Patent Publication Number: US-9836008-B2

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-043509 filed Mar. 7, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided an image forming apparatus including: an image forming unit that includes a developing device which performs development with a toner having a metal color which contains a flat metal pigment and a developing device which performs development with a toner having another color other than the metal color which does not contains the flat metal pigment, and forms a toner image on a recording medium; a fixing unit that fixes the toner image formed on the recording medium; and a controller that controls the image forming unit and the fixing unit such that a toner image is formed of the toner having the metal color and fixed on one surface of a film, and controls transport of the film such that the film in which the toner image is fixed on the one surface is output, or the film in which the toner image is fixed on the one surface has a front surface and a back surface reversed to each other so as to be supplied to the image forming unit, in a case where the film is selected as the recording medium and a metal glossiness improving mode is selected so as to improve metal glossiness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to the exemplary embodiment of the invention; 
         FIG. 2  is a schematic configuration diagram illustrating a configuration of an image forming device (a main component) of the image forming apparatus illustrated in  FIG. 1 ; 
         FIGS. 3A and 3B  are schematic diagrams illustrating an example of a shape of a flat metal pigment, of which  FIG. 3A  is a plan view and  FIG. 3B  is a side view; 
         FIGS. 4A and 4B  are schematic diagrams illustrating an example of a posture of the flat metal pigment; 
         FIG. 5  is a sectional view schematically illustrating a state in which a superimposed toner image is formed and fixed on a recording medium in a normal mode; 
         FIGS. 6A, 6B and 6C  are sectional views schematically illustrating an example of a state in which a toner image is formed and fixed on the film in a case where a back surface having a metal color is selected in a metal glossiness improving mode; 
         FIGS. 7A and 7B  are schematic diagrams illustrating a forming position of the toner image on the film and a measuring direction of a flop index value (FI value), and  FIG. 7C  is a graph illustrating a measurement result of the FI value; 
         FIGS. 8A and 8B  are sectional views schematically illustrating a state in which the toner image is formed and fixed on the film in a case where one surface having the metal color is selected in the metal glossiness improving mode; 
         FIGS. 9A, 9B and 9C  are sectional views schematically illustrating a state in which the toner image is formed and fixed on the film in a case where both surfaces having the metal color is selected in the metal glossiness improving mode; 
         FIG. 10  is a schematic configuration diagram illustrating a modification example of the configuration of the image forming device; and 
         FIG. 11  is a sectional view schematically illustrating a state in which a superimposed toner image is formed and fixed on the recording medium by the image forming device of the modification example in the normal mode. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an example of the exemplary embodiment of the invention will be described with reference to the drawings. 
     &lt;Image Forming Apparatus&gt; 
     First, the image forming apparatus will be described.  FIG. 1  is a schematic configuration diagram illustrating an example of a configuration of the image forming apparatus according to the exemplary embodiment of the invention.  FIG. 2  is a schematic configuration diagram illustrating a configuration of the image forming device (main component) of the image forming apparatus illustrated in  FIG. 1 . Note that, in the drawings, an arrow H represents a vertical direction, and an arrow W represents a horizontal direction, which is width direction of the apparatus. 
     As illustrated in  FIG. 1 , an image forming apparatus  10  is provided with an image forming device  12  that forms an image on a recording medium P as a recording medium by an electrophotographic process, a medium transport unit  50  that transports the recording medium P, and a post-processing unit  60  that performs a post process on the recording medium P on which the image is formed. In addition, the image forming apparatus  10  is provided with a power supply unit  80  that supplies power to the respective units of the apparatus, and a controller  70  that controls the respective units of the apparatus. 
     The image forming device  12  is provided with a toner image forming unit  20  that forms a toner image, a transfer unit  30  that transfers the toner image formed by the toner image forming unit  20  to the recording medium P, and a fixing unit  40  that fixes the toner image transferred to the recording medium P on the recording medium P. 
     The medium transport unit  50  is provided with a medium supply unit  52  that supplies the recording medium P to the image forming device  12 , and a medium exit unit  54  that exits the recording medium P on which the toner image is formed. In addition, the medium transport unit  50  is provided with a medium returning unit  56  and an intermediate transport unit  58  which are used at the time of forming images on both surfaces of the recording medium P. 
     The post-processing unit  60  is provided with a medium cooling unit  62  that cools the recording medium P to which the toner image is transferred by the image forming device  12 , a correcting device  64  that corrects a curve of the recording medium P, and an image inspecting unit  66  that inspects the image formed on the recording medium P. The respective components constituting the post-processing unit  60  are disposed in the medium exit unit  54  of the medium transport unit  50 . 
     The components of the image forming apparatus  10  are accommodated in a housing  90  except for an exit medium receiving portion  541 . The housing  90  in the exemplary embodiment is divided into a first housing  91  and a second housing  92  which are adjacent to each other in the width direction of the apparatus. With this, a transporting unit of the image forming apparatus  10  is miniaturized in the width direction of the apparatus. 
     The first housing  91  accommodates main components of the image forming device  12  except for the fixing unit  40  and the medium supply unit  52 . The second housing  92  accommodates the fixing unit  40 , the medium exit unit  54 , the medium cooling unit  62 , the image inspecting unit  66 , the medium returning unit  56 , the controller  70 , and the power supply unit  80  which constitute the image forming device  12 . 
     The first housing  91  and the second housing  92  are coupled to each other by a fastening tool such as a bolt and nut (not shown as one example of components). A communication opening portion  90 C 1  through which the recording medium P passes from a transfer nip NT of the image forming device  12  to a fixing nip NF, and a communication path  90 C 2  through which the recording medium P passes from the medium returning unit  56  to the medium supply unit  52  are formed between the first housing  91  and the second housing  92  in a coupled state. 
