Patent Publication Number: US-7712889-B2

Title: Image forming apparatus and liquid removal capability setting method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a Divisional of application Ser. No. 11/390,080 filed on Mar. 28, 2006, now U.S. Pat. No. 7,517,045 and for which priority is claimed under 35 U.S.C. § 120. This application also claims priority of Application No. 2005-094354 and 2005-094355 both filed in Japan on Mar. 29, 2005 under 35 U.S.C. § 119. The entire contents of all of the above applications are hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus, and a liquid removal capability setting method, and more particularly, to an inkjet recording apparatus or other image forming apparatuses which form images of high quality by efficiently removing surplus liquid on a recording medium, and to a liquid removal method for same. 
   2. Description of the Related Art 
   In image forming apparatuses, such as inkjet recording apparatuses, an image is formed on a recording medium by using liquid ink in which coloring material and additives are mixed into a solvent such as water, alcohol, or the like. Liquid (ink solvent) remains on the surface of the recording medium on which the image is formed, and this can be the cause of image degradation (image defects), rear-side image transfer, cockling, and the like. In an inkjet recording apparatus, it is necessary to swiftly remove the liquid remaining on the recording medium in this way, and various means of achieving this have been devised. In particular, in systems which promote the fixing of the ink by causing the coloring material contained in the ink to become insoluble, or causing the coloring material to aggregate, by making the ink to react with a treatment liquid on the recording medium, the amount of liquid deposited onto the recording medium is high, and there is a strong need for the liquid to be removed. 
   Japanese Patent Application Publication No. 2001-179959 discloses an ink absorbing body and an image forming apparatus and method using the ink absorbing body, in which the ink absorbing body comprises a liquid solvent absorbing body and a separating member that covers at least partially the surface of the liquid solvent absorbing body and allows the ink solvent to pass, while having separating properties with respect to the coloring material of the ink. When ink is deposited on a sheet, the liquid solvent absorbing body is placed in closed proximity to a portion of the sheet through the separating member, and the liquid solvent is absorbed into the liquid solvent absorbing body through the separating member, in such a manner that the coloring material and the liquid solvent of the liquid ink on the sheet are mutually separated. Furthermore, there is also a composition in which a liquid volume sensor which determines the liquid volume inside a high polymer absorbing body is provided, and when the sensor value has reached a prescribed value, then a squeezing mechanism is operated. 
   Japanese Patent Application Publication No. 2003-136689 discloses an inkjet process including removal of excess liquid from an intermediate member, in which a primary image formed by an inkjet device is transferred to a receiving member in a transfer process zone, and in this composition, a concentrated image is formed by an image concentrating process after the primary image is formed, and a portion of the carrier liquid is removed from the concentrated image in an excess liquid removal process zone. 
   However, in the related art, the liquid is removed by placing an absorbing body in contact with the recording medium and pressing the absorbing body against the recording medium, and this is insufficient for handling recording media of different types, thicknesses, surface characteristics, and the like. For example, since an absorbing body is pressed against the recording medium at a prescribed pressure when removing the liquid on the recording medium, regardless of the type, thickness or surface properties of the recording medium, and the like, then in a recording medium having low surface smoothness, the ink coloring material is more liable to adhere to the absorbing body, compared to a recording medium having high smoothness, and hence there is a risk of image defects, reduced density, and a concern that coloring material which once becomes attached to the absorbing body adheres to another sheet of recording medium. 
   In the ink absorbing body and image forming apparatus and method using the ink absorbing body described in Japanese Patent Application Publication No. 2001-179959, and the transfer type inkjet printer described in Japanese Patent Application Publication No. 2003-136689, there is no disclosure regarding the absorption force of the ink absorbing body, or restriction of this force, and hence there is a risk of ink coloring material becoming attached to the ink absorbing body. 
   SUMMARY OF THE INVENTION 
   The present invention has been contrived in view of the foregoing circumstances, an object thereof being to provide an image forming apparatus and a liquid removal capability setting method, whereby liquid can be removed efficiently, while suppressing the adherence of the ink coloring material, or the like, to the liquid removal member, and deterioration of image quality, such as image defects, can be prevented. 
   In order to attain the aforementioned object, the present invention is directed to an image forming apparatus, comprising: an ejection head which ejects liquid onto a recording medium to form a desired image on the recording medium; a conveyance device which moves at least one of the recording medium and the ejection head so as to move the recording medium in a conveyance direction relatively to the ejection head; a liquid removal device which performs liquid removal to remove the liquid on the recording medium and is arranged on a downstream side of the ejection head in the conveyance direction; a determination device which determines a state after the liquid removal is performed by the liquid removal device; and a liquid removal control device which implements control to adjust a liquid removal capability of the liquid removal device according to determination results of the determination device. 
   According to the present invention, since the state is determined after performing the liquid removal by means of the liquid removal device for removing the liquid from the recording medium, the liquid removal capability can be adjusted on the basis of the determination results, and therefore, the liquid on the recording medium is removed by using an optimal liquid removal capability, and a desirable image can be formed on the recording medium. 
   The state after liquid removal by the liquid removal device may be determined by determining the state of the liquid removal member of the liquid removal device, and/or by determining the recording medium after the liquid removal (the liquid on the recording medium, or the image formed on the recording medium, or the like). 
   In order to attain the aforementioned object, the present invention is also directed to an image forming apparatus, comprising: an ejection head which ejects liquid onto a recording medium to form a desired image on the recording medium; a conveyance device which moves at least one of the recording medium and the ejection head so as to move the recording medium in a conveyance direction relatively to the ejection head; a liquid removal device which performs liquid removal to remove the liquid on the recording medium and is arranged on a downstream side of the ejection head in the conveyance direction; a determination device which determines a state of the liquid removal device at least after the liquid removal is performed by the liquid removal device; and a liquid removal control device which implements control to adjust a liquid removal capability of the liquid removal device according to determination results of the determination device. 
   According to the present invention, since the state of the liquid removal device which removes the liquid from the recording medium is determined at least after the liquid removal by the liquid removal device, in such a manner that the liquid removal capability of the liquid removal device is controlled on the basis of the determination results, then the liquid (solvent) can be removed in a suitable fashion, without removing the image forming body (for example, ink coloring material) which forms the image on the recording medium. 
   The liquid removal capability adjusted by the liquid removal control device includes, for example, the amount of liquid removed per unit time, and the force (pressure) applied to the liquid to be removed, and if the liquid removal capability is too large, then there is a risk that material other than the liquid may be removed from the recording medium (the surface of the recording medium), whereas if the liquid removal capability is insufficient, then there is a risk that the prescribed amount of liquid may not be removed. 
   The mode of determining the state of the liquid removal device by means of the determination device may include a mode in which the state before liquid removal is determined, whereupon the state after liquid removal is then also determined, in such a manner that the change in the state of the liquid removal device, before and after liquid removal, can be ascertained. 
   Furthermore, the liquid ejected from the ejection head may be a liquid which includes an image forming body that forms an image on the recording medium, or a liquid which reacts with a liquid containing such an image forming body and causes the image forming body to aggregate (precipitate), or the like. 
   The ejection head may be a line type head having a row of ejection holes of a length corresponding to the full width of the recording medium (the width of the possible image formation region of the recording medium), or a serial head which uses a short head having an ejection hole row of a length that does not reach the full width of the recording medium, and which scans this head in the breadthways direction of the recording medium. 
   A line ejection head may be formed to a length corresponding to the full width of the recording medium by combining short head having rows of ejection holes which do not reach a length corresponding to the full width of the recording medium, these short heads being joined together in a staggered matrix fashion. 
   Moreover, “recording medium” indicates a medium which receives ejection of a liquid by means of an ejection head, and this term includes various types of media, irrespective of material and size, such as continuous paper, cut paper, sealed paper, resin sheets, such as sheets for overhead projector (OHP sheets), film, cloth, and other materials. 
   Preferably, the determination device includes a liquid volume determination device which determines an amount of the liquid contained in the liquid removal device; and the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device according to the determination results of the liquid volume determination device. 
   By determining the amount of the liquid contained in the liquid removal device, it is possible to determine the amount of liquid removed from the recording medium, and thus it can be determined that suitable liquid removal has been performed, if the amount of liquid thus determined lies within a prescribed range. On the other hand, if the amount of liquid thus determined lies outside the prescribed range, then it is determined that the amount of liquid removed has been excessive or insufficient and hence control is implemented in order to adjust the liquid removal capability. 
   Furthermore, it is also possible to store the determined liquid amounts and to estimate the maintenance time for the liquid removal device on the basis of the value of the amount of liquid thus stored. For example, a mode is possible in which the stored amount of liquid is added up successively, the addition result is recorded, and when the addition result exceeds a prescribed threshold value, then it is determined that the maintenance interval for the liquid removal device has been reached. After performing maintenance for the liquid removal device, desirably, the amount of liquid determination device is initialized (reset). 
   Preferably, the determination device includes an adhering matter determination device which determines a matter adhering to the liquid removal device; and the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device according to the determination results of the adhering matter determination device. 
   If the liquid removal capability of the liquid removal device (namely, the pressing force of the absorbing member or the suction force of the suction device) is too large, then the image forming body which forms an image on the recording medium may become attached to the liquid removal device. By determining the matter adhering to the liquid removal device in this way, it is possible to determine whether or not the liquid removal has been carried out satisfactorily. If the adhering matter determination device determines that there is matter adhering to the liquid removal device, then control is implemented in order to lower the liquid removal capability. 
   A desirable mode is one in which a cleaning device is provided for carrying out cleaning of the liquid removal device, and cleaning of the liquid removal device is carried out before determining the adhering matter, if adhering matter is determined to be present on the liquid removal device. This adhering matter may also include matter in a solid state, such as the image forming body, or in a liquid (solvent), or semi-solid state. Furthermore, it may also include liquid that has permeated into the liquid removing member. 
   In order to attain the aforementioned object, the present invention is also directed to an image forming apparatus, comprising: an ejection head which ejects liquid onto a recording medium to form a desired image on the recording medium; a conveyance device which moves at least one of the recording medium and the ejection head so as to move the recording medium in a conveyance direction relatively to the ejection head; a first density determination device which determines density of the image formed on the recording medium and is arranged on a downstream side of the ejection head in the conveyance direction; a liquid removal device which performs liquid removal to remove the liquid on the recording medium and is arranged on a downstream side of the first density determination device in the conveyance direction; a second density determination device which determines the density of the image from which a portion of the liquid has been removed by the liquid removal device, the second density determination device being arranged on a downstream side of the liquid removal device in the conveyance direction; and a liquid removal control device which implements control to adjust a liquid removal capability of the liquid removal device according to determination results of the first density determination device and the second density determination device. 
   According to the present invention, since the first density determination device and the second density determination device are provided for determining the density of the image on the recording medium, respectively, at positions before and after the liquid removal device which removes the liquid from the recording medium (namely, on the upstream side and the downstream side of the liquid removal device in terms of the conveyance direction of the recording medium), and since the density before the liquid removal from the image formed on the recording medium, and the density after the liquid removal are determined and control is implemented in such a manner that the liquid removal capability of the liquid removal device to is adjusted on the basis of these determination results, then the liquid (solvent) is removed in a suitable fashion, without removing the image forming body (for example ink coloring material) which forms the image on the recording medium. 
   The density of the image determined by the first density determination device and the second density determination device includes the intensity of the color of the dots which form the image. In other words, if the intensity of the color after the liquid removal from dots formed on the recording medium is weak compared to the intensity of the color before the liquid removal, then it is possible to determine that a portion of the image forming body which forms the dots has been removed when removing the liquid. If the portion of the image forming body is removed, then it is determined that the liquid removal capability is excessive, and control is implemented in such a manner that the liquid removal capability is reduced. 
   Preferably, the image forming apparatus further comprises: a processing device which calculates a density difference between the density of the image after the liquid removal as obtained by the second density determination device and the density of the image before the liquid removal as obtained by the first density determination device, wherein the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device according to the density difference calculated by the processing device. 
   In the processing device, the density difference between the density of the image determined by the first density determination device and the density of the image determined by the second density determination device is found. This relative density difference may be the difference between the determination result of the second density determination device and the determination result of the first density determination result, or it may be the ratio of the determination result of the first density determination device with respect to the determination result of the second density determination device. 
