Patent Publication Number: US-6986977-B2

Title: Image forming apparatus and image forming method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2002-077892 filed on Mar. 20, 2002, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus and an image forming method, in which a liquid developer is used for producing a toner image on a transfer medium. 
     2. Description of the Related Art 
     An electrophotographic type image forming apparatus, which produces a developed image by using a liquid developer, has following advantages: extremely fine toner particles of sub-micron in diameter can be used so that a high quality image comparable to that of the offset printing is realized, copying cost is reduced because sufficient image density can be obtained with a small amount of toner, and energy saving is accomplished because the toner can be fixed to a copy sheet at a relatively low temperature. All of those advantages are not obtained with an electrophotographic recording apparatus using a dry developer. 
     As one method for transferring the toner image formed on a photosensitive member to a transfer medium in an image forming apparatus using a liquid developer, there is a pressure transfer method that transfers toner particles on a surface of a photosensitive member with the aid of adherence of toner particles by pressing the photosensitive member to the transfer medium. In the pressure transfer method, the toner particles are transferred from the surface of the photosensitive member to the transfer medium according as their surface energy and a shearing stress. The transferability of the toner particles from the surface of the photosensitive member to the transfer medium depends on the correlation of the surface energy between the toner particles and the surface of the photosensitive member and the shearing stress between the surface of the photosensitive member and the transfer medium. 
     The pressure transfer method has an advantage that a high quality image can be obtained because electric disturbance of the toner particles does not occur when transferring is carried out unlike a transfer method using an electric field. Particularly, the pressure transfer method has advantageous in transferring the toner image to the recording medium, such as copying paper under pressure via an intermediate transfer medium because of less transferring load and wide applicability of the recording media. 
     However, in the pressure transferring method, the intermediate transfer medium requires two antithetical properties that the toner image can easily be ripped off from the photosensitive member while the toner image can easily be transferred to the recording medium. Therefore, there is a less room to select a material for the intermediate transfer medium, and then the permissible zone for transferring becomes narrow. 
     Furthermore, even if the material for the intermediate transfer medium is selected as appropriate as possible, there has been a possibility of occurrence of inferior transfer particularly at the top edge portion of the image region where the toner image becomes thick, because deterioration of adherence between the toner image and the surface of the intermediate transfer medium takes place, which is caused by the different height between the image region and the non-image region. 
     To overcome this drawback, Japanese patent publication (Kokai) No. 08-44216 discloses a method wherein a transfer layer of transparent toner is pre-formed entirely on a photosensitive member so as to rip off the toner image easily from the photosensitive member, the transparent toner is then made into a film, thereafter the toner image is formed on the filmed transfer layer, and the toner image is transferred to a transfer material together with the filmed transfer layer. In this transfer method, a thermoplastic resin is employed as the transparent toner, and the transfer layer is made into a film by developing the transparent toner on the photosensitive layer in advance, and then the transfer layer is made into a film by heating and melting the transparent toner. After the toner image is formed on the transfer layer by a conventional electrophotographic process, the toner image is transferred together with the transfer layer by heating again the transfer layer at the transferring step. 
     However, the transfer method mentioned above has disadvantages in that the properties of the photosensitive member are affected and selection of the photosensitive material is limited, and more over lengthening the life duration of the photosensitive member is prevented, because the transfer method requires a heating process at the transparent toner film making process after the development of the transparent toner on the surface of the photosensitive member. Furthermore, in view of transfer energy, the transparent toner and the photosensitive material have a problem in that they have to be satisfied properties: the toner image and the transfer layer adhere closely together while the transfer layer and the photosensitive member separate easily from each other. 
     Consequently, it has been expected to realize an image forming apparatus having high transfer efficiency and long life duration of the photosensitive member, yet a high quality image can be obtained effectively, despite the materials of the intermediate transfer medium and the photosensitive member, when the pressure transfer method is adopted to obtain high quality transfer images. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an image forming apparatus and method having high transfer efficiency by using a pressure transfer method. The object of the present invention is also provide an image forming apparatus and method, which enables wide selection of materials for an intermediate transfer medium and a photosensitive member and achieves long life duration of the photosensitive member, while obtaining a high quality transfer image. 
     In accordance with an embodiment of the invention, an image forming apparatus has an image recording member, a transferring particle layer forming equipment which forms a transferring particle layer on a part of the image recording member, a development equipment which forms a toner layer with toner particles on a surface of the image recording member according to image information with a liquid developer containing the toner particles and a liquid carrier in a manner that a part of the toner layer is superimposed on the transferring particle layer; and a transfer equipment which transfer the toner layer to a transfer medium together with a part of the transferring particle layer, wherein coagulation force among the transferring particles in the transferring particle layer is smaller than adhesive force of the transferring particle layer to the image recording member. 
     Further, according to another embodiment of the present invention, an image forming apparatus comprising, an image recording member, a transferring particle layer forming equipment which forms a transferring particle layer on a part of the image recording member, a development equipment which forms a toner layer with toner particles on a surface of the image recording member according to image information with a liquid developer containing the toner particles and a liquid carrier in a manner that a part of the toner layer is superimposed on the transferring particle layer; and a transfer equipment which transfer the toner layer to a transfer medium together with a part of the transferring particle layer, wherein the transferring particles in the transferring particle layer on either the image recording member and the transferred toner layer remains approximately not less than 90% of the whole area thereof, respectively. 
     Further, according to another embodiment of the present invention, an image forming method comprising forming a transferring particle layer with transferring particles, whose coagulation force among themselves is smaller than adhesion force thereof to an image recording member, on a part of the image recording member, forming a toner layer with toner particles on a surface of the image recording member according as image information with a liquid developer containing the toner particles and a liquid carrier in a manner that a part of the toner layer is superimposed on the transferring particle layer; and transferring the toner layer formed on the surface of the image recording member to a transfer medium together with at a part of the transferring particle layer. 
