JP5531548B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, in a tandem-type image forming apparatus in which a plurality of image carriers are arranged, a transfer device provided via a recording medium on an image carrier disposed second or later in the paper conveyance direction includes: It has been proposed to arrange an auxiliary electrode for applying a potential having a polarity opposite to that of the toner image held on the sheet on the upstream side in the sheet conveyance direction.

  Patent Document 2 proposes winding the recording medium around the surface of the image carrier before the recording medium reaches the area where the toner image held on the image carrier is transferred to the recording medium by the transfer device. Has been.

JP 2000-181245 A JP 2002-072711 A

  An object of the present invention is to provide an image forming apparatus in which the generation of carrier marks on the surface of an image carrier is suppressed as compared with a configuration that does not include the magnetic force generation apparatus according to the present invention.

According to a first aspect of the present invention, there is provided an image carrier, a charging device that charges the image carrier, a latent image forming device that forms an electrostatic latent image on the image carrier charged by the charging device, and toner and by two-component developer containing a carrier, a recording medium and a developing unit for developing the electrostatic latent image formed on the image carrier, the pre-Symbol toner image formed on the image carrier by the developing device A transfer device for transferring the image to the image carrier, and provided downstream of the developing device in the rotation direction of the image carrier and upstream of the transfer device in the rotation direction of the image carrier. And a magnetic force generator that generates a magnetic force that generates a magnetic force to release the electrostatic force of the carrier held on the image carrier by development .

  According to a second aspect of the present invention, the image carrier is a cylindrical substrate, a photosensitive layer provided on the substrate, and provided on the photosensitive layer, containing oxygen and gallium and existing outside. A protective layer having a first region and a second region that is closer to the substrate than the first region and has a larger atomic ratio of oxygen to gallium than the first region; An image forming apparatus according to claim 1.

  The invention according to claim 3 is disposed upstream of the transfer device in the conveyance direction of the recording medium, and contacts the recording medium with the surface of the image carrier upstream of the transfer device in the rotation direction of the image carrier. The magnetic force generator generates a magnetic force toward the image carrier through a region of the recording medium that is in contact with the image carrier by the contact member. Alternatively, the image forming apparatus according to claim 2.

  According to the first and third aspects of the invention, there is provided an image forming apparatus in which the generation of carrier traces on the surface of the image carrier is suppressed as compared with the configuration without the magnetic force generation apparatus according to the present invention.

  According to the second aspect of the present invention, there is provided an image forming apparatus in which the generation of carrier marks on the surface of the image carrier is suppressed even when the configuration of the image carrier is the structure according to the second aspect. .

1 is a schematic diagram illustrating an example of an image forming apparatus according to a first embodiment. (A) (B) It is the schematic diagram which expanded and showed the transfer area | region in the conventional image forming apparatus. FIG. 3 is a schematic diagram showing an enlarged transfer region in the image forming apparatus according to the present embodiment. FIG. 2 is a schematic diagram illustrating an example of a form different from FIG. 1 of the image forming apparatus according to the first embodiment. It is a schematic diagram which shows an example of the image forming apparatus of 2nd Embodiment. It is a schematic diagram which shows an example of the form different from FIG. 5 of the image forming apparatus of 2nd Embodiment. (A) (B) It is a schematic diagram which shows an example of the film-forming apparatus used for formation of the protective layer of an image carrier.

<First Embodiment>
Hereinafter, an embodiment of the image forming apparatus of the present embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment is provided with an image holding body 12 as an image holding body. The image carrier 12 has a cylindrical shape, and is rotationally driven (in the direction of arrow A in FIG. 1) by a motor (not shown). In addition, the columnar shape mentioned here includes a hollow cylindrical shape having an open end in the length direction.

  Around the image carrier 12, a charging device 15, an exposure device 16, a developing device 18, a magnetic force generator 40, a transfer device 20, a removal device 22, and a charge removal device 24 are arranged along the rotation direction of the image carrier 12. They are arranged in order.

  The charging device 15 charges the surface of the image carrier 12. The charging device 15 is provided in contact or non-contact with the surface of the image carrier 12 and charges the surface of the image carrier 12. Examples of the charging device 15 include a corotron charger and a scorotron charger.

  The exposure device 16 irradiates the surface of the image carrier 12 charged by the charging device 15 with a laser beam L modulated based on the image data of the image to be formed, and the image data on the image carrier 12. An electrostatic latent image corresponding to the image is formed.

  A known two-component developer containing toner and carrier is stored in the developing device 18. The toner is charged by being stirred together with a carrier having magnetism by a stirring mechanism (not shown) in the developing device 18 and stored in this charged state. Examples of the toner contained in the two-component developer include a toner having a volume average particle diameter of 3 μm or more and 9 μm or less obtained by a polymerization method, and a constituent material thereof is a known toner used for an electrophotographic image forming apparatus. A material may be used.

  The carrier has magnetism, and as this carrier, iron powder, glass beads, ferrite powder, nickel powder or the like coated with a resin is used. The mixing ratio with the carrier is set by a known method.

  Further, the developing device 18 includes a developing roll 18A for developing the electrostatic latent image formed on the image carrier 12 with toner. The developing roll 18 </ b> A holds the two-component developer stored in the developing device 18 on the surface, and supplies the toner contained in the two-component developer from the developing device 18 to the surface of the image carrier 12. The toner supplied onto the image carrier 12 adheres to the electrostatic latent image on the image carrier 12 by electrostatic force. As a result, the electrostatic latent image on the image carrier 12 is developed by the toner supplied from the developing roll 18 </ b> A, and a toner image corresponding to the electrostatic latent image is formed on the image carrier 12.

