Patent Publication Number: US-10310418-B2

Title: Separating device

Description:
TECHNICAL FIELD 
     The present invention relates to a separating device for separating a toner and a carrier liquid from a liquid developer, and an image forming apparatus, including the separating device, for forming an image with the liquid developer. 
     BACKGROUND ART 
     Conventionally, the image forming apparatus for forming the image with the liquid developer containing the toner and the liquid developer has been known. In the image forming apparatus, the liquid developer which is not used in an image forming step is collected and recycled. In such a recycling process of the liquid developer, toner particles which are a dispersoid in the liquid developer (liquid material) and the carrier liquid which is a dispersion medium in the liquid developer are separated, and then the carrier liquid is used again. 
     For example, a constitution in which an electrode roller, a damming roller, a blade member and a liquid accommodating container are provided has been proposed (Japanese Laid-Open Patent Application (JP-A) 2008-242436). In the constitution described in JP-A 2008-242436, as shown in (a) of  FIG. 15 , the liquid developer is supplied between an electrode roller  942  and a liquid accommodating container  941 . Then, the electrode roller  942  is rotated while applying a voltage to between the electrode roller  942  and the liquid accommodating container  941  so that the toner is attracted toward the electrode roller  942 . Here, a supply port  946   a  through which the liquid developer is supplied is positioned with respect to a substantially horizontal direction, and the liquid developer passed through between the electrode roller  942  and the liquid accommodating container  941  is discharged through a discharge port  946   b  positioned above the supply port  946   a  with respect to a direction of gravitation and then is sent to a carrier tank (not shown). 
     In a side of the electrode roller  942 , downstream of the discharge port  946   b  with respect to a rotational direction of the electrode roller  942 , the damming roller  943  is disposed in contact with the electrode roller  942 , so that the liquid developer fed (conveyed) by the electrode roller  942  is dammed by the damming roller  943 . At a position further downstream of the damming roller  943 , a blade member  944  is disposed in contact with the electrode roller  942  and solid components of the liquid developer, fed with rotation of the electrode roller  942  without being dammed by the damming roller  943 , off a surface of the electrode roller  942 . 
     Incidentally, between the supply port  946   a  and the discharge port  946   b , another discharge port  946   c  for circulating the liquid developer between itself and the supply port  946   a  is provided. The liquid developer is circulated between another discharge port  946   c  and the supply port  946   a  until a toner content (concentration) in the carrier liquid is not more than a predetermined value, and then is discharged through the discharge port  946   b.    
     In the case of the constitution described in JP-A 2008-242436, as shown in (b) of  FIG. 15 , during passing of the liquid developer through between the liquid accommodating container  941  and the electrode roller  942 , on the surface of the electrode roller  942 , an urged toner T layer and a carrier liquid C layer outside the toner T layer are formed. The toner T layer and the carrier liquid C layer which are fed with rotation of the electrode roller  942  pass through between the electrode roller  942  and the damming roller  943 . At this time, the carrier liquid C layer is divided into a portion on the damming roller  943  side and a portion on the electrode roller  942  side in a predetermined proportion. 
     Here, the carrier liquid C layer separated and fed on the damming roller  943  side is carried on the damming roller  943 , and the toner T layer passed through between the electrode roller  942  and the damming roller  943  is collected by a blade member  944 . 
     In order to enhance reuse efficiency of the carrier liquid, it would be considered that a position where the developer is supplied to the damming roller  943  is disposed in a region (from 0 o&#39;clock position to 6 o&#39;clock position) in which the surface of the electrode roller moves from above toward below. In this case, in the case where a constitution in which the toner on the electrode roller is directly scraped off is employed, a contact position of a blade is in the 6 o&#39;clock position or the later. In general, the blade is provided in contact with the electrode roller in a direction counter to a rotational direction of the electrode roller in order to improve a collecting property. For this reason, the toner collected by the blade flows back onto the electrode roller along the blade in some cases. Further, the contact position of the blade is restricted, and therefore an inclination angle of the blade with respect to a horizontal direction becomes small. As a result, the toner stagnates on the blade, so that there was a liability that a toner collecting property lowers. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in view of the above-described circumstances and a principal object of the present invention is to improve a separation property between a carrier liquid and a toner. 
     According to an aspect of the present invention, there is provided separating device for separating a toner and a carrier liquid from a liquid developer including the toner and the carrier liquid using an electric field, the separating device comprising: an electroconductive electrode roller rotatable in a predetermined direction; an electrode member provided with a gap between itself and an outer peripheral surface of the electrode roller, wherein the electrode member is capable of applying a voltage for generating an electric field for moving the toner toward the electrode roller between the electrode roller and the electrode member, wherein an upstream end portion of the gap with respect to a rotational direction of the electrode roller is provided above, with respect to a direction of gravitation, a downstream end portion of the gap with respect to the rotational direction; a supplying portion configured to supply the liquid developer into the gap from the upstream end portion of the gap; a collecting portion provided below the upstream end portion of the gap with respect to the direction of gravitation and configured to collect the carrier liquid from the electrode roller in a side downstream of the electrode member with respect to the rotational direction; a collecting roller provided downstream of the electrode member with respect to the rotational direction and rotatable in the same peripheral movement direction as the electrode roller in contact with the electrode roller at a position opposing the electrode roller, wherein the collecting roller is capable of applying a voltage for generating an electric field for moving the toner toward the collecting roller between the collecting roller and the electrode roller; and a blade member configured to collect the toner from the collecting roller in contact with the collecting roller counterdirectionally with respect to a rotational direction of the collecting roller, wherein when a line passing through a center of the electrode roller and a top of the electrode roller with respect to the direction of gravitation is 0°, the upstream end portion of the gap is positioned in a range of 0° or more and less than 180° with respect to the rotational direction of the electrode roller, and wherein when a line passing through a center of the collecting roller and a top of the collecting roller with respect to the direction of gravitation is 0°, a contact position of the blade member with the collecting roller is in a range of 35° or more in a side upstream of a position of contact between the collecting roller and the electrode roller with respect to the rotational direction of the collecting roller. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an image forming apparatus in an embodiment of the present invention. 