     Further, according to another embodiment of the present invention, an image forming method comprising forming a transferring particle layer of transferring particles on at a part of an image recording member, forming a toner layer with toner particles on a surface of the image recording member according as image information with a liquid developer containing the toner particles and a liquid carrier in a manner that a part of the toner layer is superimposed on the transferring particle layer, and transferring the toner layer formed on the surface of the image recording member to a transfer medium together with at a part of the transferring particle layer, wherein the transferring particles in the transferring particle layer on either the image recording member and the transferred toner layer remains approximately not less than 90% of the whole area thereof, respectively when the transferring step has finished. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic structural figure showing the image forming portion of the electrophotographic apparatus according to the first embodiment of the invention; 
         FIG. 2A  is a schematic cross sectional view of the transferring particle layer and the toner layer between the photosensitive drum and the intermediate transfer roller according to the first embodiment of the invention, 
         FIG. 2B  is a schematic cross sectional view of the internal breakdown of the transferring particle layer according to the first embodiment of the invention, 
         FIG. 3  is a schematic block diagram showing the pattern-generating device according to the second embodiment of the invention, 
         FIG. 4A  is an explanatory diagram showing a pattern of the toner layer of cyan (C) according to the second embodiment of the invention, 
         FIG. 4B  is an explanatory diagram showing a pattern of the toner layer of magenta (M) according to the second embodiment of the invention, 
         FIG. 4C  is an explanatory diagram showing a pattern of the toner layer of yellow (Y) according to the second embodiment of the invention, 
         FIG. 4D  is an explanatory diagram showing a pattern of the transferring particle layer according to the second embodiment of the invention, 
         FIG. 5  is an explanatory diagram showing the expansion processing for a pixel according to the second embodiment of the invention, 
         FIG. 6A  is an explanatory diagram showing a pattern of the toner layer of cyan (C) according to the second embodiment of the invention, 
         FIG. 6B  is an explanatory diagram showing a pattern of the transferring particle layer after the expansion processing according to the second embodiment of the invention, 
         FIG. 7A  is a schematic cross sectional view of the transferring particle layer and the toner layer between the photosensitive drum and the intermediate transfer roller according to the second embodiment of the invention, 
         FIG. 7B  is a schematic cross sectional view of the internal breakdown of the transferring particle layer according to the second embodiment of the invention, 
         FIG. 8  is a block diagram showing the pattern-generating device according to the third embodiment of the invention, 
         FIG. 9  is a schematic explanatory diagram showing front edge detection for a pixel according to the third embodiment of the invention, 
         FIG. 10A  is an explanatory diagram showing a pattern of the toner layer of cyan (C) according to the third embodiment of the invention, 
         FIG. 10B  is an explanatory diagram showing a pattern of the front edge of cyan (C) toner layer according to the third embodiment of the invention, 
         FIG. 10C  is an explanatory diagram showing a pattern of the transferring particle layer and cyan (C) toner layer after the front edge has been subjected to the expansion processing according to the third embodiment of the invention, 
         FIG. 11A  is a schematic cross sectional view of the transferring particle layer and the toner layer between the photosensitive drum and the intermediate transfer roller according to the third embodiment of the invention, 
         FIG. 11B  is a schematic cross sectional view of the internal breakdown of the transferring particle layer according to the third embodiment of the invention, 
         FIG. 12  is a schematic block diagram showing the pattern-generating device according to the fourth embodiment of the invention, 
         FIG. 13A  is a schematic cross sectional view of the transferring particle layer and the toner layer between the photosensitive drum and the intermediate transfer roller according to the fourth embodiment of the invention, 
         FIG. 13B  is a schematic cross sectional view of the internal breakdown of the transferring particle layer according to the fourth embodiment of the invention, 
         FIG. 14  is a schematic block diagram showing the pattern-generating device according to the fifth embodiment of the invention, and 
         FIG. 15  is a schematic structural figure showing a transferring particle layer-forming device of another variation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be explained in detail referring to the attached drawings. Fist of all, the first embodiment of the invention will be described.  FIG. 1  shows an image forming portion of an electrophotographic apparatus  10  as an image forming apparatus. A photosensitive drum  12 , which is the image recording member, has a photosensitive layer formed with such as organic or amorphous silicon resin of 10 to 40 μm in thickness on a conductive metallic drum such as aluminum. The photosensitive drum  12  is more preferably provided with a protection layer having the thickness of 5 μm or less, which is made of such as fluorine resin, silicone resin on the photosensitive layer. 
     At the periphery of the photosensitive drum  12 , a charger  13  including a well-known scorotron charger, an exposing device  17  for irradiating a light onto the charged photosensitive drum  12  according as the image information in order to form an electrostatic latent image on the photosensitive drum  12 , and a developing unit  18  for supplying liquid developers  18 Y˜ 18 C having different colors of yellow (Y), magenta (M) and cyan (C), respectively, so as to develop the electrostatic latent image are arranged along the rotational direction the photosensitive drum  12 . The charger  13 , the exposing device  17 , and the developing unit  18  constitute the image forming apparatus. 
     At the periphery of the photosensitive drum  12 , a transferring particle layer-forming device  21  for forming a transferring particle layer  40 , a squeezing device  22  for simultaneously erasing a fog of the liquid developer image formed on the photosensitive drum  12  and removing excess liquid carrier and a dryer  23  for further removing liquid carrier again from the liquid developer image are located. Furthermore, a transferring device  27  for transferring the toner image from which liquid carrier has been thus removed, to a print paper P or a transfer medium, a cleaner  28  for cleaning remaining toner on the photosensitive drum  12  by contacting the photosensitive drum  12 , and an erasing lamp  30  for erasing residual charge on the surface of the photosensitive drum  12  are arranged at downstream side of the dryer  23  on the periphery of the photosensitive drum  12   
     The exposing device  17  irradiates selectively a laser beam  14  corresponding to the light signal of yellow (Y), magenta (M) or cyan(C) modulated in accordance as the recording signal obtained from the image information, onto an exposing portion  16  of the photosensitive drum  12 . The exposing device  17  forms an electrostatic latent image on the photosensitive drum  12  by discharging the portion of the photosensitive drum  12 , where the laser beam  14  is exposed. 
     The developing unit  18  accommodates three developing devices  32 Y˜ 32 C containing liquid developers  18 Y˜ 18 C of different colors of yellow (Y),magenta (M), and cyan (C) stored in developing containers  31 Y˜ 31 C respectively on a developing unit stage  18   a.  Developing rollers  33 Y˜ 33 C supplying the liquid developers  18 Y˜ 18 C to the surface of the photosensitive drum  12  are provide d in respective developing devices  32 Y˜ 32 C. A developing bias of e.g. +600V is applied to the developing rollers  33 Y˜ 33 C The developing rollers  33 Y˜ 33 C are arrange to face the photosensitive drum  12  having a gap of approximately 100 μm by means of a gap roller (not shown) provided on the edge thereof. The developing unit stage  18   a  slides in reciprocal manner along the direction indicated by arrow t with a feeding mechanism, which is not shown in the figure. 
     The liquid developers  18 Y to  18 C have toner particles of diameter of approximately 1 μm or less containing at least resin component and coloring component dispersed in an insulating liquid carrier that is a dispersion solvent. The toner particles are being charged in the liquid carrier. As for the resin component of the toner particle, no limitation exists as long as the resin is insoluble to the liquid carrier. For example, acrylic resin, polyester resin, olefin resin, silicone resin, etc. are available. 
     With regard to the coloring components of yellow (Y), magenta (M) and-cyan (C), various dyes or pigments can be utilized. For the coloring component of yellow (Y), for example, acetoacetic acid allyl amide monoazo yellow pigment such as pigment yellow 1, ditto 3, ditto 74, ditto 97, and ditto 98, imidazolon-monoazo yellow such as pigment yellow 181, acetoacetic acid allyl amide-disazo yellow pigment such as C.I. pigment yellow 12, ditto 13, ditto 14 and ditto 17, and yellow dye such as C.I. solvent yellow 19, ditto 77, ditto 79 and C.I. disperse yellow 164 can be employed. 
     For the coloring component of magenta (M), for example, red or ponceau pigment such as C.I. pigment red 48, ditto 49:1, ditto 53:1, ditto 57, ditto 57:1, ditto 81, ditto 122, ditto 5 and ditto 146, and red dyes such as C.I. solvent red 49, ditto 52, ditto 58 and ditto 8 can be employed. For the coloring component of cyan (C), for example, blue dyes or pigments of cupper phthalocyanine such as C.I. pigment blue 15:3 and ditto 15:4, and derivatives thereof can be employed. In addition to these mentioned above, some additives such as charge control agent and wax can be blended if necessary. 
     For the embodiment mentioned above, Isoper L (produced by Exxon chemical Inc.) as the liquid carrier, positively charged acrylic resins whose glass transition temperature (hereinafter abbreviated by Tg) is 45° C., as the resin component, and pigment yellow 1, C.I. pigment red 48, and C.I. pigment blue 15:3 were utilized as the coloring components of yellow (Y), magenta (M) and cyan (C) respectively. 
