Patent Abstract:
There is provided a liquid ejecting apparatus including a liquid ejecting head that ejects liquid from an aperture of a nozzle plate toward a recording material while reciprocating over the recording material and a platen that supports the recording material from a rear face thereof to position the recording material at a position facing the nozzle plate in a direction in which the liquid is ejected. The liquid ejecting apparatus further includes: a first electrode being provided on the platen side between the liquid ejecting head and the platen; a second electrode being provided on the liquid ejecting head side between the liquid ejecting head and the platen; and a potential difference generating section of which one end is connected to the first electrode and the other end is connected to the second electrode and that generates a potential difference between the second electrode and the first electrode.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent application claims priority from Japanese Patent Applications Nos.: 2005-311950 and 2005-311951 both filed in JP on Oct. 26, 2005, the contents of which are incorporated herein by reference. 
   BACKGROUND 
   1. Field of the Invention 
   The present invention relates to a liquid ejecting apparatus, a recording apparatus, and a field generating unit. More particularly, the present invention relates to a liquid ejecting apparatus and a recording apparatus for attaching liquid discharged from an aperture of a nozzle plate mounted on a liquid ejecting head to a recording material, and a field generating unit capable of being used in these apparatuses. 
   2. Related Art 
   In a liquid ejecting apparatus, according to the demand for resolution improvement of a recording image, a droplet discharged from an aperture of a nozzle plate in a current liquid ejecting apparatus is miniaturized up to about several pl or pico-litter. Since such a minute droplet has extremely small mass, kinetic energy is rapidly lost by viscous resistances of an atmosphere once the droplet is discharged. Specifically, the speed of droplet becomes substantially zero, for example, when a droplet less than 3 pl flies a distance of about 3 mm in the atmosphere. Since a falling motion by acceleration of gravity and a viscous resistance force of an atmosphere are nearly balanced in a minute droplet of which kinetic energy is lost, it takes a long time to fall completely. 
   Moreover, in order to give larger kinetic energy to a droplet, it is also possible to raise jet velocity of liquid ejected from a liquid ejecting head. However, when actually increasing jet velocity from the nozzle plate, it is easy to produce an extremely minute droplet referred to as an ink mist when a droplet leaves the nozzle plate. Moreover, since viscous resistance of an atmosphere acting on each droplet becomes still larger, it is found that a travel distance of the droplet shortens rather than that of a droplet before increasing jet velocity. 
   A floating droplet produced as a result of various phenomena as described above is referred to as an aerosol, and floats in the vicinity of a traveling area of the liquid ejecting head. A part of aerosols floats up to an outside of the liquid ejecting apparatus, and thus adheres to the vicinity of the liquid ejecting apparatus to deface the apparatus. Moreover, most of aerosols adhere to each portion within the liquid ejecting apparatus before long. Particularly, when aerosols adhere on a carrying path of a recording material such as a platen, a recording material to be next carried is polluted. Moreover, when aerosols adhere to an electric circuit, a rotary scale, a linear scale, or various types of optical sensors of the liquid ejecting apparatus, this may cause malfunction of the apparatus. Furthermore, when a user touches a portion to which aerosols adhere, a hand of the user is polluted. 
   A liquid ejecting apparatus described in the following Japanese Patent Application Publication 2005-186290 forms an electric field between a nozzle plate and a matter to be processed to make Coulomb force facing the matter act on a droplet. In this way, it is described to make the droplet surely arrive at the matter to prevent the generation of aerosols. Moreover, Japanese Patent Application Publication 2005-186290 proposes that electrification of a matter to be processed caused by attaching the charged liquid to the matter is prevented by reversing the polarity of voltage to be applied to the matter. 
   However, the configuration disclosed in Japanese Patent Application Publication 2005-186290 includes, as essential components, a switching means for reversing the polarity of applied voltage, a control means for measuring a timing of switching, or the like, in addition to a voltage applying means for applying a voltage to a matter to be processed. Therefore, the magnitude and manufacturing cost of the liquid ejecting apparatus just have to be raised in order to realize a configuration as described in Japanese Patent Application Publication 2005-186290. 
   SUMMARY 
   Therefore, it is an object of some aspects of the present invention to provide a liquid ejecting apparatus, a recording apparatus, and a field generating unit that can solve the foregoing problems. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention. 
   To solve this problem, according to the first aspect of the present invention, there is provided a liquid ejecting apparatus including a liquid ejecting head that has a nozzle plate and ejects liquid from an aperture of the nozzle plate toward a recording material while reciprocating over the recording material and a platen that supports the recording material from a rear face thereof to position the recording material at a position facing the nozzle plate in a direction in which the liquid is ejected. The liquid ejecting apparatus includes: a first electrode being provided on the platen side between the liquid ejecting head and the platen; a second electrode being provided on the liquid ejecting head side between the liquid ejecting head and the platen; and a potential difference generating section of which one end is connected to the first electrode and the other end is connected to the second electrode and that generates a potential difference between the second electrode and the first electrode. 
   The potential difference generating section may constantly keep a potential difference between the second electrode and the first electrode. 