         FIG. 2  is a schematic illustration showing a feeding path of a liquid developer in the image forming apparatus in the embodiment. 
         FIG. 3  is a control block diagram of a feeding operation of the liquid developer in the image forming apparatus in the embodiment. 
         FIG. 4  is a flowchart showing control of the feeding operation of the liquid developer in the image forming apparatus in the embodiment. 
         FIG. 5  is a perspective view of a separation and extraction device in the embodiment. 
         FIG. 6  is a partially cut perspective view showing the separation and extraction device in the embodiment. 
         FIG. 7  is a sectional view showing a part of the separation and extraction device in the embodiment. 
         FIG. 8  is an enlarged view of portion A in  FIG. 7 . 
         FIG. 9  is a perspective view showing a part of the separation and extraction device in the embodiment. 
         FIG. 10  is a perspective view showing the part of the separation and extraction device in the embodiment as seen from an angle different from an angle in  FIG. 9 . 
         FIG. 11  is a flowchart showing control of a separation and extraction operation of the liquid developer in the embodiment. 
         FIG. 12  is a sectional view, showing a part of the separation and extraction device in the embodiment, for illustrating a flow of a toner. 
         FIG. 13  is a sectional view showing another example of the separation and extraction device in the embodiment, in which a peripheral portion of a collecting roller is shown. 
       In  FIG. 14 , (a) to (c) are sectional views showing first to third examples, respectively, of the separation and extraction device in the embodiment, in which a peripheral portion of a collecting roller is shown in each of the first to third examples. 
       In  FIG. 15 , (a) is a sectional view of a separation and extraction device in a conventional example, and (b) and (c) are enlarged views of portion B and portion C, respectively, of (a) of  FIG. 15 , each showing a relation between a toner and a carrier liquid. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described using  FIGS. 1-14 . First, a general structure of an image forming apparatus in this embodiment will be described using  FIG. 1 . 
     (Image Forming Apparatus) 
     An image forming apparatus  100  in this embodiment is a digital printer of an electrophotographic type in which a toner image is formed on a recording material (a sheet, a sheet material such as an OHP sheet and so on). The image forming apparatus  100  is operated on the basis an image signal, and a toner image formed by an image forming portion  12  is transferred onto a sheet as the recording material is successively fed from each of cassettes  11   a ,  11   b  and then is fixed on the sheet S, so that an image is obtained. The image signal is sent from an external terminal such as an unshown scanner or an unshown personal computer. 
     The image forming portion  12  includes a photosensitive drum as an image bearing member, a charger  14 , a laser exposure device  15 , a developing device  16  and a drum cleaner  19 . A surface of the photosensitive drum  13  electrically charged by the charger  14  is irradiated with laser light E from the laser exposure device  15  depending on the first signal, so that an electrostatic latent image is formed on the photosensitive drum  13 . This electrostatic latent image is developed as a toner image by the developing device  16 . In this embodiment, in the developing device  16 , a liquid developer D as a liquid material in which a powdery toner which is a dispersoid is dispersed in a carrier liquid which is a dispersion medium is accommodated, and development is effected using this liquid developer D. 
     The liquid developer D is generated by mixing and dispersing a toner T in a carrier liquid C in a predetermined ratio in a mixer  31  as a mixing device, and then is supplied to the developing device  16 . The carrier liquid C is accommodated in a carrier tank  32  as a carrier container (collecting container), and the toner T is accommodated in a toner tank  33  as a toner container. Then, depending on a mixed state of the carrier liquid C and the toner T in the mixer  31 , the carrier liquid C or the toner T is supplied from an associated tank. In the mixer  31 , a stirring blade driven by an unshown motor is accommodated, and the developer liquid D is mixed with the carrier liquid C or the toner T by being stirred, so that the toner is dispersed in the carrier liquid. 
     The liquid developer supplied from the mixer  31  to the developing device  16  is coated (supplied) on a developing roller  18  as a developer carrying member and is used for development. The developing roller  18  carries and feeds the liquid developer D on a surface thereof, and develops with the toner the electrostatic latent image formed on the photosensitive drum  13  (first bearing member). The carrier liquid C and the toner T which remain on the developing roller  18  after the development is collected in a collecting section  16   b  of the developing device  16 . Here, each coating of the liquid developer from a coating roller  17  onto the developing roller  18  and the development of the electrostatic latent image on the photosensitive drum  13  by the developing roller  18  is made using an electric field. 
     The toner image formed on the photosensitive drum  13  is transferred onto an intermediary transfer roller  20  using the electric field, and then is fed to a nip formed by the intermediary transfer roller  20  and a transfer roller  21 . The toner T and the carrier liquid C which remain on the photosensitive drum  13  after the toner image transfer onto the intermediary transfer roller  20  are collected by the drum cleaner  19 . Incidentally, at least one of the intermediary transfer roller  20  and the transfer roller  21  may also be an endless belt. 
     The sheet S accommodated in each of the cassettes  11   a ,  11   b  is fed toward a registration feeding portion  23  by an associated feeding portion  22   a  or  22   b  constituted by feeding rollers. The registration feeding portion  23  feeds the sheet S to the nip between the intermediary transfer roller  20  and the transfer roller  21  by being timed to the toner image transferred on the intermediary transfer roller  20 . 
     In the nip between the intermediary transfer roller  20  and the transfer roller  21 , the toner image is transferred onto the sheet S passing through the nip, and the sheet S on which the toner image is transferred is fed to a fixing device  25  by a feeding belt  24 , so that the toner image transferred on the sheet S is fixed. The sheet S on which the toner image is fixed is discharged to an outside of the image forming apparatus, so that an image forming step is completed. 
     The intermediary transfer roller  20  and the transfer roller  21  are provided with an intermediary transfer roller cleaner  26  and a transfer roller cleaner  27 , respectively, for collecting the toner T and the carrier liquid C which remain on the associated roller. 
     (Liquid Developer) 
     Next, the liquid developer develop will be described. As the liquid developer D, a conventionally used liquid developer may also be used, but in this embodiment, an ultraviolet-curable liquid developer D is used and will be described below. 
     The liquid developer D is an ultraviolet-curable liquid developer which contains a cation-polymerizable liquid monomer, a photo-polymerization initiator and toner particles insoluble in the cation-polymerizable liquid monomer. The cation-polymerizable liquid monomer is vinyl ether compound, and the photo-polymerization initiator is a compound represented by the following formula (1). 
     
