JP2003302811A - Image forming apparatus and process cartridge - Google Patents

Abstract

(57) Abstract: A contact part using conductive particles is used as a charging part for uniformly charging an image carrier to a predetermined polarity and potential, and a contact portion between a charging member and the image carrier is provided. (1) To prevent lateral toner jumping in an image forming apparatus having a configuration in which conductive particles are supplied to a charging nip from a developing unit without increasing the size of the apparatus. A part of the conductive particles (m) in a charging member area corresponding to a developing width (B) of a developing means is contacted with a charging member (2) and charged outside an end of the charging member area corresponding to the developing width (B). The conductive particle guide member 8 for guiding and adhering to the member area to make the charging width A ′ of the charging member 2 wider than the developing width B is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor,
Conductive particles (charging promoting particles) as charging means for uniformly charging an image carrier such as an electrostatic recording dielectric to a predetermined polarity and potential.
The present invention relates to an image forming apparatus having a configuration in which a contact charging unit using the above is adopted, and conductive particles are supplied from a developing unit to a contact nip portion between a charging member and an image carrier.

[0002]

2. Description of the Related Art FIG. 7 shows a schematic structural model of an example of an image forming apparatus having the above structure. The image forming apparatus of this example is a copying machine or printer that uses a transfer type electrophotographic process, a reversal development type, and a cleaner.

Reference numeral 1 denotes a drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

Reference numeral 2 denotes a charging roller (a conductive elastic material or a sponge roller) as a charging member of the contact charging means, which is pressed against the photosensitive drum 1 with a predetermined pressing force. Reference numeral a denotes a charging nip portion (charging portion) which is a pressure contact portion between the charging roller 2 and the photosensitive drum 1.

Conductive particles m are applied to the outer peripheral surface of the charging roller 2 in advance, and conductive particles m are applied to the charging nip portion a.
Intervenes. The charging roller 2 is rotationally driven in the clockwise direction of the arrow to move in the charging nip portion a in a direction opposite to the surface moving direction of the photosensitive drum 1, and the surface of the charging roller 2 and the surface of the photosensitive drum 1 are made of conductive particles m. Through the sliding contact with a speed difference. In addition, the charging roller 2 has a power source S1.
Is applied with a predetermined DC charging bias.

As a result, the outer peripheral surface of the rotating photosensitive drum 1 is uniformly directly injected and charged to a potential substantially equal to the charging bias applied to the charging roller 2.

Next, the uniformly charged surface of the photosensitive drum 1 is subjected to image exposure L by an image exposure means (not shown) in the exposure section b, and the potential of the exposed section of the uniformly charged surface of the photosensitive drum 1 is attenuated. (Light potential), an electrostatic latent image corresponding to the image exposure pattern is formed on the surface of the photosensitive drum 1 due to the potential contrast with the potential of the exposed dark portion (dark potential).

3 is a magnetic one-component insulating toner (negative toner)
Is a reversal developing device. A predetermined amount of conductive particles m is externally added to and mixed in the developer T. A thin layer of the developer T containing the conductive particles m is formed and carried on the rotary developing sleeve 3a, and is conveyed to the developing section c which is a close opposing portion between the photosensitive drum 1 and the developing sleeve 3a. A predetermined developing bias is applied to the developing sleeve 3a from the power source S2.

As a result, the electrostatic latent image on the surface of the rotating photosensitive drum 1 is reversely developed with negative toner in the developing section c (toner is attached to the bright potential portion on the surface of the photosensitive drum). Further, the conductive particles m contained in the developer are also attached and supplied to the surface of the photosensitive drum 1.

Reference numeral 4 is a transfer roller as a transfer means. The photosensitive drum 1 is brought into contact with the photosensitive drum 1 with a predetermined pressing force, and rotates in the forward direction in the rotational direction of the photosensitive drum at a peripheral speed substantially equal to the rotational peripheral speed of the photosensitive drum. Reference numeral d denotes a transfer nip portion which is a pressure contact portion between the transfer roller 4 and the photosensitive drum 1. A transfer material P as a recording medium is fed to the transfer nip portion d from a paper feeding unit (not shown) at a predetermined control timing, and is nipped and conveyed in the transfer nip portion d. A predetermined transfer bias is applied to the transfer roller 4 from the power source S3.

As a result, the toner images on the surface of the photosensitive drum 1 are sequentially electrostatically transferred onto the surface of the transfer material P which is nipped and conveyed in the transfer nip portion d.

The transfer material P exiting the transfer nip portion d is separated from the surface of the rotating photosensitive drum 1 and is introduced into a fixing device (not shown) to undergo a fixing process of the transferred toner image to form an image-formed product (print). , Copy) is ejected out of the machine.

The image forming apparatus of this embodiment is cleaner-less, and is a dedicated cleaner (cleaning device) for removing a small amount of transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer.
Is not provided. The transfer residual toner on the surface of the photosensitive drum 1 after the transfer is carried to the developing portion c via the charging nip portion a as the photosensitive drum 1 continues to rotate, and the developing device 3
Therefore, cleaning (collection) is performed simultaneously with development.

Further, it is contained in the developer T of the developing device 3,
Conductive particles m attached and supplied to the surface of the photosensitive drum 1 during development
Is conductive and its charging polarity is opposite to that of the developer (toner) T, so that the transfer portion d does not substantially transfer to the transfer material P and most of the photosensitive drum With the subsequent rotation of the photosensitive drum 1 while being attached to one surface, the photosensitive drum 1 is carried to the charging nip portion a and replenished and supplied to the charging nip portion a, so that a new injection site can always be obtained. Therefore, even if the toner is accumulated on the charging roller 2, it is possible to suppress the occurrence of charging failure by supplying more conductive particles m.

A) Contact charging means using conductive particles m A contact charging means using conductive particles (charge promoting particles) m is disclosed in JP-A-10-307454.
A structure in which conductive particles are supplied from a developing means to a contact nip portion between a charging member and an image carrier is disclosed in JP-A-10-30.
No. 7455, etc., the electrophotographic photosensitive member in the electrophotographic image forming apparatus / electrostatic recording image forming apparatus is disclosed.
It is effective as a charging means for directly injecting and charging an image bearing member (member to be charged) such as an electrostatic recording dielectric material with a predetermined polarity and potential.