     The-transferring particle layer-forming device  21  is located adjacent to the yellow (Y) developing device  32 Y on the developing stage  18   a  of the developing unit  18 . The transferring particle layer-forming device  21  accommodates liquid transferring material  37   a,  which contains transferring particles  37  dispersed in insulating dispersion solvent in a container  36 , and provides a roller electrode  38  to which e.g. +400V of bias is applied, in order to supply the liquid transferring material  37   a  to the surface of the photosensitive drum  12 . The roller electrode  38  faces to the photosensitive drum  12  with a gap of approximately 100 μm by means of a gap roller (not shown) provided on the edge thereof. 
     The transferring particles  37  are made of a resin component whose diameter is equal to or smaller than 1 μm, and are charged in the dispersion solvent. The resin component of the transferring particles  37  is set to be the same as the resin component of the toner particles. Thereby, each resin design for the transferring particles  37  and the toner particles becomes similar to each other and the designing is easily carried out. Though the transferring particles  37  do not require fundamentally any coloring agents and may be clear and colorless, some coloring agents as additive can be added thereto so as to impart releasability, etc., if necessary. As the additive, mica, magnesium oxide, alumina, zinc stearate, calcium stearate, silica, Al—Mg—Zn-hydrostearate, silicate, silicone resin, silicone rubber, silicone rubber-resin compound, zinc oxide, N-lauroyl-N-lysine, titanium oxide, etc. can be put to use. 
     However, materials used herein are satisfied with the following condition. That is, coagulation force of the transferring particle layer  40  formed by the transferring particles  37  that is hereinafter described as coagulation force among the transferring particles  37 , should be smaller than adhesive force between the transferring particle layer  40  and the photosensitive drum  12  during pressure transferring process. In order to realize the coagulation force among the transferring particles  37  smaller, a high Tg material as a resin component of the transferring particles  37  may be used, or it may be also realized if a proper amount of the dispersion solvent remains when the liquid transferring material  37   a  is dried. 
     Namely, in order to cause internal breakdown easily in the transferring particle layer  40  having lower coagulation force when the surface energy difference or the shearing stress is exerted in the transferring operation, it is preferable to use the transferring particles  37  having higher Tg of the resin component. Practically, the Tg of the resin component used for the transferring particles  37  is not less than 25° C., preferably 45° C. or more. In addition, the resin component used for the toner particles of the liquid developer may have a Tg lower than that of the resin component used for the transferring particles  37 , as long as internal breakdown is to be generated in the transferring particle layer  40 . 
     On the other hand, if a proper amount of the dispersion solvent of the liquid transferring material  37   a  remains during transferring process, it is easy for the transferring particle layer  40  to generate internal breakdown when the surface energy difference or the shearing stress acts in the transferring particle layer  40 . 
     In this embodiment, Isoper L (produced by Exxon chemical Inc.) as the dispersion solvent of the liquid transferring material  37   a,  positively charged acrylic resin whose Tg is 45° C. as the resin component, and silica as the additive were employed. A squeezing device  22  at downstream side of the transferring particle layer-forming device  21  on the periphery of the photosensitive drum  12  is provided with a metallic roller  22   a  arranged apart from the surface of the photosensitive drum  12  by approximately 50 μm. A voltage of approximately +600 V is applied to the metallic roller  22   a,  which rotated with a surface velocity about 3 times faster than the surface velocity of the photosensitive drum  12  to the direction indicated by arrow s which is same rotating direction to that of the photosensitive drum  12  denoted by the arrow r. 
     With regard to the liquid transferring material  37   a  supplied to the photosensitive drum  12  after having passed through the squeezing device  22 , the transferring particles  37  adhered to the surface of the photosensitive drum  12  are forced to press on the photosensitive drum  12  by an electric field force. Moreover, excess dispersion solvent on the photosensitive drum  12  is removed by rotation of the metallic roller  22   a.  In the same manner, with regard to the liquid developers  18 Y˜ 18 C to be supplied to the photosensitive drum  12  after having passed through the squeezing device  22 , the toner particles adhered to the electrostatic latent image on the surface of the photosensitive drum  12  are forced to press on the photosensitive drum  12  by an electric field force, and toner particles existing in the background are attracted to the metallic roller side and removed simultaneously. Furthermore, excess liquid developers  18 Y˜ 18 C on the photosensitive drum  12  are removed by rotation of the metallic roller  22   a.  Besides, the dryer  23  dries excess liquid carrier on the photosensitive drum  12  by blowing an air jet on the photosensitive drum  12 . 
     As shown in  FIG. 1 , a transferring device  27  has an intermediate transfer roller  27   a  as an intermediate transfer medium and a press roller  27   b,  each of which has heaters  43 ,  43  respectively therein. The transferring device  27  transfers primarily the toner layer on the photosensitive drum  12  to the intermediate transfer roller  27   a  by the aid of transferring pressure accompanied by a shearing stress, and then transfers secondarily the toner layer to the print paper P by the aid of transferring pressure. The intermediate transfer roller  27   a  has a metallic roller whose surface is wrapped with a rubber layer, and can be separated from the photosensitive drum  12 . Additionally, surface velocity V 2  of the intermediate transfer roller  27   a  is designed to be a velocity lower than the surface velocity V 1  of the photosensitive drum  12 , i.e. 0.9V 1 ˜0.98V 1 , in order to give a shearing stress to the transferring particle layer  40  and the toner layer  41 , thereby to improve transfer efficiency during the primary transferring. 
     Next, the operation of the embodiment will be described. After image forming process has started, the intermediate roller  27   a  and cleaner  28  of the transferring device  27  are separated from the photosensitive drum  12  while a full color developed image is being obtained by superimposing the transferring particle layer  40  and the toner layers  41  of yellow. (Y), magenta (M) and cyan (C) on the photosensitive drum  12 . In this way, the photosensitive drum  12  starts its rotation in the direction of the arrow r while the intermediate transfer roller  27   a  and the cleaner  28  are kept separating from the photosensitive drum  12 . The transferring particle layer  40  is formed firstly on the surface of the photosensitive drum  12  at the first turn of the photosensitive drum  12 . Thereafter, the photosensitive drum  12  rotates by  3  turns to form tricolor toner layers  41  of yellow (Y), magenta (M) and cyan (C), by superimposing the toner layer of each color on the transferring particle layer  40  at each turn. As the result a full color developed image is obtained. 
     In more detail, at the first turn of the photosensitive drum  12 , the developing unit stage  18   a  is slid so that the roller electrode  38  of the transferring particle layer-forming device  21  can face to the photosensitive drum  12 . At the time, the developing unit  18  is held in a standby position. A gap of approximately 100 μm is provided between the surface of the photosensitive drum  12  and the roller electrode  38 . The gap is filled with the liquid transferring material  37   a  as the result of the rotation of the roller electrode  38  in the direction, for example as indicated by the arrow u, and then a meniscus is formed between the photosensitive drum  12  and the roller electrode  38 . Electric field is formed in the meniscus caused by the potential difference of 400V, because a bias of about +400V is applied to the roller electrode  38  while the potential of the surface of the photosensitive drum  12  is substantially 0 volt. Due to the electric field, the positively charged transferring particles  37  are electrophoresed toward the surface of the photosensitive drum  12 . As a result, a coat of the liquid transferring material  37   a  containing the transferring particles  37  is formed on the entire surface of the photosensitive drum  12 . 
