Patent Application
20150016851
This application is based on and claims priority under 35 USC 119 iron; Japanese Patent Application No. 2013-145797 filed Jul. 11, 2013.
1. Technical Field
The present invention relates to a transfer device, an image forming apparatus, and a transfer method.
2. Summary
According to an aspect of the invention, there is provided a transfer device including a transfer portion that transfers a toner image formed, with a toner containing flat pigment particles to a recording medium; a DC voltage applying portion that applies a DC voltage to the transfer portion; and an AC voltage applying portion that applies an AC voltage to the transfer portion.
With the transfer device according to the first aspect of the present invention, it is possible to make the orientation of flat pigment particles irregular, compared with a case where only a DC voltage is applied to a transfer portion.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein;
Exemplary transfer device, image forming apparatus, and transfer method according to a first exemplary embodiment of the present invention will be described with reference to
The image forming apparatus 10 further includes a controller 70 that controls the above-mentioned sections and a power supply unit 80 described below, and the power supply unit 80 that supplies power to the above-mentioned sections, including the controller 70.
Furthermore, the image forming section 12 includes toner-image forming portions 20 that form toner images, a transfer device 30 that transfers the toner images formed by the toner-image forming portions 20 to a sheet member P, and a fixing device 40 that fixes the toner image transferred to the sheet member F onto the sheet member P.
The medium transport device 50 includes a medium feeding portion 52 that feeds a sheet member P to the image forming section 12, and a medium discharge portion 54 that discharges the sheet member P having a toner image formed thereon. Furthermore, the medium transport device 50 includes a medium returning portion 56 that is used when an image is to be formed on either side of a sheet member P, and an intermediate transport portion 58 (described below).
The post-processing section 60 includes a medium cooling unit 62 that cools a sheet member P to which a toner image has been transferred in the image forming section 12, a straightening device 64 that straightens a curled sheet member P, and an image inspection portion 66 that inspects an image formed on the sheet member P. The components of the post-processing section 60 are disposed in the medium discharge portion 54 of the medium transport device 50.
The components of the medium transport device 50, except for a discharged-medium receiving portion 541 constituting the medium discharge portion 54, are disposed in a housing 90 of the image forming apparatus 10. The housing 90 according to this exemplary embodiment is formed of a first housing 91 and a second housing 92 that are arranged side-by-side in the apparatus width direction. Thus, the unit of transportation of the image forming apparatus 10 is reduced in the apparatus width direction.
The first housing 91 accommodates the principal parts of the image forming section 12, except for the fixing device 40; and the medium feeding portion 52, The second housing 92 accommodates the fixing device 40 constituting the image forming section 12; the medium discharge portion 54, except for the discharged-medium receiving portion 541; the medium cooling unit 62; the image inspection portion 66; the medium returning portion 56; the controller 70; and the power supply unit 80. The first housing 91 and the second housing 92 are coupled together with fastening members, such as bolts and nuts (not shown), The first housing 91 and the second housing 92 have, at their boundaries, a communication opening 90C1 through which a sheet member P is transported from a transfer nip NT (described below) of the image forming section 12 to a fixing nip NF, and a communication path 90C2 through which the sheet member P is transported from the medium returning portion 56 to the medium feeding portion 52.
As has been described above, the image forming section 12 includes the toner-image forming portions 20, the transfer device 39, and the fixing device 30. The toner-image forming portions 20 are provided so as to form toner images of the respective colors. In this exemplary embodiment, six toner-image forming portions 20 corresponding to first special color (V), second special color (W), yellow (Y), magenta (M), cyan (C), and black (K) are provided. The letters (V), (W), (Y), (M), (C), and (K) shown in
In this exemplary embodiment, for example, the first special color (V) is silver, which uses a toner containing flat pigment particles for adding metallic shine or brilliance (sparkle) to an image. The second special color (W) is a corporate color specific to a user, which is more frequently used than the other colors. The silver toner and the control of the respective portions by the controller 70 when an image is formed with the silver toner will foe described below.
