JP2003057922A - Image forming device - Google Patents

Image forming device

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Publication number
JP2003057922A
JP2003057922A JP2002205503A JP2002205503A JP2003057922A JP 2003057922 A JP2003057922 A JP 2003057922A JP 2002205503 A JP2002205503 A JP 2002205503A JP 2002205503 A JP2002205503 A JP 2002205503A JP 2003057922 A JP2003057922 A JP 2003057922A
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JP
Japan
Prior art keywords
charging
image
member
forming apparatus
image forming
Prior art date
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Granted
Application number
JP2002205503A
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Japanese (ja)
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JP3652331B2 (en
Inventor
Jun Hirabayashi
Harumi Ishiyama
Yasunori Kono
Yukio Nagase
康則 児野
純 平林
幸雄 永瀬
晴美 石山
Original Assignee
Canon Inc
キヤノン株式会社
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Priority to JP9-67426 priority Critical
Priority to JP6742697 priority
Application filed by Canon Inc, キヤノン株式会社 filed Critical Canon Inc
Priority to JP2002205503A priority patent/JP3652331B2/en
Publication of JP2003057922A publication Critical patent/JP2003057922A/en
Application granted granted Critical
Publication of JP3652331B2 publication Critical patent/JP3652331B2/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

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Abstract

PROBLEM TO BE SOLVED: To use a simple member, such as an electrifying roller, as a contact electrifying member of an image forming device of a contact electrifying system, transfer system, and a toner recycle system and to ensure, for a long period of time, ozone-less, direct, and stable injection electrification at a low application voltage despite contamination of a contact electrifying member with transfer residual toner. SOLUTION: An electrifying means 2 is the electrifying member to which a voltage is applied. The electrifying means 2 has the flexible electrifying member that forms a nip n between an image carrier 1 and itself. Conductive particles m are held on the surface of the electrifying member and interposed in the nip n. Developer 4d in a developing means 4 contains toner t and conductive particles m. The conductive particles m are carried from the developing means 4 to the image carrier 1 and then replenished to the nip n.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus such as a copying machine or a printer.

More specifically, a contact charging system, a transfer system,
The present invention relates to an image forming apparatus for a toner recycling process.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic device or an electrostatic recording device, an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric is uniformly charged to a required polarity and potential. A corona charger (corona discharger) has often been used as a charging device for treatment (including static elimination treatment).

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 mechanism charges the surface of the body to be charged by a discharge phenomenon that occurs in the minute gap between the contact charging member and the body to be charged.

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. 3 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, and sufficient uniform charging by direct injection charging. In order to carry out, it is necessary to give a speed difference to the photoconductor so as to make it difficult as a mechanical structure, which is not realistic.

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

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 objects is remarkably reduced, the charging principle still mainly uses the discharge charging mechanism as in the case of the roller charging described above. 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]

1) As described in the above-mentioned section of the prior art, in the contact charging, direct injection charging is performed by a simple structure using a charging roller or a fur brush as the contact charging member. However, since the surface of the contact charging member was rough, it was not possible to secure close contact with the image bearing member as the member to be charged, and direct injection charging was impossible.

Therefore, in the contact charging, even if a simple member such as a charging roller or a fur brush is used as the contact charging member, the direct injection charging having excellent charging uniformity and stable for a long period of time can be realized. It is expected that ozone-less direct injection charging with a low applied voltage will be realized with a simple configuration.

2) In the image forming apparatus of the toner recycling process, when the contact charging device is used as the charging means of the image carrier, a cleaner is used to remove the residual transfer residual toner on the surface of the image carrier after transfer. Therefore, the transfer residual toner remaining on the surface of the image carrier after the transfer is carried as it is by the movement of the surface of the image carrier to the charging part which is the contact part between the image carrier and the contact charging member, and the contact charging member is contaminated with the toner. Therefore, the direct injection of charges from the contact charging member to the image carrier is hindered, which makes direct injection charging impossible. Further, if the charging failure occurs, the mixing of toner into the contact charger further increases, and the charging failure becomes more serious.

Therefore, the present invention uses a simple member such as a charging roller or a fur brush as the contact charging member in the image forming apparatus of the contact charging system, the transfer system and the toner recycling process (cleanerless system), Regardless of contamination by transfer residual toner on the charging member, ozone-less direct injection charging can be stably maintained for a long time with a low applied voltage, that is, a simple structure using a contact charging member such as a charging roller or a fur brush. The purpose is to realize direct injection charging and toner recycling process.

[0041]

The present invention is an image forming apparatus having the following configuration.

