JP3387815B2 - Charging device and image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for a body to be charged. More specifically, the present invention relates to a contact charging type charging method and a charging device in which a voltage is applied and a flexible charging member that forms a nip portion with a charged body charges a surface of the charged body.

Further, the present invention relates to an image forming apparatus provided with the charging device as a charging processing means for an image carrier.

[0003]

2. Description of the Related Art Conventionally, for example, an electrophotographic apparatus (copier,
In an image forming apparatus such as a printer) or an electrostatic recording device, an image carrier (charged member) such as an electrophotographic photoreceptor or an electrostatic recording dielectric is uniformly charged to a required polarity and potential (static elimination processing). A corona charger (corona discharger) was often used as a charging device.

The corona charger is a non-contact type charging device, which is provided with a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and the discharge opening is opposed to an image carrier, which is a member to be charged. The surface of the image carrier is charged in a predetermined manner by exposing the surface of the image carrier to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode.

Recently, image forming apparatuses of medium and low speed models have advantages such as low ozone and low power as a charging device for a charged member such as an image bearing member as compared with a corona charger. Many contact charging devices have been proposed and put into practical use.

The contact charging device is a conductive charging member (contact charging member / contact charger) of a roller type (charging roller), a fur brush type, a magnetic brush type, a blade type, etc. ) Is contacted and a predetermined charging bias is applied to the contact charging member to charge the surface of the body to be charged to a predetermined polarity and potential.

Charging mechanism of contact charging (charging mechanism,
In the charging principle), two types of charging mechanisms, a discharge charging mechanism and a direct injection charging mechanism, coexist, and each characteristic appears depending on which one is dominant.

[0008] Discharge Charging Mechanism This is a mechanism in which the surface of the charged body is co-charged by the discharge phenomenon that occurs in the minute gap between the contact charging member and the charged body.

Since the discharge charging mechanism has a constant discharge threshold between the contact charging member and the member to be charged, it is necessary to apply a voltage higher than the charging potential to the contact charging member. Further, compared with a corona charger, the generation amount is remarkably small, but generation of a discharge product is unavoidable in principle, so that a harmful effect due to active ions such as ozone is unavoidable.

[0010]. Direct injection charging mechanism In this system, the surface of the body to be charged is charged by directly injecting charge from the contact charging member into the body to be charged. It is also called direct charging, injection charging, or charge injection charging. More specifically, a medium-resistance contact charging member comes into contact with the surface of the member to be charged and directly injects the charge into the surface of the member to be charged without a discharge phenomenon, that is, basically without using discharge. Therefore, even if the applied voltage to the contact charging member is equal to or lower than the discharge threshold value, the charged body can be charged to a potential corresponding to the applied voltage.

Since this charging system does not generate ions, no harm is caused by discharge products. However, since it is the direct injection charging, the contact property of the contact charging member to the member to be charged greatly affects the charging property. Therefore, it is necessary to make the contact charging member more dense, have a large speed difference from the charged body, and contact the charged body more frequently.

A) Roller charging In the contact charging device, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable from the viewpoint of stability of charging and is widely used.

The charging mechanism of this roller charging is dominated by the discharge charging mechanism.

The charging roller is made of a conductive or medium-resistance rubber material or foam. Further, there is also one in which these are laminated to obtain desired characteristics.

The charging roller has elasticity in order to obtain a constant contact state with an object to be charged (hereinafter referred to as a photoconductor). Therefore, the friction roller has a large friction resistance, and in many cases, the photoconductor is driven by or follows the photoconductor. It is driven with a slight speed difference. Therefore, even if an attempt is made to directly inject and charge, it is inevitable that the absolute charging ability is deteriorated, contact is insufficient, roller-shaped unevenness and charging unevenness due to adhered matter on the photoconductor are unavoidable. The charging mechanism is dominant.

FIG. 9 is a graph showing an example of charging efficiency in contact charging. The horizontal axis represents the bias applied to the contact charging member, and the vertical axis represents the charging potential of the photoconductor obtained at that time. The charging characteristic in the case of roller charging is represented by A. That is, charging starts after the discharge threshold of about -500V is exceeded. Therefore, when charged to -500V, it is -10
Apply DC voltage of 00V or -500V
In addition to the DC charging voltage, a method is generally applied in which an AC voltage having a peak-to-peak voltage of 1200 V is applied so as to always have a potential difference equal to or higher than a discharge threshold value and the photoreceptor potential is converged to the charging potential.

More specifically, when the charging roller is brought into pressure contact with the OPC photosensitive member having a thickness of 25 μm, the surface potential of the photosensitive member rises when a voltage of about 640 V or more is applied. Starts and then slopes 1 to applied voltage
The surface potential of the photoconductor increases linearly with. This threshold voltage is defined as the charging start voltage Vth.

That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, Vd + Vth is applied to the charging roller.
More DC voltage is needed than is needed. A method of charging only by applying a DC voltage to the contact charging member in this way is called a "DC charging method".

However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations and the Vth fluctuates when the film thickness changes due to abrasion of the photoconductor, so that the potential of the photoconductor is desired. It was difficult to make it a value.

Therefore, as disclosed in Japanese Patent Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more in order to further uniformize the charging. An "AC charging method" is used in which a voltage on which an AC component is superimposed is applied to a contact charging member. This is for the purpose of leveling the potential by AC, and the potential of the body to be charged is V which is the center of the peak of the AC voltage.
It converges on d and is not affected by disturbances such as the environment.

However, even in such a contact charging device, since the essential charging mechanism uses the discharge phenomenon from the contact charging member to the photosensitive member, it is applied to the contact charging member as described above. The voltage is required to have a value equal to or higher than the surface potential of the photoconductor, and a small amount of ozone is generated.

When AC charging is performed to make the charging uniform, further ozone is generated, vibration noise (AC charging sound) between the contact charging member and the photoconductor due to the electric field of the AC voltage, and discharge are generated. Deterioration of the surface of the photoconductor has become remarkable, which has been a new problem.

B) Fur brush charging For fur brush charging, a member (fur brush charger) having a brush portion of conductive fiber is used as a contact charging member,
The conductive fiber brush portion is brought into contact with a photoconductor as a member to be charged, and a predetermined charging bias is applied to charge the surface of the photoconductor to a predetermined polarity and potential.

