JPH10307454A - Electrifying method and device, image forming device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain direct injection type electrification excellent in the uniformity of electrification and stable over a long period, even if a simple member such as an electrifying roller is used as a contact-electrifying member by interposing conductive grains in the nip part between an electrifying member and a body to be electrified. SOLUTION: In an electrifying nip part (n) being the nip part between a photoreceptor 1 as the body to be electrified and the electrifying roller 2 as the contact-electrifying member, the contact-electrification of the photoreceptor 1 is attained in a coating state with electrification accelerating grains 3. Thus, in the electrifying nip part (n), the electrifying roller 2 can come into contact with the photoreceptor 1 which having a difference between their speeds. Moreover, the electrifying roller 2 comes into close contact with the photoreceptor 1 with the electrification accelerating grains 3, that is, the grains 3 existing in the electrifying nip part (n) being the nip part between the roller 2 and the photoreceptor 1 rub the surface of the photoreceptor, without a gap, to directly inject en electric charge into the photoreceptor 1. Therefore, high electrifying efficiency which can not be obtained by conventional roller electrification can be obtained and a voltage almost equal to that applied to the electrifying roller can be applied to the photoreceptor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and a device for charging an object to be charged. More specifically, a voltage is applied,
The present invention relates to a charging method and a charging device of a contact charging method for charging a surface of an object to be charged by a flexible charging member forming a nip portion with the object to be charged.

[0002] Further, the present invention relates to an image forming apparatus provided with the charging device as a charging means for an image carrier, and a process cartridge detachable from the image forming apparatus.

[0003]

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

[0004] The corona charger is a non-contact type charging device, which includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and has a discharge opening facing the image carrier as 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, medium- and low-speed image forming apparatuses have advantages such as low ozone and low power as compared with corona chargers as a charging device for a member to be charged such as an image carrier. Many contact charging devices have been proposed and put into practical use.

[0006] The contact charging device includes a charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, a blade type, or the like. ) Is contacted, and a predetermined charging bias is applied to the contact charging member to charge the surface of the member to be charged to a predetermined polarity and potential.

[0007] The contact charging mechanism (charging mechanism,
In the charging principle), there are two types of charging mechanisms, a discharge charging mechanism and a direct injection charging mechanism, and each characteristic appears depending on which one is dominant.

[0008] Discharge Charging Mechanism This is a mechanism in which the surface of the member to be charged is charged by a discharge phenomenon occurring in a minute gap between the contact charging member and the member to be charged.

Since the discharge charging mechanism has a fixed discharge threshold for 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, although the amount of generation is much smaller than that of the corona charger, it is in principle unavoidable to generate a discharge product, so that the harmful effects of active ions such as ozone are inevitable.

[0010] Direct injection charging mechanism This is a system in which the surface of the object to be charged is charged by injecting charge directly from the contact charging member to the object to be charged. It is also called direct charging, injection charging, or charge injection charging.
More specifically, a medium-resistance contact charging member is brought into contact with the surface of the member to be charged, and charges are directly injected into the surface of the member without causing a discharge phenomenon, that is, basically without using discharge. Therefore, even when the voltage applied to the contact charging member is equal to or lower than the discharge threshold, the member to be charged can be charged to a potential corresponding to the applied voltage.

Since this charging system does not involve generation of ions, no adverse effects are caused by the discharge products. However, because of 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 form the contact charging member more densely, have a large speed difference from the member to be charged, and contact the member to be charged 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 in terms of charging stability, and is widely used.

In the roller charging, the charging mechanism is dominated by the discharging charging mechanism.

The charging roller is made of a conductive or medium-resistance rubber or foam. In some cases, these are laminated to obtain desired characteristics.

The charging roller has elasticity in order to obtain a certain contact state with a member to be charged (hereinafter, referred to as a photosensitive member). Therefore, frictional resistance is large, and in many cases, the charging roller is driven by the photosensitive member. It is driven with a slight speed difference. Therefore, even if an attempt is made to perform direct injection charging, the charging mechanism is reduced by the conventional roller charging because the absolute charging ability is reduced, the contact is insufficient, the roller is uneven, and the charging is uneven due to the adhesion of the photoconductor. The charging mechanism is dominant.

FIG. 5 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 photoconductor charging potential obtained at that time. The charging characteristic in the case of roller charging is represented by A. That is, charging starts after passing a discharge threshold of about -500V. Therefore, when charged to -500V, -10
00V DC voltage or -500V
In general, in addition to the DC charging voltage, 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 larger than the discharge threshold value so that the photoconductor potential converges on the charging potential.

More specifically, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, the surface potential of the photosensitive member increases when a voltage of about 640 V or more is applied. Start, and after that, slope 1 with applied voltage
, The photoconductor surface potential increases linearly. This threshold voltage is defined as charging start voltage Vth.

That is, in order to obtain the photosensitive member surface potential Vd required for electrophotography, the charging roller needs Vd + Vth
Therefore, a DC voltage higher than required is required. A method of applying only a DC voltage to the contact charging member to perform charging in this manner is referred to as a “DC charging method”.

However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations and the like, and Vth fluctuates when the film thickness changes due to the shaving of the photoreceptor. It was difficult to value.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more, as disclosed in JP-A-63-149669. An “AC charging method” in which a voltage on which an AC component is superimposed is applied to a contact charging member is used. This is for the purpose of effect of leveling the potential by AC, and the potential of the charged body is V V which is the center of the peak of the AC voltage.
It converges to 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 a discharge phenomenon from the contact charging member to the photosensitive member, the charging is applied to the contact charging member as described above. The voltage is required to be higher than the surface potential of the photoreceptor, and a small amount of ozone is generated.

When AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging noise) between the contact charging member and the photosensitive member due to the electric field of the AC voltage, and generation of discharge due to discharge. Deterioration of the surface of the photoreceptor becomes remarkable, and this is a new problem.

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

In the fur brush charging, the discharging mechanism is dominant in the charging mechanism.

