Abstract:
A liquid ejecting apparatus includes a liquid ejecting head, a platen, an absorption member, an electrode, a potential difference generating device. The liquid ejecting head has a conductive nozzle plate that has openings. The liquid ejecting head ejects liquid from the openings toward a front face of a recording object. The platen is arranged at a position opposed to the nozzle plate with the recording object placed between the platen and the nozzle plate. The platen contacts a rear face of the recording object to support the recording object. The absorption member is arranged at a position opposed to the nozzle plate and located farther from the openings than the recording object in a direction in which the liquid is ejected. The absorption member absorbs liquid that is ejected from the openings but not adhered to the recording object. The electrode is arranged in proximity to the absorption member. The potential difference generating device generates a difference in potential between the nozzle plate and the electrode by applying voltage to the electrode so as to form an electric field, whereby liquid ejected from the liquid ejecting head is electrically attracted toward the electrode. The platen includes a platen body, an accommodation portion and a retaining portion. The accommodation portion is depressed from the platen body and formed to include a bottom portion and a side wall portion. The accommodation portion accommodates the absorption member therein. The retaining portion retains the electrode, which is arranged along the bottom portion of the accommodation portion, toward the bottom portion.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a liquid ejecting apparatus, a platen and a recording apparatus. More specifically, the invention relates to a liquid ejecting apparatus that adheres liquid, which is discharged from openings of a nozzle plate mounted on a liquid ejecting head, to a recording object. 
         [0003]    2. Related Art 
         [0004]    When a liquid ejecting apparatus adheres liquid to a recording object without any remaining margin at the periphery of the recording object, the liquid ejecting apparatus ejects liquid toward an area slightly larger than the size of the recording object in view of an inevitable positional deviation between the recording object and a liquid ejecting head. Thus, liquid is also ejected toward an area where a recording object is not present in proximity to the side peripheries and front and rear peripheries of the recording object. Then, an absorption member is arranged at a position opposed to the liquid ejecting head and located farther from the liquid ejecting head than the recording object, and the absorption member absorbs liquid that has been ejected but not adhered to the recording object. This prevents a stain from adhering to around the recording object due to liquid that has not adhered to the recording object. 
         [0005]    In the meantime, when liquid is adhered to a recording object, the recording object may possibly form wrinkles because a portion to which the liquid is adhered may possibly expand. If the wrinkles contact the absorption member, liquid that has been absorbed by the absorption member stains the recording object. Then, in most of the liquid ejecting apparatuses, in view of the heights of wrinkles formed in the recording object, a clearance of about 2 to 4 mm is provided between the recording object and the absorption member. For the same purpose of preventing a stain due to contact, a clearance of about 1 mm is provided between the nozzle plate and the recording object. Thus, about 3 to 5 mm clearance is provided between the nozzle plate and the absorption member. 
         [0006]    On the other hand, for the purpose of improving resolution of an image that is formed on the recording object by liquid, liquid droplets discharged from the openings of the nozzle plate tend to become finer and finer. When focusing on a single liquid droplet, the amount of the liquid droplet is only about a few picoliter. These fine liquid droplets each have an extremely small weight, so that, when the liquid droplets are once discharged from the nozzle plate, they rapidly lose their kinetic energy due to the viscous drag of the atmosphere, or the like. For example, it has been proved that liquid droplets having an amount of less than 8 picoliter lose their velocity to substantially zero when they fly a distance of about 3 mm in the atmosphere. The fine liquid droplets that have thus lost kinetic energy need a relatively long time until they complete falling because falling motion due to gravitational acceleration becomes substantially equal to a viscous drag force of the atmosphere. Liquid droplets float in the air until they complete falling. These liquid droplets are termed as aerosols. 
         [0007]    Some of the thus produced aerosols float to the outside of the liquid ejecting apparatus and adhere to a peripheral area. In addition, most of the aerosols adhere to portions within the liquid ejecting apparatus. When the aerosols adhere to a path, such as a platen, along which a recording object is transported, a recording object that will be transported for the next time is stained because the aerosols adhere again to the next recording object. Further, when the aerosols are adhered to an electrical circuit, a linear scale, a rotary encoder, an optical sensor, or the like, which are mounted in the liquid ejecting apparatus, it may cause malfunction of the liquid ejecting apparatus itself. Furthermore, when a user touches the portions to which the aerosols are adhered, user&#39;s hand will be smeared with the aerosols. 
         [0008]    Japanese Unexamined Patent Application Publication No. 2004-202867 describes a liquid ejecting apparatus that has the function of actively collecting aerosols using an electric field. In the liquid ejecting apparatus described therein, for the purpose of adhering and absorbing liquid droplets that have not adhered to a recording object, an absorption member is arranged at a position opposed to a nozzle plate. In addition, a metal component, which serves as a first electrode, is arranged on the surface of the absorption member, and a metal nozzle plate having openings for ejecting liquid is used as a second electrode. 