Also in this fur brush charging, the discharge charging mechanism is dominant as the charging mechanism.

As the fur brush charger, a fixed type and a roll type have been put into practical use. The fixed type is made by folding a medium resistance fiber into a base cloth and forming it into a pile and adhering it to the electrode. The roll type is formed by winding the pile around a core metal. A fiber density of about 100 fibers / mm ² can be obtained relatively easily, but the contact property is still insufficient for sufficiently uniform charging by direct injection charging.
In order to carry out sufficiently uniform charging by direct injection charging, it is necessary to give a speed difference to the photoconductor such that it is difficult for the mechanical constitution, which is not realistic.

The charging characteristics of this fur brush charging when a DC voltage is applied have the characteristics shown in FIG. 9B. Therefore, also in the case of the fur brush charging, in both the fixed type and the roll type, charging is performed by applying a high charging bias and using discharge development.

C) Magnetic Brush Charging For magnetic brush charging, a member (magnetic brush charger) having a magnetic brush portion formed into a brush shape by magnetically restraining conductive magnetic particles with a magnet roll or the like is used as a contact charging member. The magnetic brush portion is brought into contact with a photoconductor as a member to be charged and a predetermined charging bias is applied to charge the surface of the photoconductor to a predetermined polarity and potential.

In the case of this magnetic brush charging, the direct injection charging mechanism is dominant as the charging mechanism.

By using conductive magnetic particles having a particle size of 5 to 50 μm as the magnetic brush portion and providing a sufficient speed difference from the photosensitive member, uniform direct injection charging is possible.

As indicated by C in the charging characteristic graph of FIG.
It is possible to obtain a charging potential almost proportional to the applied bias.

However, there are other problems such as a complicated structure of the device, and the conductive magnetic particles forming the magnetic brush portion are dropped and adhered to the photoconductor.

Japanese Unexamined Patent Publication No. 6-3921 proposes a method of injecting charge into a charge holding member such as a trap level on the surface of a photoreceptor or conductive particles of a charge injection layer to perform contact injection charging. . Since the discharge phenomenon is not used, the voltage required for charging is only the desired surface potential of the photoconductor, and ozone is not generated. Furthermore, since no AC voltage is applied, no charging noise is generated, and compared to the roller charging method, the charging method is ozoneless and has low power consumption.

D) Toner Recycle Process (Cleanerless System) In a transfer type image forming apparatus, transfer residual toner remaining on the photoconductor (image carrier) after transfer is removed from the photoconductor surface by a cleaner (cleaning device). It becomes waste toner, but it is desirable that this waste toner does not appear in terms of environmental protection. Therefore, the image forming apparatus of the toner recycling process is configured so that the cleaner is eliminated, and the transfer residual toner on the photoconductor after transfer is removed from the photoconductor by "developing simultaneous cleaning" by the developing device and collected and reused in the developing device. Has also appeared.

Simultaneous development cleaning means that the toner remaining on the photoconductor after transfer is fogged at the time of development of the next step and thereafter, that is, the photoconductor is continuously charged and exposed to form a latent image, and the latent image is developed. This is a method of collecting with a take-off bias (fog-removing potential difference Vback, which is a potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor). 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.

E) Powder coating for contact charging member In the contact charging device, in order to prevent uneven charging and to perform stable and uniform charging, the contact charging member is coated with powder on the contact surface with the surface to be charged. As disclosed in JP-A 7-99442, the contact charging member (charging roller) is driven to rotate (no speed difference drive) following the member to be charged (photosensitive member), and ozone is generated compared to a corona charger such as a scorotron. although the generation of an object is made much less, the charging principle is mainly have a discharge charging mechanism as still as in the above-described roller charging. Particularly, in order to obtain more stable charging uniformity, a voltage in which an AC voltage is superimposed on a DC voltage is applied, so that the ozone products are more generated by the discharge. Therefore, if you use the device for a long time,
When a cleanerless image forming apparatus is used for a long period of time, adverse effects such as image deletion due to ozone products are likely to appear.

Further, in Japanese Patent Application Laid-Open No. 5-150539, in an image forming method using contact charging, charging inhibition is caused by toner particles or silica fine particles adhering to the surface of a charging means during repeated image formation for a long time. In order to prevent the above, it is disclosed that the developer contains at least developer particles and conductive particles having an average particle size smaller than the developer particles. However, this contact charging is due to the discharge charging mechanism, not the direct injection charging mechanism, and there is the above-mentioned problem due to the discharge charging.

[0037]

As described in the above-mentioned prior art, it is difficult to carry out direct injection charging in contact charging with a simple structure using a charging roller or a fur brush as a contact charging member. In an image forming apparatus, image fogging (a white background portion is developed in the case of reversal development), uneven charging, and the like occur due to absolute charging failure.

In the contact charging device configuration in which powder is applied to the contact surface of the contact charging member with the surface to be charged and the contact charging member is driven and the discharge charging mechanism is mainly used, when the device is used for a long period of time or a cleaner is used. When an image forming apparatus without a printer is used for a long period of time, image deletion easily occurs due to accumulation of ozone products.

In the cleanerless image forming apparatus, the transfer residual toner causes charging failure in the charging section.

In the contact charging, the contact between the member to be charged and the charging member needs to be sufficiently performed, so that there are the following problems related to the contact.

A) When a fur brush (charging brush) is used as the contact charging member, the bristle tips of the charging brush are divided as shown in FIG. Can not be charged.
In FIG. 9, 1 is a member to be charged (photosensitive member), 2 is a charging brush, 2a is an electrode part of the charging brush, 2b is a fur brush part of conductive fiber, and S1 is a charging bias application power source.

B) When a magnetic brush is used as the contact charging member, if the charged magnetic particles are made smaller in order to improve the contact property, there is a drawback that the magnetic particles adhere to the surface of the body to be charged. If the magnetic force is increased to give a sufficient magnetic binding force, the chance of contact between the magnetic particles and the body to be charged is reduced, and the injection charging ability is reduced.

C) A method of mixing auxiliary conductive magnetic fine particles into the charging member in order to improve the contact property has also been devised, but the magnetic fine particles adhere to the member to be charged and are consumed in the long term. It has been pointed out that the charging property is lowered.