   The second electrode may be a conductive nozzle plate and the first electrode may be electrically coupled to the recording material supported on the platen. Moreover, the liquid ejecting apparatus may generate an electric field between the nozzle plate and the recording material on the platen to electrically attract liquid ejected from the aperture of the nozzle plate toward the recording material. In this way, an electric field is formed between the nozzle plate and the recording material. In this way, since the ejected droplet surely arrives at the recording material, the generation of aerosols is prevented. Moreover, a potential difference between the nozzle plate and the recording material generating this electric field is constantly kept by the potential difference generating section. Therefore, since the electric field is constantly kept even if the charged liquid adheres to the recording material, it is not necessary to provide a switching means of an applied voltage or a control means for controlling a switching timing. 
   Moreover, in the liquid ejecting apparatus, the first electrode may be mounted on the platen, and be electrically coupled to the recording material supported on the platen. 
   Moreover, in the liquid ejecting apparatus, the first electrode may include a conductive member mounted on a part in the platen abutting on the rear face of the recording material. In this way, since the first electrode touches the recording material right under the nozzle plate to control the potential, it is possible to efficiently control electric potential of the recording material. 
   Moreover, in the liquid ejecting apparatus, the first electrode may include a conductive member mounted through the platen in a direction in which the liquid is ejected, and one end of the first electrode may be in contact with the recording material and the other end may be electrically connected to the potential difference generating section. In this way, wiring for connecting the first electrode to the potential difference generating section can be performed in the rear face of the platen. Therefore, the layout in the liquid ejecting apparatus becomes easy. 
   Moreover, in the liquid ejecting apparatus, the first electrode may include a conductive member being in contact with the recording material on at least one side of just before and just after the platen on a carrying path of the recording material. In this way, it is possible to select an arbitrary place and an arbitrary material to form the first electrode. 
   Moreover, the liquid ejecting apparatus may further include: a carrying portion that includes a rotationally driven carrier driving roller and a carrier driven roller rotated with the rotation of the carrier driving roller while pressing the recording material on the carrier driving roller and sends the recording material onto the platen; and a discharging portion that includes a rotationally driven discharge driving roller and a discharge driven roller rotated with the rotation of the discharge driving roller while pressing the recording material on the discharge driving roller and sends away the recording material from the top of the platen, at least one of the carrier driving roller, the carrier driven roller, the discharge driving roller, and the discharge driven roller may be a conductive roller formed of a conductive material, and the conductive roller may be electrically coupled to the recording material as the first electrode. In this way, the electric field is formed between the nozzle plate and the recording material. In this way, since the ejected droplet surely arrives at the recording material, the generation of aerosols is prevented. Moreover, a potential difference between the nozzle plate and the recording material generating this electric field is constantly kept by the potential difference generating section. Therefore, since the electric field is constantly kept even if the charged liquid adheres to the recording material, it is not necessary to provide a switching means of an applied voltage or a control means controlling a switching timing. 
   Moreover, in the liquid ejecting apparatus, the carrier driving roller and the discharge driving roller may be the conductive roller. In this way, since the recording material is coupled to the potential difference generating section just before and just after the platen, the electric potential of the recording material on the platen is stabilized. 
   Moreover, in the liquid ejecting apparatus, the carrier driven roller and the discharge driven roller may be the conductive roller. In this way, the liquid ejecting apparatus can control the electric potential of recording material by means of an existing member. In this way, since the recording material is coupled to the potential difference generating section just before and just after the platen, the electric potential of recording material on the platen is stabilized. Moreover, since the carrier driven roller and the discharge driven roller have simple support structure, the electric coupling to the potential difference generating section is easy. 
   Moreover, in the liquid ejecting apparatus, all of the carrier driving roller, the carrier driven roller, the discharge driving roller, and the discharge driven roller may be the conductive roller. In this way, it is possible to surely control the electric potential of recording material passing over the platen. 
   Furthermore, according to the second aspect of the present invention, there is provided a field generating unit mounted on a liquid ejecting apparatus including a liquid ejecting head that has a nozzle plate and ejects liquid from an aperture of the nozzle plate toward a recording material while reciprocating over the recording material and a platen that supports the recording material from a rear face thereof to position the recording material at a position facing the nozzle plate in a direction in which the liquid is ejected. The field generating unit includes: a first electrode being provided on the platen side between the liquid ejecting head and the platen; a second electrode being provided on the liquid ejecting head side between the liquid ejecting head and the platen; and a potential difference generating section of which one end is connected to the first electrode and the other end is connected to the second electrode and that generates a potential difference between the second electrode and the first electrode. In this way, a generation prevention function of the described above aerosol can be added to the existing liquid ejecting apparatus that did not have such a function at first. 
   The second electrode may be a conductive nozzle plate, the first electrode may be electrically coupled to the recording material supported on the platen, and the field generating unit may generate an electric field between the nozzle plate and the recording material on the platen to electrically attract liquid ejected from the aperture of the nozzle plate toward the recording material. In this way, a generation prevention function of the described above aerosol can be added to the existing liquid ejecting apparatus that did not have such a function at first. 
   Moreover, in the liquid ejecting apparatus on which the field generating unit is mounted, the first electrode may be mounted on the platen, and be electrically coupled to the recording material supported on the platen. 