(1) Image carrier, charging means for charging the image carrier, developing means for visualizing the electrostatic latent image formed on the image carrier as a toner image with toner, and recording the toner image. In an image forming apparatus having a transfer unit for transferring to a medium and capable of collecting the toner remaining on the image carrier after the developing unit transfers the toner image to the recording medium, the charging unit is Is a charging member to which is applied, comprising a flexible charging member that forms a nip portion with the image carrier, conductive particles are previously carried on the surface of the charging member, and conductive particles are interposed in the nip portion. The image forming apparatus, wherein the developer of the developing means includes toner and conductive particles, and the conductive particles are applied to the image carrier from the developing means and supplied to the nip portion.

(2) The image forming according to (1), wherein the surface of the charging member moves with a speed difference with respect to the surface of the image carrier so that the surface of the image carrier is rubbed by the conductive particles. apparatus.

(3) The conductive particles have a resistance of 10
The image forming apparatus according to (1) or (2), which has a diameter of 12 Ω · cm or less and a particle diameter of 50 μm or less.

(4) The conductive particles have a resistance of 10
The image forming apparatus according to (1) or (2), which has a particle size of 10 Ω · cm or less and a particle size of 50 μm or less.

(5) The image forming apparatus described in any one of (1) to (4), wherein the charging member and the image carrier move in opposite directions in the nip portion.

(6) The image forming apparatus according to any one of (1) to (5), wherein the charging member is an elastic conductive roller.

(7) The image forming apparatus according to any one of (1) to (6), wherein the charging member has a foam on the surface.

(8) In the image forming apparatus described in any one of (1) to (7), the charging member carries and conveys the conductive particles in the nip portion.

(9) The volume resistance of the outermost surface layer of the image carrier is 1 × 10 9 (Ω · cm) or more and 1 × 10 14 (Ω · c).
m) or less, the image forming apparatus described in any one of (1) to (8).

(10) An image writing means for forming an electrostatic latent image on the charging surface of the image carrier charged by the charging means is provided, and any one of (1) to (9) is provided. The image forming apparatus according to item 1.

(11) The image writing means is an exposing means for exposing the image carrier (1)
The image forming apparatus according to 0).

(12) The developing means is capable of developing the electrostatic latent image on the image carrier with toner and at the same time collecting the toner remaining on the image carrier. The image forming apparatus according to any one of 11).

<Operation> a) The conductive charge promoting particles contained in the developer of the developing means have an appropriate amount together with the toner when the electrostatic latent image on the side of the image carrier is developed by the developing means. Move to.

The toner image on the image carrier is attracted and actively transferred to the recording medium side by the effect of the transfer bias in the transfer unit, but the charge promoting particles on the image carrier are conductive and thus recorded. It does not positively transfer to the medium side, but remains substantially adhered and held on the image carrier.

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 image carrier after the transfer and the above-mentioned residual charge promoting particles form an image in the nip portion between the image carrier and the contact charging member. It is carried as it is by the movement of the carrier surface and adheres to and mixes with the contact charging member.

Therefore, contact charging of the image carrier is carried out in the state where the charge promoting particles are present in the nip portion between the image carrier and the contact charging member.

Due to the presence of the charge accelerating particles, even if the toner adheres to or mixes with the contact charging member, it is possible to maintain the close contact property and the contact resistance of the contact charging member to the image carrier, so that the contact charging member is charged. It is a simple member such as a roller or a fur brush, and can directly charge the image carrier by the contact charging member regardless of contamination of the contact charging member due to transfer residual toner.

That is, the contact charging member comes into close contact with the image carrier via the charging promoting particles, and the charging promoting particles present in the nip portion between the contact charging member and the image carrier slide on the surface of the image carrier without a gap. By rubbing, the charging of the image bearing member by the contact charging member is dominated by stable and safe direct injection charging that does not use the discharge phenomenon due to the presence of charging accelerating particles, and high charging that cannot be obtained by conventional roller charging etc. Efficiency can be obtained, and a potential almost equal to the voltage applied to the contact charging member can be applied to the image carrier.

The transfer residual toner adhering to and mixed with the contact charging member is gradually discharged from the contact charging member onto the image bearing member and reaches the developing section along with the movement of the image bearing member surface. Simultaneous development cleaning (collection) in the developing means. (Toner recycling process).

Even if the charge accelerating particles fall off from the contact charging member, the image forming apparatus is operated to move the charge accelerating particles contained in the developer of the developing means to the image carrier surface in the developing section. By the movement of the image bearing surface, it is carried to the charging unit via the transfer unit and continuously supplied to the contact charging member, so that good chargeability due to the presence of the charge promoting particles is stably maintained.