     When a portion of the photosensitive drum  12  arrives at the squeezing device  22 , and the metallic roller  22   a  rotating in the direction of the arrow s scrapes off excess dispersion solvent on the portion. An electric field directing from the metallic roller  22   a  to the surface of the photosensitive drum  12  is generated when the layer of the liquid transferring material  37   a  containing the transferring particles  37  on the surface of the photosensitive drum  12  comes close to the metallic roller  22   a.  In the squeezing device  22 , a voltage of approximately +600V is applied to the metallic roller  22   a,  which is apart with a gap of about 50 μm from the surface of the photosensitive drum  12 . The transferring particles  37  are then pressed on the surface of the photosensitive drum  12 . 
     Furthermore, because the metallic roller  22   a  rotates in the direction of the arrow s at a velocity of about 3 times faster than the rotating velocity of the photosensitive drum  12 , excess dispersion solvent existing mainly on the surface portion of the layer of the liquid transferring material  37   a  is removed by the aid of fluid squeezing effect. Next, image-forming process for yellow (Y) will start. First of all, the surface of the photosensitive drum  12  is uniformly charged up to approximately +800V by the charger  13  over the transferring particle layer  40  formed on the surface of the photosensitive drum  12 . Then, a laser beam  14  of the exposing device  17  modulated with the yellow image information as the first color image information of the image information, irradiates the photosensitive drum  12  selectively to decrease the potential of the image portion to about +200V so that an electrostatic latent image corresponding to the yellow image is formed on the photosensitive drum  12 . 
     The developing unit  18  is moved from the standby position by sliding the developing unit stage  18   a  in the direction of the arrow t, and the developing roller  33 Y of yellow (Y) is moved to the developing position. The developing roller  33 Y is held with a gap of approximately 100 μm to the photosensitive drum  12  at the developing position. The gap is filled with the liquid developer  18 Y of yellow (Y) supplied by the developing roller  33 Y and a meniscus is formed. 
     When the electrostatic latent image on the photosensitive drum  12  passes through the meniscus region constituted with the liquid developer  18 Y of yellow (Y) between the photosensitive drum  12  and the developing roller  33 Y, an electric field directing from the developing roller  33 Y to the photosensitive drum  12  is formed in the image portion, whereas an electric field directing from the photosensitive drum  12  to the developing roller  33 Y is formed in the non-image portion, because a voltage of approximately +600V is applied to the developing roller  33 Y. Therefore, the toner particles stick only on the image portion due to the electric fields mentioned above. In consequence, an image of the liquid developer  18 Y of yellow (Y), which is the first color, is formed on the photosensitive drum  12  after passing through the developing device  32 Y. 
     In the squeezing device  22 , a voltage of approximately +600V is applied to the metallic roller  22   a.  Thus an electric field directing from the surface of the photosensitive drum  12  to the metallic roller  22   a  is formed in the non-image portion, whereas, an electric field in the direction of forwarding from the metallic roller  22   a  to the photosensitive drum  12  is formed in the image portion, when the image of the liquid developer  18 Y comes close to the squeezing device  22 . In consequence, floating toner particles are collected by the metallic roller  22   a  in the non-image portion, whereas the toner particles constituting the image are forced to press on the surface of the photosensitive drum  12  in the image portion. 
     An fluid squeezing effect acted in forming the transferring particle layer  40 , similarly occurs by the metallic roller  22   a,  the liquid carrier existing mainly on the surface layer portion of the liquid developer  18 Y of yellow (Y) is scraped off. A thin toner layer  40  comprised of toner particles of yellow (Y) is formed on the transferring particle layer  40  on the surface of the photosensitive drum  12 . 
     Next, image forming of magenta (M) of the second color is carried out on the toner layer  40  of yellow (Y) in the same manner as yellow (Y). Namely, at the next turn, the photosensitive drum  12  is charged and exposed, and then the developing device  32 M of magenta (M) is arranged in the developing position by further sliding the developing unit stage  18   a,  so as to carry out development with the liquid developer of magenta (M). Thereafter, liquid carrier is dried and removed through the squeezing device  22  to the extent that a proper amount of liquid carrier remains, and then the toner layer  41  of magenta (M) is superimposed on the toner layer  41  of yellow (Y) on the transferring particle layer  40  of the surface of the photosensitive drum  12 . 
     For cyan (C) of the third color, the toner layer  41  is also formed in the same manner as the above. Finally the tricolor toner layers  41  of yellow (Y), magenta (M) and cyan (C) are superimposed on the transferring particle layer  40  on the surface of the photosensitive drum  12 , and a full color developed image is obtained. The full color developed image is dried with the dryer  23  and removed to the extent that a proper amount of liquid carrier remains, before transferring process is carried out. Having stacked on the surface of the photosensitive drum  12 , the transferring particle layer  40  and the toner layers  41  became dray form the toner layers  41  in drying the surface of the photosensitive drum  12 . Therefore, the liquid carrier remains more than in the toner layers  41 , which results is decreasing the coagulation force in the transferring particle layer  40  so that internal breakdown therein is easily caused. In addition, the dryer  23  may be operated in order to remove liquid carrier further after the operation of squeezing device  22  for the three colors has been finished. 
     In the transferring process, the transferring device  27  and the cleaner  28  are contacted to the photosensitive drum  12 . The intermediate transfer roller  27   a  is so contacted to the photosensitive drum  12  that the transferring device  27  forms a nip. The intermediate transfer roller  27   a  is driven in accordance with the rotation of the photosensitive drum  12  so that it rotates to the direction indicated by arrow v with surface velocity of approximately 0.9V 1 ˜0.98V 1  when the surface velocity of the photosensitive drum  12  is V 1 . When the toner image formed on the transferring particle layer  40  arrives at the transfer nip between the intermediate transfer roller  27   a  and the photosensitive drum  12 , the transferring particle layer  40  and the toner layers  41  are subject to receive a shearing stress caused by surface velocity differences between the intermediate transfer roller  27   a  and the photosensitive drum  12  as shown in  FIGS. 2A , B. 
       FIG. 2A  shows a schematic cross sectional view of the toner layer  41  when the intermediate transfer roller  27   a  comes to contact with the photosensitive drum  12 . In the transfer nip between the intermediate transfer roller  27   a  and the photosensitive drum  12 , if the shearing stress Fs, which is generated by the difference between-the surface velocity V 1  of the photosensitive drum  12  and the surface velocity V 2  of the intermediate transfer roller  27   a,  acts on portions between the intermediate transfer roller  27   a  and the photosensitive drum  12  and in response to the shearing stress Fs, repulsions Fb and Fa are generated in the toner layer  41  and the transferring particle layer  40 , respectively. Here, because the coagulation force of the transferring particles  37  in the transferring particle layer  40  is smaller than the adhesive force between the transferring particle layer  40  and the photosensitive drum  12 , the transferring particle layer  40  is defeated by the shearing stress Fs and an internal breakdown occurs in the middle part of the transferring particle layer  40  as shown in FIG.  2 B. 
     Then the full color toner layer  41 , which is pressure-contacted to the intermediate transfer roller  27   a,  is transferred primarily with high transfer efficiency to the surface of the intermediate transfer roller  27   a  together with the transferring particle layer  40 . The full color toner layer  41  thus transferred primarily to the intermediate transfer roller  27   a  is transferred secondarily to the print paper P held with the intermediate transfer roller  27   a  and the pressure roller  27   b  and conveyed through. The pressure roller rotates in the direction indicated by arrow w in synchronism with the rotation of the intermediate transfer roller  27   a.  A full color developed image on the print paper P is obtained. Mechanism of the secondary transfer of the full color toner layer  41  from the intermediate transfer roller  27   a  to the print paper P relies principally on the difference of the surface energy between the intermediate transfer roller  27   a  and the print paper P. 
