JP6164178B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 has a secondary transfer power source that applies a secondary transfer bias including a DC component and an AC component to a secondary transfer nip between an intermediate transfer belt and a secondary transfer roller. In an image forming apparatus for transferring a toner image carried on an intermediate transfer belt to a recording paper passing through the nip by the action of a secondary transfer bias, the recording paper passes through the secondary transfer nip while the intermediate transfer belt is moving. Disclosed is an image forming apparatus that performs control so that there is an AC component change period in which the AC component is not applied or the peak-to-peak voltage of the AC component is smaller than that during image formation during a non-passing period that does not pass. Has been.

JP 2013-134293 A

There is an image forming apparatus that forms an image using toner that has a flat shape by including a flat pigment (for example, aluminum). In this image forming apparatus, a non-transfer image (for example, an image quality adjustment patch) that is not transferred to a recording medium is conveyed by a conveyance body such as an intermediate transfer belt, and the non-transfer image is transferred to the conveyance body and a secondary transfer roll. There is a configuration in which a non-transfer voltage having a polarity opposite to the transfer voltage is applied to the transfer member so that the toner containing the flat pigment is held on the transport body when passing through the transfer position between the transfer member and the transfer member.
Since the toner containing the flat pigment has a flat shape, even if only a non-transfer voltage is applied when passing through the transfer position between the carrier and the transfer member, the transfer member may be pierced depending on the posture of the toner. . When the toner containing the flat pigment pierces the transfer member, the transfer member is damaged.

  In the present invention, a non-transfer image formed with toner containing a flat pigment applies only a non-transfer voltage having a polarity opposite to the transfer voltage when passing through the transfer position. The purpose is to suppress damage.

  According to the first aspect of the present invention, a toner containing a flat pigment is used to form a non-transfer image that is not transferred to a recording medium and a transfer image that is transferred to the recording medium, and the transfer image and the non-transfer image. A transfer body that transfers to the transfer position, and a transfer voltage is applied to transfer the transferred image to a recording medium at the transfer position, and when the non-transferred image passes through the transfer position, And a transfer member to which a reverse polarity DC voltage and an AC voltage are applied.

  The invention according to claim 2 is a first forming portion as the forming portion that forms a first non-transfer image as the non-transfer image and a first transfer image as the transfer image with toner containing a flat pigment. A second non-transfer image that is not transferred to the recording medium with a toner that does not contain a flat pigment, and a second transfer image that is transferred to the recording medium, and the transport body includes: The first non-transfer image, the second non-transfer image, the first transfer image, and the second transfer image in a state where the first non-transfer image and the second non-transfer image are shifted in the transport direction. The transfer member is transferred to a transfer position, and the transfer member is applied with a transfer voltage to transfer the first transfer image and the second transfer image to the recording medium at the transfer position, and the first non-transfer image is transferred to the transfer medium. When passing through the position, the DC voltage and the AC voltage are applied. , The DC voltage without the AC voltage is applied when the second non-transferred image passes through the transfer position is applied.

  According to a third aspect of the present invention, in the first mode, the first non-transferred image that is not transferred to the recording medium and the first transferred image that is transferred to the recording medium are formed with toner containing a flat pigment. The first non-transfer image, the first forming portion that does not form the first transfer image, the second non-transfer image that is not transferred to the recording medium in the second mode, and the second transfer image that is transferred to the recording medium And a transfer region to which the first non-transfer image and the second non-transfer image are transferred, the first non-transfer image, the first non-transfer image, and the second non-transfer image. 2 a non-transferred image, a conveyance body that conveys the first transfer image and the second transfer image to a transfer position, and a transfer voltage applied to the first transfer image at the transfer position in the first mode. Transfer to a recording medium and the transfer area passes through the transfer position When that, and a transfer member to which the transfer voltage having a reverse polarity DC voltage and an AC voltage is applied.

  According to a fourth aspect of the present invention, in the second mode, the transfer member transfers the second transfer image to a recording medium at the transfer position when a transfer voltage is applied, and the transfer region is the transfer area. The DC voltage is applied without passing the AC voltage when passing through the position.

  In a fifth aspect of the present invention, the relationship between both amplitudes of the AC voltage and the DC voltage satisfies both amplitudes of the AC voltage> DC voltage × 2.

  According to the configuration of the first aspect of the present invention, the non-transfer image formed with the toner containing the flat pigment is flatter than the configuration in which only the non-transfer voltage having the opposite polarity to the transfer voltage is applied when passing through the transfer position. Damage to the transfer member due to the toner containing the pigment can be suppressed.

  According to the configuration of the second aspect of the present invention, the electrical deterioration of the transfer member can be suppressed as compared with the case where the AC voltage is applied even when the second non-transfer image passes through the transfer position.

  According to the configuration of claim 3 of the present invention, compared to the configuration in which only the non-transfer voltage having the opposite polarity to the transfer voltage is applied when the transfer region passes the transfer position in the first mode, the transfer with the toner containing the flat pigment is performed. Damage to the member can be suppressed.

  According to the configuration of the fourth aspect of the present invention, electrical deterioration of the transfer member can be suppressed as compared with the case where the AC voltage is applied even when the transfer region passes through the transfer position in the second mode.

