JP3067064B2 - Contact charging particles, method of charging object surface, method of charging photoreceptor, and image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the charging of an object, and more particularly to the charging of particles for uniformly charging an electrophotographic photosensitive member in an image forming apparatus such as a printer or a copying machine.

[0002]

2. Description of the Related Art F. Since the invention of electrophotography by Carlson (U.S. Pat. No. 2,297,691),
Various improvements and developments have been made based on this method. An electrophotographic method represented by the Carlson method is widely used at present, and its basic process is to uniformly charge a photosensitive member, form a latent image by selective exposure, form a toner image with a developer, transfer and fix.

[0003] As a charging method for charging a photoreceptor in the dark, a corona discharge method is representative, and it is still the mainstream of commercially available products. However, the corona discharge method has a problem that ozone is generated, and also has a problem that a large amount of electric power is used and an installation space is increased. Therefore, as a technique to solve the shortcomings of the corona discharge method, conductive roller,
In recent years, a contact charging method in which a conductive member such as a conductive brush or conductive particles is brought into contact with a photoreceptor and a voltage is applied through the conductive member has attracted attention in recent years.

The particle charging method using conductive particles is a method of forming a magnetic brush with magnetic particles and injecting electric charges through the magnetic particles, and has a relatively high resistance of about 10 ³ to 10 ⁷ Ω · cm. The photoreceptor was charged by applying a high bias voltage of 1 KV or more using the magnetic particles described above. For example, in JP-A-61-57958, a charging bias voltage of 2000 V is applied to magnetic particles of 10 ⁶ Ω · cm.

However, in the conventional contact particle charging method, it is difficult to uniformly charge to a desired charging potential in a short contact time, and if charging particles having a very low resistance are used in order to enhance charging efficiency, the photoconductor is insulated. There is a problem of destruction, especially in the case of a low bias charging photoconductor.

That is, when the photosensitive member is charged with the contact particles at a low charging bias voltage of about 100 V, the resistance of the magnetic particles for charging is preferably 10 ¹ to 10 ⁸ Ω · cm. For example, when magnetic particles having a level of 10 ² Ω · cm are used, if there is an abnormal current or a minute defective portion of the photoconductor, a pinhole is generated due to dielectric breakdown.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent dielectric breakdown and uniformly charge an object by contact particle charging.

[0008]

Contact charging particles <br/> of the present invention SUMMARY OF] injects charge into an object that contacts a voltage is applied, a contact charging particles for charging the surface of the object, the magnetic And a mixture of high-resistance particles having a volume resistivity of 5 × 10 ⁴ Ω · cm or more and conductive particles having a magnetic property and a volume resistivity of 5 × 10 ³ Ω · cm or less. ¹
The conductive particles have a volume resistivity of 10 ⁸ Ω · cm, the average particle size of the conductive particles is smaller than the average particle size of the high-resistance particles, and at least 10% by weight of the conductive particles has a particle size of 10 μm or less. Yes, 5% by weight or more of the whole is high resistance particles.

Further, the method of charging the invention, the contact charging
The method is characterized in that a voltage is applied to the surface of an object via the particles for contact charging while the particles for contact and the surface of the object are brought into contact and the particles for contact charging are stirred. This charging method is particularly suitable for a method of charging a photosensitive member used in an image forming method using an electrophotographic method.