       
         
         
             
             
         
       
     
     Specifically, first, the toner particles include a colorant and a toner resin material in which the colorant is incorporated. Together with the toner resin material and the colorant, another material such as a charge control agent may also be contained. As a manufacturing method of the toner particles, a well-known technique such as a coacervation in which the colorant is dispersed and a resin material is gradually polymerized so that the colorant is incorporated in the polymer or an internal pulverization method in which a resin material or the like is melted and the colorant is incorporated in the melted resin material may also be used. As the toner resin material, epoxy resin, styrene-acrylic resin or the like is used. The colorant may be a general-purpose organic or inorganic colorant. In the manufacturing method, in order to enhance a toner dispersing property, a dispersant is used but a synergist can also be used. 
     Next, a curable liquid which is the carrier liquid is constituted by the charge control agent for imparting electric charges to the toner surface, a photo-polymerization agent (initiator) for generating acid by ultraviolet (UV) irradiation and a monomer bondable by the acid. The monomer is a vinyl ether compound which is polymerizable by a cationic polymerization reaction. Separately from the photo-polymerization initiator, a sensitizer may also be contained. By photo-polymerization, a storage property lowers, and therefore a cationic polymerization inhibitor may also be added in an amount of 10-5000 ppm. In addition, a charge control aid, another additive or the like may also be used in some cases. 
     The UV curing agent (monomer) of the developer is a mixture of about 10% (weight %) of a monofunctional monomer having one vinyl ether group (formula 2 below) and about 90% (weight %) of difunctional monomer having two vinyl ether groups (formula 3 below). 
     
       
         
         
             
             
         
       
     
     As the photo-polymerization initiator, 0.1% of a compound represented by formula 4 below is mixed. By using this photo-polymerization initiator, different from the case where an ionic photo-acid generator, a high-resistance liquid developer is obtained while enabling satisfactory fixing. 
     
       
         
         
             
             
         
       
     