  According to the configuration of the fifth aspect of the present invention, the transfer member is damaged by the toner containing the flat pigment as compared with the case where the relationship between both amplitudes of the AC voltage and the DC voltage is both amplitudes of the AC voltage ≦ DC voltage × 2. Can be suppressed.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment as viewed from the front side. FIG. 3 is a schematic diagram illustrating a toner image forming unit according to the embodiment. It is the schematic which shows the partial structure of the transfer apparatus which concerns on this embodiment. In the structure shown in FIG. 3, it is a figure which shows the state which switched the power supply connected to an opposing roll. FIG. 5 is a diagram showing a state where the AC power supply is turned off in the configuration shown in FIG. 4. It is the top view and side view of the flat pigment contained in a metal color toner. It is a figure which shows the non-transfer image and transfer image on a transfer belt in a metal color mode. It is a figure which shows the non-transfer image and transfer image on the transfer belt in other color mode. It is a graph which shows the applied voltage at the time of applying an alternating voltage on a secondary transfer roll, superimposing on a non-transfer voltage (DC voltage). FIG. 4 is a diagram illustrating a posture of a metal color toner on a transfer belt. FIG. 6 is a diagram illustrating a state in which a metal color toner has pierced a secondary transfer roll. FIG. 6 is a diagram illustrating a state in which the posture of the metal color toner on the transfer belt changes. FIG. 10 is a diagram illustrating a modification of a position where a non-transferred image is transferred to a transfer belt in the metal color mode. FIG. 10 is a diagram illustrating a modification of a position where a non-transferred image is transferred to a transfer belt in the metal color mode. It is a table | surface which shows an evaluation result.

  Below, an example of an embodiment concerning the present invention is described based on a drawing. In addition, the arrow H shown to each figure shows a perpendicular direction, and the arrow W is a horizontal direction and shows an apparatus width direction.

<Configuration of Image Forming Apparatus 10>
FIG. 1 is a schematic diagram illustrating a configuration of the image forming apparatus 10 as viewed from the front side. As shown in this figure, the image forming apparatus 10 includes an image forming unit 12 that forms an image on a recording medium P such as paper by an electrophotographic method, a transport apparatus 50 that transports the recording medium P, and the image forming apparatus 10. And a control unit 70 for controlling the operation of each unit.

(Transport device 50)
As shown in FIG. 1, the transport device 50 includes a container 51 that stores the recording medium P, and a plurality of transport rolls 52 that transport the recording medium P from the container 51 to the secondary transfer position NT. doing. Further, the transport device 50 includes a plurality of transport belts 58 that transport the recording medium P from the secondary transfer position NT to the fixing device 40, and the recording medium P toward the discharge portion (not shown) of the recording medium P from the fixing device 40. A conveying belt 54 for conveying the toner.

(Image forming unit 12)
The image forming unit 12 includes a toner image forming unit 20 that forms a toner image, a transfer device 30 that transfers the toner image formed by the toner image forming unit 20 to the recording medium P, and a toner image transferred to the recording medium P. And a fixing device 40 that fixes the image to the recording medium P by heating and pressurizing the recording medium P.

  A plurality of toner image forming units 20 are provided so as to form a toner image for each color. In this embodiment, a total of six toner image forming portions 20 of the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K). Is provided. (V), (W), (Y), (M), (C), and (K) shown in FIG. 1 indicate the colors described above. As the first special color (V) and the second special color (W), for example, a color such as silver or gold is used.

[Toner image forming unit 20]
The toner image forming unit 20 for each color is basically configured in the same manner except for the toner to be used. Specifically, as shown in FIG. 2, each color toner image forming unit 20 includes a photosensitive drum 21 that rotates clockwise in FIG. 2 and a charger 22 that charges the photosensitive drum 21. Have. Further, each color toner image forming unit 20 exposes the photosensitive drum 21 charged by the charger 22 to form an electrostatic latent image on the photosensitive drum 21, and the exposure device 23 uses the photosensitive drum. And a developing device 24 that develops the electrostatic latent image formed on the toner 21 to form a toner image.

[Transfer device 30]
The transfer device 30 primarily transfers the toner image of the photosensitive drum 21 of each color on the transfer belt 31 (intermediate transfer member), and transfers the superimposed toner image onto the recording medium P at the secondary transfer position NT. Next transfer is to be done. Specifically, as illustrated in FIG. 1, the transfer device 30 includes a transfer belt 31 as an example of a conveyance body, a primary transfer roll 33, a secondary transfer roll 34 as an example of a transfer member, and a power feeding unit. 80, a cleaning device 60 for the secondary transfer roll 34, and a cleaning device 35 for the transfer belt 31.

[Transfer belt 31]
As shown in FIG. 1, the transfer belt 31 has an endless shape and is wound around a plurality of rolls 32 to determine the posture. In this embodiment, the transfer belt 31 has a reverse obtuse triangular posture that is long in the apparatus width direction when viewed from the front. Among the plurality of rolls 32, the roll 32D shown in FIG. 1 functions as a drive roll that rotates the transfer belt 31 in the arrow A direction by the power of a motor (not shown). The transfer belt 31 circulates in the direction of arrow A, thereby conveying the primary transferred image to the secondary transfer position NT.

  Of the plurality of rolls 32, the roll 32 </ b> T illustrated in FIG. 1 functions as a tension applying roll that applies tension to the transfer belt 31. Among the plurality of rolls 32, the roll 32 </ b> B illustrated in FIG. 1 functions as a counter roll 32 </ b> B of the secondary transfer roll 34. As described above, the top of the lower end side forming the obtuse angle of the transfer belt 31 in the inverted obtuse triangular shape is wound around the opposing roll 32B. The transfer belt 31 is in contact with the photosensitive drum 21 of each color from below at the upper side extending in the apparatus width direction in the above-described posture.

[Primary transfer roll 33]
The primary transfer roll 33 is a roll for transferring the toner image of each photosensitive drum 21 onto the transfer belt 31 and is disposed inside the transfer belt 31 as shown in FIG. Each primary transfer roll 33 is disposed opposite to the corresponding photosensitive drum 21 with the transfer belt 31 in between. Further, a primary transfer voltage having a polarity opposite to the toner polarity is applied to the primary transfer roll 33 by a power feeding unit (not shown). By applying the primary transfer voltage, the toner image formed on the photosensitive drum 21 is transferred to the transfer belt 31 at the primary transfer position T.