     (Image Forming Unit) 
     Hereinafter, the “image forming unit” will be described. 
     The image forming device  12  is provided with the toner image forming unit  20 , the transfer unit  30 , and the fixing unit  40 . In the exemplary embodiment, toner image forming units  20 V,  20 W,  20 Y,  20 M,  20 C, and  20 K that form a toner image are correspondingly provided for each of the colors such as a first spot color (V), a second spot color (W), yellow (Y), magenta (M), cyan (C), and black (K). 
     The toner image forming units  20 V,  20 W,  20 Y,  20 M,  20 C, and  20 K are arranged in order of  20 W→ 20 Y→ 20 M→ 20 C→ 20 K→ 20 V of the toner image forming units along the upper side portion of the transfer belt  31  from the upstream side in the moving direction of the transfer belt  31 . That is, the toner images are formed on the transfer belt  31  in order of a W color image→a Y color image→a M color image→a C color image→a K color image→a V color image. 
     In addition, in the exemplary embodiment, the first spot color (V) is “a silver color” or “a gold color”, and the toner image forming unit  20 V forms a toner image by a toner having a metal color containing a flat metal pigment. The toner having the metal color is used to impart metal glossiness to an image. On the other hand, the second spot color (W) is a user&#39;s unique corporate color which is frequently used as compared with other colors. Note that, details of the toner having the metal color, and the control of the components which is performed by the controller  70  at the time of forming an image by using the toner having the metal color will be described below. 
     Each of the toner image forming units  20 V,  20 W,  20 Y,  20 M,  20 C, and  20 K is formed in a similar way. If there is no need to distinguish the aforementioned units for each color, it is referred to as a toner image forming unit  20 . The toner image forming unit  20  is provided with an image forming unit  14 , and a toner cartridge  27  which holds toner, as illustrated in  FIG. 2 . The image forming unit  14  provided for each color will be described without being distinguished for each color. The image forming unit  14  is provided with a photoconductor drum  21  which is an example of the image carrier, a charging unit  22 , an exposure unit  23 , a developing unit  24  which is an example of a developing device, a cleaning unit  25 , and a charge eliminating unit  26 . 
     A photoreceptor layer is formed on the surface of the photoconductor drum  21 . The charging unit  22  causes a surface (the photoreceptor layer) of the photoconductor drum  21  to be charged through a corona discharge process. The exposure unit  23  irradiates the surface of the photoconductor drum  21  which is charged by the charging unit  22  with exposure light L so as to form an electrostatic latent image on the surface of the photoconductor drum  21 . The exposure light L is modulated in response to image data obtained from an image signal processing portion  71  (refer to  FIG. 1 ) of the controller  70 . The developing unit  24  develops an electrostatic latent image formed on the surface of the photoconductor drum  21  by using a developer G containing toner so as to form a toner image on the surface of the photoconductor drum  21 . 
     The cleaning unit  25  is formed into a blade shape, and scrapes the toner remaining on the surface of the photoconductor drum  21  after transferring the toner image to the transfer unit  30  from the surface of the photoconductor drum  21 . The charge eliminating unit  26  eliminates a charge by irradiating the transferred photoconductor drum  21  with light. With this, a charging history of the surface of the photoconductor drum  21  is canceled. The toner cartridge  27  supplies toner to the developing unit  24 . 
     The transfer unit  30  primarily transfers the toner image of the photoconductor drum  21  for each color which is superimposed on the transfer belt  31 , and then secondarily transfers the superimposed toner image to the recording medium P. Hereinafter, the details will be described. 
     The transfer belt  31  is an endless belt type as illustrated in  FIG. 2 , and is wound around plural rollers  32 . A roller  32 D serves as a driving roller which causes the transfer belt  31  to be rotated by a driving force of a motor (not shown) in an arrow A direction. In addition, a roller  32 T serves as a tensioning roller which imparts tension to the transfer belt  31 . A peak portion on the lower end side which forms an obtuse angle of the transfer belt  31  is wound around a roller  32 B. The roller  32 B serves as a facing roller of a secondary transfer roller  34  which is described below. The transfer belt  31  comes in contact with the lower side of the photoconductor drum  21  for each color in the upper side portion extending in the width direction of the apparatus. 
     A primary transfer roller  33  which is an example of a transfer member for transferring the toner images in the photoconductor drums  21  to the transfer belt  31  is disposed on the inside of the transfer belt  31 . Each of the primary transfer rollers  33  is disposed so as to face the photoconductor drum  21  in the corresponding color with the transfer belt  31  interposed therebetween. In addition, a transfer bias voltage having polarity which is opposite to the toner polarity is applied to the primary transfer roller  33 . By applying such a transfer bias voltage to the primary transfer roller  33 , the toner image formed on the photoconductor drum  21  is transferred to the transfer belt  31 . 
     In addition, the transfer unit  30  is provided with a secondary transfer roller  34  for transferring the toner image which is superimposed on the transfer belt  31  to the recording medium P. The secondary transfer roller  34  is disposed between the rollers  32 B with the transfer belt  31  interposed therebetween, and has the transfer nip NT formed between the secondary transfer roller  34  and the transfer belt  31 . The recording medium P is supplied to the aforementioned transfer nip NT from the medium supply unit  52  in a timely manner. A transfer bias voltage which is opposite to the toner polarity is applied to the secondary transfer roller  34  by a feeding portion (not shown). By applying the transfer bias voltage to the secondary transfer roller  34 , the toner image is transferred to the recording medium P passing through the transfer nip NT from the transfer belt  31 . 