The conductive particles m are fine particles for the purpose of assisting charging, and are directly injected by interposing the conductive particles m in the nip portion a between the photosensitive drum 1 which is an image carrier and the charging roller 2 which is a charging member. Achieved electrification. That is, by interposing the conductive particles m in the nip portion a, friction between the charging roller 2 and the charging nip portion a of the photosensitive drum 1 is reduced by the lubrication effect (friction reducing effect) by the particles m, and the rotation of the charging roller 2 is reduced. The driving torque can be reduced and the charging roller 2 can be brought into contact with the photosensitive drum 1 with a speed difference. At the same time, the charging roller 2 can be brought into close and even contact with the photosensitive drum 1 through the conductive particles m, and the conductive particles can be made to come into contact with each other at the charging nip portion a. m
By rubbing the surface of the photosensitive drum 1 without any gap, even if a simple member such as a charging roller or a charging sponge roller is used as the charging member 2, direct charging without ozone is predominantly applied at a low applied voltage. You can Further, it is possible to carry out uniform charging without charging unevenness even in a micro area.

Direct injection charging is a charging system in which the image carrier is charged by directly injecting charge from the charging member into the image carrier, which is a member to be charged, basically without using the discharge phenomenon. Even if the voltage applied to the charging member is equal to or lower than the discharge threshold, the image carrier can be charged to a potential corresponding to the applied voltage. Since the generation of ions due to the discharge phenomenon is not accompanied, no adverse effect is caused by the discharge products.

B) Cleaner-less system (toner recycling system) In the transfer type image forming apparatus, the transfer residual developer (toner) remaining on the image carrier after transfer is removed from the surface of the image carrier by the cleaner and is discarded. Although it becomes toner, it is desirable that this waste toner does not appear from the viewpoint of environmental protection. Therefore, as in the image forming apparatus of the above-described example, the cleaner is eliminated, and the transfer residual toner on the photosensitive drum 1 after the transfer is removed from the photosensitive drum 1 by the developing device 3 by the "simultaneous development cleaning", and is collected / recovered by the developing device 3. An image forming apparatus of a cleanerless system having a device configuration to be used has also appeared.

Simultaneous development cleaning means that the toner remaining on the image carrier after transfer is developed during the subsequent steps, that is, the image carrier is continuously charged and exposed to form a latent image, and the latent image is developed. It is a method of recovering with a fog removal bias (fog removal potential difference Vback which is a potential difference between the DC voltage applied to the developing device and the surface potential of the image carrier).
According to this method, the transfer residual toner is collected by the developing device and reused after the next step, so that it is possible to eliminate the waste toner and reduce the troublesome maintenance. Further, the cleaner-less structure has a great advantage in terms of space, and the image forming apparatus can be significantly downsized.

In the toner recycling system, the transfer residual toner is not removed from the surface of the image bearing member by a dedicated cleaner as described above, but is made to reach the developing device via the charging means and is used again in the developing process. Therefore, when contact charging is used as the charging means for the image bearing member, how is it done with the insulating toner intervening in the charging nip portion that is the contact portion between the image bearing member and the contact charging member? The issue is whether to charge the image carrier. In roller charging or fur brush charging, transfer residual toner on the image bearing member is often diffused to be non-patterned, and charging by discharging a large baice is often used. In the magnetic brush charging, since the conductive magnetic particles that are powder are used as the contact charging member, there is an advantage that the magnetic brush portion of the conductive magnetic particles can flexibly contact the image carrier to charge the image carrier. The device configuration is complicated,
The harmful effect due to the dropout of the conductive magnetic particles forming the magnetic brush portion is great.

In the case of the contact charging means using the above-mentioned conductive particles m, since the conductive particles m are present in the charging nip portion a, the transfer residual toner is mixed in the charging nip portion a or the charging member is charged. Even if 2 is contaminated with toner, the charging member 2
Since it is possible to maintain the close contact property and contact resistance at the charging nip portion a with respect to the image carrier 1, even if the toner is accumulated in the charging nip portion a and the charging member 2, the conductive particles m are more than that. By supplying, it becomes possible to suppress the occurrence of charging failure.

In this type, after transfer of the image on the image carrier 1, the transfer residual toner T passes between the conductive particles m in the charging nip portion a where the charging process is performed and the image carrier 1. During the process, the charge is injected similarly to the image carrier 1 so that an appropriate charge can be held, so that the developing device 3 does not pass through when passing through the developing section region where the developing process is performed. Will be collected in. Therefore, it is possible to realize an electrophotographic process without a cleaner. That is, it can be said that it is effective for both environmental protection and miniaturization of the device.

[0023]

As in the image forming apparatus of the above example, the contact charging means using conductive particles is adopted as the charging means for uniformly charging the image carrier to a predetermined polarity and potential. As shown in FIGS. 8 and 9, an image forming apparatus having a structure in which conductive particles are supplied to a charging nip portion, which is a contact portion between a charging member and an image carrier, can be developed by a developing sleeve 3a as shown in FIGS. The width, that is, the developing width B is the width at which the conductive particles m are supplied to the charging nip portion a which is the contact portion between the charging roller 2 and the photosensitive drum 1, that is, the charging width A of the charging roller 2. That is, the charging width A = developing width B.

Here, in a system in which the charging width A cannot be made sufficiently wider than the image width C, the problem of toner scattering at the edges as described below has occurred. According to the study by the present inventors, the charging width A on the photosensitive drum 1 cannot be set sufficiently wider than the image width C, and the end position of the charging width A and the image width C are not measured.
When the difference width ΔX of the end position of the toner is small, the toner on the developing sleeve 3a is apparently exposed at the potential 0V, which is the end region of the photosensitive drum outside the end of the charging width A, and the charge disappears. It has been found that the photosensitive drum uncharged portion α in the same state as described above jumps over the area of the difference width ΔX and adheres in flight. Ts is the toner that horizontally spreads and adheres to the uncharged portion α of the photosensitive drum due to this toner horizontal spreading phenomenon.

The laterally skipped toner Ts is a margin portion β of the transfer material P when the transfer material P having the maximum paper passing width D is passed.
(Marginal stain Ts' is generated on the transfer material P by being transferred to the difference width portion between the end position of the maximum sheet passing width D and the end position of the image width C).

It is effective to make ΔX large in order to avoid the toner lateral skip, but it is difficult to make ΔX large in consideration of downsizing of the printer body.

Therefore, in the present invention, the image carrier is set to have a predetermined polarity.
A contact charging means using conductive particles is adopted as the charging means for uniformly charging the electric potential, and the developing means supplies the conductive particles to the charging nip portion which is the contact portion between the charging member and the image carrier. It is an object of the present invention to prevent the above-described toner lateral jump in the image forming apparatus without increasing the size of the apparatus.