[Secondary transfer roll 34]
The secondary transfer roll 34 is a roll that transfers the toner image superimposed on the transfer belt 31 to the recording medium P. As shown in FIG. 3, the secondary transfer roll 34 is disposed so as to sandwich the transfer belt 31 between the secondary transfer roll 34 and the opposing roll 32B, and the secondary transfer roll 34 and the transfer belt 31 have a predetermined load. In contact. A space between the secondary transfer roll 34 and the transfer belt 31 in contact with each other is set as a secondary transfer position NT. The recording medium P is supplied to the secondary transfer position NT from the container 51 in a timely manner. The secondary transfer roll 34 is driven to rotate clockwise in FIG.

[Power supply unit 80]
As shown in FIG. 3, the power supply unit 80 (application unit) includes a first DC power source 80A, a second DC power source 80B, a first switch 80S ₁ (switching unit), and a second switch 80S ₂ (switching unit). ), An AC power supply 80G, and a contact roll 80C. The first DC power supply 80A is a power supply that applies a negative voltage to the opposing roll 32B via the contact roll 80C. The second DC power supply 80B is a power supply that applies a positive voltage to the opposing roll 32B via the contact roll 80C. The contact roll 80C is a roll that comes into contact with the opposing roll 32B, and is driven to rotate by the opposing roll 32B. AC power source 80G is connected to the second second DC power supply 80B via the switch 80S _2.

The switch 80S ₁ connects the first DC power supply 80A to the opposing roll 32B via the contact roll 80C (the state shown in FIG. 3), and connects the second DC power supply 80B to the opposing roll 32B via the contact roll 80C. It switches to the state (state shown in FIG.4 and FIG.5) to perform.
Second switch 80S _2, in a state where the second DC power supply 80B is connected to a counter roll 32B, a state of connecting the AC power source 80G to the opposing roll 32B via the contact roll 80C and the second DC power source 80B (FIG. 4 And a power-off state in which the AC power supply 80G is not connected to the facing roll 32B (the state shown in FIG. 5).

The feeding unit 80, when the toner image of the transfer belt 31 onto the recording medium P, as shown in FIG. 3, the switch 80S _1, the first DC power source 80A and the opposing roll 32B and the contact roll 80C Connected through.

  As a result, a negative voltage is applied to the opposing roll 32B, and a potential difference is generated between the opposing roll 32B and the secondary transfer roll 34. That is, when a negative voltage is applied to the counter roll 32B, a secondary transfer voltage (positive voltage) having a polarity opposite to the toner polarity is indirectly applied to the secondary transfer roll 34 that forms the counter electrode of the counter roll 32B. To be applied. As a result, the toner image is transferred from the transfer belt 31 to the recording medium P that passes through the secondary transfer position NT.

On the other hand, in the case where the toner image is held on the transfer belt 31 when the toner image of the transfer belt 31 passes the secondary transfer position NT, as shown in FIGS. 4 and 5, the switch 80S _1, the 2 DC power supply 80B and counter roll 32B are connected via contact roll 80C.

  As a result, a positive voltage is applied to the opposing roll 32B, and a potential difference is generated between the opposing roll 32B and the secondary transfer roll 34. That is, by applying a positive voltage to the counter roll 32B, a non-transfer voltage (negative voltage) having the same polarity as the toner polarity is indirectly applied to the secondary transfer roll 34 that forms the counter electrode of the counter roll 32B. Applied. As a result, the non-transfer image passing through the secondary transfer position NT receives a repulsive force from the secondary transfer roll 34 and is held on the transfer belt 31 without being transferred to the secondary transfer roll 34.

  Further, in the power feeding unit 80, when an AC voltage is applied to the secondary transfer roll 34 so as to be superimposed on the non-transfer voltage, a second DC power supply 80B is connected to the opposing roll 32B as shown in FIG. In the connected state, the AC power supply 80G is connected to the opposing roll 32B via the contact roll 80C and the second DC power supply 80B.

  In addition, in the power feeding unit 80, when an AC voltage is not applied to the secondary transfer roll 34 and a non-transfer voltage is applied, a second DC power supply 80B is connected to the opposing roll 32B as shown in FIG. In the connected state, the AC power supply 80G is not connected to the facing roll 32B, and the power is turned off.

[Cleaning device 60 for secondary transfer roll 34]
The transfer device 30 includes a cleaning device 60 that cleans the secondary transfer roll 34. The cleaning device 60 is a removing member that contacts the rotating secondary transfer roll 34 and removes foreign matter (toner or powder of the recording medium P) adhering to the surface of the secondary transfer roll 34 from the secondary transfer roll 34. Consists of blades.

[Cleaning device 35 of transfer belt 31]
As shown in FIG. 1, the cleaning device 35 is disposed downstream of the secondary transfer position NT and upstream of the primary transfer position T (V) in the circumferential direction of the transfer belt 31. The cleaning device 35 includes a blade 351 that scrapes off toner remaining on the surface of the transfer belt 31 from the surface of the transfer belt 31.

<Main part configuration>
Here, in the present embodiment, the toner image forming unit 20V as an example of the first forming unit is configured to form a toner image using silver toner as the second special color (V) (FIG. 1). Further, the toner image forming unit 20W as an example of the first forming unit is configured to form a toner image using gold toner as the second special color (W) (see FIG. 1).

  As shown in FIG. 10, the silver toner 100 used in the toner image forming unit 20 </ b> V includes a flat-shaped flat pigment 110 and a binder resin 111. The gold toner used in the toner image forming unit 20W includes a flat pigment 110, a yellow pigment, and a binder resin 111.

  The flat pigment 110 is made of a metal material such as aluminum, for example. Then, when the flat pigment 110 is placed on a flat surface and viewed from the side, the flat pigment 110 has a longer dimension in the horizontal direction in the figure than the vertical dimension in the figure, as shown in FIG. 6B. It is a shape. The flat pigment 110 has a dimensional ratio between the dimension in the left-right direction and the dimension in the vertical direction larger than the dimensional ratio in the pigment of other color toner described later.