     After the full color toner layer  41  is transferred to the intermediate transfer roller  27   a,  the transferring particle layer  40  remaining on the photosensitive drum  12  is cleaned by a cleaner  28 , and then residual charge thereon is erased with the erasing lamp  30 . A series of image forming process finishes. Soon after the primary transferring of the full color toner layer  41 , the transferring particle layers  40  were observed both on the toner layer  41  and the surface of the photosensitive drum  12  over the entire areas (100% area) thereof, and the breakdown favorably generated was confirmed. 
     As described above, according to the first embodiment of the present invention, being formed the transferring particle layer  40  prior to the formation of the toner layer  41  on the surface of the photosensitive drum  12 , whose coagulation force among the transferring particles  37  is smaller than adhesive force to the photosensitive drum  12 , when pressure-transfer of the toner layer  41  is carried out from the photosensitive drum  12  to the intermediate transfer roller  27   a  while supplying a shearing stress both to the toner layer  41  and the transferring particle layer  40 , inner breakdown in the transferring particle layer  40  is generated. As a result, the toner layer  41  on the transferring particle layer  40  is surely transferred with high transfer efficiency to the intermediate transfer roller  27   a  without giving any defect in the toner layer  41 , which enables to obtain a high quality developed image on the print paper P. 
     Furthermore, in the embodiment, no heat is applied to the photosensitive drum  12  to form the transferring particle layer  40  thereon. Accordingly, life duration of the photosensitive drum  12  is lengthened, and it becomes possible to use organic photosensitive materials which is easily affected by heat, so that room for selection of the photosensitive material is widened. 
     The second embodiment of the present invention will be now explained referring to  FIG. 3  to FIG.  7 B. In the second embodiment, the transferring particle layer formed on a predetermined region of the surface of the photosensitive drum  12  according as the pattern of a toner layer  71 , instead of forming the entire surface of a photosensitive drum  12  as described in the first embodiment. Other features in the second embodiment are the same as those of the aforementioned first embodiment, so that constructions corresponding to those explained in the first embodiment are denoted by the same reference characters, and detailed explanations are not provided. 
     The electrophotographic apparatus of this embodiment has a pattern generating device  50  for generating image information to an exposing device  17 , which sets the region on which the transferring particle layer  70  to be formed and generates a regional signal. The transferring particle layer  70  is formed on a specified region based on the regional information from the pattern generating device  50 . 
     As shown in  FIG. 3 , the pattern generating device  50  has an original image input unit  60  adapted to receive an original image information from an input device such as a scanner or a personal computer terminal, a preprocessing unit  61  carrying out γ correction, color adjustment, and color conversion, and other processing for each  8  bit color separation signal of red (R), green (G) and blue (B) colors supplied from the original image input unit  60 , and a binarizing processing unit  62  converting 8 bit image signals of yellow (Y), magenta (M) and cyan (C) derived from the preprocessing unit  61  into 1 bit image signals after carrying out the processing such as dither processing or error diffusion processing. 
     The pattern generating device  50  has a transferring particle layer-pattern generating unit  63 A, which is a region setup device setting the region for the formation of the transferring particle layer  70 . The transferring particle layer-pattern generating unit  63 A includes an OR circuit  66 A into which the image signals of binarized yellow (Y), magenta (M) and cyan (C) derived from the binarizing processing unit  62  are fed, and an expansion processing unit  67 A expanding the signals from the OR circuit  66 A. An expansion parameter signal  68 A indicating how to expand is fed into the expansion processing unit  67 A. In addition, the pattern generating device  50  has a recorded signal control unit  64  into which the image signals from the binarizing processing unit  62  and transferring particle layer-image T signal from the transferring particle layer-pattern generating unit  63 A are fed. 
     Then each color information of yellow (Y), magenta (M) and cyan (C) from the recorded signal control unit  64  of the pattern generating device  50  and the regional information for the formation of the transferring particle layer  70  as modulation data of the image formed on the photosensitive drum  12 , are sent to an exposing device  17 , thereby a laser beam  14  is ON/OFF controlled. The image modulation data from the pattern generating device  50  enables the formation of the transferring particle layer  70  on the specified region, as well as the formation of the toner layer  71 . In other words, based on the image modulation data derived from the pattern generating device  50 , the transferring particle layer  70  is to be formed on the region corresponding to the toner layer  71  of the color separation images on the photosensitive drum  12  (in the case of binary, a portion having the toner layer  71  is designated by e.g. “1”) and on a whole peripheral expansion region expanding from the toner layer  71  obtained through the expansion processing. 
     In practice, when the color separation images are, for example, cyan (C) toner layer  71   c,  magenta (M) toner layer  71   m  and yellow (Y) toner layer  71   y  are shown in  FIG. 4A ,  FIG. 4B , and  FIG. 4C , respectively, the region for the formation of the transferring particle layer  70  has a pattern covering the entire region on which the toner layers  71   c  to  71   y  of yellow (Y), for magenta (M) and cyan (C) are formed as shown in FIG.  4 D. 
     In general, when a full color image is formed with color separation images, misalignment among the color separation signals occurs. The misalignment between the region for the transferring particle layer  70  and the toner layer  71  may naturally occur. To complement the misalignment in this embodiment, a process to expand the region pattern for the formation of the transferring particle layer  70  is provided. The expansion processing unit  67 A shown in  FIG. 3  has a buffer memory for 3 lines (not shown), which expands the region pattern for the transferring particle layer  70  up to pixels  72   a  to  72   d,  located at 4 adjacent points whose coordinates are (i,j−1), (i−1,j), (i,j+1),and (i+1,j), respectively around “1” pixel  72  (i,j) constituting the toner layer  71 , as designated by a black square in FIG.  5 . 
     In consequence, at the region for the cyan (C) toner layer  71   c  shown in  FIG. 4A , if the expansion processing is applied to the black square of the cyan (C) toner layer  71   c  shown in  FIG. 5 , the region for the formation of the transferring particle layer  70  becomes the region as shown in FIG.  6 B. In  FIG. 6B , white squares  70   a  are the region where only the transferring particle layer  70  is formed, and crosshatched portions  70   b  designate the region where both the transferring particle layer  70  and the cyan (C) toner layer  71   c  are overlapped. By the expansion processing, the region for the transferring particle layer  70  is expanded up to the white portions  70   a  in addition to the region of the cyan (C) for toner layer  71   c.    
     Moreover, the expansion degree to the toner layer  71  is adjusted by the expansion parameter signal which is fed into the expansion processing unit  67 A. For example, 8-adjacence-processing that expands up to the whole pixels in 3×3 window with respect to “1” pixel (coordinate is (i,j)) constituting the toner layer  72  represented by a black square in  FIG. 5  is possible, or the expansion degree within the N×N window may be possible by expanding a matrix of the periphery of “1” pixel (coordinate is (i,j)) constituting the toner layer  72  represented by the black square. 
     Operation of this embodiment will be described hereinafter. In this embodiment, the transferring particle layer  70  is formed on the surface of the photosensitive drum  12  before the full color image is formed in the image forming process, as is the case of the first embodiment. The forming step of the transferring particle layer  70  will be described herein after. In accordance with rotation of the photosensitive drum  12  in the direction indicated by the arrow r in response to starting of the image forming process, the surface of the photosensitive drum  12  is charged uniformly to approximately +800V by the charger  13 . 
