Abstract:
A droplet ejection device includes: a substrate having first, second, third &amp; fourth pressure chambers extending in a first direction; a nozzle plate below the substrate &amp; having first, second, third &amp; fourth nozzle apertures continuous with first, second, third &amp; forth pressure chambers, respectively; a vibration plate above the substrate; first, second, third &amp; fourth piezoelectric elements above the vibration plate &amp; above first, second, third &amp; fourth pressure chambers. wherein, viewed in a second direction orthogonal to the first direction, the first nozzle aperture positioned to overlap the third nozzle aperture &amp; doesn&#39;t overlap the second &amp; fourth nozzle apertures; the second nozzle aperture overlaps the fourth nozzle aperture &amp; doesn&#39;t overlap the first &amp; third nozzle apertures, viewed in the second direction; the first piezoelectric element positioned to overlap the third piezoelectric element &amp; doesn&#39;t overlap the second &amp; fourth piezoelectric elements, viewed in the second direction; &amp; the second piezoelectric element overlaps the fourth piezoelectric element &amp; doesn&#39;t overlap the first &amp; third piezoelectric elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims a priority to Japanese Patent Application No. 2008-056891 filed on Mar. 6, 2008 which is hereby expressly incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to droplet ejection devices and printers using the same. 
     2. Related Art 
     As droplet ejection heads for discharging liquid, inkjet heads that may be mounted, for example, on an ink jet recording apparatus are known. Inkjet heads may be operated in a manner that pressure chambers communicating with nozzle apertures are pressurized by piezoelectric elements thereby ejecting ink droplets through the nozzle apertures. As the piezoelectric elements, laminate type piezoelectric elements formed from alternately laminated piezoelectric layers and electrode layers are known (see, for example, Japanese Laid-open Patent Application JP-A-5-193129). With droplet ejection devices that use piezoelectric elements of the type described above, it is difficult to reduce the size of the piezoelectric elements, which makes it difficult to arrange nozzle apertures at higher density. 
     SUMMARY 
     In accordance with an advantage of some aspects of the invention, it is possible to provide droplet ejection devices that can achieve high-density arrangement of nozzles when piezoelectric elements are used. Also, droplet ejection heads and printers that use the droplet ejection devices can be provided. 
     A droplet ejection device in accordance with an embodiment of the invention includes a substrate having a first pressure chamber, a second pressure chamber, a third pressure chamber and a fourth pressure chamber extending in a first direction; a nozzle plate provided below the substrate, and having a first nozzle aperture continuous with the first pressure chamber, a second nozzle aperture continuous with the second pressure chamber, a third nozzle aperture continuous with the third pressure chamber, and a fourth nozzle aperture continuous with the fourth pressure chamber; a vibration plate provided above the substrate; a first piezoelectric element provided above the vibration plate and above the first pressure chamber; a second piezoelectric element provided above the vibration plate and above the second pressure chamber; a third piezoelectric element provided above the vibration plate and above the third pressure chamber; and a fourth piezoelectric element provided above the vibration plate and above the fourth pressure chamber, wherein, as viewed in a second direction orthogonal to the first direction, the first nozzle aperture is provided at a position that overlaps the third nozzle aperture, and provided at a position that does not overlap the second nozzle aperture and the forth nozzle aperture; the second nozzle aperture is provided at a position that overlaps the fourth nozzle aperture, and provided at a position that does not overlap the first nozzle aperture and the third nozzle aperture, as viewed in the second direction; the first piezoelectric element is provided at a position that overlaps the third piezoelectric element, and provided at a position that does not overlap the second piezoelectric element and the fourth piezoelectric element, as viewed in the second direction; and the second piezoelectric element is provided at a position that overlaps the fourth piezoelectric element, and provided at a position that does not overlap the first piezoelectric element and the third piezoelectric element. 
     According to the droplet ejection device in accordance with the embodiment described above, droplets can be effectively ejected. 