Thus, in the image forming apparatus of the contact charging system, the transfer system and the toner recycling process, a simple member such as a charging roller or a fur brush is used as the contact charging member, and the contact charging member is contaminated by the transfer residual toner. Regardless of the above, direct injection charging without ozone can be stably maintained at a low applied voltage for a long period of time, uniform charging property can be given, and obstacles due to ozone products,
It is possible to obtain an image forming apparatus having a simple structure and low cost, which is free from obstacles due to poor charging.

B) By interposing charging accelerating particles in the nip portion between the contact charging member and the image bearing member, the lubrication effect (friction reducing effect) of the charging accelerating particles causes a gap between the contact charging member and the image bearing member. It is possible to easily and effectively provide the speed difference.

By providing a speed difference between the contact charging member and the image bearing member, the chances that the charge promoting particles come into contact with the image bearing member at the nip portion between the contact charging member and the image bearing member are significantly increased, which is high. Contact property can be obtained, and direct injection charging can be easily performed.

As a structure for providing a speed difference, the contact charging member is rotationally driven to provide a speed difference between the image carrier and the contact charging member. Preferably, in order to temporarily collect and level the transfer residual toner on the image carrier, which is carried to the charging section, on the contact charging member, the contact charging member is rotationally driven, and the rotation direction is the direction of the surface of the image carrier. It is desirable to be configured to rotate in the direction opposite to the moving direction. That is, it is possible to predominantly perform direct injection charging by temporarily separating the transfer residual toner on the image carrier by reverse rotation and charging.

It is also possible to move the charging member in the same direction as the moving direction of the surface of the image carrier to give a speed difference, but the charging property of the direct injection charging is the peripheral speed of the image carrier and the peripheral speed of the charging member. Therefore, in order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging member in the forward direction is larger than that in the reverse direction. It is advantageous in terms. The peripheral speed ratio described here is the peripheral speed ratio (%) = (peripheral speed of charging member−peripheral speed of image carrier) / peripheral speed of image carrier × 100 (the peripheral speed of the charging member is the surface of the charging member at the nip portion). Positive value when moving in the same direction as the image carrier surface).

C) By using an elastic conductive roller or a brush composed of conductive fibers as the contact charging member, the transfer residual toner on the image carrier is temporarily collected and the charge accelerating particles are carried and directly injected. Performs charging predominantly.

D) The volume resistance of the outermost surface layer of the image carrier is 1 ×
With 10 9 (Ω · cm) or more 1 × 10 1 4 (Ω · cm) or less, while maintaining an electrostatic latent image, even in fast device of process speed, provide sufficient charging property,
Direct injection charging can be realized with advantage.

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> (FIG. 1) FIG. 1 is a schematic structural model diagram of an example of an image forming apparatus according to the present invention.

The image forming apparatus of this example is a laser printer (recording apparatus) using a transfer type electrophotographic process, a direct injection charging system, and a toner recycling process (cleanerless system).

(1) The overall schematic configuration 1 of the printer of this example is a rotary drum type O having a diameter of 30 mm as an image carrier.
PC photoconductor (negative photoconductor), 5 in the clockwise direction of the arrow
It is rotationally driven at a peripheral speed (process speed) of 0 mm / sec.

Reference numeral 2 is a conductive elastic roller (hereinafter referred to as a charging roller) as a contact charging member.

The charging roller 2 is formed by forming a rubber or foam medium resistance layer 2b as a flexible member on the cored bar 2a. The medium resistance layer 2b is made of resin (eg urethane), conductive particles (eg carbon black),
It was formulated with a sulfiding agent, a foaming agent, etc., and formed into a roller shape on the cored bar 2a. After that, the surface was polished as needed to prepare a charging roller 2 which was a conductive elastic roller having a diameter of 12 mm and a longitudinal length of 250 mm.

When the roller resistance of the charging roller 2 of this example was measured, it was 100 kΩ. The roller resistance is φ30 so that a total pressure of 1 kg is applied to the core metal 2a of the charging roller 2.
With the charging roller 2 pressed onto an mm aluminum drum,
100 V was applied between the core metal 2a and the aluminum drum, and the measurement was performed.

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 charged body, and at the same time, have a resistance low enough to charge the moving charged body. On the other hand, it is necessary to prevent voltage leakage when there is a defective portion such as a pinhole on the charged body. When an electrophotographic photosensitive member is used as the member to be charged, 10 4 to 10 7 are required to obtain sufficient chargeability and leak resistance.
A resistance of Ω is desirable.

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 member to be charged deteriorates. If the hardness is too high, the charging nip portion cannot be secured between the charging roller 2 and the member. Since the micro contact property to the surface of the member to be charged 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 may be EPD.
Examples thereof include M, urethane, NBR, silicone rubber, a rubber material in which a conductive material such as carbon black or a metal oxide is dispersed in IR or the like for resistance adjustment, or a material obtained by foaming these. In addition, especially without dispersing a conductive substance,
It is also possible to adjust the resistance by using an ion conductive material.

