JP5954110B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that imparts gloss to a toner image using gloss adjustment toner is known (see, for example, Patent Document 1). In the image forming apparatus described in Patent Document 1, a toner in which individual particles have a flat shape is used as gloss adjustment toner.

JP 2002-328486 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of suppressing the color fading of a toner image on a sheet when gloss is applied using a gloss adjusting toner.

The image forming apparatus according to claim 1 comprises:
A plurality of arranged image holders that hold the toner image formed in response to the formation of the toner image;
A belt-like body that extends along the plurality of image carriers and receives the transfer of the toner images held on the plurality of image carriers while moving around;
For the moving direction of the portion extending along the plurality of image carriers in the belt-like body, on the first image carrier disposed at the most upstream of the plurality of image carriers, the gloss adjustment A first toner image is formed with toner, and on each image carrier after the second image carrier adjacent to the first image carrier toward the downstream side in the moving direction, according to each image carrier. An image forming unit for forming a toner image with color toner;
A primary transfer unit that transfers a plurality of toner images formed on the plurality of image holding bodies so as to sequentially overlap the belt-like body;
A pressurizing unit that pressurizes the first toner image in a stage before the first toner image reaches the second image carrier;
A secondary transfer portion for transferring the toner image transferred on the belt in order to be superimposed on the belt, onto a sheet;
And a fixing unit for fixing the toner image transferred onto the sheet by the secondary transfer unit on the sheet.

The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1,
The pressurizing unit pressurizes the first toner image by pressing the first toner image against the first image holding body while being held by the first image holding body. It is characterized by being.

  According to the image forming apparatus of the first aspect, the gloss is adjusted using the gloss adjusting toner as compared with the case where the first toner image by the gloss adjusting toner is transferred onto the paper without pressurizing. It is possible to suppress the color fading of the toner image on the paper at the time of application.

  According to the image forming apparatus of claim 2, in the image forming apparatus of claim 1, the pressurization is performed by a simple mechanism as compared with the case where the first toner image held at the belt-like body is pressed. It can be performed.

1 is a schematic configuration diagram of an image forming apparatus as an embodiment of the present invention. FIG. 6 is an explanatory diagram for explaining a phenomenon in which the color of a toner image on a sheet is faded when gloss is imparted using a gloss adjusting transparent toner. It is a figure which shows the detail of the pressurization part shown in FIG. 1 with the image formation engine of transparent toner. It is a figure which shows typically the transparent toner image pressurized with the pressurization roll of the pressurization part shown in FIG. It is a figure which shows another example of the pressurization method of a transparent toner image different from the pressurization method of the transparent toner image in this embodiment. It is a schematic diagram which shows the patch image formed in the Example.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus as an embodiment of the present invention.

  The image forming apparatus 100 shown in FIG. 1 forms toner images using yellow (Y), magenta (M), cyan (C), and black (K) toners, and adjusts glossiness. This is a color printer that gives glossiness to a toner image using a transparent toner.

  In addition, the image forming apparatus 100 includes five image forming engines 20Cr, 20Y, 20M, 20C, and 20K that form a toner image of transparent toner and toner images of each color of YMCK along the sheet conveyance direction. It is a so-called tandem type printer.

  The image forming apparatus 100 includes a sheet feed table 10 in the lower part thereof. The paper feed table 10 accommodates sheets in a stacked state.

  When forming an image, one sheet of paper is fed from the paper feed tray 10 by the pick-up roll 11 and is transported on the transport path 121 in the direction of arrow A by the transport roll 12. Then, the paper is further conveyed by adjusting the timing of the subsequent conveyance by the standby roll 13. The conveyance after the standby roll 13 will be described later.

  In the image forming apparatus 100, as described above, the five image forming engines 20Cr, 20Y, 20M, 20C, and 20K are arranged along the sheet conveyance direction.

  Each of the image forming engines 20Cr, 20Y, 20M, 20C, and 20K generates a toner image using a transparent toner for gloss adjustment, a Y color toner, an M color toner, a C color toner, and a K color toner, respectively. The engine that forms. These five image forming engines 20Cr, 20Y, 20M, 20C, and 20K have the same configuration except that the toners used are different. Here, the configuration of the five image forming engines 20Cr, 20Y, 20M, 20C, and 20K will be described by taking the single image forming engine 20K as a representative.