  The magnetic force generator 40 is located downstream of the image carrier 12 in the rotational direction of the image carrier 12 from the position where the developing device 18 is disposed, and upstream of the image carrier 12 in the rotational direction from the position where the transfer device 20 is provided. Is provided. Further, the magnetic force generation device 40 is provided on the side where the transfer device 20 is provided in the conveyance path 34 of the recording medium P (on the opposite side to the image carrier 12 via the conveyance path 34). A magnetic force is generated toward the surface of the image carrier 12 through the recording medium P passing through 34. In the present embodiment, the magnetic force generator 40A is directed toward the surface of the image carrier 12 via a region that is not in contact with the image carrier 12 in the recording medium P, as shown in FIGS. A case where the magnetic force is generated is described.

  The magnetic force generator 40 is located downstream of the developing device 18 in the rotational direction of the image carrier 12, upstream of the transfer device 20 in the rotational direction of the image carrier 12, and via the recording medium P. The magnetic force may be provided at a position where the magnetic force is generated toward the surface of the image carrier 12 and the magnetic force toward the surface of the image carrier 12 through a region not in contact with the image carrier 12 on the recording medium P as shown in FIG. However, the present invention is not limited to the above-described form, and may be a form in which a magnetic force is generated toward the surface of the image carrier 12 through a region in contact with the image carrier 12 in the recording medium P (for details, refer to the second example). Will be described in the embodiment).

  As the magnetic force generator 40, a carrier (detailed later) held on the surface of the image carrier 12 by an electrostatic force is attracted to the magnetic force generator 40 side (that is, the recording medium P side) by the magnetic force from the magnetic force generator 40. Any device that generates magnetic force may be used. Examples of the magnetic force generator 40 include a permanent magnet and an electromagnet.

  When a permanent magnet is used as the magnetic force generator 40, it is considered that external energy such as electric power is unnecessary and the configuration is simpler and cheaper than an electromagnet. However, in order to adjust the magnetic force, it is considered necessary to adjust the distance from the surface of the image carrier 12. On the other hand, when an electromagnet is used, it is necessary to pass a current through a coil provided in the electromagnet. However, it is considered that the magnetic force can be easily adjusted by adjusting the current value of this current. Therefore, whether to use a permanent magnet or an electromagnet as the magnetic force generation device 40 may be selected according to the configuration of the image forming apparatus 10 on which the magnetic force generation device 40 is mounted.

  A transfer device 20 is provided on the image holding body 12 on the downstream side in the rotation direction of the image holding body 12 from the position where the developing roller 18A is disposed. The transfer device 20 has a cylindrical shape, and rotates with the rotation of the image carrier 12 (in the direction of arrow C in FIG. 1), so that the recording medium P contacts the outer peripheral surface of the image carrier 12. Carry while transporting. The recording medium P transported to a region (transfer region 32) where the image carrier 12 and the transfer device 20 face each other is transported while being pressed toward the recording medium P by the transfer device 20. A power supply 30 for applying a transfer voltage to the transfer device 20 is electrically connected to the transfer device 20.

  When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the image carrier 12 is applied from the power supply 30, the image carrier 12 is placed in a region between the image carrier 12 and the transfer device 20. An electric field having an electric field intensity is formed to move each toner constituting the upper toner image from the image holding member 12 to the transfer device 20 side by electrostatic force.

The recording medium P is stored in a paper storage unit (not shown), and is transported (in the direction of arrow B in FIG. 1) along the transport path 34 by a plurality of transport rollers (not shown). Then, it reaches the area where the image carrier 12 and the transfer device 20 face each other (transfer area 32 in FIG. 1). The recording medium P reaching the transfer area 32 passes through an electric field formed in the transfer area 32 by the transfer apparatus 20 while being pressed from the transfer apparatus 20 to the image holding body 12 side. 12 is transferred. That is, the toner image is transferred onto the recording medium P by the movement of the toner from the surface of the image carrier 12 to the recording medium P.
The transfer area 32 indicates an area where the toner image on the image carrier 12 is transferred to the recording medium P side in an area where the image carrier 12 and the transfer device 20 face each other.

A fixing device 26 is provided on the transport path 34 of the recording medium P on the downstream side in the transport direction from the transfer region 32. The fixing device 26 fixes the toner image transferred onto the recording medium P to the recording medium P by heat or heat and pressure.
That is, the recording medium P that has been transferred along the transport path 34 and has passed the transfer region 32 between the image carrier 12 and the transfer device 20 and has the toner image transferred thereon is further transported by a transport roller (not shown). When the installation position of the fixing device 26 is reached along 34, the toner image on the recording medium P is fixed. The recording medium P on which the toner image is fixed, that is, on which an image is formed, is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance rollers (not shown).

  A removal device 22 and a charge removal device 24 are disposed downstream of the transfer region 32 in the rotational direction of the image carrier 12 in the rotational direction of the image carrier 12 (in the direction of arrow A in FIG. 1).

  The removing device 22 removes deposits such as toner and paper dust remaining on the image carrier 12. Examples of the removing device 22 include a configuration having a plate-like member that contacts the image carrier 12 at a linear pressure of 10 g / cm or more and 150 g / cm or less. The static eliminator 24 removes residual charges on the image carrier 12.

  The image carrier 12 having transferred the toner image onto the recording medium P is subjected to the removal of the adhering matter adhering to the surface by the removal device 22 by rotation, and then the residual charge is removed by the charge removal device 24 and charged again by the charging device 15. Is done.

  As described above, the image forming apparatus 10 forms an image on the recording medium P.

