JPH05150614A - Electrifying device - Google Patents

Abstract

PURPOSE:To stably form good images over a long period of time without generating unevenness in surface potential. CONSTITUTION:The contrast of an electrostatic latent image formed at the time of exposing remains on an electrostatic latent image carrying member 101 after the toner image is transferred to a recording medium 108. The contrast is returned to the uniform surface potential in the next electrification process. An electrifying member is provided so as to come into contact with the electrostatic latent image carrying member 101 in the electrifying device 102 and is connected to a power source. The electrifying member is formed of a metallic material or its volumetric resistance value is set to be smaller than 10<3>OMEGA-cm if the member is formed of conductive rubber or the like. The surface potential obtd. by one time of electrification is increased if electrification is executed by using the metallic material or the conductive rubber having the volumetric resistance value smaller than 10<3>OMEGA-cm. Since a means for limiting a current is disposed between the electrifying member and a power source, the current flowing to the electrostatic latent image carrying member 101 from the electrifying member is limited and the surface potential of the electrostatic latent image carrying member 101 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device such as a printer or a copying machine.

[0002]

2. Description of the Related Art Conventionally, when forming an image in a printer or a copying machine, an electrophotographic recording method based on the Carlson method has been generally used ("Basics and Applications of Electrophotographic Technology" (ed. Issued on June 15th by Corona) P28, 46, 47).

FIG. 2 is a conceptual diagram of an image forming apparatus using an electrophotographic recording method by the Carlson method. In the figure, first, the surface of the photosensitive drum 2 charged by the corona discharge of the corona charger 1 is exposed by the exposure device 3,
The image on the document read by the optical means is formed as an electrostatic latent image. The electrostatic latent image is developed by the developing device 4, then transferred onto the recording medium 8 by the transfer device 5, and fixed by the fixing device 6 to form an image.

Since the photosensitive drum 2 is repeatedly used, the toner remaining on the photosensitive drum 2 after the transfer is cleaned by the cleaning device 7. However, in the above conventional image forming apparatus, the corona charger 1 is generally used to charge the photosensitive drum 2, but the corona charger 1 requires a high voltage power source of 5 to 10 kV. It is dangerous and increases the cost. Further, since the corona charger 1 generates ozone, it is not only harmful to the human body, but also the charging potential of the photosensitive drum 2 fluctuates under the influence of environmental stability, particularly humidity.

Therefore, as a charging device, a contact type charging device has been proposed in which a charging brush, a charging roller, a charging belt, a charging blade and the like are brought into contact with the photosensitive drum 2 (Japanese Patent Publication Nos. 62-29788 and 62-1978). 62-2979
No. 0, see JP-A-61-42669). In this contact type charging device, since a small power source of 0.5 to 1.5 kV can be used, the price of the power source is low, ozone hardly occurs, and the environment is prevented from being polluted.

[0006]

However, in the above-mentioned conventional charging device, the charging device such as the charging brush, the charging roller, the charging belt, and the charging blade includes the charging member such as the brush, roller, belt, blade and the like. Although the volume resistance value is set to 10 ³ to 10 ¹⁰ Ω-cm, the volume resistance value becomes uneven, and the photosensitive drum 2 cannot be uniformly charged.

FIG. 3 is a diagram showing a surface potential model of the photosensitive drum. (A) of the figure shows the surface potential model after exposure,
(B) shows a surface potential model after being charged by a charging device in the next charging process. The voltage applied to the charging device is set so that the surface potential V _{S of the} photosensitive drum 2 after charging becomes −600 to −900 V, and the surface potential V _R remaining after exposure becomes −50 to −150 V. The exposure amount of the exposure device 3 is set. Further, it is generally necessary that the electrostatic latent image has a contrast of -500V or higher. The surface of the photosensitive drum 2 on which such a contrast of the electrostatic latent image is formed must be made to have a uniform surface potential V _S in the next one charging process.

However, a charging member such as a brush or a low
The volume resistance of la, belt, blade, etc. is 10³-10^Ten
Ability to charge the photosensitive drum 2 when set to Ω-cm
Is low, the potential difference obtained by a single charge is
(V₁) Becomes smaller, the surface potential V of the photosensitive drum 2 becomes smaller._Sof
The rise will be worse. That is, the photosensitive drum 2
Has a history of electrostatic latent image,
The potential difference V ₁Minute charge is done
And the surface potential after charging is V_SAnd V_R+ V₁Two of
Potential exists, and the potential difference V₂Uneven surface potential
Occurs. In this way, even after the next charging,
Surface potential of the part exposed by the exposure process of
There is a difference between the surface potential of the non-charged area and the charging
I can't do it.

