JP2008146013A - Image forming device and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that controls power consumption, while maintaining image quality without the image defects due to negative afterimage, and that can attain energy savings. <P>SOLUTION: A transfer voltage controller of a transfer device begins to apply the transfer voltage to a first transfer roller 11, prior to the arrival of a latent image region front end Is at the entrance of a transfer nip, wherein the latent image region front end Is is the front end of a latent image forming region Ai on the surface of a photoreceptor, where a latent image is formed on the latent image forming section. Furthermore, the transfer voltage controller controls transfer power supply, to stop applying the transfer voltage to the first transfer roller after a latent image region rear end Ie passes through the exit of the transfer nip, wherein the latent image region rear end Ie is the rear end of the latent image forming region Ai, and a discharge device begins a discharge operation, while the transfer power supply applies the transfer voltage to the first transfer roller 11 before a voltage application exit V1 arrives at the discharge nip, where the voltage application exit V1 is the front end of a transfer voltage applying region Av on the surface of a photoreceptor that has passed through the transfer nip. Furthermore, the discharge device stops discharge operation, after a voltage shut-down exit Ve passes through the discharge nip, where the voltage shut-down exit Ve is the rear end of the a transfer voltage applying region Av. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and a process cartridge employed in the image forming apparatus.

  Conventionally, as an image forming apparatus, the surface of a moving latent image carrier is charged with a negative polarity and then exposed to form an electrostatic latent image, and a negative polarity toner is supplied to the electrostatic latent image with a developing device. Thus, there is known one that forms a toner image on the surface of the latent image carrier. Then, the toner image formed on the surface of the latent image carrier is transferred onto the surface of the transfer member at a transfer portion where the transfer member and the latent image carrier are opposed to each other with the transfer member such as an intermediate transfer member or a recording member in between. . The surface of the latent image carrier after the toner image is transferred to the transfer body is removed by the cleaning device to remove the transfer residual toner, and is neutralized by the neutralization device. By this charge removal, the surface of the latent image carrier is initialized and prepared for the next image formation.

  A transfer apparatus including a transfer member that forms a transfer portion includes a transfer voltage application power source that applies a positive polarity transfer voltage to the transfer member. Then, by applying a positive polarity transfer voltage to the transfer member, a transfer electric field is formed between the latent image carrier and the transfer member in the transfer portion, and negative polarity toner is transferred from the surface of the latent image carrier to the transfer member. Move and transfer is done.

  As a static elimination apparatus, there is an electrostatic elimination apparatus such as that described in Patent Document 1 by using a static elimination lamp light. Further, as described in Patent Document 2, a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a counter member facing the latent image carrier, and the potential of the surface of the latent image carrier at a position facing the counter member is set. On the average, there are those equipped with a static elimination charger that eliminates static electricity.

JP 2004-302451 A JP-A-7-5734

  As a result of intensive studies by the inventors, when a positive polarity transfer voltage is applied to the transfer member, depending on the configuration of the material of the latent image carrier, the positive polarity voltage applied to the transfer member It was found that the body was positively charged at the transfer part. At this time, the non-image portion that has not been supplied with toner is charged to a potential having a larger positive polarity than the image portion that has been supplied with toner on the surface of the latent image carrier. This is because in the image area, there are toner particles between the surface of the transfer member and the surface of the latent image carrier, and the toner particles become a resistance layer, so that the current from the transfer member does not flow easily. This is because there is no current and the current easily flows in direct contact with the transfer body. In the image forming apparatus used by the present inventors, the portion that was the image portion on the surface of the latent image carrier was charged with a negative polarity even after passing through the transfer portion, but the portion that was a non-image portion was the transfer portion. After passing, it was charged with positive polarity.

  With respect to such a phenomenon, the following problems arise in a static eliminator using a static eliminator like the static eliminator provided in the image forming apparatus described in Patent Document 1. That is, in the charge removal using the charge removal lamp, it is possible to remove the negative polarity portion on the surface of the latent image carrier, but it is not possible to remove the positive polarity portion on the surface of the latent image carrier. Therefore, if there is a portion charged to the positive polarity on the surface of the latent image carrier, the potential difference from other portions remains.

  FIG. 5 is an explanatory diagram of a change in potential on the surface of the latent image carrier when the surface of the latent image carrier whose non-image portion is charged with a positive polarity is neutralized by a neutralization lamp. As shown in FIG. 5A, the image portion of the surface of the latent image carrier after transfer is charged with a negative polarity, and the non-image portion is charged with a positive polarity. When the surface of the latent image carrier is neutralized by a neutralizing lamp, as shown in FIG. 5B, the image portion charged to the negative polarity is neutralized, but the non-image portion is charged to the positive polarity. Will remain. Then, it moves to the charging portion while the potential difference remains on the surface of the latent image carrier, such as a portion charged to positive polarity and a portion having no potential. When the surface of the latent image carrier in the state shown in FIG. 5 (b) is uniformly charged to a negative polarity, there is a potential difference on the surface of the latent image carrier after passing through the charging portion as shown in FIG. 5 (c). May remain. If there is such a potential difference, a negative afterimage is generated, which may affect the image and cause an image defect.

  As a result of extensive research conducted by the present inventors, it is possible to use a static elimination charger that applies a voltage obtained by superimposing an AC voltage on a DC voltage to a counter member, such as the static elimination device included in the image forming apparatus described in Patent Document 2. It has been found that the potential of can also be removed.

  FIG. 6 is an explanatory diagram of a change in potential of the surface of the latent image carrier when the surface of the latent image carrier with the non-image portion charged to a positive polarity is discharged using a charge removal charger. FIG. 6A shows the potential of the surface of the latent image carrier after the transfer. As in FIG. 5A, the image portion is charged with a negative polarity and the non-image portion is charged with a positive polarity. Yes. When the surface of the latent image carrier is neutralized by the neutralization charger, as shown in FIG. 6B, the image portion charged to the negative polarity and the non-image portion charged to the positive polarity are uniform. Static electricity is removed. Then, when the surface of the latent image carrier that has been subjected to uniform charge removal is uniformly charged to a negative polarity, the surface of the latent image carrier is reduced to a predetermined value of a negative polarity as shown in FIG. Can be charged like this. Thereby, generation of a negative afterimage can be prevented, and the image quality can be maintained.