[0028]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus and process cartridge characterized by the following configurations.

(1) An image carrier, a charging member for forming a nip with the image carrier, and a charging means for charging the image carrier by interposing conductive particles in at least the nip portion; Image information writing means for forming an electrostatic latent image on the charged surface of the image carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, and the toner image Transfer means for transferring to the transfer member, and the conductive particles contained in the developer adhere to the surface of the image carrier when the electrostatic latent image is developed by the developing means, and the nip portion In the image forming apparatus in which conductive particles are supplied to the nip portion by being carried to the nip portion, a part of the conductive particles in the charging member area corresponding to the developing width of the developing unit is brought into contact with the charging member. Corresponds to the development width An image forming apparatus wherein a conductive particle guide member charging width of the charging member than the end of the member area deposited by induction to the outside of the charging member area wider than the developing width is arranged.

(2) A charging device which has an image carrier and a charging member which forms a nip with the image carrier, and charges the image carrier by interposing conductive particles having conductivity in at least the nip portion. Means, image information writing means for forming an electrostatic latent image on the charged surface of the image carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, A transfer unit that transfers the toner image to the transfer target member, and also serves as a cleaning unit that recovers the toner remaining on the image carrier after the developing unit transfers the toner image to the transfer target member. Cage,
The image carrier is repeatedly used for image formation, and the conductive particles contained in the developer adhere to the surface of the image carrier when the electrostatic latent image is developed by the developing unit. In an image forming apparatus in which conductive particles are supplied to the nip portion by being carried to the nip portion,
By contacting the charging member, a part of the conductive particles in the charging member region corresponding to the developing width of the developing unit is guided to the charging member region outside the end portion of the charging member region corresponding to the developing width. An image forming apparatus, characterized in that a conductive particle guide member is disposed to make the charging width of the charging member wider than the developing width.

(3) The guide member is provided from the inside of the charging member region corresponding to the developing width at the end of the charging member to the charging member region outside the end of the region. The image forming apparatus according to (1) or (2).

(4) The guide member is characterized in that its entire length is longer than the developing width and is in contact with the charging member region corresponding to the developing width and the charging member region outside the end of the region. The image forming apparatus according to (1) or (2).

(5) The image forming apparatus according to any one of (1) to (4), wherein the charging member is a flexible member and a voltage is applied.

(6) The image forming apparatus according to any one of (1) to (5), wherein a speed difference is provided between the surface of the charging member and the surface of the image carrier.

(7) The image according to any one of (1) to (6), wherein the surface of the charging member and the surface of the image carrier move in opposite directions in the nip portion. Forming equipment.

(8) The image forming apparatus according to any one of (1) to (7), wherein the charging member is a charging roller.

(9) The particle resistance of the conductive particles is 10 ¹²
Ω · cm or less (8) to (6)
The image forming apparatus according to any one of 1.

(10) The particle size of the conductive particles is 50 μm.
The image forming apparatus according to any one of (1) to (9), characterized in that:

(11) Volume resistance of the surface layer of the image bearing member
Is 1 × 10⁹ Ω · cm or more 1 × 10 ¹⁴Ω · cm or less
Any one of (1) to (10) characterized in that
The image forming apparatus described.

(12) The image forming apparatus described in any one of (1) to (11), wherein the image carrier is a photoconductor.

(13) The image forming apparatus described in any one of (1) to (12), wherein the image information writing means is an image exposure means.

(14) It is described in any one of (1) to (13) that at least the image carrier and the charging member are collectively made into a process cartridge which is detachable from the main body of the image forming apparatus. Image forming device.

(15) An image carrier, a charging member for forming a nip with the image carrier, and a charging means for charging the image carrier by interposing conductive particles in at least the nip portion; Image information writing means for forming an electrostatic latent image on the charged surface of the image carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, and the toner image Transfer means for transferring to the transfer member, and the conductive particles contained in the developer adhere to the surface of the image carrier when the electrostatic latent image is developed by the developing means, and the nip portion A process cartridge that is detachably attached to the main body of the image forming apparatus in which the conductive particles are supplied to the nip portion by being carried to the nip portion, and at least the image carrier and the charging member are integrally formed into a cartridge. A part of the conductive particles in the charging member area corresponding to the developing width of the developing means is in contact with the charging member, and the charging member outside the end of the charging member area corresponding to the developing width. A process cartridge characterized in that a conductive particle guide member for guiding and adhering to a region to make the charging width of the charging member wider than the developing width is arranged.

(16) Charging for charging the image carrier with an image carrier and a charging member forming a nip with the image carrier, with conductive particles having conductivity interposed in at least the nip portion. Means, image information writing means for forming an electrostatic latent image on the charged surface of the image carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, A transfer unit that transfers the toner image to the transfer target member, and also serves as a cleaning unit that recovers the toner remaining on the image carrier after the developing unit transfers the toner image to the transfer target member. The image carrier is repeatedly used for image formation, and the conductive particles contained in the developer adhere to the surface of the image carrier when the electrostatic latent image is developed by the developing unit. The nip part A process cartridge detachably mountable to an apparatus main body of an image forming apparatus in which conductive particles are supplied to the nip portion by being carried, and at least the image carrier and the charging member are integrally formed into a cartridge. A part of the conductive particles in the charging member area corresponding to the developing width of the developing means is brought into contact with the charging member to the charging member area outside the end of the charging member area corresponding to the developing width. A process cartridge, wherein a conductive particle guide member for guiding and adhering the charging member to make the charging width of the charging member wider than the developing width is arranged.

<Operation> That is, by the conductive particle guide member, a part of the conductive particles in the charging member area corresponding to the developing width of the developing means is located outside the end of the charging member area corresponding to the developing width. Since the charging width of the charging member can be made larger than the developing width by being guided and attached to the charging member region, ΔX described in FIGS. 8 and 9 can be sufficiently taken. That is, it is possible to avoid the toner laterally skipping phenomenon and eliminate the toner stains in which the laterally jumping toner is transferred to the end portion of the transfer target member.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> (FIGS. 1 to 3) FIG. 1 is a schematic structural model view of an example of an image forming apparatus according to the present invention.

(1) Overall Description of Image Forming Apparatus The image forming apparatus of the present embodiment employs contact charging means using conductive particles as charging means for the photosensitive drum as an image carrier, and the charging nip portion is charged. This is a laser beam printer of a transfer type, an electrophotographic process type, a reversal developing type, and a cleanerless, which is configured to supply the conductive particles from a developing device.