  Here, in the image forming apparatus 10, it is desirable that the carrier contained in the two-component developer does not adhere to the surface of the image carrier 12. However, a carrier may adhere to the surface of the image carrier 12. This adhesion of the carrier to the image carrier 12 is considered to be caused by the carrier moving from the developing device 18 to the image carrier 12 due to various factors. This carrier has magnetism and is simultaneously charged on the positive side. Accordingly, since the surface of the image carrier 12 is negatively charged, the carrier held on the image carrier 12 is held and bound on the image carrier 12 by electrostatic force. . In this way, when the carrier held and bound on the image carrier 12 reaches the transfer region 32 as the image carrier 12 rotates in the region developed by the developing device 18, Since a force is applied in a direction in which the apparatus 20 is pressed toward the image carrier 12, the carrier held and bound by the electrostatic force on the surface of the image carrier 12 as shown in FIG. 2A holds the image. In some cases, the surface of the body 12 was sunk and a carrier mark (see carrier mark 19C in FIG. 2) was generated.

Further, since the recording medium P is an aggregate of a plurality of fibrous members, when observed in an enlarged state, the surface is in a state of having irregularities according to the fibers (FIGS. 2A and 2). (See (B)). For this reason, in particular, as shown in FIG. 2B, the carrier held and constrained on the image carrier 12 corresponds to the recessed portion of the recording medium P (the gap between the fibers) in the transfer region 32. region in FIG. 2 (B), the compared with the case pressed against the image carrier 12 side corresponds) to the recess P _1, (the region corresponding to the fiber, and FIG. 2 (B) a convex portion of the recording medium P in, when pressed against the image carrier 12 side in corresponding to the convex portion P _2), the carrier due to the concentration of pressure tends sinking on the surface of the image carrier 12, the carrier marks is presumed likely to occur.

  Therefore, in the image forming apparatus 10 of the present embodiment, as described above, the image carrier 12 is rotated in the rotational direction downstream of the developing device 18 and the image carrier 12 is rotated in the rotational direction upstream of the transfer device 20. A magnetic force generator 40 is provided. The magnetic force generator 40 is provided at a position where magnetic force is generated toward the surface of the image carrier 12 via the recording medium P conveyed to the transfer region 32 in the image forming apparatus 10.

  As described above, the carrier has magnetism. For this reason, as shown in FIG. 3, the carrier 19 </ b> B held and bound by the electrostatic force on the surface of the image carrier 12 is a region where the magnetic force is applied by the magnetic force generator 40 by the rotation of the image carrier 12 (FIG. 3). Then, when reaching the region 42), the magnetic force generated from the magnetic force generator 40 releases the electrostatic force that has bound itself to the surface of the image carrier 12, and the magnetic force generator 40 side via the recording medium P is released. It is considered that the state is placed on the recording medium P.

Since the carrier 19B is in a state of being released from the electrostatic force that has bound the carrier 19B on the image carrier 12 as compared to the state of being restrained and restrained on the image carrier 12, recording is performed. by conveying and recording medium P of the medium P is reaching the transfer region 32, recessed portion (a region corresponding to the gap between the fibers and fibers between the fibers of the recording medium P, in FIG. 2 (B), the concave portion P ₁ Equivalent).
The carrier 19B which rests on the recording medium P by the magnetic force generator 40, (in FIG. 2 (B), the equivalent to the convex portion P ₂₎ convex portions of the recording medium P has reached the left transfer area 32 placed on the Even in this case, compared to the case where the carrier 19B held and bound by the electrostatic force on the image carrier 12 is in contact with the convex portion of the recording medium P in the transfer region 32, the carrier 19B is weakly applied on the recording medium P. since in the resting state, the position is likely to change, (in FIG. 2 (B), the equivalent to the recess P ₁₎ lower recessed portion of the potential energy from the recording medium P Ueno considered likely moved to.
Note that, depending on the type of the recording medium P, there may be a variation in the likelihood of occurrence of the estimation phenomenon, but the arithmetic average surface roughness Ra of a recording medium generally used in an electrophotographic image forming apparatus. Is considered to be approximately 50 μm ± 25 μm, and the volume average primary particle size of the carrier is also considered to be approximately 35 μm ± 10 μm. Therefore, the above phenomenon is considered to be easily estimated.
The arithmetic average surface roughness Ra of the recording medium P is a value measured using a stylus type surface roughness measuring machine (Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.). As the measurement conditions, based on JIS B0601-1994, the evaluation length Ln = 4 mm, the reference length L = 0.8 mm, and the cut-off value = 0.8 mm.

For this reason, in the transfer region 32, the probability that the carrier 19 </ b> B exists between the convex portion (the convex portion P _{2 in} FIG. 2B) on the recording medium P and the surface of the image holding body 12 in the recording medium P. Image formation in which the probability that the carrier 19B exists between the concave portion (the concave portion P _{1 in} FIG. 2B) and the surface of the image carrier 12 is not provided with the magnetic force generation device 40 of the present embodiment. It is considered to be higher than the device.

On the other hand, in the conventional image forming apparatus, the carrier 19B held on the image holding body 12 reaches the transfer area 32 while being held and restrained on the surface of the image holding body 12 by electrostatic force. The toner image is pressed from the transfer device 20 to the image carrier 12 side through the recording medium P while being held and bound by electrostatic force to such an extent that the position is not displaced on the image carrier 12. Therefore, the carrier 19B held on the convex portion (the convex portion P _{2 in} FIG. 2B) on the recording medium P on the image carrier 12 is pressed against the surface of the image carrier 12 as it is. It is considered that carrier marks are likely to occur.
However, according to the image forming apparatus 10 of the present embodiment, it is considered that the generation of carrier marks on the image carrier 12 is suppressed by the magnetic force generator 40 as described above.

  Therefore, in the image forming apparatus 10 of the present embodiment, the generation of carrier marks on the surface of the image carrier 12 is suppressed as compared with the conventional image forming apparatus that does not have the magnetic force generator 40 of the present embodiment. it is conceivable that.