     Incidentally, a cationic polymerizable liquid monomer may desirably be a compound selected from the group consisting of dichloropendadiene vinyl ether, cyclohexanedimethanol divinyl ether, tricyclodecane vinyl ether, trimethylolpropane trivinyl ether, 2-ethyl-1,3-hexamediol divinyl ether, 2,4-diethyl-1,5-pentanediol divinyl ether, 2-butyl-2-ethyl-1,3-propanediol divinyl ether, neopentylglycol divinyl ether, pentaerythritol tetravinyl ether, and 1,2-decanediol divinyl ether. 
     As the charge control agent, a well-known compound can be used. As a specific example, it is possible to use fats and oils such as linseed oil and soybean oil; alkyd resin; halogen polymer; oxidative condensates such as aromatic polycarboxylic acid, acidic group-containing water-soluble dye and aromatic polyamine; metallic soaps such as cobalt naphthenate, nickel naphthenate, iron naphthenate, zinc naphthenate, cobalt octylate, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, aluminum stearate, and cobalt 2-ethylhexylate; sulfonic acid metal salts such as petroleum acid metal salt and metal salt of sulfosuccinic acid; phospholipid such as lectithin; salicylic acid metal salt such as t-butylsalicylic acid metal complex; polyvinyl pyrrolidone resin; polyamide resin; sulfonic acid-containing resin; and hydroxybenzoic acid derivative. 
     (Feeding of Liquid Developer) 
     Next, feeding of the liquid developer D in this embodiment will be described using  FIGS. 2 to 4 . First, as described above, the developer collected at the image forming portion  12  including the drum cleaner  19 , the intermediary transfer roller cleaner  26  and the transfer roller cleaner  27  is subjected to separation between the toner and the carrier liquid, so that the carrier liquid is used again. Incidentally, the developer which remains on the developing roller  18  after development and which is collected into the collecting section  16   b  of the developing device is returned to the mixer  31 , but may also be fed to a separation and extraction device  34 . 
     Although details will be described later, the separation and extraction device  34  separates a reusable carrier liquid and a waste liquid W containing the toner and an impurity such as paper powder when the carrier liquid and the toner are separated from each other, so that the separated waste liquid W is collected in a waste liquid collecting container  35 . 
     Specifically, a transporting pipe from the carrier tank  32  to the mixer  31  and a transporting pipe from the toner tank  33  to the mixer  31  are provided with electromagnetic valves  41  and  42 , respectively, and a supply amount of the carrier liquid C to the mixer  31  and a supply amount of the toner T to the mixer  31  are adjusted. From the mixer  31 , the liquid developer D necessary for the development is supplied using a pump  44 . 
     The developer collected in the collecting container  16   b  of the developing device  16  is returned to the mixer  31  by a pump  43 . This is because the developer collected in the collecting container  16   b  is little used for the development or the like and therefore is little deteriorated. 
     The residual carrier liquid and the residual toner which are collected by the drum cleaner  19 , the intermediary transfer roller cleaner  26  and the transfer roller cleaner  27  are fed to the separation and extraction device  34  by pumps  48 ,  49  and  50 , respectively. 
     The reusable carrier liquid separated by the separation and extraction device  34  is fed to the carrier tank  32  by an electromagnetic valve  45 . On the other hand, the waste liquid separated by the separation and extraction device  34  is appropriately fed to the waste liquid collecting container  35  by an electromagnetic valve  47  provided to a transporting pipe through self-weight fall. 
     Transportation of the liquid developer and the like may also be made by, other than the use of the pump, using a feeding type using a self-weight of the liquid developer and the like, for example, in the case where the liquid developer and the like can be fed by the self-weight fall. 
     As shown in  FIG. 3 , the above-described pumps  43 ,  44 ,  48 ,  49 ,  50  and electromagnetic valves  41 ,  42 ,  45 ,  47  are controlled by a CPU  200  as a controller through a pump driver  201  and an electromagnetic valve driver  202 , respectively. The CPU  200  controls the respective pumps and the like on the basis of detection values of a developer amount detecting device  160 , a solid component content detecting device  310  and a carrier liquid content detecting device  34   a.    
     A feeding operation of the liquid developer will be described using  FIG. 4  while making reference to  FIGS. 2 and 3 . First, as shown in  FIGS. 2 and 3 , the developing device  16  is provided with the developer amount detecting device  160 , so that an amount of the liquid developer in the developing device  16  is detected by the developer amount detecting device  160 . Further, the mixer  31  is provided with the solid component content detecting device  310 , so that a content of a solid component such as the toner in the mixer  31  is detected. The solid component content detecting device  310  is, for example, provided with a light-emitting portion and a light-receiving portion, and a portion where the liquid in the mixer  31  passes is irradiated with light from the light-emitting portion and then the light passing through the portion is received by the light-receiving portion. Depending on the amount of the solid component at this portion, a light quantity of the light received by the light-receiving portion changes, and therefore depending on the change in light quantity, the content of the solid component in the mixer  31  can be detected. 
     As shown in  FIG. 4 , a developer amount in the developing device  16  is detected by the developer amount detecting device  160  (S 1 ). Then, in the case where the developer amount in the developing device  16  is not more than a predetermined amount (e.g., 200±10 cc), the CPU  200  drives the pump  44  (S 2 ), so that adjustment of the liquid developer amount in the developing device  16  is made. After the adjustment, the drive of the pump  44  is stopped (S 3 ). 
     Then, the content of the solid component in the mixer  31  is detected by the solid component content detecting device  310  (S 4 ). In the case where the content of the solid component in the mixer  31  is out of a predetermined range (e.g., 10±0.5%), the CPU  200  discriminates whether or not the solid component content is 10.5% or more (S 5 ). In the case where the solid component content is 10.5% or more, the electromagnetic valve  41  is opened, so that the carrier liquid is supplied from the carrier tank  32  into the mixer  31  (S 6 ). On the other hand, in the case where the solid component content is not 10.5% or more, i.e., in the case where the solid component content is 9.5% or less, the electromagnetic valve  42  is opened, so that the toner is supplied from the toner tank  33  into the mixer  31  (S 7 ). As a result, content adjustment of the liquid developer in the mixer  31  is made. 
     That is, in the case where a toner content (solid component content) is high, the carrier liquid is supplied from the carrier tank  32  to the mixer  31  through the electromagnetic valve  41 . Further, in the case where the toner content is low, the liquid developer higher in toner content than the liquid developer used in the mixer  31  is supplied from the toner tank  33  to the mixer  31  through the electromagnetic valve  42 . 
     When the solid component content in the mixer  31  falls within the predetermined range, the pump  44  is driven as desired, and then the liquid developer subjected to the content adjustment is supplied from the mixer  31  to the developing device  16  (S 8 ). Then, image formation is started (S 9 ), and at the same time, drive of the pumps  43 ,  48 ,  49 ,  50  is also started (S 10 ), and also drive of the separation and extraction device  34  is started (S 11 ). 
     (Separation and Extraction Device) 
     Next, using  FIGS. 5 to 11 , the separation and extraction device  34  as a separating device will be specifically described. The separation and extraction device  34  is a device for separating the liquid developer into the toner and the carrier liquid using the electric field and for separately extracting the carrier liquid and the toner. 
     As described above, the liquid developer collected at the image forming portion  12  such as the drum cleaner  19  is fed from an inlet  34   b  of the separation and extraction device  34  into a liquid accommodating container  346  as show by arrows in  FIGS. 5 and 6 . Then, the liquid developer is supplied to a buffer container  348  in the liquid accommodating container  346 . In this embodiment, the buffer container  348  is provided in the separation and extraction device  34 , but may also be provided separately as a single member. The liquid developer supplied to the buffer container  348  is fed by a pump  34   c  and passes through a filter  34   d.    