  Further, when the flat pigment 110 shown in FIG. 6B is viewed from above in the drawing, the flat pigment 110 has a shape that is wider than the shape viewed from the side, as shown in FIG. 6A. The flat pigment 110 has a pair of reflective surfaces 110A facing upward and downward with the flat pigment 110 placed on a flat surface (see FIG. 6B). In this way, the flat pigment 110 has a flat shape. In addition, the toner containing the flat pigment 110 has a flat shape as a toner shape.

  In the present specification, for convenience of explanation, silver (V) and gold (W) are referred to as “metal color”, and metal toner is referred to as “metal color toner”. In the figure, when distinguishing between silver (V) and gold (W), reference numerals (V) and (W) are attached.

  The toner images formed by the toner image forming units 20V and 20W include a transfer image (an example of a first transfer image) transferred to the recording medium P and a non-transfer image (a first non-transfer image of the first non-transfer image) that is not transferred to the recording medium P. An example).

  Examples of the non-transfer image include a density detection image (patch) for detecting the toner density of the toner image on the transfer belt 31 (an example of a conveyance body), and a positional shift between colors in the toner image on the transfer belt 31. There are color misregistration detection images (patches) for detecting color, images (bands) for consuming deteriorated developer (toner), and the like.

  Hereinafter, for convenience of explanation, the non-transfer images formed by the toner image forming units 20V and 20W are referred to as “metal color patches”, and the transfer images formed by the toner image forming units 20V and 20W are referred to as “metal color images”.

  In the present embodiment, the detection unit (sensor) 49 for detecting the density detection image (patch) and the color misregistration detection image (patch) is downstream of the toner image forming unit 20K (left side in FIG. 1). ).

  On the other hand, yellow (Y), magenta (M), cyan (C), and black used in toner image forming units 20Y, 20M, 20C, and 20K (hereinafter referred to as 20Y to 20K) as examples of the second forming unit. The toner (K) does not include the flat pigment 110 but includes a pigment other than the flat pigment 110 and a binder resin.

  In this specification, for convenience of explanation, yellow (Y), magenta (M), cyan (C), and black (K) are referred to as “other colors”, and other color toners are referred to as “other color toners”. Called. In the drawing, in order to distinguish yellow (Y), magenta (M), cyan (C), and black (K), reference numerals (Y), (M), (C), and (K) are attached.

  The toner images formed by the toner image forming units 20Y to 20K include a transfer image (an example of a second transfer image) transferred to the recording medium P and a non-transfer image (a second non-transfer image of the second non-transfer image) that is not transferred to the recording medium P. An example). The non-transfer image includes a density detection image (patch), a color misregistration detection image (patch), and a deteriorated developer (toner), similarly to the non-transfer images formed by the toner image forming units 20V and 20W. There are images (bands) for consumption.

  Hereinafter, for convenience of explanation, the non-transfer images formed by the toner image forming units 20Y to 20K are referred to as “other color patches”, and the transfer images formed by the toner image forming units 20Y to 20K are referred to as “other color images”.

  As shown in FIG. 7, the metal color patch 410 and the other color patch 420 are a non-transfer image area between the transfer image area R1 to which the metal color image 310 and the other color image 320 on the transfer belt 31 are transferred. Transferred to R2 (an example of a transfer region). The metal color image 310 and the other color image 320 in the transfer image region R1 pass through the secondary transfer position NT together with the recording medium P, and the metal color image 310 and the other color image 320 are transferred to the recording medium P. On the other hand, the metal color patch 410 and the other color patch 420 in the non-transfer image area R2 do not pass through the secondary transfer position NT together with the recording medium P, but pass through the secondary transfer position NT alone. The transfer image region R1 and the non-transfer image region R2 may be configured such that the position on the transfer belt 31 may be changed or not changed every time the transfer belt 31 rotates.

  Furthermore, in the present embodiment, a mode in which a toner image with at least one of the other color toners is formed on the recording medium P without forming a toner image with the metal color toner on the recording medium P (another color mode), and a metal color And a mode (metal color mode) in which a toner image by at least one toner and a toner image by at least one other color toner are formed on the recording medium P.

  The other color mode (an example of the second mode) is executed when the control unit 70 does not operate the toner image forming units 20V and 20W and operates at least one of the toner image forming units 20Y to 20K. By operating at least one of the toner image forming units 20Y to 20K, the other color image 320 is transferred to each transfer image region R1 of the transfer belt 31 and the other color patch 420 is transferred to the transfer belt, as shown in FIG. 31 is transferred to each non-transferred image region R2. FIG. 8 illustrates a case where all of the toner image forming units 20Y to 20K are activated.

  In the other color mode, the control unit 70 controls the power supply unit 80 and a voltage is applied to the secondary transfer roll 34 as described below. That is, when the transfer image region R1 (other color image 320) passes through the secondary transfer position NT, the first DC power supply 80A and the opposing roll 32B are connected via the contact roll 80C as shown in FIG. Then, a secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. Further, when the non-transfer image area R2 (the other color patch 420) passes through the secondary transfer position NT, as shown in FIG. 5, the second DC power supply 80B and the opposing roll 32B pass through the contact roll 80C. A non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B.

  In the other color mode, the AC power supply 80G is in a power-off state that is not connected to the facing roll 32B.

  On the other hand, the metal color mode (an example of the first mode) is executed when the control unit 70 operates at least one of the toner image forming units 20V and 20W and at least one of the toner image forming units 20Y to 20K. By operating at least one of the toner image forming units 20V and 20W and at least one of the toner image forming units 20Y to 20K, the metal color image 310 and the other color image 320 are transferred to the transfer belt 31 as shown in FIG. The metal color patch 410 and the other color patch 420 are transferred to each non-transfer image area R2 of the transfer belt 31 after being transferred to each transfer image area R1. More specifically, in the non-transfer image area R2, the other color patch 420 and the metal color patch 410 are transferred in this order in the state of being arranged from the upstream in the transport direction of the transfer belt 31. FIG. 7 illustrates a case where all of the toner image forming units 20Y to 20K and the toner image forming units 20V and 20W are activated.