The charging roller 2 is the photosensitive member 1 as the member to be charged.
It is arranged in pressure contact with a predetermined pressing force against the elasticity. Reference numeral n is a charging nip portion which is a nip portion between the photoconductor 1 and the charging roller 2. The width of this charging nip portion is 3 mm. In this example, the charging roller 2 was rotationally driven in the clockwise direction indicated by an arrow at about 80 rpm so as to move the charging roller surface and the photosensitive member surface in opposite directions at a constant speed in the charging nip portion n. That is, the surface of the charging roller 2 as the contact charging member has a speed difference with respect to the surface of the photoconductor 1 as the member to be charged.

The core metal 2a of the charging roller 2 is applied with a DC voltage of -700 V from the charging bias applying power source S1 as a charging bias. In this example, the surface of the photoconductor 1 is uniformly charged by a direct injection charging method to a potential (-680 V) substantially equal to the voltage applied to the charging roller 2. This will be described later.

Reference numeral 3 is a laser beam scanner (exposure device) including a laser diode, a polygon mirror and the like. 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 L the uniformly charged surface of the rotating photoconductor 1 with the laser beam. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 1.

Reference numeral 4 is a developing device. The electrostatic latent image on the surface of the rotating photoconductor 1 is developed as a toner image by this developing device. The developing device of this example is a reversal developing device using magnetic one-component insulating toner (negative toner). Reference numeral 4a designates a non-magnetic rotary developing sleeve as a developer carrying / conveying member which contains a magnet roll 4b.
Then, the developer 4d is coated in a thin layer by the regulation blade 4c. The layer thickness of the toner of the developer 4d with respect to the rotary developing sleeve 4a is regulated by the regulation blade 4c, and an electric charge is applied. The developer coated on the rotary developing sleeve 4a is conveyed by the rotation of the sleeve 4a to a developing section (developing area) a which is an opposing section of the photoconductor 1 and the sleeve 4a. A developing bias voltage is applied to the sleeve 4a from a developing bias applying power source S2. Development bias voltage is -5
A DC voltage of 00 V and a rectangular AC voltage having a frequency of 1800 Hz and a peak-to-peak voltage of 1600 V were superposed. As a result, the electrostatic latent image on the side of the photoconductor 1 is developed with the toner.

The developer 4d is a mixture of the toner t and the charge promoting particles (charge assisting particles) m, and the toner t is a binder resin.
It is prepared by mixing magnetic particles and a charge control agent, kneading, pulverizing, and classifying the mixture, and adding the charge accelerating particles m and the fluidizing agent as external additives to the mixture. The weight average particle diameter (D4) of Toner t was 7 μm. As the charging promoting particles m, conductive zinc oxide particles having a particle diameter of 3 μm were used in this example. Further, in this example, 2 parts by weight of the charge promoting particles m were externally added to 100 parts by weight of the toner t.

Although the electrification promoting particles m having conductivity are conductive zinc oxide particles having a specific resistance of 10 6 Ω · cm and an average particle diameter of 3 μm including secondary agglomerates in this example, the electrification promoting particles m As the material of (1), various conductive particles such as conductive inorganic particles such as other metal oxides or a mixture with organic materials can be used.

The particle resistance needs to be 10 12 Ω · cm or less, preferably 10 10 Ω · cm or less in order to transfer charges through the particles.

The resistance was measured by the tablet method and normalized. That is, a powder sample of about 0.5 g was placed in a cylinder having a bottom area of 2.26 cm 2 , 15 kg of pressure was applied to the upper and lower electrodes, and at the same time, a voltage of 100 V was applied to measure the resistance value, and then normalized to obtain a specific resistance. Was calculated.

The particle size is 50 in order to obtain good charging uniformity.
μm or less is desirable. The lower limit value of the particle size is 10 nm as a limit for stably obtaining the particles.

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 observation by an optical or electron microscope, the volume particle size distribution was calculated with the maximum chord length in the horizontal direction, 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.

The charge-accelerating particles m are preferably colorless or nearly white particles so as not to interfere with the latent image exposure particularly when used for charging the photoreceptor 1. Further, in the case of color recording, the charging-promoting particles m are transferred onto the recording material P
Considering the case of transfer to, it is desirable that it is colorless or close to white. Further, in order to prevent light scattering by the charge promoting particles at the time of image exposure, it is desirable that the particles have a size smaller than the constituent pixel size.

Further, the charge promoting particles m are preferably non-magnetic so as not to hinder the exposure.