  However, a static eliminator that applies a voltage in which an AC voltage is superimposed on a DC voltage, such as a static eliminator, consumes more power than a static eliminator that uses a static eliminator lamp. This leads to an increase in power consumption of the entire forming apparatus. Such a problem is not limited to a static eliminator that applies a voltage obtained by superimposing an AC voltage on a DC voltage, but can eliminate a positive polarity potential on the surface of the latent image carrier. This is a problem that can occur if the static eliminator has higher power consumption.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce power consumption and realize energy saving while maintaining image quality free from image defects due to negative afterimages. An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 is directed to a latent image carrier that moves on the surface, a charging unit that charges the surface of the latent image carrier, and the surface of the latent image carrier that is charged by the charging unit. A latent image forming means for forming an electrostatic latent image thereon; a developing means for supplying toner of a predetermined polarity to the electrostatic latent image on the surface of the latent image carrier to form a toner image; and the latent image carrier. Transfer means for transferring the toner image formed on the surface of the body to the transfer body, and the latent image support after the surface of the latent image support body is neutralized by a charge eliminating unit and the toner image is transferred to the transfer body A neutralizing unit capable of neutralizing a positive potential on the surface of the body, and the transfer unit includes a transfer member that forms a transfer portion opposite to the latent image carrier and the latent image, and the latent image Transfer voltage application for applying to the transfer member a transfer voltage that attracts the toner of the predetermined polarity on the surface of the carrier to the transfer member In the image forming apparatus including a transfer voltage control unit that controls application of the transfer voltage to the transfer member of the transfer voltage application power source, the transfer voltage control unit forms a latent image by the latent image forming unit. The application of the transfer voltage to the transfer member is started before the front end of the latent image forming area on the surface of the latent image carrier reaches the transfer section, and the rear end of the latent image forming area is the transfer section. The transfer voltage application power source is controlled so as to stop the application of the transfer voltage to the transfer member after passing through the transfer member, and the charge eliminating means applies the transfer voltage to the transfer member by the transfer voltage application power source. Before the front end of the transfer voltage application area on the surface of the latent image carrier that has passed through the transfer section reaches the charge removal section, the charge removal operation is started, and the rear end of the transfer voltage application area is the charge removal section. The static elimination operation is stopped after passing through A.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the charging unit charges the surface of the latent image carrier to a negative polarity, and the developing unit is configured to charge the electrostatic image on the surface of the latent image carrier. The predetermined polarity of the toner supplied to the latent image is a negative polarity, and the transfer voltage application power source applies a positive polarity transfer voltage to the transfer member.
According to a third aspect of the present invention, the latent image carrier has a structure in which a charge transport layer and a crosslinked charge transport layer are sequentially laminated on a charge generation layer, and the crosslinked charge transport layer has at least a charge transport property. It is formed by curing a radically polymerizable monomer having a trifunctional or higher functionality having no structure and a radically polymerizable compound having a monofunctional charge transporting structure.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the charging means is a scorotron type charging device.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, third, or fourth aspect, a cleaning unit that removes transfer residual toner on the surface of the latent image carrier is provided between the transfer unit and the charging unit. The surface of the latent image carrier is positioned opposite to the surface of the latent image carrier, and the neutralization unit is configured to be the surface of the latent image carrier between the cleaning unit and the charging unit. is there.
According to a sixth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, or fifth aspect, the static eliminator includes a static eliminator facing the surface of the latent image carrier, and the static eliminator. A neutralization voltage application power source that applies a neutralization voltage obtained by superimposing an alternating voltage on a direct current voltage; and a neutralization voltage control unit that controls the application of the neutralization voltage to the neutralization member of the neutralization voltage application power source. The neutralization voltage control means applies the neutralization voltage to the neutralization member when starting the neutralization operation and stops the neutralization operation when the neutralization operation is stopped. The discharge voltage application power source is controlled to stop the application of the discharge voltage to the member.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the charge eliminating member is a roller member that is in contact with or close to the surface of the latent image carrier.
According to an eighth aspect of the present invention, in the image forming apparatus of the sixth aspect, the neutralizing member is a scorotron member that faces the surface of the latent image carrier in a non-contact manner.
According to a ninth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, or fifth aspect, the static eliminator includes: a static eliminator that contacts the surface of the latent image carrier; A neutralization voltage application power source for applying a neutralization voltage of a DC voltage, and a neutralization voltage control means for controlling the application of the neutralization voltage to the neutralization member of the neutralization voltage application power source, wherein the neutralization unit is provided on the surface of the latent image carrier. The static elimination voltage control means applies the static elimination voltage to the static elimination member when starting the static elimination operation, and the static elimination voltage to the static elimination member when stopping the static elimination operation. The neutralization voltage application power source is controlled so as to stop the application of.
According to a tenth aspect of the present invention, in the image forming apparatus according to the sixth or ninth aspect, the charge eliminating member is a brush member that contacts the surface of the latent image carrier.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the sixth or ninth aspect, the charge eliminating member is a blade member that contacts the surface of the latent image carrier in the trailing direction.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the sixth or ninth aspect, the static eliminator is a magnetic brush roller for bringing a magnetic brush formed of magnetic particles into contact with the surface of the latent image carrier. It is what.
According to a thirteenth aspect of the present invention, in the image forming apparatus of the twelfth aspect, the developing means is a two-component developing type developing means using a two-component developer composed of toner and a magnetic carrier, and forms the magnetic brush. The magnetic particles are the same as the magnetic carrier of the two-component developer.
The invention according to claim 14 is the image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the latent image forming means is inputted. Image information identifying means for forming the electrostatic latent image on the latent image carrier on the latent image carrier based on the obtained image information, and identifying the image information before being used in the latent image forming means The latent image carrier surface passing through the static elimination unit is halftone when the image information serving as a basis for the electrostatic latent image formed when passing through the latent image forming unit after passing through the static elimination unit Only when the image information identification unit identifies that the image is an image, the neutralization unit performs a neutralization operation in the neutralization unit.
According to a fifteenth aspect of the present invention, at least one of a charging unit, a latent image forming unit, a developing unit, or a charge eliminating unit and a latent image carrier are integrally supported to be attached to and detached from the image forming apparatus. A process cartridge capable of being used in the image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14. To do.

  In the image forming apparatus according to the first to fifteenth aspects, since the transfer voltage is applied while the latent image forming region passes through the transfer portion, even when the application of the transfer voltage is stopped at another timing, The toner image formed on the surface of the latent image carrier is transferred to the transfer body. Since the charge removal operation is performed while the transfer voltage application area passes through the charge removal portion, the surface of the latent image carrier is positively charged at the transfer portion even if the charge removal operation is stopped at another timing. The generation of negative afterimages can be prevented. Further, since the neutralization operation is stopped after the trailing end of the transfer voltage application region passes through the neutralization unit, the timing for stopping the neutralization operation can be set.

  According to the first to fifteenth aspects of the present invention, image quality can be maintained by preventing the occurrence of a negative afterimage, and since there is a timing to stop the neutralization operation, power consumption is always higher than that in which the neutralization operation is always performed. There is an excellent effect that energy saving can be realized.

An embodiment in which the present invention is applied to a color laser printer (hereinafter simply referred to as “printer 100”) as an image forming apparatus will be described below.
FIG. 2 is a schematic configuration diagram of the printer 100 according to the present embodiment. In this printer, process cartridges 101Y, 101C, 101M, and 101K as four image forming units of yellow, cyan, magenta, and black are arranged side by side to constitute a tandem image forming unit. In the tandem image forming unit, process cartridges 101Y, 101C, 101M, and 101K are sequentially arranged from the left side in FIG. Here, the suffixes Y, C, M, and K of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively. In the tandem image forming unit, the individual process cartridges 101Y, 101C, 101M, and 101K are charged around the drum-shaped photosensitive members 21Y, 21C, 21M, and 21K as latent image carriers, and the charging devices and developing devices 10Y and 10C. , 10M, 10K, photoconductor cleaning device and the like. At the top of the printer 100, toner bottles 2Y, 2C, 2M, and 2K filled with yellow, cyan, magenta, and black color toners are arranged. Each color developing device 10Y, 10C, 10M, and 10K is replenished from the toner bottles 2Y, 2C, 2M, and 2K to a predetermined replenishment amount by a conveyance path (not shown).

  Further, an optical writing unit 9 as a latent image forming unit is provided below the tandem image forming unit. The optical writing unit 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each of the photoreceptors 21Y, 21C, 21M, and 21K while scanning the laser beam based on image data. It is configured as follows.

  Further, an intermediate transfer belt 1 in the form of an endless belt is provided as an intermediate transfer member immediately above the tandem image forming unit. The intermediate transfer belt 1 is wound around support rollers 1a and 1b, and a drive motor (not shown) serving as a drive source is connected to a rotation shaft of the drive roller 1a among the support rollers. When this drive motor is driven, the intermediate transfer belt 1 rotates counterclockwise in the figure and the followable support roller 1b rotates. Inside the intermediate transfer belt 1, primary transfer rollers 11Y, 11C, 11M, and 11K for transferring the toner images formed on the photoreceptors 21Y, 21C, 21M, and 21K onto the intermediate transfer belt 1 are provided.