     Further, the transfer unit  30  is provided with a cleaning unit  35  that cleans the transfer belt  31  after performing the secondary transfer. The cleaning unit  35  is disposed on the downstream side of a portion (transfer nip NT) in which the secondary transfer is performed, and the upstream side of a portion in which the primary transfer is performed in the circumference direction of the transfer belt  31 . The cleaning unit  35  is provided with a blade  351  for scrapping the toner remaining on the surface of the transfer belt  31 . 
     The fixing unit  40  fixes the toner image on the recording medium P to which the toner image is transferred in the transfer unit  30 . In the exemplary embodiment, the fixing unit  40  fixes the toner image to the recording medium P by heating and pressurizing the toner image in the fixing nip NF which is formed by the fixing belt  411  which is wound around plural rollers  413 , and the pressure roller  42 . 
     A roller  413 H is set as a heating roller which is provided with a heater therein and is rotated by a driving force transferred from a motor (not shown). With this, the fixing belt  411  is rotated in an arrow R direction. In addition, the pressure roller  42  is also rotated at the same circumferential speed as that of the fixing belt  411  by the driving force transferred from the motor (not shown). A fixing temperature and the like of the fixing unit  40  which are controlled by the controller  70  will be described below. 
     (Medium Transport Unit) 
     Here, the “medium transport unit” will be described in detail. 
     The medium transport unit  50  includes the medium supply unit  52 , the medium exit unit  54 , the medium returning unit  56 , and the intermediate transport unit  58 . 
     The medium supply unit  52  is provided with a container  521  accommodating the recording mediums P in a state of being stacked. In the exemplary embodiment, two containers  521  are disposed side by side in the width direction of the apparatus, on the lower side of the transfer unit  30 . A medium supply path  52 P is formed from each of the containers  521  to the transfer nip NT which is a portion for the secondary transfer by plural pairs of the transport roller pair  522 . 
     A feeding roller  523  for feeding the top of the recording medium P stacked on the container  521  is disposed on the upper side of each of the containers  521 . Among the plural pairs of the transport roller pair  522 , pairs of the transport roller pair  522 S on the most upstream side in the transport direction of the recording medium P serve as a separation roller which separates the recording media P, which are stacked by the feeding roller  523  and are fed from the container  521 , one by one. In addition, among the plural pairs of the transport roller pair  522 , pairs of the transport roller pair  522 R positioned on the right upstream side of transfer nip NT in the transport direction of the recording medium P are operated such that moving timing of the toner image on the transfer belt  31  and transporting timing of the recording medium P are matched with each other. 
     In addition, the medium supply unit  52  is provided with a preliminary transporting path  52 Pr. The preliminary transporting path  52 Pr is started from an opening portion  91 W on the side opposite to the second housing  92  side of the first housing  91 , and joins a turning-back portion  52 P 2  of the medium supply path  52 P. The preliminary transporting path  52 Pr is set as a transporting path at the time of sending the recording medium P which is fed from an optional recording medium supply device (not shown) disposed to be adjacent to the opening portion  91 W side of the first housing  91  to the image forming device  12 . 
     The intermediate transport unit  58  is disposed between the transfer nip NT of the transfer unit  30  and the fixing nip NF of the fixing unit  40 , and is provided with plural belt transporting members  581  including an endless transport belt which is wound around the roller. The belt transporting member  581  is configured such that the transport belt is rotated with the recording medium P being sucked onto the surface of the transport belt by suctioning air (negative pressure suction) from the inside so as to transport the recording medium P. 
     The medium exit unit  54  exits the recording medium P on which the toner image is fixed by the fixing unit  40  of the image forming device  12  to the outside of the housing  90  from the exit port  92 W of the second housing  92  which is formed at an end portion on the side opposite to the first housing  91  side. The medium exit unit  54  is provided with the exit medium receiving portion  541  for receiving the recording medium P output from the exit port  92 W. 
     The medium exit unit  54  includes a medium exit path  54 P for which the recording medium P is transported to the exit port  92 W from the fixing unit  40  (fixing nip NF). The medium exit path  54 P is formed by a belt transporting member  543 , and the plural pairs of rollers  542 . In addition, among the plural pairs of rollers  542 , a pair of rollers  542 E disposed on the most downstream side in the output direction of the recording medium P serve as exit rollers for outputting the recording medium P onto the output medium receiving portion  541 . 
     The medium returning unit  56  is provided with plural pairs of rollers  561 . The plural pairs of rollers  561  form a reverse path  56 P, into which the recording medium P having passed through the image inspecting unit  66  is fed, in a case where an image is to be formed on both sides of the recording medium. The reverse path  56 P includes a branch path  56 P 1 , a transport path  56 P 2 , and a reverse path  56 P 3 . The branch path  56 P 1  is branched from the medium exit path  54 P. The transport path  56 P 2  allows the recording medium P received from the branch path  56 P 1  to be fed into the medium supply path  52 P. The reverse path  56 P 3  is provided in the middle of the transport path  56 P 2 , allows the transport path  56 P 2  to be turned back (switched back) in the direction opposite to the direction in which the recording medium P is transported, and reverses the front surface and the back surface. 
     (Post-Processing Unit) 
     The medium cooling unit  62 , the correcting device  64 , and the image inspecting unit  66  which constitute the post-processing unit  60  are sequentially disposed, from the upstream side in the output direction, on the upstream side in the output direction of the recording medium P with respect to a portion where the branch path  56 P 1  is branched on the medium output path  54 P of the medium output unit  54 . 
     The medium cooling unit  62  is provided with an endothermic unit  621  for absorbing heat of the recording medium P and a pressing unit  622  for pressing the recording medium P to the endothermic unit  621 . The endothermic unit  621  is disposed on the upper side of the medium exit path  54 P, and the pressing unit  622  is disposed on the lower side of the medium exit path  54 P. 