Further, the charging member is prepared by dispersing conductive particles such as carbon in a polymer such as fiber, rubber or film, and
Although a volume resistance value of 0 ³ to 10 ¹⁰ Ω-cm is obtained, the technique is to accurately control the content of the conductive particles and to uniformly disperse the conductive particles in the polymer. It is very difficult to do so, the volume resistance varies, and the surface potential becomes uneven.

These two types of surface potential unevenness affect the quality of the recorded image, causing so-called fogging in which toner adheres to the non-image area, and toner missing in the image area resulting in missing or missing images. I will end up. The present invention solves the problems of the above-described conventional charging device, and provides a charging device capable of stably forming a good image for a long time without causing unevenness in the surface potential. To aim.

[0011]

To this end, in the charging device of the present invention, an electrostatic latent image bearing member carrying an electrostatic latent image is provided, and charging is performed so as to contact the electrostatic latent image bearing member. A member is provided and connected to the power supply. When the charging member is formed of a metal material or conductive rubber, the volume resistance value is set to be smaller than 10 ³ Ω-cm.

Further, means for limiting current is arranged between the charging member and the power source.

[0013]

According to the present invention, as described above, the electrostatic latent image carrier is charged by the charging device and exposed to form an electrostatic latent image. The electrostatic latent image is converted into a toner image by a developing device, and then the toner image is transferred onto a recording medium by a transfer device and fixed by a fixing device.

After the toner image has been transferred to the recording medium, the electrostatic latent image bearing member retains the contrast of the electrostatic latent image at the time of exposure, which results in a uniform surface potential in the next charging process. Will be returned. In the above charging device, a charging member is provided so as to come into contact with the electrostatic latent image carrier and is connected to a power source. When the charging member is formed of a metal material or a conductive rubber, the volume resistance value is 10 ³ Ω-c.
It is set to be smaller than m.

When a metal material or a conductive rubber having a volume resistance value of less than 10 ³ Ω-cm is used for charging, the surface potential obtained by one charging can be increased. Further, since means for limiting the current is provided between the charging member and the power source, the current flowing from the charging member to the electrostatic latent image carrier is limited, and the surface potential of the electrostatic latent image carrier is adjusted. You can

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a charging device showing an embodiment of the present invention. In the figure, a drum-shaped electrostatic latent image carrier 101 is rotated at a constant peripheral speed in the direction of arrow A by a driving unit (not shown). The electrostatic latent image carrier 101 has a photoconductive layer 101b provided on a conductive support 101a, and any of a selenium photoconductor, an organic photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, etc. is used. be able to.

Next, the image forming process in this embodiment will be described. First, the electrostatic latent image carrier 101
Are uniformly and uniformly charged by the charging device 102 provided so as to face the surface. The charging device 102 will be described in detail later. In the exposure process, light corresponding to an image signal is exposed on the electrostatic latent image carrier 101 by the exposure device 103 to form an electrostatic latent image. As the exposure device 103, not only a combination of an LED array and a SELFOC lens (trade name) but also a combination of a laser and an image forming optical system can be used.

Whether it adheres to the electrostatic latent image carrier 101,
Alternatively, the developing device 104 is provided at a small distance, and the developing device 104 adsorbs the toner 106 on the toner carrier 105 and conveys it in the direction of arrow B to form it on the electrostatic latent image carrier 101. Develop the electrostatic latent image. In this embodiment, reversal development is performed, and a bias potential is applied between the conductive support 101a of the electrostatic latent image carrier 101 and the toner carrier 105.

With the above structure, lines of electric force are generated in the space between the toner carrier 105 and the electrostatic latent image carrier 101 by the electrostatic latent image formed on the electrostatic latent image carrier 101. Therefore, the charged toner 106 on the toner carrier 105 is
It is attached to the electrostatic latent image carrier 101 by electrostatic force and is developed to form a toner image. As the developing device 104, any of a two-component magnetic brush developing device, a one-component magnetic brush developing device, a one-component non-magnetic developing device and the like can be used.