  Further, in the image forming apparatus 10 of the present embodiment, the magnetic force generator 40 is located downstream of the developing device 18 in the rotation direction of the image carrier 12, upstream of the transfer device 20 in the rotation direction of the image carrier 12, and It is provided at a position where a magnetic force is generated toward the surface of the image carrier 12 via the recording medium P. For this reason, it is considered that the carrier 19B away from the surface of the image carrier 12 is released from the electrostatic force and placed on the recording medium P. Therefore, the carrier 19B held on the image carrier 12 is brushed or plate-shaped. It is considered that the operation of removing the collected carrier is unnecessary as compared with the case where the carrier is removed and collected.

  In addition, it is considered that the carrier 19B held on the image holding body 12 can also prevent the plate-like member provided on the cleaning member 22 from being damaged.

  Further, in the image forming apparatus 10 of the present embodiment, the magnetic force generator 40 is located downstream of the developing device 18 in the rotation direction of the image carrier 12, upstream of the transfer device 20 in the rotation direction of the image carrier 12, and It is provided at a position where a magnetic force is generated toward the surface of the image carrier 12 via the recording medium P. Therefore, compared with the case where the magnetic force generation device 40 is provided on the image carrier 12 side from the conveyance path 34 of the recording medium P, the magnetic force acts on the image carrier 12 at a position farther from the developing device 18. Is done. The carrier 19B held on the image holding body 12 in the area where the developing device 18 is provided is held on the surface of the image holding body 12 by electrostatic force, but this electrostatic force is considered to decrease with time. . Therefore, the magnetic force generation device 40 of the present embodiment is held on the image holding body 12 as compared with the case where the magnetic force generation device 40 is provided closer to the image holding body 12 than the conveyance path 34 of the recording medium P. It is considered that the carrier 19B can be separated from the surface of the image carrier 12 more effectively.

In the present embodiment, the case where the transfer device 20 and the magnetic force generation device 40 are configured separately has been described. However, the transfer device 20 and the magnetic force generation device 40 may be configured integrally. . In this case, the image forming apparatus 10A having the configuration shown in FIG.
Specifically, the image forming apparatus 10 </ b> A includes an image carrier 12, a charging device 15, an exposure device 16, a developing device 18, a transfer device 36, a removing device 22, a static eliminating device 24, and a fixing device 26. The image forming apparatus 10 </ b> A has the same configuration except that a transfer apparatus 36 configured integrally with these is provided instead of the transfer apparatus 20 and the magnetic force generation apparatus 40 in the image forming apparatus 10 described with reference to FIG. 1. Therefore, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The transfer device 36 presses the recording medium P toward the image carrier 12 in the transfer region 32 to transfer the toner image on the image carrier 12 to the recording medium P. The transfer device 36 transfers the toner image on the recording medium P from the transfer region 32 in the transfer device 36. It is configured to generate a magnetic force on the surface of the image carrier 12 via the recording medium P in an area where the recording medium P is not in contact with the image carrier 12 on the upstream side in the conveyance direction (the direction of arrow B in FIG. 4). ing. The transfer device 36 has a configuration in which a pressure sufficient to transfer the toner image on the image carrier 12 to the recording medium P side in the transfer region 32 is applied to the image carrier 12 through the recording medium P, and A configuration in which a magnetic force is generated toward the surface of the image carrier 12 through a region that is not in contact with the image carrier 12 in the surface of the recording medium P, upstream of the transfer region 32 in the conveyance direction of the recording medium P. do it. As the transfer device 36, for example, a cylindrical transfer device 36 having a diameter of ± 20% with respect to the diameter of the image carrier 12 is configured, and the image carrier on the surface of the recording medium P on the upstream side. 12 may be configured to generate a magnetic force that releases the electrostatic force of the carrier 19B held on the image holding body 12 toward the surface of the image holding body 12 through a non-contact area.

  As described above, the transfer device 36 (see FIG. 4) includes the transfer device 20 and the magnetic force generation device 40 shown in FIG. 1, thereby suppressing carrier marks on the surface of the image carrier 12. It can be considered that the image forming apparatus 10A can be simplified.

<Second Embodiment>
In the first embodiment, the magnetic force generating device 40 or the transfer device 36 in which the magnetic force generating device 40 and the transfer device 20 are integrally formed is not in contact with the image carrier 12 on the surface of the recording medium P. A mode in which a magnetic force is generated toward the surface of the image carrier 12 through the region has been described.

  In the present embodiment, a mode in which a magnetic force is generated from the magnetic force generator toward the surface of the image carrier 12 through a region of the recording medium P that is in contact with the image carrier 12 will be described.

  As shown in FIG. 5, an image forming apparatus 10B according to the present embodiment includes an image carrier 12, a charging device 15, an exposure device 16, a developing device 18, a transfer device 20, a magnetic force generating device 40A, a removing device 22, and a static eliminating device. 24 and a fixing device 26 are provided. In the image forming apparatus 10B, the magnetic force generator 40 in the image forming apparatus 10 described with reference to FIG. 1 is limited to a cylindrical or columnar configuration, and the position of the recording medium P contacts the image carrier 12. Since it is the same structure except providing in the position to make (press), the same code | symbol is attached | subjected to the same part and detailed description is abbreviate | omitted.

  The magnetic force generator 40A is a magnetic force generator configured in a columnar shape or a cylindrical shape. Examples of the magnetic force generator 40A include a configuration in which the magnetic force generator 40 described in the first embodiment is formed in a columnar shape or a cylindrical shape.