     The endothermic unit  621  is provided with an endless endothermic belt  6211 , plural rollers  6212  for supporting the endothermic belt  6211 , a heat sink  6213  disposed in the inside of the endothermic belt  6211 , and a fan  6214  for cooling the heat sink  6213 . The endothermic belt  6211  comes in contact with the recording medium P on the outer circumferential surface so as to exchange the heat. Among the plural rollers  6212 , a roller  6212 D serves as a driving roller for transferring a driving force to the endothermic belt  6211 . The heat sink  6213  is in surface-contact with the inner circumferential surface of the endothermic belt  6211  in a predetermined range so as to be slidable along the medium exit path  54 P. 
     The pressing unit  622  is provided with an endless pressing belt  6221  and plural rollers  6222  for supporting the pressing belt  6221 . The pressing belt  6221  is wound around the plural rollers  6222 . The pressing unit  622  presses the recording medium P to the endothermic belt  6211  (heat sink  6213 ) so as to transport the recording medium P together with the endothermic belt  6211 . 
     The correcting device  64  is provided on the downstream side of the medium cooling unit  62  in the medium exit unit  54 . The correcting device  64  corrects a curve (curl) of the recording medium P received from the medium cooling unit  62 . In addition, an in-line sensor  661  which constitutes the main component of the image inspecting unit  66  is disposed on the downstream side of the correcting device  64  in the medium exit unit  54 . The in-line sensor  661  detects existence or the degree of a toner concentration defect, an image defect, an image position defect, and the like of the fixed toner image, based on the light, with which the recording medium P is irradiated, reflected on the recording medium P. 
     &lt;Image Forming Operation (Action)&gt; 
     Next, an image forming step and a post-processing step which are to be performed on the recording medium P by the image forming apparatus  10  will be described. The image forming step is performed based on a user&#39;s selection and various image forming conditions set in advance. In the exemplary embodiment, in the image forming step, a “normal mode” in which an image is formed in normal procedure, and a “metal glossiness improving mode” in which an image is formed in procedure of imparting high metal glossiness are prepared. 
     In addition, it is possible to select a type of the recording medium P (for example, a container accommodating a film), and in a case where a transparent film is selected as the recording medium P, it is possible to select the “metal glossiness improving mode”. Here, the expression of “transparent” means that the light is not absorbed in the visible region. In the following description, a “transparent film” is simply referred to as a “film”. 
     In the “metal glossiness improving mode”, there are additional options such as a “one surface having the metal color”, a “both surfaces having the metal color”, and a “back surface having the metal color”. The aforementioned options will be described in detail. The image signal processing portion  71  (refer to  FIG. 1 ) of the controller  70  performs an image forming command by obtaining image data and selection setting information of the image data or the like as “image forming information”. 
     (Toner Having Metal Color) 
     Hereinafter, the “toner having the metal color” will be described.  FIGS. 3A and 3B  are schematic diagrams illustrating an example of a shape of a flat metal pigment. The toner having a metal color, such as a silver color, a gold color, or the like which is used as the first spot color (V), contains a metal pigment and a binder resin, and is used to impart the metal glossiness to the image. The metal pigment is formed of aluminum or the like. As illustrated in  FIG. 3B , the metal pigment  110  is formed into a long rod shape extending in the horizontal direction when viewed from the side on a plane in the drawing. 
     In addition, when the metal pigment  110  illustrated in  FIG. 3B  is viewed from above in the drawing, the shape of the metal pigment  110  is wider than the shape when viewed from the side as illustrated in  FIG. 3A . That is, the metal pigment  110  is placed on the plane, and includes a pair of reflecting surfaces  110 A (flat surfaces) which face the upper side and the lower side. As such, the metal pigment  110  is formed into a flat shape. Hereinafter, the metal pigment formed into the flat shape is referred to as a “flat metal pigment  110 ”. 
     On the other hand, a toner having a certain color except for the metal color (hereinafter, simply referred to as a “toner having a certain color”), which is used as a second spot color (W), a yellow (Y), a magenta (M), a cyan (C), and a black (K) is formed of a pigment which does not contain a flat metal pigment (for example, an organic pigment or an inorganic pigment) and a binder resin. 
     Next, the relationship between the improvement of the metal glossiness and the posture of the flat metal pigment will be described.  FIGS. 4A and 4B  are schematic diagrams illustrating an example of the posture of the flat metal pigment. As illustrated in  FIG. 4A , in a case where the direction facing the reflecting surface  110 A of the flat metal pigment  110  is not constant, the light reflected on the image is diffused. In contrast, as illustrated in  FIG. 4B , the reflecting surface  110 A of the flat metal pigment  110  faces the direction orthogonal to the surface of the recording medium P, and the flat metal pigments  110  are arranged in the direction along the surface of the recording medium P, and thus it is possible to prevent the light reflected on the image from being diffused as compared with the case of being illustrated in  FIG. 4A . That is, the orientation of the flat metal pigment is improved, and thus the metal glossiness of the image is also improved. 
     In addition, as illustrated in  FIG. 4B , the flat metal pigments  110  of which the reflecting surface  110 A faces the direction orthogonal to the surface of the recording medium P are uniformly arranged on the recording medium P, and thus a coverage ratio which is a ratio obtained by covering the recording medium P with the flat metal pigments  110  is improved, as compared with the case of being illustrated in  FIG. 4A . A reflective area in which the light incident on the surface of the recording medium P is reflected by the flat metal pigments  110  becomes larger. That is, when the orientation of the flat metal pigment is improved, the coverage ratio by the flat metal pigments is also improved, and thus the metal glossiness of the image is improved. 