   Moreover, the liquid ejecting apparatus on which the field generating unit is mounted may further include: a carrying portion that includes a rotationally driven carrier driving roller and a carrier driven roller rotated with the rotation of the carrier driving roller while pressing the recording material on the carrier driving roller and sends the recording material onto the platen; and a discharging portion that includes a rotationally driven discharge driving roller and a discharge driven roller rotated with the rotation of the discharge driving roller while pressing the recording material on the discharge driving roller and sends away the recording material from the top of the platen, at least one of the carrier driving roller, the carrier driven roller, the discharge driving roller, and the discharge driven roller may be a conductive roller formed of a conductive material, and the conductive roller may be electrically coupled to the recording material as the first electrode. In this way, a contamination prevention function by the described above aerosol can be added to the existing liquid ejecting apparatus that did not have such a function at first. 
   Moreover, according to the third aspect of the present invention, there is provided a recording apparatus including a recording head that has a nozzle plate and discharges ink from an aperture of the nozzle plate toward a recording material while reciprocating over the recording material and a platen that supports the recording material from a rear face thereof to position the recording material at a position facing the nozzle plate in a direction in which the ink is discharged. The recording apparatus includes: a first electrode being provided on the platen side between the liquid ejecting head and the platen; a second electrode being provided on the liquid ejecting head side between the liquid ejecting head and the platen; and a potential difference generating section of which one end is connected to the first electrode and the other end is connected to the second electrode and that generates a potential difference between the second electrode and the first electrode. In this way, the recording apparatus can prevent the generation of an aerosol. 
   Moreover, the second electrode may be a conductive nozzle plate, the first electrode may be electrically coupled to the recording material supported on the platen, and the recording apparatus may generate an electric field between the nozzle plate and the recording material on the platen to electrically attract ink ejecting from the aperture of the nozzle plate toward the recording material. 
   Moreover, in the recording apparatus, the first electrode may be mounted on the platen, and be electrically coupled to the recording material supported on the platen. 
   Moreover, the recording apparatus may further include: a carrying portion that includes a rotationally driven carrier driving roller and a carrier driven roller rotated with the rotation of the carrier driving roller while pressing the recording material on the carrier driving roller and sends the recording material onto the platen; and a discharging portion that includes a rotationally driven discharge driving roller and a discharge driven roller rotated with the rotation of the discharge driving roller while pressing the recording material on the discharge driving roller and sends away the recording material from the top of the platen, at least one of the carrier driving roller, the carrier driven roller, the discharge driving roller, and the discharge driven roller may be a conductive roller formed of a conductive material, and the conductive roller may be electrically coupled to the recording material as the first electrode. In this way, the recording apparatus prevents the generation of an aerosol. 
   The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features and advantages of the present invention will become more apparent from the following description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a perspective view surveying the whole of an ink-jet type recording apparatus; 
       FIG. 2  is a perspective view showing an internal mechanism of an ink-jet type recording apparatus; 
       FIG. 3  is a sectional view showing a structure of an aerosol generation preventing mechanism according to an embodiment; 
       FIG. 4  is a schematic block diagram explaining an operation of an aerosol generation preventing mechanism; 
       FIG. 5  is a sectional view showing a structure of an aerosol generation preventing mechanism according to another embodiment; 
       FIG. 6  is a sectional view showing a structure of another aerosol generation preventing mechanism; 
       FIG. 7  is a sectional view showing a structure of further another aerosol generation preventing mechanism; 
       FIG. 8  is a sectional view showing a structure of further another aerosol generation preventing mechanism; 
       FIG. 9  is a schematic block diagram explaining an operation of an aerosol generation preventing mechanism; 
       FIG. 10  is a sectional view showing a structure of an aerosol generation preventing mechanism according to another embodiment; and 
       FIG. 11  is a sectional view showing a structure of another aerosol generation preventing mechanism. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   The embodiments of the invention will now be described based on the preferred embodiments, which do not intend to limit the scope of the present invention, but just exemplify the invention. All of the features and the combinations thereof described in the embodiment are not necessarily essential to the invention. 
     FIG. 1  is a perspective view surveying an ink-jet type recording apparatus  10  that is an example of an embodiment of the present invention, and shows a state that a top case  110  as a cover is opened. As shown in the present drawing, the ink-jet type recording apparatus  10  includes a bottom case  120  that is a base of the apparatus, a top case  110  that forms a casing with the bottom case  120 , a paper support  130  that is mounted to a rear portion of the bottom case  120 , and a discharge tray  140  that is formed on a front face of the bottom case  120 . Moreover, the ink-jet type recording apparatus  10  includes a platen  150  that is horizontally arranged in the bottom case  120  and a carriage  160  that is arranged on the upper side of the platen  150 , on the inner side of the casing. 
   In the ink-jet type recording apparatus  10  as described above, a data sheet  170  accommodated on the paper support  130  is sent onto an inside one piece by one piece by means of a feeding portion not shown, and is next sent to the platen  150  by means of a carrying portion not shown. Further, the data sheet is sent to the discharge tray  140  by means of a discharge portion not shown. Moreover, in each of the feeding portion, the carrying portion, and the discharge portion, the data sheet  170  is feed, carried, and discharged while holding the sheet between a rotationally driven driving roller and a driven roller rotated with the rotation of the driving roller. 
   Moreover, in the ink-jet type recording apparatus  10 , the carriage  160  reciprocates in the direction perpendicular to a transportation direction of the data sheet  170  on the upper side of the platen  150 . Therefore, since the transportation of the data sheet  170  and the reciprocation of the carriage  160  are performed alternately, the whole top face of the data sheet  170  can be scanned by the carriage  160 , and thus the carriage  160  can perform a record operation at an arbitrary area on the data sheet  170 . 