As the fur brush charger, a fixed type and a roll type have been put to practical use. A fixed type is formed by folding a medium-resistance fiber into a base fabric and forming it in a pile shape and bonding it to an electrode. The roll type is formed by winding a pile around a cored bar. A fiber density of about 100 fibers / mm ² can be obtained relatively easily, but the contact property is still insufficient to perform sufficiently uniform charging by direct injection charging.
In order to perform sufficiently uniform charging by direct injection charging, it is necessary to provide a photoconductor with a speed difference that is difficult as a mechanical configuration, which is not practical.

The charging characteristic of the fur brush charging when a DC voltage is applied has the characteristic shown in FIG. 5B. 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 a discharge phenomenon.

C) Magnetic Brush Charging In the magnetic brush charging, a member (magnetic brush charger) having a magnetic brush portion in which conductive magnetic particles are magnetically constrained by a magnet roll or the like to form a brush is used as a contact charging member. The magnetic brush portion is brought into contact with a photosensitive member as a member to be charged, and a predetermined charging bias is applied to charge the surface of the photosensitive member to a predetermined polarity and potential.

In the case of the magnetic brush charging, the charging mechanism is dominated by the direct injection 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, direct injection charging can be uniformly performed.

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

However, there are other disadvantages such as a complicated device configuration, and the conductive magnetic particles constituting the magnetic brush portion falling off and adhering to the photoreceptor.

Japanese Patent Application Laid-Open No. Hei 6-3921 proposes a method in which charge is injected into a charge holding member such as a trap level on the surface of a photoreceptor or conductive particles in 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 no ozone is generated. Furthermore, since no AC voltage is applied, no charging noise is generated, and the charging method is excellent in ozone-less and low-power compared to the roller charging method.

D) Toner Recycling Process (Cleanerless System) In a transfer type image forming apparatus, untransferred toner remaining on a photoconductor (image carrier) after transfer is removed from the photoconductor surface by a cleaner (cleaning device). However, it is desirable that the waste toner does not appear from the viewpoint of environmental protection. Therefore, the image forming apparatus of the toner recycling process is configured to eliminate the cleaner and remove the transfer residual toner on the photoreceptor after transfer from the photoreceptor by "development simultaneous cleaning" by the developing device, and to collect and reuse it in the developing device. Has also appeared.

Simultaneous development cleaning means that the toner remaining on the photoreceptor after transfer is developed at the next and subsequent steps, that is, the photoreceptor is subsequently charged and exposed to form a latent image. This is a method of recovering by a fogging bias (fogging potential difference Vback which is a potential difference between a DC voltage applied to the developing device and a surface potential of the photoconductor). According to this method, the transfer residual toner is collected in the developing device and reused after the next process. Therefore, waste toner can be eliminated and troublesome maintenance can be reduced. In addition, the cleaner-less system has a great advantage in terms of space, and can greatly reduce the size of the image forming apparatus.

E) Powder Coating on Contact Charging Member For the contact charging device, in order to prevent charging unevenness and to perform stable and uniform charging, a configuration in which powder is applied to the contact charging member on the contact surface with the surface of the member to be charged is particularly fair. As disclosed in Japanese Patent Application Laid-Open No. 7-99442, the contact charging member (charging roller) is driven to rotate (no speed difference driving) by the member to be charged (photoreceptor), and generates ozone as compared with a corona charger such as a scorotron. Although the generation of objects is remarkably reduced, the charging principle is mainly based on the discharge charging mechanism as in the case of the above-described roller charging. In particular, since a voltage obtained by superimposing an AC voltage on a DC voltage is applied in order to obtain more stable charging uniformity, generation of ozone products due to discharge is increased. Therefore, when using 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.

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

[0037]

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

On the other hand, a 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. When a cleaner-less image forming apparatus is used for a long period of time, an ozone product accumulates, so that image deletion easily occurs.

In a cleaner-less image forming apparatus, the transfer residual toner causes charging failure in the charging section.

Therefore, in the present invention, in contact charging,
Even when a simple member such as a charging roller or a fur brush is used as a contact charging member, it realizes direct injection charging that is more excellent in charging uniformity and stable for a long period of time, that is, ozone-less direct injection charging at a low applied voltage. With a simple configuration.

It is another object of the present invention to provide an image forming apparatus and a process cartridge which have a simple configuration and are inexpensive and free from obstacles due to ozone products and poor charging.

[0042]

According to the present invention, there is provided a charging method, a charging device, an image forming apparatus and a process cartridge having the following constitutions.

(1) This is a charging method in which a voltage is applied and the surface of the member to be charged is charged by a flexible charging member forming a nip with the member to be charged. Wherein the conductive particles move at least in a nip portion between the charging member and the member to be charged.

(2) The charging method according to (1), further comprising means for supplying the conductive particles.

(3) The charging method according to (2), wherein the conductive particle supplying means applies the conductive particles directly to the charging member.

(4) The charging method according to (2), wherein the conductive particle supply means applies the conductive particles directly to the member to be charged.

(5) The resistance value of the conductive particles is 1 × 10 ¹²
(Ω · cm) or less, wherein the charging method according to any one of (1) to (4).

(6) The resistance value of the conductive particles is 1 × 10 ¹⁰
(Ω · cm) or less, wherein the charging method according to any one of (1) to (4).

(7) The charging member rotates at a counter with respect to the member to be charged (1) to (6).
The charging method according to any one of the above.

(8) The charging method according to any one of (1) to (7), wherein the charging member is made of an elastic material.

(9) The charging method according to any one of (1) to (8), wherein the charging member is made of an elastic foam.

(10) The method according to any one of (1) to (9), wherein the outermost surface layer of the member to be charged has a volume resistance of 1 × 10 ¹⁴ (Ω · cm) or less. Charging method.

(11) The member to be charged is an electrophotographic photosensitive member, and the outermost surface layer of the electrophotographic photosensitive member has a volume resistance of 1 × 1.
The charging method according to any one of (1) to (10), wherein the charging method is not less than 0 ⁹ (Ω · cm) and not more than 1 × 10 ¹⁴ (Ω · cm).