  The magnetic force generation device 40A is provided at a position where the recording medium P is brought into contact with the image carrier 12 on the upstream side of the transfer device 20 in the conveyance direction of the recording medium P. The force (pressing force) that causes the magnetic force generation device 40A to contact the recording medium P with the image carrier 12 is adjusted to be weaker than the force that the transfer device 20 presses the recording medium P against the image carrier 12. The adjustment of the pressure is realized by, for example, providing a position where the magnetic force generation device 40A is provided or a spring member (not shown) in the magnetic force generation device 40A and adjusting the type and size of the spring member.

  By adopting the above-described configuration of the image forming apparatus 10B, the magnetic force is generated toward the surface of the image carrier 12 through a region that is not in contact with the image carrier 12 on the surface of the recording medium P. The distance between the magnetic force generator 40A and the image carrier 12 is narrowed, and the carrier 19B held by the electrostatic force on the image carrier 12 can be efficiently transferred to the recording medium P side with a smaller magnetic force.

  Note that, on the outer surface of the image carrier 12, a position where the transfer device 20 contacts the image carrier 12 via the recording medium P, and a position where the magnetic force generator 40 </ b> A contacts the image carrier 12 via the recording medium P. May be adjusted according to the configuration of the image forming apparatus 10B. For example, the shortest distance is the minimum length in the transport direction of the recording medium P to be recorded with the image forming apparatus 10B. What is necessary is as follows.

  In this way, in the image forming apparatus 10, when the recording medium P conveyed through the conveyance path 34 reaches the position where the image holding body 12 is provided, the recording medium is recorded by the transfer device 20 and the magnetic force generation device 40 </ b> A. P is in a state of surface contact along the outer peripheral surface of the image carrier 12. Therefore, the effect that the carrier 19B held by the electrostatic force on the image holding member 12 efficiently moves to the recording medium P side with a smaller magnetic force is maintained, and the arrangement position of the magnetic force generating device 40A can be freely set. It is thought that the degree will increase.

  The form in which the magnetic force is generated toward the surface of the image carrier 12 through the region in contact with the image carrier 12 in the recording medium P is not limited to the configuration shown in FIG.

  For example, the image forming apparatus 10C illustrated in FIG.

  As shown in FIG. 6, the image forming apparatus 10 </ b> C includes an image carrier 12, a charging device 15, an exposure device 16, a developing device 18, a transfer device 20, a magnetic force generator 40 </ b> B, a removal device 22, a charge removal device 24, and a fixing device. 26 is provided. Further, the image forming apparatus 10 is provided with an annular conveyance member 47, a support member 46, a support member 49, and a support member 48.

  The image forming apparatus 10C uses the magnetic force generation device 40 in the image forming apparatus 10 described with reference to FIG. 1 as the magnetic force generation device 40B, and includes a conveyance member 47, a support member 46, a support member 49, and a support member 48. Since the configuration is the same as that of the image forming apparatus 10 except for the above, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  The conveyance member 47 is an endless belt configured in an annular shape, and a known intermediate transfer belt or conveyance belt used in an electrophotographic image forming apparatus may be used.

Inside the transport member 47, a transfer device 20, a support member 46, a support member 48, and a support member 49 are provided, and the transport member 47 is supported from the inside by these members.
The conveying member 47 is supported by these members and rotated in the circumferential direction (the direction opposite to the image holding body 12, the direction of arrow D in FIG. 6), thereby holding the recording medium P on the outer surface and conveying it. To do.

  The transfer device 20 is arranged so as to press the recording medium P held on the surface thereof against the image carrier 12 via the conveying member 47. The support member 46 continuously images toward the upstream side in the conveyance direction of the recording medium P from a position where the outer surface of the conveyance member 47 is pressed against the image carrier 12 side by the transfer device 20 via the recording medium P. It arrange | positions so that the surface of the holding body 12 may be surface-contacted. Therefore, a part of the outer surface of the conveying member 47 is in surface contact with the image carrier 12 by the transfer device 20 and the support member 46. The recording medium P conveyed to the position where the image carrier 12 is provided by the conveyance member 47 is brought into surface contact with the image carrier 12 until it passes through the transfer region 32 from the upstream side of the transfer region 32 in the conveyance direction. It becomes.

  The magnetic force generation device 40B is provided at a position where the magnetic force is generated toward the surface of the image carrier 12 through the area of the recording medium P conveyed by the conveyance member 47 that is in surface contact with the image carrier 12. ing.

  In the present embodiment, as shown in FIG. 6, the magnetic force generation device 40 </ b> B is provided inside the conveyance member 47, upstream of the transfer device 20 in the conveyance direction of the recording medium P, and from the support member 46 to the recording medium P. Is provided on the downstream side in the transport direction. Then, the magnetic force generation device 40B generates a magnetic force toward the image holding body 12 through the region in contact with the conveying member 47 and the recording medium P on the image holding body 12 at this position. Therefore, the magnetic force generated by the magnetic force generator 40B acts on the area (area 42) of the recording medium P that is in contact with the image carrier 12.

  The force (pressure) at which the recording medium P is pressed against the image carrier 12 in this area 42 is adjusted to be weaker than the force (pressure) at which the recording medium P is pressed against the image carrier 12 in the transfer area 32. Is done. This pressure adjustment may be realized by adjusting the position of the support member 46, for example.

  In this way, in the image forming apparatus 10 </ b> C, when the recording medium P transported through the transport path 34 by the transport member 47 reaches the position where the image carrier 12 is provided, the image is upstream of the transfer region 23. The surface is brought into contact with the holding body 12. Then, a magnetic force is applied to the image carrier 12 from the magnetic force generator 40 through the area of the recording medium P that is in surface contact with the image carrier 12.

  For this reason, compared with the form which produces magnetic force toward the surface of the image holding body 12 through the area | region which is not in contact with the image holding body 12 in the surface of the recording medium P, the magnetic force generator 40B and the image holding body. It is considered that the carrier 19B held by the electrostatic force on the image holding body 12 is efficiently moved to the recording medium P side with a smaller magnetic force, the distance to the recording medium 12 being narrowed.