Therefore, an object of the present invention is to improve the uniformity of charging by improving the problem of insufficient contact between the member to be charged and the charging member in contact charging. Further, regardless of the performance of the contact charging member, that is, even when a simple member such as a fur brush or a charging roller is used as the contact charging member, it is possible to realize stable direct injection charging with excellent charging uniformity and for a long period of time. That is, an object is to realize ozone-less direct injection charging with a low applied voltage with a simple configuration.

Another object of the present invention is to provide an image forming apparatus having a simple structure and low cost, which is free from obstacles due to ozone products and faults due to poor charging.

[0046]

The present invention SUMMARY OF THE INVENTION is characterized by the following configurations is a static-device and an image forming apparatus.

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] (1) voltage is applied, be a charging device you inject band photoelectrically be charged member surface through the nip by the fiber brush-like charging member or elastic charging member to form a member to be charged and the nip , The surface of the charging member moves with a speed difference with respect to the surface of the body to be charged, and at least the conductive particles are provided in the nip portion, and the conductive particles have a particle resistance of 1 × 10 ¹⁰ (Ω · cm) or less.
The charging device is characterized by comprising particles having a particle diameter of 20 nm to 5 μm, and charging the charged body in a state where 10 ^{2 to} 5 × 10 ⁵ particles / mm ² are present in the nip portion.

[0056]

[0057]

[0058]

(2) The volume resistance of the outermost surface layer of the body to be charged is 1 × 10 ¹⁴ (Ω · cm) or less.
The charging device according to (1) .

(3) The charging device according to (1) or (2) , which has a means for supplying the conductive particles.

[0061]

[0062]

(4) The charging device according to any one of (1) to (3) , wherein the charging member rotates in the opposite direction to the body to be charged in the nip portion. (5) An image forming apparatus for performing image formation by applying an image forming process including a step of charging the image carrier to the image carrier, wherein the step means for charging the image carrier is from (1).
An image forming apparatus comprising the charging device according to any one of (4) .

(6) Image carrier, charging means for charging the image carrier, image writing means for forming an electrostatic latent image on the charged surface of the image carrier, and visualization of the electrostatic latent image with toner An image forming unit having a developing unit for transferring the toner image to a recording medium, and a cleaning unit for collecting the toner remaining on the image carrier after the developing unit transfers the toner image to the recording medium. An image forming apparatus, wherein the charging unit is the charging device according to any one of (1) to (4) .

(7) The image forming apparatus according to (6) , wherein the image writing unit is an image exposing unit.

[0066]

(8) The image bearing member is a photoconductor, and the volume resistance of the outermost surface layer of the photoconductor is 1 × 10 ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω · cm) or less. Characterized by
The image forming apparatus according to any one of (5) to (7) .

<Operation> That is, according to the present invention, 10 conductive particles (hereinafter, referred to as charge promoting particles ) are provided in the nip portion between the member to be charged and the flexible contact charging member.
^The charging member is moved in a state of being present at a density of ² pieces / mm ² or more and 5 × 10 ⁵ pieces / mm ² or less , and the charging member is moved with a speed difference to the charging target to perform contact charging of the charging target. Let

Due to the presence of the charge promoting particles, the contact charging member can contact the charged object with a speed difference at the nip portion between the charged object and the contact charging member, and at the same time, contact the charged object closely through the charge promoting particles. That is, the charge accelerating particles existing in the nip portion between the contact charging member and the body to be charged rub the surface of the body to be charged without a gap, so that the charge can be directly injected into the body to be charged.

That is, in the charging of the body to be charged by the contact charging member, the problem of insufficient contact of the charging member is improved by the presence of the charging promoting particles, and the charging uniformity is dramatically improved, and direct injection charging is dominant. To be the target. Since the charging uniformity is almost determined by the existing density of the charge promoting particles, it is possible to always perform uniform charging regardless of the performance of the charging member.

Therefore, a high charging efficiency, which has not been obtained by the conventional fur brush charging or roller charging, can be obtained, and a potential almost equal to the applied voltage can be applied to the member to be charged.

Thus, even when a fur brush or the like having a relatively simple structure is used as the contact charging member, the applied bias necessary for charging the contact charging member may be a voltage corresponding to the potential required for the member to be charged. Therefore, it is possible to realize a stable and safe charging method that does not use the discharge phenomenon.

That is, in the contact charging device, even when a simple member such as a charging roller is used as the contact charging member, the direct injection charging having excellent charging uniformity and stable for a long period of time is realized, that is, low application voltage is applied. Ozone-less direct injection charging with voltage can be realized with a simple configuration.

Further, this makes it possible to obtain an image forming apparatus having a simple structure, which can be provided with a uniform charging property and which is free from obstacles due to ozone products and faults due to poor charging.

By providing the means for supplying the charge promoting particles which are the conductive particles, the charging can be stably performed even when the device is used for a long period of time.

The resistance value of the electrification promoting particles which are conductive particles is 1
X10 ¹² (Ω · cm) or less, more preferably 1 x 1
When it is 0 ¹⁰ (Ω · cm) or less, uniform and stable charging is possible in direct injection charging.

The particle size of the charge promoting particles, which are conductive particles, is 20.
When the thickness is in the range of 5 to 5 μm, it is possible to provide an apparatus capable of obtaining a good image that does not hinder the exposure in the image forming apparatus.

The outermost surface layer of the member to be charged has a volume resistance of 1 × 10.
¹⁴ (Ω · cm) or less, further, the member to be charged is an electrophotographic photosensitive member, and the volume resistance of the outermost surface layer of the electrophotographic photosensitive member is 1 × 10 ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω ・ c
By being m) or less, sufficient chargeability can be provided even in a device having a high process speed.

[0079]

DETAILED DESCRIPTION OF THE INVENTION

<Embodiment 1> (FIGS. 1 to 5) FIG. 1 is a schematic configuration model diagram of an example of an image forming apparatus including a contact charging device according to the present invention. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process and a process cartridge attachment / detachment type.

(1) Overall schematic structure 1 of the printer of this example is a rotary drum type electrophotographic photosensitive member as an image bearing member (charged member). This example is a negatively charged OP with a diameter of 30 mm.
C photoconductor, 100 mm / sec in the clockwise direction indicated by the arrow
Is rotated at the process speed (peripheral speed) of.