     Then, the photosensitive drum  12  is exposed with light from the exposing device  17  in accordance with the region pattern of the transferring particle layer  70 . That is to say, the exposing device  17  exposes the ON/OFF controlled laser beam  14  based on the image modulation data transmitted from the recorded signal control unit  64  in the pattern generating device  50 . The image modulation data here is information of the region for the formation of the transferring particle layer  70 . 
     As a result, the potential at the exposed region of the surface of the photosensitive drum  12  decreases to approximately +200V, and the electrostatic latent image having the region pattern of the transferring particle layer  70  is formed on the photosensitive drum  12 . Thereafter, the exposed part of the photosensitive drum  12  arrives at the transferring particle layer-forming device  21  and the roller electrode  38  supplies the liquid transferring material  37   a  thereto. Voltage of about +600V is applied to the roller electrode  38 . When the electrostatic latent image passes through the meniscus region between the photosensitive drum  12  and the roller electrode  38 , an electric field directing from the roller electrode  38  to the photosensitive drum  12  is formed at the region for the transferring particle layer  70  while an electric field directing from the photosensitive drum  12  to the roller electrode  38  is formed at the outside region or non-formed region for the transferring particle layer  70 . Therefore the transferring particles  37  in the liquid transferring material  37   a  stick only to the region for the transferring particle layer  70 . 
     Then, the transferring particle layer  70  on the photosensitive drum  12  arrives at the squeezing device  22 , and the transferring particles  37  floating at the non-formed region of the transferring particle layer  70  are collected, while the transferring particles  37  are pressed further on the surface of the photosensitive drum  12  at the region for the transferring particle layer  70 . At the same time, excess dispersion solvent on the surface of the liquid transferring material  37   a  is scraped off with the metallic roller  22   a.  Thus, the transferring particle layer  70  of the predetermined pattern according to the image modulation data from the pattern generating device  50  is formed on the surface of the photosensitive drum  12 . 
     After the pattern of the transferring particle layer  70  is formed on the surface of the photosensitive drum  12  at the first turn of the photosensitive drum  12  in this manner, each of forming processes for the toner layers  71  of yellow (Y), magenta (M) and cyan (C) is repeated sequentially, as is the case of the first embodiment, in order to obtain the full color image in which the tricolor toner layers  71  of yellow (Y), magenta (M) and cyan (C) are superimposed. Then the dryer  23  dries and removes the liquid carrier so as to leave it moderately, and then the transferring process will start. 
     As shown in  FIG. 7A , the transferring particle layer  70  and the toner layer  71  formed on the surface of the photosensitive drum  12  in the transferring process, receive a shearing stress caused by the velocity difference between the intermediate transfer roller  27   a  and the photosensitive drum  12  when the toner layer  71  arrives at the transfer nip between the intermediate transfer roller  27   a  and the photosensitive drum  12 . As shown in  FIG. 7B , breakdown in the middle of the transferring particle layer  70 , whose coagulation force is weaker than the adhesive force to the photosensitive drum  12  occurs by the shearing stress. The full color toner layer  71 , which is pressure-contacted to the intermediate transfer roller  27   a,  is transferred primarily with high transfer efficiency to the surface of the intermediate transfer roller  27   a,  together with the transferring particle layer  70 , Therefore, it is transferred secondarily to the print paper P and the full color developed image is obtained on the print paper P. 
     In this embodiment, as shown in  FIG. 6B , if the expansion processing is applied in order to form the toner layer  71   c  shown in  FIG. 6A , consumption of the transferring particles of the transferring particle layer  70  is suppressed to approximately 39% comparing to that of the transferring particle layer  70  formed on the whole surface of the photosensitive drum  12 . Consumption test of the transferring particle layer  70 , which is formed without the expansion processing to the toner layer  71   c  of the  FIG. 6A , shows that consumption of the transferring particles of the transferring particle layer  70  could be suppressed to approximately 22% comparing to that of the transferring layer  70  formed on the whole surface of the photosensitive drum  12 . The processing in this embodiment, is carried out to the binary image, however it can also be applicable to the multi-valued image. 
     Soon after the primary transferring of the full color layer  71  and the transferring particle layers  70 , the transferring particle layers  70  were both observed on the toner layer  71  and the surface of the photosensitive drum  12  over 100 area % thereon, and the breakdown favorably generated in the inside of the transferring particle layer  70  was confirmed. 
     In this embodiment, as is the case of the first embodiment mentioned above, the transferring particle layer  70 , which has weak coagulation force among the transferring particles  37  than the adhesive force to the photosensitive drum, is formed prior to the formation of the toner layer  71 . In the primarily transferring of the toner layer  71 , which is formed on the transferring particle layer  70 , to the intermediate transfer roller  27   a  is carried while applying a shearing stress to both the toner layer  71  and the transferring particle layer  70 , the breakdown inside portions of the transferring particle layer  70 , where coagulation force among the transferring particles  37  is weak, occurs. Therefore, the toner layer  71  formed on the transferring particle layer  70  is surely transferred to the intermediate transfer roller  27   a  without any defects therein, but with high transfer efficiency, which enables to obtain a high quality developed image on the print paper P. 
     Furthermore, in this embodiment as is the case of the first embodiment, no heat is required to form the transferring particle layer  70  on the photosensitive drum  12  thereon. Accordingly, life duration of the photosensitive drum  12  is lengthened, and room for selection of the photosensitive material is also widened. Besides, consumption of the transferring particles of the transferring particle layer  70  is drastically suppressed because the region of the transferring particle layer  70  is limited to the region of the toner layer  71  and the expanded region in the periphery thereof, so that running cost caused by the consumption of transferring particles of the transferring particle layer  70  is suppressed. In addition, cleaning amount of remaining transferring particle layer  70  by the cleaner  28  decreases and life duration of the cleaner  28  is elongated. 
     The third embodiment of the present invention will be explained referring to  FIG. 8  to FIG.  11 B. The third embodiment is to further confine the region for the transferring particle layer in the second embodiment mentioned above. Other features are the same as those of the aforementioned second embodiment, so that the same constructions to those explained in the second embodiment are denoted by the same reference characters and detailed explanations are not provided. 
     An electrophotographic apparatus of this embodiment uses a pattern generating device  75 , which feeds region information of the transferring particle layer to an exposing device  17  for forming the transferring particle layer only at a front edge portion of the toner layer-forming region where adhesion to a intermediate transfer roller  27   a  is small. Namely, the electrophotographic apparatus of this embodiment prevents occurrence of inferior transfer caused by the height difference between the toner layer-formed region and the non-toner layer region at the top edge portion of the toner layer. 
     As shown in  FIG. 8 , the pattern generating device  75  has a front edge detecting unit  69  between an OR circuit  66 B and an expansion processing unit  67 B in a transferring particle layer-pattern generating unit  63 B. An expansion parameter signal  68 B indicating how to expand is fed into the expansion processing unit  67 B. In a front edge detecting unit  69  of the pattern generating device  75 , a front edge detection is performed on image signals for yellow (Y), magenta (M) and cyan (C), which are binarized at a binarizing processing unit  62  and OR operated at an OR circuit  66 B. Practically, in order for detecting the front edge, “1” pixel  78  (coordinate is (i,j)) constituting the toner layer  77   c  shown by a black square as shown in  FIG. 9  is examined, for example. Then, one of the adjacent pixel  78   a  (i, j−1) is examined. In case, the pixel  78   a  (i, j−1) is “0” (toner layer  77  does not exist), then it is concluded that the pixel  78  is the front edge. 