     FIG. 2  is a perspective view showing an internal mechanism  20  of the ink-jet type recording apparatus  10  shown in  FIG. 1  in a state that a frame  210  including side face portions  212  and  214  is pulled out. As shown in the present drawing, the internal mechanism  20  is mainly formed inside an area bounded by the frame  210  that is arranged backward and generally vertically and the pair of side face portions  212  and  214  that are extended from both ends of the frame  210  to the front parallel to each other. 
   As shown in the present drawing, in the internal mechanism  20 , the carriage  160  is supported by a guide shaft  220  penetrating through the carriage. Both ends of the guide shaft  220  are supported by the side face portions  212  and  214 , and the guide shaft  220  is arranged parallel and horizontally to the frame  210 . Therefore, the carriage  160  can horizontally move along the guide shaft  220 . 
   At the back of the carriage  160 , a pair of pulleys  232  and  234  and a timing belt  230  that is hung on the pulleys  232  and  234  are arranged in the front of the frame  210 . One pulley  234  is rotationally driven by a carriage motor  236 . Moreover, the timing belt  230  is coupled to a rear portion of the carriage  160 . Therefore, the carriage  160  can be reciprocated according to an operation of the carriage motor  236 . 
   Moreover, the carriage  160  loads an ink cartridge  162  from the upper side, and also includes a recording head  164  in the lower part. The recording head  164  includes a nozzle plate  166  made of metal including an aperture to discharge ink on the upper face. Therefore, ink is discharged from the carriage  160  toward the lower side. Furthermore, the carriage  160  is coupled with an electronic circuit  250  in the rear of the frame  210  via a tape-shaped multicore cable  240 . Since the multicore cable  240  is flexibly bended according to a movement of the carriage  160 , the multicore cable  270  does not disturb a reciprocation of the carriage  160 . 
   The platen  150  is arranged on the lower side of an area along which the carriage  160  reciprocates. The platen  150  supports the data sheet  170  passing along a bottom of the carriage  160  from the lower side, in order to hold a distance between the nozzle plate  166  and the data sheet  170  constant. Moreover, a concavity  152  is formed on a top face of the platen  150  and an absorbing member  260  is accommodated in the concavity  152 . The absorbing member  260  receives ink discharged from the recording head  164  toward an area on which the data sheet  170  does not exist. 
   In addition, as the operating time of the ink-jet type recording apparatus  10  elapses, ink adheres to the absorbing member  260 . When the data sheet  170  comes in contact with the absorbing member  260  to which ink adheres, a rear face of the data sheet  170  is contaminated with ink. Thus, since a rib-shaped portion is formed on a top face of the platen  150  to lift and support the data sheet  170  from the lower side, an interval between them is maintained to prevent them from being in contact with each other. Specifically, a gap of around 2 to 4 mm is provided between the data sheet  170  and the absorbing member  260 . In addition, an interval of about 1 mm is preserved between a surface of the nozzle plate  166  and surfaces of the data sheet  170 . 
   Moreover, since a material of the absorbing member  260  is selected in consideration of absorption velocity on the surface, absorption capacity is limited. Thus, a larger waste liquid absorbing member  262  is arranged on the lower side of the platen  150 , and the absorbing member  262  partially comes in contact with the absorbing member  260 . In the waste liquid absorbing member  262 , the absorption capacity is important, and thus a material having large absorbing power by a capillary phenomenon is selected. Therefore, the waste liquid absorbing member  262  can absorb a large quantity of ink from the absorbing member  260 . 
   Moreover, the absorbing member  260  directly receives ink not attached to the data sheet  170  while being discharged from the nozzle plate  166 . At this time, when the absorption velocity of the absorbing member  260  is slow, so-called a milk crown phenomenon occurs due to an impact by which the ink collides with the surface of the absorbing member  260 . Minute ink occurs on the periphery of a milk crown, and the ink causes the generation of aerosols. Thus, as the absorbing member  260 , a material having high absorption velocity, in other words, high percentage of voids is selected. 
   Moreover, the absorbing member  260  partially communicates with the waste liquid absorbing member  262  arranged beneath the platen  150  in  FIG. 2 , in which this configuration is not shown. For this reason, since ink absorbed by the absorbing member  260  is sequentially absorbed by the waste liquid absorbing member  262  having high absorbing power, the absorbing power of the absorbing member  260  lasts over a long term. 
   On the other hand, the carrier driving roller  282  and the carrier driven roller  284  are arranged at the back of the platen  150  to from the carrying portion  280 . The carrier driving roller  282  is rotationally driven by a carrying motor  286  arranged in the rear of the frame  210 . Moreover, the carrier driven roller  284  presses the data sheet  170  on the carrier driving roller  282 . Therefore, the carrier driven roller  284  is rotated according to the rotation of the carrier driving roller  282 , and the data sheet  170  is sent away on the platen  150 . Since ink is discharged from the carriage  160  on the platen  150  as described above, an image can be recorded by ink on the data sheet  170 . 
   Moreover, the discharge driving roller  292  and the discharge driven roller  294  are arranged at the front of the platen  150  to form the discharging portion  290 . The discharge driving roller  292  is rotationally driven by power distributed from the carrying motor  286 . Moreover, the discharge driven roller  294  presses the data sheet  170  passing over the platen  150  on the discharge driving roller  292 . Therefore, the discharge driven roller  294  is rotated according to the rotation of the discharge driving roller  292 , the data sheet  170  is sent away from the platen  150  to an outside. 