Reference numeral 2 denotes a roll-shaped charging brush (fur brush charger) as a flexible contact charging member which is brought into contact with the photoconductor 1, and forms a charging nip portion n having a width of 3 mm with the photoconductor 1. 500 rpm in the clockwise direction indicated by the arrow that moves in the direction opposite to the movement direction of the photoconductor 1 in the charging nip portion n.
It is driven to rotate. That is, the charging brush 2 as a contact charging member comes into contact with the photoconductor 1 with a peripheral speed difference and rubs the photoconductor 1. And -700V from the charging bias applying power source S1
The DC charging bias is applied to the outer peripheral surface of the rotating photoconductor 1 so that the outer peripheral surface of the rotating photoconductor 1 is uniformly directly charged to about -680V.

Time-series electricity of the target image information output from the laser beam scanner 2 including a laser diode, a polygon mirror, etc., to the charged surface of the rotating photosensitive member 1.
Corresponding to the digital pixel signal intensity-modulated laser beam by the scanning exposure L is performed, an electrostatic latent image corresponding to the objective image information with respect to the peripheral surface of the rotating photosensitive member 1 is formed.

In the present example, the electrostatic latent image is developed as a toner image by the reversal developing device 4 using the magnetic one-component insulating toner (negative toner) t.

Reference numeral 4a is a non-magnetic developing sleeve having a diameter of 16 mm as a developer carrying / conveying member having a magnet 4b contained therein. This developing sleeve 4a is 3
They are arranged facing each other with a separation distance of 00 μm, and are rotated at the same speed as the photoconductor 1 in the forward direction with respect to the rotation direction of the photoconductor 1 in the developing section (developing area portion) a which is a portion facing the photoconductor 1. It was

The rotary developing sleeve 4a is coated with a developer (toner) t in a thin layer by the regulating blade 4c. The layer thickness of the developer is regulated by the regulation blade 4c with respect to the rotary developing sleeve 4a, and the developer is charged. The developer coated on the rotary developing sleeve 4a is conveyed to the developing section a, which is an opposed portion of the photoconductor 1 and the sleeve 4a, by the rotation of the sleeve 4a. A developing bias voltage is applied to the sleeve 4a from a developing bias applying power source S2. The developing bias voltage is a DC voltage of -500V and a frequency of 1800H.
z and a rectangular AC voltage having a peak-to-peak voltage of 1600 V were superposed, and one-component jumping development was performed between the developing sleeve 4 a and the photoconductor 1.

The developer (toner) t is a known binder resin,
The magnetic particles and the charge control agent are mixed, and the mixture is kneaded, pulverized, and classified, and then produced. In this example, the weight average particle diameter (D4) of the toner t is 7 μm.

On the other hand, a transfer material P as a recording medium is supplied from a paper feeding section (not shown), and the rotary photosensitive member 1 and the contact transfer means abutting against the photosensitive member 1 with a predetermined pressing force have a medium resistance. It is introduced into the pressure contact nip portion (transfer portion) b with the transfer roller 5 at a predetermined timing. A predetermined transfer bias voltage is applied to the transfer roller 5 from the transfer bias applying power source S3. In this example, a transfer roller 5 having a resistance value of 5 × 10 ⁸ Ω was used, and transfer was performed by applying a DC voltage of + 2000V.

The transfer material P introduced into the transfer portion b is nipped and conveyed by the transfer portion b, and the toner images formed and carried on the surface of the rotary photosensitive member 1 are sequentially transferred to the surface side thereof by electrostatic force and pressing force. Will be transcribed.

The transfer material P to which the toner image has been transferred is separated from the surface of the photoconductor 1 and is introduced into a fixing device 6 such as a thermal fixing system to be fixed with the toner image to form an image formed product (print, copy). Is discharged outside the device.

The surface of the photosensitive member 1 after the transfer of the toner image onto the transfer material P is cleaned by the cleaning device 7 to remove adhering contaminants such as residual toner, and is repeatedly used for image formation.

Reference numeral 8 denotes a charging promoting particle coating device for the surface of the photosensitive member 1, which coats a predetermined amount of charging promoting particles (charging auxiliary particles) m on the surface of the photosensitive member 1 between the cleaning device 7 and the charging brush 2. . The charging-promoting particles m applied to the surface of the photoconductor 1 by the device 8 are carried to the charging unit n which is a nip between the photoconductor 1 and the charging brush 2 as a contact charging member as the photoconductor 1 rotates. The contact charging process of the photoconductor 1 by the charging brush 2 is performed in the state where the charging promoting particles m are present in the charging portion n.

In the printer of this example, five process devices including the photoconductor 1, the charging brush 2, the developing device 4, the cleaning device 7, and the electrification accelerating particle coating device 8 are included in the cartridge PC, and are integrated into the printer main body. It is a cartridge type device that can be detached and replaced. The combination of process equipment to be made into a process cartridge is not limited to the above, and is arbitrary. Reference numeral 9 denotes an attachment / detachment guide / holding member for the process cartridge PC. The image forming apparatus Te Contact have <br/> to the onset bright is not limited to the device of the cartridge type.

(2) Photoreceptor 1 The negatively charged OPC photoreceptor 1 of this example has the following structure on a drum base body (aluminum base body) 11 made of aluminum having a diameter of 30 mm, as shown in the layer structure model diagram of FIG. The first to fourth four functional layers 12 to 15 are provided in order from the bottom.

[0094] The first layer 12; a subbing layer, for leveling defects aluminum drum or the like, and the conductive layer having a thickness of about 20μm, which is provided for preventing the occurrence of moire due to reflection of the laser Heather EXPOSURE Is.

The second layer 13 is a positive charge injection preventing layer, which plays a role of preventing the positive charges injected from the aluminum base 11 from canceling out the negative charges charged on the surface of the photoconductor, and the amylan resin and methoxymethyl. 10 ⁶ by nylon
It is a medium resistance layer having a thickness of about 1 μm whose resistance is adjusted to about Ωcm.