         [0009]    When these electrode and nozzle plate are applied with different voltages, an electric field is generated therebetween. On the other hand, liquid droplets discharged from the nozzle plate, at the moment when the liquid droplets are discharged from the nozzle plate, will be charged with the same pole as that of the nozzle plate owing to a so-called lightning rod effect. Thus, fine liquid droplets, which may become aerosols, also continue flying toward the electrode without any deceleration owing to Coulomb attraction from the electric field and are then adsorbed by the electrode having an electric potential that is opposite in pole to those of their own electric charge. Furthermore, liquid droplets that are adsorbed by the electrode are absorbed by the absorption member, which is arranged in proximity to the electrode, by the action of capillarity. 
         [0010]    As described above, it has been proved that it is possible to suppress production of aerosols by means of an electric field utilizing the aerosols being electrically charged. However, there is another technical problem to be solved because of another action of electric field that is generated in order to collect aerosols. 
         [0011]    That is, when an electric field is formed, an electrostatic force that attracts the electrode, which applies voltage, toward the nozzle plate is applied to the electrode. When an electric field having a strength of about 50 to 250 kV/m is formed in order to effectively collect aerosols, an electrostatic force of 2 to 55 μN per square centimeters is applied to components arranged inside the electrode. On the other hand, because the electrode is generally formed of a thin plate material, the electrode is light in weight and low in deformation strength. For this reason, the electrode may partially be lifted up due to electrostatic force received from the electric field. 
         [0012]    In addition, to arrange an absorption member in proximity to the electrode, it is likely that the absorption member is mounted on the electrode. For this reason, when the electrode is lifted up due to the action of electrostatic force, the absorption member may also be lifted up toward the nozzle plate. 
         [0013]    Further, when the lifted electrode, the lifted absorption member, and the like, contact a recording object, the rear face of the recording object is stained with liquid that has been already absorbed by the absorption member. Moreover, when the recording object collides with the lifted absorption member from the side, it is likely that the absorption member drops off from a position where the absorption member is initially arranged. 
       SUMMARY 
       [0014]    A first aspect of the invention provides a liquid ejecting apparatus. The liquid ejecting apparatus includes a liquid ejecting head, a platen, an absorption member, an electrode, a potential difference generating device. The liquid ejecting head has a conductive nozzle plate that has openings. The liquid ejecting head ejects liquid from the openings toward a front face of a recording object. The platen is arranged at a position opposed to the nozzle plate with the recording object placed between the platen and the nozzle plate. The platen contacts a rear face of the recording object to support the recording object. The absorption member is arranged at a position opposed to the nozzle plate and located farther from the openings than the recording object in a direction in which the liquid is ejected. The absorption member absorbs liquid that is ejected from the openings but not adhered to the recording object. The electrode is arranged in proximity to the absorption member. The potential difference generating device generates a difference in potential between the nozzle plate and the electrode by applying voltage to the electrode so as to form an electric field, whereby liquid ejected from the liquid ejecting head is electrically attracted toward the electrode. The platen includes a platen body, an accommodation portion and a retaining portion. The accommodation portion is depressed from the platen body and formed to include a bottom portion and a side wall portion. The accommodation portion accommodates the absorption member therein. The retaining portion retains the electrode, which is arranged along the bottom portion of the accommodation portion, toward the bottom portion. In this manner, it is possible to prevent the electrode and the absorption member from being lifted up due to the action of electric field. Thus, it is possible to form an electric field that is able to effectively collect aerosols. 
         [0015]    In the above liquid ejecting apparatus, the retaining portion may include a protrusion that protrudes inward of the accommodation portion from portion of the side wall portion. The electrode may include a cutout portion that allows the retaining portion to pass therethrough. The electrode, after accommodated in the accommodation portion by passing the protrusion through the cutout portion, may be displaced along the bottom portion and then fitted between the bottom portion and the protrusion. In this manner, it is possible to form the above structure without increasing the number of components of the liquid ejecting apparatus. In addition, the number of assembling man-hours is not increased. Thus, it is possible to obtain the above advantageous effects without increasing costs. 
         [0016]    In the above liquid ejecting apparatus, the retaining portion may include a protrusion that protrudes inward of the accommodation portion from portion of the side wall portion. The electrode, after once contacting the protrusion, may be pressed in so as to contact the bottom portion by overcoming elastic force of at least one of the electrode and the retaining portion and then held between the bottom portion and the retaining portion. In this manner, it is possible to form the above structure without increasing the number of components of the liquid ejecting apparatus. In addition, the number of assembling man-hours is not increased. Thus, it is possible to obtain the above advantageous effects without increasing costs. 
         [0017]    In the above liquid ejecting apparatus, the retaining portion may be formed to extend from the bottom portion and, after inserted through a hole formed in the electrode, contact an upper face of the electrode by a top portion being deformed. In this manner, it is possible to form the above structure in low cost without increasing the number of components. In addition, because the tolerance relative to dimensional accuracy of components may be set large, design and manufacturing will be easy. 