The same components, members, and parts as those of the image forming apparatus shown in FIG. 7 are designated by the same reference numerals, and a duplicate description will be omitted.

In the printer of this embodiment, the electrophotographic photosensitive drum 1 as an image bearing member is driven at a predetermined peripheral speed (process speed) in the clockwise direction of the arrow by a driving means (not shown).
It is driven to rotate.

[Charging] The charging roller 2 as a contact charging member is formed by forming a medium resistance layer 2b of rubber or foam as a flexible member on the core metal 2a. The medium resistance layer 2b was formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfiding agent, a foaming agent, etc., and was formed in a roller shape on the cored bar 2a. After that, the surface was polished as needed to prepare a charging roller 2 which is a conductive elastic roller.

Here, it is important that the charging roller 2 which is a conductive elastic roller functions as an electrode. That is, it is necessary to impart elasticity to obtain a sufficient contact state with the photosensitive drum 1 and at the same time have a resistance sufficiently low to charge the moving photosensitive drum 1. On the other hand, it is necessary to prevent voltage leakage when there is a defective portion such as a pinhole on the photosensitive drum 1. In order to obtain sufficient chargeability and leak resistance, the resistance of the charging roller 2 is preferably in the range of 10 ⁴ to 10 ⁷ Ω.

If the hardness of the charging roller 2 is too low, the shape of the charging roller 2 is not stable, so that the contactability with the photosensitive drum 1 deteriorates. If the hardness is too high, the charging nip portion a cannot be secured between the charging roller 2 and the photosensitive drum 1. However, since the microscopic contact property to the surface of the photosensitive drum is deteriorated, the Asker C hardness is preferably in the range of 25 to 50 degrees.

The material of the charging roller 2 is not limited to the elastic foam, but the material of the elastic body is EP.
Examples thereof include DM, urethane, NBR, silicone rubber, rubber materials in which a conductive material such as carbon black or metal oxide is dispersed in IR or the like for resistance adjustment, and those obtained by foaming these materials. It is also possible to adjust the resistance by using an ion conductive material without particularly dispersing the conductive substance.

The outer peripheral surface of the charging roller 2 is coated with conductive particles m in advance. The charging roller 2 is pressed against the photosensitive drum 1 against elasticity with a predetermined pressing force to form a charging nip portion a having a predetermined width. The charging roller 2 is rotationally driven to give a speed difference to the surface of the photosensitive drum 1. In this example, the rotation direction of the charging roller 2 is the charging nip portion a with respect to the rotation direction of the photosensitive drum 1.
In the counter direction, it is rotated at a peripheral speed difference of 150%.

The core metal 2a of the charging roller 2 is applied with a DC voltage of -720 V from the charging bias applying power source S1 as a charging bias. In this example, the conductive particles m are present in the charging nip portion a as described above,
The surface of the photosensitive drum 1 is uniformly charged by the direct injection charging method to −700 V (dark potential Vd) which is almost equal to the voltage applied to the charging roller 2.

[Exposure] 5 is a laser beam scanner (exposure device) including a laser diode, a polygon mirror, etc. as image exposure means. This laser beam scanner outputs a laser beam whose intensity is modulated corresponding to a time-series electric digital pixel signal of target image information, and scans and exposes the uniformly charged surface of the rotary photosensitive drum 1 with the laser beam.
To do. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotary photosensitive drum 1. The surface potential of the photosensitive drum 1 when the laser beam is uniformly irradiated on the photosensitive drum 1 is set to −100 V (bright potential VL).

[Current image] The electrostatic latent image on the surface of the rotary photosensitive drum 1 is developed as a toner image by the developing device 3. The developing device 3 of this example is a reversal developing device using a magnetic one-component insulating toner (negative toner) as the developer T. A predetermined amount of conductive particles m is externally added to and mixed in the developer T.

The toner as the developer T is prepared by mixing the binder resin, the magnetic particles and the charge control agent, and kneading, pulverizing and classifying the toner. To this, conductive particles m and a fluidizing agent are added as external additives. In this example, the toner base is made of styrene resin, and 2 parts of silica as an external additive for promoting the charging of the toner with respect to the toner base, conductive particles m, a particle resistance of 10 ⁶ Ω · cm, and a secondary coagulation are used. Two parts of conductive zinc oxide particles having an average particle diameter of 3 μm including the aggregate are externally added.

Reference numeral 3a is a non-magnetic rotary developing sleeve as a developer carrying / conveying member having a magnet roll 3b contained therein. The developing sleeve 3a is formed by applying a coating agent on an aluminum tube and providing an appropriate roughness. The developing sleeve 3a is arranged to face the photosensitive drum 1 with a gap of 100 to 300 μm. It is driven by a gear (not shown) of the drum 1 and rotates in the forward direction with respect to the rotation direction of the photosensitive drum 1. The rotation developing sleeve 3a is attached to the regulating blade 3
The developer T containing the conductive particles m is coated in a thin layer with c (plate-shaped urethane rubber or the like). The layer thickness of the developer T with respect to the rotary developing sleeve 3a is regulated by the regulation blade 3c, and an electric charge is applied. The developer coated on the rotary developing sleeve 3a is conveyed to the developing section (developing area section) c which is the opposing section of the photosensitive drum 1 and the developing sleeve 3a by the rotation of the developing sleeve 3a. Further, the developing sleeve 3a
A developing bias voltage is applied to the developing bias applying power source S2. The developing bias voltage is a superposed voltage of an AC voltage of about 1.2 kV and a DC voltage of -400V. As a result, the electrostatic latent image on the photosensitive drum 1 side is reversely developed with the toner.

Here, as the material of the conductive particles m, various conductive particles such as conductive inorganic particles such as other metal oxides or a mixture with organic substances can be used. In order to obtain uniform chargeability, the particle diameter of the conductive particles m is preferably 50 μm or less, more preferably 10 μm or less. It seems that the lower limit of the particle size is 10 nm as a particle that can be stably obtained. The particle resistance preferably less 10 ¹² Ω · cm as a specific resistance for exchanging charges through the particles, more or less is desirable 10 ¹⁰ [Omega] cm. There is no problem that the conductive particles m exist not only in the state of primary particles but also in the state of agglomeration of secondary particles.