   Furthermore, in the internal mechanism  20 , a cap member  270  is arranged at a lateral side of the platen  400  near the side face portion  212 . The cap member  270  can move up and down, and thus ascends and seals a lower face of the nozzle plate  166  when the carriage  160  stops at the home position near the side face portion  212 . Moreover, an inside of the cap member  270  is coupled with a pump unit  272 . The pump unit  272  can absorb ink attached to the surface of the nozzle plate  166 . The ink absorbed by the pump unit  272  is absorbed into the waste liquid absorbing member  262  through a pipe not shown. 
   Furthermore, a wiping means  274  is arranged between the platen  150  and the cap member  270 . When the carriage  160  released from the sealing by the cap member  270  passes above the wiping means  274 , the wiping means  274  wipes out the lower part of the nozzle plate  166  to clean it. 
     FIG. 3  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  31  formed in the ink-jet type recording apparatus  10  as described above. As shown in the present drawing, the platen  150  includes a rib portion  154  protruded upward, and positions the data sheet  170  up and down by supporting the rib portion from the lower part on the upper end. Furthermore, a rib electrode  156  made of metal is mounted on an upper end of the rib portion  154 . The rib electrode  156  is electrically connected to a positive pole of the potential difference generating means  330  via a short protecting resistor  320  and also contacts a lower face of the data sheet  170 . Therefore, when the potential difference generating means  330  operates, the data sheet  170  has the same electric potential as that of the positive pole of the potential difference generating means  330 . 
   On the other hand, the nozzle plate  166  is connected to a negative pole of the potential difference generating means  330 . Therefore, a potential difference according to the potential difference generated from the potential difference generating means  330  is generated between the data sheet  170  and the nozzle plate  166 , and electric field E according to the potential difference is formed between both. In addition, the potential difference generating means  330  is a constant voltage generating circuit, and adjusts an output so that the potential difference becomes an original value when the potential difference between the nozzle plate  166  and the rib electrode  156  is changed by some kind of cause. In this manner, the rib electrode  156  forms a potential controlling electrode for the data sheet  170 . 
   In the above aerosol generation preventing mechanism  31 , the rib electrode  156  can be formed of metal having high resistance to wear and high conductivity such as stainless steel, iron plated with nickel, duralumin, iron including chrome or molybdenum, tungsten, titanium, alloy including titanium. Moreover, the rib electrode  156  can be integrated with the platen  150  by embedding, attaching, and two-body shaping using a material such as carbon, metal, conductive polymer. Furthermore, the rib electrode  156  can be formed by partially depositing an amorphous semiconductor such as selenium and silicon or metal on the rib portion  154 . 
     FIG. 4  is a schematic block diagram explaining an operation of the above aerosol generation preventing mechanism  31 . As shown in the present drawing, a plurality of apertures  168  for discharging ink is formed in the nozzle plate  166 . Moreover, as shown with an arrow X in the present drawing, the nozzle plate  166  moves from right to left on the present drawing with the movement of the carriage  160 . 
   Meanwhile, ink pushed from the aperture  168  of the nozzle plate  166  forms an ink pillar  340  drooping from the nozzle plate  166  at the moment immediately before the ink becomes an ink drop  342 . At this time, electric charges are accumulated by so-called lightning conductor effect between a leading end A of the ink pillar  340  and an area B adjacent to the ink pillar  340  on a lower face of the nozzle plate  166 . 
   That is, the above lightning conductor effect means that the area B on the surface of the nozzle plate  166  surrounded with a conical shape including a range of a vertex angle from 50° to 60° with the leading end A (a bottom end in the present drawing) of the ink pillar  340  at the top contributes to the charge of the ink drop  342 . By this lightning conductor effect, the ink drop  342  has an electric charge q larger than that corresponding to a horizontal cross-section area of the ink pillar  340  and equal to that of the nozzle plate  166 . 
   On the other hand, in the aerosol generation preventing mechanism  31 , an electric field E is formed between the nozzle plate  166  and the rib electrode  156  and the data sheet  170 . As described above, since the ink drop  342  is charged with an electric charge q, the ink drop  342  obtains kinetic energy by a Coulomb force F (qE) from the electric field E, and thus moves on the lower side without deceleration to finally arrive at the data sheet  170 . In this manner, in the electric field E, the generation of aerosols is prevented because the ink drop  344  surely arrives at the data sheet  170 . 
   In addition, in the ink-jet type recording apparatus  10  as shown in  FIGS. 1 to 4 , in order to make a Coulomb force act on the ink drop  342  to prevent the generation of aerosols, it is desirable to set field intensity of the electric field E to the order of 100 kV/m. Moreover, when a potential difference is formed using the nozzle plate  166  as one electrode in order to form such an electric field, an electric charge accumulated in a droplet discharged from the nozzle plate  166  is about 4*10-14Q. 
   On the other hand, when the data sheet  170  is general premium grade paper or paper made by coating porous silica on the premium grade paper, the volume resistivity is about 107 to 1013 Ωcm. When ink having electrical conductivity penetrates such a data sheet  170 , the volume resistivity deteriorates to 105 to 107 Ωcm. Moreover, surface resistivity of the data sheet  170  to which the ink adheres becomes about 103 to 107 Ω/square. 