         [0018]    A second aspect of the invention provides a liquid ejecting apparatus. The liquid ejecting apparatus includes a liquid ejecting head, an absorption member, a platen, and a potential difference generating device. The liquid ejecting head has a conductive nozzle plate that has openings. The liquid ejecting head ejects liquid from the openings toward a front face of a recording object. The absorption member is arranged at a position opposed to the nozzle plate and located farther from the openings than the recording object in a direction in which the liquid is ejected. The absorption member absorbs liquid that is ejected from the openings but not adhered to the recording object. The platen is integrally formed with a platen body, an accommodation portion and an electrode. The accommodation portion is depressed from a surface of the platen body. The accommodation portion accommodates the absorption member therein. The electrode is at least partially embedded in a bottom portion of the accommodation portion. The platen is arranged at a position opposed to the nozzle plate with the recording object placed between the platen and the nozzle plate. The platen contacts a rear face of the recording object to support the recording object. The potential difference generating device generates a difference in potential between the nozzle plate and the electrode by applying voltage to the electrode so as to form an electric field, whereby liquid ejected from the liquid ejecting head is electrically attracted toward the electrode. In this manner, fixing the electrode is completed at the same time with forming the platen body. Actually, it is possible to prevent the electrode and the absorption member from being lifted while reducing the number of manufacturing processes. 
         [0019]    A third aspect of the invention provides a liquid ejecting apparatus. The liquid ejecting apparatus includes a liquid ejecting head, an absorption member, a platen, an electrode and a potential difference generating device. The liquid ejecting head has a conductive nozzle plate that has openings. The liquid ejecting head ejects liquid from the openings toward a front face of a recording object. The absorption member is arranged at a position opposed to the nozzle plate and located farther from the openings than the recording object in a direction in which the liquid is ejected. The absorption member absorbs liquid that is ejected from the openings but not adhered to the recording object. The platen is integrally formed with a platen body and an accommodation portion. The accommodation portion is depressed from a surface of the platen body. The accommodation portion accommodates the absorption member therein. The platen is arranged at a position opposed to the nozzle plate with the recording object placed between the platen and the nozzle plate. The platen contacts a rear face of the recording object to support the recording object. The electrode is adhered to a bottom portion of the accommodation portion. The potential difference generating device generates a difference in potential between the nozzle plate and the electrode by applying voltage to the electrode so as to form an electric field, whereby liquid ejected from the liquid ejecting head is electrically attracted toward the electrode. In this manner, it is possible to prevent the electrode and the absorption member from being lifted using components of the existing platen body. 
         [0020]    Note that the above overview of the aspects of the invention is not intended to describe all necessary features of the invention. Accordingly, the sub-combinations of these sets of features may also be aspects of the invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
           [0022]      FIG. 1  is a perspective view that schematically shows the entire structure of a multi functional printer. 
           [0023]      FIG. 2  is a perspective view that specifically shows an internal mechanism of a recording unit. 
           [0024]      FIG. 3  is a plan view that shows the structure of the internal mechanism as viewed from above. 
           [0025]      FIG. 4  is an exploded perspective view that shows the structure of a platen alone. 
           [0026]      FIG. 5  is a conceptional view that illustrates operation of an aerosol collecting mechanism. 
           [0027]      FIG. 6  is a plan view that shows a process of assembling an electrode to a platen body. 
           [0028]      FIG. 7  is a partially enlarged view of the platen body shown in  FIG. 6 . 
           [0029]      FIG. 8  is a plan view that shows the next process of assembling the electrode to the platen body. 
           [0030]      FIG. 9  is a partially enlarged view of the platen body shown in  FIG. 8 . 
           [0031]      FIG. 10  is a cross-sectional view that shows the positional relationship between an engaging pawl and a cutout portion in a state shown in  FIG. 6 . 
           [0032]      FIG. 11  is a cross-sectional view that shows the positional relationship between an engaging pawl and a cutout portion in a state shown in  FIG. 8 . 
           [0033]      FIG. 12  is a cross-sectional view that shows the shape of the engaging pawl according to an embodiment of the invention. 
           [0034]      FIG. 13  is a cross-sectional view that shows the shape of the engaging pawls according to another embodiment of the invention. 
           [0035]      FIG. 14  is a plan view that shows a process of assembling an electrode to a platen body according to yet another embodiment of the invention. 
           [0036]      FIG. 15  is a partially enlarged view of the platen body shown in  FIG. 14 . 
           [0037]      FIG. 16  is a plan view that shows the next process of assembling the electrode to the platen body as viewed in the same direction as that of  FIG. 14 . 
           [0038]      FIG. 17  is a partially enlarged view of the platen body shown in  FIG. 16 . 
           [0039]      FIG. 18  is a cross-sectional view that shows the positional relationship between a salient and a through-hole in a state shown in  FIG. 14  and  FIG. 15 . 
           [0040]      FIG. 19  is a cross-sectional view that shows the shape of the salient and a process of forming the salient in a state shown in  FIG. 16  and  FIG. 17 . 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0041]    Embodiments of the invention will now be described, but the following embodiments are not intended to limit the scope of the invention as set forth in the appended claims. In addition, it is not always necessary to include all the combinations of the features described in the embodiments for solution of the aspects of the invention. 