[0096] The third layer 14; a charge-generating layer, the disazo pigment is a layer having a thickness of about 0.3μm dispersed in a resin, to generate a pair of positive and negative charges by receiving laser Heather EXPOSURE.

Fourth layer 15: a charge transport layer, which is a P-type semiconductor in which hydrazone is dispersed in a polycarbonate resin. Therefore, the negative charges charged on the surface of the photoconductor cannot move in this layer, and only the positive charges generated in the charge generation layer can be transported to the surface of the photoconductor.

(3) Charging Brush 2 The charging brush 2 which is a flexible member as the contact charging member used in this example is in a roll shape.

This is a tape 2b with a conductive rayon fiber REC-B made by Unitika Ltd. made into a pile and having a diameter of 6 mm.
A roll brush with an outer diameter of 14 mm, which is wound around a metal core metal 2a of mm in a spiral shape, is 300 denier / 50 filaments, 155 per square millimeter.
With the density of the book, the resistance value of the brush is 1 to 1000V applied voltage
At 1 × 10 ⁵ Ω (Metal diameter φ30 mm
(A value converted from the value of the current flowing when a voltage of 100 V was applied to the drum of No. 3 with a nip width of 3 mm).

The resistance value of the charging brush 2 prevents an image defect in which an excessive leak current flows into this portion even when a pinhole or the like is missing on the photoconductor 1 and the charging nip becomes defective in charging. Therefore, it must be 10 ⁴ Ω or more, and 10 ⁷ Ω or less in order to sufficiently inject charges into the surface of the photoconductor.

Further, as the material of the charging brush, in addition to REC-B manufactured by Unitika Ltd., REC-C, REC
-M1, REC-M10, and SA manufactured by Toray Industries, Inc.-
7. Thunderon made by Japan Silkworm Co., Ltd., Bertron made by Kanebo, Cracabo made by Kuraray Co., Ltd., carbon dispersion in rayon, Mitsubishi rayon's global etc. In terms of sex, Unitika Ltd.
REC-B, REC-C, REC-M1, REC-
M10 is preferred.

In this example, the rotation speed is 500 rpm so that the charging brush 2 moves in the direction opposite to the moving direction of the surface of the photosensitive member.
However, the number of rotations is not limited to this, and the thickness of the charging nip portion n between the charging brush 2 and the photosensitive member 1,
If the conditions such as the density of the bristles of the brush, the surface resistance of the photoconductor, and the process speed (peripheral speed of the photoconductor) change, the optimum rotation number of the charging brush also changes.

It is also possible to move in the same direction as the moving direction of the surface of the photosensitive member, but the charging property of direct injection charging depends on the ratio of the peripheral speed of the photosensitive member 1 and the peripheral speed of the charging brush 2. In order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging brush 2 in the forward direction is larger than that in the reverse direction, so it is advantageous to move the charging brush 2 in the reverse direction in terms of the rotation speed. is there.

The peripheral speed ratio described here is the peripheral speed ratio (%) = (peripheral speed of charging brush−peripheral speed of photosensitive body) / peripheral speed of photosensitive body × 100 (the peripheral speed of the charging brush is the surface of the charging member at the nip portion). Is a positive value when moving in the same direction as the photoreceptor surface).

(4) Charging Acceleration Particles m and Direct Injection Charging Direct injection charging is a medium resistance contact charging member that directly injects charges onto the surface of the photoconductor without a discharge phenomenon. Therefore, even if the applied voltage to the contact charging member is equal to or lower than the discharge threshold value, the photoconductor as the member to be charged can be charged to a potential corresponding to the applied voltage. The relationship between the applied DC voltage and the photosensitive member surface potential in this case is shown in FIG.

However, since it is necessary that the surface of the photoconductor and the charging member are sufficiently contacted with each other, when the charging brush is used as the contact charging member as described above, the bristle tips of the charging brush are as shown in FIG. As shown in the drawing, there are some areas where the surface of the photosensitive member cannot be contacted, and the surface of the photosensitive member cannot be uniformly charged.

Therefore, in this example, as shown in FIG. 1, a device 8 for coating the surface of the photosensitive member 1 as the member to be charged with the charge accelerating particles m is provided, and the charge accelerating particles m are 102 particles / mm 2 or more. By applying it, it became possible to solve the above-mentioned problem of poor contact. Charging accelerating particles coated device 8, common means for applying the powder particles, for example, by once uniformly applied to the application B <br/> over La on 8 a, be flying in a contact or an electric field on the photoreceptor It is possible to use a configuration in which coating is performed by the above method.

FIG. 4 shows a model diagram in which the contact opportunity of the charging member (in this case, the tip of the fur brush) is improved when the charging promoting particles m are present on the photoconductor.

The density of the charge-accelerating particles m applied on the photoconductor 1 to obtain the effect of uniform chargeability was determined by consideration of human visual characteristics and an experiment based on the consideration. The values are within the coating density range of the charge-accelerating particles of the present invention.

That is, although the recording resolution of the laser beam printer has been recently improved from 300 dpi to 600 dpi, it goes without saying that at the time of charging, contact charging more uniform than at least this recording resolution is required.

Regarding the visual characteristics of the human eye, as shown in the characteristic graph of FIG. 5, the spatial frequency is 10 (cycles).
/ Mm) or more, the number of identification gradations on the image approaches 1 as much as possible, that is, the density unevenness cannot be identified.

If this characteristic is positively utilized, the photosensitive member 1
When the charge accelerating particles m are attached to the upper part, the charge accelerating particles m should be present at a density of at least 10 (cycles / mm) on the photoconductor 1 and the injection charging may be performed directly based on the particles m. become.

Even if the charging failure occurs where the particles m do not exist, the density unevenness on the image caused by the charging failure occurs in the spatial frequency region beyond the visual characteristics of humans, so that there is no problem on the image. There will be no problems.

Table 1 shows the results as to whether or not defective charging as density unevenness is recognized on the image when the coating density of the charging promoting particles m is changed.

[0115]

[Table 1] The coating density of the electrification accelerating particles m was determined by observing the photoreceptor with an optical or electron microscope.

As can be seen from Table 1, even if a small amount of the charge promoting particles m are applied (for example, 10 particles / mm ² ), the effect of suppressing the charge unevenness can be recognized, but the density unevenness on the image is It is still insufficient in terms of acceptability.