  The image forming engine 20 </ b> K includes a photoconductor 21, and a charger 22, an exposure device 23, a developing device 24, a primary transfer device 25, and a photoconductor cleaner 26 are disposed around the photoconductor 21. Here, the primary transfer unit 25 is disposed at a position where an intermediate transfer belt 41 described later is sandwiched between the primary transfer unit 25 and the photosensitive member 21.

  The photoconductor 21 has a cylindrical shape, and while being rotated in the direction of arrow B, the surface thereof is charged and further exposed to form an electrostatic latent image.

  The charger 22 charges the rotating photoreceptor 21.

  Image data is input to the exposure unit 23 from a control unit 60 to be described later, and exposure light modulated in accordance with the input image data is output from the exposure unit 23. The photoreceptor 21 is irradiated with exposure light from the exposure unit 23 after being charged by the charger 22. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 21.

  The photosensitive member 21 is exposed to exposure light to form an electrostatic latent image on the surface, and then developed by the developing device 24, and a toner image is formed on the surface of the photosensitive member 21.

  The toner image formed on the photosensitive member 21 by development by the developing unit 24 is transferred onto the intermediate transfer belt 41 by the action of the primary transfer unit 25.

  Residual toner or the like remaining on the surface of the photoconductor 21 after the transfer is removed from the photoconductor 21 by the photoconductor cleaner 26.

  The intermediate transfer belt 41 is an endless belt that circulates in the direction of the arrow C and is wound around the drive roll 42 and other plural rolls 43.

  The transparent toner formed by each of the image forming engines 20Cr, 20Y, 20M, 20C, and 20K and the toner image by each of the Y, M, C, and K toners are transferred onto the intermediate transfer belt 41 as follows. . That is, these toner images are transferred onto the intermediate transfer belt 41 so that the toner images of the transparent toner formed by the image forming engine 20Cr are sequentially overlapped with the lowest layer. Then, it is conveyed to a secondary transfer position where the secondary transfer unit 44 is disposed. In synchronization with this, the sheet that has been conveyed to the standby roll 13 is conveyed to the secondary transfer position, and the toner image on the intermediate transfer belt 41 is conveyed by the action of the secondary transfer unit 44. Transcribed above. The sheet on which the toner image has been transferred is further conveyed in the direction of arrow D on the conveying belt 14, and the toner image on the sheet is fixed on the sheet by the pressurization and heating by the fixing device 50. As a result, an image composed of the fixed toner image is formed on the paper. The sheet on which the image is formed is transported in the direction of arrow E by the transport belt 15 and discharged outside the image forming apparatus 100.

  The intermediate transfer belt 41 after the toner image is transferred onto the paper by the secondary transfer unit 44 is further circulated and the toner remaining on the surface thereof is removed from the intermediate transfer belt 41 by the belt cleaner 45.

  A total of five photoconductors 21 included in the five image forming engines 20Cr, 20Y, 20M, 20C, and 20K correspond to an example of a plurality of image carriers referred to in the present invention.

  The intermediate transfer belt 41 corresponds to an example of a belt-like body referred to in the present invention.

  The photosensitive member 21 of the transparent toner image forming engine 20Cr corresponds to an example of the first image carrier in the present invention. The photosensitive member 21 of the Y-color toner image forming engine 20Y corresponds to an example of the second image carrier in the present invention.

  A combination of a total of five developing devices 24 of the five image forming engines 20Cr, 20Y, 20M, 20C, and 20K corresponds to an example of the image forming unit referred to in the present invention.

  A combination of a total of five primary transfer units 25 included in the five image forming engines 20Cr, 20Y, 20M, 20C, and 20K corresponds to an example of the primary transfer unit referred to in the present invention.

  Further, the secondary transfer unit 44 corresponds to an example of a secondary transfer unit according to the present invention.

  The fixing device 50 corresponds to an example of a fixing unit according to the present invention.

  The image forming apparatus 100 is provided with a control unit 60. Image data is input to the control unit 60. The image data includes image data of each color when the color image is color-separated into YMCK colors, and image data of each color toner and a range in which the gloss is imparted using the transparent toner in the color image. Toner image data.

  In the case where gloss is given over the entire surface of the color image, image data including image data of transparent toner representing a range corresponding to the entire surface is input to the control unit 60. In addition, when gloss is given to a part of a color image, image data including image data of transparent toner that represents a range corresponding to the part is input to the control unit 60. When gloss is not applied, image data including only image data of each color of YMCK that does not include transparent toner image data is input to the control unit 60.