The toner-image forming portions 20 for the respective colors have basically the same configuration, except for the toners they use. Therefore, image forming units 14 for the respective colors will be described below without distinction. As shown in
The photoconductor drum 21 is cylindrical, grounded, and rotated about a shaft thereof by a driving device (not shown). The photoconductor drum 21 has, for example, a negatively charged photosensitive layer on the surface thereof. As shown in
As shown in
The exposure device 23 forms an electrostatic latent image on the surface of the photoconductor drum 21. More specifically, the exposure device 23 irradiates the surface of the photoconductor drum 21, charged by the charger 22, with exposure light L modulated according to image data received from an image signal processing portion 71 (see
The developing device 24 forms a toner image on the surface of the photoconductor drum 21 by developing, with developer G containing toner, the electrostatic latent image formed on the surface of the photoconductor drum 21. The developing device 24 is supplied with toner from a toner cartridge 27 (see
The cleaning device 25 is blade-shaped and is used to scrape off the toner, remaining on the surface of the photoconductor drum 21 after the transfer of the toner image to the transfer device 30, from the surface of the photoconductor drum 21.
The static eliminator 26 eliminates static by irradiating, with light, the photoconductor drum 21 after transferring the image. By doing so, the charging history of the surface of the photoconductor drum 21 is deleted.
The transfer device 30 first-transfers, in an overlapping manner, toner images on the photoconductor drums 21 for the respective colors to the transfer bolt 31 and then second-transfers the thus-first-transferred toner image to a sheet member P. A detailed description will be given below.
As shown in
Furthermore, of the multiple rollers 32, a roller 32T shown in
As shown in
Furthermore, the first transfer rollers 33 are provided with applying portions 102 for applying transfer voltage. The applying portions 102 apply a transfer voltage having an opposite polarity to the toner to the first transfer rollers 33. Due to the application or the transfer voltage, the toner images formed on the photoconductor drums 21 are transferred to the transfer belt 31.
Details of the transfer voltage applied to the first transfer rollers 33 by the applying portions 102 will foe described below.
Furthermore, as shown in
Furthermore, an applying portion 104 that applies transfer voltage to the second transfer roller 34 is provided. The applying portion 104 applies a transfer voltage having an opposite polarity to the toner to the second transfer roller 34. Due to the application of the transfer voltage, the toner image is transferred from the transfer belt 31 to the sheet member P passing through the transfer nip NT.
Details of the transfer voltage applied to the second transfer roller 34 by the applying portion 104 will be described below.
As shown in
The fixing device 40 fixes a toner image transferred to a sheet member P in the transfer device 30 onto the sheet member P. In this exemplary embodiment, the fixing device 40 fixes the toner image onto the sheet member P by applying heat and pressure to the toner image at the fixing nip NF formed by a pressure roller 42 and a fixing belt 411 wound around multiple rollers 413. A roller 413H is a heating roller that has a heater therein and is rotated by a driving force transmitted from a motor (not shown). Thus, the fixing belt 411 is rotated in an arrow H direction.
The pressure roller 42 is also rotated by a driving force transmitted from a motor (not shown), at the same circumferential velocity as the fixing belt 411.
As shown in
The medium feeding portion 52 includes containers 521 that accommodate a stack of sheet members P. in this exemplary embodiment, two containers 521 are disposed side-by-side in the apparatus width direction, below the transfer device 30.
Medium supply paths 52P, which extend from the containers 521 to the transfer nip NT (the second transfer position), are formed of multiple transport roller pairs 522, guides (not shown), etc. Each medium supply path 52P turns back at two turn-back portions 52P1 and S2P2 in the apparatus width direction and extends upward to the transfer nip NT, forming a substantially S shape.