     In the description of the invention, the term “above” is used, for example, as in a statement “a specific component (hereinafter called ‘B’) is formed ‘above’ another specific component (hereinafter called ‘A’).” In such a case, the term “above” is used in the description of the invention, while assuming to include the case where the component B is formed directly on the component A and the case where the component B is formed over the component A through another component provided on the component A. Similarly, the term “below” is used, while assuming to include the case where the component B is formed directly under in contact with the component A and the case where the component B is formed under the component A through another component. 
     In the droplet ejection device in accordance with an aspect of the invention, the first nozzle aperture may be provided at a position that does not overlap the second piezoelectric element and the fourth piezoelectric element, as viewed in the second direction, and the second nozzle aperture may be provided at a position that does not overlap the first piezoelectric element and the third piezoelectric element, as viewed in the second direction. 
     In the droplet ejection device in accordance with an aspect of the invention, the second pressure chamber may have a long side and a short side, as viewed in a plan view, the distance between the first piezoelectric element and the third piezoelectric element may be the same as the length of the short side of the second pressure chamber, as viewed in the first direction in a plan view; and the third pressure chamber may have a long side and a short side, as viewed in a plan view, the distance between the second piezoelectric element and the fourth piezoelectric element may be the same as the length of the short side of the third pressure chamber, as viewed in the first direction in a plan view. 
     In the droplet ejection device in accordance with an aspect of the invention, the substrate may further include a reservoir; a first dam section that is provided in the first pressure chamber and provided at a flow inlet section where liquid flows from the reservoir to the first pressure chamber; a second dam section that is provided in the second pressure chamber and provided at a flow inlet section where liquid flows from the reservoir to the second pressure chamber; a third dam section that is provided in the third pressure chamber and provided at a flow inlet section where liquid flows from the reservoir to the third pressure chamber; and a fourth dam section that is provided in the fourth pressure chamber and provided at a flow inlet section where liquid flows from the reservoir to the fourth pressure chamber. 
     In the droplet ejection device in accordance with an aspect of the invention, the substrate may further include; a first dam section provided in the first pressure chamber; a second dam section provided in the second pressure chamber; a third dam section provided in the third pressure chamber; and a fourth dam section provided in the fourth pressure chamber, wherein the first dam section, the second dam section, the third dam section and the fourth dam section may be provided at the same position, as viewed in the second direction. 
     In the droplet ejection device in accordance with an aspect of the invention, the first pressure chamber may have a long side and a short side, as viewed in a plan view, the second pressure chamber may have a long side and a short side, as viewed in a plan view, the third pressure chamber may have a long side and a short side, as viewed in a plan view, and the fourth pressure chamber may have a long side and a short side, as viewed in a plan view, wherein the long side of the first pressure chamber may have the same length as the long side of the third pressure chamber, the long side of the second pressure chamber may have the same length as the long side of the fourth pressure chamber, and the long side of the first pressure chamber may be longer than the long side of the second pressure chamber. 
     In the droplet ejection device in accordance with an aspect of the invention, the first piezoelectric element may have a long side and a short side, as viewed in a plan view, the second piezoelectric element may have a long side and a short side, as viewed in a plan view, the third piezoelectric element may have a long side and a short side, as viewed in a plan view, and the fourth piezoelectric element may have a long side and a short side, as viewed in a plan view, wherein the short side of the first piezoelectric element may be longer than the short side of the first pressure chamber, the short side of the second piezoelectric element may be longer than the short side of the second pressure chamber, the short side of the third piezoelectric element may be longer than the short side of the third pressure chamber, and the short side of the fourth piezoelectric element may be longer than the short side of the fourth pressure chamber. 
     In the droplet ejection device in accordance with an aspect of the invention, the vibration plate may include, above the vibration plate, a first protrusion located below the first piezoelectric element, a second protrusion located below the second piezoelectric element, a third protrusion located below the first piezoelectric element, and a fourth protrusion located below the first piezoelectric element. 
     In the droplet ejection device in accordance with an aspect of the invention, the first protrusion may be formed in the first piezoelectric element, as viewed in a plan view, the second protrusion may be formed in the second piezoelectric element, as viewed in a plan view, the third protrusion may be formed in the third piezoelectric element, as viewed in a plan view, and the fourth protrusion may be formed in the fourth piezoelectric element, as viewed in a plan view. 