   When the density of the image before the liquid removal is determined by the first density determination device, desirably, correction is implemented to account for the effect that the liquid on the recording medium has on the determination results. 
   Preferably, the image forming apparatus further comprises: a recording medium determination device which determines a type of the recording medium, wherein the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device according to the type of the recording medium determined by the recording medium determination device. 
   Since the liquid removal capability of the liquid removal device is controlled in accordance with the type of the recording medium, then desirable liquid removal is carried out in accordance with the type of the recording medium. 
   The type of the recording medium is determined on the basis of factors such as the surface properties (flatness) and the thickness of the recording medium, and the like. For example, there is a mode in which control is implemented in order to move the position of the liquid removal device during liquid removal, in accordance with the thickness of the recording medium. 
   The mode of determining the type of the recording medium by the recording medium determination device may involve the user inputting information about the recording medium, or alternatively, the recording medium may be read in directly by means of a determination device, such as a sensor or imaging element, the type of the recording medium being determined automatically on the basis of the results thus read in. Furthermore, it is also possible to adopt a composition in which an information recording body (memory, IC tag, or the like) which stores information including information on the recording medium is provided in the supply device which supplies the recording medium, in such a manner that the type of the recording medium (recording medium type) is read in from this information recording body. 
   Preferably, the image forming apparatus further comprises: a maximum ejection region determination device which determines a maximum ejection region where a liquid ejection volume is a maximum on the image, according to data of the image to be formed on the recording medium; and an image formation control device which implements control to carry out image formation from a trailing edge side of the image to a leading edge side thereof in the conveyance direction, if the maximum ejection region is situated a side of the trailing edge from a central region of the image. 
   If the region where the liquid ejection volume is the maximum in the image formed on the recording medium is situated to the trailing edge side of the central region of the image in terms of the conveyance direction, then the image is formed from the trailing edge side toward the leading edge side in terms of the conveyance direction, in such a manner that the region of the maximum ejection volume is located in the first half of the image formation operation. Therefore, the liquid removal set to the optical liquid removal capability is carried out at least in the second half of the image formation operation. This type of control has particularly beneficial effects in the case of single-pass systems which form the image by scanning the recording medium with the ejection head just once. 
   The mode of forming an image from the trailing edge side toward the leading edge side in terms of the conveyance direction includes a mode where the image is rotated through 180 degrees. 
   Preferably, the liquid removal device comprises a suction device which suctions the liquid; and the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device by adjusting a suction force of the suction device. 
   Since the liquid removal capability of the liquid removal device is adjusted by altering the suction force of the suction device which suctions the liquid removed from the recording medium by the liquid removal device, then it is possible to remove the liquid from the recording medium in a highly efficient manner, by means of a simple control procedure. 
   A suction pump is suitable for use as the suction device. The suction force can be raised by increasing the rotational speed of the suction pump, and the suction force can be reduced by lowering the rotational speed. In other words by adjusting the rotational speed of the suction pump, the negative pressure applied to the liquid on the recording medium can be adjusted. 
   Alternatively, it is also preferable that: the liquid removal device comprises: an absorption device which absorbs and removes the liquid on the recording medium by making contact with the liquid on the recording medium; and a movement device which moves the absorption device in a direction having a component in a direction substantially perpendicular to a recording surface of the recording medium; and the liquid removal control device implements the control to adjust the liquid removal capability of the liquid removal device by adjusting a pressing force of the absorption device against the recording medium by adjusting a position of the absorption device by the movement device. 
   The liquid removal device includes the absorption device which absorbs the liquid by making contact with the liquid on the recording medium, and the pressing force of this absorption device against the recording medium can be altered by moving the absorbing member in the direction having a component that is substantially perpendicular to the recording surface of the recording medium. Therefore, the liquid removal capability of the absorbing device is controlled by varying the pressing force of the absorbing device, and therefore, highly efficient liquid removal becomes possible by means of a simple composition. 
   For the absorbing device, it is desirable to use a member which absorbs the liquid by means of capillary action, such as a porous member, nonwoven cloth, or the like. 
   In order to attain the aforementioned object, the present invention is also directed to an inkjet recording apparatus, comprising the above-described image forming apparatus. 
   Preferably, the ejection head includes: an inkjet head which ejects ink forming the image onto the recording medium; and a treatment liquid ejection head which ejects treatment liquid which fixes the ink on the recording medium by reacting with the ink. 
   In a two-liquid type of inkjet recording apparatus which promotes the fixing of the ink by causing the treatment liquid to react with the ink, unreacted ink (ink solvent) and surplus treatment liquid are removed efficiently, and furthermore, desirable liquid removal is achieved, without removing the ink coloring material. Particularly beneficial effects can be obtained in a two-liquid type of inkjet recording apparatus, which ejects a large amount of liquid (solvent) onto the recording medium. 
   In order to attain the aforementioned object, the present invention is also directed to a liquid removal capability setting method, comprising: an image formation step of ejecting liquid onto a recording medium to form a desired image on the recording medium; a liquid removal step of removing the liquid on the recording medium by means of a liquid removal device, after the image formation step; a state determination step of determining a state after the liquid removal step; and a liquid removal capability adjusting step of adjusting a liquid removal capability of the liquid removal device according to determination results in the state determination step. 
   In order to attain the aforementioned object, the present invention is also directed to a liquid removal capability setting method, comprising: an image formation step of ejecting liquid onto a recording medium to form a desired image on the recording medium; a liquid removal step of removing the liquid on the recording medium by means of a liquid removal device, after the image formation step; a state determination step of determining a state of the liquid removal device after the liquid removal step; and a liquid removal capability adjusting step of adjusting a liquid removal capability of the liquid removal device according to determination results in the state determination step. 
   It is also possible to include a determination step before the liquid removal, which determines the state of the liquid removal device before the liquid removal, between the image forming step and the liquid removal step, and the liquid removal capability of the liquid removal device may be adjusted on the basis of the change between the state of the liquid removal device after the liquid removal and the state of the liquid removal device before the liquid removal. 
   Desirably, a cleaning step is included in order to clean the liquid removal device before implementing the liquid removal step. Furthermore, a desirable mode is one which includes an initial value setting step of setting the initial value (default value) of the liquid removal capability. 
   Preferably, a test image is formed on the recording medium in the image formation step. 
   Since the test image is formed on the recording medium and the suitability or unsuitability of the liquid removal capability is determined on the basis of the liquid removal results in the test image, then desirable liquid removal is always achieved in the actual image. 
   In order to attain the aforementioned object, the present invention is also directed to a liquid removal capability setting method, comprising: an image formation step of ejecting liquid onto a recording medium from an ejection head to form a desired image on the recording medium while moving at least one of the recording medium and the ejection head so as to move the recording medium in a conveyance direction relatively to the ejection head; a first density determination step of determining density of the image formed on the recording medium; a liquid removal step of removing the liquid on the recording medium by means of a liquid removal device, after the first density determination step; a second density determination step of determining the density of the image from which a portion of the liquid has been removed by the liquid removal device, after the liquid removal step; and a liquid removal capability adjusting step of adjusting a liquid removal capability of the liquid removal device according to determination results in the first density determination step and the second density determination step. 
   Since desirable liquid removal is achieved, with the liquid removal capability being set on the basis of the density of the image before and after the liquid removal step, then it is possible to obtain a desirable image which does not produce deterioration of the image due to the liquid removal process. 
   Preferably, an actual image is formed on the recording medium in the image formation step. 
   Since the liquid removal is carried out by setting the liquid removal capability to an optimal value during actual image formation, it is possible to obtain a desirable image without lowering the productivity rate. 
   Preferably, the liquid removal capability setting method further comprises: a maximum ejection region determination step of determining a maximum ejection region where a liquid ejection volume is a maximum on the image, according to data of the image to be formed on the recording medium; and an image formation control step of implementing control in the image formation step to carry out image formation from a trailing edge side of the image to a leading edge side thereof in the conveyance direction, if the maximum ejection region is situated a side of the trailing edge from a central region of the image. 
   The image forming step may include an image processing step of performing image processing for rotating the image through 180 degrees, if the region of the maximum ejection volume is situated toward the trailing edge side of the image from the central region of the image. 
   According to the present invention, the state of the liquid removal device is determined, and the liquid removal capability is adjusted in the liquid removal device, in accordance with this determination result. Therefore, liquid removal is achieved, in which an optimal liquid removal capability is set in accordance with the state of the liquid removal device. 
   Furthermore, since the state of the liquid removal device which removes liquid from the recording medium is determined and the liquid removal capability, such as the suction force of the suction device or the pressing force of the liquid removal device, with respect to the recording medium, is controlled according to the determination results, then desirable liquid removal is carried out, without removing the image forming body which forms the image on the recording medium. 
   Furthermore, since a first density determination device for determining the density of the image before liquid removal and a second density determination device for determining the density of the image after liquid removal are provided, in such a manner that the liquid removal capability of the liquid removal device is adjusted on the basis of the determination results obtained from the first density determination device and the second density determination device, then desirable liquid removal is achieved, in which an optimal liquid removal capability is set in accordance with the determination results. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
       FIG. 1  is a general compositional diagram of an inkjet recording apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a principal plan diagram of the peripheral area of a print unit in the inkjet recording apparatus shown in  FIG. 1 ; 
       FIG. 3  is a principal schematic drawing of a liquid removal unit in the inkjet recording apparatus shown in  FIG. 1 ; 
       FIGS. 4A to 4C  are plan view perspective diagrams showing examples of the composition of the head; 
       FIG. 5  is a cross-sectional view along line  5 - 5  in  FIGS. 4A and 4B ; 
       FIG. 6  is a principal block diagram showing the configuration of the supply system of the inkjet recording apparatus shown in  FIG. 1 ; 
       FIG. 7  is a principal block diagram showing the system configuration of the inkjet recording apparatus shown in  FIG. 1 ; 
       FIG. 8  is a flowchart showing a liquid removal capability setting control procedure according to the first embodiment of the present invention; 
       FIG. 9  is a flowchart showing a default value setting sequence of the liquid removal capability setting control procedure shown in  FIG. 8 ; 
       FIG. 10  is a flowchart showing an absorbing roller initialization sequence of the liquid removal capability setting control procedure shown in  FIG. 8 ; 
       FIG. 11  is a diagram showing an example of an absorption force table; 
       FIG. 12  is a diagram showing a further example of an absorption force table; 
       FIG. 13  is a diagram showing a test print; 
       FIG. 14  is a principal schematic drawing showing a liquid removal unit in an inkjet recording apparatus according to a second embodiment of the present invention; 
       FIG. 15  is a principal block diagram showing the system configuration of the inkjet recording apparatus shown in  FIG. 14 ; 
       FIG. 16  is a flowchart showing a liquid removal capability setting control procedure according to the second embodiment of the present invention; 
       FIG. 17  is a flowchart showing a recording medium surface characteristics determination sequence of the liquid removal capability setting control procedure shown in  FIG. 16 ; 
       FIG. 18  is a flowchart showing a further mode of the liquid removal capability setting control procedure shown in  FIG. 16 ; 
       FIG. 19  is a principal schematic drawing showing a liquid removal unit in an inkjet recording apparatus according to an adaptation embodiment of the present invention; and 
       FIG. 20  is a principal block diagram showing the system configuration of the inkjet recording apparatus shown in  FIG. 19 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   General Composition of Inkjet Recording Apparatus 
     FIG. 1  is a diagram of the general composition of an inkjet recording apparatus according to an embodiment of the present invention. As shown in  FIG. 1 , this inkjet recording apparatus  10  comprises: a print unit  12  having a plurality of print heads  12 K,  12 C,  12 M and  12 Y provided for respective inks of the colors black (K), cyan (C), magenta (M) and yellow (Y) and a treatment liquid ejection head  12 S, which ejects treatment liquid promoting the fixing of the ink by reacting with the ink (hereinafter, the print heads  12 K,  12 C,  12 M and  12 Y and the treatment liquid ejection head  12 S are referred to generally as the heads  12 A,  12 K,  12 C,  12 M and  12 Y); a storing and loading unit  14  which stores the color inks corresponding to the print heads  12 K,  12 C,  12 M and  12 Y, and the treatment liquid corresponding to the treatment liquid ejection head  12 S; a paper supply unit  18 , which supplies a recording medium  16 ; a recording medium determination unit  19 , which determines the type of recording medium  16 ; a decurling unit  20 , which removes curl in the recording medium  16 ; a suction belt conveyance unit  22 , disposed opposing the ink ejection surface of the print unit  12 , which conveys the recording medium  16  while keeping the recording medium  16  flat; a print determination unit  24 , which reads out the print result created by the print unit  12 ; a liquid removal unit  25 , disposed after the print determination unit  24 , which removes liquid (solvent) on the recording medium  16 ; and a paper output unit  26 , which outputs the printed recording medium  16  (printed matter) to the exterior. 