An image forming apparatus according to the present invention comprises a charging member for uniformly charging a photoreceptor, and a charging member for selectively lowering a charging potential of the photoreceptor by selective light irradiation to form an electrostatic device comprising a low potential portion and a high potential portion. An exposure member that forms a latent image on a photoconductor, a photoconductor on which an electrostatic latent image is formed is brought into contact with a developer, and toner is selectively adhered to form an image made of toner on the photoconductor. The charging member is magnetic and has a volume resistivity of 5 × 10 ^4.
It is composed of a mixture of high resistance particles of Ω · cm or more and conductive particles having magnetism and a volume resistivity of 5 × 10 ³ Ω · cm or less, and a volume resistivity of 10 ¹ to 10 ⁸ Ω · cm as a mixture. The average particle size of the conductive particles is smaller than the average particle size of the high-resistance particles, and 10% by weight or more of the entire particles have a particle size of 10 μm.
m or less, and 5% by weight or more of the particles are high-resistance particles, and contact charging particles that come into contact with the photoreceptor under stirring.
And children, and a magnetic member attracted contact charging particles by magnetic force, it restrains the contact charging particles allows stirring, contact charging
A charging bias power supply for applying a voltage to the photoreceptor via the toner particles .

[0011]

FIG. 1 is an explanatory view showing an embodiment in which the charging method of the present invention is applied to an image forming system using an electrophotographic photosensitive member. A charging unit 21, an exposure unit (LED exposure optical system 41), a developing unit 51, a transfer unit 71, and a fixing unit 81 are arranged around the drum-shaped photoconductor 11 in which the photoconductive layer 15 is formed on the conductive support 13. Are arranged. The photoconductor 11 may be a belt-shaped (sheet-shaped).

As the photoconductor 11, an a-Si photoconductor,
Appropriate materials such as an OPC-based photoconductor (organic photoconductor) and a Se-based photoconductor can be employed. First, the photoconductor 11 is charged in the dark by the charging unit 21. The charging unit 21
Magnetic contact with a magnetic brush roller 23 (magnetic member) including a mag roller 25 and a conductive charging sleeve 27
It comprises charging particles 29 and a charging bias power supply 31. The contact charging particles 29 are applied with a voltage from a charging bias power supply 31 via a charging sleeve 27, contact the photoconductor 11, inject electric charge into the photoconductor 11, and charge the magnetic brush roller 23. The magnetic brush roller 23 rotates while contacting the photoconductor 11 with the rotation of the magnetic brush roller 23.

The photoreceptor 11 having a uniformly charged surface is exposed to an image by an LED exposure optical system 41. By the image exposure, the surface potential of the exposed portion is selectively reduced, and an electrostatic latent image composed of a low potential portion and a high potential portion is formed. In the embodiment shown in FIG. 1, the potential of a portion corresponding to a future image portion is reduced by the LED exposure optical system 61 with the use as a printer in mind. The LED exposure optical system 61 is a combination of an LED array in which LED chips are linearly arranged by the number of recording pixels and an image forming optical system such as a selfoc lens, but a rotating mirror is used instead of the LED exposure optical system. And a laser exposure optical system using an f-θ lens, or a copying optical system that irradiates reflected light from an original document when applied to a copying machine. Alternatively, the rear image may be exposed from the inside of the photoconductor 11. The photoconductor 11 on which the electrostatic latent image is formed is
Next, the image is developed by the developing unit 51.

The developing unit 51 supplies a developer 91 to the surface of the photoconductor 11 by a developing roller 53. A developing bias power source 59 for applying a developing bias voltage between the photoconductor 11 and the developing roller 53 is connected to the conductive developing sleeve 57 of the developing roller 53. Developing roller 53
Is a mag roller 5 having several magnetic poles (N and S poles).
5 is contained in a conductive developing sleeve 57. At the time of development, a bias voltage is applied from a developing bias power supply 59 to generate a developing bias electric field between the developing roller 53 and the photoconductor 11.

By the development, the toner 93 in the developer 91 is
Selectively adheres to the electrostatic latent image on the photoconductor, and an image composed of toner is formed on the photoconductor 11. The toner 93 is transferred to the paper 95 by the transfer roller 73 to which a negative bias voltage is applied by the transfer bias power supply 75 in the transfer unit 73. Reference numeral 69 denotes a registration roller that sends out the paper 95. Next, the transfer toner is applied to the paper 95 by the fixing roller 83 (heating roller) in the fixing unit 81.
Is established. Reference numeral 85 denotes a pressure roller. The residual toner remaining on the photoconductor 11 without being transferred at the time of transfer is removed by the cleaning blade 99.

