Patent Publication Number: US-7708384-B2

Title: Printing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2005-216922, filed on Jul. 27, 2005, the disclosure of which is incorporated herein by reference in its entirely. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing apparatus which performs printing by transporting a liquid onto a printing medium such as a recording paper 
     2. Description of the Related Art 
     A printing apparatus which includes an ink-jet head discharging an ink on to a printing medium, has been hitherto used widely as a printing apparatus which performs printing on various printing media such as a recording paper. Here, printing apparatuses with various structures of the ink-jet head are available, and a printing apparatus in which an ink-jet head includes a channel unit provided with a plurality of individual ink channels including a pressure chamber communicating with a nozzle, and a piezoelectric actuator which applies a pressure to an ink in the pressure chamber is an example of such printing apparatus (refer to U.S. Pat. No. 6,926,382 (corresponding to Japanese Patent Application Laid-open No. 2003-326712)). 
     A general piezoelectric actuator includes a plurality of individual electrodes corresponding with a plurality of pressure chambers, a common electrode facing the individual electrodes, and a piezoelectric layer sandwiched between the individual electrode and the common electrode, which is formed by a piezoelectric material such as lead zirconate titanate (PZT). Moreover, when a drive voltage is supplied to a predetermined individual electrode, an electric field is generated in a portion of the piezoelectric layer sandwiched between the individual electrode and the common electrode. As the electric field is generated, the piezoelectric layer is deformed partially, and with the deformation of the piezoelectric layer, a pressure is applied to the ink in the pressure chamber. As the pressure is applied to the ink, the ink is discharged from the nozzle communicating with the pressure chamber. 
     SUMMARY OF THE INVENTION 
     However, in the ink-jet head mentioned above, an actuator in which a plurality of individual ink channels of a complicated shape, in which a channel unit includes a nozzle and a pressure chamber, is formed, and a plurality of individual electrodes, a common electrode, and a piezoelectric layer are provided on a surface of the channel unit, is arranged. Since such structure is quite complicated, there is an increase in a manufacturing cost. Moreover, for discharging a certain amount of ink, it is necessary to ensure a volume of the pressure chamber more that a predetermined quantity. Therefore, it is difficult to arrange densely (compactly) the individual ink channels of the complicated shape which include the nozzle and the pressure chamber, in the channel unit (it is difficult to have highly integrated individual ink channels of the complicated shape, in the channel unit). 
     An object of the present invention is to provide a printing apparatus having a simple formation, and of which a size can be reduced easily. 
     According to a first aspect of the present invention, there is provided a printing apparatus which performs printing by discharging an electroconductive liquid onto a printing medium, including 
     a liquid transporting section which includes a channel forming surface on which a liquid channel through which the liquid flows, and a discharging section communicating with the channel unit are formed, a first electrode which is arranged on the channel forming surface, and an insulating layer formed on a surface of the electrode, which has a liquid repellent property higher than a liquid repellent property of the channel forming surface when a voltage is applied to the first electrode, and
         a transferring mechanism which transfers the liquid discharged from the discharging section of the liquid transporting section, to the printing medium.       

     According to the first aspect of the present invention, the liquid transporting section transports the liquid up to the discharging section by using a phenomenon in which, when there is an electric potential difference developed between the first electrode and the liquid, the liquid repellent property (wetting angle of the liquid) of the insulating layer on the surface of the first electrode is declined (electrowetting phenomenon: refer to Japanese Patent Application Laid-open No. 2003-177219). Therefore, as compared to the conventional ink-jet head having the complicated structure, the structure of the liquid channel and a formation of the actuator transporting the liquid are simplified, and it is possible to arrange the liquid channels and the discharging section highly densely, thereby facilitating to reduce the size of the liquid transporting section. Moreover, it is possible to transport the liquid at a comparatively lower drive voltage. 
     In the printer of the present invention, a distance between the discharging section of the liquid transporting apparatus and the transferring mechanism may be less than a diameter of a liquid which is discharged at one time from the discharging section. The transferring mechanism may be a transfer drum, and the transfer drum may be rotatably supported such that a surface of the transfer drum is close to the discharging section of the liquid transporting section. 