   Therefore, when the rib electrode  156  formed of metal having sufficiently high electrical conductivity touches the data sheet  170  to be connected to the potential difference generating means  330 , electric potential of the data sheet  170  can be controlled so as to be identical with an output voltage from the potential difference generating means  330  by going through the data sheet  170  itself and the ink on the data sheet  170 . Moreover, since electric charges in the ink drop  342  is discharged through the data sheet  170  and the ink  344  already attached to the sheet when the charged ink drop  342  is deposited on the data sheet  170 , electric potential on the data sheet  170  does not vary. 
   Moreover, in the above embodiment, the rib electrode  156  is connected to a positive pole side of the potential difference generating means  330  and the nozzle plate  166  is connected to a negative pole side of the potential difference generating means  330 . However, although all polarities are reversely connected, a similar function is realized. Moreover, it is possible to simplify wiring within the aerosol generation preventing mechanism  31  by setting electric potential of one end of the potential difference generating means  330  to ground potential. 
     FIG. 5  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  32  according to another embodiment. In addition, in  FIG. 5 , the same reference numbers are put on components common to the other drawings and the description is omitted. 
   As shown in the present drawing, a structure of the aerosol generation preventing mechanism  32  according to this embodiment has a characteristic peculiar to the shape of the rib electrode  156 . That is to say, this rib electrode  156  penetrates through the rib portion  154  of the platen  150  up and down to expose the lower end on the lower face of the platen  150 . Therefore, wiring from the rib electrode  156  and the potential difference generating means  330  can be coupled in the lower part of the platen  150 . According to such a structure, since wiring is not shown to a user even if a function as the rib electrode  156  and the aerosol generation preventing mechanism  32  equals to that of the aerosol generation preventing mechanism  31  shown in  FIG. 3 , safety and merchantability are high. 
     FIG. 6  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  33  according to further another embodiment. In addition, in  FIG. 6 , the same reference numbers are put on components common to the other drawings and the description is omitted. 
   As shown in the present drawing, a structure of the aerosol generation preventing mechanism  33  according to this embodiment has a characteristic peculiar to the shape of the rib electrode  156 . That is to say, this rib electrode  156  is formed of an electrically conducting layer  157  formed on the whole surface of the platen  150 . Such an electrically conducting layer  157  can be formed by two-body shaping with the platen  150  in addition to application or vapor deposition to the platen  150 . According to such a structure, although a function as the electrically conducting layer  157  as a potential controlling electrode and the aerosol generation preventing mechanism  33  equals to that of the aerosol generation preventing mechanism  31  shown in  FIG. 3 , since a contact area between the data sheet  170  and the rib electrode  156  becomes wide to the maximum, both stably have the same electric potential. Therefore, an operation as the aerosol generation preventing mechanism  32  is also stable. 
     FIG. 7  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  34  according to further another embodiment. In addition, in  FIG. 7 , the same reference numbers are put on components common to the other drawings and the description is omitted. 
   In the embodiment shown in the present drawing, a plurality of conductive brushes  350  is arranged closest to the platen  150  as a means for obtaining electrical connection to the data sheet  170 . Each conductive brush  350  is formed of a member having electrical conductivity and elasticity, and one end thereof is electrically connected to the potential difference generating means  330 . Moreover, the other end of the conductive brush  350  contacts the data sheet  170  at a plurality of points. That is to say, the conductive brushes  350  are arranged on a surface and a rear face of the data sheet  170  immediately before the platen  150  in a transportation direction of the data sheet  170 , and respectively contact the surface and the rear face of the data sheet  170 . Moreover, the conductive brush  350  is arranged on the rear face side of the data sheet  170  immediately after the platen  150 , and contacts the rear face of the data sheet  170 . 
   Such a configuration should introduce a dedicated member referred to as the conductive brush  350 . However, since the conductive brush  350  is a dedicated part for obtaining electrical connection, arrangement can be freely selected. Therefore, the conductive brush can be arranged closest to the platen  150 , the nozzle plate  166 , and so on related to aerosol collection, and thus electric potential of the data sheet  170  can be efficiently controlled. In addition, the conductive brush  350  can be formed of resin fiber containing carbon or metal powder in addition to a metal wire rod such as stainless steel. 
     FIG. 8  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  531  according to further another embodiment. As shown in the present drawing, the platen  150  includes a rib portion  154  protruding upward, and supports the data sheet  170  on the upper end from the lower part to position the data sheet  170  up and down. Here, in order to attach ink discharged from the recording head  164  to the data sheet  170 , it is necessary to carry the data sheet  170  from the outside to feed it onto the platen  150 . Moreover, the data sheet  170  to which ink adheres on the platen  150  is sent away from the top of the platen  150  to the outside to be discharged. Transportation and discharge of the data sheet  170  are performed by a carrying portion  280  and a discharging portion  290  each including a pair of rollers. 
