Patent Publication Number: US-8983324-B2

Title: Fixing device and 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. 2012-257505 filed Nov. 26, 2012. 
     BACKGROUND 
     (i) Technical Field 
     The present invention relates to fixing devices and image forming apparatuses. 
     (ii) Related Art 
     When an image forming apparatus, such as a photocopier or a printer, forms a glittery image having a metallic color such as gold or silver, the image of the metallic color is formed on a recording medium by using a metallic toner. Such a metallic color is reproduced by, for example, adding pigment containing metal powder, such as silver powder, as a principal component to a metallic toner. 
     SUMMARY 
     According to an aspect of the present invention, n image forming apparatus includes an image forming unit that forms a metallic toner image on a recording medium using a metallic toner containing flakes of metallic pigment; and a heating portion that heats and melts the metallic toner on the recording medium. A first shearing force is applied to the molten metallic toner in a transportation direction of the recording medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  schematically illustrates an image forming apparatus including a fixing device according to an exemplary embodiment; 
         FIG. 2  schematically illustrates the fixing device according to the exemplary embodiment; 
         FIGS. 3A and 3B  schematically illustrate how the arrangement of flakes of pigments changes when a shearing force is applied; 
         FIG. 4  schematically illustrates a fixing state of a metallic toner; 
         FIGS. 5A ,  5 B, and  5 C schematically illustrate surface roughness in different fixing states of a metallic toner; 
         FIGS. 6A ,  6 B, and  6 C schematically illustrate surface roughness in different fixing states of a metallic toner when viewed in a cross section; 
         FIG. 7  is a graph showing the relationship between the surface roughness and the metallic effect; 
         FIGS. 8A ,  8 B,  8 C, and  8 D schematically illustrate image conversion; 
         FIG. 9  is a flowchart of exemplary image processing performed by the fixing device according to the exemplary embodiment; 
         FIGS. 10A and 10B  schematically illustrate states of a metallic toner with or without additional printing; 
         FIG. 11  schematically illustrates a fixing device according to a different exemplary embodiment; and 
         FIG. 12  schematically illustrates an image forming apparatus including the fixing device according to the different exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary Embodiment 
     Referring to the drawings, an exemplary embodiment of the present invention is described below.  FIG. 1  schematically illustrates an image forming apparatus  1  including a fixing device  60  according to the exemplary embodiment of the present invention. The image forming apparatus  1  according to the exemplary embodiment includes a controller  2 , image forming units  3 K,  3 Y,  3 M,  3 C,  3 S, and  3 G, a transfer unit  50 , a fixing device  60 , and a sheet storage  80 . The image forming apparatus  1  forms an image on a sheet P, which serves as a recording medium, on the basis of input image data supplied thereto. 
     The image forming units  3 K to  3 G form toner images of black (K), yellow (Y), magenta (M), cyan (C), silver (S), and gold (G). As illustrated in  FIG. 1 , each of the image forming units  3 K to  3 G includes a corresponding one of photoconductors  10 K to  10 G, a corresponding one of charging units  20 K to  20 G, a corresponding one of exposure units  30 K to  30 G, a corresponding one of developing units  40 K to  40 G, and a corresponding one of cleaning units  70 K to  70 G. The image forming apparatus  1  forms a metallic image by using the image forming units  3 S and  3 G and forms a color image by using the image forming units  3 K to  3 C. In the case where the image forming units  3 K to  3 G do not particularly have to be distinguished from one another, each of the image forming units  3 K to  3 G is also described simply as an image forming unit  3 . 
     The controller  2  includes an arithmetic unit such as a central processing unit (CPU) and a memory to control operations of components of the image forming apparatus  1 . The controller  2  also includes a rotation controller  2   a , a shearing force controller  2   b , and an image converter  2   c . Functions of these units will be described below. 
     Each of the photoconductors  10  ( 10 K to  10 G) is a cylindrical rotating body that rotates in a direction of the arrow of  FIG. 1  and that has a photosensitive layer made of an organic photosensitive material to hold an image. 
     Each of the charging units  20  ( 20 K to  20 G) applies a predetermined charging voltage to the surface of the photoconductor  10  using, for example, a charging roller that rotates while coming into contact with the surface of the photoconductor  10 . The charging unit  20  may be a contact-type charging unit that charges the photoconductor  10  while coming into contact with the photoconductor  10  using a brush or may be a non-contact-type charging unit that charges the photoconductor  10  using a corona discharge. 