     Particularly, in a case in which the printing medium is a medium having a large number of minute recesses and projections on a surface, when the liquid discharged from the discharging section is let to be adhered directly to the printing medium, it is difficult to make the uniform amount of ink to be adhered stably due to the roughness on the surface of the printing medium, and there is a possibility of decline in a printing quality due to a variation in an amount of liquid adhered. However, in the printing apparatus of the present invention, after the ink is allowed to be adhered once on the surface of the transfer drum from the liquid transporting section, the transfer drum is rotated and the ink on the surface of the transfer drum is transferred to the printing medium. Therefore, it is possible to make the uniform amount of the liquid to be adhered stably to the printing medium. Moreover, since the distance between the discharging section of the liquid transporting apparatus and the transferring mechanism is less than the diameter of the liquid which is discharged at a time from the discharging section, the liquid which is discharged from the discharging section is adhered assuredly to the transfer drum. 
     Here, “the diameter of the liquid which is discharged at a time from the discharging section” means a diameter of a liquid drop having a spherical shape having a volume same as a volume of the liquid discharged at a time from the discharging section. 
     In the printing apparatus of the present invention, the liquid repellent property of the surface of the transfer drum may be lower than a liquid repellent property of an area around the discharging section of the liquid transporting section. In this case, the liquid discharged from the discharging section is not adhered to the area around the discharging section, and is transferred assuredly to the surface of the transfer drum. 
     In the printing apparatus of the present invention, the surface of the transfer drum may be provided with a liquid adhering area to which the liquid discharged from the discharging section is adhered, and a highly liquid repellent area surrounding the liquid adhering area, which has a liquid repellent property higher than a liquid repellent property of the liquid adhering area. In this case, on the surface of the transfer drum, even when the liquid is shifted away from an original liquid adhering position at which the liquid is supposed to be adhered, and adhered spreading across up to the highly liquid repellent area, the liquid moves naturally from the highly liquid repellent area having a superior (higher) liquid repellent property, to a liquid adhering position having an inferior liquid repellent property. Therefore, an adhering position of liquid droplets on the surface of the transfer drum is corrected, and a printing quality when the liquid is transferred to the printing medium, is improved. 
     In the printing apparatus of the present invention, a second electrode which is kept at a predetermined electric potential all the time, and which is in direct contact with the liquid may be formed on the channel forming surface of the liquid channel. In this case, an electric potential of the liquid in the liquid channel is fluctuated, and it is possible to generate assuredly a predetermined electric potential difference between the first electrode and the liquid, when a voltage is applied to the first electrode. 
     In the printing apparatus of the present invention, the liquid transporting section may transport the liquid vertically downward from the discharging section toward the transfer drum. In this case, the adhering position of the liquid on the surface of the transfer drum is not shifted due to a gravitational force acting on the liquid discharged from the discharging section. 
     In the printing apparatus of the present invention, the liquid transporting section may include a plurality of individual liquid transporting sections arranged in a circumferential direction (arranged along a circumference) of the transfer drum. In this case, various types of liquids can be discharged from the liquid transporting section, and made to be adhered to the transfer drum. 
     The printing apparatus of the present invention, may further include a foreign-matter removing mechanism (an impurity removing mechanism) which removes foreign matters (impurities) adhered to the surface of the transfer drum. In this case, it is possible to remove assuredly foreign matters such as paper dust adhered to the transfer drum. 
     In the printing apparatus of the present invention, the transferring mechanism may be a transfer belt, and a hole into which the liquid discharged from the liquid discharging section is filled may be formed in the transfer belt. In this case, it is possible to arrange the transfer belt in any shape. Moreover, when the hole is formed in the transfer belt, with the liquid discharged from the discharged section filled in this hole, the ink can be carried up to a point of transferring to the recording medium. Therefore, the position of the liquid on the surface of the transfer belt is not shifted. 