  In the metal color mode, the control unit 70 controls the power supply unit 80 and a voltage is applied to the secondary transfer roll 34 as described below. That is, when the transfer image region R1 (the metal color image 310 and the other color image 320) passes through the secondary transfer position NT, as shown in FIG. 3, the first DC power supply 80A and the opposing roll 32B are contact rolls. The secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B.

  Further, when the other color patch 420 in the non-transfer image area R2 passes through the secondary transfer position NT, as shown in FIG. 5, the second DC power supply 80B and the opposing roll 32B pass through the contact roll 80C. A non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. At this time, the AC power supply 80G is in a power-off state that is not connected to the facing roll 32B.

Further, when the metal color patch 410 in the non-transfer image area R2 passes through the secondary transfer position NT, as shown in FIG. 4, the second DC power supply 80B and the opposing roll 32B pass through the contact roll 80C. A non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. Further, the second switch 80S _2, AC power source 80G to the opposing roll 32B via the contact roll 80C and the second DC power supply 80B is connected. Thereby, an alternating voltage is applied to the secondary transfer roll 34 so as to be superimposed on the non-transfer voltage.

  At this time, the relation between the peak-to-peak value Vpp (both amplitudes) of the applied AC voltage and the non-transfer voltage (DC voltage) Vdc is as shown in FIG. The transfer voltage (DC voltage) Vdc × 2 is satisfied.

(Operation according to this embodiment)
Next, the operation according to this embodiment will be described.

(Other color mode)
When the control unit 70 receives an image formation command (print command) in the other color mode, the control unit 70 operates the toner image forming units 20Y to 20K of other colors, the transfer device 30, and the fixing device 40 (see FIG. 1). ).

  Thus, in the toner image forming units 20Y to 20K, the other color image 320 (see FIG. 8) and the other color patch 420 (see FIG. 8) are formed in the following image forming process (process). That is, the photosensitive drums 21 of the respective colors are charged by the charger 22 while being rotated. Each charged photosensitive drum 21 is exposed by each exposure device 23, and an electrostatic latent image is formed on the surface of each photosensitive drum 21. The electrostatic latent image formed on each photoconductor drum 21 is developed by the developer supplied from the developing device 24. Thus, the other color image 320 and the other color patch 420 of yellow (Y), magenta (M), cyan (C), and black (K) are formed on the photosensitive drums 21 of the respective colors.

  As shown in FIG. 8, the other color image 320 of each color formed on the photosensitive drum 21 of each color is sequentially transferred to the transfer image region R <b> 1 of the rotating transfer belt 31 by the primary transfer roll 33 of each color. The other color patches 420 of the respective colors formed on the photosensitive drums 21 of the respective colors are sequentially transferred to the non-transferred image region R2 of the rotating transfer belt 31 by the primary transfer rolls 33 of the respective colors. As a result, the other color image 320 and the other color patch 420 transferred to the transfer belt 31 are conveyed to the secondary transfer position NT by the rotation of the transfer belt 31.

  The recording medium P is supplied to the secondary transfer position NT in synchronization with the conveyance of the other color image 320 by the conveyance roll 52. When the recording medium P and the transfer image region R1 (other color image 320) pass through the secondary transfer position NT, as shown in FIG. 3, the first DC power source 80A and the opposing roll 32B set the contact roll 80C. The secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. As a result, the other color image 320 is transferred from the transfer belt 31 to the recording medium P.

  The recording medium P to which the other color image 320 has been transferred is conveyed from the secondary transfer position NT to the fixing device 40 by the conveying belt 58, and the other color image 320 on the recording medium P is transferred to the recording medium P in the fixing device 40. It is fixed.

  On the other hand, when the non-transferred image region R2 (the other color patch 420) passes through the secondary transfer position NT without passing through the recording medium P, as shown in FIG. 32B is connected via the contact roll 80C, and a non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. At this time, AC power supply 80G is in a power-off state that is not connected to opposing roll 32B.

  By applying a non-transfer voltage (negative voltage) to the secondary transfer roll 34 via the opposing roll 32B, the other color patch 420 on the transfer belt 31 receives a repulsive force from the secondary transfer roll 34. , And held by the transfer belt 31. Thus, the other color toner of the other color patch 420 is conveyed to the cleaning device 35 through the secondary transfer position NT while being held on the transfer belt 31, and is removed from the transfer belt 31 by the cleaning device 35.

(Metal color mode)
When the control unit 70 receives an image formation command (print command) in the metal color mode, the control unit 70 displays the metal color toner image forming units 20V and 20W, the other color toner image forming units 20Y to 20K, and the transfer device 30. Then, the fixing device 40 is operated (see FIG. 1).

  Thus, in the toner image forming units 20V and 20W, the metal color image 310 and the metal color patch 410 are formed on each photosensitive drum 21 through the same image forming process (process) as described above. In the toner image forming units 20 </ b> Y to 20 </ b> K, the other color image 320 and the other color patch 420 are formed on each photosensitive drum 21 through the same image forming process (process) as described above.

  As shown in FIG. 7, the other color image 320 and the metal color image 310 of each color formed on each photoconductive drum 21 are transferred to the transfer image region R1 of the transfer belt 31 that is circulated by the primary transfer roll 33 of each color. Are sequentially transferred.

  The color patches 410 of the respective colors formed on the respective photoconductive drums 21 are sequentially transferred to the downstream side in the transport direction in the non-transfer image area R2 of the rotating transfer belt 31 by the primary transfer rolls 33 of the respective colors. The other color patches 420 formed on the respective photosensitive drums 21 are sequentially transferred to the upstream side in the transport direction in the non-transfer image area R2 of the rotating transfer belt 31 by the primary transfer roll 33 of each color.