On the other hand, the recording paper 108 accommodated in the paper cassette 107 is taken out by the paper feed roller 109 and sent to the paper feed roller 110 whose rotation is stopped, and then the recording paper 10 is discharged.
A skew of 8 is corrected. Next, the paper feed roller 110 is activated, the recording paper 108 is fed to the transfer portion, and the transfer device 11
1 transfers the toner image formed on the electrostatic latent image carrier 101 to the recording paper 108. The recording paper 108 is the pressure roller 1
The sheet 12 is conveyed to the fixing device 114 including the heating roller 113 and the heating roller 113. The heat of the heat generating roller 113 melts the toner 106, and the toner 106 permeates between the fibers of the recording paper 108 by the action of pressure, and the recording paper 108 is fixed. The fixed recording paper 108 is sent out of the apparatus by the paper discharge roller 115.

On the other hand, although a small amount of toner 106 may remain on the electrostatic latent image carrier 101 after transfer, it is removed by the cleaner 116. In this way, the electrostatic latent image carrier 101 is repeatedly used. Next, the charging device 102
Will be described. FIG. 4 is an arrangement state diagram of a charging device using a charging blade as a charging member.

As shown in the figure, the charging device 102 is constructed such that the charging blade 118 is supported by a guide 119, and is arranged so that the antinode or edge of the charging blade 118 contacts the electrostatic latent image carrier 101. The charging blade 118 and the conductive support 101a of the electrostatic latent image carrier 101 are
A power supply 121 is connected via the current control resistor 120. In this case, the polarity of the voltage applied to the charging blade 118 of the power source 121 is negative, but this is because the electrostatic latent image carrier 101 of the negative charging type is used, and the electrostatic charging of the positive charging type is performed. When the electro-latent image carrier 101 is used, the polarity of the voltage applied to the charging blade 118 is positive.

The charging blade 118 is, for example, SK.
Made of steel, stainless steel, phosphor bronze, copper, etc., with a thickness of 1
A thin metal plate having elasticity of 0 to 1000 μm is used. Also, smaller than a volume resistivity 10 ³ Ω-cm, a contact width formed between the electrostatic latent image bearing member 101 in order to equalize the longitudinal direction of the contact surface, the rubber hardness of 90 ° or less (JI
It is also possible to use a blade-shaped conductive rubber as S A). In that case, for example, rubber materials such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, butadiene rubber, carbon, graphite, ferrite, aluminum, copper, bronze, stainless steel, titanium oxide, tin oxide, etc. It is formed by adding conductive powder, metal powder, metal fiber and the like.

FIG. 5 is an arrangement view of a charging device using charging blades having different mounting directions. Although the charging blade 118 is arranged in the forward direction with respect to the rotation direction A of the electrostatic latent image carrier 101 in FIG. 4, it is arranged in the reverse direction in FIG. .. Also in this case, the power supply 121 is connected to the charging blade 118 and the conductive support 101a of the electrostatic latent image carrier 101 via the current limiting resistor 120.

Next, the charging device 102 shown in FIG. 4 and FIG.
The charging characteristics when using is described. It is understood that the following results can be obtained by performing the experiment using the charging device 102 of FIGS. 4 and 5. FIG. 6 is a relationship diagram between the number of times of charging when a conductive rubber is used for the charging blade and the surface potential of the electrostatic latent image carrier, and FIG. 7 is the number of times of charging when a thin metal plate is used for the charging blade and the electrostatic latent image. FIG. 4 is a relational diagram of the surface potential of a carrier.

In this case, the charging blade 118 has a thickness of 100 μm, a short side length of 20 mm, and a long side length of 25.
Conductive carbon was added to a 0 mm stainless steel thin plate, a chloroprene rubber having a thickness of 2 mm, a short side length of 20 mm, and a long side length of 250 mm, and a volume resistance value of 10 ² Ω−. cm, rubber hardness 60 ° (JISA)
The conductive rubber of was used. The length of the long side of the charging blade 118 is determined by the length of the photoconductive layer 101b of the electrostatic latent image carrier 101 in the longitudinal direction. That is, in manufacturing the electrostatic latent image carrier 101, it is difficult to form the photoconductive layer 101b on the circumference of both ends in the longitudinal direction of the electrostatic latent image carrier 101. Therefore, the length of the long side of the charging blade 118 is made slightly shorter than the length of the photoconductive layer 101b of the electrostatic latent image carrier 101 in the longitudinal direction so that the current of the power source 121 does not leak.