         [0042]      FIG. 1  is a perspective view that shows an appearance of a multi functional printer  100  provided with an ink jet recording apparatus which is an embodiment of the invention. As shown in the drawing, the multi functional printer  100  includes both a recording unit  110  and a reading unit  120  that is overlapped on top of the recording unit  110 . 
         [0043]    The reading unit  120  is formed in a case, which also serves as an upper case  122  of the entire multi functional printer  100 . On the upper surface of the upper case  122 , a reading table is arranged to put an original document that will be read, and an upper cover  124 , which also serves as an original copy holder, is further provided to hold an original copy that is put on the reading table. 
         [0044]    On the other hand, the recording unit  110  is formed on a case bottom  111  within a case, which also serves as a lower case  112  of the entire multi functional printer  100 . In the drawing, a paper support  212  of a feeding unit  210 , which will be described later, is shown behind the upper case  122 . In addition, on the front face of the lower case  112 , a front cover  114  that installs a discharge tray  248  of a discharge unit  240 , which will be described later, on the rear face is closed. 
         [0045]    Furthermore, the multi functional printer  100  is provided with an operation panel  130  on the front side to the upper cover  124 . The operation panel  130  is provided with a plurality of operation buttons  134 , a pilot lamp  136 , and the like, in addition to a display panel  132 . When the multi functional printer  100  is operated in a stand-alone manner, various commands may be input or operating states, and the like, may be displayed. 
         [0046]    In the above described multi functional printer  100 , the image of an original copy, which is mounted on the reading unit  120  by opening the upper cover  124 , will be read from the lower side. In addition, a sheet of recording paper  150  that is set on the paper support  212  is transported through the inside of the recording unit  110  toward the front and an image is recorded on the way by means of an internal mechanism  200 , which will be described later. 
         [0047]      FIG. 2  is a perspective view that specifically shows the internal mechanism  200  of the recording unit  110  of the multi functional printer  100  shown in  FIG. 1 .  FIG. 3  is a plan view that shows the structure of the internal mechanism  200  as viewed from above. As shown in the drawings, the internal mechanism  200  includes a case bottom  111 , a frame  202 , the feeding unit  210 , a transport unit  220 , the platen  230  and the discharge unit  240 . The frame  202  extends vertically from the case bottom  111 . The feeding unit  210  is arranged behind the frame  202 . The transport unit  220 , the platen  230  and the discharge unit  240  are serially arranged in front of the frame  202 . 
         [0048]    The feeding unit  210  includes the paper support  212 , a side support  214  and a slide support  216 . The paper support  212  supports the rear face of the sheet of recording paper  150  that is set vertically. The side support  214  positions the side end portion of the sheet of recording paper  150 , which is shown to the right side of the figures. The slide support  216  prevents the sheet of recording paper  150  from inclining in such a manner that the slide support  216  contacts the side end portion of the sheet of recording paper  150 , which is shown to the left side of the figures. The slide support  216  is movable horizontally on the front face of the paper support  212 . When the sheet of recording paper  150  having a different width is set, the slide support  216  may be moved to contact the side end portion of the sheet of recording paper  150 . The feeding unit  210  further includes a feeding roller  218 , and the like, that are hidden by the frame  202 . The feeding roller  218 , and the like, when the recording unit  110  operates recording, draws a plurality of the sheets of recording paper  150  that are set on the paper support  212  into the internal mechanism  200  sheet by sheet. 
         [0049]    Note that the internal mechanism  200  also includes a horizontal paper support  211  that is arranged below a discharge tray  248 , which will be described later, and has an opening at the front face. The paper support  211  supports sheets of recording paper  150 , which are set horizontally from the front side of the internal mechanism  200 , from the lower side. In addition, the sheets of recording paper  150  that are set on the paper support  211  may also be sent to the transport unit  220  using the feeding unit  210 . Note that the paper support  211  includes an extension portion  213  and is able to support a sheet of recording paper  150  having a length longer than the depth of the paper support  211  itself. 
         [0050]    The transport unit  220  is arranged immediately before the frame  202 . The transport unit  220  includes a transporting driven roller  224  that contacts the upper face of the drawn sheet of recording paper  150  and is rotated by the movement of the sheet of recording paper  150 . A transporting drive roller is arranged just below the transporting driven roller  224  and is driven by a transporting motor (not shown) for rotation. Thus, the sheet of recording paper  150  that has been drawn into the internal mechanism  200  is pressed against the transporting drive roller by the transporting driven roller  224  and sent onto the platen  230  in accordance with the rotation of the transporting drive roller. 
         [0051]    The platen  230  includes a plurality of ribs  234  that extend upward. The ribs  234  contact the lower face of the sheet of recording paper  150  being sent at the distal ends thereof to position the sheet of recording paper  150  in a vertical direction. The sheet of recording paper  150  that has passed the upper side of the platen  230  finally arrives at the discharge unit  240 . Note that the structure of the platen  230  will be specifically described separately with reference to  FIG. 4 . 