In the above description, the case where the photoreceptor 11 is positively charged and an image is formed by reversal development using a two-component developer has been described. Other development processes can be applied. The contact charging particles are composed of a mixture of magnetic conductive particles and magnetic high-resistance particles, and the average particle diameter of the whole is 5 to 40.
μm is suitable, and preferably 5 to 30 μm. If the average particle size is too large, uniform charging becomes difficult. On the other hand, if the average particle size is too small, it becomes physically difficult to adhere to the photoreceptor 11 and to be restrained by the magnetic brush roller 13.

The average particle size of the conductive particles is smaller than that of the high-resistance particles, and is preferably 1/2 or less, more preferably 1/3 or less of the average particle size of the high-resistance particles. The average particle size of the conductive particles is preferably 0.5 to 15 μm, and more preferably 2 to 10 μm. The average particle size of the high resistance particles is 10 to 50 μm, preferably 15 to 40 μm.

Further, 10 of the total particles of the contact charging particles
At least 5% by weight, preferably 10-70% by weight of the particles are conductive particles, while at least 5% by weight, preferably 30-90% by weight of the total particles are high resistance particles. If the number of the conductive particles is too small, it is difficult to uniformly charge the photoconductor 11, and if the number of the high-resistance particles is too small, a current flows partially and suddenly through the photoconductor 11, causing dielectric breakdown. consisting of pinhole easy to generate. Contact charging
The particles for use have an overall volume resistivity of 10 ¹ to 10 ⁸ Ω · cm, preferably 10 ² to 10 ⁷ Ω · cm.

The volume resistivity of the present invention is as follows. The particle is obtained by adding a particle to a Teflon cylindrical body having an inner diameter of 20 mm and having an electrode at the bottom.
5 g, insert an electrode with an outer diameter of 20 mm
It is a value measured by applying a load of kg. The conductive particles are not more than 5 × 10 ³ Ω · cm, preferably 1 × 10 ¹ to 1
It has a volume resistivity of × 10 ³ Ω · cm. If this value is too large, the photoconductor cannot be sufficiently charged.
The high resistance particles are 5 × 10 ⁴ Ω · cm or more, preferably 5 × 10 ⁴ Ω · cm or more.
Having a volume resistivity of × 10 ^{4 to} 5 × 10 ⁹ Ω · cm;
If this value is too small, it will lead to dielectric breakdown of the photoconductor.

FIG. 2 is a schematic view of a magnetic brush formed by the contact charging particles of the present invention. The contact charging particles 101 are both magnetic, are composed of high resistance particles 103 having a large particle diameter and small conductive particles 105, are magnetically attracted to the magnetic brush roller 23, and form a magnetic brush so as to be continuous with each other. At this time, the fine conductive particles 105 of 10 μm or less adhere to the side surfaces of the high-resistance particles 103 and are held by the magnetic force. Further, the particles for contact charging are agitated by friction with the surface of the photoreceptor 11, and exhibit conductivity due to spatial movement. Conduction by space movement means that in a mixed system in which conductive particles and high-resistance particles coexist, even when little current flows in the stationary state, the particles are kept under stirring, and when they move with each other, current flows easily. Say a phenomenon.

Referring to FIG. 3, the conduction due to the spatial movement will be described. Homogeneous contact zone consisting only of high resistance particles
A charging particle and a contact charging particle of a mixed system in which conductive particles are mixed with high-resistance particles are prepared, and a voltage is applied from the charging bias power supply 31 in FIG. At this time, the photoconductor 11 and the magnetic brush roller 23 are rotated in the forward direction (indicated by arrows P and M in FIG. 1), and the peripheral speed ratio of the magnetic brush roller to the photoconductor 11 is gradually increased from 1. If the peripheral speed ratio of 1, that is, when the peripheral speed ratio of the both are equal, for contacting zone electrostatic
The particles 29 are hardly agitated and the current flowing into the photoreceptor is small. On the other hand, if the peripheral speed ratio increases, gradually contacting zone
The charging particles 29 are vigorously stirred to form a mixed charging particle.
In the child 29, the charge injection amount increases due to the movement of the conductive particles, and a large current flows. On the other hand, for uniform contact charging
Particle 29 does not change much. FIG. 3 shows a case where a charging bias voltage of 50 V is applied and a case where a charging bias voltage of 100 V is applied.