     Particularly, in a case where the recording medium P is a transparent film, the orientation and the coverage ratio of the flat metal pigment  110  are improved, and thus there is no gap between the flat metal pigments  110  through which the light transmits. For this reason, the improvement degree of the metal glossiness of the image is large as compared with the case where the recording medium P is an opaque plain paper. In this regard, in the exemplary embodiment, in a case where the transparent film is selected as the recording medium P, it is possible to select “metal glossiness improving mode”. Even in a case where the transparent film is selected as the recording medium P, the user may select the normal mode. 
     (Normal Mode) 
     An image forming step and a post-processing step in the “normal mode” will be described with reference to  FIG. 1  and  FIG. 2 . The controller  70  which receives the image forming command in the “normal mode” operates the toner image forming unit  20 , the transfer unit  30 , the fixing unit  40 , the medium transport unit  50 , the post-processing unit  60 , and the like. For example, the photoconductor drum  21  of the image forming unit  14  for each color, and a developing roller  242  of the developing unit  24  are rotated such that the transfer belt  31  is circulated. In addition, when the pressure roller  42  is rotated, the fixing belt  411  is circulated. 
     First, a toner image having a color corresponding to any one of the first spot color (V), the second spot color (W), yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photoconductor drum  21  for each color. Specifically, the photoconductor drum  21  is charged by the charging unit  22 , and is exposed to exposure light L in response to the image data of the corresponding color by the exposure unit  23 , and thereby an electrostatic latent image is formed on the surface of the photoconductor drum  21 . The electrostatic latent image which is formed on the photoconductor drum  21  is developed by using a developer of the corresponding color supplied from the developing unit  24 . With this, the toner image having the corresponding color is formed on the photoconductor drum  21  for each color. 
     The toner image for each color which is formed on the photoconductor drum  21  for each color is sequentially transferred to the circulating transfer belt  31  through the applying of a transfer bias voltage through the primary transfer roller  33  for each color. With this, a superimposed toner image obtained by superimposing six colors of toner images is formed on the transfer belt  31 . In the exemplary embodiment, the six colors of toner images are superimposed in order of a W color image, a Y color image, an M color image, a C color image, a K color image, and a V color image from the transfer belt  31  side. The superimposed toner image is transported to the transfer nip NT by the circulation of the transfer belt  31 . 
     The recording medium P is supplied to the transfer nip NT by pairs of the transport roller pair  522 R of the medium supply unit  52  in accordance with the timing of the transporting the superimposed toner image. When the transfer bias voltage is applied to the transfer nip NT, the superimposed toner image is transferred to the recording medium P from the transfer belt  31 . After performing the transfer, the six colors of toner images are superimposed in order of the V color image, the K color image, the C color image, the M color image, the Y color image, and the W color image from the recording medium P. 
     The recording medium P to which the superimposed toner image is transferred is transported to the fixing nip NF of the fixing unit  40  by the intermediate transport unit  58 . The fixing unit  40  imparts heat and pressure to the recording medium P passing through the fixing nip NF. With this, the toner image is transferred to and fixed on the recording medium P. 
     The recording medium P which is output from the fixing unit  40  is processed by the post-processing unit  60  while being transported to the exit medium receiving portion  541  outside the apparatus by the medium exit unit  54 . First, the recording medium P heated in a fixing step is cooled in the medium cooling unit  62 . Then, the curve of the recording medium P is corrected by the correcting device  64 . Further, regarding the toner image fixed on the recording medium P, the existence or the degree of a toner concentration defect, an image defect, an image position defect, and the like are detected by the image inspecting unit  66 . In addition, the recording medium P is output to the medium exit unit  54 . 
     On the other hand, in a case where an image is formed on a non-image surface which is one surface of the recording medium P on which an image is not formed (a case of duplex printing), the controller  70  switches a transporting path of the recording medium P after passing through the image inspecting unit  66  into the branch path  56 P 1  of the medium returning unit  56  from the medium exit path  54 P of the medium exit unit  54 . With this, the recording medium P having the front surface and the back surface reversed to each other via the reverse path  56 P is fed into the medium supply path  52 P. An image is formed (fixed) on the back surface of the recording medium P in the same step as that of forming the image on the front surface as described above. The recording medium P goes through the same step as the above-described processing step performed after forming the image on the front surface, and then is output to the exit medium receiving portion  541  outside the apparatus by the medium exit unit  54 . 
     (Metal Glossiness Improving Mode (Back Surface Having Metal Color)) 
     An image forming step in the “metal glossiness improving mode (back surface having metal color)” will be described with reference to  FIG. 1  and  FIG. 2 . The post-processing step is the same as that in the normal mode, and thus the description thereof will not be described below. In the “metal glossiness improving mode”, it is assumed that the recording medium P is a film, the recording medium P is referred to as a “film F”. Similar to the case of the normal mode, the controller  70  which receives the image forming command in the “metal glossiness improving mode (back surface having metal color)” operates the toner image forming unit  20 , the transfer unit  30 , the fixing unit  40 , the medium transport unit  50 , the post-processing unit  60 , and the like. 
     First, a solid image having an image density (Cin) of 100% is formed of the toner having the metal color which is the first spot color (V) on the photoconductor drum  21 V. The solid image is formed on the entire image forming region of the back surface of the film F (hereinafter, referred to as “the entire back surface”). Note that, in the exemplary embodiment, an example in which the toner image having the metal color is formed on the entire back surface will be described; however, the toner image having the metal color may be formed on a portion of the image forming region. The toner image having the metal color which is formed on the photoconductor drum  21 V having the metal color is transferred to the circulating transfer belt  31  through the applying of a transfer bias voltage through a primary transfer roller  33 V having the metal color. With this, the toner image having the metal color is formed on the transfer belt  31 . 