     Each of the exposure units  30  ( 30 K to  30 G) emits light based on image data to the surface of the corresponding photoconductor  10  charged by the corresponding charging unit  20  and forms an electrostatic latent image having a latent image potential using a potential difference. As the photoconductor  10  rotates, the electrostatic latent image moves to a position at which the corresponding developing unit  40  is disposed. 
     Each of the developing units  40  ( 40 K to  40 G) has a rotatable developing roller  41  (a corresponding one of the developing rollers  41 K to  41 G) and a toner adhering to the developing roller  41  transfers to the corresponding photoconductor  10 . Specifically, the toner transfers to the surface of the photoconductor  10  due to there being a potential difference between the charged toner and the electrostatic latent image formed on the photoconductor  10 . Consequently, a toner image is formed on the photoconductor  10 . The toner image moves to a position at which the transfer unit  50  is disposed as the photoconductor  10  rotates. 
     The transfer unit  50  includes an intermediate transfer belt  51 , a back-up roller  52 , transporting rollers  53   a  and  53   b , first transfer rollers  54  ( 54 K to  54 G), and a second transfer roller  55 . The transfer unit  50  transfers the toner images formed on the intermediate transfer belt  51  to a sheet P that has been transported thereto by transporting rollers  91   a ,  91   b , and  91   c . The sheet P to which the toner images have been transferred is transported to the fixing device  60 . 
     The intermediate transfer belt  51  is stretched by the transporting rollers  53   a  and  53   b  and the back-up roller  52 . The intermediate transfer belt  51  is driven to rotate by, for example, the transporting roller  53   a . The first transfer rollers  54  are disposed so as to face the photoconductor  10  with the intermediate transfer belt  51  interposed between the first transfer rollers  54  and the photoconductor  10 . Specifically, the first transfer roller  54 K faces the photoconductor  10 K and the other first transfer rollers  54  face the corresponding photoconductors  10 . 
     Each of the first transfer rollers  54 K to  54 G are driven to rotate as the intermediate transfer belt  51  rotates. The toner images formed on the photoconductors  10 K to  10 G are sequentially transferred to the surface of the intermediate transfer belt  51  while being superposed on top of one another. The second transfer roller  55  is disposed so as to face the back-up roller  52 . The intermediate transfer belt  51  and a sheet P are nipped between the second transfer roller  55  and the back-up roller  52  and thus the toner images that have been transferred to the intermediate transfer belt  51  are transferred to the sheet P. 
     The fixing device  60  includes a heating portion  61 , which serves as a first transportation unit, and a pressure roller  62 , which serves as a second transportation unit and transports the sheet P while pressing the sheet P. The fixing device  60  heats and presses the sheet P to fix, to the sheet P, unfixed toners that have been transferred to the sheet P. The heating portion  61  according to the exemplary embodiment includes a fixing belt  61   a , an internal heating roller  61   b , an external heating roller  61   c , transporting rollers  61   d  and  61   e , a slide sheet  61   f , and a fixing pad  61   g.    
     The fixing device  60  includes a first driving unit  63  and a second driving unit  64 , which are controlled by the rotation controller  2   a . The first driving unit  63  drives the external heating roller  61   c  and the second driving unit  64  drives the pressure roller  62 . The detail of the fixing device  60  according to the exemplary embodiment will be described below. 
     Each of the cleaning units  70  ( 70 K to  70 G) removes remnants such as a toner remaining on the surface of the corresponding photoconductor  10  after the toner image has been transferred to the sheet P. Multiple sheets P are stored in the sheet storage  80 . The sheets P are picked up by a pick-up roller  90  from the sheet storage  80  and transported to the transfer unit  50  by the transporting rollers  91   a ,  91   b , and  91   c.    
     Now, the fixing device  60  according to the exemplary embodiment will be described.  FIG. 2  illustrates a configuration of the fixing device  60 . As illustrated in  FIG. 2 , the fixing device  60  includes the heating portion  61  and the pressure roller  62 . The fixing device  60  heats and melts, by using the heating portion  61 , toners that have been transferred to the sheet P nipped between the heating portion  61  and the pressure roller  62  and presses the toners with the pressure roller  62  so that the toners are fixed to the sheet P. 