Further, a secondary transfer roller 5 as a secondary transfer device is provided downstream of the primary transfer rollers 11Y, 11C, 11M, and 11K in the driving direction of the intermediate transfer belt 1. A support roller 1b is disposed on the opposite side of the secondary transfer roller 5 and the intermediate transfer belt 1, and functions as a pressing member.
Further, a paper feed cassette 8 and a paper feed roller 7 are provided below the optical writing unit 9, and a registration roller 6 and the like are provided on the downstream side in the transport direction of the paper feed roller 7. Further, on the downstream side of the secondary transfer roller 5 in the traveling direction of the transfer paper P onto which the toner image has been transferred by the secondary transfer roller 5, a fixing device 4 for fixing the toner image on the transfer paper P and a toner image are provided. A paper discharge roller 3 for discharging the fixed transfer paper P is provided.

Next, the operation of the printer 100 will be described. The photosensitive members 21Y, 21C, 21M, and 21K are rotated by the individual process cartridges 101Y, 101C, 101M, and 101K. Along with this rotation, first, the photosensitive members 21Y, 21C, and 21C are charged by the charging chargers 17Y, 17C, 17M, and 17K of the charging device. The surfaces of 21M and 21K are uniformly charged. Next, the image data is irradiated with writing light by a laser from the optical writing unit 9 to form electrostatic latent images on the photoreceptors 21Y, 21C, 21M, and 21K. Thereafter, toner is attached by the developing devices 10Y, 10C, 10M, and 10K, and the electrostatic latent images are visualized to form yellow, cyan, magenta, and black on the photoreceptors 21Y, 21C, 21M, and 21K, respectively. A monochromatic image is formed.
Further, the drive roller 1a is driven to rotate by a drive motor (not shown), the other driven roller 1b and the secondary transfer roller 5 are driven to rotate, the intermediate transfer belt 1 is rotated and conveyed, and the visible image is transferred to the primary transfer roller. The images are sequentially transferred onto the intermediate transfer belt 1 by 11Y, 11C, 11M, and 11K. As a result, a full-color toner image is formed on the intermediate transfer belt 1. The surface of the photoconductors 21Y, 21C, 21M, and 21K after the image transfer is cleaned by removing residual toner with a photoconductor cleaning device to prepare for the next image formation.

  In accordance with the timing of image formation, the leading edge of the transfer paper P is fed out from the first paper feed cassette 8a or the second paper feed cassette 8b by the first paper feed roller 7a or the second paper feed roller 7b, and the registration roller. 6 until it stops. Then, the sheet is conveyed between the secondary transfer roller 5 and the intermediate transfer belt 1 while taking an image forming operation and timing on the intermediate transfer belt 1. Here, the intermediate transfer belt 1 and the secondary transfer roller 5 form a so-called secondary transfer nip across the transfer paper P, and the secondary transfer roller 5 transfers the toner image on the intermediate transfer belt 1 onto the transfer paper P. Secondary transfer to.

  After the image transfer, the transfer paper P is fed into the fixing device 4, where the fixing device 4 applies heat and pressure to fix the transferred image, and is discharged outside the apparatus. On the other hand, the intermediate transfer belt 1 after the image transfer is removed by the intermediate transfer body cleaning device 12 to remove residual toner remaining on the intermediate transfer belt 1 after the image transfer, so that the tandem image forming unit prepares for another image formation.

  The process cartridges 101Y, 101C, 101M, and 101K for each color integrally form the photosensitive members 21Y, 21C, 21M, and 21K, the charging device, the photosensitive member cleaning device, the developing devices 10Y, 10C, 10M, and 10K. The printer 100 can be detachably attached to the main body.

Here, each of the process cartridges 101Y, 101C, 101M, and 101K performs the same configuration and operation. Therefore, the subscripts Y, C, M, and K of the respective symbols are omitted below, and the process cartridge 101 is described in detail.
FIG. 3 is a schematic explanatory view around the process cartridge 101. As shown in FIG. 3, a photoconductor 21 that rotates the process cartridge 101 clockwise in the drawing is provided. Around the photosensitive member 21, the charging charger 17, the developing device 10, the cleaning blade 33 of the photosensitive member cleaning device 30, and the like are sequentially arranged. Further, a neutralizing roller 41 as a neutralizing member is provided between the cleaning blade 33 and the charging charger 17 in the surface movement direction of the photosensitive member 21. Thus, the process cartridge 101 forms an image forming unit for each color.

Next, the operation at the time of image formation of each member provided in the process cartridge 101 will be described.
The surface of the photosensitive member 21 as a latent image carrier is uniformly charged to a negative polarity by the charging charger 17 which is a charging means. On the uniformly charged surface of the photosensitive member 21, an electrostatic latent image is formed on the basis of image information by the laser light L of the optical writing unit 9 serving as a latent image forming unit in the latent image forming portion Lp. Then, a negative polarity toner as a predetermined polarity is supplied to the electrostatic latent image formed on the photosensitive member 21 from the developing roller 13 of the developing device 10 as a developing unit, and a toner image is formed on the surface of the photosensitive member 21. The The toner image formed on the photosensitive member 21 is transferred onto the intermediate transfer belt 1 that is a transfer member at a transfer nip N1 that is a transfer portion facing the primary transfer roller 11 as a transfer member included in the transfer device 110 that is a transfer unit. A transcription is made. The transfer residual toner is removed from the surface of the photoconductor 21 after the toner image is transferred by the transfer nip N1 by a cleaning blade of the photoconductor cleaning device 30 as a cleaning unit. Then, the surface of the photosensitive member 21 is neutralized by passing through a portion facing the neutralizing roller 41 as a neutralizing member included in the neutralizing device 40 as a neutralizing unit, and the surface of the photosensitive member 21 is initialized for this neutralization. For image formation.

The transfer device 110 has a primary transfer roller 11 that forms a transfer nip N1 across the photoreceptor 21 and the intermediate transfer belt 1, and a positive polarity transfer voltage that attracts negative polarity toner on the photoreceptor 21 to the primary transfer roller 11. A transfer power supply 111 is provided as a transfer voltage application power supply applied to the primary transfer roller 11. Furthermore, a transfer voltage control unit 112 is provided as a transfer voltage control unit that controls application of a transfer voltage to the primary transfer roller 11 of the transfer power source 111.
The neutralization device 40 includes a neutralization roller 41 facing the surface of the photosensitive member 21, and a neutralization power source 42 as a neutralization voltage application power source that applies a neutralization voltage obtained by superimposing an alternating voltage on a direct current voltage to the neutralization roller 41. Further, a neutralization voltage control unit 43 is provided as a neutralization voltage control unit that controls application of a neutralization voltage to the neutralization roller 41 of the neutralization power source 42. In the present embodiment, the neutralization roller 41 contacts the surface of the photoreceptor 21 to form a neutralization nip N2. The neutralization nip N2 serves as a neutralization portion of the photoreceptor 21. The neutralization device 40 starts the neutralization operation by starting to apply the neutralization voltage to the neutralization roller 41, and stops the neutralization operation by stopping the application of the neutralization voltage to the neutralization roller 41.
The neutralizing roller 41 is not limited to the one that contacts the surface of the photosensitive member 21 but may be disposed close to the surface.

The photoreceptor 21 has a configuration in which a charge transport layer and a cross-linked charge transport layer are sequentially stacked on a charge generation layer. The crosslinkable charge transport layer is formed by curing at least a trifunctional or higher-functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. As this photoreceptor 21, the one described in Patent Document 1 can be used.
By using such a photoreceptor 21, a highly durable and high-performance photoreceptor that does not cause cracking or film peeling, has high wear resistance and scratch resistance, and has good electrical characteristics can be obtained. . Therefore, a good image can be provided over a long period of time by using this photoreceptor 21.