Reference numeral 5 denotes a medium resistance transfer roller as a contact transfer means, which is pressed against the photoconductor 1 at a predetermined pressure to form a transfer nip portion b. A transfer material P as a recording medium is fed to the transfer nip portion b from a paper feeding unit (not shown) at a predetermined timing.
Is fed and a predetermined transfer bias voltage is applied to the transfer roller 5 from the transfer bias applying power source S3,
The toner image on the photoconductor 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion b. In this example, a roller resistance value of 5 × 10 8 Ω is used, and DC of + 2000V is used.
Transfer was performed by applying a voltage. That is, the transfer nip portion b
The transfer material P introduced into the sheet is conveyed while being sandwiched by the transfer nip portion b, and the toner images formed and carried on the surface of the rotary photoconductor 1 on the surface side thereof are sequentially transferred by electrostatic force and pressing force. Go.

Reference numeral 6 denotes a fixing device such as a heat fixing system. The transfer material P, which has been fed to the transfer nip portion b and transferred with the toner image on the photoconductor 1 side, is separated from the surface of the rotary photoconductor 1 and is introduced into the fixing device 6, where the toner image is fixed. It is discharged outside the apparatus as an image-formed product (print, copy).

The printer of this example is cleanerless,
After the transfer of the toner image onto the transfer material P, the transfer residual toner remaining on the surface of the rotating photoconductor 1 is not removed by the cleaner,
Along with the rotation of the photoconductor 1, the developing section a is passed through the charging section n.
Then, the developing device 4 performs cleaning (collection) at the same time as development (toner recycling process).

(2) Direct Injection Charging of Photoreceptor 1 a) Electrostatic charge-accelerating particles m contained in the developer 4d of the developing device 4 are electrostatic latent images on the photoconductor 1 side by the developing device 4. At the time of developing the toner, an appropriate amount moves to the photosensitive member 1 side together with the toner.

The toner image on the photosensitive member 1 is transferred to the transfer nip portion b.
In the above, due to the influence of the transfer bias, it is attracted to the transfer material P side and positively transfers, but since the charging promoting particles m on the photoconductor 1 are conductive, they do not actively transfer to the transfer material P side. , Substantially adhered to and retained on the photoconductor 1. In addition, the presence of the charging-promoting particles m substantially attached and held on the surface of the photoconductor 1 also has the effect of improving the transfer efficiency of the toner image from the photoconductor 1 side to the transfer agent P side.

Since the image forming apparatus in the toner recycling process does not use a cleaner, the photosensitive member 1 after the transfer is transferred.
The transfer residual toner remaining on the surface and the above-mentioned residual charging promoting particles m are carried as they are to the charging nip portion n of the charging roller 2 which is a contact charging member with the photosensitive member 1 by the rotation of the photosensitive member 1 and adhered to the charging roller 2. ·mixing.

Therefore, the contact charging of the photosensitive member 1 is carried out in the state where the charging promoting particles m exist in the nip portion n between the photosensitive member 1 and the charging roller 2. At the initial stage of printing, since the charging promoting particles are not supplied to the charging roller surface and charging cannot be performed, it is possible to apply the charging promoting particles to the charging roller surface in advance.

Due to the presence of the charge accelerating particles m, even if 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 member 1 can be maintained, so that the contact charging member can be used. It is a simple member such as a charging roller, and the direct injection charging of the photoconductor 1 by the charging roller 2 can be performed regardless of contamination by the transfer residual toner of the charging roller.

In other words, the charging roller 2 and the photosensitive member 1 are in close contact with the photosensitive member through the charging-promoting particles m, and the charging roller 2 and the photosensitive member 1
The charge promoting particles m existing in the nip portion of the photoconductor 1 rub the surface of the photoconductor 1 with no gap, so that the photoconductor 1 by the charging roller 2
The stable and safe direct injection charging that does not use the discharge phenomenon is dominated by the presence of the charging accelerating particles m, and a high charging efficiency that cannot be obtained by the conventional roller charging or the like is obtained. A potential almost equal to the voltage can be applied to the photoconductor 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 member 1 and reaches the developing section a along with the movement of the surface of the photosensitive member 1, and the simultaneous development cleaning is performed in the developing device 4. (Recovered) (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, it is recovered by 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 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.

Even if the charge accelerating particles m fall off from the charging roller 2, the image forming apparatus is operated so that the charge accelerating particles m contained in the developer 4d of the developing device 4 are exposed in the developing section a. The charging roller 2 is transferred to the surface of the body 1 and carried by the rotation of the photosensitive body 1 to the charging portion n through the transfer nip portion b.
Therefore, good chargeability due to the presence of the charge promoting particles m 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 charging can be stably maintained for a long period of time, uniform charging property can be given, and there is no trouble due to ozone products, no trouble due to poor charging, etc.
An image forming apparatus having a simple structure and low cost can be obtained.