A feeding roller 523 is provided above the container 521 to feed a sheet member P at the top of the stack of sheets in the container 521. Of the multiple transport roller pairs 522, a transport roller pair 522S located on the most upstream side in the sheet transport direction serves as separating rollers that separate sheet members P, fed in a stacked manner from the container 521 by the feeding roller 523, into individual sheet members P. Furthermore, of the multiple transport roller pairs 522, a transport roller pair 522R located immediately upstream of the transfer nip NT in the sheet transport direction is operated so as to match the timing of moving the toner image on the transfer belt 31 and the timing of transporting the sheet member P.
The medium feeding portion 52 further includes an auxiliary transport path 52Pr. The auxiliary transport path 52Pr extends from an opening 91W, which is provided in a wall of the first, housing 91 farther from the second housing 92, and joins the turn-back portion 52P2 of the medium supply paths 52P. The auxiliary transport path 52Pr serves as a transport path that is used to feed a sheet member P, fed. from an optional recording medium supply device (not shown) provided adjacent to the opening 91W in the first housing 91, to the image forming section 12.
As shown in
The transport portions 581 transport a sheet member P with the transport belts while sucking air (negative pressure suction) from the inside of the transport portions 581 to make the sheet, member P adhere to the surfaces of the transport belt.
As shown in
The medium discharge portion 54 includes the discharged-medium receiving portion 541 that, receives the sheet member P discharged from the discharge port 92W,
The medium discharge portion 54 includes a medium discharge path 54P that transports the sheet member P from the fixing device 40 (fixing nip NF) to the discharge port 92W. The medium discharge path 54P is formed of a belt transport portion 543, multiple roller pairs 542, guides (not shown), etc. Of the multiple roller pairs 542, a roller pair 542B disposed on the most downstream side in a sheet discharge direction serves as discharge rollers that discharge the sheet member P onto the discharged-medium receiving portion 541.
The medium returning portion 56 includes multiple roller pairs 561. The multiple roller pairs 561 form a reversing path 56P, into which a sheet member P that has passed through the image inspection portion 66 is fed when an image is to be formed on either side of the sheet member P. The reversing path 56P includes a diverging path 56P1, a transport path 56P2, and a reversing path 56P3. The diverging path 56P1 diverges from the medium discharge path 54P. The transport path 56P2 sends the sheet member P received from the diverging path 56P1 into the medium supply paths 52P. The reversing path 56P3 is provided in the middle of the transport path 56P2. By reversing the direction in which the sheet member P is transported along the transport path S6P2 (i.e., by performing switchback transportation), the reversing path 56P3 reverses the sheet member P.
The medium cooling unit 62, the straightening device 64, and the image inspection portion 66 constituting the post-processing section 60 are disposed on the upstream side, in the sheet discharge direction, of a diverging portion of the diverging path 56P1 of the medium discharge path 54P of the medium discharge portion 54, in this order from the upstream side in the discharged direction.
The medium cooling unit 62 includes a heat-absorbing device 621 that absorbs the heat of the sheet member P, and a pressing device 622 that presses the sheet member P onto the heat-absorbing device 621. The heat-absorbing device 621 is disposed above the medium discharge path 54P, and the pressing device 622 is disposed below the medium discharge path 54P.
The heat-absorbing device 621. includes an endless heat-absorbing belt 6211, multiple rollers 6212 that support the heat-absorbing belt 6211, a heat sink. 6213 disposed inside the heat-absorbing belt 6211, and a fan 6214 for cooling the heat sink 6213.
The outer circumferential surface of the heat-absorbing belt 6211 is in contact with the sheet member P so as to be able to exchange heat. Of the multiple rollers 6212, a roller 6212D serves as a driving roller that transmits a driving force to the heat-absorbing belt 6211. The surface of the heat sink 6213 is in sliding contact with the inner circumferential surface of the heat-absorbing belt 6211 in a predetermined area along the medium discharge path S4P.
The pressing device 622 includes an endless pressing belt 6221 and multiple rollers 6222 that support the pressing belt 6221. The pressing belt 6221 is wound around the multiple rollers 6222. The pressing device 622 transports the sheet member P in cooperation with the heat-absorbing belt 6211 by pressing the sheet member P against the heat-absorbing belt 6211 (heat sink 6213).