     The printing of the present invention may further include a foreign-matter removing mechanism which removes foreign matters adhered to a surface of the transfer belt. In this case, it is possible to remove assuredly impurities such as paper dust adhered to the transfer belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural diagram of a printer according to an embodiment of the present invention; 
         FIG. 2  is a side view of main components of the printer in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along a line III-III shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along a line IV-IV shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view corresponding to  FIG. 2  in a state in which ink is not discharged; 
         FIG. 6  is a cross-sectional view taken along a line VI-VI shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view corresponding to  FIG. 2  in a state in which the ink is discharged; 
         FIG. 8  is a cross-sectional view taken along a line VIII-VIII shown in  FIG. 7 ; 
         FIG. 9  is a partial development diagram of a surface of a transfer drum; 
         FIG. 10A  is a partial development diagram of the surface of the transfer drum when the ink is adhered, showing a state immediately after the ink is adhered at a position shifted from an ink adhering area; 
         FIG. 10B  is a partial development diagram of the surface of the transfer drum when the ink is adhered, showing a state in which the shifting of the ink adhering position is corrected; 
         FIG. 11  is a schematic structural diagram of a printer of a first modified embodiment; 
         FIG. 12  is a side view corresponding to  FIG. 2  of a printer of a second modified embodiment; 
         FIG. 13  is a side view corresponding to  FIG. 2  of a printer in a first example of a third modified embodiment; 
         FIG. 14  is a side view corresponding to  FIG. 2  of a printer in a second example of a third modified embodiment; 
         FIG. 15  is a partial plan view of a printer of a fifth modified embodiment; 
         FIG. 16  is a cross-sectional view taken along a line XVI-XVI shown in  FIG. 5 ; 
         FIG. 17  is a side view corresponding to  FIG. 2  of a printer of a sixth modified embodiment; 
         FIG. 18  is a side view corresponding to  FIG. 2  of a printer of a seventh modified embodiment; and 
         FIG. 19  is a partial development diagram of a transfer belt in which a hole is formed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, an embodiment of the present invention will be described below. This embodiment is an example in which the present invention is applied to a printing apparatus which performs printing by transporting an ink to a recording paper. 
     Firstly, a schematic structure of a printer  100  of this embodiment will be described below. As shown in  FIG. 1  and  FIG. 2 , the printer  100  includes an ink transporting head  1  (liquid transporting section), a transfer drum  2 , and transporting rollers  3 . The ink transporting head  1  includes a plurality of individual ink channels  12  through which an electroconductive ink flows, and a plurality of discharge ports  13  (discharging sections) communicating with the individual ink channels  12 . The transfer drum  2  on a lower side of the ink transporting head  1 , has a circular cylindrical shape and is rotatably supported by a frame  4  such that a surface of the transfer drum  2  is close (approximated) to the discharge port  13  of the ink transporting head  1 . The transporting rollers  3  carry in a forward direction in  FIG. 1 , a recording paper P which is in contact with a lower edge of the transfer drum  2 . The electroconductive ink used in this printer  100  is an aqueous dye ink having water as a main constituent and a dye and a solvent added therein, or an aqueous pigment ink having water as a main constituent and a pigment and a solvent added therein. 
     The ink transporting head  1  is connected to an ink tank  5  via a tube  6 . Moreover, ink supplied from the ink tank  5  to the ink transporting head  1  upon passing through the individual ink channels  12  in the ink transporting head  1  is discharged from the discharge ports  13  opening on a lower side, and is adhered to the surface of the transfer drum  2  rotating in a fixed direction (clockwise direction in  FIG. 2 ). Furthermore, the recording paper P, supported by a roller  7 , on the lower side of the transfer drum  2  is in contact with the lower edge of the transfer drum  2 . Therefore, an ink I which is adhered to the transfer drum  2  is moved to the lower side with rotation of the transfer drum  2 , and transferred to the recording paper P. Thus, a predetermined image is recorded on the recording paper P. After recording the image on the recording paper P, the recording paper P is discharged forward by the transporting rollers  3 . As shown in  FIG. 1 , the ink transporting head  1  and the transfer drum  2  are installed along an entire (direction of) width of the recording paper P, when the ink is transferred from the transfer drum  2  to the recording paper P, a row (line) of pixels arranged in the direction of width are recorded at a time on the recording paper P. In other words, the printer  100  of this embodiment is a line printer. 
     Next, the ink transporting head  1  will be described in detail. As shown in  FIG. 3  and  FIG. 4 , the ink transporting head  1  includes a head main body  10 . A manifold  11  extending in a longitudinal direction of the ink transporting head  1  (left and right direction in  FIG. 3 ) is formed on an upper half portion of the head main body  10 . Moreover, the individual ink channels  12  extending toward a lower side upon branching from the manifold  11  are formed to be arranged in the longitudinal direction of the ink transporting head  1 . The individual ink channels  12  are separated mutually by partition walls  14 . Only three individual ink channels  12  which are a part of the individual ink channels  12  formed in the head main body  10  are shown in  FIG. 3 . Moreover, a lower end portion of each of the individual ink channels  12  is tapered toward a front end, the discharge port  13  having an opening on the lower side is provided on the front end. 
     The manifold  11  is connected to the ink tank  5  (refer to  FIG. 1 ), and the electroconductive ink is supplied from the ink tank  5  to each individual ink channel  12  via the manifold  11 . Here, a gravitational force acts all the time in a downward direction on the ink in each individual ink channel  12  extending in a downward direction. The manifold  11  and the individual ink channels  12  correspond to the liquid channel of the invention in this application. 