The surface potential of the electrostatic latent image carrier 101 was measured using a surface electrometer. R is the resistance value of the current control resistor 120 arranged between the charging blade 118 and the power supply 121, and the applied voltage is 1.2 kV. Volume resistance is 10 ⁶
When a conventional conductive rubber of Ω-cm is used, about 4 times of charging is required until the surface potential reaches a desired potential, but the volume resistance value is 10 ² Ω-as in this embodiment. When a conductive rubber or a metal thin plate having a diameter of cm is used as the charging blade 118, the surface potential value increases with one charging.

Further, the value of the surface potential obtained by one-time charging and how the surface potential rises vary depending on the resistance value of the current control resistor 120. That is, when the resistance value is increased, the value of the surface potential obtained by one-time charging becomes smaller, so that the rising is delayed, and when the resistance value of the current control resistor 120 is decreased, the surface potential of the one-time charging becomes smaller. The higher the value, the faster the rise will occur. But,
In this case, the desired surface potential becomes equal to or higher than the desired surface potential with one charge.

FIG. 8 is a diagram showing the relationship between the resistance value of the current control resistor and the surface potential of the electrostatic latent image carrier obtained by charging once.
Generally, the unevenness of the surface potential of the electrostatic latent image carrier 101 is ± 5.
If the voltage is kept within 0 V, it is possible to prevent image dropout, chipping, fog, and the like. In this case, the electrostatic latent image carrier 101
Since the surface potential of is set to -650V, the surface potential of -600 to -700V can be obtained by one charging. From the figure, the resistance value R of the current control resistor 120 is in the range of 0.7 MΩ ≦ R ≦ 200 MΩ, and if the resistance value R of the current control resistor 120 is set in the above range, the unevenness of the surface potential of the electrostatic latent image carrier 101 is obtained. Compared with the conventional one, it is less than 1/2, missing, missing,
A good image without fogging can be obtained.

Next, a second embodiment of the charging device 102 will be described. FIG. 9 is a layout view of a charging device using a conductive rubber roller as a charging member. As shown in the figure, the charging device 102 is composed of a conductive rubber roller 124 in which a conductive rubber layer 123 is arranged around a conductive shaft 122. The conductive shaft 122 is formed of a metal shaft such as stainless steel, steel, and aluminum, and the metal shaft and the conductive support 101 of the electrostatic latent image carrier 101.
A power supply 121 is connected to a via a current control resistor 120. The conductive rubber layer 123 is formed of a conductive rubber having a volume resistance value smaller than 10 ³ Ω-cm, and the contact width formed between the conductive rubber layer 123 and the electrostatic latent image carrier 101 is the longitudinal direction of the contact surface. Rubber hardness to 90 ° (JI
S A). Then, the charging blade 118
Similarly, for example, rubber materials such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, and butadiene rubber, carbon, graphite, ferrite, aluminum, copper, bronze, stainless steel, titanium oxide, tin oxide, etc. Conductive powder, metal powder, metal fiber, etc. are added.

FIG. 10 is a diagram showing the relationship between the number of times of charging and the surface potential of the electrostatic latent image bearing member when charged by a conductive rubber roller. In this case, stainless steel having a diameter of 8 mm is used as the conductive shaft 122.
Conductive carbon was added to chloroprene rubber on the outer peripheral surface of the rubber composition to have a rubber hardness of 30 ° (JIS A) and a conductive rubber layer 123 having a volume resistance value of 10 ² Ω-cm. The diameter was 20 mm. Conductive rubber roller 1
24 is an electrostatic latent image carrier 101 by a drive system not shown.
When it is rotated in the same direction (direction a) with respect to the direction of rotation, when it is rotated in the direction (b direction) following the direction of rotation of the electrostatic latent image carrier 101, or it is fixed without rotation. The characteristic about the case is shown.

The applied voltage is 1.2 kV, and the resistance value R of the current control resistor 120 is 50 MΩ. As shown in the figure, the value of the surface potential and the rise of the surface potential obtained by one-time charging are very good regardless of the rotating direction of the conductive rubber roller 124 and the presence or absence of rotation thereof. Further, in the figure, only the case where the resistance value R of the current control resistor 120 is set to 50 MΩ is described, but the surface potential value and the rising characteristic of the surface potential are obtained by using the charging blade 118 shown in FIGS. 6 and 7. As in the case, it changes depending on the resistance value R of the current control resistor 120. If the resistance value R is increased, the rise of the surface potential becomes slower, and if the resistance value R is made smaller, the rise becomes very fast. Will exceed the surface potential of. The range of favorable resistance R is the charging blade 11
As in the case of using No. 8, 0.7 MΩ ≦ R ≦ 200 MΩ.