   In  FIG. 1 , a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit  18 ; however, more magazines with paper differences such as paper width and quality may be jointly provided. Moreover papers may be supplied with cassettes that contain cut papers loaded in layers and that are used jointly or in lieu of the magazine for rolled paper. 
   In the case of the configuration in which roll paper is used, a cutter (a first cutter)  28  is provided as shown in  FIG. 1 , and the continuous paper is cut to a desired size by the cutter  28 . The cutter  28  has a stationary blade  28 A, whose length is not less than the width of the conveyor pathway of the recording medium  16 , and a circular blade  28 B, which moves along the stationary blade  28 A. The stationary blade  28 A is disposed on the reverse side of the printed surface of the recording medium  16 , and the circular blade  28 B is disposed on the side adjacent to the printed surface across the conveyance path. When cut paper is used, the cutter  28  is not required. 
   In the case of a configuration in which a plurality of types of recording paper can be used, it is preferable that an information recording medium such as a bar code and a wireless tag containing information about the type of paper is attached to the magazine, and by reading the information contained in the information recording medium with a predetermined reading device, the type of paper to be used is automatically determined, and ink-droplet ejection is controlled so that the ink-droplets are ejected in an appropriate manner in accordance with the type of paper. 
   The inkjet recording apparatus  10  is provided with the recording medium determination unit  19 , which determines the type of recording medium  16 , on the upstream side of the print unit  12 . Although described in more detail later (see  FIG. 3 ), the recording medium determination unit  19  comprises a thickness sensor, which determines the thickness of the recording medium  16 , and a surface characteristics sensor, which determines the surface characteristics (smoothness) of the recording medium  16 . The thickness sensor and the surface characteristics sensor are not shown in  FIG. 1 , but are denoted with the reference numerals  120  and  122  in  FIG. 3 . If the above-described information recording body contains the information such as thickness information and surface characteristics information relating to the recording medium  16  to be obtained by the recording medium determination unit  19 , then the recording medium determination unit  19  can be omitted. 
   The recording medium  16  delivered from the paper supply unit  18  retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording medium  16  in the decurling unit  20  by a heating drum  30  in the direction opposite from the curl direction in the magazine. The heating temperature at this time is preferably controlled so that the recording medium  16  has a curl in which the surface on which the print is to be made is slightly round outward. 
   The decurled and cut recording medium  16  is delivered to the suction belt conveyance unit  22 . The suction belt conveyance unit  22  has a configuration in which an endless belt  33  is set around rollers  31  and  32  so that the portion of the endless belt  33  facing at least the ink (treatment liquid) ejection face of the printing unit  12  and the sensor face of the print determination unit  24  forms a horizontal plane (flat plane). 
   The belt  33  has a width that is greater than the width of the recording medium  16 , and a plurality of suction apertures (not shown) are formed on the belt surface. A suction chamber  34  is disposed in a position facing the sensor surface of the print determination unit  24  and the nozzle surface of the printing unit  12  on the interior side of the belt  33 , which is set around the rollers  31  and  32 , as shown in  FIG. 1 . The suction chamber  34  provides suction with a fan  35  to generate a negative pressure, and the recording medium  16  on the belt  33  is held by suction. 
   The belt  33  is driven in the clockwise direction in  FIG. 1  by the motive force of a motor  88  (not shown in  FIG. 1 , but shown in  FIG. 7 ) being transmitted to at least one of the rollers  31  and  32 , which the belt  33  is set around, and the recording medium  16  held on the belt  33  is conveyed from left to right in  FIG. 1 . 
   Since ink adheres to the belt  33  when a marginless print job or the like is performed, a belt-cleaning unit  36  is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt  33 . Although the details of the configuration of the belt-cleaning unit  36  are not shown, examples thereof include a configuration in which the belt  33  is nipped with cleaning rollers such as a brush roller and a liquid absorbent roller, an air blow configuration in which clean air is blown onto the belt  33 , or a combination of these. In the case of the configuration in which the belt  33  is nipped with the cleaning rollers, it is preferable to make the line velocity of the cleaning rollers different than that of the belt  33  to improve the cleaning effect. 
   The inkjet recording apparatus  10  can comprise a roller nip conveyance mechanism, in which the recording paper  16  is pinched and conveyed with nip rollers, instead of the suction belt conveyance unit  22 . However, there is a drawback in the roller nip conveyance mechanism that the print tends to be smeared when the printing area is conveyed by the roller nip action because the nip roller makes contact with the printed surface of the paper immediately after printing. Therefore, the above-described suction belt conveyance is preferable, in which nothing comes into contact with the image surface in the printing area where the recording medium  16  opposes the heads  12 S,  12 K,  12 C,  12 M and  12 Y and receives ejected droplets of the treatment liquid and the ink. 
   A heating fan  40  is disposed on the upstream side of the printing unit  12  in the conveyance pathway formed by the suction belt conveyance unit  22 . The heating fan  40  blows heated air onto the recording medium  16  to heat the recording medium  16  immediately before printing so that the ink deposited on the recording medium  16  dries more easily. 
   The print unit  12  is a so-called “full line head” in which a line head having a length corresponding to the maximum paper width is arranged in a direction that is perpendicular to the paper feed direction (see  FIG. 2 ). An example of the detailed structure is described later, and each of the heads  12 S,  12 K,  12 C,  12 M, and  12 Y is constituted by a line head, in which a plurality of nozzles are arranged along a length that exceeds at least one side of the maximum-size recording medium  16  intended for use in the inkjet recording apparatus  10 , as shown in  FIG. 2 . 
   The heads are arranged in the order of the treatment liquid ejection head  12 S corresponding to the treatment liquid (S), and the print heads  12 K,  12 C,  12 M, and  12 Y corresponding to the respective color inks of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side, following the feed direction of the recording medium  16  (hereinafter, referred to as the paper feed direction). A color print can be formed on the recording medium  16  by ejecting treatment liquid from the treatment liquid ejection head  12 S and by ejecting color inks respectively from the print heads  12 K,  12 C,  12 M, and  12 Y, onto the recording medium  16  onto which treatment liquid has been deposited (in other words, onto the treatment liquid), while conveying the recording medium  16 . 
   The print unit  12 , in which the full-line heads covering the entire width of the paper are thus provided for the respective ink colors, can record an image over the entire surface of the recording medium  16  by performing the action of moving the recording medium  16  and the print unit  12  relatively to each other in the sub-scanning direction just once (in other words, by means of a single sub-scan). Higher-speed printing is thereby made possible and productivity can be improved in comparison with a shuttle type head configuration in which a head moves reciprocally in the main scanning direction. 
   Although a configuration with the KCMY four standard colors is described in the present embodiment, the combinations of the ink colors and the number of colors are not limited to these, and light and/or dark inks can be added as required. For example, a configuration is possible in which print heads for ejecting light-color inks such as light cyan and light magenta are added. 
   As shown in  FIG. 1 , the storing and loading unit  14  comprises a treatment liquid tank  14 S, which stores the treatment liquid corresponding to the treatment liquid ejection head  12 S, and ink supply tanks  14 K,  14 C,  14 M and  14 Y, which store color inks corresponding to the respective print heads  12 K,  12 C,  12 M,  12 Y. The tanks are connected to the heads  12 S,  12 K,  12 C,  12 M and  12 Y, through prescribed tubing channels (not shown). 
   Furthermore, the ink storing and loading unit  14  also comprises a warning device (for example, a display device or an alarm sound generator) for warning when the remaining amount of any of treatment liquid and ink is low, and has a mechanism for preventing loading errors between inks of different colors and between the inks and treatment liquid. 
   The print determination unit  24  has an image sensor for capturing an image of the print result of the printing unit  12 , and functions as a device to check for ejection defects such as clogs of the nozzles in the printing unit  12  from the image read by the image sensor. 
   The print determination unit  24  of the present embodiment is configured with at least a line sensor having rows of photoelectric transducing elements with a width that is greater than the width (printable width) of the treatment liquid and ink ejection of the heads  12 S,  12 K,  12 C,  12 M, and  12 Y. This line sensor has a color separation line CCD sensor including a red (R) sensor row composed of photoelectric transducing elements (pixels) arranged in a line provided with an R filter, a green (G) sensor row with a G filter, and a blue (B) sensor row with a B filter. Instead of a line sensor, it is possible to use an area sensor composed of photoelectric transducing elements which are arranged two-dimensionally. 
   The print determination unit  24  reads a test pattern image printed by the heads  12 S,  12 K,  12 C,  12 M, and  12 Y, and the ejection of each heads  12 S,  12 K,  12 C,  12 M, and  12 Y is determined. The ejection determination includes the presence of the ejection, measurement of the dot size, and measurement of the dot deposition position. 
   The liquid removal unit  25 , which removes the un-reacted treatment liquid remaining on the recording medium  16  and the ink solvent remaining on the recording medium  16 , is disposed at a stage after the print determination unit  24  (on the downstream side thereof in terms of the paper feed direction). The details of the liquid removal unit  25  are described later. 
   A heating and pressurizing unit  44  is provided at a stage following the liquid removal unit  25 . The heating and pressurizing unit  44  is a device which dries the recording medium  16  and serves to control the luster of the image surface. It applies pressure to the image surface by means of pressure rollers  45  having prescribed surface indentations, while heating same, and hence an undulating form is transferred to the image surface. 
   In cases in which printing is performed with dye-based ink on porous paper, blocking the pores of the paper by the application of pressure prevents the ink from coming contact with ozone and other substance that cause dye molecules to break down, and has the effect of increasing the durability of the print. 
   The printed matter generated in this manner is output from the paper output unit  26 . The target print and the test print are preferably output separately. In the inkjet recording apparatus  10 , a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the test print, and to send them to paper output units  26 A and  26 B, respectively. When the target print and the test print are simultaneously formed in parallel on the same large sheet of paper, the test print portion is cut and separated by a cutter (second cutter)  48 . The cutter  48  is disposed directly in front of the paper output unit  26 , and is used for cutting the test print portion from the target print portion when a test print has been performed in the blank portion of the target print. The structure of the cutter  48  is the same as the first cutter  28  described above, and has a stationary blade  48 A and a round blade  48 B. 
   Although not shown in  FIG. 1 , the paper output unit  26 A for the target prints is provided with a sorter for collecting prints according to print orders. 
   Description of Liquid Removal Unit 
   Next, the liquid removal unit  25  is described in detail with reference to  FIG. 3 .  FIG. 3  is a principal schematic drawing of the liquid removal unit  25 . 
   As shown in  FIG. 3 , the liquid removal unit  25  comprises: an absorbing roller  100  having a length corresponding to the breadthways dimension of the recording medium  16  in the direction substantially perpendicular to the paper feed direction (a length substantially equal to or greater than the full width of the recording medium  16 ); a pressing arm  104 , which supports the absorbing roller  100  through a supporting member  101  coupled to both ends of the absorbing roller  100  and is driven by a drive source  102  so as to vary the distance between the absorbing roller  100  and the recording medium  16  (in such a manner that the absorbing roller  100  is moved in a substantially perpendicular direction to the recording surface of the recording medium  16 ); a suction device (pump)  108 , which suctions the liquid absorbed by the absorbing roller  100  (and accommodated inside the absorbing roller  100 ), through a tube  106 ; a liquid receptacle  110 , which receives the liquid suctioned from the absorbing roller  100  through the suction device  108 ; and a cleaning roller  112 , which abuts against the absorbing roller  100  and removes ink coloring material and foreign matter adhering to the surface of the absorbing roller  100 , and liquid in the vicinity of the surface of absorbing roller  100 . 