     In the droplet ejection device in accordance with an aspect of the invention, the first piezoelectric element may be provided at the same position as the third piezoelectric element, as viewed in the second direction, and the second piezoelectric element may be provided at the same position as the fourth piezoelectric element, as viewed in the second direction. 
     A droplet ejection device in accordance with an embodiment of the invention includes a substrate having a first pressure chamber, a second pressure chamber, a third pressure chamber and a fourth pressure chamber extending in a first direction; a nozzle plate provided below the substrate, and having a first nozzle aperture continuous with the first pressure chamber, a second nozzle aperture continuous with the second pressure chamber, a third nozzle aperture continuous with the third pressure chamber, and a fourth nozzle aperture continuous with the fourth pressure chamber; a vibration plate provided above the substrate; a first piezoelectric element provided above the vibration plate and above the first pressure chamber; a second piezoelectric element provided above the vibration plate and above the second pressure chamber; a third piezoelectric element provided above the vibration plate and above the third pressure chamber; and a fourth piezoelectric element provided above the vibration plate and above the fourth pressure chamber, wherein, as viewed in a second direction orthogonal to the first direction, the first piezoelectric element is provided at a position that overlaps the third piezoelectric element, and the second piezoelectric element is provided at a position that overlaps the fourth piezoelectric element, as viewed in the second direction. 
     A droplet ejection device in accordance with an embodiment of the invention includes a substrate having a first pressure chamber, a second pressure chamber, a third pressure chamber and a fourth pressure chamber extending in a first direction; a nozzle plate provided below the substrate, and having a first nozzle aperture continuous with the first pressure chamber, a second nozzle aperture continuous with the second pressure chamber, a third nozzle aperture continuous with the third pressure chamber, and a fourth nozzle aperture continuous with the fourth pressure chamber; a vibration plate provided above the substrate; a first piezoelectric element provided above the vibration plate and above the first pressure chamber; a second piezoelectric element provided above the vibration plate and above the second pressure chamber; a third piezoelectric element provided above the vibration plate and above the third pressure chamber; and a fourth piezoelectric element provided above the vibration plate and above the fourth pressure chamber, wherein, as viewed in a second direction orthogonal to the first direction, the first nozzle aperture is provided at a position that overlaps the third nozzle aperture, and the second nozzle aperture is provided at a position that overlaps the fourth nozzle aperture, as viewed in the second direction. 
     A printer in accordance with an embodiment of the invention includes any one of the droplet ejection devices described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a droplet ejection device in accordance with an embodiment of the invention. 
         FIG. 2  is a perspective view of the droplet ejection device showing the state thereof as being cut along a line A-A in  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along a line B-B in  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken along a line C-C in  FIG. 1 . 
         FIG. 5  is a perspective view showing a state of arrangement of piezoelectric elements. 
         FIG. 6  is a schematic view showing a droplet ejection head in accordance with an embodiment of the invention. 
         FIG. 7  is a schematic view of a printer in accordance with an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Preferred embodiments of the invention are described below with reference to the accompanying drawings. 
     1. Droplet Ejection Device 
       FIGS. 1 through 5  are schematic views of a droplet ejection device  100  in accordance with an embodiment of the invention.  FIG. 1  is a plan view in part of the droplet ejection device  100 .  FIG. 2  is a perspective view showing the state of the droplet ejection device  100  which is cut along a line A-A in  FIG. 1 .  FIG. 3  is a cross-sectional view taken along a line B-B in  FIG. 1 .  FIG. 4  is a cross-sectional view taken along a line C-C in  FIG. 1 .  FIG. 5  is a perspective view of piezoelectric elements. It is noted that  FIG. 1  does not illustrate a vibration plate. 
     The droplet ejection device  100  has, as shown in  FIG. 1  through  FIG. 4 , a substrate  10 , a nozzle plate  20  provided below the substrate  10 , a vibration plate  50  provided on the substrate  10 , and piezoelectric elements  30  provided on the vibration plate  50 . 