  Then, the other color patch 420, the metal color patch 410, the other color image 320, and the metal color image 310 are secondary by the rotation of the transfer belt 31 in a state where the other color patch 420 and the metal color patch 410 are shifted in the transport direction. It is conveyed to the transfer position NT.

  The recording medium P is supplied to the secondary transfer position NT in synchronization with the transport of the other color image 320 and the metal color image 310 by the transport roll 52. When the recording medium P, the other color image 320 and the metal color image 310 (transfer image region R1) pass through the secondary transfer position NT, as shown in FIG. 3, the first DC power supply 80A and the opposing roll 32B Are connected via a contact roll 80C, and a secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via a counter roll 32B. As a result, the other color image 320 and the metal color image 310 are transferred from the transfer belt 31 to the recording medium P.

  The recording medium P to which the other color image 320 and the metal color image 310 have been transferred is transported from the secondary transfer position NT to the fixing device 40 by the transport belt 58, and the other color image 320 on the recording medium P is transferred by the fixing device 40. Is fixed to the recording medium P.

  When the other color patch 420 passes through the secondary transfer position NT without passing through the recording medium P, as shown in FIG. 5, the second DC power supply 80B and the opposing roll 32B pass through the contact roll 80C. A non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. Accordingly, the other color patch 420 on the transfer belt 31 receives a repulsive force from the secondary transfer roll 34 and is held by the transfer belt 31. Thus, the other color toner of the other color patch 420 is conveyed to the cleaning device 35 through the secondary transfer position NT while being held on the transfer belt 31, and is removed from the transfer belt 31 by the cleaning device 35. At this time, AC power supply 80G is in a power-off state that is not connected to opposing roll 32B.

Further, when the metal color patch 410 passes through the secondary transfer position NT without passing through the recording medium P, as shown in FIG. 4, the second DC power supply 80B and the opposing roll 32B move the contact roll 80C. And a non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. Further, at this time, the second switch 80S _2, AC power source 80G to the opposing roll 32B via the contact roll 80C and the second DC power supply 80B is connected. Thereby, an alternating voltage is applied to the secondary transfer roll 34 so as to be superimposed on the non-transfer voltage.

  Here, the metal color toner 100 of the metal color patch 410 on the transfer belt 31 is charged on the transfer belt 31 after passing the primary transfer position T due to the flat shape as shown in FIG. It is localized and easily stands on the transfer belt 31.

  Therefore, in the comparative example in which only the non-transfer voltage is applied to the secondary transfer roll 34 when the metal color patch 410 passes through the secondary transfer position NT, as shown in FIG. The color toner 100 tends to pierce the secondary transfer roll 34, and the surface layer 34A of the secondary transfer roll 34 may be damaged.

  In contrast, in the present embodiment, when the metal color patch 410 passes through the secondary transfer position NT, an AC voltage is applied to the secondary transfer roll 34 so as to be superimposed on the non-transfer voltage. Since the AC voltage periodically changes in voltage magnitude and voltage polarity, for example, the charge localized in the metal color toner 100 changes, and the metal color on the transfer belt 31 changes as shown in FIG. The state of the toner 100 changes alternately between a sleeping posture (tilted state) and a standing posture.

  As a result, the metal color toner is less likely to pierce the secondary transfer roll 34, and damage to the surface layer 34A of the secondary transfer roll 34 is suppressed. Therefore, the formation failure of the electric field due to the low resistance due to the damage of the secondary transfer roll 34 is suppressed, and the image quality failure due to the formation failure of the electric field is suppressed.

  Further, in this embodiment, the relationship between the peak-to-peak value Vpp of the applied AC voltage and the non-transfer voltage (DC voltage) Vdc is as shown in FIG. The transfer voltage (DC voltage) Vdc × 2 is satisfied. For this reason, the polarity of the voltage in a state where the AC voltage is superimposed on the non-transfer voltage is reversed to the negative polarity (see the arrow D portion in FIG. 9). As a result, the charges localized on the metal color toner 100 change the polarity, and the state of the metal color toner 100 on the transfer belt 31 is effectively changed alternately between the sleeping position and the standing position.

  In the present embodiment, as shown in FIG. 7, when the metal color patch 410 passes through the secondary transfer position NT, an AC voltage is applied to the secondary transfer roll 34 to record the secondary transfer position NT. When the other color patch 420 passes without the medium P passing, no AC voltage is applied to the secondary transfer roll 34.

  For this reason, the application time of the AC voltage applied to the secondary transfer roll 34 is shortened compared to the case where the AC voltage is applied to the secondary transfer roll 34 even when the other color patch 420 passes. For this reason, the time during which the high voltage is applied to the secondary transfer roll 34 by superimposing the DC voltage and the AC voltage is shortened, and electrical deterioration of the secondary transfer roll 34 is suppressed. Therefore, the formation failure of the electric field due to the electrical deterioration of the secondary transfer roll 34 (that is, the resistance reduction of the secondary transfer roll 34) is suppressed, and the image quality failure due to the formation failure of the electric field is suppressed. The

(First modification)
In the present embodiment, as shown in FIG. 7, the other color patch 420 is transferred to the upstream side in the transport direction in the non-transfer image area R <b> 2 of the transfer belt 31, and the transport direction in the non-transfer image area R <b> 2 of the transfer belt 31. Although the metal color patch 410 is transferred downstream, the present invention is not limited thereto. For example, as shown in FIG. 13, one of the other color patch 420 and the metal color patch 410 may be transferred for each non-transfer image region R <b> 2 of the transfer belt 31. In this configuration, the other color patch 420 and the metal color patch 410 are alternately transferred to the non-transfer image region R2 of the transfer belt 31, for example. The other color patch 420 and the metal color patch 410 are conveyed to the secondary transfer position NT while being shifted in the conveyance direction of the transfer belt 31.