As described above, the contact charging particles of the present invention are:
It is necessary to use it with stirring. This can be achieved by separately providing a stirring means.However, the photoconductor and the magnetic brush roller are rotated in opposite directions, or the photoconductor and the magnetic brush roller are rotated in a forward direction at different peripheral speed ratios. Can be easily realized. When rotating in the forward direction, the peripheral speed ratio is preferably set to 2 to 5. Also,
Similar effects can be obtained by rotating the magnet and stirring the contact charging particles .

In the contact charging particles of the present invention, current flows mainly on the surface of the high-resistance particles, and a large amount of charge can be injected into the photoreceptor by the large space movement effect of the conductive particles. In addition, since the current flows through the surface of the high-resistance particles, the high-resistance particles function as a kind of resistance layer, and the flow of the excessive current is prevented. For this reason, the tip of the magnetic brush exerts a charging function as an aggregate of electrodes, and can uniformly charge the photosensitive member in a short time, and furthermore, excessive current causes dielectric breakdown of the photosensitive layer and occurrence of pinholes. Is prevented.

At the time of charging, the voltage applied from the charging bias power supply 31 to the photoconductor 11 in the darkness depends on the photoconductor 1 used.
1 is appropriately determined according to the charging capability of the photosensitive member 11 required for the image forming system. The present invention is suitable, for example, when charging with a low bias voltage of 400 volts or less, more preferably 25%.
0 volts or less, more preferably 30 to 150 volts.

If the particles having the conductivity necessary for injecting electric charges are used alone, the current directly flows into the photoreceptor through the contact points of the particles. If there is, the photosensitive layer causes dielectric breakdown and pinholes are generated. This is particularly remarkable in the case of a low-charging photoconductor having a thin photosensitive layer.

As the magnetic high-resistance particles 103, a material used as a carrier of a developer in electrophotography can be used as it is. Specifically, ferrite particles, resin-coated ferrite particles, Magnetite particles, magnetic resin particles in which fine particles of ferrite or magnetite are dispersed in a resin, and the like are used. The magnetic conductive particles 105 may be particles in which the material itself has both conductivity and magnetism, such as iron powder formed by forming a surface resistance layer and stabilized, or a conductive layer may be formed on the surface of core particles having magnetism. The core particles of the latter type are typically represented by the following two types.

(1) A magnetic resin particle core in which magnetic material fine particles are dispersed and supported in a binder resin. (2) A magnetic powder particle core made of magnetic powder particles such as ferrite and magnetite. On the other hand, any of the following (a) to (c) can be applied as a method for forming a conductive surface layer on the particle core, that is, a method for making the particle core conductive.

(A) Conductive fine particles such as conductive carbon black are fixed to the surface of the magnetic particle core. This method is particularly suitable for the magnetic resin particle core of the above (1). The adhesion of the conductive fine particles to the particle core is performed by uniformly mixing the conductive fine particles with the magnetic particle core in which the magnetic material fine particles are dispersed in a binder resin, and attaching the conductive fine particles to the surface of the particle core. This is performed by applying a thermal and thermal impact force to drive and fix the conductive fine particles into the surface layer of the magnetic particle core. As such a surface reforming apparatus, for example, there is a hybridizer (manufactured by Nara Machinery Co., Ltd.). Such conductive magnetic particles are described in European Patent EP 0 492 665.