  The control unit 60 converts this image data into image data suitable for exposure light exposure in the exposure unit 23 of each image forming engine 20Cr, 20Y, 20M, 20C, 20K. The control unit 60 transmits the converted image data to each exposure unit 23, and the exposure unit 23 outputs each image corresponding to the input transparent toner and Y, M, C, and K color toners. The photosensitive member 21 is irradiated with exposure light according to the data.

  As a result, each of the image forming engines 20Cr, 20Y, 20M, 20C, and 20K forms an electrostatic latent image based on the image data, and further forms a toner image based on the image data. Then, the toner image is transferred and fixed on the paper indicated by the information attached to the image data. In addition, when image data is input to the transparent toner image forming engine 20Cr, gloss is given to the range represented by the image data.

  Here, the description of the image forming apparatus 100 of the present embodiment is once different, and in general, the color of the toner image on the paper is faded when the gloss is applied using the gloss adjusting transparent toner. The phenomenon will be described.

  FIG. 2 is an explanatory diagram for explaining a phenomenon in which the color of a toner image on a sheet is faded when gloss is imparted using a transparent toner for gloss adjustment.

  In FIG. 2, elements equivalent to those of the photosensitive member 21, the intermediate transfer belt 41, the secondary transfer device 44, and the fixing device 50 shown in FIG. 1 are shown. The same reference numerals as those in FIG. Is attached.

  FIG. 2 shows the paper P from the primary transfer to the intermediate transfer belt 41 when the glossy toner image (colored toner) T1 of YMCK is given gloss using the transparent toner T2. A series of processes up to fixing is schematically shown.

  As shown in Part (A) of FIG. 2, in the primary transfer from the photoreceptor 21 to the intermediate transfer belt 41, first, a toner image of transparent toner T2 is transferred, and a toner image of colored toner T1 is superimposed thereon. Is transcribed. At this time, the toner image of the colored toner T1 is transferred onto the uneven surface of the toner image of the transparent toner T2. The colored toner T1 gathers on the concave portion and the toner image tends to be thick, and the colored toner T1 is dispersed on the convex portion and the toner image tends to become thin. As a result, the toner image of the colored toner T1 transferred onto the toner image of the transparent toner T2 has a non-uniform thickness.

  Next, secondary transfer from the intermediate transfer belt 41 to the paper P by the secondary transfer unit 44 is performed.

  Here, the diameter of the colored toner T1 is generally about 3.8 μm, whereas the diameter of the transparent toner T2 is about 5.8 μm, which is larger than the diameter of the colored toner T1. For this reason, the transparent toner T2 has a larger amount of charge per toner than the colored toner T1, while the non-electrostatic adhesion between the toners or to the intermediate transfer belt 41 is smaller than that of the colored toner T1. .

  As a result, during secondary transfer, the transparent toner T2 is more easily moved toward the paper P than the colored toner T1. Further, as described above, the thickness of the toner image of the colored toner T1 on the toner image of the transparent toner T2 at the time of primary transfer is non-uniform, so that the transparent toner T2 is not transferred at the time of secondary transfer. The colored toner T1 may be pushed away and get into the paper P side.

  In part (B) of FIG. 2, the transparent toner T2 that should be secondarily transferred in a state of being overlaid on the toner image of the colored toner T1 on the paper P is pushed away from the colored toner T1 and the paper P A state of sinking to the side is schematically illustrated.

  Then, the paper P after the secondary transfer is sent to the fixing device 50, and as shown in part (C) of FIG. 2, the transparent toner T2 pushes away the colored toner T1 and remains on the paper P side while entering the paper P side. It will become established.

  Thus, in the toner image fixed with the transparent toner T2 pushing away the colored toner T1 and entering the paper P side, the holes formed by the transparent toner T2 are scattered in the toner image of the colored toner T1. Yes. In such a hole portion, the ground color of the paper P is transparent, so that the toner image fixed on the paper P becomes an image with an apparent color fading.

  This is the end of the explanation about the phenomenon that the color of the toner image on the paper fades when the gloss is applied using the gloss adjusting transparent toner, and the explanation of the image forming apparatus 100 of the present embodiment is completed. Return.

  The image forming apparatus 100 shown in FIG. 1 presses the transparent toner image formed on the photosensitive member 21 of the transparent toner image forming engine 20Cr against the photosensitive member 21 while being held on the photosensitive member 21. A pressurizing unit 30 for pressurizing is provided. The pressurizing unit 30 corresponds to an example of the pressurizing unit referred to in the present invention.