     When such front edge detection processing is carried out to the toner layer  77   c  shown in  FIG. 10A , which is the same as that shown in  FIG. 6A  of the second embodiment, detection result is obtained as shown in FIG.  10 B. In  FIG. 10B  hatched square portions denote the front edge pixels  77   a.  Then, an expansion processing is carried out on the detected front edge pixels  77   a.  Content of the expansion processing is the same as the second embodiment, so that the result is shown in  FIG. 10C  if 4-vicinity processing is applied, for example. White squares  76   a  and crosshatched squares  76   b  in the figure are the region for the transferring particle layer  76 . 
     In the image forming process in this embodiment, the transferring particle layer  76  is formed on the surface of the photosensitive drum  12  as is the case of the second embodiment before forming the full color image. The transferring particles  37  contains a resin component having a Tg temperature higher than the room temperature, for example about 45° C. for the transferring particles  37  while the toner particles contains similar resin component having a Tg temperature higher than the room temperature, for example about 45° C. The forming process of the transferring particle layer  76  is the same as the second embodiment except that the exposing pattern to the photosensitive drum  12  with the exposing device  17  is limited to the front edge of the toner layer  77  and its vicinity on the photosensitive drum  12 . 
     Thereafter, the full color image is obtained by superimposing the tricolor toner layers  77  of yellow (Y), magenta (M) and cyan (C) as is the case with the second embodiment. At that time, only the front edge portion of the toner layer  77  and its vicinity are superimposed on the transferring particle layer  76 . 
     In the transferring process, when the toner layer  77  formed on the transferring particle layer  76  arrives at the transferring nip between the intermediate transfer roller  27   a  and the photosensitive drum  12  as shown in  FIG. 11A , the transferring particle layer  76  at the front edge portion of the toner layer  77 , which has inferior adhesiveness to the intermediate transfer roller  27   a  breaks down in the middle thereof as shown in  FIG. 11B  because coagulation force among the transferring particles  37  is weaker than the adhesive force to the photosensitive drum  12 . Therefore, inferior transfer is prevented in spite of poor adhesion between the toner layer  77  and the intermediate transfer roller  27   a.  Since the region of the toner layer  77  other than the front edge portion thereof has superior adhesion to the intermediate transfer roller  27   a,  the toner layer  77  is favorably transferred to the surface of the intermediate transfer roller  27   a.  Then, the toner layer  77  on the surface of the intermediate transfer roller  27   a  is transferred secondarily to the print paper P, thereby the full color developed image is obtained on the print paper P. 
     When the transferring particle layer  76  is formed on the region shown in  FIG. 10C  according to this embodiment, consumption of the transferring particles of the transferring particle layer  76  can be suppressed to approximately 20% comparing to that of transferring particle layer  76  formed on the entire surface of the photosensitive drum  12 . 
     Soon after the primary transferring of the full color toner layer  77  and the transferring particle layers  76 , the transferring particle layers  76  were observed on both surfaces of the toner layer  77  and the photosensitive drum  12  the transferred primarily to the intermediate transfer roller  27   a  and the surface of after, it was proven that remained on both surfaces of the toner layer  77  and the photosensitive drum  12  over 100 area % thereof, and breakdown was favorably generated in the inside of the transferring particle layer  76 . 
     As constructed above, since the transferring particle layer  76  under the toner layer  77  breaks down internally at the front edge portion of the toner layer  77 , inferior transfer, which is apt to occur due to deterioration of adhesion to the intermediate transfer roller  27   a,  is prevented. On the other hand, as the region of the toner layer  77  other than the front edge portion adheres favorably to the intermediate transfer roller  27   a,  transferring to the intermediate transfer roller  27   a  is favorably carried out, and the image quality is improved. 
     Furthermore, in the embodiment as is the case of the second embodiment, no heat is required to form the transferring particle layer  76  on the photosensitive drum  12 . Accordingly, life duration of the photosensitive drum  12  is lengthened and room for selection of the photosensitive material is widened. Besides, consumption of the transferring particles of the transferring particle layer  76  can be drastically suppressed because the region of the transferring particle layer  76  is confined only to the region of the toner layers, so that running cost is saved. In addition, cleaning amount of remaining transferring particle layer  76  with the cleaner  28  decreases and life duration of the cleaner  28  is elongated. 
     The fourth embodiment of the present invention will be explained referring to FIG.  12  and FIG.  13 B. The fourth embodiment is to regulate the thickness of the transferring particle layer in accordance with the density (thickness) of the toner layer in the third embodiment. Other features are the same as those of the aforementioned third embodiment, so that the same element portions to those explained in the third embodiment are denoted by the same reference characters and detailed explanations are not provided. 
     The electrophotographic apparatus according to this embodiment forms the transferring particle layer thick if the toner layer is thick and has high image density, and forms it thin if the toner layer is thin and has low image density, which then prevents occurrence of the inferior transfer caused by high image density. 
     As shown in  FIG. 12 , the pattern generating device  80  has an OR circuit  66 C, an expansion processing unit  67 C, a front edge detecting unit  69  and a density detecting unit  81  in the transferring particle layer-pattern generating unit  63 C. An expansion parameter signal  68 C indicating how to expand is fed into the expansion processing unit  67 C. At the density detecting unit  81 , superimposing color information according as the binarized image signals of yellow (Y), magenta (M) and cyan (C), which is derived from a binarizing processing unit  62 , is obtained. Namely, the thickness of the toner layers (1 to 3 layers) to be determined by these three image signals is detected. The transferring particle layer image T signal fed to a recorded signal control unit  64  contains the exposing intensity information converted from the thickness of the aforementioned toner layers as well as the exposing pattern information to an exposing device  17  (T is 2bit in this embodiment). In the image forming process in this embodiment, a transferring particle layer  82  is formed on a surface of a photosensitive drum  12 , before the full color image is formed, as is the case of the third embodiment. However the thickness of a transferring particle layer  82  is regulated by the irradiation intensity of a laser beam  14  from the exposing device  17  in accordance with the detection result of the density detecting unit  81 . In consequence, the transferring particle layer  82  is made thick if the density of the toner layer  83  on the photosensitive drum  12  is high (the toner layer  83  is thick) as shown in  FIG. 13A , and the transferring particle layer  82  is made thin if the density of the toner layer  83  on the photosensitive drum  12  is low (the toner layer  83  is thin) as shown in FIG.  13 B. 
     Thereafter, the full color developed image is obtained on a print paper P via the full color image forming process and the transferring process, as is the case of the third embodiment. Because the thickness of the transferring particle layer  82  is controlled in accordance with change of the thickness of the toner layer at the transferring process, favorable transferring is achieved without inferior transfer even in the region where adhesion to the intermediate transfer roller  27   a  is small due to the thick toner layer  83 . 
     As constructed above, in this embodiment, since the thickness of the transferring particle layer  82  is increased at the region, where inferior transfer is apt to occur due to the deterioration of adhesion to the intermediate transfer roller  27   a,  is prevented. Image quality is enhanced by the improvement of the transferability. When the transferring particle layer  82  forms thin at the region where the toner layer  83  is thin, consumption of the transferring particles for the transferring particle layer  82  is suppressed. 