(B) A conductive resin coating layer in which conductive fine particles are dispersed in a synthetic resin is formed on the surface of the magnetic particle core. This method can be applied to both the magnetic resin particle core (2) and the magnetic resin particle core (1). Specifically, the following methods (1) to (3) can be adopted. (1) A method in which a resin is dissolved in a solvent or the like, conductive fine particles are dispersed therein, and the dispersion is applied on a particle core, and the solvent is volatilized and removed by heating to form a conductive resin coating layer. (2) Dissolve the resin in a solvent or the like, disperse conductive fine particles therein, apply it on the particle core, remove the solvent by heating, promote crosslinking and polymerization of the resin component, A method for forming a conductive resin coating layer. (3) A method in which a monomer is directly polymerized on the surface of a particle core such as ferrite particles in the presence of conductive fine particles such as carbon black, and a conductive resin coating layer is grown and formed so as to involve the conductive fine particles. This method is described in, for example, Japanese Patent Application Laid-Open No.
No. 6808 is cited and described.

(C) ITO (Indium-T) is formed by a thin film forming method such as a CVD method, a vapor deposition method, and a sputtering method.
in-Oxide), a conductive thin film of indium oxide, tin oxide, aluminum, nickel, chromium, gold, etc.,
Formed on the surface of the magnetic particle core.

The magnetic force of the high-resistance particles and the conductive particles needs to be larger than a certain level, preferably 5K.
The maximum magnetization (magnetic flux density) in a magnetic field of Oe (Oersted) is 50 emu / g or more, more preferably 55 to 20 emu / g.
0 emu / g. Further, the maximum magnetization in a magnetic field of 1 KOe is preferably 30 emu / g or more, and preferably 4 emu / g or more.
0 to 100 emu / g. In the present invention, as long as the effect is not impaired, conductive particles exceeding 10 μm,
High-resistance particles having a small particle size can be present in the contact charging particles .

[0032]

According to the present invention, a mixture of conductive particles and high-resistance particles is used as a contact charging particle to provide a distribution of conductivity, and furthermore, by optimizing the particle size and the resistance, the excess is obtained. Dielectric breakdown due to current can be prevented, and the photosensitive member can be uniformly charged in a short time by contact particle charging.
In the above description, mainly the electrophotographic photosensitive member has been mainly described, but the present invention is not limited to this, and can be used for charging various objects.

[0033]

EXAMPLES (1) Preparation of Contact Charging Particles A polyethylene resin was mixed with 85% by weight of magnetite.
After kneading, coarsely pulverized with a rotoplex, average 8 μm
Particles were obtained. Then, the particles were removed from the particles by an air classifier.
The coarse powder having a size of not less than μm and the fine powder having a size of not more than 2 μm were removed to obtain classified particles having an average particle size of 7 μm.

After 2% by weight of conductive carbon black was mixed with the classified particles using a Henschel mixer, the conductive carbon black was fixed to the particle surface with a hybridizer (Nara Machinery Co., Ltd.), and the maximum magnetization was 75 emu /
g, and conductive particles having a resistance of 1 × 10 ² Ω · cm were obtained.

On the other hand, the average particle diameter is 50 μm, and the maximum magnetization is 65 e.
Mu / g, non-coated ferrite particles having a resistance of 8 × 10 ⁷ Ω · cm are prepared to obtain high-resistance particles, and the conductive particles are added to the high-resistance particles in an amount of 0 to 25% by weight and mixed.
The particles were used for contact charging . The characteristics of each contact charging particle are as shown in Table 1 below.

[0036]

[Table 1] Amount of conductive particles (%) Average particle size (μm) Resistance (Ω · cm) Contact charging particles A 25 35 3 × 10 ⁴ Contact charging particles B 15 40 8 × 10 ⁴ Contact charging Particles C 5 485 5 × 10 ⁶ Contact charging particles D 0 50 8 × 10 ⁷

(2) Measurement of Charging Characteristics of Photoconductor The developing unit 51 is removed from the apparatus shown in FIG. 1, a potential measuring device is installed at the position, and the charging unit is driven without driving the LED exposure optical system 41. The charge amount of the photoreceptor according to No. 21 was measured by a potential measuring device in the dark.