     On one surface of an inner surface (channel forming surface) of the head main body  10 , which forms a lower end portion having a tapered shape of each individual ink channel  12 , an individual electrode  15  (a first electrode) having a trapezoidal shape substantially covering this surface is formed. As shown in  FIG. 4 , each individual electrode  15  is connected to a driver IC  17 , and it is possible to apply a predetermined drive voltage to each individual electrode  15  by the driver IC  17 . Furthermore, on surfaces of the individual electrodes  15 , an insulating layer  16  made of a fluororesin is provided so as to cover completely the individual electrodes  15 . Here, when the drive voltage is not applied to the individual electrodes  15 , a liquid repellent property (a liquid repellence) of a surface of the insulating layer  16  is higher than a liquid repellent property of the inner surface of the individual ink channel  12 . The insulating layer  16  can be formed by coating a fluororesin on the surfaces of the individual electrodes  15  by a method such as a spin coating. 
     On one of surfaces (right side surface in  FIG. 4 ) of the inner surface of the manifold  11  (channel forming surface), a common electrode  18  (second electrode) which is in direct contact with the ink in the manifold  11  is formed. This common electrode  18  is also connected to the driver IC  17 , and the common electrode  18  is kept at a ground electric potential all the time via the driver IC  17 . Consequently, the ink in the manifold  11 , which is in contact with the common electrode  18 , is kept at the ground electric potential all the time. 
     Next, an ink transporting action of the ink transporting head  1  will be described by referring to  FIG. 5  to  FIG. 8 . In  FIG. 6  and  FIG. 8 , “+” signs of contact points of the individual electrodes  15  denote a state in which the voltage is applied to the individual electrodes  15 , and “GND” denotes a state in which the voltage is not applied to the individual electrodes  15  (state of being at the ground electric potential). 
     In the state in which the drive voltage is not applied to the individual electrode  15  from the driver IC  17 , the liquid repellent property of the surface of the insulating layer  16  becomes higher than a liquid repellent property of the inner surfaces of the individual ink channels  12 . Therefore, as shown in  FIG. 5  and  FIG. 6 , meniscuses of the ink I in the individual ink channels  12  which tend to flow downward cannot move to the discharge ports  13  by crossing over the surface of the insulating layer  16 , and the ink I is not discharged from the discharge ports  13 . However, when the drive voltage is applied to a certain individual electrode (the individual electrode  15  positioned at a right end in  FIG. 7 ) from the driver IC  17 , the liquid repellent property (wetting angle of ink) on the surface of the insulating layer  16  covering this individual electrode  15  is declined (electrowetting phenomenon), and the liquid repellent property of the surface of the insulating layer  16  becomes lower than the liquid repellent property of the inner surfaces of the individual ink channels  12 . In this case, as shown in  FIG. 7  and  FIG. 8 , the ink I can move downward up to the discharge ports  13  by wetting the surface of the insulating layer  16 , and the ink I is discharged from the discharge ports  13  toward the transfer drum  2  on the lower side. 
     Since the ink in the manifold  11  is in contact with the common electrode  18  kept at the ground electric potential all the time, the electric potential of the ink in the individual ink channels  12  is not fluctuated. Consequently, when the drive voltage is applied to a certain individual electrode  15 , a predetermined electric potential difference is generated assuredly between that individual electrode  15  and the ink. Therefore, in the individual ink channels  12 , the ink can move smoothly to the discharge ports  13 . 
     Moreover, as shown in  FIG. 3  to  FIG. 8 , liquid repellent films  19  are provided in areas around the discharge ports  13  on a lower end of the head main body  10 , and the liquid repellent property of the areas around the discharge ports  13  have become higher than the liquid repellent property of the inner surfaces of the individual ink channels  12  (liquid repellent property of the surfaces of the insulating films  16  when the drive voltage is applied to the individual electrodes  15 ). Therefore, the ink discharged form the ink ports  13  is prevented from adhering around the discharge ports  13 . 
     Next, the transfer drum  2  will be described below. As shown in  FIG. 1  and  FIG. 2 , the transfer drum  2  is formed to have the circular cylindrical shape having a length substantially same as a length of the ink transporting head  1 , and is provided rotatably (and is rotatably supported) by the frame  4  of the printer  100 . Moreover, the transfer drum  2  is rotated by driving in the clockwise direction in  FIG. 2 , by a drive motor not shown in the diagram. 