When the conductive rubber roller 124 is rotated in the b direction, good results are obtained even if the peripheral speed of the electrostatic latent image carrier 101 and the conductive rubber roller 124 are different or the same. is there. When the peripheral speed of the electrostatic latent image carrier 101 and the peripheral speed of the conductive rubber roller 124 are the same,
The conductive rubber roller 124 does not become a rotational load of the electrostatic latent image carrier 101, which is particularly good.

As described above, the conductive rubber roller 124
Even if the rotation direction and the rotation speed are set arbitrarily, the same result as when the charging blade 118 is used can be obtained, and the value of the surface potential obtained by one charging can be increased as compared with the conventional technique. As a result, the unevenness of the surface potential of the electrostatic latent image carrier 101 is reduced, and it is possible to obtain a good image without image loss, chipping, or fogging.

Next, a third embodiment of the charging device 102 will be described. FIG. 11 is a layout view of a charging device using a nickel electroformed sleeve as a charging member. As shown in the figure, the charging device 102 includes drive rollers 125a and 125a.
b and a nickel electroformed sleeve 126 that comes into contact with the outer circumferences of the b and follow them. Conductive support 1 of the nickel electroformed sleeve 126 and the electrostatic latent image carrier 101
A power supply 121 is connected to 01a via a current control resistor 120. In addition, the drive rollers 125a and 125b
Is an electrostatic latent image carrier 101 by a drive system (not shown).
It can be rotated in the same direction (direction a) as the rotation direction (direction b), and can be fixed so as not to rotate.

FIG. 12 is a diagram showing the relationship between the number of times of charging and the surface potential of the electrostatic latent image bearing member when charged by a nickel electroformed sleeve. A nickel electroformed sleeve 126 having a thickness of 30 μm is used, and the applied voltage is 1.2.
The resistance value R of the kV and the current control resistor 120 is 50 MΩ. The surface potential value and the rise of the surface potential obtained by one-time charging are very good regardless of whether the nickel electroformed sleeve 126 is rotated or not.

Further, in the figure, only the case where the resistance value R of the current control resistor 120 is set to 50 MΩ is described.
The surface potential value and the rising characteristic of the surface potential change depending on the resistance value R of the current control resistor 120 as in the case of using the charging blade 118 shown in FIGS.
Is larger, the rising of the surface potential is slower, and if the resistance value R is smaller, the rising is much faster. The range of favorable resistance value R is 0.7 MΩ ≦ R ≦ 200 MΩ as in the case of using the charging blade 118.

The nickel electroformed sleeve 126 having a thickness of 30 μm is used.
In order to make the contact width with 01 uniform in the longitudinal direction of the contact surface, the thickness is preferably 10 to 500 μm. The results are also good when the peripheral speed of the nickel electroformed sleeve 126 is changed. The value of the surface potential obtained by one-time charging can be made larger than that of the conventional one, and the unevenness of the surface potential of the electrostatic latent image carrier 101 is reduced, resulting in a missing image,
A good image without chipping or fogging can be obtained.

Next, a fourth embodiment of the charging device 102 will be described. FIG. 13 is an arrangement state diagram of a charging device using a charging belt as a charging member. As shown in the figure, the charging device 102 includes drive rollers 125a and 125b and a charging belt 128. The charging belt 12
8 and the conductive support 101a of the electrostatic latent image carrier 101 are connected to a power supply 121 via a current control resistor 1120. The drive rollers 125a and 126b can be rotated by a drive system (not shown) in the same direction (direction a) as the direction of rotation of the electrostatic latent image carrier 101 (direction b), but do not rotate. It can also be fixed.

The charging belt 128 is formed of a film having a volume resistance value of less than 10 ³ Ω-cm, such as polyimide, polyamide, polyester, polystyrene,
Carbon, graphite, soft resin film made of resin such as polycarbonate, nylon, fluorine resin, etc.
Conductive powder such as ferrite, aluminum, copper, bronze, stainless steel, titanium oxide, tin oxide, metal powder,
Metal foil added, metal resin such as aluminum or copper, or Indium-T to the resin film of the above-mentioned soft fat.
It is configured by coating a conductive thin film such as in Oxide.

FIG. 14 is a diagram showing the relationship between the number of times of charging when charged by the charging belt and the surface potential of the electrostatic latent image carrier. In this case, a transparent conductive film having a thickness of 75 μm is used, the applied voltage is 1.2 kV, and the resistance value R of the current control resistor 120 is 50 MΩ. The surface potential value and the rise of the surface potential obtained by one-time charging are very good regardless of the rotation direction of the charging belt 128 and the presence / absence of rotation of the charging belt 128.