   The absorbing roller  100  has a liquid contacting section  100 A, which makes contact with the liquid on the recording medium  16  and is made of a member having excellent liquid absorbing properties, such as a nonwoven cloth, a hydrophilic porous member, polyvinyl alcohol (PVA), polyurethane-type material, or the like, and the liquid on the recording medium  16  (principally, the ink solvent and the treatment liquid solvent) is absorbed and removed by capillary action. 
   The absorbing roller  100  is connected to the suction device  108  through the tube  106 . By operating this suction device  108  and generating a negative pressure in the hollow portion provided in the absorbing roller  100 , the liquid suctioned and removed from the recording medium  16  by the absorbing roller  100  is expelled to the liquid receptacle  110 . 
   The absorbing roller  100  is constituted rotatably about an axis of rotation formed by the supporting member  101 , by means of a rotating mechanism (not shown). More specifically, when executing liquid removal, the absorbing roller  100  is rotated while the absorbing roller  100  makes contact with the liquid on the recording medium  16  (or with the recording medium  16  itself). 
   For the drive source  102  which drives the pressing arm  104  that varies the pressure of the absorbing roller  100  (the position of the absorbing roller  100  in the thickness direction of the recording medium  16 ), it is suitable to use a motor compatible with positional control (control of the amount of rotation), such as a stepping motor, servo motor, or the like. The amount of movement of the pressing arm  104  is controlled by governing the drive signal supplied to the drive source  102 , and the distance (clearance) between the absorbing roller  100  and the recording medium  16  is varied. 
   If the thickness of the recording medium  16  changes, or the pressure applied to the recording medium  16  by the absorbing roller  100  is altered, or the like, then the distance between the absorbing roller  100  and the recording medium  16  is varied. The term that “the distance between the absorbing roller  100  and the recording medium  16  is varied” includes that the absorbing roller  100  is moved from a state in which it makes contact with the surface of the recording medium  16  (and more specifically, a state where the distance between the absorbing roller  100  and recording medium  16  is zero) further toward the recording medium  16  (namely, pressing the absorbing roller  100  against the recording medium  16  with a prescribed pressure). In other words, taking the distance in the direction in which the absorbing roller  100  is moved away from the recording medium  16 , with reference to the position at which the absorbing roller  100  makes contact with the recording medium  16 , to be the positive direction, it is also possible to drive the drive source  102  in such a manner that the absorbing roller  100  is moved in the negative direction. 
   It is also possible to compose the liquid contacting section  100 A of the absorbing roller  100  by means of a hollow member made of metal, resin, or the like, having a plurality of holes (absorption holes) so that the liquid on the recording medium  16  is suctioned and removed by generating a negative pressure in the hollow section by means of the suction device  108 . In a mode where the liquid on the recording medium  16  is suctioned and removed in this manner, it is possible to control the volume of liquid removed by the absorbing roller  100  per unit time, by altering the negative pressure generated by the suction device  108 . 
   In other words, the liquid volume removed per unit time by the absorbing roller  100  increases when the absolute value of the negative pressure generated by the suction device  108  is raised, whereas when the absolute value of the negative pressure is reduced, then the liquid volume removed per unit time by the absorbing roller  100  is reduced. 
   The cleaning roller  112  has substantially the same length as the absorbing roller  100  in the breadthways direction of the recording medium  16 , and either end section thereof is supported by the pressing arm  104  through the supporting member  114 . If a porous member, or the like, is used for the liquid contacting section  100 A of the absorbing roller  100 , then a member having greater permeability than the liquid contacting section  100 A is used for the cleaning roller  112 . 
   The cleaning roller  112  is constituted in such a manner that it can be moved between a cleaning position where it makes contact with the absorbing roller  100 , and a withdrawal position where it does not make contact with the absorbing roller  100 , by means of a movement mechanism (not shown). When carrying out the cleaning of the absorbing roller  100 , the cleaning roller  112  is moved to the cleaning position, and when not carrying out the cleaning of the absorbing roller  100 , the cleaning roller  112  is moved to the withdrawal position. Furthermore, the cleaning roller  112  is composed in such a manner that it can idly rotate about the supporting member  114 , which forms an axis of rotation. 
   In a case where a metal member or resin member having a plurality of absorbing holes is used in the liquid contacting section  100 A of the absorbing roller  100 , then a blade-shaped member can be used instead of the cleaning roller, and the liquid and solid matter, such as ink coloring material, attached to the surface of the liquid contacting section  100 A can be removed by sliding this blade over the liquid contacting section  100 A. 
   The thickness sensor  120 , which measures the thickness of the recording medium  16 , and the surface characteristics sensor  122 , which determines the surface characteristics of the recording medium  16 , are arranged on the upstream side of the absorbing roller  100  in terms of the paper feed direction. The thickness sensor  120  and the surface characteristics sensor  122  are incorporated into the recording medium determination unit  19  shown in  FIG. 1 . It is possible to use commonly known technology for the method of measuring the thickness and determining the surface characteristics of the recording medium  16  (the surface smoothness of the recording medium  16 ), by means of the thickness sensor  120  and the surface characteristics sensor  122 . For example, in order to determine the surface characteristics of the recording medium  16 , a mode is possible which uses a sensor having a light emitting section that irradiates light onto the recording medium  16  and a light receiving section that receives reflected light from the recording medium  16 , the surface characteristics of the recording medium  16  being determined on the basis of the information, such as the light quantity and wavelength, measured by the light receiving section. 
   On the other hand, a soiling sensor  124 , which detects ink coloring material, foreign matter, or the like, adhering to the surface of the absorbing roller  100 , and a carriage  126 , which moves the soiling sensor  124  in the lengthwise direction of the absorbing roller  100 , are provided on the downstream side of the absorbing roller  100  in terms of the paper feed direction. The soiling sensor  124  has a width that is shorter than the length of the absorbing roller  100  in its lengthwise direction, and by moving the carriage  126  through the full range of the absorbing roller  100  in the lengthwise direction, in line with this lengthwise direction, it is possible to scan the whole region of the absorbing roller  100  to detect adhering matter (soiling) that has become attached to the surface of the absorbing roller  100 . A commonly known technique is used for the method of detecting adhering matter on the surface of the absorbing roller  100 , by means of the soiling sensor  124 . For example, a mode is possible which uses a light-emitting element that irradiates a prescribed light onto the surface of the absorbing roller  100 , and a light receiving section that receives the reflected light reflected by the surface of the absorbing roller  100 , thereby determining the presence or absence of the adhering matter on the surface of the absorbing roller  100 , on the basis of the difference between the reflectivity of the surface of the absorbing roller  100  and the adhering matter. 
     FIG. 3  shows the mode in which adhering matter is detected throughout the full width of the absorbing roller  100  by scanning with the soiling sensor  124  having a width that is shorter than that of the absorbing roller  100 . However, it is also possible to provide a soiling sensor  124  having a width corresponding to the width of the absorbing roller  100 . 
   Furthermore, the absorbing roller  100  is provided with a liquid volume measurement unit  150  (not shown in  FIG. 3 , but shown in  FIG. 7 ), which measures the amount of liquid contained in the absorbing roller  100 . The liquid volume measurement unit  150  is constituted by a liquid content sensor  134  having a pair of electrodes  130  and  132  disposed inside the absorbing roller  100 , and information (a signal) relating to the amount of liquid contained in the absorbing roller  100  is estimated on the basis of the resistance value between the electrodes  130  and  132  obtained from the liquid content sensor  134 . 
   As shown in  FIG. 3 , a phase determination mark  140  is provided at the rotational position (phase) of the absorbing roller  100  where the liquid content sensor  134  is provided, in such a manner that the phase of the absorbing roller  100  in the rotational direction can be determined by using a phase determination sensor  142  provided on the main body. More specifically, when determining the amount of liquid in the absorbing roller  100 , the absorbing roller  100  is rotated so that it is aligned in phase with the liquid content sensor  134 . The liquid content measured by the liquid content sensor  134  includes any solvent (e.g., water, alcohol, or the like) which may be contained in the ink solvent and treatment liquid. 
   Structure of Head 
   Next, the structure of the heads  12 S,  12 K,  12 C,  12 M, and  12 Y is described. The heads  12 S,  12 K,  12 C,  12 M and  12 Y have the same structure, and a reference numeral  50  is hereinafter designated to any of the heads. 
     FIG. 4A  is a plan view perspective diagram showing an example of the structure of a head  50 , and  FIG. 4B  is an enlarged diagram of a portion of same. Furthermore,  FIG. 4C  is a plan view perspective diagram showing a further example of the composition of a print head  50 , and  FIG. 5  is a cross-sectional diagram showing a three-dimensional composition of an ink chamber unit (being a cross-sectional view along line  5 - 5  in  FIGS. 4A and 4B ). In order to achieve a high resolution of dots printed on the surface of the recording medium, it is necessary to achieve a high density of the nozzles in the print head  50 . As shown in  FIGS. 4A to 5 , the print head  50  in the present embodiment has a structure in which a plurality of ink chamber units  53  including nozzles  51  for ejecting ink droplets and pressure chambers  52  connecting to the nozzles  51  are disposed in the form of a staggered matrix, and the effective nozzle pitch is thereby made small (the nozzle density is made high). 
   More specifically, as shown in  FIGS. 4A and 4B , the print head  50  according to the present embodiment is a full-line head having one or more nozzle rows in which the plurality of nozzles  51  for ejecting ink are arranged through a length corresponding to the entire width (printable width) of the recording medium  16  in a direction substantially perpendicular to the paper feed direction. 
   Moreover, as shown in  FIG. 4C , it is also possible to use heads  50 ′ of nozzles arranged to a short length in a two-dimensional fashion, and to combine same in a zigzag arrangement, whereby a length corresponding to the full width of the recording medium is achieved. 
   Since it is sufficient that the treatment liquid is applied to the recording medium  16  in a substantially uniform (even) fashion in the region where ink droplets are to be ejected, then it is not necessary to form dots of the treatment liquid to a high density, in comparison with the ink. Consequently, it is possible that the treatment liquid ejection head  12 S is composed with a reduced number of nozzles (a reduced nozzle density) in comparison with the print heads  50  ( 12 K,  12 C,  12 M and  12 Y) for ejecting ink. Furthermore, a composition may also be adopted in which the nozzle diameter of the treatment liquid ejection head  12 S is greater than the nozzle diameter of the print heads  50  for ejecting ink. 
   As shown in  FIG. 5 , the pressure chamber  52  provided correspondingly to each of the nozzles  51  is approximately square-shaped in plan view, and the nozzle  51  and a supply port  54  are provided respectively at corners on a diagonal of the pressure chamber  52 . Each pressure chamber  52  is connected through the supply port  54  to a common flow channel  55 . 
   A piezoelectric element  58  provided with an individual electrode  57  is bonded to a pressure plate (diaphragm)  56 , which forms the upper faces of the pressure chambers  52 . When a drive voltage is applied between the individual electrode  57  and a common electrode, as which the pressure plate  56  also serves, the piezoelectric element  58  deforms, thereby changing the volume of the pressure chamber  52 . This causes a pressure change which results in ink being ejected from the nozzle  51 . When ink is ejected, new ink is supplied to the pressure chamber  52  from the common flow channel  55  through the supply port  54 . The structure of the ink chamber unit  53  shown in  FIG. 5  is merely one example, and it is of course also possible to use another structure. 
   As shown in  FIGS. 4A and 4B , the plurality of ink chamber units  53  having this structure are arranged in a lattice arrangement, based on a fixed arrangement pattern aligned in a main scanning direction, which is the lengthwise direction of the print head  50 , and an oblique direction which, rather than being perpendicular to the main scanning direction, is inclined at a fixed angle of θ with respect to the main scanning direction. By adopting a structure wherein a plurality of ink chamber units  53  are arranged at a uniform pitch d in a direction having an angle θ with respect to the main scanning direction, the pitch P of the nozzles when projected to an alignment in the main scanning direction is d×cos θ. 
   More specifically, the arrangement can be treated equivalently to one in which the respective nozzles  51  are arranged in a linear fashion at uniform pitch P, in the main scanning direction. By means of this composition, it is possible to achieve a nozzle of high density, in which the nozzle columns projected to align in the main scanning direction reach a total of 2,400 per inch (2,400 nozzles per inch, 2400 dpi). Below, in order to facilitate the description, it is supposed that the nozzles  51  are arranged in a linear fashion at a uniform pitch (P), in the main scanning direction. Here, the main scanning direction shown in  FIGS. 4A and 4B  is substantially parallel to the sensor scanning direction shown in  FIG. 3 , and the sub-scanning direction shown in  FIG. 4A  is substantially parallel to the paper feed direction shown in  FIG. 3 . 