     The liquid developer passed through the filter  34   d  is poured on a supply tray  346   a  as a supplying portion as shown in  FIG. 6 . As described later specifically, the liquid developer poured on the supply tray  346   a  is separated into the toner and the carrier liquid by the separation and extraction device  34 . Then, the extracted toner is sent to the waste liquid collecting container  35 , and the extracted carrier liquid is fed to the carrier tank  32 . 
     Next, a constitution of separation and extraction of the toner and the carrier liquid in the separation and extraction device  34  will be described. As shown in  FIGS. 6 and 7 , in the liquid accommodating container  346 , a coating electrode member  341  as an external electrode member, an electrode roller  342  as an electroconductive roller, a toner collecting device  350  and the like are provided. The liquid accommodating container  346  is a container capable of accommodating the liquid developer and includes the above-described supply tray  346   a , a discharge portion  346   b  through which a reusable carrier liquid is to be discharged as described later, and a collecting portion  354  for collecting the developer which is the waste liquid. 
     The electrode roller  342  is an electroconductive roller which is, for example, formed by integrally molding a core metal, formed with a solid stainless steel material in an outer diameter of 40 mm, with an urethane rubber elastic layer formed on a surface of the core metal. As shown in  FIG. 3 , a driving force is externally inputted into the electrode roller  342  by a driving motor  205 , so that the electrode roller  342  is rotated in a predetermined direction (arrow directions of  FIGS. 6 and 7 ). In this embodiment, a rotational speed of the driving motor  205  is 2000 rpm. Then, the electrode roller  342  is rotated at a rotational speed of, e.g., 400 rpm by reducing the rotational speed of the driving motor  205  by a speed reducer. Incidentally, a voltage applying device  345  is controlled by the CPU  200  through a high-voltage driver  204 , and the driving motor  205  is controlled by the CPU  200  through a motor driver  203 . 
     The coating electrode member  341  is disposed with a gap  347  with a part of the electrode roller  342  as shown in  FIGS. 7 and 8 . With an upstream end portion  347   a  of the gap  347  with respect to a rotational direction of the electrode roller  342 , the supply tray  346   a  is connected. Further, the liquid developer poured in the supply tray  346   a  as described above is supplied into the gap  347  through the upstream end portion  347   a . The gap  347  is sealed at both end portions thereof with respect to a rotational axis direction of the electrode roller  342 , so that the liquid developer supplied into the gap  347  is fed through the gap  347  toward a downstream side of the gap  347  with respect to the rotational direction of the electrode roller  342  with rotation of the end portion  342 . With a downstream end portion  347   a  of the gap  347  with respect to the rotational direction of the electrode roller  342 , the discharge portion  346   b  is connected ( FIG. 6 ). Further, the liquid developer passed through the gap  347  is sent to the carrier tank  32  through the discharge portion  346   b  via a transporting pipe  346   c  ( FIGS. 2 and 6 ). 
     Incidentally, the transporting pipe  346   c  is connected with also a path through which the discharge liquid developer is returned to the separation and extraction device  34  again. The discharge portion  346   b  is provided with the carrier liquid content detecting device  34   a , so that the toner content in the carrier liquid of the liquid developer sent into the discharge portion  346   b  is detected. A constitution of the carrier liquid content detecting device  34   a  is the same as the constitution of the above-described solid component content detecting device  310 . Further, in the case where the toner content of the liquid developer sent to the discharge portion  346   b  is larger than a predetermined value (e.g., 0.02%), the liquid developer is returned to the separation and extraction device  34  again, so that the separation of the liquid developer into the toner and the carrier liquid is effected. 
     This is because, for example, the case where an abnormal situation such that a power source is shut down during an operation of the separation and extraction device  34  generates and thus the carrier liquid and the toner cannot be sufficiently separated from each other by the separation and extraction device  34  is assumed. In such a case, the toner content of the liquid developer sent to the discharge portion  346   b  is larger than the predetermined value, and therefore in this case, the liquid developer is returned to the separation and extraction device  34 . Ordinarily, as described later, the liquid developer passes through the gap  347 , so that the toner and the carrier liquid are separated from each other and then the extracted carrier liquid is sent to the discharge portion  346   b . Accordingly, the toner content of the liquid developer sent to the discharge portion  346   b  is not more than the predetermined value, so that the carrier liquid is sent to the carrier tank  32  without being returned to the separation and extraction device  34 . Incidentally, such a path for returning the carrier liquid to the separation and extraction device  34  may also be omitted. 
     As described above, the coating electrode member  341  disposed opposite to the electrode roller  342  with the gap  347  is formed of an electroconductive material at least at a surface of a portion  341   x  on which the liquid passes through the gap  347 . The coating electrode member  341  is formed of, e.g., a solid stainless steel material in width of 400 mm. The portion  341   x  on which the liquid passes has a shape of accommodating a part of the electrode roller  342 , and an opposing surface of the portion  341   x  to the electrode roller  342  has a curved shape such that a predetermined distance (i.e., the gap  347 ) is maintained between the opposing surface and the surface of the electrode roller  342 . This predetermined distance is, e.g., 0.2 mm. 
     As shown in  FIG. 3 , with the coating electrode member  341  and the electrode roller  342 , the voltage applying device  345  as a voltage applying means is connected. Further, between the coating electrode member  341  and the electrode roller  342 , a voltage is applied by the voltage applying device  345  so that an electric field for moving the toner toward the electrode roller  342  side. That is, to the gap  347 , a voltage such that an electric field for attracting the toner to the electrode roller  342  is generated is applied. 
     In this embodiment, the toner is negatively charged by the charge control agent, and therefore for example, a voltage of −300 V is applied to the electrode roller  342 , and a voltage of −1000 V is applied to the coating electrode member  341 . Thus, the toner in the liquid developer passing through the gap  347  is moved from the coating electrode member  341  to the electrode roller  342 . As a result, during the passing of the liquid developer through the gap  347 , the toner is carried on the electrode roller  342 , so that the toner and the carrier liquid are separated from each other. The separated carrier liquid is discharged to the discharge portion  346   b  connected with the downstream end portion  347   b  of the gap  347 , and then is sent to the carrier tank  32  as a collecting container as described above. 
     The toner collecting device  350  is positioned downstream of the coating electrode member  341  with respect to the rotational direction of the electrode roller  342 , and collects the toner carried on the electrode roller  342 . The toner collecting device  350  includes a collecting roller  351 , the voltage applying device  345  as a collecting voltage applying means, and a blade member  352  as a scraping member. 
     The collecting roller  351  is an electroconductive roller formed of, e.g., a solid stainless steel material in an outer diameter of 20 mm, and is provided in contact with the electrode roller  342 . Further, the collecting roller  351  contacts the electrode roller  342  and is rotated by the electrode roller  342  in arrow directions of  FIGS. 6 and 7 . Incidentally, a rotational speed of the collecting roller  351  is, e.g., 800 rpm. 