When an image is formed with an image forming apparatus provided with such a photoreceptor 21 using a static elimination lamp as a static elimination device, a potential difference is generated between the charged image portion and the non-image, and this potential difference is reduced to half. In the tone, it appeared in the image and became a negative afterimage.
This is due to the following reason.
That is, the photosensitive member 21 is charged by a positive voltage applied to the primary transfer roller 11 when passing through the transfer nip N1. Further, since toner particles exist between the surface of the photoreceptor 21 and the intermediate transfer belt 1 in the image portion, and the toner particles become a resistance layer, the image portion is difficult to be charged with a long current. On the other hand, in the non-image portion, the photosensitive member 21 and the intermediate transfer belt 1 are in direct contact, and current easily flows and is easily charged. As a result, a potential difference occurs between the image portion and the non-image on the surface of the photoreceptor 21 after passing through the transfer nip N1. In addition, since the photosensitive member 21 has a multilayer structure, trap sites that hinder the movement of electric charges are easily generated on the surface thereof, and the electric potential is difficult to be uniformly formed on the photosensitive member 21, so that it was an image portion even after charging. A potential difference is generated between the location and the location that was non-image (see FIG. 5). In addition, the configuration is not limited to the configuration of the photoconductor 21 of the present embodiment. When the charging capability of the photoconductor or the charging member used is low, the potential difference between the portion that was the image portion and the non-image portion after charging is also provided. Will occur.
The photoreceptor in which a negative afterimage is generated is not limited to that described above, and the present invention is useful as long as the photoreceptor is charged by the transfer voltage of the transfer portion. As other photoreceptors, a photoreceptor having a phthalocyanine CGL layer tends to generate a negative afterimage. Examples of such a photoreceptor include those described in JP-A-2005-290365.

As described above, when the photosensitive member 21 is charged by the positive voltage applied to the primary transfer roller 11, the potential difference on the surface of the photosensitive member 21 causes the alternating voltage to be superimposed on the direct current voltage as in the present embodiment. It was found that this can be prevented by applying a static elimination voltage to the static elimination roller 41 (see FIG. 6).
However, since the static eliminator 40 that applies the static eliminator voltage obtained by superimposing the AC voltage on the dc voltage to the static eliminator roller 41 consumes more power than the static eliminator using the static eliminator lamp, the static eliminator 40 is always operated. This leads to an increase in power consumption of the entire printer 100.

Next, the characteristic part of this embodiment is demonstrated.
FIG. 1 is a timing chart of ON / OFF switching between a transfer voltage and a discharge voltage with respect to the presence / absence of an image signal in the latent image forming portion Lp on the surface of the photosensitive member 21 of the present embodiment.
In FIG. 1, Is, Ie, Vs, Ve, Rs, and Re indicate positions on the surface of the photosensitive member 21. In FIG. 1, each position on the surface of the photosensitive member 21 is the entrance of the transfer nip N1 or the neutralization nip N2. The timing to reach the entrance is shown.
In the timing chart of FIG. 1, the front end of the latent image forming area Ai where image formation is performed in the latent image forming portion Lp is shown as the latent image area front end Is, and the rear end of the latent image forming area Ai is shown as the latent image area rear end Ie. .

The transfer voltage control unit 112 moves to the primary transfer roller 11 before the latent image region front end Is of the latent image formation region Ai on the surface of the photosensitive member 21 on which the latent image is formed by the latent image formation unit Lp reaches the transfer nip N. Application of the transfer voltage is started. Then, after the latent image area rear end Ie passes through the transfer nip N, the transfer power supply 111 is controlled so as to stop the application of the transfer voltage to the primary transfer roller 11.
In FIG. 1, a position on the surface of the photosensitive member 21 positioned at the entrance of the transfer nip N1 at the timing when the application of the transfer voltage to the primary transfer roller 11 is started is indicated as a voltage application entrance portion Vs. Further, the position on the surface of the photosensitive member 21 that is located at the entrance of the transfer nip N1 at the timing when the application of the transfer voltage is stopped is indicated as a voltage stop entrance portion Ve. Further, a position on the surface of the photosensitive member 21 that is located at the exit of the transfer nip N1 at the timing of starting application of the transfer voltage is indicated by a voltage application exit portion V1. At this time, the region affected by the transfer voltage on the surface of the photosensitive member 21 is between the voltage application outlet V1 and the voltage stop inlet Ve, and the transfer power supply 111 applies the transfer voltage to the primary transfer roller 11. The transfer voltage application region Av on the surface of the photosensitive member 21 that passes through the transfer nip N1 during this time is a region from the voltage application outlet V1 to the voltage stop inlet Ve.

A time T1 from when the voltage application inlet Vs reaches the entrance of the transfer nip N1 until the latent image area front end Is reaches the entrance of the transfer nip N1 is determined by the rise time of the transfer voltage. In the printer 100 of the present embodiment, 100 [ms] or more is necessary due to the power pack capability. Therefore, in the printer 100, the time T1 from when the transfer voltage is turned on until the leading edge Is of the latent image area reaches the entrance of the transfer nip N1 is controlled to be 100 [ms].
Further, at least the latent image region rear end Ie is transferred at a time T2 from when the latent image region rear end Ie reaches the entrance of the transfer nip N1 until the voltage stop entrance Ve reaches the entrance of the transfer nip N1. It takes time to reach the exit of the nip N1. In the printer 100 of the present embodiment, the diameter of the primary transfer roller: φ13 [mm], the surface resistance of the intermediate transfer belt: 1.0 × 10 ⁻¹¹ [Ω], and the surface of the photoreceptor 21 that contributes to transfer at the transfer nip N1. The length of was 3 [mm]. That is, the length from the entrance to the exit of the transfer nip N1 is 3 [mm]. The linear velocity of the photosensitive member 21 was 182 [mm / s]. In this configuration, it takes 17 [ms] from when a certain point on the photosensitive member 21 reaches the entrance of the transfer nip N1 until it reaches the exit of the transfer nip N1. Therefore, the time T2 from when the latent image area Ie reaches the entrance of the transfer nip N1 until the transfer voltage is turned off needs to be set to 17 [ms] or more, but in the printer 100, 17 [ms]. And

In this way, while the latent image forming area Ai passes through the transfer nip N1, a predetermined transfer voltage is applied, and good primary transfer can be performed, and transfer voltage is applied at other timings. Even if the operation is stopped, no problem occurs in image formation. That is, when there is no toner image on the surface of the photosensitive member 21 that passes through the transfer nip N, it is not necessary to apply a transfer voltage, and this causes a negative afterimage while the non-image portion passes through the transfer nip N. Even if the application of the transfer voltage is stopped, no problem in image quality occurs.
Further, since the time from the entrance of the transfer nip N1 to the exit of the transfer nip N1 is 17 [ms], the voltage-applying entrance portion Vs is changed after the voltage-applying exit portion V1 reaches the entrance of the transfer nip N1. The time t required to reach the transfer nip N is 17 [ms].

  The static elimination voltage control part 43 controls the static elimination power supply 42 as follows. That is, the voltage application outlet V1 that is the front end of the transfer voltage application area Av on the surface of the photosensitive member 21 that has passed through the transfer nip N1 while the transfer power supply 111 is applying the transfer voltage to the primary transfer roller 11 is the neutralization nip. Before reaching N2, application of a static elimination voltage to the static elimination roller 41 is started. Then, after the voltage stop entrance Ve, which is the rear end of the transfer voltage application area Av, passes through the static elimination nip N2, the application of the static elimination voltage to the static elimination roller 41 is stopped.

In FIG. 1, when applying a static elimination voltage to the static elimination roller 41, a position on the surface of the photosensitive member 21 positioned at the entrance of the static elimination nip N <b> 2 is indicated as a static elimination start entrance portion Rs. Further, the position on the surface of the photosensitive member 21 that is located at the entrance of the static elimination nip N2 at the timing when the application of the static elimination voltage is stopped is referred to as a static elimination stop entrance Re.
The time T3 from when the static elimination start inlet portion Rs reaches the entrance of the static elimination nip N2 to when the voltage application inlet portion Vs reaches the entrance of the static elimination nip N2 is the rise time of the static elimination voltage and the rise of the transfer voltage. It depends on the relationship with time. In the printer 100, 100 [ms] is required as in the case of the transfer voltage because of the power pack.