[Transfer] The transfer roller 4 is a roller having a medium resistance, and the transfer material P as a transfer target member (recording medium, recording material) is supplied to the transfer nip portion d from the paper feeding portion 7 at a predetermined control timing. By applying a predetermined transfer bias voltage to the transfer roller 4 from the transfer bias applying power source S3, the toner images on the photosensitive drum 1 side are sequentially transferred to the surface of the transfer material P fed to the transfer nip portion d. Will be transferred to.
That is, the transfer material P introduced into the transfer nip portion d is nipped and conveyed through the transfer nip portion d, and the toner images formed and carried on the surface of the rotary photosensitive drum 1 are sequentially pressed by the electrostatic force with the transfer nip portion d. Transferred by pressure.

[Fixing] 6 is a fixing device such as a heat fixing system. The transfer material P, which has been fed to the transfer nip portion d and has undergone the transfer of the toner image on the photosensitive drum 1 side, is separated from the surface of the rotating photosensitive drum 1 and is introduced into the fixing device 6, where it is subjected to the toner image fixing. It is ejected outside the apparatus as an image-formed product (print, copy).

The printer of this example is cleanerless, and the transfer residual toner remaining on the surface of the rotating photosensitive drum 1 after the toner image is transferred onto the transfer material P is not removed by the cleaner, and is charged as the photosensitive drum 1 rotates. The toner reaches the developing portion c via the nip portion a and is simultaneously cleaned (collected) during development in the developing device 3 (toner recycling process).

(2) Supply of Conductive Particles m from Developing Device 3 to Photosensitive Drum 1 The conductive particles m contained in the developer T of the developing device 3 are electrostatic latent particles on the photosensitive drum 1 side by the developing device 3. At the time of toner development of the image, an appropriate amount is transferred to the photosensitive drum 1 side.

This will be specifically described with reference to FIG. Vm
ax · Vmin is the maximum potential and the minimum potential of the developing AC component,
In this example, they are -1000V and + 200V, respectively. ,
Vd · VL is the dark potential (non-image portion) and the bright potential (image portion) of the electrostatic latent image, and in this example, −700 V and −1, respectively.
It is 00V. Vdc is a developing DC potential, which is −400V in this example. Since the conductive particles m tend to be weakly positive as an external additive, the conductive particles m alone are used for the developing sleeve 3a with respect to the non-image portion (dark potential Vd portion) of the electrostatic latent image on the surface of the photosensitive drum 1. From photosensitive drum 1 to 900V (| Vmin-Vd | = | 200- (170
It flies with a contrast of 0) |).

In addition, the conductive particles m may be attached to the toner T, and thus the image portion (bright potential VL portion) of the electrostatic latent image.
In contrast, 900 V (| VL-Vmax | = | -100-(-10
It flies with a contrast of 00) |).

That is, the conductive particles m contained in the developer T of the developing device 3 fly to the photosensitive drum 1 side during the toner development of the electrostatic latent image on the photosensitive drum 1 side by the developing device 3. Transition.

The toner image on the photosensitive drum 1 is attracted to the transfer material P side due to the effect of the transfer bias in the transfer nip portion d and positively transferred, but the conductive particles m on the photosensitive drum 1 are transferred.
Is positive, it is not positively transferred to the transfer material P side, and is substantially attached and retained on the photosensitive drum 1 and remains. Further, the presence of the conductive particles m substantially attached and held on the surface of the photosensitive drum 1 also has an effect of improving the transfer efficiency of the toner image from the photosensitive drum 1 side to the transfer material P side.

Since the image forming apparatus in the toner recycling process does not use a cleaner, the transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer and the above-mentioned residual conductive particles m are charged to the photosensitive drum 1 as a contact charging member. The photosensitive drum 1 is directly carried to the charging nip portion a of the roller 2 by the rotation of the photosensitive drum 1. Most of the conductive particles m carried to the charging nip portion a are stripped off by the charging roller 2 which rotates in the counter direction with respect to the photosensitive drum 1, whereby the conductive particles m are applied onto the charging roller 2. I can do things. In this way, even if the conductive particles m initially applied to the charging roller 2 decrease due to an increase in the number of sheets passed, the conductive particles m are transferred from the developing device 3 through the photosensitive drum 1 to the charging roller 2 Direct injection charging is realized by being supplied to.

Due to the presence of the conductive particles m in the charging nip portion a, even when toner adheres to or mixes with the charging roller 2, the close contact property and the contact resistance of the charging roller 2 to the photosensitive drum 1 can be maintained. The contact charging member is a simple member such as a charging roller, and the charging roller 2 is not affected by contamination by transfer residual toner on the charging roller.
The direct injection charging of the photosensitive drum 1 can be performed. That is, the charging roller 2 comes into close contact with the photoconductor through the conductive particles m, and the conductive particles m existing in the nip portion between the charging roller 2 and the photosensitive drum 1 rub the surface of the photosensitive drum 1 without any gap. As a result, the charging of the photosensitive drum 1 by the charging roller 2 is dominated by stable and safe direct injection charging that does not use the discharge phenomenon due to the presence of the conductive particles m, and high charging efficiency that cannot be obtained by conventional roller charging or the like. Therefore, a potential almost equal to the voltage applied to the charging roller 2 can be applied to the photosensitive drum 1.

The transfer residual toner adhering to and mixed with the charging roller 2 is gradually discharged from the charging roller 2 onto the photosensitive drum 1 and reaches the developing section c with the movement of the surface of the photosensitive drum 1, and the developing device 3 simultaneously cleans the development. (Recovered) (Toner recycling process). As described above, the simultaneous cleaning with development is performed by developing the latent image by developing the latent image by continuously charging the photosensitive member with the toner remaining on the photosensitive drum 1 after the transfer in the subsequent image forming process, that is, by exposing the photoreceptor. At this time, it is recovered by the fog removing bias of the developing device, that is, the fog removing potential difference Vback which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor. In the case of reversal development as in the printer of the present embodiment, this simultaneous development cleaning involves an electric field for collecting toner from the dark potential portion of the photoconductor to the developing sleeve and adhesion of toner from the developing sleeve to the bright potential portion of the photoconductor. It is done by the action of an electric field.

Further, even if the conductive particles m fall off from the charging roller 2, the developing device 3 can be operated by operating the printer.
The conductive particles m contained in the developer T of FIG. 2 are transferred to the surface of the photosensitive drum 1 at the developing portion a, and are carried to the charging nip portion a via the transfer nip portion d by the rotation of the photosensitive drum 1 and are charged to the charging roller 2 To be continuously supplied to the conductive particles m
The good chargeability due to the presence of is stably maintained.