     As shown in  FIGS. 9 and 10 , the electrode roller  342  and the collecting roller  351  are disposed substantially parallel to each other, and both end portions of these rollers  342  and  351  with respect to a rotational axis direction are rotatably supported by frames  346   e  constituting the liquid accommodating container  346 . At both end portions of the collecting roller  351 , urging mechanisms  353  such as springs are provided. The collecting roller  351  is urged toward the electrode roller  342  by the urging mechanisms  353 , so that the electrode roller  342  is elastically deformed. An urging force for urging the collecting roller  351  toward the electrode roller  342  by the urging mechanisms  353  is, e.g., 3 kgf (29.4 N). 
     The coating electrode member  341  and the collecting roller  351  are positioned on the basis of the electrode roller  342 , so that the electrode roller  342  is a positional basis for these members  341  and  351 . 
     The voltage applying device  345  is connected with the electrode roller  342  and the collecting roller  351  as shown in  FIG. 3 , and applies a voltage to between the collecting roller  351  and the electrode roller  342  so that an electric field for moving the toner toward the collecting roller  351  is generated. In this embodiment, the voltage applying device connected with the electrode roller  342  and the collecting roller  351  and the voltage applying device connected with the electrode roller  342  and the coating electrode member  341  are used in common, but may also be separately provided. In this embodiment, for example, a voltage of −300 V is applied to the electrode roller  342 , and a voltage of −200 V is applied to the collecting roller  351 . Thus, the toner which is carried on the electrode roller  342  and which is fed toward the collecting roller  351  is moved from the electrode roller  342  scrapes to the collecting roller  351 . 
     The blade member  352  scrapes solid components off the toner on the collecting roller  351  in contact with the collecting roller  351 . The blade member  352  is disposed at a position downstream of a position of contact between the electrode roller  342  and the collecting roller  351  with respect to a rotational direction of the collecting roller  351  so that the blade member  352  contacts the collecting roller  351  with respect to a counter direction to the rotational direction of the collecting roller  351 . The blade member  352  is urged so that a free end portion  351   a  thereof contacts the surface of the collecting roller  351 . Incidentally, the counter direction is a direction such that a direction in which the free end portion  352   a  contacting the surface of the collecting roller  351  extends is opposite to a tangential direction along the rotational direction of the collecting roller  351 . Further, the blade member  352  is a plate(-like) member extending along a longitudinal direction (rotational axis direction) of the collecting roller  351  and for example, a stainless steel material is used as a material of the collecting roller  351 . 
     As described above, the toner moved from the electrode roller  342  to the collecting roller  351  is scraped off by the blade member  352  and then is sent to the collecting portion  354  as a toner collecting portion. The toner collected in the collecting portion  354  is sent to the waste liquid collecting container  35  as described above. Incidentally, a scraping member for scraping the toner off the collecting roller  351  is not limited to the blade member. For example, the blade member may also be formed in a brush shape other than the blade shape. 
     (Positional Relation Between End Portions of Gap) 
     In the case of this embodiment, as described above, the liquid developer which is collected at the image forming portion  12  and which is supplied from the supply tray  346   a  to the gap  347  passes through the gap  347 , so that the liquid developer is separated into the toner and the carrier liquid. Here, the liquid flows from above to below along a direction of gravitation. For this reason, it is undesirable that the downstream end portion  347   b  (outlet) through which the liquid developer passed through the gap  347  is to be discharged is positioned above the upstream end portion  347   a  (inlet), through which the liquid developer is to be supplied into the gap  347 , with respect to the direction of gravitation. For a similar reason, it is undesirable that the discharge portion  346   b  is positioned above the upstream end portion  347   a  (inlet) with respect to the direction of gravitation. 
     Particularly, in order to enhance a reuse factor of the carrier liquid, it is preferable that a T/D ratio (mixing ratio between the toner and the carrier liquid) of the developer at the toner scraping portion (contact position of the blade member  352 ) is increased to the possible extent. However, the liquid developer having a high T/D ratio has a higher viscosity, so that a developer feeding property lowers, and therefore when the outlet of the gap  347  is positioned above the inlet of the gap  347 , a recycling efficiency lowers. 
     Therefore, in this embodiment, as shown in  FIG. 7 , in the case where a line α passing through a center O of the electrode roller  342  and a top of the electrode roller  342  with respect to the direction of gravitation is 0°, the upstream end portion  347   a  of the gap  347  is positioned in a range of 0° or more and less than 180° with respect to the rotational direction of the electrode roller  342 . In other words, an angle formed between the line α and a line β passing through the upstream end portion  347   a  of the gap  347  and the center O is θ, the upstream end portion  347   a  is positioned so that the angle θ is 0° or more and less than 180°. In a preferred example, the upstream end portion  347   a  of the gap  347  is positioned in a range of 60° or more and 120° or less with respect to the rotational direction of the electrode roller  342 . In this embodiment, the upstream end portion  347   a  is positioned in a range from 90° to 120° with respect to the rotational direction of the electrode roller  342 . 
     The downstream end portion  347   b  of the gap  347  is positioned below the upstream end portion  347   a  with respect to the direction of gravitation. In a preferred example, the downstream end portion  347   b  of the gap  347  is positioned in a range of 180° or less with respect to the rotational direction of the electrode roller  342 . That is, it is preferable that the downstream end portion  347   b  is positioned in a range which includes the position of 180° and in which the downstream end portion  347   b  is positioned upstream of the position of 180° with respect to the rotational direction of the electrode roller  342 . As a result, the liquid developer passing through the gap  347  is prevented from being fed against gravitation, so that the reuse efficiency can be further enhanced. In this embodiment, the downstream end portion  347   b  is in the position of 180° with respect to the rotational direction of the electrode roller  342 . 
     Incidentally, a length of the gap  347 , i.e., a length from the upstream end portion  347   a  to the downstream end portion  347   b  along the electrode roller  342  may preferably be not less than ⅕ of a peripheral length of an outer peripheral surface of the electrode roller  342 . This length of the gap  347  may also be set depending on the rotational speed of the electrode roller  342 . For example, in the case where the rotational speed of the electrode roller  342  is slow, the length of the gap  347  can be shortened. In summary, it is only required that a length in which the toner and the carrier liquid are separated from each other is ensured during the passing of the liquid developer through the gap  347 . 
     (Control Flow of Separation and Extraction Operation of Liquid Developer) 
     Next, a control flow of a separation and extraction operation of the liquid developer in this embodiment constituted as described above will be described using  FIGS. 11 and 12 . First, the respective pumps  48 ,  49 ,  50  are driven, so that the developers collected by the drum cleaner  19 , the intermediary transfer roller cleaner  26  and the transfer roller cleaner  27  are fed to the separation and extraction device  34 . Then, after the developers in a predetermined amount are sent to the separation and extraction device  34 , the drive of the pumps  48 ,  49 ,  50  is stopped (S 21 ). 
     Then, the drive of the driving motor  205  is started, so that the electrode roller  342  is rotated (S 22 ). As a result, the liquid developer is fed with rotation of the electrode roller  342 . At this time, the collecting roller  351  is rotated by the electrode roller  342 . Further, the voltage applying device  345  is turned on (S 23 ). As a result, a voltage is applied to between the coating electrode member  341  and the electrode roller  342  so that an electric field for moving the toner toward the electrode roller  342  is generated, and a voltage is applied to between the collecting roller  351  and the electrode roller  342  so that an electric field for moving the toner toward the collecting roller  351  is generated. For this reason, the toner in the liquid developer is first moved toward the electrode roller  342  and then is moved toward the collecting roller  351 . The carrier liquid having no electric charge remains on the coating electrode member  341  side. 