     The surface of the transfer drum  2  is close to the discharge ports  13  of the ink transporting head  1 . Here, as shown in  FIG. 8 , a distance L between the ink transporting head  1  and the transfer drum  2  is set to be less than a diameter of a liquid droplet equivalent to ink discharged at a time from one discharge port  13 , when the drive voltage is applied to the individual electrode  15  of the individual ink channel  12 . In other words, the distance L isolating the ink transporting head  1  and the transfer drum  2  is less than a diameter of a spherical ink droplet having a volume same as a volume of the ink discharged at a time from one discharge nozzle  13 . For example, when the volume of the ink discharged at a time from one discharge port  13  is approximately 5 p1, the distance L is set to be less than approximately 21 μm which is equivalent to the diameter of the droplet of ink having the volume of approximately 5 p1 (L=10 μm for example). Therefore, the ink discharged from the discharge port  13  is adhered assuredly to the surface of the transfer drum  2 . 
     Moreover, as shown in  FIG. 9 , the surface of the transfer drum  2  is provided with a plurality of ink adhering areas  2   a  (liquid adhering areas) to which the liquid droplets which are discharged from each of the discharge ports  13  of the ink transporting head  1  are adhered. Moreover, the ink adhering areas  2   a  are surrounded (enclosed) by a liquid repellent film  20 , and each of the ink adhering areas  2   a  has circular shape in a plan view. Furthermore, as shown in  FIG. 9 , the ink adhering areas  2   a  are arranged in a row in a longitudinal direction (left and right direction in  FIG. 9 ) of the transfer drum  2 , corresponding to the discharge ports  13 , and a plurality of rows of the ink adhering areas  21   a  are arranged at equal intervals in a circumferential direction (vertical direction in  FIG. 9 ) of the transfer drum  2 . Moreover, the liquid repellent property of the ink adhering area  2   a  is lower than the liquid repellent property of the liquid repellent films formed around the discharge ports  13  of the ink transporting head  1 . Therefore, the ink discharged from the discharge ports  13  are not adhered around the discharge ports  13 , and are moved assuredly to the surface of the transfer drum  2 . 
     Furthermore, the liquid repellent film  20  is formed on the surface of the transfer drum  2 , in an area surrounding the ink adhering areas  2   a , and forms a highly liquid repellent area  2   b  having the liquid repellent property higher than the liquid repellent property of the ink adhering areas  2   a . Consequently, for example, when an ink droplet Id discharged from each of the discharge ports  13  is adhered to the transfer drum  2 , in an unstable state, as shown in  FIG. 10A , the ink droplet Id is sometimes shifted slightly from the ink adhering area  2   a  on the surface of the transfer drum  2  to which the ink droplet Id is to be adhered originally, and is adhered spreading even up to the highly liquid repellent area  2   b . Even in such a case, as shown in  FIG. 10B , the liquid droplet Id is moved automatically in a direction indicated by an arrow, from the highly liquid repellent area  2   b  which is highly liquid repellent, toward the ink adhering area  2   a  which is less liquid repellent. In other words, since the adhering position of the liquid droplet on the surface of the transfer drum  2  is corrected, the printing quality when the ink is transferred to the recording paper is improved. 
     Such shift in the adhering position of the liquid droplet occurs due to various factors such as an external force acting on the liquid droplet like the gravitational force and wind. However, in the printer  10  of this embodiment, as shown in  FIG. 2 , since the liquid transporting head  1  discharges (transports) the ink vertically downward from the discharge ports  13  toward the transfer drum  2 , the shift in the adhering position due to the gravitational force acting on the liquid droplet does not occur. Moreover, for performing the correction mentioned above, the shift in the adhering position of the liquid droplet right before transferring to the recording paper is decreased substantially. 
     As shown in  FIG. 2 , the roller  7  is rotatably arranged to support the recording paper P from the lower side in order that the recording paper P is in contact with the lower end surface of the transfer drum  2 . Moreover, the ink adhered to the transfer drum  2 , after moving downward with the rotation of the transfer drum  2 , is transferred assuredly to the recording paper P pinched between the transfer drum  2  and the roller  7 . 
     According to the printer  100  mentioned above the following effects are achieved. The ink transporting head  1  transports the ink up to the discharge ports  13  by using a phenomenon of decline in the liquid repellent property of the surface of the insulating layer  16  which covers the individual electrodes  15 , when the electric potential difference is generated between the individual electrodes  15  and the ink (electrowetting phenomenon). Therefore, as compared to a conventional ink-jet head having a complicated formation, a structure of the ink channels and a formation of the actuator which transports the ink are simplified, and it is possible to arrange the individual ink channels  12  and the discharge ports  13  highly densely. Therefore, a reduction in a size of the ink transporting head  1  is facilitated. Furthermore, it is possible to transport the ink at a comparatively low drive voltage. 