  FIG. 3 is a diagram showing details of the pressure unit shown in FIG. 1 together with an image forming engine of transparent toner.

  The pressure unit 30 includes a pressure roll 31, a support frame 32, and a pressure roll cleaner 33. The pressure roll 31 is disposed at a position downstream of the developing device 24 and upstream of the primary transfer device 25 in the rotation direction (arrow B) of the photosensitive member 21. The support frame 32 supports the rotating shaft 31a of the pressure roll 31 while urging the rotating shaft 31a toward the photoreceptor 21 by a spring 32a. The pressure roller 31 is pressed against the photoconductor 21 by the urging of the support frame 32 by the spring 32 a and rotates following the rotation of the photoconductor 21.

  The transparent toner image formed on the photoconductor 21 by the development of the developing device 24 is added by being pressed against the photoconductor 21 by the pressure roll 31 before the primary transfer to the intermediate transfer belt 41 by the primary transfer device 25. Pressed.

  FIG. 4 is a diagram schematically showing a transparent toner image pressed by the pressure roll of the pressure unit shown in FIG.

  As shown in FIG. 4, the transparent toner that forms the toner image on the photoreceptor 21 is flattened by being pressurized by the pressure roll 31. Then, the toner image in which the transparent toner is flattened is conveyed to the primary transfer device 25 by the rotation of the photosensitive member 21 in the arrow B direction, and is primarily transferred to the intermediate transfer belt 41.

  Further, when the transparent toner is pressed, the transparent toner may adhere to the pressure roll 31. The transparent toner adhering to the pressure roll 31 in this way is removed by the pressure roll cleaner 33 shown in FIG.

  In the image forming apparatus 100 of FIG. 1, toner images of respective colors Y, M, C, and K are superimposed and primarily transferred onto a toner image in which the transparent toner is flattened. At this time, the unevenness on the surface of the transparent toner image in the lowermost layer is suppressed as compared with the unevenness on the surface of the transparent toner image that is not flat. For this reason, the non-uniform thickness of the toner images of Y, M, C, and K colors transferred onto the transparent toner image is transferred onto the original transparent toner image that is not flat. Compared to

  Further, the flat-shaped transparent toner has a force to push away toners of Y, M, C, and K colors at the time of secondary transfer as compared with the original transparent toner that is not flat. weak. Further, since the flat transparent toner has a larger contact area with the intermediate transfer belt 41 than the original transparent toner that is not flat, it has a non-electrostatic adhesion force to the intermediate transfer belt 41. Is strong. In the image forming apparatus 100 of FIG. 1, these things combine to suppress the displacement of the toner of each color of Y, M, C, and K by the transparent toner at the time of secondary transfer. Thinning of the color of the toner image on the paper can be suppressed.

  Further, it is conceivable that transparent toner having a flat shape is accommodated in the developing device 24 from the beginning, and development is performed with the transparent toner having the flat shape. However, if transparent toner having a flat shape is accommodated in the developing device 24 from the beginning, charging failure occurs when the transparent toner is stirred and charged in the developing device 24, and the accuracy of development itself is reduced. There is a fear. On the other hand, in the present embodiment, since the transparent toner in the developing device 24 has a substantially spherical shape, charging failure is suppressed and development is performed with high accuracy as compared with the transparent toner having a flat shape.

  Here, in the present embodiment, the pressure of the transparent toner image is performed by pressing the toner image against the photoconductor 21 by the pressurizing unit 30.

  However, as a method for pressurizing the transparent toner image, the following pressurizing method can be considered in addition to the pressurizing by pressing on the photosensitive member 21 as in the present embodiment.

  FIG. 5 is a diagram illustrating another example of a method for pressing a transparent toner image, which is different from the method for pressing a transparent toner image in the present embodiment.

  In FIG. 5, constituent elements that are equivalent to the constituent elements of the image forming apparatus 100 of the present embodiment shown in FIG.

  In this alternative example, the transparent toner image is pressed against the intermediate transfer belt 41 at the stage after the primary transfer to the intermediate transfer belt 41 and before the Y-color toner image is primarily transferred. Pressurized with.

  In this alternative example, the pressurizing unit 70 that performs the pressurization is disposed between the image forming engine 20Cr of transparent toner and the image forming engine 20Y of Y color.

