case, although the laminated member  20  appears to have layers in excess of three layers, such a configuration is not beyond the scope of the present invention. 
     As described above, the vibration plate  10  is formed of the etching-resistant resin member  21 , and the triple-layer member is formed by sandwiching the vibration plate  10  with different metals. Therefore, the structure located on both sides of the vibration plate is formed with a metal that can be etched, without misalignment. Further, the vibration unit  4  can be produced relatively easily and at low cost, and a liquid ejecting head whose degree of assembly accuracy is high can be produced at low cost. 
     Further, as described above, the ionization tendencies of the different metals are different, that is, one has an ionization tendency higher than that of hydrogen and the other has an ionization tendency lower than that of hydrogen. Therefore, etching characteristics of these metals are different. Since the two metal layers are etched using different etching liquid, one metal layer can be etched without masking the other metal layer. Therefore, etching time can be set optimally for the thickness of metal layer or the pattern respectively, and flexibility in setting the thickness of metal layer or the pattern can be increased. Therefore, a liquid ejecting head with excellent characteristic can be obtained. 
     As the metal whose ionization tendency is higher than hydrogen, for example, magnesium (Mg), titanium (Ti), aluminum (Al), chromium (Cr), iron (Fe), nickel (Ni), or stainless steel such as SUS304, SUS316 and SUS430 formed of an alloy of chromium, iron, and nickel, can be used. As the metal whose ionization tendency is lower than hydrogen, for example, copper (Cu), silver (Ag), gold (Au), or platinum (Pt) can be used. 
     It is to be noted that, although in the present embodiment, the partition wall  11  is formed of the first metal layer  22  whose ionization tendency is higher than hydrogen and the convex portions  12  and thick-walled portions  13  are formed of the second metal layer  23  whose ionization tendency is lower than hydrogen, this invention is not limited to the specific present embodiment. That is, the partition wall  11  can be formed of the second metal layer whose ionization tendency is lower than hydrogen, and the convex portions  12  and thick-walled portions  13  can be formed of the first metal layer whose ionization tendency is higher than hydrogen. However, it is preferable that the partition wall  11  is formed of the first metal layer  22  whose ionization tendency is higher than hydrogen, as shown in the present embodiment, because the metal whose ionization tendency is higher than hydrogen generally has higher resistivity against alkalinity. When the liquid ejecting head  300  is used as the liquid ejecting head, high resistivity against alkalinity is required for the partition wall that mainly contacts the ink directly because the ink for ink jet image forming apparatuses is alkalinity. Therefore, the partition wall  11  is formed of the metal whose ionization tendency is higher than hydrogen, and thus, the liquid ejecting head  300  can have higher resistivity against the ink and have increased durability. 
     Further, because the resin layer  21  is electrically insulative, the resin layer  21  can isolate the first metal layer  22  from the second metal layer  23 , which can prevent the first metal layer  22  and the second metal layer  23  from forming a battery when the compression chamber  7  and the common liquid chamber  9  are filled with the ink, and thus preventing the metal material from liquating out. 
     Additionally, although the first metal layer  22  is etched after the second metal layer  23  is etched in the present embodiment, the order of the etching process can be permutated as appropriate. 
     In the above-described several configurations, the vibration plate  10  and the partition walls  11  can be integrally formed as a single unit, and the patterns are formed after these members are connected. As a result, misalignment can be caused by only the masking position of both sides, and the convex portions  12  can be positioned with respect to the compression chamber  7  with a higher degree of accuracy. Additionally, the protrusion to the connection portion is decreased, and a higher degree of shape accuracy can be achieved. 
     A part of both the partition wall  11  and the thick-walled portion  13  formed in this manner contact the ink, and therefore those members are required to have high resistivity against ink. However, even if the material of those members has low resistivity against ink, the ink resistivity can be enhanced by coating the surface of the material with an appropriate organic or inorganic material. Such a coated configuration is within the scope of the present invention. 
     As the etching-resistant material that forms the vibration plate  10  in the vibration unit  4 , the resin layer  21  is preferable. The deformation of the driving mechanism should be efficiently transmitted by the etching-resistant material that forms vibration plate, and the vibration should not be transmitted to the structure around the etching-resistant material. Therefore, it is preferable that the vibration plate  10  be formed of the resin material that has a relatively low stiffness. When the vibration is transmitted to the surrounding structure such as the partition wall  11 , the compression chamber  7  and the nozzle  6  are vibrated in conjunction with the partition wall  11 , and therefore the ejecting operation can be significantly destabilized. 