     Moreover, after the ink is made to be adhered to the surface of the transfer drum  2  from the ink transporting head  1 , the ink on the surface of the transfer drum  2  is transferred to the recording paper P by rotating the transfer drum  2 . Therefore, it is possible to make a predetermined amount of ink to be adhered stably to the recording paper P having a rough surface. Since the distance between the discharge port  13  of the ink transporting head  1  and the transfer drum  2  is less than the diameter of the liquid droplet equivalent to the amount of ink discharged at a time from the discharge port  13 , the ink discharged from the discharge port  13  is adhered assuredly to the transfer drum  2 . 
     Modified embodiments in which various modifications are made in the embodiment will be described below. However, same reference numerals are assigned to components having a similar structure as the structure of the components in the embodiment, and the description of such components is omitted. 
     First Embodiment 
     As shown in  FIG. 11 , a pressurizing pump  30  (booster pump) may be provided between the ink tank  5  and the ink transporting head  1 , and the ink in the ink tank  5  may be pressurized by the pressurizing pump  30 , and supplied to the ink transporting head  1 . In this modified embodiment, since the pressure is applied to the ink in the ink transporting head  1  by the pressurizing pump  30 , in addition to the gravitational force, the ink is susceptible to be discharged from the discharge ports  13  (refer to  FIG. 2 ). Particularly, it is appropriate for a case in which there is no component of the gravitational force acting on the ink in the individual ink channels  12  toward the discharge ports  13  such as a case in which the discharge ports  13  of the ink transporting head  1  are toward a horizontal direction. It is also appropriate for a case in which the component of the gravitational force toward the discharge port  13  is small such as a case in which the discharge port  13  is toward a direction slightly inclined with respect to the vertical direction. 
     Second Modified Embodiment 
     Sometimes, foreign matters (impurities) such as paper dust are adhered to a surface of the transfer drum  2  while transferring to a recording paper, and when it is left in a state in which the impurities are adhered, there is a possibility that the ink discharged from a discharge port  13  of an ink transporting head  1  may not be adhered to a predetermined ink adhering area of the surface of the transfer drum. Therefore, a foreign-matter removing mechanism which removes such foreign matters may be provided to the printer. For example, as shown in  FIG. 12 , a foreign-matter removing member  31  which is in contact with the surface of the transfer drum  2  all the time, may be provided along the longitudinal direction of the surface of the transfer drum  2  (direction perpendicular to a paper surface in  FIG. 12 ). A front end of the foreign-matter removing member  31  is in contact with a portion (left side portion in  FIG. 12 ) between an upper end portion of the transfer drum  2  to which the ink discharged from the ink transporting head  1  is adhered, and a lower end portion of the transfer drum  2  which comes in contact with the recording paper P. Therefore, till the subsequent ink is adhered after the ink is transferred to the recording paper P, the ink adhered to the surface of the transfer drum  2  can be scraped off by the foreign-matter removing member  31 . 
     Third Embodiment 
     A structure supporting the recording paper P from the lower side such that the recording paper P which is carried is in contact with the transfer drum  2  all the time, is not restricted to the roller  7  of the embodiment (refer to  FIG. 2 ), and various other structures may be used. For example, as shown in  FIG. 13 , the recording paper P may be supported by a horizontal supporting platform  32  which is arranged under the transfer drum  2 . Or as shown in  FIG. 14 , the recording paper P may be supported by rollers  33  and  34  pinching the recording paper P from the upper side and the lower side, which are arranged on both sides (both left and right sides in  FIG. 14 ) of a paper transporting direction, of the transfer drum  2 . 
     Fourth Modified Embodiment 
     When the shift in the adhering position of the ink on the surface of the transfer drum  2  is small, the liquid repellent film  20  which is formed around the ink adhering areas  2   a  (refer to  FIG. 9 ) for correcting the shift may be omitted. 
     Fifth Modified Embodiment 
     An ink transporting head which transports the ink to the transfer drum by using the electrowetting phenomenon is not restricted to the ink transporting head  1  in the first embodiment, and ink transporting heads having various structures can be used. For example, an ink transporting head  41  shown in  FIG. 15  and  FIG. 16  includes an ink storage section  43 , a plurality of individual ink channels  44 , and a plurality of discharging sections  45 . The ink storage section  43  is formed on an upper surface of an end portion of a substrate  42 . The individual ink channels  44  are extended from a plurality of leading ports  43   a  of the ink storage section  43  to the transfer drum  2  respectively, on the upper surface of the substrate  42 . Each of the discharging sections  45  is continued (communicates) with each of the individual ink channels  44 . 