   In implementing the present invention, the arrangement of the nozzles is not limited to that of the embodiment illustrated. Moreover, the piezo jet method is employed in the present embodiment where an ink droplet is ejected by means of the deformation of the piezoelectric element  58 ; however, in implementing the present invention, the method used for discharging ink is not limited in particular, and instead of the piezo jet method, it is also possible to apply various types of methods, such as a thermal jet method where the ink is heated and bubbles are caused to form therein by means of a heat generating body such as a heater, ink being ejected by means of the pressure applied by these bubbles. 
   Description of Ink Supply System and Treatment Liquid Supply System 
   Next, the treatment liquid supply system and the ink supply system of the inkjet recording apparatus  10  are described. In the present embodiment, the treatment liquid supply system and the ink supply system have the same basic composition, and are described with respect to the ink supply system shown in  FIG. 6 . Below, the treatment liquid supply system and the ink supply system may be referred to jointly as the &lt;“supply system”. 
     FIG. 6  shows the composition of an ink supply system provided in the inkjet recording apparatus  10 . The ink supply system shown in  FIG. 6  corresponds to the storing and loading unit  14  shown in  FIG. 1 . 
   An ink supply tank (treatment liquid supply tank)  60  forming a base tank for supplying ink (treatment liquid) is disposed in the ink supply system shown in  FIG. 6 . The ink supply tank  60  may adopt a system for replenishing ink by means of a replenishing opening (not shown), or a cartridge system wherein cartridges are exchanged independently for each tank, whenever the residual amount of ink has become low. If the type of ink is changed in accordance with the type of application, then a cartridge based system is suitable. In this case, desirably, type information relating to the ink is identified by means of a bar code, or the like, and the ejection of the ink is controlled in accordance with the ink type. 
   Furthermore, the ink in the ink supply tank  60  is supplied to the head  50  through prescribed tubing channels (not shown) and a filter  62 , in order to remove foreign matter and air bubbles. The filter mesh size in the filter  62  is preferably equivalent to or less than the diameter of the nozzle and is commonly about 20 μm. 
   Although not shown in  FIG. 6 , it is preferable to provide a sub-tank integrally to the head  50  or nearby the head  50 . The sub-tank has a damper function for preventing variation in the internal pressure of the head  50  and a function for improving refilling of the print head. 
   The inkjet recording apparatus  10  is also provided with a cap  64  as a device to prevent the nozzles  51  from drying out or to prevent an increase in the ink and treatment liquid viscosity in the vicinity of the nozzles  51 , and a cleaning blade  66  as a device to clean the nozzle face. 
   A maintenance unit including the cap  64  and the cleaning blade  66  can be relatively moved with respect to the head  50  by a movement mechanism (not shown), and is moved from a predetermined holding position to a maintenance position below the head  50  as required. 
   The cap  64  is moved up and down relatively with respect to the head  50  by an elevator mechanism (not shown). When the power of the inkjet recording apparatus  10  is turned OFF or when in a print standby state, the cap  64  is raised to a predetermined elevated position so as to come into close contact with the head  50 , and the nozzle face is thereby covered with the cap  64 . 
   During printing or standby, if the use frequency of a particular nozzle  51  is low, and if it continues in a state of not ejecting ink or treatment liquid for a prescribed time period or more, then the solvent of the ink or treatment liquid in the vicinity of the nozzle evaporates and the viscosity of the ink or treatment liquid increase. In a situation of this kind, it will become impossible to eject ink or treatment liquid from the nozzle  51 , even if the piezoelectric element  58  is operated. Therefore, before a situation of this kind develops (while the ink or treatment liquid is within a range of viscosity which allows it to be ejected by operation of the piezoelectric element  58 ), the piezoelectric element  58  is operated, and a preliminary ejection (“purge”, “blank ejection”, “liquid ejection” or “dummy ejection”) is carried out toward the cap (ink receptacle), in order to expel the degraded ink or treatment liquid (namely, the ink or treatment liquid in the vicinity of the nozzle which has increased in viscosity). 
   Furthermore, if air bubbles enter into the ink or treatment liquid inside the head  50  (inside the pressure chamber  52 ), then even if the piezoelectric element  58  is operated, it will not be possible to eject the ink or treatment liquid from the nozzle. In a case of this kind, the cap  64  is placed on the head  50 , the ink or treatment liquid (the ink or treatment liquid containing air bubbles) inside the pressure chamber  52  is removed by suction, by means of a suction pump  67 , and the ink or treatment liquid removed by suction is then sent to a collection tank  68 . 
   This suction operation is also carried out in order to remove degraded ink or treatment liquid having increased viscosity (hardened ink or treatment liquid), when ink or treatment liquid is loaded into the head for the first time, and when the head starts to be used after having been out of use for a long period of time. Since the suction operation is carried out with respect to all of the ink or treatment liquid inside the pressure chambers  52 , the ink or treatment liquid consumption is considerably large. Therefore, desirably, preliminary ejection is carried out when the increase in the viscosity of the ink or treatment liquid is still minor. 
   The cleaning blade  66  is composed of rubber or another elastic member, and can slide on the ink ejection surface (surface of the nozzle plate) of the head  50  by means of a blade movement mechanism (wiper) (not shown). When ink droplets or foreign matter has adhered to the nozzle plate, the surface of the nozzle plate is wiped and cleaned by sliding the cleaning blade  66  on the nozzle plate. When the soiling on the ink ejection surface is cleaned away by the blade mechanism, a preliminary ejection is also carried out in order to prevent the foreign matter from becoming mixed inside the nozzle  51  by the blade. 
   Description of Control System 
     FIG. 7  is a principal block diagram showing the system configuration of the inkjet recording apparatus  10 . The inkjet recording apparatus  10  comprises a communication interface  70 , a system controller  72 , a memory  74 , a motor driver  76 , a heater driver  78 , a print controller  80 , an image buffer memory  82 , a head driver  84 , a pressing control unit  85 , a suction control unit  87 , and the like. 
   The communication interface  70  is an interface unit for receiving image data sent from a host computer  86 . A serial interface such as USB, IEEE1394, Ethernet, wireless network, or a parallel interface such as a Centronics interface may be used as the communication interface  70 . A buffer memory (not shown) may be mounted in this portion in order to increase the communication speed. The image data sent from the host computer  86  is received by the inkjet recording apparatus  10  through the communication interface  70 , and is temporarily stored in the memory  74 . 
   The memory  74  is a storage device for temporarily storing images input through the communication interface  70 , and data is written and read to and from the image memory  74  through the system controller  72 . The memory  74  is not limited to a memory composed of semiconductor elements, and a hard disk drive or another magnetic medium may be used. 
   The system controller  72  is constituted by a central processing unit (CPU) and peripheral circuits thereof, and the like, and it functions as a control device for controlling the whole of the inkjet recording apparatus  10  in accordance with a prescribed program, as well as a calculation device for performing various calculations. More specifically, the system controller  72  controls the various sections, such as the communication interface  70 , memory  74 , motor driver  76 , heater driver  78 , pressing control unit  85 , and the like, as well as controlling communications with the host computer  86  and writing and reading to and from the memory  74 , and it also generates control signals for controlling the motor  88  and heater  89  of the conveyance system. 
   The motor driver  76  drives the motor  88  in accordance with commands from the system controller  72 . The heater driver  78  drives the heater  89  of the heating fan  40  or the like in accordance with commands from the system controller  72 . 
     FIG. 7  shows only one motor  88 , but in practice, a plurality of motors (actuators) are provided, such as a drive motor for the suction belt conveyance unit  22 , the motors of the rotational mechanism and movement mechanism of the absorbing roller  100 , and the like. Furthermore, a plurality of motor drivers  76  are provided for controlling the plurality of motors  88 . Of course, it is also possible to integrate all or a portion of the plurality of motor drivers. 
   The print controller  80  has a signal processing function for performing various tasks, compensations, and other types of processing for generating print control signals from the image data stored in the memory  74  in accordance with commands from the system controller  72  so as to supply the generated print data to the head driver  84 . Prescribed signal processing is carried out in the print controller  80 , and the ejection amount and the ejection timing of the ink droplets and treatment liquid from the respective print heads  50  are controlled through the head driver  84 . 
   The print controller  80  is provided with the image buffer memory  82 ; and image data, parameters, and other data are temporarily stored in the image buffer memory  82  when image data is processed in the print controller  80 . The aspect shown in  FIG. 7  is one in which the image buffer memory  82  accompanies the print controller  80 ; however, the image memory  74  may also serve as the image buffer memory  82 . Also possible is an aspect in which the print controller  80  and the system controller  72  are integrated to form a single processor. 
   The head driver  84  generates a drive signal on the basis of print data supplied by the print controller  80 , and drives the piezoelectric elements of the heads  12 S,  12 K,  12 C,  12 M and  12 Y, on the basis of this drive signal. A feedback control system for maintaining constant drive conditions in the head may be included in the head driver  84 . 
   The pressing control unit  85  generates a drive signal (pulse signal) on the basis of a command signal supplied by the system controller  72 , and drives the drive source  102  of the pressing arm  104  by means of this drive signal. More specifically, a positional control type of motor, such as a stepping motor, servo motor, or the like, is used for the drive source  102 , and the amount of movement of the pressing arm  104  is governed by means of the number of pulses of the pulse signal (the movement amount information in the drive signal). 
   The image data to be printed is externally (for example, from the host computer  86 ) input through the communication interface  70 , and is stored in the memory  74 . In this stage, the RGB image data is stored in the memory  74 . 
   The image data stored in the memory  74  is sent to the print controller  80  through the system controller  72 , and is converted to the dot data for each ink color in the print controller  80 . In other words, the print controller  80  performs processing for converting the input ROB image data into dot data for four colors, K, C, M and Y. The dot data generated by the print controller  80  is stored in the image buffer memory  82 . 
   In the present embodiment, the memory  74  is shown as a storage unit attached to the system controller  72 , but the memory  74  may also be constituted by a plurality of memories (storage media). Furthermore, it is also possible to incorporate the memory  74  into the system controller  72 . The information stored in the memory  74  may include, in addition to the RGB image data described above, various setting information, system parameters, a threshold value table used to judge conditions, various types of data tables, corrective coefficients used for various corrections, and the like. 
   The suction control unit  87  controls the on and off switching of the suction device  108 , and the rotational speed and rotational frequency of the suction device  108 , on the basis of a control signal output from the system controller  72 . By controlling the driving force of the suction device  108 , through the suction control unit  87 , it is possible to vary the absorption force (liquid removal capability) of the absorbing roller  100  shown in  FIG. 3 . 
   Various control programs are stored in a program storage section  90 , and a control program is read out and executed in accordance with commands from the system controller  72 . The program storage section  90  may use a semiconductor memory, such as a ROM, EEPROM, or a magnetic disk, or the like. An external interface may be provided, and a memory card or PC card may also be used. Naturally, a plurality of these storage media may also be provided. 
   The program storage unit  90  may also be combined with a storage device (memory) (not shown) for storing operational parameters (system parameters), and the like. 
   The print determination unit  24  is a block that includes the line sensor as described above with reference to  FIG. 1 , reads the image printed on the recording medium  16 , determines the ejection conditions (presence of the ejection, variation in the dot formation, and the like) by performing desired signal processing, or the like, and provides the determination results of the print conditions to the print controller  80 . 
   According to requirements, the print controller  80  makes various corrections with respect to the head  50  on the basis of information obtained from the print determination unit  24 . 
   The inkjet recording apparatus  10  comprises a temperature measurement unit  92  and a humidity measurement unit  94 , which measure the ambient temperature and the ambient humidity of the head  50  and the recording medium  16  in the print region. A temperature signal (temperature information) which indicates the temperature measured by the temperature measurement unit  92 , and a humidity signal (humidity information) indicating the humidity measured by the humidity measurement unit  94  are sent to the system controller  72 . The system controller  72  controls a temperature modification device, such as the heater  89 , cooling fan (not shown), or the like, in such a manner that a prescribed (settled) temperature and humidity are maintained on the basis of the temperature signal and the humidity signal. 