     By contrast, when the vibration  10  is formed of the resin layer  21 , less vibration can be transmitted to the surrounding structure because the rate of Young&#39;s modulus of resin is lower by two orders of magnitude than that of materials such as metal, and the resin material is soft. 
     As the resin layer  21 , for example, acrylic resin, polyimide resin, or aramid resin can be used. However, because the vibration plate  10  contacts the ink, it is favorable that the resin layer  23  has a relatively high resistibility against ink. As a high ink-resistant resin, for example polyimide resin, aramid resin, or the like can be used. 
     Even if the vibration material is formed of low ink-resistant resin, the ink resistivity can be enhanced by coating the surface of the resin with an appropriate organic or inorganic material. Such a coated configuration is within the scope of the present invention. Because the vibration plate formed of the resin has a relatively low rate of Young&#39;s modulus, the vibration plate can be relatively thick, that is, with a thickness within a range of from 5 μm to 100 μm. With such a thickness, pin-hole defects are seldom generated in the vibration plate and its handling is relatively easy, which can boost process yield. 
     Second Embodiment 
     Next, a second embodiment of the present invention is described below with reference to the  FIG. 6 .  FIG. 6  is a cross-sectional view of a liquid ejecting head  301  taken along a shorter side of the compression chamber  7  (direction of nozzle alignment). In the present embodiment, similar to the first embodiment, the first metal layer  22  forms a partition wall  111 , and the second metal layer  23  forms a thick-walled portion  131  that is located between the resin layer  21  and the piezo-electric element member  2  serving as the driving mechanism and located in a corresponding portion of the partition wall  111 . 
     In the portion in which the pattern of the first metal layer  22  faces the pattern of the second metal layer  23 , the area of partition wall  111  that is the pattern of the first metal layer  22  is larger than the area of the thick-wall portion  131  that is the pattern of the second metal layer  23 . Namely, the area of a planar portion of the partition wall  111  is larger than the area of a planar portion of the thick-wall portion  131  that corresponds to the partition wall  111 . 
     In the present embodiment, similarly to the first embodiment, the displacement in the d33 direction is used as a piezoelectric direction of the piezoelectric element member  2  to move and deform the vibration plate  101  in a direction toward the compression chamber  7 , and thus, the nozzle  6  ejects ink droplets. 
     When the displacement in the d33 direction is thus used as a piezo-electric direction of the piezo-electric element member  2  to compress the ink in the liquid chamber  7  by moving and deforming the vibration plate  101  in the direction toward the liquid chamber  7 , in order not to degrade the polarization of the piezo-electric element member  2 , voltage is applied in the same direction as the polarization direction. 
     Therefore, when the displacement in the d33 direction is used, as shown in  FIG. 6 , the piezo-electric element rod  2 A in the piezo-electric element member  2  deforms in a direction in which the vibration plate  101  is pressed. When the piezo-electric element rod  2 A deforms, the vibration plate  101  receives stress at fixed end portions surrounded by dashed line circle A in  FIG. 6 . 
     At this time, the partition wall  111  that is the pattern of the first metal layer  21  is larger than the thick-wall portion  131  that is the pattern of the second metal layer  23 . As a result, the force to peel the partition wall  111  or the thick-wall portion  131  from the vibration plate  101  acting on the connection face between the vibration plate  101  and the partition wall  111  or the thick-wall portion  131  can be reduced. Therefore, durability against peeling at the connection face between the vibration plate  101  and partition wall  111  or the thick-wall portion  131  can be increased. 
     Further, when the piezo-electric element member  2  is vibrated at a relatively high frequency, an edge portion of the partition wall  111  is stressed. Therefore, the reliability of the connection face between the partition wall  111  and the resin member  21  may be damaged over time. 
     However, as described above, because the partition wall  111  is formed with the first metal layer  21  whose ionization tendency is higher than hydrogen, a metal oxide film tends to be formed on the surface of the first metal layer  21 . Since the metal oxide film includes a hydroxyl group and goes well together with the resin layer  21  and adhesive, the reliability of the connection between the partition wall  111  and resin layer  21  can be enhanced. 
     Third Embodiment 
     Next, the third embodiment of the present invention is described below with reference to the  FIG. 7 .  FIG. 7  is a cross-sectional view of a liquid ejecting head  302  taken along a shorter side of the compression chamber  7  (direction of nozzle alignment). 