         [0052]    The discharge unit  240  is arranged to the front side of the platen  230 . The discharge unit  240  includes a discharge driven roller  244  that contacts the upper face of the sheet of recording paper  150 , which has been sent through the upper side of the platen  230 , and is rotated in accordance with the movement of the sheet of recording paper  150 . A discharge drive roller is arranged just below the discharge driven roller  244  and is driven by the transporting motor for rotation through a rotation transmitting mechanism (not shown). The sheet of recording paper  150  is pressed against the transporting drive roller by the discharge driven roller  244  and is sent to the front side of the recording unit  110  in accordance with the rotation of the discharge drive roller. The discharge tray  248  is arranged to the front side of the discharge unit  240 . The sheets of recording paper  150  that have been discharged outside the recording unit  110  will be stacked on the discharge tray  248 . 
         [0053]    Furthermore, the internal mechanism  200  includes a carriage  250  that reciprocally moves above the platen  230 . That is, the carriage  250  is mounted so that it is movable horizontally in the longitudinal direction of the frame  202  along a guide member (not shown) that is provided on the front face of the frame  202  and extends in the longitudinal direction of the frame  202 . In addition, a timing belt  253  is arranged to the front face of the frame  202  and is wound around a pair of pulleys  251 . Furthermore, the carriage  250  is connected to the timing belt  253  at the rear face thereof. 
         [0054]    In the meantime, because one of the pulleys  251  is driven by the carriage motor  255  for rotation, the carriage  250  moves in accordance with the displacement of the timing belt  253 . Thus, by controlling the operation and rotating direction of the carriage motor  255 , it is possible to move the carriage  250  to the upper side of an arbitrary region on the platen  230 . Furthermore, the carriage  250  includes a recording head (not shown), which includes a nozzle plate  252 , at the lower face thereof. Thus, the carriage  250  is able to discharge ink toward an arbitrary region on the platen  230 . 
         [0055]    In the multi functional printer  100  provided with the internal mechanism  200  having the above described structure, the sheets of recording paper  150  that are set on the front paper support  211  or the rear paper support  212  are drawn by the feeding unit  210  into the transport unit  220  sheet by sheet. The sheet of recording paper  150  that has been drawn to the transport unit  220  passes the upper side of the platen  230  and then reaches the discharge unit  240 . The sheet of recording paper  150  is finally sent by the discharge unit  240  outside the internal mechanism  200 . 
         [0056]    In addition, when the sheet of recording paper  150  is present above the platen  230 , the carriage  250  discharges ink downward while reciprocally moving above the platen  230 . Thus, it is possible to discharge ink and adhere the ink to an arbitrary region on the surface of the sheet of recording paper  150 . Further, the sheet of recording paper  150  is transported intermittently line by line, while the carriage  250  is reciprocally moved during the transportation is interrupted. Thus, an image may be recorded over the entire surface of the sheet of recording paper  150 . 
         [0057]    Note that a control unit  260  is mounted behind the frame  202  and controls a series of recording operations as described above. The control unit  260  controls the recording unit  110  to operate appropriately on the basis of commands input through an information processing device, or the like, which is connected to the multi functional printer  100 , or commands input through the operation panel  130 . In addition, the control unit  260  is also an interface that receives image information that will be recorded by the recording unit  110 . The image information received by the control unit  260  may include, in addition to the information that indicates resolution of a recording image, a recording quality such as the number of colors, recording object information such as size and material. 
         [0058]      FIG. 4  is an exploded perspective view that specifically shows the structure of the platen  230  in the internal mechanism  200 . As shown in the drawing, the platen  230  includes a platen body  232 , an electrode  310  and absorption members  236 ,  238 . The electrode  310  is accommodated in the platen body  232 . 
         [0059]    The platen body  232  is integrally formed from a resin material to include the plurality of ribs  234 , an accommodation portion  235  and an accommodation portion  237 . The plurality of ribs  234  extend upward from the upper face of the platen body  232 . The accommodation portion  235  having a larger width is depressed from the upper face of the platen body  232  and formed to include a bottom portion  231  and a side wall portion  233 . The accommodation portion  237  having a smaller width is formed to the side of a region in which the ribs  234  are formed. When the sheet of recording paper  150  passes above the platen  230 , the upper ends of the ribs  234  contact the lower face (rear face) of the sheet of recording paper  150  to position the sheet of recording paper  150  in the vertical direction. 
         [0060]    In addition, the absorption members  236 ,  238  have a size to fill the inside of the platen bodies  232 ,  237 . Further, the absorption members  236 ,  238  are formed of a material that is selected by laying emphasis on absorption velocity of the surfaces thereof with respect to liquid. For this reason, the amount of ink that the absorption members  236 ,  238  can hold is limited. Then, a waste liquid absorption member, which has a larger capacity than these absorption members  236 ,  238 , may be additionally arranged below the platen  230 . 