B) By interposing the charging promoting particles m in the nip portion n between the charging roller 2 and the photosensitive member 1, the charging roller 2 and the photosensitive member 1 are separated by the lubrication effect (friction reducing effect) of the charging promoting particles m. It becomes possible to easily and effectively provide a speed difference between them.

By providing a speed difference between the charging roller 2 and the photoconductor 1, the chances of the charging promoting particles m coming into contact with the photoconductor 1 at the nip portion n between the charging roller 2 and the photoconductor 1 are significantly increased. , High contact can be obtained, and easy direct injection charging is possible.

In order to temporarily collect the transfer residual toner on the photosensitive member 1 carried to the charging portion n to the charging roller 2 and to even out it, the charging roller 2 is rotationally driven so as to provide a speed difference. Further, it is desirable that the rotation direction thereof is set to rotate in the direction opposite to the movement direction of the surface of the photoconductor 1. That is, it is possible to predominantly perform direct injection charging by temporarily separating the transfer residual toner on the photoconductor 1 by reverse rotation and charging.

If the intervening amount of the charging promoting particles m in the nip portion n between the photosensitive member 1 as the image bearing member and the charging roller 2 as the contact charging member is too small, the lubricating effect by the particles cannot be sufficiently obtained. The friction between the charging roller 2 and the photoconductor 1 is large, and it is difficult to rotate the charging roller 2 on the photoconductor 1 with a speed difference. In other words, the driving torque becomes excessively large, and the surface of the charging roller 2 and the photoconductor 1 will be scraped if it is forcibly rotated. Further, the effect of increasing contact opportunities due to the particles may not be obtained, and sufficient charging performance may not be obtained. On the other hand, if the intervening amount is too large, the fall of the charging promoting particles from the charging roller 2 remarkably increases, which adversely affects the image formation.

According to the experiment, the intervening amount is 10 3 pieces / mm 2
The above is desirable. If it is lower than 10 3 pieces / mm 2 , sufficient lubrication effect and effect of increasing contact opportunity cannot be obtained, and charging performance is deteriorated.

More preferably, 10 3 to 5 × 10 5 pieces / m
The intervening amount of m 2 is preferred. When it exceeds 5 × 10 5 particles / mm 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. When the amount of particles dropped off on the photoconductor 1 is measured in the intervening amount range, it is 10 2
Since it was 10 5 pieces / mm 2 , it is desired that the existing amount that does not have a bad effect on image formation be 10 5 pieces / mm 2 or less.

A method of measuring the intervening amount and the existing amount on the photoreceptor 1 will be described. It is desirable to directly measure the intervening amount at the contact surface portion between the charging roller 2 and the photosensitive member 1, but most of the particles existing on the photosensitive member 1 before contacting the charging roller 2 move while moving in the opposite direction. Since the toner is peeled off by the roller 2, the amount of particles on the surface of the charging roller 2 immediately before reaching the contact surface portion is defined as the intervening amount in the present invention. Specifically, the rotation of the photosensitive drum 1 and the charging roller 2 is stopped without applying the charging bias, and the surfaces of the photosensitive member 1 and the charging roller 2 are covered with a video microscope (OLYMPUS).
Made by OVM1000N) and digital still recorder (D
Photographed with ELTIS SR-3100). The charging roller 2 is brought into contact with the slide glass under the same conditions as when the charging roller 2 is brought into contact with the photosensitive drum 1, and the contact surface is removed from the back surface of the slide glass with a video microscope.
Images were taken at 10 or more places with a 000 × objective lens. To separate individual particles from the resulting 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.

The amount of interposition is adjusted by the developer 4 of the developing device 4.
It was carried out by setting the blending amount of the charging promoting particles m in d. Generally, the charge-accelerating particles m are 0.01 to 20 parts by weight with respect to 100 parts by weight of the developer (toner) t.

<Embodiment 2> (FIG. 2) In this embodiment, in the image forming apparatus of Embodiment 1, by adjusting the surface resistance of the photoconductor 1 which is an image carrier, more stable and uniform charging is achieved. Is to do.

That is, even when the transfer residual toner is mixed in the contact charging member and the contact area with the photosensitive member 1 is reduced, the interposition of the charge promoting particles and the surface resistance on the photosensitive member side are set to be low in the area where the latent image can be formed. By doing so, it is possible to more efficiently transfer charges.

In this example, a charge injection layer is provided on the surface of the photoconductor 1 to adjust the resistance of the photoconductor surface. FIG. 2 is a layer configuration model diagram of the photoconductor 1 used in this example and having a surface on which a charge injection layer is provided. That is, the photoconductor 1 is a general coating in which an undercoat layer 12, a positive charge injection prevention layer 13, a charge generation layer 14, and a charge transport layer 15 are laminated in this order on an aluminum drum base (Al drum base) 11. The charge performance is improved by applying the charge injection layer 16 to the organic photoconductor drum.