     The substrate  10  may include pressure chambers  12 , a reservoir  14  continuous with the pressure chambers  12 , and dam sections  16 . The pressure chambers  12  and the reservoir  14  may be formed by dividing the space between the nozzle plate  20  and the vibration plate  50  by the substrate  10 . An area where each dam section  16  is formed has a narrow flow path connecting between the reservoir  14  and each pressure chamber  12 . This area is called a flow inlet section  13 . The reservoir  14  is capable of storing liquid supplied from outside through an unshown liquid supply aperture. The liquid is supplied from the reservoir  14  to each pressure chamber  12  through the flow inlet section  13 . 
     The pressure chambers  12  extend in a first direction (a Y direction in  FIG. 1 ). Also, each of the pressure chambers  12  may be composed of an elongated space having a long side and a short side. Also, in the illustrated example, first pressure chambers  12   a  each having a first long side, and second pressure chambers  12   b  each having a long side shorter than the first long side of the first pressure chamber  12   a  are alternately disposed. The number of the pressure chambers  12  is not particularly limited. 
     Each of the pressure chambers  12  may have a columnar dam section  16  for controlling the flow quantity of liquid. The dam section  16  may be provided between the piezoelectric element  30  and the reservoir  14 , as viewed in a plan view. In the illustrated example, the dam sections  16  are provided in proximity of the reservoir  14 . The dam sections  16  are capable of controlling the speed of liquid supply to the pressure chambers  12 , respectively, and also capable of controlling the speed of liquid that returns from the pressure chambers  12  to the reservoir  14  upon deformation of the pressure chambers  12 , respectively. Also, the positions of the dam sections  16  are not limited to those in the illustrated example, but may be suitably changed for controlling the liquid flow. For example, the dam sections  16  may be positioned at different locations in the first pressure chamber  12   a  and the second pressure chamber  12   b , respectively. 
     The substrate  10  may be composed of, for example, a (110) single crystal silicon substrate. The (110) single crystal silicon substrate may be accurately processed by anisotropic etching with a potassium hydroxide solution or the like. In accordance with the present embodiment, the pressure chambers  12 , the dam sections  16  and the reservoir  14  can be accurately formed through processing the substrate  10 . 
     The nozzle plate  20  has nozzle apertures  22  that are continuous with the pressure chambers  12  of the substrate, respectively, as shown in  FIG. 1 ,  FIG. 3  and  FIG. 4 . More specifically, the nozzle apertures  22  include first nozzle apertures  22   a  that are continuous with the first pressure chambers  12   a , respectively, and second nozzle apertures  22   b  that are continuous with the second pressure chambers  12   b , respectively. The first nozzle apertures  22   a  are arranged at equal intervals in a second direction (an X direction in  FIG. 1 ). A line of the first nozzle apertures  22   a  is referred to as a first nozzle line  24 . Similarly, the second nozzle apertures  22   b  are arranged at equal intervals in the X direction. A line of the second nozzle apertures  22   b  is referred to as a second nozzle line  26 . 
     In accordance with the present embodiment, the first nozzle line  24  and the second nozzle line  26 , i.e., two lines of nozzle apertures are provided in a Y direction. Further, the first nozzle apertures  22   a  of the first nozzle line  24  and the second nozzle apertures  22   b  of the second nozzle line  26  are provided in a way mutually shifted in the X direction. In other words, the first nozzle apertures  22   a  and the second nozzle apertures  22   b  are arranged in a so-called staggered fashion. Also, when projected onto a plane extending in a direction orthogonal to the X direction and the Y direction (i.e., a Z direction in  FIG. 1 ), the first nozzle apertures  22   a  and the second nozzle apertures  22   b  are arranged at equal intervals. Accordingly, in accordance with the present embodiment, the pitch of the nozzle apertures  22   a  and  22   b  can be reduced in half, compared to the case where only a single line of nozzle apertures is provided, such that nozzle arrangement at higher density can be achieved. 
     The vibration plate  50  includes protrusions  52 . Piezoelectric elements  30  are provided on the protrusions  52 , respectively. Each of the protrusions  52  is located inside the outer periphery of each of the piezoelectric elements  30 , as viewed in a plan view. Due to the protrusions  52 , pressure caused by deformation of the piezoelectric elements  30  can be effectively transmitted to the vibration plate  50 . As the material for the vibration plate  50 , any material can be used without any particular limitation as long as it can be deformed by the piezoelectric elements  30 , and plastic material, metal or the like may be used. Also, the protrusions  52  may be formed from a material different from the material composing the entire vibration plate  50  (the vibration plate main body). For example, the vibration plate main body may be formed from a plastic material, and the protrusions  52  may be formed from a metal. 