         [0061]    The platen  230  further includes the electrode  310  below the absorption member  236  inside the wider accommodation portion  235 . The electrode  310  is arranged to substantially cover the bottom portion  231  of the accommodation portion  235 . Further, a connecting portion  312  and a terminal portion  314  are integrally formed at one end of the electrode  310 . The connecting portion  312  extends outward over the side wall portion  233  of the accommodation portion  235 . The terminal portion  314  is exposed to the outside of the platen  230 . When the electrode  310  is connected through the terminal portion  314  to one end of a voltage source  270 , which operates under the control of the control unit  260 , it is possible to apply voltage to the electrode  310 . The other end of the voltage source  270  is connected to the nozzle plate  252 , which is mounted on the carriage  250 . Thus, it is possible to generate a difference in potential between the nozzle plate  252  and the electrode  310  to form an electric field. 
         [0062]    The material of the absorption members  236 ,  238  may preferably include a material that is made by foaming a resin material, such as polystylene or polyurethane. In addition, for the purpose of applying the same potential to the absorption member  236  as that of the electrode  310 , it is preferable that the absorption member  236  is formed of a conductive material that will have a surface resistance of 108Ω or below. Such a material may be a material that is formed by foaming a resin, such as polyethylene or polyurethane, that has been mixed with a conductive material, such as metal or carbon or a material in which a conductive material, such as metal or carbon, is adhered or plated onto a foamed resin made from a material, such as polyethylene or polyurethane. In addition, it may also be used as the material that electrolytic solution is impregnated into a foamed resin made from a material, such as polyethylene or polyurethane. 
         [0063]    On the other hand, the material of the electrode  310  may include a metal that is anticorrosive to ink, such as a wire, a plate or a foil that is made of gold, stainless, or nickel; a wire, a plate or a foil that is plated with these metals; or a mesh or a grid like member that combines some of these materials. Moreover, according to another embodiment, a conductive coating film layer, a plating layer, a thick film layer, a thin film layer, or the like, which is directly formed on the bottom portion  231  of the accommodation portion  235  of the platen  230 , may also be used as the electrode  310 . 
         [0064]      FIG. 5  is a schematic view that illustrates the structure and operation of an aerosol collecting mechanism  300  formed in the internal mechanism  200  of the recording unit  100 . As shown in the drawing, the nozzle plate  252  that has openings  254  for discharging ink is, for example, made of metal and has a conductivity. Moreover, the nozzle plate  252  is connected to the negative electrode of the voltage source  270 . On the other hand, the positive electrode of the voltage source  270  is connected to the electrode  310  that is accommodated in the platen  230 . Further, the absorption member  236 , which is stacked on the electrode  310  and accommodated in the platen  230 , has a conductivity, so that the entire absorption member  236  is applied with the same potential as that of the electrode  310 . Thus, an electric field E caused by a difference in potential generated by the voltage source  270  is uniformly formed between the lower face of the nozzle plate  252  and the surface of the absorption member  236 . Note that, even when all the polarities may be inverted and connected, the same function may be achieved. 
         [0065]    During recording operation, the nozzle plate  252  discharges ink  311  through the openings  254  downward. Here, when the sheet of recording paper  150  is present just below the openings  254 , the discharged ink  311  is adhered onto the upper face of the sheet of recording paper  150  to form an image  319 . On the other hand, when the ink  311  is intended to be adhered to the peripheral portion of the sheet of recording paper  150  without any margin, there is a possibility that the sheet of recording paper  150  is not present just below a portion of the openings  254  around the side periphery, front end and rear end of the sheet of recording paper  150 . 
         [0066]    In this case, kinetic energy given to ink droplets  317  that are generated through the discharge from the openings  254  is rapidly lost due to the viscous drag of the atmosphere. For this reason, portions of the ink droplets  317  lose their kinetic energy far before they reach the conductive absorption member  236 . Since the weight of each ink droplet  317  is extremely small, when the ink droplet  317  loses its kinetic energy, the following falling velocity becomes extremely small because falling motion due to gravitational acceleration becomes substantially equal to a viscous drag force of the atmosphere. In this way, aerosols that float below the nozzle plate  252  are produced. In addition, part of the ink droplet  317  may be split to become further fine ink droplets, that is, satellite inks  315 , this also becomes aerosols. 
         [0067]    However, in the aerosol collecting mechanism  300 , as is already described above, the electric field E is formed between the surface of the absorption member  236  and the lower face of the nozzle plate  252 . Thus, the ink droplet  317  having an electric charge q gains kinetic energy owing to Coulomb force Fe (qE) that is received from the electric field E and moves downward without any deceleration to reach the absorption member  236 . 
         [0068]    Note that the inks  311  that are pushed out from the openings  254  each form an ink column  313  that hangs down from the nozzle plate  252  at the moment immediately before each ink  311  leaves from the nozzle plate  252  to become the ink droplet  317 . At this time, an electric charge is stored between a distal end A of the ink column  313  and a region B around the ink column  313  on the lower face of the nozzle plate  252  due to a so-called lightning rod effect. Due to this lightning rod effect, each of the ink droplets  317  is charged with an electric charge q that is larger than an electric charge corresponding to a horizontal cross-sectional area of the ink column  313 . Note that the lightning rod effect means a phenomenon that the region B on the surface of the nozzle plate  252 , surrounded by a conical shape which has a vertex positioned at the distal end A (lower end in the drawing) of the ink column  313  and a vertical angle of 50 degrees to 60 degrees, contributes to charging of the ink droplet  317 . Thus, each of the ink droplets  317  receives a relatively large Coulomb force and flies in the electric field E to the absorption member  236  without losing its kinetic energy. 