(12) A charging device to which a voltage is applied and charges the surface of the member to be charged by a flexible charging member forming a nip portion with the member to be charged. Wherein the conductive particles are interposed at least in a nip portion between the charging member and the member to be charged.

(13) The charging device according to (12), further comprising means for supplying the conductive particles.

(14) The charging device according to (13), wherein the conductive particle supply means applies the conductive particles directly to the charging member.

(15) The charging device according to (13), wherein the conductive particle supply means applies the conductive particles directly to the member to be charged.

(16) The resistance value of the conductive particles is 1 × 10
The charging method according to any one of (12) to (15), wherein the charging method is ¹² (Ω · cm) or less.

(17) The resistance value of the conductive particles is 1 × 10
The charging device according to any one of (12) to (15), wherein the charging device is ¹⁰ (Ω · cm) or less.

(18) The charging device according to any one of (12) to (17), wherein the charging member rotates at a counter with respect to the member to be charged.

(19) The charging device according to any one of (12) to (18), wherein the charging member is formed of an elastic body.

(20) The charging device according to any one of (12) to (19), wherein the charging member is made of an elastic foam.

(21) The method according to any one of (12) to (20), wherein the volume resistance of the outermost surface layer of the member to be charged is 1 × 10 ¹⁴ (Ω · cm) or less. Charging device.

(22) The member to be charged is an electrophotographic photosensitive member, and the outermost surface layer of the electrophotographic photosensitive member has a volume resistance of 1 × 1.
The charging device according to any one of (12) to (21), wherein the charging device has a value of not less than 0 ⁹ (Ω · cm) and not more than 1 × 10 ¹⁴ (Ω · cm).

(23) An image forming apparatus for forming an image by applying an image forming process including a step of charging the image carrier to the image carrier, wherein the step of charging the image carrier comprises (12) An image forming apparatus, which is the charging device according to any one of (1) to (22).

(24) An image carrier, charging means for charging the image carrier, image information writing means for forming an electrostatic latent image on the charged surface of the image carrier, and the electrostatic latent image Developing means for visualizing, and transfer means for transferring the toner image to a recording medium, and also serves as a cleaning means for collecting the toner remaining on the image carrier after the developing means transfers the toner image to the recording medium, The image carrier is an image forming apparatus that repeatedly performs image formation, and the charging unit that charges the image carrier is the charging device according to any one of (12) to (22). Image forming device.

(25) The image forming apparatus according to (24), wherein the image information writing means for forming an electrostatic latent image on the charged surface of the image carrier is an image exposure means.

(26) The conductive particles have a particle size of 10 nm.
The size is not less than the size of one pixel or more (2
The image forming apparatus according to any one of 3) to 25).

(27) A process cartridge detachably mountable to an image forming apparatus main body for executing image formation by applying an image forming process including a step of charging the image bearing member to the image bearing member. Means for charging the body and the image bearing member, wherein the charging means comprises (12)
(22) A process cartridge, which is the charging device according to any one of (22) to (22).

(28) The conductive particles have a particle size of 10 nm.
The size is not less than the size of one pixel or more (2
A process cartridge according to 7).

<Operation> Specifically, the speed difference between the charging member and the member to be charged is determined by moving the surface of the charging member to provide a speed difference between the member and the member to be charged. Preferably, the charging member is driven to rotate, and the rotation direction is rotated in a direction opposite to the moving direction of the surface of the charged member.

Although it is possible to move the surface of the charging member in the same direction as the moving direction of the surface of the member to be charged so as to have a speed difference, the charging property of the direct injection charging is different from the peripheral speed of the member to be charged and the peripheral speed of the charging member. In order to obtain the same peripheral speed ratio as that in the reverse direction, the rotation speed of the charging member in the forward direction is larger than that in the reverse direction because it depends on the speed ratio. It is advantageous in the point. The peripheral speed ratio described here is the peripheral speed ratio (%) = (the peripheral speed of the charging member−the peripheral speed of the member to be charged) / the peripheral speed of the member to be charged × 100. It is a positive value when it moves in the same direction as the surface of the member to be charged).

The conductive particles are charge accelerating particles for the purpose of assisting charging. Then, contact charging of the member to be charged is performed in a state where the charge promoting particles are present in a nip portion between the member to be charged and the contact charging member.

The presence of the charge-promoting particles allows the contact charging member to contact the charged member at a speed difference at the nip portion between the charged member and the contact charging member, and at the same time, makes the contact with the charged member densely via the charge-promoting particles. Charges can be directly injected into the object to be charged by contacting, that is, the charge-promoting particles present in the nip portion between the contact charging member and the object to be charged rub the surface of the object to be charged without gaps. That is, direct injection charging is dominant in charging the member to be charged by the contact charging member due to the presence of the charge promoting particles.

Accordingly, a high charging efficiency which cannot be obtained by the conventional roller charging or the like can be obtained, and a potential substantially equal to the voltage applied to the contact charging member can be applied to the member to be charged.

Thus, even when a charging roller or a fur brush having a relatively simple structure is used as the contact charging member, the applied bias necessary for charging the contact charging member is a voltage corresponding to the potential required for the member to be charged. Is sufficient, and a stable and safe charging method without using a discharge phenomenon can be realized.

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

In addition, it is possible to obtain an image forming apparatus and a process cartridge which can provide uniform chargeability, have no trouble due to ozone products, trouble due to poor charging, and have a simple configuration and a low cost.

The provision of the means for supplying the charge-promoting particles, which are conductive particles, enables stable charging even when the apparatus is used for a long period of time.

The resistance value of the charge accelerating particles, which are conductive particles, is 1
× 10 ¹² (Ω · cm) or less, more preferably 1 × 10
^{When it is 10} (Ω · cm) or less, uniform and stable charging can be achieved in direct injection charging.

The particle size of the charge-promoting particles, which are conductive particles, is 10
When the size is equal to or more than nm and equal to or less than the size of one pixel, it is possible to provide an image forming apparatus capable of obtaining a good image which does not hinder exposure.

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

[0083]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIG. 1) FIG. 1 is a schematic structural diagram of an example of a contact charging device according to the present invention.