   The carrying portion  280  includes a carrier driving roller  282  contacting the lower face of the data sheet  170  and a carrier driven roller  284  contacting the upper face of the data sheet  170  to press it on the carrier driving roller  282 . Here, the carrier driving roller  282  is rotationally driven by a carrying motor  286 . On the other hand, the carrier driven roller  284  does not have driving force, and is rotated with the rotation of the carrier driving roller  282  while pressing the data sheet  170  on the carrier driving roller  282 . These carrier driving roller  282  and carrier driven roller  284  continues to touch the data sheet  170  from the leading end to the rear end of the data sheet  170  during carrying the sheet. Therefore, the carrier driving roller  282  is formed of a conductive material and is also connected to the potential difference generating means  330  so that electric potential of the data sheet  170  can be controlled via the carrying portion  280 . 
   The discharging portion  290  includes a discharge driving roller  292  contacting the lower face of the data sheet  170  and a discharge driven roller  294  contacting the upper face of the data sheet  170  to press it on the discharge driving roller  292 . Here, the discharge driving roller  292  is rotationally driven by the carrying motor  286  via transfer mechanism not shown. On the other hand, the discharge driven roller  294  does not have driving force, and is rotated with the rotation of the discharge driving roller  292  while pressing the data sheet  170  on the discharge driving roller  292 . These discharge driving roller  292  and discharge driven roller  294  continues to touch the data sheet  170  from the leading end to the rear end of the data sheet  170  during carrying the sheet. Therefore, the discharge driving roller  292  is formed of a conductive material and is connected to the potential difference generating means  330  so that electric potential of the data sheet  170  can be controlled via the discharging portion  290 . 
   Furthermore, both of the discharge driving roller  292  and the discharge driven roller  294  are formed of a conductive material and is electrically connected to the potential difference generating means  330 , so that electric potential of the data sheet  170  can be continuously controlled from when the leading end of the data sheet  170  comes to the platen  150  to when the rear end passes over the platen  150 . In this embodiment, the carrier driven roller  284  and the discharge driven roller  294  are together connected to a positive pole of the potential difference generating means  330  via a short protecting resistor  320 . On the other hand, the nozzle plate  166  is connected to a negative pole of the potential difference generating means  330 . Therefore, in the ink-jet type recording apparatus  10 , electric field E is formed between the nozzle plate  166  and the data sheet  170 . 
   In addition, materials of these carrier driving roller  282  and discharge driving roller  292  can include metal material having rigidity and electrical conductivity such as iron, iron plated with nickel, stainless steel. Furthermore, in order to prevent the carrier driving roller  282  from sliding on the data sheet  170 , it is preferable to attach alumina grains to a surface of the carrier driving roller to improve frictional force of the surface. Moreover, the surface may be coated with conductive rubber instead of attaching alumina grains to the surface. 
     FIG. 9  is a schematic block diagram explaining an operation of the aerosol generation preventing mechanism  531 . As shown in the present drawing, a plurality of apertures  168  for discharging ink is formed in the nozzle plate  166 . Moreover, as shown with an arrow X in the drawing, the nozzle plate  166  moves from right toward left on the drawing with the movement of the carriage  160 . 
   When the data sheet  170  exists right under the nozzle plate  166 , the ink drop  342  is discharged from the aperture  168  of the nozzle plate  166  toward the data sheet  170 . Kinetic energy given to the ink drop  342  after being discharged from the aperture  168  is rapidly lost by viscous resistance of an atmosphere, and a part of the ink drops  342  is perfectly lost far before arriving at the data sheet  170 . Moreover, since the mass of the ink drop  342  is extremely small, a falling motion by acceleration of gravity and a viscous resistance force nearly balances, and thus fall velocity of the ink drop  342  becomes extremely late. In this way, the ink drop  342  floating beneath the nozzle plate  166  becomes an aerosol. 
   Meanwhile, ink pushed from the aperture  168  of the nozzle plate  166  becomes the ink pillar  340  drooping from the nozzle plate  166  at the moment immediately before being the ink drop  342 . At this time, electric charges are accumulated by so-called lightning conductor effect between a leading end A of the ink pillar  340  and an area B adjacent to the ink pillar  340  on the lower face of the nozzle plate  166 . 
   That is to say, the lightning conductor effect means that the area B on the surface of the nozzle plate  166  surrounded with a conical shape including a range of a vertex angle from 50° to 60° with the leading end A (a bottom end in the present drawing) of the ink pillar  340  at the top contributes to the charge of the ink drop  342 . By this lightning conductor effect, the ink drop  342  has an electric charge q larger than that corresponding to a horizontal cross-section area of the ink pillar  340  and equal to that of the nozzle plate  166 . 
   On the other hand, in the aerosol generation preventing mechanism  531 , an electric field E is formed between the nozzle plate  166  and the data sheet  170 . As described above, since the ink drop  342  is charged with the electric charge q equal to that of the nozzle plate  166 , the ink drop  342  obtains kinetic energy by a Coulomb force F (qE) from the electric field E, and thus moves on the lower side without deceleration to finally arrive at the data sheet  170 . In this manner, the generation of aerosols is prevented because the ink drop  342  in the electric field E surely arrives at the data sheet  170 . 
   In addition, in the ink-jet type recording apparatus  10  as shown in  FIGS. 2 to 9 , in order to make a Coulomb force act on the ink drop to prevent the generation of aerosols, it is desirable to set field intensity of the electric field E to the order of 100 kV/m. Moreover, when a potential difference is formed using the nozzle plate as one electrode in order to form such an electric field, an electric charge accumulated in a droplet discharged from the nozzle plate  166  is about 4*10 −14 Q. 