Although the ability to neutralize the surface of the photoconductor 21 at the static elimination nip N2 is low at the beginning of the rise of the static elimination voltage, the ability to charge the photoconductor at the transfer nip N1 is low even at the beginning of the rise of the transfer voltage. In the printer 100, even if the discharge voltage starts to rise, if the area passes through the transfer nip N1 at the start of the transfer voltage, no potential difference occurs on the surface of the photoreceptor 21 that has passed through the discharge nip N2. Therefore, in the printer 100, the application of the static elimination voltage is started at the front end of the region that has passed through the transfer nip N1 at the beginning of the rise of the transfer voltage, that is, at the timing when the voltage application outlet V1 reaches the entrance of the static elimination nip N2. That is, the charge removal start entrance Rs and the voltage application exit V1 on the surface of the photoreceptor 21 are at the same position. Therefore, the time T3 from when the static elimination start entrance Rs reaches the entrance of the static elimination nip N2 until the voltage application entrance Vs reaches the entrance of the static elimination nip N2 is 17 [ms]. Further, a time T5 from when the static elimination start entrance Rs reaches the entrance of the static elimination nip N2 until the latent image area front end Is reaches the entrance of the static elimination nip N2 is 117 [ms].
Thereby, it is possible to start the application of the neutralizing voltage to the neutralizing roller 41 before the front end of the transfer voltage application area Av on the surface of the photosensitive member 21 reaches the neutralizing nip N2.
In the case where the rise time of the static elimination voltage is delayed compared to the rise time of the transfer voltage, the static entry start portion Rs reaches the entrance of the static elimination nip N2 after the neutralization start entrance Rs reaches the entrance of the static elimination nip N2. It is set so as to ensure a long time T3 until reaching the entrance of the nip N2.

In addition, at least the time when the voltage stop inlet Ve is discharged is at least a time T4 from when the voltage stop inlet Ve reaches the inlet of the static elimination nip N2 until the static elimination stop inlet Re reaches the inlet of the static nip N2. It takes time to reach the exit of the nip N2. In the printer 100, the diameter of the static elimination roller was φ12 [mm], and the length of the surface of the photoreceptor 21 from which static elimination was performed in the static elimination nip N2 was 2 [mm]. That is, the length from the entrance to the exit of the static elimination nip N2 is 2 [mm]. Further, since the linear velocity of the photosensitive member 21 is 182 [mm / s], in this configuration, a certain point on the photosensitive member 21 reaches the outlet of the static elimination nip N2 after it reaches the inlet of the static elimination nip N2. It takes 11 [ms]. Therefore, the time T4 from when the voltage stop entrance Ve reaches the entrance of the static elimination nip N2 until the static elimination voltage is turned off needs to be set to 11 [ms] or more. [Ms]. At this time, the time T6 from when the rear end Ie of the latent image area reaches the entrance of the static elimination nip N2 until the static elimination voltage is turned off is controlled to be 28 [ms].
Thereby, the application of the static elimination voltage to the static elimination roller 41 can be stopped after the rear end of the transfer voltage application area Av on the surface of the photosensitive member 21 passes through the outlet of the static elimination nip N2.

As described above, while the transfer voltage application region Av passes through the neutralization nip N2, the surface of the photoconductor 21 can be positively charged even at the transfer nip N1, and the neutralization voltage can be applied at other timings. Even if the operation is stopped, it is possible to prevent a negative afterimage from remaining on the surface of the photosensitive member 21 that has passed through the neutralization nip N2. Thereby, the transfer image quality can be maintained. In addition, since the application of the static elimination voltage is stopped after the voltage stop entrance Ve, which is the rear end of the transfer voltage application area Av, passes through the static elimination nip N2, the power consumption is suppressed compared to the case where the static elimination voltage is always applied. And energy saving can be realized.
Moreover, in the static elimination apparatus 40 which applies the static elimination voltage which superimposes an alternating voltage on a DC voltage, ozone may generate | occur | produce while applying the static elimination voltage. In the printer 100, since the timing for stopping the application of the static elimination voltage is provided, the generation of ozone can be suppressed as compared with the printer that always applies the static elimination voltage.
In addition, since the power consumption can be suppressed as the time for stopping the application of the static elimination voltage is longer, it is desirable to stop the application of the static elimination voltage as much as possible. In the printer 100, the time from when the latent image area rear end Ie of the previous latent image forming area Ai passes a certain position until the latent image area front end Is of the next latent image forming area Ai passes a certain position. When longer than 145 [ms] (T5 + T6), the application of the transfer voltage is stopped, and the control of stopping the voltage of the static elimination voltage is executed.

In the printer 100, as shown in FIG. 3, the neutralization member included in the neutralization device 40 is a neutralization roller 41 that is a roller member that contacts the surface of the photoreceptor 21. By using a roller member as a charge removal member in the charge removal device 40 for removing the charge on the surface of the photoconductor 21 by charging the surface of the photoconductor 21 with a charge removal member that applies a charge removal voltage obtained by superimposing an AC voltage on a DC voltage. Compared with a configuration using a non-contact charger, the overall configuration can be designed to be compact, and the amount of ozone generation can be suppressed.
Further, as shown in FIG. 3, the printer 100 is configured such that a charging nip N <b> 2 is formed on the downstream side of the surface movement direction of the photosensitive member 21 with respect to the cleaning device 30. With this configuration, the transfer residual toner is removed, and the surface of the photoconductor 21 is neutralized by the neutralization device 40. Therefore, the neutralization is not hindered by the residual transfer toner, and the neutralization can be performed efficiently.
Further, in the printer 100, as shown in FIG. 3, a scorotron charging charger 17 is used as charging means. When the present inventors used a scorotron charging charger 17 as a charging means, it was confirmed that even if there is a negatively charged portion on the surface of the photosensitive member 21 before charging and a potential difference occurs, charging can be performed uniformly. It was.

  The scorotron charging method has a higher charging capability than the charging roller charging method. This is because the configuration of both charging systems is different. The scorotron system generates plasma (ions and electrons) in the scorotron and charges it by the difference between the grid voltage and the photoreceptor surface potential. ) And the charging efficiency is good. On the other hand, the charging roller system is charged by discharging due to the potential difference between the surface of the charging roller and the photoconductor. If there is a difference in the surface potential of the photoconductor before entering the charging nip, the effect is likely to occur even after charging (charging). The ability is low). For this reason, when the electric potential difference is large, the charging roller is difficult to uniformly charge.

[Modification 1]
In the embodiment, the configuration in which the roller member is used as the charge removal member of the charge removal apparatus 40 has been described. However, the charge removal member is not limited to the roller member. Hereinafter, as a first modification, a configuration using a non-contact charger as a charge removal member will be described.
FIG. 4 is a schematic explanatory diagram of the periphery of the process cartridge 101 in the first modification. Compared to the configuration described with reference to FIG. 3, the charge removal member is different only in that the charge removal member is the charge removal charger 44, and the other points are common to the above-described embodiment. That is, control is performed so that the transfer voltage and the static elimination voltage are applied at the same timing as in the first embodiment described with reference to FIG. Accordingly, as in the first embodiment, it is possible to reduce power consumption and realize energy saving as compared with the one that always applies a static elimination voltage while maintaining the transfer image quality.
The neutralization charger 44 of the first modification can also neutralize the positive polarity potential on the surface of the photosensitive member 21 by superimposing the alternating voltage on the direct current voltage on the grid portion.