At this time, by using the contact charging particles A to D, the peripheral speed ratio of the magnetic brush roller 23 to the photoreceptor is kept constant, and the photosensitive drums 1 to 3 of the drum-shaped photoreceptor 11 are exposed. Body potential was measured. At this time, the voltage applied by the charging bias power supply 31 was set to 100V. Further, as the photoconductor 11, an a-Si-based photoconductor drum having a diameter of 30 mmφ was used. Printing of A41 sheets is possible with three rotations of the photoconductor, but in an actual apparatus, it is necessary to apply uniform charging to the photoconductor from the first rotation.

FIG. 4 shows the above results. By adding conductive particles and keeping the peripheral speed ratio of the magnetic brush roller 23 to the photoconductor 11 constant and placing the contact charging particles 29 under stirring, the photoconductor potential is raised to a level at which an image can be formed. It can be seen that the photoconductor can be charged.

Depending on the image forming system, it may be necessary to charge the photosensitive member to a higher potential. In such a case, the voltage applied by the charging bias power supply may be increased. Also, in general, the dark decay cannot be ignored, so that the measured charging potential does not rise to 100 V in the case of FIG.

(3) Image formation Styrene / n-butyl acrylate copolymer (copolymerization ratio 80/20) 25 parts by weight Magnetite 75 parts by weight After kneading the above mixture, pulverizing and classifying with a jet mill to form a carrier core. Obtained. To 100 parts by weight of the carrier core, 2 parts by weight of conductive carbon black (conductive fine particles, average particle size of 20 to 30 nm) were sufficiently mixed with a Henschel mixer to uniformly adhere to the surface of the carrier core.

Next, a surface treatment device (hybridizer,
Using Nara Machinery Co., Ltd.), these fine particles were fixed to the surface layer of the carrier core by mechanical impact to obtain a conductive magnetic resin carrier. The properties of this carrier were as follows. Volume resistivity: 5 × 10 ³ Ω · cm Saturation magnetization: 64 emu / g Ratio of particles occupying 35 μm or less: 40% by weight Styrene / n-butyl acrylate copolymer (copolymerization ratio 80/20) 73 parts by weight magnetite 15 parts by weight Carbon black 5 parts by weight Polypropylene wax 5 parts by weight Charge control agent 2 parts by weight

After kneading the above mixture, it was pulverized with a jet mill and classified to obtain a toner having an average particle diameter of 10 μm. The above carrier and toner are mixed to a toner concentration (T / D) of 20% by weight, and a developer (volume resistivity of 2 × 10
⁴ Ω · cm), and an image was formed under the following conditions using the above-described contact charging particles A or B using the apparatus shown in FIG. ~ 1.4 clear images were obtained. Here, a drum-shaped a-Si photosensitive member having a photosensitive layer thickness of 10 μm and a diameter of 30 mmφ was used as the photosensitive member. Charging bias voltage: 100 V Developing bias voltage: 70 V In the above embodiment, by using the developing method described in Japanese Patent Application No. 5-42069, it is possible to form an image with a low charging bias voltage and a low developing bias voltage. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an image forming method of the present invention.

FIG. 2 is a schematic view of a magnetic brush formed by the contact charging particles of the present invention.

FIG. 3 is a graph showing conduction due to spatial movement.

FIG. 4 is a graph showing a charging potential of a photoconductor in an example.