However, when the coating amount is 10 ² pieces / mm ² or more, a desirable result can be rapidly obtained in the objective evaluation of the image.

Further, by increasing the coating amount by 10 ³ pieces / mm ² or more, there will be no problem on the image due to poor charging.

The charging by the direct injection charging system is fundamentally different from the discharge charging system, and the charging is performed by the reliable contact of the charging member with the photosensitive member. Even if it is applied onto the photoconductor 1, there are always parts that cannot be contacted. However, by applying the charging-promoting particles that positively utilize the human visual characteristics of the present invention, this problem can be practically solved.

Further, the upper limit of the coating amount of the particles m is as follows.
Is evenly applied to the photosensitive member 1 in a single layer, and the effect is not improved even if it is applied more, and conversely, there is a problem that the exposure light source is blocked or scattered.

The upper limit value of the coating density varies depending on the particle size of the particle m, so it cannot be said unconditionally. However, if it is forcedly described, the amount of the particle m coated uniformly on the photosensitive member 1 layer. Is the upper limit.

The amount of charge promoting particles is 5 × 10 ⁵ particles / mm
^When it exceeds ² , the amount of the particles falling off to the photoreceptor 1 remarkably increases, and the exposure amount to the photoreceptor 1 is insufficient regardless of the light transmittance of the particles themselves. When it is 5 × 10 ⁵ particles / mm ² or less, the amount of particles that fall off is suppressed to a low level, and the adverse effect can be improved. Since the photosensitive member 1 measuring the abundance of shed particles on the 10 ² to 10 ⁵ / mm was ² in the intervening weight range. As the abundance on the no adverse effect imaging 10 ⁵ / mm ² or less is desired.

A method of measuring the intervening amount and the existing amount on the photoreceptor 1 will be described. The interposition amount is the charging member (brush) 2
Although it is desirable to directly measure the charging nip portion n of the photosensitive member 1, the amount of particles on the surface of the photosensitive member immediately before reaching the charging nip portion n is defined as the intervening amount. Specifically, the rotations of the photoconductor 1 and the charging member 2 are stopped without applying the charging bias, and the surfaces of the photoconductor 1 and the charging member 2 are covered with a video microscope (OVM1000 made by OLYMPUS).
N) and Digital Still Recorder (DELTIS SR
-3100). Regarding the charging member 2, the charging member 2 is brought into contact with the slide glass under the same conditions as the case where the charging member 2 is brought into contact with the photoconductor 1.
I photographed more than 0 places. In order to separate individual particles from the obtained digital image, binarization processing was performed with a certain threshold value, and the number of areas where particles were present was measured using desired image processing software. Further, the amount of existence on the photoconductor 1 was measured by photographing the photoconductor 1 with the same video microscope and performing the same processing.

Further, the charging member used in the present invention is preferably a fur brush having a brush density as high as possible in this example, but it is sufficient to use a brush having a brush density as used in this example. . This is because the charging point of the direct injection charging is mainly determined not by the charging member but by the coating density of the charging accelerating particles m, as described above, so that the selection range of the charging member is considerably large. There is an effect that there is a margin.

The charge-accelerating particles m to be used are preferably non-magnetic so as not to hinder the exposure.

Further, it is preferable to use those having the following particle sizes and characteristics.

In this example, as the charge promoting particles m, conductive zinc oxide particles having a specific resistance of 10 ⁶ Ω · cm and an average particle size of 3 μm including secondary aggregates were used. Various conductive particles such as conductive inorganic particles such as other metal oxides and a mixture with organic substances can be used.

The particle resistance is preferably 10 ¹² Ω · cm or less, more preferably 10 ¹⁰ Ω · cm or less, because the electrical resistance is transferred via particles. The resistance was measured by the tablet method and normalized. A 0.5 g powder sample was placed in a cylinder with a low area of 2.26 cm ² , 15 kg of pressure was applied to the upper and lower electrodes, a voltage of 100 V was applied at the same time, the resistance value was measured, and then normalized to calculate the specific resistance. did.

Further, the particle size is effective at 50 μm or less in order to obtain good charging uniformity, but in view of human visual characteristics, the use of fine particles of about 5 μm or less makes it possible to prevent charging failure that occurs during charging. The effect on the image of the part,
A state in which it is difficult to be visually recognized is obtained.

In the present invention, the particle size when the particles are formed as an aggregate is defined as the average particle size of the aggregate. To measure the particle size, 100 or more particles were extracted from the observation by an optical or electron microscope, the maximum chord length in the horizontal direction was measured to calculate the volume particle size distribution, and the 50% average particle size was determined.

As described above, the charging-promoting particles m exist not only in the state of primary particles but also in the state of agglomeration of secondary particles without any problem. Whatever the aggregated state, the form is not important as long as the function as the charge promoting particles can be realized as the aggregate, and what is important is the particle density.

<Embodiment 2> (FIG. 6) FIG. 6 is a schematic configuration diagram of an image forming apparatus of this embodiment. In the image forming apparatus of this example, in the printer (FIG. 1) of the above-described embodiment, the cleaning device 7 is eliminated to form a cleanerless system, and the electrification promoting particle coating device 8 is eliminated.
Instead, the charge promoting particles m are externally added to the developer (toner) t of the developing device 4 so that the developing device 4 serves also as a means for supplying / applying the charge promoting particles to the photoconductor 1.

The toner t is a known binder resin, magnetic particles,
It is prepared by mixing a charge control agent, kneading, pulverizing, and classifying, and then adding the above-mentioned charge accelerating particles m to the toner as an external additive. The weight average particle diameter (D4) of the toner t was 7 μm, whereas the particle diameter of the conductive zinc oxide particles as the charging promoting particles m was 3 μm. By configuring the particle size of the charging promoting particles m to be 10 nm or more and the toner particle size or less, it becomes possible to function as a fluidizing agent for the toner t.

The amount of the charge-accelerating particles m mixed with the toner t is generally 0.01 to 100 parts by weight of the toner.
It is set in the range of 20 parts by weight.

In the case of the cleanerless system, the transfer residual toner remaining on the surface of the rotating photoconductor 1 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and the charging portion n is removed as the photoconductor 1 rotates. It reaches the developing section a via the developing device 4 and simultaneously cleans (collects) in the developing device 4.
(Toner recycling process).