     The toner image having the metal color is transported to the transfer nip NT by the circulation of the transfer belt  31 . The film F is supplied to the transfer nip NT by pairs of the transport roller pair  522 R of the medium supply unit  52  in accordance with the timing of the transporting the toner image. When the transfer bias voltage is applied to the transfer nip NT, the toner image having the metal color is transferred to the back surface of the film F from the transfer belt  31 . 
     The film F to which the toner image having the metal color is transferred is transported to the fixing nip NF of the fixing unit  40  by the intermediate transport unit  58 . The fixing unit  40  imparts heat and pressure to the film F passing through the fixing nip NF. With this, the toner image is transferred to and fixed on the back surface of the film F. The film F which is output from the fixing unit  40  is processed by the post-processing unit  60 . 
     The controller  70  switches a transporting path of the film F after passing through the image inspecting unit  66  of the post-processing unit  60  into the branch path  56 P 1  of the medium returning unit  56  from the medium exit path  54 P of the medium exit unit  54 . With this, the film F in which the toner image having the metal color is formed on the entire back surface has the front surface and the back surface reversed to each other via the reverse path  56 P, and then is fed into the medium supply path  52 P. 
     Next, a toner image having a color corresponding to any one of the first spot color (V), the second spot color (W), yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photoconductor drum  21  for each color. The toner image for each color which is formed on the photoconductor drum  21  for each color is sequentially transferred to the circulating transfer belt  31  through the applying of a transfer bias voltage through the primary transfer roller  33  for each color. With this, a superimposed toner image obtained by superimposing five colors of toner images is formed on the transfer belt  31 . In the exemplary embodiment, the five colors of toner images are superimposed in order of the W color image, the Y color image, the M color image, the C color image, and the K color image from the transfer belt  31  side. 
     The superimposed toner image is transported to the transfer nip NT by the circulation of the transfer belt  31 . The film F in which the toner image having the metal color is formed on the entire back surface is supplied to the transfer nip NT by pairs of the transport roller pair  522 R of the medium supply unit  52  in accordance with the timing of the transporting the toner image. When the transfer bias voltage is applied to the transfer nip NT, the superimposed toner image is transferred to the front surface of the film F from the transfer belt  31 . After performing the transfer, the five colors of toner images are superimposed in order of the K color image, the C color image, the M color image, the Y color image, and the W color image from the film F side. 
     The film F to which the superimposed toner image is transferred is transported to the fixing nip NF of the fixing unit  40  by the intermediate transport unit  58 . The fixing unit  40  imparts heat and pressure to the film F passing through the fixing nip NF. With this, the toner image is transferred to and fixed on the front surface of the film F. The film F which is output from the fixing unit  40  is processed by the post-processing unit  60  while being transported to the exit medium receiving portion  541  outside the apparatus by the medium exit unit  54 . The film F processed by the post-processing unit  60  is output to the exit medium receiving portion  541  outside of the apparatus by the medium exit unit  54 . 
     Note that, in a case where the controller  70  controls the fixing unit  40 , and performs the fixing of the toner having the metal color, an amount of the heat imparted to the toner image may be set to be greater that a case of the toner having another color. Specifically, the controller  70  increases the amount of the heat imparted to the toner image at the time of fixing by controlling the fixing unit  40  to change at least one of the fixing temperature, the fixing pressure, and the fixing time. For example, the amount of heat imparted to the toner image is increased by raising the fixing temperature and the fixing pressure, and extending the fixing time. 
     With the above-described operation, the toner image having the metal color is formed on the entire back surface of the film F so as to perform baking on the film F, and the toner image having another color is formed on the surface of the film F. Here, in consideration of the fixing step for the toner image having the metal color, the normal mode and the “metal glossiness improving mode (back surface having metal color)” are compared with each other.  FIG. 5  is a sectional view illustrating an example of a state in which the superimposed toner image is formed and fixed on the recording medium in the normal mode. In addition,  FIGS. 6A to 6C  are sectional views illustrating an example of a state in which the toner image is formed and fixed on the film in a case where a back surface having the metal color is selected in the metal glossiness improving mode. 
     As illustrated in  FIG. 5 , in the normal mode, a toner  200  having the metal color which contains the flat metal pigment  110  and a toner  202  having another color except for the metal color are superimposed on the film F to which the image is transferred but is not fixed yet. The toner image having the metal color is a so-called a base image, and thus is formed on the lowermost layer. In addition, in order to avoid unevenness caused by the toner image having another color, the toner image having the metal color is formed on the lowermost layer. However, in consideration of the fixing step of the toner image having the metal color, since the toner  202  having another color exists on the upper side of the toner having the metal color  200 , a shearing force from the fixing unit  40  is not directly imparted to the toner  200  having the metal color, and thus the orientation of the flat metal pigment  110  is deteriorated. 
     In contrast, in the metal glossiness improving mode (back surface having metal color), as illustrated in  FIG. 6A  to  FIG. 6C , when the toner image having the metal color is fixed on the entire back surface of the film F, the toner  200  having the metal color which contains the flat metal pigment  110  only exists on the film F to which the image is transferred but is not fixed yet, and thus the shearing force from the fixing unit  40  is directly imparted to the toner having the metal color  200  in the transport direction of the film F. With this, the reflecting surface  110 A of the flat metal pigment  110  faces the direction orthogonal to the surface of the film F, and the flat metal pigments  110  are arranged in the direction along the surface of the film F. That is, the orientation of the flat metal pigment  110  is improved. 