     In the present embodiment, by contrast to the first embodiment, the second metal layer  23  forms a partition wall  112 , and the first metal layer  22  forms a thick-walled portion  132  that is located between the resin layer  21  and a non-driving piezo-electric element rod  32 B serving as a support rod and located in a corresponding portion of the partition wall  112 . 
     In the portion in which the pattern of the first metal layer  22  faces the pattern of the second metal layer  23 , the area of thick-wall portion  132  that is pattern of the first metal layer  22  is larger than the area of the partition wall  112  that is the pattern of the second metal layer  23 . Namely, the area of a planar portion of the thick-wall portion  132  that corresponds to the partition wall  112  is larger than the area of a planar portion of the partition wall  112 . 
     In the present embodiment, differently from the first embodiment, a piezo-electric element member  32  that includes a driving piezo-electric element rod  32 A and the non-driving piezo-electric element rod  32 B is disposed on the base  1 . 
     Then, the displacement in the d31 direction is used as a piezoelectric direction of the piezo-electric element member  32  to move and deform the vibration plate  102  in a direction opposite to the liquid chamber  7 , and thus, the nozzle  6  ejects ink droplets. 
     In this way, the displacement in the d31 direction is used as a piezo-electric direction of the piezo-electric element member  32  to compress the ink in the liquid chamber  7  using a force of the vibration plate  102  to return from the deformation in the direction opposite to the compress liquid chamber  7 . 
     In this case, because the piezo-electric element rod  32 A in the piezo-electric element member  2  deforms in a direction in which the vibration plate  102  is pulled as shown in  FIG. 7 , the vibration plate  102  receives a relatively large stress at fixed end portions surrounded by dashed line circle B in  FIG. 7 . 
     At this time, the thick-wall portion  132  that is the pattern of the first metal layer  21  is larger than the partition wall  112  that is the pattern of the second metal layer  23 . As a result, the force to peel the partition wall  112  or the thick-wall portion  132  from the vibration plate  102  acting on the connection face between the vibration plate  102  and the partition wall  112  or the thick-wall portion  132  can be reduced. Therefore, durability against peeling at the connection face between the vibration plate  102  and partition wall  112  or the thick-wall portion  132  can be increased. 
     Further, when the piezo-electric element member  2  is vibrated at a relatively high frequency, an edge portion of the partition wall  112  is stressed. Therefore, the reliability of the connection face between the thick-wall portion  132  and the resin member  21  may be damaged over time. However, as described above, because the thick-wall portion  132  is formed with the first metal layer  21  whose ionization tendency is higher than hydrogen, a metal oxide film tends to be formed on the surface of the first metal layer  21 . Since the metal oxide film includes a hydroxyl group and goes well together with the resin layer  21  and adhesive, the reliability of the connection between the thick-wall portion  132  and resin layer  21  can be enhanced. 
     Fourth Embodiment 
     Next, the fourth embodiment of the present invention is described below with reference to the  FIGS. 8A through 8E . Each of  FIGS. 8A through 8E  is a cross section diagram illustrating a manufacturing process of the vibration unit  4 A according to the fourth embodiment. 
     The vibration unit  4 A is formed of a three-layered laminated member  20 A. In center of the laminated member  20 A, a resin layer  21 A formed of etching-resistant material such as polyimide (PI) or polyphenylensulfide (PPS) is formed. As shown in  FIG. 8A , the resin layer  21 A is sandwiched by a first metal layer  22 A disposed on an upper side thereof and a second metal layer  23 A disposed on a lower side thereof that are formed of different metals. 
     As shown in  FIG. 8A , In the present embodiment, as the material of the laminated member  20 A, the first metal layer  22 A is formed of SUS304H whose ionization tendency is higher than hydrogen, and the second metal layer  23 A is formed of copper whose ionization tendency is lower than hydrogen. 
     Initially, the entire surface of the laminated member  20 A is coated with a photo-resist, and then, as shown in  FIG. 8B , patterning of the photo-resist is executed. As a result, a resist pattern  24 A opened at portions corresponding to the compression chambers  73  is formed on the side of the first metal layer  22 A, and a resist pattern  25 A opened at portions except the convex portions  123  and the thick-walled portions  133  is formed on the side of the second metal layer  23 A. 