  Also in the first modification, for example, the power feeding unit 80 is operated as follows. That is, when the other color image 320 and the metal color image 310 (transfer image region R1) pass through the secondary transfer position NT, as shown in FIG. 3, the second transfer image is transferred to the secondary transfer roll 34 via the opposing roll 32B. Next transfer voltage (positive voltage) is applied. As a result, the other color image 320 and the metal color image 310 are transferred from the transfer belt 31 to the recording medium P.

  Further, when the other color patch 420 passes through the secondary transfer position NT without passing through the recording medium P, the non-transfer voltage is applied to the secondary transfer roll 34 via the opposing roll 32B as shown in FIG. (Negative voltage) is applied. At this time, AC power supply 80G is in a power-off state that is not connected to opposing roll 32B.

  Further, when the recording medium P does not pass through the secondary transfer position NT but passes through the metal color patch 410, as shown in FIG. 4, the non-transfer voltage is applied to the secondary transfer roll 34 via the opposing roll 32B. While (negative voltage) is applied, an alternating voltage is applied.

(Second modification)
In the present embodiment, in the metal color mode, when the other color patch 420 in the non-transfer image area R2 passes through the secondary transfer position NT, an AC voltage is not applied to the secondary transfer roll 34, and the secondary transfer position NT is not applied. Although the AC voltage is applied to the secondary transfer roll 34 when the metal color patch 410 in the non-transfer image area R2 passes through the transfer position NT, the present invention is not limited to this.

  For example, when the control unit 70 receives an image formation command (print command) in the metal color mode, the secondary transfer position NT is set on the transfer belt 31 regardless of the non-transfer image formed in the non-transfer image region R2. When the non-transfer image region R2 passes, as shown in FIG. 4, a non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B, and an AC voltage is applied. May be.

  In this configuration, there are no restrictions on the positions where the metal color patch 410 and the other color patch 420 are transferred in the non-transfer image area R2, and the metal color patch 410 and the other color patch 420 are moved in the transport direction as shown in FIG. No need to shift to

(Third Modification)
In the present embodiment, in the metal color mode, the other color image 320 and the other color patch 420 are formed using the other color toner. However, in the metal color mode, the other color image 320 and the other color using the other color toner are formed. The patch 420 may not be included. In this case, the control unit 70 does not operate the toner image forming units 20Y to 20K, and operates at least one of the toner image forming units 20V and 20W. By operating at least one of the toner image forming units 20V and 20W, the metal color image 310 is transferred to each transfer image region R1 of the transfer belt 31, and the metal color patch 410 is transferred to each non-transfer image region R2 of the transfer belt 31. Is transferred to.

  Also in this configuration, for example, the power feeding unit 80 is operated as follows. That is, when the transfer image area R1 passes through the secondary transfer position NT, a secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B, and the non-transfer image area R2 is When passing through the secondary transfer position NT, a non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 and an alternating voltage is applied.

(Other variations)
In this embodiment, as shown in FIG. 7, the other color patch 420 is arranged on the upstream side in the transport direction in the non-transfer image area R <b> 2 of the transfer belt 31, and the non-transfer image area R <b> 2 of the transfer belt 31. Although the metal color patch 410 is disposed on the downstream side in the transport direction, the present invention is not limited to this. For example, the metal color patch 410 is disposed on the upstream side in the transport direction in the non-transfer image region R2 of the transfer belt 31, and the other color patch 420 is disposed on the downstream side in the transport direction in the non-transfer image region R2 of the transfer belt 31. It may be a configuration.

  In the present embodiment, the secondary transfer roll 34 is used as an example of the transfer member, but the transfer member may be, for example, a secondary transfer belt.

  In this embodiment, the transfer belt 31 is used as an example of the transport body. However, the transport body may be a transfer drum, for example.

  In this embodiment, the secondary transfer voltage, the non-transfer voltage, and the AC voltage are applied to the secondary transfer roll 34 via the opposing roll 32B. However, the present invention is not limited to this, and the secondary transfer roll 34 is directly applied to the secondary transfer roll 34. Various voltages may be applied. In this case, a voltage having a reverse polarity to the voltage applied to the opposing roll 32B is applied to the secondary transfer roll 34.

  In this embodiment, a configuration in which a lubricant (for example, ZnSt) is supplied to the secondary transfer roll 34 to form a lubricant film on the secondary transfer roll 34 may be applied. According to this configuration, even when the metal color toner standing on the transfer belt 31 passes through the secondary transfer position NT, the tip of the metal color toner tends to slip and lie down on the secondary transfer roll 34. Further, the secondary transfer roll 34 is prevented from being pierced.

  In the present embodiment, the surface roughness of the secondary transfer roll 34 may be set to Rz = 2 μm or less. According to this configuration, even when the metal color toner standing on the transfer belt 31 passes through the secondary transfer position NT, the tip of the metal color toner tends to slip and lie down on the secondary transfer roll 34. Further, the secondary transfer roll 34 is prevented from being pierced.

(Evaluation)
In this evaluation, image quality evaluation by continuous paper feeding was performed (room temperature 10 ° C., relative humidity 15%). In the image quality evaluation, “○” indicates that there is no problem in the image quality in the transferred image formed on the sheet as the recording medium P, and “X” indicates that there is a white spot.

Example 1
In the image forming apparatus 10 described above, the following transfer belt 31, counter roll 32B, and secondary transfer roll 34 were used.
Transfer belt 31: volume resistivity 10 [log Ω · cm], thickness 80 [um],
Opposing roll 32B: φ20, volume resistance 6.5 [logΩ], hardness 65 ° (Asker C),
Secondary transfer roll 34: φ24, volume resistance 7.0 [logΩ], hardness 75 ° (Asker C)

  In the non-transfer image area R2 (inter-image), as shown in FIG. 7, a toner patch 20 mm × 20 mm for adjusting image quality as the other color patch 420 is transferred upstream in the transport direction, and metal is transported downstream in the transport direction. A toner patch 20 mm × 20 mm for adjusting image quality as a color patch 410 was transferred. A specific other color image 320 and a metal color image 310 were transferred to the transfer image region R1. The process speed of the image forming apparatus 10 was set to 440 mm / s.