  The pressure unit 70 of this other example includes a first pressure roll 71, a second pressure roll 72, a support frame 73, and a pressure roll cleaner 74.

  The first pressure roll 71 is disposed in contact with the surface of the intermediate transfer belt 41 on which the toner image is primarily transferred. The second pressure roll 72 is disposed in contact with the back surface of the intermediate transfer belt 41 with the intermediate transfer belt 41 sandwiched between the first pressure roll 71.

  The support frame 73 supports the rotating shaft 72a of the second pressure roll 72 while urging it toward the first pressure roll 71 by a spring 73a. The second pressure roll 72 is pressed against the first pressure roll 71 with the intermediate transfer belt 41 interposed therebetween by the biasing of the support frame 73 by the spring 73a. The first pressure roll 71 and the second pressure roll 72 rotate following the movement of the intermediate transfer belt 41 in the arrow C direction.

  The transparent toner image primarily transferred from the transparent toner image forming engine 20Cr is transferred to the first pressure roll 71 and the second additional roller before the Y toner image is primarily transferred from the Y image forming engine 20Y. It is pressed against the intermediate transfer belt 41 by the pressure roll 72. By this pressing, the transparent toner image is pressurized before the Y-color toner image is primarily transferred, and the transparent toner is crushed into a flat shape. Further, the transparent toner adhering to the second pressure roll 72 during the pressing is removed by the pressure roll cleaner 74.

  Also in this example, the toner images of each color of YMCK are primarily transferred onto the transparent toner image in which the unevenness is suppressed. Then, the displacement by the transparent toner is suppressed and the toner image is secondarily transferred onto the sheet, and the color of the toner image on the sheet is suppressed from fading.

  Here, the pressing unit 30 of the present embodiment shown in FIG. 3 presses the transparent toner image against the photosensitive member 21 that can withstand the pressing force, so that only one pressing roll 31 is required for pressing. . On the other hand, another pressurizing unit 70 shown in FIG. 5 includes a first pressurizing roll 71 to support the pressing force from the back surface of the intermediate transfer belt by the second pressurizing roll 72. The pressurizing unit 30 of the present embodiment shown in FIG. 3 has a simpler mechanism than the pressurizing unit 70 of another example shown in FIG. It has become.

  In this embodiment, a tandem type color printer is exemplified as the image forming apparatus of the present invention. However, the image forming apparatus of the present invention may be a rotary type color printer other than the tandem type, or may be a monochrome printer instead of color. However, in the case of a rotary type color printer, the pressure unit that pressurizes the transparent toner image has a mechanism that comes into contact with the photoconductor when developing the transparent toner and separates from the photoconductor when developing other color toners. It becomes. Further, the image forming apparatus of the present invention may be other than a printer, such as a copying machine or a facsimile.

  Next, the present invention will be described more specifically based on examples corresponding to the above-described embodiment, but the present invention is not limited to the following examples. In the following, a comparative example with respect to this embodiment is also referred to as appropriate.

[First embodiment]
As the image forming apparatus, a 700 Digital Color Press (Pinot) manufactured by Fuji Xerox Co., Ltd., on which the pressing unit 30 shown in FIG.

  Further, as the pressing force of the pressing roll 31 against the photoconductor 21 in the pressing unit 30, a pressing force with which the pressing degree calculated by the following formula becomes 10% was adopted.

Degree of pressing = (Decrease in toner image height by pressurization) ÷ (Height of toner image before pressurization) × 100
Further, when adjusting the pressing force while confirming the pressing degree, a transparent toner image is formed on the photoconductor 21 and the height of the toner image before and after the pressurization is measured by a laser displacement meter VK- manufactured by Keyence. Measured using 9500. Then, the pressing force was adjusted so that the pressing degree calculated using the above formula based on the measurement result was 10%.

  In addition, a transparent toner having a diameter of 5.8 μm was used as the transparent toner, and a toner having a diameter of 3.8 μm was used as the toner of each color of YMCK.

  Then, the following patch image including a C-color toner image and a transparent toner image was formed.

  FIG. 6 is a schematic diagram illustrating a patch image formed in the embodiment.

The patch image Pt is to concentration some 50% of the C-color rectangular toner image _{C 50} of a concentration covered with 100% of the rectangular transparent toner image _{Cr 100.}

In the first example, the patch image Pt shown in FIG. 6 was formed on a coated paper having a basis weight of 127 g / m ² in an environment with an air temperature of 28 ° C. and a humidity of 85%.