The straightening device 64 is provided on the downstream side of the medium cooling unit 62 in the medium discharge portion 54. The straightening device 64 straightens the curled sheet member P received from the medium cooling unit 62.
An in-line sensor 661 that constitutes the principal part of the image inspection portion 66 is disposed on the downstream side of the straightening device 64 in the medium discharge portion 54. The in-line sensor 661 detects the presence/absence and level of toner intensity defect, image defect, image position defect, etc, in a fixed toner image, on the basis of light emitted onto and reflected from the sheet member P.
Next, the outline of an image forming process and subsequent post-processing process performed on a sheet member P by the image forming apparatus 10 will be described.
As shown in
As a result, the photoconductor drums 21 for the respective colors are charged, by the chargers 22 while being rotated. Furthermore, the controller 70 sends image data processed in the image signal processing portion to the exposure devices 23. The exposure devices 23 expose the charged photoconductor drums 21 to exposure light L modulated according to the image data. As a result, electrostatic latent images are formed on the surfaces of the photoconductor drums 21. The electrostatic latent images formed on the photoconductor drums 21 are developed by developer supplied from the developing devices 24. in this way, toner images of first special color (V), second special color (W) , yellow (Y), magenta (M), cyan (C), and black (K) are formed on the corresponding photoconductor drums 21.
The color toner images formed on the photoconductor drums 21 are sequentially transferred to the rotating transfer belt 31 due to the application of a transfer voltage via the first transfer rollers 33. Thus, an overlapping toner image, in which toner images of six colors overlap one another, is formed on the transfer belt 31. This overlapping toner image is transported to the transfer nip hT by the rotation of the transfer belt 31,
As shown in
The sheet member P to which the toner image has been transferred is transported from the transfer nip NT in the transfer device 30 to the fixing nip NF in the fixing device 40 by the intermediate transport portion 58. The fixing device 40 applies heat and pressure to the sheet member P passing through the fixing nip NF. Thus, the toner image transferred to the sheet member P is fixed.
The sheet member P discharged from the fixing device 40 is transported to the discharged-medium receiving portion 541 outside the apparatus by the medium discharge portion 54 and, at the same time, is processed by the post-processing section 60. The sheet member P heated in the fixing process is first cooled by the medium cooling unit 62. Then, the sheet member P is straightened by the straightening device 64. Then, the toner image fixed to the sheet member P is subjected to the detection for the presence/absence and level of toner intensity defect, image defect, image position defect, etc. by the image inspection portion 66. Finally, the sheet member P is discharged onto the medium discharge portion 54.
On the other hand, when an image is to be formed on a non-image surface (a surface having no image) of a sheet member P (i.e., when double-sided printing is performed), the controller 70 switches the transport path for the sheet member P after passing the image inspection portion 66 from the medium discharge path 54P of the medium, discharge portion 54 to the diverging path 56P1 of the medium returning portion 56. As a result, the sheer member P is reversed via the reversing path 56P and is sent to the medium supply paths 51P. An image is formed (fixed) on the back surface of this sheet member P through the same image forming process as that performed on the front surface thereof. This sheet member P is discharged onto the discharged-medium receiving portion 541 outside the apparatus after going through the same process as that performed on the front surface thereof after forming an image.
Next, sliver toner used as first special color (V) will be described.
The silver toner used as the first special color (V) (hereinbelow, simply “silver toner”) contains, as shown in
The pigment particle 110 is composed of, for example, aluminum. When the pigment particle 110 disposed on a flat surface is viewed from the side, the pigment particle 110 is larger in the left-right direction (direction Y) than in the top-bottom direction (direction X), as shown in
Furthermore, the pigment particle 110 in plan view (
In this way, in the first exemplary embodiment, the toner-image forming portion 20V serves as an exemplary first image portion that forms a toner image with a toner containing the pigment particles 110.