Thus, in the image forming apparatus of the contact charging system, the transfer system and the toner recycling process, the charging roller is used as the contact charging member, and the applied voltage is low regardless of the contamination of the charging roller 2 due to the transfer residual toner. Ozone-less direct injection Charge can be maintained stably for a long period of time, uniform chargeability can be given, and there is no trouble due to ozone products or trouble due to poor charging, simple structure, low-cost image formation. The device can be obtained.

(3) Expansion of charging width A by conductive particle guide member In FIGS. 1 and 3, 8 and 8 are conductive particle guide members, and in this embodiment, both ends of the charging roller 2 are developed. From the charging roller region corresponding to the width B to the region outside the end of the region and the charging roller 2
With respect to each of the conductive particle guide members 8 and 8 which are arranged so as to abut in the counter direction with respect to the rotation of, the contact surface with the charging roller 2 is cut obliquely, and the photosensitive drum 1 from the developing device 3 is removed. Conductive particles m that are carried and replenished to the charging nip portion a via the charging nip portion a, adhere to the charging roller 2 from the surface of the photosensitive drum 1 and are conveyed as the charging roller 2 rotates.
Scrape off a part of each of the
That is, it is guided in the direction of arrow e to the area outside the end of the charging roller area corresponding to the developing width B. At this time,
The conductive particles m not scraped off by the guide member 8.8 remain on the charging roller as they are and are used in the charging process.
Insufficient charging does not occur in the portion of the photosensitive drum corresponding to the contact portion.

As described above, the abutting position of the guide member 8 on the charging roller 2 is arranged at the end portion on the charging roller 2 across the position corresponding to the end portion of the developing width B. , Conductive particles m within the developing width B on the charging roller 2
Is guided to the charging roller area surface outside the end of the developing width B and adheres to the charging roller area surface so that the charging nip portion a intervenes. As a result, the charging width of the charging roller 2 is developed. The width A'is wider than the width B. That is, as described above, the charging width A of the charging roller 2 in the case where the guide member 8 is not provided is the same as the developing width B, whereas the charging roller 2 in the case where the guide member 8 is provided is used.
The charging width of A is expanded to A'which is wider than the developing width B.

As a result, the difference width ΔX ′ between the end position of the charging width A ′ after the width expansion and the end position of the image width C is determined by the difference width ΔX ′ between the end position of the charging width A before the width expansion and the end of the image width C. It is possible to make the difference width ΔX of the partial position sufficiently larger, and it is possible to prevent the lateral toner skipping phenomenon and eliminate the toner smear that the laterally skipped toner is transferred to the end portion of the transfer material P.

If the conductive particles m on the charging roller 2 can be guided outside the developing width B, the conductive particle guide member 8
Of course, the contact surface of 8 does not necessarily have to be cut obliquely.

Further, the contact direction of the conductive particle guide members 8 and 8 with the charging roller 2 is not limited to the counter direction, and of course the contact direction of the charging roller may be provided as long as the same effect can be obtained.

<Second Embodiment> (FIG. 4) In this embodiment, in the printer of the first embodiment described above, the conductive particle guide member 8 is arranged so that the total length is smaller than the developing width B as shown in FIG. Is also a long member, and is disposed in contact with the charging roller region corresponding to the developing width B and the charging roller region outside the end portion of the region. That is, the present embodiment is characterized in that the conductive particle guide member 8 is brought into contact with the charging roller 2 over the entire length and the total length of the conductive particle guide member 8 is longer than the developing width B. The other printer configuration is the same as the printer configuration of the first embodiment, and therefore the repetitive description will be omitted.

Also in this embodiment, the contact surface of the conductive particle guide member 8 scrapes off a part of the conductive particles m conveyed as the charging roller 2 rotates, and the charging roller 2 is rotated.
Is guided to the end side (direction of arrow e in the figure). At this time, the conductive particles that have not been scraped off by the conductive particle guide member 8 remain on the charging roller as they are and are used in the charging step, and therefore correspond to the contact portion of the conductive particle guide member 8 of the charging roller. Insufficient charging does not occur at the photosensitive drum position. Further, since the entire length of the contact surface of the conductive particle guide member 8 is longer than the developing width B, the conductive particles m are guided to the outside of the developing width B at the end portion of the charging roller 2. Therefore, since the charging width can be expanded like A'to be larger than the developing width B, the difference width ΔX 'between the end position of the charging width A'and the end position of the image width C after the width expansion.
However, it is possible to make it sufficiently larger than the difference width ΔX between the end position of the charging width A and the end position of the image width C before the width expansion, so that the toner lateral skipping phenomenon is prevented and the laterally skipping toner is transferred. It is possible to eliminate toner stains transferred to the end portion of the material P.

Even if the conductive particle guide member 8 is abutted over the entire length for a length not less than the developing width B and only the abutting surfaces at both ends are obliquely cut as in the first embodiment, the developing width can be increased. B
Needless to say, the conductive particles m can be guided further outward.

<Third Embodiment> (FIG. 5) In this embodiment, the printer of the first or second embodiment is of a process cartridge mounting / demounting type. In this embodiment, as shown in FIG. 5, the photosensitive drum 1, the charging roller 2 on which the conductive particle guide member 8 is arranged, and the developing device 3 are integrated with each other by an exterior, and are integrated with the printer main body. Integrated cartridge 10 that can be replaced together
There is. Reference numeral 11 denotes a process cartridge attachment / detachment guide / holding member on the printer body side.

In the case of this integral type cartridge 10, when the toner T stored in the developing device 3 is used up, other devices are designed to reach the end of their lives almost at the same time. Therefore, the user can obtain a stable image at all times while the toner in the cartridge 10 is present, and since it is an integrated type, there is an advantage that the replacement can be easily performed. Then, on the charging roller 2 in the cartridge 10,
By providing the conductive particle guide member 8 of the present invention, in addition to the original advantage of the integral type cartridge, the advantage that the laterally skipped toner Ts is not caused to fly is added.

Here, the process cartridge is a cartridge in which the charging means, the developing means or the cleaning means and the electrophotographic photosensitive member are integrally formed, and the cartridge can be attached to and detached from the main body of the image forming apparatus.
Also, at least one of the charging means, the developing means, and the cleaning means and the electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. Further, it means that at least the developing means and the electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus.