  In the first and second embodiments, the magnetic force generator 40 (transfer device 36, magnetic force generator 40A, magnetic force generator 40B) is applied to the image carrier 12 through the recording medium P. The magnetic force may be adjusted so as to be generated at least only during a period in which the recording medium P passes through the region 42 where the magnetic force acts, or a period during which the recording medium P passes through the region 42 and a period outside the period. It may be adjusted so as to continuously generate a magnetic force. The adjustment of the generation and cancellation of the magnetic force is performed by using an electromagnet as a magnetic force generator, and is provided in the image forming apparatus 10 (image forming apparatuses 10, 10A, 10B, and 10C) and controls each part of the apparatus (not shown). To adjust the current value of the current applied to the electromagnet. Further, when the adjustment is made so that the magnetic force is generated only during the period when the recording medium P passes through the region 42 where the magnetic force acts, for example, the recording medium is arranged upstream of the region 42 in the transport direction of the recording medium P. A sensor for detecting P is provided, the sensor and the control unit are electrically connected, and while a signal indicating detection of the recording medium P is input from the sensor, the magnetic force generator 40 (the transfer device 36, The current value of the current may be adjusted so that a magnetic force is generated from the magnetic force generation device 40A and the magnetic force generation device 40B) toward the image carrier 12 via the recording medium P.

The configuration of the image carrier 12 used in each of the image forming apparatus 10, the image forming apparatus 10B, and the image forming apparatus 10C described in the first embodiment and the second embodiment is any configuration. However, the image carrier 12 having the following configuration may be used from the viewpoint of suppressing a decrease in sensitivity. Although the following image carrier 12 is desirable from the viewpoint of suppressing the decrease in sensitivity, the magnetic force generator 40 of the present embodiment, the transfer device 36 formed integrally with the magnetic force generator, or the magnetic force generator. In an image forming apparatus that does not include 40A or the magnetic force generator 40B, carrier traces are likely to occur.
However, in the image forming apparatus 10, the image forming apparatus 10 </ b> B, and the image forming apparatus 10 </ b> C described in the first embodiment and the second embodiment, the carrier 19 </ b> B held on the image holding body 12 is used as the image. Before the carrier 19B held by the holding body 12 reaches the transfer area 32, recording is performed by separating from the surface of the image holding body 12 by the magnetic force generator 40 (magnetic force generator 40, magnetic force generator 40A, magnetic force generator 40B). Since it is placed on the medium P side, it is considered that carrier traces are suppressed even when the image carrier 12 having the following configuration is used.

  As the image carrier 12, a known charge transport layer and charge generation layer may be used.

  Hereinafter, the image forming apparatus of the present embodiment will be specifically described with reference to examples, but the present invention is not limited to these examples. Further, unless otherwise specified, “part” represents “part by mass” and “%” represents “mass%”.

-Adjustment of image carrier-
(Image carrier 1)
First, an undercoat layer, a charge generation layer, and a charge transport layer were stacked in this order on an aluminum (Al) substrate by the procedure described below.

  20 parts by mass of a zirconium compound (trade name: Organotix ZC540 manufactured by Matsumoto Pharmaceutical Co., Ltd.), 2.5 parts by mass of a silane compound (trade name: A1100 manufactured by Nihon Unicar Co., Ltd.), a polyvinyl butyral resin (trade name: S-REC BM- manufactured by Sekisui Chemical Co., Ltd.) S) A solution obtained by stirring and mixing 10 parts by weight and 45 parts by weight of butanol was applied to the surface of an Al substrate having an outer diameter of 84 mm and dried by heating at 150 ° C. for 10 minutes, whereby the layer thickness was 1.0 μm. A layer was formed.

Next, a mixture obtained by mixing 1 part by mass of chlorogallium phthalocyanine as a charge generation material with 1 part by mass of polyvinyl butyral (trade name: S-REC BM-S manufactured by Sekisui Chemical Co., Ltd.) and 100 parts by mass of n-butyl acetate. Dispersion with a glass bead with a paint shaker for 1 hour gave a dispersion for forming a charge generation layer.
This dispersion was applied on the undercoat layer by the dipping method and then dried at 100 ° C. for 10 minutes to form a charge generation layer having a layer thickness of 0.15 μm.

  Next, 2 parts by mass of a compound represented by the following structural formula (1) and 3 parts by mass of a polymer compound (viscosity average molecular weight: 39000) represented by the following structural formula (2) are used as chlorobenzene 20 A coating solution for forming a charge transport layer was obtained by dissolving in part by mass.

  This coating solution is applied onto the charge generation layer by an immersion method, heated at 110 ° C. for 40 minutes to form a charge transport layer having a layer thickness of 20 μm, and an undercoat layer, a charge generation layer, and a charge are formed on the Al substrate. A laminated body (hereinafter referred to as “non-coated image carrier”) in which the transport layer was stacked in this order was obtained.

Next, a protective layer was formed on the surface of the adjusted non-coated image carrier.
First, a second layer was formed on the surface of the non-coated image carrier.
The formation of the second layer on the surface of the non-coated image holding member was performed using a film forming apparatus having the configuration shown in FIGS. 7A and 7B.
First, the non-coated image carrier 12A is placed on the substrate support member 130 in the film forming chamber 100 of the film forming apparatus, and the inside of the film forming chamber 10 is evacuated through the exhaust port 110 until the pressure becomes 0.1 Pa. did.
Next, He diluted 20% oxygen gas (20 sccm), He gas (100 sccm), and H ₂ gas (500 sccm) are introduced from the gas introduction tube 200 into the high-frequency discharge tube section 210 provided with the electrode 190 having a diameter of 50 mm. Then, a radio wave of 13.56 MHz was set to an output of 100 W by a high frequency power supply unit 180 and a matching circuit (not shown in FIG. 7), matching was performed with a tuner, and discharge from the electrode 190 was performed. The reflected wave at this time was 0 W.