     The heating portion  61  includes the fixing belt  61   a , which is a rotatable endless belt, the internal heating roller  61   b , the external heating roller  61   c , and the transporting rollers  61   d  and  61   e . The internal heating roller  61   b , the external heating roller  61   c , and the transporting rollers  61   d  and  61   e  are disposed so as to stretch the fixing belt  61   a . The internal heating roller  61   b  has a heater and heats the inner side (inner surface) of the fixing belt  61   a . The external heating roller  61   c  has a heater and heats the outer side (outer surface) of the fixing belt  61   a . The toners that have been transferred to the sheet P nipped between the thus heated fixing belt  61   a  and the pressure roller  62  are heated and pressed, and thus fixed to the sheet P. 
     The heating portion  61  includes a slide sheet  61   f , which is attached to the surface of the fixing pad  61   g  so as to face the pressure roller  62  and slide over the fixing belt  61   a . The slide sheet  61   f  is made of a glass fiber sheet impregnated with, for example, a fluoropolymer and has a small sliding resistance to the fixing belt  61   a.    
     The fixing device  60  also includes the first driving unit  63  and the second driving unit  64 . The first driving unit  63  drives the external heating roller  61   c  to rotate such that the fixing belt  61   a  moves at a first speed S 1 . The second driving unit  64  drives the pressure roller  62  to rotate at a second speed S 2 . The first driving unit  63  and the second driving unit  64  are controlled by the rotation controller  2   a  of the controller  2  such that the fixing belt  61   a  moves at the first speed S 1  and the pressure roller  62  rotates at the second speed S 2 . 
     A shearing force applying unit  100  is described now. Here, an application of a shearing force means applying a shearing force to a metallic toner containing molten metallic pigment flakes by the heating portion  61  (fixing belt  61   a ) heating the toner and by the pressure roller  62  pressing the toner. Specifically, a shearing force is applied to the metallic toner, particularly to the metallic pigment flakes included in the metallic toner. 
     When the rotation controller  2   a  controls the first driving unit  63  and the second driving unit  64  so as to make the first speed S 1 , at which the recording medium is transported and the fixing belt  61   a  is driven to move by the first driving unit  63 , different from the second speed, at which the recording medium is transported and the pressure roller  62  is driven by the second driving unit  64  to rotate, the shearing force applying unit  100  applies a shearing force to the metallic toner on the sheet P. 
     In other words, when a sheet P is transported while being nipped between and pressed by the fixing belt  61   a  and the pressure roller  62 , a surface M 1  of the sheet P to which the metallic toner has been transferred and a surface M 2  of the sheet P that is on the back of the surface M 1  move at different speeds, thereby applying a shearing force between the surface M 1  and the surface M 2 . 
     Referring now to  FIGS. 3A and 3B , a sheet P to which a shearing force is applied by the shearing force applying unit  100  is described.  FIG. 3A  illustrates a state of the sheet P to which a metallic toner has been transferred and a shearing force has not been applied.  FIG. 3B  illustrates a state of the sheet P to which the metallic toner has been transferred and a shearing force has been applied. An aluminum toner layer AT illustrated in each of  FIGS. 3A and 3B  is an example of a toner layer formed on the sheet P including a metallic toner image. 
     As illustrated in  FIG. 3A , in the aluminum toner layer AT that has been transferred to paper KA before a shearing force is applied to the paper KA, aluminum pigment flakes AG, which are examples of metallic pigment flakes, are disposed so as to be superposed on top of one another in a resin JU. Here, a thermoplastic resin is used as an example of the resin JU. 
       FIG. 3B  illustrates the state where the area coated by the aluminum pigment flakes AG is increased as a result of an application of a shearing force to the aluminum toner layer AT. In other words, by applying a shearing force between the surface M 1 , which moves at the first speed S 1 , and the surface M 2 , which moves at the second speed S 2 , the superposed aluminum pigment flakes AG are moved in a transportation direction as a result of the application of the shearing force. Thus, the aluminum pigment flakes AG form a wide coating as illustrated in  FIG. 3B . 
       FIG. 4  schematically illustrates a state of the surface M 1  that has been subjected to a fixing operation when viewed from above. As illustrated in  FIG. 4 , the aluminum pigment flakes AG are superposed on top of one another in the resin JU. Here, the area coated by the aluminum pigment flakes AG is not sufficiently large and thus a large area of the paper KA is exposed to the outside. When the surface M 1  is in such a state, the amount of reflected light from the aluminum pigment flakes AG is said to be insufficient. 