Simultaneous development cleaning is performed as described above.
The toner remaining on the photoconductor 1 after transfer is continuously developed during the image forming process, that is, the photoconductor is continuously charged and exposed to form a latent image, and the latent image is developed. That is, the fog removal potential difference Vback, which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor. Are to be collected by. In the case of reversal development as in the printer of the present embodiment, this simultaneous cleaning of development causes the toner to adhere to the developing sleeve from the dark potential of the photoconductor to the developing sleeve and to the light potential of the photoconductor from the developing sleeve. It is made by the action of an electric field.

An appropriate amount of the charge promoting particles m mixed in the developer t of the developing device 4 moves to the photosensitive member 1 side together with the toner when the electrostatic latent image on the photosensitive member 1 side is developed by the developing device 4.

The toner image on the photoconductor 1 is attracted and actively transferred to the transfer material P side which is a recording medium at the transfer portion b due to the influence of the transfer bias, but the charge promoting particles m on the photoconductor 1 are electrically conductive. Since it has a property, it is not positively transferred to the transfer material P side, and is substantially adhered and retained on the photoconductor 1 and remains.

Since there is no cleaning device, the transfer residual toner remaining on the surface of the photoconductor 1 after the transfer and the above-mentioned residual charging promoting particles m are charged at the nip portion of the photoconductor 1 and the charging brush 2 which is a contact charging member. The surface of the photoconductor 1 is moved to the part n as it is. Therefore, the contact charging of the photoconductor 1 is performed in the state where the charging promoting particles m are present in the nip portion n between the photoconductor 1 and the charging brush 2.

The transfer residual toner and the charge promoting particles m passing through the charging section n, and the transfer residual toner and the charge promoting particles m adhering to and mixed with the charging brush 2 are gradually discharged from the charging brush 2 onto the photoconductor 1. As the surface of the photosensitive member 1 moves, it reaches the developing section a and is cleaned (recovered) by the developing device 4 at the same time of development.

Further, in the case of the image forming apparatus of the cleanerless system, when the apparatus is operated, the charge promoting particles m mixed in the developer t of the developing device 4 are applied to the surface of the photosensitive member 1 at the developing portion a. The particles move to the charging section n through the transfer section b by the movement of the image bearing surface and new particles m are continuously supplied to the charging section n, so that the charging accelerating particles m drop off at the charging section n. Even when the particle m is reduced or the particle m is deteriorated, the deterioration of the charging property is prevented from occurring, and the good charging property is stably maintained. Since the cleaning device does not remove the charge accelerating particles applied to the photoconductor, it is possible that there are always sufficient charge accelerating particles m on the surface of the photoconductor, and a small amount of the accelerating particles m are contained in the toner t. It became possible to dramatically improve the charging property by just externally adding to.

Of course, the transfer residual toner is also reused, and the toner can be effectively used.

At the initial stage of printing, the charging promoting particles are not supplied to the contact portion n between the charging brush 2 and the photosensitive member 1. Therefore, it is possible to interpose an appropriate amount of the charging promoting particles in the contact portion n in advance. .

<Embodiment 3> (FIG. 7) In this embodiment, as the photoreceptor 1 as the member to be charged in Embodiments 1 and 2, the one in which the resistance of the surface layer is controlled is used.

In this example, a charge injection layer is provided on the surface of the body to be charged, and the resistance of the surface of the body to be charged is adjusted to more stably and uniformly charge.

FIG. 7 is a schematic diagram of the layer structure of the photoconductor 1 used in this example and provided with a charge injection layer on the surface. That is, the photoconductor 1 is the photoconductor 1 having the layer structure shown in FIG.
By applying a charge injection layer 16 to a general organic photoreceptor 1 in which a subbing layer 12, a positive charge injection prevention layer 13, a charge generation layer 14, and a charge transport layer 15 are applied in this order on top of 1. , With improved charging performance.

The charge injection layer 16 which is the surface layer of the photoreceptor 1.
Has a resistance value reduced by dispersing ultrafine conductive particles such as SnO ₂ as conductive particles (conductive filler) in a curable resin such as a photocurable acrylic resin as a binder.

Specifically, doping with antimony,
This is a coating layer made of a material in which 70% by weight of SnO ₂ particles having a low resistance and a particle diameter of about 0.03 μm are dispersed in a resin.

The coating solution thus prepared is applied by dipping to a thickness of 1 μm. for that reason,
The resistance value is about 1 × 10 ¹³ Ω · cm. When the conductive particles were not dispersed, it was about 1 × 10 ¹⁵ Ω · cm. In addition, this measurement was performed in an environment of a temperature of 25 ° C. and a humidity of 40%.

By using a photosensitive member having such a surface resistance value, it is possible to obtain a better charging property.

An important point of the charge injection layer 16 is the resistance of the surface layer. In the charging method that directly injects electric charges, it is possible to transfer the electric charges more efficiently by lowering the resistance on the side of the body to be charged. On the other hand, when used as a photoconductor, it is necessary to hold the electrostatic latent image for a certain period of time,
The volume resistance value of the charge injection layer 16 is 1 × 10 ⁹ to 1 ×.
The range of 10 ¹⁴ (Ω · cm) is suitable.

[0152] Even when not using a charge injection layer 16 as in this configuration, for example, the charge transport layer 15 when Ru Ah in the resistance range similar effect can be obtained.

Further, the surface layer has a volume resistance of about 10 ¹³ Ωcm.
The same effect can be obtained by using the amorphous silicon photoconductor or the like.

By using the photoconductor 1 whose surface layer resistance is controlled, an electrostatic latent image is maintained and sufficient chargeability is given even in a device having a high process speed, and direct injection charging is realized predominantly. can do.

<Others> 1) The charging-promoting particle supply / coating means 4 for the member to be charged 1 and the contact charging member 2 is not limited to the embodiment, and other, for example, foam containing the charging-promoting particles m. The body or the fur brush may be arranged so as to be brought into contact with the member to be charged 1 or the contact charging member 2 and the like.

2) The flexible contact charging member 2 is a felt,
Material and shape such as cloth can also be used. It is also possible to stack these to obtain more appropriate elasticity and conductivity. It may be a charging roller.