On the other hand, toners of second special, color (W), yellow (Y), magenta (M), cyan (C), and black (K) that are used in the toner-image forming portions 20W, 20Y, 20M, 20C, and 20K (hereinbelow, 20W to 20K) do not contain a Hat pigment, but contain a binder resin and a pigment other than a flat pigment (for example, an organic pigment, or an inorganic pigment). These pigments have ball-like shape, compared, with the pigment particles 110. Herein, for ease of explanation, second special color (W), 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”.
In this way, in the first exemplary embodiment, the toner-image forming portions 20W to 20K serve as exemplary second image portions that form toner images with toners that do not contain a flat pigment.
Furthermore, the image forming apparatus 10 according to the first exemplary embodiment has monochrome mode for forming a silver toner image on a sheet member P without forming other color toner images; other color mode for forming ah least one other color toner image on a sheet member P without forming a silver toner image; and mixed-color mode for forming a silver toner image and at least one other color toner image on a sheet member P. In the mixed-color mode, a silver toner image and another color toner image may be formed either in an overlapping manner or side-by-side.
The monochrome mode further includes monochrome brilliance mode for increasing the brilliance (sparkle), and monochrome glossy mode for increasing the metallic gloss. Similarly, the mixed-color mode has mixed-color brilliance mode for increasing the brilliance (sparkle) and mixed-color glossy mode for increasing the metallic gloss.
As shown in
On the other hand, the applying portion 104 that applies a transfer voltage to the second transfer roller 34 includes, as shown in
The other color mode is performed by the controller 70 operating at least one of the toner-image forming portions 20W to 20K, and not the toner-image forming portion 20V. Furthermore, when the other color mode is performed, as shown in
In addition, in the other color mode, the controller 70 operates the applying portions 102 to apply the same DC voltages to the first transfer rollers 33 for the respective colors (see
The monochrome brilliance mode is performed by the controller 70 operating the toner-image forming portion 20V, and not the toner-image forming portions 20W to 20K. Furthermore, in the monochrome brilliance mode, as shown in
Furthermore, in the monochrome brilliance mode, the controller 70 operates the applying portions 102 to apply a predetermined DC voltage to the first transfer rollers 33 (see
The monochrome glossy mode is performed by the controller 70 operating the toner-image forming portion 20V, and not the toner-image forming portions 20W to 20K. Furthermore, in the monochrome glossy mode, as shown in
Furthermore, in the monochrome glossy mode, the controller 70 operates the applying portions 102 to apply a predetermined DC voltage to the first transfer rollers 33 (see
The mixed-color brilliance mode is performed by the controller 70 operating at least one of the toner-image forming portions 20W to 20K, and the toner-image forming portion 20V. Furthermore, in the mixed-color brilliance mode, similarly to the monochrome brilliance mode, the controller 70 operates the DC voltage applying portion 104A and the AC voltage applying portion 1G4B to apply a superimposed voltage, which is obtained by superimposing an AC voltage on a DC voltage, to the second transfer roller 34 (superimpose mode).
Furthermore, in the mixed-color brilliance mode, the controller 70 operates the applying portions 102 to apply a DC voltage to the first transfer rollers 33 (see
The mixed-color glossy mode is performed by the controller 70 operating the toner-image forming portions 20W to 20K and the toner-image forming portion 20V. Furthermore, in the mixed-color glossy mode, similarly to the monochrome glossy mode, the; controller 70 operates the DC voltage applying portion 104A, not the AC voltage applying portion 104B, to apply only the DC voltage to the second transfer roller 34 (direct-current mode).
Furthermore, in the mixed-color glossy mode, the controller 70 operates the applying portions 102 to apply a DC voltage to the first transfer rollers 33 (see
Next, actions of the relevant configuration will be described.
In the monochrome brilliance mode or the mixed-color brilliance mode, the controller 70 operates the DC voltage applying portion 104A and the AC voltage applying portion 1Q4B to apply a super imposed voltage, which is obtained by superimposing an AC voltage on a DC voltage, to the second transfer roller 34, as shown in
When the superimposed voltage serving as a transfer voltage is applied, the pigment particles 110 composed of aluminum, fly (vibrate) between the transfer belt 31. and the sheet member P in a reciprocating manner due to an alternating electric field and then move to the sheet member P.