   Furthermore, the present inkjet recording apparatus  10  comprises a recording medium determination unit  96  which determines the type of recording medium used, and implements various types of control, such as control of the distance between the absorbing roller  100  and the recording medium  16 , the suction force of the suction device  108 , and the ejection of treatment liquid and ink, control of the temperature and humidity in the head  50 , and the like, in accordance with the type of recording medium determined by the recording medium determination unit  96 . In other words, a composition is adopted wherein, when the recording medium type information obtained by the recording medium determination unit  96  is sent to the system controller  72 , the system controller  72  controls the respective units on the basis of this recording medium type information. 
   The mode of determining the type of recording medium by means of the recording medium determination unit  96  may involve an operator inputting the prescribed recording medium type through a man-machine interface, such as a keyboard, touch panel, or the like, or the type of paper used may be determined automatically by reading in information from an information recording body, such as a barcode or wireless tag, in which paper type information is recorded, this information recording body being attached to the magazine or tray of the recording medium  16 . 
   On the other hand, the type of recording medium  16  to be used may be determined directly by means of the recording medium determination unit  19 , and the recording medium type may be judged on the basis of these determination results. The system controller  72  can obtain the thickness information and the surface properties information of the recording medium  16  through the thickness sensor  120  and the surface properties sensor  122  contained in the recording medium determination unit  19 . In the system controller  72 , the distance between the absorbing roller  100  and the recording medium  16  (the pressure exerted by the absorbing roller  100 ) shown in  FIG. 3 , and the suction force of the suction device  108 , and the like, are controlled on the basis of the thickness information and surface properties information of the recording medium  16 . 
   For example, when a recording medium having a rough surface, such as a coated paper, recycled paper, or the like, is used for the recording medium  16 , then the ink coloring material is less liable to become attached to the recording medium, and it is necessary to weaken the force with which the absorbing roller  100  is pressed against the recording medium  16 , or the suction force of suction device  108 , in such a manner that the coloring material is not transferred to the surface of the absorbing roller  100 . On the other hand, in the case of a smooth recording medium having good surface properties, such as an OHP sheet the coloring material is less liable to be removed from the surface of the recording medium, and the ink coloring material is less liable to become attached to the absorbing roller  100 . Therefore, the pressing force of the absorbing roller  100  against the recording medium  16  or the suction force of the suction device  108  is increased, thereby raising the efficiency of the liquid removal operation. 
   The surface state information of the absorbing roller  100  obtained by the soiling sensor  124  is sent to the system controller  72 . In the system controller  72 , the surface state information of the absorbing roller  100  obtained beforehand through the soiling sensor  124  is stored in a storage medium such as the memory  74 , the difference between the surface state information of the absorbing roller  100  stored in the storage medium and the surface state information of the absorbing roller  100  obtained from the soiling sensor  124  is determined, and the pressing force of the absorbing roller  100  against the recording medium  16  or the suction force of the suction device  108  is controlled in accordance with the result of the comparison between this difference and a beforehand settled threshold value. By using a method of this kind, the effect of the adhering matter which is originally attached to the absorbing roller  100  is cancelled out (this is equivalent to calibrating the absorbing roller  100 ). Furthermore, the surface state information of the absorbing roller  100  is stored at regular intervals, and by successively adding up (integrating) this information, it is possible to calculate the speed at which the surface state of the absorbing roller  100  changes (the speed of progress of the soiling), and hence the replacement time for the absorbing roller  100  may be estimated on the basis of this speed of progress of the soiling. Moreover, it is also possible to adopt a composition in which the replacement time of the absorbing roller  100  estimated in this way is reported to the user. 
   On the other hand, information relating to the amount of liquid contained in the absorbing roller  100  (liquid volume information), as obtained by the liquid volume measurement unit  150  including the liquid content sensor  134  and a liquid content meter  136 , is supplied to the system controller  72 . In the system controller  72 , the liquid volume information obtained from the liquid volume measurement unit  150  is compared with a beforehand settled threshold value, and it is determined whether or not the liquid volume removed from the recording medium  16  is a suitable volume, on the basis of this comparison result. Furthermore, by successively adding up the liquid volume value measured by the liquid volume measurement unit  150 , the timing of maintenance for the absorbing roller  100  (liquid removal processing) can be determined. 
   Description of Liquid Removal Control 
   There follows a description of a liquid removal capability setting and control procedure, which sets the liquid removal capability of the absorbing roller  100  (namely, the pressing force against the recording medium  16  and the suction force of the suction device  108 ), in the liquid removal control implemented in the inkjet recording apparatus  10 . The inkjet recording apparatus  10  is composed in such a manner that solvent remaining on the recording medium  16  is removed, thereby preventing rear-side transfer or image deterioration occurring when the print surface of the recording medium  16  makes contact with another recording medium  16  after printing, as well as preventing cockling of the recording medium  16 . In the liquid removal control performed in the inkjet recording apparatus  10 , the liquid removal capability of the absorbing roller  100  is set (adjusted) in accordance with the type of recording medium  16 , and hence desirable liquid removal is performed in accordance with the various conditions of the recording medium  16 . The present embodiment exemplifies a mode where the liquid removal capability of the absorbing roller  100  is controlled by altering the suction force of the suction device  108 . 
     FIGS. 8 to 10  are flowcharts showing the sequence of liquid removal capability setting control according to the present embodiment.  FIG. 8  is a flowchart of the main control sequence, and  FIGS. 9 and 10  relate to  FIG. 8  and are flowcharts of a default value setting subroutine, and an absorbing roller initialization sub-routine, respectively. 
   As shown in  FIG. 8 , when the liquid removal capability setting control is started (step S 10 ), default value setting is carried out in order to set default values for the position of the absorbing roller  100  in the thickness direction of the recording medium  16  during liquid removal, and the suction force of the suction device  108  (step S 12 ).  FIG. 9  shows the details of the default value setting process in step S 12  in  FIG. 8 . 
   As shown in  FIG. 9 , when the default value setting process is started (step S 100 ), the recording medium is determined or selected (preset) (step S 102 ). In the case of a preset in step S 102 , it is possible to determine the type of recording medium  16  by means of the recording medium determination unit  96  shown in  FIG. 7 , and the thickness and surface properties of the recording medium  16  can be determined by using the recording medium determination unit  19 . 
   In step S 104  shown in  FIG. 9 , the default value of the suction force of the suction device  108  is settled in accordance with the type of recording medium  16  preset at step S 102 . A composition may be adopted in which the relationship between the types of recording media  16  and the default values of the suction force of the suction device  108  is stored beforehand in a data table, and the default value of the suction force of the suction device  108  is determined by referring to the data table on the basis of the type of recording medium  16  preset at step S 102 . 
   Next, when the thickness information of the recording medium  16  is acquired (or when the thickness of the recording medium is determined) (step S 106 ), the default position of the absorbing roller  100  during liquid removal (during the roller is being switched on) is settled on the basis of the thickness information of the recording medium  16  (step S 108 ), and the default value of the speed of rotation of the suction device  108  during solvent removal is also determined (step S 110 ), thereby completing the default value setting process (step S 112 ). More specifically, in the default value setting shown in  FIG. 9 , various conditions in the liquid removal unit  25  are determined, such as the default position of the absorbing roller  100  during liquid removal, and the default value of the rotational speed of the suction device  108 , and the like. 
   When the default value setting in step S 12  in  FIG. 8  has terminated, an initialization process of the absorbing roller  100  is carried out (step S 14 ).  FIG. 10  shows the details of the initialization process for the absorbing roller  100  in step S 14  in  FIG. 8 . 
   As shown in  FIG. 10 , when the initialization of the absorbing roller  100  is started (step S 140 ), the start of operation of the suction device  108  is set (or a timer indicating an operational start timing of the suction device  108  is set), and the suction device  108  is operated at high speed, thereby removing the liquid content on the surface of the absorbing roller  100  and the liquid content inside the absorbing roller  100 . At the same time, the liquid content meter  136  is reset (step S 142 ). As a method for removing the liquid contained inside the absorbing roller  100 , it is also possible to adopt a method which dries the absorbing roller  100  by blowing heated air onto the absorbing roller  100 , for example. 
   Thereupon, the absorbing roller  100  is cleaned by means of a cleaning roller  112  (step S 144 ), and the initialization of the absorbing roller  100  in step S 14  in  FIG. 8  then terminates (step S 146 ). It is possible to adopt a composition in which a timer indicating the timing to implement the cleaning of the absorbing roller  100  is set in step S 144  in  FIG. 10 . The cleaning of the absorbing roller  100  may be based on a dry cleaning method (a method in which heated air is blown onto the absorbing roller  100 , thus drying the absorbing roller  100  and causing the foreign matter adhering to the surface of the roller to peel away), or on a wet cleaning method (a method in which a cleaning liquid is blown onto the absorbing roller  100 , thus removing the soiling). 
   When the initialization of the absorbing roller  100  shown in  FIG. 10  is concluded, then the surface state of the absorbing roller  100  is determined by scanning with the soiling sensor  124  (step S 16  in  FIG. 8 ), and the determination results are stored as “data  1 ” (step S 18 ). The data  1  acquired at step S 18  indicates the initial surface state of the absorbing roller  100  (the soiling information of the initial state). 
   Thereupon, the absorbing roller  100  is aligned in phase (step S 20 ) in such a manner that the liquid removal on the recording medium  16  is carried out at the position where the liquid content sensor  134  is installed and a test print is then carried out (step S 22 ). In the test print carried out at step S 22 , ink is ejected under conditions of the maximum ejection volume for the type of recording medium  16  preset at step S 102  in  FIG. 9 . 
   When the test print implemented at step S 22  has been carried out, the absorbing roller  100  is made to contact the liquid on the recording medium  16  (the absorbing roller  100  is switched on) and the liquid is removed from the recording medium  16  (step S 24 ), and after a prescribed time period has elapsed, the liquid removal is ended by switching off the absorbing roller  100  in such a manner that the absorbing roller  100  and the recording medium  16  assume a non-contact state (step S 26 ). The surface state of the absorbing roller  100  is then determined by scanning with the soiling sensor  124  (step S 28 ), and the determination results are stored as “data  2 ” (step S 30 ). 
   When the surface state information (data  2 ) relating to the absorbing roller  100  acquired in step S 28  has been stored (step S 30 ), the differential data relating to the surface state obtained by subtracting data  1  from data  2  is compared with a beforehand settled threshold value (step S 32 ). The differential data of the surface state indicates the amount of change in the surface state of the absorbing roller  100  (and corresponds to the amount of the adhering matter that has become attached to the roller during liquid removal). 
   In step S 32 , when the differential data ((data  2 )−(data  1 )) is not greater than the beforehand settled threshold value (NO verdict), in other words, when foreign matter such as ink coloring material has not become attached to the surface of the absorbing roller  100  (or when foreign matter has become attached to the roller, but the amount thereof is extremely small and hence is not problematic), then the procedure advances to step S 34 . 
   In step S 34 , the liquid content of the absorbing roller  100  (the amount of liquid removed from the recording medium  16  by the absorbing roller  100  during liquid removal) is compared with a beforehand settled threshold value, and if the liquid content is not less than the threshold value (NO verdict), then this means that a prescribed amount of liquid has been removed from the absorbing roller  100 , while at the same time, the ink coloring material has not been removed during liquid removal. Therefore, the suction force of the suction device  108  is judged to be suitable, and the suction force of the suction device  108  is set to the default value (or left at the default value), whereupon the liquid removal capability setting control procedure terminates (step S 36 ). 
   On the other hand, if the liquid content of the absorbing roller  100  is less than the threshold value at step S 34  (YES verdict), then it is judged that the suction force of the suction device  108  is insufficient (in other words, the prescribed amount of liquid cannot be removed at the current suction force setting), and the suction force of the suction device  108  is increased by one level (step S 38 ), whereupon the procedure returns to step S 14 . 
   Furthermore, at step S 32 , if the differential data ((data  2 )−(data  1 )) is greater than the beforehand settled threshold value, in other words, if an intolerable level of foreign matter such as ink coloring material has become attached to the surface of the absorbing roller  100  (YES verdict), then the suction force of the suction device  108  is reduced by one level (step S 40 ), and the procedure then returns to step S 14 . 