1 is a member to be charged, 2 is a contact charging member disposed in contact with the member to be charged, 3 is conductive particles, and 4 is means for supplying conductive particles.

(1) Charged Member 1 In this example, the charged member 1 will be described as an electrophotographic photosensitive member. The photoreceptor 1 is a drum-shaped OPC photoreceptor (negative photoreceptor) having a diameter of 30 mm, and is driven to rotate clockwise as indicated by an arrow at a constant peripheral speed of 50 mm / sec.

(2) Contact Charging Member 2 In this embodiment, the contact charging member 2 is a conductive elastic roller (hereinafter referred to as a charging roller).

The charging roller 2 is formed by forming a medium resistance layer 2b of rubber or foam as a flexible member on a cored bar 2a.

The middle resistance layer 2b is made of resin (for example, urethane),
It was formulated with conductive particles (for example, carbon black), a sulfide agent, a foaming agent, and the like, and was formed in a roller shape on the cored bar 2a. Then the surface is polished as necessary, 12 mm in diameter,
A charging roller 2 as a conductive elastic roller having a longitudinal length of 250 mm was prepared.

When the roller resistance of the charging roller 2 of this example was measured, it was 100 kΩ. The roller resistance is set to φ30 so that a total pressure of 1 kg is applied to the metal core 2 a of the charging roller 2.
mm with the charging roller 2 pressed against an aluminum drum,
100 V was applied between the cored bar 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 have elasticity to obtain a sufficient contact state with the member to be charged, and at the same time, to have a resistance low enough to charge the moving member to be charged. On the other hand, it is necessary to prevent voltage leakage when a defect site such as a pinhole is present in the member to be charged. When a photoreceptor for electrophotography is used as a member to be charged, 10 ⁴ to 10 ⁷ are required to obtain sufficient chargeability and leakage resistance.
A resistance of Ω is desirable.

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

The material of the charging roller 2 is not limited to an elastic foam.
M, urethane, NBR, silicone rubber, a rubber material in which a conductive substance such as carbon black or metal oxide is dispersed in IR or the like for resistance adjustment, or a foamed material thereof. Also, without dispersing the conductive material,
It is also possible to adjust the resistance using an ion conductive material.

The charging roller 2 includes a photosensitive member 1 as a member to be charged.
Are pressed against each other with a predetermined pressing force against the elasticity. n is a charging nip portion which is a mutual contact nip portion between the photosensitive member 1 and the charging roller 2. This charging nip width is 3
mm. In this embodiment, the charging roller 2 is rotated at approximately 80 rpm in a clockwise direction indicated by an arrow so that the surface of the charging roller and the surface of the photoreceptor are moved at a constant speed in opposite directions to each other in the charging nip portion n. That is, the surface of the charging roller 2 as a contact charging member has a speed difference with respect to the surface of the photosensitive member 1 as a member to be charged.

Further, a DC voltage of -700 V was applied as a charging bias from the charging bias applying power source S1 to the core metal 2a of the charging roller 2.

(3) Conductive Particles 3 The conductive particles 3 are charge accelerating particles for assisting charging. Hereinafter, the particles are referred to as charge promoting particles. It is preferable to use the following materials, particle sizes, characteristics, and the like of the charge promotion particles 3.

In this example, conductive zinc oxide particles having a specific resistance of 10 ⁶ Ω · cm and an average particle diameter of 3 μm including secondary aggregates were used.

As the material of the charge accelerating particles 3, various conductive particles such as conductive inorganic particles such as other metal oxides and mixtures with organic substances can be used.

The particle resistance is desirably 10 ¹² Ω · cm or less, more preferably 10 ¹⁰ Ω · cm or less, in order to transfer charges via the particles.

The resistance was measured by the tablet method and normalized. That is, about 0.5 g of a powder sample was placed in a cylinder having a bottom area of 2.26 cm ² , and 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. Was calculated.

The particle size is 50 in order to obtain good charging uniformity.
μm or less is desirable. The lower limit of the particle size is limited to 10 nm as long as the particles can be obtained stably.

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.

In the measurement of the particle size, 100 or more samples were extracted from the observation with an optical or electron microscope, the volume particle size distribution was calculated using the maximum chord length in the horizontal direction, and the 50% average particle size was determined.

As described above, there is no problem that the charge accelerating particles 3 exist not only in the state of primary particles but also in the state of aggregation of secondary particles. Regardless of the state of aggregation, the form is not important as long as the function as the charge accelerating particles can be realized as an aggregate.

The charge accelerating particles 3 are preferably non-magnetic so as not to hinder exposure.

(4) Conductive Particle Supplying Means (Charging Acceleration Particle Coating Means) 4 In the present example, the charging nip n, which is the nip between the photosensitive member 1 as a member to be charged and the charging roller 2 as a contact charging member, is provided. In order to interpose the charge accelerating particles 3, a means 4 for supplying the charge accelerating particles 3 to the surface of the photoreceptor 1 is provided upstream of the charging nip n in the photoreceptor rotation direction.

In the present embodiment, the charge-promoting particle supply 4 is a regulating blade. The regulating blade 4 is brought into contact with the photosensitive member 1, and the charge-promoting particles 3 are stored between the photosensitive member 1 and the regulating blade 4.
In this case, the charge accelerating particles 3 are applied to the surface of the photoconductor 1 and supplied.

That is, as the photoreceptor 1 rotates, a certain amount of the charge-promoting particles 3 is applied to the surface of the photoreceptor 1 and is carried to the charging nip portion n so that the charge-promoting particles 3 are uniformly supplied to the charging nip portion n. As a result, the charge promotion particles 3 are interposed in the charge nip n.

The charging roller 2 as a contact charging member is rotated with a speed difference with respect to the photosensitive member 1 as a member to be charged. For this reason, the vicinity of the charging nip n, which is the contact nip portion of the charging roller 2 made of an elastic body with the photosensitive member 1, is greatly deformed as compared with the case where the charging roller is driven, and adheres to the surface of the charging roller 2. The charge accelerating particles 3 are
It tends to move upward, and the number of charge promoting particles on the surface of the charging roller decreases as the device is used. Therefore, the charging promotion particle supply means 4 always supplies a certain amount of the charging promotion particles to the photosensitive member 1.
The toner is applied to the surface and supplied to a charging nip n, which is a contact nip between the charging roller 2 and the photoconductor 1.