     Subsequently, as shown in  FIG. 8C , the second metal layer  23  and the second metal layer  23 A are etched by Iron(II)chloride (FeCl 2 ) serving as a first etching liquid. Iron(II)chloride can etch both metals of SUS304H that forms the first metal layer  22 A and copper that forms the second metal layer  23 A. The etching operation is stopped when the resin layer  21 A, which is etching-resistant member, is exposed, and thus the first metal layer  22 A and the second metal layer  23 A that can be etched are engraved. 
     Next, as shown in  FIG. 8D , the first metal layer  22 A is etched by a liquid mixture of hydrochloric acid (HCl) and nitric acid (HNO 3 ), serving as a second etching liquid. Because the ionization tendency of the second metal layer  23  is lower than hydrogen, the second metal layer  23 A can be resistant against acid and is not engraved. 
     Thereafter, as shown in  FIG. 8E , the resist patterns  24 A and  25 A are removed so that the partition walls  113  serving as structures and concave portions  7   a  each of which forms the compression chamber  73  are formed with the first metal layer  22 A, the convex portion  123  and the thick-walled portion  133  are formed with the second metal layer  23 A, and the vibration plate  103  is formed with the resin layer  21 A. Thus, the vibration unit  4 A is obtained. 
     As described above, in the present embodiment, Iron(II)chloride serving as the first etching liquid etches both metals of SUS304H that forms the first metal layer  22 A and copper that forms the second metal layer  23 A, and thereafter, the liquid mixture of hydrochloric acid and nitric acid serving as the second etching liquid etches SUS304H that forms the first metal layer  22 A. 
     Because the second etching liquid cannot engrave the second metal layer  23 A, the shape of the second metal layer  23 A is determined in accordance with the first etching. On the other hand, because the first metal layer  22 A is engraved also by the first etching liquid, the etching process in which the first metal layer  22 A is engraved by the second etching liquid can require less time. Therefore, production time shortens and the cost of production can be reduced. 
     Fifth Embodiment 
     Next, a fifth embodiment of the present invention is described below with reference to  FIGS. 9 and 10 .  FIG. 9  is a cross-sectional view of a liquid ejecting head  304  taken along a longitudinal direction of a compression chamber  7  thereof (orthogonal to a direction of nozzle alignment).  FIG. 10  is a cross-sectional view of the liquid ejecting head  304  taken along a shorter side of the compression chamber  7  (direction of nozzle alignment). 
     In the present embodiment, a partition wall  110  is a double-layer structure that consists of a lower partition wall  11 A and an upper partition wall  11 B. 
     The lower partition wall  11 A is formed with the first metal layer  22  in the vibration unit  4 , and the upper partition wall  11 B that is formed with a liquid chamber member  26  is stacked on the lower partition wall  11 A. 
     The liquid chamber member  26  is formed by processing such as etching and pressing and is adhesively connected to the lower partition wall  11 A. The partition wall  110  requires a certain height so as to contain a certain amount of flowing liquid. 
     However, because the lower partition wall  11 A that is formed of the first metal layer  22  in the vibration unit  4  is formed by etching, when the compression chambers  7  are arranged relatively closely to each other, the lower partition wall  11 A cannot be formed unless the height thereof is reduced. To solve this problem, the liquid chamber member  26  that is a separate member is provided on the lower partition wall  11 A so that the height of the partition wall  110  can be increased even if the compression chambers  7  are arranged at high density. 
     The above-described various embodiments are applicable to a cartridge integrated with a liquid ejecting head or liquid ejecting head integrated with a cartridge, which is a liquid ejecting head integrally connected with the cartridge that supplies the ink to the liquid ejecting head. 
     Then, as described above, one of liquid ejecting heads  300 ,  302 , or  304  can be used as the recording head in the image forming apparatus  200  shown in  FIG. 1 , manufactured through any of the methods shown in  FIGS. 5A  trough  5 E or  FIGS. 8A  though  8 E. Therefore, the configuration can reduce production cost and provide improved reliability of the recording heads  234  and stable image formation. 
     It is to be noted that, although according to the above-described embodiments the liquid ejecting heads can be used in the image forming apparatus  200 , which functions as a printer, the image forming apparatus is not limited thereto. Alternatively, the above described liquid ejecting heads may be used in an image forming apparatus which functions as a multifunction printer having at least one of copying, printing, plotter, and facsimile functions, for example. Further, the liquid ejecting heads  300  though  304  may be used in an image forming apparatus using liquid other than ink, fixing liquid, and/or the like. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.