[Modification 2]
Next, as a second modified example (hereinafter referred to as modified example 2), a configuration using a brush member that contacts the photoreceptor 21 as a charge eliminating member will be described.
FIG. 7 is a schematic explanatory diagram of the periphery of the process cartridge 101 in the second modification. Compared to the configuration described with reference to FIG. 3, the difference is only in that the charge removal member is a charge removal brush 45 as a brush member, and the other points are common to the above-described embodiment. That is, control is performed so that the transfer voltage and the static elimination voltage are applied at the same timing as in the first embodiment described with reference to FIG. Accordingly, as in the first embodiment, it is possible to reduce power consumption and realize energy saving as compared with the one that always applies a static elimination voltage while maintaining the transfer image quality.
The neutralizing brush 45 of Modification 2 can also neutralize the positive polarity potential on the surface of the photoconductor 21 by applying a voltage obtained by superimposing an alternating voltage on a rotating shaft.
Thus, by using the static elimination brush 45 to which the voltage which superimposed the alternating voltage on the direct current voltage was applied to the static elimination apparatus 40, the whole structure is designed more compactly compared with the structure which uses a scorotron type static elimination charger. Is possible. In the scorotron method, a gap corresponding to the bias applied to the wire is required to suppress leakage between the case and the wire. Furthermore, the scorotron method also requires a wire cleaning mechanism, and the adoption of the scorotron requires a certain size as a whole. On the other hand, it becomes possible to design the whole structure compactly by setting it as the brush-type static elimination member which used the static elimination brush instead of the scorotron system.
Further, by setting the resistance of the static elimination brush 45 to 10 × 10 ⁴ to 10 × 10 ¹⁰ [Ω], the static elimination brush 45 can be stably charged.

[Modification 3]
Next, as a third modified example (hereinafter referred to as modified example 3), a configuration using a blade member that contacts the photosensitive member 21 in the trailing direction as a charge eliminating member will be described.
FIG. 8 is a schematic explanatory diagram of the periphery of the process cartridge 101 in the third modification. Compared to the configuration described with reference to FIG. 3, the only difference is that the charge removal member is a charge removal blade 46 as a blade member, and the other points are common to the above-described embodiment. That is, control is performed so that the transfer voltage and the static elimination voltage are applied at the same timing as in the first embodiment described with reference to FIG. Accordingly, as in the first embodiment, it is possible to reduce power consumption and realize energy saving as compared with the one that always applies a static elimination voltage while maintaining the transfer image quality.
The static elimination blade 46 of the modification 3 can also neutralize a positive polarity potential on the surface of the photoconductor 21 by applying a voltage in which an AC voltage is superimposed on a DC voltage.
As described above, by using the static elimination blade 46 to which the voltage obtained by superimposing the AC voltage on the DC voltage is applied to the static elimination device 40, it is possible to design the entire configuration more compactly. Moreover, the static elimination blade 46 can be stably charged by setting the resistance of the static elimination blade 46 to 10 × 10 ⁴ to 10 × 10 ¹⁰ [Ω].

[Modification 4]
Next, as a fourth modified example (hereinafter referred to as modified example 4), a configuration using a magnetic brush formed of magnetic particles in contact with the photoreceptor 21 as a charge eliminating member will be described.
FIG. 9 is a schematic explanatory diagram of the periphery of the process cartridge 101 in the fourth modification. Compared to the configuration described with reference to FIG. 3, the difference is only in that the charge removal member is a charge removal magnetic brush roller 47 as a magnetic brush roller, and the other points are common to the above-described embodiment. That is, control is performed so that the transfer voltage and the static elimination voltage are applied at the same timing as in the first embodiment described with reference to FIG. Accordingly, as in the first embodiment, it is possible to reduce power consumption and realize energy saving as compared with the one that always applies a static elimination voltage while maintaining the transfer image quality.
As shown in FIG. 7, the static elimination magnetic brush roller 47 has a fixed magnet member 47b arranged inside a conductive electrode sleeve 47a. And the magnetic particle 47c is hold | maintained on the surface of the electrode sleeve 47a with the magnetic restraint force of the magnet member 47b, and the magnetic brush is formed. In the static elimination magnetic brush roller 47, by applying the voltage from the static elimination power source 42 to the electrode sleeve 47a, the static elimination voltage can be applied to the magnetic brush formed by the magnetic particles 47c held on the surface thereof. Further, in order to make the contact width between the magnetic particles 47c and the photoconductor 21 appropriate, the gap between the electrode sleeve 47a and the photoconductor 21 is set appropriately, for example, with a gap width of about 0.4 [mm]. It is good to use.
The static elimination magnetic brush roller 47 of the modified example 4 can also eliminate the positive polarity potential on the surface of the photosensitive member 21 by applying a voltage in which an AC voltage is superimposed on a DC voltage.
Thus, by using the static elimination magnetic brush roller 47 to which the voltage obtained by superimposing the AC voltage on the DC voltage is applied to the static elimination device 40, it is possible to design the overall configuration more compactly.
The developing device 10 of Modification 4 is a two-component developing type developing device using a two-component developer composed of toner and carrier. In the fourth modification, the magnetic particles 47c held on the electrode sleeve 47a by the magnetic restraint force adhere to the photoconductor 21 when the rubbing force and the centrifugal force with the photoconductor 21 overcome the magnetic restraint force. End up. The magnetic particles 47c adhering to the photosensitive member 21 are collected by the developing device 10 mainly in the developing region where the developing roller 13 faces the photosensitive member 21. At this time, if the magnetic carrier used for development and the magnetic particle 47c are different, image defects such as partial fluctuations in developing ability and white spots due to carrier adhesion occur. Therefore, the occurrence of the above-described image defect can be prevented by using the same magnetic carrier 47c used for the static elimination magnetic brush roller 47 as the magnetic carrier contained in the two-component developer used in the developing device 10. .

The neutralization members of the modified examples 2, 3 and 4 are contact-type neutralization members, and are injection charging systems that do not use discharge, so that charging efficiency is good. For this reason, if a contact-type static eliminator is used as the static eliminator as in Modifications 2, 3, and 4, the generation of negative afterimages is suppressed even when only a DC voltage is applied as the static eliminator. It becomes possible.
In this way, a DC voltage can be used as a static elimination voltage with a contact-type static elimination member, but by using a static elimination voltage obtained by superimposing an AC voltage on a DC voltage, it is in a state where it is repeatedly charged with its oscillating electric field. Therefore, more uniform charging is possible, and the charge removal efficiency can be improved.

  In any of the embodiments and the first, second, third, and fourth embodiments described above, the negative afterimage occurs when the image is a halftone image. This is because, when a halftone image is formed, even a minute potential difference generated from the history of the previous image remaining on the photoconductor 21 is easily seen as a density difference. Therefore, there is no problem in the image even if the neutralization device 40 is not operated at the timing when the region on the photoconductor 21 other than the portion where the halftone image is written passes through the neutralization nip N2.

  The optical writing unit 9 which is a latent image forming unit of the printer 100 forms an electrostatic latent image on the photosensitive member 21 which is a latent image carrier based on the input image information by the latent image forming unit Lp. . The static elimination voltage control unit 43 may include image information identification means for identifying image information before being used in the optical writing unit 9. Then, the image information that is the basis of the electrostatic latent image formed when the surface of the photosensitive member 21 that passes through the static elimination nip N2 that is the static elimination portion passes through the latent image forming portion Lp after passing through the static elimination nip 21 is halftone Only when the image information identification means identifies that the image is an image, the neutralization operation at the neutralization nip N2 is controlled. That is, if the latent image formed when the surface of the photoreceptor 21 passing through the neutralization nip N2 reaches the latent image forming portion Lp due to the surface movement of the photoreceptor 21, the neutralization device 40 is used. Stops the discharging operation at the discharging nip N2. In this way, the operation time of the static eliminator 40 can be further shortened by not operating the static eliminator except at the timing when the portion where the halftone image is written passes through the static nip N2. For this reason, the power consumption in the static elimination apparatus 40 can be suppressed, and the generation amount of ozone can also be suppressed.