     Leading electrodes  46  are provided on the upper surface (channel forming surface) of the substrate  42  which forms each individual ink channel  44 , adjacent to the leading ports  43   a  of the ink storage section  43 . Furthermore, five transporting electrodes  47  are provided such that the five transporting electrodes  47  are arranged along a direction extending from a position adjacent to the leading electrodes  46  to the individual ink channels  44  respectively. The leading electrodes  46  and the transporting electrodes  47  are connected to a driver IC which is not shown in the diagram, and the driver IC can apply a drive voltage independently to each of the leading electrodes  46  and each of the transporting electrodes  47 . The substrate  42  is formed of an insulating material, and the leading electrodes  46  and the transporting electrodes  47  are mutually insulated by the substrate  42 . Moreover, an insulating layer  48  is formed continuously on the upper surface of the substrate  42  to cover the entire leading electrodes  46  and the transporting electrodes  47 . Furthermore, a common electrode  49  which is extended in a direction in which the individual ink channels  44  are extended on both side of the individual ink channels  44  are formed on an upper surface of the insulating layer  48 . The common electrode  49  is also connected to the driver IC, and is kept at the ground electric potential all the time via the driver IC. 
     When the drive voltage is not applied to the leading electrodes  46 , a liquid repellent property of the insulating layer  48  covering the surface is higher than a liquid repellent property of an inner surface of the ink storage section  43  on which the insulating layer  48  is not formed, and the ink is not lead from the leading ports  43   a . On the other hand, when the drive voltage is applied to the leading electrodes  46 , since the liquid repellent property of the insulating layer  48  on the surface of the leading electrodes  46  becomes lower than the liquid repellent property of the inner surface of the ink storage section  43 , the ink is lead from the leading ports  43   a  of the ink storage section  43 . Furthermore, as the drive voltage applied to the leading electrodes  46  is released and the leading electrodes  46  come to the ground electric potential, when the drive voltage is applied to the transporting electrodes  47  adjacent to the leading electrodes  46  at the same time, the liquid repellent property of the insulating layer  48  on the surface of the leading electrodes  46  is improved (becomes superior) and the liquid repellent property of the insulating layer  48  on the surface of the transporting electrodes  47  is declined. Therefore, the ink on the leading electrodes  46  is moved to the transporting electrodes  47 . Thus, by switching the leading electrodes  46  and the transporting electrodes  47  to which the drive voltage is applied, it is possible to transport the liquid droplet Id of ink lead from the leading ports  43   a  up to the discharging sections  45  along the individual ink channels  44 , and to adhere it from the discharging sections  45  to the transfer drum  2 . The ink storage section  43  and the individual ink channels  44  correspond to the liquid channel of the (patent) application for the present invention. Moreover, the leading electrodes  46  and the transporting electrodes  47  correspond to the first electrode of the application for the present invention, and the common electrode  49  corresponds to the second electrode of the application for the present invention. 
     Moreover, even in the ink transporting head  41  of the fifth modified embodiment, similarly as in the embodiment, the distance L between the discharging section of the ink transporting head  41  and the transfer drum  2  is less than the diameter of the (liquid) droplet Id of the ink having the volume same as the volume of the ink discharged at a time from one of the discharging sections  45 . Furthermore, a liquid repellent film  50  is provided around the discharging sections  45 , and the liquid repellent property around the discharging sections  45  is higher than the liquid repellent property of the surface of the transfer drum  2  and the upper surface of the substrate  42  (insulating layer  48 ) forming the individual ink channels  44 . Therefore, the liquid discharged from the discharging section  45  is transported assuredly to the surface of the transfer drum  2  without adhering around the discharging sections  45 . 
     Sixth Modified Embodiment 
     As shown in  FIG. 17 , four individual ink transporting heads (individual liquid transporting sections)  1   a  to  1   d  each having a structure same as the structure of the ink transporting head  1  may be arranged in a circumferential direction of the transfer drum  2 . According to this structure, it is possible to record a color image on the recording paper P by discharging ink I of different color from each of the individual ink transporting heads  1   a  to  1   d , then making the ink adhere to the transfer drum  2 , and transferring to the recording paper P. The number and arrangement of the individual ink transporting heads may be voluntary. 