     Referring now to  FIGS. 5A to 7 , a metallic effect will be described.  FIGS. 5A to 5C  each illustrate a state of the surface M 1  that has been subjected to a fixing operation when viewed from above.  FIG. 5A  schematically illustrates the surface M 1  having a small surface roughness,  FIG. 5B  schematically illustrates the surface M 1  having a medium surface roughness, and  FIG. 5C  schematically illustrates the surface M 1  having a large surface roughness.  FIGS. 6A to 6C  are cross sectional views of the surface M 1  illustrated in  FIGS. 5A to 5C , where  FIG. 5A  corresponds to  FIG. 6A ,  FIG. 5B  corresponds to  FIG. 6B , and  FIG. 5C  corresponds to  FIG. 6C .  FIG. 7  is a graph in which the horizontal axis indicates the surface roughness (μm) of the surface M 1  and the vertical axis indicates the grade of the metallic effect. 
     As illustrated in  FIGS. 5A to 6C , when the metallic toner includes a small number of aluminum pigment flakes AG, the surface roughness is small, whereas when the metallic toner includes a large number of aluminum pigment flakes AG, the surface roughness is large. As illustrated in  FIG. 7 , when the surface roughness is large, the metallic effect is graded low. 
     In other words, as illustrated in  FIGS. 5A to 7 , when there are a small number of aluminum pigment flakes AG, the metallic effect is graded medium or 3. In this case, because there are a small number of pigment flakes AG, an improvement of the metallic effect is not expected even when a shearing force is applied to the pigment flakes AG. On the other hand, when there are a large number of aluminum pigment flakes AG, the metallic effect is graded low or 1. Here, when a shearing force is applied to the aluminum pigment flakes AG that cause a large surface roughness due to the flakes AG being superposed on top of one another, the pigment flakes AG are spread to a wider area. Thus, the surface roughness is reduced and the flakes are arranged more evenly. 
     The image forming apparatus  1  may operate in a quality-first mode and a highly metallic mode. The controller  2  switches between the quality-first mode and the highly metallic mode. In the quality-first mode, the image forming units  3 S and  3 G form metallic toner images containing a small number of metallic pigment flakes and a small magnitude of shearing force is applied to the metallic toner. In the highly metallic mode, the image forming units  3 S and  3 G form metallic toner images containing a large number of metallic pigment flakes and a large magnitude of shearing force is applied to the metallic toner. 
     In the quality-first mode, the consumption of metallic toner is small. The shearing force is reduced by making the difference between the first speed S 1  and the second speed S 2  illustrated in  FIGS. 3A and 3B  smaller. 
     In the highly metallic mode, on the other hand, the consumption of metallic toner is large and the metallic effect improves. The shearing force is increased by making the difference between the first speed S 1  and the second speed S 2  illustrated in  FIGS. 3A and 3B  larger. 
     Now, an operation of the image forming apparatus  1  including the fixing device  60  according to the exemplary embodiment will be described. First, the shearing force controller  2   b  and the image converter  2   c  illustrated in  FIG. 1  will be described. When a metallic image is to be formed on a sheet P, the shearing force controller  2   b  operates the rotation controller  2   a  and performs such a control that the first speed S 1  is made different from the second speed S 2 . 
     When, on the other hand, a color image is to be formed on a sheet P, the shearing force controller  2   b  does not operate the rotation controller  2   a  so that, for example, the first speed S 1  coincides with the second speed S 2 . 
     The image converter  2   c  converts an image on the basis of the input image data such that an end portion of the input image in the transportation direction is shortened in response to an application of the shearing force from the shearing force applying unit  100 . By converting the input image in this manner, misregistration of the image is prevented. The image converter  2   c  will be described with reference to  FIGS. 8A to 8D . 
       FIGS. 8A to 8D  schematically illustrate how the image converter  2   c  converts the input image.  FIG. 8A  illustrates the state where the edge of an input image that is not converted and to which a shearing force is not applied is located at an image edge GT 1 .  FIG. 8B  illustrates the state where the edge of an input image that is not converted and to which a shearing force has been applied is located at an image edge GT 2 . 
     As illustrated in  FIG. 83 , the image edge GT 2  is shifted a distance H from the image edge GT 1  in the direction in which the shearing force is applied. As illustrated in  FIGS. 8A and 8B , an application of a shearing force to an image causes misregistration of the image. FIG.  8 C illustrates the state where the edge of an input image that has been converted and to which a shearing force is not applied is located at an image edge GT 3 .  FIG. 8D  illustrates the state where the edge of an input image that has been converted and to which a shearing force has been applied is located at the image edge GT 1 . 