If the amount of the charge-promoting particles 3 in the charging nip portion between the photosensitive member 1 and the charging roller 2 as the contact charging member is too small, the lubricating effect of the particles cannot be sufficiently obtained, and The friction with the photoreceptor 1 is large, and it is difficult to drive the charging roller 2 to rotate the photoreceptor 1 with a speed difference. In other words, the driving torque becomes excessive,
If it is forcibly rotated, the surfaces of the charging roller 2 and the photoconductor 1 will be scraped. Further, the effect of increasing the chance of contact by the particles may not be obtained, so that sufficient charging performance cannot be obtained. On the other hand, if the intervening amount is too large, the detachment of the charge-promoting particles 3 from the charging roller 2 is remarkably increased, which adversely affects image formation.

According to the experiment, the intervening amount was 10 ³ pieces / mm ²
The above is desirable. If it is lower than 10 ³ / mm ² , a sufficient lubricating effect and an effect of increasing the contact chance cannot be obtained, and the charging performance is lowered.

More desirably, 10 ^{3 to} 5 × 10 ⁵ pieces / m
The intervening amount of m ² is preferred. If the number exceeds 5 × 10 ⁵ particles / mm ² , the particles drop off to the photoreceptor 1 significantly, resulting in insufficient exposure of the photoreceptor 1 irrespective of the light transmittance of the particles themselves. If it is less than 5 × 10 ⁵ particles / mm ² , the amount of particles falling off can be kept low, and the adverse effect can be improved. When the abundance of the particles dropped on the photoreceptor 1 in the intervening amount range is measured, it is 10 ²
Since it was 10 ⁵ / mm ² , it is desired that the abundance having no adverse effect on image formation be 10 ⁵ / mm ² or less.

A method for measuring the intervening amount and the abundance amount on the photosensitive member 1 will be described. It is desirable to directly measure the interposed amount between the charging roller 2 and the charging nip portion n of the photoconductor 1, but most of the particles existing on the photoconductor 1 before coming into contact with the charging roller 2 come into contact while moving in the opposite direction. In the present invention, the amount of particles on the surface of the charging roller 2 immediately before reaching the charging nip n is defined as the intervening amount. Specifically, the rotation of the photosensitive drum 1 and the charging roller 2 is stopped without applying a charging bias, and the surfaces of the photosensitive member 1 and the charging roller 2 are cleaned with a video microscope (OVM1000N made by OLYMPUS) and a digital still recorder (made by DELTAS). SR-3100). Regarding the charging roller 2, the charging roller 2 is brought into contact with the slide glass under the same conditions as the contact with the photosensitive drum 1, and the contact surface is viewed from the back of the slide glass with a video microscope at 10 or more locations using a 1000 × objective lens. Taken. In order to separate individual particles from the obtained digital image, binarization processing was performed with a certain threshold value, and the number of regions where particles were present was measured using desired image processing software. The amount of the photoconductor 1 on the photoconductor 1 is also determined.
The upper part was photographed with the same video microscope, and the same processing was performed to measure.

The adjustment of the intervening amount was performed by changing the setting of the regulating blade.

(5) Charging of the photoreceptor 1 The charge-promoting particles 3 are applied to the charging nip n, which is the nip between the photoreceptor 1 to be charged and the charging roller 2 as a contact charging member. In this state, contact charging of the photoconductor 1 is performed.

As a result, at the charging nip n, the charging roller 2 can come into contact with the photosensitive member 1 with a speed difference, and at the same time, the charging roller 2 contacts the photosensitive member 1 densely through the charge promoting particles 3.
That is, charges can be directly injected into the photoconductor 1 by the charge-promoting particles 3 present in the charging nip n, which is a nip portion between the charging roller 2 and the photoconductor 1, rubbing the photoconductor surface without gaps. That is, the charging of the photoconductor 1 by the charging roller 2 is dominated by direct injection charging due to the presence of the charge promoting particles 3.

Accordingly, a high charging efficiency, which cannot be obtained by the conventional roller charging, can be obtained, and a potential substantially equal to the voltage applied to the charging roller can be applied to the photosensitive member 1. In this example, the photosensitive member 1 is charged to a potential of -680 V, which is substantially the same as the -700 V DC voltage applied to the charging roller 2.

Thus, even when a charging roller having a relatively simple structure is used as the contact charging member, the charging roller 2
The applied bias required for the charging of the photosensitive member 1 is sufficient to be a voltage corresponding to the potential required for the photosensitive member 1 to be charged, and a stable and safe charging method using no discharge phenomenon can be realized. In other words, even when a simple member such as a charging roller is used as a contact charging member in the contact charging device, it is possible to realize direct injection charging that is more excellent in charging uniformity and stable for a long period of time. Can be realized with a simple configuration.

<Embodiment 2> (FIG. 2) FIG. 2 is a schematic structural diagram of another example of the contact charging device according to the present invention.

This embodiment is different from the contact charging device of Embodiment 1 described above in that the charging-promoting particle supply means 4 is provided not on the photosensitive member 1 as a member to be charged but on the charging roller 2 as a contact charging member. It is. Other device configurations are the first embodiment.
Since it is the same as the contact charging device described above, the description thereof will not be repeated.

Also in the case of this embodiment, the charging-promoting particle supply means 4 is a regulating blade, and the regulating blade 4 is brought into contact with the charging roller 2 to store the charging-promoting particles 3 between the charging roller 2 and the regulating blade 4. Take a configuration to hold.

With the rotation of the charging roller 2, a certain amount of the charge-promoting particles 3 is applied to the surface of the charging roller 2 and carried to the charging nip n, where the charge-promoting particles 3 are uniformly supplied to the charging nip n. In this state, the charge promotion particles 3 are interposed in the charge nip n.