     That is, as shown in  FIG. 12 , the toner T (solid line in  FIG. 12 ) in the liquid developer passing through the gap  347  not only is electrically attracted to the electrode roller  342  but also receives an electrically repelling force from the coating electrode member  341 . As a result, the toner T is electrically urged toward the electrode roller  342 . At this time, similarly as in the above-described case shown in (b) of  FIG. 15 , the toner T layer is positioned on the electrode roller  342  side, and the carrier liquid C layer is positioned on the toner T layer. By the rotation of the electrode roller  342 , the liquid including the toner T layer and the carrier liquid C layer is fed to a position opposing the collecting roller  351 , and then the toner T layer is moved to the collecting roller  351  by the electric field. 
     The toner T which passed through the gap  347  and which was then fed to the collecting roller  351  by the electrode roller  342  not only is electrically attracted to the collecting roller  351  but also receives an electrically repelling force from the electrode roller  342 . As a result, the toner is electrically urged in a direction of being spaced from the electrode roller  342 , i.e., toward the collecting roller  351 . At this time, the carrier liquid C is divided into a portion on the electrode roller  342  side and a portion on the collecting roller  351  side with a predetermined proportion, so that the divided carrier liquid C layer (chain line of  FIG. 12 ) on the electrode roller  342  side is fed to the upstream end portion  347   a  of the gap  347  by the rotation of the electrode roller  342 . That is, the divided carrier liquid C on the electrode roller  342  side between the electrode roller  342  and the collecting roller  351  is returned to the inlet. Then, the carrier liquid C merges with the liquid developer supplied from the supply tray  346   a  and is then fed again into the gap  347 . 
     The toner electrically deposited on the collecting roller  351  is scraped off by the blade member  352 . Here, the electromagnetic valve  47  is opened (S 24 ). As a result, the toner scraped by the blade member  352  falls by its own weight and then is collected into the waste liquid collecting container  35  through the collecting portion  354 . Incidentally, the toner may be disposed of or reused. 
     Further, the carrier liquid discharged to the discharge portion  346   b  through the downstream end portion  347   b  of the gap  347  is subjected to detection of the toner content by the carrier liquid content detecting device  34   a , and whether or not the detected toner content is a predetermined value (e.g., 0.02%) or more is discriminated (S 25 ). When the toner content is the predetermined value or less, the electromagnetic valve  45  is opened, so that the carrier liquid is sent to the carrier tank  32  (S 26 ). 
     Then, when the separation and extraction of the carrier liquid from the separation and extraction device  34  is completed (S 27 ), the electromagnetic valves  45  and  47  are closed (S 28 ), and the voltage applying device  345  and the driving motor  205  are successively stopped (S 29 , S 30 ). 
     Then, the residual developers in a predetermined amount are fed again into the separation and extraction device  34  by the pumps  48 ,  49 ,  50 , and a subsequent separation process is performed. Thereafter, such an operation is repeated. 
     In the separation and extraction device  34  in this embodiment, from 100.0 cc of the liquid developer (containing 90.0 cc of the carrier liquid and 10.0 cc of the toner), 88.0 cc of the carrier liquid can be extracted. A required time in one separation process is 30 seconds, for example, and in this case, it is possible to meet a process speed up to 800 mm/s. 
     (Arrangement of Blade Member) 
     Arrangement of the blade member  352  will be described using  FIGS. 12 to 14 . As described above, the blade member  352  scrapes off the toner moved to the collecting roller  351 . The blade member  352  is provided so that the blade member  352  extends in the counter direction against the collecting roller  351  and so that the blade member  352  contacts the collecting roller  351  along a tangential direction of the collecting roller  351 . In the case where a free end portion  352   a , of the blade member  352 , contacting the collecting roller  351  is on an upper half surface (portion) of the collecting roller  351  with respect to the direction of gravitation, the blade member  352  is disposed in the following manner. That is, in order to move the toner T on the blade member  352  by gravitation, the blade member  352  is disposed so that the free end portion  352   a  thereof where the blade member  352  is supported is positioned on an upper side and a base end portion thereof is positioned on a lower side with respect to the direction of gravitation. In other words, the blade member  352  is disposed so that the free end portion  352   a  is positioned above the base end portion with respect to the direction of gravitation. 
     At this time, there is a possibility that the toner T layer stagnates on the blade member  352  depending on an angle at which the blade member  352  contacts the collecting roller  351 . For example, as shown in  FIG. 13 , in the case where the blade member  352  is in such an attitude that an angle θ 1  of the blade member  352  with respect to the horizontal direction is approximately 35° or less (θ 1 ≤35°), the toner does not readily run on the blade member  352 . Further, on the collecting roller  351  rotating in an arrow direction (counterclockwise direction) of  FIG. 13 , at a portion upstream of the free end portion  352   a  of the blade member  352 , the toner T is liable to stagnate while forming an agglomeration T-t. 
     In order to suppress stagnation of the toner T as described above, when the free end portion  352   a  of the blade member  352  is on the upper(-half) surface of the collecting roller  351  with respect to the direction of gravitation, it is preferable that the blade member  352  is disposed so that the angle thereof with respect to the horizontal direction is larger than 35°. In other words, the attitude of the blade member  352  may preferably be disposed in a side closer to a vertical side, with respect to the direction of gravitation, than the angle of an approximately 35° with respect to the horizontal direction (i.e., θ 1 &gt;35°). 
     Here, in the case where a position of contact of the free end portion  352   a  of the blade member  352  with the collecting roller  351  is a position as shown in (a) of  FIG. 14 , the attitude of the blade member  352  is about 35° with respect to the horizontal direction. The position shown in (a) of  FIG. 14  is, in the case where a line α 1  ( FIG. 12 ) passing through a center O 1  and a top of the collecting roller  351  with respect to the direction of gravitation is 0°, such that the position of the free end portion  352   a  contacting the collecting roller  351  is a position of 35° along the rotational direction of the collecting roller  351 . In other words, in the case where an angle formed between the line α 1  and a line β 1  passing through the contact position of the free end portion  352   a  with the collecting roller  351  and the center O 1  is θ 2  ( FIG. 12 ), when θ 2  is 35°, the attitude of the blade member  352  is about 35° with respect to the horizontal direction. Accordingly, the blade member  352  may preferably be disposed so that the position of the free end portion  352   a  contacting the collecting roller  351  is a position of 35° or more along the rotational direction of the collecting roller  351 . 
     Further, as shown in (b) of  FIG. 14 , in the case where the position of the free end portion  352   a  contacting the collecting roller  51  is a position of 90° along the rotational direction of the collecting roller  351 , the attitude of the blade member  352  is about 90° (vertical) with respect to the horizontal direction. Accordingly, in the case where the free end portion  352   a  of the blade member  352  is on the upper-half surface of the collecting roller  351  with respect to the direction of gravitation, the position of the free end portion  352   a  may preferably be a position of 35° or more and 90° or less along the rotational direction of the collecting roller  351 . In this case, the blade member  352  is disposed so that the angle thereof with respect to the horizontal direction is larger than about 35°, and therefore it is possible to suppress that the toner T stagnates on the collecting roller  351  in the neighborhood of the free end portion  352   a  of the blade member  352 . As a result, scraping-off of the toner by the blade member  352  can be satisfactorily effected. 