   In this way, the suction force setting that is suited to the type of the recording medium  16  is determined for the suction device  108  by repeating step S 14  to step S 40  shown in  FIG. 8 . 
     FIG. 8  shows the mode in which the liquid removal capability of the absorbing roller  100  is changed by altering the suction force of the suction device  108 , but in a mode where the liquid removal capability of the absorbing roller  100  is changed by altering the pressing force of the absorbing roller  100 , at step S 38 , the pressing arm  104  is operated so as to raise the pressing force of the absorbing roller  100  against the recording medium  16 , by one level, instead of raising the suction force of the suction device  108  by one level, and at step S 40 , the pressing arm  104  is operated so as to reduce the pressing force of the absorbing roller  100  against the recording medium  16 , by one level, instead of reducing the suction force of the suction device  108  by one level. 
   Liquid Removal Capability of Absorbing Roller 
   As described above, the method for changing the liquid removal capability of the absorbing roller  100  may be a method which changes the pressing force of the absorbing roller  100  against the recording medium  16  (the position of the absorbing roller  100  in the thickness direction), or a method which changes the suction force (rotational speed) of the suction device  108 . Either one of these factors, or both of these factors may be changed. Furthermore, it is also possible to beforehand store liquid removal capability tables (absorption force tables) in accordance with the properties of the recording medium  16 , and to change the liquid removal capability in accordance with the absorption force tables. 
     FIGS. 11 and 12  show embodiments of the absorption force tables. The absorption force table  200  shown in  FIG. 11  corresponds to OHP sheets (resin film), and the absorption force table  202  shown in  FIG. 12  corresponds to art paper. 
   When using an OHP sheet as the recording medium  16 , the ink coloring material is not liable to adhere to the absorbing roller  100  during liquid removal, and the liquid removal capability of the absorbing roller  100  is mainly adjusted by changing the suction force (rotational speed) of the suction device  108 . In other words, if the liquid removal capability is increased by one level (at (+1) in  FIG. 11 ), then the position of the absorbing roller  100  is not changed and the rotational speed of suction device  108  is controlled to a value of 1.2 times the default value (at (0) in  FIG. 11 ). Furthermore, if the liquid removal capability is increased by two levels (at (+2) in  FIG. 11 ), then the absorbing roller  100  is moved in such a manner that the position of the absorbing roller  100  (clearance) is 0.8 times the default value (in other words, so that the absorbing roller  100  is positioned closer to the recording medium  16  than the default position), and furthermore, the rotational speed of the suction device  108  is controlled to be 1.4 times the default value. 
   On the other hand, if the liquid removal capability of the absorbing roller  100  is reduced by one level (at (−1) in  FIG. 11 ), then the position of the absorbing roller  100  is not changed from the default position, while the rotational speed of the suction device  108  is set to 0.8 times the default value. If the liquid removal capability of the absorbing roller  100  is reduced by two levels (at (−2) in  FIG. 11 ), then the absorbing roller  100  is moved in such a manner that the position of the absorbing roller  100  (clearance) is 1.2 times the default value (in other words, the absorbing roller  100  is distanced further from the recording medium  16  than the default position), and the rotational speed of the suction device  108  is controlled so as to be 0.6 times the default value. 
   When art paper is used for the recording medium  16 , the ink coloring material is liable to become attached to the absorbing roller  100  during liquid removal, and hence the liquid removal capability is adjusted mainly by changing the position of the absorbing roller  100  in the thickness direction of the recording medium  16 . In other words, if the liquid removal capability is increased by one level (at (+1) in  FIG. 12 ), then the rotational speed of the suction device  108  is not changed from the default value (at (0) in  FIG. 12 ) and the position of the absorbing roller  100  is controlled to a value of 0.9 times the default value. 
   Furthermore, if the liquid removal capability is increased by two levels (at (+2) in  FIG. 12 ), then the rotational speed of the suction device  108  is set to 1.1 times the default value, and the absorbing roller  100  is moved in such a manner that the position of the absorbing roller  100  (clearance) becomes 0.8 times the default value. 
   On the other hand, if the liquid removal capability of the absorbing roller  100  is reduced by one level (at (−1) in  FIG. 12 ), then the rotational speed of the suction device  108  is not changed from the default value ((0) in  FIG. 12 ) and the position of the absorbing roller  100  is controlled to a value of 1.1 times the default value. Furthermore, if the liquid removal capability is reduced by two levels (at (−2) in  FIG. 12 ), then the rotational speed of the suction device  108  is set to 0.9 times the default value, and the absorbing roller  100  is moved in such a manner that the position of the absorbing roller  100  (clearance) becomes 1.2 times the default value. 
   The absorption force tables such as shown in  FIGS. 11 and 12  are stored beforehand for types of recording media  16 , and the liquid removal capability of the absorbing roller  100  is adjusted by referring to the absorption force tables. Furthermore, desirably, a composition is adopted in which the adsorption force tables are updated in accordance with the temporal change of the absorbing roller  100 . 
   Since there are types of ink having properties whereby the ink is liable to peel away from the recording medium  16  and other types of ink having properties whereby the ink is liable to adhere to the absorbing roller  100 , then the liquid removal capability of the absorbing roller  100  may be changed in accordance with the type of ink. 
   Other Mode of Test Print 
   In the liquid removal capability setting control shown by the flowchart in  FIG. 8 , the liquid removal capability that is suitable for the recording medium  16  in use is set by printing test patches while changing the liquid removal capability by one level for each patch. As shown in  FIG. 13 , it is also possible to set the optimum liquid removal capability by printing a continuous test patch and changing the liquid removal capability in a stepwise fashion.  FIG. 13  shows a case where a test pattern  230  comprising five test patches  220  to  228  arranged in the paper feed direction is formed, and liquid removal is carried out by changing the liquid removal capability for the test patches, the surface state and liquid content of the absorbing roller  100  being determined accordingly, and the optimal liquid removal capability of the absorbing roller  100  being set on the basis of these determination results. 
   The test patches  220  to  228  shown in  FIG. 13  are aligned at constant intervals at a pitch of L. By setting the arrangement pitch L of the test patches to be substantially the same as the circumference length of the absorbing roller  100 , it is possible to remove liquid with the liquid content sensor  134  always being located in a certain position. Furthermore, the liquid removal capability of the absorbing roller  100  is settled with reference to the absorption force table  200  (or  202 ) shown in  FIG. 11  (or  FIG. 12 ). 
   In the embodiment shown in  FIG. 13 , the liquid removal capability in the liquid removal of the test patch  220  is set to the 2-level-down (−2) liquid removal capability shown in  FIG. 11 , and the liquid removal capability in the liquid removal of the test patch  222  is set to the 1-level-down (−1) liquid removal capability shown in  FIG. 11 . Furthermore, the liquid removal capability in the liquid removal of the test patch  224  is set to the default value (0) liquid removal capability, and the liquid removal capability in the liquid removal of test patches  226  and  228  is set respectively to the 1-level-up (+1) and 2-level-up (+2) liquid removal capabilities shown in  FIG. 11 . In other words, the liquid removal capabilities in the liquid removal of test patches  220  to  228  are changed, one level at a time, from the 2-level-down liquid removal capability in  FIG. 11 , to the 2-level-up liquid removal capability. When forming the test patches, ink is ejected under conditions of the maximum ejection volume. 
   In the inkjet recording apparatus  10  having the composition shown above, the liquid removal capability of the absorbing roller  100  during liquid removal is set in accordance with the thickness and surface characteristics of the recording medium  16 , and the like. More specifically, a test pattern is printed on the recording medium  16 , liquid removal is carried out with respect to the test pattern, the adhering matter, such as ink coloring material, which adheres to the absorbing roller  100  after the completion of liquid removal, and the liquid volume contained in the absorbing roller  100 , are determined, and the liquid removal capability of the absorbing roller  100  is adjusted on the basis of these determination results. Consequently, suitable liquid removal corresponding to the type of recording medium  16  is implemented, and cockling caused by an insufficient liquid removal capability, or peeling away of the ink coloring material due to an excessive liquid removal capability, or the like, is prevented. Therefore, a desirable image is formed on the recording medium  16 . 
   In the aforementioned embodiments, the two-liquid system is used in which the ink coloring material is fixed onto the recording medium by making the treatment liquid react with the ink on the recording medium  16 , but the present invention may also be applied to a mode in which the ink is fixed onto the surface or interior of the recording medium  16  without using treatment liquid. 
   Furthermore, when the temperature or humidity varies, then the viscosity, surface tension, and the like, of the ink and treatment liquid may change and the surface state, thickness, and the like, of the recording medium  16  may also change. Therefore, correctional coefficients are beforehand set for the pressing force of the absorbing roller  100  or the suction force of the suction device  108 , in accordance with the temperature and humidity (in other words, a correction table for temperature and humidity is stored), and the liquid removal capability of the absorbing roller  100  is also controlled on the basis of the measurement results of the temperature measurement unit  92  and the humidity measurement unit  94 . 
   Second Embodiment 
   Next an inkjet recording apparatus  300  according to a second embodiment of the present invention is described. In the inkjet recording apparatus  300 , the recording medium  16  is observed, and the liquid removal capability of the absorbing roller  100  during liquid removal is controlled on the basis of the result of the observing operation. The present embodiment exemplifies a mode where the liquid removal capability of the absorbing roller  100  is controlled by altering the suction force of the suction device  108 . 
     FIG. 14  is a principal schematic drawing showing the composition of the liquid removal unit  302  of the inkjet recording apparatus  300 , and  FIG. 15  is a principal block diagram showing the system composition of the inkjet recording apparatus  300 . The overall composition of the inkjet recording apparatus  300  is similar to that of the inkjet recording apparatus  10  shown in  FIG. 1 , and here, a general description is omitted and those parts which are different to the inkjet recording apparatus  10  shown in  FIG. 1  are described. Furthermore, parts in  FIG. 14  which are the same as or similar to those in  FIG. 3 , and parts in  FIG. 15  which are the same as or similar to those in  FIG. 7  are denoted with the same reference numerals and description thereof is omitted. 
   The liquid removal unit  302  of the inkjet recording apparatus  300  shown in  FIG. 14  is provided with a density meter  304  (density meter  1 ) on the upstream side of the absorbing roller  100  in terms of the paper feed direction, and a density meter  306  (density meter  2 ) on the downstream side of the absorbing roller  100  in terms of the paper feed direction. The density of the ink coloring material in the image (dots forming the image) formed on the recording medium  16  is measured with the density meter  1  and the density meter  2 , and the measurement results are fed back into the procedure for setting the liquid removal capability of the absorbing roller  100 . More specifically, as shown in  FIG. 15 , the system controller  72  obtains information on the density of the ink coloring material before liquid removal, as measured through the density meter  1 , and information on the density of the ink coloring material after liquid removal, as measured through the density meter  2 . The system controller  72  finds the density difference from the obtained information, and if the density difference is greater than a prescribed threshold value, then it is determined that ink coloring material has been removed, together with the liquid, during the liquid removal process, and control is implemented in order to reduce the suction force of the suction device  108 . 
   Each of the density meters  1  and  2  used in the present embodiment includes a light emitting section and a light receiving section. The light irradiated from the light emitting section onto the recording medium  16  and reflected by the ink coloring material (reflected light component) is received by the light receiving unit, and the density of the ink coloring material is found from the strength of the color of the ink coloring material (color intensity), on the basis of the amount of reflective light measured by the light receiving unit (the strength of the reflected light). The density of the ink coloring material measured by the density meter  1  needs to be corrected in respect the reflected light component created by the ink solvent (mainly water). In other words, in the density meter  1 , a corrected light amount is determined by correcting the amount of light measured by the light receiving unit in respect of the amount of light reflected by the ink solvent. A corrected density before liquid removal is determined on the basis of this corrected light amount. 
   In concrete terms, a light receiving unit capable of measuring light reflected at 45° and light reflected at 90° is provided, and the magnitude of the reflection component caused by the ink solvent in the 45° reflected light is measured. Correction for the reflection component caused by the ink solvent is carried out by using the 45° reflection component (the reflection component caused by the ink solvent) as a correction parameter for the 90° reflection component (the reflection component caused by the ink coloring material). 