Then, the formed patch image Pt, color difference was measured between the portion covered with the transparent toner image Cr _100, a portion not covered with the transparent toner image Cr _100. For measurement of the color difference, 938 Spectrodensitometer manufactured by X-Rite was used.

  In addition to the patch image Pt shown in FIG. 6, a rectangular transparent toner image having a density of 50% was formed. However, in this formation, the image forming apparatus was temporarily stopped when the transparent toner image was still held on the photosensitive member 21 after being pressed by the pressing unit 30. Then, a visual evaluation was performed on the degree of variation in the shape of the dots in the toner image after pressing on the photoreceptor 21. For this visual evaluation, a digital microscope VK-9500 manufactured by Keyence was used.

[Second Embodiment]
In the second embodiment, the patch image Pt is formed and the color difference is measured under the same conditions as in the first embodiment except that a pressing force with a pressing degree of 40% is adopted as the pressing force in the pressing unit 30. went. Further, visual evaluation was performed on the degree of formation of a rectangular transparent toner image having a density of 50% and the variation in dot shape.

[Third embodiment]
In the third embodiment, the patch image Pt is formed and the color difference is measured under the same conditions as in the first embodiment except that a pressing force with a pressing degree of 90% is adopted as the pressing force in the pressing unit 30. went. Further, visual evaluation was performed on the degree of formation of a rectangular transparent toner image having a density of 50% and the variation in dot shape.

[Fourth embodiment]
In the fourth embodiment, as the image forming apparatus, a 700 Digital Color Press (Pinot) manufactured by Fuji Xerox Co., Ltd., on which the pressurizing unit 70 shown in FIG.

  Further, as the pressing force of the first pressing roll 72 and the second pressing roll 72 on the intermediate transfer belt 41 in the pressing unit 70, a pressing force with a pressing degree calculated by the above formula of 10% is adopted. did.

  Other than that, the patch image Pt formation and color difference measurement, the formation of a rectangular transparent toner image having a density of 50%, and the degree of variation in dot shape are the same as in the first embodiment. Visual evaluation was performed.

[Fifth embodiment]
In the fifth embodiment, the patch image Pt is formed and the color difference is measured under the same conditions as in the fourth embodiment except that a pressing force with a pressing degree of 40% is used as the pressing force in the pressing unit 70. went. Further, visual evaluation was performed on the degree of formation of a rectangular transparent toner image having a density of 50% and the variation in dot shape.

[Sixth embodiment]
In the sixth embodiment, the patch image Pt is formed and the color difference is measured under the same conditions as in the fourth embodiment, except that a pressing force with a pressing degree of 90% is used as the pressing force in the pressing unit 70. went. Further, visual evaluation was performed on the degree of formation of a rectangular transparent toner image having a density of 50% and the variation in dot shape.

[First Comparative Example]
In the first comparative example, 700 Digital Color Press (Pinot) itself manufactured by Fuji Xerox Co., Ltd. was used as the image forming apparatus.

  Other than that, the patch image Pt formation and color difference measurement, the formation of a rectangular transparent toner image having a density of 50%, and the degree of variation in dot shape are the same as in the first embodiment. Visual evaluation was performed.

[Second Comparative Example]
In the second comparative example, as the image forming apparatus, a 700 Digital Color Press (Pinot) manufactured by Fuji Xerox Co., Ltd., equipped with a pressure unit equivalent to the above-described pressure unit 70 shown in FIG. 5 was used. However, in the second comparative example, a pressurizing unit is disposed between the image forming engine 20 </ b> K of the most downstream color K and the secondary transfer unit 44 in the moving direction of the intermediate transfer belt 41.

  Other than that, the patch image Pt formation and color difference measurement, the formation of a rectangular transparent toner image having a density of 50%, and the degree of variation in dot shape are the same as in the first embodiment. Visual evaluation was performed.

  Table 1 below shows the evaluation results for the color differences and the evaluation results for the visual evaluation of the dots for the first to sixth examples, the first and second comparative examples.

  In both the first and second comparative examples, the color difference value is as large as 4.5 or more, and the above-described toner image is thinned. In Table 1, this evaluation result is indicated by a cross.

  Table 1 also shows the difference from the reference when the first comparative example is set to the reference “0” for the color difference.

  On the other hand, the dot shape in the transparent toner image has little variation in any of the comparative examples. In Table 1, the evaluation results are indicated by circles.