<Others> 1) It is desirable that the image bearing member has a surface layer having a surface resistance of 10 ⁹ to 10 ¹⁴ Ω · cm in order to perform stable direct injection charging.

FIG. 6 is a schematic diagram of the layer structure of a photoreceptor having a charge injection layer on the surface. That is, the photoconductor 1 is generally formed by coating an aluminum drum substrate (Al drum substrate) 1a on a subbing layer 1b, a positive charge injection preventing layer 1c, a charge generation layer 1d, and a charge transport layer 1e in this order. The charging performance is improved by applying the charge injection layer 1f to such an organic photoreceptor.

The charge injection layer 1f is composed of a photo-curing acrylic resin as a binder and conductive particles (conductive filler).
Of SnO ₂ ultrafine particles as a particle (diameter is about 0.03μ
m) A lubricant such as a tetrafluoroethylene resin (trade name Teflon), a polymerization initiator and the like are mixed and dispersed, and after coating, a film is formed by a photo-curing method.

The important points of the charge injection layer 1f are the resistance and surface energy of the surface layer. In the charging method based on the direct injection of electric charges, the electric charges can be transferred more efficiently by lowering the resistance on the photoconductor side. On the other hand, since it is necessary to hold the electrostatic latent image for a certain time, the charge injection layer 1f
Volume resistance of 1 × 10 ⁹ to 1 × 10 ¹⁴ (Ω · c
The range of m) is suitable.

In addition, the surface energy of the photoconductor is reduced by including the lubricant in the charge injection layer 1f. Therefore, the toner easily moves to the transfer material, and the paper dust does not easily adhere to the photoconductor, so that the contact charging member is less contaminated by the toner and the paper dust, and the charging ability of the charging roller is maintained for a long time. Further, since the frictional force between the conductive particles and the photoconductor is reduced, abrasion of the photoconductor is significantly reduced.

Even when the charge injection layer 1f is not used,
For example, the same effect can be obtained when the charge transport layer 1e is in the above resistance range. Surface volume resistance is about 10 ¹³ Ω ・ c
The same effect can be obtained with an amorphous silicon photoconductor having m.

2) As the flexible contact charging member 2, in addition to the charging roller, a fur brush, felt, cloth or the like having a shape and material can be used. Moreover, more appropriate elasticity, conductivity, surface property, and durability can be obtained by combining various materials.

3) The charging bias applied to the charging member may include an alternating voltage component (AC component, voltage whose voltage value changes periodically). As the waveform of the alternating voltage component, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. It may be a rectangular wave formed by periodically turning on / off the DC power supply.

4) In the case of the image forming apparatus, the image exposing means as the information writing means for the charged surface of the photoconductor as the image bearing member is not limited to the laser scanning means of the embodiment, but may be solid light emitting such as LED. It may be a digital exposure means using an element array. It may be an analog image exposure means using a halogen lamp, a fluorescent lamp or the like as a document illumination light source. In short, what is necessary is just to form an electrostatic latent image corresponding to image information.

5) The image carrier may be an electrostatic recording dielectric or the like. In this case, after uniformly charging the dielectric surface,
The charged surface is selectively neutralized by a neutralizing means such as a neutralizing needle head or an electron gun to write and form an electrostatic latent image corresponding to target image information.

6) The toner developing method / means for the electrostatic latent image is arbitrary. The regular development method or the reversal development method may be used.

Generally, in the method of developing an electrostatic latent image, a non-magnetic toner is coated with a blade or the like on a developer carrying member such as a sleeve, and a magnetic toner is coated with the developer carrying member. A method of coating an electrostatic latent image on the image bearing member in a non-contact state by coating it with a magnetic force and developing it (one-component non-contact developing);
A method of developing an electrostatic latent image by applying the toner coated on the developer carrying member as described above to the image carrier (one-component contact development), and a carrier magnetic to the toner particles. And a method of developing an electrostatic latent image by applying a mixture of the above as a developer (two-component developer) by magnetic force and applying it in contact with an image carrier (two-component contact development); The two-component developer is applied to the image carrier in a non-contact state to develop an electrostatic latent image (two-component non-contact development).

7) Although the image forming apparatus of the embodiment is a cleanerless apparatus, the image forming apparatus is equipped with a dedicated cleaning device for collecting and removing transfer residual toner from the surface of the image carrier after transfer. May be Also in this case,
Since the conductive particles supplied from the developing device to the image bearing member are fine, the transfer residual toner is captured by the cleaning device, but the conductive particles easily pass through the cleaning blade of the cleaning device and are carried to the charging nip portion. It is carried and supplied to the charging member.

8) The transfer means is not limited to the roller transfer of the embodiment, but may be a blade transfer, a belt transfer or any other contact transfer charging method, or a contact transfer charging method using a corona charger. .

9) The present invention can be applied not only to the formation of a single color image using an intermediate transfer member such as a transfer drum or a transfer belt, but also to an image forming apparatus for forming a multicolor or full color image by multiple transfer or the like.

[0101]

As described above in detail, according to the present invention, the contact charging means using conductive particles is adopted as the charging means for uniformly charging the image carrier to a predetermined polarity and potential, and the charging member is It is possible to prevent lateral toner skipping in an image forming apparatus configured to supply the conductive particles to the charging nip portion, which is a contact portion between the image carrier and the image carrier, without increasing the size of the apparatus. It is possible to eliminate the toner stain transferred to the end of the transfer target member.

[Brief description of drawings]

FIG. 1 is a schematic configuration model diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating transfer of conductive particles from a developing device to a photosensitive drum.

FIG. 3 is an explanatory diagram of charging width expansion by a conductive particle guide member.

FIG. 4 is an explanatory view of charging width extension by a conductive particle guide member in the image forming apparatus of the second embodiment.

FIG. 5 is a schematic configuration model diagram of an image forming apparatus according to a second embodiment.

FIG. 6 is a layer structure model diagram of a photoconductor provided with a charge injection layer.

FIG. 7 is a schematic configuration model diagram of an image forming apparatus that employs contact charging means using conductive particles.