     FIG. 16  shows a flowchart of liquid removal capability setting control for solvent removal in the inkjet recording apparatus  300 . In  FIG. 16 , the steps which are the same as or similar to those in  FIG. 8  are denoted with the same reference numerals and description thereof is omitted here. 
   In the liquid removal capability setting control shown in  FIG. 16 , after initializing the absorbing roller shown in  FIG. 8  (step S 12 ), the surface characteristics of the recording medium  16  are determined by using the surface characteristics sensor  122  shown in  FIG. 14  (step S 15 ).  FIG. 17  shows the details of determining the surface characteristics of the recording medium  16  in step S 15 . 
   As shown in  FIG. 17 , when the determination of surface characteristics of the recording medium  16  is started (step S 240 ), firstly, the surface characteristics of the recording medium  16  are observed by using the surface characteristics sensor  122  (step S 242 ), and the amount of light reflected by the recording medium  16  (amount of reflected light) is compared with a prescribed threshold value (threshold value 1) (step S 244 ). At step S 244 , if the amount of reflected light is not less than the threshold value 1 (NO verdict), then the procedure advances to step S 246 , and the amount of reflected light is compared with another prescribed threshold value (threshold value 2, where the threshold value 1&lt;the threshold value 2). 
   At step S 246 , if the amount of reflected light is greater than the threshold value 2 (YES verdict), then the recording medium  16  is judged to have high smoothness, and control is implemented in order to increase the suction force of the suction device  108  (step S 248 ). The suction force of the suction device  108  corrected at step S 248  is settled (step S 252 ), and the control procedure for determining the surface characteristics of the recording medium  16  then terminates (step S 254 ). 
   If the amount of reflected light is not greater than the threshold value 2 at step S 246  (NO verdict), then the suction force of the suction device  108  is settled without correcting the suction force of the suction device  108  on the basis of the surface characteristics of the recording medium  16  (step S 252 ), and the procedure then advances to step S 254 . 
   On the other hand, at step S 244 , if the amount of reflected light is less than the threshold value 1 (YES verdict), then the recording medium  16  is judged to have low smoothness (in other words, a rough surface), and control is implemented in such a manner that the suction force of the suction device  108  is reduced (step S 250 ). The suction force of the suction device  108  corrected at step S 250  is settled (step S 252 ), and the procedure then advances to step S 254 . 
   In other words, if the amount of reflected light is in a range between the threshold value 1, which is a lower limit value of the surface characteristics determination value, and the threshold value 2, which is an upper limit value of same, then the suction force of the suction device  108  is not corrected in accordance with the surface characteristics of the recording medium  16 . On the other hand, if the amount of reflected light lies outside the range between the threshold value 1 and the threshold value 2, then the suction force of the suction device  108  is corrected in accordance with the surface characteristics of the recording medium  16 . The determination of the surface characteristics of the recording medium  16  as shown in  FIG. 17  (step S 15  in  FIG. 16 ) may also be carried out between step S 14  and step S 16  of the liquid removal capability setting procedure shown in  FIG. 8 . 
   When the suction force of the suction device  108  has been corrected by the process of determining the surface characteristics of the recording medium  16  as shown in  FIG. 17  (in other words, when the corrected suction force has been settled in accordance with the determined surface characteristics), then a test print is created (step S 22  in  FIG. 16 ), and the procedure then advances to step S 202 . 
   At step S 202 , the ink coloring material density before liquid removal (density  1 ) is measured by means of the density meter  1 . As described previously, the density meter  1  obtains a corrected density value (the corrected density  1  in  FIG. 16 ). Thereupon, when liquid removal has been carried out (step S 204 ), the ink coloring material density after liquid removal (density  2 ) is measured by means of the density meter  2  (step S 210 ). 
   The density difference between the density  2  measured at step S 210  and the corrected density  1  determined at step S 202  is calculated, and this density difference is compared with a beforehand established threshold value (step S 212 ). At step S 212 , if the density difference is not greater than the threshold value (NO verdict), then the procedure advances to step S 216 , where it is judged whether or not there is print data. If there is print data at step S 216  (YES verdict), then the procedure advances to step S 218 , where it is judged whether or not the recording medium used for printing the print data is of the same type, and if the recording medium to be used in printing is a recording medium of a different type (NO verdict), then the procedure advances to step S 12 , whereas if it is the same type of recording medium (YES verdict), then the procedure advances to step S 36 , and the liquid removal capability setting control procedure terminates. If there is no print data at step S 216  (NO verdict), then the procedure advances to step S 36 , and the liquid removal capability control procedure then terminates. 
   Although the liquid removal capability control procedure is preferably carried out by using a test pattern, the liquid removal capability may also be controlled by using an actual image.  FIG. 18  is a flowchart of a liquid removal capability control procedure during actual image printing. The present embodiment exemplifies a mode where the liquid removal capability of the absorbing roller  100  is controlled by altering the suction force of the suction device  108 . 
   As shown in  FIG. 18 , when printing starts (step S 300 ), the ejection volumes of the liquids (the ejection volumes of the treatment liquid and the ejection volumes of the ink) are calculated on the basis of the print data (step S 302 ), and the maximum value of these liquid ejection volumes and the position of the maximum value are determined (step S 304 ). Thereupon, the default value setting procedure shown in step S 12  in  FIG. 8  (step S 306  in  FIG. 18 ) and the initialization of the absorbing roller  100  shown in step S 14  in  FIG. 8  (step S 308  in  FIG. 18 ) are carried out, the surface characteristics determination procedure for the recording medium  16  shown in step S 15  in  FIG. 16  (step S 310  in  FIG. 18 ) is implemented, and a corrected suction force based on the surface characteristics of the recording medium  16  is set for the suction device  108 , by taking the surface characteristics of the recording medium  16  into account (step S 312 ). 
   Thereupon, it is judged whether the position of the maximum ejection volume is located in the lower half of the image (the trailing edge side in terms of the paper feed direction) or the upper half of the image (the leading edge side in terms of the paper feed direction) (step S 314 ), and if the location of the position of the maximum ejection volume is judged to be in the lower half of the image (YES verdict), then the image is rotated through 180° (step S 316 ), whereupon the procedure advances to step S 318 . On the other hand, if, at step S 314 , it is judged that the position of the maximum ejection volume is located in the upper half of the image (NO verdict), then the procedure advances to step S 318 . 
   In step S 318 , the density meters  1  and  2  are moved so as to correspond to the location of the position of the maximum ejection volume, and the procedure then advances to step S 320 , where an actual image is printed. 
   When performing liquid removal for removing the liquid on the recording medium  16 , the suction force of the suction device  108  is set as shown in step S 200  to step S 214  in  FIG. 16  (the suction force is corrected in accordance with the image density) (step S 322  in  FIG. 18 ), and when the prescribed image has been formed on the recording medium  16 , the print control sequence terminates (step S 324 ). 
   In the mode where the suction force of the suction device  108  is thus varied by observing the type of recording medium  16 , since the recording medium  16 , which is the final product, is directly observed, then there is little risk of supplying an image of degraded quality to the user, and furthermore, desirable liquid removal can be achieved by means of the apparatus having a simple composition. 
   Furthermore, in order to improve the beneficial effects, it is preferable that the thickness of the recording medium  16  is measured by using the thickness sensor  120  (shown in  FIG. 15 ), and the clearance between the recording medium  16  and the absorbing roller  100  (in other words, the position of the absorbing roller  100  during liquid removal) is adjusted in accordance with the thickness of the recording medium  16 . 
   Moreover, it is also possible to determine or select (preset) the type of recording medium  16 , and to control the suction force (speed of rotation) of the suction device  108  (shown in  FIG. 15 ) in accordance with the type of recording medium  16 . It is possible to use the surface characteristics sensor  122  shown in  FIG. 15 , or the density meters  1  and  2 , in order to determine the recording medium  16 . In a mode where the density meters  1  and  2  are provided, it is possible to omit the surface characteristics sensor  122 . 
   Adaptation Embodiment 
   Next, an adaptation embodiment of the first and second embodiments described above is explained.  FIG. 19  is a principal schematic drawing showing the composition of a liquid removal unit  402  of an inkjet recording apparatus  400  according to the adaptation embodiment, and  FIG. 20  is a principal block diagram showing the system composition of the inkjet recording apparatus  400 . The overall composition of the inkjet recording apparatus  400  is similar to that of the inkjet recording apparatus  10  shown in  FIG. 1 , and here, a general description is omitted and those parts which are different to the inkjet recording apparatus  10  shown in  FIG. 1  are described. Furthermore, parts in  FIG. 19  which are the same as or similar to those in  FIG. 3 , and parts in  FIG. 20  which are the same as or similar to those in  FIG. 7  are denoted with the same reference numerals and description thereof is omitted. 
   As shown in  FIG. 19  and the inkjet recording apparatus  400  comprises the soiling sensor  124 , which observes the surface of the absorbing roller  100 , the liquid volume measurement unit  150  (shown in  FIG. 20 ), which measures the amount of liquid contained in the absorbing roller  100 , and the density meters  1  and  2 , which measure the density of the ink coloring material on the recording medium  16 . 
   In the inkjet recording apparatus  400  having this composition, when printing an actual print, the suction force of the suction device  108  (or the pressing force of the absorbing roller  100 ) is adjusted by measuring the density of the ink coloring material on the recording medium  16 , and at the same time, the surface state of the absorbing roller  100  and the liquid content of the absorbing roller  100  are determined at prescribed intervals, and these determination results are added up to predict the cleaning timing for the absorbing roller  100 , and the replacement timing for the absorbing roller  100  and the cleaning roller  112 . The results of these predictions are reported to the user. By combining the use of the device which observing the absorbing roller  100  and the device which observing the recording medium  16  in this way, it is possible to achieve highly efficient liquid removal, while also improving the maintenance properties of the liquid removal unit  25 . 
   Further Embodiments 
   The one treatment liquid ejection head  12 S is disposed at the furthest upstream position of the print unit  12  (see  FIG. 1 ) in the above-described embodiments; however, in implementing the present invention, the arrangement of the treatment liquid ejection head is not limited to this, and it is also possible to adopt a composition in which a treatment liquid ejection head is appended at least one position between the color ink ejection heads in the print unit  12 . 
   Furthermore, an ejection head based on an inkjet method is used as the device for applying treatment liquid in the embodiments described above, but instead of or in combination with this, it is also possible to use a device which applies treatment liquid to the recording medium  16  by using a contacting member, such as a roller, brush, blade, or the like. 
   In the above-described embodiments, the treatment liquid ejection head  12 S which ejects one type of treatment liquid is shown, but it is also possible to compose the treatment liquid ejection head  12 S from a plurality of heads, or to use a composition in which treatment liquid of two or more types can be ejected selectively. Furthermore, the mode is shown in which one type of ink is provided in the inkjet recording apparatus  10  ( 300 ,  400 ) in the above-described embodiments, but it is also possible to adopt a composition in which a plurality of heads are provided in such a manner that inks of a plurality of types can be ejected selectively. 
   In the above-described embodiments, the inkjet recording apparatus using the page-wide full line type heads having the nozzle rows of the length corresponding to the entire width of the recording medium  16  is described, but the scope of application of the present invention is not limited to this, and the present invention may also be applied to an inkjet recording apparatus using a shuttle head which performs image recording while moving a recording head of short dimensions, in a reciprocal fashion. 
   In the above-described embodiments, the absorbing roller  100  has a length corresponding to the width of the recording medium  16  in the lengthwise direction, but it is also possible to adopt a composition where the absorbing roller  100  has a structure which is divided in the lengthwise direction thereof, in such a manner that liquid removal can be performed independently by means of each divided portion of the absorbing roller  100 . In this case, the absorbing roller  100  can be controlled finely in accordance with the distribution of solvent on the recording medium  16 , and moreover, improved maintenance characteristics can be expected in the absorbing roller  100 . 
   In the above-described embodiments, the inkjet recording apparatus for forming images on a recording medium  16  by ejecting ink from nozzles provided in print heads is described, but the scope of application of the present invention is not limited to this, and it may also be applied broadly to image forming apparatuses which form images (three-dimensional shapes) by means of liquids other than ink, such as resist, or to liquid ejection apparatuses, such as dispensers, which eject liquid chemicals, water, or the like, from nozzles (ejection holes). 
   It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.