     Furthermore, in this embodiment as is the case of the third embodiment, no heat is required to form the transferring particle layer  82  on the photosensitive drum  12 . Accordingly, life duration of the photosensitive drum  12  is lengthened, and room for selection of the photosensitive material is also widened. Besides, consumption of the transferring particles for the transferring particle layer  82  is suppressed because the region for the transferring particle layer  82  is confined to only the front edge portion of the region of the toner layer  83 , so that running cost can is saved. In addition, cleaning amount of remaining transferring particle layer  82  with the cleaner  28  decreases and life duration of the cleaner  28  is extended. 
     The fifth embodiment of the present invention will be explained referring to FIG.  14 . The fifth embodiment is to regulate furthermore the pattern region of the transferring particle layer in accordance with the thickness of the toner layer in the fourth embodiment. Other feature are the same as those of the aforementioned fourth embodiment, so that the same element portions to those explained in the fourth embodiment are denoted by the same references characters and detailed explanations are not provided. 
     The electrophotographic apparatus according to this embodiment expands region of the transferring particle layer when the toner layer is thick and high image density, and narrows it when the toner layer is thin and has low image density, which thus prevents occurrence of the inferior transfer due to high image density. 
     As shown in  FIG. 14 , the pattern generating device  80  has an OR circuit  66 D, an expansion processing unit  67 D, the front edge detecting unit  69  and an expansion parameter selecting unit  600  in a transferring particle layer-pattern generating unit  63 D. At the expansion parameter selecting unit  600  in the pattern generating device  80 , superimposing color information according as the binarized image signals of yellow (Y), magenta (M) and cyan (C) derived from the binarizing processing unit  62  is obtained. Namely, the thickness of the toner layer (1 to 3 layers) to be formed by three image signals is detected. The expansion parameter is selected from such thickness information. 
     For example, 4-vicinity processing is selected if the toner layer is thin (1 layer), and 8-vicinity processing is selected if the toner layer is thick (2 to 3 layers). The information for such a binary processing is fed as the expansion parameter signal to the expansion processing portion, and expansion processing of the region in accordance with the expansion parameter is carried out. 
     In this embodiment, the transferring particle layer (not shown) is formed on a surface of a photosensitive drum  12  before the full color image is formed at the image forming process, as is the case of the third embodiment. However the region for the transferring particle layer is regulated by the irradiation region of a laser beam  14  by an exposing device  17 , in accordance with the information derived from the expansion processing unit  67 D. In consequence, the transferring particle layer is formed on a widen region including the image forming region and 8 vicinity regions thereof when the toner layer on the photosensitive drum  12  is thick, and the transferring particle layer is formed on a narrowed region including the image forming region and 4 vicinity regions thereof when the toner layer is thin. 
     Thereafter, the full color developed image is obtained on a print paper P via the full color image forming process and the transferring process, as is the case of the third embodiment. Because the thickness of the transferring particle layer is controlled in accordance with change of the thickness of the toner layer at the transferring process, favorable transferring is achieved without inferior transfer even in the region where adhesion to a intermediate transfer roller  27   a  is small due to the thick toner layer. 
     According to this embodiment, the forming region of the transferring particle layer is so widened at the portion, where the toner layer is thick, that inferior transfer caused by deterioration of adhesion to the intermediate transfer roller  27   a  is prevented. Quality of image is enhanced due to the improvement of the transferability. On the other hand, when the region for the transferring particle layer forms narrow at the region where a toner layer  83  is thin, consumption of the transferring particles of the transferring particle layer  82  is suppressed by making. 
     Furthermore, in this embodiment as is the case of the third embodiment, no heat is required to form the transferring particle layer  82  on the photo the photosensitive drum  12 . Accordingly, life duration of the photosensitive drum  12  is lengthened, so that room for selection of the photosensitive material is widened. Besides, consumption of the transferring particles of the transferring particle layer  82  is suppressed because the region of the transferring particle layer  82  is confined only to the front edge portion of the region for the toner layers, so that running cost is saved. In addition, cleaning amount of remaining transferring particle layer with a cleaner  28  decreases and life duration of the cleaner  28  is elongated. 
     The present invention is not limited to the embodiments mentioned above, but many changes and modifications can, of course, be carried out without departing from the scope of the present invention. For example, the structure and the process of the image forming apparatus are not limited to the aforementioned features. Color of the developer used for the developing process is not limited to three colors, but it is arbitrary. It may be one or two colors. Developing with 4 colors or more is also possible. Materials for the developer and the transferring particles are not limited as long as the coagulation force among the transferring particles in the transferring particle layer does not exceed the adhesive force between the transferring particle layer and the photosensitive drum. The transferring particle may be clear, colorless, or colored moderately. With respect to the material, for the intermediate transfer medium and the image recording member, they are freely selected if favorable transferring or image forming properties are obtained. 
     In order to realize that remaining rates of the transferring particle layer on the image recording member and the toner layer are both 100 area % of the area of the transferring layer after the toner layer is transferred to the medium, the coagulation force among the transferring particles of the transferring particle layer is preferably enough to cause the breakdown in the inside of the transferring particle layer. The coagulation force among the transferring particles of the transferring particle layer is not limited to the above, but may be any coagulation force satisfying the remaining rates of the transferring particle layer on both the image recording member and the toner layer being approximately 90 area % over the area of the transferring particle layer after the toner layer is transferred to the medium to be transferred to. 
     Moreover the resin component of the transferring particle is not necessarily one kind, but it may include. In that case, the same effects to those mentioned above will be expected as long as the Tg of at least one kind of resin is not less than 25° C., preferably it is not less than 45° C. Furthermore, the transferring particle can be constituted only with the materials, which are used as the additives shown in the embodiments mentioned above. Namely, the transferring particle constituted with a metal oxide such as SiO 2 , TiO 2 , SnO 2 , and ZnO, may have the same performance. 
     In addition, the transfer device can naturally be any device that does not add any shearing stress as long as it is a pressure transferring type. Because the coagulation force among the transferring particles of the transferring particle layer is weak, inner breakdown occurs in the transferring particle layer even if the transfer process, which utilizes only the difference of surface energy is applied. The toner layer is then prevented from remaining on the image recording member, thereby a high transfer efficiency is obtained. 
     The structure of the transferring particle-forming device forming the transferring particle layer on the image recording member is also not limited to the embodiments mentioned above. For example, when the transferring particle layer is formed electrostatically on a photosensitive drum  12 , as done in the first embodiment, instead of using the roller electrode, a fixed disc electrode  87  which applies a bias potential to a transferring particle layer-forming device  86  is used as a variation as shown in FIG.  15 . 
     Moreover in the third embodiment for example, detecting method of the front edge of the toner layer  77  is arbitrary, and any general detecting device such as Sobel Operator can be available. Regulation of the layer thickness of the transferring particle layer  82  in accordance with the thickness of the toner layer  83  in the fourth embodiment may be freely applicable to the first embodiment, the second embodiment, or other embodiments. 
     According to the present invention as described hitherto in detail, transfer efficiency of the toner layer is drastically improved by forming the transferring particle layer before forming the toner layer on the surface of the image recording member and by making the coagulation force among the transferring particles in the transferring particle-layer be smaller than the adhesive force between the transferring particle layer and the image recording member. Therefore a high quality transferred image due to high transfer efficiency can be obtained, and an image forming apparatus which realizes high image quality is provided. Furthermore, the image recording member are not affected by heat when the transferring particle layer is formed, life duration of the image recording member is lengthened, and room for selection of the photosensitive material becomes wide.