     That is, when the input image has been converted, the edge of the image to which a shearing force is not applied is located at the image edge GT 3 , while the edge of the image to which a shearing force has been applied is located at the image edge GT 1 . As described above, by operating the image converter  2   c  and shifting the edge of the image a distance H in the direction in which a shearing force is applied, misregistration of the image is preventable when a shearing force is applied to an image. 
       FIG. 9  is a flowchart showing an exemplary operation of the image forming apparatus  1 . As illustrated in  FIG. 9 , when the image forming apparatus  1  starts image formation, the shearing force controller  2   b  determines whether or not a metallic image is to be formed (Step S 100 ). 
     When the shearing force controller  2   b  determines that “a metallic image is to be formed” (YES in Step S 100 ), metallic images are started to be formed and the image converter  2   c  that converts an input image is operated (Step S 110 ). Metallic toner images are formed by the image forming units  3 S and  3 G on the basis of the input image thus converted, first transferred by the transfer unit  50 , and then second transferred to a sheet P. 
     The sheet P to which the metallic toner images have been transferred is transported to the fixing device  60 , at which a shearing force is applied to the sheet P, and the metallic toner images are fixed to the sheet P by the shearing force controller  2   b  operating the rotation controller  2   a  (Step S 120 ). The sheet P to which the shearing force has been applied and the metallic toner images have been fixed is transported to the transfer unit  50  by the transporting rollers  91   d ,  91   f ,  91   g ,  91   b , and  91   c.    
     The transfer unit  50  performs additional printing on the sheet P that has been transported to the transfer unit  50  and to which the metallic toner images have been fixed (Step S 130 ). Here, the additional printing is an operation of transferring an additional toner image to a recording medium to which a previous toner image has been fixed in order to fix the toner images to the recording medium. 
     Subsequently, color images are started to be formed on the sheet P to which the metallic toner images have been fixed (Step S 140 ). Specifically, when an operation of forming color images is started, color toner images are formed by the image forming units  3 K to  3 C on the basis of the input image, first transferred to the transfer unit  50 , and then second transferred to (additionally printed on) the sheet P. 
     The sheet P on which the color toner images have been additionally printed is transported to the fixing device  60 , at which the color toner images are fixed to the sheet P (Step S 150 ). During the fixing operation, the shearing force controller  2   b  determines the images as color images and thus the rotation controller  2   a  does not apply a shearing force to the sheet P. The sheet P on which the color images have been additionally printed on the metallic images is transported by the transporting rollers  91   h  and thus the image forming apparatus  1  finishes the image formation. 
     On the other hand, when the shearing force controller  2   b  determines that “a metallic image is not to be formed” (NO in Step S 100 ), color images are started to be formed (Step S 140 ). Specifically, when an operation of forming color images is started, color toner images are formed by the image forming units  3 K to  3 C on the basis of the input image, first transferred to the transfer unit  50 , and then second transferred to the sheet P. The sheet P to which the color toner images have been transferred is transported to the fixing device  60 , at which the color toner images are fixed to the sheet P (Step S 150 ). The sheet P to which the color images have been transferred is transported by the transporting rollers  91   h  and thus the image forming apparatus  1  finishes the image formation. 
     In the flowchart of  FIG. 9 , the image forming apparatus  1  additionally prints the color images on the sheet P on which the metallic images have been formed, but the present invention is not limited to this. For example, the image forming apparatus  1  may additionally print metallic images on a sheet P on which color images have been formed. In the case of this additional printing, the sheet P is spotted with metallic pigment flakes and thus has an intensive metallic effect although the metallic pigment flakes are not spread uniformly. 
       FIGS. 10A and 10B  schematically illustrate the cases where the additional printing is performed and not performed.  FIG. 10A  illustrates the case where additional printing is performed and an aluminum toner layer AT underlies a yellow toner layer YT.  FIG. 10B  illustrates the case where additional printing is not performed and an aluminum toner layer AT underlies a yellow toner layer YT. As illustrated in  FIG. 10A , by performing additional printing, the aluminum pigment flakes AG are maintained at a state of being included in the aluminum toner layer AT and thus are evenly arranged. On the other hand, as illustrated in  FIG. 10B , without the additional printing, the aluminum pigment flakes AG are included in the aluminum toner layer AT and the yellow toner layer YT and thus are unevenly arranged. 