   On the other hand, when the data sheet  170  is general premium grade paper or paper made by coating porous silica on the premium grade paper, the volume resistivity is about 10 7  to 10 13  Ωcm. When ink having electrical conductivity penetrates such a data sheet  170 , the volume resistivity deteriorates to 10 5  to 10 7  Ωcm. Moreover, surface resistivity of the data sheet  170  to which the ink adheres becomes about 10 3  to 10 7  Ω/square. 
   Therefore, when the carrier driving roller  282  and the discharge driving roller  292  formed of metal having sufficiently high electrical conductivity touches the data sheet  170  to be connected to the potential difference generating means  330 , electric potential of the data sheet  170  can be controlled so as to be identical with an output voltage from the potential difference generating means  330  by going through the data sheet  170  itself and the ink drop  344  on the data sheet  170 . Moreover, since electric charges in the ink drop  344  is discharged through the data sheet  170  and the ink attached to the sheet when the charged ink drop  344  is deposited on the data sheet  170 , electric potential on the data sheet  170  does not vary. 
   Moreover, in the above embodiment, the data sheet  170  side is connected to a positive pole side of the potential difference generating means  330  and the nozzle plate  166  is connected to a negative pole side of the potential difference generating means  330 . However, although all polarities are reversely connected, a similar function is realized. Moreover, it is possible to simplify wiring within the aerosol generation preventing mechanism  531  by setting electric potential of one end of the potential difference generating means  330  to ground potential. 
     FIG. 10  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  532  according to further another embodiment. In  FIG. 10 , the same reference numbers are put on components common to the other drawings and the description is omitted. 
   As shown in the present drawing, in this embodiment, the carrier driven roller  284  and the discharge driven roller  294  are electrically connected to the potential difference generating means  330  in each of the carrying portion  280  and the discharging portion  290 . A function obtained in this way is similar to that of the configuration shown in  FIG. 8 . However, this embodiment has the following advantage. That is to say, the carrier driving roller  282  and the discharge driving roller  292  are mechanically coupled with rotation transfer mechanism such as a gear group for rotational driving. Therefore, using mechanical contact in the transfer mechanism, they can be electrically connected to the potential difference generating means  330 . However, in order to realize this, the whole of the rotation transfer mechanism should be formed of a conductive material. However, this kind of rotation transfer mechanism is formed of gears formed of a resin material in many cases. When this resin material is changed into a metal material, this change causes the increase of manufacturing cost and the increase of operating noises. 
   In this regard, since the carrier driven roller  284  and the discharge driven roller  294  are only supported to be able to be rotated, a potential difference controlling means can be simply formed when these rollers are formed of a conductive material and a shaft supporting means is electrically connected to the potential difference generating means  330 . In addition, materials of the carrier driven roller  284  and the discharge driven roller  294  can include iron, iron plated with nickel, metal having electrical conductivity such as stainless steel, or a resin material containing carbon or metal powder and having electrical conductivity. 
     FIG. 11  is a sectional view typically showing a structure of an aerosol generation preventing mechanism  533  according to further another embodiment. In  FIG. 11 , the same reference numbers are put on components common to the other drawings and the description is omitted. 
   As shown in the present drawing, in this embodiment, all of the carrier driving roller  282 , the carrier driven roller  284 , the discharge driving roller  292 , and the discharge driven roller  294  are formed of a conductive material and electrically connected to the potential difference generating means  330  in each of the carrying portion  280  and the discharging portion  290 . A function obtained in this way is similar to that of the configuration shown in  FIGS. 8 and 10 . However, this embodiment has the following advantage. That is to say, although each roller touches the data sheet  170 , each roller microscopically repeats contact and detachment when really carrying or discharging the data sheet  170 . For this reason, focusing attention on single roller, the roller is not stably connected to the data sheet  170 . However, since either of rollers touches the data sheet  170  as a whole by increasing the number of rollers having contact with the data sheet  170 , electric potential of the data sheet  170  can be stabilized. 
   As described above in detail, the ink-jet type recording apparatus  10  can actively collect droplets by forming an electric field between the nozzle plate  166  and the data sheet  170  to prevent the generation of aerosols. Moreover, since the data sheet can be coupled with the potential difference generating means  330  via a potential controlling electrode in order to constantly preserve electric potential of the data sheet  170 , it is not necessary to perform a complicated control such as an inversion of an applied voltage. Therefore, a liquid ejecting apparatus that does not generate aerosols can be realized with a plain structure. Furthermore, it is possible to realize a function similar to that of the existing liquid ejecting apparatus by providing the apparatus as a configuration of a field generating unit. 
   In addition, in the above embodiment, a concrete configuration has been described using the ink-jet type recording apparatus  10  as an example. However, the liquid ejecting apparatus can be implemented as a color material injection system in manufacture of a color filter for a liquid crystal display, an electrode formation apparatus in manufacture of an organic EL display, FED (a plane emission display), or the like, a sample injection head used in manufacture of a biochip, a sample injection head as a precise pipette, an apparatus that pictures a picture and a character on artificial nails, and so on, and further the liquid ejecting apparatus is not limited to them. 
   Although the present invention has been described by way of an exemplary embodiment, it should be understood that those skilled in the art might make many changes and substitutions without departing from the spirit and the scope of the present invention. It is obvious from the definition of the appended claims that embodiments with such modifications also belong to the scope of the present invention.

Technology Classification (CPC): 1