     In the illustrated example, each of the piezoelectric elements  30  is a piezoelectric element of the type in which piezoelectric layers are laminated among multiple electrodes, and is characterized in that it deforms upon application of a voltage. The piezoelectric element  30  has, for example, as shown in  FIG. 3  through  FIG. 5 , piezoelectric layers  32 , first electrodes  34  and second electrodes  36 . The first electrodes  34  and the second electrodes  36  are alternately arranged. In the illustrated example, the first electrodes  34  are provided in a manner to extend from the lower end to the central area of the piezoelectric element  30 , and the second electrodes  36  are provided in a manner to extend from the upper end to an area near the bottom end of the piezoelectric element  30 . Also, on the outer circumference of the piezoelectric element  30  is provided a first external electrode  38  that connects the first electrodes  32 , and a second external electrode  40  that connects the second electrodes  34 . Also, the short side of the piezoelectric element  30  is longer than the short side of the pressure chamber  12 . 
     The piezoelectric elements  30  are arranged corresponding to the nozzle apertures  22 , respectively, as shown in  FIG. 1 . In other words, the first piezoelectric elements  30   a  are arranged corresponding to the first nozzle apertures  22   a  of the first nozzle line  24 , and the second piezoelectric elements  30   b  are arranged corresponding to the second nozzle apertures  22   b  of the second nozzle line  26 . Accordingly, a first piezoelectric element line  44  is formed corresponding to the first nozzle line  24 , and a second piezoelectric element line  46  is formed corresponding to the second nozzle line  26 . In the illustrated example, the piezoelectric element lines  44  and  46  in two lines are provided in the Y direction. The positions of the piezoelectric elements  30  can be set in relation with the positions of the nozzle apertures  22  according to droplet ejection conditions. 
     The arrangement relation among the nozzle apertures  22  and among the piezoelectric elements  30 , and the arrangement relation between the nozzle apertures  22  and the piezoelectric elements  30  can be summarized as follows. 
     As viewed in the X direction, the first nozzle aperture  22   a  is provided at a position that overlaps adjacent ones of the first nozzle apertures  22   a , but provided at a position that does not overlap the second nozzle apertures  22   b . As viewed in the X direction, the second nozzle aperture  22   b  is provided at a position that overlaps adjacent ones of the second nozzle apertures  22   b , but provided at a position that does not overlap the first nozzle apertures  22   a . Similarly, as viewed in the X direction, the first piezoelectric element  30   a  is provided at a position that overlaps adjacent ones of the first piezoelectric elements  30   a , but provided at a position that does not overlap the second piezoelectric elements  30   b . As viewed in the X direction, the second piezoelectric element  30   b  is provided at a position that overlaps adjacent ones of the second piezoelectric elements  30   b , but provided at a position that does not overlap the first piezoelectric elements  30   a.    
     As viewed in the X direction, the first nozzle apertures  22   a  are provided at positions that do not overlap the second piezoelectric elements  30   b . Also, as viewed in the X direction, the second nozzle apertures  22   b  are provided at positions that do not overlap the first piezoelectric elements  30   a.    
     Furthermore, in a plan view, the distance between adjacent ones of the first piezoelectric elements  30   a , as viewed in the Y direction, is the same as the length of the short side of the second pressure chamber  12 . Also, in a plan view, the distance between adjacent ones of the second piezoelectric elements  30   b , as viewed in the Y direction, is the same as the length of the short side of the first pressure chamber  12   a.    
     On the vibration plate  50  is provided a retaining member  70  for protecting the piezoelectric elements  30 . Furthermore, spacers  60  are provided between the first piezoelectric element line  44  and the second piezoelectric element line  46  and between the second piezoelectric element line  46  and the retaining member  70 , respectively. 