     Although the sheet P is transported by the transporting rollers  91   h  as described above, the sheet P may be directed to the transporting rollers  91   d  so that an image is formed on the back side. In this case, the sheet P directed to the transporting rollers  91   d  is transported to the transporting rollers  91   e , at which the sheet P is reversed. Then, the sheet P is transported to the transfer unit  50  via the transporting rollers  91   f ,  91   g ,  91   b , and  91   c.    
     According to the exemplary embodiment described above, the metallic effect is improved by having a simple configuration in which the heating portion  61  is driven by the first driving unit  63 , the pressure roller  62  is driven by the second driving unit  64 , and the heating portion  61  and the pressure roller  62  move at different speeds so that a shearing force is applied to aluminum pigment flakes AG. 
     Other Exemplary Embodiments 
     The fixing device  60  according to the exemplary embodiment and the image forming apparatus  1  including the fixing device  60  have been described thus far. The present invention, however, is not limited to the above-described exemplary embodiment and may include other exemplary embodiments. Some of the other exemplary embodiments are described below. 
     Although the fixing device  60  according to the exemplary embodiment includes a second driving unit  64  to drive the pressure roller  62 , the present invention is not limited to this configuration. For example, a fixing device  60   a  as illustrated in  FIG. 11  may be included instead. The fixing device  60   a  does not include the second driving unit  64  to drive the pressure roller  62  and the pressure roller  62  is driven to rotate by rotation of the fixing belt. 
     As illustrated in  FIG. 11 , the fixing device  60   a  includes a decelerating mechanism  65  to rotate the pressure roller  62  at the second speed. The decelerating mechanism  65  may be controlled by the rotation controller  2   a . The configuration of the fixing device  60   a  is simplified by eliminating the second driving unit  64 . 
     The image forming apparatus  1  according to the exemplary embodiment includes the image forming units  3 K to  3 G that form color images and metallic images, but the present invention is not limited to this configuration. For example, an image forming apparatus  1 A obtained by combining a first image forming apparatus  1   a  and a second image forming apparatus  1   b  as illustrated in  FIG. 12  may be employed. 
     The first image forming apparatus  1   a  includes, for example, image forming units  3 S and  3 G and a fixing device  60  that includes a shearing force applying unit  100  and that fixes metallic toner images to a sheet. The first image forming apparatus  1   a  forms metallic images. The second image forming apparatus  1   b  includes, for example, image forming units  3 K to  3 C and a fixing device  60   b  that fixes color toner images to a sheet. The second image forming apparatus  1   b  forms color images. 
     The image forming apparatus  1 A is flexibly operable as having a configuration formed by combining the first image forming apparatus  1   a , which forms metallic images and includes the fixing device  60  according to the exemplary embodiment, and the second image forming apparatus  1   b , which forms color images and includes the fixing device  60   b  that does not include the shearing force applying unit  100 . Other components of the image forming apparatus  1 A are the same as those of the image forming apparatus  1  and thus are not described here. 
     In another exemplary embodiment, a metallic toner having a melt viscosity lower than that of a color toner may be used. 
     In the case where the metallic toner has a melt viscosity lower than that of a color toner, a shearing force is more effectively applied to the metallic pigment flakes included in the metallic toner due to the melt viscosity of the metallic toner being lower. Moreover, a confusion of the metallic toner and the color toner that occurs when an image is formed without additional printing is prevented. 
     The image forming apparatus  1  according to the exemplary embodiment includes the image converter  2   c  that converts an image such that an end portion of an input image is shortened in a transportation direction, but the present invention is not limited to this configuration. For example, the image forming apparatus  1  may exclude the image converter  2   c  if misregistration of the image does not affect the sense of sight even after the shearing force applying unit  100  is operated. 
     In this exemplary embodiment, metallic images are formed by the image forming units  3 S and  3 G and color images are formed by the image forming units  3 K to  3 C, but the present invention is not limited to this configuration. For example, only the image forming unit  3 S may form a metallic image and an image forming unit that forms an image with a transparent toner as a color image may be included. 
     In this exemplary embodiment, the heating portion, which heats and melts the metallic toner on the sheet P, and the shearing force applying unit  100 , which applies a shearing force to the molten metallic toner in the transportation direction of the sheet P, form the fixing device  60 , but the present invention is not limited to this configuration. For example, the heating portion and the shearing force applying unit do not have to form the fixing device  60 . 
     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.