Because the pigment particles 110 move to the sheet member P after flying between the transfer belt 31 and the sheet member P in a reciprocating manner due the orientation of the pigment particles 110 is irregular (random), as shown in
As a result, diffused reflection light increases as compared with a case where the reflection surfaces 110A of the pigment particles 110 are oriented in the same direction, (see
On the other hand, in the monochrome glossy mode or the mixed-color glossy mode, the controller 70 operates the DC voltage applying portion 104A and not the AC voltage applying portion 104B, to apply only the DC voltage to the second transfer roller 34, as shown in
When only a DC voltage, serving as a transfer voltage, is applied, the pigment particles 110 move to the sheet member P without flying between the transfer belt 31 and the sheet member P in a reciprocating manner.
In this way, because the pigment particles 110 move to the sheet member P without flying between the transfer belt 31 and the sheet member P in a reciprocating manner, the pigment particles 110 are oriented such that the flat surfaces 110A are parallel to the surface of the sheet member P, as shown in
More specifically, as shown in
As a result, the flop index (FI), which is the index showing the metallic gloss measured according to ASTM E2194, increases (the metallic gloss increases).
On the other hand, in the mixed-color brilliance mode or the mixed-color glossy mode, the controller 70 individually controls the applying portions 102 so that a lower transfer voltage is applied when a toner image is transferred to the transfer belt 31 by the first transfer roller 33V than when toner images are transferred to the transfer belt 31 by the first transfer rollers 33W to 33K.
As a result, the amount of charge of the pigment particles 110 due to charge injection becomes lower than that in a case where the same transfer voltage is applied to the first transfer roller 33V and to the first transfer rollers 33W to 33K when the toner images are first-transferred to the transfer belt 31. Hence, in the second transfer of the toner image to the sheet member P, the orientation of the pigment particles 110 is easily controlled.
As has been described above, in the monochrome brilliance mode or the mixed-color brilliance mode, the controller 70 applies a superimposed voltage, which is obtained by superimposing an AC voltage on a DC voltage, to the second transfer roller 34, As a result, an image in which the orientation of the reflection surfaces 110A of the pigment particles 110 is irregular is obtained.
Furthermore, in an image in which the orientation of the reflection surfaces 110A of the pigment particles 110 is irregular, the direction of reflected light from the image is irregular. Therefore, compared with a case where the orientation of the reflection surfaces 110A of the pigment particles 110 is uniform, the diffused reflection light increases, increasing the brilliance (sparkle).
Furthermore, in the monochrome glossy mode or the mixed-color glossy mode, the controller 70 applies only a DC voltage to the second transfer roller 34. As a result, the pigment particles 110 are arrayed in the direction parallel to the surface of the sheet member P (direction Y). That is, the pigment particles 110 are arrayed regularly, and hence, the direction of reflected light from the image is also regular. Therefore, the above-mentioned flop index increases (metallic gloss increases), compared with a case where the orientation of the pigment particles 110 is irregular.
In this manner, it is possible to switch between the monochrome glossy mode or the mixed-color glossy mode for increasing the metallic gloss of an image and the monochrome brilliance mode or the mixed-color brilliance mode for increasing the brilliance (sparkle) of an image, due to the controller 70 operating the respective portions.
Furthermore, in the mixed-color brilliance mode or the mixed-color glossy mode, the controller 70 makes the transfer voltage to be applied when a toner image is transferred to the transfer belt 31 by the first transfer roller 33V lower than that to be applied when toner images are transferred to the transfer belt 31 by the first transfer rollers 33W to 33K. As a result, the charge generated in the pigment particles 110 due to charge injection in the first transfer decreases, compared with a case where the same transfer voltage is applied to the first transfer roller 33V and to the first transfer rollers 33W to 33K. Hence, in the second transfer of the toner image to the sheet member P, the orientation of the pigment particles 110 is easily controlled.