As described above, according to the present embodiment, the transfer voltage control unit 112 that is a transfer voltage control unit of the transfer device 110 that is a transfer unit is a photoconductor that is a latent image carrier on which a latent image is formed by the latent image forming unit Lp. Application of a transfer voltage to the primary transfer roller 11 serving as a transfer member is started before the latent image area front end Is which is the front end of the latent image forming area Ai on the surface 21 reaches the entrance of the transfer nip N1 serving as a transfer portion. The transfer power supply as a transfer voltage application power supply is stopped so that the application of the transfer voltage to the primary transfer roller 11 is stopped after the latent image area rear end Ie, which is the rear end of the latent image forming area Ai, passes through the exit of the transfer nip N1. 111 is controlled, so that the transfer voltage is applied while the latent image forming area Ai passes through the transfer nip N1, so that the photosensitive member 21 can be applied even if the transfer voltage application is stopped at other timings. Toner formed on The transfer is made to the intermediate transfer belt 1 is transferred member. The static eliminator 40 serving as a static eliminator is the front end of the transfer voltage application area Av on the surface of the photoreceptor 21 that has passed through the transfer nip N1 while the transfer power supply 111 is applying the transfer voltage to the primary transfer roller 11. The neutralization operation is started before the voltage application outlet V1 reaches the neutralization nip N2, which is the neutralization unit. After the voltage stop inlet Ve, which is the rear end of the transfer voltage application area Av, passes through the neutralization nip N2, the static elimination operation is performed. Stop operation. For this reason, even if the static elimination operation is stopped at another timing, it is possible to prevent the occurrence of a negative afterimage due to the photosensitive member 21 being charged to the positive polarity at the transfer nip N1. Further, since the static elimination operation is stopped after the voltage stop-time entrance portion Ve, which is the rear end of the transfer voltage application area Av, passes through the static elimination nip N2, it is possible to set the timing for stopping the static elimination operation. As a result, it is possible to maintain image quality by preventing the occurrence of negative afterimages, and because there is a timing to stop the static elimination operation, power consumption is reduced and energy saving is realized compared to those that always perform the static elimination operation. can do.
The charging charger 17 as charging means charges the surface of the photosensitive member 21 to a negative polarity, and the predetermined polarity of the toner supplied to the electrostatic latent image on the photosensitive member 21 by the developing device 10 as the developing means is negative. In addition, the transfer power supply 111 is configured to apply a positive transfer voltage to the primary transfer roller 11, and includes a charge removal device 40 that can also remove the positive polarity potential on the surface of the photoconductor 21, thereby charging the charger on the surface of the photoconductor 21. In addition to the negative polarity potential due to 17, the positive polarity potential due to the positive polarity transfer voltage can be eliminated at the transfer nip N1.
Further, the photoconductor 21 has a structure in which a charge transport layer and a cross-linked charge transport layer are sequentially laminated on the charge generation layer, and the cross-linkable charge transport layer has at least a trifunctional or higher functional radical polymerization property having no charge transport structure. By using what is formed by curing a monomer and a radically polymerizable compound having a monofunctional charge transport structure, cracks and film peeling do not occur, and wear resistance and scratch resistance are high. It becomes the highly durable and high-performance photoreceptor 21 having good electrical characteristics, and can provide a good image for a long time.
Further, by using a charging device including the scorotron charging charger 17 as the charging means, the surface of the photoreceptor 21 can be more uniformly charged.
Further, a photoconductor cleaning device 30 that is a cleaning unit for removing the transfer residual toner on the surface of the photoconductor 21 is provided at a position facing the surface of the photoconductor 21 between the transfer nip N1 and the charging charger 17, and a charge eliminating nip N2 is provided. By configuring the surface of the photosensitive member 21 between the photosensitive member cleaning device 30 and the charging charger 17, the transfer residual toner is removed, and the surface of the photosensitive member 21 is discharged by the charge removing device 40. Therefore, the neutralization can be performed efficiently without being obstructed.
Further, the static eliminator 40 is a static eliminator 41 serving as a static eliminator facing the surface of the photosensitive member 21, and a static eliminator serving as a static eliminator voltage application power source for applying a static eliminator voltage obtained by superimposing an AC voltage on a dc voltage to the neutralizer roller 41 A neutralization voltage control unit 43 serving as a neutralization voltage control unit that controls application of a neutralization voltage to the neutralization roller 41 of the neutralization power supply 42 is provided, and a neutralization nip N2 facing the neutralization roller 41 on the surface of the photosensitive member 21 is neutralized. The static elimination voltage controller 43 applies a static elimination voltage to the static elimination roller 41 when starting the static elimination operation, and removes the static elimination power supply 42 so as to stop applying the static elimination voltage to the static elimination roller 41 when stopping the static elimination operation. By controlling the above, it is possible to control the discharging operation on the surface of the photoreceptor 21 by the discharging device 40.
Moreover, by using the static elimination roller 41 which consists of a roller member as a static elimination member, compared with the structure which uses a non-contact charger, the whole structure can be designed compactly and the amount of ozone generation can be suppressed.
Further, even if the neutralization voltage applied by superimposing the alternating current voltage on the direct current voltage is applied to the neutralization charger 44 made of a scorotron member that faces the surface of the photoconductor 21 in a non-contact manner with respect to the surface of the photoconductor 21, it is charged with a positive polarity. The surface of the photosensitive member 21 can be neutralized, and image quality can be maintained by preventing negative afterimages.
Further, a process cartridge 101 that is formed by integrally supporting the photosensitive member 21, the developing device 10, the photosensitive member cleaning device 30, the charging charger 17, and the like, and is detachable from the printer 100 that is an image forming device. To do. By taking the form of such a process cartridge, user exchange can be easily performed. Further, by replacing the process cartridge, it is possible to return an image having deteriorated (image deterioration due to photoconductor wear, developer deterioration, cleaning blade wear, etc.) to a state equivalent to the initial state.
Further, as in Modification 2, by using the static elimination brush 45 that is a brush member that contacts the surface of the photosensitive member 21 that is a latent image carrier as the static elimination member, the overall configuration can be designed more compactly. is there.
Further, as in the third modified example, by using the static elimination blade 46 that is a blade member that contacts the surface of the photosensitive member 21 that is a latent image carrier as the static elimination member in the trailing direction, the overall configuration is designed to be more compact. It is possible.
Further, as in Modification 4, by using the static elimination magnetic brush roller 47 that is a magnetic brush roller that brings the magnetic brush formed of the magnetic particles 47c into contact with the surface of the photoreceptor 21 that is the latent image carrier as the static elimination member, It is possible to design the entire configuration more compactly.
Further, the developing device 10 as the developing means of the modified example 4 is a two-component developing type developing device using a two-component developer composed of toner and a magnetic carrier, and the magnetic particles 47c forming the magnetic brush are two-component developer. By using the same magnetic carrier as the magnetic carrier 47, it is possible to prevent image defects due to the magnetic particles 47c being mixed in the developing device 10.
Further, as in the second modification, by using the charge eliminating brush 45 that is a charge eliminating member that is in contact with the surface of the photosensitive member 21 that is the latent image carrier as the charge eliminating means, the charging efficiency is reduced because of the injection charging method that does not use discharge. Therefore, a direct current voltage can be used as a static elimination voltage applied by the static elimination power source 42.
The optical writing unit 9 serving as a latent image forming unit forms an electrostatic latent image on the photosensitive member 21 serving as a latent image carrier on the basis of input image information by a latent image forming unit Lp. The neutralization voltage control unit 43 includes image information identification means for identifying image information before being used in the optical writing unit 9, and the surface of the photosensitive member 21 that passes through the neutralization nip N2 passes through the neutralization nip N2 to form a latent image forming unit. Only when the image information identification unit identifies that the image information that is the basis of the electrostatic latent image formed when passing through Lp is a halftone image, the neutralization device 40, which is a neutralization unit, performs the neutralization nip N2. Perform static elimination operation at. That is, when the surface of the photosensitive member 21 that passes through the static elimination nip N2 passes through the latent image forming portion Lp and the upper portion of the image that is the basis of the electrostatic latent image is other than a halftone image, the static elimination device 40 is The neutralization operation at the neutralization nip N2 is stopped. For this reason, the operation time of the static elimination apparatus 40 can be shortened and the power consumption in the static elimination apparatus 40 can be suppressed.