     On the other hand, as shown in (c) of  FIG. 14 , in the case where the free end portion  352   a , of the blade member  352 , contacting the collecting roller  351  is on the lower-half surface of the collecting roller  351  with respect to the direction of gravitation, the blade member  352  is disposed as follows. That is, in the case where the free end portion  352   a  contacts the collecting roller  351  at the lower-half portion of the collecting roller  351 , the position of the free end portion  352   a  may be any position if the position of the free end portion  352   a  is in a range to the position of contact between the collecting roller  351  and the electrode roller  342 . In this case, even at any position of the free end portion  352   a , the toner T scraped by the blade member  352  falls downward by gravitation. Accordingly, when the free end portion  352   a  contacting the collecting roller  351  is positioned in a range from the position of the free end portion  352   a  being 90° or more along the rotational direction of the collecting roller  351  to the position of contact between the collecting roller  351  and the electrode roller  342 , the toner scraping by the blade member  352  can be satisfactorily performed. 
     From the above, in order to satisfactorily perform the scraping of the toner T by the blade member  352 , first, the blade member  352  is disposed along the counter direction against the collecting roller  351  and along the tangential direction of the collecting roller  351 . Further, the free end portion  352   a  contacting the collecting roller  351  may preferably be positioned in a range from the position of 35° or more along the rotational direction of the collecting roller  351  to the position of contact between the collecting roller  351  and the electrode roller  342 . In a further preferred example, the attitude of the blade member  352  is in a position of about 90° (vertical) with respect to the horizontal direction, i.e., in a position of the free end portion  352   a , contacting the collecting roller  351 , being about 90° along the rotational direction of the collecting roller  351 . 
     Further, the collecting roller  351  is, in the case where the line α passing through the center O of the electrode roller  342  and the top of the electrode roller  342  with respect to the direction of gravitation is 0° ( FIG. 7 ), positioned in a range of 180° (preferably 270°) or more and 360° or less along the rotational direction of the electrode roller  342 . 
     (Toner Collecting Portion) 
     Next, the collecting portion  354  for collecting the toner scraped by the blade member  352  as described above will be described using  FIG. 12 . The collecting portion  354  includes the wall portion  354   a , to which the base end portion of the blade member  352  is fixed, for guiding the toner, scraped by the blade member  352 , downwardly with respect to the direction of gravitation. The wall portion  354   a  is, in the case where an angle of the blade member  352  with respect to the direction of gravitation is a predetermined angle, disposed with an angle which is the predetermined angle or less with respect to the direction of gravitation. For example, in the case where the blade member  352  inclines with an angle of 30° (predetermined angle) with respect to the direction of gravitation, the wall portion  354   a  is disposed with an angle of 30° or less (i.e., 0° to 30°) with respect to the direction of gravitation. In a preferred example, the wall portion  354   a  is disposed with an angle of substantially 0° (vertical) with respect to the direction of gravitation. 
     As a result, the toner which is scraped by the blade member  352  and which is moved along the surface of the blade member  352  is guided smoothly along the wall portion  3534   a . That is, in the case where the wall portion  354   a  inclines with respect to the direction of gravitation in a degree larger than the blade member  352  inclines, there is a possibility that the toner moved along the surface of the blade member  352  stagnates at a connecting portion between the blade member  352  and the wall portion  354   a . On the other hand, as in this embodiment, the wall portion  354   a  is caused to approach the vertical direction (direction of gravitation) more than the blade member  352  approaches, so that such a stagnation of the toner can be suppressed and thus the scraped toner can be smoothly collected. Incidentally, in order to suppress the toner stagnation, it is preferable that a toner guiding surface of the wall portion  354   a  approaches the vertical direction as the toner guiding surface extends from the toner scraping position by the blade member  352  toward the downstream side with respect to a toner collecting direction (circumferential direction), and in such a constitution, a constitution other than the above-described constitution may also be employed. For example, the wall portion  354   a  may also be curved so that the wall portion  354   a  gradually approaches the vertical direction from a downstream end portion with respect to the collecting direction of the toner by the blade member  352 . 
     In the case of this embodiment as described above, a collection rate (ratio) of the carrier liquid can be enhanced. That is, as shown in  FIG. 12 , the toner T in the liquid developer supplied into the gap  347  between the electrode roller  342  and the coating electrode member  351  is first moved toward the electrode roller  342  side by the electric field. At this time, a part of the carrier liquid C is moved together with the toner T toward the electrode roller  342  side, and a remaining carrier liquid C is discharged to the discharge portion  346   b.    
     The toner T and the part of the carrier liquid C which are moved to the electrode roller  342  are fed to the position opposing the collecting roller  351 , and then the toner T layer is moved to the collecting roller  351  by the electric field. At this time, the carrier liquid C is divided into the portion on the electrode roller  342  side and the portion on the collecting roller  351  side with the predetermined proportion, and then the divided carrier liquid C on the electrode roller  342  side is fed to the upstream end portion  347   a  of the gap  347  by the rotation of the electrode roller  342 . That is, the divided carrier liquid C on the electrode roller  342  side between the electrode roller  342  and the collecting roller  351  is returned to the inlet of the gap  347 . Then, the carrier liquid C merges with the liquid developer supplied from the supply tray  346   a  and then passes through the gap  347  again. At this time, as described above, a part of the carrier liquid C is moved together with the toner T toward the electrode roller  342  side, and a remaining carrier liquid C is discharged to the discharge portion  346   b.    
     Accordingly, in the case of this embodiment, the carrier liquid C fed to between the collecting roller  351  and the electrode roller  342  little increases in amount. That is, the carrier liquid fed to the position opposing the collecting roller  351  and then remaining on the electrode roller  342  side is fed again into the gap  347 . For this reason, the amount of the carrier liquid C which passes through the gap  347  and which is then fed by the rotation of the electrode roller  346  to the position opposing the collecting roller  351  little increases. For this reason, it is also possible to suppress an increase in amount of the carrier liquid scraped together with the toner, so that the collection rate of the carrier liquid can be increased. 
     Further, the toner moved to the collecting roller  351  is scraped by the blade member  352 , but the blade member  352  is disposed as described above, and therefore the toner scraping can be performed satisfactorily. Further, the angle of the wall portion  354   a , with respect to the direction of gravitation, of the collecting portion  354  to which the base end portion of the blade member  352  is fixed is set as described above, and therefore collection of the scraped toner can be smoothly performed. 
     [Another Embodiment] 
     In the above-described embodiment, the example in which the toner is used as the dispersoid and the carrier liquid is used as the dispersion medium was described, but the present invention is applicable if the dispersoid and the dispersion medium are separable by the electric field. For example, a constitution in which the dispersoid is the charge control agent and the dispersion medium is the carrier liquid may also be employed. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, the separating property between the carrier liquid and the toner can be improved.