         [0069]      FIG. 6  is one of figures that show the attaching structure of the electrode  310  in the platen  230  using the procedure of attaching the electrode  310 . As shown in the drawing, the electrode  310  that is shown to the upper side of the platen body  232  in  FIG. 4  is accommodated in the bottom portion  231  of the accommodation portion  235  that is formed in the platen  230 . In addition, the electrode  310  has a plate-like shape that follows the shape of the bottom portion  231 . 
         [0070]    However, the electrode  310  is not fixed in a state shown in  FIG. 6 . That is, a plurality of engaging pawls  239  are formed on the side wall portion  233  of the accommodation portion  235  so as to extend inward of the accommodation portion  235 . On the other hand, cutout portions  316  are formed at the periphery of the electrode  310  and located at positions corresponding to the engaging pawls  239 . 
         [0071]      FIG. 7  is a partially enlarged view that shows a state just after the engaging pawl  239  is passed through the cutout portion  316 .  FIG. 7  corresponds to a portion surrounded by dotted line VII shown in  FIG. 6 . As shown in the drawing, the planar shape of the cutout portion  316  is larger in area than the planar shape of the engaging pawl  239 . Thus, by passing the engaging pawl  239  through the cutout portion  316 , it is possible to easily insert the electrode  310  into the accommodation portion  235  to such an extent that the electrode  310  contacts the bottom portion  231 . 
         [0072]      FIG. 8  is a plan view that shows the next process of assembling the electrode  310  to the platen body  232 . As shown in the drawing, in comparison with the state shown in  FIG. 6 , the electrode  310  is displaced to the left side in the drawing. 
         [0073]      FIG. 9  is a partially enlarged view of the platen body  232  shown in  FIG. 8 .  FIG. 9  shows a region surrounded by dotted line IX in  FIG. 8 . As shown in the drawing, because the cutout portion  316  is displaced in accordance with the movement of the electrode  310 , the engaging pawl  239  adjacent to the platen body  232  is positioned outside the cutout portion  316 . 
         [0074]      FIG. 10  is a cross-sectional view, taken along the dotted line S 1  in  FIG. 6 , that shows the positional relationship between the engaging pawl  239  and the cutout portion  316  in a state shown in  FIG. 6 . As shown in the drawing, immediately after the electrode  310  has been set into the accommodation portion  235 , the electrode  310  is not located just below the engaging pawl  239 . 
         [0075]      FIG. 11  is a cross-sectional view, taken along the dotted line S 1  in  FIG. 8 , that shows the positional relationship between the engaging pawl  239  and the cutout portion  316  in a state shown in  FIG. 8 . As shown in the drawing, when the electrode  310  is displaced horizontally from the state shown in  FIG. 10 , the cutout portion  316  moves to a position that is offset from the position just below the engaging pawl  239 . Thus, portion of the upper face of the electrode  310  is located below the engaging pawl  239 . For this reason, even when electrostatic force acts on the electrode  310  by applying voltage, upward movement of the electrode  310  is stopped by the engaging pawl  239 . 
         [0076]      FIG. 12  is a cross-sectional view that shows the shape of one of the engaging pawls  239  according to an embodiment. The engaging pawl  239  is formed on the side wall face of the accommodation portion  235  in order to prevent the electrode  310  from being lifted, and the surface of the engaging pawl  239  is formed to include side faces that are inclined relative to the side wall portion  233  and extend inward of the accommodation portion. For this reason, because the absorption member  236  is accommodated in the accommodation portion  235  and pressed against the engaging pawl  239 , a stress that includes a component to displace the absorption member  236  upward is applied to the absorption member  236 . Then, as shown in  FIG. 12 , a large number of small-sized engaging pawls  225  are formed on the inclined face, so that it is possible to prevent the absorption member  236  to be displaced upward of the absorption member  236 . 
         [0077]      FIG. 13  is a cross-sectional view that shows the shape of the engaging pawls  239  according to another embodiment. As shown in the drawing, the engaging pawls  239  each extend relatively small from the side wall portion  233  of the accommodation portion  235 . Therefore, the side face formed inside the accommodation portion  235  is inclined steeply. The electrode  310  may be set to the engaging pawl  239  having such a shape by pressing from above using elastic deformation of the engaging pawls  239  themselves and elastic deformation of the electrode  310 , while the electrode  310 , once set, does not move upward but contacts the lower faces of the engaging pawls  239 . 
         [0078]    Note that, when the platen  230  according to a series of embodiments as described above is supplied as a single piece to replace the platen  230  having the existing electrode, the same advantageous effects may be obtained in the existing liquid ejecting apparatus and the existing recording medium. In addition, in the case of the embodiment shown in  FIG. 13 , it is possible to assemble the electrode  310 , the absorption member  236 , or the like, which are removed from the existing platen  230 , to the platen body  232 , which is supplied as a single piece. 