FIG. 8 is an explanatory diagram of a toner laterally skipping phenomenon (No. 1)

FIG. 9 is an explanatory diagram of a toner laterally skipping phenomenon (No. 2)

[Explanation of symbols]

1 ... Image carrier, 2 charging roller, 3 developing device, 4 transfer roller, 5 optical scanner, 6 fixing device, 8 conductive particle guide member, S1 to S3 ...
High voltage power source, P ... Transfer material, m ... Conductive particles (charge promoting particles), T ... Developer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/18 G03G 15/08 507B 2H200 (72) Inventor Hiroyuki Ohba 3-30-2 Shimomaruko, Ota-ku, Tokyo No. Canon Inc. (72) Inventor Junichi Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasushi Shimizu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. In-house F-term (reference) 2H005 AA08 CB07 DA09 EA01 2H035 CA07 CB01 2H068 AA05 AA08 CA37 2H077 AA37 AD00 AD06 DB12 DB14 2H171 FA02 FA09 FA11 FA17 FA28 GA03 GA29 JA23 JA27 WA23 WA23 WA21 WA23 WA23 WA23 WA23 Q23 QB23QC23 QB03 QB32 Q23 QB03 Q23 QB03 QC23 FA08 FA16 GA23 GB14 GB37 HA03 HA29 HB12 HB17 HB23 HB46 HB47 MB04 MC16 NA01 PA11

Claims (16)

[Claims] 1. An image carrier, a charging member that forms a nip with the image carrier, and a charging unit that charges the image carrier by interposing conductive particles in at least the nip portion, and the image. Image information writing means for forming an electrostatic latent image on the charged surface of the carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, and the toner image to be transferred. Transfer means for transferring to the member, and the conductive particles contained in the developer adhere to the surface of the image carrier during the development of the electrostatic latent image by the developing means and adhere to the nip portion. In an image forming apparatus in which conductive particles are supplied to the nip portion by being carried, a part of the conductive particles in the charging member area corresponding to the developing width of the developing unit is brought into contact with the charging member. Charge corresponding to development width An image forming apparatus, characterized in that a conductive particle guide member is arranged which guides and adheres to a charging member region outside the end of the member region to make the charging width of the charging member wider than the developing width. 2. A charging unit that has an image carrier and a charging member that forms a nip with the image carrier, and charges the image carrier by interposing conductive particles having conductivity in at least the nip portion. An image information writing unit that forms an electrostatic latent image on the charged surface of the image carrier; a developing unit that visualizes the electrostatic latent image as a toner image with a developer containing toner and conductive particles; A transfer unit that transfers the image to the transfer target member, and also serves as a cleaning unit that recovers the toner remaining on the image carrier after the developing unit transfers the toner image to the transfer target member. , The image carrier is repeatedly subjected to image formation, and the conductive particles contained in the developer adhere to the surface of the image carrier during the development of the electrostatic latent image by the developing means. Hold in the nip In an image forming apparatus in which conductive particles are supplied to the nip portion by being carried, a part of the conductive particles in the charging member area corresponding to the developing width of the developing unit is developed by contacting the charging member. A conductive particle guide member for guiding and adhering to the charging member region outside the end of the charging member region corresponding to the width to make the charging width of the charging member wider than the developing width. Image forming apparatus. 3. The guide member is provided from the charging member region corresponding to the developing width at the end of the charging member to the charging member region outside the end of the region. The image forming apparatus according to claim 1. 4. The guide member has a total length longer than a developing width and is in contact with a charging member region corresponding to the developing width and a charging member region outside an end portion of the region. The image forming apparatus according to Item 1 or 2. 5. The image forming apparatus according to claim 1, wherein the charging member is a flexible member and a voltage is applied. 6. The speed difference is provided between the surface of the charging member and the surface of the image carrier.
The image forming apparatus according to any one of 1. 7. The image forming apparatus according to claim 1, wherein the surface of the charging member and the surface of the image carrier move in opposite directions in the nip portion. 8. The image forming apparatus according to claim 1, wherein the charging member is a charging roller. 9. The particle resistance of the conductive particles is 10 ¹² Ω.multidot.
The image forming apparatus according to claim 8, wherein the image forming apparatus has a size of not more than cm. 10. The image forming apparatus according to claim 1, wherein the charge promoting particles have a particle size of 50 μm or less. 11. The volume resistance of the surface layer of the image carrier is 1
The image forming apparatus according to any one of claims 1 to 10, wherein the image forming apparatus has a density of not less than × 10 ⁹ Ω · cm and not more than 1 × 10 ¹⁴ Ω · cm. 12. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor. 13. The image information writing means is an image exposure means, according to any one of claims 1 to 12.
The image forming apparatus described in 1. 14. The process cartridge, wherein at least the image bearing member and the charging member are collectively attached to and detachable from the image forming apparatus main body.
The image forming apparatus according to any one of 1. 15. An image carrier, a charging member that forms a nip with the image carrier, and a charging unit that charges the image carrier by interposing conductive particles in at least the nip portion, and the image. Image information writing means for forming an electrostatic latent image on the charged surface of the carrier, developing means for visualizing the electrostatic latent image as a toner image with a developer containing toner and conductive particles, and the toner image to be transferred. Transfer means for transferring to the member, and the conductive particles contained in the developer adhere to the surface of the image carrier during the development of the electrostatic latent image by the developing means and adhere to the nip portion. A process cartridge detachably mountable to an apparatus main body of an image forming apparatus in which conductive particles are supplied to the nip portion by being carried, and at least the image carrier and the charging member are integrally formed into a cartridge. A part of the conductive particles in the charging member area corresponding to the developing width of the developing means is in contact with the charging member, and the charging member area outside the end of the charging member area corresponding to the developing width. A process cartridge characterized in that a conductive particle guide member for guiding and adhering to the charging member to make the charging width of the charging member wider than the developing width is arranged. 16. A charging unit that has an image carrier and a charging member that forms a nip with the image carrier, and that charges the image carrier by interposing conductive particles having conductivity in at least the nip portion. An image information writing unit that forms an electrostatic latent image on the charged surface of the image carrier; a developing unit that visualizes the electrostatic latent image as a toner image with a developer containing toner and conductive particles; A transfer unit that transfers the image to the transfer target member, and also serves as a cleaning unit that recovers the toner remaining on the image carrier after the developing unit transfers the toner image to the transfer target member. , The image carrier is repeatedly subjected to image formation, and the conductive particles contained in the developer adhere to the surface of the image carrier during the development of the electrostatic latent image by the developing means. On the nip A process cartridge detachably mountable to the main body of an image forming apparatus in which conductive particles are supplied to the nip portion by being carried, and at least the image carrier and the charging member are integrally formed into a cartridge. And contacting the charging member to guide a part of the conductive particles in the charging member region corresponding to the developing width of the developing means to the charging member region outside the end of the charging member region corresponding to the developing width. And a conductive particle guide member for making the charging width of the charging member wider than the developing width.