     In addition, the film F is transparent, and thus even when the toner image having the metal color is formed on the back surface, the metal glossiness of the image is not damaged. That is, as compared with the case where the toner image having the metal color and the toner image having another color are superimposed on the front surface of the film F, the orientation of the flat metal pigment  110  is improved and thus the metal glossiness is also improved. 
     Here, regarding the toner image formed in the normal mode and the toner image formed in the metal glossiness improving mode (back surface having silver color), a flop index value is measured. The flop index value (FI value) means an index indicates the metal glossiness, and as the value thereof is large, the metal glossiness is improved. The FI value is measured based on ASTME 2194.  FIGS. 7A and 7B  are schematic diagrams illustrating a forming position of the toner image on the film and a measuring direction of the FI value, and  FIG. 7C  is a graph illustrating a measurement result of the FI value. 
     In the normal mode, as illustrated in  FIG. 7A , the toner image having the silver color and the color toner image having any one of the Y color, M color, and C color are formed to be superimposed on the front surface of the film, and then the FI value is measured from the front surface side of the film. On the other hand, in the metal glossiness improving mode (back surface having metal color), the toner image having the silver color is formed on the back surface of the film so as to perform the backing on the back surface as illustrated in  FIG. 7B , and the color toner image having any one of the Y color, the M color, and the C color is formed on the front surface of the film, and then the FI value is measured from the front surface side of the film. In both of the above-described modes, the toner image having the silver color is set as a solid image having an image density Cin of 100%, and the color toner image is set as an image having an image density Cin of 80%. 
     A modified machine of “COLOR 1000 PRESS” manufactured by Fuji Xerox Co., Ltd. is used as the image forming apparatus, an “OHP film for PPC laser” manufactured by KISO CHEMICAL Co., Ltd. is used as the film, and a matt toner equipped with “COLOR 1000 PRESS” manufactured by Fuji Xerox Co., Ltd. is used as the Y color toner, the M color toner, and the C color toner. The fixing conditions is set such that the fixing rate is 445 [mm/sec] and the fixing temperature is 155° C. A multi-angle colorimeter “BYK-MAC” manufactured by TOYO SEIKI Co., Ltd. is used to measure the FI value. 
     As illustrated in  FIG. 7C , in the Y color, the FI value of the toner image formed in the metal glossiness improving mode (backing) is more improved than the FI value of the toner image formed in the normal mode (overlapping) by 1.56 times. In addition, in the M color, the FI value of the toner image formed in the metal glossiness improving mode is more improved than the FI value of the toner image formed in the normal mode by 1.47 times. In addition, in the C color, the FI value of the toner image formed in the metal glossiness improving mode is more improved than the FI value of the toner image formed in the normal mode by 1.67 times. It is found from the above results that as compared with the case where the toner image having the metal color and the toner image having another color are formed to be superimposed on the surface of the film F, the metal glossiness is improved in the case where the toner image having the metal color is formed on the entire back surface of the film F. 
     Note that, in the above description, the case of receiving the image forming command in “metal glossiness improving mode (back surface having metal color)” is described; however, the “metal glossiness improving mode” has options such as “one surface having a metal color” and “both surfaces having a metal color”, in addition to the “back surface having the metal color” in which the toner image having the metal color is formed on the back surface and the toner image having another color is formed on the front surface. In the “one surface having the metal color”, the toner image having the metal color is formed the one surface of the film. In the “both surfaces having the metal color”, the toner image having the metal color is formed on both sides of the film. Hereinafter, the image forming step of the above cases will be described. 
     (Metal Glossiness Improving Mode (One Surface Having Metal Color)) 
     Similar to the case of the normal mode, the controller  70  which receives the image forming command in the “metal glossiness improving mode (one surface having the metal color)” operates the toner image forming unit  20 , the transfer unit  30 , the fixing unit  40 , the medium transport unit  50 , the post-processing unit  60 , and the like. 
     First, a solid image is formed of the toner having the metal color which is the first spot color (V) on the photoconductor drum  21 V. The solid image is formed on the entire image forming region of the one surface of the film F (hereinafter, referred to as “the entire one surface”). The toner image having the metal color formed on the photoconductor drum  21 V is transferred to the transfer belt  31  by the primary transfer roller  33 V. The toner image having the metal color on the transfer belt  31  is transferred to the one surface of the film F at the transfer nip NT. 
     Next, the toner image is transferred to and fixed on the one surface of the film F when the film F passes through the fixing nip NF of the fixing unit  40 . The film F which is output from the fixing unit  40  is processed by the post-processing unit  60  and then is output to the exit medium receiving portion  541 . 
     With the above-described operation, the toner image having the metal color is formed on the entire one surface of the film F.  FIGS. 8A and 8B  are sectional views illustrating a state in which the toner image is formed and fixed on the film in a case where one surface having the metal color is selected in the metal glossiness improving mode. Also in this case, when the toner image having the metal color is fixed on the entire one surface of the film F, the toner  200  having the metal color which contains the flat metal pigment  110  only exists on the film. F to which the image is transferred but is not fixed yet, and the shearing force from the fixing unit  40  is directly imparted to the toner having the metal color  200 , and thus the orientation of the flat metal pigment  110  is improved. 
     In addition, the film F is transparent, and thus even when the toner image having the metal color is formed on the one surface, the metal glossiness of the image is not damaged. That is, as compared with the case where the toner image having the metal color and the toner image having another color are superimposed on the one surface of the film F, the orientation of the flat metal pigment  110  is improved and thus the metal glossiness is also improved. 