         [0079]      FIG. 14  is a plan view that shows a process of assembling the electrode  310  to the platen body  232  according to yet another embodiment. As shown in the drawing, in this embodiment, a plurality of through-holes  318  are formed in the electrode  310 . On the other hand, salients  229 , each having a smaller diameter than the inner diameter of the through-hole  318  of the electrode  310 , are formed on the bottom portion  231  of the accommodation portion  235  of the platen  230  at positions corresponding to the through-holes  318 . 
         [0080]      FIG. 15  is a partially enlarged view that shows the platen body  232  in a state shown in  FIG. 14 .  FIG. 15  shows a region surrounded by dotted line XV in  FIG. 14 . As shown in the drawing, by inserting the salients  229  to the corresponding through-holes  318 , it is possible to set the electrode  310  so as to contact the bottom portion  231  of the accommodation portion  235 . 
         [0081]      FIG. 16  is a plan view that shows the next process of assembling the electrode  310  to the platen body  232  as viewed in the same direction as that of  FIG. 14 . As shown in the drawing, in this process, the distal end of each salient  229  is expanded to have a diameter larger than the inner diameter of the through-hole  318 . In this manner, the electrode  310  is fixed to the bottom portion  231  of the accommodation portion  235 . 
         [0082]      FIG. 17  is a partially enlarged view of the platen body  232  shown in  FIG. 16 .  FIG. 17  shows a region surrounded by dotted line XVII in  FIG. 16 . As shown in the drawing, the distal end of each salient  229  is caulked through a method, which will be described later, and caulked dents  227  are formed as shown in the drawing. 
         [0083]      FIG. 18  is a cross-sectional view that shows the positional relationship between the salient  229  and the through-hole  318  in a state shown in  FIG. 14  and  FIG. 15 . As shown in the drawing, each of the salients  229  extends upward from the bottom portion  231  of the accommodation portion  235  is inserted into the corresponding through-hole  318  of the electrode  310  and then extends to the upper side beyond the upper face of the electrode  310 . 
         [0084]      FIG. 19  is a cross-sectional view that shows the shape of each salient  229  and a process of forming the salient  229  in a state shown in  FIG. 16  and  FIG. 17 . As shown in the drawing, by pressing a heating jig  226  against the distal end of the salient  229 , the salient  229  is spread out horizontally. In this manner, portion of the salient  229  is expanded to the upper face of the electrode  310  beyond a region of the through-hole  318 . Thus, it is possible to prevent the electrode  310  from being displaced upward. 
         [0085]    Note that, in the structures shown in  FIG. 14  to  FIG. 19 , because the salients  229  are deformed in a state where the salients  229  are inserted in the through-holes  318 , the tolerance of each through-hole  318  and the tolerance of each salient  229  may be set relatively large. Thus, extremely high machining accuracy is not required for manufacturing the electrode  310  and the platen body  232  and, therefore, manufacturing is easy. 
         [0086]    In addition, the shape of a retaining portion of the platen body  232  for retaining the electrode  310  is not limited to the above described columnar shape of the salient  229 . Furthermore, in the above embodiment, the procedure of assembling the electrode  310  to the platen body  232  is described. However, when the platen body  232  is manufactured, it is possible to initially manufacture the platen body  232  together with the electrode  310  integrally using molding. In this case, it is possible to omit a process of deforming the distal end of the salient  229 . Furthermore, in place of the retaining portion, the electrode  310  may be bonded to the platen body  232  with an adhesive. 
         [0087]    Moreover, the platen  230  provided with the electrode that is fixed to the platen body  232  as described above may be supplied as a single piece. In this manner, in the existing liquid ejecting apparatus provided with the electrode  310  as well, it is possible to prevent failure caused by a displacement of the electrode  310  due to electric field. 
         [0088]    In addition, the ink jet recording apparatus, which is mounted in the multi functional printer  100  as the recording unit  110 , is described as an example of the liquid ejecting apparatus here. However, the liquid ejecting apparatus may include an apparatus provided with a color material ejecting head, as a liquid ejecting head, used for manufacturing a color filter for a liquid crystal display, an apparatus provided with an electrode material (conductive paste) ejecting head, as a liquid ejecting head, used for forming an electrode for an organic EL display or a field emission display (FED), an apparatus provided with a bio-organic material ejecting head and a precision pipette, as a liquid ejecting head, used for manufacturing a bio-chip. In addition, the recording object generally indicates an object to which liquid ejected from a liquid ejecting head may be adhered. The recording object may include, in addition to the sheet of recording paper, a circuit board, a disc-shaped optical recording medium, a preparation, and the like. 
         [0089]    Furthermore, the aspects of the invention are described using the embodiments, but the scope of the invention is not limited to the embodiments described above. It is apparent to a person skilled in the art that the above embodiments may be modified into various forms. In addition, the scope of the invention also encompasses such modified embodiments and will be apparent from the appended claims.