In the case of this embodiment, as in the case of the first embodiment, the charging of the photosensitive member 1 by the charging roller 2 is dominated by direct injection charging due to the presence of the charge promoting particles 3.

As in the present embodiment, the structure in which the charge accelerating particle coating means 4 is provided on the side of the charging roller 2 as a contact charging member is as follows.
The application of the charge-promoting particles 3 can be performed without increasing the number of devices around the photoreceptor 1 which is the member to be charged, which is effective in reducing the size of the device.

<Embodiment 3> (FIG. 3) This embodiment relates to the charging device of Embodiment 1 or 2 described above.
By adjusting the surface resistance of the member 1 to be charged, charging is performed more stably and uniformly. In this embodiment, a charge injection layer is provided on the surface of the photoreceptor 1 as a member to be charged, and the resistance of the surface of the photoreceptor is adjusted to stably and uniformly charge.

FIG. 3 is a schematic diagram of the layer structure of the photoreceptor 1 used in this example and having a charge injection layer on the surface. That is, the photoreceptor 1 has an undercoat layer 12, a positive charge injection prevention layer 13, and a charge generation layer 1 on an aluminum drum substrate (Al drum substrate) 11.
4. The charge performance is improved by applying the charge injection layer 16 to a general organic photoreceptor drum which is coated in the order of the charge transport layer 15.

The charge injection layer 16 is formed by adding a photo-curable acrylic resin as a binder to conductive particles (conductive filler).
SnO ₂ ultrafine particles 16a (having a diameter of about 0.03 μm)
m) A film is formed by mixing and dispersing a lubricant such as tetrafluoroethylene resin (trade name: Teflon), a polymerization initiator, and the like, coating the mixture, and then performing photo-curing.

An important point for the charge injection layer 16 is the resistance of the surface layer. In the charging method by direct injection of electric charges, the electric charges can be transferred more efficiently by lowering the resistance of the object to be charged. On the other hand, an image carrier (photoconductor)
, It is necessary to hold the electrostatic latent image for a certain time, so that the volume resistance of the charge injection layer 16 is 1 ×
A range of 10 ⁹ to 1 × 10 ¹⁴ (Ω · cm) is appropriate.

Even when the charge injection layer 16 is not used as in the present configuration, the same effect can be obtained, for example, when the charge transport layer 15 is within the above resistance range.

Further, the volume resistance of the surface layer is about 10 ¹³ Ωcm
A similar effect can be obtained by using an amorphous silicon photosensitive member or the like.

Embodiment 4 (FIG. 4) This embodiment is an example of an image forming apparatus provided with a contact charging device according to the present invention. FIG. 4 is a schematic model diagram of the image forming apparatus.

The image forming apparatus of this embodiment is a laser printer (recording apparatus) using a transfer type electrophotographic process, a process cartridge attaching / detaching method, and a toner recycling process (cleanerless system).

By using the contact charging device according to the present invention as the charging means for the image bearing member, good direct charging performance can be obtained even in an image forming apparatus of a cleanerless system having no cleaning device.

(1) Overall Schematic Configuration of the Printer In this example, reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member having a diameter of 30 mm as an image carrier, and a predetermined peripheral speed (process speed PS) in a clockwise direction indicated by an arrow. Is driven to rotate. In this example, PS = 50 mm / sec or PS = 100 mm
/ Sec.

Reference numeral 2 denotes a charging roller as a contact charging member for the photosensitive member 1. In this embodiment, the contact charging device of the second embodiment is used, and a charging-promoting particle supply unit 4 is provided on the charging roller 2 side. The charging roller 2 is rotationally driven in a clockwise direction indicated by an arrow with a difference in peripheral speed so that the surface of the charging roller and the surface of the photosensitive member move in directions opposite to each other in the charging nip portion n. Also, a core metal 2a of the charging roller 2
, A DC voltage of -700 V was applied from the charging bias application power source S1.

Therefore, as described above, the surface of the rotating photoconductor 1 is contacted by the charging roller 2 with a peripheral speed difference, and
Since the charge accelerating particles 3 applied by the charging roller 2 are present in the charging nip portion n, the charging of the photoconductor 1 by the charging roller 2 becomes dominant by direct injection charging, and has substantially the same potential as the charging bias voltage applied to the charging roller 2. Is uniformly charged.

Reference numeral 5 denotes 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 in accordance with a time-series electric digital pixel signal of target image information, and scans and uniformly exposes the uniformly charged surface of the rotary photoreceptor 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 6 denotes a developing device. The electrostatic latent image on the rotating photoreceptor 1 is developed as a toner image by this developing device. The developing device 6 is, for example, a one-component or two-component non-contact reversal developing device having a non-magnetic developing sleeve 6b containing a magnet roller 6a as a developer carrying member. Reference symbol a denotes a developing area portion which is an opposing portion between the photosensitive member 1 and the developing sleeve 6b. S2 is the developing sleeve 6b
Is a developing bias application power supply.

Reference numeral 7 denotes a transfer roller as transfer means.
The transfer nip b is formed by pressing the photosensitive member 1 in a predetermined manner. A transfer material P as a recording medium is supplied to the transfer nip b from a paper supply unit (not shown) at a predetermined timing.
In addition, when a predetermined transfer bias is applied to the transfer roller 7 from the power supply S3, the toner image on the photoconductor 1 is sequentially transferred to the surface of the transfer material P fed to the transfer nip portion b.

Reference numeral 8 denotes a fixing device. Transfer material P fed to transfer nip portion b and receiving the transfer of the toner image on photoconductor 1 side
Is separated from the surface of the rotating photoreceptor 1 and introduced into the fixing device 8, where the toner image is fixed to form an image formed product (print, copy).

The printer of this embodiment is cleaner-less,
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,
As the photoconductor 1 rotates, it reaches the developing area a via the charging roller position and is cleaned (collected) at the same time as the development in the developing device 6 (toner recycling process).