3) The applied charging bias or applied developing bias to the contact charging member 2 or the developing sleeve 4a may be a DC voltage with an alternating voltage (AC voltage) superimposed thereon.

As the waveform of the alternating voltage, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. Further, it may be a rectangular wave formed by periodically turning on / off the DC power supply. Thus, as the waveform of the alternating voltage, a bias whose voltage value changes periodically can be used.

4) The image exposure means for forming an electrostatic latent image is not limited to the laser scanning exposure means for forming a digital latent image as in the embodiment, but a normal analog type. Other light emitting elements such as image exposure and LEDs may be used, or a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter may be used as long as it can form an electrostatic latent image corresponding to image information.

The photoconductor 1 may be an electrostatic recording dielectric or the like. In this case, after the primary surface of the dielectric surface is uniformly charged to a predetermined polarity and potential, the target electrostatic latent image is written and formed by selectively neutralizing with a neutralizing means such as a neutralizing needle head or an electron gun.

5) In the embodiment, the developing device 4 is a one-component non-contact type developing device using a magnetic developer, but a two-component developing device or a non-contact type developing device using a non-magnetic developer. But it doesn't matter. It may be a one-component or two-component contact type developing device.

6) The recording medium to which the toner image is transferred from the photoconductor 1 may be an intermediate transfer body such as a transfer drum.

7) An example of the method for measuring the toner particle size will be described. As a measuring device, Coulter Counter TA-2
Interface (manufactured by Nikkaki) and CX that outputs number average distribution and volume average distribution using a mold (manufactured by Coulter)
-1 Connect a personal computer (made by Canon),
As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride.

As a measuring method, the electrolytic solution 100 to
Surfactant as a dispersant in 150 ml, preferably
Add 0.1 to 5 ml of alkylbenzene sulfonate, and add 0.5 to 50 mg of the measurement sample.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter counter TA-2 type was used to make a particle size of 2 to 40 μm using a 100 μ aperture as an aperture. The distribution is measured to obtain the volume average distribution. The volume average particle size is obtained from the obtained volume average distribution.

[0166]

As described above, according to the present invention, in the contact charging device, the problem of insufficient contact between the member to be charged and the charging member can be improved, and the charging uniformity can be improved. Further, regardless of the performance of the contact charging member, that is, even when a simple member such as a fur brush or a charging roller is used as the contact charging member, it is possible to realize stable direct injection charging with excellent charging uniformity and for a long period of time. That is, it becomes possible to realize ozone-less injection charging with a low voltage and a simple configuration.

As a result, it is possible to obtain an image forming apparatus having a simple structure and a low cost, which is free from obstacles due to ozone products and faults due to poor charging.

[Brief description of drawings]

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

FIG. 2 is a model diagram of the layer structure of a photoconductor.

FIG. 3 is a graph showing charging characteristics of direct injection charging.

FIG. 4 is a model diagram of a contact state of a charging brush with a photoconductor in the presence of charging promoting particles.

FIG. 5 is a diagram illustrating the visual characteristics of the human eye.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 7 is a schematic diagram of the layer structure of a photoconductor used in the image forming apparatus according to the third embodiment.

FIG. 8 is a model diagram of a contact state of a charging brush with a photoconductor (a state where a brush tip has a split portion).

FIG. 9 is a charging characteristic graph in each case of roller charging, fur brush charging, and magnetic brush charging.

[Explanation of symbols]

1 Photoconductor (image bearing member, charged body) 2 Charging brush (contact charging member) 2a core metal 2b brush pile 4 Developing device 8 Charge accelerating particle coating device m Charge promoting particles P transfer material

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-7-5748 (JP, A) JP-A-6 -348106 (JP, A) JP-A-7-36322 (JP, A) JP-A-3-103878 (JP, A) JP-A-9-15935 (JP, A) JP-A-9-190046 (JP, A) ) JP-A-6-138753 (JP, A) JP-A-5-241423 (JP, A) JP-A-7-234571 (JP, A) JP-A-6-11948 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (8)

(57) [Claims] 1. A voltage is applied, a charging device you inject band photoelectrically be charged member surface through the nip by the fiber brush-like charging member or elastic charging member to form a member to be charged and the nip, the charging member surface moves with a speed difference relative to the charged member surface, comprising a conductive particle at least the nip portion, the conductive particles are particles
Resistance is 1 × 10 ¹⁰ (Ω · cm) or less, particle size is 20 nm
A charging device comprising particles of ˜5 μm, wherein charging of a member to be charged is performed in a state where 10 ^{2 to} 5 × 10 ⁵ particles / mm ² are present in a nip portion. 2. The volume resistance of the outermost surface layer of the body to be charged is 1
Claims characterized by being less than × 10 ¹⁴ (Ω · cm)
Item 1. The charging device according to Item 1 . 3. The charging device according to claim 1, further comprising means for supplying the conductive particles. Wherein said charging member is 請, characterized in that rotate in the opposite direction to the member to be charged at the nip portion
The charging device according to any one of claims 1 to 3 . 5. Apply the image forming process comprising the step of charging the image bearing member to the image bearing member is an image forming apparatus for executing image formation, the process means according to claim 1 for charging said image bearing member An image forming apparatus, wherein the image forming apparatus is the charging apparatus according to any one of 1 to 4 . 6. An image carrier, charging means for charging the image carrier, image writing means for forming an electrostatic latent image on the charged surface of the image carrier, and visualization of the electrostatic latent image with toner. An image forming apparatus having a developing means and a transfer means for transferring the toner image onto a recording medium, and also serving as a cleaning means for collecting the toner remaining on the image carrier after the developing means transfers the toner image onto the recording medium. The image forming apparatus according to claim 1 , wherein the charging unit is the charging device according to any one of claims 1 to 4 . 7. The image forming apparatus according to claim 6, wherein said image writing means is an image exposure means. Wherein said image bearing member is a photosensitive member, the volume resistivity of the outermost surface layer of the photosensitive body is ^{1 × 10 9 (Ω · cm} ) or more 1
Claims characterized by being less than × 10 ¹⁴ (Ω · cm)
The image forming apparatus according to any one of items 5 to 7 .