Further, although the drawing shows only the case where the resistance value R of the current control resistor 120 is 50 MΩ,
The surface potential value and the rising characteristic of the surface potential change depending on the resistance value R of the current control resistor 120 as in the case of using the charging blade 118 shown in FIGS.
Is larger, the rising of the surface potential is slower, and if the resistance value R is smaller, the rising is much faster. The range of favorable resistance value R is 0.7 MΩ ≦ R ≦ 200 MΩ as in the case of using the charging blade 118.

The present invention is not limited to the above embodiments, but various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention. For example, the charging device 102 is not limited to the shape of each embodiment, and the charging member is brought into contact with the electrostatic latent image carrier 101, for example, by making the volume resistance value of the brush fiber smaller than 10 ³ Ω-cm. Volume resistance value of the part is 10 ³
Similar results can be obtained by making it smaller than Ω-cm.

Further, in the above embodiment, the charging member and the power source 12
A current control resistor 120 is added between the two to control the current flowing from the charging member to the electrostatic latent image carrier 101. Generally used operational amplifiers, constant current diodes, transistors, FETs, etc. It is also possible to use a current control circuit using.

[0045]

As described in detail above, according to the present invention, a charging member is provided so as to contact the electrostatic latent image carrier and is connected to a power source, and the charging member is formed of a metal material. Alternatively, in the case of conductive rubber, the volume resistance value is 10 ³ Ω.
It is set to be smaller than -cm.

When a metal material or a conductive rubber having a volume resistance value of less than 10 ³ Ω-cm is used for charging, the surface potential obtained by one charging can be increased. In the charging device, the contrast of the surface potential remaining on the electrostatic latent image carrier after the toner image is transferred to the recording medium is
It is possible to return to a uniform surface potential only by charging once.

Further, since the means for limiting the current is provided between the charging member and the power source, the current flowing from the charging member to the electrostatic latent image carrier is limited, and the surface potential of the electrostatic latent image carrier is reduced. It can be adjusted. Therefore, unevenness does not occur in the surface potential of the electrostatic latent image carrier, and a good image without chipping, omission, fog, etc. can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a charging device showing an embodiment of the present invention.

FIG. 2 is a conceptual diagram of an image forming apparatus using an electrophotographic recording method by the Carlson method.

FIG. 3 is a diagram showing a surface potential model of a photosensitive drum.

FIG. 4 is an arrangement state diagram of a charging device using a charging blade as a charging member.

FIG. 5 is a diagram showing the arrangement of a charging device using charging blades with different mounting directions.

FIG. 6 is a diagram showing the relationship between the number of times of charging and the surface potential of the electrostatic latent image carrier when a conductive rubber is used for the charging blade.

FIG. 7 is a diagram showing the relationship between the number of times of charging and the surface potential of the electrostatic latent image carrier when a thin metal plate is used as the charging blade.

FIG. 8 is a relationship diagram between the resistance value of the current control resistor and the surface potential of the electrostatic latent image carrier obtained by one charging.

FIG. 9 is an arrangement view of a charging device using a conductive rubber roller as a charging member.

FIG. 10 is a diagram showing the relationship between the number of times charging is performed by a conductive rubber roller and the surface potential of the electrostatic latent image carrier.

FIG. 11 is an arrangement view of a charging device using a nickel electroformed sleeve as a charging member.

FIG. 12 is a diagram showing the relationship between the number of times of charging and the surface potential of the electrostatic latent image bearing member when charged by a nickel electroformed sleeve.

FIG. 13 is an arrangement view of a charging device using a charging belt as a charging member.

FIG. 14 is a diagram showing the relationship between the number of times of charging when charged by a charging belt and the surface potential of the electrostatic latent image carrier.

[Explanation of symbols]

 Reference Signs List 101 electrostatic latent image carrier 102 charging device 118 charging blade 120 current control resistor 121 power supply 124 conductive rubber roller 126 nickel electroformed sleeve 128 charging belt

Claims (2)

[Claims] 1. An electrostatic latent image carrier carrying (a) an electrostatic latent image, (b) a charging member provided in contact with the electrostatic latent image carrier, and (c) the charging member. And (d) a volume resistance value of the charging member is 10 ³ Ω-cm.
A charging device characterized by being set smaller. 2. The charging device according to claim 1, further comprising a means for controlling a current between the charging member and the power source.