  Next, trimethylgallium gas (3 sccm) was introduced from the shower nozzle 160 into the plasma diffusion unit 170 in the film formation chamber 100 through the gas introduction pipe 150. At this time, the reaction pressure in the film forming chamber 100 measured with a Baratron vacuum gauge was 40 Pa.

  In this state, a film was formed for 120 minutes while rotating the non-coated image carrier 12A at a speed of 100 rpm, and a second layer having a thickness of 3.5 μm was formed on the surface of the charge transport layer of the non-coated image carrier.

Next, a first layer was formed on the second layer.
As the formation of the first layer, first, the high frequency discharge was stopped, the flow rate of He diluted 20% oxygen gas was changed to 1 sccm, and then high frequency discharge was started again.
In this state, the non-coated image carrier on which the second layer was formed was formed for 30 minutes while rotating at a speed of 100 rpm, and a first layer having a layer thickness of 0.3 μm was formed on the second layer.

As described above, an image carrier (image carrier with a protective layer) having the second layer and the first layer in this order as protective layers on the charge transport layer of the non-coated image carrier was obtained.
Note that when the protective layers (second layer and first layer) were formed, the non-coated image carrier was not subjected to heat treatment. In addition, in order to monitor the temperature at the time of film formation, the color of the temperature measurement sticker (manufactured by Wahl, Temp Plate P / N101) previously attached to the surface of the non-coated image carrier before film formation is It was 45 degreeC when it confirmed after film-forming of the 1st layer.

-Analysis and evaluation of the first layer-
A sample film for analysis was formed on a Si substrate having a thickness of 300 μm under the same conditions as those for forming the first layer. As a substrate on which the sample film for analysis was formed, a Si wafer having a thickness of 400 μm cut into 5 mm × 10 mm was used. About the formed 1st layer (sample film | membrane), the composition of the film | membrane was measured using Rutherford back scattering (RBS) and hydrogen forward scattering (HFS). The atomic ratio [O / Ga] and the hydrogen content (ratio of the number of H atoms to the total number of atoms of Ga, O, and H; atomic%) were 1.20.

-Analysis and evaluation of the second layer-
The second layer was analyzed and evaluated in the same manner as the analysis and evaluation of the first layer.
The atomic ratio [O / Ga] and the hydrogen content (ratio of the atomic number of H to the total atomic number of Ga, O, and H; atomic%) are 1.50, and oxygen relative to gallium from the first layer. The atomic ratio of was large.

(Image carrier 2)
In the image carrier 1, the flow rate of He diluted 20% oxygen gas is changed to 2 sccm in the formation of the first layer, and the flow rate of He diluted 20% oxygen gas is changed to 1 sccm in the formation of the second layer. An image carrier 2 with a protective layer was produced in the same manner as the image carrier 1 except that the filming time was changed to 180 minutes, and the same analysis as the image carrier 1 with a protective layer was performed. The results of the analysis are shown in Table 1 below.
The second layer (analytical sample film) formed on the quartz substrate was colored brown, and the transmittance at 780 nm was 50%.

(Image carrier 3)
In the prepared image carrier 1, the “non-coated image carrier” in a state before providing a protective layer (a laminate in which an undercoat layer, a charge generation layer, and a charge transport layer are stacked in this order on an Al base) Was prepared as an image carrier 3.

-Adjustment of magnetic force generator-
As a magnetic force generator, Hitachi Metals' NEOMAX (neodymium magnet) was prepared.

-Adjustment of two-component developer-
As the two-component developer, a developer for DocuCentre Color 5540 made by Fuji Xerox Co., Ltd. comprising toner and carrier was prepared. The volume average primary particle size of the carrier contained in this two-component developer was 35 μm.

-recoding media-
As a recording medium used for evaluation, copy paper L paper manufactured by Fuji Xerox Co., Ltd. was prepared.

  The arithmetic average surface roughness Ra of this recording medium was measured and found to be 42 μm. The arithmetic average surface roughness Ra was measured using a stylus type surface roughness measuring machine (Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.). As the measurement conditions, based on JIS B0601-1994, the evaluation length Ln = 4 mm, the reference length L = 0.8 mm, and the cutoff value = 0.8 mm.

Example 1
The image carrier 1 with the protective layer was attached to DocuPrint 505 manufactured by Fuji Xerox Co., Ltd. as an image carrier. In addition, as shown in FIG. 1, the magnetic force generator is arranged on the upstream side in the rotation direction of the image carrier from the transfer device and on the downstream side in the rotation direction of the image carrier from the developing device. In a non-contact state, it was attached to a position where a magnetic force was generated toward the image carrier through the recording medium. At this time, the shortest distance between the recording medium (recording medium conveyance path) and the neodymium magnet of the magnetic force generator was 1.5 mm.
When a magnetic force is generated from the installed magnetic force generator toward the image carrier via a recording medium, the maximum value of the magnetic force applied to the surface of the image carrier is measured by GM-5307. As a result, it was 480 mT.