Exemplary transfer device and image forming apparatus according to a second exemplary embodiment of the present invention will be described below with reference to PIG. 9, focusing on the differences in structure from the first exemplary embodiment. Note that the same components as those in the first exemplary embodiment will be denoted by the same reference numerals, and a description thereof will be omitted.
As shown in
Furthermore, a guiding portion 124 is provided, which directs a sheet member P transported along the transport path 56P2 to the reversing path 56P3 or to the medium supply paths 52P via the direct path 122. The controller 70 controls the direction in which the guiding portion 124 guides the sheet member P.
Next, the control of the respective portions performed by the controller 70 in an additional printing mode will be described as its action. In the additional printing mode, a toner image is formed on a sheet member P with a toner containing the pigment particles 110, and toner images formed with other color toners are overlaid thereon.
In the additional printing mode, the controller 70 first operates the toner-image forming portion 20V to form only a toner image, among the image data, that is to be formed by the toner-image forming portion 20V. The toner image thus-formed by the toner-image forming portion 20V is transferred, at the transfer nip NT, to a surface of a sheet member P transported thereto (see
The controller 70 then controls the medium transport device 50 to direct the sheet member P having the toner image transferred and fixed thereto to the medium, returning unit 120, without discharging it to the discharged-medium receiving portion 541. Furthermore, the controller 72 controls the guiding portion 124 to direct, the sheet member P directed to the medium returning unit 120 to the medium supply paths 52P via the direct path 122 (see
The controller 70 then operates the toner-image forming portions 20W to 20K to form only toner images, among the image data, that are to be formed by the toner-image forming portions 20W to 20K.
The toner images formed by the toner-image forming portions 20W to 20K are transferred, at the transfer nip NT, to the surface of the sheet member P directed to the medium supply paths 52P via the direct path 122. Then, the sheet member P is discharged, onto the discharged-medium receiving portion 541 by the medium transport device 50 (see
In the additional printing mode, a toner image formed with a toner containing the pigment particles 110 is formed on a sheet member P, and toner images formed with other color toners are overlaid thereon.
By changing the order in which the toner-image forming portions 20 are arranged, a toner image formed with the toner containing the pigment particles 110 and toner images formed with other color toners may be formed on a sheet member P in this order. However, in this case, the toner-image forming portion. 20V has to be provided on the downstream side of the toner-image forming portions 20W to 20K in the rotation direction of the transfer belt 31. In such a configuration, toner images formed on the transfer belt 31 with the other color toners are subjected to the transfer history of the toner-image forming portion 20V located on the downstream, side thereof, increasing the amount of toner transferred back to the photoconductor drums 21. As a result, the color development of the toner images formed with the other color toners decrease.
That is, by forming a toner image with the toner containing the pigment particles 110 on a sheet member P, feeding this sheet member P again to the transfer nip NT, and then overlaying toner images formed with the other color toners on the toner image formed with the toner containing the pigment particles 110, it is possible to obtain an image in which degradation in the color development of the toner images formed with the other color toners is suppressed and in which the metallic gloss or the brilliance (sparkle) is enhanced.
The foregoing detailed descriptions of specific exemplary embodiments of the present invention are not intended to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible. For example, although not described in the first and second exemplary embodiments, when a toner image formed with the toner containing the pigment particles 110 is to be transferred to a sheet member P, the superimpose mode may be always chosen to enhance the brilliance (sparkle).
Furthermore, although a sine wave voltage is used as the AC voltage in the first and second exemplary embodiments, a rectangular wave voltage, as shown in
Furthermore, in the second exemplary embodiment, a sheet member P is fed again to the transfer nip NT via the direct path 122 without reversing the sheet member P. However, it is also possible that a sheet .member P having a toner image formed by the toner-image forming portion 20V transferred thereto is discharged onto the discharged-medium receiving portion 541, and the discharged sheet member P is stored again in the container 521 so that the sheet member P is fed again to the transfer nip NT by being transported by the medium feeding portion 52.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-145797 | Jul 2013 | JP | national |