The charge injection layer 16 is composed of a photo-curing acrylic resin as a binder and conductive particles (conductive filler).
SnO 2 ultrafine particles 16a (having a diameter of 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.

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.

Even when the charge injection layer 16 is not used as in this structure, the same effect can be obtained when the charge transport layer 15 is in the above resistance range.

Further, the surface layer has a volume resistance of about 10 13 Ωc.
The same effect can be obtained by using an amorphous silicon photoconductor having m.

<Evaluation of Embodiments> Table 1 summarizes the advantages of the present invention together with the comparative examples.

[0121]

[Table 1] Comparative Example 1 In Comparative Example 1, a charging roller is used as the charging member, and the charging roller is driven by the photosensitive member. Further, the developer 4d is configured not to include the charge accelerating particles m. That is, the device does not use the charge promoting particles m.

[Comparative Example 2] In Comparative Example 2, the charging roller in which the charging promoting particles are applied in advance in the configuration of Comparative Example 1 is used.

[Evaluation] In each example, the chargeability was evaluated by using image recording devices having different printing speeds and evaluating the superiority or inferiority of the ghost image.

Since this example is performed by the reversal development system, the ghost here means that the image-exposed portion (toner image portion) in the first round of the photoconductor is charged in the second round of the photoconductor. Since the shortage occurs, the previous image pattern on the photoconductor is more strongly developed and a ghost image is generated.

Here, the image evaluation was performed according to the following criteria.

X: A ghost is seen in the white background after solid black.

◯: No ghost is seen in the white background portion after solid black, but a ghost pattern is slightly seen in the halftone portion.

A: No ghost is seen in either the white background portion or the halftone portion after solid black.

The evaluation was made at the beginning of printing and 1000 sheets (A4 size).
It was performed after printing in the (vertical direction). In the table, the upper part of the slash line (diagonal line) represents the initial result, and the lower part represents the evaluation result after printing.

As is apparent from the table, in Comparative Example 1, the chargeability was not satisfied at the initial stage even at the initial stage. That is, this means that the charging member (charging roller) cannot sufficiently contact the photosensitive member, and thus direct charging is impossible.

Further, in Comparative Example 2, no ghost is observed at the initial stage of applying the charge promoting particles, but when printing is continued, the charging roller is rapidly soiled, and at the same time, the charge promoting particles fall off and the image is remarkably reduced. Deteriorated.

In the first embodiment, the charge promoting particles m can be mixed with the developer 4d and the particles can be stably supplied to the charging member via the photoconductor, so that sufficient contact with the photoconductor can be achieved. Property is obtained, the chargeability is satisfied, and it can be maintained. Further, although the chargeability is excellent even when the speeds of the photosensitive drum and the charging member are both increased, when the speed of the charging member is decreased, a slight shortage of charging occurs. Therefore,
If the charging member and the photosensitive member are provided with a speed difference, charging can be performed more efficiently.

Further, in the second embodiment, by setting the resistance of the surface layer of the photoconductor to be low within the range in which the electrostatic latent image can be maintained, even if the contact state is the same, the transfer of charges can be performed more efficiently. You can do it. It is effective when the process is run faster and the photoreceptor speed in the table is 1
This is clear because the evaluations of 00 mm / sec and charging member speed of 50 mm / sec can be satisfied.

<Others> 1) The charging roller 2 as the contact charging member is not limited to the charging roller of the embodiment.

As the flexible contact charging member, in addition to the elastic charging roller, a fur brush, felt, cloth or the like having a material and shape can be used. It is also possible to stack these to obtain more appropriate elasticity and conductivity.

2) As for the charging bias applied or the developing bias applied to the contact charging member 2 and the developing sleeve 4a, an alternating voltage (AC voltage) may be superimposed on the DC voltage.

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.

3) 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 image carrier 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.

4) In the embodiments, the developing means 4 has been described by taking a developing device using a one-component magnetic toner as an example, but the developing device structure is not particularly limited.

5) The recording medium to which the toner image is transferred from the image carrier may be an intermediate transfer member such as a transfer drum.

6) An example of the method for measuring 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.

The measuring method is as follows:
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 with an ultrasonic disperser for about 1 to 3 minutes, 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.

[0145]

As described above, according to the present invention, a simple member such as a charging roller or a fur brush is used as the contact charging member in the image forming apparatus of the contact charging system, the transfer system and the toner recycling process (cleanerless system). By mixing the charge-accelerating particles with the developer of the developing means, it is possible to recycle the toner and at the same time improve the contact density of the contact charging member to the image carrier and maintain the direct injection charging for a long time. did. With this configuration, even when the toner, which is an insulator, is mixed in the contact charging member, the charge promoting particles, which are conductive particles, are stably supplied at the same time so that the toner is interposed between the contact charging member and the image carrier. By directly improving the contactability of the contact charging member to the image carrier, the direct injection charging could be continued.