     The piezoelectric elements  30  may be formed by a known method described, for example, in Japanese Laid-open Patent Application JP-A-5-193129. The piezoelectric elements  30  may be formed by, for example, the following method. First, a first electrode  34  is formed on a first piezoelectric sheet by a screen printing method or the like. Then, a second electrode  36  is formed over the first piezoelectric sheet and the first electrode  34 . The foregoing steps are repeated multiple times, thereby forming a laminate. The laminate is cut by a wire saw or the like, whereby a line of piezoelectric elements  30  in which the piezoelectric elements  30  are arranged at a predetermined pitch can be obtained. The material for the piezoelectric layers  32  is not particularly limited, and for example, perovskite type oxides such as lead zirconate titanate and the like may be used. The piezoelectric elements  30  may be formed from a combination of piezoelectric layers of different kinds. 
     According to the droplet ejection device  100  in accordance with the present embodiment, liquid such as ink is supplied from the reservoir  14  to the pressure chambers  12 . Each of the pressure chambers  12  has a variable volume that can be changed by deformation of the vibration plate  30 . Therefore, by applying a voltage to the piezoelectric element  30 , the volume of the pressure chamber  12  can be changed, whereby liquid can be ejected from the nozzle aperture  22 . 
     The droplet ejection device  100  in accordance with the present embodiment can be manufactured by a known method. For example, the droplet ejection device  100  may be obtained by the following manufacturing method. 
     A nozzle plate  20 , a substrate  10  and vibration plate  50  are bonded together by adhesive or the like. Then, as shown in  FIG. 2  through  FIG. 5 , a first laminate (not shown) for forming second piezoelectric elements  30   b  is disposed on the vibration plate  50 , more specifically, on protrusions  52  of the vibration plate  50  which are located above the second pressure chambers  12   b . The first laminate may be affixed to a spacer  60  affixed to a retaining member  70  by adhesive or other suitable method. The first laminate is cut by, for example, a wire saw, thereby forming a second line of piezoelectric elements  46 . Similarly, a second laminate (not shown) similar to the first laminate is disposed on protrusions  52  of the vibration plate  50  which are located above first pressure chambers  12   a . The second laminate may be affixed to a spacer  60  affixed to the second line of piezoelectric elements  46  by adhesive or other suitable method. The second laminate is cut by, for example, a wire saw, thereby forming a first line of piezoelectric elements  44 . Then, a flexible wire substrate is connected to external electrodes  38  and  40 . The method used for forming the first line of piezoelectric elements  44  and the second line of piezoelectric elements  46  is not limited to the method described above. 
     The droplet ejection device  100  in accordance with the present embodiment has the following characteristics. 
     The droplet ejection device  100  has multiple nozzle lines, more specifically, the first nozzle line  24  and the second nozzle line  26  in which nozzle apertures are arranged in the X direction, which are disposed in the Y direction, and the first nozzle apertures  22   a  and the second nozzle apertures  22   b  are arranged mutually shifted in the X direction. As a result, the substantial nozzle pitch in the X direction can be made smaller. For this reason, the nozzle apertures can be arranged at high density, and thus high-speed and high-resolution printing can be achieved. 
     Moreover, the piezoelectric elements  30   a  forming the first line of piezoelectric elements  44  are mutually separated by mechanically cutting the laminate by a wire saw or the like. For this reason, adjacent ones of the first piezoelectric elements  30  are inevitably spaced from each other by a width between them. In accordance with the present embodiment, the spaces between the first piezoelectric elements  30   a  thus formed are used for disposing the second line of piezoelectric elements  46 . Therefore, without changing the nozzle pitch in a droplet ejection device in related art of the type described above, a plurality of nozzle lines can be disposed, such that the nozzle pitch can be made smaller, and the nozzles can be arranged at higher density, while retaining the size of the droplet ejection head. 
     In the illustrated embodiment, an example having two lines of piezoelectric elements is described. However, the invention is not limited to the above-described embodiment, and three or more lines of piezoelectric elements can be provided. Moreover, by mutually shifting the nozzle apertures in the piezoelectric element lines in the X direction, the substantial nozzle pitch can be made smaller, and higher density arrangement can be achieved. 