As described above, the simultaneous cleaning for development is as follows.
The toner remaining on the photoreceptor 1 after the transfer is developed in a subsequent image forming process, that is, the photoreceptor is charged and exposed to form a latent image. That is, a fog removal potential difference Vback which is a potential difference between a DC voltage applied to the developing device and a surface potential of the photosensitive member. Is to be recovered. In the case of the reversal development as in the printer in this embodiment, the simultaneous cleaning of development involves applying the electric field for collecting the toner from the dark portion potential of the photoconductor to the developing sleeve and attaching the toner from the developing sleeve to the bright portion potential of the photoconductor. This is done by the action of an electric field.

Reference numeral 9 denotes a process cartridge which is detachable from the printer main body. In the printer of this embodiment, a photoreceptor 1, a charging roller 2 including a charge accelerating particle supply unit 4, and a developing device 6 are collectively configured as a process cartridge detachably mountable to a printer main body. The combination of the process devices to be formed into the process cartridge is not limited to the above, and is optional. 1
Reference numerals 0 and 10 denote attachment / detachment / holding members for the process cartridge.

The color-promoting particles 3 are preferably colorless or nearly white particles so as not to hinder the exposure of the latent image when the photoconductor 1 is charged. Further, when performing color recording, the charge accelerating particles 3 are transferred from the photosensitive member to the recording material P.
Considering the case where the image is transferred to a colorless image, a colorless or nearly white color is desirable. Also, in order to prevent light scattering by the charge-promoting particles during image exposure, it is desirable that the particles have a size equal to or less than the constituent pixel size.

In the transfer nip portion b, the toner image on the photosensitive member 1 is attracted to the transfer material P by the influence of the transfer bias and is positively transferred, but the charge promoting particles 3 on the photosensitive member 1 are electrically conductive. Does not positively transfer to the transfer material P side,
It is substantially adhered and held on the surface of the photoconductor 1. Further, the effect of improving the transfer efficiency of the toner image from the photoconductor 1 side to the transfer material P side is obtained by the presence of the charge promoting particles 3 substantially adhered and held on the photoconductor 1 surface.

(2) Examples and Comparative Examples Table 1 summarizes the superiority of the present invention together with the comparative examples.

[0146]

[Table 1] In the comparative example, in the printer of FIG. 4, the charge accelerating particles 3 are previously applied to the surface of the charging roller 2, but the charge accelerating particles 3 are not supplied.

The charging performance was evaluated using printers (PS = 50 mm / s) having different printing speeds (process speed PS).
ec, PS = 100 mm / sec), and the ghost image was evaluated according to the superiority. Ghosts include exposure ghosts and transfer residual ghosts. Exposure ghosts, when the imagewise exposed portion of the first round of the photoconductor has insufficient chargeability,
It means that a ghost image is developed due to charging failure in the second round. In the case of a cleaner-less transfer residual ghost, the transfer residual toner inhibits charging and causes poor charging, resulting in a ghost image. Here, both ghost images were evaluated together based on the following criteria.

X: A ghost pattern is seen in a white background portion after exposure.

Δ: No ghost pattern is observed in a white background portion after exposure, but a ghost pattern is observed in a halftone portion after exposure.

：: No ghost pattern was observed in any of the white background portion and the halftone portion after exposure.

The ghost evaluation was performed after printing 100 sheets (A4 vertical direction).

As is evident from Table 1, in the comparative example, the charging performance was not satisfied by any of the apparatuses at any speed.

In Examples 1 and 2 in which the charge accelerating particles 3 were applied to the photoreceptor 1 or the charging roller 2 and supplied, the chargeability was almost satisfied at any speed.

Further, by adjusting the resistance of the surface layer of the photoreceptor as in the third embodiment as in the third embodiment, the chargeability is improved, and sufficient charging can be performed even in a printer of 100 mm / sec. there were.

Further, even in the case of the cleanerless apparatus as in the fourth embodiment, the charging property was almost satisfied at any speed.

In addition, although the surface of the photoreceptor has a low resistance due to adsorption of ozone products and the like, the image flow caused by blurring (flowing) of the latent image is likely to occur in a high-temperature and high-humidity environment. No image deletion was observed.

<Others> 1) The means for supplying the charge-promoting particles 4 for the member 1 to be charged and the contact charging member 2 is not limited to the embodiment described above. The fur brush may be arbitrarily arranged such that the fur brush is disposed in contact with the member to be charged 1 or the contact charging member 2.

2) The charging roller 2 as a flexible contact charging member is not limited to the charging roller of the embodiment. In addition to the charging roller, a material and a shape such as a fur brush, felt, and cloth can be used as the contact charging member. It is also possible to obtain a more appropriate elasticity and conductivity by laminating them.

For example, an elastic body such as a fur brush in which each pile has elasticity can be used. Here, the fur brush roller is a fiber whose resistance is adjusted (Unitika-Re
c) are planted and formed into a pile with a density of 155 / mm ² and a fiber length of 3 mm, and thereafter the pile is wound around a φ6 mm core metal and fixed, and formed into a roller shape.

3) As the applied charging bias or the applied developing bias to the contact charging member 2 and the developing sleeve 6a, an alternating voltage (AC voltage) may be superimposed on a DC voltage.

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

4) The image forming apparatus and the process cartridge may have a cleaning device.

5) The image exposing means for forming an electrostatic latent image is not limited to the laser scanning exposing means for forming a digital latent image as in the embodiment, but may be a general analog type. Other light-emitting elements such as an image exposure or LED may be used, and any device that can form an electrostatic latent image corresponding to image information, such as a combination of a light-emitting device such as a fluorescent lamp and a liquid crystal shutter, may be used.

The image carrier may be an electrostatic recording dielectric or the like. In this case, after the dielectric surface is uniformly charged to a predetermined polarity and potential, the charge is selectively removed by a charge removing means such as a charge removing needle head or an electron gun to write and form a desired electrostatic latent image.

6) The recording medium that receives the transfer of the toner image from the image carrier may be an intermediate transfer member such as a transfer drum.

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

The measuring method is as follows.
A surfactant as a dispersant in 150 ml, preferably
0.1 to 5 ml of an alkylbenzene sulfonate is added, and 0.5 to 50 mg of a measurement sample is further added.