6 is a timing chart of ON / OFF switching between a transfer voltage and a charge removal voltage with respect to the presence or absence of an image signal in a latent image forming unit. 1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 2 is a schematic explanatory view around a process cartridge according to an embodiment. FIG. 10 is a schematic explanatory diagram around a process cartridge according to a first modification. Explanatory drawing of the change in potential of the latent image carrier surface when the surface of the latent image carrier charged with a positive polarity in the non-image part is neutralized by a static elimination lamp, (a) after transfer, (b) after static elimination, (C) after charging. Explanatory drawing of the change of the potential of the latent image carrier surface when the surface of the latent image carrier charged with a positive polarity in the non-image part is neutralized using a static elimination charger, (a) is after transfer, (b) is After neutralization, (c) is after charging. FIG. 10 is a schematic explanatory diagram around a process cartridge according to a second modification. FIG. 10 is a schematic explanatory diagram of the periphery of a process cartridge according to Modification 3. FIG. 10 is a schematic explanatory diagram of the periphery of a process cartridge according to Modification 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 2 Toner bottle 3 Paper discharge roller 4 Fixing device 5 Secondary transfer roller 6 Registration roller 7 Paper feed roller 8 Paper feed cassette 9 Optical writing unit 10 Developing device 11 Primary transfer roller 12 Intermediate transfer body cleaning device 17 Charging Charger 21 Photoconductor 30 Photoconductor cleaning device 33 Cleaning blade 40 Static elimination device 41 Static elimination roller 42 Static elimination power supply 43 Static elimination voltage control unit 100 Printer 101 Process cartridge 110 Transfer device 111 Transfer power source 112 Transfer voltage control unit

Claims (15)

A latent image carrier that moves on the surface;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the surface of the latent image carrier charged by the charging means;
Developing means for supplying toner of a predetermined polarity to the electrostatic latent image on the surface of the latent image carrier to form a toner image;
Transfer means for transferring the toner image formed on the surface of the latent image carrier to a transfer member;
Neutralizing means for neutralizing the surface of the latent image carrier by a neutralization unit, and capable of neutralizing a positive potential on the surface of the latent image carrier after transferring the toner image to the transfer body;
The transfer means includes a transfer member that forms a transfer portion facing the latent image carrier with the transfer member interposed therebetween, and a transfer that attracts the toner of the predetermined polarity on the surface of the latent image carrier to the transfer member. In an image forming apparatus comprising: a transfer voltage application power source that applies a voltage to the transfer member; and a transfer voltage control unit that controls application of the transfer voltage to the transfer member of the transfer voltage application power source.
The transfer voltage control means is configured to transfer the transfer voltage to the transfer member before the front end of the latent image forming area on the surface of the latent image carrier on which the latent image is formed by the latent image forming means reaches the transfer portion. The transfer voltage application power source is controlled so as to stop the application of the transfer voltage to the transfer member after the rear end of the latent image forming region has passed through the transfer portion,
The neutralizing means has a front end of a transfer voltage application region on the surface of the latent image carrier that has passed through the transfer portion while the transfer voltage application power source applies the transfer voltage to the transfer member. An image forming apparatus, comprising: starting a static elimination operation before reaching the discharge voltage, and stopping the static elimination operation after the trailing end of the transfer voltage application region has passed through the static elimination unit. The image forming apparatus according to claim 1.
The charging means charges the surface of the latent image carrier to negative polarity,
The predetermined polarity of the toner supplied to the electrostatic latent image on the surface of the latent image carrier by the developing means is a negative polarity.
The image forming apparatus, wherein the transfer voltage applying power source applies a positive polarity transfer voltage to the transfer member. The latent image carrier has a structure in which a charge transport layer and a crosslinkable charge transport layer are sequentially laminated on a charge generation layer, and the crosslinkable charge transport layer has at least a trifunctional or higher functional radical having no charge transport structure. An image forming apparatus formed by curing a polymerizable monomer and a radical polymerizable compound having a monofunctional charge transport structure. The image forming apparatus according to claim 1, 2 or 3.
An image forming apparatus, wherein the charging means is a scorotron charging device. The image forming apparatus according to claim 1, 2, 3, or 4.
A cleaning means for removing transfer residual toner on the surface of the latent image carrier at a position facing the surface of the latent image carrier between the transfer portion and the charging means;
An image forming apparatus, wherein the charge eliminating portion is configured to be on the surface of the latent image carrier between the cleaning unit and the charging unit. The image forming apparatus according to claim 1, 2, 3, 4, or 5.
The static elimination means includes: a static elimination member that faces the surface of the latent image carrier; a static elimination voltage application power source that applies a static elimination voltage obtained by superimposing an alternating voltage on a DC voltage to the static elimination member; and A neutralization voltage control means for controlling application of a neutralization voltage to the neutralization member, and the neutralization portion is a position facing the neutralization member on the surface of the latent image carrier,
The static elimination voltage control means applies the static elimination voltage to the static elimination member when starting the static elimination operation, and stops the application of the static elimination voltage to the static elimination member when stopping the static elimination operation. An image forming apparatus that controls an applied power source. The image forming apparatus according to claim 6.
An image forming apparatus, wherein the charge eliminating member is a roller member in contact with or close to the surface of the latent image carrier. The image forming apparatus according to claim 6.
An image forming apparatus, wherein the charge eliminating member is a scorotron member facing the surface of the latent image carrier in a non-contact manner. The image forming apparatus according to claim 1, 2, 3, 4, or 5.
The static elimination means includes a static elimination member that contacts the surface of the latent image carrier, a static elimination voltage application power source that applies a neutralization voltage of a DC voltage to the static elimination member, and a static elimination voltage of the static elimination voltage application power source to the static elimination member A neutralization voltage control means for controlling the application of the neutralization voltage, the neutralization portion is a position in contact with the neutralization member on the surface of the latent image carrier,
The static elimination voltage control means applies the static elimination voltage to the static elimination member when starting the static elimination operation, and stops the application of the static elimination voltage to the static elimination member when stopping the static elimination operation. An image forming apparatus that controls an applied power source. The image forming apparatus according to claim 6 or 9,
An image forming apparatus, wherein the charge eliminating member is a brush member that contacts the surface of the latent image carrier. The image forming apparatus according to claim 6 or 9,
An image forming apparatus, wherein the charge eliminating member is a blade member that contacts the surface of the latent image carrier in a trailing direction. The image forming apparatus according to claim 6 or 9,
An image forming apparatus, wherein the static eliminating member is a magnetic brush roller for bringing a magnetic brush formed of magnetic particles into contact with the surface of the latent image carrier. The image forming apparatus according to claim 12.
The developing means is a two-component developing type developing means using a two-component developer composed of a toner and a magnetic carrier,
An image forming apparatus, wherein the magnetic particles forming the magnetic brush are the same as the magnetic carrier of the two-component developer. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13.
The latent image forming means forms the electrostatic latent image on the latent image carrier on the basis of input image information by a latent image forming unit,
Image information identifying means for identifying the image information before being used in the latent image forming means,
The image information that forms the basis of the electrostatic latent image formed when the surface of the latent image carrier that passes through the static elimination unit passes through the latent image forming unit after passing through the static elimination unit is a halftone image. Only when the image information identifying means identifies this, the above-mentioned static eliminating means performs the static eliminating operation in the static eliminating section. A process cartridge that is formed by integrally supporting at least one of a charging unit, a latent image forming unit, a developing unit, or a charge eliminating unit and a latent image carrier, and is detachable from the image forming apparatus,
A process cartridge employed in the image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14.

Images