     2. Droplet Ejection Head 
     A droplet ejection head in accordance with an embodiment of the invention may include a droplet ejection device in accordance with the embodiment of the invention. For example, as shown in  FIG. 6 , a plurality of droplet ejection heads  100  may be arranged in the Y direction, whereby a droplet ejection head  1000  that is capable of ejecting droplets of plural kinds can be formed. In the illustrated example, eight droplet ejection devices  100  are arranged. However, the number of droplet ejection devices  100  can be suitably set. Of course, the droplet ejection device  100  alone can be used as a single unit. 
     3. Printer 
     Next, a printer in accordance with an embodiment of the invention having a liquid jet head of the invention shall be described. The embodiment is described here using an example in which a printer  300  in accordance with the present embodiment is an ink jet printer. 
       FIG. 7  is a schematic perspective view of the printer  300  in accordance with the present embodiment. 
     The printer  300  includes a head unit  330 , a driving section  310 , and a controller section  360 . Also, the printer  300  may include an apparatus main body  320 , a paper feed section  350 , a tray  321  for holding recording paper P, a discharge port  322  for discharging the recording paper P, and an operation panel  370  disposed on an upper surface of the apparatus main body  320 . 
     The head unit  330  includes an ink jet recording head (hereafter simply referred to as the “head”) that is formed from liquid jet heads  1000  of the embodiment described above. The head unit  330  is further equipped with ink cartridges  331  that supply inks to the head, and a transfer section (carriage)  332  on which the head and the ink cartridges  331  are mounted. 
     The driving section  310  is capable of reciprocally moving the head unit  330 . The driving section  310  includes a carriage motor  341  that is a driving source for the head unit  330 , and a reciprocating mechanism  342  that receives rotations of the carriage motor  341  to reciprocate the head unit  330 . 
     The reciprocating mechanism  342  includes a carriage guide shaft  344  with its both ends being supported by a frame (not shown), and a timing belt  343  that extends in parallel with the carriage guide shaft  344 . The carriage  332  is supported by the carriage guide shaft  344 , in a manner that the carriage  332  can be freely reciprocally moved. Further, the carriage  332  is affixed to a portion of the timing belt  343 . By operations of the carriage motor  341 , the timing belt  343  is moved, and the head unit  330  is reciprocally moved, guided by the carriage guide shaft  344 . During these reciprocal movements, ink is discharged from the head and printed on the recording paper P. 
     The control section  360  can control the head unit  330 , the driving section  310  and the paper feeding section  350 . 
     The paper feeding section  350  can feed the recoding paper P from the tray  321  toward the head unit  330 . The paper feeding section  350  includes a paper feeding motor  351  as its driving source and a paper feeding roller  352  that is rotated by operations of the paper feeding motor  351 . The paper feeding roller  352  is equipped with a follower roller  352   a  and a driving roller  352   b  that are disposed up and down and opposite to each other with a feeding path of the recording paper P being interposed between them. The driving roller  352   b  is coupled to the paper feeding motor  351 . When the paper feeding section  350  is driven by the control section  360 , the recording paper P is fed in a manner to pass below the head unit  330 . 
     The head unit  330 , the driving section  310 , the control section  360  and the paper feeding section  350  are provided inside the apparatus main body  320 . 
     The printer  300  has, for example, the following characteristics. 
     The printer  300  may have a liquid ejection head in accordance with an embodiment of the invention. The liquid jet head in accordance with the embodiment is highly reliable, and can be manufactured by a low cost and simple process. Therefore, the printer  300  that is highly reliable and can be manufactured by a low cost and simple process can be obtained. 
     It is noted that, in the example described above, an example in which the printer  300  is an ink jet printer is described. However, the printer in accordance with the invention may also be used as an industrial liquid ejection device. Liquid (liquid material) that may be ejected in this case may be liquid composed of any one of various kinds of functional materials whose viscosity is appropriately adjusted with a solvent or a dispersion medium. 
     The embodiments of the invention are described above in detail. However, those skilled in the art should readily understand that many modifications can be made without departing in substance from the novel matter and effects of the invention. Accordingly, all of those modified examples are deemed to be included in the scope of the invention.