     (Metal Glossiness Improving Mode (Both Surfaces Having the Metal Color)) 
     Similar to the case of the normal mode, the controller  70  which receives the image forming command in the “metal glossiness improving mode (both surfaces having the metal color)” operates the toner image forming unit  20 , the transfer unit  30 , the fixing unit  40 , the medium transport unit  50 , the post-processing unit  60 , and the like. 
     First, a solid image is formed of the toner having the metal color which is the first spot color (V) on the photoconductor drum  21 V. The solid image is formed on the entire image forming region of the one surface of the film F (hereinafter, referred to as “the entire one surface”). The toner image having the metal color formed on the photoconductor drum  21 V is transferred to the transfer belt  31  by the primary transfer roller  33 V. The toner image having the metal color on the transfer belt  31  is transferred to the one surface of the film F at the transfer nip NT. 
     Next, the toner image is transferred to and fixed on the one surface of the film F when the film F passes through the fixing nip NF of the fixing unit  40 . The film F which is output from the fixing unit  40  is processed by the post-processing unit  60 . 
     The controller  70  switches a transporting path of the film F after passing through the image inspecting unit  66  of the post-processing unit  60  into the branch path  56 P 1  of the medium returning unit  56  from the medium exit path  54 P of the medium exit unit  54 . With this, the film F in which the toner image having the metal color is formed on the entire one surface has the front surface and the back surface reversed to each other via the reverse path  56 P, and then is fed into the medium supply path  52 P. 
     Next, a solid image is formed of the toner having the metal color which is the first spot color (V) on the photoconductor drum  21 V. The solid image is formed on the entire image forming region of the other one surface of the film F (hereinafter, referred to as “the entirety of the other one surface”). The toner image having the metal color formed on the photoconductor drum  21 V is transferred to the transfer belt  31  by the primary transfer roller  33 V. The toner image having the metal color on the transfer belt  31  is transferred to the entirety of the other one surface of the film F in which the toner image having the metal color is formed on the one surface. 
     Next, the toner image having the metal color is transferred to and fixed on the entirety of the other one surface of the film F when the film F passes through the fixing nip NF of the fixing unit  40 . The film F which is output from the fixing unit  40  is processed by the post-processing unit  60  and then is output to the external output medium receiving portion  541 . 
     With the above-described operation, the toner image having the metal color is formed on the entire surface of each of the both surface of the film F.  FIG. 9A to 9C  are sectional views illustrating a state in which the toner image formed on the film is fixed in a case where both surfaces having the metal color is selected in the metal glossiness improving mode. Also in this case, when the toner image having the metal color is fixed on the entire surface of each of the film F, the toner  200  having the metal color which contains the flat metal pigment  110  only exists on the film F to which the image is transferred but is not fixed yet, and the shearing force from the fixing unit  40  is directly imparted to the toner having the metal color  200 , and thus the orientation of the flat metal pigment  110  is improved. 
     That is, as compared with the case where the toner image having the metal color and the toner image having another color are superimposed on the one surface of the film F, the orientation of the flat metal pigment  110  is improved and thus the metal glossiness is also improved. Further, as compared with the case where the toner image having the metal color is formed on only the one surface of the film, the coverage ratio by the flat metal pigments is also improved, and thus the metal glossiness is further improved. 
     Modification Example 
     Note that, it is needless to say that the configuration of the image forming apparatus described in the exemplary embodiments is an example, and the configuration may be changed within the scope of the invention without departing the gist thereof. 
     For example, in the above exemplary embodiment embodiments, an example in which the toner image forming units  20 V,  20 W,  20 Y,  20 M,  20 C, and  20 K of the image forming device  12  are arranged in order of  20 W→ 20 Y→ 20 M→ 20 C→ 20 K→ 20 V of the toner image forming units along the upper side portion of the transfer belt  31  from the upstream side in the moving direction of the transfer belt  31  is described, however, the color type and the order are not limited to those in the above exemplary embodiment. For example, the toner image forming unit  20 W of the second spot color (W) may be omitted. 
     In addition, for example, the order of the toner image forming units may be changed such that the toner image forming units are arranged in order of  20 V→ 20 Y→ 20 M→ 20 C→ 20 K→ 20 W from the upstream side in the moving direction of the transfer belt  31  as illustrated in  FIG. 10 . In this case, as illustrated in  FIG. 11 , in the normal mode, the toner  202  having another color except for the metal color exists under the toner  200  having the metal color which contains the flat metal pigment  110  on the film F to which the image is transferred but is not fixed yet. For this reason, the unevenness caused by the toner image having another color cannot be avoided, and thus the orientation of the flat metal pigment  110  is deteriorated. However, when the metal glossiness improving mode is selected, the toner  200  having the metal color which contains the flat metal pigment  110  only exists on the film F to which the image is transferred but is not fixed yet, and thus regardless of the order of arrangement of plural toner image forming units  20 , the orientation of the flat metal pigment  110  is improved, and thus the metal glossiness is also improved. 
     In addition, in the above exemplary embodiment, an example in which the “normal mode” or the “metal glossiness improving mode” is selected for each film, and any one of the “back surface having the metal color”, the “one surface having the metal color”, and the “both surfaces having the metal color” is selected for each film F is described; however, the mode setting is not necessarily performed based on a film unit. The “normal mode” or the “metal glossiness improving mode” may be selected for each region, and any one of the “back surface having the metal color”, the “one surface having the metal color”, and the “both surfaces having the metal color” may be selected for each region by dividing one film into plural regions. For example, a region in which the toner image having another color is formed only on the front surface, a region in which the toner image having another color is formed on the front surface and the toner image having the metal color is formed on the back surface, and a region in which the toner image having the metal color is formed on both surfaces may be mixed on the same film. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.