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

[0169]

As described above, according to the present invention,
Even a simple contact charging member such as a charging roller or a fur brush is moved with a speed difference with respect to a member to be charged, and at least a nip portion between the contact charging member and the member to be charged is charged with conductive particles as conductive particles. Intermediate, sufficient contact properties are obtained, direct injection charging becomes dominant, and uniform charge injection charging becomes possible.

Further, by providing a means for supplying the charge accelerating particles, the charge can be stably performed even when the apparatus is used for a long time.

Further, even in an image forming apparatus having a step of charging an image carrier, particularly an image forming apparatus having no cleaning device, uniform charging properties can be obtained.

Therefore, even when a simple member such as a charging roller or a fur brush is used as the contact charging member in the contact charging device, it is possible to realize direct injection charging that is more excellent in charging uniformity and stable for a long period of time. In addition, ozone-less direct injection charging at a low applied voltage can be realized with a simple configuration.

In addition, it is possible to obtain an image forming apparatus or a process cartridge which is simple in structure and inexpensive and has no troubles due to ozone products and troubles due to poor charging. Achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a contact charging device according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a contact charging device according to a second embodiment.

FIG. 3 is a schematic diagram illustrating a layer configuration of a photoconductor provided with a charge injection layer on a surface according to a third embodiment.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to a fourth embodiment.

FIG. 5: Charging characteristic graph

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive member (image bearing member, member to be charged) 2 Charging roller (contact charging member) 3 Charging promoting particles (conductive particles) 4 Control blade (particle supply means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Nagase 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (28)

[Claims] 1. A charging method in which a voltage is applied and a surface of a member to be charged is charged by a flexible charging member forming a nip portion with the member to be charged. A charging method characterized in that conductive particles are interposed at least in a nip portion between a charging member and a member to be charged. 2. The charging method according to claim 1, further comprising means for supplying the conductive particles. 3. The charging method according to claim 2, wherein said conductive particle supply means directly applies conductive particles to a charging member. 4. The charging method according to claim 2, wherein said conductive particle supply means applies the conductive particles directly to the member to be charged. 5. The conductive particles have a resistance value of 1 × 10 ¹² (Ω).
··· cm) or less, wherein the charging method according to any one of claims 1 to 4, wherein 6. The conductive particles have a resistance value of 1 × 10 ¹⁰ (Ω).
··· cm) or less, wherein the charging method according to any one of claims 1 to 4, wherein 7. The charging method according to claim 1, wherein the charging member rotates at a counter with respect to the member to be charged. 8. The charging method according to claim 1, wherein the charging member is made of an elastic body. 9. The charging method according to claim 1, wherein the charging member is made of an elastic foam. 10. The charging method according to claim 1, wherein a volume resistance of an outermost surface layer of the member to be charged is 1 × 10 ¹⁴ (Ω · cm) or less. 11. The object to be charged is an electrophotographic photosensitive member, and the outermost surface layer of the electrophotographic photosensitive member has a volume resistance of 1 × 10
The charging method according to claim 1, wherein the charging rate is ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω · cm) or less. 12. A charging device to which a voltage is applied and charges a surface of a member to be charged by a flexible charging member forming a nip with the member to be charged, wherein the surface of the charging member has a speed difference with respect to the surface of the member to be charged. A charging device, wherein the charging device moves with at least a nip portion between a charging member and a member to be charged. 13. The charging device according to claim 12, further comprising means for supplying the conductive particles. 14. The charging device according to claim 13, wherein said conductive particle supply means directly applies conductive particles to a charging member. 15. The charging device according to claim 13, wherein the conductive particle supply means applies the conductive particles directly to the member to be charged. 16. The conductive particles have a resistance value of 1 × 10
13. The method according to claim 12, wherein the resistance is not more than ¹² (Ω · cm).
16. The charging method according to any one of items 15 to 15. 17. The conductive particles having a resistance value of 1 × 10
13. The resistance value is equal to or less than ¹⁰ (Ω · cm).
The charging device according to any one of items 1 to 15, wherein 18. The apparatus according to claim 12, wherein said charging member rotates at a counter with respect to the member to be charged.
The charging device according to any one of the above. 19. The charging device according to claim 12, wherein the charging member is formed of an elastic body. 20. The charging device according to claim 12, wherein the charging member is made of an elastic foam. 21. The charging device according to claim 12, wherein a volume resistance of an outermost surface layer of the member to be charged is 1 × 10 ¹⁴ (Ω · cm) or less. 22. The member to be charged is an electrophotographic photosensitive member, and the outermost surface layer of the electrophotographic photosensitive member has a volume resistance of 1 × 10
The charging device according to any one of claims 12 to 21, wherein the charging amount is ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω · cm) or less. 23. 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 of charging the image carrier is performed. From 22
An image forming apparatus, which is the charging device according to any one of the above. 24. An image bearing member, charging means for charging the image bearing member, image information writing means for forming an electrostatic latent image on a charged surface of the image bearing member, and visualizing the electrostatic latent image with toner Developing means for transferring the toner image to a recording medium, and cleaning means for collecting toner remaining on the image carrier after the developing means transfers the toner image to the recording medium. 23. An image forming apparatus wherein the carrier is repeatedly used for image formation, and a charging unit for charging the image carrier is provided.
An image forming apparatus, which is the charging device according to any one of the above. 25. The image forming apparatus according to claim 24, wherein the image information writing means for forming an electrostatic latent image on the charged surface of the image carrier is an image exposure means. 26. The method according to claim 23, wherein the particle size of the conductive particles is not less than 10 nm and not more than one pixel.
25. The image forming apparatus according to any one of items 25 to 25. 27. A process cartridge detachably mountable to an image forming apparatus main body for performing image formation by applying an image forming process including a step of charging the image carrier to the image carrier, and at least the image carrier. 23. A process cartridge comprising: charging means for charging the image bearing member; and the charging means is the charging device according to any one of claims 12 to 22. 28. The method according to claim 27, wherein the particle size of the conductive particles is not less than 10 nm and not more than one pixel.
The process cartridge according to 1.