  In the metal color mode, when the transfer image region R1 passes through the secondary transfer position NT, a secondary transfer voltage (positive voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. The voltage applied to the facing roll 32B is set to -2 kV.

  Further, in the metal color mode, when the other color patch 420 passes through the secondary transfer position NT, a non-transfer voltage (negative DC voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. The voltage Vdo applied to the facing roll 32B is +0.4 kV.

  Further, in the metal color mode, when the metal color patch 410 passes through the secondary transfer position NT, a non-transfer voltage (negative voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. An alternating voltage was applied. The AC voltage applied to the facing roll 32B has a peak-to-peak value Vpp of +2 kV and a frequency of 0.5 to 1 kHz.

(Example 2)
In the metal color mode, the secondary transfer voltage (positive electrode) is applied to the secondary transfer roll 34 via the opposing roll 32B when the transfer image region R1 passes through the secondary transfer position NT in the metal color mode. Sex voltage) was applied. The voltage applied to the facing roll 32B is set to -2 kV.

  Further, in the metal color mode, when the non-transfer image area R2 passes through the secondary transfer position NT, a non-transfer voltage (negative DC voltage) is applied to the secondary transfer roll 34 via the opposing roll 32B. At the same time, an alternating voltage was applied. The DC voltage Vdo applied to the facing roll 32B is +0.4 kV. The AC voltage applied to the facing roll 32B has a peak-to-peak value Vpp of +2 kV and a frequency of 0.5 to 1 kHz.

(Comparative Example 1)
In the metal color mode, the secondary transfer voltage (positive electrode) is applied to the secondary transfer roll 34 via the opposing roll 32B when the transfer image region R1 passes through the secondary transfer position NT in the metal color mode. Sex voltage) was applied. The voltage applied to the facing roll 32B is set to -2 kV.

  In the metal color mode, when the non-transfer image area R2 passes through the secondary transfer position NT, no AC voltage is applied, and the non-transfer voltage (negative polarity) is applied to the secondary transfer roll 34 via the opposing roll 32B. Voltage) was applied. The DC voltage Vdo applied to the facing roll 32B is +0.4 kV.

  As a result of evaluating Examples 1 and 2 and Comparative Example 1, as shown in FIG. 15, in Examples 1 and 2, there was no problem in image quality even when 500000 sheets were passed. On the other hand, in the comparative example, white spots occurred after 100,000 sheets were passed. Note that the white spots are caused by the resistance of the secondary transfer roll 34 being lowered due to the metal toner sticking into the secondary transfer roll 34 and damaging the surface layer 34A of the secondary transfer roll 34. It is speculated that this will occur.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the spirit of the present invention. For example, the modification examples described above may be appropriately combined.

10 Image forming apparatus 20V, 20W toner image forming unit (an example of a forming unit, an example of a first forming unit)
20Y, 20M, 20C, 20K toner image forming unit (an example of a second forming unit)
31 Transfer belt (an example of a carrier)
34 Secondary transfer roll (an example of a transfer member)

Claims (5)

A non-transferred image that is not transferred to the recording medium with a toner containing a flat pigment, and a transfer portion that is transferred to the recording medium;
A transport body for transporting the transfer image and the non-transfer image to a transfer position;
When the transfer voltage is applied, the transfer image is transferred to the recording medium at the transfer position, and when the non-transfer image passes through the transfer position, a DC voltage and an AC voltage having a polarity opposite to the transfer voltage are obtained. A transfer member to which is applied;
An image forming apparatus. A first forming portion as the forming portion for forming a first non-transfer image as the non-transfer image and a first transfer image as the transfer image with toner containing a flat pigment;
A second forming portion that forms a second non-transfer image that is not transferred to the recording medium with a toner that does not contain a flat pigment, and a second transfer image that is transferred to the recording medium;
With
The carrier is
The first non-transfer image, the second non-transfer image, the first transfer image, and the second transfer image are transferred in a state where the first non-transfer image and the second non-transfer image are shifted in the transport direction. To the position,
The transfer member is
When the transfer voltage is applied, the first transfer image and the second transfer image are transferred to a recording medium at the transfer position, and when the first non-transfer image passes through the transfer position, the DC voltage and the The image forming apparatus according to claim 1, wherein an AC voltage is applied and the DC voltage is applied without applying the AC voltage when the second non-transfer image passes through the transfer position. In the first mode, a first non-transfer image that is not transferred to the recording medium and a first transfer image that is transferred to the recording medium are formed with toner containing a flat pigment. In the second mode, the first non-transfer image And a first forming portion that does not form the first transfer image,
A second forming unit that forms, in the second mode, a second non-transferred image that is not transferred to the recording medium and a second transferred image that is transferred to the recording medium with toner containing no flat pigment;
A transfer region to which the first non-transfer image and the second non-transfer image are transferred; and the first non-transfer image, the second non-transfer image, the first transfer image, and the second transfer image are transferred. A transport body for transporting to a position;
In the first mode, when the transfer voltage is applied, the first transfer image is transferred to the recording medium at the transfer position, and when the transfer region passes the transfer position, the transfer voltage is opposite to the transfer voltage. A transfer member to which a direct current voltage and an alternating voltage are applied;
An image forming apparatus. The transfer member is
In the second mode, when the transfer voltage is applied, the second transfer image is transferred to the recording medium at the transfer position, and the AC voltage is applied when the transfer region passes the transfer position. The image forming apparatus according to claim 3, wherein the DC voltage is applied. The relationship between both amplitudes of the AC voltage and the DC voltage is
Both amplitudes of AC voltage> DC voltage x 2
The image forming apparatus according to any one of claims 1 to 4.