     Seventh Modified Embodiment 
     A printer  200  in a seventh modified embodiment has a structure similar to the structure of the printer  100  of the embodiment except for points that a transfer belt  202 , spindle rollers  203   a  to  203   d , and a belt rotating roller  204  are provided instead of the transfer drum  2  of the embodiment, and has an impurity removing mechanism  231  similar to the second embodiment. As shown in  FIG. 18 , the transfer belt  202  is arranged to make a contact with the spindle rollers  203   a  to  203   d , and the belt rotating roller  204 . Each of the spindle rollers  203   a  to  203   d  is rotatably supported by a core in the form of a rod which is not shown in the diagram, but extended in a direction of arrangement of the discharge port  13  of the ink transporting head  1 . The belt rotating roller  204  is extended along the direction of arrangement of the discharge port  13  of the ink transporting head  1 , and connected to a driving source which is not shown in the diagram. Moreover, the belt rotating roller  204  is rotatably pivoted by the frame  4  (refer to  FIG. 1 ) of the printer  200 . With the rotation of the belt rotating roller  204 , the transfer belt  202  is rotated in a clockwise direction in  FIG. 18 . Here, a width of the transfer belt  202  is substantially the same as a length of the discharge port  13  of the ink transporting head  1  in the direction of arrangement. Moreover, the transfer belt  202  is arranged between the spindle rollers  203   a  and  203   b , and uniformly spaced from the ink transporting head  1 . Here, a distance between the transfer belt  202  and the ink transporting head  1  is less than a diameter of a spherical drop of ink having a volume same as the volume of the ink discharged at a time from the ink transporting head  1 . Between the spindle roller  203   a  and  203   b , the ink I discharged from the ink transporting head  1  is adhered to a surface of the transfer belt  202 . The ink adhered to the surface of the transfer belt  202  is carried toward a lower side in  FIG. 18 , with the rotation of the transfer belt  202 , and is transferred assuredly to the recording paper P pinched between the spindle roller  203   d  and the roller  7 . 
     In the seventh modified embodiment, a shape, a material, the number and/or an arrangement of the spindle rollers, and the belt rotating roller may be voluntary. Moreover, also a shape, a material and/or a thickness of the transfer belt may be voluntary. Moreover, the modifications made in the other modified embodiments mentioned above can be applied also in the seventh modified embodiment. For example, an ink adhering area and a highly liquid repellent area as formed on the surface of the transfer drum in the embodiment may be formed on the surface of the transfer belt. Furthermore, as a transfer belt  212  shown in  FIG. 19 , a hole  212   a  may be formed in the transfer belt  212  in a portion corresponding to the ink adhering area. When the hole  212   a  is formed in the transfer belt  212  in the portion corresponding to the ink adhering area, the ink discharged from the ink transporting head  1  is carried in a state of being filled in the hole  212   a , and is transferred to the recording paper P. 
     In the embodiment and the modified embodiments, a pattern of the ink adhering area and the highly liquid repellent area of the surface of the transfer belt and the transfer drum may be formed voluntarily. For example, the ink adhering area may be formed in the form of a line along the circumferential direction of the transfer drum and the transfer belt, or may be formed in the form of a line along a direction orthogonal to the circumferential direction. Or, the ink adhering area may be formed in the form of a lattice in both the circumferential direction and the direction orthogonal to the circumferential direction. Moreover, a transfer member (transfer mechanism) for transferring the ink discharged from the ink transporting head to a recording medium such as a recording paper, is not restricted to the transfer drum or the transfer belt, and any transfer member may be used. 
     The embodiment mentioned above is an example in which the present invention is applied to a printer which records an image by transferring the ink to the recording paper. However, the present invention is also applicable to other printing apparatuses which transfer a liquid other than the ink to a printing medium. For example, the present invention is also applicable to a printing apparatus which forms a wiring pattern by transferring an electroconductive liquid in which metallic nano particles are dispersed, to a substrate, a printing apparatus which manufactures DNA chips by using a solution in which a DNA is dispersed, a printing apparatus which manufactures a display panel by using a solution in which an EL light emitting material (luminescent material) such as an organic compound is dispersed, and a printing apparatus which manufactures a color filter for a liquid crystal display by using a liquid in which pigments for the color filter are dispersed. Moreover, a liquid used in these printing apparatuses is not restricted to an electroconductive liquid, and may be a liquid which has the electroconductive property similarly as the electroconductive liquid, by dispersing an electroconductive additive (addition agent) in a nonconductive liquid.