<Evaluation>
Next, carrier marks on the image carrier were evaluated under the following conditions.
・ Environment: 28 ℃, 80% RH
Process speed: 173 mm / sec. Peripheral speed ratio between developer carrier and photosensitive drum: 1.03: 1
-Distance between developer carrier and photosensitive drum: 200 μm
-Potential of photosensitive drum: Vh = -420V, Vl = -100V
・ Development bias: Voltage obtained by superimposing an AC voltage of 1.8 kVp-p2.1 kHz on DC-300 V. Transfer material: urethane foam. Transfer member diameter: 20 mm.
A pressing pressure at which the transfer member presses the recording medium against the image carrier: 0.2 N / cm
・ Magnetic force generator

Under the above-mentioned conditions, an image forming test was performed in which 20,000 sheets of 10% halftone images were continuously formed on the recording medium, and the area on the surface of the image carrier after the image forming test through which the recording medium passed The number of carrier marks was examined for each of the (paper passing portion) and the area that did not pass (non-paper passing portion). Of the scratches generated on the image carrier, those observed as isolated spots with an average diameter of 2 μm or more were recognized as “carrier marks”.
Then, for each of any 10 points on the surface of the image carrier "per 1 mm ^2, less than 5 [mu] m the number of carriers mark size", per "1 mm ^2, less than 5 [mu] m 10 [mu] m size of carrier scars Each of “number” and “the number of carrier traces of 10 μm or more and less than 15 μm per 1 mm ² ” was obtained, and the average value of 10 points measured for the number of carrier traces in each size range was obtained. The measurement results are shown in Table 1.

(Example 2)
An image forming test was performed under the same conditions as in Example 1 except that the image carrier 2 was used instead of the image carrier 1 used in Example 1, and the carrier marks were evaluated by the same evaluation method as in Example 1. went. The evaluation results are shown in Table 1.

(Example 3)
An image forming test was performed under the same conditions as in Example 1 except that the image carrier 3 was used instead of the image carrier 1 used in Example 1, and the carrier marks were evaluated by the same evaluation method as in Example 1. went. The evaluation results are shown in Table 1.

(Example 4) The image carrier 1 with a protective layer was attached to DocuCentre f900 manufactured by Fuji Xerox Co., Ltd. as an image carrier. Further, the DocuCentre f900 manufactured by Fuji Xerox Co., Ltd. was modified to an image forming apparatus having the configuration shown in FIG.
Specifically, an annular member (belt) was prepared and supported from the inside by a plurality of cylindrical support members and a transfer device. The annular member is pressed against the surface of the image carrier by the transfer device, and the cylindrical support member causes the outer surface of the tubular member to come into contact with the outer surface of the image carrier by the transfer device. Then, one of the plurality of support members was arranged so as to make surface contact along the outer surface of the image carrier 1 up to a distance of 45 mm toward the upstream side in the rotation direction of the image carrier 1. Other support members were arranged at positions where they were supported from the inside so that the conveying member would not bend.

Then, as shown in FIG. 6, the magnetic force generator is arranged on the inner side of the conveying member (corresponding to the conveying member 47 in FIG. 6) on the upstream side in the rotational direction of the image carrier from the transfer device. The magnetic recording medium is provided at a position where the magnetic force is generated toward the image carrier through the area where the recording medium is in contact with the image carrier on the downstream side in the rotation direction. At this time, the shortest distance between the recording medium (recording medium conveyance path) and the neodymium magnet of the magnetic force generator was 2 mm.
When a magnetic force is generated from the installed magnetic force generator toward the image carrier through the recording medium, the maximum value of the magnetic force applied to the surface of the image carrier is measured by GM-5307. As a result, it was 760 mT.

  Next, an image formation test was performed under the same conditions as in Example 1, and carrier marks were evaluated by the same evaluation method as in Example 1. The evaluation results are shown in Table 1.

(Comparative Examples 1 to 3)
For each of the above Examples 1 to 3, except that the magnetic force generator was removed, the image formation test was performed under the same conditions, and the carrier marks were evaluated by the same evaluation method. Example 3 was used. The evaluation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 4 provided with a magnetic force generation device, carrier traces on the surface of the image carrier are suppressed compared to Comparative Examples 1 to 3 that do not include the magnetic force generation device. Had been removed.
Comparative Example 1 includes both Example 1 including the image carrier 1 including the protective layer and Example 3 including the image carrier 3 having the same configuration except that the protective layer is not provided. Compared with Comparative Example 3, carrier traces were suppressed.

10, 10A, 10B, 10C Image forming device, 12 Image carrier, 15 Charging device, 16 Exposure device, 18 Developing device, 20 Transfer device, 26 Fixing device, 40, 40A, 40B Magnetic force generator, 1 Substrate, 2 Photosensitive Layer, 3, 53, 63 Protective layer

Claims (3)

An image carrier,
A charging device for charging the image carrier;
A latent image forming device that forms an electrostatic latent image on the image carrier charged by the charging device;
A developing device for developing the electrostatic latent image formed on the image carrier with a two-component developer containing toner and a carrier;
A transfer device for transferring to a recording medium the toner image formed on the image carrier by the pre-Symbol developing device,
Wherein at the downstream side in the rotational direction of the image carrier from the developing device, and the provided upstream in the rotational direction of the image carrier from the transfer device, the magnetic force generated toward the image carrier via the recording medium A magnetic force generator for generating a magnetic force for releasing the electrostatic force of the carrier held on the image carrier by development ;
An image forming apparatus. The image carrier is
A cylindrical substrate;
A photosensitive layer provided on the substrate;
A first region which is provided on the photosensitive layer and contains oxygen and gallium and which is present on the outer side, and is present on a side closer to the substrate than the first region, and is more gallium than the first region; A protective layer having a second region with a large atomic ratio of oxygen to
The image forming apparatus according to claim 1, comprising: A contact member disposed upstream of the transfer device in the conveyance direction of the recording medium, and contacting the recording medium with the surface of the image carrier on the upstream side of the transfer device in the rotation direction of the image carrier;
Have
3. The image formation according to claim 1, wherein the magnetic force generator generates a magnetic force toward the image carrier through an area of the recording medium that is in contact with the image carrier by the contact member. apparatus.