Further, the image carrier and the contact charging member are brought into contact with each other with a speed difference. More preferably, by rotating and charging so as to move in the opposite direction, the contact property between the image carrier and the contact charging member and the contact opportunity are further increased, and the influence of transfer residual toner is suppressed to maintain good charging. Is possible.

Further, by adjusting the resistance of the surface of the image bearing member, it becomes possible to construct a charging device suitable for higher speed charging. In a high-speed recording apparatus, long service life of the members is required, so it is desirable to reduce the speed of the charging member to reduce abrasion of each member such as the photoconductor. In that sense, by improving the charging efficiency by adjusting the resistance of the surface layer of the image bearing member, sufficient charging performance is obtained even when the charging member is driven at a low speed, and it is maintained for a long period of time. It became possible to do.

As described above, according to the present invention, a simple member such as a charging roller or a fur brush is used as the contact charging member in the image forming apparatus of the contact charging system, the transfer system, or the toner recycling process. Regardless of contamination by residual toner after transfer, ozone-free direct injection with low applied voltage can be achieved by maintaining stable charging over a long period of time, that is, with a simple configuration using a contact charging member such as a charging roller or a fur brush. The injection charging and the toner recycling process could be realized, and the initial purpose was well achieved.

[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 schematic diagram of a layer structure of a photoconductor in which a charge injection layer is provided on a surface in the second embodiment.

[Fig. 3] Charging characteristic graph

[Explanation of symbols]

1 Photoconductor (image bearing member, charged body) 2 Charging roller (contact charging member) 3 Laser beam scanner (exposure device) 4 Developing device 4a Development sleeve 4d developer (toner t + charge promoting particles m) 5 Transfer roller 6 fixing device P transfer material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jun Hirabayashi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Yukio Nagase             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F term (reference) 2H077 AA37 AC16 AD06 AD31 AD36                       EA11 GA04                 2H200 FA02 FA07 FA14 GA16 GA23                       GA29 GA46 GA49 GA57 GB37                       HA03 HA21 HA28 HB08 HB17                       HB45 HB46 HB48 LC02 MA03                       MA08 MA14 MB01 MB04 MB06                       MC01 MC02 NA02 NA06 PA11                       PB14

Claims (12)

[Claims]
1. An image bearing member, a charging unit for charging the image bearing member, a developing unit for visualizing an electrostatic latent image formed on the image bearing member as a toner image with toner, and the toner image. In an image forming apparatus that has a transfer unit that transfers the toner image to a recording medium after the developing unit transfers the toner image to a recording medium, the charging unit has a voltage An applied charging member,
A flexible charging member that forms a nip portion with the image carrier is provided, and conductive particles are preliminarily carried on the surface of the charging member so that the conductive particles intervene in the nip portion. An image forming apparatus comprising particles, wherein the conductive particles are supplied to the image carrier from the developing unit and supplied to the nip portion.
2. The image forming apparatus according to claim 1, wherein the surface of the charging member moves with a speed difference with respect to the surface of the image carrier so as to rub the surface of the image carrier with conductive particles. .
3. The conductive particles have a resistance of 10 12 Ω.
The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus has a size of cm or less and a particle size of 50 μm or less.
4. The conductive particles have a resistance of 10 10 Ω.
The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus has a size of cm or less and a particle size of 50 μm or less.
5. The image forming apparatus according to claim 1, wherein the charging member and the image carrier move in mutually opposite directions in the nip portion.
6. The image forming apparatus according to claim 1, wherein the charging member is an elastic conductive roller.
7. The image forming apparatus according to claim 1, wherein the charging member has a foam on its surface.
8. The charging member carries and conveys the conductive particles in the nip portion.
The image forming apparatus according to any one of 1.
9. The volume resistance of the outermost surface layer of the image carrier is 1
9. The image forming apparatus according to claim 1, 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).
10. The image writing means for forming an electrostatic latent image on the charged surface of the image carrier charged by the charging means, according to claim 1.
The image forming apparatus described in 1.
11. The image writing means is an exposing means for exposing the image carrier.
The image forming apparatus according to item 0.
12. The developing means is capable of developing the electrostatic latent image on the image carrier with toner and at the same time collecting the toner remaining on the image carrier.
11. The image forming apparatus according to any one of 1 to 11. Item 6. The image forming apparatus according to any one of items 1 to 5.
JP2002205503A 1997-03-05 2002-07-15 Image forming apparatus Expired - Fee Related JP3652331B2 (en)

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