[Explanation of symbols]

Reference Signs List 11 photoconductor 13 conductive support 15 photosensitive layer 21 charging unit 23 magnetic brush roller 25 mag roller 27 charging sleeve 29 contact charging particles 31 charging bias power supply 41 LED exposure optical system 51 developing unit 53 developing roller 55 mag roller 57 sleeve 59 developing bias Power supply 71 Transfer unit 73 Transfer roller 77 Transfer bias power supply 81 Fixing unit 83 Fixing roller 85 Pressure roller 91 Developer 93 Toner 95 Paper 99 Cleaning blade 101 Contact charging particles 103 High resistance particles 105 Conductive particles

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-183822 (JP, A) JP-A-3-186823 (JP, A) JP-A-6-258918 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/02-15/02 103 G03G 15/09-15/09 101 G03G 21/06

Claims (8)

(57) [Claims] 1. A contact charging particle for injecting electric charge into an object to which a voltage is applied and in contact with the object to charge the surface of the object, and having a magnetic property and a volume resistivity of 5 × 10 ⁴ Ω · cm or more. Resistive particles, magnetic and volume specific resistance 5 × 10 ³ Ω
cm and a mixture with conductive particles having a volume resistivity of 10 ¹ to 10 ⁸ Ωcm as a mixture, wherein the average particle size of the conductive particles is smaller than the average particle size of the high resistance particles, Contact charging particles, wherein 10% by weight or more of the whole are conductive particles having a particle size of 10 μm or less, and 5% by weight or more of the whole are high resistance particles . 2. A magnetic material having a volume resistivity of 5 × 10 ⁴ Ω.
A mixture of high-resistance particles of at least 10 cm and conductive particles having magnetism and a volume resistivity of 5 × 10 ³ Ω · cm or less, and a volume resistivity of 10 ¹ to 10 ⁸ Ω · cm as a mixture. The average particle size of the conductive particles is smaller than the average particle size of the high-resistance particles, and 10% by weight or more of the conductive particles are conductive particles having a particle size of 10 μm or less, and 5% by weight or more of the whole are high-resistance particles. Is a particle
Contacting the charging particles is brought into contact with the object surface, for contact charging
A method for charging a surface of an object, wherein a voltage is applied to the surface of the object via the particles for contact charging while stirring the particles . 3. The charging method according to claim 2, wherein a voltage of 400 volts or less is applied. 4. The charging method according to claim 2, wherein the contact charging particles are agitated by relatively moving the contact charging particles and the object. 5. The method for charging a photoconductor according to claim 2, wherein the object is a photoconductor that becomes conductive when exposed to an image signal. 6. A charging member for uniformly charging a photoconductor, selectively lowering the charging potential of the photoconductor by selective light irradiation to form an electrostatic latent image formed of a low potential portion and a high potential portion on the photoconductor. Contacting the photosensitive member with the electrostatic latent image formed thereon with the developer,
An image forming apparatus comprising a developing member for selectively adhering toner and forming an image made of toner on a photoreceptor, wherein the charging member has magnetism and a volume resistivity of 5 × 10 ⁴ Ω · cm or more High-resistance particles and a volume resistivity of 5 × 10 ³ Ω
cm and a mixture with conductive particles having a volume resistivity of 10 ¹ to 10 ⁸ Ωcm as a mixture, wherein the average particle size of the conductive particles is smaller than the average particle size of the high resistance particles, 10% by weight or more of the whole are conductive particles having a particle diameter of 10 μm or less, 5% by weight or more of the whole are high resistance particles, and contact charging particles which come into contact with the photoreceptor under stirring, and contact charging by magnetic force Attract particles and allow agitation
An image forming apparatus comprising: the magnetic member for restraining the contact charging particles, and a charging bias power source for applying a voltage to the photosensitive member via the contact charging particles. 7. The image forming apparatus according to claim 6, wherein the charging bias power supply applies a voltage of 400 volts or less. 8. The photoconductor sequentially moves to a position where a charging member, an exposure member, and a developing member are installed, while the contact charging particles move while being restrained by a magnetic member, and the photoconductor and the contact charging particles move relative to each other. The contact charging particles are agitated by moving in the opposite direction, or by moving the photosensitive member and the contact charging particles relatively in the same direction and moving at different speeds. An image forming apparatus according to claim 1.