  In the first embodiment, with respect to the thinning of the toner image on the paper, there is an improvement that the color difference value is about 1.03 compared to the first comparative example. In Table 1, this evaluation result is indicated by a triangle. Regarding the shape of the dots in the transparent toner image, the variation is small. In Table 1, the evaluation result is indicated by a circle.

  In the second embodiment, the toner image thinning on the sheet is greatly improved compared to the first comparative example in which the color difference value is about 2.39. In Table 1, this evaluation result is indicated by a circle. The dot shape of the transparent toner image is also less varied, and in Table 1, the evaluation result is indicated by a circle.

  In the third embodiment, the toner image thinning on the paper is greatly improved as compared with the first comparative example in which the color difference value is about 3.55. In Table 1, this evaluation result is indicated by a circle. Regarding the shape of the dots in the transparent toner image, there is a variation that causes no problem in practical use. In Table 1, the evaluation results are indicated by triangles.

  In the fourth example, with respect to the thinning of the toner image on the paper, there is an improvement that the color difference value is about 0.89 compared to the first comparative example. In Table 1, this evaluation result is indicated by a triangle. Regarding the shape of the dots in the transparent toner image, the variation is small. In Table 1, the evaluation result is indicated by a circle.

  In the fifth embodiment, the toner image thinning on the sheet is greatly improved as compared with the first comparative example in which the color difference value is about 2.10. In Table 1, this evaluation result is indicated by a circle. The dot shape of the transparent toner image is also less varied, and in Table 1, the evaluation result is indicated by a circle.

  In the sixth embodiment, the toner image thinning on the sheet is greatly improved from the first comparative example in which the color difference value is about 3.13. In Table 1, this evaluation result is indicated by a circle. Regarding the shape of the dots in the transparent toner image, there is a variation that causes no problem in practical use. In Table 1, the evaluation results are indicated by triangles.

  In the first and fourth embodiments, the degree of improvement with respect to the thinning of the toner image on the paper is lower than that in the other embodiments. This is probably because the level of toner flatness is small. Further, in the third and sixth embodiments, the dot shape was slightly varied because the pressing force at the pressurizing portion was larger than that in the other embodiments, and the amount of transparent toner adhering to the pressurizing portion was large. This is thought to have increased. From these examples, it is considered that the pressing force at the pressing portion is preferably a pressing force with a pressing degree of about 40%.

DESCRIPTION OF SYMBOLS 10 Paper supply stand 11 Pickup roll 12 Conveyance roll 13 Standby roll 14,15 Conveyance belt 20Cr, 20Y, 20M, 20C, 20K Image formation engine 21 Photoconductor 22 Charger 23 Exposure device 24 Developer 25 Primary transfer device 26 Photoconductor cleaner 30, 70 Pressure unit 31 Pressure roll 31a, 72a Rotating shaft 32, 73 Support frame 32a, 73a Spring 33, 74 Pressure roll cleaner 41 Intermediate transfer belt 42 Drive roll 43 Roll 44 Secondary transfer device 45 Belt cleaner 50 Fixing Device 60 Control unit 71 First pressure roll 72 Second pressure roll 121 Transport path

Claims (2)

A plurality of arranged image holders that hold the toner image formed in response to the formation of the toner image;
A belt-like member that extends along the plurality of image carriers and receives a transfer of toner images held on the plurality of image carriers while moving around;
Gloss adjustment on the first image carrier disposed at the uppermost stream of the plurality of image carriers with respect to the moving direction of the portion extending along the plurality of image carriers in the strip. The first toner image is formed by the toner of the first image, and the image holding members are held on the image holding members after the second image holding member adjacent to the first image holding member toward the downstream side in the moving direction. An image forming unit that forms a toner image with toner of a color according to the body;
A primary transfer unit that transfers a plurality of toner images formed on the plurality of image holding bodies so as to sequentially overlap the belt-like body;
A pressurizing unit that pressurizes the first toner image at a stage before the first toner image reaches the second image carrier;
A secondary transfer unit for transferring the toner image transferred so as to sequentially overlap the belt-like body onto a sheet;
An image forming apparatus comprising: a fixing unit that fixes a toner image transferred onto a sheet by the secondary transfer unit onto the sheet.   The pressurizing unit presses the first toner image by pressing the first toner image against the first image holding body while the first toner image is held on the first image holding body. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images